Design of Low-Delay Distributed Joint Source-Channel Codes Using Irregular LDPC Codes

A practical approach to designing distributed joint source channel (DJSC) codes for correlated binary sources using LDPC codes is presented. In this approach, both distributed compression and channel error protection are achieved by optimally puncturing bits of a systematic channel code to match the source correlation and channel error probability. This requires the design of a channel code with a specific unequal error protection (UEP) property. Towards this end, we present a linear-programming based algorithm for optimizing an irregular LDPC code for a given level of source correlation and channel noise. Experimental results are presented for both binary symmetric channels and Gaussian channels, which demonstrate that the proposed DJSC codes can significantly outperform the best code found through random search, tandem source-channel codes and previously reported schemes based on turbo codes when the encoding delay is constrained.