Differential transmission for amplify-and-forward broadband cooperative communications

A distributed differential space-time-frequency (STF) coding scheme is proposed for single-relay assisted cooperative communication networks over frequency-selective fading channels. Using full diversity rotation and Cayley transformation at the source node, our proposed scheme can achieve both spatial and multipath diversity without any instantaneous channel state information at the destination node. Both theoretic analysis and simulation results demonstrate that a diversity gain of L₃ + min(L₁, L₂) can be achieved by the scheme, where L₁, L₂, and L₃ are the channel memory length for the source-to-relay (S rarr R), relay-to-destination (R rarr D), and source-to-destination (S rarr D) links, respectively. This simple transmission scheme needs neither complicated processing at the relay node, nor channel estimation at the destination node. Furthermore, a rate of 1.5 real symbols per channel use can be achieved when the relay node retransmits the information symbols to the destination node.