Faculty Profiles - YAMAZATO Takaya

Papers - YAMAZATO Takaya

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

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

IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences Vol. E80-A ( 12 ) page： 2526 - 2532 1997

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences

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.

Scopus

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. E80-B ( 12 ) page： 1790 - 1796 1997

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：IEICE Transactions on Communications

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.

Scopus

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

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

ECSC-4: 4TH EUROPEAN CONFERENCE ON SATELLITE COMMUNICATIONS page： 176 - 181 1997

Language：English Publishing type：Research paper (international conference proceedings) Publisher：ASSOC ELETTROTECHNICA ED ELETTRONICA ITALIANA

In this paper, we focus on an integrated voice and data system over unslotted CDMA system. We propose a method to accommodate the data packet into the silence period of voice signal by using a traffic control based on the channel load sensing protocol. We evaluate the system by the throughput and delay performance for data packet, the blocking probability for voice users. From the results, we show the advantages of the proposed system.

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Approximation Method for CDMA Unslotted ALOHA Systems with Fixed Packet Length

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

Technical Report of IEICE Vol. SST96 ( 61 ) page： 13-18 1996.12

Throughput of CDMA ALOHA in Cellular Environment

T. Yamazato, Y. Asai, A. Jamalipour, M. Katayama, A. Ogawa

Symposium on Information Theory and Its Applications (SITA) Vol. SITA96 ( D-4-2 ) page： 313-316 1996.12

CDMA ALOHA systems with modified channel load sensing protocol for satellite communications Reviewed

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

IEICE TRANSACTIONS ON FUNDAMENTALS OF ELECTRONICS COMMUNICATIONS AND COMPUTER SCIENCES Vol. E79A ( 12 ) page： 2035 - 2042 1996.12

DS/SS/GMSK with differential detection over multipath Rayleigh fading channels Reviewed

Wakaki I, Ishiguro T, Yamazato T, Katayama M, Ogawa A

IEICE TRANSACTIONS ON FUNDAMENTALS OF ELECTRONICS COMMUNICATIONS AND COMPUTER SCIENCES Vol. E79A ( 12 ) page： 1957 - 1962 1996.12

Quasi-synchronous code division multiple access (CDMA) with binary shift-register sequences Reviewed

S Kuno, T Yamazato, M Katayama, A Ogawa

ELECTRONICS AND COMMUNICATIONS IN JAPAN PART III-FUNDAMENTAL ELECTRONIC SCIENCE Vol. 79 ( 12 ) page： 71 - 81 1996.12

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

This paper discusses the quasi-synchronous code-division multiple access system (QS-CDMA), where the time error in the synchronized access is allowed for a certain range, based on the spread-spectrum communication technique. The Gold sequence and the M sequence, which are the binary shift-register sequences, are used to derive the set of quasi-synchronous spread sequences (QS-sequence) considering the auto- and cross-correlation characteristics, realizing a wide tolerable range for the timing error.
The QS-CDMA system using such QS-sequence is investigated, and the effectiveness is examined. As a result, it is seen that the performance is improved greatly by using the QS-sequence presented in this paper, compared to the asynchronous CDMA system. It is shown also that the tolerable range for the access timing error is enlarged compared to the synchronous CDMA system.

DOI： 10.1002/ecjc.4430791208

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Transmit permission control on spread ALOHA packets in LEO satellite systems Reviewed Open Access

A Jamalipour, M Katayama, T Yamazato, A Ogawa

IEEE JOURNAL ON SELECTED AREAS IN COMMUNICATIONS Vol. 14 ( 9 ) page： 1748 - 1757 1996.12

Language：English Publishing type：Research paper (scientific journal) Publisher：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC

A transmit permission control method for improving the throughput characteristics of a low earth orbit (LEG) satellite communication system employing spread-slotted ALOHA multiple-access scheme is proposed, Both nonfading and fading satellite links are considered, The basic idea of the proposed scheme is to decrease the level of interference at each satellite and, hence, to increase the probability of packet success, by prohibiting the packet transmission from the users with relatively high propagation loss to their connecting satellites, It is shown that the method has the ability to improve the throughput performance in heavy traffic loads and the peak value of the throughput, significantly, It is also shown that the average delay performance of the system employing the proposed scheme is superior to that of the conventional system at heavy traffic loads.

DOI： 10.1109/49.545697

Open Access

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A Study of the Receiver for Observing Ecology of Sea Animals Utilizing Low Orbit Satellite

T. Tokuyasu, T. Wada, T. Yamazato, M. Katayama and A. Ogawa

Technical Report of IEICE Vol. SANE96 ( 64 ) page： 67-72 1996.10

A New M-ary Spread-Spectrum Multiple-Access Scheme in the Presence of Carrier Frequency Offset Reviewed

WADA Tadahiro, YAMAZATO Takaya, KATAYAMA Masaaki, OGAWA Akira

IEICE transactions on fundamentals of electronics, communications and computer sciences Vol. 79 ( 9 ) page： 1415 - 1422 1996.9

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

The performance of an M-ary spread-spectrum multiple-access (Al-ary/SSMA) scheme in the presence of carrier frequency offset is discussed in this paper. The influence of carrier frequency offset on the non-coherent reception of M-ary/SSMA signals is examined and it is shown that the carrier frequency off-set degrades the performance remarkably, yet, this influence has a distinctive property. Making use of this property, we propose a new M-ary/SSMA scheme that can mitigate the influence of the carrier frequency offset. The scheme is based on the assignment of two distinctive Hadamard codes to in-phase and quadrature components of the transmitted signal. The effect of simultaneous transmission is evaluated in terms of bit-error-rate performance with the carrier frequency offset. As the result, it is observed that the satisfactory bit-error-rate performance can be achieved in the presence of carrier frequency offset.

CiNii Research

A Study of The System for Observing Ecology of Sea Animals Utilizing Low Orbit Satellite

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

1996 Society Conference of IEICE Vol. SB-2 ( 12 ) page： - 1996.9

A new M-ary spread-spectrum multiple-access scheme in the presence of carrier frequency offset Reviewed

Wada T, Yamazato T, Katayama M, Ogawa A

IEICE TRANSACTIONS ON FUNDAMENTALS OF ELECTRONICS COMMUNICATIONS AND COMPUTER SCIENCES Vol. E79A ( 9 ) page： 1415 - 1422 1996.9

Coordinate interleaved trellis coded QPSK with T-algorithm on Rayleigh fading channel Reviewed

Nakamura H, Yamazato T, Katayama M, Ogawa A

IEICE TRANSACTIONS ON COMMUNICATIONS Vol. E79B ( 9 ) page： 1248 - 1255 1996.9

Effects of the access timing delay on CDMA unslotted ALOHA with channel load sensing Reviewed

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

IEICE TRANSACTIONS ON COMMUNICATIONS Vol. E79B ( 9 ) page： 1339 - 1345 1996.9

Effects of multiple access interference in a multi-rate SSMA system Reviewed

Ichiba M, Katayama M, Yamazato T, Ogawa A

IEICE TRANSACTIONS ON COMMUNICATIONS Vol. E79B ( 9 ) page： 1333 - 1338 1996.9

A new M-ary spread-spectrum multiple-access scheme in the presence of carrier frequency offset Reviewed

T Wada, T Yamazato, M Katayama, A Ogawa

IEICE TRANSACTIONS ON FUNDAMENTALS OF ELECTRONICS COMMUNICATIONS AND COMPUTER SCIENCES Vol. E79A ( 9 ) page： 1415 - 1422 1996.9

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

The performance of an M-ary spread-spectrum multiple-access (M-ary/SSMA) scheme in the presence of carrier frequency offset is discussed in this paper. The influence of carrier frequency offset on the non-coherent reception of M-ary/SSMA signals is examined and it is shown that the carrier frequency offset degrades the performance remarkably, yet, this influence has a distinctive property. Making use of this property, we propose a new M-ary/SSMA scheme that can mitigate the influence of the carrier frequency offset. The scheme is based on the assignment of two distinctive Hadamard codes to in-phase and quadrature components of the transmitted signal. The effect of simultaneous transmission is evaluated in terms of bit-error-rate performance with the carrier frequency offset. As the result, it is observed that the satisfactory bit-error-rate performance can be achieved in the presence of carrier frequency offset.

Web of Science

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DS/SS/GMSK with Differential Detection over Multipath Rayleigh Fading Channels

I. Wakaki, T. Yamazato, M. Katayama and A. Ogawa

Technical Report of IEICE Vol. SST96 ( 34 ) page： 37-42 1996.7

CDMA unslotted ALOHA systems with packet retransmission control Reviewed

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

IEICE TRANSACTIONS ON FUNDAMENTALS OF ELECTRONICS COMMUNICATIONS AND COMPUTER SCIENCES Vol. E79A ( 7 ) page： 1004 - 1010 1996.7

A Study on an Initial Acquisition Method for M-ary Spread-Spectrum Signals with Carrier Frequency Offset

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

Technical Report of IEICE Vol. SST96 ( 14 ) page： 81-86 1996.6

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Papers - YAMAZATO Takaya