Method for transmitting an information sequence
View Patent ↗Methods and apparatus are disclosed for applying successive multi-rank beamforming strategies (e.g., successive precoding strategies) for the design of precoders over a set of parallel channels. Successive beamforming is applied to a narrow band channel model and is also applied for finer quantization of a single beamforming vector (e.g., recursive beamforming). A first embodiment provides the optimal approach with high complexity. An alternative embodiment provides successive beamforming for near optimal precoding selection with medium complexity. A low complexity method for precoder selection is also provided wherein a channel representative matrix for the set of parallel channels is determined and successive beamforming on the calculated channel representative is applied.
1. A base station used in a wireless communications system, the base station comprising:
a precoding unit to precode data with a precoding matrix based on a codebook which includes entries that are expressed as
A
(
v
1
,
v
2
,
v
3
,
…
)
=
[
v
1
,
HH
(
v
1
-
e
1
M
)
[
0
v
2
]
,
HH
(
v
1
-
e
1
M
)
[
0
HH
(
v
2
-
e
1
M
-
1
)
[
0
v
3
]
]
,
…
]
,
where the base station has M transmit antennas, e 1 N =[1,0 . . . , 0] T εC N (N=M, M−1, . . . ), C N being N-dimensional complex space, ν a denotes a column vector, and HH(ν k −e 1 l ) is a rotation matrix that transforms vector ν k to the unit vector e 1 i ; and
a transmission unit to transmit the precoded data to a user equipment.
2. The base station as in claim 1 , wherein ν a is selected from a set V a where V 1 ={{circumflex over (ν)} i 1 εC M } i=1 N 1 , V 2 ={e 1 M-1 }, V 3 ={e 1 M-2 }, . . . .
3. The base station as in claim 1 , wherein the number of transmit antennas is 2.
4. The base station as in claim 1 , wherein the number of transmit antennas is 4.
5. The base station as in claim 1 , wherein the precoding matrix is formed by selecting one or more columns of matrix A.
6. The base station as in claim 5 , wherein the number of selected columns to form the precoding matrix is less than the number of transmit antennas.
7. The base station as in claim 1 , wherein
HH
(
w
)
=
{
I
-
2
ww
H
w
2
if
w
≠
0
I
if
w
=
0
is
the
house
-
holder
transformation
.
8. A wireless communications system comprising:
a base station to precode data with a precoding matrix based on a codebook which includes entries that are expressed as
A
(
v
1
,
v
2
,
v
3
,
…
)
=
[
v
1
,
HH
(
v
1
-
e
1
M
)
[
0
v
2
]
,
HH
(
v
1
-
e
1
M
)
[
0
HH
(
v
2
-
e
1
M
-
1
)
[
0
v
3
]
]
,
…
]
,
where the base station has M transmit antennas, e 1 N =[1,0 . . . , 0] T εC N (N=M, M−1, . . . ), C N being N-dimensional complex space, ν a denotes a column vector, and HH(ν k −e 1 l ) is a rotation matrix that transforms vector ν k to the unit vector e 1 l ; and
a user equipment to receive the precoded data from the base station.
9. A wireless communications system comprising:
a base station to receive feedback information for transmission; and
a user equipment to provide the feedback information in order for the base station to select a precoding matrix from a codebook comprising a matrix that is expressed as
A
(
v
1
,
v
2
,
v
3
,
…
)
=
[
v
1
,
HH
(
v
1
-
e
1
M
)
[
0
v
2
]
,
HH
(
v
1
-
e
1
M
)
[
0
HH
(
v
2
-
e
1
M
-
1
)
[
0
v
3
]
]
,
…
]
,
where the base station has M transmit antennas, e 1 N =[1,0 . . . , 0] T εC N (N=M, M−1, . . . ), C N being N-dimensional complex space, ν a denotes a column vector, and HH(ν k −e 1 l ) is a rotation matrix that transforms vector ν k to the unit vector e 1 l .