Method and apparatus to enable CSI reporting based on non-uniform space-frequency compression

1. A user equipment (UE) for a 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 including a number (K 0 ) of coefficients for the CSI feedback; and

a processor operably connected to the transceiver, the processor configured to derive, based on the CSI feedback configuration information, the CSI feedback including K 1 coefficients that are a subset of a total of Q coefficients, wherein K 1 ≤K 0 and K 0 <Q,

wherein the transceiver is further configured to transmit, to the BS, the CSI feedback including the K 1 coefficients over an uplink channel.

2. The UE of claim 1 , wherein:

Q=2LM;

the total of Q coefficients forms a 2L×M coefficient matrix C 1 comprising 2L rows and M columns;

the K 1 coefficients correspond to non-zero coefficients of the 2L×M coefficient matrix C 1 ; and

the remaining 2LM−K 1 coefficients of the 2L×M coefficient matrix C 1 are zero.

3. The UE of claim 1 , wherein:

the processor is further configured to determine a number K 1 ; and

the transceiver is further configured to transmit, to the BS, the CSI feedback including the number K 1 .

4. The UE of claim 2 , wherein:

the processor is further configured to determine a bit sequence B=b 0 b 1 b 2LM−1 comprising 2LM bits to indicate indices of the K 1 coefficients; and

the transceiver is further configured to transmit, to the BS, the CSI feedback including the bit sequence B,

where the bit sequence B comprises K 1 ones and 2LM−K 1 zeros, and an i-th bit b i of the bit sequence B is set to one when an i-th coefficient of the total of 2LM coefficients is included in the K 1 coefficients.

5. The UE of claim 2 , wherein:

the K 0 is determined as K 0 =[a×2LM] where a≤1; and

an a is configured via higher layer signaling.

6. The UE of claim 5 , wherein a is configured from a set of values including {¼, ½}.

7. The UE of claim 2 , wherein the CSI feedback includes a precoding matrix indicator (PMI) indicating the 2L×M coefficient matrix C l , a spatial domain (SD) basis matrix A l and a frequency domain (FD) basis matrix B l for each l=1, . . . , v, and

wherein:

l is a layer index with a range of l=1, . . . , v, v is an associated rank indicator (RI) value,

a precoding matrix for each FD unit of a total number (N 3 ) of FD units is determined by columns of

W

=

1

v

[

W

1

W

2

…

W

v

]

⁢

where

⁢

W

l

=

[

A

l

0

0

A

l

]

⁢

C

l

⁢

B

l

H

=

[

∑

k

=

0

M

-

1

∑

i

=

0

L

-

1

c

l

,

i

,

k

(

a

l

,

i

⁢

b

l

,

k

H

)

∑

k

=

0

M

-

1

∑

i

=

0

L

-

1

c

l

,

i

+

L

,

k

(

a

l

,

i

⁢

b

l

,

k

H

)

]

,

A l =[a l,0 a l,1 . . . a l,L-1 ], a l,i is a N 1 N 2 ×1 column vector for SD antenna ports where N 1 and N 2 are number of antenna ports, respectively, with a same antenna polarization in a first and a second dimensions of a two-dimensional dual-polarized channel state information-reference signal (CSI-RS) antenna ports at the BS;

B l =[b l,0 b l,1 . . . b l,M−1 ], b l,k is a N 3 ×1 column vector for FD units;

the 2L×M matrix C 1 comprises coefficients C l,i,k ; and

a number (L) of column vectors for the SD antenna ports, a number (M) of column vectors for the FD units, and the total number (N 3 ) of the FD units are configured via higher layer signaling.

8. A base station (BS) for a channel state information (CSI) feedback in a wireless communication system, the BS comprising:

a transceiver configured to:

transmit, to a user equipment (UE), CSI feedback configuration information including a number (K 0 ) of coefficients for the CSI feedback; and

receive, from the UE, the CSI feedback including K 1 coefficients over an uplink channel; and

a processor operably connected to the transceiver, the processor is configured to decode the CSI feedback including K 1 coefficients, wherein:

the CSI feedback is derived based on the CSI feedback configuration information; and

the CSI feedback includes the K 1 coefficients that are a subset of a total of Q coefficients, wherein K 1 ≤K 0 and K 0 <Q.

9. The BS of claim 8 , wherein:

Q=2LM;

the total of Q coefficients forms a 2L×M coefficient matrix C l comprising 2L rows and M columns;

the K 1 coefficients correspond to non-zero coefficients of the 2L×M coefficient matrix C l ; and

the remaining 2LM−K 1 coefficients of the 2L×M coefficient matrix C l are zero.

10. The BS of claim 8 , wherein the transceiver is further configured to receive, from the UE, the CSI feedback including a number K l .

11. The BS of claim 9 , wherein:

the transceiver is further configured to receive, from the UE, the CSI feedback including a bit sequence B=b 0 b 1 . . . b 2LM−1 comprising 2LM bits to indicate indices of the K 1 coefficients, where the bit sequence B comprises K 1 ones and 2LM−K 1 zeros, and an i-th bit b i of the bit sequence B is set to one when an i-th coefficient of the total of 2LM coefficients is included in the K 1 coefficients.

12. The BS of claim 9 , wherein:

the K 0 is determined as K 0 =[a×2LM] where a≤1; and

an a is configured via higher layer signaling.

13. The BS of claim 12 , wherein a is configured from a set of values including {¼, ½}.

14. The BS of claim 9 , wherein the CSI feedback includes a precoding matrix indicator (PMI) indicating the 2L×M coefficient matrix C l , a spatial domain (SD) basis matrix A l and a frequency domain (FD) basis matrix B l for each l=1, . . . ,v, and

wherein:

l is a layer index with a range of l=1, . . . ,v, v is an associated rank indicator (RI) value,

a precoding matrix for each FD unit of a total number (N 3 ) of FD units is determined by columns of

W

=

1

v

[

W

1

W

2

…

W

v

]

⁢

where

⁢

W

l

=

[

A

l

0

0

A

l

]

⁢

C

l

⁢

B

l

H

=

[

∑

k

=

0

M

-

1

∑

i

=

0

L

-

1

c

l

,

i

,

k

(

a

l

,

i

⁢

b

l

,

k

H

)

∑

k

=

0

M

-

1

∑

i

=

0

L

-

1

c

l

,

i

+

L

,

k

(

a

l

,

i

⁢

b

l

,

k

H

)

]

,

A l =[a l,0 a l,1 . . . a l,L−1 ], a l,i is a N 1 N 2 ×1 column vector for SD antenna ports where N 1 and N 2 are number of antenna ports, respectively, with a same antenna polarization in a first and a second dimensions of a two-dimensional dual-polarized channel state information-reference signal (CSI-RS) antenna ports at the BS;

B l =[b l,0 k l,1 . . . b l,M−1 ], b l,k is a N 3 ×1 column vector for FD units;

the 2L×M matrix C l comprises coefficients C l,i,k ; and

a number (L) of column vectors for the SD antenna ports, a number (M) of column vectors for the FD units, and the total number (N 3 ) of the FD units are configured via higher layer signaling.

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

receiving, from a base station (BS), CSI feedback configuration information including a number (K 0 ) of coefficients for the CSI feedback;

deriving, based on the CSI feedback configuration information, the CSI feedback including K 1 coefficients that are a subset of a total of Q coefficients, wherein K 1 ≤K 0 and K 0 <Q; and

transmitting, to the BS, the CSI feedback including the K 1 coefficients over an uplink channel.

16. The method of claim 15 , wherein:

Q=2LM;

the total of Q coefficients forms a 2L×M coefficient matrix C l comprising 2L rows and M columns;

the K 1 coefficients correspond to non-zero coefficients of the 2L×M coefficient matrix C 1 ; and

the remaining 2LM−K 1 coefficients of the 2L×M coefficient matrix C l are zero.

17. The method of claim 15 , further comprising:

determining a number K 1 ; and

transmitting, to the BS, the CSI feedback including the number K 1 .

18. The method of claim 16 , further comprising:

determining a bit sequence B=b 0 b 1 b 2LM−1 comprising 2LM bits to indicate indices of the K 1 coefficient; and

transmitting, to the BS, the CSI feedback including the bit sequence B, where the bit sequence B comprises K 1 ones and 2LM−K 1 zeros, and an i-th bit b i of the bit sequence B is set to one when an i-th coefficient of the total of 2LM coefficients is included in the K 1 coefficients.

19. The method of claim 16 , wherein:

the K 0 is determined as K 0 =[a×2LM] where a≤1;

an a is configured via higher layer signaling; and

the a is configured from a set of values including {¼, ½}.

20. The method of claim 16 , wherein the CSI feedback includes a precoding matrix indicator (PMI) indicating the 2L×M coefficient matrix C l , a spatial domain (SD) basis matrix A l and a frequency domain (FD) basis matrix B l for each l=1, . . . , v, and

wherein:

l is a layer index with a range of l=1, . . . ,v, v is an associated rank indicator (RI) value,

a precoding matrix for each FD unit of a total number (N 3 ) of FD units is determined by columns of

W

=

1

v

[

W

1

W

2

…

W

v

]

⁢

where

⁢

W

l

=

[

A

l

0

0

A

l

]

⁢

C

l

⁢

B

l

H

=

[

∑

k

=

0

M

-

1

∑

i

=

0

L

-

1

c

l

,

i

,

k

(

a

l

,

i

⁢

b

l

,

k

H

)

∑

k

=

0

M

-

1

∑

i

=

0

L

-

1

c

l

,

i

+

L

,

k

(

a

l

,

i

⁢

b

l

,

k

H

)

]

,

A l =[a l,0 a l,1 . . . a l,L−1 ], a l,i is a N 1 N 2 ×1 column vector for SD antenna ports where N 1 and N 2 are number of antenna ports, respectively, with a same antenna polarization in a first and a second dimensions of a two-dimensional dual-polarized channel state information-reference signal (CSI-RS) antenna ports at the BS;

B l =[b l,0 b l,1 . . . b l,M−1 ], b l,k is a N 3 ×1 column vector for FD units;

the 2L×M matrix C l comprises coefficients C l,i,k ; and

a number (L) of column vectors for the SD antenna ports, a number (M) of column vectors for the FD units, and the total number (N 3 ) of the FD units are configured via higher layer signaling.