Microsoft researchers have taken the next step toward turning old UHF analog TV spectrum into rural wireless broadband networks that would operate like Wi-Fi but with greater range, bypassing incumbent Internet providers like AT&T in the process. “Imagine the potential if you could connect to your home [Internet] router from up to a mile,” Ranveer Chandra, a Microsoft researcher, told MIT’s Technology Review in an article posted today.
Working with researchers at Harvard University, Microsoft developed a set of protocols for wireless Internet networks using “white space,” the unlicensed spectrum previously used for broadcast television signals, in a manner similar to today’s Wi-Fi systems. They call it “White-Fi.” Redmond has been working on such technology for more than two years and was one of several companies to get a license from the Federal Communications Commission to create prototype white-space devices. Google, Dell, HP, Philips and Intel have all voiced plans to develop white-space devices, with many seeing the former TV spectrum as a way to bypass the last-mile networks of incumbent broadband providers like AT&T and Qwest Communications. In addition, the white-space spectrum Microsoft is using (between 512 megahertz and 698 MHz) offers a longer range than today’s 2.4GHz Wi-Fi networks, promising greater reach in rural areas.
One of the key obstacles for Microsoft was creating a technological fix that would comply with the FCC’s strict white-space regulations that ban anyone using the spectrum from interfering with its primary existing user, usually a TV broadcaster. And it’s not easy to predict which part of the spectrum that incumbent is using at any given time. It’s also tricky because wireless microphones, which operate in the same spectrum, can suddenly become active without warning, and even a single-packet transmission can cause audible interference.
Microsoft dealt with this by creating an “adaptive spectrum assignment algorithm” with which devices measure the spectrum around them and work with other gadgets to find available frequencies, much like laptops search for and identify Wi-Fi networks. If interference occurs, the devices move to a backup channel in a different frequency range. In Microsoft’s experiment, its devices would switch to the backup channel within 3 seconds of a wireless microphone being turned on.
Other researchers have already focused on the first step: finding a way to establish a single link between an access point and user device without interference. Microsoft made the next move, designing an entire network with an access point and multiple clients (like Wi-Fi), leaving for another day the task of tackling multiple access points.
White-Fi won’t yield as much bandwidth as WiMAX or LTE networks, and its speed will depend on how much spectrum is available in each particular area. (It could be comparable to Wi-Fi but with a much longer range.) But unlike WiMAX or LTE, which will be deployed in urban areas, the spectrum isn’t owned by major carriers, so it lets new providers get in the game, and because no one has to buy the spectrum, the network’s cost would be lower as well. Of course, whoever is providing the service will still have to pay for the backhaul to connect the White-Fi network back to the Internet.