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Performing Spectrum Analysis

Get the details about how Chanalyzer works, learn how to interpret displayed data, and review the best practices for using Chanalyzer when you're on-site.

How Chanalyzer Works

Chanalyzer combines data from Wi-Spy and your computer's wireless network adapter into a series of interactive graphs and charts. While the Wi-Spy will show you all RF activity, it is not a Wi-Fi adapter. It can "hear" transmissions from wireless devices but it does not decipher which devices are transmitting like a network adapter would. This is similar to hearing a conversation in another language -- you know people are talking, but you don't know what they're saying. Chanalyzer is also capable of displaying data from a Cisco CleanAir-enabled access point. Wi-Spy doesn't distinguish between Wi-Fi and non-Wi-Fi sources, so Chanalyzer utilizes your Wi-Fi adapter to display information about nearby access points including their channel, RSSI, and security type. If your computer is connected to a Wi-Fi network, your Wi-Spy may display all of your Wi-Fi adapter's transmissions. If you are in an extremely saturated environment, it might be beneficial to turn off your Wi-Fi adapter completely.

Data Display

Waterfall Navigation

The moment you connect your Wi-Spy to Chanalyzer, Chanalyzer begins to record, just like your television’s DVR. Using Waterfall Navigation, you can "rewind" your recording to the precise time interference occurred while current data is still being captured.The time frame selected in the waterfall controls the range of the data displayed in the Details and Overview Panes

Overview Pane

Chanalyzer’s Overview Pane graphically displays the data that Wi-Spy is currently collecting. In the toolbar above the pane, you will find different display options for Wi-Fi network overlays and interferers. The Density View displays the data in a range of colours from blue for infrequent transmissions, to red for constant utilization (and high risk of interference).

The Overview Pane also features a Waterfall View representing the amplitude history of your selected time frame.

Details Pane

The Details Pane is located below the Overview Pane. Here you will find a number of tabs with more in-depth information about your surrounding Wi-Fi networks and the spectrum congestion levels calculated for each Wi-Fi channel.

Of particular interest in the Details Pane is the Networks Table, which displays a list of all of the Wi-Fi access points within range of your current location. This table can be filtered to display only the network(s) belonging to you or your client. Keep in mind that Wi-Spy is unable to read Wi-Fi at the packet layer, so your computer needs a dedicated wireless network adapter in order to populate this table. If running Chanalyzer in a VM, a USB Wi-Fi adapter must be used to capture network data.

Learn more about the other tabs in the Chanalyzer User Guide.

Best Practices

Here are some suggestions that will help you get the most out of Chanalyzer:

  • Perform your survey during peak usage. When you're looking for interference issues your clients are experiencing, it's important to be there when the problem is most likely to happen. Spend more time in the areas where people have complained of connectivity issues.

 

  • Turn on every possibly-interfering device you see. By creating the "dirtiest" RF environment possible, you'll be able to better determine how interference affects your Wi-Fi networks. Be sure to check wireless cameras, security sensors, and badge readers to see if they change anything in your environment.

 

  • Let the waterfall guide you to noisy areas. If you see a continuous vertical line in either of Chanalyzer’s waterfall views, that's indicative of constant activity. You'll have to examine the signature shape in the Overview Pane to determine if this is regular Wi-Fi transmissions or non-Wi-Fi interference. No matter which it is, the closer you get to a transmitter, the more red you will start to see in the waterfall.

 

  • Adjust the time span to fit the spectrum event. When you select a time span (for example, a red area in the Waterfall Navigation pane), Chanalyzer adjusts the data it's displaying to only show what happened during the time you've chosen. When you keep your time span short, you allow old data to drop off from your view. This keeps the data you do see relevant to your current location in the recording.

 

  • Log your location using sessions. The Session Manager in Chanalyzer is a great way to keep track of where you were during your survey. For example, you can rename your session to "Office," and start a new session when you enter a different room. When you revisit your recording later for analysis, it will be much easier to narrow down possible interference sources when you know where you were when it showed up. By default, the session names reflect the band you're recording, but these can be changed on the fly. You can view any session in the list without disrupting your current recording.

 

  • When analyzing the 5 GHz band, use Chanalyzer’s UNII band presets for higher resolution. The 5 GHz band is much larger than the 2.4 GHz band, so it can be helpful to zoom in to a particular UNII band for more detail.

Save a .wsx File

After you've completed the survey of your area, you can save your recording in Chanalyzer's file format, .wsx. You should also consider documenting your findings with a spectrum report.