# US 9,438,328 B2 · Method for feeding backchannel state information, user equipment, and base station

> Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt

- Number: US 9,438,328 B2
- Document ID: US9438328B2
- Status: Granted
- Kind: B2
- Application number: 14/753,490
- Filed: 2015-06-29
- Published: 2015-10-22
- Granted: 2016-09-06
- Earliest claimed: 2012-12-27
- Assignees: Huawei Technologies Co., Ltd.
- Applicants: Huawei Technologies Co., Ltd.
- Inventors: Jianguo Wang; Yongxing Zhou; Leiming Zhang
- Web page: https://patentgrep.com/patent/US9438328B2

## CPC

- H04B 7/0626: {Channel coefficients, e.g. channel state information [CSI]}
- H04B 7/0456: Selection of precoding matrices or codebooks, e.g. using matrices antenna weighting
- H04B 7/0634: {Antenna weights or vector/matrix coefficients}
- H04B 7/0639: {Using selective indices, e.g. of a codebook, e.g. pre-distortion matrix index [PMI] or for beam selection}
- G06F 17/16: Matrix or vector computation {, e.g. matrix-matrix or matrix-vector multiplication, matrix factorization (matrix transposition G06F7/78)}
- H04B 7/0413: MIMO systems
- H04N 19/124: Quantisation
- H04B: TRANSMISSION
- G06F: ELECTRIC DIGITAL DATA PROCESSING (computer systems based on specific computational models G06N)
- H04N: PICTORIAL COMMUNICATION, e.g. TELEVISION

## Abstract

Embodiments of the present invention provide a method for feeding back channel state information, a user equipment, and a base station, to improve feedback precision of channel state information. The method includes: receiving a reference signal sent by a base station; selecting a precoding matrix W from a codebook according to the reference signal, where a column vector of the precoding matrix W may be expressed as α[v ejφv]T, v=[1 ejθ]; and sending a precoding matrix indicator PMI to the base station, where the PMI is corresponding to the selected precoding matrix W. The present invention may further improve quantization precision and achieve balance between overheads and the quantization precision. The base station performs precoding on a sent signal according to a fed back precoding matrix indicator, which can improve precoding precision, thereby improving a data transmission rate and system throughput.

## Claims

### Claim 1

A method for feeding back channel state information performed by a user equipment (UE), the method comprising:
receiving a reference signal sent by a base station;
selecting a precoding matrix W from a matrix set based on the reference signal, wherein α column vector of the precoding matrix W is expressed as α[v ejφv]T, v=[1 ejθ], wherein α is a constant, θ and φ are phases, and [ ]T indicates transposing of a matrix or vector; and
sending a precoding matrix indicator (PMI) to the base station, wherein the PMI corresponds to the selected precoding matrix W;
wherein the matrix set is one of:
{
1
2
⁡
[
1
ⅇ
jθ
1
ⅇ
jθ
]
,
1
2
⁡
[
1
ⅇ
jθ
j
jⅇ
jθ
]
,
1
2
⁡
[
1
ⅇ
jθ
-
1
-
ⅇ
jθ
]
,
1
2
⁡
[
1
ⅇ
jθ
-
j
-
jⅇ
jθ
]
}
;
{
1
8
⁡
[
1
1
ⅇ
jθ
ⅇ
jθ
1
-
1
ⅇ
jθ
-
ⅇ
jθ
]
,
1
8
⁡
[
1
1
ⅇ
jθ
ⅇ
jθ
j
-
j
jⅇ
jθ
-
jⅇ
jθ
]
}
⁢
⁢
or
{
1
8
⁡
[
1
1
ⅇ
jθ
ⅇ
j
⁡
(
θ
+
φ
)
1
-
1
ⅇ
jθ
-
ⅇ
j
⁡
(
θ
+
φ
)
]
,
1
8
⁡
[
1
1
ⅇ
jθ
ⅇ
j
⁡
(
θ
+
φ
)
j
-
j
jⅇ
jθ
-
jⅇ
j
⁡
(
θ
+
φ
)
⁢
]
}
wherein
⁢
⁢
θ
=
π
16
⁢
(
2
⁢
i
1
+
⌊
i
2
/
4
⌋
)
,
i
1
=
0
,
…
⁢
,
15
,
i
2
=
0
,
…
⁢
,
15
,
⁢
φ
=
π
16
,
π
8
,
…
⁢
,
and └i2/4┘ indicates the greatest integer not greater than i2/4.

### Claim 2 (depends on 1)

The method according to claim 1, wherein sending, by the UE, the precoding matrix indicator (PMI) to the base station comprises:
sending, by the UE, a first precoding matrix indicator (PMI1) and a second precoding matrix indicator (PMI2) to the base station, wherein the PMI1 and the PMI2 are respectively used to indicate indexes i1 and i2 corresponding to the selected precoding matrix W.

### Claim 3

A method for receiving channel state information performed by a base station, the method comprising:
sending a reference signal to a user equipment (UE);
receiving a precoding matrix indicator (PMI) sent by the UE, wherein the PMI is corresponding to a precoding matrix W that is selected by the UE from a matrix set based on the reference signal, and a column vector of the precoding matrix W is expressed as α[v ejφv]T, v=[1 ejθ], wherein α is a constant, and φ are phases, and [ ]T indicates transposing of a matrix or vector;
wherein the matrix set is:
{
1
2
⁡
[
1
ⅇ
jθ
1
ⅇ
jθ
]
,
1
2
⁡
[
1
ⅇ
jθ
j
jⅇ
jθ
]
,
1
2
⁡
[
1
ⅇ
jθ
-
1
-
ⅇ
jθ
]
,
1
2
⁡
[
1
ⅇ
jθ
-
j
-
jⅇ
jθ
]
}
;
{
1
8
⁡
[
1
1
ⅇ
jθ
ⅇ
jθ
1
-
1
ⅇ
jθ
-
ⅇ
jθ
]
,
1
8
⁡
[
1
1
ⅇ
jθ
ⅇ
jθ
j
-
j
jⅇ
jθ
-
jⅇ
jθ
]
}
or
{
1
8
⁡
[
1
1
ⅇ
jθ
ⅇ
j
⁡
(
θ
+
φ
)
1
-
1
ⅇ
jθ
-
ⅇ
j
⁡
(
θ
+
φ
)
]
,
1
8
⁡
[
1
1
ⅇ
jθ
ⅇ
j
⁡
(
θ
+
φ
)
j
-
j
jⅇ
jθ
-
jⅇ
j
⁡
(
θ
+
φ
)
⁢
]
}
wherein
⁢
⁢
θ
=
π
16
⁢
(
2
⁢
i
1
+
⌊
i
2
/
4
⌋
)
,
i
1
=
0
,
…
⁢
,
15
,
i
2
=
0
,
…
⁢
,
15
,
⁢
φ
=
π
16
,
π
8
,
…
⁢
,
and └i2/4┘ indicates the greatest integer not greater than i2/4.

### Claim 4 (depends on 3)

The method according to claim 3, wherein receiving the precoding matrix indicator (PMI) sent by the UE comprises:
receiving a first precoding matrix indicator (PMI1) and a second precoding matrix indicator (PM12) that are sent by the UE, wherein the PMI1 and the PMI2 are respectively used to indicate indexes i1 and i2 corresponding to the selected precoding matrix.

### Claim 5

A user equipment, comprising:
a receiver, configured to receive a reference signal sent by a base station;
a processor, configured to select a precoding matrix W from a matrix set based on the reference signal received by the receiver, wherein α column vector of the precoding matrix W is expressed as α[v ejφv]T, v=[1 ejθ], wherein α is a constant, θ and φ are phases, and [ ]T indicates transposing of a matrix or vector; and
a transmitter, configured to send a precoding matrix indicator (PMI) to the base station, wherein the PMI is corresponding to the precoding matrix W selected by the processor;
wherein the matrix set is:
{
1
2
⁡
[
1
ⅇ
jθ
1
ⅇ
jθ
]
,
1
2
⁡
[
1
ⅇ
jθ
j
jⅇ
jθ
]
,
1
2
⁡
[
1
ⅇ
jθ
-
1
-
ⅇ
jθ
]
,
1
2
⁡
[
1
ⅇ
jθ
-
j
-
jⅇ
jθ
]
}
;
{
1
8
⁡
[
1
1
ⅇ
jθ
ⅇ
jθ
1
-
1
ⅇ
jθ
-
ⅇ
jθ
]
,
1
8
⁡
[
1
1
ⅇ
jθ
ⅇ
jθ
j
-
j
jⅇ
jθ
-
jⅇ
jθ
]
}
⁢
⁢
or
{
1
8
⁡
[
1
1
ⅇ
jθ
ⅇ
j
⁡
(
θ
+
φ
)
1
-
1
ⅇ
jθ
-
ⅇ
j
⁡
(
θ
+
φ
)
]
,
1
8
⁡
[
1
1
ⅇ
jθ
ⅇ
j
⁡
(
θ
+
φ
)
j
-
j
jⅇ
jθ
-
jⅇ
j
⁡
(
θ
+
φ
)
⁢
]
}
wherein
⁢
⁢
θ
=
π
16
⁢
(
2
⁢
i
1
+
⌊
i
2
/
4
⌋
)
,
i
1
=
0
,
…
⁢
,
15
,
i
2
=
0
,
…
⁢
,
15
,
⁢
φ
=
π
16
,
π
8
,
…
⁢
,
⁢
and └i2/4┘ indicates the greatest integer not greater than i2/4.

### Claim 6 (depends on 5)

The user equipment according to claim 5, wherein the transmitter is configured to:
send a first precoding matrix indicator (PMI1) and a second precoding matrix indicator (PMI2) to the base station, wherein the PMI1 and the PMI2 are respectively used to indicate indexes i1 and i2 corresponding to the selected precoding matrix.

### Claim 7

A base station, comprising:
a transmitter, configured to send a reference signal to a user equipment (UE);
a receiver, configured to receive a precoding matrix indicator (PMI) sent by the UE, wherein the PMI is corresponding to a precoding matrix W that is selected by the UE from a matrix set based on the reference signal, and a column vector of the precoding matrix W is expressed as α[v ejφv]T, v=[1 ejθ], wherein α is a constant, θ and φ are phases, and [ ]T indicates transposing of a matrix or vector;
wherein the matrix set is:
{
1
2
⁡
[
1
ⅇ
jθ
1
ⅇ
jθ
]
,
1
2
⁡
[
1
ⅇ
jθ
j
jⅇ
jθ
]
,
1
2
⁡
[
1
ⅇ
jθ
-
1
-
ⅇ
jθ
]
,
1
2
⁡
[
1
ⅇ
jθ
-
j
-
jⅇ
jθ
]
}
;
{
1
8
⁡
[
1
1
ⅇ
jθ
ⅇ
jθ
1
-
1
ⅇ
jθ
-
ⅇ
jθ
]
,
1
8
⁡
[
1
1
ⅇ
jθ
ⅇ
jθ
j
-
j
jⅇ
jθ
-
jⅇ
jθ
]
}
⁢
⁢
or
{
1
8
⁡
[
1
1
ⅇ
jθ
ⅇ
j
⁡
(
θ
+
φ
)
1
-
1
ⅇ
jθ
-
ⅇ
j
⁡
(
θ
+
φ
)
]
,
1
8
⁡
[
1
1
ⅇ
jθ
ⅇ
j
⁡
(
θ
+
φ
)
j
-
j
jⅇ
jθ
-
jⅇ
j
⁡
(
θ
+
φ
)
⁢
]
}
wherein
⁢
⁢
θ
=
π
16
⁢
(
2
⁢
i
1
+
⌊
i
2
/
4
⌋
)
,
i
1
=
0
,
…
⁢
,
15
,
i
2
=
0
,
…
⁢
,
15
,
⁢
φ
=
π
16
,
π
8
,
…
⁢
,
and └i2/4┘ indicates the greatest integer not greater than i2/4.

### Claim 8 (depends on 7)

The base station according to claim 7, wherein the receiver is configured to:
receive a first precoding matrix indicator (PMI1) and a second precoding matrix indicator (PM12) that are sent by the user equipment to the base station, wherein the PMI1 and the PMI2 are respectively used to indicate indexes i1 and i2 corresponding to the selected precoding matrix.