PLS of NOMA Relaying Networks Under Fisher-Snedecor $\mathcal{F}$ Composite Fading

Non-orthogonal-multiple-access (NOMA) technique has been considered to fulfill the exponential increase in wireless devices, data traffic, and access demand. Still, NOMA-aided systems are subject to wireless attacks such as eavesdropping. As a solution to encounter such menace, physical layer security (PLS) has been widely adopted to protect the networks from an information theoretic perspective. In this paper, we analyze the PLS of a downlink NOMA-aided network while employing a decode-and-forward (DF) relaying system. We assume the generalized Fisher-Snedecor composite fading
$\mathcal{F}$
, wherein Nakagami-m, Rayleigh, and one-sided Gaussian are special cases. Under those assumptions, we derive the closed-form expressions of the outage probability (OP), ergodic capacity, average secrecy capacity (ASC), and upper bound approximations. Our results are validated with Monte Carlo simulations, where they indicated that the power allocation ratio in NOMA and the fading parameters have a major impact on the system's robustness against the eavesdropping attack.