Most of the existing literature on cooperative relay networks has focused on frequency– nonselective channels or frequency–selective channels with multi–carrier transmission. However, several practical systems employ single–carrier transmission over frequency–selective channels and the design of corresponding relaying schemes is a largely under–explored topic. In this paper, we investigate filter–and–forward beamforming (FF–BF) for relay networks employing single–carrier transmission over frequency–selective channels. In contrast to prior work, we assume that the destination node is equipped with a simple linear or decision feedback equalizer. The FF–BF filters at the relays are optimized for maximization of the signal–to–noise ratio at the equalizer output under a joint relay power constraint. For infinite impulse response (IIR) FF–BF filters, we derive a unified expression for the filter frequency response valid for linear equalization, decision f...
Yang-wen Liang, Aïssa Ikhlef, Wolfgang H. Ger