Research on Physical Layer Security of Downlink UAV Cooperative NOMA System

This paper mainly studies the physical layer security issues of the downlink UAV-assisted cooperative NOMA system, aiming to improve security while ensuring user reliability. The article establishes a UAV-assisted cooperative NOMA transmission system model, which consists of a base station, cooperative UAV, eavesdropping UAV, and two ground users (near and far). The relay strategy is decode-and-forward (DF). In the paper, the symbol error rate (SER) and secrecy outage probability (SOP) of the two users are theoretically derived and simulated, and the impacts of the positions of the cooperative UAV and eavesdropping UAV, the transmission power of the base station and cooperative UAV, as well as the power allocation coefficient on the system reliability and security are explored. Finally, strategies for improving system performance are proposed. The research results show that the secrecy outage probability of the near-end user is significantly higher than that of the far-end user, so it is necessary to focus on improving the security of the far-end user. The scheme of adding a Ground-based Cooperative Jamming station (GCJS) can effectively enhance the security of the far-end user.