Phase tracking reference signal for sub-symbol phase tracking

1. A method for wireless communication, comprising:

identifying a discrete Fourier transform (DFT) configuration for a plurality of DFT-precoded symbols;

receiving the plurality of DFT-precoded symbols via a corresponding plurality of subcarriers within a wireless signal and non-DFT precoded symbols via additional subcarriers apart from the plurality of subcarriers within the wireless signal, the plurality of subcarriers including at least a subset of subcarriers that are adjacent in frequency;

estimating a phase error based at least in part on the plurality of DFT-precoded symbols and the DFT configuration; and

applying a phase correction based at least in part on the phase error to the non-DFT precoded symbols.

2. The method of claim 1 , further comprising:

processing the plurality of DFT-precoded symbols based at least in part on the DFT configuration to obtain a corresponding plurality of symbols.

3. The method of claim 2 , wherein estimating the phase error comprises:

comparing the plurality of symbols to a corresponding plurality of reference symbols in the time domain.

4. The method of claim 3 , further comprising:

receiving an indication of the plurality of reference symbols.

5. The method of claim 3 , wherein estimating the phase error further comprises:

computing a phase error trajectory for at least one of the plurality of subcarriers.

6. The method of claim 2 , wherein processing the plurality of DFT-precoded symbols comprises:

applying an inverse DFT (IDFT) to the plurality of DFT-precoded symbols.

7. The method of claim 2 , wherein processing the plurality of DFT-precoded symbols comprises:

accessing a lookup table that associates the plurality of symbols with the plurality of DFT-precoded symbols based at least in part on the DFT configuration; and

retrieving the plurality of symbols from memory.

8. The method of claim 1 , further comprising:

transmitting an indication of a preferred subcarrier.

9. The method of claim 1 , further comprising:

transmitting an indication of a preferred DFT configuration.

10. The method of claim 1 , wherein identifying the DFT configuration comprises:

receiving an indication of a number of DFT precoding units and a size of each DFT precoding unit.

11. The method of claim 1 , further comprising:

receiving an indication of the plurality of subcarriers.

12. The method of claim 1 , wherein applying the phase correction to the non-DFT precoded symbols occurs in either the time domain or the frequency domain.

13. The method of claim 1 , further comprising:

receiving at least one of the non-DFT precoded symbols via a subcarrier within the wireless signal that is interposed in frequency between two of the plurality of subcarriers.

14. The method of claim 1 , wherein receiving the plurality of DFT-precoded symbols comprises:

receiving subsets of the plurality of DFT-precoded symbols via respective subsets of the plurality of subcarriers, each subset of the plurality of DFT-precoded symbols associated with a respective DFT precoding unit, and each respective subset of the plurality of subcarriers comprising subcarriers that are adjacent in frequency.

15. The method of claim 1 , wherein the plurality of DFT-precoded symbols correspond to a plurality of phase tracking reference signal (PT-RS) symbols.

16. The method of claim 15 , wherein each of the plurality of PT-RS symbols corresponds to a distinct PT-RS sequence.

17. An apparatus for wireless communication, comprising:

a processor;

memory coupled to the processor; and

instructions stored in the memory and executable by the processor to cause the apparatus to:

identify a discrete Fourier transform (DFT) configuration for a plurality of DFT-precoded symbols;

receive the plurality of DFT-precoded symbols via a corresponding plurality of subcarriers within a wireless signal and non-DFT precoded symbols via additional subcarriers apart from the plurality of subcarriers within the wireless signal, the plurality of subcarriers including at least a subset of subcarriers that are adjacent in frequency;

estimate a phase error based at least in part on the plurality of DFT-precoded symbols and the DFT configuration; and

apply a phase correction based at least in part on the phase error to the non-DFT precoded symbols.

18. The apparatus of claim 17 , wherein the instructions are further executable by the processor to cause the apparatus to:

process the plurality of DFT-precoded symbols based at least in part on the DFT configuration to obtain a corresponding plurality of symbols.

19. The apparatus of claim 18 , wherein the instructions to estimate the phase error are executable by the processor to further cause the apparatus to:

compare the plurality of symbols to a corresponding plurality of reference symbols in the time domain.

20. The apparatus of claim 19 , wherein the instructions are further executable by the processor to cause the apparatus to:

receive an indication of the plurality of reference symbols.

21. The apparatus of claim 19 , wherein the instructions to estimate the phase error are executable by the processor to further cause the apparatus to:

compute a phase error trajectory for at least one of the plurality of subcarriers.

22. The apparatus of claim 18 , wherein the instructions to process the plurality of DFT-precoded symbols are executable by the processor to further cause the apparatus to:

apply an inverse DFT (IDFT) to the plurality of DFT-precoded symbols.

23. The apparatus of claim 18 , wherein the instructions to process the plurality of DFT-precoded symbols are executable by the processor to further cause the apparatus to:

access a lookup table that associates the plurality of symbols with the plurality of DFT-precoded symbols based at least in part on the DFT configuration; and

retrieve the plurality of symbols from memory.

24. The apparatus of claim 17 , wherein the instructions are further executable by the processor to cause the apparatus to:

transmit an indication of a preferred DFT configuration.

25. The apparatus of claim 17 , wherein the instructions to identify the DFT configuration are executable by the processor to further cause the apparatus to:

receive an indication of a number of DFT precoding units and a size of each DFT precoding unit.

26. The apparatus of claim 17 , wherein the instructions are further executable by the processor to cause the apparatus to:

receive at least one of the non-DFT precoded symbols via a subcarrier within the wireless signal that is interposed in frequency between two of the plurality of subcarriers.

27. The apparatus of claim 17 , wherein the instructions to receive the plurality of DFT-precoded symbols are executable by the processor to further cause the apparatus to:

receive subsets of the plurality of DFT-precoded symbols via respective subsets of the plurality of subcarriers, each subset of the plurality of DFT-precoded symbols associated with a respective DFT precoding unit, and each respective subset of the plurality of subcarriers comprising subcarriers that are adjacent in frequency.

28. The apparatus of claim 17 , wherein the plurality of DFT-precoded symbols correspond to a plurality of phase tracking reference signal (PT-RS) symbols.

29. An apparatus for wireless communication, comprising:

means for identifying a discrete Fourier transform (DFT) configuration for a plurality of DFT-precoded symbols;

means for receiving the plurality of DFT-precoded symbols via a corresponding plurality of subcarriers within a wireless signal and non-DFT precoded symbols via additional subcarriers apart from the plurality of subcarriers within the wireless signal, the plurality of subcarriers including at least a subset of subcarriers that are adjacent in frequency;

means for estimating a phase error based at least in part on the plurality of DFT-precoded symbols and the DFT configuration; and

means for applying a phase correction based at least in part on the phase error to the non-DFT precoded symbols.

30. A non-transitory computer-readable medium storing code for wireless communications, the code comprising instructions executable by a processor to:

identify a discrete Fourier transform (DFT) configuration for a plurality of DFT-precoded symbols;

receive the plurality of DFT-precoded symbols via a corresponding plurality of subcarriers within a wireless signal and non-DFT precoded symbols via additional subcarriers apart from the plurality of subcarriers within the wireless signal, the plurality of subcarriers including at least a subset of subcarriers that are adjacent in frequency;

estimate a phase error based at least in part on the plurality of DFT-precoded symbols and the DFT configuration; and

apply a phase correction based at least in part on the phase error to the non-DFT precoded symbols.