If you see a device swapping channel instantly, it seems like it's associated with your AP, more than anything.
Not necessarily. There are a lot of mesh devices around these days - they often sniff around to see what other devices are available to mesh with. If you change channels it looks like a new device has appeared, so it will be checked out.
I said “instantly” ie within a few seconds. You rarely find a mesh setup to change a channel the very second it detects a network on its channel, as the mesh by its very nature is usually occupying 1 6 and 11.
On wireless mesh 5GHz is used for back haul most of the time and again this rarely changes as this can impact everything connected for a small amount of time. I have seen it happen when a 5Ghz channel just stops working entirely but with the mess of DFS channels often they only have 36 to 48 to work with and at 80MHz that really and changing from 36 to 40 is somewhat pointless.
I do see a few mesh systems which roll to 2.4GHz as backhaul whilst changing 5GHZ mesh channel and then band steer over time devices back to the underlying new 5GHZ network. This is more common when there’s so much congestion on channels 36 to 48 that it changes from 80MHz to 40 or even 20 to avoid significant interference whereby the benefits of higher channel width and usual speed are not worth it considering the interference levels and service impact.
Let’s not forget depending on the home users setup 2.4GHz can be used as backhaul. Take BT Smarthub 2, their complete WiFi will say “good signal” in areas where there is no 5GHz signal that’s usable but it manages to get a decent 2.4GHz and uses that as backhaul. Here I wouldn’t expect an instant channel change by the mesh point every time a neighbour turned on their WiFi on that channel.
Likewise, a simple device being on the same channel isn’t a big deal, or usually reason to change channel. Networks (mesh and wireless controllers) generally do not simply take into account nearby access points on the same channel. They can usually co exist just fine, it focuses more on it being service affecting. An example is there’s an AP on the same channel, not part of the mesh. If this was on channel 1, 20Mhz, with 35 associated clients and had overall heavy channel usage, clearly it may be service impacting to warrant a channel adjustment.
Even with all this in mind, if the existing mesh has very minimal data throughput eg imagine a user is just doing a radio stream at 64Kbps. The mesh / controller does not typically initiate an immediate switch, which could be service affecting, as the level of minimal usage is sustainable without interruption, and it will try to maintain that constant low usage stream without interruption.
If usage is higher, then there often reason to switch the channel sooner, as the interference can be service affecting to a great extent.
It is true that a mesh may steer all clients to another AP when they need to switch channel on the mesh device although this approach often causes issues with devices that simply refuse to connect into anything but the mesh with the greatest signal snd even though they can’t associate, they won’t pick the one further away.
If any system is such that it’s adjust channels with large frequency, this is not good for any sort of stability.
If a user notes that every single time they change channel, another WiFi AP follows them (which is not part of their own network) that is extremely suspicious. Why would an AP move to the channel that the users device has just chosen, surely it would see the channel they were initially on now has lower utilisation? There’s no need for it to follow an AP every change of channel.
On the whole mesh and controllers make adjustments based on issues such as adjacent channel interference and packet collision noted, consistently causing retransmission. Random non WiFi device interference which won’t work in the same manner as an AP producing co-channel interference which is generally ok.
While the WiFi environment and devices are getting smarter, change changes are not often, plenty of devices do not associate nicely after a channel change. Users see drops, sometimes have to manually reconnect. Issues such as devices being far away from the AP and dropping encoding down to QPSK, are far bigger concerns for mesh and controllers than co channel interference. To avoid this the mesh tries to route data in the most efficient manner without a specific bad apple causing overall slowdown snd limiting MU-MIMO.
Some people get mad when their iPad with 1 bar won’t stay on 5GHz and they prefer it to. They may split their SSID. The mesh / controller in a complex system may see a device on slower but more robust and guaranteed data encoding to support Netflix with 1 bar of WiFi, but then there’s an impact on several devices which don’t have poor signal. It can make more sense to steer that one service impacting device onto 2.4GHz.
It’s complex but there’s no system designed to switch WiFi channel to follow another AP that’s not part of its own mesh or controller.