A lot of folks are wondering, rightly so, how it is that the aviation community’s problems with 5G in the C-band are just now coming up. Other than, you know, AT&T and Verizon are spending more than $68 billion for spectrum and maybe the aviation industry can get them to pay for new altimeter technology.
Why wasn’t this brought up years ago, before the FCC even auctioned the 3.7 GHz band for 5G? After all, there was a long, drawn-out process that involved many meetings, private and public, and even hearings before lawmakers in Congress where all of this dirty laundry could have been aired, debated and cleared for public consumption.
Instead, the aviation community decided that just before the wireless industry prepares to launch C-band for 5G in early December – and when the flying and (hopefully) vaccinated public is itching to get back on planes to see loved ones near and far – is the right time to bring this up.
RELATED: What do FAA C-band delays mean for AT&T, Verizon?
One of the people who was at the Federal Communications Commission (FCC) leading up to this point was Mike O’Rielly, who left the commission about a year ago and is now principal of MPORielly Consulting. O’Rielly, a Republican, worked hard on a lot of mid-band spectrum issues, and you’d be hard-pressed to find someone to say otherwise. He was in the thick of the C-band issues, including when satellite companies resisted moving an inch and content companies screamed bloody murder about losing their connections to the airwaves.
In a conversation this week, O’Rielly told me he thinks the answer to the “Why now?” question is two-fold.
First, the aviation industry representatives believe they can get someone in industry to pay for the necessary upgrades because let’s face it, the industry is in a very awkward position. Second, they have a new sympathetic ear in the administration. “We were told this administration was going to be better… and it looks to be the same game as the last go-around,” he said, referring to the inter-agency fights between government entities.
Let’s also be clear: Any time an agency can use its public safety function as a threat, “we’re not going to get very far,” he said. That’s despite the science, and here, “the science is not on their side.”
O’Rielly said his concern is the delay to January will get extended indefinitely. “This is the critical band for 5G in mid bands,” he said. The 3.45 GHz auction is still going on, and it’s not going to be cleared for a while. “What have you got as an alternative? This is the big piece.”
O’Rielly should know. He worked on C-band for about five years – maybe more, depending on how you count it. There aren’t a lot of other mid-band options. “They’re smaller and will take more time, and the CBRS spectrum has power limits. I love CBRS – don’t get me wrong, but it’s not the same,” he said.
(By the way, while the CBRS auction wasn’t as fruitful as C-band, O’Rielly views the CBRS band as a smashing success. And when you get down to it, it shouldn’t matter how much money the auction raised for the U.S. Treasury. “It’s really about putting licenses into the right hands, and that’s what the auction process does, more than any other mechanism,” he said. “I’m really happy how things turned out.”)
Back to C-band, it’s worth noting, as CTIA has done on more than one occasion (pdf), that nearly 40 other countries safety operate 5G without harmful interference to air traffic.
By the way, it would be very tempting to disregard the wireless industry because it represents the big companies that want to make money from the C-band. But take a note from the page of Public Knowledge SVP Harold Feld, who wrote this commentary spelling out a lot of what’s happening. Feld and O’Rielly probably have disagreed more than they’ve agreed on most other issues, yet they’re on pretty much the same page here.
Anyone following me knows that I'm quite critical of the @FCC when they get things wrong.— Christopher Mitchell (@communitynets) November 10, 2021
But the beginning of Harold's long take on C-BAND and @FAANews is spot on. Agencies like DOT and FAA act like whiny children when it comes to spectrum and need to be reigned in.
Like any flying member of the American public, I’m curious whether 5G will alter the course of planes.
Dennis Roberson is president and CEO of Roberson & Associates; he’s been chair of the FCC's Technological Advisory Council for the past eight years. He’s been involved in a lot wireless proceedings over the years, and he told me that in order to understand the role of altimeters in flight safety, it was helpful for him to consult his brother, who’s a retired airline pilot. Pilots rely on altimeters when landing planes and sometimes during take-offs.
Here’s how I understand it, based on the conversation. The planes used by big airlines often will have three of these altimeters, one on each wing and one on the body of the plane for triple redundancy. They also have at least two other means to sense altitude, one of those being GPS and another of the old-fashioned gauge variety that measures pressure. So there’s a system of checks and balances, if you will.
The C-band is 3.7-3.98 GHz and the spectrum band the altimeters are using is from 4.2-4.4 GHz, so the radio altimeters are more than 200 megahertz away from the C-band equipment.
“Two hundred megahertz is huge. Remember, with the FM radio band, the whole thing is 20 megahertz, so this is 10 times the entire FM band, from the lowest station to the highest station. So it’s a very long ways away,” Roberson said. Therefore, you should be safe to get on an airplane even with C-band 5G being deployed.
The first tranche of C-band spectrum to be deployed is on the lowest side – remember, the satellite companies that have been using the entire 500 MHz C-band and the plan is for them to move up to the highest part of the band.
The first section of the C-band to be used for 5G is the 3.7-3.8 GHz part. That’s 400 megahertz away from the radio altimeter, “so it’s a very, very long ways away, spectrally speaking,” he said. “There really should be no interference.”
However, in some instances, the radio altimeters can be decades old. For the older systems, there’s no filtering, so instead of using their assigned frequencies, they’re looking outside the band and that’s not cool.
Think of the spectrum as a neighborhood, except that there are no houses on the block except for yours. You’ve got the whole block to use. “Then when somebody builds a house on one of the lots that you don’t own, then you complain about it. That’s really what’s going on,” he said. In that scenario, “the filters ensure that you’re only using your own lot.”
The more modern radio altimeters are fine, but because ancient radio altimeters still exist (and you know, haven’t been recalled by the FAA), there’s what Roberson calls an “extreme edge case” where there could be a problem. For example, an old helicopter hovering in dense fog could have a problem if it’s relying on ancient altimeter technology.
The FAA should have put out a mandatory requirement for all altimeters to be upgraded and there wouldn’t be a problem, even for old helicopters hovering above 5G in the fog. But they didn’t do that, so there’s a remote possibility there could be a problem.
I don’t put this one on the FCC or the wireless industry. I reached out to the aviation community for more on their side of the story, and remain eager to hear it.—Monica @malleven33
Editor's Corners are opinion columns written by a member of the Fierce editorial team. They are edited for balance and accuracy.