Differential space-time coding for cooperative relay system over frequency-selective channels

In this paper, a differential space-time coding (D-STC) scheme is presented for relay assisted cooperative wireless communication networks over frequency selective fading channels. Two most common schemes, i.e., differential amplify-and-forward (DAF) and differential decode-and-forward (DDF), are both investigated in our single relay assisted system. Leveraging spectral encoder and differential space-time modulation, our proposed scheme can achieve multipath diversity without instantaneous channel state information at each node. Moreover, the direct link is also taken into consideration. Theoretical analysis demonstrates a diversity gain of L₃ + min {L₁, L₂} +2, where L₁, L₂ and L₃ are the channel order for source-relay (S → R), relay-destination (R → D) and source-destination (S → D) links, respectively. Simulation results are presented to validate the good performance of the coding scheme and DST modulation of DAF and DDF.