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Flagging Interference

July 24, 2008
by Kate Huvane
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Hospitals are leveraging technologies — and getting creative — to keep wireless networks free from interference

Fernando martinez

Fernando Martinez

When Fernando Martinez came to Broward Health (Fort Lauderdale, Fla.) as the new CTO in the fall of 2007, he had his work cut out for him. Martinez, who had previously served as CIO at Mercy Hospital in Miami, said his orders were simple at Broward: solve the wireless interference problems at the multi-facility, 716-bed health system.

The task may have sounded simple, but what lay ahead of Martinez was anything but. As soon as he began analyzing the wireless system, he found that the issues had previously been addressed by deploying more radios rather than tuning them.

“There was a lack of obsolescence in capacity planning where networking was concerned,” says Martinez. “It was kind of like poking-hole wireless diagnostics, which led to a proliferation of wireless devices and radios and that resulted in a lot of interference.”

The first step was to conduct a survey. But before that could even begin, Martinez and his staff had to transition from the earlier version of Cisco's (San Jose, Calif.) network to the current technology — the Cisco Spectrum Expert Wi-Fi — which integrates with Cisco's Unified Wireless Network to deliver spectrum intelligence for Wi-Fi networks. It could then be leveraged to troubleshoot sources of interference.

Once the architecture was in place, Martinez was able to run spectrum analysis. Not surprisingly, a great deal of noise was detected in the wireless space; so much, in fact, that he and his staff began to turn off radios in order to obtain a better read, according to Martinez. As soon as they were able to accurately identify the location and number of radios, they began turning off radios and powering down those that were left on. Martinez was then able to utilize more advanced tools to examine and measure activity by device and by channel to more effectively zero in on areas of interference.

According to John Collins, director of engineering compliance at the American Society for Healthcare Engineering (ASHE, Chicago), conducting spectrum surveys is essential to maintaining a healthy wireless network, particularly since outside devices such as laptops and Blackberries are regularly brought into hospitals by patients and visitors, where they can radiate information and take up space in the hospital airwaves.

“The devices by themselves don't really cause a problem; they're kind of low-level power things,” says Collins. “However, when all these devices come into hospitals, there is a noise level involved with that, and you may not know about it because it's electronic. But if you have a spectrum analyzer, you can see the basic noise level start to increase, and this eventually will cause problems, unless it's controlled,” he explains.

Once Martinez was able to identify the problems, he quickly devised and began testing a proposed solution. A number of devices at Broward were operating on 802.11B and 802.11G, which use the 2.4 GHz ISM (Industry Science and Medicine) frequency band, and offers just three non-overlapping channels. As a result, they are more likely to experience interference issues, he says. With that in mind, Martinez began to move a few devices, starting with the wireless carts, onto the 802.11A band, which operates with a frequency of 5 GHz or higher, and offers eight non-overlapping channels.

“Because clinical carts have access to the most sensitive or critical information, we chose those devices to pull to a different frequency, just from a workflow optimization point of view,” says Martinez. “It gave us a lot more flexibility to then deal with the remaining devices that were competing for 802.11 B/G traffic, so that worked out well.”

Martinez and his staff are looking to move more devices off of 802.11 B/G, which he says will allow “an opportunity to more tactfully design how channelization issues could be minimized. Part of what we're doing in the redesign process is collapsing in the other devices. Using the tools we have, we're able to architect them. We know where we have the capacity to integrate them and bring them in.”

The ultimate goal, he says, is to have one network to manage and monitor.

However, because Broward is part of a multihospital system, spectrum analysis needs to be performed at each individual facility. When fixing a problem as complicated as wireless interference, he says, CTOs and CIOs won't find a one-size-fits-all solution.

“A wireless survey for a facility is a wireless survey for that particular facility, not for the enterprise,” says Martinez. At Broward, “each one of the facilities has proven to have a uniqueness to the way it was cabled, the way it was built, and what devices existed that create interference. Your work is not done until you examine each facility independently.”

Tom kerwin

Tom Kerwin

Once that has been done, Martinez says, the IT staff can look for common threads. As the enterprise wireless network is designed, CTOs and CIOs can build on those commonalities and begin to architect, design, and engineer based on the one-offs from each facility.

Frequency hopping, one facility at a time

At Memorial Health System (Colorado Springs, Colo.), the IT team is looking to build off the success of a one-off experiment with frequency-hopping telemetry to create a new standard of best practices across the network.


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