Aviation Concerns Not Expected to Derail C Band

With C-band deployments starting this year, aviation concerns about protecting radio altimeters aren't expected to be an initial big impediment, experts said in recent interviews. Aviation safety advocates expect the FCC and the FAA to continue watching closely for any issues. The FCC’s record-setting C-band auction was of licenses at 3.7-3.98 GHz; altimeters are at 4.2-4.4 GHz.

Aviation groups and companies seek a joint FAA/FCC oversight process (see 2108160029). The 220 MHz separation between the bands “falls well short of protecting radio altimeters given the flexible use power levels permitted under the rules adopted” by the FCC, the groups said. The FCC and FAA didn’t comment Monday.

The aviation industry takes the potential for interference “very seriously,” emailed an International Air Transport Association spokesperson. “Along with other stakeholders including aircraft and avionics manufacturers, we are advocating for collaboration between the FAA and the FCC to safeguard aircraft altimeters,” the spokesperson said. “France and Japan have issued technical and deployment conditions protecting aircraft radio altimeters from possible 5G interference. Canada is now considering a similar approach. We encourage the US to follow this important trend.”

There are challenges for the FCC, said BitPath Chief Operating Officer Sasha Javid. “At this point, it is too difficult to say what the FCC should and will do.” The wireless industry’s strongest argument may be “that Japan has already deployed thousands of 5G base stations just 100 MHz away from the altimeter band … with no claims of interference,” he said: “But the aviation organizations have been pretty consistent that interference will occur, and the FCC certainly want[s] to independently vet these arguments, given the public safety implications. With limited time before the carriers plan to light up the first tranche of expensive C-band spectrum, the pressure is certainly on FCC staff.”

“My sense is that the FCC will stay on the current course until measurable interference can be shown rather than calculated,” said Brian Goemmer, president of AllNet Insights & Analytics. The FCC “has an institutional incentive to accelerate, not retard, deployment,” said New Street’s Blair Levin.

“The FCC studied this issue extensively, and it is now time to deploy,” a CTIA spokesperson emailed: “Numerous other countries are actively and successfully using this band in their 5G networks without any real-world evidence of interference.”

The C-band auction was “incredibly important” and altering the parameters to the degree sought by the aviation industry “seems unlikely at this point given the commission staff already examined and rejected the arguments,” said former Commissioner Mike O’Rielly.

Aviation advocates remain hopeful the FCC and FAA will act. “There is strong lobbying on both sides of the issue and I expect some action” by both agencies “this year,” said Daniel Schwarzbach, CEO of the Airborne Public Safety Association.

“The FAA and FCC should work together with the aviation and telecommunication industries to ensure the safety of the airspace and public,” emailed an Aerospace Industries Association spokesperson: “While we understand and support the importance of making spectrum available to enable next generation commercial wireless communications, there should be more inter-agency and industry coordination to identify mitigations that each user community can introduce to reduce risks.”

The protections sought by aviation interests from the C band is an example of why sharing is difficult, said Andrew Clegg, Google spectrum engineering lead, at a recent Silicon Flatirons conference (see 2109100068). “They’re worried about interference from the 3.7 GHz service, 220 MHz away” and since altimeters mostly use the center part, it’s closer to 270 MHz, he said: “The overprotection of incumbents based on questionable interference criteria and assumptions is a real challenge to spectrum sharing.”