Method and apparatus to CSI reporting using multiple antenna panels in advanced wireless communication systems
A user equipment (UE) for channel state information (CSI) feedback is provided. The UE comprises a transceiver configured to receive, from a base station (BS), configuration information for the CSI feedback, the configuration information indicating a number of antenna panels (N g ) at the BS and a codebook mode, wherein N g >1 and each of the antenna panels comprises antenna ports with a first polarization (P 1 ) and antenna ports with a second polarization (P 2 ). The UE further comprises a processor operably connected to the transceiver, the processor configured to identify the number of antenna panels (N g ) at the BS, identify a codebook for the CSI feedback based on the codebook mode configured between a first codebook mode and a second codebook mode, and generate the CSI feedback using the identified codebook. The transceiver is further configured to transmit the generated CSI feedback to the BS.
1. A user equipment (UE) for channel state information (CSI) feedback, the UE comprising
a transceiver configured to receive, from a base station (BS), configuration information for the CSI feedback, the configuration information indicating a number of antenna panels (N g ) at the BS and a codebook mode, wherein N g >1 and each of the antenna panels comprises antenna ports with a first polarization (P 1 ) and antenna ports with a second polarization (P 2 ); and
a processor operably connected to the transceiver, the processor configured to:
identify the number of antenna panels at the BS,
identify a codebook for the CSI feedback based on the codebook mode configured between a first codebook mode and a second codebook mode, and
generate the CSI feedback using the identified codebook,
wherein the transceiver is further configured to transmit the generated CSI feedback to the BS,
wherein the codebook corresponding to the first codebook mode is used to generate the CSI feedback based on a wideband inter-panel co-phase that is common for a plurality of subbands configured for the CSI feedback,
wherein the codebook corresponding to the second codebook mode is used to generate the CSI feedback based on at least one of (i) a wideband inter-panel co-phase that is common for the plurality of subbands, and (ii) a subband inter-panel co-phase for each of the plurality of subbands,
wherein the number of antenna panels is two or four, wherein if the number of antenna panels is two (N g =2), one of the first codebook mode or the second codebook mode is configured, and wherein if the number of antenna panels is four (N g =4), only the first codebook mode is configured.
2. The UE of claim 1 , wherein:
the number of antenna panels is two (N g =2),
the second codebook mode is configured,
the wideband inter-panel co-phase for each polarization (P i ) of a second of the two antenna panels is given by a p =e jπ/ 4e jπp/ 2, and
the subband inter-panel co-phase for each polarization (P i ) of the second antenna panel is given by b n =e −jπ/ 4e jπn/ 2,
where p=0,1,2,3 and n=0,1.
3. The UE of claim 1 , wherein:
a combination of (N g , N 1 , N 2 ), configured via the configuration information for the CSI feedback, for a given number of antenna ports and corresponding values of (O 1 , O 2 ) are determined according to:
Number of
antenna ports
(N g , N 1 , N 2 )
(O 1 , O 2 )
8
(2, 2, 1)
(4, 1)
16
(2, 4, 1)
(4, 1)
(4, 2, 1)
(4, 1)
(2, 2, 2)
(4, 4)
32
(2, 8, 1)
(4, 1)
(4, 4, 1)
(4, 1)
(2, 4, 2)
(4, 4)
(4, 2, 2)
(4, 4),
N 1 and N 2 respectively are a number of antenna ports with a polarization (P 1 or P 2 ) in first and second dimensions of each of the antenna panels, and
O 1 and O 2 are oversampling factors in the first and second dimensions, respectively, and
N 1 , N 2 , O 1 and O 2 are used to obtain a set of two-dimensional discrete Fourier transform (DFT) beams, v i,m ,
where l=0, 1, . . . , O 1 N 1 , m=0, 1, . . . , O 2 N 2 , and
u
m
=
{
[
1
e
j
2
π
m
O
2
N
2
…
e
j
2
π
m
(
N
2
-
1
)
O
2
N
2
]
N
2
>
1
1
N
2
=
1
,
v
l
,
m
=
[
u
m
e
j
2
π
l
O
1
N
1
u
m
…
e
j
2
π
l
(
N
1
-
1
)
O
1
N
1
u
m
]
T
.
4. The UE of claim 3 , wherein:
for the first codebook mode, the codebook for generating the CSI feedback for N g =2,4 is constructed using vectors:
W
l
,
m
,
p
,
n
1
,
2
,
1
=
1
P
CSI
-
RS
[
v
l
,
m
φ
n
v
l
,
m
φ
p
1
v
l
,
m
φ
n
φ
p
1
v
l
,
m
]
,
W
l
,
m
,
p
,
n
2
,
2
,
1
=
1
P
CSI
-
RS
[
v
l
,
m
-
φ
n
v
l
,
m
φ
p
1
v
l
,
m
-
φ
n
φ
p
1
v
l
,
m
]
,
W
l
,
m
,
p
,
n
1
,
4
,
1
=
1
P
CSI
-
RS
[
v
l
,
m
φ
n
v
l
,
m
φ
p
1
v
l
,
m
φ
n
φ
p
1
v
l
,
m
φ
p
2
v
l
,
m
φ
n
φ
p
2
v
l
,
m
φ
p
3
v
l
,
m
φ
n
φ
p
3
v
l
,
m
]
,
W
l
,
m
,
p
,
n
2
,
4
,
1
=
1
P
CSI
-
RS
[
v
l
,
m
-
φ
n
v
l
,
m
φ
p
1
v
l
,
m
-
φ
n
φ
p
1
v
l
,
m
φ
p
2
v
l
,
m
-
φ
n
φ
p
2
v
l
,
m
φ
p
3
v
l
,
m
-
φ
n
φ
p
3
v
l
,
m
]
,
where
p
=
{
P
1
N
g
=
2
[
P
1
P
2
P
3
]
N
g
=
4
,
and
for the second codebook mode, the codebook for generating the CSI feedback for N g =2 is constructed using vectors:
W
l
,
m
,
p
,
n
1
,
2
,
2
=
1
P
CSI
-
RS
[
v
l
,
m
φ
n
0
v
l
,
m
a
p
1
b
n
1
v
l
,
m
a
p
2
b
n
2
v
l
,
m
]
,
W
l
,
m
,
p
,
n
2
,
2
,
2
=
1
P
CSI
-
RS
[
v
l
,
m
-
φ
n
0
v
l
,
m
a
p
1
b
n
1
v
l
,
m
-
a
p
2
b
n
2
v
l
,
m
]
,
where:
p=[P 1 P 2 ], n=[n 0 n 1 n 2 ], n, n 0 =0,1,2,3, p 1 , p 2 , p 3 =0,1,2,3, n 1 , n 2 =0,1, and P CSI-RS is the number of antenna ports,
φ n ==e jπn/2 ,
a p =e jπ/4 e jπp/2 , and
b n =e −jπ/4 e jπn/2 .
5. The UE of claim 4 , wherein:
the CSI feedback includes a pre-coding matrix indicator (PMI) that includes PMI indices i 1,1 , i 1,2 , i 1,3 , i 1,4 , and i 2 ,
for 1-layer CSI feedback:
for the first codebook mode, the codebook comprises pre-coding matrices:
W l,m,p,n (1) =W l,m,p,n 1,N g ,1 , and
for the second codebook mode, the codebook comprises pre-coding matrices:
W l,m,p,n (1) =W l,m,p,n 1,N g ,2 ,
for 2-layer CSI feedback:
for the first codebook mode, the codebook comprises pre-coding matrices:
W
l
,
l
′
,
m
,
m
′
,
p
,
n
(
2
)
=
1
2
[
W
l
,
m
,
p
,
n
1
,
N
g
,
1
W
l
′
,
m
′
,
p
,
n
2
,
N
g
,
1
]
,
and
for the second codebook mode, the codebook comprises pre-coding matrices:
W
l
,
l
′
,
m
,
m
′
,
p
,
n
(
2
)
=
1
2
[
W
l
,
m
,
p
,
n
1
,
N
g
,
2
W
l
′
,
m
,
p
,
n
2
,
N
g
,
2
]
,
for 3-layer CSI feedback:
for the first codebook mode, the codebook comprises pre-coding matrices:
W
l
,
l
′
,
m
,
m
′
,
p
,
n
(
3
)
=
1
3
[
W
l
,
m
,
p
,
n
1
,
N
g
,
1
W
l
′
,
m
′
,
p
,
n
1
,
N
g
,
1
W
l
,
m
,
p
,
n
2
,
N
g
,
1
]
,
and
for the second codebook mode, the codebook comprises pre-coding matrices:
W
l
,
l
′
,
m
,
m
′
,
p
,
n
(
3
)
=
1
3
[
W
l
,
m
,
p
,
n
1
,
N
g
,
2
W
l
′
,
m
′
,
p
,
n
1
,
N
g
,
2
W
l
,
m
,
p
,
n
2
,
N
g
,
2
]
,
and
for 4-layer CSI feedback:
for the first codebook mode, the codebook comprises pre-coding matrices:
W
l
,
l
′
,
m
,
m
′
,
p
,
n
(
4
)
=
1
4
[
W
l
,
m
,
p
,
n
1
,
N
g
,
1
W
l
′
,
m
′
,
p
,
n
1
,
N
g
,
1
W
l
,
m
,
p
,
n
2
,
N
g
,
1
W
l
′
,
m
′
,
p
,
n
2
,
N
g
,
1
]
,
and
for the second codebook mode, the codebook comprises pre-coding matrices:
W
l
,
l
′
,
m
,
m
′
,
p
,
n
(
4
)
=
1
4
[
W
l
,
m
,
p
,
n
1
,
N
g
,
2
W
l
′
,
m
′
,
p
,
n
1
,
N
g
,
2
W
l
,
m
,
p
,
n
2
,
N
g
,
2
W
l
′
,
m
′
,
p
,
n
2
,
N
g
,
2
]
,
where:
l=i 1,1 , m=i 1,2 , l′=i 1,1 +k 1 , m′=i 1,2 +k 2 ,
for the first codebook mode,
p
=
{
p
1
=
i
1
,
4
,
1
=
i
1
,
4
,
N
g
=
2
[
p
1
p
2
p
3
]
=
[
i
1
,
4
,
1
i
1
,
4
,
2
i
1
,
4
,
3
]
=
i
1
,
4
,
N
g
=
4
,
and n=i 2 ,
for the second codebook mode, N g =2, p 1 =[i 1,4,1 i 1,4,2 ]=i 1,4 , n=[n 0 n 1 n 2 ]=[i 2,0 i 2,1 i 2,2 ]=i 2 ,
i 1,1 and i 1,2 are PMI indices that indicate a first beam v i 1,1 i 1,2 ,
i 1,3 is a PMI index that indicates a distance (k 1 , k 2 ) of a second beam v i 1,1 +k 1 ,i 1,2 +k 2 with respect to the first beam v i 1,1 ,i 1,2 ,
i 1,4 is a PMI index that indicates the wideband inter-panel co-phase, and
i 2 is a PMI index that indicates:
for the first codebook mode, a subband co-phase between two polarizations is common for all of the antenna panels, and
for the second codebook mode, the subband co-phase between two polarizations of a first of the antenna panels (via i 2,0 ), and the subband inter-panel co-phase for each polarization of a second of the antenna panels (via i 2,1 , i 2,2 ).
6. The UE of claim 5 , wherein:
k 1 =0, k 2 =0, and i 1,3 is not included for the 1-layer CSI feedback,
mapping of i 1,3 to k 1 and k 2 for the 2-layer CSI feedback for N g =2 or 4 is determined according to:
N 1 > N 2 > 1
N 1 = N 2
N 1 = 2, N 2 = l
N 1 > 2, N 2 = 1
i 1, 3
k 1
k 2
k 1
k 2
k 1
k 2
k 1
k 2
0
0
0
0
0
0
0
0
0
1
O 1
0
O 1
0
O 1
0
O 1
0
2
0
O 2
0
O 2
2O 1
0
3
2O 1
0
O 1
O 2
3O 1
0,
and
mapping of i 1,3 to k 1 and k 2 for the 3-layer or 4-layer CSI feedback for N g =2 or 4 is determined according to:
N 1 = 2, N 2 = 1
N 1 = 4, N 2 = 1
N 1 = 2, N 2 = 2
N 1 = 2, N 2 = 2
N 1 = 4, N 2 = 2
i 1, 3
k 1
k 2
k 1
k 2
k 1
k 2
k 1
k 2
k 1
k 2
0
O 1
0
O 1
0
O 1
0
O 1
0
O 1
0
1
2O 1
0
2O 1
0
0
O 2
0
O 2
2
3O 1
0
3O 1
0
O 1
O 2
O 1
O 2
3
4O 1
0
2O 1
0.
7. A base station (BS), the BS comprising
a processor configured to generate configuration information for channel state information (CSI) feedback, the configuration information indicating a number of antenna panels (N g ) at the BS and a codebook mode, the codebook mode indicating a codebook for the CSI feedback and configured between a first codebook mode and a second codebook mode, wherein N g >1 and each of the antenna panels comprises antenna ports with a first polarization (P 1 ) and antenna ports with a second polarization (P 2 ); and
a transceiver operably connected to the processor, the transceiver configured to:
transmit, to a user equipment (UE), the configuration information, and
receive the CSI feedback from the UE generated in accordance with the indicated codebook,
wherein the codebook corresponding to the first codebook mode is used to generate the CSI feedback based on a wideband inter-panel co-phase that is common for a plurality of subbands configured for the CSI feedback, and
wherein the codebook corresponding to the second codebook mode is used to generate the CSI feedback based on at least one of (i) a wideband inter-panel co-phase that is common for the plurality of subbands, and (ii) a subband inter-panel co-phase for each of the plurality of subbands,
wherein the number of antenna panels is two or four, wherein if the number of antenna panels is two (N g =2), one of the first codebook mode or the second codebook mode is configured, and wherein if the number of antenna panels is four (N g =4), only the first codebook mode is configured.
8. The BS of claim 7 , wherein:
the number of antenna panels is two (N g =2),
the second codebook mode is configured,
the wideband inter-panel co-phase for each polarization (P i ) of a second of the two antenna panels is given by a p =e jπ/ 4e jπp/ 2, and
the subband inter-panel co-phase for each polarization (P i ) of the second antenna panel is given by b n =e −jπ/ 4e jπn/ 2,
where p=0,1,2,3 and n=0,1.
9. The BS of claim 7 , wherein:
a combination of (N g , N 1 , N 2 ), configured via the configuration information for the CSI feedback, for a given number of antenna ports and corresponding values of (O 1 , O 2 ) are determined according to:
Number of
antenna ports
(N g , N 1 , N 2 )
(O 1 , O 2 )
8
(2, 2, 1)
(4, 1)
16
(2, 4, 1)
(4, 1)
(4, 2, 1)
(4, 1)
(2, 2, 2)
(4, 4)
32
(2, 8, 1)
(4, 1)
(4, 4, 1)
(4, 1)
(2, 4, 2)
(4, 4)
(4, 2, 2)
(4, 4),
N 1 and N 2 respectively are a number of antenna ports with a polarization (P 1 or P 2 ) in first and second dimensions of each of the antenna panels,
O 1 and O 2 are oversampling factors in the first and second dimensions, respectively, and
N 1 , N 2 , O 1 and O 2 are used to obtain a set of two-dimensional discrete Fourier transform (DFT) beams, v i,m ,
where l=0,1, . . . , O 1 N 1 , m=0,1, . . . , O 2 N 2 , and
u
m
=
{
[
1
e
j
2
π
m
O
2
N
2
…
e
j
2
π
m
(
N
2
-
1
)
O
2
N
2
]
N
2
>
1
1
N
2
=
1
,
v
l
,
m
=
[
u
m
e
j
2
π
l
O
1
N
1
u
m
…
e
j
2
π
l
(
N
1
-
1
)
O
1
N
1
u
m
]
T
.
10. The BS of claim 9 , wherein:
for the first codebook mode, the codebook for generating the CSI feedback for N g =2,4 is constructed using vectors:
W
l
,
m
,
p
,
n
1
,
2
,
1
=
1
P
CSI
-
RS
[
v
l
,
m
φ
n
v
l
,
m
φ
p
1
v
l
,
m
φ
n
φ
p
1
v
l
,
m
]
,
W
l
,
m
,
p
,
n
2
,
2
,
1
=
1
P
CSI
-
RS
[
v
l
,
m
-
φ
n
v
l
,
m
φ
p
1
v
l
,
m
-
φ
n
φ
p
1
v
l
,
m
]
,
W
l
,
m
,
p
,
n
1
,
4
,
1
=
1
P
CSI
-
RS
[
v
l
,
m
φ
n
v
l
,
m
φ
p
1
v
l
,
m
φ
n
φ
p
1
v
l
,
m
φ
p
2
v
l
,
m
φ
n
φ
p
2
v
l
,
m
φ
p
3
v
l
,
m
φ
n
φ
p
3
v
l
,
m
]
,
W
l
,
m
,
p
,
n
2
,
4
,
1
=
1
P
CSI
-
RS
[
v
l
,
m
-
φ
n
v
l
,
m
φ
p
1
v
l
,
m
-
φ
n
φ
p
1
v
l
,
m
φ
p
2
v
l
,
m
-
φ
n
φ
p
2
v
l
,
m
φ
p
3
v
l
,
m
-
φ
n
φ
p
3
v
l
,
m
]
,
where
p
=
{
P
1
N
g
=
2
[
P
1
P
2
P
3
]
N
g
=
4
,
and
for the second codebook mode, the codebook for generating the CSI feedback for N g =2 is constructed using vectors:
W
l
,
m
,
p
,
n
1
,
2
,
2
=
1
P
CSI
-
RS
[
v
l
,
m
φ
n
0
v
l
,
m
a
p
1
b
n
1
v
l
,
m
a
p
2
b
n
2
v
l
,
m
]
,
W
l
,
m
,
p
,
n
2
,
2
,
2
=
1
P
CSI
-
RS
[
v
l
,
m
-
φ
n
0
v
l
,
m
a
p
1
b
n
1
v
l
,
m
-
a
p
2
b
n
2
v
l
,
m
]
,
where:
p=[P 1 P 2 ], n=[n 0 n 1 n 2 ], n, n 0 =0,1,2,3, p 1 , p 2 , p 3 =n 1 , n 2 =0,1, and P CSI-RS is the number of antenna ports,
φ n =e jπn/2 ,
a p =e jπ/4 e jπp/2 , and
b n =e −jπ/4 e jπn/2 .
11. The BS of claim 10 , wherein:
the CSI feedback includes a pre-coding matrix indicator (PMI) that includes PMI indices i 1,1 , i 1,2 , i 1,3 , i 1,4 , and i 2 ,
for 1-layer CSI feedback:
for the first codebook mode, the codebook comprises pre-coding matrices:
W i,m,p,n (1) =W l,m,p,n 1,N g ,1 , and
for the second codebook mode, the codebook comprises pre-coding matrices:
W l,m,p,n (1) =W l,m,p,n 1,N g ,2 ,
for 2-layer CSI feedback:
for the first codebook mode, the codebook comprises pre-coding matrices:
W
l
,
l
′
,
m
,
m
′
,
p
,
n
(
2
)
=
1
2
[
W
l
,
m
,
p
,
n
1
,
N
g
,
1
W
l
′
,
m
′
,
p
,
n
2
,
N
g
,
1
]
,
and
for the second codebook mode, the codebook comprises pre-coding matrices:
W
l
,
l
′
,
m
,
m
′
,
p
,
n
(
2
)
=
1
2
[
W
l
,
m
,
p
,
n
1
,
N
g
,
2
W
l
′
,
m
′
,
p
,
n
2
,
N
g
,
2
]
,
for 3-layer CSI feedback:
for the first codebook mode, the codebook comprises pre-coding matrices:
W
l
,
l
′
,
m
,
m
′
,
p
,
n
(
3
)
=
1
3
[
W
l
,
m
,
p
,
n
1
,
N
g
,
1
W
l
′
,
m
′
,
p
,
n
1
,
N
g
,
1
W
l
,
m
,
p
,
n
2
,
N
g
,
1
]
,
and
for the second codebook mode, the codebook comprises pre-coding matrices:
W
l
,
l
′
,
m
,
m
′
,
p
,
n
(
3
)
=
1
3
[
W
l
,
m
,
p
,
n
1
,
N
g
,
2
W
l
′
,
m
′
,
p
,
n
1
,
N
g
,
2
W
l
,
m
,
p
,
n
2
,
N
g
,
2
]
,
and
for 4-layer CSI feedback:
for the first codebook mode, the codebook comprises pre-coding matrices:
W
l
,
l
′
,
m
,
m
′
,
p
,
n
(
4
)
=
1
4
[
W
l
,
m
,
p
,
n
1
,
N
g
,
1
W
l
′
,
m
′
,
p
,
n
1
,
N
g
,
1
W
l
,
m
,
p
,
n
2
,
N
g
,
1
W
l
′
,
m
′
,
p
,
n
2
,
N
g
,
1
]
,
and
for the second codebook mode, the codebook comprises pre-coding matrices:
W
l
,
l
′
,
m
,
m
′
,
p
,
n
(
4
)
=
1
4
[
W
l
,
m
,
p
,
n
1
,
N
g
,
2
W
l
′
,
m
′
,
p
,
n
1
,
N
g
,
2
W
l
,
m
,
p
,
n
2
,
N
g
,
2
W
l
′
,
m
′
,
p
,
n
2
,
N
g
,
2
]
,
where:
l=i 1,1 , m=i 1,2 , l′=i 1,1 +k 1 , m′=i 1,2 +k 2 ,
for the first codebook mode,
p
=
{
p
1
=
i
1
,
4
,
1
=
i
1
,
4
,
N
g
=
2
[
p
1
p
2
p
3
]
=
[
i
1
,
4
,
1
i
1
,
4
,
2
i
1
,
4
,
3
]
=
i
1
,
4
,
N
g
=
4
,
and n=i 2 ,
for the second codebook mode, N g =2, p 1 =[i 1,4,1 i 1,4,2 ]=i 1,4 , n=[n 0 n 1 n 2 ]=[i 2,0 i 2,1 i 2,2 ]=i 2 ,
i 1,1 and i 1,2 are PMI indices that indicate a first beam v i 1,1 i 1,2 ,
i 1,3 is a PMI index that indicates a distance (k 1 , k 2 ) of a second beam v i 1,1 +k 1 ,i 1,2 +k 2 with respect to the first beam v i 1,1 ,i 1,2 ,
i 1,4 is a PMI index that indicates the wideband inter-panel co-phase, and
i 2 is a PMI index that indicates:
for the first codebook mode, a subband co-phase between two polarizations is common for all of the antenna panels, and
for the second codebook mode, the subband co-phase between two polarizations of a first of the antenna panels (via i 2,0 ), and the subband inter-panel co-phase for each polarization of a second of the antenna panels (via i 2,1 , i 2,2 ).
12. The BS of claim 11 , wherein:
k 1 =0, k 2 =0, and i 1,3 is not included for the 1-layer CSI feedback,
mapping of i 1,3 to k 1 and k 2 for the 2-layer CSI feedback for N g =2 or 4 is determined according to:
N 1 > N 2 > 1
N 1 = N 2
N 1 = 2, N 2 = l
N 1 > 2, N 2 = 1
i 1, 3
k 1
k 2
k 1
k 2
k 1
k 2
k 1
k 2
0
0
0
0
0
0
0
0
0
1
O 1
0
O 1
0
O 1
0
O 1
0
2
0
O 2
0
O 2
2O 1
0
3
2O 1
0
O 1
O 2
3O 1
0,
and
mapping of i 1,3 to k 1 and k 2 for the 3-layer or 4-layer CSI feedback for N g =2 or 4 is determined according to:
N 1 = 2, N 2 = 1
N 1 = 4, N 2 = 1
N 1 = 2, N 2 = 2
N 1 = 2, N 2 = 2
N 1 = 4, N 2 = 2
i 1, 3
k 1
k 2
k 1
k 2
k 1
k 2
k 1
k 2
k 1
k 2
0
O 1
0
O 1
0
O 1
0
O 1
0
O 1
0
1
2O 1
0
2O 1
0
0
O 2
0
O 2
2
3O 1
0
3O 1
0
O 1
O 2
O 1
O 2
3
4O 1
0
2O 1
0.
13. A method for channel state information (CSI) feedback by a user equipment (UE), the method comprising
receiving, from a base station (BS), configuration information for the CSI feedback, the configuration information indicating a number of antenna panels (N g ) at the BS and a codebook mode, wherein N g >1 and each of the antenna panels comprises antenna ports with a first polarization (P 1 ) and antenna ports with a second polarization (P 2 );
identifying the number of antenna panels at the BS;
identifying a codebook for the CSI feedback based on the codebook mode configured between a first codebook mode and a second codebook mode;
generating the CSI feedback using the identified codebook; and
transmitting the generated CSI feedback to the BS,
wherein the codebook corresponding to the first codebook mode is used to generate the CSI feedback based on a wideband inter-panel co-phase that is common for a plurality of subbands configured for the CSI feedback,
wherein the codebook corresponding to the second codebook mode is used to generate the CSI feedback based on at least one of (i) a wideband inter-panel co-phase that is common for the plurality of subbands, and (ii) a subband inter-panel co-phase for each of the plurality of subbands,
wherein the number of antenna panels is two or four, wherein if the number of antenna panels is two (N g =2), one of the first codebook mode or the second codebook mode is configured, and wherein if the number of antenna panels is four (N g =4), only the first codebook mode is configured.
14. The method of claim 13 , wherein:
the number of antenna panels is two (N g =2),
the second codebook mode is configured,
the wideband inter-panel co-phase for each polarization (P i ) of a second of the two antenna panels is given by a p =e jπ/ 4e jπp/ 2, and
the subband inter-panel co-phase for each polarization (P i ) of the second antenna panel is given by b n =e −jπ/ 4e jπn/ 2,
where p=0,1,2,3 and n=0,1.
15. The method of claim 13 , wherein:
a combination of (N g , N 1 , N 2 ), configured via the configuration information for the CSI feedback, for a given number of antenna ports and corresponding values of (O 1 , O 2 ) are determined according to:
Number of
antenna ports
(N g , N 1 , N 2 )
(O 1 , O 2 )
8
(2, 2, 1)
(4, 1)
16
(2, 4, 1)
(4, 1)
(4, 2, 1)
(4, 1)
(2, 2, 2)
(4, 4)
32
(2, 8, 1)
(4, 1)
(4, 4, 1)
(4, 1)
(2, 4, 2)
(4, 4)
(4, 2, 2)
(4, 4),
N 1 and N 2 respectively are a number of antenna ports with a polarization (P 1 or P 2 ) in first and second dimensions of each of the antenna panels,
O 1 and O 2 are oversampling factors in the first and second dimensions, respectively, and
N 1 , N 2 , O 1 and O 2 are used to obtain a set of two-dimensional discrete Fourier transform (DFT) beams, v i,m ,
where l=0,1, . . . , O 1 N 1 , m=0,1, . . . , O 2 N 2 , and
u
m
=
{
[
1
e
j
2
π
m
O
2
N
2
…
e
j
2
π
m
(
N
2
-
1
)
O
2
N
2
]
N
2
>
1
1
N
2
=
1
,
v
l
,
m
=
[
u
m
e
j
2
π
l
O
1
N
1
u
m
…
e
j
2
π
l
(
N
1
-
1
)
O
1
N
1
u
m
]
T
.
16. The method of claim 15 , wherein:
for the first codebook mode, the codebook for generating the CSI feedback for N g =2,4 is constructed using vectors:
W
l
,
m
,
p
,
n
1
,
2
,
1
=
1
P
CSI
-
RS
[
v
l
,
m
φ
n
v
l
,
m
φ
p
1
v
l
,
m
φ
n
φ
p
1
v
l
,
m
]
,
W
l
,
m
,
p
,
n
2
,
2
,
1
=
1
P
CSI
-
RS
[
v
l
,
m
-
φ
n
v
l
,
m
φ
p
1
v
l
,
m
-
φ
n
φ
p
1
v
l
,
m
]
,
W
l
,
m
,
p
,
n
1
,
4
,
1
=
1
P
CSI
-
RS
[
v
l
,
m
φ
n
v
l
,
m
φ
p
1
v
l
,
m
φ
n
φ
p
1
v
l
,
m
φ
p
2
v
l
,
m
φ
n
φ
p
2
v
l
,
m
φ
p
3
v
l
,
m
φ
n
φ
p
3
v
l
,
m
]
,
W
l
,
m
,
p
,
n
2
,
4
,
1
=
1
P
CSI
-
RS
[
v
l
,
m
-
φ
n
v
l
,
m
φ
p
1
v
l
,
m
-
φ
n
φ
p
1
v
l
,
m
φ
p
2
v
l
,
m
-
φ
n
φ
p
2
v
l
,
m
φ
p
3
v
l
,
m
-
φ
n
φ
p
3
v
l
,
m
]
,
where
p
=
{
P
1
N
g
=
2
[
P
1
P
2
P
3
]
N
g
=
4
,
and
for the second codebook mode, the codebook for generating the CSI feedback for N g =2 is constructed using vectors:
W
l
,
m
,
p
,
n
1
,
2
,
2
=
1
P
CSI
-
RS
[
v
l
,
m
φ
n
0
v
l
,
m
a
p
1
b
n
1
v
l
,
m
a
p
2
b
n
2
v
l
,
m
]
,
W
l
,
m
,
p
,
n
2
,
2
,
2
=
1
P
CSI
-
RS
[
v
l
,
m
-
φ
n
0
v
l
,
m
a
p
1
b
n
1
v
l
,
m
-
a
p
2
b
n
2
v
l
,
m
]
,
where:
p=[P 1 P 2 ], n=[n 0 n 1 n 2 ], n, n 0 =0,1,2,3, p 1 , p 2 , p 3 =0,1,2,3, n 1 , n 2 =0,1, and P CSI-RS is the number of antenna ports, and
φ n ==e jπn/2 ,
a p =e jπ4 e jπp/2 , and
b n =e −jπ/4 e jπn/2 .
17. The method of claim 16 , wherein:
the CSI feedback includes a pre-coding matrix indicator (PMI) that includes PMI indices i 1,1 , i 1,2 , i 1,3 , i 1,4 , and i 2 ,
for 1-layer CSI feedback:
for the first codebook mode, the codebook comprises pre-coding matrices:
W i,m,p,n (1) =W l,m,p,n 1,N g ,1 , and
for the second codebook mode, the codebook comprises pre-coding matrices:
W l,m,p,n (1) =W l,m,p,n 1,N g ,2 ,
for 2-layer CSI feedback:
for the first codebook mode, the codebook comprises pre-coding matrices:
W
l
,
l
′
,
m
,
m
′
,
p
,
n
(
2
)
=
1
2
[
W
l
,
m
,
p
,
n
1
,
N
g
,
1
W
l
′
,
m
′
,
p
,
n
2
,
N
g
,
1
]
,
and
for the second codebook mode, the codebook comprises pre-coding matrices:
W
l
,
l
′
,
m
,
m
′
,
p
,
n
(
2
)
=
1
2
[
W
l
,
m
,
p
,
n
1
,
N
g
,
2
W
l
′
,
m
′
,
p
,
n
2
,
N
g
,
2
]
,
for 3-layer CSI feedback:
for the first codebook mode, the codebook comprises pre-coding matrices:
W
l
,
l
′
,
m
,
m
′
,
p
,
n
(
3
)
=
1
3
[
W
l
,
m
,
p
,
n
1
,
N
g
,
1
W
l
′
,
m
′
,
p
,
n
1
,
N
g
,
1
W
l
,
m
,
p
,
n
2
,
N
g
,
1
]
,
and
for the second codebook mode, the codebook comprises pre-coding matrices:
W
l
,
l
′
,
m
,
m
′
,
p
,
n
(
3
)
=
1
3
[
W
l
,
m
,
p
,
n
1
,
N
g
,
2
W
l
′
,
m
′
,
p
,
n
1
,
N
g
,
2
W
l
,
m
,
p
,
n
2
,
N
g
,
2
]
,
and
for 4-layer CSI feedback:
for the first codebook mode, the codebook comprises pre-coding matrices:
W
l
,
l
′
,
m
,
m
′
,
p
,
n
(
4
)
=
1
4
[
W
l
,
m
,
p
,
n
1
,
N
g
,
1
W
l
′
,
m
′
,
p
,
n
1
,
N
g
,
1
W
l
,
m
,
p
,
n
2
,
N
g
,
1
W
l
′
,
m
′
,
p
,
n
2
,
N
g
,
1
]
,
and
for the second codebook mode, the codebook comprises pre-coding matrices:
W
l
,
l
′
,
m
,
m
′
,
p
,
n
(
4
)
=
1
4
[
W
l
,
m
,
p
,
n
1
,
N
g
,
2
W
l
′
,
m
′
,
p
,
n
1
,
N
g
,
2
W
l
,
m
,
p
,
n
2
,
N
g
,
2
W
l
′
,
m
′
,
p
,
n
2
,
N
g
,
2
]
,
where:
l=i 1,1 , m=i 1,2 , l′=i 1,1 +k 1 , m′=i 1,2 +k 2 ,
for the first codebook mode,
p
=
{
p
1
=
i
1
,
4
,
1
=
i
1
,
4
,
N
g
=
2
[
p
1
p
2
p
3
]
=
[
i
1
,
4
,
1
i
1
,
4
,
2`
i
1
,
4
,
3
]
=
i
1
,
4
,
N
g
=
4
,
and n=i 2 ,
for the second codebook mode, N g =2, p 1 =[i 1,4,1 i 1,4,2 ]=i 1,4 , n=[n 0 n 1 n 2 ]=[i 2,0 i 2,1 i 2,2 ]=i 2 ,
i 1,1 and i 1,2 are PMI indices that indicate a first beam v i 1,1 ,i 1,2 ,
i 1,3 is a PMI index that indicates a distance (k 1 , k 2 ) of a second beam v i 1,1 +k 1 ,i 1,2 +k 2 with respect to the first beam v i 1,1 ,v 1,2 ,
i 1,4 is a PMI index that indicates the wideband inter-panel co-phase, and
i 2 is a PMI index that indicates:
for the first codebook mode, a subband co-phase between two polarizations is common for all of the antenna panels, and
for the second codebook mode, the subband co-phase between two polarizations of a first of the antenna panels (via i 2,0 ), and the subband inter-panel co-phase for each polarization of a second of the antenna panels (via i 2,1 , i 2,2 ).