Did You Know Non-802.11 Devices Can Interfere With Your Wi-Fi?

Connectivity issues have many culprits, but where do fingers point first? The Wi-Fi. In this Don’t Blame the Wi-Fi series, we look at the many causes of connectivity problems. This week, we are looking at interference from non-802.11 sources.

Non-802.11 devices include Bluetooth, microwave ovens, motion detection, wireless cameras, etc. When these devices are present, they may occupy one or more of your channels which will then reduce the wireless users’ Signal-to-Noise Ratio (SNR). 

In most cases, the SNR is too low and the channels become unusable. Staying on these channels means no communications and on the other hand moving away from these channels means less non-overlapping channels can be utilized, which can lead to co-channel interference issue.



Figure 1 – non-802.11l Interferences
Figure 1 – non-802.11l Interferences


A spectrum analyser can be used to detect non-802.11 interferences. The following is an example of the spectrum analyser output from an Aerohive AP


Figure 2 – Spectrum Analyser Output

In this case, there is a non-802.11 interference detected on channel eight. With top duty cycle around 80%, it potentially degrades the wireless service by 80% – at this level, no communications can happen. Channel six and eleven are overlapped with channel eight and are more likely to be impacted by this interference. The only usable channel in this area will be channel one. Having only one available channel is far from ideal as it will introduce co-channel interference.

In order to address this issue, you may either need to remove the source of interference or move the service to another band – in this case, 5GHz band. It is true that in some cases where capacity is very crucial this solution may not be desirable as shutting down the 2.4GHz will reduce the user capacity on the AP. Deploying an AP with dual 5GHz radios may help address this requirement.

Next up for discussion: Mismatch Transmit-Power or Asymmetric Power. I’ll be talking about this in in my next post. Stay tuned.


Eastman Rivai is a Senior Technical Support Engineer for Aerohive Networks. He has been working within the wireless industry for over a decade where he has been involved in many complex wireless deployments and dealing with challenging wireless solutions. He holds a Master of Engineering Science degree in Communications.

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