Time and frequency tracking reference signals in new radio
In NR, a slot structure of a UE may be dynamic due the number of symbols of PDCCH and whether the slot has UL data, among other considerations. Additionally, to support multi-TRP/multi-panel/multi-BWP operation, a UE may be configured with multiple TRSs, and when a UE needs to receive multiple TRSs in the same slot, efficient signaling of the TRSs is important because of the high overhead involved. During a transmission, a UE may need to do beam switching when there is a beam failure, but existing systems do not have mechanisms for the UE to synchronize time and frequency with a new beam. Further, when a UE switches to a new beam, the effect on scheduled TRS transmission for old beams is unclear. Fine frequency and time tracking may also be required during an initial access procedure. Existing NR systems do not address how a UE may perform time and frequency tracking during an initial access procedure. Additionally, URLLC data may need to be transmitted to a UE immediately in an NR system. Existing NR systems do not address sending a TRS to a UE with URLLC data. Embodiments described herein address these and other issues.
1. A wireless transmit/receive unit (WTRU) comprising a processor and memory storing instructions which, when executed by the processor, cause the WTRU to perform operations comprising:
receiving a tracking reference signal comprising resources located in one or more slots, wherein the resources are located in one or more symbols used for receiving a demodulation reference signal, and
wherein the one or more symbols in which the resources of the tracking reference signal are located are within a first five symbols in each of the one or more slots.
2. The WTRU of claim 1 , wherein at least one resource of the tracking reference signal is multiplexed with the demodulation reference signal.
3. The WTRU of claim 1 , wherein at least one resource of the tracking reference signal is multiplexed with one or more resources of a control resource set.
4. The WTRU of claim 1 , wherein:
a first symbol in which resources of the tracking reference signal are located is located within a symbol carrying at least one resource of a control resource set; and
a second symbol in which the resources of the tracking reference signal are located is located within a symbol carrying the demodulation reference signal.
5. The WTRU of claim 1 , wherein the one or more symbols in which the resources of the tracking reference signal are located in a first slot are repeated in a second slot.
6. The WTRU of claim 1 , wherein the instructions, when executed by the processor, further cause the WTRU to receive a configuration associated with the tracking reference signal dynamically in a downlink control information in a physical downlink control channel.
7. The WTRU of claim 6 , wherein the configuration associated with the tracking reference signal is received in an aperiodic reference signal.
8. The WTRU of claim 1 , wherein the instructions, when executed, further cause the WTRU to receive a tracking reference signal sequence, wherein the tracking reference signal sequence is generated based on a pseudo-noise sequence generation having an initializer that is a function of a WTRU-specific identifier and a symbol index.
9. The WTRU of claim 1 , wherein the instructions, when executed, further cause the WTRU to receive a configuration associated with the tracking reference signal via radio resource control (RRC) signaling.
10. A wireless transmit/receive unit (WTRU) comprising a processor and memory storing instructions which, when executed by the processor, cause the WTRU to perform operations comprising:
receiving a tracking reference signal comprising resources located in one or more slots, wherein the resources are located in one or more symbols used for receiving a demodulation reference signal, and
wherein at least one resource of the received tracking reference signal is frequency multiplexed with the demodulation reference signal.
11. The WTRU of claim 10 , wherein at least one resource of the tracking reference signal is frequency multiplexed with one or more resources of a control resource set.
12. The WTRU of claim 10 , wherein:
a first symbol in which resources of the tracking reference signal are located is located within a symbol carrying at least one resource of a control resource set; and
a second symbol in which the resources of the tracking reference signal are located is located within a symbol carrying the demodulation reference signal.
13. The WTRU of claim 10 , wherein the one or more symbols in which the resources of the tracking reference signal are located in a first slot are repeated in a second slot.
14. The WTRU of claim 10 , wherein the instructions, when executed by the processor, further cause the WTRU to receive a configuration associated with the tracking reference signal dynamically in a downlink control information in a physical downlink control channel.
15. The WTRU of claim 14 , wherein the configuration associated with the tracking reference signal is received in an aperiodic reference signal.
16. The WTRU of claim 10 , wherein the instructions, when executed, further cause the WTRU to receive a tracking reference signal sequence, wherein the tracking reference signal sequence is generated based on a pseudo-noise sequence generation having an initializer that is a function of a WTRU-specific identifier and a symbol index.
17. The WTRU of claim 10 , wherein the instructions, when executed, further cause the WTRU to receive a configuration associated with the tracking reference signal via radio resource control (RRC) signaling.