Receiver Standards Can Help Address 5G, Aviation Interference Concerns, Experts Say
Monday, April 04, 2022 | Comments
Receiver standards can help address concerns between 5G networks and aviation interference, industry experts said during a panel at the International Wireless Communications Expo (IWCE) last month.

“This is a long term issue,” said Dennis Roberson, CEO and president of Roberson and Associates and an industry veteran who testified on the issue in front of Congress earlier this year. “It relates to the fact that the FCC regulates transmitters but does not regulate receivers.”

Near the end of last year, as major wireless carriers prepared to turn on 5G spectrum in the C-band, concerns emerged about potential interference to altimeters used in planes.

Anna Gomez, an attorney with Wiley Rein, noted that concerns about 5G’s impact on aviation systems arose years ago but had not been properly addressed before the issue came to a head at the end of 2021.

In March 2018, Congress passed the MOBILE NOW Act, which required the FCC to explore the feasibility of allowing carriers to use the 3.7 – 4.2 band. In May of that year, the FCC released a notice on the act and then a notice of proposed rulemaking (NPRM) in July. That NPRM asked if there were specific emission limits that were needed to protect aviation uses.

“So they specifically asked that question in 2018,” Gomez said.

Several years later, in March 2020, the FCC released a report and order that decided to allocate 280 megahertz to auction and create a 220 megahertz guard band. The report found that with that guard band, “well-designed” equipment should not have issues with interference and encouraged the industry to form a working group to address the issue, Gomez said.

That working group was eventually created but could not agree on recommendations so it sent the FCC a letter in November 2020 saying that it would not be offering recommendations, Gomez said. Prior to that, in May 2020, a group of aviation organizations came together and filed a petition of reconsideration of the rules, which was never ruled on by the FCC.

Gomez also noted that in December 2020, the Department of Transportation (DoT) and the Federal Aviation Administration (FAA) asked the National Telecommunications and Information Administration (NTIA) to intercede in the issue but the NTIA declined.

The C-band auction was then held between December 2021 and February 2021. The issue began coming to a head in November when the FAA issued the first of several airworthiness information bulletins addressing the issue.

Then in December, AT&T and Verizon agreed to delay their 5G C-band deployments until January 5 and later said they would work with aviation industry organizations, the FCC and FAA to address the interference issues.

At the end of December, Airlines for America (A4A) filed an emergency petition with the FCC asking for a delay of the activation of the C-band 5G frequencies. On January 4, the White House announced that it had reached an agreement with Verizon and AT&T to delay activation of the band until January 18 and not to activate transmitters near specific airports for another six months, Gomez said.

Roberson said that the issues arose because the altimeters used in airplanes were not designed with the spectrum near them in mind.

“In many instances, good designers design for their environment and not necessarily for the regulated spectrum they’re allowed to use,” Roberson said. “That creates the problem, and it’s a problem that occurs many years after the design occurred. The altimeters were designed for an environment that was really quiet.”

When many of the radio altimeters used in the 4.2 – 4.4 GHz band were first designed, the spectrum was pretty quiet and filtering was not included in the devices, Roberson said. That changed when the C-band was created and the spectrum was auctioned.

While there is a 220 megahertz guard band between the C-band and the radar altimeter band, the altimeters are still able to see that far and because there is no filter in the altimeter, interference can occur.

However, Roberson said, while this problem exists, designers are already working on new altimeters that include filtering. Additional, the interference problem does not affect commercial planes as the major commercial airlines have filtering built-in, he said.

“All the hoopla about the commercial airlines and crashing, that was all just that, hoopla,” Roberson said.

Aircraft affected by the issue are smaller and older aircraft such as fixed-wing planes and helicopters, he said. The issue is especially present during bad weather when there is little to no visibility and the pilots are dependent on their altimeters to land.

Telecommunications attorney Alan Tilles said the situation was not new and had happened in other bands and other industries.

“Every time it happens, it’s because we got new equipment,” he said. “These engineers came up with these great new things. But the new equipment interferes with the old adjacent equipment.”

Tilles argued that the situation can be complex because the users of that older equipment are still operating within the rules and it’s the new equipment that is interfering with the old equipment. One of the questions that always needs to be determined is who will pay for any change of operations to the older equipment, he said.

Enterprise Wireless Alliance (EWA) Chief Strategy Officer Mark Crosby agreed that the same situation constantly happens in the wireless industry. He argued that the FCC and NTIA should consider who could be harmed by auctions when they make decisions to auction that spectrum. “FCC and NTIA need to consider who will be harmed by it when they auction it off in the future,” he said. “This happens over and over again.”

The panel agreed that standard requirements for receivers would help solve future problems with interference. FCC Chairwoman Jessica Rosenworcel has said recently that she wants to look at potential receiver standards.

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