Relay beamforming for multi-pair two-way MIMO relay systems with max-min fairness

Two-way relaying showed distinct advantages in spectral efficiency for pairs of source nodes to exchange information via a multiple-input multiple-output (MIMO) amplify-and-forward (AF) relay node. This paper studies the relay beamforming problem in the scenario where multiple pairs of users communicate via a MIMO relay node, in order to achieve a beer rate and guarantee the fairness of user´s rate. In the relay beamforming design we consider the maximum of minimum information rate among the user pairs as the target and the total relay transmit power as the constrain. The corresponding optimization problem can be built into a difference-of-convex functions (DC) program, and it can be well solved by an effective algorithm. Numerical results show that, the proposed method enjoys the merits of both max-min fairness and sum-rate when compared with existing relay beamforming methods.