The Performance Analysis And Optimization Of Terminated Protograph-based LDPC Convolutional Codes

Low-density parity-check(LDPC)codes have been widely used in practical communication systems due to the iterative decoding thresholds close to the Shannon limit.Compared with traditional LDPC codes,Protograph-based LDPC(P-LDPC)codes possess better performance and lower-complexity implementation;and LDPC convolutional codes have advantage of encoding and decoding delay.With the development of research on P-LDPC codes and LDPC convolutional codes,protograph-based LDPC convolutional codes(P-LDPC-CCs)are investigated.The results indicate that terminated P-LDPC-CCs(TP-LDPC-CCs)have variable encoding constructed schemes and excellent decoding performance.This thesis focus on the performance analysis and optimization of TP-LDPC-CCs.the main works are list as follows:(1)For different constructed schemes of TP-LDPC-CCs,such as JFZ method and diagonal decomposition method,the protograph-based EXIT analysis and simulation results indicate that the TP-LDPC-CCs constructed by the diagonal decomposition method possess better decoding performance.(2)In the joint source and channel coding(JSCC)system based on double P-LDPC(DP-LDPC)codes,the advantage of TP-LDPC-CCs on the the structural encoding delay are analyzed theoretically.Then one scheme of TP-LDPC-CCs based on the diagonal decomposition method with relatively uniform degree distributions is proposed.Simulation results indicate that the proposed TP-LDPC-CCs scheme possesses a better decoding performance than traditional P-LDPC codes scheme in the channel encoder of the JSCC system based on DP-LDPC codes.(3)In partial response(PR)channel,it can be discovered that the performance of TP-LDPC-CCs scheme of(2)is worse than that of regular TP-LDPC-CCs through the finite-length EXIT analysis and simulations.Therefore,one new scheme of TP-LDPC-CCs based on the diagonal decomposition method is proposed.Different from the scheme of(2),the proposed scheme requires non-uniform degree distributions.The finite-length EXIT analysis and simulation results show that the proposed scheme performs better than regular TP-LDPC-CCs under the PR channel.