Faculty Profiles - YAMAZATO Takaya

Papers - YAMAZATO Takaya

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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.

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.

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.

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

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.

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, no.7, pp.34-40 Vol. 3 ( 7 ) page： 34-40 2008.7

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

相関のある情報源の分散符号化・統合復号法のEXIT解析

小林健太郎，山里敬也，片山正昭

第4回無線分散ネットワークに関するワークショップ page： - 2008.6

A modulation scheme for a cognitive radio system to overlay on a secondary user Reviewed

NAGANAWA Jun, YAMAZATO Takaya, KATAYAMA Masaaki

IEICE technical report Vol. 108 ( 62 ) page： 5 - 10 2008.5

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

As an answer to increasing demands for frequency spectrum, secondary spectrum licensing, in which a secondary wireless system overlays on the frequency band of an existing primary system, is taking attention. In overlay communications, the secondary system is demanded not to be a cause of performance degradation of the primary system, while the primary system does not considers the secondary system. This manuscript proposes a modulation scheme for such a secondary system. In the proposed scheme, the secondary system modifies its transmitting signal parameters adapting channel states and transmitted signal of the primary system. This set of reference information is also used at the receiver of the secondary system. We derive the symbol error rates of both the systems analytically, and show that it is possble to realize the communication of the secondary system with the same quality as the primary system, which has any degradation by the signal of the secondary system.

Spatial Diversity Scheme with Multiple-Transmit/Receive Antennas and Relay Terminals for Reliable Wireless Control Reviewed

R. Uchida, H. Okada, T. Yamazato, M. Katayama

IEICE Transactions on Communications Vol. J91-B ( 5 ) page： 585-594 2008.5

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

In this manuscript, a communication system for wireless control of industrial machines in indoor environment is discussed. In order to combat indoor fading and shadowing, an STBC cooperative relaying scheme, which uses multiple transmit and receive antennas together with multiple relay terminals, is introduced. In the proposed scheme each relay terminal transmits all STBC branch-signals with random phase rotations, and no exchange of information between the relay terminals is required to achieve high diversity order. In numerical evaluations, the proposed scheme is compared with conventional deterministic signal assignment or random branch selection schemes using average and outage probability of the frame-error rate as performance measures. As a result, the impact of the random phase rotations is clarified.

A modulation scheme for a cognitive radio system to overlay on a secondary user

Jun Naganawa, Takaya Yamazato, Masaaki Katayama

Technical Report of IEICE Vol. SR2008-2 page： - 2008.5

Language：Japanese

As an answer to increasing demands for frequency spectrum, secondary spe ctrum licensing, in which a secondary wireless system overlays on the fr equency band of an existing primary system, is taking attention. In ove rlay communications, the secondary system is demanded not to be a cause of performance degradation of the primary system, while the primary syst em does not considers the secondary system. This manuscript proposes a modulation scheme for such a secondary system . In the proposed scheme, the secondary system modifies its transmitting signal parameters adapting channel states and transmitted signal of the primary system. This set of reference information is also used at the r eceiver of the secondary system. We derive the symbol error rates of both the systems analytically, and s how that it is possble to realize the communication of the secondary sys tem with the same quality as the primary system, which has any degradati on by the signal of the secondary system.

Spatial Diversity Scheme with Multiple-Transmit/Receive Antennas and Relay Terminals for Reliable Wireless Control Reviewed

R. Uchida, H. Okada, T. Yamazato, M. Katayama

IEICE Transactions on Communications Vol. J91-B ( 5 ) page： 585-594 - 594 2008.5

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Papers - YAMAZATO Takaya