Strange Xbox signal suspected of jamming wireless LANs

Microsoft's popular Xbox 360 game console can create a strong and strange signal on wireless LANs, according to IT staff at Morrisville State College.

It's not clear whether the signal disrupts the college's WLAN access points or students' wireless notebooks. There is some anecdotal evidence, however, that it at least affects other radios in the same 2.4GHz band.

Morrisville IT staff typically use Bluetooth headsets, which run in the 2.4GHz band, with their cell phones when they troubleshoot problems on the spacious campus. "We had problems syncing our headsets to our phone where this signal was strong," says Matt Barber, the college's network administrator. A phone user had to physically touch the headset to the cell phone to make the initial connection, he says.

There may be effects on the WLAN that the equipment itself, from Meru Networks, is circumventing, according to Barber. Part of Meru's WLAN architecture employs software that gives the access points more control over wireless-client transmission behavior than does the software of some of Meru's rivals. An access point near a radiating Xbox may be compensating for interference by in effect guiding a wireless laptop to send and receive when open spectrum is available, essentially dodging around the Xbox signal.

Working with Meru, the small IT staff is planning to test soon the effect of multiple Xbox consoles in a dorm with a large number of active notebook clients.

Network World has asked Microsoft to comment on the Xbox signal phenomenon, but the company was not able to reply before this story was posted. We'll update this report as soon Microsoft provides information.

The latest version of the Xbox, the Xbox 360 Elite, went on sale earlier this year with a 120G-byte hard disk and a high-definition video interface.

Morrisville is a small college in rural New York state, taking its name from a nearby town. In summer 2007, the college deployed a campuswide 802.11a/b/g WLAN based on equipment from Meru.. The plan was to replace those access points with Meru's new, two-radio devices that added support for Draft 2 of 802.11n, the IEEE standard that boosts throughput from 22M to 25Mbps to at least 150M to180Mbps. That replacement was just completed, creating the first large-scale deployment.

During the fall, Morrisville IT staff, working with Meru engineers and IBM, the network integrator, detected an unusual signal in the 2.4GHz band. "We wanted to look at the [radio frequency] environment in our dorms," Barber says. "We always thought we'd run into some strange stuff [there] in the 2.4 range."

The signal was discovered using Cognio Spectrum Expert, from Cognio (recently bought by Cisco). Spectrum Expert is RF-analysis software packaged with a WLAN adapter card that slots into any laptop PC. (See our April 2007 Clear Choice Test of four WLAN protocol analyzers.) Among other capabilities, Spectrum Expert identifies sources of radio energy in the 2.4GHz and 5GHz WLAN bands, and identifies the cause, such as a brand of access point or a microwave oven.