Joint Differential Evolution and Successive Convex Approximation in UAV-Enabled Mobile Edge Computing

UAV-enabled mobile edge computing (MEC) is an emerging technology to support resource-intensive yet delay-sensitive applications with edge clouds (ECs) deployed in the proximity to mobile users and UAVs served as computing base stations in the air. The formulated optimization problems therein are highly nonconvex and thus difficult to solve. To tackle the nonconvexity, the successive convex approximation (SCA) technique has been widely used to solve for the nonconvex optimization problems by transforming the nonconvex objective functions and constraints into suitable convex surrogates. However, the optimal solutions are based on the approximated optimization problem not the original one and they are highly dependent on the feasible solution initialization. Unlike SCA, Differential Evolution (DE) is a global optimization method that iteratively updates the best candidate solutions with respect to the predefined objective functions. DE works well especially in unconstrained optimization problems since it can freely search very large regions of possible solutions without considering the convexity of the original problem. However, when it comes to the constrained optimization problem, DE becomes inefficient to find the feasible and optimal solutions within given time limits. In view of the shortcomings incurred in both DE and SCA, we propose an innovative algorithm by jointly applying DE and SCA (DE-SCA) to solve for the nonconvex optimization problems. However, directly using full DE solutions to initialize the SCA-based algorithm will result in worse objective function values as the DE solutions are often infeasible. Therefore, we further design to screen the feasible parts from the DE solutions and utilize them to initialize the SCA-based algorithm. In experimental simulations, we consider a system of UAV-enabled MEC where IoT devices, the UAV and ECs interact with each other. The simulation results demonstrate that our proposed Screened DE-SCA algorithm largely outperforms the benchmarks including DE, SCA-based and state-of-the-art algorithms in the UAV-enabled MEC system.