ENGINEERING NEWS

Crossing Disciplines to Squeeze Out Space on the Wireless Spectrum

One hundred years ago, anyone with the right equipment, an antenna, and something to say could transmit their radio waves over any part of the wireless spectrum they deemed fit.

In the 1930s, however, the Federal Communications Commission began regulating the airwaves, delegating bandwidth as new technologies like television came online. But now, with cell phone signals clamoring for space, the spectrum is getting full.

“The usable spectrum has been mostly allocated,” says Randy Berry, professor of electrical engineering and computer science. Berry has studied resource allocation problems since his working on his PhD 12 years ago. He devises mathematical models that show the strengths and weaknesses of a system’s design. “We have new devices like iPads and iPhones that all need part of the spectrum, and its not there. So how do we better utilize the spectrum that we have?”

To help answer this, Berry has teamed up with Michael Honig, professor of electrical engineering and computer science, and Rakesh Vohra, John L. and Helen Kellogg Professor of Managerial Economics and Decision Sciences at Northwestern’s Kellogg School of Management. The cross-disciplinary team has developed models that they hope will help influence spectrum policy.

“We’re really trying to work at the interface of technical and economic issues,” Berry says.

One barrier to spectrum allocation is the process: the FCC can take up to a decade to decide whether to auction space, and once space is licensed, that license is generally automatically renewed.

But often that space is underutilized. A rural area might only have two television channels that take up a portion of the allocated space. That space could be opened for general use – perhaps as space for wirelessly transmitting Internet connections, which generally aren’t available in rural areas.

It’s a potential solution that the FCC is pushing. Starting in 2008, the FCC began ruling to allow other devices to use such vacant television spectrum or white spaces. The first devices to do this were recently approved in December 2011.

But Berry and his collaborators have created a model that suggests such a plan might lead to worse conditions for residents in that area. A large provider might dump traffic in the spectrum to crowd out competition and charge higher prices.

“It suggests we should be careful with an open spectrum,” Berry says. “It’s something that’s not immediately intuitive.”

The group has also created models that argue for creating markets for spectrum use, specifically flexible markets: Much of today’s communication technology, like cell phones, can jump from band to band in the spectrum. That dynamic use could translate into dynamic markets, Berry says.

The team held a conference in the summer of 2011 in which computer scientists, electrical engineers, and economists gathered to talk about spectrum markets. They hope to continue their research and to write more policy position papers based on their work.

“This research has the opportunity to influence both technology and public policy, which is what attracted me to this area,” Berry says. “We hope we can say something about how different market structures and spectrum sharing structures would impact the welfare of citizens.”