Techniques to facilitate phase continuity of sidelink DMRS bundling

1. An apparatus for wireless communication at a first user equipment (UE), comprising:

memory; and

at least one processor coupled to the memory, the memory and the at least one processor configured to:

receive a first sidelink transmission including at least a first demodulation reference signal (DMRS);

receive a second sidelink transmission, the first sidelink transmission and the second sidelink transmission together including at least the first DMRS and a second DMRS;

receive, from a second UE, an indication of a bundling relationship between the first sidelink transmission and the second sidelink transmission, the bundling relationship including at least one of strong bundling, weak bundling, or no bundling; and

perform channel estimation for a channel associated with the first sidelink transmission and the second sidelink transmission based at least in part on the bundling relationship.

2. The apparatus of claim 1 , wherein the bundling relationship further includes a structure of a transmitting UE matrix D t .

3. The apparatus of claim 1 , wherein the bundling relationship further includes one or more of:

an amplitude jump value,

a phase jump value,

an amplitude jump range,

a phase jump range, and

a bundling class associated with at least one of the amplitude jump range and the phase jump range.

4. The apparatus of claim 1 , wherein the memory and the at least one processor are further configured to:

receive a phase-tracking reference signals (PTRS) indication indicating a PTRS transmission mode, the PTRS transmission mode including an event-based PTRS inclusion mode and a PTRS inclusion in each transmission mode; and

estimate at least one of an amplitude jump and a phase jump based on received PTRS.

5. The apparatus of claim 4 , wherein the PTRS indication indicates the event-based PTRS inclusion mode, and wherein the memory and the at least one processor are configured to:

receive the first sidelink transmission excluding PTRS, and

receive the second sidelink transmission including PTRS.

6. The apparatus of claim 5 , wherein the memory and the at least one processor are further configured to:

transmit an event indication indicating an occurrence of a phase discontinuity event, wherein reception of the second sidelink transmission including the PTRS occurs after transmission of the event indication.

7. The apparatus of claim 4 , wherein the PTRS indication indicates the PTRS inclusion in each transmission mode, and wherein the memory and the at least one processor are configured to:

receive the first sidelink transmission including first PTRS, and

receive the second sidelink transmission including second PTRS.

8. The apparatus of claim 1 , wherein the memory and the at least one processor are further configured to:

receive a DMRS reduction pattern indicating one or more omitted DMRS.

9. The apparatus of claim 8 , wherein the DMRS reduction pattern indicates that:

the first sidelink transmission includes the first DMRS and the second DMRS, and

the second sidelink transmission excludes DMRS.

10. The apparatus of claim 8 , wherein the DMRS reduction pattern indicates that:

the first sidelink transmission includes the first DMRS, and

the second sidelink transmission includes the second DMRS.

11. The apparatus of claim 1 , further comprising:

at least one antenna; and

a transceiver coupled to the at least one antenna and the transceiver.

12. A method of wireless communication at a first user equipment (UE), comprising:

receiving a first sidelink transmission including at least a first demodulation reference signal (DMRS);

receiving a second sidelink transmission, the first sidelink transmission and the second sidelink transmission together including at least the first DMRS and a second DMRS;

receiving, from a second UE, an indication of a bundling relationship between the first sidelink transmission and the second sidelink transmission, the bundling relationship including at least one of strong bundling, weak bundling, or no bundling; and

performing channel estimation for a channel associated with the first sidelink transmission and the second sidelink transmission based at least in part on the bundling relationship.

13. The method of claim 12 , further comprising:

receiving a phase-tracking reference signals (PTRS) indication indicating a PTRS transmission mode, the PTRS transmission mode including an event-based PTRS inclusion mode and a PTRS inclusion in each transmission mode; and

estimating at least one of an amplitude jump and a phase jump based on received PTRS.

14. The method of claim 13 , wherein the PTRS indication indicates the event-based PTRS inclusion mode, and wherein the first UE:

receives the first sidelink transmission excluding PTRS, and

receives the second sidelink transmission including PTRS.

15. The method of claim 13 , wherein the PTRS indication indicates the PTRS inclusion in each transmission mode, and wherein the first UE:

receives the first sidelink transmission including first PTRS, and

receives the second sidelink transmission including second PTRS.

16. The method of claim 12 , further comprising:

receiving a DMRS reduction pattern indicating one or more omitted DMRS.

17. An apparatus for wireless communication at a first user equipment (UE), comprising:

memory; and

at least one processor coupled to the memory, the memory and the at least one processor configured to:

transmit a first sidelink transmission including at least a first demodulation reference signal (DMRS);

transmit a second sidelink transmission, the first sidelink transmission and the second sidelink transmission together including at least the first DMRS and a second DMRS; and

transmit, to a second UE, an indication of a bundling relationship between the first sidelink transmission and the second sidelink transmission, the bundling relationship including at least one of strong bundling, weak bundling, or no bundling.

18. The apparatus of claim 17 , wherein the bundling relationship further includes a structure of a transmitting UE matrix D t .

19. The apparatus of claim 17 , wherein the bundling relationship further includes one or more of:

an amplitude jump value,

a phase jump value,

an amplitude jump range,

a phase jump range, and

a bundling class associated with at least one of the amplitude jump range and the phase jump range.

20. The apparatus of claim 17 , wherein the memory and the at least one processor are further configured to:

transmit a phase-tracking reference signals (PTRS) indication indicating a PTRS transmission mode, the PTRS transmission mode including an event-based PTRS inclusion mode and a PTRS inclusion in each transmission mode.

21. The apparatus of claim 20 , wherein the PTRS indication indicates the event-based PTRS inclusion mode, and wherein the memory and the at least one processor are configured to:

transmit the first sidelink transmission excluding PTRS, and

transmit the second sidelink transmission including PTRS.

22. The apparatus of claim 21 , wherein the memory and the at least one processor are further configured to:

detect an occurrence of a phase discontinuity event,

wherein transmission of the second sidelink transmission including the PTRS occurs after detection of the occurrence of the phase discontinuity event.

23. The apparatus of claim 20 , wherein the PTRS indication indicates the PTRS inclusion in each transmission mode, and wherein the memory and the at least one processor are configured to:

transmit the first sidelink transmission including first PTRS, and

transmit the second sidelink transmission including second PTRS.

24. The apparatus of claim 17 , wherein the memory and the at least one processor are further configured to:

transmit a DMRS reduction pattern indicating one or more omitted DMRS.

25. The apparatus of claim 24 , wherein the DMRS reduction pattern indicates that:

the first sidelink transmission includes the first DMRS and the second DMRS, and

the second sidelink transmission excludes DMRS.

26. The apparatus of claim 24 , wherein the DMRS reduction pattern indicates that:

the first sidelink transmission includes the first DMRS, and

the second sidelink transmission includes the second DMRS.

27. The apparatus of claim 17 , further comprising:

at least one antenna; and

a transceiver coupled to the at least one antenna and the transceiver.

28. A method of wireless communication at a first user equipment (UE), comprising:

transmitting a first sidelink transmission including at least a first demodulation reference signal (DMRS);

transmitting a second sidelink transmission, the first sidelink transmission and the second sidelink transmission together including at least the first DMRS and a second DMRS; and

transmitting, to a second UE, an indication of a bundling relationship between the first sidelink transmission and the second sidelink transmission, the bundling relationship including at least one of strong bundling, weak bundling, or no bundling.

29. The method of claim 28 , further comprising:

transmitting a phase-tracking reference signals (PTRS) indication indicating a PTRS transmission mode, the PTRS transmission mode including an event-based PTRS inclusion mode and a PTRS inclusion in each transmission mode.

30. The method of claim 28 , further comprising:

transmitting a DMRS reduction pattern indicating one or more omitted DMRS.