Case 2. The association acknowledgement information further includes a dummy association identifier. The dummy association identifier is used to indicate that the association acknowledgement information is the acknowledgement information of the association request message. The dummy association identifier may be indicated by using 11 bits of 0, or may be a special identifier specified by the AP. As shown in FIG. 4, after receiving the M-BA frame, if the first STA reads the dummy association identifier, it is considered that the BA/ACK Info in the M-BA frame is association acknowledgement information. The first STA reads a MAC address that is located after per traffic identifier information, and then, determines whether the MAC address is a MAC address of the first STA. If the MAC address is the MAC address of the first STA, it indicates that the AP successfully receives the association request message from the first STA.
