First Step Toward a 500-Mbps WLAN

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

Corporate alliances are key to the process, and they, too, form out ofboth common technical vision and market position. Rivals take sides. Themost heavily publicized alliances so far are TGn Sync, promoted by WLANchip pioneers Agere, Atheros and others. A competing alliance, known asWWiSE, includes semiconductor heavyweights Broadcom, Conexant (formerlyIntersil) and Texas Instruments, along with chip startup Airgo, which isalready delivering 802.11-compliant chipsets that incorporate MIMO(multiple-input, multiple-output) technology. Nearly everyone agreesthat MIMO will be the foundation upon which 802.11n will be built.

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

Airgo's design is first-generation MIMO. The company can legitimatelylay claim to the position of industry leader. But first-generationtechnologies are seldom sustainable. All of Airgo's well-financedcompetitors have engineers working on MIMO, and the prospect of a newstandard gives them license to think ahead. For example, TGn Syncobviously sees future high-speed WLANs running in the 5-GHz band, whichmakes it practical to consider doubling performance by doubling thecurrent 20-MHz channel size. By doubling the channel and supporting4-transmitter-by-4-receiver MIMO, TGn Sync claims it can achieve datarates of 500 Mbps.Clearly, backward compatibility is a critical issue. Even if the 11ncommittee sets records for efficiency, we're looking at a minimum of twoyears before commercially viable products are widely available. In themeantime, current generation WLANs will see much broader deployment.Integrating support for legacy 2.4-GHz 802.11g should prove relativelyeasy, and dynamic channel selection algorithms should allow 802.11a and802.11n systems to share the generous bandwidth available at 5 GHz inmost countries.

Some look at the standards process and lament the fact that thetechnology pioneer--in this case Airgo--ends up getting shafted becauseits competitors are loathe to approve a standard that concedes to thatcompany a substantial benefit of being first-to-market. There is sometruth to that. But in the end, Airgo's success will depend on thecompany's ability to execute--to translate its early experience andexpertise into future market success. And that's the way it should be.

For more information about the TGn Sync proposal

For an analysis that casts 802.11n as a battle just begun, see EricGiffith's excellent summary.

-- Dave Molta, [email protected]1022