The FCC Notice of Proposed Rule Making that seeks to allow unlicensed wireless devices to use TV channels spectrum reveals details of methods the commission proposes to protect broadcasters from harmful interference.
The NPRM, which was covered extensively in the last edition of RF Update, was released to the public May 25. The commission is seeking comment on details of its plan to let unlicensed broadband devices operate on vacant channels in the television band.
The proposal identifies two types of unlicensed devices it wishes to see sharing unused TV spectrum: personal/portable Internet devices, such as Wi-Fi equipment, and fixed/access unlicensed devices used by Wideband Internet Service Providers (WISPs) and others.
Among the details of the proposal designed to prevent harmful interference from personal/portable devices are:
- The use of a control signal that must be received by such devices that positively identifies which TV channels are vacant and, therefore, can be used. Without such reception, no transmissions would be permitted.
- The voluntary transmission of the control signal data many sources, including: in a data stream from a digital TV station, information transmitted in the vertical blanking interval (VBI) of an analog TV station, subcarrier data from an FM radio station, data transmitted by a licensed wireless provider or channel availability data from a fixed/access unlicensed device.
- The limitation of maximum power output of these devices to 100 milliwatts (mW) and requirement that they have a permanently attached integral antenna with a maximum permissible gain of 6dBi.
- The automatic and periodic transmission of a unique identification signal from such devices.
Among the details pertaining to preventing interference from fixed/access unlicensed devices are:
- Operation of such devices under the same technical provisions as digital transmission systems that operate under Section 15.247 of the rules, including transmission output power of up to one watt and use of higher gain directional antennas, with requirements for transmitter output reductions for antennas with gains above 6dBi.
- Automatic and periodic transmission of a unique identification so that any harmful interference situation can be identified and remedied.
- Incorporation of a way to determine the geographic location of such a device with a minimum accuracy of 10 meters.
Comments are due 75 days after the NPRM’s release in the Federal Register and reply comments are due 105 days from publication there.
For more information, please visit: http://hraunfoss.fcc.gov/edocs_public/attachmatch/FCC-04-113A1.doc.