Characterization of the Indoor-to-Outdoor Wireless Channel in Air-to-Ground Communication Systems

Wireless communication between User Terminals (UTs) inside a building and an outdoor base station mounted onboard an unmanned aerial vehicle (UAV) is receiving a higher interest in emergency management scenarios and where users require on demand high throughput services. In such applications, a fundamental aspect is the thorough characterization of the propagation environment through parameters such as the UTUAV distance and the number of walls and floors crossed. In this paper, we characterize the indoor-to-outdoor wireless channel by using a commercial ray-tracing software. The reference scenario is a four-floor building. The UTs are uniformly distributed within each floor and two UAV positions are considered nearby the building. As a main contribution, we present numerical results in terms of path loss against the UT-UAV distance. The dependence of the path loss on the number of floors between the UT and the UAV is highlighted as well. Finally, the ray-tracing results are compared with those predicted by a few available propagation models.