Vacant spectrum between television channels—often described as “white spaces”—can be used to deliver low-power, fixed wireless services after the digital television (DTV) transition is completed, the FCC tentatively concluded today.

Approved unanimously, the FCC’s notice of proposed rulemaking (NPRM) addresses rules governing spectrum reserved to transmit TV channels 2 through 51. While television broadcasters will continue to use their allocated spectrum to deliver content in their channels, low-power devices will be allowed to operate in the unused frequencies between active TV channels, or “white spaces.”

While the amount of white-space spectrum in large population centers can be somewhat limited, there are significant airwaves available in rural areas. Regulators are hopeful that the favorable propagation characteristics of the TV spectrum will make it economically feasible to offer broadband services to remote locations.

“The need for new broadband options is especially pressing in rural and high-cost areas, which may eventually be the greatest beneficiaries of white-space technology,” Commissioner Michael Copps said. “We must bring every part of this great nation with us as we move into the digital age. It is not just the right thing to do; it is an enlightened investment in our future that I am certain will pay for itself many times over.”

The FCC’s NPRM concludes that no fixed services can be offered in the white spaces until after the DTV transition is completed—something that is scheduled to occur in February 2009. In addition, white-space services cannot be offered on Channel 37, which is reserved for astronomy use.

Many other questions about the TV white spaces remain in limbo, and the FCC is seeking comments on them. Although the commission nixed the notion of mobile and portable white-space services from Channels 14-20—spectrum allocated to public safety—such applications will be considered for other qualifying channels. In addition, the FCC is seeking comments whether fixed white-space services should be allowed in Channels 14-20.

Still to be determined are the technical requirements that will be associated with using white-space spectrum. Broadcasters have expressed fears that white-space users could interfere with their signals, while proponents contend that there are technological solutions to the issue.

Another significant question is whether usage of white-space spectrum should be licensed, unlicensed or some combination. Democratic Commissioners Copps and Jonathan Adelstein both said they wished the NPRM included a tentative conclusion that the white spaces be reserved for unlicensed use, citing the success of the unlicensed 2.4 GHz band and the fact that AWS licensed spectrum was just auctioned and a scheduled 700 MHz auction is a little more than a year away.

“Unlicensed services, with their low barriers to entry, present such a great opportunity for the deployment of broadband offerings in communities across the country no matter their size or financial status,” Adelstein said. “Considering the favorable propagation characteristics for wireless broadband services in the 700 MHz band and the important obligation to protect existing television operations from harmful interference, I believe that unlicensed operations present the best use of the spectrum for this country.”