  Unmanned Aerial Vehicle (UAV) systems are being increasingly used in a broad
range of scenarios and applications. However, their deployment in urban areas
poses important technical challenges. One of the most prominent concerns is the
robustness of communications between the ground stations and the UAVs in a
highly dynamic and crowded spectrum. Indeed, competing data streams may create
local or temporary congestion impairing the ground stations to control the
UAVs. The main contribution of this paper is a robust multi-path communication
framework for UAV systems. The framework continuously probes the performance of
multiple wireless multi-hop paths from the ground stations to each UAV, and
dynamically selects the path providing the best performance to support timely
control. Numerical results, based on a real-world implementation and extensive
field experimentation, demonstrate the ability of the proposed framework to
provide robust control against exogenous interference and network congestion.
