Method and apparatus for performing block ACK in multiple link of wireless LAN communication system

A station (STA) multi-link device (MLD) in a communication system, comprising:

• a first STA having a first medium access control (MAC) address and operating in a first link of multi-links;
• a second STA having a second MAC address and operating in a second link of the multi-links;
• a first MAC service access point (SAP) having a MAC-SAP1 address;
• and
• a memory storing one or more instructions for controlling operations of the first STA, the second STA, and the first MAC SAP, wherein the one or more instructions execute to:
• transmit, by the first STA, a block acknowledgement (BA) agreement request to an access point (AP) MLD in the first link among the multi-links, wherein the AP MLD includes a first AP having a fourth MAC address and operating in the first link of the multi-links, a second AP having a fifth MAC address and operating in the second link of the multi-links, and a second MAC SAP having a MAC-SAP2 address;
• receive, by the first STA, a BA agreement response from the AP MLD in the first link among the multi-links;
• configure, by the STA MLD, a buffer for the BA agreement for transmission;
• transmit, to the first AP, a first data unit of which a transmitter address (TA) is the first MAC address in the first link;
• transmit, to the second AP, a second data unit of which a TA is the second MAC address in the second link among the multi-links;
• receive, by the STA MLD, a first BA frame from the AP MLD of which a TA is the fourth MAC address in the first link among the multi-links;
• and
• receive, by the STA MLD, a second BA frame from the AP MLD of which a TA is the fifth MAC address in the second link among the multi-links;
• wherein the buffer for transmission is configured for the <second MAC SAP, TID> tuple, based on the first BA frame and the second BA frame, an updating operation is applied for the <second MAC SAP, TID> tuple, and the BA agreement is not performed between the second STA and the second AP.