Faculty Profiles - YAMAZATO Takaya

Papers - YAMAZATO Takaya

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

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

IEICE Technical Report ( ITS2013-39 ) page： pp.55-60 2014.2

Language：Japanese

This paper focuses on road-to-vehicle visible light communication using an LED array as a transmitter and a high-speed camera as a receiver. In this communication, LED array acquisition has a significant role. The spatio-temporal images are essential for a robust LED array acquisition because the time-gradient and space-gradient values can be an important feature value of an LED array. In this paper, we focus on the time-gradient and the space-gradient values in the captured images and draws both gradient value as a scatter diagram. This scatter diagram enables us to regard the LED acquisition as discriminant analysis. From the above, this paper proposes a new acquisition method and confirms its effectiveness by the experiment in a driving situation.

Distance Estimation Scheme for Integrated V2I-VLC in Driving Vehicle

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

IEICE Technical Report ( ITS2013-38 ) page： pp.49-54 2014.2

Language：Japanese

This paper discusses an issue of estimating the distance between an on-vehicle transmitter and a roadside equipment for vehicular-to-infrastructure visible light communication (V2I-VLC). The system integrates the VLC as well as distance estimation functions. In this paper, we discuss a technique overcoming a vehicle vibration by using a particular transmitting LED pattern and the sub-pixel estimation using the phase-only correlation. As the results, we achieve less than 0.5m errors for the distance up to 60 m by the proposed system.

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

AMANO Yuta, KAMAKURA Koji, YAMAZATO Takaya

Vol. 113 ( 433 ) page： 43 - 48 2014.2

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

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

CiNii Research

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

AMANO Yuta, KAMAKURA Koji, YAMAZATO Takaya

IEICE technical report. Image engineering Vol. 113 ( 434 ) page： 43 - 48 2014.2

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

CiNii Research

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

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

Vol. 113 ( 433 ) page： 49 - 54 2014.2

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

This paper discusses an issue of estimating the distance between an on-vehicle transmitter and a road-side equipment for vehicular-to-infrastructure visible light communication (V2I-VLC). The system integrates the VLC as well as distance estimation functions. In this paper, we discuss a technique overcoming a vehicle vibration by using a particular transmitting LED pattern and the sub-pixel estimation using the phase-only correlation. As the results, we achieve less than 0.5m errors for the distance up to 60 m by the proposed system.

CiNii Research

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

USUI Syunsuke, YAMAZATO Takaya, OKADA Hiraku, FUJII Toshiaki, TAKAHASHI Keita, ARAI Shintaro, YENDO Tomohiro

IEICE technical report. Image engineering Vol. 113 ( 434 ) page： 55 - 60 2014.2

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

This paper focuses on road-to-vehicle visible light communication using an LED array as a transmitter and a high-speed camera as a receiver. In this communication, LED array acquisition has a significant role. The spatio-temporal images are essential for a robust LED array acquisition because the time-gradient and space-gradient values can be an important feature value of an LED array. In this paper, we focus on the time-gradient and the space-gradient values in the captured images and draws both gradient value as a scatter diagram. This scatter diagram enables us to regard the LED acquisition as discriminant analysis. Prom the above, this paper proposes a new acquisition method and confirms its effectiveness by the experiment in a driving situation.

CiNii Research

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

USUI Syunsuke, YAMAZATO Takaya, OKADA Hiraku, FUJII Toshiaki, TAKAHASHI Keita, ARAI Shintaro, YENDO Tomohiro

Vol. 113 ( 433 ) page： 55 - 60 2014.2

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

This paper focuses on road-to-vehicle visible light communication using an LED array as a transmitter and a high-speed camera as a receiver. In this communication, LED array acquisition has a significant role. The spatio-temporal images are essential for a robust LED array acquisition because the time-gradient and space-gradient values can be an important feature value of an LED array. In this paper, we focus on the time-gradient and the space-gradient values in the captured images and draws both gradient value as a scatter diagram. This scatter diagram enables us to regard the LED acquisition as discriminant analysis. Prom the above, this paper proposes a new acquisition method and confirms its effectiveness by the experiment in a driving situation.

CiNii Research

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

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

IEICE technical report. Image engineering Vol. 113 ( 434 ) page： 49 - 54 2014.2

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

CiNii Research

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

H. Yokota, S. Arai, T. Yamazato and Y. Tadokoro

Proceedings of 2014 RISP International Workshop on Nonlinear Circuits, Communications and Signal Processing (NCSP'14) page： 61-64 2014.2

Language：English

The present paper focuses on an application of Stochastic Resonance (SR) for an LED visible light communication (LED-VLC) receiver. SR is well-known as a phenomenon, which enhances the response by additive noise. We consider that a weak optical signal, which is distorted due to an influence of ambient light noise, can be detected by using SR system. This study makes a simple SR circuit for LED VLC and performs its circuit experiment for exploring the possibility and availability of the LED-VLC receiver using SR system.

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

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

IEICE Technical Report Vol. ITS2013-39 page： 55-60 2014.2

Language：Japanese

Driver Assistant System using Visible Light Communications : Road-to-Vehicle Visible Light Communications using LED Array and On-Vehicle High-Speed Camera Reviewed Open Access

YAMAZATO Takaya

Technical report of IEICE. OCS Vol. 113 ( 391 ) page： 17 - 23 2014.1

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

We are conducting a study on viheicle-infrastractuctre cooperateive systems using visible light communications for driving safty applications. This paper introduces our studies on such VLC supported ITS systems using a high-speed image sensor as a VLC receiver equiped on a vehicle. The image sensors are now adopted for a lane keeping, an obstables recognition, a range estimation and many other applications. If we could add a VLC function to those safety applications, then a driver can recognize his environment visually and also he recognize his environment by signals transmitted through an LED traffic lights, LED tail lights, LED signage board, etc in a form of VLC signals. Together, it can contribute to more extensive safety driving.

Open Access

CiNii Research

Driver Assistant System using Visible Light Communications : Road-to-Vehicle Visible Light Communications using LED Array and On-Vehicle High-Speed Camera Reviewed Open Access

YAMAZATO Takaya

IEICE technical report. Communication systems Vol. 113 ( 390 ) page： 57 - 63 2014.1

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

Open Access

CiNii Research

Application of visible light communication to LED traffic light Reviewed Open Access

T. Yamazato

Journal of Light & Visual Environment (JLVE) Vol. 98 ( no.1 ) page： pp.17-20 2014.1

Language：Japanese

Visible light communications (VLC) is the latest optical wireless communications technologies that uses low-power light emitting diodes, or LEDs, not only to provide light but also to broadcast data. LEDs are extremely energy-efficient and predicted to become widespread in general lighting application. Because LED is a solid-state lighting device, it can be modulated at high-speed compared with other lighting sources. VLC uses LEDs, which send data by flashing light at speeds undetectable to the human eye.Widespread use of LEDs in traffic applications and growing interest in Intelligent Transport System (ITS) presents an opportunity for VLC. Data transmission using LED traffic lights, LED road illumination, and LED brake lights are typical application.In this paper, an on-going research, road-to-vehicle visible light communication, will be introduced. The LED array, assumed to be an LED traffic light, is used as a transmitter and it sends data to a moving vehicle. By providing data together with a traffic signal that is visible to a driver, a safety driving support can be realized.Finally, the author suggests readers a glimpse of wealth on "dual use of LEDs" and concludes the paper.

DOI： 10.2150/jieij.98.17

Open Access

Driver Assistant System using Visible Light Communications Invited Open Access

Takaya Yamazato

IEICE Technical Report Vol. CS2013-94 page： 57-63 2014.1

Authorship：Lead author Language：Japanese

We are conducting a study on viheicle-infrastractuctre cooperateive systems using visible light commu- nications for driving safty applications. This paper introduces our studies on such VLC supported ITS systems using a high-speed image sensor as a VLC receiver equiped on a vehicle. The image sensors are now adopted for a lane keeping, an obstables recognition, a range estimation and many other applications. If we could add a VLC function to those safety applications, then a driver can recognize his environment visually and also he recognize his environment by signals transmitted through an LED traffic lights, LED tail lights, LED signage board, etc in a form of VLC signals. Together, it can contribute to more extensive safety driving.

Open Access

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

S. Arai, Y. Shiraki, T. Yamazato, H. Okada, T. Fujii, T. Yendo

IEEE Consumer Communications and Networking Conference page： 605-610 2014.1

Language：English

The present paper proposes a novel multiple-LED-arrays acquisition for an infrastructure-to-vehicle visible light communication (I2V-VLC) using LED arrays (transmitter) and an in-vehicle high-speed image sensor (receiver). In order to achieve a robust detection of LED arrays, we employ the block matching algorithm, which is a way of finding a corresponding position between two successive frames. The proposed method divides a captured image into a number of small domains (blocks) and determines if the LED array is present or absent using the block matching. We perform I2V-VLC experiments with multiple-LED arrays and evaluate the acquisition capability of the proposed method.

M-ary modulation scheme based on separation of deterministic chaotic dynamics for noncoherent chaos-based communications

Arai Shintaro, Nishio Yoshifumi, Yamazato Takaya

Nonlinear Theory and Its Applications, IEICE Vol. 5 ( 2 ) page： 210 - 221 2014

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

The present paper proposes a novel M-ary modulation scheme based on separation and reconstruction of deterministic chaotic dynamics for noncoherent chaos-based communications. The M-ary modulation scheme can transmit b-bit data at a time by using M=2b distinct sequences. In order to generate M distinct sequences and recover b-bit data, the proposed system separates the chaotic dynamics having the chaotic sequence by using M interleavers, and reconstructs the original sequence based on the chaotic dynamics from the separated one by using M deinterleavers. In advance, each data symbol among M symbols is allocated to each interleaver-deinterleaver pair. The transmitter selects an interleaver corresponding to a data symbol and separates the order of samples of the chaotic sequence using the selected interleaver. The receiver feeds the received sequence into all M deinterleavers and outputs M reconstructed sequences. The proposed system can reconstruct the original chaotic sequence only when the correct deinterleaver, which becomes paired with the interleaver, is selected. Therefore, the receiver can recover b-bit data by analyzing the chaotic dynamics of each reconstructed sequence. We carry out computer simulations and evaluate performances of the proposed M-ary modulation scheme.

DOI： 10.1587/nolta.5.210

CiNii Research

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BER Characteristic of Optical-OFDM using OCI Reviewed

Yuki Goto, Isamu Takai, Takaya Yamazato, Hiraku Okada, Akitoshi Fujii, Shoji Kawahito, Shintaro Arai, Tomohiro Yendo, Koji Kamakura

2014 IEEE ASIA PACIFIC CONFERENCE ON CIRCUITS AND SYSTEMS (APCCAS) Vol. 2015-February ( February ) page： 328 - 331 2014

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

Light-emitting diode (LED) transmitters based optical wireless communication (OWC) systems offer the potential for new generation communication systems. Particularly, an image sensor based OWC systems consist of the LED transmitters and camera receivers are expected to contribute to intelligent transport system (ITS) for driving supports. For high achievable data rates, orthogonal frequency division multiplexing (OFDM) based OWC systems have attracted a great deal of attention. Despite attractive features of optical OFDM, only few attempts have so far been made to adopt it as a modulation scheme of an image sensor based OWC system. There remains a need for an evaluation of adopting an optical OFDM to the image sensor based OWC systems. Another important issue needs to be addressed is the performance degradation due to a frequency response of an actual image sensor device, especially a signal attenuation loss in higher frequency. In addition to such loss, a narrow band noise generated by its circuits also degrades the performance. The purpose of this paper is to investigate BER performances of the optical-OFDM using an actual image sensor device, the optical communication image sensor (OCI). From simulation results, it is found that the frequency response and the narrowband noise at 12MHz of the OCI lead to the significant reduction of BER performances. Additionally, the results shows that ACO-OFDM shows a little better performance compared to DCO-OFDM with the same bandwidth efficiency.

DOI： 10.1109/APCCAS.2014.7032786

Web of Science

Scopus

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Channel Fluctuation Measurement 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 IEEE ASIA PACIFIC CONFERENCE ON CIRCUITS AND SYSTEMS (APCCAS) Vol. 2015-February ( February ) page： 332 - 335 2014

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

In image sensor based VLC, transmitter acquisition and tracking are critical issue. However, the fluctuation of the VLC transmitter in the image plane caused by vehicle movement, complicates correct data reception. Therefore, in this paper, we present results of channel fluctuation measurements for infrastructure-to-vehicle VLC (I2V-VLC), vehicle-to-infrastructure VLC (V2I-VLC), and vehicle-to-vehicle VLC (V2V-VLC). We analyze channel fluctuation in terms of optical flow from measured data.

DOI： 10.1109/APCCAS.2014.7032787

Web of Science

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IEICE knowledge discovery (I-Scover) Reviewed

Yamazato, T., Chimura, Y., Nishino, F., Ikada, S., Akiyama, T., Nakano, M., Inoue, Y.

Journal of the Institute of Electronics, Information and Communication Engineers Vol. 97 ( 3 ) page： 240 - 246 2014

Improving communication rate of visible light communication system using high-speed camera Reviewed

Daigo Iwase, Makoto Kasai, Tomohiro Yendo, Shintaro Arai, Takaya Yamazato, Hiraku Okada, Toshiaki Fujii

2014 IEEE ASIA PACIFIC CONFERENCE ON CIRCUITS AND SYSTEMS (APCCAS) Vol. 2015-February ( February ) page： 336 - 339 2014

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

We focus on the road-to-vehicle visible light communication that system is composed of LED matrix as transmitter and high-speed camera as receiver. Conventionally, the transmitting rate has been reduced to half of the frame rate of the camera, to avoid intersymbol interference because of exposure time of camera frame. We propose a method to improve the communication rate. The transmitting rate is set same to receiver's frame rate, and the sent data is estimated from pattern mixed image. Using 8b/10b encoding instead of conventional reversal pattern to reduce the flickering of transmitter's lighting is also proposed.

DOI： 10.1109/APCCAS.2014.7032788

Web of Science

Scopus

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Papers - YAMAZATO Takaya