FCC Considers Issuing New Rules for Wireless Receivers to “prevent future conflicts”

By B.N. Frank

The Federal Communications Commission (FCC) is supposed to protect Americans by regulating the telecommunications industries. Instead, it has catered to these industries for decades (see 1, 2). This has led to numerous lawsuits being filed against the agency. Recently, most attention is being paid to 5G deployment causing aviation safety risks (see 1, 2, 3, 4, 5, 6).

However, 5G-related cybersecurity risks (see 1, 2, 3, 4), weather forecasting satellite interference risks, and utility infrastructure interference risks have been reported as well. FCC-approved unlicensed frequency uses for 6G routers and other wireless devices have also been cited for significant interference risks.

The FCC has announced it may be willing to do something about this. We’ll see.

From Ars Technica:

FCC considers crackdown on bad wireless receivers after 5G/altimeter debacle

Receivers that ignore spectrum boundaries are a problem for new wireless services.

Jon Brodkin

The Federal Communications Commission will consider issuing new rules for wireless receivers that could prevent future conflicts like the ongoing battle between the aviation and cellular industries.

There are strict rules requiring wireless devices to transmit only in their licensed frequencies. That means, for example, that AT&T and Verizon’s 5G transmissions in C-band spectrum (3.7 to 3.98 GHz) have to stay within the C-band.

But there isn’t much to prevent devices from receiving transmissions from outside their allotted frequencies. The altimeters used in airplanes to measure altitude officially rely on spectrum from 4.2 GHz to 4.4 GHz, but the Federal Aviation Administration has said that 5G transmissions in the C-band could interfere with the operation of some of those altimeters.

If an altimeter is affected by 5G, that means it is receiving transmissions from the wrong spectrum band despite a buffer zone of at least 220 MHz. The 220 MHz guard band is actually 400 MHz in practice this year because AT&T and Verizon have not yet deployed above 3.8 GHz, but the FAA still says the current level of transmissions can interfere with some altimeters. There are also satellite transmissions between4.0 and 4.2 GHz, but those haven’t been a concern for the FAA.

Chair: Bad receivers “diminish broader opportunities”

In a speech Tuesday at Mobile World Congress, FCC Chairwoman Jessica Rosenworcel said the commission needs to get tough on wireless receivers. Rosenworcel did not mention airplane altimeters but explained that faulty receivers that cannot avoid transmissions from other spectrum bands can prevent new services in unused frequencies.

She continued:

In the past, our discussions of spectrum efficiency have been a one-way effort. They have focused almost exclusively on transmitters. We’ve put a lot rules in place about how and when transmitters can operate in order to control interference levels. But here’s the thing: Wireless communications only exists when transmitters are connected to receivers. Both are vital. Both matter. And going forward policymakers need to consider both transmitting and receiving. Not just the former at the expense of the latter.

That’s because minimally performing receivers can make it more difficult to introduce new services in the same or nearby frequencies. They can diminish broader opportunities with radio-frequency and put constraints on what is possible in the new wireless world.

FCC to ask for input on possible regulations

Rosenworcel said she will propose launching “a new inquiry to explore receiver performance and standards.” The notice of inquiry would ask for public input on possible solutions, including new “regulatory requirements,” Rosenworcel said.

She went on:

This inquiry would ask how receiver improvements could provide greater opportunities for access to spectrum. It would explore how these specifications could come in the form of incentives, guidelines, or regulatory requirements—in specific frequency bands or across all bands. And it would seek comment on legal authority and market-based mechanisms that could help create a more transparent and predictable radio-frequency environment for all spectrum users—new and old.

Rosenworcel said she will make the proposal in April. While the FCC still has a 2-2 partisan deadlock, the Democratic chair has bipartisan support. Rosenworcel thanked Republican Commissioner Nathan Simington “for his leadership on these issues and his willingness to work with me on a path forward.”

Simington issued a statement applauding “Chairwoman Rosenworcel’s decision to consider exploring a new regulatory framework for commercial spectrum allocations.” Simington’s statement went on to cite the problem with altimeters:

An approach that looks at both the receiver and transmitter ends of the equation is the only framework truly capable of timely accommodating the interests of federal users of spectrum, and other incumbents. We see a lot of value in getting to a place where conflicts such as the C-band/altimeter fight are headed off at the pass.

This model will provide all interested parties sufficient advanced warning about problematic band edges adjacent to any new commercial spectrum. Clear rights regarding interference protection can provide incentives for innovation and collaboration among spectrum users in a way that avoids regulatory dictate.

FCC urged aviation industry to act two years ago

When the FCC voted to allow cellular transmissions in the C-band in February 2020, the commission adopted power limits and the 220 MHz guard band between 5G and altimeters. “The technical rules on power and emission limits we set for the 3.7 GHz service and the spectral separation of 220 megahertz should offer all due protection to services in the 4.2-4.4 GHz band,” the FCC said.

While the FCC found no evidence that “harmful interference would likely result under reasonable scenarios,” it urged the aviation industry to conduct more testing on altimeters. “[F]urther 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,” the FCC said. Despite that warning, the FAA and aviation industry seemingly weren’t prepared for the 5G transmissions when the rollout occurred almost two years later.

Receiver design is fundamental problem

“Fundamentally, the problem is a design issue with the aviation industry’s radar altimeters,” Dennis Roberson, who runs a technology consulting firm and is a research professor at Illinois Institute of Technology, told lawmakers during a House subcommittee hearing last month. When altimeters were first designed decades ago, “they had very low-power neighbors, i.e., satellites beaming their information to the earth from very distant orbits,” he said.

Roberson continued:

Since the altimeters operate on a radar principle looking for a signal reflected from the ground, their receivers couldn’t detect the very low-power neighboring satellite signals. This led the early designers of the altimeters to decide they really could ignore their assigned spectrum boundaries and as a result they allow transmitted energy far outside their band into the receiver. For decades this was not an issue given their quiet neighborhood, but with new neighbors now moving in (AT&T and Verizon), the spectral space that they were allowing into the receiver is now a potential problem.

Roberson said the current 400 MHz separation between altimeters and 5G “is very, very large,” pointing out that the entire FM radio band is 20 MHz wide. The FCC “determined that there shouldn’t be an issue because of the vast separation between the 5G cellular use of the new spectrum and the altimeter spectrum allocation,” Roberson said. “Unfortunately, this is not the case for old, technically ‘wide open’ altimeters. These radar altimeters may send out a signal and be unable to discern the reflected signal because of energy from the faraway 5G towers entering the receiver, causing the radar altimeter to either fail to function or possibly provide a false reading.”

Making matters worse, altimeters today are “highly integrated into the avionics for modern aircraft,” he said. “If, for instance, the altimeter says the aircraft is still in the air when it has actually landed, it will cause the reverse thrusters and spoilers that normally create a rapid reduction in the airplane’s speed on the ground to not operate.”

During that hearing on February 3, FAA Administrator Steve Dickson told Congress that “we are confident we will work through this issue safely with minimal disruptions, but we acknowledge that some altimeters—especially older models used by certain segments of the aviation industry—may not receive approval as being safe in the presence of 5G emissions and interference and may need to be replaced.” Dickson subsequently announced his resignation.

Receiver regulation is an old idea

The potential that poorly designed receivers may prevent new wireless services on underutilized spectrum bands has been known for many years. The FCC adopted a notice of inquiry into potential receiver performance regulation in 2003 but closed the proceeding in 2007. Commissioners Michael Copps and Jonathan Adelstein expressed concern about the inquiry being closed, saying that “the agency has a statutory duty to encourage more efficient uses of the radio spectrum” and that the record in the proceeding “suggests that an integrated approach to regulating receiver performance could play an important role in achieving this goal.”

An Obama White House report in 2012 raised the problem again, saying there is a “need for receiver regulation.”

“Spectrum management has traditionally focused on the characteristics of transmitters, but receiver performance also limits the utilization of spectrum,” the report said. That report said the need for receiver regulation was illustrated by the then-recent LightSquared/GPS controversy, which involved a much smaller guard band than the 220 MHz or 400 MHz ones in the 5G/altimeter dispute.

In that 10-year-old battle, LightSquared proposed a 23 MHz guard band between its planned cellular network and GPS. Meanwhile, the GPS industry asked for a 34 MHz guard band. The FCC rejected LightSquared’s proposal, and the company declared bankruptcy, but a different version of the plan was approved by the FCC in 2020 with power reductions and a 23 MHz guard band. The Defense Department and Department of Transportation opposed that FCC decision.

5G/altimeter controversy not over

Despite the FCC making a final decision on the C-band in February 2020 and urging the aviation industry to investigate the altimeter problem, the FAA stuck to its strategy of trying to stop or delay the 5G rollouts. AT&T and Verizon agreed to delay their C-band deployments from December 5, 2021, to January 19, and they adopted voluntary limits around airports for six months.

The FAA subsequently began testing altimeters and by the end of January had cleared 90 percent of the US commercial aircraft fleet for low-visibility approaches in areas with C-band deployment. Airline CEOs also began striking an upbeat tone, with American Airlines CEO Doug Parker saying the process of ensuring that airplane altimeters work in 5G areas is “really not that complicated.”

But the FAA issued another warning that “revis[es] the landing requirements for certain Boeing 737 series airplanes at airports where 5G interference could occur” on February 23. The FAA said this latest warning would have little practical effect because “it does not apply to aircraft flying into areas where the 5G environment has been rendered safe for aviation, which the FAA said includes nearly all airports,” according to Reuters. However, the controversy could flare up again in July when AT&T and Verizon are scheduled to end their voluntary limits around airports.

In regard to 5G, other risks have been associated with it including

Environmental risks (see 1, 2, 3, 4, 5, 6, 7, 8)
Health risks (see 1, 2, 3, 4, 5, 6, 7)
Privacy risks (see 1, 2, 3)

Additionally, studies have revealed that 4G is still better, more reliable, and safer than 5G (see 1, 2, 3, 4, 5, 6, 7). Opposition to 5G has also stopped or delayed deployment in some locations.

Of course, there are environmental and health risks associated with other sources of wireless radiation as well. In 2021, a U.S. federal court ruled in favor of organizations and petitioners that sued the FCC for NOT adequately protecting Americans from wireless radiation exposure (including 5G). More recently, non-profit groups petitioned the U.S. Health and Human Services Department (HHS) and Food and Drug Administration (FDA) to declare wireless radiation an “imminent” health hazard and to start warning the public. Got pets? Exposure can affect them too.

Nevertheless, 5G and wireless expansion continues throughout the U.S., much of it being funded by the U.S. government. Boo! Hiss!