Spectrum Sharing and Energy Cooperation in Wireless Powered Cognitive Radio Networks

Abstract

In this work, we consider a cognitive radio system, where the primary user (PU) owns the spectrum but has scarce energy while the secondary users (SUs) have adequate energy but lack of spectrum. Thus, a spectrum sharing and energy cooperation scheme is proposed, where the SUs help transfer energy to the PU in the first phase, and in return, the PU allows the SUs to access the spectrum in the second phase. This is particularly beneficial when the PU is energy-limited wireless sensor node or internet of things and the transmitters of SUs are base stations or access points with sufficient energy supply. Without loss of generality, we aim to maximize the minimum data rate among all SUs by jointly optimizing the time- splitting factor between the two phases, the transmission power at the primary transmitter (PT) and the precoding vectors for secondary transmitters (STs) under the minimum data rate requirement of the PU, and the power constraint at each ST. We also guarantee the energy causality constraint at the PT, i.e., the total consumed energy should be no larger than the total available energy. To solve this non-convex problem, we propose an efficient iterative algorithm by applying the successive convex approximation (SCA) and further show that the proposed algorithm is guaranteed to converge. Simulation results are finally presented to show the effectiveness of our proposed scheme.