Research And Realization In Pixelated Modulation Visible Light Communication System

Pixelated Modulation Visible Light Communication System uses image display and image devices. It is safe,secure and its equipment is simple to choose. In recent years it has been widely concerned. The thesis studies pixelated modulation visible light communication system based on LCDs and cameras.Firstly, to solve coding region problem for LCD monitor, the thesis designs the image boundary. The thesis analyzes Moravec, Harris and Susan corner detection algorithms and their performance in pixelated modulation visible light communication system. Then the thesis proposes an improved Harris corner detection algorithm. The performance greatly improves. It’s more suitable for this real-time systems.Secondly, to solve perspective distortion between LCD and camera, the thesis restores signal. The coordinate relationship is derived by image coordinates and world coordinates using pinhole camera model. The homography is derived. Then the thesis deduces coordinate transformation between LCD and camera. Then we gets the restored image by bilinear interpolation.Thirdly, to solve signal modulation problems for LCD monitor, the thesis designs scheme for modulation based on RGB color, grayscale and space according to the characteristics of pixelated modulation visible light communication system.Fourthly, the thesis designs modulation decoding. To decode the received signal after the resumption, the thesis designes threshold decoding technology and analyzes the performance of the average gray threshold, histogram peaks threshold and Otsu algorithm. The system meets right decoding needs. The design of the code block has good anti-noise property. To solve ISI between image coding block boundary in the received signal, the thesis uses spatial filtering. To solve the nonlinear response of each camera channel grayscale, a pre-distortion algorithm is proposed to simplify decision method.Fifthly, the thesis implements software solutions for pixelated modulation visible light communication system. The user interface is developed. The thesis designs mult-sampling receiver to solve gray response time problems of the LCD monitor. The header format is designed which includes frame number, the parity bit and the idle bit. The header format is placed on the sending pictures. Finally, the present system hardware and software configuration and software environment parameter configuration is introduced. The results show that the program is running steadily and reaching high information transmission rate at a low bit error ratio.