Research On The Encoding And Decoding Of Internal Codes In DVB-S2

Low Density Parity-Check (LDPC) Codes were first discovered by Gallager in the early 1962, This class of codes decoded with soft-in soft-out (SISO) iterative decoding performs amazingly well. But due to the calculating effort in implementing, they were mostly ignored. Turbo codes was discovered by C.berrou et al.in 1993,which was a break in error-correcting coding theory for its performance can approach to the Shannon limit. Since then Mackey and Luby rediscoverd Gallager codes by finding that its performance can also approach Shannon limit in 1995. LDPC codes are one of the hottest topics in coding theory today.DVB-S2 is the next generation standard of the digital satellite broadcasting,which adopts the more effective technique of channel coding and self-adapting code modulation,Among them, channel coding adopts LDPC as its inner code and BCH as its outer code. Compare with DVB-S, it has been specified around three concepts: best transmission performance approaching the Shannon limit, total flexibility, and reasonable receiver complexity, 30% higher transmission eficiency than DVB-S.First the thesis introduce basic knowledge of LDPC codes. Then the thesis discuss the problem of linear encoding of LDPC codes and introduce the encoding algorithm based on approximate lower triangulations. Next the thesis discusses the basic principle of LDPC encoding and decoding and then explains the LDPC encoding and decoding in the standing of DVB-S2. Afterward, it introduces the coding schemes used in DVB-S2 and gets the parity check matrix by simulation.In the light of the principle of LDPC encoding in the standing of DVB-S2, the thesis expound general encoding of LDPC,parity-check matrix in lower triangular of LDPC encoding and the complexity of encoding , and the coding scheme with linear time complexity. the dissertation study log-likelihood-ratio-based Belief-Propagation decoding algorithms and it's improve. In order to avoid the"tanh"function in the check-node updates,the min-sum algorithm,simplified min-sum algorithm is used in the decoding. Si mulation results show that these reduced-complexity decoding algorithms for LDPC codes achieve a performance very close to that of the BP algorithm.