Dynamically adding additional demodulation reference signal (A-DMRS) for PUSCH
Certain aspects of the present disclosure provide techniques for wireless communication by detecting at least one condition related to a channel between a network entity and a user equipment (UE); triggering the UE to transmit additional demodulation reference signal (A-DMRS) for a physical uplink shared channel (PUSCH) transmission, relative to DMRS indicated in a current PUSCH DMRS configuration; and monitoring for a PUSCH transmission from the UE including the A-DMRS.
1. A method for wireless communications by a user equipment (UE), comprising:
receiving, from a network entity, signaling that triggers the UE to transmit additional demodulation reference signal (A-DMRS) for at least one physical uplink shared channel (PUSCH), relative to DMRS indicated in a current PUSCH DMRS configuration; and
transmitting the at least one PUSCH including the A-DMRS, wherein the A-DMRS is triggered only when a number of resource blocks (RBs) allocated for the at least one PUSCH is at or below a threshold value.
2. The method of claim 1 , wherein:
the current PUSCH DMRS configuration was signaled via radio resource control (RRC) signaling; and
the DMRS indicated in the current DMRS configuration are not impacted by triggering the A-DMRS.
3. The method of claim 1 , wherein the A-DMRS occupies one or more symbols not allocated for the at least one PUSCH or for the DMRS indicated in the current DMRS configuration.
4. The method of claim 1 , wherein the A-DMRS spans a larger bandwidth than at least one of the DMRS indicated in the current DMRS configuration or the at least one PUSCH.
5. The method of claim 4 , wherein a bandwidth of the A-DMRS is centered around bandwidth allocated for at least one of the DMRS indicated in the current DMRS configuration or the at least one PUSCH.
6. The method of claim 4 , wherein the A-DMRS is limited to a number of resource blocks (RBs).
7. The method of claim 6 , wherein the number of RBs depends at least in part on a number of RBs allocated for the at least one PUSCH.
8. The method of claim 4 , wherein the A-DMRS is limited to resource blocks (RBs) from an edge of a transmission band.
9. The method of claim 1 , wherein the A-DMRS is triggered via at least one of: a downlink control information (DCI) or a medium access control (MAC) control element (CE).
10. The method of claim 9 , wherein the A-DMRS is applied a number of slots after transmission of the DCI or MAC CE.
11. The method of claim 9 , wherein the A-DMRS is triggered for one or more uplink slots.
12. The method of claim 11 , wherein the DCI or MAC-CE indicates the number of uplink slots for which the A-DMRS is triggered.
13. The method of claim 11 , wherein the number of uplink slots for which the A-DMRS is triggered is indicated in a configuration signaled via radio resource control (RRC) signaling.
14. The method of claim 1 , wherein the A-DMRS shares at least one of: a same antenna port, quasi co location (QCL) assumptions, or uplink spatial filters with the at least one PUSCH.
15. The method of claim 1 , wherein the A-DMRS is transmitted at a same transmit power as the at least one PUSCH and the DMRS indicated in the PUSCH DMRS configuration.
16. The method of claim 1 , wherein the A-DMRS spans a wider bandwidth than the at least one PUSCH.
17. The method of claim 1 , further comprising implicitly determining a bandwidth of the A-DMRS based on resources of the at least one PUSCH and a scaling factor that is greater than or equal to 1.
18. The method of claim 1 , wherein the A-DMRS is sent using aperiodic sounding reference signal (A-SRS) resources configured for the UE with a use case that indicates A-DMRS.
19. The method of claim 18 , wherein the A-DMRS sent using A-DMRS resources is generated using an SRS sequence.
20. The method of claim 1 , further comprising determining priority handling when a collision between resources of the triggered A-DMRS and resources for another uplink transmission.
21. The method of claim 20 , wherein the priority handling is based at least one of:
a relative number of scheduled transmissions for the A-DMRS and the other uplink transmission; or
a type of information conveyed in the uplink transmission.
22. The method of claim 1 , further comprising multiplexing one or more other uplink transmissions in a same symbol as A-DMRS.
23. The method of claim 1 , further comprising:
receiving signaling, from the network entity, regarding presence of the A-DMRS from another UE; and
at least temporarily transmitting zero power in A-DMRS resources indicated in the signaling as used by the other UE.
24. The method of claim 1 , wherein transmitting the at least one PUSCH including the A-DMRS comprises transmitting the at least one PUSCH in at least two slots, and wherein the A-DMRS is located in a different slot adjacent to a slot of the at least one PUSCH.
25. The method of claim 24 , wherein the at least one PUSCH in the at least two slots comprises two PUSCH repetitions.
26. The method of claim 25 , wherein:
the current PUSCH DMRS configuration was signaled via radio resource control (RRC) signaling; and
the DMRS indicated in the current DMRS configuration are not impacted by triggering the A-DMRS.
27. A method for wireless communications by a network entity, comprising:
detecting at least one condition related to a channel between the network entity and a user equipment (UE);
triggering, based on the detection, the UE to transmit additional demodulation reference signal (A-DMRS) for at least one physical uplink shared channel (PUSCH), relative to DMRS indicated in a current PUSCH DMRS configuration, wherein the A-DMRS is triggered only when a number of resource blocks (RBs) allocated for the at least one PUSCH is at or below a threshold value; and
monitoring for the at least one PUSCH from the UE including the A-DMRS.
28. An apparatus for wireless communications by a user equipment (UE), comprising:
a memory; and
at least one processor coupled to the memory, the at least one processor configured to:
receive, from a network entity, signaling that triggers the UE to transmit additional demodulation reference signal (A-DMRS) for at least one physical uplink shared channel (PUSCH) transmission, relative to DMRS indicated in a current PUSCH DMRS configuration; and
transmit the at least one PUSCH including the A-DMRS, wherein the A-DMRS is triggered only when a number of resource blocks (RBs) allocated for the at least one PUSCH is at or below a threshold value.
29. An apparatus for wireless communications by a network entity, comprising:
a memory; and
at least one processor coupled to the memory, the at least one processor configured to:
detect at least one condition related to a channel between the network entity and a user equipment (UE);
trigger, based on the detection, the UE to transmit additional demodulation reference signal (A-DMRS) for at least one physical uplink shared channel (PUSCH), relative to DMRS indicated in a current PUSCH DMRS configuration, wherein the A-DMRS is triggered only when a number of resource blocks (RBs) allocated for the at least one PUSCH is at or below a threshold value; and
monitor for the at least one PUSCH from the UE including the A-DMRS.