What the Eff, FAA? My Insanely Long Field Guide to the FAA/FCC 5G C-Band Fight.

5G has been accused a lot of ridiculous things — causing Covid, causing cancer, causing autism. This article provides a list of 9 separate conspiracy theory/whacky things 5G is supposed to do, from killing birds to depopulating the planet. Today we can add another thing to the list to make an even ten — causing planes to fall out of the sky. Unfortunately, the source of this particular new rumor is the Federal Aviation Authority (FAA). Specifically, the new FAA “Special Airworthiness Information Bulletin” on “Risk of Potential Adverse Effects on Radio Altimeters” (generally referred to as “FAA guidance” by the industry). This has lead to a spate of articles where FAA folks anonymously leak statements about how sister agency the Federal Communications Commission (FCC) is outa control and does what she wants, bitch, whatevah! and planes are gonna fall outa the sky and shut down air travel for everyone unless the FCC stops the roll out of 5G in something called “C-Band” (with phased in roll out scheduled to start in December — now delayed until January).


If this sounds familiar, it’s because a different agency within the Department of Transportation pulled the same nonsense over the FCC’s efforts to reclaim unused spectrum from the auto industry in the 5.9 GHz band. The Department of Defense has made similar accusations against the FCC wrt its approval of Ligado. I could list several more cases, but they basically boil down to the same thing — the federal government’s processes for addressing spectrum policy is severely broken. Unhappy federal agencies that don’t like the outcome of an FCC proceeding respond by undermining the FCC in the press and trying to wage proxy wars through allies in Congress. But the FAA’s actions here take this behavior to new heights of irresponsibility and danger.


As I explain in greater detail below, the technical evidence on which the FAA bases its interference concerns have a lot of problems — not least of which that about 40 other countries operate similar 5G deployments in the same C-Band without any interference showing up. Either physics works differently in the U.S., or the report at the center of this controversy needs to explain why this hasn’t shown up in any other country where deployments are either authorized or have already taken place. What is worse, the FAA has basically been playing “chicken” with the FCC by failing to turn over needed information to verify the report or replicate the results until literally the day before FAA staff leaked the “planes are gonna fall out of the sky” story to the Wall St. J.


But more importantly, we need this inter-agency warfare over 5G spectrum policy to stop. Things have always been difficult That we now have an FAA that would prefer to actively undermine confidence in the safety of air travel than actually work with the FCC (and trust the FCC to do its job) underscores just how bad this problem has become. Congress can help by swiftly confirming Alan Davidson as head of NTIA (the federal agency that is supposed to mange the spectrum management process on the federal side) and Jessica Rosenworcel and Gigi Sohn at the FCC.


More below . . .

If you have a hankering to find out more about the C-Band, you can read my explainer from the end of 2019 over here. Briefly and of relevance here, “C-Band” (don’t worry about what the C stands for) stretches from 3.7 GHz to 4.2 GHz, 500 MHz worth of prime midband spectrum. After a whole bunch of shenanigans, the FCC finally decided at the beginning of 2020 to reclaim the bottom 300 MHz (from 3.7 GHz to 4.0 GHz) for 5G.

Adjacent to C-Band is a band globally reserved for air altimeters and “wireless avionic intra-communications systems,” operating from 4.2 GHz to 4,4 GHz. Altimeters are specialized radar-like devices that provide planes and helicopters super accurate altitude levels when close to the ground (2500 feet or lower). While the FCC was developing rules for using the lower 300 MHz in C-Band, aviation industry folks showed up to express concern over the possibility that changing the rules in C-Band might cause interference with altimeter readings. As this is a safety of life system, the FCC studied the evidence, which primarily consisted of one study by the Aeronautic Vehicles Systems Institute (AVSI) and a counter study by T-Mo explaining why the AVSI study was garbage and a counter argument from AVSI that while more study was needed, the existing study still supported not doing anything anytime soon. The FCC chewed over all this and decided that (a) AVSI report had a lot of problems; (b) The FCC added another 20 MHz to the guard band separation between the new 5G band and the altimeter band, for a total separation of 220 MHz; and (c) just in case, the FCC encouraged everyone to set up a multi-stakeholder group of the wireless and aviation folks to continue to study the issue to see if there was any risk to any models of altimeters still in use. You can read all this in the FCC’s March 2020 Order at paragraphs 390-395.

Importantly, the FCC also said:

“We nonetheless agree with AVSI that further analysis is warranted on why there may even be a potential for some interference given that well-designed equipment should not ordinarily receive any significant interference (let alone harmful interference) given these circumstances. . . . We expect the aviation industry to take account of the RF environment that is evolving below the 3980 MHz band edge and take appropriate action, if necessary, to ensure protection of such devices.”

To translate from the FCC-esse: “Air industry, we cannot screw over the U.S. deployment in 5G by taking the single largest, most useful allocation of 5G spectrum off the shelf indefinitely because a handful of older, crappy altimeters might under some wildly improbable set of circumstances experience harmful interference. While we take air safety issues seriously, you guys are gonna need to recognize that “no 5G in lower C-Band” is not a realistic expectation. So please work with the wireless industry here to figure out if you are going to need to get people to upgrade their equipment.”


We Pause for A Brief Digression on Why this Keeps Coming Up in 5G Allocation Fights.


Regular readers will recognize this as being fairly par for the course in spectrum proceedings. Incumbent users will always explain how changing the rules (when it doesn’t benefit them personally) anywhere in the same neighborhood is going to create horrible interference and planes will fall out of the sky and everyone will hate you. Proponents of rule changes counter that the studies submitted by the incumbents make ridiculous and unrealistic assumptions, don’t take crucial things into account, and submit their own technical studies showing everything will be totally safe and awesome.


So this is not the FCC engineer’s first rodeo. In my experience, the FCC’s engineers are extremely aware that if they screw up people could die. At the same time, they are also painfully aware that if we don’t find new ways to expand out spectrum use, people are also gonna die from our failure to upgrade technology to handle things like mobile telemedicine and so forth. Being too conservative freezes technology. So sorting through the conflicting evidence and coming up with recommendations on how to thread this needle (and figuring out how to respond if something unexpected happens) is what the FCC engineers do all the time.


By contrast, federal agencies in spectrum fights don’t give a crap about wireless technology, “winning the 5G race” or anything other than their specific mission. There is also a tendency for sector-specific regulators to act as advocates for their industry sector. So the FAA is not interested in working with the FCC to take reasonable steps to mitigate risk on their end so we can actually have working 5G networks. They want to protect aviation from even the smidgin of a possibility of risk (at least, when that risk does not come inside the aviation industry itself — remember the “safety self-certification” fiasco?) and they don’t want anyone in their industry sector to have to do squat about it.


Add to this the problem that predicting harmful interference is damn hard. There is always going to be “interference,” meaning unwanted noise detected by the receiver along with the desired signal. The question is whether that unwanted noise reaches levels that significantly degrade performance of the system. Designers of systems want to make them as cheap as possible. Adding filters or other things to make receivers more robust and resistant to harmful interference makes these systems more expensive. So there is always a trade off in design of equipment between high-end (which can be quite robust even for sensitive systems) and cheap-ass (which is designed with the minimum shielding you can get away with). So whenever we change the rules on spectrum use, you have to deal with the question “how much deference are we going to give to cheap-ass systems that are not terribly robust” and “what kind of standards should we assume for our testing models?” This is further aggravated by the fact that usually no one knows what equipment is out there or what the cost would be to upgrade/replace it.


Finally, in the 5G context, we have competing federal policy goals. When you ask about 5G, pretty much everybody will tell you that we must “win the race with China” and “maintain or global leadership” and “ensure to Americans the benefits of 5G as quickly as possible.” So the FCC is pushed to get a much spectrum out there as quickly as possible. Additionally, Congress keeps mandating auctions as “pay fors” to offset expenditures without raising taxes. On the other hand, the airwaves are now so crowded that it is impossible to find any useful spectrum without making changes that are going to run into the spectrum interests of some federal agency or the sector it regulates. This is particularly true for the two agencies that use the most spectrum and have had the allocations for the longest time — the Department of Defense and the Department of Transportation.


So we have a situation where things were already tense. We add to that the fact that the airwaves are getting more and more crowded, making it harder and harder to squeeze in new users, and a national policy that makes clearing spectrum to add in these new users a national priority. How the heck does anything get done?


Both the George W. Bush and Obama Administrations invested a fair amount of White House clout in herding the cats and making the system work. Agencies don’t have authority over each other, but the executive branch reports to the White House. One specific federal agency, the NTIA, is designated by statute as the official Executive Branch interface with the FCC (with a couple of exceptions, such as the Small Business Administration Office of Advocacy). The Obama folks in particular invested time and effort from the Office of Science and Technology Policy (OSTP) and the President’s Council of Advisors on Science and Technology (S.H.I.E.L.D.) to develop a framework (The PCAST Report). Trump, by contrast, repealed the PCAST framework and never developed any replacement. Trump blessed then-Chairman Ajit Pai’s “5G Fast” plan, told Pai to win the 5G race, and then moved on. The Executive Branch agencies responded by ignoring the required federal process, trashing the FCC in the press, and trying to run proxy wars with against the Commerce Committee with competing committees in Congress (notably the Armed Services committees and the House Transportation Committee). Things got so bad that the Government Accountability Office gave testimony and issued a report which explained (politely) just how screwed up things have gotten.


We Now Return to the FAA v. FCC Fight Already In Progress.


So by the end of the Trump Administration when this all took place, FAA and the FCC were not exactly cooperating with each other in the spirit of harmony. FAA’s attitude can basically be summed up as “you are so not the boss of me! I don’t have to listen to you! Whatevah! I do what I want!” Needless to say, the Transportation Working Group (TWG) did not produce the hoped for kumbia moment where everyone agreed to put aside their differences and work together to ensure the rapid deployment of 5G consistent with preserving the safety of U.S. air travel.


On October 20, 2020 (i.e., over a year ago), the AVSI released another report from a consulting firm (RTCA, Inc.) The report once again concluded that yup, definitely, based on a bunch of tests we made up using standards we decided on ourselves, there is a definite possibility of maybe their being some interference — so the FCC needs to totally not go ahead with the auction of the C-Band spectrum scheduled for December 2020. CTIA responded that RTCA had deliberately used performance standards for the report that go well beyond the industry standards the FAA actually uses to measure altimeter  sensitivity to interference, RTCA had cherry picked data to deliberately make the results look as bad as possible, the report was completely inaccurate in key details as to how 5G networks operate, and RTCA withheld critical data that would allow CTIA (or the FCC) to actually replicate the study to confirm the results. CTIA also managed to imply in their tone that (a) RTCA engineers were ugly; and, (b) their mothers dressed them funny before the Working Group meetings. AVSI responded that the parameters used for wireless network operations came from the wireless industry, so that any errors in operational parameters were the wireless industry’s fault — and that CTIA’s mothers were so fat they aren’t allowed near airpots without landing gear. Unsurprisingly, things went downhill from there.


On December 1, 2020, Steve Dickson, FAA Administrator, sent a letter via NTIA for filing with the FCC (this is the proper procedure, NTIA is the interface between the Executive Branch and the FCC). The letter recapped everything from the FAA’s perspective and asked that the FCC hold up the C-Band auction until FAA felt that it had resolved the outstanding issues between flight safety and operation of 5G. The letter also warned of potentially dire consequences if the FCC proceeded with the auction. Notably:

In the event that 5G network implementation moves forward without addressing these safety issues, the aviation industry needs a considerable transition period to develop updated radar altimeter performance standards; to design, manufacture, and certify new avionics; and then to integrate and install that equipment into aircraft and helicopters. Given the scope of the safety risk, and based upon our current knowledge, it is unclear what measures will be necessary to ensure safe operations in the NAS, or how long it will take to implement such measures. Depending upon the results of further analysis, it may be appropriate to place restrictions on 3 certain types of operations, which would reduce access to core airports in the U.S. and, thus, reduce the capacity and efficiency of the NAS. We also expect that the cost of replacement or retrofit of radar altimeters will be substantial. The Commission does not appear to have taken these factors into account in its decision-making process.


In other words, to translate from the FAA-ese: We can’t stop you from going ahead with the auction. But if we aren’t happy when the time comes to switch the systems on, we may need to place all kinds of restrictions on operation of air vehicles in the U.S. to protect safety. Also, if this is going to require equipment upgrades, it will take a long time to phase these in and will cost some unpredictable (but we’re sure fairly hefty) amount of money.


Unsurprisingly, the FCC went ahead with the auction anyway. It earned a record-breaking approximately $80 billion in winning bids — with Verizon and AT&T as the biggest winners. Both companies promised to use the spectrum to deploy 5G networks to consumers as quickly as possible. Under the FCC’s established schedule, the first tranche of licenses would go online December 5, 2021.


No Cooperation and No One at Home In Spectrumland.


Needless to say, one would expect that the deadline would have focused FAA and the aviation industry to move to gather needed information on air altimeters and work with the wireless industry to identify potential safety issues and determine what remediation steps on the part of both the aviation industry and the wireless industry were necessary to equitably share the burden of protecting safety while permitting 5G deployment. And maybe some of that happened at the non-public Working Group meetings. But if you read the record of the FCC proceeding (Docket No. 18-122) between the time the FAA sent their letter on December 1, 2020, and the end of October 2021, what you mostly find is back and forth fighting by the aviation industry and the wireless industry over various tests submitted into the record, and accusations by CTIA that the aviation industry had zero interest in actually cooperating on trying to solve the problem.


I’m inclined to be more sympathetic to CTIA and the wireless industry here for a couple of reasons. First, as we’ll see, the AVSI/RTCA folks did not respond to the requests for additional data relevant to their reports (more on that below). Also, especially looking at this report over here on air helicopter ambulances from July 2020, the negative data comes from a single model of super-cheap altimeter, called “Altimeter 7” in the report. As CTIA pointed out, if the problem is that certain cheap models of altimeter might experience harmful interference, then the solution would be to upgrade the altimeters — not impose massive mitigation measures on 5G network deployments.


Regular readers will recognize this as another standard problem that resurfaces repeatedly in fights about expanding spectrum use. The people who manufacture equipment have incentive to make the equipment as cheap as possible consistent with safety — which they estimate based on the rules at the time they build the devices. Depending on the life cycle of the equipment, it may take awhile to clear out cheaper models that are incompatible with new uses. The question becomes how much should we hold up the advancement and deployment of new wireless technologies (for which there is generally a significant demand for a wide variety of purposes, many of them potentially life saving) to allow for the phase out or upgrade of older technology. After all, the folks using the older technology followed the rules and didn’t do anything wrong. Why should they pay so the wireless industry can deploy new services and make boatloads of money? OTOH, how much do we want to hold back new technology for everyone because of some unknown number of crappy old equipment models out there? This difficult question is usually made worse when, as here, we really don’t have any idea how many older models are out there and how susceptible they may or may not be to harmful interference.


Which is another point about how FAA and the airline industry handled this that irritates me and makes me side with CTIA on this. FAA had a year to collect information on what altimeters were out there and start collecting data on whether 5G would cause harmful interference to any models, and what interference mitigation might be necessary to avoid any potential for harmful interference. That was basically why the FCC told the aviation industry to form a working group with in the first place. FAA could have issued a bulletin (or whatever thy call such an inquiry) over a year ago. Even without the FAA acting, the industry could have begun gathering and sharing that data on a voluntary basis.


Instead, the aviation industry (with the silent support of FAA) basically went for all or nothing. Every correspondence in the FCC record requests that the FCC prevent activation of 5G networks on any part of the C-Band until the aviation industry was satisfied that there was no potential risk of harmful interference. Needless to say, CTIA was not willing to accept what would amount to an indefinite delay with no indication as to what conditions would satisfy the aviation industry — or how much it might cost to remediate any issues identified. As the FAA letter of December 2020 observed: “We also expect that the cost of replacement or retrofit of radar altimeters will be substantial.” The aviation industry also made clear they expected the wireless industry to bear that undefined “substantial” cost. And while that might be trivial in the grand scheme of things if we’re talking a handful of aging altimeters, no one wants to agree to a blank check — especially after spending $80 billion to get the spectrum in the first place.


Under normal circumstances, we would expect the Administrator of NTIA and the Chair of the FCC to work things out with the Administrator of the FAA — and that various agency engineering staff would be working with each other to address the concerns. Unfortunately, although FAA Administrator Dickson apparently has some number of years to go as Administrator (and therefore didn’t need a nomination from the Biden Administration), we had acting heads of NTIA and the FCC. While the agencies do not shut down without confirmed political leadership, they generally operate in a holding pattern. After all, the next politically appointed member may have their own ideas, and will not appreciate an acting head locking them into policy.


Finally, it’s worth noting that about 40 other countries have approved use of 5G in C-Band. Japan in particular operates 5G networks today much closer to the altimeter band than the 220 MHz separation adopted by the FCC. So far, there are no reliable reports of any harmful interference with air altimeters. It’s possible for the FCC to make a mistake on this, sure. But regulators in 40 different countries? And with no incidents where operation has already begun? While there could still be a problem, the international experience suggests that if there is a real danger, it involves something unique to the U.S. — perhaps a particular brand of altimeter. But in any event, in the face of rules adopted by about 40 or so other countries, the aviation industry needs to show why the U.S. is different.


So while FAA had a politically appointed leader, neither NTIA nor FCC has a politically appointed head to offset this and work things out. To make matters worse, no one knew how long this lack of politically confirmed leadership would last. No one expected that we would get to November without a confirmed administrator of the FAA or a full strength FCC capable of dealing with sister agencies and with their own regulatees. Meanwhile, the aviation industry kept insisting that nothing less than an indefinite delay on activating 5G C-Band licenses could adequate protect air safety — without providing the underlying data necessary to verify the results of their one major study.  The FCC, OTOH, was asking various wireless equipment manufacturers about their emissions and whether they could reduce emissions if necessary. (See here, here and here). From the outside, it looks like the FAA — despite public commitments to working with NTIA and the FCC to resolve outstanding issues — decided they wanted to see 5G in C-Band stopped. Period. Which is not a very realistic and set up the head-to-head conflict we saw over the last two weeks.


What Happened to Blow This Up?


The last week of October, several things happened. On October 26, President Biden named Jessica Rosenworcel full chair of the FCC and nominated Gigi Sohn as the third Democrat. On October 28, AVSI finally provided to the FCC documents to back up its now 1-yr old study on potential interference. Unfortunately, because AVSI used the procedure for filing proprietary documents, there is no way to evaluate his filing. On October29, the first story about possible interference problems between altimeters and 5G in C-Band was leaked by FAA staff to the Wall St. J. The story and subsequent stories warned that the FAA might have to take some kind of action that would impact the operation of air travel in the U.S.


On November 2, the FAA released its initial “Special Airworthiness Bulletin.” The Bulletin directed altimeter manufacturers to share information with the FAA, NTIA and FCC (finally!), and directed airplane manufacturers to provide information about what models were installed in which airplanes (finally!). Additionally, it also warned pilots that, while there was no evidence of any actual interference, pilots should be prepared for their altimeters to suddenly stop working or give false readings, resulting in violent smacking into the ground. Needless to say, the pilots union took this less than subtle warning real well. Basically, the pilot’s union said that FAA should be prepared to take additional steps because 5G would make planes fall out of the sky. The FAA also hinted that it might take additional steps, like grounding air traffic in the 46 top markets (where the 5G C-Band phase in was scheduled to start on December 5).


Faced with the possibility of getting blamed for grounding air traffic in the holiday season, AT&T and Verizon blinked. The companies agreed to a “voluntary” delay of one month before turning on the relevant 5G systems — although both also managed to make clear that they did not think there were any serious interference issues to worry about. The FCC and FAA issued a joint statement declaring aviation safety and 5G deployment important national goals, they appreciate AT&T and Verizon’s commitment to both aviation safety and 5G deployment, and everyone will work together to resolve concerns so that we can have both safe air travel and 5G on C-Band. Rah rah. Yay team.


So Now What?


If nothing else, this exercise should make it abundantly clear why the Senate needs to confirm Davison, Rosenworcel and Sohn as quickly as possible. We cannot have spectrum disputes between agency fought out in the press in ways that destabilize confidence in the safety of air travel. Federal policy at this level is not a game of chicken, and cannot be fought out like this in the press. We need the key agencies here at full strength and able to resolve the systemic problem — not just the existing problem.


As for what is going to happen here, that all depends on whether the FAA and the aviation industry are interested in trying to resolve the problem — or are still hoping to prevent any use of the C-Band in the country for 5G. Assuming their is potential risk, there are a number of ways to potentially address it. But it depends on what the actual engineering data shows. If it turns out to be a bunch of low-end cheap altimeters, then someone (probably Congress, possibly the wireless industry or the aviation industry depending on the total cost) sets up a fund for the folks with equipment susceptible to harmful interference to upgrade their equipment. If the problem is more substantial, then it probably means adjusting power levels or other technical fixes for 5G near airports. We’ll have to see.


A delay of a month in the grand scheme of things will not set back AT&T or Verizon deployment plans. What would cause real problems, and ripple effects in the industry, is if this stretches on indefinitely. As I keep saying, just about every piece of spectrum has federal operations on it or near it at this point — or operations that somehow relate to a federal agency. (The altimeter band is not controlled by the FAA. It is allocated by the FCC for use by altimeters. But the FAA cares about the safety of altimeter operations.) If wireless companies get held up for some indefinite period for some unknown amount of money after investing multiple years and well over $100 billion ($80 billion for the spectrum licenses, plus whatever they have to pay to build the network), it is going to have a destabilizing effect on the industry as a whole. No one can afford to spend this kind of money and then get thrown into limbo indefinitely, with no clear idea how to even resolve the situation.


Stay tuned . . . .

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