  This paper designs a novel ground-to-air communication scheme to serve
unmanned aerial vehicles (UAVs) through legacy terrestrial base stations (BSs).
In particular, a tractable coordinated multi-point (CoMP) transmission based on
the geometry of Poisson-Delaunay triangulation is developed, which provides
reliable and seamless connectivity for UAVs. An effective dynamic frequency
allocation scheme is designed to eliminate inter-cell interference by using the
theory of circle packing. For exact performance evaluation, the handoff
probability of a typical UAV is characterized, and then the coverage
probability with handoffs is attained. Simulation and numerical results
corroborate that the proposed scheme outperforms the conventional CoMP scheme
with three nearest cooperating BSs in terms of handoff and coverage
probabilities. Moreover, as each UAV has a fixed and unique CoMP BS set, it
avoids the real-time dynamic BS searching process, thus reducing the feedback
overhead.
