The aviation industry has been worried that 5G transmissions on C-Band frequencies will interfere with airplane altimeters which the telcos claim is unproven.
The commitment came Monday night, when AT&T and Verizon agreed to one more delay of two weeks, pushing their deployment off until January 19. They had previously agreed to a delay from December 5 until January 5. Terms of Monday's deal were described in an attachment to a letter (PDF) that Secretary of Transportation Pete Buttigieg sent to the carriers. "In light of the foregoing, and subject to any unforeseen aviation safety issues, DOT and FAA will not seek or demand any further delays of C-Band deployment," the deal terms say.
Buttigieg thanked the AT&T and Verizon CEOs, writing, "Your voluntary agreement both to delay initial deployment by two weeks, and to subsequently adopt some additional mitigations, will give us additional time and space to reduce the impacts to commercial flights... We are confident that your voluntary steps will support the safe coexistence of 5G C-Band deployment and aviation activities."
The deal incorporates voluntary commitments that AT&T and Verizon previously made, including "C-Band radio exclusion zones" around airports for six months. The aviation industry will give carriers "a list of no more than 50 priority airports" where the exclusion zones will apply.
AT&T and Verizon will provide data on base stations, operating characteristics, and planned deployment locations. They will also "continue to work in good faith with aviation stakeholders to support the technical assessment of individual altimeters and airport environments," the deal says.
The FAA previously said it "will safely expedite the approvals of Alternate Means of Compliance (AMOCs) for operators with high-performing radio altimeters to operate at those airports," signalling that airlines may already be using altimeters that can co-exist with C-Band transmissions. AT&T and Verizon's C-Band spectrum licenses are for the frequencies from 3.7 GHz to 3.98 GHz, but the companies don't plan to deploy between 3.8 GHZ and 3.98 GHz until 2023. The radio altimeters used to determine airplane altitudes rely on spectrum from 4.2 GHz to 4.4 GHz."
Assuming there are no further problems, AT&T and Verizon would be able to use their spectrum licenses without extra restrictions after July 5, the report says.
"At the end of the commitment period specified in the Voluntary Commitments (i.e. through July 5, 2022), Licensees intend to deploy 5G base stations in any manner consistent with their C-Band Licenses, all customary rules and regulations, and any additional airport-specific mitigation measures Licensees have committed to take based on their continued engagement with the FAA and the aviation industry," the agreement said.