Method and device for multi-cell communication interference cancellation based on reconfigurable refractive metasurface

Abstract

The application discloses a multi-cell communication interference elimination method and device based on a reconfigurable refractive metasurface, and the method comprises the following steps: acquiring communication parameters; jointly designing the height and the pitch angle of the reconfigurable refractive metasurface of a base station c; based on the height and the pitch angle, calculating the total channel matrix value instantaneous value of each unit of the reconfigurable refractive metasurface of the base station c and each user in each cell; jointly designing the digital beamforming matrix set of the base station and the transmission coefficient matrix set of the reconfigurable refractive metasurface, so as to maximize the total transmission rate of the users in each cell; based on the digital beamforming matrix set, using the corresponding digital beamforming matrix to set the digital beamforming matrix inside each base station, and based on the transmission coefficient matrix set, using the corresponding transmission coefficient matrix to set the state of each unit of the reconfigurable refractive metasurface. The application can eliminate the interference in the multi-cell communication system based on the reconfigurable refractive metasurface antenna, so as to maximize the sum rate.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of electronics, in particular to a multi-cell communication interference cancellation method and device based on reconfigurable refractive metasurface. BACKGROUND

[0002] Massive MIMO is an important part of future wireless communication. In existing massive MIMO systems, a traditional phased array antenna is used to realize beamforming. However, the traditional phased array has the disadvantages of high power consumption and high cost. In order to solve this problem, recently, people have proposed a reconfigurable reflective metasurface antenna. However, this antenna has the following disadvantages: due to the shielding effect of the feed on the reflected wave, the antenna radiation efficiency is not high. Therefore, people have proposed a reconfigurable refractive metasurface (RRS) antenna. Since the reconfigurable refractive metasurface does not have the problem of feed shielding, its radiation efficiency is higher than that of the traditional reconfigurable reflective metasurface antenna. However, existing research on reconfigurable refractive metasurface antennas is basically focused on how to design the antenna to optimize and antenna-related indicators such as bandwidth, loss, etc., without considering communication systems based on RRS antennas. Moreover, existing research is only on reconfigurable refractive metasurface antennas containing a single feed, so it cannot be used in multi-user systems. SUMMARY

[0003] In order to solve the above problems, the present application provides a multi-cell communication interference cancellation method and device based on reconfigurable refractive metasurface, which generates a communication interference cancellation scheme by modeling and solving an optimization problem to eliminate interference.

[0004] The technical scheme of the present application includes:

[0005] A multi-cell communication interference cancellation method based on reconfigurable refractive metasurface, applicable to a communication system composed of C cells, wherein each cell is provided with a base station c configured with a reconfigurable refractive metasurface antenna and L users, the reconfigurable refractive metasurface antenna is composed of K c feed sources and a reconfigurable refractive metasurface, the reconfigurable refractive metasurface includes a plurality of units, and the method comprises the following steps:

[0006] Obtaining communication parameters, including: the number of feed sources and the number of units included in the reconfigurable refractive metasurface antenna of the base station, the number of users, the distribution of small-scale fading in the total channel matrix of each unit of the reconfigurable refractive metasurface of the base station c and each user in each cell, the variance of the total channel matrix H c between each feed source of the base station c and each unit and the variance of additive white Gaussian noise;

[0007] Based on the number of users, the distribution of small-scale fading in the total channel matrix of each cell of the reconfigurable refractive metasurface of base station c and each user in each cell, and the total channel matrix H c The variance of additive white Gaussian noise is used to jointly design the height and pitch angle of the reconfigurable refractive metasurface of base station c;

[0008] Based on the height and pitch angle, calculate the instantaneous values ​​of the total channel matrix for each cell of the reconfigurable refractive metasurface of base station c and for each user in each cell;

[0009] Based on the number of feed sources, element numbers, user numbers, instantaneous value of the total channel matrix, and variance of additive white Gaussian noise contained in the reconfigurable refractive metasurface antenna of the base station, the digital beamforming matrix set {V} of the base station is jointly designed. c} and the set of transmission coefficient matrices of reconfigurable refractive metasurfaces {R c}, to maximize the total transmission rate S for users in each cell;

[0010] Based on the digital beamforming matrix set {V c}, using the corresponding digital beamforming matrix V c Configure the digital beamforming matrix within each base station, and based on the transmission coefficient matrix set {R} c}, using the corresponding transmission coefficient matrix R c Configure the state of each unit cell of the reconfigurable refractive metasurface.

[0011] Furthermore, the reconfigurable refractive metasurface height and pitch angle of the designed base station c include:

[0012] 1) Maintain height Keeping the total transmission rate constant, calculate the optimal total transmission rate S. t Record the corresponding pitch angle. Where t is the number of the first iteration;

[0013] 2) Maintain pitch angle Keeping the total transmission rate constant, calculate the optimal total transmission rate S′. t And record the corresponding height.

[0014] 3) When the optimal total user transmission rate S′ t With the optimal total user transmission rate S′ t+1 When the difference is less than a preset threshold, based on height With pitch angle Design the reconfigurable refractive metasurface height and pitch angle of base station c.

[0015] Further, the instantaneous value of the total channel matrix is ​​obtained through the following steps:

[0016] 1) Calculate the path loss in each channel based on the designed height and elevation angle;

[0017] 2) Measure the instantaneous value of small-scale fading in the total channel matrix of each cell and each user of the base station c's reconfigurable metasurface at this height and elevation angle;

[0018] 3) Obtain the total channel matrix value instantaneous value according to the path loss and the instantaneous value.

[0019] Further, the digital beamforming matrix set {V c} and the reconfigurable metasurface transmission coefficient matrix set {R c} of the base station of each cell are designed by the following steps:

[0020] 1) Keep the transmission coefficient matrix R unchanged, calculate the optimal user total transmission rate S t′ , and record the corresponding digital beamforming matrix set V , where t' is the second iteration number;

[0021] 2) Keep the digital beamforming matrix set V unchanged, calculate the optimal user total transmission rate S' t′ , and record the corresponding transmission coefficient matrix R

[0022] 3) When the difference between the optimal user total transmission rate S' t′ and the optimal user total transmission rate S' t′+1 is less than a preset threshold, the digital beamforming matrix set {V } and the transmission coefficient matrix set {R } of the base station of each cell are designed based on the digital beamforming matrix set V c and the transmission coefficient matrix R c .

[0023] Further, when designing the digital beamforming matrix set {V c} and the transmission coefficient matrix set {R c} of the base station, the constraint conditions include the phase constraint of each unit and the total power constraint of the base station.

[0024] Further, the method for constructing the transmission coefficient matrix R c includes taking the transmission coefficient of each unit as the diagonal element of the transmission coefficient matrix R c .

[0025] A storage medium having a computer program stored therein, wherein the computer program is configured to execute any of the above methods when running.

[0026] An electronic device comprising a memory having stored therein a computer program and a processor arranged to run the computer program to perform any of the above methods.

[0027] A multi-cell communication method based on reconfigurable refractive metasurface, comprising the steps of:

[0028] performing digital beamforming on the signal s c c intended for users in the c-th cell based on the digital beamforming matrix V c and inputting the digitally beamformed signal into a feed of a reconfigurable refractive metasurface antenna;

[0029] performing analog beamforming on the signal transmitted by the feed based on the transmission coefficient matrix R c after the signal transmitted by the feed is incident on the reconfigurable refractive metasurface;

[0030] receiving the analog beamformed signal after channel transmission by corresponding users in the c-th cell.

[0031] A multi-cell communication system based on reconfigurable refractive metasurface, each cell comprising:

[0032] a base station c configured to perform digital beamforming on the signal s c c intended for users in the c-th cell based on the digital beamforming matrix V c and inputting the digitally beamformed signal into a feed of a reconfigurable refractive metasurface antenna; performing analog beamforming on the signal transmitted by the feed based on the transmission coefficient matrix R c after the signal transmitted by the feed is incident on the reconfigurable refractive metasurface; and transmitting the analog beamformed signal; wherein the reconfigurable refractive metasurface antenna is composed of K c feeds and a reconfigurable refractive metasurface comprising a plurality of units, the digital beamforming matrix V c and the transmission coefficient matrix R c are obtained by:

[0033] obtaining communication parameters, including: the number of feeds and the number of units included in the reconfigurable refractive metasurface antenna of the base station, the number of users, the total channel matrix of each unit of the reconfigurable refractive metasurface of the base station c and each user in each cell, the total channel matrix H c between each feed and each unit of the base station c, and the variance of additive white Gaussian noise;

[0034] According to the number of users, the total channel matrix of each unit of the reconfigurable refractive metasurface of the base station c and each user in each cell, the total channel matrix H c The height and the pitch angle of the reconfigurable refractive metasurface of the base station c are jointly designed according to the variance of the additive white Gaussian noise.

[0035] Based on the height and the pitch angle, the total channel matrix value instantaneous value of each unit of the reconfigurable refractive metasurface of the base station c and each user in each cell is calculated.

[0036] According to the number of feed sources and the number of units of the reconfigurable refractive metasurface antenna of the base station, the number of users, the total channel matrix value instantaneous value, and the variance of the additive white Gaussian noise, the digital beamforming matrix set {V c} and the transmission coefficient matrix set {R c} of the reconfigurable refractive metasurface of the base station are jointly designed to maximize the total transmission rate S of the users in each cell.

[0037] Based on the digital beamforming matrix set {V c}, the corresponding digital beamforming matrix V c is set for each base station, and based on the transmission coefficient matrix set {R c}, the corresponding transmission coefficient matrix R c is set for each unit of the reconfigurable refractive metasurface.

[0038] L users, each user l uses to receive the corresponding analog beamformed signal after the channel transmission.

[0039] Compared with the prior art, the present application has the following advantages:

[0040] 1. The reconfigurable refractive metasurface antenna of the present application can simultaneously transmit data to multiple users.

[0041] 2. The interference cancellation method of the present application can be used to cancel the interference in the multi-cell communication system based on the reconfigurable refractive metasurface antenna, thereby maximizing the sum rate. BRIEF DESCRIPTION OF DRAWINGS

[0042] Figure 1 Reconfigurable refractive metasurface antenna.

[0043] Figure 2 Multi-cell communication system based on reconfigurable refractive metasurface antenna.

[0044] Figure 3 Method flowchart of the present application.

[0045] Figure 4 Method for canceling interference in multi-cell communication system based on reconfigurable refractive metasurface antenna.

[0046] Figure 5 A comparison chart of simulation results between the present invention and existing technologies. Detailed Implementation

[0047] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only specific embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0048] 1. Reconfigurable refractive metasurface antenna

[0049] A reconfigurable refractive metasurface (RRS) antenna consists of multiple feed sources and a refractive metasurface. For example... Figure 1 As shown, a refractive metasurface is an array of multiple subwavelength units. Each unit has a PIN diode, which can be switched between ON and OFF by adjusting the bias voltage across it. When a signal is incident on each unit, it is refracted. By adjusting the state of the diode on the unit, the phase of the refracted wave can be changed.

[0050] The beamforming process of this reconfigurable refractive metasurface antenna is as follows: After the signal emitted by the feed is incident on each element, it undergoes refraction. During this refraction process, the metasurface element applies a certain phase shift to the signal. By adjusting the bias voltage on the diodes, the refraction phase shift of the element is appropriately set, thereby achieving beamforming.

[0051] 2. Multi-cell communication system based on reconfigurable refractive metasurface antenna

[0052] In this multi-cell communication system, there are C cells, each with a base station equipped with an RRS antenna, which communicates with L mobile users within that cell. To maximize the total data rate for all users in the multi-cell wireless communication system, the base station first performs digital beamforming on the signal sent to the users. Then, the encoded signal is input into the feedhorn of the RRS. The signal transmitted from the feedhorn is transmitted onto the RRS and undergoes a phase shift before being transmitted to and received by each user, thus forming a hybrid beamforming scheme (digital + analog).

[0053] 3. System Modeling

[0054] like Figure 2 As shown, assume that each base station c sends a signal s to the users in its own cell. c , where s cIt is an L-dimensional column vector, s c,l This represents the signal sent to user l. Assume V c It is the digital beamforming matrix of the c-th cell, with a size of K×L, V c,l It is V c The lth column.

[0055] Let M*N denote the number of elements contained in the RRS, and let K denote the number of feed sources contained in the RRS. c The transmission coefficient matrix of this RRS is denoted as R. c The elements on the diagonal of this transmittance matrix represent the transmittance coefficients of each element in the RRS, and can be denoted as... Furthermore, when the state of a cell changes, the phase shift of that cell can vary within the range of (0, 2π). The total channel matrix between each cell of the RRS of base station c and user l of the c-th cell is then expressed using... Represented. The total channel matrix between each unit of the RRS of base station c and user l′ of the c′-th cell is represented by... It is represented as having a dimension of 1×MN. The total channel matrix between each feed of base station c and each element of the RRS of that base station is represented as H. c Its dimensions are MN×K t .

[0056] The signal received by user l in the c-th cell can be represented as:

[0057]

[0058] The first term is the signal that user l in cell c wants to receive, the second term is the interference between users within the cell, the third term is the interference between cells, and the fourth term is the Gaussian white noise in the channel.

[0059] 4. Interference cancellation methods in multi-cell communication systems

[0060] The interference cancellation method of the present invention, such as Figure 3 The process involves first obtaining communication system parameters, then designing the deployment of reconfigurable refractive metasurfaces for each base station, and finally, based on this deployment, designing the digital beamforming matrix and the transmission coefficient matrix for each RRS.

[0061] 1) Obtain communication system parameters

[0062] To perform interference cancellation, this invention first obtains the communication system parameters based on the above modeling. These communication system parameters include, but are not limited to: the number of feed sources and elements in the reconfigurable refractive metasurface antenna of the base station, the number of users, and the total channel matrix between each element of the reconfigurable refractive metasurface of base station c and each user in the cell. distribution of the small-scale fading in H total channel matrix H between each feed of base station c to each unit in H c variance of the additive white Gaussian noise in the user received signal 2 etc.

[0063] 2) Design the deployment of the reconfigurable refractive metasurface of each base station

[0064] The deployment of the reconfigurable refractive metasurface of base station c contains the height l c and the tilt angle θ c of the reconfigurable refractive metasurface. To design the deployment, we model this problem as an optimization problem. The objective function is the expectation of the total transmission rate of the users in each cell, and the optimization variable is the deployment of the reconfigurable refractive metasurface of each base station. The optimization problem can be written as:

[0065]

[0066]

[0067] where σ 2 is the variance of the noise in the user received signal.

[0068] Solving the above optimization problem by the method of alternating optimization, we can obtain the height l c and the tilt angle θ c of the reconfigurable refractive metasurface.

[0069] 3) Design the digital beamforming matrix of each base station and the transmission coefficient matrix of each RRS

[0070] Based on the deployment of the reconfigurable refractive metasurface of each base station, we can calculate the path loss in each channel; then we measure the instantaneous value of the small-scale fading in H and H From the small-scale fading and the path loss, we can calculate the instantaneous value of H and H and H

[0071] Finally, we combine the expression of the sum rate to construct a problem of maximizing the total transmission rate of the users:

[0072]

[0073]

[0074]

[0075] ​Wherein, the first constraint means that the transmission coefficient of each RRS unit has and only has L possible values, the amplitudes of which are the same and the phases of which are different. The second constraint is a power constraint, that is, the sum of the powers transmitted by each base station c to each user must be less than the total power of the base station. In order to solve the problem, we adopt the following iterative algorithm

[0076] As shown in Figure 4 The present application adopts an iterative algorithm, 1) keeping the transmission matrix of the RRS unchanged, solving the digital beamforming problem; 2) given the digital beamforming matrix, optimizing the RRS transmission matrix; 3) repeating step 1) until the difference between the sum rates of two adjacent iterations is less than a preset threshold.

[0077] The simulation environment of the present application and the conventional phased array is as follows: the working frequency of the system is set to 26GHz, there are three cells in total, each cell contains one base station and 2 users, the distance between the two users and the metasurface array (or phased array array) is 200m, and the respective distance is 50m, each user adopts an omnidirectional antenna for receiving signals. For the reconfigurable refractive metasurface antenna, it is assumed that it has 4 feed sources. Each feed source is an omnidirectional antenna, and the distance between the feed source and the metasurface array is 0.1m. It is assumed that the unit transmittance is 1, and the size of the unit is wherein λ is the wavelength corresponding to the working frequency of the system. As a comparison, consider when 4 small phased arrays are used as base station antennas. For each phased array antenna, the distance between the antenna units is set to half the wavelength, and it is assumed that the antenna units are omnidirectional antennas. The maximum power consumption (the power consumption required to maintain normal operation of the antenna) of the two kinds of antennas is set to 20W. From Figure 5 As shown in

[0078] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A multi-cell communication interference cancellation method based on reconfigurable metasurface, suitable for a communication system composed of C cells, wherein each of the cells is provided with a base station c configured with a reconfigurable metasurface antenna and L users, the reconfigurable metasurface antenna is composed of K c feed sources and a reconfigurable metasurface, the reconfigurable metasurface includes a plurality of units, the steps of the method comprising: Obtaining communication parameters, the communication parameters including: the number of feeds and the number of units included in the reconfigurable refractive metasurface antenna of the base station, the number of users, the distribution of small-scale fading in the total channel matrix of each user in each cell of each unit of the reconfigurable refractive metasurface of the base station c, the total channel matrix H between each feed and each unit of the base station c c and the variance of additive white Gaussian noise; According to the number of users, the distribution of small-scale fading in the total channel matrix of each user and each cell of each unit of the reconfigurable refractive metasurface of base station c, the total channel matrix H c The height and the pitch angle of the reconfigurable refractive metasurface of base station c are jointly designed with the variance of additive white Gaussian noise. Based on the height and pitch angle, calculate the instantaneous values ​​of the total channel matrix for each cell of the reconfigurable refractive metasurface of base station c and for each user in each cell; According to the number of feed sources, the number of units, the number of users, the total channel matrix value instantaneous value, and the variance of additive white Gaussian noise contained in the reconfigurable refractive metasurface antenna of the base station, the digital beamforming matrix set {V c} of the base station and the transmission coefficient matrix set {R c} of the reconfigurable refractive metasurface are jointly designed to maximize the total transmission rate S of the users in each cell. Based on a set of digital beamforming matrices {V c}, using the corresponding digital beamforming matrix V c Setting the digital beamforming matrix inside each base station, and based on a set of transmission coefficient matrices {R c}, using the corresponding transmission coefficient matrix R c Setting the state of each unit of the reconfigurable refractive metasurface.

2. The method of claim 1, wherein, The reconfigurable refractive metasurface height and pitch angle of the designed base station c include: 1) keep the height unchanged, compute the optimal total transmission rate S t and record the corresponding pitch angle where t is the first iteration number; 2) keep the pitch angle constant and calculate the optimal total transmission rate S' t and record the corresponding height 3) when the optimal user total transmission rate S' t is less than a preset threshold, based on the height t+1 of the difference between the optimal user total transmission rate S' and the pitch angle Design the height and pitch angle of the reconfigurable refractive metasurface of the base station c.

3. The method of claim 1, wherein, The instantaneous value of the total channel matrix is ​​obtained through the following steps: 1) Based on the designed altitude and pitch angle, calculate the path loss in each channel; 2) At this altitude and pitch angle, measure the instantaneous values ​​of small-scale fading in the total channel matrix of each cell of the reconfigurable refractive metasurface of base station c and each user in each cell; 3) Based on the path loss and instantaneous value, the instantaneous value of the total channel matrix is ​​obtained.

4. The method as described in claim 1, characterized in that, The set of digital beamforming matrices {V c} and the set of reconfigurable refractive metasurface transmission coefficient matrices {R c} for the base stations of each cell are designed by the following steps: 1) Maintain the transmission coefficient matrix Keeping constant, calculate the optimal total user transmission rate S. t′ And record the corresponding set of digital beamforming matrices. Where t′ is the second iteration number; 2) Maintain the digital beamforming matrix set Keeping constant, calculate the optimal total user transmission rate S′ t′ And record the corresponding transmission coefficient matrix. 3) When the optimal total user transmission rate S′ t′ With the optimal total user transmission rate S′ t′+1 When the difference is less than a preset threshold, based on the digital beamforming matrix set With the transmission coefficient matrix Design the digital beamforming matrix set {V} for each cell's base station. c } and the set of transmission coefficient matrices {R c } 5. The method as described in claim 1, characterized in that, A set of digital beamforming matrices {V c} and a set of transmission coefficient matrices {R c} for a base station are designed, with constraints including phase constraints for each element and total power constraints for the base station.

6. The method as described in claim 1, characterized in that, The method of constructing the transmission coefficient matrix R c includes taking the transmission coefficient of each unit as a diagonal element of the transmission coefficient matrix R c .

7. A storage medium storing a computer program, wherein, The computer program is configured to execute the method of any one of claims 1-6 at runtime.

8. An electronic device comprising a memory and a processor, the memory storing a computer program, the processor being configured to run the computer program to perform the method as claimed in any one of claims 1-6.

9. A multi-cell communication method based on a reconfigurable refractive metasurface, comprising the following steps: based on the digital beamforming matrix V obtained in any of the methods of claims 1-6 c The base station c performs digital beamforming on the signal s c directed to the users of the c-th cell and inputs the digitally beamformed signal into the feed of the reconfigurable diffractive metasurface antenna. The signal transmitted by the feed source is incident on the reconfigurable refractive metasurface, and based on the transmission coefficient matrix R obtained in any of the methods of claims 1-6 c Analog beamforming is performed on the signal transmitted by the feed source; The simulated beamforming signal is transmitted through the channel and received by the corresponding user in the c-th cell.

10. A multi-cell communication system based on a reconfigurable refractive metasurface, wherein each cell includes: A base station c configured with a reconfigurable refractive metasurface antenna, configured to perform digital beamforming on a signal s c to users of the c-th cell based on a digital beamforming matrix V c , and input the digitally beamformed signal into a feed of the reconfigurable refractive metasurface antenna; after the signal transmitted by the feed is incident on the reconfigurable refractive metasurface, analog beamforming is performed on the signal transmitted by the feed based on a transmission coefficient matrix R c ; and the analog beamformed signal is transmitted; wherein the reconfigurable refractive metasurface antenna is composed of K c feeds and a reconfigurable refractive metasurface, the reconfigurable refractive metasurface comprises a plurality of units, and the digital beamforming matrix V c and the transmission coefficient matrix R c are obtained by the following steps: Obtaining communication parameters, the communication parameters including: the number of feeds and the number of units included in the reconfigurable refractive metasurface antenna of the base station, the number of users, the total channel matrix of each unit of the reconfigurable refractive metasurface of the base station c to each user in each cell, the total channel matrix H between each feed and each unit of the base station c c and the variance of additive white Gaussian noise; According to the number of users, the total channel matrix of each user in each cell and each unit of the reconfigurable refractive metasurface of base station c, the total channel matrix H c The height and the pitch angle of the reconfigurable refractive metasurface of base station c are jointly designed with the variance of additive white Gaussian noise. Based on the height and pitch angle, calculate the instantaneous values ​​of the total channel matrix for each cell of the reconfigurable refractive metasurface of base station c and for each user in each cell; According to the number of feed sources, the number of units, the number of users, the total channel matrix value instantaneous value, and the variance of additive white Gaussian noise contained in the reconfigurable refractive metasurface antenna of the base station, the digital beamforming matrix set {V c} of the base station and the transmission coefficient matrix set {R c} of the reconfigurable refractive metasurface are jointly designed to maximize the total transmission rate S of the users in each cell. based on a set of digital beamforming matrices {V c} using the corresponding digital beamforming matrix V c setting the digital beamforming matrices within each base station and based on a set of transmission coefficient matrices {R c} using the corresponding transmission coefficient matrix R c setting the state of each cell of the reconfigurable refractive metasurface; There are L users, each user l, which receives the corresponding analog beamformed signal after transmission through the channel.

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