MIMO techniques are the heart of the two major proposals now remaining in the IEEE 802.11n task group, which is charged with crafting a standard for WLANs that can sustain up to 100M bit/sec throughput.
At last month's meeting, the group's voting left two complete 11n proposals on the table, each backed by a group of vendors.
One group is World-Wide Spectrum Efficiency (WWiSE ). The group proposes using the existing 20-MHz channel structure that is almost universally adopted by nations, two MIMO antennas on either end of a wireless link, and changes to the media access control (MAC) layer to boost throughput on a single channel to 135M bit/sec.
WWiSE members include Airgo, which was the first to ship a MIMO chipset in 2004, Broadcom, Conexant Systems, STMicroelectronics, Texas Instruments and several others.
The other group is TGn Sync , which includes Agere, Atheros, Intel, Sony, and most recently Qualcomm. Among other things, TGn Sync proposes "expanding" the channel size from 20 MHz to 40 MHz, which would boost maximum throughput to 315M bit/sec. The change would cut the number of available channels from 22 to 11 in the 5-GHz band.
In the most recent balloting, TGn Sync won about 50% of the votes, WWiSE about 35%. To become the basis of an IEEE standard, a proposal has to collect 75%.
But negotiating the technical differences may be less difficult, and less important, than negotiating issues regarding the licensing of intellectual property, and which features are mandatory, and which optional, in the final standard.
The next few months will give some indication of how quickly, or whether, the two groups can compromise. Most observers say they expect a final 11n standard some time in 2006.
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