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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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🏛️國立陽明交通大學機構典藏

Author: search.filters.author.Liu, YangSubject: search.filters.subject.Light emitting diode (LED)

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Now showing 1 - 7 of 7
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    Analysis of Non-Hermitian symmetry (NHS) IFFT/FFT size efficient OFDM for multiple-client non-orthogonal multiple access (NOMA) visible light communication (VLC) system
    (2020-10-01)
    Adnan, Assaidah
    ;
    Liu, Yang
    ;
    Chow, Chi-Wai
    ;
    Yeh, Chien-Hung
    ;
    交大名義發表
    Orthogonal-frequency-division-multiplexing (OFDM) format is widely deployed in visible-light-communication (VLC) systems due to its high spectral efficiency. To produce real-valued OFDM signal for VLC, Hermitian-symmetry (HS) is needed during the inverse-fast-Fourier-transform (IFFT) encoding process. However the HS requirement doubles the IFFT/FFT size and increase the encoding complexity. Non-Hermitian symmetry (NHS)-OFDM schemes are proposed, but they have different limitations. In this work, we propose and investigate a non-orthogonal multiple access (NOMA) VLC network serving 2, 3 or 4 clients simultaneously using NHS-OFDM IFFT/FFT size efficient (SE) OFDM format. Numerical analysis of signal amplitude effect to the bit-error-ratio (BER) performance for different users are performed, showing that the BER < 7% forward-error-correction (FEC) limit can be achieved as long as the required signal amplitude ratio of each user is fulfilled. We also compare the proposed system with a typical example of HS-OFDM modulation, i.e. direct-current optical (DCO)-OFDM NOMA-VLC system.
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    Angle-of-Arrival (AOA) Visible Light Positioning (VLP) System Using Solar Cells With Third-Order Regression and Ridge Regression Algorithms
    (2020-06-01)
    Hong, Chong-You
    ;
    Wu, Yu-Chun
    ;
    Liu, Yang
    ;
    Chow, Chi-Wai
    ;
    Yeh, Chien-Hung
    We put forward and demonstrate a angle-of-arrival (AOA) based visible-light-positioning (VLP) system using quadrant-solar-cell (QSC) and third-order ridge regression machine learning (RRML) to improve the positioning accuracy.
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    Demonstration of Non-Hermitian Symmetry (NHS) IFFT/FFT Size Efficient OFDM Non-Orthogonal Multiple Access (NOMA) for Visible Light Communication
    (2020-06-01)
    Assaidah, Assaidah
    ;
    Liu, Yang
    ;
    Chow, Chi-Wai
    ;
    Yeh, Ching-Hua
    ;
    交大名義發表
    We propose and experimentally demonstrate a non-orthogonal multiple access (NOMA) visible light communication (VLC) system using non-Hermitian symmetry (NHS) inverse-fast-Fourier-transform (IFFT)/FFT size efficient (SE) orthogonal frequency division multiplexing (OFDM). Fix power allocation and successive interference cancellation (SIC) algorithms are realized. The power ratio between different users, transmission distance, network cell coverage are investigated. The proposed scheme is also compared with the HS based direct-current optical (DCO)-OFDM NOMA-VLC system.
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    Performance enhancement technique of visible light communications using passive photovoltaic cell
    (2017-06-01)
    Wu, Jhao-Ting
    ;
    Chow, Chi-Wai
    ;
    Liu, Yang
    ;
    Hsu, Chin-Wei
    ;
    Yeh, Chien-Hung
    The light emitting diode (LED) based visible light communication (VLC) system can provide lighting and communication simultaneously. It has attracted much attenuation recently. As the photovoltaic cell (also known as solar cell) is physically flexible, low cost, and easily available, it could be a good choice for the VLC receiver (Rx). Furthermore, besides acting as the VLC Rx, the solar cell can convert VLC signal into electricity for charging up the Rx devices. Hence, it could be a promising candidate for the future internet-of-thing (IoT) networks. However, using solar cell as VLC Rx is challenging, since the response of the solar cell is highly limited and it will limit the VLC data rate. In this work, we propose and demonstrate for the first time using pre-distortion Manchester coding (MC) signal to enhance the signal performance of solar cell Rx based VLC. The proposed scheme can significantly mitigate the slow response, as well as the direct-current (DC) wandering effect of the solar cell; hence 50 times increase in data rate can be experimentally achieved.
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    Using pre-distorted PAM-4 signal and parallel resistance circuit to enhance the passive solar cell based visible light communication
    (2018-01-15)
    Wang, Hao-Yu
    ;
    Wu, Jhao-Ting
    ;
    Chow, Chi-Wai
    ;
    Liu, Yang
    ;
    Yeh, Chien-Hung
    Using solar cell (or photovoltaic cell) for visible light communication (VLC) is attractive. Apart from acting as a VLC receiver (Rx), the solar cell can provide energy harvesting. This can be used in self-powered smart devices, particularly in the emerging "Internet of Things (IoT)'' networks. Here, we propose and demonstrate for the first time using pre-distortion pulse-amplitude-modulation (PAM)-4 signal and parallel resistance circuit to enhance the transmission performance of solar cell Rx based VLC. Pre-distortion is a simple non-adaptive equalization technique that can significantly mitigate the slow charging and discharging of the solar cell. The equivalent circuit model of the solar cell and the operation of using parallel resistance to increase the bandwidth of the solar cell are discussed. By using the proposed schemes, the experimental results show that the data rate of the solar cell Rx based VLC can increase from 20 kbit/s to 1.25 Mbit/s (about 60 times) with the bit error-rate (BER) satisfying the 7% forward error correction (FEC) limit. (C) 2017 Elsevier B.V. All rights reserved.
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    Demonstration of Using Digital FIR Filter and Matched Filter to Increase Data Rate in Visible Light Communication
    (2013)
    Liu, Yu-Feng
    ;
    Yeh, Chien-Hung
    ;
    Chow, Chi-Wai
    ;
    Huang, Po-Yen
    ;
    Liu, Yang
    Using digital-filters in time domain are demonstrated to enhance the modulation-speed of 1 MHz bandwidth white LED communication. Digital FIR filter and matched filtering are used to reduce the inter-symbol-interference (ISI). Hence, 20-Mbps is achieved by using 4-ASK modulation.
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    QPSK Modulation for AC-Power-Signal-Biased Visible Light Communication System
    (2013)
    Liu, Yu-Feng
    ;
    Yeh, Chien-Hung
    ;
    Chow, Chi-Wai
    ;
    Liu, Yang
    ;
    光電工程學系
    With the integration of light emitting diode (LED), visible light communication (VLC) can provide wireless communication link using the lightning system. Due to the consideration of power efficiency, AC-LED has the design of reducing energy waste with alternating current from the power outlet. In this work, we propose an AC-power-signal-biased system that provides communication on both DC-LED and AC-LED. The bias circuit is designed to combine AC-power signal and the message signal with QPSK format. This driving scheme needs no AC-to-DC converters and it is suitable for driving AC LED. Synchronization is completed to avoid threshold effect of LED.