High-resolution CSI reporting based on unequal bit allocation in advanced wireless communication systems

1. A user equipment (UE) comprising

a processor configured to generate a report including a precoding matrix indicator (PMI), the report including (i) a wideband amplitude coefficient indicator that is common for a plurality of subbands configured for reporting and (ii) a subband amplitude coefficient indicator and a subband phase coefficient indicator for each of the subbands; and

a transceiver operably connected to the processor, the transceiver configured to transmit the generated report for the PMI to a base station.

2. The UE of claim 1 , wherein:

the report includes 2*L number of beam coefficients for each of the subbands and for each of a plurality of ν layers,

each of one or more of the beam coefficients includes (i) the wideband amplitude coefficient indicator that is common for the subbands and (ii) the subband amplitude coefficient indicator and the subband phase coefficient indicator for each of the subbands,

at least one of the beam coefficients is reported using a number of bits that is unequal to number of bits used to report another of the beam coefficients,

L is a number of beams configured for reporting, and

ν is a rank indicator (RI) value associated with the reported PMI.

3. The UE of claim 2 , wherein the processor is configured to:

include in the report, for each of the ν layers, a strongest of the 2*L number of beam coefficients that is common for the subbands, and

group the remaining 2*L−1 number of beam coefficients into two groups, and

wherein a fewer number of bits are used to report the beam coefficients in a second of the two groups than the beam coefficients in a first of the two groups.

4. The UE of claim 3 , wherein:

the first group includes min(M,K)−1 beam coefficients,

the second group includes 2L−min(M,K) beam coefficients,

the first group includes strongest coefficients of the remaining 2*L−1 number of beam coefficients,

the report does not include subband amplitude coefficient indicators for the second group of beam coefficients,

M is a number of beam coefficients whose wideband amplitude coefficient indicators indicate non-zero wideband amplitude values, and

K is a positive integer.

5. The UE of claim 4 , wherein:

for each beam coefficient in the first group:

3 bits are used to report the wideband amplitude coefficient indicator,

1 bit is used to report the subband amplitude coefficient indicator, and

2 or 3 bits are configured to report the subband phase coefficient indicator; and

for the second group:

for each beam coefficient, 3 bits are used to report the wideband amplitude coefficient indicator,

for each beam coefficient in the M−min(M,K) beam coefficients whose wideband amplitude coefficient indicators indicate non-zero wideband amplitude values, 2 bits are used to report the subband phase coefficient indicator, and

for the remaining 2L−M beam coefficients whose wideband amplitude coefficient indicators indicate a zero wideband amplitude value, subband phase coefficient indicators are not reported.

6. The UE of claim 4 , wherein K is determined based on L according to:

L

K

2

4

3

4

4

6.

7. The UE of claim 4 , wherein the strongest coefficients used to group the remaining 2*L−1 beam coefficients into the two groups are determined based on the wideband amplitude coefficient indicator for each of the beam coefficients.

8. The UE of claim 1 , wherein a value (p) of the subband amplitude indicated by the subband amplitude coefficient indicator (k) is determined according to:

k

p

0

{square root over (1/2)}

1

1.

9. A base station (BS), comprising:

a transceiver configured to receive a report including a precoding matrix indicator (PMI), the report including (i) a wideband amplitude coefficient indicator that is common for a plurality of subbands configured for reporting and (ii) a subband amplitude coefficient indicator and a subband phase coefficient indicator for each of the subbands; and

a processor operably connected to the transceiver.

10. The BS of claim 9 , wherein:

the report includes 2*L number of beam coefficients for each of the subbands and for each of a plurality of ν layers,

each of one or more of the beam coefficients includes (i) the wideband amplitude coefficient indicator that is common for the subbands and (ii) the subband amplitude coefficient indicator and the subband phase coefficient indicator for each of the subbands,

at least one of the beam coefficients is reported using a number of bits that is unequal to number of bits used to report another of the beam coefficients,

L is a number of beams configured for reporting, and

ν is a rank indicator (RI) value associated with the reported PMI.

11. The BS of claim 10 , wherein:

for each of the ν layers, a strongest of the 2*L number of beam coefficients that is common for the subbands is included in the report,

the remaining 2*L−1 number of beam coefficients are reported in two groups, and

a fewer number of bits are used to report the beam coefficients in a second of the two groups than the beam coefficients in a first of the two groups.

12. The BS of claim 11 , wherein:

the first group includes min(M,K)−1 beam coefficients,

the second group includes 2L−min(M,K) beam coefficients,

the first group includes strongest coefficients of the remaining 2*L−1 number of beam coefficients,

the report does not include subband amplitude coefficient indicators for the second group of beam coefficients,

M is a number of beam coefficients whose wideband amplitude coefficient indicators indicate non-zero wideband amplitude values, and

K is a positive integer.

13. The BS of claim 12 , wherein:

for each beam coefficient in the first group:

3 bits are used to report the wideband amplitude coefficient indicator,

1 bit is used to report the subband amplitude coefficient indicator, and

2 or 3 bits are configured to report the subband phase coefficient indicator; and

for the second group:

for each beam coefficient, 3 bits are used to report the wideband amplitude coefficient indicator,

for each beam coefficient in the M−min(M,K) beam coefficients whose wideband amplitude coefficient indicators indicate non-zero wideband amplitude values, 2 bits are used to report the subband phase coefficient indicator, and

for the remaining 2L−M beam coefficients whose wideband amplitude coefficient indicators indicate a zero wideband amplitude value, subband phase coefficient indicators are not reported.

14. The BS of claim 12 , wherein K is determined based on L according to:

L

K

2

4

3

4

4

6.

15. The BS of claim 12 , wherein the strongest coefficients used to group the remaining 2*L−1 beam coefficients into the two groups are determined based on the wideband amplitude coefficient indicator for each of the beam coefficients.

16. The BS of claim 9 , wherein a value (p) of the subband amplitude indicated by the subband amplitude coefficient indicator (k) is determined according to:

k

p

0

{square root over (1/2)}

1

1.

17. A method for reporting a precoding matrix indicator (PMI) by a user equipment (UE), the method comprising

generating a report including the PMI, the report including (i) a wideband amplitude coefficient indicator that is common for a plurality of subbands configured for reporting and (ii) a subband amplitude coefficient indicator and a subband phase coefficient indicator for each of the subbands; and

transmitting the generated report for the PMI to a base station.

18. The method of claim 17 , wherein:

the report includes 2*L number of beam coefficients for each of the subbands and for each of a plurality of ν layers,

each of one or more of the beam coefficients includes (i) the wideband amplitude coefficient indicator that is common for the subbands and (ii) the subband amplitude coefficient indicator and the subband phase coefficient indicator for each of the subbands,

at least one of the beam coefficients is reported using a number of bits that is unequal to number of bits used to report another of the beam coefficients,

L is a number of beams configured for reporting, and

ν is a rank indicator (RI) value associated with the reported PMI.

19. The method of claim 17 , wherein generating the report further comprises:

including in the report, for each of the ν layers, a strongest of the 2*L number of beam coefficients that is common for the subbands; and

grouping the remaining 2*L−1 number of beam coefficients into two groups,

wherein a fewer number of bits are used to report the beam coefficients in a second of the two groups than the beam coefficients in a first of the two groups.

20. The method of claim 19 , wherein:

the first group includes min(M,K)−1 beam coefficients,

the second group includes 2L−min(M,K) beam coefficients,

the first group includes strongest coefficients of the remaining 2*L−1 number of beam coefficients,

the report does not include subband amplitude coefficient indicators for the second group of beam coefficients,

M is a number of beam coefficients whose wideband amplitude coefficient indicators indicate non-zero wideband amplitude values, and

K is a positive integer.