WO2018032492A1

WO2018032492A1 - Downlink transmission method and network device

Info

Publication number: WO2018032492A1
Application number: PCT/CN2016/095970
Authority: WO
Inventors: 杨非; 陈凯; 王智鹰
Original assignee: 华为技术有限公司
Priority date: 2016-08-19
Filing date: 2016-08-19
Publication date: 2018-02-22
Also published as: CN109196789A

Abstract

Disclosed in the embodiments of the present invention are a downlink transmission method and a network device, used for solving the existing problem wherein transmission mode 4 (TM4) in a multiple-input multiple-output system is not suitable for use in performing downlink transmission for multiple users (MU). The method comprises: a network device receiving N precoding matrix indicators PMI, the N PMI being determined by N user equipments (UE) according to a first weighted pilot signal sent by the network device, the first weighted pilot signal being determined by the network device weighting a first pilot signal according to a first pilot weighting matrix; the network device determining N reconstruction channel primary feature vectors according to the N PMI and the first pilot weighting matrix; the network device determining M scheduled UE from within the N UE and determining a second pilot weighting matrix according to a reconstruction channel primary feature vector of each of the M scheduled UE; and the network device sending a second weighted pilot signal to the N UE, the second weighted pilot signal being obtained by the network device weighting a second pilot signal according to a second pilot weighting matrix.

Description

Downlink transmission method and network device

Technical field

The present invention relates to the field of communications, and in particular, to a downlink transmission method and a network device.

Background technique

In a multi-input multi-output (MIMO) system, since the channel reciprocity of the uplink and downlink channels in the time division duplex (TDD) system is established, the network device passes the user. The uplink reference signal sent by the user equipment (UE) is detected to obtain accurate instantaneous downlink channel state information (CSI), so that accurate beamforming transmission can be performed. The reciprocity of the uplink and downlink channels in the frequency division duplex (FDD) system is generally not established. The network device cannot directly use the uplink channel estimation result to transmit the downlink beamforming, but adopts a fixed codebook for the channel. Feature direction quantization, the UE selects an optimal precoding codeword based on a certain criterion in the codebook according to the downlink channel estimation result, and feeds back an index to the network device, that is, a precoding matrix indicator (PMI) After detecting the PMI, the network device uses the precoding codeword corresponding to the PMI to perform weighted transmission on the downlink data signal.

In the transmission mode (TM) 4 of the MIMO system, the network device and the UE in the FDD system store the same set of precoding codebooks, wherein the precoding codebook includes a plurality of precoding matrices. In the communication process, as shown in FIG. 1, the network device sends a pilot signal, for example, a cell-specific reference signal (CRS), to the UE, and the UE estimates the downlink channel by detecting the CRS, according to its internal setting. The criterion selects the optimal quantization result of the current downlink channel estimation result in the pre-coded codebook, and sends it as the PMI to the network device. The network device detects the PMI sent by the UE, and sets the precoding matrix corresponding to the PMI as the downlink single. User (single-user, SU) precoding matrix.

Since TM4 adopts a precoding matrix based on a precoding codebook, wherein a codebook of 2 antenna ports is defined in a related protocol of 3GPP, and four 2-dimensional complex vectors are included as PMI codewords of rank=1; The codebook of the 4 antenna port includes 16 4-dimensional complex vectors as the PMI codeword of Rank=1. For the SU, the UE can select a PMI codeword that matches the actual downlink channel from the 16 PMI codewords, and then the network device determines the precoding matrix according to the PMI codeword selected by the UE, but for multiple users (multiple- User, MU), the 16 PMI codewords and each UE pair The quantization error of the actual downlink channel is large, and the PMI codeword selected by each UE from the 16 PMI codewords does not match the actual downlink channel corresponding to each UE, and the network device determines according to the PMI codeword selected by each UE. The precoding matrix and weighted transmission of the downlink data signal can cause serious user interference.

Summary of the invention

The embodiment of the invention provides a downlink transmission method and a network device, which are used to solve the problem that the TM4 of the existing multiple input multiple output system is not suitable for downlink transmission to the MU.

The first aspect of the present invention provides a downlink transmission method, which is applied to a multiple input multiple output system. With the technical solution of the present invention, the TM4 of the multiple input multiple output system is not only suitable for downlink transmission to the SU, but also applicable to the MU. Performing downlink transmission, the method includes: the network device receives N PMIs, where N is an integer greater than 1, and the N PMIs are downlink channel estimates by the N UEs according to the first weighted pilot signals sent by the network device, and according to Determining, by the result of the downlink channel estimation, the first weighted pilot signal is obtained by the network device weighting the first pilot signal according to the first pilot weight matrix, and the network device is configured according to the N PMIs and the first pilot Determining, by the weighting matrix, N reconstructed channel main eigenvectors, the network device determining M scheduled UEs from the N UEs, and reconstructing channel main eigenvectors according to each of the M scheduled UEs Determining a second pilot weighting matrix, where M is an integer not greater than N, and the network device sends a second weighted pilot signal to the N UEs, where the second weighted pilot signal is determined by the network device According to the second pilot of the second pilot signal weight matrix obtained by frequency weighting.

Different from the prior art, the network device receives N PMIs, where N is an integer greater than 1, and the N PMIs are determined by the N UEs according to the first weighted pilot signals sent by the network device, and the The first weighted pilot signal is obtained by the network device weighting the first pilot signal according to the first pilot weight matrix. When the network device weights the first pilot signal, the UE actually sees that it is not the first guide. The frequency signal is not determined by the first pilot signal, and the UE actually sees the first weighted pilot signal, which is determined by the first weighted pilot signal for downlink channel estimation, thereby expanding the PMI. The selection range of the PMI, since the N PMIs are not the quantization of the real downlink channel, but the quantization of the downlink channel weighted by the first pilot weight matrix by the first pilot weight matrix, therefore, the network device needs to perform corresponding The inverse transform can correctly restore the real downlink channel, and the network device determines N reconstructed channel main feature vectors according to the N PMIs and the first pilot weight matrix, and then Determining M scheduled UEs among the N UEs, and then determining a second pilot weighting matrix according to the reconstructed channel main feature vector of each of the M scheduled UEs, so that the second weighting matrix can be adopted Weighting the second pilot signal to obtain a second weighted pilot signal, and transmitting the second weighted pilot signal to the N UEs, thereby reducing quantization error of the downlink channel, better suppressing interference between users, and improving The accuracy of the downlink channel.

In some possible implementation manners, the first pilot weighting matrix is a target pilot weighting matrix determined by a previous pilot weighting, used to weight the pilot signal of this time, since the pilot is not used in the prior art. Signal weighting, so the first pilot weighting matrix weighting the pilot signal for the first time is at least one of a unit weight matrix and a preset pilot weight matrix, and the target pilot weight matrix determined by weighting the second pilot signal The third pilot weighting matrix is used as the third pilot weighting matrix, and the third pilot signal is weighted according to the first pilot weighting matrix, and so on, which is not specifically limited herein.

In some possible implementation manners, the network device determines, according to the N PMIs and the first pilot weight matrix, N reconstructed channel main feature vectors in a plurality of manners. One possible manner includes: the network device first according to the manner The N PMIs determine N precoding codewords corresponding to the N PMIs, and then the network device determines a conjugate transposed matrix corresponding to the N precoding codewords and a conjugate transposed matrix corresponding to the first pilot weight matrix And second, the network device, according to the N precoding codewords, the first pilot weight matrix, the conjugate transposed matrix corresponding to the N precoding codewords, and the conjugate transpose corresponding to the first pilot weight matrix The matrix determines the N reconstructed channel main feature vectors. Since the N PMIs are not the quantization of the real downlink channel, but the quantization of the downlink channel weighted by the first pilot weight matrix by the first pilot weight matrix, the network device determines the N reconstructed channel masters. The feature vector is used to correctly restore the true downlink channel.

In some possible implementation manners, the network device, according to the N precoding codewords, the first pilot weight matrix, the conjugate transposed matrix corresponding to the N precoding codewords, and the first pilot weight matrix The conjugate transposed matrix determines the N reconstructed channel main eigenvectors, the network device, according to the N precoding codewords, the first pilot weight matrix, and the conjugate transpose corresponding to the N precoding codewords The matrix and the conjugate transposed matrix corresponding to the first pilot weighting matrix determine the N reconstructed channel main eigenvectors by using a first formula, wherein the first formula is expressed as:

among them,

Representing the reconstructed channel main feature vector of the user equipment u determined on the subframe t, PrimEigVec represents the main feature vector of the matrix, L represents the total number of measurement subframes within the preset length, and m is the measurement subframe number.

Representing a first pilot weighting matrix in which the measurement subframe is s _m ,

Determining a PMI selected by the user equipment u after channel estimation of the first pilot signal of the measurement subframe s _m ,

Indicates that the PMI is

Corresponding precoding codeword,

Express

Corresponding conjugate transpose matrix,

Express

Corresponding conjugate transpose matrix.

In order to make the pilot power weighted by the first pilot signal unchanged, and keep the correlation of the PMI before and after the rotation unchanged, the network device constrains the first pilot weight matrix to be a unitary matrix, and then the network device maintains a local The queue is configured to store the first pilot weight matrix, and maintain another queue for storing the PMI fed back by each UE, and determine N reconstructed channel main feature vectors by using the first formula.

In some possible implementations, before determining the second pilot weight matrix according to the reconstructed channel main feature vector of each of the M scheduled UEs, determining the candidate pilot weight matrix set, and then The candidate pilot weight matrix is selected in a certain manner to select an alternative pilot weight matrix as the second pilot weight matrix. The specific implementation process includes the following possible ways:

The first possible manner is: if the first pilot weight matrix is a unit weight matrix, before determining the second pilot weight matrix according to the reconstructed channel main feature vector of each of the M scheduled UEs, If M is 1, the network device determines the candidate pilot weighting matrix set according to the reconstructed channel main feature vector corresponding to one UE and the precoding codeword corresponding to the one UE.

In some possible implementation manners, the determining, by the network device, the candidate pilot weighting matrix set according to the reconstructed channel primary feature vector corresponding to the UE and the precoding codeword corresponding to the one UE, includes: the network device according to the weight of one UE Constructing a channel main eigenvector and a precoding codeword corresponding to the one UE, using a second formula, determining an alternative pilot weighting matrix set, wherein the second formula is expressed as:

Among them, W _i ∈w ₁ ,

Representing a set of candidate pilot weighting matrices, W _i representing a precoding codeword of rank rank=1 with a PMI of i,

Represents a reconstructed channel main eigenvector corresponding to one UE, and w ₁ represents a PMI codebook with rank=1.

It can be seen that, if the single pilot is scheduled to be a single user, and the first pilot weight matrix is a unit weight matrix, the network device directly according to the reconstructed channel primary feature vector corresponding to one UE and the precoding codeword corresponding to the one UE. The second formula determines the set of candidate pilot weighting matrices with a small amount of computation.

The second possible manner is: if the first pilot weight matrix is at least one of a unit weight matrix and a preset pilot weight matrix, according to the reconstructed channel of each of the M scheduled UEs Before the primary eigenvector determines the second pilot weighting matrix, if M is 2, the network device determines the target weight matrix according to the reconstructed channel primary eigenvectors corresponding to the two UEs respectively, and then, when the two UEs respectively correspond to the reconstructed channel When the correlation of the primary eigenvectors is less than the first preset threshold, the network device determines the set of candidate pilot weighting matrices according to the precoding codewords corresponding to the two UEs and the target weight matrix.

In some possible implementation manners, the determining, by the network device, the target weight matrix according to the reconstructed channel primary feature vector corresponding to the two UEs includes: determining, by the network device, the reconstructed channel primary feature vector corresponding to the two UEs by using a third formula The target weight matrix, wherein the third formula is expressed as:

,among them,

Represents the target weight matrix,

Representing the reconstructed channel main eigenvector corresponding to u ₁ ,

Representing the reconstructed channel main eigenvector corresponding to u ₂ ,

Represents the weight vector corresponding to u ₁ ,

Represents the weight vector corresponding to u ₂ ,

Express

Conjugate transposed matrix,

Express

Conjugate transposed matrix,

Represents a diagonal array.

In some possible implementation manners, determining, by the network device, the candidate pilot weight matrix set according to the precoding codeword and the target weight matrix corresponding to the two UEs includes: the network device according to the precoding codewords and target rights corresponding to the two UEs The value matrix determines the set of candidate pilot weighting matrices using a fourth formula, wherein the fourth formula is expressed as:

among them,

Representing a set of candidate pilot weighting matrices, W _i representing a precoding codeword of rank=2 with a PMI of i,

Represents the target weight matrix.

It can be seen that if two users are scheduled, and if the first pilot weight matrix is a unit weight matrix and For at least one of the preset pilot weighting matrices, the network device first determines the target weight matrix corresponding to the two UEs, and the specific determining manner is, for example, a third formula. In general, the target weight matrix corresponding to each UE The corresponding power is the same. Then, the correlation of the reconstructed channel main feature vectors corresponding to the two UEs is compared. When the correlation between the reconstructed channel main feature vectors of the two UEs is less than the first preset threshold, the downlink channels corresponding to the two UEs are not The interference or the interference is small, wherein the first preset threshold is generally 1. The first preset threshold may be determined according to an actual situation, and is not specifically limited herein, and the network device is based on the target weight matrix and two The precoding codewords corresponding to the UEs respectively determine a corresponding set of candidate pilot weighting matrices, and the specific determining manner is the fourth formula.

A third possible manner is: if the first pilot weight matrix is at least one of a unit weight matrix and a preset pilot weight matrix, according to the reconstructed channel of each of the M scheduled UEs Before the main feature vector determines the second pilot weight matrix, if the M is greater than or equal to 2, the network device first determines the target weight matrix according to the reconstructed channel main feature vector corresponding to the at least two UEs respectively; when any two UEs correspond to the target When the correlation of the weight matrix is less than the second preset threshold, the network device determines the candidate pilot weight matrix set according to the precoding codeword corresponding to the at least two UEs and the target weight matrix.

In some possible implementations, determining, by the network device, the candidate pilot weight matrix set according to the precoding codeword corresponding to the at least two UEs and the target weight matrix comprises: precoding corresponding to the at least two UEs by the network device The codeword and the target weight matrix determine the set of candidate pilot weighting matrices using a fifth formula, wherein the fifth formula is expressed as:

among them,

Representing a set of candidate pilot weighting matrices, W _i representing a precoding codeword with a rank ≥ 2 and a PMI of i,

Represents the target weight matrix.

It can be seen that if at least two users are scheduled, and if the first pilot weight matrix is at least one of a unit weight matrix and a preset pilot weight matrix, the network device first determines target rights corresponding to the at least two UEs. The value matrix is determined by the third formula. Generally, the power corresponding to the target weight matrix corresponding to each UE is the same. When the correlation of the target weight matrix corresponding to any two of the at least two UEs is less than the second preset threshold, determining the preparation according to the target weight matrix and the precoding codeword corresponding to the at least two UEs The second preset threshold is determined by the network device according to the actual situation, for example, the second preset threshold is 1, where the second preset threshold is determined by the network device. No specific restrictions.

After determining the set of candidate pilot weighting matrices, selecting an alternative pilot weighting matrix from the candidate pilot weighting matrix set as the second pilot weighting matrix according to a preset manner, the specific implementation process includes the following: Several possible ways:

The first possible manner is: if the first pilot weight matrix is at least one of a unit weight matrix and a preset pilot weight matrix, according to the reconstructed channel main feature of each of the M scheduled UEs Determining, by the vector, the second pilot weighting matrix comprises: the network device randomly selecting the target precoding codeword, and selecting the candidate pilot weighting matrix corresponding to the target precoding codeword from the candidate pilot weighting matrix set according to the target precoding matrix, the network The device determines the candidate pilot weight matrix corresponding to the target precoding codeword as the second pilot weight matrix.

It can be seen that, if the first pilot weight matrix is at least one of a unit weight matrix and a preset pilot weight matrix, the network device randomly selects a precoding codeword from the N precoding codewords corresponding to the N UEs. Decoding a codeword, and selecting, from the candidate pilot weighting matrix set, an candidate pilot weighting matrix corresponding to the target precoding codeword according to the target precoding codeword, and then preparing the target precoding codeword corresponding to the target Selecting a pilot weighting matrix as the second pilot weighting matrix, wherein the mode is used for the second pilot weighting matrix determined under the non-measurement subframe, and the second pilot weighting matrix is used for the next pilot signal Weighted transmission, thereby improving the accuracy of the downlink channel.

The second possible manner is: if the first pilot weight matrix is a unit weight matrix, determining the second pilot weight matrix according to the reconstructed channel main feature vector of each of the M scheduled UEs includes: The network device determines the target precoding codeword according to a preset rule, and selects an alternative pilot weighting matrix corresponding to the target precoding codeword from the candidate pilot weighting matrix set according to the target precoding matrix, and then the network device pre-targets the target The candidate pilot weighting matrix corresponding to the encoded codeword is determined as the second pilot weighting matrix.

In some possible implementation manners, the determining, by the network device, the target precoding codeword according to the preset rule includes: determining, by the network device, the target precoding codeword by using a sixth formula, where the sixth formula is expressed as:

among them,

Indicates the target precoding codeword, and n denotes the sequence number of the measurement subframe before the measurement subframe s _m ,

Indicates that the measurement subframe is an alternate pilot weight matrix corresponding to s _m .

It can be seen that if the first pilot weighting matrix is a unit weighting matrix, the network device determines the target precoding codeword according to the sixth formula, and selects the target precoding codeword from the candidate pilot weighting matrix set according to the target precoding codeword. Corresponding candidate pilot weight matrix is used as the second pilot weight matrix, wherein the mode is used to measure a second pilot weight matrix determined under the subframe, and the second pilot weight matrix is used for the next pilot The frequency signal is weighted and transmitted, and the second pilot weighting matrix and the target precoding codeword are used for weighted transmission of the primary data signal, thereby effectively improving the accuracy of the downlink channel.

In a practical application, the network device may further determine the second pilot weight matrix according to the first pilot weight matrix, and the specific implementation process includes the following possible manners:

The first possible manner is: if the first pilot weight matrix is a preset pilot weight matrix, determining the second guide according to the reconstructed channel main feature vector of each of the M scheduled UEs The frequency weighting matrix includes: if the M is 1, the network device first acquires a target weight matrix of the UE, and then the network device determines the second pilot weight matrix according to the first pilot weight matrix and the target weight matrix of the UE. .

In some possible implementations, determining, by the network device, the second pilot weight matrix according to the first pilot weight matrix and the target weight matrix of the one UE, the network device first determining the first pilot weight matrix and the Whether the target weight matrix satisfies the seventh formula, wherein the seventh formula is expressed as:

Wherein, W _i represents a precoding codeword with a P=1 of rank=1, and w ₁ represents a PMI codebook of rank=1,

Express

a conjugate transposed matrix, Qmod(m, L) represents a first pilot weighting matrix in which the measurement subframe number of the L measurement subframes is m, and δ represents a constraint threshold value;

The network device determines the first pilot weighting matrix satisfying the seventh formula as the second pilot weighting matrix.

It can be seen that, if the first pilot weight matrix is a preset pilot weight matrix, and when scheduled as a single user, the network device first acquires a target weight matrix of the UE, and according to the first pilot weight matrix Determining the target pilot weight matrix with the target weight matrix of the one UE, and the specific determining manner is the seventh formula, where the method is used to measure the target pilot weight matrix determined under the subframe, where the target pilot The weighting matrix is used to weight the next pilot signal to effectively improve the downlink signal. The accuracy of the road.

In some possible implementation manners, the network device further needs to determine a target precoding codeword, and weight the next data signal according to the target precoding codeword and the second pilot weight matrix to improve accuracy of the downlink channel. After the network device may determine the second pilot weight matrix, and the target precoding codeword is not determined, the network device determines the second pilot weight matrix according to the first pilot weight matrix and the target weight matrix. The network device determines the target precoding codeword by using the eighth formula, wherein the eighth formula is expressed as:

among them,

Represents the target precoding codeword.

In some possible implementations, after determining the second pilot weight matrix according to the reconstructed channel primary feature vector of each of the M scheduled UEs, the network device sends the first weighted data signal to the N UEs, wherein the first weighted data signal is obtained by the network device weighting the first data signal according to the target precoding codeword and the second pilot weight matrix.

It can be seen that the network device weights the first data signal according to the target precoding codeword and the second pilot weight matrix, thereby obtaining a first weighted data signal, where the first data signal includes control information, etc., and the first weighting The data signal is sent to the N UEs to improve the accuracy of the downlink channel, and the TM4 in the MIMO system is suitable for downlink transmission to the MU, thereby effectively reducing signal interference between the MUs.

A second aspect of the present invention provides a network device configured to implement the functions of the method provided by the first aspect above. The function may be implemented by hardware or by executing corresponding software implemented by hardware, and the hardware or software includes one or more modules corresponding to the above functions.

The network device includes: a receiving module, a first determining module, a second determining module, a third determining module, and a sending module.

a receiving module, configured to receive N precoding matrix indication PMIs, where N is an integer greater than 1, the N PMIs are determined by the N user equipment UEs according to the first weighted pilot signals sent by the network device, where the A weighted pilot signal is obtained by the network device weighting the first pilot signal according to the first pilot weighting matrix.

The first determining module is configured to determine N reconstructed channel main feature vectors according to the N PMIs and the first pilot weight matrix received by the receiving module.

And a second determining module, configured to determine M scheduled UEs from the N UEs.

a third determining module, configured to determine a second pilot weighting matrix according to the reconstructed channel main feature vector of each of the M scheduled UEs determined by the second determining module, where M is an integer not greater than N .

a sending module, configured to send the second weighted pilot signal determined by the third determining module to the N UEs, where the second weighted pilot signal is determined by the network device according to the second pilot weighting matrix pair The second pilot signal is weighted.

A third aspect of the present invention provides a network device including a processor, a memory, a bus system, and an input/output I/O device, wherein the processor, the memory, and the I/O device are connected by a bus system, wherein the memory is stored One or more programs for providing to the processor operational instructions and data included in the one or more programs, the processor executing the program stored in the memory for implementing the steps in the method provided by the first aspect above .

The I/O device is configured to receive N precoding matrix indication PMIs, where N is an integer greater than 1, and the N PMIs are determined by the N user equipment UEs according to the first weighted pilot signals sent by the network device. The first weighted pilot signal is obtained by the network device weighting the first pilot signal according to the first pilot weight matrix.

The processor 301 is configured to determine N reconstructed channel main feature vectors according to the N PMIs and the first pilot weight matrix.

The processor 301 is further configured to determine M scheduled UEs from the N UEs, and determine a second pilot weight matrix according to the reconstructed channel main feature vector of each of the M scheduled UEs, where Where M is an integer not greater than N.

The I/O device 304 is further configured to send the second weighted pilot signal to the N UEs, where the second weighted pilot signal is used by the network device according to the second pilot weight matrix to the second The frequency signal is weighted.

A fourth aspect of the present invention provides a downlink transmission system, including a network device and N user equipment UEs, where N is an integer greater than 1, and the network device is in communication connection with the N UEs;

The network device is the network device described in the foregoing second aspect or any optional implementation manner of the second aspect.

A fifth aspect of the present invention provides a computer storage medium storing the above The program of the downlink transmission described in the first aspect or any alternative implementation of the first aspect.

Different from the prior art, the network device receives N PMIs, where the N PMIs are determined according to the first weighted pilot signals sent by the network device, and the first weighted pilot signals are the network. And the weighting of the first pilot signal by the device according to the first pilot weighting matrix. After the network device weights the first pilot signal, the UE does not see the first pilot signal, nor does it pass the first guide. The frequency signal determines the PMI, and the UE actually sees the first weighted pilot signal, which is determined by the first weighted pilot signal for downlink channel estimation, thereby expanding the PMI selection range, because the N The PMI is not the quantization of the real downlink channel, but the quantization of the downlink channel weighted by the first pilot weight matrix to the first pilot signal. Therefore, the network device needs to perform the corresponding inverse transform to correctly restore the real downlink channel. And determining, by the network device, the N reconstructed channel primary eigenvectors according to the N PMIs and the first pilot weighting matrix, and determining M scheduled UEs from the N UEs, and then according to the M scheduled UEs. Each of The reconstructed channel main feature vector of the UE determines the second pilot weight matrix, so that the second pilot signal can be weighted by the second weight matrix to obtain the second weighted pilot signal, and the second weighted pilot signal is obtained. The method is sent to N UEs, thereby reducing the quantization error of the downlink channel, better suppressing interference between users, and improving the accuracy of the downlink channel.

DRAWINGS

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly described below. It is obvious that the drawings in the following description are only some embodiments of the present invention. Other drawings can also be obtained from those skilled in the art based on these drawings without paying any creative effort.

1 is a schematic diagram of an embodiment of downlink transmission in the prior art;

2 is a network architecture diagram of a MIMO system according to an embodiment of the present invention;

3 is a schematic structural diagram of a network device according to an embodiment of the present invention;

4 is a schematic diagram of an embodiment of a downlink transmission method according to an embodiment of the present invention;

FIG. 5 is a schematic diagram of an application scenario of a downlink transmission method according to an embodiment of the present disclosure;

FIG. 6 is a schematic diagram of another application scenario of a downlink transmission method according to an embodiment of the present disclosure;

FIG. 7 is another schematic structural diagram of a network device according to an embodiment of the present invention;

FIG. 8 is another schematic structural diagram of a network device according to an embodiment of the present invention.

Detailed ways

The technical solutions in the embodiments of the present invention are clearly and completely described in the following with reference to the accompanying drawings in the embodiments of the present invention. It is obvious that the described embodiments are only a part of the embodiments of the present invention, but not all embodiments. All other embodiments obtained by a person skilled in the art based on the embodiments of the present invention without creative efforts are within the scope of the present invention.

The terms "first", "second", "third", "fourth", etc. (if present) in the specification and claims of the present invention and the above figures are used to distinguish similar objects without having to use To describe a specific order or order. It is to be understood that the data so used may be interchanged where appropriate so that the embodiments described herein can be implemented in a sequence other than what is illustrated or described herein. In addition, the terms "comprises" and "comprises" and "the" and "the" are intended to cover a non-exclusive inclusion, for example, a process, method, system, product, or device that comprises a series of steps or units is not necessarily limited to Those steps or units may include other steps or units not explicitly listed or inherent to such processes, methods, products or devices.

Before introducing the embodiments of the present invention, the terms that may be involved in the embodiments of the present invention are first introduced:

The term "precoding codebook": a matrix or vector for quantizing a MIMO channel set in a long term evolution (LTE) protocol, wherein the precoding codebook is represented as

Each precoding codebook includes a plurality of precoding matrices, wherein the precoding matrix is represented as

B denotes a precoding codebook size, the number of rows N _{T of the} matrix represents the number of antennas of the network device, the column number r represents the rank of the precoding matrix, and i represents the index of each codeword W in the precoding codebook.

The term "rank": is the rank based on the precoding codebook w. When the rank is 1, each PMI codeword is an N _T -dimensional complex sequence vector. When the rank is 2, each codeword is a complex matrix of N _T ×2. The rank may be determined by the UE according to the downlink signaling sent by the network device, or may be selected by the UE according to the current channel, and the UE feeds back the rank adopted by the UE while feeding back the PMI.

The term "pilot weighting matrix": a pilot signal matrix for weighting multiple antennas is N _T unitary matrix of dimension.

The term "CSI": is accurate instantaneous channel state information. For a MIMO channel, including a channel coefficient matrix, a channel correlation matrix, a channel feature vector, etc., the CSI fed back by the UE includes a PMI, a channel quality indicator (CQI). .

The term "channel main feature vector": The channel coefficient matrix is singular value decomposition (SVD), and the right singular vector corresponding to the largest singular value is the main eigenvector of the channel.

The term "measurement subframe": the network device transmits a CRS in each subframe, the UE performs downlink channel estimation on the CRS in each subframe, and the downlink channel estimation result is used for data channel demodulation of the subframe, but the UE The downlink channel estimation result is used to calculate CSI only in a partial subframe, and these subframes are measurement subframes. The subframes whose downlink channel estimation results are only used for demodulation are referred to as non-measurement subframes, and the measurement subframes are configured by the network device according to the LTE protocol, and all UEs served by the UE are notified by signaling.

It should be understood that the technical solution of the embodiments of the present invention may be applied to a MIMO system, where the MIMO technology refers to using multiple transmit antennas at the transmitting end, using multiple receiving antennas at the receiving end, and transmitting signals through multiple antennas at the transmitting end. Multi-antenna reception at the receiving end, thereby effectively improving the signal transmission efficiency. As shown in FIG. 2, in the framework of the MIMO system, the network device includes: a network device and a user equipment, where the network device sends data to the user equipment by means of downlink transmission, and the user equipment sends data to the network device by means of uplink transmission.

The user equipment can communicate with one or more core networks via a radio access network (RAN), and the user equipment can refer to (user equipment, UE), access user equipment, subscriber unit, subscriber station, mobile station, Mobile station, remote station, remote user equipment, mobile device, wireless communication device, user agent or user device. The access user equipment may be a cellular phone, a cordless phone, a session initiation protocol (SIP) phone, a wireless local loop (WLL) station, a personal digital assistant (PDA), and a wireless device. A communication-enabled handheld device, a computing device, or other processing device connected to a wireless modem, an in-vehicle device, a wearable device, a user device in a future 5G network, and the like.

The network device may be a device for communicating with the user equipment, for example, may be a GSM system or a base transceiver station (BTS) in CDMA, or may be a network device (nodeB, NB) in a WCDMA system. Can be an evolved network device in an LTE system (evolutional node B, eNB or eNodeB), or the network device may be a relay station, an access point, an in-vehicle device, a wearable device, and a network side device in a future 5G network or a network device in a future evolved PLMN network.

The following describes the structure of the network device in the embodiment of the present invention. As shown in FIG. 3, the network device 300 includes a processor 301, a memory 302, a bus system 303, and an input/output (I/O) device 304. The processor 301, the memory 302, and the I/O device 304 are connected by the bus system 303, wherein the memory 302 stores one or more programs, and the memory 302 is used to the processor. 301 providing operation instructions and data included in the one or more programs;

The I/O device 304 is configured to receive N precoding matrix indication PMIs, where N is an integer greater than 1, and the N PMIs are determined by the N user equipment UEs according to the first weighted pilot signals sent by the network device. The first weighted pilot signal is obtained by the network device weighting the first pilot signal according to the first pilot weight matrix;

The processor 301 is configured to determine N reconstructed channel main feature vectors according to the N PMIs and the first pilot weight matrix;

The processor 301 is further configured to determine M scheduled UEs from the N UEs, and determine a second pilot weight matrix according to the reconstructed channel main feature vector of each of the M scheduled UEs, where Where M is an integer not greater than N;

In some possible implementations, the first pilot weight matrix is at least one of a unit weight matrix and a preset pilot weight matrix.

In some possible implementations, the processor 301 is specifically configured to determine, according to the N PMIs, precoding codewords corresponding to the N PMIs, determine a conjugate transposed matrix corresponding to the N precoding codewords, and the first a conjugate transposed matrix corresponding to a pilot weighting matrix; the first pilot weight matrix, the conjugate transposed matrix corresponding to the N precoding codewords, and the first according to the precoding codewords corresponding to the N PMIs A conjugate transpose matrix corresponding to a pilot weight matrix determines the N reconstructed channel main eigenvectors.

In some possible implementations, the processor 301 is specifically configured to: according to the precoding codeword corresponding to the N PMIs, the first pilot weight matrix, and the conjugate transpose moment corresponding to the N precoding codewords And the conjugate transposed matrix corresponding to the first pilot weighting matrix determines the N reconstructed channel main eigenvectors by using a first formula, wherein the first formula is expressed as:

among them,

Indicates that the PMI is

Corresponding precoding codeword,

Express

Corresponding conjugate transpose matrix,

Express

Corresponding conjugate transpose matrix.

In an actual application, the processor 301 may determine the candidate pilot weight matrix set before determining the second pilot weight matrix, and select the second pilot weight matrix from the candidate pilot weight matrix set, and according to The second pilot weighting matrix weights the second pilot signal to obtain a second weighted pilot signal, and sends the second weighted pilot signal to the N UEs to improve the accuracy of the downlink channel, where the second pilot The signal is weighted by the first pilot signal for the next transmitted pilot signal for weighting. In practical applications, there are many ways to determine the set of alternative pilot weighting matrices. The following are some possible ways:

In some possible implementations, the processor 301 is further configured to determine, according to the reconstructed channel main feature vector of each of the M scheduled UEs, if the first pilot weight matrix is a unit weight matrix Before the two pilot weighting matrix, if M is 1, the candidate pilot weighting matrix set is determined according to the reconstructed channel primary eigenvector corresponding to one UE and the precoding codeword corresponding to the one UE.

In some possible implementations, the processor 301 is specifically configured to determine, by using a second formula, the candidate pilot weighting matrix set according to a reconstructed channel primary feature vector corresponding to one UE and a precoding codeword corresponding to the one UE, where , the second formula is expressed as:

Among them, W _i ∈w ₁ ,

It can be seen that if the single pilot is scheduled, and the first pilot weight matrix is a unit weight matrix, then The processor 301 directly determines the candidate pilot weighting matrix set according to the reconstructed channel main feature vector corresponding to one UE and the precoding codeword corresponding to one UE, and the specific determining manner is as follows, and the calculation amount is small.

In some possible implementations, the processor 301 is further configured to: if the first pilot weight matrix is at least one of a unit weight matrix and a preset pilot weight matrix, according to the M scheduled UEs Before the reconstructed channel main feature vector of each UE determines the second pilot weight matrix, if M is 2, the target weight matrix is determined according to the reconstructed channel main feature vector corresponding to the two UEs; when the two UEs respectively correspond When the correlation of the reconstructed channel main feature vector is less than the first preset threshold, the candidate pilot weight matrix set is determined according to the precoding codeword corresponding to the two UEs and the target weight matrix.

In some possible implementation manners, the processor 301 is specifically configured to determine, according to the reconstructed channel main feature vector corresponding to the two UEs, the target weight matrix by using a third formula, where the third formula is expressed as:

,among them,

Represents the target weight matrix,

Represents the weight vector corresponding to u ₁ ,

Represents the weight vector corresponding to u ₂ ,

Express

Conjugate transposed matrix,

Express

Conjugate transposed matrix,

Representing a diagonal array, used to make

with

The square of the modulus is 1/2.

In some possible implementation manners, the processor 301 is specifically configured to determine, according to the precoding codeword corresponding to the two UEs and the target weight matrix, the candidate pilot weighting matrix set by using a fourth formula, where The fourth formula is expressed as:

among them,

Represents the target weight matrix.

It can be seen that if two users are scheduled, and the first pilot weight matrix is at least one of a unit weight matrix and a preset pilot weight matrix, the processor 301 first determines target weights corresponding to the two UEs. Matrix, the way to determine the target weight matrix is as in the third formula. When the correlation between the reconstructed channel main feature vectors corresponding to the two UEs is less than the first preset threshold, the candidate pilot weight matrix is determined according to the target weight matrix and the precoding codewords corresponding to the two UEs respectively. Set, the specific method of determination is the fourth formula.

In some possible implementations, the processor 301 is further configured to: if the first pilot weight matrix is at least one of a unit weight matrix and a preset pilot weight matrix, according to the M scheduled UEs Before the reconstructed channel main feature vector of each UE determines the second pilot weight matrix, if M is greater than or equal to 2, the target weight matrix is determined according to the reconstructed channel main feature vector corresponding to the at least two UEs respectively; When the correlation of the target weight matrix corresponding to the UE is less than the second preset threshold, the candidate pilot weight matrix set is determined according to the precoding codeword corresponding to the at least two UEs and the target weight matrix.

In some possible implementation manners, the processor 301 is specifically configured to determine, according to the precoding codeword corresponding to the at least two UEs and the target weight matrix, the candidate pilot weighting matrix set by using a fifth formula, where the The five formula is expressed as:

among them,

Represents the target weight matrix.

It can be seen that when the at least two users are scheduled, the processor 301 first determines a target weight matrix corresponding to the at least two UEs, and the manner of determining the target weight matrix is as follows. When the correlation of the target weight matrix corresponding to any two of the at least two UEs is less than the second preset threshold, determining the candidate according to the target weight matrix and the precoding codeword corresponding to the at least two UEs The set of pilot weighting matrices is determined in a manner such as the fifth formula.

After the network device determines the candidate pilot weight matrix set, the second pilot weight matrix is determined from the candidate pilot weight matrix set. In practical applications, there are many ways to determine the second pilot weight matrix. Introduce possible ways:

In some possible implementations, if the first pilot weight matrix is a unit weight matrix and a preset At least one of the pilot weighting matrix, the processor 301 is specifically configured to randomly select a target precoding codeword, and select, according to the target precoding matrix, the target precoding codeword corresponding to the target pilot precoding matrix An alternative pilot weighting matrix; the candidate pilot weighting matrix corresponding to the target precoding codeword is determined as the second pilot weighting matrix.

It can be seen that when the first pilot weight matrix is at least one of a unit weight matrix and a preset pilot weight matrix, the processor 301 randomly selects a precoding codeword corresponding to any one of the UEs as the target precoding codeword, and The candidate pilot weighting matrix corresponding to the target precoding codeword is used as the second pilot weighting matrix, where the mode is used for the second pilot weighting matrix determined under the non-measurement subframe, and the second pilot weighting matrix For performing weighted transmission on the next pilot signal, for example, according to the second pilot weight matrix, the second pilot signal (the first pilot signal is downlink weighted for the next downlink weighted pilot signal) And weighting the second weighted pilot signal, and transmitting the second weighted pilot signal to the N UEs, thereby improving the accuracy of the downlink channel.

In some possible implementations, if the first pilot weight matrix is a unit weight matrix, the processor 301 is specifically configured to determine a target precoding codeword according to a preset rule, and according to the target precoding matrix, the candidate guide The candidate weighting matrix corresponding to the target precoding codeword is selected in the frequency weighting matrix; the candidate pilot weighting matrix corresponding to the target precoding codeword is determined as the second pilot weighting matrix.

In some possible implementations, the processor 301 is specifically configured to determine the target pre-coded codeword by using a sixth formula, where the sixth formula is expressed as:

among them,

Indicates that the measurement subframe is an alternate pilot weight matrix corresponding to s _m . Correspondingly,

As the second pilot weighting matrix.

It can be seen that if the first pilot weight matrix is a unit weight matrix, the processor 301 determines the target precoding codeword from the precoding codewords corresponding to the N UEs according to the sixth formula, and prepares the target precoding codewords. Selecting a pilot weighting matrix as the second pilot weighting matrix, wherein the method is used to measure a second pilot weighting matrix determined under a subframe, and the second pilot weighting matrix is used for the next pilot signal Weighted transmission, the second pilot weight matrix and the target precoding codeword are used for the next data signal Weighted transmission, thereby effectively improving the accuracy of the downlink channel.

In an actual application, the second pilot weight matrix may also be determined according to the first pilot weight matrix, and the following may be introduced in several ways:

In some possible implementations, if the first pilot weight matrix is a preset pilot weight matrix, the processor 301 is specifically configured to acquire a target weight matrix of a UE if M is 1, according to the first guide. The second weighting matrix is determined by a frequency weighting matrix and a target weight matrix of the one UE.

In some possible implementation manners, the processor 301 is specifically configured to determine whether the first pilot weight matrix and the target weight matrix satisfy the seventh formula, where the seventh formula is expressed as:

Express

The conjugate transposed matrix, Qmod(m, L) represents the first pilot weighting matrix of the measurement subframe number in the L measurement subframes, m, and δ represents the constraint threshold; the first formula will be satisfied A pilot weighting matrix is determined as the second pilot weighting matrix.

It can be seen that if the first pilot weight matrix is the preset pilot weight matrix, and if it is scheduled as a single user, the processor 301 first acquires a target weight matrix of the UE, and according to the first The pilot weighting matrix and the target weight matrix of the one UE determine the second pilot weight matrix, and the specific determining manner is the seventh formula, where the method is used to measure the second pilot weighting matrix determined under the subframe. The second pilot weight matrix is used for weighted transmission of the next pilot signal, thereby effectively improving the accuracy of the downlink channel.

In some possible implementations, after the processor 301 is further configured to determine the second pilot weight matrix according to the first pilot weight matrix and the target weight matrix, determine a target precoding codeword by using an eighth formula, where The eighth formula is expressed as:

among them,

Represents the target precoding codeword.

In some possible implementations, the processor 301 is further configured to: after determining the second pilot weight matrix according to the reconstructed channel primary feature vector of each of the M scheduled UEs, send the first weighted data signal Up to the N UEs, wherein the first weighted data signal is obtained by the network device weighting the first data signal according to the target precoding codeword and the second pilot weighting matrix.

It can be seen that, if the first pilot weight matrix is the preset pilot weight matrix, after the processor 301 first determines the second pilot weight matrix, and determining the target precoding codeword according to the eighth formula, where The second pilot weight matrix and the target precoding codeword are used for weighted transmission of the next data signal, thereby effectively improving the accuracy of the downlink channel.

Different from the prior art, the I/O device 304 receives N PMIs, where N is an integer greater than 1, and the N PMIs are the first weighted pilot signals transmitted by the N UEs according to the I/O device 304. Determining, the first weighted pilot signal is obtained by the processor 301 weighting the first pilot signal according to the first pilot weight matrix, and after the processor 301 weights the first pilot signal, the UE actually sees It is not the first pilot signal, nor the PMI is determined by the first pilot signal, and the UE actually sees the first weighted pilot signal, and the PMI is determined by using the first weighted pilot signal for downlink channel estimation. Therefore, the selection range of the PMI is expanded, because the N PMIs are not the quantization of the real downlink channel, but the quantization of the downlink channel weighted by the first pilot weight matrix by the first pilot weight matrix, therefore, the processor 301 The corresponding inverse transform is required to correctly restore the real downlink channel, and the processor 301 determines N reconstructed channel main feature vectors according to the N PMIs and the first pilot weight matrix, and then determines M of the N UEs from the N UEs. The scheduled UE is then based on the M scheduled UEs The reconstructed channel main feature vector of each UE determines a second pilot weight matrix, so that the second pilot signal can be weighted by the second weight matrix to obtain a second weighted pilot signal and passed through the I/O device. The second weighted pilot signal is sent to the N UEs, thereby reducing the quantization error of the downlink channel, better suppressing interference between users, and improving the accuracy of the downlink channel.

In the embodiment of the present invention, the processor 301 may also be referred to as a central processing unit (CPU). Memory 302 can include read only memory and random access memory and provides instructions and data to processor 301. A portion of the memory 302 may also include non-volatile random access memory (NVRAM). The specific components of the network device 300 are coupled together by a bus system 303 in a specific application. The bus system 303 may include a power bus, a control bus, a status signal bus, and the like in addition to the data bus. However, for clarity of description, various buses are labeled as bus system 303 in FIG.

The method disclosed in the foregoing embodiments of the present invention may be applied to the processor 301 or implemented by the processor 301. Processor 301 may be an integrated circuit chip with signal processing capabilities. In the implementation process, each step of the above method may pass through the integrated logic circuit of the hardware in the processor 301 or soft. The instructions in the form of pieces are completed. The processor 301 described above may be a general purpose processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), an off-the-shelf programmable gate array (FPGA) or other programmable logic device, a discrete gate or transistor logic device, or discrete hardware. Component. The methods, steps, and logical block diagrams disclosed in the embodiments of the present invention may be implemented or carried out. The general purpose processor may be a microprocessor or the processor or any conventional processor or the like. The steps of the method disclosed in the embodiments of the present invention may be directly implemented by the hardware decoding processor, or may be performed by a combination of hardware and software modules in the decoding processor. The software module can be located in a conventional storage medium such as random access memory, flash memory, read only memory, programmable read only memory or electrically erasable programmable memory, registers, and the like. The storage medium is located in the memory 302, and the processor 301 reads the information in the memory 302 and completes the steps of the above method in combination with its hardware.

FIG. 4 is a schematic diagram of an embodiment of a downlink transmission method according to an embodiment of the present invention. The downlink transmission method is applied to a MIMO system, and the specific process is as follows:

Step 401: The network device determines a first pilot signal used for downlink channel estimation.

In the embodiment of the present invention, the first pilot signal is used by the UE to perform channel estimation on the downlink channel. Therefore, the network device first determines the first pilot signal. Generally, the first pilot signal is a single frequency, and the network device is random. Selecting a part of the communication signal as the first pilot signal or determining the first pilot signal according to a preset rule, for example, the network device side has a pilot signal dedicated for downlink channel estimation.

Step 402: The network device determines a first pilot weight matrix according to the first pilot signal.

Different from the prior art, the network device does not directly send the first pilot signal to the UE, but first determines a first pilot weight matrix according to the first pilot signal, where the first pilot weight matrix is A precursor pilot weighting matrix for weighting the first pilot signal. In an actual application, the first pilot weight matrix may be an identity matrix, or may be a unitary matrix set in advance for the first pilot signal. Since the pilot weighting matrix is not used in the prior art to weight the pilot signal, Therefore, the first pilot weighting matrix used for weighting the pilot signal for the first time may be at least one of an identity matrix and a preset pilot weighting matrix, when the first pilot is used by using the first pilot weighting matrix for the first time. After the signal is weighted, the next pilot weight matrix is determined as a weighting of the next pilot signal, which is not specifically limited herein.

Step 403: The network device weights the first pilot signal according to the first pilot weight matrix to obtain a first weighted pilot signal, and sends the first weighted pilot signal to the N UEs.

The first weighted pilot signal is used by the N UEs for downlink channel estimation, and according to the downlink. The result of the channel estimation determines N PMIs, and then transmits the determined N PMIs to the network device, where N is an integer greater than one.

The network equipment obtains the first weighted pilot signal by weighting the first pilot signal according to the first pilot weight matrix, and the N UEs perform channel estimation on the first weighted pilot signal according to the existing channel estimation method, and the effect thereof is obtained. The downlink channel seen by the UE is transformed by the first pilot weight matrix. What the UE actually sees is not the first pilot signal, nor is the PMI determined by the first pilot signal, and the UE actually sees the first weighting. The pilot signal is determined by the first weighted pilot signal for downlink channel estimation, thereby expanding the PMI selection range.

Step 404: The N UEs determine N PMIs according to the first weighted pilot signal.

The N UEs perform downlink channel estimation according to the received first weighted pilot signal, and determine a corresponding PMI according to the result of the downlink channel estimation, wherein, in order to improve the accuracy of the PMI, each UE according to the received first weighted pilot signal The PMI corresponding to the precoding codeword with the best downlink channel quality is selected.

Step 405: The N UEs send the N PMIs to the network device.

Since the N PMIs are used by the network device to determine N reconstructed channel primary eigenvectors, the N UEs send the respective determined PMIs to the network device.

Step 406: The network device receives the N PMIs sent by the N UEs.

The network device receives the N PMIs sent by the N UEs, and may locally cache the N PMIs, so that the N PMIs are obtained in time for subsequent use.

Step 407: The network device determines N reconstructed channel main feature vectors according to the N PMIs and the first pilot weight matrix.

Different from the prior art, after weighting the first pilot signal, the N PMIs determined by the N UEs are not the quantization of the real downlink channel, but the downlink channel after the first pilot weight matrix transformation. Quantization, therefore, the corresponding inverse transformation needs to be performed on the network device side to correctly restore the real downlink channel. The specific method is to determine the main features of the N reconstructed channels according to the N PMIs and the first pilot weighting matrix fed back by the N UEs. vector.

In some possible implementation manners, after acquiring the N PMIs and the first pilot weight matrix, the network device determines, according to the N PMIs, N precoding codewords corresponding to the N PMIs, and then the network device determines the N a conjugate transposed matrix corresponding to the precoding codewords and a conjugate transposed matrix corresponding to the first pilot weight matrix, the first pilot weight matrix, the N according to the N precoding codewords The conjugate transposed matrix corresponding to the precoding codewords and the conjugate transposed matrix corresponding to the first pilot weight matrix determine the N reconstructed channel main eigenvectors.

The network device first determines corresponding N precoding codewords according to the N PMIs, and the pilot powers that are weighted by the first pilot signal are unchanged, and are kept N, because there is a corresponding relationship between the PMI and the precoding codewords. The correlation between the PMI codewords before and after the rotation is unchanged, and the first pilot weighting matrix is constrained to be a unitary matrix, and the conjugate transposed matrix corresponding to the N precoding codewords and the conjugate corresponding to the first pilot weighting matrix are determined. Transpose matrix.

In a practical application, the network device determines, according to the N precoding codewords, the first pilot weight matrix, the conjugate transposed matrix corresponding to the N precoding codewords, and the conjugate transposed matrix corresponding to the first pilot weight matrix. There are many ways to reconstruct the main feature vector of the channel. Among them, the following is one of the ways:

The network device determines, according to the N precoding codewords, the first pilot weight matrix, the conjugate transposed matrix corresponding to the N precoding codewords, and the conjugate transposed matrix corresponding to the first pilot weight matrix by using the first formula. Reconstructing the channel main feature vector, wherein the first formula is expressed as:

among them,

Indicates that the PMI is

Corresponding precoding codeword,

Express

Corresponding conjugate transpose matrix,

Express

Corresponding conjugate transpose matrix.

Step 408: The network device determines M scheduled UEs from the N UEs.

Where M is an integer not greater than N. In practical applications, not the quality of the downlink channel corresponding to each UE is good. Therefore, in order to improve the accuracy of the downlink channel, the network device determines to be scheduled according to the N reconstructed channel primary feature vectors and N CQIs of the N UEs. The UE, wherein the CQIs of the N UEs are stored locally in the network device, therefore, the network device can directly obtain the CQIs of the N UEs locally.

Step 409: The network device reconstructs a channel according to each of the M scheduled UEs. The main feature vector determines a second pilot weighting matrix.

Before the network device determines the second pilot weight matrix according to the reconstructed channel main feature vector of each of the M scheduled UEs, the network device generally determines the candidate pilot weight matrix set first, and prepares according to the preset rule. The selected pilot weighting matrix selects an alternative pilot weighting matrix as the second pilot weighting matrix. There are many ways to determine the candidate pilot weighting matrix set. The following are several ways that may be implemented:

In some possible implementation manners, if the first pilot weight matrix is a unit weight matrix, if M is 1, the network device determines, according to the reconstructed channel main feature vector corresponding to one UE and the precoding codeword corresponding to the one UE. A set of alternative pilot weighting matrices.

In a practical application, the network device may determine the second pilot weight matrix by using a second formula according to a reconstructed channel primary feature vector corresponding to a UE and a precoding codeword corresponding to the first UE, where the second formula represents for:

Among them, W _i ∈w ₁ ,

It can be seen that, if the single pilot is scheduled to be a single user, and the first pilot weight matrix is a unit weight matrix, the network device directly according to the reconstructed channel primary feature vector corresponding to one UE and the precoding codeword corresponding to one UE according to the second The formula determines the set of candidate pilot weighting matrices with a small amount of computation.

In another possible implementation manner, if the first pilot weight matrix is at least one of a unit weight matrix and a preset pilot weight matrix, if M is 2, the network device respectively reconstructs according to the two UEs. a channel principal feature vector determines a target weight matrix;

The network device determines the candidate pilot according to the precoding codeword corresponding to the two UEs and the target weight matrix when the correlation between the reconstructed channel main feature vectors of the two UEs is less than a first preset threshold. A set of weighting matrices.

In a practical application, the network device may determine the target weight matrix by using a third formula according to the reconstructed channel main feature vector corresponding to the two UEs, where the third formula is expressed as:

,among them,

Represents the target weight matrix,

Represents the weight vector corresponding to u ₁ ,

Represents the weight vector corresponding to u ₂ ,

Express

Conjugate transposed matrix,

Express

Conjugate transposed matrix,

Representing a diagonal array, used to make

with

The square of the modulus is 1/2.

The network device determines, according to the precoding codeword corresponding to the two UEs and the target weight matrix, a candidate pilot weighting matrix set by using a fourth formula, where the fourth formula is expressed as:

among them,

Represents the target weight matrix.

It can be seen that if two users are scheduled, and if the first pilot weight matrix is at least one of a unit weight matrix and a preset pilot weight matrix, the network device first determines a target weight matrix corresponding to the two UEs. The specific determining manner is the third formula. Generally, the power corresponding to the target weight matrix corresponding to each UE is the same. Then, the correlation of the reconstructed channel main feature vectors corresponding to the two UEs is compared. When the correlation between the reconstructed channel main feature vectors of the two UEs is less than the first preset threshold, the downlink channels corresponding to the two UEs are not The interference or the interference is small, wherein the first preset threshold is generally 1. The first preset threshold may be determined according to an actual situation, and is not specifically limited herein, and the network device is based on the target weight matrix and two The precoding codewords corresponding to the UEs respectively determine a corresponding set of candidate pilot weighting matrices, and the specific determining manner is the fourth formula.

In another possible implementation, if the first pilot weight matrix is at least one of a unit weight matrix and a preset pilot weight matrix, if M is greater than or equal to 2, the network device respectively corresponds to at least two UEs. Reconstructing the channel main feature vector to determine the target weight matrix;

When the correlation of the target weight matrix corresponding to any two UEs is less than the second preset threshold, the network The device determines an alternative pilot weighting matrix set according to the precoding codeword corresponding to the at least two UEs and the target weight matrix.

In a practical application, the network device may determine, according to the precoding codeword corresponding to the at least two UEs and the target weight matrix, the candidate pilot weighting matrix set by using a fifth formula, where the fifth formula is expressed as:

among them,

Represents the target weight matrix.

It can be seen that if at least two users are scheduled, and if the first pilot weight matrix is at least one of a unit weight matrix and a preset pilot weight matrix, the network device first determines target rights corresponding to the at least two UEs. The value matrix is determined by the third formula. Generally, the power corresponding to the target weight matrix corresponding to each UE is the same. When the correlation of the target weight matrix corresponding to any two of the at least two UEs is less than the second preset threshold, the network device determines, according to the target weight matrix and the precoding codeword corresponding to the at least two UEs. The second set of preset thresholds is determined by the network device according to the actual situation, for example, the second preset threshold is 1, This is not specifically limited.

In the embodiment of the present invention, after determining the set of candidate pilot weighting matrices, an alternative pilot weighting matrix may be selected from the pilot weighting matrix set to determine the second pilot weighting matrix, wherein the second is determined. There are many ways to use the pilot weighting matrix. Here are a few ways that you might implement:

In some possible implementation manners, if the first pilot weight matrix is at least one of a unit weight matrix and a preset pilot weight matrix, the network device first randomly selects a target precoding codeword, and according to the target precoding code Selecting, from the candidate pilot weighting matrix, the candidate pilot weighting matrix corresponding to the target precoding codeword, and then determining, by the network device, the candidate pilot weighting matrix corresponding to the target precoding codeword as the second Pilot weighting matrix.

It can be seen that, if the first pilot weight matrix is at least one of a unit weight matrix and a preset pilot weight matrix, the network device randomly selects a precoding codeword from the N precoding codewords corresponding to the N UEs. Decoding a codeword, and selecting, from the candidate pilot weighting matrix set, an candidate pilot weighting matrix corresponding to the target precoding codeword according to the target precoding codeword, and then preparing the target precoding codeword corresponding to the target Selecting a pilot weighting matrix as the second pilot weighting matrix, wherein the mode is used for non-measurement A second pilot weighting matrix determined under the subframe, the second pilot weighting matrix is used for weighted transmission of the next pilot signal, thereby improving the accuracy of the downlink channel.

In other possible implementation manners, if the first pilot weight matrix is a unit weight matrix, the network device selects a precoding codeword from the N corresponding N precoding codewords according to a preset rule to determine the target pre- Encoding a codeword, and selecting an candidate pilot weighting matrix corresponding to the target precoding codeword from the candidate pilot weighting matrix set according to the target precoding codeword, and then selecting the candidate pilot corresponding to the target precoding codeword The weighting matrix is determined as the second pilot weighting matrix.

In an actual application, the network device may determine the target pre-encoded codeword by using a sixth formula, where the sixth formula is expressed as:

among them,

In a practical application, the network device may further determine the second pilot weight matrix according to the first pilot weight matrix, wherein there are many ways to determine the second pilot weight matrix, and the following are possible ways. :

In some possible implementation manners, if the first pilot weight matrix is a preset pilot weight matrix, if M is 1, the network device acquires a target weight matrix of the UE, and then according to the first pilot weight matrix The target weight matrix of the one UE determines the second pilot weight matrix.

In an actual application, the network device determines whether the first pilot weight matrix and the target weight matrix satisfy the seventh formula, wherein the seventh formula is expressed as:

Express

It can be seen that, if the first pilot weight matrix is a preset pilot weight matrix, and when scheduled as a single user, the network device first acquires a target weight matrix of the UE, and according to the first pilot weight matrix Determining the target pilot weight matrix with the target weight matrix of the one UE, and the specific determining manner is the seventh formula, where the method is used to measure the target pilot weight matrix determined under the subframe, where the target pilot The weighting matrix is used for weighted transmission of the next pilot signal, thereby effectively improving the accuracy of the downlink channel.

In some possible implementation manners, the network device further needs to determine a target precoding codeword, and weight the next data signal according to the target precoding codeword and the second pilot weight matrix to improve accuracy of the downlink channel. Since the network device may first determine the second pilot weighting matrix and does not determine the target precoding codeword, the network device determines the target precoding codeword by using the eighth formula, wherein the eighth formula is expressed as:

among them,

Represents the target precoding codeword.

It can be seen that, if the first pilot weight matrix is a preset pilot weight matrix, after the network device first determines the target pilot weight matrix, and determining the target precoding codeword according to the eighth formula, where the second guide The frequency weighting matrix and the target precoding codeword are used for weighted transmission of the next data signal, thereby effectively improving the accuracy of the downlink channel.

Step 410: The network device weights the second pilot signal according to the second pilot weight matrix to obtain a second weighted pilot signal.

Step 411: The network device sends the second weighted pilot signal to the N UEs.

After determining the second pilot weight matrix, the network device weights the second pilot signal according to the second pilot weight matrix, thereby obtaining a second weighted pilot signal, and sending the second weighted pilot signal to the N UEs, thereby improving the accuracy of the downlink channel.

The embodiment shown in FIG. 4 introduces a process in which a network device first determines a second pilot weight matrix, and then weights the second pilot signal according to the second pilot weight matrix to obtain a second weighted pilot signal, where possible. In an embodiment, the network device weights the first data signal according to the target precoding codeword and the second pilot weight matrix, thereby obtaining a first weighted data signal, where the first data signal includes control information, etc., and the A weighted data signal is sent to the N UEs to improve the accuracy of the downlink channel, and the TM4 in the MIMO system is suitable for downlink transmission to the MU, thereby effectively reducing signal interference between the MUs.

The following describes the downlink transmission method in the embodiment of the present invention with reference to a specific example. As shown in FIG. 5, a schematic diagram of an application scenario of the downlink transmission method in the embodiment of the present disclosure includes:

In practical applications, the network device is used as the base station, and the first pilot signal and the second pilot signal are both CRS:

The base station determines a CRS for downlink channel estimation, and generates a first pilot weight matrix according to the CRS. If the first pilot weight matrix is a unit weight matrix, the base station buffers the generated first pilot weight matrix, the first guide A frequency weighting matrix is used to weight the CRS.

The base station performs weighting processing on the CRS according to the first pilot weight matrix to obtain a weighted pilot signal, that is, a first weighted pilot signal, and sends the first weighted pilot signal to N UEs, where N is greater than An integer of 1 such that the N UEs perform downlink channel estimation according to the first weighted pilot signal, and the N UEs determine N PMIs and N CQIs of the corresponding downlink channel according to the result of the downlink channel estimation, and then, N The UE feeds back the N PMIs and the N CQIs to the base station, and the base station locally buffers the N PMIs and N CQIs received from the N UEs for subsequent direct use.

The base station performs channel reconstruction according to the determined first pilot weight matrix and the N PMIs received from the N UEs, because the N PMIs determined by the N UEs are not the quantization of the real channel, but are subjected to the first pilot weighting. Quantization of the downlink channel after the matrix transformation. Therefore, the base station side needs to perform the corresponding inverse transform to correctly restore the real downlink channel. The specific method is that the base station determines N according to the N PMIs and the first pilot weight matrix. Reconstructing the channel main feature vector, wherein the specific process of determining the N reconstructed channel main feature vectors is: recording that the downlink channel of UE _u is H _u (N _R × N _T complex matrix, and N _R is the number of UE receiving antenna ports, N _T is the number of antenna ports transmitted by the base station), and the base station weights the CRS by using the first pilot weight matrix Q _T (N _R × N _T complex matrix) used in the subframe t, but to maintain the CRS weighted pilot The power is unchanged, and the correlation before and after the rotation of the PMI codeword is kept unchanged, and the first pilot weight matrix is constrained to be a unitary matrix. UE _u performs channel estimation based on the CRS of subframe t and selects rank=1 PMI as i _u,t , and the corresponding rank=1 precoding codeword is recorded as

The measurement subframe is denoted as s ₁ , s ₂ ... s _m , and the base station maintains a queue of length L for each UE _u

For storing the PMI fed back by the UE, and maintaining a queue of length L, Que ^Wgt, for storing the used first pilot weight matrix, the queue is from the ^beginning to the end, and each time a measurement subframe s _m is used, the subframe is used. First pilot weighting matrix used by t

In the queue Que ^Wgt , the base station receives the UE _u calculated for the measurement subframe s _m

Then queue it

Assume that in subframe t, the measurement subframe corresponding to the last L feedback PMI received by the base station is: s ₁ , s ₂ ... s _m , then the elements from the beginning to the end of the queue Que ^Wgt are Q ₁ , Q ₂ ... Q _m ,queue

The elements from beginning to end are:

The base station determines N reconstructed channel main eigenvectors (hereinafter abbreviated as reconstructed channels) as follows:

among them,

Indicates the PMI selected by the user equipment u after channel estimation for the CRS of the measurement subframe s _m ,

Indicates that the PMI is

Corresponding precoding codeword,

Express

Corresponding conjugate transpose matrix,

Express

Corresponding conjugate transpose matrix.

The specific approach is: seeking

The SVD is then taken to the right singular vector corresponding to its largest singular value. The setting criterion of the queue length L (ie, the length of the reconstruction window) is that the time used for the L times of feedback is within the channel coherence time, and L is as large as possible. For example: Calculate the formula according to the coherence time

For a carrier frequency of 2 GHz, the user mobility is 3 km/h, the coherence time is about 76 ms, and if the feedback period is 10 ms, then L ≤ 8. For the sake of conservatism, L=5 may be taken, but is not limited to this value, and the calculation of the reconstructed channel is performed only when the base station receives the PMI fed back by the UE. In a subframe between two PMI feedbacks of one UE, the reconstructed channel is equal to the result of the latest channel reconstruction calculation, and the reconstructed channel is used together with the fed back CQI as a downlink scheduling module (for determining the number of users scheduled) Input.

After the base station determines the reconstructed channel, the cached user CQI is obtained, and the base station determines whether the single-user scheduling or the multi-user scheduling is performed according to the CQI and the result of the reconstructed channel, that is, determining M scheduled UEs from the N UEs, where M is not An integer greater than N. If the scheduling module decides to schedule only one UE in the subframe t, the reconstructed channel of one UE

As the target weight for downlink transmission. Since TM4 only allows the selection of the weight matrix from the precoding codebook, it is necessary to find a PMI codeword W _i ∈w _{1 with} rank= ₁ (w ₁ is the rank=1 PMI codebook, and each codeword is N _T × 1 complex vector, as defined in 3GPP TS 36.211), such that there is an alternative pilot weighting matrix set

Rotate W _i to

The existence of the unitary matrix satisfying the above formula is not unique, and one is to solve the set of alternative pilot weighting matrices.

The method is as follows:

First, two sets of complex vectors are randomly generated, each group containing (N _T -1) N _T ×1 complex vectors:

and

among them,

Is the first set of auxiliary vectors,

Is the second set of auxiliary vectors.

Then right

versus

Run the Gram-Schmidt orthogonalization operation (as detailed below), so as to constitute two orthonormal basis (since W _i and

Are unit vectors, which are themselves in the standard orthonormal basis):

a unitary matrix composed of the above-mentioned standard orthogonal basis

Then the set of candidate pilot weighting matrices is:

The step of the Gram-Schmidt orthogonalization is to transform a set of N N-dimensional vectors {X ₁ , X ₂ , X _N } into a set of standard orthogonal sets.

If the scheduling module decides that a total of r user pairs are paired by the UE subset U={u ₁ ,...u _r } in the subframe t, according to the current reconstructed channel of the users

The calculated downlink transmission weight matrix is recorded as

(N _T × r complex matrix, which is hereinafter referred to as channel reconstruction-beamforming (English full name: Channel Reconstruction-BeamForming, abbreviated: CR-BF) weight), each column represents the transmission weight of each paired user , each user's weight power is equally divided, namely:

Since TM4 only allows the selection of the weight matrix from the codebook, a rank=r PMI codeword W _i ∈w _{r is found} (w _r is the rank=r PMI codebook, and each codeword is N _T ×r Complex matrix, as defined in 3GPP TS 36.211), such that there is an alternative pilot weighting matrix set

Just rotate W _i to

which is

The PMI codebook defined by the LTE protocol has such a property that each column of each codeword matrix is orthogonal, and since the matrix matrix transformation maintains the correlation between vectors, it must be guaranteed.

The columns are also orthogonal, and there is a unitary matrix that strictly satisfies the above formula. However, in practical applications, it is not guaranteed that the weights of the scheduled multiple users are strictly orthogonal. Therefore, the present invention proposes the following method for solving the candidate pilot weighting matrix set based on scheduling constraints:

First, a constraint is added to the existing user pairing criteria: the correlation between the CR-BF weights of any two paired users must be lower than a preset threshold z∈(0,1), namely:

For example: take z=0.1, the actual value is not limited to this value.

In some possible implementation manners, in a scenario for pairing up to two users, it is directly determined according to the reconstructed channel of the user whether the matching requirement is met, and if u ₁ and u _{2 are} paired, according to the weight of the two users Construct a channel to calculate the transmission weight:

,among them,

Represents the target weight matrix,

Represents the weight vector corresponding to u ₁ ,

Represents the weight vector corresponding to u ₂ ,

Express

Conjugate transposed matrix,

Express

Conjugate transposed matrix,

Representing a diagonal array, used to make

with

The square of the modulus is 1/2.

Among them, diagonal array

The effect is that the weight vector of the weight matrix is 0.5, and the weight vector sent by the two users is 1, that is:

Since the weight has the following important properties, the correlation between the weights of the two users is equal to the correlation between the reconstructed channels, namely:

It can be seen that when two users are paired, whether the pairing condition is satisfied is directly determined according to the reconstructed channels of the two users.

Thereby reducing the computational complexity in the user scheduling process.

Then, two sets of complex vectors are randomly generated, each group containing N _T -r N _T ×1 complex vectors:

and

Second, remember that W _i =[W _i,1 ,...,W _i,r ],

versus

The Gram-Schmidt orthogonalization operation is performed separately to form two sets of standard orthogonal bases:

Finally, the unitary matrix composed of the above-mentioned standard orthogonal basis

Then determine the set of candidate pilot weighting matrices as:

In the above process, the calculation of the set of alternative pilot weighting matrices depends on the selected PMI. For the precoding codewords W _i (rank=1 or rank>1) corresponding to different PMIs, the corresponding candidate pilot weighting matrix set can be obtained, but the first pilot weighting matrix pair is not considered in this process. The impact of channel reconstruction performance. In principle, in the channel reconstruction window, it is desirable that the first pilot weight matrix rotates the channel as uniformly as possible, so that the PMI quantization error is uniformly distributed, and the quantization error can be reduced by the reconstruction operation, that is, from the candidate pilot. The second pilot weighting matrix is selected as the weighted transmission of the next CRS, and the target precoding codeword corresponding to the second pilot weight matrix and the second pilot weight matrix are used as the weighted transmission of the next data signal. . Therefore, the present invention proposes a selection method of the second pilot weighting matrix as follows:

The first type: in the initial state of the subframe t, for the downlink measurement subframe s ₀ , the scheduled user set is U ₀ , the number of scheduling users is r ₀ , and the CR-BF weight is

Randomly selecting a precoding codeword in a precoding codebook with rank=r ₀

Calculate

The second pilot weighting matrix of the CRS as the subframe s ₀ is:

The second type: in the downlink measurement subframe s _m , m = 1, 2, ..., the scheduling user set is U _m , the number of scheduling users is r _m , and the CR-BF weight is

The target precoding codeword is selected in the precoding codebook of rank=r _m according to the following formula:

The meaning of the formula is: in the measurement sub-frame s _m , calculate the rotation matrix corresponding to all possible pre-coded code words W _i

Then the determined pilot weighting matrix of the previous measurement subframes one by one

Compare, select the precoding codeword that maximizes the minimum distance

Weighting of data signals for subframe s _m , corresponding candidate pilot weighting matrix

The second pilot weighting matrix of the CRS as the subframe s _m is:

Where dist(A, B) is defined as the distance between two 酉 matrices A=[a ₁ , a ₂ ,...a _N ] and B=[b ₁ ,b ₂ ,...b _N ], which represents the 酉 matrix The effect of the channel transformation, the greater the distance, the more uniform the rotation of the channel. One specific definition that can be used is:

The third type: in the non-measurement subframe s, the CR-BF weight calculated according to the scheduling result of the subframe is recorded as

In the precoding codebook, W _i ∈w _r (r is the number of scheduled users of the subframe s) is selected in an arbitrary manner, and the calculation is performed.

Any of the ways referred to herein include random selection, or the same selection as the measurement sub-frame, or remain consistent with the PMI used in the previous measurement sub-frame.

It can be seen that the accuracy of the downlink channel is improved by weighting the CRS and channel reconstruction. Obtaining an alternative pilot weighting matrix set, and selecting a precoding codeword from the corresponding precoding codeword in the candidate pilot weighting matrix set to rotate to a BF weight corresponding to the SU or the MU, thereby making the codebook based The precoding codeword can achieve the effect of non-codebook based BF. The accuracy of channel reconstruction is maximized by selecting the second pilot weighting matrix of the most uniform rotation channel in the candidate pilot weight matrix.

FIG. 6 is a schematic diagram of another application scenario embodiment of a downlink transmission method according to an embodiment of the present disclosure, where a specific process includes:

Different from the embodiment shown in FIG. 5, in the embodiment of FIG. 6, the base station sets the first pilot weight matrix in advance, and weights the first pilot signal according to the preset first pilot weight matrix. Wherein, the first pilot weight matrix used in the measurement subframe is set offline, and a set of L N _T × N _T酉 matrices is pre-set, which is denoted as p={Q ₀ , Q ₁ , ..., Q _L-1 }, L is equal to the reconstructed window length, as illustrated in Figure 5. The specific first pilot weight matrix form includes but is not limited to the following three types:

The first is the MUB weighting matrix:

For the d-dimensional complex vector space, the two sets of standard orthogonal bases E={e ₀ , e ₁ ,..., e _d-1 } and F={f ₀ ,f ₁ ,...,f _d-1 } are called "Mutually Unbiased Bases" (English: Muttaly Unbiased Bases, abbreviated: MUB), if and only if the modulus square of the inner product between any two base vectors is equal to the reciprocal of the space dimension:

It has been proved theoretically that if the spatial dimension d is exactly the integer power of a prime number, then the (d+1) set of standard orthogonal bases must be found to form the MUB of the space.

Current LTE system design, the number of antenna ports of the base station is always N _T is an integer power of 2, so the total structure can comprise (N _T +1) orthonormal basis of MUB:

l=0,1,...,N _T , and each base vector in each set of standard orthogonal bases is arranged in a matrix to obtain (N _T +1) unitary matrices:

In general, the reconstruction window length is set to L ≤ (N _T +1), so the set of the first L matrices Q={Q ₀ , Q ₁ , . . . , Q _L-1 } is taken as the first pilot weight matrix. set.

The second is the Kerdock weighting matrix:

For a base station of 2 antenna ports or 4 antenna ports, there is a simplified MUB weighting matrix, which is characterized in that each element in the matrix only takes values in {0, ±1, ±j}. This feature is beneficial to reduce the storage overhead of the offline weight matrix and the computational overhead when weighting.

The first pilot weighting matrix set when the base station is a 2-antenna port is Q={Q ₀ , Q ₁ , Q ₂ }, where

The first pilot weighting matrix set when the base station is a 4-antenna port is Q={Q ₀ , Q ₁ , Q ₂ , Q ₃ , Q ₄ }, where

The third is the phase rotation weighting matrix:

At present, most LTE base stations use cross-polarized antennas, that is, antenna arrays can be divided into two sets of polarization directions. Generally, antenna port numbers 0 to (N _T /2-1) are assigned to one polarization direction antenna, and antenna ports are used. The number N _T /2 to (N _T -1) is assigned to the antenna of the other polarization direction.

When the base station is a 2-antenna port, the first pilot weight matrix is in the following form:

An example of the value of the rotational phase is L = 3, θ ₀ =0, θ ₁ = π/2, θ ₂ = π / 4, but is not necessarily limited thereto, and θ _l represents the angle of rotation between the two polarization directions.

When the base station is a 4-antenna port, the first pilot weight matrix is in the following form:

Where m=0,1,...,M-1,n=0,1,...,N-1 are the indices of the two sets of phase rotation angles respectively, M×N=L, total index l=m+(n-1) M.

Indicates the angle of rotation between adjacent antennas in the same polarization direction. An example of a rotational phase value is:

But it is not necessarily limited to this.

In practical applications, regardless of the offline setting of the first pilot weighting matrix set, the first pilot signal is weighted using the respective matrices in the set in the measurement subframe. Assuming that the measurement subframe is s ₀ , s ₁ , s ₂ , . . . , in the subframe s _m , the first pilot weight matrix Q _l , l=mod(m, L) is used, where mod(m, L) represents The integer m takes the remainder of the integer L.

The measurement subframe is only used for SU scheduling. The reason why the MU is not used is that the preset first pilot weighting matrix cannot guarantee that the transmission weight is consistent with the precoding codeword. At this time, the demodulation performance of the UE is lost, and the robustness of the SU is strong, and the demodulation loss is high. The impact on user rate is small, and if MU is used, the user rate loss may be large.

Adding a constraint based on the existing SU scheduling criteria requires that a precoding matrix can be found for the scheduled users. After the first pilot weight matrix is rotated, the correlation between the CR-BF weights and the CR-BF weights is not lower. A certain threshold. Specifically, in measuring the subframe s _m , suppose the CR-BF weight of a certain UEu is

The first pilot weighting matrix used is Qmod(m,L), and the increased scheduling constraint is:

The threshold value ranges from δ∈(0,1), and the larger the constraint, the stricter the constraint. An example is δ = 0.8, but is not limited to this. It can be seen that the first pilot weight matrix that satisfies the above formula is used as the second pilot weight matrix, and the second pilot weight matrix is used for weighted transmission of the next pilot signal.

Users who do not satisfy this constraint cannot be scheduled in the current subframe. If the constraint is satisfied, the selected precoding matrix is:

among them,

Represents the target precoding codeword. After determining the target precoding codeword, the target precoding codeword and the second pilot weighting matrix are used for weighted transmission of the next data signal.

The MU scheduling in the non-measurement subframe, the scheduling criterion modification, the CR-BF weight calculation, the second pilot weight matrix calculation and the PMI selection are similar to the embodiment shown in FIG. 5, except that in the non-measurement subframe There is no need to consider the influence of the first pilot weighting matrix on channel reconstruction, so the PMI can be arbitrarily chosen.

In order to facilitate the implementation of the above related method of the embodiments of the present invention, a network device for supporting the foregoing method is also provided below.

Referring to FIG. 7, a schematic structural diagram of a network device 700 in the embodiment of the present invention, the network device is a device in a multiple input multiple output system, the network device 700 includes: a receiving module 701, a first determining module 702, and a second determining Module 703, third determining module 704 and transmitting module 705.

The receiving module 701 is configured to receive N precoding matrix indication PMIs, where N is an integer greater than 1, and the N PMIs are determined by the N user equipment UEs according to the first weighted pilot signals sent by the network device. The first weighted pilot signal is obtained by the network device weighting the first pilot signal according to the first pilot weight matrix;

The first determining module 702 is configured to determine N reconstructed channel main feature vectors according to the N PMIs and the first pilot weight matrix received by the receiving module 701;

a second determining module 703, configured to determine M scheduled UEs from the N UEs;

a third determining module 704, configured to determine, according to the second determining module 703, the M Determining, by the reconstructed channel main feature vector of each of the scheduled UEs, a second pilot weighting matrix, where M is an integer not greater than N;

The sending module 705 is configured to send the second weighted pilot signal determined by the third determining module 704 to the N UEs, where the second weighted pilot signal is determined by the network device The second pilot weight matrix is weighted by the second pilot signal.

Different from the prior art, the receiving module 701 receives N PMIs, where N is an integer greater than 1, and the N PMIs are determined by the N UEs according to the first weighted pilot signals sent by the network device, and The first weighted pilot signal is obtained by the network device weighting the first pilot signal according to the first pilot weight matrix. When the network device weights the first pilot signal, the UE actually sees that the first pilot signal is not the first one. The pilot signal does not determine the PMI by using the first pilot signal, and the UE actually sees the first weighted pilot signal, which is determined by using the first weighted pilot signal for downlink channel estimation, thereby expanding the PMI. The selection range of the PMI, since the N PMIs are not the quantization of the real downlink channel, but the quantization of the downlink channel weighted by the first pilot weight matrix by the first pilot weight matrix, therefore, the network device needs to respond The inverse transform can correctly restore the real downlink channel, and the network device determines N reconstructed channel main feature vectors according to the N PMIs and the first pilot weight matrix, and the second determining module 703 determines M from the N UEs. Being scheduled The UE, and then the third determining module 704 determines the second pilot weighting matrix according to the reconstructed channel main feature vector of each of the M scheduled UEs determined by the second determining module 703, so that the first pilot weighting matrix can be adopted. The second weighting matrix weights the second pilot signal to obtain the second weighted pilot signal, and the sending module 705 sends the second weighted pilot signal to the N UEs, thereby reducing the quantization error of the downlink channel and better suppressing the inter-user The interference improves the accuracy of the downlink channel.

Please refer to FIG. 8 , which is another schematic structural diagram of a network device 700. The network device 700 includes: a receiving module 701, a first determining module 702, a second determining module 703, a third determining module 704, and a sending module 705, and a fourth determining. Module 706.

The receiving module 701 is configured to receive N precoding matrix indication PMIs, where N is an integer greater than 1, and the N PMIs are determined by the N user equipment UEs according to the first weighted pilot signals sent by the network device. The first weighted pilot signal is obtained by the network device weighting the first pilot signal according to the first pilot weight matrix.

In some possible implementation manners, the first pilot weight matrix is a unit weight matrix, preset At least one of the pilot weighting matrices.

The first pilot weighting matrix is a target pilot weighting matrix determined by the last pilot weighting, and is used to weight the pilot signal of this time. Since the pilot signal is not weighted in the prior art, the pilot is initially used. The signal-weighted first pilot weighting matrix is at least one of a unit weighting matrix and a preset pilot weighting matrix, and the target pilot weighting matrix determined by weighting the second pilot signal is used as the third first guiding And frequency-weighting the matrix, and weighting the third pilot signal according to the first pilot weight matrix, and so on, which is not specifically limited herein.

The first determining module 702 is configured to determine N reconstructed channel main feature vectors according to the N PMIs and the first pilot weight matrix received by the receiving module 701.

The first determining module 702 determines a plurality of reconstructed channel main feature vectors according to the N PMIs and the first pilot weight matrix. One possible manner includes:

The first determining module 702 is specifically configured to determine N precoding codewords corresponding to the N PMIs according to the N PMIs; determine a conjugate transposed matrix corresponding to the N precoding codewords, and the a conjugate transposed matrix corresponding to the first pilot weight matrix; the first pilot weight matrix, the conjugate transposed matrix corresponding to the N precoded codewords according to the N precoding codewords The conjugate transposed matrix corresponding to the first pilot weight matrix determines the N reconstructed channel main eigenvectors.

In some possible implementations, the first determining module 702 is specifically configured to: according to the N precoding codewords, the first pilot weight matrix, and the conjugate transitions corresponding to the N precoding codewords The set matrix and the conjugate transposed matrix corresponding to the first pilot weight matrix determine the N reconstructed channel main feature vectors by using a first formula, wherein the first formula is expressed as:

among them,

Indicates that the PMI is

Corresponding precoding codeword,

Express

Corresponding conjugate transpose matrix,

Express

Corresponding conjugate transpose matrix.

The second determining module 703 is configured to determine M scheduled UEs from the N UEs.

a third determining module 704, configured to determine a second pilot weighting matrix according to the reconstructed channel main feature vector of each of the M scheduled UEs determined by the second determining module 703, where An integer not greater than N.

In some possible implementation manners, the third determining module 704 determines the candidate pilot weight matrix before determining the second pilot weight matrix according to the reconstructed channel primary feature vector of each of the M scheduled UEs. The set, and then selects an alternative pilot weighting matrix as the second pilot weighting matrix in a certain manner in the candidate pilot weighting matrix set. The specific implementation process includes the following possible ways:

The first possible mode is: a fourth determining module 706, configured to: if the first pilot weight matrix is the unit weight matrix, the third determining module 704 is configured according to the M scheduled UEs Before the reconstructed channel main feature vector of each UE determines the second pilot weight matrix, if the M is 1, the reconstructed channel main feature vector corresponding to one UE and the precoding codeword corresponding to the one UE are determined. Select the pilot weighting matrix set.

In some possible implementation manners, the fourth determining module 706 is specifically configured to determine, by using a second formula, an alternative pilot weighting according to a reconstructed channel primary feature vector corresponding to one UE and a precoding codeword corresponding to the one UE. a set of matrices, wherein the second formula is expressed as:

Among them, W _i ∈w ₁ ,

The second possible mode is: the fourth determining module 706 is configured to: if the first pilot weight matrix is at least one of the unit weight matrix and the preset pilot weight matrix, the third The determining module 704 determines, according to the reconstructed channel main feature vector of each of the M scheduled UEs, the second pilot weighting matrix, if the M is 2, according to the reconstructed channel corresponding to the two UEs respectively The main feature vector determines a target weight matrix; when the two UEs respectively correspond to the reconstructed channel main feature direction When the correlation of the quantity is less than the first preset threshold, the candidate pilot weight matrix set is determined according to the precoding codeword corresponding to the two UEs and the target weight matrix.

In some possible implementation manners, the fourth determining module 706 is specifically configured to determine, according to the reconstructed channel main feature vector corresponding to the two UEs, the target weight matrix by using a third formula, where the third formula is Expressed as:

,among them,

Represents the target weight matrix,

Represents the weight vector corresponding to u ₁ ,

Represents the weight vector corresponding to u ₂ ,

Express

Conjugate transposed matrix,

Express

Conjugate transposed matrix,

Representing a diagonal array, used to make

with

The square of the modulus is 1/2.

In some possible implementation manners, the fourth determining module 706 is specifically configured to determine, according to the precoding codewords corresponding to the two UEs and the target weight matrix, a fourth pilot formula to determine an candidate pilot weighting matrix set. Wherein the fourth formula is expressed as:

among them,

Represents the target weight matrix.

It can be seen that if two users are scheduled, and if the first pilot weight matrix is at least one of a unit weight matrix and a preset pilot weight matrix, the network device first determines target weights corresponding to the two UEs. The matrix is determined in a specific manner, such as the third formula. Generally, the power corresponding to the target weight matrix corresponding to each UE is the same. Then, the correlation of the reconstructed channel main feature vectors corresponding to the two UEs is compared. When the correlation between the reconstructed channel main feature vectors of the two UEs is less than the first preset threshold, the downlink channels corresponding to the two UEs are not Less interference or interference, wherein the first pre- The threshold is generally set to 1. The first preset threshold may be determined according to an actual situation, and is not specifically limited herein. The network device determines the corresponding preparation according to the target weight matrix and the precoding codewords corresponding to the two UEs respectively. The pilot weighting matrix set is selected, and the specific determination manner is as the fourth formula.

A third possible module is: a fourth determining module 706, configured to: if the first pilot weight matrix is the unit weight matrix and the preset pilot weight matrix, the third determining module is configured according to the Before the reconstructed channel main feature vector of each of the M scheduled UEs determines the second pilot weighting matrix, if the M is greater than or equal to 2, the reconstructed channel main features corresponding to the at least two UEs respectively The vector determines a target weight matrix; when the correlation of the target weight matrix corresponding to any two UEs is less than a second preset threshold, determining according to the precoding codeword corresponding to the at least two UEs and the target weight matrix A set of alternative pilot weighting matrices.

In some possible implementations, the fourth determining module 706 is specifically configured to determine, by using a fifth formula, an alternative pilot weighting matrix set according to the precoding codeword corresponding to the at least two UEs and the target weight matrix. Wherein the fifth formula is expressed as:

among them,

Represents the target weight matrix.

After the fourth determining module 706 determines the candidate pilot weighting matrix set, the candidate pilot weighting matrix is selected from the candidate pilot weighting matrix set as the second pilot weighting matrix according to a preset manner. The specific implementation process includes the following possible ways:

The first possible mode is: if the first pilot weight matrix is at least one of the unit weight matrix and the preset pilot weight matrix, the third determining module 704 is specifically configured to randomly select Obtaining a target precoding codeword, and selecting, from the candidate pilot weighting matrix set, an candidate pilot weighting matrix corresponding to the target precoding codeword according to the target precoding matrix; and using the target precoding codeword A corresponding candidate pilot weighting matrix is determined as the second pilot weighting matrix.

The second possible mode is: when the first pilot weight matrix is the unit weight matrix, the third determining module 704 is specifically configured to determine a target precoding codeword according to a preset rule, and according to the Selecting, by the target precoding matrix, an candidate pilot weighting matrix corresponding to the target precoding codeword from the candidate pilot weighting matrix; determining an candidate pilot weighting matrix corresponding to the target precoding codeword as The second pilot weighting matrix is described.

In some possible implementations, the third determining module 707 is specifically configured to determine the target pre-coded codeword by using a sixth formula, where the sixth formula is expressed as:

among them,

In a practical application, the network device may further determine the second guide according to the first pilot weight matrix. The frequency weighting matrix, the specific implementation process includes the following possible ways:

The first possible mode is: if the first pilot weight matrix is the preset pilot weight matrix, the third determining module 704 is specifically configured to acquire a UE target if the M is 1. a weight matrix; determining the second pilot weight matrix according to the first pilot weight matrix and the target weight matrix of the one UE.

In some possible implementation manners, the third determining module 704 is specifically configured to determine whether the first pilot weight matrix and the target weight matrix satisfy a seventh formula, where the seventh formula is expressed as:

Express

a conjugate transposed matrix, Qmod(m, L) represents a first pilot weighting matrix with measurement subframe number m in L measurement subframes, δ represents a constraint threshold; and the seventh formula will be satisfied The first pilot weighting matrix is determined as the second pilot weighting matrix.

In some possible implementation manners, the network device further needs to determine a target precoding codeword, and weight the next data signal according to the target precoding codeword and the second pilot weight matrix to improve accuracy of the downlink channel. The fourth determining module 706 is further configured to use, according to the first pilot weight matrix and the target weight matrix, that the network device may determine the second pilot weight matrix and determine the target precoding codeword. After determining the second pilot weighting matrix, the target precoding codeword is determined by using an eighth formula, wherein the eighth formula is expressed as:

among them,

Represents the target precoding codeword.

a sending module 705, configured to determine, by the third determining module 704, the second weighted pilot signal The number is sent to the N UEs, wherein the second weighted pilot signal is obtained by the network device weighting the second pilot signal according to the second pilot weight matrix.

In some possible implementations, the sending module 705 is further configured by the third determining module 704 to determine a second pilot according to a reconstructed channel main feature vector of each of the M scheduled UEs. After the weighting matrix, the first weighted data signal is sent to the N UEs, wherein the first weighted data signal is determined by the network device according to the target precoding codeword and the second pilot weight matrix Weighted from the first data signal.

In the above embodiments, the descriptions of the various embodiments are different, and the details that are not detailed in a certain embodiment can be referred to the related descriptions of other embodiments.

A person skilled in the art can clearly understand that for the convenience and brevity of the description, the specific working process of the system, the device and the unit described above can refer to the corresponding process in the foregoing method embodiment, and details are not described herein again.

In the several embodiments provided by the present application, it should be understood that the disclosed system, apparatus, and method may be implemented in other manners. For example, the device embodiments described above are merely illustrative. For example, the division of cells is only a logical function division. In actual implementation, there may be another division manner. For example, multiple units or components may be combined or integrated. Go to another system, or some features can be ignored or not executed. In addition, the mutual coupling or direct coupling or communication connection shown or discussed may be an indirect coupling or communication connection through some interface, device or unit, and may be in an electrical, mechanical or other form.

The units described as separate components may or may not be physically separate, and the components displayed as units may or may not be physical units, that is, may be located in one place, or may be distributed to multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of the embodiment.

In addition, each functional unit in each embodiment of the present invention may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated in one unit. In the unit. The above integrated unit can be implemented in the form of hardware or in the form of a software functional unit.

An integrated unit, if implemented in the form of a software functional unit and sold or used as a standalone product, can be stored in a computer readable storage medium. Based on such understanding, the technical solution of the present invention, which is essential or contributes to the prior art, or all or part of the technical solution, may be embodied in the form of a software product stored in a storage medium. A number of instructions are included to cause a computer device (which may be a personal computer, server, or network device, etc.) to perform all or part of the steps of the various embodiments of the present invention. The foregoing storage medium includes: a U disk, a mobile hard disk, a read-only memory (ROM), a random access memory (RAM), a magnetic disk, or an optical disk, and the like. .

The operation method and the terminal of an application group provided by the present invention are described in detail above. The principles and implementation manners of the present invention are described in the specific examples. The description of the above embodiments is only used to help understand the present invention. The method of the present invention and its core idea; at the same time, those skilled in the art, according to the idea of the present invention, there will be changes in the specific embodiments and application scope. In summary, the contents of this specification should not be construed as Limitations of the invention.

Claims

A downlink transmission method, characterized in that the method is applied to a multiple input multiple output system, the method comprising:

The network device receives N precoding matrix indication PMIs, where N is an integer greater than 1, and the N PMIs are determined by the N user equipment UEs according to the first weighted pilot signals sent by the network device, The first weighted pilot signal is obtained by the network device weighting the first pilot signal according to the first pilot weight matrix;

Determining, by the network device, N reconstructed channel main feature vectors according to the N PMIs and the first pilot weight matrix;

Determining, by the network device, the M scheduled UEs from the N UEs, and determining a second pilot weighting matrix according to the reconstructed channel main feature vector of each of the M scheduled UEs, where , M is an integer not greater than N;

Transmitting, by the network device, the second weighted pilot signal to the N UEs, where the second weighted pilot signal is used by the network device to compare the second pilot signal according to the second pilot weight matrix Weighted.
The method of claim 1 wherein

The first pilot weight matrix is at least one of a unit weight matrix and a preset pilot weight matrix.
The method according to claim 1, wherein the determining, by the network device, the N reconstructed channel main feature vectors according to the N PMIs and the first pilot weight matrix comprises:

Determining, by the network device, N precoding codewords corresponding to the N PMIs according to the N PMIs;

Determining, by the network device, a conjugate transposed matrix corresponding to the N precoding codewords and a conjugate transposed matrix corresponding to the first pilot weight matrix;

The network device, according to the N precoding codewords, the first pilot weight matrix, the conjugate transposed matrix corresponding to the N precoding codewords, and the first pilot weight matrix The yoke transpose matrix determines the N reconstructed channel main feature vectors.
The method according to claim 3, wherein the network device, according to the N precoding codewords, the first pilot weight matrix, and the conjugate rotation corresponding to the N precoding codewords Determining the matrix and the conjugate transposed matrix corresponding to the first pilot weight matrix to determine the N reconstructed channel main feature vectors includes:

The network device, according to the N precoding codewords, the first pilot weight matrix, the conjugate transposed matrix corresponding to the N precoding codewords, and the first pilot weight matrix The yoke transposed matrix determines the N reconstructed channel main feature vectors using a first formula, wherein the first formula is expressed as:

among them,
Representing the reconstructed channel main feature vector of the user equipment u determined on the subframe t, PrimEigVec represents the main feature vector of the matrix, L represents the total number of measurement subframes within the preset length, and m is the measurement subframe number.
Representing a first pilot weighting matrix in which the measurement subframe is s m ,
Determining a PMI selected by the user equipment u after channel estimation of the first pilot signal of the measurement subframe s m ,
Indicates that the PMI is
Corresponding precoding codeword,
Express
Corresponding conjugate transpose matrix,
Express
Corresponding conjugate transpose matrix.
The method according to claim 2, wherein if the first pilot weight matrix is the unit weight matrix, the reconstructed channel master according to each of the M scheduled UEs Before the feature vector determines the second pilot weight matrix, the method further includes:

If the M is 1, the network device determines the candidate pilot weighting matrix set according to the reconstructed channel main feature vector corresponding to one UE and the precoding codeword corresponding to the one UE.
The method according to claim 5, wherein the determining, by the network device, the candidate pilot weighting matrix set according to the reconstructed channel primary feature vector corresponding to one UE and the precoding codeword corresponding to the one UE comprises:

The network device determines, by using a second formula, an alternative pilot weighting matrix set according to a reconstructed channel primary feature vector corresponding to one UE and a precoding codeword corresponding to the one UE, where the second formula is expressed as:

among them,
Representing a set of candidate pilot weighting matrices, W i representing a precoding codeword of rank rank=1 with a PMI of i,
Represents a reconstructed channel main eigenvector corresponding to one UE, and w 1 represents a PMI codebook with rank=1.
The method according to claim 2, wherein said first pilot weighting matrix Determining, according to at least one of the unit weighting matrix and the preset pilot weighting matrix, the second pilot weighting according to the reconstructed channel main feature vector of each of the M scheduled UEs Before the matrix, the method further includes:

If the M is 2, the network device determines a target weight matrix according to the reconstructed channel main feature vector corresponding to the two UEs respectively;

And determining, by the network device, the precoding codeword corresponding to the two UEs and the target weight matrix, when the correlation between the reconstructed channel main feature vectors corresponding to the two UEs is less than a first preset threshold. A set of alternative pilot weighting matrices.
The method according to claim 7, wherein the determining, by the network device, the target weight matrix according to the reconstructed channel main feature vector corresponding to the two UEs comprises:

The network device determines the target weight matrix by using a third formula according to the reconstructed channel main feature vector corresponding to the two UEs, where the third formula is expressed as:

,among them,
Represents the target weight matrix,
Representing the reconstructed channel main eigenvector corresponding to u 1 ,
Representing the reconstructed channel main eigenvector corresponding to u 2 ,
Represents the weight vector corresponding to u 1 ,
Represents the weight vector corresponding to u 2 ,
Express
Conjugate transposed matrix,
Express
Conjugate transposed matrix,
Represents a diagonal array.
The method according to claim 7, wherein the determining, by the network device, the candidate pilot weight matrix set according to the precoding codeword corresponding to the two UEs and the target weight matrix comprises:

The network device determines, according to the precoding codeword corresponding to the two UEs and the target weight matrix, a candidate pilot weighting matrix set by using a fourth formula, where the fourth formula is expressed as:

among them,
Representing a set of candidate pilot weighting matrices, W i representing a precoding codeword of rank=2 with a PMI of i,
Represents the target weight matrix.
The method according to claim 2, wherein if the first pilot weight matrix is at least one of the unit weight matrix and the preset pilot weight matrix, the M according to the M Before the reconstructed channel main feature vector of each of the scheduled UEs determines the second pilot weight matrix, the method further includes:

If the M is greater than or equal to 2, the network device determines a target weight matrix according to the reconstructed channel main feature vector corresponding to the at least two UEs respectively;

When the correlation between the target weight matrix corresponding to the two UEs is less than the second preset threshold, the network device determines the candidate guide according to the precoding codeword corresponding to the at least two UEs and the target weight matrix. Frequency weighting matrix set.
The method according to claim 10, wherein the determining, by the network device, the candidate pilot weight matrix set according to the precoding codeword corresponding to the at least two UEs and the target weight matrix comprises:

The network device determines, according to the precoding codeword corresponding to the at least two UEs and the target weight matrix, a candidate pilot weighting matrix set by using a fifth formula, where the fifth formula is expressed as:

among them,
Representing a set of candidate pilot weighting matrices, W i representing a precoding codeword with a rank ≥ 2 and a PMI of i,
Represents the target weight matrix.
The method according to any one of claims 5 to 11, wherein if the first pilot weight matrix is at least one of the unit weight matrix and the preset pilot weight matrix, Determining, according to the reconstructed channel main feature vector of each of the M scheduled UEs, the second pilot weight matrix comprises:

The network device randomly selects a target precoding codeword, and selects an alternative pilot weighting matrix corresponding to the target precoding codeword from the candidate pilot weighting matrix set according to the target precoding matrix;

The network device determines an alternative pilot weighting matrix corresponding to the target precoding codeword as the second pilot weighting matrix.
The method according to any one of claims 5 to 11, wherein if the first pilot weight matrix is the unit weight matrix, the UE according to each of the M scheduled UEs The reconstructed channel main feature vector determines the second pilot weight matrix including:

Determining, by the network device, a target precoding codeword according to a preset rule, and selecting, from the candidate pilot weighting matrix set, an candidate pilot weight matrix corresponding to the target precoding codeword according to the target precoding matrix;

The network device determines an alternative pilot weighting matrix corresponding to the target precoding codeword as the second pilot weighting matrix.
The method according to claim 13, wherein the determining, by the network device, the target precoding codeword according to the preset rule comprises:

The network device determines the target precoding codeword by using a sixth formula, wherein the sixth formula is expressed as:

among them,
Indicates the target precoding codeword, and n denotes the sequence number of the measurement subframe before the measurement subframe s m ,
Indicates that the measurement subframe is an alternate pilot weight matrix corresponding to s m .
The method according to any one of claims 2 to 11, wherein if the first pilot weight matrix is the preset pilot weight matrix, the according to the M scheduled UEs Determining the second pilot weighting matrix by the reconstructed channel main feature vector of each UE includes:

If the M is 1, the network device acquires a target weight matrix of a UE;

The network device determines the second pilot weight matrix according to the first pilot weight matrix and the target weight matrix of the one UE.
The method according to claim 15, wherein the determining, by the network device, the second pilot weight matrix according to the first pilot weight matrix and the target weight matrix of the one UE comprises:

Determining, by the network device, whether the first pilot weight matrix and the target weight matrix satisfy a seventh formula, wherein the seventh formula is expressed as:

Wherein, W i represents a precoding codeword with a P=1 of rank=1, and w 1 represents a PMI codebook of rank=1,
Express
a conjugate transposed matrix, Q mod(m, L) represents a first pilot weighting matrix in which the measurement subframe number of the L measurement subframes is m, and δ represents a constraint threshold value;

The network device determines a first pilot weighting matrix that satisfies the seventh formula as the second pilot weighting matrix.
The method according to claim 16, wherein after the network device determines the second pilot weight matrix according to the first pilot weight matrix and the target weight matrix, the method further includes:

The network device determines a target precoding codeword by using an eighth formula, wherein the eighth formula is expressed as:

among them,
Represents the target precoding codeword.
The method according to any one of claims 11 to 17, wherein after determining the second pilot weighting matrix according to the reconstructed channel main feature vector of each of the M scheduled UEs, The method further includes:

Transmitting, by the network device, a first weighted data signal to the N UEs, wherein the first weighted data signal is determined by the network device according to the target precoding codeword and the second pilot weighting matrix Weighted from the first data signal.
A network device, wherein the network device is a device in a multiple input multiple output system, and the network device includes:

a receiving module, configured to receive N precoding matrix indication PMIs, where N is an integer greater than 1, and the N PMIs are determined by the N user equipment UEs according to the first weighted pilot signals sent by the network device The first weighted pilot signal is obtained by the network device weighting the first pilot signal according to the first pilot weight matrix;

a first determining module, configured to determine N reconstructed channel main feature vectors according to the N PMIs and the first pilot weight matrix received by the receiving module;

a second determining module, configured to determine M scheduled UEs from the N UEs;

a third determining module, configured to determine a second pilot weighting matrix according to the reconstructed channel main feature vector of each of the M scheduled UEs determined by the second determining module, where M is not greater than An integer of N;

a sending module, configured to send the second weighted pilot signal determined by the third determining module to The N UEs, wherein the second weighted pilot signal is obtained by the network device weighting the second pilot signal according to the second pilot weight matrix.
The network device according to claim 19, comprising:

The first pilot weight matrix is at least one of a unit weight matrix and a preset pilot weight matrix.
The network device according to claim 20, wherein the first determining module is specifically configured to determine N precoding codewords corresponding to the N PMIs according to the N PMIs; and determine the N pre- a conjugate transposed matrix corresponding to the encoded codeword and a conjugate transposed matrix corresponding to the first pilot weight matrix; the first pilot weighting matrix, the N according to the N precoding codewords The conjugate transposed matrix corresponding to the precoding codeword and the conjugate transposed matrix corresponding to the first pilot weight matrix determine the N reconstructed channel main eigenvectors.
The network device according to claim 21, wherein the first determining module is specifically configured to: according to the N precoding codewords, the first pilot weight matrix, the N precoding codewords Corresponding conjugate transposed matrix and conjugate transposed matrix corresponding to the first pilot weight matrix determine the N reconstructed channel main eigenvectors by using a first formula, wherein the first formula is expressed as:

among them,
Representing the reconstructed channel main feature vector of the user equipment u determined on the subframe t, PrimEigVec represents the main feature vector of the matrix, L represents the total number of measurement subframes within the preset length, and m is the measurement subframe number.
Representing a first pilot weighting matrix in which the measurement subframe is s m ,
Determining a PMI selected by the user equipment u after channel estimation of the first pilot signal of the measurement subframe s m ,
Indicates that the PMI is
Corresponding precoding words,
Express
Corresponding conjugate transpose matrix,
Express
Corresponding conjugate transpose matrix.
The network device according to claim 20, wherein the network device further comprises:

a fourth determining module, configured to: if the first pilot weight matrix is the unit weight matrix, in the third determining module, according to a reconstructed channel main feature of each of the M scheduled UEs Before the vector determines the second pilot weighting matrix, if the M is 1, according to a reconstructed signal corresponding to one UE The track master feature vector and the precoding codeword corresponding to the one UE determine an alternative pilot weighting matrix set.
The network device according to claim 23, wherein the fourth determining module is specifically configured to determine, according to a reconstructed channel main feature vector corresponding to one UE and a precoding codeword corresponding to the one UE, by using a second formula An alternative pilot weighting matrix set, wherein the second formula is expressed as:

Among them, W i ∈w 1 ,
Representing an alternative pilot weighted moment set, W i representing a pre-coded codeword of rank rank=1 with a PMI of i,
Represents a reconstructed channel main eigenvector corresponding to one UE, and w 1 represents a PMI codebook with rank=1.
The network device according to claim 20, wherein the network device further comprises:

a fourth determining module, configured to: when the first pilot weight matrix is at least one of the unit weight matrix and the preset pilot weight matrix, in the third determining module according to the M Before the reconstructed channel main feature vector of each of the scheduled UEs determines the second pilot weight matrix, if the M is 2, the target weight matrix is determined according to the reconstructed channel main feature vectors respectively corresponding to the two UEs; Determining the candidate pilot according to the precoding codeword corresponding to the two UEs and the target weight matrix when the correlation between the reconstructed channel main feature vectors corresponding to the two UEs is less than a first preset threshold A set of weighting matrices.
The network device according to claim 25, wherein the fourth determining module is configured to determine the target weight matrix by using a third formula according to a reconstructed channel main feature vector corresponding to each of the two UEs, where The third formula is expressed as:

,among them,
Represents the target weight matrix,
Representing the reconstructed channel main eigenvector corresponding to u 1 ,
Representing the reconstructed channel main eigenvector corresponding to u 2 ,
Represents the weight vector corresponding to u 1 ,
Represents the weight vector corresponding to u 2 ,
Express
Conjugate transposed matrix,
Express
Conjugate transposed matrix,
Represents a diagonal array.
The network device according to claim 25, wherein the fourth determining module is configured to determine, according to the precoding codeword corresponding to the two UEs and the target weight matrix, a fourth formula to determine an alternative guide a set of frequency weighting matrices, wherein the fourth formula is expressed as:

among them,
Representing a set of candidate pilot weighting matrices, W i representing a precoding codeword of rank=2 with a PMI of i,
Represents the target weight matrix.
The network device according to claim 20, wherein the network device further comprises:

a fourth determining module, configured to: when the first pilot weight matrix is at least one of the unit weight matrix and the preset pilot weight matrix, in the third determining module according to the M Before the reconstructed channel main feature vector of each of the scheduled UEs determines the second pilot weighting matrix, if the M is greater than or equal to 2, the target weight is determined according to the reconstructed channel main feature vector corresponding to the at least two UEs respectively a value matrix; when the correlation of the target weight matrix corresponding to any two UEs is less than a second preset threshold, determining the candidate pilot according to the precoding codeword corresponding to the at least two UEs and the target weight matrix A set of weighting matrices.
The network device according to claim 28, wherein the fourth determining module is configured to determine an candidate by using a fifth formula according to the precoding codeword corresponding to the at least two UEs and the target weight matrix a set of pilot weighting matrices, wherein the fifth formula is expressed as:

among them,
Representing a set of candidate pilot weighting matrices, W i representing a precoding codeword with a rank ≥ 2 and a PMI of i,
Represents the target weight matrix.
The network device according to any one of claims 23 to 29, wherein, when the first pilot weight matrix is at least one of the unit weight matrix and the preset pilot weight matrix, The third determining module is specifically configured to randomly select a target precoding codeword, and select, according to the target precoding matrix, the target precoding codeword corresponding to the target pilot precoding matrix An alternative pilot weighting matrix; determining an alternative pilot weighting matrix corresponding to the target precoding codeword as the second pilot weighting matrix.
The network device according to any one of claims 23 to 29, wherein, if the first pilot weight matrix is the unit weight matrix, the third determining module is specifically configured to determine a target according to a preset rule. Precoding a codeword, and selecting, from the candidate pilot weighting matrix set, an alternative pilot weighting matrix corresponding to the target precoding codeword according to the target precoding matrix; and corresponding to the target precoding codeword An alternative pilot weighting matrix is determined as the second pilot weighting matrix.
The network device according to claim 31, wherein the third determining module is specifically configured to determine the target pre-coded codeword by using a sixth formula, wherein the sixth formula is expressed as:

among them,
Indicates the target precoding codeword, and n denotes the sequence number of the measurement subframe before the measurement subframe s m ,
Indicates that the measurement subframe is an alternate pilot weight matrix corresponding to s m .
The network device according to any one of claims 20 to 29, wherein if the first pilot weight matrix is the preset pilot weight matrix, the third determining module is specifically used for The M is 1 and obtains a target weight matrix of one UE; and the second pilot weight matrix is determined according to the first pilot weight matrix and the target weight matrix of the one UE.
The network device according to claim 33, wherein the third determining module is specifically configured to determine whether the first pilot weight matrix and the target weight matrix satisfy a seventh formula, wherein the The seven formula is expressed as:

Wherein, W i represents a precoding codeword with a P=1 of rank=1, and w 1 represents a PMI codebook of rank=1,
Express
a conjugate transposed matrix, Q mod(m, L) represents a first pilot weighting matrix with measurement subframe number m in L measurement subframes, δ represents a constraint threshold; the seventh formula will be satisfied The first pilot weighting matrix is determined as the second pilot weighting matrix.
The network device according to claim 34, wherein the fourth determining module is further configured to: in the third determining module, according to the first pilot weight matrix and the target weight matrix After determining the second pilot weighting matrix, the target precoding codeword is determined by using an eighth formula, wherein the eighth formula is expressed as:

among them,
Represents the target precoding codeword.
A network device according to any one of claims 29 to 35, characterized in that

The sending module is further configured to: after the third determining module determines the second pilot weighting matrix according to the reconstructed channel main feature vector of each of the M scheduled UEs, the first weighting data Sending a signal to the N UEs, wherein the first weighted data signal is obtained by the network device weighting the first data signal according to the target precoding codeword and the second pilot weighting matrix.