US 2012/0257685 A1 · Codebook With Nested Structure

Abstract

A multi-rank beamforming (MRBF) scheme in which the downlink channel is estimated and an optimal precoding matrix to be used by the MRBF transmitter is determined accordingly. The optimal precoding matrix is selected from a codebook of matrices having a recursive structure which allows for efficient computation of the optimal precoding matrix and corresponding Signal to Interference and Noise Ratio (SINR). The codebook also enjoys a small storage footprint. Due to the computational efficiency and modest memory requirements, the optimal precoding determination can be made at user equipment (UE) and communicated to a transmitting base station over a limited uplink channel for implementation over the downlink channel.

Claims30

Dependent claims

A transmitter used in a wireless communications system, the transmitter comprising:

a precoding unit to precode a symbol using with a precoding matrix selected from a codebook comprising a plurality of matrices;
and
a transmission unit to transmit to a receiver the precoded symbol using at least two transmit antennas,
wherein the plurality of matrices have a nested structure and are in accordance with the following expression:
A
(
v
i
1
1
,
v
i
2
2
,
v
i
3
3
,
…

)
=
[
v
i
1
1
,
H


(
v
i
1
1


e
1
M
)

[
0
v
i
2
2
]
,
H


(
v
i
1
1


e
1
M
)

[
0
HH

(
v
i
2
2
-
e
1
M
-
1
)

[
0
v
i
3
3
]
]
,
…
]
,
wherein e1N=[1,0, . . . , 0]T ∈ CN, M is the number of transmit antennas, CN is an N-dimensional complex space, and
HH

(
w
)
=
{
I
-
2

ww
H

w

2
if


w
≠
0
I
if


w
=
0
and {vijj ∈ CM−j+1} is a vector codebook, and
wherein the wireless communications system comprises a multi-rank beamforming (MRBF) system.

128 more elements

Dependencies are inferred from the claim text.

Codebook With Nested Structure

Life of this patent

Codebook With Nested Structure

Life of this patent

Abstract

Claims30