Faculty Profiles - YAMAZATO Takaya

Papers - YAMAZATO Takaya

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EXIT Analysis for MAP-Based Joint Iterative Decoding of Separately Encoded Correlated Sources Reviewed

Kentaro Kobayashi, Takaya Yamazato, Masaaki Katayama

IEICE TRANSACTIONS ON COMMUNICATIONS Vol. E93B ( 12 ) page： 3509 - 3513 2010.12

Language：English Publishing type：Research paper (scientific journal) Publisher：IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG

We develop a mathematical framework for the extrinsic information transfer (EXIT) analysis to assess the convergence behavior of maximum a posteriori (MAP) based joint iterative decoding of correlated sources which are separately encoded and transmitted over noisy channels Unlike the previous work our approach focuses on the case side information about the correlation is not perfectly given at the joint decoder but is extracted from decoder output and updated in an iterative manner The presented framework provides a convenient way to compare between schemes We show that it allows us to easily and accurately predict Joint decoding gain and turbo cliff position

DOI： 10.1587/transcom.E93.B.3509

Recent Advances in Satellite and Space Communications Reviewed

Bisio Igor, De Gaudenzi Riccardo, Nguyen Hung, Pavlidou Fotini-Niovi, Yamazato Takaya

JOURNAL OF COMMUNICATIONS AND NETWORKS Vol. 12 ( 6 ) page： 523 - 528 2010.12

Recent Advances in Satellite and Space Communications Reviewed

Igor Bisio, Riccardo De Gaudenzi, Hung Nguyen, Fotini-Niovi Pavlidou, Takaya Yamazato

JOURNAL OF COMMUNICATIONS AND NETWORKS Vol. 12 ( 6 ) page： 523 - 528 2010.12

TOA UWB Positioning with Two Receivers Using Known Indoor Features Reviewed

Jan Kietlinski-Zaleski, Takaya Yamazato, Masaaki Katayama

IEICE TRANSACTIONS ON COMMUNICATIONS Vol. E93B ( 12 ) page： 3624 - 3631 2010.12

Language：English Publishing type：Research paper (scientific journal) Publisher：IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG

Ultra Wideband is an attractive technology for short range positioning especially Indoors However for normal Time of Arrival (ToA) positioning at least three receivers with unblocked direct path to the trans miner are required A requirement that is not always met In this work a novel algorithm for ToA positioning using only two receivers is presented This is possible by exploiting the knowledge of some of the indoor features namely positions of big flat reflective surfaces for example ceiling and walls The proposed algorithm was tested using data from a measurement campaign

DOI： 10.1587/transcom.E93.B.3624

UWB positioning using known indoor features- Environment comparison Reviewed Open Access

Kietlinski-Zaleski J.

2010 International Conference on Indoor Positioning and Indoor Navigation, IPIN 2010 - Conference Proceedings 2010.12

Distributed Error Correcting Coding and Joint Decoding Scheme Using Spatial Correlation of Sensor ADC Output in Wireless Sensor networks Reviewed

KOBAYASHI Kentaro, YAMAZATO Takaya, KATAYAMA Masaaki

IEICE technical report Vol. 110 ( 326 ) page： 23 - 28 2010.11

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

In wireless sensor networks, sensor nodes are densely deployed for reliable sensing of physical phenomenon. Due to the high density in the sensing field, sensor observations are spatially correlated. In this paper, we focus on joint channel decoding utilizing the spatial correlation of multiple sensor observations. Our proposed scheme makes use of an estimation of the correlation according to ADC bit levels. In addition, the proposed scheme makes use of Gray code for avoiding multiple bit-flipping between adjacent ADC output values. The performance of our approach is examined by simulations using sensor data from experiments in a real indoor environment.

CiNii Research

Experimental Results on Simple Distributed Cooperative Transmission Scheme with Visible Light Communication Reviewed

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

IEICE Transactions on Communications Vol. E93-B ( 11 ) page： 2959-2962 2010.11

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

We consider a distributed transmission of data packet to a sink where the distance of a sensor node to a sink is much longer than the maximum communication range of each sensor node. We give a simple modification to the transmitter, i.e., multiplication of random phase before the transmission. Thanks to Turbo Code, it is possible to extend the trans- mission range as the received amplitude varies symbol by symbol for our scheme while whole data packet may be lost for the conventional scheme. In this letter, we report the experimental results of our scheme equivalently developed using visible light communication.

Experimental Results on Simple Distributed Cooperative Transmission Scheme with Visible Light Communication Reviewed

Takaya Yamazato, Koji Nakao, Hiraku Okada, Masaaki Katayama

IEICE TRANSACTIONS ON COMMUNICATIONS Vol. E93B ( 11 ) page： 2959 - 2962 2010.11

Language：English Publishing type：Research paper (scientific journal) Publisher：IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG

We consider a distributed transmission of data packet to a sink where the distance of a sensor node to a sink is much longer than the maximum communication range of each sensor node We give a simple modification to the transmitter i e multiplication of random phase before the transmission Thanks to Turbo Code it is possible to extend the trans mission range as the received amplitude vanes symbol by symbol for our scheme while whole data packet may be lost for the conventional scheme In this letter we report the experimental results of our scheme equivalently developed using visible light communication

DOI： 10.1587/transcom.E93.B.2959

Performance evaluation of the cognitive piggyback overlay systems with dirty paper coding Reviewed

J. Naganawa, K. Kobayashi, M. Katayama, T. Yamazato

10th International Symposium on Communications and Information Technologies (ISCIT2010) Vol. FA1-1-4 page： 974-979 2010.10

Language：English

This manuscript considers a secondary system sharing the spectrum with the primary system at the same time and on the same frequency. We propose a cognitive overlay system in which the secondary system relays the primary signal and piggybacks its own data on it. Furthermore, the secondary system uses the channel coding based on the dirty paper coding (DPC). The result of the analysis shows that the proposed scheme allows the secondary system to communicate at the same speed as the primary system without any harm to it.

Improvement of Sequential-Test-Based Cooperative Spectrum Sensing Systems in Band Limited Control Channels Reviewed

S. Mitsuya, K. Kobayashi, T. Yamazato, M. Katayama

10th International Symposium on Communications and Information Technologies (ISCIT2010) Vol. FA1-1-3 page： 968-973 2010.10

Language：English

In a cooperative spectrum sensing system, many nodes perform spectrum sensing and report their decisions to one fusion center via control channels. This paper considers efficient use of the frequency band for the control channels. For this purpose, sequential-test is introduced for the local decision at each node. With this scheme, the transmission timing of the reports from the nodes becomes at random and necessary maximum bandwidth for the control channels decreases. Numerical results show that this sequential-test-base-scheme not only decreases the number of simultaneous reports but also improves sensing reliability. For further improvement, this paper also introduces a decision scheme at the fusion center based on probabilistic features of the reports from the nodes.

Inband and Outband Spectrum Analysis of the BFDM and BFDM/OQAM Signals with Truncated Gaussian Pulses Reviewed

B. Mongol, T. Yamazato, M. Katayama

International Symposium on Information Theory and Its Applications page： CD-ROM 2010.10

Language：English

Pulse-shaping OFDM, or more generally BFDM and BFDM/OQAM, systems are originally proposed to combat inter- carrier interference (ICI) caused by time-variance of the channel. The main property that makes these signals robust against ICI is that they allow to employ time-frequency well localized pulses, particularly Gaussian pulse which has the best time-frequency localization. However, this property also suppresses the outband or inband spectral leakage of the BFDM and BFDM/OQAM signal, making them attractive physical layer modulation scheme for cognitive radio. In this paper we analyze the power density spectra of the BFDM and BFDM/OQAM signals and numerically evaluate the inband and outband spectra for truncated Gaussian pulses.

Error-correcting scheme based on chaotic dynamics and its performance for noncoherent chaos communications Reviewed

S. Arai, Y. Nishio and T. Yamazato

NOLTA, IEICE Vol. 1 ( 1 ) page： 196-206 2010.10

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

This paper proposes a novel error-correcting scheme using chaotic dynamics for noncoherent chaos communications. In our proposed system, two successive chaotic sequences are generated from the same chaotic map; the second sequence is generated with an initial value which is the last value of the first sequence. In this case, successive chaotic sequences having the same chaotic dynamics are created. This feature gives the receiver additional information to correctly recover the information data and thus improves the bit error performance of the receiver. As results of the computer simulation, we confirm that the advantage gained in BER performance of the proposed error-correcting method is about 1-1.5 dB compared to conventional method. In addition, we achieve that the proposed error-correcting scheme is performed without the new additional redundancy code by using the chaotic dynamics.

Kalman Channel Estimator for BFDM/OQAM system in Time-Frequency Dispersive Channels Reviewed

B. Mongol, T. Yamazato, M. Katayama

IEICE Transactions on Communications Vol. J93-B ( 10 ) page： 1466-1480 2010.10

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

Biorthogonal Frequency Division Multiplexing / Offset QAM (BFDM/OQAM) allows to employ a Gaus- sian transmitter pulse. Thus, it performs well in the time-frequency dispersive channels as it can suppress ISI and ICI without having guard interval. However, in the highly mobile environment the performance deteriorates and channel estimation schemes became essential for further improvement of BFDM/OQAM systems. This paper proposes a novel adaptive channel estimator based on Kalman filter. Especially, we derive the essential equations to design Kalman filter, namely, the process equation and the measurement equation.

Kalman Channel Estimator for BFDM/OQAM System in Time-Frequency Dispersive Channels Reviewed

MONGOL Bayarpurev, YAMAZATO Takaya, KATAYAMA Masaaki

The IEICE transactions on communications B Vol. 93 ( 10 ) page： 1466 - 1480 2010.10

A Study on Joint Channel Decoding Using Spatial Correlation of Sensor Observations According to ADC Bit levels Reviewed

K. Kobayashi, T. Yamazato, M. Katayama

IEEE International Workshop on Wireless Distributed Networks (WDN2010) page： 484-489 2010.9

Language：English

In densely deployed wireless sensor networks, observations of the sensor nodes are spatially correlated. In this paper, we study a joint channel decoding scheme utilizing bit correlation of the sensor observations according to bit levels of analog-digital converter (ADC). If sensor ADC output is interpreted as natural binary numeral, carry propagation may occur between adjacent ADC output values. Such carry propagation leads to the degradation of joint decoding gain. We focus on the use of Gray code for avoiding the carry propagation. The performance of our approach is demonstrated by simulations using sensor data from experiments in a real indoor environment.

TDOA UWB Positioning with Three Receivers Using Known Indoor Features Reviewed

J. Kietlinski-Zaleski, T. Yamazato, M. Katayama

2010 IEEE International Conference on Ultra-Wideband page： CD-ROM 2010.9

Language：English

Ultra-Wideband is an attractive technology for short range positioning, especially indoors. However, for normal 3D Time Difference of Arrival (TDoA) positioning, at least four receivers with unblocked direct path to the transmitter are required. A requirement that is not always met. In this work, a novel method for TDoA positioning using only three receivers is presented and tested using real-world measurements. Positioning with three receivers is possible by exploiting the knowledge of some of the indoor features, namely positions of big flat reflective surfaces, reflectors, for example ceiling and walls.

Tracking an LED Array Transmitter for Visible Light Communications in the Driving Situation Reviewed

T. Nagura, T. Yamazato, M. Katayama, T. Yendo, T. Fujii, H. Okada

IEEE International Symposium on Wireless Communication Systems (ISWCS2010) page： 765-769 2010.9

Language：English

In this paper, we discuss on a decoding algorithm for visible light communication systems in the driving situation using an LED array transmitter and a high-speed camera receiver. We propose an LED array detection method using M-sequence and an LED array tracking method using inverted signals. We confirm that we can distinguish LED array candidates correctly with M-sequence. We also confirm that we can suppress the flicker of the LED and improve the data rate as compared with the previous method.

UWB Positioning Using Known Indoor Features - Environment Comparison Reviewed

J. Kietlinski-Zaleski, T. Yamazato

2010 International Conference on Indoor Positioning and Indoor Navigation (IPIN) page： CD-ROM 2010.9

Language：English

Ultra-Wideband is an attractive technology for short range positioning, especially indoors. However, for normal Time of Arrival (TOA) positioning, at least three receivers with unblocked direct path to the transmitter are required. A requirement that is not always met. In our previous work, we presented a novel 3D TOA UWB indoor positioning method that uses only two receivers. This is possible by exploiting the knowledge of some of the indoor features, namely ceiling and walls. In this work, we verify the usability of the method using measurement results in three environments: a lecture room, a cluttered laboratory and a corridor. By comparing the results of the method for three environments, we draw conclusions about its strengths and weaknesses.

Fast Recognition of LED Array by High-Speed Camera Invited

T. Yamazato

Enginnering Sciences Society Conference of IEICE Vol. AP-2 page： CD-ROM 2010.9

Implovement Method of transmission speed for Visible Light Communication System using LED Array and High-Speed Camera

T. Ozawa, T. Nagura, T. Yamazato, T. Yendo, T. Fujii, H. Okada

Enginnering Sciences Society Conference of IEICE Vol. A-17-8 page： 154 2010.9

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Papers - YAMAZATO Takaya