Faculty Profiles - YAMAZATO Takaya

Papers - YAMAZATO Takaya

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A Simple Transmit/Receive Antenna Diversity for Indoor DS/CDMA Wireless Communication Systems Reviewed

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

IEICE Transaction on Communications Vol. E80-B ( 12 ) page： 1790-1796 1997

A Constant Amplitude Coding for Orthogonal Multi-Code CDMA Systems Reviewed

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

IEICE Transaction on Fundamentals of Electronics, Communications and Computer Sciences Vol. E80-A ( 12 ) page： 2477-2484 1997

[Invited Paper] CDMA for Personal Communications Based on Low Earth Orbital Satellite Systems Invited Reviewed

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

IEICE Transaction on Fundamentals of Electronics, Communications and Computer Sciences Vol. E80-A ( 12 ) page： 2347-2356 1997

低軌道周回衛星を用いた海亀生態観測システムにおける海亀搭載送信用アンテナ

天野良晃、徳安朋浩、山里敬也、片山正昭、小川明

1997年電気関係学会東海支部連合大会 page： 507 1997

低軌道周回衛星を用いた海亀生態観測システムにおける海亀搭載データ処理装置

北村唯夫、徳安朋浩、山里敬也、片山正昭、小川明

1997年電気関係学会東海支部連合大会 page： 506 1997

レイリーフェージング下におけるスペクトル拡散信号のダイバシチ同期補捉手法の提案

猪飼洋平、片山正昭、山里敬也、小川明

1997年電気関係学会東海支部連合大会 page： 508 1997

マルチコードCDMA方式における振幅変動の影響

藤原昭博、山里敬也、片山正昭、小川明

1997年電気関係学会東海支部連合大会 page： 509 1997

A proposal of SS communication system using LEO satellite for observing ecology of sea turtles Reviewed

Tokuyasu T, Wada T, Yamazato T, Katayama M, Ogawa A

GLOBECOM 97 - IEEE GLOBAL TELECOMMUNICATIONS CONFERENCE, CONFERENCE RECORD, VOLS 1-3 page： 1157 - 1161 1997

CDMA for personal communications based on low earth-orbital satellite systems Reviewed

Ogawa A.

IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences Vol. E80-A ( 12 ) page： 2347 - 2355 1997

Convolutionally coded DS/CDMA system using multi-antenna transmission Reviewed

Ban K, Katayama M, Stark WE, Yamazato T, Ogawa A

GLOBECOM 97 - IEEE GLOBAL TELECOMMUNICATIONS CONFERENCE, CONFERENCE RECORD, VOLS 1-3 page： 92 - 96 1997

Performance analysis of CDMA-unslotted ALOHA operating over CDMA voice signals Reviewed

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

1997 IEEE PACIFIC RIM CONFERENCE ON COMMUNICATIONS, COMPUTERS AND SIGNAL PROCESSING, VOLS 1 AND 2 page： 603 - 606 1997

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

In this paper, we analyse system performance of CDMA data terminals operating over CDMA voice signals. Outage probability for voice users and throughput for data users are evaluated taking into account the effect of interference from both media. Since we have two different media with different characteristics, the analysis is rather difficult because the behavior of the system will be dependent on both voice and data offered loads. We get over this difficulty profiting from the characteristics of both media. Consequently, we obtain the performance of both media by using the queueing theory.

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Simultaneous estimation of code and frequency of DS/SS signals of multiple-LEO-satellite communication systems Reviewed

M Ishizu, M Katayama, T Yamazato, A Ogawa

PIMRC '97 - EIGHTH IEEE INTERNATIONAL SYMPOSIUM ON PERSONAL, INDOOR AND MOBILE RADIO COMMUNICATIONS: WAVES OF THE YEAR 2000+, TECHNICAL PROGRAM, PROCEEDINGS, VOLS 1-3 page： 1019 - 1023 1997

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

In this manuscript, we consider a receiver with satellite diversity by using DS/SS signals from different LEO satellites. Since the signals from the different LEO satellites may have different frequency offsets due to Doppler effect, we propose an acquisition scheme which can estimate code timings and carrier frequencies of these signals at once. We evaluate characteristics of the proposed scheme by mean acquisition time.

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System capacity of an integrated voice and data CDMA network in channel load sensing protocol Reviewed

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

GLOBECOM 97 - IEEE GLOBAL TELECOMMUNICATIONS CONFERENCE, CONFERENCE RECORD, VOLS 1-3 page： 899 - 903 1997

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

In this paper, we analyze an integrated voice and data system over a CDMA Unslotted ALOHA with Channel Load Sensing Protocol, considering the effect of each traffic. We can And that the threshold for the number of data transmissions is very effective to improve both performances of the throughput for data and the Erlang capacity for voice users. Furthermore, to optimize this system, we define the system capacity. As a result. we obtain an optimum threshold for data to make the;best use of the channel capacity.

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A 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. E80-A ( 12 ) page： 2477 - 2483 1997

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences

In this paper, we present orthogonal multi-code CDMA systems with the constant amplitude transmission. In general, the dynamic range of the amplitude of the transmitting signal is very large in the case of orthogonal multi-code CDMA systems. In order to realize the constant amplitude transmission for orthogonal multi-code CDMA systems, we propose a constant amplitude coding. First, we show the basic concept of the constant amplitude coding. And then, we show that the constant amplitude transmission can be realized by the combination of the conventional orthogonal multi-code CDMA and the constant amplitude coding. Finally, the effectiveness of the proposed method is evaluated in terms of the bit error rate performance and it is shown that the proposed method is robust to the non-linear distortion caused by a high power amplifier (HPA).

Scopus

A spread-spectrum system with dual processing gains designed for cyclic noise in power line communications Reviewed

Niwa H., Oonq O., Katayama M., Yamazato T., Ogawa A., Isaka N.

IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences Vol. E80-A ( 12 ) page： 2526 - 2532 1997

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences

We propose a spread-spectrum power line communication system considering the cyclic features of the noise in the lines. For this purpose, we model the noise as the sum of a time-invariant stationary process and two cyclostationary processes, i.e., cyclic continuous noise and cyclic impulsive noise. The proposed system employs two different countermeasures to each of these two classes of cyclic noise. For the cyclic continuous noise, it uses multiple-processing-gain spread spectrum technique: the smaller processing gains are assigned for the periods with lower instantaneous noise power and the larger ones for the periods of higher noise power. Considering the cyclic impulsive noise, convolutional coding with interleaving is applied. In order to analyze the performance improvement due to the employment of multiple processing gains, we introduce a simple model of the continuous noise. The overall performance is evaluated by computer simulation with the actual noise wave-form measured in power lines.

Scopus

A simple transmit/receive antenna diversity for indoor DS/CDMA wireless communication systems Reviewed

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

IEICE Transactions on Communications Vol. E80-B ( 12 ) page： 1790 - 1796 1997

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：IEICE Transactions on Communications

This paper proposes a direct-sequence spread spectrum (DS/SS) communication system with a new diversity technique designed for indoor multi-path fading channels where path diversity isn't available. In this system, the transmitter sends a same signal from multiple antennas at the same time with intentional time delays, which allows the receiver to distinguish and combine the signals from different antennas. We also consider the combination of this scheme with the conventional receiving antenna diversity for additional diversity gain. Furthermore, it is found that the use of the multiple transmitting antennas decreases the effect of the multiple access interference.

Scopus

A proposal of SS communication system using LEO satellite for observing ecology of sea turtles Reviewed

T Tokuyasu, T Wada, T Yamazato, M Katayama, A Ogawa

GLOBECOM 97 - IEEE GLOBAL TELECOMMUNICATIONS CONFERENCE, CONFERENCE RECORD, VOLS 1-3 page： 1157 - 1161 1997

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

In this paper, we examine the system for observing ecology of sea animals by means of a low earth orbital observatory satellite. We consider the system performance in the uplink, which is the communication link from the animal stations to the observatory satellite. Since the up-link condition is much severe, we employ the M-ary/SS with CDMA ALOHA as a multiple access scheme. A key issue to realize the system depends on an acquisition technique which is robust to the effect of large Doppler shift caused by the rapid movement of the low earth orbital satellite. Ih this paper, we discuss code-acquisition and estimation of carrier frequency considering the M-ary/SS/CDMA technique to realize this observatory system.

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An initial acquisition method for M-ary spread-spectrum signals using hadamard code sequences Reviewed

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

IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences Vol. E80-A ( 11 ) page： 2172 - 2179 1997

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences

In this paper, we examine a new initial symbol acquisition method for M-ary spread-spectrum (M-ary/SS) signals that are affected by large carrier frequency offset. By the effect of the carrier frequency offset, preamble signal energy is dispersed to the undesired outputs. The proposed method is based on the collection of such dispersed signal energies by using reference patterns. The reference patterns are constructed by using the characteristic of Hadamard code sequences. The effectiveness of the proposed method is evaluated in terms of mean acquisition time.

Scopus

Effects of transmission control considering voice activation in an integrated voice and data CDMA Reviewed

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

ECSC-4: 4TH EUROPEAN CONFERENCE ON SATELLITE COMMUNICATIONS page： 176 - 181 1997

Language：English Publishing type：Research paper (international conference proceedings) Publisher：ASSOC ELETTROTECHNICA ED ELETTRONICA ITALIANA

In this paper, we focus on an integrated voice and data system over unslotted CDMA system. We propose a method to accommodate the data packet into the silence period of voice signal by using a traffic control based on the channel load sensing protocol. We evaluate the system by the throughput and delay performance for data packet, the blocking probability for voice users. From the results, we show the advantages of the proposed system.

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Approximation Method for CDMA Unslotted ALOHA Systems with Fixed Packet Length

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

Technical Report of IEICE Vol. SST96 ( 61 ) page： 13-18 1996.12

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Papers - YAMAZATO Takaya