Faculty Profiles - YAMAZATO Takaya

Papers - YAMAZATO Takaya

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The Real-Time Parallel Video Decoder Considered on the Complexity and Delay of Error Correcting Decoding Reviewed

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

IEICE Transaction on Fundamentals of Electronics, Communications and Computer Sciences Vol. J85-A ( 2 ) page： pp.214-230 2002.2

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

In this paper, a new video decoding scheme integrating error correcting decoder is proposed. In video data transmission, some error correcting code should be equipped to keep video data quality. But in many cases it would need much complex calculation and delay at the decoder when high quality of video data is required. Then, we prepare the two error correcting decoders against one error correcting encoder, where they are different in the delay and the reliability. Due to reconstructing output frame and reference frame separately with two outputs, less delay and less degradation is accomplished. The video quality is analyzed with the 3-D DPCM parallel decoder. Here we show that the degradation of output frame is minimized when no error exists in the reference frame. And we evaluate the simulation results using concatenating code as an example of two output error correcting decoder. Here we show that it is possible to maintain the video quality and achieves graceful degradation in low channel energy, especially in Rayleigh fading channel. Furthermore in the subjective evaluation, we can confirm that the degradation seems to less impression than general decoding in the same PSNR.

The Real-Time Parallel Video Decoder Considered on the Complexity and Delay of Error Correcting Decoding Reviewed

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

IEICE Transaction on Fundamentals Vol. J85-A ( 2 ) page： 214-230 2002.2

An access control protocol based on estimation of multimedia traffic with an adaptive algorithm in CDMA packet network Reviewed

Hirayama Y, Okada H, Yamazato T, Katayama M

13TH IEEE INTERNATIONAL SYMPOSIUM ON PERSONAL, INDOOR AND MOBILE RADIO COMMUNICATIONS, VOL 1-5, PROCEEDINGS page： 619 - 623 2002

CDMA packet recognition and signal acquisition using LMS-based adaptive receiver Reviewed

T Kume, Yamazato, I, K Ban, H Okada, M Katayama

WCNC 2002: IEEE WIRELESS COMMUNICATIONS AND NETWORKING CONFERENCE RECORD, VOLS 1 & 2 Vol. 1 page： 379 - 383 2002

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

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.

DOI： 10.1109/WCNC.2002.993525

Web of Science

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An access control protocol based on estimation of multimedia traffic with an adaptive algorithm in CDMA packet network Reviewed

Y Hirayama, H Okada, T Yamazato, M Katayama

13TH IEEE INTERNATIONAL SYMPOSIUM ON PERSONAL, INDOOR AND MOBILE RADIO COMMUNICATIONS, VOL 1-5, PROCEEDINGS Vol. 2 page： 619 - 623 2002

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

In multimedia wireless communications, various types of traffic are handled. Generally, each of these traffic has a different stochastic property. An access control protocol for multimedia wireless communications, therefore, are required to adopt a stochastic property of multimedia traffic. Conventional access control protocols, however, do not consider such characteristics of multimedia traffic. In this paper, we propose an access control protocol for multimedia CDMA packet communications. The proposed protocol controls the data packet transmissions based on the estimation of the instantaneous number of simultaneously transmitted voice and video packets. This estimation exploits the stochastic property of multimedia traffic. To carry out such estimation, we employ an adaptive algorithm as an estimation method. We evaluate the performance of the proposed protocol by comparing it with the performance in the case where a stochastic property of traffic is not considered.

DOI： 10.1109/PIMRC.2002.1047296

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Effect of interleaving and FEC on the throughput of CDMA unslotted aloha system with adaptive multiuser receiver Reviewed

H Okada, T Yamazato, M Katayama

13TH IEEE INTERNATIONAL SYMPOSIUM ON PERSONAL, INDOOR AND MOBILE RADIO COMMUNICATIONS, VOL 1-5, PROCEEDINGS Vol. 2 page： 941 - 945 2002

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

A CDMA unslotted ALOHA system is a connectionless-type of CDMA packet communication system. In this system, a user station can transmit a packet asynchronously and randomly, and so the packet birth/death event is one of the most important problems for multiuser detection. We have proposed the CDMA unslotted ALOHA system using an adaptive filter receiver based on minimum mean square error criterion in [8], and shown the improvement in the throughput performance even considering the effect of birth/death event. The ensemble-averaged squared error, however, increases at the point of packet birth. In this paper, we employ interleaving and forward error correction (FEC) coding techniques to mitigate the momentary increase in ensemble-averaged squared error. The use of FEC, however, causes the increase in MAI due to redundancy bits of FEC. Moreover, signal power is reduced under the condition that the energy of an information bit is the same. In such cases, whether an adaptive filter can operate effectively or not interests us,,. We evaluate the system performance and show that the improvement in throughput is achieved with interleaving and FEC techniques.

DOI： 10.1109/PIMRC.2002.1047360

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Effect of interleaving and FEC on the throughput of CDMA unslotted aloha system with adaptive multiuser receiver Reviewed

Okada H, Yamazato T, Katayama M

13TH IEEE INTERNATIONAL SYMPOSIUM ON PERSONAL, INDOOR AND MOBILE RADIO COMMUNICATIONS, VOL 1-5, PROCEEDINGS page： 941 - 945 2002

Turbo decoding for hard-detected signals of fiber optical communications Reviewed

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

PROCEEDINGS OF THE IASTED INTERNATIONAL CONFERENCE ON WIRELESS AND OPTICAL COMMUNICATIONS page： 125 - 130 2002

A Study on Reducing Peak Power of MTCM OFDM Systems

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

Symposium on Information Theory and Its Applications (SITA) Vol. 1 page： 71-74 2001.12

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

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

Conference Record / IEEE Global Telecommunications Conference Vol. 5 page： 3173 - 3177 2001.12

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Conference Record / IEEE Global Telecommunications Conference

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.

Scopus

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

Honjo M.

Conference Record / IEEE Global Telecommunications Conference Vol. 6 page： 3395 - 3399 2001.12

A New Packet Detection Scheme in CDMA Unslotted ALOHA System with Successive Interference Cancellation Reviewed

Y. Tadokoro, H. Okada, T. Yamazato, M. Katayama and A. Ogawa

IEEE Global Communications Conference Vol. 5 page： pp.3173-3177 2001.11

Language：English

Spread Spectrum Techniques and its Applications --CDMA, bluetooth, 2.4GHz Wireless LAN and the latest topics-- Invited

Takaya Yamazato

MST2001 Vol. D-4 page： 39-59 2001.11

Hierarchical Transmission of Video Signal Using Multi-Code DS/SS Modulation Based on DCT Coefficients Reviewed

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

IEEE Global Communications Conference Vol. 6 page： pp.3395-3399 2001.11

Language：English

In this paper, we propose a hierarchical transmission of video signal using multi-code DS/SS modulation. Assigning an appropriate distribution of transmission energy to DCT coefficients, it is possible to control the picture quality depending on the channel quality. We consider a hierarchical structure based on the variance of DCT coefficient and transmit each coefficient using multi-code DS/SS modulation. The analysis is carried out to show the effectiveness of our scheme using 2-D Gauss-Markov random field, which represents image data. It is shown that by an appropriate energy assignment to each stratum (a branch of multi-code DS/SS), it is possible to maintain picture quality even in bad channel quality

A Study on the Packet Detection Scheme Using Successive Interference Cancellation on CDMA Unslotted ALOHA System

Y.Tadokoro, H.Okada, T.Yamazato, M.Katayama and A.Ogawa

Technical Report of IEICE Vol. SST2001-41 page： 1-6 2001.10

Language：English

In wireless packet communication systems, it is well known that the system performance(throughput) depends on the errors of packet detection. Moreover, in a CDMA Unslotted ALOHA system, Multiple Access Interference(MAI) has much influence on the performance of packet detection, and the system performance. Our aim is to improve the system performance. To achieve it, we study the new packet detection scheme to reduce the effect of MAI on packet detection in this paper. In the proposed scheme, the effect is reduced by Successive Interference Cancellation(SIC) and the received signal with less MAI is left. The packet's signal is detected for the received signal with less MAI. This scheme gives good performance of the packet detection and throughput.

A Connection Service for Personal Terminals via LAN Sockets/Wireless LAN at CIMS, Nagoya University

H. Okada, T. Yamazato

IPSJ SIG Notes page： 31-36 2001.10

Language：Japanese

Center for Information Media Studies (CIMS) in Nagoya University was established with the aim of development of information education systems. We aim not only at the fulfillment of the computer literacy education, but also at the educational breakthrough by utilizing the multi-media technologies. More than 800 terminals are located campus wide in Nagoya University. In the future, it is expected that many students take their own computer to the campus, connect it to the information education network, and take lessons. To realize this plan, a connection service for personal terminals via LAN sockets/wireless LAN has been in experimental operation since May 2000. In this report, we describe a brief summary about this system, and discuss the issue of the system.

DS-CDMA v.s. MC-CDMA Invited

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

Technical Report of IEICE Vol. SST2001-47 page： 37-44 2001.10

Language：Japanese

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.

A Study on Digital Signal Processing in Frequency Domain for a Broadband Software-Defined Base Station

T. Morikami, H. Okada, T. Yamazato, M. Katayama

Technical Report of IEICE Vol. SR01-17 page： 71-77 2001.10

Language：Japanese

In this study, we consider a broadband software-defined base station receiver, which simultaneously processes signals of different modulation and multiple access schemes. For such a system, division/selection of individual signals is an important task. In this manuscript,discrete Fourier transform (DFT) is employed for this purpose, and after the separation of signals, they are processed all in frequency domain. In addition, we discuss the influence of key parameters of DFT to BER performance.

A Study for TCP Throughput in a wireless CDMA system

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

Communications Society Conference of IEICE page： - 2001.9

BER Analysis of Orthogonal Multi-carrier DS-CDMA with Multi-rate Traffic Reviewed

A. Sandouk, M. Harada, H. Okada, T. Yamazato, M. Katayama, A. Ogawa

IEICE Transaction on Fundamentals of Electronics, Communications and Computer Sciences Vol. E84-B ( 7 ) page： pp.1723-1731 2001.7

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Papers - YAMAZATO Takaya