  Unmanned aerial vehicle (UAV) base stations (BSs) are reliable and efficient
alternative to full fill the coverage and capacity requirements when the
backbone network fails to provide such requirements due to disasters. In this
paper, we consider optimal UAV-deployment problem in 3D space for a mmWave
network. The objective is to deploy multiple aerial BSs simultaneously to
completely serve the ground users. We develop a novel algorithm to find the
feasible positions for a set of UAV-BSs from a predefined set of locations,
subject to a signal-to-interference-plus-noise ratio (SINR) constraint of every
associated user, UAV-BS's limited hovering altitude constraint and restricted
operating zone constraint. We cast this 3D positioning problem as an l_0
minimization problem. This is a combinatorial, NP-hard problem. We approximate
the l_0 minimization problem as non-combinatorial l_1-norm problem. Therefore,
we provide a suboptimal algorithm to find a set of feasible locations for the
UAV-BSs to operate. The analysis shows that the proposed algorithm achieves a
set of the location to deploy multiple UVA-BSs simultaneously while satisfying
the constraints.

Signal Processing;Optimization and Control