Security Enhancement With a Hybrid Cooperative NOMA Scheme for MEC System

This article investigates how to exploit the cooperative mechanism between non-orthogonal multiple access (NOMA) user pairs to enhance the security of the mobile-edge computing (MEC) system. Considering the different delay requirements of Internet of Things (IoT) users, we propose a two-slot hybrid cooperative NOMA security (THCNS) scheme that utilizes the cooperative interference between NOMA user pairs to enhance the security of offloading. In the first time slot, the interference to the eavesdropper comes from the task signals (TSs) transmitted by the two users, while in the second time slot comes from jamming signal (JS) transmitted by the user who has completed the offloading tasks. The weighted sum secrecy outage probability (wSOP) and secrecy computation probability (SCP) are utilized to measure the security performance of users in the proposed scheme. To confirm the feasibility and applicability of the proposed scheme, we analyze the impact of some key parameters on users' security, including the users' local computation time and offloading time, transmit power, task allocation coefficients of two time slots. The analysis results indicate that the proposed scheme is more suitable for the case where the wiretap channel outperforms the main channel, and it can enhance the system security when selecting the optimal parameters. Finally, the numerical simulation results reveal how the analysis parameters affect the security performance of users and validate the theoretical analysis, it provides good insights about how to design parameters of IoT users to enhance their security performance in MEC system.