Purdue, USF test-drive Cisco CleanAir, uncover RF interference

New 802.11n radio chip monitors RF to show hidden interference

CleanAir gives Cisco WLAN administrators something they never had before: a real-time, remote view of RF interference anywhere in the network.

Asked if he was interested in being a beta test site for Cisco's newest Wi-Fi controller software and access points, Purdue's Scott Ksander clearly remembers his reaction. "Beta tests come and go, so there's a natural skepticism," he says. "I thought 'it might be interesting.' Then, when we got it, it really was interesting. We sat there saying, 'Good Lord, look at that.'"

"That" is what Cisco calls its CleanAir technology for mitigating interference. Essentially, Cisco migrated a chunk of the radio spectrum analysis code, Spectrum Expert, from its Cognio acquisition into a Cisco-designed radio chip for a new line of 802.11n access points, the Aironet 3500 series. The algorithms capture RF data, process it and pass it upstream to a Cisco wireless LAN controller and the Cisco Wireless Control System (WCS) for analysis and display.

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With this combination of silicon and software, network administrators can see a live view of the radio frequency noise on their network, identify specific interferers and, with other Cisco products, locate the source and automatically change channels to improve performance for end users linked to that access point.

Among Cisco's rivals, Ruckus Wireless promotes interference avoidance and mitigation based on its patented antenna design, which is made up of different components that can be reconfigured on the fly to "shape" an optimal RF signal for each wireless client, in response to inference.

Cisco's new chip lets the access point radio handle data traffic as usual, but also lets it monitor its assigned radio channel for other RF activity. Alternatively, the access point can be changed into a RF scanner only, able to monitor all channels on all its frequencies. Based in silicon, CleanAir provides very fast response without affecting the access point's radio performance or CPU cycles.

The combination gives Cisco WLAN administrators something they never had before: a real-time remote view of the RF interference anywhere in the network. Cisco integrated CleanAir technology with its existing Radio Resource Manager (RRM) application, so that once an interferer is found, the access point can reset automatically to a different, cleaner channel or change its radio power level. CleanAir data can also be processed by Cisco's Mobility Services Engine (MSE), which can pinpoint where the interfering radio can be found.

In the case of Purdue, the university got the beta code and a handful of the new 3500 series access points. It deployed some of them at the Union, a major congregating point for students and staff, where there's a diverse radio environment. To the astonishment of Ksander's team, CleanAir identified a previously unknown radio interferer: a Motorola Canopy radio, used for high-throughput wireless backhaul or similar applications.

"We really didn't expect that," says Ksander, who is the university's executive director of networks and security. "We're still looking for it." Without more access points and the other tools in the beta code, they haven't been able to track down the Canopy transmissions, which could be on campus near the Union or in a building off-campus.

Being able to "see" the previously unknown radio source was an eye-opener for Ksander and his staff. "The software very clearly identified it as a Motorola Canopy," he says. They'd never have realized it was even present unless an administrator had spent time with a conventional spectrum analyzer roaming the Union. "We have a sufficient staff, but we're not spending a lot of time looking for things that aren't gobbling at us," Ksander says.

"I can think of a dozen situations in the past 12 months where I would have killed to have this" kind of capability, he says.

Cisco executives say CleanAir can detect and distinguish at least two radio sources at the same time, something that rival, software-only products such as Motorola's AirDefense can't do. For example, it can show the relative impact of a wireless camera and a microwave oven on the wireless users. Further, because CleanAir is based in the access points, the data it collects can be correlated across several affected access points to pinpoint the interferer, instead of registering separate unique interferers with each access point.

The University of South Florida, at Tampa, is another beta site for Cisco CleanAir. The IT group set up three 3500 series access points, with the Version 7.0 system software loaded on a dedicated controller, and then they switched on a microwave oven.

"Within 30 seconds, the access points picked it up, and identified the source as a microwave oven, and showed which channels were being zapped," recalls Joe Rogers, a network administrator for the university. "We could always [in the past] pull data from the access point about the level of channel noise [interference]. But now, the software tells us 'this is what's causing it, here are the channels it's killing, here's the impact on the users, and here's its location.'"

The access points automatically shifted to different channels, which were clear of the oven's interference. Administrators are notified about what's happening by alerts that pop up on the controllers and on the WCS management application.

Rogers' excitement is apparent in his voice. Although USF isn't planning yet to upgrade the residence halls to the new 3500 series access points, the dorms represent a particularly challenging RF environment: microwaves, game controllers, cordless phones. "With CleanAir, when a user calls and says 'I'm getting kicked off the network,' I can go and troubleshoot the area [remotely] and see what's happening, as well as see the historical information, and location," he says.

One big annoyance has been wireless surveillance cameras popping up around campus on the 2.4GHz band. These are transmitting constantly, and their power and RF profiles completely destroy Wi-Fi connectivity nearby. Attempts to track them down manually, with a portable spectrum analyzer and directional antenna were time consuming and frustrating. CleanAir lets them pinpoint the camera's location in a fraction of the time, Rogers says.

In addition to this kind of live monitoring, CleanAir also lets an administrator switch any 3500 access point into a pure radio probe: scanning all channels on both 2.4- and 5-GHz bands. In this mode, which Cisco dubbed Spectrum Expert Connect, the access point can't be used for data traffic. The CleanAir code mimics the full function of the traditional laptop radio card for Cognio's Spectrum Expert application. A network administrator with Spectrum Expert on his laptop can connect directly or over a network to any 3500 access point to run RF scans and analysis.

CleanAir data shows up in a set of screens called "Air Quality" which can show the data graphically, for example as a floor plan layout, with each radio located and identified and zones color-coded to show the varying impacts of the interference.

Version 7.0 of the Cisco Unified Wireless Network software will integrate CleanAir with Wireless Control System, the 3300 Series Mobility Service Engine, and the full range of Cisco WLAN controllers. It's a free upgrade to qualified existing customers, starting in May.

The new Cisco Aironet 3500 Series access points with CleanAir technology will ship in May. Models vary based on the number of radios and use of internal or external antennas. Pricing ranges from $1,095 to $1,495.

The Cisco 5500 controller now doubles the number of access points it can support, to 500.

Cisco Aironet 1260 access points, for customers that don't need or want CleanAir, are being upgraded to deliver full 802.11n performance over standard 802.3af power-over-Ethernet. The 1260 will ship in May with prices starting at $995. Finally, Cisco will now offer a new limited lifetime warranty for Cisco Aironet 1140, 1250, 1260, and 3500 Series Access Points (both standalone and controller-based versions are covered).

John Cox covers wireless networking and mobile computing for Network World. Twitter: http://twitter.com/johnwcoxnww

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