Channel state information reference signal for wideband operation

1. A method of wireless communication performed by an apparatus of a user equipment (UE), comprising:

receiving configuration information for a channel state information reference signal (CSI-RS),

wherein the configuration information indicates that the CSI-RS is configured on a plurality of sub-bands of a wideband structure;

selectively receiving the CSI-RS based on the configuration information and based on a sub-band valid indication associated with the plurality of sub-bands,

wherein, when all sub-bands of the plurality of sub-bands are available for the CSI-RS, the CSI-RS is received, and when at least one sub-band of the plurality of sub-bands is not available for the CSI-RS, the CSI-RS is not received; and

if the CSI-RS is received, transmitting channel state information (CSI) feedback based on the configuration information.

2. The method of claim 1 , further comprising:

receiving downlink control information indicating the sub-band valid indication.

3. The method of claim 1 , further comprising:

rate matching a shared channel around a resource of the CSI-RS irrespective of whether the CSI-RS is received.

4. The method of claim 1 , further comprising:

determining that the CSI-RS is to be received based on sub-band usage information received before a resource associated with the CSI-RS; and

performing a processing operation associated with the CSI-RS with respect to the plurality of sub-bands based on determining that the CSI-RS is to be received.

5. The method of claim 1 , wherein the CSI-RS is received on a subset of sub-bands of the plurality of sub-bands.

6. The method of claim 5 , wherein a sequence for the CSI-RS for the plurality of sub-bands is punctured to generate the CSI-RS for the subset of sub-bands.

7. The method of claim 5 , wherein the CSI-RS for the subset of sub-bands is generated based on a shortened sequence relative to a sequence for the CSI-RS for the plurality of sub-bands.

8. The method of claim 1 , further comprising:

receiving a trigger for the CSI feedback based on all sub-bands, of the plurality of sub-bands, being available for the CSI-RS.

9. The method of claim 1 , wherein, when the CSI-RS is received on a subset of sub-bands, of the plurality of sub-bands, the CSI-RS is received on resource elements on the subset of sub-bands that correspond to a widest bandwidth of the wideband structure.

10. The method of claim 9 , wherein the CSI-RS is generated based on a same sequence with respect to the widest bandwidth and with respect to the subset of sub-bands.

11. The method of claim 9 , wherein the CSI-RS spans 48 resource blocks in a sub-band of the subset of sub-bands.

12. The method of claim 9 , wherein the resource elements intersect with resource elements of the wideband structure.

13. The method of claim 1 , wherein the CSI-RS is for periodic or semi-persistent CSI feedback.

14. The method of claim 1 , wherein the CSI-RS is for aperiodic CSI feedback.

15. A method of wireless communication performed by an apparatus of a base station, comprising:

transmitting configuration information for a channel state information reference signal (CSI-RS),

wherein the configuration information indicates a plurality of sub-bands of a wideband structure for the CSI-RS;

performing a listen-before-talk (LBT) operation to identify a subset of sub-bands, of the plurality of sub-bands, that are available for the CSI-RS,

wherein the subset of sub-bands includes up to all sub-bands of the plurality of sub-bands; and

selectively transmitting the CSI-RS based on a result of the LBT operation,

wherein, when all sub-bands of the plurality of sub-bands are available for the CSI-RS, the CSI-RS is transmitted, and when at least one sub-band of the plurality of sub-bands is not available for the CSI-RS, the CSI-RS is not transmitted.

16. The method of claim 15 , further comprising:

rate matching a shared channel around a resource of the CSI-RS irrespective of whether the CSI-RS is transmitted.

17. The method of claim 15 , wherein the subset of sub-bands includes less than all sub-bands of the plurality of sub-bands.

18. The method of claim 17 , wherein a sequence for the CSI-RS for the plurality of sub-bands is punctured to generate the CSI-RS for the subset of sub-bands.

19. The method of claim 17 , wherein the CSI-RS for the subset of sub-bands is generated based on a shortened sequence, relative to a sequence for the CSI-RS for the plurality of sub-bands.

20. The method of claim 15 , further comprising:

transmitting a trigger for CSI feedback associated with the CSI-RS based on all sub-bands, of the plurality of sub-bands, being available for the CSI-RS.

21. The method of claim 15 , wherein, when the CSI-RS is transmitted on the subset of sub-bands of the plurality of sub-bands, the CSI-RS is transmitted on resource elements on the subset of sub-bands that correspond to a widest bandwidth of the wideband structure.

22. The method of claim 21 , wherein the CSI-RS is based on a same sequence with respect to the widest bandwidth and with respect to the subset of sub-bands.

23. The method of claim 21 , wherein the CSI-RS spans 48 resource blocks in a sub-band of the subset of sub-bands.

24. The method of claim 21 , wherein the resource elements intersect with resource elements of the wideband structure.

25. An apparatus of a user equipment (UE) for wireless communication, comprising:

a first interface configured to:

obtain configuration information for a channel state information reference signal (CSI-RS),

wherein the configuration information indicates that the CSI-RS is configured on a plurality of sub-bands of a wideband structure; and

selectively obtain the CSI-RS based on the configuration information and based on a sub-band valid indication associated with the plurality of sub-bands,

wherein, when all sub-bands of the plurality of sub-bands are available for the CSI-RS, the CSI-RS is obtained, and when at least one sub-band of the plurality of sub-bands is not available for the CSI-RS, the CSI-RS is not obtained; and

a second interface configured to transmit, if the CSI-RS is obtained, channel state information (CSI) feedback based on the configuration information.

26. An apparatus of a base station for wireless communication, comprising:

a first interface configured to:

output configuration information for a channel state information reference signal (CSI-RS),

wherein the configuration information indicates a plurality of sub-bands of a wideband structure for the CSI-RS; and

a processing system configured to:

perform a listen-before-talk (LBT) operation to identify a subset of sub-bands, of the plurality of sub-bands, that are available for the CSI-RS,

wherein the subset of sub-bands includes up to all sub-bands of the plurality of sub-bands,

wherein the first interface is further configured to:

selectively output the CSI-RS based on a result of the LBT operation,

wherein, when all sub-bands of the plurality of sub-bands are available for the CSI-RS, the CSI-RS is outputted, and when at least one sub-band of the plurality of sub-bands is not available for the CSI-RS, the CSI-RS is not outputted.

27. A method of wireless communication performed by an apparatus of a user equipment (UE), comprising:

receiving configuration information for a channel state information reference signal (CSI-RS),

wherein the configuration information indicates that the CSI-RS is configured on a plurality of sub-bands of a wideband structure;

selectively receiving the CSI-RS based on the configuration information and based on a sub-band valid indication associated with the plurality of sub-bands,

wherein the sub-band valid indication includes information indicating one or more sub-bands, of the plurality of sub-bands, that are valid or are not valid for communication; and

if the CSI-RS is received, transmitting channel state information (CSI) feedback based on the configuration information.

28. The method of claim 27 , wherein the sub-band valid indication includes a bitmap indicating the one or more sub-bands, listen-before-talk (LBT) bandwidths, or resource block (RB) sets on which communication is valid.

29. An apparatus of a user equipment (UE) for wireless communication, comprising:

a first interface configured to:

obtain configuration information for a channel state information reference signal (CSI-RS),

wherein the configuration information indicates that the CSI-RS is configured on a plurality of sub-bands of a wideband structure; and

selectively obtain the CSI-RS based on the configuration information and based on a sub-band valid indication associated with the plurality of sub-bands,

wherein the sub-band valid indication includes information indicating one or more sub-bands, of the plurality of sub-bands, that are valid or are not valid for communication; and

a second interface configured to transmit, if the CSI-RS is obtained, channel state information (CSI) feedback based on the configuration information.

30. The apparatus of claim 29 , wherein the sub-band valid indication includes a bitmap indicating the one or more sub-bands, listen-before-talk (LBT) bandwidths, or resource block (RB) sets on which communication is valid.

31. A method of wireless communication performed by an apparatus of a base station, comprising:

transmitting configuration information for a channel state information reference signal (CSI-RS),

wherein the configuration information indicates a plurality of sub-bands of a wideband structure for the CSI-RS;

performing a listen-before-talk (LBT) operation to identify a subset of sub-bands, of the plurality of sub-bands, that are available for the CSI-RS,

wherein the subset of sub-bands includes up to all sub-bands of the plurality of sub-bands,

wherein a sub-band valid indication indicates a result of the LBT operation, and

wherein the sub-band valid indication includes information indicating whether the subset of sub-bands are valid or are not valid for communication; and

selectively transmitting the CSI-RS based on the result of the LBT operation.

32. The method of claim 31 , wherein the sub-band valid indication includes a bitmap indicating the subset of sub-bands, LBT bandwidths, or resource block (RB) sets on which communication is valid.

33. An apparatus of a base station for wireless communication, comprising:

a first interface configured to:

output configuration information for a channel state information reference signal (CSI-RS),

wherein the configuration information indicates a plurality of sub-bands of a wideband structure for the CSI-RS; and

a processing system configured to:

perform a listen-before-talk (LBT) operation to identify a subset of sub-bands, of the plurality of sub-bands, that are available for the CSI-RS,

wherein the subset of sub-bands includes up to all sub-bands of the plurality of sub-bands,

wherein a sub-band valid indication indicates a result of the LBT operation, and

wherein the sub-band valid indication includes information indicating whether the subset of sub-bands are valid or are not valid for communication,

wherein the first interface is further configured to:

selectively output the CSI-RS based on the result of the LBT operation.

34. The apparatus of claim 33 , wherein the sub-band valid indication includes a bitmap indicating the subset of sub-bands, LBT bandwidths, or resource block (RB) sets on which communication is valid.