Distributed Beamforming Design on Amplify and Forward Two-Way Relaying Channels

A distributed scenario of amplify-and-forward (AF) two-way relaying channel, where two single antenna equipped source nodes exchange data through M distributed relays, is studied in this work. The relays are all equipped with one antenna and with individual power constraint while helping source nodes transmitting their data. A scaled-and-forward (SF) beamforming strategy is first introduced, and it follows an optimal distributed beamforming design based on minimizing the sum of mean square errors (MSMSE) of both source nodes. This system model is then extended to a MIMO scenario, where source nodes are equipped with multiple antennas. Transmit beamforming and receive beamforming of two communication nodes are jointly designed with the relay beamforming in this scheme. A generative iterative algorithm is proposed for the MSMSE-based schemes. Simulation results show that, system performance is greatly enhanced by the optimal beamforming, and with multiple antennas at two source nodes, the system performance is further improved due to the increased space diversity.