Joint Communication and Computation Cooperation in Wireless-Powered Mobile-Edge Computing Networks With NOMA

Abstract

Incorporating wireless power transfer (WPT) into mobile edge computing (MEC) is an effective way to enhance the self-sustainability of the MEC network. However, it is susceptible to the effect of double-far-near. Meanwhile, inspired by the fact that non-orthogonal multiple access (NOMA) has shown its great potential in improving the spectral efficiency of the network over OMA, this paper investigates a cooperative computation offloading scheme for a basic three-node wireless powered MEC scenario with NOMA, where users overcome the effect of double-far-near through joint communication and computation cooperation. Specifically, we consider a “harvest-then-offload” protocol composed of three stages. In the first stage, users harvest wireless energy signals from the access point (AP). In the second and third stages, based on NOMA, users offload their partial computing tasks on the same time-frequency resource block by using the harvested energy, in which the near user can cooperatively compute and forward the computing task of the far user. We formulate an optimization problem to minimize the transmission energy consumption of the AP by jointly optimizing the transmission power, the offloading coefficient and the duration of each stage. Due to the non-convexity of the formulated problem, we first transform it into an equivalent one by using the variable substitution method. Then, we propose an efficient iterative algorithm based on the successive convex approximation (SCA) and Lagrangian duality method to solve this transformed problem. Simulation results show that the proposed algorithm has good convergence and the proposed scheme can achieve the best performance compared with several baseline schemes, which highlights the superiority of the proposed scheme.