An access point generates a beacon frame that carries a trigger frame information element comprising sending information of a trigger frame for indicating a sending period of the trigger frame; and sends the beacon frame. In this case, the station switches to an active state, and receives the trigger frame by listening to the channel, and the station performs uplink transmission according to indication of the trigger frame after receiving the trigger frame. In this way, when signaling overheads are not increased and reliability is ensured, a station can learn of a sending time of a trigger frame, and the station remains in a receiving state in an appropriate period of time.