IEEE Approves Next Draft of 802.11n Standard

The IEEE 802.11n Working Group this week approved draft 2.0 of the standard, paving the way for 100+Mbps wireless LAN products as early as this summer.

Just over 83 percent of working group members cast their vote to approve the draft, well over the minimum 75 percent needed. The vote indicates that after more than a year of often acrimonious debate, the group has finally coalesced behind the core technology.

One practical effect is that vendors of WLAN adapters and access points can now introduce products that should require no substantive changes when the final standard is authorized, probably in the fall of 2008.

The Wi-Fi Alliance last year said it was preparing an interoperability testing program for draft 2 equipment. Alliance officials said then that if draft 2 is approved in this month as expected, testing could begin in June 2007 or earlier. The alliance will certify and brand WLAN products as draft 2 compliant, reversing a long-held policy to test only products that comply with a final IEEE standard.

The heart of the new standard is a technique called MIMO, for multiple input multiple output. MIMO takes a stream of data, separates it via some digital signal processing magic into several streams and transmits it over two or more antennas. The streams are received by two or more antennas and re-assembled into the original. But because of how this is done, and the way MIMO antennas exploit radio reflections called multipath, much more data can be packed into these transmissions.

The IEEE standard originally called for a minimum of 100+Mbps throughput. But so-called “draft 1” or “pre-11n” products already on the market are delivering 140 to 160Mbps. With more antennas, more power and other tweaks, many vendors say they expect to achieve over 200Mbps, sometimes much more.

At the regular IEEE 802.11 plenary meeting this week in Orlando, one attendee was network security guru Matthew Gast. In his blog, Gast reported that of the 325 eligible voters, 306 voted. Of that number, 231 approved the draft, 46 voted against and 28 abstained. Four votes were invalidated. Draft 2 received 3,163 comments roughly evenly divided between editorial and technical comments. Those indicate that there may be some additional changes to the draft over the coming months, but they are likely to be minor.

-John Cox, Network World

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