Is There Room for White Space Devices?

At last week's Open Commission Meeting the FCC adopted the Second Memorandum Opinion and Order (FCC 10-174) establishing rules for TV band or "white space" devices. While the Order has received a lot of press during the past week, describing it as "Wi-Fi on steroids," and, to a lesser extent, as a threat to off-air and cable TV, little attention has been paid to the fact that in many parts of the country there could be few if any "vacant" TV channels for these devices.

In smaller markets, where some channels are available, most will disappear should the FCC follow through on the National Broadband Plan recommendation to reallocate almost half the usable TV spectrum for wireless broadband carrier use.

The FCC recognized this in the Order, stating:

"If the Commission makes changes to the rules concerning the channels available for operation for TV and other authorized services, the channels available for use by unlicensed TV bands devices and wireless microphones could change, and any TV bands device or wireless microphone that operates on a channel that is later designated for another use would have to cease operation on that channel."

To reduce uncertainty for manufacturers, the Order further says that to prevent this problem, equipment makers could create products that can tune through a wider frequency range than the current rules permit. However, the products must "incorporate measures to limit operation to the frequency range over which the device is certified."

To get an understanding of how few channels are available for white space devices, see Spectrum Bridge's Show My White Space.

Spectrum Bridge is one of the companies that applied to be a white space database manager. In using their Web application, I found that I got different results depending on whether I entered a ZIP code or a city name. For example, when I entered 10002 (a Manhattan ZIP code), it showed no channels reserved for wireless microphones, nor any channels available for white space devices. When I changed the search to "New York, N.Y.," I got different results—seven channels for wireless microphones and four UHF channels for 40 mW personal/portable white space devices. In neither case were any channels shown for fixed white space devices or 100 mW personal/portable devices.

In searching the Los Angeles area, I found three channels for wireless microphones and only one for low power (40 mW) portable white space devices, Channel 27. Channels 2, 5 and 6 were shown to be available for fixed white space devices. When I entered the Los Angeles ZIP code 90001, I got similar results.

In checking a small rural community--Fairfield, Iowa, for instance—I found 20 UHF channels available for portable devices, plus an additional seven VHF channels for fixed devices, as well as Channel 20. I didn't do as well in Trenton, N.J. It showed only five channels for portable devices, and only Channels 2 and 51 for fixed link use.

To make sure there was enough spectrum for wireless mics used for ENG and other purposes at unspecified locations and at unscheduled times, the FCC set aside two channels for wireless microphones nationwide. This further limits the number of channels for white space devices. I plan to discuss that in detail in another article this week.

I expect there will be some changes to the software behind the Spectrum Bridge white spaces Webpage, now that the Order has been released. However, it should be obvious that white space devices are unlikely to find a home in Los Angeles, New York, or other major cities and their suburbs.

Doug Lung

Doug Lung is one of America's foremost authorities on broadcast RF technology. He has been with NBC since 1985 and is currently vice president of broadcast technology for NBC/Telemundo stations.