Security Energy Efficiency Maximization for Untrusted Relay Assisted NOMA-MEC Network With WPT

Relay assisted transmission can effectively improve the range of coverage and offloading efficiency of non-orthogonal multiple access-mobile edge computing (NOMA-MEC) system. However, the relay will become untrusted relay when it is attacked by malicious users, resulting in the leakage of information. To solve this problem, this article uses destination-assisted jamming to prevent the leakage of information during the offloading process. Under the condition of time delay and energy consumption, we jointly optimize the transmission power allocated to relay, central processing unit (CPU) frequency and offloading time to maximize the security energy efficiency of the user (UE). Since it is a non-convex multi-objective optimization problem, it is decomposed into several suboptimal single-objective sub-problems, and the single-objective sub-problems are transformed into convex problems by Taylor approximation method, then be solved by Lagrange dual method. Besides, the multi-objective iterative algorithm (MOIA) is further proposed to achieve joint optimal solution. The simulation results show that the proposed method can effectively improve the security offloading performance and security energy efficiency compared with other relay assisted offloading methods.