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First Step Toward a 500-Mbps WLAN

As per 802.11 rules, parties intending to submit standards proposals by
the August 13 deadline number 61, with 22 being "complete" and 39 being
"partial." No wonder the process takes so long to complete. As is the
case with many standards, parallel efforts are already under way: one,
to hammer out the technical details of modulation design, channel
bandwidth and backward compatibility, and another, where the various
participants try to serve the market interests of their employers.

Corporate alliances are key to the process, and they, too, form out of
both common technical vision and market position. Rivals take sides. The
most heavily publicized alliances so far are TGn Sync, promoted by WLAN
chip pioneers Agere, Atheros and others. A competing alliance, known as
WWiSE, includes semiconductor heavyweights Broadcom, Conexant (formerly
Intersil) and Texas Instruments, along with chip startup Airgo, which is
already delivering 802.11-compliant chipsets that incorporate MIMO
(multiple-input, multiple-output) technology. Nearly everyone agrees
that MIMO will be the foundation upon which 802.11n will be built.


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We tested early Airgo prototypes several months ago in our labs. (The
company has recently announced the partners that are embedding Airgo
chips in their own product offerings.) The prototypes delivered the
highest throughput and longest range of any single-channel product we
have tested. However, they didn't blow us away on either count,
delivering throughput comparable to other proprietary channel-bonding
implementations and extended range that fell far short of the company's
early marketing promise of an order of magnitude greater coverage. While
Airgo deserves credit as a market innovator, it was clear at the time
that more work remained to be done before the 100-Mbps-throughput
threshold was reached at any reasonable physical distance.

Airgo's design is first-generation MIMO. The company can legitimately
lay claim to the position of industry leader. But first-generation
technologies are seldom sustainable. All of Airgo's well-financed
competitors have engineers working on MIMO, and the prospect of a new
standard gives them license to think ahead. For example, TGn Sync
obviously sees future high-speed WLANs running in the 5-GHz band, which
makes it practical to consider doubling performance by doubling the
current 20-MHz channel size. By doubling the channel and supporting
4-transmitter-by-4-receiver MIMO, TGn Sync claims it can achieve data
rates of 500 Mbps.

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