5G Providers Hope to Solve 6GHz Spectrum-Sharing Concerns

5G providers like AT&T, Verizon and others are hoping to apply new spectrum-sharing technologies to the 6GHz band in a move that they argue could open up the spectrum for a much wider variety of uses -- including 5G.

AT&T, Verizon, Federated Wireless and others are urging the FCC to apply a technology called automated frequency coordination (AFC) in the 6GHz band. Such a technology could both protect existing users in the band and also allow for a wider variety of new uses in the band, including high-power operations and, potentially, 5G. AFC is similar to the spectrum-sharing technology that the FCC is currently evaluating for commercial operations in the 3.5GHz CBRS band.

"AFC is the key to finding a long-term solution that provides incumbent's 100% protection from harmful interference from unlicensed use in the 6 GHz band," AT&T, Verizon and Comsearch (a unit of CommScope) wrote in a recent joint filing to the FCC.

Federated added, in its own filing to the FCC, that AFC technology in the 6GHz band could potentially "enable swift access to critical 5G spectrum."

However, not everyone is completely on board. "While some parties have urged the Commission to require the use of Automatic Frequency Coordination (AFC) for all unlicensed devices, across the entire 6GHz band, we urged the Commission to reject this approach," wrote the Wi-Fi Alliance in a recent filing to the FCC. "While AFC will offer robust protection for standard power operations, it will be unnecessary to burden low power indoor-only (LPI) devices with this additional complexity."

And the Utilities Technology Council (UTC), a global association focused on the intersection of telecommunications and utility infrastructure, argued that AFC systems need to be carefully tested and evaluated so that new transmissions in the 6GHz band don't interfere with existing utility operations in the band. "AFC is untested and lacks transparency," the association wrote to the FCC.

Nonetheless, Federated in particular is pushing AFC as a technology that the FCC should consider not only for the CBRS and 6GHz bands but also for the C-Band, and potentially other bands as well. "Federated Wireless is confident that an AFC based on a simplified version of the technology employed in CBRS is an ideal solution for the 6GHz band, offering incumbents assurances that they will be fully protected while also ensuring that new unlicensed users are able to maximize access to critical new bands as quickly and as efficiently as possible," the company wrote. Federated even built an AFC setup in 6GHz for testing purposes.

Continued Federated: "Expanding sharing frameworks to other bands will serve the Commission and industry well, whether as a transitional mechanism that can make unused spectrum available immediately while transition efforts proceed in parallel, or as a more permanent solution that protects incumbent operations and maximizes intensive use of available spectrum resources. By leveraging the technology initially developed for the CBRS band, the Commission can rapidly make available hundreds of MHz of spectrum for more intensive commercial use in a matter of months, not years."

Federated's position is not a huge surprise, given that the startup is hoping to make a major splash as a provider of sharing technologies in the 3.5GHz CBRS band. The US Navy has long used the 3.5GHz CBRS band for radar along the US coastline. But based on new rules from the FCC, the band will soon be opened to commercial operations thanks to Environmental Sensing Capability (ESC) monitors and Spectrum Access System (SAS) sharing databases. The ESC is needed to see whether US Navy radar systems are using the 3.5GHz band. If they are using the band, the ESC would tell SAS databases about the situation, so that a SAS vendor could move around actual users in the CBRS band to prevent them from interfering with US Navy operations.

"Federated Wireless and its many industry partners eagerly await the opportunity to deploy CBRS spectrum and SAS technology, confirming the efficiency and effectiveness of spectrum sharing in the CBRS frequencies and beyond," the company wrote.

It's no surprise that the 6GHz band is generating so much interest. The band stretches across a whopping 1200MHz of spectrum and also offers the kinds of performance characteristics that 5G providers are interested in. Meaning, the 6GHz band offers a good balance between capacity and coverage, unlike low-band spectrum (which doesn't offer much capacity) and high-band spectrum (which doesn't offer much coverage).

The FCC, for its part, is currently evaluating a number of proposals to open the 6GHz band for commercial operations, including licensed and unlicensed scenarios. "The 6GHz band is populated by microwave services that are used to support utilities, public safety and wireless backhaul," FCC Chairman Ajit Pai said in a recent speech. "Each of these serves an important function that we must protect. We're working through some complex technical issues both internally and with outside stakeholders."

Some in the industry believe the FCC will move forward on a 6GHz ruling in the coming months, and could potentially be commercialized in 2021.

Mike Dano, Editorial Director, 5G & Mobile Strategies, Light Reading | @mikeddano

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