FCC moves toward TV-Fi

LAST WEEK the FCC (www.fcc.gov) agreed to propose rules for unlicensed wireless devices to operate in unused Yank TV spectrum, with an actual document to appear on the FCC web site sometime in the next week or two. Spectrum policy advocates are tickled that their cries for more unlicensed spectrum in the so-called "Beachfront Property" range below 1 GHz have been heard. Spectrum in the VHF and UHF bands has the keen ability to easily penetrate through objects like trees and buildings, obstacles that can easily defeat a line-of-sight 2.4 GHz long-haul wireless link.

Telly in North America is divvied up into channels from 2-69, with each channel a 6 Mhz chunk. Figuring out what is available in free space is more of a headache. When broadcast television stations were originally setup in America, a lot of unused channels were set up between operating stations in order to avoid interference, so for any typical large viewing market, there are maybe 6-9 stations on air at any give time. Add to that the free gift each TV station received of another channel for U.S. Digital TV (DTV) transition. Broadcasters are also spread out by distance, so adjacent cities don't have the potential to interfere with another's TV signals. You might have channel 4 operating in Washington DC, but not in Baltimore, but Baltimore may operate channel 13 while DC doesn't have anyone there.

Beyond the operating stations, the FCC has blocked out a number of channels that can't be used regardless to prevent interference, including 2-4 (potential interference with VCRs, DVD players, cable set-top boxes), 14-20 (Land mobile radio services), and 37 (Radio astronomy). Channels 52-69 are also off-limits. Those channels and frequencies associated with them have already been sold off at FCC auction for licensed use with some set aside for use by public safety. At some vague future date, the U.S TV analog licences are supposed to be returned to the FCC, but that and the 52-69 saga are an ugly story for a different day.

The FCC has described TV-Fi in two different flavours - an indoor LAN version and long-haul broadband networks. The indoor LAN version will likely be a mutant version of Wi-Fi with higher data rates and the ability to cleanly penetrate through walls and floors - no noise from microwave ovens or cordless phones, either.

TV-Fi's real strength is in WISP applications. A single transmitter at one watt power should be able to offer coverage of everything within a mile or two of a city environment and coverage distances up to 30 miles on flat terrain. Devices will incorporate smart-radio features to avoid interfering with existing TV broadcasters by using a combination of geo-location techniques and other to-be-determined methods. One trial balloon floated is the broadcast of an "access list" of open TV channels within a geographic region that could be sampled and loaded by a smart-radio before firing up operation.

TV broadcasters are being strangely quiet about the trial balloon. They haven't gone into full-blown battle-mode against it yet, like they did against low-power FM radio, but they may be keeping a lower profile given the stink some Congressmen raised about the freebie licenses they received for DTV transition. There's also an underlying reality that at least 80% of U.S. households receive their television either through cable or satellite hookups, making the broadcast towers and other assorted equipment very expensive legacy hardware. µ