The 802.11n Standard: Grown Up at Last

Even for a wireless-communications standard, the 802.11n specification has over the last several years been subject to an exceptionally messy development process. Battling vendors and standards proposals, predraft and postdraft 1.0 silicon and box products, and multiple interoperability issues have continued to plague this latest generation of Wi-Fi technology. The 802.11n spec is now mostly past the difficult stage and about to fulfill its promise: a range approximately twice as great and transmitting speeds five to 10 times as fast as those of legacy 802.11a/b/g products. It's about time, too, because the spec has a big job to do in designs for consumer, enterprise, campus, and metroscale markets. Unfortunately, the spec is complex and has a huge number of possible variants and options.

Those complexities are at least one reason that the process has taken so long. According to some industry participants, vendor infighting has been another major reason that the approval process has taken so long. Even before the IEEE committee approved Draft 1.0, at least three vendors had offered different proposals for the standard's core technology. TGn (Task Group N), the IEEE group that handles the spec, eventually narrowed down these competing proposals to two, says Jagdish Rebello, director and principal analyst of wireless communications for iSuppli. "Last year, [the two proposals] merged, and TGn submitted a joint proposal to the full body in May 2006." But TGn failed to achieve the necessary 75% approval level for a Draft 1.0 version. In March 2007, the committee voted to approve Draft 2.0, which came with approximately 3000 technical and editorial comments. Industry participants expect TGn to issue Draft 3.0 for a recirculation ballot this month, when the group expects to have completed the comment resolutions. As is usual for an IEEE standard, the specification will likely go through some more tweaking for another six to 12 months or so. The unprecedented number of options in this 802.11x spec makes this fine-tuning especially necessary, but participants agree that the mandatory sections are unlikely to change now.

During this lengthy, drawn-out process, at least one vendor coalition arose to develop an alternative specification so that products could more quickly get to market than the standards committee's work would support. In frustration at the length of time involved, manufacturers began releasing products even before Draft 1.0, based on different vendors? silicon designs. As tested by various external labs and research companies, many of these designs did not interoperate with each other.

To help push forward the standards-development process and provide interoperability certification, the WFA (Wi-Fi Alliance) in August 2006 announced that, during the first half of 2007, it would launch an extensive certification process for products that included baseline features from the developing standard. In May 2007, after TGn approved Draft 2.0, the WFA unveiled the Certified for 802.11n Draft 2.0 program, which it based on the mandatory sections of Draft 2.0, and announced the first certified chip, card, and box products, which form the testbed for certifying additional products. The formal certification program began in June 2007. Many vendors have stated that their WFA-certified 802.11n Draft 2.0 products will be firmware-upgradable to the final IEEE 802.11n standard.

Netgear, whose products have now passed WFA certification, in 2005 launched Draft n products that it based on chips from two suppliers. "At that point, interoperability across chip vendors was an issue, and we had to supply two lines of adapters," says Som Pal Choudhury, Netgear's product-line manager for advanced wireless. The company's latest router product automatically detects and self-installs the most recent firmware from the company's Web site.

802.11n advantages

The 802.11n WLAN (wireless-local-area-network) technology is the only Wi-Fi technology today with the bandwidth to support multiple HDTV (high-definition-TV) streams at 20 Mbps each. This performance is sufficient for implementing some long-standing goals of Wi-Fi networks. One of these goals, wireless multimedia, comprises voice/VOIP (voice over Internet Protocol), data, video, and gaming in residential applications. Another goal is achieving throughput, QOS (quality-of-service), and security levels that compare favorably with those of Ethernet which are necessary for enterprise-grade, campus, and municipal networks. But the methods of achieving this performance are complex, leading to many of the options and variants in the standard. Another main reason for all the options is the large number of device types that users want to connect to Wi-Fi networks, each with its own distinct set of requirements. Because the market for Wi-Fi has become much more heterogeneous than it was in the early days of 802.11x, 802.11n networks must accommodate a much wider range of device types; many of the standard?s optional-requirement portions reflect that range. New requirements from consumer-electronics companies, such as video applications, or from the handset market, in which manufacturers are interested in power savings and better coverage, have contributed to the long, drawn-out IEEE process, as well as to the standard?s complications, says Frank Hanzlik, managing director of the WFA. "There are a lot more people to please, so the compromise process has been more complex," he says.

But now that WLAN capability has penetrated the consumer and communications-device markets and is increasingly embedded into DSL (digital-subscriber-line) and cable modems, as well as into Apple TV, the markets are bigger, and the stakes are much higher, increasing motivation and helping to drive resolution of those conflicts. As a result, 802.11n Draft 2.0 has turned into more of a framework than a standard, says Craig Mathias, principal of the Farpoint Group. How difficult it will be for engineers to navigate that framework remains to be seen.