IEEE takes another step toward 802.11n ratification

Network World - The IEEE 802.11n Working Group this week approved draft 2.0 of the standard, paving the way for speedier 100+Mbit/sec. wireless LAN products as early as this summer.

Just over 83% of working group members cast their vote to approve the draft, well over the minimum 75% 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 that if, as expected, Draft 2 was approved this month, testing could begin in June or earlier. The alliance will certify and brand WLAN products as Draft 2 compliant, reversing a long-held policy to only test products that comply with a final IEEE standard.

The heart of the new standard is a technique called MIMO, or multiple-input, multiple-output. MIMO takes a stream of data, separates it through digital signal processing into several streams and transmits it over two or more antennas. The streams are received by two or more antennas and reassembled 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+Mbit/sec. throughput. But so-called Draft 1 or pre-11n products already on the market are delivering 140Mbit/sec. to 160Mbit/sec. With more antennas, more power and other tweaks, many vendors say they expect to achieve more than 200Mbit/sec., sometimes much more.

At the regular IEEE 802.11 plenary this week in Orlando, one attendee, network security guru Matthew Gast, reported in his blog that of the eligible voters, 231 approved the draft, 46 voted against and 28 abstained. Four votes were invalidated. Draft 2 received 3,163 comments, about 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.