The Design Of Bit-interleaver, LDPC Code And LDPC-BICM Scheme Combined With The Constellations

The low-density parity-check bit-interleaved coded modulation?LDPC-BICM?scheme is an effective combination with the Shannon Limit approaching LDPC code and the BICM scheme.The LDPC-BICM scheme can not only jointly design the demodulation and decoding process,but also optimize the decoding performance.Thus,the LDPC-BICM scheme has succesfully attracted enormous attentions from academics and industries.Till now,the LDPC-BICM scheme has been adopted as a standard physical-layer transmission scheme in the digital video broadcasting-satellite?DVB-S?system and the digital television terrestrial multimedia broadcasting?DTMB?system.Investigation and design of the LDPC-BICM scheme to further improve its decoding performance has theoretical and practical values.This dissertation has conducted researches and obtained some results in the four related areas listed as follows:the design of the bit-interleaver and the LDPC code;the design of the joint demodulation and decoding;the design of an LDPC-BICM scheme with M-PSK?LDPC-BICM-MPSK?in a two-way relay channel;the design of high power efficient LDPC-BICM schemes in a two-user multiple access channel.?1?The design of the bit-interleaver and the LDPC codeHigh order modulated LDPC-BICM schemes have unequal error protections?UEPs?.This brings more severe challenges to design the bit-interleaver and the code.For the design of the bit-interleaver,this dissertation proposes a notion of system factor graph and models the bit-interleaver as its edges.Based on it,this dissertation proposes a novel progressive edge growth?PEG?algorithm to design the bit-interleavers.For an LDPC-BICM scheme with rate-0.5 LDPC code and Gray labelled 256-QAM,the designed bit-interleaver in this dissertation can achieve 0.38 dB and 0.52 dB signal-to-noise ratio?SNR?gain at a BER level of 10^-5,compared to the bit-interleaver designed in[72]and the consecutive bit-interleaver[73],respectively.For the design of the LDPC code,this dissertation employs the notion of multi-edge-type?MET?LDPC code and proposes both variable-node decoder and check-node decoder MET extrinsic information transfer?EXIT?functions.Based on them,the dissertation further proposes a modified PEG algorithm to design LDPC codes.For an LDPC-BICM scheme with a rate-0.5 LDPC code and Gray labelled 16-QAM,the designed LDPC code in this dissertation achieves 0.16 dB and 0.1 dB SNR gain at a BER level of 10^-5,compared to the LDPC codes designed in[65]and[84],respectively.?2?The design of the joint demodulation and decoding algorithmThe conventional LDPC-BICM scheme ignores the correlation of the coded bits allocated in the same symbol.This dissertation proposes the factor graph of the LDPC-BICM scheme and develops a joint demodulation and decoding algorithm with a better decoding performance.This dissertation also investigates the UEP property in the BICM schemes with joint demodulation and decoding,and further modifies the conventional EXIT functions to design bit-interleavers accordingly.Compared to an LDPC-BICM scheme with 32-QAM and the independent decoding algorithm,the designed LDPC-BICM scheme with joint demodulation and decoding algorithm in this dissertation can further achieve 0.65 d B SNR gain at a BER level of 10^-5.?3?The PSK modulated LDPC-BICM schemes in the two-way relay channelThis dissertation investigates the properties of the constellations and modifies the differential evolution algorithm to optimize the constellation symbol labeling with a maximized value of the channel mutual information.This dissertation also investigates the UEP property in the LDPC-BICM-MPSK scheme for the first time,and designs the bit-interleavers.For a scheme with a rate-0.5 LDPC code and Gray labelled 256-PSK,the designed bit-interleaver can achieve 0.625 dB SNR gain at a BER level of 10^-5.?4?The LDPC-BICM schemes in the two-user multiple access channelThis dissertation proposes two LDPC-BICM schemes for the applications in the two-user multiple access channel:the power allocation based LDPC-BICM scheme and the binary physical-layer network coding?PNC?based LDPC-BICM scheme.The former scheme aims to improve the decoding performance by optimizing the power ratio between the two power levels of users'signals in terms of the largest mutual information.The latter scheme introduces PNC and employs the belief propagation algorithm instead of the joint decoding algorithm to reduce the computational complexity and improve the throughput of the schemes.Compared to the LDPC-BICM scheme[116]with rate-0.6 and length-20000 LDPC code,the two LDPC-BICM schemes can achieve 1.9 dB and 2.05 d B SNR gain at a BER level of 10^-5,respectively.