Faculty Profiles - YAMAZATO Takaya

Papers - YAMAZATO Takaya

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A Simplified Regenerative Repeater for Satellite Communications

H. Kuwamura, S. Saiki, A. Ogawa, T. Yamazato, S. Kawai

IEICE General Conference Vol. B-3-17 page： 345 2005.3

Performance Evaluation of Multi-route Turbo Coding using Parity Check Codes

N. Nakagawa, H. Okada, T. Wada, T. Yamazato, M. Katayama

IEICE General Conference Vol. B-5-141 page： 590 2005.3

A Study on Hierarchical Coding for Parallel Optical Wireless Communication Systems

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

IEICE General Conference Vol. A-5-26 page： 142 2005.3

A Study on Successive Interference Cancellation for Hierarchical Coding in Parallel Optical Wireless Communication Systems

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

IEICE General Conference Vol. A-5-25 page： 141 2005.3

An Adaptive Receiver for Power-Line Communications with the Estimation of Instantaneous Noise Power Reviewed

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

IEICE Transaction on Fundamentals of Electronics, Communications and Computer Sciences Vol. E88-A ( 3 ) page： 755-760 2005.3

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

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.

A Prototype for a Broadband Software-Defined Base Station Which Processes Signals with Widely Differing Intensity

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

Technical Report of IEICE Vol. SR04-23 page： 17-22 2005.3

Language：Japanese

This paper discusses the preliminary examinations of a broadband software-defined base station receiver. The authors have been concentrating on the concept of Intelligent Super Base-station (ISB), which processes multiple signals with different modulation schemes at the same time. For the receiver of the ISB, the introduction of a superconductive analog to digital converter (ADC), which has a large bandwidth and high sensitivity, has been proposed. For the realization of such a receiver, as the first step, we designed a prototype receiver with a semi-conductive ADC, which receives and demodulates two FM broadcasting signals at the same time. As a result of the experimentations, influence of the difference of the signal level is clarified, and importance of signal selection algorithm is confirmed.

An adaptive receiver for power-line communications with the estimation of instantaneous noise power Reviewed

Y Hirayama, H Okada, T Yamazato, M Katayama

IEICE TRANSACTIONS ON FUNDAMENTALS OF ELECTRONICS COMMUNICATIONS AND COMPUTER SCIENCES Vol. E88A ( 3 ) page： 755 - 760 2005.3

Language：English Publishing type：Research paper (scientific journal) Publisher：IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG

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 his 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.

DOI： 10.1093/ietfec/e88-a.3.755

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逐次型干渉除去法を用いたCDMAパケット通信システムにおける最大スループットの解析 Reviewed

田所幸浩, 岡田啓, 山里敬也, 片山正昭

電子情報通信学会論文誌 A Vol. J88-A ( 3 ) page： 429 - 433 2005.3

An Adaptive Receiver for Power-Line Communications with the Estimation of Instantaneous Noise Power Reviewed

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

IEICE Transaction on Fundamentals of Electronics, Communications and Computer Sciences Vol. E88-A ( 3 ) page： 755-760 2005.2

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

*A Tutorial on Multiple Access Technologies for Beyond 3G Mobile Networks Invited Reviewed

A. Jamalipour, T. Yamazato, T. Wada

IEEE Communication Magazine Vol. 43 ( 2 ) page： 110-117 2005.2

Authorship：Lead author Language：English

Beyond third-generation (B3G) wireless cellular systems are recognized as systems that can achieve high data-rate transmission beyond those currently provided by the second- and third-generation (2G/3G) wireless cellular systems and are capable of delivering multiple services to users at different locations under very diverse channel conditions. B3G systems should provide services comparable to those offered by wired networks for a variety of applications such as interactive multimedia, VoIP (voice over Internet protocol), network games, videoconferencing, etc. The current trend is that B3G will be based on IP technology, and therefore, all-IP [1] architecture design has been an important research topic in the past few years. Those systems will need to support multiple services ubiquitously in different types of environment including indoor, outdoor (with low and high velocity), and up to global broadband access (satellite). Thus, they would be deployed in a heterogeneous environment of various physical access networks of wireless and wired systems. The network heterogeneity means that the physical access network underlying the B3G system will support different levels of data rates and different mobility and traffic management techniques govern individual systems. In this context, the B3G mobile systems will face at least two predominant constraints: a) heterogeneity in physical access network, and b) change of application types from commonly low data rates into more bandwidth demanding real-time and multimedia ones. In such situation, providing quality of service to users would become even more difficult that what we are currently dealing. One of the main issues involved in the development of B3G systems is the choice of multiple access (MA) technology that could efficiently share the available bandwidth to large number of users. The choice of MA technique could significantly enhance or damage the service quality delivered to end users. It is known that the existin

A tutorial on multiple access technologies for beyond 3G mobile networks Reviewed

A Jamalipour, T Wada, T Yamazato

IEEE COMMUNICATIONS MAGAZINE Vol. 43 ( 2 ) page： 110 - 117 2005.2

Language：English Publishing type：Research paper (scientific journal) Publisher：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC

In this article some fundamental technical concepts of the main multiple access schemes for wireless mobile systems are reviewed, and a path for development of appropriate multiple access technologies for next-generation mobile networks, or so-called beyond 3G (B3G), is established. We first review the multiple access technologies in second- and third-gene ration wireless cellular systems from historical and technical points of view. This review is followed by a novel formulization of the multiple access schemes through mathematical expressions that could simplify the process of development of new multiple access schemes for B3G wireless cellular systems. We then list the most important features of multiple access schemes in 3G mobile systems. Finally, we conclude the article by reviewing the most promising multiple access technologies for B3G mobile cellular systems.

DOI： 10.1109/MCOM.2005.1391509

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A tutorial on multiple access technologies for beyond 3G mobile networks Reviewed

Jamalipour A, Wada T, Yamazato T

IEEE COMMUNICATIONS MAGAZINE Vol. 43 ( 2 ) page： 110 - 117 2005.2

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

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

IEICE Transactions on Communications Vol. J88-B ( 1 ) page： 269-279 2005.1

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

In this paper, we consider real-time packet communications in wireless multihop networks. In real-time packet communications, packet retransmission cannot be used because it may produce undesired delays. In this case, it is necessary to be employed a technique which can reduce the influence of packet errors. We propose to apply a multi-route packet combining scheme to wireless multihop networks. We analyze two characteristics of the proposed system. One is the average packet error probability, which is obtained as a function of a elapsed time. The other is the required time for achieving a required packet error probability.

Time-Dependent Analysis of the Multiple-Route Packet Combining Scheme in Wireless Multihop Networks Reviewed

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

International Journal of Wireless Information Networks Vol. 12 ( 1 ) page： 35-45 2005.1

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

In this paper, we apply the multiple-route packet combining scheme to wireless multihop networks in order to support delay-sensitive applications. The performance of the system is time-dependent and is greatly affected by network-level performance. Therefore, it is necessary to develop an analytical framework to evaluate the per- formance of the system with taking into account its time-dependency. We use queuing theory to analyze the performance of the system. From numerical results, it is shown that the performance degradation of the system is mainly caused by the increase of packet delay, which is due to the increase of the traffic intensity. To prevent the increase of traffic,we propose a packet discarding scheme. We analyze the average packet error probability of the proposed system with the equilibrium point analysis (EPA). Numerical results show that the packet discarding scheme can improve the average packet error probability under heavy traffic conditions.

Clutter reduction methods of a UWB chaos radar

Natsumi Dake, Yoshifumi Nishio, Takaya Yamazato

Technical Report of IEICE Vol. NLP2004-108 page： 49-52 2005.1

Language：Japanese

We have proposed a UWB chaos radar, whose transmitted signal is generated by a chaotic map. If the feature of chaos is exploited, a radar with outstanding performance can be expected. It is important to remove various noises called clutter in a radar. In this study, we focus mainly on removal of clutters by employing two noise reduction methods. We use the Minimum Distance Approximation method and Maximum Likelihood Decodings method to remove the clutter.

Time-dependent analysis of the multiple-route packet combining scheme in wireless multihop networks Reviewed

Yasuhiro Hirayama, Hiraku Okada, Takaya Yamazato, Masaaki Katayama

International Journal of Wireless Information Networks Vol. 12 ( 1 ) page： 35 - 45 2005.1

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

In this paper, we apply the multiple-route packet combining scheme (In Proceedings of the 1st International Symposium on Wireless Communication Systems, pp. 183-187, Mauritius, 2004) to wireless multihop networks in order to support delay-sensitive applications. The performance of the system is time-dependent and is greatly affected by network-level performance. Therefore, it is necessary to develop an analytical framework to evaluate the performance of the system with taking into account its time-dependency. We use queuing theory to analyze the performance of the system. From numerical results, it is shown that the performance degradation of the system is mainly caused by the increase of packet delay, which is due to the increase of the traffic intensity. To prevent the increase of traffic, we propose a packet discarding scheme. We analyze the average packet error probability of the proposed system with the equilibrium point analysis (EPA). Numerical results show that the packet discarding scheme can improve the average packet error probability under heavy traffic conditions. © 2005 Springer Science+Business Media, Inc.

DOI： 10.1007/s10776-005-5161-6

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On the Second-order Statistics of the Channel Parameters for BFDM/OQAM Systems Reviewed

B. Mongol, T. Yamazato, H. Okada, M. Katayama

2nd International Symposium on Wireless Communication Systems page： 534-538 2005

Language：English

Recently, there has been increased interest in using multicarrier systems in rapidly time-varying multipath environment. Biorthogonal Frequency Division Multiplexing based on Offset QAM (BFDM/OQAM) is an attractive modulation method since it allows time-frequency well-localized pulses even at critical sampling (i.e. maximum spectral ef ciency). BFDM/OQAM system is naturally strong against intersymbol and intercarrier interference (ISI/ICI). However, for further improvement of the system a study on the channel statistics is needed. In this paper we analytically examine the channel parameters for BFDM/OQAM and derive their second-order statistics.

A MIMO system with relay terminals for reliable wireless control. Reviewed

Ryosuke Uchida, Hiraku Okada, Takaya Yamazato, Masaaki Katayama

Proceedings of the IEEE 16th International Symposium on Personal, Indoor and Mobile Radio Communications, Berlin, Germany, September 11-14, 2005 page： 1626 - 1630 2005

A study of wireless TCP access with base station diversity Reviewed

K Naito, H Okada, T Yamazato, M Katayama

ELECTRONICS AND COMMUNICATIONS IN JAPAN PART I-COMMUNICATIONS Vol. 88 ( 9 ) page： 49 - 61 2005

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

It is known that performance is degraded in Internet access using TCP in a wireless environment, making communications almost impossible. This study proposes a cellular system in which a wireless terminal evaluates its own wireless environment and TCP performance and connects to multiple base stations. The TCP performance in the proposed system is evaluated and it is found to be greatly improved by applying base station diversity. By applying the proposed procedure for selecting the base station to which it will connect, the unnecessary use of wireless resources can be avoided. It is shown that in order to improve TCP performance, the cell radius should be set appropriately for the required TCP performance. (c) 2005 Wiley Periodicals, Inc.

DOI： 10.1002/ecja.20169

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On the second-order statistics of the channel parameters for BFDM/OQAM systems Reviewed

Mongol B, Yamazato T, Okada H, Katayama M

2ND INTERNATIONAL SYMPOSIUM ON WIRELESS COMMUNICATIONS SYSTEMS 2005 (ISWCS 2005) page： 534 - 538 2005

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Papers - YAMAZATO Takaya