Methods and apparatus for port selection codebook enhancement

1. A method for a user equipment (UE), the method comprising:

receiving, at the UE from a base station, an indication of parameter settings of a port selection codebook, the port selection codebook comprising a port selection matrix W 1 , a combinational coefficient matrix W 2 , and a frequency basis selection matrix W f ;

based at least in part on the parameter settings, selecting, at the UE:

for the port selection matrix W 1 , L channel state information reference signal (CSI-RS) ports out of P CSI-RS ports configured for measuring and reporting CSI, wherein L is a first value indicated in the parameter settings;

for the frequency basis selection matrix W f , Mv frequency basis from a window of N consecutive frequency basis, wherein Mv is a second value indicated in the parameter settings; and

for the combinational coefficient matrix W 2 , up to beta*L*Mv entries per layer, wherein beta is a third value indicated in the parameter settings and corresponds to a percentage of the L*Mv entries per layer configured by the parameter settings; and

reporting, from the UE to the base station, one or more of the port selection matrix W 1 , the up to beta*L*Mv entries in the combinational coefficient matrix W 2 per layer, and the frequency basis selection matrix W f .

2. The method of claim 1 , wherein the parameter settings include a value of L that is independent of a value of P, except that the value of L is less than or equal to the value of P.

3. The method of claim 1 , wherein the parameter settings include a value of L selected from a range that depends on a value of P.

4. The method of claim 3 , wherein for a lower value of P the range includes lower values of L and higher values of L, and for a higher value of P the range includes only the lower values of L.

5. The method of claim 3 , wherein for a lower value of P the range includes lower values of L and higher values of L, and for a higher value of P the range includes only the higher values of L.

6. The method of claim 1 , wherein the port selection matrix W 1 is polarization common, frequency basis common, and layer independent, and wherein reporting the port selection matrix W 1 comprises independently reporting for each layer regardless of the polarization and frequency basis, where is a layer index.

7. The method of claim 1 , wherein the port selection matrix W 1 is polarization common, frequency basis common, and layer common, and wherein reporting the port selection matrix W 1 comprises reporting a single port selection matrix W 1 regardless of polarization, frequency basis, and layer.

8. The method of claim 1 , wherein reporting, from the UE to the base station, the up to beta*L*Mv entries in the combinational coefficient matrix W 2 per layer further comprises using a bitmap to report locations of the up to beta*L*Mv entries of the combinational coefficient matrix W 2 per layer unless one or more conditions are met, wherein the one or more conditions comprise beta=1, the base station configured the locations of the up to beta*L*Mv entries, the UE is not configured to report the frequency basis selection matrix W f , and Mv=1.

9. The method of claim 8 , wherein the bitmap is frequency basis independent, polarization independent, and layer independent.

10. The method of claim 8 , wherein the bitmap is frequency basis independent, and wherein the bitmap is at least one of polarization common and layer common.

11. The method of claim 1 , The method of claim 1 , further comprising:

determining a strongest coefficient among the up to beta*L*Mv entries of the combinational coefficient matrix W 2 per layer; and

using a bitwidth of ┌log 2 (L*Mv)┐ per layer to report a strongest coefficient indicator (SCI) corresponding to a location of the strongest coefficient.

12. The method of claim 1 , further comprising:

determining a strongest coefficient from a predetermined frequency basis of the combinational coefficient matrix W 2 per layer; and

using a bitwidth of ┌log 2 (L)┐ per layer to report a strongest coefficient indicator (SCI) corresponding to a location of the strongest coefficient.

13. The method of claim 12 , wherein the predetermined frequency basis corresponds to a zero frequency component.

14. The method of claim 1 , further comprising:

determining a first strongest coefficient among the up to beta*L*Mv entries of the combinational coefficient matrix W 2 per layer;

determining that the first strongest coefficient corresponds to a first polarization; and

for a second polarization that is different than the first polarization, determining a second strongest coefficient corresponding to the second polarization.

15. The method of claim 14 , further comprising not explicitly reporting, from the UE to the base station, a location of the second strongest coefficient corresponding to the second polarization.

16. The method of claim 14 , further comprising using a bitwidth of ┌log 2 ((L−1)*Mv)┐ per layer to report a strongest coefficient indicator (SCI) corresponding to a location of the second strongest coefficient corresponding to the second polarization.

17. The method of claim 14 , further comprising indicating from the UE to the base station, with a predetermined value of an amplitude coefficient indicator, that no values are fed back to the base station for non-zero coefficients that correspond to the second polarization that does not include the first strongest coefficient.

18. The method of claim 1 , further comprising indicating from the UE to the base station, with a predetermined value of an amplitude coefficient indicator, an error in reporting an amplitude coefficient, an extended value of an amplitude coefficient, or use of a selected channel state information compression.

19. The method of claim 1 , wherein the UE is configured with N=Mv or N>Mv for selecting the Mv frequency basis from the window of N consecutive frequency basis.

20. The method of claim 19 , wherein when N>Mv, N is restricted to a fixed value with respect to Mv.