Faculty Profiles - YAMAZATO Takaya

Papers - YAMAZATO Takaya

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Bit and power allocation for power-line communications under nonwhite and cyclostationary noise environment Reviewed

Sawada N.

2009 IEEE International Symposium on Power Line Communications and its Applications, ISPLC 2009 page： 307 - 312 2009.9

Luminance Extraction Method for Visible Light Communication System using LED Array and High-Speed Camera

T. Nagura, T. Yamazato, M. Katayama

Enginnering Sciences Society Conference of IEICE, A-17-17, p.181 Vol. A-17-17 page： p.181 2009.9

Impact of Pilot Interpolation Techniques on a Channel Estimation Scheme for Inter-Vehicle Communication

N. Hiraiwa, T. Yamazato, M. Katayama

Enginnering Sciences Society Conference of IEICE, A-17-15, p.179 Vol. A-17-15 page： p.179 2009.9

A study on transmission speed on visible light communication systems using LED array and high-speed camera

T. Nagura, T. Yamazato, M. Katayama

Proc. of 11th DSPS Educators Conference, pp.45-46 page： pp.45-46 2009.9

A Note on Joint Decoding using Correlation Estimation of Multiple Sources according to ADC Bit-Level

K. Kobayashi, T. Yamazato, M. Katayama

Communications Society Conference of IEICE, B-20-7, p.388 Vol. B-20-7 page： p.388 2009.9

Image Processing for Visible Light Communication Using LED Traffic lights

S. Arai, T. Yamazato, S. Ozawa

Technical meeting of Electronics, Information and Systems [Division C], IEEJ, Sep., 2009. page： - 2009.9

Language：Japanese

In this paper, we focus on a road-to-vehicle visible light communications using LED traffic light (transmitter) and an in-vehicle camera (receiver). As advantages using the camera, the recognition of objects as well as their locations can easily be realized and the reception of LED modulated data is also possible at the same time. Unfortunately, if the receiver is far from the transmitter, the received data pattern degrades due to reduction of pixel size and defocusing of the LED data pattern. This paper discusses these problems from image processing approaches.

TOA UWB Position Estimation with Two Receivers and a Set of Known Reflectors Reviewed

J. KIETLINSKI-ZALESKI, T. YAMAZATO, M. KATAYAMA

ICUWB 2009 pp.376-380, page： - 2009.9

Language：English

Ultra-Wideband is an attractive technology for short range positioning, especially indoors. However, for normal Time of Arrival(ToA) positioning, at least 3 receivers with unblocked direct path to the transmitter are required. A requirement that is not always met. In this work, a novel algorithm for ToA positioning using only 2 receivers is presented. This is possible by exploiting reflections from a set of known flat reflectors, for example ceiling and walls. The proposed algorithm was tested using self-developed UWB propagation simulator testbed.

Traffic Prediction Scheme for Resource Assignment of Satellite/Terrestrial Frequency Sharing Mobile Communication System Reviewed

T. Aman, T. Yamazato, M. Katayama

International Workshop on Satellite and Space Communications page： - 2009.9

Language：English

The recent development of large aperture on-board multi-beam antennas enables a small-size, low-powered and cellular phone like hand-held terminal as a satellite earth terminal. A single mobile terminal can communicate to both mobile satellite systems and terrestrial systems depend upon his location, QoS and availability of resources among satellite and terrestrial communication systems. In this paper, we propose a new traffic prediction scheme for the integrated satellite/terrestrial frequency sharing mobile communication system. The system shares a common frequency bandwidth in order to enhance the total capacity by a dynamic bandwidth allocation. A key for this allocation depends on a traffic prediction scheme of a few hundreds of terrestrial cells under a footprint of a satellite with a large aperture onboard multi-beam antennas. We propose three traffic predictors based on neural networks for dynamic resource allocation. The performances of the proposed schemes are evaluated in terms of the Relative Traffic Prediction Error and Maximum Traffic Prediction Error by the computer simulation. For the evaluation, we adopt the actual traffic statistic published by Ministry of Internal Affairs and Communications of Japan with population density of terrestrial cells based on the actual population of Aichi, Japan. As results, average traffic prediction error of less than 0.25 is achieved for the prediction interval of one hour, enough for dynamic resource allocation.

Cognitive Radio with Relay of a Primary Signal and Piggyback Modulation Reviewed

J. Naganawa, T. Yamazato, M. Katayama

IEEE International Symposium on Personal, Indoor and Mobile Radio Communication page： - 2009.9

Language：English

This manuscript proposes a cognitive radio system that shares a frequency with an existing primary system. In the proposed method, a secondary transmitter relays the primary signal and piggybacks its own data on it. Symbol error probabilities of the system are derived analytically. The result shows that the proposed system can communicate at a relatively high speed on the same frequency of the primary system without harm to it.

10-219 Nagoya Univeristy OCW Reviewed

Yamazato Takaya

Proceedings of Annual Conference of Japanese Society for Engineering Education Vol. 2009 ( 0 ) page： 416 - 417 2009.8

Detection of LED Traffic Light by Image Processing for Visible Light Communication System Reviewed

H.C. N. Premachandra, T. Yendo, T. Yamazato, T. Fujii, M. Tanimoto, Y. Kimura

Proceedings of 2009 IEEE Intelligent Vehicles Symposium (IV'09), June 2009 page： - 2009.8

Language：English

We propose a visible light road-to-vehicle communication system at intersection for ITS. In this system, the communication between vehicle and a LED traffic light is approached using LED traffic light as the transmitter, and on-vehicle high-speed camera as the receiver. The LEDs in the transmitter are emitted with 500Hz and the images of those emitting LEDs are captured by a high-speed camera for conducting communication. In this communication, it is extremely necessary to find the transmitter and detect it for consecutive frames while vehicle is moving. In this paper, we introduce proposals for finding and detecting it for consecutive frames by image processing. Experimental results using appropriate images showed the effectiveness of the proposal.

巻頭言～創刊５００号を迎えて～和文論文誌Bは優れた通信技術・研究を蓄える

山里敬也

電子情報通信学会論文誌 Vol. Vol. J92-B ( No. 8 ) page： pp. 1211-1211 2009.8

An Access Control Method for Multipoint Data Gatheringh over Power-Line Communications Reviewed

OHTOMO Yuzo, YAMAZATO Takaya, KATAYAMA Masaaki

IEICE technical report Vol. 109 ( 144 ) page： 37 - 42 2009.7

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

This paper proposes a media access control method for a multipoint data gathering system using power-line communications. In large-scale power-line communication systems, it is difficult to use a CSMA scheme because of hidden terminal problem. In such condition, by broadcasting acknowledgements, the proposed method ensures assignment of a time slot for each node once the node succeeds to transfer its data to the base-station. It is confirmed that the proposed scheme reduces packet collisions and outperforms conventional slotted-ALOHA scheme in throughput of data. In addition, proposed scheme provides an adaptive slot assignment under cyclo-stationary channel environment.

An Access Control Method for Multipoint Data Gathering over Power-Line Communications

Y. Ohtomo, T. Yamazato, M. Katayama

Technical Report of IEICE, vol.WBS2009-13, pp.37-42 Vol. Vol.WBS2009-13 page： pp.37-42 2009.7

Language：Japanese

Edge-Based Tracking of an LED Traffic Light for a Road-to-Vehicle Visible Light Communication System Reviewed

H.C. N. Premachandra, T. Yendo, M. P. Tehrani, T. Yamazato, T. Fujii, M. Tanimoto, Y. Kimura

Journal of Broadcast Engineering published by KoSBE, the Korean Society for Broadcast Engineers, Vol. 14, No. 4, pp.475-487, July 2009 Vol. Vol. 14 ( No. 4 ) page： pp.475-487 2009.7

Language：English

We propose a visible light road-to-vehicle communication system at intersection as one of ITS technique. In this system, the communication between vehicle and a LED traffic light is approached using LED traffic light as a transmitter, and on-vehicle high-speed camera as a receiver. The LEDs in the transmitter are emitted in 500Hz and those emitting LEDs are captured by a high-speed camera for making communication. Here, the luminance value of each LED in the transmitter should be found for consecutive frames to achieve effective communication. For this purpose, first the transmitter should be identified, then it should be tracked for consecutive frames while the vehicle is moving, by processing the images from the high-speed camera. In our previous work, the transmitter was identified by getting the subtraction of two consecutive frames. In this paper, we mainly introduce an algorithm to track the identified transmitter in consecutive frames. Experimental results using appropriate images showed the effectiveness of the proposal.

Construction of a Kalman estimator for BFDM/OQAM system in the time-frequency dispersive channels Reviewed

MONGOL Bayarpurev, YAMAZATO Takaya, KATAYAMA Masaaki

IEICE technical report Vol. 109 ( 105 ) page： 125 - 130 2009.6

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

BFDM/OQAM allows to employ a gaussian transmitter pulse at maximal spectral efficiency. Thus, it performs well in the time-frequency dispersive channels and is considered to be a promising candidate for the next generation mobile communications modulation scheme. However, in the highly mobile environment the performance deteriorates and channel equalization and estimation schemes became essential for further improvement of BFDM/OQAM systems. This paper proposes a novel adaptive channel estimator based on a Kalman filter. We approximate the channel state with a number of samples of its fading processes at each delay tap. The idea behind our estimator is to employ a linear predictor to derive a process equation for the Kalman filter. To reduce the convergence time the bayesian estimation is employed to provide an initial value for the Kalman filter. The mean-square-error performance of the proposed estimator is evaluated using computer simulation.

Channel Estimation and Tracking Schemes for the Pulse-Shaping OFDM Systems Reviewed

B. Mongol, T. Yamazato, M. Katayama

IEEE International Conference on Communications, SPC-10-4 (in the CD) Vol. SPC-10-4 page： - 2009.6

Language：English

Robust channel estimation scheme is essential for pulse-shaping OFDM systems in the multipath mobile environment. This paper proposes three types of channel estimation schemes for the general class of pulse-shaping OFDM systems. The first two types are suboptimal low-complexity maximum likelihood estimators. The last type is adaptive Kalman filter channel estimator. We numerically evaluate the performance of each estimator using computer simulation.

Evaluation and Performance Improvement of a Cooperative Sensing System with Losses of Information from Sensing Nodes Reviewed

TAKANASHI Makoto, YAMAZATO Takaya, KATAYAMA Masaaki

IEICE technical report Vol. 109 ( 61 ) page： 75 - 79 2009.5

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

At a location and time, there may be frequencies not in use by their licensed (primary) users. Spectrum sharing, in which a secondary radio system uses such white spaces of frequency, is one of advantageous means to mitigate the spectrum scarcity. In order to realize the spectrum sharing, spectrum sensing that detects the presence of a primary user signal is a key technology. For reliable sensing of the primary signal, cooperative sensing where information from multiple sensing nodes is incorporated at a fusion center is currently being investigated by many researchers. Majority of these works consider the imperfectness of the channels between a primary transmitter and sensor nodes under noise and fading environments. On the contrary, this manuscript deals with the transmission between sensor nodes to a fusion center. For a cooperative spectrum sensing system, in which the analog outputs of energy detectors at sensor nodes are transmitted to a fusion center, the influence of losses of information from the nodes on detection performance is derived analytically. In addition, it is shown that the adaptive processing with the consideration of information loss at the fusion center improves system performance.

No Redundant Error-Correcting Scheme Using Chaotic Dynamics for Noncoherent Chaos Communications Reviewed

S. Arai, Y. Nishio, T. Yamazato

Proceedings of 2009 IEEE International Symposium on Circuits and Systems, pp. 2633-2636 page： pp. 2633-2636 2009.5

Language：English

This paper proposes the error-correcting scheme without redundancy sequences based on the chaotic dynamics for noncoherent chaos communications. We generate successive chaotic sequences from the identical chaotic map. And for the next sequence we set the initial value to the end value of the former sequence. By such way we can create the successive chaotic sequences having the same chaotic dynamics. This feature gives the receiver additional information to correctly recover the received noisy signal. Therefore, by analyzing the chaotic dynamics at the receiver, it is possible to improve the error performance without redundancy signal. As results of computer simulations, we confirm about 3 dB gain in BER performance as compared with the conventional suboptimal receiver when using the short chaotic sequence length per 1 bit.

Evaluation and Performance Improvement of a Cooperative Sensing System with Losses of Information from Sensing Nodes

M. Takanashi, T. Yamazato, M. Katayama

Technical Report of IEICE, vol.109, no.61 (SR2009-5), pp.75-79, Vol. Vol.109 ( No.61 (SR2009-5) ) page： - 2009.5

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Papers - YAMAZATO Takaya