  To reap the benefits of dense small base station (SBS) deployment, innovative
backhaul solutions are needed in order to manage scenarios in which high-speed
ground backhaul links are either unavailable or limited in capacity. In this
paper, a novel backhaul scheme that utilizes unmanned aerial vehicles (UAVs) as
an on-demand flying network linking ground SBSs and the core network is
proposed. The design of the aerial backhaul scheme is formulated as a network
formation game among UAVs that seek to form a multi-hop backhaul network in the
air. To solve this game, a myopic network formation algorithm which reaches a
pairwise stable network upon convergence, is introduced. The proposed network
formation algorithm enables the UAVs to form the necessary multi-hop backhaul
network in a decentralized manner thus adapting the backhaul architecture to
the dynamics of the network. Simulation results show that the proposed network
formation algorithm achieves substantial performance gains in terms of both
rate and delay reaching, respectively, up to 40% and 41% compared to the
formation of direct communication links with the gateway node (for a network
with 15 UAVs).
