Tech giants challenge AT&T’s assessment of 6 GHz band for unlicensed use

spectrum
The 5.925-7.125 GHz band represents 1200 MHz of spectrum and it's currently used by many different sets of incumbents. (Pixabay)

A group of tech industry giants is challenging assertions made by AT&T in its analysis of the 6 GHz band for unlicensed use, saying just two assumptions cause AT&T to “exaggerate all of its interference predictions by more than 1000%.”

The tech companies—Apple, Broadcom, Cisco Systems, Facebook, Google, Hewlett Packard Enterprise, Intel Corporation, Microsoft Corporation, NXP Semiconductors and Qualcomm—this week submitted their analysis (PDF) to the Federal Communications Commission (FCC) in response to filings that AT&T made last month (PDF).

It’s all part of a proceeding that the FCC kicked off last year looking at how it can allow unlicensed use in portions of the 1200 megahertz of spectrum in the 5.925-7.125 GHz (6 GHz) band while ensuring that licensed services operating in the band are protected. In a note to investors today, Wells Fargo Securities analysts said the upper 6 GHz band could emerge as the “dark horse” for future 5G spectrum.

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“The plans for this spectrum are facing a bit of a recent power struggle between different constituents—namely the Wi-Fi community (who want all 1200 MHz for free for unlicensed access) and the carriers (who want part of this spectrum sold at auction for 5G use),” wrote the team of analysts led by Jennifer Fritzsche. “We believe the FCC has earmarked a significant amount of this spectrum for future unlicensed use, and the question is whether a portion of the band will be reserved for future licensed use.”

In previous filings, AT&T has noted that it is one of the country’s largest users of Wi-Fi technology and supports the “rational introduction of unlicensed technologies into new bands on a non-interference basis,” but it’s not buying claims made by Radio Local Area Network (RLAN) advocates, which include the aforementioned tech companies.

To be sure, AT&T is not the only incumbent concerned about what happens to this band. AT&T disclosed (PDF) that it holds 8,138 licenses in the 6 GHz fixed service (FS) bands supporting backhaul for its mobile networks, as well as telecom links for its landline assets. But it also estimates 25% of the links in the 6 GHz band support public safety and critical infrastructure industry licensees and 27% of the links in the band support utilities. Utilities, too, have warned about their extensive reliance on microwave systems in the 6 GHz band.

RELATED: 6 GHz band pits CTIA against Apple, Google and other tech behemoths

Other stakeholders include CTIA, Ericsson and Huawei, some of the biggest proponents for using at least part of the band for licensed services.

CTIA and carrier executives met with FCC staff last month (PDF) and advocated for making the upper portion of the 6 GHz band available for licensed, flexible use services. They also said they can see unlicensed in a portion of the 6 GHz band, so long as a positive control interference protection framework is adopted for all unlicensed devices, including low-power indoor and very low power indoor/outdoor devices. Positive control via Automated Frequency Coordination is necessary both to prevent interference and to resolve interference when it does occur, regardless of unlicensed device location or power level, they said.

In a recent interview, Paul Challoner, VP Network Product Solutions at Ericsson, said the upper part of the band should be licensed. They want to see the C-band teed up for 5G—FCC Chairman Ajit Pai has announced his intention for that auction to start before the end of 2020—but that’s not going to be enough. In fact, “we think that’s a pivotal spectrum policy decision in the U.S.,” Challoner said, referring to the 6 GHz band. He added that it’s not talked about enough because people are so focused on C-band, but “it’s critical.”

At a spectrum management conference in September, the FCC chairman noted the FCC began to explore opening up 1,200 megahertz of spectrum in the 6 GHz band for different types of unlicensed uses and that studies have shown that sharing in the band with unlicensed operations is feasible. “We’re aiming to have the best of both worlds: protect today’s incumbent users of the band while turbocharging the Wi-Fi networks and applications of the future,” Pai said.

Members of the Wireless Internet Service Providers Association (WISPA) say they're excited at the possibilities of seeing the chairman's 6 GHz proposal go through. “1,200 MHz of new unlicensed spectrum—850 MHz of which could be allocated for higher power use with automated frequency coordination—would be a boon to the WiFi economy, as well as for rural WISP providers who would use it to deliver broadband to unserved and underserved Americans,” a WISPA spokesperson said in a statement. “Taken as a whole, the proposal would help all players in the broadband ecosystem thrive. And, it would deliver on the Commission’s promises—virtually overnight—to bridge the stubborn, rural digital divide.

“Though the Commission will be subject to great pressure to auction off some of that for 5G, we hope it resists those attempts,” the WISPA spokesperson added. “New spectrum like this has not been allocated for decades. If the FCC relents, it could undermine the very wireless ecosystem it seeks to promote—one which depends so heavily on unlicensed spectrum to work and give benefit to American broadband consumers.”  

Diverse set of players

Indeed, the 6 GHz band is attracting more than the usual suspects when it comes to spectrum management. Amazon says (PDF) the band will play a critical role in supporting the development of innovative wireless devices and technologies that offer consumers valuable new services.

Facebook has met with FCC officials (PDF) to discuss how access to unlicensed spectrum within the 6 GHz band will be critically important to Facebook’s future innovations in Artificial Intelligence (AI) and Virtual Reality (VR). Cable companies, like Comcast and Charter Communications, currently use the 6 GHz band to deliver their services and they’ve expressed support for authorizing unlicensed use of the full 1200 megahertz in the band provided that existing incumbent operations are protected.

FCC Commissioner Michael O’Rielly has said the 6 GHz band, which serves as the corresponding C-band uplink, also is a prime location for unlicensed spectrum because it can be combined with the 5 GHz and 5.9 GHz bands to provide the large spectrum channels needed to achieve 5G-like results. Opening the band to additional uses is doable as long as the incumbent protections are reasonable, he said in comments at the spectrum management conference earlier this year.

“Some entities are interested in this band for licensed use, but if we address other license spectrum needs, such as 3.7-4.2 GHz and perhaps 7.125 to 8.5 GHz band, that would relieve significant pressure,” he said at the time. “Accordingly, it would be wise to start studying the 7 GHz band to see if it can accommodate commercial operations. Additionally, efforts should be made to allow low-power indoor use, across the entire band, without the intervention of an automatic frequency coordinator, which would otherwise add expense for those wishing to use the band for devices like in-home wireless routers.”

FCC Chairman Pai recently tweeted how a diverse coalition of 35 entities supports the FCC’s commitment for opening up the 6 GHz band for Wi-Fi.

“The unlicensed community has been steadfastly working with technical experts and conducting detailed engineering analyses that demonstrate how coexistence between incumbent and new unlicensed users will work,” the coalition wrote (PDF). “These analyses include very-low-power (VLP) and low-power indoor (LPI) devices and use cases that will be deployed quickly, in addition to an Automated Frequency Control (AFC) system to ensure standard power unlicensed devices do not cause harmful interference.”

Such signs are encouraging, according to Chris Szymanski, director of product marketing at Broadcom. The bipartisan support from O’Rielly, a Republican, and Commissioner Jessica Rosenworcel, a Democrat, on finding more spectrum for Wi-Fi “has really set the tone” for both the 5.9 GHz and 6 GHz bands.

In fact, Szymanski, who had a hand in crafting the technical response to AT&T, said he appreciates AT&T’s latest technical response, with real-world examples, allowing for substantive discussions. That helps move the discussion forward rather than trying to respond to broad complaints with no technical analysis. “There was sufficient technical information available and we were able to respond,” he said, adding: “I absolutely believe that all of the issues raised by AT&T are addressable.”

Szymanski and colleagues have been looking at the band for several years and have found it to be the ideal band to address the unlicensed crunch. On the other hand, Szymanski said “licensing a portion of the band would be a disaster for incumbents and would add years of delay.” The band is perfect for sharing, and Wi-Fi by its very nature is predicated on sharing. “That’s something we do well,” he said, with Wi-Fi proving that it could take what once were considered “junk” bands and turning them into massive information highways, so much so that the existing bands used for Wi-Fi—5 GHz and 2.4 GHz—are now becoming heavily congested. 

The FCC is considering three device classes, not only standard power Wi-Fi, governed by automatic frequency coordination, but also low power indoor and very low power portable device classes. Indoor low power devices would address most of the residential broadband demand. By leveraging technical limitations such as power and indoor conditions, unlicensed emissions would stay clear of the incumbent users. No one wants to jeopardize public safety, utilities and other mission-critical services, according to Szymanski. “At the end of the day, we’re not trying to put energy in the direction where you have these fixed service operations,” he said.

While nothing official has come from the chairman’s office, it’s not going out on a limb to say the FCC is poised to do something with the band sooner rather than later. Last week, O’Rielly expressed his belief that incumbents can be protected, with an eye toward getting something done in the first quarter of 2020.

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