Faculty Profiles - YAMAZATO Takaya

Papers - YAMAZATO Takaya

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A study of wireless TCP access with base station diversity Reviewed

K Naito, H Okada, T Yamazato, M Katayama

ELECTRONICS AND COMMUNICATIONS IN JAPAN PART I-COMMUNICATIONS Vol. 88 ( 9 ) page： 49 - 61 2005

Language：English Publishing type：Research paper (scientific journal) Publisher：SCRIPTA TECHNICA-JOHN WILEY & SONS

It is known that performance is degraded in Internet access using TCP in a wireless environment, making communications almost impossible. This study proposes a cellular system in which a wireless terminal evaluates its own wireless environment and TCP performance and connects to multiple base stations. The TCP performance in the proposed system is evaluated and it is found to be greatly improved by applying base station diversity. By applying the proposed procedure for selecting the base station to which it will connect, the unnecessary use of wireless resources can be avoided. It is shown that in order to improve TCP performance, the cell radius should be set appropriately for the required TCP performance. (c) 2005 Wiley Periodicals, Inc.

DOI： 10.1002/ecja.20169

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On the second-order statistics of the channel parameters for BFDM/OQAM systems Reviewed

Mongol B, Yamazato T, Okada H, Katayama M

2ND INTERNATIONAL SYMPOSIUM ON WIRELESS COMMUNICATIONS SYSTEMS 2005 (ISWCS 2005) page： 534 - 538 2005

Performance evaluation of route coding scheme in wireless multi-hop networks Reviewed

Okada H, Wada T, Ohuchi K, Saito M, Yamazato T, Katayama M

VTC2005-SPRING: 2005 IEEE 61ST VEHICULAR TECHNOLOGY CONFERENCE, VOLS 1-5, PROCEEDINGS page： 3092 - 3096 2005

Successive interference cancellation for hierarchical parallel optical wireless communication systems Reviewed

Okada H, Masuda K, Yamazato T, Katayama M

2005 ASIA-PACIFIC CONFERENCE ON COMMUNICATIONS (APCC), VOLS 1& 2 page： 788 - 792 2005

A simple data relay process and turbo code application to wireless sensor networks Reviewed

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

1st International Symposium on Wireless Communication Systems 2004, Proceedings ISWCS '04 page： 398 - 402 2004.12

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：1st International Symposium on Wireless Communication Systems 2004, Proceedings ISWCS '04

In this study, we focus on relay process of intermediate node of wireless sensor networks. In conventional wireless sensor networks, the intermediate node performs the regenerative repeating process such that error correction, detection and re-encoding are processed. This is reliable, but it requires a lot of processing effort and may take much energy. To reduce a burden of relay process, we propose to omit error decoding and/or reencoding process at the intermediate nodes. Farther, we propose a method that realizes soft-decision decoding for hard-detected signals. With this method, we can employ Turbo code to wireless sensor networks. As results, we show that though omitting the decoding and re-encoding process at the intermediate node may not affect much to the performance. © 2004 IEEE.

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A study on error correcting and diversity combiner scheme on multiple routes in wireless multi-hop networks Reviewed

Okada H., Koie N., Nakagawa N., Yamazato T., Katayama M.

1st International Symposium on Wireless Communication Systems 2004, Proceedings ISWCS '04 page： 183 - 187 2004.12

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：1st International Symposium on Wireless Communication Systems 2004, Proceedings ISWCS '04

Wireless multi-hop networks have been much attention for the possibility of flexible construction of the network topology. One of the important and interesting techniques for multi-hop networks is a multi-path routing. By using the multi-path routing, multiple routes from a source node to a destination node can be established. In this paper, we propose the error correcting and diversity combiner scheme on multiple routes in wireless multi-hop networks to reduce bit errors. The diversity combiner outputs the likelihood information from the packets transmitted via multiple routes. By feeding the likelihood information into the Viterbi decoder, the diversity gain can be obtained. We evaluate the packet error rate and the total traffic. As a result, the packet error rate can be improved. Furthermore, the total traffic can be reduced in the low Eb/N0 in spite of the traffic increase due to transmission via redundant routes. © 2004 IEEE.

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Performance analysis of MC-CDMA system with and without guard interval in two-path channel Reviewed

Yamamoto H.

IEEE International Symposium on Spread Spectrum Techniques and Applications page： 67 - 71 2004.12

Performance analysis of UWB impulse radar using parallel IPCP receiver Reviewed

Hatano H.

1st International Symposium on Wireless Communication Systems 2004, Proceedings ISWCS '04 page： 115 - 119 2004.12

Performance analysis of multiple-route packet combining scheme for real-time communications in wireless multihop networks Reviewed

Hirayama Y.

IEEE International Symposium on Personal, Indoor and Mobile Radio Communications, PIMRC Vol. 1 page： 140 - 144 2004.12

The optimum received signal-power distribution for CDMA packet communication systems employing successive interference cancellation Reviewed

Tadokoro Y.

IEEE International Symposium on Spread Spectrum Techniques and Applications page： 37 - 41 2004.12

Hierarchical transmission of DCT coefficients using multi-code DS/SS modulation Reviewed

Honjo M, Makido S, Yamazato T, Okada H, Katayama M, Ogawa A

IEICE TRANSACTIONS ON FUNDAMENTALS OF ELECTRONICS COMMUNICATIONS AND COMPUTER SCIENCES Vol. E87A ( 11 ) page： 3001 - 3007 2004.11

Hierarchical transmission of DCT coefficients using multi-code DS/SS modulation Reviewed

Honjo M.

IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences Vol. E87-A ( 11 ) page： 3001 - 3007 2004.11

Hierarchical transmission of DCT coefficients using multi-code DS/SS modulation Reviewed

M Honjo, S Makido, T Yamazato, H Okada, M Katayama, A Ogawa

IEICE TRANSACTIONS ON FUNDAMENTALS OF ELECTRONICS COMMUNICATIONS AND COMPUTER SCIENCES Vol. E87A ( 11 ) page： 3001 - 3007 2004.11

Language：English Publishing type：Research paper (scientific journal) Publisher：IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG

We propose a novel hierarchical transmission method of DCT coefficients using multi-code DS/SS modulation. For low resolution image transmission over noisy channel, an error resilient and graceful degradation technique is necessary. Here, the DCT coefficients are divided into each stratum (a branch of multi-code DS/SS) and transmitted simultaneously through a noisy channel. By assigning an appropriate transmission energy that corresponds to their source energy variances, energy assignment, it is possible to maintain picture quality effectively even in a noisy channel. Analysis of this method was performed using an image data model, 2-D Gauss-Markov random field, which showed that picture quality is maintained even in the noisy channel condition.

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[Invited Paper] Information and Signal Processing for Sensor Networks Invited Reviewed

A. Ogawa, T. Yamazato, T. Ohtsuki

IEICE Transaction on Fundamentals of Electronics, Communications and Computer Sciences Vol. E87-A ( 10 ) page： 2599-2606 2004.10

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

Sensor networks, in which a large number of sensor nodes are connected with each other through communication networks, are potential to provide extensive new applications with various research and technical challenges and attracting much attention all over the world. In this paper we describe information and signal processing for sensor networks with emphasis on the concepts of collaboration and fusion as one of the most important issues for the sensor networks. We also review some basic aspects of sensor networks in terms of their features and the network architecture.

A Macro and Micro MIMO Diversity Scheme for a Shadowing Environment Reviewed

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

The 2004 International Symposium on Information Theory and Its Applications page： 1535-1539 2004.10

Performance Evaluation for Error Correcting Scheme on Multiple Routes in Wireless Multi-hop Networks Reviewed

N. Nakagawa, H. Okada, T. Wada, T. Yamazato, M. Katayama

The 2004 International Symposium on Information Theory and Its Applications page： 1535-1539 2004.10

Language：English

In this paper, we consider the improvement of packet error rate on wireless multi-hop networks. One of the important and interesting techniques for wireless multi-hop networks is multi-path routing. By using multi-path routing, multiple routes can be established from a source node to a destination node. In this paper, we propose the error correcting scheme in which the coded different packets are transmitted using multiple routes on wireless multi-hop networks. Hence, we can achieve a coding gain for multiple routes and expect the improvement of performance. In wireless multi-hop networks, the route loss due to topological change or recognizing failure may be happened. From the above discussion, we evaluate the proposed scheme by packet error rate in consideration of the influence of the route loss.

Information and signal processing for sensor networks Reviewed

Ogawa A, Yamazato T, Ohtsuki T

IEICE TRANSACTIONS ON FUNDAMENTALS OF ELECTRONICS COMMUNICATIONS AND COMPUTER SCIENCES Vol. E87A ( 10 ) page： 2599 - 2606 2004.10

Information and signal processing for sensor networks Reviewed

Ogawa A.

IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences Vol. E87-A ( 10 ) page： 2599 - 2606 2004.10

Information and signal processing for sensor networks Reviewed

A Ogawa, T Yamazato, T Ohtsuki

IEICE TRANSACTIONS ON FUNDAMENTALS OF ELECTRONICS COMMUNICATIONS AND COMPUTER SCIENCES Vol. E87A ( 10 ) page： 2599 - 2606 2004.10

Language：English Publishing type：Research paper (scientific journal) Publisher：IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG

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Performance Analysis of MC-CDMA System with and without Guard Interval in Two-Path Channel Reviewed

H. Yamamoto, T. Yamazato, H. Okada, and M. Katayama

IEEE International Symposium on Spread Spectrum Techniques and Applications (ISSSTA) page： 67-71 2004.9

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Papers - YAMAZATO Takaya