Faculty Profiles - YAMAZATO Takaya

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

Y Hirayama, N Nakagawa, H Okada, T Yamazato, M Katayama

ELECTRONICS AND COMMUNICATIONS IN JAPAN PART I-COMMUNICATIONS Vol. 89 ( 1 ) page： 34 - 44 2006

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

In this research, real-time packet cornmunications on wireless multihop networks is considered. Since the communications quality is substantially degraded by packet delay in real-time packet communications, packet retransmission is not usually used. In order to suppress the effect of packet errors in the Communications channel on communications quality in such cases, this paper proposes an application of a multiroute packet combining scheme on a wireless multihop network. The performance of the proposed scheme depends on the time required for transmission of a packet on each route and the start time of packet combining at the destination node, in addition to the number of transmitted duplicate packets at the source node. In order to evaluate the constantly changing system performance from the viewpoint of the quality of service (QoS) required in real-time communications, the distribution function of the time needed for attaining a certain required packet error rate and the average packet error rate attainable at a certain time are analytically derived. From numerical examples, it is proven that there exists a number of transmitted duplicate packets minimizing the required time for attaining the required packet error rate, and also a number of transmitted duplicate packets minimizing the average packet rate attainable within an allowed delay time. (c) 2005 Wiley Periodicals, Inc.

DOI： 10.1002/ecja.20238

Single-user MAP based soft-in/soft-output parallel interference canceler utilizing retransmission diversity Reviewed

Y Tadokoro, H Okada, T Yamazato, M Katayama

ELECTRONICS AND COMMUNICATIONS IN JAPAN PART III-FUNDAMENTAL ELECTRONIC SCIENCE Vol. 89 ( 6 ) page： 1 - 12 2006

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

In packet communications, packets whose transmission Fails are retransmitted. If the likelihood information on a failed packet is used, the demodulation of the retransmitted packets and the operation of interference cancellation can be performed more accurately. Hence, several interference cancellation techniques using such retransmission diversify have been proposed. However, in these methods, the algorithm for interference cancellation is identical to the conventional one. Only the matched filter outputs of the packets with failed packet are combined at the output of the interference canceler. In the present research, the likelihood information on the failed packets is used and an interference cancellation algorithm is proposed that maximizes the a posteriori probability. As a result of performance evaluation, it is found that the newly transmitted packets in addition to the retransmitted packets can be sent successfully in the proposed interference cancellation method. (c) 2006 Wiley Periodicals, Inc.

DOI： 10.1002/ecjc.20217

Throughput Evaluation of ARQ Scheme for Multi-route Coding in Wireless Multi-hop Networks Reviewed

Hiraku Okada, Tadahiro Wada, Kouji Ohuchi, Masato Saito, Takaya Yamazato, Masaaki Katayama

2006 IEEE 63RD VEHICULAR TECHNOLOGY CONFERENCE, VOLS 1-6 page： 668 - + 2006

Language：English Publishing type：Research paper (international conference proceedings) Publisher：IEEE

For reduction in bit errors on wireless channels, we proposed the multi-route coding scheme on multiple routes for wireless multi-hop networks. In this paper, we introduce ARQ to the multi-route coding. In the multi-route coding, the destination node combines and decodes sub packets which are encoded and divided by the source node. The intermediate node relays a sub packet, that is, only a part of a packet. Therefore, the intermediate node cannot detect packet errors, and only the destination node can do after combining and decoding sub packets. We propose the ARQ scheme between the source node and the destination node. We analyze the proposed ARQ scheme and evaluate the throughput performance.

DOI： 10.1109/VETECS.2006.1682908

Throughput Evaluation of ARQ Scheme for Multi-route Coding in Wireless Multi-hop Networks Reviewed

Okada Hiraku, Wada Tadahiro, Ohuchi Kouji, Saito Masato, Yamazato Takaya, Katayama Masaaki

2006 IEEE 63RD VEHICULAR TECHNOLOGY CONFERENCE, VOLS 1-6 page： 668 - + 2006

The effect of multipath hybrid routing protocol in multihop cellular networks Reviewed

Hitoshi Imai, Hiraku Okada, Takaya Yamazato, Masaaki Katayama

IEEE International Symposium on Personal, Indoor and Mobile Radio Communications, PIMRC page： 1 - 5 2006

Language：English Publishing type：Research paper (international conference proceedings) Publisher：IEEE

This paper examines multihop cellular networks. There are some issues in these networks, such as route loss due to topological change and packet errors due to wireless nodes relay. To overcome these issues, we use a multiple route coding scheme in which packets are transmitted on multiple routes from a user node to multiple base stations. This scheme can achieve a diversity gain by combining packets that are transmitted along multiple routes. Some challenges must be met to establish multiple routes for this scheme. In this paper, we propose a routing protocol for multiple route coding. The key idea of this proposed scheme is using a hybrid routing protocol. This can mitigate an increase in control packets and multiple disjoint routes can be constructed. We evaluate the performance of this proposed scheme. © 2006 IEEE.

DOI： 10.1109/PIMRC.2006.254216

Target Position Estimation using MMSE for A Radar Network Reviewed Open Access

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

IEICE Transaction on Fundamentals of Electronics, Communications and Computer Sciences Vol. J88-A ( 12 ) page： - 2005.12

An improvement of the transmission quality using the correlation of the observation data in sensor networks Reviewed Open Access

An improvement of the transmission quality using the correlation of the observation data in sensor networks

IEICE Transaction on Fundamentals of Electronics, Communications and Computer Sciences Vol. J88-A ( 12 ) page： - 2005.12

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

In sensor networks, many sensor nodes are densely deployed and observation data obtained by each sensor node is correlated. Such observation data are collected at a fusion center. In this paper, we discuss the observation accuracy at the fusion center from the viewpoint of the amount of Kullback-Leibler (KL) information. Especially, we consider channel error caused when data are transmitted from sensor nodes through wireless communication channels. The channel error deteriorates the observation accuracy. We discuss this influence and a method to decrease it. In this paper, we consider a case when all the correlation between the observation data is equal and when the correlation is uniformly distributed. In both cases, we discuss degradation of KL information under the influence of channel errors. We show that it possible to avoid such degradation using the correlation between the observation data by a estimation of correct value of the erroneous data. In addition, we show a method to estimate the correlation between the observation data and an example of estimating a correct value from erroneous data using correlation.

Open Access

Ultra-Wideband Chaotic Radar and Clutter Reduction Methods Reviewed

N. Dake, Y. Uwate, Y. Nishio, T. Yamazato

Journal of Signal Processing Vol. 9 ( 6 ) page： 473-478 2005.12

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

Chaos could generate nonperiodic sequences with infinite lengths theoretically. In this paper, we propose a UWB (ultra-wideband) chaotic radar, whose transmitted signal is generated by a chaotic map. Since it is important to remove various noises called clutter in a radar, we focus mainly on the removal of clutter by applying three clutter reduction methods. We derive the probability density function of power, the distances between the transmitted signals and the recovered signals, and the detection probability, using computer simulations, and the performance of the proposed radar is evaluated.

A mathematical model of narrowband power-line noise based on measurements Reviewed

Katayama M., Yamazato T., Okada H.

2005 International Symposium on Power Line Communications and Its Applications, ISPLC 2005 Vol. 2005 page： 152 - 156 2005.12

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：2005 International Symposium on Power Line Communications and Its Applications, ISPLC 2005

This manuscript introduces a mathematically tractable and accurate model of narrowband power-line noise based on experimental measurements. In this model, the noise is expressed as the sum of cyclostationary Gaussian processes. The non-stationary features of power-line noise are represented with a small number of parameters, and the noise waveforms generated with the model achieve good agreement with those of actually measured noise. © 2005 IEEE.

DOI： 10.1109/ISPLC.2005.1430486