Faculty Profiles - YAMAZATO Takaya

Papers - YAMAZATO Takaya

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Cooperative Transmission Scheme in Distributed Sensor Network for Extension of Transmission Range Reviewed

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

Fourth International Conference on Networked Sensing Systems page： 89-92 2007.6

Language：English

We consider a distributed transmission of data packet to a sink where the distance for a sensor node to the sink is much longer than a sensor node can transmit. We give a simple modification in the transmitter, i.e., multiplication of random phase before the transmission. Thanks to a strong error correcting code, it is possible to extend the transmission range as the received amplitude varies symbol by symbol for our scheme while whole data packet may be lost for the conventional scheme.

Throughput Comparison of CSMA and CDMA slotted ALOHA in Inter-Vehicle Communication Reviewed

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

The 7th International Conference on ITS Telecommunications page： 52-57 2007.6

Language：English

This paper compare the throughput performance of a carrier-sense multiple access (CSMA) scheme that uses an orthogonal frequency division multiple access (OFDM) physical layer and a CDMA slotted ALOHA scheme based on multicarrier CDMA (MC-CDMA) in inter-vehicle communication (IVC). In particular, we compare the throughputs in a situation where a hidden terminal is no longer negligible. We encounter such a situation in an intersection where two or more cars are crossing by. In a hidden terminal situation, the CSMA scheme may degrade throughput. On the other hand, CDMA slotted ALOHA has a resistance to the hidden terminal situation as it can support simultaneous packets. However, the transmission data rate is much slow because of the spreading. Thus the total throughput may not be as high as the CSMA based OFDM even in a hidden terminal situation. As a result, we show that the CSMA based OFDM system shows better total throughput than CDMA slotted ALOHA in all region. But, only the signal from the nearest car can be received. On the contrary, CDMA slotted ALOHA can be received many packets simultaneously. This is much preferable feature for safety driving.

Experiments on a Wireless Visible-Light Communication System using an LED Sign Panel

T. Ohtsuji, T. Yamazato, M. Katayama

Technical Report of IEICE Vol. OCS2007-14 page： 25-29 2007.6

Language：Japanese

This manuscript focuses on a wireless visible-light communication system with an LED-back-lighted sign board. Possibilities of the system are confirmed by experiment. In the experimental system, the transmitter uses frequency shift keying (FSK), which has constant envelope to avoid fluctuation of luminance and can be received without carrier phase synchronization. Since the noise and signal propagation in Electric/Optical/Electric channel are not flat in frequency, we introduce a weighting equalization before the decision circuit of the receiver. Experimental results show that this weighting improves bit error rate (BER) performance and extend distance between the transmitter and the receiver.

Channel measurement of a visible light communication system with an LED sign panel

D. Ishida , T. Yamazato, M. Katayama

Technical Report of IEICE Vol. OCS2007-15 page： 31-35 2007.6

Language：Japanese

As one of visible light communications systems, this paper focuses on a system using LED sign panel as a transmitter. The characteristic between the panel (E/O) input and the APD(O/E) output is measured. Linearity, frequency response, and the levels of harmonics of the channel is measured. The effects of the distance between the panel and the APD on the signal level is clarified. After the measurement of noise spectrum caused by an inverter-driven fluorescent lamp, the SNR in frequency is calculated.

A Study on Joint Decoding for Wireless Sensor Networks

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

Proc. of Academia Program, Wireless Technology Park 2007 page： 26-27 2007.4

Language：Japanese

Development of tiny sensor equipped with wireless communication function is remarkable with the advancement of small, light, and high-performance wireless devices. In the near future, we will see tens or hundreds of these nodes deployed in town and inside buildings. In such an environment, since many sensor nodes observe a same target or field, the information observed by each sensor node are correlated. Such correlated information are collected at a fusion center. Our purpose is to reduce channel error by using the correlation properties of observed data at the fusion center. Related works on the distributed encoding and joint decoding are the case of two correlated sources. By using the weighted correlation feedback, we extend the iterative joint decoding scheme for the general case where more than two sensor nodes are employed. We show that when the number of sensor nodes is increased, decoding performance improvement cannot be achieved by simple weighting. For more appropriate weighting, we find the weight that minimizes the bit error rate from the analytical formula of MAP decision and apply it to the case of Turbo code.

A Simple Estimator of Multiple Target Positions for Automotive Short Range Radar Networks Reviewed

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

IEEE Vehicular Technology Conference (VTC) page： 2511-2515 2007.4

Language：English

For safety applications, automotive radar networks show an interesting potential. Apart from long range radars, networked short range radar systems are under development. Additional applications can be accomplished, such includes precrash detection, parking aid and blind spot surveillance. We research the automotive radar networks using short range radars. The network is built with multiple radars. In this paper, we consider data processing using measured ranges provided by the radars in order to estimate multiple target positions with high accuracy. Firstly, we derive a method based on MAP stimation. Secondly, we propose a method which reduces the calculation complexity compared to the above MAP method. Finally, we introduce a method which can detect targets with low ndetected targets. The case often happens when the measured ranges are lost because of miss-detections.We evaluate the performance th computer simulations.

Visible Light Communication using LED TrafficLight and car equipped with camera

T. Yamazato, M. Katayama

Proc. of Academia Program, Wireless Technology Park 2007 page： 38-39 2007.4

MIMO Equalizer for Pulse-ShapingOFDM Systems in Dispersive Time-Varying Channels

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

Proc. of Academia Program, Wireless Technology Park 2007 page： 50-51 2007.4

Language：Japanese

Pulse-shaping OFDM is well-known that it performs well in a mobile environment, i.e. time-varying channel, compared with conventional OFDM. However, as the time-variance becomes higher, the intersymbol and intercarrier interferences (ISI/ICIs) increase and can no longer be neglected. These ISI/ICIs deteriorate the performance of the systems. Proper channel equalization is needed for further improvement of the systems. In this paper, we have proposed a multi-input multi-output (MIMO) transversal filter to equalize the time-frequency dispersive channel. Tap weights are calculated using the zero-forcing (ZF) algorithm. We also have proposed maximum-likelihood channel estimator and its low-complexity version. The proposed system can significantly improve the performance of the pulse-shaping systems in the dispersive time-varying channels.

A-21-25 Noncoherent Detection for Cooperative Transmission in Distributed Sensor Network Reviewed

Nakao Kouji, Yamazato Takaya, Okada Hiraku, Katayama Masaaki

Proceedings of the IEICE General Conference Vol. 2007 page： 416 2007.3

*Nagoya University OpenCourseWare Invited

T. Yamazato

Annals of Nagoya UniversityAnnals of Nagoya University Vol. 第５号 page： 51-55 2007.3

Language：Japanese Publishing type：Research paper (bulletin of university, research institution)

The Nagoya University OpenCourseWare Committee is currently working to make some of the university's teaching materials openly available for instructors, students and self-directed learners around the world via the Internet. In this report, OpenCourseWare activity in Nagoya University is introduced.

Inter-Network Communication Method for Multihop Token Line Protocol

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

IEICE General Conference page： - 2007.3

Power-line communication system using correlations of instantaneous noise powers at a transmitter and a receiver

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

IEICE General Conference Vol. A-5-22 page： - 2007.3

Performance Improvement of MC-CDMA System using Different Arrival Time of the Other Cell Signal

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

IEICE General Conference page： - 2007.3

Radio Resource Allocation using Priority Based on User Position for Multiuser OFDM

K. Kimura T. Yamazato, M. Katayama

IEICE General Conference Vol. B-5-122 page： 536 2007.3

Noncoherent Detection for Cooperative Transmission in Distributed Sensor Network

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

IEICE General Conference Vol. A-21-25 page： 416 2007.3

Coded Modulation in Consideration of State of Signals for M-ary PSK Coherent Signals Reviewed

T. Otake, H. Okada, T. Yamazato, K. Yamazaki, M. Katayama

IEICE Transaction on Fundamentals of Electronics, Communications and Computer Sciences Vol. J90-A ( 3 ) page： 257-261 2007.3

Coded Modulation in Consideration of State of Signals for M-ary PSK Coherent Signals Reviewed

T. Otake, H. Okada, T. Yamazato, K. Yamazaki, M. Katayama

IEICE Transaction on Fundamentals Vol. J90-A ( 3 ) page： 257-261 - 261 2007.3

Compensation Scheme for Nonlinear Distortion with 8PSK/OFDM Transmission in Nonlinear Satellite Channel Reviewed

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

IEICE Transactions on Communications Vol. J90-B ( 2 ) page： 138-147 2007.2

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

This paper discusses 8PSK/OFDM transmission in nonlinear satellite channel. We propose an effective compensation scheme for nonlinear distortion with high coding rate. Proposed compensation scheme is composed by bit-interleaved coded modulation with iterative decoding and original compensation for nonlinear distortion. The proposed scheme has lower complexity by combining two feedback systems and achieves good error performance under large nonlinear distortion in satellite channel.

Compensation Scheme for Nonlinear Distortion with 8PSK/OFDM Transmission in Nonlinear Satellite Channel Reviewed

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

IEICE Transactions on Communications Vol. J90-B ( 2 ) page： 138-147 - 147 2007.2

Route Characteristic Estimation for Multi-Route Coding in Wireless Multihop Networks Reviewed

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

IEICE Transactions on Communications Vol. J90-B ( 1 ) page： 93-96 2007.1

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

In the multi-route coding, encoded subpackets are transmitted via multiple routes and decoded at a destination node to get diversity gain. Because the characteristic of each route is usually different, the performance will be improved by considering it. In this letter, we propose the estimation scheme of route characteristic.

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Papers - YAMAZATO Takaya