Specifically, a value of the association indication bit may be specifically as follows: For example, if the bit is set to 1, it indicates that the block acknowledgement/acknowledgement information is acknowledgement information of the association request message; otherwise, it indicates that the block acknowledgement/acknowledgement information is not acknowledgement information of the association request message. Further, a MAC address in the M-BA frame is located after per traffic identifier information and occupies 6 bytes. In this case, a first AID that is allocated by the AP to a station that successfully sends an association request is filled in an AID subfield in each traffic identifier field. It should be noted that a name of the first AID may be Pre-AID or another similar name.
Further, a piece of BA/ACK Info in one M-BA frame may include acknowledgements of association requests sent by multiple unassociated STAs. That is, the M-BA frame includes one piece of BA/ACK Info. The BA/ACK Info includes acknowledgements of association requests sent by multiple unassociated STAs.