Latency-Oriented Time Scheduling and 3D Trajectory Design for Hybrid UAV-MEC Systems

This paper studies a latency-oriented air-ground hybrid mobile edge computing (MEC) system with an assistant unmanned aerial vehicle (UAV) and a ground base station (GBS) to serve and charge multiple users under the time-division multiple access (TDMA) protocol. The task completion latency minimization problem is formulated by jointly optimizing the time slot scheduling, UAV's three-dimensional (3D) trajectory design, transmit power allocation, as well as the number of required time slots. To address such a mixed integer nonconvex optimization problem, we introduce an efficient alternating optimization algorithm with a double-loop structure. In the outer loop, we constantly adjust the number of time slots by employing the bisection search method and determine the search range via feasibility check. In the inner loop, we first transform the original subproblem into an equivalent problem that maximizes the minimum computation completion ratio of the users. Then we further decompose this transformed problem into three subproblems, which can be solved by a proposed iterative algorithm. Extensive experiments are conducted to illustrate the efficacy and superiority of the proposed algorithm over the other benchmark schemes in minimizing the task completion latency.