AT&T, Verizon Propose to Limit Power on C-Band to Assuage FAA Concerns

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AT&T and Verizon have offered to transmit at lower power around airports for six months on their new C-band spectrum. That’s to give the FAA more time to figure out a fix for potential interference from 5G operations on 3.7 GHz to the 4.2-4.4 GHz band, where aircraft radio altimeters operate. Altimeters measure the distance from the ground to the aircraft, and the FAA and aviation and aerospace industries fear there could be harmful interference to those operations from 5G.

In a letter to the FCC on Friday, both carriers reminded the agencies that combined, they paid over $80 billion for the licenses and will hand over another $15 billion to satellite users who cleared the spectrum early. The carriers also re-iterated the FCC concluded, “after 17 years of global study and interagency dialogue across all relevant federal agencies—’the technical rules on power and emission limits we set for the 3.7 GHz Service and the spectral separation of 220 megahertz should offer all due protection to [radio altimeter] services in the 4.2-4.4 GHz band.’”  

However, AT&T and Verizon outlined several mitigation efforts they propose to put in place when they start using C-band beginning January 5, 2022. “While we remain confident that 5G poses no risk to air safety, we are also sensitive to the FAA’s desire for additional analysis of this issue,” they wrote. “Thus, to allow time for that continued analysis while also ensuring no additional delay to the launch of 5G using C-band, AT&T and Verizon commit—for a period of six months—to voluntarily adopt additional precautionary measures to supplement those protections already included in the FCC’s rules.”

Those measures include steps to minimize energy coming from 5G base stations nationwide and to a greater degree around public airports and heliports. AT&T and Verizon said: “These precautionary measures should allay concerns about radio altimeter performance.” The carriers are proposing the mitigation measures in addition to their pledge already to delay 5G operations for 30 days. They opened the door to keeping the limits in place longer, if “credible evidence emerges that real-world interference would occur if the measures were relaxed,” the carriers said in the letter.

In a note to clients, New Street Research Policy Advisor Blair Levin noted that the letter was worked out with the FCC’s engineers as the agency is negotiating with the FAA on the issue. He stated New Street analysts don’t believe the mitigation efforts will negatively impact the economics of the carriers’ 5G economic performance because they won’t affect customers’ perception of the service.

The question now is what the FAA will do. “We think the letter, in conjunction with significant support, we believe, from the White House and the Hill, should move the FAA to declare victory and move on,” wrote Levin.

An FAA spokesman called the proposals “an important and encouraging step, and we are committed to continued constructive dialogue with all of the stakeholders,” reported The Hill. “The FAA believes that aviation and 5G C-band wireless service can safely co-exist.”  

By Leslie Stimson, Inside Towers Washington Bureau Chief

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