Select your localized edition:

Close ×

More Ways to Connect

Discover one of our 28 local entrepreneurial communities »

Be the first to know as we launch in new countries and markets around the globe.

Interested in bringing MIT Technology Review to your local market?

MIT Technology ReviewMIT Technology Review - logo


Unsupported browser: Your browser does not meet modern web standards. See how it scores »

{ action.text }

Some of the challenges that faced the group came about because of the undefined nature of white-space frequencies. . The researchers designed their algorithms to determine the ideal amount of frequency bandwidth to use for a broadcast, balancing the desire for strong signal against the possibility of interference with neighboring frequencies. They also had to design a way for mobile devices to find a signal from an access point.

One of the most important parts of the White Fi system is a protocol for dealing with collisions among different signals (particularly those from wireless microphones, which can turn on at any time). Even a single packet of interference is enough to produce audible disruptions for a microphone. Even if interference affects only one device on the network, strict regulations forbid all devices on the network from using that channel. The researchers got around this by designing the access point so that it maintains a backup channel. If another user is detected, the white-space device or access point immediately switches to the backup channel, which reassigns bandwidth use as needed.

Peter Steenkiste, a professor of computer science at Carnegie Mellon University who specializes in networking, says that previous work on white spaces has focused on addressing one problem at a time. “The thing that I think is very interesting about this paper is that it really has looked at how you put a complete system together,” he says.

Steenkiste adds that “there are a lot of practical issues that they’ve worried about.” In particular, he says, the researchers did not assume an ideal, controlled environment for their system. Rather, they took into account such problems as measurement “noise” and the unpredictable behavior of wireless microphones. “[The research] has an answer for every question,” Steenkiste says.

Chandra says that his group recently received an experimental license from the FCC that allows them to build a prototype White Fi system on the Microsoft Research Campus in Redmond, WA. They plan to send their findings to the FCC in the hope that the data will help determine future white-space regulations. Chandra notes that since the transition from analog to digital television is happening worldwide, there is a high level of international interest in US white-space experiments. Researchers and companies all over the world are looking for technologies to take advantage of the fragments of spectrum that will open up in the coming years, he says.

6 comments. Share your thoughts »

Credit: Microsoft Research

Tagged: Computing, Communications, Microsoft, radio, white space, wireless communications networks, wireless networks, spectrum, rural broadband access

Reprints and Permissions | Send feedback to the editor

From the Archives


Introducing MIT Technology Review Insider.

Already a Magazine subscriber?

You're automatically an Insider. It's easy to activate or upgrade your account.

Activate Your Account

Become an Insider

It's the new way to subscribe. Get even more of the tech news, research, and discoveries you crave.

Sign Up

Learn More

Find out why MIT Technology Review Insider is for you and explore your options.

Show Me