A method includes: a first communication apparatus sending a first request message to a second communication apparatus, where the first request message is for requesting to enter a PSM mode. The second communication apparatus sends a first response message to the first communication apparatus based on the first request message, where the first response message includes first indication information and second indication information, the first indication information indicates the first communication apparatus to enter the PSM mode, the second indication information indicates X wakeup occasion windows for the first communication apparatus in the PSM mode, and X is greater than or equal to 0. The first communication apparatus enters the PSM mode based on the first response message.