Faculty Profiles - YAMAZATO Takaya

Papers - YAMAZATO Takaya

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Clutter reduction methods of a UWB chaos radar

Natsumi Dake, Yoshifumi Nishio, Takaya Yamazato

Technical Report of IEICE Vol. NLP2004-108 page： 49-52 2005.1

Language：Japanese

We have proposed a UWB chaos radar, whose transmitted signal is generated by a chaotic map. If the feature of chaos is exploited, a radar with outstanding performance can be expected. It is important to remove various noises called clutter in a radar. In this study, we focus mainly on removal of clutters by employing two noise reduction methods. We use the Minimum Distance Approximation method and Maximum Likelihood Decodings method to remove the clutter.

Time-dependent analysis of the multiple-route packet combining scheme in wireless multihop networks Reviewed

Yasuhiro Hirayama, Hiraku Okada, Takaya Yamazato, Masaaki Katayama

International Journal of Wireless Information Networks Vol. 12 ( 1 ) page： 35 - 45 2005.1

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

In this paper, we apply the multiple-route packet combining scheme (In Proceedings of the 1st International Symposium on Wireless Communication Systems, pp. 183-187, Mauritius, 2004) to wireless multihop networks in order to support delay-sensitive applications. The performance of the system is time-dependent and is greatly affected by network-level performance. Therefore, it is necessary to develop an analytical framework to evaluate the performance of the system with taking into account its time-dependency. We use queuing theory to analyze the performance of the system. From numerical results, it is shown that the performance degradation of the system is mainly caused by the increase of packet delay, which is due to the increase of the traffic intensity. To prevent the increase of traffic, we propose a packet discarding scheme. We analyze the average packet error probability of the proposed system with the equilibrium point analysis (EPA). Numerical results show that the packet discarding scheme can improve the average packet error probability under heavy traffic conditions. © 2005 Springer Science+Business Media, Inc.

DOI： 10.1007/s10776-005-5161-6

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On the Second-order Statistics of the Channel Parameters for BFDM/OQAM Systems Reviewed

B. Mongol, T. Yamazato, H. Okada, M. Katayama

2nd International Symposium on Wireless Communication Systems page： 534-538 2005

Language：English

Recently, there has been increased interest in using multicarrier systems in rapidly time-varying multipath environment. Biorthogonal Frequency Division Multiplexing based on Offset QAM (BFDM/OQAM) is an attractive modulation method since it allows time-frequency well-localized pulses even at critical sampling (i.e. maximum spectral ef ciency). BFDM/OQAM system is naturally strong against intersymbol and intercarrier interference (ISI/ICI). However, for further improvement of the system a study on the channel statistics is needed. In this paper we analytically examine the channel parameters for BFDM/OQAM and derive their second-order statistics.

A MIMO system with relay terminals for reliable wireless control. Reviewed

Ryosuke Uchida, Hiraku Okada, Takaya Yamazato, Masaaki Katayama

Proceedings of the IEEE 16th International Symposium on Personal, Indoor and Mobile Radio Communications, Berlin, Germany, September 11-14, 2005 page： 1626 - 1630 2005

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.

Scopus

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.

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Papers - YAMAZATO Takaya