A Hidden Wi-Fi Killer: Interference

Spectrogram showing microwave interference (frequency vs sweep cycle)

Jan 30, 2015 by Justin Cottrell

Like we’ve explained before, there are a lot of factors that play into getting your wireless network right. From the materials your building is made out of to how you orient your APs, it all takes careful consideration. One aspect that sometimes gets overlooked is interference.

Self-Imposed Interference

The largest and most known concern when designing your wireless network is co-channel interference, otherwise known as APs interfering with each other. While most APs today come standard with features to prevent them from stepping on each other’s channel, it’s a best practice to properly place your APs as not to introduce large amounts of co-channel interference. Ever heard of too much of a good thing?

If you work in an office building (this even applies to your home network if you’ve got neighbors close by), other wireless networks might be interfering with your signal. If that’s the case, you might want to adjust the channels your APs transmit on and maybe your power settings so as not to run over top of your other APs.

Non-Wi-Fi Interference

On top of the interference that we create by adding access points, there are many other sources of interference. Most of the non-Wi-Fi sources of interference are not so much of a problem anymore as users move to 5GHz spectrum. Most non-Wi-Fi interference sources run in the 2.4GHz spectrum. These sources can be anything from a microwave, gaming controller, Bluetooth headset or cordless phones.

I had a client that was reporting consistent wireless trouble around noon. They had a wireless projector in their conference room that experienced difficulty in projecting around that time every day. After performed a spectrum analysis, we discovered that there was considerable interference on the 2.4GHz spectrum…and it was coming from the room across the hall. Turns out, that was the break room and the microwave running (around lunch time) was interfering with the network.

Microwaves are notorious for causing Wi-Fi trouble in the 2.4 GHz spectrum.


Graph on the left: Mirazon’s wireless network
Graph on the right: Mirazon’s network with microwaves running

For example, pictured above is a scan of the wireless spectrum in our office. The left side is normal use — you can see our AP dominating one channel. The right side is when we turned on our microwaves. Every single channel is experiencing interference.

Another client of mine was also experiencing inconsistent Voice over Wi-Fi. When I went out to check on it, I found out that they had cordless conference phones that were interfering on the 2.4GHz spectrum. Even though they weren’t using Wi-Fi, they were still using that spectrum to communicate. Since they weren’t going to get rid of their conference room phones any time soon, we had to switch their wireless network completely over to 5GHz.

Every wireless design/install is different. Each client has different goals and uses they want Wi-Fi to fulfill. These are just a few of the issues we have seen here at Mirazon.

What can you do to help alleviate some of these problems?

  • Proper AP channel reuse
  • Proper AP placement/power settings – More APs does not mean it works better
  • Spectrum surveys to try and avoid or even remove RF

Need help addressing Wi-Fi trouble in your office? Send us an email or give us a call at 502-240-0404 and we’ll come out and help you make it right.

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