Method and apparatus for codebook subset restriction
A method for operating a user equipment (UE) for channel state information (CSI) reporting in a wireless communication system comprises receiving, from a base station (BS), higher layer signaling including codebook subset restriction (CBSR) information, determining a bitmap sequence B based on the CBSR information, identifying, based on a portion of the bitmap sequence B, a restriction on P spatial domain (SD) vector groups out of a total of Q SD vector groups, generating a CSI report based on the P SD vector groups with the identified restriction and remaining Q minus P SD vector groups without any restrictions, and transmitting the CSI report to the BS, wherein the restriction on P SD vector groups corresponds to restricting an average amplitude (A i avg ) associated with an SD vector a i in the P SD vector groups to a maximum allowed average amplitude (γ i ).
1. A user equipment (UE) for channel state information (CSI) reporting in a wireless communication system, the UE comprising:
a transceiver configured to receive, from a base station (BS), higher layer signaling including codebook subset restriction (CBSR) information; and
a processor operably connected to the transceiver, the processor configured to:
determine a bitmap sequence B based on the CBSR information,
identify, based on a portion of the bitmap sequence B, a restriction on P spatial domain (SD) vector groups out of a total of Q SD vector groups, and
generate a CSI report based on the P SD vector groups with the identified restriction and remaining Q minus P SD vector groups without any restrictions,
wherein the transceiver is further configured to transmit the CSI report to the BS,
wherein the restriction on P SD vector groups corresponds to restricting an average amplitude (A i avg ) associated with an SD vector a i in the P SD vector groups to a maximum allowed average amplitude (γ i ).
2. The UE of claim 1 , wherein the average amplitude (A i avg ) associated with an SD vector a i is determined as a square root of an average power (P i avg ), where the average power (P i avg ) is determined by averaging P i,m over M frequency domain (FD) indices, m=0, 1, . . . , M−1, and P i,m is a power of a coefficient with an SD index i and a FD index m.
3. The UE of claim 2 , wherein:
the coefficient with an SD index i and a FD index m is c i,m ,
the power (P i,m ) of the coefficient c i,m , equals a square of p i,m , where p i,m is an amplitude of the coefficient c i,m ,
the average power
P
i
a
v
g
=
1
n
∑
m
=
0
M
-
1
P
i
,
m
=
1
n
∑
m
=
0
M
-
1
p
i
,
m
2
,
and
the restriction on the average amplitude (A i avg ) is applied as follows:
A
i
a
v
g
=
1
n
∑
m
=
0
M
-
1
p
i
,
m
2
≤
γ
i
,
where n is a normalization factor.
4. The UE of claim 2 , wherein, for each layer l=1, . . . , υ, where υ is a rank value:
the coefficient with an SD index i and a FD index m is c l,i,m ,
the power (P i,m ) of the coefficient c l,i,m , equals a square of p l,i,m , where
p
l
,
i
,
m
=
p
l
,
⌊
i
L
⌋
(
1
)
p
l
,
i
,
m
(
2
)
is an amplitude of the coefficient c l,i,m , where └ ┘ a flooring function,
the average power
P
i
a
v
g
=
1
n
∑
m
=
0
M
-
1
P
i
,
m
=
1
Σ
m
=
0
M
-
1
b
l
,
i
,
m
∑
m
=
0
M
-
1
b
l
,
i
,
m
p
l
,
i
,
m
2
,
and
the restriction on the average amplitude (A i avg ) is applied as follows:
A
i
a
v
g
=
1
∑
m
=
0
M
-
1
b
l
,
i
,
m
∑
m
=
0
M
-
1
b
l
,
i
,
m
p
l
,
i
,
m
2
≤
γ
i
,
where n is a number of non-zero coefficients associated with an SD index i such that
n
=
∑
m
=
0
M
-
1
b
l
,
i
,
m
,
and
where b l,i,m =1 if c l,i,m is non-zero and b l,i,m =0 if c l,i,m , is zero.
5. The UE of claim 4 , wherein the CSI report includes a precoding matrix indicator (PMI) indicating, for each layer l=1, . . . , υ, a precoding vector for each FD unit of a total number (N 3 ) of FD units as determined by columns of
W
l
=
[
∑
i
=
0
L
-
1
a
i
∑
m
=
0
M
-
1
c
l
,
i
,
m
(
b
l
,
m
H
)
∑
i
=
0
L
-
1
a
i
∑
m
=
0
M
-
1
c
l
,
i
+
L
,
m
(
b
l
,
m
H
)
]
,
wherein:
a i , i=0, 1, . . . , L−1, are L SD vectors,
b l,m , m=0, 1, . . . , M−1, are M FD vectors for layer l,
c l,i+pL,m , i=0, 1, . . . , L−1, p=0,1, and m=0, 1, . . . , M−1, are 2LM coefficients for layer l, and
the restriction on the average amplitude associated with an SD vector a i in the P SD vector groups is applied as follows:
1
∑
m
=
0
M
-
1
b
l
,
i
+
pL
,
m
∑
m
=
0
M
-
1
b
l
,
i
+
pL
,
m
(
p
l
,
p
(
1
)
p
l
,
i
,
m
(
2
)
)
2
≤
γ
i
+
pL
.
6. The UE of claim 1 , wherein:
the portion of the bitmap sequence B equals B 2 =(B 2 (1) B 2 (2) . . . B 2 (P) , a concatenation of P bitmaps B 2 (k) for k=0, 1, . . . , P−1;
the restriction on a k-th SD vector group of the P SD vector groups is indicated via a k-th bitmap B 2 (k) of the P bitmaps;
the k-th bitmap B 2 (k) =b 2 (k,2N 1 N 2 −1) . . . b 2 (k,0) is of length 2N 1 N 2 , where a bit pair b 2 (k,2(N 1 x 2 +x 1 )+1) , b 2 (k,2(N 1 x 2 +x 1 )) indicates the maximum allowed average amplitude (γ i ) for an SD vector a i indexed by i=(x 1 , x 2 ) in the k-th SD vector group of the P SD vector groups, where N 1 and N 2 are higher layer configured; and
a mapping of the bit pair to the maximum allowed average amplitude (γ i ) is determined based on a table given by:
bit-pair
Maximum allowed average
b 2 (k,2(N 1 x 2 +x 1 )+1) b 2 (k,2(N 1 x 2 +x 1 ))
amplitude (γ i )
00
0
01
{square root over (1/4)} = {square root over (0.25)}
10
{square root over (1/2)} = {square root over (0.5 )}
11
1.
7. The UE of claim 6 , wherein a bit-pair value b 2 (k,2(N 1 x 2 +x 1 )+1) b 2 (k,2(N 1 x 2 +x 1 )) =01 or 10 is not configured via the CBSR information if the UE does not report that it is capable of supporting amplitude restriction in its capability signalling.
8. A base station (BS) in a wireless communication system, the BS comprising:
a processor configured to generate higher layer signaling including codebook subset restriction (CBSR) information; and
a transceiver operably connected to the processor, the transceiver configured to:
transmit, to a user equipment (UE), the higher layer signaling including the codebook subset restriction (CBSR) information, and
receive, from the UE, a channel state information (CSI) report;
wherein a bitmap sequence B is determined based on the CBSR information,
wherein a restriction on P spatial domain (SD) vector groups out of a total of Q SD vector groups is identified based on a portion of the bitmap sequence B,
wherein the CSI report is generated based on the P SD vector groups with the identified restriction and remaining Q minus P SD vector groups without any restrictions, and
wherein the restriction on P SD vector groups corresponds to restricting an average amplitude (A i avg ) associated with an SD vector a i in the P SD vector groups to a maximum allowed average amplitude (γ i ).
9. The BS of claim 8 , wherein the average amplitude (A i avg ) associated with an SD vector a 1 is determined as a square root of an average power (P i avg ), where the average power (P i avg ) is determined by averaging P i,m over M frequency domain (FD) indices, m=0, 1, . . . , M−1, and P i,m is a power of a coefficient with an SD index i and a FD index m.
10. The BS of claim 9 , wherein:
the coefficient with an SD index i and a FD index m is c i,m ,
the power (P i,m ) of the coefficient c i,m equals a square of p i,m , where p i,m is an amplitude of the coefficient c i,m ,
the average power
P
i
avg
=
1
n
∑
m
=
0
M
-
1
P
i
,
m
=
1
n
∑
m
=
0
M
-
1
p
i
,
m
2
,
and
the restriction on the average amplitude (A i avg ) is applied as follows:
A
i
avg
=
1
n
∑
m
=
0
M
-
1
p
i
,
m
2
≤
γ
i
,
where n is a normalization factor.
11. The BS of claim 9 , wherein, for each layer l=1, . . . , υ, where υ is a rank value:
the coefficient with an SD index i and a FD index m is c l,i,m ,
the power (P i,m ) of the coefficient c l,i,m , equals a square of p l,i,m , where
p
l
,
i
,
m
=
p
l
,
⌊
i
L
⌋
(
1
)
p
l
,
i
,
m
(
2
)
is an amplitude of the coefficient c l,i,m , where └ ┘ is a flooring function,
the average power
P
i
avg
=
1
n
∑
m
=
0
M
-
1
P
i
,
m
=
1
∑
m
=
0
M
-
1
b
l
,
i
,
m
∑
m
=
0
M
-
1
b
l
,
i
,
m
p
l
,
i
,
m
2
,
and
the restriction on the average amplitude (A i avg ) is applied as follows:
A
i
avg
=
1
∑
m
=
0
M
-
1
b
l
,
i
,
m
∑
m
=
0
M
-
1
b
l
,
i
,
m
p
l
,
i
,
m
2
≤
γ
i
,
where n is a number of non-zero coefficients associated with an index i such that
n
=
∑
m
=
0
M
-
1
b
l
,
i
,
m
,
and
where b l,i,m =1 if c l,i,m is non-zero and b l,i,m =0 if c l,i,m is zero.
12. The BS of claim 11 , wherein the CSI report includes a precoding matrix indicator (PMI) indicating, for each layer l=1, . . . , υ, a precoding vector for each FD unit of a total number (N 3 ) of FD units as determined by columns of
W
l
=
[
∑
i
=
0
L
-
1
a
i
∑
m
=
0
M
-
1
c
l
,
i
,
m
(
b
l
,
m
H
)
∑
i
=
0
L
-
1
a
i
∑
m
=
0
M
-
1
c
l
,
i
+
L
,
m
(
b
l
,
m
H
)
]
,
wherein:
a i , i=0, 1, . . . , L−1, are L SD vectors,
b l,m , m=0, 1, . . . , M−1, are M FD vectors for layer l,
c l,i+pL,m , i=0, 1, . . . , L−1, p=0, 1, and m=0, 1, . . . , M−1, are 2LM coefficients for layer l, and
the restriction on the average amplitude associated with an SD vector a i in the P SD vector groups is applied as follows:
1
∑
m
=
0
M
-
1
b
l
,
i
+
pL
,
m
∑
m
=
0
M
-
1
b
l
,
i
+
pL
,
m
(
p
l
,
p
(
1
)
p
l
,
i
,
m
(
2
)
)
2
≤
γ
i
+
pL
.
13. The BS of claim 8 , wherein:
the portion of the bitmap sequence B equals B 2 =B 2 (1) B 2 (2) . . . B 2 (P) , a concatenation of P bitmaps B 2 (k) for k=0, 1, . . . , P−1;
the restriction on a k-th SD vector group of the P SD vector groups is indicated via a k-th bitmap B 2 (k) of the P bitmaps;
the k-th bitmap B 2 (k) =b 2 (k,2N 1 N 2 −1) . . . b 2 (k,0) is of length 2N 1 N 2 , where a bit pair b 2 (k,2(N 1 x 2 +x 1 )+1) , b 2 (k,2(N 1 x 2 +x 1 )) indicates the maximum allowed average amplitude (γ i ) for an SD vector a i indexed by i=(x 1 , x 2 ) in the k-th SD vector group of the P SD vector groups, where N 1 and N 2 are higher layer configured; and
a mapping of the bit pair to the maximum allowed average amplitude (γ i ) is determined based on a table given by:
bit-pair
Maximum allowed average
b 2 (k,2(N 1 x 2 +x 1 )+1) b 2 (k,2(N 1 x 2 +x 1 ))
amplitude (γ i )
00
0
01
{square root over (1/4)} = {square root over (0.25)}
10
{square root over (1/2)} = {square root over (0.5 )}
11
1.
14. The BS of claim 13 , wherein a bit-pair value b 2 (k,2(N 1 x 2 +x 1 )+1) b 2 (k,2(N 1 x 2 +x 1 )) =01 or 10 is not configured via the CBSR information if the UE does not report that it is capable of supporting amplitude restriction in its capability signalling.
15. A method for operating a user equipment (UE) for channel state information (CSI) reporting in a wireless communication system, the method comprising:
receiving, from a base station (BS), higher layer signaling including codebook subset restriction (CBSR) information;
determining a bitmap sequence B based on the CBSR information;
identifying, based on a portion of the bitmap sequence B, a restriction on P spatial domain (SD) vector groups out of a total of Q SD vector groups;
generating a CSI report based on the P SD vector groups with the identified restriction and remaining Q minus P SD vector groups without any restrictions; and
transmitting the CSI report to the BS,
wherein the restriction on P SD vector groups corresponds to restricting an average amplitude (A i avg ) associated with an SD vector a i in the P SD vector groups to a maximum allowed average amplitude (γ i ).
16. The method of claim 15 , wherein the average amplitude (A i avg ) associated with an SD vector a i is determined as a square root of an average power (P i avg ), where the average power (P i avg ) is determined by averaging P i,m over M frequency domain (FD) indices, m=0, 1, . . . , M−1, and P i,m is a power of a coefficient c i,m with a SD index i and a FD index m.
17. The method of claim 16 , wherein:
the coefficient with an SD index i and a FD index m is c i,m ,
the power (P i,m ) of the coefficient c i,m equals a square of p i,m , where p i,m is an amplitude of the coefficient c i,m ,
the average power and
P
i
avg
=
1
n
∑
m
=
0
M
-
1
P
i
,
m
=
1
n
∑
m
=
0
M
-
1
p
i
,
m
2
,
the restriction on the average amplitude (A i avg ) is applied as follows:
A
i
avg
=
1
n
∑
m
=
0
M
-
1
p
i
,
m
2
≤
γ
i
,
where n is a normalization factor.
18. The method of claim 16 , wherein, for each layer l=1, . . . , υ, where υ is a rank value:
the coefficient with an SD index i and a FD index m is c l,i,m ,
the power (P i,m ) of the coefficient c l,i,m , equals a square of p l,i,m , where
p
l
,
i
,
m
=
p
l
,
⌊
i
L
⌋
(
1
)
p
l
,
i
,
m
(
2
)
is an amplitude of the coefficient c l,i,m , where └ ┘ is a flooring function,
the average power
P
i
avg
=
1
n
∑
m
=
0
M
-
1
P
i
,
m
=
1
∑
m
=
0
M
-
1
b
l
,
i
,
m
∑
m
=
0
M
-
1
b
l
,
i
,
m
p
l
,
i
,
m
2
,
and
the restriction on the average amplitude (A i avg ) is applied as follows:
A
i
avg
=
1
∑
m
=
0
M
-
1
b
l
,
i
,
m
∑
m
=
0
M
-
1
b
l
,
i
,
m
p
l
,
i
,
m
2
≤
γ
i
,
where n is a number of non-zero coefficients associated with an SD index i such that
n
=
∑
m
=
0
M
-
1
b
l
,
i
,
m
,
and
where b l,i,m =1 if c l,i,m is non-zero and b l,i,m =0 if c l,i,m is zero.
19. The method of claim 18 , wherein the CSI report includes a precoding matrix indicator (PMI) indicating, for each layer l=1, . . . , υ, a precoding vector for each FD unit of a total number (N 3 ) of FD units as determined by columns of
W
l
=
[
∑
i
=
0
L
-
1
a
i
∑
m
=
0
M
-
1
c
l
,
i
,
m
(
b
l
,
m
H
)
∑
i
=
0
L
-
1
a
i
∑
m
=
0
M
-
1
c
l
,
i
+
L
,
m
(
b
l
,
m
H
)
]
,
wherein:
a i , i=0, 1, . . . , L−1, are L SD vectors,
b l,m , m=0, 1, . . . , M−1, are M FD vectors for layer l,
c l,i+pL,m , i=0, 1, . . . , L−1, p=0, 1, and m=0, 1, . . . , M−1, are 2LM coefficients for layer l, and
the restriction on the average amplitude associated with an SD vector a i in the P SD vector groups is applied as follows:
1
∑
m
=
0
M
-
1
b
l
,
i
+
pL
,
m
∑
m
=
0
M
-
1
b
l
,
i
+
pL
,
m
(
p
l
,
p
(
1
)
p
l
,
i
,
m
(
2
)
)
2
≤
γ
i
+
pL
.
20. The method of claim 15 , wherein:
the portion of the bitmap sequence B equals B 2 =(B 2 (1) B 2 (2) . . . B 2 (P) , a concatenation of P bitmaps B 2 (k) for k=0, 1, . . . , P−1;
the restriction on a k-th SD vector group of the P SD vector groups is indicated via a k-th bitmap B 2 (k) of the P bitmaps;
the k-th bitmap B 2 (k) =b 2 (k,2N 1 N 2 −1) . . . b 2 (k,0) is of length 2N 1 N 2 , where a bit pair b 2 (k,2(N 1 x 2 +x 1 )+1) , b 2 (k,2(N 1 x 2 +x 1 )) indicates the maximum allowed average amplitude (γ i ) for an SD vector a i indexed by i=(x 1 , x 2 ) in the k-th SD vector group of the P SD vector groups, where N 1 and N 2 are higher layer configured; and
a mapping of the bit pair to the maximum allowed average amplitude (γ i ) is determined based on a table given by:
bit-pair
Maximum allowed average
b 2 (k,2(N 1 x 2 +x 1 )+1) b 2 (k,2(N 1 x 2 +x 1 ))
amplitude (γ i )
00
0
01
{square root over (1/4)} = {square root over (0.25)}
10
{square root over (1/2)} = {square root over (0.5 )}
11
1.