The terribly named “White-Fi” is a research effort to bring WiFi transmission to the unlicensed TV spectrum — the so-called “whitespace” (get it? White-Fi!) of TV channels in the UHF band . Big whoop, right? Well, with transmission ranges up to 1 kilometer, that actually is a pretty big deal. Mesh networking is also in the works. But most interesting of all are the requirements that the FCC has imposed on White-Fi devices to make sure they don’t interfere with any television broadcasts or wireless microphones. Basically, any White-Fi device needs to immediately switch frequencies the instant it detects a signal from a television or microphone.
Consider: at ranges of 1 km, a frequency that’s free to use at one end may be in use at the other end. White-Fi devices will need to figure out some way to find a shared free frequency. And they’ll need to be able to find a new frequency to use quickly should something else pop up on that frequency somewhere.
The actual engineering requirements to accomplish this frequency switch are non-trivial. Microsoft Research’s Networking Over Whitespace (“KNOWS”) project has taken up the task and made some pretty remarkable advances. Disconnects can occur within 4 seconds, and a new channel can be located by means of “chirps” sent out at regular intervals on a back-up channel.
Microsoft isn’t the only company working on White-Fi solutions, so stay tuned for announcements from other players in the wireless industry. And as usual, it’ll be a while before you and I can use this technology. One wonders how long it’ll be before White-Fi is replaced altogether by the next new wireless technology…
Via Ars Technica.