Filter-and-Forward Distributed Beamforming for Two-Way Relay Networks with Frequency Selective Channels

A new approach to distributed cooperative beamforming in two-way half-duplex relay networks with frequency selective channels is proposed. In our scheme, two transceivers simultaneously transmit the signals they wish to exchange to the relays. The relay received signals are the sum of the channel-convoluted versions of the transmitted signals. Each relay retransmits a filtered version of its received signal to both transceivers. The proposed distributed beamforming approach is based on minimizing the total relay transmitted power subject to the quality-of-service requirements for both transceivers. We show that this problem is convex, and thus, it can be efficiently solved as a second-order cone program. Simulation results demonstrate that the transmitted power can be significantly reduced and the problem feasibility can be substantially improved by using such a filter-and-forward relaying strategy instead of the traditional amplify-and-forward relaying approach.