On the Secrecy Performance of Cooperative Uplink NOMA Network with SIC Imperfections

Abstract

This paper investigates the physical-layer security (PLS) aspects of the uplink cooperative non-orthogonal multiple access (NOMA) in the context of two user scenario. More specifically, this work employs the decode-and-forward (DF) relay for not only establishing a connection between the far user and base station (BS) but also enhancing the performance of far user whose channel is prone to the detrimental effects of fading and shadowing. The secrecy performance comparison between two users i.e., near user and far user is obtained under perfect and imperfect successive interference cancellation (SIC) assumptions and even the performance of FU is improved by using DF relay and instantaneous channel gain decoding order is considered at the BS under two cases. This paper analyses the performance of cooperative uplink NOMA network in the presence of an external eavesdropper in terms of secrecy ergodic capacity (SEC), secrecy ergodic sum capacity (SESC), and secrecy outage probability (SOP). This work derives the closed-form analytical expressions of SOP and SEC metrics for both strong and weak users with perfect and imperfect SIC cases in order to characterise the secrecy performance of the proposed secure cooperative NOMA network. Further, the outcomes of the simulations are shown as evidence for both the validation of the mathematical analysis and the performance of the proposed method.