Research On Efficient LDPC-Coded Modulation Systems

Low-density parity-check (LDPC) codes are a class of codes which can achieve thechannel capacity asymptotically. So it is a good candidate for future communicationsystems. In this thesis, rate-compatible LDPC codes, coded modulation systems basedon LDPC codes and other related topics are studied, and some main results are obtainedas follows:The asymptotic performance of binary rate-compatible (RC) LDPC codes is analyzedby Gaussian approximation (GA) technique. It is also pointed out that the principle ofdesigning RC-LDPC codes with indefnite length is fnding good RC degree distributions;A method for construction of binary punctured RC-LDPC codes with short andmoderate code-length is discussed, and then it is extended to non-binary LDPC codes toobtain non-binary punctured RC-LDPC with code-rate1/2–5/6. Compared with binarycodes, the proposed non-binary punctured RC-LDPC codes get better performance;The author propose a irregular bit-wise shortening method for construction of non-binary shortened RC-LDPC codes with code-rate1/10–1/2, and they perform better thaneither binary RC-LDPC codes or symbol-wise shortened non-binary RC-LDPC codes;Three design rules of optimized Gallager mapping for bit-interleaved coded modula-tion scheme with iterative decoding (BICM-ID) are proposed. The extrinsic informationtransfer (EXIT) technique is utilized to design and analyze the proposed mapping rules.And the author also provide the design method of LDPC degree distributions based onthe proposed coded modulation system;The author provide the system model of adaptive coded modulation (ACM) based onthe proposed non-binary RC-LDPC codes. The performance of diferent code-rates anddiferent modulation types over fading channels is simulated and the switch protocol ofACM is provided, too. The proposed ACM system based on non-binary LDPC codes canachieve a fexible spectrum efciency from0.33to5bits/s/Hz;The system model of ACM based on concatenated two-state trellis-coded modulation(CT-TCM) and the switch protocol of ACM are designed. Compared with conventionalturbo-TCM system, the proposed ACM system based on CT-TCM can obtain higherspectrum efciency with lower complexity.