  For emergency response scenarios like firefighting in urban environments,
there is a need to both localize emergency responders inside the building and
also support a high bandwidth communication link between the responders and a
command-and-control center. The emergency networks for such scenarios can be
established with the quick deployment of Unmanned Aerial Vehicles (UAVs).
Further, the 3D mobility of UAVs can be leveraged to improve the quality of the
wireless link by maneuvering them into advantageous locations. This has
motivated recent propagation measurement campaigns to study low-altitude
air-to-ground channels in both 5G-sub6 GHz and 5G-mmWave bands. In this paper,
we develop a model for the link in a UAV-assisted emergency location and/or
communication system. Specifically, given the importance of Line-of-Sight (LoS)
links in localization as well as mmWave communication, we derive a closed-form
expression for the LoS probability. This probability is parameterized by the
UAV base station location, the size of the building, and the size of the window
that offers the best propagation path. An expression for coverage probability
is also derived.
  The LoS probability and coverage probabilities derived in this paper can be
used to analyze the outdoor UAV-to-indoor propagation environment to determine
optimal UAV positioning and the number of UAVs needed to achieve the desired
performance of the emergency network.
