Port selection codebook enhancement

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

decoding, at the UE, a channel state information (CSI) report configuration (CSI-ReportConfig) from a base station, the CSI-ReportConfig indicating up to L CSI reference signal (CSI-RS) ports for selection by the UE out of P CSI-RS ports configured for measuring and reporting CSI;

determining, at the UE, selected CSI-RS ports out of the P CSI-RS ports, wherein the selected CSI-RS ports comprise the L CSI-RS ports or less;

generating, at the UE, a port selection matrix Wi corresponding to the selected CSI-RS ports out of the P CSI-RS ports,

wherein the port selection matrix W 1 is a P×L matrix, wherein each of L columns in the port selection matrix W 1 is P×1 with only one entry in each of the L columns comprising a 1 and other entries in each of the L columns comprising a 0, and wherein different ones of the L columns in the port selection matrix Wi are not the same as one another, and

wherein the UE selects less than or equal to the L CSI-RS ports out of the P CSI-RS ports, and wherein transmitting the port selection matrix W 1 comprises using a bit width of

⌈

log

2

(

∑

l

=

1

L

C

⁡

(

P

,

l

)

)

⌉

,

where C is a combinational function; and

transmitting, from the UE, the port selection matrix Wi to the base station.

2. The method of claim 1 , wherein the CSI-ReportConfig configures more than one CSI-RS resource for channel measurement resource (CMR), wherein total CSI-RS ports are a union of all ports in all CSI-RS resources configured in the CSI-ReportConfig, and wherein a CSI-RS port index is based on a CSI-RS resource identifier (ID).

3. The method of claim 1 , wherein the CSI-ReportConfig configures more than one CSI-RS resource for channel measurement resource (CMR), wherein the method further comprises:

reporting a selected CSI-RS resource identifier (ID); and

reporting a port selection configured in the selected CSI-RS resource ID.

4. The method of claim 1 , wherein the port selection matrix Wi is layer independent, and wherein transmitting the port selection matrix W 1 comprises independently reporting as where is a layer index.

5. The method of claim 1 , wherein the port selection matrix W 1 is layer common, and wherein transmitting the port selection matrix W 1 comprises reporting a single port selection matrix for all layers.

6. The method of claim 1 , wherein the port selection matrix W 1 is subband independent, and wherein transmitting the port selection matrix W 1 comprises independently reporting as W 1 n where n is a subband index.

7. The method of claim 1 , wherein the port selection matrix W 1 is subband common, and wherein transmitting the port selection matrix W 1 comprises reporting a single port selection matrix for all subbands.

8. The method of claim 1 , wherein the CSI-ReportConfig further configures the UE to select a subset of frequency basis, the method further comprising:

determining a selected subset of frequency basis;

generating a frequency basis selection matrix W f corresponding to the selected subset of frequency basis, wherein a precoding matrix index (PMI) matrix W=W 1 W 2 W f ,

where W 2 is a matrix comprising compressed combination coefficients; and

reporting the frequency basis selection matrix W f to the base station.

9. The method of claim 8 , further comprising processing an instruction from the base station to turn off the frequency basis selection matrix W f , wherein the PMI matrix W degenerates into W=W 1 , wherein the port selection matrix W 1 is a column vector that selects the L CSI-RS ports, wherein the port selection matrix W 1 comprises L non-zero entries, and wherein each of the L non-zero entries comprises a phase and amplitude factor to select and report a combination coefficient for a corresponding port.

10. A baseband processor for a user equipment (UE) configured to:

decode, at the UE, a channel state information (CSI) report configuration (CSI-ReportConfig) from a base station, the CSI-ReportConfig indicating up to L CSI reference signal (CSI-RS) ports for selection by the UE out of P CSI-RS ports configured for measuring and reporting CSI;

determine, at the UE, selected CSI-RS ports out of the P CSI-RS ports, wherein the selected CSI-RS ports comprise the L CSI-RS ports or less;

generate, at the UE, a port selection matrix Wi corresponding to the selected CSI-RS ports out of the P CSI-RS ports, wherein the port selection matrix W 1 is a P×L matrix,

wherein each of L columns in the port selection matrix W 1 is P×1 with only one entry in each of the L columns comprising a 1 and other entries in each of the L columns comprising a 0, and wherein different ones of the L columns in the port selection matrix W 1 are not the same as one another, and

wherein the UE selects less than or equal to the L CSI-RS ports out of the P CSI-RS ports, and wherein transmitting the port selection matrix W 1 comprises using a bit width of

⌈

log

2

(

∑

l

=

1

L

C

⁡

(

P

/

2

,

l

)

)

⌉

,

where C is a combinatorial function; and

encode for transmission, from the UE, the port selection matrix Wi to the base station.

11. The baseband processor of claim 10 , wherein the CSI-ReportConfig configures more than one CSI-RS resource for channel measurement resource (CMR), wherein total CSI-RS ports are a union of all ports in all CSI-RS resources configured in the CSI-ReportConfig, and wherein a CSI-RS port index is based on a CSI-RS resource identifier (ID).

12. The baseband processor of claim 10 , wherein the CSI-ReportConfig configures more than one CSI-RS resource for channel measurement resource (CMR), and wherein the baseband processor is further configured to:

report a selected CSI-RS resource identifier (ID); and

report a port selection configured in the selected CSI-RS resource ID.

13. The baseband processor of claim 10 , wherein the port selection matrix W 1 is layer independent, and wherein transmitting the port selection matrix W 1 comprises independently reporting as where is a layer index.

14. The baseband processor of claim 10 , wherein the port selection matrix W 1 is layer common, and wherein transmitting the port selection matrix W 1 comprises reporting a single port selection matrix for all layers.

15. The baseband processor of claim 10 , wherein the port selection matrix W 1 is subband independent, and wherein transmitting the port selection matrix W 1 comprises independently reporting as W 1 n where n is a subband index.

16. The baseband processor of claim 10 , wherein the port selection matrix W 1 is subband common, and wherein transmitting the port selection matrix W 1 comprises reporting a single port selection matrix for all subbands.

17. The baseband processor of claim 10 , wherein the CSI-ReportConfig further configures the UE to select a subset of frequency basis, and wherein the baseband processor is further configured to:

determine a selected subset of frequency basis;

generate a frequency basis selection matrix W f corresponding to the selected subset of frequency basis, wherein a precoding matrix index (PMI) matrix W=W 1 W 2 W f ,

where W 2 is a matrix comprising compressed combination coefficients; and

report the frequency basis selection matrix W f to the base station.

18. The baseband processor of claim 17 , wherein the baseband processor is further configured to process an instruction from the base station to turn off the frequency basis selection matrix W f , wherein the PMI matrix W degenerates into W=W 1 , wherein the port selection matrix W 1 is a column vector that selects the L CSI-RS ports, wherein the port selection matrix W 1 comprises L non-zero entries, and wherein each of the L non-zero entries comprises a phase and amplitude factor to select and report a combination coefficient for a corresponding port.