Research On Encoding And Modulation Of LDPC

Besides turbo codes, low-density parity-check(LDPC)codes form another class of Shannon limit (or channel capacity)-approaching codes which has attracted booming interest in the last few years because of their excellent decoding performance. In practice, communication is usually working under band limited channels, so it is very important to investigate the performance of m-ary modulation and its decoding.This paper first summarizes the algorithms of LDPC decoding under m-ray modulation which contains generic iterative decoding algorithms and binary iterative decoding algorithms. Then we focus on the decoding algorithms of multilevel coded modulation, including multi-stage decoding, parallel decoding and hybrid decoding, and their simulation results under AWGN channel are compared. It implies that the performance of hybrid decoding is better than other decoding algorithms. Next, the decomposable LDPC is improved, which changes the Ungerboeck setting partition to block partition and changes multi-stage decoding to hybrid decoding. The simulation under both AWGN and Rayleigh fading channel shows that not only the bit error rate performance is improved significantly but also the unequal error protection feature can be utilized.