In an urban environment, the linkage between UAVs and ground control stations are
subjected to multipath interference due to reflection, diffraction, and scattering between the
transmitter and receiver. Severe multipath can result in a nearly complete loss of command
signals, which can limit the UAV’s operational area or even cause a loss of the vehicle. This
paper examines the propagation of RF signals through an urbanized area using a ray-tracing
computational electromagnetics software package. Several scenarios were developed to
approximate actual operational situations. Given the UAV’s transmitter power and other system
parameters, the signal levels are computed on a grid of specified observation points. Variations
in the simulation included observation point locations, building material composition, building
density, UAV operating altitude and frequency, number of deployed UAVs and their locations,
and theoretical ray bounce considerations.
Based on a large number of simulations several guidelines for operating a UAV in a
dense urban environment are suggested, such as how to select an optimum altitude and the
potential use of “urban canyons” for communications.
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