Spectrum sharing: Easier said than done

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Spectrum sharing has been front of mind ever since the National Telecommunications and Information Administration found in late March that 95 MHz of spectrum currently in federal hands, the 1755-1850 MHz band, could be repurposed for commercial use. One of the NTIA's key conclusions was that sharing the airwaves might be a way to get the spectrum into the wireless market.

As with many things that get talked about in Washington though, spectrum sharing--specifically between government entities and commercial carriers--is more conjecture at this point than anything else. It will take years to make such sharing a reality, and the biggest hurdles will not be technical but more basic elements like how much spectrum government agencies--especially the Department of Defense--will be willing to give up. In order to get both sides on the same page to make spectrum sharing a reality, there is going to have to be significant and consistent socialization of both government spectrum administrators and the wireless industry.

What would it take to make spectrum sharing happen? First, there are technical issues to sort through. Interference will need to be prevented, and government users and carriers will need to coordinate on when and where they can share spectrum. Commercial devices that want to access that government spectrum will need to access a government database of spectrum users to make sure that it can properly hand off at the right time.

"It's a real-time, location-based technology overlay that would have to go into your network and be capable of directing that device off those forbidden channels when you're in the proximity of that system," said Tolaga Research analyst Phil Marshall. For some perspective, Marshall, who wrote his Ph.D. dissertation on sharing spectrum between cellular and point-to-point microwave technologies before PCS spectrum was opened to cellular, called it "complicated." Gulp.

Even more difficult to overcome may be the human factors at play. When federal users were moved in the late 1990s and around the turn of the millennium to free up commercial 3G spectrum, they dealt with it. After the Sept. 11 attacks, federal agencies, and the department of Defense in particular, became careful guardians of their spectrum, according to Jeffrey Silva, an analyst at Medley Global Advisors. Essentially, the agencies already feel like they've accommodated the needs of the wireless industry enough. "There's a sense within the Pentagon and other federal agencies that they've already given at the office," Silva said.

Which companies will want to share spectrum with government agencies? Arguably, the most inclined to do will be companies that are starved for spectrum right now. AT&T (NYSE:T) CEO Randall Stephenson wasn't too high on the idea, saying that the process will take too long to solve AT&T's immediate spectrum needs. Verizon Communications' (NYSE:VZ) CTO recently said commercial spectrum sharing solutions are likely "years away." The most likely candidates are companies like T-Mobile USA and MetroPCS (NASDAQ:PCS) that use AWS spectrum near where government spectrum might be shared.

Ultimately, CTIA is interested in sharing in a way that's as predictable as possible. CTIA wants sharing to be done on a temporal or geographic basis, i.e. being able to use government spectrum except not in certain areas of the country or during certain periods of the year.

Peter Stanforth, CTO of Spectrum Bridge, which manages an FCC database that helps keep track of who is using white space spectrum, said that spectrum sharing needs to be coordinated in such a way so that if a carrier or government entity is using government spectrum on Monday it knows it will be able to use it again on Tuesday. 

Government agencies are not likely to share their spectrum willingly. CTIA and the wireless carriers want maximum flexibility if they do decide to go down the sharing route. Getting the technical issue ironed out will be one thing. Getting every player on the same page is something else altogether. --Phil

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