Faculty Profiles - YAMAZATO Takaya

Papers - YAMAZATO Takaya

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Luminance Inversion for Parallel Transmission Visible Light Communication Between LCD and Image Sensor Camera Reviewed Open Access

Kotomi Takahashi, Koji Kamakura, Masayuki Kinoshita, Takaya Yamazato

Journal of Lightwave Technology 2021.11

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

T. Yamamoto, T. Yamazato, H. Okada, M. Kinoshita, K. Kamakura, S. Arai, T. Yendo, T. Fujii

IEICE Transactions on Communications Vol. J104-B ( 11 ) page： 938 - 948 2021.11

Vehicle distance measurement based on visible light communication using stereo cameras Reviewed

Ruiyi Huang, Takaya Yamazato, Masayuki Kinoshita, Hiraku Okada, Koji Kamakura, Shintaro Arai, Tomohiro Yendo, Toshiaki Fujii

IEEE Intelligent Vehicles Symposium, Proceedings Vol. 2021-July page： 853 - 858 2021.7

Publishing type：Research paper (international conference proceedings)

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.

DOI： 10.1109/IV48863.2021.9575534

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Luminance Inversion for Parallel Transmission VLC between LCD and Image Sensor Camera Reviewed

Kotomi Takahashi, Koji Kamakura, Masayuki Kinoshita, Takaya Yamazato

IEEE International Conference on Communications 2021.6

Language：English Publishing type：Research paper (international conference proceedings) Publisher：Institute of Electrical and Electronics Engineers Inc.

Luminance inversion (LI) is proposed to compensate for nonlinear characteristics between a liquid crystal display (LCD) and an image sensor (IS) camera of the parallel transmission (PT) visible light communication (VLC). In the PT system reported in [1], which incorporates N spatial frequencies with phase shift keying (PSK) through M-point inverse discrete Fourier transform (IDFT), data are transmitted from M different regions of pixels on an LCD spatially in parallel. Since the transfer characteristics between the LCD and IS camera is nonlinear, the received signal at IS camera receiver is distorted. The effect is severe because signals of the PT system are, in essence, the OFDM signal, thus suffering from high peak-to-average ratio (PAPR). To linearize it between the LCD and IS camera, our approach is to calculate a complement of the digital data fed to the driver of the pixel and then to feed the pair of the digital data and its complement to the driver during two successive frames. In the receiver, the difference of the signals during the two frames is calculated for each of the M detected regions on the IS plane, and then they input to the following M-point DFT in the PT system. By introducing this LI process, wider linear characteristics in the PT system is obtained than without LI. Experimental results show that the number of bits per frame that the PT system with LI can accommodate without any error is 315bits/frame and 100bits/frame for 8- and 16-PSK, which are much larger than 12bits/frame and 0bits/frame for the 8- and 16-PSK PT system without LI, respectively.

DOI： 10.1109/ICC42927.2021.9500287

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Special section on intelligent transport systems Reviewed

Saho K.

IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences Vol. E104A ( 2 ) 2021.2

Optical Wireless Communication: A Candidate 6G Technology? Reviewed Open Access

Shintaro Arai, Masayuki Kinoshita, Takaya Yamazato

IEICE TRANSACTIONS ON FUNDAMENTALS OF ELECTRONICS COMMUNICATIONS AND COMPUTER SCIENCES Vol. E104A ( 1 ) page： 227 - 234 2021.1

Language：English Publishing type：Research paper (scientific journal) Publisher：IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG

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.

DOI： 10.1587/transfun.2020WBI0001

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

Shintaro Arai, Wataru Tamura, Takaya Yamazato, Hiroyuki Hatano, Masato Saito, Hiroya Tanaka, Yukihiro Tadokoro

2021 IEEE INTERNATIONAL SYMPOSIUM ON CIRCUITS AND SYSTEMS (ISCAS) Vol. 2021-May 2021

Language：English Publishing type：Research paper (international conference proceedings) Publisher：IEEE

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.

DOI： 10.1109/ISCAS51556.2021.9401452

Web of Science

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Comparison of distance performances of modulation schemes in intelligent transport system image sensor communication Reviewed Open Access

Takuya Yamamoto, Takaya Yamazato, Hiraku Okada, Masayuki Kinoshita, Koji Kamakura, Shintaro Arai, Tomohiro Yendo, Toshiaki Fujii

IEICE COMMUNICATIONS EXPRESS Vol. 10 ( 8 ) page： 498 - 504 2021

Language：English Publishing type：Research paper (scientific journal) Publisher：IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG

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.

DOI： 10.1587/comex.2021ETL0032

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

Okema R.

2020 IEEE Global Communications Conference, GLOBECOM 2020 - Proceedings Vol. 2020-January 2020.12

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

Ruiyi Huang, Masayuki Kinoshita, Takaya Yamazato, Hiraku Okada, Koji Kamakura, Shintaro Arai, Tomohiro Yendo, Toshiaki Fujii

2020 IEEE Globecom Workshops, GC Wkshps 2020 - Proceedings 2020.12

Publishing type：Research paper (international conference proceedings)

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 selection. The proposed scheme using stereo cameras exhibited a ranging accuracy of 60± 0.15m in static conditions.

DOI： 10.1109/GCWkshps50303.2020.9367540

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Estimation for direction of signal arrival based on area density of estimated lines for ultrasonic sensor array Reviewed

Morita E.

2020 IEEE 9th Global Conference on Consumer Electronics, GCCE 2020 page： 333 - 335 2020.10

Sequential maximum likelihood decoding incorporating reliability determination for image sensor communication Reviewed Open Access

Zhengqiang Tang, Shintaro Arai, Tomohiro Yendo, Di He, Takaya Yamazato

IEICE Communications Express Vol. 9 ( 8 ) page： 365 - 370 2020.8

Language：English Publishing type：Research paper (scientific journal) Publisher：IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG

In this study, the sequential maximum likelihood decoding (S-MLD) for image sensor based visible light communication, referred to as image sensor communication, is proposed. The conventional system cannot correctly decode degraded captured images. To overcome this problem, S-MLD partitions the LED area on the image into two segments and sequentially creates pseudo-captured images, which imitate all possible LED blinking patterns. This approach is based on MLD for each segment. Moreover, reliability determination is incorporated to improve communication quality. We performed computer simulations and confirmed that S-MLD exhibits superior decoding performance and approximately 90% computational cost reduction compared to the previous MLD.

DOI： 10.1587/comex.2020XBL0058

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

Takahashi K.

IEEE International Conference on Communications Vol. 2020-June 2020.6

Visible Light Communications for Automotive Intelligence Reviewed

Yamazato T.

2020 Optical Fiber Communications Conference and Exhibition, OFC 2020 - Proceedings 2020.3

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

Arisue T.

2020 IEEE 17th Annual Consumer Communications and Networking Conference, CCNC 2020 2020.1

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

Takahashi Kotomi, Kamakura Koji, Kinoshita Masayuki, Yamazato Takaya

ICC 2020 - 2020 IEEE INTERNATIONAL CONFERENCE ON COMMUNICATIONS (ICC) 2020

Visible light communications for automotive intelligence Reviewed

Yamazato T.

Optics InfoBase Conference Papers Vol. Part F174-OFC 2020 2020

Stereo ranging method using led transmitter for visible light communication Reviewed

Masayuki Kinoshita, Koji Kamakura, Takaya Yamazato, Hiraku Okada, Toshiaki Fujii, Shitaro Arai, Tomohiro Yendo

2019 IEEE Global Communications Conference, GLOBECOM 2019 - Proceedings 2019.12

Publishing type：Research paper (international conference proceedings)

This paper focuses on high-speed stereo cameraã receivers for visible light communication (VLC) in intelligent transport systems (ITSs), contrary to conventional studies where a single (high-speed) camera is used. An advantage of high-speed stereo cameras as VLC receivers is that both front-facing ranging and wireless communication can be achieved in one device. In this paper, utilizing features of VLC, we consider stereo ranging with high accuracy. Moreover, it is known that an LED transmitter for VLC has specific features, high-luminance and high- speed blinking. This paper proposes stereo ranging by applying LED transmitter detection (utilizing these features) to disparity estimation. Additionally, we introduce subpixel estimation using equiangular line fitting to obtain more accurate disparity. Finally, we experimentally demonstrate that the proposed stereo ranging achieves an accuracy of 60 m Â± 0.1 m.

DOI： 10.1109/GLOBECOM38437.2019.9013641

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

Takuya Mitani, Takaya Yamazato, Katsuhiro Naito, Yuki Mori

IEEE International Conference on Connected Vehicles and Expo:ICCVE 2019 2019.11

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

Mitani T., Yamazato T., Naito K., Mori Y.

2019 8th IEEE International Conference on Connected Vehicles and Expo, ICCVE 2019 - Proceedings 2019.11

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：2019 8th IEEE International Conference on Connected Vehicles and Expo, ICCVE 2019 - Proceedings

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.

DOI： 10.1109/ICCVE45908.2019.8965232

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Papers - YAMAZATO Takaya