Phase tracking reference signal for multi-transmit/receive points
A phase tracking reference signal (PT-RS) may be transmitted to enable a receiver to correct phase noise in wireless communication. A UE scheduled for one PDSCH with DMRS ports in two or more DMRS CDM groups that are associated with two TCI states may be configured for PT-RS using two PT-RS ports. Therefore, rather than limiting PT-RS to a single port, the PT-RS may be transmitted to the UE using two PT-RS ports. The apparatus transmits a capability indication for more than one PT-RS port for receiving a downlink shared channel based on a first TCI and a second TCI. The apparatus receives a configuration for a maximum number of downlink PT-RS ports from a base station.
1. A method of wireless communication at a user equipment (UE), comprising:
receiving downlink control information (DCI), a DCI field of the DCI indicating two transmission configuration indication (TCI) states for a PDSCH;
determining frequency division multiplexing (FDM) is to be used for the PDSCH, and a phase tracking reference signal (PT-RS) present in the PDSCH;
determining a PT-RS density in a frequency domain based on the two TCI states and based on determining that FDM is to be used for the PDSCH;
determining first resource elements for the PT-RS based on a first set of resource blocks (RBs) for a first TCI state; and
determining second resource elements for the PT-RS based on a second set of RBs for a second TCI state;
wherein determining the PT-RS density in the frequency domain comprises determining a first PT-RS density in the frequency domain that is based on a first number of allocated RBs for the first set of RBs and determining a second PT-RS density in the frequency domain that is based on a second number of allocated RBs for the second set of RBs, wherein the first resource elements are determined using the first PT-RS density and the second resource elements are determined using the second PT-RS density.
2. The method of claim 1 , further comprising receiving a configuration for a precoding resource block group (PRG) of two resource blocks (RBs), wherein the PT-RS density is determined further based on the PRG having the two RBs.
3. The method of claim 1 , wherein the UE determines that FDM is to be used for the PT-RS based on radio resource control (RRC) signaling or the DCI.
4. The method of claim 1 , wherein the first resource elements are determined based on a first RB offset that is based on a first number of allocated RBs for the first set of RBs and the second resource elements are determined based on a second RB offset that is based on a second number of allocated RBs for the second set of RBs.
5. The method of claim 1 , wherein the first resource elements and the second resource elements are determined based on a common resource element offset.
6. The method of claim 1 , wherein the UE uses a common set of thresholds to determine the first PT-RS density and the second PT-RS density.
7. A method of wireless communication at a base station, comprising:
transmitting downlink control information (DCI) to a user equipment (UE), a DCI field of the DCI indicating two transmission configuration indication (TCI) states for a PDSCH; and
transmitting a phase tracking reference signal (PT-RS) using frequency division multiplexing (FDM) and using a PT-RS density in a frequency domain that is based on the two TCI states, and the use of FDM for the PDSCH;
wherein the base station transmits the PT-RS using first resource elements for the PT-RS based on a first set of RBs for a first TCI state and using second resource elements for the PT-RS based on a second set of RBs for a second TCI state; and
wherein transmitting the PT-RS using the PT-RS density in the frequency domain comprises transmitting the PT-RS using a first PT-RS density in the frequency domain that is based on a first number of allocated RBs for the first set of RBs and a second PT-RS density in the frequency domain that is based on a second number of allocated RBs for the second set of RBs, wherein the first resource elements have the first PT-RS density and the second resource elements have the second PT-RS density.
8. The method of claim 7 , further comprising configuring the UE for a precoding resource block group (PRG) of two resource blocks (RBs), wherein the PT-RS density in the frequency domain is further based on the PRG having the two RBs.
9. The method of claim 7 , further comprising indicating to the UE that FDM is to be used for the PT-RS using radio resource control (RRC) signaling or the DCI.
10. The method of claim 7 , wherein the first resource elements are based on a first RB offset that is based on a first number of allocated RBs for the first set of RBs and the second resource elements are based on a second RB offset that is based on a second number of allocated RBs for the second set of RBs.
11. The method of claim 7 , wherein the first resource elements and the second resource elements are based on a common resource element offset.
12. The method of claim 7 , wherein a common set of thresholds is used to determine the first PT-RS density and the second PT-RS density.
13. An apparatus for wireless communication at a user equipment (UE), comprising:
a memory; and
at least one processor coupled to the memory and configured to:
receive downlink control information (DCI), a DCI field of the DCI indicating two transmission configuration indication (TCI) states for a PDSCH;
determine frequency division multiplexing (FDM) is to be used for the PDSCH, and a phase tracking reference signal (PT-RS) present in the PDSCH;
determine a PT-RS density in a frequency domain based on the two TCI states and based on determining that FDM is to be used for the PDSCH;
determine first resource elements for the PT-RS based on a first set of resource blocks (RBs) for a first TCI state; and
determine second resource elements for the PT-RS based on a second set of RBs for a second TCI state;
wherein the at least one processor is configured to determine the PT-RS density in the frequency domain by being configured to determine a first PT-RS density in the frequency domain that is based on a first number of allocated RBs for the first set of RBs and determine a second PT-RS density in the frequency domain that is based on a second number of allocated RBs for the second set of RBs, wherein the first resource elements are determined using the first PT-RS density and the second resource elements are determined using the second PT-RS density.
14. The apparatus of claim 13 , wherein the at least one processor is further configured to receive a configuration for a precoding resource block group (PRG) of two resource blocks (RBs), wherein the PT-RS density is determined further based on the PRG having the two RBs.
15. The apparatus of claim 13 , wherein the at least one processor determines that FDM is to be used for the PT-RS based on radio resource control (RRC) signaling or the DCI.
16. The apparatus of claim 13 , wherein the first resource elements are determined based on a first RB offset that is based on a first number of allocated RBs for the first set of RBs and the second resource elements are determined based on a second RB offset that is based on a second number of allocated RBs for the second set of RBs.
17. The apparatus of claim 13 , wherein the first resource elements and the second resource elements are determined based on a common resource element offset.
18. The apparatus of claim 13 , wherein the UE uses a common set of thresholds to determine the first PT-RS density and the second PT-RS density.
19. An apparatus for wireless communication at a base station, comprising:
a memory; and
at least one processor coupled to the memory and configured to:
transmit downlink control information (DCI) to a user equipment (UE), a DCI field of the DCI indicating two transmission configuration indication (TCI) states for a PDSCH; and
transmit a phase tracking reference signal (PT-RS) using frequency division multiplexing (FDM) and using a PT-RS density in a frequency domain that is based on the two TCI states, and the use of FDM for the PDSCH;
wherein the base station transmits the PT-RS using first resource elements for the PT-RS based on a first set of RBs for a first TCI state and using second resource elements for the PT-RS based on a second set of RBs for a second TCI state; and
wherein the at least one processor is configured to transmit the PT-RS using the PT-RS density in the frequency domain by being configured to transmit the PT-RS using a first PT-RS density in the frequency domain that is based on a first number of allocated RBs for the first set of RBs and a second PT-RS density in the frequency domain that is based on a second number of allocated RBs for the second set of RBs, wherein the first resource elements have the first PT-RS density and the second resource elements have the second PT-RS density.
20. The apparatus of claim 19 , wherein the at least one processor is further configured to configure the UE for a precoding resource block group (PRG) of two resource blocks (RBs), wherein the PT-RS density in the frequency domain is further based on the PRG having the two RBs.
21. The apparatus of claim 19 , wherein the at least one processor is further configured to indicate to the UE that FDM is to be used for the PT-RS using radio resource control RRC) signaling or the DCI.
22. The apparatus of claim 19 , wherein the first resource elements are based on a first RB offset that is based on a first number of allocated RBs for the first set of RBs and the second resource elements are based on a second RB offset that is based on a second number of allocated RBs for the second set of RBs.
23. The apparatus of claim 19 , wherein the first resource elements and the second resource elements are based on a common resource element offset.
24. The apparatus of claim 19 , wherein a common set of thresholds is used to determine the first PT-RS density and the second PT-RS density.