On the Secrecy Outage Probability of NOMA Systems Affected by Imperfect SIC over κ-μ Fading Channels

Fifth-generation (5G) and beyond fifth-generation (B5G) wireless systems increase the transmission capabilities of simple devices, such as Internet of Things (IoT) devices. However, they are vulnerable to eavesdropping attacks due to their low computational processing capacity. Thus, physical layer security (PLS) appears as an interesting alternative essential for their proper operation. In this work, the secrecy performance of power-domain non-orthogonal-multiple-access (NOMA) systems affected by imperfect successive interference cancellation (SIC) is evaluated in a scenario consisting of two users operating over κ−μ fading channels. By considering that the user furthest from the base station (BS) is an untrusted user, expressions to calculate the signal-to-noise-plus-interference ratio (SNIR) of both users are derived, and with these results, an expression to evaluate the secrecy-outage-probability (SOP) for the trusted user is derived. Numerical results using Monte-Carlo simulations are carried out in some scenarios to validate the derived expressions. The results also evidence a simple strategy to minimize the SOP for the trusted user based on the κ and μ fading parameters.