Zero-delay joint source-channel coding for the Gaussian Wyner-Ziv problem

We study the zero-delay joint source-channel coding problem of transmitting a Gaussian source over a Gaussian channel in the presence of side information known only to the receiver. To achieve zero-delay, after applying scalar quantization to the source, the properly scaled analog information, namely the quantization error, is superimposed on the scaled digital information, i.e., the quantized source, and then transmitted. At the decoder, two decoding schemes are proposed, both of which estimate digital component first, followed by the analog component. It is shown that both schemes, when optimized over all related parameters, are superior to pure analog transmission for high enough correlation between source and side information. The robustness of one of the proposed HDA schemes against varying channel and side information conditions is also compared with that of the purely analog scheme.