After several weeks of false starts and dire warnings from the aviation industry, today marks the day that AT&T and Verizon go live with their new C-band 5G spectrum.
Today’s rollout marks the culmination of more than a year of work by the Federal Communications Commission (FCC) and the carriers to allocate and auction off the new spectrum, after both AT&T and Verizon won record-breaking bids to secure large chunks of it.
However, it’s also been a year of wrangling between the Federal Aviation Administration (FAA), U.S. Department of Transportation, and officials from within the aviation industry, many of whom have predicted near-catastrophic consequences for air travel should the new spectrum go live.
Igor Starkov / Unsplash
The story so far
Had it been up to the FAA and the U.S. Department of Transportation, there never would have been a C-band spectrum auction at all. As far back as December 2020, aviation experts from both the civil and military sides were warning of “catastrophic” consequences due to potential interference between the new 5G frequencies and common aircraft instruments like radar altimeters.
A December 2020 report by Defense News was the first to spotlight internal discussions between the head of the FAA and the number two at the Department of Transportation. These two senior officials sent a joint memo to then-FCC Chair Ajit Pai, calling on the FCC to pause the sale of the new C-band spectrum so that the issue could be studied more closely.
The FCC responded by saying that it had conducted its own technical studies showing there was little to no risk involved. It refused to delay the spectrum auction, stating that it intended to continue moving forward as planned.
Following the FCC’s decision, the U.S. Defense Department and Department of Homeland Security began scrambling to ensure that the proposed spectrum wouldn’t have any negative effects on military aircraft. At the time, Defense News noted that the Pentagon had not studied the effects, and therefore hadn’t established a formal position on the sale.
The best-case scenario, according to officials, was that the department would have to “spend millions of dollars and thousands of man-hours to design, procure, and install new radar altimeters across the military’s fleet of airborne systems.”
The worst case, as one senior government official put it, was that “there will be accidents, property’s going to be destroyed, and people are going to die.”
A civil matter
Interestingly, even though the civil aviation industry has been sounding the alarm for the past few months, the military side has been remarkably quiet. While the most charitable interpretation would be that the Pentagon studied the issue and determined that it wasn’t a big deal, it’s equally possible that the Department of Defense simply dipped into its relatively deep pockets and quietly upgraded its hardware behind the scenes.
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The airline industry doesn’t necessarily have the same option. For one thing, it’s responsible for the safety of civilian passengers, and for another, these are for-profit companies that have considerably more limited budgets, and arguably larger and more diverse fleets of aircraft.
There have been discussions between the airlines, the FAA, and the U.S. Department of Transportation about allocating resources to help upgrade or replace potentially affected equipment, but that’s still a massive undertaking, both logistically and politically.
To date, the airlines have instead been clamoring for AT&T and Verizon to hold off on deploying the new spectrum. In November, the two carriers agreed to delay their rollouts from December 5, 2021, to January 5, 2022, to give the FAA and other experts more time to study the effects.
In December, the carriers also agreed to limit C-band 5G power levels around airports for the first six months to help avoid interference, and by the new year, they had gone a step further, agreeing to set up exclusion zones where the new C-band frequencies wouldn’t be deployed at all for at least six months.
Insisting these concessions should be more than enough to quell the fears of aviation officials, AT&T and Verizon’s CEOs originally denied a request earlier this month for another two-week extension, only relenting after a day of intense talks between the White House, FAA, FCC, and other industry stakeholders.
In the end, the carriers reluctantly agreed to give the FAA its two weeks, in exchange for what seemed like a firm statement from President Joe Biden himself that the rollout would go ahead as scheduled on January 19.
Bandwidth pollution
It appears that this concession hasn’t placated the airline industry, however. Officials and executives continue to warn of catastrophic consequences should the new spectrum go online as scheduled — even though both AT&T and Verizon have agreed to give airports a wide berth for now.
At the root of the concern is the proximity of the frequencies in the new C-band 5G spectrum with those used by critical aircraft instruments.
The controversial C-band spectrum, located in the 3.7–3.98 GHz range, sits just below the 4.2–4.4 GHz frequencies used by radar altimeters. Modern military, commercial, and civil aircraft, and even many unmanned aerial systems and high-end drones, all use these instruments. They’re crucial for measuring how far an aircraft is above the ground when dealing with the kind of inclement weather conditions that prevent traditional barometric altimeters from working properly.
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It’s this that makes radar altimeters such an important piece of safety equipment. In ideal weather conditions, pilots can rely on other instruments, and even their own eyes, to gauge distances when landing at an airport. In poor visibility, however, the radar altimeter is all they’ve got, and if it’s not working, or shows an altitude that’s too high, then the pilot has no way of knowing when they’re about to hit the ground.
Technically speaking, 4.2GHz, which is the bottom end of the radar altimeter frequencies, is still over 200MHz way from the highest C-band spectrum frequencies, which top out at 3.98GHz. So, you might think that’s a healthy margin of safety to prevent interference, and this is precisely the point that the FCC and the carriers are making.
Unfortunately, other experts disagree, citing a phenomenon known as bandwidth pollution. As Interesting Engineering explains, it’s possible for a strong concentration of signals in a given frequency range to “bleed through” in higher frequencies, causing at least some interference.
This is analogous to the problem of light pollution that makes it hard to see the stars at night when you’re close to a city. You could be 20 miles outside a major city, but the concentration of millions of lights emanating from it is still going to make it hard to see much of anything in the night sky.
While the FCC insists that it’s studied the issue and determined this won’t happen, the aviation industry has its own studies that have become a source of concern. A 2020 research paper by the Radio Technical Commission for Aeronautics (RTCA), an independent technology standards group that represents the air transportation industry, showed evidence that 5G telecommunications in the C-band spectrum does have the potential to cause “harmful interference” to radar altimeters.
Although AT&T and Verizon continue to insist there’s no problem, they’ve also agreed to create an exclusion zone around an FAA-designed list of airports, similar to what’s done in other countries like France. However, they’ve also only committed to doing this for six months, after which all bets are off.
Airlines grounded
It’s hard to say what aviation officials were hoping for when all sides appeared to agree to a two-week delay. By all reports, things seemed congenial two weeks ago, but perhaps some simply presumed that things would end up being extended further.
As today’s rollout loomed on the horizon, however, airline companies became considerably more agitated. A joint letter sent out earlier this week by the CEOs of all the major U.S. airlines and air cargo companies warned that turning on the new C-band radio frequencies “could potentially strand tens of thousands of Americans overseas” and cause “chaos” for domestic flights within the U.S. “The nation’s commerce will grind to a halt,” the letter warned.
Several foreign airlines announced on January 18 that they would be canceling flights to the U.S. as a result of the new spectrum rollout. Explicitly citing the new 5G rollout, Emirates indefinitely suspended all flights to Boston, Chicago, Dallas-Fort Worth, Houston, Miami, San Francisco, and Seattle, as well as Newark, New Jersey, and Orlando, Florida.
JAL Group
Meanwhile, Japan Airlines (JAL) canceled U.S. flights for Boeing 777s into Chicago, Los Angeles, and New York’s JFK airport, citing potential interference with radio altimeters from the 5G rollout on those specific aircraft. Japan’s Air Nippon Airlines (ANA) also made a similar announcement, as did Air India.
The airlines in question later relented, at least partially, likely as a result of the White House clarifying that 5G would be delayed near “key airports.” A statement by Biden late yesterday thanked Verizon and AT&T for “agreeing to delay 5G deployment around key airports and to continue working with the Department of Transportation on safe 5G deployment at this limited set of locations.”
JUST IN: The President of Emirates tells CNN that the airline was not aware of some of the potential 5G rollout issues until yesterday morning, calling it "one of the most delinquent, utterly irresponsible" situations he has seen in his aviation career https://t.co/Z3a4gTQ6Fo
— CNN (@CNN) January 19, 2022
Following this statement, Japan’s JAL and ANA both announced they would reinstate their normal U.S. schedules from January 20 onward, while Emirates agreed to resume select flights to Boston, Houston, and San Francisco, although the others remain suspended for now, despite those airports also being on the FAA’s exclusion list.
“This agreement protects flight safety and allows aviation operations to continue without significant disruption and will bring more high-speed internet options to millions of Americans,” Biden said.
How we got here
There are clear political factors at work here, particularly the pressure on the FCC by the current and former administration to rapidly expand 5G technology across the U.S. However, the deployment of 5G by most U.S. carriers has been something of a mess from the beginning, and the FCC certainly can’t take all the blame for that.
Unlike the cellular technologies that have come before, 5G uses a much wider swath of frequency ranges, and there are trade-offs across the entire spectrum.
On one end, you have the ultra-high-frequency mmWave spectrum, which runs at the bottom edge of the Extremely High Frequency (EHF) range: 26GHz and above. This is well out of the range of any frequencies used by civil aviation, or pretty much anything else that normal folks are likely to be concerned with.
One of the reasons for this is the frequencies in the EHF spectrum are extremely short range. Other equipment that operates in this range include high-end telecommunication systems, satellite atmospheric monitoring systems, military weapons radar, security screen systems at airport checkpoints, police speed radar, and some medical applications.
At the other end of the spectrum are the 600MHz 5G deployments, which have great range, but don’t offer speeds that are all that much of an improvement over current 4G/LTE technologies.
When the U.S. carriers began rolling out 5G a few years ago, they all took dramatically different approaches. Verizon went for speed over coverage, deploying mmWave transceivers in major urban centers across the country. This allowed them to boast speeds in the 500Mbps to 2Gbps range, but the problem is that 99 percent of Verizon customers don’t get 5G at all.
T-Mobile took the opposite approach, with the goal of rolling out coverage far and wide, letting its customers get the “5G” indicator on their devices even if the speed improvements were only marginal. T-Mobile primarily used the 600MHz spectrum to pull this off, so it could rapidly expand 5G coverage without building too many more towers. The result was that T-Mobile became the first U.S. carrier to boast 5G coverage in all 50 states.
AT&T took the middle ground, choosing to commit itself to neither approach. Perhaps learning its lesson from the 5G Evolution debacle, it decided to remain quieter about promoting 5G, taking a slow-and-steady approach to rolling things out nationwide, using a mixture of mmWave and sub-6GHz technologies.
kris / Unsplash
Why C-Band is important
The biggest challenge with getting 5G properly deployed in the U.S. is that the FCC regulates most of the wireless frequencies in the U.S. We don’t need to look much farther than the current controversy with the aviation industry to see why this is necessary.
The sweet spot for 5G technology — the solution that provides the best balance between performance and coverage — is in what’s commonly called the midband spectrum. While mmWave provides great performance that only extends for a distance of about a city block, 600MHz goes far, but can’t handle much more data than 4G/LTE already can.
Right in the middle of that frequency soup sits the 2GHz to 4 GHz frequencies. These provide enough bandwidth to deliver the speeds users are expecting from 5G, while also ensuring that carriers don’t have to put up millions of cellular towers just to get 5G to all their customers.
Unfortunately, many other technologies and devices use this midband spectrum too. For example, you’re probably already aware that 2.4GHz is commonly where Wi-Fi routers, cordless telephones, baby monitors, and garage door openers live. Even microwave ovens emit signals in this frequency range. This is in an area known as the “S band.”
Pre-5G cellular technologies mostly live below the S band, generally in the range from 600MHz up to around 2.3GHz, with most concentrated around 800MHz and 1.9GHz.
Above this is the C-band spectrum, commonly used by amateur radio services, fixed satellite services, maritime radio, and radio location services.
In 2018, however, the FCC figured out a way to free up a small chunk of 500MHz C-band spectrum, in the 3.7GHz to 4.2GHz range, for use by “next-generation wireless services.” Although there had been satellite services operating in that band, the commission revised all the licenses to free up as much space as possible for use by new 5G deployments.
Two years later, when the dust had settled, the FCC put up 280 MHz of this spectrum for auction to the cellular carriers. This is the 3.7 to 3.98GHz range where new 5G services are rolling out today.
The new spectrum promises to be a game-changer for 5G technology in the U.S., particularly from Verizon and AT&T. Verizon has already boasted of how it will allow it to reach millions of additional customers with “speeds up to 10x faster than 4G LTE.” The new spectrum will form part of Verizon’s 5G Ultra Wideband network, which was previously limited to its 28GHz and 39GHz mmWave frequencies.
Along the same lines, AT&T has announced its new C-band rollouts in eight metro areas, promising that it will cover 200 million people by the end of 2023.
What about T-Mobile?
You may have noticed that T-Mobile has been conspicuously absent from this entire fray, even though it dropped $9.3 billion in the C-band auction last year.
This is likely because T-Mobile hasn’t shown any intent to begin using its new C-band spectrum in the same way as its rivals.
From the beginning, T-Mobile has had an ace up its sleeve. It already owned licenses for a sizeable chunk of 2.5 GHz S-band spectrum that came out of its merger with Sprint a few years ago.
Sprint originally used those 2.5 GHz frequencies for 4G/LTE service, but after the merger, the new T-Mobile began shutting down those older Sprint towers, clearing the way to reuse those frequencies for newer 5G deployments.
When T-Mobile also picked up some new C-band spectrum last year, it announced this was a “strategic investment” intended to “supplement its much broader 2.5 GHz footprint in select urban and suburban areas where it already has a dense network.” The result, the carrier said, would be a “more meaningful performance boost for customers.”
The lower-frequency spectrum also provides better range than the new C-band, while still delivering impressive 5G performance, so T-Mobile really has no motivation to begin rolling out the C-band spectrum in the way that AT&T and Verizon are. It has its midband spectrum, and it’s been rolling that out as part of its Ultra Capacity 5G service, which already covers more thgan 200 million customers.
Where are we going from here?
Now that both AT&T and Verizon have begun fulfilling their C-band visions, it’s going to be interesting to see what happens next. While both carriers are working to catch up to T-Mobile with this new C-band, there may be a limit to how far and how fast they can actually get there.
As PCMag’s Sascha Segan points out, Verizon may have made a tactical error by betting too heavily on C-band. It certainly bought the biggest chunk of it last year, spending a whopping $45 billion to acquire it.
So here's why @ATT and @TMobile might want to hang @Verizon out to dry on C-Band: Verizon is (1) having congestion issues and (2) has put many eggs in the C-Band basket. With the new Auction 110 result, by the end of this year @ATT will have 40MHz of
— Sascha Segan (@saschasegan) January 18, 2022
The problem is that Verizon has spent a fortune to invest in the most contentious piece of spectrum out there, and it’s likely that this controversy won’t die down any time soon. It’s possible that Verizon may never be able to deploy its new spectrum near airports, leaving its customers either stuck with 4G/LTE service, or a 5G offering that’s really no better than 4G/LTE.
On the other hand, AT&T has hedged its bets slightly. More recently, it picked 40MHz of spectrum the airlines aren’t going to care about, which could explain why it’s taking a considerably more reserved approach to the entire situation. As Segan suggests, AT&T may very well be playing both sides against the middle, embracing longer delays and larger excursion zones to give it a competitive edge over Verizon, which would be much more hampered by such moves.
Meanwhile, T-Mobile is sitting pretty, having no part in the current controversy, while holding an undisputed 100MHz chunk of 2.5GHz spectrum that it was already rolling out to customers months before the new C-band even came up for auction.
One thing that’s still clear is that T-Mobile has a considerable lead in the 5G game, consistently earning the highest scores of any U.S. carrier for speed, coverage, and reliability — a lead that only seems to be increasing. We can’t count Verizon and AT&T out just yet, but it’s clear that both carriers have their work cut out for them in carving out enough C-band to make true 5G a reality for their customers.