The Federal Aviation Administration is hurling unfounded accusations against 5G wireless networks deemed safe for aviation by experts at the Federal Communications Commission.
Despite FCC engineering studies demonstrating safe coexistence between 5G and aviation, the aviation agency claims “deep concern about the potential impact to aviation safety resulting from interference to radar altimeter performance from 5G network operations in the C band.”
The FAA is wrong on the analytical side of the question and its tactics—taking the dispute to the media—are inappropriate.
In response to the radio spectrum crunch brought to the public’s attention in the 2010 National Broadband Plan, the nation’s spectrum managers (FCC and the National Telecommunications and Information Administration) have proposed to license so-called mid-band radio frequencies to commercial networks serving the general public. The mid-band is between the frequencies used by the carriers today and those used by super-high-performance data services.
Aviation uses frequencies in this general neighborhood as well, so the FCC created rules in 2020 to ensure there would be no harmful interference between the 5G mid-band and radar altimeters in spectrum 220 MHz away that have been used in aircraft for decades. This rulemaking acknowledged aviation’s fears and dealt with them by creating a large quiet zone or guard band.
There Is No Real Problem to Solve
The experience of other countries and the FCC’s engineering analysis confirm that the FCC’s rules are adequate to protect these radar altimeters.
As the U.S. has been slow to the mid-band party, we can benefit from the experience of other countries. In Japan, 90,000 mid-band 5G base station antennas operate adjacent to aviation services with less than half the quiet zone required by the FCC.
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.” The list goes on.
How Did FAA Get It So Wrong?
FAA’s 5G fears are stoked by a predictive model created by aviation industry group RTCA (a private, non-profit association founded as the Radio Technical Commission for Aeronautics), and aviation industry group AVSI (Aerospace Vehicle Systems Institute), that tested various altimeters. The model seeks to predict interference between 5G and altimeters by making a number of unwarranted assumptions about the behavior of radio waves outside their licensed frequencies.
This is long standing aviation industry practice. As RTCA notes in its analysis, the International Civil Aviation Organization (ICAO) recommends nothing but worst-case assumptions when modeling aviation radio issues in its Handbook on Radio Frequency Spectrum Requirements for Civil Aviation.
In practice, this means that RTCA’s study is a hazard analysis rather than a risk assessment. The confusion between hazard and risk pops up in many sectors, from cancer research to pesticides to epidemiology and to radios. Hazard is the possibility that a given agent can cause harm under artificial conditions, while risk is the likelihood of such conditions occurring in the real world.
Yes, Radio Can Be Weaponized
FAA, RTCA, and AVSI offer the well-understood truth that malicious actors can make radio waves cause all sorts of mischief if they try hard enough. In their zeal to protect their clients, the organizations have erased the boundary between hazard and risk.
Communications regulators need to know whether it’s at all likely that commercial data systems will damage aviation electronics in operational scenarios. Simulations like the one made by AVSI are useful in answering this question, but only when their worst-case assumptions are replaced with realistic ones.
Realistic Risk Analysis
In the network engineering business, we rely on simulations to answer all sorts of questions that would be very expensive to analyze with nothing but real hardware and system software.
Engineers calibrate their models to bring them into alignment with real phenomena. The standards committee that created the first public standard for Ethernet required cables the size of garden hoses for 10 Mbps data signals on the basis of worst-case assumptions about interference.
Realistic interference assumptions enable today’s Ethernet to pump a thousand times more data through small, flexible cables without incident. Competent risk analysis is one of the most important keys to technological progress.
In the rest of the world, mid-band deployments are taking place in nearly 40 countries following models confirmed by real-world testing. The catastrophe scenarios forecast by FAA have not been observed outside AVSI’s Texas laboratory. If RTCA’s analysis were correct, airplanes would be falling out of the sky today due to interference caused by altimeters themselves.
FAA needs education on radio risk assessments. Lucky for them, they have genuine experts available at NTIA and FCC. The FCC would like to see the numbers used by the RTCA model, something that should have been shared more than a year ago.
Strong leadership at the FCC and NTIA can help make this happen. Both agencies are effectively leaderless today, but Senate confirmation of acting FCC chairwoman Jessica Rosenworcel as chairwoman, and Alan Davidson for NTIA administrator can put them on track again.
In the meantime, there is no demonstrable reason to slow down the rollout of 5G base stations using the C band mid-band spectrum block. The onus is on the FAA to show credible data that backs up its overheated charges or they can get out of the way.
This column does not necessarily reflect the opinion of The Bureau of National Affairs, Inc. or its owners.
Richard Bennett founded High Tech Forum and consults with industry and government on wireless network policy. Formerly affiliated with the American Enterprise Institute, he played key roles in writing the technical standards for Ethernet and Wi-Fi.