FCC prepares AFC for 6 GHz band

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The Federal Communications Commission on Tuesday asked for proposals from those wishing to coordinate frequencies in the 6 GHz band for unlicensed standard power devices in order to avoid interference with existing users.

It comes less than two weeks after the regulator and AT&T clashed over unlicensed use of the 6 GHz band in oral arguments in the United States Court of Appeals for the DC Circuit.

Automated Frequency Coordination (AFC) was a topic covered in AT&T’s appeal against the FCC’s unanimous decision and order of 2020 that opened 1,200 megahertz of spectrum in the 6 GHz band for unlicensed users, including Wi-Fi.

RELATED: FCC Votes To Make 1200 MHz To 6 GHz Available To Unlicensed Users

In a public notice (PDF) released this week ahead of the commission’s public meeting, the FCC initiated the process for licensing AFC systems in the 6 GHz band and adopted the item during circulation.

“This element is another step towards fully exploiting the potential of the 6 GHz band, by starting the process of authorizing operators of automatic frequency control (AFC) systems to offer their services to parties seeking to operate in certain parts. of the 6 GHz band outdoors at standard power levels, ”FCC Commissioner Geoffrey Starks said in a statement. “Thanks to such AFC systems, standard unlicensed power devices will be able to coexist in the 6 GHz band with historical fixed microwave links and radio astronomy observatories. I look forward to reviewing the applications and continuing our progress in making unlicensed spectrum available without interference. “

This decision was applauded by the WifiForward Coalition and WISPA.

Federated Wireless is a party that has expressed interest and has already indicated that they will be working on the AFC for the 6 GHz band. Federated is already one of five FCC-licensed Spectrum Access System (SAS) administrators for the Citizens Broadband Radio Service (CBRS) shared band.

RELATED: Facebook, Cisco, and Broadcom Launch AFC Group for 6GHz Wi-Fi

The FCC may designate one or more AFC System Managers, who would be required to serve for five years and could then be renewed based on performance.

Interested parties can submit initial proposals by November 30, 2021, with comments due by December 21.

AFC for low consumption devices?

As the FCC seeks proposals for the AFC to mitigate interference with fixed microwave links from standard power devices in the 6 GHz band, AT&T recently continued its legal battle.

On September 17, attorneys for AT&T told a three-judge panel that the FCC had no reason not to require the same AFC technology for low-power devices, like indoor Wi-Fi routers and points. access, operating in the same spectrum to avoid this he claims that this is most likely harmful interference with fixed microwave links.

AT&T and others’ struggle, including Association of Public Safety Communications Officials International (APCO), is not new – concerns have been raised throughout the 6 GHz proceedings and the Court of Appeal of DC in October denied motions to stay the FCC’s order. AT&T initially filed a lawsuit challenging the FCC on 6 GHz in June 2020.

The FCC has had some big hitters with support led by Apple, as well as Broadcom, Cisco, Google, Intel and Microsoft.

RELATED: Tech Giants Challenge AT&T Rating of 6 GHz Band for Unlicensed Use

The operator was licensed for fixed services supporting mobile links and fixed telecommunications lines, but the 6 GHz band also supports microwave links for public safety and critical infrastructure.

In oral argument, Jonathan Nuechterlein, attorney for AT&T and APCO, called the FCC’s decision not to require AFC for low-power devices a “mystery”.

“The FCC had an opportunity in that order to do everything right, could have opened up the 6 GHz band for Wi-Fi while protecting public safety, the power grid and other permitted uses. Specifically, like the NPRM [Notice of Proposed Rulemaking] itself proposed, the FCC could have required that all unlicensed devices that share spectrum with fixed microwave links use automated frequency coordination, also known as AFC, ”the attorney said. “An effective AFC mechanism would minimize the potential for interference by preventing these devices from transmitting on the same frequencies as nearby microwave links.”

He said the FCC order identifies no downside to what the agency said is simple and easy to implement for standard-powered devices, or that it would add significant costs.

During the hearing, circuit judges noted that the Commission said the order was designed to prevent the risk of significant interference, but not all, citing that “harmful interference would be a rare but possible occurrence” .

AT&T, on the other hand, argued that there is more than insignificant risk.

RELATED: AT&T Slams FCC Plans for 6 GHz Band

AT&T said it was showing “that it is very, very likely that at some point in the next 10 years some of these billions of devices will interfere with some of the 100,000 microwave links” and that the government was not giving a clear position on his answer to this.

AT&T is also concerned that Wi-Fi devices supporting the 6 GHz band are starting to hit the market and argued that a device like a Wi-Fi router without AFC could interrupt signals on a mic receiver. -waves – including the links responsible for the preservation of food. first responder grids and communications.

The FCC, a judge noted, said that if harmful interference occurs, the commission has the legal authority to step in and stop it. However, AT&T said this is a different context where after the fact steps don’t help.

“If one of these links goes down, the damage for that day is already done and there will be calls to 911 that will not go through, there will be a failure of communication with the nuclear reactors … that is the concern we have here, ”AT&T argued. “Again, all of these concerns could be significantly alleviated by imposing this AFC requirement. “

Attorneys for the FCC have pointed to disturbances in the atmosphere that could cause microwave links to lose power and degrade from low-power devices, but without these fading events – called deep atmospheric path fading. multiples – which they say don’t happen often, low-power devices will win doesn’t really interfere.

The FCC told the three-judge panel that AT&T provided a “worst-case” analysis and that low-power access points or routers are unlikely to interfere with powerful microwave transmissions. point to point.

The judges raised questions about the technical aspects of the interference, as well as the robustness of the studies used, including one from CableLabs that used data points in New York. They wondered if this could be representative of interference in very different geographic areas across the country.

During oral argument, one of the judges indicated that the AFC was one of three ways the FCC could have acted arbitrarily and capriciously if it had not explained why the technology was not a better one. choice than the other actions that the commission described taking instead.

The FCC again argued that this was because the technology is not necessary for low-power devices, as there is an insignificant risk of harmful interference.

A judge asked if the court disagreed with the FCC why the order should be sent back to the regulator for clarification rather than dismissed altogether.

“Rescinding this order would be incredibly disruptive given that the devices have already started to be deployed,” said attorney James Carr for the FCC, adding that if the court wanted more explanation, the FCC is able to provide it. .


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