  Unmanned aerial vehicles (UAVs) are a convenient choice for carrying mobile
base stations to rapidly setup communication services for ground users. Unlike
terrestrial networks, UAVs do not have fiber optic back-haul connectivity
except when they are tethered to the ground, which restricts their mobility. In
the absence of back-haul, e.g., in remote areas, emergency situations, or in
battlefields, there is a need to ensure connectivity among UAVs in addition to
coverage of ground users for creating local area networks. This paper provides
a distributed and dynamic approach for UAV formation-based control for coverage
and connectivity of spatially dispersed users. We use flocking dynamics as a
guide to constructing tailored formations of UAVs on the fly. Simulation
results demonstrate that if sufficient aerial base stations are available, the
proposed approach results in a strongly connected network of UAVs that is able
to provide both a backhaul and fronthaul network. The approach can be further
extended to create multi-tier extra-terrestrial networks to cater for
large-scale applications.
