Research On Joint Coding System Based On LDPC Code And Modulation

In a communication system, channel coding is a powerful method toimprove system reliability, modulation is to convert the digital baseband signal isa signal to facilitate the transmission of the necessary steps. Low density paritycheck LDPC code is a kind of very important error correcting code in recent years toput forward, a great influence on the degree distribution performance for differentmodulation modes. The optimal different modulation modes corresponding tothe degreedistribution of LDPC codes are combined, can greatly reduce the bit errorrate of thecommunication system.The degree distribution of non-uniform LDPC code thanthe degree distribution of LDPC codes with excellent performance, and for specificmodulation type, there are some certain degree distribution of LDPC codes to thelowest error rate of communication system. This paper presentsasymptotic expansion method of node add edge (PEG) algorithm, to construct aspecific degree distribution of the random LDPC codes based on PEG algorithm isgiven, and theoptimization methods of constructing arbitrary degree distribution ofquasi cyclic LDPCcodes.According to different modulation mode, LDPC code and modulation methodwithdifferent. To overcome the phase fuzzy differential modulation, the receiving endis needed to external information iterative decoding and LDPC decoding tocompensate for the difference in price; modulation Gray mapping ordinary, thereceiving end can’titerate between the demodulation and LDPC code. In order to adaptto differentcommunication environments, the modulation and demodulation indifferent ways, this paper presents a joint system LDPC code combined withspecific modulation.Extrinsic information transfer chart (EXIT) is an effective method toanalyze whether the receiving end iterative decoding convergence, using extrinsicinformation transferchart can be predicted in different degree distribution of LDPC codes in differentmodulation mode is convergent and critical signal-to-noiseratio. In this paper, using the extrinsic information transfer isoptimized for different modulation of LDPC codedegree distribution, to obtain theoptimal performance of different modulation schemes under the degree distribution ofLDPC codes. By constructing the degree distribution of the random or quasi cyclicLDPC codes, its application to LDPC codemodulation combination system. Simulation results show that, fordifferent modulationoptimal degree distribution of LDPC codes cansignificantly improve the performance of the system.