Secrecy and reliability performance of an energy-harvesting-enabled two-user NOMA system

We analyze the secrecy attributes of an energy-harvesting-enabled decode-and-forward relay-based cooperative nonorthogonal multiple access (NOMA) system in the presence of an eavesdropper. Information flow through the wireless channel exposes legitimate users to eavesdropping by unintended users on confidential information. We study the secrecy performance of two-user NOMA systems by calculating the secrecy outage probability (SOP) and ergodic secrecy capacity (ESC). An eavesdropper overhears the signal from a source and relays it from a relay node. We evaluate the secrecy performance of both nodes (i.e., relay node ( $U_1$) and distant node ( $U_2$)) by developing a novel closed-form expression for node $U_1$. For node $U_2$, we evaluate an analytical but intractable expression of SOP and tractable analytical expression of ESC. We examine the effects of network parameters on secrecy and link outages. We also observe the reliability of the link outage probability of node $U_2$ and system outage probability. Monte Carlo simulations are conducted to verify the analytical results and evaluate the effect of SOP on imperfect channel state information and perfect channel state information.