Source and channel coding for cooperative relaying

We consider the end-to-end distortion achieved by a half-duplex relay system where a continuous amplitude source is transmitted over a quasi-static Rayleigh fading channel. We investigate layered source coding (LS) where different source layers are sent at different times. The relay only forwards the important layers, leading to higher multiplexing gains. Alternatively, different source layers can be superimposed using a broadcast code (BS). The third strategy we consider is uncoded transmission (UT) followed by amplify-and-forward relaying. In all cases we perform a high SNR analysis and find the optimal distortion exponent which is the exponential decay rate of expected distortion with increasing SNR. We show that layered compression and broadcast coding is optimal in distortion exponent sense for large bandwidth expansions.