  For crowded and hotspot area, unmanned aerial vehicles (UAVs) are usually
deployed to increase the coverage rate. In the considered model, there are
three types of services for UAV assisted communication: control message,
non-realtime communication, and real-time communication, which can cover most
of the actual demands of users in a UAV assisted communication system. A
bandwidth allocation problem is considered to minimize the total energy
consumption of this system while satisfying the requirements. Two techniques
are introduced to enhance the performance of the system. The first method is to
categorize the ground users into multiple user groups and offer each group a
unique RF channel with different bandwidth. The second method is to deploy more
than one UAVs in the system. Bandwidth optimization in each scheme is proved to
be a convex problem. Simulation results show the superiority of the proposed
schemes in terms of energy consumption.
