Faculty Profiles - YAMAZATO Takaya

Papers - YAMAZATO Takaya

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Hierarchical Transmission of DCT Coefficients Using Multi-Code DS/SS Modulation

M. Honjo, S. Makido, T. Yamazato, H. Okada, M. Katayama, and A. Ogawa

Technical Report of IEICE Vol. SST2001 ( 17 ) page： - 2001

Language：Japanese

In this paper, we propose a hierarchical transmission of image signal using multi-code DS/SS modulation. DCT is originally invoked in the image coding at the aim of compacting the input variance and compressing efficiently. We achieve an error torelant transmission system by using this property in transmit energy. We introduce the energy assingment (EA) to reduce the channel noise in hierarchical transmission. Assigning an appropriate transmitt energy corresponding to its variance, we show that it is possible to maintain the picuture quality even in low channel condition. The analysis is carried out to show the effectiveness of our scheme using 2-D Gauss-Markov random field in the case of MC DS/SS modulation used. We also verify the same characteristic in several sample movies.

Comparison of CDMA and FDMA/TDMA in non-GEO Satellite Systems Reviewed

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

IEEE International Conference on Communications (ICC2001) Vol. G76.5 page： - 2001

Language：English

We compare CDMA and FDMA (or TDMA) schemes in multi-beam non-geostationary satellite systems, taking the effects of antenna patterns on inter-cell interference into consideration. The maximum acceptable number of users per cell in uplink is employed as a measure of the system capacity. We have found that in FDMA (or TDMA) systems the maximum acceptable number of users varies according to the altitude of the satellites, while the performance is insensitive to the altitude in CDMA systems. For this reason, the altitude of the satellites is found to be an important factor for selecting multiple access schemes in non-geostationary satellite systems.

A Study on High Rate Serially Concatenated Coding Scheme for Optical Communication Systems Reviewed

C. Zheng, T. Yamazato, M. Katayama and A. Ogawa

International Technical Conference on Circuits/Systems, Computers and Communications (ITC-CSCC), Tokushima, Japan page： - 2001

Language：English

In this work, a serially concatenated coding scheme of an outer Reed-Solomon code and an inner high rate Turbo code is proposed for the optical communication systems. The simulation results show the reduction of the ``error floor'' influence of the Turbo code. This reduction is due to the outer cascaded Reed-Solomon decoding process and the increase of the interleaver size of the inner Turbo code. The effect of quantization is also considered for inner Turbo decoder. As results, 4-bit quantization is satisfied.

Communication System for Time and Frequency Dependent Power-Line Channel

K.Sugimoto, H.Okada, T.Yamazato, M.Katayama

Technical Report of IEICE page： - 2001

Language：Japanese

In power-line communication, channel characteristics and the man-made noise from appliances are time and frequency dependent. This noise is known to be modeled by colored cyclo-stationary Gaussian noise. In consideration of frequency dependence of noise, in this manuscript, we employ OFDM signaling scheme. Under this environment, the space spanned by time and frequency can be subdivided into small cells by symbol duration and sub-carriers of OFDM. The bit error rate (BER) of each cell is analytically derived. In addition, we consider performance improvement by combining some cells (transmitting same information in some cells with iterative coding) according to the knowledge on stochastic features of the cyclo-stationary power-line channel.

An access control protocol based on correlation of multimedia traffic for CDMA ALOHA

Y. Hirayama, H. Okada, T. Yamazato, and M. Katayama

Technical Report of IEICE page： - 2001

Language：Japanese

In this paper, we consider wireless multimedia packet communications which support voice, video, and data traffic. Multimedia traffic includes various types of traffic which has different characteristics of packet generation. We propose a new access control protocol for multimedia traffic. This protocol controls data packet transmission based on estimation of number of packets which will generate in future. This estimation is derived from correlation of voice packet traffic. We evaluate the performance of proposed protocol when it applied to the CDMA slotted ALOHA. Simulation results show that proposed protocol can maintain the data packet throughput and the packet loss rate at a certain level when the offered load of data increases.

A design of source matched MAP receiver for image transmission Reviewed

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

Materials Research Society Symposium - Proceedings Vol. 626 2001

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Materials Research Society Symposium - Proceedings

In this paper we will discuss the MAP receiver design for the reception of the image signal. It is impractical to use the MAP algorithm for the source detection because of its huge calculation costs. To solve this problem we propose a novel MAP receiver structure, where the receiver contains a predictor within it. With an aid of the predictor we can reduce the calculation. Furthermore we can approximate the a priori probability by the prediction error distribution.

Scopus

A new packet detection scheme in CDMA unslotted ALOHA system with successive interference cancellation Reviewed

Tadokoro Y, Okada H, Yamazato T, Katayama A, Ogawa A

GLOBECOM '01: IEEE GLOBAL TELECOMMUNICATIONS CONFERENCE, VOLS 1-6 page： 3173 - 3177 2001

An adaptive antenna selection scheme for transmit diversity in OFDM systems Reviewed

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

IEEE 54TH VEHICULAR TECHNOLOGY CONFERENCE, VTC FALL 2001, VOLS 1-4, PROCEEDINGS page： 2168 - 2172 2001

An adaptive antenna selection scheme for transmit diversity in OFDM systems Reviewed

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

IEEE 54TH VEHICULAR TECHNOLOGY CONFERENCE, VTC FALL 2001, VOLS 1-4, PROCEEDINGS page： 2168 - 2172 2001

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

In wireless communication systems, as one of effective techniques for combating fading, transmit diversity has attracted much attention, especially when receive diversity is expensive or impractical due to the constraint of terminal size. In this study we consider an adaptive carrier-by-carrier basis antenna selection scheme for transmit diversity, in OFDM systems under the assumption that a transmitter has priori knowledge of the Channel State Information(CSI). In the proposed schemes transmit antennas are selected adaptively for each subcarrier according to CSI.

DOI： 10.1109/VTC.2001.957128

Web of Science

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An adaptive antenna selection scheme for transmit diversity in OFDM systems Reviewed

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

IEEE Vehicular Technology Conference Vol. 4 ( 54ND ) page： 2168 - 2172 2001

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：IEEE Vehicular Technology Conference

In wireless communication systems, as one of effective techniques for combating fading, transmit diversity has attracted much attention, especially when receive diversity is expensive or impractical due to the constraint of terminal size. In this study we consider an adaptive carrier-by-carrier basis antenna selection scheme for transmit diversity in OFDM systems under the assumption that a transmitter has priori knowledge of the Channel State Information(CSI). In the proposed schemes transmit antennas are selected adaptively for each subcarrier according to CSI.

Scopus

Comparison of CDMA and FDMA/TDMA in non-GEO satellite systems Reviewed

Ichikawa N.

IEEE International Conference on Communications Vol. 10 page： 3167 - 3172 2001

Comparison of CDMA and FDMA/TDMA in non-GEO satellite systems Reviewed Open Access

N Ichikawa, M Katayama, H Okada

2001 IEEE INTERNATIONAL CONFERENCE ON COMMUNICATIONS, VOLS 1-10, CONFERENCE RECORD page： 3167 - 3171 2001

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

DOI： 10.1109/ICC.2001.937256

Open Access

Web of Science

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Hierarchical transmission of video signal using multi-code DS/SS modulation based on DCT coefficients Reviewed

Honjo M, Makido S, Yamazato T, Okada H, Katayama M, Ogawa A

GLOBECOM '01: IEEE GLOBAL TELECOMMUNICATIONS CONFERENCE, VOLS 1-6 page： 3395 - 3399 2001

New analytical model for the TCP throughput in wireless environment Reviewed

Naito K.

IEEE Vehicular Technology Conference Vol. 3 ( 53ND ) page： 2128 - 2132 2001

New analytical model for the TCP throughput in wireless environment Reviewed

Naito K, Okada H, Yamazato T, Katayama M, Ogawa A

IEEE VTC 53RD VEHICULAR TECHNOLOGY CONFERENCE, SPRING 2001, VOLS 1-4, PROCEEDINGS page： 2128 - 2132 2001

Throughput performance of CDMA Slotted ALOHA systems based on average packet success probability considering bit-to-bit dependence Reviewed

Saito M.

IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences Vol. E84-A ( 2 ) page： 653 - 659 2001

A new packet detection scheme in CDMA unslotted ALOHA system with successive interference cancellation Reviewed

Y Tadokoro, H Okada, T Yamazato, A Katayama, A Ogawa

GLOBECOM '01: IEEE GLOBAL TELECOMMUNICATIONS CONFERENCE, VOLS 1-6 page： 3173 - 3177 2001

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

A packet detection is one of the most important problems in packet communication systems. In a CDMA Unslotted ALOHA system, which is one of the wireless packet communication systems, Multiple Access Interference(MAI) makes the performance of the packet detection worse. To reduce the effect of MAI, we propose a new packet detection scheme in this paper. In this scheme, Successive Interference Cancellation(SIC) is applied. The packet's signal is detected after the cancellation of MAI using SIC. This proposed scheme gives good performance of the packet detection.

DOI： 10.1109/GLOCOM.2001.966012

Web of Science

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Modified HPSK Modulation Scheme for Wideband CDMA Systems Invited Reviewed Open Access

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

IEICE Transaction on Fundamentals of Electronics, Communications and Computer Sciences Vol. J83-A ( 12 ) page： 1552-1557 2000.12

OFDM systems with multiple trellis coded modulation Reviewed

Harada M.

IEEE International Symposium on Personal, Indoor and Mobile Radio Communications, PIMRC Vol. 2 page： 814 - 818 2000.12

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

SANDOUK Abbas, YAMAZATO Takaya, KATAYAMA Masaaki, OGAWA Akira

IEICE Transactions on Fundamentals, A Vol. 83 ( 11 ) page： 2085 - 2092 2000.11

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

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 consideraed in voice transmission.

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