It always looked good on paper. Every city has dozens of TV channels sitting empty. Why not use them for something? As Wi-Fi became popular, Wi-Fi-like unlicensed operation became the application of choice for these “white space” channels – so called because they show up in white on a frequency map. Big money signed on: Microsoft, Google, Motorola, and Intel, among others. Coalitions formed. Websites launched. Herds of dark-suited lawyers roamed the halls of the FCC.
As plans for digital TV took shape, the white space idea should have lost some of its gleam. Digital channels can be packed together much more tightly than analog – enough to have freed up 18 former TV channels for other uses. That leaves a lot less white space, and a lot less spectrum for white space devices. But this is Washington, after all, where policy routinely comes unhooked from the underlying facts. The proponents of white space devices continued to press their cause with undiminished fervor.
The prospect of millions of consumer-grade transmitters on TV frequencies makes two groups very nervous. One is the broadcast industry, which fears these products will stray into occupied TV channels and cause interference to viewers. Equally concerned are users of the wireless microphones licensed to TV and motion picture producers, and sometimes used also by other groups such as churches and live music venues. These microphones have long used vacant TV channels without causing harm, but are highly susceptible to interference from white space devices.
Not a problem! insisted the white space proponents. Their products, they said, could “sniff out” TV and microphone signals and thereby avoid any channels in use. To prove it, they handed over five prototypes to the FCC’s engineers for testing. Earlier prototypes had failed badly – some did not work at all – but the FCC tried again. It ran extensive studies both in its laboratory at Columbia, Maryland and at twelve field sites: a downtown-area office building, three residences, several suburban and rural locations, and major sports and entertainment venues.
This week the FCC released the results. The devices actually work pretty well under laboratory conditions, in spectrum that is utterly quiet except for one clean TV or wireless microphone signal. So those people who live in shielded laboratory chambers should expect no problems. But the rest of us may not fare as well. In particular, the presence of a TV signal on a channel adjacent to that being sensed tends to degrade the sensor’s performance badly, causing it to miss the signal on the channel it’s actually sniffing. Suppose a white space is checking channel 21, say, while a station is broadcasting on channel 22. The device stands a good chance of missing an active TV station or wireless microphone on channel 21, leading it to think it was clear to transmit on that channel. It would thereby cause interference to viewers of the TV station or users of the microphones it had overlooked.
Back to the drawing board, one might think. After all, this batch worked better than the last ones, so maybe the next generation will actually pass. But the FCC does not think that way. This is Washington, where facts don’t matter much. On the same day that it released the test results, the FCC announced plans for a vote at its November 4 meeting to authorize white space devices. There will be no opportunity for the public to study and respond to the test report first.
Perhaps because of doubtful results with the sensing approach, the FCC signaled its intent to authorize an alternative: the “geolocation” option. Before transmitting, each white space device would locate itself via GPS and consult a database to identify unused TV channels in that area. But GPS works poorly indoors, or not at all. Moreover, the database will omit wireless microphones, except perhaps at certain very large sporting events. The only geolocation device that the FCC tested is the size of a microwave oven, and may not work as well in a portable version. Given these limitations, the FCC also plans to allow devices that rely on sensing TV and wireless microphone signals, if they can be shown to work properly in field tests. The all-important details have not been announced.
We can only speculate on the FCC’s haste to authorize a technology that repeated and extensive testing has shown to be inadequate. True, the technical report found the tests had established “proof of concept.” But so did the Wright brothers at Kitty Hawk, yet no one was standing in line the next day to check luggage at O’Hare. The election that coincides with the FCC meeting date may be a factor. And we have no doubt that Microsoft et al. handled the lobbying, if not the engineering, with great skill. But the Commissioners should understand the importance of making sure these gadgets work properly before unleashing millions of them on a nation just trying to watch TV in peace.
