New white space rules

Just before Thanksgiving, the FCC issued a comprehensive order authorizing unlicensed devices on TV frequencies. This lengthy order includes multiple justifications intended to protect against the inevitable court appeals. The rules are 15 single-spaced pages long, making this by far the most complex regulatory regime for any unlicensed service.

What the rules entail

The broadcast industry has long been doubtful that any workable set of rules could adequately protect TV stations and wireless microphones from interference. Poor device performance in recent engineering tests only deepened that skepticism.

Nevertheless, the basic regulatory structure for unlicensed white space usage seems workable. In actual practice, whether the manufacture, marketing and use of these devices can provide adequate protection for licensed operations remains the big question. It will take a year or two to see how this plays out.

A rulemaking like this one — dropping new users into an occupied band — always involves a delicate trade-off between adequate power and flexibility for the newcomer versus protection for the incumbent. Having made the decision to allow the devices at all, the FCC seems to have resolved most doubts in favor of the incumbent TV stations. The new rules are intended to protect, among others:

  • TV service (full-power digital, Class A and low-power digital and analog, translators, and boosters);
  • wireless microphones (and other low-power auxiliary devices);
  • TV translator receive sites;
  • cable headends; and
  • broadcast auxiliary service fixed links.

Potential interference to these services, and many others in nonbroadcast services, necessarily puts a lot of constraints on TV band devices (TVBDs), as unlicensed white space devices are now known. These are the three main constraints:

  • Operation is flatly prohibited on certain channels in specific areas and on some channels in particular areas.
  • Every TVBD must know where it is and have a current list of open channels for that location, or else it must operate under the direct control of a TVBD having that information.
  • Every TVBD must sense the spectrum for incumbents on the channel it is using.

Device locations must be determined to within 164ft, a requirement that only GPS can fulfill today. The catalog of available channels should be updated at least daily. Sensing must achieve a detection level of -114dBm, equivalent to 0.004 trillionths of a watt, yet even this sensitivity could miss TV signals that are viewable with a good outdoor antenna.

In this proceeding, the FCC is being unusually sensitive to the starkly differing interpretations that TVBD advocates and their opponents have put on past sensing-only test data used in the equipment certification process. Rather than simply trusting an applicant's own test results, the FCC will rerun the tests itself, not only in the laboratory, but also in the field. The testing will be open to the public. And the FCC will put the test results on public notice and invite comment.

The last two proceedings for new, unlicensed services — ultrawideband and broadband over power line — prevailed despite vehement opposition. But both fell short of expectations in the marketplace. Because TVBDs are closer to existing successful products, such as Wi-Fi, they may have an easier route to breaking that pattern.

Harry C. Martin is a member of Fletcher, Heald and Hildreth, PLC.

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