Zero-Delay Joint Source-Channel Coding Using Hybrid Digital-Analog Schemes in the Wyner-Ziv Setting

This paper studies zero-delay joint source-channel coding (JSCC) of Gaussian sources over additive white Gaussian noise (AWGN) channels in the Wyner-Ziv scenario, that is, when there is side information about the source available only to the receiver. The proposed encoding scheme is based on hybrid digital-analog (HDA) transmission in a zero-delay fashion. Specifically, to achieve zero-delay, after applying scalar quantization to the source, the properly scaled analog information (quantization error) is superimposed on the scaled digital information (quantized source), and then transmitted. At the receiver side, several reconstruction schemes are analyzed. It is shown that all the schemes, when optimized, are superior to existing uncoded, digital, or hybrid transmission methods. It is also shown that the proposed HDA transmission may result in increased robustness to channel and/or side information mismatch compared to uncoded transmission. Observing that the bandwidth-matched Wyner-Ziv problem is intimately related to the coding scenario without side information but with bandwidth expansion factor 2, the proposed scheme is applied to the latter problem. It is shown that this application results in a better performance than the well-known inverse spiral mapping.