TV band devices or TVBDs are unlicensed radio frequency devices operating in the vacant channels or white spaces between US television channels in the range of 54 to 698 MHz. The rules defining these devices were announced on November 4, 2008, and published by the U.S. Federal Communications Commission (FCC) on November 14, 2008. The rules were finalized on September 23, 2010. Much of the work behind the definition of these devices was done by the White Spaces Coalition.
Fixed devices may use any of the vacant US TV channels 2, 5-36 and 38-51 with a power of up to 1 watt (4 watts EIRP). They may communicate with each other on any of these channels, and also with personal/portable devices in the TV channels 21 through 51. Fixed devices must be location-aware, query an FCC-mandated database at least daily to retrieve a list of usable channels at their location, and must also monitor the spectrum locally. They may transmit only within the TV channels where both the database indicates operation is permissible, and no signals are detected locally. Personal/portable stations may operate only on channels 21-36 and 38-51, with a power of 100 mW EIRP, or 40 mW if on a channel adjacent to a nearby television channel. They may either retrieve a list of permissible channels from an associated fixed station, or may accept a lower output power of 50 mW EIRP and use only spectrum sensing.<r
The maximum power transmitted in any 100 kHz segment of spectrum is subject to the following limitations
All TVBDs must incorporate a feature to reduce transmitted power to the minimum level necessary to maintain successful communication.
The transmit antenna used with fixed devices may not be more than 30 meters above the ground. Fixed devices may not be located at sites where the height above average terrain (HAAT) is greater than 76 meters.