Secrecy Outage Performance of a Unified Non-Orthogonal Multiple Access Framework

Abstract

This paper investigates the impact of physical layer secrecy on the performance of a unified non-orthogonal multiple access (NOMA) framework. The spatial locations of legitimate users (LUs) and eavesdroppers are governed by invoking stochastic geometry. To characterize the secrecy performance of the unified framework, new exact and asymptotic expressions of secrecy outage probabilities are derived, in which both imperfect successive interference cancellation (ipSIC) and perfect SIC (pSIC) schemes are taken into account. The secrecy diversity orders achieved by a pair of LUs (the n-th user and m-th user) for CD/PD-NOMA are obtained. Analytical results make known that the secrecy diversity orders of LUs with ipSIC/pSIC for CD/PD-NOMA are equal to zero/K and zero/one, respectively. Finally, numerical results are present to confirm the accuracy of the developed analytical results.