  The deployment of aerial base stations (ABSs) on unmanned aerial vehicles
(UAVs) presents a promising solution for extending cellular connectivity to
areas where terrestrial infrastructure is overloaded, damaged, or absent. A
pivotal challenge in this domain is to decide the locations of a set of ABSs to
effectively serve ground-based users. Most existing approaches oversimplify
this problem by assuming that the channel gain between two points is a function
of solely distance and, sometimes, also the elevation angle. In turn, this
paper leverages propagation radio maps to account for arbitrary air-to-ground
channel gains. This methodology enables the identification of an approximately
minimal set of locations where ABSs need to be deployed to ensure that all
ground terminals achieve a target service rate, while adhering to backhaul
capacity limitations and avoiding designated no-fly zones. Relying on a convex
relaxation technique and the alternating direction method of multipliers
(ADMM), this paper puts forth a solver whose computational complexity scales
linearly with the number of ground terminals. Convergence is established
analytically and an extensive set of simulations corroborate the merits of the
proposed scheme relative to conventional methods.
