Faculty Profiles - YAMAZATO Takaya

Papers - YAMAZATO Takaya

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BER analysis for multi-carrier DS CDMA with multi-rate traffic Reviewed

Sandouk A, Harada M, Okada H, Yamazato T, Katayama M, Ogawa A

IEICE TRANSACTIONS ON FUNDAMENTALS OF ELECTRONICS COMMUNICATIONS AND COMPUTER SCIENCES Vol. E84A ( 7 ) page： 1723 - 1731 2001.7

BER analysis for multi-carrier DS CDMA with multi-rate traffic Reviewed

Sandouk A.

IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences Vol. E84-A ( 7 ) page： 1723 - 1731 2001.7

BER Analysis for Multi-carrier DS CDMA with Multi-rate Traffic Reviewed

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

IEICE Transactions on Fundamentals Vol. E84-A ( 7 ) page： 1723-1731 - 1731 2001.7

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

In this letter, we present bit error analysis(BER) of orthogonal multi-carrier direct sequence code division multiple access(DS-CDMA) system with multi-rate (multimedia) traffic. Analysis is carried out with random signature codes for an AWGN channel. Interference in such a system is severe because all users of all media transmit over the same assigned sub-carriers. This makes the analysis difficult. In our analysis, we divide this interference into different types and carry out our analysis to obtain the BER taking into account all these types. We show that the performance of the system is improved as the number of assigned sub-carriers M increases until a limit where the improvement does not continue even when M increases more. This is because of, as we show, the interference due to other sub-carriers becomes constant even in the case of M → ∞, and the interference in a multi-rate multi-carrier system is bigger than that in a single-carrier (M = 1) by a factor of π^2/3.

CiNii Research

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QoS and capacity comparison of CDMA ALOHA protocols in multimedia networks Reviewed

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

IEICE Transactions on Communications Vol. E84-B ( 6 ) page： 1588-1595 2001.6

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

In this letter, performance evaluation of a system that combines between Code-Division Multiple Access (CDMA) and ALOHA protocol in multimedia networks is presented. In our analysis, we compare the performance between the two basic techniques of ALOHA protocol, i.e., Slotted-ALOHA (S-ALOHA) and Unslotted-ALOHA (U-ALOHA), when combined with CDMA scheme to support voice and data users operating in same CDMA channel. The quality of service (QoS) required for voice and data media is completely taken care of. We obtain the throughput of data media, and the outage probability for voice considering both voice and data offered loads. Throughput performance of S-ALOHA technique is almost twice of that of U-ALOHA. However, we show in this letter that when we combine CDMA with the two basic techniques of ALOHA to accomplish multimedia transmission, both techniques have almost same performance. And, thus, CDMA U-ALOHA can be a good candidate for multimedia networks.

QoS and capacity comparison of CDMA ALOHA protocols in multimedia networks Reviewed

Sandouk A, Yamazato T, Katayama M, Ogawa A

IEICE TRANSACTIONS ON COMMUNICATIONS Vol. E84B ( 6 ) page： 1588 - 1595 2001.6

QoS and capacity comparison of CDMA ALOHA protocols in multimedia networks Reviewed

Sandouk A.

IEICE Transactions on Communications Vol. E84-B ( 6 ) page： 1588 - 1595 2001.6

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 ( 6 ) page： 886-893 - 893 2001.6

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：The Institute of Image Information and Television Engineers

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 the decision procedure. However, it is very difficult to implement a MAP algorithm at the front of the receiver because of 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

Other Link： https://jlc.jst.go.jp/DN/JALC/00075825751?from=CiNii

New Analytical Model for the TCP Throughput in Wireless Environment Reviewed

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

IEEE Vehicular Technology Conference (VTC-Spring 2001) Vol. 3 2001.5

SNIR Analysis of Asynchronous Multicarrier CDMA Systems Reviewed

MURAMATSU Hiroki, YAMAZATO Takaya, OKADA Hiraku, KATAYAMA Masaaki

Proceedings of the IEICE General Conference Vol. 2001 page： 181 2001.3

A STUDY ON MAP RECEIVER DESIGN FOR IMAGE COMMUNICATIONS Reviewed

Makido Satoshi, Honjo Masaru, Yamazato Takaya, Okada Hiraku, Katayama Masaaki, Ogawa Akira

Proceedings of the IEICE General Conference Vol. 2001 page： 186 2001.3

Joint Multi-dimensional Channel Parameter Estimation Schemes for DS-CDMA Systems Using a Modified version of the SAGE Algorithm Reviewed

Youssef R. Senhaji, T. Yamazato, M. Katayama, A. Ogawa

IEICE Transactions on Communications Vol. E84-B ( 3 ) page： 511-519 2001.3

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

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 when 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.

A Study on MAP Receiver Design for Image Communications

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

IEICE General Conference Vol. A-6 ( 4 ) page： 186 2001.3

Adaptive Subcarrier Assignment Schemes for OFDM Systems with Transmit Diversity

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

IEICE General Conference Vol. SB-139 page： 17-18 2001.3

SNIR Analysis of Multicarrier CDMA Systems

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

IEICE General Conference Vol. A-5 ( 22 ) page： 181 2001.3

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

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

IEICE Transactions on Communications Vol. EB-84 ( 3 ) page： 576-580 2001.3

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

In this letter, we present a method to generate sets of sequences suitable for multicode transmission in quasi-synchronous (QS) CDMA systems. We focus on Gold code but extension to orthogonal Gold code is straightforward. We show that by appropriate classification of sequences, it is possible to have sets whose cross correlation is small in QS situations.

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

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

IEICE TRANSACTIONS ON COMMUNICATIONS Vol. E84B ( 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

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

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

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Papers - YAMAZATO Takaya