September 10, 2008

IEEE considers Gigabit speeds Wi-Fi

Could sink moribund UWB?

By Peter Judge, Techworld

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The IEEE is considering two possible technologies which could take Wi-Fi to Gigabit speeds by 2012 - even though the standards body won't finally publish the 802.11n fast Wi-Fi specification until November 2009.

Gigabit Wi-Fi is practical, according to the IEEE's Very High Throughput (VHT) study group, which is lobbying to get work started on a faster wireless LAN standard - a move which could drive a nail in the coffin of a potentially faster technology, ultra-wideband. However, the IEEE is not moving quickly on today's current top Wi-Fi, 802.11n, having quietly postponed its final publication until November 2009.

All Wi-Fi vendors (except Nortel) have products which meet the draft 802.11n specification,and claim speeds (or "symbol rates") of up to 300Mbit/s, but actual throughput is much lower - approaching the 100Mbit/s of normal Ethernet.

The VHT study group has suggested two avenues to real Gigabit throughput on Wi-Fi networks, and will request the IEEE's permission to develop either or both as standards, possibly as soon as the IEEE's standards board meeting, in Seoul this month.

One VHT proposal uses frequencies below 6GHz, where current Wi-Fi networks operate, and the other is above 60GHz, where a lot of unlicensed short range radio spectrum is available. Either could lead to products by 2011 or 2012, according to a report in ExtremeTech.

The lower frequency proposal would be backward compatible with 802.11n, but finally abandon the crowded 2.4GHz spectrum. It would only reach about 500Mbit/s throughput per link, but would aggregate multiple links to reach Gigabit speeds.

The 60GHz could have use existing prototype technology, since Gigabit links similar to Wi-Fi have been demonstrated in that range, by US scientists at the Georgia Electronic Design Center (GEDC). However, 60GHz radio waves only have a short range, and their potential has been felt to be limited.

The VHT proposal plans to improve on that using directional antennas to focus the energy in beams that will make the most of the available energy and achieve a range of 10 metres or more.

There are already two short-range wireless standards efforts in or near the Gigabit range. One, ultrawideband (UWB), uses low power across a broad spectrum, but is currently languishing, apparently unable to deliver the products that were promised some years ago, although wireless USB ports that use UWB are available on some laptops.

The other, WirelessHD, uses the spectrum above 60GHz, and has been demonstrated at 5Gbit/s. This has a product timescale similar to suggestions for VHT.

Since some of the same people are involved in both WirelessHD and VHT, (including James Gilb, technical editor for the WirelessHD consortium, who maintains of the 802.11 VHT PAR page), it seems likely that a 60GHz VHT proposal might re-use the physical layer of WirelessHD.

The biggest loser looks like being ultrawideband, once seen as very promising, but now looking shaky as big players like TI pull out.

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