Leveraging CSI temporal correlation for efficient beam domain CSI compression

1 . A Wireless Transmit/Receive Unit (WTRU) comprising:

a memory; and

a processor coupled to the memory, the processor configured to:

receive configuration information for channel state information (CSI) feedback;

receive a first CSI reference signal (CSI-RS) transmission;

receive a second CSI-RS transmission;

determine, based on the first CSI-RS transmission and the second CSI-RS transmission, a first subset of beams of a plurality of beams and a second subset of beams of the plurality of beams;

determine, based on the first CSI-RS transmission and the second CSI-RS transmission, a first parameter associated with the first subset of beams and a second parameter associated with the second subset of beams, wherein the first parameter comprises a first validity time, a first beam range, or a first beam step, wherein the second parameter comprises a second validity time, a second beam range, or a second beam step, and wherein the first subset of beams is associated with at least one of: (i) a longer validity time than a validity time of the second subset of beams, (ii) a lower beam range than a beam range of the second subset of beams, or (iii) a smaller beam step than a beam step of the second subset of beams; and

send one or more reports, wherein the one or more reports comprise an indication of the first subset of beams, an indication of the first parameter associated with the first subset of beams, an indication of the second subset of beams, and an indication of the second parameter associated with the second subset of beams.

2 . The WTRU of claim 1 , wherein the configuration information comprises one or more of an indication of a number of beam subsets, an indication of a minimum number of beams per subset, an indication of a maximum number of beams per subset, or an indication of a default number of beams per subset.

3 . The WTRU of claim 1 , wherein the configuration information comprises one or more of an indication of an initial validity time associated with each beam subset, an indication of a minimum validity time associated with each beam subset, or an indication of a maximum validity time associated with each beam subset.

4 . The WTRU of claim 1 , wherein the configuration information comprises one or more of an indication of a beam range threshold or an indication of a differential beam step threshold.

5 . The WTRU of claim 1 , wherein the configuration information comprises an indication of a beam subset reporting format.

6 . The WTRU of claim 1 , wherein the processor is configured to:

determine CSI measurements based on the first CSI-RS transmission and the second CSI-RS transmission; and

determine which beam is included in the first subset of beams of the plurality of beams and which beam is included in the second subset of beams of the plurality of beams based on the CSI measurements.

7 . The WTRU of claim 1 , wherein one or more first reports of the one or more reports comprise the indication of the first parameter associated with the first subset of beams, wherein one or more second reports of the one or more reports comprise the indication of the second parameter associated with the second subset of beams, and wherein a lower number of reporting instances are utilized to send the one or more first reports than a number of reporting instances utilized to send the one or more second reports.

8 . The WTRU of claim 1 , wherein one or more first reports of the one or more reports comprise information associated with the first subset of beams, and wherein the one or more first reports are sent in response to a determination that transmission performance associated is less than a threshold.

9 . The WTRU of claim 1 , wherein the processor is configured to:

pre-process a first CSI associated with the first CSI-RS transmission utilizing the first subset of beams and the second subset of beams;

perform CSI compression utilizing a beam domain auto encoder (BDAE) based on the pre-processed first CSI; and

send the compressed CSI to a network.

10 . The WTRU of claim 1 , wherein the validity time indicates how long a beam subset is valid for beam transformation, wherein the beam range indicates a difference between a maximum beam index and a minimum beam index of a beam subset over a time period, and wherein the beam step indicates a maximum difference between beam indices associated with consecutive beam domain reporting instances of a beam subset.

11 . A method performed by a Wireless Transmit/Receive Unit (WTRU), the method comprising:

receiving configuration information for channel state information (CSI) feedback;

receiving a first CSI reference signal (CSI-RS) transmission;

receiving a second CSI-RS transmission;

determining, based on the first CSI-RS transmission and the second CSI-RS transmission, a first subset of beams of a plurality of beams and a second subset of beams of the plurality of beams;

determining, based on the first CSI-RS transmission and the second CSI-RS transmission, a first parameter associated with the first subset of beams and a second parameter associated with the second subset of beams, wherein the first parameter comprises a first validity time, a first beam range, or a first beam step, wherein the second parameter comprises a second validity time, a second beam range, or a second beam step, and wherein the first subset of beams is associated with at least one of: (i) a longer validity time than a validity time of the second subset of beams, (ii) a lower beam range than a beam range of the second subset of beams, or (iii) a smaller beam step than a beam step of the second subset of beams; and

sending one or more reports, wherein the one or more reports comprise an indication of the first subset of beams, an indication of the first parameter associated with the first subset of beams, an indication of the second subset of beams, and an indication of the second parameter associated with the second subset of beams.

12 . The method of claim 11 , wherein the configuration information comprises one or more of an indication of a number of beam subsets, an indication of a minimum number of beams per subset, an indication of a maximum number of beams per subset, or an indication of a default number of beams per subset.

13 . The method of claim 11 , wherein the configuration information comprises one or more of an indication of an initial validity time associated with each beam subset, an indication of a minimum validity time associated with each beam subset, or an indication of a maximum validity time associated with each beam subset.

14 . The method of claim 11 , wherein the configuration information comprises one or more of an indication of a beam range threshold or an indication of a differential beam step threshold.

15 . The method of claim 11 , wherein the configuration information comprises an indication of a beam subset reporting format.

16 . The method of claim 11 , further comprising:

determining CSI measurements based on the first CSI-RS transmission and the second CSI-RS transmission; and

determining which beam is included in the first subset of beams of the plurality of beams and which beam is included in the second subset of beams of the plurality of beams based on the CSI measurements.

17 . The method of claim 11 , wherein one or more first reports of the one or more reports comprise the indication of the first parameter associated with the first subset of beams, wherein one or more second reports of the one or more reports comprise the indication of the second parameter associated with the second subset of beams, and wherein a lower number of reporting instances are utilized to send the one or more first reports than a number of reporting instances utilized to send the one or more second reports.

18 . The method of claim 11 , wherein one or more first reports of the one or more reports comprise information associated with the first subset of beams, and wherein the one or more first reports are sent in response to a determination that transmission performance is less than a threshold.

19 . The method of claim 11 , further comprising:

pre-processing a first CSI associated with the first CSI-RS transmission utilizing the first subset of beams and the second subset of beams;

performing CSI compression utilizing a beam domain auto encoder (BDAE) based on the pre-processed first CSI; and

sending the compressed CSI to a network.

20 . The method of claim 11 , wherein the validity time indicates how long a beam subset is valid for beam transformation, wherein the beam range indicates a difference between a maximum beam index and a minimum beam index of a beam subset over a time period, and wherein the beam step indicates a maximum difference between beam indices associated with consecutive beam domain reporting instances of a beam subset.