3D-Trajectory Design for Outage Minimization in UAV-Assisted 5G Communication System

In this paper, we study and optimize the trajectory for unmanned aerial vehicle (UAV) to provide fifth-generation (5G) cellular service to users in a given area. We consider a single UAV launched from the fixed initial to the final location, during which it serves the ground users that are distributed in a circular field. We introduced an optimization problem to minimize the average outage probability of the system by optimizing the three-dimensional (3D) trajectory of the UAV. As this problem is nonconvex, we proposed an efficient approach that involves two steps, firstly it frames a new problem to obtain a globally optimal location in 3D space for minimal average outage probability. This problem is shown to be conditionally convex and an efficient algorithm is proposed to obtain a globally optimal location within an acceptable tolerance. Thereafter, a sub-optimal solution is proposed for the original problem. Simulation results provide useful insights into the sub-optimal trajectory of UAV and show that our proposed approach on an average provides 24% outage improvement over the benchmark scheme. This improvement is further enhanced with the increase in the velocity of UAV.