Faculty Profiles - YAMAZATO Takaya

A novel contention-free medium access control protocol for inter-vehicle communication systems Reviewed

Mitsuru Masamura, Hiraku Okada, Satoshi Makido, Takaya Yamazato, Masaaki Katayama

2007 IEEE INTERNATIONAL CONFERENCE ON MOBILE AD-HOC AND SENSOR SYSTEMS, VOLS 1-3 page： 995 - + 2007

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

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.

DOI： 10.1109/MOBHOC.2007.4428733

A simple estimator of multiple target positions for automotive short range radar networks Reviewed

Hatano Hiroyuki, Yamazato Takaya, Okada Hiraku, Katayama Masaaki

2007 IEEE 65TH VEHICULAR TECHNOLOGY CONFERENCE, VOLS 1-6 page： 2511 - + 2007

A route selection scheme for multi-route coding in multihop cellular networks Reviewed

Hiraku Okada, Hitoshi Imai, Takaya Yamazato, Masaaki Katayama, Kenichi Mase

2007 IEEE 66TH VEHICULAR TECHNOLOGY CONFERENCE, VOLS 1-5 page： 6 - + 2007

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

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.

DOI： 10.1109/VETECF.2007.18

A route selection scheme for multi-route coding in multihop cellular networks Reviewed

Okada Hiraku, Imai Hitoshi, Yamazato Takaya, Katayama Masaaki, Mase Kenichi

2007 IEEE 66TH VEHICULAR TECHNOLOGY CONFERENCE, VOLS 1-5 page： 6 - + 2007

Automotive ultrasonic array emitter for short-range targets detection Reviewed

Hatano Hiroyuki, Yamazato Takaya, Katayama Masaaki

2007 FOURTH INTERNATIONAL SYMPOSIUM ON WIRELESS COMMUNICATION SYSTEMS, VOLS 1 AND 2 page： 582 - 586 2007

Automotive ultrasonic array emitter for short-range targets detection Reviewed

Hiroyuki Hatano, Takaya Yamazato, Masaaki Katayama

2007 FOURTH INTERNATIONAL SYMPOSIUM ON WIRELESS COMMUNICATION SYSTEMS, VOLS 1 AND 2 page： 582 - 586 2007

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

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.

Distributed space-time block coding for large and undetermined set of relay terminals Reviewed

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

Nakao Koji, Yamazato Takaya, Katayama Masaaki, Okada Hiraku

INSS 07: PROCEEDINGS OF THE FOURTH INTERNATIONAL CONFERENCE ON NETWORKED SENSING SYSTEMS page： 89 - + 2007

Ryosuke Uchida, Hiraku Okada, Takaya Yamazato, Masaaki Katayama

2007 IEEE 18TH INTERNATIONAL SYMPOSIUM ON PERSONAL, INDOOR AND MOBILE RADIO COMMUNICATIONS, VOLS 1-9 page： 2727 - + 2007

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

In this manuscript, a decode-and-forward cooperative diversity scheme for wireless packet transmission network with large and undetermined set of relay terminals is considered. Correctly received signals at some relay terminals are retransmitted to the receiver with the STBC-based cooperative relaying scheme. For large and undetermined set of relay terminals, performance of the conventional STBC-based cooperative diversity is known to be degraded due to the loss of the diversity gain and increasement of decoding complexity. In this manuscript, we propose a signaling scheme to reduce the performance loss. Our proposed scheme is based on the linear transformation of the STBC matrix by a signature vector, which has more degrees of freedom for the assignment of signals compared to the conventional STBC-based cooperative diversity.

DOI： 10.1109/PIMRC.2007.4394668

Improvement of transmission quality using correlation of observational data in sensor networks Reviewed

Distributed space-time block coding for large and undetermined set of relay terminals Reviewed

Uchida Ryosuke, Okada Hiraku, Yamazato Takaya, Katayama Masaaki

2007 IEEE 18TH INTERNATIONAL SYMPOSIUM ON PERSONAL, INDOOR AND MOBILE RADIO COMMUNICATIONS, VOLS 1-9 page： 2727 - + 2007

Experiment on hierarchical transmission scheme for visible light communication using LED traffic light and high-speed camera Reviewed

Arai Shintaro, Mase Shohei, Yamazato Takaya, Endo Tomohiro, Fujii Toshiaki, Tanimoto Masayuki, Kidono Kiyosumi, Kimura Yoshikatsu, Ninomiya Yoshiki

2007 IEEE 66TH VEHICULAR TECHNOLOGY CONFERENCE, VOLS 1-5 page： 2174 - + 2007

Kentaro Kobayashi, Takaya Yamazato, Hiraku Okada, Masaaki Katayama

ELECTRONICS AND COMMUNICATIONS IN JAPAN PART III-FUNDAMENTAL ELECTRONIC SCIENCE Vol. 90 ( 11 ) page： 1 - 10 2007

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

In sensor networks, many of the sensor nodes are often positioned in clusters, and there is a correlation between the data obtained at the various sensor nodes by observation. This kind of observational data is collected at fusion centers. In this paper, we study the observation precision at fusion centers from the viewpoint of the Kullback-Leibler (KL) information. In particular, we consider transmission path errors arising when transmission is made from each sensor node via wireless communication paths, as a factor in the deterioration of the KL information, or in other words, observation precision, and study its effects and methods for reducing it. In this paper, We Study the KL information obtained in fusion centers when there have been transmission path errors in cases where the correlation between observational data is all equal, and where the correlation is random. We show that the deterioration of the KL information can be reduced in fusion centers by using the correlation of observational data in the estimates of error data. In addition, we present examples of estimating the correlation between observational data in fusion centers that use correlation, and of estimating error data using correlation. (C) 2007 Wiley Periodicals, Inc. Electron Comm Jpn Pt 3. 90(11): 1-10, 2007; Published online in Wiley InterScience (www.interscience.wiley.com).

DOI： 10.1002/ecjc.20250

Experiment on hierarchical transmission scheme for visible light communication using LED traffic light and high-speed camera Reviewed

Shintaro Arai, Shohei Mase, Takaya Yamazato, Tomohiro Endo, Toshiaki Fujii, Masayuki Tanimoto, Kiyosumi Kidono, Yoshikatsu Kimura, Yoshiki Ninomiya

2007 IEEE 66TH VEHICULAR TECHNOLOGY CONFERENCE, VOLS 1-5 page： 2174 - + 2007

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

LEDs are expected as lighting sources for next generation, and data transmission system using LEDs attract attention. In this paper, we present hierarchical coding scheme using LED traffic lights and high-speed camera for Intelligent Transport Systems (ITS) application. Further, if each of LEDs in. traffic lights is individually modulated, parallel data transmissions are possible using a camera as a reception device. Such parallel LED-camera channel can be in deled as spatial low-pass filtered channel of which the cut-off frequency vanes according to the distance. To overcome, we propose hierarchical coding scheme based on 2D fast Haar wavelet transform. As results, the proposed hierarchical transmission schemes outperform the conventional on-off keying and the reception of high priority data is guaranteed even LED-camera distance is further.

DOI： 10.1109/VETECF.2007.456

Route diversity effect of joint decoding using correlation between observed data sequences in sensor networks Reviewed

Performance analysis of UWB impulse radar receiver using parallel IPCP Reviewed

Hatano Hiroyuki, Yamazato Takaya, Okada Hiraku, Katayama Masaaki

ELECTRONICS AND COMMUNICATIONS IN JAPAN PART III-FUNDAMENTAL ELECTRONIC SCIENCE Vol. 90 ( 7 ) page： 1 - 14 2007

Hiraku Okada, Kentaro Kobayashit, Takaya Yamazato, Kenichi Mase

2007 IEEE 65TH VEHICULAR TECHNOLOGY CONFERENCE, VOLS 1-6 page： 217 - 221 2007

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

In sensor networks, because of densely deployment of sensor nodes, sensing area of each sensor node is overlapped with each other and its observed data sequence is correlated. The joint decoding scheme that uses the correlation between the observed data sequences can reduce bit errors in the wireless channel. In this paper, we extend the joint decoding to the case of more than two-hop transmission. For such extension, selection of fusion scheme is very important issue. If the global fusion scheme is employed and the observed data sequence of each sensor node is transmitted on an independent route, route diversity effect could be obtained by using the correlation between observed data sequences. We compare the bit error rate performance of local and global fusion schemes and clarify the route diversity effect.

DOI： 10.1109/VETECS.2007.57