Agere touts promise of 250M bit/sec WLAN

Agere Systems Monday unveiled proposals for a 250M bit/sec wireless LAN specification, which it plans to submit next month to the IEEE 802.11n task group.

The proposal is joint effort by Agere, Intel, Sony, Atheros, Nokia, and several other, as yet unannounced, companies, which are part of an ad hoc industry group called TGn Sync. The group's purpose is to outline a viable technology that could be adopted by the 11n group as the core of a future IEEE standard.

The 11n group is charged with overseeing changes to the 802.11 physical and media access layers to boost WLAN throughput to 100M bit/sec, compared to the 20M to 25M bit/sec typically available to users on 802.11g and 11a WLANs.

Aug. 12 is the deadline for submissions to the IEEE task group, according to Mary Cramer, strategic product manager for the Computer Connectivity Division of Agere in Allentown, Pa. The standards group will then hear presentations in September from companies and groups that have made submissions, and begin a process of combining and winnowing the proposals.

Ratification probably will be sometime in 2006, but MIMO (multiple-inputs, multiple-outputs) products that bear some resemblance to an emerging 11n standard may start appearing late 2005 and early 2006, according to Cramer.

The 802.11 WLAN standard includes an array of features, for such things as error checking, that cut the maximum data rate by roughly half. As a result, the 54M-bits/sec data rate of both 11g and 11a yield a typical available throughput of 20M to 25M bit/sec. By using two innovations, Agere plans to boost the overall data rate to 250M bit/sec, yielding a throughput of 175M bit/sec.

The first innovation is MIMO, which uses two to four antennas on both ends of the wireless connection. The MIMO chipsets, in effect, load more data into the multiple pathways between the two sets of antennas, boosting capacity. One of the first companies to introduce a MIMO chipset is Airgo, which is also planning to offer an 11n proposal.

The second innovation from Agere is to increase the size of the WLAN radio channels, from about 20 MHz to 40 MHz, somewhat analogous to using a large data pipe between the two radios. The combination of these two innovations creates a data stream between any two MIMO antennas of 125M bit/sec. With four antennas on each end -- the maximum in the Agere proposal -- the aggregate data rate is 500M bit/sec, according to Cramer.

Cramer acknowledges that doubling the size of each channel will halve the total number of channels available, from 22 to 11 in the 5-GHz band used by 802.11a. But that would still be nearly four times the three channels available to 11g and 11b in the 2.4-GHz band. Additional channels let enterprises deploy more access points in a given area, thus giving more users more bandwidth.

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