Faculty Profiles - YAMAZATO Takaya

Papers - YAMAZATO Takaya

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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.

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

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

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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.

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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

Throughput analysis of DS/SSMA unslotted ALOHA system with fixed packet length Reviewed

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

IEEE JOURNAL ON SELECTED AREAS IN COMMUNICATIONS Vol. 14 ( 4 ) page： 750 - 756 1996.5

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

Throughput analysis of direct-sequence spread spectrum multiple access (DS/SSMA) unslotted ALOHA with fixed packet length is presented. As the levels of multi-user interference fluctuate during the packet transmission, we calculate the packet error probability and the throughput by considering not only the number of overlapped packets but also the amount of time overlap, On the assumption that packet generation is Poisson, the system can be thought as the queueing system M/D/infinity. With Gaussian approximation of multi-user interference, we obtain the throughput as the function of the number of chips in a bit, the packet length, and the offered load of the system, We also analyze the channel load sensing protocol (CLSP), and obtain the optimum threshold pf CLSP.

DOI： 10.1109/49.490426

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Adaptive Transmit Permission Control on Spread-Slotted Aloha Packets Applicable in LEOS Systems Reviewed

JAMALIPOUR Abbas, KATAYAMA Masaaki, YAMAZATO Takaya, OGAWA Akira

IEICE transactions on communications Vol. 79 ( 3 ) page： 257 - 265 1996.3

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

A new transmit permission control scheme applicable in multi-cell communication systems is proposed. In this scheme, by prohibiting the transmissions from the users with relatively high propagation loss to their connecting hub stations, level of multiple access interference is decreased, and hence throughput characteristics are improved. Moreover, we continue our discussion to propose two adaptive forms of the transmit permission control scheme, in which the prohibition condition becomes more intelligent by considering the level of the offered traffic loads to hub stations. These methods are utilized in a slotted Aloha random transmission of the spread spectrum packets, and on the uplinks of a low earth orbit satellite communication system as an example of the multi-cell systems. It is shown that the adaptive schemes exhibits significantly improved characteristics at all offered traffic loads in these systems.

CiNii Research

Throughput Analysis of CDMA ALOHA System in Fading Channel with Near-Far Problem

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

1996 IEICE General Conference Vol. SA-5 ( 4 ) page： 472 1996.3

A Study of Multiple Access Interference Using M-ary/SS/CDMA Signals

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

Technical Report of IEICE Vol. SST95 ( 141 ) page： 65-70 1996.3

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