Minimizing the expected distortion of two-hop networks using multi-layer source coding

This paper concerns minimizing the expected distortion of a Gaussian source, transmitted over a two-hop block fading channel, under the mean square-error measure. It is assumed that there is not a direct link between the source and destination, and a simple Decode and Forward (DF) relay, handles the communication. The channel state information (CSI) associated with each hop is available at the corresponding receiver, while the transmitters are unaware of associated CSIs. It is assumed that the source node performs successive refinement source coding approach, together with multi-layer channel coding to send its information to the relay. Then, the relay re-encodes its received information with a multi-layer channel code, and forwards it to the destination. Accordingly, the optimal power allocation policy across code layers in terms of minimizing the expected achievable distortion are formulated and addressed and then the results are numerically derived for Rayleigh block fading environment, showing the proposed method performs better than the Amplify and Forward (AF) relaying for source-channel mismatch factors greater than one.