Aruba extends radio management to wireless LAN clients

Aruba Networks has unveiled a new release of software that’s designed to improve wireless LAN throughput and reliability.

The 2.0 version its Adaptive Radio Management software adds features that automatically shift WLAN clients to different channels or frequencies for better performance, schedule equal client access, and reduce co-channel interference among access points. Overall, these automated adjustments can boost throughput for individual clients, and increase the network’s overall capacity, Aruba says.

The original ARM software was designed to let network managers control access points, by such actions as selecting channels and changing radio power levels. The new release tries to fill in a major gap in the current 802.11 WLAN standard: extending controls to the 802.11 clients, and coordinating their requirements, behavior and activities with that of the access point infrastructure.

Through the Aruba WLAN controller, with data supplied by clients and access points, ARM 2.0 offers four major changes for clients. None of the changes require putting code on WLAN clients or configuring them in any way. (Compare WLAN management products.)

The Aruba WLAN now can move 2.4GHz clients to a specific access point with available bandwidth on a given radio frequency channel. Clients that might have  flocked to a particular access point, over-subscribing it and reducing performance, will get assigned to less crowded bandwidth.

The WLAN controller can also switch 802.11a and 11n clients from the 2.4GHz band to the 5GHz band, and without the presence of 11b and 11g clients, they can associate at higher data rates.

The controller also can use a new timing method to schedule fair access for all clients on all bands, either giving them equal access or giving 11a and 11n clients longer access. That’s important because an uncontrolled WLAN client can hog the connection to the access point. With what Aruba calls airtime fairness, “no single client is going to dominate the spectrum,” says Michael Tennefoss, head of strategic marketing for Aruba.

In addition, the controller can in effect shut down selected access points (by switching them over to just monitoring the radio spectrum) if there is extra capacity in that channel. The goal is to reduce the number of nearby radio transceivers, and therefore reduce the chance of interference.

“Wireless clients are capable of sharing more information [about their state and behavior] if you ask them,” Tennefoss says. “We extract this information, build a map of all the [wireless] devices present, and then optimize the network and optimize the performance levels of the client.”

Wireless consultant Craig Mathias, principal of wireless consultancy Farpoint Group, was invited to a test of the ARM 2.0 software release at a University of Washington lecture hall in Seattle. He prepared a whitepaper on the results, “Advances in Wireless Infrastructure Control.”

The test involved an Aruba 3600 Multi-Service Mobility Controller, with four Aruba AP 125 802.11n access points, serving about 100 mainly Windows notebook PCs. Mathias noted that the evaluation was not a true benchmark test; the university network was not being used by students and it had been designed to minimize external radio interference.

But with those caveats, he witnessed consistent improvements in individual client performance and aggregate network performance for each of the four new ARM features. For example, one test looked at the impact on four clients (11b and 11g in the 2.4 band, and 11a and 11n in the 5GHz band), of automatically shifting the 11n client to the 5.4 band.

Performance for the 11n notebook jumped 216%, though it came at the expense of the 11a client on the same band. For the 11b and 11g notebooks still on the 2.4 band, performance also jumped, 108% and 162% respectively. With this “band steering,” the WLAN’s aggregate throughput improved by 70%, from a total of just over 45Mbps to just under 80Mbps.

In his report, Mathias concluded, “We expect that the benefits noted above will carry over [from an educational setting] to any densely deployed [infrastructure and users] environment, which we believe will clearly become the norm as users migrate from wired connection to wireless [especially 802.11n] installations.”

The Adaptive Radio Management 2.0 software is undergoing field tests and will ship in the fourth calendar quarter 2008 as part of the Aruba controller software. Aruba customers under maintenance contracts will receive it as a standard software upgrade.

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