A short guide to Wi-Fi network testers

 

Access to the Internet via Wi-Fi (802.11) is now ubiquitous, so much so that a cartoon recently showed Maslov’s hierarchy of basic human needs with Wi-Fi being more important than our physiological requirements of food and shelter. Joking aside, the prevalence of multiple Wi-Fi networks and other signals in the 2.4GHz and 5GHz bands almost everywhere we go has driven the need for easy-to-use Wi-Fi test equipment that can quickly establish any connectivity problems that exist and enable network technicians to optimise these networks.

Fluke Networks leads the offerings for Wi-Fi test equipment, with a full range of products catering for different needs. At the entry level end of the scale is the simple-to-use AirMagnet AirMedic, which is essentially a spectrum analyser housed in a USB dongle. Connect it to any computer to see the RF activity in any of the bands commonly used for Wi-Fi, including 2.4GHz and 5 GHz. This should enable visibility of any sources of interference present, in order to fix unreliable or slow connections.

Fluke Networks’s AirMagnet AirMedic is a spectrum analyser in a USB
dongle for diagnosing Wi-Fi network problems.

The interface for AirMedic is just one screen which can be configured to show all the information required for whatever diagnostic technique is being used. Bands can be scanned individually, or information from multiple bands can be shown. The network technician can select which graphs are shown, but the most frequently used chart is the Real Time FFT, which shows the maximum, current and average levels of RF energy present in that frequency band, in real time. A spectrum density chart may also be helpful as this shows which signals have been present a lot during that particular session, making it easier to spot intermittent interfering signals which may only be appearing briefly every few seconds and are therefore tricky to spot in the Real Time FFT.

AirMedic provides data on how much RF energy is present in each channel (left) and graphs such as Real Time FFT and Spectrum Density (right).

Another tool for identifying intermittent sources of interference is the spectrogram, which adds colour coded intensity levels with each sweep of the spectrum analyser. Other charts available in AirMedic are channel power, which shows maximum and average power in each channel, plus a channel duty cycle graph, showing how often the interfering signal is present in that channel.

The software can also list any Wi-Fi access points (APs) present, with their MAC addresses and SSIDs, alongside their signal strength and security settings. Signal strength in each channel can be shown by access point, and a special channel occupancy chart shows which APs are operating in which channel and at what centre frequency.

AirMedic also allows recording of captured data for future analysis, especially useful when investigating Layer 1 denial of service attacks. The saved files may also be shared to facilitate collaborative troubleshooting efforts.

One step up from the AirMedic is the AirMagnet Spectrum XT, intended for professional network diagnostic use.  It offers the same easy to use interface as the AirMedic, but with enhanced features. For example, it can classify sources of interference into likely categories such as Bluetooth devices, cordless phones and baby monitors, microwave ovens, wireless game controllers or even RF jammers. It can also help find the location of these culprit devices, operating like a ‘Geiger counter’ by beeping louder as the user gets closer to the source of the interference.

Fluke Networks’s AirMagnet Spectrum XT is a higher end version of AirMedic
with enhanced features for professional use.

Over and above the RF graphs provided by the AirMedic, it can also show an event spectrogram, as well as trending charts of channel duty cycle and interference power. Additional data about the APs on the network may also be provided, such as channel utilisation and signal to noise ratio, fastest APs, and which APs are most active. It can also show device IDs and names of interfering Bluetooth sources detected.

Spectrum XT comes with a function for physically locating any sources of interference.

If no computer is available, or for applications where portability is essential, Fluke Networks also offers a handheld integrated Wi-Fi network tester called AirCheck. AirCheck weighs only 0.4kg, so it’s easy to carry, and its battery life is up to 5.5 hours. It’s also foolproof to use – pressing the AutoTest button provides a quick pass or fail verdict on the Wi-Fi environment in that location. AutoTest checks for Wi-Fi and non-Wi-Fi devices using each channel and verifies coverage, interference and security. It can identify any rogue access points present as well as any ad-hoc networks which may prove to be a security risk. It also helps the technician to find any source of interference as it comes with similar locate functions to the Spectrum XT. More experienced technicians can then delve deeper into the data and look at signal to noise ratios for each AP, as well as channel usage data and a variety of other diagnostic information.

 

Fluke Networks’s AirCheck is a handheld meter for tracking down any sources
of interference or any unsecured ad-hoc networks.