Faculty Profiles - YAMAZATO Takaya

Improvement of sequential-test-based cooperative spectrum sensing systems in band limited control channels Reviewed

Shohei Mitsuya, Kentaro Kobayashi, Takaya Yamazato, Masaaki Katayama

ISCIT 2010 - 2010 10th International Symposium on Communications and Information Technologies page： 968 - 973 2010

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

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. ©2010 IEEE.

DOI： 10.1109/ISCIT.2010.5665127

Improved Decoding Methods of Visible Light Communication System for ITS using LED Array and High-Speed Camera Reviewed

Toru Nagura, Takaya Yamazato, Masaaki Katayama, Tomohiro Yendo, Toshiaki Fujii, Hiraku Okada

2010 IEEE 71ST VEHICULAR TECHNOLOGY CONFERENCE page： 1 - 5 2010

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

In this paper, we consider visible light communication system using LED array as a transmitter and high-speed camera as a receiver for Intelligent Transport System (ITS). Previously, we have proposed the hierarchical coding scheme which allocates data to spatial frequency components of the image depending on the priority. This scheme is possible to receive information of the high-priority even if communication distance is long. However, we need to distinguish multi-valued data from the received image by using a hierarchical coding. In this paper, we propose two improved decoding methods, and demonstrate to distinguish multi-valued data more correctly in the experiment.

DOI： 10.1109/VETECS.2010.5493958

High-speed-camera Image Processing Based LED Traffic Light Detection for Road-to-vehicle Visible Light Communication Reviewed

Improved Decoding Methods of Visible Light Communication System for ITS using LED Array and High-Speed Camera Reviewed

Nagura Toru, Yamazato Takaya, Katayama Masaaki, Yendo Tomohiro, Fujii Toshiaki, Okada Hiraku

2010 IEEE 71ST VEHICULAR TECHNOLOGY CONFERENCE 2010

H. Chinthaka N. Premachandra, Tomohiro Yendo, Mehrdad Panahpour Tehrani, Takaya Yamazato, Hiraku Okada, Toshiaki Fujii, Masayuki Tanimoto

2010 IEEE INTELLIGENT VEHICLES SYMPOSIUM (IV) page： 793 - 798 2010

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

As one of ITS technique, a new visible light road-to-vehicle communication system at intersections is proposed. In this system, the communication between a vehicle and an LED traffic light is conducted using an LED traffic light as a transmitter, and an on-vehicle high-speed camera as a receiver. The LEDs in the transmitter emit light in high frequency and those emitting LEDs are captured by the high-speed camera for making communication. Here, the luminance value of LEDs in the transmitter should be captured in consecutive frames to achieve effective communication. For this purpose, first the transmitter should be found, then it should be tracked in consecutive frames by processing the images from the high-speed camera. In this paper, we propose new effective algorithms for finding and tracking the transmitter, which result in a increased communication speed, compared to the previous methods. Experiments using appropriate images showed the effectiveness of the proposals.

DOI： 10.1109/IVS.2010.5548097

High-speed-camera Image Processing Based LED Traffic Light Detection for Road-to-vehicle Visible Light Communication Reviewed

Premachandra H. Chinthaka N., Yendo Tomohiro, Tehrani Mehrdad Panahpour, Yamazato Takaya, Okada Hiraku, Fujii Toshiaki, Tanimoto Masayuki

2010 IEEE INTELLIGENT VEHICLES SYMPOSIUM (IV) page： 793 - 798 2010

Experimental Validation of TOA UWB Positioning with Two Receivers Using Known Indoor Features Reviewed

Jan Kietlinski-Zaleski, Takaya Yamazato, Masaaki Katayama

2010 IEEE-ION POSITION LOCATION AND NAVIGATION SYMPOSIUM PLANS page： 748 - 752 2010

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

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. This requirement is not always met. In this work, a novel algorithm for ToA positioning using only two receivers is presented and validated using data from a measurement campaign. Positioning with two receivers is possible by exploiting the knowledge of some of the indoor features, namely positions of big flat reflective surfaces, for example ceiling and walls.

Successive Interference Cancellation for Hierarchical Coding in Optical Wireless Communication Systems using LED array and High speed camera Reviewed

Experimental Validation of TOA UWB Positioning with Two Receivers Using Known Indoor Features Reviewed

Kietlinski-Zaleski Jan, Yamazato Takaya, Katayama Masaaki

2010 IEEE-ION POSITION LOCATION AND NAVIGATION SYMPOSIUM PLANS page： 748 - 752 2010

OZAWA Toshiyuki, NAGURA Toru, YAMAZATO Takaya, KATAYAMA Masaaki, YENDO Tomohiro, FUJII Toshiaki, OKADA Hiraku

ITE Technical Report Vol. 34 ( 0 ) page： 53 - 58 2010

Publishing type：Research paper (scientific journal) Publisher：The Institute of Image Information and Television Engineers

We propose a successive interference cancellation scheme (SIC)for the hierarchical coding parallel optical communication system using LED array and high-speed camera. The high priority data is first demodulated and Turbo-decoded. The retrieved high priority data is then re-modulated and subtracted from the received signal. In this way, the reliability of the middle priority data can be improved as the interference caused by the high priority data can be reduced. By the way, the performance of SIC depends on the performance of Turbo code. In this paper, we apply LogMAP decoding to improve the performance instead of MaxLogMAP algorithm that we have used in the previous.

DOI： 10.11485/itetr.34.6.0_53

Kalman Channel Estimator for MC-CDMA based Inter-Vehicle Communication Reviewed

HIRAIWA Noriaki, YAMAZATO Takaya, KATAYAMA Masaaki

ITE Technical Report Vol. 34 ( 0 ) page： 47 - 52 2010

Publishing type：Research paper (scientific journal) Publisher：The Institute of Image Information and Television Engineers

In this paper, we propose a kalman channel estimator for MC-CDMA based Inter-Vehicle Communication (IVC). In IVC, the channel characteristic of each car is different among pilot signals because of a doppler shift, a multipath fading, and the difference of receiving power. Our proposed kalman channel estimator uses a kalman filter to track the channel fluctuation and implements a pilot-based channel estimation which interpolates among pilot signals by using an/interpolation polynomial into our proposed channel estimator to suppress an estimation error. As results, we show that the kalman channel estimator shows better performance than a pilot-based channel estimation.

DOI： 10.11485/itetr.34.6.0_47

Optimal cluster partitioning for wireless sensor networks with cooperative MISO scheme Reviewed

Zheng Huang, Takaya Yamazato, Masaaki Katayama

6th Advanced International Conference on Telecommunications, AICT 2010 page： 323 - 328 2010

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

The paper discusses the optimal cluster partitioning for wireless sensor networks deployed in continuous areas. Both single-hop and multi-hop transmissions with cooperative Multi-Input Single-Output (MISO) scheme are considered for inter-cluster communications. The effects of cluster size in the energy consumption of intra-cluster communication and the amount of fused data are included in calculation. As a result, the dominant factors of the maximal network lifetimes are listed as: the cluster farthest from base station in single-hop transmission and the closest cluster in multi-hop transmission. In addition, the maximal network lifetimes of single-hop and multi-hop transmissions are compared and it is found that there exists a threshold of network size that determines which transmission is the better candidate. © 2010 IEEE.

DOI： 10.1109/AICT.2010.67

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

Jun Naganawa, Kentaro Kobayashi, Masaaki Katayama, Takaya Yamazato

ISCIT 2010 - 2010 10th International Symposium on Communications and Information Technologies page： 974 - 979 2010

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

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. ©2010 IEEE.

DOI： 10.1109/ISCIT.2010.5665130

Performance Evaluation of Error-Correcting Scheme Without Redundancy Code for Noncoherent Chaos Communications Reviewed

Shintaro Arai, Yoshifumi Nishio, Takaya Yamazato, Shinji Ozawa

2010 IEEE INTERNATIONAL SYMPOSIUM ON CIRCUITS AND SYSTEMS page： 2458 - 2461 2010

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

This paper considers a novel error-correcting scheme exploiting chaotic dynamics for noncoherent chaos communication. 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. Further, enhanced efficiency also comes from operating on successively modulated data; by involving less redundancy in the error correction system, it can be designed with high coding rate. In this paper, we analyze the scheme's capability, by examining computational times and accuracy rates of error correction. bounds on its capability.

DOI： 10.1109/ISCAS.2010.5537140

Tracking an LED array transmitter for visible light communications in the driving situation Reviewed

Performance Evaluation of Error-Correcting Scheme Without Redundancy Code for Noncoherent Chaos Communications Reviewed

Arai Shintaro, Nishio Yoshifumi, Yamazato Takaya, Ozawa Shinji

2010 IEEE INTERNATIONAL SYMPOSIUM ON CIRCUITS AND SYSTEMS page： 2458 - 2461 2010

Toru Nagura, Takaya Yamazato, Masaaki Katayama, Tomohiro Yendo, Toshiaki Fujii, Hiraku Okada

Proceedings of the 2010 7th International Symposium on Wireless Communication Systems, ISWCS'10 page： 765 - 769 2010

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

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. © 2010 IEEE.

DOI： 10.1109/ISWCS.2010.5624361

B-17-3 Introduction of dirty paper coding for the cognitive piggyback overlay systems Reviewed

Naganawa Jun, Yamazato Takaya, Katayama Masaaki

Proceedings of the IEICE General Conference 2010

お熱いのがお好き Reviewed

山里敬也

電子情報通信学会　通信ソサイエティマガジン Vol. 2010 ( 15 ) page： 15_79 - 15_79 2010

UWB Positioning Using Known Indoor Features - Environment Comparison Reviewed

Jan Kietlinski-Zaleski, Takaya Yamazato

2010 INTERNATIONAL CONFERENCE ON INDOOR POSITIONING AND INDOOR NAVIGATION 2010

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

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 [1] 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.