Research And Implementation Of Block Markov Superposition Transmission For Wireless Optical Communication In Turbulent Channel

Anti-channel interference coding is a hot spot and frontier technology in the research field of atmospheric turbulence wireless optical communication.At present,the frontier research of channel coding is commercial Polar codes and various spatial coupling codes.There is a strong demand for flexible coding technology in the wireless optical communication system using variable code rate transmission according to the characteristics of variable channel,and the current research results can not support the demand.Therefore,the research on flexible coding technology under the application of variable code rate has practical research significance.BMST is a kind of coding transmission technology to construct spatial coupling codes,and its biggest characteristic is convenient and flexible design.Therefore,aiming at the requirements of different performance and bandwidth of optical communication system in complex environment,BMST system is used to build DBCH-BMST system with variable code rate,and implement it with FPGA.The main contents of this thesis are as follows:1.Complete the design of anti-channel interference coding scheme under the condition of variable code rateThe Cartesian product of two BCH codes with different code rates is used as the basic code to achieve the purpose of code rate adjustment.The spatial coupling technology BMST coding is used to enhance its anti-interference performance,and the binary symmetric erasure channel is constructed by using the channel information to improve the problem of insufficient performance of hard decision decoding in optical communication.2.Build the transmission model and hardware model of BMST transmission system,and verify the feasibility of the scheme by simulationThe basic parameters needed to design the BMST system are obtained by software simulation: binary symmetric erasure channel decision threshold T,BCH code type and memory length M of the BMST system.The design of BMST frame length with variable length.Finally,the BMST system has two code rates of 3/8 and 53/64 in the simulation experiment,and the performance is improved by 3 to 4 orders of magnitude compared with the basic code.3.Complete the hardware development,build the transmission platform,and complete the experimental verificationImplement the BMST coding system with FPGA,build the actual wireless optical communication transmission platform,carry out the corresponding experimental verification.In the process of designing and developing BMST system,the performance of binary symmetric erasure channel,the performance of BCH code,and the performance prediction of BMST system by GA equivalent system are analyzed,and the reason why BMST system has working threshold is deduced.The experimental results show that the BER of the uncoded system is about 1E-4,the BER of the two transmission systems with code rate of 3/8 and 53/64 is below 1E-7,and the BER is reduced by 2-3 orders of magnitude.The coding system designed in this thesis has the characteristics of flexible coding on the basis of certain coding gain.