Microsoft leads internet industry bid to fill up white space

US heavyweights eye spectrum gaps for mobile internet

Microsoft says devices based on the coalition's platform and on Windows Mobile would be ready for commercial release early in 2009. At their heart will be a cognitive radio that can avoid interfering with other signals in nearby spectrum. Such technology is the core of most approaches to freeing up broadcast frequencies round the world in the 700-900MHz range, including the important IEEE 802.22 (or Wi- TV) standards effort, which started work two years ago on an "intelligent" air interface that could tap into unused spectrum within an occupied band.

It aims to create a standard for fixed wireless (up to 1W power) and nomadic embedded systems (up to 100mW), and potentially for mobility in future, using cognitive radio techniques to switch automatically to a clear area of the band, and to avoid interfering with other occupying devices.

The WiMAX community has been particularly keen to claim TV bands for its own, and in March 2004 when the 802.22 group was set up, the 802.16 faction was angered when its proposal that the cognitive radio work should be under its auspices, rather than in a separate group, was defeated. However, this has not halted its supporters, led by Intel, in their quest to turn the 802.22 efforts to their advantage.

It seems that, as in other areas, Microsoft and Intel are leaping ahead of the IEEE work to try to create a de facto standard that can be brought to market rapidly, and possibly presented to the standards body as a fait accompli at a later stage.

They have certainly moved quickly in the past few months. In October the FCC gave the green light to technologies to use unused TV frequencies, provided they could demonstrate non-interference. Just three months later the Microsoft coalition had outlined its technology and sent a statement of support to the FCC, and on February 5 the specifications for the machine were sent for testing to the regulator's Office of Engineering and Technology (OET).

A drawing of the cognitive radio's test set-up, included in the filing, indicates that it will be able to access white space signals for a UHF radio, a CR scanner, and a laptop computer attached to network processor through an Ethernet interface. Users would at first specify a TV channel for the device to pick up. The machine would search for other signals if that one was already taken.

In its January statement, the coalition asked the FCC to:

• Authorise the use of "spectrum sensing" rather than geolocation technology (the main technique used in existing solutions, though not in 802.22, to find white space. The group argues that spectrum sensors do not need databases of available channels to function, and so are more flexible.
• Recommend that such devices check whether the channel is being used by a TV broadcaster once a minute, rather than every 10 seconds as recommended by the commission's first proposal.
• Avoid any delays in deployment of unlicensed devices. The FCC has provisionally okayed white space detecting devices to go on sale on February 18 2009, the day after all analog TV signals are due to cease.

Opposition to such demands will come not only from the broadcasters, which are still trying to delay the hour when they must vacate the spectrum, but also potentially from the telcos, facing yet more competitive threat, and the mobile giants, which will be keen to take the initiative themselves in mobile internet.

Qualcomm, for one, was quick to react, submitting remarks to the FCC urging it to insist that white space detection systems must be licensed. We'll now be on the look-out for the first sign of a cognitive radio internet device from Nokia, and then the battle really will begin.

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