Faculty Profiles - YAMAZATO Takaya

Papers - YAMAZATO Takaya

Division display 861 - 880 of about 1,493 ／ All the affair displays >>

A Simple Data Relay Process and Turbo Code Application to Wireless Sensor Networks Reviewed

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

1st International Symposium on Wireless Communication Systems page： 398-402 2004.9

Language：English

In this study, we focus on relay process of intermediate node of wireless sensor networks. In conventional wireless sensor networks, the intermediate node performs the regenerative repeating process such that error correction, detection and re-encoding are processed. This is reliable, but it requires a lot of processing effort and may take much energy. To reduce a burden of relay process, we propose to omit error decoding and/or re-encoding process at the intermediate nodes. Further, we propose a method that realizes soft-decision decoding for hard-detected signals. With this method, we can employ Turbo code to wireless sensor networks. As results, we show that though omitting the decoding and re-encoding process at the intermediate node may not affect much to the performance.

Performance analysis of multiple-route packet combining scheme for real-time communications in wireless multihop networks Reviewed

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

IEEE International Symposium on Personal, Indoor and Mobile Radio Communications (PIMRC) Vol. PIMRC2004 page： - 2004.9

Language：English

In real-time packet communications, packet retransmission is generally not used because it may produce undesired delays. In this case, however, packet errors caused by a channel may lead to a loss of transmitted information directly. Then, it is necessary to employ a technique which can reduce the influence of packet errors. We propose to employ a multiple-route packet combining scheme in real-time communications on wireless multihop networks. The scheme can achieve a diversity gain by combining multiple copies of the same packet that are transmitted along different routes. We analyze two characteristics of the proposed system. One is the average packet error probability, which is obtained as a function of elapsed time after transmission requests for copied packets are generated. The other is the required time for achieving a required packet error probability. The results are evaluated from a quality of service (QoS) point of view. From numerical results, it is shown that for a given tolerable delay, there exists a number of multiple routes that minimizes the achievable average packet error probability. Moreover, if the number of multiple routes is selected appropriately, the required time for achieving a required packet error probability can be minimized.

The Optimum Received Signal-Power Distribution for CDMA Packet Communication Systems Employing Successive Interference Cancellation Reviewed

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

IEEE International Symposium on Spread Spectrum Techniques and Applications (ISSSTA) page： 37-41 2004.9

Language：English

In CDMA packet communication systems employing Successive Interference Cancellation(SIC) scheme, the suppression of MAI depends on the received signal-power distribution, in addition to the cross-correlation characteristic of spreading sequences and the number of transmitted packets. Some works have been done about discovering the received signal-power distribution which makes MAI be suppressed effectively. This distribution minimizes the averaged Bit Error Rate(BER). However, in packet communication systems, it is dominant to the performance if packets can be transmitted successfully or not. Even if the averaged BER is high, many packets can be correctly transmitted. It implies that the optimum distribution on averaged BER does not give the best performance of packet transmission.In this paper, the received signal-power distribution which gives the best performance of packet transmission is derived. Such a distribution will make clear the limit of performance improvement using SIC.

Assisted Highway System Using Reference Course Information and Inter-Vehicle Communications Reviewed

D. Yamakage, T. Yamazato, H. Okada, M. Katayama

The 4th International Workshop on ITS Telecommunications page： 181-185 2004.7

Language：English

In this paper, we propose AHS system using DGPS, RVC and IVC. And, we evaluate the system performance in simulation. From simulation results, we find that if the RVC bit error rate is about 10^-5, it is possible to accomplish the same tracking performance as the case that RVC bit error does not occur. Moreover, we confirm that when IVC packet error rate is less than 10^-3, it can be enough to achieve ideal platooning performance.

A Study for Wireless TCP Access with Base Station Diversity Reviewed

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

IEICE Transactions on Communications Vol. J87-B ( 4 ) page： 512-523 2004.4

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

The performance of TCP degrades and it can not communicate each other in a wireless environment. In this paper, we propose a new base station diversity cellular system which evaluates the relations between wireless environments and TCP characteristics. From our result, the proposed system can improve the TCP characteristics without over consumption of wireless resource. Further, it is important to consider a cell radius from a view point of required TCP characteristics.

A Study for Wireless TCP Access with Base Station Diversity Reviewed

Katsuhiro Naito, Hiraku Okada, Takaya Yamazato, Masaaki Katayama

IEICE Transaction on Communications (Japanese) Vol. J87-B ( 4 ) page： 512 - 523 2004.4

B-17-17 Influence of the Sampling Jitter on the Performance of a Software-Defined Receiver Reviewed

Suzuki Kensuke, Okada Hikaru, Yamazato Takaya, Katayama Masaaki

Proceedings of the IEICE General Conference Vol. 2004 ( 1 ) page： 852 2004.3

An Adaptive PLC Receiver with the Estimation of Instantaneous Noise Power Reviewed

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

8th International Symposium on Power-Line Communications and Its Applications page： 116-121 2004.3

Language：English

The noise on power-lines is non-stationary, while the instantaneous noise power in different frequency bands are dependent. Under such noise environments, the instantaneous noise power in a frequency band can be estimated by observing the noise in other frequency bands. In this paper, we propose a receiver structure which uses the estimated instantaneous noise power in the decoding process and show its superiority in BER performance to conventional systems.

Performance evaluation for a diversity decoding scheme under multipath environment with OFDM Reviewed

H. Shibata, A. Ogawa, T. Yamazato

2004 RISP International Workshop on Nonlinear Circuits and Signal Processing (NCSP04) page： 25-28 2004.3

Language：English

This paper is concerned with the performance evaluation for the diversity decoding scheme in which space diversity technique and iterative decoding for non systematic convolutional error-correcting code are effectively combined. The concept of the diversity decoding is applied to an OFDM system (e.g. the digital terrestrial TV broadcasting system). This paper shows the performance evaluation for the diversity decoding scheme under multipath environment with OFDM.

A study of adaptive MMSE receiver operating in thefrequency domain for CDMA system Reviewed

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

2004 RISP International Workshop on Nonlinear Circuits and Signal Processing (NCSP04) page： 57-60 2004.3

A study on error correcting and diversity combiner scheme on multiple routes in wireless multi-hop networks Reviewed

Okada H, Koie N, Nakagawa N, Yamazato T, Katayama M

1ST INTERNATIONAL SYMPOSIUM ON WIRELESS COMMUNICATION SYSTEMS 2004, PROCEEDINGS page： 183 - 187 2004

Performance analysis of CDMA Unslotted ALOHA system employing successive interference cancellation Reviewed

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

ELECTRONICS AND COMMUNICATIONS IN JAPAN PART III-FUNDAMENTAL ELECTRONIC SCIENCE Vol. 87 ( 6 ) page： 32 - 43 2004

Publishing type：Research paper (scientific journal) Publisher：SCRIPTA TECHNICA-JOHN WILEY & SONS

Multiple access interference (MAI) occurs in the CDMA Unslotted ALOHA system and is a significant factor for degradation of performances. Further, in this system, there are frequent situations in which the received signal power becomes inhomogeneous so that the effect of the MAI is enhanced. Presently, an interference cancellation technique is developed as a way to Suppress the MAI. However, this method mainly deals with a system that transmits and receives signals continuously in time. The evaluation of the performances is also by means of the bit error rate. In the packet communication system, success or failure of the transmission of each packet rather than of the transmission of each bit is the key to system performances. Hence, in the present study, a system is proposed that uses a successive interference cancellation as one of the interference cancellation techniques to the CDMA Unslotted ALOHA system. The throughput performance is analytically derived for performance evaluation. Also, in general, the performances under the situation of unequal received signal power are worse than those for equal received power. However, in the proposed system, performance can be better in an unequal received power environment than in the equal power case. (C) 2004 Wiley Periodicals, Inc.

DOI： 10.1002/ecjc.10116

Web of Science

Scopus

researchmap

Performance analysis of UWB impulse radar using parallel IPCP receiver Reviewed

Hatano H, Okada H, Yamazato T, Katayama M

1ST INTERNATIONAL SYMPOSIUM ON WIRELESS COMMUNICATION SYSTEMS 2004, PROCEEDINGS page： 115 - 119 2004

Performance analysis of multiple-route packet combining scheme for real-time communications in wireless multihop networks Reviewed

Y Hirayama, N Nakagawa, H Okada, T Yamazato, M Katayama

2004 IEEE 15TH INTERNATIONAL SYMPOSIUM ON PERSONAL, INDOOR AND MOBILE RADIO COMMUNICATIONS, VOLS 1-4, PROCEEDINGS page： 140 - 144 2004

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

In real-time packet communications, packet retransmission is generally not used because it may produce undesired delays. In this case, however, packet errors caused by a channel may lead to a loss of transmitted information directly. Then, it is necessary to employ a technique which can reduce the influence of packet errors. We propose to employ a multiple-route packet combining scheme in real-time communications on wireless multihop networks. The scheme, which is proposed in [1], can achieve a diversity gain by combining multiple copies of the same packet that are transmitted along different routes. We analyze two characteristics of the proposed system. One is the average packet error probability, which is obtained as a function of elapsed time after transmission requests for copied packets are generated. The other is the required time for achieving a required packet error probability. The results are evaluated from a quality of service (QoS) point of view. From numerical results, it is shown that for a given tolerable delay, there exists a number of multiple routes that minimizes the achievable average packet error probability. Moreover, if the number of multiple routes is selected appropriately, the required time for achieving a required packet error probability can be minimized.

DOI： 10.1109/PIMRC.2004.1370852

Web of Science

researchmap

Performance analysis of multiple-route packet combining scheme for real-time communications in wireless multihop networks Reviewed

Hirayama Y, Nakagawa N, Okada H, Yamazato T, Katayama M

2004 IEEE 15TH INTERNATIONAL SYMPOSIUM ON PERSONAL, INDOOR AND MOBILE RADIO COMMUNICATIONS, VOLS 1-4, PROCEEDINGS page： 140 - 144 2004

SNIR Analysis of Asynchronous MC-CDMA System in Frequency Selective Fading Channel Reviewed

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

IEICE Transaction on Fundamentals Vol. J86-A ( 12 ) page： 1426-1430 2003.12

SNIR Analysis of Asynchronous MC-CDMA System in Frequency Selective Fading Channel Reviewed

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

IEICE Transaction on Fundamentals of Electronics, Communications and Computer Sciences Vol. J86-A ( 12 ) page： 1426-1430 2003.10

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

This paper presents the signal to noise plus interference ratio(SNIR) analysis of the asynchronous Multicarrier (MC)-CDMA system with multipath fading channel. We derive the SNIR of the MC-CDMA system and compared with that of the DS-CDMA. We found that the SNIR of the MC-CDMA is equal to that of the band-limited DS-CDMA system under the same bandwidth and the same spreading factor.

Reducing Peak Power of Coded OFDM Systems with Multiple Symbol Mapping Reviewed

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

IEICE Transaction on Fundamentals of Electronics, Communications and Computer Sciences Vol. J86-A ( 10 ) page： 1058-1067 2003.10

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

In this paper, we propose a novel coding scheme to reduce a peak envelope power (PEP) of convolutionally coded orthogonal frequency devision multiplex (OFDM) signals. In this system, convolutionally coded bits are mapped into symbol sequence. The symbol sequence have multiple symbols which are adjusted so as to show low PEP. 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.

Reducing Peak Power of Coded OFDM Systems with Multiple Symbol Mapping Reviewed

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

IEICE Transaction on Fundamentals Vol. J86-A ( 10 ) page： 1058-1067 2003.10

基地局ダイバシチを用いたTCPによる無線インターネット接続に関する一検討

内藤克浩, 岡田啓, 山里敬也, 片山正昭

電子情報通信学会ネットワークシステム研究会 Vol. 103 ( 204 ) page： 31 - 36 2003.7

　 PREV - NEXT 　

<YAMAZATO Takaya>

Papers - YAMAZATO Takaya