Faculty Profiles - YAMAZATO Takaya

Papers - YAMAZATO Takaya

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Cooperative Diversity via Simple Relaying with Quasi-Orthogonal Space-Time Block Code Reviewed

T. Yamaoka, Y. Hara, K. Ishioka, T. Hara, T. Yamazato

IEICE Transaction on Communication page： - 2014.12

Language：Japanese Publishing type：Research paper (scientific journal)

We have been proposed cooperative diversity receiving ABBA code as cooperative diversity via simple relaying with QOSTBC(Quasi-Orthogonal Space-Time Block Code). This scheme offers codinggain by permutation of space-time coded signal sequences in the relay nodes. So the relay nodes don't need carrier recovery and complete the signal process in the intermediate frequency band. In this paper we discuss two improved scheme with various channel model. These schemes improve the previous scheme without loss of the merit in its relay process. Moreover we sum up cooperative diversity via simple relaying with QOSTBC to discuss these schemes with various channel model. We evaluate effect of these scheme in terms of signal matrixes and simulate bit error rate of the prposed and improved scheme with with various channel model, respectively.

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

Y. Amano, K. Kamakura, T. Yamazato

IEICE Transactions on Communications (to be published) page： - 2014.12

Language：Japanese Publishing type：Research paper (scientific journal)

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

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

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

IEEE Workshop on Optical Wireless Communications page： - 2014.12

Language：English Publishing type：Research paper (scientific journal)

Visible light communication (VLC) using light-emitting diodes (LEDs) is drawing much attention. There are two types of VLC reception devices, a photodiode and an image sensor. VLC using image sensor is called image sensor based VLC. As the receiver only uses the image sensor pixels that sense LED transmission sources and discards other pixels, including those sensing noise sources, image sensor based VLC is an attractive solution for outdoor mobile applications. However, little evidence is available for channel modeling of image sensor based VLC in mobile outdoor environments, especially for motion modeling of VLC transmitter. In this paper, we propose a motion model of VLC transmitter. In particular, we consider three cases; infrastructure-to-vehicle VLC (I2V-VLC), vehicle-to-infrastructure VLC (V2I-VLC), and vehicle-to-vehicle VLC (V2V-VLC). As a result, we show that the motion model of the VLC transmitter on the captured image for the three aforementioned situations (i.e., I2V-VLC, V2I-VLC, and V2V-VLC) can be expressed in the identical pinhole camera model.

Cooperative Diversity via Simple Relaying with Quasi-Orthogonal Space-Time Block Code Reviewed

Tomoya YAMAOKA, Yoshitaka HARA, Kazuaki ISHIOKA Teruyuki HARA, Takaya Yamazato

IEICE Transactions on Communications Vol. J97-B ( 12 ) page： 1213-1223 2014.12

Language：Japanese Publishing type：Research paper (scientific journal)

We have been proposed cooperative diversity receiving ABBA code as cooperative diversity via simple relaying with QOSTBC(Quasi-Orthogonal Space-Time Block Code). This scheme offers coding gain by permutation of space-time coded signal sequences in the relay nodes. So the relay nodes don't need carrier recovery and complete the signal process in the intermediate frequency band. In this paper, we discuss two improved scheme with various channel model. These schemes improve the previous scheme without loss of the merit in its relay process. Moreover, we sum up cooperative diversity via simple relaying with QOSTBC to discuss these schemes with various channel model. We evaluate effect of these scheme in terms of signal matrixes and simulate bit error rate of the prposed and improved scheme with with various channel model, respectively.

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

E. Souke, Y. Ohira, S. Arai, T. Yamazato, T. Yendo, H. Okada, T. Fujii and K. Kamakura

Proceedings of 2014 IEEE Workshop on Nonlinear Circuit Networks (NCN'14) page： 93-94 2014.12

Language：English

The present paper considers an optical spatial channel in visible light communication (VLC) using LED and a high-speed camera. In general, the optical spatial channel affects the communication performance. However, the previous studies have not enough discussed the channel for VLC. This study focuses on the communication distance, which is one of channel parameters, and investigates the relationship between the distance and a receiving characteristic in the VLC.

Layered Space-Time Coding Using LED Array for Image-Sensor-Based Visible Light Communications Reviewed

EBIHARA Katsunori, KAMAKURA Koji, YAMAZATO Takaya

IEICE technical report. Communication systems Vol. 114 ( 289 ) page： 81 - 86 2014.11

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

This paper demonstrates the feasibility of layered space-time coding (STC) in an outdoor image-sensor-based (IS-based) visible light communication (VLC) system. We examined that for low-resolution IS-based VLC channel where intensity modulated signals from two different light emitting diodes (LEDs) are detected at one pixel on the image plane, STC allows to decouple them, thus receiving data with no errors. Consequently, STC offers extending the transmission distance. In the layered STC presented here, additional bit streams are aligned in the 2^n × 2^n LED array for increasing the transmission rate per symbol duration for the case where the spatial resolution is improved. A prototype of three layered STC is built with an 8 × 8 LED array. Our experimental results validate that additional bit streams (layer-2 and -3), aligned in the layer-1 STC matrix pair, are extracted with no errors when the receiver comes within 155m and 55m, respectively, from the LED array, without decreasing 210m of the transmission distance of layer-1 bit stream.

DOI： 10.1109/ICC.2015.7249124

CiNii Research

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

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

2014 IEEE Asia Pacific Conferece on Circuits and Systems page： - 2014.11

Language：English

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), vehicleto- infrastructure VLC (V2I-VLC), and vehicle-to-vehicle VLC (V2V-VLC). We analyze channel fluctuation in terms of optical flow from measured data.

データを伴う照明 Invited Reviewed

山里敬也

電波技術協会報 page： - 2014.11

Authorship：Lead author Language：Japanese

可視光通信とは，LEDを人の目に分からないほど高速に点滅（変調）させることで情報伝送を行う通信のことである．可視光通信では発光ダイオード（light emitting diode: LED）を送信デバイスに用いるのだが，LEDはものすごい勢いで普及が進みつつあり，それこそ至る所にある．つまりLEDにデータ伝送機能を追加する可視光通信はユビキタスのインフラ基盤になりうるのである．

BER Characteristic of Optical-OFDM using OCI Reviewed

Y. Goto, I. Takai, T. Yamazato, H. Okada, T. Fujii, S. Kawahito, S. Arai, T. Yendo, K. Kamakura

2014 IEEE Asia Pacific Conferece on Circuits and Systems page： - 2014.11

Language：English

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.

A Novel Study on Coded Modulation with Triangular Costellation Reviewed

YAMAOKA Tomoya, HARA Teruyuki, OKAZAKI Akihiro, YAMAZATO Takaya

Technical report of IEICE. RCS Vol. 114 ( 254 ) page： 111 - 116 2014.10

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

For improvement of the coded modulation, we propose the signal sets with triangular constellation and label shaping. The proposed signal set can gain the merits of them despite of a few signal points and a simple modification. We indicate the channel capacity, PAPR (Peak to Average Power Ratio), BER (Bit Error Rate) in case of BICM-ID (Bit Interleaved Coded Modulation with Iterative Decoding) and PAPR with band limited of the 7APSK (Amplitude and Phase-Shift Keying) and modified 14APSK. Especially, the results shows modified 14APSK we proposed can improve 16QAM (Quadrature Amplitude Modulation) in terms of BER and PAPR, simultaneously.

CiNii Research

A Transmit Diversity with a Simple Transmitter Reviewed

YAMAOKA Tomoya, HARA Teruyuki, OKAZAKI Akihiro, YAMAZATO Takaya

Technical report of IEICE. RCS Vol. 114 ( 254 ) page： 117 - 122 2014.10

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

In this paper, we proposed a transmit diversity with a simple transmitter. Specifically, we connect simplex RF (Radio Frequency) circuits with two antennas and transmit the signals whose phases are rotated and IQ component are interleaved alternately via two antennas. In the receiver, the signals with the signal space diversity are received in spite of the simple transmitter. So we can achieve space diversity and reliable wireless communications. In the performance evaluation, we confirm the 4dB gain at BER=10^<-2> in bit error rate performance.

CiNii Research

ITS Visible Light Communication using High-Speed Image Sensor Invited

Takaya Yamazato

The 133 Microoptics Meeting, Optical Society of Japan/The Japan Society of Applied Physics page： - 2014.10

Authorship：Lead author Language：Japanese

This paper presents the visible light communication using image sensor and its application to intelligent transport systems (ITS). As an example, mage-sensor based VLC for automotive application that is currently carried out by the author is also introduced. The paper is a continuation of the paper by Prof. Matsumoto, "Evaluation of optical wireless communication," and by Prof. Haruyama, "Recent trends of visible light communication," appeared on 2014 March issue of Microoptics News.

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

KINOSHITA Masayuki, YAMAZATO Takaya, OKADA Hiraku, FUJII Toshiaki, ARAI Shintaro, YENDO Tomohiro, KAMAKURA Koji

Vol. 114 ( 225 ) page： 77 - 81 2014.9

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

In image sensor based VLC for automotive applications, transmitter acquisition and tracking are critical. 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 automotive applications. Especially, we examined the channel fluctuation based on mobile movements in the image plane detected by phase only correlation (POC) in the subpixel accuracy.

CiNii Research

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

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

Vol. 2014 ( 13 ) page： 1 - 5 2014.9

Publishing type：Research paper (scientific journal) Publisher：Information Processing Society of Japan (IPSJ)

CiNii Research

A-2-7 An influence of Noise Bandwidth on an application of Stochastic Resonance to Radio Communication Reviewed

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

Proceedings of the Society Conference of IEICE Vol. 2014 page： 28 2014.9

A-5-2 A Study on Influence of Communication Distance in Visible Light Communication Using LED and High-Speed Camera Reviewed

SOUKE Eisho, OHIRA Yuki, ARAI Shintaro, YAMAZATO Takaya, YENDO Tomohiro, OKADA Hiraku, FUJII Toshiaki, KAMAKURA Koji

Proceedings of the Society Conference of IEICE Vol. 2014 page： 84 2014.9

A-5-1 A Study on Signal Demodulation Method Based on Blurred Camera Image in Visible Light Communication Using LED Array and High-Speed Camera Reviewed

OHIRA Yuki, ARAI Shintaro, YENDO Tomohiro, YAMAZATO Takaya, OKADA Hiraku, FUJII Toshiaki, KAMAKURA Koji

Proceedings of the Society Conference of IEICE Vol. 2014 page： 83 2014.9

LEDアレーと高速度カメラを用いた可視光通信における画像のボケの影響を考慮した信号復調手法の一検討

大平祐生，荒井伸太郎，圓道知博，山里敬也，岡田啓，藤井俊彰，鎌倉浩嗣

電子情報通信学会基礎・境界ソサイエティ大会 page： - 2014.9

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

T. Yamazato, S. Haruyama

IEICE Transactions on Communications Vol. E97-B ( 9 ) page： 1759-1765 2014.9

Language：English

This study introduces an image sensor based visible light communication (VLC) and its application to pose, position, and range estimations. There are two types of visible-light receiver: a photodiode and an image sensor. A photodiode is usually used as a reception device of VLC, and an image sensor consisting of a large number of pixels can also be used as a VLC reception device. A photodiode detects the signal intensity of incoming light, while an image sensor not only detects the incoming signal intensity but also an accurate angle of arrival of light emitted from a visible light transmitter such as a white LED light. After angles of arrival of light are detected by an image sensor, positioning and data reception can be performed. The ability of an image sensor to detect an accurate angle of arrival will provide attractive applications of VLC such as pose, position calculation, and range estimation. Furthermore, because the image sensor has the ability to spatially separate sources, outdoor positioning even with strong sunlight is possible by discarding the associated pixels of noise sources.

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

K. Chiga, H. Tanaka, T. Yamazato, Y. Tadokoro, S. Arai

International Symposium on Nonlinear Theory and its Application page： - 2014.9

Language：English

Stochastic Resonance (SR) is well known as a phenomenon in which the weak signal in a nonlinear system can be detected by added noise. We consider the application of SR phenomenon to a wireless communication system. The receiver using SR phenomenon can detect the subthreshold signal which is not detectable by the conventional receiver. The effect of SR receiver has been verified, but it has never been verified in radio frequency which is used by a wireless system. In this paper, we consider the implementation of SR System for Radio Frequency and evaluate its performance of Signal to Noise Ratio (SNR).

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Papers - YAMAZATO Takaya