Faculty Profiles - YAMAZATO Takaya

Papers - YAMAZATO Takaya

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Measurement of narrowband channel characteristics in single-phase three-wire indoor power-line channels Reviewed Open Access

Sugiura Y.

IEEE ISPLC 2008 - 2008 IEEE International Symposium on Power Line Communications and Its Applications page： 18 - 23 2008.9

Performance improvement of downlink MC-CDMA cellular system with an intermittent transmission Reviewed Open Access

Fushiki M.

2008 IEEE Radio and Wireless Symposium, RWS page： 275 - 278 2008.9

B-20-6 A note on joint decoding of spatially and temporally correlated sources Reviewed

KOBAYASHI Kentaro, YAMAZATO Takaya, OKADA Hiraku, KATAYAMA Masaaki

Proceedings of the Society Conference of IEICE Vol. 2008 ( 2 ) 2008.9

Bit and power allocation for power-line communications under nonwhite and cyclostationary noise environment

N. Sawada, T. Yamazato, M. Katayama

Communications Society Conference of IEICE Vol. A-5-2 page： 89 2008.9

Error-Correcting Method Based on Chaotic Dynamics for Noncoherent Chaos Communications Reviewed

S. Arai, Y. Nishio, T. Yamazato

Proceedings of International Symposium on Nonlinear Theory and its Applications (NOLTA'08) page： 652-655 2008.9

Language：English

This paper proposes the error-correcting method based on the chaotic dynamics for noncoherent chaos communications. We generate successive chaotic sequences from the identical chaotic map. And for the next sequence we set the initial value to the end value of the former sequence. By such way we can create the successive chaotic sequences having the same chaotic dynamics. This feature gives the receiver additional information to correctly recover the received noisy signal. Therefore, by analyzing the chaotic dynamics at the receiver, it is possible to improve the error performance. In other words, error performance of the receiver can be improved by the utilization of the suboptimal receiver with the analysis of chaotic dynamics of the successive received sequence. As results of computer simulations, we confirm about 3 dB gain in BER performance compared to the conventional suboptimal receiver.

A New SC/MMSE Turbo Equalization for MC-CDMA to use in Inter-Vehicle Communication Reviewed

N. Hiraiwa, A. Sakata, T. Yamazato, M. Katayama

IEEE Vehicular Technology Conference 2008-Fall page： CD-ROM 2008.9

Language：English

In this paper, we propose a new SC/MMSE Turbo equalizer for MC-CDMA to use in inter-vehicle communication (IVC). We modify the weight of the MMSE filter of SC/MMSE Turbo equalizer so that it can combat with frequency-selective fading in highly mobile IVC environment and also can mitigate the effect of multiple access interferences (MAI). As results, we show that better throughput is obtained by the proposed SC/MMSE equalization than the conventional one. The average reception range can be up to 70 [m] and the signals from 16 surrounding cars can be received. While for the conventional scheme, only three signals from the nearest cars are achieved.

Cooperative transmission in distributed sensor networks using visible light communication

K. Kobayashi, K. Nakao, T. Yamazato, M. Katayama

Proc. of 10th DSPS Educators Conference page： 72-73 2008.9

A modulation scheme without channel state information for cognitive radio overlay systems

J. Naganawa, T. Yamazato, M. Katayama

Communications Society Conference of IEICE Vol. B-17-9 page： 452 2008.9

A note on joint decoding of spatially and temporally correlated sources

K. Kobayashi, T. Yamazato, H. Okada, M. Katayama

Communications Society Conference of IEICE Vol. B-20-6 page： 342 2008.9

CDMA slotted ALOHA System with Successive Interference Cancellation for Inter-Vehicle Communications Reviewed

A.Sakata, T.Yamazato, H.Okada, M.Katayama

IEEE International Symposium on Spread Spectrum Techniques and Applications page： 188-193 2008.8

Language：English

This paper compares the throughput performance of orthogonal frequency division multiple access (OFDM) and multicarrier CDMA (MC-CDMA) in inter-vehicle communications (IVC).In particular, we compare the throughputs in a situation where hidden terminals are no longer negligible. We encounter the situation in an intersection where two or more cars are crossing by. Due to the hidden terminal degradation, poor throughput performance is obtained with OFDM scheme. On the other hand, MC-CDMA has a resistance to the hidden terminals as it can support simultaneous packets. However, the transmission data rate is much slow because of the spreading. Thus the total throughput may not be as high as the OFDM. As results, we show that throughput of the OFDM is better than the MC-CDMA in a low traffic region. We found that the OFDM can communicate only with the nearest car. On the contrary, when the traffic is high, the MC-CDMA shows better throughput than the OFDM. In addition, we show that many packets can be received simultaneously in MC-CDMA. These results lead to the conclusion that when we want high-speed communication to a few cars, the OFDM is a good candidate. And when low speed but simultaneous communication with many surrounding cars is our desire, then the MC-CDMA is our choice. As MC-CDMA has a compatibility with an OFDM by setting a spreading factor to one, MC-CDMA system may be the preferable choice for IVC.

Performance Comparison of OFDM and MC-CDMA in Inter-Vehicle Communications Reviewed

SAKATA Atsunori, YAMAZATO Takaya, OKADA Hiraku, KATAYAMA Masaaki

IEICE technical report Vol. 108 ( 171 ) page： 1 - 6 2008.7

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

This paper evaluates the packet success rate of aa orthogonal frequency division multiplexing (OFDM), a multicarrier CDMA (MC-CDMA) and a multicarrier orthogonal frequency division multiple access (MC-OFDMA) based on MC-CDMA. In particular, we compare the packet success rate in a high traffic situation where a hidden terminal is no longer negligible. A hidden terminal problem tends to occur in a situation of sight limitation such as intersection. We focus on physical layer and adopt MC-CDMA so that simultaneous reception is possible. This feature gives possible resistance to hidden terminal problem. In this paper, we investigate how the packet success rate performance varies with spreading factor and how to assign subcarrier. As results, we show that MC-OFDMA based on MC-CDMA shows better packet success rate than OFDM.

CiNii Research

Improvement of Robustness for Road-to-Vehicle Visible Light Communication using Hiearachical Coding Reviewed

MASE Shohei, ARAI Shintaro, YAMAZATO Takaya, YENDO Tomohiro, FUJII Toshiaki, TANIMOTO Masayuki, KIMURA Yoshikatsu

IEICE technical report Vol. 108 ( 171 ) page： 19 - 24 2008.7

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

In this paper, we propose an improved coding scheme for optical wireless communication systems using a LED array transmitter and a high-speed camera as the receiver on a vehicle. Previously, we have proposed a hierarchical coding scheme which allocated the data to spatial frequency components depending on the priority. In that scheme, the high-priority data can be received even if the receiver was far from the transmitter. We confirmed the advantage of the hierarchical coding scheme, but the bit error performance was not sufficient. In this paper, we divide the data into spatial frequency components, and use error correcting code for each spatial frequency components' data. Experimental evaluation demonstrates the improvement in BER performance. This improvement implies that the system range increased compared to the previous method.

CiNii Research

Road-to-Vehicle Visible Light Communication using LED Array and High-Speed Camera Reviewed

YAMAZATO Takaya, ARAI Shintaro, MASE Shohei, ENDO Tomohiro, FIJII Toshiaki, TANIMOTO Masayuki, KIMURA Yoshikatsu

IEICE technical report Vol. 108 ( 165 ) page： 47 - 52 2008.7

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

In this paper, we present hierarchical coding scheme using LED traffic lights and high-speed camera for Intelligent Transport Systems (ITS) application. If each of LEDs in traffic lights is individually modulated, parallel data transmissions are possible using a camera as a reception device. Such parallel LED-camera channel can be modeled as spatial low-pass filtered channel of which the cut-off frequency varies according to the distance. To overcome, we introduce hierarchical coding scheme based on 2D fast Haar wavelet transform.

CiNii Research

Road-to-Vehicle Visible Light Communication using LED Array and High-Speed Camera Reviewed

YAMAZATO Takaya, ARAI Shintaro, MASE Shohei, ENDO Tomohiro, FIJII Toshiaki, TANIMOTO Masayuki, KIMURA Yoshikatsu

IEICE technical report Vol. 108 ( 163 ) page： 47 - 52 2008.7

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

CiNii Research

Ultrasonic Array Emitter for Automotive Short-range Radar Networks Reviewed

HATANO Hiroyuki, YAMAZATO Takaya, KATAYAMA Masaaki

Vol. 62 ( 7 ) page： 29 - 34 2008.7

*Ultrasonic Array Emitter for Automotive Short-range Radar Networks Invited Reviewed

H. Hatano, T. Yamazato, M. Katayama

Journal of Society of Automotive Engineers of Japan, Vol.62, No.7, pp.29-34 Vol. 62 ( 7 ) page： 19-34 2008.7

Language：Japanese

We consider radar network systems using multiple ultrasonic radars for parking assistance. Our radar network has an ultrasonic array emitter and multiple sensors. The ultrasonic array emitter is composed of multiple ultrasonic emitters and can emit signals to the side area which is the desired monitoring area of parking aid. Target positions are estimated by the data processing form multiple ultrasonic sensors which are set at distributed points of the front bumper. In this paper we especially describe our proposed array emitter.

Road-to-Vehicle Visible Light Communication using LED Array and High-Speed Camera Invited

Takaya Yamazato, Shintaro Arai, Shohei Mase, Tomohiro Yendo (Nagoya Univ.), Toshiaki Fujii (Tokyo Inst. of TEch.), Masayuki Tanimoto (Nagoya Univ.), Yoshikatsu Kimura (Toyota Central R&D Labs.)

Technical Report of IEICE, IEICE Tech. Rep. Vol. SIP2008-76 ( 163 ) page： 47-52 2008.7

Language：Japanese

Performance Comparison of OFDM and MC-CDMA in Inter-Vehicle Communications

A.Sakata, T.Yamazato, H.Okada, M.Katayama

Technical Report of IEICE Vol. ITS2008-8 page： - 2008.7

Language：Japanese

This paper evaluates the packet success rate of aa orthogonal frequency division multiplexing(OFDM) , a multicarrier CDMA(MC-CDMA) and a multicarrier orthogonal frequency division multiple access(MC-OFDMA) based on MC-CDMA. In particular, we compare the packet success rate in a high traffic situation where a hidden terminal is no longer negligible. A hidden terminal problem tends to occur in a situation of sight limitation such as intersection. We focus on physical layer and adopt MC-CDMA so that simultaneous reception is possible. This feature gives possible resistance to hidden terminal problem. In this paper, we investigate how the packet success rate performance varies with spreading factor and how to assign subcarrier. As results, we show that MC-OFDMA based on MC-CDMA shows better packet success rate than OFDM.

Improvement of Robustness for Road-to-Vehicle Visible Light Communication using Hiearachical Coding

Shohei MASE, Shintro ARAI, Takaya YAMAZATO, Tomohiro YENDO, Toshiaki FUJII, Masayuki TANIMOTO, Yoshikatsu KIMURA

Technical Report of IEICE page： - 2008.7

Language：Japanese

A Route Establishment Scheme for Multi-route Coding in Multihop Cellular Networks Reviewed

H. Okada, H. Imai, T. Yamazato, M. Katayama, K. Mase

Academy Publisher Journal of Netowkrs Vol. 3 ( 7 ) page： 34-40 2008.7

Language：English

Since the network topology in multihop cellular networks is flexible, multiple routes from a user station to a base station can be established. To reduce packet reception errors of wireless links, a multi-route coding scheme was proposed. An important issue of the multi-route coding is to develop an efficient route establishment scheme. In this paper, we propose a route establishment scheme for multi-route coding in multihop cellular networks. Our proposed scheme consists of a route selection method based on the bit error rate of each wireless link and a hybrid-type multiple-tree routing protocol. We evaluate the performance of our proposed scheme by a computer simulation and show the resulting improvement in the packet error.

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Papers - YAMAZATO Takaya