Spectrum Expert Digs Deep for Problems

Review: Cognio's new tool goes beyond ordinary analyzers by working at the network layer.

Cognios Spectrum Expert for WiFi 2.0 provides in-depth insight into the radio spectra that are home to Wi-Fi technology, allowing administrators to identify, evaluate and locate potential sources of interference that could hamper wireless LAN deployments.

Since the 2.4GHz and 5GHz spectra are both unlicensed, many non-Wi-Fi devices operate at those frequencies, often using different modulation schemes that can play hit and run with a wireless network. Too many transmitters can lead to outages, service interruptions or signal degradations that will become all the more noticeable as companies move to leverage WLANs for real-time communications, such as voice over wireless or video streaming.

Spectrum Expert for WiFi 2.0, which is available now for $3,995, helps administrators address this problem by providing insight into the physical layer of wireless networking—a capability not present in ordinary Wi-Fi analyzers.

/zimages/1/28571.gifClick here to read a review of site survey tool for wireless networks AirMagnet Survey Pro 3.0.

Spectrum analysis cannot be performed with a regular Wi-Fi adapter, so, during tests, eWeek Labs needed instead a special CardBus adapter that Cognio provides with Spectrum Expert. This adapter comes with an integrated antenna as well as an optional external antenna that plugs into the end of the adapter for higher gain.

The Swept Spectrogram graph, a color-coded chart displaying the entire band (the 2.4GHz and 5GHz spectrums are displayed on different tabs), is the most visually compelling chart in Spectrum Expert, as it shows which channels show the strongest signals over time. In this view (see screen), its simple to identify which channels are most crowded and for how long the signals have been detected.

Meanwhile, the Real Time FFT (fast Fourier transform) chart shows currently detected RF (radio frequency) power as a function of frequency. In the default view, the Real Time FFT plot shows the maximum current power detected, but we could also add traces for average and MaxHold (a more static representation that shows the maximum level seen throughout the session).

With all three traces enabled, we were able to glean the same information we did with the spectrum analysis feature in AirMagnets Survey Pro 3.0, but without the location tracking.

Other graphs showed the FFT duty cycle and the number of devices detected in each channel, broken out by type. Users should remember that any RF device will be heard across multiple channels and will therefore show up in multiple columns in the latter depiction.

During some lunch-hour testing of the 2.4GHz band near the Labs, Spectrum Expert identified a nearby microwave oven and a pair of Bluetooth devices, as well as a number of access points. From the dashboard, a right click on one of the Bluetooth devices showed the channels affected by the device, as well as the devices signal power (measured in dBm), duty cycle and center frequency.

The Bluetooth devices—a cell phone and headset located quite close to the testbed—proved particularly noisy at close range, affecting all channels on the 802.11b/g spectrum at fairly strong signal strength. Companies will find the Bluetooth conundrum particularly vexing as the promised dexterity afforded by cordless desktops and headsets directly competes with productivity gains offered by wireless networks.

From the Active Devices pane, we could also drill down into each detected access point to see its MAC (media access control) address, network name, WEP (Wired Equivalent Privacy) status and supported data rates. Spectrum Expert 3.0 actually culls information from two sources to provide this WLAN-specific data.

Some 802.11 information was gathered via a regular Wi-Fi adapter in our test system (in this case, an integrated Dell-branded 802.11g adapter based on an Atheros chip set). This data was combined with RF and channel-specific information gathered by the CardBus adapter Cognio provides, offering a more complete view of how a WLAN device affects the spectrum.

Cognios technology is also available through OEM partners. At a cursory glance, we could not tell Spectrum Analyzer for WiFi 2.0 apart from AirMagnets Spectrum Analyzer 2.0, which integrates the Cognio technology—save for a slight font difference. Given the lack of distinction between the products, customers already invested in AirMagnets technology should probably opt for the AirMagnet-branded solution for the promise of current and future integration with existing platforms.

Technical Analyst Andrew Garcia can be reached at andrew_garcia@ziffdavis.com.

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