Multi-level modulation LDPC Decoding Algorithm for New Generation DVB-S2 system

In this paper, we introduce four kinds of simplified Soft-Decision Demapping algorithms for DVB-S2 system. First, A Log Likelihood Ratio Method, the optimal solution but high complexity, is introduced. Second, Euclidean distance method, a little performance degradation, third, Phase sector Method, low complexity, are presented. Lastly, SubLLR(Max operation) algorithm is proposed, which is little performance degradation and has a low complexity compared to LLR method.