Meet the newest 5G acronym: incumbent-informing capability (IIC).

It's a new technological concept that might – just might – propel the American 5G industry into the stratosphere by potentially releasing roughly 1GHz of valuable midband spectrum for 5G operations. It would do so by allowing the US military to relinquish some of the midband spectrum it's currently using to commercial 5G operators, while still being able to use that spectrum when soldiers need it.

Specifically, IIC would allow US military commanders to tell operators like AT&T and Verizon when they can – and can't – use government spectrum for 5G.

And why is that important? Midband licenses have been described as "Goldilocks spectrum" because they create an ideal balance between broad geographic coverage and blazing-fast speeds. Indeed, those are the spectrum bands that form the backbone of a wide number of international 5G rollouts, including in South Korea and China.

In the US, however, there is a distinct lack of midband spectrum licenses – which generally range from around 2GHz to 5GHz – for commercial 5G operations. T-Mobile commands around 150MHz of midband spectrum in the 2.5GHz band, and the FCC recently auctioned around 70MHz of midband spectrum in the 3.5GHz band. Further, the FCC plans to auction fully 280MHz of midband spectrum next month in the C-band auction for 3.7GHz-4.2GHz spectrum licenses.

But that's not enough, according to some in the industry who are worried that the US could fall behind China and other countries in the development of robust 5G networks. Sluggish or spotty 5G in the US – due to a lack midband spectrum – could push 5G entrepreneurs and innovators to develop their applications in other countries, or so the theory goes.

That's exactly the concern that has given rise to the IIC concept.

Floating the proposal

IIC traces its origins to a summer agreement between the White House and the US Department of Defense (DoD) to release 100MHz in the 3.45-3.55GHz band for 5G in an auction next year. The NTIA is the government agency tasked with handling the re-allocation of that spectrum from the US military to the commercial 5G industry.

As always, though, the devil is in the detail. The 3.45-3.55GHz band isn't completely empty; the DoD still manages some operations in the band, including radar. As a result, the DoD wants to make sure those operations won't be affected by commercial 5G operations in the same band.

But how?

In a July research paper, the NTIA offered the outlines of a potential solution for the 3.45-3.55GHz band and other bands: "NTIA will examine the development of an automated, real-time, incumbent-informing spectrum sharing system (incumbent-informing system) that NTIA would operate in conjunction with DoD to notify commercial entities when the latter would need to cease operations."

ESC concerns

IIC might sound familiar. That's because there's already a very similar technology working in the 3.5GHz CBRS band to move commercial users off the band when the US Navy needs it. That spectrum-sharing setup relies on monitoring stations – dubbed Environmental Sensing Capability (ESC) networks – along the US coast that look for US Navy communications. If they discover such communications, commercial users are immediately kicked off that portion of the band.

One ESC network is jointly operated by Google and CommScope and another is operated by Federated Wireless.

But, according to a number of companies, the ESC developed for the 3.5GHz CBRS band won't work for the 3.45-3.55GHz band.

Indeed, Google – a company that helped pioneer spectrum sharing in the CBRS band – has officially stepped out against ESC technology in general. The company recently wrote that the FCC "should adopt the incumbent-informing capability (IIC) framework for the 3.45GHz service and extend it to the CBRS band to remedy spectrum waste caused by the current Environmental Sensing Capability (ESC) regime."

Federated, too, isn't a huge fan of the ESC it operates. The company wrote to the FCC that it doesn't care whether the NTIA uses an ESC or an IIC, as long as the setup still relies on a Spectrum Access System (SAS) that can actively shift users from one spectrum band to another. (Unsurprisingly, Federated sells SAS services for the CBRS band.)

Big-name opposition

The NTIA's IIC proposal faces plenty of opposition, however. At the heart of the issue is the fact that an IIC would create uncertainty for 5G operators.

"This approach is ineffective for the shared use of spectrum between federal operations and commercial terrestrial wireless operations and should be rejected," T-Mobile wrote to the FCC of the NTIA's IIC proposal, explaining that "carriers require reliable and predictable access to spectrum to deliver the high-quality service that businesses and consumers need and have come to expect from wireless carriers. Accordingly, the commission should not prescribe the use of a sensing or notification-based mechanism to coordinate federal and nonfederal operations."

T-Mobile isn't alone.

"Microsoft is not supportive of any scheme in which a primary user can turn off all the spectrum afforded to a commercial operator at a given time," the company wrote to the FCC. "A system that would force commercial users to vacate their channels at a moment's notice ... is unlikely to allow for the certainty needed for 5G services. "

Instead, Verizon, AT&T and T-Mobile all urged the FCC and the NTIA to take a less flexible approach to the 3.45-3.55GHz band. Much like federal operations in the AWS-3 spectrum band, which was auctioned for 4G in 2015, the three operators urged regulators to set up specific Cooperative Planning Areas (CPAs) and Periodic Use Areas (PUAs) for DoD operations. Basically, they want the US military to set aside specific geographic locations and times of day when it wants to use the 3.45-3.55GHz band. That way, they'll be 100% certain they'll get it outside of those parameters.

"The commission should ensure ... the coordination framework between new licensees and federal incumbents is transparent, predictable and simple," Verizon wrote to the FCC.

Finally, it's worth noting that some top DoD officials appear to share this view: DoD CIO Dana Deasy in August said he expects rules for the 3.45-3.55GHz band to be similar to those for the AWS-3 band.

Looking beyond 3.45-3.55GHz

There's obviously plenty of interest in exactly how the NTIA and FCC decide to release the 100MHz of valuable midband spectrum between 3.45GHz and 3.55GHz. But at the heart of the IIC issue is how the DoD might release additional midband spectrum ranging all the way down to 3.1GHz.

Indeed, the debate could ultimately affect the entire 3GHz band, which comprises fully 1GHz (or 1,000MHz) of midband spectrum. That's more midband spectrum than any country has allocated for 5G, anywhere in the world.

The DoD, for its part, has set its sights squarely on sharing its spectrum rather than allocating it outright for 5G, as T-Mobile, Microsoft and others want. "The traditional model of static frequency allocation is not sufficient, and a new model is needed," the DoD wrote of its new spectrum strategy. "Spectrum sharing offers a new model for greater freedom of action."

Others agree.

"I have proposed, and others have proposed as well, that the military share that spectrum using dynamic spectrum sharing," Eric Schmidt told the Wall Street Journal. Schmidt is the former CEO of Google and the former chairman of the Defense Innovation Board, which advises the Pentagon and produced a pivotal paper on midband spectrum. He is now the chairman of the National Security Commission for Artificial Intelligence and co-founder of Schmidt Futures, a philanthropic initiative. "We now know how to make that available, and have the [telecom companies] be able to access that without owning the frequency. The military should continue to own the frequency."

Indeed, that idea appears to be at the center of a controversial DoD Request for Information issued in September that asks how the US military might "lease" its spectrum holdings. The RFI did not provide details on how that might work.

However, according to a new report from the Washington Post citing unnamed sources, the US military has not embraced the spectrum-leasing proposal, even though it was pushed directly by White House Chief of Staff Mark Meadows.

"There are just so many issues at play including bringing in receipts and dollars into the department, and we don't know how the DoD would even do that," a senior defense official told the Washington Post. "We're looking for industry and [other government agencies] to give us some innovative ideas about how that might happen."

The Biden factor

How exactly the DoD might release its vast spectrum holdings for 5G remains unclear. T-Mobile and other operators continue to argue for exclusive access to the spectrum, while startups like Rivada have proposed a more flexible approach "where everyone can buy network capacity directly" in a wholesale model. (Rivada, for its part, is also pursuing similar proposals in locations ranging from Jamaica to Chile, though it has little to show for almost two decades of such efforts all over the globe.)

As the apparent incoming commander in chief of the US military and the person who will appoint the next chief of the FCC, Joe Biden likely will have a major impact on the process.

Although Biden hasn't spoken directly about the DoD's leasing proposal or IIC technology, his transition website does explicitly endorse the concept of "universal broadband."

Former Obama administration officials, who worked with Biden when he was vice president, offered slightly divergent views on the topic. For example, Tom Wheeler, an FCC chairman during Biden's second term as VP, argued in support of the kind of spectrum sharing enabled in the CBRS band. He described the DoD's latest proposals as a "consequence of having no spectrum policy."

But Julius Genachowski, who headed the agency just before Wheeler, during Biden's first term as VP, appeared to voice support for the spectrum-leasing scenario included in the DoD's RFI. Genachowski spoke at a recent event hosted by the financial analysts at MofftettNathanson, and according to the firm he "thinks spectrum sharing between the public and private sector has to be part of the solution, and he is optimistic that the DoD's Request for Information (RFI) shows some recognition of that. The coordination of the public and private sectors would be advantageous to both sides: the private sector would benefit from access to needed spectrum that would otherwise be underutilized, and the public sector would benefit from access to the standards and technology developed by the private sector."

Whatever the result, it will have serious implications. After all, the trade group for the US wireless industry, CTIA, estimates 5G will add $500 billion to the US economy, and "spectrum is the critical input for wireless service."

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