Method for determining precoding matrix and corresponding communication methods and devices
View Patent ↗A method for determining precoding matrix for the sub-band precoding in a transmitter with M transmitting antennas. The method includes determining an optimized first matrix W 1 according to wideband and/or long-term channel properties, multiplying the optimized first matrix W 1 , with each second matrix W 2 , in a second codebook, to obtain a plurality of candidate precoding matrices, the second matrix W 2 corresponds to frequency-selective and/or short-term channel properties; selecting an optimized one from the plurality of candidate preceding matrices for precoding the data to be transmitted, according to a frequency selection and/or a short-term channel state information. The amount of DFT beams may be increased to improve the spatial resolution; a diagonal matrix is involved in the first matrix W 1 ; and phase adjustment is involved in the second matrix W 2 , so as to guarantee the adjusted phase is evenly distributed among the whole phase space.
1. A method for determining precoding matrix for the sub-band precoding in a transmitter, wherein the transmitter has M transmitting antennas, and the method comprises:
determining an optimized first matrix W 1 according to wideband and/or long-term channel properties, with the first matrix W 1 corresponding to wideband and/or long-term channel properties;
multiplying the optimized first matrix W 1 with a second matrix W 2 in a second codebook, so as to obtain a plurality of candidate precoding matrices, with the second matrix W 2 corresponding to frequency-selective and/or short-term channel properties;
selecting an optimized one from the plurality of candidate precoding matrices for precoding the data to be transmitted, according to a frequency selection and/or a short-term channel state information;
wherein, the amount of discrete Fourier transform (DFT) beams is increased to improve the spatial resolution; a diagonal matrix is involved in said first matrix W 1 ; and phase adjustment is involved in said second matrix W 2 , so as to guarantee the adjusted phase is evenly distributed among the whole phase space.
2. A method as claimed in claim 1 , wherein the amount of DFT beams is increased to improve the spatial resolution,
the first matrix W 1 is selected from the following first codebook C 1 :
C
1
=
{
W
1
(
0
)
,
W
1
(
1
)
,
…
,
W
1
(
p
-
1
)
}
,
W
1
(
k
)
=
[
X
(
k
)
0
0
X
(
k
)
Λ
(
k
)
]
,
k
=
0
,
1
,
…
,
p
-
1
wherein, p is the amount of the first matrix in the first codebook C 1 , and
X
(
k
)
=
[
f
k
1
f
k
2
…
f
k
q
]
,
Λ
(
k
)
=
diag
[
(
ⅇ
jθ
k
1
·
(
M
/
2
)
,
ⅇ
jθ
k
2
·
(
M
/
2
)
,
…
ⅇ
jθ
k
q
·
(
M
/
2
)
]
)
,
Wherein, q is the amount of each group of beam,
f
k
n
=
[
1
ⅇ
jθ
k
n
·
1
…
ⅇ
jθ
k
n
·
(
M
/
2
-
1
)
]
T
,
θ k n is the phase difference between two neighboring element in the DFT vector with a value range of [0,2π);
and when the amount of data flows is 1, said second codebook comprises second matrices W 2 as follows:
C
2
=
{
W
2
(
0
)
,
W
2
(
1
)
,
…
,
W
2
(
q
-
1
)
}
,
W
2
(
k
)
=
1
2
[
e
k
a
e
k
]
,
k
=
0
,
1
,
…
,
q
-
1
and when the amount of data flows is 2, said second codebook comprises second matrices W 2 as follows:
C
2
=
{
W
2
(
0
)
,
W
2
(
1
)
,
…
,
W
2
(
q
-
1
)
}
,
W
2
(
k
)
=
1
2
[
e
k
e
k
a
e
k
-
a
e
k
]
,
k
=
0
,
1
,
…
,
q
-
1
Wherein, e k is an elementary vector with the (k+1)th element being 1 and other elements being zero, and a is a parameter related with the polarization manner of the antennas.
3. A method, in the user equipments, for feeding precoding matrix for sub-band precoding back to an eNodeB, comprising :
determining the optimized first matrix W 1 and the precoding matrix, by using a method as claimed in claim 1 ;
determining an optimized second matrix W 2 corresponding to said optimized precoding matrix;
providing, for the eNodeB, identifications of said optimized first matrix W 1 and said second matrix W 2 .
4. A method, in eNodeBs, for precoding data, comprising:
receiving identifications of an optimized first matrix W 1 and an optimized second matrix W 2 , fed back by user equipments;
determining, from the first codebook and the second code book in a method according to claim 1 , the optimized first matrix W 1 and the optimized second matrix W 2 , according to the identifications;
multiplying the optimized first matrix W 1 and the optimized second matrix W 2 , and obtaining an optimized precoding matrix;
precoding the data to be transmitted, by using the optimized precoding matrix.
5. A device, in user equipments, for feeding precoding matrix for sub-band precoding back to an eNodeB, comprising:
a processor that determines the optimized first matrix W 1 and the precoding matrix, by using a method as claimed in claim 1 , and an optimized second matrix W 2 corresponding to said optimized precoding matrix;
a transmitter that provides to the eNodeB identifications of said optimized first matrix W 1 and said second matrix W 2 .
6. A device, in eNodeBs, for precoding data, comprising:
a receiver that receives identifications of an optimized first matrix W 1 and an optimized second matrix W 2 , fed back by user equipments;
a processor that determines from the first codebook and the second code book in a method according to claim 1 , the optimized first matrix W 1 and the optimized second matrix W 2 , from the identifications;
a calculator that multiplies the optimized first matrix W 1 and the optimized second matrix W 2 , and obtaining an optimized precoding matrix for the sub-band precoding;
a precoder that precodes the data to be transmitted, by using the optimized precoding matrix.
7. A method as claimed in claim 2 , wherein the value of a is 1 when the polarization manner of the antennas is uniform linear array.
8. A method as claimed in claim 2 , wherein when the polarization manner of the antennas is cross polarized linear array or when the same codebook is used for various polarization manner of the antennas, a is selected from a set {e jβ 1 , e jβ 2 , . . . e jβ m }, wherein m is the amount of values of a, the values of β 1 , β 2 , . . . , β m are selected in a range of [0,2π), generally selected as evenly distributed among [0,2π) namely
β
k
=
2
π
(
k
-
1
)
m
,
k
=
1
,
2
,
…
,
m
.
9. A method as claimed in claim 2 , wherein, when the transmitter has 8 antenna elements, for codebook C 1 ,
B
=
[
b
0
b
1
…
b
31
]
,
[
B
]
1
+
m
,
1
+
n
=
ⅇ
j
2
π
mn
32
,
m
=
0
,
1
,
2
,
3
,
n
=
0
,
1
,
…
,
31
X
(
k
)
∈
{
[
b
2
k
mod
32
b
(
2
k
+
1
)
mod
32
b
(
2
k
+
2
)
mod
32
b
(
2
k
+
3
)
mod
32
]
:
k
=
0
,
1
,
…
,
15
}
W
1
(
k
)
=
[
X
(
k
)
0
0
X
(
k
)
Λ
(
k
)
]
Λ
(
k
)
=
diag
(
[
ⅇ
j
2
π
4
32
(
2
k
mod
32
)
,
ⅇ
j
2
π
4
32
(
(
2
k
+
1
)
mod
32
)
,
ⅇ
j
2
π
4
32
(
(
2
k
+
2
)
mod
32
)
,
ⅇ
j
2
π
4
32
(
(
2
k
+
3
)
mod
32
)
]
)
C
1
=
{
W
1
(
0
)
,
W
1
(
1
)
,
W
1
(
2
)
,
…
,
W
1
(
15
)
}
,
for codebook C 2 ,
when the amount of data flows is 1,
W
2
∈
C
2
=
{
1
2
[
Y
a
Y
]
}
Y
∈
{
e
0
,
e
1
,
e
2
,
e
3
}
,
a
=
{
1
U
L
A
{
l
,
-
l
,
j
,
-
j
}
U
L
A
and
C
L
A
wherein e k is an elementary vector with the (k+1)th element being 1 and other elements being zero,
when the amount of data flows is 2, namely rank 2,
W
2
∈
C
2
=
{
1
2
[
Y
1
Y
2
a
Y
1
-
a
Y
2
]
}
(
Y
1
,
Y
2
)
∈
{
(
e
0
,
e
0
)
,
(
e
1
,
e
1
)
,
(
e
2
,
e
2
)
,
(
e
3
,
e
3
)
}
a
=
{
1
U
L
A
{
l
,
-
l
,
j
,
-
j
}
U
L
A
and
C
L
A
,
when the codebook C 2 is used for ULA, C 2 comprises four second matrices W 2 , and when the codebook C 2 is used for both ULA and CLA simultaneously, C 2 comprises sixteen second matrices W 2 .