U.S. airlines fear of 5G, explained

EVANSTON, Ill. — Randall Berry, a professor of electrical engineering at Northwestern University and an expert on wireless spectrum policy, said that there are some solutions that could assuage the fears of U.S. airlines around the deployment of 5G networks.

Berry is available to speak with media. He can be reached by contacting Mohamed Abdelfattah at mohamed@northwestern.edu.

Possible solutions 
Said Berry: “One way to solve this problem is to use better RF filters to protect the radiometers and filter out more of the out-of-band interference. The big issue here is then who would pay for upgrading these filters -- the airline industry or the companies with the 5G licenses. Other solutions that have been talked about are to limit the power of 5G base stations near airports and/or to require that 5G antennas be tilted downward (away from aircraft).

“Some of these solutions the 5G companies have said that they would voluntarily implement -- some of these for 6 months, but doing so indefinitely would decrease the value of the licenses that they purchased.”

What’s the backstory?
Said Berry: “Last year, the FCC auctioned C-Band licenses for 5G deployments. Companies like Verizon and AT&T paid a lot of money for these licenses and would now like to use this spectrum to deploy their 5G networks. The spectrum auctioned is separated by 220 MHz from the spectrum that is used by radio altimeters in aircraft. These are used to determine the height of an aircraft above ground. This is used by other systems in the aircraft for landing when visibility is poor.

“Before auctioning the spectrum, the FCC established rules to avoid interfering with the altimeters that include setting limits on the power that 5G devices can transmit at and establishing the 220MHz separation mentioned above. This was done as part of a multiyear process in which input was solicited from stakeholders. 

“The underlying issue here is that radio signals cannot be perfectly confined to their assigned frequency band and will result in some energy being transmitted in neighboring bands. Also, radio receivers cannot perfectly filter out the signals transmitted in neighboring bands and so will receive some out-of-band interference. Both of these effects result in interference from a neighboring band.  

“The FCC guidelines are an attempt to keep this interference at a low enough level. The FCC commissioners and others in the commercial wireless space feel that the established guidelines do this. The airline industry and the FAA are concerned that these measures may not be enough.”