Faculty Profiles - YAMAZATO Takaya

Papers - YAMAZATO Takaya

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Error Correcting Scheme for Road-to-Vehicle Visible Light Communication using LED Array Reviewed

Shohei Mase, Shintaro Arai, Takaya Yamazato, Tomohiro Yendo, Toshiaki Fujii, Masayuki Tanimoto, Yoshikatsu Kimura

PROCEEDINGS OF THE 11TH INTERNATIONAL IEEE CONFERENCE ON INTELLIGENT TRANSPORTATION SYSTEMS page： 1113 - + 2008

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

In this paper, we propose an improved coding scheme for optical wireless communication systems using a LED array transmitter and a high-speed camera as the receiver on a vehicle. Previously, we have proposed a hierarchical coding scheme which allocated the data to spatial frequency components depending on the priority. In that scheme, the high-priority data can be received even if the receiver was far from the transmitter: We confirmed the advantage of the hierarchical coding scheme, but the bit error performance was not sufficient. In this paper, we divide the data into spatial frequency components, and us: error correcting code for each spatial frequency components' data. Experimental evaluation demonstrates the improvement in BE R performance. This improvement implies that the system range increased compared to the previous method.

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Energy Efficiency of Cooperative MISO Technique in Multi-Hop Wireless Sensor Networks Reviewed

Zheng Huang, Takaya Yamazato, Masaaki Katayama

ISSNIP 2008: PROCEEDINGS OF THE 2008 INTERNATIONAL CONFERENCE ON INTELLIGENT SENSORS, SENSOR NETWORKS, AND INFORMATION PROCESSING page： 511 - + 2008

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

In this paper, the energy efficiency of cooperative Multiple-Input Single-Output (MISO) technique for a multi-hop wireless sensor network is investigated and compared with other transmission schemes. Firstly, we present different schemes or data transmission of the cluster farther from base station and calculate their energy consumptions. The results show that the optimal transmission scheme varies with the inter-cluster distance in different networks. Then we explore the lifetime of the network and find that it is not always the optimal to employ the multi-hop transmission and the single-hop transmission outperform the multi-hop under a certain distance threshold. In addition, the effects of the transmission bit rate and the required bit error ratio (BER) on the distance threshold are also clarified.

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Joint Channel Decoding of Spatially and Temporally Correlated Data in Wireless Sensor Networks Reviewed

Kobayashi Kentaro, Yamazato Takaya, Okada Hiraku, Katayama Masaaki

2008 INTERNATIONAL SYMPOSIUM ON INFORMATION THEORY AND ITS APPLICATIONS, VOLS 1-3 page： 930 - + 2008

Joint Channel Decoding of Spatially and Temporally Correlated Data in Wireless Sensor Networks Reviewed

Kentaro Kobayashi, Takaya Yamazato, Hiraku Okada, Masaaki Katayama

2008 INTERNATIONAL SYMPOSIUM ON INFORMATION THEORY AND ITS APPLICATIONS, VOLS 1-3 page： 930 - + 2008

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

In densely deployed wireless sensor networks, sensor observations are spatially correlated. Furthermore, the nature of physical phenomena constitutes a temporal correlation between transmitted observations of an individual sensor node. In this paper, we propose a joint iterative channel decoding scheme using turbo codes. The proposed decoder exploits the spatial and temporal correlations of two binary data sequences to achieve additional coding gain. Simultaneously exploiting the spatial and temporal correlation, the proposed decoder achieves large performance gain.

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Measurement of narrowband channel characteristics in single-phase three-wire indoor power-line channels Reviewed

Sugiura Yoshie, Yamazato Takaya, Katayama Masaaki

IEEE ISPLC: 2008 IEEE INTERNATIONAL SYMPOSIUM ON POWER LINE COMMUNICATIONS AND ITS APPLICATIONS page： 18 - + 2008

Measurement of narrowband channel characteristics in single-phase three-wire indoor power-line channels Reviewed

Yoshie Sugiura, Takaya Yamazato, Masaaki Katayama

IEEE ISPLC: 2008 IEEE INTERNATIONAL SYMPOSIUM ON POWER LINE COMMUNICATIONS AND ITS APPLICATIONS page： 18 - + 2008

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

This manuscript reports the measurement results of narrowband signal propagation of PLC channels. In Japan, in-house wiring is single-phase three-wire, and each branch between an outlet of 100V and the panel board is connected to one of two live conductors and the neutral. Thus a pair of outlets can be classified into three types: connected to different live conductors, connected to the same five conductors by different branches from the panel board, and on the same branch to the same live conductor. It is confirmed that the results of the measurements can be classified by these three types of paths. The results show that frequency responses of narrowband PLC channels are relatively smooth, compared with that of wideband PLC. It is also found that propagation loss in lower frequency range is larger than in higher frequency range. The time independence of narrowband PLC channels are confirmed when no electric appliance is connected to the same live conductor.

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Performance improvement of downlink MC-CDMA cellular system with an intermittent transmission Reviewed

Fushiki Masashi, Yamazato Takaya, Katayama Masaaki

2008 IEEE RADIO AND WIRELESS SYMPOSIUM, VOLS 1 AND 2 page： 275 - + 2008

Performance improvement of downlink MC-CDMA cellular system with an intermittent transmission Reviewed

Masashi Fushiki, Takaya Yamazato, Masaaki Katayama

2008 IEEE RADIO AND WIRELESS SYMPOSIUM, VOLS 1 AND 2 page： 275 - + 2008

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

Throughput performance of MC-CDMA systems depends on the success in managing interference arising from intercell transmission. In this paper, we propose a new intercell interference mitigation scheme for downlink MC-CDMA scheme. In the proposed scheme, a base station transmits downlink signals intermittently to mobile terminals at the edge of cell. The intercell interference can be seen as a partial interference depend upon the on and off period of the adjacent downlink signals. So it is possible for the channel equalizer to suppress this partial intercell interference by setting the weight changes in accordance with the intercell interference. As results, the frame error rate of the proposed scheme is always better than that of the conventional scheme and good throughput performance is achieved especially when the traffic is high.

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A note on EXIT analysis for distributed encoding and joint decoding of correlated sources

K. Kobayashi, T. Yamazato, M. Katayama

Technical Report of IEICE page： - 2007.12

Language：Japanese

Extrinsic information transfer (EXIT) charts are used to predict the behavior of the iterative decoder by solely looking at the input/output relation of individual constituent decoders. This allows the prediction of turbo cliff region. In the recent research on the distributed coding and joint decoding, there has been a significant interest in utilizing iteratively decodable codes. Hence, it is expected that EXIT analysis can be employed for assessing the convergence behavior of such iterative schemes. In this paper, we present a turbo based iterative joint of two correlated binary sources. The convergence behavior of the proposed system is studied using EXIT charts.

Improvement of Error Performance for Noncoherent Chaos Communications Reviewed

Shintaro ARAI, Yoshifumi NISHIO and Takaya YAMAZATO

Proceedings of IEEE Workshop on Nonlinear Circuit Networks (NCN'07) page： 54-56 2007.12

Language：English

This paper proposes the error-correcting for noncoherent chaos communications. To improve the error performance, we focus attention on the successive chaotic sequence based on the chaotic dynamics. Concretely, error performance of a noncoherent receiver improves by analyzing the chaotic dynamics of the successive received sequence. As results of computer simulations, we confirm about 3 dB gain in BER performance compared to the conventional suboptimal receiver.

A note on EXIT analysis for distributed encoding and joint decoding of correlated sources

K. Kobayashi, T. Yamazato, M. Katayama

Technical Report of IEICE Vol. RCS2007-125 page： 79-83 2007.12

Language：Japanese

Extrinsic information transfer (EXIT) charts are used to predict the behavior of the iterative decoder by solely looking at the input/output relation of individual constituent decoders. This allows the prediction of turbo cliff region. In the recent research on the distributed coding and joint decoding, there has been a significant interest in utilizing iteratively decodable codes. Hence, it is expected that EXIT analysis can be employed for assessing the convergence behavior of such iterative schemes. In this paper, we present a turbo based iterative joint decoding scheme of two correlated binary sources. The convergence behavior of the proposed system is studied using EXIT charts.

Automotive ultrasonic array emitter for short-range targets detection Reviewed

Hatano H., Yamazato T., Katayama M.

Proceedings of 4th IEEE Internatilonal Symposium on Wireless Communication Systems 2007, ISWCS page： 355 - 359 2007.12

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Proceedings of 4th IEEE Internatilonal Symposium on Wireless Communication Systems 2007, ISWCS

We consider an application of a ultrasonic array emitter to automotive targets detection systems for short-range. Ultrasonic sensors are low cost and widely used. However detectable ranges do not meet the requirements for short-range applications, such as parking aid systems. In this paper, we propose a method which may achieve the emission to a desired area within limited time. We evaluate the expected accuracy of target position estimations by computer simulations. As a result, we show the ability of the ultrasonic sensors for parking aid systems. © 2007 IEEE.

DOI： 10.1109/ISWCS.2007.4392361

Scopus

Cooperative transmission scheme in distributed sensor network for extension of transmission range Reviewed

Nakao K.

4th International Conference on Networked Sensing Systems, INSS page： 89 - 92 2007.12

Throughput comparison of CSMA and CDMA slotted ALOHA in inter-vehicle communication Reviewed

Sakata A.

ITST 2007 - 7th International Conference on Intelligent Transport Systems Telecommunications, Proceedings page： 52 - 57 2007.12

Indoor Propagation Measurements for Wireless Controls

K. Endou, T. Yamazato, M. Katayama

Technical Report of IEICE page： - 2007.11

Language：Japanese

In order to collect basic reference data for wireless controls of industrial equipments, we have constructed a system to measure the continuous (five seconds) wideband (23MHz) simultaneous propagation characteristics of multiple channels in 2.4GHz band. As a result, the propagation characteristics of two indoor wireless channels measured simultaneously, are expressed as functions of time and frequency. The result shows that the propagation loss considerably exceed its mean value locally in time--frequency plane, and that the probability of this drops of the signal is not negligible. In addition, we show that the probability of the deep fades which continues more than the permissible delay time for the control communication system (20ms) is also non-negligible. Moreover, we clarify that, even when the antennas are separated by several wavelength, still the correlation of the time-varying faded signal levels at the antennas is relatively high and should be taken into account in designing a wireless control systems.

Correlations of noise waveforms at different outlets of power-line network Reviewed

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

IEICE Transactions on Fundamentals, vol. J90-A, no.11, pp 851-860 Vol. J90-A ( 11 ) page： 851-860 2007.11

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

This manuscript discusses the relationships of noise waveforms measured at different outlets in a three-wire single-phase (one neutral and two live conductors) power-line network. As a result of experimental measurements, it is shown that instantaneous noise voltages at two different outlets have high correlations if they are connected to the same live conductor. It is also found that the instantaneous noise powers and cyclic averaged noise powers have large correlations even for a pair of outlets connected to the different live conductors. The correlation coefficients for instantaneous voltages and powers are calculated as the frequency functions.

Correlations of noise waveforms at different outlets of power-line network Reviewed

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

IEICE Transaction on Fundamentals Vol. J90-A ( 11 ) page： 851-860 2007.11

A Novel Contention-Free Medium Access Control Protocol for Inter-Vehicle Communication Systems Reviewed

M. Masamura, H. Okada, S. Makido, T. Yamazato, M. Katayama

The First International Workshop on Mobile Vehicular Networks at MASS 2007 page： - 2007.10

Language：English

We propose a contention-free medium access control (MAC) protocol for inter-vehicle communication systems that share information for the improvement of safety drive on the highway. In the proposed system, contention-free medium access is achieved by periodical one-way token transmissions. The token contains the frame information about the transmission/reception phase. While the token is relaid by one-way, the vehicle which has the token can send a packet to both up- and down-link. The token transmission interval is set not to be interfered from other transmit vehicles at a receive vehicle. In addition, multiple channels are used and allocated dynamically for every token transmission to reduce the transmission waiting time. We also evaluate the maximum end-to-end transmission delay of the proposed protocol, and clarify that the proposed protocol can guarantee the transmission within allowable delay time.

Automotive Ultrasonic Array Emitter for Short-range Targets Detection Reviewed

H, Hatano, T. Yamazato, M. Katayama

IEEE International Symposium on Wireless Communication Systems page： - 2007.10

Language：English

A Route Selection Scheme for Multi-Route Coding in Multihop Cellular Networks Reviewed

H. Okada, H. Imai, T. Yamazato, M. Katayama, K. Mase

IEEE Vehicular Technology Conference (VTC) page： - 2007.10

Language：English

In the multihop cellular networks, multiple routes from a user station to a base station can be established because of the flexibility of network topology. In order to reduce packet errors of wireless transmissions, we proposed the multi-route coding scheme, in which packets are encoded and divided into subpackets, and they are transmitted on several routes from the user station to the base station. In order to improve the performance of the multi-route coding, a route selection scheme is very important issue. In this paper, we propose the route selection scheme for the multi-route coding in multihop cellular networks. The proposed scheme is based on the bit error rate of wireless links. We also apply the proposed route selection scheme to a hybrid routing protocol and evaluate its performance.

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Papers - YAMAZATO Takaya