Research On Differential Chaos Shift Keying In Visible Light Communication

In recent years,visible light communication(VLC),which uses light-emitting diodes(LEDs)as the light source,has rapidly gained attention due to its unique advantages in spectrum resources,confidentiality and energy consumption.This paper starts with the feasibility level,aiming at indoor VLC modulation technology,research on indoor VLC modulation sche me based on Differential Chaos Shift Keying(DCSK).The main work is as follows:(1)Two binary visible light chaotic modulation,DC-bias Optical Code-Shifted Differential Chaos Shift Keying(DCO-CS-DCSK)and Flip Optical Code-Shifted Differential Chaos Shift Keying(Flip-CS-DCSK)are proposed.The method of "adding DC-bias" and "positive and negative module polarity transmission" is used to achieve unipolar signal,so as to meet the requirements of "Intensity Modulation/Direct Detection(IM/DD)" of VLC system.The theoretical bit error rate(BER)expression of the two systems under the AWGN channel are deduced and the accuracy of the theoretical analysis is verified by simulation experiments.(2)In order to improve the transmission rate of visible light chaotic modulation,the DCO-CS-MDCSK system and the Flip-CS-MDCSK system,based on circular constellation are proposed.Two systems transmit the real part and the imaginary part of constellation symbol through mutually orthogonal Walsh codes,thereby realizing M-ary transmission.Then,the theoretical BER of two M-ary visible light chaotic modulation systems in AWGN channel is derived.The simulation results show that the error performance of Flip-CS-MDCSK system is better than DCO-CS-MDCSK system under the same parameters.And the 4-ary system has the best bit error rate performance.In addition,the analysis compares the complexity,frequency band utilization,and optical power efficiency of the two systems.(3)The BER expressions of two M-ary visible light chaotic modulation is derived under the indoor VLC channel.The accuracy of theoretical derivation and the feasibility of the scheme are verified by simulation experiments.At the same time,the influence of channel parameters on the performance of visible light chaotic modulation system is also analyzed.The experimental results show that the radiation angle of the light source and the transmission distance between the transceivers are inversely proportional to the system bit error rate performance,that is,the larger the radiation angle or the greater the distance between the transceivers,the higher the system bit error rate will be.