Channel Switch Announcement element was used for the AP to inform the cell that all stations had to move to another channel because radar was detected on the current frequency. This Channel Switch Announcement is present in beacons and probe responses and announces a future switch.
The following pictures show structure and elements of Channel Switch Announcement.
The following pictures show structure and elements of Channel Switch Announcement.
above pictures from CWAP
Reference from Action Frame post, we could know that Category is set to 0, and action value is set to 4. By using New Channel Number, the AP informs the cell about the next channel. The channel switch count can be set to 0 to indicate that the change will occur any time after the present beacon was sent. It can be set to 1 to show that the jump will occur just before the next beacon.
For example, AP to inform the cell that all stations had to move to another channel because radar was detected on the current frequency.
For example, AP to inform the cell that all stations had to move to another channel because radar was detected on the current frequency.
Why design a special frame if the information element is already present in beacons and probe responses ? The AP can send the Channel Switch Action frame between beacons to any station that may not have received the beacon or to instruct a client that it should not send traffic until the switch occurs.
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