  In this paper, we investigate the resource allocation design for multicarrier
(MC) systems employing a solar powered unmanned aerial vehicle (UAV) for
providing communication services to multiple downlink users. We study the joint
design of the three-dimensional positioning of the UAV and the power and
subcarrier allocation for maximization of the system sum throughput. The
algorithm design is formulated as a mixed-integer non-convex optimization
problem, which requires a prohibitive computational complexity for obtaining
the globally optimal solution. Therefore, a low-complexity suboptimal iterative
solution based on successive convex approximation is proposed. Simulation
results confirm that the proposed suboptimal algorithm achieves a substantially
higher system sum throughput compared to several baseline schemes.
