Potential RF interference to control links of small unmanned aircraft

The control links of small unmanned aircraft (UA) systems (UAS) typically operate in the 72-73, 902-928, and 2400-2483.5 MHz bands. They share those bands with many radio-frequency (RF) emitters that expose the links to the possibility of RF interference (RFI) and resultant control link interruptions. In this analysis we quantitatively assess the potential interference levels to which such links may be subjected. We characterize unlicensed emitters in the bands of interest, and estimate the resultant aggregate RFI levels to which small UAS uplink receivers may be exposed while operating at various altitudes above representative locales within the U.S. We also analyze the potential interference impacts of licensed RF transmitters, which are far less numerous but often individually much more powerful than the unlicensed emitters. We conclude that the possibility of RFI from the two classes of emitters may degrade the reliability of UAS control links operating in these bands, especially in populated areas. However, before any firm conclusions can be drawn from our findings, it will be necessary to validate our methodology by performing field measurements of ambient power densities and uplink performance at typical small-UA altitudes in a variety of locales within U.S. airspace.