Distributed Beamforming with Receive Filter

In this paper, a new distributed beamforming technique for relay networks in frequency selective channels is proposed. The relay network consists of one transmitter, multiple relays and one receiver. To equalize the transmitter-to-relay and relay-to-receiver frequency selective channels, a Finite Impulse Response (FIR) filter at the receiver is used in addition to employing Filter-and-Forward (FF) relaying strategy at the relays. The FIR filters at the relays and the receiver are designed jointly to maximize the receive quality-of-service subject to the constraint of total relay transmitted power. Simulation results demonstrate that the proposed beamforming technique outperforms both the amplify-and-forward based beamforming method and the FF based beamforming technique without receiver filtering in frequency selective fading environments.