CN106712820B - Self-interference-suppressed multi-stream diversity BD precoding method and device - Google Patents
Self-interference-suppressed multi-stream diversity BD precoding method and device Download PDFInfo
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- H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
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Abstract
The invention discloses a self-interference suppression multi-stream diversity BD pre-coding method and a device, wherein the method comprises the following steps: a base station acquires channel matrixes of all users; determining an interference matrix of each user receiving antenna so as to construct a null space orthogonal basis of all the receiving antennas of the user; constructing a self-interference suppression equivalent channel matrix of each user according to the self-interference suppression equivalent channel matrix, and further constructing a multi-stream diversity BD precoding and receiving decoding matrix of each user; carrying out multi-stream diversity BD pre-coding on original signals sent to each user by a base station, adding the signals, and then transmitting the signals from the base station; the users process the received signals by using the corresponding receiving decoding matrixes, combine the data streams received by each user and estimate the original data transmitted by the users. The invention solves the technical problem of self-interference between receiving end antennas in an MU-MIMO system, suppresses the self-interference of an equivalent channel while eliminating multi-user interference, combines multiple paths of data streams, increases space diversity gain and improves reliability. The method is used for resisting interference in the field of wireless communication.
Description
Technical Field
The invention belongs to the technical field of wireless communication, particularly relates to precoding in a downlink of a multi-user multiple-input multiple-output (MU-MIMO) system, and particularly relates to a self-interference suppression multi-stream diversity BD precoding method and a self-interference suppression multi-stream diversity BD precoding device, which are used for interference resistance in the field of wireless communication.
Background
The MU-MIMIO system can transmit multiplexed spatial multiplexing signals to multiple users on the same time and frequency resource block while achieving high system capacity and the benefits of canceling multi-user interference from spatial division multiple access processing. In the system, since a base station (BS for short) simultaneously transmits signals to multiple users, multi-user interference (MUI for short) is inevitably introduced, and since receiving antennas belong to different users, cooperation processing cannot be performed between the users, precoding suppression needs to be performed on the transmitted signals at the BS end or MUI needs to be completely eliminated.
Precoding for MU-MIMO is classified into nonlinear precoding and linear precoding in type. Non-linear precoding such as dirty paper coding (DPC for short) can achieve optimal system performance, but is difficult to be applied in practice due to high complexity. Linear precoding like BD precoding achieves sub-optimal system performance but is widely adopted in MU-MIMO systems due to its lower complexity. The BD precoding method can completely eliminate the MUI using Channel State Information (CSI) of all users, but does not consider self-interference.
In the BD pre-coding widely adopted in the existing MU-MIMO system, a BS (base station) end firstly acquires channel matrixes of all users; then constructing an interference matrix of the expected user, and obtaining a pre-coding matrix and a decoding matrix of the expected user according to the interference matrix; the base station performs precoding on the sent original signals by using the obtained precoding matrix, and the precoded signals are transmitted out through the base station; and the user receives the signal and decodes the signal by using the decoding matrix to obtain an original signal. Since BD precoding only considers channel matrices of other users when constructing an interference channel matrix of a desired user, and does not consider interference between antennas of the desired user, when transmitting multiple data streams, error rate performance is degraded.
Secondly, because equivalent channel gains of different data streams in BD precoding are different, if multiple identical data streams are transmitted, the receiving end merges the multiple data streams, and the error rate performance depends on the worst equivalent channel condition, so the condition of transmitting the multiple identical data streams is not considered to improve the reliability of the system.
In the prior art, the BD precoding method only considers the MUI interference and does not consider self-interference between antennas when constructing an interference channel, and when a user has multiple data streams, the error rate performance is poor.
Disclosure of Invention
The invention aims to provide a multi-stream diversity BD pre-coding method and device with better system error rate performance and self-interference suppression, aiming at the problem that the BD pre-coding method in the prior art has poor error rate performance when multiple data streams are sent.
The invention discloses a self-interference suppression multi-stream diversity BD precoding method, which is characterized by comprising the following steps:
step 1: determining all user channel matrixes, acquiring downlink channel matrixes of all users by a base station, and determining all user channel matrixes
HkA downlink channel matrix of user K, K being 1,2, …, K being the number of users in the system, [ ·]TRepresents a transpose of a matrix;
step 2: determining the null space orthogonal base of user receiving antenna, firstly constructing the interference matrix of each receiving antenna of each user, then calculating the null space orthogonal base of the interference matrix of each receiving antenna of each user, thus obtaining the null space orthogonal base of all receiving antennas of each user, taking user k as an example, the interference matrix of the ith receiving antenna of user k is taken as
WhereinDownlink channel matrix H for user kkRemoving the channel matrix after the ith row, namely the interference matrix not only contains the channel state information of other users, but also contains the channel state information of the interference matrix;
and step 3: constructing an equivalent channel matrix, a linear precoding matrix and a receiving decoding matrix, constructing a self-interference suppression equivalent channel matrix of each user according to the zero-space orthogonal basis of the interference matrixes of all receiving antennas of each user and the downlink channel matrix of the user, and constructing the linear precoding matrix and the receiving decoding matrix of each user according to the self-interference suppression equivalent channel matrix;
and 4, step 4: performing multi-stream diversity BD precoding on signals sent by a base station, performing multi-stream diversity BD precoding on the signals sent by each user by using a constructed linear precoding matrix, adding the signals subjected to the multi-stream diversity BD precoding, and transmitting the signals through a base station end antenna;
and 5: the user decodes, combines and estimates the received signals, the expected user processes the signals received from the base station by using the corresponding multi-stream diversity BD receiving and decoding matrix, the data streams of the expected user after the multi-stream diversity BD receiving and decoding matrix processing are combined, a plurality of data streams are utilized to provide space diversity gain, and the original sending data is estimated.
The invention also relates to a self-interference-suppressed multi-stream diversity BD pre-coding device, which is characterized in that the self-interference-suppressed multi-stream diversity BD pre-coding device is sequentially connected with the following components according to a signal processing flow: the device comprises a channel matrix acquisition module, a zero-space orthogonal basis construction module, a precoding matrix and receiving decoding matrix construction module, a precoding processing module and a received signal processing module, wherein the modules are as follows:
the channel matrix acquisition module is used for acquiring the channel matrixes of all users, inputting the channel matrixes into each user and outputting the channel matrixes into all the users;
the zero-space orthogonal base constructing module is used for obtaining the zero-space orthogonal base of each user receiving antenna, inputting the zero-space orthogonal base into the channel matrix of all users and outputting the zero-space orthogonal base of all receiving antennas of each user;
a precoding matrix and receiving decoding matrix constructing module, configured to obtain a multi-stream diversity BD precoding matrix and a multi-stream diversity BD receiving decoding matrix of a user, input zero-space orthogonal bases of all receiving antennas of each user, and output the multi-stream diversity BD precoding matrix and the multi-stream diversity BD receiving decoding matrix of each user;
the precoding processing module is used for carrying out multi-stream diversity BD precoding processing on original signals sent to all users by utilizing the precoding matrix constructed by the precoding matrix construction module, summing the signals subjected to multi-stream diversity BD precoding of all the users, transmitting the sum through a base station end, inputting the sum into the original signals sent to the users, and outputting the sum into the signals subjected to multi-stream diversity BD precoding;
and the received signal processing module is used for receiving the received signals of the users by using the obtained multi-stream diversity BD receiving and decoding matrix, merging the user data streams obtained after the multi-stream diversity BD receiving and decoding matrix processing, and estimating original data. The input of the received signal processing module is the signal received by the user through the antenna, and the output is the original signal estimation sent by the base station to the expected user.
Compared with the prior art, the invention has the advantages that:
1. the main purpose of the existing BD precoding method is to eliminate multi-user interference, when constructing an interference matrix and solving a precoding matrix of an expected user, only the interference of other users to the expected user is considered, namely the interference matrix only contains channel state information of other users.
2. When a user has multiple data streams, the existing BD pre-coding method has large equivalent channel gain difference between different data streams, and the system error rate performance depends on the worst equivalent channel condition, so that the merging technology is not considered to improve the system reliability. The invention balances the equivalent channel gains of different data streams by eliminating self-interference among user antennas, and transmits multiple paths of same data streams through the base station, and the user side carries out the method of combining multiple paths of data streams, thereby increasing the space diversity gain and improving the reliability of the system.
Drawings
FIG. 1 is a schematic diagram of a downlink structure of a MU-MIMO system;
FIG. 2 is a flow chart of a precoding method of the present invention;
FIG. 3 is a schematic diagram of a precoding apparatus according to the present invention;
FIG. 4 is a schematic diagram of a zero-space orthogonal basis structure module in the precoding apparatus of the present invention;
FIG. 5 is a schematic diagram of a received signal processing module in the precoding apparatus according to the present invention;
fig. 6 is a graph comparing the performance of the error bit rate according to the present invention with that of the BD pre-coding method.
Detailed Description
The invention is described in detail below with reference to the accompanying drawings
Example 1
The precoding in the existing MU-MIMO system mainly includes two categories of nonlinear precoding and linear precoding. Among them, nonlinear precoding can provide better system performance, but due to high implementation complexity, the application range is limited. Linear precoding has gained wide application, such as BD precoding, despite performing slightly worse in terms of performance due to lower complexity compared to non-linear precoding. However, the block diagonalized BD precoding only eliminates interference between multiple users and does not consider self-interference between self-antennas, and when multiple data streams exist in a user, the error rate performance is degraded. The invention develops research and innovation on the problem, provides a self-interference suppression multi-stream diversity BD precoding method, introduces self-channel state information when constructing an interference matrix, and suppresses self-interference among antennas while eliminating multi-user interference. And the multi-channel data are merged at the user side by the mode of sending the multi-channel same data streams at the base station side, thereby increasing the space diversity gain and improving the reliability of the system.
The invention relates to a self-interference suppression multi-stream diversity BD precoding method, and the method is shown in figure 1, and figure 1 is a schematic diagram of a downlink structure of an MU-MIMO system. One base station in the system simultaneously provides service for K users. Base station has NTWith N users k having transmitting antennasRkRoot receiving antenna, system satisfies NT≥NRWherein
I.e. the number of transmitting antennas of the base station is greater than or equal to the sum of the number of receiving antennas of all users. The signals sent by the base station are the sum of the signals after all users are precoded, and the number of data streams sent to the users by the base station is equal to the number of receiving antennas of the users. According to the channel reciprocity in the TDD mode, the base station can know the channel matrices of all users. The channel matrix for user k is denoted as HkSo that user k receives a signal ofxkFor the original signal sent by the base station to user k, FkPrecoding matrix for user k, nkAdditive white gaussian noise with zero mean and unit variance. The first term to the right of the equal sign in the above equation represents the useful signal of user k, and the second term to the right of the equal sign represents the MUI.
Referring to fig. 2, the self-interference suppression multi-stream diversity BD pre-coding method of the present invention includes the following steps:
step 1: all user channel matrices are determined.
The base station obtains the downlink channel matrix of each user and determines the channel matrix of all users
HkA downlink channel matrix of user K, K being 1,2, …, K being the number of users in the system, [ ·]TRepresenting the transpose of the matrix.
The base station acquires the channel state information of the user, and can perform precoding operation on the base station end by using the information, so that the detection operation of the user end is reduced, and the hardware complexity of the user end is reduced.
Step 2: a null-space orthogonal basis for the user receive antennas is determined.
Firstly, constructing an interference matrix of each receiving antenna of each user; and then calculating the null-space orthogonal basis of the interference matrix of each receiving antenna of each user, thereby obtaining the null-space orthogonal basis of all the receiving antennas of each user. Taking user k as an example, the interference matrix of the ith receiving antenna of user k is
Wherein
Downlink channel matrix H for user kkAnd removing the channel matrix after the ith row, namely the interference matrix not only contains the channel state information of other users, but also contains the channel state information of the interference matrix.
The interference matrix of each receiving antenna of each user constructed by the invention introduces the self-channel state information of the expected user, thereby ensuring that the self-interference among the self-antennas of the expected user is eliminated while the multi-user interference of the acquired null-space orthogonal basis is eliminated. The desired user is each user in the system, the user is the desired user during signal reception, and the other users are interfering users. In the invention, each user in the system can be used as an expected user to participate in the calculation of the null-space orthogonal basis of the antenna of the user.
And step 3: and constructing an equivalent channel matrix, a linear precoding matrix and a receiving decoding matrix.
Combining interference matrixes of all receiving antennas of each user together to form interference matrixes of all receiving antennas of each user, constructing a self-interference suppression equivalent channel matrix of each user according to null-space orthogonal basis of the interference matrixes of all receiving antennas of the users and a downlink channel matrix of the users, and constructing a multi-stream diversity BD precoding matrix and a multi-stream diversity BD receiving decoding matrix of each user according to the self-interference suppression equivalent channel matrix, wherein the self-interference suppression equivalent channel matrix of each user is abbreviated as an equivalent channel matrix, the multi-stream diversity BD precoding matrix is abbreviated as a linear precoding matrix, and the multi-stream diversity BD receiving decoding matrix is abbreviated as a receiving decoding matrix.
Constructing an equivalent channel matrix, a linear precoding matrix and a receiving decoding matrix, which specifically comprises the following steps:
3.1: constructing a self-interference suppression equivalent channel from the null-space orthogonal basis of the interference matrix of all receiving antennas of user k and the channel matrix of user k
The self-interference suppression equivalent channel is a virtual channel through which a signal precoded by a user equivalently passes, and is not a channel which actually exists.
3.2: performing singular value decomposition on the self-interference suppression equivalent channel to obtainWhereinIs that
The left-hand singular vector matrix of (a),
is that
The matrix of singular values of (a) is,
is that
The right singular vector matrix of (a) is,
is a right singular vector matrix corresponding to non-zero singular values,
is a right singular vector matrix corresponding to zero singular values.
Precoding matrix fetching for user k
Wherein
Express get
Front N ofRkColumn, user k's receive decoding matrix is
Wherein
Express get
Front N ofRkAnd (4) columns.
The purpose of singular value decomposition is to obtain left and right singular matrixes of the self-interference suppression equivalent channel, so as to determine a precoding matrix and a receiving decoding matrix of a user.
3.3: and repeating the step 3.1 and the step 3.2, and determining the precoding matrixes and the receiving decoding matrixes of all the users except the user k.
Since an interference matrix is constructed for each receiving antenna of the user in step 2, and a null-space orthogonal basis of each receiving antenna of the user is obtained, the self-interference suppression is realized by the equivalent channel constructed in the step.
And 4, step 4: and performing multi-stream diversity BD precoding on signals transmitted by the base station.
Performing multi-stream diversity BD precoding on the transmission signals of each user by using the constructed linear precoding matrix, adding the signals subjected to the multi-stream diversity BD precoding, and transmitting the signals through a base station end antenna, wherein the method specifically comprises the following steps:
4.1: and (3) precoding the transmission signals of each user by using the linear precoding matrix constructed in the step (3): specifically, an original signal sent by a base station to a user is multiplied by a multi-stream diversity BD precoding matrix, taking user k as an example, a signal obtained after multi-stream diversity BD precoding by user k is represented as FkxkAnd completing the multi-stream diversity BD precoding of each user.
4.2: the base station adds the signals of all users after multi-stream diversity BD precoding, and transmits the signals through the base station end antenna, which is represented as
And x is a signal which is sent by the base station and comprises a signal after precoding of all users by the multi-stream diversity BD, and each user in the system can receive the signal.
Because the base station needs to communicate with multiple users at the same time, and the signals sent by the base station contain information of all users served by the base station, the system automatically introduces interference among multiple users, and in order to eliminate the interference among the multiple users, the base station needs to perform multi-stream diversity BD pre-coding processing on the original signals sent to all users.
And 5: the user decodes, combines and estimates the received signal.
The expected user end uses a multi-stream diversity BD receiving and decoding matrix corresponding to the multi-stream diversity BD pre-coding matrix to decode the received signal which is subjected to the multi-stream diversity BD pre-coding processing of the base station, combines data streams which are subjected to the multi-stream diversity BD receiving and decoding matrix processing, provides space diversity gain by using a plurality of data streams, and estimates original sending data.
Because the invention considers the influence among the receiving antennas when designing the precoding, the interference matrix of each receiving antenna of each user is constructed aiming at each receiving antenna, and the self-interference among the antennas is eliminated. When a user has a plurality of data streams, the equivalent channel gains of different data streams are effectively balanced, so that the plurality of data streams of the user can be combined by utilizing a combining technology, the plurality of data streams provide space diversity gain, and the reliability of the MU-MIMO system is further improved.
Compared with the existing BD precoding method, when the interference matrix is constructed to solve the precoding matrix of the expected user, the interference matrix of each receiving antenna of each user not only contains the channel state information of other users, but also introduces the channel state information of the expected user, and constructs the interference matrix of each receiving antenna of the expected user, so that the invention effectively eliminates the interference among the users, and simultaneously eliminates the self-interference among the antennas of the expected user.
Example 2
The self-interference-suppressed multi-stream diversity BD precoding method is the same as that in embodiment 1, wherein the determining of the null-space orthogonal basis of the user receiving antenna in step 2 specifically includes:
2.1: constructing interference matrix of ith receiving antenna of any user k
The matrix contains both the channel state information of other users and the channel state information of the matrix itself.
2.2: solving the ith root of user kNull-space orthogonal basis of interference matrix of receiving antenna, pair
Performing singular value decomposition to obtainWherein
Is that
The left-hand singular vector matrix of (a),
is thatThe matrix of singular values of (a) is,
is that
The matrix of the right singular vector is,
is a right singular vector matrix corresponding to non-zero singular values,
is a right singular vector matrix corresponding to zero singular values, which can be known from the knowledge of matrix theory,form aA null-space orthogonal basis.
2.3: solving the null space of the interference matrix of all the receiving antennas of the user k, traversing all the receiving antennas of the user k, and repeatingStep 2.1 and step 2.2, obtaining the null-space orthogonal basis of the interference matrix of all receiving antennas of user k
Wherein N isRkThe number of receive antennas for user k.
2.4: and (4) repeating the step 2.1, the step 2.2 and the step 2.3, traversing all users, constructing an interference matrix of each receiving antenna of all the users, wherein all the users comprise a user k and all the users except the user k, and solving a zero-space orthogonal basis of the interference matrix of all the receiving antennas of each user.
The invention utilizes the multi-stream diversity BD pre-coding matrix F obtained by calculating the interference matrix of each receiving antenna of each userkThe method eliminates multi-user interference, greatly inhibits the self-interference of an equivalent channel, and effectively reduces the error rate of the system when the user has multi-channel data streams.
Example 3
The invention is also a self-interference-suppressed multi-stream diversity BD pre-coding apparatus, referring to fig. 3, which is sequentially connected with: the device comprises a channel matrix acquisition module, a zero-space orthogonal basis construction module, a precoding matrix and receiving decoding matrix construction module, a precoding processing module and a received signal processing module, wherein the modules are as follows:
and the channel matrix acquisition module is used for acquiring the channel matrixes of all the users, inputting the channel matrixes into each user and outputting the channel matrixes into all the users. For a time division duplex system, a user channel matrix is obtained by a training sequence or a pilot sequence of an uplink received by a base station; for frequency division duplex systems, the user channel matrix is obtained by feedback.
And the zero-space orthogonal base construction module is used for obtaining the zero-space orthogonal base of each user receiving antenna, inputting the zero-space orthogonal base into the channel matrix of all users and outputting the zero-space orthogonal base of all receiving antennas of each user.
And the precoding matrix and receiving decoding matrix constructing module is used for acquiring a multi-stream diversity BD precoding matrix and a multi-stream diversity BD receiving decoding matrix of the user, inputting the zero-space orthogonal basis of all receiving antennas of each user, and outputting the multi-stream diversity BD precoding matrix and the multi-stream diversity BD receiving decoding matrix of the user. The precoding matrix is used for performing multi-stream diversity BD precoding processing on an original signal sent by a base station, and the receiving decoding matrix is used for performing multi-stream diversity BD decoding processing on a received signal by a user.
And the precoding processing module is used for carrying out multi-stream diversity BD precoding processing on the original signals sent to all users by utilizing the precoding matrix constructed by the precoding matrix construction module, summing the signals subjected to multi-stream diversity BD precoding of all the users, transmitting the sum through a base station end, inputting the sum into the original signals sent to the users, and outputting the sum into the signals subjected to multi-stream diversity BD precoding. The base station sends signals containing all user information, and system capacity is increased.
And the received signal processing module is used for receiving the received signals of the users by using the obtained multi-stream diversity BD receiving and decoding matrix, merging the user data streams obtained after the multi-stream diversity BD receiving and decoding matrix processing, and estimating original data. The input of the received signal processing module is the signal received by the user through the antenna, and the output is the original signal estimation sent by the base station to the expected user.
Example 4
The self-interference-suppressed multi-stream diversity BD pre-coding apparatus is configured as in embodiment 3, and see fig. 4, wherein the zero-space orthogonal basis configuration module is connected with an interference matrix configuration sub-module and a singular value decomposition sub-module according to a signal processing flow, and each sub-module is as follows:
an interference matrix constructing submodule for constructing an interference channel matrix of each receiving antenna of a user according to the obtained channel matrix, inputting the channel state information of all users obtained by the channel matrix obtaining module, and outputting the channel state information as an interference matrix of the receiving antenna of the user, taking any user k as an example, the interference matrix of the ith receiving antenna of the user k is
From the above formula, the method for constructing the interference matrix of each receiving antenna of each user is different from the conventional BD precoding method, and the interference matrix includes the channel matrices of other users except user k to eliminate multi-user interference, and also includes the channel state information of user k itself to eliminate self-interference between its own antennas.
And the singular value decomposition submodule is used for carrying out singular value decomposition on the interference matrix of each receiving antenna of each user to obtain a zero-space orthogonal base of each receiving antenna of each user, further obtain zero-space orthogonal bases of all receiving antennas of each user, input the interference matrix of each receiving antenna of each user obtained by the interference matrix construction submodule, and output the interference matrix as the zero-space orthogonal base corresponding to the interference matrix.
Taking the interference matrix of the ith receiving antenna of the user k as an example, performing singular value decomposition on the interference matrix to obtain a zero-space orthogonal basis of the interference matrix of the ith receiving antenna of the user kThe zero space orthogonal basis of the interference matrix of all receiving antennas of the user k can be obtained by the same method
And a foundation is laid for further constructing a user self-interference suppression equivalent channel matrix and a multi-stream diversity BD precoding matrix.
Example 5
The self-interference-suppressed multi-stream diversity BD pre-coding apparatus is configured in the same manner as in embodiments 3-4, referring to fig. 5, wherein the received signal processing module is sequentially connected to a signal decoding sub-module, a data stream combining sub-module, and a signal decision sub-module according to a signal processing procedure, and each sub-module is as follows:
a signal decoding submodule for decoding the received signal of the user, inputting the received signal of the user and outputting the decoded multi-channel data stream, and the user utilizes a receiving and decoding matrix DkDecoding the received signal to obtain a decoded signal
Received for user kOf the decoded data stream, LkNumber of data streams, y, sent to user kkIs the received signal for user k.
A data stream merging submodule for merging the decoded L of the user kkAnd merging the data streams, inputting the multi-channel data streams decoded by the user k, and outputting merged signals merged by the multi-channel data streams.
The merging technique may employ an equal ratio merging method, a maximum ratio merging method, a selective merging method, or a free combination of several merging methods.
And the signal judgment sub-module is used for judging the combined signal, inputting the combined signal into a user and outputting the combined signal into an estimation of an original signal sent to the user by the base station.
A more complete example is given below to further illustrate the invention:
example 6
As shown in fig. 2, the self-interference-suppressed multi-stream diversity BD precoding method of the present invention is the same as that in embodiment 1-2, and includes the steps of:
step 1: determining all user channel matrixes, acquiring downlink channel matrixes of all users by a base station, and determining all user channel matrixes
For a time division duplex system, the training or pilot sequence of the uplink received by the base station is obtained; for a frequency division duplex system, the feedback can be obtained; hkA downlink channel matrix of user K, K being 1,2, …, K being the number of users in the system, [ ·]TRepresenting the transpose of the matrix.
Step 2: determining the null space orthogonal base of the user receiving antenna, firstly, constructing the interference matrix of each receiving antenna of each user, then calculating the null space orthogonal base of the interference matrix of each receiving antenna of each user, thereby obtaining the null space orthogonal base of all receiving antennas of each user, taking the user k as an example, the interference matrix of the ith receiving antenna of the user k is taken as theWherein
Downlink channel matrix H for user kkRemoving the channel matrix after the ith row, namely the interference matrix not only contains the channel state information of other users, but also contains the channel state information of the interference matrix; the method comprises the following specific steps:
2.1: constructing interference matrix of ith receiving antenna of any user k
The interference matrix in the invention not only contains the channel state information of other users, but also contains the self channel state information of the user k.
2.2: solving the null-space orthogonal basis of the interference matrix of the ith receiving antenna of user kPerforming singular value decomposition to obtain
Wherein
Is that
The left-hand singular vector matrix of (a),
is that
The matrix of singular values of (a) is,
is that
The matrix of the right singular vector is,
is a right singular vector matrix corresponding to non-zero singular values,
is a right singular vector matrix corresponding to zero singular values, which can be known from the knowledge of matrix theory,form a
A null-space orthogonal basis.
2.3: solving the null space of the interference matrix of all receiving antennas of the user k, traversing all the receiving antennas of the user k, repeating the step 2.1 and the step 2.2, and obtaining the null space orthogonal basis of the interference matrix of all the receiving antennas of the user k
Wherein N isRkThe number of receive antennas for user k.
2.4: and (4) repeating the step 2.1, the step 2.2 and the step 2.3, traversing all users, constructing the interference matrix of each receiving antenna of the users except the user k, and solving the zero-space orthogonal basis of the interference matrix of all the receiving antennas of each user. User k and other users constitute all users.
And step 3: constructing a self-interference suppression equivalent channel matrix of each user according to the zero-space orthogonal basis of the interference matrixes of all receiving antennas of each user and the downlink channel matrix of the user, and constructing a multi-stream diversity BD pre-coding matrix and a multi-stream diversity BD receiving decoding matrix of each user according to the self-interference suppression equivalent channel matrix; the method comprises the following specific steps:
3.1: and constructing a self-interference suppression equivalent channel matrix of the user k. Obtaining a self-interference suppression equivalent channel matrix of the user k by using the channel matrix of the user k and the null space matrix of all antennas of the user k
Wherein
A null-space matrix for all receive antennas for user k; will be provided with
Expanded, expressed in the form
The self-interference is inhibited to form a block diagonal form of the equivalent channel matrix, namely the self-interference of the equivalent channel is effectively eliminated by the construction method of the interference matrix in the step 2, wherein hkIs HkThe k-th row of (1).
3.2: and determining a multi-stream diversity BD precoding matrix and a multi-stream diversity BD receiving decoding matrix of the user k. To pair
Performing SVD decomposition
Wherein
Is that
The left-hand singular vector matrix of (a),
is that
The matrix of singular values of (a) is,
is that
Right singular vector matrix of (a);
is a right singular vector matrix corresponding to non-zero singular values,
is a right singular vector matrix corresponding to zero singular values; precoding matrix fetching for user k
WhereinExpress get
Front N ofRkColumns; the receive matrix for user k is
Wherein
Express get
Front N ofRkAnd (4) columns.
3.3: and repeating the step 3.1 and the step 3.2, traversing all users, and determining the multi-stream diversity BD precoding matrix and the multi-stream diversity BD receiving decoding matrix of all users.
And 4, step 4: and precoding the signal transmitted by the base station.
4.1: and 3, performing multi-stream diversity BD precoding on the transmission signals of each user by using the linear precoding matrix constructed in the step 3: specifically, a signal of a user is multiplied by a multi-stream diversity BD precoding matrix, for example, a user k is taken as an example, and a signal after the pre-coding of the user k and the multi-stream diversity BD is represented as Fkxk。
4.2: the base station adds the signals of all users after multi-stream diversity BD precoding, and transmits the signals through the base station end antenna, which is represented as
And x is a multi-stream diversity BD pre-coded signal sent by the base station.
And 5: and the user terminal processes the received signal subjected to the base station multi-stream diversity BD precoding by using a corresponding multi-stream diversity BD receiving decoding matrix, merges the data streams of the user subjected to the processing of the receiving decoding matrix, and estimates the original sending data of the user. The method comprises the following specific steps:
5.1: processing the received signal of the user by using the obtained multi-stream diversity BD receiving and decoding matrix of the user to obtain a decoded signal
For the decoded data stream received by user k, LkNumber of data streams, y, sent by the base station to user kkIs the signal received by user k.
5.2: decoding L of user kkThe data streams are merged, and the weight value of each data stream during merging is assumed to be complex { omegan,n＝1,2,…,LkWeighting the combined signal to represent
The merging technique can adopt an equal ratio merging method, a maximum ratio merging method, a selective merging method or a free combination of several merging methods.
5.3: for the combined signal
Making a decision to obtain an estimate of the original data sent by the base station to the user
And completing the self-interference suppression multi-stream diversity BD precoding and receiving process to obtain a signal with higher accuracy.
The multi-stream diversity BD pre-coding effectively balances the equivalent channel gains of different data streams, inhibits the self-interference of the equivalent channel, transmits multiple paths of the same data streams through the base station, and combines the multiple paths of the data streams at the user side, thereby increasing the space diversity gain and improving the system reliability.
Example 7
Similar to embodiments 1 to 6, the following simulation comparison of error bit rate performance of the self-interference suppression multi-stream diversity BD precoding method and the BD precoding method in the prior art is performed.
Fig. 6 is a simulation diagram of comparison of error bit rate performance between the self-interference-suppressed multi-stream diversity BD pre-coding method of the present invention and the BD pre-coding method in the prior art. The horizontal axis represents the received signal-to-noise ratio of the user and the vertical axis represents the error bit rate.
The simulation conditions are as follows: the MU-MIMO system comprises a base station, the number of base station antennas is 6, the number of receiving antennas of each user is 2, the number of users is 3, a channel model is modeled into a perfect single-path Rayleigh fading channel, a Monte Carlo simulation method is adopted, and the self-interference suppression multi-stream diversity BD pre-coding method and the traditional BD pre-coding method are involved in simulation. The transmitted signal is modulated by QPSK, and the error rate is the statistical average error rate of multiple experiments.
As shown in fig. 6, compared with the conventional BD precoding method, the self-interference-suppressed multi-stream diversity BD precoding method of the present invention has a significant advantage in bit error rate performance, and when the bit error rate is 10-3Compared with the traditional BD precoding method, the self-interference suppression multi-stream diversity BD precoding method obtains about 1.5dB gain. And with the increase of the receiving signal-to-noise ratio, the self-interference suppression multi-stream diversity BD pre-coding method has lower bit error rate compared with the traditional BD pre-coding method under the same signal-to-noise ratio, namely the advantage of the bit error rate performance is more obvious. The technical scheme of the invention is used for carrying out multi-stream diversity BD precoding processing, so that the system can obtain better error code performance, and the transmission reliability of the system is improved.
In summary, the self-interference suppression multi-stream diversity BD pre-coding method and apparatus disclosed in the present invention include: a base station acquires a downlink channel matrix of each user and determines a total user channel matrix; the base station end determines the zero space orthogonal basis of the interference channel matrix of each user receiving antenna; constructing a self-interference suppression equivalent channel matrix of each user according to the zero-space orthogonal basis of interference matrixes of all receiving antennas of the user and a downlink channel matrix of the user, and constructing a multi-stream diversity BD pre-coding matrix and a multi-stream diversity BD receiving decoding matrix of each user according to the equivalent channel matrix; performing multi-stream diversity BD precoding on original signals sent to all users by a base station, adding the precoded signals, and transmitting the signals from an antenna at the base station end; and the user end receives and processes the received signals by using the corresponding multi-stream diversity BD receiving and decoding matrix, combines the data streams received and processed by each user, and estimates the original sending data. The self-interference suppression multi-stream diversity BD pre-coding method solves the technical problem of self-interference between receiving end antennas in an MU-MIMO system, greatly suppresses the self-interference of an equivalent channel while eliminating multi-user interference, increases space diversity gain through combination of multi-path data streams, and improves the reliability of the system. The method is used for resisting interference in the field of wireless communication.
Claims (4)
1. A self-interference-suppressed multi-stream diversity BD precoding method is characterized by comprising the following steps:
step 1: determining all user channel matrixes, acquiring downlink channel matrixes of all users by a base station, and determining all user channel matrixes
HkA downlink channel matrix of user K, K being 1,2, …, K being the number of users in the system, [ ·]TRepresents a transpose of a matrix;
step 2: determining the null space orthogonal base of user receiving antenna, firstly constructing the interference matrix of every receiving antenna of every user, then calculating the null space orthogonal base of the interference matrix of every receiving antenna of every user so as to obtain the null space orthogonal base of all receiving antennas of every user, using user k as example, the interference matrix of ith receiving antenna of user kIs composed of
WhereinDownlink channel matrix H for user kkRemoving the channel matrix after the ith row, namely the interference matrix not only contains the channel state information of other users, but also contains the channel state information of the interference matrix;
and step 3: constructing an equivalent channel matrix, a linear precoding matrix and a receiving decoding matrix, constructing a self-interference suppression equivalent channel matrix of each user according to the zero-space orthogonal basis of the interference matrixes of all receiving antennas of each user and the downlink channel matrix of the user, and constructing the linear precoding matrix and the receiving decoding matrix of each user according to the self-interference suppression equivalent channel matrix;
and 4, step 4: performing multi-stream diversity BD precoding on signals sent by a base station, performing multi-stream diversity BD precoding on the signals sent by each user by using a constructed linear precoding matrix, adding the signals subjected to the multi-stream diversity BD precoding, and transmitting the signals through a base station end antenna;
and 5: the user decodes, combines and estimates the received signals, the expected user processes the signals received from the base station by using the corresponding multi-stream diversity BD receiving and decoding matrix, the data streams of the expected user after the multi-stream diversity BD receiving and decoding matrix processing are combined, a plurality of data streams are utilized to provide space diversity gain, and the original sending data is estimated.
2. The self-interference suppressing multi-stream diversity BD precoding method of claim 1, wherein the determining the null-space orthogonal basis of the user receive antennas in step 2 specifically includes:
2.1: constructing interference matrix of ith receiving antenna of any user k
The interference matrix contains information of other usersThe channel state information also comprises self channel state information;
2.2: solving the null-space orthogonal basis of the interference matrix of the ith receiving antenna of user k
Performing singular value decomposition to obtainWherein
Is that
The left-hand singular vector matrix of (a),
is that
The matrix of singular values of (a) is,is that
The matrix of the right singular vector is,
is a right singular vector matrix corresponding to non-zero singular values,
is a right singular vector matrix corresponding to zero singular values, which can be known from the knowledge of matrix theory,
form aA null-space orthogonal basis of (a);
2.3: solving the null space of the interference matrix of all the receiving antennas of the user k, traversing all the receiving antennas of the user k, repeating the step 2.1 and the step 2.2 to obtain the null space orthogonal basis of the interference matrix of all the receiving antennas of the user k
Wherein N isRkThe number of receive antennas for user k;
2.4: and (4) repeating the step 2.1, the step 2.2 and the step 2.3, traversing all the users, constructing the interference matrix of each receiving antenna of all the users, and solving the zero-space orthogonal basis of the interference matrix of all the receiving antennas of each user.
3. The self-interference-suppressed multi-stream diversity BD pre-coding device is characterized in that the self-interference-suppressed multi-stream diversity BD pre-coding device is sequentially connected with the following components in a signal processing flow: the device comprises a channel matrix acquisition module, a zero-space orthogonal basis construction module, a precoding matrix and receiving decoding matrix construction module, a precoding processing module and a received signal processing module, wherein the modules are as follows:
the channel matrix acquisition module is used for acquiring the channel matrixes of all users, inputting the channel matrixes into each user and outputting the channel matrixes into all the users;
the zero-space orthogonal base construction module is used for obtaining the zero-space orthogonal base of each user receiving antenna, inputting the zero-space orthogonal base of all users and outputting the zero-space orthogonal base of all the receiving antennas of each user, the zero-space orthogonal base construction module is connected with an interference matrix construction submodule and a singular value decomposition submodule according to a signal processing flow, and each submodule is as follows:
an interference matrix constructing submodule for constructing an interference channel matrix of each receiving antenna of a user according to the obtained channel matrix, inputting the channel state information of all users obtained by the channel matrix obtaining module, and outputting the channel state information as an interference matrix of the receiving antenna of the user, taking any user k as an exampleThe interference matrix of the ith receiving antenna of the k is
The singular value decomposition submodule is used for carrying out singular value decomposition on the interference matrix of each receiving antenna of each user to obtain a zero-space orthogonal base of each receiving antenna of each user and further obtain zero-space orthogonal bases of all receiving antennas of each user, inputting the interference matrix of each receiving antenna of each user obtained by the interference matrix construction submodule, and outputting the interference matrix as the zero-space orthogonal base corresponding to the interference matrix;
a precoding matrix and receiving decoding matrix constructing module, configured to obtain a multi-stream diversity BD precoding matrix and a multi-stream diversity BD receiving decoding matrix of a user, input zero-space orthogonal bases of all receiving antennas of each user, and output the multi-stream diversity BD precoding matrix and the multi-stream diversity BD receiving decoding matrix of each user;
the precoding processing module is used for carrying out multi-stream diversity BD precoding processing on original signals sent to all users by utilizing the precoding matrix constructed by the precoding matrix construction module, summing the signals subjected to multi-stream diversity BD precoding of all the users, transmitting the sum through a base station end, inputting the sum into the original signals sent to the users, and outputting the sum into the signals subjected to multi-stream diversity BD precoding;
a received signal processing module, configured to utilize the obtained multi-stream diversity BD to receive a received signal of a user through decoding matrix processing, and merge user data streams obtained after the multi-stream diversity BD receives the decoding matrix processing, so as to estimate original data; the input of the received signal processing module is the signal received by the user through the antenna, and the output is the original signal estimation sent by the base station to the expected user.
4. The self-interference suppressing multi-stream diversity BD pre-coding device of claim 3, wherein the received signal processing module is connected to a signal decoding sub-module, a data stream combining sub-module and a signal decision sub-module according to a signal processing procedure, and each sub-module is as follows:
a signal decoding submodule for decoding user received signals, inputting the user received signals and outputting the decoded multipath data streams, wherein the user utilizes a receiving decoding matrix DkDecoding the received signal to obtain a decoded signal 
For the decoded data stream received by user k, LkNumber of data streams, y, sent to user kkA received signal for user k;
a data stream merging submodule for merging the decoded L of the user kkMerging the data streams, inputting a plurality of paths of data streams decoded by a user k, and outputting merged signals merged by the plurality of paths of data streams;
and the signal judgment sub-module is used for judging the combined signal, inputting the combined signal into a user and outputting the combined signal into an estimation of an original signal sent to the user by the base station.
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