Executives at Mimosa Networks are encouraged by a recent letter a bipartisan group of Congressional leaders sent to the FCC urging the commission to explore spectrum-sharing opportunities in the 10 GHz band.
In their letter to the FCC, the lawmakers note the crowded nature of existing Wi-Fi spectrum and the need to support the emerging Internet of Things (IoT). "Sharing opportunities in the 10 GHz band could make more spectrum available and provide another avenue for consumers and innovators to tap into the Internet economy," the letter said. "This band could be used for expanding Wi-Fi capabilities to bring Internet access to more Americans. It could also provide an opportunity to expand affordable, high-speed, Internet access to Americans living in urban and rural communities."
Leading the effort are Rep. Doris Matsui (D-CA) and Rep. Brett Guthrie (R-KY), co-chairs of the Spectrum Working Group. The letter was also signed by Reps. Anna Eshoo (D-CA) and Bob Latta (R-OH) and Sens. Cory Booker (D-NJ) and Marco Rubio (R-FL).
It's another step in what Mimosa CEO and co-founder Brian Hinman knew would be a long road, but the process is moving along, with the company working directly with the U.S. Department of Defense (DoD) on a key part of the plan.
In 2013, Mimosa submitted a Petition for Rulemaking to the FCC seeking to allocate the 10.0-10.5 GHz band for lightly licensed fixed wireless broadband use. In March 2014, the FCC issued a Public Notice seeking comment on Mimosa's petition. Wireless ISPs (WISPs) largely supported the plan, but the amateur-radio community came out in opposition.
Hinman jokes that it is sort of an "I love puppy" type of topic--unless you're the DoD or ham-radio operators--in that pretty much everyone agrees that the unlicensed 5 GHz spectrum is crowded and that there's a need for more spectrum for broadband services. The 10 GHz band is a "beautiful band" for several reasons, including the fact that it is well suited for providing long-distance, high-capacity links for broadband access in underserved rural areas and for cellular backhaul.
But first they need to show that the technology can work without interfering with the band's existing primary and secondary users: radar for the DoD, and ham-radio enthusiasts. Hinman and his team are making progress when it comes to the first camp.
Through the process of presenting its petition to the FCC, Mimosa was encouraged to talk directly with the DoD, a procedure that, it turns out, isn't as difficult as one might have thought.
Radar is a "supersensitive" application that involves sending out pulses of energy through space; they hit an object and bounce back, "and you're listening for very weak signals," Hinman told FierceWirelessTech. To try to mix that in with high-power broadband radios can be tricky, but "it's incumbent upon us to be able to detect the presence of the radar" and jump to another channel before interfering with the radar services, he added.
This type of process is already done in the 5 GHz band, but the techniques used so far have been mostly focused on ground-based radars, which are inherently higher power. "The thing we were warned about when we first went to the DoD with this proposal in the ten-gig band is up in ten gigahertz those are mostly airborne radars, and being lower power it's going to be challenging to come up with ways of detecting and mitigating interference" with airborne radar, he said.
The problem actually relates to some of the other issues going on right now with federal spectrum sharing. The DoD has offered guidelines for detection thresholds that are very low in that band, and people are pushing back on that, but "it is sort of the reality, you go through the math and when you're dealing with airborne radars, you have to have a much lower detection threshold than what we've previously dealt with" in terms of dynamic frequency selection, Hinman explained.
Mimosa's engineers have developed three new technologies, and they plan to demonstrate to the DoD that by applying all three approaches they can successfully detect and avoid interference with airborne radar. They expect to deliver a document outlining their analysis to the DoD before the end of this month.
Notably, Mimosa doesn't plan on filing patents on the techniques. "We plan on making it public domain," Hinman said, because it would be self-defeating to go through the process and be the only company able to build products for the band.
If the solution meets the DoD's satisfaction, the FCC can start taking action. But there is the other matter of the amateur radio operators who came out in strong opposition to Mimosa's proposal.
Hinman said he can sympathize with the amateur-radio community--he was an amateur radio operator himself as a kid--and as a whole, they're losing spectrum, not gaining it, as spectrum gets set aside for broadband purposes or for what's considered the "greater good." And he points out that Mimosa's earlier proposal called for carving out a total of 70 MHz specifically for the amateur radio operators.
Meanwhile, the wireless ISPs, or WISPs, have come out in favor for the proposal. "Our industry is greatly encouraged by the letter issued by the United States Congress regarding the exploration of the 10 GHz band for use in broadband services," said Chuck Hogg, the president of WISPA, in a press release. "As broadband expansion becomes increasingly important to our nation, seeking out and reallocating underutilized spectrum will become more and more vital."
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