| Summary: | 碩士 === 國立交通大學 === 顯示科技研究所 === 103 === Visible light communication is the wireless communications. Mainly utilizes light-emitting diode as the transmitter and it can be used as communication, because it rapid response to the input signal. It can have different signal intensity by flicker. In this thesis, we use mobile-phone camera (CMOS image sensor) as the receiver and we propose a synchronization signal in this communication system. As a result the clock information can be recovered automatically.
Typical mobile-phone camera has a frame rate of 30 frame per second (FPS). In this thesis, we use the rolling shutter effect of the CMOS image sensor. Bright and dark fringes can be observed in each received image. Hence, by using the rolling shutter effect, the receiver data rate can be much higher than the frame rate of the CMOS image sensor. The data rate is 0.9kbps. Approximately, it is thirty times as fast as camera frame rate. However, the post-processing of the bright and dark fringes in each image is very challenging. In this thesis, we propose and demonstrate using second order polynomial approximation to mitigate the blooming effect of the CMOS sensor. In addition, we propose and demonstrate using sharpening image processing technique to recovery the header information. Hence, the VLC transmission capacity can be enhanced while the bit-error-rate can be significantly reduced. In the experimental, the bit error rate can be reduced from 〖10〗^(-2) to 〖10〗^(-4).At the same time we also evaluation of the bit error rate under different circumstances with using different kinds of threshold algorithm.
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