Computation Capacity Maximization for UAV and RIS Cooperative MEC System with NOMA

In this letter, we investigate the mobile edge computing framework with unmanned aerial vehicle (UAV) and reconfigurable intelligent surface (RIS) collaboration, in which a dedicated non-orthogonal multiple access (NOMA) based protocol is introduced for task offloading. In the model, the UAV acts as a relay node and computation server to support multiple ground users for offloading computation tasks to remote access point with the assistance of the RIS. To explore the impact of the joint UAV and RIS design with NOMA on computation performance, the sum computation bits maximization problem is formulated by optimizing computation and offloading bits, RIS phase shift design, UAV trajectory and bandwidth allocation. In order to obtain the solution, the original problem is decomposed into three more tractable subproblems, which can be solved by applying semidefinite relaxation method and successive convex approximation technique. Finally, the numerical solution demonstrates that our proposed algorithm achieves improvements on computation capacity compared with the benchmark and outperforms considerably the scheme without collaboration of the UAV and RIS.