Publications

As of October 24, 2023, we published and presented 1145 articles.
Please also refer to Katayama Laboratory / Yamazato Laboratory research results page.

205
Journal Articles
299
Peer-Reviewed Conference Papers
641
Oral Presentation

  • 16QAM-OFDM Receiver Using 1-bit ADC that Utilizes Noise and Performs Frequency Conversion in the Digital Domain Characterization in a Frequency Flat Rician Fading Channel

    • A.Isozaki, T.Yamazato, M.Saito
    • International Conference on Emerging Technologies for Communications (ICETC)
    • Dec. 2023
    • In this study, we propose the 1-bit ADC receiver that performs frequency conversion in the digital domain to simplify the circuitry in the receiver and reduce power consumption. Then, we evaluate the SNR vs. BER of the 1-bit ADC receiver we propose. In the proposed receiver, the average of the 1-bit ADC outputs in parallel is taken, the received signal is restored, and the baseband signal is demodulated by multiplying the restored received signal by the carrier wave.

  • High-Speed Image Sensor Communication Using High Dynamic Range Combining

    • R. Huang, T. Yamazato, M. Kinoshita, H. Okada, S. Arai, K. Kamakura, T. Yendo, T. Fujii
    • IEICE Communications Express
    • Nov. 2023
    • https://doi.org/10.1587/comex.2023XBL0075
    • An essential issue in image sensor communication (ISC) is reliable and high-speed data transmission. In order to increase the data rate, this study uses pulse-width modulation (PWM). However, the symbol decision for PWM will become challenging with increasing numbers of luminance levels because of pixel saturation. In this study, we mitigate the pixel saturation problem by achieving high dynamic range (HDR) using two high-speed image sensors with varied exposure settings. Furthermore, we proposed HDR combining for signal demodulation. The field trial experiment results show that a throughput of higher than 87.5 kbps within the communication distance of 50 m can be achieved.

  • Image Sensor Communication Via Light Trail Using Propeller LED Transmitter

    • Z. Tang, J. Zheng, T. Yamazato, S. Arai
    • IEEE Photonics Journal, vol.15, no.5, pp.1-12
    • Oct. 2023
    • https://doi.org/10.1109/JPHOT.2023.3317082
    • This paper proposes an image sensor communication (ISC) system based on light trails using rotary LEDs. The light trail refers to an optical phenomenon where light appears elongated and forms a trajectory due to the movement of luminous objects. In this study, we developed a propeller LED transmitter (P-Tx) that rotates LEDs with a propeller to generate and transmit light trail signals. According to the LED's rotation radius, the proposed system segments light trails to achieve high-capacity data transmission at short distances and high-trust transmission at long distances. In addition, we perform the rotation coordinates system conversion for the captured light trails to accurately and simply detect the signal LEDs' coordinates. We experimentally evaluate the proposed system's communication performance and data rate. The experimental results demonstrate that our system is capable of meeting communication requirements at various distances and exhibits significant potential in enhancing the data transmission rate of ISC.

  • Experimental Investigation of Weak Signal Enhancement through Iterative Short-Term Power Delay Profile Estimation

    • F. Ojika, T. Yamazato, M. Saito, H. Omote, A. Sato, S. Kimura, S. Tanaka, H. Lin
    • Communications Society Conference of IEICE, B-1-31, p.31
    • Sep. 2023

  • A Study on Ultrasonic-based Angle Measurement System and adding Communication Function

    • S. Kitagawa, H. Hatano, K. Mori, K. Sanada, T. Kasashima, A. Tsujii, T. Yamazato
    • Enginnering Sciences Society Conference of IEICE, A-13-7, p.108
    • Sep. 2023

  • Zone-segment transmission for light-trail based image sensor communication using propeller LED transmitter

    • Z. Tang, J. Zheng, T. Yamazato, S. Arai
    • Enginnering Sciences Society Conference of IEICE, A-9-5, p.68
    • Sep. 2023

  • Expanding Private 5G Coverage by Integrating Optical Wireless Communication

    • J. Zheng, T. Yamazato
    • Enginnering Sciences Society Conference of IEICE, A-9-4, p.67
    • Sep. 2023

  • Experimental Evaluation of Superimposed Iterative Transmission for Varying Communication Ranges in Rolling Shutter Based Visible Light Communication

    • R. Maeda, M. Kinoshita, K. Kamakura, T. Yamazato
    • Enginnering Sciences Society Conference of IEICE, A-9-11, p.74
    • Sep. 2023

  • Performance Evaluation of the Camera-Based Visible Light Communication Using Half-Wave Rectified Waveform

    • H. Matsunaga, K. Kai, K. Fujii, T. Yendo, S. Arai, T. Yamazato
    • Enginnering Sciences Society Conference of IEICE, A-9-13, p.76
    • Sep. 2023

  • Detecting Light-trail Signals Transmitted by LED Propeller in Drone-based Visible Light Communication

    • C. Cao, Z. Tang, J. Zheng, T. Yamazato
    • Enginnering Sciences Society Conference of IEICE, A-9-6, p.69
    • Sep. 2023

  • An Experimental Study on Visible Light Communication Based on High-Dynamic Range Images

    • R. Huang, T. Yamazato, M. Kinoshita, H. Okada, K. Kamakura, S. Arai, T. Yendo, Fujii
    • Enginnering Sciences Society Conference of IEICE, A-9-7, p.70
    • Sep. 2023

  • Tracking Multiple LEDs Using an Event Camera in a Receiver Moving Environment

    • D. Ehara, Z. Tang, M. Kinoshita, T. Yamazato, H. Okada, K. Kamakura, S. Arai, T. Yendo, T. Fujii
    • Enginnering Sciences Society Conference of IEICE, A-9-8, p.71
    • Sep. 2023

  • Achieving Successful VLC Signal Reception Using A Rolling Shutter Image Sensor While Driving at 40 km/h

    • S. Kamiya, Z. Tang, T. Yamazato, M. Kinoshita, K. Kamakura, S. Arai, T. Yendo, T. Fujii
    • IEEE Photonics Journal, vol. 15, no. 4, pp. 1-11
    • Aug. 2023
    • https://doi.org/10.1109/JPHOT.2023.3287211
    • This paper presents the successful reception of visible light communication (VLC) signals, transmitted from an LED array, by an image sensor that utilizes a rolling shutter while driving at 40 km/h. The rolling shutter image sensors used in commercial cameras, such as those found in smartphones and dashcams, capture images line by line at a fast rate, allowing for VLC signal reception in vehicular environments. By analyzing the relationship between the signal reception rate for each line and the frame rate, we demonstrate that parallel VLC signals transmitted from the LED array can be received even while in motion. Notably, to our knowledge, this is the first time that an automobile moving at 40 km/h has successfully received a VLC signal.

  • Image Sensor Communication and its Transmitting Devices

    • Z. Tang, T. Yamazato
    • Elsevier, Optics Communications, vol. 541
    • Aug. 2023
    • https://doi.org/https://doi.org/10.1016/j.optcom.2023.129545
    • This paper focuses on image sensor communication (ISC) using cameras to receive wireless signals transmitted by visible lights. We summarize the technical principles of ISC from the perspective of transmitting devices. An introduction to the development and applications of ISC was provided, starting with the history of image sensors and visible light communication (VLC). Moreover, the communication mechanism of ISC using complementary metal–oxide–semiconductor (CMOS) sensors is explained in this paper. Specifically, we investigate studies using an optical communication image sensor and the rolling shutter technique for high-speed ISC. Further, we highlight three distinctive transmitting devices in ISC: a LED array, rotating LEDs, and displays, and explain them in terms of structure and signal transmission methods. In particular, we present the parallel transmission of LED arrays and their application in traffic systems and introduce an optical flow-based signal transmission method using rotating LEDs. In addition, two visual transmission techniques in displays-based-ISC using brightness-difference and high-frequency flashing are introduced, respectively. This paper intuitively explains these ISC techniques and reveals ISC's high versatility.

  • MAP estimation using two temporally consecutive data for ultrasonic sensor arrays

    • M. Hattori, A. Tsujii, T. Kasashima, H. Hatano, T. Yamazato
    • IEICE Communications Express, vol.12, no.8, pp.444-449
    • Aug. 2023
    • https://doi.org/10.1587/comex.2023XBL0045
    • This paper proposes MAP estimation using two temporally consecutive data using signals from eight ultrasonic sensors forming a linear array. First, we estimate the distance to the obstacle from the time difference between the eight received signals. Then, assuming that the ranging error follows a Gaussian distribution and that each of the eight ranging values is independent, we can get the existence probability of the obstacle’s position by a pair of two obtained distances. Finally, we estimate the position of the obstacle by multiplying 28 (8C2) existence probabilities obtained. The conventional method estimates the position of an obstacle by the above procedure. However, the estimation accuracy in the angular direction was poor, resulting in the spread of the existence probability in the horizontal direction. In the proposed MAP estimation using two temporally consecutive data, we obtain the existence probability of an obstacle by the procedure shown above, and then use it as a prior probability of the obstacle’s estimated position. Furthermore, we recursively perform the same process to obtain the existence probability of the obstacle. In this way, we improve the accuracy of the estimation of the position of the obstacle by the existence probability. We present the experiment results to show the effectiveness of the proposed method.

  • Experimental Evaluation of Rolling Shutter Based Optical OFDM Using Polarity Separated Transmission

    • H. Shimizu, M. Kinoshita, K. Kamakura, T. Yamazato
    • IEICE Technical Report, CS2023-20, pp.5-8
    • Jul. 2023

  • Communication Performance Evaluation of Dual Camera Receivers in M-PAM Rolling Shutter Based Visible Light Communication

    • A. Takada, T. Saito, M. Kinoshita, K. Kamakura, T. Yamazato
    • IEICE Technical Report, CS2023-21, pp.9-13
    • Jul. 2023

  • 16QAM-OFDM Receiver Using a 1-bit ADC That Multiplies the Carrier Wave in the Digital Domain -Characterization in 2-pass Fading Channels and AWGN Channels-

    • A.Isozaki, T.Yamazato, M.Saito
    • IEICE Technical Report,CS2023-26, pp.30-34
    • Jul. 2023

  • Influence of Walsh-Hadmard codes Multiplied by pseudo-random sequences on Visible Light Communication Using an Event Camera

    • D. Ehara, Z. Tang, M. Kinoshita, T. Yamazato, H. Okada, K. Kamakura, S. Arai, T. Yendo, T. Fujii
    • IEICE Technical Report, CS2023-22, pp.14-17
    • Jul. 2023
    • Visible light communication using an event camera in a receiver moving environment can transmit information by using Walsh-Hadmard codes. However, some parts of the Walsh-Hadmard code have a low spreading ratio and cannot be used for information transmission, which degrades communication performance. In this study, we introduced a spread spectrum communication scheme that multiplies Walsh-Hadmard codes with pseudo-random (PN) sequences and achieved improved communication performance.

  • A Testbed to Integrate Private 5G Networks with Visible Light Communication for Service Area Expansion

    • J. Zheng, T. Yamazato, K. Naito
    • IEEE Symposium on Computers and Communications (ISCC) Workshop on Optical Wireless Communications
    • Jul. 2023
    • https://doi.org/10.1109/ISCC58397.2023.10218188
    • This paper reports an extension of the private 5G service area to the outside of the licensed area by integrating visible light communication (VLC). As VLC is license-free, integrating the VLC function into the private 5G networks gives a more flexible system design. For example, it will be possible to provide services to mobile vehicles and robots working outside the service area of a private 5G network. Alternatively, private 5G networks in different locations can be connected. A challenge is integrating the VLC function into a 5G core network. We successfully designed a testbed and an experiment using open-source 5G projects to evaluate and compare methods to integrate VLC and private 5G, including the simulation of poor network environments. Experimental results demonstrate the availability of integrating private 5G with VLC, which are compared with image-based methods and show better latency performance.

  • [Keynote] Visible light communication (VLC) for cars

    • T. Yamazato
    • IEEE Symposium on Computers and Communications (ISCC) Workshop on Optical Wireless Communications
    • Jul. 2023
    • Visible light communications (VLC) is a promising technology for automotive applications because it offers several advantages over traditional wireless communication technologies using radio waves. For example, VLC is more secure, as it is difficult to intercept VLC signals, and VLC is more reliable, as VLC signals are less susceptible to interference from other signals. As a result of these advantages, VLC is being considered for various automotive applications, such as in-car infotainment and navigation systems, advanced driver assistance systems (ADAS), and autonomous driving. In this talk, he will explain VLC for cars using image sensor communication, one of the VLCs that use a camera as a receiver.

  • Simultaneous Visible Light Communication and Ranging Using High-Speed Stereo Cameras Based on Bicubic Interpolation Considering Multi-Level Pulse-Width Modulation

    • R. Huang, M. Kinoshita, T. Yamazato, H. Okada, K. Kamakura, S. Arai, T. Yendo, T. Fujii
    • IEICE Transactions on Fundamentals, vol.E106-A, no.7, pp.990-997
    • Jul. 2023
    • https://doi.org/10.1587/transfun.2022EAP1078
    • Visible light communication (VLC) and visible light ranging are applicable techniques for intelligent transportation systems (ITS). They use every unique light-emitting diode (LED) on roads for data transmission and range estimation. The simultaneous VLC and ranging can be applied to improve the performance of both. It is necessary to achieve rapid data rate and high-accuracy ranging when transmitting VLC data and estimating the range simultaneously. We use the signal modulation method of pulse-width modulation (PWM) to increase the data rate. However, when using PWM for VLC data transmission, images of the LED transmitters are captured at different luminance levels and are easily saturated, and LED saturation leads to inaccurate range estimation. In this paper, we establish a novel simultaneous visible light communication and ranging system for ITS using PWM. Here, we analyze the LED saturation problems and apply bicubic interpolation to solve the LED saturation problem and thus, improve the communication and ranging performance. Simultaneous communication and ranging are enabled using a stereo camera. Communication is realized using maximal-ratio combining (MRC) while ranging is achieved using phase-only correlation (POC) and sinc function approximation. Furthermore, we measured the performance of our proposed system using a field trial experiment. The results show that error-free performance can be achieved up to a communication distance of 55 m and the range estimation errors are below 0.5 m within 60 m.

  • Reduction of Noise Power by Iterative Short-Term Power Delay Profile Estimation

    • F. Ojika, T. Yamazato, M. Saito, H. Omote, A. Sato, S. Kimura, S. Tanaka, H. Lin
    • IEEE Vehicular Technology Conference (VTC)
    • Jun. 2023
    • https://doi.org/10.1109/VTC2023-Spring57618.2023.10201065
    • This paper proposes a new estimation method of short-term power delay profile to reduce the noise power included in the short-term power delay profile. By reducing the noise, the multipath signal components buried in the noise can be utilized, thereby reducing the transmitted signal power and extending the cell range of a mobile communications. The proposed method iteratively creates the short-term power delay profile while lowering the threshold which distinguishes between signal and noise. The purpose of the threshold is to suppress the noise in each profile and to extract the effective multipath components. Furthermore, the method aligns and averages the phase of each instantaneous delay profile. In this way, only the noise component can be reduced while maintaining a high multipath power. As a result, we successfully reduced the noise power by 15 dB by analyzing the raw data of 200 instantaneous delay profiles measured in the 50 MHz bands at 3.35 GHz. Furthermore, the delay spread increased from 0.66 μs to 1.47 μs.

  • Extended frequency coverage of clutter loss model for high base station environments

    • H. Omote, A. Sato, S. Kimura, S. Tanaka, H. Y. Lin, T. Yamazato
    • IEEE Vehicular Technology Conference (VTC), pp. 1-4
    • Jun. 2023
    • https://doi.org/10.1109/VTC2023-Spring57618.2023.10199433
    • High-Altitude Platform Station (HAPS) has recently been attracting much attention as a new mobile communication platform for ultra-wide coverage areas and disaster-resilient networks since it can provide communication services from an altitude of approximately 20 km via a balloon, an Unmanned Aerial Vehicle (UAV) or other aircraft. In order to design efficient cell configurations for HAPS-based services, we need radio wave propagation models that consider various factors of vegetation, terrain, urban-suburban areas, and building entry loss. This paper focuses on propagation loss at high-elevation angles in urban and suburban areas. Recommendation ITU-R (International Telecommunication Union Radio communication sector) P.2108-1 describes the clutter loss model, which is the propagation loss caused by features such as buildings. The applicable frequency for ITU-R P.2108-1 is above 10 GHz; however, this model has no parameters for urban structure. Therefore, it needs to consider a correction for an urban structure to precisely evaluate clutter loss. We propose a new model that corrects Recommendation ITU-R P.2108 using shielding building heights as the urban structure. Since this new model was created based on measurements from 0.7 GHz to 5.7 GHz, the applicable frequencies are from 0.7 GHz to 5.7 GHz. Therefore, it is necessary to confirm whether the model applies to frequencies above 5.7 GHz. This paper compares the results of new propagation measurements at 29.3 GHz using a helicopter with the predicted results of the proposed model. The results show that the proposed model is applicable above 5.7 GHz.

  • Visible Light Communications

    • T. Yamazato
    • IEICE Tokai Section 2023 1st General Lecture
    • Jun. 2023
    • This lecture introduces Visible Light Communication (VLC) using visible light (visible light). The principle of VLC and the application of VLC using a high-speed image sensor for automotive applications that the speaker is working on will be explained with the latest technological trends.

  • A Review on Image Sensor Communication and Its Applications to Vehicles

    • R. Huang, T. Yamazato
    • Photonics, vol.10, no.6, 617
    • Jun. 2023
    • https://doi.org/10.3390/photonics10060617
    • Image sensor communication (ISC), also known as optical camera communication, is a form of visible light communication that utilizes image sensors rather than a single photodiode, for data reception. ISC offers spatial separation properties and robustness to ambient noise, making it suitable for outdoor applications such as intelligent transportation systems (ITSs). This review analyzes the research trends in ISC, specifically concerning its application in ITSs. Our focus is on various ISC receivers, including rolling shutter cameras, global shutter high-speed cameras, optical communication image sensors, and event cameras. We analyze how each of these receivers is being utilized in ISC vehicular applications. In addition, we highlight the use of ISC in range estimation techniques and the ability to achieve simultaneous communication and range estimation. By examining these topics, we aim to provide a comprehensive overview of the role of ISC technology in ITSs and its potential for future development.

  • Experimental Demonstration of Optical OFDM With Polarity-Separated Transmission in Rolling Shutter Based Visible Light Communication

    • H. Shimizu, K. Kanata, M. Kinoshita, K. Kamakura, S. Arai, T. Yamazato
    • 2023 IEEE International Symposium on Circuits and Systems (ISCAS)
    • May 2023
    • https://doi.org/10.1109/ISCAS46773.2023.10181518
    • Using a rolling shutter camera as a receiver, visible light communication (VLC) can achieve a significantly higher sampling rate than the frame rate because of its sequential exposure mechanism. This study focuses on optical orthogonal frequency division multiplexing (OFDM) in a rolling shutter based VLC for further high-speed data rates. Because an image sensor is employed, conventional optical OFDM, such as DC-biased optical OFDM (DCO-OFDM), must fit in the grayscale range of 0–255 levels. Therefore, DCO-OFDM suffers from poor error performance owing to its high PAPR. To address this problem, we propose a polarity-separated transmission, in which the bipolar OFDM signal is separated into positive and negative parts and then transmitted by two LEDs simultaneously. Polarity-separated transmission is expected to double the grayscale range, i.e. 0–511, and improve error performance because it reconstructs the original bipolar signal by combining the received signals from two LEDs. We experimentally demonstrate and compare the symbol error rate (SER) performance of DCO-OFDM and polarity-separated transmissions. Consequently, polarity-separated transmission improved the SER performance by 10– 2 in the fundamental frequency range of 300–700 Hz when 16-PSK was adopted for subcarrier modulation.

    • A. Tsujii, T. Kasashima, H. Hatano, T. Yamazato
    • IEICE General Conference, B-15-15, p.417
    • Mar. 2023

  • Proposal of a method to improve position estimation in multiple obstacles with ultrasonic arrays

    • M. Hattori, A. Tsujii, T. Kasashima, H. Hatano, T. Yamazato
    • IEICE General Conference, B-5-69, p.314
    • Mar. 2023

  • 2D Encoding for Visible Light Communication Using Dual Orthogonal Rolling Shutter Image Sensors

    • A. Otsuka，Z. Tang，T. Yamazato
    • IEICE General Conference, A-9-4, p.83
    • Mar. 2023

  • Analysis of Event Occurrence under the Moving Situation of the Event-Based Camera

    • K. Furukawa, T. Yamazato, D. Ehara, H. Okada, M. Kinoshita, T. Yendo, S. Arai, K. Kamakura, T. Fujii
    • IEICE General Conference, A-9-3, p.82
    • Mar. 2023

  • Communication Performance Improvement for Rolling Shutter Based Visible Light Communication Using Polarity-Separated Optical OFDM

    • H. Shimizu, K. Kaneda, M. Kinoshta, K. Kamakura, T. Yamazato
    • IEICE General Conference, A-9-5, p.84
    • Mar. 2023

  • Evaluation of the effect of nonlinear amplifiers on the input/output analysis of 1-bit-ADC

    • A.Isozaki, T.Yamazato, M.Saito, H.Hatano
    • IEICE General Conference, B-5-19, p.264
    • Mar. 2023

  • 16QAM/OFDM Signal Reception Experiment Using Noise and 1bit ADC

    • T. Ohtaguro, M. Saito, T. Yamazato
    • IEICE General Conference, B-5-20, p.265
    • Mar. 2023

    • A. Otsuka
    • IEICE Tokai-Section, Graduation Research Presentation, 2-3
    • Mar. 2023

    • IEICE Tokai-Section, Graduation Research Presentation, 2-10
    • Mar. 2023

  • Evaluation of the impact of nonlinear amplifiers on 1-bit ADC receivers that take advantage of noise.

    • A.Isozaki
    • IEICE Tokai-Section, Graduation Research Presentation, 2-8
    • Mar. 2023

  • Experimental study on reception of 16QAM-OFDM signals using wideband noise and 1bit ADC

    • T. Ohtaguro, M. Saito, T. Yamazato
    • IEICE Technical Report, RCS2022-247, pp.1-8
    • Mar. 2023

  • Evaluation of Demodulation Error Performance for Parallel Transmission Image Sensor-based VLC Using M-point Combinatory Modulation

    • T. Sato, K. Kamakura, M. Kinoshita, T. Yamazato
    • IEICE Technical Report, CS2022-79, pp.35-40
    • Mar. 2023

  • [Invited Lecture] Image Sensor Communications These Days

    • T. Yamazato
    • IEICE Technical Report, WBS2022-43, pp. 48-53, Ritsumeikan University, BKC, EPOCH RITSUMEI 21, 3F
    • Dec. 2022
    • Image sensor communication (ISC) is a visible light communication that uses a two-dimensional sensor such as a CMOS image sensor as a receiver. It is basically the same as optical camera communication (OCC) standardized in IEEE 802.15.7. However, we call it ISC in this paper after Mr. Nobuo Iizuka of Casio Computer Co. ISC is characterized by the use of two-dimensional sensors and therefore has spatial separation characteristics. Furthermore, by using LED arrays, spatial parallel transmission is possible. It also has unique characteristics not found in visible light communication that use a PD as a receiver, such as the ability to communicate and ranging (position estimation) simultaneously. This paper describes the outline of image sensor communication these days; visible light communication that uses a high-speed camera, a rolling shutter image sensor, and an event camera as receivers.

  • An Experimental Study on A Noise-aided 1-bit ADC Receiver for 4-PAM

    • J. Zheng, T. Yamazato, M. Saito
    • IEICE Communications Express, vol.11, no.12, pp.817-822
    • Dec. 2022
    • https://doi.org/10.1587/comex.2022COL0032
    • 1-bit analog-to-digital converters (ADCs) have low power consumption and can easily speed up the analog-to-digital conversion and sampling. However, due to their resolution of only 1 bit, the nonlinearity between the input with multiple amplitude levels and output is large. With the method of utilizing noise proposed in previous studies, 1-bit ADCs can be linearized to demodulate signals with multi-level amplitude modulation like pulse amplitude modulation (PAM) and quadrature amplitude modulation (QAM). In this letter, we construct a receiver circuit using a 1-bit ADC, evaluate its performance, and show its availability through demodulation experiments on 4-PAM signals.

  • A. Tsujii, T. Kasashima, Y. Hatano, T. Yamazato

    • Design and Evaluation of the Ultrasonic Sensor Array System for Low-Speed Vehicle
    • IEICE Transactions on Communications, Vol.J105-B, No.12, pp.918-927
    • Dec. 2022
    • https://doi.org/10.14923/transcomj.2022JBP3008
    • We aim to develop a system using ultrasonic sensors for an autonomous low-speed vehicle by solving ultrasonic sensors' detection distance and speed problems. The proposed system uses a fan-shaped beam that arrays the transmitters vertically to the detection plane. Experimental results show that the proposed system can detect and estimate the position of an obstacle driving at 20 km/h at a distance of 15 m. These results show that the proposed system is effective in low-speed driving conditions.

  • Position estimation method using recursive MAP estimation for ultrasonic sensor arrays

    • M. Hattori, A. Tsujii, T. Kasashima, H. Hatano, T. Yamazato
    • International Conference on Emerging Technologies for Communications (ICETC), O5-5, Waseda University
    • Dec. 2022
    • We are working on the measurement of obstacle positions by an ultrasonic sensor array. This paper proposes a recursive position estimation method using signals from eight ultrasonic sensors forming a linear array. First, we estimate the distance to the obstacle from the time difference between the eight received signals. Then, assuming that the ranging error follows a Gaussian distribution and that each of the eight ranging values is independent, we can get the existence probability of the obstacle's position by a pair of two obtained distances. Finally, we estimate the position of the obstacle by multiplying 28 (8C2) existence probabilities obtained. The conventional method estimates the position of an obstacle by the above procedure. However, the estimation accuracy in the angular direction was poor, resulting in the spread of the existence probability in the horizontal direction. In the proposed recursive position estimation, we obtain the existence probability of an obstacle by the procedure shown above, and then use it as the prior probability of the obstacle's estimated position. Furthermore, we recursively perform the same process to obtain the existence probability of the obstacle. In this way, we improve the accuracy of the estimation of the position of the obstacle by the existence probability. We present the experiment results to show the effectiveness of the proposed method.

  • Influence of Walsh-Hadamard Code Sequency in Visible Light Communication Using an Event Camera

    • D. Ehara, Z. Tang, M. Kinoshita, T. Yamazato, H. Okada, K. Kamakura, S. Arai, T. Yendo, T. Fujii
    • International Conference on Emerging Technologies for Communications (ICETC), S9-5, Tokyo
    • Dec. 2022

  • Z. Tang, T. Yamazato, S. Arai

    • [Technology Exhibit] An Implementation of Propeller-type Rotary LED Transmitter for Event Camera-based Image Sensor Communication
    • IEICE Technical Report, SR2022-55, pp.52-57, Fukuoka
    • Nov. 2022

  • Synchronization Method for Time Division Multiplexed Image Sensor Communication with Phase Shift Keying

    • H. Matsunaga, T. Yendo, S. Arai, T. Yamazato
    • Multiple Innovative Kenkyu-kai Association for Wireless Communications (MIKA), Niigata
    • Oct. 2022

  • Considerations of Transmit Waveforms in Image Sensor Communications Based on I/Q Demodulator

    • K. Kai, T. Yendo, S. Arai, T. Yamazato
    • Multiple Innovative Kenkyu-kai Association for Wireless Communications (MIKA), Niigata
    • Oct. 2022

  • For an experimental verification of MIMO-OFDM signals reception using noise and 1-bit ADCs

    • M. Saito, T. Yamazato
    • Multiple Innovative Kenkyu-kai Association for Wireless Communications (MIKA), Niigata
    • Oct. 2022

  • LED Array Acquisition For Road-to-Vehicle Visible Light Communication Using Spatial-Temporal Gradient Values For a High-Speed Vehicle

    • K．Nakamura，T．Yamazato，M．Kinoshita，H．Okada，K．Kamakura，S．Arai，T．Yendo，T．Fujii
    • Multiple Innovative Kenkyu-kai Association for Wireless Communications (MIKA), Niigata，Japan
    • Oct. 2022
    • For the development of Intelligent Transport Systems (ITS), road-to-vehicle Visible Light Communication(VLC) has been expected. In this study, we considered a case where the transmitter position in the captured image of the vehicle's receiver move at high speed. We propose a method to detect the amount of movement of the transmitter in the captured image by analyzing the time-gradient value of the parallel shift of the captured image using image processing. We conducted an experiment in a high-speed driving environment. We detected the movement of the transmitter in the captured image, corrected for the movement, and calculated the spatial-temporal gradient values. In this way, it is possible to acquire the LED array in the captured image. Furthermore, we confirmed that it is possible to demodulate data error-free from the acquired LED array.

  • A Study on Frequency Estimation by using Multiple Ultrasonic Sensors for Burst Signals

    • T. Matsushima, H. Hatano, K. Sanada, K. Mori, A. Tsuji, T. Kasashima, T. Yamazato
    • IEICE Technical Report, ITS2022-6, pp.1-6, Tokyo
    • Sep. 2022

  • A Study on Receiving SFBC-MIMO-OFDM Signals by 1bit ADC and Oversampling

    • M. Saito, T. Yamazato
    • Enginnering Sciences Society Conference of IEICE, A-9-8, p.54, online
    • Sep. 2022

  • Development of Rotary LED Transmitter for High-Speed Image Sensor Communication

    • S. Arai, Z. Tang, T. Yamazato, T. Yendo
    • Enginnering Sciences Society Conference of IEICE, AS-2-1, pp.S-4 - S-5, online
    • Sep. 2022

  • A Study on Communication Performance of PD-Type Visible Light Communication Using Stochastic Resonance

    • H. Fujii, S. Arai, T. Yamazato, H. Hatano, M. Saito
    • Enginnering Sciences Society Conference of IEICE, AS-2-3, pp.S-8 - S-9, online
    • Sep. 2022

  • Roadside LED Array Acquisition For Road-to-Vehicle Visible Light Communication Using Spatial-Temporal Gradient Values

    • K. Nakamura, R. Huang, T. Yamazato, M. Kinoshita, K. Kamakura, S. Arai, T. Yendo, T. Fujii
    • IEICE Communications Express, vol.X11-B, no.8, pp. -
    • Aug. 2022
    • https://doi.org/10.1587/comex.2022TCL0008
    • Most of the previous research on the acquisition of the LED Array transmitter assumes that the onboard receiver approaches the LED transmitter from the car’s front. In this study, we considered a case where the vehicle’s receiver crosses the LED transmitter. This letter modifies the algorithm using spatial-temporal gradient values to detect LED arrays. As a result, we achieved error-free acquisition and successfully communicated up to 9728 [bits] at a vehicle speed of 25 [km/h].

  • Visible Light Communication System Using Rolling Shutter Image Sensor for ITS

    • S. Kamiya, Z. Tang, T. Yamazato,
    • IEEE ICC Workshop on Optical Wireless Communications (OWC), Seoul, South Korea
    • May 2022
    • In this study, we investigate the application of visible light communication (VLC) to intelligent transport systems (ITS) using rolling shutter image sensors as receivers. The use of a global shutter high-speed image sensor as a receiver has been widely examined in ITS-VLC so far. However, this image sensor is impractical for general-purpose applications due to the high cost. This study aims to perform ITS-VLC using the rolling shutter image sensor. The rolling shutter image sensor is widely used in the smartphone camera. By using it as a receiver, ITS-VLC can be used in more opportunities. In this study, we propose a ITSVLC system using rolling shutter image sensor. The proposed system demodulates data from images captured in a moving environment. We evaluate the communication performance by measuring the bit error rate for the ITS-VLC experiments.

  • A Preliminary Investigation For Event Camera-Based Visible Light Communication Using The Propeller-type Rotary LED Transmitter

    • Z. Tang,T. Yamazato, S. Arai
    • IEEE ICC Workshop on Optical Wireless Communications (OWC), Seoul, South Korea
    • May 2022
    • This study investigates a new communication scheme for the event camera-based visible light communication (VLC) using a propeller-type rotary LED transmitter. Conventional camera-based VLC suffers from low data rates and high latency due to the limited camera frame rates. To solve this problem, the event camera has been used as the receiver in VLC. Event cameras detect changes in brightness and asynchronously output these changes as events in microsecond order. The high temporal resolution gives the event camera-based VLC good potential in terms of high speed and low latency. However, when an event camera is used as the VLC receiver, the light of the transmitter needs to be changed constantly. If the transmitter LED is continuously in the same blinking state, the event camera may not output any events and the data could not be recovered until the blinking state changes. To transmit the optical signal for event cameras, we use a propeller-type rotary LED transmitter for the event camera-based VLC. The transmitter rotates the blinking LED in circles and uses the afterimage of LED light to transmit signals. The event camera detects the afterimages and constantly outputs them as a stream of events. We filter the noise events and recover data using signal events. This study verifies the operation for the proposed system through an implementation experiment. As a result, we achieved the communication in the proposed system and provided a basic evaluation in terms of communication speed and quality.

  • Performance Evaluation of RSSI-Based Positioning with Dither method by using Interference Signals

    • S. Horiuchi, H. hatano, K. Sanada, K. Mori, T. Yamazato, S. Arai, M. Saito, K. Tadokoro, H. Tanaka
    • IEICE General Conference, A-13-8, p.104, online
    • Mar. 2022

  • An Experimental Study on A Noise-aided 1-bit ADC Receiver for 4-PAM

    • J. Zheng, T. Yamazato
    • IEICE General Conference, B-8-24, p.148, online
    • Mar. 2022

  • Design of the ultrasonic sensor array system for slow vehicle

    • A. Tsujii, T. Kasashima, H. Hatano, T. Yamazato
    • IEICE General Conference, B-15-16, p.454, online
    • Mar. 2022

  • Reduction of Noise Power by Multi-stage Estimation of Delay Profile in 3.35 GHz Mobile Environment

    • F.Ojika, T.Yamazato, M.Saito, S.Kimura, S.Tanaka, H.Lin, A.Sato, H.Omote
    • IEICE General Conference, B-1-44, p.44, Online
    • Mar. 2022

  • Multi-stage estimation of delay profiles using phase estimation and phase correction in 3.35 GHz multipath environment

    • F. Ojika
    • IEICE Tokai Section Graduation Research Presentation, 5-4, p.67, online
    • Mar. 2022

  • Simplified Alamouti-Type Space-Time Coding for Image Sensor Communication Using Rotary LED Transmitter

    • Z. Tang, S. Arai, T. Yamazato
    • IEEE Photonics Journal, vol. 14, no. 1, pp. 1-7
    • Feb. 2022
    • https://doi.org/10.1109/JPHOT.2021.3137601
    • This study proposes a simplified Alamouti-type space-time coding (STC), improving the performance of image sensor communication (ISC) using a rotary LED transmitter. The rotary LED transmitter was developed to increase the data rate of ISC using afterimages of LED lights. The transmitter simultaneously causes the LEDs to blink and rotates them around a vertical axis. Owing to the movement of the blinking LEDs that occurs within the exposure time of the camera, multiple blinking states are captured as afterimages, thus increasing the amount of information that can be received per image. However, with increasing communication distance, the size of the LED light captured on the image sensor decreases. In this case, it is difficult to distinguish each LED blinking state, leading to a degradation of the demodulation performance. To overcome this problem, the proposed STC encodes adjacent angular afterimages as symbol pairs and transmits these symbol pairs using two symbol times. In addition, we simplified the data decoding process by using normalized LED luminance values. We evaluate the demodulation performance of the proposed method through experiments. Compared with conventional coding methods, the proposed STC requires no channel estimation and significantly improves the demodulation performance.

  • Performance Enhancement of Rolling Shutter Based Visible Light Communication via Selective Reception Using Dual Cameras

  • LED array acquisition in Road to Vehicle Visible Light Communication when receiver crosses transmitter

    • K. Nakamura, T. Yamazato, M. Kinoshita, K. Kamakura, S. Arai, T. Yendo, T. Fujii
    • International Conference on Emerging Technologies for Communications (ICETC), online
    • Dec. 2021
    • https://doi.org/10.34385/proc.68.B3-5
    • Intelligent Transport Systems Visible Light Communication (ITS-VLC) is attracting significant attention as a solution to solve various problems that vehicles have, or for the installation of new systems in the vehicles. In ITS-VLC, the acquisition of the VLC transmitter via light-emitting diodes (LEDs) in the onboard camera’s captured image is the first and essential step when receiving the VLC signal. Most of the previous research on the acquisition of the LEDs assumes that the vehicles approach the LEDs source from the front of the vehicle. However, there are many situations in which vehicles cross the LEDs. In this study, we considered a case in which the vehicle’s receiver crosses the LED transmitter. We modified the acquisition algorithm based on the spatial-temporal gradient utilized in our model in which the transmitter and the receiver cross each other. We found that we can acquire the transmitter by correcting the difference of the ransmitter’s position in the captured image. When validating the specific signal, we achieved 100% acquisition success rate.

  • WWRF46 Panel Session

    • T. Yamazato
    • Wireless World Research Forum Meeting 46, Paris, France
    • Dec. 2021
    • Optical wireless communication has been around since the 1980s. Why has its time come now in 5G/6G? What is the change?

  • Experimental Verification of 4-ary Pulse Amplitude Modulated Signal Receiver with Noise-added One-bit Analogue-to-digital Converter

    • T. Ohtaguro, M. Saito, T. Yamazato
    • International Conference on Materials and Systems for Sustainability (ICMaSS), online
    • Nov. 2021

  • A Cancellation of Inter-LEDs Interference Using Deconvolution In Visible Light Communication between LED Traffic Light and High-speed Image Sensor

  • Experimental Study on Noise Aided 4PAM Receiver with 1bit ADC

    • T. Ohtaguro, M. Saito, T. Yamazato
    • Multiple Innovative Kenkyu-kai Association for Wireless Communications (MIKA), Naha/online
    • Oct. 2021

  • Can Optical Wireless Communication Be a Candidate for Post 5G or 6G?

    • T. Yamazato, S. Arai, M. Kinoshita
    • Communications Society Conference of IEICE, BI-5-5, pp.SS-69 - SS-70, online
    • Sep. 2021

  • Comparison of Distance Performances of Modulation Schemes in Intelligent Transport System Image Sensor Communication

    • T. Yamamoto, T. Yamazato, H, Okada, M. Kinoshita, K. Kamakura, S. Arai, T. Yendo, T. Fujii
    • IEICE Communications Express, vol.10, no.8, pp.498-504
    • Aug. 2021
    • https://doi.org/10.1587/comex.2021ETL0032
    • This study describes intelligent transport image sensor communication (ITS-ISC) systems that use LED arrays as transmitters that imitate traffic lights. Three signal-transmission schemes -luminance modulation, spatial modulation, and combined luminance and spatial modulation- use LED array. However, their suitability for ITS-ISC has not been explored yet. Therefore, we compare the communication performance of these three systems under strong saturation and present the results.

  • [Poster Presentation] A Study on Signal Demodulation Method for LED Visible Light Communication Using Event Based Camera

    • Y. Ohira, T. Yendo, T. Yamazato, S. Arai
    • IEICE Technical Report, WBS2021-25, pp.19-23, online
    • Jul. 2021

  • [Poster Presentation] Multiple Access Method for Image-Sensor-Based Visible Light Communication Using Coded Exposure

    • H. Matsunaga, T. Yendo, S. Arai, T. Yamazato
    • IEICE Technical Report, WBS2021-29, pp.39-44, online
    • Jul. 2021

  • Visible Light Vehicle Ranging using High-speed Stereo Cameras

    • Ruiyi Huang, Takaya Yamazato, Hiraku Okada, Masayuki Kinoshita, Shintaro Arai, Koji Kamakura, Tomohiro Yendo, Toshiaki Fujii
    • IEICE Technical Report, CS2021-22, pp.33-37, Yakushima, Japan
    • Jul. 2021
    • This study presents a performance evaluation of range estimation between vehicles and infrastructures in an ITS-VLC system. In the proposed ITS-VLC system, it is easy to simultaneously conduct communication and ranging using stereo cameras. However, the stereo camera calibration becomes a problem during simultaneous communication and ranging due to vehicle vibration. Using the data from LED transmitters and stereo cameras, it can obtain multiple measurements of distance. The monocular-stereo fusion algorithm is applied to visible light ranging in the proposed scheme using particle swarm optimization. We employed real data from the field trial experiment and achieved a ranging accuracy of 60 +- 1.0 m.

  • Light Sources Combination Modulation for Parallel Transmission Image Sensor-based Visible Light Communication

    • T. Sato, K. Kamakura, M. Kinoshita, T. Yamazato
    • IEICE Technical Report, CS2021-15, pp.9-14, online
    • Jul. 2021

  • Luminance Inversion for LCD and Camera Parallel Transmission Visible Light Communication

    • K. Takahashi, K. Kamakura, M. Kinoshita, T. Yamazato
    • IEICE Technical Report, CS2021-20, pp.25-30, online
    • Jul. 2021

  • Vehicle Distance Measurement based on Visible Light Communication Using Stereo Cameras

    • R. Huang, T. Yamazato, M. Kinoshita, H. Okada, K. Kamakura, S. Arai, T. Yendo, T. Fujii
    • IEEE Intelligent Vehicles Symposium, Nagoya, Japan
    • Jul. 2021
    • https://doi.org/10.1109/IV48863.2021.9575534
    • Visible light communication based intelligent transportation systems (ITS-VLC) show great potential for future urban mobility. This study presents a performance evaluation of range estimation between vehicles and infrastructures in an ITS-VLC system. In the proposed ITS-VLC system, it is easy to simultaneously conduct communication and ranging using stereo cameras. However, the stereo camera calibration becomes a problem during simultaneous communication and ranging due to vehicle vibration. Using the data from LED transmitters and stereo cameras, it can obtain multiple measurements of distance. The monocular-stereo fusion algorithm is applied to visible light ranging in the proposed scheme using particle swarm optimization. We employed real data from the field trial experiment and achieved a ranging accuracy of 60±1.0 m.

  • Error Reduction Method employing Dither Method with Interfering Signals for Distance Estimation Technique

    • S. Horiuchi, H. Hatano, K. Sanada, K. Mori, T. Yamazato, S. Arai, M. Saito, K. Tadokoro, H. Tanaka
    • IEICE Technical Report, ITS2021-1, pp.1-6, online
    • Jul. 2021

  • Method for considering angle error in the position estimation of a moving target using ultrasonic array

    • M. Hattori, A. Tsujii, T. Kasashima, H. Hatano, T.Yamazato
    • IEICE Communications Express, vol.10, no.7, pp.374-379
    • Jul. 2021
    • https://doi.org/10.1587/comex.2021XBL0088
    • In this study, we propose a method for reducing angle error in position estimation of a moving target. The distance between the transmitting array and target is approximated by two receiving sensors close to the transmitting array. This enables more accurate distance measurement between the receiving sensor and the target.

  • Initial Study of Demodulation Method for ITS Visible Light Communication Using Rolling Shutter Image Sensor

    • S. Kamiya, T. Yamazato, H. Okada, T. Fujii, M. Kinoshita, K. Kamakura, S. Arai, T. Yendo
    • IEICE Technical Report, RCS2021-52, pp.139-144, online
    • Jun. 2021
    • This paper focuses on a receiver of image sensor communication for the intelligent transportation system (ITS). The use of a global shutter image sensor as a receiver has been widely examined in ITS Visible Light Communication so far. However, this image sensor has not been widely used due to its high cost. Therefore, in this paper, the initial study of ITS Visible Light Communication using the rolling shutter image sensor is performed. The rolling shutter method is also used in smart phones, and the ITS Visible Light Communication can be used in many occasions by using it as a receiver. In this study, the communication system using the LED array for the transmitter and the rolling shutter method image sensor for the receiver was constructed in the short distance static environment, and the influence that the photographing condition such as the exposure time gives to the communication quality was confirmed by doing the photographing experiment.

  • An experimental study on the demodulation of 4-PAM signals using 1bit ADC with noise

    • T. Ohtaguro, M. Saito, T. Yamazato
    • IEICE Technical Report, RCS2021-51, pp.133-138, online
    • Jun. 2021

  • Circuit Experiment of Photodiode-Type Visible Light Communication Using the Stochastic Resonance Generated by Interfering Light Noise

    • S. Arai, W. Tamura, T. Yamazato, H. Hatano, M. Saito, H. Tanaka, and Y. Tadokoro
    • IEEE International Symposium on Circuits and Systems (ISCAS), pp. 1-5, Daegu, Korea (On-site & Virtual)
    • May 2021
    • https://doi.org/10.1109/ISCAS51556.2021.9401452
    • This study focuses on visible light communication (VLC) using a photodiode as a receiver. Accurate data transmission by this type of VLC is a challenge because the photodiode cannot detect weak light of subthreshold intensity owing to its insufficient light sensitivity. To overcome this problem, we employ a stochastic resonance, which is a nonlinear phenomenon in which the response characteristics of a system improve as its noise intensity increases, for the receiver of this VLC system. We also employ additive light-emitting diode light, which interferes in the photodiode as intentional noise. As an experimental result, the stochastic resonance was achieved by setting the parameters of the noise source appropriately, and we recovered the weak transmitting signal at the receiver.

  • Experimental evaluation of a long distance and high speed ８×８ MIMO optical wireless communication system

    • T. Nakamura, C. Ben Naila, K. Kobayashi, H. Okada, M. Katayama
    • IEICE General Conference, A-9-3, p.88, Online
    • Mar. 2021

  • A channel estimation and demodulation in a noise-aided 1bit ADC receiver

    • Y. Nakashima, T. Yamazato, S. Arai, M. Saito, H. Hatano, H. Tanaka, Y. Tadokoro
    • IEICE General Conference, B-8-27, p.148, online
    • Mar. 2021

  • Determination Method of Data Receiving Range for Alamouti-type Space-Time Coding in Image Sensor Communication Using a Rotary LED Transmitter

    • Z. Tang, S. Arai, T. Yamazato
    • IEICE General Conference, A-9-4, p.89, online
    • Mar. 2021

  • A Method for Improving Accuracy of Position Estimation of Moving Objects Using Ultrasonic Array

    • M. Hattori
    • IEICE Tokai Branch Graduation Research Meeting, 2-2, Online
    • Mar. 2021

  • A study of demodulation method in ITS visible light communication using rolling shutter type image sensor

    • S. Kamiya
    • IEICE Tokai Branch Graduation Research Meeting, 2-7, Online
    • Mar. 2021

  • [Poster Presentation] Experimental Evaluation for Alamouti-type Spatio-temporal Coding in Image Sensor Communication Using a Rotary LED Transmitter

    • Z. Tang, S. Arai, T. Yamazato
    • IEICE Technical Report, WBS2020-44, pp.86-91, online
    • Mar. 2021

  • [Poster Presentation] Performance Enhancement of Rolling Shutter Based Visible Light Communication by Selective Reception Using Dual Camera

    • S. Ibaraki, T. Toguma, S. Yamaguchi, M. Kinoshita, K. Kamakura, T. Yamazato
    • IEICE Technical Report, WBS2020-48, pp.110-114, online
    • Mar. 2021

  • LEO-MIMO transmission techniques using multiple Low Earth Orbit satellites

    • D. Goto, F. Yamashita, T. Yamazato, R. Okema, H. Shibayama, K. Itokawa
    • IEICE Technical Report, SAT2020-36, p.41, online
    • Feb. 2021

  • Optical Wireless Communication: A Candidate 6G Technology?

    • S. Arai, M. Kinoshita, T. Yamazato
    • IEICE Transactions on Fundamentals, vol.E104-A , no.1, pp.227-234
    • Jan. 2021
    • https://doi.org/10.1587/transfun.2020WBI0001
    • We discuss herein whether an optical wireless communication (OWC) system can be a candidate for post 5G or 6G cellular communication. Almost once per decade, cellular mobile communication is transformed by a significant evolution, with each generation developing a distinctive concept or technology. Interestingly, similar trends have occurred in OWC systems based on visible light and light fidelity (Li-Fi). Unfortunately, OWC is currently relegated to a limited role in any 5G scenario, but the debate whether this is unavoidable has yet to be settled. Whether OWC is adopted post 5G or 6G is not the vital issue; rather, the aim should be that OWC coexists with 5G and 6G communication technologies. In working toward this goal, research and development in OWC will continue to extend its benefits and standardize its systems so that it can be widely deployed in the market. For example, given that a standard already exists for a visible-light beacon identifier and Li-Fi, a service using this standard should be developed to satisfy user demand. Toward this end, we propose herein a method for visible-light beacon identification that involves using a rolling shutter to receive visible-light communications with a smartphone camera. In addition, we introduce a rotary LED transmitter for image-sensor communication.

  • Deep Learning Detection for superimposed control signal in LEO-MIMO

    • R. Okema, D. Goto, T. Yamazato, F. Yamashita, H. Shibayama
    • IEEE Global Communications Conference (GLOBECOM), Taipei, Taiwan
    • Dec. 2020
    • https://doi.org/10.1109/GLOBECOM42002.2020.9348012
    • Multiple-input multiple-output (MIMO) communication systems using multiple low-Earth orbital (LEO) satellites achieve higher capacity than conventional LEO systems. However, in previous research, control signals are allocated to a different frequency band for each satellite signal in order to estimate its Doppler frequency. The increase in the number of satellites reduces unoccupied MIMO signal bandwidth and hence the overall capacity. This study aimed to prevent such capacity reduction by introducing the superimposition of control signals. Such control signals occupy a frequency bandwidth of the equivalent of only one control signal; therefore, they can prevent the reduction of the overall capacity. The main challenge is estimating the satellites' Doppler frequencies from the waveforms of Doppler-affected superimposed control signals. To overcome this challenge, we propose the adoption of a deep learning technique.

  • Performance Evaluation of Range Estimation for Image Sensor Communication Using Phase-only Correlation

    • R. Huang, M. Kinoshita, T. Yamazato, H. Okada, K. Kamakura, S. Arai, T. Yendo, T. Fujii
    • IEEE GLOBECOM Workshop on Optical Wireless Communications (OWC), Taipei, Taiwan
    • Dec. 2020
    • https://doi.org/10.1109/GCWkshps50303.2020.9367540
    • Stereo cameras, serving as the “eyes” of automotive vehicles, can determine the distance between objects and the vehicles. In this paper, stereo cameras are introduced into image-sensor-based visible light communication (IS-VLC) systems, in which the combination of VLC and stereo ranging shows promising prospects for intelligent transport systems. However, one of the problems of IS-VLC stereo ranging is that the luminance level of LEDs in the captured images would greatly affect disparity estimation, which would result in inaccurate range estimation. This paper gives the performance evaluation of this problem using phase-only correlation algorithm with luminance election. The proposed scheme using stereo cameras exhibited a ranging accuracy of 60±0.15 m in static conditions.

  • A Comparison of Distance Performances of Modulation Schemes in an ITS Image Sensor Communication

    • T. Yamamoto, T. Yamazato, H, Okada, M. Kinoshita, K. Kamakura, S. Arai, T. Yendo, T. Fujii
    • International Conference on Emerging Technologies for Communications (ICETC), B4-1, online
    • Dec. 2020
    • https://doi.org/10.34385/proc.63.B4-1
    • Image sensor communication uses an LED light as a transmitter and an image sensor as a receiver. LED light sources are widely used in traffic lights and car tail lights. In addition, since image sensors are used for driving assistance and drive recorder applications, image sensor communication can be used in parallel with other intelligent transport systems(ITS) applications. This study describes an ITS image sensor communication (ITS-ISC) system, which uses an LED array as a transmitter to imitate traffic lights. There are three schemes of signal transmission using an LED array: luminance modulation, spatial modulation, and both luminance and spatial modulation. However, which of these schemes is the most suitable for ITS-ISC is not yet considered. In this study, we compare the communication performance of these three modulation schemes, present-ing the configuration of an LED array capture simulator and performance comparison results.

  • Method for considering angle error in the position estimation of a moving target using ultrasonic array

    • M.Hattori, A. Tsujii, T. Kasashima, H. Hatano, T. Yamazato
    • International Conference on Emerging Technologies for Communications (ICETC), I2-4, Online
    • Dec. 2020
    • https://doi.org/10.34385/proc.63.I2-4
    • In this study, a method for reducing the angle error in the position estimation of a target is proposed. In this method, the distance between the transmitting array and the target approximates two receiving sensors close to the transmitting array. This enables the attainment of a more accurate distance between the receiving sensor and the target.

  • Preliminary Circuit Experiment of Photodiode-Type Visible Light Communication by Stochastic Resonance Using Interfering Light as Intentional Noise

    • S. Arai, T. Yamazato, H. Hatano, M. Saito, H. Tanaka, Y. Tadokoro
    • International Symposium on Nonlinear Theory and its Application (NOLTA), pp.97-100, online
    • Nov. 2020

  • RSSI-based Distance Estimation Enhanced by Interference Signals

    • S. Horiuchi, H. Hatano, K. Sanada, K. Mori, T. Yamazato, A. Shintaro, M. Saito, Y. Tadokoro, H. Tanaka
    • International Symposium on Nonlinear Theory and its Application (NOLTA), pp.101-104, online
    • Nov. 2020

  • A Study on Required FFT Sizes for Demodulation of OFDM Signals by Intentionally Added Noise and 1bit ADC

    • M. Saito, T. Ohtaguro, Y. Nakashima, T. Yamazato, S. Arai, H. Hatano, H. Tanaka, Y. Tadokoro
    • International Symposium on Nonlinear Theory and its Application (NOLTA), pp.105-108, online
    • Nov. 2020

  • Experimental Performance Evaluation of Image Sensor Based Visible Light Communication Using a DMD Projector in a Driving Condition

  • Image sensor communications for automotive intelligence

    • T. Yamazato
    • International Conference on Optoelectronic and Microelectronic Technology and Application 2020, Nanjing, China
    • Oct. 2020
    • Almost once per decade, cellular mobile communication is transformed by a significant evolution, with each generation developing a distinctive concept or technology. Interestingly, similar trends have occurred in visible light communication systems and vehicle automation. In this talk, the presenter looks back to the brief history of vehicle automation and related communication technologies. He then introduces visible light communication and its application for automotive intelligence. Some of his research results on VLC for automotive applications will also be provided.

  • Doppler frequency estimation of Superimposed Control Signal of multiple satellites by Deep Learning in LEO-MIMO

    • R. Okema, D. Goto, T. Yamazato, F. Yamashita, K. Itokawa
    • IEICE Technical Report, SAT2020-19, pp.47-52, online
    • Aug. 2020
    • This paper focuses on satellite MIMO (Multi-Input Multi-Output) technology to increase the capacity of Low Earth Orbit (LEO) satellite communications. In previous research, LEO-MIMO communication requires control signals to estimate the Doppler frequencies of each satellite. The control signal is allocated a different frequency band to avoid inter-carrier interference with other signals. However, as the number of communication LEO satellites increases, the bandwidth of the control signal becomes wider and the bandwidth for the MIMO signal becomes narrower. In other words, the problem is that the capacity of LEO-MIMO decreases with the increase in the number of communication LEO satellites. Therefore, this study attempts to suppress the communication capacity reduction by superimposing control signals. This technique can improve the bandwidth of the control signal is constant regardless of the number of satellites, and suppress capacity reduction regardless the number of satellites. On the other hands, superimposed control signals technique degrades the Doppler frequency estimation accuracy due to inter-carrier interference. To tackle of the problem, we propose the novel Doppler frequency estimation using Deep learning techniques. This paper deal with Doppler shift estimation for control signals with three or more superimposed waveforms and unlearned waveforms. In order to improve the estimation accuracy, we employed convolutional neural networks in addition to deep neural networks and compared their performance.

  • Sequential Maximum Likelihood Decoding Incorporating Reliability Determination for Image Sensor Communication

  • Current Status and Issues of Visible Light Communications

    • T. Yamazato
    • The 2nd Geospatial Information Seminar in FY2020 co-sponsored by Hokushinetsu Branch of the Japanese Society of Photogrammetry
    • Jul. 2020

  • An Analysis of a Noise-aided One-bit Analog-to-Digital Converter for a Multi-Antenna Receiver

    • Y. Nakashima, T. Yamazato, S. Arai, M. Saito, H. Hatano, H. Tanaka, Y. Tadokoro
    • IEICE Technical Report, CS2020-20, pp.25-26
    • Jul. 2020

  • Visible light beacon

    • T. Yamazato
    • Signal Processing in Photonic Communications (SPPCom), The 2020 OSA Advanced Photonics Congress, 2020., Online
    • Jul. 2020
    • Since the LED (light-emitting diode) is a semiconductor device, high-speed modulation is possible. The communication for transmitting information by blinking (modulating) the LED at such a high speed that the human eye cannot recognize is called visible light communication (VLC) [1]. The visible light beacon is an exciting application of VLC that transmits the short ID. In this article, the trend of the visible light beacon, a part of VLC is described.

  • Nonlinear Transform for Parallel Transmission for Image-Sensor-based Visible Light Communication

  • A Comparison between a Noise-Aided 1bit ADC Receiver and a Linear Receiver

    • Y. Nakashima, T. Yamazato, S. Arai, M. Saito, H. Hatano, H. Tanaka, Y. Tadokoro
    • IEICE General Conference, B-8-38, p.185, Hiroshima
    • Mar. 2020

  • Distance and Velocity Measurement of Approaching Target Via 45 kHz Ultrasonic Sensor Array

    • Y.H.J Lai, A. Tsujii, T. Kasashima, T. Yamazato, H. Hatano
    • IEICE General Conference, A-4-2, p.35, Hiroshima, Japan
    • Mar. 2020
    • Ultrasonic sensors are an attractive option for target detection purposes due to their low cost, functionality in all light and weather conditions and easy implementation. Multiple ultrasonic sensors arranged in an array were shown to strengthen ultrasonic waves and increase detection range at static conditions in an indoor environment. In this article, we report a conducted experiment on a moving target in an outdoor environment to analyze its performance and will aim to use the obtained data for localization in future works.

  • Range Estimation of LED Transmitter Using Phase-Only Correlation for ITS-VLC System via High-speed Stereo Cameras

    • R. Huang, M. Kinoshita, T. Yamazato, H. Okada, K. Kamakura, S. Arai, T. Yendo, T. Fujii
    • IEICE General Conference, A-9-21, p.100, Hiroshima, Japan
    • Mar. 2020

  • A Study on FFT Sizes of Demodulating OFDM Signals by Intentionally Added Noise and 1bit ADC

    • M. Saito, Y. Nakashima, T. Yamazato, S. Arai, H. Hatano, H. Tanaka, Y. Tadokoro
    • IEICE General Conference, A-9-11, p.90, Hiroshima
    • Mar. 2020

  • A Study on Photo-Diode-Type Visible Light Communication by Stochastic Resonance Using Interfering Light as Noise

    • M. Takaki, S. Arai, T. Yamazato, H. Hatano, M. Saito, H. Tanaka, Y. Tadokoro
    • IEICE General Conference, A-9-23, p.102, Hiroshima
    • Mar. 2020

  • A Study on Applying Dither Method with Interference to RSSI Based Distance Estimation

    • S. Horiuchi, H. Hatano, K. Sanada, K. Mori, T. Yamazato, A. Shintaro, M. Saito, Y. Tadokoro, H. Tanaka
    • IEICE General Conference, A-14-1, p.118, Hiroshima
    • Mar. 2020

  • Doppler Frequency Estimation of Two Superimposed LEO-MIMO’s Control Signals by Convolutional neural networks

    • R. Okema, D. Goto, T. Yamazato, F. Yamashita, H. Shibayama
    • IEICE General Conference, B-3-7, p.199, Hiroshima, Japan
    • Mar. 2020

  • Visible Light Communications for Automotive Intelligence

    • T. Yamazato
    • The Optical Networking and Communication Conference & Exhibition (OFC2020), San Diego, USA
    • Mar. 2020

  • BER Measurement for Transmission Pattern Design of ITS Image Sensor Communication Using DMD Projector

    • T. Arisue, T. Yamazato, H, Okada, M. Kinoshita, S. Arai, T. Yendo, K. Kamakura, T. Fujii
    • IEEE Consumer Communications and Networking Conference (CCNC), Las Vegas, US
    • Jan. 2020
    • https://doi.org/10.1109/CCNC46108.2020.9045147
    • This paper presents an image sensor communication (ISC) using a digital micromirror device (DMD) projector as a transmitter. In particular, we focus on ISC for intelligent transport systems (ITSs) because DMD projectors are expected to be used in road traffic, such as vehicle headlights, street lights, and traffic signs. The DMD projector controls light patterns by switching tilt of micromirrors at high speed. Compared to the conventional LED array transmitter, DMD projector can design and alter the shape of the light pattern and data rate of transmission more easily. In the proposed system, the data rate can be easily increased by increasing the number of multiplexes. However, as the number of multiplexes is increased, the number of received pixels on the image sensor is decreased, and thus the performance of symbol detection deteriorates. Therefore, the purpose of this paper is to examine the relation between the num- ber of received pixels per cell and communication performance for transmission pattern design. Hence, we experimentally clarify this relation using our prototype system via a DMD projector and a high-speed camera.

  • Range Estimation for Traffic Light based on Visible Light Communication using Stereo Cameras

    • R. Huang, T. Yamazato, H. Okada, M. Kinoshita, K. Kamakura, S. Arai, T. Yendo, T. Fujii
    • Workshop on Optical Wireless Communication for Smart City (OWC2), pp.49-52, Toyota, Japan
    • Dec. 2019
    • The recognition of traffic light is important in self-driving cars nowadays. In this paper, we proposed a ranging method for traffic light on the road based on stereo ranging. By introducing the idea of visible light communication, it is simple to extract the traffic light from a complicated background. Experimental result shows that it can work well for the real traffic light.

  • Nonlinearity Mitigation of Received Luminance Using Inverse Pattern of the LED array in Image Sensor Communication

    • T. Yamamoto, T. Yamazato, H, Okada, M. Kinoshita, K. Kamakura, S. Arai, T. Yendo, T. Fujii
    • Workshop on Optical Wireless Communication for Smart City (OWC2), pp.53-56, Toyota, Japan
    • Dec. 2019
    • In this research, we describe visible light communication (VLC) using an LED array as a transmitter and a high-speed image sensor as a receiver. Such VLC is called an image sensor communication (ISC), and it assigns a symbol to the multilevel brightness of the LED. An issue is a nonlinearity caused by both LED and image sensors. In order to increase the data rate, it is necessary to handle this nonlinearity. In this paper, we first show the nonlinearity by experimental results. We then show that we can ease such nonlinearity by an introduction of an inverse pattern used to track the LED array. We show by the experimental result that the inverse pattern can mitigate the nonlinearity and thus improve the data rate.

  • Three-Frame Demodulation for Non-Synchronous Square Wave Quadrature Amplitude Modulation

    • K. Yamamura, K. Kamakura, M. Kinoshita, T. Yamazato
    • Workshop on Optical Wireless Communication for Smart City (OWC2), pp.33-36, Toyota, Japan
    • Dec. 2019

  • An Experiment of Image Sensor Communication Using Digital Micromirror Device Projector as a Vehicle Headlight

    • T. Arisue, T. Yamazato, H, Okada, M. Kinoshita, S. Arai, T. Yendo, K. Kamakura, T. Fujii
    • Workshop on Optical Wireless Communication for Smart City (OWC2), pp.1-4, Toyota, Japan
    • Dec. 2019
    • This paper presents an image sensor communication (ISC) using a digital micromirror device (DMD) projector as a transmitter. In particular, we focus on ISC for intelligent transport systems (ITSs). DMD projectors are expected to use in road traffic, such as vehicle headlights, street lights, and projectors of traffic signs. Our proposed system projects data patterns on a road or signage for transmission in addition to primary lighting/display function. In this paper, we report a basic experiment of the proposed system using the DMD projector as a vehicle headlight in driving conditions.

  • Nonlinear Companding Scheme for Parallel Transmission for Image-Sensor-Based Visible Light Communication

    • K. Takahashi, K. Kamakura, M. Kinoshita, T. Yamazato
    • Workshop on Optical Wireless Communication for Smart City (OWC2), pp.9-12, Toyota, Japan
    • Dec. 2019

  • Performance Evaluation of Precoded Pulse Width Modulation for Visible Light Communicatino Using Image Sensor

  • Calibration method for an integrated ranging and visible light communication system using stereo cameras

    • R. Huang, M. Kinoshita, T. Yamazato, H. Okada, T. Fujii, S. Arai, T. Yendo, K. Kamakura
    • International Conference on Materials and Systems for Sustainability (ICMaSS), Nagoya, Japan
    • Nov. 2019
    • Camera calibration is an essential part of stereo camera system. By using stereo cameras, it enables simultaneous range estimation and visible light communication (VLC) data transmission, and we can use them for VLC-based intelligent transport system (ITS-VLC). The ranging accuracy greatly relies on the accurate camera calibration. As the range increases, the estimation error of calibration parameters will make the ranging result worse. In this paper, we introduce stereo cameras into ITS-VLC system, and discuss the calibration method for range estimation. Considering the effect of camera calibration, the proposed scheme using stereo cameras confirms a great ranging accuracy in a static condition, and the estimation errors of calibration parameters are given within 0.05%.

  • Analysis of Data Collected by the 700 MHz Band Intelligent Transport Systems for Reducing Ambulance Transportation Time

    • T. Mitani, T. Yamazato, K. Naito, Y. Mori
    • The 8th IEEE International Conference on Conected Vehicles and Expo (ICCVE), Gratz, Austlia
    • Nov. 2019
    • https://doi.org/10.1109/ICCVE45908.2019.8965232
    • Emergency services around the world face the problem of increasing patient transportation times. The operation of emergency vehicles is fundamentally different from that of general vehicles ; hence, algorithms recommending optimal routes in a conventional way are not always applicable to emergency vehicles. In this study, we analyzed data of inter-vehicle and road-vehicle communication collected at 700 MHz band intelligent transport systems and demonstrated that the overall travel time of emergency vehicles can be reduced by decreasing their travel time at intersections.

  • Basic Experiment on ITS Visible Light Communication Transmitter Using DMD Projector Usable as Street Lights

    • T. Arisue, T. Yamazato, H, Okada, M. Kinoshita, S. Arai, T. Yendo, K. Kamakura, T. Fujii
    • Enginnering Sciences Society Conference of IEICE, A-9-1, p.64, Osaka, Japan
    • Sep. 2019

  • Noise-aided linearization of a receiver with one-bit analog-to-digital converter

    • Y. Nakashima, T. Yamazato, S. Arai, H. Tanaka, K. Tadokoro
    • Communications Society Conference of IEICE,B-8-23,p97
    • Sep. 2019

  • An analysis of a noise-aided linearization range on a receiver with one-bit analog-to-digital converter

    • Y. Nakashima, T. Yamazato, S. Arai, H. Tanaka, K. Tadokoro
    • IEICE Technical Report, RCS2019-149, pp.19-24
    • Aug. 2019
    • In this study, we assume the receiver with analog-to-digital converter(s) that has only one-bit resolution(1bit-ADC). The advantages of 1bit ADC are low power consumption, potential to realize high sampling rate, the simple structure and the small circuit area. Also, 1bit ADC does not need the gain control for the ADC dynamic range. However, the 1bit ADC has a nonlinearity and that cause the large amplitude distortion. Therefore, we focus on the noise-aided linearization known as stochastic resonance. the output of the 1bit ADC is stochastically linearized by noise and the amplitude distortion is restrained. In this paper, we shows an analysis for the stochastic input-output property of the 1bit ADC. The result shows the linearized range is decided from the distribution and the variance of the input noise.

  • Noise-aided demodulation of direct spread-code division multiple access signals with a 1bit analog-to-digital converter

  • Capacity Evaluation of Low-earth Orbit Satellite-MIMO Systems

    • D. GOTO, H. SHIBAYAMA, F. YAMASHITA, R. OKEMA, T. YAMAZATO
    • IEICE Transactions on Communications, Vol. J102B, No.8, pp.614-623
    • Aug. 2019
    • https://doi.org/10.14923/transcomj.2018WFP0016
    • In this paper, we evaluate the transmission capacity of LEO-MIMO systems by low-earth orbit (LEO) satellite communication using Muti-Input/Multi-Output (MIMO). In LEO systems, Doppler shift is always caused by fluctuation of satellite orbit may affect the performance of LEO-MIMO. In this system, guard bands and control carriers are used for synchronization and channel estimation for MIMO demodulation. Simulation results show that MIMO transmission with five satellites at the center frequency of 12 GHz achieves the highest transmission capacity by approximately 2.7bps/Hz. And the transmission capacity with three satellites at 20GHz is maximized, approximately 1.6 bps/Hz.

  • High performance demodulation method with less complexity for image-sensor communication

    • Y. Ohira, T. Yendo, S. Arai, and T. Yamazato
    • Optics Express, vol.27, no.15, pp.21565-21578
    • Jul. 2019
    • https://doi.org/10.1364/OE.27.021565
    • This study presents a novel method for signal demodulation for use with visible light communication systems composed of an image sensor as a receiver and light-emitting diode (LED) transmitters. Demodulation is a central challenge in the design of such a system, as the image captured at the image-sensor receiver is deteriorated by distance and noise. We propose a demodulation method that offers performance approaching that of the maximum-likelihood decoding (MLD) method and with significantly less complexity. The proposed method first applies the minimum mean square error (MMSE) method to each LED into reliable LEDs and unreliable LEDs according to the MMSE results and it demodulates the LEDs judged as reliable directly. Then, the MLD method is applied only to the unreliable LEDs to demodulate their signals. The results of numerical simulations and lab experiments are presented to evaluate the performance of this modified demodulation method.

  • [Invited Talk] Visible Light Communication and Ranging Using High-speed Stereo Cameras

    • M. Kinoshita, K. Kamakura, T. Yamazato
    • 2019 IEEE SUMMER TOPICALS MEETING SERIES, Photonics in Artificial Intelligence (Photonics-AI), Ft. Lauderdale, FL
    • Jul. 2019
    • https://doi.org/10.1109/PHOSST.2019.8794881
    • We will introduce an integrated system of visible light communication (VLC) and ranging using high-speed stereo imaging. The system simultaneously decodes a VLC signal while its source tracking portion outputs ranging information. These image sensors are mainly used to provide visual information to the driver.

  • For the Applications of Stochastic Resonance in the Telecommunications

    • Y. Tadokoro, T. Yamazato, H. Tanaka, S. Arai, Y. Nakashima, S. Hiraoka
    • IEICE Transactions on Communications, vol.J102-B, no.6, pp.445-458
    • Jun. 2019
    • https://doi.org/10.14923/transcomj.2018JBR0001
    • A nonlinear phenomenon of Stochastic resonance~(SR) was found in 1981 to describe the 100,000-year cycle of the ice age on Earth. In this framework, noise has an important role in the system behavior; the system response, especially response to weak signal, is strongly enhanced by exploiting noise. This unique feature has attracted interests in diverse fields, including biological systems, electron devices, and signal processing methods. For developing the future applications with SR in the telecommunication fields, this survey article provides the fundamental aspects and recent progress of SR. This article is divided into halves. The first part of the paper provides a review of the history, investigations, and fundamental theory of SR. The second part introduces practical applications of SR. To be more specific, the part describes an SR receiver for sub-threshold signal detection, its error rate analysis, and an example of implementation. A capacity analysis is also discussed using the derived error rate equation. Further, the part introduces multi-signal demodulation using one bit AD converter and hypothesis testing.

  • Detection of Two Superimposed LEO-MIMO’s Control Signals by Deep Learning

    • R. Okema, D. GOoto, T. Yamazato, F. Yamashita, D. Shibayama
    • IEICE Technical Report, SAT2019-3, pp.13-17, Nagoya,Japan
    • May 2019
    • A MIMO communication system using multiple low-earth orbital (LEO) satellites achieves higher capacity than a conventional LEO system.However, as it requires to allocate different frequency bandwidth for each satellite signal to estimate its Doppler-shift, increase in the number of satellites decreases occupied MIMO signal bandwidth, and hence lower the capacity.This paper tries to prevent such capacity reduction by an introduction of superimposition of the control signals. The superposition of the control signals occupy only a frequency bandwidth of one control signal, thus can prevent the capacity reduction. A challenge is how to estimate each satellites’ Doppler frequency from the superimposed control signal. In this paper, we propose to adopt deep learning to estimate each satellites’ Doppler frequency from the waveform of Doppler affected control signals. In particular, we consider the case of two superimposed control signal and show the result in terms of average frequency estimation error.

  • Maximum Likelihood Decoding Based on Pseudo-Captured Image Templates for Image Sensor Communication

    • S. Arai, H. Matsushita, Y. Ohira, T. Yendo, D. He, T. Yamazato
    • NOLTA, IEICE, vol.10, no.2, pp.173-189
    • Apr. 2019
    • https://doi.org/10.1587/nolta.10.173
    • This paper focuses on an image sensor communication system that uses an LED as the transmitter and a high-speed image sensor (camera) as the receiver. Communication in this scheme depends on the quality of images transmitted from the LED to the sensor. If the image becomes unfocused on the way to the receiver, the LED luminance that make up the signal cannot be detected, so the receiver cannot demodulate the signal data. To overcome this problem, this study proposes a novel demodulation scheme to recover data from a degraded image, based on a maximum likelihood decoding (MLD) algorithm. The proposed method creates template images that imitate all possible blinking patterns produced by the LED transmitter, and then calculates the Euclidean distances between pixels in the captured image and the pseudo images for all possible blinking patterns. Finally, the algorithm chooses the image template with the smallest Euclidian distance from the received signal as the recovered data. Though an exhaustive set of image templates must be prepared for the proposed MLD, the number of templates depends on the number of LEDs on the transmitter. Thus, the computational complexity of this method increases as the number of transmitter LEDs increases. To reduce the computational complexity of the proposed MLD algorithm, the binary differential evolution (BDE) algorithm is used, which is a swarm intelligence technique. Computer simulations are used to evaluate the BDE algorithm's usefulness for reducing computational complexity and improving the BER of the communication system.

  • An LED Transmitter Detection using Linear SVM and CNN for ITS Image Sensor Communication

    • M. Hori, M. Kinoshita, T. Yamazato, H. Okada, T. Fujii, K. Kamakura, T. Yendo, S. Arai
    • 3rd International Conference and Exhibition on Visible Light Communications (ICELVC), Seoul, Korea
    • Mar. 2019
    • Image sensor communication (ISC) is a type of visible light communications (VLC) that has high affinity with the field of intelligent transport systems (ITSs). In an ISC, accurate detection of the transmitter from a captured image is critical, because the receiver uses pixels that sense VLC signal for data reception. The purpose of this study is to reduce the false-positive and the false-negative probabilities of the transmitter. To achieve this goal, we propose a novel LED transmitter detection method composed of two stages: the candidate extraction stage by a linear support vector machine (SVM) and the classification stage by a convolutional neural network (CNN). Then, we show that the proposed method is robust to vehicle vibration and other noises such as non-transmitter LED compared to the conventional method.

  • Employing the Arrayed Network Improves the Error Rate in the Receiver Exploiting Stochastic Resonance

    • K. Tadokoro, H. Tanaka, Y. Nakashima, T. Yamazato, S. Arai
    • IEICE General Conference, N-1-28, p.276, Tokyo
    • Mar. 2019

  • Development of 45kHz ultrasonic sensor array system and experimental evaluation of obstacle position estimation method

    • T．Nishio，A．Tsujii，T，Kasashima，H．Hatano，T．Yamazato
    • Enginnering Sciences Society Conference of IEICE
    • Mar. 2019

  • A demodulation for DS-CDMA signals with different intensities by 1bit analog-to-digital converter and noise

    • Y. Nakashima, T. Yamazato, S. Arai, H. Tanaka, Y. Tadokoro
    • IEICE General Conference, B-8-13, p.145, Tokyo
    • Mar. 2019

  • Doppler Frequency Estimation of Two Superimposed LEO-MIMO's Control Signals by Deep Learning

    • R.Okema,D.Goto,T.Yamazato,H.Shibayama,H.Yamashita
    • IEICE General Conference
    • Mar. 2019

  • Large Capacity MIMO Techniques Using Multiple Low Earth Orbit (LEO) Satellites

    • D. Goto, H. Shibayama, F. Yamashita, R. Okema, T. Yamazato
    • IEICE General Conference, B-3-20, p.210, Tokyo
    • Mar. 2019

  • Experimental Evaluation of Visible Light Communication Performance Applying Pixel Selection / Maximal Ratio Combining Reception by High-speed Stereo Camera

    • M. Kinoshita, T. Yamazato, H, Okada, T. Fujii, S. Arai, T. Yendo, K. Kamakura
    • IEICE Transactions on Communications, vol.J102-B,no.2,pp.90-97
    • Feb. 2019
    • https://doi.org/10.14923/transcomj.2018GTP0003
    • In-vehicle cameras can be used as receivers for visible light communication in addition to their primary functions: for viewing assistance and object recognition. Because image sensor spatially separates transmission signals by image processing, it is attractive device for outdoor mobile environment in which number of noise sources (e.g. sunlight or street light) are existed, especially the field of intelligent transport systems. Most studies with this design perform tests via a single high-speed camera that is used as the receiver, but this study employs a receiver that uses a high-speed stereo camera. In the high-speed stereo camera, it is possible not only to estimate distance but also to improve the visible light communication performance by effectively utilizing the stereo image. In this paper, we propose pixel selection and maximum ratio combining as a reception method of high-speed stereo camera to improve visible light communication performance. Communication performance is then evaluated comparing to the conventional single-camera reception by experimental tests conducted under static and driving conditions.

  • Academic Databases and Search Tools

    • T. Yamazato, F. Nishino, N. Kato, Y. Chimura
    • The Journal of the Institute of Television Engineers of Japan, vol.73, no.1, pp.96-99
    • Jan. 2019

  • Enhancing a BPSK receiver by employing a practical parallel network with Stochastic resonance

    • Y. Tadokoro, H. Tanaka, Y. Nakashima, T. Yamazato, S. Arai
    • NOLTA, IEICE, vol. E10-N, no. 1, pp. 106-114, 2019.
    • Jan. 2019
    • https://doi.org/10.1587/nolta.10.106
    • Stochastic resonance (SR) is a noise-enhancement phenomenon that enables the detection of sub-threshold signals by adding noise and using nonlinear systems. This paper explores the applicability of SR in a BPSK receiver with sub-threshold signals. Although received signals are amplified as a result of the nonlinear behavior of the receiver, they are somewhat distorted. This results in the lower performance of SR receivers in comparison with linear receivers. Employing a parallel network of SR systems is expected to solve this problem. The present theoretical analysis demonstrates that in a certain noise intensity range, the output of the network can fully describe an input sub-threshold signal, and hence, the performance close to that of the linear receivers can be obtained. The effectiveness of the SR receiver was also demonstrated through a numerical example of the bit error rate (BER). However, achieving good BER performance requires an infinite number of arrayed SR systems, which is not realistic in practical systems. A design framework for an SR network with a finite number of elements and an appropriate noise intensity that can realize BER performance close to that in linear systems is also provided.

  • A Comparison of Reception Methods for Visible Light Communication Using High-speed Stereo Cameras

    • M. Kinoshita, T. Yamazato, H, Okada, T. Fujii, S. Arai, T. Yendo, K. Kamakura
    • IEEE Global Communications Conference (GLOBECOM), Abu Dhabi, UAE
    • Dec. 2018
    • https://doi.org/10.1109/GLOCOM.2018.8647953
    • In-vehicle cameras can be used as receivers for visible light communication in addition to their primary functions: for viewing assistance and object recognition. Most studies with this design perform tests via a single high-speed camera that is used as the receiver, but this study employs a receiver that uses a high-speed stereo camera. The reception method developed in this paper effectively utilizes left and right stereo images to improve communication performance. Although the selective diversity reception method proposed in previous work improved communication performance, it cannot deal with cases wherein both the left and right cameras introduce errors. To further improve the communication performance of this system, maximal ratio combining (MRC) diversity is applied to the high-speed stereo camera in this study. Communication performance is then evaluated comparing to the selective diversity reception and conventional single-camera reception by experimental tests conducted under static and driving conditions.

  • LEO-MIMO Satellite Systems for High Capacity Transmission

  • Performance Evaluation of Precoded Pulse Width Modulation for Image Sensor Communication

    • S. Kamegawa, M. Kinoshita, T. Yamazato, H. Okada, T. Fujii, K. Kamakura, T. Yendo, S. Arai
    • IEEE GLOBECOM Workshop on Optical Wireless Communications, Abu Dhabi, UAE
    • Dec. 2018
    • https://doi.org/10.1109/GLOCOMW.2018.8644347
    • Light-emitting diodes (LEDs) can add visible light communication (VLC) by high-speed blinking to their original lighting function. VLC using image sensors as receivers is referred to as image sensor communication (ISC). ISC eliminates noise and interference and enables multiple and simultaneous communication; hence it is suitable for outdoor mobile environments such as intelligent transport systems (ITSs). On the other hand, since the communication rate depends on the frame rate, it is difficult to increase. Therefore, the purpose of this study is to increase the communication rate by multilevel pulse width modulation (PWM). When the modulation level is increased, demodulation becomes difficult due to the bit per pixel (bpp) limitation of the image sensor. First, in order to perform efficient luminance extraction in limited bpp, we compare the maximum luminance extraction and the average luminance extraction. Then, we propose improving the nonlinearity between the transmitter and receiver, which is a problem in average luminance extraction suitable for a mobile environment, by applying precoded PWM. Finally, we evaluate effectiveness of precoded PWM experimentally.

  • Noise-aided Demodulation with One-bit ADC for Quadrature Amplitude Modulated Signals

    • Y. Nakashima, T. Yamazato, S. Arai, H. Tanaka, Y. Tadokoro
    • IEEE Global Communications Conference (GLOBECOM), Abu Dhabi, UAE
    • Dec. 2018
    • https://doi.org/10.1109/GLOCOM.2018.8648114
    • This paper proposes a new demodulation method using a one-bit analog-to-digital converter (ADC). With one bit resolution, a signal having a multilevel signal, such as a quadrature amplitude modulated (QAM) signal, is largely degraded by nonlinearity. To demodulate the signals, a high-resolution ADC is used to receive the signals with high linearity. This study sets out to demodulate the QAM signals using a one-bit ADC, whose resolution is the lowest (one-bit) and possesses outputs of binary (nonlinear) values. We propose to solve the issue by focusing on the statistical characteristics of the output signals of the one-bit ADC combined with noise. The proposed demodulation method is based on maximum a posteriori (MAP) criterion. The theoretical analysis presented illustrates that reliable demodulation is possible even with the one-bit ADC, provided the output probability of the ADC corresponds to each transmitted symbol is known.

  • A Basic Study on Transmitting Pattern for ITS Visible Light Communication Using DMD Projector

    • T. Arisue, M. Kinoshita, T. Yamazato, H, Okada, T. Fujii, S. Arai, T. Yendo, K. Kamakura
    • IEICE Technical Report, WBS2018-70, pp.237-241, Miyako, Japan
    • Dec. 2018
    • This paper focuses on a transmitter of image sensor communication (ISC) for the intelligent transportation system (ITS). ISC is a kind of visible light communications (VLC) that use an image sensor as a reception device. A commonly used transmitter device for ISC is an LED array as it can transmit multiple data transmission. However, it is necessary to decide the design of LED array and its transmission pattern in advance. Therefore changing the LED design and transmission pattern is difficult. In this paper, we propose to use a DMD projector for the ISC transmitter which can easily design and change a shape of transmission pattern and data rate compared with the LED array. A headlight of a vehicle, street lights, a projector of road signage are a typical example of the DMD projector usage. We, therefore, assume that a transmission pattern is projected on a road or signage for communication. In this paper, we describe our prototype using DMD projector and a high-speed camera and report an essential examination of the transmission pattern.

  • Possibility of learning pathway analytics and AI conversion

    • T. Yamazato and K. Takeda
    • 2018 Axies Anual Conference, Sapporo, Japan
    • Nov. 2018

  • Interference-Aided Detection of Subthreshold Signal Using Stochastic Resonance Receiver ～ Characteristic Evaluation Using PSK Modulation Method ～

    • S. Hiraoka, T. Yamazato, S. Arai, Y. Tadokoro, H. Tanaka
    • IEICE Technical Report, RCS2018-179, pp.7-12, Naha, Japan
    • Nov. 2018

  • [Encouragement Talk] Vehicle Vibration Modeling Inducing Transmitter Displacement in Image Plane for ITS Image Sensor Communication

    • M. Kinoshita, T. Yamazato, H, Okada, T. Fujii, S. Arai, T. Yendo, K. Kamakura
    • IEICE Technical Report, WBS2018-26, pp.47-52, Hiroshima
    • Oct. 2018

  • Noise-aided demodulation with one-bit comparator for multilevel pulse-amplitude-modulated signals

    • Y. Nakashima, T. Yamazato, S. Arai, H. Tanaka, Y. Tadokoro
    • IEEE Wireless Communications Letters, vol.7, no.5, pp.848-851
    • Oct. 2018
    • https://doi.org/10.1109/LWC.2018.2831683,28646
    • This paper proposes a demodulation method using a one-bit comparator for signals processed by multilevel pulse amplitude modulation (PAM). The proposed method is simple and provides an alternative to using an analog-to-digital converter to describe multilevel input signals. Because of the noise present in the transmitted multilevel PAM signal, the two-level output of the one-bit comparator shows different statistical behavior for each level of the signal. Thus, it is possible to detect the signal level, or perform symbol decision, based on the maximum likelihood (ML) criterion. The present theoretical analysis reveals that reliable demodulation is possible even with a one-bit comparator if the probability mass function of the two-level outputs of each received symbol plus intentionally added noise is known.

  • [Poster Presentation]Experimental evaluation of the effect of asynchronous information exchanges in wireless feedback control of multiple machines

    • M. Yamaguchi, K. Kobayashi, H. Okada, M. Katayama
    • Multiple Innovative Kenkyu-kai Association for Wireless Communications 2018, no.4-14
    • Sep. 2018

  • Noise-aided demodulation of OFDM signals with a 1bit analog-to-digital converter

    • Y. Nakashima，T. Yamazato, S. Arai, Y. Tadokoro, H. Tanaka
    • Communications Society Conference of IEICE
    • Sep. 2018

  • A Validation of Synchronization and Channel Estimation Performance for Low Earth Orbit (LEO) MIMO Systems

    • D. Goto, H. Shibayama, F. Yamashita, T. Yamazato
    • Communications Society Conference of IEICE, B-3-2, p.196, Kanazawa
    • Sep. 2018

  • Detectability enhancement using interference signals in wireless communication systems

    • S. Hiraoka, Y. Nakashima, T. Yamazato, S. Arai, Y. Tadokoro, H. Tanaka
    • International Symposium on Nonlinear Theory and its Application (NOLTA), pp. 705-708, Tarragona, Spain
    • Sep. 2018
    • We present a numerical study of an interference-aided detection of a weak (subthreshold) signal in a polarization diversity. We show that the nonlinear signal processing dramatically improves the detectability of the weak signal, supported by an interference signal generated by an appropriate beam control of the antenna arrays. The method takes advantage of subthreshold signal detection by the Stochastic resonance. To postulate a performance of the interference-aided detection, we numerically evaluate the channel capacity provided by the proposed diversity reception on a fading model. Through the numerical analysis, we find that the channel capacity depends on the threshold level of the detector and also the beam pattern determined by the diversity weights in the antenna arrays.

  • Interference-Aided Detection of Subthreshold Signal Using Beam Control in Polarization Diversity Reception

    • S. Hiraoka, Y. Nakashima, T. Yamazato, S. Arai, Y. Tadokoro, H. Tanaka
    • IEEE Communications Letters, vol.22, no.9, pp.1926-1929
    • Sep. 2018
    • https://doi.org/10.1109/LCOMM.2018.2851583,28616
    • The present letter discusses a detectability enhancement induced by co-channel interference signals in the polarization diversity reception. The challenge is the detection of weak (subthreshold) signals, the level of which is less than the detection limit of radio receivers. To understand the theory underlying the mechanism in the presented diversity scheme, we introduce an analytic model of a dual polarized antenna array in the fading channel. In addition, the channel capacity in a binary data transmission is derived. As a result, we reveal that the interference-aided diversity reception enables us to detect signals even below the detection limit of the receiver. Moreover, the appropriate source code is needed to achieve the channel capacity because the transmission channel is asymmetric in the present reception scheme.

  • Image Sensor Communications for Automotive

    • T. Yamazato
    • Progress In Electromagnetics Research Symposium (PIERS), Toyama International Conference Center, Toyama, Japan
    • Aug. 2018
    • This article introduces image sensor communications (ISC), a subset of visible light communication (VLC), that use high-speed image sensor and its application to automotive. Li-Fi (light fidelity) and OCC (optical camera communication) or also know as CamCom are also VLC family. Li-Fi is a high-speed wireless system and is currently in the process of being standardized in IEEE 802.11. The OCC uses an ordinary camera, e.g. a smartphone camera, as a receiver while ISC uses a high-speed image sensor as a reception device. The principal component of a camera, an image sensor, is used for both ISC and OCC. The main difference is that ISC focuses on a high-speed image sensor while OCC concentrates on low-cost consumer applications using smartphones and similar contemporary devices. For automotive usage, a high-speed image sensor is the best choice for the VLC receiver because the image sensor has a spatial separation of noise and target source. The VLC family uses LED as the transmitter and LED light sources are everywhere on streets: in signs, traffic lights, street lights, and other stationary objects. So if we can send IDs or exact location data (latitude and longitude) by way of VLC from those LEDs, then they can be used as anchor nodes placed on roads, sidewalks, or landmarks. Those anchor nodes help autonomous cars and connected vehicle for robust navigation with centimeter accuracy. The image sensor is the suitable detection device as it can be used for both positioning and VLC data detection. The author has been working on ISC for automotive applications. In this article, some of the author research, as well as his findings, are introduced.

  • Overview of image-sensor communication

    • T. Yamazato
    • Visible Light Communications Workshop, Pacific Rim Conference on Lasers and Electro-Optics (CLEO-PR), Hong Kong Convention and Exhibition Centre, Hong Kong
    • Jul. 2018
    • Back in 1998, Prof. Masao Nakagawa invented the concept of visible light communications (VLC) that adopts light emitting diodes (LEDs) as a transmitter. Twenty years of research progress make VLC attractive not only to researchers but also to practitioners. We are about to see blooms of VLC products. Image-sensor communication (ISC) is a form of VLC that uses image-sensor as a reception device. A particular advantage of ISC is an ability to spatially separate light sources. We can use ISC in the outdoor mobile environment. In this presentation, I will review ISC, its application, and future perspective. Some results from the author vis-a-vis ISC and its application to the automobile are also introduced.

  • Detection of Visible Light Communication Transmitter by Machine Learning using Time Gradient Feature

    • M. Hori, M. Kinoshita, T. Yamazato, H. Okada, T. Fujii, K. Kamakura, T. Yendo, S. Arai
    • IEICE Technical Report, ASN2018-30, pp.85-90, Hakodate, Japan
    • Jul. 2018
    • In this paper, we focus on an image sensor visible light communication (VLC) for Intelligent Transport System (ITS). In this system, the transmitter is an LED array, and the receiver is a high-speed image sensor. To receive VLC signals, it is necessary to specify the position of the LED array transmitter from captured images. Previous studies showed that the transmitter has high time gradient values and low spatial gradient values, and proposed a transmitter detection method using these features. In this paper, we focus on time gradient periodicity, and use frequency component in addition to time gradient value and spatial gradient value. Then, we propose a transmitter detection method by machine learning with these features.

  • Application of Precoding for Image Sensor Based Visble Light Communication and Its Performance Evaluation in a Stationary Environment

    • S.Kamegawa, T. Yamazato, H, Okada, T. Fujii, S. Arai, T. Yendo, K. Kamakura
    • , Hakodate,Japan
    • Jul. 2018
    • In this paper, we compare the performance of two modulation schemes used for ITS image sensor communication. The one is a pulse-width modulation (PWM) that simply convert source data into a width of a pulse, and then convey the signal by the multi-level intensity of a LED. The other is a virtual sinusoidal wave, proposed to adopt amplitude and phase signal reception for the image sensor receiver. The wave can convey data mapped on both amplitude and phase signal. We compare those two schemes regarding data rate and error rate performance.

  • Image Sensor Communications for future ITS

    • T. Yamazato
    • 2018 Advanced Photonics Conference, ETH Zrich, Zrich, Switzerland
    • Jul. 2018
    • This article overviews image sensor communication (ISC), a subset of visible light communication (VLC) system that uses a high-speed image sensor as a reception device. Owing to a massive number of pixels and spatial separation of multiple light souces, ISC can be used in an outdoor mobile environment, suitable for automotive applications. The paper also introduces some results from the authors’ work on ISC and its application to vehicle-to-everything (V2X) communication.

  • Emergency vehicle data corrected by 700 MHz Intelligent Transport System and its analysis -Emergency vehicle location and speed analysis of the Nagoya-shi Showa-ku Yagoto Firefighting Station-

    • T. Mitani, T. Yamazato
    • IEICE Technical Report, SR2018-5, pp.29-34, Tokyo Big Sight
    • May 2018
    • An issue of emeregency vehicle is that patient conveying time is increasing year by year. Here, the patient conveying time is defined as a time duration of the first emergency call and transport a patient to a hospital. It has been said that the half of the patient conveying time is the emergency vehicle traveling time. To analyze the patient conveying time, we focus on the data corrected by 700 MHz Intelligent Transport System and analyze the location and speed of emergency vehicle of the Nagoya-shi Showa-ku Yagoto Firefighting Station. In particular, we show the average communication time, vehicle speed histogram, vehicle speed heat-map to find the bottleneck of the emergency vehicle traveling time.

  • Communication performance enhancement by maximal ratio combining for ITS visible light communication using high-speed stereo camera

    • M. Kinoshita, T. Yamazato, H, Okada, T. Fujii, S. Arai, T. Yendo, K. Kamakura
    • IEICE General Conference, A-9-8, p.95, Tokyo
    • Mar. 2018

  • A Demodulation Concept for 16QAM Signals by 1bit Analog to Digital Converter

    • Y. Nakashima, S. Hiraoka, T. Yamazato, S. Arai, H. Tanaka, Y. Tadokoro
    • IEICE General Conference, B-8-25, p.166, Tokyo
    • Mar. 2018

  • Image Sensor Communications for ITS

    • T. Yamazato
    • IEICE General Conference, CI-2-5, pp.SS-17 - SS-18, Tokyo
    • Mar. 2018

  • Performance Enhancement for Image Sensor Communication in an Intelligent Transport System Using a High-speed Stereo Camera

    • M. Kinoshita, T. Yamazato, H, Okada, T. Fujii, S. Arai, T. Yendo, K. Kamakura
    • International Conference and Exhibition on Visible Light Communications (ICEVLC), Yokohama, Japan
    • Mar. 2018
    • In this paper, we propose using a high-speed stereo camera as the image sensor communication (ISC) receiver of an intelligent transport system (ITS). The stereo camera is used for front recognition of the vehicle, making it possible to estimate distances and enabling an integrative system that comprises vehicle front recognition and communication. Furthermore, several stereo images from slightly different views can be obtained at the same time, which provides diversity. Thus the proposed method enhances communication performance owing to the stereo diversity. We also provide experimental results obtained using the high-speed stereo camera and compare them with that of a conventional single high-speed camera. The proposed method improves the bit error rate (BER) performance with respect to the conventional method.

  • High-speed image processing of VLC signals for automotive applications

    • Takaya Yamazato
    • International Conference on Optical Wireless Communications, Beijing, China
    • Mar. 2018

  • Technical Issues on IEEE 802.15.7m Image Sensor Communication Standardization

    • T. Nguyen, A. Islam, T. Yamazato, Y. M. Jang
    • IEEE Communications Magazine, vol. 56, no. 2, pp. 213-218
    • Feb. 2018
    • https://doi.org/10.1109/MCOM.2018.1700134
    • This tutorial article presents an outline of image sensor communication (ISC) technologies realized by light sources and cameras. It discusses the revision of the IEEE 802.15.7-2011 standard, namely, the IEEE 802.15.7m Optical Wireless Communications Task Group, which has significantly influenced the development of the ISC technology. It also reviews the ISC technical proposals of the task group and compares them with related works. The essential technical considerations of the ISC specifications are presented, and the future directions of research and development are discussed.

  • [Invited] Stochastic resonance and its applicability to communication systems

    • Takaya YAMAZATO, Yukihiro TADOKORO, Hiroya TANAKA, Hiroya TANAKA, Shintaro ARAI, Yasuo NAKASHIMA, and Shintaro HIRAOKA
    • IEICE Technical Report, RCS2017-297, pp.167-174, Takamatsu, Japan.
    • Jan. 2018
    • Stochastic resonance (SR) is a nonlinear phenomenon where system response can be boosted by adding noise. Traditionally, noise has been treated as a disturbance to a system, and therefore we remove the noise using a filter. In SR, we take a different approach that we give a positive role to the noise to increase the system response. For example, some creature use noise to detect a signal buried in noise. If we can use this mechanism, we may be able to detect a sub-threshold signal that can not be detected by an ordinary receiver. In this paper, we will present SR and its application to a communication system, with some reference to our research results.

  • Simplified Vehicle Vibration Modeling for Image Sensor Communication

    • M. Kinoshita, T. Yamazato, H, Okada, T. Fujii, S. Arai, T. Yendo, K. Kamakura
    • IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences, vol.E101-A, no.1, pp.176-184
    • Jan. 2018
    • https://doi.org/10.1587/transfun.E101.A.176
    • Image sensor communication (ISC), derived from visible light communication (VLC) is an attractive solution for outdoor mobile environments, particularly for intelligent transport systems (ITS). In ITS-ISC, tracking a transmitter in the image plane is critical issue since vehicle vibrations make it difficult to select the correct pixels for data reception. Our goal in this study is to develop a precise tracking method. To accomplish this, vehicle vibration modeling and its parameters estimation, i.e., representative frequencies and their amplitudes for inherent vehicle vibration, and the variance of the Gaussian random process representing road surface irregularity, are required. In this paper, we measured actual vehicle vibration in a driving situation and determined parameters based on the frequency characteristics. Then, we demonstrate that vehicle vibration that induces transmitter displacement in an image plane can be modeled by only Gaussian random processes that represent road surface irregularity when a high frame rate (e.g., 1000 fps) image sensor is used as an ISC receiver. The simplified vehicle vibration model and its parameters are evaluated by numerical analysis and experimental measurement and obtained result shows that the proposed model can reproduce the characteristics of the transmitter displacement sufficiently.

  • Practical Applications of Visible Light Communications

    • T. Yamazato, H. Okada
    • Journal of IEICE, vol.101, no.1, pp.59-65
    • Jan. 2018

  • V2X communications with an image sensor

    • Takaya Yamazato
    • Journal of Communications and Information Networks, vol.2, no.4, pp.65-74
    • Dec. 2017
    • https://doi.org/10.1007/s41650-017-0044-4
    • This paper introduces infrastructure-to-vehicle and vehicle-to-vehicle communications using VLC. A VLC coupled with a high-speed image sensor is introduced (i.e., image sensor communication). The high-speed image sensors provide eyes for autonomous and connected vehicles. VLC imparts data reception capability to image sensors with necessary functions, which can then be provided to autonomous and connected vehicles. In this paper, some of our research on coupling VLC to high-speed image sensors is introduced, including our key findings: the basics of ISC, a vehicle motion model, and range estimation.

  • LED array detection method using SVM for ITS image sensor visible light communication

    • M. Hori, M. Kinoshita, T. Yamazato, H. Okada, T. Fujii, K. Kamakura, T. Yendo, S. Arai
    • IEICE Technical Report, Okinawa, Japan
    • Dec. 2017
    • In this paper, we focus on an image sensor visible light communication (VLC) for Intelligent Transport System (ITS). In this system, a transmitter is an LED array, and a receiver is a high-speed camera. To receive VLC signals, it is necessary to specify the position of the LED array transmitter from captured images. Previous studies showed that the LED array has a high temporal gradient value and a low spatial gradient value, and proposed an LED array detection method using these features. However, the method has difficulty to distinguish between information-contained LED array transmitter and an artificial light source without information. Also, since the number of pixels corresponding to the non-LED array is much larger than that of the LED array, such data imbalance should be considered. Therefore, in this paper, to detect LED array more accurately, we performed undersampling based on the k-means method. Then, we propose an LED array detection method using SVM model from these data.

  • Overview of visible light communications with emphasis on image sensor communications

    • Takaya Yamazato
    • Asia-Pacific Conference on Communications (APCC), Perth, WA, Australia
    • Dec. 2017
    • https://doi.org/10.23919/APCC.2017.8304093
    • The concept of visible light communications (VLC) originates from an Asian professor and adopts light emitting diodes (LEDs) as a transmitter. Three Asian born Nobel Prize winners developed blue LEDs, key devices that produce white lighting. Consequently, VLC and its other forms can be considered as an Asian born wireless technology. This paper overviews VLC with emphasis on image sensor communication (ISC) that uses an image sensor as a reception device for VLC signals. Some results from the author vis-a-vis ISC and its application to automobile are also introduced.

  • A Stochastic Resonance Receiver for 4-PAM Signals

    • Y. Nakashima, T. Yamazato, Y. Tadokoro, S. Arai
    • International Symposium on Nonlinear Theory and its Application (NOLTA), pp.291-294, Cancun, Mexico
    • Dec. 2017
    • Stochastic Resonance (SR) is considered as a noise enhanced phenomenon, that a response of a nonlinear system is improved by noise. In previous studies, an application of SR for wireless communication has been discussed and an SR receiver, the receiver that demodulate a received signal by SR, was proposed. However, these studies have used a basic modulation signal and have not focused on a signal that transmit information by multi-level amplitude. In this paper, we consider an SR receiver for 4-pulse amplitude modulation (4-PAM) signals. By applying SR, it can demodulate 4-PAM signals by a 1-bit resolution device. We show the system model of the receiver, evaluate its performance by simulation, and show its availability.

  • N-Stream Superimposed System with m-Point DFT for Image-Sensor-Based Visible Light Communication

    • S. Kibe, K. Kamakura, T. Yamazato
    • IEEE Global Communications Conference (GLOBECOM), pp. 1-6, Singapore, Singapore
    • Dec. 2017
    • https://doi.org/10.1109/GLOCOM.2017.8254784
    • This paper proposes an N-stream superimposed system for image-sensor-based visible light communications (ISbased VLC). Based on the principle of m-point discrete Fourier transform (DFT), a phase shift keying (PSK) signal is transmitted over m consecutive time slots mT, where T is a slot duration. In practice, the symbol rate of this paper is R/(m + 1) because a guard slot is inserted every m slots. In the superimposed system, N data streams where the symbol rate of the nth data stream, n = {1, 2, . . . , N}, is 1/(m + 1)n-1 times the symbol rate of the first data stream are combined to form a pulse-width modulated (PWM) wave with a period time T. An IS receiver with a camera operating at a frame rate of R/(m + 1)n-1 fps demodulates data streams whose symbol rate is R/m + 1)n symbol/s or lower. Our experimental results validate that from a superimposed PWM wave of 500-symbol/s and 125-symbol/s data streams, a 2000-fps camera receiver demodulates both of the two data streams and the 500-fps camera receiver does the 125-symbol/s data stream successfully, without shortening individual error-free transmission ranges, compared with non-superimposed systems in which 500-symbol/s and 125-symbol/s data streams are independently transmitted by different light emitting diode (LED) transmitters and received by 2000-fps and 500-fps camera receivers, respectively.

  • N-Stream Superimposed System with m-point DFT for Image-Sensor-Based Visible Light Communication

    • S. Kibe, K. Kamakura, T. Yamazato
    • IEICE Technical Report, CS2017-58, pp.21-2, Aso
    • Nov. 2017

  • The Uplink Visible Light Communication Beacon System for Universal Traffic Management

    • T. Yamazato, N. Kawagita, H. Okada, T. Fujii, T. Yendo, S. Arai, K. Kamakura
    • IEEE Access, vol.5, pp.22282-22290
    • Oct. 2017
    • https://doi.org/10.1109/ACCESS.2017.2759179
    • This paper presents a feasibility study of the uplink visible light communication (VLC) beacon system for the universal traffic management system (UTMS). The UTMS is a traffic management system beneath the National Police Agency of Japan. Currently, 55 000 UTMS infrared beacon systems have been installed, and they provide expressway and ordinary road information to cars. However, the data rate is 1 Mbps, and a faster data rate is necessary to support automotive and smart mobility devices. In this paper, we propose an uplink V2I system for the UTMS. The system is designed to match the current beacon system as closely as possible, so that the system can easily be replaced and still provide sufficient bandwidth for future automotive and smart mobility devices. We adopt a photo diode (PD) as the VLC receiver and a commercially available off-the-shelf LED headlight as a transmitter. Unfortunately, the bandwidth of such an LED is usually small, so we consider applying a bit-loading algorithm to direct-current-biased optical orthogonal frequency division multiplexing. To reduce strong background noise, such as from the sun, we narrow down the field-of-view by applying a lens to the PD, which forms a tiny communication area, smaller than the current infrared beacon system. We then consider multiple PDs with the lens to create a similar communication area as the infrared beacon system. As a result, we achieve 3.1-Mbps throughput.

  • Modulation and coding for image sensor communication

    • K. Kamakura, T. Yamazato
    • IEEE Photonics Conference (IPC), pp.235-236, Orlando, FL, USA
    • Oct. 2017
    • https://doi.org/10.1109/IPCon.2017.8116086
    • Most practical visible light communication (VLC) systems being currently deployed with image sensor receivers use intensity modulation and direct detection scheme for outdoor and indoor applications. A number of modulation and coding techniques that are used for image sensor-based VLC systems are presented.

  • Improvement of communication performance using high-speed stereo camera for ITS image sensor communication

    • M. Kinoshita, T. Yamazato, H, Okada, T. Fujii, S. Arai, T. Yendo, K. Kamakura
    • IEICE Society Conference, A-9-7, p.92
    • Sep. 2017

  • A Feasibility Study on a Stochastic Resonance Receiver Based on Noise Level Control with Adaptive Array Antenna

    • S. Hiraoka, Y. Nakashima, T. Yamazato, S. Arai, Y. Tadokoro, H. Tanaka
    • IEICE Society Conference, N-2-3, p.196
    • Sep. 2017

  • Effect of a Root-Raised-Cosine Filter on a BPSK Stochastic Resonance Receiver

    • Y. Nakashima, H. Tanaka, T. Yamazato, Y. Tadokoro, S. Arai
    • NOLTA, IEICE, vol.E8-N, no.3, pp.204-214
    • Jul. 2017
    • https://doi.org/10.1587/nolta.8.204,26846
    • Signal filtering is necessary for wireless communication. However it causes the signal amplitude to fluctuate and affects the performance of stochastic resonance (SR) receivers. In this study, we evaluate the bit error rate (BER) performance of filtered binary phase-shift keying (BPSK) on an SR receiver. The results show that filtering improves the BER performance of the SR receiver because the amplitude fluctuation contributes to improving the SR effect. We also evaluate the effect of the roll-off factor, which determines the bandwidth of the filter and the amplitude fluctuation. The results demonstrate the applicability of the SR receiver to bandlimited BPSK signals.

  • A Comparison of Transmission Methods to Accelerate Data Rate for Image Sensor Based Visible Light Communication in Intelligent Transport Systems

    • S. Kamegawa, T. Yamazato, H, Okada, T. Fujii, S. Arai, T. Yendo, K. Kamakura
    • IEICE Technical Report,RCS2017-69, pp.115-120
    • Jun. 2017
    • In this paper, we compare the performance of two modulation schemes used for ITS image sensor communication. The one is a pulse-width modulation (PWM) that simply convert source data into a width of a pulse, and then convey the signal by the multi-level intensity of a LED. The other is a virtual sinusoidal wave, proposed to adopt amplitude and phase signal reception for the image sensor receiver. The wave can convey data mapped on both amplitude and phase signal. We compare those two schemes regarding data rate and error rate performance.

  • A Stochastic Resonance Receiver for 4 Pulse Amplitude Modulation

    • Y. Nakashima, H. Tanaka, T. Yamazato, Y. Tadokoro, S. Arai
    • IEICE NOLTA Society Conference, NLS-3, Nagoya, Japan
    • Jun. 2017

  • Modeling and Parameter Estimation of Vehicle Vibration Inducing Transmitter Displacement in ITS Image Sensor Communication

    • M. Kinoshita, T. Yamazato, H, Okada, T. Fujii, S. Arai, T. Yendo, K. Kamakura
    • IEEE International Conference on Communications Workshop on Optical Wireless Communications, pp.144-149, Paris, France
    • May 2017
    • https://doi.org/10.1109/ICCW.2017.7962648
    • Image sensor communication (ISC), which is derived from visible light communication (VLC), is a novel form of wireless communication that uses an image sensor as a receiver. ISC is an attractive solution for outdoor mobile environments and is particularly wellsuited to intelligent transport systems (ITS). The purpose of this paper is to derive the dominant components of vehicle vibrations and road surface irregularities that induce transmitter displacement in ITS-ICS in paved road scenarios. Such displacements make it difficult for a ISC receiver to select the correct pixels. We measured vehicle vibrations during an actual driving scenario using a sixaxis acceleration sensor installed in a smartphone. Using the results obtained, we performed a frequency analysis of the vehicle vibrations and determined the parameters of vehicle vibrations based on the frequency characteristics. This paper explains that the vehicle vibrations that affect the communication performance can be modeled by solely using Gaussian random processes when a high frame rate (e.g. 1000 fps) image sensor is used as the ISC receiver.

  • Prameter Estimation of the Channel Fluctuation Based on the Vehicle Vibration Measurement in ITS Image Sensor Communication

    • M. Kinoshita, T. Yamazato, H, Okada, T. Fujii, S. Arai, T. Yendo, K. Kamakura
    • IEICE General Conference, A-9-14, p.123, Nagoya
    • Mar. 2017

  • Implementation of the Experimental System for Simultaneous Reception from Asynchronous Multiple Sources in ITS Image Sensor Communication

    • T.Arai
    • IEICE General Conference, A-9-15, p.124, Nagoya
    • Mar. 2017

  • An Examination of Transmission Methods to Accelerate Data Rate for Visible Light Communication Using Image Sensor

    • S. Kamegawa, T. Yamazato, H, Okada, T. Fujii, S. Arai, T. Yendo, K. Kamakura
    • IEICE General Conference, A-9-13, p.122, Nagoya
    • Mar. 2017

  • Method to Detect Phase for Visible Light Communication using Normal Camera

    • W. Kihara, T. Yendo, S. Arai, T. Yamazato, H. Okada, K. Kamakura
    • IEICE General Conference, A-9-10, p.119, Nagoya
    • Mar. 2017

  • Spatial Modulation in Layered Space-Time Coding for Image-Sensor-Based Visible Light Communication

    • K. Masuda, K. Kamakura, T. Yamazato
    • IEICE General Conference, B-10-57, p.310, Nagoya
    • Mar. 2017

  • Wireless Communication System for Automotive

    • T. Yamazato
    • IEICE General Conference, BI-10-2, pp.SS-81 - SS-82, Nagoya
    • Mar. 2017

  • Internet Distribution of Teaching Materials and Copyright Movements

    • T. Yamazato
    • Nagoya University Library Research and Development Office Report Meeting
    • Mar. 2017

  • Simultaneous reception method of multiple transmitted signals asynchronous to each other in ITS image sensor visible light communication

    • Y. Arai
    • Graduation Research Presentation of IEICE Tokai Branch
    • Mar. 2017

  • The Impact on Increase of Penetration of the V2X System Based on ARIB STD-T109 on the Traffic Flow Management at an Intersection

    • R. Ohno, T. Yamazato
    • RISP International Workshop on Nonlinear Circuits, Communications and Signal Processing (NCSP), pp.81-84, Guam, USA
    • Mar. 2017
    • In this paper, we propose a traffic flow management at an intersection using the 760 MHz band V2X (Vehicle-to-X) system based on ARIB STD-T109. Using the V2X system, a road side unit (RSU) can obtain the vehicular information such as the vehicle position, speed and route. Based on the vehicular information, a ``support phase'' can be inserted to a cycle of traffic signal that controls traffic flow at an intersection. We define the “support phase” as the phase of changing the stop/go sign of the traffic signal on an intersection as necessary. In this way, it is expected to shorten the travel time of the vehicles. We evaluate the algorithm by a traffic simulator in terms of mean speed of all vehicles while passing through the intersection with considering V2X penetration rate.

  • Vehicle to Infrastructure Visible Light Communication using DCO-OFDM

    • N. Kawagita, T. Yamazato, H. Okada, T. Fujii, S. Arai, T. Yendo, K.Kamakura
    • RISP International Workshop on Nonlinear Circuits, Communications and Signal Processing (NCSP), pp.129-132, Guam
    • Mar. 2017
    • In this paper, we focus on the vehicle to infrastructure visible light communication (V2I-VLC) for intelligent transportation systems (ITS). We propose a V2I-VLC system using LED headlights as transmitters and photodiodes (PDs) with an optical lens as receivers. We adopt DC biased optical orthogonal frequency division multiplexing (DCO-OFDM) as a modulation scheme in order to realize high speed communication. As a results of the data transmission experiments in the driving situation, we achieve data rate of 2.7 Mbps using 32QAM.

  • A Modulation Method to Detect Phase Shift from Asynchronous Camera Image for Visible Light Communication

    • W. Kihara, T. Yendo, S. Arai, T. Yamazato, H. Okada, K. Kamakura
    • RISP International Workshop on Nonlinear Circuits, Communications and Signal Processing (NCSP), pp.133-136, Guan, USA
    • Mar. 2017

  • Range Estimation Scheme for Integrated I2V-VLC using a High-Speed Image Sensor

    • T. Yamazato
    • Presentation at Professor Jean Armstrong's Laboratory, Monash University, Monash University, Australia.
    • Mar. 2017

  • Nagoya University's Approach to Copyright Handling

    • T. Yamazato
    • The 39th Tokai IS Conference, Nagoya University, Nagoya, Japan
    • Feb. 2017

  • Global Communications Newsletter -- Asia/Pacific Region Interview with Takaya Yamazato, Director of the AP Region --

    • Stefano Bregni, Takaya Yamazato, Vasile Bota, Liangping Ma
    • IEEE Communications Magazine, Vol. 55, No. 2, pp.13-16
    • Feb. 2017
    • https://doi.org/10.1109/MCOM.2017.7841463
    • This is the fourth article in the series of eight, started in November 2016 and published monthly in the IEEE ComSoc Global Communi- cations Newsletter, which covers all areas of IEEE ComSoc Member and Global Activities. In this series of articles, I am introducing the six MGA Directors (Sister and Related Societies; Membership Services; AP, NA, LA, EMEA Regions) and the two Chairs of the Women in Communications Engineering (WICE) and Young Professionals (YP) Standing Committees. In each article, one by one they present their sector activities and plans. In this issue, I interview Takaya Yamazato, Director of the Asia/ Paci c Region (AP). Takaya is a professor at the Institute of Liberal Arts and Sciences, Nagoya University, Japan. He received the Ph.D. degree from Keio University, Yokohama, Japan, in 1993. From 1993 to 1998 he was an assistant professor in the Department of Information Electronics, Nagoya University, Japan. From 1997 to 1998 he was a visiting researcher in the Research Group for RF Communications, Department of Electrical Engineering and Information Technology, University of Kaiserslautern, Germany. In 2006 he received the IEEE Communication Society Best Tutorial Paper Award. He served as symposium co-chair of ICC 2009 and ICC 2011. From 2008 to 2010 he was the chair of the IEEE ComSoc Satellite and Space Communications Technical Committee and the editor-in-chief of the Japanese Section of IEICE Transactions on Communications. His research interests include visible light communication, intelligent transport systems, stochastic resonance, and open educational resources. It is a pleasure for me to interview Takaya for this issue and o er him this opportunity to outline his current activities and plans as Director of the AP Region.

  • A note on an application of space Time Block Coded DCO-OFDM to Vehicle to Infrastructure Visible Light Communication

    • N. Kawagita, T. Yamazato, H. Okada, T. Fujii, S. Arai, T. Yendo, K.Kamakura
    • Symposium on Information Theory and Its Applications (SITA), pp.555-560, Takayama, Japan
    • Dec. 2016
    • This paper focuses on vehicle to infrastructure visible lightcommunication (V2I-VLC) using two LED headlights as transmitters and photodiodes (PDs) with an optical lens as receiver.We adopt DC-biased optical orthgonal frequency division multiplexing (DCO-OFDM) to realize high data rata V2I-VLC. In V2I-VLC,it is possible to remove background light noise sources by narrowing the receiver's field of view (FOV) by using an optical lens.However,small FOV causes received signal intensity fluctuations ,especially in a driving situation ,and performance may be degraded.To overcome the problem,we adopt a Alamouti-type Space Time Block Coding (STBC). In this paper, we experimentally demonstrate a 2×1 STBC performance and compare it with the conventional system which the same signals simultaneously transmitted from two headlights. Experimental results show that STBC can't improve bit-error-rate performance because two signals transmitted from each headlights have high space correlation.

  • Vehicle to Vehicle and Vehicle to Infrastracture Communication

    • T. Yamazato
    • Electromagnetic Environmental Engineering Information Monthly EMC, vol.29, no.8, pp.98-109
    • Dec. 2016

  • An Application of Collins Network to Stochastic Resonance Receiver

    • H. Tanaka, Y. Nakashima, T. Yamazato, Y. Tadokoro, S. Arai
    • The 39th Symposium on Information Theory and its Applications (SITA2016), pp.147-151, Gifu, Japan
    • Dec. 2016
    • This paper presents an application of Collins Network to Stochastic Resonance Receiver. In stochastic resonance (SR) systems, sub-threshold signals can be detected by noise. This nonlinear phenomenon has been attracted much attention among many researchers. However, there has ever been no practical application of SR systems, because it is difficult to design them. In contrast to the conventional SR, the Collins network, which was proposed by Collins in 1995, is a good system with outstanding ability in detecting sub-threshold signals. The present paper evaluates the performance of the Collins network with in-out correlation.

  • Position estimation of LED matrix in image sensor communication

    • T. Asai, T. Yendo, S. Arai, T. Yamazato, H. Okada, T. Fujii, K. Kamakura
    • Asia-Pacific Signal and Information Processing Association Annual Summit and Conference (APSIPA), pp.1 - 5
    • Dec. 2016
    • https://doi.org/10.1109/APSIPA.2016.7820809
    • We focus on the road-to-vehicle visible light communication (VLC) that system is composed of a LED matrix as a transmitter and a high-speed camera as a receiver. In this VLC system, intensity of each LED cannot be determined from received image directly in case that the receiver is distant from the transmitter. In previous research, a method to estimate intensity of the LED from received image is proposed. In this method, intensity of LED is estimated by using Moore-Penrose pseudo-inverse matrix of coefficient matrix, which expresses relation between intensity of LEDs and pixel values. However, the coefficient matrix changes every moment because it is determined by positional relation between the receiver and the LED traffic light in VLC system. In this paper, we propose a method to estimate position of the LED matrix using simulated images. We measure sensitivity distribution of image sensor to generate simulated images. We evaluated degree of similarity between simulated images and real images.

  • Vehicle Vibration Model that Induces Channel Fluctuation in ITS Image Sensor Communication

    • M. Kinoshita, T. Yamazato, H, Okada, T. Fujii, S. Arai, T. Yendo, K. Kamakura
    • Cambodia-Japan Joint Workshop on Ambient Intelligence and Sensor Networks, シュムリアップ
    • Dec. 2016
    • Image sensor communication (ISC) enables multiple and simultaneous signal reception because of its　ability spatially separate multiple sources. Therefore, ISC is an attractive solution for an outdoor mobile environment, in particular, in the field of intelligent transport systems (ITS). In ISC, since a transmitter position moves in an image plane according to vehicle movement, detection and tracking of transmitter is critical issue for robust data reception. Such movement referred to as optical ow causes ISC channel to fluctuate and must be considered to receive the signal accurately. In this paper, we conducted vehicle vibration measurement in well paved road and analyzed the frequency characteristic. According to the measured result, we proposed a vehicle vibration model and determined its parameters.

  • [Poster Presentation] Evaluation of the video quality and communication quality in digital signage VLC using information embedding

    • S. Sato, H. Okada, T. Yamazato, T. Wada, K. Kobayashi, M. Katayama
    • VLCWS2016, Tokyo, Japan
    • Nov. 2016

  • Effect of a Root-Raised-Cosine Filtered BPSK Signal on a Stochastic Resonance Receiver

    • Y. Nakashima, H. Tanaka, T. Yamazato, Y. Tadokoro and S. Arai
    • International Symposium on Nonlinear Theory and its Application (NOLTA), pp.407-410, Yugawara,Japan
    • Nov. 2016
    • Signal filtering is necessary for wireless communication however it fluctuates the signal amplitude and affects the performance of a stochastic resonance (SR) receiver. In this paper, we evaluate the bit error rate (BER) performance of filtered binary phase shift keying (BPSK) on an SR receiver. The result shows that filtering improves the BER performance of the SR receiver because the amplitude fluctuation contributes to improving the SR effect, indicating the applicability of the SR receiver to bandlimited BPSK signals.

  • Channel Measurement of Infrastructure-to-Vehicle Image Sensor Communication

    • M. Kinoshita, T. Yamazato, H, Okada, T. Fujii, S. Arai, T. Yendo, K. Kamakura
    • 23rd World Congress on Intelligent Transport Systems , Melbourne, Australia
    • Oct. 2016
    • In this paper, we focus on the visible light communication (VLC) for ITS application using LED light source as a transmitter and high-speed image sensor as a receiver (image sensor communication: ISC). In ISC, the data reception is performed by extracting luminance corresponding to the transmitter from captured images. However, since either transmitter, receiver, or both moves with vehicles, the transmitter position is moved between frames and it confuses receiver to select the correct pixels. Hence, we treat such movement referred to as optical flow as channel fluctuation. In our previous work, we proposed a model that expressed motion of transmitter in captured images by using a single pinhole camera. In this paper, we derive channel fluctuation characteristic by numerical analysis based on the proposed model and evaluate its validity by comparing with channel fluctuation characteristic obtained by actual measurement.

  • Performance Comparison of Stochastic Reosonance Receiver with BPSK and QPSK Modulations

    • Y. Nakashima, H. Tanaka, T. Yamazato, Y. Tadokoro, S. Arai
    • Communications Society Conference of IEICE, Sapporo,Hokkaido
    • Sep. 2016

  • Visible Light Communication Systems Using Blue Color Difference Modulation for Digital Signage

    • S. Sato, H. Okada, K. Kobayashi, T. Yamazato, M. Katayama
    • IEEE International Symposium on Personal, Indoor and Mobile Radio Communication (PIMRC), pp.1242-1247, Valencia, Spain
    • Sep. 2016
    • https://doi.org/10.1109/PIMRC.2016.7794761
    • Digital signage, which is advertising media using a liquid crystal display (LCD), is increasing in popularity. One possible application is wireless communications between digital signage and viewers. We focus on image-sensor-based visible light communication (VLC). Image-sensor-based VLC requires only an image sensor (IS), which is common equipment in smart phones. In the proposed method, an nformation signal is displayed on LCD. However, embedding the information signal into an advertisement may decrease the quality. We propose blue color difference modulation to make such signals imperceptible. We implemented a VLC system between digital signage and IS to demonstrate, the effectiveness of the proposed modulation in a real environment.

  • Spatial Modulation in Layered Space-Time Coding for Image-Sensor-Based Visible Light Communication

  • Parameter Fitting of Vehicle Vibration and Road Surface Irregularity in ITS Image Sensor Communication

    • M. Kinoshita, T. Yamazato, H, Okada, T. Fujii, S. Arai, T. Yendo, K. Kamakura
    • IEICE Technical Report, RCS2016-112, pp.99-103, Nagoya, Japan
    • Jul. 2016
    • Image sensor communication (ISC) enables multiple and simultaneous signal reception because of its ability spatially separate multiple sources. Therefore, ISC is an attractive solution for an outdoor mobile environment, in particular, in the field of intelligent transport systems (ITS). In ISC, since a transmitter position moves in an image plane according to vehicle movement, detection and tracking of transmitter is critical issue for robust data reception. Such movement referred to as optical flow causes ISC channel to fluctuate and must be considered to receive the signal accurately. In previous work, we have proposed a channel model focused on the motion of an LED transmitter in the image plane. However, vehicle vibration and road surface irregularity parameters have not been examined in detail. Therefore, in this paper, we estimated vehicle vibration and road surface irregularity parameters based on the measured data of vehicle vibration.

  • Performance comparison of stochastic resonance receiver with Schmitt trigger, comparator, and three-level device for subthreshold signal reception

    • H. Tanaka, T. Yamazato, Y. Tadokoro, S. Arai
    • Nonlinear Theory and Its Applications, IEICE, vol.7, no.3, pp.407-418
    • Jul. 2016
    • https://doi.org/10.1587/nolta.7.407
    • This paper discusses the stochastic resonance (SR) effect in a binary communication system for subthreshold signal reception. We focus on the problem of no communication when received signal strength is below receiver sensitivity. Subthreshold signal reception requires a device that exhibits SR, such as a Schmitt trigger or a comparator. Previously, we proposed an alternative three-level device and demonstrated its high performance for subthreshold signal reception in an SR receiver. In the present study, we show that our proposed three-level device outperforms the three devices and discuss reasons for this superior performance. Contributions of our present paper are twofold: first, we analytically derive bit error rate (BER) performances of SR receivers installed with a Schmitt trigger and a comparator; second, we compare performances of the Schmitt trigger, comparator, and three-level device.

  • High-Speed Image Sensor Communications and Its Application to Vehicle-to-Vehicle and Vehicle-to-Infrastructure Communications

    • T. Yamazato
    • JIEP Advanced Electronics Packaging (JISSO) Technology Symposium, Tokyo Big Sight, Japan
    • Jun. 2016

  • A New Automotive VLC System Using Optical Communication Image Sensor

    • Y. Goto, I. Takai, T. Yamazato, H. Okada, T. Fujii, S. Kawahito, S. Arai, T. Yendo, K. Kamakura
    • IEEE Photonics Journal, vol.8, no.3
    • Jun. 2016
    • https://doi.org/10.1109/JPHOT.2016.2555582
    • As a new technology for next-generation vehicle-to-everything (V2X) communication, visible-light communication (VLC) using light-emitting diode (LED) transmitters and camera receivers has been energetically studied. Toward the future in which vehicles are connected anytime and anywhere by optical signals, the cutting-edge camera receiver employing a special CMOS image sensor, i.e., the optical communication image sensor (OCI), has been prototyped, and an optical V2V communication system applying this OCI-based camera receiver has already demonstrated 10-Mb/s optical signal transmission between real vehicles during outside driving. In this paper, to reach a transmission performance of 54 Mb/s, which is standardized as the maximum data rate in IEEE 802.11p for V2X communication, a more advanced OCI-based automotive VLC system is described. By introducing optical orthogonal frequency-division multiplexing (opticalOFDM), the new system achieves a more than fivefold higher data rate. Additionally, the frequency response characteristics and circuit noise of the OCI are closely analyzed and taken into account in the signal design. Furthermore, the forward-current limitation of an actual LED is also considered for long operational reliability, i.e., the LED is not operated in overdrive. Bit-error-rate experiments verify a system performance of 45 Mb/s without bit errors and 55 Mb/s with BER < 10-5.

  • Range estimation scheme for integrated I2V-VLC using a high-speed image sensor

    • T. Yamazato, A. Ohmura, H. Okada, T. Fujii, T. Yendo; S. Arai, K. Kamakura
    • IEEE International Conference on Communications Workshops (ICC), pp.326-330, Kuala Lumpur, Malaysia
    • May 2016
    • https://doi.org/10.1109/ICCW.2016.7503808
    • High-speed image sensors, designed for machine vision and control, provide the eyes for autonomous and connected vehicle. A noteworthy feature of high-speed image sensors is their ability to be used as a reception device for visible light communication (VLC) signals. Due to the massive number of pixels available and the ability to spatially separate sources, a signal-receiving pixel in the image sensor plane represents the actual position of the transmitter. The VLC signal can be represented not only by a VLC time domain signal but also by the position of the transmitter. In this paper, we propose a robust range estimation scheme that integrates with a VLC function for infrastructure-to-vehicle visible light communication (I2V-VLC). The scheme is composed of an LED array transmitter and a high-speed image sensor receiver. It measures a range by taking phase-only correlation (POC) and avoids vehicle vibration from road irregularity. Field trials confirm an accuracy range of 0.3 m, even on rough road conditions, with the measurement time of 2 ms, which is much faster than that of light detection and ranging (LIDAR).

  • A Study on Traffic Flow Management using 700MHz Band Vehicle-to-Infrastructure Cooperative System

    • R. Ohno, T. Yamazato
    • IEICE Technical Report, RCS2016-3, pp.13-18, Hirosaki, Japan
    • Apr. 2016
    • In this paper, we propose traffic flow management using vehicle-to-infrastructure communication system. At present, traffic signals and traffic signs are used mainly to traffic flow management at the intersection. However, dynamic change of the signal phase in response to variation and congestion of traffic is not supported, and the indication displayed in the traffic signs are fixed. On the contrast, flexible traffic flow management is possible using vehicle-to-infrastructure communication system (V2I). For example, signal phase timing can be managed to achieve smooth and ecological driving depending on the traffic situation. In this paper, we aim to propose and consider the effectiveness of traffic flow management method which applies the 700MHz band vehicle-to-infrastructure cooperative system that has been introduced, researched and developed in Japan. As its initial investigation, we propose the algorithm applicable to a cross-shaped intersection of the straight lane. We consider the mixture case of that cars follow the indications transmitted via V2I and cars obey legacy traffic signals.

  • Free Educational Resources Provided by Nagoya University

    • T. Yamazato
    • Annals of Nagoya University Library Studies, No.13
    • Apr. 2016
    • In this report, details of free educational resources and copyright issue are discussed. The report also introduces free educational resources provided by Nagoya University and presents the results of the ratio of the commercial textbook usages in Department of Science and Department of Engineering of Nagoya University. The results suggest that the percentages of lecturers who create their own teaching materials are rather high. So we are ready to publish open education materials. However, the launching of open educational resources does not advance because of lack of copyright clearance office. For launching of open educational resources, copyright clearance, a grant of the bibliography information (metadata), and appropriate platform that contributes to a wide recognition of the published contents are necessary. The author thinks that a university library should have this function. In this report, an opinion of the author on the opening of the educational materials and the role of the library is also described.

  • High Speed Image Sensor Based I2V-VLC Channel Modeling in Outdoor Mobile Environment

    • M. Kinoshita, T. Yamazato, H, Okada, T. Fujii, S. Arai, T. Yendo, K. Kamakura
    • IEICE General Conference, AS-3-10, pp.S-53 - S-54, Fukuoka, Japan
    • Mar. 2016

  • BER Performance of NLOS Vehicle to Vehicle Visible Light Communication Using Optical OFDM

    • N. Kawagita, T. Yamazato, H. Okada, T. Fujii, S. Arai, T. Yendo, K. Kamakura
    • IEICE General Conference, A-9-17, p.153, Fukuoka,Japan
    • Mar. 2016

  • Performance Improvement of Stochastic Resonance Receiver by Uniform Noise and Binary Noise

    • H. Tanaka, Y. Nakashima, T. Yamazato, Y. Tadokoro, S. Arai
    • IEICE General Conference, NBS-1-1, pp.S-113 - S-114, Fukuoka, Japan
    • Mar. 2016

  • erformance Evaluation of Stochastic Resonance Receiver in Bandlimited BPSK Modulations

    • Y. Nakashima, H. Tanaka, T. Yamazato, Y. Tadokoro, S. Arai
    • IEICE General Conference, N-2-2, p.369, Fukuoka, Japan
    • Mar. 2016

  • Preliminary Study of Platoon Management using 700 MHz Band Vehicle-to-Infrastructure Cooperative System

    • R. Ohno, T. Yamazato
    • IEICE General Conference, A-14-8, p.194, Fukuoka, Japan
    • Mar. 2016

  • Transmit diversity with single RF front-end using CIOD

    • T. Yamaoka, T. Hara, A. Okazaki, T. Yamazato
    • IEICE Communications Express, vol.5, no.2, pp.44-48
    • Feb. 2016
    • https://doi.org/10.1587/comex.2015XBL0170
    • Complex interleaved orthogonal design (CIOD) can offers diversity gain to the part of the source in spatial modulation which has single radio frequency (RF) front-end at the transmitter despite multiple-inputmultiple-output, but emits the undesired component out-of-band. For the reducing out-of-band emission, we give up indicating the information source by the antenna switching and increase both the interleaver size and the antenna switching interval. The increase reduces the discontinuities in the waveform and out-of-band emission. We propose such a scheme as transmit diversity with single RF front-end using CIOD. The diversity gain of the proposed scheme is equivalent to the case for CIOD. Moreover, we evaluate the increase of out-of-band emission and confirm that of the proposed scheme compared to the ideal case is only 3dB.

  • Poor man’s Flipped Classroom

    • T. Yamazato
    • Nagoya Journal of Higher Education (in Japanese), No.16
    • Feb. 2016
    • This report introduces the active learning techniques employed by the author. Among a variety of active learning pedagogical methods, this report focuses on a flipped classroom. A lecture given during class time is self-learnt outside of a school hours, and typical learning that is completed outside the classroom is performed during in-class time. The spread of massive open online course (MOOC) promotes short video lectures to be viewed by students at home, and it is often seen as the key element in the flipped classroom. However, the production costs of the video lectures are usually high. So the author attempted a so-called “poor man’s flipped classroom.” Given it is an on-going trial it is too early to evaluate it; however, the author has a generally positive feeling about it. Various methods are available for active learning, and one may turn his or her thoughts to the meaning of related pedagogy. Those thoughts lead to questions about what we should be teaching and what students should learn at university. In this report, I also include my opinion with regards to the question.

  • Improving Communication Rate of Road-to-Vehicle Visible Light Communication System Using High-Speed Camera and LED Traffic Light

    • D. Iwase, M. Kasai, T. Yendo, S. Arai, H. Okada, K. Kamakura, T. Fujii
    • IEICE Transactions on Communications, vol.J99-B, no.2, pp.97-104
    • Feb. 2016

  • Novel Demodulation Scheme Based on Blurred Images for Image-Sensor-Based Visible Light Communication

    • Y. Ohira, S. Arai, T. Yendo, T. Yamazato, H. Okada, T. Fujii and K. Kamakura
    • IEEE GLOBECOM Workshop on Optical Wireless Communication, San Diego, CA, USA
    • Dec. 2015
    • https://doi.org/10.1109/GLOCOMW.2015.7414144
    • This paper proposes a novel data detection scheme based on the occurrence of blurred output images in image-sensor-based visible light communication systems. This system's receiver suffers from an inability to detect correct LED luminance values and demodulation of data because the captured image blurs owing to defocusing. The proposed method assumes that the light emitted by all LEDs that is diffused by the blur can be approximated by applying a Gaussian filter and expressesall LED luminance values as convolution equations based on this diffusion of the LED light. We estimate each LED light's condition by simultaneously solving these convolution equations and recover data according to the estimated result. To confirm the accuracy of the proposed method, we conduct computer simulations and an implementation experiment to evaluate the bit error rate performance of the proposed method.

  • A note on subthreshold signal reception using stochastic resonance receiver - Comparison of dynamical and non-dynamical devices -

    • H. Tanaka, T. Yamazato, Y. Tadokoro, S. Arai
    • International Symposium on Nonlinear Theory and its Application (NOLTA), Hong Kong, China
    • Dec. 2015
    • Stochastic resonance (SR) is an interesting phenomenon in that noise enhances system responses. Despite an attractive phenomenon of SR that noise enhances a weak signal below a receiver sensitivity, few researchers have addressed the SR effect in communication systems. Previously, we proposed an analysis method for the SR receiver with a device exhibiting SR and evaluated its bit error rate (BER) performance. However, the device was limited to a non-dynamical device, and there is room for improving the performance of the SR receiver by changing the device. In this paper, we use two typical devices exhibiting SR, i.e., a comparator as a non-dynamical device and a Schmitt trigger as a dynamical device. We evaluate the BER performances of these devices with analysis methods and numerical simulations. A performance comparison of these devices is also shown.

  • Performance Analysis of Wireless Mesh Networks Using Forward/Reverse-Link Multi-User MIMO

    • C. Fuwa, H. Okada, K. Kobayashi, M. Katayama
    • International Symposium on EcoTopia Science (ISETS), no.P-6-2, Nagoya, Japan
    • Nov. 2015
    • IEEE 802.11ac, which is the latest standard of IEEE 802.11, supports forward-link (downlink) MU (Multi-User)-MIMO (Multiple-Input Multiple-Output), and it can improve the transmission efficiency. IEEE 802.11ax, which is under standardization, is considered to apply reverse-link (uplink) MU-MIMO, and a further improvement of the efficiency is expected. In this paper, we propose to introduce reverse-link MU-MIMO in addition to forward-link MU-MIMO for wireless mesh networks, and evaluate the performance in terms of area transmission efficiency, which indicates a number of packets in a unit area. Then, we clarify that the proposed system achieves the higher area transmission efficiency than forward-link MU-MIMO.

  • I2V-VLC Vehicle Motion Modeling Using Actual Vehicle Vibration

    • M. Kinoshita, T. Yamazato, H, Okada, T. Fujii, S. Arai, T. Yendo, K. Kamakura
    • International Workshop on Vision, Communications and Circuits (IWVCC) , Yokohama, Japan
    • Nov. 2015
    • Image-sensor-based visible light communications (IS-VLC), or also known as image sensor communication (ISC) and camera communications (CamCom), is one of emerging segment in the field of visible light communications (VLC). As the name indicates, IS-VLC uses light-emitting diodes (LEDs) or an LED array for the transmitter by modulating LED’s intensity at high speeds that are undetectable to the human eye. For the reception device, IS-VLC adopts image-sensor. In our previous work, we have proposed vehicle motion model that expresses the motion of VLC transmitter in image plane by single pinhole camera model. In this paper, we performed a simulation based on vehicle motion model for infrastructure-to-vehicle VLC (I2V-VLC) with actual vehicle vibration measured by 6- axis acceleration sensor of smartphone and evaluated its channel characterized by optical flow.

  • Performance Evaluation of Stochastic Resonance Receiver for Dynamical and Non-Dynamical Devices in QPSK Modulation

    • H. Tanaka, T. Yamazato, S. Arai
    • International Workshop on Vision, Communications and Circuits (IWVCC) , Yokohama, Japan
    • Nov. 2015
    • This paper evaluates the performance of the stochastic resonance (SR) receiver for subthreshold signal reception. We focus on the problem of no communication when received signal strength is below receiver sensitivity. Previously, we proposed a SR receiver installed with a typical device exhibiting SR in BPSK modulation and presented the performance improvement for subthreshold signals. However, the performances of other nonlinear devices exhibiting SR are not clear, and we require the performance evaluation for various nonlinear devices. And also, the performance evaluation in multi-level modulation is not presented. In this paper, we evaluate bit error rate (BER) performances of SR receivers installed with a three-level device, a Schmitt trigger and a comparator in QPSK modulation.

  • [Exhibition] An Optical Camera Communication System Using Digital Signage

    • S. Sato, H. Okada, K. Kobayashi, T. Yamazato, M. Katayama
    • International Conference and Exhibition on Visible Light Communications (ICEVLC), Yokohama, Japan
    • Oct. 2015

  • Tracking of LED headlights considering NLOS for an image sensor based V2I-VLC

    • Y. Kawai, T. Yamazato, H. Okada, T. Fujii, T. Yendo, S. Arai, K. Kamakura
    • International Conference and Exhibition on Visible Light Communications (ICEVLC), Yokohama, Japan
    • Oct. 2015
    • This paper focuses on image sensor based vehicle-to-infrastructure visible light communication (V2IVLC) for Intelligent Transport Systems (ITSs). Because the image sensor can spatially separate multiple or noise sources, its receiver can simultaneously demodulate multiple sources. Thus, we consider multiple source reception from multiple vehicles. In image sensor based VLC, the transmitted data are received by extracting the luminance corresponding to the VLC transmitter from the captured image. Transmitter detection and tracking are an important requirement of these systems but are degraded by occlusion, which causes non-line of sight (NLOS). We focus on tracking of transmitters that may be occluded by moving vehicles in V2I-VLC. Our proposed method detects multiple LED headlights by combining a background difference method with an LED detection method based on time and space gradients. We also propose a tracking method based on optical flow-based tracking, which handles occlusion by linear or second-curve interpolation. The proposed methods were evaluated by a high-speed camera placed by the roadside. The false-positive and falsenegative tracking rates were 6.25% and 3.32%, respectively, at κ = 60 (where κ defines the permissible error in the optical flow).

  • [Invited Lecture] Optical Camera Communications Using Digital Signage

    • H. Okada, S. Sato, T. Wada, T. Yamazato, M. Katayama
    • ITE Technical Report, BCT2015-74, pp.21-24, Yamagata
    • Oct. 2015
    • In this paper, we discuss optical cammera communication systems using digital signage, which is composed of a liquid crystal display (LCD). The digital signage, which is used as a transmitter, displays advertisement contents as visual information. The optical camera communication system using digital signage has to transmit data information not to obstruct the visual information. In this paper, we propose blue color difference modulation for the optical camera communication system using digital signage. We clarify the performance of the proposed system by data transmission experiments.

  • Development of add-on stochastic resonance device for the detection of subthreshold RF signals

    • K. Chiga, H. Tanaka, T. Yamazato, Y. Tadokoro, S. Arai
    • Nonlinear Theory and Its Applications, IEICE, vol. 6, no. 4, pp. 520-533
    • Oct. 2015
    • https://doi.org/10.1587/nolta.6.520
    • Stochastic resonance (SR) is a nonlinear phenomenon that, under certain conditions, can enhance system response by adding noise to the signals of some nonlinear system. A particular advantage of SR over conventional linear systems is that it is able to detect subthreshold signals that linear systems hardly sense. Unfortunately, most research of SR in wireless communication systems has focused on fundamental analysis, leaving work to be done in experimental SR research despite the attractiveness of its application. Few attempts have so far addressed the development of SR receivers to show the feasibility of subthreshold signal detection. Those receivers that have been developed are simple ones specially made to confirm the usefulness of SR without needing to support state-of-the-art wireless radio technology. The purpose of this study is to examine the feasibility of using an SR receiver to receive subthreshold radio frequency (RF) signals. A new add-on SR device is developed and confirmation that the SR phenomenon exists within RF is obtained when using software defined radio (SDR) as the post-processing receiver. Furthermore, bit error rate (BER) performance is mainly governed by the add-on SR device's output signal quality.

  • Performance Evaluation of Stochastic Resonance Receiver in QPSK Modulations

    • Y. Nakashima, H.Tanaka, T.Yamazato, Y.Tadokoro,S.Arai
    • Tokai-Section Joint Conference on Electrical, Electronics, Information and Related Engineering, K5-4, Nagoya
    • Sep. 2015

  • Vehicle Motion and Pixel Illumination Modeling for Image Sensor Based Visible Light Communication

    • T. Yamazato, M. Kinoshita, S. Arai, E. Souke, T. Yendo, T. Fujii, K. Kamakura, H. Okada
    • IEEE Journal on Selected Areas in Communications, vol.33, no.9, pp.1793-1805
    • Sep. 2015
    • https://doi.org/10.1109/JSAC.2015.2432511
    • Channel modeling is critical for the design and performance evaluation of visible light communication (VLC). Although a considerable amount of research has focused on indoor VLC systems using singleelement photodiodes, there remains a need for channel modeling of VLC systems for outdoor mobile environments. In this paper, we describe and provide results for modeling image sensor based VLC for automotive applications. In particular, we examine the channel model for mobile movements in the image plane as well as channel decay according to the distance between the transmitter and the receiver. Optical flow measurements were conducted for three VLC situations for automotive use: infrastructure to vehicle VLC (I2V-VLC); vehicle to infrastructure VLC (V2I- VLC); and vehicle to vehicle VLC (V2V-VLC). We describe vehicle motion by optical flow with subpixel accuracy using phase-only correlation (POC) analysis and show that a single-pinhole camera model successfully describes these three VLC cases. In addition, the luminance of the central pixel from the projected LED area versus the distance between the LED and the camera was measured. Our key findings are twofold. First, a single-pinhole camera model can be applied to vehicle motion modeling of a I2V-VLC, V2I-VLC, and V2V-VLC. Second, the DC gain at a pixel remains constant as long as the projected image of the transmitter LED occupies several pixels. In other words, if we choose a pixel with highest luminance among the projected image of transmitter LED, the value remains constant, and the signal-to-noise ratio does not change according to the distance.

  • Layered Transmission of Space-Time Coded Signals for Image-Sensor-Based Visible Light Communications

    • Katsunori Ebihara, Koji Kamakura, Takaya Yamazato
    • Journal of Lightwave Technology, Vol.33, No.20, pp.4193 - 4206
    • Aug. 2015
    • https://doi.org/10.1109/JLT.2015.2470091
    • This paper demonstrates the feasibility of layered space-time coding (STC) in an outdoor image-sensor-based (ISbased) visible light communication (VLC) system. We examined that for low-resolution IS-based VLC channel where intensity-modulated signals from two different light emitting diodes (LEDs) are detected by one pixel of an IS, STC allows us to decouple them; thus, succeeding to receive them with no errors. Consequently, STC offers extended transmission distance to pixel-resolution-limited IS-based VLC links. In the layered STC presented in this paper, additional bit streams are laid on the 2n × 2n LED array for increasing the transmission rate per symbol duration for the case where the pixel resolution is improved. A prototype of a threelayered STC is built with an 8 × 8 LED array, where each of the LEDs is modulated at 1 kb/s and a high-speed camera with IS operating at 1000 fps. Our experimental results validate that the two additional bit streams (layer-2 and -3), aligned in the layer-1 STC matrix pair, are extracted with no errors when the receiver comes within 155 and 55 m, respectively, from the LED array, without decreasing 210 m of the transmission distance of layer-1 bit stream.

  • [Invited Talk] Visible Light Communications and V2X

    • T. Yamazato
    • Photonics Technology Forum, The 1st Study Group on Next Generation Optical Devices in 2015, Osaka Science & Technology Center, Japan
    • Jul. 2015

  • [Invited Talk] Image Sensor Based Visible Light Communication for V2X

  • Signal Demodulation Method from Degraded Image for Visible Light Communication Using LED and High-Speed Camera

    • Y. Ohira, S. Arai, T. Yendo, T. Yamazato, H. Okada, T. Fujii, K. Kamakura
    • IEICE Transactions on Communications, vol.J98-B, no.7, pp.696-706
    • Jul. 2015

  • LED acquisition methods for image-sensor-based visible light communication

    • Shintaro Arai, Takaya Yamazato, Hiraku Okada, Toshiaki Fujii, Tomohiro Yendo
    • Opto-Electronics and Communications Conference (OECC), pp.1-3
    • Jun. 2015
    • https://doi.org/10.1109/OECC.2015.7340210
    • This invited paper focuses on a high-speed image sensor as a visible light communication (VLC) reception device to develop the intelligent transport systems (ITS) application using VLC technique. We refer to the VLC using a high-speed image sensor as image-sensor-based VLC. A major advantage of the image sensor is the ability to spatially separate multiple sources. Based on this ability, we proposed several methods for the image-sensor-based VLC in our previous researches. Especially, we focused on unique characteristics of the image sensor and proposed the hierarchical coding and the overlay coding to improve the data reception performance. However, to perform the image-sensor-based VLC in an actual environment, the receiver has to acquire the VLC transmitter from captured images before recovering data. Namely, the VLC transmitter acquisition and tracking are critical problem. the image-sensor-based VLC technique. This invited paper introduces two proposed methods to acquire the VLC transmitter from images captured by the image sensor.

  • Layered space-time coding using LED array for image-sensor-based visible light communications

    • Katsunori Ebihara, Koji Kamakura, Takaya Yamazato
    • IEEE International Conference on Communications (ICC), pp.5048-5053, London, UK
    • Jun. 2015
    • https://doi.org/10.1109/ICC.2015.7249124
    • This paper demonstrates the feasibility of layered space-time coding (STC) in an outdoor image-sensor-based (IS-based) visible light communication (VLC) system. We examined that for low-resolution IS-based VLC channel where intensity modulated signals from two different light emitting diodes (LEDs) are detected at one pixel on the image plane, STC allows to decouple them, thus receiving data with no errors. Consequently, STC offers extending the transmission distance. In the layered STC presented here, additional bit streams are aligned in the 2n×2n LED array for increasing the transmission rate per symbol duration for the case where the spatial resolution is improved. A prototype of three layered STC is built with an 8×8LED array, where each of the LEDs is modulated at 1 kbps and a high-speed camera with IS operating at 1000 fps. Our experimental results validate that additional bit streams (layer-2 and -3), aligned in the layer-1 STC matrix pair, are extracted with no errors when the receiver comes within 155m and 55 m, respectively, from the LED array, without decreasing 210m of the transmission distance of layer-1 bit stream.

  • Blue Color Difference Modulation for Digital Signage Visible Light Communication Systems

    • S. Sato, H. Okada, K. Kobayashi, T. Yamazato, M. Katayama
    • IEICE Technical Report, ASN2015-1, pp.1-6, Tokyo, Japan
    • May 2015
    • Digital signage, which is advertising media by liquid crystal display (LCD), is expanded into many scenes. The digital signage can use digital techniques, and has a possibility of a lot of applications. As an application, it is desired to realize, wireless communications between the digital signage and viewers. In this study, we focus on the image-sensor-base visible light communication (ISVLC). ISVLC needs only an image sensor (IS), which is prevalent equipment of smart phone, and LCD since it can solve the cost problem of introduction of wireless communications. In ISVLC, the digital signage displays information signal on LCD. Therefore there is an issue, in which the information signal embedding in signage images decreases the quality of signage images. In this study, we propose blue color difference modulation, which makes imperceptible signal. By the construction of ISVLC system between digital signage and IS, we show the effect of the proposal modulation in real environment.

  • [Invited Lecture] ITS and its perspective on wireless communications

    • T. Yamazato
    • IEICE Technical Report, vol. 115, no. 2, RCS2015-6, pp. 31-31, , Yufuin, Yufugoukan
    • Apr. 2015
    • Automated driving system becomes a hot topic and the R&D in US, EU, and Japan focuses near future market deployment of the system. For example, Council for Science, Technology and Innovation of Cabinet Office, Japanese Government initiated a research project on automated driving system under “Cross Ministerial Strategic Innovation Promotion Program” (SIP). They expect to launch a combined function of automated driving, in 2017 and limited self-driving automation in the first half of 2020s. Example systems of the combined function of automated driving are tracking/following system, steering for collision avoidance, automated driving in multiple lanes, and the limited self-driving automation is automated merging, etc. Needless to say, one of essential elements of the automated driving system is wireless communications, infrastructure-to-vehicle (I2V), vehicle-to-vehicle (V2V), and vehicle-to-pedestrian (V2P) communications. In this talk, I will introduce some of the on-going R&D activities of automated driving system and try to mash-up the trends from my perspective on wireless communications.

  • Noise-Enhanced Subthreshold Signal Reception by a Stochastic Resonance Receiver using a Non-Dynamical Device

    • H. Tanaka, K. Chiga, T. Yamazato, Y. Tadokoro, S. Arai
    • Nonlinear Theory and Its Applications, IEICE, vol.6, no.2, pp.303-312
    • Apr. 2015
    • https://doi.org/10.1587/nolta.6.303
    • Stochastic resonance (SR) is an interesting phenomenon in that noise enhances system response. Despite attractive phenomenon of SR that noise enhances system response, enhancement of the weak signal below device sensitivity, and few researchers have addressed the SR effect in communication systems. This paper discusses the SR effect in communication systems. We focus on the problem in which communication cannot be established when the received signal strength is below receiver sensitivity. The purpose of this study is to evaluate the bit error rate (BER) performance of the SR receiver and reveal the SR effect in communication systems. We propose an analysis method for the SR receiver using a non-dynamical device that exhibits SR effect. The numerical results show that the SR effect can improve the BER compared to a system without SR. The contribution of the paper is two folds: The first contribution of our present study is that the BER of the SR receiver using a non-dynamical device can analytically be derived. The second contribution of our study is that the number of samples per symbol, the received signal amplitude, and the receiver sensitivity are three important parameters. We further derive the maximum performance gain by the SR system. Although our focus is on primary communication systems; however, our findings can be applied to other systems.

  • Performance Evaluation of Stochastic Resonance Receiver in BPSK and OOK Modulations

    • Hiroya TANAKA, Keita CHIGA, Takaya YAMAZATO, Yukihiro TADOKORO, Shintaro ARAI
    • IEICE General Conference, A-2-18, p.49, Shiga, JAPAN
    • Mar. 2015

  • Preliminary Study on NLOS V2V Visible Light Communication Using Retroreflective Traffic Control Devices

    • T. Takada, T. Yamazato, H. Okada, T. Fujii, S. Arai, T. Yendo, K. Kamakura
    • IEICE General Conference, A-17-16, p.249, Shiga, Japan
    • Mar. 2015

  • Detection method of the LED headlight and LED headlight identification method considering occlusion for V2I-VLC

    • Y. Kawai,T. Yamazato, H. Okada, T. Fujii, T. Yendo, S. Arai, K. Kamakura
    • IEICE Technical Report, Kyoto,Japan
    • Mar. 2015
    • In this paper, we focus on the image sensor based vehicle-to-infrastructure visible light communication (V2I-VLC) for Intelligent Transport System (ITS). In this communication system, individual detection and tracking of multiple transmitters is critical. In other words, it is identification of the LED headlight between the frames. However, when occlusion occurs due to vehicle’s movement, it becomes NLOS. I have the problem that it comes to have difficulty in identification of LED headlight then. Therefore, in this paper, we propose LED identification method that predict the position of the LED headlight on the image sensor when occlusion occurs. I install a high-speed camera in the roadside and test it and evaluate proposal technique. As a result, false negative rate is 1.38%,false positive rate is 3.26%. I confirmed that I could perform LED identification even if occlusion occurred.

  • Alamouti-Type Space Time Coding for Visible Light Communication Based on Direct Detection Using Image Sensor

    • Y. Amano, K. Kamakura, T. Yamazato
    • IEICE Transactions on Communications, vol.J98-B, no.3, pp.307-318
    • Mar. 2015
    • This paper proposes Alamouti-type space time (ST) coding to visible light communication (VLC) using light emitting diodes (LEDs) and image sensor-based direct detection with a high-speed camera. Although multiple LEDs of an array are used as transmitters to communicate to individual pixel elements of an image sensor which act as multiple receive elements, the received signal is essentially the image of the transmitting element, whose size in pixel reduces with distance. When the receiver captures the LED array at a distance where images of two neighboring LEDs in the array are not separated at the image plane, such distortion depreciates the symbol decision quality. Our proposed scheme aims at expanding the communication range limited by the pixel resolution of image sensor. Our implemented prototype demonstrates that ST coding is feasible to achieve 48-meter error-free transmission range while the repetition transmission achieves 26-meter error-free range.

  • Investigation on Relationship Between Communication Distance and Receiving Characteristics in Image-Sensor-Based Visible Light Communication

    • Y. Ohira, E. Souke, S. Arai, T. Yamazato, T. Yendo, H. Okada, T. Fujii and K. Kamakura
    • RISP International Workshop on Nonlinear Circuits, Communications and Signal Processing (NCSP), pp.274-277, Kuala Lumpur, Malaysia
    • Feb. 2015
    • The present paper considers receiving characteristics of an image-sensor-based visible light communication (VLC) using　an LED and a high-speed-image sensor. In general, a size of LED on an image decreases with increasing a communication distance. In this case, the receiver is difficult to recover data because the intensity of brightness of LED (i.e., luminance) cannot be enough recognized from the image. However,　the previous studies about the image-sensor-based VLC have not enough discussed the communication distance and the recognition of LED on the image, i.e., the receiving characteristics. We focus on the communication distance and investigates the relationship between the distance and the receiving characteristics in the image-sensor-based VLC.

    • T. Yamazato
    • Visible Light Communication Association, Key University, Japan
    • Feb. 2015

  • Visible light communication

    • Shlomi Arnon, Jae Kyun Kwon, Sang Hyun Lee, Wen-De Zhong, Zixiong Wang, Mohsen Kavehrad, Weizhi Zhang, Zhengyuan Xu, Chen Gong, Bo Bai, Kang Tae-Gyu, Klaus-Dieter Langer, Shinichiro Haruyama, Takaya Yamazato
    • Cambridge University Press
    • Feb. 2015

  • Outdoor Road-to-Vehicle Visible Light Communication Using On-Vehicle High-Speed Camera

    • C. Premachandra, T. Yendo, M. P. Tehrani, T. Yamazato, H. Okada, T. Fujii, M. Tanimoto
    • International Journal of Intelligent Transportation Systems Research, vol.13, no.1, pp.28-36
    • Jan. 2015
    • https://doi.org/10.1007/s13177-014-0079-y
    • We propose a road-to-vehicle Visible Light Communication (VLC) system for ITS. Here, the communication between road and a vehicle is approached using an LED array as a transmitter and an on-vehicle high-speed camera as a receiver. Modulation is conducted at the transmitter by blinking LEDs in high frequency and demodulation is conducted at the receiver by capturing the blinking patterns of the transmitter, by processing the high-speed camera images captured in high frame rate. This paper proposes an effective image processing method for capturing those blinking patterns. Out door communication experiments of the proposed VLC system are also present.

  • Investigation on Relationship between Communication Distance and Receiving Characteristic in Visible Light Communication Using LED and High-Speed Camera

    • E. Souke, Y. Ohira, S. Arai, T. Yamazato, T. Yendo, H. Okada, T. Fujii and K. Kamakura
    • Proceedings of 2014 IEEE Workshop on Nonlinear Circuit Networks (NCN'14), pp. 93-94, Tokushima, Japan
    • Dec. 2014
    • The present paper considers an optical spatial channel in visible light communication (VLC) using LED and a high-speed camera. In general, the optical spatial channel affects the communication performance. However, the previous studies have not enough discussed the channel for VLC. This study focuses on the communication distance, which is one of channel parameters, and investigates the relationship between the distance and a receiving characteristic in the VLC.

  • Motion Modeling of Mobile Transmitter for Image Sensor Based I2V-VLC, V2I-VLC, and V2V-VLC

    • M. Kinoshita, T. Yamazato, H, Okada, T. Fujii, S. Arai, T. Yendo, K. Kamakura
    • IEEE GLOBECOM Workshop on Optical Wireless Communications, pp.535-540, Austin, USA
    • Dec. 2014
    • https://doi.org/10.1109/GLOCOMW.2014.7063473
    • Visible light communication (VLC) using light-emitting diodes (LEDs) is drawing much attention. There are two types of VLC reception devices, a photodiode and an image sensor. VLC using image sensor is called image sensor based VLC. As the receiver only uses the image sensor pixels that sense LED transmission sources and discards other pixels, including those sensing noise sources, image sensor based VLC is an attractive solution for outdoor mobile applications. However, little evidence is available for channel modeling of image sensor based VLC in mobile outdoor environments, especially for motion modeling of VLC transmitter. In this paper, we propose a motion model of VLC transmitter. In particular, we consider three cases; infrastructure-to-vehicle VLC (I2V-VLC), vehicle-to-infrastructure VLC (V2I-VLC), and vehicle-to-vehicle VLC (V2V-VLC). As a result, we show that the motion model of the VLC transmitter on the captured image for the three aforementioned situations (i.e., I2V-VLC, V2I-VLC, and V2V-VLC) can be expressed in the identical pinhole camera model.

  • Cooperative Diversity via Simple Relaying with Quasi-Orthogonal Space-Time Block Code Takaya YAMAZATO

    • Tomoya YAMAOKA, Yoshitaka HARA, Kazuaki ISHIOKA Teruyuki HARA and
    • IEICE Transactions on Communications, vol.J97-B, no.12, pp.1213-1223
    • Dec. 2014
    • We have been proposed cooperative diversity receiving ABBA code as cooperative diversity via simple relaying with QOSTBC(Quasi-Orthogonal Space-Time Block Code). This scheme offers coding gain by permutation of space-time coded signal sequences in the relay nodes. So the relay nodes don't need carrier recovery and complete the signal process in the intermediate frequency band. In this paper, we discuss two improved scheme with various channel model. These schemes improve the previous scheme without loss of the merit in its relay process. Moreover, we sum up cooperative diversity via simple relaying with QOSTBC to discuss these schemes with various channel model. We evaluate effect of these scheme in terms of signal matrixes and simulate bit error rate of the prposed and improved scheme with with various channel model, respectively.

  • Channel Fluctuation Measurement for Image Sensor Based I2V-VLC, V2I-VLC, and V2V-VLC

    • M. Kinoshita, T. Yamazato, H, Okada, T. Fujii, S. Arai, T. Yendo, K. Kamakura
    • IEEE Asia Pacific Conferece on Circuits and Systems (APCCAS), pp.332-335, Okinawa, Japan
    • Nov. 2014
    • https://doi.org/10.1109/APCCAS.2014.7032787
    • In image sensor based VLC, transmitter acquisition and tracking are critical issue. However, the fluctuation of the VLC transmitter in the image plane caused by vehicle movement, complicates correct data reception. Therefore, in this paper, we present results of channel fluctuation measurements for infrastructure-to-vehicle VLC (I2V-VLC), vehicle-to-infrastructure VLC (V2I-VLC), and vehicle-to-vehicle VLC (V2V-VLC). We analyze channel fluctuation in terms of optical flow from measured data.

  • BER Characteristic of Optical-OFDM using OCI

    • Y. Goto, I. Takai, T. Yamazato, H. Okada, T. Fujii, S. Kawahito, S. Arai, T. Yendo, K. Kamakura
    • IEEE Asia Pacific Conferece on Circuits and Systems (APCCAS), pp.328-331, Okinawa, Japan
    • Nov. 2014
    • https://doi.org/10.1109/APCCAS.2014.7032786
    • Light-emitting diode (LED) transmitters based optical wireless communication (OWC) systems offer the potential for new generation communication systems. Particularly, an image sensor based OWC systems consist of the LED transmitters and camera receivers are expected to contribute to intelligent transport system (ITS) for driving supports. For high achievable data rates, orthogonal frequency division multiplexing (OFDM) based OWC systems have attracted a great deal of attention. Despite attractive features of optical OFDM, only few attempts have so far been made to adopt it as a modulation scheme of an image sensor based OWC system. There remains a need for an evaluation of adopting an optical OFDM to the image sensor based OWC systems. Another important issue needs to be addressed is the performance degradation due to a frequency response of an actual image sensor device, especially a signal attenuation loss in higher frequency. In addition to such loss, a narrow band noise generated by its circuits also degrades the performance. The purpose of this paper is to investigate BER performances of the optical-OFDM using an actual image sensor device, the optical communication image sensor (OCI). From simulation results, it is found that the frequency response and the narrowband noise at 12MHz of the OCI lead to the significant reduction of BER performances. Additionally, the results shows that ACO-OFDM shows a little better performance compared to DCO-OFDM with the same bandwidth efficiency.

  • Lighting with Data

    • T. Yamazato
    • Journal of the Association of Radio Engineers of Japan, vol. 301, No. 11, pp. 40-43
    • Nov. 2014

  • A Novel Study on Coded Modulation with Triangular Costellation

    • Tomoya YAMAOKA, Teruyuki HARA, Akihiro OKAZAKI and Takaya YAMAZATO
    • IEICE Technical Report, RCS2014-176, pp.111-116, Keio Univ
    • Oct. 2014

  • A Transmit Diversity with a Simple Transmitter

    • Tomoya YAMAOKA, Teruyuki HARA, Akihiro OKAZAKI and Takaya YAMAZATO
    • IEICE Technical Report, RCS2014-177, pp.117-122, Keio Univ.
    • Oct. 2014

  • ITS Visible Light Communication using High-Speed Image Sensor

    • Takaya Yamazato
    • The 133 Microoptics Meeting, Optical Society of Japan/The Japan Society of Applied Physics, Japan Women's University
    • Oct. 2014
    • This paper presents the visible light communication using image sensor and its application to intelligent transport systems (ITS). As an example, image-sensor based VLC for automotive application that is currently carried out by the author is also introduced. The paper is a continuation of the paper by Prof. Matsumoto, Evaluation of optical wireless communication, and by Prof. Haruyama, Recent trends of visible light communication, appeared on 2014 March issue of Microoptics News.

  • Connected Vehicle and Security

    • T. Yamazato
    • , Nagoya University
    • Sep. 2014

  • A Study on Signal Demodulation Method Based on Blurred Camera Image in Visible Light Communication Using LED Array and High-Speed Camera

    • Y. Ohira, S. Arai, T. Yendo, T. Yamazato, H. Okada, T. Fujii, K. Kamakura
    • Enginnering Sciences Society Conference of IEICE, A-5-1, p.83, Tokushima
    • Sep. 2014

  • A Study on Influence of Communication Distance in Visible Light Communication Using LED and High-Speed Camera

    • E. Souke, Y. Ohira, S. Arai, T. Yamazato, T. Yendo, H. Okada, T. Fujii, K. Kamakura
    • Enginnering Sciences Society Conference of IEICE, A-5-2, p.84, Tokushima
    • Sep. 2014

  • Channel Fluctuation Measurement for I2V-VLC, V2I-VLC, and V2V-VLC Using Image Sensor

    • M. Kinoshita, T. Yamazato, H, Okada, T. Fujii, S. Arai, T. Yendo, K. Kamakura
    • IEICE Technical Report, ITS2014-18, pp.77-81
    • Sep. 2014
    • In image sensor based VLC for automotive applications, transmitter acquisition and tracking are critical. However, the uctuation of the VLC transmitter in the image plane caused by vehicle movement, complicates correct data reception. Therefore, in this paper, we present results of channel uctuation measurements for automotive applications. Especially, we examined the channel uctuation based on mobile movements in the image plane detected by phase only correlation (POC) in the subpixel accuracy.

  • An Analysis Method of a Stochastic Resonance Receiver using a Schmitt Trigger

    • H. Tanaka, K. Chiga, T. Yamazato, Y. Tadokoro, and S. Arai
    • International Symposium on Nonlinear Theory and its Application (NOLTA), pp.193-196, Luzern, Switzerland
    • Sep. 2014
    • Stochastic resonance (SR) enhances system responses by increasing noise. By applying SR to a receiver, a subthreshold signal not receivable by a conventional linear receiver could be received. Previously, we proposed an analysis method of the SR receiver using a comparator, and evaluated its bit error rate performance. The comparator is known as a simple non-dynamical system exhibiting SR. However, a dynamical system can have better performance since it has a memory effect. In this sense, we propose an analysis method of the SR receiver using a Schmitt trigger known as a simple dynamical system, and evaluate its bit error rate performance. A performance comparison of the comparator and the Schmitt trigger is also shown.

  • An influence of Noise Bandwidth on an application of Stochastic Resonance to Radio Communication

    • K. Chiga, H. Tanaka, T. Yamazato, Y. Tadokoro, S. Arai
    • Enginnering Sciences Society Conference of IEICE, A-2-7, p.28
    • Sep. 2014

  • SNR Improvement by Stochastic Resonance Receiver for Subthreshold Signal in Radio Frequency

    • K. Chiga, H. Tanaka, T. Yamazato, Y. Tadokoro, S. Arai
    • International Symposium on Nonlinear Theory and its Application (NOLTA), Luzern, Switzerland
    • Sep. 2014
    • Stochastic Resonance (SR) is well known as a phenomenon in which the weak signal in a nonlinear system can be detected by added noise. We consider the application of SR phenomenon to a wireless communication system. The receiver using SR phenomenon can detect the subthreshold signal which is not detectable by the conventional receiver. The effect of SR receiver has been verified, but it has never been verified in radio frequency which is used by a wireless system. In this paper, we consider the implementation of SR System for Radio Frequency and evaluate its performance of Signal to Noise Ratio (SNR).

  • Image Sensor Based Visible Light Communication and Its Application to Pose, Position, and Range Estimations

    • T. Yamazato, S. Haruyama
    • IEICE Transactions on Communications, vol.E97-B, no.9, pp.1759-1765
    • Sep. 2014
    • https://doi.org/10.1587/transcom.E97.B.1759
    • This study introduces an image sensor based visible light communication (VLC) and its application to pose, position, and range estimations. There are two types of visible-light receiver: a photodiode and an image sensor. A photodiode is usually used as a reception device of VLC, and an image sensor consisting of a large number of pixels can also be used as a VLC reception device. A photodiode detects the signal intensity of incoming light, while an image sensor not only detects the incoming signal intensity but also an accurate angle of arrival of light emitted from a visible light transmitter such as a white LED light. After angles of arrival of light are detected by an image sensor, positioning and data reception can be performed. The ability of an image sensor to detect an accurate angle of arrival will provide attractive applications of VLC such as pose, position calculation, and range estimation. Furthermore, because the image sensor has the ability to spatially separate sources, outdoor positioning even with strong sunlight is possible by discarding the associated pixels of noise sources.

  • Performance evaluation of stochastic resonance receiver using Schmitt trigger

    • Hiroya Tanaka, Keita Chiga, Takaya Yamazato, Yukihiro Tadokoro, Shintaro Arai
    • IEICE Complex Communication Sciences, Hokkaido, Japan
    • Aug. 2014

  • Optical Signal Detection by Stochastic Resonance Receiver Using Schmitt Trigger for LED Visible Light Communications

    • S. Arai, T. Yamazato, Y. Tadokoro
    • The 27th Workshop on Circuits and Systems, pp.116-120, Awaji, Japan
    • Aug. 2014

  • Distance Estimation Scheme for Integrated V2I-VLC for driving vehicle

    • A. Ohmura, T. Yamazato, H. Okada, T. Fujii, T. Yendo, S. Arai, K. Kamakura
    • IEICE Transaction on Communications, vol.J97-B, no.8, pp.695-696
    • Aug. 2014
    • A distance estimation scheme for vehicle to infrastructure using visible light communication is discussed. As vehicle vibration severely affect the distance estimation performance, we introduce a new LED lighting patterns for the distance estimation. As the result, we acheive nearly the same distance estimation performance for the case of non-driving.

  • A New LED Array Acquisition Method Focusing on Time-gradient and Space-gradient Values for Road to Vehicle Visible Light Communication

    • S.Usui, T.Yamazato, H.Okada, T.Fujii, K.Takahashi, T.Yendo, S.Arai
    • IEICE Transactions on Communications, vol.J97-B, no.7, pp.536-545
    • Jul. 2014
    • This paper proposes a new LED acquisition method for visible light communication systems using an LED array as a transmitter and a high-speed camera as a receiver for road-to-vehicle communications. The first process of the receiver is to search the target LED array from the captured image (LED array acquisition). This paper focuses on the time-gradient and the space-gradient values in the captured images, and draws both gradient value as a scatter diagram. This scatter diagram enables us to regard the LED acquisition as discriminant analysis. From the above, this paper proposes a new acquisition method and confirms its effectiveness by the experiment in a driving situation.

  • Image-sensor-based Visible Light Communication for Automotive Applications

    • T. Yamazato, I. Takai, H. Okada, T. Fujii, T. Yendo, S. Arai, M. Andoh, T. Harada, K. Yasutomi, K. Kagawa, S. Kawahito
    • IEEE Communications Magazine, vol.52, no.7, pp.88-97
    • Jul. 2014
    • https://doi.org/10.1109/MCOM.2014.6852088
    • The present article introduces VLC for automotive applications using an image sensor. In particular, V2I-VLC and V2V-VLC are presented. While previous studies have documented the effectiveness of V2I and V2V communication using radio technology in terms of improving automotive safety, in the present article, we identify characteristics unique to image-sensor-based VLC as compared to radio wave technology. The two primary advantages of a VLC system are its line-of-sight feature and an image sensor that not only provides VLC functions, but also the potential vehicle safety applications made possible by image and video processing. Herein, we present two ongoing image-sensor-based V2I-VLC and V2VVLC projects. In the first, a transmitter using an LED array (which is assumed to be an LED traffic light) and a receiver using a high-framerate CMOS image sensor camera is introduced as a potential V2I-VLC system. For this system, real-time transmission of the audio signal has been confirmed through a field trial. In the second project, we introduce a newly developed CMOS image sensor capable of receiving highspeed optical signals and demonstrate its effectiveness through a V2V communication field trial. In experiments, due to the high-speed signal reception capability of the camera receiver using the developed image sensor, a data transmission rate of 10 Mb/s has been achieved, and image (320 × 240, color) reception has been confirmed together with simultaneous reception of various internal vehicle data, such as vehicle ID and speed.

  • M-ary Modulation Scheme Based on Separation of Deterministic Chaotic Dynamics for Noncoherent Chaos-Based Communications

    • S. Arai, Y. Nishio, T. Yamazato
    • NOLTA, IEICE, vol. 5, no.2, pp.210-221
    • Apr. 2014
    • https://doi.org/10.1587/nolta.5.210
    • The present paper proposes a novel M-ary modulation scheme based on separation and reconstruction of deterministic chaotic dynamics for noncoherent chaos-based communications. The M-ary modulation scheme can transmit b-bit data at a time by using M=2b distinct sequences. In order to generate M distinct sequences and recover b-bit data, the proposed system separates the chaotic dynamics having the chaotic sequence by using M interleavers, and reconstructs the original sequence based on the chaotic dynamics from the separated one by using M deinterleavers. In advance, each data symbol among M symbols is allocated to each interleaver-deinterleaver pair. The transmitter selects an interleaver corresponding to a data symbol and separates the order of samples of the chaotic sequence using the selected interleaver. The receiver feeds the received sequence into all M deinterleavers and outputs M reconstructed sequences. The proposed system can reconstruct the original chaotic sequence only when the correct deinterleaver, which becomes paired with the interleaver, is selected. Therefore, the receiver can recover b-bit data by analyzing the chaotic dynamics of each reconstructed sequence. We carry out computer simulations and evaluate performances of the proposed M-ary modulation scheme.

  • Derivation of the Max of Sensitivity Improvement Rate of Stochastic Resonance Receiver for Subthreshold Bi-Polar Pulse

    • H. Tanaka, K. Chiga, T. Yamazato, Y. Tadokoro, S. Arai
    • IEICE General Conference, A-2-15, p.40, Niigata
    • Mar. 2014

  • A Study on Adaptation of Optical OFDM to Visible Light Communication using Optical Communication Imaging Sensor

    • Y.Goto,T.Yamazato,H.Okada,T.Fujii,I.Takai,S.Kawahito,T.Yendo,S.Arai,K.Kamakura
    • IEICE General Conference, B-10-20, p.388, Niigata,Japan
    • Mar. 2014

  • Application of Optical OFDM Method to Inter-Vehicle Visible Light Communications Using Optical Communication Image Sensor

    • Y. Goto
    • IEICE Tokai Branch Graduation Research Conference, Mie, Japan
    • Mar. 2014

  • IEICE Knowledge Discovery（I-Scover）

    • Takaya Yamazato, Yasubumi Chimura, Fumihito Nishino, Satoshi Ikada, Toyokazu Akiyama, Miyuki Nakano, Yuji Inoue
    • The Journal of IEICE Vol.97 No.3, pp.240-246
    • Mar. 2014
    • I-Scover, officially known as IEICE Knowledge Discovery, is a new reference search engine developed by the Institute of Electronics, Information and Communication Engineers (IEICE). It is not just a system for cross-searching articles published by IEICE. It also aims to maximize significance of the IEICE articles by organically linking related information with the articles, making them accessible on the Internet for many users. With I-Scover, berry-picking exploratory search, which has been difficult with conventional reference search engines, is possible. In this article, we will describe I-Scover in terms of its developmental background and aim, introduce its various features and characteristics, and discuss the promotional activity plan to spread I-Scover, as well as its future development plans.

  • Preliminary Study on LED VLC with Simple SR Receiver Using Schmitt Trigger

    • H. Yokota, S. Arai, T. Yamazato and Y. Tadokoro
    • RISP International Workshop on Nonlinear Circuits, Communications and Signal Processing (NCSP), pp. 61-64., Hawaii, USA
    • Feb. 2014
    • The present paper focuses on an application of Stochastic Resonance (SR) for an LED visible light communication (LED-VLC) receiver. SR is well-known as a phenomenon, which enhances the response by additive noise. We consider that a weak optical signal, which is distorted due to an influence of ambient light noise, can be detected by using SR system. This study makes a simple SR circuit for LED VLC and performs its circuit experiment for exploring the possibility and availability of the LED-VLC receiver using SR system.

  • LED Array Acquisition Method Based on Time-gradient and Space-gradient Values for Road to Vehicle Visible Light Communication Using High-Speed Camera

    • S.Usui, T.Yamazato, H.Okada, T.Fujii, K.Takahashi, T.Yendo, S.Arai
    • IEICE Technical Report, ITS2013-39, pp.55-60, Sapporo, Japan
    • Feb. 2014
    • This paper focuses on road-to-vehicle visible light communication using an LED array as a transmitter and a high-speed camera as a receiver. In this communication, LED array acquisition has a significant role. The spatio-temporal images are essential for a robust LED array acquisition because the time-gradient and space-gradient values can be an important feature value of an LED array. In this paper, we focus on the time-gradient and the space-gradient values in the captured images and draws both gradient value as a scatter diagram. This scatter diagram enables us to regard the LED acquisition as discriminant analysis. From the above, this paper proposes a new acquisition method and confirms its effectiveness by the experiment in a driving situation.

  • Distance Estimation Scheme for Integrated V2I-VLC in Driving Vehicle

    • A. Ohmura, T. Yamazato, H. Okada, T. Fujii, T. Yendo, S. Arai, K. Kamakura
    • IEICE Technical Report, ITS2013-38, pp.49-54, Sapporo
    • Feb. 2014
    • This paper discusses an issue of estimating the distance between an on-vehicle transmitter and a roadside equipment for vehicular-to-infrastructure visible light communication (V2I-VLC). The system integrates the VLC as well as distance estimation functions. In this paper, we discuss a technique overcoming a vehicle vibration by using a particular transmitting LED pattern and the sub-pixel estimation using the phase-only correlation. As the results, we achieve less than 0.5m errors for the distance up to 60 m by the proposed system.

  • Alamouti-Type Coding for Visible Light Communication Based on Direct Detection Using Image Sensor

    • Y. Amano, K. Kamakura, T. Yamazato
    • IEICE Technical Report, ITS2013-37, pp.43-48, Sapporo
    • Feb. 2014
    • This paper proposes Alamouti-type space time (ST) coding to visible light communication (VLC) using light emitting diodes (LEDs) and image sensor with a high-speed camera. Although multiple LEDs of an array are used as transmitters, the received signal is essentially the image of the transmitting element, whose size in pixel reduces with distance. When the receiver captures the LED array at a distance where images of two neighboring LEDs in the array are not separated at the image plane, such distortion depreciates the symbol decision quality. Our proposed scheme aims at expanding the communication range limited by the pixel resolution of image sensor. Our implemented prototype demonstrates that ST coding is feasible to achieve 48,m error-free transmission range while the repetition transmission achieves 26,m error-free range.

  • Driver Assistant System using Visible Light Communications

    • Takaya Yamazato
    • IEICE Technical Report, vol. 113, no. 390, CS2013-94, pp. 57-63, Hajijo-jima Ohgagou Kouminkan
    • Jan. 2014
    • We are conducting a study on viheicle-infrastractuctre cooperateive systems using visible light commu- nications for driving safty applications. This paper introduces our studies on such VLC supported ITS systems using a high-speed image sensor as a VLC receiver equiped on a vehicle. The image sensors are now adopted for a lane keeping, an obstables recognition, a range estimation and many other applications. If we could add a VLC function to those safety applications, then a driver can recognize his environment visually and also he recognize his environment by signals transmitted through an LED traffic lights, LED tail lights, LED signage board, etc in a form of VLC signals. Together, it can contribute to more extensive safety driving.

  • Multiple LED Arrays Acquisition for Image-Sensor-Based I2V-VLC Using Block Matching

    • S. Arai, Y. Shiraki, T. Yamazato, H. Okada, T. Fujii, T. Yendo
    • IEEE Consumer Communications and Networking Conference (CCNC), pp.605-610, Las Vegas, USA
    • Jan. 2014
    • https://doi.org/10.1109/CCNC.2014.6866634
    • The present paper proposes a novel multiple-LED-arrays acquisition for an infrastructure-to-vehicle visible light communication (I2V-VLC) using LED arrays (transmitter) and an in-vehicle high-speed image sensor (receiver). In order to achieve a robust detection of LED arrays, we employ the block matching algorithm, which is a way of finding a corresponding position between two successive frames. The proposed method divides a captured image into a number of small domains (blocks) and determines if the LED array is present or absent using the block matching. We perform I2V-VLC experiments with multiple-LED arrays and evaluate the acquisition capability of the proposed method.

  • Application of visible light communication to LED traffic light

    • T. Yamazato
    • Journal of Light & Visual Environment (JLVE), vol.98, no.1, pp.17-20
    • Jan. 2014
    • Visible light communications (VLC) is the latest optical wireless communications technologies that uses low-power light emitting diodes, or LEDs, not only to provide light but also to broadcast data. LEDs are extremely energy-efficient and predicted to become widespread in general lighting application. Because LED is a solid-state lighting device, it can be modulated at high-speed compared with other lighting sources. VLC uses LEDs, which send data by flashing light at speeds undetectable to the human eye.Widespread use of LEDs in traffic applications and growing interest in Intelligent Transport System (ITS) presents an opportunity for VLC. Data transmission using LED traffic lights, LED road illumination, and LED brake lights are typical application. In this paper, an on-going research, road-to-vehicle visible light communication, will be introduced. The LED array, assumed to be an LED traffic light, is used as a transmitter and it sends data to a moving vehicle. By providing data together with a traffic signal that is visible to a driver, a safety driving support can be realized. Finally, the author suggests readers a glimpse of wealth on “dual use of LEDs” and concludes the paper.

  • A Study on Simple LED-VLC Flashlight Transmitter for Disaster Situation

    • K. Miyazaki, Y. Ohira, S. Arai, T. Yendo, T. Yamazato, H. Okada, T. Fujii
    • Proceedings of 2013 IEEE Workshop on Nonlinear Circuit Networks (NCN'13), Tokushima, Japan
    • Dec. 2013
    • This study focuses on the visible light communication (VLC) system using LED and a high-speed camera in order to develop robust and adaptable communication systems in the disaster situation, such as an earthquake. Especially, we consider utilization of a flashlight, which is often used in disaster situations, as a transmitter. We develop a simple LED-VLC transmitter using a flashlight and perform a communication experiment using it.

  • Accuracy Improvement by Phase Only Correlation for Distance Estimation Scheme for Visible Light Communications Using an LED Array and a High-speed Camera

    • A. Ohmura, T. Yamazato, H. Okada, T. Fujii, T. Yendo, S. Arai
    • IEICE Transaction on Communications, vol.J96-B, no.12, pp.1365-1368
    • Dec. 2013
    • In this paper, we focus on a distance estimation scheme in road to vehicle communication system. We use LED transmitter and high-speed camera. The accuracy of camera based scheme is governed by the size of pixel. Therefore we introduce phase only correlation (POC) to estimate with high accuracy.

  • [Invited Talk] SN, USN, and then ASN

    • T. Yamazato
    • IEICE Technical Report, ASN2013-112, pp.121-124, Tokyo
    • Nov. 2013

  • Performance Evaluation of Error-Correcting Scheme Using Separation of Chaotic Dynamics for Number of Transmitting Data

    • S. Arai, Y. Nishio and T. Yamazato
    • IEICE Technical Report, NLP2013-108, pp. 205-209, Takamatsu, Kagawa, JAPAN
    • Oct. 2013
    • Noncoherent chaos communications, which do not need to use basis signals (unmodulated carriers) for demodulation, are unique communication systems using characteristics of chaos. However, the communication performance of the noncoherent system is lower as compared with the standard communication systems. Thus, it is important to advance noncoherent system in order to improve its performance. In our previous research, we have proposed a novel error-correcting method using a separation and reconstruction of the chaotic dynamics, which is one of characteristics of chaos. As simulation results, we have confirmed that the advantage gained in BER performance of our error-correcting method is about 2--2.5 dB compared to the conventional one (w/o coding). This paper focuses on a number of transmitting data and a combination of symbols, and analyzes an error-correcting capability for evaluating advantages of the separation and reconstruction of the chaotic dynamics in detail.

  • Performance evaluation of the weak signal detection of the Stochastic Resonance Receiver using Schmitt Trigger

    • K.Chiga, H.Tanaka, T.Yamazato, Y.tadokoro, S.Arai
    • IEICE Technical Report, NLP2013-73, pp.19-23
    • Oct. 2013
    • Stochastic Resonance(SR) is a nonlinear phenomena in which the Signal-to-Noise Ratio(SNR) is enhanced by an increase of the noise. By using SR, we can detect the weak signal which cannot detect by the conventional receiver. In this paper, we consider the application of SR to the communication systems. we implement the Stochastic Resonance Receiver using Schmitt Trigger as the Stochastic Resonance system. We evaluate the performance of the weak signal responce and we discuss about the weak signal detection.

  • Utilization of Spatio-temporal Image for LED Array Acquisition in Road to Vehicle Visible Light Communication

    • S. Usui, T. Yamazato, S. Arai, T. Yendo, T. Fujii, H. Okada
    • 20th World Congress on Intelligent Transport Systems , Tokyo, Japan
    • Oct. 2013
    • In this paper, we focus attention on visible light communication systems using an LED array as a transmitter and a high-speed camera as a receiver for road-to-vehicle communications (R2V-VLC) in intelligent transport systems. To implement R2V-VLC, it is necessary for the receiver to search the target LED array from the captured images (LED array acquisition) before data demodulation. We propose a new approach for LED array acquisition. We focus on spatio-temporal image and spatio-temporal cross-section image and show LED array in the spatio-temporal image has high time-gradient value and low space-gradient value. Using such characteristic gradient values, we propose new LED array acquisition method. As the results of the experiment in driving situation, we can achieve acquisition miss rate = 0%.

  • Accuracy Improvement by Phase Only Correlation for Distance Estimation Scheme for Visible Light Communications Using an LED Array and a High-speed Camera

    • A. Ohmura, T. Yamazato, H. Okada, T. Fujii, T. Yendo, S. Arai
    • 20th World Congress on Intelligent Transport Systems, Tokyo, Japan
    • Oct. 2013
    • In this paper, we focus on a distance estimation scheme using camera. Our distance estimation scheme is based on triangulation. The accuracy of camera based scheme is governed by resolution of a camera, or equivalently the size of pixel. Therefore we introduce phase only correlation (POC) to estimate with subpixel accuracy. As a result of experiment, we will show that our scheme achieves less than 0.3m estimation error at the distance of 60m. By using POC, the resolution of estimation reaches nearly 0.02 pixel, much less than one pixel.

  • A Study on Implementation of Stochastic Resonance Receiver using Schmitt Trigger

    • K. Chiga, H. Tanaka, T. Yamazato, Y. Tadokoro, S. Arai
    • Enginnering Sciences Society Conference of IEICE, A-2-13, p.32, Fukuoka
    • Sep. 2013

  • The outline of I-Scover (IEICE Knowledge Discovery)

    • T. Yamazato
    • IEICE Society Conference, Fukuoka Institute of Technology, Japan
    • Sep. 2013

  • A Study on the Signal Sensitivity of Stochastic Resonance Receiver for the Subthreshold Bi-Polar Pulse Detection

    • H. Tanaka, K. Chiga, T. Yamazato, Y. Tadokoro, S. Arai
    • Enginnering Sciences Society Conference of IEICE, Fukuoka, Japam
    • Sep. 2013

  • Implementation of Bi-Polar Pulse SR Receiver Using Schmitt Trigger and Evaluation of its Performance

    • K. Chiga, H. Tanaka, T. Yamazato, Y. Tadokoro, S. Arai
    • International Symposium on Nonlinear Theory and its Application (NOLTA), pp.269-271, Santa Fe, USA
    • Sep. 2013
    • We consider an application of Stochastic Resonance to wireless communication system. Stochastic Resonance (SR) is well known as a phenomenon in which weak signal in nonlinear system can be detected by added noise. A receiver using Stochastic Resonance (SR Receiver) can detect a weak signal which is not detectable in the conventional receiver. In this paper, we consider the implementation of bi-polar pulse SR Receiver using Schmitt Trigger and evaluate the performance in Signal-to-Noise Ratio (SNR) and Bit Error Rate (BER).

  • [Invited Talk] Application of visible light communication to LED traffic light

    • T. Yamazato
    • Proceeding of 2013 Annual Conference of IEIJ, Nagoya University, Japan
    • Sep. 2013

  • Lectures in Nagoya University OCW that providing play and learning experiences

    • T. Yamazato
    • 2013 JSEE Annual Conference, Niigata University
    • Aug. 2013

  • Let’s Search IEICE Contents through New Meta-Data System “I-Scover”!

    • T. Yamazato
    • IEICE Global Plaza, No.55, Aug., 2013
    • Aug. 2013
    • IEICE launched the new metadata search system called “I-Scover” on April 3, 2013[1]. For the time being, I-Scover provides the metadata search service of all papers published in IEICE transactions covering from the first edition published in 1968 up to the present edition, Technical Reports (from 2006) and international conference papers of ISPA and EMC. The total number of searchable contents reaches 150,000 as listed in Table.1. This article briefly introduces I-Scover. Before going to the details, let me start with a quiz. What phrase do you guess if you say “I-Scover” for three times?

  • M-ary Modulation Method Using Separation of Chaotic Dynamics for Noncoherent Chaos Communications

    • S. Arai, Y. Nishio and T. Yamazato
    • The 26th Workshop on Circuits and Systems, pp. 7-11, Awaji, Japan
    • Jul. 2013

  • LED array acquisition method based on Spatio-temporal image in Road to Vehicle Visible Light Communication

    • S.Usui, T.Yamazato, S.Arai, T.Yendo, T.Fujii, H.Okada
    • Technical Report of IEICE, ASN2013-55, pp.47-52, Hamamatsu,Japan
    • Jul. 2013
    • In this paper, we focus attention on road-to-vehicle visible light communication(R2V-VLC) in intelligent transport systems. This system uses an LED array as a transmitter and a high-speed camera as a receiver. To implement R2V-VLC, it is necessary to acquire the target LED array from the captured images at receiver before data demodulation. To achieve accurate aquisition, we analyze LED array by use of Spatio-temporal image. As the result of the analysis, we show the LED array in the spatio-temporal image has high time-gradient value and low space-gradient value. After that we propose a new LED array acquisition method using such characteristic gradient values.

  • Distance Estimation Scheme for Integrated V2I-VLC Simulating the Vibration of Driving Vehicle

    • A.OHMURA, T.YAMAZATO, H.OKADA, T. FUJII, T. YENDO, S. ARAI
    • Technical Report of IEICE, ASN2013-55, pp.41-46, Hamamatsu, Japan
    • Jul. 2013
    • In road-to-vehicle visible light communication data is transmitted toward moving vehicles from the LED array installed on roads. Robust data reception and fast communication are possible by using a high-speed camera as it can reduce the vibration of vehicles. In this road-to-vehicle visible light communication, we propose an integrated system of communication and distance estimation by sending a known data pattern from the LED array. On issues which is distance estimation performance deterioration by the vibration of the running vehicle, try to resolve them using the technique using the phase-only correlation method.

  • Performance Evaluation of Stochastic Resonance Receiver for the Multi Carrier Detection

    • H. Tanaka, K. chiga, T. Yamazato, Y, Tadokoro, S. Arai
    • NANOENERGY2013, pp.58-59, Perugia, Italy
    • Jul. 2013
    • Stochastic Resonance (SR), known as a noise-enhanced phenomenon, can improve the performance of communication systems. By applying SR in the receiver, it is possible to detect a weak signal that is not detectable in the traditional linear receiver. In the SR systems, the input of multi-carrier has not ever been discussed. So this paper proposes the SR receiver for multi-carrier detection and evaluates its Bit-Error-Rate (BER) performance．

  • Image Sensor based Visible Light Communication for Automotive Applications

    • T. Yamazato, I. Takai, H. Okada, T. Fujii, T. Yendo, S. Arai, M. Andoh, K. Yasutomi, K. Kagawa, S. Kawahito
    • International Symposium on Optical Wireless Communications, Beijing Jade Palace Hotel, China
    • Jun. 2013
    • This talk introduces visible light communication (VLC) for automotive applications using an image sensor. In particular, vehicle-to-infrastructure visible light communication (V2I-VLC) and vehicle-to-vehicle visible light communication (V2V-VLC) are presented. Previous studies have documented the effectiveness of V2I and V2V communication using radio technology for improving automotive safety. In this talk, I identify characteristics unique to the introduced image sensor based VLC as compared to radio wave technology. The advantages of VCL are twofold: the line-of-sight feature of visible light links and an image sensor that provides not only the VLC function but also vehicle safety applications using image and video processing. We present two on-going image sensors based V2I-VLC and V2V-VLC projects.

  • Channel Information Estimation for Error Correcting Code in Road-to-Vehicle Visible Light Communication Systems

    • H. Okada, S. Misawa, T. Yamazato, T. Fujii, T. Yendo
    • IEEE International Symposium on Wireless Vehicular Communications (WiVeC), Dresden, Germany
    • Jun. 2013
    • https://doi.org/10.1109/wivec.2013.6698229
    • This paper focuses on a road-to-vehicle visible light communication (VLC) system using LED traffic lights and high-speed cameras on cars. So as to improve the transmission reliability, an error correcting code like a low-density parity-check (LDPC) is applied to the road-to-vehicle VLC system. The decoder of the LDPC code needs channel information in order to maximize decoding performance. Usually, it is calculated from a signal-to-noise ratio (SNR) or bit error rate (BER) of a channel, where noise is a dominant factor of the channel characteristic. In the road-to-vehicle VLC system, not noise but interference among LEDs decides the channel characteristic. In this paper, we propose a channel information estimation method for the road-to-vehicle VLC system. The proposed method estimates a signal-to-interference ratio (SIR) from the receiving image, and calculates the channel information using the SIR. The proposed method is evaluated by experiment. As a result, the proposed method can achieve almost the same performance with the optimum case, and then maximize the decoding performance.

  • Interpixel Interference Cancellation Method for Road-to-Vehicle Visible Light Communication

    • T. Kasashima, T. Yamazato, H. OKada, T. Fujii, T. Yendo, S. Arai
    • IEEE International Symposium on Wireless Vehicular Communications (WiVeC), Dresden, Germany
    • Jun. 2013
    • https://doi.org/10.1109/wivec.2013.6698237
    • This paper aims to improve the transmission distance for the road-to-vehicle visible light communication system (R2V-VLC) using LED array and high-speed camera by reducing interference caused at the receiver. As we can transmit multiple data using LED array and high-speed camera, parallel data transmission can be possible. However, due to the diffusion of LED and the finiteness of the pixel size of image sensor, the focused LED will affect not only the actual corresponding pixel but also its surrounding pixels. We call this phenomenon as “interpixel interference (IPI)” and it causes degradation in error rate performance. To mitigate the IPI, we propose IPI cancellation scheme for the R2V-VLC system. As the results of the experiment, we can extend the error-free distance from 40m to 60m by the IPI cancellation.

  • Discover IEICE Contents Using I-Scover

    • T. Yamazato
    • IEICE Communications Society &#8211; GLOBAL NEWSLETTER Vol. 37, No. 2, Jun., 2013.
    • Jun. 2013
    • The IEICE launched new metadata search system called I-Scover (http://i-scover.ieice.org) from April 3rd, 2013. I-Scover provides metadata search of the IEICE transactions papers (from its first edition published in 1968), Technical Reports (from 2006) and international conference papers of ISPA and EMC. The total of the contents that can be searched is more than 150,000. This article briefly introduces I-Scover. Before going to detail, let me start with a quiz. What phrase do you guess if you say I-Scover for three times?

  • Input-output phase difference performance of Stochastic Resonance Schmitt Trigger receiver

    • K. Chiga, H. Tanaka, T. Yamazato, Y.Tadokoro, S. Arai
    • IEICE General Conference, A-2-11, p.38, Gifu
    • Mar. 2013

  • The outline of I-Scover

    • T. Yamazato
    • IEICE General Conference, Gifu University, Japan
    • Mar. 2013

  • A performance analysis of the stochastic resonance receiver for the subthreshold bi-polar pulse detection

    • H. Tanaka, K. Chiga, T. Yamazato, Y. Tadokoro, S. Arai
    • IEICE General Conference, A-2-13, p.40, Gifu, Japan
    • Mar. 2013

  • Intensity Estimation Method of LED Array for Visible Light Communication

    • T. Ito, T. Yendo, S. Arai, T. Yamazato, H. Okada, T. Fujii
    • Proc. SPIE 8663, Video Surveillance and Transportation Imaging Applications, 86630V, Burlingame, California, USA
    • Mar. 2013
    • https://doi.org/10.1117/12.2005738
    • This paper focuses on a road-to-vehicle visible light communication (VLC) system using LED traffic light as the transmitter and camera as the receiver. The traffic light is composed of a hundred of LEDs on two dimensional plain. In this system, data is sent as two dimensional brightness patterns by controlling each LED of the traffic light individually, and they are received as images by the camera. Here, there are problems that neighboring LEDs on the received image are merged due to less number of pixels in case that the receiver is distant from the transmitter, and/or due to blurring by defocus of the camera. Because of that, bit error rate (BER) increases due to recognition error of intensity of LEDs To solve the problem, we propose a method that estimates the intensity of LEDs by solving the inverse problem of communication channel characteristic from the transmitter to the receiver. The proposed method is evaluated by BER characteristics which are obtained by computer simulation and experiments. In the result, the proposed method can estimate with better accuracy than the conventional methods, especially in case that the received image is blurred a lot, and the number of pixels is small. &copy; (2013) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.

  • Characterization of Stochastic Resonance Circuits with Application to Weak Signals

    • K. Chiga
    • IEICE Tokai Section Graduation Research Conference, OA-3-2, p.14, Nagoya, Japan
    • Mar. 2013

  • Development of Simple Simulator for Visible Light Communication Using LED and Camera

    • T. Fukumoto, S. Arai, T. Yendo, T. Yamazato, H. Okada and T. Fujii
    • RISP International Workshop on Nonlinear Circuits, Communications and Signal Processing (NCSP), pp. 33-36, Hawaii, USA
    • Mar. 2013
    • This paper develops a simple simulator for the visible light communication (VLC) system using a LED traffic light and a camera for intelligent transport systems (ITS). We use image processing techniques for simulating effects of optical spatial channel which is a unique channel in VLC. We describe a system model of the VLC simulator and perform the simulation with various parameters of the image processing.

  • Performance Analysis of Error-Correcting Method Using Separation of Chaos for Noncoherent Chaos Communications

    • S. Arai, Y. Nishio and T. Yamazato
    • RISP International Workshop on Nonlinear Circuits, Communications and Signal Processing (NCSP), pp. 225-228, Hawaii, USA
    • Mar. 2013
    • This paper analyzes the performance of the error-correcting method, which was proposed in the previous research, using the separation and the reconstruction of chaos for noncoherent chaos communications. Especially, we focus on a number of transmitting data and a combination of symbols (i.e., data pattern). We consider that the capability of the error correction depends on the number of data and the data pattern because the proposed method performs the error correction using successive data symbols. This study performs simulations for the number of data and the data pattern, and evaluates BER performance of the proposed method.

  • A bit-error-rate analysis on the stochastic resonance receiver for the weak bi-polar pulse

    • Hiroya TANAKA, Keita CHIGA, Takaya YAMAZATO, Yukihiro TADOKORO, Shintaro ARAI
    • IEICE Complex Communication Sciences, CCS-2012-039, Tokyo, Japan
    • Mar. 2013
    • Stochastic resonance has an effect of improving the detection by increasing noise in the system. By applying this stochastic resonance in the receiver, it is possible to detect the subthreshold signal which is not detectable in the traditional linear receiver. This paper proposes an analysis method of the stochastic resonance receiver for the detection of the bi-polar pulse, which has good compatibility to stochastic resonance, and evaluates its bit-error-rate performance. And, the optimal noise power which maximizes the effect of stochastic resonance is discussed.

  • Performance Evaluation of Stochastic Resonance Bi-Polar Pulse receiver Using Schmitt Trigger

    • Keita CHIGA, Hiroya TANAKA, Takaya YAMAZATO, Yukihiro TADOKORO, Shintaro ARAI
    • IEICE Complex Communication Sciences, CCS-2012-038, Tokyo
    • Mar. 2013
    • We consider an application of Stochastic Resonance to wireless communication system. Stochastic Resonance(SR) is well known as a phenomenon in which weak signal in nonlinear system can be detected by added noise. A receiver using Stochastic Resonance(SR Receiver) can detect a weak signal which is not detectable in the conventional receiver. In this paper, we consider the implementation of Bi-Polar Pulse SR Receiver using Schmitt Trigger and the evaluation of the performance in Signal-to-Noise Ratio(SNR) and Bit Error Rate(BER).

  • Overlay Coding of Long Range Data and Short Range Data for Road-to-Vehicle Visible Light Communication Using LED Array and High-Speed Camera

    • S. Nishimoto, T. Yamazato, H. Okada, T. Fujii, T. Yendo, S. Arai
    • IEICE Transactions on Communications, vol.J96-B, no.2, pp.191-201
    • Feb. 2013

  • A Study on the Simulator Development for Visible Light Communication Using LED and Camera

    • T. Fukumoto, S. Arai, T. Yendo, T. Yamazato, H. Okada and T. Fujii
    • Proceedings of IEEE Workshop on Nonlinear Circuit Networks (NCN'12), pp. 124-127, Tokushima, Japan
    • Dec. 2012
    • This paper develops a simple simulation program for visible light communication (VLC) systems using LED (Transmitter) and a camera (Receiver). In the simulation, we generate an image of LED array transmitter which consists of LEDs arranged in a square matrix. In addition, effects of optical spatial channel, which is a unique channel in VLC, are constructed by using image processing techniques. We describe a system model of the VLC simulator and carry out the simulation with various parameters of the image processing.

  • Intensity estimation of LED array for parallel visible light communication

    • T. Ito, S. Arai, T. Yendo T. Yamazato, H. Okada and T. Fujii
    • Technical Report of IEICE, CS2012-90, pp.113-118, Fukui, Japan
    • Dec. 2012

  • Visible light communication system using real-time software processing of high-speed camera image

    • M. Kasai, T. Yendo T. Yamazato, H. Okada, T. Fujii and S. Arai
    • Technical Report of IEICE, CS2012-83, pp.71-75, Fukui, Japan
    • Dec. 2012

  • High-speed Transmission of Overlay Coding for Road-to-Vehicle Visible Light Communication Using LED Array and High-Speed Camera

    • S. Nishimoto, T. Yamazato, H. Okada, T. Fujii, T. Yendo, S. Arai
    • IEEE GLOBECOM Workshop on Optical Wireless Communications, pp.1234-1238, Anaheim, USA
    • Dec. 2012
    • https://doi.org/10.1109/GLOCOMW.2012.6477757
    • This paper aims to the improve the data rate for the visible light communication system using LED array and high-speed camera. Previously, we have proposed the decoding algorithm using inverted signals for driving situation. However, using this method the data rate become a half, because we transmit original signals and inverted signals alternately for LED array tracking. In this paper, we propose the data rate improving method for overlay coding which is coding method that overlay two data which are called as the long range data and the short range data. In the proposed method, for the long range data, we transmit original signals and inverted signals alternately. On the other hand, for the short range data, we transmit only original signals while we transmit inverted signals of long range data. We confirm that we can improve data rate as compared with the previous method.

  • The key to peer-review an IEICE article

    • T. Yamazato, T. Saba, S. Shiota, C. Ohta
    • IEICE Communication Society Magazine, B-Plus, no.23, pp.222-230
    • Dec. 2012

  • A Study on Error-Correcting Method for Noncoherent Chaos Communications

    • S. Arai, Y. Nishio, T. Yamazato
    • Japan-Korea Joint Workshop on Complex Communication Sciences, Seoul, Korea
    • Nov. 2012

  • Multiple Information Sources Recognition Method for Ubiquitous Visible Light Communication Using on-Vehicle High-Speed Camera

    • Y. Shiraki, T. Yamazato, H. Okada, T. Fujii, T. Yendo, S. Arai
    • IEICE Transactions on Communications, vol.J95-B, no.11, pp.1517-1528
    • Nov. 2012

  • Improvement of Error-Correcting Method Based on Chaotic Dynamics for Noncoherent Chaos Communications

    • S. Arai, Y. Nishio, T. Yamazato
    • International Symposium on Nonlinear Theory and its Applications (NOLTA), pp.801-804, Palma, Majorca, Spain
    • Oct. 2012
    • This paper focuses on characteristics of the chaotic dynamics and improves our previous errorcorrecting method using them for noncoherent chaos communications. Our previous method is performed by using a chaotic sequence generated according to the chaotic dynamics. In this case, it is very difficult to recover data without a successive sequence based on the chaotic dynamics. We focus on this feature and consider that an improved method separates and reconstructs the chaotic dynamics of the sequence according to a specific rule. Namely, the separation and reconstruction of the chaotic dynamics can be applied for our improved method as additional information. As results of simulations, we have confirmed that the advantage gained in BER performance of our improved method is about 2&#8211;2.5 dB compared to a conventional method (without coding).

  • Introduction of Nagoya University OCW

    • T. Yamazato
    • ICTSFC Workshop, Nagoya, Japan
    • Sep. 2012

  • Performance Evaluation of 2 users BFSK Receiver Stochastic Resonance

    • H. Tanaka, T. Yamazato, S. Arai
    • Enginnering Sciences Society Conference of IEICE, Toyama, Japan
    • Sep. 2012

  • Stochastic Resonance BFSK Receiver using Schmitt Trigger

    • K. Chiga, H. Tanaka, T. Yamazato, S. Arai
    • Enginnering Sciences Society Conference of IEICE, A-2-1, p.24
    • Sep. 2012

  • Phase Only Correlation Based Distance Estimation Scheme for Integrated R2V-VLC

    • A.Ohmura,T.Yamazato,H.Okada,T.Fujii,T.Yendo,S.Arai
    • , Tokyo, Japan
    • Sep. 2012

  • A Study on Cluster Lifetime in Multi-Hop Wireless Sensor Networks with Cooperative MISO Scheme

    • Z. Huang, H. Okada, K. Kobayashi, M. Katayama
    • Journal of Communications and Networks, vol.14, no.4, pp.443-450
    • Aug. 2012
    • https://doi.org/10.1109/JCN.2012.6292251
    • As for cluster-based wireless sensor networks (WSNs), cluster lifetime is one of the most important subjects in recent researches. Besides reducing the energy consumptions of the clusters, it is necessary to make the clusters achieve equal lifetimes so that the whole network can survive longer. In this paper, we focus on the cluster lifetimes in multi-hop WSNs with cooperative multi-input single-output scheme. With a simplified model of multi-hop WSNs, we change the transmission schemes, the sizes and transmission distances of clusters to investigate their effects on the cluster lifetimes. Furthermore, linear and uniform data aggregations are considered in our model. As a result, we analyze the cluster lifetimes in different situations and discuss the requirements on the sizes and transmission distances of clusters for equal lifetimes.

  • Demand of Teaching Material Development and OCW

    • T. Yamazato
    • 60th JSEE Anual Conference Proceedings, 8-331, Toyosu Campus, Shibaura Institute of Technology
    • Aug. 2012

  • Evbaluation of Error-Correcting Method Using Separation of Chaotic Dynamics for Noncoherent Chaos Communications

    • S. Arai, Y. Nishio and T. Yamazato
    • Proc. 25th Circuits and Systems Workshop, pp. 261-266, Awaji Island
    • Jul. 2012

  • Improvement Method of Data Rate for Overlay Hierarchical Coding for Road-to-Vehicle Visible Light Communication Using LED Array and High-Speed Camera

    • S. Nishimoto, T. Yamazato, H. Okada, T. Fujii, T. Yendo, S. Arai
    • Technical Report of IEICE, vol.112, no.148, ITS2012-9, pp.19-24, Nagoya, Japan
    • Jul. 2012
    • This paper aims to improve the data rate for the visible light communication system using LED array and high-speed camera. Previously, we have proposed the decoding algorithm using inverted signals for driving situation. However, using this method the data rate become a half, because we transmit original signals and inverted signals alternately for LED array tracking. In this paper, we propose the data rate improving method for overlay coding which is coding method that overlay two data. We confirm that we can improve data rate as compared with the previous method.

  • [Poster Presentation] Road-to-Vehicle Communication and Distance Estimation System using Visible Light Communication

    • A.Ohmura,T.Yamazato,H.Okada,T.Fujii,T.Yendo,S.Arai
    • Technical Report of IEICE, USN2012-9, pp.63-68, Toyohasi,Japan
    • May 2012
    • In road-to-vehicle visible light communication data is transmitted toward moving vehicles from the LED array installed on roads. Robust data reception and fast communication are possible by using a high-speed camera as it can reduce the vibration of vehicles. In this road-to-vehicle visible light communication, we propose an integrated system of communication and distance estimation by sending a known data pattern from the LED array.

  • A Study on Cluster Partitioning with Cooperative MISO Scheme in Wireless Sensor Networks

    • Z. Huang, H. Okada, M. Katayama, T. Yamazato
    • International Journal of Distributed Sensor Networks, vol.2012, Article ID 490823, 9 pages
    • Mar. 2012
    • https://doi.org/10.1155/2012/490823
    • This paper addresses the cluster partitioning problem in wireless sensor networks deployed in a continuous area. We present the model of the network and describe its operational details firstly. Both single-hop and multi-hop transmissions with cooperative Multi-Input Single-Output (MISO) scheme are considered for the inter-cluster communications. Besides, uniform and linear data fusions are discussed. Then the calculations of energy consumptions are derived. Different from other researches, the energy consumptions of intra-cluster communication in each cluster are included and modeled as functions of the cluster size. Finally, we simulate all possible cluster partitions by changing the numbers of clusters and cooperative transmitting nodes, and find the maximal network lifetimes. As a result, the relationships between cluster partitions and network lifetimes are clarified in different situations.

  • Preliminary Study on Bi-Polar Pulse Receiver using Stochastic Resonance

    • H. Tanaka, T. Yamazato, S. Arai
    • IEICE General Conference, A-2-34, p.79, Okayama, Japan
    • Mar. 2012

  • A Distance Estimation Scheme between the LED Array and On-Vihicle High-Speed Camera Using Visible Light

    • A.Ohmura,T.Yamazato,H.Okada,T.Fujii,T.Yendo,S.Arai
    • IEICE General Conference, B-10-104, p.427, Okayama
    • Mar. 2012

  • State Analysis of Stochastic Resonance in Quadruple-Well Potential

    • S. Ozaki, S. Arai, T. Yamazato and Y. Nishio
    • IEICE General Conference, Okayama
    • Mar. 2012

  • Relay Selection Scheme with Harvested Solar Energy Prediction for Solar-Powered Wireless Sensor Networks

    • K. Ota, K. Kobayashi, T. Yamazato, M. Katayama
    • IPSJ SIG Technical Report, vol.2012-MBL-61, no.31, pp.1-8, Tokyo, Japan
    • Mar. 2012
    • Our goal is to make efficient use of the energy and therefore achieve network operation with a high packet delivery ratio, regardless of day, night and weather variations, in solar powered wireless sensor networks. One method to optimize the consumption energy in the entire network is to employ a cooperative transmission scheme in which a node uses another node as a relay, when sending its data. If we do not consider the changes in the harvested energy in the network, the packet delivery ratio declines during nights and cloudy days. In this paper, however, we propose a new relay selection scheme with harvested solar energy prediction to maintain the required high packet delivery ratio by reducing the effect of the weather variations.

  • Analysis of Stochastic Resonance in Quadruple-Well Potential

    • S. Arai, S. Ozaki, T. Yamazato, Y. Nishio
    • RISP International Workshop on Nonlinear Circuits, Communications and Signal Processing (NCSP), pp.60-63, Honolulu, Hawaii, USA
    • Mar. 2012
    • This paper analyzes a stochastic resonance (SR) in a quadruple-well potential, which extended the SR in a doublewell potential, to control of SR. For achieving the control of SR, it is important to analyze the state of the SR by injecting the noise. In this study, we calculate existence probabilities of the SR’s state to analyze how the state changes by a noise intensity.

  • Preliminary Study on BPSK Receiver using Stochastic Resonance

    • H. Tanaka, T. Yamazato, S. Arai
    • RISP International Workshop on Nonlinear Circuits, Commuations and Signal Processing (NCSP), pp.64-67, Honolulu, Hawaii, USA
    • Mar. 2012
    • Stochastic Resonance (SR), known as a noise-enhanced phenomenon, can improve the performance of commutation systems. In this paper, we present a preliminary study on SR and its application to BPSK receiver. We discuss a basic question arises from a receiver using SR that shall we perform SR process in a radio-frequency (RF) band or in a baseband (BB)? As results, we found that SR process in RF band shows better Bit Error Rate (BER) performance. This comes from the fact that a down conversion process that reduces the signal amplitude causes weak noise suppression by SR. While a double frequency term obtained also by the down conversion process do not affect much to the noise reduction performance.

  • Cancellation Method for Intersymbol Interference on Road-to-Vehicle Visible Light Communication using LED Array and High-Speed Camera

    • T.Kasashima, T. Yamazato, H. Okada, T. Fujii, T. Yendo, S. Arai
    • Technical Report of IEICE, ITS2011-38, pp.129-134, Sapporo, Japan
    • Feb. 2012
    • In this paper, we discuss on visible light communications using an LED array as the transmitter and a highspeed camera as the receiver. LED array, composed of many LEDs, transmits information by flashing LEDs, unfortunately an LED light diffuses around and affects neighboring LEDs. This problem causes degradation in error rate performance. We treat this ploblem as intersymbol interference (ISI) and try to cancel. In this paper, we first propose an area average quantization for the reduction of ISI. Next, we propose a new ISI cancellation method for overlay decoding and evaluate this method.

  • LED Array Tracking Method for Road-to-Vehicle Visible Light Communications in the Driving Situation

    • T. Nagura, T. Yamazato, S. Arai, H. Okada, T. Yendo, T. Fujii
    • IEICE Transactions on Communications, vol.J95-B, no.2, pp.326-336
    • Feb. 2012

  • Cooperative Transmission Scheme with the Reactivation Condition of Inactive Nodes in Solar-Powered Wireless Sensor Networks

    • K. Ota, K. Kobayashi, T. Yamazato, M. Katayama
    • IEICE Transactions on Communications, vol.J95-B, no.2, pp.246-256
    • Feb. 2012
    • http://hdl.handle.net/2237/23923
    • Our goal is the improvement of the data arrival rate in solar-powered wireless sensor networks. We consider the application of a cooperative transmission scheme that uses a relay node when a node sends data to reduce the consumption of energy of the entire network. In this paper, we propose the selection method of a relay node based on node battery and consumption energy. The overall data arrival rate is improved through the method. However, if we do not consider the variations in energy harvesting, the data arrival rate declines during nighttime. Then, we smooth out the day-and-night data arrival rate variations by introducing the new inactive node reactivation condition to the cooperative transmission scheme and achieve the required high data arrival rate.

  • Gaussian Pulse Shape Optimization of BFDM in Highly Mobile Environments

    • D. Goto, T. Yayazato, B. Mongol
    • IEICE Transactions on Communications, vol.J95-B, no.2, pp.317-325
    • Feb. 2012
    • In this paper, we focus on reducing intersymbol interference (ISI) and intercarrier interference (ICI) in a highly mobile environment by optimizing the Gaussian pulse shape of Biorthogonal Frequency Division Multiplexing (BFDM). In time-frequency dispersive channels, reducing the signal interference depends on the shaping of signal pulse. BFDM was invented to reduce the interference through a flexible design of signal pulse shaping. However, the shape of Gaussian pulses used in BFDM is not always optimized in every situation and as a result the interference is not always minimized. This research is to optimize the shape of Gaussian pulse. In particular, we optimize the Gaussian pulse in BFDM by maximizing the ratio of the ambiguity function of the transmitter (Gaussian) and its receiver pulses. Numerical results obtained show that the proposed method is effective for the optimization of BFDM. Furthermore, we show that the BFDM outperforms the conventional OFDM in time-frequency dispersive channels.

  • A Simple Cooperative Relaying with Alamouti Coded Transmission

    • T. Yamaoka, Y. Hara, N. Fukui, H. Kubo, T. Yamazato
    • IEICE Transactions on Communications, vol .E95-B, no. 2, pp.643-646
    • Feb. 2012
    • Cooperative diversity using space-time codes offers effective space diversity with low complexity, but the scheme needs the space-time coding process in the relay nodes. We propose a simple cooperative relay scheme that uses space-time coding. In the scheme, the source node transmits the Alamouti coded signal sequences and the sink node receives the signal sequence via the two coordinated relay nodes. At the relay nodes, the operation procedure is just permutation and forwarding of the signal sequence. In the proposed scheme, none of the relay nodes need quadrature detection and space-time coding and the simple relay process offers effective space diversity. Moreover, simulations show the effectiveness of the proposed relay process by some simulations.

  • [Technology Exhibition] Real-Time Data Transmission of Road-to-Vehicle Visible Light Communication System Using LED array and High-Speed Camera

    • T.Kasashima, Y.Shiraki, T. Yamazato, H. Okada, T. Fujii, T. Yendo, S. Arai
    • Technical Report of IEICE, USN2011-89, pp.173-175, Toba, Japan
    • Jan. 2012
    • In this paper, we discuss road-to-vehicle visible light communications using an LED array as the transmitter and a high-speed camera as the receiver. The visible light communication (VLC) is a wireless communication that a transmitter consists of LED array and it transmit data by Turing LEDs on and off at high speed. We consider applying this VLC technique to the road (infrastructure) -to-vehicle communication for a purpose to support safety driving. So far, we have confirmed effectiveness of the VLC system through static and driving experiments. However, all those experimental results were obtained by off-line processing. In this paper, we introduce a real-time processing of the VLC receiver that captures not only the captured images by also the data transmitted from the LED array. The detail of the VLC receiver will be shown at the technology exhibition.

  • Decline in Probability of False Recognition of Non-Information Sources in Visible Light Communication for Intelligent Transport System

    • Y. Shiraki, T. Yamazato, S. Arai, T. Yendo, H. Okada, T. Fujii
    • Technical Report of IEICE, USN2011-59, pp.13-18, Toba
    • Jan. 2012

  • Research on Visible Light Communication using LED Array and High-Speed Camera

    • T. Yamazato
    • Information and Communication Frontier Seminar 2011, Winc Aichi, Naogya, Japan
    • Jan. 2012

  • High-Speed LED Traffic Light Tracking Method Using Image/High-Speed Communication Hybrid Sensor

    • K. Maeno, M. Tehrani, T. Fujii, H. Okada, T. Yamazato, M. Tanimoto, T. Yendo
    • International Workshop on Advanced Image Technology (IWAIT), Ho Chi Minh City, Vietnam
    • Jan. 2012

  • Relay Selection Scheme Using Prediction of Harvested Energy for Solar-Powered Wireless Sensor Networks

    • K. Ota, K. Kobayashi, T. Yamazato, M. Katayama
    • International Symposium on EcoTopia Science (ISETS), p.106, Nagoya, Japan
    • Dec. 2011
    • Solar-powered wireless sensor networks are attracting attention for outdoor long time operation such as environmental monitoring. Even if sensor nodes are charged by solar energy, nodes far from the BS (Base-Station) are stopped due to the lack of energy during nighttime. To prevent this problem, we consider the use of cooperative transmission. In cooperative transmission, energy consumption is balanced among the nodes because of the use of another node as a relay for data transmission of distant nodes. The conventional scheme to select a relay node is based on available battery energy and the expectation of energy consumption of each node. In this paper, we propose a relay selection scheme which is based on the prediction of harvested energy in addition to the available battery energy and the expected value of energy consumption. We evaluate the proposed scheme through packet delivery ratio and show its effectiveness.

  • Interference Comparison of BFDM with Optimum Gaussian Pulse and Wavelet Based OFDM in Highly Mobile Environments

    • D. Goto, T. Yayazato, B. Mongol
    • Technical Report of IEICE, RCS2011-11, pp.91-95 , Nagoya, Japan
    • Nov. 2011
    • In this paper, we conduct a comparison between the Biorthogonal Frequency Division Multiplexing (BFDM) and the Wavelet Based Orthogonal Frequency Division Multiplexing (OFDM) in terms of intersymbol interference (ISI) and intercarrier interference (ICI) reduction in highly mobile environments with assumed time-frequency dispersive channels. ISI and ICI depend largely on the pulse shaping of the signal. BFDM can reduce the signal interference by applying a Gaussian pulse known as a properly localized time-frequency pulse with adaptable characteristics. On the other hand, Wavelet Based OFDM is known to lower interference due to its wavelet basis. In this paper, we propose an optimization method for the Gaussian pulse in BFDM to minimize ISI/ICI by maximizing the ratio of the ambiguity function. In addition, we compare its performance with BFDM and Wavelet Based OFDM.

  • Teaching tips and Nagoya University OCW

    • T. Yamazato
    • Asia Regional OpenCourseWare Conference (AROCC) 2011, Meiji University, Tokyo, Japan
    • Nov. 2011

  • ITS Visible Light Communication using LED Array and High-Speed Camera

    • T. Yamazato
    • Autumn Symposium 2011, The Japan Society of Applied Science, Tokyo, Japan
    • Oct. 2011

  • Robust Receiver Design for Road-to-Vehicle Communication System Using LED Array and High-Speed Camera

    • Y. Shiraki, T. Nagura, T. Yamazato, S. Arai, T. Yendo, T. Fujii, H. Okada
    • 18th World Congress on Intelligent Transport Systems , Orlando, Florida, USA
    • Oct. 2011
    • In this paper, we focus attention on the visible light communication systems using an LED array as a transmitter and a high-speed camera as a receiver for road-to-vehicle communications in intelligent transport systems. Previously, we have proposed the hierarchical coding scheme which enables reception of high-priority data even if the receiver is far from the transmitter and have confirmed the effectiveness of the hierarchical coding scheme from results of primitive implementation experiments. However, there are many important works to develop the real-time communication system for an actual driving situation. In this paper, we discuss a robust receiver design in an actual driving situation. We introduce a series of image processing operations and demonstrate their effectiveness by field trials. As the results of the field trials, we have achieved 16kbps transmission and error-free communication up to communication distance of 70m using 16x16 LED array (transmitter) and high-speed camera (receiver) with the frame rate of 1000.

  • Overlay Coding for Road-to-Vehicle Visible Light Communication using LED Array and High-Speed Camera

    • S. Nishimoto, T. Nagura, T. Yamazato, T. Yendo, T. Fujii, H. Okada, S. Arai
    • International IEEE Conference on Intelligent Transportation Systems (ITSC), pp.1704-1709, Washington D.C., USA
    • Oct. 2011
    • https://doi.org/10.1109/ITSC.2011.6082943
    • This paper aims to improve the visible light communication system using LED array and high-speed camera by proposing what we call “overlay coding”. “Overlay coding” is a new coding method to realize a hierarchical coding, through which a high-priority data can be received even if the receiver is far from a transmitter. Conventionally, the hierarchical coding has been realized through the wavelet transform that has a limitation of number and disposition of LEDs, and as a result it does not always match with the design of the transmitters (e.g. traffic lights, etc.) used in real life. To solve the limitation problem, we propose a more flexible way of designing the application of LEDs depending on the transmitters. In particular, overlay coding is realized through the procedures of coding and decoding. In coding, we replace one LED with a flexible number of LEDs, and the number depends on whether the data is high-priority or low-priority, then high-priority data and low-priority data are overlaid. In decoding, we first obtain the high-priority data, and then the low-priority data using retrieved high-priority data. The experimental result shows that the distance for receiving error-free data is extended from 30m to 70m in the overlay coding.

  • Research on Visible Light Communication using LED Array and High-Speed Camera

    • T. Yamazato
    • ICT Inovation Forum 2011, Makuhari Messe, Chiba, Japan
    • Oct. 2011

  • A Study on Cluster Lifetime of Single-hop Wireless Sensor Networks with Cooperative MISO Scheme

    • Z. Huang, K. Kobayashi, M. Katayama, T. Yamazato
    • IEICE Transactions on Communications, vol.E94-B, no.10, pp.2881-2885
    • Oct. 2011
    • https://doi.org/10.1587/transcom.E94.B.2881
    • This letter investigates the cluster lifetime of single-hop wireless sensor networks with cooperative Multi-Input Single-Output (MISO) scheme. The energy consumptions of both intra-cluster and out-cluster communications are considered. Moreover, uniform and linear data aggregations are discussed. It is found the optimal transmission scheme varies with the distance from the cluster to the base station. More interestingly and novelly, the effect of cluster size on the cluster lifetime has been clarified.

  • Estimation of Channel Information for Error Correcting Code in Visible Light Communication Using LED Array and High-Speed Camera

    • S. Misawa, H. Okada, T. Yamazato, T. Yendo, T. Fujii
    • Enginnering Sciences Society Conference of IEICE, A-17-6, p.210, Sapporo
    • Sep. 2011

  • Cooperative Transmission Scheme with Inactive Node Reactivation Condition for Solar-Powered Wireless Sensor Networks

    • K. Ota, K. Kobayashi, T. Yamazato, M. Katayama
    • IEEE International Workshop on Wireless Distributed Networks (WDN), pp.2394-2398, Toronto, Canada
    • Sep. 2011
    • https://doi.org/10.1109/PIMRC.2011.6139948
    • Our goal is the improvement of the node activity rate in solar-powered wireless sensor networks. We consider the application of a cooperative transmission scheme that uses a relay node when a node sends data to reduce the consumption of energy of the entire network. However, if we do not consider the variations in energy harvesting, the node activity rate declines during nighttime. In this paper, we smooth out the day-and-night node activity rate variations by introducing the new inactive node reactivation condition and achieve the required high node activity rate.

  • Unique Classroom Practices Published in Nagoya University OCW (NUOCW)

    • T. Yamazato
    • Proceedings of 2011 Engineering Education Research Conference, 9-217, Hokkaido University, Sapporo, Japan
    • Sep. 2011

  • Unique teaching practices presented at Nagoya University OCW

    • T. Yamazato
    • Journal of Japanese Society for Engineering Education (JSEE), Vol. 59，No. 4，pp.4_105-4_107
    • Aug. 2011
    • Of the courses, that have been presented in Nagoya University OCW site, are taken up and discussed in terms of how the educative effect can be improved by stimulating student's intellectual curiosity.

  • Multiple LED Arrays Recognition Using Block Matching for Road-to-Vehicle Visible Light Communication

    • Y. Shiraki, T. Yamazato, S. Arai, T. Yendo, H. Okada, T. Fujii
    • Technical Report of IEICE, USN2011-18, pp.73-78, Fukuoka, Japan
    • Jul. 2011
    • Visible light communication systems which enable data transmission by blinking LEDs at fast rate attract attention for their applications to Intelligent Transport Systems (ITS). In this paper, we assume that there are multiple information sources and we recognize them with on-vehicle high-speed camera in such systems. To distinguish multiple sources, we propose multiple sources recognition method based block matching. We evaluate the proposed method by performing experiments.

  • Visible Light Communication and Its Application to ITS

    • T. Yamazato
    • International Symposium on Emerging Short Range Communications, Room 1-312, FIT Building, Tsinghua University, China
    • Jun. 2011

  • Gaussian Pulse Shape Optimization of BFDM in Highly Mobile Environments

    • D. Goto, T. Yamazato, B. Mongol
    • Technical Report of IEICE, RCS2011-06, pp221-226, Okinawa, Japan
    • Jun. 2011
    • In this paper, we focus on reducing intersymbol interference (ISI) and intercarrier interference (ICI) in a highly mobile environment by optimizing the Gaussian pulse shape of Biorthogonal Frequency Division Multiplexing (BFDM). In time-frequency dispersive channels, reducing the signal interference depends on the shaping of signal pulse. BFDM was invented to reduce the interference through a flexible design of signal pulse shaping. However, the shape of Gaussian pulses used in BFDM is not always optimized in every situation and as a result the interference is not always minimized. This research is to optimize the shape of Gaussian pulse. In particular, we optimize the Gaussian pulse in BFDM by maximizing the ratio of the ambiguity function of the transmitter (Gaussian) and its receiver pulses. Numerical results obtained show that the proposed method is effective for the optimization of BFDM. Furthermore, we show that the BFDM outperforms the conventional OFDM in time-frequency dispersive channels.

  • [Requested Talk] What Visible Light Communication (VLC) can do, what VLC cannot do. What I found from the research on VLC using LED array and High-Speed

    • T. Yamazato
    • Technical Report of IEICE, RCS2011-49, pp.85-90, University of Ryukyus, Okinawa, Japan
    • Jun. 2011
    • We are conducting a study on visible light communications (VLC) using an LED traffic light and a high-speed camera equipped in a vehicle. Since we use the camera, we can capture and record surround images of the vehicle while receiving the data transmitted from the LED traffic light. This paper introduces the VLC system we are working on.

  • Making Open Learning Come Alive: Takaya Yamazato of Nagoya University Talks About Engaging Students in OpenCourseWare

    • T. Yamazato
    • EDUCATION Inside
    • Jun. 2011
    • Dr. Takaya Yamazato is a professor at Japan's Nagoya University, where he also heads the OpenCourseWare (OCW) team. The Education Insider caught up with him after the 2011 OCW Consortium conference to learn more about Nagoya's unique approach to putting course materials on the Web.

  • [Tutorial] Visible Light Communications

    • T. Yamazato, S. Haruyama
    • IEEE International Conference on Communications (ICC), Kyoto, Japan
    • Jun. 2011
    • Visible light communications (VLC) is the latest optical wireless communications technologies that uses low-power light emitting diodes, or LEDs, not only to provide light but also to broadcast data. LEDs are extremely energy-efficient and predicted to become widespread in general lighting application. It is expected that LED market will reach $29 billion in 2017 that is comparable to today's NAND and DRAM markets [1]. Because LED is a solid-state lighting device, it can be modulated at high-speed compared with other lighting sources. VLC uses LEDs, which send data by flashing light at speeds undetectable to the human eye. The pioneer of VLC using LEDs is Professor Masao Nakagawa of Keio University. His first paper on this subject appeared in the early 2000, together with his successor Prof. Shinichiro Haruyama, the instructor of this tutorial. Later in 2003, he formed Visible Light Communication Consortium (VLCC). Now VLCC is lead by Prof. Haruyama. Please see the following video, an interview of Prof. Haruyama about VLC, which has been broadcast by NHK World in June 4, 2009. http://www.naka-lab.jp/movie/nhk_world.wmv So far various experimental VLC systems and prototypes are demonstrated. Such includes 4.8kbps visible light ID as an infrastructure to mobile-terminal application, independent sound transmission through RGB visible lights and 100Mbps VLC wireless LAN system. Using LED array, the data rate of 1 Gbps achieved by Keio University (Prof. Haruyama) that is the fastest at the moment [1]. In terms of longer range, there has been a demonstration by VLCC that achieved 1kbps transmission of the distance 2km, that is the world's longest distance for VLC. Samsung and ETRI are also active in developing VLC applications. They have demonstrated 120Mbps full duplex mobile-to-mobile transmission and 100Mbps signboard transmission. Please see the following video of Nakagawa lab. http://www.youtube.com/watch?v=QEh5f49LsB4 Widespread use of LEDs in traffic applications and growing interest in Intelligent Transport System (ITS) presents an opportunity for VLC. Data transmission using LED traffic lights, LED road illumination, and LED brake lights are typical application. Dr. Yamazato, the instructor of this tutorial, is a leader in VLC application to ITS and he recently achieved 16kbps data transmission and distance up to 70m in a driving situation with a vehicle moving with 30km/h. Today VLC using LED is a hot topic and VLC projects have been initiated in Europe and US. In 2006 Siemens launched VLC project. Later in 2008, European Commission established OMEGA project with a consortium of 20 European partners from industry and the scientific community [3]. Meanwhile, in 2008, the US National Science Foundation has approved a grant of $18.5 million to help establish and the Engineering Research Center focuses on VLC. The members of the Center include the Rensselaer Polytechnic Institute in New York, Boston University and the University of New Mexico. The University of California also have launched five-year research project called the Ubiquitous Communication by Light (UC-Light) that is founded with $3.5 million from the University. The project is anticipated to begin in 2009 and run for five years. VLC is in the process of standardization by the IEEE 802.15 TG7 and VLCC as well as other standard organizations. The first VLC specification standard was released from JEITA in conjunction with VLCC in 2007. Later in 2008, VLCC released their first specification standard adopting and expanding the IrDA physical layer. IrDA transceiver transmission wavelength (IrDA physical layer) is expanded to accommodate the visible light wavelength. By adapting this specification, the existing IrDA optical modules can be used for VLCC data transmission with slight modification. In January 2009, IEEE 802.15 (Wireless Personal Area Networks) Task Group 7 (Visible Light Communication) has been launched. At the 6th meeting held in November 2009 they adopted the baseline draft text for the development of the 802.15.7 standard. The goal of this tutorial is to introduce current VLC technology and its trends. Starting with an overview of VLC, participants will learn basics of VLC, on-going standardization activities and VLC. We will provide some experimental results and furthermore detail to enhance VLC application.

  • Visible Light Communication and its application to ITS

    • T. Yamazato
    • OBN, Tokyo, Japan
    • Jun. 2011

  • Road-to-Vehicle Visible Light Communication using LED array and on-vehicle high-speed camera

    • T. Yamazato
    • Technical Report of IEICE, AN2011-5, pp.21-26, Tokyo, Japan
    • May 2011
    • We are conducting a study on visible light communications (VLC) using an LED traffic light and a high-speed camera equipped in a vehicle. Since we use the camera, we can capture and record surround images of the vehicle while receiving the data transmitted from the LED traffic light. This paper introduces the VLC system we are working on.

  • Sharing your Teaching Tips through OCW

    • T. Yamazato
    • OCWC-Global-2011, MIT, May 2011., MIT, Cambridge, MA, USA
    • May 2011

  • Wireless Distributed Networks

    • S. Sampei, K. Sakaguchi, T. Yamazato, H. Okada, et. al.
    • Corona Publishing Co.
    • Mar. 2011

  • Information to Cars by Traffic Light": New Possibilities for Deterring Accidents at Intersections"

    • T. Yamazato
    • Chunichi News Paper
    • Mar. 2011

  • Flashing Traffic Signals Provide Information to Cars at Intersections - System Experiment at Nagoya University

    • T. Yamazato
    • Mainichi Newspaper
    • Mar. 2011

  • Dynamic Resource Allocation for Improvement of Spectrum Efficiency of\\Satellite Terrestrial Integrated Mobile Communication System

    • T. Aman, T. Yamazato
    • IEICE Transactions on Communications, Vol.J94-B No.3 pp.373-382
    • Mar. 2011
    • In Satellite Terrestrial Integrated Mobile Communication System, a single mobile terminal can communicate to both satellite and terrestrial communication systems depend upon his location, QoS and availability of resources among satellite and terrestrial communication systems. But it is hard to achieve high spectrum efficiency of Satellite Terrestrial Integrated Mobile Communication System using fixed resource allocation schemes because variation of satellite traffic and terrestrial traffic is different. In this paper, we propose dynamic resource allocation schemes according to traffic of satellite communication systems and terrestrial communication systems. Finally we show spectrum efficiency is improved by proposed scheme.

  • TDOA UWB Positioning with Three Receivers Using Known Indoor Features

    • J. Kietlinski-Zaleski, T. Yamazato
    • IEICE Transactions on Fundamentals, Vol.E94-A No.3 pp.964-971
    • Mar. 2011
    • Ultra-Wideband is an attractive technology for short range positioning, especially indoors. However, for normal 3D Time Difference of Arrival (TDOA) positioning, at least four receivers with an unblocked direct path to the transmitter are required. A requirement that is not always met. In this work, a novel method for TDOA positioning using only three receivers is presented. TDOA positioning with three receivers is possible by exploiting the knowledge of some of the indoor features, namely positions of big flat reflective surfaces, for example ceiling and walls. The proposed method was verified using data from a measurement campaign.

  • Optimization of gaussian pulse using ambiguity function in Biorthogonal Frequency Division Multiplexing (BFDM)

    • D. Goto, T. Yamazato, B. Mongol
    • IEICE General Conference, B-5-28, p.414, Tokyo, Japan
    • Feb. 2011

  • Channel model for Road to Vehicle Visible Light Communication System using LED Array and High-Speed Camera

    • T. Ozawa, T. Nagura, T. Yamazato, T. Yendo, T.Fujii, H. Okada
    • IEICE General Conference, A-17-6, p.252, Tokyo, Japan
    • Feb. 2011

  • A note on turbo compression and joint error correction of temporally and spatially correlated sources

    • K. Kobayashi, T. Yamazato, M. Katayama
    • IEICE General Conference, B-20-15, p.610, Tokyo, Japan
    • Feb. 2011

  • High-Speed LED Traffic Sign Tracking Method Using Image Sensor with High-Speed Capturing Ability of Partial Area

    • K. Maeno, T. Yendo, M. P. Tehrani, T. Fujii, T. Yamazato, H. Okada, M. Tanimoto
    • Technical Report of IEICE, ITS2010-41, pp.101-106, Sapporo
    • Feb. 2011
    • Visible Light Communication(VLC) using LEDs has been proposed as a wireless communication method. As an application of VLC in ITS, we propose a road-to-vehicle visible light communication system using an LED traffic sign as a transmitter and an image sensor as a receiver. For conducting the communication, it is necessary to have high-speed tracking of the LED traffic sign by the image sensor. In this paper, we propose new high-speed tracking method for this system.

  • Performance Improvement with the Inverted Signal to Track an LED Array Transmitter on Road-to-Vehicle Visible Light Communications

    • T. Nagura, T. Yamazato, T. Yendo, T. Fujii, H. Okada
    • Technical Report of IEICE
    • Feb. 2011

  • Overlay Coding for Visible Light Communication using LED Array and High-Speed Camera

    • S. Nishimoto, T. Nagura, T. Yamazato, T. Yendo, T. Fujii, H. Okada, S. Arai
    • Technical Report of IEICE, Hokkaido, Japan
    • Feb. 2011

  • Channel Estimator by Sum of Kalman-Based Estimation and Interpolation Estimation for MC-CDMA based Inter-Vehicle Communication

    • H. Hiraiwa, T. Yamazato, M. Katayama
    • IEICE Transactions on Communications, vol.J94-B, no.2, pp.304-307
    • Feb. 2011
    • In this letter, we propose a new channel estimator for MC-CDMA based inter-vehicle communication. The proposed channel estimator estimates the channel recursively by weighted sum of Kalman-based channel estimator and an interpolation estimator. As results, the proposed channel estimator can suppress estimation error, which occurs when using Kalman channel estimator.

  • LED Traffic Light Detection Using High-speed-camera Image Processing for Visible Light Communication System,

    • H. C. N. Premachandra, T. Yendo, M. P. Tehrani, T. Yamazato, H. Okada, T. Fujii, M. Tanimoto
    • The Journal of the Institute of Television Engineers of Japan, vol.65, no.3, pp.354-360
    • Feb. 2011
    • We propose a visible light road-to-vehicle communication system at intersection as an ITS (Intelligent Transport System) technique. In this system, the communication between a vehicle and an LED traffic light is conducted using an LED traffic light as a transmitter and an on-vehicle high-speed camera as a receiver. The LEDs in the transmitter emit light at high frequency, and those emitted light is captured by the high-speed camera for communications. Here, the luminance value of the LEDs in the transmitter should be found, and then it should be tracked in consecutive frames while the vehicle is moving by processing the images from the high-speed camera. In this paper, we propose new algorithms for finding and tracking the transmitter, which result in increased communication speed and data rate compared to the previous methods. Experiments using appropriate images showed the effectiveness of the proposals.

  • Improvement of the Node Activity Rate by Introduction of New Inactive Node Reactivation Condition in Solar-Powered Wireless Sensor Networks

    • K. Ota, K. Kobayashi, T. Yamazato, M. Katayama
    • Technical Report of IEICE, USN2010-63, pp.137-142, Hiroshima, Japan
    • Jan. 2011
    • Our goal is improvement of the node activity rate in solar-powered wireless sensor networks. One method to reduce the consumption energy of the entire network is a cooperative transmission that uses a relay node when a node sends data. But if we don\\\'t consider the change in harvesting energy, the node activity rate is declined during nighttime. In this paper, we smooth the day-and-night node activity rate by introducing the new inactive node reactivation condition and achieve the required high node activity rate.

  • Erasure Coding for Road-to-Vehicle Visible Light Communication Systems

    • H. Okada, T. Ishizaki, T. Yamazato, T. Yendo, T. Fujii
    • IEEE Intelligent Vehicular Communications System Workshop, pp.970-974, Las Vegas, USA
    • Jan. 2011
    • https://doi.org/10.1109/CCNC.2011.5766593
    • In this paper, we focus on a road-to-vehicle visible light communication (VLC) system using LED traffic lights. In this system, an LED traffic light consists of a 2-dimensional LED array (2D LED array), and cars are equipped with high-speed 2-dimensional cameras (2D image sensors). An important issue of this system is frame loss. Sometimes, 2D image sensor in a car fails to get a frame. So as to mitigate the influence of frame loss, we propose to apply erasure coding to the road-to-vehicle VLC system. In the proposed system, a data sequence is encoded by LDPC code whose length is much longer than the size of 2D LED array. In addition, code synchronization is required for the proposed system. We also propose a code synchronization scheme, which makes use of error detection capability of LDPC code. We evaluate the performance of our proposed system, and show that it can recover frame loss for high SNR when less than 8 frames among total 18 frames are lost. In addition, we show that our proposed code synchronization scheme can ignore its errors.

  • Parallel Communication Using Visually Non-Lighting LEDs

    • K. Maeno, T. Yendo, M. P. Tehrani, T. Fujii, H. Okada, T. Yamazato, M. Tanimoto
    • International Workshop on Advanced Image Technology (IWAIT), Jakarta, Indonesia
    • Jan. 2011
    • Previous studies on visible light communication uses visually lighting LEDs. However, LEDs are not always lighting. In this paper, we propose visible light communication method using visually non-lighting LEDs. This method enables us to communicate in different situations, e.g. using visually non-lighting tail lamps of cars or visually non-lighting traffic lights. We realize visually non-lighting LEDs by reducing luminescence energy of LEDs according to the brightness in the environment. To reduce luminescence energy of LEDs, we reduce the number of emitting LEDs, increase the interval of emitting, and decrease the luminance of emitting LEDs. In our research we consider the case that the transmitter is tail lamps of cars and the receiver is high-speed camera. We conduct two types of experiments to demonstrate the performance of the proposed system. One is to confirm that LEDs are visually non-lighting. The other is measurement of Bit Error Rate of communication using visually non-lighting LEDs. Experimental results demonstrate that it is possible to make communication using visually non-lighting LEDs. In our future work, we plan to use different sensor devices such as photo diode or CCD in order to decrease the error rate in communication.

  • Hierarchical Encoding System of Road-to-Vehicle Communication

    • T. Masuda, T. Yendo, T. Yamazato, H. Okada, M. P. Tehrani, T. Fujii, M. Tanimoto
    • International Workshop on Advanced Image Technology (IWAIT), Jakarta, Indonesia
    • Jan. 2011
    • In this paper, we propose the new visible light road-to-vehicle communication system. We use the LED traffic light as the transmitter and the high-speed camera on the vehicle as the receiver. In this system, the data is encoded hierarchically and assign with the each frequency components of the image. We use the DFT for hierarchical encoding considering channel characteristic and quantization of the luminance. The communication experiments were conducted to confirm the effectiveness of the proposed method.

  • Image Processing Based Road-to-vehicle Visible Light Communication

    • H. C. N. Premachandra, T. Yendo, M. P. Tehrani, T. Yamasato, H. Okada, T. Fujii, M. Tanimoto
    • International Workshop on Advanced Image Technology (IWAIT), Jakarta, Indonesia
    • Jan. 2011
    • Visible Light Communication(VLC) has been introduced as a new wireless communication method. In this paper, we propose a VLC system for Intelligent Transport System (ITS) to communicate between infrastructure and the vehicle. In this system, we use a LED array as a transmitter and on-vehicle high speed camera as a receiver. Here, LEDs in the transmitter emit light in 500Hz and the emission patterns are used to achieve communication, by capturing them using the high speed camera in high frame rate. The images captured by high speed camera are processed to find the transmitter, track the found transmitter, and capture the emission pattern of transmitter in consecutive frames. In our previous work, we proposed algorithms to finding and tracking. In this paper, we introduce method to capture the emission pattern of the transmitter. Then out door communication experiments were conducted to confirm the effectiveness of the proposed VLC system.

  • Dynamic Bandwidth Allocation of Satellite/Terrestrial Integrated Mobile Communication System

    • T. Yamazato, T. Aman, M. Katayama
    • IEEE Global Communications Conference (GLOBECOM), FLORIDA, U.S.A
    • Dec. 2010
    • In this paper, we propose two dynamic bandwidth allocation (DBA) schemes, a game theory based DBA and a successive DBA, for satellite/terrestrial integrated mobile communication system (STICS). The game theory based DBA allocate the bandwidth according to a utility function based on a weighted demand bandwidth of both satellite and terrestrial system. The successive DBA recursively allocates an unit of bandwidth according to a weighted number of bandwidth unfilled cells of both satellite and terrestrial systems, until the total bandwidth is fulfilled. As results, both DBA outperform the conventional fixed bandwidth allocation scheme. Between two proposed DBA, the successive DBA shows better spectral improvement ratio than the game theory based DBA.

  • LED Traffic Light Detection Using High-speed-camera Image Processing for Visible Light Communication System,

    • H. C. N. Premachandra, T. Yendo, M. P. Tehrani, T. Yamazato, H. Okada, T. Fujii, M. Tanimoto
    • Workshop on Picture Coding and Image Processing, PCSJ2010/IMPS2010, Nagoya, Japan
    • Dec. 2010
    • Intelligent transport system has been introduced to reduce traffic problems such traffic accidents and traffic congestions. In this paper, we introduce a receiver for a road to vehicle Visible Light Communication (VLC) system which is proposed as an Intelligent Transport System (ITS) technique. In this system, an on-vehicle high-speed camera is used as a receiver and an LED array is used as a transmitter. VLC is a wireless communication using luminance. Here, transmitter send information by emitting light and receiver receive them by capturing the luminance of emitting LEDs in the array(Luminance: whether each LED is on or off). For capturing the Luminance, it is necessary to find the transmitter and track it in consecutive frames. In our previous works we introduced methods for finding and tracking. In this paper, we shortly explain the proposed transmitter finding and tracking methods and then a new method is proposed for capturing the luminance of LEDs to achieve communication.

  • Hierarchical Encoding System for Road-to-Vehicle Communication Using LED Traffic Light

    • T. Masuda, T. Yendo, T. Yamazato, H. Okada, M. P. Tehrani, T. Fujii, M. Tanimoto
    • Workshop on Picture Coding and Image Processing, PCSJ2010/IMPS2010, Nagoya, Japan
    • Dec. 2010
    • This paper discusses the visible light road-to-vehicle communication system at intersection as one of ITS (Intelligent Transport System) technique. The communication between a vehicle and an LED traffic light is approached using an LED traffic light as a transmitter, and on-vehicle high-speed camera as a receiver. In this system, it is able to send data by blinking the LEDs of the traffic light in two dimensional patterns, and able to receive them by high-speed camera with image processing. Here, we aim to conduct long-distance high-speed visible light communication. When the distance between transmitter and receiver is far, the image of the LED traffic light captured by on-vehicle high-speed camera is very small. So, if the data are put on two dimension patterns without modification, data would be mistaken, because the two dimension patterns can’t be realized correctly. To solve this problem, data are encoded hierarchically before they are lighted by the LED traffic light. This is called as hierarchical encoding that the data are assigned with each spatial frequency.

  • Parallel Visible Light Communication Using Visually Non-Lighting LEDs

    • K. Maeno, T. Yendo, M. P. Tehrani, T. Fujii, T. Yamazato, H. Okada, M. Tanimoto
    • Workshop on Picture Coding and Image Processing, PCSJ2010/IMPS2010, Nagoya, Japan
    • Dec. 2010
    • The proposed visible light communication method uses visually non-lighting LEDs, which enables us to communicate in different situations, e.g. using visually non- lighting tail lamps of cars or visually non-lighting traffic lights. We realize visually non-lighting LEDs by reducing luminescence energy of LEDs according to the brightness in the environment. Experimental results demonstrate that it is possible to make communication using visually non-lighting LEDs.

  • [Encouragement Talk] Distributed Error Correcting Coding and Joint Decoding Scheme Using Spatial Correlation of Sensor ADC Output in Wireless Sensor networks

    • K. Kobayashi, T. Yamazato, M. Katayama
    • Technical Report of IEICE, WBS2010-39, pp.23-28, Tsukuba, Japan
    • Dec. 2010
    • In wireless sensor networks, sensor nodes are densely deployed for reliable sensing of physical phenomenon. Due to the high density in the sensing field, sensor observations are spatially correlated. In this paper, we focus on joint channel decoding utilizing the spatial correlation of multiple sensor observations. Our proposed scheme makes use of an estimation of the correlation according to ADC bit levels. In addition, the proposed scheme makes use of Gray code for avoiding multiple bit-flipping between adjacent ADC output values. The performance of our approach is examined by simulations using sensor data from experiments in a real indoor environment.

  • EXIT Analysis for MAP-based Joint Iterative Decoding of Separately Encoded Correlated Sources

    • K. Kobayashi, T. Yamazato, M. Katayama
    • IEICE Transactions on Communications, vol.E93-B, no.12, pp.3509-3513
    • Dec. 2010
    • https://doi.org/10.1587/transcom.E93.B.3509
    • We develop a mathematical framework for the extrinsic information transfer (EXIT) analysis to assess the convergence behavior of maximum a posteriori (MAP)-based joint iterative decoding of correlated sources, which are separately encoded and transmitted over noisy channels. Unlike the previous work, side information about the correlation is not perfectly given at the joint decoder but is extracted from decoder output and updated in an iterative manner. The presented framework provides a convenient way to compare between schemes. We show that it allows us to easily and accurately predict joint decoding gain and turbo cliff position.

  • TOA UWB Positioning with Two Receivers Using Known Indoor Features

    • J. Kietlinski-Zaleski, T. Yamazato, M. Katayama
    • IEICE Transactions on Communications, vol.E93-B, no.12, pp.3624-3631
    • Dec. 2010
    • Ultra-Wideband is an attractive technology for short range positioning, especially indoors. However, for normal Time of Arrival (ToA) positioning, at least three receivers with unblocked direct path to the transmitter are required. A requirement that is not always met. In this work, a novel algorithm for ToA positioning using only two receivers is presented. This is possible by exploiting the knowledge of some of the indoor features, namely positions of big flat reflective surfaces, for example ceiling and walls. The proposed algorithm was tested using data from a measurement campaign.

  • Experimental Results on Simple Distributed Cooperative Transmission Scheme with Visible Light Communication

    • T. Yamazato, K. Nakao, H. Okada, M. Katayama
    • IEICE Transactions on Communications, vol.E93-B, no.11, pp.2959-2962
    • Nov. 2010
    • We consider a distributed transmission of data packet to a sink where the distance of a sensor node to a sink is much longer than the maximum communication range of each sensor node. We give a simple modification to the transmitter, i.e., multiplication of random phase before the transmission. Thanks to Turbo Code, it is possible to extend the trans- mission range as the received amplitude varies symbol by symbol for our scheme while whole data packet may be lost for the conventional scheme. In this letter, we report the experimental results of our scheme equivalently developed using visible light communication.

  • Performance evaluation of the cognitive piggyback overlay systems with dirty paper coding

    • J. Naganawa, K. Kobayashi, M. Katayama, T. Yamazato
    • International Symposium on Communications and Information Technologies (ISCIT), no. FA1-1-4, pp.974-979, Tokyo, Japan
    • Oct. 2010
    • https://doi.org/10.1109/ISCIT.2010.5665130
    • This manuscript considers a secondary system sharing the spectrum with the primary system at the same time and on the same frequency. We propose a cognitive overlay system in which the secondary system relays the primary signal and piggybacks its own data on it. Furthermore, the secondary system uses the channel coding based on the dirty paper coding (DPC). The result of the analysis shows that the proposed scheme allows the secondary system to communicate at the same speed as the primary system without any harm to it.

  • Improvement of Sequential-Test-Based Cooperative Spectrum Sensing Systems in Band Limited Control Channels

    • S. Mitsuya, K. Kobayashi, T. Yamazato, M. Katayama
    • International Symposium on Communications and Information Technologies (ISCIT), no. FA1-1-3, pp.968-973, Tokyo, Japan
    • Oct. 2010
    • https://doi.org/10.1109/ISCIT.2010.5665127
    • In a cooperative spectrum sensing system, many nodes perform spectrum sensing and report their decisions to one fusion center via control channels. This paper considers efficient use of the frequency band for the control channels. For this purpose, sequential-test is introduced for the local decision at each node. With this scheme, the transmission timing of the reports from the nodes becomes at random and necessary maximum bandwidth for the control channels decreases. Numerical results show that this sequential-test-base-scheme not only decreases the number of simultaneous reports but also improves sensing reliability. For further improvement, this paper also introduces a decision scheme at the fusion center based on probabilistic features of the reports from the nodes.

  • Inband and Outband Spectrum Analysis of the BFDM and BFDM/OQAM Signals with Truncated Gaussian Pulses

    • B. Mongol, T. Yamazato, M. Katayama
    • International Symposium on Information Theory and Its Applications (ISITA), Taichung, Taiwan
    • Oct. 2010
    • Pulse-shaping OFDM, or more generally BFDM and BFDM/OQAM, systems are originally proposed to combat inter- carrier interference (ICI) caused by time-variance of the channel. The main property that makes these signals robust against ICI is that they allow to employ time-frequency well localized pulses, particularly Gaussian pulse which has the best time-frequency localization. However, this property also suppresses the outband or inband spectral leakage of the BFDM and BFDM/OQAM signal, making them attractive physical layer modulation scheme for cognitive radio. In this paper we analyze the power density spectra of the BFDM and BFDM/OQAM signals and numerically evaluate the inband and outband spectra for truncated Gaussian pulses.

  • Error-correcting scheme based on chaotic dynamics and its performance for noncoherent chaos communications

    • S. Arai, Y. Nishio and T. Yamazato
    • NOLTA, IEICE, vol. 1, no. 1, pp. 196-206, Oct. 2010.
    • Oct. 2010
    • This paper proposes a novel error-correcting scheme using chaotic dynamics for noncoherent chaos communications. In our proposed system, two successive chaotic sequences are generated from the same chaotic map; the second sequence is generated with an initial value which is the last value of the first sequence. In this case, successive chaotic sequences having the same chaotic dynamics are created. This feature gives the receiver additional information to correctly recover the information data and thus improves the bit error performance of the receiver. As results of the computer simulation, we confirm that the advantage gained in BER performance of the proposed error-correcting method is about 1-1.5 dB compared to conventional method. In addition, we achieve that the proposed error-correcting scheme is performed without the new additional redundancy code by using the chaotic dynamics.

  • Kalman Channel Estimator for BFDM/OQAM system in Time-Frequency Dispersive Channels

    • B. Mongol, T. Yamazato, M. Katayama
    • IEICE Transactions on Communications, vol.J93-B, no.10, pp.1466-1480
    • Oct. 2010
    • Biorthogonal Frequency Division Multiplexing / Offset QAM (BFDM/OQAM) allows to employ a Gaus- sian transmitter pulse. Thus, it performs well in the time-frequency dispersive channels as it can suppress ISI and ICI without having guard interval. However, in the highly mobile environment the performance deteriorates and channel estimation schemes became essential for further improvement of BFDM/OQAM systems. This paper proposes a novel adaptive channel estimator based on Kalman filter. Especially, we derive the essential equations to design Kalman filter, namely, the process equation and the measurement equation.

  • A Study on Joint Channel Decoding Using Spatial Correlation of Sensor Observations According to ADC Bit levels

    • K. Kobayashi, T. Yamazato, M. Katayama
    • IEEE International Workshop on Wireless Distributed Networks (WDN), pp.484-489, Istanbul, Turkey
    • Sep. 2010
    • https://doi.org/10.1109/PIMRCW.2010.5670522
    • In densely deployed wireless sensor networks, observations of the sensor nodes are spatially correlated. In this paper, we study a joint channel decoding scheme utilizing bit correlation of the sensor observations according to bit levels of analog-digital converter (ADC). If sensor ADC output is interpreted as natural binary numeral, carry propagation may occur between adjacent ADC output values. Such carry propagation leads to the degradation of joint decoding gain. We focus on the use of Gray code for avoiding the carry propagation. The performance of our approach is demonstrated by simulations using sensor data from experiments in a real indoor environment.

  • TDOA UWB Positioning with Three Receivers Using Known Indoor Features

    • J. Kietlinski-Zaleski, T. Yamazato, M. Katayama
    • IEEE International Conference on Ultra-Wideband (ICUWB), Nanjing. China
    • Sep. 2010
    • https://doi.org/10.1109/ICUWB.2010.5616909
    • Ultra-Wideband is an attractive technology for short range positioning, especially indoors. However, for normal 3D Time Difference of Arrival (TDoA) positioning, at least four receivers with unblocked direct path to the transmitter are required. A requirement that is not always met. In this work, a novel method for TDoA positioning using only three receivers is presented and tested using real-world measurements. Positioning with three receivers is possible by exploiting the knowledge of some of the indoor features, namely positions of big flat reflective surfaces, reflectors, for example ceiling and walls.

  • Tracking an LED Array Transmitter for Visible Light Communications in the Driving Situation

    • T. Nagura, T. Yamazato, M. Katayama, T. Yendo, T. Fujii, H. Okada
    • IEEE International Symposium on Wireless Communication Systems (ISWCS), pp.765-769, York, United Kingdom
    • Sep. 2010
    • https://doi.org/10.1109/ISWCS.2010.5624361
    • In this paper, we discuss on a decoding algorithm for visible light communication systems in the driving situation using an LED array transmitter and a high-speed camera receiver. We propose an LED array detection method using M-sequence and an LED array tracking method using inverted signals. We confirm that we can distinguish LED array candidates correctly with M-sequence. We also confirm that we can suppress the flicker of the LED and improve the data rate as compared with the previous method.

  • UWB Positioning Using Known Indoor Features - Environment Comparison

    • J. Kietlinski-Zaleski, T. Yamazato
    • International Conference on Indoor Positioning and Indoor Navigation (IPIN), Zurich, Switzerland
    • Sep. 2010
    • https://doi.org/10.1109/IPIN.2010.5648089
    • Ultra-Wideband is an attractive technology for short range positioning, especially indoors. However, for normal Time of Arrival (TOA) positioning, at least three receivers with unblocked direct path to the transmitter are required. A requirement that is not always met. In our previous work \\\\cite{Kietlinski-Zaleski2010PLANS} we presented a novel 3D TOA UWB indoor positioning method that uses only two receivers. This is possible by exploiting the knowledge of some of the indoor features, namely ceiling and walls. In this work, we verify the usability of the method using measurement results in three environments: a lecture room, a cluttered laboratory and a corridor. By comparing the results of the method for three environments, we draw conclusions about its strengths and weaknesses.

  • Fast Recognition of LED Array by High-Speed Camera

    • T. Yamazato
    • Enginnering Sciences Society Conference of IEICE, AP-2-6, Osaka, Japan
    • Sep. 2010

  • Implovement Method of transmission speed for Visible Light Communication System using LED Array and High-Speed Camera

    • T. Ozawa, T. Nagura, T. Yamazato, T. Yendo, T. Fujii, H. Okada
    • Enginnering Sciences Society Conference of IEICE, Osaka, Japan
    • Sep. 2010

    • K. Maeno, T. Yendo, T. Yamazato, H. Okada, M. P. Tehrani, T. Fujii, M. Tanimoto
    • Forum on Informatio Technology, RM-003, Fukuoka
    • Sep. 2010

  • LED Traffic Light Detection Using a High-speed-camera for a Road-to-vehicle Visible Light Communication System

    • H. C. N. Premachandra, T. Yendo, M. P. Tehrani, T. Yamazato, H. Okada, T. Fujii, M. Tanimoto
    • Forum on Informatio Technology, RM-002, Fukuoka
    • Sep. 2010

  • Study on parallel visible light communication using visually non-lighting LED

    • K. Maeno, T. Yendo, M. P. Tehrani, T. Fujii, T. Yamazato, H. Okada, M. Tanimoto
    • IEEJ General Conference, , Matsuyama, Japan
    • Aug. 2010
    • The proposed visible light communication method uses visually non-lighting LED, which enable us to communicate by using tail lamps of cars. In addition, this method can communicate with visually non-lighting traffic lights.

  • Influence of quantization of brightness in road-vehicle communication

    • K. Masuda, T. Yendo, T. Yamazato, H. Okada, P. Tehrani, T. Fujii, M. Tanimoto
    • Tokai-Section Joint Conference on Electrical and Related Engineering, Kasugai, Japan
    • Aug. 2010

  • Inter-vehicle visible light communication using visually non-lighting LED

    • K. Maeno, T. Yendo, M. P. Tehrani, T. Fujii, T. Yamazato, M. Tanimoto
    • 2010 IEE of Japan, Tokai Section, Wakate Seminar., Nagoya, Japan
    • Aug. 2010
    • Previous studies on visible light communication uses visually lighting LED. However, LEDs isn’t always lighting. In this paper, we propose visible light communication method using visually non-lighting LED. This method enables us to communicate using visually non-lighting tail lamps of cars and visually non-lighting traffic lights and so on. We conduct two types of experiments to demonstrate the performance of the proposed system. The result shows possibility of communication using visually non-lighting LED.

  • Unique teaching practices presented at Nagoya Univeristy OCW

    • T. Yamazato
    • Japanese Society for Engineering Education 58th Annual Conference & Exposition, Tohoku University, Sendai, Japan
    • Aug. 2010

  • Performance evaluation of the cognitive piggyback overlay systems using QAM modulation

    • J. Naganawa, K. Kobayashi, T. Yamazato, M. Katayama
    • Technical Report of IEICE, vol.110, no.153, SR2010-31, pp.89-940, ATR (Kyoto), Japan
    • Jul. 2010
    • This manuscript considers a secondary system sharing the spectrum with the primary system at the same time and frequency. The proposed cognitive overlay system relays the primary signal and piggybacks its own data on it. As the modulation scheme, phase shift keying and quadrature amplitude modulation are considered and performance with them are compared. The result of the analysis for Rayleigh fading environment shows that the proposed scheme with regenerative relay allows the secondary signal to communicate at the same speed of the primary signal without any harm to it.

  • Improvement of the Sequential-Test-Based Cooperative Spectrum Sensing Systems in Band Limited Control Channels

    • S. Mitsuya, K. Kobayashi, T. Yamazato, M. Katayama
    • Technical Report of IEICE, vol.SR2010-19 pp.19-24, ATR(Kyoto), Japan
    • Jul. 2010
    • In a cooperative spectrum sensing system, many nodes perform spectrum sensing and report their decisions to one fusion center via control channels. This paper considers efficient use of the frequency band for the control channels. For this purpose, sequential-test is introduced for the local decision at each node. With this scheme, the transmission timing of the reports from nodes becomes at random and necessary maximum bandwidth for the control channels decreases. Numerical results show that this sequential-test-base-scheme not only decreases the number of simultaneous reports but also improves sensing reliability. For further improvement, this paper introduces a decision scheme at the fusion center based on probabilistic features of the reports from nodes.

  • Visible Light Communication Between LED Array and On-vehicle High Speed Camera

    • H. C. N. Premachandra, T. Yendo, M. P. Tehrani, T. Yamazato, H. Okada, T. Fujii, M. Tanimoto
    • Technical Report of IEICE, ITS2010-10, pp.25-30
    • Jul. 2010

  • Study on parallel visible light communication using visually non-lighting LED

    • K. Maeno, T. Yendo, M. P. Tehrani, T. Fujii, T. Yamazato, H. Okada, M. Tanimoto
    • Technical Report of IEICE, ITS2010-9, pp.19-24
    • Jul. 2010

  • Visible Light Communications using LED Array and Image Sensor

    • T. Yamazato
    • Visible Light Communication Consortium, #74 VLCC Promotion Committee, Tokyo, Japan
    • Jul. 2010

  • Spectrum Efficiency Improvement by Dynamic Resource Allocation for Satellite Terrestrial Integrated Mobile Communication System

    • T. Aman, T. Yamazato
    • Technical Report of IEICE, Vol. SAT2010-27, pp.97-102, Kitami Institute of Technology, Kitami, Japan
    • Jul. 2010
    • In Satellite Terrestrial Integrated Mobile Communication System, a single mobile terminal can com- municate to both satellite and terrestrial communication systems depend upon his location, QoS and availability of resources among satellite and terrestrial communication systems. But it is hard to achieve high spectrum efficiency of Satellite Terrestrial Integrated Mobile Communication System using fixed resource allocation schemes because variation of satellite traffic and terrestrial traffic is different. In this paper, we propose dynamic resource allocation schemes according to traffic of satellite communication systems and terrestrial communication systems. Finally we show spectrum efficiency is improved by proposed scheme.

  • Effect of Slanted LED Traffic Light on Road-to-Vehicle Visible Light Communication

    • Y. Shiraki, T. Yamazato, T. Yendo, T. Fujii, H. Okada, S. Arai
    • Technical Report of IEICE, Vol. ITS2010-12, pp. 31-36, Gamagori
    • Jul. 2010
    • In this paper, we discuss on road-to-vehicle visible light communications using an LED traffic light and a high-speed camera fixed to a vehicle. We assume that the camera is facing forwards and that it is parallel to the surface of the road. In our study, the LED traffic light in the image is slanted to represent the case in which the camera and the LED traffic light are not directly facing each other in an intersection. In order to demodulate data, we consider the slanting of the LED traffic light on the image. In this paper, we evaluate the effect the slanting of the LED traffic light on communication.

  • High-speed-camera Image Processing Based LED Traffic Light Detection for Road-to-vehicle Visible Light Communication

    • H.C.N. Premachandra, T. Yendo, M. P. Tehrani, T. Yamazato, H. Okada, T. Fujii, M. Tanimoto
    • IEEE Intelligent Vehicles Symposium (IV), pp.793-798, San Diego, California, USA
    • Jun. 2010
    • https://doi.org/10.1109/IVS.2010.5548097
    • As one of ITS technique, a new visible light road to- vehicle communication system at intersections is proposed. In this system, the communication between a vehicle and an LED traffic light is conducted using an LED traffic light as a transmitter, and an on-vehicle high-speed camera as a receiver. The LEDs in the transmitter emit light in high frequency and those emitting LEDs are captured by the high-speed camera for making communication. Here, the luminance value of LEDs in the transmitter should be captured in consecutive frames to achieve effective communication. For this purpose, first the transmitter should be found, then it should be tracked in consecutive frames by processing the images from the high-speed camera. In this paper, we propose new effective algorithms for finding and tracking the transmitter, which result in a increased communication speed, compared to the previous methods. Experiments using appropriate images showed the effectiveness of the proposals.

  • Performance evaluation of a power supply overlaid communication for cooperative motion of multiple machines.

    • F.Minamiyama, H.Koga, T.Yamazato, M.Katayama
    • Technical Report of IEICE, Vol.110 No.72 (WBS2010-12) pp.63-68, Okinawa,Japan
    • Jun. 2010
    • In order to reduce wiring in industrial machinery, we consider a cooperative-action system in which various devices (slaves) are multidrop-connected through a bus topology to a controlling master. Additionally, power is supplied together with communication signals over the same wiring. To accurately deliver timing information to the slaves, we propose the use of a spread spectrum(SS) signal. Together with the this signal, the control information signal is transmitted by applying an OFDM scheme. This manuscript provide an example of a set of system parameter to be used for an actual application. To assess the proposed method, the reception characteristics and mutual influence of the two overlaid signals is also explained.

  • Effects and Mitigation of Channel Errors in a Wireless Control System for Cooperative Motion of Machines

    • T. Kondo T. Yamazato M. Katayama
    • Technical Report of IEICE, Okinawa, Japan
    • Jun. 2010
    • This manuscript discusses a wireless control system for cooperative motion of machines, and clarifies the influence of channel errors to a cooperative motion system. In addition, a new wireless control method is proposed to improve performance of cooperative motion when the channel errors occur. As an example of the controlled objects, rotary inverted pendulums with wireless connections in feedback loops are considered. In this study, we select a simple setting for cooperative motion, two rotary inverted pendulums are operated symmetrically. In order to improve the synchronization of their cooperative motion, we propose a system in which each pendulum receives control signals of it and also of the other pendulum. In addition, the main controller generates control signals for them based on the state information of both objects. The proposed system provides a better performance of cooperative motion than a conventional system with two independent feedback loops does.

  • Extension of Network Lifetime Using Cooperative ARQ Protocol for Solar Energy Harvesting Wireless Sensor Networks

    • K. Ota, K. Kobayashi, T. Yamazato, M. Katayama
    • Technical Report of IEICE, vol.110, no.50, USN2010-1, pp.1-4,, Tokyo, Japan
    • May 2010
    • Wireless sensor networks require long-term operation of sensor nodes and reliable data transmission. Attention is being focused on the use of environmental energy for battery charging as a long-term operation method for sensor nodes. Besides this, one of the reliable data transmission methods is cooperative ARQ (Automatic Repeat reQuest) protocol. In this paper, we apply a cooperative ARQ protocol to solar energy harvesting wireless sensor networks. By evaluating the cooperative ARQ protocol with network lifetime, we show that it is effective for extension of network lifetime.

  • [Encouragement Talk] Joint Decoding Scheme Using Correlation of Observed Data According to ADC Bit Levels - Evaluation of Performance Improvement by Avoiding Carry Propagation of ADC Output -

    • K. Kobayashi, T. Yamazato, M. Katayama
    • Technical Report of IEICE, vol.MoMuC2010-5, pp.69-74, Okinawa, Japan
    • May 2010
    • In wireless sensor networks, sensor nodes are densely deployed for reliable sensing of physical phenomenon. Due to the high density in the sensing field, sensor observations are spatially correlated. In this paper, we focus on a joint channel decoding scheme utilizing correlation of the sensor observations according to ADC bit levels. Our proposed scheme makes use of Gray code mapping to avoid carry propagation of sensor ADC outputs. The performance of our approach is examined by simulations using sensing data from experiments in a real indoor environment.

  • Improved Decoding Methods of Visible Light Communication System for ITS using LED Array and High-Speed Camera

    • T. Nagura, T. Yamazato, M. Katayama, T. Yendo, T. Fujii, H. Okada
    • IEEE Vehicular Technology Conference (VTC-Spring), Taipei, Taiwan
    • May 2010
    • https://doi.org/10.1109/VETECS.2010.5493958
    • In this paper, we consider visible light communication systems using LED array as a transmitter and high-speed camera as a receiver for Intelligent Transport System (ITS). Previously, we have proposed the hierarchical coding scheme which allocates data to spatial frequency components of the image depending on the priority. This scheme is possible to receive information of the high-priority even if communication distance is long. However, we need to distinguish multi-valued data from the received image by using a hierarchical coding. In this paper, we propose two improved decoding methods, and demonstrate to distinguish multi-valued data more correctly in the experiment.

  • Optimal Cluster Partitioning for Wireless Sensor Networks with Cooperative MISO Scheme

    • Z. Huang, T. Yamazato, M. Katayama
    • Advanced International Conference on Telecommunications (AICT), pp.323-328, Barcelona, Spain
    • May 2010
    • https://doi.org/10.1109/AICT.2010.67,14500
    • The paper discusses the optimal cluster partitioning for wireless sensor networks deployed in continuous areas. Both single-hop and multi-hop transmissions with cooperative Multi-Input Single-Output (MISO) scheme are considered for inter-cluster communications. The effects of cluster size in the energy consumption of intra-cluster communication and the amount of fused data are included in calculation. As a result, the dominant factors of the maximal network lifetimes are listed as: the cluster farthest from base station in single-hop transmission and the closest cluster in multi-hop transmission. In addition, the maximal network lifetimes of single-hop and multi-hop transmissions are compared and it is found that there exists a threshold of network size that determines which transmission is the better candidate.

  • Experimental Validation of TOA UWB Positioning with Two Receivers Using Known Indoor Features

    • J. Kietlinski-Zaleski, T. Yamazato, M. Katayama
    • IEEE/ION Position Location and Navigation Symposium (PLANS), Palm Springs, California, USA
    • May 2010
    • https://doi.org/10.1109/PLANS.2010.5507253
    • Ultra-Wideband is an attractive technology for short range positioning, especially indoors. However, for normal Time of Arrival (ToA) positioning, at least three receivers with unblocked direct path to the transmitter are required. This requirement is not always met. In this work, a novel algorithm for ToA positioning using only two receivers is presented and validated using data from a measurement campaign. Positioning with two receivers is possible by exploiting the knowledge of some of the indoor features, namely positions of big flat reflective surfaces, for example ceiling and walls.

  • Performance Evaluation of Error-Correcting Scheme Without Redundancy Code for Noncoherent Chaos Communications

    • S. Arai, Y. Nishio, T. Yamazato, S. Ozawa
    • IEEE International Symposium on Circuits and Systems (ISCAS), Paris, France
    • May 2010
    • https://doi.org/10.1109/ISCAS.2010.5537140
    • This paper considers a novel error-correcting scheme exploiting chaotic dynamics for noncoherent chaos communication. In our proposed system, two successive chaotic sequences are generated from the same chaotic map; the second sequence is generated with an initial value which is the last value of the first sequence. In this case, successive chaotic sequences having the same chaotic dynamics are created. This feature gives the receiver additional information to correctly recover the information data and thus improves the bit error performance of the receiver. Further, enhanced efficiency also comes from operating on successively modulated data; by involving less redundancy in the error correction system, it can be designed with high coding rate. In this paper, we analyze the scheme’s capability, by examining computational times and accuracy rates of error correction. bounds on its capability.

  • Correlation Estimation for Joint Decoding of Correlated Observations According to ADC Bit Levels

    • K. Kobayashi, T. Yamazato, M. Katayama
    • IEICE Transactions on Fundamentals, vol.J93-A, no.5, pp.353-364
    • May 2010
    • In wireless sensor networks, a large number of sensor nodes are densely deployed for reliable environmental sensing. Due to the high density in the sensing field, sensor observations are spatially correlated. We focus on a property that such correlated observations are available in the form of ADC\'s binary output. In this paper, we study a joint decoding of transmitted data with correlation estimation according to ADC bit levels. Based on analysis of correlation estimation error, we propose a simple but effective estimation method. Our proposal achieves good decoding performance even when correlation of some bit levels have different amplitude and sign.

  • An Access Control Method for Multipoint Cyclic Data Gathering over a PLC Network

    • Y. Ohtomo, T. Yamazato, M. Katayama
    • IEEE International Symposium on Power Line Communications and Its Applications (ISPLC), Rio de Janeiro, Brazil
    • Mar. 2010
    • https://doi.org/10.1109/ISPLC.2010.5479914
    • This paper proposes a media access control method for a multipoint cyclic data gathering system, in which each node transmits its data to the base-station periodically. In such condition, by broadcasting ACK/NACK signals from the base-station, the proposed method ensures assignment of a time slot for each node once the node succeeds to transfer its data. It is confirmed that the proposed scheme reduces packet collisions and outperforms conventional slotted-ALOHA scheme in throughput of data even with ACK/NACK errors. Furthermore the proposed scheme realizes adaptive slot assignment under cyclostationary channel environment.

  • Wireless Control Scheme with Noisy Channels for Cooperative Motion Systems

    • T. Kondo, T. Yamazato, M. Katayama
    • IEICE General Conference, Sendai
    • Mar. 2010

  • Improvement of Spectrum Efficiency by Dynamic Resource Allocation for Satellite Terrestrial Integrated Mobile Communication System

    • T. Aman, T. Yamazato, M. Katayama
    • IEICE General Conference, B-3-33, p.346
    • Mar. 2010

  • Introduction of dirty paper coding for the cognitive piggyback overlay systems

    • J. Naganawa, T. Yamazato, M. Katayama
    • IEICE General Conference, Sendai, Japan
    • Mar. 2010

  • Sub-pixel Estimation of LED Position for Visible Light Communication System using LED Array and High-Speed Camera

    • T. Nagura, T. Yamazato, M. Katayama, T. Yendo, T. Fujii, H. Okada
    • IEICE General Conference, A-17-16, p.244
    • Mar. 2010

  • BER Property of Visible Light Communication System Using LED Array and High-Speed Camera

    • Y. Shiraki, T. Yamazato, M. Katayama, T. Yendo, T. Fujii, H. Okada
    • IEICE General Conference, A-4-3, p.76
    • Mar. 2010

  • A Weight Combination Scheme for Sequential-Test-Based Cooperative Spectrum Sensing Systems

    • Ｍ．Ｍitsuya, T. Yamazato, M. Katayama
    • IEICE General Conference, B17-15, p664, Sendai, Japan
    • Mar. 2010

  • Kalman Channel Estimator for MC-CDMA based Inter-Vehicle Communication

    • N. Hiraiwa, T. Yamazato, M. Katayama
    • IEICE Transaction on Communications, vol.ITS2010-45, pp.47-52,
    • Feb. 2010
    • In this paper, we propose a kalman channel estimator for MC-CDMA based Inter-Vehicle Communication(IVC). In IVC, the channel characteristic of each car is different among pilot signals because of a doppler shift, a multipath fading, and the difference of receiving power. Our proposed kalman channel estimator uses a kalman filter to track the channel fluctuation and implements a pilot-based channel estimation which interpolates among pilot signals by using an interpolation polynomial into our proposed channel estimator to suppress an estimation error. As results, we show that the kalman channel estimator shows better performance than a pilot-based channel estimation.

  • Detection and Tracking of LED Array Transmitter for Visible Light Communications on Driving Situation

    • T. Nagura, T. Ozawa, T. Yamazato, M. Katayama, T. Yendo, T. Fujii, H. Okada
    • Technical Report of IEICE, vol..ITS2010-47, pp.59-64, Hokkaido, Japan
    • Feb. 2010
    • In this paper, we discuss on a decoding algorithm for visible light communication systems on driving situation using a LED array transmitter and a high-speed camera receiver. We propose a LED array detection method using M-sequence and a LED array tracking method using inversion signals. We demonstrate that we can distinguish LED array candidates correctly with M-sequence. We also demonstrate that we can suppress the flicker of LED and improve the data rate compared with the conventional method.

  • Successive Interference Cancellation for Hierarchical Coding in Optical Wireless Communication Systems using LED array and High speed camera

    • T.Ozawa, T.Nagura, T.Yamazato, M.Katayama, T.Yendo T.Fujii, H.Okada
    • Technical Report of IEICE, vol.ITS2010-46, pp53-58,, Hokkaido, Japan
    • Feb. 2010
    • We propose a successive interference cancellation scheme (SIC) for the hierarchical coding parallel optical communication system using LED array and high-speed camera. The high priority data is first demodulated and Turbo-decoded. The retrieved high priority data is then re-modulated and subtracted from the received signal. In this way, the reliability of the middle priority data can be improved as the interference caused by the high priority data can be reduced. By the way, the performance of SIC depends on the performance of Turbo code. In this paper, we apply LogMAP decoding to improve the performance instead of MaxLogMAP algorithm that we have used in the previous.

  • An application of regenerative relay to the cognitive piggyback overlay system

    • J.Naganawa, T.Yamazato, M.Katayama
    • Technical Report of IEICE, vol.109, no.383 (SR2009-75), pp.9-14, Tokyo, Japan
    • Jan. 2010
    • This manuscript considers a secondary system sharing the spectrum with the primary system at the same time and same frequency. This manuscript proposes a cognitive overlay system, in which the secondary system relays the primary signal and piggybacks its own data on it. As the relay procedure, non-regenerative and regenerative repeaters are considered and performance with them are compared. The result of the analysis shows that the proposed scheme with regenerative relay allows the secondary signal to communicate at the same speed of the primary signal without any harm to it.

  • An access control method for multipoint data gathering with ACK/NACK errors

    • Y. Ohtomo, T. Yamazato, M. Katayama
    • The Papers of Technical Meeting on Communications, IEE Japan, pp21-26, Okinawa, Japan
    • Jan. 2010
    • This manuscript proposes a media access control method for a multipoint cyclic data gathering system, in witch a base-station collects data generated periodically at each node. In such condition, by broadcasting ACK/NACK signals form the base-station, the proposed method ensures assignment a time slot for each node once the node succeeds to transfer its data. It is confirmed that the proposed method outperforms conventional slotted-ALOHA in throughput of data even with ACK/NACK errors. Furthermore, the proposed method realizes adaptive slot assignment under cyclostationary channel environment.

  • Tracking an LED Array Using Optical Flow for Visible Light Communication System

    • H. Chinthaka N. Premachandra, T. Yendo, M. P. Tehrani, T. Yamazato, H. Okada, T. Fujii, M. Tanimoto
    • 2009 ITE Winter Annual Convention, Tokyo, Japan
    • Dec. 2009
    • We propose a visible light road-to-vehicle communication system at intersection as one of ITS technique. In this system, the communication between vehicle and an LED array is approached using LED array as a transmitter, and on-vehicle high-speed camera as a receiver. The LEDs in the transmitter are emitted in 500Hz and those emitting LEDs are captured by a high-speed camera for making communication. Here, the luminance value of LEDs in the transmitter should be captured in consecutive frames to achieve effective communication. For this purpose, first the transmitter should be identified, then it should be tracked in consecutive frames while the vehicle is moving, by processing the images from the high-speed camera. In this paper, we mainly introduce an algorithm to track the transmitterusing optical flow and edge information.

  • On-Vehicle Receiver for Visible Light Road-to-Vehicle Communication

    • S. Okada, T. Yendo, T. Yamazato, H. Okada, M.P. Tehrani, A. Fujii, M. Tanimoto
    • Technical Report of IEICE, CS2009-64, pp.77-81, Nagoya
    • Dec. 2009
    • We consider an on-vehicle receiving system for long-distance and high-speed visible light communication. There are several problems associated with applying visible light communication to the field of ITS. It is necessary to receive information from long distance. And tracking the transmitter for a certain moving distance of the vehicle is also important. We applied an imaging optics to receive information over long distance, and two cameras are used to solve the relationship between the transmitter and the receiver position changes with time, and vibrational correction technique is also fixed to the system to minimize vibrational affections.

  • Wireless Communication Engineering

    • M. Katayama[Editor/Author], H. Uehara, Y. Iwanami, T. Wada, T. Yamazato, H. Kobayashi, H. Okada
    • Ohm Publishing Co., New Interuniversity Series (Communications and Signal Processing Division)
    • Nov. 2009

  • Encoding system based on spatial frequency characteristics of road-vehicle communication

    • Y. Masuda, T. Yendo, T. Yamazato, H. Okada, M.P. Tehrani, A. Fujii, M. Tanimoto
    • Technical Report of IEICE, CS2009-54, pp.71-76, Shikotsuko
    • Nov. 2009
    • In this paper we propose a method for analyzing spatial frequency characteristics of road-vehicle communication. In the proposed communication, we use LED traffic lights as transmitter and high-speed camera on car as receiver. So the distance between LED traffic lights and high-speed camera change from far to near, and as the distance is farther, received pictures are smaller. Therefore it is thought that high frequencies of sending data deteriorate, and Moir occurs in received pictures. In this paper, we analyze the deterioration and confirm improvement of communication using simulation.

  • A Note on Joint Decoding of Correlated Data Observed by Multiple Sensor Nodes - Correlation Estimation According to ADC Bit Levels of Experimentally Observed Data -

    • K. Kobayashi, T. Yamazato, M. Katayama
    • Technical Report of IEICE, vol.USN2009-42, pp.95-100, Sendai, Japan
    • Oct. 2009
    • In wireless sensor networks, a large number of sensor nodes are densely deployed for reliable environmental sensing. Due to the high density in the sensing field, sensor observations are spatially correlated. In this paper, we focus on joint channel decoding utilizing the spatial correlation of multiple sensor observations. Our proposed scheme makes use of an estimation of the correlation according to ADC bit levels of the sensor observations. The performance of our approach is examined by simulations using sensing data from experiments in a real indoor environment.

  • M-ary Modulation Scheme Using Separation of Chaotic Dynamics for Noncoherent Chaos-Based Communications

    • S. Arai, Y. Nishio, T. Yamazato, S. Ozawa
    • International Symposium on Nonlinear Theory and its Applications (NOLTA), Chateraise Gateaux Kingdom Sapporo Hotel & Spa Resort, Sapporo, Japan,
    • Oct. 2009
    • This paper proposes a new M-ary modulation scheme for noncoherent chaos-based communications. A chaotic sequence is successive based on the chaotic dynamics. Without the successive sequence based on the chaotic dynamics, general noncoherent systems are very dif&#64257;cult to demodulate the data. However, we consider that the systematic separation and the reconstruction of the chaotic dynamics can be applied as additional information. Namely, M -ary data symbols can be expressed by separating the chaotic dynamics purposely. We carry out computer simulations of the proposed scheme and con&#64257;rm that a saving of over 3&#8211;4 dB is realized in transmitter energy by increasing M.

  • An access control scheme for passenger wireless communication systems considering the passing of an opposite train

    • M. Yamamoto, T. Yamazato, M. Katayama
    • Technical Report of IEICE
    • Oct. 2009
    • This manuscript discusses on a wireless cellular communication system for railroad passengers, in which base stations are placed along the railroad. In this system, all users or passengers are on trains. Thus there is high concentration in user distribution, and a group of the users on a train move to the same direction with the same speed. In such a system, when two opposite trains enter in the same cell before they pass each other, the number of users in the cell abruptly increases, and forced terminations of communication, i.e. call dropping, may occur due to the concentration of traffic. This paper proposes access control methods that mitigate the probability of the dropping, by limiting the number of channels allowed to use on each train dynamically or statically before the two trains enter the same cell. As a result, it is shown that the probability of the forced termination of an existing call can be decreased with the cost of increase in blocking probability. It is also confirmed that the dynamic access control method can inhibit increase of the rejection of newly arrived calls compared to the static access control method when the control duration is enough large. In conclusion, the proposed methods provide lower dropping probability than the conventional(no-control) system, under the same blocking probability.

  • Tra&#64259;c Light Detection for Visible Light Communication Image Sensor

    • D Takasao, T. Yendo, T. Yamazato, H. Okada, M. P. Tehrani, T. Fujii, M. Tanimoto
    • PCSJ/IMPS 2009, Shuzenji, Japan
    • Oct. 2009
    • The visible light communication used as telecommunications equipment by modulating LED at high speed is researched. And the road-to-vehicle visible light communication applied to the ITS &#64257;eld is researched. In this paper, the visible light communication is done by using a special image sensor. The pixel for the video that can capture video with 30fps and the pixel for the communication that can be communicated at high speed exist in the image sensor. We can detect the position of the tra&#64259;c light in the image, and communicate by the pixel for the communication. We propose the detection method of the tra&#64259;c light that makes the best use of the feature of the image sensor.

  • The Receiver for visible Light Road-to-Vehicle Communication

    • S. Okada, T. Yendo, T. Yamazato, Hiraku Okada, M. P. Tehrani, T. Fujii, M. Tanimoto
    • PCSJ/IMPS 2009, Shuzenji, Japan
    • Oct. 2009
    • In this paper, we propose a road-to-vehicle visible communication system for ITS. In this system, a LED tra&#64259;c light is used as transmitter and a photodiode is used as receiver. There are several problems associated with applying visible light communication to the &#64257;eld of ITS. It is necessary to receive information from long distance. And tracking the transmitter for a certain moving distance of the vehicle is also important. We applied an imaging optics to receive information over long distance, and two cameras are used to solve the relationship between the transmitter and the receiver position changes with time, and vibrational correction technique is also &#64257;xed to the system to minimize vibrational a&#64256;ections. We developed algorithms to track the transmitter. The experiments were conducted to con&#64257;rm the proposals.

  • Phase Compensation for Narrowband PLC Channels with Cyclic Time-Varying Features

    • Y. Sugiura, T. Yamazto, M. Katayama
    • Third Workshop on Power Line Communications , Udine, Italy
    • Oct. 2009
    • Phase transfer functions of power-line channels often show sharp and periodic variation synchronous to the (double of) mains frequency. This is a result of impedance change of nonlinear devices connected to the power-lines. This manuscript proposes a phase estimation strategy for phase compensation at a receiver under such environment. In the proposed method, phase estimates are calculated using cyclic observation (average) of the channel phase. The numerical examples under periodic phase variation of the channel and cyclostationary noise show that the receiver with the proposed phase estimation scheme outperforms that with the conventional phase estimation, which uses average over the whole observation period without considering the periodic feature of the channel.

  • Visible Light Communications using LED Array and High-Speed Camera for ITS Applications

    • T. Yamazato
    • IEICE Fundamentals Review, vol.3, no.2, pp.45-53
    • Oct. 2009

  • Decoding of Separately Encoded Multiple Correlated Sources Transmitted over Noisy Channels

    • K. Kobayashi, T. Yamazato, M. Katayama
    • IEICE Transactions on Fundamentals, vol.E92-A, no.10, pp.2402-2410
    • Oct. 2009
    • https://doi.org/10.1587/transfun.E92.A.2402
    • We propose an iterative channel decoding scheme for two or more multiple correlated sources. The correlated sources are separately turbo encoded without knowledge of the correlation and transmitted over noisy channels. The proposed decoder exploits the correlation of the multiple sources in an iterative soft decision decoding manner for joint detection of each of the transmitted data. Simulation results show that achieved performance for the more than two sources is also close to the Shannon and Slepian-Wolf limit and large additional SNR gain is obtained in comparison with the case of two sources. We also verify through simulation that no significant penalty results from the estimation of the source correlation in the decoding process and the code with a low error floor achieves good performance for a large number of the correlated sources.

  • Luminance Extraction Method for Visible Light Communication System using LED Array and High-Speed Camera

    • T. Nagura, T. Yamazato, M. Katayama
    • Enginnering Sciences Society Conference of IEICE, A-17-17, p.181, Niigata, Japan
    • Sep. 2009

  • A Note on Joint Decoding using Correlation Estimation of Multiple Sources according to ADC Bit-Level

    • K. Kobayashi, T. Yamazato, M. Katayama
    • Communications Society Conference of IEICE, B-20-7, p.388, Niigata, Japan
    • Sep. 2009

  • Cognitive Radio with Relay of a Primary Signal and Piggyback Modulation

    • J. Naganawa, T. Yamazato, M. Katayama
    • IEEE International Symposium on Personal, Indoor and Mobile Radio Communication (PIMRC), pp.147-151 , Tokyo, Japan
    • Sep. 2009
    • https://doi.org/10.1109/PIMRC.2009.5450056
    • This manuscript proposes a cognitive radio system that shares a frequency with an existing primary system. In the proposed method, a secondary transmitter relays the primary signal and piggybacks its own data on it. Symbol error probabilities of the system are derived analytically. The result shows that the proposed system can communicate at a relatively high speed on the same frequency of the primary system without harm to it.

  • A Study of Coding Scheme Based on Spatial Frequency Characteristics for Roadside-to-Vehicle Parallel Optical Communication

    • Y. Masuda, T. Yendo, T. Yamazato, H. Okada, M.P. Tehrani, A. Fujii, M. Tanimoto
    • Tokai-Section Joint Conference on Electrical and Related Engineering, O-438
    • Sep. 2009

  • Study of Roadside-to-Vehicle Optical Communication Using Image Sensor for Optical Communication

    • D. Takasao, T. Yendo, T. Yamazato, H. Okada, M.P. Tehrani, A. Fujii, M. Tanimoto
    • Tokai-Section Joint Conference on Electrical and Related Engineering, O-441
    • Sep. 2009

  • In-Vehicle Receiver for Visible Light Communication Using LED Signal

    • S. Okada, T. Yendo, T. Yamazato, H. Okada, M.P. Tehrani, A. Fujii, M. Tanimoto
    • Tokai-Section Joint Conference on Electrical and Related Engineering, O-439
    • Sep. 2009

  • Traffic Prediction Scheme for Resource Assignment of Satellite/Terrestrial Frequency Sharing Mobile Communication System

    • T. Aman, T. Yamazato, M. Katayama
    • International Workshop on Satellite and Space Communications (IWSSC), Siena-Tuscany, Italy
    • Sep. 2009
    • https://doi.org/10.1109/IWSSC.2009.5286430
    • The recent development of large aperture on-board multi-beam antennas enables a small-size, low-powered and cellular phone like hand-held terminal as a satellite earth terminal. A single mobile terminal can communicate to both mobile satellite systems and terrestrial systems depend upon his location, QoS and availability of resources among satellite and terrestrial communication systems. In this paper, we propose a new traffic prediction scheme for the integrated satellite/terrestrial frequency sharing mobile communication system. The system shares a common frequency bandwidth in order to enhance the total capacity by a dynamic bandwidth allocation. A key for this allocation depends on a traffic prediction scheme of a few hundreds of terrestrial cells under a footprint of a satellite with a large aperture onboard multi-beam antennas. We propose three traffic predictors based on neural networks for dynamic resource allocation. The performances of the proposed schemes are evaluated in terms of the Relative Traffic Prediction Error and Maximum Traffic Prediction Error by the computer simulation. For the evaluation, we adopt the actual traffic statistic published by Ministry of Internal Affairs and Communications of Japan with population density of terrestrial cells based on the actual population of Aichi, Japan. As results, average traffic prediction error of less than 0.25 is achieved for the prediction interval of one hour, enough for dynamic resource allocation.

  • TOA UWB Position Estimation with Two Receivers and a Set of Known Reflectors

    • J. Kietlinski-Zaleski, T. Yamazato, M. Katayama
    • International Conference on Ultra-Wideband (ICUWB), pp.376-380, Vancouver, Canada
    • Sep. 2009
    • https://doi.org/10.1109/ICUWB.2009.5288686
    • Ultra-Wideband is an attractive technology for short range positioning, especially indoors. However, for normal Time of Arrival(ToA) positioning, at least 3 receivers with unblocked direct path to the transmitter are required. A requirement that is not always met. In this work, a novel algorithm for ToA positioning using only 2 receivers is presented. This is possible by exploiting reflections from a set of known flat reflectors, for example ceiling and walls. The proposed algorithm was tested using self-developed UWB propagation simulator testbed.

  • Image Processing for Visible Light Communication Using LED Traffic lights

    • S. Arai, T. Yamazato, S. Ozawa
    • Technical meeting of Electronics, Information and Systems [Division C], IEEJ, Sep., 2009., Tokushima, Japan
    • Sep. 2009
    • In this paper, we focus on a road-to-vehicle visible light communications using LED traffic light (transmitter) and an in-vehicle camera (receiver). As advantages using the camera, the recognition of objects as well as their locations can easily be realized and the reception of LED modulated data is also possible at the same time. Unfortunately, if the receiver is far from the transmitter, the received data pattern degrades due to reduction of pixel size and defocusing of the LED data pattern. This paper discusses these problems from image processing approaches.

  • A study on transmission speed on visible light communication systems using LED array and high-speed camera

    • T. Nagura, T. Yamazato, M. Katayama
    • Proc. of 11th DSPS Educators Conference, pp.45-46
    • Sep. 2009

  • Impact of Pilot Interpolation Techniques on a Channel Estimation Scheme for Inter-Vehicle Communication

    • N. Hiraiwa, T. Yamazato, M. Katayama
    • Enginnering Sciences Society Conference of IEICE, A-17-15, p.179, Niigata, Japan
    • Sep. 2009

  • Nagoya Univeristy OCW

    • T. YAMAZATO
    • Japanese Society for Engineering Education 57th Annual Conference, Nagoya, Japan
    • Aug. 2009

  • Forward - Celebrating its 500th Issue - IEICE Transactions on Communications B (Japanese-language) Accumulates Superior Communication Technology and Research

    • T. Yamazato
    • IEICE Transactions on Communications, Vol. J92-B, No. 8, pp. 1211-1211, 2009
    • Aug. 2009

  • Detection of LED Traffic Light by Image Processing for Visible Light Communication System

    • H.C. N. Premachandra, T. Yendo, T. Yamazato, T. Fujii, M. Tanimoto, Y. Kimura
    • IEEE Intelligent Vehicles Symposium (IV), pp.179-184, Kempinski Hotel Xi\'an, Shaanxi, China
    • Aug. 2009
    • https://doi.org/10.1109/IVS.2009.5164274
    • We propose a visible light road-to-vehicle communication system at intersection for ITS. In this system, the communication between vehicle and a LED traffic light is approached using LED traffic light as the transmitter, and on-vehicle high-speed camera as the receiver. The LEDs in the transmitter are emitted with 500Hz and the images of those emitting LEDs are captured by a high-speed camera for conducting communication. In this communication, it is extremely necessary to find the transmitter and detect it for consecutive frames while vehicle is moving. In this paper, we introduce proposals for finding and detecting it for consecutive frames by image processing. Experimental results using appropriate images showed the effectiveness of the proposal.

  • Edge-Based Tracking of an LED Traffic Light for a Road-to-Vehicle Visible Light Communication System

    • H.C. N. Premachandra, T. Yendo, M. P. Tehrani, T. Yamazato, T. Fujii, M. Tanimoto, Y. Kimura
    • Journal of Broadcast Engineering published by KoSBE, the Korean Society for Broadcast Engineers, Vol. 14, No. 4, pp.475-487, July 2009
    • Jul. 2009
    • We propose a visible light road-to-vehicle communication system at intersection as one of ITS technique. In this system, the communication between vehicle and a LED traffic light is approached using LED traffic light as a transmitter, and on-vehicle high-speed camera as a receiver. The LEDs in the transmitter are emitted in 500Hz and those emitting LEDs are captured by a high-speed camera for making communication. Here, the luminance value of each LED in the transmitter should be found for consecutive frames to achieve effective communication. For this purpose, first the transmitter should be identified, then it should be tracked for consecutive frames while the vehicle is moving, by processing the images from the high-speed camera. In our previous work, the transmitter was identified by getting the subtraction of two consecutive frames. In this paper, we mainly introduce an algorithm to track the identified transmitter in consecutive frames. Experimental results using appropriate images showed the effectiveness of the proposal.

  • An Access Control Method for Multipoint Data Gathering over Power-Line Communications

    • Y. Ohtomo, T. Yamazato, M. Katayama
    • Technical Report of IEICE, vol.WBS2009-13, pp.37-42
    • Jul. 2009
    • This paper proposes a media access control method for a multipoint data gathering system using power-line communications. In large-scale power-line communication systems, it is difficult to use a CSMA scheme because of hidden terminal problem. In such condition, by broadcasting acknowledgements, the proposed method ensures assignment of a time slot for each node once the node succeeds to transfer its data to the base-station. It is confirmed that the proposed scheme reduces packet collisions and outperforms conventional slotted-ALOHA scheme in throughput of data. In addition, proposed scheme provides an adaptive slot assignment under cyclo-stationary channel environment.

  • Kalman Channel Estimator for BFDM/OQAM system in Time-Frequency Dispersive Channels

    • B.Mongol, T.Yamazato, M. Katayama
    • Technical Report of IEICE, Nagoya, Japan
    • Jun. 2009
    • BFDM/OQAM allows to employ a gaussian transmitter pulse at maximal spectral efficiency. Thus, it performs well in the time-frequency dispersive channels and is considered to be a promising candidate for the next generation mobile communications modulation scheme. However, in the highly mobile environment the performance deteriorates and channel equalization and estimation schemes became essential for further improvement of BFDM/OQAM systems. This paper proposes a novel adaptive channel estimator based on a Kalman filter. We approximate the channel state with a number of samples of its fading processes at each delay tap. The idea behind our estimator is to employ a linear predictor to derive a process equation for the Kalman filter. To reduce the convergence time the bayesian estimation is employed to provide an initial value for the Kalman filter. The mean-square-error performance of the proposed estimator is evaluated using computer simulation.

  • Channel Estimation and Tracking Schemes for the Pulse-Shaping OFDM Systems

    • B. Mongol, T. Yamazato, M. Katayama
    • IEEE International Conference on Communications (ICC), SPC-10-4, Dresden, Germany
    • Jun. 2009
    • https://doi.org/10.1109/ICC.2009.5198817
    • Robust channel estimation scheme is essential for pulse-shaping OFDM systems in the multipath mobile environment. This paper proposes three types of channel estimation schemes for the general class of pulse-shaping OFDM systems. The first two types are suboptimal low-complexity maximum likelihood estimators. The last type is adaptive Kalman filter channel estimator. We numerically evaluate the performance of each estimator using computer simulation.

  • No Redundant Error-Correcting Scheme Using Chaotic Dynamics for Noncoherent Chaos Communications

    • S. Arai, Y. Nishio, T. Yamazato
    • IEEE International Symposium on Circuits and Systems (ISCAS), pp.2633-2636, Taipei, Taiwan
    • May 2009
    • https://doi.org/10.1109/ISCAS.2009.5118342
    • This paper proposes the error-correcting scheme without redundancy sequences based on the chaotic dynamics for noncoherent chaos communications. We generate successive chaotic sequences from the identical chaotic map. And for the next sequence we set the initial value to the end value of the former sequence. By such way we can create the successive chaotic sequences having the same chaotic dynamics. This feature gives the receiver additional information to correctly recover the received noisy signal. Therefore, by analyzing the chaotic dynamics at the receiver, it is possible to improve the error performance without redundancy signal. As results of computer simulations, we confirm about 3 dB gain in BER performance as compared with the conventional suboptimal receiver when using the short chaotic sequence length per 1 bit.

  • Joint decoding scheme using bit-level correlation of experimentally observed data

    • K. Kobayashi, T. Yamazato, M. Katayama
    • Technical Report of IEICE, vol.MoMuC2009-2, pp.7-12, Okinawa, Japan
    • May 2009
    • In wireless sensor networks, a large number of sensor nodes are densely deployed for a reliable sensing of physical phenomenon. Due to the high density in the sensing field, sensor observations are spatially correlated. In this paper, we focus on joint channel decoding schemes utilizing the correlation of sensor observations. Our proposed scheme makes use of a bit-level correlation property of data observed in the real environment. The performance of our approach is examined by simulations using sensing data from experiments in a real indoor environment.

  • Evaluation and Performance Improvement of a Cooperative Sensing System with Losses of Information from Sensing Nodes

    • M. Takanashi, T. Yamazato, M. Katayama
    • Technical Report of IEICE, vol.109, no.61 (SR2009-5), pp.75-79, , Niigata, Japan
    • May 2009
    • At a location and time, there may be frequencies not in use by their licensed (primary) users. Spectrum sharing, in which a secondary radio system uses such white spaces of frequency, is one of advantageous means to mitigate the spectrum scarcity. In order to realize the spectrum sharing, spectrum sensing that detects the presence of a primary user signal is a key technology. For reliable sensing of the primary signal, cooperative sensing where information from multiple sensing nodes is incorporated at a fusion center is currently being investigated by many researchers. Majority of these works consider the imperfectness of the channels between a primary transmitter and sensor nodes under noise and fading environments. On the contrary, this manuscript deals with the transmission between sensor nodes to a fusion center. For a cooperative spectrum sensing system, in which the analog outputs of energy detectors at sensor nodes are transmitted to a fusion center, the influence of losses of information from the nodes on detection performance is derived analytically. In addition, it is shown that the adaptive processing with the consideration of information loss at the fusion center improves system performance.

  • Bit and Power Allocation for Power-Line Communications under Nonwhite and Cyclostationary Noise Environment

    • N. Sawada, T. Yamazato, M. Katayama
    • IEEE International Symposium on Power Line Communications and Its Applications (ISPLC), pp.307-312, Dresden, Germany
    • Apr. 2009
    • https://doi.org/10.1109/ISPLC.2009.4913448
    • This manuscript discusses the adaptive OFDM system for narrow-band power-line communications with nonwhite and cyclostationary noise environment. The bit and power allocation algorithm is proposed with the considerations on the cyclostationarity of power-line noise. Numerical evaluation shows that the proposed method can improve the average BER performance under PLC noise environment.

  • Detection of Luminance for Road-to-Vehicle Visible Light Communication using LED Array and High-Speed Camera

    • S. Arai, S. Mase, T. Nagura, T. Yamazato, T. Yendo, T. Fujii, M. Tanimoto, Y. Kimura
    • IEICE General Conference
    • Mar. 2009

  • ISOMAC based Energy Efficient TDMA-MAC Protocol for Sensor Networks

    • H. Chen, T. Yamazato, M. Katayama
    • IEICE General Conference, B-20-42, p.646, Matsuyama, Japan
    • Mar. 2009

  • Phase Compensation for Narrowband Power-Line Communication Channels with Cyclic Time-Varying Features

    • Y. Sugiura, T. Yamazato, M. Katayama
    • Technical Report of IEICE, Hakodate, Japan
    • Mar. 2009
    • Phase transfer functions of power-line channels often show sharp and periodic variation synchronous to the (double of) mains frequency. This is a result of impedance change of nonlinear devices connected to the power-lines. This manuscript proposes a phase estimation strategy for phase compensation at a receiver under such environment. In the proposed method, phase estimates are calculated using cyclic observation (average) of the channel characteristics. The numerical examples under periodic phase variation of the channel and cyclostationary noise, show that the receiver with the proposed phase estimation scheme outperforms that with the conventional phase estimation which uses average over the whole observation period without considering the periodic feature of the channel.

  • TOA UWB Position Estimation with 2 receivers and one known reflector

    • J. Kietlinski-Zaleski, T. Yamazato, M. Katayama
    • Technical Report of IEICE, vol.WBS2008-90, pp.211-216, Hakodate, Japan
    • Mar. 2009
    • Ultra-Wideband is an attractive technology for short range positioning, especially indoors. However, for normal Time of Arrival(ToA) positioning, at least 3 receivers with unblocked direct path to the transmitter are required. A requirement that is not always met. In this work, a novel algorithm for ToA positioning using only 2 receivers is presented. This is possible by exploiting reflections from one known flat reflector, for example ceiling or wall. The proposed algorithm was tested using self-developed UWB propagation simulator testbed.

  • 128k Transmission of Visible Light Communication System using LED Array and High-Speed Camera

    • T. Nagura, S. Arai, S. Mase, T. Yamazato, T. Yendo, T. Fujii, M. Tanimoto, Y. Kimura
    • IEICE General Conference, A-17-18, p.310
    • Mar. 2009

  • Influence of channel errors on a wireless-controlled rotary inverted pendulum

    • R. Kohinata, T. Yamazato, M. Katayama
    • Technical Report of IEICE, Hakodate, Japan
    • Mar. 2009
    • This paper discusses the influence of channel features to the performance of a wireless-controlled system. As an example of the system, a rotary inverted pendulum that has wireless connections in its feedback loop between a controller and the controlled system. As for the wireless channels, both a random error model and a burst error model are employed and the effects of transmission rate and errors to the control quality are evaluated. As a result, it is confirmed that the system with transmission errors can keep the pendulum stable when data rate of the communication is enough high and error rate is below a certain level. In addition, it is clarified that that burst errors in wireless channels affect more when the control quality is kept by compensating errors with higher transmission rate.

  • The Frontline of Visible Light Communications

    • T. Yamazato
    • IEICE Tokushima Section Presentation for Students, Tokushima, Japan
    • Feb. 2009

  • How to get your paper accepted in IEEE major conference

    • T. Yamazato
    • The University of Tokushima & Nagoya University IEEE Student Branches Joint-Workshop, The University of Tokushima, Tokushima, Japan
    • Feb. 2009

    • T. Aman, T. Yamazato, M. Katayama
    • Technical Report of IEICE
    • Feb. 2009
    • Satellite/Terrestrial Frequency Sharing Mobile Communication System is drawing an attention for interpolation between satellite mobile communication and terrestrial mobile communication and improvement of spectrum utilization efficiency. Spectrum utilization efficiency can be improved in this system by sharing common frequency bands in satellite mobile and terrestrial mobile communication system and using dynamic resource assignment. But it is need to traffic prediction for dynamic resource assignment. This report propose traffic prediction method using neural network.

  • Turbo Equalization for Inter-Vehicle Communication based on MC-CDMA

    • N. Hiraiwa, A. Sakata, T. Yamazato, M. Katayama
    • IEICE Transactions on Communications, vol.J92-B, no.1, pp.367-369
    • Jan. 2009
    • In this letter, we propose a new SC/MMSE Turbo equalizer for inter-vehicle communication based on MC-CDMA. We modify the MMSE filter in SC/MMSE Turbo equalizer focusing on the difference of channel transfer function of each car. As results, we show that better performance is obtained.

  • Cluster-based Cooperative Transmission considering Residual Power of Wireless Sensor Nodes

    • K. Takeshima, T. Yamazato, M. Katayama
    • Technical Report of IEICE, vol.USN2008-76, pp.83-87, Nagoya, Japan
    • Jan. 2009
    • Cooperative transmission can extend the transmission range by transmitting the same data from multiple wireless nodes, and consequently can reduce the consumed power of each node. In this paper, we apply the cooperative transmission to a wireless sensor network where the sensor nodes are organized into multiple clusters. To perform the cluster-based cooperative transmission, it has to choose a cluster head which broadcasts its decoded data to other nodes in a cluster. The overall dissipation power is, however, governed by the cluster head selection criterion. In this paper, we propose a simple cluster head selection criterion considering the residual power of each sensor node, and aim to extend the network lifetime. As results, the proposed scheme shows the best in the active sensor node rate and outage probability.

  • Detecting and A LED Traffic Light for Visible Light Communication System

    • H.C. N. Premachandra, T. Yendo, T. Yamazato, T. Fujii, M. Tanimoto, Y. Kimura
    • International Workshop on Advanced Image Technology (IWAIT), Korean Hall of Science and Technology, Seoul, Kore
    • Jan. 2009
    • In this paper, we propose a visible light road-to-vehicle communication system at intersection as one of ITS technique. In this system, the communication between vehicle and a LED traffic light is approached using LED traffic light as the transmitter, and on-vehicle high-speed camera as the receiver. The LEDs in the transmitter are emitted with 500Hz and those emitting LEDs are captured by a high-speed camera for making communication. The images from the high-speed camera are processed to get luminance value of each LED in the transmitter. For this purpose, first transmitter should be found, then it should be tracked for each frame, and the luminance value of each LED in the transmitter should be captured. In our previous work, transmitter was found by getting the subtraction of two consecutive frames. In this paper, we mainly introduce an algorithm to detect the found transmitter in consecutive frames. Experimental results using appropriate images showed the effectiveness of the proposal.

  • Suboptimal Receiver Using Chaotic Sequences with Biased Values

    • S. Arai, Y. Nishio, T. Yamazato
    • Proceedings of IEEE Workshop on Nonlinear Circuit Networks (NCN'08), pp. 49-51, Tokushima, Japan
    • Dec. 2008
    • We investigate and evaluate a suboptimal receiver using chaotic sequences with biased values. In our previous research, we investigated a differential chaos shift keying (DCSK) using chaotic sequences with biased values purposely and confirmed its better performance. However, our previous study only performed the computer simulation of DCSK using these chaotic sequences. In this study, we focus on the suboptimal receiver and evaluate its performance with chaotic sequences with biased values.

  • Energy Efficiency of Cooperative MISO Technique in Multi-hop Wireless Sensor Networks

    • Z. Huang, T. Yamazato, M. Katayama
    • International Conference on Intelligent Sensors, Sensor Networks and Information Processing (ISSNIP), pp. 511-515, Sydney, Australia
    • Dec. 2008
    • https://doi.org/10.1109/ISSNIP.2008.4762040
    • In this paper, the energy efficiency of cooperative Multiple-Input Single-Output (MISO) technique for a multi-hop wireless sensor network is investigated and compared with other transmission schemes. Firstly, we present different schemes for data transmission of the cluster farther from base station and calculate their energy consumptions. The results show that the optimal transmission scheme varies with the inter-cluster distance in different networks. Then we explore the lifetime of the network and find that it is not always the optimal to employ the multi-hop transmission and the single-hop transmission outperform the multi-hop under a certain distance threshold. In addition, the effects of the transmission bit rate and the required bit error ratio (BER) on the distance threshold are also clarified.

  • Mitigation of Satellite Non-linear Effect using SLM and Iterative Distortion Compensation for OFDM in Satellite Channel

    • T. Aman, T. Yamazato, M. Katayama, A. Ogawa
    • IEICE Transactions on Communications, vol.J91-B, no.12, pp.1644-1646
    • Dec. 2008
    • OFDM suffers from the nonlinear distortion caused by TWTA in satellite communication. In this letter, we adopt SLM PAPR reduction that suppress out of bandemission. Furthermore, we improve BER by the terative distortion compensation.

  • Road-to-Vehicle Visible Light Communication using LED Array and High-Speed Camera

    • Takaya YAMAZATO, Shintaro ARAI, Shohei MASE, Tomohiro YENDO, Toshiaki FUJII, Masayuki TANIMOTO and Yoshikatsu KIMURA
    • International Workshop on Smart Info-Media Systems in Bangkok (SISB), PS-4, pp.69-74, Swissotel Le Concorde, Bangkok, Thailand
    • Dec. 2008
    • In this paper, we present hierarchical coding scheme using LED traffic lights and high-speed camera for Intelligent Transport Systems (ITS) application. If each of LEDs in traffic lights is individually modulated, parallel data transmissions are possible using a camera as a reception device. Such parallel LED-camera channel can be modeled as spatial low-pass filtered channel of which the cut-off frequency varies according to the distance. To overcome, we introduce hierarchical coding scheme based on 2D fast Haar wavelet transform.

  • Joint Channel Decoding of Spatially and Temporally Correlated Data in Wireless Sensor Networks

    • K. Kobayashi, T. Yamazato, H. Okada, M. Katayama
    • International Symposium on Information Theory and Its Applications (ISITA), pp.930-934, Auckland, New Zealand
    • Dec. 2008
    • https://doi.org/10.1109/ISITA.2008.4895540
    • In densely deployed wireless sensor networks, sensor observations are spatially correlated. Furthermore, the nature of physical phenomena constitutes a temporal correlation between transmitted observations of an individual sensor node. In this paper, we propose a joint iterative channel decoding scheme using turbo codes. The proposed decoder exploits the spatial and temporal correlations of two binary data sequences to achieve additional coding gain. Simultaneously exploiting the spatial and temporal correlation, the proposed decoder achieves large performance gain.

  • Feasible Study of Road-to-Vehicle Communication System Using LED Array and High-Speed Camera

    • S. Arai, S. Mase, T. Yamazato, T. Yendo, T. Fujii, M. Tanimoto, Y. Kimura
    • 15th World Congress on ITS, New York, USA
    • Nov. 2008
    • In this study, we focus attention on the parallel optical wireless communication systems using LED array transmitter and a high-speed camera as the receiver for road-to-vehicle communications in ITS. Previously, we have proposed a hierarchical coding scheme which allocates data to spatial frequency components depending on the priority. This scheme is possible to receive the high priority data even if the receiver is far from the transmitter. However, since vehicles drive on a road in actual road-to-vehicle communications, there are many important works to develop the real-time communication system. For example, it is a difficult to synchronize the timing to release the shutter with the lighting cycle of LEDs, i.e., the sampling of the data. This paper details our road-to-vehicle communication system using the LED array and the high-speed camera and proposes their solutions. Moreover, based on proposed solutions, we perform a driving field trial using the LED array and a vehicle with the high speed camera. As the result, we observe the bit error rate and confirm the reception of the data during the driving.

  • Investigation of Noncoherent Detection Using Chaotic Sequence with Biased Values

    • S. Arai, Y. Nishio, T. Yamazato
    • International Workshop on Vision, Communications and Circuits (IWVCC), pp.221-224, Xi'an, China
    • Nov. 2008
    • We investigate the chaotic sequence with biased values in chaos-based communication systems. In our previous research, we investigated the the performance of chaos communications using the sequence with biased values purposely. As results, we concluded that the chaotic dynamics affect the performance of chaos communications greatly. However, our previous study only performed the computer simulation the DCSK system using the chaotic sequence with biased values. In this study, we focus on the suboptimal receiver as one of chaos communication systems and observe its performance with the chaotic sequence with biased values.

  • Energy-aware Protocol for Cluster-based Cooperative Transmission in Wireless Sensor Networks

    • K. Takeshima, T. Yamazato, M. Katayama
    • International Workshop on Vision, Communications and Circuits (IWVCC), pp.149-152, Xi'an, China
    • Nov. 2008
    • In this paper, we look at communication protocol designed for cluster-based cooperative transmission. As it can increase the spatial diversity of wireless channel, cluster-based cooperative transmission is effective not only for reliable transmission but also in reduction of the transmitted power. The overall energy dissipation is, however, governed by a cluster head selection criterion. We show that the conventional random cluster head selection, as in low-energy adaptive clustering hierarchy (LEACH), and the best link quality cluster head selection may not be optimal for cluster-based cooperative transmission. Based on our finding, we propose a new energy-aware protocol for cluster-based cooperative transmission that considers not only the link quality but also the residual energy of sensor nodes. As results, our protocol shows the best in the availability ratio of sensor nodes and outage probability for the number of cluster-to-cluster transmissions.

  • Performance evaluation of turbo encoding and joint iterative decoding for multiple correlated sources

    • K. Kobayashi, T. Yamazato, M. Katayama
    • Technical Report of IEICE, vol.USN2008-47, pp.51-55, Okinawa, Japan
    • Oct. 2008
    • We present a joint iterative decoding scheme for multiple correlated data which are separately turbo encoded and transmitted over noisy channels. The proposed decoder exploits the correlation in an iterative manner for achieving additional coding gain. Simulation results show that close to Shannon and Slepian-Wolf limit performance is achieved, and large SNR gain is achieved in comparison with the standard turbo decoder. We also verify through simulation that the codes with a low error floor is crucial to achieve good performance for a large number of the correlated data and no significant penalty results from the estimation of the correlation in the decoding process.

  • Error Correcting Scheme for Road-to-Vehicle Visible Light Communication using LED Array

    • S. Mase, S. Arai, T. Yamazato, T. Yendo, T. Fujii, M. Tanimoto, Y. Kimura
    • International IEEE Conference on Intelligent Transportation Systems (ITSC), pp.1113-1117, Beijing, China
    • Oct. 2008
    • https://doi.org/10.1109/ITSC.2008.4732586
    • In this paper, we propose an improved coding scheme for optical wireless communication systems using a LED array transmitter and a high-speed camera as the receiver on a vehicle. Previously, we have proposed a hierarchical coding scheme which allocated the data to spatial frequency components depending on the priority. In that scheme, the high-priority data can be received even if the receiver was far from the transmitter. We confirmed the advantage of the hierarchical coding scheme, but the bit error performance was not sufficient. In this paper, we divide the data into spatial frequency components, and use error correcting code for each spatial frequency components’ data. Experimental evaluation demonstrates the improvement in BER performance. This improvement implies that the system range increased compared to the previous method.

  • A note on joint decoding of spatially and temporally correlated sources

    • K. Kobayashi, T. Yamazato, H. Okada, M. Katayama
    • Communications Society Conference of IEICE, B-20-6, p.342, Kawasaki, Japan
    • Sep. 2008

  • Cooperative transmission in distributed sensor networks using visible light communication

    • K. Kobayashi, K. Nakao, T. Yamazato, M. Katayama
    • Proc. of 10th DSPS Educators Conference, pp.72-73, Tokyo, Japan
    • Sep. 2008

  • A modulation scheme without channel state information for cognitive radio overlay systems

    • J. Naganawa, T. Yamazato, M. Katayama
    • Communications Society Conference of IEICE, B-17-9, p.452, Kawasaki, Japan
    • Sep. 2008

  • A New SC/MMSE Turbo Equalization for MC-CDMA to use in Inter-Vehicle Communication

    • N. Hiraiwa, A. Sakata, T. Yamazato, M. Katayama
    • IEEE Vehicular Technology Conference (VTC-Fall), Calgary, Canada
    • Sep. 2008
    • https://doi.org/10.1109/VETECF.2008.257
    • In this paper, we propose a new SC/MMSE Turbo equalizer for MC-CDMA to use in inter-vehicle communication (IVC). We modify the weight of the MMSE filter of SC/MMSE Turbo equalizer so that it can combat with frequency-selective fading in highly mobile IVC environment and also can mitigate the effect of multiple access interferences (MAI). As results, we show that better throughput is obtained by the proposed SC/MMSE equalization than the conventional one. The average reception range can be up to 70 [m] and the signals from 16 surrounding cars can be received. While for the conventional scheme, only three signals from the nearest cars are achieved.

  • Error-Correcting Method Based on Chaotic Dynamics for Noncoherent Chaos Communications

    • S. Arai, Y. Nishio, T. Yamazato
    • International Symposium on Nonlinear Theory and its Applications (NOLTA), pp. 652-655, Budapest, Republic of Hungary
    • Sep. 2008
    • This paper proposes the error-correcting method based on the chaotic dynamics for noncoherent chaos communications. We generate successive chaotic sequences from the identical chaotic map. And for the next sequence we set the initial value to the end value of the former sequence. By such way we can create the successive chaotic sequences having the same chaotic dynamics. This feature gives the receiver additional information to correctly recover the received noisy signal. Therefore, by analyzing the chaotic dynamics at the receiver, it is possible to improve the error performance. In other words, error performance of the receiver can be improved by the utilization of the suboptimal receiver with the analysis of chaotic dynamics of the successive received sequence. As results of computer simulations, we confirm about 3 dB gain in BER performance compared to the conventional suboptimal receiver.

  • Bit and power allocation for power-line communications under nonwhite and cyclostationary noise environment

    • N. Sawada, T. Yamazato, M. Katayama
    • Enginnering Sciences Society Conference of IEICE, A-5-2, p.89, Kawasaki, Japan
    • Sep. 2008

  • CDMA slotted ALOHA System with Successive Interference Cancellation for Inter-Vehicle Communications

    • A. Sakata, T. Yamazato, H. Okada, M. Katayama
    • IEEE International Symposium on Spread Spectrum Techniques and Applications (ISSSTA), pp.188-193, Bologna,Italy
    • Aug. 2008
    • https://doi.org/10.1109/ISSSTA.2008.40
    • This paper compares the throughput performance of orthogonal frequency division multiple access (OFDM) and multicarrier CDMA (MC-CDMA) in inter-vehicle communications (IVC).In particular, we compare the throughputs in a situation where hidden terminals are no longer negligible. We encounter the situation in an intersection where two or more cars are crossing by. Due to the hidden terminal degradation, poor throughput performance is obtained with OFDM scheme. On the other hand, MC-CDMA has a resistance to the hidden terminals as it can support simultaneous packets. However, the transmission data rate is much slow because of the spreading. Thus the total throughput may not be as high as the OFDM. As results, we show that throughput of the OFDM is better than the MC-CDMA in a low traffic region. We found that the OFDM can communicate only with the nearest car. On the contrary, when the traffic is high, the MC-CDMA shows better throughput than the OFDM. In addition, we show that many packets can be received simultaneously in MC-CDMA. These results lead to the conclusion that when we want high-speed communication to a few cars, the OFDM is a good candidate. And when low speed but simultaneous communication with many surrounding cars is our desire, then the MC-CDMA is our choice. As MC-CDMA has a compatibility with an OFDM by setting a spreading factor to one, MC-CDMA system may be the preferable choice for IVC.

  • Ultrasonic Array Emitter for Automotive Short-range Radar Networks

    • H. Hatano, T. Yamazato, M. Katayama
    • Journal of Society of Automotive Engineers of Japan, vol.62, no.7, pp.29-34
    • Jul. 2008
    • We consider radar network systems using multiple ultrasonic radars for parking assistance. Our radar network has an ultrasonic array emitter and multiple sensors. The ultrasonic array emitter is composed of multiple ultrasonic emitters and can emit signals to the side area which is the desired monitoring area of parking aid. Target positions are estimated by the data processing form multiple ultrasonic sensors which are set at distributed points of the front bumper. In this paper we especially describe our proposed array emitter.

  • Road-to-Vehicle Visible Light Communication using LED Array and High-Speed Camera

    • T. Yamazato, S. Arai, S. Mase, T. Yendo, T. Fujii, M. Tanimoto, Y. Kimura
    • Technical Report of IEICE, vol.108, no.163, SIP2008-76, pp.47-52, Hiroshima University
    • Jul. 2008
    • In this paper, we present hierarchical coding scheme using LED traffic lights and high-speed camera for Intelligent Transport Systems (ITS) application. If each of LEDs in traffic lights is individually modulated, parallel data transmissions are possible using a camera as a reception device. Such parallel LED-camera channel can be modeled as spatial low-pass filtered channel of which the cut-off frequency varies according to the distance. To overcome, we introduce hierarchical coding scheme based on 2D fast Haar wavelet transform.

  • Improvement of Robustness for Road-to-Vehicle Visible Light Communication using Hiearachical Coding

    • Shohei MASE, Shintro ARAI, Takaya YAMAZATO, Tomohiro YENDO, Toshiaki FUJII, Masayuki TANIMOTO, Yoshikatsu KIMURA
    • Technical Report of IEICE, vol. ITS2008-11, pp. 19-24, Nagoya, Japan
    • Jul. 2008
    • In this paper, we propose an improved coding scheme for optical wireless communication systems using a LED array transmitter and a high-speed camera as the receiver on a vehicle. Previously, we have proposed a hierarchical coding scheme which allocated the data to spatial frequency components depending on the priority. In that scheme, the high-priority data can be received even if the receiver was far from the transmitter. We confirmed the advantage of the hierarchical coding scheme, but the bit error performance was not sufficient. In this paper, we divide the data into spatial frequency components, and use error correcting code for each spatial frequency components\' data. Experimental evaluation demonstrates the improvement in BER performance. This improvement implies that the system range increased compared to the previous method.

  • A Route Establishment Scheme for Multi-route Coding in Multihop Cellular Networks

    • H. Okada, H. Imai, T. Yamazato, M. Katayama, K. Mase
    • Academy Publisher Journal of Netowkrs, vol.3, no.7, pp.34-40
    • Jul. 2008
    • Since the network topology in multihop cellular networks is flexible, multiple routes from a user station to a base station can be established. To reduce packet reception errors of wireless links, a multi-route coding scheme was proposed. An important issue of the multi-route coding is to develop an efficient route establishment scheme. In this paper, we propose a route establishment scheme for multi-route coding in multihop cellular networks. Our proposed scheme consists of a route selection method based on the bit error rate of each wireless link and a hybrid-type multiple-tree routing protocol. We evaluate the performance of our proposed scheme by a computer simulation and show the resulting improvement in the packet error.

  • Performance Comparison of OFDM and MC-CDMA in Inter-Vehicle Communications

    • A.Sakata, T.Yamazato, H.Okada, M.Katayama
    • Technical Report of IEICE, vol.ITS2008-8, pp.1-6, Nagoya,Japan
    • Jul. 2008
    • This paper evaluates the packet success rate of aa orthogonal frequency division multiplexing(OFDM) , a multicarrier CDMA(MC-CDMA) and a multicarrier orthogonal frequency division multiple access(MC-OFDMA) based on MC-CDMA. In particular, we compare the packet success rate in a high traffic situation where a hidden terminal is no longer negligible. A hidden terminal problem tends to occur in a situation of sight limitation such as intersection. We focus on physical layer and adopt MC-CDMA so that simultaneous reception is possible. This feature gives possible resistance to hidden terminal problem. In this paper, we investigate how the packet success rate performance varies with spreading factor and how to assign subcarrier. As results, we show that MC-OFDMA based on MC-CDMA shows better packet success rate than OFDM.

  • EXIT Analysis for distributed encoding and joint iterative decoding of correlated sources

    • K. Kobayashi, T. Yamazato, M. Katayama
    • 4th Workshop on Wireless Distributed Networks, Nagoya, Japan
    • Jun. 2008

  • A modulation scheme for a cognitive radio system to overlay on a secondary user

    • Jun Naganawa, Takaya Yamazato, Masaaki Katayama
    • Technical Report of IEICE, vol.SR2008-2, pp.5-10, Yokohama, Japan
    • May 2008
    • As an answer to increasing demands for frequency spectrum, secondary spectrum licensing, in which a secondary wireless system overlays on the frequency band of an existing primary system, is taking attention. In overlay communications, the secondary system is demanded not to be a cause of performance degradation of the primary system, while the primary system does not considers the secondary system. This manuscript proposes a modulation scheme for such a secondary system. In the proposed scheme, the secondary system modifies its transmitting signal parameters adapting channel states and transmitted signal of the primary system. This set of reference information is also used at the receiver of the secondary system. We derive the symbol error rates of both the systems analytically, and show that it is possble to realize the communication of the secondary system with the same quality as the primary system, which has any degradation by the signal of the secondary system.

  • Spatial Diversity Scheme with Multiple-Transmit/Receive Antennas and Relay Terminals for Reliable Wireless Control

    • R. Uchida, H. Okada, T. Yamazato, M. Katayama
    • IEICE Transactions on Communications, vol.J91-B, no.5, pp.585-594
    • May 2008
    • In this manuscript, a communication system for wireless control of industrial machines in indoor environment is discussed. In order to combat indoor fading and shadowing, an STBC cooperative relaying scheme, which uses multiple transmit and receive antennas together with multiple relay terminals, is introduced. In the proposed scheme each relay terminal transmits all STBC branch-signals with random phase rotations, and no exchange of information between the relay terminals is required to achieve high diversity order. In numerical evaluations, the proposed scheme is compared with conventional deterministic signal assignment or random branch selection schemes using average and outage probability of the frame-error rate as performance measures. As a result, the impact of the random phase rotations is clarified.

  • Measurement of Narrowband Channel Characteristics in Single-Phase Three-Wire Indoor Power-Line Channels

    • Y. Sugiura, T. Yamazato, M. Katayama
    • IEEE International Symposium on Power Line Communications and Its Applications (ISPLC), pp.18-23, Jeju,Korea
    • Apr. 2008
    • https://doi.org/10.1109/ISPLC.2008.4510392
    • This manuscript reports the measurement results of narrowband signal propagation of PLC channels. In Japan, in-house wiring is single-phase three-wire, and each branch between an outlet of 100V and the panel board is connected to one of two live conductors and the neutral. Thus a pair of outlets can be classified into three types: connected to different live conductors, connected to the same live conductors by different branches from the panel board, and on the same branch to the same live conductor. It is confirmed that the results of the measurements can be classified by these three types of paths. The results show that frequency responses of narrowband PLC channels are relatively smooth, compared with that of wideband PLC. It is also found that propagation loss in lower frequency range is larger than in higher frequency range. The time independence of narrowband PLC channels are confirmed when no electric appliance is connected to the same live conductor.

  • Iterative joint decoding of multiple correlated sources using Turbo codes

    • K. Kobayashi, T. Yamazato, M. Katayama
    • IEICE General Conference, B-20-4, p.545
    • Mar. 2008

  • Adaptive modulation for power-line communications with nonwhite and cyclostationary noise

    • N. Sawada, T. Yamazato, M. Katayama
    • IEICE General Conference, A-5-18, p.145
    • Mar. 2008

  • Autonomous Collision-less Slot Assignment Algorithm for Wireless Sensor Networks

    • R. Chandradasa, T. Yamazato, M. Katayama
    • IEICE General Conference, B-20-28, p.569, Kyushu, Japan
    • Mar. 2008
    • Traditional MAC protocols for Sensor Networks are mostly based on random access methods, which cause message collision and energy loss. Several TDMA based methods have been proposed to prevent signal collision with the help of a base station. We propose an algorithm which assigns time slots to sensor nodes without the help of a base station and realizes time-slot reuse.

  • Carrier Assignment to Improve the Transmission Efficiency of Edge Terminal in OFDMA Downlink Cellular System

    • M. Fushiki, T. Yamazato, M. Katayama
    • IEICE General Conference, B-5-44, p.430, Kitakyusyu, Japan
    • Mar. 2008

  • Performance Comparison of SC/MMSE Turbo Equalization and MMSE Equalization in Inter-Vehicle Communication using MC-CDMA

    • N. Hiraiwa, A. Sakata, T. Yamazato, M. Katayama
    • IEICE General Conference, B-5-65, p.451
    • Mar. 2008

  • Introduction of Fractional Frequency Reuse and Fast Retrial Algorithm for uplink of Multi-Cell OFDMA s-ALOHA systems

    • K. Kimura T. Yamazato, M. Katayama
    • IEICE General Conference, B-5-47, p.433
    • Mar. 2008

  • Time Variation of Narrowband Channel Characteristics of Indoor Power-Line Channels

    • Y. Sugiura T. Yamazato, M. Katayama
    • IEICE General Conference, A-5-17, p.144
    • Mar. 2008

    • S. Arai, Y. Nishio, T. Yamazato
    • IEICE General Conference, A-2-35, p.74
    • Mar. 2008

  • CDMA slotted ALOHA Systems with Successive Interference Cancellation for Inter-Vehicle Communications

    • A.Sakata, T.Yamazato, H.Okada, M.Katayama
    • IEICE General Conference, A-17-12, p.323
    • Mar. 2008

  • Experiment on Road-to-Vehicle Visible Light Communication for Hierarchical Coding Scheme using LED Array and High-Speed Camera

    • S. Arai, S. Mase, T. Yamazato, T. Yendo, T. Fujii, M. Tanimoto, Y. Kimura
    • Technical Report of IEICE, vol.ITS2007-61, pp.151-156
    • Feb. 2008
    • In this study, we focus attention on the parallel optical wireless communication systems using LED array transmitter and high-speed camera as the receiver for road-to-vehicle communications in ITS. Previously, we proposed a hiearachical coding scheme which allocates data to spatial frequency components depending on the priority. This scheme is possible to receive the high priority data even if the receiver is far from the transmitter. However, since vehicles drive on a road in actual road-to-vehicle communications, it is difficult that synchronizing the timing to release the shutter with the lighting cycle of LEDs, namely, sampling of the data is important work. This paper proposes a sampling method for road-to-vehicle communications during driving and performs driving experiments using a car with the high-speed camera. Moreover, we not only analyze received images by off-line operations but also investigate future problems for the communication system design.

  • Performance Improvement ofDownlink MC-CDMA Cellular Systemwith an Intermittent Transmission

    • M. Fushiki, T. Yamazato, M. Katayama
    • IEEE Radio and Wireless Symposium, pp.275-278, Orlando
    • Jan. 2008
    • https://doi.org/10.1109/RWS.2008.4463482
    • Throughput performance of MC-CDMA systems depends on the success in managing interference arising from intercell transmission. In this paper, we propose a new intercell interference mitigation scheme for downlink MC-CDMA scheme. In the proposed scheme, a base station transmits downlink signals intermittently to mobile terminals at the edge of cell. The intercell interference can be seen as a partial interference depend upon the on and off period of the adjacent downlink signals. So it is possible for the channel equalizer to suppress this partial intercell interference by setting the weight changes in accordance with the intercell interference. As results, the frame error rate of the proposed scheme is always better than that of the conventional scheme and good throughput performance is achieved especially when the traffic is high.

  • A note on EXIT analysis for distributed encoding and joint decoding of correlated sources

    • K. Kobayashi, T. Yamazato, M. Katayama
    • Technical Report of IEICE, vol.RCS2007-125, pp.79-83, Ohita, Japan
    • Dec. 2007
    • Extrinsic information transfer (EXIT) charts are used to predict the behavior of the iterative decoder by solely looking at the input/output relation of individual constituent decoders. This allows the prediction of turbo cliff region. In the recent research on the distributed coding and joint decoding, there has been a significant interest in utilizing iteratively decodable codes. Hence, it is expected that EXIT analysis can be employed for assessing the convergence behavior of such iterative schemes. In this paper, we present a turbo based iterative joint decoding scheme of two correlated binary sources. The convergence behavior of the proposed system is studied using EXIT charts.

  • Visible Light Communication

    • T. Yamazato
    • IEICE Shinetsu Section Lecture, IEEE Shinetsu Section Lecture , Shinshu University
    • Dec. 2007

  • Improvement of Error Performance for Noncoherent Chaos Communications

    • S. Arai, Y. Nishio, T. Yamazato
    • Proceedings of IEEE Workshop on Nonlinear Circuit Networks (NCN'07), pp. 54-56, Tokushima, Japan
    • Dec. 2007
    • This paper proposes the error-correcting for noncoherent chaos communications. To improve the error performance, we focus attention on the successive chaotic sequence based on the chaotic dynamics. Concretely, error performance of a noncoherent receiver improves by analyzing the chaotic dynamics of the successive received sequence. As results of computer simulations, we confirm about 3 dB gain in BER performance compared to the conventional suboptimal receiver.

  • Indoor Propagation Measurements for Wireless Controls

    • K. Endou, T. Yamazato, M. Katayama
    • Technical Report of IEICE, vol.RCS2007-97, pp.1-6, Tokyo, Japan
    • Nov. 2007
    • In order to collect basic reference data for wireless controls of industrial equipments, we have constructed a system to measure the continuous (five seconds) wideband (23MHz) simultaneous propagation characteristics of multiple channels in 2.4GHz band. As a result, the propagation characteristics of two indoor wireless channels measured simultaneously, are expressed as functions of time and frequency. The result shows that the propagation loss considerably exceed its mean value locally in time--frequency plane, and that the probability of this drops of the signal is not negligible. In addition, we show that the probability of the deep fades which continues more than the permissible delay time for the control communication system (20ms) is also non-negligible. Moreover, we clarify that, even when the antennas are separated by several wavelength, still the correlation of the time-varying faded signal levels at the antennas is relatively high and should be taken into account in designing a wireless control systems.

  • Correlations of noise waveforms at different outlets of power-line network

    • A. Kawaguchi, H. Okada, T. Yamazato, M. Katayama
    • IEICE Transactions on Fundamentals, vol.J90-A, no.11, pp 851-860
    • Nov. 2007
    • This manuscript discusses the relationships of noise waveforms measured at different outlets in a three-wire single-phase (one neutral and two live conductors) power-line network. As a result of experimental measurements, it is shown that instantaneous noise voltages at two different outlets have high correlations if they are connected to the same live conductor. It is also found that the instantaneous noise powers and cyclic averaged noise powers have large correlations even for a pair of outlets connected to the different live conductors. The correlation coefficients for instantaneous voltages and powers are calculated as the frequency functions.

  • OFDM for satellite communications

    • T. Yamazato, A. Ogawa
    • Technical Report of IEICE, vol. 107, no. 299, SAT2007-29, pp. 59-64, Okinawa, Japan
    • Nov. 2007
    • OFDM or multicarrier systems have emerged as a key technology for current existing terrestrial wireless systems. Because of their advantages over a single carrier system, OFDM is undergoing rapid progress and inspiring numerous applications. However, many technical issues still exist for adopting OFDM to satellite communications, i.e., non-linear amplifier compensation. In this article, we present a detailed investigation of various non-linear compensation techniques and provide a better understanding of the research challenges.

  • Automotive Ultrasonic Array Emitter for Short-range Targets Detection

    • H. Hatano, T. Yamazato, M. Katayama
    • IEEE International Symposium on Wireless Communication Systems (ISWCS), pp.355-359, Trondheim, Norway
    • Oct. 2007
    • https://doi.org/10.1109/ISWCS.2007.4392361
    • We consider an application of a ultrasonic array emitter to automotive targets detection systems for short-range. Ultrasonic sensors are low cost and widely used. However detectable ranges do not meet the requirements for short-range applications, such as parking aid systems. In this paper, we propose a method which may achieve the emission to a desired area within limited time. We evaluate the expected accuracy of target position estimations by computer simulations. As a result, we show the ability of the ultrasonic sensors for parking aid systems.

  • Performance evaluation of cooperative transmission

    • K. Nakao, T. Yamazato, M. Katayama
    • Technical Report of IEICE, , USN2007-48, pp.73-76, Nagoya, Japan
    • Oct. 2007
    • Since sensor nodes are typically small and power limited, they are only able to achieve short-range transmission with low complexity processing. Therefore, we need to realize extension of the transmission range by cooperative transmission among the distributed nodes. In this paper, we propose a simple cooperative scheme without tight synchronization, i.e., multiplication of random phase in the transmitter before the transmission. Thanks to a strong error correcting code, it is possible to extend the transmission range. We evaluate the performance of this proposed scheme by LED optical communication equivalently using FPGA.

  • A Novel Contention-Free Medium Access Control Protocol for Inter-Vehicle Communication Systems

    • M. Masamura, H. Okada, S. Makido, T. Yamazato, M. Katayama
    • First International Workshop on Mobile Vehicular Networks, Pisa, Italy
    • Oct. 2007
    • https://doi.org/10.1109/MOBHOC.2007.4428733
    • We propose a contention-free medium access control (MAC) protocol for inter-vehicle communication systems that share information for the improvement of safety drive on the highway. In the proposed system, contention-free medium access is achieved by periodical one-way token transmissions. The token contains the frame information about the transmission/reception phase. While the token is relaid by one-way, the vehicle which has the token can send a packet to both up- and down-link. The token transmission interval is set not to be interfered from other transmit vehicles at a receive vehicle. In addition, multiple channels are used and allocated dynamically for every token transmission to reduce the transmission waiting time. We also evaluate the maximum end-to-end transmission delay of the proposed protocol, and clarify that the proposed protocol can guarantee the transmission within allowable delay time.

  • A Route Selection Scheme for Multi-Route Coding in Multihop Cellular Networks

    • H. Okada, H. Imai, T. Yamazato, M. Katayama, K. Mase
    • IEEE Vehicular Technology Conference (VTC-Fall), Baltimore, USA
    • Oct. 2007
    • https://doi.org/10.1109/VETECF.2007.18
    • In the multihop cellular networks, multiple routes from a user station to a base station can be established because of the flexibility of network topology. In order to reduce packet errors of wireless transmissions, we proposed the multi-route coding scheme, in which packets are encoded and divided into subpackets, and they are transmitted on several routes from the user station to the base station. In order to improve the performance of the multi-route coding, a route selection scheme is very important issue. In this paper, we propose the route selection scheme for the multi-route coding in multihop cellular networks. The proposed scheme is based on the bit error rate of wireless links. We also apply the proposed route selection scheme to a hybrid routing protocol and evaluate its performance.

  • Analysis on Chaotic Sequence with Biased Values for Noncoherent Chaos Communication

    • S. Arai, Y. Nishio, T. Yamazato
    • International Symposium on Nonlinear Theory and its Applications (NOLTA), pp.144-147, Vancouver, Canada
    • Sep. 2007
    • In this paper, we analyze a chaotic dynamics generating a chaotic sequence with biased values and apply it to noncoherent chaos communications. We examine a behavior of the chaotic dynamics by increasing the slope of the chaotic map and investigate the invariant measure and the correlation function. A high quality performance of noncoherent chaos communications is obtained by controlling the distribution of the chaotic sequence with biased values. Finally we carry out the computer simulation using its sequence and discuss the obtained results and the future problem for chaos communication.

  • Experiment on Hierarchical Transmission Scheme for Visible Light Communication using LED Traffic Light and High-Speed Camera

    • S. Arai, S. Mase, T. Yamazato, T. Endo, T. Fujii, M. Tanimoto, K. Kidono, Y. Kimura, Y. Ninomiya
    • IEEE International Symposium on Wireless Vehicular Communications (WiVeC), Baltimore, USA
    • Sep. 2007
    • https://doi.org/10.1109/VETECF.2007.456
    • LEDs are expected as lighting sources for next generation, and data transmission system using LEDs attract attention. In this paper, we present hierarchical coding scheme using LED traffic lights and high-speed camera for Intelligent Transport Systems (ITS) application. Further, if each of LEDs in traffic lights is individually modulated, parallel data transmissions are possible using a camera as a reception device. Such parallel LED-camera channel can be modeled as spatial low-pass filtered channel of which the cut-off frequency varies according to the distance. To overcome, we propose hierarchical coding scheme based on 2D fast Haar wavelet transform. As results, the proposed hierarchical transmission schemes outperform the conventional on-off keying and the reception of high priority data is guaranteed even LED-camera distance is further.

  • A Study on Random Access Scheme using Channel Division for Multi-Cell OFDMA uplink

    • K. Kimura T. Yamazato, M. Katayama
    • Communications Society Conference of IEICE, B-5-62, p.384
    • Sep. 2007

  • Efficient Channel Estimation Scheme for Pulse-shaping OFDM Systems

    • B.Mongol, T. Yamazato, M. Katayama
    • International Symposium on Nonlinear Theory and its Applications (NOLTA), pp.92-95, Vancouver, Canada
    • Sep. 2007
    • This paper proposes a low-complexity channel estimation sheme for the pulse-shaping OFDM systems in the highly mobile multipath environment. The estimation scheme is based on the tapped-delay-line model for the channel. The main idea behind our scheme is to approximate the fading process for each tap with finite terms of its Taylor series expansion. The proposed scheme also tracks the channel. We show that the channel can be estimated and tracked with reasonable mismatch error while using considerably short training period.

  • Distributed Space-Time Block Coding for Large and Undetermined Set of Relay Terminals

    • R. Uchida, H. Okada, T. Yamazato, M. Katayama
    • IEEE International Symposium on Personal, Indoor and Mobile Radio Communication (PIMRC), Athens, Greece
    • Sep. 2007
    • In this manuscript, a spatial diversity scheme with multiple transmit and receive antennas together with multiple relay terminals for packet radio is considered. Correctly received signals at some relay terminals are re-transmitted to the receiver with the spatial diversity by STBC cooperative relaying scheme. To achieve high diversity order with the conventional STBC cooperative relaying scheme, relay terminals which re-transmit the signals are required to exchange signaling information with each another. However, the exchanging of the information causes delay of the signal transmission. Thus, in this manuscript, a novel signaling scheme for the STBC cooperative relaying is proposed. The proposed scheme releases relay terminals exchanging the signaling information. The proposed scheme also saves communication resources to provide flexibility for installation of relay terminals.

  • A study on position estimation method for multiple targets detection for automotive radar networks

    • H. Hatano, T. Yamazato, H. Okada, M. Katayama
    • Transactions of Society of Automotive Engineers of Japan, vol.38, no.5, pp.191-196
    • Sep. 2007
    • We research automotive radar networks with multiple radars set in the front of car. Especially, we consider data processing using measured ranges provided by the radars in order to estimate multiple target positions with high accuracy. This paper is composed of three steps. Firstly, we derive a method based on MAP estimation. Secondly, we propose a method which reduces the calculation complexity compared with the above MAP method. Finally, we introduce a method which can detect targets without ghost-targets in case the lacks of measured ranges are happened because of miss-detection. We evaluate the methods with computer simulations.

  • Hierarchical Coding Scheme for Optical Wireless Communicaiton using LED Traffic Light and High-Speed Camera

    • K. Masuda, T. Yamazato, H. Okada, M. Katayama
    • IEICE Transactions on Fundamentals, vol.J90A, no.9, pp.696-704
    • Sep. 2007
    • LEDs are expected as lightning sources for next generation, and data transmission system using LEDs attract attention. In this paper, we present hierarchical coding scheme using LED traffic lights and high-speed camera for Intelligent Transport Systems (ITS) application. Further, if each of LEDs in traffic lights is individually modulated, parallel data transmissions are possible using a camera as a reception device. Such parallel LED-camera channel can be modeled as spatial low-pass filtered channel of which the cut-off frequency varies according to the distance. To overcome, we propose hierarchical coding scheme based on 2D fast Haar wavelet transform. As results, the proposed hierarchical transmission schemes outperform the conventional on-off keying and the reception of high priority data is guaranteed even LED-camera distance is further.

  • Performance comparison of CSMA and CDMA slotted ALOHA in Inter-Vehicle communication

    • A.Sakata, T.Yamazato, H.Okada, M.Katayama
    • Communications Society Conference of IEICE, B-5-89, p.411
    • Sep. 2007

  • Performance evaluation of cooperative transmission in distributed sensor networks using FPGA

    • K. Nakao, T. Yamazato, M. Katayama
    • Proceedings of 9th DSPS Educators Conference, pp.91-92, Tokyo, Japan
    • Aug. 2007

  • Performance Improvement of Downlink MC-CDMA Cellular System using Different Arrival Time of the Adjacent Cell Signal

    • M. Fushiki, T. Yamazato, M. Katayama
    • Technical Report of IEICE, vol.RCS2007-68, pp.87-91, Niigata, Japan
    • Aug. 2007
    • Throughput performance of MC-CDMA systems depends on the success in managing interference arising from intercell transmission. In this paper, we propose a new intercell interference mitigation scheme for downlink MC-CDMA scheme. In the proposed scheme, a base station transmits downlink signals intermittently to mobile terminals at the edge of cell. The intercell interference can be seen as a partial interference depend upon the on and off period of the adjacent downlink signals. So it is possible for the channel equalizer to suppress this partial intercell interference by setting the weight changes in accordance with the intercell interference. As results, the frame error rate of the proposed scheme is always better than that of the conventional scheme and good throughput performance is achieved especially when the adjacent cell signal power is large.

  • Measurement of the Narrowband Channel Characteristics \\in Single-Phase Three-Wire Indoor Power-Line Channels

    • Y. Sugiura , T. Yamazato, M. Katayama
    • Technical Report of IEICE, vol.WBS2007-30, SIP2007-81, pp.53-58, Kochi, Japan
    • Aug. 2007
    • This manuscript reports the measurement results of narrow-band signal propagation of PLC channels between a pair of outlets. In Japan, in-house wiring is of single-phase three-wire, and each branch between an outlet of 100V and the panel board is connected to one of two live conductors and the neutral. Thus a pair of outlets can be classified into three types: connected to different live conductors, connected to the same live conductors by different branches from the panel board, and on the same branch to the same live conductor. It is confirmed that the results of the measurements are also classified by these three types of paths. The results show that frequency responses of narrow-band PLC channels are relatively smooth, compared with that of wide-band PLC. It is also found that propagation loss in lower frequency range is larger than in higher frequency range. The time independence of narrow-band PLC channels are confirmed when no electric appliance is connected to the same live conductor.

  • Throughput evaluation of CSMA and CDMA slotted ALOHA in Inter-Vehicle communication

    • A.Sakata, T.Yamazato, H.Okada, M.Katayama
    • Technical Report of IEICE, vol.RCS2007-55, pp.13-18
    • Aug. 2007
    • This paper evaluate the throughput performance of a carrier-sense multiple access (CSMA) scheme that uses an orthogonal frequency division multiple access (OFDM) physical layer and a CDMA slotted ALOHA scheme based on multicarrier CDMA (MC-CDMA) in inter-vehicle communication (IVC). In particular, we compare the throughputs in a situation where a hidden terminal is no longer negligible. We encounter such a situation in an intersection where two or more cars are crossing by. In a hidden terminal situation, the CSMA scheme may degrade throughput. On the other hand, CDMA slotted ALOHA has a resistance to the hidden terminal situation as it can support simultaneous packets. However, the transmission data rate is much slow because of the spreading. Thus the total throughput may not be as high as the CSMA based OFDM even in a hidden terminal situation. As results, we show that the CSMA based OFDM system shows better total throughput than CDMA slotted ALOHA in all region. But, only the signal from the nearest car can be received. On the contrary, CDMA slotted ALOHA can receive many packets simultaneously. This is much preferable feature for safety driving.

  • Ultrasonic Array Emitter for Short-range Automotive Targets Detection System

    • H. Hatano, T. Yamazato, M. Katayama
    • Technical Report of IEICE, vol.ITS2007-12, pp.15-20, Tokyo, Japan
    • Jul. 2007
    • We consider application of ultrasonic sensor to automotive targets detection system for short-range. The ultrasonic sensors are low cost and widely used. However the detection range is short. In addition, wide detection area is needed. To apply for high functional parking aid system, we propose the array emitter which can emit signals to desired area within desired cycle time. As a result, we show the ability of the ultrasonic sensor for parking aid systems.

  • Channel measurement of a visible light communication system with an LED sign panel

    • D. Ishida , T. Yamazato, M. Katayama
    • Technical Report of IEICE, Vol.OCS2007-15, pp.31-35, Hokkaido, Japan
    • Jun. 2007
    • As one of visible light communications systems, this paper focuses on a system using LED sign panel as a transmitter. The characteristic between the panel (E/O) input and the APD(O/E) output is measured. Linearity, frequency response, and the levels of harmonics of the channel is measured. The effects of the distance between the panel and the APD on the signal level is clarified. After the measurement of noise spectrum caused by an inverter-driven fluorescent lamp, the SNR in frequency is calculated.

  • A Method for Reducing the Influence of the Interference Considering ADC Nonlinearity in an OFDM Receiver

    • M. Sawada, T. Yamazato, M. Katayama
    • IEICE Transactions on Communications, vol.J90-B, no.6, pp.577-584
    • Jun. 2007
    • In this paper we propose an OFDM receiver that mitigates the performance degradation caused by interference. The mitigation process is done all in digital after ADCs. The receiver estimates the reliability of each OFDM symbol based on its number of out-of-range samples. This reliability is then used as the external information in soft Viterbi decoding process. The results of numerical simulations for 16QAM/OFDM show that the proposed receiver is robust to strong interference.

  • Experiments on a Wireless Visible-Light Communication System using an LED Sign Panel

    • T. Ohtsuji, T. Yamazato, M. Katayama
    • Technical Report of IEICE, Vol.OCS2007-14, pp.25-29, Chitose, Japan
    • Jun. 2007
    • This manuscript focuses on a wireless visible-light communication system with an LED-back-lighted sign board. Possibilities of the system are confirmed by experiment. In the experimental system, the transmitter uses frequency shift keying (FSK), which has constant envelope to avoid fluctuation of luminance and can be received without carrier phase synchronization. Since the noise and signal propagation in Electric/Optical/Electric channel are not flat in frequency, we introduce a weighting equalization before the decision circuit of the receiver. Experimental results show that this weighting improves bit error rate (BER) performance and extend distance between the transmitter and the receiver.

  • Cooperative Transmission Scheme in Distributed Sensor Network for Extension of Transmission Range

    • K. Nakao, T. Yamazato, H. Okada, M. Katayama
    • Fourth International Conference on Networked Sensing Systems, pp.89-92, Braunschweig, Germany
    • Jun. 2007
    • https://doi.org/10.1109/INSS.2007.4297396
    • We consider a distributed transmission of data packet to a sink where the distance for a sensor node to the sink is much longer than a sensor node can transmit. We give a simple modification in the transmitter, i.e., multiplication of random phase before the transmission. Thanks to a strong error correcting code, it is possible to extend the transmission range as the received amplitude varies symbol by symbol for our scheme while whole data packet may be lost for the conventional scheme.

  • Throughput Comparison of CSMA and CDMA slotted ALOHA in Inter-Vehicle Communication

    • A. Sakata, H. Okada, T. Yamazato, M. Katayama
    • 7th International Conference on ITS Telecommunications, pp.52-57, Sophia antipolis, France
    • Jun. 2007
    • https://doi.org/10.1109/ITST.2007.4295832
    • This paper compare the throughput performance of a carrier-sense multiple access (CSMA) scheme that uses an orthogonal frequency division multiple access (OFDM) physical layer and a CDMA slotted ALOHA scheme based on multicarrier CDMA (MC-CDMA) in inter-vehicle communication (IVC). In particular, we compare the throughputs in a situation where a hidden terminal is no longer negligible. We encounter such a situation in an intersection where two or more cars are crossing by. In a hidden terminal situation, the CSMA scheme may degrade throughput. On the other hand, CDMA slotted ALOHA has a resistance to the hidden terminal situation as it can support simultaneous packets. However, the transmission data rate is much slow because of the spreading. Thus the total throughput may not be as high as the CSMA based OFDM even in a hidden terminal situation. As a result, we show that the CSMA based OFDM system shows better total throughput than CDMA slotted ALOHA in all region. But, only the signal from the nearest car can be received. On the contrary, CDMA slotted ALOHA can be received many packets simultaneously. This is much preferable feature for safety driving.

  • Visible Light Communications using LED Traffic Light and High Speed Camera

    • T. Yamazato
    • Visible Light Communication Consortium, Tokyo, Japan
    • May 2007

  • A Study on Joint Decoding for Wireless Sensor Networks

    • K. Kobayashi, T. Yamazato, H. Okada, M. Katayama
    • Proc. of Academia Program, Wireless Technology Park 2007, pp.26-27, Yokohama, Kanagawa
    • Apr. 2007
    • Development of tiny sensor equipped with wireless communication function is remarkable with the advancement of small, light, and high-performance wireless devices. In the near future, we will see tens or hundreds of these nodes deployed in town and inside buildings. In such an environment, since many sensor nodes observe a same target or field, the information observed by each sensor node are correlated. Such correlated information are collected at a fusion center. Our purpose is to reduce channel error by using the correlation properties of observed data at the fusion center. Related works on the distributed encoding and joint decoding are the case of two correlated sources. By using the weighted correlation feedback, we extend the iterative joint decoding scheme for the general case where more than two sensor nodes are employed. We show that when the number of sensor nodes is increased, decoding performance improvement cannot be achieved by simple weighting. For more appropriate weighting, we find the weight that minimizes the bit error rate from the analytical formula of MAP decision and apply it to the case of Turbo code.

  • Visible Light Communication using LED TrafficLight and car equipped with camera

    • T. Yamazato, M. Katayama
    • Proc. of Academia Program, Wireless Technology Park 2007, pp.38-39, Yokohama, Kanagawa
    • Apr. 2007

  • A Simple Estimator of Multiple Target Positions for Automotive Short Range Radar Networks

    • H. Hatano, T. Yamazato, H. Okada, M. Katayama
    • IEEE Vehicular Technology Conference (VTC-Spring), pp.2511-2515, Dubliln, Ireland
    • Apr. 2007
    • https://doi.org/10.1109/VETECS.2007.517
    • For safety applications, automotive radar networks show an interesting potential. Apart from long range radars, networked short range radar systems are under development. Additional applications can be accomplished, such includes precrash detection, parking aid and blind spot surveillance. We research the automotive radar networks using short range radars. The network is built with multiple radars. In this paper, we consider data processing using measured ranges provided by the radars in order to estimate multiple target positions with high accuracy. Firstly, we derive a method based on MAP stimation. Secondly, we propose a method which reduces the calculation complexity compared to the above MAP method. Finally, we introduce a method which can detect targets with low ndetected targets. The case often happens when the measured ranges are lost because of miss-detections.We evaluate the performance th computer simulations.

  • Route Diversity Effect of Joint Decoding Using Correlation between Observed Data Sequences in Sensor Networks

    • H. Okada, K. Kobayashi, T. Yamazato, K. Mase
    • IEEE Vehicular Technology Conference (VTC-Spring), pp.217-221, Dublin, Ireland
    • Apr. 2007
    • https://doi.org/10.1109/VETECS.2007.57
    • In sensor networks, because of densely deployment of sensor nodes, sensing area of each sensor node is overlapped with each other and its observed data sequence is correlated. The joint decoding scheme that uses the correlation between the observed data sequences can reduce bit errors in the wireless channel. In this paper, we extend the joint decoding to the case of more than two-hop transmission. For such extension, selection of fusion scheme is very important issue. If the global fusion scheme is employed and the observed data sequence of each sensor node is transmitted on an independent route, route diversity effect could be obtained by using the correlation between observed data sequences. We compare the bit error rate performance of local and global fusion schemes and clarify the route diversity effect.

  • MIMO Equalizer for Pulse-ShapingOFDM Systems in Dispersive Time-Varying Channels

    • B. Mongol , T. Yamazato, H. Okada, M. Katayama
    • Proc. of Academia Program, Wireless Technology Park 2007, pp.50-51, Yokohama, Kanagawa
    • Apr. 2007
    • Pulse-shaping OFDM is well-known that it performs well in a mobile environment, i.e. time-varying channel, compared with conventional OFDM. However, as the time-variance becomes higher, the intersymbol and intercarrier interferences (ISI/ICIs) increase and can no longer be neglected. These ISI/ICIs deteriorate the performance of the systems. Proper channel equalization is needed for further improvement of the systems. In this paper, we have proposed a multi-input multi-output (MIMO) transversal filter to equalize the time-frequency dispersive channel. Tap weights are calculated using the zero-forcing (ZF) algorithm. We also have proposed maximum-likelihood channel estimator and its low-complexity version. The proposed system can significantly improve the performance of the pulse-shaping systems in the dispersive time-varying channels.

  • Nagoya University OpenCourseWare

    • T. Yamazato
    • Annals of Nagoya UniversityAnnals of Nagoya University, No.5
    • Mar. 2007
    • The Nagoya University OpenCourseWare Committee is currently working to make some of the university's teaching materials openly available for instructors, students and self-directed learners around the world via the Internet. In this report, OpenCourseWare activity in Nagoya University is introduced.

  • Radio Resource Allocation using Priority Based on User Position for Multiuser OFDM

    • K. Kimura T. Yamazato, M. Katayama
    • IEICE General Conference, B-5-122, p.536, Nagoya, Japan
    • Mar. 2007

  • Performance Improvement of MC-CDMA System using Different Arrival Time of the Other Cell Signal

    • M. Fushiki, T. Yamazato, H. Okada, M. Katayama
    • IEICE General Conference, B-5-41, p.455
    • Mar. 2007

  • Coded Modulation in Consideration of State of Signals for M-ary PSK Coherent Signals

    • T. Otake, H. Okada, T. Yamazato, K. Yamazaki, M. Katayama
    • IEICE Transactions on Fundamentals, vol.J90-A, no.3, pp.257-261
    • Mar. 2007
    • In this letter, we introduce coded modulation for M-ary PSK coherent state signals in quantum communication systems in which quantum signals are demodulated individually. We propose the design method of coded modulation and evaluate the performance of bit error probability.

  • Power-line communication system using correlations of instantaneous noise powers at a transmitter and a receiver

    • A. Kawaguchi, H. Okada, T. Yamazato, M. Katayama
    • IEICE General Conference
    • Mar. 2007

  • Inter-Network Communication Method for Multihop Token Line Protocol

    • M. Masamura, H. Okada, T. Yamazato, M. Katayama
    • IEICE General Conference, BS-2-2, pp.S-29 - S-30, Nagoya, Japan
    • Mar. 2007

  • Noncoherent Detection for Cooperative Transmission in Distributed Sensor Network

    • K. Nakao, T. Yamazato, H. Okada, M. Katayama
    • IEICE General Conference, A-21-25, p.416, Nagoya, Japan
    • Mar. 2007

  • Compensation Scheme for Nonlinear Distortion with 8PSK/OFDM Transmission in Nonlinear Satellite Channel

    • T. Yamaoka, T. Yamazato, H. Okada, M. Katayama
    • IEICE Transactions on Communications, vol.J90-B, no.2, pp.138-147
    • Feb. 2007
    • This paper discusses 8PSK/OFDM transmission in nonlinear satellite channel. We propose an effective compensation scheme for nonlinear distortion with high coding rate. Proposed compensation scheme is composed by bit-interleaved coded modulation with iterative decoding and original compensation for nonlinear distortion. The proposed scheme has lower complexity by combining two feedback systems and achieves good error performance under large nonlinear distortion in satellite channel.

  • Route Characteristic Estimation for Multi-Route Coding in Wireless Multihop Networks

    • H. Okada, M. Umakoshi, T. Yamazato, M. Katayama
    • IEICE Transactions on Communications, vol.J90-B, no.1, pp.93-96
    • Jan. 2007
    • In the multi-route coding, encoded subpackets are transmitted via multiple routes and decoded at a destination node to get diversity gain. Because the characteristic of each route is usually different, the performance will be improved by considering it. In this letter, we propose the estimation scheme of route characteristic.

  • Routing Protocol for Multi-Route Coding Based on Link Quality in Multihop Cellular Networks

    • H. Imai, H. Okada, T. Yamazato and M. Katayama
    • 6th Ad-hoc Network Workshop, pp.5-5 - 5-8, Okinawa
    • Jan. 2007
    • Multihop cellular networks using wireless multihop communications for cellular system are considered in this paper. In this networks, we proposed the multi-route coding scheme. In the multi-route coding, packets are encoded and divided into sub packets, and they are transmitted on multiple routes from usernode to multiple base stations. In this paper, we introduce the bit error rate on each route as route selection metrics in a routing protocol for the multi-route coding. We evaluate the performance of the multi-route coding using the bit error rate metric and show that the routing protocol based on its metric improve the packet error rate.

  • Iterative Channel Decoding Scheme Using Correlation between Transmitting Data Sequences for Fading Channels

    • K. Kobayashi, T. Yamazato, H. Okada and M. Katayama
    • Technical Report of IEICE, vol.SN2006-45, pp.45-51, Tokyo, Japan
    • Dec. 2006
    • In sensor networks, many sensor nodes are densely deployed and observation data obtained by each sensor node is correlated. The observation data is encoded and transmitted from each sensor node. Such observation data are collected at a fusion center. We consider a channel decoding scheme using the correlation of observation data at the fusion center. In our previous work, we have proposed an iterative joint channel decoding scheme for more than two sensor nodes. In this paper, based on our previous work in AWGN channels, we show that our proposed joint decoding scheme is effective in fading channels, too. As a result, we can obtain larger performance improvement than that in AWGN channel.

  • Influence of Characteristics of Wireless Channels on Quality of Wireless Control Systems

    • R. Uchida, H. Okada, T. Yamazato, M. Katayama
    • IEICE Transactions on Fundamentals, vol.J89-A, no.12, pp.1104-1107
    • Dec. 2006
    • In this manuscript, the employment of wireless data transmission for control of industrial machines in an indoor fading environment is considered. The relationship between the performance of the wireless control and that of the wireless transmission is studied in two types of the systems: the system with wireless transmission both for a control signal to a controlled target and a feedback signal from a sensor at the target; and the system that employs wireless transmission only for a control signal. As a result, it is shown that the performance of the systems can be improved by increasing the transmission rate as well as decreasing the error rate. The fact suggests how the wireless transmission should be designed to maintain high quality in wireless-controlled systems.

  • Influence of ADC Nonlinearity on the Performance of an OFDM Receiver

    • M. Sawada, H. Okada, T. Yamazato, M. Katayama
    • IEICE Transactions on Communications, vol.E89-B, no.12, pp.3250-3256
    • Dec. 2006
    • This paper discusses the influence of the nonlinearity of analog-to-digital converters (ADCs) on the performance of orthogonal frequency division multiplexing (OFDM) receivers. We evaluate signal constellations and bit error rate performances while considering quantization errors and clippings. The optimum range for an ADC input amplitude is found as a result of the trade-off between quantization error and the effects of clipping. In addition, it is shown that the peak-to-average power ratio (PAPR) of the signal is not a good measure of the bit error rate (BER) performance, since the largest peaks occur only with very low probabilities. The relationship between the location of a subcarrier and its performance is studied. As a result, it is shown that the influence of the quantization error is identical for all subcarriers, while the effects of clipping depend on the subcarrier frequency. When clipping occurs, the BER performance of a subcarrier near the center frequency is worse than that near the edges.

  • Iterative channel decoding scheme using the correlation of transmitted information sequences in sensor networks

    • K. Kobayashi, T. Yamazato, H. Okada and M. Katayama
    • IEICE Transactions on Fundamentals, vol.J89-A, no.12, pp.1044-1056
    • Dec. 2006
    • In sensor networks, many sensor nodes are densely deployed and observation data obtained by each sensor node are correlated. The observation data are encoded and transmitted from each sensor node. Such observation data are collected at a fusion center. In this paper, we extend the iterative channel decoding scheme using the correlation of transmitted information sequences to the case of more than two sensor nodes. An approach to use practical channel codes for more than two correlated data is still not presented. A problem in the extension to cases of more than two sensor nodes is how to use the information of correlation obtained from observation data. In this paper, we propose an iterative channel decoding scheme that uses them with weighting. We show that when the number of sensor nodes is increased, decoding performance improvement cannot be achieved by simple weighting, and so a more appropriate weight is needed. We find the weight that minimizes the bit error rate from the analytical formula for uncoded BPSK and apply it to the case of Turbo code.

  • Mobile Techniques for Safety Drive Assistance

    • T. Yamazato
    • , Conference Room, Venture Business Laboratory, Nagoya University
    • Nov. 2006

  • A study on the Method for Reducing the Influence of the Interference Considering ADC Nonlinearity in an OFDM Receiver

    • M. Sawada, T. Yamazato, M. Katayama
    • Symposium on Information Theory and Its Applications (SITA)，vol.2, pp. 691&#8211;694,, Hakodate, Hokkaido, Japan,
    • Nov. 2006
    • In this paper we propose an OFDM receiver that mitigates the performance degradation caused by interference. The mitigation process is done all in digital after ADCs. The receiver estimates the reliability of each OFDM symbol based on its number of out-of-range samples. This reliability is then used as the external information in soft Viterbi decoding process. The results of numerical simulations for 16QAM/OFDM show that the proposed receiver is robust to strong interference.

  • Influence of Transmit and Receive Correlations on Performance of the MIMO System with Multiple Antennas and Relay Terminals

    • R. Uchida, H. Okada, T. Yamazato, M. Katayama
    • MObile Radio Interdisciplinary Workshop (MORI Workshop), Daejeon, Korea
    • Nov. 2006

  • MIMO Zero-forcing Equalizer for BFDM/OQAM Systems in the Highly Mobile Environments

    • B. Mongol, T. Yamazato, H. Okada, M. Katayama
    • IEEE Global Communications Conference (GLOBECOM), WLC01-6, San Francisco, CA, USA
    • Nov. 2006
    • https://doi.org/10.1109/GLOCOM.2006.620
    • Pulse-shaping OFDM is well-known that it performs well in a mobile environment comparing with conventional OFDM. However, in highly mobile environment intersymbol and intercarrier interferences (ISI/ICIs) increase and can no longer be neglected. These ISI/ICIs deteriorate the performance of the systems. Proper channel equalization is needed for further improvement of the systems. In this paper, more general case, namely Biorthogonal Frequency Division System based on Offset QAM (BFDM/OQAM) is considered. We propose a multi-input multi-output (MIMO) transversal filter to equalize the time-frequency dispersive channel. Tap weights are calculated using the zero-forcing (ZF) algorithm. We also propose maximum-likelihood channel estimator and its low-complexity version. The proposed system can significantly improve the performance of BFDM/OQAM systems in the highly mobile environment.

  • MIMO Zero-forcing Equalizer for BFDM/OQAM Systems in Time-Frequency Dispersive Channels

    • B. Mongol, T. Yamazato, H. Okada, M. Katayama
    • IEICE Transactions on Fundamentals, vol.E89-A, no.11, pp.3114-3122
    • Nov. 2006
    • Pulse-shaping OFDM is well-known that it performs well in a mobile environment compared with conventional OFDM. However, in a highly mobile environment intersymbol and intercarrier interferences (ISI/ICIs) increase and can no longer be neglected. These ISI/ICIs deteriorate the performance of the systems. Proper channel equalization is needed for further improvement of the systems. In this paper, a more general case, namely Biorthogonal Frequency Division System based on Offset QAM (BFDM/OQAM) is considered. We propose a multi-input multi-output (MIMO) transversal filter to equalize the time-frequency dispersive channel. Tap weights are calculated using the zero-forcing (ZF) algorithm. We also propose maximum-likelihood channel estimator and its low-complexity version. The proposed system can significantly improve the performance of BFDM/OQAM systems in the highly mobile environment.

  • Handbook of Antennas and Radios (VI-3.3 Spread Spectrum Modulation)

    • T. Yamazato (in charge of VI-3.3)
    • Ohmsha, 972 pages
    • Oct. 2006

  • Influence of Transmit and Receive Correlations on Performance of the MIMO System with Multiple Antennas and Relay Terminals

    • R. Uchida, H. Okada, T. Yamazato, M. Katayama
    • International Symposium on Information Theory and Its Applications (ISITA), pp.454-459, Seoul, Korea
    • Oct. 2006
    • In this manuscript, spatial diversity for in-factory environments is considered. The proposed scheme uses multiple antennas at a transmitter and a receiver, and also multiple relay terminals to provide diversity gain against fading and shadowing. If the separation of antennas at the transmitter or the receiver is not enough, then diversity gain is influenced by correlation at the transmitter or the receiver. This manuscript shows the analytical and numerical results of the effects of transmit and receive correlations on bit error performance of the proposed spatial diversity scheme.

  • A study on route selection metrics for the multiple-route packet combining scheme in wireless multihop networks

    • Y. Hirayama, H. Okada, T. Yamazato, M. Katayama
    • IEICE Transactions on Communications, vol.J89-B, no.10, pp.2047-2051
    • Oct. 2006
    • The multiple-route packet combining (MRPC) is a diversity combining and error correction scheme for wireless multihop networks. In this letter, we propose two different route selection metrics for MRPC based on channel quality and packet arrival probability and evaluate the packet error performance of MRPC.

  • Iterative Joint Channel-Decoding Scheme Using the Correlation of Transmitted Information Sequences in Sensor Networks

    • K. Kobayashi, T. Yamazato, H. Okada, M. Katayama
    • International Symposium on Information Theory and Its Applications (ISITA), pp.808-813, Seoul, Korea
    • Oct. 2006
    • In this study, we consider joint channel decoding of Turbo code for multiple correlated data that are observed by sensor nodes densely deployed in a sensor field. We focus on the correlation properties of observation data and try to reduce decoding error by an iterative procedure. An approach to use practical channel codes for more than two correlated data is still not presented. A problem in the extension to cases of more than two sensor nodes is how to use the information of correlation obtained from observation data. In this study, we propose an iterative channel decoding scheme that uses them with weighting. We show that when the number of sensor nodes is increased, decoding performance improvement cannot be achieved by simple weighting, and so a more appropriate weight is needed. We find the optimum weight that minimizes the bit error rate from the analytical formula for uncoded BPSK and apply it to the case of Turbo code.

  • A Study on Blind Cooperative Relaying Scheme with Space-Time Block Coding

    • R. Uchida, H. Okada, T. Yamazato, M. Katayama
    • Technical Report of IEICE, vol.RCS-2006-142, pp.55-60, Kagawa, Japan
    • Oct. 2006
    • In this manuscript, a spatial diversity scheme with multiple transmit and receive antennas together with multiple relay terminals for packet radio is considered. Correctly received signals at relay terminals are re-transmitted to the base station with the spatial diversity by STBC cooperative relaying scheme. To achieve high diversity order with the conventional STBC cooperative relaying scheme, the relay terminals are required to exchange signaling information with each other. In this manuscript, a novel signaling scheme for the STBC cooperative relaying is proposed. The proposed scheme releases relay terminals exchanging of the signaling information and saves the communication rosource to provide flexibility for installation of relay terminals. As a benchmark to the proposed scheme, optimum signaling case is also considered.

  • Route Diversity Effect of Joint Decoding Using Correlation between Transmitting Data Sequences

    • H. Okada, K. Kobayashi, T. Yamazato, K. Mase
    • Ad Hoc Network Workshop, pp.2-5 - 2-8, Tokyo
    • Oct. 2006
    • When the sensing data is dispersed in wireless networks such as ITS or sensor networks, sensing area of each node is overlapped with each other and the transmitting data sequence is correlated. The joint decoding scheme that uses the correlation between the transmitting data sequences can reduce bit errors in the wireless link. If the data sequence of each sensing node is transmitted on an independent route, route diversity effect could be obtained by using the correlation between the transmitting data sequences. In this paper, we compare the bit error rate performance of local and global fusion schemes and clarify the route diversity effect.

  • A Study on Fusion Schemes for Joint Decoding Using Correlation between Observed Data Sequences

    • H. Okada, K. Kobayashi, T. Yamazato, K. Mase
    • Enginnering Sciences Society Conference of IEICE, A-21-15, p.227, Kanazawa
    • Sep. 2006

  • Teaching material design for course improvement

    • T. Yamazato
    • 2008 1st WebCT course at Nagoya Women's University, Nagoya, Japan
    • Sep. 2006
    • N.A.

  • A study on the reduction of the influence of the interference using ADC nonlinearity in an OFDM receiver

    • M. Sawada, T. Yamazato, M. Katayama
    • Communications Society Conference of IEICE, B-17-5, p.515, Kanazawa, Japan
    • Sep. 2006

  • The Effect of Multipath Hybrid Routing Protocol in Multihop Cellular Networks

    • H. Imai, H. Okada, T. Yamazato, M. Katayama
    • IEEE International Symposium on Personal Indoor and Mobile Radio Communication (PIMRC), Helsinki, Finland
    • Sep. 2006
    • This paper examines multihop cellular networks. There are some issues in these networks, such as route loss due to topological change and packet errors due to wireless nodes relay. To overcome these issues, we use a multiple route coding scheme in which packets are transmitted on multiple routes from a user node to multiple base stations. This scheme can achieve a diversity gain by combining packets that are transmitted along multiple routes. Some challenges must be met to establish multiple routes for this scheme. In this paper, we propose a routing protocol for multiple route coding. The key idea of this proposed scheme is using a hybrid routing protocol. This can mitigate an increase in control packets and multiple disjoint routes can be constructed. We evaluate the performance of this proposed scheme.

  • A Correlation Tolerant Relaying Scheme for the Spatial Diversity with Multiple Transmit and Receive Antennas

    • R. Uchida, H. Okada, T. Yamazato, M. Katayama
    • Communications Society Conference of IEICE, B-5-122, p.482, Kanazawa, Japan
    • Sep. 2006

  • A study on position estimation method for multiple targets detection for automotive radar networks

    • H. Hatano, T. Yamazato, H. Okada, M. Katayama
    • JSAE Annual Congress Fall, No. 134-06, pp.21-26, Sept. 2006., Sapporo, Japan
    • Sep. 2006
    • We research automotive radar networks with multiple radars set in the front of car. Especially, we consider data processing using measured ranges provided by the radars in order to estimate multiple target positions with high accuracy. This paper is composed of three steps. Firstly, we derive a method based on MAP estimation. Secondly, we propose a method which reduces the calculation complexity compared with the above MAP method. Finally, we introduce a method which can detect targets without ghost-targets in case the lacks of measured ranges are happened because of miss-detection. We evaluate the methods with computer simulations.

  • Channel Estimation for BFDM/OQAM System in Dispersive Time-Varying Channels

    • B. Mongol, T. Yamazato, H. Okada, and M. Katayama
    • International Symposium on Wireless Communication Systems (ISWCS), pp.159-163, Valencia, Spain
    • Sep. 2006
    • https://doi.org/10.1109/ISWCS.2006.4362279
    • Pulse-shaping OFDM is well-known that it performs well in a mobile environment comparing with conventional OFDM. However, in highly mobile environment intersymbol and intercarrier interferences (ISI/ICIs) increase and can no longer be neglected. These ISI/ICIs deteriorate the performance of the systems. Practically, proper channel equalization and estimation are needed for further improvement of the systems. In this paper, more general case, namely Biorthogonal Frequency Division System based on Offset QAM (BFDM/OQAM) is considered. We first derive analytical equations for the channel statistics. Further, we propose maximum-likelihood channel estimator and its low-complexity versions. The performance analysis shows that the estimators are robust against Doppler spread of the channels.

  • A Mathematical Model of Noise in Narrowband Power-Line Communication Systems

    • M. Katayama, T. Yamazato, H. Okada
    • IEEE Journal on Selected Areas in Communications, vol.24, no.7, pp.1267-1275
    • Jul. 2006
    • This manuscript introduces a mathematically tractable and accurate model of narrowband power-line noise based on experimental measurements. In this paper, the noise is expressed as a Gaussian process whose instantaneous variance is a periodic time function. With this assumption and representation, the cyclostationary features of power-line noise can be described in close form. The periodic function that represents the variance is then approximated with a small number of parameters. The noise waveform generated with this model shows good agreement with that of actually measured noise. Noise waveforms generated by different models are also compared to that of the proposed mode.

  • Optical Wireless Communicaiton using LED Traffic Light and High-Speed Camera

    • T. Yamazato, K. Masuda, H. Okada, M. Katayama
    • Technical Report of IEICE, vol.SIP2006-58, pp. 25-30, Nagaoka, Japan
    • Jul. 2006
    • LEDs are expected as lightning sources for next generation, and data transmission system using LEDs attract attention. In this paper, we present hierarchical coding scheme using LED traffic lights and high-speed camera for Intelligent Transport Systems (ITS) application. Further, if each of LEDs in traffic lights is individually modulated, parallel data transmissions are possible using a camera as a reception device. Such parallel LED-camera channel can be modeled as spatial low-pass filtered channel of which the cut-off frequency varies according to the distance. To overcome, we propose hierarchical coding scheme based on 2D fast Haar wavelet transform.

  • Seven Suggestions from TIPS Teachers <Classes Utilizing IT

    • Nagoya University Research Center for Higher Education and Information Media Education Center
    • Printec
    • Jul. 2006

  • Peformance analysis of UWB Impulse Radar Receiver using Parallel IPCP

    • H. Hatano, T. Yamazato, H. Okada, M. Katayama
    • IEICE Transaction on Communications, vol.J89-A, no.6, pp.544-556
    • Jun. 2006
    • In this paper, we consider two novel inter-period correlation processing (IPCP) receivers for UWB impulse radar. The conventional IPCP receiver uses the signal periodicity of signals, so it avoids estimation of unknown parameters determined by the targets. However, its accuracy of measurement is poor because the interval of receiver outputs is restricted to a code length. We propose a parallel IPCP receiver to improve accuracy. When there are multiple targets, the conventional IPCP receiver needs multiple thresholds to detect. This results in complexity of the receiver. So, we propose a parallel differential IPCP receiver. We present the analysis of proposed receivers.

  • An Analysis on Influence of Transmit and Receive Correlations on Performance of the MIMO System with Relay Terminals

    • R. Uchida, H. Okada, T. Yamazato, and M. Katayama
    • Technical Report of IEICE, vol. RCS2006-46, pp. 65-70, Nagoya Instutute of Technology, Nagoya, Japan
    • Jun. 2006
    • In this manuscript, a spatial diversity scheme with multiple transmit and receive antennas and relay terminals for indoor factory fading/shadowing environment is considered. The scheme uses multiple transmit and receive antennas and relay terminals to provide diversity gain against the fading and shadowing. However, if the separations of antennas at a transmitter or a receiver are not enough, then the signals of the diversity branches may be influenced by transmit or receive correlation. This manuscript shows the analytical and numerical results of the effect of the transmit and receive correlations on the performance of the spatial diversity scheme.

  • An Inter-Vehicle Two-Way Communication System

    • M. Masamura, H.Okada, S. Makido, T. Yamazato, M. Katayama
    • 4th Ad-hoc Network Workshop, pp.4-21 - 4-24, Osaka, Japan
    • Jun. 2006
    • We propose an inter-vehicle two-way communication system for safety applications. The proposed system synchronizes with transmission timings mong cars by one-direction token transmissions in a linear network. The token contains the frame information about transmission/reception phase. The token transmission interval is set so that adjacent reception cars do not affect interference from other cars. Moreover, multiple channels are used in order to make the same transmission delays despite of their transmission directions and reduce them. This system can adapt changes of the network structure by allocating channels dynamically for every token.

  • Iterative channel decoding scheme using the correlation of transmitted information sequences - Extension to the case of more than two sensor nodes -

    • K. Kobayashi, T. Yamazato, H. Okada and M. Katayama
    • Technical Report of IEICE, vol.SN2006-32, pp.91-97, Tokyo, Japan
    • May 2006
    • In sensor networks, many sensor nodes are densely deployed and observation data obtained by each sensor node is correlated. The observation data is encoded and transmitted from each sensor node. Such observation data are collected at a fusion center. In this paper, we consider a channel decoding scheme using the correlation of observation data. Related works on the encoding and decoding scheme using the correlation of observation data are for the case of two correlated sources. An approach for more than two sources is still not presented. In this paper, we extend the iterative channel decoding scheme using the correlation of transmitted information sequences to the case of more than two sensor nodes. A problem in the extension to the case of more than two sensor nodes is how to use the information of correlation obtained from other sequences. Specifically, it is needed to use them with weighting to minimize the bit error rate. In this paper, we find the optimum weight that minimizes the BER from the analytical formula in the case of uncoded BPSK and apply it to the case of Turbo code.

  • Throughput Evaluation of ARQ Scheme for Multi-route Coding in Wireless Multi-hop Networks

    • H. Okada, T. Wada, K. Ohuchi, M. Saito, T. Yamazato, M. Katayama
    • IEEE Vehicular Technology Conference (VTC-Spring), pp.668-672 , Melbourne, Australia
    • May 2006
    • https://doi.org/10.1109/VETECS.2006.1682908
    • For reduction in bit errors on wireless channels, we proposed the multi-route coding scheme on multiple routes for wireless multi-hop networks. In this paper, we introduce ARQ to the multi-route coding. In the multi-route coding, the destination node combines and decodes sub packets which are encoded and divided by the source node. The intermediate node relays a sub packet, that is, only a part of a packet. Therefore, the intermediate node cannot detect packet errors, and only the destination node can do after combining and decoding sub packets. We propose the ARQ scheme between the source node and the destination node. We analyze the proposed ARQ scheme and evaluate the throughput performance.

  • Multi-route Coding in Wireless Multi-hop Networks

    • H. Okada, N. Nakagawa, T. Wada, T. Yamazato, M. Katayama
    • IEICE Transactions on Communications, vol.E89-B, no.5, pp.1620-1626
    • May 2006
    • Wireless multi-hop networks have drawn much attention for the future generation mobile communication systems. These networks can establish multiple routes from a source node to a destination node because of flexible construction of network topology. The transmission by multiple routes has enough capability to achieve reliable communication because we can expect to obtain diversity gain by multiple routes. In this paper, we propose the multi-route coding scheme. At first, we discuss a channel model in multi-hop networks employing regenerative relay, which we named the virtual channel model. By using the virtual channel model, a packet is encoded on multiple routes as follows; a bit sequence of a packet is encoded and divided into subpackets, and each subpacket is transmitted on each route. We evaluate its packet error rate performance, and clarify effectiveness of the proposed scheme. In general, we should face degradation of a route condition such as the case when a subpacket does not reach a destination node. Hence, we have to consider the influence of subpacket loss. We also investigate it, and show tolerance of the proposed scheme over that.

  • Cooperative transmission scheme using coded FSK

    • K. Nakao, T. Yamazato, H. Okada, M. Katayama
    • Technical Report of IEICE, vol.SN2006-28, pp.67-72, Tokyo, Japan
    • May 2006
    • In sensor networks, many sensor nodes are distributed. The observation data are collected at a fusion center. They are transmitted to a fusion center by direct or multihop transmission. In this paper, we consider the situation that the transmission by those ways is not possible (e.g. a helicopter collects the data). We realize the transmission by a cooperative transmission among the nodes. An approach proposed for cooperative transmission is assumed coherent propagation or multi-channel, or applied to only a few nodes. In this paper, we propose a scheme to achieve the cooperative co-channel transmission only coding by multiplying a random phase per symbol.

  • A study on position estimation method based on MAP estimation for multiple targets in car radar networks

    • H. Hatano, T. Yamazato, H. Okada, M. Katayama
    • Technical Report of IEICE, vol.ITS2006-3, pp.11-16,, Yokosuka, Japan
    • May 2006
    • In this paper, we consider radar networks for cars. The radar networks are the networks built with multiple radars. Using measured ranges provided by radars, target positions are estimated. The measured ranges include measurement errors. The estimation method of the target positions using a MAP stimation is an optimum method. However, when the number of targets increases, the MAP estimation method becomes complex. So we introduce the simpler methods based on the MAP estimation method. The performance is evaluated by computer simulations.

  • A study on the mitigation of the influence of ADC nonlinearity in an OFDM receiver

    • M. Sawada, H. Okada, T. Yamazato, M. Katayama
    • DENSO TECHNICAL REVIEW, vol.11, no.1, pp.115-120,
    • May 2006
    • An orthogonal frequency division multiplexing (OFDM) scheme, with highly spectrum efficiency and robustness against frequency selective fading, is applied to IEEE802.11a/g for high-speed wireless local area network (LAN) systems and digital terrestrial television broadcasting (DTTB) systems. The OFDM signal has large fluctuation in its amplitude, large dynamic range and high linearity are required for its transmitter and receiver. In the receiver, the Bit Error Rate (BER) performance is degraded by analog-to-digital converter (ADC) nonlinearity. We propose a new scheme to mitigate the influence of ADC nonlinearity in an OFDM receiver. In the proposed receiver, the weight for the soft Viterbi decoder is controlled based on the ADC output amplitude. We evaluate the BER performance for the proposed receiver when the control errors occur in the AGC amplifier. As a result, the effect of the proposed receiver on the BER performance is shown.

  • Reliable Robust Radio for Wireless Control of Industrial Machines

    • R. Uchida, H. Okada, T. Yamazato, M. Katayama
    • Proc. of Academia Program, Wireless Technology Park 2006, Yokohama, Japan
    • Apr. 2006
    • Wireless control of industrial machines in factories has a lots of advantages over wired control. To achieve wireless control safely, high reliability of the wireless transmission system is required. In this manuscript, wireless transmission system with high reliability in indoor environment is considered. In indoor environment, transmitted signal fluctuates due to fading and shadowing. To combat the fading and shadowing, macro / micro spatial diversity can be used as an effective countermeasure. In this manuscript, macro / micro diversity is achieved by multiple wireless relay terminals, which is convenient in setting and moving the macro diversity branches. In the proposed scheme, channel between the transmitter and the receiver through relay terminals is considered as a MIMO channel and separation of the signals re-transmitted from the relay terminals is not required. This feature makes it possible to have higher order diversity without the cost of bandwidth inefficiency. By numerical calculations, performance of the proposed scheme is evaluated and the improvement of the reliability of the transmission system is confirmed.

  • Automotive radar network technique for short range

    • H. Hatano, T. Yamazato, H. Okada, M. Katayama
    • Proc. of Academia Program, Wireless Technology Park 2006, pp.34-35, Yokohama, Japan
    • Apr. 2006
    • We consider a radar system for vehicles in order to detect obstacles in a short range (up to 10m). In comparison with a long range radar, a short range radar needs wide angular range. Therefore a radar network which is set at front of a vehicle with multiple radars is being considered. The short range radar system also needs estimating obstacle positions with high accuracy. Therefore, by this research, we consider improving accuracy of the position estimation with the radar network. We use MMSE (Minimum Mean Square Error) and estimate parameters to get accurate positions from ranges measured by multiple radars. For MMSE, we consider three methods which differ in terms of objective functions to minimize or parameters to estimate. For these methods, we evaluate position estimation characteristics using computer simulations. We show that each method has characteristic performance at environment of use of cars.

  • Joint Decoding of Convolutional Codes using the Correlation of Transmitted Information Sequences in Sensor Networks

    • K. Kobayashi, T. Yamazato, H. Okada and M. Katayama
    • IEICE General Conference, A-21-19, p.367, Tokyo, Japan
    • Mar. 2006

  • A method to mitigate the influence of ADC nonlinearity in an OFDM receiver

    • M. Sawada, H. Okada, T. Yamazato, M. Katayama
    • IEICE General Conference, B-17-4, p.583, Tokyo, Japan
    • Mar. 2006

  • Correlations of noise waveforms at different outlets in a power-line network

    • A. Kawaguchi, H. Okada, T. Yamazato, M. Katayama
    • IEEE International Symposium on Power Line Communications and Its Applications (ISPLC), pp.92-97, Orlando, Florida, USA
    • Mar. 2006
    • This manuscript discusses the relationships of noise waveforms measured at different outlets in a three-wire single-phase (one neutral and two live conductors) power-line network. As a result of experimental measurements, it is confirmed that instantaneous noise voltages at two different outlets have high correlations if the outlets are connected to the same live conductor in a distribution board, while the outlets for the different live conductors provide noise waveforms with low correlations. It is also shown that the instantaneous noise powers and cyclic averaged noise powers as time functions have large correlations even at a pair of outlets connected to the different live conductors. The correlation coefficients for instantaneous voltages and powers are also calculated as the frequency functions.

  • A Study on Signal Separation Scheme for Wideband Software-defined Radio Base Station

    • Toru KITAYABU, Hiraku OKADA, Takaya YAMAZATO, Masaaki KATAYAMA
    • IEICE General Conference, Tokyo, Japan
    • Mar. 2006

  • Performance Evaluation of Packet Combining and ARQ Schemes of Multiple Route Coding in Wireless Multihop Networks

    • H. Okada, M. Saito, T. Wada, K. Ohuchi, T. Yamazato, M. Katayama
    • Technical Report of IEICE, vol.RCS2005-207, pp.175-180, YRP
    • Mar. 2006
    • For reduction in bit errors on wireless channels, we proposed the multi-route coding scheme on multiple routes for wireless multi-hop networks. In this paper, we introduce packet combining and ARQ to the multi-route coding. In the multi-route coding, the destination node combines and decodes sub packets which are encoded and divided by the source node. The intermediate node relays a sub packet, that is, only a part of a packet. Therefore, the intermediate node cannot detect packet errors, and only the destination node can do after combining and decoding sub packets. We propose the ARQ scheme between the source node and the destination node, and evaluate the performance of the proposed scheme.

  • Experiment on Hierarchical Coding Scheme for Parallel Optical Wireless Communications

    • K. Masuda, T. Yamazato, H. Okada, M. Katayama
    • Technical Report of IEICE, vol.WBS2005-91, pp.75-79, Nagoya, Japan
    • Mar. 2006
    • In this paper, we evaluate the performance of hierarchical transmission scheme using LED traffic lights and high-speed camera for ITS application. By using camera as a receiving device, parallel data transmissions are possible if each of LEDs in traffic lights is individually modulated. In such parallel LED-camera channel, if a receiver is far from a transmitter the received data pattern degrade and it is hard to distinguish adjacent LEDs. To overcome, we have proposed hierarchical coding schemes. Experimental results show that the proposed hierarchical coding schemes outperform the conventional on-off keying(OOK) if LED-camera distance is further.

  • A Study on Effects of Transmit/Receive Correlations on Performance of Diversity with Multiple Antennae/Relay Terminals

    • R. Uchida, H. Okada, T. Yamazato, M. Katayama
    • IEICE General Conference, B-5-161, p.514, Tokyo, Japan
    • Mar. 2006

  • Robust BFDM/OQAM Receiver for Time-Frequency Dispersive Channels

    • B. Mongol, T. Yamazato, H. Okada, and M. Katayama
    • Technical Report of IEICE, vol.WBS2005-112, pp.19-24, Nagoya, Japan
    • Mar. 2006
    • Biorthogonal Frequency Division Multiplexing based on Offset QAM (BFDM/OQAM) system is one of the pulse-shaping versions of Orthogonal Frequency Division Multiplexing (OFDM) systems. It allows optimal Gaussian transmitting pulse at critical sampling i.e., maximum spectral efficiency. In this paper we propose a robust receiver for BFDM/OQAM systems in highly mobile environment. The idea behind our approach is to employ Multi-Input Multi-Output zero-forcing (MIMO-ZF) transversal filter to equalize the channel. The equalizer requires knowledge of the channel status. The channel is estimated by using Maximum-Likelihood method. We evaluate the error rate performance of the proposed system in the time-frequency dispersive channels.

  • An Implementation of Multiple Route Coding Scheme in Wireless Multihop Networks

    • M.Umakoshi,H.Okada,K.Suzuki,T.Yamazato,M.Katayama
    • IEICE General Conference, B-21-9, p.569, Tokyo,Japan
    • Mar. 2006

  • A Proposal of Iterative Nonlinear Distiortion Compensation Scheme for OFDM Trandmission in Satellite Channel

    • T. Yamaoka, T. Yamazato, H. Okada, M. Katayama
    • Technical Report of IEICE, vol.SAT2005-56, pp.37-42, Kanazawa
    • Feb. 2006

  • An Error Control Scheme for the Control Signal Onboard the Simplified Satellite Repeater

    • S. Saiki, H. Kuwamura, A. Ogawa, T. Yamazato
    • Technical Report of IEICE, vol.SAT2005-54, pp.29-32, Kanazawa
    • Feb. 2006
    • This paper is concerned with performance evaluation for error control of the routing information onboard the simplified satellite repeater for broadband satellite communications. The necessary information for the onboard routing is carried on the preamble portion placed at the top of the packet and modulated with the differential binary PSK. In this paper, we adopt simplified two dimensional parity check code for the routing information onboard the simplified satellite repeater. It is decoded by iterated soft decision decoding, then the error correction is performed together with error detection. We describe the results obtained by computer simulation in terms of the block error rate.

  • An Effct of Nonlinerity Onboard the Simplified Satellite Repeater for OFDM Signal Transmission

    • H. Kuwamura, A. Ogawa, T. Yamazato
    • Technical Report of IEICE, vol.SAT2005-55, pp.33-36, Kanazawa
    • Feb. 2006
    • This paper is concerned with performance evaluation for an experimental model of a repeater for broadband satellite communications. For the purpose of realizing a high speed and flexible internet satellite communication system, we propose a simplified configuration of satellite regenerative repeater. In this repeater, the amount of signal processing is limited so that the input signal is only AD converted and stored, but a complex function of error control is left to the earth stations. While the information data are modulated with multi-level QAM based on OFDM, the necessary information for the onboard routing is carried on the preamble potion placed at the top of the packet and modulated with the differential binary PSK .In this paper, measured results of the bit error rate for this simplified regenerative repeater are described.

  • Applying OFDM modulation to Simple Regenerative Repeating Process of Broadband Satellite

    • T. Yamazato, H. Kuwamura, A. Ogawa
    • Technical Report of IEICE, vol.SAT2005-53, pp.23-28, Kanazawa
    • Feb. 2006
    • The authors have been working on the simple regenerative repeater for satellite communication systems that omit the process of error-correction-decoding and re-encoding in the satellite side. We have implemented coded QAM system to FPGA board and confirmed the effectiveness till now. If a header part is common by this simple regenerative, transmission is theoretically possible with a signal of any kind of signal format. In this study, we introduce the FPGA implementation of OFDM signal and show the effectiveness of regenerative repeating process for OFDM transmission.

  • A note on error correct decoding scheme using the correlation of transmitted information sequences in sensor networks

    • K. Kobayashi, T. Yamazato, H. Okada and M. Katayama
    • Technical Report of IEICE, vol.SN2006-10, pp.59-64, Tokyo
    • Jan. 2006
    • In sensor networks, many sensor nodes are densely deployed and observation data obtained by each sensor node is correlated. The observation data is encoded and transmitted from each sensor node. Such observation data are collected at a fusion center. In this paper, we consider an error correct decoding scheme (joint decoding) using the correlation of transmitted information sequences. We focus on how the correlation property affect on the improvement of the BER performance when the joint decoding is applied. We evaluate the case when each sensor node is equipped with a turbo code and a convolutional code. We show that in both cases the contribution of the correlation property on the BER performance can be confirmed, however their gains are nearly the same.

  • Routing Protocol for Multiple Route Coding in Multihop Cellular Networks

    • H. Imai, H. Okada, T. Yamazato and M. Katayama
    • Ad-hoc Network Workshop, pp.7-5 - 7-8, Hiroshima
    • Jan. 2006
    • Multihop cellular network using wireless multihop communications for cellular system are considered in this paper. In this networks, there are some issues such as the route loss due to topological change and packet errors due to wireless nodes delay. To overcome these issues, we use the multiple route coding scheme in which packets are transmitted on multiple route from usernode to multiple base stations. In this paper, we propose a routing protocol for multiple route coding. The key idea of the proposed scheme is to employ the hybrid routing protocol. It can mitigate the increase in control packets and construct multiple disjoint routes. We evaluate the performance of the proposed scheme.

  • Ultra-Wideband Chaotic Radar and Clutter Reduction Methods

    • N. Dake, Y. Uwate, Y. Nishio, T. Yamazato
    • Journal of Signal Processing, vol.9, no.6, pp.473-478
    • Dec. 2005
    • Chaos could generate nonperiodic sequences with infinite lengths theoretically. In this paper, we propose a UWB (ultra-wideband) chaotic radar, whose transmitted signal is generated by a chaotic map. Since it is important to remove various noises called clutter in a radar, we focus mainly on the removal of clutter by applying three clutter reduction methods. We derive the probability density function of power, the distances between the transmitted signals and the recovered signals, and the detection probability, using computer simulations, and the performance of the proposed radar is evaluated.

  • Target Position Estimation using MMSE for A Radar Network

    • H.Hatano, T. Yamazato, H. Okada, and M. Katayama
    • IEICE Transactions on Fundamentals, vol.J88-A, no.12, pp.1456-1459
    • Dec. 2005
    • We cosider to improve accuracy for a target position estimation using multiple radars and MMSE algorithm for short short range. In this paper, we discussed three objective functions for MMSE algorithms in terms of accuracy of the position estimation.

  • An improvement of the transmission quality using the correlation of the observation data in sensor networks

    • K. Kobayashi, T. Yamazato, H. Okada and M. Katayama
    • IEICE Transactions on Fundamentals, vol.J88-A no.12 pp.1442-1451
    • Dec. 2005
    • In sensor networks, many sensor nodes are densely deployed and observation data obtained by each sensor node is correlated. Such observation data are collected at a fusion center. In this paper, we discuss the observation accuracy at the fusion center from the viewpoint of the amount of Kullback-Leibler (KL) information. Especially, we consider channel error caused when data are transmitted from sensor nodes through wireless communication channels. The channel error deteriorates the observation accuracy. We discuss this influence and a method to decrease it. In this paper, we consider a case when all the correlation between the observation data is equal and when the correlation is uniformly distributed. In both cases, we discuss degradation of KL information under the influence of channel errors. We show that it possible to avoid such degradation using the correlation between the observation data by a estimation of correct value of the erroneous data. In addition, we show a method to estimate the correlation between the observation data and an example of estimating a correct value from erroneous data using correlation.

  • Introduction on Nagoya University Open Courseware

    • T. Egawa, T. Yamazato
    • 2005 Conference on Education for Information Processing, Kyushu University
    • Nov. 2005
    • We are now working on the open courseware project.

  • [Invited Talk] Information Theory Providing Fundamentals of Sensor Networks

    • T. Yamazato
    • Technical Report of IEICE, vol.IT2005-62, pp.17-26, Okinawa, Japan
    • Nov. 2005
    • Despite the known objective, to achieve advance sensing by connecting many sensing devices by an information and communication networks, sensor networks may give a significant impact throughout the field of information and communication technology and may become a basis of the information revolution. Applications of sensor networks ranges from environmental observations, security, building of intelligent space, to disaster rescue, amusement and so on. The unique feature of Sensor Networks is that the sensing nodes must operate under a set of unique constraints and requirement that network itself is unstable and unreliable. The limited amount of energy available to wireless sensors has a significant impact on all aspects of wireless sensor networks, from the amount of information that the node can process, to the volume of wireless communication it can carry across. In this paper, information theory that providing fundamentals of sensor networks is addressed, especially its theoretical outline and issues are introduced.

  • The Faculty Inventory for Student Involvement in Web-Enhanced Learning －The Online Survey of WebCT Users－

    • T. Yamazato, T. Nakai, H. Nakajima, H. Okada, M. Omura
    • The 3rd WebCT Research Conference, pp.73-77, Fukui, Japan
    • Nov. 2005
    • The paper analyzes good teaching examples of online classrooms accumulated in the United States and proposes a faculty inventory for student involvement in Web-Enhanced learning in Japanese higher education. In the proposed inventory, practical examples are categorized into seven principles which are well-known for the good practices for undergraduate education in the United States.

  • A study on the mitigation of the influence of ADC nonlinearity in an OFDM receiver

    • M. Sawada, H. Okada, T. Yamazato, M. Katayama
    • Symposium on Information Theory and Its Applications (SITA), vol.1, pp.143-146, Okinawa, Japan
    • Nov. 2005
    • We propose a new scheme to mitigate the influence of ADC nonlinearity in an OFDM receiver. In the proposed receiver, the weight for the soft Viterbi decoder is controlled based on the ADC output amplitude. As a result, the effect of the receiver on the BER performance is shown.

  • A Study on Route Selection Metrics for the Multiple-Route Packet

    • Y. Hirayama, H. Okadaa, T. Yamazato, and M. Katayama
    • Symposium on Information Theory and Its Applications (SITA), vol.1, pp.151-154, Okinawa
    • Nov. 2005
    • The multiple-route packet combining (MRPC) is a diversity combining and error correction scheme for wireless multihop networks. In this scheme, multiple replicas of a coded packet are transmitted along different disjoint routes from a source node. These replicas are received, combined and decoded by the destination. If a conventional multipath routing protocol, such as MDSR, is employed, smaller hop routes tend to be selected to transmit packets. However, the performance of MRPC depends on the packet reception probability and the bit error rate of each route. It is therefore expected that the performance mproves if these statics are utilized as a route selection metric. In this paper, we compare the packet error performance of MRPC for different route selection metrics. Three different metrics are considered, that is, the log-likelihood ratio (LLR), the packet reception probability, and the number of hops of a route. From the performance comparison, we show that LLR is the best metric when packet decoding errors are dominant over packet losses.

  • Channel Coding for M-Ary Coherent-State Signals with Signal Constellations in Consideration of Signal States

    • T. Otake, H. Okada, T. Yamazato, K. Yamazaki, and M. Katayama
    • Symposium on Information Theory and Its Applications (SITA), vol.1, pp.203-206
    • Nov. 2005
    • In quantum communication systems, the optimum detection process for M-ary PSK coherent-state signals which minimizes symbol error probability is Square-root Measurement(SRM). To minimize the bit error probability of the M-ary PSK coherent-state signals, it is effective to consider the allocation of the code words to the signals. In this paper, we show that the average bit error probability for such coded signals improves more than that of the uncoded signals which have the same information rate as the coded signals.

  • Characterization of a simplified regenerative repeater for broadband satellite communications

    • H. Kuwamura, A. Ogawa, T. Yamazato
    • Technical Report of IEICE, vol.SAT2005-22, pp.33-35
    • Oct. 2005

  • Successive Interference Cancellation for Hierarchical Parallel Optical Wireless Communication Systems

    • H. Okada, K. Masuda, T. Yamazato, M. Katayama
    • Asia-Pacific Conference on Communications (APCC), pp.788-792, Perth, Australia
    • Oct. 2005
    • A parallel optical wireless communication system using two-dimensional LED array (2D LED array) and two-dimensional image sensor (2D image sensor) was proposed for the visible light communication systems. In this system, each LED of the 2D LED array is individually modulated, and the 2D image sensor recognizes each LED modulated data. However, the received data pattern will be degraded due to reduction of pixel size and/or defocussing of the LED data pattern. This phenomenon corresponds to the degradation of high spatial frequency components of the received data pattern. To overcome, we employ a hierarchical transmission scheme at a transmitter and a successive interference cancellation at a receiver. By allocating high priority data to low frequency components and low priority data to high frequency components, the reception of high priority data can be guaranteed. We also attempt to apply interference cancellation to overcome the degradation of high spatial frequency components of the received data pattern. By evaluating the bit error rate, we clarify the effect of the proposed system.

  • Outage Probability of a Macro and Micro MIMO Diversity Scheme in an Indoor Fading and Shadowing Environment

    • R. Uchida, H. Okada, T. Yamazato, M. Katayama
    • IEICE Transactions on Fundamentals, vol.E88-A, no.10, pp.2945-2951
    • Oct. 2005
    • In this manuscript, a layered macro / micro diversity scheme is introduced at the receiver side of a MIMO STBC wireless control system under fading and shadowing environment. The combination of the outputs of micro diversity is based on soft-decision values, while the macro diversity branches are combined based on hard decision values. As a measure of the reliability of the system, the outage probability of frame-error rate is employed. The performance of the proposed system is analytically and numerically evaluated and the impact of the macro diversity in the outage probability is clarified.

  • A Note on the Simple Regenerative Repeating Process for Communication Satellite

    • T. Yamazato, A. Ogawa
    • Technical Report of IEICE, vol.SAT2005-21, pp.27-32, Nagoya, Japan
    • Oct. 2005
    • We have been working on a relay process of communication satellite. We omit the regenerative process at the satellite. Only routing and other necessary operation are performed at satellite. Simple configuration and signal processing may promise robust and long-lasting operations in space. We call it simple regenerating repeater. However, an issue is how to realize the reliable transmission even if we omit the error correcting and detecting process at the satellite. To overcome this issue, we propose to place the error detection code prior to QAM mapping. Using the status of error detector, it is possible to give accuracy to the received signal so we can improve the performance by soft decoding. The FPGA experimental boards of the system are also introduced

  • A Study on ARQ Schemes of Multiple Route Coding for Wireless Multihop Networks

    • H. Okada, M. Saito, T. Wada, K. Ohuchi, T. Yamazato, M. Katayama
    • Communications Society Conference of IEICE, B-5-149, p.549
    • Sep. 2005

  • Performance Analysis of a Multi-Route Packet Combining Sheme in Sensor Networks

    • K. Nakao, Y. Hirayama, T. Yamazato, H. Okada, and M. Katayama
    • Enginnering Sciences Society Conference of IEICE, A-21-5, p.274
    • Sep. 2005

  • A Study on Effects of Variations of Transmitter LED’s Luminance for Hierarchical Coding in Parallel Optical Wireless Communication Systems

    • K. Masuda, T. Yamazato, H. Okada, and M. Katayama
    • Communications Society Conference of IEICE, B-8-17, p.209, Sapporo, Japan
    • Sep. 2005

  • Effects of Error Rate and Transmission Rate on the Performance of Wireless Control Systems

    • R. Uchida, H. Okada, T. Yamazato, and M. Katayama
    • Communications Society Conference of IEICE, B-5-156, p.556, Sapporo, Japan
    • Sep. 2005

  • On the Second-order Statistics of the Channel Parameters for BFDM/OQAM Systems

    • B. Mongol, T. Yamazato, H. Okada, M. Katayama
    • International Symposium on Wireless Communication Systems (ISWCS), WS4-6, Siena, Italy
    • Sep. 2005
    • Recently, there has been increased interest in using multicarrier systems in rapidly time-varying multipath environment.　Biorthogonal Frequency Division Multiplexing based on　Offset QAM (BFDM/OQAM) is an attractive modulation method　since it allows time-frequency well-localized pulses even at critical　sampling (i.e. maximum spectral ef ciency). BFDM/OQAM　system is naturally strong against intersymbol and intercarrier　interference (ISI/ICI). However, for further improvement of the　system a study on the channel statistics is needed. In this paper we　analytically examine the channel parameters for BFDM/OQAM　and derive their second-order statistics.

  • A Simple Regenerative Repeating Process for Broadband Communication Satellite

    • T. Yamazato, A. Ogawa
    • AIAA International Communications Satellite Systems Conference (ICSSC), MOD-1-1, Rome, Italy
    • Sep. 2005
    • In this paper, we focus on relay process of broadband communication satellite. We omit the demodulation, error decoding and re-encoding process at the satellite. Just store the received signal as it is and then forward it to the destination in which the information is extracted from the header. We discuss the issue of analog-to-digital converter for this relay process. For given quantization level, reduction of signal accuracy can improve the transmission rate as we can adopt higher order of QAM. However, the degradation occurred due to the reduction of available quantized bit for accuracy. To overcome this issue, we propose to place the error detection code prior to QAM mapping. Using the status of error detector, it is possible to give an accuracy to the received signal so we can improve the performance by soft decoding.

  • A New Coded QAM Modulation Scheme for Broadband Satellite Communication

    • T. Yamazato, T. Yamaoka, H. Okada, M. Katayama, A. Ogawa
    • AIAA International Communications Satellite Systems Conference (ICSSC), MOD-3-3, Rome, Italy
    • Sep. 2005
    • In this paper, we propose a new multi-rate coded QAM for broadband satellite communication system. The overall coding rate is (m?2)/2 and Turbo code is adopted. The mapping is similar to bit-interleaved coded modulation (BICM) systems; unlike BICM mapping, we only assign four of Turbo coded bits. This brings a et-partitioning. We also consider the effect of quantization bits. Actually we try to realize high-order QAM by using the available quantization bits, which reduces the signal accuracy so the performance may degrade. As results, our proposed scheme achieve good performance even when the available quantization bits are less.

  • A MIMO System with Relay Terminals for Reliable Wireless Control

    • R. Uchida, H. Okada, T. Yamazato, M. Katayama
    • IEEE International Symposium on Personal, Indoor and Mobile Radio Communication (PIMRC), pp.1626-1630, Berlin, Germany
    • Sep. 2005
    • In this manuscript, wireless communication system for reliable wireless control of industrial machines in indoor environment is considered. In indoor environment, transmitted signal fluctuates due to fading and shadowing. To combat the fading and shadowing, macro / micro spatial diversity can be used as an effective countermeasure. In this manuscript, macro / micro diversity is achieved by multiple wireless relay terminals, which is convenient in setting and moving the macro diversity branches. In the proposed scheme, channel between the transmitter and the receiver through relay terminals is considered as a MIMO channel and separation of the signals re-transmitted from the relay terminals is not required. This feature makes it possible to have higher order diversity without the cost of bandwidth inefficiency. In numerical examples, the performance of the proposed scheme is evaluated by average frame-error rate and outage probability of frame-error rate. With two relay terminals, the diversity gain of the proposed scheme is about 5-6 dB, which is 1 dB higher than that of conventional macroscopic diversity.

  • Influence of the Nonlinearity of the ADC in an OFDM Receiver

    • M. Sawada, H. Okada, T. Yamazato, and M. Katayama
    • 10th International OFDM-Workshop 2005, pp.220-224, Hamburug, Germany
    • Aug. 2005
    • This paper discusses the influence of the nonlinearity of an analog-to-digital converter (ADC) in an orthogonal frequency division multiplexing (OFDM) receiver. We evaluate a signal constellation and a bit error rate (BER) performance with the consideration of quantization errors and clippings. As a result, the trade off between the quantization error and the clipping and the optimum range for an ADC input amplitude are shown. In addition, it is shown that the peak to average power ratio (PAPR) of the signal is not a good measure of the BER performance, since the peaks occur only with very low probabilities.

  • Target position detection using MMSE in radar networks

    • H. Hatano, T. Yamazato, H. Okada, and M. Katayama
    • Technical Report of IEICE, vol.ITS2005-15, pp.45-49, Nagoya, Japan
    • Jul. 2005
    • A radar has limitted ranging accuracy. In this paper, to improve ranging accuracy, we consider a target position estimation scheme ushing MMSE algorithm. We discuss three objective functions for MMSE algorithms to estimate a target position.

  • [Technical Exhibition] Software Defined Receiver with SFQ Digital Devices

    • A. Sekiya, Y. Nishido, H. Akaike, H. Okada, M. Inoue, T. Yamazato, A. Fujimaki, M. Katayama
    • Technical Report of IEICE, vol.SR2005-34, pp.91-96, Yokosuka
    • Jul. 2005

  • Improvement of the estimation quality using the correlation of the observation data - When sensor nodes are uniformly distributed -

    • K. Kobayashi, T. Yamazato, H. Okada and M. Katayama
    • Technical Report of IEICE, vol.SN2005-5, pp.15-20, Tokyo, Japan
    • Jun. 2005
    • We discuss the quality of estimation at a fusion centor and the influence of channel errors when sensor nodes are uniformly distributed around an observation object. Even in that case, the channel error will be suppressed by using the correlation between the observation data. In this paper, we show a method to use the correlation.

  • Faculty Inventories for Student Involvement in Web-Enhanced Learning

    • H. Nakajima, H. Okada, T. Nakai, T. Yamazato
    • Webct User Conference, pp.109-113, Tokyo
    • Jun. 2005
    • The paper analyzes good teaching examples of online classrooms accumulated in the United States and proposes a faculty inventory for student involvement in Web-Enhanced learning in Japanese higher education. In the proposed inventory, practical examples are categorized into seven principles which are well-known for the good practices for undergraduate education in the United States.

  • Performance Evaluation of Route Coding Scheme in Wireless Multi-hop Networks

    • H. Okada, T. Wada, K. Ohuchi, M. Saito, T. Yamazato, M. Katayama
    • IEEE Vehicular Technology Conference (VTC-Spring), pp.3092-3096, Stockholm
    • Jun. 2005
    • Wireless multi-hop networks have been much attention for the future generation mobile communication systems. Due to the possibility of flexible construction in the wireless multi-hop networks, multiple routes from a source node to a destination node can be established. In this paper, we propose the route coding scheme in the wireless multi-hop networks. In the proposed scheme, a packeted data sequence is encoded by the convolutional code at the source node. Each digit of the code word is assigned to sub-packets on multiple routes. At the intermediate nodes, the sub-packets are regenerated-relayed to the next node. The sub-packets transmitted via multiple routes are decoded by the Viterbi decoder with the modified metric computation at the destination node. We also evaluate the system performance, and clarify the improvement of the packet error rate by the proposed scheme. Furthermore, we investigate the influence of the route loss due to topological change or recognizing failure.

  • Application of Successive Interference Cancellation to a Packet-Recognition/Code-Acquisition Scheme in CDMA Unslotted ALOHA Systems

    • Y. Tadokoro, H. Okada, T. Yamazato, M. Katayama
    • IEICE Transactions on Fundamentals, vol.E88-A,no.6, pp.1605-1612
    • Jun. 2005
    • Packet-recognition/code-acquisition (PR/CA) is one of the most important issues in packet communication systems. In a CDMA Unslotted ALOHA system, Multiple Access Interference (MAI) may bring about error in PR/CA. The MAI mainly stems from already recognized packets and newly arriving packets under the execution of PR/CA. This characteristic of asynchronous transmission in CDMA U-ALOHA systems implies that only one or a few packets arrive at the receiver within a short interval of a execution. Furthermore, newly arriving packets are recognized and code-acquired by using a short preamble part. Consequently, the MAI from the packets under the execution of the PR/CA will be small. Focusing on that point, this paper proposes applying the IC scheme in order to suppress the MAI from the already recognized and code-acquired packets. A performance evaluation demonstrates that such an application is valid due to the small amount of MAI from the packets under the execution of PR/CA. In addition, we demonstrates that the scheme reduces false recognition rather than mis-recognition. Such a scheme improves the performance of not only PR/CA, but also the throughput.

  • Performance Analysis of Multiple-route Packet Combining Scheme for Real-time Performance Analysis of Multiple-route Packet Combining Scheme for Real-time Performance Analysis of Multiple-route Packet Combining Scheme for Real-time Communications in Wireless Multihop Networks

    • Y. Hirayama, H. Okada, T. Yamazato, and M. Katayama
    • Proc. of Cooperation Industry Academia Government 2005, pp. 92--93,, Yokosuka, Japan
    • Jun. 2005

  • Evaluation of the Channel Parameter Statistics for BFDM/OQAM System in Multipath Time-Varying Channels

    • B. Mongol, H. Okada, T. Yamazato, M. Katayama
    • Technical Report of IEICE, vol.RCS2005-33, pp.35-40, Nagoya
    • Jun. 2005
    • Recently, there has been increased interest in using Orthogonal Frequency Division Modulation (OFDM) systems in rapidly time-varying multipath environment. The performance of the systems in such time-frequency dispersive channels, depends critically on the time-frequency localization of the transmitter pulse. Biorthogonal Frequency Division Multiplexing based on Offset QAM (BFDM/OQAM) is attractive modulation method since it allows time-frequency well-localized pulses at critical sampling (i.e. maximum spectral efficiency). In this paper we consider BFDM/OQAM system with Gaussian transmitter pulse and evaluate channel parameter statistics in multipath time-varying channels.

  • A Macro and Micro Diversity Scheme with Relay Terminals for Reliable Wireless Control

    • R. Uchida, H. Okada, T. Yamazato, and M. Katayama
    • Technical Report of IEICE, vol.RCS2005-28, pp.7-12, Nagoya Univ., Nagoya, Japan
    • Jun. 2005
    • In this manuscript, wireless communication system for reliable wireless control of industrial machines in indoor environment is considered. In indoor environment, transmitted signal fluctuates due to fading and shadowing. To combat the fading and shadowing, macro / micro spatial diversity can be used as an effective countermeasure. In this manuscript, macro / micro diversity is achieved by multiple wireless relay terminals, which is convenient in setting and moving the macro diversity branches. In the proposed scheme, channel between the transmitter and the receiver through relay terminals is considered as a MIMO channel and separation of the signals re-transmitted from the relay terminals is not required. This feature makes it possible to have higher order diversity without the cost of bandwidth inefficiency. By numerical calculations, performance of the proposed scheme is evaluated and the improvement of the reliability of the communication system is confirmed.

  • Target position estimation using MMSE for UWB IPCP receivers

    • H. Hatano, T. Yamazato, H. Okada, M. Katayama
    • 5th International Conference on ITS Telecommunications, pp.131-134, Brest, France
    • Jun. 2005
    • In this work, we present target position estimation methods using minimum mean-square error (MMSE) algorithm for short-range radar systems. We consider UWB IPCP (inter-period correlation processor) receiver and improve target position accuracy by using a set of measured ranges. Depend on how we set the objective functions for MMSE, we propose three methods. And we evaluate the performance of position estimations using computer simulations.

  • Single-user MAP Based Soft-in/Soft-output Parallel Interference Canceler Utilizing Retransmission Diversity

    • Y. Tadokoro, H. Okada, T. Yamazato, and M. Katayama
    • IEICE Transactions on Fundamentals, vol.J88-A, no.6, pp.739-750
    • Jun. 2005
    • In packet communication systems, unsuccessful packets should be retransmitted. By exploiting the information on the unsuccessful packets such as log-likelihood ratio(LLR), the retransmitted packets may be correctly demodulated. Some authors have proposed the interference cancellation schemes using such a retransmission diversity technique. However, these schemes uses the traditional approach of interference cancellation. In addition, the received signals are just combined at the output of the canceler. This paper develops the novel interference cancellation scheme which maximize a posteriori probability utilizing the LLR on unsuccessful packets. Performance evaluation shows that not only retransmitted packets but also new-generated packets can be successfully transmitted in the proposed scheme.

  • Research on relation between error performance of coded QAM and qauntized bits ～Proposal of multi-rate coded QAM～

    • T. Yamaoka,T.Yamazato,H.Okada,M.Katayama and A.Ogawa
    • Technical Report of IEICE, vol.SAT2005-9, pp.19-23, Numadu,Japan
    • Jun. 2005
    • We proposed multi-rate coded QAM which achives good error performance and facilitetes metric calculation and change of modulation. Moreover,we cleafy relation between its error performance of coded QAM and qauntized bits.

  • Activity Report of Information Security Promotion Agency, Nagoya University

    • Y. Takeuchi, Y. Yamaguchi, N. Kawaguchi, T. Yamazato, A. Hasegawa, T. Sakabe
    • IPSJ SIG Technical Report, 2005-CSEC-29(1), pp.1-6, Nagoya
    • May 2005
    • The Informaton Security Promotion Agency (ISPA), Nagoya University was established in November, 2003. It is an expert group of information security and technology operation as promptly and actively as possible to respond information security incidents. There are two missions in ISPA. One is to engage in educational activities on information security for all members in Nagoya University. The other is to respond information security incidents as promptly and actively. In this report, we describe information security training, building of information security incident database, investigation of wireless LAN and information security audit. We also report security incidents which occur in our university.

  • A Mathematical Model of Narrowband Power-Line Noise Based on Measurements

    • M. Katayama, T. Yamazato, H. Okada
    • 9th International Symposium on Power-Line Communications and Its Applications, pp.152-156, Vancouver, Canada
    • Apr. 2005
    • https://doi.org/10.1109/ISPLC.2005.1430486
    • This manuscript introduces a mathematically tractable and accurate model of narrowband power-line noise based on experimental measurements. In this model, the noise is expressed as the sum of cyclostationary Gaussian processes. The non-stationary features of power-line noise are represented with a small number of parameters, and the noise waveforms generated with the model achieve good agreement with those of actually measured noise.

  • A Study on Hierarchical Coding for Parallel Optical Wireless Communication Systems

    • K. Masuda, T. Yamazato, H. Okada, and M. Katayama
    • IEICE General Conference, A-5-26, p.142, Osaka, Japan
    • Mar. 2005

  • Research on Clutter Reduction Methods of a UWB Chaotic Radar

    • N. Dake, Y. Uwate, Y. Nishio, T. Yamazato
    • RISP International Workshop on Nonlinear Circuits and Signal Processing (NCSP), pp. 367-370, Honolulu, Hawaii
    • Mar. 2005

  • A Study on Successive Interference Cancellation for Hierarchical Coding in Parallel Optical Wireless Communication Systems

    • H. Okada, K. Masuda, T. Yamazato, M. Katayama
    • IEICE General Conference, A-5-25, p.141, Osaka
    • Mar. 2005

  • Performance Evaluation of Multi-route Turbo Coding using Parity Check Codes

    • N. Nakagawa, H. Okada, T. Wada, T. Yamazato, M. Katayama
    • IEICE General Conference, B-5-141, p.590
    • Mar. 2005

  • An Analysis of the Maximum Throughput on CDMA Packet Communication Systems Employing Successive Interference Cancellation

    • Y. Tadokoro, H. Okada, T. Yamazato, and M. Katayama
    • IEICE Transactions on Fundamentals, vol.J88-A, no.3, pp.429-433
    • Mar. 2005
    • This letter analyzes the maximum throughput on CDMA packet communication systems employing successive interference cancellation. This analysis is performed in terms of received signal-power distribution. The optimum received signal-power distribution which achieves the maximum throughput is shown to be the optimum one on BER with the limitation of packet transmission.

  • A Prototype for a Broadband Software-Defined Base Station Which Processes Signals with Widely Differing Intensity

    • T. Kitayabu, H. Okada, T. Yamazato, M. Katayama
    • Technical Report of IEICE, vol.SR04-23, pp.17-22
    • Mar. 2005
    • This paper discusses the preliminary examinations of a broadband software-defined base station receiver. The authors have been concentrating on the concept of Intelligent Super Base-station (ISB), which processes multiple signals with different modulation schemes at the same time. For the receiver of the ISB, the introduction of a superconductive analog to digital converter (ADC), which has a large bandwidth and high sensitivity, has been proposed. For the realization of such a receiver, as the first step, we designed a prototype receiver with a semi-conductive ADC, which receives and demodulates two FM broadcasting signals at the same time. As a result of the experimentations, influence of the difference of the signal level is clarified, and importance of signal selection algorithm is confirmed.

  • An Adaptive Receiver for Power-Line Communications with the Estimation of Instantaneous Noise Power

    • Y. Hirayama, H. Okada, T. Yamazato, M. Katayama
    • IEICE Transactions on Fundamentals, vol.E88-A, no.3, pp.755-760
    • Mar. 2005
    • The noise on power-lines is non-stationary, while the instantaneous noise power in different frequency bands are dependent. Under such noise environments, the instantaneous noise power in a frequency band can be estimated by observing the noise in other frequency bands. In this paper, we propose a receiver structure which uses the estimated instantaneous noise power in the decoding process and show its superiority in BER performance to conventional systems.

  • A course enhanced by WebCT

    • T. Yamazato
    • Nagoya Journal of Higher Education, Vol.5, pp.49-64
    • Mar. 2005
    • WebCT (Web Course Tools) is a course management systems (CMS) that have been developed at British Columbia University to support faculty members for designing, developing and managing his/her class. The WebCT offers many useful tools, such as displaying html-files, discussion board, e-mail, online-quiz, and so on. After using WebCT for several years, I found that it is possible to teach dynamically and interactively. Some of experiences I have learned using WebCT are reported, such includes a dynamic course administration, discussions among students, extensive study contents, and so on. As a conclusion, a need of faculty support is essential to enhance teaching and learning in Nagoya University especially for those sing WebCT.

  • A Simplified Regenerative Repeater for Satellite Communications

    • H. Kuwamura, S. Saiki, A. Ogawa, T. Yamazato, S. Kawai
    • IEICE General Conference, B-3-17, p.345, Osaka
    • Mar. 2005

  • A Tutorial on Multiple Access Technologies for Beyond 3G Mobile Networks

    • A. Jamalipour, T. Yamazato, T. Wada
    • IEEE Communication Magazine, vol.43, no.2, pp.110-117
    • Feb. 2005
    • Beyond third-generation (B3G) wireless cellular systems are recognized as systems that can achieve high data-rate transmission beyond those currently provided by the second- and third-generation (2G/3G) wireless cellular systems and are capable of delivering multiple services to users at different locations under very diverse channel conditions. B3G systems should provide services comparable to those offered by wired networks for a variety of applications such as interactive multimedia, VoIP (voice over Internet protocol), network games, videoconferencing, etc. The current trend is that B3G will be based on IP technology, and therefore, all-IP [1] architecture design has been an important research topic in the past few years. Those systems will need to support multiple services ubiquitously in different types of environment including indoor, outdoor (with low and high velocity), and up to global broadband access (satellite). Thus, they would be deployed in a heterogeneous environment of various physical access networks of wireless and wired systems. The network heterogeneity means that the physical access network underlying the B3G system will support different levels of data rates and different mobility and traffic management techniques govern individual systems. In this context, the B3G mobile systems will face at least two predominant constraints: a) heterogeneity in physical access network, and b) change of application types from commonly low data rates into more bandwidth demanding real-time and multimedia ones. In such situation, providing quality of service to users would become even more difficult that what we are currently dealing. One of the main issues involved in the development of B3G systems is the choice of multiple access (MA) technology that could efficiently share the available bandwidth to large number of users. The choice of MA technique could significantly enhance or damage the service quality delivered to end users. It is known that the existing MA techniques used in 2G/3G systems, including those based on time division multiple access (TDMA) and direct sequence code division multiple access (DS-CDMA) [2], and other combinations of the two schemes are basically suitable for voice communications and not for the burst data traffic, which would be the dominant portion of traffic load in B3G systems. Therefore, the need for developing new MA techniques for B3G becomes imperative. In this article, we will review the main technical concepts of the MA schemes in wireless mobile systems and try to find the path for the development of an appropriate MA scheme for B3G through those fundamentals govern the existing MA schemes. In the following section, multiple access technologies will be reviewed from historical and technical points of view. This review will be followed by a section that provides simple formulization of MA schemes through mathematical expressions that could simplify the process of developing new MA schemes for B3G wireless cellular systems. We will then list the most important features of multiple access schemes in 3G mobile system. Finally we conclude this article by reviewing the most promising MA schemes for B3G mobile systems.

  • Clutter reduction methods of a UWB chaos radar

    • Natsumi Dake, Yoshifumi Nishio, Takaya Yamazato
    • Technical Report of IEICE, vol.NLP2004-108, pp.49-52, Kagawa, Japan
    • Jan. 2005
    • We have proposed a UWB chaos radar, whose transmitted signal is generated by a chaotic map. If the feature of chaos is exploited, a radar with outstanding performance can be expected. It is important to remove various noises called clutter in a radar. In this study, we focus mainly on removal of clutters by employing two noise reduction methods. We use the Minimum Distance Approximation method and Maximum Likelihood Decodings method to remove the clutter.

  • Performance analysis of multi-route packet combining scheme for real-time communications in wireless multihop networks

    • Y. Hirayama, N. Nakagawa, H. Okada, T. Yamazato, and M. Katayama
    • IEICE Transactions on Communications, vol.J88-B, no.1, pp.269-279
    • Jan. 2005
    • In this paper, we consider real-time packet communications in wireless multihop networks. In real-time packet communications, packet retransmission cannot be used because it may produce undesired delays. In this case, it is necessary to be employed a technique which can reduce the influence of packet errors. We propose to apply a multi-route packet combining scheme to wireless multihop networks. We analyze two characteristics of the proposed system. One is the average packet error probability, which is obtained as a function of a elapsed time. The other is the required time for achieving a required packet error probability.

  • Time-Dependent Analysis of the Multiple-Route Packet Combining Scheme in Wireless Multihop Networks

    • Y. Hirayama, H. Okada, T. Yamazato, M. Katayama
    • International Journal of Wireless Information Networks, vol.12, no.1, pp.35-45
    • Jan. 2005
    • In this paper, we apply the multiple-route packet combining scheme to wireless multihop networks in order to support delay-sensitive applications. The performance of the system is time-dependent and is greatly affected by network-level performance. Therefore, it is necessary to develop an analytical framework to evaluate the per- formance of the system with taking into account its time-dependency. We use queuing theory to analyze the performance of the system. From numerical results, it is shown that the performance degradation of the system is mainly caused by the increase of packet delay, which is due to the increase of the traffic intensity. To prevent the increase of traffic,we propose a packet discarding scheme. We analyze the average packet error probability of the proposed system with the equilibrium point analysis (EPA). Numerical results show that the packet discarding scheme can improve the average packet error probability under heavy traffic conditions.

  • An improvement of the communication quality using correlation of the observation data in sensor networks

    • K. Kobayashi, T. Yamazato, H. Okada and M. Katayama
    • Technical Report of IEICE, vol.SN2004-01, pp.1-4, Tokyo, Japan
    • Dec. 2004
    • In sensor networks, many sensor nodes are densely deployed. So the observation data obtained by each sensor node is correlated. For this reason, the correlation portion of the observation data can be used for the improvement of communication quality in the fusion center which collects data. We show that the decrease of the amount of information by the transmission error can be suppressed using the correlation of the observation data.

  • A Proposal on Hierarchical Coding Scheme of Visible Light Communication using LED Traffic Lights

    • K. Masuda, T. Yamazato, H. Okada, M. Katayama, and T. Fujii
    • Symposium on Information Theory and Its Applications (SITA), vol.1, pp.187-190, Gifu, Japan
    • Dec. 2004
    • Wireless optical communication which uses an LED traffic light as a transmitter and a high-speed camera as a receiver has been proposed. In this paper, we propose a hierarchical coding scheme using 2D discrete wavelet transaform. We describe the coding method and evalate the performance by the computer simulations.

  • Analysis of the effect of packet discarding on multiple-route packet combining scheme

    • Y. Hirayama, H. Okada, T. Yamazato, and M. Katayama
    • Symposium on Information Theory and Its Applications (SITA), vol.1, pp.303-306, Gifu, Japan
    • Dec. 2004
    • The multiple-route packet combining scheme is one of error control techniques in wireless multihop networks. This scheme can achieve a diversity gain by combining multiple copies of the same packet, which are transmitted along different routes. In this scheme, the performance degradation is mainly caused by the increase of the amount of traffic. To prevent the increase of traffic, we propose to apply a packet discarding scheme. The performance of the proposed scheme is analyzed by using queuing theory and equilibrium point analysis (EPA). From the numerical results, the proposed system can prevent the increase of traffic and improve the average packet error probability.

  • Bit Error Rate of Trellis Coded Modulation on M-Ary Coherent-State Signal

    • T. Otake, H. Okada, T. Yamazato, K. Yamazaki, and M. Katayama
    • Symposium on Information Theory and Its Applications (SITA), Gifu, Japan
    • Dec. 2004
    • In quantum signal detection theory, the optimum detection process which minimizes symbol error probability is Square-root Measurement(SRM) for M-ary PSK coherent-state signal. To minimize bit error probability of that quantum signal detection system using M-ary PSK coherent-state signal and SRM, we propose to apply trellis coded modulation which is classical error correct coding and modulation method. The average bit error probability for such coded signal is calculated by computer simulation and compared with uncoded signal which has the same information rate as the coded signal.

  • Route Characteristic Estimation Using Path Metric in Multiple-Routing Error Correcting Scheme

    • M. Umakoshi, H. Okada, T. Yamazato, and M. Katayama
    • Symposium on Information Theory and Its Applications (SITA), vol.1, pp.299-302, Gifu
    • Dec. 2004
    • In multihop networks, the coded packet can be transmitted via multiple routes. At this time, a characteristic of each route is usually different. It is expected that the packet error rate can be reduced by using the characteristic of each route. In this paper, we propose the estimation method of route characteristic at the destination node. In the proposed scheme, route characteristic is estimated by using path metric of Viterbi algorithm. The performance of the proposed scheme is evaluated by the estimation error between estimated value and actual value of route characteristic. Furthermore, the packet error rate can be improved by using the estimated route characteristic.

  • Influence of the Signal Level at ADC-input on the Performance of an OFDM Receiver

    • M. Sawada, H. Okada, T. Yamazato, and M. Katayama
    • Symposium on Information Theory and Its Applications (SITA), vol.2, pp.403-406, Gifu, Japan
    • Dec. 2004
    • This paper deals with a study result on the influence of the signal level at ADC-input on the performance in the QPSK/OFDM system. We show that there are two degradation factors. One is degradation by quantization error, and the other is degradation by clipping. Furthermore, we evaluate BER performance of every subcarrier in a clipping case. And we show that the BER performance of the carrier closer to center is degraded.

  • A Simplified Regenerative Repeater for Satellite Communications

    • H. Kuwamura, S. Saiki, A. Ogawa, T. Yamazato, S. Kawai
    • Symposium on Information Theory and Its Applications (SITA), vol.1, pp.179-182, Gifu, Japan
    • Dec. 2004

  • Performance evaluation of the diversity decoding scheme applied to the terrestrial digital TV reception under multipath environment

    • H. Shibara, T. Yamazato, A. Ogawa
    • Symposium on Information Theory and Its Applications (SITA), vol.2, pp.579-582, Gifu, Japan
    • Dec. 2004

  • Fundamentals of Multiplexing and Multiple Access Technologies, and 4G Mobile Systems

    • T. Yamazato
    • Benrishi-kai Johotsushin Gijyutsu Kenshu-kai, Nagoya
    • Nov. 2004

  • Fundamentals of Multiplexing and Multiple Access Technologies

    • T. Yamazato
    • Proc. of 2004 Microwave Workshops and Exhibition, MWE, Yokohama, Japan
    • Nov. 2004
    • The paper introduces the fundamentals of multiplexing and multiple access (MA) technologies for mobile communication systems. We first provide a simple formulization of MA schemes through mathematical expression that is based on CDMA. Using the expression, three concepts of MA are introduced. We also introduce two important performance measures: signal to interference-and-noise ratio (SNIR) and spectral efficiency. Based on the discussion on MA, we then introduce multiplexing techniques. We focus on OFDM, multi-code transmission, and MIMO, known as high-speed transmission schemes based on multiplexing technique.

  • A proposal of the single-user MAP based soft-in/soft-output parallel interference canceller utilizing retransmission diversity

    • Y. Tadokoro, H. Okada, T. Yamazato and M. Katayama
    • Technical Report of IEICE, vol.WBS2004-44, pp.37-42, Sendai, Japan
    • Oct. 2004
    • The retransmitted packets may be correctly demodulated by using the information on the unsuccessful packets, such as matched filter output. To suppress the MAI on the retransmitted packets effectively, the interference cancellation schemes exploiting the information have been proposed. However, these schemes uses the traditional scheme of interference cancellation. In addition, the matched filter outputs are just combined after the suppression of MAI. This paper proposes the novel interference cancellation scheme which maximize a posteriori probability by using the log-likelihood ratio on the unsuccessful packets. Performance evaluation shows that the proposed scheme makes not only the retransmitted packets but also the new-generated packets be successfully transmitted.

  • A Signal Separation Scheme using Discrete Fourier Transform for Software-Defined Radio Base Station

    • K.Takeuchi, H.Okada, T.Yamazato, and M.Katayama
    • Technical Report of IEICE, Nagoya,Japan
    • Oct. 2004
    • In a base station with software-defined radio technique, which proecces the signals of multiple communication systems, it is required to separate the signals of each communication system . This report discusses the scheme of the signal separation by Discrete Fourier Transform(DFT), where the received signal is transformed to frequency components and separated in frequency domain. As the result, it is demonstrated that, even if an input signal is a sinusoidal wave, the output signal may have not only the same frequency components, but also the different frequency components. The influence of the undesired components in time/frequency domain is also discussed.

  • A Macro and Micro MIMO Diversity Scheme for a Shadowing Environment

    • R. Uchida, H. Okada, T. Yamazato, M. Katayama
    • International Symposium on Information Theory and Its Applications (ISITA), pp.1353-1358, Parma, Italy
    • Oct. 2004
    • In this paper, we propose a 2-layer spatial diversity scheme to guarantee the reliability of indoor wireless communication/control systems. The performance in uplink is numerically evaluated with the outage probability of a required bit-error rate (BER). As a result, the superiority of the proposed system to conventional ones is clarified.

  • Performance Evaluation for Error Correcting Scheme on Multiple Routes in Wireless Multi-hop Networks

    • N. Nakagawa, H. Okada, T. Wada, T. Yamazato, M. Katayama
    • International Symposium on Information Theory and Its Applications (ISITA), pp.1535-1539, Parma, Italy
    • Oct. 2004
    • In this paper, we consider the improvement of packet error rate on wireless multi-hop networks. One of the important and interesting techniques for wireless multi-hop networks is multi-path routing. By using multi-path routing, multiple routes can be established from a source node to a destination node. In this paper, we propose the error correcting scheme in which the coded different packets are transmitted using multiple routes on wireless multi-hop networks. Hence, we can achieve a coding gain for multiple routes and expect the improvement of performance. In wireless multi-hop networks, the route loss due to topological change or recognizing failure may be happened. From the above discussion, we evaluate the proposed scheme by packet error rate in consideration of the influence of the route loss.

  • [Invited Paper] Information and Signal Processing for Sensor Networks

    • A. Ogawa, T. Yamazato, T. Ohtsuki
    • IEICE Transactions on Fundamentals, vol.E87-A, no.10, pp.2599-2606
    • Oct. 2004
    • Sensor networks, in which a large number of sensor nodes are connected with each other through communication networks, are potential to provide extensive new applications with various research and technical challenges and attracting much attention all over the world. In this paper we describe information and signal processing for sensor networks with emphasis on the concepts of collaboration and fusion as one of the most important issues for the sensor networks. We also review some basic aspects of sensor networks in terms of their features and the network architecture.

  • New Error Correcting Scheme for Hard Detected QAM Signal

    • T. Yamaoka, T. Yamazato, H. Okada, M. Katayama and A. Ogawa
    • Technical Report of IEICE, vol.SAT2004-148, Seoul Korea
    • Oct. 2004
    • In order to achieve high speed satellite communication, we propose a new R=m-2/m error correcting scheme for hard detected 2^m-QAM signal, where we consider m

  • An improvement of the communication quality using correlation of the observation data in sensor networks

    • K. Kobayashi, T. Yamazato, H. Okada, and M. Katayama
    • Tokai-Section Joint Conference on Electrical and Related Engineering, O-272, Nagoya, Japan
    • Sep. 2004

  • A Study on Channel Estimation Using Malti-path in Wireless Multi-hop Networks

    • M. Umakoshi, H. Okada, T. Yamazato, and M. Katayama
    • Tokai-Section Joint Conference on Electrical and Related Engineering, O-294
    • Sep. 2004

  • Quantum Channel Coding Using Trellis Coded Modulation in Consideration of the Inner Product Between Signals

    • T. Otake, H. Okada, T. Yamazato, K. Yamazaki and M. Katayama
    • Tokai-Section Joint Conference on Electrical and Related Engineering, O-266, Nagoya, Japan
    • Sep. 2004

  • Trends for Collaborative Activities among Institutions Using WebCT Vista

    • S. Kajita, T. Yamazato
    • The 2nd WebCT Research Meeting, pp.9-12, Awaji Island
    • Sep. 2004

  • Maximum-Likelihood Decodings for a Chaotic UWB Radar

    • N. Dake, Y. Nishio, T. Yamazato
    • Shikoku Shibu Rengo Taikai, no.17-11, p.319, Kagawa, Japan
    • Sep. 2004
    • In this study, we propose UWB random noise radar, whose noise signal is generated by a chaotic sequence [1]. Chaos is non-periodic and could generate sequences with infinite length theoretically. Although the sequences appear like noise, the values can be predicted exactly if the dynamics and the initial value are provided. Thus, it is suitable to use a chaotic sequence for generation of noise signal than a sequence generated by a Gaussian random noise formally used for the UWB radar [2]. In this study, we focus mainly on removal of clutters by employing three ML (Maximum-Likelihood) decodings [3]. The ML algorithms are based on the characteristics of chaos and good performances are expected.

  • WebCT and Learners’ Community

    • T. Yamazato
    • Nagoya Journal of Higher Education, Vol.5, pp.49-64, Center for Higher Education Studies, Nagoya University
    • Sep. 2004

  • Application to Information Security Course

    • T. Yamazato, H. Okada, H. Nakajima, S. Kajita
    • The 2nd WebCT Research Meeting, pp.31-36, Awaji Island
    • Sep. 2004

  • A Study On Weighted Coefficient Among Routes For Error Correcting Using Multiple Routes

    • N.Nakagawa, H.Okada, T. Wada, T.Yamazato, M.Katayama
    • Communications Society Conference of IEICE，B-5-185, p. 519, Tokushima, Japan
    • Sep. 2004

  • Effect of ADC Input Amplitude on the Degradation of BER Performance in OFDM System

    • M. Sawada, H. Okada, T. Yamazato and M. Katayama
    • Communications Society Conference of IEICE，B-5-80, p. 414, Tokushima, Japan
    • Sep. 2004

  • Effect of packet discarding on multiple-route packet combining

    • Y. Hirayama, H. Okada, T. Yamazato, and M. Katayama
    • Communications Society Conference of IEICE，B-5-184, p. 518, Tokushima, Japan
    • Sep. 2004

  • Performance Analysis of UWB Impulse Radar Using Parallel IPCP Receiver

    • H. Hatano, H. Okada, T. Yamazato, M. Katayama
    • 1st International Symposium on Wireless Communication Systems, pp.115-119, Port Louis, Mauritius
    • Sep. 2004
    • UWB impulse radar has high accuracy of measurement because it uses a transmitted signal whose pulse length is below some nanosecond. In this paper, we propose two novel inter-period correlation processing (IPCP) receivers for UWB impulse radar. The conventional IPCP receiver uses the signal periodicity of signals, so it avoids estimation of unknown parameters determined by the targets and propagation. However, its accuracy of measurement is poor because the time resolution is restricted to a signal periodicity. We propose a parallel IPCP receiver to improve accuracy. When there are multiple targets, the conventional IPCP receiver needs multiple thresholds to detect. This results in complexity of the receiver. So, we propose a parallel differential IPCP receiver. We present the analysis of the outputs, and the performance of proposed receivers.

  • A Study on Error Correcting and Diversity Combiner Scheme on Multiple Routes in Wireless Multi-hop Networks

    • H. Okada, N. Koie, N. Nakagawa, T. Yamazato, M. Katayama
    • 1st International Symposium on Wireless Communication Systems, pp.183-187, Mauritius
    • Sep. 2004
    • Wireless multi-hop networks have been much attention for the possibility of flexible construction of the network topology. One of the important and interesting techniques for multi-hop networks is a multi-path routing. By using the multi-path routing, multiple routes from a source node to a destination node can be established. In this paper, we propose the error correcting and diversity combiner scheme on multiple routes in wireless multi-hop networks to reduce bit errors. The diversity combiner outputs the likelihood information from the packets transmitted via multiple routes. By feeding the likelihood information into the Viterbi decoder, the diversity gain can be obtained. We evaluate the packet error rate and the total traffic. As a result, the packet error rate can be improved. Furthermore, the total traffic can be reduced in the low Eb/N0 in spite of the traffic increase due to transmission via redundant routes.

  • The Optimum Received Signal-Power Distribution for CDMA Packet Communication Systems Employing Successive Interference Cancellation

    • Y. Tadokoro, H. Okada, T. Yamazato, M. Katayama
    • IEEE International Symposium on Spread Spectrum Techniques and Applications, pp.37-41, Sydney, Australia
    • Sep. 2004
    • In CDMA packet communication systems employing Successive Interference Cancellation(SIC) scheme, the suppression of MAI depends on the received signal-power distribution, in addition to the cross-correlation characteristic of spreading sequences and the number of transmitted packets. Some works have been done about discovering the received signal-power distribution which makes MAI be suppressed effectively. This distribution minimizes the averaged Bit Error Rate(BER). However, in packet communication systems, it is dominant to the performance if packets can be transmitted successfully or not. Even if the averaged BER is high, many packets can be correctly transmitted. It implies that the optimum distribution on averaged BER does not give the best performance of packet transmission.In this paper, the received signal-power distribution which gives the best performance of packet transmission is derived. Such a distribution will make clear the limit of performance improvement using SIC.

  • Performance Analysis of MC-CDMA System with and without Guard Interval in Two-Path Channel

    • H. Yamamoto, T. Yamazato, H. Okada, and M. Katayama
    • IEEE International Symposium on Spread Spectrum Techniques and Applications, pp.67-71, Sydney, Australia
    • Sep. 2004
    • In this paper, we analyze the performance of multi-carrier CDMA (MC-CDMA) system with and without guard interval (GI) in two-path channel. As results, we show that the BER performance of two cases are almost the same. This implies the removal of GI for the MC-CDMA system.

  • Performance analysis of multiple-route packet combining scheme for real-time communications in wireless multihop networks

    • Y. Hirayama, N. Nakagawa, H. Okada, T. Yamazato, M. Katayama
    • IEEE International Symposium on Personal, Indoor and Mobile Radio Communication (PIMRC), vol.1, pp.140-144, Barcelona, Spain
    • Sep. 2004
    • In real-time packet communications, packet retransmission is generally not used because it may produce undesired delays. In this case, however, packet errors caused by a channel may lead to a loss of transmitted information directly. Then, it is necessary to employ a technique which can reduce the influence of packet errors. We propose to employ a multiple-route packet combining scheme in real-time communications on wireless multihop networks. The scheme can achieve a diversity gain by combining multiple copies of the same packet that are transmitted along different routes. We analyze two characteristics of the proposed system. One is the average packet error probability, which is obtained as a function of elapsed time after transmission requests for copied packets are generated. The other is the required time for achieving a required packet error probability. The results are evaluated from a quality of service (QoS) point of view. From numerical results, it is shown that for a given tolerable delay, there exists a number of multiple routes that minimizes the achievable average packet error probability. Moreover, if the number of multiple routes is selected appropriately, the required time for achieving a required packet error probability can be minimized.

  • Performance Evaluation for a Diversity Decoding Scheme under Multipath Environment with OFDM

    • H. Shibata, A. Ogawa, T. Yamazato
    • Tokai-Section Joint Conference on Electrical and Related Engineering, O-267, Nagoya
    • Sep. 2004

  • A Simple Data Relay Process and Turbo Code Application to Wireless Sensor Networks

    • T. Yamazato, H. Okada, M. Katayama, A. Ogawa
    • 1st International Symposium on Wireless Communication Systems, pp.398-402, Mauritius
    • Sep. 2004
    • In this study, we focus on relay process of intermediate node of wireless sensor networks. In conventional wireless sensor networks, the intermediate node performs the regenerative repeating process such that error correction, detection and re-encoding are processed. This is reliable, but it requires a lot of processing effort and may take much energy. To reduce a burden of relay process, we propose to omit error decoding and/or re-encoding process at the intermediate nodes. Further, we propose a method that realizes soft-decision decoding for hard-detected signals. With this method, we can employ Turbo code to wireless sensor networks. As results, we show that though omitting the decoding and re-encoding process at the intermediate node may not affect much to the performance.

  • Performance of a Cooperative Diversity System with Space-Time-Coding between a Transmitter and a Receiver

    • R. Uchida, H. Okada, T. Yamazato, and M. Katayama
    • Technical Report of IEICE, vol. RCS2004-150, pp. 85-90, Sapporo, Japan
    • Aug. 2004
    • Cooperative diversity, in which radio terminals located near a source and a destination terminals help the communication by relaying the data transmitted by the source terminal, can provide spatial diversity gain against fading. In this paper, cooperative diversity with the radio terminals which have multiple antennas are considered, and space-time coding are introduced. In conventional cooperative diversity systems, space-time coding is used for the separation of the signal from relay terminals. However, these relaying schemes increase the complexity of relay terminals. In this paper, space-time coding is used for a Multiple-Input Multiple-Output (MIMO) channel between the source and the destination terminal via relay terminals. The relationships between the diversity gain and the number of antennas are analyzed, and the bit-error performance is evaluated.

  • Lecture Assistant System, WebCT

    • Takaya Yamazato
    • 2004 Daigaku Denki Kyoukan Kyougikai Kenkyu Shukai, The University of Tokushima
    • Jul. 2004

  • Assisted Highway System Using Reference Course Information and Inter-Vehicle Communications

    • D. Yamakage, T. Yamazato, H. Okada, M. Katayama
    • 4th International Workshop on ITS Telecommunications, pp.181-185, Singapore
    • Jul. 2004
    • In this paper, we propose AHS system using DGPS, RVC and IVC. And, we evaluate the system performance in simulation. From simulation results, we find that if the RVC bit error rate is about 10^-5, it is possible to accomplish the same tracking performance as the case that RVC bit error does not occur. Moreover, we confirm that when IVC packet error rate is less than 10^-3, it can be enough to achieve ideal platooning performance.

  • Proposal of UWB Impulse Radar on parallel IPCP

    • H. Hatano, T. Yamazato, H. Okada, M. Katayama
    • Technical Report of IEICE, vol.WBS2004-29, pp.17-22, Nigata, Japan
    • Jul. 2004
    • In this paper, we consider two novel inter-period correlation processing (IPCP) receivers for UWB impulse radar. The conventional IPCP receiver uses the periodicity of signals, so it avoids estimation of unknown parameters determined by the targets. However, its accuracy of measurement is poor because the time resolution is restricted to a code length. We propose a parallel IPCP receiver to improve accuracy. When there are multiple targets, the conventional IPCP receiver needs multiple thresholds to detect. This results in complexity of the receiver. So, we propose a parallel differential IPCP receiver. We present the analysis of proposed receivers.

  • Introduction on 21st COE program, Intelligent Media Integration for Social Information Infrastructure, and IEICE Technical Group on Sensor Networks

    • T. Yamazato
    • NETS: Finland-Japan Workshop on Future Networks 4th June 2004 in Oulu, Oulu, Finland
    • Jun. 2004
    • Under the 21st Century COE Program by the Ministry of Education, Culture, Sports, Science and Technology in Japan, Intelligent Media (Speech and Images) Integration for Social Information Infrastructure (IMI) seeks to form the Intelligent Media Integration (IMI) Research and Education Center to promote world-class research and educational activities. As members of IMI, (Prof. Kawaguchi and) I will talk about our COE project. Further, I will introduce the IEICE Technical Group on Sensor Networks (SN). The SN is a new technical group under Engineering Science Society (ESS), which officially will start from this June. On be half of start up members of SN, I will introduce our objective and goals of this technical committee.

  • Influence of Route Loss on Error Correcting Scheme using Multiple Routes in Wireless Multi-hop Networks

    • N. Nakagawa, H. okada, T. Wada, T. Yamazato, and M. Katayama
    • Technical Report of IEICE, vol.MoMuC2004-15, pp.11-16, Okinawa
    • May 2004
    • In this paper, we propose to transmit the coded packet using multiple routes on wireless multi-hop networks. Wireless multi-hop etworks are　consisted of wireless station which can communicate directly. Therefore, we should consider the influence of the route loss due to topological change or recognizing failure. In this paper, we propose the scheme that a packet is encoded by turbo code,scrambled, divided into N sequences and transmitted from the source node to destination node by N routes. We evaluate that the tolerance over route loss by computer simulation.

  • A Study for Wireless TCP Access with Base Station Diversity

    • K. Naito, H. Okada, T. Yamazato, M. Katayama
    • IEICE Transactions on Communications, vol.J87-B, no.4, pp.512-523
    • Apr. 2004
    • The performance of TCP degrades and it can not communicate each other in a wireless environment. In this paper, we propose a new base station diversity cellular system which evaluates the relations between wireless environments and TCP characteristics. From our result, the proposed system can improve the TCP characteristics without over consumption of wireless resource. Further, it is important to consider a cell radius from a view point of required TCP characteristics.

  • A Macro Diversity Scheme for STBC in a Shadowed Fading Channel

    • R. Uchida, H. Okada, T. Yamazato, and M. Katayama
    • IEICE General Conference, B-5-18, p.505, Tokyo, Japan
    • Mar. 2004

  • UWB Radar System Using Chaotic Signal

    • N. Dake, Y. Nishio and T.Yamazato
    • IEICE General Conference, SA-2-6, pp.S-11 - S-12, Tokyo, Japan
    • Mar. 2004

  • An Evaluation Form for Online Teaching

    • T. Yamazato, H. Nakajima, H. Okada, T. Nakai
    • Webct User Conference, pp.53-58
    • Mar. 2004

  • A study of adaptive MMSE receiver operating in the frequency domain for CDMA system

    • H. Takeuchi, T. Yamazato, H. Okada, M. Katayama
    • RISP International Workshop on Nonlinear Circuits and Signal Processing (NCSP), pp.57-60, Hawaii, USA
    • Mar. 2004
    • This paper evaluates the performance of adaptive MMSE receiver operating in the frequency-domain for(time-domain) DS-CDMA systems. As results, the frequency-domain MMSE receiver shows the robustness of multipath, noise, dynamic channe land the rate change, compared to the time-domain MMSE receiver

  • Influence of the Sampling Jitter on the Performance of a Software-Defined Receiver

    • K. Suzuki, H. Okada, T. Yamazato, and M. Katayama
    • IEICE General Conference, B-17-17, p.852, Tokyo, Japan
    • Mar. 2004

  • An Adaptive PLC Receiver with the Estimation of Instantaneous Noise Power

    • Y. Hirayama, H. Okada, T. Yamazato and M. Katayama
    • 8th International Symposium on Power-Line Communications and Its Applications, pp.116-121, Zaragoza, Spain
    • Mar. 2004
    • The noise on power-lines is non-stationary, while the instantaneous noise power in different frequency bands are dependent. Under such noise environments, the instantaneous noise power in a frequency band can be estimated by observing the noise in other frequency bands. In this paper, we propose a receiver structure which uses the estimated instantaneous noise power in the decoding process and show its superiority in BER performance to conventional systems.

  • Performance analysis of multiple-route packet combining scheme for real-time communications in wireless multihop networks

    • Y. Hirayama, N. Nakagawa, H. Okada, T. Yamazato, M. Katayama
    • Technical Report of IEICE, vol.RCS2003-335, pp.13-18, Yosuka, Japan
    • Mar. 2004
    • In real-time packet communications, packet retransmission is generally not used because it may produce undesired delays. In this case, it is necessary to employ a scheme which can reduce the influence of packet errors. We propose to employ a multiple-route packet combining scheme in wireless multihop networks. We analyze two characteristics of the proposed system. One is the average packet error probability, which is obtained as a function of elapsed time after copies of a packet are transmitted. The other is the required time for achieving a required packet error probability.

  • Performance Evaluation for a Diversity Decoding Scheme

    • H. Shibata, A. Ogawa, T. Yamazato
    • Technical Report of IEICE, vol.WBS2003-203, pp.69-74
    • Mar. 2004

  • [Invited Paper] Sensor Network

    • Akira OGAWA, Takaya YAMAZATO, Tomoaki OHTSUKI
    • Technical Report of IEICE, Tokyo, Japan
    • Mar. 2004
    • Sensor networks achieve a significant improvement over traditional sensors. This advisable feature is lead by the development of low-cost, low-power, multifunctional sensor nodes that are small in size and capable of wireless communication in short distance. In this presentation, introduction of sensor networks are presented.

  • Performance evaluation for a diversity decoding scheme under multipath environment with OFDM

    • H. Shibata, A. Ogawa, T. Yamazato
    • RISP International Workshop on Nonlinear Circuits and Signal Processing (NCSP), pp.25-28, Honolulu, USA
    • Mar. 2004
    • This paper is concerned with the performance evaluation for the diversity decoding scheme in which space diversity technique and iterative decoding for non systematic convolutional error-correcting code are effectively combined. The concept of the diversity decoding is applied to an OFDM system (e.g. the digital terrestrial TV broadcasting system). This paper shows the performance evaluation for the diversity decoding scheme under multipath environment with OFDM.

  • A Study of the Latency Reduction and the Mitigation of Quality Degradation in Mobile Communication Systems

    • M. Honjo, T. Yamazato, T. Wada, H. Okada, M. Katayama, and A. Ogawa
    • Technical Report of IEICE, vol.CS2003-177, pp.111-116
    • Mar. 2004

  • Introduction of e-Learning activity at Nagoya University

    • T. Yamazato
    • Opinion exchange meeting on Educational improvement using information technology, Matsumoto, Japan
    • Feb. 2004

  • SNIR Analysis of Multi-Carrier CDMA System with and without GI in Two-Path Channel

    • H. Yamamoto, T. Yamazato, H. Okada, M. Katayama
    • Symposium on Information Theory and Its Applications (SITA), vol.2, pp.429-432
    • Dec. 2003
    • In this paper, we analyze the performance of the multi-carrier CDMA (MC-CDMA) system with and without guard interval (GI) in two-path channel. As results, we show that the BER performance of two cases are almost the same. This implies the removal of GI for the MC-CDMA system.

  • SNIR Analysis of Asynchronous MC-CDMA System in Frequency Selective Fading Channel

    • H. Takeuchi, T. Yamazato, H. Okada and M. Katayama
    • IEICE Transactions on Fundamentals vol.J86-A, no.12, pp.1426-1430
    • Dec. 2003
    • This paper presents the signal to noise plus interference ratio(SNIR) analysis of the asynchronous Multicarrier (MC)-CDMA system with multipath fading channel. We derive the SNIR of the MC-CDMA system and compared with that of the DS-CDMA. We found that the SNIR of the MC-CDMA is equal to that of the band-limited DS-CDMA system under the same bandwidth and the same spreading factor.

  • [Invited Talk] Ubiquitous Era

    • T. Yamazato
    • The Institute of Electrical Engineers of Japan, Tokai Section., Nagoya, Japan
    • Nov. 2003
    • This seminar breifly introduces a ubiquitous computing and its effect to our every day life.

  • Performance of MC-CDMA on two path AWGN channel

    • H. Yamamoto, T. Yamazato, H. Okada, and M. Katayama
    • Tokai-Section Joint Conference on Electrical and Related Engineering, 379, p.190
    • Oct. 2003

  • Range-finding performance using UWB impulse radar with multi-IPCP

    • H. Hatano,T. Yamazato,H.Okada, and M. Katayama
    • Tokai-Section Joint Conference on Electrical and Related Engineering, 392, p.196
    • Oct. 2003
    • In this paper,we propose the Range-finding performance using UWB impulse radar with multi-IPCP.

  • The Optimum Received Signal-Power Distribution for CDMA Packet Communication Systems Employing Successive Interference Cancellation

    • Y.Tadokoro, H.Okada, T.Yamazato, and M.Katayama
    • Technical Report of IEICE, vol.WBS2003-72, pp.37-42, Shimonoseki, Japan
    • Oct. 2003
    • In CDMA packet communication systems employing Successive Interference Cancellation scheme, the reduction of MAI depends on the received signal-power distribution, in addition to the cross-correlation characteristic of spreading sequences and the number of transmitted packets.Many works have been done about the received signal-power distribution which makes MAI be suppressed effectively. The distribution minimizes Bit Error Rate(BER), but could not maximize throughput. In this paper, the received signal-power distribution which maximizes the throughput is derived. Such a distribution may be obtained by applying an access control scheme to the optimum received signal-power distribution on BER performance.

  • A Study on Handover and Channel Allocation Scheme with Cost Function in Low Earth-Orbital Satellite Systems

    • K.Nisihara, H.Okada,T. Yamazato, and M. Katayama
    • Technical Report of IEICE, vol.SAT2003-122, pp.95-100, Tokyo,Japan
    • Oct. 2003
    • To increase the channel efficiency, most of the Low Earth-Orbital satellites (LEOs) systems use the multibeam antenna and reuse the available channels. But in such systems, a beam handover occurs very frequently and a dropping probability becomes very high compared with the one beam systems. In this paper, we propose the nondropping handover and channel allocation scheme in the above LEOs systems. In the proposed scheme, we allocate an extra idle channel for a new call. Because of the predictable change of channel reuse distances, each user can always use the same channel as before. Furthermore, we propose some cost functions used by channel selection and channel reassignment. For comparison, we show the lower bound of blocking probability by maximal complete dependent set (MCDS). We confirm that the proposed channel selection scheme improves the system performance by computer simulation.

  • The Receiver for Power-Line Communication Systems with the Estimation of Instantaneous Noise Level

    • Y. Hirayama, H. Okada, T. Yamazato and M. Katayama
    • Technical Report of IEICE, vol.WBS2003-67, pp.7-12, Shimonoseki, Japan
    • Oct. 2003
    • The noise on power-lines is mainly caused by electric appliances connected to the lines, and its statistical behavior is quite different from that of stationary white Gaussian noise. For an example, the noise on power-lines has wide-sense cyclo-stationary features with the period of a half cycle of the power supplying AC voltage. In this manuscript, it is shown that the instantaneous power of noise of different frequency bands are dependent to each other. By using this dependency, the instantaneous power of noise in a communication band can be estimated from that of the noise in other frequency band. Then, we propose the receiver which uses this estimated instantaneous power in the decoding process and show its performance.

  • Reducing Peak Power of Coded OFDM Systems with Multiple Symbol Mapping

    • M. Harada, T. Yamazato, H. Okada, M. Katayama, and A. Ogawa
    • IEICE Transactions on Fundamentals, vol.J86-A, no.10, pp.1058-1067
    • Oct. 2003
    • In this paper, we propose a novel coding scheme to reduce a peak envelope power (PEP) of convolutionally coded orthogonal frequency devision multiplex (OFDM) signals. In this system, convolutionally coded bits are mapped into symbol sequence. The symbol sequence have multiple symbols which are adjusted so as to show low PEP. Also, applying a set partition to the symbol sequence enable to enlarge an Euclidean distance between each sequence. We evaluate the performance of proposed system under the effect of nonlinear amplifier.

  • Handbook for Effective Online Teaching

    • H. Nakajima, T. Yamazato, H. Okada, T. Nakai
    • The 1st WebCT Research Conference, pp.47-52, Fukuoka
    • Sep. 2003
    • This paper reports on the development of the teaching handbook for online course. The proposition we have made of the handbook includes a greater emphasis on these aspects: Write clear objectives, Promote active learning, Promote communication between teachers and students, Respect for diversity among students and Develop skills of teaching materials.

  • Temporal Characteristics of an Error Correcting Method using Multi-path in Wireless Multihop Networks

    • Y. Hirayama, N. Nakagawa, H. Okada, T. Yamazato, and M. Katayama
    • Communications Society Conference of IEICE, B-5-121, p.498, Niigata, Japan
    • Sep. 2003

  • A Study for TCP Performance Improvement with a Congestion Window Size Estimation in a Wireless Environment

    • K. Naito, H. Okada, T. Yamazato, M. Katayama
    • Communications Society Conference of IEICE, B-5-131, p.508, Niigata
    • Sep. 2003

  • An Error Correcting Method Using Multi-path in Wireless Multihop Networks

    • N. Nakgawa, N. Koie, H. Okada, T. Yamazato, and M. Katayama
    • Communications Society Conference of IEICE, B-5-119, p.496, Niigata, Japan
    • Sep. 2003

  • e-Learning Handbook -Smart Teaching Materials Created in Steps

    • T. Nakai, T. Yamazato, H. Nakajima, H. Okada
    • Mana House
    • Jul. 2003

  • A Study for Wireless Internet Access using TCP with a Base Station Diversity System

    • K. Naito, H. Okada, T. Yamazato, M. Katayama
    • Technical Report of IEICE, vol.RCS2003-95, pp.31-36, Toyohashi
    • Jul. 2003
    • The characteristic of TCP is degraded and communications can be hardly achieved when TCP is used to access to Internet in wireless environment. In this paper, we propose the novel system of a base station diversity. In this system, the relation between TCP characteristics and wireless environment is evaluated, and the number of connections to base stations is controlled. From our result, the proposed system can improve the TCP characteristics without the over consumption of the wireless resource.

  • Assisted Highway System by Broadcasting the Information of Course Prediction

    • D. Yamakage, T. Yamazato, H. Okada, M. Katayama
    • Technical Report of IEICE, vol.ITS2003-10, pp.5-10
    • Jul. 2003
    • In this paper we propose an automated highway system using a broadcasted map information. In this system a road-to-vehicle base station transmits the map information to a car. The car side computer estimates its future position using both the present car position obtained by DGPS and map information. And it decides the steering angle to track the reference course from that estimate. The performances of this system are evaluated in terms of the tracking accuracy and the stability under the conditions that the reference cource is straight or curve. As result , we discuss how the precision of DGPS and the error probability of broadcasted informations affect the system performances.

  • A study of adaptive MMSE receivers in frequency domain for DS-CDMA

    • H.takeuchi, T.yamazato, H.okada and M.katayama
    • Technical Report of IEICE, vol.WBS2003-23, pp.5-8, Naha，Japan
    • Jun. 2003
    • In this paper, we consider the DS-CDMA system and the OFDM system is operated in the same area. And, FFT is used to transmit and receive for OFDM system. We consider an adaptive MMSE receivers using FFT for DS-CDMA system. This receiver performs better than the conventional receiver not using FFT. Furthermore, we show this method can be used for multicarrier(MC)-CDMA system, result in good performance.

  • Influence of Jitter of Sampling Clock on the Performance of a Wideband Software-Defined Radio Base Station

    • K. Suzuki, H. Okada, T. Yamazato, and M. Katayama
    • Technical Report of IEICE vol.SR03-7,pp.55-59, Kusatsu
    • Jun. 2003
    • One of the most important components in software-defined receiver is an Analog-to-Digital Converter(ADC). The quantization error in amplitude domain and the jitter of sampling clock in time domain are impotant features of the ADC. When the bandpass sampling is performed in a software-defined receiver which is used for wide-band systems, such as base stations of cellular systems, the sampling jitter may dominate the performance. Thus this manuscript discusses the influence of the sampling jitter to bit error rate performance in wide-band software-defined receiver which receives and demodulates multiple signals at the same time.

  • Space-Frequency Block Codes for Power Line Communication Systems with Mutual Coupling between Wires

    • H. Furukawa, H. Okada, T. Yamazato, M. Katayama
    • Technical Report of IEICE, vol.WBS2003-29, pp.29-32, Naha
    • Jun. 2003
    • In Japan the pair of in-house 100V power-line consists of the grounded wire and one of hot wires of the single phase three-wire type power-line from a distribution transformer. In this configuration, the two pairs of in-house power-line sharing the same ground-wire have mutual coupling to each other in radio frequency. Under this condition, this manuscript proposes the employment of Space-Frequency Block Codes for communication between a transmitter connected to all of the three wires and a receiver connected to more than one pair of wires. The performance improvement by the proposed method is confirmed by numerical examples.

  • Performance Improvement for Coded OFDM Systems with Adaptive Interleaving in Frequency Selective Fading Channel

    • M. Harada, T. Yamazato, H. Okada, M. Katayama, A. Ogawa
    • IEICE Transactions on Fundamentals, vol.E86-A, no.6, pp.1541-1549
    • Jun. 2003
    • In an attempt to improve the performance under frequency selective fading environment, we develope in this paper an orthogonal frequency division multiplex (OFDM) system in which adaptive interleaving is applied. The adaptive interleaving is a method that assigns symbols adaptively to the subcarriers in order to cope with frequency selective fading based on a channel state information (CSI) sent back from the reception end. The concept of adaptive interleaving is to maximize a free Euclidean distance in the limited interleave size. In this paper, we extend the method by an introduction of bit interleaving and multiple trellis coded modulation (MTCM). MTCM assigns two or more symbols to one trellis branch and shows good performance in frequency selective fading. If we could assign those set of symbols with an aid of the adaptive interleaving, the performance improvement can be expected. Another improvement method considered in this paper is the use of bit interleaving. The bit interleaving techniques randomize the effect of channel more efficiently compared to the case of symbols interleaving. Thus the further performance improvement is expected. One draw back is that since the interleaving process is done in bit level, bit interleaving can not be applied to TCM nor MTCM. In this paper, we mainly focus on adaptive bit and symbol interleaving and discuss the performance from the point of interleaving effect, and the error correcting code (convolutional code and MTCM).

  • Examples of Contents for Common Education

    • H. Okada, T. Egawa, T. Yamazato
    • Japan WebCT User Conference, Nagoya
    • Mar. 2003
    • In this presentation, we introduce course contents for common education. One is “The Basics of Computer Theory”, which is opened for humanity and science students. This content is made according to the advice from Center for the Studies of Higher Education. The other is “From Bigbang to Today.” It is a simple content making use of video on demand.

  • A study on linear filtering in frequency domain for DS-CDMA systems

    • H.Takeuchi, T.Yamazato, H.Okada, and M.Katayama
    • IEICE General Conference, A-5-1, p.154, Sendai,Japan
    • Mar. 2003

  • Signaling methods for broadcast transmission in power-line communication systems

    • H. Furukawa, H. Okada, T. Yamazato, M. Katayama
    • 7th International Symposium on Power Line Communications and Its Applications,pp.185-190, Kyoto,Japan
    • Mar. 2003
    • This manuscript discusses on the signaling method for inhouse power-line communication(PLC) system with server-client model. The power-lines considered are three-wire type, and the transmitter of the server is on all of the three wires, while each client receiver of clients is on a pair of power-lines. Because of the mutual coupling between wires, the communication between the transmitter and a receiver is as on two mutually connected channels. Thus transmit diversity technique is introduced to the PLC broad cast system, and the performance of the system with three types of coding schemes for transmit diversity technique is compared by numerical examples.

  • Noise analysis on wide-band PLC with high sampling rate and long observation time

    • Y. Hirayama, H. Okada, T. Yamazato and M. Katayama
    • 7th International Symposium on Power-Line Communications and Its Applications, pp.142-147, Kyoto, Japan
    • Mar. 2003
    • This manuscript reports the results of the measurement of wide-band PLC noise with high speed (50MHz) sampling and long (10.4s) observation duration. The measured noise is divided in frequency, and stochastic properties of the noise waveforms in each frequency bands, such as autocorrelations, probability density functions, and correlation coefficients between noise waveforms of different frequency bands are discussed. Cyclostationary features of the noise in each band is confirmed. It is found that the amplitude distribution in each band is different, and that Gaussian noise model is not a good approximation in higher frequency bands.

  • A Study on Turbo Soft-Decision Decoding for Hard Detected Optical Communication Signals

    • C. Zheng, T. Yamazato, H. Okada, M. Katayama, A. Ogawa
    • IEICE Transactions on Communications, vol.E86-B, no.3, pp.1022-1030
    • Mar. 2003
    • We propose a method to realize soft-decision decoding for hard-detected signals. In this paper, a novel concept is introduced as error-detected reliability. The method is very useful for optical fiber communications (OFC) as hard detection is the only detection method for the OFC systems. We demonstrate our proposed method using the turbo code in which soft information is required for decoding. As a result, the simulation shows slight difference in the range of moderate to high signal-to-noise ratio between the proposed decoding scheme and the conventional turbo decoding scheme. Moreover, the bit error rate of 10-11 can be achieved by serial concatenation of a Reed-Solomon code and a turbo code for Q-factor lower than 8.0 dB with a bandwidth expansion ratio of 33.3%.

  • Soft-Decision Decoding of Low-Density Parity-Check Codes for Hard-Detected Optical Communication Signals

    • C. Zheng, T. Yamazato, H. Okada, M. Katayama, A. Ogawa
    • IEICE Transactions on Communications, vol.E86-B, no.3, pp.1132-1135
    • Mar. 2003
    • A soft-decision decoding scheme of low-density parity-check codes (LDPC) is proposed for hard-detected signals of optical fiber communication (OFC) systems. Based on the error detection, the proposed scheme converts the received hard-decision into soft reliability for the input of the LDPC decoder, and soft-decision decoding is performed. Simulation results under OFC channels are shown and superior performance is obtained by using the proposed decoding scheme of the LDPC codes.

  • Comparison of Multiple Access Schemes in Multibeam Non-GEO Satellite Communication Systems

    • N. Ichikawa, M. Katayama, H. Okada, T. Yamazato, A. Ogawa
    • IEICE Transactions on Communications, vol.E86-B, no.2, pp.785-791
    • Feb. 2003
    • This paper describes an analytical method to estimate the amount of interference in multibeam non-geostationary satellite systems. The performance of CDMA is compared with that of FDMA (or TDMA) by employing the maximum acceptable number of users per cell in uplink as a measure. Numerical examples shows that the maximum acceptable number of users in FDMA (or TDMA) systems varies according to the altitude of the satellites, while the performance is insensitive to the altitude in CDMA systems. Then, it is found that the superior multiple access scheme depends on the altitude of the satellite.

  • Performance Analysis of CDMA Unslotted ALOHA System Employing Successive Interference Cancellation

    • Y. Tadokoro, H. Okada, T. Yamazato, M. Katayama, A. Ogawa
    • IEICE Transactions on Fundamentals, vol.J86-A, no.2, pp.168-178
    • Feb. 2003
    • In a CDMA Unslotted ALOHA system, multiple access interference(MAI) has a great influence on the system performance. The unequalness of signals\' power (e.x. Rayleigh fading) makes the influence more serious. The MAI may be suppressed by using interference cancellation technique. Such a technique has been considered in the system in which signals are transmitted continuously. In addition, the performance is evaluated by bit error rate. However, in a packet system, the performance depends on whether packets are successfully transmitted or not. In this paper, to suppress the MAI, CDMA Unslotted ALOHA system employing successive interference cancellation is proposed. The throughput performance of the proposed system is analyzed and evaluated. As the result, the performance is improved, and the performance under Rayleigh fading is better than that in the case of equal signals\' power.

  • {The measurement of indoor propagation channel and dependece charactarictcs of frequency, time, and physical space for space-time coding technic

    • Y. Kubo, H. Okada, T. Yamazato, and M. Katayama
    • Technical Report of IEICE vol.AP2002-136, pp.13-17, Kumamoto, Japan
    • Jan. 2003
    • For high reliablity of radio systems, employment of space-time coding is effective. There are, however, few reports on the measurement of indoor propagation, which can be used for considerations of space-time coding. In this manuscript, we report the measurement results of indoor propagation for the employment of space-time coding and discuss the characteristics of indoor propagation, especially the dependence on frequency, time, and physical space and the correlation characteristics about propagation loss.

  • A study on statistical characteristic of bit-error rate with transmitter diversity in fading channels

    • R. Uchida, H. Okada, T. Yamazato, and M. Katayama
    • Symposium on Information Theory and Its Applications (SITA), vol.1, pp.319-322, Ikaho, Gunma, Japan
    • Dec. 2002
    • In this paper, we analize a characteristic of wireless communication system from a viewpoint of probability distribution of bit-error rate (BER) for aiming to guarantee the reliability of wireless communication systems. A single transmission space diversity (time space repetitional coding) with M transmit antennas through independent slow Rayleigh fading channels is considered. The influence of combining method of the receiver, and the number of transmit antennas, to the BER distribution is clarified.

  • Medium Access Control Protocol Based on Estimation of Multimedia Traffic with an Adaptive Algorithm in CDMA Packet Communications

    • Y. Hirayama, H. Okada, T. Yamazato, and M. Katayama
    • IEICE Transactions on Fundamentals, vol.E85-A, no.12, pp.2868-2876
    • Dec. 2002
    • In this paper, we propose a medium access control (MAC) protocol for multimedia code division multiple access (CDMA) communications. In the proposed protocol, a base station (BS) estimates the instantaneous number of simultaneously transmitted packets in the future slots with exploiting a stochastic property of traffic. In order to carry out this estimation, we employ an adaptive algorithm. We evaluate the performance of the proposed protocol by comparing that with two different cases. One is no estimation case and the other is perfect estimation case. From these results, we clarify the advantage of the proposed MAC protocol.

  • Performance Improvement of OFDM System with Consideration on the Characteristics of Power-Line Noise

    • K. Sugimoto, H. Okada, T. Yamazato, M. Katayama
    • IEICE Transactions on Fundamentals, vol.E85-A, no.12 pp.2822-2829
    • Dec. 2002
    • In narrow band power-line communication (PLC) systems, which use frequency band below a few hundred kHz, the noise on power-line is non-white and non-stationary. Under such environment, the performance of Orthogonal Frequency Division Multiplex (OFDM) modulation system is analyzed, and time and frequency dependence of bit error rate (BER) is clarified. In addition, the possibility of performance improvement with the symbol level repetition coding employing cyclo-stationary feature of power-line noise is presented.

  • A Study on the Application of Error Concealment Technique to Real-Time Parallel Video Decoder

    • M. Honjo, T. Yamazato, H. Okada, M. Katayama, A. Ogawa
    • IEICE Transactions on Fundamentals, vol.J85-A, no.12, pp.1463-1468
    • Dec. 2002
    • As high error resilience and low delay decoding technique, RT-PVD (real-time parallel video decoder) has been proposed[1]. In this paper, we consider the performance of the RT-PVD in which error concealment (EC) technique is included. Ordinary, even if the EC was applied, secondary error propagation would be eventually caused. But in the RT-PVD, the random block noise was replaced by appropriate block of the reference frame sequence. So we could establish high PSNR gain and good perceptual quality without error propagation.

  • Calculation of Mobile Location using a Statistical Scatterer

    • N. J. Thomas, H. Okada, T. Yamazato, M. Katayama
    • Technical Report of IEICE, SST2002-34, pp.45-50, Akiho
    • Oct. 2002
    • A statistical technique to calculate the location of a signal source, e.g. a mobile phone, in a multipath, non--line of sight environment, is proposed. The technique relies on angular spread and relative time of arrival measurements of multipath signals received at a base station antenna array. The source location is estimated using an a priori known statistical model for the distribution of single bounce multipath scatterers around the signal source, and fitting the measured channel impulse response received at the base station to this model. Further improvement in location estimation accuracy is demonstrated using the Kalman filter, or time average filter on the time sequence of location estimates in a moving scenario.

  • Spread Sequence for Multicarrier CDMA under the Effect of Nonlinear Amplifier

    • M. Harada, T. Yamazato, H. Okada, and M. Katayama
    • International Symposium on Information Theory and Its Applications (ISITA), pp.435-438, Xi'an
    • Oct. 2002
    • In this paper, we propose a spread sequence for asynchronous multicarrier code division multiple access (MC-CDMA). In MC-CDMA systems, performance degradation is mainly caused by nonlinear distortion due to high power amplifier (HPA) and multi-user interference. Since the peak envelope power (PEP) of multicarrier signals show large value, it is desirable to reduce the PEP as well as the multiuser interference components. The sequence, we propose, is based on the Hadamard and complementary sequence. Both of sequences are generated by similar procedures. To evaluate the performance of MC-CDMA system applying proposed sequence, we simulate the system under the effect of nonlinear amplifier.

  • Performance Evaluation of a Diversity Decoding Scheme for Punctured Convolutional Code

    • M. Ito, A. Ogawa, T. Yamazato
    • International Symposium on Information Theory and Its Applications (ISITA), pp.183-186, Xian, China
    • Oct. 2002
    • This paper discusses a scheme in which space diversity technique and iterative decoding for non systematic convolutional error-correcting code are effectively combined. Simulation results of the bit-error-rate performance of this scheme with respect to the punctured convolutional codes under AWGN and Rayleigh fading environment are presented.

  • A Proposal of OFDM Synchronization Scheme with Subtraction Operation

    • T. Shibata, N. Itoh, M. Fujimoto, N. Suzuki, A. Ogawa, T. Yamazato
    • International Symposium on Information Theory and Its Applications (ISITA), pp.539-542, Xian, China
    • Oct. 2002
    • In this paper, a novel symbol synchronization scheme for OFDM signals is propsed. The scheme is based on the subtraction operation for the purpose of achieving reliable synchronization and frequence offset detection capabilities with a simple implementation.

  • Decoding of low-density parity-check codes for hard-detected optical fiber communication signals

    • C. Zheng, T. Yamazato, H. Okada, M. Katayama, A. Ogawa
    • International Symposium on Information Theory and Its Applications (ISITA), pp.331-334, Xi'an, China
    • Oct. 2002
    • A soft-decision decoding scheme of low-density parity-check codes (LDPC) is proposed for hard-detected signals of optical fiber communication (OFC) systems. The scheme converts the received hard-decision into soft reliability for the input of the LDPC decoder, and soft-decision decoding is performed. Simulation results under OFC channels are shown and superior performance is obtained by using the proposed decoding scheme of the LDPC codes.

  • BER Performance of Asynchronous Multicarrier-CDMA System and Asynchronous DS-CDMA System in Frequency Selective Fading

    • H. Takeuchi, T. Yamazato, H. Okada, and M. Katayama
    • 7th International-OFDM Workshop 2002, PP.26-30, Hamburk, Germany
    • Sep. 2002

  • Reduced Peak Power Transmission for Convolutionally Coded OFDM Signals

    • M. Harada, T. Yamazato, H. Okada, and M. Katayama
    • 7th International-OFDM Workshop 2002, pp.102-106, Hamburk, Germany
    • Sep. 2002
    • In this paper, we propose a novel coding scheme to reduce a peak envelope power of convolutionally coded orthogonal frequency devision multiplexing (OFDM) signals. In this system, convolutionally coded bits are mapped onto symbol sequence. The symbol sequence have multiple symbols which are adjusted so as to show low peak envelope power. Also, applying a set partition to the symbol sequence enable to enlarge an Euclidean distance between each sequence. We evaluate the performance of proposed system under the effect of nonlinear amplifier.

  • Effect of Interleaving and FEC on the Throughput of CDMA Unslotted ALOHA System with Adaptive Multiuser Receiver

    • H. Okada, T. Yamazato, M. Katayama
    • IEEE International Symposium on Personal, Indoor and Mobile Radio Communication (PIMRC), vol.2, pp.941-945, Lisbon, Portugal
    • Sep. 2002
    • A CDMA unslotted ALOHA system is a connectionless-type of CDMA packet communication system. In this system, a user station can transmit a packet asynchronously and randomly, and so the packet birth/death event is one of the most important problems for multiuser detection. We have proposed the CDMA unslotted ALOHA system using an adaptive filter receiver based on minimum mean square error criterion in [8], and shown the improvement in the throughput performance even considering the effect of birth/death event. The ensemble-averaged squared error, however, increases at the point of packet birth. In this paper, we employ interleaving and forward error correction (FEC) coding techniques to mitigate the momentary increase in ensemble-averaged squared error. The use of FEC, however, causes the increase in MAI due to redundancy bits of FEC. Moreover, signal power is reduced under the condition that the energy of an information bit is the same. In such cases, whether an adaptive filter can operate effectively or not interests us. We evaluate the system performance and show that the improvement in throughput is achieved with interleaving and FEC techniques.

  • An access control protocol based on estimation of multimedia traffic with an adaptive algorithm in CDMA packet network

    • Y. Hirayama, H. Okada, T. Yamazato, M. Katayama
    • IEEE International Symposium on Personal, Indoor and Mobile Radio Communication (PIMRC), vol.2, pp.619-623, Lisboa, Portugal
    • Sep. 2002
    • In multimedia wireless communications, various types of traffic are handled. Generally, each of these traffic has a different stochastic property. An access control protocol for multimedia wireless communications, therefore, are required to adopt a stochastic property of multimedia traffic. Conventional access control protocols, however, do not consider such characteristics of multimedia traffic. In this paper, we propose an access control protocol for multimedia CDMA packet communications. The proposed protocol controls the data packet transmissions based on the estimation of the instantaneous number of simultaneously transmitted voice and video packets. This estimation exploits the stochastic property of multimedia traffic. To carry out such estimation, we employ an adaptive algorithm as an estimation method. We evaluate the performance of the proposed protocol by comparing it with the performance in the case where a stochastic property of traffic is not considered.

  • A Proposal of OFDM Synchronization Scheme with Subtraction Operation

    • T. Shibata, N. Itoh, M. Fujimoto, N. Suzuki, A. Ogawa, T. Yamazato, M. Harada
    • 7th International-OFDM Workshop 2002, pp.237-240, Hamburk, Germany
    • Sep. 2002

  • Power Line Communication Systems

    • M. Katayama [supervisor] (M. Katayama, S. Tsuzuki, K. Yamazato, et al.)
    • Trikeps
    • Jul. 2002

  • New Analytical Model for TCP in wireless Environments

    • K. Naito, H. Okada, M. Saito, T. Yamazato, and M. Katayama
    • IEICE Transactions on Fundamentals, vol.E85-A, no.7, pp.1501-1510
    • Jul. 2002
    • We propose a new analytical model of Transmission Control Protocol (TCP) in wireless environments where transmission errors occur frequently. In our proposed model, we consider the exponential increase of a congestion window and the exponential increase of a timeout back-off. Finally, we have clarified the behavior of TCP mechanisms of different versions and TCP throughput characteristics analytically. From our result, the behavior of TCP mechanisms is different in each implementation version. These differences mean that the required characteristics of wireless links are different in each implementation version. Therefore, our proposed model is a base analysis of designing wireless link mechanisms.

  • An Access Control Protocol Based on Estimation of Traffic with an Adaptive Algorithm in Multimedia CDMA Packet Communications

    • Y. Hirayama, H. Okada, T. Yamazato, and M. Katayama
    • Technical Report of IEICE, vol.102, no.204, RCS2002-99, pp.55-60, Hokkaido, Japan
    • Jul. 2002
    • In a multimedia communication, various types of traffic are handled. Generally, each traffic in a multimedia communication has a different stochastic property. Conventional access control protocols do not consider such characteristics of multimedia traffic. We propose a new access control protocol for multimedia CDMA packet communications in which stochastic properties of multimedia traffic is considers. The proposed protocol controls packet transmissions based on estimation of the instantaneous number of simultaneously transmitted packets. This estimation is carried out by an adaptive algorithm. Simulation results show the advantage of the proposed protocol over the protocol which does not estimate the number of simultaneously transmitted packets.

  • Statistical Noise Characterization for Wide Band Power Line

    • Y. HIRAYAMA, H. OKADA, T. YAMAZATO, and M. KATAYAMA
    • Technical Report of IEICE, vol.SST2002-13, pp.7-12, Nigata, Japan
    • Jul. 2002
    • The wide band power-line communication system (PLC) has been drawing much attention as an alternative communication system. To realize reliable high-speed data transmissions, it is essential to understand the noise feature on the power-line. Noise characteristics of the narrow band PLC have been discussed in previous papers, however, there is few report on the wide band PLC noise. In this paper, we prepare a noise measurement system and discuss on the measured noise characteristics in wide band. As a result, we show that the noise characteristics differ greatly dependents on frequency.

  • Transmitting/Receiving Diversity Method using Single-phase Three-wire Power-Line for Power-Line Communication

    • H. Furukawa, H. Okada, T. Yamazato, M. Katayama
    • Technical Report of IEICE, vol.SST2002-14, pp.13-17, Nagaoka, Japan
    • Jul. 2002
    • The low voltage distribution power-lines from the distribution transformer to the fuse box are single-phase and three-wire type and the In-house power-lines are single-phase and two-wire type in Japan. The two-wire type power-lines are constructed of a pair of wires of the three-wire type power-lines. And the two-wire type power-lines are used as 200V or 100V AC. Under this condition, there is mutual coupling between different pair of power-lines. Therefore it is possible to improve performance of the power-line for communication by using the Space-Frequency Coding when the transmitter or receiver is on at least two pairs of power-lines. In this paper, the transmitting/receiving diversity method using the Space-Frequency Code for Power-Line communication is proposed and the effectiveness of this method has been confirmed by experiments.

  • Turbo Decoding for Hard-Detected Signals of Fiber Optical Communications

    • C. Zheng, T. Yamazato, H. Okada, M. Katayama, and A. Ogawa
    • IASTED Wireless and Optical Communications 2002 (WOC 2002) Conference, Banff, Canada
    • Jul. 2002
    • We propose a method to realize the soft-decision decoding for the hard-detected signals. In this paper, a novel concept is introduced as error-detected reliability. The method is very useful for fiber optical communication systems as hard detection is the only detection method for the systems. We demonstrate our proposed method using the turbo code in which the soft information is required for the decoding. As a result, the simulation shows slight difference in the range of moderate to high signal-to-noise ratio between the proposed decoding scheme and the conventional turbo decoding. Moreover,the bit error rate of 10^-11 can be achieved by serial concatenation of Reed-Solomon and turbo code for Q-factor lower than 8.0 dB with the bandwidth expansion ratio of 33.3%.

  • A Study on Handover and Channel Allocation Scheme using Linear Shift Property of the Servicearea in Low Earth-Orbital Satellite

    • K.Nisihara, H.Okada, T.Yamazato, and M.Katayama
    • Technical Report of IEICE, vol.102, no.144,pp.15-18, Nagoya, Japan
    • Jun. 2002
    • In this paper, we discuss the handover and channel allocation scheme for cellular systems of Low Earth-Orbital (LEO) satellite. By using the linear sift property of LEO satellite, we propose the handover scheme in which a user use the same channel even if a handover occurs. Furthermore, we propose the dynamic channel allocation scheme taking account of the centralized cellular system of LEO Satellite. In this scheme, a channel is assigned according to the objective function which is calculated by user and channel distribution. From comparison of numerical results, we show that the proposed scheme can improve the blocking probability.

  • A study on SOVA based Turbo-decoding with threshold

    • M. Matsui, T. Yamazato, M. Katayama, A. Ogawa
    • IEICE Transactions on Fundamentals, vol.J85-A, no.5, pp.606-609
    • May 2002
    • In this paper, we propose a new SOVA based Turbo-decoding scheme which applys a variable threshold to the output of each of the component decoder. The value of the threshold is determined accoding to the distribution of the observed output of each of the component decoder. We show that our proposed scheme gives the better BER performance than conventional one.

  • Performance Evaluation of PredictionError Based MAP Receiver for DCT Compressed Image Transmission

    • S. Makido, M. Honjo, T. Yamazato, H. OKada, M. Katayama, A. Ogawa
    • The Journal of the Institute of Television Engineers of Japan, vol.56, no.5, pp.842-845
    • May 2002

  • Potentiality of Campus Portal

    • T. Yamazato, S. Kajita, H. Okada
    • IEICE General Conference, KD-1-2, pp.257-258, Tokyo, Japan
    • Mar. 2002

  • BER Performance Analysis of Multicarrier-CDMA Systems in Multipath Fading Channel

    • H.takeuchi, T.yamazato, H.okada and M.katayama
    • Technical Report of IEICE, vol.SST2001-171, pp.13-18, Ibaragi, Japan
    • Mar. 2002
    • This paper presents the BER analysis of the asynchronous Multicarrier (MC)-CDMA system in multipath fading channel. We derive the BER of the MC-CDMA and compared with that of the DS-CDMA. We found that the BER of the MC-CDMA is a little worse than that of the band-limited DS-CDMA under the same bandwidth and the same spreading factor, and when the number of multipath is infinity, the BER of both systems are regarded as being that for the case without fading channel. However, if the number of multipath is more than the number of finger of Rake receiver, the MC-CDMA system can perform better than the DS-CDMA system.

  • CDMA Packet Recognition and Signal Acquisition using LMS-based Adaptive Receiver

    • T. Kume, T. Yamazato, K. Ban, H. Okada, and M. Katayama
    • IEEE Wireless Communications and Networking Conference (WCNC), vol.1, pp.379-383, Orlando, USA
    • Mar. 2002
    • In this paper, we propose a new packet recognition and signal acquisition scheme with an adaptive linear filter based on an Least Mean Square (LMS) algorithm for code-division multiple access (CDMA) packet systems. In CDMA systems, conventional receivers with matched filtering suffer from the near-far problem due to multiple access interference (MAI). In general, closed-loop power control is used in order to reduce the influence of the near-far problem. However, closed-loop power control is unsuitable for packet systems. Hence, in order to eliminate the influences of the near-far problem, we focus on an adaptive receiver based on an LMS algorithm for a packet recognition and signal acquisition in CDMA packet systems.

  • Effect of Nonlinear Amplifiers of Transmitters in Multicarrier CDMA Systems

    • H. Muramatsu, M. Harada, T. Yamazato, H. Okada, M. Katayama
    • IEICE Transactions on Fundamentals, vol.J85-A, no.3, pp.340-348
    • Mar. 2002
    • In this paper, we compare Multicarrier(MC-) CDMA systems with DS-CDMA systems in the asynchronous uplink channel. First, we analysis signal to noise inteference ratio (SNIR) of asynchronous MC-CDMA systmes in AWGN channel, in order to show the basic performance of MC-CDMA systems. Then, we discuss the effect of nonlinear amplifiers of trnasmitters in MC-CDMA systems, which are usually required using in the mobile terminals for the uplink. We evaluate bit error rate preformance taking account of out-of-band emission.

  • A study on Iterative Decoding and Diversity Scheme for Correlated Rayleigh Fading Signals

    • R. Chang, C. Zheng, T. Yamazato, M. Katayama, A. Ogawa
    • IEICE General Conference, B-5-221, p.672, Tokyo, Japan
    • Mar. 2002

  • The Real-Time Parallel Video Decoder Considered on the Complexity and Delay of Error Correcting Decoding

    • M. Honjo, S. Makido, T. Yamazato, H. Okada, M. Katayama, A. Ogawa
    • IEICE Transactions on Fundamentals, vol.J85-A, no.2, pp.214-230
    • Feb. 2002
    • In this paper, a new video decoding scheme integrating error correcting decoder is proposed. In video data transmission, some error correcting code should be equipped to keep video data quality. But in many cases it would need much complex calculation and delay at the decoder when high quality of video data is required. Then, we prepare the two error correcting decoders against one error correcting encoder, where they are different in the delay and the reliability. Due to reconstructing output frame and reference frame separately with two outputs, less delay and less degradation is accomplished. The video quality is analyzed with the 3-D DPCM parallel decoder. Here we show that the degradation of output frame is minimized when no error exists in the reference frame. And we evaluate the simulation results using concatenating code as an example of two output error correcting decoder. Here we show that it is possible to maintain the video quality and achieves graceful degradation in low channel energy, especially in Rayleigh fading channel. Furthermore in the subjective evaluation, we can confirm that the degradation seems to less impression than general decoding in the same PSNR.

  • A Study on Reducing Peak Power of MTCM OFDM Systems

    • M. Harada, T. Yamazato, H. Okada, and M. Katayama
    • Symposium on Information Theory and Its Applications (SITA), vol.1, pp.71-74, Kobe, Japan
    • Dec. 2001
    • In this paper, we discuss about the multiple trellis coded modulation (MTCM) OFDM system. Several methd for ceded modulation have been reported. Here we propose the code which is designed based on the complementary sequence for aiming to reduce the peak power of OFDM signals. We evaluate the performance of this system under the effect of nonlinear amplifier.

  • [Invited talk] Spread spectrum technology and its applications -- from CDMA, bluetooth, 2.4GHz wireless LAN to future topics

    • Takaya Yamazato
    • Society of Signal Processing Applications and Technology, MST2001 DSP Symposium, D-4, pp.39-59, Tokyo Big Sight, Chiba, Japan
    • Nov. 2001

  • Hierarchical Transmission of Video Signal Using Multi-Code DS/SS Modulation Based on DCT Coefficients

    • M. Honjo, S. Makido, T. Yamazato, H. Okada, M. Katayama, A. Ogawa
    • IEEE Global Communications Conference (GLOBECOM), vol.6, pp.3395-3399, San Antonio, USA
    • Nov. 2001
    • In this paper, we propose a hierarchical transmission of video signal using multi-code DS/SS modulation. Assigning an appropriate distribution of transmission energy to DCT coefficients, it is possible to control the picture quality depending on the channel quality. We consider a hierarchical structure based on the variance of DCT coefficient and transmit each coefficient using multi-code DS/SS modulation. The analysis is carried out to show the effectiveness of our scheme using 2-D Gauss-Markov random field, which represents image data. It is shown that by an appropriate energy assignment to each stratum (a branch of multi-code DS/SS), it is possible to maintain picture quality even in bad channel quality.

  • A New Packet Detection Scheme in CDMA Unslotted ALOHA System with Successive Interference Cancellation

    • Y. Tadokoro, H. Okada, T. Yamazato, M. Katayama, A. Ogawa
    • IEEE Global Communications Conference (GLOBECOM), vol.5, pp.3173-3177, San Antonio, U.S.A
    • Nov. 2001
    • A packet detection is one of the most important problems in packet communication systems. In a CDMA Unslotted ALOHA system, which is one of the wireless packet communication systems, Multiple Access Interference(MAI) makes the performance of the packet detection worse. To reduce the effect of MAI, we propose a new packet detection scheme in this paper. In this scheme, Successive Interference Cancellation(SIC) is applied. The packet's signal is detected after the cancellation of MAI using SIC. This proposed scheme gives good performance of the packet detection.

  • A Connection Service for Personal Terminals via LAN Sockets/Wireless LAN at CIMS, Nagoya University

    • H. Okada, T. Yamazato
    • IPSJ SIG Notes, DSM, pp.31-36, Iwate, Japan
    • Oct. 2001
    • Center for Information Media Studies (CIMS) in Nagoya University was established with the aim of development of information education systems. We aim not only at the fulfillment of the computer literacy education, but also at the educational breakthrough by utilizing the multi-media technologies. More than 800 terminals are located campus wide in Nagoya University. In the future, it is expected that many students take their own computer to the campus, connect it to the information education network, and take lessons. To realize this plan, a connection service for personal terminals via LAN sockets/wireless LAN has been in experimental operation since May 2000. In this report, we describe a brief summary about this system, and discuss the issue of the system.

  • DS-CDMA v.s. MC-CDMA

    • T. Yamazato, M. Harada, H. Muramatsu, H. Okada and M. Katayama
    • Technical Report of IEICE, SST2001-47, pp.37-44, Tokyo Japan
    • Oct. 2001
    • In this paper, we compare Multicarrier (MC-) CDMA systems with DS-CDMA systems in the asynchronous uplink channel. First, we analysis signal to noise inteference ratio (SNIR) of asynchronous MC-CDMA systmes in AWGN channel, in order to show the basic performance of MC-CDMA systems. Then, we discuss the effect of nonlinear amplifiers of trnasmitters in MC-CDMA systems, which are usually required using in the mobile terminals for the uplink. We evaluate bit error rate preformance taking account of out-of-band emission.

  • A Study on Digital Signal Processing in Frequency Domain for a Broadband Software-Defined Base Station

    • T. Morikami, H. Okada, T. Yamazato, M. Katayama
    • Technical Report of IEICE, SR01-17, pp.71-77
    • Oct. 2001
    • In this study, we consider a broadband software-defined base station receiver, which simultaneously processes signals of different modulation and multiple access schemes. For such a system, division/selection of individual signals is an important task. In this manuscript,discrete Fourier transform (DFT) is employed for this purpose, and after the separation of signals, they are processed all in frequency domain. In addition, we discuss the influence of key parameters of DFT to BER performance.

  • An Adaptive Antenna Selection Scheme for Transmit Diversity in OFDM Systems

    • H. Shi, M. Katayama, T. Yamazato, H.Okada, A.Ogawa
    • IEEE Vehicular Technology Conference (VTC-Fall), vol.4, pp.2168-2172, Atlantic City, USA
    • Oct. 2001
    • https://doi.org/10.1109/VTC.2001.957128
    • We consider an adaptive antenna selection scheme for transmit diversity in OFDM systems. In the proposed system, the mapping of the subcarriers to antennas is adaptively operated by transmitter according to the Channel State Information(CSI). The performance of the system is improved greatly with this scheme even in slow fading environment. In addition, major modification is necessary only at the transmitter. This is very advantageous for systems with small terminals.

  • A Study on the Packet Detection Scheme Using Successive Interference Cancellation on CDMA Unslotted ALOHA System

    • Y.Tadokoro, H.Okada, T.Yamazato, M.Katayama and A.Ogawa
    • Technical Report of IEICE, vol.SST2001-41, pp.1-6, Tokyo, Japan
    • Oct. 2001
    • In wireless packet communication systems, it is well known that the system performance(throughput) depends on the errors of packet detection. Moreover, in a CDMA Unslotted ALOHA system, Multiple Access Interference(MAI) has much influence on the performance of packet detection, and the system performance. Our aim is to improve the system performance. To achieve it, we study the new packet detection scheme to reduce the effect of MAI on packet detection in this paper. In the proposed scheme, the effect is reduced by Successive Interference Cancellation(SIC) and the received signal with less MAI is left. The packet's signal is detected for the received signal with less MAI. This scheme gives good performance of the packet detection and throughput.

  • Will Spread Spectrum Technique be the coretechnology for post IMT-2000?

    • T. Yamazato
    • Enginnering Sciences Society Conference of IEICE, Panel Discussion, , Tokyo, Japan
    • Sep. 2001

  • A Study for TCP Throughput in a wireless CDMA system

    • K. Naito, H. Okada, T. Yamazato and M. Katayama
    • Communications Society Conference of IEICE, B-5-57, p.343, Tokyo, Japan
    • Sep. 2001

  • Special Session -- Broadband Communication Systems --

    • T. Yamazato (Session Organizer)
    • International Technical Conference on Circuits/Systems, Computers and Communications (ITC-CSCC), Tokushima, Japan
    • Jul. 2001

  • An access control protocol based on correlation of multimedia traffic for CDMA ALOHA

    • Y. Hirayama, H. Okada, T. Yamazato, and M. Katayama
    • Technical Report of IEICE, vol.101, no.241, SST 2001-36, pp.43-49, Saitama, Japan
    • Jul. 2001
    • In this paper, we consider wireless multimedia packet communications which support voice, video, and data traffic. Multimedia traffic includes various types of traffic which has different characteristics of packet generation. We propose a new access control protocol for multimedia traffic. This protocol controls data packet transmission based on estimation of number of packets which will generate in future. This estimation is derived from correlation of voice packet traffic. We evaluate the performance of proposed protocol when it applied to the CDMA slotted ALOHA. Simulation results show that proposed protocol can maintain the data packet throughput and the packet loss rate at a certain level when the offered load of data increases.

  • Communication System for Time and Frequency Dependent Power-Line Channel

    • K.Sugimoto, H.Okada, T.Yamazato, M.Katayama
    • Technical Report of IEICE, vol.SST2001-37, pp.51-57, Saitama, Japan
    • Jul. 2001
    • In power-line communication, channel characteristics and the man-made noise from appliances are time and frequency dependent. This noise is known to be modeled by colored cyclo-stationary Gaussian noise. In consideration of frequency dependence of noise, in this manuscript, we employ OFDM signaling scheme. Under this environment, the space spanned by time and frequency can be subdivided into small cells by symbol duration and sub-carriers of OFDM. The bit error rate (BER) of each cell is analytically derived. In addition, we consider performance improvement by combining some cells (transmitting same information in some cells with iterative coding) according to the knowledge on stochastic features of the cyclo-stationary power-line channel.

  • A Study on High Rate Serially Concatenated Coding Scheme for Optical Communication Systems

    • C. Zheng, T. Yamazato, M. Katayama and A. Ogawa
    • International Technical Conference on Circuits/Systems, Computers and Communications (ITC-CSCC), Tokushima, Japan
    • Jul. 2001
    • In this work, a serially concatenated coding scheme of an outer Reed-Solomon code and an inner high rate Turbo code is proposed for the optical communication systems. The simulation results show the reduction of the error floor influence of the Turbo code. This reduction is due to the outer cascaded Reed-Solomon decoding process and the increase of the interleaver size of the inner Turbo code. The effect of quantization is also considered for inner Turbo decoder. As results, 4-bit quantization is satisfied.

  • BER Analysis for Multi-carrier DS CDMA with Multi-rate Traffic

    • A. Sandouk, M. Harada, H. Okada, T. Yamazato, M. Katayama, A. Ogawa
    • IEICE Transactions on Fundamentals, vol.E84-A, no.7, pp.1723-1731
    • Jul. 2001
    • In this letter, we present bit error analysis (BER) of orthogonal multi-carrier direct sequence code division multiple access (DS-CDMA) system with multi-rate (multimedia) traffic. Analysis is carried out with random signature codes for an AWGN channel. Interference in such a system is severe because all users of all media transmit over the same assigned sub-carriers. This makes the analysis difficult. In our analysis, we divide this interference into different types and carry out our analysis to obtain the BER taking into account all these types. We show that the performance of the system is improved as the number of assigned sub-carriers M increases until a limit where the improvement does not continue even when M increases more. This is because of, as we show, the interference due to other sub-carriers becomes constant even in the case of M->infinite and the interference in a multi-rate multi-carrier system is bigger than that in a single-carrier (M=1) by a factor of pai^2/3.

  • QoS and capacity comparison of CDMA ALOHA protocols in multimedia networks

    • A. Sandouk, T. Yamazato, M. Katayama, A. Ogawa
    • IEICE Transactions on Communications, vol. E84-B, no. 6, pp. 1588-1595
    • Jun. 2001
    • In this letter, performance evaluation of a system that combines between Code-Division Multiple Access (CDMA) and ALOHA protocol in multimedia networks is presented. In our analysis, we compare the performance between the two basic techniques of ALOHA protocol, i.e., Slotted-ALOHA (S-ALOHA) and Unslotted-ALOHA (U-ALOHA), when combined with CDMA scheme to support voice and data users operating in same CDMA channel. The quality of service (QoS) required for voice and data media is completely taken care of. We obtain the throughput of data media, and the outage probability for voice considering both voice and data offered loads. Throughput performance of S-ALOHA technique is almost twice of that of U-ALOHA. However, we show in this letter that when we combine CDMA with the two basic techniques of ALOHA to accomplish multimedia transmission, both techniques have almost same performance. And, thus, CDMA U-ALOHA can be a good candidate for multimedia networks.

  • Comparison of CDMA and FDMA/TDMA in non-GEO Satellite Systems

    • N. Ichikawa, M. Katayama, H. Okada, T. Yamazato, and Akira Ogawa
    • IEEE International Conference on Communications (ICC), pp.3167-3171, Helsinki, Finland
    • Jun. 2001
    • We compare CDMA and FDMA (or TDMA) schemes in multi-beam non-geostationary satellite systems, taking the effects of antenna patterns on inter-cell interference into consideration. The maximum acceptable number of users per cell in uplink is employed as a measure of the system capacity. We have found that in FDMA (or TDMA) systems the maximum acceptable number of users varies according to the altitude of the satellites, while the performance is insensitive to the altitude in CDMA systems. For this reason, the altitude of the satellites is found to be an important factor for selecting multiple access schemes in non-geostationary satellite systems.

  • Hierarchical Transmission of DCT Coefficients Using Multi-Code DS/SS Modulation

    • M. Honjo, S. Makido, T. Yamazato, H. Okada, M. Katayama, and A. Ogawa
    • Technical Report of IEICE, SST2001-17, pp.1-7, Nagoya, Japan
    • Jun. 2001
    • In this paper, we propose a hierarchical transmission of image signal using multi-code DS/SS modulation. DCT is originally invoked in the image coding at the aim of compacting the input variance and compressing efficiently. We achieve an error torelant transmission system by using this property in transmit energy. We introduce the energy assingment (EA) to reduce the channel noise in hierarchical transmission. Assigning an appropriate transmitt energy corresponding to its variance, we show that it is possible to maintain the picuture quality even in low channel condition. The analysis is carried out to show the effectiveness of our scheme using 2-D Gauss-Markov random field in the case of MC DS/SS modulation used. We also verify the same characteristic in several sample movies.

  • A MAP Receiver Based on Prediction Error

    • S. Makido, T. Yamazato, H. Okada, M. Katayama, A. Ogawa
    • The Journal of the Institute of Television Engineers of Japan, vol.55, no.6, pp.886-893
    • Jun. 2001
    • A MAP (Maximum A posteriori Probability) receiver is described that is designed for Markovian sources in a wireless environment. A MAP receiver, a well-known efficient receiver, uses the stochastic characteristics of the source in its calculation costs. To reduce these costs we introduce a source predictor in the receiver. With the aid of the predictor, the MAP detector can be operated with a small calculation cost. Experimental PCM (Pulse Coded Modulation) image transmission demonstrated the feasibility of the proposed receiver. Simulation of the receiver's performance showed it had better MSE (Mean Squared Error) performance in spite of its implementation simplicity.

  • Handobook of CIMS

    • T. Watanabe, T. Uchiyama, T. Yamazato. S. Kajita, H. Okada, T. Tonoike, S. Yuen, K Agusa, T. Hamaguchi
    • Shoko-do
    • May 2001

  • New Analytical Model for the TCP Throughput in Wireless Environment

    • K. Naito, H. Okada, T. Yamazato, M. Katayama, and A. Ogawa
    • IEEE Vehicular Technology Conference (VTC-Spring), vol.3, pp.2128-2132, Rhodes Island, Greece
    • May 2001
    • In this paper, we propose a new analytical model for the TCP, and analyze the bulk throughput performance of different versions of TCP Transmission Control Protocol), viz., Tahoe, Reno and NewReno. We focus on the performance of a single wireless TCP connection which has random segment losses. In our analytical model, we model the TCP mechanisms as a Markov chain. In our result, we found that TCP Tahoe, Reno and NewReno have similar performance with random segment losses. This will lead us to design a lower layer mechanisms.

  • A Design of Source Matched MAP Receiver for Image Transmission

    • S. Makido, T. Yamazato, H. Okada, M. Katayama, and A. Ogawa
    • IEEE International Symposium on Circuit and Systems, vol.IV, pp.136-139, Sydney, Australia
    • May 2001
    • In this paper we will discuss the MAP receiver design for the reception of the image signal. It is impractical to use the MAP algorithm for the source detection because of its huge calculation costs. To solve this problem we propose a novel MAP receiver structure, where the receiver contains a predictor within it. With an aid of the predictor we can reduce the calculation. Furthermore we can approximate the a priori probability by the prediction error distribution.

  • Fundamentals of CDMA

    • Takaya Yamazato
    • 14th Circuits and Systems (Karuizawa) Workshop, Karuizawa, Nagano, Japan
    • Apr. 2001
    • In this study, the fundamentals of CDMA is presented. Chaos modulation, as a view of Spread Spectrums siganal, is also discussed.

  • A novel signal recognition and detection scheme for CDMA packet systems

    • T.Kume, T.Yamazato, K.Ban, H.Okada, and M.Katayama
    • Technical Report of IEICE, IEICE Technical report vol.101, no.27, pp.33-38, Naha, Japan
    • Apr. 2001
    • In this paper, a novel signal recognition and acquisition scheme with an adaptive filter is proposed for direct-sequence code-division multiple access (DS-CDMA) packet systems. In CDMA systems, conventional matched filter receivers suffer from the near-far problem due to multiple access interference (MAI). In general, closed-loop power control is used in order to reduce the influence of the near-far problem. However, in packet systems, closed-loop power control is unsuitable. Hence, we focus on an adaptive receiver with an adaptive linear filter based on LMS algorithm, which eliminate the influences of MAI and the near-far problem, for a signal recognition and acquisition in CDMA packet systems.

  • The influence of analog to digital conversion on the performance of a broadband software-defined base station

    • M. Okuma, T. Yamazato, H.Okada, M.Katayama
    • Technical Report of IEICE, vol.SR01-2, pp.9-15, Tokyo
    • Apr. 2001
    • In this study, we consider a broadband software-defined base station receiver, which emploies superconductive analog to digital converter (ADC) and simultaneously processes signals of different modulation and multiple access schemes. In such a system, we show the influence of the key parameters of an ADC (such as a number of bits per sample, and full-scale-range) on the bit error rate performance for various conditions.

  • Performance of an OFDM Communication Systemunder a Frequency and Time Dependent Power-Line Channel

    • K. Sugimoto, M. Katayama, T. Yamazato, H. Okada
    • 5th International Symposium on Power-line Communications and Its Applications, pp35-40, Scandic Triangeln, Malmo, Sweden
    • Apr. 2001
    • In this manuscript, we employ OFDM (Orthogonal Frequency Division Multiplexing) modulator with the cyclo-stationary Gaussian model for power-line noise. Under this environment, the relation of the bit error rate (BER) to time and frequency is analyzed. In addition, we introduce guaranteed BER as a measure of the performance and show performance improvement by changing the number of sub-carriers and omitting a part of data from transmission.

  • SNIR Analysis of Multicarrier CDMA Systems

    • H. Muramatsu, T. Yamazato, H.Okada, M. Katayama
    • IEICE General Conference, A-5-22, p.181
    • Mar. 2001

  • Joint Multi-dimensional Channel Parameter Estimation Schemes for DS-CDMA Systems Using a Modified version of the SAGE Algorithm

    • Y. R. Senhaji, T. Yamazato, M. Katayama, A. Ogawa
    • IEICE Transactions on Communications, vol.E84-B, no.3, pp.511-519
    • Mar. 2001
    • A modified version of the SAGE algorithm is presented for joint delay-azimuth-attenuation parameters' estimation in a multiuser DS-CDMA system. The introduced modification consists of using different time interval lengths when calculating the time correlations for optimizing the different channel parameters. This modification was proposed for the purpose of a further reduction in the algorithm's computational weight in case of receiving sufficiently resolvable waves. Specifically, we found that short interval windows are sufficient for estimating delays and azimuth angles, which is quite effective in reducing the computational burden in their optimization processes. As for the estimation of the attenuation parameters, a longer time window, equal to the preamble length, is considered for more accurate estimation. Also two other estimators are proposed. The first one combining the modified SAGE with a sequential estimation of the attenuation parameters, suitable for slowly varying channels. Another one, similar to the first, and primarily designed to alleviate the influence of present strong interferers. Through a numerical example, the performances of the three presented estimation schemes, in terms of their near-far resistance, are compared. And it is shown that the proposed second combined estimator outperforms the modified SAGE in environments with high MAI levels.

  • A Proposal of High Efficiency MAP Receiver with Predictor for Markov Sources

    • S. Makido, M. Honjo, T. Yamazato, H. Okada, M. Katayama, A. Ogawa
    • IEEJ Tokai Section 2000 2nd Young Researchers Seminar on Signal Processing Technologies for Multimedia Information and Communications, Nagoya, Japan
    • Mar. 2001

  • A Study on MAP Receiver Design for Image Communications

    • S. Makido, M. Honjo, T. Yamazato, H. Okada, M. Katayama, A. Ogawa
    • IEICE General Conference, A-6-4, p.186
    • Mar. 2001

  • A Study on Multi-carrier DS-CDMA Systems with Multi-rate Traffic

    • A. Sandouk, M. Harada, H. OKada, T. Yamazato, M. Katayama, A. Ogawa
    • Technical Report of IEICE, vol.SST2000-87, pp.137-142, Yokosuka, Japan
    • Mar. 2001
    • In this work, orthogonal multi-carrier direct sequence code division multiple access (DS-CDMA) system with multi-rate traffic is presented. Interference in such a system is severe because all users of all media transmit over the same assigned sub-carriers. We divide this interference into different types and analyze the system to obtain the bit error rate (BER) with random signature codes for an AWGN channel taking into account all interference types.

  • Adaptive Subcarrier Assignment Schemes for OFDM Systems with Transmit Diversity

    • H. Shi, M. Katayama, T. Yamazato, H. Okada, A. Ogawa
    • IEICE General Conference, SB-139, pp.17-18, Siga, Japan
    • Mar. 2001
    • Adaptive Subcarrier Assignment(ASA) schemes for OFDM systems with multiple transmit antennas are proposed and compared to the Fixed Subcarrier Selection(FSS)[3] scheme. In the proposed schemes each subcarrier is assigned to one of the transmit antennas adaptively with the priori knowledge of Channel State Information(CSI).

  • Generation of Sets of Sequences Suitable for Multicode Transmission in Quasi-Synchronous CDMA Systems

    • M. Saito, H. Okada, T. Yamazato, M. Katayama, and A. Ogawa
    • IEICE Transactions on Communications, vol. E84-B, no.3, pp.576-580
    • Mar. 2001
    • In this letter, we present a method to generate sets of sequences suitable for multicode transmission in quasi-synchronous (QS) CDMA systems. We focus on Gold code but extension to orthogonal Gold code is straightforward. We show that by appropriate classification of sequences, it is possible to have sets whose cross correlation is small in QS situations.

  • Throughput Performance of CDMA Slotted ALOHA Systems Based on Average Packet Success Probability Considering Bit-to-Bit Dependence

    • M. Saito, T. Yamazato, M. Katayama, and A. Ogawa
    • IEICE Transactions on Fundamentals, vol.E84-A, no.2, pp.653-659
    • Feb. 2001
    • We propose the analytical calculation method of average packet success probability of CDMA slotted ALOHA systems, which derives accurate probability, and that is applicable to the system with any spreading codes and any amplitude distributions. In the method, we consider the bit-to-bit dependence of amplitude of signals, used spreading sequences, relative timing delays, and relative carrier phases. This bit-to-bit dependence is the case that the parameters above mentioned are constant for a slot time. By using the method to obtain the average packet success probability, we derive useful throughput performance of CDMA slotted ALOHA systems on fading channel, and show that the normalized throughput becomes worse in the case of larger spreading factor.

  • Study on TCP throughput with FEC and ARQ in a wireless link

    • K. Naito, H. Okada, T. Yamazato, M. Katayama, and A. Ogawa
    • IEICE Transactions on Fundamentals, vol.J84-A, no.1, pp.122-126
    • Jan. 2001
    • It is reported that the performance of the TCP is very poor in wireless environments. In this paper, we attempt FEC or ARQ to better performance of the TCP in a wireless link, and clarify the TCP throughput. As shown in results, it is necessary for better performance of the TCP to apply FEC or ARQ, which suited to occurrence distribution of transmission errors.

  • A symbol detection scheme for OFDM signals with subtraction operation

    • T. Shibata, N. Itoh, M. Fujimoto, N. Suzuki, T. Yamazato, A. Ogawa
    • The Journal of the Institute of Television Engineers of Japan, The Journal of the Institute of Television Engineers of Japan, vol.54, No.12, pp.1788-1791
    • Dec. 2000

  • Modified HPSK Modulation Scheme for Wideband CDMA Systems

    • A. Fujiwara, T. Yamazato, M. Katayama, A. Ogawa
    • IEICE Transactions on Fundamentals, vol.J83-A, no.12, pp.1552-1557
    • Dec. 2000

  • A Study on Constant Amplitude Transmission for Orthogonal Multicode Systems

    • T. Wada, and T. Yamazato
    • International Symposium on Information Theory and Its Applications, pp.576-579, Honolulu, USA
    • Nov. 2000
    • In this paper, we deal with the constant amplitude orthogonal multicode systems. The constant amplitude transmission has the advantage of the high power efficiency because the high power amplifier which has non-linear characteristic can be applied for the amplification of the signals. In this paper, we show the bent sequences can achieve the constant amplitude transmission and also show the effectiveness of the constant amplitude transmission in terms of symbol error rate.

  • An Access Control Protocol for a Heterogenous Traffic with a Multi-Code CDMA Scheme

    • A. Sandouk, T. Yamazato, M. Katayama, and A. Ogawa
    • IEICE Transactions on Fundamentals, vol.E83-A, no.11, pp.2085-2092
    • Nov. 2000
    • In this paper, we discuss the access control in multimedia CDMA ALOHA protocol. We introduce a new algorithm for the access control based on Modified Channel Load Sensing Protocol (MCLSP) in an integrated voice and two different classes of data users, high bit rate and low bit rate, exist in a multi-code CDMA Slotted ALOHA system. With our new algorithm, we show that the throughput of high bit rate data users, as well as, the total throughput of the data medium can be optimized and take a maximum value even at high values of offered loads. We also investigate the performance when voice activity detection (VAD) is considered in voice transmission.

  • Efficient Channel Parameter Estimators for DS-CDMA Systems in Slow Time-Varying Channels Using a Modified version of the SAGE Algorithm

    • Y. R. Senhaji, T. Yamazato, M. Katayama, and A. Ogawa
    • IEEE Global Communications Conference, vol.3, no.3, pp.1483-87, San Francisco, California, U.S.A.
    • Nov. 2000
    • A modified version of the SAGE algorithm applied for joint estimation of delays, incidence azimuths and attenuation parameters characterizing the channel is presented. The modifications are based on using different observation intervals in optimizing the parameters and using time correlation in estimating delays, for the purpose of a further reduction in SAGE's computational weight, and improving its accuracy in delay estimation. We show analytically that short observation intervals are sufficient for optimizing the delays and the azimuths, and verify through simulation the reliability of using time correlation. Two other estimators are proposed combining the modified SAGE with a sequential estimation of the attenuation parameters suitable for slowly varying channels.

  • An Initial Code Acquisition Scheme for Indoor Packet DS/SS Systems with Macro/Micro Antenna Diversity

    • Y. Ikai, M. Katayama, T. Yamazato, A. Ogawa
    • IEICE Transaction on Fundamentals, vol.E83-A, no.11, pp. 2070-2077
    • Nov. 2000
    • In this paper, we study macro/micro diversity techniques for code acquisition of a direct-sequence spread-spectrum signal in an indoor packet communication system. In the system discussed, the base station has several radio ports each with a cluster of antennas, and the terminal also has multiple antennas. The performance in the uplink of this system is analyzed under Lognormal shadowing and flat Rayleigh fading. The numerical results show great performance improvements by proposed diversity techniques. In addition, it is clarified that the mean acquisition time, which is often used as the measure of performance, is not suitable for packet radio systems as it underestimates the necessary preamble length for initial code acquisition.

  • Throughput Performance of CDMA Unslotted ALOHA System with Successive Interference Cancellation considering Detection Error of Packet Existance

    • Y. Tadokoro, H. Okada, M. Saito, T. Yamazato, M. Katayama, A. Ogawa
    • International Symposium on Information Theory and Its Applications, pp. 728-731, Honolulu, Hawaii, USA
    • Nov. 2000
    • In CDMA ALOHA system, Multiple Access Interference(MAI) is in existence and it has large influence on the system performance. To suppress the influence, we proposed new system in which SIC is applied to CDMA Unslotted ALOHA. But because of random access and time-short packets, it is very difficult to detect packet existence perfectly. So, in this paper, we evaluate the influence of detection error of packet existence in proposed system by throughput performance.

  • A New Diversity Reception and Decoding Scheme for Convolutional Encoded Signal

    • W.Z. Wang, T. Yamazato, C. Zheng, H. Okada, M. Katayama, and A. Ogawa
    • International Symposium on Information Theory and Its Applications, pp.964-967, Honolulu, Hawaii, USA
    • Nov. 2000
    • In this paper, we propose a new diversity reception and decoding scheme for a convolutionally encoded signal. Aiming at obtaining an additional gain by combining diversity reception and decoding technique, we extend notion of space diversity technique to error correction coded signal and consider an iterative decoding. As a result, we have found $2.0$ dB coding gain in 2 path Rayleigh fading channels at BER $=10^{-5}$ after 6 iterations. This reception technique is particularly useful when used in mobile communications.

  • A Time/Frequency/Space Coding Scheme for Indoor Wireless Communications Systems

    • H.shi H.Oowa M.katayama H.Okada and T.Yamazato
    • Symposium on Information Theory and Its Applications (SITA), vol.1, pp.93-96, Aso, Kumamoto
    • Oct. 2000
    • In this paper we introduce a new type of transmit diversity scheme that combines forward error correction code(FEC) with space diversity in OFDM systems. With this scheme, coding uses not only time dimension but also space and frequency diversities. In addition, we consider dynamic assignment of subcarriers to transmit antennas. As the results of simulations under indoor wireless environment with slow and frequency selective fading, we confirm the great performance improvement by the proposed transmit diversity scheme and additional gain with the dynamic assignment of subcarriers.

  • A Study on Reducing the Nonlinear Distortion in Multicarrier Systems

    • M. Harada, T. Yamazato, M. Katayama, A. Ogawa
    • IEICE Transactions on Fundamentals, vol.E83-a, no.10, pp.1992-1995
    • Oct. 2000
    • In this paper, we discuss on the realization of reduced peak power transmission for the multicarrier systems. Since the signals have large amplitude fluctuations in conventional multicarrier systems, signals amplified by a nonlinear amplifier are greatly distorted, resulting in severe performance degradation. In order to avoid this large amplitude fluctuation, we propose a scheme for reducing the nonlinear distortion by using the set of the signal point series which show low peak to mean envelope power ratio (PMEPR) value. In this system, one symbol is transmitted with multicarriers and the received signal is detected with maximum likelihood sequence detection.

  • EM-Based Schemes for Multiuser Data-Detection in Asynchronous CDMA Systems

    • Y. R. Senhaji, T. Yamazato, M. Katayama, and A. Ogawa
    • IEICE General Conference, SB-11-4, pp. 525-526, Nagoya Institute of Technology, Japan
    • Oct. 2000
    • Many valuable sub-optimum schemes for multiuser demodulation of CDMA systems have been proposed. Among these schemes, there is the Multi-Stage receiver described by Varanasi for asynchronous systems, which proved to be computationally efficient compared with the optimum maximum-likelihood receiver. Other sub-optimum multiuser detectors were proposed by Nelson, based on the expectation-maximization (EM) approach. These EM-based multiuser receivers showed, similarly to the Multi-Stage receiver interesting performance improvements, as well as good resistance against near-far situations. However, the EM-based demodulation schemes were debated in the special case of synchronous CDMA systems only. In this work, we present the EM and its extended version, the space-alternating generalized EM (SAGE) algorithms for multiuser detection of the more general situation of asynchronous CDMA systems.

  • Generation of Sets of Quasi-Synchronous Multi Code from Gold Code and Orthogonal Gold Code

    • M. Saito, T. Yamazato, H. Okada, M. Katayama, and A. Ogawa
    • Symposium on Information Theory and Its Applications (SITA), vol. 2, 32.1, pp. 555-558, Aso, Kumamoto, Japan
    • Oct. 2000
    • In this study, we introduce classification methods of Gold codes and Gold sequences aiming to generate a pair of Quasi-Synchronous Multi Code (QSMC) sets, suitable for multicode transmission. Each set of QSMC pair have small cross correlation to each other in quasi-synchronous (QS) situation. We mainly focus on Gold code but extension to orthogonal Gold code is straightforward.

  • Performance of a Wireless Communication Systems with Time/Frequency/Space Coding

    • H. Shi, H. Oowa, M. Katayama, H. Okada, T. Yamazato, and A. Ogawa
    • IEICE General Conference, SB-11-5, pp. 527-528, Nagoya, Japan
    • Oct. 2000
    • Under slow fading environment, FEC which relies on time diversity is not effective. Thus in this paper we introduce a new type of trnsmit diversity scheme which shows its great performance improvement.

  • New Analytical Model for the TCP Algorithms Over Wireless Links with Random Losses

    • K. Naito, H. Okada, M. Saito, T. Yamazato, M.Katayama, and A. Ogawa
    • Mobile Multimedia Communications(MoMuC2000), pp.4B-4-1 -- 4B-4-6, Tokyo, Japan
    • Oct. 2000
    • In the INTERNET, TCP (Transmission Control Protocol) is used for a reliable transport protocol. Originally, the TCP has been designed for wired networks, and not for wireless ones. It is reported that the performance of TCP is very poor in wireless environments. In this paper, we propose a new analytical model of the TCP, where the congestion window is modeled as a Markov chain. In the presence of random bit errors on a wireless link, we analyze the throughput of the TCP for the proposed model. Also, in a wireless link, we attempt to employ Reed Solomon code as FEC or Go-Back-N as ARQ, and discuss about throughput of TCP with FEC or ARQ.

  • Multiuser Detector Equipped with Less Matched Filters than Simultaneous Transmismit Signals

    • T. Yamazato, H. Okada, M. Katayama and Akira Ogawa
    • Technical Report of IEICE, SST2000-41, pp.7-10, Sendai, Japan
    • Oct. 2000
    • Suppose, there are K users simultaneously transmit their signals. Most common approach to detect all those signals is to recieve those with multiuser detector (MUD) equipped with the same number of matched filters (MF). In this paper, we consider detecting of those signals with MUD with less MF than simultaneous users. Mathematically, this is the underestimate problem. The solution to such problem lies on the mininum recieved power of data. In this paper, we describe main concept to realize such detection.

  • Throughput Characteristics of CDMA Unslotted ALOHA Scheme Assuming WWW Traffic

    • Y. Hirayama, Y, Tadokoro, K. Naito, H. Okada, T. Yamazato, and M. Katayama
    • 2000 Tokai-Section Joint Conference of the Eight Institutes of Electrical and Related Engineers, 416, p.208, Shizuoka, Japan
    • Sep. 2000

  • A Study about Power Distribution of Received Signals under Multi-path Indoor Environment

    • Y. Kubo, M. Katayama, T. Yamazato and Hiraku Okada
    • Record of 2000 Tokai-Section Joint Conference of the Eight Institutes of Electrical and Related Engineers, pp.206, Shizuoka, Japan
    • Sep. 2000

  • Throughput evaluation in CDMA/shared-TDD packet systems in a cellular environment

    • K. Mori, T. Kobayashi, T. Yamazato, A. Ogawa
    • Wireless Communications and Networking Conference, pp.321-326
    • Sep. 2000

  • Transmission power control for downlinks in CDMA/shared-TDD cellular packet systems

    • K. Mori, T. Kobayashi, T. Yamazato, A. Ogawa
    • IEEE International Symposium on Personal, Indoor and Mobile Radio Communication, pp.1520-1524
    • Sep. 2000

  • Correlation for Chip-by-Chip Turbo Coding Scheme on DS/SS Systems

    • C. Zheng, T. Yamazato, M. Katayama, and A. Ogawa
    • IEICE General Conference, A-5-10, p.146, Nagoya, Japan
    • Sep. 2000
    • The chip-by-chip Turbo coding is a coding scheme for DS/SS systems. The input data is first spread by spreading sequence and then fed into the Turbo code which operates in chip timing. We would have long sequence length in Turbo code to improve the performance. The main problem to realize this coding scheme is how the received sequence is compensated, since the chip sequence has lower energy than that of bit. In this paper, a correlating operation for the chip-by-chip Turbo coding scheme is proposed. The coded sequence is transmitted repetitively. Thus the repetitive coding affects as a compensation due to the correlation of received chips. The correlating effects are discussed.

  • Performance Evaluation of Modified HPSK for Wideband CDMA

    • T. Yamazato, A. Fujiwara, M. Katayama and A. Ogawa
    • IEEE International Symposium on Spread Spectrum Techniques and Applications, Vol.F3B.5, pp.751-755, New Jersery, USA
    • Sep. 2000
    • In mobile communications, power is a very important factor and non-linear amplification of power amplifier cannot be avoided due to their high power efficiency. HPSK modulation scheme has been proposed as the spreading technique for W-CDMA and cdma2000. HPSK is a complex spreading scheme that is designed to minimize the zero-crossing signal transition. However, there is a possibility that signal transition of HPSK go through zero. In this paper, we propose a new modulation scheme for W-CDMA and cdma2000. The scheme is based on HPSK, but we modified the complex scrambling to avoid zero-crossing. We call it as modified HPSK (m-HPSK). It is shown that m-HPSK outperforms HPSK in the presence of non-linear amplification.

  • A Study on Approximation Effects of TCP Analysis

    • K. Naito, H. Okada, T. Yamazato, M. Katayama and A. Ogawa
    • Communications Society Conference of IEICE, B-5-50, p.338, Nagoya, Japan
    • Sep. 2000

  • A study on parallel video decoder and the application of the concatenated codes

    • M. Honjo, T. Yamazato, H. Okada, M. Katayama, and A. Ogawa
    • The Institute of Electrical Engineers of Japan, Tokai Branch, FY 2000 1st Signal Processing Technologies for Multimedia Information and Communication Young Researchers Seminar, Nagoya, Japan
    • Sep. 2000

  • Influence of two kinds of Packet Existence Detection Error on CDMA Unslotted ALOHA System Employing Successive Interference Cancellation

    • Y. Tadokoro, H. Okada, M. Saito, T. Yamazato, M. Katayama and A. Ogawa
    • Enginnering Sciences Society Conference of IEICE, A-5-9, p.145, Nagoya, Japan
    • Sep. 2000
    • In CDMA Unslotted ALOHA system, Multiple Access Interference(MAI) is in existence and it has large influence on the system performance . To suppress the influence, we proposed new system in which SIC is applied to CDMA Unslotted ALOHA. But because of random access and time-short packets, it is very difficult to detect packet existence perfectly. So, in this paper, we evaluate the influence of detection error of packet existence in propsed system by throughput performance.

  • An OFDM System with Reduced Non-linear Effect

    • M. Harada, T. Yamazato, H. Okada, M. Katayama, and A. Ogawa
    • IEEE Vehicular Technology Conference, pp.1794-1798, Boston,MA
    • Sep. 2000
    • In this paper, we discuss on the realization of reduced peak power transmission for the OFDM systems. Since the signals have large amplitude fluctuations in conventional OFDM systems, signals amplified by a non-linear amplifier are greatly distorted, resulting in severe performance degradation. In order to avoid this large amplitude fluctuation, we propose a scheme for reducing the non-linear distortion by using the set of the signal point series which show low Peak-to-Mean-Envelope-Power-Ratio (PMEPR) value. In this system, one symbol is transmitted with multicarriers and the received signal is detected with maximum likelihood sequence (MLS) detection.

  • OFDM Systems with Multiple Trellis Coded Modulation

    • M. Harada, T. Yamazato, M. Katayama, and A. Ogawa
    • IEEE International Symposium on Personal, Indoor and Mobile Radio Communication, vol. 1, pp. 814-818, London, United Kingdom.
    • Sep. 2000
    • In an attempt to improve the performance under frequency selective fading environment, we propose in this paper an Orthogonal-Frequency-Division-Multiple-Access (OFDM) system in which MTCM (Multiple Trellis Coded Modulation) is applied to a set of multiple subcarriers. The code is designed to enlarge the summation of the Euclidean distance and the product distance. We also propose a scheme for assigning the symbols to subcarriers adaptively based on the channel state information (CSI) fed back from the reception receive end, and evaluate the performance applying these two codes and the proposed scheme under a multipath Rayleigh fading environment.

  • Hierarchical Channel Structure to Improve Handover Performance of LEO Satellite Communication Systems

    • T. Hara, M. Katayama, H. Okada, T. Yamazato, A. Ogawa
    • Third European Workshop on Mobile/Personal Satcoms, pp.215-220, London, UK
    • Sep. 2000
    • In Low Earth-Orbital(LEO) satellite mobile communication systems, one of the most important technical issues is handover between cells formed by spot-beams of a satellite. In this study, we proposed a three-layered hierarchical channel structure to improve handover performance of a LEO satellite system. Uniform and non-uniform distributions of users are considered in analysis the system performance. As the result, it is shown that the hierarchical channel structure improves overall performance and mitigates performance degradation caused by non-uniformity of user distribution.

  • Joint Optimization of Transmitter/Receiver with Multiple Transmit/Receive Antennas in Band-limited Channels

    • K. Ban, M. Katayama, T. Yamazato, A. Ogawa
    • IEICE Transactions on Communications, vol.E83-B, no.8, pp.1697-1704
    • Aug. 2000
    • We study the joint optimization problem of a transmitter with multiple transmit antennas and a receiver with multiple receive antennas in a narrow-band communication system. We discuss the problem of designing a pre-filter at the transmitter, a post-filter at the receiver, and a bit allocation pattern to multiple symbols in the sense of minimizing the average bit error rate. With the optimized filters and the bit allocation, we could realize high efficiency and high data rate in band-limited channels.

  • Chip by Chip Turbo Coded CDMA System

    • T. Yamazato
    • YRP Telecom Summit, YRP, Yokosuka, Japan
    • Jul. 2000

  • Adaptive Transmit Permission Probability Control in CDMA Cellular Packet Communications with Site Diversity

    • K. Mori, T. Kobayashi, T. Yamazato, A. Ogawa
    • IEICE Transaction on Communications, vol.E83-B, no.7, pp.1445-1453
    • Jul. 2000
    • Site diversity causes unfairness in packet reception that depends on the location of the mobile stations in the up-link of CDMA cellular packet communication systems. This paper proposes an adaptive transmit permission probability control scheme that reduces this unfairness in CDMA cellular slotted-ALOHA systems with site diversity. The proposed scheme adaptively controls the transmit permission probability according to the offered load and the location of the mobile stations. Successful packet reception rate, fairness coefficient and throughput performance are evaluated in fading environments with imperfect power control. Computer simulation shows that adaptive transmit permission probability control improves fairness of service for all mobile stations and throughput performance across all channel loads compared with the conventional scheme.

  • A Note on a Transmit Adaptive Array Antennas and its Capacity Enhancementin a cellular CDMA

    • T. Yamazato, Youssef. Senhaji, H. Okada, M. Katayama, A. Ogawa
    • Technical Report of IEICE, vol.SST-2000-20, pp.7-12, Sapporo, Japan
    • Jul. 2000
    • The concept of diversity in space using adaptive array antennas at the base stations of wireless communication systems have long been debated, and have demonstrated great ability in increasing system capacity, as well as suppressing interferences from undesired users. This paper shows that implementing array antennas at both the base and mobile stations in a cellular CDMA system results in a substantial increase in capacity. Such is realized only with transmission of signal to multiple direction. The concentration of transmit power to one direction provide no improvement.

  • Comparison of Multiple Access Schemes in Multibeam LEO Satellite Communication Systems

    • N. Ichikawa, M. Katayama, H. Okada, T. Yamazato and A. Ogawa
    • Technical Report of IEICE, vol.SAT2000-18, pp.7-12, Nagoya, Japan
    • Jun. 2000
    • This study investigates a low earth-orbital satellite (LEOS) communication system with cellular concept, where each satellite uses multi-beam to form cells. In terrestrial systems, the power of a received desired/interfering signal is mainly determined by the propagation loss, which is often modeled to be proportional to the fourth power of the propagation distance. On the contrary, in satellite systems, the loss varies as the square of distance and, in addition to the loss, the gain of the beam also affects the interference power. Because of this difference, the superiority or inferiority of multiple access schemes discussed terrestrial systems may not be adopted for satellite systems. Thus in this manuscript, the performance of FDMA and CDMA for LEO and terrestrial systems are compared. As a result, it is found that the well-known statement for terrestrial system, i.e., CDMA is superior to FDMA, may not always stands for LEOS systems.

  • A Study on Noise Enhancement and Cross Correlation in Synchronous CDMA Systems with Decorrelating Detector

    • Masato Saito, Hiraku Okada, Takaya Yamazato, Masaaki Katayama, Akira Ogawa
    • Technical Report of IEICE, vol. SST2000-16, pp. 57-62, Nagoya
    • Jun. 2000
    • Bit error probability and noise enhancement of synchronous CDMA with decorrelating detector is analized on condition of identical cross correlation values. And the performance of the systems is compared with conventional matched filtering detector. We evaluate the relationship between the noise enhancement, which is one of issues of decorrelating detector, and cross correlation. From the evaluation, we find that small positive cross correlation values well reduce the effect of noise enhancement and result in obtaining comparable performance to it by the system with orthogonal code.

  • Hierarchical Channel Structure to Improve Handover Performance of LEOS Communication Systems

    • T.Hara, M.Katayama, H.Okada, T.Yamazato, and A.Ogawa
    • Technical Report of IEICE, vol.SAT2000-19, pp.13-18, Nagoya, Japan
    • Jun. 2000
    • In Low Earth-Orbital Satellite(LEOS) mobile communication systems, one of the most important technical issues is handover between cells formed by spot-beams of a satellite. In this study, we consider a hierarchical channel structure to improve handover performance of a LEOS system. In order to measure the Quality of Service, the probability of the rejection of a newly arrived call and the forced termination due to the failure of a handover are derived. Using this performance measures, we discuss the sysytem performance. As the result, it is shown that the performance can be improved by the hierarchical channel strucure with the global handover channels and the number of channels of each group has the optimum ratio.

  • A Study on Cross-Correlation Property in Orthogonal Multi-Code CDMA Systems

    • A. Fujiwara, T. Wada, T. Yamazato, M. Katayama and A. Ogawa
    • IEIEC Transaction on Fundamentals, vol.J83-A, no.5, pp.589-593
    • May 2000

  • A Study on Weight Control Scheme of Adaptive Array Antennas with Interference Canceler

    • Takayuki Suzuki, Masaaki Katayama, Takaya Yamazato, Akira Ogawa
    • Technical Report of IEICE, vol.RCS2000-15, pp.21-26
    • May 2000
    • This manuscript discusses the application of an adaptive array antenna and an interference canceller to a base station of CDMA mobile communication systems. First, it is shown that the interference cancellation for the output of the adaptive array antenna does not improve the performance in many cases, if the antenna and the canceller work independently. Then, the weight control scheme based on the output of the interference canceller is consider. In this case, the interference canceller achieves good performance for all direction of interfering signals. In addition, it is found that imperfect cancellation may have better SINR than perfect cancellation under a certain condition.

  • Effects of Cell Structure on Quality of Service of LEOS Communication Systems

    • K.Ono, M. Katayama, T. Yamazato, A. Ogawa
    • IEICE Transaction on Communications, vol.E83-B, no.4, pp.782-790
    • Apr. 2000
    • In this paper, we analytically study the effects of overlap and overlay structure on the quality of service (QoS) of Low Earth-Orbital Satellite (LEOS) communication systems. We consider two-layered overlay of cells and intentional overlap of neighboring small cells. In order to measure the QoS, the probabilities of rejection of a newly arrived call (blocking) and forced termination due to failure of a handover (call dropping) are derived. In addition to these measures, the largest traffic intensity which guarantees the required blocking and dropping probabilities is also used.

  • Modeling of Cyclostationary and Frequency Dependent Power-Line Channels for Communications

    • M. Katayama, S. Itou, T.Yamazato, A. Ogawa
    • 4th International Symposium on Power-Line Communications and its Applications, pp.123-127, , Limerick, Ireland
    • Apr. 2000
    • This manuscript introduces a mathematically tractable and accurate model of power-line noise, in which the nose is expressed as the sum of cyclostationary Gaussian processes. This model can represent non-stationary power-line noise with a small number of parameters and generate the waveforms which achieve good agreement with actually measured noise waveforms. In this manuscript, parameter determination method is explained and then necessary observation length, influence of the frequency of a reference signal, and fidelity of determined parameters are discussed.

  • Performance Evaluation of the CDMA Unslotted ALOHA System Employing Successive Interference Cancellation Considering Packet Detection Error

    • K. Tadokoro, H. Okada, M. Saito, T. Yamazato, M. Katayama and A. Ogawa
    • IEICE General Conference, vol.A-5-13, p.167
    • Mar. 2000

  • Evaluation of Interference between UP- and Down-Links on CDMA Cellular Packet Systems Employing a Shared-TDD Scheme

    • K. Mori, T. Kobayashi, T. Yamazato, and A. Ogawa
    • 2000 IEICE General Conference, vol.SB-3-2, p.739
    • Mar. 2000

  • An Analysis Model of TCP in Wireless Environments

    • K. Naito, H. Okada, M. Saito, T. Yamazato, M. Katayama and A. Ogawa
    • IEICE General Conference, vol.B-5-185, p.570
    • Mar. 2000

  • Throughput Analysis of TCP in Wireless Environment

    • K. Naito, H. Okada, M. Saito, T. Yamazato, M. Katayama and A. Ogawa
    • Technical Report of IEICE, vol.RCS99-232, pp.107-113, YRP
    • Feb. 2000
    • In the INTERNET, TCP(Transmission Control Protocol) is used for a reliable transport protocol . With the advance of wireless communication technologies, the need to access to the internet via radio media is expected to increase more and more in the future. The TCP is, however, designed for wired networks, and not for wireless ones. It is reported that the performance of the TCP is very poor in wireless environments. In this paper, we propose an analytical model, in which the congestion window is modeled as a Markov chain. In the presence of random bit errors on a wireless link, we analyze the throughput of the TCP for the proposed model. Moreover, in a radio link, we attempt to employ Reed Solomon code as FEC or Go-Back-N as ARQ, and discuss about throughput of TCP with FEC or ARQ.

  • The Performance of MTCM Coded Multicarrier System

    • M. Harada, T. Yamazato, M. Katayama, and A. Ogawa
    • Symposium on Information Theory and Its Applications (SITA), pp.563-566
    • Dec. 1999

  • Service Fairness in CDMA Cellular Packet Systems with Site Diversity Reception

    • K. Mori, T. Kobayashi, T. Yamazato, A. Ogawa
    • IEICE Transaction on Communications, vol.E82-B, no.12, pp.1964-1973
    • Dec. 1999

  • Service Fairness in CDMA Cellular Slotted-ALOHA Packet Systems

    • K. Mori, T. Kobayashi, T. Yamazato and A. Ogawa
    • IEEE Global Communications Conference, pp.655-660, Rio de Janeiro, Brazil
    • Dec. 1999

  • A study on SOVA based Turbo-decoding with threshold

    • M. Matsui, T. Yamazato, M. Katayama, and A. Ogawa
    • Symposium on Information Theory and Its Applications (SITA), vol.1, pp.13-16
    • Dec. 1999

  • Adaptive Array Antennas for the Base Station of a Multi Processing Gain CDMA System

    • A. Morimoto, M. Katayama,T. Yamazato, A. Ogawa
    • IEICE Transaction on Communications, vol.E82-A, no.12, pp.2687-2696
    • Dec. 1999
    • This paper discusses the employment of adaptive array antennas at the base station of a Multi Processing Gain (MPG) CDMA system. It is shown that the adaptive array antenna with the weight control scheme based on the signal before despreading procedure does not increase but even decreases the performance than that with an omni-directional antenna, and the cause of this serious performance degradation is revealed. Then it is shown that the performance with the weight control scheme based on the signal after despreading procedure is always better than that with an omni-directional antenna. Furthermore, the possibilities of performance improvement by the combination of adaptive array antenna and interference cancellation techniques are mentioned.

  • Code Acquisition of a DS/SS Signal with Transmit and Receive Antenna Diversity

    • Y. Ikai, M. Katayama,T. Yamazato, A. Ogawa
    • IEICE Transaction on Communications, vol.E82-A, no.12, pp.2728-2734
    • Dec. 1999
    • In this paper, we propose the introduction of space diversity techniques to the code acquisition of a direct-sequence spread-spectrum signal. In this scheme, both a transmitter and a receiver have multiple antennas and the signals corresponding to all the combinations of the transmitter and receiver antennas are combined at the acquisition circuit of the receiver. The performance is evaluated for an indoor packet radio communication system from the viewpoints of the average time for acquisition, the probability of success of acquisition, and the necessary preamble length. As the result, we show great performance improvements by the proposed scheme under slow and flat Rayleigh fading environment.

  • Decorrelating Detector for Multi-Processing Gain CDMA Systems

    • H. Hiraiwa, M. Katayama,T. Yamazato, A. Ogawa
    • IEICE Transaction on Fundamentals, vol.E82-A, no.12, pp.2774-2777.
    • Dec. 1999
    • The design of a liner decorrelating detector for multi-processing gain code-division multiple-access (MPG-CDMA) systems is proposed, and its performance is discussed. As the result, the performance improvement by this detector is confirmed. Also, it is found that that the degrees of the noise enhancement depend on the processing gains of the signals.

  • Chip-by-Chip Turbo Coding for DS/SS Systems

    • C. Zheng, T. Yamazato, M. Katayama, A. Ogawa
    • IEICE Transaction on Fundamentals, vol.E82-A, no.12, pp.2751-2757
    • Dec. 1999
    • Most of error correcting codes applying to DS/SS systems are such that information data is first (bit-by-bit) encoded and then spread by pseudo noise (PN) sequence. Thus, coding gain achieved by such systems are mainly due to the error correcting codes and the redundancy produced by the spreading codes shows no effect on the coding gain. In this paper, a chip-by-chip Turbo coding for DS/SS systems is proposed. The input information data is first spread by PN sequence and then fed into the Turbo-encoder which operates in chip timing. As the Turbo-encoder operates in chip timing, a large interleaving size would be obtained, which improves the performance. As results, superior performances with coding gain of more than 3.0 dB and 5.0 dB for AWGN and Rayleigh-fading channel, respectively, were found with short frame size of information data.

  • A Study on Fast Decoding Algorithm of Turbo Coded OFDM

    • W. Wang, T. Yamazato, M. Katayama, and A. Ogawa
    • Symposium on Information Theory and Its Applications (SITA), pp.165-168
    • Dec. 1999

  • A Synopsis of CIMS at Nagoya University

    • T. Yamazato, S. Kajita, T. Hamaguchi, S. Yuen
    • vol.DMS99-16, pp.55-60
    • Nov. 1999

  • Fundamentals of CDMA

    • Takaya Yamazato
    • Proc. of 2001 Microwave Workshops and Exhibition, MWE2001., Pacifico, Yokohama, Japan
    • Nov. 1999
    • Fundamentals of code division multiple access (CDMA) is presented in this tutorial lecture. The techniques to improve the performance of CDMA are introduced, such includes transmission power control, RAKE combining, soft handoff, interference cancellation, adaptive array antenna and error correcting code. Capacity of CDMA is compared with FDMA/TDMA to show advantages of CDMA.

  • Control of Transmit Permission Probability to Improve Service Fairness in CDMA Cellular Packet Communications

    • K. Mori, T. Kobayashi, T. Yamazato, and A. Ogawa,
    • IEEE International Workshop on Mobile Multimedia Communications (MOMUC'99), pp.35-42, San Diego, California, USA
    • Nov. 1999

  • Influence of Beam Pattern on the Capacity of LEOS Communication Systems

    • N. Ichikawa, M. Katayama T. Yamazato and A. Ogawa
    • International Symposium on Communications, pp.534-538 Kaohsiung, , Kaohsiung, Taiwan
    • Nov. 1999

  • The Influence of an ADC on Bit Error Rate Performance of a Software-Defined Base Station

    • K. Matsubara, M. Katayama, T. Yamazato, A. Ogawa
    • Technical Report of IEICE, vol.SR99-19, pp.67-72
    • Nov. 1999

  • A Study on OFDM Synchronization Scheme with Subtraction Operation

    • T. Shibata, N. Itoh, M. Fujimoto, H. Itoh, N. Suzuki, K. Ohtsuka T. Yamazato, A. Ogawa
    • Technical Report of IEICE, vol.RCS99-135, pp.97-101
    • Oct. 1999

  • An Integrated Voice/Data CDMA Packet Communications with Multi-Code CDMA Scheme

    • A. Sandouk, T. Yamazato, M. Katayama, A. Ogawa
    • IEICE Transaction on Communications, vol.E82-A, no.10, pp.2105-2114
    • Oct. 1999

  • A Study on Multiple Trellis Coded Modulation for Multicarrier Systems

    • M. Harada, T. Yamazato, M. Katayama, A. Ogawa
    • Technical Report of IEICE, vol.SST99-32, pp.13-18
    • Sep. 1999

  • Chip-by-chip Turbo coded DS/SS systems

    • T. Yamazato, C. Zheng, M. Katayama, A. Ogawa
    • 1999 IEICE General Conference, vol.A-5-14, p.97
    • Sep. 1999

  • Applying Successive Interference Cancellation to CDMA Unslotted ALOHA System

    • Y. Tadokoro, H. Okada, M. Saito, T. Yamazato, M. Katayama, A. Ogawa
    • Technical Report of IEICE, vol.SST99-34, pp.25-30
    • Sep. 1999

  • Throughput Performance of CDMA Slotted ALOHA Systems with Accurate Packet Success Probability

    • M. Saito, T. Yamazato, M. Katayama, and A. Ogawa
    • Second International Symposium on Wireless Personal Multimedia Communications (WPMC'99), vol. 1, no. 9.5, pp. 354-359, Amsterdam, The Netherlands
    • Sep. 1999

  • A Scheme for Throughput Improvement in Voice/Data CDMA Packet Communications

    • A. Sandouk, T. Yamazato, M. Katayama, and A. Ogawa
    • IEEE Vehicular Technology Conference, pp.362-366, Amsterdam, Netherlands
    • Sep. 1999

  • Transmitter Precoding with Multiple Transmit/Receive Antennas for High Date Rate Communication in Bandwidth-limited Channels

    • K. Ban, M. Katayama, T. Yamazato, and A. Ogawa
    • IEEE Vehicular Technology Conference Fall, pp.1946-1950, Amsterdam, Netherlands
    • Sep. 1999

  • Acquisition of a DS/SS Signal with Macro/Micro Antenna Diversity under Rayleigh Fading and Log-normal Shadowing

    • Y. Ikai, M. Katayama, T. Yamazato and A. Ogawa
    • IEEE International Symposium on Personal, Indoor and Mobile Radio Communication (PIMRC), pp.1526-1530, Osaka, Japan
    • Sep. 1999

  • Error Resilient Video Coding System for Wireless Communication -Using Motion Compensated Field

    • M. Honjo, S. Makido, T. Yamazato, M. Katayama and A. Ogawa
    • Second International Symposium on Wireless Personal Multimedia Communications (WPMC), vol. 1, no. 4.2, pp. 214-218, Amsterdam, The Netherlands
    • Sep. 1999
    • In this paper, we propose a new video coding system which maintains picture quality and keeps frame rate. In the event of error, the system requests only high priority frame data for retransmission. Low priority frame data is positively discarded. This discarding frame data helps not to lower the frame rate, while it is important to maintain the picture quality to some extent. We realize such by the coding algorithm which processes on the premise of the discarded frame data. The simulation results shows that proposal system is more efficient in wireless communications.

  • Performance Improvements applying an Adaptive Array Antenna at both the Base and Mobile Stations in Cellular CDMA

    • Youssef R. Senhaji, H. Okada, T. Yamazato, M. Katayama and A. Ogawa
    • IEEE International Symposium on Personal, Indoor and Mobile Radio Communication (PIMRC), vol.3, pp.982-986, Osaka, Japan
    • Sep. 1999
    • The concept of diversity in space using adaptive array antennas at the base stations of wireless communication systems have long been debated, and have demonstrated great ability in increasing system capacity, as well as suppressing interferences from undesired users. But, yet the increasing demand for mobile communication services with more improvements in performance is motivating the search for new techniques. This paper shows that implementing array antennas at both the base and mobile stations in a cellular CDMA system results in a substantial increase in capacity over the conventional system using the array antennas at the base station only.

  • Permission Probability Control to Improve Service Fairness in CDMA Cellular Slotted-ALOHA Systems

    • K. Mori, T. Kobayashi, T. Yamazato, A. Ogawa
    • Technical Report of IEICE, vol.RCS99-91, pp.29-36
    • Aug. 1999

  • A Study on Applying Coded Modulation for Multicarrier Systems

    • M. Harada, T. Yamazato, M. Katayama, A. Ogawa
    • Technical Report of IEICE, vol.IT99-34, pp.7-12 (1999-7)
    • Jul. 1999

  • A Study for the Throughput Performance of CDMA Slotted ALOHA Systems

    • M. Saito, T. Yamazato, M. Katayama, A. Ogawa
    • Technical Report of IEICE, vol.SST99-21, pp.37-42 (1999-7)
    • Jul. 1999

  • A Study of Chip-by-Chip Turbo Coding for DS-CDMA Systems

    • C. Zheng, T. Yamazato, M. Katayama, and A. Ogawa
    • Technical Report of IEICE, vol.SST99-8, 06.1999, pp.49-54, Nagoya, Japan
    • Jun. 1999

  • Throughput Improvement of a Dual-Class Multi-code CDMA ALOHA System with Modified Channel Load Sensing Protocol

    • A. Sandouk, H. Okada, T. Yamazato, M. Katayama, and A. Ogawa
    • IEEE International Conference on Communications (ICC), pp.1079-1083, Vancouver, Canada
    • Jun. 1999
    • https://doi.org/10.1109/ICC.1999.765445

  • Effect of Beam Pattern on Capacity of Multibeam LEOS Communication Systems

    • N. Ichikawa, T. Yamazato, M. Katayama and A. Ogawa
    • Technical Report of IEICE, vol.SAT99-39, pp.83-90 (1999.6)
    • Jun. 1999

  • A New Acquisition Scheme of a DS/SS Signal with Transmit and Receive Antenna Diversity

  • Throughput Performance of CDMA ALOHA (invited)

    • A. Ogawa, T. Yamazato, H. Okada, M. Katayama
    • Technical Report of IEICE, vol.SAT99-41, p.99 (1999-6)
    • Jun. 1999

  • A Study on Decorrelating Detector for Multi-Processing Gain CDMA Systems

    • H. Hiraiwa, M. Katayama, T. Yamazato and A. Ogawa
    • 1999 IEICE General Conference, vol.B-5-111, p.462
    • Mar. 1999

  • A Study of Error Correcting Codes Applied to OFDM Systems

    • W. Wang, C.Zheng, T. Yamazato, M. Katayama and A. Ogawa
    • Technical Report of IEICE, vol.IT98-75, pp.49-54 (1999-03)
    • Mar. 1999

  • Application of ARQ Scheme to Inter-frame Picture Decoding

    • M. Honjo, S. Makido, T. Yamazato, M. Katayama and A. Ogawa
    • 1999 IEICE General Conference, vol. B-5-243, pp.594
    • Mar. 1999

  • Performance Improvements applying an Adaptive Array Antenna for Transmission at a Mobile Station

    • Y. R. Senhaji, T. Yamazato, M. Katayama, and A. Ogawa
    • 1999 IEICE General Conference, vol.B-5-37, p.388, Keiyou-Univ, Japna
    • Mar. 1999
    • In this work, we are concerned with inhancing transmission performance from a mobile towards a base station. Aware of its ability to concentrate radiation power at desired transmit directions by reducing power at undesired ones, we propose the use of an adaptive array antenna at a mobile station supported by an eigenstructure based algorithm for updating transmission beams. After introducing the beamforming algorithm, we show through comparison with the conventional omnidirectional system that our proposed one can insure heigher received power at the base station with similar dynamic range.

  • A Study on the Error Control Scheme in Data Transmission for Positioning of Sea Turtles

    • Y. Amano, T. Yamazato, M. Katayama, and A. Ogawa
    • Technical Report of IEICE, vol.SANE99-64, pp.105-108 (1999-02)
    • Feb. 1999

  • A Channel Control Method for Multi-Carrier Transmission Considering Channel Response

    • T. Shibata, N. Suzuki, M. Fujimoto, K. Nishikawa, T. Yamazato and A. Ogawa
    • Asia-Pacific Microwave Conference, vol.3, pp.853-856, Yokohama, Japan
    • Dec. 1998

  • Hierarchical Transmission of Huffman Code Using Multi-Code/Multi-Rate DS/SS Modulation with appropriate Power Control

    • A. Makido, T. Yamazato, M. Katayama, A. Ogawa
    • IEICE Transaction on Communications, vol.E81-B, no.12, pp.2283-2289
    • Dec. 1998

  • An Integrated Voice and Multi-Code CDMA Data System for CDMA Slotted-ALOHA with Modified Channel Load Sensing Protocol

    • A. Sandouk, T. Yamazato, M. Katayama, and A. Ogawa
    • SITA'98 vol.2, pp. 523-526 (1998-12)
    • Dec. 1998

  • Multimedia Packet Transmission using CDMA

    • T. Yamazato, M. Katayama and A. Ogawa
    • Technical Report of IEICE, vol.SST98-42, pp.9-14 (1998.12.10)
    • Dec. 1998

  • Parallel Transmission of Huffman Code Under Fading Environment

    • S. Makido, T. Yamazato, M. Katayama and A. Ogawa
    • Technical Report of IEICE, vol.CS98-117,IE98-96, pp.21-27 (1998.12.10)
    • Dec. 1998

  • Application of TURBO Code to Band-limited VIDEO Signal Transmission

    • M. Honjo, M. Matsui, T. Yamazato, M. Katayama, and A. Ogawa
    • SITA'98, 26.7, vol.2, pp.619-622 (1998-12), Gifu, Japan
    • Dec. 1998
    • In wireless video transmission, powerful forward error correction such as TURBO code may be used to avoid the effect of channel errors. But it may not be appropriate for successive video signal processing because of its complexity. In this paper, we propose a new decoding scheme for compressed video signal with TURBO code. Powerful error correction can be achieved as a result of recursive decoding structure of TURBO code. In proposed scheme, reference frame for interframe is decoded by alternative H.263 decoder and TURBO decoder. Thus, error correction may be achieved more as a result of longer decoding process time by TURBO decoder.

  • New Quasi-Synchronous Sequences for CDMA Slotted ALOHA Systems

    • M. Saito, T. Yamazato, M. Katayama, A. Ogawa
    • IEICE Transaction on Fundamentals, vol.E81-A, no.11, pp.2274-2280
    • Nov. 1998

  • Performance Evaluation of DS/CDMA Communications Systems Modulated with pi/2-Shift BPSK over Multipath Rayleigh Fading Channels

    • A. Galib, T. Yamazato, M. Katayama, A. Ogawa
    • IEICE Transaction on Fundamentals, vol.E81-A, no.11, pp.2304-2310
    • Nov. 1998

  • Hierarchical Transmission System using Multi-Code/Multi-Rate DS/SS Modulation

  • A Channel Control Scheme Considering Channel Response for Multi-carrier Transmission

    • T. Shibata, N. Suzuki, M. Fujimoto, K. Nishikawa, T. Yamazato, A. Ogawa
    • IEICE Transaction on Communications, vol.J81-BI, no.11, pp.700-708 (1998.11)
    • Nov. 1998

  • A Control Scheme of Multi-Carrier Transmission Considering Channel Response for Mobile Communication

    • T. Shibata, N. Suzuki, M. Fujimoto, K. Nishikawa, T. Yamazato and A. Ogawa
    • Asia-Pacific Conference on Communications (APCC), vol.2, pp.543-546, Singapore
    • Nov. 1998

  • Performance of a LEOS Communication System with Overlaid and Overlapped Cell Arrangement

    • K.Ono, M.Katayama, T.Yamazato and A.Ogawa
    • Third European Workshop on Mobile/Personal Satcoms, vol.1, pp.131-145, Venis, Italy
    • Nov. 1998

  • Tutorial : Introduction to CDMA ALOHA

    • T. Yamazato, A. Ogawa, M. Katayama and A. Jamalipour
    • Tutorial Note, TI-13, IEEE Global Telecommunications Conference
    • Nov. 1998

  • Performance Evaluation of DS/CDMA Communications Systems Modulated with pi/2-Shift BPSK over Multipath Rayleigh Fading Channels

    • A. Galib, T. Yamazato, M. Katayama and A. Ogawa
    • IEEE Global Telecommunications Conference, Sydney, Communications Theory Mini
    • Nov. 1998

  • Initial Acquisition of Code Timings and Carrier Frequencies of CDMA Downlink Signals in Multiple-LEO-Satellite Communication Systems

    • M. Ishizu, M. Katayama, T. Yamazato, A. Ogawa
    • IEICE Transaction on Fundamentals, vol.E81-A, no.11, pp.2281-2290
    • Nov. 1998

  • Evaluation of the Interference with Small Number of Users in Orthogonal Multi-Code CDMA Systems

    • A. Fujiwara, T. Wada, T. Yamazato, M. Katayama and A. Ogawa
    • International Symposium on Wireless Personal Multimedia Communications, vol.1, pp.422-427, Yokosuka, Japan
    • Nov. 1998

  • Performance of a LEOS Communication System with Overlaid and Overlapped Cell Arrangement

    • K. Ono, M. Katayama, T. Yamazato and A. Ogawa
    • Technical Report of IEICE, vol.SAT98-42,CS98-105, pp.1-8 (1998-10)
    • Oct. 1998

  • Performance of Transmit/Receive Antenna Diversity with FEC Coding under Correlated Rician Fading Channels

    • K. Ban, M. Katayama, T. Yamazato and A. Ogawa
    • 1998 IEICE General Conference, vol.A-5-8, p.98
    • Oct. 1998

  • Handoff Performance of LEO Satellite Communication Systems with Overlapped-Cell Arrangement

    • K. Ono, M. Katayama, T. Yamazato, A. Ogawa
    • IEICE General Conference，vol.SB-3-13, pp.556-557
    • Oct. 1998

  • Error Correcting Capability of Constant Amplitude Coding for Orthogonal Multi-Code CDMA Systems

    • T. Wada, T. Yamazato, M. Katayama, A. Ogawa
    • IEICE Transaction on Fundamentals, vol.E81-A, no.10, pp.2166-2169
    • Oct. 1998

  • Quasi-Synchronous CDMA Slotted ALOHA System Through Flat Fading Channel

    • Masato Saito, Takaya Yamazato, Masaaki Katayama, Akira Ogawa
    • International Symposium on Information Theory and its Applications (ISITA), FA4-3, vol.2, pp.487-490
    • Oct. 1998

  • A Study on the Throughput of Multi-Code CDMA ALOHA System with Modified Channel Load Sensing Protocol

    • A. Sandouk, T. Yamazato, M. Katayama, and A. Ogawa
    • Technical Report of IEICE, vol.SST98-40, pp.61-68 (1998-10)
    • Oct. 1998

  • An Access Control Scheme Based on Transmit Power for CDMA ALOHA System under a Cellular Environment

    • Y. Asai, T. Yamazato, M. Katayama and A. Ogawa
    • International Symposium on Information Theory and Its Applications (ISITA), vol.2, pp.491-494, Mexico City,Mexico
    • Oct. 1998

  • Throughput Performance of QS-CDMA Slotted ALOHA System on 2-path Rayleigh Fading Environment

    • M. Saito, T. Yamazato, M. Katayama and A. Ogawa
    • 1998 Society Conference of IEICE, vol.A-5-9, p.99
    • Oct. 1998

  • CDMA Unslotted ALOHA Systems with Finite Buffers

    • H. Okada, T. Yamazato, M. Katayama and A. Ogawa
    • IEEE International Conference on Universal Personal Communications (ICUPC), vol.2, pp.1143-1147, Florence, Italy
    • Oct. 1998
    • https://doi.org/10.1109/ICUPC.1998.733679
    • A CDMA unslotted ALOHA system with finite size of queueing buffers is discussed. We introduce an analytical model in which the system is divided into two Markov chains; one is in user part, and the other is in channel part. We analyze the queueing system using this analytical model, and evaluate the effect of buffer capacity in terms of the throughput, rejection probability and average delay. As a result, increase in the buffer size brings about an improvement in the grade of service in terms of higher throughput and lower rejection probability.

  • Queueing Analysis of CDMA Unslotted ALOHA Systems with Finite Buffers

    • H. Okada, T. Yamazato, M. Katayama, A. Ogawa
    • IEICE Transaction on Fundamentals, vol.E81-A, no.10, pp.2083-2091
    • Oct. 1998
    • CDMA unslotted ALOHA system with finite size of queueing buffers is discussed in this paper. We introduce an analytical model in which the system is divided into two Markov chains; one is in the user part, and the other is in the channel part. In the user part, we can model the queueing behavior of the user station as an M/G/1/B queue. In the channel part, we can consider the number of simultaneously transmitted packets as an M1+M2/D/infinity//K queue. We analyze the queueing system by using this analytical model, and evaluate the effect of buffer capacity in terms of the throughput, the rejection probability and the average delay. As a result, increase in the buffer size brings about an improvement in the grade of service in terms of higher throughput and lower rejection probability.

  • Effect of Nonlinear Amplification on Multi-Code DS/SS System

    • T. Yamazato, A. Fujiwara, M. Katayama, A. Ogawa
    • International Symposium on Nonlinear Theory and its Applications (NOLTA), pp.1233-1236, Crans-Montana, Switzerland
    • Sep. 1998

  • Problems of Implementing Adaptive Array Antennas in CDMA Systems

    • A. Morimoto, M. Katayama, T. Yamazato and A. Ogawa
    • IEEE International Symposium on Personal, Indoor and Mobile Radio Communication (PIMRC), vol.3, pp1422-1426, Boston, USA
    • Sep. 1998
    • https://doi.org/10.1109/PIMRC.1998.731432

  • Access Control Techniques for CDMA ALOHA

    • T. Yamazato, H. Okada,M. Katayama and A. Ogawa
    • IEEE International Symposium on Spread Spectrum Techniques and Applications (ISSSTA), vol.1, pp.293-297, Sun City, South Africa
    • Sep. 1998
    • https://doi.org/10.1109/ISSSTA.1998.726245

  • Performance Analysis of an Integrated Voice and Data CDMA System

    • T. Sato, A. Sandouk, T. Yamazato, M. Katayama, and A. Ogawa
    • IEICE Transaction on Communications, vol.J81-B-II, no.08, pp.733-741
    • Aug. 1998

  • CDMA Slotted ALOHA System with Finite Buffers

    • H. Okada, T. Yamazato, M. Katayama, A. Ogawa
    • IEICE Transaction on Fundamentals, vol.E81-A, no.7, pp.1473-1478
    • Jul. 1998
    • In this paper, CDMA slotted ALOHA system with finite size of buffers is proposed. To analyze the system performance, we use the linear approximate solution based on restricted occupancy urn models. We evaluate the system performance in terms of throughput, average delay, and rejection probability and clarify the effect of buffer capacity.

  • A Study on Reducing the Nonlinear Distortion in OFDM Systems

    • M. Harada, T. Yamazato, M. Katayama, and A. Ogawa
    • Technical Report of IEICE, vol.RCS98-61, pp.25-30 (1998-07)
    • Jul. 1998

  • A Study on Parallel Decording of Turbo-Codes Using Soft-output Viterbi Decorder

    • M. Matsui, S. Makido, T. Yamazato, M. Katayama and A. Ogawa
    • Technical Report of IEICE, vol.IT98-21, pp.17-22 (1998-07)
    • Jul. 1998

  • Weight Control Scheme of Adaptive Array Antennas in CDMA Systems

    • A. Morimoto, M. Katayama, T. Yamazato and A. Ogawa
    • Technical Report of IEICE, vol.CS98-56, pp.7-14 (1998-07)
    • Jul. 1998

  • A New Acquisition Scheme of DS/SS Signals using Space Diversity Techniques

    • Y. Ikai, M. Katayama, T. Yamazato and A. Ogawa
    • Technical Report of IEICE, vol.SST98-24, pp.53-59 (1998-07)
    • Jul. 1998

  • Throughput Analysis for CDMA Unslotted ALOHA Systems with Finite Population Assumption

    • H. Okada, T. Yamazato, M. Katayama, A. Ogawa
    • IEICE Transaction on Fundamentals, vol.J81-A, no.7, pp.1089-1092
    • Jul. 1998
    • We analyze the CDMA unslotted ALOHA system with finite population assumption in terms of the Markov chain model. We evaluate the throughput performance and clarify the effect in the case of finite population assumption. We also analyze the CDMA unslotted ALOHA system using the Channel Load Sensing Protocol.

  • A Study on Cross-Correlation Property in Orthogonal Multi-Code SYstems

    • A. Fujiwara, T. Wada, T. Yamazato, M. Katayama, and A. Ogawa
    • Technical Report of IEICE, vol.SST98-13, pp.19-24 (1998-06)
    • Jun. 1998

  • Queueing Analysis of CDMA Slotted ALOHA Systems with Finite Buffer and Finite Population Assumptions

    • H. Okada, T. Yamazato, M. Katayama and A. Ogawa
    • IEEE International Conference on Communications (ICC), vol.1, pp.407-411, Atlanta, USA
    • Jun. 1998
    • https://doi.org/10.1109/ICC.1998.682883
    • In this paper, we analyze the CDMA slotted ALOHA systems with finite buffer and finite population assumptions by expanding the linear approximate solution based on restricted occupancy models. We evaluate the system performance in terms of throughput, average delay, and rejection probability. Moreover, we clarify the effect of buffer capacity by changing the buffer size.

  • A Channel Control Scheme using Channel State Information in Multi-Carrier Transmission

    • T. Shibata, M. Fujimoto, N. Suzuki, K. Nishikawa, T. Yamazato and A. Ogawa
    • 1998 IEICE General Conference, vol.B-5-23, p.387
    • Mar. 1998

  • Wireless Transmission of Huffman Code Using Parallel Weighted DS/SS Modulation

    • S. Makido, T. Yamazato, M. Katayama and A. Ogawa
    • Technical Report of IEICE, vol.IT97-90,SST97-117, pp.19-24 (1998-03)
    • Mar. 1998

  • A Simple Model of Cyclostationary Power-line Noise for Communication Systems

    • O. Ohno, M. Katayama, T. Yamazato and A. Ogawa
    • International Symposium on Power-Line Communications and its Applications, pp.115-222, Tokyo, Japan
    • Mar. 1998

  • The Effect of Channel Error on H.263 Image Transmission

    • M. Honjo, S. Makido, T. Yamazato, M. Katayama and A. Ogawa
    • 1998 IEICE General Conference, vol. B-5-234, pp. 598
    • Mar. 1998

  • Performance Analysis of a Multi Processing-Gain CDMA System with Adaptive Array Antenna at Base Station

    • A. Morimoto, M. Katayama, T. Yamazato and A. Ogawa
    • Technical Report of IEICE, vol.AP97-215, pp.101-108 (1998-02)
    • Feb. 1998

  • Wireless Transmission of Huffman Code Using DS/SS modulation

    • S. Makido, T. Yamazato, M. Katayama, A. Ogawa
    • Technical Report of IEICE, vol.CS97-173,, pp.37-42 (1998-01)
    • Jan. 1998

  • Performance Analysis of a Multi Processing-Gain CDMA System with Interference Cancellation

    • L. Zhang, M. Katayama, T. Yamazato and A. Ogawa
    • Technical Report of IEICE, vol.CS97-165, pp.119-124 (1998-01)
    • Jan. 1998

  • Constant Amplitude Orthogonal Multi-Code CDMA System

    • T. Wada, T. Yamazato, M. Katayama and A. Ogawa
    • Asia-Pacific Conference on Communications (APCC), vol.1, pp.362-366, Sydney
    • Dec. 1997

  • A Spread-Spectrum System with Dual Processing Gains Designed for Cyclic Noise in Power Line Communications

    • H. Niwa, O. Oono, M. katayama, T. Yamazato, A. Ogawa, N. Isaka
    • IEICE Transaction on Fundamentals, vol.E80-A, no.12, pp.2526-2533
    • Dec. 1997

  • Performance Analysis of CDMA ALOHA Systems with Finite Buffer

    • Hiraku Okada, Takaya Yamazato, Masaaki Katayama, Akira Ogawa
    • The 20th Symposium on Information Theory and Its Applications, 4-3-6, pp.409-412 (1997-12)
    • Dec. 1997

  • A Simple Transmit/Receive Antenna Diversity for Indoor DS/CDMA Wireless Communication Systems

    • K. Ban, M. Katayama, T. yamazato and A. Ogawa
    • IEICE Transaction on Communications, vol.E80-B, no.12, pp.1790-1796
    • Dec. 1997

  • Effects of Transmission Control in an Integrated Voice and Data CDMA System

    • T. Sato, S. Abbas, T. Yamazato, M. Katayama, A. Ogawa
    • IEICE Transaction on Fundamentals, vol.E80-A, no.12, pp.2500-2516
    • Dec. 1997

  • Quasi-Synchronous CDMA ALOHA System Using the Sequences Generated from Orthogonal Gold Sequences

    • Masato Saito, Takaya Yamazato, Masaaki Katayama, Akira Ogawa
    • The 20th Symposium on Information Theory and Its Applications, 5-4-5, pp.589-592 (1997-12)
    • Dec. 1997

  • A Study on Error Correcting Capability of Constant Amplitude Coding for Orthogonal Multi-Code CDMA Systems

    • Tadahiro Wada, Takaya Yamazato, Masaaki Katayama, Akira Ogawa
    • The 20th Symposium on Information Theory and Its Applications, 5-4-6, pp.593-596 (1997-12)
    • Dec. 1997

  • Performance Evaluation of DS-CDMA Communication Systems Modulated with pi/2-Shift BPSK over Multipath Rayleigh Fading Channels

    • M. M. Asadullah Galib, Takaya Yamazato, Masaaki Katayama, Akira Ogawa
    • The 20th Symposium on Information Theory and Its Applications, 5-4-7, pp.597-600 (1997-12)
    • Dec. 1997

  • A Constant Amplitude Coding for Orthogonal Multi-Code CDMA Systems

    • T. Wada, T. Yamazato, M. Katayama, A. Ogawa
    • IEICE Transaction on Fundamentals, vol.E80-A, no.12, pp.2477-2484
    • Dec. 1997

  • Multi-Antenna Transmission Scheme for Convolutionally Coded DS/CDMA System

    • K. Ban, M. Katayama, W .E .Stark, T. Yamazato, A. Ogawa
    • IEICE Transaction on Fundamentals, vol.E80-A, no.12, pp.2437-2444
    • Dec. 1997

  • Influence of Multiple-Access Interference in a Multi Processing-Gain SSMA System

    • H. Hiraiwa, M. Katayama, T. Yamazato and A. Ogawa
    • Asia-Pacific Conference on Communications (APCC), vol.3, pp.1611-1615, Sydney
    • Dec. 1997

  • [Invited Paper] CDMA for Personal Communications Based on Low Earth Orbital Satellite Systems

    • A. Ogawa, M. Katayama, T. Yamazato, A. Jamalipour
    • IEICE Transaction on Fundamental, vol.E80-A, no.12, pp.2347-2356
    • Dec. 1997
    • This paper is concerned with CDMA applied to personal and mobile communications on a global basis using multiple low earth orbital satellites (LEOS). We focus our attention on some unique aspects of LEOS systems and discuss their influences on the CDMA system performance as well as the techniques for coping with these aspects. We deal with three kinds of important items that are unique to LEOS systems; Doppler frequency shift due to satellite movement, propagation delay affecting packetized data transmission and geographical nonunifomity in traffic.

  • Convolutionally Coded DS/CDMA System using Multi-Antenna Transmission,

  • An Initial Acquisition Method for M-ary Spread-Spectrum Signals Using Hadamard Code Sequences

    • T. Wada, T. Yamazato, M. Katayama,A. Ogawa
    • IEICE Transaction on Fundamentals, vol.E80-A, no.11, pp.2172-2179
    • Nov. 1997

  • Effects of Transmission Control Considering Voice Activation in an Integrated Voice and Data CDMA System

    • T. Sato, S. Abbas, T. Yamazato, M. Katayama and A. Ogawa
    • Fourth European Conference on Satellite Communications, pp.176-181, Roma, Italy
    • Nov. 1997

  • System Capacity of an Integrated Voice and Data CDMA Network in Channel Load Sensing Protocol

  • A Proposal of SS Communication System Using LEO Satellite for Observing Ecology of Sea Turtle

  • Onboard Data Processing System for Sea Turtle Ecological Observation System Using Low Earth Orbit Satellite

    • T. Kitamura, T. Tokuyasu, T. Yamazato, M. Katayama, A. Ogawa
    • 1997 Tokai Section Joint Convention of the Institutes of Electrical and Related Engineers, 506
    • Sep. 1997

  • Transmission Antenna for Sea Turtles in Ecological Observation System Using Low Earth Orbit Satellite

    • Y Amano, T. Tokuyasu, T. Yamazato, M. Katayama A. Ogawa
    • 1997 Tokai Section Joint Convention of the Institutes of Electrical and Related Engineers, 507
    • Sep. 1997

  • A Study of Marine Turtle Ecology Observation System Using Low Orbit Orbiting Satellite

    • T. Tokuyasu, T. Yamazato, M. Katayama, A. Ogawa
    • 1997 Tokai Branch Joint Convention of the Institutes of Electrical and Related Engineers, 505
    • Sep. 1997

  • Influence of Amplitude Variation in Multicode CDMA System

    • A. Fujiwara, T. Yamazato, M. Katayama, A. Ogawa
    • 1997 Tokai Section Joint Convention of Institutes of Electrical and Related Engineers, 509
    • Sep. 1997

  • Performance Analysis of the CDMA Unslotted ALOHA Systems with Finite Population and Fixed Packet Length

    • H. Okada, T. Yamazato, M. Katayama and A. Ogawa
    • 1997 IEICE General Conference, vol.A-5-11, pp.112
    • Sep. 1997

  • Proposal of a Diversified Synchronous Acquisition Method for Spread Spectrum Signals under Rayleigh Fading

    • Y. Ikai, M. Katayama, T. Yamazato, A. Ogawa
    • 1997 Tokai Section Joint Convention of Institutes of Electrical and Related Engineers, 508
    • Sep. 1997

  • A Study on the Capacity of a Multi Processing-Gain SSMA System

    • L. Zhang, M. Katayama, T. Yamazato and A. Ogawa
    • Technical Report of IEICE, vol.SST97-59, pp.19-24 (1997-09)
    • Sep. 1997

  • A study on the performance of CDMA ALOHA system under a cellular environment

    • Y. Asai, T. Yamazato, M. Katayama and A. Ogawa
    • Technical Report of IEICE, vol.SST97-96, pp.7-12 (1997-09)
    • Sep. 1997

  • A Study on CDMA-Unslotted ALOHA with Data Packets Over CDMA Voice Signals

    • A. Sandouk, T. Sato, T. Yamazato, M. Katayama and A. Ogawa
    • Technical Report of IEICE, vol.SST97-27, pp.43-48 (1997-07)
    • Sep. 1997

  • pi/2-shift BPSK - A Modulation Scheme Robust to Nonlinear Amplification for CDMA Mobile Communication

    • K. Kashyap, T. Wada, M. Katayama, T .Yamazato, A .Ogawa
    • IEICE Transaction on Fundamentals, vol.E80-A, no.9, pp.1634-1639
    • Sep. 1997

  • Simultaneous Estimation of Code and Frequency of DS/SS Signals of Multiple-LEO-Satellite Communication Systems

    • M. Ishidu, M. Katayama, T. Yamazato and A. Ogawa
    • IEEE International Symposium on Personal, Indoor and Mobile Radio Communication (PIMRC), pp.1019-1027, Helsinki, Finland
    • Sep. 1997
    • https://doi.org/10.1109/PIMRC.1997.627040

  • Performance Analysis of CDMA-Unslotted ALOHA Operating over CDMA Voice Signals

    • A. Sandouk, T. Sato, T. Yamazato, M. Katayama and A. Ogawa
    • IEEE Pacific Rim Conference on Communications, Computers and Signal Processing, pp.603-606, Victoria. B.C, Canada
    • Aug. 1997
    • https://doi.org/10.1109/PACRIM.1997.620335

  • A Modeling of the Noise for Power Line Communication Systems

    • O. Ohno, M. Katayama, T. Yamazato, and A. Ogawa
    • Technical Report of IEICE, vol.SST97-21,CS97-46, pp.7-12 (1997-07)
    • Jul. 1997

  • A Study on Wireless Transmission of MPEG Encoded Image Signals Using DS/SS Modulation

    • S. Makido, T. Yamazato, M. Katayama and A. Ogawa
    • Technical Report of IEICE, vol.SST97-26,CS97-51, pp.37-42 (1997-07)
    • Jul. 1997

  • Performance Analysis of Integrated Voice and Data System in CDMA Unslotted ALOHA with Channel Load Sensing

    • T. Sato, S. Abbas, T. Yamazato, M. Katayama and A. Ogawa
    • International Technical Conference On Circuits/Systems, Computers And Communications, vol.2, pp.853-856, Okinawa, Japan
    • Jul. 1997

  • Effect of Non-uniform Traffic and Power Control on CDMA Unslotted ALOHA system

    • T. Yamazato, Y. Asai, M. Katayama and A. Ogawa
    • International Technical Conference On Circuits/Systems, Computers And Communications, vol.2, pp.857-860, Okinawa, Japan
    • Jul. 1997

  • A Study on Orthogonal Multi-Code CDMA Systems Using Constant Amplitude Coding

    • T. Wada, T. Yamazato, M. Katayama and A. Ogawa
    • Technical Report of IEICE, vol.SSE97-40,RCS97-35, pp.19-24 (1997-06)
    • Jun. 1997

  • Multi-Antenna Transmission Scheme for a Convolutionally Coded DS/CDMA System

    • K. Ban, M. Katayama, T. Yamazato, and A. Ogawa
    • Technical Report of IEICE, vol.SST97-1,SAT97-13, pp.1-6 (1997-06)
    • Jun. 1997

  • Influence of Multiple-Access Interference in a Multi Processing-Gain SSMA System

    • H. Hiraiwa, M. Katayama, T. Yamazato, and A. Ogawa
    • Technical Report of IEICE, vol.SST97-2,SAT97-14, pp.7-12 (1997-06)
    • Jun. 1997

  • Prospective Performance of LEO Satellite Systems Employing Spread-Spectrum Techniques

    • A. Jamalipour, M. Katayama, T. Yamazato, and A. Ogawa
    • Technical Report of IEICE, vol.SST97-18,SAT97-30, pp.31-38 (1997-06)
    • Jun. 1997

  • An Initial Acquisition Method for Observing Ecology of Sea Animals Using LEO Satellite

    • T. Tokuyasu, T. Yamazato, M. Katayama and A. Ogawa
    • Technical Report of IEICE, vol.SANE97-8,SAT97-8, pp.45-50 (1997-04)
    • Apr. 1997

  • Simultaneous Acquisition of DS/SS Signals with Doppler Shift in Multi-LEO-Satellite Communication Systems

    • M. Ishizu, M. Katayama, T. Yamazato, and A. Ogawa
    • Technical Report of IEICE, vol.AP97-15,SANE97-6,SAT97-6, pp.35-40 (1997-04)
    • Apr. 1997

  • Throughput Analysis of CDMA-Unslotted ALOHA System With Voice and Data Packets

    • Abbas SANDOUK, Takeshi SATO, Takaya YAMAZATO, Masaaki KATAYAMA, and Akira OGAWA
    • 1997 IEICE General Conference, vol.A-5-14
    • Mar. 1997

  • The Effect of Throughput Performance in the CDMA Unslotted ALOHA with Optimal Access Control Protocol by Access Timing Delay

    • H. Okada, T. Sato, T. Yamazato, M. Katayama and A. Ogawa
    • 1997 IEICE General Conference, vol.B-5-39, pp.426
    • Mar. 1997

  • An Integration of Voice and Data in CDMA Unslotted ALOHA with Channel Load Sensing

    • T. Sato, A. Sandouk, T. Yamazato, M. Katayama and A. Ogawa
    • Technical Report of IEICE, vol.SST96-105, pp.43-48 (1997-03)
    • Mar. 1997

  • An Analytically Estimation of DS/SS/CDMA Using GMSK

    • T. Ishiguro, T. Yamazato, M. Katayama, and A. Ogawa
    • IEICE Transaction on Communications, vol.J80-BII, no.1, pp.131-136
    • Jan. 1997

  • An Improvement of Performance of DS/SS/CDMA with GMSK

    • T. Ishiguro, T. Yamazato, M. Katayama, and A. Ogawa
    • IEICE Transaction on Communications, vol.J80-BII, no.1, pp.18-26
    • Jan. 1997

  • Bit Interleaved Trellis Coded 16DAPSK on Fading Channels

    • H. Nakagawa, T. Yamazato, M. Katayama, and A. Ogawa
    • IEICE Transaction on Communications, vol.J80-BII, no.1, pp.1-9
    • Jan. 1997

  • Throughput Improvement of CDMA Slotted ALOHA System

    • M. Saito, H. Okada, T. Sato, T. Yamazato, M. Katayama, A. Ogawa
    • IEICE Transaction on Communications, vol.E80-B, no.1, pp.74-80
    • Jan. 1997

  • DS/SS/GMSK with Differential Detection over Multipath Rayleigh Fading Channels

    • I. Wakaki, T. Ishiguro, T. Yamazato, M. Katayama, A. Ogawa
    • IEICE Transaction on Fundamentals, vol.E79-A, no.12, pp.1957-1962
    • Dec. 1996

  • Throughput of CDMA ALOHA in Cellular Environment

    • T. Yamazato, Y. Asai, A. Jamalipour, M. Katayama, A. Ogawa
    • SITA'96, D-4-2, pp.313-316 (1996-12)
    • Dec. 1996

  • Transmission Characteristics of Band-Limited Signals for DS/SS/CDMA

    • A. Ogawa, K. Kashyap, T. Wada, M. Katayama and T. Yamazato
    • Asia-Pacific Microwave Conference, vol.4, E12.INV2, pp.1329-1332
    • Dec. 1996

  • Transmit Permission Control on Spread ALOHA Packets in LEO Satellites Systems

    • A. Jamalipour, M. Katayama, T. Yamazato, A. Ogawa
    • IEEE Journal on Selected Areas in Communications, vol.14, no.9, pp.1748-1757
    • Dec. 1996

  • Approximation Method for CDMA Unslotted ALOHA Systems with Fixed Packet Length

    • H. Okada, T. Sato, T. Yamazato, M. Katayama and A. Ogawa
    • Technical Report of IEICE, vol.SST96-61, pp.13-18 (1996-12)
    • Dec. 1996

  • CDMA ALOHA Systems with Modified Channel Load Sensing Protocol for Satellite Communications

    • H. Okada, M. Saito, T. Sato, T. Yamazato, M. Katayama, A. Ogawa
    • IEICE Transaction on Fundamentals, vol.E79-A, no.12, pp.2035-2042
    • Dec. 1996
    • The one of the problems in the satellite packet communication system is the existence of a long time delay, which may cause an improper packet access control resulting in a great deal of degradation of the system performance. In this paper, we clarify the effect of long time delay on the performance of CDMA ALOHA systems and then propose a new access control protocol, called Modified Channel Load Sensing Protocol (MCLSP), for the CDMA ALOHA systems. As a result, we show that a significant improvement in the throughput performance was obtained with MCLSP even in the presence of a long time delay.

  • A New M-ary/SSMA Scheme Applicable in LEO Satellite Systems

  • Performance Evaluation of CDMA ALOHA Systems with Modified Channel Load Sensing Protocol

    • H. Okada, M. Saito, T. Sato, T. Yamazato, M. Katayama and A. Ogawa
    • IEEE Global Telecommunications Conference (GLOBECOM), vol.2, pp.1291-1295, London, UK
    • Nov. 1996
    • https://doi.org/10.1109/GLOCOM.1996.587653
    • The one of the problems that arise in the satellite packet communication system is the existence of a long access timing delay. In this paper, we clarify the effect of this access timing delay on the performance of CDMA ALOHA systems and then propose a new access control protocol, called Modified Channel Load Sensing Protocol (MCLSP), for the CDMA ALOHA systems. As a result, we found that by employing MCLSP, a significant improvement in the throughput performance was obtained even in the presence of a long access timing delay.

  • Throughput Improvement of CDMA Slotted ALOHA Systems by Modified Channel Load Sensing Protocol

    • M. Saito, H. Okada, T. Sato, T. Yamazato, M. Katayama and A. Ogawa
    • IEEE International Symposium on Personal, Indoor and Mobile Radio Communications (PIMRC), vol. 1, no. C1.5, pp.103--107, Taipei, Taiwan, ROC
    • Oct. 1996
    • https://doi.org/10.1109/PIMRC.1996.567525

  • Improvement of Throughput Characteristics of CDMA ALOHA Scheme under Multipath Fading

    • Y. Asai, K. Nishida, T. Yamazato, M. Katayama, A. Ogawa
    • 1996 Tokai Section Joint Convention of Institutes of Electrical and Related Engineers, 511
    • Oct. 1996

  • The Performance of CDMA System Using π/4-shift QPSK and π/2-shift BPSK with the Nonlinearity of HPA

    • K. Kashyap, T. Wada, M. Katayama, T. Yamazato and A. Ogawa
    • IEEE International Symposium on Personal, Indoor and Mobile Radio Communications (PIMRC), pp.492-496
    • Oct. 1996
    • https://doi.org/10.1109/PIMRC.1996.567443

  • The Receiver with an Adaptive Array Antenna and Satellite Diversity for Low Earth-Orbital Multiple Satellite Communication Systems

  • A Study of the Receiver for Observing Ecology of Sea Animals Utilizing Low Orbit Satellite

    • T. Tokuyasu, T. Wada, T. Yamazato, M. Katayama and A. Ogawa
    • Technical Report of IEICE, vol.SANE96-64, pp.67-72 (1996-10)
    • Oct. 1996

  • A New Acquisition Scheme for the DS/SS Signal with Large Carrier Frequency Offset

    • S. Okuda, M. Katayama, T. Yamazato, A. Ogawa
    • IEICE Transaction on Fundamentals, vol.J79-A, no.10, pp.1725-1733
    • Oct. 1996

  • The DS/CDMA System using Transmission Diversity for Indoor Wireless Communications

    • K. Ban, M. Katayama, T. Yamazato and A. Ogawa
    • IEEE International Symposium on Personal, Indoor and Mobile Radio Communications (PIMRC), vol.2, pp.802-812, Taipei, Taiwan
    • Oct. 1996
    • https://doi.org/10.1109/PIMRC.1996.568393

  • Coordinate Interleaving Trellis Coded QPSK with T-algorithm on Rayleigh Fading Cannels

    • H. Nakamura, T. Yamazato, M. Katayama, A. Ogawa
    • IEICE Transaction on Communications, vol.E79-B, no.9, pp.1248-1255
    • Sep. 1996

  • A New M-ary Spread-Spectrum Multiple-Access Scheme in the Presence of Carrier Frequency Offset

    • T. Wada, T. Yamazato, M. Katayama, A. Ogawa
    • IEICE Transaction on Fundamentals, vol.E79-A, no.9, pp.1415-1422
    • Sep. 1996

  • Performance Degradation due to the Access Timing Delay on CDMA Unslotted ALOHA with Channel Load Sensing

    • T. Sato, H. Okada, T. Yamazato, M. Katayama and A. Ogawa
    • IEEE International Conference on Universal Personal Communications (ICUPC), vol.1, pp.111-114, Massachusetts, U.S.A.
    • Sep. 1996
    • https://doi.org/10.1109/ICUPC.1996.557772

  • Throughput of CDMA Unslotted-ALOHA System in Cellular Environment

    • A. Ogawa, T. Yamazato, K. Nishida, H. Okada, T. Sato and M. Katayama
    • Japan-Canada International Workshop on Multimedia Wireless Communications and Computing, pp.23-24
    • Sep. 1996

  • Effects of Multiple Access Interference in a Multi-Rate SSMA System

    • M. Ichiba, M. Katayama, T. Yamazato, A. Ogawa
    • IEICE Transaction on Communications, vol.E79-B, no.9, pp.1333-1338
    • Sep. 1996

  • A Study of The System for Observing Ecology of Sea Animals Utilizing Low Orbit Satellite

    • T. Tokuyasu, T. Yamazato, M. Katayama and A. Ogawa
    • 1996 Society Conference of IEICE, vol.SB-2-12
    • Sep. 1996

  • Performance of Bit-by-Bit Interleaved Trellis Coded 16DAPSK on Rayleigh Fading Channel

  • DS/SS/GMSK with Differential Detection over Multipath Rayleigh Fading Channels

  • A New Initial Acquisition Methods for M-ary Spread-Spectrum Communication Systems

    • T. Wada, T. Yamazato, M. Katayama and A. Ogawa
    • International Symposium on Information Theory and Its Applications (ISITA), pp.770-773
    • Sep. 1996

  • A Spread-Spectrum System with Dual Processing Gains Designed for Cycric Noise in Power line Communications

  • Effects of the Access Timing Delay on CDMA Unslotted ALOHA with Channle Load Sensing

    • T. Sato, H. Okada, T. Yamazato, M. Katayama, A. Ogawa
    • IEICE Transaction on Communications, vol.E79-B, no.9, pp.1339-1345
    • Sep. 1996

  • On the Average Delay-Throughput Performance Improvement of LEO Satellite Systems by Adaptive Transmit Permission Control Scheme

    • A. Jamalipour, M. Katayama, T. Yamazato and A. Ogawa
    • XXVth General Assembly of the International Union of Radio Science, C8.3, p157
    • Aug. 1996

  • DS/SS/GMSK with Differential Detection over Multipath Rayleigh Fading Channels

    • I. Wakaki, T. Yamazato, M. Katayama and A. Ogawa
    • Technical Report of IEICE, vol.SST96-34, pp.37-42 (1996-7)
    • Jul. 1996

  • A Novel Access Control Method for CDMA Unslotted ALOHA Systems

    • H. Okada, T. Sato, T. Yamazato, M. Katayama and A. Ogawa
    • 2nd International Workshop on Multi-Dimensional Mobile Communications, pp.391-395, Seoul, Korea
    • Jul. 1996
    • A novel access control method for CDMA unslotted ALOHA systems is presented. We analyze the throughput performance considering packet retransmission and the stability of the systems. Based on these results, we propose an optimal access control protocol (OACP). The OACP is the method controlling the packet transmission and the packet retransmission. As a result, we indicate that the throughput performance with OACP is better before.

  • CDMA Unslotted ALOHA Systems with Packet Retransmission Control

    • H. Okada, T. Sato, T. Yamazato, M. Katayama, A. Ogawa
    • IEICE Transaction on Fundamentals, vol.E79-A, no.7, pp.1004-1010
    • Jul. 1996
    • In this paper, we analyze the throughput and delay performances of the CDMA unslotted ALOHA system considering packet retransmission. We also clarify the stability of the system. Based on these results, we propose the optimal retransmission control (ORC) to improve the performances. The ORC is the scheme to prevent the system from drifting to an undesirable operating point by controlling the birth rate of retransmitted packets. As a result, it is shown that the throughput and delay performances of the system with the ORC are better than without the ORC and the system does not drift to an undesirable operating point.

  • Throughput Performance Improvement of Spread-Slotted Aloha in Mobile Satellite Communications

  • A Study on an Initial Acquisition Method for M-ary Spread-Spectrum Signals with Carrier Frequency Offset

    • T. Wada, T. Yamazato, M. Katayama and A. Ogawa
    • Technical Report of IEICE, vol.SST96-14, pp.81-86 (1996-6)
    • Jun. 1996

  • Throughput Analysis of DS/SSMA Unslotted ALOHA System with Fixed Packet Length

    • T. Sato, H. Okada, T. Yamazato,M. Katayama, A. Ogawa
    • IEEE Journal on Selected Areas in Communications, vol.14, no.4, pp.750-756
    • May 1996

  • A Block Demodulator for Low Earth-Orbital Satellite Communication System with Large Doppler Shift

    • M. Ise, M. Katayama, T. Yamazato and A. Ogawa
    • IEEE Vehicular Technology Conference(not included in proceedings)
    • Apr. 1996

  • The DS/SS System using Transmission Diversity for Indoor Wireless Communications

    • K. Ban, M. Katayama, T. Yamazato and A. Ogawa
    • 1996 IEICE General Conference, vol.A-235 (1996-3)
    • Mar. 1996

  • Throughput Analysis of CDMA ALOHA System in Fading Channel with Near-Far Problem

    • K. Nishida, H. Okada, T. Sato, T. Yamazato, M. Katayama and A. Ogawa
    • 1996 IEICE General Conference, vol.SA-5-4, pp.472
    • Mar. 1996

  • A Study of Multiple Access Interference Using M-ary/SS/CDMA Signals

    • H. Kojima, T. Wada, T. Yamazato, M. Katayama and A. Ogawa
    • Technical Report of IEICE, vol.SST95-141, pp.65-70 (1996-3)
    • Mar. 1996

  • A Study on Code Division Duplex (CDD) for Distributed CDMA Networks

    • H. Asada, K. Sato, T. Yamazato, M. Katayama and A. Ogawa
    • Technical Report of IEICE, vol.SST95-145, pp.89-94 (1996-3)
    • Mar. 1996

  • A study on the performance of the CDMA system using pi/4-shift QPSK and pi/2-shift BPSK

    • K. Kashyap, T. Wada, M. Katayama, T. Yamazato and A. Ogawa
    • Technical Report of IEICE, vol.SST95-127, pp.95-100 (1996-3)
    • Mar. 1996

  • Adaptive Transmit Permission Control on Spread-Slotted Aloha Packets Applicable in LEO Systems

    • A. Jamalipour, M. Katayama, T. Yamazato, A. Ogawa
    • IEICE Transaction on Communications, vol.E79-B, no.3, pp.257-265
    • Mar. 1996

  • Throughput Performance of CDMA Unslotted ALOHA using Error Correcting Code

    • T. Yamazato, K. Nishida, T. Sato, H. Okada, M. Katayama and A. Ogawa
    • 1996 IEICE General Conference, vol.SA-5-3
    • Mar. 1996

  • A Modified Power Control Scheme for Remedying the Effects of Traffic Nonuniformity in LEO Satellite Communications Systems

    • A. Jamalipour, M. Katayama, T. Yamazato, A. Ogawa
    • IEEE International Journal of Wireless Information Networks, vol.3, no.1, pp.29-39
    • Jan. 1996

  • Quasi-Synchronous CDMA with Binary Shift-Register Sequences

    • S. Kuno, T. Yamazato,M. Katayama, A. Ogawa
    • IEICE Transaction on Fundamentals, vol.J79-A, no.1, pp.105-114
    • Jan. 1996

  • Parallel Acquisition of a Direct-Sequence Spread-Spectrum Signal with Frequency Offset

    • M. Mizutani, M. Katayama, T. Yamazato, A. Ogawa
    • IEICE Transaction on Fundamentals, vol.J79-A, no.1, pp.98-104
    • Jan. 1996

  • Performance Analysis of CDMA ALOHA

    • T. Yamazato, T. Sato, H. Okada, K. Nishida, M. Katayama and A. Ogawa
    • International Symposium on Communications (ISOCOM), pp.434-441
    • Dec. 1995

  • A Study on Improvement of Performance of CDMA with DS/SS/GMSK

    • T. Ishiguro, T. Yamazato, M. Katayama and A. Ogawa
    • International Symposium on Communications (ISCOM), pp.605-612
    • Dec. 1995

  • Throughput Analysis of Spread-Slotted ALOHA in LEO Satellite Communication Systems with Nonuniform Traffic Distribution

    • A. Jamalipour, M. Katayama, T. Yamazato, A. Ogawa
    • IEICE Transaction on Communications, vol.E78-B, no.12, pp.1657-1665
    • Dec. 1995

  • A Spread-Spectrum System with Dual Processing Gains Designed for Cyclic Noise in Power Line Communications

    • H. Niwa, M. Katayama, T. Yamazato, A. Ogawa and N. Isaka
    • Technical Report of IEICE, vol.SST95-95, pp.31-36 (1995-12)
    • Dec. 1995

  • Throughput performance of Spread Slotted ALOHA System with Modified Channel Load Sensing Protocol

    • M. Saito, H. Okada, T. Sato, T. Yamazato, M. Katayama and A. Ogawa
    • Technical Report of IEICE, vol.SAT95-83, pp.67-72 (1995-12)
    • Dec. 1995

  • A New Access Control Method for Spread Unslotted ALOHA Systems

    • H. Okada, T. Sato, T. Yamazato, M, Katayama and A. Ogawa
    • Technical Report of IEICE, vol.SST95-101, pp.67-72 (1995-12)
    • Dec. 1995

  • Performance Analysis of DS/SSMA with Error Correcting Code in Rayleigh Fading Channel

  • Throughput of DS/SS unslotted ALOHA system with channel load sensing

  • A Study on Non-Coherent Reception of M-ary Spread-Spectrum Signals in the Presence of Carrier Frequency Offset

  • Throughput and Delay Analysis of DS/SSMA Unslotted Aloha by Non-perfect Capture

  • A Study on M-ary Spread-Spectrum Scheme Using Pseudo Noise Sequences in the Presence of Carrier Frequency Offset

    • T. Wada, T. Yamazato, M. Katayama, and A. Ogawa
    • Symposium on Information Theory and Its Applications (SITA), C-6-3, pp.597-600 (1995-10)
    • Oct. 1995

  • Performance of Bit Interleaved Trellis Coded 16DAPSK in Land Mobile Radio Communicatinon

    • H. Nakagawa, T. Yamazato, M. Katayama, A. Ogawa
    • Symposium on Information Theory and Its Applications (SITA), D-3-1, pp.297-300 (1995-10)
    • Oct. 1995

  • Adaptive Transmission Control Scheme for Spread-Slotted Aloha Mobile Satellite Communication Systems

    • Abbas Jamalipour, M. Katayama, T. Yamazato, A. Ogawa
    • Symposium on Information Theory and Its Applications (SITA), C-8-4, pp.777-780 (1995-10)
    • Oct. 1995

  • A Study of DS/SS/GMSK with Differential Detection

    • I. Wakaki, T. Ishiguro, T. Yamazato, M, Katayama and A. Ogawa
    • Technical Report of IEICE, vol.SST95-85, pp.25-30 (1995-10)
    • Oct. 1995

  • Comparison of ALOHA and Diffusion ALOHA Methods

    • Kunio Nishida, Hiraku Okada, Takeshi Sato, Takaya Yamazato, Masaaki Katayama, Akira Ogawa
    • 1995 Tokai Section Joint Convention of Institutes of Electrical and Related Engineers, 537
    • Sep. 1995

  • Initial Synchronization Capture Characteristics of Spread Signals Using Segmented MFs in the Case of Imperfect Chip Synchronization

    • M. Ishizu, S. Okuda, M. Katayama, T. Yamazato, A. Ogawa
    • 1995 Tokai Section Joint Convention of Institutes of Electrical and Related Engineers, 538
    • Sep. 1995

  • Non-coherent Reception of M-ary Spread-Spectrum Signals in the presence of Carrier Frequency Offset

    • T. Wada, T. Yamazato, M. Katayama and A. Ogawa
    • IEICE Transaction on Fundamentals, vol.E78-A, no.9, pp.1102-1108
    • Sep. 1995

  • A Preliminary Study of a Multimedia SSMA System Considering the Interactions between the Signals

  • A New Block Demodulator for DS/SS Signal with Carrier Frequency Offset

  • Coordinate-by-coordinate Interleaved Trellis Coded QPSK with T-algorithm on Rayleigh Fading Channels

  • A Doppler Frequency Estimation Scheme for Block Demodulators in LEO Satellite Communication Systems

    • M. Ise, M. Katayama, T. Yamazato and A. Ogawa
    • Technical Report of IEICE, vol.SAT95-47, pp.1-6 (1995-9)
    • Sep. 1995

  • An analytically estimation of GMSK spread spectrum communication system

    • T. Ishiguro, T. Yamazato, M. Katayama and A. Ogawa
    • Technical Report of IEICE, vol.SST95-49, pp.21-26 (1995-9)
    • Sep. 1995

  • A Time-Differential Transmission Diversity Scheme Using Spread Spectrum Signals

    • K. Ban, M. Katayama, T. Yamazato, A. Ogawa
    • 1995 Tokai Section Joint Convention of Institutes of Electrical and Related Engineers, 536
    • Sep. 1995

  • Performance of Bit-Interleaved Trellis Coded 16-QAM with Maximized Code Diversity

    • A. Aoyama, T. Yamazato, M. Katayama and A. Ogawa
    • IEICE Transaction on Fundamentals, vol.E78-A, no.9, pp.1215-1219
    • Sep. 1995

  • Throughput Analysis of Spread Unslotted Aloha System in Rayleigh Channel

    • T. Yamazato, T. Sato, H. Okada, M. Katayama and A. Ogawa
    • 1995 Society Conference of IEICE, vol.SB-4-2 (1995-9)
    • Sep. 1995

  • The Effect of Access Timing Delay on Spread Aloha with Channel Load Sensing

    • T. Sato, H. Okada, T. Yamazato, M. Katayama and A. Ogawa
    • Technical Report of IEICE, vol.SST95-47, pp.7-12 (1995-9)
    • Sep. 1995

  • A Study on Improvement of Performance of GMSK with DS/SS/CDMA

    • T. Ishiguro, T. Yamazato, M. Katayama and A. Ogawa
    • Technical Report of IEICE, vol.SST95-41, pp.43-48 (1995-7)
    • Jul. 1995

  • On Remedying the Traffic Nonuniformity Effects in LEO Satellite Communication Systems

  • Bit-by-bit Interleaved Trellis Coded MPSK with Differential Detection on Rayleigh Fading Channels

  • Bit-by-Bit Interleaved Trellis Coded Modulation with Differential Detection on Fading Channels

    • H. Nakagawa, T. Yamazato, M. Katayama and A. Ogawa
    • Technical Report of IEICE, vol.RCS95-47, pp.25-30 (1995-7)
    • Jul. 1995

  • A Receiver Structure with Adaptive Array Antennas for LEO Satellite Communication Systems

    • H. Sumino, M. Katayama, T. Yamazato and A. Ogawa
    • Technical Report of IEICE, vol.SAT95-18, pp.67-72 (1995-7)
    • Jul. 1995

  • Transmit Permission Control Scheme for Spread-Slotted ALOHA in LEO Satellite Communication Systems

    • A. Jamalipour, M. Katayama, T. Yamazato and A. Ogawa
    • Asia-Pacific Conference on Communications (APCC), 7E.4, pp.848-852
    • Jun. 1995

  • A Study on Non-Coherent Reception of M-ary/Spread-Spectrum Signals with Carrier Frequency Offset

    • T. Wada, T. Yamazato, M. Katayama and A. Ogawa
    • Technical Report of IEICE, vol.SST95-3, pp.13-18 (1995-5)
    • May 1995

  • A Differential Positioning Scheme witn a Single Satellite to be incorporated into Mobile Communications

    • Y. Yabumoto, T. Yamazato, M. Katayama and A. Ogawa
    • IEICE Transaction on Communications, vol.78-B, no.5, pp.297-305
    • May 1995

  • Performance Analysis of Spread Unslotted Aloha System Considering Packet Retransmission

    • H. Okada, T. Sato, T. Yamazato, M. Katayama and A. Ogawa
    • Technical Report of IEICE, vol.SST95-4, pp.19-24 (1995-5)
    • May 1995

  • CDMA Scheme and Mobile Communication Systems

    • A. Ogawa, M. Katayama, T. Yamazato, T. Mizuno
    • TRIKEPS
    • Apr. 1995

  • Diversity Effect on Coded Modulation System with Bit Interleaver

    • T. Yamazato, M. Katayama and A. Ogawa
    • 1995 IEICE General Conference, vol.B-396 (1995-3)
    • Mar. 1995

  • Throughput of Spread Unslotted Aloha System with Fixed Packet Lengths

    • T. Sato, T. Yamazato, M. Katayama and A. Ogawa
    • Technical Report of IEICE, vol.SST94-98, pp.31-36 (1995-3)
    • Mar. 1995

  • Throughput and Delay of Spread Unslotted Aloha System

    • H. Okada, T. Sato, T. Yamazato, M. Katayama and A. Ogawa
    • 1995 IEICE General Conference, vol.A-233 (1995-3)
    • Mar. 1995

  • Performance of an Integrated Voice/Data System in Nonuniform Traffic Low Earth-Orbit Satellite Communication Systems

    • A. Jamalipou, T. Yamazato, M. Katayama and A.Ogawa
    • IEEE Journal on Selected Areas in Communications, vol.13, no.2, pp.465-473
    • Feb. 1995

  • Influence of Crosscorrelation Properties on Simultaneous Transmission of Spread-Spectrum with Different Process Gains

    • M. Ichiba, M. Katayama, T. Yamazato and A. Ogawa
    • Technical Report of IEICE, vol.SST94-64, pp.27-32 (1994-12)
    • Dec. 1994

  • Effect of Nonlinear Amplification on a Spread Spectrum Signal and Receiver Configurations

    • M. Sawada, T. Yamazato, M. Katayama and A. Ogawa
    • IEICE Transaction on Fundamentals, vol.77-A, no.11, pp.1855-1862
    • Nov. 1994

  • A New Access Protocol for Asynchronous Packet CDMA Systems

    • A. Ogawa, T. Yamazato, M. Katayama and K. Toshimitsu
    • International Symposium on Information Theory and Its Applications (ISITA), pp.917-920
    • Nov. 1994

  • Near-Far Problem of Hybrid DS/SFH-SSMA with Multi-Level Power Control

    • T. Yamazato, Y. Shinkaji, M. Katayama and A. Ogawa
    • International Symposium on Information Theory and Its Applications (ISITA), pp.109-113
    • Nov. 1994

  • Performance of 16-QAM with Increased Diversity on Rayleigh Fading Channels

    • A. Aoyama, T. Yamazato, M. Katayama and A. Ogawa
    • International Symposium on Information Theory and Its Applications (ISITA), pp.1133-1137
    • Nov. 1994

  • Simultaneous Transmission of Spread-Spectrum Signals of Different Process Gains

  • Spread-Slotted ALOHA Throughput in Nonuniform Traffic Situation for LEO Satellite Communication Systems

  • A New Code Acquisition Scheme Using Divided Matched Filters for a DS/SS Signal with Frequency Offset

  • A Study on Reception of M-ary/Spread-Spectrum Signals with Carrier Frequency Offset

    • T. Wada, T. Yamazato, M. Katayama and A. Ogawa
    • The 17th Symposium on Information Theory and Its Applications, vol.W44-5, pp.417-420 (1994-11)
    • Nov. 1994

  • Signal-to-interference ratio of CDMA in low Earth-orbital satellite communication systems with nonuniform traffic distribution

  • Performance of DS/FH-CDMA Over Fading Channels with Near-Far Problem

    • Y. Shinkaji, T. Yamazato, M. Katayama and A. Ogawa
    • IEICE Transaction on Communications, vol.77-B, no.11, pp.681-690
    • Nov. 1994

  • Throughput Characteristics of Spread Unslotted Aloha Method

    • Hiraku Okada, Takeshi Sato, Takaya Yamazato, Masaaki Katayama, Akira Ogawa
    • 1994 Tokai Section Joint Convention of Institutes of Electrical and Related Engineers, 516
    • Oct. 1994

  • A New Acquisition Scheme for a DS/SS Signal with Frequency Offset

    • S. Okuda, T. Wada, T. Yamazato, M. Katayama and A. Ogawa
    • Technical Report of IEICE, vol.SST94-50, pp.19-24 (1994-10)
    • Oct. 1994

  • LEO Satellite Communication Systems under Nonuniform Traffic Distribution with Spread-Slotted ALOHA

    • A. Jamalipour, M. Katayama, T. Yamazato and A. Ogawa
    • Technical Report of IEICE, vol.SAT94-57, pp.15-21 (1994-10)
    • Oct. 1994

  • Simulation of the Effect of Sampling Error in SS System Using GMSK

    • I. Wakaki, T. Ishiguro, M. Katayama, T. Yamazato, A. Ogawa
    • 1994 Tokai Section Joint Convention of Institutes of Electrical and Related Engineers, 517
    • Oct. 1994

  • Near-Far Problem on Hybrid Direct-Sequence/Slow-Frequency-Hopping Spread-Spectrum Multiple-Access

  • Spectral Efficiency of DS/SS/GMSK System with RAKE

    • T. Ishiguro, M. Katayama, T. Yamazato, A. Ogawa and T. Maebara
    • 1994 IEICE Fall Conference, vol.A-146 (1994-9)
    • Sep. 1994

  • A Study on Reception of M-ary/Spread-Spectrum Signals with Carrier Frequency Offset

    • T. Wada, T. Yamazato, M. Katayama and A. Ogawa
    • 1994 IEICE Fall Conference, vol.A-145 (1994-9)
    • Sep. 1994

  • Differential Positioning with a Single Satellite

  • A Study on Reception of M-ary/Spread-Spectrum Signals with Carrier Frequency Offset

    • T. Wada, T. Yamazato, M. Katayama and A. Ogawa
    • Technical Report of IEICE, vol.SST94-41, pp.51-56 (1994-8)
    • Aug. 1994

  • A Study on Quasi-Synchronous CDMA Based on Selected PN Signature Sequences

  • Performance of CDMA with DS/SS/GMSK

  • A Study of M-algorithm combined with Pre-Decoding

    • H. Nakamura, T. Yamazato, M. Katayama and A. Ogawa
    • Technical Report of IEICE, vol.CS94-37, pp.7-12 (1994-6)
    • Jun. 1994

  • Multiple-Symbol Differential Detection on 16 Circular Shaped Signal Constellation

    • H. Nakagawa, T. Yamazato, M. Katayama and A. Ogawa
    • Technical Report of IEICE, vol.RCS94-36, pp.55-60 (1994-6)
    • Jun. 1994

  • Throughput of Spread Unslotted Aloha in an Additive White Gaussian Noise Channel

    • T. Sato, K. Toshimitsu, T. Yamazato, M. Katayama and A. Ogawa
    • Technical Report of IEICE, vol.SST94-9, pp.25-30 (1994-6)
    • Jun. 1994

  • Inter-chip interference rejection in DS/SS/GMSK applied RAKE

    • T. Ishiguro, M. Katayama, T. Yamazato, A. Ogawa and T. Maebara
    • Technical Report of IEICE, vol.SST94-10, pp.31-36 (1994-6)
    • Jun. 1994

  • A Novel Spread Slotted Aloha System with Channel Load Sensing Protocol

    • K. Toshimitsu, T. Yamazato, M. Katayama and A. Ogawa
    • IEEE Journal on Selected Areas in Communications, vol.12, no.4, pp.665-672
    • May 1994

  • Performance of Bit-by-Bit Interleaved Trellis-Coded 16QAM in Land Mobile Communications

    • K. Ohkawa, T. Yamazato and I. Sasase
    • 1994 IEICE Spring Conference, vol.B-358 (1994-3)
    • Mar. 1994

  • A Novel Variable Source Coding Algorithm Based on LZW Adopting Move to Front Method

    • S. Hayashi, J. Kubo, T. Yamazato and I. Sasase
    • 1994 IEICE Spring Conference, vol.A-370 (1994-3)
    • Mar. 1994

  • Throuput of Spread Unslotted Aloha System

    • T. Sato, K. Toshimitsu, T. Yamazato, M. Katayama and A. Ogawa
    • 1994 IEICE Spring Conference, vol.A-278 (1994-3)
    • Mar. 1994

  • Diversity Effect on Coded Modulation System in Rayleigh Channel

    • T. Yamazato, M. Katayama and A. Ogawa
    • 1994 IEICE Spring Conference, vol.A-364 (1994-3)
    • Mar. 1994

  • Acquisition of DS/SS Signal with Frequency Offset using Matched Filters

    • M. Mizutani, M. Katayama, T. Yamazato and A. Ogawa
    • Technical Report of IEICE, vol.SST93-109, pp.55-60 (1994-3)
    • Mar. 1994

  • A Study on Bit-Interleaved Coded Modulation for a Rayleigh Fading Channel

    • A. Aoyama, T. Yamazato, M. Katayama and A. Ogawa
    • Technical Report of IEICE, vol.IT93-116, pp.61-66 (1994-3)
    • Mar. 1994

  • Simultaneous Transmission of two Spread Spectrum Signals of Different Process Gains

    • A. Kakami, M. Katayama, T. Yamazato and A. Ogawa
    • Technical Report of IEICE, vol.SAT93-90, pp.17-24 (1994-2)
    • Feb. 1994

  • Configuration of the Receiver for Nonlinearly Amplified Spread Spectrum Signals in CDMA Systems

    • M. Sawada, M. Katayama, T. Yamazato and A. Ogawa
    • International Symposium on Nonlinear Theory and its Application (NOLTA), 7.5-5, pp.875-878
    • Dec. 1993

  • Performance of bit-by-bit interleaved trellis-coded 16QAM with PSAM in Rayleigh fading channels

    • Kouichi Ohkawa, Takaya Yamazato, Iwao Sasase and Shinsaku Mori
    • Malaysia International Conference on Communications (MICC), B7.2.1-B7.2.5, Kuala lumpur, Malaysia
    • Nov. 1993

  • Viterbi decoding with adaptive path reduction

    • T. Yamazato, M. Katayama, A. Ogawa
    • 1993 Tokai Section Joint Convention of the Institutes of Electrical and Related Engineers
    • Oct. 1993

  • Differential Positioning with a Single Satellite

    • Y. Yabumoto, T. Yamazato, M. Katayama and A. Ogawa
    • Technical Report of IEICE, vol.SAT93-59, pp.23-30 (1993-10)
    • Oct. 1993

  • A novel trellis coded modulation system without signal point expansion

    • Masaki Ariyoshi, Takaya Yamazato, Iwao Sasase and Shinsaku Mori
    • 2nd International Conference on Universal Personal Communications (ICUPC), pp.653-657, Ottawa, Canada
    • Oct. 1993
    • https://doi.org/10.1109/ICUPC.1993.528462

  • A Performance Analysis on the Effects of Traffic Non-Uniformity in Low Earth-Orbit Satellite Communication Systems

    • A. Jamalipour, M. Katayama, T. Yamazato and A. Ogawa
    • The 16th Symposium on Information Theory and Its Applications, vol.W33-3, pp.203-206 (1993-10)
    • Oct. 1993

  • Spread Aloha system which controls the packet transmission by the channel load

    • K. Toshimitsu, T. Yamazato, M. Katayama and A. Ogawa
    • Technical Report of IEICE, vol.SST93-49, pp.31-36 (1993-10)
    • Oct. 1993

  • One Way of Integrated Mobile Communication and Positioning System Using Three Satellites

    • M. Takeda, M. Katayama, T. Yamazato, A. Ogawa
    • 1993 Tokai Section Joint Convention of Institutes of Electrical and Related Engineers, 512
    • Oct. 1993

  • A New Viterbi Algorithm with Adaptive Path Reduction Method

    • Takaya Yamazato, Iwao Sasase, Shinsaku Mori
    • IEICE Transactions on Fundamentals, Vol.E 76-A, No.9, pp.1422-1429
    • Sep. 1993

  • Carrier Regeneration in a Block Demodulator for Low Earth-Orbital Satellite Communication Systems

    • Y. Uno, M. Katayama, T. Yamazato and A. Ogawa
    • Fourth International Symposium on Personal Indoor and Mobile Radio Communications, C3.6, pp.458-462
    • Sep. 1993

  • The Spread ALOHA System with Modified Channel Load Sensing Protocol

    • K. Toshimitsu, K. Yonekura, T. Yamazato, M. Katayama and A. Ogawa
    • 1993 IEICE Fall Conference, vol.A-124 (1993-9)
    • Sep. 1993

  • An Experiment of Superposed Transmission on Satellite Communication Channel using Spread Spectrum

    • A. Kakami, M. Katayama, T. Yamazato and A. Ogawa
    • 1993 IEICE Fall Conference, vol.SB-2-5 (1993-9)
    • Sep. 1993

  • Near-Far Effect on Coded DS/FH/SSMA

    • Y. Shinkaji, T. Yamazato, M. Katayama and A. Ogawa
    • Technical Report of IEICE, vol.SST93-33, pp.7-12 (1993-8)
    • Aug. 1993

  • Computational Carrier Regeneration for Low Earth-Orbital Satellite Communication Systems

    • Y. Uno, M. Katayama, T. Yamazato and A. Ogawa
    • Technical Report of IEICE, vol.SAT93-21, pp.13-18 (1993-8)
    • Aug. 1993

  • Block Demodulation for Low Earth-Orbital Satellite Communication Systems

    • M. Katayama, Y. Uno, T. Yamazato and A. Ogawa
    • XXIVth General Assembly of the International Union of Radio Science, C9-3, pp.124
    • Aug. 1993

  • A Study on Quasi-Synchronous Spread Spectrum

    • S. Kuno, T. Yamazato, M. Katayama and A. Ogawa
    • Technical Report of IEICE, vol.SST93-26, pp.43-48 (1993-8)
    • Aug. 1993

  • Effect of Nonlinear Amplifiers of Transmitters in the CDMA Systems Using Offset-QPSK

    • M. Sawada, T. Yamazato, M. Katayama and A. Ogawa
    • IEICE Transaction on Communications, vol.E76-B, no.7, pp.741-744
    • Jul. 1993

  • A Analytic Study on Superposed Transmission of Spread-Spectrum and Conventional QPSK Signals with Interference Cancellation

    • A. Kakami, M. Katayama, T. Yamazato and A. Ogawa
    • Technical Report of IEICE, vol.SST93-3, pp.13-18 (1993-6)
    • Jun. 1993

  • The Spread Slotted ALOHA System with Channel Load Sensing Protocol

    • K. Toshimitsu, T. Yamazato, M. Katayama and A. Ogawa
    • Technical Report of IEICE, vol.SST93-4, pp.19-24 (1993-6)
    • Jun. 1993

  • A novel detection technique for CPM using variable mapping method

    • Koji Nemoto, Takaya Yamazato, Iwao Sasase and Shinsaku Mori
    • IEEE Pacific Rim Conference on Communications, Computers and Signal Processing, vol.2, pp.573-576, Victoria, Canada
    • May 1993
    • https://doi.org/10.1109/PACRIM.1993.407296

  • A new source coding method based on LZW adopting the least recently used deletion heuristic

    • Sadataka Hayashi, Takaya Yamazato, Iwao Sasase and Shinsaku Mori
    • IEEE Pacific Rim Conference on Communications, Computers and Signal Processing, vol.1, pp.190-193, Victoria, Canada
    • May 1993
    • https://doi.org/10.1109/PACRIM.1993.407191

  • Reduced path Viterbi decoder with inverse circuit of the encoder

    • T. Yamazato, I. Sasase, S. Mori, M. Katayama and A. Ogawa
    • IEEE Pacific Rim Conference on Communications, Computers and Signal Processing, vol.2, pp.569-572, Victoria, BC, Canada
    • May 1993
    • https://doi.org/10.1109/PACRIM.1993.407297

  • Trellis Coded Modulation using Totally Overlapped Signal Sets

    • Masayuki Ariyoshi, Takaya Yamazato, Iwao Sasase, Shinsaku Mori
    • IEICE Transactions on Communications, Vol.E 76-B, No.3, pp.304-309
    • Mar. 1993

  • A fast Viterbi decoding using the information of most-frequent symbol of convolutional code

    • Takaya Yamazato, Iwao Sasase and Shinsaku Mori
    • International Symposium on Information Theory and Its Applications (ICCS/ISITA), pp.1302-1306, Singapore
    • Nov. 1992
    • https://doi.org/10.1109/ICCS.1992.255049

  • A novel source coding technique with high convergence speed based on the LZW algorithm

    • Junichi Kubo, Takaya Yamazato, Iwao Sasase , Shinsaku Mori
    • 15th Symposium on Information Theory and Its Applications, pp.429-432
    • Sep. 1992

  • A new trellis coded modulation using an arithmetic additional encoder

    • Masayuki Ariyoshi, Takaya Yamazato, Iwao Sasase , Shinsaku Mori
    • 15th Symposium on Information Theory and Its Applications, pp.153-156
    • Sep. 1992

  • Multilevel modulation / TCM schemes for coherent optical POLSK phase-diversity homodyne system

    • Ichiro Seto, Takaya Yamazato, Tomoaki Ohtsuki, Iwao Sasase , Shinsaku Mori
    • 15th Symposium on Information Theory and Its Applications, pp.401-404
    • Sep. 1992

  • Simple detection for CPFSK using variable mapping method

    • K. Nemoto, T. Yamazato, I. Sasase, S. Mori
    • Technical Report of IEICE, vol. rcs92-42, pp.31-34
    • Jul. 1992

  • Trellis coded modulation using totally overlapped signal sets

    • M. Ariyoshi, T. Yamazato, I. Sasase, S. Mori
    • Technical Report of IEICE, vol. rcs92-42, pp.35-40
    • Jul. 1992

  • Interlace Coding System Involvind Data Compaction Code, Data Encryption Code and Error Correcting Code

    • T. Yamazato, I. Sasase, S. Mori
    • IEICE Transactions, Vol. E 75-B, No.6, pp.458-465
    • Jun. 1992

  • Interlace coding system to avoid error propagation of source coding system

    • T. Yamazato, I. Sasase, S. Mori
    • International Conference on Selected Topics in Wireless Communications, pp.80-83, Vancouver, Canada
    • Jun. 1992
    • https://doi.org/10.1109/ICWC.1