Wi-Fi for White Spaces: Will Microsoft's WiFi-NC set new network standard?

Microsoft Research has found a way to tap white spaces in the spectrum that were previously used by analogue TV broadcasts. WiFi-NC would bundle together narrow channels to provide wireless transmissions at top speeds. Microsoft is hoping to set the new Wi-Fi network standard, but will Congress approve?

Once upon a time, Microsoft had applied to the FCC to become an approved white spaces administrator. However, in December, the FCC approved Spectrum Bridge to administer a database system of television white spaces, "which may provide service to devices beginning January 26, 2012." So now the software giant is proposing WiFi-NC which operates over low bandwidth channels, but when bundled together all of these white space narrow channels can provide a "full purpose signal" and screaming speeds.

Wi-Fi frequencies can carry a signal only a short distance, but TV stations use parts of the radio spectrum that allow signals to travel long distances. Microsoft Mobile Computing Researcher Ranveer Chandra said when TV stations moved from analogue to digital broadcasts, it opened up "unused slices of the spectrum between stations." These "white spaces" could be used for wireless Internet service, if there was a way to ensure there would be no interference with TV broadcasts. Yet research proved that "an HD movie stream can be transmitted over the same channel being used by a wireless microphone (which use frequencies close to TV broadcasts) without causing any noticeable degradation to the sound recorded. That shows that the current rules may be too conservative." As it stands now, white space devices "must avoid any channel in use by a wireless microphone as well as the channels on either side of a TV broadcast."

This was about the time it was reported that Microsoft wanted "to rule the white spaces" and Microsoft Research presented "SenseLess, a database driven white spaces network." That system was able to tell wireless devices where there were available white spaces and if it would be legal to broadcast. Well now Microsoft has Wi-Fi over narrow channels, dubbed WiFi-NC which could operate at fast speeds. WiFi-NC would bundle multiple narrow signals to create bandwidth and, like the fastest Wi-Fi networks, be able to transmit data up to a gigabit per second in those white spaces.

Physorg explained that WiFi-NC devices would work by "combining a large group of very low power radios and receivers (which they call transmitterlets and recieverlets) each of which would be temporarily dedicated to one free band in the spectrum. The signals would then be combined to create one full purpose signal and used in what the team calls a compound radio."

According to Microsoft Research, "We propose WiFi-NC, a novel PHY-MAC design that allows radios to use WiFi over multiple narrow channels simultaneously. To enable WiFi-NC, we have developed the compound radio, a single wideband radio that exposes the abstraction of multiple narrow channel radios, each with independent transmission, reception and carrier sensing capabilities. The architecture of WiFi-NC makes it especially suitable for use in white spaces where free spectrum may be fragmented."

"Not only would such new devices allow Wi-Fi suppliers and users to take advantage of the additional bandwidth, but moving to such a new system wouldn't necessitate throwing out current hardware, as the reception and transmission logic would remain the same. Moving to such a new standard, Microsoft argues, would be both fair and efficient, allowing everyone access to more bandwidth, which is always a concern as more and more devices come to rely on Wi-Fi hardware and software solutions for moving data," reported Physorg.

Microsoft researcher Krishna Chintalapudi told Technology Review, "It is our opinion that WiFi-NC's approach of using multiple narrow channels as opposed to the current model of using wider channels in an all-or-nothing style is the more prudent approach for the future of Wi-Fi and white spaces." Chintalapudi added that the goal of the Microsoft Research team "is to propose WiFi-NC as a new wireless standard for the hardware and software industries."

Convincing Congress of the necessity to approve wider white spaces may be the biggest challenge Microsoft faces.

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