The Channel Switch Announcement element can be very useful when your AP must change its channel quickly, for example, in face of a radar event when using DFS channels. It can be informed on the beacons, as you can see below, and also on Action Frames.
On the example below, I have “simulated” a radar event on the previously used channel, 60. According to the regulation, the AP must change the channel in max 10 seconds. When CSA is enabled, the AP can inform the STAs it is moving to another channel. In this case, you can see it is moving to U-NII-1 channel 44.
It can also inform the countdown in TBTTs until the expected change. Here, I got the Count = 3, meaning the change will happen in the next 2 TBTTs time (around 200 ms).
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