Back in November of 2008, the FCC approved the unlicensed use of white space, provided users of this space abided by two rules. First, they were not permitted to transmit a signal if any legacy wireless microphone had been used in the space in the past 60 seconds. In addition, the user needed to check an FCC White Space database to determine which channels were available at a given location.
Earlier this week the FCC introduced some new constraints on the use of white space in the TV station broadcast spectrum. The order still requires the database lookup, but it no longer calls for spectrum sensing for wireless microphones and instead reserves two vacant channels on the UHF band for limited local use. For others that have a need for more channels the FCC recommends registering with the TV band database.
The use of these frequencies tends to be very limited in major metropolitan areas where there are virtually no available white spaces. However in rural America there are opportunities galore. The primary talk around use of the frequencies has been "White-Fi", which is simply a wireless network operating on the 6 Mhz white space channels. Microsoft has been a pioneer in this space, as is evident in the prototype "white-fi" network on their Redmond campus. The IEEE 802.22 working group has also been working on techniques to use the spaces for Wireless Regional Area Networks.
Time will tell if white space broadband makes its way through rural America, or if it will go the way of Broadband over Powerlines. Although the town of Claudville, VA has already been successful in adopting the technology.