Browsing by Author "Liang, Kevin"

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Comparison of thresholding schemes for visible light communication using mobile-phone image sensor
(2016-02-08)
Liu, Yang
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Chow, Chi-Wai
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Liang, Kevin
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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
Light Encryption Scheme Using Light-Emitting Diode and Camera Image Sensor
(2016-02-01)
Liu, Yang
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Liang, Kevin
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Chen, Hung-Yu
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Wei, Liang-Yu
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Hsu, Chin-Wei
Visible light communication (VLC) is regarded as relatively secure communication when compared with other wireless communications using radio frequency (RF). However, due to the visual nature, the VLC signals are still subject to eavesdropping when they are emitted by the light source. Here, we propose a light encryption scheme using devices having light-emitting diode (LED) and a camera image sensor, such as a mobile phone. The original visible signal sending from the lamp can be first received by the proposed light encrypter. The information can be encrypted and then emitted. The light encrypter acts as an encryption gateway for signals in optical domain. The rolling shutter effect of the complementary metal-oxide semiconductor (CMOS) camera in the mobile phone can be used. By demodulating the rolling shutter pattern, the data information can be obtained. We also propose and demonstrate using the Otsu thresholding scheme to define the data logic in the rolling shutter pattern. We show that the Otsu scheme is effective for estimating the bit error rate (BER). The optimum number of intervals (segmentations) and the process time of the Otsu method are also studied.
Mobile-phone based visible light communication using region-grow light source tracking for unstable light source
(2016-07-25)
Liang, Kevin
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Chow, Chi-Wai
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Liu, Yang
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光電工程學系
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光電工程研究所
In order to increase the data rate of the camera-based visible light communication (VLC) system, using rolling shutter effect has been demonstrated successfully, in which the pixel rows of the complementary-metal-oxide-semiconductor (CMOS) image sensor are activated sequentially. Previous camera-based VLCs focused on using a stable LED light source, and its illumination area is positioned at the center of an image frame. In this work, we investigate the performance of a camera-based VLC with light source at different parts of an image frame. We propose and demonstrate using region-grow algorithm to track the light source. We also evaluate and discuss different scenarios when the light source is moved. Besides, a recorded > 5 kbit/s net data rate can be achieved by using only a single phosphor-based white-light LED source. Here, we demonstrate that 4.502 pixel/bit can be achieved. (C) 2016 Optical Society of America
Passive Optical Receiver for Visible Light Communication (VLC)
(2015-01-01)
Chen, Hung-Yu
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Liang, Kevin
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Chen, Chung-Yen
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Chen, Shih-Hao
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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 pre-distortion 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.
Passive Optical Receiver for Visible Light Communication (VLC)
(2015-01-01)
Chen, Hung-Yu
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Liang, Kevin
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Chen, Chung-Yen
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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.
RGB visible light communication using mobile-phone camera and multi-input multi-output
(2016-05-02)
Liang, Kevin
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Chow, Chi-Wai
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Liu, Yang
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光電工程學系
;
光電工程研究所
Red, green, blue (RGB) light-emitting-diodes (LEDs) are used to increase the visible light communication (VLC) transmission capacity via wavelength-division-multiplexing (WDM), and the color image sensor in mobile phone is used to separate different color signals via a color filter array. However, due to the wide optical bandwidths of the color filters, there is a high spectral overlap among different channels, and a high interchannel interference (ICI) happens. Here, we propose and demonstrate an RGB VLC transmission using CMOS image sensor with multi-input multioutput (MIMO) technique to mitigate the ICI and retrieve the three independent color channels in the rolling shutter pattern. Data pattern extinction-ratio (ER) enhancement and thresholding are deployed. (C) 2016 Optical Society of America
Thresholding schemes for visible light communications with CMOS camera using entropy-based algorithms
(2016-10-31)
Liang, Kevin
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Chow, Chi-Wai
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Liu, Yang
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Yeh, Chien-Hung
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光電工程學系
Recent visible light communication (VLC) studies mainly used positive-intrinsicnegative (PIN) and avalanche photodiode (APD). VLC using embedded complementarymetal- oxide-semiconductor (CMOS) camera is attractive. Using the rolling shutter effect of CMOS camera can increase the VLC data rate; and different techniques have been proposed for improving the demodulation of the rolling shutter pattern. Important steps to demodulate the rolling shutter pattern are the smoothing and the application of efficient thresholding to distinguish data logic. Here, we propose and demonstrate for the first time two entropy thresholding algorithms, including maximum entropy thresholding and minimum cross entropy thresholding. Experimental evaluation to compare their bit-error-rate (BER) performances and efficiencies are also performed. (C) 2016 Optical Society of America
Visible Light Communication Using Receivers of Camera Image Sensor and Solar Cell
(2016-02-01)
Liu, Yang
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Chen, Hung-Yu
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Liang, Kevin
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Hsu, Chin-Wei
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Chow, Chi-Wai
We propose an electronic label and sensor system using visible light communication (VLC). The downlink signal is transmitted by a white-light light-emitting diode (LED) lamp that can provide lighting, VLC, and energy harvesting for mobile devices. The downlink is received by a solar cell. The uplink can be captured by a surveillance camera image sensor. However, using the camera image sensor as a VLC receiver (Rx) is challenging since the data rate is limited by the frame rate and due to uneven light exposure. The rolling shutter effect of the image sensor can be used to increase the data rate. In this paper, we propose and demonstrate how to demodulate the obtained rolling shutter pattern using a second-order polynomial (SOP) extinction ratio (ER) enhancement scheme, together with iterative and modified quick adaptive thresholding schemes. The ER enhancement scheme can significantly reduce the large ER fluctuation. Experimental results show that by using the proposed SOP ER enhancement scheme, the bit error rate (BER) improvement can be up to two orders of magnitude. We also believe that the proposed electronic label and sensor system may be applicable to Internet-of-Things sensing networks for connecting a number of mobile devices.
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)
Visible light communications using predistortion signal to enhance the response of passive optical receiver
(2016-01-01)
Liu, Yang
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Chen, Hung-Yu
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Liang, Kevin
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Wei, Liang-Yu
;
Chow, Chi-Wai
Traditional visible light communication (VLC) uses positive-intrinsic-negative photodiode (PD) or avalanche PD as the optical receivers (Rx). We demonstrate using a solar cell as the VLC Rx. The solar cell is flexible and low cost and converts the optical signal into an electrical signal directly without the need of external power supply. In addition to acting as the VLC passive Rx, the converted electrical signal from the solar cell can charge up the battery of the Rx nodes. Hence, the proposed scheme can be a promising candidate for the future Internet of Things network. However, a solar cell acting as a VLC Rx is very challenging, since the response of the solar cell is limited. Here, we propose and demonstrate using predistortion to significantly enhance the solar cell Rx response for the first time up to the authors' knowledge. Experimental results show that the response of the solar cell Rx is significantly enhanced; and the original 2-kHz detection bandwidth of the solar cell can be enhanced by 250 times for receiving 500-kbit/s VLC signal at a transmission distance of 1 m. The operation principle, the generated voltage by the solar cell, and the maximum data rates achieved at different transmission distances are also studied. (C) 2016 Society of Photo-Optical Instrumentation Engineers (SPIE)
Visible Light Encryption System Using Camera Image Sensor
(2016)
Hsu, Chin-Wei
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Liang, Kevin
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Chen, Hung-Yu
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Wei, Liang-Yu
;
Yeh, Chien-Hung
We propose and experimentally demonstrate a light encryption scheme using camera image sensor. Besides, rolling-shutter effect of the CMOS camera in the mobile-phone can be used to enhance the data rate of transmission.
Visible-light communication multiple-input multiple-output technology for indoor lighting, communication, and positioning
(2015-12-01)
Liu, Yang
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Hsu, Chin-Wei
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Chen, Hung-Yu
;
Liang, Kevin
;
Chow, Chi-Wai
Visible-light communication (VLC) is license free and electromagnetic-interference free; it thus can be deployed in radio-frequency forbidden areas. The light-emitting diode (LED) system providing simultaneously lighting, VLC, and positioning is highly desirable for providing real-time tracking, monitoring, and navigating with very little extra cost. We propose and demonstrate a multiple-input multiple-output (MIMO) VLC-positioning system using white-light LEDs. Our scheme is based on MIMO to provide both position and VLC. Experimental results show that the proposed MIMO VLC system can achieve a bit-error rate of 10(-10), while the positioning errors are within 1 cm. Numerical analyses are also performed, showing the positioning error can be measured within 1 cm. Further analysis of tilting angle of the receiver is also presented. (C) 2015 Society of Photo-Optical Instrumentation Engineers (SPIE)
Visible-light communication multiple-input multiple-output technology for indoor lighting, communication, and positioning
(2015-12-01)
Liu, Yang
;
Hsu, Chin-Wei
;
Chen, Hung-Yu
;
Liang, Kevin
;
Chow, Chi-Wai
Visible-light communication (VLC) is license free and electromagnetic-interference free; it thus can be deployed in radio-frequency forbidden areas. The light-emitting diode (LED) system providing simultaneously lighting, VLC, and positioning is highly desirable for providing real-time tracking, monitoring, and navigating with very little extra cost. We propose and demonstrate a multiple-input multiple-output (MIMO) VLC-positioning system using white-light LEDs. Our scheme is based on MIMO to provide both position and VLC. Experimental results show that the proposed MIMO VLC system can achieve a bit-error rate of 10(-10), while the positioning errors are within 1 cm. Numerical analyses are also performed, showing the positioning error can be measured within 1 cm. Further analysis of tilting angle of the receiver is also presented. (C) 2015 Society of Photo-Optical Instrumentation Engineers (SPIE)