A new cognitive radio strategy for SWIPT system

In this paper, we consider the rate maximization of a new cognitive ratio (CR) scenario when multiple primary users (PU) are operating under the simultaneous wireless information and power transfer (SWIPT) mode. Since the rate maximization problem is NP-hard, we separate the derivation approach into the following two steps: (i) we prove that the optimal transmit covariance is of rank-one; (ii) we apply the semi-definite programming (SDP) relaxation. Two suboptimal algorithms that provide the upper bound and the lower bound of the original solutions are proposed to cope with this NP-hard problem. The duality gap is demonstrated to be very small by Monte Carlo simulations.