Design And Implementation Of OFDM System For Visible Light Communication Based On FPGA

Visible light communication (VLC) is a way to communicate information with a carrier of visible light, it is also emerging technique of wireless optical communication technology in recent years. It is not only has the flexibility of wireless communication, but also could save the increasingly tense radio spectrum resources. VLC was developed on the indoor LED lighting. In practical application, it could take care of both the lighting and communication, and could save energy and reduce the communication infrastructure funding. Communicate rate of VLC is fast, and VLC has no RF radiation, need not to setup optical fiber, apply to special occasions that was sensitive to electromagnetic interference, It has great potential for development in the short-range communication, and has become a hot research field of wireless communications at home and abroad.In the visible light communication system, to ensure the normal communication, must consider the randomness of atmospheric channel, absorption of light, refraction of light in communication channel, Inter-carrier interference caused by multipath propagation, and environmental noise on the whole communication system, in order to achieve better communication effect, this thesis used a way of data modulation and demodulation named orthogonal frequency division multiplexing (OFDM), that has the ability of anti-multipath interference and anti-fading.OFDM technology has the advantage in eliminating inter-symbol interference, it also enhance the band utilization rate, and easy to implement, etc. OFDM is comparatively mature technology in the wireless communication, if applied it to the visible light communication system, it could provide great help to improve the visible light communication system performance. According to the above, this paper instructs corresponding theoretical research and design, and the corresponding results are as follow:1. Study the theory of OFDM technology. After theoretical analysis about the modem principle, this paper analyzed the technology of synchronization in detail, improve the algorithm, and simulate the timing accuracy between the classical algorithm and improved algorithm, the results show that the improved algorithm has better timing effect. Analyze and compare the algorithms about Discrete Fourier transform, provide theoretical support for the whole OFDM system.2. Complete the design of the OFDM modulation and demodulation on FPGA development board. The core module of modulation part adopted Winograd algorithm to calculate the Discrete Fourier transform, this algorithm has small count of calculation, fast speed, could reduce resource consumption, improve the efficiency of the system. In the part of demodulation, in order to achieve better synchronization effect, and ensure system’s normal communication, this paper improve the algorithm on implementation.3. Analyze the technology of indoor positioning, study the theory of applied visible light communication to the positioning. The content includes LED optical parameters, channel model, as well as the localization algorithm and so on. This paper simulated and analyzed the influence of light source layout for indoor lighting, and the precision that the article chooses. Through the simulation analysis, the study on applied VLC to the indoor positioning could provide some reference for the actual project.