A ris codebook acquisition method

Abstract

This invention belongs to the field of communication technology, and its purpose is to provide a method for obtaining the RIS codebook. This invention constructs a signal transmission model, then obtains the amplitude of the output signal reflected by the RIS reflection module to the base station module or user terminal module in the signal transmission model, subsequently obtains the output signal power of the RIS reflection module, and constructs an optimization problem based on the output signal power. By solving the optimal solution to the optimization problem, the phase angle of the optimal solution is used as the RIS codebook for the RIS reflection module. This allows the RIS reflection module to perform beamforming on the electromagnetic wave signal received from the base station module or user terminal module based on the RIS codebook. In this process, when modeling the signal transmission model, only the base station location information and the user terminal location information need to be considered. Therefore, based on the signal arrival angle of the RIS reflection module and the angle of the direction to be enhanced, the optimization problem can be established and the RIS codebook obtained, avoiding the complex channel estimation process.

Description

Technical Field

[0001] This invention belongs to the field of communication technology, specifically relating to a method for obtaining RIS codebooks. Background Technology

[0002] RIS (Reconfigurable Intelligent Surface) is one of the candidate technologies for 6G. It is an artificial electromagnetic surface structure with programmable electromagnetic properties. It is usually composed of a large number of electromagnetic units. By controlling the state of each electromagnetic unit on the surface, an electromagnetic field with controllable parameters such as amplitude, phase, polarization and frequency can be formed, thereby realizing the active control of spatial electromagnetic waves. RIS has revolutionized the dilemma of the wireless environment being unchangeable in traditional communication.

[0003] Basic scenarios of RIS-assisted communication, such as Figure 1 As shown, base station x and user y are separated by an obstacle, and a RIS board W is artificially introduced to enhance the signal. In RIS-assisted communication, a codebook is used to implement beamforming of the RIS, so that the beam reflected by the RIS is concentrated in the direction of the user, thereby enhancing the signal power on the user side and improving the user's communication quality.

[0004] Obtaining a valid RIS codebook is an important means of achieving beamforming; however, in using existing technologies, the inventors have discovered at least the following problems:

[0005] While various methods exist for obtaining RIS codebooks, current technologies rely heavily on CSI (Channel State Information) between the base station, RIS, and the user. The introduction of RIS exponentially increases the number of communication links, making channel estimation extremely difficult. Furthermore, since RIS primarily relies on passive reflection and lacks sensing capabilities, obtaining CSI between the base station and RIS, and between RIS and the user, becomes even more challenging.

[0006] Furthermore, because acquiring CSI requires signal feedback and time delay, and in actual communication systems, especially in high-speed communication, the location of user terminals often changes rapidly, this further increases the difficulty of applying RIS. Summary of the Invention

[0007] The present invention aims to solve the above-mentioned technical problems to at least some extent, and provides a method for obtaining RIS codebooks.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] This invention provides a method for obtaining RIS codebooks, comprising:

[0010] Construct a RIS reflection module, which includes multiple RIS units uniformly distributed on a specified plane;

[0011] Obtain base station location information and user terminal location information, and construct a signal transmission model including a base station module, a user terminal module and the RIS reflection module based on the base station location information, the user terminal location information and the RIS reflection module;

[0012] In the signal transmission model, obtain the amplitude of the output signal reflected by the RIS reflection module to the base station module or the user terminal module;

[0013] The output signal power of the RIS reflection module is obtained based on the amplitude of the output signal reflected by the RIS reflection module to the base station module or the user terminal module, and an optimization problem is constructed based on the output signal power.

[0014] Obtain the optimal solution to the optimization problem;

[0015] The phase angle of the optimal solution is obtained and used as the RIS codebook of the RIS reflection module, so that the RIS reflection module can perform beamforming on the electromagnetic wave signal received from the base station module or the user terminal module based on the RIS codebook.

[0016] This invention enables rapid acquisition of the RIS codebook. During the acquisition process, channel estimation is not required, and there is no CSI dependency, saving channel estimation resources and facilitating RIS beamforming, thereby improving the received signal power of the base station or user terminal. Specifically, in implementation, this invention first constructs a signal transmission model including a base station module, a user terminal module, and the RIS reflection module. Then, the amplitude of the output signal reflected by the RIS reflection module to the base station module or user terminal module in the signal transmission model is obtained. Subsequently, the output signal power of the RIS reflection module is obtained, and an optimization problem is constructed based on this output signal power. By solving the optimal solution to the optimization problem, the phase angle of the optimal solution is used as the RIS codebook for the RIS reflection module. The RIS reflection module then performs beamforming on the electromagnetic wave signal received from the base station module or user terminal module based on the RIS codebook. In this process, when modeling the signal transmission model, only the base station location information and user terminal location information need to be considered. Therefore, based on the signal arrival angle of the RIS reflection module and the angle of the direction to be enhanced, the optimization problem can be established and the RIS codebook obtained, avoiding the complex channel estimation process.

[0017] In one possible design, obtaining the amplitude of the output signal reflected by the RIS reflection module to the base station module or the user terminal module in the signal transmission model includes:

[0018] In the signal transmission model, obtain the total phase shift caused by the i-th RIS unit in any row / column of the RIS reflection module to the electromagnetic wave signal incident on the RIS reflection module;

[0019] Based on the total phase shift caused by all RIS units of the RIS reflection module to the electromagnetic wave signal incident on the RIS reflection module, the amplitude of the output signal reflected by the RIS reflection module to the base station module or the user terminal module in the specified reflection direction in the signal transmission model is obtained.

[0020] In one possible design, the total phase shift caused by the i-th RIS unit in any row / column of the RIS reflection module to the electromagnetic wave signal incident on the RIS reflection module is:

[0021]

[0022] In the formula, w i Let be the reflection coefficient of the i-th RIS unit. The phase shift value is j, where j is the complex unit and i = 1, 2, ..., N; θ is the total phase shift difference between the i-th RIS unit and the first RIS unit; Arr θ represents the incident direction of the electromagnetic wave signal. Dep λ represents the direction of electromagnetic wave signal reflection; d represents the spacing between adjacent RIS units in the RIS reflection module; and λ represents the wavelength of the electromagnetic wave signal. This is the incident phase shift difference; This represents the phase shift difference in reflection.

[0023] In one possible design, the reflection direction is specified as θ. Dep In the signal transmission model, the RIS reflection module is in the reflection direction θ Dep The amplitude of the output signal reflected to the base station module or the user terminal module is:

[0024]

[0025]

[0026] In the formula, M is the angle of electromagnetic wave discreteness in space; These respectively represent the incident directions as At that time, the electromagnetic wave signal received by the RIS reflection module; α is the path loss of the electromagnetic wave signal, which is a constant term from 0 to 1.

[0027] In one possible design, an optimization problem is constructed based on the output signal power, including:

[0028] With maximizing the output signal power as the optimization objective and the constraint that the absolute value of the reflection coefficient of each RIS unit is equal to 1, an optimization problem is constructed; wherein, the optimization problem is:

[0029]

[0030]

[0031] In the formula, |y(θ) yep )| 2 The output signal power of the RIS reflection module.

[0032] In a possible design, obtaining the optimal solution to the optimization problem includes:

[0033] The optimization objective of the optimization problem is transformed to obtain the transformed optimization objective;

[0034] The constraints of the optimization problem are relaxed to obtain the relaxed constraints.

[0035] Based on the transformed optimization objective and the relaxed constraints, the optimization problem is solved to obtain the optimal solution to the optimization problem.

[0036] In one possible design, the optimization objective of the optimization problem is transformed to obtain the transformed optimization objective, including:

[0037] Let y(θ) Dep )=αaWBX;

[0038]

[0039] In the formula,

[0040] but

[0041] In the formula, vector w = [w1, w2, ... w N ] T P = BXX H B H Q = a H a; ☉ denotes the Hadamard product; tr(A) denotes the trace of matrix A;

[0042] Let R = Q☉P T The initial optimization objective after transformation is obtained; wherein, the initial optimization objective after transformation is:

[0043]

[0044] According to w H Rw = tr(Rww) H ), and through the variable substitution formula V = ww H The vector w to be optimized in the transformed optimization objective is transformed into a composite matrix V to obtain the transformed optimization objective; wherein, the transformed optimization objective is:

[0045]

[0046] In one possible design, the relaxed constraint condition is:

[0047] V≥0 and rank(V)=1.

[0048] In one possible design, based on the transformed optimization objective and the relaxed constraints, the optimization problem is solved to obtain the optimal solution to the optimization problem, including:

[0049] The optimization problem was solved by using the CVX toolbox in MATLAB software, and the solution to the composite matrix V was obtained.

[0050] The optimal solution to the optimization problem is obtained based on the solution of the composite matrix V.

[0051] In one possible design, the optimal solution to the optimization problem is obtained based on the solution of the composite matrix V, including:

[0052] Multiple complex Gaussian vectors r with a mean of 0 and a variance of 1 are randomly generated, and then calculated multiple times. Multiple pseudo solutions to the optimization problem were obtained.

[0053] Multiple pseudo-solutions Substitute into the expression respectively We obtain multiple intermediate values, and then find the pseudo solution corresponding to the maximum value among these intermediate values. As a pseudo-solution vector;

[0054] Phase angle recovery is performed on the pseudo-solution vector to obtain the optimal solution to the optimization problem. Attached Figure Description

[0055] Figure 1 This is a structural diagram of a basic scenario for RIS-assisted communication in existing technologies;

[0056] Figure 2 Flowchart of the RIS codebook acquisition method in Example 1;

[0057] Figure 3This is a schematic diagram showing the positions of all RIS units in any row / column of the RIS reflection module;

[0058] Figure 4 This is a power diagram of the signal received by the user terminal from the RIS board before an effective codebook was adopted;

[0059] Figure 5 This is a schematic diagram of the power of the signal received by the user terminal after the effective codebook is calculated using the method in Example 1;

[0060] Figure 6 This is a block diagram of the RIS codebook acquisition system in Example 2. Detailed Implementation

[0061] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the present invention will be briefly introduced below in conjunction with the accompanying drawings and descriptions of the embodiments or the prior art. Obviously, the following description of the structure of the accompanying drawings is only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. It should be noted that the description of these embodiments is for the purpose of helping to understand the present invention, but does not constitute a limitation of the present invention.

[0062] Example 1:

[0063] This embodiment discloses a method for obtaining RIS codebooks, such as... Figure 2 As shown, a method for obtaining a RIS codebook may include, but is not limited to, the following steps:

[0064] S1. Construct a RIS reflection module, wherein the RIS reflection module includes multiple RIS units uniformly distributed on a specified plane.

[0065] Specifically, as an example, in a RIS reflection module, multiple RIS units are uniformly and linearly distributed on the O-yz plane, and the distance between adjacent RIS units is d. Specifically, a schematic diagram of the positions of all RIS units in any row / column of the RIS reflection module is shown below. Figure 3 As shown.

[0066] S2. Obtain base station location information and user terminal location information, and construct a signal transmission model including a base station module, a user terminal module, and the RIS reflection module based on the base station location information, the user terminal location information, and the RIS reflection module; In this embodiment, the base station location information includes location information such as the distance and angle between the base station module and the RIS reflection module, and similarly, the user terminal location information includes location information such as the distance and angle between the user terminal module and the RIS reflection module.

[0067] S3. Obtain the amplitude of the output signal reflected by the RIS reflection module to the base station module or the user terminal module in the signal transmission model.

[0068] In the signal transmission model, obtaining the amplitude of the output signal reflected by the RIS reflection module to the base station module or the user terminal module includes:

[0069] S301. In the signal transmission model, obtain the total phase shift caused by the i-th RIS unit in any row / column of the RIS reflection module to the electromagnetic wave signal incident on the RIS reflection module.

[0070] Wherein, the total phase shift caused by the i-th RIS unit in any row / column of the RIS reflection module to the electromagnetic wave signal incident on the RIS reflection module is:

[0071]

[0072] In the formula, w i Let be the reflection coefficient of the i-th RIS unit. The phase shift value is j, where j is the complex unit and i = 1, 2, ..., N; θ is the total phase shift difference between the i-th RIS unit and the first RIS unit; Arr θ represents the incident direction of the electromagnetic wave signal. Dep λ represents the direction of electromagnetic wave signal reflection; d represents the spacing between adjacent RIS units in the RIS reflection module; and λ represents the wavelength of the electromagnetic wave signal. This is the incident phase shift difference; This represents the phase shift difference in reflection.

[0073] It should be noted that the incident displacement difference between the electromagnetic wave signal reaching the last RIS unit and the first RIS unit is... The difference in reflection displacement is

[0074] S302. Based on the total phase shift caused by all RIS units of the RIS reflection module to the electromagnetic wave signal incident on the RIS reflection module, the amplitude of the output signal reflected by the RIS reflection module to the base station module or the user terminal module in the specified reflection direction in the signal transmission model is obtained.

[0075] Specifically, in the signal transmission model, the RIS reflection module is set to have an incident direction of θ. Arr The received electromagnetic wave signal is x(θ) Arr In the signal transmission model, the RIS reflection module is in the reflection direction θ. DepThe amplitude of the output signal reflected to the base station module or the user terminal module (i.e., the signal received by the base station module or the user terminal module from the RIS reflection module) is:

[0076]

[0077] In the formula, The electromagnetic wave signal received by the i-th RIS unit in the RIS reflection module is x(θ) Arr The amplitude of the output signal when ), where α is the path loss of the electromagnetic wave signal, a constant term from 0 to 1;

[0078] Therefore, in this embodiment, when the incident direction of the electromagnetic waves received by all RIS units is multiple directions, and the specified reflection direction is θ Dep In the signal transmission model, the RIS reflection module is in the reflection direction θ Dep The amplitude of the output signal reflected to the base station module or the user terminal module (i.e., the signal received by the base station module or the user terminal module from the RIS reflection module) is:

[0079]

[0080]

[0081] In the formula, M is the discrete angle of electromagnetic waves in space. Specifically, M can be set according to actual needs. On a plane, it is generally set to one for each degree, from -90 degrees to +90 degrees, for a total of 181. These respectively represent the incident directions as At that time, the electromagnetic wave signal received by the RIS reflection module; α is the path loss of the electromagnetic wave signal, which is a constant term from 0 to 1.

[0082] S4. Based on the amplitude of the output signal reflected by the RIS reflection module to the base station module or the user terminal module, obtain the output signal power of the RIS reflection module, and construct an optimization problem based on the output signal power.

[0083] In this embodiment, an optimization problem is constructed based on the output signal power, including:

[0084] With maximizing the output signal power as the optimization objective and the constraint that the absolute value of the reflection coefficient of each RIS unit is equal to 1, an optimization problem is constructed; wherein, the optimization problem is:

[0085]

[0086]

[0087] In the formula, |y(θ) Dep )| 2 The output signal power of the RIS reflection module.

[0088] S5. Obtain the optimal solution to the optimization problem.

[0089] In this embodiment, obtaining the optimal solution to the optimization problem includes:

[0090] S501. Transform the optimization objective of the optimization problem to obtain the transformed optimization objective.

[0091] Specifically, in this embodiment, the optimization objective of the optimization problem is transformed to obtain the transformed optimization objective, including:

[0092] Let y(θ) Dep )=αaWBX;

[0093]

[0094] In the formula,

[0095] but

[0096] In the formula, vector w = [w1, w2, ... w N ] T P = BXX H B H Q = a H a; ☉ represents the Hadamard product; tr(A) represents the trace of matrix A; where the vector w contains the vector composed of all the reflection coefficients to be solved, and its whole is an unknown vector containing codebook information, which is the vector that this application needs to solve.

[0097] Let R = Q☉P T The initial optimization objective after transformation is obtained; wherein, the initial optimization objective after transformation is:

[0098]

[0099] At this point, the optimization problem is transformed into:

[0100]

[0101]

[0102] According to w H Rw = tr(Rww) H ), and through the variable substitution formula V = ww HThe vector w to be optimized in the transformed optimization objective is transformed into a composite matrix V to obtain the transformed optimization objective; wherein, the transformed optimization objective is:

[0103]

[0104] S502. Relax the constraints of the optimization problem to obtain the relaxed constraints.

[0105] In this embodiment, the relaxed constraint condition is:

[0106] V≥0 and rank(V)=1.

[0107] Based on the transformed optimization objective and the relaxed constraints, the optimization problem is further transformed into:

[0108]

[0109]

[0110] V≥0;

[0111] in, This means that all diagonal elements of matrix V are 1.

[0112] S503. Based on the transformed optimization objective and the relaxed constraints, solve the optimization problem to obtain the optimal solution to the optimization problem.

[0113] In this embodiment, the optimization problem is solved based on the transformed optimization objective and the relaxed constraints to obtain the optimal solution to the optimization problem, including:

[0114] S503a. Use the CVX toolbox in MATLAB to solve the optimization problem and obtain the solution to the composite matrix V;

[0115] S503b. Based on the solution of the composite matrix V, the optimal solution to the optimization problem is obtained.

[0116] Specifically, the CVX toolbox in MATLAB software is called as follows:

[0117]

[0118] In this embodiment, to solve the optimization problem, the value of the composite matrix V can be obtained first, and then eigenvalue decomposition can be performed on V, i.e., V = U∑U H Then, Gaussian randomization is performed to obtain a pseudo solution. Finally, regarding the pseudo-solution By performing phase recovery, the optimal solution to the optimization problem can be obtained.

[0119] Specifically, in step S503b, the optimal solution to the optimization problem is obtained based on the solution of the composite matrix V, including:

[0120] Multiple complex Gaussian vectors r with a mean of 0 and a variance of 1 are randomly generated, and then calculated multiple times. Multiple pseudo solutions to the optimization problem were obtained.

[0121] Multiple pseudo-solutions Substitute into the expression respectively We obtain multiple intermediate values, and then find the pseudo solution corresponding to the maximum value among these intermediate values. As a pseudo-solution vector;

[0122] Phase angle recovery is performed on the pseudo-solution vector to obtain the optimal solution to the optimization problem.

[0123] Specifically, the optimal solution to the optimization problem is:

[0124]

[0125] The phase angle of the optimal solution w is Ph = arg(), where arg() represents the argument angle.

[0126] S6. Obtain the phase angle of the optimal solution and use the phase angle as the RIS codebook of the RIS reflection module so that the RIS reflection module can perform beamforming on the electromagnetic wave signal received from the base station module or the user terminal module based on the RIS codebook.

[0127] This embodiment can quickly acquire the RIS codebook. During the acquisition process, channel estimation is not required, and there is no CSI dependency, which saves channel estimation resources and facilitates RIS beamforming, thereby improving the received signal power of the base station or user terminal. Specifically, in the implementation process, this embodiment first constructs a signal transmission model including a base station module, a user terminal module, and the RIS reflection module. Then, it acquires the amplitude of the output signal reflected by the RIS reflection module to the base station module or the user terminal module in the signal transmission model. Subsequently, it obtains the output signal power of the RIS reflection module and constructs an optimization problem based on the output signal power. By solving the optimal solution to the optimization problem, the phase angle of the optimal solution is used as the RIS codebook of the RIS reflection module. The RIS reflection module then uses the RIS codebook to perform beamforming on the electromagnetic wave signal received from the base station module or the user terminal module. In this process, when modeling the signal transmission model, only the base station location information and the user terminal location information need to be considered. Therefore, based on the signal arrival angle of the RIS reflection module and the angle of the direction to be enhanced, the optimization problem can be established and the RIS codebook acquired, avoiding the complex channel estimation process and possessing value for widespread application.

[0128] As an example, when the RIS board corresponding to the RIS reflection module does not use the codebook of this embodiment for beamforming, the power of the signal received by the user terminal from the RIS board corresponding to the RIS reflection module is as follows: Figure 4 As shown, the signal power gain that the user terminal can obtain after acquiring the codebook using this embodiment is as follows: Figure 5 As shown, it can be seen that the received signal power of the user terminal can be increased by more than 10dB when the codebook calculated using this embodiment is compared with the case where no codebook is used for beamforming.

[0129] Example 2:

[0130] This embodiment discloses a RIS codebook acquisition system for implementing the RIS codebook acquisition method in Embodiment 1; such as Figure 6 As shown, the RIS codebook acquisition system includes:

[0131] The model building module is used to build a RIS reflection module, which includes multiple RIS units uniformly distributed on a specified plane; it is also used to acquire base station location information and user terminal location information, and to build a signal transmission model including a base station module, a user terminal module and the RIS reflection module based on the base station location information, the user terminal location information and the RIS reflection module.

[0132] The codebook calculation module, communicatively connected to the model construction module, is used to obtain the amplitude of the output signal reflected by the RIS reflection module to the base station module or the user terminal module in the signal transmission model; and to obtain the output signal power of the RIS reflection module based on the amplitude of the output signal reflected by the RIS reflection module to the base station module or the user terminal module, and to construct an optimization problem based on the output signal power; it is also used to obtain the optimal solution of the optimization problem; and to obtain the phase angle of the optimal solution, and to use the phase angle as the RIS codebook of the RIS reflection module, so that the RIS reflection module can perform beamforming on the electromagnetic wave signal received from the base station module or the user terminal module based on the RIS codebook.

[0133] Example 3:

[0134] Based on Embodiment 1 or 2, this embodiment discloses an electronic device, which may be a smartphone, tablet computer, laptop computer, or desktop computer, etc. The electronic device may be referred to as a terminal, portable terminal, desktop terminal, etc., and includes:

[0135] Memory, used to store computer program instructions; and,

[0136] A processor is configured to execute the computer program instructions to perform the operations of the RIS codebook acquisition method as described in any of Embodiment 1.

[0137] Example 4:

[0138] Based on any one of the embodiments 1 to 3, this embodiment discloses a computer-readable storage medium for storing computer-readable computer program instructions, which are configured to perform operations as described in Embodiment 1 when executed.

[0139] Obviously, those skilled in the art will understand that the modules or steps of the present invention described above can be implemented using general-purpose computing devices. They can be centralized on a single computing device or distributed across a network of multiple computing devices. Optionally, they can be implemented using computer-executable program code, thereby storing them in a storage device for execution by a computing device, or fabricating them separately as individual integrated circuit modules, or fabricating multiple modules or steps as a single integrated circuit module. Thus, the present invention is not limited to any particular hardware and software combination.

[0140] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

[0141] Finally, it should be noted that the above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for obtaining a RIS codebook, characterized in that: include: Construct a RIS reflection module, which includes multiple RIS units uniformly distributed on a specified plane; Obtain base station location information and user terminal location information, and construct a signal transmission model including a base station module, a user terminal module and the RIS reflection module based on the base station location information, the user terminal location information and the RIS reflection module; In the signal transmission model, obtain the amplitude of the output signal reflected by the RIS reflection module to the base station module or the user terminal module; The output signal power of the RIS reflection module is obtained based on the amplitude of the output signal reflected by the RIS reflection module to the base station module or the user terminal module, and an optimization problem is constructed based on the output signal power. Obtain the optimal solution to the optimization problem; The phase angle of the optimal solution is obtained and used as the RIS codebook of the RIS reflection module, so that the RIS reflection module can perform beamforming on the electromagnetic wave signal received from the base station module or the user terminal module based on the RIS codebook. In the signal transmission model, obtaining the amplitude of the output signal reflected by the RIS reflection module to the base station module or the user terminal module includes: In the signal transmission model, obtain the first row / column of the RIS reflection module. i The total phase shift caused by each RIS unit to the electromagnetic wave signal incident on the RIS reflection module; Based on the total phase shift caused by all RIS units of the RIS reflection module to the electromagnetic wave signal incident on the RIS reflection module, the amplitude of the output signal reflected by the RIS reflection module to the base station module or the user terminal module in the specified reflection direction in the signal transmission model is obtained. The RIS reflection module in any row / column of the first i The total phase shift caused by each RIS unit to the electromagnetic wave signal incident on the RIS reflection module is: ； In the formula, For the first i The reflection coefficient of each RIS unit. , The phase shift value, j For complex units, i= 1 , 2 ,……, N ; For the first i The total phase shift difference between each RIS unit and the first RIS unit; The direction of incidence of the electromagnetic wave signal; The direction of electromagnetic wave signal reflection; d The spacing between adjacent RIS units in the RIS reflection module; λ The wavelength of the electromagnetic wave signal; This is the incident phase shift difference; This represents the phase shift difference in reflection.

2. The RIS codebook acquisition method according to claim 1, characterized in that: The specified reflection direction is In the signal transmission model, the RIS reflection module is in the reflection direction. The amplitude of the output signal reflected to the base station module or the user terminal module is: ； In the formula, M The angle at which electromagnetic waves are discrete in space; ,……, These respectively represent the incident directions as At that time, the electromagnetic wave signal received by the RIS reflection module; α denoted as path loss of the electromagnetic wave signal, and denoted as a constant term between 0 and 1.

3. The RIS codebook acquisition method according to claim 2, characterized in that: An optimization problem is constructed based on the output signal power, including: With maximizing the output signal power as the optimization objective and the constraint that the absolute value of the reflection coefficient of each RIS unit is equal to 1, an optimization problem is constructed; wherein, the optimization problem is: ； In the formula, The output signal power of the RIS reflection module.

4. The RIS codebook acquisition method according to claim 3, characterized in that: Obtaining the optimal solution to the optimization problem includes: The optimization objective of the optimization problem is transformed to obtain the transformed optimization objective; The constraints of the optimization problem are relaxed to obtain the relaxed constraints. Based on the transformed optimization objective and the relaxed constraints, the optimization problem is solved to obtain the optimal solution to the optimization problem.

5. A method for obtaining a RIS codebook according to claim 4, characterized in that: The optimization objective of the optimization problem is transformed to obtain the transformed optimization objective, including: make ; In the formula, ; but ; In the formula, vector ; ☉ represents the Hadamarda accumulation; Representation matrix traces; make ☉ The initial optimization objective after transformation is obtained; wherein, the initial optimization objective after transformation is: ； according to And through variable substitution The vector to be optimized in the transformed optimization objective Transform into a composite matrix The transformed optimization objective is obtained; wherein the transformed optimization objective is: 。 6. A method for obtaining a RIS codebook according to claim 5, characterized in that: The relaxed constraint condition is: 0 and .

7. A method for obtaining a RIS codebook according to claim 6, characterized in that: Based on the transformed optimization objective and the relaxed constraints, the optimization problem is solved to obtain the optimal solution, including: The optimization problem was solved using the CVX toolbox in MATLAB, yielding the composite matrix. The solution; According to the composite matrix The solution is obtained by finding the optimal solution to the optimization problem.

8. A method for obtaining a RIS codebook according to claim 7, characterized in that: According to the composite matrix The solution to the optimization problem is obtained by finding the optimal solution, including: Randomly generate multiple complex Gaussian vectors with a mean of 0 and a variance of 1. And through multiple calculations This yields multiple pseudo-solutions to the optimization problem. ; Multiple pseudo-solutions Substitute into the expression respectively This yields multiple intermediate values, and the pseudo solution corresponding to the maximum value among these intermediate values ​​is then identified. As a pseudo-solution vector; Phase angle recovery is performed on the pseudo-solution vector to obtain the optimal solution to the optimization problem.

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