Secrecy Outage Probability Analysis for Downlink Untrusted NOMA Under Practical SIC Error

Abstract

Non-orthogonal multiple access (NOMA) serves multiple users simultaneously via the same resource block by exploiting superposition coding at the transmitter and successive interference cancellation (SIC) at the receivers. Under practical considerations, perfect SIC may not be achieved. Thus, residual interference (RI) occurs inevitably due to imperfect SIC. In this work, we first propose a novel model for characterizing RI to provide a more realistic secrecy performance analysis of a downlink NOMA system under imperfect SIC at receivers. In the presence of untrusted users, NOMA has an inherent security flaw. Therefore, for this untrusted users' scenario, we derive new analytical expressions of secrecy outage probability (SOP) for each user in a two-user untrusted NOMA system by using the proposed RI model. To further shed light on the obtained results and obtain a deeper understanding, a high signal-to-noise ratio approximation of the SOPs are also obtained. Lastly, numerical investigations are provided to validate the accuracy of the desired analytical results and present valuable insights into the impact of various system parameters on the secrecy rate performance of the secure NOMA communication system.

Investigations on Secrecy Performance of Downlink Overlay CR-NOMA System With SIC Imperfections

“…However, all these aforementioned research works are confined to analyzing the performance of cooperative NOMA system under imperfect SIC assumptions but they have not considered CR-NOMA systems. In order to study the effect of SIC on real-world detectors, the authors in [31] present a new generalized residual interference (RI) approach. They used the proposed method to analyze RI at receivers in a two-user untrusted NOMA network and found the analytical and asymptotic formulations of SOP for both users.…”

“…where χ ∈ {sc, mrc}, R p is the target rate of symbol x p , and the secrecy outages P 1 (already evaluated and solution given in (31), and now P sc 2 & P mrc 2 can be derived as follows: Case-1: SC Diversity…”