Filter-and-forward distributed beamforming for relay networks in frequency selective fading channels

A half-duplex distributed beamforming technique for relay networks with frequency selective fading channels is developed. The network relays use the filter-and-forward (FF) strategy to compensate for the transmitter-to-relay and relay-to-destination channels using finite impulse response (FIR) filters. With the channel state information (CSI) being available at the receiver, the transmit relay power is minimized subject to the destination quality-of-service (QoS) constraint. This distributed beamforming problem is shown to have a closed-form solution. Simulation results demonstrate substantial improvements in terms of the relay transmitted power and feasibility of the destination QoS constraint as compared to amplify-and-forward (AF) distributed beamforming techniques.