Research on Physical Layer Security of Cooperative NOMA System Based on MF Protocol

For evaluating the problem of information security transmission in cooperative Non-Orthogonal Multiple Access (NOMA) system, a Physical Layer Secure (PLS) transmission scheme based on Modify-and Forward (MF) relay is proposed. The scheme uses MF relay to modify the decoded information and then forward it, to avoid disclosing the legitimate information to the eavesdropping node. Firstly, the NOMA-MF system is modeled, and then Secrecy Outage Probability (SOP), Strictly Positive Security Capacity (SPSC) and Intercept Probability (IP) are deduced to measure the confidentiality and security of the system and Outage Probability (OP) to measure its reliability. In addition, the asymptotic performance of the system is derived, and the performance of NOMA-DF system and NOMA-MF system under Decode-and-Forward (DF) protocol is compared. The derivation and the simulation results show that: The confidentiality and security performance of NOMA-MF system has more advantages than that of NOMA-DF system; There is an optimal Signal-to-Noise Ratio (SNR) between OP and IP of NOMA-MF system to achieve the balance of system safety and reliability; There is an optimal power allocation parameter to achieve the lowest SOP and OP.