Research And Implementation Of OFDM Based Indoor High-Speed Visible Light Communication Systems

As an emerging wireless optical communication technology, visible light communication (VLC) technology, which possesses strong secrecy, little radiation and free frequency spectrum, has become a research hotspot at home and abroad. White LEDs are usually adopted in VLC systems because of its short responsive time. With an optical filter, the3dB bandwidth of this kind of system can achieve about20MHz. In order to increase the spectrum efficiency and overcome the multipath effect, OFDM technology has been regarded as one of the important means of modulation.In this paper, in order to make full use of the spectrum and achieve indoor high-speed communication links, the following three aspects of the OFDM based VLC system has been studied.In the aspect of theory, the following four aspects were discussed. First, the system performance of DCO-OFDM and ACO-OFDM was compared. Second, two kinds of the synchronization algorithms were simulated and compared under certain VLC channel. Then, clipping’s influence on the performance of VLC system was analyzed. Finally, the improvement of the PLCC6based VLC system’s performance with predistortion was illustrated.In the aspect of offline processing transmission, the following research had been done. First, the influence of some algorithms and parameters for the experiment was discussed. Second, the bandwidth and noises of three groups of experiment device were tested and compared. Finally, offline processing transmission experiments were done by using advanced algorithms and different groups of device, whose results complied with the international standards.In the aspect of hardware implementation, digital function modules for DCO-OFDM modulator and demodulator were designed and tested on the FPGA development board, which could bear the100Mbit/s bit steam.Some innovative work has been done during the above-mentioned research. First, the experimental platform has been built based Matlab and DCO-OFDM, which can be used for performance simulation and offline processing transmission. Second, the equalization algorithm for offline processing has been advanced. Finally,140Mbit/s and715Mbit/s single-channel VLC links have been built based on the above work.This paper provides an idea and an experiment platform for following work. But compared with the most outstanding research around the world, some further more experimental work could be done in the future.