Channel state information (CSI) for unlicensed spectrum
This disclosure provides systems, methods, and apparatuses for the identification of a channel state information reference signal (CSI-RS) resource. In some aspects, a UE that receives the CSI-RS may determine CSI feedback based at least in part on the CSI-RS after detecting the CSI-RS resource that includes the CSI-RS. Signaling or techniques for when no CSI-RS is detected (such as when the base station fails a channel access operation for all available CSI-RS resources) are also provided. Furthermore, approaches for rate matching for a shared channel around CSI-RS resources or for CSI interference management (CSI-IM) resources are provided, as well as CSI reporting approaches for cases when the UE fails to transmit CSI feedback due to a failed channel access operation, such as a triggered or re-triggered CSI report.
1. A method of wireless communication performed at a user equipment (UE), comprising:
receiving configuration information that indicates a plurality of channel state information reference signal (CSI-RS) resources associated with a CSI-RS;
using a measurement-based approach based on not receiving an explicit indication that indicates the CSI-RS was transmitted using one of the plurality of CSI-RS resources, wherein using the measurement-based approach comprises:
measuring one or more CSI-RS resources of the plurality of CSI-RS resources; and
selecting one of the plurality of CSI-RS resources based on the measurement of the one or more CSI-RS resources; and
transmitting, based on a particular signal strength value of the selected one of the plurality of CSI-RS resources, a CSI report that includes channel state information (CSI) or other information associated with the CSI-RS.
2. The method of claim 1 , further comprising:
receiving the CSI-RS, wherein the CSI report is transmitted after receiving the CSI-RS.
3. The method of claim 1 , wherein, when the CSI-RS is not received, the CSI report relates to another CSI-RS received by the UE before receiving the configuration information that indicates the plurality of CSI-RS resources.
4. The method of claim 1 , wherein, when the CSI-RS is not received, the CSI report indicates that the CSI-RS is not received.
5. The method of claim 1 , wherein the CSI report comprises at least one of:
an indication that the selected one of the plurality of CSI-RS resources is associated with the CSI report,
an indication of a CSI period associated with the CSI report, or
an indication of whether the CSI report is valid.
6. The method of claim 1 , further comprising:
receiving a grant for a shared channel that overlaps at least one CSI-RS resource of the plurality of CSI-RS resources; and
rate matching the shared channel around the at least one CSI-RS resource.
7. The method of claim 6 , wherein the at least one CSI-RS resource is for a zero-power CSI-RS.
8. The method of claim 1 , further comprising:
receiving a trigger for a retransmission of the CSI report, wherein the trigger identifies the CSI report as an aperiodic CSI report, a periodic CSI report, or a semi-persistent CSI report; and
performing the retransmission of the CSI report in accordance with the trigger.
9. The method of claim 8 , wherein the trigger includes an indication that the trigger is an aperiodic retransmission trigger for the CSI report.
10. The method of claim 8 , wherein the trigger includes an indication of at least one of:
an uplink resource for the retransmission of the CSI report,
encoding information for the retransmission of the CSI report, or
a channel access type for the retransmission of the CSI report.
11. The method of claim 8 , wherein the trigger identifies the CSI report as the semi-persistent CSI report.
12. The method of claim 8 , wherein performing the retransmission of the CSI report in accordance with the trigger further comprises performing the retransmission based on a maximum time limit associated with the trigger and a previous trigger for the CSI report.
13. An apparatus for wireless communication, comprising:
memory comprising instructions; and
one or more processors configured to execute the instructions and cause the apparatus to:
obtain configuration information that indicates a plurality of channel state information reference signal (CSI-RS) resources associated with a CSI-RS;
use a measurement-based approach based on not obtaining an explicit indication that indicates the CSI-RS was transmitted using one of the plurality of CSI-RS resources, wherein, to use the measurement-based approach, the one or more processors are configured to execute the instructions and cause the apparatus to:
measure one or more CSI-RS resources of the plurality of CSI-RS resources; and
select the one of the plurality of CSI-RS resources based on the measurement of the one or more CSI-RS resources; and
output, based on a particular signal strength value of the selected one of the plurality of CSI-RS resources, a CSI report that includes channel state information (CSI) or other information associated with the CSI-RS.
14. The apparatus of claim 13 , wherein the one or more processors are configured to execute the instructions and cause the apparatus further to:
obtain the CSI-RS before outputting the CSI report.
15. The apparatus of claim 13 ,
wherein the configuration information further indicates that the CSI-RS is transmittable on the plurality of CSI-RS resources, and
wherein the configuration information identifies one or more slot offsets for resource allocations for the plurality of CSI-RS resources.
16. The apparatus of claim 13 , wherein the explicit indication is a bitmap obtained via a common physical downlink control channel (PDCCH).
17. The apparatus of claim 13 , wherein, when the CSI-RS has not been obtained, the CSI report relates to another CSI-RS obtained by the apparatus before the configuration information that indicates the plurality of CSI-RS resources is obtained.
18. The apparatus of claim 13 , wherein, when the CSI-RS has not been obtained, the CSI report indicates that the CSI-RS has not been obtained.
19. The apparatus of claim 13 , wherein the CSI report comprises at least one of:
an indication that the selected one of the plurality of CSI-RS resources is associated with the CSI report,
an indication of a CSI period associated with the CSI report, or
an indication of whether the CSI report is valid.
20. The apparatus of claim 13 ,
wherein the one or more processors are configured to execute the instructions and cause the apparatus further to:
obtain a grant for a shared channel that overlaps at least one CSI-RS resource of the plurality of CSI-RS resources; and
wherein the shared channel is rate matched around the at least one CSI-RS resource.
21. The apparatus of claim 20 , wherein the at least one CSI-RS resource is for a zero-power CSI-RS.
22. The apparatus of claim 13 , wherein the one or more processors are configured to execute the instructions and cause the apparatus further to:
obtain a trigger for a retransmission of the CSI report, wherein the trigger identifies the CSI report as an aperiodic CSI report, a periodic CSI report, or a semi-persistent CSI report; and
output, for retransmission, the CSI report in accordance with the trigger.
23. The apparatus of claim 22 , wherein the trigger includes an indication that the trigger is an aperiodic retransmission trigger for the CSI report.
24. The apparatus of claim 22 , wherein the trigger includes an indication of at least one of:
an uplink resource for the retransmission of the CSI report,
encoding information for the retransmission of the CSI report, or
a channel access type for the retransmission of the CSI report.
25. The apparatus of claim 22 , wherein the trigger identifies the CSI report as the semi-persistent CSI report.
26. The apparatus of claim 22 , wherein, to output, for retransmission, the CSI report in accordance with the trigger, the one or more processors are configured to execute the instructions and cause the apparatus to:
output, for retransmission, the CSI report based on a maximum time limit associated with the trigger and a previous trigger for the CSI report.
27. A user equipment (UE), comprising:
a transceiver;
memory comprising instructions; and
one or more processors configured to execute the instructions and cause the user equipment to:
receive, via the transceiver, configuration information that indicates a plurality of channel state information reference signal (CSI-RS) resources associated with a CSI-RS;
use a measurement-based approach based on not receiving an explicit indication that indicates the CSI-RS was transmitted using one of the plurality of CSI-RS resources, wherein, to use the measurement-based approach, the one or more processors are configured to execute the instructions and cause the user equipment to:
measure one or more CSI-RS resources of the plurality of CSI-RS resources; and
select the one of the plurality of CSI-RS resources based on the measurement of the one or more CSI-RS resources; and
transmit, via the transceiver and based on a particular signal strength value of the selected one of the plurality of CSI-RS resources, a CSI report that includes channel state information (CSI) or other information associated with the CSI-RS.
28. The UE of claim 27 ,
wherein the configuration information further indicates that the CSI-RS is transmittable on the plurality of CSI-RS resources, and
wherein the configuration information identifies one or more slot offsets for resource allocations for the plurality of CSI-RS resources.
29. The UE of claim 27 , wherein the explicit indication is a bitmap received via a common physical downlink control channel (PDCCH).
30. The UE of claim 27 , wherein, when the CSI-RS is not received, the CSI report relates to another CSI-RS received by the UE before the configuration information that indicates the plurality of CSI-RS resources is obtained.
31. The UE of claim 27 , wherein the particular signal strength value is a highest signal strength value of one or more signal strength values associated with the one or more CSI-RS resources or the particular signal strength value satisfies a signal strength threshold used for In-Sync metric evaluation.
32. The UE of claim 27 , wherein the explicit indication is configured to be provided via a common physical downlink control channel (PDCCH) or a UE-specific PDCCH, and indicates whether one or more CSI-RSs were transmitted in a CSI-RS period.
33. The UE of claim 27 , wherein the particular signal strength value is a highest signal strength value of one or more signal strength values associated with the one or more measured CSI-RS resources.