Faculty Profiles - YAMAZATO Takaya

Papers - YAMAZATO Takaya

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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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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.

CiNii Books

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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

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.

Hierarchical Transmission of DCT Coefficients Using Multi-Code DS/SS Modulation

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

Technical Report of IEICE Vol. SST2001 ( 17 ) page： - 2001

Language：Japanese

In this paper, we propose a hierarchical transmission of image signal using multi-code DS/SS modulation. DCT is originally invoked in the image coding at the aim of compacting the input variance and compressing efficiently. We achieve an error torelant transmission system by using this property in transmit energy. We introduce the energy assingment (EA) to reduce the channel noise in hierarchical transmission. Assigning an appropriate transmitt energy corresponding to its variance, we show that it is possible to maintain the picuture quality even in low channel condition. The analysis is carried out to show the effectiveness of our scheme using 2-D Gauss-Markov random field in the case of MC DS/SS modulation used. We also verify the same characteristic in several sample movies.

Comparison of CDMA and FDMA/TDMA in non-GEO Satellite Systems Reviewed

N. Ichikawa, M. Katayama, H. Okada, T. Yamazato, and Akira Ogawa

IEEE International Conference on Communications (ICC2001) Vol. G76.5 page： - 2001

Language：English

We compare CDMA and FDMA (or TDMA) schemes in multi-beam non-geostationary satellite systems, taking the effects of antenna patterns on inter-cell interference into consideration. The maximum acceptable number of users per cell in uplink is employed as a measure of the system capacity. We have found that in FDMA (or TDMA) systems the maximum acceptable number of users varies according to the altitude of the satellites, while the performance is insensitive to the altitude in CDMA systems. For this reason, the altitude of the satellites is found to be an important factor for selecting multiple access schemes in non-geostationary satellite systems.

A Study on High Rate Serially Concatenated Coding Scheme for Optical Communication Systems Reviewed

C. Zheng, T. Yamazato, M. Katayama and A. Ogawa

International Technical Conference on Circuits/Systems, Computers and Communications (ITC-CSCC), Tokushima, Japan page： - 2001

Language：English

In this work, a serially concatenated coding scheme of an outer Reed-Solomon code and an inner high rate Turbo code is proposed for the optical communication systems. The simulation results show the reduction of the ``error floor'' influence of the Turbo code. This reduction is due to the outer cascaded Reed-Solomon decoding process and the increase of the interleaver size of the inner Turbo code. The effect of quantization is also considered for inner Turbo decoder. As results, 4-bit quantization is satisfied.

Communication System for Time and Frequency Dependent Power-Line Channel

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

Technical Report of IEICE page： - 2001

Language：Japanese

In power-line communication, channel characteristics and the man-made noise from appliances are time and frequency dependent. This noise is known to be modeled by colored cyclo-stationary Gaussian noise. In consideration of frequency dependence of noise, in this manuscript, we employ OFDM signaling scheme. Under this environment, the space spanned by time and frequency can be subdivided into small cells by symbol duration and sub-carriers of OFDM. The bit error rate (BER) of each cell is analytically derived. In addition, we consider performance improvement by combining some cells (transmitting same information in some cells with iterative coding) according to the knowledge on stochastic features of the cyclo-stationary power-line channel.

An access control protocol based on correlation of multimedia traffic for CDMA ALOHA

Y. Hirayama, H. Okada, T. Yamazato, and M. Katayama

Technical Report of IEICE page： - 2001

Language：Japanese

In this paper, we consider wireless multimedia packet communications which support voice, video, and data traffic. Multimedia traffic includes various types of traffic which has different characteristics of packet generation. We propose a new access control protocol for multimedia traffic. This protocol controls data packet transmission based on estimation of number of packets which will generate in future. This estimation is derived from correlation of voice packet traffic. We evaluate the performance of proposed protocol when it applied to the CDMA slotted ALOHA. Simulation results show that proposed protocol can maintain the data packet throughput and the packet loss rate at a certain level when the offered load of data increases.

A design of source matched MAP receiver for image transmission Reviewed

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

Materials Research Society Symposium - Proceedings Vol. 626 2001

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Materials Research Society Symposium - Proceedings

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Papers - YAMAZATO Takaya