Minor changes may signal an end to almost a decade of rulemaking.

The FCC has released yet another decision in its long-running effort to implement rules allowing unlicensed “white space” devices in the television bands. The latest revision does not represent any wholesale changes, but will make it easier for some devices to operate.

White space devices (TV Band Devices or TVBDs, in the FCC’s nomenclature) rely on the fact that every location has some TV spectrum not being used. Those vacant frequencies typically show up as white spaces on a map of spectrum occupancy – hence the name. Technical studies show that properly controlled unlicensed devices can use these channels without causing interference to TV operation and other authorized users, including wireless microphones.

Following a Notice of Inquiry late in 2002, and a 2004 Notice of Proposed Rulemaking, the FCC first adopted rules allowing white space devices in 2006, but left the technical specifics for a later date. Those came in 2008, and then in 2010 the FCC responded to petitions for reconsideration with a number of revisions. Now the FCC has addressed petitions for reconsideration of the 2010 order.

The rules categorize each white space device as either fixed or mobile. A fixed device must have its location either professionally programmed in or determined by an on-board GPS device, and is subject to limits on operating power, antenna height, and antenna gain limits. Before operating, it must query a database of available spectrum for its location. A mobile device may similarly use GPS to determine its location and then query a database (Mode II devices); alternatively, it can contact another white space device that will in turn query the database (Mode I devices). The FCC has so far approved ten private companies to administer the databases, of which two have completed testing to the FCC’s satisfaction.

In its recent order disposing of the petitions for reconsiderations, the Commission provided the following changes and clarifications:

 Antenna Height. The 2010 rules limited fixed device antenna heights to a maximum of 30 meters above ground, and the height above the average terrain (HAAT) to no more than 76 meters. Several parties requested reconsideration of this restriction, particularly the HAAT portion. (According to one, the majority of the state of West Virginia would have been off-limits.) The FCC now allows fixed white space devices to have antennas up to 250 meters above average terrain, although still no more than 30 meters above ground level. At the same time, the FCC revised the separation distances between fixed white space devices and television contours to allow for the greater HAAT, but left unchanged the separations for wireless microphones and the exclusion zones around MVPD, LPTV, and BAS receive sites.  A device that provides database information to Mode I portable devices must comply with the previous HAAT limitations, so as to keep the Mode I device from straying too far from a known location.

Out-of-Band Emissions: The 2010 rules limited out-of-band emissions to 72.8 dB below the device’s highest in-band emissions. Now the out-of-band emissions are relaxed to 72.8 dB below the maximum power allowed within the 6 MHz bandwidth. The new order also cuts back the required occupied bandwidth from 6 MHz to 5.5 MHz, so as to ease the roll-off at the channel edges, and slightly increases the allowable power spectral density so as to leave total power unchanged.

Channel 52 Protection:  As part of the transition to digital television, the FCC auctioned former TV channels 52 and above for wireless use. The wireless companies have long sought restrictions on channel 51 TV operation to protect their frequencies just above, and similarly requested limits on white space devices on channel 51. The FCC refused, partly on procedural grounds, and partly on the principle that white space devices, being unlicensed, are already required to protect licensed wireless operations.

Classes of Devices: The FCC rejected a new class of white space device, similar to “Mode II” but for indoor use only, without GPS capabilities. The FCC feared these could be easily moved without updating their locations, thus creating interference. It also found the new class to be largely unnecessary, as Mode I portable devices may operate without geolocation (although they must query a Mode II or fixed device periodically).

Confidentiality of Database Information: The FCC makes publicly available all information required to be included in the databases that white spaces devices must search before operating.  A cable association asked the FCC to withhold certain data, including coordinates of cable headends and towers, claiming this type of equipment was “critical infrastructure” that could be subject to terrorist attack. The FCC disagreed with the premise and refused the rule change.

Finally, the FCC clarified two points. It emphasized that LPTV, television translator, and Class A television stations will have their receive sites protected based on the coordinates available in the existing CDBS database. The FCC will create a new web interface so that broadcasters can update the information. Second, the recent order corrects the coordinates of certain radio astronomy sites, which must be included in white spaces databases and protected by white spaces devices.

Most of the rule changes will take effect 30 days after publication in the Federal Register. Revisions to the filing of receive site information and entry of other information into the white spaces databases require OMB sign-off, and will probably take a few months longer.   Check back here for updates.

So far all of these rules control only a limited deployment in Wilmington, NC. But with the rules approaching final form, and more databases coming on line, white space devices may finally take the big step from PowerPoint to reality.