On the same day that U.S. citizens elected a new president,
the FCC voted in “white spaces.”.
In a long-awaited move, the FCC elected to allow unlicensed use of so-called “white spaces,” unused spectrum allocated to TV broadcasting, for broadband data transmissions. This decision 
was surrounded by controversy and fierce lobbying on the part of powerful business interests.
Among the biggest cheerleaders for opening the spectrum were Google and Microsoft, who hope to launch networks providing wide area Internet access.
Opponents included broadcasters and cable TV operators who fear interference, particularly with new digital TV signals, and the entertainment industry, which already uses white spaces extensively for wireless microphone transmissions. Commercial wireless data network operators are cool to the idea for the obvious reason that “free” Internet access provided by the likes of Google (likely supported by advertising) will attract users who might otherwise be willing to pay for service. And as might be expected, technophiles everywhere are positively giddy over the prospect of abundant “free” high-speed Internet wherever and whenever they want it.
Déjà Vu
We’ve seen this story before. A few years ago, the idea was to blanket urban areas with thousands of Wi-Fi access ports, thus providing high-speed wireless Internet access to anyone with an inexpensive modem within or attached to their computer. These “Mu-Fi” networks were never really practical for a bevy of technical reasons, so the obvious question is whether “white space” networks will be more viable. Considering the advantages and limitations of the spectrum the FCC just opened up, the answer is most likely “yes,” but it won’t be a slam-dunk by any means.
What the FCC has done is allow the use of unlicensed devices to operate in the band occupied by TV channels 21-36, which is 512.0-608.0 MHz. That’s a lot of spectrum, but there also are a lot of caveats and limitations. Most critically, approved devices will have to incorporate means to avoid, or at least limit the likelihood of, interference with reception of broadcast TV signals.
Two such means have been identified. The simpler requires that each device be equipped with a sensor that can detect the presence of a broadcast TV signal at a level sufficient for normal reception. The device would not be allowed to transmit on any such “occupied” channel and would be severely restricted in power on any adjacent channel.
The second approved means for interference avoidance is a combination of geolocation and database. A device would have to be able to figure out where it is (for mobile devices this would probably involve use of GPS) and an internal database would specify channels that could not be used in that particular location.
Muddy Waters
Based upon laboratory trials, the FCC feels that signal sensing and geolocation/data base methods have demonstrated sufficient efficacy. Broadcasting interests have expressed extreme skepticism. It appears their concerns did not persuade the FCC, but the matter remains somewhat murky.
Even murkier is the potential for interference with wireless microphones and cable TV operations. The new FCC rules will mandate that white space devices also sense nearby use of wireless microphones, but it isn’t at all clear that this protection will work as well as it does for broadcast TV signals. Wireless mics operate over short range at very low power, and a relatively strong data device transmission from a modest distance could severely interfere. The FCC will likely prohibit use of data devices in areas, like New York’s Theater District, where wireless mics abound, but they also are used in small scale cabarets and night clubs just about everywhere.
Cable TV doesn’t rely on reception of broadcast signals, of course, but the signals in the cables that connect to set-top boxes may be at very low level. A nearby strong radio signal transmission could certainly interfere. What’s more, there are typically no “unused” channels in cable systems. The cable industry is worried that extensive use of white space devices will cause widespread service disruption, and that resolving such problems may require costly cable network reconfiguration.
While the FCC is satisfied that limited laboratory testing has demonstrated interference from white noise devices is manageable, it’s by no means certain that things will remain as sanguine when there are tens of millions of such devices in use.
Even if interference with other services proves to be tolerable, the road to success for white space network operators will hardly be an easy one. Sure, the spectrum is “free” and there’s a lot of it, but some will be unusable because of local TV broadcasting. What is available will have to be shared among all users, including competing public networks and private local area networks. And because all of this use will be largely unregulated, interference levels may preclude use of high level modulation. Operators of data networks on licensed spectrum can manage interference levels; those using unlicensed bands don’t have that luxury.
Compared with the 2.4 GHz band available for failed Mu-Fi systems, the 500 MHz band used by white space networks is more amenable to serving large areas.
But the lower frequency will actually make it harder to concentrate capacity in areas of highest traffic volumes. And while the spectrum may be free, buildout of white space networks – infrastructure equipment, site leases, backhaul and such – won’t be any cheaper than for commercial broadband networks.
Can all these costs really be supported strictly by advertising revenues?
All in all, exploitation of white space spectrum may eventually result in a new, and potentially disruptive, avenue for wireless broadband service. But anyone who thinks it will be simple just isn’t being realistic.
Drucker is president of Drucker Associates.
He may be contacted at [email protected].
Filed Under: Industry regulations + certifications