Analysis of PHY-Layer Security and Covert Communication in Hybrid Power-Frequency Multiple Access Systems

This study analyzes the physical-layer security and covert communication in hybrid power-frequency multiple-access (PFMA) systems. By partially overlapping users’ signals in power domains coupled with orthogonal transmission, PFMA exhibits strong resistance to untrusted users exploiting information intended for a distant user in non-orthogonal multiple access (NOMA), for its ability to successive interference cancellation-free approach. In the context of internal users intercepting signals within the same power domain, external users eavesdropping on legitimate users, and external wardens monitoring communications, we derive closed-form expressions for the connection outage probability (COP), secrecy outage probability (SOP), and detection error probability (DEP). Furthermore, we establish closed-form approximations for the optimal transmitting signal-to-noise ratio and the warden’s detection threshold factors to minimize the DEP. Numerical results are studied to very demonstrate the superiority of PFMA in improving COP and SOP compared to NOMA. The study also examines the impacts of different knowledge communication channels on DEP performance.