Faculty Profiles - YAMAZATO Takaya

Papers - YAMAZATO Takaya

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Reduced Peak Power Transmission for Convolutionally Coded OFDM Signals Reviewed

M. Harada, T. Yamazato, H. Okada, and M. Katayama

7th International-OFDM Workshop 2002 page： 102-106 2002.9

Language：English

In this paper, we propose a novel coding scheme to reduce a peak envelope power of convolutionally coded orthogonal frequency devision multiplexing (OFDM) signals. In this system, convolutionally coded bits are mapped onto symbol sequence. The symbol sequence have multiple symbols which are adjusted so as to show low peak envelope power. Also, applying a set partition to the symbol sequence enable to enlarge an Euclidean distance between each sequence. We evaluate the performance of proposed system under the effect of nonlinear amplifier.

Turbo Decoding for Hard-Detected Signals of Fiber Optical Communications Reviewed

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

IASTED Wireless and Optical Communications 2002 (WOC 2002) Conference page： - 2002.7

Language：English

We propose a method to realize the soft-decision decoding for the hard-detected signals. In this paper, a novel concept is introduced as error-detected reliability. The method is very useful for fiber optical communication systems as hard detection is the only detection method for the systems. We demonstrate our proposed method using the turbo code in which the soft information is required for the decoding. As a result, the simulation shows slight difference in the range of moderate to high signal-to-noise ratio between the proposed decoding scheme and the conventional turbo decoding. Moreover, the bit error rate of $10^{-11}$ can be achieved by serial Concatenation of Reed-Solomon and turbo code for Q-factor lower than $8.0$ dB with the bandwidth expansion ratio of $33.3\%$.

Transmitting/Receiving Diversity Method using Single-phase Three-wire Power-Line for Power-Line Communication

H. Furukawa, H. Okada, T. Yamazato, and M. Katayama

Technical Report of IEICE Vol. SST2002-14 page： 13-17 2002.7

Language：Japanese

The low voltage distribution power-lines from the distribution transformer to the fuse box are single-phase and three-wire type and the In-house power-lines are single-phase and two-wire type in Japan. The two-wire type power-lines are constructed of a pair of wires of the three-wire type power-lines. And the two-wire type power-lines are used as 200V or 100V AC. Under this condition, there is mutual coupling between different pair of power-lines. Therefore it is possible to improve performance of the power-line for communication by using the Space-Frequency Coding when the transmitter or receiver is on at least two pairs of power-lines. In this paper, the transmitting/receiving diversity method using the Space-Frequency Code for Power-Line communication is proposed and the effectiveness of this method has been confirmed by experiments.

New Analytical Model for TCP in wireless Environments Reviewed

K. Naito, H. Okada, M. Saito, T. Yamazato, and M. Katayama

IEICE Transaction on Fundamentals of Electronics, Communications and Computer Sciences Vol. E85-A ( 7 ) page： pp.1501-1510 2002.7

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

We propose a new analytical model of Transmission Control Protocol (TCP) in wireless environments where transmission errors occur frequently. In our proposed model, we consider the exponential increase of a congestion window and the exponential increase of a timeout back-off. Finally, we have clarified the behavior of TCP mechanisms of different versions and TCP throughput characteristics analytically. From our result, the behavior of TCP mechanisms is different in each implementation version. These differences mean that the required characteristics of wireless links are different in each implementation version. Therefore, our proposed model is a base analysis of designing wireless link mechanisms.

An Access Control Protocol Based on Estimation of Traffic with an Adaptive Algorithm in Multimedia CDMA Packet Communications

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

Technical Report of IEICE Vol. 102 ( 204 ) page： 55-60 2002.7

Language：Japanese

In a multimedia communication, various types of traffic are handled. Generally, each traffic in a multimedia communication has a different stochastic property. Conventional access control protocols do not consider such characteristics of multimedia traffic. We propose a new access control protocol for multimedia CDMA packet communications in which stochastic properties of multimedia traffic is considers. The proposed protocol controls packet transmissions based on estimation of the instantaneous number of simultaneously transmitted packets. This estimation is carried out by an adaptive algorithm. Simulation results show the advantage of the proposed protocol over the protocol which does not estimate the number of simultaneously transmitted packets

Statistical Noise Characterization for Wide Band Power Line

Y. HIRAYAMA, H. OKADA, T. YAMAZATO, and M. KATAYAMA

Technical Report of IEICE Vol. SST2002-13 page： 7-12 2002.7

Language：Japanese

The wide band power-line communication system (PLC) has been drawing much attention as an alternative communication system. To realize reliable high-speed data transmissions, it is essential to understand the noise feature on the power-line. Noise characteristics of the narrow band PLC have been discussed in previous papers, however, there is few report on the wide band PLC noise. In this paper, we prepare a noise measurement system and discuss on the measured noise characteristics in wide band. As a result, we show that the noise characteristics differ greatly dependents on frequency.

New analytical model for TCP in wireless environments Reviewed

Naito K, Okada H, Saito M, Yamazato T, Katayama M

IEICE TRANSACTIONS ON FUNDAMENTALS OF ELECTRONICS COMMUNICATIONS AND COMPUTER SCIENCES Vol. E85A ( 7 ) page： 1501 - 1510 2002.7

New analytical model for TCP in wireless environments Reviewed

Naito K.

IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences Vol. E85-A ( 7 ) page： 1501 - 1510 2002.7

New Analytical Model for TCP in Wireless Environments Reviewed

Katsuhiro Naito, Hiraku Okada, Masato Saito, Takaya Yamazato, Masaaki Katayama

IEICE Transactions on Fundamentals Vol. E85-A ( 7 ) page： 1501 - 1510 2002.7

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

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A Study on Handover and Channel Allocation Scheme using Linear Shift Property of the Servicearea in Low Earth-Orbital Satellite

K.Nisihara, H.Okada, T.Yamazato, and M.Katayama

Technical Report of IEICE Vol. 102 ( 144 ) page： 15-18 2002.6

Language：Japanese

In this paper, we discuss the handover and channel allocation scheme for cellular systems of Low Earth-Orbital (LEO) satellite. By using the linear sift property of LEO satellite, we propose the handover scheme in which a user use the same channel even if a handover occurs. Furthermore, we propose the dynamic channel allocation scheme taking account of the centralized cellular system of LEO Satellite. In this scheme, a channel is assigned according to the objective function which is calculated by user and channel distribution. From comparison of numerical results, we show that the proposed scheme can improve the blocking probability.

A study on SOVA based Turbo-decoding with threshold Reviewed

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

IEICE Transaction on Fundamentals of Electronics, Communications and Computer Sciences Vol. J85-A ( 5 ) page： pp.606-609 2002.5

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

In this paper, we propose a new SOVA based Turbo-decoding scheme which applys a variable threshold to the output of each of the component decoder. The value of the threshold is determined accoding to the distribution of the observed output of each of the component decoder. We show that our proposed scheme gives the better BER performance than conventional one.

Performance Evaluation of PredictionError Based MAP Receiver for DCT Compressed Image Transmission Reviewed

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

The Journal of the Institute of Television Engineers of Japan Vol. 56 ( 5 ) page： pp.842-845 2002.5

Performance Evaluation of PredictionError Based MAP Receiver for DCT Compressed Image Transmission Reviewed

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

The Journal of the Institute of Television Engineers of Japan Vol. 56 ( 5 ) page： 842-845 - 845 2002.5

Potentiality of Campus Portal

T. Yamazato, S. Kajita, H. Okada

IEICE General Conference Vol. KD-1-2 page： 257-258 2002.3

BER Performance Analysis of Multicarrier-CDMA Systems in Multipath Fading Channel

H.takeuchi, T.yamazato, H.okada and M.katayama

Technical Report of IEICE Vol. SST2001-171 page： pp.13-18 2002.3

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

This paper presents the BER analysis of the asynchronous Multicarrier (MC)-CDMA system in multipath fading channel. We derive the BER of the MC-CDMA and compared with that of the DS-CDMA. We found that the BER of the MC-CDMA is a little worse than that of the band-limited DS-CDMA under the same bandwidth and the same spreading factor, and when the number of multipath is infinity, the BER of both systems are regarded as being that for the case without fading channel. However, if the number of multipath is more than the number of finger of Rake receiver, the MC-CDMA system can perform better than the DS-CDMA system.

A study on Iterative Decoding and Diversity Scheme for Correlated Rayleigh Fading Signals

R. Chang, C. Zheng, T. Yamazato, M. Katayama, A. Ogawa

IEICE General Conference Vol. B-5-221 page： p.672 2002.3

CDMA Packet Recognition and Signal Acquisition using LMS-based Adaptive Receiver Reviewed

T. Kume, T. Yamazato, K. Ban, H. Okada, and M. Katayama

IEEE Wireless Communications and Networking Conference Vol. 1 page： pp.379-383 2002.3

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

In this paper, we propose a new packet recognition and signal acquisition scheme with an adaptive linear filter based on an Least Mean Square (LMS) algorithm for code-division multiple access (CDMA) packet systems. In CDMA systems, conventional receivers with matched filtering suffer from the near-far problem due to multiple access interference (MAI). In general, closed-loop power control is used in order to reduce the influence of the near-far problem. However, closed-loop power control is unsuitable for packet systems. Hence, in order to eliminate the influences of the near-far problem, we focus on an adaptive receiver based on an LMS algorithm for a packet recognition and signal acquisition in CDMA packet systems.

Effect of Nonlinear Amplifiers of Transmitters in Multicarrier CDMA Systems Reviewed

H. Muramatsu, M. Harada, T. Yamazato, H. Okada, M. Katayama

IEICE Transaction on Fundamentals of Electronics, Communications and Computer Sciences Vol. J85-A ( 3 ) page： pp.340-348 2002.3

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

In this paper, we compare Multicarrier(MC-) CDMA systems with DS-CDMA systems in the asynchronous uplink channel. First, we analysis signal to noise inteference ratio (SNIR) of asynchronous MC-CDMA systmes in AWGN channel, in order to show the basic performance of MC-CDMA systems. Then, we discuss the effect of nonlinear amplifiers of trnasmitters in MC-CDMA systems, which are usually required using in the mobile terminals for the uplink. We evaluate bit error rate preformance taking account of out-of-band emission.

Effect of Nonlinear Amplifiers of Transmitters in Multicarrier CDMA Systems Reviewed

H. Muramatsu, M. Harada, T. Yamazato, H. Okada, M. Katayama

IEICE Transaction on Fundamentals Vol. J85-A ( 3 ) page： 340-348 2002.3

Comparison of Multiple Access Schemes in Multibeam Non-GEO Satellite Communication Systems Reviewed

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

IEICE Transactions on Communications Vol. E86-B ( 2 ) page： 785-791 2002.2

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

This paper describes an analytical method to estimate the amount of interference in multibeam non-geostationary satellite systems. The performance of CDMA is compared with that of FDMA (or TDMA) by employing the maximum acceptable number of users per cell in uplink as a measure. Numerical examples shows that the maximum acceptable number of users in FDMA (or TDMA) systems varies according to the altitude of the satellites, while the performance is insensitive to the altitude in CDMA systems. Then, it is found that the superior multiple access scheme depends on the altitude of the satellite.

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Papers - YAMAZATO Takaya