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收集所有交通大學研究人員與學生個人或團體所發表之各項學術著作，涵蓋期刊論文、教師專書、學位論文等項。;;Collections of Publications of NCTU Researchers and Students Like Journal Papers and Thesis.

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Author: search.filters.author.Chen, Shih-Hao

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Now showing 1 - 10 of 22
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    Comparison of thresholding schemes for visible light communication using mobile-phone image sensor
    (2016-02-08)
    Liu, Yang
    ;
    Chow, Chi-Wai
    ;
    Liang, Kevin
    ;
    Chen, Hung-Yu
    ;
    Hsu, Chin-Wei
    Based on the rolling shutter effect of the complementary metal-oxide-semiconductor (CMOS) image sensor, bright and dark fringes can be observed in each received frame. By demodulating the bright and dark fringes, the visible light communication (VLC) data logic can be retrieved. However, demodulating the bright and dark fringes is challenging as there is a high data fluctuation and large extinction ratio (ER) variation in each frame due. Hence proper thresholding scheme is needed. In this work, we propose and compare experimentally three thresholding schemes; including third-order polynomial curve fitting, iterative scheme and quick adaptive scheme. The evaluation of these three thresholding schemes is performed. (C) 2016 Optical Society of America
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    Color-filter-free spatial visible light communication using RGB-LED and mobile-phone camera
    (2014-12-15)
    Chen, Shih-Hao
    ;
    Chow, Chi-Wai
    ;
    光電工程學系
    ;
    光電工程研究所
    ;
    Department of Photonics
    A novel color-filter-free visible-light communication (VLC) system using red-green-blue (RGB) light emitting diode (LED) and mobile-phone camera is proposed and demonstrated for the first time. A feature matching method, which is based on the scale-invariant feature transform (SIFT) algorithm for the received grayscale image is used instead of the chromatic information decoding method. The proposed method is simple and saves the computation complexity. The signal processing is based on the grayscale image computation; hence neither color-filter nor chromatic channel information is required. A proof-of-concept experiment is performed and high performance channel recognition is achieved. (C) 2014 Optical Society of America
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    Color-Shift Keying and Code-Division Multiple-Access Transmission for RGB-LED Visible Light Communications Using Mobile Phone Camera
    (2014-12-01)
    Chen, Shih-Hao
    ;
    Chow, Chi-Wai
    ;
    光電工程學系
    ;
    光電工程研究所
    ;
    Department of Photonics
    Light-emitting diodes (LEDs) have been deployed for various applications in our daily lives. Similarly, image sensors or cameras integrated into mobile phones have become common. Hence, visible light communication (VLC) using LED and mobile phone cameras is attractive and provides low-cost wireless communication. In this paper, we propose and demonstrate a VLC system using color-shift-keying (CSK) modulation and code-division multiple-access (CDMA) technology simultaneously for the first time; a mobile phone camera is used as the receiver (Rx). CSK is used to enhance the VLC system capacity and to mitigate the single color light interference, whereas CDMA allows multiple users to access the network. The system design and operation mechanism of the proposed CSK-CDMA VLC system are discussed. A proof-of-concept demonstration is performed, and error-free transmission is achieved for multiple-access users. A 3-dB transmission gain is also obtained in each user when compared with the traditional on-off keying (OOK) modulation.
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    Visible light communication using mobile-phone camera with data rate higher than frame rate
    (2015-10-05)
    Chow, Chi-Wai
    ;
    Chen, Chung-Yen
    ;
    Chen, Shih-Hao
    ;
    光電工程學系
    ;
    光電工程研究所
    Complementary Metal-Oxide-Semiconductor (CMOS) image sensors are widely used in mobile-phone and cameras. Hence, it is attractive if these image sensors can be used as the visible light communication (VLC) receivers (Rxs). However, using these CMOS image sensors are challenging. In this work, we propose and demonstrate a VLC link using mobile-phone camera with data rate higher than frame rate of the CMOS image sensor. We first discuss and analyze the features of using CMOS image sensor as VLC Rx, including the rolling shutter effect, overlapping of exposure time of each row of pixels, frame-to-frame processing time gap, and also the image sensor "blooming" effect. Then, we describe the procedure of synchronization and demodulation. This includes file format conversion, grayscale conversion, column matrix selection avoiding blooming, polynomial fitting for threshold location. Finally, the evaluation of bit-error-rate (BER) is performed satisfying the forward error correction (FEC) limit. (C)2015 Optical Society of America
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    Enhancement of Signal Performance in LED Visible Light Communications Using Mobile Phone Camera
    (2015-10-01)
    Chow, Chi-Wai
    ;
    Chen, Chung-Yen
    ;
    Chen, Shih-Hao
    ;
    光電工程學系
    ;
    光電工程研究所
    Visible light communication (VLC) is attractive as a supplementary method for future fifth-generation (5G) wireless communication owing to the shortage of radio-frequency bandwidth in conventional wireless communications. The VLC systems reported in the literature are mainly based on PIN receivers (Rxs). It is highly desirable if these VLC signals can be detected by using built-in complementary metal-oxide-semiconductor (CMOS) cameras as Rxs to provide flexible and low-cost wireless communications. However, using the CMOS camera is challenging. In this paper, we propose and demonstrate a VLC link using a CMOS mobile phone camera as Rx. By using the rolling shutter effect of the CMOS sensor, the VLC data rate can be significantly enhanced. We first use a second-order polynomial fitting to mitigate the "blooming effect" (saturation of pixels) of the CMOS sensor. In order to extend the VLC transmission distance and mitigate the influence of the background noise, we also propose and demonstrate using histogram equalization and Sobel filter to enhance VLC signal performance. Finally, a third-order polynomial fitting is used to define the threshold. The experimental results show that significant improvement of bit error rate (BER) for about an order of magnitude under different illuminances can be achieved.
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    Passive Optical Receiver for Visible Light Communication (VLC)
    (2015-01-01)
    Chen, Hung-Yu
    ;
    Liang, Kevin
    ;
    Chen, Chung-Yen
    ;
    Chen, Shih-Hao
    ;
    Chow, Chi-Wai
    We demonstrate using solar cell as optical receiver (Rx) for visible light communication (VLC). The solar cell is low cost and can convert the VLC optical signal into electrical signal without external power supply. As the response of the solar cell is very limited; we also propose and demonstrate using predistortion to significantly enhance the response of the solar cell Rx. A VLC capacity of 0.4 Mbit/s at bit-error-rate (BER) of 10(-9) under wireless transmission distance of 75 cm; and a capacity of 0.3 Mbit/s at BER of 10-9 under wireless transmission distance of 125 cm can be achieved.
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    HIERARCHICAL SCHEME FOR DETECTION OF ROTATING MIMO VISIBLE LIGHT COMMUNICATION SYSTEMS USING MOBILE-PHONE CAMERA
    (2014-01-01)
    Chen, Shih-Hao
    ;
    Chow, Chi-Wai
    ;
    光電工程學系
    ;
    Department of Photonics
    Multiple-input and multiple-output (MIMO) scheme can extend the transmission capacity for the light-emitting-diode (LED) visible light communication (VLC) system. The MIMO VLC system using the popular mobile-phone camera as the optical receiver (Rx) to receive MIMO signal from n x n Red-Green-Blue (RGB) LED array is desirable. The key step of decoding the received RGB LED array signals is detecting the direction of received array signals. If the LED transmitter (Tx) is rotated, the signal may not be received correctly and cause an error in the received signal. In this work, we propose and demonstrate a novel hierarchical transmission scheme which can reduce the computation complexity of rotation detection in LED array VLC system. We use the n x n RGB LED array as the MIMO Tx. A novel two dimension Hadamard coding scheme is proposed and demonstrated. The detection correction rate is above 95% in the indoor usage distance. Experimental results confirm the feasibility of the proposed scheme.
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    DIRECT-DETECTION ALL-OPTICAL OFDM SUPERCHANNEL FOR LONG-REACH PON
    (2014-01-01)
    Chow, Chi-Wai
    ;
    Yeh, Chien-Hung
    ;
    Sung, Jiun-Yu
    ;
    Chen, Shih-Hao
    ;
    光電工程學系
    Orthogonal-frequency-division-multiplexing (OFDM) is a promising candidate for the future high-speed optical access networks. As the OFDM signal is electronically generated and demodulated by fast Fourier transform (FFT) in the digital domain via electronic digital-to-analog and analog-to-digital converters (DAC/ADC) respectively, the OFDM signal bandwidth is limited by the sampling rate of the DAC/ADC. In this work, we present the feasibility of using all-optical OFDM for the future high-speed PON. All-optical OFDM is another class of optical multiple carrier transmission that relies on all-optically generated or demodulated orthogonal subcarriers. Hence, high data rate can be easily achieved. A 200 Gb/s OFDMA-LR-PON using all-optical OFDM super-channel (SC) is demonstrated. Apart from the optical wired transmission, w-band (100-GHz) millimeter-wave (MMW) wireless transmission is also demonstrated to support the in-building mobile broadband services.
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    COLOR-FILTER-FREE WDM MIMO RGB-LED VISIBLE LIGHT COMMUNICATION SYSTEM USING MOBILE-PHONE CAMERA
    (2014-01-01)
    Chen, Shih-Hao
    ;
    Chow, Chi-Wai
    ;
    光電工程學系
    ;
    Department of Photonics
    Color-Filter-Free wavelength division multiplexing (WDM) Multiple-input and multiple-output (MIMO) Red-Green-Blue (RGB)-light emitting diode (LED) visible light communication (VLC) system using mobile-phone camera is proposed and demonstrated. Neither color filter nor chromatic color information is required in the proposed receiver (Rx). All image signal processing is based on the grayscale image, which can greatly simplify the WDM MIMO RGB-LED VLC system and save the cost of color splitting process. A proof-of-concept experiment is conducted. Optimized Scale-invariant feature transform (SIFT) algorithm is used to achieve the design.
  • Thumbnail Image
    Item type:Item,
    Color-Shift Keying and Code-Division Multiple-Access Transmission for RGB-LED Visible Light Communications Using Mobile Phone Camera
    (2014-12)
    Chen, Shih-Hao
    ;
    Chow, Chi-Wai
    ;
    光電工程學系
    ;
    Department of Photonics
    Light-emitting diodes (LEDs) have been deployed for various applications in our daily lives. Similarly, image sensors or cameras integrated into mobile phones have become common. Hence, visible light communication (VLC) using LED and mobile phone cameras is attractive and provides low-cost wireless communication. In this paper, we propose and demonstrate a VLC system using color-shift-keying (CSK) modulation and code-division multiple-access (CDMA) technology simultaneously for the first time; a mobile phone camera is used as the receiver (Rx). CSK is used to enhance the VLC system capacity and to mitigate the single color light interference, whereas CDMA allows multiple users to access the network. The system design and operation mechanism of the proposed CSK-CDMA VLC system are discussed. A proof-of-concept demonstration is performed, and error-free transmission is achieved for multiple-access users. A 3-dB transmission gain is also obtained in each user when compared with the traditional on-off keying (OOK) modulation.