Secrecy Communication for Wireless-Powered Cooperative NOMA Systems With a Friendly Jammer

Abstract

In this paper, we investigate the physical layer security of wireless-powered cooperative non-orthogonal multiple access (NOMA) systems with an energy harvesting (EH) friendly jammer. In particular, the eavesdropper intends to wiretap the transmitted signals from relay, and a friendly jammer, with the EH capability, emits a jamming signal to confuse the eavesdropper. We design two time phases to achieve source-to-users transmission in the systems. In the first phase, the source transmits a superimposed signal to the near user and the EH relay, which harvests energy and decodes the information simultaneously, and the jammer can harvest energy from the radio frequency signals. In the second phase, the relay forwards the signals to the two users and the transmitted signals can be wiretapped by an eavesdropper. A wireless-powered friendly jammer is applied to emit artificial noise to confuse the eavesdropper. Under the proposed scheme, we derive the closed-form expression for the secrecy throughput to evaluate the secure performance. Simulation results verify the theoretical analysis of the proposed scheme, and demonstrate that our scheme obtains better secrecy performance, as compared to the conventional cooperative NOMA scheme.