Assessing 5G Radar Altimeter Interference for Realistic Instrument Landing System Approaches

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  • Author: Kenneth M. O’Hara

On June 17, 2022, the Federal Aviation Administration (FAA) announced that Verizon and AT&T have voluntarily agreed to delay some C-Band 5G usage until July 2023 to allow the process of retrofitting airplanes to complete. Nevertheless,Verizon noted that the agreement will allow the wireless carriers to “lift the voluntary limitations on our 5G network deployment around airports in a staged approach over the coming months. There is therefore a need in the coming months to accurately determine the degree to which 5G interference with legacy radar altimeters poses a risk for landing approaches around US airports on a site-specific basis so that 5G base stations within the formerly restricted zones can be turned on while simultaneously ensuring safety.

The present article provides an example of one such study. Specifically, the potential for 5G radar altimeter interference during a precision Category II/III (CAT II/III) ILS landing approach to runway 27L at O’Hare International Airport (ORD) is examined.This particular scenario was chosen as it was also considered in the RTCA technical report. In contrast to the analysis performed in the RTCA technical report, however, the present study includes interactions of 5G emissions with terrain and building structures in analyzing the potential risk for interference. We find that the inclusion of interactions with terrain and building structures using realistic geometry obtained from OpenStreetMap (OSM) [12] can significantly increase the predicted strength of received power from 5G emissions at the location of a radar altimeter for an aircraft following this ILS approach. For certain locations along the approach and for certain terrain conditions, the increase can be so substantial that the Interference Tolerance Mask (ITM) used in the RTCA study for commercial air transport aircraft and/or an associated safety margin become violated.

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