  For reliable and efficient communications of aerial platforms, such as
unmanned aerial vehicles (UAVs), the cellular network is envisioned to provide
connectivity for the aerial and ground user equipment (GUE) simultaneously,
which brings challenges to the existing pattern of the base station (BS)
tailored for ground-level services. Thus, we focus on the coverage probability
analysis to investigate the coexistence of aerial and terrestrial users, by
employing realistic antenna and channel models reported in the 3rd Generation
Partnership Project (3GPP). The homogeneous Poisson point process (PPP) is used
to describe the BS distribution, and the BS antenna is adjustable in the
down-tilted angle and the number of the antenna array. Meantime,
omnidirectional antennas are used for cellular users. We first derive the
approximation of coverage probability and then conduct numerous simulations to
evaluate the impacts of antenna numbers, down-tilted angles, carrier
frequencies, and user heights. One of the essential findings indicates that the
coverage probabilities of high-altitude users become less sensitive to the
down-tilted angle. Moreover, we found that the aerial user equipment (AUE) in a
certain range of heights can achieve the same or better coverage probability
than that of GUE, which provides an insight into the effective deployment of
cellular-connected aerial communications.
