Adaptive Compress-and-Forward Relaying in Fading Environments with or without Wyner-Ziv Coding

Compress-and-Forward is a protocol for transmission over relay networks in which the relay forwards a compressed version of the signal it observes. The compression method used by the relay is source coding with side information, i.e. Wyner-Ziv coding, since the destination can use the signal it receives directly from the source as side information. This paper addresses the case of a wireless relay network with orthogonal transmissions from the source and the relay terminals; we show that when the transmitters have no instantaneous channel state information the optimal compression parameters often make Wyner-Ziv coding reduce to conventional source compression, i.e. compression that does not take into account the side information available at the destination. This result simplifies the implementation of the CF protocol in the case we consider, since it shows that in several situations one can use more convenient compression methods without significant performance loss.