Frequency tracking and timing tracking using wideband reference signal(s)
Certain aspects of the present disclosure provide techniques for frequency tracking and timing tracking using wideband reference signals (RSs). A method that may be performed by a user equipment (UE) includes monitoring for a wideband RS from a network entity when one or more conditions are met, the wideband RS occupying a wider band of frequency resources than a tracking reference signal (TRS) transmitted by the network entity; and performing at least one of frequency tracking or timing tracking based on the monitoring.
1. An apparatus for wireless communications at a user equipment (UE), the apparatus comprising:
memory capable of storing computer-executable code;
a transceiver; and
one or more processors coupled to the memory and the transceiver, the one or more processors configured to, before receiving a tracking reference signal (TRS) configuration from a network entity:
monitor for a wideband reference signal (RS) from the network entity, the wideband RS occupying a wider band of frequency resources than a TRS; and
perform at least one of frequency tracking or timing tracking based on the monitoring.
2. The apparatus of claim 1 , wherein the wideband RS comprises a wideband demodulation reference signal (DMRS) transmitted from the network entity using a wideband precoder.
3. The apparatus of claim 2 , wherein the one or more processors are further configured to:
receive, via the transceiver, a radio resource control (RRC) configuration indicating the wideband precoder;
receive, via the transceiver, a downlink control information (DCI) message scheduling a transmission; and
receive, via the transceiver, the transmission, wherein the transmission is transmitted by the network with the wideband DMRS using the wideband precoder.
4. The apparatus of claim 1 , wherein the monitoring the wideband RS from the network entity is in response to at least one of:
a synchronization signal block (SSB) subcarrier spacing (SCS) being less than a physical downlink shared channel (PDSCH) SCS; or
the UE receiving system information (SI) indicating the UE is to use the wideband RS to perform at least one of frequency tracking or timing tracking for an upcoming transmission.
5. The apparatus of claim 1 , wherein the one or more processors are further configured to transmit an indication to the network entity that the UE supports timing offset compensation (TOC) using the wideband RS, and wherein the monitoring the wideband RS is in response to transmitting the indication.
6. The apparatus of claim 5 , wherein the one or more processors are further configured to:
receive, via the transceiver, signaling indicating for the UE to perform time refinement based on the wideband RS; and
in a radio resource control (RRC) connected mode, after receiving the TRS configuration:
monitor the wideband RS from the network entity; and
perform TOC based on the monitoring.
7. The apparatus of claim 1 , wherein the one or more processors are further configured to:
receive, via the transceiver, a downlink control information (DCI) message indicating at least two transmission configuration indicator (TCI) states; and
apply different bundle sizes for transmissions using the at least two TCI states.
8. The apparatus of claim 7 , wherein the applying the different bundle sizes for the transmissions using the at least two TCI states comprises:
applying a first bundle size indicated in the DCI for transmissions using a first TCI state of the at least two TCI states; and
applying a second bundle size for transmissions using a second TCI state of the at least two TCI states, wherein the second bundle size is indicated via a radio resource control (RRC) message, indicated via a medium access control (MAC) control element (CE) message, derived from a TRS transmission, or indicated in the DCI.
9. The apparatus of claim 7 , wherein the different bundle sizes are configured for the at least two TCI states.
10. The apparatus of claim 7 , wherein the different bundle sizes are determined based on a field in the DCI that maps to a vector of bundling sizes for the at least two TCI states.
11. The apparatus of claim 1 , wherein the one or more processors are further configured to, after receiving the TRS configuration:
monitor for the TRS with one or more beams that are quasi co-located (QCL'ed) with one or more beams used for monitoring for the wideband RS; and
jointly process the wideband RS and the TRS to perform at least one of frequency tracking, timing tracking, or frequency offset estimation refinement.
12. The apparatus of claim 11 , wherein the one or more processors are further configured to refine a frequency offset estimation based on the joint processing.
13. The apparatus of claim 11 , wherein the one or more processors are further configured to receive, via the transceiver, an indication of whether or not a same precoder was used for the wideband RS and the TRS, and wherein the indication is received via at least one of: a radio resource control (RRC) message, a medium access control (MAC) control element (CE) message, or downlink control information (DCI).
14. The apparatus of claim 1 , wherein the monitoring for the wideband RS from the network entity is in response to the UE being in a radio resource control (RRC) idle or RRC inactive state.
15. An apparatus for wireless communications by a network entity, the apparatus comprising:
memory capable of storing computer-executable code; and
one or more processors coupled to the memory, the one or more processors configured to, before transmitting a tracking reference signal (TRS) configuration to a user equipment (UE):
transmit, to the UE, wideband reference signals (RS) that occupy a wider band of frequency resources than TRS transmitted by the network entity; and
transmit data to the UE after transmitting the wideband RS.
16. The apparatus of claim 15 , wherein the wideband RS comprises a wideband demodulation reference signal (DMRS) transmitted from the network entity using a wideband precoder.
17. The apparatus of claim 16 , wherein the one or more processors are further configured to:
transmit a radio resource control (RRC) configuration indicating the wideband precoder;
transmit a downlink control information (DCI) message scheduling a transmission; and
transmit the transmission with the wideband DMRS using the wideband precoder.
18. The apparatus of claim 16 , wherein the monitoring the wideband RS from the network entity is in response to at least one of:
a synchronization signal block (SSB) subcarrier spacing (SCS) being less than a physical downlink shared channel (PDSCH) SCS; or
the UE receiving system information (SI) indicating the UE is to use the wideband DMRS to perform at least one of frequency tracking or timing tracking for an upcoming transmission.
19. The apparatus of claim 15 , wherein the one or more processors are further configured to receive an indication from the UE that the UE supports timing offset compensation (TOC) using the wideband RS, and wherein the transmitting the wideband RS is in response to receiving the indication.
20. The apparatus of claim 19 , wherein the one or more processors are further configured to configure:
a first set of one or more user equipments (UEs) that indicate support of TOC using the wideband RS with fewer TRS transmissions than configured for a second set of one or more UEs that do not indicate support of TOC using the wideband RS.
21. The apparatus of claim 19 , wherein the one or more processors are further configured to transmit signaling for the UE to perform time refinement based on the wideband RS in a radio resource control (RRC) connected mode.
22. The apparatus of claim 15 , wherein the one or more processors are further configured to transmit a downlink control information (DCI) message indicating at least two transmission configuration indicator (TCI) states associated with different bundling sizes.
23. The apparatus of claim 22 , wherein the different bundling sizes comprise:
a first bundle size indicated in the DCI for transmissions using a first TCI state; and
a second bundle size for transmissions using a second TCI state, wherein the second bundle size is indicated via a radio resource control (RRC) message, indicated via a medium access control (MAC) control element (CE) message, derived from a TRS transmission, or indicated in the DCI.
24. The apparatus of claim 15 , wherein the one or more processors are further configured to transmit TRS to the UE, wherein the network entity transmits the wideband RS and the TRS with beams that are quasi co-located (QCL'ed).
25. The apparatus of claim 24 , wherein the one or more processors are further configured to transmit an indication of whether or not a same precoder was used for the wideband RS and the TRS, and wherein the indication is transmitted via at least one of a radio resource control (RRC) message, a medium access control (MAC) control element (CE) message, or downlink control information (DCI).
26. The apparatus of claim 15 , wherein the transmitting the wideband RS to the UE is in response to the UE being in a radio resource control (RRC) idle or RRC inactive state.
27. A method for wireless communications by a user equipment (UE), the method comprising:
before receiving a tracking reference signal (TRS) configuration from a network entity:
monitoring for a wideband reference signal (RS) from the network entity, the wideband RS occupying a wider band of frequency resources than a TRS; and
performing at least one of frequency tracking or timing tracking based on the monitoring.
28. The method of claim 27 , wherein the wideband RS comprises a wideband demodulation reference signal (DMRS) transmitted from the network entity using a wideband precoder.
29. A method for wireless communications by a network entity, method comprising:
before transmitting a tracking reference signal (TRS) configuration to a user equipment (UE):
transmitting, to the UE, wideband reference signals (RS) that occupy a wider band of frequency resources than a TRS transmitted by the network entity; and
transmitting data to the UE after transmitting the wideband RS.