How 802.11n Changes the Game

For wireless analysis and planning tools, extending support to include 802.11n is not just a matter of tossing an N-enabled sensor into an overlay network or of supporting an N-enabled client driver for a portable analyzer. 802.11n introduces a number of profound technology changes to the WLAN standard that will require significant product overhauls.

As Chris Roeckl, AirMagnet’s vice president of marketing, explained it: “There is a huge delta between how the current technologies work and what will happen with 802.11n. 802.11n changes virtually all the rules. Our job is to solve that problem for people and make it simple to implement this new technology.”

The changes that 802.11n brings are reflected in both the PHY (physical) and MAC (media access control) layers, and while these changes combine to dramatically boost overall throughput performance of an 802.11n wireless network, they also put a kink in the planning and analysis schemes that these products employ.

For an excellent overview of the technology changes that 802.11n brings, check out the AirMagnet Web-inar, “802.11n Primer: What You Need to Know,” which is available at airmagnet.com/news/webinars/archived (registration required).

While there are numerous enhancements in 802.11n when compared with legacy standards, there are a handful of new features that most directly impact analysis tools. These new features include: the use of MIMO (multiple input, multiple output); the use of wide (40MHz) channels that boost the number of possible subcarriers and modulation rates; the introduction of beamforming for extending range and reducing interference and the use of frame aggregation techniques that maximize the amount of data frames transmitted while simultaneously reducing the amount of over-the-air management traffic.

Good 802.11n analysis tools should provide insight into each of these characteristics to help administrators troubleshoot their speedy new wireless networks.

Analysis Tools

MIMO, a technology that leverages multipath reflection to simultaneously send different data over multiple paths, will necessitate a broad set of changes in analysis tools. For instance, access point placement will likely be different for 802.11n networks as opposed to legacy APs, as 802.11n devices may experience better behavior in places legacy devices struggled.

“We are discovering some of the assumptions we have for 802.11abg don’t apply to 11n,” said Manish Rai, Motorola’s director of product marketing for enterprise WLANs. “11n works really well in multipath-rich environments because of the MIMO technology. You get more reflections that actually improve performance.”

In particular, survey tools are going to need much more flexibility in their predictive capabilities to deal with the changes in the 802.11n PHY that come with MIMO. The tools will need to take into account antenna configurations, for instance, allowing the administrator to simulate the effects of an 802.11n AP running with 2-by-2 (2 transmit with 2 receive), 2-by-3 or 3-by-3 modes.

Likewise, location-tracking analysis systems will require extensive changes to their predictive placement algorithms because multipath propagation will provide conflicting information to sensors on where a device may be.