Research On Synchronization Technology In OFDM Visible Light Communication System

In recent years,due to the rich spectrum,green health,good confidentiality and high security advantages,in the field of communications visible light communication has been widely used.In this paper,based on the DCO-OFDM structure of the visible light communication system in the receiver synchronization technology and related modules of the hardware implementation,this work is as follows:Firstly,the mathematical model of symbol timing error is deduced and analyzed,and the simulation shows that the constellation of the received signal is different in different cases.Two kinds of symbol timing schemes are compared,one is based on the sequence synchronization autocorrelation timing synchronization algorithm,and the other is based on the local sequence cross correlation algorithm.The simulation results show that the frame error rate of the cross correlation algorithm is lower than that of the autocorrelation algorithm.Finally,an improved multi-period cross correlation algorithm is proposed.The simulation results show that the improved algorithm is superior to other algorithms in terms of frame error rate and timing mean square error.Secondly,the traditional symbol synchronization algorithm based on CP is studied,and then an improved symbol synchronization algorithm based on HCA-CP is studied.In the scheme of DCO-OFDM system,the symbol timing synchronization algorithm based on HCA-CP and the traditional ML algorithm based on CP are deduced,and the peak of the correlation function is given by simulation.Finally,the simulation results show that the performance of symbol synchronization algorithm based on HCA-CP is better than that of the traditional symbol synchronization algorithm based on CP.Thirdly,the mathematical model of sampling clock error is deduced and the simulation shows that the constellation of the received signal is different under different conditions.Based on the traditional pilot-based LS algorithm,two different pilot insertion methods are simulated and compared,and it is concluded that the continuous insertion pilots are better than the traditional interval insertion pilot.Finally,an improved pilot-based sampling clock synchronization algorithm is proposed,which simplifies the complexity of the algorithm and is easy to implement.The simulation results show that the improved bit error rate performance of the improved algorithm is basically no loss.Fourthly,the FPGA implementation of the sampling clock synchronization module is designed and introduced,including the extraction of the pilot,the calculation of the rotation angle,the estimation of the rotation factor and the sampling clock deviation.Finally,the simulation timing chart is given on the Vivado platform.The correctness and feasibility of the pilot-based sampling clock synchronization algorithm are verified.