# US 2019/0173538 A1 · Precoding matrix determining method and apparatus

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- Number: US 2019/0173538 A1
- Document ID: US20190173538A1
- Status: Published application
- Kind: A1
- Application number: 16/266,635
- Filed: 2019-02-04
- Published: 2019-06-06
- Earliest claimed: 2016-08-10
- Assignees: Huawei Technologies Co., Ltd.
- Applicants: Huawei Technologies Co., Ltd.
- Inventors: Lu WU; Wei HAN; Hongzhe SHI
- Web page: https://patentgrep.com/patent/US20190173538A1

## CPC

- H04B 7/0469: {taking special antenna structures, e.g. cross polarized antennas into account}
- H04B 7/0408: using two or more beams, i.e. beam diversity
- H04B 7/0479: {for multi-dimensional arrays, e.g. horizontal or vertical pre-distortion matrix index [PMI]}
- H04B 7/0626: {Channel coefficients, e.g. channel state information [CSI]}
- H04B 7/0639: {Using selective indices, e.g. of a codebook, e.g. pre-distortion matrix index [PMI] or for beam selection}
- H04L 5/0048: {Allocation of pilot signals, i.e. of signals known to the receiver (allocation of control signalling H04L5/0053; use of control signalling H04L5/0091)}
- H04B: TRANSMISSION
- H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M)

## Abstract

Embodiments of this application disclose a precoding matrix determining method and apparatus, to determine a stage-1 precoding matrix based on indication information that is of a spatial correlation matrix and that is fed back by a terminal, thereby implementing three-dimensional precoding based on a channel state and increasing a channel capacity. The method includes: sending, by a base station, a plurality of groups of first reference signals, where the plurality of groups of first reference signals are in a one-to-one correspondence with a plurality of dimensions of an antenna array, and each of the plurality of groups of first reference signals is used by a terminal to estimate spatial correlation matrix information in a corresponding dimension; receiving the spatial correlation matrix information fed back by the terminal based on the plurality of groups of first reference signals; and determining a stage-1 precoding matrix based on the spatial correlation matrix information.

## Claims

### Claim 1

A precoding matrix determining method, comprising:
sending, by a base station, a plurality of groups of first reference signals, wherein the plurality of groups of first reference signals are in a one-to-one correspondence with a plurality of dimensions of an antenna array, each of the plurality of groups of first reference signals for use by a terminal to estimate spatial correlation matrix information in a corresponding dimension;
receiving, by the base station, the spatial correlation matrix information fed back by the terminal based on the plurality of groups of first reference signals; and
determining, by the base station, a stage-1 precoding matrix based on the spatial correlation matrix information.

### Claim 2 (depends on 1)

The method according to claim 1, wherein:
the spatial correlation matrix information comprises an index of a codeword of a spatial correlation matrix;
before receiving the spatial correlation matrix information fed back by the terminal based on the plurality of groups of first reference signals, the method further comprises:
sending, by the base station, codebook parameter information for indicating a codebook parameter group corresponding to a spatial correlation matrix of each dimension, and wherein both the base station and the terminal pre-store codebooks of the spatial correlation matrices of the plurality of dimensions; and
receiving the spatial correlation matrix information fed back by the terminal based on the plurality of groups of first reference signals comprises:
receiving the index of the codeword of the spatial correlation matrix that is fed back by the terminal based on the plurality of groups of first reference signals and the codebook parameter information.

### Claim 3 (depends on 2)

The method according to claim 2, wherein:
the plurality of dimensions comprise a horizontal single-polarization dimension, a vertical single-polarization dimension, and a cross-polarization dimension; and
the codebooks of the spatial correlation matrices of the plurality of dimensions have a same structure form, and the same structure form is:
U

(
ρ
,
n
,
{
β
1
,
β
2
,
⋯

,
β
n
-
1
}
)
=
[
1
ρ
⋯
ρ
n
-
1
ρ
*
β
1
ρ
n
-
2
⋮
⋮
⋱
(
ρ
*
)
n
-
1
(
ρ
*
)
n
-
2
⋯
β
n
-
1
]
,
wherein
ρ represents a coefficient of a correlation between adjacent antennas in the antenna array, and ρ=αejθ, wherein 0≤α≤1, 0≤θ<2π, α represents an amplitude difference between adjacent antenna ports in the antenna array, and θ represents a phase difference between adjacent antenna ports in the antenna array, βi represents a ratio of channel power of an (i+1)th antenna to channel power of a first antenna in the antenna array, wherein βi>0, i∈[1, n−1], and i is an integer, and n is a quantity of antenna ports in the antenna array.

### Claim 4 (depends on 1)

The method according to claim 1, wherein:
the spatial correlation matrix information comprises an index of a codeword of a spatial correlation matrix;
before receiving the spatial correlation matrix information fed back by the terminal based on the plurality of groups of first reference signals, the method further comprises:
sending, by the base station, codebook type information of a plurality of codebooks corresponding to the plurality of dimensions for indicating a codebook used to estimate a spatial correlation matrix of a corresponding dimension, wherein both the base station and the terminal pre-store the plurality of codebooks corresponding to the plurality of dimensions and a correspondence between codebook types of the plurality of codebooks and a plurality of codebook parameter groups; and
receiving the spatial correlation matrix information fed back by the terminal based on the plurality of groups of first reference signals comprises:
receiving the index of the codeword of the spatial correlation matrix that is fed back by the terminal based on the plurality of groups of first reference signals and the codebook type information.

### Claim 5 (depends on 4)

The method according to claim 4, wherein:
the plurality of codebooks corresponding to the plurality of dimensions comprise a first codebook and a second codebook;
the first codebook is a codebook of a spatial correlation matrix of a first dimension;
the second codebook is a codebook of a spatial correlation matrix of a second dimension;
the first dimension is a vertical single-polarization dimension and the second dimension is a horizontal cross-polarization dimension, or the first dimension is a horizontal single-polarization dimension and the second dimension is a vertical cross-polarization dimension;
a codeword {circumflex over (R)}1 in the first codebook meets {circumflex over (R)}1=U(ρ1,n1), wherein
U

(
ρ
1
,
n
1
)
=
[
1
ρ
1
⋯
ρ
1
n
1
-
1
ρ
1
*
1
ρ
1
n
1
-
2
⋮
⋮
⋱
⋮
(
ρ
1
*
)
n
1
-
1
(
ρ
1
*
)
n
1
-
2
⋯
1
]
,
wherein
ρ1 represents a coefficient of a correlation between adjacent antenna ports in a single-polarization antenna array, and ρ1=α1ejθ, wherein 0≤α1≤1, 0≤θ1<2π, α1 represents an amplitude difference between adjacent antenna ports in the single-polarization antenna array, and θ1 represents a phase difference between adjacent antenna ports in the single-polarization antenna array, n1 is a quantity of antenna ports in the single-polarization antenna array; and the single-polarization antenna array consists of antenna ports in a same polarization direction in a same row or a same column of the antenna array; and
a codeword {circumflex over (R)}2 in the second codebook meets:
R
^
2
=
[
U

(
ρ
2
,
n
2
)
β
1

e
j


φ
1

U

(
ρ
2
,
n
2
)
β
1

e
-
j


φ
1

U

(
ρ
2
,
n
2
)
β
2

U

(
ρ
2
,
n
2
)
]
,
wherein
U

(
ρ
2
,
n
2
)
=
[
1
ρ
2
⋯
ρ
2
n
2
-
1
ρ
2
*
1
ρ
2
n
2
-
2
⋮
⋮
⋱
⋮
(
ρ
2
*
)
n
2
-
1
(
ρ
2
*
)
n
2
-
2
⋯
1
]
,
wherein
ρ2 represents a coefficient of a correlation between adjacent co-polarization antenna ports in a cross-polarization antenna array, and ρ2=α2ejθ2, wherein 0≤α2≤1, 0≤θ2<2π, α2 represents an amplitude difference between adjacent co-polarization antenna ports in the cross-polarization antenna array, and 02 represents a phase difference between adjacent co-polarization antenna ports in the cross-polarization antenna array, β1, ϕ1, and β2 represent a correlation between antenna ports and a correlation between two polarization directions, wherein β1≤0 , 0≤ϕ12π, and β2>0, n2 is a quantity of antenna ports in a same polarization direction in the cross-polarization antenna array, and the cross-polarization antenna array comprises of antenna ports in two polarization directions in a same row or a same column of the antenna array.

### Claim 6 (depends on 1)

The method according to claim 1, wherein after determining a stage-1 precoding matrix based on the spatial correlation matrix information, the method further comprises:
sending, by the base station, at least one second reference signal encoded by the stage-1 precoding matrix, wherein the at least one second reference signal is in a one-to-one correspondence with at least one spatial direction;
receiving, by the base station, a stage-2 precoding matrix indicator (PMI) fed back by the terminal based on the at least one second reference signal; and
determining, by the base station, a stage-2 precoding matrix based on the stage-2 PMI, wherein a codebook used to feed back the stage-2 PMI comprises:
W
=
W
1

W
2
=
[
G
1
G
2
]

[
[
β
1
β
2
⋮
β
M
]
αω
j


θ

[
η
1
η
2
⋮
η
M
]
]
,
wherein
W1 is determined based on the stage-1 precoding matrix, G1 is used to represent a group of bases in a first polarization direction, G2 is used to represent a group of bases in a second polarization direction, G1=[g1 g2 . . . gM], G2=[g′1 g′2 . . . g′M], a quantity of non-zero elements in W2 is greater than 1, β and η are quantized coefficients, a is an amplitude difference between the polarization directions, and θ is a phase difference between the polarization directions.

### Claim 7 (depends on 6)

The method according to claim 6, wherein a codeword Ĉ in the stage-1 precoding codebook meets the following:
Ĉ=[v1 v2 . . . vS], wherein
v1 to vS are column vectors of N×1 dimensions and are different from each other; or
C
^
=
[
v
1
v
2
⋱
v
S
]
,
wherein
v1 to vS are column vectors of N/S×1 dimensions, N is a quantity of antenna ports in the antenna array, S is a quantity of antenna ports that send a reference signal obtained after stage-1 precoding, and S≤N.

### Claim 8 (depends on 7)

The method according to claim 7, wherein before receiving a stage-2 PMI fed back by the terminal based on the at least one second reference signal, the method further comprises:
sending, by the base station, indication information of the stage-1 precoding matrix for indicating a codebook type of the stage-1 precoding matrix to enable the terminal to determine the stage-2 PMI.

### Claim 9

A precoding matrix determining method, comprising:
receiving, by a terminal, a plurality of groups of first reference signals sent by a base station, wherein the plurality of groups of first reference signals are in a one-to-one correspondence with a plurality of dimensions of an antenna array, and each of the plurality of groups of first reference signals is used by the terminal to estimate spatial correlation matrix information in a corresponding dimension;
estimating, by the terminal, the spatial correlation matrix information based on the plurality of groups of first reference signals; and
sending, by the terminal, the spatial correlation matrix information to the base station for determining a stage-1 precoding matrix.

### Claim 10 (depends on 9)

The method according to claim 9, wherein:
the spatial correlation matrix information comprises an index of a codeword of a spatial correlation matrix;
before estimating the spatial correlation matrix information based on the plurality of groups of first reference signals, the method further comprises:
receiving, by the terminal, codebook parameter information sent by the base station, wherein the codebook parameter information is used to indicate a codebook parameter group corresponding to a spatial correlation matrix of each dimension, and wherein both the base station and the terminal pre-store codebooks of the spatial correlation matrices of the plurality of dimensions; and
estimating the spatial correlation matrix information based on the plurality of groups of first reference signals comprises:
estimating, by the terminal, the spatial correlation matrix information based on the plurality of groups of first reference signals and the codebook parameter information.

### Claim 11 (depends on 10)

The method according to claim 10, wherein:
the plurality of dimensions comprise a horizontal single-polarization dimension, a vertical single-polarization dimension, and a cross-polarization dimension; and
the codebooks of the spatial correlation matrices of the plurality of dimensions have a same structure form, and the same structure form is:
U

(
ρ
,
n
,
{
β
1
,
β
2
,
⋯

,
β
n
-
1
}
)
=
[
1
ρ
⋯
ρ
n
-
1
ρ
*
β
1
ρ
n
-
2
⋮
⋮
⋱
(
ρ
*
)
n
-
1
(
ρ
*
)
n
-
2
⋯
β
n
-
1
]
,
wherein
ρ represents a coefficient of a correlation between adjacent antennas in the antenna array, and ρ=αejθ, wherein 0≤α≤1, 0≤θ<2π, α represents an amplitude difference between adjacent antenna ports in the antenna array, and θ represents a phase difference between adjacent antenna ports in the antenna array, βi represents a ratio of channel power of an (i+1)th antenna to channel power of a first antenna in the antenna array, wherein βi>0, i∈[1, n−1], and i is an integer, and n is a quantity of antenna ports in the antenna array.

### Claim 12 (depends on 9)

The method according to claim 9, wherein:
the spatial correlation matrix information comprises an index of a codeword of a spatial correlation matrix;
before estimating the spatial correlation matrix information based on the plurality of groups of first reference signals, the method further comprises:
receiving, by the terminal, codebook type information sent by the base station and that is of a plurality of codebooks corresponding to the plurality of dimensions, wherein the codebook type information of each codebook is used to indicate a codebook used to estimate a spatial correlation matrix of a corresponding dimension, and wherein both the base station and the terminal pre-store the plurality of codebooks corresponding to the plurality of dimensions and a correspondence between codebook types of the plurality of codebooks and a plurality of codebook parameter groups; and
estimating the spatial correlation matrix information based on the plurality of groups of first reference signals comprises:
estimating, by the terminal, the spatial correlation matrix information based on the plurality of groups of first reference signals and the codebook type information.

### Claim 13 (depends on 12)

The method according to claim 12, wherein:
the plurality of codebooks corresponding to the plurality of dimensions comprise a first codebook and a second codebook;
the first codebook is a codebook of a spatial correlation matrix of a first dimension;
the second codebook is a codebook of a spatial correlation matrix of a second dimension;
the first dimension is a vertical single-polarization dimension and the second dimension is a horizontal cross-polarization dimension, or the first dimension is a horizontal single-polarization dimension and the second dimension is a vertical cross-polarization dimension;
a codeword {circumflex over (R)}1 in the first codebook meets {circumflex over (R)}1=U(ρ1,n1), wherein
U

(
ρ
1
,
n
1
)
=
[
1
ρ
1
⋯
ρ
1
n
1
-
1
ρ
1
*
1
ρ
1
n
1
-
2
⋮
⋮
⋱
⋮
(
ρ
1
*
)
n
1
-
1
(
ρ
1
*
)
n
1
-
2
⋯
1
]
,
wherein
ρ1 represents a coefficient of a correlation between adjacent antenna ports in a single-polarization antenna array, and ρ1=α1ejθ1, wherein 0≤α1≤1, 0≤θ1<2π,α1 represents an amplitude difference between adjacent antenna ports in the single-polarization antenna array, and θ1 represents a phase difference between adjacent antenna ports in the single-polarization antenna array, n1 is a quantity of antenna ports in the single-polarization antenna array, and the single-polarization antenna array consists of antenna ports in a same polarization direction in a same row or a same column of the antenna array; and
a codeword {circumflex over (R)}2 in the second codebook meets:
R
^
2
=
[
U

(
ρ
2
,
n
2
)
β
1

e
j


φ
1

U

(
ρ
2
,
n
2
)
β
1

e
-
j


φ
1

U

(
ρ
2
,
n
2
)
β
2

U

(
ρ
2
,
n
2
)
]
,
wherein
U

(
ρ
2
,
n
2
)
=
[
1
ρ
2
⋯
ρ
2
n
2
-
1
ρ
2
*
1
ρ
2
n
2
-
2
⋮
⋮
⋱
⋮
(
ρ
2
*
)
n
2
-
1
(
ρ
2
*
)
n
2
-
2
⋯
1
]
,
wherein
ρ2 represents a coefficient of a correlation between adjacent co-polarization antenna ports in a cross-polarization antenna array, and ρ2=α2ejθ2, wherein 0α2≤1, 0≤θ2<2π, α2 represents an amplitude difference between adjacent co-polarization antenna ports in the cross-polarization antenna array, and θ2 represents a phase difference between adjacent co-polarization antenna ports in the cross-polarization antenna array, β1, ϕ1, and β2 represent a correlation between antenna ports and a correlation between two polarization directions, wherein β10, 0≤ϕ1<2ϕ, and β2>0, n2 is a quantity of antenna ports in a same polarization direction in the cross-polarization antenna array, and the cross-polarization antenna array comprises of antenna ports in two polarization directions in a same row or a same column of the antenna array.

### Claim 14 (depends on 9)

The method according to claim 9, wherein after sending the spatial correlation matrix information to the base station, the method further comprises:
receiving, by the terminal, at least one second reference signal encoded by the stage-1 precoding matrix and sent by the base station, wherein the at least one second reference signal is in a one-to-one correspondence with at least one spatial direction;
determining, by the terminal, a stage-2 precoding matrix indicator (PMI) based on the at least one second reference signal; and
sending, by the terminal, the stage-2 PMI to the base station for determining a stage-2 precoding matrix, wherein a codebook used to feed back the stage-2 PMI comprises:
W
=
W
1

W
2
=
[
G
1
G
2
]

[
[
β
1
β
2
⋮
β
M
]
αω
j


θ

[
η
1
η
2
⋮
η
M
]
]
,
wherein
W1 is determined based on the stage-1 precoding matrix, G1 is used to represent a group of bases in a first polarization direction, G2 is used to represent a group of bases in a second polarization direction, G1=[g1 g2 . . . gM], G2=[g′1 g′2 . . . g′M], a quantity of non-zero elements in W2 is greater than 1, β and η are quantized coefficients, a is an amplitude difference between the polarization directions, and θ is a phase difference between the polarization directions.

### Claim 15 (depends on 14)

The method according to claim 14, wherein a codeword Ĉ in the stage-1 precoding codebook meets the following:
Ĉ=[v1 v2 . . . vS], wherein
v1 to vS are column vectors of N×1 dimensions and are different from each other; or
C
^
=
[
v
1
v
2
⋱
v
S
]
,
wherein
v1 to vS are column vectors of N/S×1 dimensions, N is a quantity of antenna ports in the antenna array, S is a quantity of antenna ports that send a reference signal obtained after stage-1 precoding, and S≤N.

### Claim 16 (depends on 15)

The method according to claim 15, wherein before determining a stage-2 PMI based on the at least one second reference signal, the method further comprises:
receiving, by the terminal, indication information of the stage-1 precoding matrix sent by the base station for indicating a codebook type of the stage-1 precoding matrix; and
determining, by the terminal, the stage-2 PMI based on the codebook type of the stage-1 precoding matrix.

### Claim 17

A precoding matrix determining apparatus, comprising:
a receiver, configured to receive a plurality of groups of first reference signals sent by a base station, wherein the plurality of groups of first reference signals are in a one-to-one correspondence with a plurality of dimensions of an antenna array, and each of the plurality of groups of first reference signals is used by the terminal to estimate spatial correlation matrix information in a corresponding dimension;
a processor, configured to estimate the spatial correlation matrix information based on the plurality of groups of first reference signals; and
a transmitter, configured to send the spatial correlation matrix information to the base station for for determining a stage-1 precoding matrix.

### Claim 18 (depends on 17)

The apparatus according to claim 17, wherein:
the spatial correlation matrix information comprises an index of a codeword of a spatial correlation matrix;
the receiver is further configured to receive codebook parameter information sent by the base station, wherein the codebook parameter information is used to indicate a codebook parameter group corresponding to a spatial correlation matrix of each dimension, and wherein both the base station and the terminal pre-store codebooks of the spatial correlation matrices of the plurality of dimensions; and
the processor is configured to estimate the spatial correlation matrix information based on the plurality of groups of first reference signals and the codebook parameter information.

### Claim 19 (depends on 18)

The apparatus according to claim 18, wherein:
the plurality of dimensions comprise a horizontal single-polarization dimension, a vertical single-polarization dimension, and a cross-polarization dimension; and
the codebooks of the spatial correlation matrices of the plurality of dimensions have a same structure form, and the same structure form is:
U

(
ρ
,
n
,
{
β
1
,
β
2
,
⋯

,
β
n
-
1
}
)
=
[
1
ρ
⋯
ρ
n
-
1
ρ
*
β
1
ρ
n
-
2
⋮
⋮
⋱
(
ρ
*
)
n
-
1
(
ρ
*
)
n
-
2
⋯
β
n
-
1
]
,
wherein
ρ represents a coefficient of a correlation between adjacent antennas in the antenna array, and ρ=αejθ, wherein 0≤α≤1, 0≤θ<2π, α represents an amplitude difference between adjacent antenna ports in the antenna array, and θ represents a phase difference between adjacent antenna ports in the antenna array, βi represents a ratio of channel power of an (i+1)th antenna to channel power of a first antenna in the antenna array, wherein βi>0, i∈[1, n−1], and i is an integer, and n is a quantity of antenna ports in the antenna array.

### Claim 20 (depends on 17)

The apparatus according to claim 17, wherein:
the spatial correlation matrix information comprises an index of a codeword of a spatial correlation matrix;
the receiver is further configured to receive codebook type information sent by the base station and that is of a plurality of codebooks corresponding to the plurality of dimensions, wherein the codebook type information of each codebook is used to indicate a codebook used to estimate a spatial correlation matrix of a corresponding dimension, and wherein both the base station and the terminal pre-store the plurality of codebooks corresponding to the plurality of dimensions and a correspondence between codebook types of the plurality of codebooks and a plurality of codebook parameter groups; and
the processor is configured to estimate the spatial correlation matrix information based on the plurality of groups of first reference signals and the codebook type information.