Phase tracking reference signal (PT-RS) configuration

1. A method, comprising:

by a user equipment (UE):

determining one or more phase tracking reference signal (PT-RS) time domain positions based on a modulation and coding scheme (MCS) index and one or more positions of one or more demodulation reference signal (DM-RS) symbols, wherein the one or more DMRS symbols comprise at least one front-loaded DM-RS symbol; and

generating at least one PT-RS using one or more of orthogonal frequency division multiplex (OFDM) symbols based on the determined one or more PT-RS time domain positions, wherein the at least one PT-RS occurs a first number of symbols subsequent to the at least one front-loaded DM-RS symbol, and wherein the first number of symbols is based on a PT-RS time domain density.

2. The method of claim 1 , further comprising:

determining the PT-RS time domain density based on the MCS index.

3. The method of claim 2 , wherein the PT-RS time domain density is determined based on the MCS index and a number count of the one or more DM-RS symbols.

4. The method of claim 2 , wherein the one or more DM-RS symbols comprise one or more additional DM-RS symbols, and wherein the method further comprises:

mapping a second PT-RS such that a second PT-RS time domain position occurs a second number of symbols subsequent to the one or more additional DM-RS symbols, wherein the second number of symbols is based on the PT-RS time domain density.

5. The method of claim 4 , further comprising:

determining that at least one of the one or more additional DM-RS symbols will collide with at least one PT-RS symbol at a common resource element; and

puncturing the at least one PT-RS symbol that is determined to collide with the at least one of the one or more additional DM-RS symbols at the common resource element.

6. The method of claim 4 , further comprising:

determining that at least one of the one or more additional DM-RS symbols will collide with at least one PT-RS symbol at a common resource element; and

shifting the at least one PT-RS symbol that is determined to collide with the at least one of the one or more additional DM-RS symbols to a neighboring symbol.

7. The method of claim 4 , further comprising:

determining that at least one of the one or more additional DM-RS symbols will collide with at least one PT-RS symbol at a common resource element; and

re-mapping the at least one PT-RS symbol for transmission in one or more neighboring symbols.

8. A processor configured to cause a user equipment (UE) to:

determine one or more phase tracking reference signal (PT-RS) time domain positions based on a modulation and coding scheme (MCS) index and one or more positions of one or more demodulation reference signal (DM-RS) symbols, wherein the one or more DMRS symbols comprise at least one front-loaded DM-RS symbol; and

generate at least one PT-RS using one or more of orthogonal frequency division multiplex (OFDM) symbols based on the determined one or more PT-RS time domain positions, wherein the at least one PT-RS occurs a first number of symbols subsequent to the at least one front-loaded DM-RS symbol, and wherein the first number of symbols is based on a PT-RS time domain density.

9. The processor of claim 8 , wherein the processor is further configured to cause the UE to:

determine the PT-RS time domain density based on the MCS index.

10. The processor of claim 9 , wherein the one or more DM-RS symbols comprise one or more additional DM-RS symbols, and wherein the processor is further configured to cause the UE to:

map a second PT-RS such that a second PT-RS time domain position occurs a second number of symbols subsequent to the one or more additional DM-RS symbols, wherein the second number of symbols is based on the PT-RS time domain density.

11. The processor of claim 8 , wherein the at least one PT-RS is encoded for transmission via a digital Fourier transform spread orthogonal frequency division multiplexing (DFT-s-OFDM) waveform, wherein the processor is further configured to cause the UE to:

decode downlink control information (DCI) from a base station, and wherein the DCI further configures at least one of the following: a configured sub-carrier spacing (SCS) threshold, a configured bandwidth (BW) threshold, or a configured MCS threshold.

12. The processor of claim 11 , wherein the processor is further configured to cause the UE to:

determine at least one of a number count of chunks or a chunk size for transmitting PT-RS symbols based on at least one of the following:

the configured SCS threshold,

the configured BW threshold, or

the configured MCS threshold.

13. The processor of claim 8 , wherein the processor is further configured to cause the UE to:

decode downlink control information (DCI) from a base station; and

decode a redundancy version indicator using the DCI, wherein the redundancy version indicator is associated with re-transmission of previously transmitted uplink data for a hybrid automatic repeat request (HARQ) process.

14. The processor of claim 13 , wherein the MCS index is a reserved MCS index indicating a modulation order without indicating a modulation coding scheme, and wherein the processor is further configured to cause the UE to:

determine an MCS index used in a prior transmission of the previously transmitted uplink data;

determine a second time domain PT-RS density for a second PT-RS associated with data re-transmission; and

encode the previously transmitted uplink data for re-transmission with the second PT-RS at the determined second PT-RS density.

15. A non-transitory computer readable storage medium storing program instructions executable by one or more baseband processors to cause a user equipment (UE) to:

determine one or more phase tracking reference signal (PT-RS) time domain positions based on a modulation and coding scheme (MCS) index and one or more positions of one or more demodulation reference signal (DM-RS) symbols, wherein the one or more DMRS symbols comprise at least one front-loaded DM-RS symbol; and

generate at least one PT-RS using one or more of orthogonal frequency division multiplex (OFDM) symbols based on the determined one or more PT-RS time domain positions, wherein the at least one PT-RS occurs a first number of symbols subsequent to the at least one front-loaded DM-RS symbol, and wherein the first number of symbols is based on a PT-RS time domain density.

16. The non-transitory computer readable storage medium of claim 15 , wherein the program instructions are further executable by the one or more baseband processors to cause the UE to:

determine the PT-RS time domain density based on the MCS index.

17. The non-transitory computer readable storage medium of claim 16 , wherein the one or more DM-RS symbols comprise one or more additional DM-RS symbols, and wherein the program instructions are further executable by the one or more baseband processors to cause the UE to:

map a second PT-RS such that a second PT-RS time domain position occurs a second number of symbols subsequent to the one or more additional DM-RS symbols, wherein the second number of symbols is based on the PT-RS time domain density.

18. The non-transitory computer readable storage medium of claim 15 , wherein the program instructions are further executable by the one or more baseband processors to cause the UE to:

decode downlink control information (DCI) from a base station, wherein the DCI includes scheduling of at least two physical downlink shared channel (PDSCH) codewords mapped to different multiple-input-multiple-output (MIMO) layers, and wherein each of the at least two PDSCH codewords is associated with a corresponding MCS indicator.

19. The non-transitory computer readable storage medium of claim 18 , wherein the program instructions are further executable by the one or more baseband processors to cause the UE to:

determine a density pattern for the at least one PT-RS based on the corresponding MCS indicators associated with the at least two PDSCH codewords; and

encode the at least one PT-RS for transmission using one or more PT-RS antenna ports and based on the determined density pattern.

20. The non-transitory computer readable storage medium of claim 19 , wherein the program instructions are further executable by the one or more baseband processors to cause the UE to:

select an extreme-valued MCS indicator of the corresponding MCS indicators; and

determine the density pattern based on the extreme-valued MCS indicator.