First Step Toward A 500 Mbps WLAN

The IEEE 802.11n task group this week kicks off a serious effort to define what might be the most significant wireless LAN standard ever. Cynics might suggest it is really the latest real-world laboratory experiment designed to determine whether the IEEE version of the open standards process can operate at speeds exceeding that of the snail. Tomorrow's wireless performance threshold has been pegged at a throughput of 100 Mbps. It can be done, in lots of ways. That's what makes it interesting.

First, remember history. The original 802.11 standard took seven years to define. It was a complex undertaking, both technically and politically, and the end result has proven to be a market success. So give the IEEE some credit. Yes, the wisdom of hindsight reveals that there were design shortcomings, many of them patched up with the bailing wire of subsequent standards. But like Ethernet, it has largely been good enough.

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.

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.

Clearly, backward compatibility is a critical issue. Even if the 11n committee sets records for efficiency, we're looking at a minimum of two years before commercially viable products are widely available. In the meantime, current generation WLANs will see much broader deployment. Integrating support for legacy 2.4-GHz 802.11g should prove relatively easy, and dynamic channel selection algorithms should allow 802.11a and 802.11n systems to share the generous bandwidth available at 5 GHz in most countries.

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