IEEE Global Communications Conference (GLOBECOM) 2024, Capetown, South Africa
2024年12月
This paper proposes a transmitter that rearranges the 16-QAM constellation for a 1-bit ADC receiver. A 1-bit ADC receiver is more eco-friendly and lower-cost than receivers with a high-resolution ADC. However, in conventional 1-bit ADC receivers, severe degradation of SER (Symbol Error Rate) in high Es/N0 poses a critical problem. This degradation is due to the lack of noise power in high Es/N0, which prevents the receiver from sufficiently benefiting from stochastic resonance. To solve this issue, we propose a novel transmitter that rearranges a 16-QAM constellation based on the probability density function of noise. The rearrangement of constellations mitigates the nonlinearity of a 1-bit ADC, enabling reliable demodulation of multilevel signals in high Es/N0. Numerical examples demonstrate that the proposed transmitter achieves good SER performance across a wide range of Es/N0, even when a 1-bit ADC receiver is employed, compared to conventional transmitters.
小鹿文也，山里敬也，齋藤将人，表英毅，佐藤彰弘，木村翔，田中翔馬，林合祐
電子情報通信学会論文誌, Vol.J107-B,No.11,pp.-
24年11月
移動無線通信システムにおいて，伝搬路特性を把握することは極めて重要である．特に，移動無線通信システムのチャネル推定において，雑音電力を相対的に低減させ，低信号対雑音電力比 (SNR) の信号の利用は重要である．仮にこのような低信号対雑音電力比の信号を利用できるようになれば，本来通信ができなかった環境でも通信を可能にすることができ，基地局の通信範囲の拡大が可能となる．そこで筆者らは，短区間電力遅延プロファイルを用いて雑音電力を低減させる手法を提案した．本論文では，アッテネータを使用することであえて微弱信号を再現した電波伝搬測定を行うことで提案手法の有効性を確認した．提案手法ではパスが同じ方向から発生するという仮定をおいているが，これをシミュレーションによって検証した．提案手法によって短区間電力遅延プロファイルで SNR が 10dB の信号を 30 dB まで改善することができた．
In this study, authors evaluate 1-bit ADC receivers proposed in previous studies in Rician and Rayleigh fading channels where the ampli- tude and phase of the signal fluctuate dynamically in terms of SNR (Signal- to-Noise Ratio) vs. BER (Bit Error Rate). We confirm that the 1-bit ADC receiver is effective even in such environments. However, the degree of degradation of SNR vs. BER due to variations in signal amplitude and phase depends on the demodulation method.
A rolling shutter based visible light communication (VLC) system is possible to achieve high data rate by utilizing characteristics of rolling shutter image sensors, but some signal loss occur. In this study, we propose a synchronization method to decode a loss correct code in a rolling shutter based VLC system. To synchronize the received signal with the transmitted signal, we employ a combination of pulse width modulation (PWM) and Barker codes. The PWM technique helps in aligning the timing of the received signal with the transmitted signal, while the Barker codes provide a correlation property that aids in identifying the synchronization points. The experimental results show that this synchronization method enables us to use loss correct codes. Additionally, the bit error rate depends on a parameter of image processing on received images and the way to set a posteriori probabilities in the decoding.
Z. Tang, T. Yamazato, S. Arai
International Conference on Emerging Technologies for Communications (ICETC), O1-1, Sapporo, Japan
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.
A. Isozaki, T. Yamazato, M. Saito
International Conference on Emerging Technologies for Communications (ICETC)
2023年12月
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.
R. Huang, T. Yamazato, M. Kinoshita, H. Okada, S. Arai, K. Kamakura, T. Yendo, T. Fujii
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.
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.
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.
S. Kamiya, Z. Tang, T. Yamazato, M. Kinoshita, K. Kamakura, S. Arai, T. Yendo, T. Fujii
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.
M. Hattori, A. Tsujii, T. Kasashima, H. Hatano, T. Yamazato
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.
J. Zheng, T. Yamazato, K. Naito
IEEE Symposium on Computers and Communications (ISCC) Workshop on Optical Wireless Communications
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.
T. Yamazato
IEEE Symposium on Computers and Communications (ISCC) Workshop on Optical Wireless Communications
2023年7月
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.
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
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.
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.
H. Omote, A. Sato, S. Kimura, S. Tanaka, H. Y. Lin, T. Yamazato
IEEE Vehicular Technology Conference (VTC), pp. 1-4
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.
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.
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.
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.
M. Hattori, A. Tsujii, T. Kasashima, H. Hatano, T. Yamazato
International Conference on Emerging Technologies for Communications (ICETC), O5-5, Waseda University
2022年12月
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.
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
2022年12月
山里敬也
電子情報通信学会技術研究報告, WBS2022-43, pp. 48-53, 立命館大学 BKC エポック立命21 3階
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].
S. Kamiya, Z. Tang, T. Yamazato,
IEEE ICC Workshop on Optical Wireless Communications (OWC), Seoul, South Korea
2022年5月
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.
Z. Tang,T. Yamazato, S. Arai
IEEE ICC Workshop on Optical Wireless Communications (OWC), Seoul, South Korea
2022年5月
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.
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.
M. Kinoshita, T. Toguma, S. Yamaguchi, S. Ibaraki, K. Kamakura, T. Yamazato
IEEE Consumer Communications and Networking Conference (CCNC), pp.843-847, online
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 transmitter’s position in the captured image. When validating the specific signal, we achieved 100% acquisition success rate.
T. Yamazato
Wireless World Research Forum Meeting 46, Paris, France
2021年12月
Optical wireless communication has been around since the 1980s. Why has its time come now in 5G/6G? What is the change?
T. Ohtaguro, M. Saito, T. Yamazato
International Conference on Materials and Systems for Sustainability (ICMaSS), online
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.
R. Huang, T. Yamazato, M. Kinoshita, H. Okada, K. Kamakura, S. Arai, T. Yendo, T. Fujii
IEEE Intelligent Vehicles Symposium, Nagoya, Japan
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.
M. Hattori, A. Tsujii, T. Kasashima, H. Hatano, T.Yamazato
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.
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.
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.
2020
R. Okema, D. Goto, T. Yamazato, F. Yamashita, H. Shibayama
IEEE Global Communications Conference (GLOBECOM), Taipei, Taiwan
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.
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
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.
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
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.
M.Hattori, A. Tsujii, T. Kasashima, H. Hatano, T. Yamazato
International Conference on Emerging Technologies for Communications (ICETC), I2-4, Online
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.
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
2020年11月
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
2020年11月
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
本研究では，画像の高速・高輝度投映が可能なDMD (Digital Micromirror Device)プロジェクタをITS (Intelligent Transport Systems)イメージセンサ可視光通信の送信機として応用することを検討する．実機を用いて構築したシステムにより，屋外移動環境において行った通信性能評価について報告する．
T. Yamazato
International Conference on Optoelectronic and Microelectronic Technology and Application 2020, Nanjing, China
2020年10月
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.
Signal Processing in Photonic Communications (SPPCom), The 2020 OSA Advanced Photonics Congress, 2020., Online
2020年7月
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.
Y.H.J Lai, A. Tsujii, T. Kasashima, T. Yamazato, H. Hatano
IEICE General Conference, A-4-2, p.35, Hiroshima, Japan
2020年3月
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.
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
2020年3月
T. Yamazato
The Optical Networking and Communication Conference & Exhibition (OFC2020), San Diego, USA
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.
2019
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
2019年12月
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.
K. Yamamura, K. Kamakura, M. Kinoshita, T. Yamazato
Workshop on Optical Wireless Communication for Smart City (OWC2), pp.33-36, Toyota, Japan
2019年12月
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
2019年12月
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.
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
2019年12月
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.
K. Takahashi, K. Kamakura, M. Kinoshita, T. Yamazato
Workshop on Optical Wireless Communication for Smart City (OWC2), pp.9-12, Toyota, Japan
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
2019年11月
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%.
T. Mitani, T. Yamazato, K. Naito, Y. Mori
The 8th IEEE International Conference on Conected Vehicles and Expo (ICCVE), Gratz, Austlia
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.
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.
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.
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.
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
2019年3月
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.
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.
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.
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
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.
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.
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.
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
2018年9月
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.
Progress In Electromagnetics Research Symposium (PIERS), Toyama International Conference Center, Toyama, Japan
2018年8月
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.
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.
T. Yamazato
Visible Light Communications Workshop, Pacific Rim Conference on Lasers and Electro-Optics (CLEO-PR), Hong Kong Convention and Exhibition Centre, Hong Kong
2018年7月
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.
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
2018年3月
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.
Takaya Yamazato
International Conference on Optical Wireless Communications, Beijing, China
2018年3月
木下雅之，山里敬也，岡田啓，藤井俊彰，荒井伸太郎，圓道知博，鎌倉浩嗣
電子情報通信学会 総合大会, A-9-8, p.95, 東京
2018年3月
本稿では LED 光源を送信機,高速イメージセンサを受信機に想定した ITS( 高度道路交通システム ) イメージセンサ可視光通信を扱う.従来のイメージセンサ可視光通信では受信機に単眼カメラを用いていたが, 本稿では高速二眼カメラを用いる受信機構成を提案し, 左右の撮影画像から得られるダイバーシティを利用した通信性能の改善手法について検討する.
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.
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
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.
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.
S. Kibe, K. Kamakura, T. Yamazato
IEEE Global Communications Conference (GLOBECOM), pp. 1-6, Singapore, Singapore
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.
Y. Nakashima, T. Yamazato, Y. Tadokoro, S. Arai
International Symposium on Nonlinear Theory and its Application (NOLTA), pp.291-294, Cancun, Mexico
2017年12月
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.
Takaya Yamazato
Journal of Communications and Information Networks, vol.2, no.4, pp.65-74
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.
堀将大，木下雅之，山里敬也，岡田啓，藤井俊彰，鎌倉浩嗣，圓道知博，荒井伸太郎
電子情報通信学会技術研究報告, ITS2017-56, pp.251-256, 沖縄
2017年12月
本稿では高度道路交通システム（ITS）のためのイメージセンサ可視光通信に着目する．この通信では送信機として LED アレイを，受信機として高速度カメラを用いる．可視光通信を行うために、高速度カメラで撮影した画像中のLEDアレイ送信機の位置を特定する必要がある．先行研究では LED アレイは高い時間勾配と低い空間勾配を持つことを示し，これらの特徴量を用いたLEDアレイ検出手法を提案した．しかし，その手法では情報源であるLEDアレイ送信機と情報を持たない人工光源を区別することが困難である．また，LEDアレイに比べ非LEDアレイの画素が非常に多いため，データの不均衡性の問題も生じた．そこで，本稿ではより正確なLEDアレイの検出を行うため，k平均法に基づくアンダーサンプリングを行い，それらのデータからSVMで学習したモデルを用いるLEDアレイ検出手法を提案する．
木部修斗，鎌倉浩嗣，山里敬也
電子情報通信学会技術研究報告, CS2017-58, pp.21-2, 阿蘇
2017年11月
T. Yamazato, N. Kawagita, H. Okada, T. Fujii, T. Yendo, S. Arai, K. Kamakura
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.
K. Kamakura, T. Yamazato
IEEE Photonics Conference (IPC), pp.235-236, Orlando, FL, USA
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.
木下雅之，山里敬也，岡田啓，藤井俊彰，荒井伸太郎，圓道知博，鎌倉浩嗣
電子情報通信学会ソサイエティ大会, A-9-7, p.92, 東京
2017年9月
本稿では LED 光源を送信機,高速イメージセンサを受信機に想定した ITS( 高度道路交通システム ) イメージセンサ通信を扱う.従来のイメージセンサ通信では受信機に単眼カメラを用いていたが,本稿では高速二眼カメラを用いる受信機構成を提案する.高速二眼カメラでは左右のカメラで見え方が異なり,この違いを利用することで通信性能の改善を図る.
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.
ITS(Intelligent Transport Systems:高度道路交通システム)可視光通信にイメージセンサを用いる場合,イメージセンサの特性から高速化が課題となる.従来の伝送方式は,送信信号の変調にPWM(Pulse Width Modulation:パルス幅変調)を用いる方式であり,受信側で振幅変調として捉えて通信を行う.これに対して,高速伝送を実現できる伝送方式の候補として,仮想正弦波を用いる方式がある.仮想正弦波方式は,送信信号のパルスの振幅,位置の変調を,受信側で振幅,位相の変調として捉えて通信を行う.しかし,この 2 つの伝送方式の優位性が明らかでないため,本研究では比較実験を行い, ITS イメージセンサ可視光通信の高速化のための伝送方式について検討する.
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
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.
T. Yamazato
Presentation at Professor Jean Armstrong's Laboratory, Monash University, Monash University, Australia.
2017年3月
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
2017年3月
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.
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
2017年3月
R. Ohno, T. Yamazato
RISP International Workshop on Nonlinear Circuits, Communications and Signal Processing (NCSP), pp.81-84, Guam, USA
2017年3月
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.
本稿では LED 光源を送信機,高速イメージセンサを受信機に想定した ITS( 高度道路交通システム ) イメージセンサ通信を扱う. ITS イメージセンサ通信では車輌の移動や振動により,画像上での送信機の位置がフレームごとで変動する.こうしたフレーム間での送信機の移動は通信路変動として扱われ,情報を持つ正しいピクセルの選択を困難にし,誤りの原因となる.本稿では,通信路変動の要因となる車輌振動のモデル化とそのパラメータ推定を舗装路及び未舗装路における振動測定の結果を基に行う.
新井雄大，山里敬也，岡田啓，藤井俊彰，荒井伸太郎，圓道知博，鎌倉浩嗣
電子情報通信学会 総合大会, A-9-15, p.124, 名古屋
2017年3月
本研究では車輌のヘッドランプや信号機,照明,標示などへの普及が増えつつある LED を用いてイメージセンサ通信を行うことにより,次世代 ITS の技術として期待されている車車間・路車間通信を含んだ運転支援システムの実現を目指す.ITS イメージセンサ通信の環境を想定すると,多数の送信機からの信号を同時に受信する必要がある.これらの信号は互いに同期がとれていないので,それぞれの信号の復調のタイミングは異なり,一度に復調する手法は提案されていない.本稿では,この互いに非同期な複数信号の同時受信・復調を行うための実験系を構築した
増田圭亮，鎌倉浩嗣，山里敬也
電子情報通信学会 総合大会, B-10-57, p.310, 名古屋
2017年3月
山里敬也
電子情報通信学会 総合大会, BI-10-2, pp.SS-81 - SS-82, 名古屋
2017年3月
無線通信方式は移動体を相手とする通信手段としてはほとんど唯一のものであり，とりわけ自動車については，携帯電話，無線LANの普及に歩調を合わせるようにして発展してきている．図1に1980年以降の車車間・路車間通信と携帯電話，GPSの略史を示す．こうして並べてみると，自動車での無線利用は携帯電話の10年遅れて推移しているように思えてくる．もっとも，車車間・路車間通信は携帯電話のように人を対象にしたものでは無く，モノ（自動車）を対象にしたものであり，その意味ではIoT(Internet of Things)を先取りしているとも言える．本稿では路車・車車間通信システムについて解説する．とりわけ，現行の路車・車車間通信システムである700 MHz 帯高度道路交通システム（ARIB STD-T109）を取り上げ，その概要を紹介する．
新井雄大
電子情報通信学会東海支部卒業研究発表会
2017年3月
山里敬也
名古屋大学附属図書館研究開発室報告会, 名古屋大学
2017年3月
Stefano Bregni, Takaya Yamazato, Vasile Bota, Liangping Ma
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,