Faculty Profiles - YAMAZATO Takaya

Papers - YAMAZATO Takaya

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Performance evaluation of cooperative transmission in wireless sensor networks using FPGA

K. Nakao, T. Yamazato, M. Katayama

Technical Report of IEICE page： - 2007.10

Language：Japanese

Since sensor nodes are typically small and power limited, they are only able to achieve short-range transmission with low complexity processing. Therefore, we need to realize extension of the transmission range by cooperative transmission among the distributed nodes. In this paper, we propose a simple cooperative scheme without tight synchronization, i.e., multiplication of random phase in the transmitter before the transmission. Thanks to a strong error correcting code, it is possible to extend the transmission range. We evaluate the performance of this proposed scheme by LED optical communication equivalently using FPGA.

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.

Hierarchical Coding Scheme for Optical Wireless Communicaiton using LED Traffic Light and High-Speed Camera Reviewed

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

IEICE Transaction on Fundamentals of Electronics, Communications and Computer Sciences Vol. Vol.J90A ( 9 ) page： 696-704 2007.9

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

LEDs are expected as lightning 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 modeled as spatial low-pass filtered channel of which the cut-off frequency varies 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.

Distributed Space-Time Block Coding for Large and Undetermined Set of Relay Terminals Reviewed

R. Uchida, H. Okada, T. Yamazato, M. Katayama

IEEE International Symposium on Personal, Indoor and Mobile Radio Communications (PIMRC) Vol. PIMRC2007 page： - 2007.9

Language：English

In this manuscript, a spatial diversity scheme with multiple transmit and receive antennas together with multiple relay terminals for packet radio is considered. Correctly received signals at some relay terminals are re-transmitted to the receiver with the spatial diversity by STBC cooperative relaying scheme. To achieve high diversity order with the conventional STBC cooperative relaying scheme, relay terminals which re-transmit the signals are required to exchange signaling information with each another. However, the exchanging of the information causes delay of the signal transmission. Thus, in this manuscript, a novel signaling scheme for the STBC cooperative relaying is proposed. The proposed scheme releases relay terminals exchanging the signaling information. The proposed scheme also saves communication resources to provide flexibility for installation of relay terminals.

Experiment on Hierarchical Transmission Scheme for Visible Light Communication using LED Traffic Light and High-Speed Camera Reviewed

S. Arai, S. Mase, T. Yamazato, T. Endo, T. Fujii, M. Tanimoto, K. Kidono, Y. Kimura, Y. Ninomiya

IEEE International Symposium on Wireless Vehicular Communications (WiVeC'07) page： - 2007.9

Language：English

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 modeled as spatial low-pass filtered channel of which the cut-off frequency varies 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.

Analysis on Chaotic Sequence with Biased Values for Noncoherent Chaos Communication Reviewed

S. Arai, Y. Nishio, T. Yamazato

International Symposium on Nonlinear Theory and its Applications (NOLTA) Vol. NOLTA2007 page： 144-147 2007.9

Language：English

In this paper, we analyze a chaotic dynamics generating a chaotic sequence with biased values and apply it to noncoherent chaos communications. We examine a behavior of the chaotic dynamics by increasing the slope of the chaotic map and investigate the invariant measure and the correlation function. A high quality performance of noncoherent chaos communications is obtained by controlling the distribution of the chaotic sequence with biased values. Finally we carry out the computer simulation using its sequence and discuss the obtained results and the future problem for chaos communication.

Efficient Channel Estimation Scheme for Pulse-shaping OFDM Systems Reviewed

B.Mongol, T. Yamazato, M. Katayama

International Symposium on Nonlinear Theory and its Applications (NOLTA) Vol. NOLTA2007 page： - 2007.9

Language：Japanese

This paper proposes a low-complexity channel estimation sheme for the pulse-shaping OFDM systems in the highly mobile multipath environment. The estimation scheme is based on the tapped-delay-line model for the channel. The main idea behind our scheme is to approximate the fading process for each tap with finite terms of its Taylor series expansion. The proposed scheme also tracks the channel. We show that the channel can be estimated and tracked with reasonable mismatch error while using considerably short training period.

A study on position estimation method for multiple targets detection for automotive radar networks Reviewed

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

Transactions of Society of Automotive Engineers of Japan Vol. 38 ( 5 ) page： 191-196 2007.9

Language：Japanese

We research automotive radar networks with multiple radars set in the front of car. Especially, we consider data processing using measured ranges provided by the radars in order to estimate multiple target positions with high accuracy. This paper is composed of three steps. Firstly, we derive a method based on MAP estimation. Secondly, we propose a method which reduces the calculation complexity compared with the above MAP method. Finally, we introduce a method which can detect targets without ghost-targets in case the lacks of measured ranges are happened because of miss-detection. We evaluate the methods with computer simulations.

Performance comparison of CSMA and CDMA slotted ALOHA in Inter-Vehicle communication

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

Communications Society Conference of IEICE page： - 2007.9

A Study on Random Access Scheme using Channel Division for Multi-Cell OFDMA uplink

K. Kimura T. Yamazato, M. Katayama

Communications Society Conference of IEICE Vol. B-5-62 page： 384 2007.9

Experiment on Hierarchical Transmission Scheme for Visible Light Communication using LED Traffic Light and High-Speed Camera Reviewed

S. Arai, S. Mase, T. Yamazato, T. Endo, T. Fujii, M. Tanimoto, K. Kidono, Y. Kimura, Y. Ninomiya

Proceedings of IEEE International Symposium on Wireless Vehicular Communications (WiVeC'07) page： - 2007.9

Language：English

Efficient Channel Estimation Scheme for Pulse-shaping OFDM Systems Reviewed

B.Mongol, T. Yamazato, M. Katayama

International Symposium on Nonlinear Theory and its Applications page： - 2007.9

Language：English

Hierarchical Coding Scheme for Optical Wireless Communicaiton using LED Traffic Light and High-Speed Camera Reviewed

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

IEICE Transaction on Fundamentals Vol. J90-A ( 9 ) page： 696-704 - 704 2007.9

A study on position estimation method for multiple targets detection for automotive radar networks Reviewed

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

Transactions of Society of Automotive Engineers of Japan Vol. 38 ( 5 ) page： 191-196 2007.9

Performance Improvement of Downlink MC-CDMA Cellular System using Different Arrival Time of the Adjacent Cell Signal

M. Fushiki, T. Yamazato, M. Katayama

Technical Report of IEICE Vol. RCS2007-68 page： 87-91 2007.8

Language：Japanese

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 adjacent cell signal power is large. Key wor

Performance evaluation of cooperative transmission in distributed sensor networks using FPGA

K. Nakao, T. Yamazato, M. Katayama

Proceedings of 9th DSPS Educators Conference page： 91-92 2007.8

Throughput evaluation of CSMA and CDMA slotted ALOHA in Inter-Vehicle communication

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

Technical Report of IEICE Vol. RCS2007-55 page： 13-18 2007.8

Language：Japanese

This paper evaluate 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 results, 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 receive many packets simultaneously. This is much preferable feature for safety driving.

Measurement of the Narrowband Channel Characteristics \\in Single-Phase Three-Wire Indoor Power-Line Channels

Y. Sugiura , T. Yamazato, M. Katayama

Technical Report of IEICE page： - 2007.8

Language：Japanese

This manuscript reports the measurement results of narrow-band signal propagation of PLC channels between a pair of outlets. In Japan, in-house wiring is of 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 live 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 are also classified by these three types of paths. The results show that frequency responses of narrow-band PLC channels are relatively smooth, compared with that of wide-band PLC. It is also found that propagation loss in lower frequency range is larger than in higher frequency range. The time independence of narrow-band PLC channels are confirmed when no electric appliance is connected to the same live conductor.

Ultrasonic Array Emitter for Short-range Automotive Targets Detection System

H. Hatano, T. Yamazato, M. Katayama

Technical Report of IEICE Vol. ITS2007-12 page： 15-20 2007.7

Language：Japanese

We consider application of ultrasonic sensor to automotive targets detection system for short-range. The ultrasonic sensors are low cost and widely used. However the detection range is short. In addition, wide detection area is needed. To apply for high functional parking aid system, we propose the array emitter which can emit signals to desired area within desired cycle time. As a result, we show the ability of the ultrasonic sensor for parking aid systems.

A Method for Reducing the Influence of the Interference Considering ADC Nonlinearity in an OFDM Receiver Reviewed

M. Sawada, T. Yamazato, M. Katayama

IEICE Transactions on Communications Vol. J90-B ( 6 ) page： 577-584 2007.6

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

In this paper we propose an OFDM receiver that mitigates the performance degradation caused by interference. The mitigation process is done all in digital after ADCs. The receiver estimates the reliability of each OFDM symbol based on its number of out-of-range samples. This reliability is then used as the external information in soft Viterbi decoding process. The results of numerical simulations for 16QAM/OFDM show that the proposed receiver is robust to strong interference.

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Papers - YAMAZATO Takaya