  In this paper, we consider an unmanned aerial vehicle-enabled interference
channel (UAV-IC), where each of the $K$ UAVs communicates with its associated
ground terminals (GTs) at the same time and over the same spectrum. To exploit
the new degree of freedom of UAV mobility for interference coordination between
the UAV-GT links, we formulate a joint trajectory and power control (TPC)
problem for maximizing the aggregate sum rate of the UAV-IC for a given flight
interval, under the practical constraints on the UAV flying speed, altitude, as
well as collision avoidance. These constraints couple the TPC variables across
different time slots and UAVs, leading to a challenging large-scale and
non-convex optimization problem. By exploiting the problem structure, we show
that the optimal TPC solution follows the fly-hover-fly strategy, based on
which the problem can be handled by firstly finding an optimal hovering
locations followed by solving a dimension-reduced TPC problem with given
initial and hovering locations of UAVs. For the reduced TPC problem, we propose
a successive convex approximation algorithm. To improve the computational
efficiency, we further develop a parallel TPC algorithm that is effciently
implementable over multi-core CPUs. We also propose a {segment-by-segment
method} %virtual waypoint model which decomposes the TPC problem into
sequential TPC subproblems each with a smaller problem dimension. Simulation
results demonstrate the superior computation time efficiency of the proposed
algorithms, and also show that the UAV-IC can yield higher network sum rate
than the benchmark orthogonal schemes.
