Faculty Profiles - YAMAZATO Takaya

Papers - YAMAZATO Takaya

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Joint multi-dimensional channel parameter estimation schemes for DS-CDMA systems using a modified version of the SAGE algorithm Reviewed

YR Senhaji, T Yamazato, M Katayama, A Ogawa

IEICE TRANSACTIONS ON COMMUNICATIONS Vol. E84B ( 3 ) page： 511 - 519 2001.3

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

A modified version of the SAGE algorithm is presented for joint delay-azimuth-attenuation parameters' estimation in a multiuser DS-CDMA system. The introduced modification consists of using different time interval lengths wizen calculating the time correlations for optimizing the different channel parameters. This modification was proposed for the purpose of a further reduction in the algorithm's computational weight in case of receiving sufficiently resolvable waves. Specifically, we found that short interval windows are sufficient for estimating delays and azimuth angles, which is quite effective in reducing the computational burden in their optimization processes. As for the estimation of the attenuation parameters, a longer time window, equal to the preamble length, is considered for more accurate estimation. Also two other estimators are proposed. The first one combining the modified SAGE with a sequential estimation of the attenuation parameters, suitable for slowly varying channels. Another one, similar to the first, and primarily designed to alleviate the influence of present strong interferers. Through a numerical example, the performances of the three presented estimation schemes, in terms of their near-far resistance, are compared. And it is shown that the proposed second combined estimator outperforms the modified SAGE in environments with high MAI levels.

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Joint multi-dimensional channel parameter estimation schemes for DS-CDMA systems using a modified version of the SAGE algorithm Reviewed

Senhaji YR, Yamazato T, Katayama M, Ogawa A

IEICE TRANSACTIONS ON COMMUNICATIONS Vol. E84B ( 3 ) page： 511 - 519 2001.3

Generation of Sets of Sequences Suitable for MulticodeTransmission in Quasi-Synchronous CDMA Systems Reviewed

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

IEICE Transactions on Communications Vol. E84-B ( 3 ) page： 576-580 2001.3

Generation of sets of sequences suitable for multicode transmission in quasi-synchronous CDMA systems Reviewed

Saito M.

IEICE Transactions on Communications Vol. E84-B ( 3 ) page： 576 - 580 2001.3

Throughput Performance of CDMA Slotted ALOHA Systems Based on Average Packet Success Probability Considering Bit-to-Bit Dependence Reviewed

M. Saito, T. Yamazato, M. Katayama, and A. Ogawa

IEICE Transaction on Fundamentals of Electronics, Communications and Computer Sciences Vol. EA-84 ( 2 ) page： 653-659 2001.2

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

We propose the analytical calculation method of average packet success probability of CDMA slotted ALOHA systems, which derives accurate probability, and that is applicable to the system with any spreading codes and any amplitude distributions. In the method, we consider the bit-to-bit dependence of amplitude of signals, used spreading sequences, relative timing delays, and relative carrier phases. This bit-to-bit dependence is the case that the parameters above mentioned are constant for a slot time. By using the method to obtain the average packet success probability, we derive useful throughput performance of CDMA slotted ALOHA systems on fading channel, and show that the normalized throughput becomes worse in the case of larger spreading factor.

Throughput performance of CDMA slotted ALOHA systems based on average packet success probability considering bit-to-bit dependence Reviewed

Saito M, Yamazato T, Katayama M, Ogawa A

IEICE TRANSACTIONS ON FUNDAMENTALS OF ELECTRONICS COMMUNICATIONS AND COMPUTER SCIENCES Vol. E84A ( 2 ) page： 653 - 659 2001.2

Throughput performance of CDMA slotted ALOHA systems based on average packet success probability considering bit-to-bit dependence Reviewed

M. Saito, T. Yamazato, M. Katayama, A. Ogawa

IEICE Transactions on Fundamentals Vol. E84-A ( 2 ) page： 653 - 659 2001.2

Language：English Publishing type：Research paper (scientific journal) Publisher：電子情報通信学会

We propose the analytical calculation method of average packet success probability of CDMA Slotted ALOHA systems, which derives accurate probability, and that is applicable to the system with any spreading codes and any amplitude distributions. In the method, we consider the bit-to-bit dependence of amplitude of signals, used spreading sequences, relative timing delays, and relative carrier phases. This bit-to-bit dependence is the case that the parameters above mentioned are constant for a slot time. By using the method to obtain the sverage packet success probability, we derive useful throughput performance of CDMA Slotted ALOHA systems on fading channel, and show that the normalized throughput becomes worse in the case of larger spreading factor.

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Throughput performance of CDMA slotted ALOHA systems based on average packet success probability considering bit-to-bit dependence Reviewed

M Saito, T Yamazato, M Katayama, A Ogawa

IEICE TRANSACTIONS ON FUNDAMENTALS OF ELECTRONICS COMMUNICATIONS AND COMPUTER SCIENCES Vol. E84A ( 2 ) page： 653 - 659 2001.2

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

We propose the analytical calculation method of average packet success probability of CDMA Slotted ALOHA systems, which derives accurate probability, and that is applicable to the system with any spreading codes and any amplitude distributions. In the method, we consider the bit-to-bit dependence of amplitude of signals, used spreading sequences, relative timing delays, and relative carrier phases. This bit-to-bit dependence is the case that the parameters above mentioned are constant for a slot time. By using the method to obtain the average packet success probability, we derive useful throughput performance of CDMA Slotted ALOHA systems on fading channel, and show that the normalized throughput becomes worse in the case of larger spreading factor.

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Study on TCP throughput with FEC and ARQ in a wireless link Reviewed

K. Naito, H. Okada, T. Yamazato, M. Katayama, and A. Ogawa

IEICE Transaction on Fundamentals of Electronics, Communications and Computer Sciences Vol. J84-A ( 1 ) page： 122-126 2001.1

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

It is reported that the performance of the TCP is very poor in wireless environments. In this paper, we attempt FEC or ARQ to better performance of the TCP in a wireless link, and clarify the TCP throughput. As shown in results, it is necessary for better performance of the TCP to apply FEC or ARQ, which suited to occurrence distribution of transmission errors.

Study on TCP Throughput with FEC and ARQ in a Wireless Link Reviewed

Katsuhiro Naito, Hiraku Okada, Takaya Yamazato, Masaaki Katayama, Akira Ogawa

IEICE Transaction on Fundamentals (Japanese) Vol. J84-A ( 1 ) page： 122 - 126 2001.1

An Adaptive Antenna Selection Scheme for Transmit Diversity in OFDM Systems Reviewed

H. Shi M. Katayama T. Yamazato H.Okada and A.Ogawa

IEEE Vehicular Technology Conference (VTC) page： - 2001

Language：English

We consider an adaptive antenna selection scheme for transmit diversity in OFDM systems. In the proposed system, the mapping of the subcarriers to antennas is adaptively operated by transmitter according to the Channel State Information(CSI). The performance of the system is improved greatly with this scheme even in slow fading environment. In addition, major modification is necessary only at the transmitter. This is very advantageous for systems with small terminals.

マルコフ情報源に対する予測器を用いた高能率MAP受信機の提案

牧戸知史，本庄勝，山里敬也，岡田啓，片山正昭，小川明

電気学会東海支部平成１２年度第２回「マルチメディア情報通信のための信号処理技術」若手セミナー page： - 2001

A Study on Multi-carrier DS-CDMA Systems with Multi-rate Traffic

A. Sandouk, M. Harada, H. OKada, T. Yamazato, M. Katayama, A. Ogawa

Technical Report of IEICE Vol. SST2000 ( 87 ) page： 137-142 2001

Language：English

In this work, orthogonal multi-carrier direct sequence code division multiple access (DS-CDMA) system with multi-rate traffic is presented. Interference in such a system is severe because all users of all media transmit over the same assigned sub-carriers. We divide this interference into different types and analyze the system to obtain the bit error rate (BER) with random signature codes for an AWGN channel taking into account all interference types.

The influence of analog to digital conversion on the performance of a broadband software-defined base station

M. Okuma, T. Yamazato, H.Okada, M.Katayama

Technical Report of IEICE Vol. SR01 ( 2 ) page： 39340 2001

Language：Japanese

In this study, we consider a broadband software-defined base station receiver, which emploies superconductive analog to digital converter (ADC) and simultaneously processes signals of different modulation and multiple access schemes. In such a system, we show the influence of the key parameters of an ADC (such as a number of bits per sample, and full-scale-range) on the bit error rate performance for various conditions.

A novel signal recognition and detection scheme for CDMA packet systems

T.Kume, T.Yamazato, K.Ban, H.Okada, and M.Katayama

Technical Report of IEICE ( 27 ) page： 33-38 2001

Language：Japanese

In this paper, a novel signal recognition and acquisition scheme with an adaptive filter is proposed for direct-sequence code-division multiple access (DS-CDMA) packet systems. In CDMA systems, conventional matched filter receivers suffer from the near-far problem due to multiple access interference (MAI). In general, closed-loop power control is used in order to reduce the influence of the near-far problem. However, in packet systems, closed-loop power control is unsuitable. Hence, we focus on an adaptive receiver with an adaptive linear filter based on LMS algorithm, which eliminate the influences of MAI and the near-far problem, for a signal recognition and acquisition in CDMA packet systems.

Performance of an OFDM Communication Systemunder a Frequency and Time Dependent Power-Line Channel Reviewed

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

5th International Symposium on Power-line Communications and Its Applications page： 35-40 2001

Language：English

In this manuscript, we employ OFDM (Orthogonal Frequency Division Multiplexing) modulator with the cyclo-stationary Gaussian model for power-line noise. Under this environment, the relation of the bit error rate (BER) to time and frequency is analyzed. In addition, we introduce guaranteed BER as a measure of the performance and show performance improvement by changing the number of sub-carriers and omitting a part of data from transmission.

Fundamentals of CDMA Invited Reviewed

Takaya Yamazato

2001 Karuizawa Workshop, Karuizawa, Nagano, Japan page： - 2001

A Design of Source Matched MAP Receiver for Image Transmission Reviewed

S. Makido, T. Yamazato, H. Okada, M. Katayama, and A. Ogawa

IEEE International Symposium on Circuit and Systems ( IV ) page： 136-139 2001

Language：English

In this paper we will discuss the MAP receiver design for the reception of the image signal. It is impractical to use the MAP algorithm for the source detection because of its huge calculation costs. To solve this problem we propose a novel MAP receiver structure, where the receiver contains a predictor within it. With an aid of the predictor we can reduce the calculation. Furthermore we can approximate the a priori probability by the prediction error distribution.

New Analytical Model for the TCP Throughput in Wireless Environment Reviewed

K. Naito, H. Okada, T. Yamazato, M. Katayama, and A. Ogawa

IEEE Vehicular Technology Conference (VTC) page： - 2001

Language：Japanese

In this paper, we propose a new analytical model for the TCP, and analyze the bulk throughput performance of different versions of TCP Transmission Control Protocol), viz., Tahoe, Reno and NewReno. We focus on the performance of a single wireless TCP connection which has random segment losses. In our analytical model, we model the TCP mechanisms as a Markov chain. In our result, we found that TCP Tahoe, Reno and NewReno have similar performance with random segment losses. This will lead us to design a lower layer mechanisms.

A MAP Receiver Based on Prediction Error Reviewed Open Access

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

The Journal of the Institute of Television Engineers of Japan, vol.55, no.6, pp.886-893, June 2001 Vol. 55 ( 6 ) page： - 2001

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

A MAP (Maximum A posteriori Probability) receiver is described that is designed for Markovian sources in a wireless environment. A MAP receiver, a well-known efficient receiver, uses the stochastic characteristics of the source in its calculation costs. To reduce these costs we introduce a source predictor in the receiver. With the aid of the predictor, the MAP detector can be operated with a small calculation cost. Experimental PCM (Pulse Coded Modulation) image transmission demonstrated the feasibility of the proposed receiver. Simulation of the receiver's performance showed it had better MSE (Mean Squared Error) performance in spite of its implementation simplicity.

DOI： 10.3169/itej.55.886

Open Access

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Papers - YAMAZATO Takaya