FCC, Public Safety, Critical Infrastructure Grapple Over 6 GHz Unlicensed Use
Tuesday, April 20, 2021 | Comments

The FCC asked the U.S. Court of Appeals for the District of Columbia to deny a variety of public-safety and industry organizations’ petition for reconsideration of its decision to allow unlicensed use of the 6 GHz band. The groups meanwhile asked the FCC to vacate the order allowing unlicensed use and remand it back to the commission for improvement.

The organizations, which include the Association of Public-Safety Communications Officials (APCO) International, AT&T Services, the Edison, Electric Institute (EEI), the National Association of Broadcasters (NAB), the Utilities Technology Council (UTC), the National Rural Electric Cooperative Association (NRECA), and the American Public Power Organization (APA), argued that the FCC did not properly consider the potential for harmful interference to public-safety incumbents in the band or take proper steps to mitigate that interference in it rulemaking. In its response to those organizations lawsuit, the FCC disagreed.

“The commission’s decision was made after careful consideration of the evidence presented by both proponents and opponents of unlicensed operations,” the FCC said in its filing. “Over the course of a nearly three-year rulemaking, the agency reviewed a voluminous and highly technical record that included roughly 100 studies and thousands of filings from interested parties.”

The FCC argued that throughout the rulemaking process, it had recognized that it needed to protect existing licensed operations from harmful interference.

“The commission accordingly adopted a set of restrictions on unlicensed operations that it reasonably determined would ensure that the risk of harmful interference to licensed operations would be insignificant,” the FCC said.

In their own brief to the court, the industry and public-safety organizations reiterated their concerns that the FCC’s technical conclusions in the order were based on basic logic errors and that the current safeguards are not enough to protect incumbents users. The group urged the court to push the FCC to consider stronger safeguards.

“In defending the order, the FCC and its supporters mischaracterize the basic choices before the FCC,” the organizations said in their filing. “That choice was not whether to allow unlicensed devices to operate in the 6 GHz band at all but how to mitigate their interference risks. … This and other failures of reasoned decision-making have enormous real-world consequences. Without some of petitioners’ proposed safeguards, some of these billion-odd devices will almost certainly disrupt some of the nation’s nearly 100,000 fixed-microwave links essential to public-safety communications and critical infrastructure.”

The FCC argued that while the organizations had accused it of ignoring evidence relative to the harmful interference, the record actually showed that it had “grappled at length with these issues and addressed the concerns raised by petitioners.”

The commission said that it has defined harmful interference as operation that “endangers the functioning of a radio navigation service or other safety services or seriously degrades, obstructs or repeatedly interrupts a radiocommunications service.” In its response, the commission touted the ability of the 6 GHz order to open up new spectrum for new wireless uses while preventing interference to incumbents.

For standard-power devices, the FCC adopted an automated frequency coordination (AFC) system that would prevent interference to incumbent operations. Meanwhile, the FCC permitted unlicensed low-power devices to operate in all 6 GHz bands without an AFC.

However, the commission said it implemented three safeguards to prevent interference to incumbent devices. Under those safeguards, low-power unlicensed devices can only operate indoors; all low-power access points must use a “contention-based protocol,” which allows multiple users to share spectrum; and low-power access points can only have a reduced power spectral density of 5 dBm per megahertz effective isotropic radiated power (EIRP), which was much lower than the initially proposed 17 dBm per megahertz the FCC originally proposed.

“At this power limit and with the other constraints imposed on these operations, the commission found the risk of harmful interference to incumbent operations to be insignificant,” the FCC’s order said.

The FCC argued it had reviewed what it called an “enormous and highly complex record” and through that analysis had determined that the technical and operational limits it imposed on unlicensed devices would ensure that “there would be no significant risk of harmful interference to licensed operations.”

“In determining that there would be no significant risk of harmful interference to incumbent licensed operations in the 6 GHz band, the commission did not find that its rules would ‘prevent harmful interference under all circumstances,’ ” the filing said. “As the order explained, attempting to meet that impossible standard ‘would rule out virtually all services and unlicensed operations given that there is virtually no type of RF-emitting device that does not have the potential for causing such interference if used incorrectly.”

The FCC said that instead it determined that the risk of such harmful interference would be insignificant and if a device caused harmful interference, it would be required to cease operations.

The organizations said in their own filing that the FCC was misrepresenting their position on the potential for harmful interference.

“First, we do not argue, as intervenors claim, ‘that the commission may not authorize unlicensed operations in the 6 GHz band if there is any possibility, no matter how remote, that any device will cause harmful interference to any fixed-service link at any time,’ ” the organizations said in their filing. “We challenge the order because it is very likely to result in harmful interference at unpredictable places and times and because, without explanation, it arbitrarily rejects readily available safeguards.”

The groups argued that the FCC’s order and its court filings assume away worst case scenarios, which they said are the scenarios most likely to cause serious interference.

“But worst cases are real cases,” the filing said. “As petitioners’ studies illustrated, some of these billion 6 GHz devices will almost certainly harm some microwave links over the comping years. Whether or not such worst-case scenarios constitute a small percentage of total scenarios, their absolute numbers will be unacceptable, and they will endanger public safety and the electric grid.”

In its filing, the FCC also addressed the argument that it does not have the necessary tools to identify and address any harmful interference issues in the band.

“The commission explained that its enforcement bureau has the ability to investigate reports of interference caused by low-power devices and ‘take appropriate enforcement action as necessary,’ ” the filing said. “As the commission noted, unlicensed wireless ‘devices have been deployed … in abundance’ in the 2.4 GHz and 5 GHz bands ‘for well over 20 years’ and the agency has ‘effectively identified and addressed’ harmful interference issues in those bands.”

The FCC argued that steps it took in the order, such as requiring AFC systems with information about devices, to identify the source of interference and resolve any issues.

“In sum, the order rests on a reasonable resolution of radiofrequency engineering issues, following exhaustive examination of a voluminous record,” the FCC’s filing said. “These issues lie at the heart of the commission’s experience and expertise. The petitions for review should be denied.”

The organizations argued that the FCC’s traditional enforcement procedures will not be enough to curtail interference from the many unlicensed devices.

“When some of the billion-odd portable devices sporadically disrupt some of America’s 100,000 microwave links, an affected link operator will not know what is causing the interference, let alone where the interfering device is located,” the organization’s filing said. “Even the FCC does not contend that it or the operator could immediately identify the source and eliminate the interference.”

The groups noted that the most optimistic timeframe the FCC had offered for corrective action was within a week.

“But a week without a mission-critical microwave link is a week with dropped emergency calls or systemic power outages,” the groups’ filing said. “The damage to life and property within that timeframe can be catastrophic. In all events, even a one-week timeframe is unrealistically optimistic for the pragmatic reasons that we have discussed and the FCC ignores.”

The groups contested the FCC’s assertion that its enforcement efforts had helped prevent interference in similar bands such as 2.4 and 5 GHz.

“As to the 2.4 GHz band, NAB submitted, and the order ignores extensive evidence that the FCC’s enforcement efforts have amounted to a futile game of whack-a-mole and that repeated interference has made the band partially unusable for licensees,” the filing said.

The groups asked the court to vacate the FCC’s order allowing unlicensed use and remand it back to FCC to be improved.

It is unclear when the appeals court will rule on the petitions for reconsideration.

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