Physical Layer Security in Overlay Cognitive Radio Networks With Energy Harvesting

Abstract

In this correspondence paper, we investigate the security and efficiency of data transmission for overlay cognitive radio networks, which consist of a pair of primary users, multiple pairs of energy-limited secondary users and multiple eavesdroppers. Specifically, to achieve a better tradeoff between the security of primary transmission and the efficiency of secondary transmission, we propose an optimal relay selection (ORS) based on two energy harvesting (EH) protocols, i.e., the time switching relay (TSR) protocol and power splitting relay (PSR) protocol. Building in this, the exact closed-form expressions for the secrecy outage probability (SOP) of primary transmission and ergodic rate of secondary transmission are derived with the two EH protocols, respectively. Moreover, to deeply analyze the secrecy performance, two asymptotic expressions for SOP of primary transmission are also derived under high main-to-eavesdropper ratio and the infinity number of secondary user conditions, respectively. Through the simulation analysis, we find that the ORS based on EH protocols can achieve better performance than that of ORS without EH protocol in terms of tradeoff. Moreover, PSR protocol is superior to TSR protocol.