FCC will vote next month on plan to share valuable 3.5GHz spectrum

The CBRS (Citizens Broadband Radio Service) would open up frequencies from 3550-3700MHz to three classes of users, including owners of new mobile devices who could use the service like they do Wi-Fi. The FCC vote comes after several rounds of study and public comment on the proposal for more than two years.

In that time, growing demand for wireless spectrum has boosted pressure on the government to share or auction off some of the many frequencies it exclusively controls. Bandwidth-hungry services like streaming video and audio, plus wireless links for a growing array of connected devices, are expected to eventually place strains on the spectrum currently allocated to wireless data.

The CBRS plan could lead to better wireless data performance for users in crowded places like stadiums, as well as better rural broadband services and new spectrum for industrial uses not suited to Wi-Fi or LTE, according to the FCC. It could also be a proving ground for a spectrum-sharing approach that might be applied to other government bands.

The 3.5GHz band is used mostly by Army and Navy radar systems and satellite equipment. The CBRS plan calls for them to share the band with effectively unlicensed access that anyone could get just by buying an authorized mobile device. But the FCC would also auction off licenses to service providers, who would enjoy some protection from interference by the unlicensed users.

A cloud-based Spectrum Access System would keep track of the existing radios and the licensed services in order to manage interference. But large swaths of the country that previously would have been reserved for the incumbent users are much smaller in the latest version of the plan, thanks in part to improved technology. Those so-called exclusion zones previously would have covered much of the country's east and west coasts, home to a majority of the population, but now are 77 percent smaller, the FCC says.

The exclusion zones could disappear completely if there were a service that could sense protected users nearby and automatically prevent interference, the agency says. It envisions that as a second phase of the technology but would seek proposals for both a Spectrum Access System and sensing services at the same time. It's not likely either of those technologies would be approved before next year.

Stephen Lawson covers mobile, storage and networking technologies for The IDG News Service. Follow Stephen on Twitter at @sdlawsonmedia. Stephen's e-mail address is stephen_lawson@idg.com