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Microwaves ruin Wi-Fi networks

New device aims to reduce interference

Cisco Systems this week focused on reducing the radio frequency noise in Wi-Fi networks and announced it has teamed up with Cognio, which sells wireless LAN spectrum-analysis gear.

Cisco plans to sell Cognio's Spectrum Expert with its own Wireless Control System. Spectrum Expert runs on a laptop with an antenna connected to a laptop card and starts at US$3,995, according to Cognio officials.

"With wireless LANs more pervasive, RF interference becomes more important than ever," said Ben Gibson, director of mobility solutions marketing at Cisco.

RF interference can come from a nearby Wi-Fi network, wireless telephones, Bluetooth wireless transmissions, microwave ovens and even flourescent lights, according to Wi-Fi users and analysts.

The Spectrum Expert can give an IT manager a readout of radio waves in a sector of a Wi-Fi network and provide a fingerprint of an interfering device, said Jeffrey White, executive vice president of Cognio.

Kerry Kulp, a wireless systems consultant at Cumulus Consulting Group has used Cognio's product many times to help spot interference in business Wi-Fi networks that in some cases completely eliminated Wi-Fi capability.

Lost signals

In one example, a pharmaceutical manufacturing facility in Connecticut could not transmit over a Wi-Fi network with more than 30 access points, Kulp said. When Kulp consulted there a year ago, spectrum analysis revealed the outage was caused by three small ultraviolet lights used to dry an adhesive that was part of a drug-making process. The dryers used microwaves, which obliterated the Wi-Fi signal, he said.

In a more recent example, a warehouse in Chicago traced intermittent outages to an outside source from a nearby building, Kulp said. While the source of RF interference has not been eliminated, the Wi-Fi network was adjusted to prevent the interference from causing problems, he said.

"IT managers are surprised by what causes the interference sometimes," Kulp said. "When we ask if their Wi-Fi is down outside break rooms where they might be running old microwave ovens, they look at us funny. There's more RF noise out there than people realize."

Kulp said he has tried spectrum-analysis products from other vendors but found Cognio's the easiest to use because it is contained within a standard laptop; other products require a separate box. The partnership with Cisco gives Cognio's product "instant credibility that Cognio would not have had otherwise," he said.

Cisco's partnership with Cognio comes as Wi-Fi is becoming more commonplace and IT shops strive to make Wi-Fi networks more efficient, said Philip Redman, an analyst at Gartner. "Analyzing coverage can reduce interference, increase capability for voice over wireless and reduce costs."

"Many Wi-Fi customers are finding they have overbuilt certain areas and haven't put in an efficient network," Redman said.

For more information on wireless networks, our sister site Techworld has a comprehensive wireless network resource page.


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