Aruba Networks

Architectural Insights

Do You Really Want to be Handcuffed to a Single Channel?

Thinking about deploying a single-channel 802.11n Wireless LAN architecture? The Wireless LAN industry has produced some truly amazing innovations over the years. In just a short period of time, secure mobility in the enterprise has gone from "nice to have" to an integral part of your network infrastructure. We've seen a monumental increase in the number of wireless devices accessing the network, including laptops, smartphones, handheld devices, etc. But how do you separate true innovation from marketing hype?

Some wireless vendors tout the benefits of a single-channel wireless architecture, or "Virtual Cell", "Channel Blanket" and other cute terms. The benefits of this approach are clear, they say. The theory sounds something like this: if I run my entire network on a single channel, it will be easier to deploy, wireless clients will roam faster and I'll never have any interference or client roaming issues. Sounds good, right?

Think Again.

This is real-world RF we're talking about. We live and work in an increasingly dynamic environment, with new and increasing sources of RF interference sprouting up each and every day. Single channel is a simple theory, but one that limits your total network performance to...well, single channel...adding more access points one next to each other in order to increase coverage does not increase your total network capacity.

Let's say you have four access points on one floor all operating in a single channel. Assume 802.11bg legacy wireless LAN - instead of three 802.11bg channels, you will be limited to one. Performance difference? 25Mbps vs. 75Mbps with real world applications. Things get worse with 802.11n...MUCH worse. 802.11n actually allows clients to utilize the 5GHz band more than ever before. Instead of four 5GHz 40MHz and three 2.4GHz 20MHz channels, you will be limiting yourself to one of each. Performance difference? 225Mbps vs. 825Mbps - a whopping 600Mbps difference, 12 times the difference observed with 802.11bg legacy wireless LAN. Ouch.

So you have two choices. Adopt an architecture that is intelligent enough to tackle the dynamic RF challenges of the real world and provide with the capacity you need or build an enormous RF chamber around your facility to give yourself the perfectly controlled environment necessary for the single channel experiment to work. Forget "Virtual Cell", that sounds like a Virtual Prison.

Separating Facts from Marketing Hype

So we've established that none of us work or live or exist in a controlled laboratory environment. We have real issues to deal with every day. You might take the same basic route to work every day, but you certainly don't have the ability to pre-program that route and stick to it inch-by-inch. Things change, and you need to adapt. Traffic patterns, collisions, weather, road construction...these are all factors beyond your control that affect your commute patterns. But you are intelligent enough to recognize these circumstances and adjust your route in order to minimize the impact they have on your daily commute. Deploying a single channel architecture is analogous to stubbornly keeping your car in a particular lane on the highway, regardless of any unforeseen obstacles that might slow your progress. Why would you continue to stick behind that 1978 Mercedes turbo-diesel creeping along at 45 miles per hour spewing black death smoke when you have four or five other lanes from which to choose? Doesn't make much sense.

Why would you expect that your mission-critical wireless infrastructure would be any different? Your RF environment changes every day, every hour, every minute. Take a "stay the course" strategy with a single-channel architecture, and you'll soon find yourself in a serious RF quagmire. This is simple environmental physics we're talking about. No software, no architecture, can change the fundamental physics. Intelligent RF software, however, can adapt to the constant change and deliver the most optimal RF performance possible, no matter the obstacles thrown in its way.

Aruba's Adaptive Radio Management (ARM) is, as its name clearly indicates, an intelligent RF solution that continually adapts to the ever-changing environment. ARM allows mixed 802.11a/b/g/n client types to interoperate at the highest performance levels, RF airtime to be allocated fairly. Even if all access points in an Aruba WLAN operate in the same channel, how close the access points might be or what their power level might be, ARM mitigates the co-channel interference. ARM ensures low-latency roaming, consistently high performance, and maximum client compatibility in a multi-channel environment. Unlike proprietary single-channel architectures, ARM is designed to enable maximum efficiency and performance across the access points (AP) deployed without compromising interference mitigation, scalability, or interoperability - common problems of single-channel architectures.

Wireless LAN RF Management	Aruba ARM	Single Channel
Uses same RF Management Architecture for 802.11a/b/g and 802.11n	YES	NO
Supports 802.11a/b/g and 802.11n access points in the same WLAN	YES	NO
Increases total network coapacity as more access points are added to the WLAN in an effort to increase RF coverage	YES	NO
Adapts to noise and neighbor 802.11 interference	YES	NO
Assigns RF channels to access points automatically	YES	NO
Manages co-channel interference among access points that are on the same channel at any distance and power level	YES	MUST
DFS certified enabling 14 additional 5 GHz 20 MHz channels	YES	NO
Enables fast roaming across access points within the same WLAN controller	YES	YES
Enables fast roaming across VLANs (i.e. L3 roaming)	YES	NO
Enables high performance video multicast distribution	YES	Single Channel
Can be turned on with Polycom / Spectralink wireless handsets	YES	NO
Offers location tracking, live RF heatmaps, and wireless IPS	YES	OEM Partner
Steers dual-band clients to higher performance 5 GHz band	YES	NO

Still thinking about deploying a single channel architecture for your wireless needs? Think Again.