Rank indicator and layer indicator signaling in non-coherent joint transmission channel state information

1. A method for wireless communications at a user equipment (UE), comprising:

receiving an indication of a first channel measurement resource and a second channel measurement resource, each configured for measuring channel state information reference signals, the first channel measurement resource associated with a first transmission configuration indicator state and the second channel measurement resource associated with a second transmission configuration indicator state;

receiving a rank restriction parameter to obtain channel state information for a joint transmission hypothesis associated with the first channel measurement resource and the second channel measurement resource; and

transmitting a channel state information report that includes at least two rank indicators reported via a joint rank indication field that maps the at least two rank indicators to at least one rank combination of a plurality of allowed rank combinations corresponding to the joint transmission hypothesis in accordance with the rank restriction parameter, the at least two rank indicators comprising a first rank indicator associated with the first channel measurement resource and a second rank indicator associated with the second channel measurement resource.

2. The method of claim 1 , further comprising:

transmitting the at least two rank indicators in the joint rank indication field in a first portion of the channel state information report associated with the first transmission configuration indicator state and the second transmission configuration indicator state corresponding to the joint transmission hypothesis.

3. The method of claim 2 , wherein the channel state information report comprises first channel state information corresponding to the joint transmission hypothesis and second channel state information corresponding to a single transmission hypothesis, the method further comprising:

determining a bit width of the joint rank indication field based at least in part on the plurality of allowed rank combinations.

4. The method of claim 2 , wherein the channel state information report comprises channel state information corresponding to either the joint transmission hypothesis or a single transmission hypothesis, the method further comprising:

identifying, based at least in part on the rank restriction parameter, a first number of bits associated with the channel state information of the joint transmission hypothesis and a second number of bits associated with the channel state information of the single transmission hypothesis; and

determining a bit width of the joint rank indication field based at least in part on the first number of bits and the second number of bits.

5. The method of claim 4 , wherein the bit width of the joint rank indication field is further based at least in part on a maximum value of the first number of bits and the second number of bits, the bit width being equal to the joint rank indication field associated with the joint transmission hypothesis or the single transmission hypothesis.

6. The method of claim 1 , wherein the rank restriction parameter is configured for a single transmission hypothesis via a first control parameter, and for the joint transmission hypothesis via a second control parameter, the first control parameter being different from the second control parameter.

7. The method of claim 1 , wherein the at least two rank indicators are associated with at least two layer indicators, the method further comprising:

transmitting, to a network entity, an indication of the at least two layer indicators in at least two separate layer indication fields.

8. The method of claim 7 , wherein the at least two separate layer indication fields comprise a first layer indication field and a second layer indication field, the method further comprising:

determining a bit width of the first layer indication field and the second layer indication field based at least in part on corresponding reported values of the at least two rank indicators.

9. The method of claim 1 , further comprising:

transmitting, to a network entity, a capability of the UE to transmit the channel state information report comprising the at least two rank indicators for the joint transmission hypothesis or a single transmission hypothesis in accordance with the rank restriction parameter.

10. The method of claim 1 , further comprising:

transmitting the at least two rank indicators in separate rank indication fields in at least one portion of the channel state information report.

11. The method of claim 10 , further comprising:

transmitting the separate rank indication fields in a first portion of the channel state information report, the first portion of the channel state information report having a constant payload size.

12. The method of claim 11 , wherein the separate rank indication fields comprise a first rank indication field and a second rank indication field, the method further comprising:

determining a bit width of the first rank indication field and the second rank indication field based at least in part on respective ranks of the first channel measurement resource and the second channel measurement resource of the channel state information report.

13. The method of claim 10 , wherein the separate rank indication fields comprise a first rank indication field and a second rank indication field, the method further comprising:

transmitting the first rank indication field in a first portion of the channel state information report and the second rank indication field in a second portion of the channel state information report.

14. The method of claim 13 , wherein a bit width for the first rank indication field is based at least in part on a first number of bits associated with channel state information of the joint transmission hypothesis and a second number of bits associated with channel state information of a single transmission hypothesis.

15. The method of claim 14 , wherein the bit width of the first rank indication field is further based at least in part on a maximum value of the first number of bits and the second number of bits, the bit width being equal to the first rank indication field associated with the joint transmission hypothesis or the single transmission hypothesis.

16. The method of claim 13 , wherein a bit width for the second rank indication field is based at least in part on a rank restriction for a second rank associated with the joint transmission hypothesis.

17. The method of claim 1 , wherein the rank restriction parameter for obtaining the channel state information is applied only for the channel state information report associated with a single transmission hypothesis.

18. The method of claim 17 , further comprising:

determining a rank or rank combination associated with the joint transmission hypothesis based at least in part on a multiplexing scheme for the channel state information report irrespective of the rank restriction parameter.

19. The method of claim 1 , wherein the rank restriction parameter for obtaining the channel state information for the joint transmission hypothesis is based at least in part on the rank restriction parameter for obtaining channel state information for a single transmission hypothesis.

20. The method of claim 19 , wherein the rank restriction parameter applies to the first rank indicator of the at least two rank indicators, the second rank indicator of the at least two rank indicators, or a sum of the first rank indicator and the second rank indicator.

21. The method of claim 1 , wherein the at least two rank indicators are associated with at least two layer indicators, the method further comprising:

transmitting, to a network entity, an indication of the at least two layer indicators in a joint layer indication field.

22. The method of claim 21 , further comprising:

determining a bit width of the joint layer indication field based at least in part on a reported value of the at least two rank indicators.

23. A method for wireless communications at a network entity, comprising:

transmitting, to a user equipment (UE), an indication of a first channel measurement resource and a second channel measurement resource, each configured for measuring channel state information reference signals, the first channel measurement resource associated with a first transmission configuration indicator state and the second channel measurement resource associated with a second transmission configuration indicator state;

transmitting, to the UE, a rank restriction parameter for obtaining channel state information for a joint transmission hypothesis associated with the first channel measurement resource and the second channel measurement resource; and

receiving, in a channel state information report that includes the channel state information, at least two rank indicators reported via a joint rank indication field that maps the at least two rank indicators to at least one rank combination of a plurality of allowed rank combinations corresponding to the rank restriction parameter or a different rank restriction parameter based at least in part on the at least two rank indicators being associated with the joint transmission hypothesis, the at least two rank indicators comprising a first rank indicator associated with the first channel measurement resource and a second rank indicator associated with the second channel measurement resource.

24. The method of claim 23 , further comprising:

receiving the at least two rank indicators in the joint rank indication field in a first portion of the channel state information report associated with the first transmission configuration indicator state and the second transmission configuration indicator state corresponding to the joint transmission hypothesis.

25. The method of claim 24 , wherein the channel state information report comprises first channel state information corresponding to the joint transmission hypothesis and second channel state information corresponding to a single transmission hypothesis, the method further comprising:

receiving the channel state information report having a bit width that is based at least in part on the plurality of allowed rank combinations for the joint transmission hypothesis.

26. The method of claim 24 , wherein the channel state information report comprises channel state information corresponding to either the joint transmission hypothesis or a single transmission hypothesis, the method further comprising:

receiving the joint rank indication field having a bit width that is based at least in part on a first number of bits associated with the channel state information of the joint transmission hypothesis and a second number of bits associated with the channel state information of the single transmission hypothesis.

27. The method of claim 23 , wherein the rank restriction parameter is configured for a single transmission hypothesis via a first control parameter, and for the joint transmission hypothesis via a second control parameter, the first control parameter being different from the second control parameter.

28. The method of claim 23 , wherein the at least two rank indicators are associated with at least two layer indicators, the method further comprising:

receiving, from the UE, an indication of the at least two layer indicators in at least two separate layer indication fields.

29. An apparatus for wireless communications at a user equipment (UE), comprising:

a memory; and

a processor coupled to the memory and configured to:

receive an indication of a first channel measurement resource and a second channel measurement resource, each configured for measuring channel state information reference signals, the first channel measurement resource associated with a first transmission configuration indicator state and the second channel measurement resource associated with a second transmission configuration indicator state;

receive a rank restriction parameter to obtain channel state information for a joint transmission hypothesis associated with the first channel measurement resource and the second channel measurement resource; and

transmit a channel state information report that includes at least two rank indicators reported via a joint rank indication field that maps the at least two rank indicators to at least one rank combination of a plurality of allowed rank combinations corresponding to the joint transmission hypothesis in accordance with the rank restriction parameter, the at least two rank indicators comprising a first rank indicator associated with the first channel measurement resource and a second rank indicator associated with the second channel measurement resource.

30. An apparatus for wireless communications at a network entity, comprising:

a memory; and

a processor coupled to the memory and configured to:

transmit, to a user equipment (UE), an indication of a first channel measurement resource and a second channel measurement resource, each configured for measuring channel state information reference signals, the first channel measurement resource associated with a first transmission configuration indicator state and the second channel measurement resource associated with a second transmission configuration indicator state;

transmit, to the UE, a rank restriction parameter for obtaining channel state information for a joint transmission hypothesis associated with the first channel measurement resource and the second channel measurement resource; and

receive, in a channel state information report that includes the channel state information, at least two rank indicators reported via a joint rank indication field that maps the at least two rank indicators to at least one rank combination of a plurality of allowed rank combinations corresponding to the rank restriction parameter or a different rank restriction parameter based at least in part on the at least two rank indicators being associated with the joint transmission hypothesis, the at least two rank indicators comprising a first rank indicator associated with the first channel measurement resource and a second rank indicator associated with the second channel measurement resource.