Faculty Profiles - YAMAZATO Takaya

Papers - YAMAZATO Takaya

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

S. Nishimoto, T. Nagura, T. Yamazato, T. Yendo, T. Fujii, H. Okada, S. Arai

Technical Report of IEICE Vol. ITS2010-39 page： 89-94 2011.2

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

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

Technical Report of IEICE Vol. ITS2010-40 page： 95-99 2011.2

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

IEICE technical report Vol. 110 ( 420 ) page： 89 - 94 2011.2

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

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

IEICE technical report Vol. 110 ( 421 ) page： 89 - 94 2011.2

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

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

IEICE technical report Vol. 110 ( 421 ) page： 95 - 99 2011.2

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

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

IEICE technical report Vol. 110 ( 420 ) page： 95 - 99 2011.2

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

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

IEICE technical report Vol. 110 ( 420 ) page： 101 - 106 2011.2

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

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

IEICE technical report Vol. 110 ( 421 ) page： 101 - 106 2011.2

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

Channel Estimator by Sum of Kalman-Based Estimation and Interpolation Estimation for MC-CDMA based Inter-Vehicle Communication Reviewed

H. Hiraiwa, T. Yamazato, M. Katayama

IEICE Transactions on Communications Vol. J94-B ( 2 ) page： 304-307 2011.2

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

In Satellite Terrestrial Integrated Mobile Communication System, a single mobile terminal can communicate to both satellite and terrestrial communication systems depend upon his location, QoS and availability of resources among satellite and terrestrial communication systems. But it is hard to achieve high spectrum efficiency of Satellite Terrestrial Integrated Mobile Communication System using fixed resource allocation schemes because variation of satellite traffic and terrestrial traffic is different.

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

The Journal of the Institute of Television Engineers of Japan Vol. 65 ( 3 ) page： 354-360 2011.2

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

We propose a visible light road-to-vehicle communication system at intersection 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 communications. Here, the luminance value of the LEDs in 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.

Channel Estimator by Sum of Kalman-Based Estimation and Interpolation Estimation for MC-CDMA Based Inter-Vehicle Communication Reviewed

HIRAIWA Noriaki, YAMAZATO Takaya, KATAYAMA Masaaki

The IEICE transactions on communications B Vol. 94 ( 2 ) page： 304 - 307 2011.2

Improvement of the Node Activity Rate by Introduction of New Inactive Node Reactivation Condition in Solar-Powered Wireless Sensor Networks Reviewed

K. Ota, K. Kobayashi, T. Yamazato, M. Katayama

Technical Report of IEICE Vol. USN2010-63 page： 137-142 2011.1

Improvement of the Node Activity Rate by Introduction of New Inactive Node Reactivation Condition in Solar-Powered Wireless Sensor Networks Reviewed

OTA Kentaro, KOBAYASHI Kentaro, YAMAZATO Takaya, KATAYAMA Masaaki

IEICE technical report Vol. 110 ( 378 ) page： 137 - 142 2011.1

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

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 don't 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.

Erasure Coding for Road-to-Vehicle Visible Light Communication Systems Reviewed

H. Okada, T. Ishizaki, T. Yamazato, T. Yendo, T. Fujii

IEEE Intelligent Vehicular Communications System Workshop page： 970-974 2011.1

Language：English

In this paper, we focus on a road-to-vehicle visible light communication (VLC) system using LED traffic lights. In this system, an LED traffic light consists of a 2-dimensional LED array (2D LED array), and cars are equipped with high-speed 2-dimensional cameras (2D image sensors). An important issue of this system is frame loss. Sometimes, 2D image sensor in a car fails to get a frame. So as to mitigate the influence of frame loss, we propose to apply erasure coding to the road-to-vehicle VLC system. In the proposed system, a data sequence is encoded by LDPC code whose length is much longer than the size of 2D LED array. In addition, code synchronization is required for the proposed system. We also propose a code synchronization scheme, which makes use of error detection capability of LDPC code. We evaluate the performance of our proposed system, and show that it can recover frame loss for high SNR when less than 8 frames among total 18 frames are lost. In addition, we show that our proposed code synchronization scheme can ignore its errors.

Hierarchical Encoding System of Road-to-Vehicle Communication Reviewed

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

International Workshop on Advanced Image Technology (IWAIT2011) page： CD-ROM 2011.1

Language：English

In this paper, we propose the new visible light road-to-vehicle communication system. We use the LED traffic light as the transmitter and the high-speed camera on the vehicle as the receiver. In this system, the data is encoded hierarchically and assign with the each frequency components of the image. We use the DFT for hierarchical encoding considering channel characteristic and quantization of the luminance. The communication experiments were conducted to confirm the effectiveness of the proposed method.

Parallel Communication Using Visually Non-Lighting LEDs Reviewed

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

International Workshop on Advanced Image Technology (IWAIT2011) page： CD-ROM 2011.1

Language：English

Previous studies on visible light communication uses visually lighting LEDs. However, LEDs are not always lighting. In this paper, we propose visible light communication method using visually non-lighting LEDs. This method enables us to communicate in different situations, e.g. using visually non-lighting tail lamps of cars or visually non-lighting traffic lights. We realize visually non-lighting LEDs by reducing luminescence energy of LEDs according to the brightness in the environment. To reduce luminescence energy of LEDs, we reduce the number of emitting LEDs, increase the interval of emitting, and decrease the luminance of emitting LEDs. In our research we consider the case that the transmitter is tail lamps of cars and the receiver is high-speed camera. We conduct two types of experiments to demonstrate the performance of the proposed system. One is to confirm that LEDs are visually non-lighting. The other is measurement of Bit Error Rate of communication using visually non-lighting LEDs. Experimental results demonstrate that it is possible to make communication using visually non-lighting LEDs. In our future work, we plan to use different sensor devices such as photo diode or CCD in order to decrease the error rate in communication.

Image Processing Based Road-to-vehicle Visible Light Communication Reviewed

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

International Workshop on Advanced Image Technology (IWAIT2011) page： CD-ROM 2011.1

Language：English

Visible Light Communication(VLC) has been introduced as a new wireless communication method. In this paper, we propose a VLC system for Intelligent Transport System (ITS) to communicate between infrastructure and the vehicle. In this system, we use a LED array as a transmitter and on-vehicle high speed camera as a receiver. Here, LEDs in the transmitter emit light in 500Hz and the emission patterns are used to achieve communication, by capturing them using the high speed camera in high frame rate. The images captured by high speed camera are processed to find the transmitter, track the found transmitter, and capture the emission pattern of transmitter in consecutive frames. In our previous work, we proposed algorithms to finding and tracking. In this paper, we introduce method to capture the emission pattern of the transmitter. Then out door communication experiments were conducted to confirm the effectiveness of the proposed VLC system.

9-217 Messages provided by a teacher that can be read from the Nagoya Univeristy OCW Reviewed

Yamazato Takaya

Proceedings of Annual Conference of Japanese Society for Engineering Education Vol. 2011 ( 0 ) page： 440 - 441 2011

Cooperative Transmission Scheme with Inactive Node Reactivation Condition for Solar-Powered Wireless Sensor Networks Reviewed

Ota Kentaro, Kobayashi Kentaro, Yamazato Takaya, Katayama Masaaki

2011 IEEE 22ND INTERNATIONAL SYMPOSIUM ON PERSONAL INDOOR AND MOBILE RADIO COMMUNICATIONS (PIMRC) page： 2384 - 2388 2011

Cooperative Transmission Scheme with Inactive Node Reactivation Condition for Solar-Powered Wireless Sensor Networks Reviewed

Kentaro Ota, Kentaro Kobayashi, Takaya Yamazato, Masaaki Katayama

2011 IEEE 22ND INTERNATIONAL SYMPOSIUM ON PERSONAL INDOOR AND MOBILE RADIO COMMUNICATIONS (PIMRC) page： 2384 - 2388 2011

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

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

DOI： 10.1109/PIMRC.2011.6139948

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Papers - YAMAZATO Takaya