Research On High Performance Irregular LDPC Codes

LDPC codes have been paid more and more attention in recent years. They are not only in favor with a variety of communication standards, which have to incorporate them into their own channel coding scheme, but also have aroused extensive attention in the military and civil applications. This paper attempts to present a kind of acoustic communication system which has both LDPC codes and spread spectrum technology.The paper first focuses on the check matrix construction of binary LDPC codes, proposing LDPC graph theory and SC LDPC; then paper studies the decoding algorithm of non binary LDPC codes, manly analyzing decoding algorithm on the log-domain and algorithm based on binary thinking of the BP.Finally paper focus on the application of LDPC codes in acoustic communication:The communication system model "LDPC+DSSS+BPSK" can be built through the analysis of acoustic channel, and then simulation of different code length, code rate, decoding iterations and spreading sequence length is needed to determine the parameters of the program. Through the performance comparison among LDPC codes, RS codes and convolutional codes, we can get the conclusion that "LDPC+DSSS+BPSK" could have a more effective resistance to multipath fading, Doppler frequency shift, delay and other factors in the acoustic communication system.