Method and apparatus for multi-link data transmission

1. A method of multi-link communications, the method comprising:

at a first multi-link device (MLD) that supports a first link, link1, and a second link, link2, transmitting a first frame during a first Transmission Opportunity (TXOP) on link1, and a second frame during a second TXOP on link2, simultaneously to a second MLD;

receiving, at the first MLD, a first response frame to the first frame transmitted on link1 after a transmission end time of the first frame;

identifying, at the first MLD, that a response frame to the second frame transmitted on link2 was not received after the transmission end time of the second frame; and

transmitting, at the first MLD, a third frame on link1 and a fourth frame on link2 simultaneously, after receiving the first response frame on link1.

2. The method of claim 1 , wherein the transmission end time of the first frame and the transmission end time of the second frame are within a first predetermined time.

3. The method of claim 1 , wherein the third frame is transmitted at a second predetermined time of at least one of SIFS and PIFS after the reception of the first response frame.

4. The method of claim 1 , further comprising identifying, at the first MLD, that link2 is idle for a third predetermined time before the transmission of the fourth frame.

5. The method of claim 4 , wherein the third predetermined time is Point Coordination Function (PCF) Interframe Space (PIFS).

6. The method of claim 1 , wherein transmitting the third frame on link1 and the fourth frame on link2 simultaneously after receiving the first response frame on link1 involves transmitting the third frame and the fourth frame within a predetermined time interval of each other.

7. The method of claim 1 , wherein at least the first MLD or the second MLD is operating in synchronous mode operation in response to at least one of the following conditions:

(i) the first MLD is a Simultaneous Transmit/Receive (STR) MLD and the second MLD is a non-STR MLD; and

(ii) the first MLD is a non-STR MLD and the second MLD is a STR MLD.

8. The method of claim 1 , wherein after transmitting the second frame at the first MLD further involves:

monitoring, at the first MLD, a wireless medium of link2 to identify link2 as an idle channel.

9. A first multi-link device (MLD), the first MLD comprising:

a processor configured to:

communicate with a second MLD via a first link, link1, and a second link, link2;

transmit a first frame during a first Transmission Opportunity (TXOP) on link1, and a second frame during a second TXOP on link2 simultaneously to a second MLD;

receive a first response frame to the first frame transmitted on link1 a second predetermined time after a transmission end time of the first frame;

identify that a response frame to the second frame transmitted on link2 was not received after the transmission end time of the second frame; and

transmit a third frame on link1 and a fourth frame on link2 simultaneously after receiving the first response frame on link1.

10. The first MLD of claim 9 , wherein the transmission end time of the first frame and the transmission end time of the second frame is within a first predetermined time.

11. The first MLD of claim 9 , wherein the third frame is transmitted at a second predetermined time of at least one of SIFS and PIFS after the reception of the first response frame.

12. The first MLD of claim 9 , wherein the first MLD identifies that link2 is idle for a third predetermined time before the transmission of the fourth frame.

13. The third predetermined time of claim 12 , wherein the third predetermined time is Point Coordination Function (PCF) Interframe Space (PIFS).

14. The first MLD of claim 9 , wherein transmission of the third frame on link1 and the fourth frame on link2 simultaneously after receiving the first response frame on link1 involves transmitting the third frame and the fourth frame within a predetermined time interval of each other.

15. The first MLD of claim 9 , wherein at least the first MLD or the second MLD is operating in synchronous mode operation in response to at least one of:

(i) the first MLD is a Simultaneous Transmit/Receive (STR) MLD and the second MLD is a non-STR MLD; and

(ii) the first MLD is a non-STR MLD and the second MLD is a STR MLD.

16. The first MLD of claim 9 , wherein transmission of the second frame at the first MLD further involves, at the first MLD, a monitor of a wireless medium of link2 to identify link2 as an idle channel.

17. A method of multi-link communications, the method comprising:

at a first multi-link device (MLD) that supports a first link, link1, and a second link, link2, transmitting a first frame during a first Transmission Opportunity (TXOP) on link1, and a second frame during a second TXOP on link2 to a second MLD, wherein a transmission end time of Physical Protocol Data Units (PPDUs) carrying the first frame and the second frame is aligned within a first predetermined time, and wherein the first frame solicits a first immediate response frame and the second frame solicits a second immediate response frame;

receiving, at the first MLD, the first immediate response frame on link1;

identifying, at the first MLD, that an immediate response frame to the second frame transmitted on link2 was not received after the transmission end time of the second frame;

transmitting, at the first MLD, a third frame on link1 at a second predetermined time after receiving the first immediate response frame; and

transmitting, at the first MLD, a fourth frame on link2 when the first MLD identifies that link2 is idle.

18. The method of claim 17 , wherein transmitting, at the first MLD, the fourth frame on link2 involves at least one of:

(i) transmitting, at the first MLD, the fourth frame on link2 at the second predetermined time after an expected end time of a reception of the second immediate response frame in response to failing to identify, at the first MLD, a start of a PPDU in a third predetermined time after the transmission of the second frame; and

(ii) transmitting, at the first MLD, the fourth frame on link2 a fourth time after the end of a PPDU reception in response to identifying, at the first MLD, the start of the PPDU in the third predetermined time after the transmission of the second frame but failing to recognize, at the first MLD, the second immediate response frame.

19. The method of claim 17 , wherein the first, second, third, and fourth predetermined times include at least one of:

(i) the first predetermined time is equal to or less than Short Interframe Space (SIFS);

(ii) the second predetermined time is at least one of SIFS and Point Coordination Function (PCF) Interframe Space (PIFS);

(iii) the third predetermined time is aSIFSTime+aSlotTime+aRxPHYStartDelay; and

(iv) the fourth predetermined time is PIFS.

20. The method of claim 17 , wherein at least the first MLD or the second MLD is operating in synchronous mode operation in response to at least one of:

(iii) the first MLD is a Simultaneous Transmit/Receive (STR) MLD and the second MLD is a non-STR MLD; and

(iv) the first MLD is a non-STR MLD and the second MLD is a STR MLD.