In most regions of the country, ample swaths of the television spectrum go unused. Such “white space” in the TV band once comprised useful buffer zones between broadcasters that cut the risk of interference, the way medians divide highway lanes. But research at the University of Kansas shows that the digital revolution has lifted the need for unoccupied gaps in the TV spectrum and opened white space for use by a new generation of personal electronic devices.
“Where you are in the range of spectrum is very important,” said Joseph Evans, the Deane E. Ackers Distinguished Professor of Electrical Engineering and Computer Science at KU. “They call the spectrum below one gigahertz ‘beachfront property.’ That is by far the best spectrum for covering a reasonably wide area. The TV bands are down smack in the middle of that. And they could be used for any number of applications.”
In May, Evans was named director of the Information and Telecommunication Technology Center, one of KU’s largest research centers. The center explores and develops state-of-the-art information technology, ranging from devices like RFID tags to applications such as bioinformatics. Recently, Evans and colleagues at the center conducted research into unlicensed devices using white space that showed the potential of such technology.
As part of the study, the team built the “KU Unlicensed Device Emulator and Testbed,” an apparatus that mimicked the effects of unlicensed devices on digital television receivers.
“We were testing against real TV signals that you’d expect a normal user to see,” said Evans. “We could generate digital TV signals, then crank in an amount of power from the prototype of what a white space transmitter would look like — and we’d crank more power until the digital TV signal would fall over.”
The KU team found that operation of unlicensed devices in the television band could be accomplished with no significant impact upon DTV receivers in the area. Moreover, Evans said devices using the TV band could bring about better, more interoperable public safety communication, a drop in broadband costs and easier deployment of wireless technology to rural areas.
The findings are timely: A profusion of new white space will emerge in February as TV stations switch from analog to all-digital broadcasting.
“I’d certainly recommend that policies do not block good technology,” said Evans. “I’ve become a believer that white space technology is feasible. I do believe it is fair and prudent that the engineering details be carefully worked through — we’re still some distance from being able to field those types of devices. But there is great opportunity for white space devices in the next five to 10 years.”
This fall, the Federal Communications Commission will choose whether to permit use of devices that scan TV frequencies for white space and use these idle bands for transmission. But the FCC rulemaking is caught in a storm of controversy. Current licensees of the television spectrum stand firmly against giving personal devices access to their wedge of bandwidth.
“The TV channel operators really don’t want their customers inconvenienced or bothered by Johnny-come-latelys in the spectrum regions,” Evans said. “If you’re a broadcaster and your customers suddenly are reporting that they’re not seeing their signal as well, that could end up in loss of revenue. They do have legitimate concerns to make sure that any new technology isn’t negatively affecting them.”
On the other side, technology companies such as Microsoft, Intel, Google and Dell have joined to press the FCC to approve white space devices. Groups that advocate for public access to airwaves also are urging the commission to OK the innovative transmitters.
The research conducted at KU has informed this important public debate. Last year, Evans presented evidence to the FCC citing the center’s work to show that white space devices do not create interference for TV viewers when operated under appropriate rules.
“If technology comes along that can better serve the public, then we should enable those technologies to flourish,” said Evans. “We can do that by carefully understating the science and the technology before making those policy decisions. That’s not to say there are important vested interests — broadcast TV remains an important part of our media landscape. But we need to allow for the possibility of evolution.”