Maximizing the Sum-Rate of Secondary Cognitive Radio Networks by Jointly Optimizing Beamforming and Energy Harvesting Time

Abstract

In this paper, we consider an energy harvesting (EH) cooperative cognitive radio network (CCRN) framework, in which the primary network (consisting of a transmitter-receiver pair) shares both energy and spectrum with the secondary network (consisting of two transceivers and multiple amplify-and-forward (AF)-based relays). Since the relays have no power source, they periodically switch between the EH and information transmission (IT) tasks. In particular, we apply a sum-rate maximization strategy to jointly obtain the optimal EH time allocation factor and distributed beamforming coefficients that achieve the best system performance for the secondary network under the individual EH power constraints at relays and an interference power constraint at the primary receiver. Although the formulated optimization problem is non-convex and complicated, we devise an efficient iterative scheme by applying the semi-definite relaxation (SDR) technique followed by the successive upper-bound minimization (SUM) strategy. Our simulation results confirm that the proposed method is spectrally and energy efficient.