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5G

5G industry struggles with spectrum sharing

"Sharing is becoming a necessity," said Google's Andrew Clegg during a recent regulatory event. Clegg is Google's spectrum engineering lead with decades of experience in spectrum policy.

Others agree.

"Spectrum sharing must be the new normal," argued Vernita Harris, director of spectrum policy and programs for the chief information officer of the US Department of Defense (DoD). "It's an operational need that we can't get away from."

Harris's comments aren't surprising following a recent DoD spectrum initiative stating that "the traditional model of static frequency allocation is not sufficient."

But the idea of widespread spectrum sharing is a bitter pill for those in the US commercial wireless industry to swallow.

"I don't think we should pursue sharing just for sharing's sake," argued Leonard Cali, AT&T's SVP for global public policy. Cali said that "the devil is in the details," and that spectrum sharing should only be considered when it makes sense.

Cali said the traditional, winner-takes-all approach to exclusive-use spectrum licensing "provides the certainty you need to create an economic business case."

Cali's position highlights decades of lobbying by the wireless industry to ensure a steady supply of licensed, exclusive-use spectrum. "Auctioning spectrum provides operators with exclusive use rights, which helps ensure the quality of service we all rely on today," CTIA, the US trade association that represents the nation's biggest wireless network operators, wrote on its website. "Auctioned, exclusive-use spectrum forms the core of today's mobile broadband networks, providing clear protection from interference, enabling investment and high quality, reliable wireless service."

Importantly, the association noted that exclusive-use spectrum auctions have raised a total of $200 billion in proceeds for the US government.

CBRS vs. C-band

Recent FCC spectrum auctions help highlight the discrepancy between shared spectrum licenses and spectrum reserved exclusively for one licensee. The C-band spectrum auction of exclusive-use licenses recently generated more than $80 billion in total bids. But the similar 3.5GHz CBRS spectrum auction of shared licenses raised only $4.6 billion in bids. And though there are plenty of differences between the two bands, sharing sits front and center considering the CBRS band is one of the first in the world to be dynamically shared between commercial and federal users.

CBRS "is showing really good promise," argued Harris, with the US Department of Defense. Indeed, CBRS proponents have noted that there are currently more than 150,000 network nodes already deployed in the CBRS band – including some by Verizonand no reported cases of interference.

But others aren't sold on the idea of sharing spectrum. "I think the jury is still out" on CBRS and spectrum sharing, said AT&T's Cali. For example, he said there are reports of disturbances in the 6GHz band, an indication that sharing remains troublesome.

"The data show harmful interference to primary, incumbent microwave licensees is inevitable," AT&T told the FCC recently, pointing to new research from Southern Company focusing on 6GHz inference.

Sharing expands

To be clear, the concept of spectrum sharing is not new. For example, spectrum in the AWS-1 band was auctioned in 2006 and involved commercial and federal uses of spectrally adjacent licenses. And the FCC's 2015 auction of AWS-3 licenses included manual frequency coordination between commercial and DoD users.

Further, automated spectrum sharing approaches have been applied to bands ranging from 5GHz to TV White Spaces (TVWSs) in the 600MHz band.

Now, though, there are a number of new sharing proposals stretching from 6GHz to 37GHz.

For example, the FCC later this month is scheduled to approve an Automated Frequency Coordination (AFC) system that promises to allow higher-power, outdoor transmissions in the 6GHz band while also protecting incumbent services. Already Broadcom, Cisco and Facebook are working with the Telecom Infra Project (TIP) to create open source software for an AFC system.

And Qualcomm – a main technology vendor for established wireless network operators – recently issued a major new proposal that contemplates a two-tiered sharing scheme in the 37GHz band. "Qualcomm's proposal opens the entire band for sharing," Qualcomm explained to the FCC. However, Qualcomm's proposal covers sharing only among commercial users and not federal users.

Political desire runs into political capital

A number of policy makers across all levels of government have expressed interest in furthering spectrum sharing.

"We're going to have to get creative about the policies we put in place," said Acting FCC Chairwoman Jessica Rosenworcel earlier this year. She said spectrum sharing in the CBRS band is a "terrific example" of creative spectrum management policies.

"It's something that I think we're going to need to study going forward, because as we scour the airwaves for more opportunities for commercial services, we're going to need to be mindful of the fact that there are just many more actors who are going to want access to spectrum," she continued. "And more ways to be creative and efficient are going to be important."

Indeed, the White House recently requested $39 million in 2022 "for advanced communications research at the National Telecommunications and Information Administration (NTIA), which would support the development and deployment of broadband and 5G technologies by identifying innovative approaches to spectrum sharing."

Likely in response, the NTIA has scheduled a spectrum symposium later this month that will "talk about plans for midband spectrum access, spectrum sharing approaches and techniques, and innovative, dynamic spectrum management tools and concepts." A number of government officials have discussed the potential for incumbent-informing capability (IIC) to underpin sharing in a wide range of spectrum bands.

But some financial analysts believe that – ultimately – money talks. For example, the analysts at New Street Research noted that a recent proposal among Senators would help fund President Biden's massive broadband infrastructure bill in part with money raised from exclusive-use spectrum auctions. That makes sense considering conservatives do not want to pay for the infrastructure bill with increased taxes, and exclusive-use spectrum auctions can be lucrative.

The New Street analysts described the Senators' proposal as "a win for the wireless industry as it will put pressure on the [Biden] administration to put pressure on the Department of Defense to free up more midband spectrum. And it will put pressure on the FCC to allocate spectrum through exclusive licensing, which raises more money than shared or unlicensed allocations."

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

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