Faculty Profiles - YAMAZATO Takaya

Papers - YAMAZATO Takaya

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LED Traffic Light Detection Using High-speed-camera Image Processing for Visible Light Communication Reviewed

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

Information and Media Technologies Vol. 6 ( 3 ) page： 785 - 791 2011

Publishing type：Research paper (scientific journal) Publisher：Information and Media Technologies 編集運営会議

We propose a visible light road-to-vehicle communication system at intersections as an ITS(Intelligent Transport System) technique. 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 at high frequency, and those emitted light is captured by the high-speed camera for communication. Here, the luminance value of the LEDs in the transmitter should be captured in consecutive frames to achieve communication. For this purpose, first the transmitter should be found, and then it should be tracked in consecutive frames while the vehicle is moving by processing the images from the high-speed camera. In this paper, we propose new algorithms for finding and tracking the transmitter, which result in increased communication speed and data rate compared to the previous methods. Experiments using appropriate images showed the effectiveness of the proposals.

DOI： 10.11185/imt.6.785

Overlay Coding for Visible Light Communication using LED Array and High-Speed Camera Reviewed

NISHIMOTO Sayaka, NAGURA Toru, YAMAZATO Takaya, YENDO Tomohiro, FUJII Toshiaki, OKADA Hiraku, ARAI Shintaro

ITE Technical Report Vol. 35 ( 0 ) page： 89 - 94 2011

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

In this paper, we discuss on visible light communications using an LED array as the transmitter and a highspeed camera as the receiver. A challenge is that the longer the distance between the transmitter and the receiver, the more reduction in the resolution of the receive image occurs. To solve the problem, we allocate high priority data to low frequency components of spatial frequency. Then, we can receive high priority data even if the receiver is far from the transmitter. For that, we have used the Wavelet transform in our previous researches. However, the conventional scheme limits the number and the disposition of LEDs which can be allocated data. In other words, the hierarchical coding using the Wavelet transform has a low degree of freedom of design. In this paper, to improve a degree of freedom of design, we propose the overlay coding which does not limit the number and the disposition of LEDs.

DOI： 10.11485/itetr.35.9.0_89

Performance Improvement with the Inverted Signal to Track an LED Array Transmitter on Road-to-Vehicle Visible Light Communications Reviewed

NAGURA Toru, YAMAZATO Takaya, YENDO Tomohiro, FUJII Toshiaki, OKADA Hiraku

ITE Technical Report Vol. 35 ( 0 ) page： 95 - 99 2011

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

In this paper, we consider road-to-vehicle visible light communication systems on driving situation using a LED array transmitter and a high-speed camera receiver. In our previous research, we have proposed inverted signal to track an LED array transmitter. We propose decoding method with inverted signal to improve BER performance. Furthermore, we confirm that we can suppress the flicker of LED in PDF.

DOI： 10.11485/itetr.35.9.0_95

Overlay Coding for Road-to-Vehicle Visible Light Communication using LED Array and High-Speed Camera Reviewed

Nishimoto Sayaka, Nagura Toru, Yamazato Takaya, Yendo Tomohiro, Fujii Toshiaki, Okada Hiraku, Arai Shintaro

2011 14TH INTERNATIONAL IEEE CONFERENCE ON INTELLIGENT TRANSPORTATION SYSTEMS (ITSC) page： 1704 - 1709 2011

Overlay Coding for Road-to-Vehicle Visible Light Communication using LED Array and High-Speed Camera Reviewed

Sayaka Nishimoto, Toru Nagura, Takaya Yamazato, Tomohiro Yendo, Toshiaki Fujii, Hiraku Okada, Shintaro Arai

2011 14TH INTERNATIONAL IEEE CONFERENCE ON INTELLIGENT TRANSPORTATION SYSTEMS (ITSC) page： 1704 - 1709 2011

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

This paper aims to improve the visible light communication system using LED array and high-speed camera by proposing what we call "overlay coding". "Overlay coding" is a new coding method to realize a hierarchical coding, through which a high-priority data can be received even if the receiver is far from a transmitter. Conventionally, the hierarchical coding has been realized through the wavelet transform that has a limitation of number and disposition of LEDs, and as a result it does not always match with the design of the transmitters (e.g. traffic lights, etc.) used in real life. To solve the limitation problem, we propose a more flexible way of designing the application of LEDs depending on the transmitters. In particular, overlay coding is realized through the procedures of coding and decoding. In coding, we replace one LED with a flexible number of LEDs, and the number depends on whether the data is high-priority or low-priority, then high-priority data and low-priority data are overlaid (section III-B1). In decoding, we first obtain the high-priority data, and then the low-priority data using retrieved high-priority data (section III-B2). The experimental result shows that the distance for receiving error-free data is extended from 30m to 70m in the overlay coding (section IV-B).

DOI： 10.1109/ITSC.2011.6082943

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High-Speed LED Traffic Sign Tracking Method Using Image Sensor with High-Speed Capturing Ability of Partial Area Reviewed

MAENO Keita, YENDO Tomohiro, PANAHPOUR TEHRANI Mehrdad, FUJII Toshiaki, YAMAZATO Takaya, OKADA Hiraku, TANIMOTO Masayuki

ITE Technical Report Vol. 35 ( 0 ) page： 101 - 106 2011

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

Visible Light Communication (VLC) using LEDs has been proposed as a wireless communication method. As an application of VLC in ITS, we propose a road-to-vehicle visible light communication system using an LED traffic sign as a transmitter and an image sensor as a receiver. For conducting the communication, it is necessary to have high-speed tracking of the LED traffic sign by the image sensor. In this paper, we propose new high-speed tracking method for this system.

DOI： 10.11485/itetr.35.9.0_101

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TDOA UWB positioning with three receivers using known indoor features Reviewed

Kietlinski-Zaleski J.

2010 IEEE International Conference on Ultra-Wideband, ICUWB2010 - Proceedings Vol. 2 2010.12

Dynamic Bandwidth Allocation of Satellite/Terrestrial Integrated Mobile Communication System Reviewed

T. Yamazato, T. Aman, M. Katayama

IEEE Global Communications Conference page： CD-ROM 2010.12

Language：English

In this paper, we propose two dynamic bandwidth allocation (DBA) schemes, a game theory based DBA and a successive DBA, for satellite/terrestrial integrated mobile communication system (STICS). The game theory based DBA allocate the bandwidth according to a utility function based on a weighted demand bandwidth of both satellite and terrestrial system. The successive DBA recursively allocates an unit of bandwidth according to a weighted number of bandwidth unfilled cells of both satellite and terrestrial systems, until the total bandwidth is fulfilled. As results, both DBA outperform the conventional fixed bandwidth allocation scheme. Between two proposed DBA, the successive DBA shows better spectral improvement ratio than the game theory based DBA.

LED Traffic Light Detection Using High-speed-camera Image Processing for Visible Light Communication System, Reviewed

H. C. N. Premachandra, T. Yendo, M. P. Tehrani, T. Yamazato, H. Okada, T. Fujii, M. Tanimoto

Workshop on Picture Coding and Image Processing, PCSJ2010/IMPS2010 page： CD-ROM 2010.12

Language：English

Intelligent transport system has been introduced to reduce traffic problems such traffic accidents and traffic congestions. In this paper, we introduce a receiver for a road to vehicle Visible Light Communication (VLC) system which is proposed as an Intelligent Transport System (ITS) technique. In this system, an on-vehicle high-speed camera is used as a receiver and an LED array is used as a transmitter. VLC is a wireless communication using luminance. Here, transmitter send information by emitting light and receiver receive them by capturing the luminance of emitting LEDs in the array(Luminance: whether each LED is on or off). For capturing the Luminance, it is necessary to find the transmitter and track it in consecutive frames. In our previous works we introduced methods for finding and tracking. In this paper, we shortly explain the proposed transmitter finding and tracking methods and then a new method is proposed for capturing the luminance of LEDs to achieve communication.

Parallel Visible Light Communication Using Visually Non-Lighting LEDs Reviewed

K. Maeno, T. Yendo, M. P. Tehrani, T. Fujii, T. Yamazato, H. Okada, M. Tanimoto

Workshop on Picture Coding and Image Processing, PCSJ2010/IMPS2010 page： CD-ROM 2010.12

Language：English

Our goal is improvement of the node activity rate in solar-powered wireless sensor networks. One method to reduce the consumption energy of the entire network is a cooperative transmission that uses a relay node when a node sends data. But if we do not consider the change in harvesting energy, the node activity rate is declined during nighttime. In this paper, we smooth the day-and-night node activity rate by introducing the new inactive node reactivation condition and achieve the required high node activity rate.

Hierarchical Encoding System for Road-to-Vehicle Communication Using LED Traffic Light Reviewed

T. Masuda, T. Yendo, T. Yamazato, H. Okada, M. P. Tehrani, T. Fujii, M. Tanimoto

Workshop on Picture Coding and Image Processing, PCSJ2010/IMPS2010 page： CD-ROM 2010.12

Language：English

This paper discusses the visible light road-to-vehicle communication system at intersection as one of ITS (Intelligent Transport System) technique. The communication between a vehicle and an LED traffic light is approached using an LED traffic light as a transmitter, and on-vehicle high-speed camera as a receiver. In this system, it is able to send data by blinking the LEDs of the traffic light in two dimensional patterns, and able to receive them by high-speed camera with image processing [1]. Here, we aim to conduct long-distance high-speed visible light communication. When the distance between transmitter and receiver is far, the image of the LED traffic light captured by on-vehicle high-speed camera is very small. So, if the data are put on two dimension patterns without modification, data would be mistaken, because the two dimension patterns can't be realized correctly. To solve this problem, data are encoded hierarchically before they are lighted by the LED traffic light. This is called as hierarchical encoding that the data are assigned with each spatial frequency.

[Encouragement Talk] Distributed Error Correcting Coding and Joint Decoding Scheme Using Spatial Correlation of Sensor ADC Output in Wireless Sensor networks Invited

K. Kobayashi, T. Yamazato, M. Katayama

Technical Report of IEICE Vol. WBS2010-39 page： 23-28 2010.12

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

K. Kobayashi, T. Yamazato, M. Katayama

IEICE Transactions on Communications Vol. E93-B ( 12 ) page： 3509-3513 2010.12

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

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, 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.

TOA UWB Positioning with Two Receivers Using Known Indoor Features Reviewed

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

IEICE Transactions on Communications Vol. E93-B ( 12 ) page： 3624-3631 2010.12

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

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 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.

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

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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

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UWB positioning using known indoor features- Environment comparison Reviewed

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.

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Papers - YAMAZATO Takaya