Abstract
In this paper, we investigate the energy efficiency maximization (EEM) problem for underlay cognitive multiuser two-way relay networks, by jointly optimizing the power allocation of secondary users and the beamforming matrix of the cognitive relay. The EEM problem is highly non-convex and thus the global optimum is intractable. We first show that the EEM problem can be equivalently transformed to a difference of convex program. Then an efficient iterative algorithm based on the constrained concave convex procedure is proposed to obtain a local optimum of the EEM problem. Simulation results are presented to demonstrate that our proposed solution performs much better than existing schemes even when the iterative number is very small.