Feds look to share spectrum for commercial broadband

The federal government is trying to get a handle on its actual use of spectrum as it works to free up bandwidth for commercial mobile broadband providers, but a detailed, public-facing database of government spectrum use is not in the cards.

The commercial wireless industry is champing at the bit for more federally controlled spectrum to come up for auction. President Barack Obama ordered an inventory of actual federal spectrum use in a June 14 memorandum to agency heads as part of a larger administration plan to free up 500 megahertz of spectrum from the public and private sector to devote to mobile broadband.

Details on the nature of federal spectrum use will help private companies make decisions on what kinds of services they want to offer in what frequency bands. But for security reasons, much of that information is likely to remain under wraps.

The National Telecommunications and Information Agency, the component of the Commerce Department that manages federal spectrum, has so far identified 405 MHz for possible commercial use. NTIA Administrator Larry Strickling, speaking at the agency's first-ever Innovative Spectrum Sharing Technology Day at Commerce headquarters, said that soon the Federal Communications Commission will be able to bring spectrum to market. This could include the 5 GHz band, which can be used for high-speed Wi-Fi; the 3.5 GHz band; and the coveted 1755 MHz band, which wireless providers want to use to build out nationwide, high-speed services.

Because of the complex nature of agency spectrum use, the government is looking to technologies that allow for sharing of spectrum. Such spectrum sharing is already a fact of life. For example, medical body area networks that allow for very short-range wireless communication between medical sensors and base units share spectrum with a system used in aircraft testing.

As a result of the president's memo, the NTIA and its Commerce Department cousin, the National Institute of Standards and Technology, are looking to promote technology that allows for the dynamic sharing of spectrum between users. A special steering committee was formed to collect and publish information about test beds for companies, researchers and government agencies to develop methods for co-locating spectrum services.

Next May, the full inventory of federal spectrum use will be completed, but it won't be available to the general public. The problem, said Karl Nebbia, who heads the Office of Spectrum Management at NTIA, is security.

"Agencies are concerned about releasing specific frequencies and locations and characteristics of specific operations that they have," Nebbia said. "They've got a requirement to operate those systems. They do not want to open up themselves to somebody intentionally trying to interfere with the specific operation." The government publishes a spectrum allocation chart that includes information on the type of use, and whether the user is commercial or governmental, but it does not drill down to the precise level that is described in the executive memorandum.

Nebbia suggests that government can share more detailed information on how spectrum is being used in specific bands so that researchers can understand the technical challenges they might be facing in trying to co-locate a service in that band. Some government uses might be low-powered, or intermittent, or confined to specific geographic locations. Others, like fixed air traffic radar, operate continuously, nationwide, and at high power, and might not lend themselves to sharing. Highly classified spectrum uses, like mobile radar and law enforcement surveillance, will likely remain non-public, if affected agencies have anything to say about it.

There is some precedent for sharing non-public information on spectrum use with industry. Commercial stakeholders and Defense Department officials negotiated non-disclosure agreements as part of a collaboration to examine commercial uses of the 1755-1780 MHz band. However, Strickling noted, "we need a simpler and more predictable approach to this problem." Possible alternatives will be examined at a December meeting of spectrum policy officials.