A growing chorus of voices is calling for the US government to release more mid-band spectrum for 5G -- and most of the FCC's commissioners have vowed to do just that.

However, the devil appears to be in the details.

One major point of contention currently centers on the C-Band -- a strip of spectrum licenses stretching from 3.7GHz to 4.2GHz -- that is currently used by a range of satellite companies and others, mainly for video transmissions. A group of satellite companies has banded together under the C-Band Alliance (CBA) to sell around 200MHz of that spectrum to mobile network operators for 5G -- but some in the wireless industry believe they should get more. Like, all 500MHz of it.

This is where two of the FCC's five commissioners aren't seeing eye to eye. Yesterday FCC Commissioner Michael O'Rielly argued that it would be "nearly impossible" to release all 500MHz of the C-Band for 5G. Instead, he said, "we must be willing to adopt a plan that gets midband spectrum into providers' hands as soon as possible."

Meaning, the 5G industry -- represented by the wireless industry trade group CTIA -- should settle for 200MHz-300MHz of spectrum in the C-Band, rather than all of it.

But in an interview with Light Reading yesterday, FCC Commissioner Brendan Carr said that "what I'm focused on right now are options that are going to get us more than 200MHz in big cities or in places where population density puts a lot of capacity constraint on networks. So what are our paths to getting more than 200MHz in those big cities? We're still working through different options here, but that's what my focus is: How do we get more than what's been put out there through the CBA proposal."

But Carr added that "I haven't made a final decision on which way we should go."

At stake are billions of dollars. According to Deutsche Bank, 200MHz of C-Band spectrum could generate $11 billion in total sales. And the ACA Connects group, which represents the cable industry, said that the full 500MHz of C-Band spectrum could be worth up to $60 billion to 5G operators.

While Carr and O’Rielly of the FCC appear to differ on the details of the C-Band, there's one thing they do appear to agree on: That the government should release mid-band spectrum more quickly.

Specifically, O'Rielly argued the FCC shouldn't wait until 2020 to conduct auctions of 3.5GHz CBRS spectrum licenses in order to first conduct an auction of 37, 39, and 47GHz spectrum. Instead, he said, the agency should "make procedural changes to enable auctions to be held closer together and ideally even simultaneously. It cannot take months on end to upscale, reconfigure, and test our software between each auction. This is inexcusable."

"I'm open to all kinds of ideas," Carr responded when questioned about the possibility of the FCC conducting simultaneous auctions.

The reason the debate around mid-band spectrum for 5G has suddenly taken on such urgency is because there's a growing consensus that widespread 5G services won't happen quickly in the kinds of millimeter-wave bands like 28GHz and 24GHz that the FCC is currently releasing under auction. And 5G proponents in the United States warn that if the US can't quickly deploy widespread 5G services, other countries like China will use mid-band spectrum to do so -- thus gaining a leg up in an potential economic benefits from 5G.

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