Faculty Profiles - YAMAZATO Takaya

Papers - YAMAZATO Takaya

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Transmission power control for downlinks in CDMA/shared-TDD cellular packet systems Reviewed

K Mori, T Kobayashi, T Yamazato, A Ogawa

PIMRC 2000: 11TH IEEE INTERNATIONAL SYMPOSIUM ON PERSONAL, INDOOR AND MOBILE RADIO COMMUNICATIONS, VOLS 1 AND 2, PROCEEDINGS page： 1520 - 1524 2000

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

This paper proposes a transmission power control scheme for downlinks in CDMA/shared-TDD cellular packet systems that experience inter-cell interference between uplinks and downlinks. The proposed scheme increases the downlink transmission power for re-transmission packets and thus improves the signal-to-interference ratio for the packets. Simulation results show that the proposed scheme improves downlink throughput without sacrificing the uplink throughput.

DOI： 10.1109/PIMRC.2000.881672

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Adaptive Array Antennas for the Base Station of a Multi Processing Gain CDMA System Reviewed

MORIMOTO Akihito, KATAYAMA Masaaki, YAMAZATO Takaya, OGAWA Akira

IEICE Trans. Fundamentals Vol. 82 ( 12 ) page： 2687 - 2696 1999.12

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

This paper discusses the employment of adaptive array antennas at the base station of a Multi Processing Gain (MPG) CDMA system. It is shown that the adaptive array antenna with the weight control scheme based on the signal before despreading procedure does not increase but even decreases the performance than that with an omni-directional antenna, and the cause of this serious performance degradation is revealed. Then it is shown that the performance with the weight control scheme based on the signal after despreading procedure is always better than that with an omni-directional antenna. Furthermore, the possibilities of performance improvement by the combination of adaptive array antenna and interference cancellation techniques are mentioned.

CiNii Research

The Performance of MTCM Coded Multicarrier System

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

Symposium on Information Theory and Its Applications (SITA) Vol. SITA99 page： 563-566 1999.12

A study on SOVA based Turbo-decoding with threshold

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

Symposium on Information Theory and Its Applications (SITA) Vol. SITA99 ( 1 ) page： 13-16 1999.12

Adaptive array antennas for the base station of a multi processing gain CDMA system Reviewed

Morimoto A, Katayama M, Yamazato T, Ogawa A

IEICE TRANSACTIONS ON FUNDAMENTALS OF ELECTRONICS COMMUNICATIONS AND COMPUTER SCIENCES Vol. E82A ( 12 ) page： 2687 - 2696 1999.12

Adaptive array antennas for the base station of a multi processing gain CDMA system Reviewed

A Morimoto, M Katayama, T Yamazato, A Ogawa

IEICE TRANSACTIONS ON FUNDAMENTALS OF ELECTRONICS COMMUNICATIONS AND COMPUTER SCIENCES Vol. E82A ( 12 ) page： 2687 - 2696 1999.12

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

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Chip-by-chip turbo coding for DS/SS systems Reviewed

Zheng C, Yamazato T, Katayama M, Ogawa A

IEICE TRANSACTIONS ON FUNDAMENTALS OF ELECTRONICS COMMUNICATIONS AND COMPUTER SCIENCES Vol. E82A ( 12 ) page： 2751 - 2757 1999.12

Decorrelating detector for multi-processing gain CDMA systems Reviewed

Hiraiwa H.

IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences Vol. E82-A ( 12 ) page： 2774 - 2777 1999.12

Decorrelating detector for multi-processing gain CDMA systems Reviewed

Hiraiwa H, Katayama M, Yamazato T, Ogawa A

IEICE TRANSACTIONS ON FUNDAMENTALS OF ELECTRONICS COMMUNICATIONS AND COMPUTER SCIENCES Vol. E82A ( 12 ) page： 2774 - 2777 1999.12

Code acquisition of a DS/SS signal with transmit and receive antenna diversity Reviewed

Y Ikai, M Katayama, T Yamazato, A Ogawa

IEICE TRANSACTIONS ON FUNDAMENTALS OF ELECTRONICS COMMUNICATIONS AND COMPUTER SCIENCES Vol. E82A ( 12 ) page： 2728 - 2734 1999.12

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

In this paper, we propose the introduction of space diversity techniques to the code acquisition of a direct-sequence spread-spectrum signal. In this scheme, both a transmitter and a receiver have multiple antennas and the signals corresponding to all the combinations of the transmitter and receiver antennas are combined at the acquisition circuit of the receiver. The performance is evaluated for an indoor packet radio communication system from the viewpoints of the average time for acquisition, the probability of success of acquisition, and the necessary preamble length. As the result, we show great performance improvements by the proposed scheme under slow and Rat Rayleigh fading environment.

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Code acquisition of a DS/SS signal with transmit and receive antenna diversity Reviewed

Ikai Y, Katayama M, Yamazato T, Ogawa A

IEICE TRANSACTIONS ON FUNDAMENTALS OF ELECTRONICS COMMUNICATIONS AND COMPUTER SCIENCES Vol. E82A ( 12 ) page： 2728 - 2734 1999.12

Chip-by-chip turbo coding for DS/SS systems Reviewed

C Zheng, T Yamazato, M Katayama, A Ogawa

IEICE TRANSACTIONS ON FUNDAMENTALS OF ELECTRONICS COMMUNICATIONS AND COMPUTER SCIENCES Vol. E82A ( 12 ) page： 2751 - 2757 1999.12

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

Most of error correcting codes applying to DS/SS systems are such that information data is first (bit-by-bit) encoded and then spread by pseudo noise (PN) sequence. Thus, coding; gain achieved by such systems are mainly due to the error correcting codes and the redundancy produced by the spreading codes shows no effect on the coding gain. In this paper, a chip-by-chip Turbo coding for DS/SS systems is proposed. The input information data is first spread by PN sequence and then fed into the Turbo-encoder which operates in chip timing. As the Turbo-encoder operates in chip timing, a large interleaving size would be obtained, which improves the performance. As results, superior performances with coding gain of more than 3.0 dB and 5.0 dB for AWGN and Rayleigh-fading channel, respectively, were found with short frame size of information data.

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Service Fairness in CDMA Cellular Packet Systems with Site Diversity Reception Reviewed

Kazuo MORI, Takehiko KOBAYASHI, Takaya YAMAZATO, Akira OGAWA

IEICE Transactions on Communications Vol. Vol. E82-B, No. 12 page： 1964 - 1973 1999.12

Service Fairness in CDMA Cellular Slotted-ALOHA Packet Systems Reviewed

Kazuo MORI, Takehiko KOBAYASHI, Takaya YAMAZATO, Akira OGAWA

Proc. of IEEE 1999 Global Telecommunications Conference (GLOBECOM'99) Vol. Vol. 1b page： 655 - 660 1999.12

Control of Transmit Permission Probability to Improve Service Fairness in CDMA Cellular Packet Communications Reviewed

K. Mori, T. Kobayashi, T. Yamazato, and A. Ogawa,

The 6th IEEE International Workshop on Mobile Multimedia Communications (MOMUC'99) Vol. MOMUC'99 page： 35-42 1999.11

Language：English

In the INTERNET, TCP (Transmission Control Protocol) is used for a reliable transport protocol. Originally, the TCP has been designed for wired networks, and not for wireless ones. It is reported that the performance of TCP is very poor in wireless environments. In this paper, we propose a new analytical model of the TCP, where the congestion window is modeled as a Markov chain. In the presence of random bit errors on a wireless link, we analyze the throughput of the TCP for the proposed model. Also, in a wireless link, we attempt to employ Reed Solomon code as FEC or Go-Back-N as ARQ, and discuss about throughput of TCP with FEC or ARQ.

A Synopsis of CIMS at Nagoya University

T. Yamazato, S. Kajita, T. Hamaguchi, S. Yuen

IPSJ SIG Technical Report Vol. DMS99 ( 16 ) page： 55-60 1999.11

The Influence of an ADC on Bit Error Rate Performance of a Software-Defined Base Station

K. Matsubara, M. Katayama, T. Yamazato, A. Ogawa

Technical Report of IEICE Vol. SR99 ( 19 ) page： 67-72 1999.11

A Study on OFDM Synchronization Scheme with Subtraction Operation

T. Shibata, N. Itoh, M. Fujimoto, H. Itoh, N. Suzuki, K. Ohtsuka T. Yamazato, A. Ogawa

Technical Report of IEICE Vol. RCS99 ( 135 ) page： 97-101 1999.10

An integrated voice/data CDMA packet communications with multi-code CDMA scheme Reviewed

Sandouk A, Yamazato T, Katayama M, Ogawa A

IEICE TRANSACTIONS ON FUNDAMENTALS OF ELECTRONICS COMMUNICATIONS AND COMPUTER SCIENCES Vol. E82A ( 10 ) page： 2105 - 2114 1999.10

An integrated voice/data CDMA packet communications with multi-code CDMA scheme Reviewed

A Sandouk, T Yamazato, M Katayama, A Ogawa

IEICE TRANSACTIONS ON FUNDAMENTALS OF ELECTRONICS COMMUNICATIONS AND COMPUTER SCIENCES Vol. E82A ( 10 ) page： 2105 - 2114 1999.10

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

In this paper, we consider an integrated voice and data system over CDMA Slotted-ALOHA (CDMA S-ALOBA). We investigate its performance when multi-code CDMA (MC-CDMA) is applied as a multi-rate scheme to support users which require transmission with different bit rates. Two different classes of data users are transmitted together with voice. Performance measurement is obtained in respect of throughput for data and outage probability for voice. Moreover, we consider the Modified Channel Load Sensing Protocol (MCLSP) as a traffic control to improve the throughput of data. As a result, we show that the MC-CDMA technique is an effective one to obtain good throughput for data users at an acceptable voice outage probability. Furthermore, we show that with MCLSP, the throughput of data can be improved to reach a constant value even at a high offered load of data users.

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Papers - YAMAZATO Takaya