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I'm trying to set up a roaming wireless network. For this, I have tried to analyze the area of coverage for any external network interference.

I do know that networks can change over time and Wifi signal strength is not completely uniform, but I was able to notice some tendencies ("room X gets almost no networks on channel Y").

However, I also regularly saw something like the following signal pattern, which makes it difficult for me to decide which channel to choose:

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In this case, Channel 1 would have the least amount of outside signals, but also the strongest.

Channel 6 has a few different signals in medium strength, maybe fluctuating a bit.

Channel 11 shows quite a lot of external SSIDs, but frequently fluctuating and all are relatively weak.

It's obvious to me that Channel 6 would be the worst choice for an additional network, but I'm not sure if many weak or few strong signals cause the least interference for a new network.

What would be the best channel in this case?

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  • You don't show the vertical scale, so it's hard to judge. There may be no practical difference. As you know, signal strength will change continuously. I would choose based on one (or even a few) samples.
    – Ron Trunk
    Apr 14, 2021 at 17:22
  • It all depends on your local environment. A single channel scan doesn't really paint a picture - you'd need to do a proper survey and possibly repeat it regularly.
    – Zac67 ♦
    Apr 14, 2021 at 17:22
  • You need to do a wireless survey to accurately design your channels, or dont use 2.4 unless you're supporting manufacturing or legacy as its overloaded with congestion as you only have 3 channels at 20Mhz to use. The other point to consider is that depending on the type of equipment used by outside sources it will constantly change channels due to dynamic assignment's .
    – onxx
    Oct 2, 2021 at 21:24

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When talking about interference there are two types: 802.11 and non-802.11 (e.g. microwave ovens, wireless microphones) In both cases, the number of BSSIDs on a channel is not giving you all of the information to know the availability of a channel.

If you are only looking at number of BSSIDs, the signal strength doesn't really matter if it's above the threshold of your devices to demodulate during DCF. You will still have to wait for that transmission to complete whether it is at -40 dBm or -70 dBm. The threshold is usually at -85 dBm to detect 802.11 channel interference.

A better way to measure 802.11 interference is to measure airtime or channel-utilization with a tool like aircheck. However this can vary widely and change over time.

A better way to measure non-802.11 noise is to use a spectrum analyzer. Energy detected above about -62 dBm will prevent transmission, regardless of the source being 802.11 or something else. This type of noise is also often transient.

Many enterprise WiFi solutions will include some ability to detect channel use, neighbors, noise, and client performance and adjust channel and power dynamically. In many environments this is probably easier than trying to chase these down manually and creating a static plan.

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