Research On Coding And Modulation Technology In Visible Light Communication

Visible light communication,as a new research field,is an important research direction in the field of communication.It has the advantages of high bandwidth,high stability,high speed,safety and environmental protection,but it is sensitive to environmental changes,and has poor bit error rate performance in the case of occlusion.In visible light communication,spatial orthogonal modulation and color shift keying modulation are widely concerned.Therefore,this paper optimized the algorithm and constellation based on spatial modulation and color shift keying modulation,and studied a new spatial orthogonal modulation scheme and constellation structure to improve the error performance of indoor visible light communication system and improve the transmission quality of visible light communication signals.On this basis,the finite state machine principle is introduced,and the design of FSM coding scheme based on color shift keying modulation is further studied to further reduce the bit error rate.The research contents of this paper are as follows:(1)From the perspective of spatial Modulation,to solve the problem of poor bit error rate performance of traditional Space Quadrature Modulation,to investigate SQM's error performance,adopt the way to minimize the error on the boundaries,and proposed an improved Modulation method,a New spatial orthogonal Modulation scheme to improve the error performance of indoor visible light communication system,then design the M-NSQM(M=4,8,16,64)mapping scheme.Simulation results show that,compared with the traditional SQM,the proposed NSQM scheme has better error performance.When BER=10^-5,when M=16 and M=64,the proposed NSQM scheme gain approximately 2.3 dB and 1.0 dB SNR respectively.(2)From the perspective of Color Shift Keying modulation,for the extended circular constellation color shift keying modulation in visible light communication,the bit error rate performance is poor when the modulation order is fixed,the constellation points are optimized based on the extended constellation structure,and the extended constellation structure is redesigned under the white light constraint condition.The optimized extended constellation structure is proposed to improve the bit error rate performance.The simulation results show that compared with the traditional color shift keyed modulation technology,the optimized extended circular4-CSK code proposed in this paper has better bit error rate performance.At the level of10^-5bit error rate,the optimized extended circular 4-CSK code has a gain of 0.7dB compared with the original extended circular 4-CSK code.(3)From the perspective of coding,to further improve the transmission quality of visible light communication signals,the Finite State Machine coding scheme based on color shift keying modulation is studied,and the CSK-FSM joint coding method or scheme is proposed based on white light constraint color shift keying modulation.Simulation results show that compared with the traditional color shift keying modulation technology,the proposed color shift keying and finite state machine combined coding method has better bit error rate performance.At the level of10^-5error rate,triangular 4CC-FSM code has a gain of 2.1 dB compared with triangular 4-CSK code.