Research On Demapping Algorithm Of Non-uniform Constellation

Non-Uniform constellations(NUCs)have been adopted in digital broadcasting systems due to their abilities of reducing the shapping gap to Shannon theoretical limit.Two-dimensional NUCs(2D-NUCs)provide a better performance than one-dimensional NUCs(1D-NUCs)but bring higher demapping complexity at the receiver.This has also become a bottleneck which restricts 2D-NUCs' development and application in the convergence network of broadcasting and mobile communications.This article focuses on this situation and comes up with three algorithms to reduce demapping complexity while using APSK like 2D-NUCs.APSK like 2D-NUC structure is a kind of constellation structure that universally exists in ATSC3.0 2D-NUCs for low to medium code rates.For APSK like NUCs,a simplified demapping algorithm called Virtual-PointsSearching-Based(VPS)Simplified Demapping algorithm is proposed in this article.By further analysis and reduction,two demapping algorithms with lower complexity are also proposed in this article,which are entitled Further-Approximated-Virtual-Point-Searching-Based(FAVPS)Simplified Demapping Algorithm and Condensed-Virtual-Point-Searching-Based(CVPS)Simplified Demapping Algorithm respectively.Theoretical analysis and simulation results are used to prove the advantages of these three simplified demapping algorithms.The complexity of the proposed VPS simplified demapper is reduced by 65.63% without performance degradation while demapping APSK like 2D-256 NUCs in ATSC3.0 compared with traditional Max-Log-MAP demapper.With FAVPS demapping algorithm,the complexity can be reduced by 84.38% with negligible performance degradation(<0.05 dB,when BER=1e-6,compared with traditional demapper)while demapping APSK like 2D-256 NUCs in ATSC3.0.Compared with VPS and FAVPS simplified demapping algorithm,with CVPS simplified demapping algorithm,the complexity of demapping is further reduced.With the performance degradation lower than 0.1dB,the complexity of CVPS simplified demapper can be reduced by 68.36~96.09% while demapping APSK like 2D-256 NUCs.