Iterative Decoder Design for Joint Source-Channel LDPC Coding

We consider joint source-channel coding with variable length codes (VLCs) and LDPC codes. We propose an iterative source-channel decoding system, which involves message passing between a soft-input-soft-output VLC decoder and an LDPC decoder. The proposed system utilizes the residual redundancy of the variable length code during the iterative decoding process, and is expected to exhibit decoding convergence at a lower SNR relative to the system in which source and channel decoding are performed separately. We present computer simulation results that confirm the expected gain of the proposed system.