Outage Performance Analysis of Downlink NOMA Systems with Imperfect SIC Over $κ-μ$ Shadowed Fading Channels

This paper investigates the outage performance of a two-user power domain downlink Nonorthogonal multiple access (NOMA) system with imperfect successive interference cancellation (SIC) over $κ-μ$ shadowed fading channels. Specifically, by exploiting the Gamma approximation, we derive the expressions of the cumulative distribution functions (CDFs) of the instantaneous signal-to-interference-plus-noise ratios (SINRs) and hence obtain the exact expressions of the outage probabilities (OPs) of both users over different channel conditions under the consideration of imperfect SIC at the receiving end. We investigate numerous situations of $κ-μ$ channels by altering the parameters $κ$ and $μ$ to study the effects of varied channel conditions. We also discuss the flawed SIC on the system's outage performance and find that when SIC error levels drop, outage performance rises due to increased SINR. Finally, we obtained the system's diversity order for both users. To validate our numerical analysis, we use Monte Carlo simulations.