Novel Outage-Aware NOMA Protocol for Secrecy Fairness Maximization Among Untrusted Users

Abstract

Observing the significance of spectrally-efficient secure non-orthogonal multiple access (NOMA), this paper proposes a novel quality of service (QoS) aware secure NOMA protocol that maximizes secrecy fairness among untrusted users. Considering a base station (BS) and two users, a novel decoding order is designed that provides security to both users. With the objective of ensuring secrecy fairness between users, while satisfying their QoS requirements under BS transmit power budget constraint, we explore the problem of minimizing the maximum secrecy outage probability (SOP). Closed-form expression of pair outage probability (POP) and optimal power allocation (PA) minimizing POP are obtained. To analyze secrecy performance, analytical expressions of SOP for both users are derived, and individual SOP minimization problems are solved using concept of generalized-convexity. High signal-to-noise ratio approximation of SOP and asymptotically optimized solution minimizing this approximation is also found. Furthermore, global-optimal solution from secrecy fairness standpoint is obtained at low computational complexity, and tight approximation is derived to get analytical insights. Numerical results present useful insights on globally optimized PA which ensure secrecy fairness and provide performance gain of about 55.12%, 69.30%, and 19.11%, respectively, compared to fixed PA and individual users' optimal PAs. Finally, a tradeoff between secrecy fairness performance and QoS demands is presented.

Decoding Orders and Power Allocation for Untrusted NOMA: A Secrecy Perspective

“…Besides, [11] assumes perfect SIC that cancels the interference from the decoded users entirely which is a strong assumption due to practical implementation issues [2]. Therefore, imperfect SIC model is highly realistic to explore secure NOMA which has been considered in [13] for two-user NOMA case. To this end, we focus to secure a three-user untrusted NOMA system under practical imperfect SIC based decoding at receivers, which to the best of our knowledge, has not been investigated yet in the literature.…”

Secrecy Fairness Aware NOMA for Untrusted Users

“…However, in real scenarios, perfect SIC cannot be readily satisfied due to various implementation problems such as error propagation. Therefore, imperfect SIC model where residual interference from imperfectly decoded user exists after SIC, is highly realistic to explore secure NOMA which has been considered in the extended version of this work [12].…”

Secure Transmission Design for Cooperative NOMA in the Presence of Internal Eavesdropping

“…hand, it is difficult to achieve positive secrecy rates for a far user since an untrusted near user can easily intercept messages intended for the former due to the stronger channel gain between the BS and the near user [11]. On the other hand, an untrusted far user may access the information of a near user, which results in confidential information leakage.…”