Multi-link block acknowledgment (BA)

1. A method for wireless communication by a first multi-link device (MLD) that includes a first station (STA) and a second STA, the method comprising:

transmitting, by the first STA of the first MLD to a third STA of a second MLD via a first wireless link between the first STA and the third STA, one or more first Medium Access Control (MAC) Protocol Data Unit (MPDUs);

transmitting, by the second STA of the first MLD to a fourth STA of the second MLD via a second wireless link between the second STA and the fourth STA, one or more second MPDUs;

receiving, by the first STA of the first MLD from the third STA of the second MLD via the first wireless link, a first block acknowledgment (BA) including a first set of one or more bits providing receive status indicating positive or negative acknowledgement for the one or more first MPDUs, wherein the first BA further includes a third set of one or more bits providing receive status indicating positive acknowledgement for at least one second MPDU of the one or more second MPDUs when the receive status for the at least one second MPDU of the one or more second MPDUs is available at the third STA; and

receiving, by the second STA of the first MLD from the fourth STA of the second MLD via the second wireless link, a second BA including a second set of one or more bits providing receive status indicating positive or negative acknowledgement for the one or more second MPDUs, wherein the second BA further includes a fourth set of one or more bits providing receive status indicating positive acknowledgement for at least one first MPDU of the one or more first MPDUs when the receive status for the at least one first MPDU of the one or more first MPDUs is available at the fourth STA.

2. The method of claim 1 , wherein:

the logical entity comprises a common MAC layer entity configured to assign one or more first MPDUs to the first STA and one or more second MPDUS to the second STA; and

the method further comprises receiving an assignment of one or more first MPDUs to the first STA from the common MAC layer entity.

3. The method of claim 2 , further comprising receiving, from the common MAC layer entity, a re-assignment of one or more MPDUs to the first STA based on one or more BA status reports received from at least one of the first or second STAs.

4. The method of claim 1 , wherein:

the first STA has a policy for retransmitting one or more first MPDUs that have corresponding bits of the first set of bits that indicate negative acknowledgments; and

the first STA is configured to forward one or more updated BA status reports to the logical entity before exhausting a maximum number of retransmissions according to the policy, wherein the policy indicates that the maximum number of retransmissions is set to a nonzero value.

5. The method of claim 1 , further comprising:

determining a state of each of the one or more first MPDUs based on at least one of: the first set of bits or the fourth set of bits;

determining a state of each of the one or more second MPDUs based on at least one of: the second set of bits or the third set of bits;

generating a BA status report based on the determined states of the one or more first MPDUs and the determined states of the one or more second MPDUs; and

providing the BA status report to a logical entity of the first MLD.

6. The method of claim 5 , wherein determining a state of each of the one or more first MPDUs based on the first set of bits comprises:

determining a state of an MPDU of the one or more first MPDUs as successfully received by the second MLD based on a corresponding bit of the first set of bits indicating a positive acknowledgment;

determining a state of an MPDU of the one or more first MPDUs as pending based on a corresponding bit of the first set of bits indicating a negative acknowledgment and the first STA has yet to transmit the MPDU or is retransmitting the MPDU; and

determining a state of an MPDU of the one or more first MPDUs as failed based on a corresponding bit of the first set of bits indicating a negative acknowledgment and the first STA has transmitted the MPDU and is not retransmitting the MPDU.

7. The method of claim 5 , wherein determining a state of each of the one or more second MPDUs based on the second set of bits comprises:

determining a state of an MPDU of the one or more second MPDUs as successfully received by the second MLD based on a corresponding bit of the second set of bits indicating a positive acknowledgment; and

determining a state of an MPDU of the one or more second MPDUs as unknown based on a corresponding bit of the first set of bits indicating a negative acknowledgment.

8. A method for wireless communications by a logical entity of a first multi-link device (MLD), comprising:

assigning a first set of one or more Medium Access Control (MAC) Protocol Data Unit (MPDUs) to a first station (STA) of the first MLD for transmission on a first wireless link between the first STA and a third STA of a second MLD;

assigning a second set of one or more MPDUs to a second STA of the first MLD for transmission on a second wireless link between the second STA and a fourth STA of the second MILD;

receiving one or more block acknowledgment (BA) status reports from at least one of the first STA or the second STA indicating a state of each MPDU in the first set of one or more MPDUs assigned to the first STA and a state of each MPDU in the second set of one or more MPDUs assigned to the second STA, wherein the state of each MPDU is indicated as a state value selected from one of at least four state values, and wherein:

the one or more BA status reports comprises a first BA report and a second BA report,

the first BA report includes a first set of one or more bits providing receive status indicating positive or negative acknowledgement for the first set of one or more MPDUs and a third set of one or more bits providing receive status indicating positive acknowledgement for at least one second MPDU of the second set of one or more MPDUs when the receive status for the at least one second MPDU of the second set of one or more MPDUs is available at the third STA, and

the second BA report includes a second set of one or more bits providing receive status indicating positive or negative acknowledgement for the second set of one or more MPDUs and a fourth set of one or more bits providing receive status indicating positive acknowledgement for at least one first MPDU of the first set of one or more MPDUs when the receive status for the at least one first MPDU of the first set of one or more MPDUs is available at the fourth STA; and

updating a common scoreboard used to track the states of the one or more MPDUs in the first set transmitted across the first wireless link and the one or more MPDUs in the second set transmitted across the second wireless link, based on the one or more BA status reports.

9. The method of claim 8 , wherein:

the first STA and second STA each have a policy for retransmitting one or more MPDUs of the first or second set that have corresponding bits that indicate negative acknowledgments; and

the first STA and second STA are configured to forward one or more updated BA status reports to the logical entity before exhausting a maximum number of retransmissions according to the policy.

10. The method of claim 8 , wherein:

the logical entity comprises a common MAC layer entity that assigns MPDUs to the first and second STAs; and

the method further comprising assigning MPDUs to the first and second STAs based on the updated common scoreboard.

11. The method of claim 10 , further comprising:

re-assigning one or more MPDUs of the first set from the first STA to the second STA based on the BA status reports; or

re-assigning one or more MPDUs of the second set from the second STA to the first STA based on the BA status reports.

12. The method of claim 8 , wherein the common scoreboard reflects the states of the first and second sets of one or more MPDUs associated with different sequence numbers (SNs).

13. The method of claim 8 , wherein the four state values comprise:

a first value that indicates an MPDU of the one or more MPDUs of the first set assigned to the first STA or one or more MPDUs of the second set assigned to the second STA as successfully received by the second MLD;

a second value that indicates an MPDU of the one or more MPDUs of the first set assigned to the first STA or one or more MPDUs of the second set assigned to the second STA as pending if the STA to which that MPDU is assigned has yet to transmit the MPDU or is retransmitting the MPDU;

a third value that indicates an MPDU of the one or more MPDUs of the first set assigned to the first STA or one or more MPDUs of the second set assigned to the second STA as failed if the STA to which that MPDU is assigned has transmitted the MPDU and is not retransmitting the MPDU; and

a fourth value that indicates a state of an MPDU of the one or more MPDUs of the first set assigned to the first STA or the one or more MPDUs of the second set assigned to the second STA as unknown if the STA that generated the report is not assigned that MPDU and is unable to determine that MPDU was successfully received by the second MLD.

14. The method of claim 13 , wherein:

receiving the one or more BA status reports comprises receiving one or more BA status reports from the first STA and one or more BA status reports from the second STA; and

updating the common scoreboard includes consolidating the BA status reports from the first STA and the second STA.

15. The method of claim 8 , further comprising:

transmitting, via at least one of the first STA or the second STA, a first frame to request the second MLD to send BAs for one or more MPDUs transmitted on multiple wireless links; and

receiving, via at least one of the first STA or the second STA, a second frame, in response to the first frame, indicating the second MLD will send BAs for one or more MPDUs transmitted on the first and second wireless links.

16. An apparatus for wireless communications by a first multi-link device (MLD) that includes a first station (STA) and a second STA, the apparatus comprising:

at least one processor; and

at least one memory communicatively coupled with the at least one processor and storing processor-readable code that, when executed by the at least one processor, is configured to:

transmit, by the first STA of the first MLD to a third STA of a second MLD via a first wireless link between the first STA and the third STA, one or more first Medium Access Control (MAC) Protocol Data Unit (MPDUs);

transmit, by the second STA of the first MLD to a fourth STA of the second MLD via a second wireless link between the second STA and the fourth STA, one or more second MPDUs;

receive, by the first STA of the first MLD from the third STA of the second MLD via the first wireless link, a first block acknowledgment (BA) including a first set of one or more bits providing receive status indicating positive or negative acknowledgement for the one or more first MPDUs, wherein the first BA further includes a third set of one or more bits providing receive status indicating positive acknowledgement for at least one second MPDU of the one or more second MPDUs when the receive status for the at least one second MPDU of the one or more second MPDUs is available at the third STA; and

receive, by the second STA of the first MLD from the fourth STA of the second MLD via second first wireless link, a second BA including a second set of one or more bits providing receive status indicating positive or negative acknowledgement for the one or more second MPDUs, wherein the second BA further includes a fourth set of one or more bits providing receive status indicating positive acknowledgement for at least one first MPDU of the one or more first MPDUs when the receive status for the at least one first MPDU of the one or more first MPDUs is available at the fourth STA.

17. The apparatus of claim 16 , wherein: the logical entity comprises a common MAC layer entity configured to assign one or more first MPDUs to the first STA and one or more second MPDUs to the second STAs; and

the memory and the one or more processors are further configured to receive an assignment of one or more first MPDUs to the first STA from the common MAC layer entity.

18. The apparatus of claim 17 , wherein the memory and the one or more processors are further configured to receive, from the common MAC layer entity, a re-assignment of one or more MPDUs to the first STA based on one or more BA status reports received from at least one of the first or second STAs.

19. The apparatus of claim 16 , wherein:

the first STA has a policy for retransmitting one or more first MPDUs that have corresponding bits of the first set of bits that indicate negative acknowledgments; and

the first STA is configured to forward one or more updated BA status reports to a logical entity before exhausting a maximum number of retransmissions according to the policy, wherein the policy indicates that the maximum number of retransmissions is set to a nonzero value.

20. The apparatus of claim 16 , wherein the memory and the one or more processors are further configured to:

determine a state of each of the one or more first MPDUs based on at least one of: the first set of bits or the fourth set of bits;

determine a state of each of the one or more second MPDUs based on at least one of: the second set of bits or the third set of bits;

generate a BA status report based on the determined states of the one or more first MPDUs and the determined states of the one or more second MPDUs; and

provide the BA status report to a logical entity of the first MLD.

21. The apparatus of claim 20 , wherein determining a state of each of the one or more first MPDUs based on the first set of bits comprises:

determining a state of an MPDU of the one or more first MPDUs as successfully received by the second MLD based on a corresponding bit of the first set of bits indicating a positive acknowledgment;

determining a state of an MPDU of the one or more first MPDUs as pending based on a corresponding bit of the first set of bits indicating a negative acknowledgment and the first STA has yet to transmit the MPDU or is retransmitting the MPDU; and

determining a state of an MPDU of the one or more first MPDUs as failed based on a corresponding bit of the first set of bits indicating a negative acknowledgment and the first STA has transmitted the MPDU and is retransmitting the MPDU.

22. The apparatus of claim 20 , wherein determining a state of each of the one or more second MPDUs based on the second set of bits comprises:

determining a state of an MPDU of the one or more second MPDUs as successfully received by the second MLD based on a corresponding bit of the second set of bits indicating a positive acknowledgment; and

determining a state of an MPDU of the one or more second MPDUs as unknown based on a corresponding bit of the first set of bits indicating a negative acknowledgment.

23. An apparatus for wireless communications by a logical entity of a first multi-link device (MLD), comprising:

at least one processor; and

at least one memory communicatively coupled with the at least one processor and storing processor-readable code that, when executed by the at least one processor, is configured to:

assign a first set of one or more Medium Access Control (MAC) Protocol Data Unit (MPDUs) to a first station (STA) of the first MLD for transmission on a first wireless link between the first STA and a third STA of a second MLD;

assign a second set of one or more MPDUs to a second STA of the first MLD for transmission on a second wireless link between the second STA and a fourth STA of the second MLD;

receive one or more block acknowledgment (BA) status reports from at least one of the first STA or the second STA indicating a state of each MPDU in the first set of one or more MPDUs assigned to the first STA and a state of each MPDU in the second set of one or more MPDUs assigned to the second STA, wherein the state of each MPDU is indicated as a state value selected from one of at least four state values, and wherein:

the one or more BA status reports comprises a first BA report and a second BA report,

the first BA report includes a first set of one or more bits providing receive status indicating positive or negative acknowledgement for the first set of one or more MPDUs and a third set of one or more bits providing receive status indicating positive acknowledgement for at least one second MPDU of the second set of one or more MPDUs when the receive status for the at least one second MPDU of the second set of one or more MPDUs is available at the third STA, and

the second BA report includes a second set of one or more bits providing receive status indicating positive or negative acknowledgement for the second set of one or more MPDUs and a fourth set of one or more bits providing receive status indicating positive acknowledgement for at least one first MPDU of the first set of one or more MPDUs when the receive status for the at least one first MPDU of the first set of one or more MPDUs is available at the fourth STA; and

update a common scoreboard used to track the states of the one or more MPDUs in the first set transmitted across the first wireless link and the one or more MPDUs in the second set transmitted across the second wireless link, based on the one or more BA status reports.

24. The apparatus of claim 23 , wherein:

the first STA and second STA each have a policy for retransmitting one or more MPDUs of the first set or second set that have corresponding bits that indicate negative acknowledgments; and

the first STA and second STA are configured to forward one or more updated BA status reports to the logical entity before exhausting a maximum number of retransmissions according to the policy.

25. The apparatus of claim 23 , wherein:

the logical entity comprises a common MAC layer entity that assigns MPDUs to the first and second STAs; and

the memory and the one or more processors are further configured to assign MPDUs to the first and second STAs based on the updated common scoreboard.

26. The apparatus of claim 25 , wherein the memory and the one or more processors are further configured to:

re-assign one or more MPDUs of the first set from the first STA to the second STA based on the BA status reports; or

re-assign one or more MPDUs of the second set from the second STA to the first STA based on the BA status reports.

27. The apparatus of claim 23 , wherein the common scoreboard reflects the states of the first and second sets of one or more MPDUs associated with different sequence numbers (SNs).

28. The apparatus of claim 23 , wherein the four state values comprise:

a first value that indicates an MPDU of the one or more MPDUs of the first set assigned to the first STA or one or more MPDUs of the second set assigned to the second STA as successfully received by the second MLD;

a second value that indicates an MPDU of the one or more MPDUs assigned to the first STA or one or more MPDUs of the second set assigned to the second STA as pending if the STA to which that MPDU is assigned has yet to transmit the MPDU or is retransmitting the MPDU;

a third value that indicates an MPDU of the one or more MPDUs of the first set assigned to the first STA or one or more MPDUs of the second set assigned to the second STA as failed if the STA to which that MPDU is assigned has transmitted the MPDU and is not retransmitting the MPDU; and

a fourth value that indicates a state of an MPDU of the one or more MPDUs of the first set assigned to the first STA or one or more MPDUs of the second set assigned to the second STA as unknown if the STA that generated the report is not assigned that MPDU and is unable to determine that MPDU was successfully received by the second MLD.

29. The apparatus of claim 28 , wherein:

receiving the one or more BA status reports comprises receiving one or more BA status reports from the first STA and one or more BA status reports from the second STA; and

updating the common scoreboard includes consolidating the BA status reports from the first STA and the second STA.

30. The apparatus of claim 23 , wherein the memory and the one or more processors are further configured to:

transmit, via at least one of the first STA or the second STA, a first frame to request the second MLD to send BAs for one or more MPDUs transmitted on multiple wireless links; and

receive, via at least one of the first STA or the second STA, a second frame, in response to the first frame, indicating the second MLD will send BAs for one or more MPDUs transmitted on the first and second wireless links.