Properly Documenting Interference with Report Builder

We take signal-to-noise seriously here at MetaGeek. In Wi-Fi a Signal to Noise Ratio represents the distance between the peak of the signal and the noise floor. It is a measurement of how quiet an environment is compared to how loud a transmitter is. Think about how loud you must talk in a noisy bar vs an office cubicle. Signal to Noise is what you care about vs what you don’t. We can apply this concept to Wi-Fi report generation too.

Reports in general can contain too much data. The recipient of a report is more likely to fully read a 5 page report than a 30 page report. Chanalyzer includes the functionality to drill down and highlight small events that may have occurred during the wireless site survey. After a long sight survey you may end up with hours of spectrum data spanning several sessions. Keep the recording but generate a report that summarizes the survey concisely.

Establishing a Baseline

Similar to a networking baseline, a spectrum baseline is essential to creating a starting point to measure radio noise levels in a wireless environment. A spectrum baseline is a snapshot of what normal activity looks like so comparisons can be made when new transmitters appear. A good baseline will help determine the actual intensity of future problems by means of comparison. Please remember these tips in creating a baseline:

  • Capture the wireless spectrum in the most common scenario possible. Try to perform the survey when all users are present and performing their daily tasks. If there are non-Wi-Fi devices like wireless headsets that are critical to the business make sure they are on.
  • Perform a wireless throughput test and add the achieved test results to the report. Test results help show a quantifiable impact a non-wi-fi transmitter may have on a WLAN. They also help describe performance degradation from an increased usage of frequency hopping bluetooth devices.
  • Add snapshots of the Density, Waterfall, Channel and Networks Tables. These graphs provide both visual and table representations of the wireless spectrum. Should any changes in the environment occur, these will provide a good base reference point.

*TIP* Create a default text block in Chanalyzer Pro to introduce the baseline and what it is. This will help the reader know the baseline blocks are not documenting interference.

Documenting Interference

A claim presented in a report should have substantial supporting evidence including graphs and tables that can help the readers understand the claim. Some professionals say you haven’t find found the device until you can turn it off and use the waterfall view to show that the transmitter is no longer operating. If you are unable to shut an interfering device off, use a directional antenna to measure the transmission from multiple angles to help you find the device. Avoid relying on the device identification when claiming the presence of wireless interference. A snapshot of the density view can support the claim of interference quite nicely.

The waterfall view is a good visual history of transmitting devices because it graphs amplitude levels over time. Once you have found the device, shrink the time frame in Chanalyzer to the start and end of any abnormal activity in the waterfall view to drill down on the interference. The Density View will rewind similar to a instant replay video of the transmitter. Take a snapshot to add it to the spectrum analysis report.

When generating spectrum analysis reports, use discretion when adding multiple blocks of the same event to the report. Generally speaking, reports should only mention events with high variations of the noise in the wireless environment. Unless directed otherwise, try to summarize the data and point out what the reader should be looking at to understand the wireless environment better:

  • Use the Wi-Fi channels label as the x-axis in the Density View. Most readers will not understand the frequency labels as well as the Wi-Fi Channel labels.
  • Briefly point out the curves and flat tops of Wi-Fi. Read more about them here.
  • Add photographs of any devices causing wireless interference. In some cases a picture of a motion detector may be much better than a description in words.

In the report builder highlight the Wi-Fi channels affected by interference levels and add a density block from when the transmitting wireless device was on. Add a channels table from the same time segment to highlight instances in which the Wi-Fi channel utilization increased due to interference.

*TIP*To learn more about navigation by waterfall read Time Segment Spectrum Analysis.

Documenting a Rogue AP

There are many great resources for tracking down rogue access points. In Chanalyzer, sort Wi-Fi networks by name, RSSI and encryption to locate WLANs that may potentially be transmitting from within the workplace.

Use the checkmarks to select a WLAN and track it in the networks graph. As you approach a selected WLAN the RSSI level will increase in the networks strength graph.

*TIP* Write a default text block explaining the security risks of Rogue APs and how they should be handled in a business environment.

Discuss Possible WLAN Improvements

In Chanalyzer Pro’s Report Builder, add new text blocks to discuss industry best practices and how they can help increase productivity. There are many options to discuss but try to limit the suggestions to a few practical ideas. Here are a few default text block ideas:

  • Wi-Fi Channel Placement. If the Wi-Fi channels are overlapping in their spectrum add a text block discussing the use of non-overlapping channels and how to properly reuse Wi-Fi channels 1, 6 and 11.
  • Upgrading the WLAN to support 5 GHz. There are more Wi-Fi channels in the 5 GHz spectrum to choose from and not nearly as many potential interferers operating there.
  • Voice over Wi-Fi. If cordless phones are causing Wi-Fi interference, suggest a voice over Wi-Fi solution.

It can be very easy to go overboard in a Wi-Fi report. Keep it simple and highlight only noteworthy activity. Save the recording in case the reader has questions and would like additional results from the survey.

Similar Blog Entries: