  Unmanned aerial vehicle-aided communication (UAB-BS) is a promising solution
to establish rapid wireless connectivity in sudden/temporary crowded events
because of its more flexibility and mobility features than conventional ground
base station (GBS). Because of these benefits, UAV-BSs can easily be deployed
at high altitudes to provide more line of sight (LoS) links than GBS.
Therefore, users on the ground can obtain more reliable wireless channels. In
practice, the mobile nature of the ground user can create uneven user density
at different times and spaces. This phenomenon leads to unbalanced user
associations among UAV-BSs and may cause frequent UAV-BS overload. We propose a
three-dimensional adaptive and fair deployment approach to solve this problem.
The proposed approach can jointly optimize the altitude and transmission power
of UAV-BS to offload the traffic from overloaded UAV-BSs. The simulation
results show that the network performance improves by 37.71% in total capacity,
37.48% in total energy efficiency and 16.12% in the Jain fairness index
compared to the straightforward greedy approach.
