Intelligent Reflecting Surface and Artificial-Noise-Assisted Secure Transmission of MEC System

Mobile-edge computing (MEC) and intelligent reflecting surface (IRS) have attracted much attention as promising technologies for the next-generation mobile networks and Internet of Things (IoT). In this article, we investigate how to improve the security of the MEC system with the assistance of IRS and artificial noise (AN) in the IoT. By adjusting the phase of the IRS, the users' signals can be enhanced and the eavesdroppers' signal can be weakened. In addition, the full-duplex base station (FD-BS) transmits AN to destroy the eavesdroppers' signal and further enhance the users' security. We minimize the users' secure energy consumption by jointly optimizing the base station receive beamforming vectors, AN covariance matrix, IRS phase shifts, users' offloading time, transmit power, and local computation tasks. The formulated problem is a nonconvex problem that is hard to solve directly, so we decompose it into tractable subproblems and develop an alternating optimization approach by combining the semidefinite relaxation (SDR) algorithm and Dinkelbach's method. The results show that the proposed scheme can greatly reduce the secure energy consumption compared with other benchmark scheme.