Faculty Profiles - YAMAZATO Takaya

Papers - YAMAZATO Takaya

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Performance Evaluation of DS/CDMA communications systems modulated with f -shift bpsk over multipath rayleigh fading channels Reviewed

Asadullah Galib M.

IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences Vol. E81-A ( 11 ) page： 2304 - 2310 1998

Problems of implementing adaptive array antennas in CDMA systems Reviewed

A Morimoto, M Katayama, T Yamazato, A Ogawa

NINTH IEEE INTERNATIONAL SYMPOSIUM ON PERSONAL, INDOOR AND MOBILE RADIO COMMUNICATIONS, VOLS 1-3 page： 1422 - 1426 1998

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

In this paper, we discuss the performance of a system in which multi processing gain(MPG) spread spectrum signals are transmitted to a base station within the same bandwidth. At the receiver of the base station, an adaptive array antenna is employed. We evaluate the system performance in terms of Signal to Interference-and-Noise Ratio(SINR) and also of outage probability of low-rate users. We find that the employment of the adaptive array antenna may result in serious degradation of the outage probability of low-rate users. We then show that the cause of this serious degradation is the inadequate guidelines of conventional adaptive array antennas.

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Queueing analysis of CDMA slotted ALOHA systems with finite buffer and finite population assumptions Reviewed

Okada H, Yamazato T, Katayama M, Ogawa A

ICC 98 - 1998 IEEE INTERNATIONAL CONFERENCE ON COMMUNICATIONS VOLS 1-3 page： 407 - 411 1998

A Constant Amplitude Coding for Orthogonal Multi-Code CDMA Systems Reviewed

WADA Tadahiro, YAMAZATO Takaya, KATAYAMA Masaaki, OGAWA Akira

IEICE TRANS. FUNDAMENTALS, A Vol. 80 ( 12 ) page： 2477 - 2484 1997.12

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

In this paper, we present orthogonal multi-code CDMA systems with the constant amplitude transmission. In general, the dynamic range of the amplitude of the transmitting signal is very large in the case of orthogonal multi-code CDMA systems. In order to realize the constant amplitude transmission for orthogonal multi-code CDMA systems, we propose a constant amplitude coding. First, we show the basic concept of the constant amplitude coding. And then, we show that the constant amplitude transmission can be realized by the combination of the conventional orthogonal multi-code CDMA and the constant amplitude coding. Finally, the effectiveness of the proposed method is evaluated in terms of the bit error rate performance and it is shown that the proposed method is robust to the non-linear distortion caused by a high power amplifier(HPA).

CiNii Research

A Spread-Spectrum System with Dual Processing Gains Designed for Cyclic Noise in Power Line Communications Reviewed

NIWA Hisashi, OONO Osamu, KATAYAMA Masaaki, YAMAZATO Takaya, OGAWA Akira, ISAKA Noriyuki

IEICE Trans. Fundamentals, A Vol. 80 ( 12 ) page： 2526 - 2533 1997.12

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

We propose a spread-spectrum power line communication system considering the cyclic features of the noise in the lines. For this purpose, we model the noise as the sum of a time-invariant stationary process and two cyclostationary processes, i.e., cyclic continuous noise and cyclic impulsive noise. The proposed system employs two different countermeasures to each of these two classes of cyclic noise. For the cyclic continuous noise, it uses multiple-processing-gain spread spectrum technique: the smaller processing gains are assigned for the periods with lower instantaneous noise power and the larger ones for the periods of higher noise power. Considering the cyclic impulsive noise, convolutional coding with interleaving is applied. In order to analyze the performance improvement, due to the employment of multiple processing gains, we introduce a simple model of the continuous noise. The overall performance is evaluated by computer simulation with the actual noise wave-form measured in power lines.

CiNii Research

A Simple Transmit/Receive Antenna Diversity for Indoor DS/CDMA Wireless Communication Systems Reviewed

BAN Koichiro, KATAYAMA Masaaki, YAMAZATO Takaya, OGAWA Akira

IEICE Trans. Commun. Vol. 80 ( 12 ) page： 1790 - 1796 1997.12

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

This paper proposes a direct-sequence spread spectrum (DS/SS) communication system with a new diversity technique designed for indoor multi-path fading channels where path diversity isn't available. In this system, the transmitter sends a same signal from multiple antennas at the same time with intentional time delays, which allows the receiver to distinguish and combine the signals from different antennas. We also consider the combination of this scheme with the conventional receiving antenna diversity for additional diversity gain. Furthermore, it is found that the use of the multiple transmitting antennas decreases the effect of the multiple access interference.

CiNii Research

Q uasi-Synchronous CDMA ALOHA System Using the Sequences Generated from Orthogonal Gold Sequences

Masato Saito, Takaya Yamazato, Masaaki Katayama, Akira Ogawa

Symposium on Information Theory and Its Applications (SITA) Vol. SITA97 ( 5-4-5 ) page： 589-592 1997.12

Performance Analysis of CDMA ALOHA Systems with Finite Buffer

Hiraku Okada, Takaya Yamazato, Masaaki Katayama, Akira Ogawa

Symposium on Information Theory and Its Applications (SITA) Vol. SITA97 ( 4-3-6 ) page： 409-412 1997.12

A Study on Error Correcting Capability of Constant Amplitude Coding for Orthogonal Multi-Code CDMA Systems

Tadahiro Wada, Takaya Yamazato, Masaaki Katayama, Akira Ogawa

Symposium on Information Theory and Its Applications (SITA) Vol. SITA97 ( 5-4-6 ) page： 593-596 1997.12

A constant amplitude coding for orthogonal multi-code CDMA systems Reviewed

Wada T, Yamazato T, Katayama M, Ogawa A

IEICE TRANSACTIONS ON FUNDAMENTALS OF ELECTRONICS COMMUNICATIONS AND COMPUTER SCIENCES Vol. E80A ( 12 ) page： 2477 - 2484 1997.12

A simple transmit/receive antenna diversity for indoor DS/CDMA wireless communication systems Reviewed

Ban K, Katayama M, Yamazato T, Ogawa A

IEICE TRANSACTIONS ON COMMUNICATIONS Vol. E80B ( 12 ) page： 1790 - 1796 1997.12

A spread-spectrum system with dual processing gains designed for cyclic noise in power line communications Reviewed

Niwa H, Oono O, Katayama M, Yamazato T, Ogawa A, Isaka N

IEICE TRANSACTIONS ON FUNDAMENTALS OF ELECTRONICS COMMUNICATIONS AND COMPUTER SCIENCES Vol. E80A ( 12 ) page： 2526 - 2533 1997.12

CDMA for personal communications based on low Earth-orbital satellite systems Reviewed

Ogawa A, Katayama M, Yamazato T, Jamalipour A

IEICE TRANSACTIONS ON FUNDAMENTALS OF ELECTRONICS COMMUNICATIONS AND COMPUTER SCIENCES Vol. E80A ( 12 ) page： 2347 - 2356 1997.12

Effects of transmission control in an integrated voice and data CDMA system Reviewed

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

IEICE TRANSACTIONS ON FUNDAMENTALS OF ELECTRONICS COMMUNICATIONS AND COMPUTER SCIENCES Vol. E80A ( 12 ) page： 2509 - 2516 1997.12

Multi-antenna transmission scheme for convolutionally coded DS/CDMA system Reviewed

Ban K, Katayama M, Stark WE, Yamazato T, Ogawa A

IEICE TRANSACTIONS ON FUNDAMENTALS OF ELECTRONICS COMMUNICATIONS AND COMPUTER SCIENCES Vol. E80A ( 12 ) page： 2437 - 2444 1997.12

A constant amplitude coding for orthogonal multi-code CDMA systems Reviewed

T Wada, T Yamazato, M Katayama, A Ogawa

IEICE TRANSACTIONS ON FUNDAMENTALS OF ELECTRONICS COMMUNICATIONS AND COMPUTER SCIENCES Vol. E80A ( 12 ) page： 2477 - 2484 1997.12

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

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A spread-spectrum system with dual processing gains designed for cyclic noise in power line communications Reviewed

H Niwa, O Oono, M Katayama, T Yamazato, A Ogawa, N Isaka

IEICE TRANSACTIONS ON FUNDAMENTALS OF ELECTRONICS COMMUNICATIONS AND COMPUTER SCIENCES Vol. E80A ( 12 ) page： 2526 - 2533 1997.12

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

We propose a spread-spectrum power line communication system considering the cyclic features of the noise in the lines. For this purpose, we model the noise as the sum of a time-invariant stationary process and two cyclostationary processes, i.e., cyclic continuous noise and cyclic impulsive noise. The proposed system employs two different countermeasures to each of these two classes of cyclic noise. For the cyclic continuous noise, it uses multiple-processing-gain spread spectrum technique: the smaller processing gains are assigned for the periods with lower instantaneous noise power and the larger ones for the periods of higher noise power, Considering the cyclic impulsive noise, convolutional coding with interleaving is applied. In order to analyze the performance improvement due to the employment of multiple processing gains, we introduce a simple model of the continuous noise. The overall performance is evaluated bu computer simulation with the actual noise wave-form measured in power lines.

Web of Science

researchmap

A simple transmit/receive antenna diversity for indoor DS/CDMA wireless communication systems Reviewed

K Ban, M Katayama, T Yamazato, A Ogawa

IEICE TRANSACTIONS ON COMMUNICATIONS Vol. E80B ( 12 ) page： 1790 - 1796 1997.12

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

This paper proposes a direct-sequence spread spectrum (DS/SS) communication system with a new diversity technique designed for indoor multi-path Fading channels where path diversity isn't available. In this system, the transmitter sends a same signal from multiple antennas at the same time with intentional time delays, which allows the receiver to distinguish and combine the signals from different antennas. We also consider the combination of this scheme with the conventional receiving antenna diversity for additional diversity gain. Furthermore, it is found that the use of the multiple transmitting antennas decreases the effect of the multiple access interference.

Web of Science

researchmap

An Initial Acquisition Method for M-ary Spread-Spectrum Signals Using Hadamard Code Sequences Reviewed

WADA Tadahiro, YAMAZATO Takaya, KATAYAMA Masaaki, OGAWA Akira

IEICE Trans. Fundamentals Vol. 80 ( 11 ) page： 2172 - 2179 1997.11

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

In this paper, we examine a new initial symbol acquisition method for M-ary spread-spectrum (M-ary/SS) signals that are affected by large carrier frequency offset. By the effect of the carrier frequency offset, preamble signal energy is dispersed to the undesired outputs. The proposed method is based on the collection of such dispersed signal energies by using reference patterns. The reference patterns are constructed by using the characteristic of Hadamard code sequences. The effectiveness of the proposed method is evaluated in terms of mean acquisition time.

CiNii Research

An initial acquisition method for M-ary spread-spectrum signals using Hadamard code sequences Reviewed

Wada T, Yamazato T, Katayama M, Ogawa A

IEICE TRANSACTIONS ON FUNDAMENTALS OF ELECTRONICS COMMUNICATIONS AND COMPUTER SCIENCES Vol. E80A ( 11 ) page： 2172 - 2179 1997.11

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Papers - YAMAZATO Takaya