INTERFERENCE: Digital television is on its way, and broadcasters want to make sure that their digital broadcasts are not interrupted by new wireless devices trying to use "white space" bandwidth between TV channels.
Courtesy of iStockphoto; Copyright: Xavi Arnau

It's fourth and goal and the home team's football quarterback can't get through to his coach on the sideline; the cast of a Broadway musical goes silent mid-show; a television news crew has to scramble to dig up cables that let reporters broadcast live on location—all because you tried to use your fancy new wireless device to download streaming video from the Internet, and it knocked out nearby wireless microphones.

That has not happened yet, but the Federal Communications Commission (FCC) is concerned enough with the possibility that it is having doubts about opening up "white spaces"—the slots of unused bandwidth built into the spectrum to keep broadcast signals from interfering with one another and to provide bandwidth for licensed wireless devices such as wireless microphones—to new, unlicensed cell phones, computers and other wireless devices that benefit from faster data downloads than those available today through Wi-Fi connections. The FCC is only going to grow more concerned as the deadline approaches in February for broadcasters to move from analog to digital TV, opening up more white spaces.

Broadcasters are concerned that unlicensed wireless devices will disrupt digital television service. "If the interference with broadcast channels is severe, and the FCC allows unlicensed wireless devices to use white spaces anyway, there's no way to put the genie back in the bottle," says Dennis Wharton, executive vice president of media relations for the National Association of Broadcasters (NAB), a Washington, D.C., trade association for local television and radio stations.

The FCC is wrapping up months of testing prototype sensors that detect white space, manufactured by companies including Adaptrum, Inc., Microsoft, Motorola, Philips Electronics and Singapore's Institute for Infocomm Research. Motorola's device, for example, is actually a rack of equipment that includes a receiver and a small computer with 300 MHz of processing power and one megabyte of memory.

On Tuesday, the commission tested the Infocomm and Philips white space devices' ability to detect wireless microphones at a performance of The Phantom of the Opera at New York City's Majestic Theater. On August 9, they tested these devices at FedExField in Landover, Md., during a National Football League game between the Washington Redskins and the Buffalo Bills. "Our prototype was tested for its ability to detect over-the-air ATSC (Advanced Television System Committee, or digital TV) and NTSC (National Television System Committee, or analog) signals, in addition to wireless microphones," says Kiran Challapali, a project leader in Philips Research North America's wireless communications and networking department. "We also successfully detected wireless microphones when switched on, in every instance."

Microsoft's device malfunctioned in the FCC's lab tests months ago, the company did not submit a device for field testing. Neither Motorola nor Adaptrum's devices are designed to detect wireless mic signals.

The FCC will not say what they have found in their field tests, which began July 14, but they stated in a press release earlier this year they would issue a report within six weeks of test completion. All of the devices being tested have access to an FCC database that lists all licenses issued for broadcasts and for wireless microphone use in a given area.

The commission is also trying to figure out whether it would be possible to use beacons to alert nonlicensed devices—personal cell phones, for example—that a licensed device is in the area as well as block the nonlicensed devices out of the white space. Such a beacon could be placed, for example, on a news van and emit a signal that would alert white space–sensing devices when licensed wireless mics used by a news crew are in the area, thereby giving the mics white space priority. In other words, during this time you could still use your cell phone on regular signals but not tap into the extra signal reserved for the reporters' wireless mics.