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Globalstar: Don't be afraid of our private Wi-Fi superhighway plan

Bluetooth SIG and Wi-Fi group: But you'll run us off the road!

Globalstar's plan to refarm its satellite spectrum into a privately held Wi-Fi channel has come under fire from the Wi-Fi Alliance and Bluetooth SIG, which reckon it will edge out the unlicensed users.

Globalstar maintains that the Wi-Fi Alliance has misunderstood its FCC request, which asks the regulator to let it run a private Wi-Fi channel in its satellite bands, publishing an open letter (PDF, short) reiterating that it's not looking for ownership of the (internationally unlicensed) ISM band or even protection from interference, it just wants to deploy Wi-Fi in the bands it already owns, and promises to connect up schools for free too.

The channel concerned is 14, the top half of which belongs to Globalstar and is currently reserved (in the USA) for satellite communications. But if Globalstar can get FCC approval then it will deploy existing Wi-Fi kit into the band and license it out to hospitals, schools, colleges and so forth where the free-to-use bands are getting overcrowded.

In America, Wi-Fi tops out at Channel 11, which runs from 2.451 to 2.473 GHz. In Europe we use another two channels above there: 12 and 13, which run up to 2.483GHz - but the US keeps that area empty as a guard band to avoid interfering with Globalstar's satellite comms which start at 2.4835GHz.

Globalstar's band, therefore, covers the Wi-Fi channel number 14, which is used in Japan and thus will be within the range of existing hardware once the software is patched.

But the width of a Wi-Fi signal means that using Globalstar's band will also fill the existing "buffer" band and that's what has the Wi-Fi Alliance and Bluetooth SIG worried.

Bluetooth squeezes into much smaller slots, but bounces well into the bottom half of Channel 14 as it hops around to avoid interference. So if 14 became full of private Wi-Fi networks, then Bluetooth could suffer, but more concerning is the idea of losing a third of current Wi-Fi capability.

The 11 numbered Wi-Fi channels available to US users are only 5MHz wide - while even 802.11b fills a band 22MHz across. So to avoid interference, Americans try to use channels 1, 6 and 11, as only those three can be certain of not touching each other, but a new network at 14 would impinge on the last of those and could hit network speeds.

Not that Wi-Fi needs empty spectrum, the protocol is robust enough to cope with neighbouring signals and even multiple networks on the same channel - the overlap costs all users speed but is an acceptable part of using unlicensed bands. However, the Wi-Fi Alliance was concerned enough to file a representation to the FCC.

Globalstar's final response to those concerns will be published at the end of this month, and the company will be hoping that its promise of 20,000 free (Channel 14) Wi-Fi points in schools and colleges will sway the regulator in its favour... and of course it has to be hoping no one mentions LightSquared during the deliberation process. ®

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