Unused Television Spectrum Could Deliver New Broadband Services

In September 2008, Wilmington, N.C., became the first major market to switch from analog to digital TV. Now the city is continuing the grand tradition, this time serving as a digital guinea pig for the nation's first "smart city."

Cameras, sensors and other devices have been installed throughout New Hanover County as part of a test that began in February and will last for several months. These devices will transmit real-time data for the city to analyze. Information travels through a new wireless network that utilizes unused broadcast television spectrum, called "white spaces" created by 2008's digital TV conversion. Because digital TV uses spectrum more efficiently, it's possible to use the leftover spectrum to provide broadband services.

For instance, Wilmington will use wireless traffic cameras at intersections for the transportation department to monitor traffic, travel time and fuel consumption, and to support local law enforcement. With water-level sensors, officials also can monitor and manage wetland areas in the coastal city without a boat trip.

"The possibilities of this technology, in my opinion, are endless," said Mayor Bill Saffo, estimating that using the white spaces could save the city 80 to 90 percent of the cost of creating a wired network. "So many possibilities that I feel will help local governments deliver services much more effectively and efficiently. You can literally cover your entire city in Wi-Fi without having to lay all these wires."

In a dozen cities across the country, broadcast TV channels 14 through 20 have already been allocated for public safety use, and the FCC reserved channel 37 for medical devices, said John Chapin, Massachusetts Institute of Technology researcher and a consultant for TV Band Services. Authorized by the FCC under an experimental license, Wilmington's network is a test bed for locally based TV Band Service and Spectrum Bridge, a Florida-based white space database provider.

But the idea of using TV white spaces to create a web of wireless extension cords for local governments has its hang-ups. For one, the FCC hasn't yet released official rules for how municipalities can use white spaces. And contrary to networks owned by cable and telecom companies, white spaces are unlicensed. That means, in theory, anybody can hop on one of the white space frequencies -- a critical concern for broadcasters because, without regulation, devices can potentially cause interference with regular broadcast channels.

"It's the unlicensed aspects that cause grave concerns," said David Donovan, president of the Association for Maximum Service Television (MSTV), "because if there is interference, there's no one to hold accountable. Who's responsible?"

Path Interference

A few months after the FCC published its first set of rules for white space use in November 2008, the floor was opened for concerns, Chapin said, which led to 17 petitions for reconsideration and three additional lawsuits.

The biggest problem, he said, was the issue of interference and how to accurately determine which frequencies are available in a given area and which ones aren't. Picture this: You're sitting at home trying to watch TV. Someone somewhere fires up a device on the same channel thinking it was an open white space frequency. The person may not know the device is causing interference, but all of a sudden you can't get a signal for that channel on your TV set. That is MSTV's concern.

"It's not that we have a problem with spectrum use per se," Donovan said. "We share with the police in major markets. We share with licensed LAN mobile operations. But sharing the band with millions of unlicensed entities will create significant hazardous interference to TV stations in the band."

To avoid the problem, MSTV supports the creation of a neutral database, which would be connected to devices built to FCC specs. This way, certified devices would only tune to available channels after getting the