FAA Embarrasses Itself
The Federal Aviation Administration’s objections to the mobile communication industry’s use of C-Band spectrum are utterly ridiculous. It would be one thing if an appropriate federal agency – the National Telecommunications and Information Administration (NTIA) or the Federal Communications Commission (FCC) – had found harm to aviation in their rigorous interference analysis of C-Band devices, but that didn’t happen.
In its place, we have little more than conjecture from an agency with no particular expertise in wireless networks and a history of cowboy behavior. This is, after all, the agency that approved the Boeing 737 MAX without a serious review.
If that doesn’t spell “captured agency” I don’t know what does. On top of that, FAA’s current administrator – controversial Trump appointee Steve Dickson – is perhaps a bit more inclined to publicity stunts than to serious scientific analysis.
When Boeing submitted the corrected MAX for review, a big part of the FAA’s analysis was a test flight piloted by Administrator Dickson himself:
The head of the Federal Aviation Administration conducted his own test flight of a Boeing 737 Max Wednesday, and he’s giving it a positive review, as the regulatory agency gets closer to allowing the troubled jet to return to commercial passenger service more than 18 months after it was grounded.
Born-Again Safety Hawks
The MAX has been fixed, more or less, and FAA doesn’t want that sort of thing to happen again. The agency doesn’t particularly care if Americans can take full advantage of 5G now, or ever, as long as it doesn’t have the eggs of another debacle on its face.
Sadly, the FAA’s new-found safety hawkishness threatens a huge portion of the non-aviation economy. 5G is a major technical advance – the most significant upgrade in mobile networks since the broadband capability that made the iPhone app store come to life in 2008.
We don’t know exactly what applications the 5G C-Band will enable, but history alone suggests they’ll be significant economic drivers. One of the rare examples of bi-partisan consensus in the halls of Congress is agreement on the urgency of doing well in the global race to 5G. A speedy rollout of the new, better networks is a precondition to building and benefitting from new and better apps.
What it Takes to Win
The US is uniquely hampered in wireless by our government’s historical tendency to keep more of the airwaves to itself than the global norm. This makes less of the radio spectrum available to US citizens than to those in Europe and Asia.
Defense and aviation are the largest culprits, for easily understandable reasons. You can’t operate airliners, bombers, and drones without reliable radios.
Mission-focused federal agencies have limited incentives to help each other as well as limited knowledge of the finer points of radio engineering. They also have a strong bias in favor of the status quo. And 5G simply isn’t the FAA’s problem.
FAA’s Interests are Protected by NTIA
NTIA harmonizes spectrum use by government agencies and acts as the official interface between the agencies and the FCC, the arbiter of spectrum use by the private sector. Both have excellent spectrum engineering teams.
NTIA has the harder job because agencies aren’t disciplined by market efficiency and economic opportunity as the FCC’s clients are. Both agencies have been led by acting heads for far too long, and this has enabled the FAA to go rogue.
If there were a genuine interference problem with aviation and the C-Band, it would be the job of NTIA and the FCC to find and characterize it. They’ve both examined the question and determined that the FCC’s current buffer – 220 MHz of separation between 5G services and the radio altimeter band – is much more than enough to protect airplanes. Japan, for example, gets by with a 100 MHz guard band.
The Sweet Spot for 5G
President Obama’s National Broadband Plan warned us in 2010 that without a sizable transfer of spectrum rights from government to industry we would face a “spectrum crunch” that would impair our technical progress. This insight has proved especially true for 5G, a technology designed to use three major frequency bands (low, middle, and high.)
The mid band overlaps classic Wi-Fi and new Wi-Fi and fills part of the gap between them. The gap includes a number of mission-specific assignments, following a pattern established when every radio system was unlike all the others. One of these quaint artifacts is radar altimeters, devices that measure altitude in an embarrassingly crude way.
Making progress with 5G is going to require the use of the C-Band spectrum that FAA wants to keep silent. So let’s see what science has to say about the controversy.
How Captured Agencies Behave
In the absence of NTIA leadership, FAA beseeched aviation industry lobbying group RTCA, Inc. to contract with aviation industry think tank AVSI to forecast interference between altimeters and 5G. Lacking 5G expertise, AVSI conducted bench tests of common altimeters to see how easy it is to make them fail. It’s quite easy.
Some of the altimeters used in private planes and helicopters – frequency-modulated continuous wave (FMCW) devices – are cheaply made and easy to break. They simply emit energy and measure how long it takes signals to bounce back from the earth.
So the fact that a lab test can put them out of commission isn’t surprising. It’s not only perfectly predictable that high-power radio signals can saturate radio receivers, it’s routine. This is how radio jamming has worked for a hundred years and a big part of the reason Hedy Lamarr invented frequency hopping.
What Does Realistic Testing Show?
AVSI simply blasted altimeters with high power signals from every direction and noted the point at which they began to give faulty readings. RTCA then took this data and wrapped it in a model – a simulation – purporting to show that the fatal lab conditions exist in the real world.
FAA’s claims are entirely based on the analysis and data collection done by its industry clients, data it has so far refused to share. FAA’s argument boils down to: “Trust me, I are a engineer.”
Practically anybody can create a simulation that shows any result at any time, that’s not an issue. The question is whether the FAA’s clients are in touch with reality.
Back in the Real World
This is very much an American problem; in the rest of the world mid-band deployments are taking place in 40 countries following real-world testing of current altimeters and live radio networks. The catastrophe scenarios forecast by RTCA have not been observed outside the AVSI lab.
In France, the military (ANFR) tested helicopters with live 5G base stations, finding that “the emission of 5G NR base station had no impact on the operational behavior of the radio altimeter.” In Norway the Communications Authority tested an active 5G base station on several different aircraft approaching Bergen-Flesland Airport and found “no abnormalities on the radio altimeters.”
It’s not a leap to conclude that RTCA has failed to create a realistic simulation of mid-band spectrum signal propagation in the real world. Effectively, they assumed that every altimeter had a hundred bars of signal on a five bar scale. If RTCA’s model were correct, aircraft would already be falling out of the sky.
Shall We Call the Whole Thing Off?
While we can all appreciate the desire of the FAA to avoid a 737 MAX replay, we have to recognize that every engineering model is simply a prediction that cannot be trusted unless it agrees with measured data. Even if some altimeters need replacing – which remains to be shown – the pace of the mid-band rollout is likely to be slow enough to allow defective gauges to be upgraded before anyone’s life is in threatened.
We have expert agencies such as NTIA and the FCC because expertise on radio engineering is not nearly as widely dispersed as are the applications that depend on radios. Just as the ability to pilot an aircraft doesn’t imply the expertise to design one, an agency’s desire to protect its sector doesn’t correspond with knowledge of the best means to do so.
The proper role of FAA in this and any similar controversy is to conduct its own measurements and share them with the responsible parties. It should share its findings on altimeter vulnerabilities and leave the modeling of 5G emissions to the experts.
This is the one thing the cowboy agency has not done.