802.11n: Wireless Rookies Need Not Apply

New standard is complex, and even with careful planning, it may not pan out for everyone.

December 11, 2008

6 Min Read
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Make no mistake: even in draft form, 802.11n is a game-changer.

The fledgling standard promises better-quality cells that benefit from multiple in, multiple out (MIMO) antenna arrays and throughputs that are, at a minimum, on par with 11a and 11g at 54 Mbps but more stable. And at best, they're amazing, with triple-digit data rates.

But when analysis and troubleshooting are needed, 802.11n's advanced features can greatly slow problem resolution.

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Whether you plan on squeezing as much bandwidth as possible out of 802.11n networks or you need to provide connectivity to as many users as possible in an 11n setting, you'll need to thoroughly plan and evaluate your new wireless environments. And without the right monitoring tools, you're sunk.

To succeed in an 802.11n world, wireless administrators need to do some homework. 802.11n brings a whole new vocabulary and new concepts to be mastered.

First, admins need to learn what makes 802.11n tick, then answer these questions: Should the organization maximize its network efficiency, with throughput speeds that are dizzying but with certain clients blocked? Or is compatibility mode more appropriate, accommodating more legacy users but at lower overall cell speeds? What about the special options, like frame aggregation and short guard intervals? And how many spatial streams (the number of receivers and transmitters) can you actually use, given the makeup of your wireless clients and switching infrastructure?

After determining which configuration option will best serve their environments, 802.11n wireless network admins need to assess the analysis tools they have on hand and figure out which ones will play well with this unique wireless technology and what emerging support tools they'll need to purchase.



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Successful rollouts will no doubt take budget dollars away from other IT projects, although some environments will find their infrastructure is 802.11n-ready when it comes to switches, wireless controllers, and power. In these cases, 802.11n will come much cheaper than for organizations that need an infrastructure upgrade to get ready for it. But even if companies face substantial up-front costs to revamp their infrastructure, the advantages of high-speed wireless--greater mobility and portability among them--will make its adoption an imperative.

Along with an overall better radio environment, 802.11n is good news for the applications that run on it. For example, wireless streaming video and voice over a wireless LAN should perform more reliably and predictably with 802.11n. And although ratification of the final standard is still possibly a year away, vendors such as AirMagnet, Berkeley Varitronics Systems, and Ekahau already are offering 802.11n-capable support tools to ease implementation as well as transition.


THE PROMISE802.11n, with theoretical data rates to 600 Mbps, can deliver faster cells with better signal quality and has the potential to decrease overall infrastructure costs and enable new applications.THE PLAYERSMany spectrum analysis tools developed for 802.11a/g will work with 802.11n. Bigger vendors, including AirMagnet, Berkeley Varitronics, Cisco, and Fluke Networks--along with smaller players like AirSleuth and MetaGeek--provide tools that characterize the spectrum in which 11n operates. However, packet analysis will require a new breed of tools. AirMagnet, WildPackets, and Cace Technologies (AirPcap) are players in the 802.11n packet analysis market.THE PROSPECTSThose blistering data rates don't come easy. And 802.11n shares spectrum with legacy protocols. To squeeze the most out of 802.11n wireless environments, a well-thought-out game plan and a decent toolkit are required. Understanding 802.11n's nuances will be half the support battle, and knowing what tool to use for a specific problem will be the other half.

Before 11n networks can be installed (or current 11a/g networks can be upgraded to 11n), organizations will need to survey the spaces to be covered or resurvey areas where current WLANs live. This is because 802.11n works in the same frequency slices (2.4 and 5 GHz) as 802.11a/g networks.

For most of us, the site survey has become an exercise in merging the virtual with the physical, using a modeling tool like AirMagnet Surveyor or Ekahau Site Survey to virtually plan WLANs, followed by feet-on-the-ground verification.

Post-installation support means monitoring the airspace to find competing or offending signals and packet analysis with commercial or open source tools to reveal connectivity or application issues.

These basic premises don't change with 802.11n, but the underlying mechanics can take on a whole new feel, depending on which of the many options and operational modes are invoked.

802.11a/g spectrum analyzer tools from AirMagnet, Cisco, Fluke Networks, MetaGeek, and others will still find noise and interference. It's logical to expect that analyzers will eventually detect 802.11n devices along with everything they can classify today.

For survey products, 802.11n really raises the bar. Cells tend to have increased data rates at farther distances, so you'll need to relearn the fundamentals of survey procedures. The new standard can use multiple channel bonding that doubles spectrum width to achieve higher data rates, so survey tool providers need to accommodate the new options in their various allowed combinations for 11n cells. MIMO antennas in various configurations can drastically alter a given cell shape and size. Again, survey and modeling tools must address all 802.11n variables to be as effective as possible.

In addition, because one goal of the survey process is to predict and ensure (as much as possible) minimum data rates, 11n-oriented survey products must deliver graphical "what-if" reporting abilities that reflect hundreds of potential scenarios for each access point that's being considered.

Wireless packet analysis is already complex in 11a/g networks, and it gets even more so with 11n. Because of MIMO, the location of the client becomes critical in attempting to get an accurate read on the traffic. Ideally, the capture happens at one or both endpoints. Although the wireless payload will remain the same in 11a/g and 802.11n networks, traffic headers and how traffic is fragmented may differ, which may be a concern to those who like to go deep on packet analysis.

802.11n's channel bonding, different "guard intervals" that manipulate interframe spacing, frame aggregation options, and the number of antennas, will redefine what wireless traffic looks like. Analysis tools must support the full suite of options in the draft standard in order to be effective when the final version is approved.

For WLAN administrators who've been in the game for a while, 802.11n brings a whole new bag of intricacies to be reconciled, both before and after installation. Some existing tools--mainly spectrum analyzers--are still relevant in their current incarnations. But for packet analysis and survey work, make sure your tools are tuned to 802.11n, or you'll be missing a lot.

Evolution Of 802.11n





Work begins on 802.11n standard

Draft 2 of 802.11n completed; Wi-Fi Alliance starts interoperability testing

Finalization of Draft 7 of 802.11n base standard and some features

Additional options for 802.11n to be finalized next year; ratification expected in early 2010

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