  Unmanned aerial vehicles (UAVs) are expected to coexist with conventional
terrestrial cellular networks and become an important component to support high
rate transmissions. This paper presents an analytical framework for evaluating
the throughput performance of a downlink two-tier heterogeneous network.
Considering the minimum distance constraint among UAVs, Mat\'{e}rn hardcore
point process (MHP) is utilized to model the locations of UAVs. The locations
of terrestrial base stations (BSs) are modeled by Poisson point process (PPP).
Tools of stochastic geometry are invoked to derive tractable expressions for
average data rates of users. With the analytical results, we discuss the
optimal combinations of UAVs' height and power control factor. The result shows
that an appropriate power control factor can effectively maximize UAV users'
average data rate as well as guaranteeing the BS users' performance under our
proposed model.
