WASHINGTON — The Federal Communications Commission has told Congress it still hasn’t determined whether its dynamic spectrum sharing model can be used to allow larger commercial carriers to share the 3.5 Gigahertz allocated for unlicensed Citizens Broadband Radio Service (CBRS).

That finding came in a report from the Wireless Telecommunications Bureau and Office of Engineering and Technology (OET). Currently on the witness stand is television’s white spaces regime, with the CBRS band the next up.

The FCC has finalized the rules and granted conditional approval to the dynamic sharing system for CBRS and is moving toward final approval and initial commercial deployments. It has also certified equipment, and has told Congress that collaboration among the stakeholders has been excellent.

Companies — most notably Amazon — and cable operators have been eyeing the CBRS band.

Dynamic sharing employs devices that can sense available spectrum and adjust their power levels to avoid interference, as well as databases for protected services that the devices can access, and advanced antennas to steer signals away from incumbents.

But there is a “but” in that dynamic spectrum future.

In a mandatory “Spectrum Pipeline” report to Congress this month on the agency’s progress in freeing up new spectrum by reallocation or sharing — a report required by the RAY BAUM’S Act FCC reauthorization bill — the agency said it and its stakeholders are “confident and excited” about the prospects of CBRS for commercial use, and dynamic sharing, but the consensus comments for that report advocate a “wait-and-see” approach.

That makes the white spaces and CBRS groups a sort of spectrum “canary in the coal mine” for dynamic sharing, and the FCC signaled it will wait and see how the canary fares.

On the white spaces side, broadcasters have registered complaints about how the all-important database identifying existing users is being managed and how effective it is at steering the unlicensed devices clear of TV station signals.

The FCC is still weighing that input and made it clear in the report that dynamic sharing in general is a work in progress.

“It is too soon to know whether other bands may be suitable for licensed or unlicensed use based on the techniques used in the 3.5 GHz band,” the agency told Congress. “The commission will continue to monitor and consider relevant developments.”

White Spaces Sharing OK’d

While the jury is still out on other bands, the FCC has already concluded such dynamic sharing can be used in the TV spectrum band, represented by the TV white spaces regime, a point the FCC made to Congress.

“[D]ynamic spectrum access techniques formed the basis for unlicensed access to spectrum in the TV white spaces,” it said. “This, in turn, was the precursor to the development of the more sophisticated sharing techniques that are manifest in the Citizens Broadband Radio Service.”

But whether “sophisticated” in concept translates to “effective” in practice remains open for cross examination.

FCC chair Ajit Pai said during an FCC reauthorization hearing in the House Communications Subcommittee that if the facts warrant and the law allows it, the FCC will be aggressive about freeing up TV band white spaces for rural broadband.

Rep. Peter Welch (D-Vt.) said rural broadband is being left behind, with slower speeds and capacity. He said there was a potential opportunity with the White Spaces proceeding and the Microsoft proposal, though he did not identify it by name.

Microsoft has pitched reserving TV channels after the repack for rural broadband.

Welch pressed each commissioner about using white spaces to expand rural broadband, while still protecting broadcast signals and important local news.

Commissioner Mignon Clyburn said she would be the wind beneath the wings of using white spaces for broadband, and Commissioner Michael O'Rielly noted that he has long supported white spaces for unlicensed, but not at the expense of full-power broadcast channels if it came to a fight.

The National Association of Broadcasters has argued that Microsoft's plan is a threat to broadcasting, and said if the company wanted the channels, it should have bid on them in the incentive auction.

Groups representing cattlemen, wheat growers, women in farming and state agriculture departments are all pushing back on Microsoft's proposal for reserved TV spectrum channels for unlicensed use, saying broadcasting is a vital rural connection.

Nine agri groups made their case against the the Microsoft plan in a letter to FCC chair Ajit Pai, who has made rural broadband a prime directive for the agency. Microsoft is arguing it needs the spectrum to provide rural broadband connectivity.

Related: Microsoft Claims Rural White Spaces Plan Could Cost Less Than $12 Billion

"While our organizations certainly understand the need for improved broadband access in rural America and support the deployment of high-speed broadband in our communities, this proposal will only serve to deprive our members of critical access to local broadcast television coverage," the groups said in the letter.

The National Association of Broadcasters, which circulated the letter to reporters, has told the FCC that Microsoft's proposal should be a nonstarter.

Related: ATBA: Microsoft Plan Would Destroy Community TV

The agri groups, which includes the National Association of State Departments of Agriculture, agree, using the letter to sing the praises of local agricultural news

"Our members rely heavily on local broadcast stations to stay up to date on the important issues in our communities and the rest of the country," they wrote. "Farmers and ranchers rely on local news and weather reports to make production and marketing decisions. When fast-moving weather emergencies arise – a frequent occurrence in rural America – we turn to local broadcast TV for lifesaving information on where those weather patterns are headed."

Also signing the letter were the American Agri-Women, Intertribal Agriculture Council, National Association of Wheat Growers, National Black Growers Council, National Farmers Union, Rural & Agriculture Council of America, U.S. Cattlemen’s Association and Women Involved in Farm Economics.

They noted that having to move almost 1,000 TV stations in the post incentive auction repack would be complication enough without having to find new homes for TV translators and low-power stations, which are often the only means of receiving free TV, they said.

The groups pushed back in 2013 and 2015 when the FCC proposed reserving so-called TV white spaces for unlicensed use, and are looking to plant those seeds of concern once again with the Microsoft proposal to reserve a channel in each market for unlicensed, leaving less room for LPTV and translators, which are not guaranteed a channel at all in the repack, only ones available, if there are any available, after all the full-powers are accommodated.

"Combining this loss of spectrum for unlicensed use with the sheer number of full power stations needing to be repacked and the interference protections between neighboring stations, many LPTVs and television translators could be left without a new home and would be forced out of business," they said. "When local broadcast stations go dark, rural communities are deprived of a vital source of information that is essential for managing ouer day-to-day lives."

The Advanced Television Broadcasting Alliance said Microsoft's push for reserving channels in the broadcast band for unlicensed use as a way to promote rural broadband would "destroy" hundreds of its member LPTV and translator stations.

That is because those stations are not protected in the TV station repack. They can get new channels only if there are ones left over after full powers have been accommodated. So the fewer remaining channels exist, the more LPTVs and translators will be left homeless.

Related: Microsoft Claims Rural White Spaces Plan Could Cost Less Than $12 Billion

The ATBA said its members will be able to help advance the rural broadband cause if they are allowed to find as many new homes as possible without Microsoft getting first dibs on some of them.

Microsoft president Brad Smith this week outlined the company's proposal for more access to so-called "white spaces' in a speech in Washington.

The ATBA wants the FCC to let the 39-month repack and displacement window for LPTVs and translators to play out first.

"Once all existing broadcast licensees and previously approved construction permit holders have been granted their Congressional authorized rights of displacement, the available spectrum for TV White Space users will be known nationwide," the group said. "There is a synergy of opportunity for broadcast television stations and Microsoft to work together to bring about this ambitious goal. After years of being stranded behind an obsolete digital television standard, the broadcast industry and the Federal Communication Commission is nearing final approval of the new ATSC 3.0 broadcasting standard that is fully IP based and provides both mobile and fixed reception. TV White Space is an excellent partner to ATSC 3.0 services, but is no replacement for its powerful licensed capabilities."

The National Association of Broadcasters pointed out this week in pushing back on the proposal that Microsoft's successful push for white spaces channels following the 2009 DTV transition has yet to bear fruit.

"It's the height of arrogance for Microsoft — a $540 billion company — to demand free, unlicensed spectrum after refusing to bid on broadcast TV airwaves in the recent FCC incentive auction," NAB spokesman Dennis Wharton said. "Microsoft's white space device development has been a well-documented, unmitigated failure.