Faculty Profiles - YAMAZATO Takaya

Papers - YAMAZATO Takaya

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Initial acquisition of code timings and carrier frequencies of CDM down-link signals in multiple-LEO-satellite communication systems Reviewed

Ishizu M, Katayama M, Yamazato T, Ogawa A

IEICE TRANSACTIONS ON FUNDAMENTALS OF ELECTRONICS COMMUNICATIONS AND COMPUTER SCIENCES Vol. E81A ( 11 ) page： 2281 - 2290 1998.11

Initial acquisition of code timings and carrier frequencies of CDM down-link signals in multiple-LEO-satellite communication systems Reviewed

M Ishizu, M Katayama, T Yamazato, A Ogawa

IEICE TRANSACTIONS ON FUNDAMENTALS OF ELECTRONICS COMMUNICATIONS AND COMPUTER SCIENCES Vol. E81A ( 11 ) page： 2281 - 2290 1998.11

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

In this paper, we discuss the initial acquisition of the code division multiplexed DS/SS down-link signals at a user terminal of multiple LEO mobile satellite communication systems. In LEO systems, a receiver generally receives signals from plural satellites for soft hand-off and for satellite diversity as a countermeasure to shadowing. In this situation, the signal from each satellite becomes the interference to the signals from other satellites. In addition to this inter-satellite interference, we have to consider the intra-satellite interference from user channels to a pilot channel because of the loss of orthogonality of channels at initial acquisition stage especially under frequency offsets due to Doppler effect. Thus in this paper, we analytically evaluate the performance of an initial acquisition scheme, taking the intra/inter-satellite interference under Doppler shift into account.

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New quasi-synchronous sequences for CDMA slotted ALOHA systems Reviewed

Saito M, Yamazato T, Katayama M, Ogawa A

IEICE TRANSACTIONS ON FUNDAMENTALS OF ELECTRONICS COMMUNICATIONS AND COMPUTER SCIENCES Vol. E81A ( 11 ) page： 2274 - 2280 1998.11

New quasi-synchronous sequences for CDMA slotted ALOHA systems Reviewed

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

IEICE Transactions on Fundamentals Vol. E81-A ( 11 ) page： 2274 - 2280 1998.11

Language：English Publishing type：Research paper (scientific journal) Publisher：電子情報通信学会

One of unique features of CDMA slotted ALOHA (CDMA S-ALOHA) is that user must synchronize his transmission to give slot. thus orthogonal sequence as spreading sequence would achieve ideal throughput if each of packets accomplish perfect synchronization. In ths presence of any ambiguity in synchronizations, however, quasi-synchronous (QS) sequences suit well with CDMA S-ALOHA system. In this paper, we introduce new QS-sequences obtained from the orthogonal Gold sequences and discuss their performance when applying to CDMA S-ALOHA systems. As a result, withstanding to access timing error, good performance is ensured with this sequence under the environment of AWGN, MAI (multiple access interference) and frequency non-selective fading, that is, micro or pico cellular systems and indoor wireless LANs.

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Performance evaluation of DS/CDMA communications systems modulated with pi/2-shift BPSK over multipath Rayleigh fading channels Reviewed

Galib MMA, Yamazato T, Katayama M, Ogawa A

IEICE TRANSACTIONS ON FUNDAMENTALS OF ELECTRONICS COMMUNICATIONS AND COMPUTER SCIENCES Vol. E81A ( 11 ) page： 2304 - 2310 1998.11

Performance evaluation of DS/CDMA communications systems modulated with pi/2-shift BPSK over multipath Rayleigh fading channels Reviewed

MMA Galib, T Yamazato, M Katayama, A Ogawa

IEICE TRANSACTIONS ON FUNDAMENTALS OF ELECTRONICS COMMUNICATIONS AND COMPUTER SCIENCES Vol. E81A ( 11 ) page： 2304 - 2310 1998.11

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

In mobile communications, power is a very important factor and nonlinear amplification of power amplifiers cannot be avoided due to their high power efficiency. This article presents the performance of pi/2-shift BPSK modulation scheme used in DS/SS/CDMA wireless communications over multipath Rayleigh fading channel and compares the performance with the performance of conventional BPSK and offset QPSK CDMA systems. The performance parameters: Out-of-Band power, average Bit Error Rate (BER) and Spectral Efficiency have been evaluated. In order to obtain improved performance on fading channels, a RAKE receiver has been employed. Finally it is shown that pi/2-shift BPSK outperforms conventional BPSK and offset QPSK in the presence of nonlinear amplification.

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A Study on the Throughput of Multi-Code CDMA ALOHA System with Modified Channel Load Sensing Protocol

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

Technical Report of IEICE Vol. SST98 ( 40 ) page： 61-68 1998.10

Parallel Transmission of Huffman Code Under Fading Environment Open Access

S. Makido, T. Yamazato, M. Katayama and A. Ogawa

Technical Report of IEICE Vol. CS98 ( 117 ) page： IE98-96 1998.10

Performance of a LEOS Communication System with Overlaid and Overlapped Cell Arrangement

K. Ono, M. Katayama, T. Yamazato and A. Ogawa

Technical Report of IEICE Vol. SAT98 ( 42 ) page： 39090 1998.10

Handoff Performance of LEO Satellite Communication Systems with Overlapped-Cell Arrangement

K. Ono, M. Katayama, T. Yamazato and A. Ogawa

1998 IEICE General Conference Vol. SB-3 ( 13 ) page： 556-557 1998.10

Error correcting capability of 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. E81A ( 10 ) page： 2166 - 2169 1998.10

Queueing analysis of CDMA unslotted ALOHA systems with finite buffers Reviewed

Okada H, Yamazato T, Katayama M, Ogawa A

IEICE TRANSACTIONS ON FUNDAMENTALS OF ELECTRONICS COMMUNICATIONS AND COMPUTER SCIENCES Vol. E81A ( 10 ) page： 2083 - 2091 1998.10

Queueing Analysis of CDMA Unslotted ALOHA Systems with Finite Buffers Reviewed

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

IEICE Transaction on Fundamentals Vol. E81-A ( 10 ) page： 2083-2091 - 2091 1998.10

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

CDMA unslotted ALOHA system with finite size of quenueing buffers is discussed in this paper. We introduce an analytical model in which the system is divided into two Markov chains; one is in the user part, and the other is in the channel part. In the user part, we can model the queueing behavior of the user station as an M/G/1/B queue. In the channel part, we can consider the number of simulataneously transmitted packets as an M_1+M_2/D/∞//K queue. We analyze the queueing system by using this analytical model, and evaluate the effect of buffer capacity in terms of the throughput, the rejection probability and the average delay. As a result, increase in the buffer size brings about an improvement in the grade of service in terms of higher throughput and lower rejection probability.

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Throughput Performance of QS-CDMA Slotted ALOHA System on 2-path Rayleigh Fading Environment Reviewed

SAITO Masato, YAMAZATO Takaya, KATAYAMA Masaaki, OGAWA Akira

Proceedings of the Society Conference of IEICE Vol. 1998 page： 99 1998.9

Performance of Transmit/Receive Antenna Diversity with FEC Coding under Correlated Rician Fading Channels

K. Ban, M. Katayama, T. Yamazato and A. Ogawa

1998 IEICE General Conference Vol. A-5 ( 8 ) page： 98 1998.9

Throughput Performance of QS-CDMA Slotted ALOHA System on 2-path Rayleigh Fading Environment

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

1998 Society Conference of IEICE Vol. A-5-9 page： 99 1998.9

A Study on Reducing the Nonlinear Distortion in OFDM Systems

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

Technical Report of IEICE Vol. RCS98 ( 61 ) page： 25-30 1998.7

Throughput Analysis for CDMA Unslotted ALOHA Systems with Finite Population Assumption Reviewed Open Access

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

IEICE Transaction on Fundamentals of Electronics, Communications and Computer Sciences Vol. J81-A ( 7 ) page： 1089-1092 1998.7

CDMA slotted ALOHA system with finite buffers Reviewed

Okada H, Yamazato T, Katayama M, Ogawa A

IEICE TRANSACTIONS ON FUNDAMENTALS OF ELECTRONICS COMMUNICATIONS AND COMPUTER SCIENCES Vol. E81A ( 7 ) page： 1473 - 1478 1998.7

CDMA Slotted ALOHA System with Finite Buffers Reviewed

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

IEICE Transaction on Fundamentals Vol. E81-A ( 7 ) page： 1473-1478 - 1478 1998.7

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

In this paper, CDMA slotted ALOHA system with finite size of buffers is proposed. To analyze the system performance, we use the linear approximate solution based on restricted occupancy urn models. We evaluate the system performance in terms of throughput, average delay, and rejection probability and clarify the effect of buffer capacity.

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