Transmission with M antennas using precoding
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 method of transmission implemented in a wireless communication system using precoding, comprising:
precoding data using a precoding matrix based on a codebook which has entries in the following form
A
(
v
1
,
v
2
,
v
3
,
…
)
=
[
v
1
,
H
H
(
v
1
-
e
1
M
)
[
0
v
2
]
,
H
H
(
v
1
-
e
1
M
)
[
0
H
H
(
v
2
-
e
1
M
-
1
)
[
0
v
3
]
]
]
,
…
where a transmitter has M antennas, e 1 N =[1,0, . . . ,0] T εC N (N=M, M−1, . . .), C N being N-dimensional complex space, V a denotes a column vector, and HH(v k −e 1 l ) is a rotation matrix that transforms vector v k to the unit vector e 1 l .
2. The method of claim 1 , wherein
H
H
(
w
)
=
I
-
2
w
w
T
w
2
is the house-holder transformation.
3. The method of claim 1 , wherein a transmission rank is determined by the transmitter.
4. The method of claim 1 , wherein the a transmission rank is determined by a user equipment.
5. The method of claim 1 , wherein a scaled version of the precoding matrix is used.
6. The method of claim 1 , wherein the number of transmit antennas is 4.
7. The method of claim 1 , wherein the number of transmit antennas is 2.