Browsing by Author "Wang, Wei-Chung"

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Beacon Jointed Packet Reconstruction Scheme for Mobile-Phone Based Visible Light Communications Using Rolling Shutter
(2017-12-01)
Wang, Wei-Chung
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Chow, Chi-Wai
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Chen, Chia-Wei
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Hsieh, Hsiang-Chain
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Chen, Yen-Ting
Mobile-phone based visible light communication (VLC) is an attractive method for optical wireless communication. However, the data rate is typically limited by the complementary metal-oxide-semiconductor image sensor frame rate and the processing time gap in the rolling shutter mode operation. Here, we propose and demonstrate a packet-reconstruction scheme, known as beacon jointed rolling shutter pattern scheme. The mobile-phone based VLC data rate can be increased to a record 10.32 kb/s. The implementation algorithm is discussed; and the bit-error-rate experimental evaluations at different transmission distances and horizontal offsets are performed.
Latent class nested logit model for analyzing high-speed rail access mode choice
(2012-03-01)
Wen, Chieh-Hua
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Wang, Wei-Chung
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Fu, Chiang
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運輸與物流管理系註：原交通所+運管所
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Department of Transportation and Logistics Management
This paper explores access mode choice behavior, using a survey data collected in Taiwan. The latent class nested logit model is used to capture flexible substitution patterns among alternatives and preference heterogeneity across individuals while simultaneously identifying the number, sizes, and characteristics of market segments. The results indicate that a four-segment latent class nested logit model with individual characteristics in segment membership functions is the most preferred specification. Most high-speed rail travelers were cost-sensitive to access modes, and thus strategies that reduce the access costs can be more effective than reducing the access times. (C) 2011 Elsevier Ltd. All rights reserved.
Long distance non-line-of-sight (NLOS) visible light signal detection based on rolling-shutter-patterning of mobile-phone camera
(2017-05-01)
Wang, Wei-Chung
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Chow, Chi-Wai
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Wei, Liang-Yu
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Liu, Yang
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Yeh, Chien-Hung
We propose and demonstrate a long distance non-line-of-sight (NLOS) visible light signal detection based on the rolling shutter patterning using commercial mobile phone camera. By using our improved rolling shutter pattern demodulation algorithm, such as the background compensation (BC) blooming mitigation, extinction-ratio (ER) enhancement and Bradley adaptive thresholding, a 1.5 m NLOS visible signal (at low illumination of 145 lux) can be retrieved. (C) 2017 Optical Society of America
Mitigation of performance degradation due to dynamic display contents in visible light communication using TV backlight and CMOS image sensor
(2018-08-20)
Chow, Chi-Wai
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Shiu, Ruei-Jie
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Liu, Yen-Chun
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Wang, Wei-Chung
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Liao, Xin-Lan
Here, we propose and demonstrate a performance degradation mitigation scheme in TV backlight and smart-phone-based visible light communication (VLC) system when the display content in the light-panel is dynamically changing. In order to evaluate the influence of the dynamic display contents to the VLC performance, we use a noise-ratio (NR) and noise-ratio standard deviation (NRSD) as the figure-of-merits for the bright-and-dark contrast of the display content; and the dispersal of the changing display content regarding the brightand-dark contrast respectively. Performances of 4 dynamic display contents with different combinations of NR and NRSD are analyzed. They are: low NR and low NRSD (NR 36.69%; NRSD = 0.0226); low NR and high NRSD (MR = 30.09%; NRSD = 0.2698); high NR and low NRSD (NR = 81.66%; NRSD = 0.0052); high NR and high NRSD (NR = 73.91%; and NRSD = 0.2717). The proposed scheme can work well; that is, even the transmission distance is up to 200 cm in both smart-phones. If the proposed scheme is not used, then high success rate can be observed only at the low NR and low NRSD display content when the transmission distance is < 100 cm. (C) 2018 Optical Society of America under the terms of the OSA Open Access Publishing Agreement
Visible light communications for the implementation of internet-of-things
(2016-06-01)
Chen, Chia-Wei
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Wang, Wei-Chung
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Wu, Jhao-Ting
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Chen, Hung-Yu
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Liang, Kevin
It is predicted that the number of internet-of-things (IoT) devices will be >28 billion in 2020. Due to the shortage of the conventional radio-frequency spectrum, using visible light communication (VLC) for IoT can be promising. IoT networks may only require very low-data rate communication for transmitting sensing or identity information. The implementation of a VLC link on existing computer communication standards and interfaces is important. Among the standards, universal asynchronous receiver/transmitter (UART) is very popular. We propose and demonstrate a VLC-over-UART system. Bit error rate analysis is performed. Different components and modules used in the proposed VLC-over-UART system are discussed. Then, we also demonstrate a real-time simultaneous temperature, humidity, and illuminance monitoring using the proposed VLC link. (C) 2016 Society of Photo-Optical Instrumentation Engineers (SPIE)