Physical Layer Security And Low-latency Transmission Design For NOMA-MEC Systems

The popularity of mobile terminals and the large-scale growth of Io T devices have led to an exponential increase in the amount of transmission data in the network,which has placed tremendous pressure on the current communication network.As a key technology in 5G networks,the combination of Mobile Edge Computing and Non-orthogonal Multiple Access not only provides cloud storage and computing resources for mobile devices,which alleviates the pressure brought by the rapid growth of data volume,but also greatly enhance the communication system's large-scale access capabilities.In order to further improve the performance of the communication system and enhance the service quality of users,this paper studies the optimization of the secure transmission capability of the MEC system assisted by NOMA and the optimization of the system delay under different offload modes.The specific content is as follows:1.We studies the security performance optimization of the hybrid NOMA-MEC system in the full offload mode.Due to the fact that the security performance of the primary user in this system is the same as that in the OMA mode,the focus is only on the security performance optimization of the secondary user.At the same time,in order to overcome the problem that the eavesdropper's channel state information is difficult to obtain accurately,we introduce the concept of AEA to transform the minimization problem ofthe probability of security interruption into the maximization problem of AEA.Since the problem is non-convex,we propose an iterative algorithm to solve it based on the alternating optimization method.Simulation results show that the scheme can effectively improve the security performance of the system.2.The minimization problem of the delay in the multi-user NOMA-MEC system under the full offload mode is studied.In the full offloading process,because the uplink transmission process,the server calculation and user download calculation results are independent,and there are a lot of research on the uplink transmission process,so we only study the delay optimization problem in the server calculation and user download calculation results,which is a non-convex optimization problem.This problem is transformed into a convex optimization problem after some manipulations,for which we can obtain the closed-form solution of the problem by the Lagrangian multiplier method.At the same time,simulation results show the superiority of this scheme over the benchmark scheme.3.The problem of delay optimization of multi-user NOMA-MEC system under partial offload mode is studied.Since this problem is a complex non-convex optimization problem,we propose a joint communication and computing resource optimization algorithm based on the block coordinate descent method.To tackle the non-convexity of this problem,we decompose the problem into four sub-problems,and the closed-form solutions are obtained,respectively.Simulation results show that the algorithm can siginificantly reduce the delay comparead to the benchmark method.