Better Wireless
Unused portions of the TV spectrum could improve long-range Internet ­connectivity.

Source: “White Space Networking with Wi-Fi like Connectivity”
Paramvir Bahl et al.
ACM SIGCOMM Conference, August 18, 2009, Barcelona, Spain

Results: Researchers at Microsoft and Harvard University have developed software that makes it possible to deliver long-range wireless Internet access over unused or underused fragments of the electromagnetic spectrum, known as “white spaces.” Last November, the Federal Communications Commission (FCC) made white spaces in the part of the spectrum used by television stations available to unlicensed devices as long as they didn’t interfere with existing broadcasts from TV stations or from devices licensed to operate within that spectrum, such as wireless microphones. The new system uses algorithms to detect and avoid interference.

Why it matters: Wi-Fi works over ranges of only a few dozen meters, but the new system, which the researchers call “WhiteFi,” uses frequencies that can carry information much farther, allowing users to connect to a router from more than a kilometer away. WhiteFi could be useful for rural or citywide wireless networks.

Methods: In the new system, white-space devices are connected in a network with a central access point, and each device detects the frequency use around it. The researchers developed algorithms that compare these results to select a range of frequencies that all devices in the network can use without interfering with other broadcasts. The system also monitors the selected spectrum and quickly moves signals to a backup slice of spectrum if there is interference from neighboring frequencies or if other devices need to use it (for example, if a wireless microphone is switched on).

Next steps: The group at Microsoft Research recently received an experimental license from the FCC allowing it to build and test a prototype system that will span the Microsoft campus in Redmond, WA.