Smaller sub-band size for PMI than for CQI

1. A method performed by a wireless device for transmitting channel state information, CSI, feedback using a multi-beam precoder codebook, the method comprising:

obtaining a configuration for a sub-band channel quality indicator, CQI, granularity and a sub-band precoding matrix indicator, PMI, granularity for the wireless device, wherein the sub-band PMI granularity corresponds to a first sub-band size and the sub-band CQI granularity corresponds to a second sub-band size;

determining CSI feedback according to the configured sub-band CQI granularity and the sub-band PMI granularity, wherein the CSI feedback indicates a linear combination of precoder vectors, wherein the precoder vectors correspond to respective frequency sub-bands having the first sub-band size, wherein the coefficients for the precoder vectors in the linear combination of precoder vectors are parameterized in the frequency-domain as a linear combination of a set of basis vectors and a set of coefficients for the basis vectors in the linear combination of the set of basis vectors; and

transmitting, to a network node, the determined CSI feedback,

wherein the first sub-band size is smaller than the second sub-band size.

2. The method of claim 1 , wherein the precoder vectors are DFT vectors.

3. The method of claim 1 , wherein the CSI feedback is transmitted using a NR Type II codebook.

4. The method of claim 1 , wherein the CSI feedback is transmitted using Rel-16 enhanced Type II CSI reporting.

5. The method of claim 1 , wherein the second sub-band size is an integer multiple of the first sub-band size.

6. The method of claim 1 , wherein the sub-band CQI granularity configuration is obtained from a subbandSize radio resource control parameter in a CSI-ReportConfig.

7. The method of claim 1 , wherein the sub-band PMI granularity is obtained from a CSI-ReportConfig using a subbandPMI-Size parameter.

8. A method performed by a network node for receiving channel state information, CSI, feedback using a multi-beam precoder codebook, the method comprising:

receiving CSI feedback from a wireless device according to a sub-band channel quality indicator, CQI, granularity and a sub-band precoding matrix indicator, PMI, granularity, wherein the sub-band PMI granularity corresponds to a first sub-band size and the sub-band CQI granularity corresponds to a second sub-band size, wherein the CSI feedback indicates a linear combination of precoder vectors, wherein the precoder vectors correspond to respective frequency sub-bands having the first sub-band size, wherein the coefficients for the precoder vectors in the linear combination of precoder vectors are parameterized in the frequency-domain as a linear combination of a set of basis vectors and a set of coefficients for the basis vectors in the linear combination of the set of basis vectors, and wherein the first sub-band size is smaller than the second sub-band size.

9. The method of claim 8 , further comprising:

determining the sub-band CQI granularity;

determining the sub-band PMI; and

configuring the wireless device with the sub-band CQI granularity and the sub-band PMI granularity.

10. A wireless device for transmitting channel state information, CSI, feedback using a multi-beam precoder codebook, the wireless device comprising:

a receiver;

a transmitter; and

processing circuitry coupled to the receiver and the transmitter, the processing circuitry configured to:

obtain a configuration for a sub-band channel quality indicator, CQI, granularity and a sub-band precoding matrix indicator, PMI, granularity for the wireless device, wherein the sub-band PMI granularity corresponds to a first sub-band size and the sub-band CQI granularity corresponds to a second sub-band size;

determine CSI feedback according to the configured sub-band CQI granularity and the sub-band PMI granularity, wherein the CSI feedback indicates a linear combination of precoder vectors, wherein the precoder vectors correspond to respective frequency sub-bands having the first sub-band size, wherein the coefficients for the precoder vectors in the linear combination of precoder vectors are parameterized in the frequency-domain as a linear combination of a set of basis vectors and a set of coefficients for the basis vectors in the linear combination of the set of basis vectors; and

transmit, to a network node, the determined CSI feedback,

wherein the first sub-band size is smaller than the second sub-band size.

11. The wireless device of claim 10 , wherein the precoder vectors are DFT vectors.

12. The wireless device of claim 10 , wherein the CSI feedback is transmitted using a NR Type II codebook.

13. The wireless device of claim 10 , wherein the CSI feedback is transmitted using Rel-16 enhanced Type II CSI reporting.

14. The wireless device of claim 10 , wherein the second sub-band size is an integer multiple of the first sub-band size.

15. The wireless device of claim 10 , wherein the processing circuitry is configured to obtain the sub-band CQI granularity configuration from a subbandSize radio resource control parameter in a CSI-ReportConfig.

16. The wireless device of claim 10 , wherein the processing circuitry is configured to obtain the sub-band PMI granularity from a CSI-ReportConfig using a subbandPMI-Size parameter.

17. A network node for receiving channel state information, CSI, feedback using a multi-beam precoder codebook, the network node comprising:

a receiver;

a transmitter; and

processing circuitry coupled to the receiver and the transmitter, the processing circuitry configured to:

receive CSI feedback from a wireless device according to a sub-band channel quality indicator, CQI, granularity and a sub-band precoding matrix indicator, PMI, granularity, wherein the sub-band PMI granularity corresponds to a first sub-band size and the sub-band CQI granularity corresponds to a second sub-band size, wherein the CSI feedback indicates a linear combination of precoder vectors, wherein the precoder vectors correspond to respective frequency sub-bands having the first sub-band size, wherein the coefficients for the precoder vectors in the linear combination of precoder vectors are parameterized in the frequency-domain as a linear combination of a set of basis vectors and a set of coefficients for the basis vectors in the linear combination of the set of basis vectors, and wherein the first sub-band size is smaller than the second sub-band size.

18. The network node of claim 17 , wherein the processing circuitry is further configured to:

determine the sub-band CQI granularity;

determine the sub-band PMI; and

configure the wireless device with the sub-band CQI granularity and the sub-band PMI granularity.