Energy Efficient Two-Way AF Relay System with Multiple-Antennas

In this paper, we study an energy efficient two-way amplify-and-forward (AF) relay network equipped with multiple antennas at both sources and relay. To minimize the transmit power while satisfying quality of service (QoS) of both sources, transmit beamformers and receive combiners are designed with ZF-based relay processing matrix. Due to the non-convexity of the optimization problem, the original problem is decomposed into two simpler optimization problems which can be solved through iteration algorithm. As an alternative, eigen-beamforming based technique is also provided to reduce the complexity of the iterative solution at the expense of the power usage. Numerical results show that the proposed solution efficiently reduces the additional power usage of the system compared to the eigenbeamforming based technique while meeting the QoS constraint of each source. Moreover, we can see the proposed algorithm converges to the steady-state value in a reasonable number of iterations.