Research On CAP Modulation Technology Of Indoor Visible Light Communication Coding

Visible Light Communications(VLC)is a kind of wireless communication technology which uses Light in the vsible spectrum domain as information carrier to transmit optical signals in the air.Its advantages are high bandwidth,high speed,high security and no electromagnetic interference.However,the effective modulation bandwidth of LED used in VLC system limits the transmission rate of VLC system.Therefore,Carrierless Am PLitude and Phase(CAP)modulation technology to improve spectrum utilization has attracted extensive attention.On the other hand,the introduction of 5G standard also provides technical support for VLC system to introduce 5G standard.In order to further improve the reliability of information transmission of CAP-based VLC system,and to explore the application of 5G standard in VLC field,this theis studies the CAP modulation technology of VLC coding.Based on the modulation theory of DC Biased Optical CAP(DCO-CAP)system,the basic principle and modulation model of DCO-CAP system are presented.Based on the VLC range transmission model and the CAP signal model,the block error rate analytical formula of DCOCAP system is derived and the system simulation is performed.Secondly,in order to reduce the information transmission delay of VLC system and improve the reliability of information transmission,an indoor visible light CAP system transmission scheme based on 5G-Turbo code is proposed.The scheme uses the parallel cascade encoding structure,transforms the component codes into long codes by interleaver,realizes the random encoding,and adopts the maximal logarithmic posterior probability(maxlog-map)decoding algorithm for decoding.Through the analysis of the coding and decoding principle of 5G-Turbo code and the simulation of the performance of DCO-CAP visible light communication system based on 5G-Turbo code,the results show that the transmission performance with low delay and high reliability can be obtained.Thirdly,in order to improve the reliability of short code transmission in VLC system information transmission,an indoor visible light CAP transmission system based on 5GPOLAR code is proposed.Parity Check-Cac-Aid Successive Cancellation list(PC-CA-SCL)is used for decoding in this scheme to ensure the reliability of information transmission by means of information transmission polarization,and the Parity Check-Cac-Aid Successive Cancellation list(PC-CA-SCL)is used for decoding.Through the analysis of the coding and decoding principle of 5G-POLAR code and the simulation of the performance of DCO-CAP visible light communication system based on 5G-POLAR code,the results show that the transmission performance of high throughput and high reliability can be obtained.Finally,in order to improve the reliability of long code transmission in VLC system information transmission,an indoor visible light CAP system transmission scheme based on5G-LDPC code is proposed.In this scheme,the sparse property of check matrix is used to reduce transmission errors,and the Believing Propagation Decoding Algorithm(BP)is used to decode.Through the analysis of the coding and decoding principle of 5G-LDPC code and the simulation of the performance of DCO-CAP visible light communication system based on 5GLDPC code,the results show that the transmission performance with low complexity and high reliability can be obtained.