Joint Trajectory Optimization and Time Slot Allocation for Buffer-Aided UAV Mobile Relaying

Unmanned aerial vehicle (UAV) communication has been attracting increasing research interests recently. In this work, we study a buffer-aided single-UAV mobile relaying system which assists communication between a source node and a destination node on the ground. Specifically, in a slotted time system where each time slot experiences quasi-static channel condition, the buffer-aided UAV relay’s flight trajectory and the allocation of the time slots for transmission and reception are jointly optimized, subject to the information causality and UAV mobility constraints. The formulated problem is non-convex and the two sets of design variables, i.e., the trajectory position variables and the time slot allocation variables, are coupled. In order to make the problem tractable, we relax and decompose the original problem into two subproblems, i.e., the flight trajectory optimization subproblem and the time slot allocation subproblem, such that the two sets of design variables are decoupled. The two subproblems are optimized in an alternating manner until convergence to obtain solution to the joint optimization problem. Simulation results show that the proposed iterative alternating optimization algorithm is efficient and fast converging.