Faculty Profiles - YAMAZATO Takaya

Papers - YAMAZATO Takaya

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An Initial Code Acqusition Scheme for Indoor Packet DS/SS Systems with Macro/Micro Antenna Diversity Reviewed

Y. Ikai, M. Katayama, T. Yamazato, A. Ogawa

IEICE Transaction on Fundamentals of Electronics, Communications and Computer Sciences Vol. E83-A ( 11 ) page： 2072-2077 2000.11

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

In this paper, we study macro/micro diversity techniques for code acquisition of a direct-sequence spread-spectrum signal in an indoor packet communication system. In the system discussed, the base station has several radio ports each with a cluster of antennas, and the terminal also has multiple antennas. The performance in the uplink of this system is analyzed under Lognormal shadowing and flat Rayleigh fading. The numerical results show great performance improvements by proposed diversity techniques. In addition, it is clarified that the mean acquisition time, which is often used as the measure of performance, is not suitable for packet radio systems as it underestimates the necessary preamble length for initial code acquisition.

Efficient Channel Parameter Estimators for DS-CDMA Systems in Slow Time-Varying Channels Using a Modified version of the SAGE Algorithm Reviewed

Y. R. Senhaji, T. Yamazato, M. Katayama, and A. Ogawa

IEEE Global Communications Conference (Globecom2000) Vol. 3 ( 3 ) page： 1483-1487 2000.11

Language：Japanese

A modified version of the SAGE algorithm applied for joint estimation of delays, incidence azimuths and attenuation parameters characterizing the channel is presented. The modifications are based on using different observation intervals in optimizing the parameters and using time correlation in estimating delays, for the purpose of a further reduction in SAGE's computational weight, and improving its accuracy in delay estimation. We show analytically that short observation intervals are sufficient for optimizing the delays and the azimuths, and verify through simulation the reliability of using time correlation. Two other estimators are proposed combining the modified SAGE with a sequential estimation of the attenuation parameters suitable for slowly varying channels.

An Access Control Protocol for a Heterogenous Traffic with a Multi-Code CDMA Scheme Reviewed

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

IEICE Transaction on Fundamentals of Electronics, Communications and Computer Sciences Vol. E83-A ( 11 ) page： 2085-2092 2000.11

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

In this paper, we discuss the access control in multimedia CDMA ALOHA protocol. We introduce a new algorithm for the access control based on Modified Channel Load Sensing Protocol (MCLSP) in an integrated voice and two different classes of data users, high bit rate and low bit rate, exist in a multi-code CDMA Slotted ALOHA system. With our new algorithm, we show that the throughput of high bit rate data users, as well as, the total throughput of the data medium can be optimized and take a maximum value even at high values of offered loads. We also investigate the performance when voice activity detection (VAD) is considered in voice transmission.

An access control protocol for a heterogeneous traffic with a multi-code CDMA scheme Reviewed

Sandouk A, Yamazato T, Katayama M, Ogawa A

IEICE TRANSACTIONS ON FUNDAMENTALS OF ELECTRONICS COMMUNICATIONS AND COMPUTER SCIENCES Vol. E83A ( 11 ) page： 2085 - 2092 2000.11

An initial code acquisition scheme for indoor packet DS/SS systems with macro/micro antenna diversity Reviewed

Ikai Y, Katayama M, Yamazato T, Ogawa A

IEICE TRANSACTIONS ON FUNDAMENTALS OF ELECTRONICS COMMUNICATIONS AND COMPUTER SCIENCES Vol. E83A ( 11 ) page： 2070 - 2077 2000.11

An initial code acquisition scheme for indoor packet DS/SS systems with macro/micro antenna diversity Reviewed

Y Ikai, M Katayama, T Yamazato, A Ogawa

IEICE TRANSACTIONS ON FUNDAMENTALS OF ELECTRONICS COMMUNICATIONS AND COMPUTER SCIENCES Vol. E83A ( 11 ) page： 2070 - 2077 2000.11

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

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An access control protocol for a heterogeneous traffic with a multi-code CDMA scheme Reviewed

A Sandouk, T Yamazato, M Katayama, A Ogawa

IEICE TRANSACTIONS ON FUNDAMENTALS OF ELECTRONICS COMMUNICATIONS AND COMPUTER SCIENCES Vol. E83A ( 11 ) page： 2085 - 2092 2000.11

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

In this paper, we discuss the access control in multimedia CDMA ALOHA protocol. We introduce a new algorithm for the access control based on Modified Channel Load Sensing Protocol (MCLSP) in an integrated Voice and two different classes of data users, high bit rate and low bit rate, exist in a multi-code CDMA Slotted ALOHA system. With our new algorithm, we show that the throughput of high bit rate data users, as well as, the total throughput of the data medium can be optimized and take a maximum value even at high values of offered loads. We also investigate the performance when voice activity detection (VAD) is considered in voice transmission.

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A Study on Reducing tne Nonlinear Distortion in Multicarrier Systems Reviewed

HARADA Masaaki, YAMAZATO Takaya, KATAYAMA Masaaki, OGAWA Akira

IEICE Trans. Fundamentals, A Vol. 83 ( 10 ) page： 1992 - 1995 2000.10

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

In this paper, we discuss on the realization of reduced peak power transmission for the multicarrier systems. Since the signals have large amplitude fluctuations in conventional multicarrier systems, signals amplified by a nonlinear amplifier are greatly distorted, resulting in severe performance degradation. In order to avoid this large amplitude fluctuation, we propose a scheme for reducing the nonlinear distortion by using the set of the signal point series which show low peak to mean envelope power ratio(PMEPR)value. In this system, one symbol is transmitted with multicarriers and the received signal is detected with maximum likelihood sequence detection.

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An Study on Reducing the Nonlinear Distortion on Multicarrier Systems Reviewed

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

IEICE Transaction on Fundamentals of Electronics, Communications and Computer Sciences Vol. E83-A ( 10 ) page： 1992-1995 2000.10

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

In this paper, we discuss on the realization of reduced peak power transmission for the multicarrier systems. Since the signals have large amplitude fluctuations in conventional multicarrier systems, signals amplified by a nonlinear amplifier are greatly distorted, resulting in severe performance degradation. In order to avoid this large amplitude fluctuation, we propose a scheme for reducing the nonlinear distortion by using the set of the signal point series which show low peak to mean envelope power ratio (PMEPR) value. In this system, one symbol is transmitted with multicarriers and the received signal is detected with maximum likelihood sequence detection.

A study on reducing the nonlinear distortion in multicarrier systems Reviewed

Harada M, Yamazato T, Katayama M, Ogawa A

IEICE TRANSACTIONS ON FUNDAMENTALS OF ELECTRONICS COMMUNICATIONS AND COMPUTER SCIENCES Vol. E83A ( 10 ) page： 1992 - 1995 2000.10

Influence of two kinds of Packet Existence Detection Error on CDMA Unslotted ALOHA System Reviewed

TADOKORO Yukihiro, OKADA Hiraku, SAITO Masato, YAMAZATO Takaya, KATAYAMA Masaaki, OGAWA Akira

Proceedings of the Society Conference of IEICE Vol. 2000 page： 145 2000.9

Joint optimization of transmitter/receiver with multiple transmit/receive antennas in band-limited channels Reviewed

Ban K, Katayama M, Yamazato T, Ogawa A

IEICE TRANSACTIONS ON COMMUNICATIONS Vol. E83B ( 8 ) page： 1697 - 1704 2000.8

Joint optimization of transmitter/receiver with multiple transmit/receive antennas in band-limited channels Reviewed

K Ban, M Katayama, T Yamazato, A Ogawa

IEICE TRANSACTIONS ON COMMUNICATIONS Vol. E83B ( 8 ) page： 1697 - 1704 2000.8

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

We study the joint optimization problem of a transmitter with multiple transmit antennas and a receiver with multiple receive antennas in a narrow-band communication system. We discuss the problem of designing a pre-filter at the transmitter, a post-filter at the receiver, and a bit allocation pattern to multiple symbols in the sense of minimizing the average bit error rate. With the optimized filters and the bit allocation, we could realize high efficiency and high data rate in band-limited channels.

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Adaptive Transmit Permission Probability Control in CDMA Cellular Packet Communications with Site Diversity Reviewed

MORI Kazuo, KOBAYASHI Takehiko, YAMAZATO Takaya, OGAWA Akira

IEICE transactions on communications Vol. 83 ( 7 ) page： 1445 - 1453 2000.7

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

Site diversity causes unfairness in packet reception that depends on the location of the mobile stations in the uplink of CDMA cellular packet communication systems.This paper proposes an adaptive transmit permission probability control scheme that reduces this unfairness in CDMA cellular slotted-ALOHA systems with site diversity.The proposed scheme adaptively controls the transmit permission probability according to the offered load and the location of the mobile stations.Successful packet reception rate, fairness coefficient and throughput performance are evaluated in fading environments with imperfect power control.Computer simulation shows that adaptive transmit permission probability control improves fairness of service for all mobile stations and throughput performance across all channel loads compared with the conventional scheme.

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Adaptive transmit permission probability control in CDMA cellular packet communications with site diversity Reviewed

Mori K, Kobayashi T, Yamazato T, Ogawa A

IEICE TRANSACTIONS ON COMMUNICATIONS Vol. E83B ( 7 ) page： 1445 - 1453 2000.7

Adaptive transmit permission probability control in CDMA cellular packet communications with site diversity Reviewed

K Mori, T Kobayashi, T Yamazato, A Ogawa

IEICE TRANSACTIONS ON COMMUNICATIONS Vol. E83B ( 7 ) page： 1445 - 1453 2000.7

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

Site diversity causes unfairness in packet reception that depends on the location of the mobile stations in the uplink of CDMA cellular packet communication systems. This paper proposes an adaptive transmit permission probability control scheme that reduces this unfairness in CDMA cellular slotted-ALOHA systems with site diversity. The proposed scheme adaptively controls the transmit permission probability according to the offered load and the location of the mobile stations. Successful packet reception rate, fairness coefficient and throughput performance are evaluated in fading environments with imperfect power control. Computer simulation shows that adaptive transmit permission probability control improves fairness of service for all mobile stations and throughput performance across all channel loads compared with the conventional scheme.

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Hierarchical Channel Structure to Improve Handover Performance of LEOS Communication Systems

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

Technical Report of IEICE Vol. SAT page： - 2000.6

Hierarchical Channel Structure to Improve Handover Performance of LEOS Communication Systems

N. Ichikawa, M. Katayama, H. Okada, T. Yamazato and A. Ogawa

Technical Report of IEICE Vol. SAT2000 page： - 2000.6

Effects of cell structure on quality of service of LEOS communication systems Reviewed

Ono K, Katayama M, Yamazato T, Ogawa A

IEICE TRANSACTIONS ON COMMUNICATIONS Vol. E83B ( 4 ) page： 782 - 790 2000.4

Effects of cell structure on quality of service of LEOS communication systems Reviewed

K Ono, M Katayama, T Yamazato, A Ogawa

IEICE TRANSACTIONS ON COMMUNICATIONS Vol. E83B ( 4 ) page： 782 - 790 2000.4

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

In this paper, we analytically study the effects of overlap and overlay structure on the quality of service (QoS) of Low Earth-Orbital Satellite (LEOS) communication systems. We consider two-layered overlay of cells and intentional overlap of neighboring small cells. In order to measure the QoS, the probabilities of rejection of a newly arrived call (blocking) and Forced termination due to failure of a handover (call dropping) are derived. In addition to these measures, the largest traffic intensity which guarantees the required blocking and dropping probabilities is also used.

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Papers - YAMAZATO Takaya