Cross-link interference elimination method, device and equipment

Abstract

The invention discloses a cross-link interference elimination method, device and equipment, and belongs to the technical field of wireless communication. The method comprises the following steps of: acquiring a statistical channel state matrix between a disturbing station and a disturbed station by the disturbing station, performing eigenvalue decomposition on the matrix, determining the number of eigenvectors needing interference elimination according to a link suppression threshold value, acquiring a downlink channel matrix between the disturbing station and a served terminal device, and performing preprocessing to obtain a downlink channel matrix between the disturbing station and the terminal device; and calculating a final beam forming matrix and applying the final beam forming matrix to downlink communication. The device disclosed by the invention is deployed at a disturbance station, and comprises a statistical channel state information acquisition module, a characteristic value decomposition module, a preprocessing module and a beam forming matrix calculation module. According to the invention, the occupation of normal transmission resources of the base stations for serving users can be reduced, the pilot frequency overhead of channel estimation between the base stations is saved, the bit error rate of an uplink disturbed station is reduced, and the downlink average user rate is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of wireless communications, and in particular relates to a method, device and equipment for eliminating cross-link interference. Background Art

[0002] 1. Dynamic Time Division Duplexing (D-TDD) technology.

[0003] Dynamic time division duplex technology is a flexible duplex technology with important potential application value. It can realize the dynamic configuration of time domain resources in uplink and downlink transmission to meet the business needs of asymmetric uplink and downlink traffic. In the same-frequency multi-base station system using dynamic time division duplex technology, due to the shared frequency band and different uplink and downlink time slot ratios of different base stations, the crossover of uplink and downlink time slots of multiple base stations or terminals will cause co-frequency cross-link interference, seriously affecting system performance. There are two main types of cross-link interference, namely, interference from downlink base stations to uplink base stations and interference from uplink terminals to downlink terminals. In dynamic time division duplex technology, since the transmission power of general base stations is larger than that of user equipment, the uplink signal of the disturbed base station is greatly affected by the downlink signal of the disturbing base station. Therefore, it is necessary to solve the problem of cross-link interference time slot interference between base stations.

[0004] 2. Beamforming technology.

[0005] Beamforming technology uses the principle of constructive and destructive interference. By adjusting the amplitude and phase of the transmitted signals on different antennas to produce destructive interference, the power of the superimposed signals can be reduced or even zero. At the same time, constructive interference is performed at other locations to increase the power of the superimposed signals or even reach a peak value. In the same time-frequency resources, beamforming technology can also be used to achieve signal enhancement, interference suppression and other effects. The prior art provides a variety of methods for cross-link interference elimination based on beamforming technology. However, the methods in the prior art have poor performance in eliminating cross-link interference.

[0006] A Chinese patent application with publication number CN113727365A disclosed an interference control method and device on November 30, 2021. Figure 1 As shown, the method is applied to an interfering base station, including: 1) sending a first channel state information reference signal to the interfered base station to obtain a target interfering beam whose reference signal receiving power is greater than a preset threshold; 2) receiving a first signaling message sent by the interfered base station in response to the first channel state information reference signal, the first signaling message including an identifier of the target interfering beam; 3) adjusting the beam parameters of the target interfering beam according to a pre-set beam adjustment strategy. This method requires frequent transmission of channel state information reference signals and signaling messages between base stations, occupying the transmission resources of the base station used to normally serve users. Summary of the invention

[0007] In view of the shortcomings of the prior art that reference signals and signaling messages need to be frequently sent between base stations, occupying a large amount of normal transmission resources, the present invention provides a cross-link interference elimination method, device and equipment to improve the cross-link interference elimination performance in dynamic time division duplex scenarios.

[0008] In a first aspect, the present invention provides a method for eliminating cross-link interference, comprising the following steps:

[0009] Step 1: The interfering station obtains statistical channel state information between the interfering station and the interfered station; the statistical channel state information is the channel covariance matrix between base stations;

[0010] Step 2: The interfering station performs eigenvalue decomposition on the channel covariance matrix and determines the number of eigenvectors that need to be eliminated according to the set link suppression threshold. ;

[0011] Suppose the channel covariance matrix is ​​subjected to eigenvalue decomposition to obtain the eigenvalue , is the number of antennas configured for the interfering station; the unitary matrix composed of the eigenvectors corresponding to the eigenvalues ​​is ; The calculation is as follows:

[0012] ; Among them, the link suppression threshold ;

[0013] Step 3: The interfering station obtains the downlink channel matrix between the terminal device it serves and performs preprocessing; the preprocessing is to combine the obtained downlink channel matrix with the unitary matrix Multiply and according to the , divide the multiplied matrix into two sub-matrices according to the column dimension, corresponding to the previous Column and all remaining columns;

[0014] Step 4: The interfering station calculates the final beamforming matrix and uses it for downlink communication, including:

[0015] For the sub-matrix Find the pseudo-inverse matrix ; The superscript H indicates conjugate transpose, and the superscript -1 indicates inverse matrix;

[0016] According to the unitary matrix With the matrix Get the final beamforming matrix ; The superscript T indicates transpose.

[0017] In the step 1, calculating the statistical channel state information between the interfering station and the interfered station includes: obtaining the covariance matrix of the channel between the base stations includes: obtaining the channel matrices between the multiple interfering stations and the interfered stations ; For each channel matrix obtained calculate , the superscript H indicates the conjugate transpose; calculate all The channel covariance matrix between the interfering station and the victim station is obtained by taking the average value of .

[0018] In a second aspect, the present invention provides a cross-link interference elimination device, which is deployed on an interfering station, and includes:

[0019] A statistical channel state information acquisition module, which acquires statistical channel state information between the interfering station and the disturbed station according to the channel matrix between the interfering station and the disturbed station; the statistical channel state information is a channel covariance matrix between base stations;

[0020] The eigenvalue decomposition module performs eigenvalue decomposition on the channel covariance matrix, and the eigenvalues ​​are obtained. , The number of antennas configured for the interfering station; then the number of feature vectors that need to be eliminated for interference is determined based on the set link suppression threshold ; The calculation formula is: ; where link suppression threshold ;

[0021] The preprocessing module obtains the downlink channel matrix between the interfering station and the served terminal device and performs preprocessing; the preprocessing is to combine the obtained downlink channel matrix with the unitary matrix Multiply and according to the , divide the matrix obtained by multiplication into the first Submatrix of columns After Submatrix of columns ; The unitary matrix The eigenvectors corresponding to the eigenvalues ​​of the channel covariance matrix decomposition are composed;

[0022] The beamforming matrix calculation module calculates the sub-matrix Find the pseudo-inverse matrix , and then according to the unitary matrix With the matrix Get the final beamforming matrix ;in, , , the superscript H represents conjugate transpose, the superscript T represents transpose, and the superscript -1 represents the inverse matrix.

[0023] The present invention also provides a device, on which a cross-link interference elimination device is deployed or a memory for implementing a cross-link interference elimination method program is deployed. The device is used for an interfering station, and the interfering station executes the cross-link interference elimination device or the cross-link interference elimination method to calculate a final beamforming matrix for a downlink channel between the interfering station and the served terminal device to suppress cross-link interference.

[0024] Compared with the prior art, the advantages and positive effects of the present invention are: the cross-link interference elimination method, device and equipment of the present invention utilize statistical channel state information between base stations, and then utilize the instantaneous channel state information between the interfering station and the user terminal it serves to suppress interference with the user terminal in the cell, and do not require a long-term real-time process in which the interfering station sends a channel state information reference signal and the interfered base station replies to the signaling message. The cross-link interference elimination method, device and equipment of the present invention can reduce the occupation of normal transmission resources used by base stations to serve users; there is no need to frequently exchange instantaneous channel state information between base stations, which can save pilot overhead for channel estimation between base stations; the burden of channel state information data transmission is reduced, and the pressure on the return link between base stations is reduced; the bit error rate of the uplink interfered station is reduced, the power ratio of the receiver signal of the uplink interfered station to the cross-link interference between base stations is improved, and the downlink average user rate is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a flow chart of an interference control method of an existing interference base station;

[0026] Figure 2 It is a system architecture diagram using dynamic time division duplex technology;

[0027] Figure 3 is a flow chart of a cross-link interference elimination method of the present invention;

[0028] Figure 4 It is a CDF comparison diagram of the uplink signal and cross-link interference (CLI) power ratio between base stations of different methods in the experiment of the present invention;

[0029] Figure 5 is a comparison chart of uplink bit error rates of different methods in the experiment of the present invention;

[0030] Figure 6 It is a comparison chart of the average downlink user rates of different methods in the experiment of the present invention. DETAILED DESCRIPTION

[0031] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0032] The cross-link interference elimination method provided by the present invention first uses the statistical channel state information between base stations to suppress cross-link interference, and then uses the instantaneous channel state information between the interfering station and the downlink user terminal it serves to suppress interference between user terminals in the cell. Compared with the existing scheme, the present invention does not require frequent information exchange between base stations, can save the pilot overhead of channel estimation between base stations and reduce the burden of channel state information data transmission, thereby reducing the pressure on the return link between base stations; reducing the bit error rate of the uplink interfered station, improving the power ratio of the receiver signal at the uplink interfered station to the cross-link interference, and improving the downlink average user rate.

[0033] like Figure 2 As shown, the system using dynamic time division duplex technology in the application scenario of the embodiment of the present invention has an overall architecture including a disturbing base station, a disturbed base station, user equipment served by the cell where the disturbing base station is located, and user equipment served by the cell where the disturbed base station is located. Among them, the base station can be any type of multi-antenna base station, including but not limited to macro base stations, pico base stations and micro base stations; the user equipment can be any terminal device that accesses the wireless network, including but not limited to mobile phones, computers and smart tablets. The disturbing base station and the disturbed base station are referred to as the disturbing station and the disturbed station respectively.

[0034] Both the interfering station and the interfered station can serve multiple user devices at the same time, and both the interfering station and the interfered station support obtaining the channel information between base stations through channel estimation and other methods, including but not limited to channel information based on pilot channel estimation. Antenna and service Downlink terminal equipment, disturbed station configuration Antenna and service A terminal device.

[0035] like Figure 3 As shown, the cross-link interference elimination method of the embodiment of the present invention includes the following steps.

[0036] Step 1: The interfering station obtains the statistical channel status information between itself and the interfered station.

[0037] In the embodiment of the present invention, the interfering station obtains a plurality of channel matrices between the interfering station and the interfered station. , and further calculate the channel covariance matrix based on the obtained channel matrix between base stations. The statistical channel state information in the embodiment of the present invention is the channel covariance matrix between base stations. The interfering station calculates the channel covariance matrix based on the obtained channel matrix between each base station. calculate , and then through multiple calculations Find the average value and obtain the channel covariance matrix between base stations The superscript H indicates the conjugate transpose. represents a complex set, Represents the mean.

[0038] Among them, the method of obtaining the above inter-base station channel matrix includes but is not limited to a method in which the interfering station sends a reference signal for channel estimation or channel quality measurement to the interfered station, and the receiving interfered station estimates the channel according to the reference signal and feeds back.

[0039] Step 2: The interfering station performs eigenvalue decomposition on the channel covariance matrix to obtain a number of eigenvalues ​​and corresponding eigenvectors, and determines the number of eigenvectors that need to be eliminated according to the set link suppression threshold.

[0040] In the embodiment of the present invention, the interfering station processing unit first Perform eigenvalue decomposition, that is ,in, The eigenvalue A diagonal matrix in descending order, Is The unitary matrix consisting of the eigenvectors corresponding to each eigenvalue in , is the number of eigenvalues, corresponding to the number of antennas configured at the interfering station.

[0041] Furthermore, the interfering station processing unit performs a link suppression operation according to a preset link suppression threshold. Select the corresponding matrix eigenvector to eliminate cross-link interference. First, determine the number of eigenvectors to be selected based on the link suppression threshold. , The value is calculated as follows:

[0042]

[0043] The link suppression threshold is the predefined suppression threshold of cross-link interference between base stations. The above formula argmin is the minimum value from [1,M] that satisfies the link suppression threshold condition. . For the feature values.

[0044] Step 3: The interfering station obtains the downlink channel matrix between the terminal devices it serves , and preprocess it.

[0045] Among them, the method of obtaining the downlink channel matrix includes but is not limited to a method in which the interfering station sends a reference signal for channel estimation or channel quality measurement to each downlink terminal device, each receiving end receives and estimates the channel based on the reference signal and feeds back to the interfering station.

[0046] The preprocessing includes obtaining a downlink channel matrix After processing, , and based on the confirmed Value It is divided into two parts according to the dimension, expressed as ,in and Respectively represent matrices Before Column and back List.

[0047] Step 4: The processing unit of the interfering station calculates the final beamforming matrix. First, according to the matrix decomposition Taking the pseudo-inverse we get , further, according to the above and Get the final beamforming matrix and use it for downlink communication.

[0048] Accordingly, an embodiment of the present invention implements a cross-link interference elimination device, which is deployed on the interfering station and includes: a statistical channel state information acquisition module, an eigenvalue decomposition module, a preprocessing module and a beamforming matrix calculation module. The statistical channel state information acquisition module obtains the statistical channel state information between the interfering station and the interfered station based on the channel matrix between the interfering station and the interfered station. The statistical channel state information of the present invention is the channel covariance matrix between base stations. The eigenvalue decomposition module performs eigenvalue decomposition on the obtained channel covariance matrix, as in step 2 above, to obtain the eigenvalue ; Based on the pre-set link suppression threshold Determine the number of eigenvectors that need to be eliminated The preprocessing module obtains the downlink channel matrix between the interfering station and the terminal device it serves and performs preprocessing. The preprocessing is to combine the obtained downlink channel matrix with the unitary matrix Multiply and according to The matrix obtained by multiplication is divided into the first Submatrix of columns After Submatrix of columns The beamforming matrix calculation module is a sub-matrix Find the pseudo-inverse matrix , and then according to the unitary matrix With the matrix Get the final beamforming matrix .

[0049] According to the above embodiments, the present invention also implements a device for an interfering station, on which a cross-link interference elimination device is deployed or a memory for implementing a cross-link interference elimination method program is deployed, and in a downlink channel between the interfering station and the served terminal device, the processor of the interfering station can execute the cross-link interference elimination device or the cross-link interference elimination method, calculate the final beamforming matrix for the downlink channel, and perform cross-link interference suppression.

[0050] In order to illustrate the technical effect of the method of the present invention, an experimental comparison is conducted between the method and the prior art.

[0051] The existing technologies compared include: the cross-link interference suppression beamforming method based on singular value decomposition (SVD-based) in massive MIMO system, the traditional maximum ratio transmission (MRT) linear beamforming method, and the zero forcing (ZF) linear beamforming method.

[0052] The transmission power parameters of the base station and the terminal are set the same in the comparison method and the method of the present invention. The channels between the terminal and the base station are Rayleigh channels. The calculation complexity of the beamforming matrix of the ZF, SVD-based method and the method of the present invention are , but the method of the present invention saves the channel estimation overhead compared with the SVD-based method. The performance of the method of the present invention and the comparative method is demonstrated by the Monte Carlo method.

[0053] like Figure 4 As shown, it is assumed that the user equipment is evenly distributed in a circle with a radius of 100 meters from the interfering station. The Monte Carlo method is used to simulate the cumulative density function (CDF) of the ratio of the uplink signal to the cross-link interference power between base stations, where the cross-link interference power between base stations is fixed at -80dB. As can be seen from the figure, the method of the present invention is a suboptimal solution, and the optimal solution is the SVD-based solution. The ZF and MRT solutions have poor interference suppression effects because they do not consider the interference elimination design. Among them, the SVD-based solution requires the use of instantaneous channel state information between base stations, and requires frequent channel estimation between base stations and feedback to the interfering station. The method of the present invention uses statistical channel state information between base stations. This method avoids frequent channel estimation between base stations, reduces the overhead of channel state information collection and the frequency of channel estimation between base stations, but also sacrifices a certain degree of accuracy. Figure 4 The horizontal axis is the ratio of the uplink signal power to the CLI power between base stations, and the vertical axis is the CDF value.

[0054] like Figure 5As shown in the figure, the uplink bit error rate of the method of the present invention is significantly lower than that of other comparative methods. The method of the present invention reduces the average cross-link interference power between base stations through the preprocessing operation in the beamforming design, and its uplink bit error rate is improved by about 7 dB compared with the traditional MRT algorithm and ZF algorithm. Figure 5 The horizontal axis is the signal-to-noise ratio, and the vertical axis is the bit error rate.

[0055] like Figure 6 As shown in the figure, the growth trend of the average downlink user rate of the method of the present invention is almost the same as that of the traditional ZF algorithm, and the performance in the high signal-to-noise ratio area (SNR>10dB) is better than that of the MRT and SVD-based algorithms. The method of the present invention can effectively suppress the intra-cell interference of the downlink, but because the degree of freedom is sacrificed in the preprocessing for interference elimination design, the communication performance is slightly lower than that of the traditional ZF method. Figure 6 The horizontal axis is the signal-to-noise ratio, and the vertical axis is the average downlink user rate.

[0056] Except for the technical features described in the specification, all of them are known technologies to those skilled in the art. The present invention omits the description of known components and known technologies to avoid redundancy and unnecessary limitation of the present invention. The implementation methods described in the above embodiments do not represent all implementation methods consistent with the present application. On the basis of the technical solution of the present invention, various modifications or variations that can be made by those skilled in the art without creative labor are still within the protection scope of the present invention.

Claims

1. A cross-link interference suppression method based on beamforming technology, characterized in that: The steps include: Step 1: The interfering station obtains statistical channel state information between the interfering station and the interfered station; the statistical channel state information is a channel covariance matrix between base stations; Step 2: The interfering station performs eigenvalue decomposition on the channel covariance matrix, and then determines the number of eigenvectors that need to be eliminated based on the set link suppression threshold. ; Suppose the channel covariance matrix is ​​subjected to eigenvalue decomposition to obtain the eigenvalue , is the number of antennas configured for the interfering station; the unitary matrix composed of the eigenvectors corresponding to the eigenvalues ​​is ; The calculation is as follows: ; Among them, the link suppression threshold ; Step 3: The interfering station obtains the downlink channel matrix between the terminal device it serves and performs preprocessing; the preprocessing is to combine the obtained downlink channel matrix with the unitary matrix Multiply and according to the , divide the matrix obtained by multiplication into the first Submatrix of columns After Submatrix of columns ; Step 4: The interfering station calculates the final beamforming matrix and uses it for downlink communication, including: Find the pseudo-inverse matrix , and then according to the unitary matrix With the matrix Get the final beamforming matrix ; Among them, the superscript H represents conjugate transpose, the superscript T represents transpose, and the superscript -1 represents the inverse matrix.

2. The method according to claim 1, characterized in that In the step 1, obtaining the covariance matrix of the channel between the base stations includes: obtaining the channel matrix between the multiple interfering stations and the interfered stations ; For each channel matrix obtained calculate , calculate all The channel covariance matrix between the interfering station and the victim station is obtained by taking the average value of .

3. The method according to claim 1, characterized in that In the step 3, the preprocessing includes: the facility interference station obtains the downlink channel matrix between the terminal device served ,right Processed , and then according to Will The column dimension is divided into two parts, ,in and Corresponding matrices Before Column and back List.

4. A cross-link interference elimination device, deployed on an interference station, characterized in that: The device includes: A statistical channel state information acquisition module, which acquires statistical channel state information between the interfering station and the disturbed station according to the channel matrix between the interfering station and the disturbed station; the statistical channel state information is a channel covariance matrix between base stations; The eigenvalue decomposition module performs eigenvalue decomposition on the channel covariance matrix, and the eigenvalues ​​are obtained. , The number of antennas configured for the interfering station; then the number of feature vectors that need to be eliminated for interference is determined based on the set link suppression threshold ; The calculation formula is: ; where link suppression threshold ; The preprocessing module obtains the downlink channel matrix between the interfering station and the served terminal device and performs preprocessing; the preprocessing is to combine the obtained downlink channel matrix with the unitary matrix Multiply and according to the , divide the matrix obtained by multiplication into the first Submatrix of columns After Submatrix of columns ; The unitary matrix The eigenvectors corresponding to the eigenvalues ​​of the channel covariance matrix decomposition are composed; The beamforming matrix calculation module calculates the sub-matrix Find the pseudo-inverse matrix , and then according to the unitary matrix With the matrix Get the final beamforming matrix ;in, , , the superscript H represents conjugate transpose, the superscript T represents transpose, and the superscript -1 represents the inverse matrix.

5. The device according to claim 4, characterized in that The statistical channel state information acquisition module acquires the channel matrix between the multiple interfering stations and the interfered stations. , for each channel matrix obtained calculate , calculate all The channel covariance matrix between the interfering station and the victim station is obtained by taking the average value of .

6. A device installed at an interference station, on which a memory is deployed to store a program for implementing a cross-link interference suppression method as described in claim 1, 2 or 3, or a cross-link interference elimination device as described in claim 4 or 5 is deployed. The interference station executes the cross-link interference elimination device or the cross-link interference elimination method to calculate a final beamforming matrix for use in a downlink channel between the terminal device being served.

Images