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Wi-Fi Eagle Monitors 802.11 Performance

Nuts About Net's Wi-Fi Eagle is a 802.11 wireless spectrum analyzer that determines how much bandwidth is available on the 802.11 channels by actively probing the airwaves. The idea is to provide a picture of the the airspace as a 802.11 device sees it, rather than inferring, or letting the user infer, with what Wi-Fi performance will be based on single-to-noise ratios, transmission power, Beacon Quality and other metrics spectrum analyzers use. The product comes in two models: an 802.11 a/b/g that analyzes the 2.4 Ghz spectrum, and a dual mode model that also probes the 5 Ghz spectrum. The probe is USB 2.0 NIC with an external antenna and the analyzer software. Listed at $249.95, Wi-Fi Eagle provides a snapshot in time of the air space.

Wi-Fi Eagle is a relatively simple 802.11 analyzer compared to other products like Cisco's Spectrum Expert, which attempts to name the source of interference such as 2.4 Ghz phones, Bluetooth, or microwave ovens. This is useful for tracking down pernicious interference. Wireless packet analyzers like Wild Packets OmniPeek and Wireshark can capture 802.11 frames for network analysis and decode and also offer DbM and SnR analysis. Airmagnet's Wi-Fi Analyzer and Spectrum Analyzer products have advanced tools such as packet capture, interfering device identification, interactive testing, and guidance on Wi-fi deployment and solutions. Wi-Fi Eagle doesn't have these advanced features; its aim is to provide an intuitive measure of Wi-Fi throughput.

Wi-Fi Eagle acts like a 802.11 NIC that is associated with an AP. The product continually hops through channels sequentially, attempting to transmit frames over the air. The number of successful transmissions determines the maximal throughput for each channel that a Wi-Fi device could expect to achieve. For example, if two access points occupy channel 6, they will co-cooperatively moderate access to the airwaves so that no single AP dominates the air, which is how 802.11 is supposed to work. However, if two access points are in overlapping channels, such as Channels 6 and 7, they will see the other channel transmission as interference. The ability to transmit frames is an indirect measurement of interference as viewed by an 802.11 device.

wifi-timecourse.jpgWi-Fi Eagle presents the airwaves through a series of charts based on channels or access points. The various channel charts, for instance, show the similar information in different views. The Timecourse Channel view shows the maximum throughput percentage per channel over time, which is good for seeing how the maximum throughput changes in near real time per channel.

You can highlight one of the channels in the current chart to bold the line for easy viewing. The Average/Standard Deviation chart shows the average throughput and standard deviation, which you can use to determine average throughput. This may be a better indicator of longterm performance than the Time Course chart, assuming the wider the standard deviation, the bigger the range of maximum throughput while the narrower the standard deviation, the more consistent performance will be.

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