Groups Ask Court to Remand New 6 GHz Rules to FCC for More Interference Safeguards
Wednesday, January 06, 2021 | Comments

A group of public-safety, critical infrastructure and industry organizations asked a federal appeals court to remand the FCC’s recent order allowing unlicensed use in the 6 GHz band for stronger safeguards against interference to critical microwave links.

In April, the FCC adopted an order that makes 1,200 megahertz of spectrum in the 6 GHz band available for unlicensed use. The 6 GHz band is populated by, among others, microwave services that are used to support utilities, public-safety and wireless backhaul.

Following the adoption of the rules, several entities including the Association of Public-Safety Communications Officials (APCO) International and the Edison Electric Institute (EEI) filed for appeal of the rules to the U.S. States Court of Appeals for the District of Columbia Circuit. Those lawsuits were all consolidated into one suit.

All of the petitioners on the consolidated suit are APCO, EEI, AT&T Services, the National Association of Broadcasters (NAB), the Utilities Technology Council (UTC), the National Rural Electric Cooperative Association (NRECA), the American Public Power Association (APPA) and CenturyLink.

In their first briefing in the case, the entities said that they do not oppose deployment of unlicensed devices in the 6 GHz band. Instead, they are asking for the necessary safeguards to prevent interference to critical communications links that could threaten lives and safety.

The entities noted that the FCC in passing the rules did not conclude that the safeguards against interference would be infeasible or costly but instead concluded that there was no significant risk of interference without the safeguards.

“That conclusion is unsupported and insupportable, and the FCC reached it only by unlawfully ignoring evidence and committing blatant statistical errors,” the filing said. “The order should be vacated and the case remanded for the FCC to adopt the requested safeguards.”

The organizations argued that the rules posed a significant threat to critical microwave links without the proper safeguards.

“It is undisputed that most of the fixed microwave links at issue here support 9-1-1 calls, first responder communications and other critical safety services,” the filing said. “It is also undisputed that even for a short burst of radiofrequency energy from unlicensed devices can interrupt such links for a quarter hour or more, as microwave networks must resynchronize before resuming communications.”

The final rules approved by the commission allowed unlicensed standard-powered devices under automated frequency coordination (AFC) and lower power unlicensed devices that are not controlled by AFC but should only be used indoors. Under the rules, three restrictions apply to lower power devices: they have a lower power limit, they have restrictions that are meant to deter use 6 GHz routers and Wi-Fi access points outside of buildings, and they must use a contention-based protocol to prevent interference.

All of the petitioners said that they are opposed to the current rules for the lower power devices, and APCO also said it is concerned that the AFC technology has not been properly tested to ensure that standard power devices won’t cause interference to microwave links.

The organizations argued that the steps the FCC took to prevent interference from lower power devices will not be enough to prevent interference.

“But those indoor-only restrictions will in fact be ineffective, again for reasons that petitioners explained but the commission ignored,” the filing said. “As to access points, the FCC made outdoor usage only somewhat inconvenient, not impossible. Consumers can and will take these devices outside, where the absence of signal attenuating walls will present a severe threat to microwave receivers.”

The organizations also argued that the FCC did not claim that one of those requirements standing alone would be enough to prevent interference.

“The validity of the FCC’s rules for low power devices thus depends on the independent efficacy of each requirement; if any fails, the order is invalid,” the filing said.

Meanwhile, the organizations argued that the contention-based protocol will only prevent interference between unlicensed devices and not between unlicensed devices and microwave links.

“A contention-based protocol can enable Wi-Fi and similar devices to avoid interfering with each other by listening for one another’s omnidirectional transmissions before using the same frequencies,” the filing said. “But such devices cannot even hear the narrow point-to-point beams transmitted between outdoor microwave towers, as petitioners explained in vain.”

The organizations said they had brought these concerns before the FCC during the public comment period, but the FCC had ignored them, instead relying on a study submitted by CableLabs, which they said lobbied on behalf of the cable industry for less interference safeguards.

“Although the FCC described the so-called ‘CableLabs Study’ as the ‘best evidence in the record,’ it had no basis for making that judgment because CableLabs had not disclosed data and assumptions,” the filing said. “And what little has been disclosed about CableLabs’ assumptions revealed obvious errors that the FCC itself acknowledged it could not fix. In contrast, the order dismissed petitioners’ own studies, including those that unlike the CableLabs study rested on fully disclosed inputs concerning real-world interference scenarios.”

APCO also argued against the use of AFC for standard power devices, noting that the FCC had not proven that the technology would be able to prevent interference.

“Given the life-or-death nature of these communications, APCO is concerned that the FCC’s reliance on automated frequency coordination to prevent all interference from standard-power devices is flawed,” the filing said. “Preventing interference depends on a coordination technology’s ability to stop unlicensed devices from transmitting in locations where they could interfere with licensed users. A coordination technology should not permit an unlicensed device to share the channel used by a public-safety receiver unless the device is outside the area that would pose a threat to the receiver.”

APCO pointed to the order’s creation of a requirement that standard-power device access points must be reported to an AFC. APCO argued that the requirement wouldn’t prevent interference because the order does not establish an accuracy requirement for how close the estimated location must be to the true location.

“Thus, some standard-power access points will be authorized by an automated frequency coordination to transmit on the same channel being used by public safety in a location that should be off limits,” the filing said. “The FCC’s failure to establish an accuracy requirement violates its own logic in requiring that some unlicensed devices be controlled by automated frequency coordination and without real-world testing, any accuracy requirement established by the FCC would be arbitrary.”

Finally, the organizations argued that because it was convinced interference would not occur, the FCC had not put into place procedures for alleviating any interference that does occur from interference.

“The FCC all but ignored that point because it erroneously assumed its rules ‘eliminated any significant risk’ that such harmful interference would rise in the first place,” the filing said, noting that the FCC only said that if the assumption was wrong, its Enforcement Bureau would be able to investigate the reports and take action.

The organizations argued that the interference caused by unlicensed devices would be different from the interference normally investigated by the Enforcement Bureau.

“The FCC’s post-hoc enforcement mechanisms are designed to locate interference caused by pirate radio transmitters or enterprise-grade machinery, not the types of portable, sporadically transmitting consumer devices bought by millions of consumers at Amazon or Walmart,” the filing said. “When one of those devices creates harmful interference, neither 6 GHz licensees nor the FCC will have any ready means of tracing the degraded performance to interference from any unlicensed 6 GHz device, let alone identifying which unlicensed device, out of thousands of nearby suspects, is the one responsible for interrupting the link.”

The organizations concluded by arguing that the court should vacate the order and remand it back to the FCC to address these interference issues before moving forward unlicensed 6 GHz use.

“Here, the court should vacate the order because the FCC identified no way to reconcile its current rules with petitioners’ acknowledged legal right to conduct their operations without episodic harmful interference by unlicensed 6 GHz devices,” the filing said.

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