Faculty Profiles - YAMAZATO Takaya

Papers - YAMAZATO Takaya

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

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

2014 GLOBECOM WORKSHOPS (GC WKSHPS) page： 450 - 455 2014

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

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.

DOI： 10.1109/GLOCOMW.2014.7063473

Web of Science

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Spatially-Modulated Space-Time Coding in Visible Light Communications Using 2 x 2 LED Array Reviewed

Ebihara Katsunori, Kamakura Koji, Yamazato Takaya

2014 IEEE ASIA PACIFIC CONFERENCE ON CIRCUITS AND SYSTEMS (APCCAS) page： 320 - 323 2014

Spatially-Modulated Space-Time Coding in Visible Light Communications Using 2 x 2 LED Array Reviewed

Katsunori Ebihara, Koji Kamakura, Takaya Yamazato

2014 IEEE ASIA PACIFIC CONFERENCE ON CIRCUITS AND SYSTEMS (APCCAS) Vol. 2015-February ( February ) page： 320 - 323 2014

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

This paper demonstrates the feasibility of binary spatially-modulated space-time (SM-ST) coding in an outdoor image-sensor-based visible light communication (VLC) system. We showed that at the transmission distance where intensity modulated symbols from two different light emitting diodes (LEDs) are detected at one pixel of the image plane of the image sensor, space time (ST) coding enables to decouple the two symbols and to extend error-free transmission distance. We furthermore aim at increasing transmission rate per symbol duration when the spatial resolution is improved when the receiver approaches the LED array of the transmitter, by superimposing space shift keying (SSK) signal with the diagonal and anti-diagonal set of the 2 x 2 matrix onto the LED patterns. We built an experimental testbed with LEDs modulated at 1 kbps and a high-speed camera operating at 1,000 fps. Our experimental results validate that SM-ST coding achieves 30m of the error-free transmission distance for the additional bit based on SSK, without deteriorating the reception quality and range of the space-time coded bits.

DOI： 10.1109/APCCAS.2014.7032784

Web of Science

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Application of Visible Light Communication to LED Traffic Light(<Special Issue>For the Further Spread of SSL and the Expansion of the Application Field) Reviewed

Yamazato Takaya

JOURNAL OF THE ILLUMINATING ENGINEERING INSTITUTE OF JAPAN Vol. 98 ( 1 ) page： 17 - 20 2014

Publishing type：Research paper (scientific journal) Publisher：The Illuminating Engineering Institute of Japan

Visible light communications (VLC) is the latest optical wireless communications technology 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.

DOI： 10.2150/jieij.98.17

[招待論文]可視光通信の交通信号への適用 Reviewed

山里敬也

照明学会誌 Vol. vol.98, no.1 page： 17 - 20 2014

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

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) page： - 2013.12

Language：Japanese

This study focuses on the visible light communication(VLC) system using LED and a high-speed camera inorder to develop robust and adaptable communication systemsin 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 Reviewed

A. Ohmura, T. Yamazato, H. Okada, T. Fujii, T. Yendo, S. Arai

IEICE Transaction on Communications Vol. J96-B ( no.12 ) page： pp.1365-1368 2013.12

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

A. Ohmura, T. Yamazato, H. Okada, T. Fujii, T. Yendo, S. Arai

IEICE Transaction on Communications Vol. J96-B ( 12 ) page： 1365-1368 2013.12

Accuracy Improvement by POC for Distance Estimation Scheme for VLC Using an LED Array and a High-Speed Camera Reviewed

OHMURA Akihiro, YAMAZATO Takaya, ARAI Shintaro, YENDO Tomohiro, FUJII Toshiaki, OKADA Hiraku

The transactions of the Institute of Electronics, Information and Communication Engineers. B Vol. 96 ( 12 ) page： 1365 - 1368 2013.12

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

T. Yamazato

IEICE Technical Report ( ASN2013-112 ) page： pp.121-124 2013.11

Invited Talk : SN, USN, and then ASN Reviewed

YAMAZATO Takaya

IEICE technical report. ASN, Ambient intelligence and sensor networks Vol. 113 ( 328 ) page： 121 - 124 2013.11

Publishing type：Research paper (scientific journal) Publisher：The Institute of Electronics, Information and Communication Engineers

Technical Committees (TCs) on Ad Hoc Networks (AN) and Ubiquitous and Sensor Networks (USN) have been consolidated in new TC, Ambient Intelligence and Sensor Networks (ASN). USN was the result of integrating two TCs in different societies, Ubiquitous and Real-World Oriented Networking (URON) in Communication Society and Sensor Networks (SN) in Engineering Science Society. The author has been engaged in SN, USN, and ASN. The present article looks back the aims and backgrounds of those TCs. In expectation of the further advancement of ASN, a few concluding remarks are presented.

Image Sensor based Visible Light Communication for Automotive Applications Reviewed

T. Yamazato, I. Takai, H. Okada, T. Fujii, T. Yendo, S. Arai, M. Andoh, K. Yasutomi, K. Kagawa, S. Kawahito

Proc. of International Symposium on Optical Wireless Communications page： - 2013.11

Language：English

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.

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 ) page： pp. 205-209 2013.10

Language：Japanese

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 ) page： pp.19-23 2013.10

Language：Japanese

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.

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

CHIGA Keita, TANAKA Hiroya, YAMAZATO Takaya, TADOKORO Yukihiro, ARAI Shintaro

IEICE technical report. Nonlinear problems Vol. 113 ( 271 ) page： 19 - 23 2013.10

Publishing type：Research paper (scientific journal) Publisher：The Institute of Electronics, Information and Communication Engineers

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

ARAI Shintaro, NISHIO Yoshifumi, YAMAZATO Takaya

IEICE technical report. Nonlinear problems Vol. 113 ( 271 ) page： 205 - 209 2013.10

Publishing type：Research paper (scientific journal) Publisher：The Institute of Electronics, Information and Communication Engineers

Utilization of Spatio-temporal image for LED array acquisition in Road to Vehicle Visible Light Communication Reviewed

S.Usui, T.Yamazato, S.Arai, T.Yendo, T.Fujii, H.Okada

20th World Congress on Intelligent Transport Systems page： - 2013.10

Language：English

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 Reviewed

A. Ohmura, T. Yamazato, H. Okada, T. Fujii, T. Yendo, S. Arai

20th World Congress on Intelligent Transport Systems page： - 2013.10

Language：English

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

IEICE Society Conference ( A-2-13 ) page： p.32 2013.9

The outline of I-Scover (IEICE Knowledge Discovery)

T. Yamazato

IEICE Society Conference page： - 2013.9

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Papers - YAMAZATO Takaya