Energy efficient power allocation and beamforming in non-regenerative two-way MIMO relay networks

This paper developed a joint power allocation and beamforming scheme to minimize the energy consumed per bit transmitted of the non-regenerative two-way multiple input multiple output (MIMO) relay network, while satisfying the QoS requirement of the two sources. Due to the non-convexity, the objective problem is decomposed into two sub-problems: transmit power allocation and transceiver beamforming design. The optimal transmit power at the two sources are first derived. Then the transmitting vectors at the sources, the beamforming matrix at the relay, and the receiving processing vectors at the destinations are obtained, respectively. Finally, the power allocation and the beamforming are carried out iteratively. For comparison, the scheme with equal gain beamforming at the sources (EGBS), equal gain beamforming at the relay (EGBR) and eigen beamforming at the sources (EBS) are considered, respectively. Numerical results demonstrate that the proposed scheme can significantly reduce the energy consumed per bit transmitted of the system effectively with high convergence rate. The simulations also reveal that beamforming at the relay plays a more important role than beamforming at the sources for the sake of energy saving.