CN104144006A - Channel state information transmission method, user equipment and base station in MIMO system - Google Patents

Abstract

The present application discloses a channel state information transmission method, user equipment, and base station in a MIMO system, wherein the method includes: according to the obtained CSI of the channel, searching for the first-layer codebook of the planar antenna array The corresponding first precoding matrix and the first PMI, wherein the first PMI is the PMI of the first precoding matrix; according to the CSI and the first PMI, the corresponding first PMI is found in the second layer codebook of the planar antenna array Two precoding matrices and the second PMI, wherein the second PMI is the PMI of the second precoding matrix; the first PMI and the second PMI are reported to the base station; wherein the first layer codebook of the planar antenna array is a pair of planar The antenna array is obtained by performing a direct product operation on the first-layer codebook of the linear array in the x-axis direction and the y-axis direction, and the x-axis and y-axis are respectively the straight lines where the two mutually perpendicular sides of the planar antenna array are located. The application improves system precoding performance, and provides effective CSI feedback and precoding operations for large-scale antenna systems.

Description

Transmission method of channel state information in MIMO system, user equipment and base station

Technical Field

The present invention relates to the field of wireless communication technologies, and in particular, to a method, a User Equipment (UE) and a base station for transmitting channel state information in a MIMO system.

Background

In a Multiple-Input Multiple-Output (MIMO) system, in order to improve system transmission performance by performing precoding at a transmitting end, the transmitting end needs to acquire Channel State Information (CSI), and the CSI is usually obtained by a receiving end by using a reference sequence to perform channel estimation, which requires the receiving end to feed back the CSI to the transmitting end. However, the limitations of the CSI feedback channel determine that the design of the precoding codebook is necessary.

Many precoding codebooks have been proposed, for example: a Discrete Fourier Transform (DFT) -based dual codebook applied to LTE (Long Term Evolution) Release 10. The double codebook is designed for the correlation characteristics of the channel and consists of two layers: a first layer codebook and a second layer codebook. The first layer codebook is used for describing the long-term statistical characteristics of the channel, and the second layer codebook is used for reflecting the short-term variation of the channel. Assuming that W1 is the precoding matrix of the first layer codebook and W2 is the precoding matrix of the second layer codebook, the final precoding matrix W is W1 × W2.

The long-term statistical properties of the channel mainly depend on the channel correlation of the channel, which is influenced by the antenna array layout. In a conventional multi-antenna system (with a small number of antenna elements), the antenna Array layout usually adopts a Linear antenna Array layout, such as a Uniform Linear Array (ULA); however, in a large-scale antenna system (the number of antenna elements is large), due to space constraints, the antenna Array layout tends to adopt a planar antenna Array layout, such as a Uniform Rectangular Array (URA). However, most of the current dual codebooks are designed for linear antenna array layout, so for planar antenna array layout, these dual codebooks cannot well describe the long-term statistical characteristics of the channel, and thus have a large influence on the system precoding performance.

Disclosure of Invention

The application provides a transmission method of channel state information in an MIMO system, user equipment and a base station, which are used for solving the problems that most double codebooks in the prior art are not suitable for planar antenna array layout, and the long-term statistical characteristics of a channel adopting the planar antenna array layout cannot be well described, so that the precoding performance of the system is greatly influenced.

The technical scheme of the application is as follows:

in one aspect, a method for transmitting CSI in a MIMO system is provided, where an antenna array layout of the MIMO system employs a planar antenna array, and the method is applied to a UE, and the method includes:

according to the obtained CSI of the channel, finding a corresponding first precoding matrix and a first PMI in a first layer codebook of the planar antenna array, wherein the first PMI is a PMI of the first precoding matrix;

according to the CSI and the first PMI, finding a corresponding second precoding matrix and a second PMI in a second layer codebook of the planar antenna array, wherein the second PMI is a PMI of the second precoding matrix;

reporting the first PMI and the second PMI to a base station;

the first layer codebook of the planar antenna array is obtained by performing direct product operation on the first layer codebook of the linear array of the planar antenna array in the x-axis direction and the y-axis direction, and the x-axis and the y-axis are respectively straight lines where two mutually perpendicular edges of the planar antenna array are located.

In another aspect, a method for transmitting CSI in a MIMO system is further provided, where an antenna array layout of the MIMO system employs a planar antenna array, and the method is applied to a base station, and the method includes:

receiving a first PMI and a second PMI reported by UE;

according to the received first PMI, finding a corresponding first precoding matrix in a first layer codebook of the planar antenna array, and according to the received second PMI, finding a corresponding second precoding matrix in a second layer codebook of the planar antenna array;

when data is to be transmitted, precoding the data by using the product of the first precoding matrix and the second precoding matrix;

the first layer codebook of the planar antenna array is obtained by performing direct product operation on the first layer codebook of the linear array of the planar antenna array in the x-axis direction and the y-axis direction, and the x-axis and the y-axis are respectively straight lines where two mutually perpendicular edges of the planar antenna array are located.

In another aspect, a UE in a MIMO system is further provided, where an antenna array layout of the MIMO system employs a planar antenna array, and the UE includes:

an obtaining module, configured to obtain CSI of a channel;

the searching module is used for searching a corresponding first precoding matrix and a first PMI in a first layer codebook of the planar antenna array according to the CSI of the channel acquired by the acquiring module, wherein the first PMI is a PMI of the first precoding matrix; the antenna array is further used for finding a corresponding second precoding matrix and a second PMI in a second layer codebook of the planar antenna array according to the CSI and the first PMI, wherein the second PMI is a PMI of the second precoding matrix;

the sending module is used for reporting the first PMI and the second PMI searched by the searching module to the base station;

the first layer codebook of the planar antenna array is obtained by performing direct product operation on the first layer codebook of the linear array of the planar antenna array in the x-axis direction and the y-axis direction, and the x-axis and the y-axis are respectively straight lines where two mutually perpendicular edges of the planar antenna array are located.

In another aspect, a base station in a MIMO system is provided, where an antenna array layout of the MIMO system employs a planar antenna array, and the base station includes:

the receiving module is used for receiving a first PMI and a second PMI reported by User Equipment (UE);

the searching module is used for searching a corresponding first precoding matrix in a first layer codebook of the planar antenna array according to the first PMI received by the receiving module, and searching a corresponding second precoding matrix in a second layer codebook of the planar antenna array according to the received second PMI;

the pre-coding module is used for pre-coding the data by using the product of the first pre-coding matrix and the second pre-coding matrix searched by the searching module when the data is to be sent;

the first layer codebook of the planar antenna array is obtained by performing direct product operation on the first layer codebook of the linear array of the planar antenna array in the x-axis direction and the y-axis direction, and the x-axis and the y-axis are respectively straight lines where two mutually perpendicular edges of the planar antenna array are located.

In the technical scheme of the application, based on the URA correlation Crohn's-Neck approximation principle, the first layer codebook of the planar antenna array is obtained by performing direct product operation on the first layer codebook of the linear array of the planar antenna array in two mutually perpendicular directions, so that the first layer codebook of the dual-codebook is constructed for the planar antenna array layout, the method is suitable for application under the planar antenna array layout, the long-term statistical characteristic of a channel adopting the planar antenna array layout is well described, the system precoding performance is improved, and effective CSI feedback and precoding operation are provided for a large-scale antenna system.

Drawings

Fig. 1 is a flowchart of a method for transmitting CSI in a MIMO system according to a first embodiment of the present application;

fig. 2 is a flowchart of a CSI transmission method in a MIMO system according to a second embodiment of the present application;

fig. 3 is a URA4 × 4 layout diagram of 32 crossed antenna elements according to the third embodiment of the present application;

fig. 4 is a URA 4x4 layout schematic of 16 single-polarized antenna elements of embodiment four of the present application;

fig. 5 is a URA8 x4 layout schematic of 32 single-polarized antenna elements of example five of the present application;

fig. 6 is a schematic structural diagram of a UE in a MIMO system according to a sixth embodiment of the present application;

fig. 7 is a schematic structural diagram of a base station in a MIMO system according to a seventh embodiment of the present application.

Detailed Description

In order to solve the problem that most of dual codebooks in the prior art are designed for a linear antenna array layout, are not suitable for a planar antenna array layout, and cannot well describe long-term statistical characteristics of a channel adopting the planar antenna array layout, thereby having a large influence on system precoding performance, the following embodiments of the present application provide a transmission method of channel state information in an MIMO system, and a UE and a base station that can apply the method.

In the following embodiments, the antenna array layout of the MIMO system adopts a planar antenna array, for example, URA, etc., which is not limited in this application.

Example one

The CSI transmission method in the MIMO system according to the first embodiment may be performed by any UE. As shown in fig. 1, the method comprises the steps of:

step S102, according to the obtained CSI of the channel, finding a corresponding first precoding matrix and a first PMI in a first layer codebook of the planar antenna array, wherein the first PMI is a PMI of the first precoding matrix;

in practical implementation, the UE may perform channel estimation according to the received pilot sequence to obtain CSI.

Since each Precoding Matrix in the codebook corresponds to a PMI (Precoding Matrix Indicator), a corresponding Precoding Matrix (referred to as a first Precoding Matrix) and a PMI (referred to as a first PMI) corresponding to the first Precoding Matrix can be found in a first layer codebook of the planar antenna array according to the obtained CSI. The first layer codebook of the planar antenna array is used to characterize the long-term statistics of the channel.

The first layer codebook of the planar antenna array is obtained by performing direct product operation on the first layer codebook of the linear array of the planar antenna array in the x-axis direction and the y-axis direction, and the x-axis and the y-axis are respectively straight lines where two mutually perpendicular edges of the planar antenna array are located.

Step S104, according to the obtained CSI and the first PMI, finding a corresponding second precoding matrix and a second PMI in a second layer codebook of the planar antenna array, wherein the second PMI is a PMI of the second precoding matrix;

also, since each precoding matrix in the codebook corresponds to one PMI, according to the obtained CSI and the first PMI found in step S102, a corresponding precoding matrix (referred to as a second precoding matrix) and a PMI corresponding to the second precoding matrix (referred to as a second PMI) may be found in the second layer codebook of the planar antenna array. The second layer codebook of the planar antenna array is used to reflect the short term variations of the channel.

And step S106, reporting the first PMI and the second PMI to the base station.

In an actual implementation procedure, after receiving the transmission indication in the scheduling grant, the UE may report the first PMI and the second PMI periodically or aperiodically through a PUCCH (Physical Uplink Control CHannel) or a PUSCH (Physical Uplink Shared CHannel).

In the prior art, most of the double codebooks are designed for a linear antenna array layout, and are not suitable for a planar antenna array layout, and long-term statistical characteristics of a channel adopting the planar antenna array layout cannot be well described, so that the system precoding performance is greatly influenced.

The construction of a dual codebook for a planar antenna array layout may be based on a dual codebook construction for a linear antenna array layout. Taking the planar antenna array layout as URA as an example, consider a URA on the XY plane, and let the correlation matrix of the URA be R, and the correlation matrix of the antenna elements in the x direction be R_xThe correlation matrix of the antenna elements in the y-direction is R_yLet R be_xIndependent (i.e. independent) of R_yThen, the following properties are provided:

<math> <mrow> <mi>R</mi> <mo>=</mo> <msub> <mi>R</mi> <mi>x</mi> </msub> <mo>&CircleTimes;</mo> <msub> <mi>R</mi> <mi>y</mi> </msub> </mrow> </math>

wherein,is the direct product operator of the matrix.

This property is called the kronecker approximation principle of URA correlation, and can be used as a basis for constructing a dual codebook for a planar antenna array layout.

Therefore, the specific construction process of the first layer codebook and the second layer codebook of the planar antenna array is as follows:

step S201, taking straight lines where two mutually perpendicular edges of a planar antenna array are located as an x axis and a y axis respectively;

step S202, constructing a first layer codebook of the linear array of the planar antenna array in the x-axis direction, and recording as:

wherein,precoding matrices in a first layer codebook being a linear array of a planar antenna array in the x-axis direction, G_xCodebook size of a first layer codebook that is a linear array of a planar antenna array in the x-axis direction.

Step S203, constructing a first layer codebook of the linear array of the planar antenna array in the y-axis direction, and recording as:

wherein,precoding matrices in a first layer codebook being a linear array of planar antenna arrays in the y-axis direction, G_yCodebook size of the first layer codebook of a linear array of a planar antenna array in the y-axis direction.

Step S204 is to construct the first layer codebook of the planar antenna array according to the first layer codebook of the linear array of the planar antenna array in the x-axis direction in step S202 and the first layer codebook of the linear array of the planar antenna array in the y-axis direction in step S203, and may be performed according to the following two conditions:

the first condition is as follows: when all antenna elements in the planar antenna array are polarized in the same direction, each precoding matrix W1 in the first layer codebook of the planar antenna array is:

<math> <mrow> <mi>W</mi> <mn>1</mn> <mo>=</mo> <msub> <mi>X</mi> <msub> <mi>g</mi> <mn>1</mn> </msub> </msub> <mo>&CircleTimes;</mo> <msub> <mi>Y</mi> <msub> <mi>g</mi> <mn>2</mn> </msub> </msub> <mo>,</mo> <msub> <mi>g</mi> <mn>1</mn> </msub> <mo>=</mo> <mn>0,1</mn> <mo>,</mo> <mo>.</mo> <mo>.</mo> <mo>.</mo> <mo>,</mo> <msub> <mi>G</mi> <mi>x</mi> </msub> <mo>-</mo> <mn>1</mn> <mo>,</mo> <msub> <mi>g</mi> <mn>2</mn> </msub> <mo>=</mo> <mn>0,1</mn> <mo>,</mo> <mo>.</mo> <mo>.</mo> <mo>.</mo> <mo>,</mo> <msub> <mi>G</mi> <mi>y</mi> </msub> <mo>-</mo> <mn>1</mn> <mo>,</mo> </mrow> </math> wherein,w1 is the direct product operator of the matrix with size M₁×N₁，M₁Total number of elements of planar antenna array, N₁≥1。

Case two: when the antenna elements in the planar antenna array are cross-polarized, that is, half of the antenna elements and the other half of the antenna elements are cross-polarized, each precoding matrix W1 in the first layer codebook of the planar antenna array is:

<math> <mrow> <mi>W</mi> <mn>1</mn> <mo>=</mo> <mfenced open='[' close=']'> <mtable> <mtr> <mtd> <msub> <mi>X</mi> <msub> <mi>g</mi> <mn>1</mn> </msub> </msub> <mo>&CircleTimes;</mo> <msub> <mi>Y</mi> <msub> <mi>g</mi> <mn>2</mn> </msub> </msub> </mtd> <mtd> <mn>0</mn> </mtd> </mtr> <mtr> <mtd> <mn>0</mn> </mtd> <mtd> <msub> <mi>X</mi> <msub> <mi>g</mi> <mn>1</mn> </msub> </msub> <mo>&CircleTimes;</mo> <msub> <mi>Y</mi> <msub> <mi>g</mi> <mn>2</mn> </msub> </msub> </mtd> </mtr> </mtable> </mfenced> <mo>,</mo> </mrow> </math> g₁＝0,1,...,G_x-1,g₂＝0,1,...,G_y-1, wherein,w1 is the direct product operator of the matrix with size M₁×N₁，M₁Total number of elements of planar antenna array, N₁≥2。

Step S205, the size of each precoding matrix in the second layer codebook of the planar antenna array is M₂×N₂Wherein N is₂For spatially multiplexing the number of data streams, M₂=N₁. The specific construction method of the second layer codebook of the planar antenna array may adopt a method in the prior art, which is not limited in this application.

Example two

The CSI transmission method in the MIMO system according to the second embodiment may be performed by any base station. As shown in fig. 2, the method comprises the steps of:

step S302, a first PMI and a second PMI reported by UE are received;

in actual implementation, the base station acquires the first PMI and the second PMI from an uplink channel.

Step S304, according to the received first PMI, finding a corresponding first precoding matrix in a first layer codebook of the planar antenna array, and according to the received second PMI, finding a corresponding second precoding matrix in a second layer codebook of the planar antenna array;

the first layer codebook of the planar antenna array is obtained by performing direct product operation on the first layer codebook of the linear array of the planar antenna array in the x-axis direction and the y-axis direction, and the x-axis and the y-axis are respectively straight lines where two mutually perpendicular edges of the planar antenna array are located.

Step S306, when data is to be transmitted, the product of the first precoding matrix and the second precoding matrix is used to precode the data.

In step S306, assuming that the data vector to be transmitted by the base station is x, the precoded data is: x, the product of the first precoding matrix and the second precoding matrix.

The specific construction process of the first layer codebook and the second layer codebook of the planar antenna array may refer to step S201 to step S205 in the first embodiment, which is not described herein again.

EXAMPLE III

Third embodiment is based on the codebook design idea of Discrete Fourier Transform (DFT), and the method in the first and second embodiments is described in detail by taking URA4 × 4 layout of 32 dual-polarized antenna elements as shown in fig. 3 as an example. In fig. 3, each line segment represents 1 antenna element, and the line segments with the same direction represent the same polarization direction of the corresponding antenna elements.

The specific construction method of the first layer codebook and the second layer codebook for URA comprises the following steps:

step S401, taking the straight line where two mutually perpendicular sides of URA shown in figure 3 are positioned as the x-axis direction and the y-axis direction;

step S402, aiming at the linear array corresponding to the URA in the x-axis direction, a first layer codebook is constructed based on the rotating DFT matrix and is recorded as:

$\left\{X_{g_1}\right|g_1=\mathrm{0,1},...,G_x-1\}$

wherein,is a M_x×N_xMatrix of G_xIs a size of the codebook, and is,the elements in row m and column n are calculated as follows:

<math> <mrow> <msub> <mrow> <mo>[</mo> <msub> <mi>X</mi> <msub> <mi>g</mi> <mn>1</mn> </msub> </msub> <mo>]</mo> </mrow> <mrow> <mi>m</mi> <mo>,</mo> <mi>n</mi> </mrow> </msub> <mo>=</mo> <mfrac> <mn>1</mn> <msqrt> <msub> <mi>N</mi> <mi>x</mi> </msub> </msqrt> </mfrac> <mi>exp</mi> <mrow> <mo>(</mo> <mi>j</mi> <mfrac> <mrow> <mn>2</mn> <mi>&pi;</mi> </mrow> <msub> <mi>N</mi> <mi>x</mi> </msub> </mfrac> <mi>m</mi> <mrow> <mo>(</mo> <mi>n</mi> <mo>+</mo> <mfrac> <msub> <mi>g</mi> <mn>1</mn> </msub> <msub> <mi>G</mi> <mi>x</mi> </msub> </mfrac> <mo>)</mo> </mrow> <mo>)</mo> </mrow> <mo>,</mo> <mi>m</mi> <mo>=</mo> <mn>0</mn> <mo>,</mo> <mo>.</mo> <mo>.</mo> <mo>.</mo> <mo>,</mo> <msub> <mi>M</mi> <mi>x</mi> </msub> <mo>-</mo> <mn>1</mn> <mo>,</mo> <mi>n</mi> <mo>=</mo> <mn>0</mn> <mo>,</mo> <mo>.</mo> <mo>.</mo> <mo>.</mo> <mo>,</mo> <msub> <mi>N</mi> <mi>x</mi> </msub> <mo>-</mo> <mn>1</mn> <mo>,</mo> <msub> <mi>g</mi> <mn>1</mn> </msub> <mo>=</mo> <mn>0</mn> <mo>,</mo> <mo>.</mo> <mo>.</mo> <mo>.</mo> <mo>,</mo> <msub> <mi>G</mi> <mi>x</mi> </msub> <mo>-</mo> <mn>1</mn> </mrow> </math>

can order M_x=4，N_x=4，G_x=4, so 4 × 4 rotated DFT matrices are obtained: x₀、X₁、X₂、X₃That is, the URA includes the 4 rotated DFT matrices in the first layer codebook of the linear array corresponding to the x-axis direction.

Step S403, constructing a first layer codebook of the URA based on the rotated DFT matrix for the linear array corresponding to the URA in the y-axis direction. Since the antenna elements in the y-axis direction are equal to those in the x-axis direction, the same 4 × 4 rotated DFT matrices are obtained: x₀、X₁、X₂、X₃That is, the first layer codebook of the linear array corresponding to the URA in the y-axis direction includes the 4 rotated DFT matrices.

Step S404, based on the results obtained in step S402 and step S403, for the case of cross polarization of antenna elements, a precoding matrix in the first layer codebook for URA is constructed, and the matrix size of the precoding matrix is 32 × 32, that is, the precoding matrix is a 32 × 32 matrix. Ith in first layer codebook of URA₁（i₁Expressions of =0,1,.. 15) precoding matrices are as follows:

<math> <mrow> <msub> <mi>W</mi> <mn>1</mn> </msub> <mrow> <mo>(</mo> <msub> <mi>i</mi> <mn>1</mn> </msub> <mo>)</mo> </mrow> <mo>=</mo> <mfenced open='[' close=']'> <mtable> <mtr> <mtd> <msub> <mi>X</mi> <msub> <mi>g</mi> <mn>1</mn> </msub> </msub> <mo>&CircleTimes;</mo> <msub> <mi>Y</mi> <msub> <mi>g</mi> <mn>2</mn> </msub> </msub> </mtd> <mtd> <mn>0</mn> </mtd> </mtr> <mtr> <mtd> <mn>0</mn> </mtd> <mtd> <msub> <mi>X</mi> <msub> <mi>g</mi> <mn>1</mn> </msub> </msub> <mo>&CircleTimes;</mo> <msub> <mi>Y</mi> <msub> <mi>g</mi> <mn>2</mn> </msub> </msub> </mtd> </mtr> </mtable> </mfenced> <mo>,</mo> </mrow> </math> g₁＝0,1,2,3,g₂＝0,1,2,3,i₁=4g₁+g₂

step S405, for the case that the number of spatial multiplexing data stream is 1, the second layer of URAThe size of the precoding matrix in the codebook is 32 × 1, ith₂（i₂0, 1.., 63) precoding matrices are expressed as follows:

<math> <mrow> <msub> <mi>W</mi> <mn>2</mn> </msub> <mrow> <mo>(</mo> <msub> <mi>i</mi> <mn>2</mn> </msub> <mo>)</mo> </mrow> <mo>=</mo> <mfenced open='[' close=']'> <mtable> <mtr> <mtd> <msub> <mi>v</mi> <msub> <mi>k</mi> <mn>1</mn> </msub> </msub> </mtd> </mtr> <mtr> <mtd> <msup> <mi>e</mi> <mrow> <mi>j&pi;</mi> <msub> <mi>k</mi> <mn>2</mn> </msub> <mo>/</mo> <mn>2</mn> </mrow> </msup> <msub> <mi>v</mi> <msub> <mi>k</mi> <mn>1</mn> </msub> </msub> </mtd> </mtr> </mtable> </mfenced> <mo>,</mo> </mrow> </math> k₁＝0,1,...,15,k₂＝0,1,2,3,i₂=4k₁+k₂

wherein,is a unit column vector, the k-th of the unit column vector₁Action 1, the remaining actions 0.

The specific operation steps of the CSI transmission method in the third embodiment are as follows:

step S501, the UE carries out channel estimation according to the received pilot frequency sequence to obtain CSI;

step S502, according to the CSI obtained in step S501, the UE finds out a corresponding precoding matrix and PMI1 thereof for describing the long-term statistical characteristics of the channel from the first layer codebook of the URA;

step S503, according to the CSI obtained in step S501 and the PMI1 found in step S502, the UE finds a corresponding precoding matrix for reflecting short-term variation of the channel and a PMI2 thereof from the second layer codebook of the URA;

step S504, after receiving the sending instruction in the scheduling permission, the UE reports PMI1 and PMI2 to the base station periodically/non-periodically through PUCCH or PUSCH;

step S505, the base station receives PMI1 and PMI2 from the uplink channel;

step S506, the base station finds the corresponding precoding matrix W1 from the first layer codebook of the URA according to the PMI1, and finds the corresponding precoding matrix W2 from the second layer codebook of the URA according to the PMI2, so that the final precoding matrix is W1 × W2;

in step S507, it is assumed that the information symbol vector transmitted by the base station is x, and y is W × x after precoding.

Example four

The fourth embodiment is based on the codebook design idea of Discrete Fourier Transform (DFT), and the method in the first and second embodiments is described in detail by taking the URA 4x4 layout of 16 single-polarized antenna elements as shown in fig. 4 as an example. In fig. 4, each arrow represents 1 antenna element.

Step S601, taking the straight line where two mutually perpendicular sides of URA shown in FIG. 4 are positioned as the x-axis direction and the y-axis direction;

step S602, constructing a first layer codebook of the linear array corresponding to the URA in the x-axis direction based on the rotated DFT matrix, and recording as:

$\left\{X_{g_1}\right|g_1=\mathrm{0,1},...,G_x-1\}$

wherein,is a M_x×N_xMatrix of G_xIs a size of the codebook, and is,the elements in row m and column n are calculated as follows:

<math> <mrow> <msub> <mrow> <mo>[</mo> <msub> <mi>X</mi> <msub> <mi>g</mi> <mn>1</mn> </msub> </msub> <mo>]</mo> </mrow> <mrow> <mi>m</mi> <mo>,</mo> <mi>n</mi> </mrow> </msub> <mo>=</mo> <mfrac> <mn>1</mn> <msqrt> <msub> <mi>N</mi> <mi>x</mi> </msub> </msqrt> </mfrac> <mi>exp</mi> <mrow> <mo>(</mo> <mi>j</mi> <mfrac> <mrow> <mn>2</mn> <mi>&pi;</mi> </mrow> <msub> <mi>N</mi> <mi>x</mi> </msub> </mfrac> <mi>m</mi> <mrow> <mo>(</mo> <mi>n</mi> <mo>+</mo> <mfrac> <msub> <mi>g</mi> <mn>1</mn> </msub> <msub> <mi>G</mi> <mi>x</mi> </msub> </mfrac> <mo>)</mo> </mrow> <mo>)</mo> </mrow> <mo>,</mo> <mi>m</mi> <mo>=</mo> <mn>0</mn> <mo>,</mo> <mo>.</mo> <mo>.</mo> <mo>.</mo> <mo>,</mo> <msub> <mi>M</mi> <mi>x</mi> </msub> <mo>-</mo> <mn>1</mn> <mo>,</mo> <mi>n</mi> <mo>=</mo> <mn>0</mn> <mo>,</mo> <mo>.</mo> <mo>.</mo> <mo>.</mo> <mo>,</mo> <msub> <mi>N</mi> <mi>x</mi> </msub> <mo>-</mo> <mn>1</mn> <mo>,</mo> <msub> <mi>g</mi> <mn>1</mn> </msub> <mo>=</mo> <mn>0</mn> <mo>,</mo> <mo>.</mo> <mo>.</mo> <mo>.</mo> <mo>,</mo> <msub> <mi>G</mi> <mi>x</mi> </msub> <mo>-</mo> <mn>1</mn> </mrow> </math>

can order M_x=4，N_x=4，G_x=4, so 4 × 4 rotated DFT matrices are obtained: x₀、X₁、X₂、X₃That is, the URA includes the 4 rotated DFT matrices in the first layer codebook of the linear array corresponding to the x-axis direction.

Step S603, constructing a first layer codebook of the URA based on the rotated DFT matrix for the linear array corresponding to the URA in the y-axis direction. Since the antenna elements in the y-axis direction are equal to those in the x-axis direction, the same 4 × 4 rotated DFT matrices are obtained: x₀、X₁、X₂、X₃That is, the first layer codebook of the linear array corresponding to the URA in the y-axis direction includes the 4 rotated DFT matrices.

Step S604, based on the results obtained in step S602 and step S603, for the case of single polarization of the antenna elements, a precoding matrix in the first layer codebook for URA is constructed, and the matrix size of the precoding matrix is 16 × 16, that is, the precoding matrix is a 16 × 16 matrix. Ith in first layer codebook of URA₁（i₁Expressions of =0,1,.. 15) precoding matrices are as follows:

<math> <mrow> <msub> <mi>W</mi> <mn>1</mn> </msub> <mrow> <mo>(</mo> <msub> <mi>i</mi> <mn>1</mn> </msub> <mo>)</mo> </mrow> <mo>=</mo> <msub> <mi>X</mi> <msub> <mi>g</mi> <mn>1</mn> </msub> </msub> <mo>&CircleTimes;</mo> <msub> <mi>Y</mi> <msub> <mi>g</mi> <mn>2</mn> </msub> </msub> <mo>,</mo> <msub> <mi>g</mi> <mn>1</mn> </msub> <mo>=</mo> <mn>0,1,2,3</mn> <mo>,</mo> <msub> <mi>g</mi> <mn>2</mn> </msub> <mo>=</mo> <mn>0,1,2,3</mn> <mo>,</mo> <msub> <mi>i</mi> <mn>1</mn> </msub> <mo>=</mo> <mn>4</mn> <msub> <mi>g</mi> <mn>1</mn> </msub> <mo>+</mo> <msub> <mi>g</mi> <mn>2</mn> </msub> </mrow> </math>

step S605, when the number of spatially multiplexed data streams is 1, the size of the precoding matrix in the second layer codebook of URA is 16 × 1, i-th₂（i₂The expression of 0, 1.. 15) precoding matrices is as follows:

$W_2\left(i_2\right)=v_{i_2},i_2=\mathrm{0,1},...,15$

wherein,is a unit column vector, i-th of the unit column vector₂Action 1, the remaining actions 0.

The specific operation steps of the CSI transmission method in the fourth embodiment are the same as steps S501 to S507 in the third embodiment, and are not described again here.

EXAMPLE five

Fifth embodiment is based on the codebook design idea of Discrete Fourier Transform (DFT), and the method in the first and second embodiments is described in detail by taking URA8 × 4 layout of 32 single-polarized antenna elements as shown in fig. 5 as an example. In fig. 5, each arrow represents 1 antenna element.

Step S701, using straight lines where two mutually perpendicular sides of the URA shown in fig. 5 are located as an x-axis direction and a y-axis direction;

step S702, for the linear array corresponding to the URA in the x-axis direction, a first layer codebook is constructed based on the rotated DFT matrix, and is recorded as:

$\left\{X_{g_1}\right|g_1=\mathrm{0,1},...,G_x-1\}$

wherein,is a M_x×N_xMatrix of G_xIs a size of the codebook, and is,the elements in row m and column n are calculated as follows:

<math> <mrow> <msub> <mrow> <mo>[</mo> <msub> <mi>X</mi> <msub> <mi>g</mi> <mn>1</mn> </msub> </msub> <mo>]</mo> </mrow> <mrow> <mi>m</mi> <mo>,</mo> <mi>n</mi> </mrow> </msub> <mo>=</mo> <mfrac> <mn>1</mn> <msqrt> <msub> <mi>N</mi> <mi>x</mi> </msub> </msqrt> </mfrac> <mi>exp</mi> <mrow> <mo>(</mo> <mi>j</mi> <mfrac> <mrow> <mn>2</mn> <mi>&pi;</mi> </mrow> <msub> <mi>N</mi> <mi>x</mi> </msub> </mfrac> <mi>m</mi> <mrow> <mo>(</mo> <mi>n</mi> <mo>+</mo> <mfrac> <msub> <mi>g</mi> <mn>1</mn> </msub> <msub> <mi>G</mi> <mi>x</mi> </msub> </mfrac> <mo>)</mo> </mrow> <mo>)</mo> </mrow> <mo>,</mo> <mi>m</mi> <mo>=</mo> <mn>0</mn> <mo>,</mo> <mo>.</mo> <mo>.</mo> <mo>.</mo> <mo>,</mo> <msub> <mi>M</mi> <mi>x</mi> </msub> <mo>-</mo> <mn>1</mn> <mo>,</mo> <mi>n</mi> <mo>=</mo> <mn>0</mn> <mo>,</mo> <mo>.</mo> <mo>.</mo> <mo>.</mo> <mo>,</mo> <msub> <mi>N</mi> <mi>x</mi> </msub> <mo>-</mo> <mn>1</mn> <mo>,</mo> <msub> <mi>g</mi> <mn>1</mn> </msub> <mo>=</mo> <mn>0</mn> <mo>,</mo> <mo>.</mo> <mo>.</mo> <mo>.</mo> <mo>,</mo> <msub> <mi>G</mi> <mi>x</mi> </msub> <mo>-</mo> <mn>1</mn> </mrow> </math>

can order M_x=8，N_x=4，G_x=8, thus obtaining 8 × 4 rotated DFT matricesThat is, the URA includes the 8 rotated DFT matrices in the first layer codebook of the linear array corresponding to the x-axis direction.

Step S703, constructing a first layer codebook of the linear array corresponding to the URA in the y-axis direction based on the rotated DFT matrix, and recording as:

$\left\{Y_{g_2}\right|g_2=\mathrm{0,1},...,G_y-1\}$

wherein,is a M_y×N_yMatrix of G_yIs a size of the codebook, and is,the elements in row m and column n are calculated as follows:

<math> <mrow> <msub> <mrow> <mo>[</mo> <msub> <mi>Y</mi> <msub> <mi>g</mi> <mn>2</mn> </msub> </msub> <mo>]</mo> </mrow> <mrow> <mi>m</mi> <mo>,</mo> <mi>n</mi> </mrow> </msub> <mo>=</mo> <mfrac> <mn>1</mn> <msqrt> <msub> <mi>N</mi> <mi>y</mi> </msub> </msqrt> </mfrac> <mi>exp</mi> <mrow> <mo>(</mo> <mi>j</mi> <mfrac> <mrow> <mn>2</mn> <mi>&pi;</mi> </mrow> <msub> <mi>N</mi> <mi>y</mi> </msub> </mfrac> <mi>m</mi> <mrow> <mo>(</mo> <mi>n</mi> <mo>+</mo> <mfrac> <msub> <mi>g</mi> <mn>2</mn> </msub> <msub> <mi>G</mi> <mi>y</mi> </msub> </mfrac> <mo>)</mo> </mrow> <mo>)</mo> </mrow> <mo>,</mo> <mi>m</mi> <mo>=</mo> <mn>0</mn> <mo>,</mo> <mo>.</mo> <mo>.</mo> <mo>.</mo> <mo>,</mo> <msub> <mi>M</mi> <mi>y</mi> </msub> <mo>-</mo> <mn>1</mn> <mo>,</mo> <mi>n</mi> <mo>=</mo> <mn>0</mn> <mo>,</mo> <mo>.</mo> <mo>.</mo> <mo>.</mo> <mo>,</mo> <msub> <mi>N</mi> <mi>y</mi> </msub> <mo>-</mo> <mn>1</mn> <mo>,</mo> <msub> <mi>g</mi> <mn>2</mn> </msub> <mo>=</mo> <mn>0</mn> <mo>,</mo> <mo>.</mo> <mo>.</mo> <mo>.</mo> <mo>,</mo> <msub> <mi>G</mi> <mi>y</mi> </msub> <mo>-</mo> <mn>1</mn> </mrow> </math>

can order M_y＝4，N_y＝4，G_y=4, so that 4 × 4 rotated DFT matrices are obtainedThat is, the URA includes these 4 rotated DFT matrices in the first layer codebook of the linear array corresponding to the y-axis direction.

Step S704, based on the results obtained in step S702 and step S703, for the case of single polarization of the antenna element, constructing a single polarization antennaThe precoding matrix in the first layer codebook of URA has a matrix size of 32 × 16, i.e., the precoding matrix is a 32 × 16 matrix. Ith in first layer codebook of URA₁（i₁Expression of =0,1,.. 31) precoding matrices is as follows:

<math> <mrow> <msub> <mi>W</mi> <mn>1</mn> </msub> <mrow> <mo>(</mo> <msub> <mi>i</mi> <mn>1</mn> </msub> <mo>)</mo> </mrow> <mo>=</mo> <msub> <mi>X</mi> <msub> <mi>g</mi> <mn>1</mn> </msub> </msub> <mo>&CircleTimes;</mo> <msub> <mi>Y</mi> <msub> <mi>g</mi> <mn>2</mn> </msub> </msub> <mo>,</mo> <msub> <mi>g</mi> <mn>1</mn> </msub> <mo>=</mo> <mn>0,1</mn> <mo>,</mo> <mo>.</mo> <mo>.</mo> <mo>.</mo> <mo>,</mo> <mn>7</mn> <mo>,</mo> <msub> <mi>g</mi> <mn>2</mn> </msub> <mo>=</mo> <mn>0,1,2,3</mn> <mo>,</mo> <msub> <mi>i</mi> <mn>1</mn> </msub> <mo>=</mo> <mn>4</mn> <msub> <mi>g</mi> <mn>1</mn> </msub> <mo>+</mo> <msub> <mi>g</mi> <mn>2</mn> </msub> </mrow> </math>

step S705, for the case where the number of spatially multiplexed data streams is 1, the size of the precoding matrix in the second layer codebook of URA is 16 × 1, i-th₂（i₂The expression of 0, 1.. 15) precoding matrices is as follows:

$W_2\left(i_2\right)=v_{i_2},i_2=\mathrm{0,1},...,15$

wherein,is a unit column vector, i-th of the unit column vector₂Action 1, the remaining actions 0.

The specific operation steps of the CSI transmission method in the fifth embodiment are the same as steps S501 to S507 in the third embodiment, and are not described again here.

EXAMPLE six

For the method in the first embodiment, the sixth embodiment provides a UE in a MIMO system. As shown in fig. 6, the UE includes the following modules: an obtaining module 101, a searching module 102 and a sending module 103, wherein:

an obtaining module 101, configured to obtain CSI of a channel;

a searching module 102, configured to search, according to the CSI of the channel acquired by the acquiring module 101, a corresponding first precoding matrix and a corresponding first PMI in a first layer codebook of the planar antenna array, where the first PMI is a PMI of the first precoding matrix; the antenna array is further used for finding a corresponding second precoding matrix and a second PMI in a second layer codebook of the planar antenna array according to the CSI and the first PMI, wherein the second PMI is a PMI of the second precoding matrix;

a sending module 103, configured to report the first PMI and the second PMI found by the searching module 103 to the base station;

the first layer codebook of the planar antenna array is obtained by performing direct product operation on the first layer codebook of the linear array of the planar antenna array in the x-axis direction and the y-axis direction, and the x-axis and the y-axis are respectively straight lines where two mutually perpendicular edges of the planar antenna array are located.

EXAMPLE seven

For the method in the second embodiment, a seventh embodiment provides a base station in a MIMO system. As shown in fig. 7, the base station includes the following modules:

a receiving module 201, configured to receive a first PMI and a second PMI reported by a user equipment UE;

a searching module 202, configured to search, according to the first PMI received by the receiving module 201, a corresponding first precoding matrix in a first layer codebook of the planar antenna array, and search, according to the received second PMI, a corresponding second precoding matrix in a second layer codebook of the planar antenna array;

a pre-coding module 203, configured to pre-code the data by using the product of the first pre-coding matrix and the second pre-coding matrix found by the searching module 202 when the data is to be sent;

the first layer codebook of the planar antenna array is obtained by performing direct product operation on the first layer codebook of the linear array of the planar antenna array in the x-axis direction and the y-axis direction, and the x-axis and the y-axis are respectively straight lines where two mutually perpendicular edges of the planar antenna array are located.

In summary, the above embodiments of the present application can achieve the following technical effects:

in the technical scheme of the application, based on the URA correlation Crohn's-Neck approximation principle, the first layer codebook of the planar antenna array is obtained by performing direct product operation on the first layer codebook of the linear array of the planar antenna array in two mutually perpendicular directions, so that the first layer codebook in the double codebooks is constructed for the planar antenna array layout, the method is suitable for application under the planar antenna array layout, the long-term statistical characteristic of a channel adopting the planar antenna array layout is well described, the system precoding performance is improved, and effective CSI feedback and precoding operation are provided for a large-scale antenna system.

The above description is only exemplary of the present application and should not be taken as limiting the present application, as any modification, equivalent replacement, or improvement made within the spirit and principle of the present application should be included in the scope of protection of the present application.

Claims (14)

1. A method for transmitting Channel State Information (CSI) in a multiple-input multiple-output (MIMO) system, wherein a planar antenna array is adopted in the antenna array layout of the MIMO system, and the method is applied to User Equipment (UE), and is characterized by comprising the following steps:

according to the obtained CSI of the channel, a corresponding first precoding matrix and a first precoding matrix indication PMI are found in a first layer codebook of the planar antenna array, wherein the first PMI is a PMI of the first precoding matrix;

according to the CSI and the first PMI, finding a corresponding second precoding matrix and a second PMI in a second layer codebook of the planar antenna array, wherein the second PMI is a PMI of the second precoding matrix;

reporting the first PMI and the second PMI to a base station;

the first layer codebook of the planar antenna array is obtained by performing direct product operation on the first layer codebook of the linear array of the planar antenna array in the x-axis direction and the y-axis direction, and the x-axis and the y-axis are respectively straight lines where two mutually perpendicular edges of the planar antenna array are located.

2. The method of claim 1, wherein the first layer codebook of the linear array of the planar antenna array in the x-axis direction is:

wherein,a precoding matrix in a first layer codebook of a linear array of the planar antenna array in the x-axis direction, G_xThe codebook size of the first layer codebook of the linear array of the planar antenna array in the x-axis direction.

3. The method of claim 1, wherein the first layer codebook of the linear array of the planar antenna array in the y-axis direction is:

wherein,a precoding matrix in a first layer codebook of a linear array of the planar antenna array in the y-axis direction, G_yIs the day of the planeCodebook size of the first layer codebook for linear arrays of lines in the y-axis direction.

4. The method of claim 1, wherein when the antenna elements in the planar antenna array are co-polarized, each precoding matrix W1 in the first layer codebook of the planar antenna array is:

<math> <mrow> <mi>W</mi> <mn>1</mn> <mo>=</mo> <msub> <mi>X</mi> <msub> <mi>g</mi> <mn>1</mn> </msub> </msub> <mo>&CircleTimes;</mo> <msub> <mi>Y</mi> <msub> <mi>g</mi> <mn>2</mn> </msub> </msub> <mo>,</mo> <msub> <mi>g</mi> <mn>1</mn> </msub> <mo>=</mo> <mn>0,1</mn> <mo>,</mo> <mo>.</mo> <mo>.</mo> <mo>.</mo> <mo>,</mo> <msub> <mi>G</mi> <mi>x</mi> </msub> <mo>-</mo> <mn>1</mn> <mo>,</mo> <msub> <mi>g</mi> <mn>2</mn> </msub> <mo>=</mo> <mn>0,1</mn> <mo>,</mo> <mo>.</mo> <mo>.</mo> <mo>.</mo> <mo>,</mo> <msub> <mi>G</mi> <mi>y</mi> </msub> <mo>-</mo> <mn>1</mn> <mo>,</mo> </mrow> </math> wherein,a precoding matrix in a first layer codebook of a linear array of the planar antenna array in the x-axis direction, G_xA codebook size of a first layer codebook of a linear array of the planar antenna array in an x-axis direction,a precoding matrix in a first layer codebook of a linear array of the planar antenna array in the y-axis direction, G_yOf a first layer of code book being a linear array of said planar antenna array in the direction of the y-axisThe size of the codebook is such that,w1 is the direct product operator of the matrix with size M₁×N₁，M₁Total number of antenna elements of the planar antenna array, N₁≥1。

5. The method of claim 1, wherein when the antenna elements in the planar antenna array are cross-polarized, each precoding matrix W1 in the first layer codebook of the planar antenna array is:

<math> <mrow> <mi>W</mi> <mn>1</mn> <mo>=</mo> <mfenced open='[' close=']'> <mtable> <mtr> <mtd> <msub> <mi>X</mi> <msub> <mi>g</mi> <mn>1</mn> </msub> </msub> <mo>&CircleTimes;</mo> <msub> <mi>Y</mi> <msub> <mi>g</mi> <mn>2</mn> </msub> </msub> </mtd> <mtd> <mn>0</mn> </mtd> </mtr> <mtr> <mtd> <mn>0</mn> </mtd> <mtd> <msub> <mi>X</mi> <msub> <mi>g</mi> <mn>1</mn> </msub> </msub> <mo>&CircleTimes;</mo> <msub> <mi>Y</mi> <msub> <mi>g</mi> <mn>2</mn> </msub> </msub> </mtd> </mtr> </mtable> </mfenced> <mo>,</mo> </mrow> </math> g₁＝0,1,...,G_x-1,g₂＝0,1,...,G_y-1, wherein,a precoding matrix in a first layer codebook of a linear array of the planar antenna array in the x-axis direction, G_xA codebook size of a first layer codebook of a linear array of the planar antenna array in an x-axis direction,a precoding matrix in a first layer codebook of a linear array of the planar antenna array in the y-axis direction, G_yA codebook size of a first layer codebook that is a linear array of the planar antenna array in the y-axis direction,w1 is the direct product operator of the matrix with size M₁×N₁，M₁Total number of antenna elements of the planar antenna array, N₁≥2。

6. The method of claim 4 or 5, wherein each precoding matrix in the second layer codebook of the planar antenna array has a size of M₂×N₂Wherein N is₂For spatially multiplexing the number of data streams, M₂=N₁。

7. A method for transmitting Channel State Information (CSI) in a multiple-input multiple-output (MIMO) system, wherein a planar antenna array is adopted for the antenna array layout of the MIMO system, and the method is applied to a base station, and is characterized by comprising the following steps:

receiving a first Precoding Matrix Indicator (PMI) and a second PMI reported by User Equipment (UE);

according to the received first PMI, finding a corresponding first precoding matrix in a first layer codebook of the planar antenna array, and according to the received second PMI, finding a corresponding second precoding matrix in a second layer codebook of the planar antenna array;

when data is to be transmitted, precoding the data by using the product of a first precoding matrix and a second precoding matrix;

the first layer codebook of the planar antenna array is obtained by performing direct product operation on the first layer codebook of the linear array of the planar antenna array in the x-axis direction and the y-axis direction, and the x-axis and the y-axis are respectively straight lines where two mutually perpendicular edges of the planar antenna array are located.

8. The method of claim 7, wherein the first layer codebook of the linear array of the planar antenna array in the x-axis direction is:

wherein,a precoding matrix in a first layer codebook of a linear array of the planar antenna array in the x-axis direction, G_xThe codebook size of the first layer codebook of the linear array of the planar antenna array in the x-axis direction.

9. The method of claim 7, wherein the first layer codebook of the linear array of the planar antenna array in the y-axis direction is:

wherein,a precoding matrix in a first layer codebook of a linear array of the planar antenna array in the y-axis direction, G_yThe codebook size of the first layer codebook of the linear array of the planar antenna array in the y-axis direction.

10. The method of claim 7, wherein when the antenna elements in the planar antenna array are co-polarized, each precoding matrix W1 in the first layer codebook of the planar antenna array is:

<math> <mrow> <mi>W</mi> <mn>1</mn> <mo>=</mo> <msub> <mi>X</mi> <msub> <mi>g</mi> <mn>1</mn> </msub> </msub> <mo>&CircleTimes;</mo> <msub> <mi>Y</mi> <msub> <mi>g</mi> <mn>2</mn> </msub> </msub> <mo>,</mo> <msub> <mi>g</mi> <mn>1</mn> </msub> <mo>=</mo> <mn>0,1</mn> <mo>,</mo> <mo>.</mo> <mo>.</mo> <mo>.</mo> <mo>,</mo> <msub> <mi>G</mi> <mi>x</mi> </msub> <mo>-</mo> <mn>1</mn> <mo>,</mo> <msub> <mi>g</mi> <mn>2</mn> </msub> <mo>=</mo> <mn>0,1</mn> <mo>,</mo> <mo>.</mo> <mo>.</mo> <mo>.</mo> <mo>,</mo> <msub> <mi>G</mi> <mi>y</mi> </msub> <mo>-</mo> <mn>1</mn> <mo>,</mo> </mrow> </math> wherein,a precoding matrix in a first layer codebook of a linear array of the planar antenna array in the x-axis direction, G_xA codebook size of a first layer codebook of a linear array of the planar antenna array in an x-axis direction,a precoding matrix in a first layer codebook of a linear array of the planar antenna array in the y-axis direction, G_yA codebook size of a first layer codebook that is a linear array of the planar antenna array in the y-axis direction,w1 is the direct product operator of the matrix with size M₁×N₁，M₁Total number of antenna elements of the planar antenna array, N₁≥1。

11. The method of claim 7, wherein when the antenna elements in the planar antenna array are cross-polarized, each precoding matrix W1 in the first layer codebook of the planar antenna array is:

<math> <mrow> <mi>W</mi> <mn>1</mn> <mo>=</mo> <mfenced open='[' close=']'> <mtable> <mtr> <mtd> <msub> <mi>X</mi> <msub> <mi>g</mi> <mn>1</mn> </msub> </msub> <mo>&CircleTimes;</mo> <msub> <mi>Y</mi> <msub> <mi>g</mi> <mn>2</mn> </msub> </msub> </mtd> <mtd> <mn>0</mn> </mtd> </mtr> <mtr> <mtd> <mn>0</mn> </mtd> <mtd> <msub> <mi>X</mi> <msub> <mi>g</mi> <mn>1</mn> </msub> </msub> <mo>&CircleTimes;</mo> <msub> <mi>Y</mi> <msub> <mi>g</mi> <mn>2</mn> </msub> </msub> </mtd> </mtr> </mtable> </mfenced> <mo>,</mo> </mrow> </math> g₁＝0,1,...,G_x-1,g₂＝0,1,...,G_y-1, wherein,precoding moments in a first layer codebook that is a linear array of the planar antenna array in the x-axis directionArray, G_xA codebook size of a first layer codebook of a linear array of the planar antenna array in an x-axis direction,a precoding matrix in a first layer codebook of a linear array of the planar antenna array in the y-axis direction, G_yA codebook size of a first layer codebook that is a linear array of the planar antenna array in the y-axis direction,w1 is the direct product operator of the matrix with size M₁×N₁，M₁Total number of antenna elements of the planar antenna array, N₁≥2。

12. The method of claim 10 or 11, wherein the size of each precoding matrix in the second layer codebook of the planar antenna array is M₂×N₂Wherein N is₂For spatially multiplexing the number of data streams, M₂=N₁。

13. A user equipment, UE, in a multiple-input multiple-output, MIMO, system, wherein an antenna array layout of the MIMO employs a planar antenna array, the UE comprising:

the acquisition module is used for acquiring Channel State Information (CSI) of a channel;

the searching module is used for searching a corresponding first precoding matrix and a first precoding matrix indication PMI in a first layer codebook of the planar antenna array according to the CSI of the channel acquired by the acquiring module, wherein the first PMI is a PMI of the first precoding matrix; the second precoding matrix and the second PMI are also used for finding the corresponding second precoding matrix and second PMI in a second layer codebook of the planar antenna array according to the CSI and the first PMI;

the sending module is used for reporting the first PMI and the second PMI searched by the searching module to the base station;

the first layer codebook of the planar antenna array is obtained by performing direct product operation on the first layer codebook of the linear array of the planar antenna array in the x-axis direction and the y-axis direction, and the x-axis and the y-axis are respectively straight lines where two mutually perpendicular edges of the planar antenna array are located.

14. A base station in a multiple-input multiple-output, MIMO, system, wherein an antenna array layout of the MIMO system employs planar antenna arrays, the base station comprising:

the receiving module is used for receiving a first precoding matrix indicator PMI and a second PMI reported by user equipment UE;

the searching module is used for searching a corresponding first precoding matrix in a first layer codebook of the planar antenna array according to the first PMI received by the receiving module, and searching a corresponding second precoding matrix in a second layer codebook of the planar antenna array according to the received second PMI;

the pre-coding module is used for pre-coding the data by using the product of the first pre-coding matrix and the second pre-coding matrix searched by the searching module when the data is to be sent;

the first layer codebook of the planar antenna array is obtained by performing direct product operation on the first layer codebook of the linear array of the planar antenna array in the x-axis direction and the y-axis direction, and the x-axis and the y-axis are respectively straight lines where two mutually perpendicular edges of the planar antenna array are located.