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Wireless Troubleshooting: Measuring WiFi Signal Strength

I am a big fan of teaching methodology. I always ask people who attend my presentations not to focus on my results, but rather to understand how I do things so they can reproduce my test.

In this video, I discuss the merits of measuring WiFi signal strength by understanding how well your WiFi access points hear your clients. I chose a popular Samsung Galaxy S2 smartphone and recorded the receive signal strength from the access point’s perspective.

When you conduct this type of test, you should be aware that many WiFi devices will change the radio behavior depending on power and if it's transmitting any data. To ensure consistency, I simply "pinged" the phone’s IP address every 10 millisecond using hrping.

As I explain in the video, I’m not expecting you to do this for every device, in every location in every orientation, but think it's important to understand this behavior for those tricky WiFi issues.

I actually used this methodology when troubleshooting a problem in a warehouse with WiFi terminals mounted in forklifts that were dropping their connections. In the end, I found two very important details:

  • The signal strength was marginal at best since the survey was completed using highly sensitive directional antennas and the terminals had less-sensitive omnidirectional antennas.
  • There was an area of the warehouse with a lot of metal shelving that, in combination with the forklift orientation, caused the RF signal to drop and the connection to drop.

Good luck with your wireless troubleshooting! 

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