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IEEE struggles with video Wi-Fi standard

'Tedious and time-consuming' process

A second draft of the proposed IEEE standard for 100+Mbps wireless LANs is being pushed back several months, with a vote on it likely for January 2007 instead of late autumn.

The IEEE task group charged with crafting the 802.11n standard has been slogging through an astonishing 12,000 comments that were filed in response to draft 1.0, issued earlier this year. About half of these filings have been dealt with so far.

"There were a lot of duplicate comments, and three people filed comments for each and every blank line in the document," says Bill McFarland, CTO for Atheros Communications, a WLAN chip vendor. "The physical process of dealing with so many comments is tedious and time-consuming."

The task group has divided the comments into groups and assigned "tiger teams" of members to sift through them quickly during weekly conference calls between the regular meetings, McFarland says.

The underlying technology for 11n is the use of multiple antennae and signal processing, called multiple input multiple output or Mimo, that more than quadruples the current 20-24Mbps throughput for 802.11g and 11a WLANs. Mimo also boosts WLAN ranges, maintaining higher throughput over longer distances than is currently possible.

In general, industry participants are optimistic that the remaining comments will be dealt with and a second draft completed, no later than the November meeting. Some members had thought the next draft would be ready at the September meeting. The new schedule would let the task group send out the draft for what's called a letter ballot in January.

That ballot would need backing by 75 percent of the task group members to be accepted, a critical step because it would signal that the draft has reached a level of stability that could unleash a new wave of radio chipsets and products based on the draft standard. Final ratification of the standard might not occur until early 2008, though typically it is very rare for any changes to be made during that last stage.

But some of the remaining issues are both more complex and potentially more divisive than those considered so far.

One issue is that 11n allows for the combining of two 20MHz channels into one 40MHz channel, to boost throughput. At least three methods have been proposed but, according to Atheros' McFarland, there's been no agreement so far on which one or ones to use.

The results are evident in the first crop of "draft 11n" high-throughput wireless gear which has been shipping for a few months.

"The initial crop of products have 'bad neighbour' characteristics in early tests," says Rolf De Vegt, senior director of business development at Airgo Networks, the first chipmaker to come out with a Mimo chipset, nearly 18 months ago. That means Mimo products can step on other WLAN transmissions and that Mimo products from different vendors don't work together well.


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