The FCC has announced yet another round of tests on TV "white space" mobile devices. These products — if they ever reach the market — will be used for unlicensed, Wi-Fi-type communications on locally vacant TV channels. The ongoing tests are intended to determine whether the devices can successfully avoid interfering with TV signals.
The FCC has proposed three mechanisms for avoiding occupied TV channels in a given area:
- have the unlicensed device detect and avoid TV signals;
- equip the unlicensed device with a GPS receiver and a table of occupied TV channels listed by location for automatic look-up; or
- disable the unlicensed device unless it receives a "control signal" that identifies locally vacant channels.
The FCC has spent many months on laboratory tests of devices using various combinations of these techniques. There has been no comprehensive report of the results, although the trade press has carried stories of some spectacular failures.
The FCC has now announced plans to move out of the laboratory to commence field testing. Ten locations are specified: a state park, an airport observation area, two suburban residences, an office building, and five rural sites.
A separate set of tests, to be conducted at an unspecified sports venue and entertainment venue, will evaluate compatibility with the original white-space technology: wireless microphones that operate on unused TV frequencies.
The press seems to think these tests will settle once and for all whether white-space devices can coexist with broadcast television. More likely, one side or the other — maybe both — will challenge the assumptions underlying the test procedures, and will question the FCC’s interpretation of the numerical results. Rather than end the debate, the test results will simply push it into a new phase.