Research Report

802.11n WLAN architecture strategies: The 2.4 vs. 5 ghz. band debate

802.11n technology has brought unprecedented speeds to wireless LANs (WLANs), but capacity isn't the sole answer to optimal network performance. Deploying innovative 802.11n WLAN architecture and enabling automatic provisioning of multiple channels can be just as crucial in serving the growing number of clients and applications on the network. The Farpoint Group examined the importance of innovative 802.11n WLAN architecture and band provisioning by testing Cisco BandSelect, a feature on the company's wireless controllers that ensures clients are moved to 5 ghz band when possible. Specifically, the tests look at speed, the simultaneous operation of .11n and .11g in the same channel and the differences in function in the 2.4 and 5 ghz bands particularly with the use of 40 mhz. channels.

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Innovative WLAN architecture

With the approval this month of the final 802.11n standard, many have assumed that any remaining questions with respect to wireless LAN performance have been consequently settled. After all, 802.11n, in the form of products approved under the 2007 Draft Specification from the Wi-Fi Alliance, has been available for some time. Many of these products offer raw performance of 300 Mbps, and products with 450 and 600 Mbps capabilities are also available. It is no longer unusual to see realized (Layer 7) single-client performance well in excess of 150 Mbps, and, thanks to a corresponding improvement in overall system capacity enabled by 802.11n and, importantly, architectural innovations implemented by WLAN system vendors, .11n is expected to be broadly influential across essentially all application areas over the next few years.

Of course, .11n cannot reach the magic 1 Gbps level, but, while we do not expect these activities to result in a replacement for 802.11n, the IEEE 802.11 organization now has two additional task groups (.11ac and .11ad) looking into this level of performance and beyond. One might regardless therefore be tempted to make the statement that brute force has once again obviated the need for more sophisticated approaches to improving the throughput and, even more importantly, again, the capacity of wireless-LAN networks, but one should give a bit of pause before proceeding down that path -- a path that Farpoint Group believes is, in fact, dead wrong.

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And the reasons for this are less than subtle. To begin, the demands on networks only grow over time. This demand materializes in the form of an ever-increasing number of clients, with corresponding ever-growing application requirements, and not just for throughput, but also with respect to time-boundedness, responsiveness, and network-wide capacity. While the throughput embodied in 802.11n is most welcome, to be sure, we would argue that such alone is insufficient for enterprise-class performance -- proper deployment, aided by architectural innovations from WLAN system vendors, is of at least equal importance. And, finally, keep in mind that access to any given 802.11 channel is serialized and that contention is almost always a factor in realized performance. It therefore behooves us to make the best use of the scare resource that the airwaves always are, with significant burden falling here to system-level architectural approaches and innovations. Brute force alone is thus no solution at all.

This challenge thus introduces another dimension to explore, the subject of this Farpoint Group Tech Note. Specifically, we set out to examine the importance of wireless-LAN system architecture in provisioning optimal solutions based on 802.11n. It is, however, very difficult to examine the benefits of a given architectural strategy directly, because such is complicated by the specifics of a given implementation. We therefore decided to run a few tests on a particular (and very popular) implementation to evaluate a specific architectural feature -- in this case, Cisco's BandSelect capability....

 Read the rest of this paper on innovative WLAN architecture and the 2.4 vs. 5 ghz band debate.

 

About the author:
Craig J. Mathias is a principal with Farpoint Group, a wireless and mobile advisory firm based in Ashland, Mass. The company works with manufacturers, network operators, enterprises, and the financial community in technology assessment and analysis, strategy development, product specification and design, product marketing, program management, education and training, and the integration of emerging technologies into new and existing business operations, across a broad range of markets and applications. Craig is an internationally recognized expert on wireless communications and mobile computing technologies and has published numerous technical and overview articles on a variety of topics.

This was first published in October 2009

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