Analysis on Secrecy Capacity of Cooperative Non-Orthogonal Multiple Access With Proactive Jamming

This paper analyzes the secrecy capacity of a cooperative relaying system using non-orthogonal multiple access (NOMA). A new cooperative NOMA scheme is proposed, where the source actively sends jamming signals while the relay is forwarding, thereby enhancing the security of intended communication links. Closed-form expressions for the ergodic secrecy rate are derived in the presence of an eavesdropper. Asymptotic approximate expressions for the ergodic secrecy rate are established in high signal-to-noise ratio (SNR) regime, which provides insights on secure NOMA transmission. Numerical results reveal the critical condition, under which NOMA is able to outperform orthogonal multiple access (OMA) in terms of secrecy rate. The proposed NOMA scheme can improve the secrecy rate by about 78.1%.