The 3.7-4.2 GHz band is substantially underused by the satellite industry and Google is studying how much more intensively the band could be used for a variety of applications, including point-to-multipoint deployments.
“We think that point-to-multipoint could be deployed in the band very rapidly even given the existing fixed satellite service earth stations that exist in the band, and that the band could also be used for other things,” said Google’s Spectrum Engineering Lead Andrew Clegg during a Tuesday panel session hosted by the Open Technology Institute in Washington, D.C.
“One of the things to remember here is it’s 500 megahertz worth of spectrum in 3.7 to 4.2 GHz,” and to put that into perspective, that’s more bandwidth than the cellular, PCS, AWS-1, AWS-2, AWS-3, the 600 MHz and both 700 MHz bands combined, he said.
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The topic of the panel was the 3.7-4.2 GHz band—one of the bands the FCC will consider at its open August meeting when it contemplates a Notice of Inquiry in several spectrum bands. The Broadband Access Coalition filed a petition for rulemaking with the FCC last month calling on the commission to authorize a new, licensed, point-to-multipoint (P2MP) fixed wireless service in the 3700-4200 MHz spectrum band, and several coalition members were represented on Tuesday’s panel.
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And while the American Library Association may sound like an unlikely ally, panelist Ellen Satterwhite, policy fellow at the association, said broadband has become a mission-critical service for libraries across the country. There are 120,000 libraries in America—public, academic, law and schools—and what unites them all is broadband is mission-critical. “What used to be nice to have is now so integrated into how libraries serve their communities and also what people have come to expect” that the library association got involved and signed onto the Broadband Access Coalition’s petition.
But before anything gets done in the 3.7-4.2 GHz band, interest is very high in “cleaning up” the FCC’s database that is supposed to show where ground-based fixed satellite service (FSS) equipment is located and approved to operate. Google examined the database and found that 29% of the sites didn’t exist; however, that doesn’t include sites that may no longer be operational because the imaging technology doesn’t provide that level of detail.
“We think that one of the first steps to examining the use of 3.7 to 4.2 GHz would be a clean up of the database” and get an accurate picture of the satellite sites that exist and that really require protection, Clegg said.
As for protecting the satellite dishes, from Google’s experience designing a Spectrum Access System (SAS) and Environmental Sensing Capabilities (ESC) to deal with the military incumbents in the CBRS band, coming up with a system for 3.7-4.2 GHz would be far easier. In the 3.5 GHz CBRS band, the military’s radar along coastlines must be protected, but the military is never going to tell the spectrum administrators exactly where they’re located as that’s classified information. “We have to sense them and avoid them,” Clegg said. With the satellite dishes, their location can be known and thereby easier to protect in a spectrum sharing scenario.
Similar to the 3.5 GHz band, mobile operators could insist on long-term licensing scenarios for the 3.7-4.2 GHz band, but Jeff Kohler, co-founder of Rise Broadband, said he doesn’t think the mid-bands like 3-4 GHz are great for mobile operators.
“I think the mobile use for this band would be for urban hotspot" applications to address discreet capacity issues that operators are facing, rather than for carrying critical traffic, he said. Whereas in a fixed environment, it’s prime grade spectrum—there’s a lot of it available and it has the right propagation characteristics that it can be put to good use quickly.
Brian Hinman, CEO and co-founder of Mimosa Networks, said the concept of “flexible use” spectrum that has been talked about at the FCC for a while now is a “complete fallacy.” If the spectrum came up for auction, “they [wireless operators] would pay the big dollars” and use it for infill and providing better capacity in dense urban areas, but the economics don’t work out for a “flexible use.” Flexible use ultimately doesn’t happen because when operators pay that kind of money for the spectrum, they can’t afford to provide affordable service for consumers who need fixed access at home. And the U.S. would lose the opportunity to have a competitive market for fixed access if it were to go that route.
Of course, the satellite industry is very interested in protecting its incumbent users and that was not lost on the panelists. Kalpak Gude, president of the Dynamic Spectrum Alliance, said the satellite players are not going away, but their business is changing. While he believes global harmonization is important, trying to find more ways to share with incumbents is a much faster, more effective way of making spectrum more available and better utilized than trying to clear incumbents from a band.
A representative from ViaSat was in the audience and noted that ViaSat has been promoting shared spectrum for several years. But spectrum is clearly underutilized in not only satellite bands but in cellular and certain places in the Wi-Fi bands, he said, suggesting that the real solution to interference is cognitive radios that are smart enough to move to other bands when they need to avoid interference.