Papers - YAMAZATO Takaya

A-17-16 Preliminary Study on NLOS V2V Visible Light Communication Using Retroreflective Traffic Control Devices Reviewed

TAKADA Takuma, YAMAZATO Takaya, OKADA Hiraku, FUJII Toshiaki, ARAI Shintaro, YENDO Tomohiro, KAMAKURA Koji

Proceedings of the IEICE General Conference   Vol. 2015   page： 249   2015.2

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

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A-2-18 Performance Evaluation of Stochastic Resonance Receiver in BPSK and OOK Modulations Reviewed

TANAKA Hiroya, CHIGA Keita, YAMAZATO Takaya, TADOKORO Yukihiro, ARAI Shintaro

Proceedings of the IEICE General Conference   Vol. 2015   page： 49   2015.2

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

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Investigation on Relationship Between Communication Distance and Receiving Characteristics in Image-Sensor-Based Visible Light Communication Reviewed

Y. Ohira, E. Souke, S. Arai, T. Yamazato, T. Yendo, H. Okada, T. Fujii and K. Kamakura

Proceedings of 2015 RISP International Workshop on Nonlinear Circuits, Communications and Signal Processing (NCSP'15)     page： 274-277   2015.2

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Language：English  

The present paper considers receiving characteristics of an image-sensor-based visible light communication (VLC) using an LED and a high-speed-image sensor. In general, a size of LED on an image decreases with increasing a communication distance. In this case, the receiver is difficult to recover data because the intensity of brightness of LED (i.e., luminance) cannot be enough recognized from the image. However, the previous studies about the image-sensor-based VLC have not enough discussed the communication distance and the recognition of LED on the image, i.e., the receiving characteristics. We focus on the communication distance and investigates the relationship between the distance and the receiving characteristics in the image-sensor-based VLC.

Outdoor Road-to-Vehicle Visible Light Communication Using On-Vehicle High-Speed Camera Reviewed

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

International Journal of Intelligent Transportation Systems Research   Vol. 13 ( 1 ) page： 28-36   2015.1

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We propose a road-to-vehicle Visible Light Communication (VLC) system for ITS. Here, the communication between road and a vehicle is approached using an LED array as a transmitter and an on-vehicle high-speed camera as a receiver. Modulation is conducted at the transmitter by blinking LEDs in high frequency and demodulation is conducted at the receiver by capturing the blinking patterns of the transmitter, by processing the high-speed camera images captured in high frame rate. This paper proposes an effective image processing method for capturing those blinking patterns. Out door communication experiments of the proposed VLC system are also present.

Image sensor based visible light communication Reviewed

Shinichiro Haruyama, Takaya Yamazato

Visible Light Communication     page： 181 - 205   2015.1

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Language：English   Publishing type：Part of collection (book)   Publisher：Cambridge University Press  

Overview Image sensors are used in digital cameras and a large number of imaging devices for industrial, media, medical, and consumer electronics applications. An image sensor consists of a number of pixels
each pixel contains a photodiode (PD), which is generally used as a receiver in visible light communications (VLC). Thus, an image sensor consisting of a number of pixels can also be used as a VLC receiver. A particular advantage of using image sensors, due to the massive number of available pixels, is the ability to spatially separate sources. Owing to the spatial separation of multiple sources, the VLC receiver uses only the pixels that sense LED transmission sources, discarding other pixels, including those sensing ambient noise. The ability to spatially separate sources also provides an additional feature to VLC, i.e., the ability to receive and process multiple transmitting sources. In this chapter, we introduce VLC using an image sensor [1]. After presenting an overview of image sensors in Section 9.2, we introduce the use of an image sensor as a VLC receiver in Section 9.3. We provide a design of an image sensor based VLC system in Section 9.4. In Sections 9.5 and 9.6, we respectively introduce the following two unique applications of VLC systems using an image sensor: (1) massively parallel visible light transmission that can theoretically achieve a maximum data rate of 1.28 Gigabits per second
and (2) accurate sensor pose estimation that cannot be realized by a VLC system using a single-element PD. Applications of image sensor based communication are also presented in Section 9.7 for traffic signal communication, position measurements in civil engineering, and bridge position monitoring. Finally, in Section 9.8, we summarize our conclusions.

DOI： 10.1017/CBO9781107447981.009

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Intensity Estimation of LEDs from Spatially and Temporally Mixed Images in Image Sensor Communication Reviewed

Takazumi Asai, Daigo Iwase, Ryoko Ieki, Tomohiro Yendo, Shintaro Arai, Takaya Yamazato, Hiraku Okada, Toshiaki Fujii, Koji Kamakura

2015 ASIA-PACIFIC SIGNAL AND INFORMATION PROCESSING ASSOCIATION ANNUAL SUMMIT AND CONFERENCE (APSIPA)     page： 877 - 883   2015

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

We focus on the road-to-vehicle visible light communication that system is composed of LED matrix as transmitter and high-speed camera as receiver. In proposed method, there are two problems. First problem is in case of long distance. It is difficult to receive data correctly because neighboring LEDs on the received image are merged due to less number of pixels and/or blurring by defocus. In this paper, we propose estimation method of LED intensity from merged image. We evaluated the method by measuring Bit Error Rate and confirmed effectiveness of the method. We also performed real time communication and succeeded to extend communication distance from the previous work by applying the method. Second problem is that, the transmitting rate has been reduced to half of the frame rate of the camera, to avoid intersymbol interference because of exposure time of camera frame. We propose a method to improve the communication rate. The transmitting rate is set same to receiver's frame rate, and the sent data is estimated from pattern mixed image. Using 8b/10b encoding instead of conventional reversal pattern to reduce the flickering of transmitter's lighting is also proposed.

DOI： 10.1109/APSIPA.2015.7415396

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Novel Demodulation Scheme Based on Blurred Images for Image-Sensor-Based Visible Light Communication Reviewed

Yuki Ohira, Shintaro Arai, Tomohiro Yendo, Takaya Yamazato, Hiraku Okada, Toshiaki Fujii, Koji Kamakura

2015 IEEE GLOBECOM WORKSHOPS (GC WKSHPS)     page： 1 - 6   2015

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

This paper proposes a novel data detection scheme based on the occurrence of blurred output images in image-sensor-based visible light communication systems. This system's receiver suffers from an inability to detect correct LED luminance values and demodulation of data because the captured image blurs owing to defocusing. The proposed method assumes that the light emitted by all LEDs that is diffused by the blur can be approximated by applying a Gaussian filter and expresses all LED luminance values as convolution equations based on this diffusion of the LED light. We estimate each LED light's condition by simultaneously solving these convolution equations and recover data according to the estimated result. To confirm the accuracy of the proposed method, we conduct computer simulations and an implementation experiment to evaluate the bit error rate performance of the proposed method.

DOI： 10.1109/GLOCOMW.2015.7414144

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Layered Space-Time Coding Using LED Array for Image-Sensor-Based Visible Light Communications Reviewed

Katsunori Ebihara, Koji Kamakura, Takaya Yamazato

2015 IEEE INTERNATIONAL CONFERENCE ON COMMUNICATIONS (ICC)   Vol. 2015-September   page： 5048 - 5053   2015

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

This paper demonstrates the feasibility of layered space-time coding (STC) in an outdoor image-sensor-based (IS-based) visible light communication (VLC) system. We examined that for low-resolution IS-based VLC channel where intensity modulated signals from two different light emitting diodes (LEDs) are detected at one pixel on the image plane, STC allows to decouple them, thus receiving data with no errors. Consequently, STC offers extending the transmission distance. In the layered STC presented here, additional bit streams are aligned in the 2(n) x 2(n) LED array for increasing the transmission rate per symbol duration for the case where the spatial resolution is improved. A prototype of three layered STC is built with an 8 x 8 LED array, where each of the LEDs is modulated at 1 kbps and a high-speed camera with IS operating at 1000 fps. Our experimental results validate that additional bit streams (layer-2 and -3), aligned in the layer-1 STC matrix pair, are extracted with no errors when the receiver comes within 155m and 55 m, respectively, from the LED array, without decreasing 210m of the transmission distance of layer-1 bit stream.

DOI： 10.1109/ICC.2015.7249124

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Development of add-on stochastic resonance device for the detection of subthreshold RF signals Reviewed

Keita Chiga, Hiroya Tanaka, Takaya Yamazato, Yukihiro Tadokoro, Shintaro Arai

Nonlinear Theory and Its Applications, IEICE   Vol. 6 ( 4 ) page： 520 - 533   2015

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DOI： 10.1587/nolta.6.520

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Intensity Estimation of LEDs from Spatially and Temporally Mixed Images in Image Sensor Communication Reviewed

Asai Takazumi, Iwase Daigo, Ieki Ryoko, Yendo Tomohiro, Arai Shintaro, Yamazato Takaya, Okada Hiraku, Fujii Toshiaki, Kamakura Koji

2015 ASIA-PACIFIC SIGNAL AND INFORMATION PROCESSING ASSOCIATION ANNUAL SUMMIT AND CONFERENCE (APSIPA)     page： 877 - 883   2015

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LED Acquisition Methods for Image-Sensor-Based Visible Light Communication Reviewed

Shintaro Arai, Takaya Yamazato, Hiraku Okada, Toshiaki Fujii, Tomohiro Yendo

2015 OPTO-ELECTRONICS AND COMMUNICATIONS CONFERENCE (OECC)     2015

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

This invited paper focuses on a high-speed image sensor as a visible light communication (VLC) reception device to develop the intelligent transport systems (ITS) application using VLC technique. We refer to the VLC using a high-speed image sensor as image-sensor-based VLC. A major advantage of the image sensor is the ability to spatially separate multiple sources. Based on this ability, we proposed several methods for the image-sensor-based VLC in our previous researches. Especially, we focused on unique characteristics of the image sensor and proposed the hierarchical coding and the overlay coding to improve the data reception performance. However, to perform the image-sensor-based VLC in an actual environment, the receiver has to acquire the VLC transmitter from captured images before recovering data. Namely, the VLC transmitter acquisition and tracking are critical problem. the image-sensor-based VLC technique. This invited paper introduces two proposed methods to acquire the VLC transmitter from images captured by the image sensor.

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LED Acquisition Methods for Image-Sensor-Based Visible Light Communication Reviewed

Arai Shintaro, Yamazato Takaya, Okada Hiraku, Fujii Toshiaki, Yendo Tomohiro

2015 OPTO-ELECTRONICS AND COMMUNICATIONS CONFERENCE (OECC)     2015

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Layered Space-Time Coding Using LED Array for Image-Sensor-Based Visible Light Communications Reviewed

Ebihara Katsunori, Kamakura Koji, Yamazato Takaya

2015 IEEE INTERNATIONAL CONFERENCE ON COMMUNICATIONS (ICC)     page： 5048 - 5053   2015

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Novel Demodulation Scheme Based on Blurred Images for Image-Sensor-Based Visible Light Communication Reviewed

Ohira Yuki, Arai Shintaro, Yendo Tomohiro, Yamazato Takaya, Okada Hiraku, Fujii Toshiaki, Kamakura Koji

2015 IEEE GLOBECOM WORKSHOPS (GC WKSHPS)     2015

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Web of Science

Outdoor road-to-vehicle visible light communication using on-vehicle high-speed camera Reviewed

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

International Journal of Intelligent Transportation Systems Research   Vol. 13 ( 1 ) page： 28 - 36   2015

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Springer New York LLC  

We propose a road-to-vehicle Visible Light Communication (VLC) system for ITS. Here, the communication between road and a vehicle is approached using an LED array as a transmitter and an on-vehicle high-speed camera as a receiver. Modulation is conducted at the transmitter by blinking LEDs in high frequency and demodulation is conducted at the receiver by capturing the blinking patterns of the transmitter, by processing the high-speed camera images captured in high frame rate. This paper proposes an effective image processing method for capturing those blinking patterns. Out door communication experiments of the proposed VLC system are also present.

DOI： 10.1007/s13177-014-0079-y

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Optical Camera Communications Using Digital Signage Reviewed

OKADA Hiraku, SATO Sho, WADA Tadahiro, YAMAZATO Takaya, KATAYAMA Masaaki

ITE Technical Report   Vol. 39 ( 0 ) page： 21 - 24   2015

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

In this paper, we discuss optical cammera communication systems using digital signage, which is composed of a liquid crystal display (LCD). The digital signage, which is used as a transmitter, displays advertisement contents as visual information. The optical camera communication system using digital signage has to transmit data information not to obstruct the visual information. In this paper, we propose blue color difference modulation for the optical camera communication system using digital signage. We clarify the performance of the proposed system by data transmission experiments.

DOI： 10.11485/itetr.39.38.0_21

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Cooperative Diversity via Simple Relaying with Quasi-Orthogonal Space-Time Block Code Reviewed

T. Yamaoka, Y. Hara, K. Ishioka, T. Hara, T. Yamazato

IEICE Transaction on Communication     page： -   2014.12

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

We have been proposed cooperative diversity receiving ABBA code as cooperative diversity via simple relaying with QOSTBC(Quasi-Orthogonal Space-Time Block Code). This scheme offers codinggain by permutation of space-time coded signal sequences in the relay nodes. So the relay nodes don't need carrier recovery and complete the signal process in the intermediate frequency band. In this paper we discuss two improved scheme with various channel model. These schemes improve the previous scheme without loss of the merit in its relay process. Moreover we sum up cooperative diversity via simple relaying with QOSTBC to discuss these schemes with various channel model. We evaluate effect of these scheme in terms of signal matrixes and simulate bit error rate of the prposed and improved scheme with with various channel model, respectively.

Alamouti-Type Space Time Coding for Visible Light Communication Based on Direct Detection Using Image Sensor Reviewed

Y. Amano, K. Kamakura, T. Yamazato

IEICE Transactions on Communications (to be published)     page： -   2014.12

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

This paper proposes Alamouti-type space time (ST) coding to visible light communication (VLC) using light emitting diodes (LEDs) and image sensor-based direct detection with a high-speed camera. Although multiple LEDs of an array are used as transmitters to communicate to individual pixel elements of an image sensor which act as multiple receive elements, the received signal is essentially the image of the transmitting element, whose size in pixel reduces with distance. When the receiver captures the LED array at a distance where images of two neighboring LEDs in the array are not separated at the image plane, such distortion depreciates the symbol decision quality. Our proposed scheme aims at expanding the communication range limited by the pixel resolution of image sensor. Our implemented prototype demonstrates that ST coding is feasible to achieve 48-meter error-free transmission range while the repetition transmission achieves 26-meter error-free range.

Motion Modeling of Mobile Transmitter for Image Sensor Based I2V-VLC, V2I-VLC, and V2V-VLC Reviewed

M. Kinoshita, T. Yamazato, H, Okada, T. Fujii, S. Arai, T. Yendo, K. Kamakura

IEEE Workshop on Optical Wireless Communications     page： -   2014.12

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

Visible light communication (VLC) using light-emitting diodes (LEDs) is drawing much attention. There are two types of VLC reception devices, a photodiode and an image sensor. VLC using image sensor is called image sensor based VLC. As the receiver only uses the image sensor pixels that sense LED transmission sources and discards other pixels, including those sensing noise sources, image sensor based VLC is an attractive solution for outdoor mobile applications. However, little evidence is available for channel modeling of image sensor based VLC in mobile outdoor environments, especially for motion modeling of VLC transmitter. In this paper, we propose a motion model of VLC transmitter. In particular, we consider three cases; infrastructure-to-vehicle VLC (I2V-VLC), vehicle-to-infrastructure VLC (V2I-VLC), and vehicle-to-vehicle VLC (V2V-VLC). As a result, we show that the motion model of the VLC transmitter on the captured image for the three aforementioned situations (i.e., I2V-VLC, V2I-VLC, and V2V-VLC) can be expressed in the identical pinhole camera model.

Cooperative Diversity via Simple Relaying with Quasi-Orthogonal Space-Time Block Code Reviewed

Tomoya YAMAOKA, Yoshitaka HARA, Kazuaki ISHIOKA Teruyuki HARA, Takaya Yamazato

IEICE Transactions on Communications   Vol. J97-B ( 12 ) page： 1213-1223   2014.12

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

We have been proposed cooperative diversity receiving ABBA code as cooperative diversity via simple relaying with QOSTBC(Quasi-Orthogonal Space-Time Block Code). This scheme offers coding gain by permutation of space-time coded signal sequences in the relay nodes. So the relay nodes don't need carrier recovery and complete the signal process in the intermediate frequency band. In this paper, we discuss two improved scheme with various channel model. These schemes improve the previous scheme without loss of the merit in its relay process. Moreover, we sum up cooperative diversity via simple relaying with QOSTBC to discuss these schemes with various channel model. We evaluate effect of these scheme in terms of signal matrixes and simulate bit error rate of the prposed and improved scheme with with various channel model, respectively.