New rules eliminate back-up protection for TV stations and wireless microphones.

The FCC has ruled on 17 petitions for reconsideration of the TV “white spaces” rules. This action allows unlicensed wireless networks and devices – “Wi-Fi on steroids,” some call them – to operate on locally vacant TV channels, called “white space” frequencies because they show up as white areas on maps of frequency usage. 

The FCC earlier tried to rename the gadgets “TV band devices,” or TVBDs, but the white space nomenclature is hard to shake.

Whatever the name, companies like Google, Microsoft, and Dell Computer are drooling at the prospect. They have told the FCC to expect a lot of hot spots and campus networks, and they are using all the right technical and political buzzwords.   Here in the CommLawBlog bunker, though, we’re accustomed to dazzling PowerPoint that never materializes into actual products, so we tend to take a wait-and-see attitude.

The technical problems with white space devices center on avoiding interference to TV stations and the wireless microphones that have long used vacant TV channels. The original plan called for each device both to use geolocation – ascertaining its own position using GPS and consulting a database to find locally vacant channels – and also to “sniff” for TV stations and wireless microphones, a process called spectrum sensing. (The FCC exempted from geolocation certain devices under the control of other devices and, separately, allowed for the possibility of some sensing-only devices.)

The new decision confirms the geolocation requirement, with many critical details still to be fleshed out by the Office of Engineering and Technology. But the FCC has pulled back on sensing. When it tested spectrum sensing technologies several months ago, none of them worked well. This result surprised us, as white space proponents had touted sensing as the ultimate safeguard against interference. In some other universe, the agency might insist the promised technology function properly before it allowed deployment. This universe, though, works differently: the FCC’s spectrum-exploding train will not be de-railed, so they simply dropped the sensing requirement for devices that use geolocation.

Sensing-only devices are still allowed, but only under very rigid technical constraints that will be hard for manufacturers to satisfy. Because database checking will usually be the sole feature for avoiding interference, the FCC promised a rigorous certification procedure to make sure devices handle this function properly. Again, no details.

The FCC struggled, with only limited success, to accommodate users of wireless microphones in broadcasting, theater, movie-making, sporting events, and public gathering places like churches and auditoriums. The FCC will reserve two TV channels in each geographic area for wireless microphones, which it thinks will accommodate 12-16 microphone voice channels. Some parts of the country will also have other channels closed to white space devices and available for wireless microphones. Large productions, though, often use 100 or more. Microphone operators may request to have specific events entered into the white space database, which should (if all goes according to plan, that is) automatically keep white space devices away. Requests to protect unlicensed microphones must show that the channels free of white space devices cannot do the job. These requests will be subject to public comment, which requires 30 days advance notice. Without a database entry, and in the absence of spectrum sensing, the microphones will have no protection against white space devices on the same channel. 

In the end, the FCC believes wireless microphones should move to more efficient digital technology. But it did not address the difficult engineering problems that so far have barred this option.

The question of using vacant TV channels for backhaul links in rural areas is deferred.

Read the FCC’s news release on the decision and the full text of the White Spaces order.

[Blogmeister’s Note:  This post has been updated as of 9/24/10 to provide additional information culled from the full text of the Commission’s white spaces order.]