  In this paper, we consider the multi-UAV deployment problem for a two-hop
relaying system. For a better network performance, UAVs carry directional
antennas that are modeled by a realistic radiation pattern. The goal is to
maximize the minimum user rates, and therefore achieve fairness in the network.
We propose an iterative algorithm to optimize the TDMA scheduling in both hops,
UAV trajectories, antenna beamwidths, and transmit power of the base station
and relays. Simulation results show the throughput improvement as a result of
optimizing the directional antenna radiation patterns. In addition, we derive
the optimal power allocation, which combined with the beamwidth optimization
yields to a much better performance.
