Analysis and optimization of irregular LDPC codes for joint source-channel decoding

• Published in: IEEE communications letters Vol. 9; no. 12; pp. 1064 - 1066
• Main Authors: Poulliat, C., Declercq, D., Lamy-Bergot, C., Fijalkow, I.
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01.12.2005; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Applied sciences; Coding, codes; Convergence; Equations; Exact sciences and technology; Gaussian approximation; Information, signal and communications theory; Iterative decoding; Linear programming; Mutual information; Optimization methods; Parity check codes; Signal and communications theory; Stability; Telecommunications and information theory; Transfer functions; joint source and channel decoding (JSCD); Simulation; irregularity optimization; Data transmission; Parity check codes; Decoding; Joint source channel coding; LDPC codes; Optimization
• ISSN: 1089-7798; 1558-2558
• DOI: 10.1109/LCOMM.2005.1576589

In this paper, we present a characterization, through its convergence analysis, and an optimisation of a joint source-channel receiver composed of a LDPC decoder and a Soft Input Soft Output (SISO) source decoder. Under Gaussian approximation, assuming the knowledge of the extrinsic mutual information transfer function (EXIT chart) of the source decoder, we derive the Mutual Information evolution equations, that semianalytically describe the convergence of the iterative system behavior and, to complete the study, the stability condition at the convergence fixed point is derived for the joint receiver. From this analysis, a general optimisation method of the irregularity of the LDPC codes is proposed, which can be reduced to a linear programming optimisation problem. Simulation results show improved performance when compared to an AWGN optimized LDPC code.