Faculty Profiles - YAMAZATO Takaya

Papers - YAMAZATO Takaya

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Performance Analysis of CDMA Unslotted ALOHA System \\Employing Successive Interference Cancellation Reviewed

Yukihiro TADOKORO, Hiraku OKADA,\\ Takaya YAMAZATO, Masaaki KATAYAMA,

IEICE Transaction on Fundamentals of Electronics, Communications and Computer Sciences page： - 2003.1

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

In a CDMA Unslotted ALOHA system, multiple access interference(MAI) has a great influence on the system performance. The unequalness of signals' power (e.x. Rayleigh fading) makes the influence more serious. The MAI may be suppressed by using interference cancellation technique. Such a technique has been considered in the system in which signals are transmitted continuously. In addition, the performance is evaluated by bit error rate. However, in a packet system, the performance depends on whether packets are successfully transmitted or not. In this paper, to suppress the MAI, CDMA Unslotted ALOHA system employing successive interference cancellation is proposed. The throughput performance of the proposed system is analyzed and evaluated. As the result, the performance is improved, and the performance under Rayleigh fading is better than that in the case of equal signals' power.

Soft-Decision Decoding of Low-Density Parity-Check Codes for Hard-Detected Optical Communication Signals Reviewed

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

IEICE Transactions on Communications page： - 2003.1

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

A soft-decision decoding scheme of low-density parity-check codes (LDPC) is proposed for hard-detected signals of optical fiber communication (OFC) systems. Based on the error detection, the proposed scheme converts the received hard-decision into soft reliability for the input of the LDPC decoder, and soft-decision decoding is performed. Simulation results under OFC channels are shown and superior performance is obtained by using the proposed decoding scheme of the LDPC codes.

Medium Access Control Protocol Based on Estimation ofMultimedia Traffic with an Adaptive Algorithm in CDMA PacketCommunications Reviewed

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

IEICE Transaction on Fundamentals of Electronics, Communications and Computer Sciences page： - 2002.12

A Study on the Application of Error Concealment Technique to Real-Time Parallel Video Decoder Reviewed

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

IEICE Transaction on Fundamentals of Electronics, Communications and Computer Sciences page： - 2002.12

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

As high error resilience and low delay decoding technique, RT-PVD (real-time parallel video decoder) has been proposed[1]. In this paper, we consider the performance of the RT-PVD in which error concealment (EC) technique is included. Ordinary, even if the EC was applied, secondary error propagation would be eventually caused. But in the RT-PVD, the random block noise was replaced by appropriate block of the reference frame sequence. So we could establish high PSNR gain and good perceptual quality without error propagation.

A Study on Turbo Soft-Decision Decoding for Hard Detected Optical Communication Signals Reviewed

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

IEICE Transactions on Communications page： - 2002.12

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

We propose a method to realize soft-decision decoding for hard-detected signals. In this paper, a novel concept is introduced as ``error-detected reliability''. The method is very useful for optical fiber communications (OFC) as hard detection is the only detection method for the OFC systems. We demonstrate our proposed method using the turbo code in which soft information is required for 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 scheme. Moreover, the bit error rate of $10^{-11}$ can be achieved by serial concatenation of a Reed-Solomon code and a turbo code for Q-factor lower than $8.0$ dB with a bandwidth expansion ratio of $33.3\%$.

A study on statistical characteristic of bit-error rate with transmitter diversity in fading channels

R. Uchida, H. Okada, T. Yamazato, and M. Katayama

Symposium on Information Theory and Its Applications (SITA) page： - 2002.12

Language：Japanese

In this paper, we analize a characteristic of wireless communication system from a viewpoint of probability distribution of bit-error rate (BER) for aiming to guarantee the reliability of wireless communication systems. A single transmission space diversity (time space repetitional coding) with M transmit antennas through independent slow Rayleigh fading channels is considered. The influence of combining method of the receiver, and the number of transmit antennas, to the BER distribution is clarified.

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

Hirayama Y, Okada H, Yamazato T, Katayama M

IEICE TRANSACTIONS ON FUNDAMENTALS OF ELECTRONICS COMMUNICATIONS AND COMPUTER SCIENCES Vol. E85A ( 12 ) page： 2868 - 2876 2002.12

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

Hirayama Y.

IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences Vol. E85-A ( 12 ) page： 2868 - 2876 2002.12

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

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

IEICE Transactions on Fundamentals Vol. E85-A ( 12 ) page： 2868-2876 - 2876 2002.12

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

In this paper, we propose a medium access control (MAC) protocol for multimedia code division multiple access (CDMA) communications. In the proposed protocol, a base station (BS) estimates the instantaneous number of simultaneously transmitted packets in the future slots with exploiting a stochastic property of traffic. In order to carry out this estimation, we employ an adaptive algorithm. We evaluate the performance of the proposed protocol by comparing that with two different cases. One is no estimation case and the other is perfect estimation case. From these results, we clarify the advantage of the proposed MAC protocol.

CiNii Books

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Performance improvement of OFDM system with consideration on the characteristics of power-line noise Reviewed

Sugimoto K, Okada H, Yamazato T, Katayama M

IEICE TRANSACTIONS ON FUNDAMENTALS OF ELECTRONICS COMMUNICATIONS AND COMPUTER SCIENCES Vol. E85A ( 12 ) page： 2822 - 2829 2002.12

Performance improvement of OFDM system with consideration on the characteristics of power-line noise Reviewed

Sugimoto K.

IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences Vol. E85-A ( 12 ) page： 2822 - 2829 2002.12

Performance Improvement of OFDM System with Consideration on the Characteristics of Power-Line Noise Reviewed

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

IEICE Transactions on Fundamentals Vol. E85-A ( 12 ) page： 2822-2829 - 2829 2002.12

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

In narrow band power-line communication (PLC) systems, which use frequency band below a few hundred kHz, the noise on power-line is non-white and non-stationary. Under such environment, the performance of Orthogonal Frequency Division Multiplex (OFDM) modulation system is analyzed, and time and frequency dependence of bit error rate (BER) is clarified. In addition, the possibility of performance improvement with the symbol level repetition coding employing cyclo-stationary feature of power-line noise is presented.

CiNii Books

researchmap

A Study on the Application of Error Concealment Technique to Real-Time Parallel Video Decoder Reviewed

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

IEICE Transaction on Fundamentals Vol. J85-A ( 12 ) page： 1463-1468 2002.12

Calculation of Mobile Location using a Statistical Scatterer

N. J. Thomas, H. Okada, T. Yamazato, M. Katayama

Technical Report of IEICE Vol. SST2002-34 page： 45-50 2002.10

Language：English

A statistical technique to calculate the location of a signal source, e.g. a mobile phone, in a multipath, non--line of sight environment, is proposed. The technique relies on angular spread and relative time of arrival measurements of multipath signals received at a base station antenna array. The source location is estimated using an a priori known statistical model for the distribution of single bounce multipath scatterers around the signal source, and fitting the measured channel impulse response received at the base station to this model. Further improvement in location estimation accuracy is demonstrated using the Kalman filter, or time average filter on the time sequence of location estimates in a moving scenario.

Spread Sequence for Multicarrier CDMA under the Effect of Nonlinear Amplifier Reviewed

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

International Symposium on Information Theory and Its Applications (ISITA) Vol. ISITA2002 page： - 2002.10

Decoding of low-density parity-check codes for hard-detected optical fiber communication signals Reviewed

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

International Symposium on Information Theory and Its Applications (ISITA) Vol. ISITA2002 page： - 2002.10

Language：English

A soft-decision decoding scheme of low-density parity-check codes (LDPC) is proposed for hard-detected signals of optical fiber communication (OFC) systems. The scheme converts the received hard-decision into soft reliability for the input of the LDPC decoder, and soft-decision decoding is performed. Simulation results under OFC channels are shown and superior performance is obtained by using the proposed decoding scheme of the LDPC codes.

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

IEEE International Symposium on Personal, Indoor and Mobile Radio Communications (PIMRC) Vol. PIMRC2002 page： 619-623 2002.9

Language：English

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.

Effect of Interleaving and FEC on the Throughput of CDMA Unslotted ALOHA System with Adaptive Multiuser Receiver Reviewed

H. Okada, T. Yamazato, M. Katayama

IEEE International Symposium on Personal, Indoor and Mobile Radio Communications (PIMRC) Vol. PIMRC2002 ( 2 ) page： 941-945 2002.9

Language：English

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.

A Proposal of OFDM Synchronization Scheme with Subtraction Operation Reviewed

T. Shibata, N. Itoh, M. Fujimoto, N. Suzuki, A. Ogawa, T. Yamazato, M. Harada

7th International-OFDM Workshop 2002 page： 237-240 2002.9

BER Performance of Asynchronous Multicarrier-CDMA System and Asynchronous DS-CDMA System in Frequency Selective Fading Reviewed

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

7th International-OFDM Workshop 2002 page： 26-30 2002.9

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Papers - YAMAZATO Takaya