Orthogonal time frequency space precoding for tracking reference signal
Various aspects of the present disclosure generally relate to wireless communication. In some aspects, a first network node may apply an orthogonal time frequency space (OTFS) precoding to a plurality of tracking reference signal (TRS) resource samples allocated in a delay-Doppler domain to obtain a plurality of TRS symbols with the OTFS precoding. The first network node may transmit, to a second network node, a TRS in which the plurality of TRS symbols with the OTFS precoding have a uniform spacing in a time domain. Numerous other aspects are described.
1. A first network node for wireless communication, comprising:
a memory; and
one or more processors communicatively coupled to the memory, wherein the one or more processors are configured to:
apply an orthogonal time frequency space (OTFS) precoding to a plurality of tracking reference signal (TRS) resource samples allocated in a delay-Doppler domain to obtain a plurality of TRS symbols with the OTFS precoding; and
transmit, to a second network node, a TRS in which the plurality of TRS symbols with the OTFS precoding have a uniform spacing in a time domain.
2. The first network node of claim 1 , wherein the TRS is transmitted in a plurality of slots, and wherein each respective slot of the plurality of slots includes a single respective TRS symbol of the plurality of TRS symbols.
3. The first network node of claim 1 , wherein the plurality of TRS symbols occupy a plurality of subcarriers that have a uniform spacing in a frequency domain.
4. The first network node of claim 1 , wherein the plurality of TRS symbols occupy a continuous plurality of subcarriers in a frequency domain.
5. The first network node of claim 4 , wherein the continuous plurality of subcarriers includes edge subcarriers that are occupied by guard symbols.
6. The first network node of claim 5 , wherein the guard symbols include zeros or a cyclic prefix portion of the TRS.
7. The first network node of claim 1 , wherein the one or more processors are configured to apply the OTFS precoding to the plurality of TRS resource samples by applying an inverse symplectic fast Fourier transform (ISFFT) to the plurality of TRS resource samples to convert the plurality of TRS resource samples from the delay-Doppler domain to a time-frequency domain.
8. The first network node of claim 7 , wherein the ISFFT is applied to a data structure in which the plurality of TRS resource samples are positioned.
9. The first network node of claim 8 , wherein the data structure is a matrix comprising M×N matrix entries, wherein M is an integer greater than one and Nis an integer greater than one, wherein each respective matrix entry in a first column of the M×N matrix entries includes a respective TRS resource sample of the plurality of TRS resource samples, and wherein each respective matrix entry in each column other than the first column of the M×N matrix entries includes a zero.
10. The first network node of claim 1 , wherein the one or more processors are further configured to:
transmit signaling to the second network node, wherein the signaling indicates a respective location for one or more respective TRS symbols of the plurality of TRS symbols within one or more respective slots.
11. The first network node of claim 1 , wherein the one or more processors are further configured to:
transmit, to the second network node, signaling that indicates a resource allocation associated with the plurality of TRS symbols in a frequency domain.
12. The first network node of claim 1 , wherein the one or more processors are further configured to:
select a resource allocation associated with the plurality of TRS symbols in a frequency domain based on a channel delay or a Doppler spread between the first network node and the second network node.
13. The first network node of claim 1 , wherein the one or more processors are further configured to:
receive, from the second network node, signaling that indicates whether the second network node has a capability to support an OTFS-precoded TRS, wherein the OTFS precoding is applied based on the signaling that indicates whether the second network node has the capability to support the OTFS-precoded TRS.
14. The first network node of claim 13 , wherein the signaling that indicates whether the second network node has the capability to support the OTFS-precoded TRS indicates that the second network node has the capability to support the OTFS-precoded TRS.
15. A first network node of wireless communication performed by a first network node, comprising:
a memory; and
one or more processors communicatively coupled to the memory, wherein the one or more processors are configured to:
receive, from a second network node, a tracking reference signal (TRS) that includes a plurality of TRS symbols with an orthogonal time frequency space (OTFS) precoding, wherein the plurality of TRS symbols have a uniform spacing in a time domain; and
decode the TRS based on the OTFS precoding to obtain a plurality of TRS resource samples in a delay-Doppler domain.
16. The first network node of claim 15 , wherein the TRS is received in a plurality of slots, and wherein each respective slot of the plurality of slots includes a single respective TRS symbol of the plurality of TRS symbols.
17. The first network node of claim 15 , wherein the plurality of TRS symbols occupy a plurality of subcarriers that have a uniform spacing in a frequency domain.
18. The first network node of claim 15 , wherein the plurality of TRS symbols occupy a continuous plurality of subcarriers in a frequency domain.
19. The first network node of claim 18 , wherein the continuous plurality of subcarriers includes edge subcarriers that are occupied by guard symbols.
20. The first network node of claim 19 , wherein the guard symbols include zeros or a cyclic prefix portion of the TRS.
21. The first network node of claim 15 , wherein the one or more processors are configured to decode the TRS by applying a symplectic fast Fourier transform (SFFT) to the plurality of TRS symbols to convert the plurality of TRS symbols from a time-frequency domain to the delay-Doppler domain.
22. The first network node of claim 15 , wherein the one or more processors are further configured to:
receive signaling from the second network node, wherein the signaling indicates a respective location for one or more respective TRS symbols of the plurality of TRS symbols within one or more respective slots.
23. The first network node of claim 15 , wherein the one or more processors are further configured to:
receive, from the second network node, signaling that indicates a resource allocation associated with the plurality of TRS symbols in a frequency domain.
24. The first network node of claim 15 , wherein the one or more processors are further configured to:
transmit, to the second network node, signaling that indicates whether the first network node has a capability to support an OTFS-precoded TRS.
25. The first network node of claim 15 , wherein the one or more processors are further configured to:
estimate a Doppler frequency from the second network node based on the plurality of TRS resource samples in the delay-Doppler domain.
26. The first network node of claim 25 , wherein the one or more processors are further configured to:
transmit, to the second network node, a sounding reference signal that indicates the estimated Doppler frequency from the second network node.
27. A method of wireless communication performed by a first network node, comprising:
applying an orthogonal time frequency space (OTFS) precoding to a plurality of tracking reference signal (TRS) resource samples allocated in a delay-Doppler domain to obtain a plurality of TRS symbols with the OTFS precoding; and
transmitting, to a second network node, a TRS in which the plurality of TRS symbols with the OTFS precoding have a uniform spacing in a time domain.
28. The method of claim 27 , wherein the TRS is transmitted in a plurality of slots, and wherein each respective slot of the plurality of slots includes a single respective TRS symbol of the plurality of TRS symbols.
29. A method of wireless communication performed by a first network node, comprising:
receiving, from a second network node, a tracking reference signal (TRS) that includes a plurality of TRS symbols with an orthogonal time frequency space (OTFS) precoding, wherein the plurality of TRS symbols have a uniform spacing in a time domain; and
decoding the TRS based on the OTFS precoding to obtain a plurality of TRS resource samples in a delay-Doppler domain.
30. The method of claim 29 , wherein the TRS is received in a plurality of slots, and wherein each respective slot of the plurality of slots includes a single respective TRS symbol of the plurality of TRS symbols.