Faculty Profiles - YAMAZATO Takaya

Papers - YAMAZATO Takaya

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Energy Efficiency of Cooperative MISO Technique in Multi-hop Wireless Sensor Networks Reviewed

Z. Huang, T. Yamazato, M. Katayama

2008 The Fourth International Conference on Intelligent Sensors, Sensor Networks and Information Processing page： 511-515 2008.12

Language：English

In this paper, the energy efficiency of cooperative Multiple-Input Single-Output (MISO) technique for a multi-hop wireless sensor network is investigated and compared with other transmission schemes. Firstly, we present different schemes for data transmission of the cluster farther from base station and calculate their energy consumptions. The results show that the optimal transmission scheme varies with the inter-cluster distance in different networks. Then we explore the lifetime of the network and find that it is not always the optimal to employ the multi-hop transmission and the single-hop transmission outperform the multi-hop under a certain distance threshold. In addition, the effects of the transmission bit rate and the required bit error ratio (BER) on the distance threshold are also clarified.

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

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

2008 International Workshop on Smart Info-Media Systems in Bangkok (SISB 2008) page： CD-ROM 2008.12

Language：English

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.

Joint Channel Decoding of Spatially and Temporally Correlated Data in Wireless Sensor Networks Reviewed

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

The 2008 International Symposium on Information Theory and Its Applications page： 930-934 2008.12

Language：English

In densely deployed wireless sensor networks, sensor observations are spatially correlated. Furthermore, the nature of physical phenomena constitutes a temporal correlation between transmitted observations of an individual sensor node. In this paper, we propose a joint iterative channel decoding scheme using turbo codes. The proposed decoder exploits the spatial and temporal correlations of two binary data sequences to achieve additional coding gain. Simultaneously exploiting the spatial and temporal correlation, the proposed decoder achieves large performance gain.

Joint Channel Decoding of Spatially and Temporally Correlated Data in Wireless Sensor Networks Reviewed

S. Arai, Y. Nishio, T. Yamazato

Proceedings of IEEE Workshop on Nonlinear Circuit Networks (NCN'08) page： 49-51 2008.12

Language：English

We investigate and evaluate a suboptimal receiver using chaotic sequences with biased values. In our previous research, we investigated a differential chaos shift keying (DCSK) using chaotic sequences with biased values purposely and confirmed its better performance. However, our previous study only performed the computer simulation of DCSK using these chaotic sequences. In this study, we focus on the suboptimal receiver and evaluate its performance with chaotic sequences with biased values.

Energy efficiency of cooperative MISO technique in multi-hop wireless sensor networks Reviewed

Huang Z.

ISSNIP 2008 - Proceedings of the 2008 International Conference on Intelligent Sensors, Sensor Networks and Information Processing page： 511 - 516 2008.12

Error correcting scheme for road-to-vehicle visible light communication using LED array Reviewed

Mase S.

IEEE Conference on Intelligent Transportation Systems, Proceedings, ITSC page： 1113 - 1117 2008.12

Feasible study of road-to-vehicle communication system using led array and high-speed camera Reviewed

Arai S.

15th World Congress on Intelligent Transport Systems and ITS America Annual Meeting 2008 Vol. 4 page： 2911 - 2922 2008.12

Joint channel decoding of spatially and temporally correlated data in wireless sensor networks Reviewed

Kobayashi K.

2008 International Symposium on Information Theory and its Applications, ISITA2008 2008.12

*Feasible Study of Road-to-Vehicle Communication System Using LED Array and High-Speed Camera Reviewed

S. Arai, S. Mase, T. Yamazato, T. Yendo, T. Fujii, M. Tanimoto, Y. Kimura

Proceedings of the 15th World Congress on ITS page： CD-ROM 2008.11

Language：English

In this study, we focus attention on the parallel optical wireless communication systems using LED array transmitter and a high-speed camera as the receiver for road-to-vehicle communications in ITS. Previously, we have proposed a hierarchical coding scheme which allocates data to spatial frequency components depending on the priority. This scheme is possible to receive the high priority data even if the receiver is far from the transmitter. However, since vehicles drive on a road in actual road-to-vehicle communications, there are many important works to develop the real-time communication system. For example, it is a difficult to synchronize the timing to release the shutter with the lighting cycle of LEDs, i.e., the sampling of the data. This paper details our road-to-vehicle communication system using the LED array and the high-speed camera and proposes their solutions. Moreover, based on proposed solutions, we perform a driving field trial using the LED array and a vehicle with the high speed camera. As the result, we observe the bit error rate and confirm the reception of the data during the driving.

Energy-aware Protocol for Cluster-based Cooperative Transmission in Wireless Sensor Networks Reviewed

K. Takeshima, T. Yamazato, M. Katayama

Proceedings of International Workshop on Vision, Communications and Circuits (IWVCC'08) page： 149-152 2008.11

Language：English

In this paper, we look at communication protocol designed for cluster-based cooperative transmission. As it can increase the spatial diversity of wireless channel, cluster-based cooperative transmission is effective not only for reliable transmission but also in reduction of the transmitted power. The overall energy dissipation is, however, governed by a cluster head selection criterion. We show that the conventional random cluster head selection, as in low-energy adaptive clustering hierarchy (LEACH), and the best link quality cluster head selection may not be optimal for cluster-based cooperative transmission. Based on our finding, we propose a new energy-aware protocol for cluster-based cooperative transmission that considers not only the link quality but also the residual energy of sensor nodes. As results, our protocol shows the best in the availability ratio of sensor nodes and outage probability for the number of cluster-to-cluster transmissions.

Investigation of Noncoherent Detection Using Chaotic Sequence with Biased Values Reviewed

S. Arai, Y. Nishio, T. Yamazato

Proceedings of International Workshop on Vision, Communications and Circuits (IWVCC'08) page： 221-224 2008.11

Language：English

We investigate the chaotic sequence with biased values in chaos-based communication systems. In our previous research, we investigated the the performance of chaos communications using the sequence with biased values purposely. As results, we concluded that the chaotic dynamics affect the performance of chaos communications greatly. However, our previous study only performed the computer simulation the DCSK system using the chaotic sequence with biased values. In this study, we focus on the suboptimal receiver as one of chaos communication systems and observe its performance with the chaotic sequence with biased values.

Performance evaluation of turbo encoding and joint iterative decoding for multiple correlated sources Reviewed

KOBAYASHI Kentaro, YAMAZATO Takaya, KATAYAMA Masaaki

IEICE technical report Vol. 108 ( 252 ) page： 51 - 55 2008.10

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

We present a joint iterative decoding scheme for multiple correlated data which are separately turbo encoded and transmitted over noisy channels. The proposed decoder exploits the correlation in an iterative manner for achieving additional coding gain. Simulation results show that close to Shannon and Slepian-Wolf limit performance is achieved, and large SNR gain is achieved in comparison with the standard turbo decoder. We also verify through simulation that the codes with a low error floor is crucial to achieve good performance for a large number of the correlated data and no significant penalty results from the estimation of the correlation in the decoding process.

Performance evaluation of turbo encoding and joint iterative decoding for multiple correlated sources

K. Kobayashi, T. Yamazato, M. Katayama

Technical Report of IEICE Vol. USN2008-47 page： 51-55 2008.10

Language：Japanese

Error Correcting Scheme for Road-to-Vehicle Visible Light Communication using LED Array Reviewed

S. Mase, S. Arai, T. Yamazato, T. Yendo, T. Fujii, M. Tanimoto, Y. Kimura

IEEE International IEEE Conference on Intelligent Transportation Systems page： CD-ROM 2008.10

Language：English

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.

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

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

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.

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Papers - YAMAZATO Takaya