Faculty Profiles - YAMAZATO Takaya

Papers - YAMAZATO Takaya

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Performance analysis of an integrated voice and data CDMA system Reviewed

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

ELECTRONICS AND COMMUNICATIONS IN JAPAN PART II-ELECTRONICS Vol. 83 ( 4 ) page： 61 - 70 2000

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

This research is an analysis of the mixed system of data packets and CDMA voice signals transmitted by the channel load sensing protocol. The voice signal is a medium requiring instantaneous action to complete the transmission within a certain time whereas the data packet is a medium requiring high reliability but allows temporal delay. The blocking probability and Erlang capacity are derived for the voice signal while the throughput is derived for the data packet. The characteristics in the system using CDMA strongly depend on the number of simultaneously transmitting stations. In particular, in the present system, due to the mixture of different media, the effect of traffic on each medium needs to be considered. In regard to this point, this paper analyzes the effect of traffic on each medium from the relationship of the required quality of the media and the number of simultaneously transmitting stations. Then the optimization of the system with two kinds of media is considered. Further, the system capacity is derived as a guideline for the system optimization. The data offered load is derived to make maximally efficient use of the channel. (C) 2000 Scripta Technica.

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Performance analysis of an integrated voice and data CDMA system Reviewed

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

ELECTRONICS AND COMMUNICATIONS IN JAPAN PART II-ELECTRONICS Vol. 83 ( 4 ) page： 61 - 70 2000

OFDM systems with Multiple Trellis Coded Modulation Reviewed Open Access

M Harada, T Yamazato, M Katayama, A Ogawa

PIMRC 2000: 11TH IEEE INTERNATIONAL SYMPOSIUM ON PERSONAL, INDOOR AND MOBILE RADIO COMMUNICATIONS, VOLS 1 AND 2, PROCEEDINGS page： 814 - 818 2000

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

In an attempt to improve the performance under frequency selective fading environment, we propose in this paper an Orthogonal-Frequency-Division-Multiple-Access (OFDM) system in which MTCM (Multiple Trellis Coded Modulation) is applied to a set of multiple subcarriers. The code is designed to enlarge the summation of the Euclidean distance and the product distance. We also propose a scheme for assigning the symbols to subcarriers adaptively based on the channel state information (CSI) fed back from the reception receive end, and evaluate the performance applying these two codes and the proposed scheme under a multipath Rayleigh fading environment.

DOI： 10.1109/PIMRC.2000.881535

Open Access

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Throughput evaluation in CDMA/shared-TDD packet systems in a cellular environment Reviewed

K Mori, T Kobayashi, T Yamazato, A Ogawa

WCNC: 2000 IEEE WIRELESS COMMUNICATIONS AND NETWORKING CONFERENCE, VOLS 1-3 page： 321 - 326 2000

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

This paper examines the inter-cell interference between uplinks and downlinks when a shared-TDD scheme is applied to CDMA packet communication systems in cellular environments. The CDMA/shared-TDD cellular packet systems experience two additional types of interference: one is the interference between base stations and the other is between mobile stations. The effect of these interferences on the throughput performance Is evaluated. Computer simulation demonstrated that interference between base stations rarely degrades uplink throughput, but interference between mobile stations substantially degrades downlink throughput.

DOI： 10.1109/WCNC.2000.904650

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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 Open Access

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

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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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

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

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

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Papers - YAMAZATO Takaya