Method and apparatus to enable high rank CSI reporting in wireless communication systems

1. A user equipment (UE) for channel state information (CSI) feedback in a wireless communication system, the UE comprising:

a transceiver configured to receive, from a base station (BS), CSI feedback configuration information; and

a processor operably connected to the transceiver, the processor configured to:

determine, based on the CSI feedback configuration information, the CSI feedback including, for each layer l of a total number of v layers, a strongest coefficient indicator (SCI) for indicating an index of a strongest coefficient among K Nz,l coefficients, wherein l∈{1, . . . , v} is a layer index, v≥1 is a rank value, SCI l is the SCI for layer l, and K Nz,l is a number of non-zero coefficients for layer l; and

determine a payload of the SCI l for each layer of the total number of v layers based on the rank value;

wherein the transceiver is configured to transmit, to the BS, over an uplink (UL) channel, the CSI feedback including the SCI l for each layer of the total number of v layers, and

wherein when the rank value v=1, the payload of the SCI l is ┌log 2 K Nz,l ┐ bits, and when the rank value v>1, the payload of the SCI l is ┌log e (2L)┐ bits, where L is a number of first vectors.

2. The UE of claim 1 , wherein when the rank value v=1, the SCI l corresponds to i 1,8,l =Σ i=0 i 1 * k 1,i,0 (3) −1, and k 1,i,0 (3) =1 if a coefficient with an index i and an index m=0 is non-zero, and k 1,i,0 (3) =0 otherwise.

3. The UE of claim 1 , wherein when the rank value v>1, the SCI l corresponds to i 1,8,l =i l *, and i l *∈{0, 1, . . . , 2L−1}.

4. The UE of claim 1 , wherein, for each layer l, the processor is further configured to remap each index m 1 of the non-zero coefficients with respect to an index m l * associated with the strongest coefficient using a modulo function such that the index m l * is 0, where m l *∈{0, 1, . . . , M−1}.

5. The UE of claim 1 , wherein, for each layer l, the processor is further configured to remap each column index k m l with respect to an index k m l * associated with the strongest coefficient using a modulo function such that the index k m l * is 0, where m l =0, 1, . . . , M−1 of M second vectors.

6. The UE of claim 4 , wherein the CSI feedback includes amplitude and phase coefficient indicators and a bitmap indicating locations of the non-zero coefficients after remapping.

7. The UE of claim 5 , wherein the CSI feedback includes amplitude and phase coefficient indicators and a bitmap indicating locations of the non-zero coefficients after remapping.

8. A base station (BS), the BS comprising:

a transceiver configured to:

transmit channel state information (CSI) feedback configuration information to a user equipment (UE); and

receive, from the UE, CSI feedback including, for each layer l of a total number of v layers, a strongest coefficient indicator (SCI) for indicating an index of a strongest coefficient among K Nz,l coefficients, wherein l∈{1, . . . , v} is a layer index, v≥1 is a rank value, SCI l is the SCI for layer l, K Nz,l is a number of non-zero coefficients for layer l, and a payload of the SCI for each layer for each layer of the total number of v layers is based on the rank value; and

a processor operably coupled to the transceiver, the processor configured to:

generate the CSI feedback configuration information; and

obtain the strongest coefficient among the K Nz,l coefficients for each layer l of the total number of v layers based on the SCI l for each layer of the total number of v layers,

wherein when the rank value v=1, the payload of the SCI l is ┌log 2 K NZ,1 1┐ bits, and when the rank value v>1, the payload of the SCI l is ┌log 2 (2L)┐ bits, where L is a number of first vectors.

9. The BS of claim 8 , wherein when the rank value v=1, the SCI l corresponds to i 1,8,l =Σ i=0 i 1 * k 1,i,0 (3) −1, and k 1,i,0 (3) =1 if a coefficient with an index i and an index m=0 is non-zero, and k 1,i,0 (3) =0 otherwise.

10. The BS of claim 8 , wherein when the rank value v>1, the SCI l corresponds to i 1,8,l =i l *, and i l *∈{0, 1, . . . , 2L−1}.

11. The BS of claim 8 , wherein, for each layer l, each index m l of the non-zero coefficients is remapped with respect to an index m l * associated with the strongest coefficient using a modulo function such that the index m l * is 0, where m l *∈{0, 1, . . . , M−1}.

12. The BS of claim 8 , wherein, for each layer l, each index k m l is remapped with respect to an index k m l * associated with the strongest coefficient using a modulo function such that the index k m l * is 0, where m l =0, 1, . . . , M−1 of M second vectors.

13. The BS of claim 11 , wherein the CSI feedback includes amplitude and phase coefficient indicators and a bitmap indicating locations of the non-zero coefficients after remapping.

14. The BS of claim 12 , wherein the CSI feedback includes amplitude and phase coefficient indicators and a bitmap indicating locations of the non-zero coefficients after remapping.

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

receiving, from a base station (BS), CSI feedback configuration information;

determining, based on the CSI feedback configuration information, CSI feedback including, for each layer/of a total number of v layers, a strongest coefficient indicator (SCI) for indicating an index of a strongest coefficient among K NZ,l coefficients, wherein l∈{1, . . . , v} is a layer index, v≥1 is a rank value, SCI l is the SCI for layer l, and K NZ,l is a number of non-zero coefficients for layer l;

determining a payload of the SCI l for each layer of the total number of v layers based on the rank value; and

transmitting, to the BS, over an uplink (UL) channel, the CSI feedback including the SCI l for each layer of the total number of v layers,

wherein when the rank value v=1, the payload of the SCI l is ┌log 2 K NZ,1 ┐ bits, and when the rank value v>1, the payload of the SCI l is ┌log 2 (2L)┐ bits, where L is a number of first vectors.

16. The method of claim 15 , further comprising:

for each layer l, remapping each index m l of the non-zero coefficients with respect to an index m l * associated with the strongest coefficient using a modulo function such that the index m l * is 0, where m l *∈{0, 1, . . . , M−1}.

17. The method of claim 15 , further comprising, for each layer l, remapping each column index k m l with respect to an index k m l * associated with the strongest coefficient using a modulo function such that the index k m l * is 0, where m l =0, 1, . . . , M−1 of M second vectors.

18. The method of claim 15 , wherein:

when the rank value v=1, the SCI l corresponds to i 1,8,l =Σ i=0 i 1 * k 1,i,0 (3) −1, and k 1,i,0 (3) =1 if a coefficient with an index i and an index m=0 is non-zero, and k 1,i,0 (3) =0 otherwise, and

when the rank value v>1, the SCI l corresponds to i 1,8,l =i l *, and i l *∈{0, 1, . . . , 2L−1}.

19. The method of claim 16 , wherein the CSI feedback includes amplitude and phase coefficient indicators and a bitmap indicating locations of the non-zero coefficients after remapping.

20. The method of claim 17 , wherein the CSI feedback includes amplitude and phase coefficient indicators and a bitmap indicating locations of the non-zero coefficients after remapping.