Hybrid analog-digital coding for nonuniform memoryless sources

In this paper, we propose a hybrid analog-digital scheme for the transmission of non-uniform memoryless sources over Additive White Gaussian Noise (AWGN) channels. The hybrid scheme is constructed by generating most of the output symbols from standard linear combinations of the input bits, as in Rate Compatible Modulation (RCM), and a few of them using a Low Density Generator Matrix (LDGM) code. The basic idea is that the RCM scheme corrects most of errors, leaving residual errors to be corrected by the LDGM code. Source non-uniformity is exploited at the decoder and the encoder is optimized depending on the source non-uniformity to further improve the system performance.