Cooperative multi-eavesdropping-resisting STAR-RIS auxiliary security communication method and device, and medium

Abstract

According to the STAR-RIS auxiliary security communication method and device for resisting cooperation and multi-eavesdropping and the medium, the problem of improving the system and security rate under the condition that a plurality of malicious users cooperate with each other to eavesdrop legal users in a communication system is solved. The method comprises the following steps: S1, initializing a beam forming vector of each legal user and a transmission and reflection coefficient of STAR-RIS; s2, fixing a transmission and reflection coefficient, constraining the upper bound of the rate of a malicious eavesdropping user, and obtaining a beam forming vector by maximizing the rate of a legal user; s3, fixing a beam forming vector, relaxing a feasible region of a transmission and reflection coefficient, and obtaining a solution of the transmission and reflection coefficient by using a penalty concave-convex process; and S4, repeating the steps S2 and S3, so that the sum safety rate of the system is continuously increased until convergence. The method is suitable for an STAR-RIS auxiliary security communication system in a cooperative multi-eavesdropping scene, a common single-eavesdropping model and an independent multi-eavesdropping model can be covered, and the sum security rate of the system is improved.

Description

Technical Field

[0001] The present invention relates to the field of communication technology, and in particular to a STAR-RIS-assisted secure communication method, device and storage medium for counteracting collaborative multi-eavesdropping. Background Art

[0002] Traditional smart reflecting surfaces (RIS) can only cover their reflection range, which limits their application flexibility and electromagnetic propagation regulation capabilities. In this context, a simultaneous transmission and reflection RIS (STAR-RIS) is proposed, which can cover the entire space range and expand its application scenarios. However, the unique ability of STAR-RIS to reconfigure the full-space radio propagation environment will inevitably lead to full-space eavesdropping. In other words, an eavesdropper located on any side of the STAR-RIS can obtain confidential information passing through the STAR-RIS.

[0003] In existing physical layer security research, most scenarios consider eavesdroppers to decode the confidential information of legitimate users independently. However, in actual networks, eavesdroppers usually cooperate with each other to jointly decode confidential information. The full-space eavesdropping problem introduced by STAR-RIS requires optimizing the minimum security rate when the user is eavesdropped by all eavesdroppers, and the mutual cooperation of eavesdroppers introduces new non-convexity in the optimization problem, making the existing algorithm no longer applicable. Therefore, a new solution is needed to improve the security of wireless communication networks. Summary of the invention

[0004] The present invention proposes a STAR-RIS assisted secure communication method, device and storage medium for counteracting collaborative multi-eavesdropping, so as to solve the problem that the existing eavesdroppers collaborate to eavesdrop on the confidential information of legitimate users.

[0005] To achieve the above object, the present invention adopts the following technical solutions: A STAR-RIS-assisted secure communication method against cooperative multi-eavesdropping comprises the following steps: S1. Initialize the beamforming vectors of each legitimate user and the transmission and reflection coefficients of STAR-RIS; S2, fix the transmission and reflection coefficients, constrain the upper bound of the rate of malicious eavesdropping users, and obtain the beamforming vector by maximizing the rate of legitimate users; S3, fix the beamforming vector, relax the feasible domain of TARCs, and use the penalty concave-convex process to obtain the solution of TARCs; S4. Repeat S2 and S3 to make the system's safety rate continue to increase until convergence.

[0006] On the other hand, the present invention further discloses a computer-readable storage medium storing a computer program, wherein when the computer program is executed by a processor, the processor executes the steps of the above method.

[0007] On the other hand, the present invention further discloses a computer device, including a memory and a processor, wherein the memory stores a computer program, and when the computer program is executed by the processor, the processor executes the steps of the above method.

[0008] It can be seen from the above technical solution that the STAR-RIS assisted secure communication method for counteracting collaborative multi-eavesdropping of the present invention can be used in scenarios where there are multiple eavesdroppers who cooperate with each other. The solution can effectively improve the user's secure communication rate and ensure the security of the communication system under certain transmission power constraints.

[0009] The present invention specifically discloses a secure transmission scheme against cooperative multi-eavesdropping assisted by a smart metasurface (STAR-RIS) that simultaneously reflects and transmits, which mainly solves the problem of improving the system and security rates when multiple malicious users cooperate to eavesdrop on legitimate users in a communication system. The implementation steps are: 1. Initialize the beamforming vectors of each legitimate user and the transmission reflection coefficients (TARCs) of STAR-RIS; 2. Fix the transmission reflection coefficients of STAR-RIS, constrain the upper bound of the rate of malicious eavesdropping users, and obtain the beamforming vector by maximizing the legitimate user rate; 3. Fix the beamforming vector, relax the feasible domain of TARCs and obtain the solution of TARCs using the penalty convex-concave process. 4. Alternately execute the second and third steps to gradually improve the system and security rates until convergence. Simulation experiments verify the effectiveness of this scheme.

[0010] The present invention considers a STAR-RIS-assisted secure transmission scheme against collaborative eavesdropping, and alternately optimizes the beamforming vector of the base station and the transmittance and reflection coefficient of STAR-RIS under certain transmission power constraints to improve the system and security rate. In order to solve the non-convexity of the security rate, the rates of the legitimate user and the eavesdropper are first convexly approximated to obtain their lower and upper bounds respectively, and then auxiliary variables are introduced to perform equivalent processing on the minimum security rate. At the same time, in order to deal with the non-convexity of the transmittance and reflection coefficient, a slack variable is introduced to perform a convex approximation on it. The simulation results verify the performance of the proposed scheme, and it is improved over the existing scheme.

[0011] Specifically, compared with the prior art, the present invention has the following advantages: 1. The present invention is applicable to the STAR-RIS assisted secure communication system in a collaborative multi-eavesdropping scenario. The system model covers the general single-eavesdropping model and the independent multi-eavesdropping model, thereby improving the system's security rate.

[0012] 2. Compared with other existing solutions, the present invention can achieve higher system and safety rates. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 This is a conceptual scene diagram of the present invention; Figure 2 It is the convergence diagram of the algorithm scheme proposed by the present invention and the comparative scheme; Figure 3 Comparison of the security rate at different transmission powers; Figure 4 Comparison of the sum and safety rates under different numbers of STAR-RIS units; Figure 5 The figure is a flow chart of the method of the present invention. DETAILED DESCRIPTION

[0014] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments.

[0015] like Figure 5 As shown, the STAR-RIS assisted secure communication method against cooperative multi-eavesdropping described in this embodiment includes the following steps: Consider a STAR-RIS-assisted secure communication system consisting of a M A base station with antennas and a N There is a legitimate user in the transmission area and reflection area of ​​STAR-RIS. There are several eavesdroppers who cooperate with each other around each legitimate user. eavesdroppers in two areas cannot cooperate with each other due to the area separation. legitimate users, STAR-RIS to eavesdropper, base station to Legal users, base stations to The channels of the eavesdroppers are , , , , ,in , , and are the set of legitimate users and the set of eavesdroppers respectively. is a plural set. Base station broadcast signal ,in The base station sends k The power normalized signal of each user. for The beamforming vector of . Limited by the maximum transmit power of the base station, Must meet .use represents the transmission coefficient matrix and reflection coefficient matrix of STAR-RIS, where , , For the transmission area, is the reflection area; The received signal of each user and The received signals of the eavesdroppers are (1) (2) in is the mapping of users / eavesdroppers to their zones. There are legitimate users in the transmission area of ​​STAR-RIS, then , if in the reflection area, then . and Respectively Users and The received noise of each eavesdropper follows a complex Gaussian distribution. .

[0016] make , , then The achievable rate of a legitimate user is (3) Located in ξ The eavesdroppers in the area cooperated to eavesdrop on The achievable rate of a legitimate user is (4) in , For ξ Considering that an eavesdropper in any area can eavesdrop on the signals of two users in the transmission area and the reflection area at the same time, the first The safe rate for each user is ,in Therefore, this security communication system needs to solve the following optimization problems: (5a) (5b) (5c) (5e) (5d) (5e) in .

[0017] Step 1: Initialize the beamforming vectors of each legitimate user and the transmittance and reflectance coefficients of STAR-RIS, and make the beamforming vectors and transmittance and reflectance coefficients satisfy the constraints of the optimization problem (5).

[0018] Step 2: Fix the transmission and reflection coefficients and optimize the beamforming vector. The specific implementation method is as follows: Perform a first-order Taylor expansion on the rates of the legitimate user and the eavesdropper, and at the fixed point Everywhere and The lower and upper bounds of are (6) (7) in (8) (9) (10) (11) (12) (13) (14) The optimization objective is converted to , the optimization objective is still non-convex. Further introduction of auxiliary variables and , can be obtained The upper bound of (15) in (16) (17) (18) at this time It is a quadratic function divided by a linear function, which is a convex function.

[0019] In order to smooth the objective function, ignore , and transforms the problem of optimizing the beamforming vector into (19a) (19b) (19c) The above problem is a convex problem and can be solved using the CVX toolkit.

[0020] Step 3: Fix the beamforming vector and optimize the transmission and reflection coefficients. The specific implementation method is as follows: For the non-convex constraints (5c) and (5d), they are equivalent to ; and the non-convex constraint (5e) can be equivalent to (20) Introducing slack variables , relax the feasible domain to (twenty one) (twenty two) (twenty three) (twenty four) Constraint (22) is still non-convex, and further at the fixed point Perform a first-order Taylor expansion on the left side of (22), and we get (25) By introducing the penalty term To approximate the original constraint, the subproblem of optimizing the transflection coefficient can be transformed into (26a) (26b) After each iteration, optimization Need to update later , that is, The iteration used ,in , and then continue to optimize , until Less than the target accuracy.

[0021] Step 4: Repeat steps 2 and 3, performing alternating optimization until the safe rate converges.

[0022] like Figure 5 As shown, the overall algorithm flow includes: First, initialize the optimization variables , , and , and then optimize the beamforming vector and the transmission and reflection coefficients alternately until convergence.

[0023] The method in the embodiment of the present invention is simulated and verified as follows in conjunction with specific implementation methods. In the experimental scenario, the coordinates of the base station and STAR-RIS in three-dimensional space are (0, 0, 10) and (0, 70,5), respectively, and the coordinates of the legal user are (-10, 70, 0) and (10, 70, 0), respectively. The base station is equipped with 8 antennas. Eavesdroppers are randomly generated within 5 meters of the legal user, and there are 3 eavesdroppers around each legal user. The channels from the base station to STAR-RIS and from the base station to the user and the eavesdropper are Rice channels, modeled as ,in hour , and are the path loss factor and Rice factor, respectively. The path loss factors of the channels from the base station to STAR-RIS, from STAR-RIS to legitimate users / eavesdroppers, and from the base station to legitimate users / eavesdroppers are 2.2, 2.5, and 3.5, respectively. The channel from the base station to the legitimate user / eavesdropper is a Rayleigh channel. The power of Gaussian white noise is The experiment uses the Monte Carlo method to randomly generate 1,000 eavesdropper locations and channel parameters and optimize them. The average of the security rate obtained after each optimization is taken as the system security performance.

[0024] Experimental content (1) Based on the above simulation experiment scenario, complete the modeling in MATLAB, write the corresponding solution algorithm code, and complete the convergence experiment.

[0025] (2) Changing the upper limit of the transmit power while keeping other variables unchanged, the impact of the upper limit of the transmit power on the entire system and the safety rate is demonstrated through comparison.

[0026] (3) Changing the number of STAR-RIS units while keeping other variables unchanged, the impact of the number of STAR-RIS units on the entire system and safety rate is demonstrated through comparison.

[0027] (4) In order to verify whether this scheme has excellent performance, multiple groups of control experiments were carried out to test it.

[0028] Experimental Results Figure 2 The convergence of the scheme proposed by the present invention and the comparative scheme at different transmit powers is shown. It can be seen that the convergence speed of the algorithm proposed by the present invention is faster than that of the comparative scheme.

[0029] Figure 3 The sum and safety rates under different transmission powers are compared. It can be seen that as the transmission power upper limit increases, the sum and safety rates of this scheme increase accordingly. Moreover, this scheme has advantages over the non-RIS, traditional RIS and PDD-BSUM schemes, and can still maintain good performance under 4-bit discrete phase shift. Although the performance gap between the PDD-BSUM scheme and this scheme is reduced at higher transmission powers, according to Figure 2 As a result, this scheme converges faster at higher transmit power and still has advantages over the PDD-BSUM scheme.

[0030] Figure 4 The sum safety rate comparison under different numbers of STAR-RIS units is shown. It can be seen that as the number of STAR-RIS units increases, the sum safety rate of this scheme increases accordingly. This scheme has advantages over all other schemes and can still maintain good performance under 4-bit discrete phase shift.

[0031] On the other hand, the present invention further discloses a computer-readable storage medium storing a computer program, wherein when the computer program is executed by a processor, the processor executes the steps of the above method.

[0032] On the other hand, the present invention further discloses a computer device, including a memory and a processor, wherein the memory stores a computer program, and when the computer program is executed by the processor, the processor executes the steps of the above method.

[0033] In another embodiment provided by the present application, a computer program product including instructions is also provided, which, when executed on a computer, enables the computer to execute any of the STAR-RIS-assisted secure communication methods for counteracting collaborative multi-eavesdropping in the above embodiments.

[0034] It is understandable that the system, device and storage medium provided in the embodiments of the present invention correspond to the method provided in the embodiments of the present invention, and the explanation, examples and beneficial effects of the relevant contents can refer to the corresponding parts in the above methods.

[0035] In the above embodiments, it can be implemented in whole or in part by software, hardware, firmware or any combination thereof. When implemented using software, it can be implemented in whole or in part in the form of a computer program product. The computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, the process or function described in the embodiment of the present application is generated in whole or in part. The computer may be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions may be stored in a computer-readable storage medium, or transmitted from one computer-readable storage medium to another computer-readable storage medium. For example, the computer instructions may be transmitted from a website site, a computer, a server or a data center by wired (e.g., coaxial cable, optical fiber, digital subscriber line (DSL)) or wireless (e.g., infrared, wireless, microwave, etc.) mode to another website site, computer, server or data center. The computer-readable storage medium may be any available medium that a computer can access or a data storage device such as a server or a data center that includes one or more available media integrated. The available medium may be a magnetic medium (e.g., a floppy disk, a hard disk, a tape), an optical medium (e.g., a DVD), or a semiconductor medium (e.g., a solid-state drive Solid State Disk (SSD)), etc.

[0036] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the existence of other identical elements in the process, method, article or device including the elements.

[0037] Each embodiment in this specification is described in a related manner, and the same or similar parts between the embodiments can be referred to each other, and each embodiment focuses on the differences from other embodiments. In particular, for the system embodiment, since it is basically similar to the method embodiment, the description is relatively simple, and the relevant parts can be referred to the partial description of the method embodiment.

[0038] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A STAR-RIS-assisted secure communication method against cooperative multi-eavesdropping, characterized in that: The following steps are included: S1. Initialize the beamforming vectors of each legitimate user and the transmission and reflection coefficients of STAR-RIS; S2, fix the transmission and reflection coefficients, constrain the upper bound of the rate of malicious eavesdropping users, and obtain the beamforming vector by maximizing the rate of legitimate users; S3, fix the beamforming vector, relax the feasible domain of the transflection coefficient, and use the penalty concave-convex process to obtain the solution of the transflection coefficient; S4. Repeat S2 and S3 to make the system's safety rate continue to increase until convergence.

2. The STAR-RIS-assisted secure communication method against cooperative multi-eavesdropping according to claim 1, characterized in that: Step S1 specifically includes: Consider a STAR-RIS-assisted secure communication system consisting of a M A base station with antennas and a N STAR-RIS of 1 unit; There is a legitimate user in the transmission area and reflection area of ​​STAR-RIS. There are several cooperative eavesdroppers around each legitimate user. an eavesdropper; Due to the area separation, eavesdroppers in the two areas cannot cooperate with each other. legitimate users, STAR-RIS to eavesdropper, base station to Legal users, base stations to The channels of the eavesdroppers are , , , , ,in , , and are the set of legitimate users and the set of eavesdroppers respectively. is a plural set; Base station broadcast signal ,in The base station sends k The power normalized signal of each user; for The beamforming vector of is limited by the maximum transmit power of the base station. Must meet ;use represents the transmission coefficient matrix and reflection coefficient matrix of STAR-RIS, where , , For the transmission area, is the reflection area; The received signal of each user and The received signals of the eavesdroppers are Formula (1) Formula (2) in is the mapping of the user or eavesdropper to the area where he is located. There are legitimate users in the transmission area of ​​STAR-RIS, then , and Respectively k Users and l The received noise of each eavesdropper follows a complex Gaussian distribution. ; make , , then k The achievable rate of a legitimate user is Formula (3) Located in ξ The eavesdroppers in the area cooperated to eavesdrop on k The achievable rate of a legitimate user is Formula (4) in , For ξ Considering that an eavesdropper in any area can eavesdrop on the signals of two users in the transmission area and the reflection area at the same time, the first k The safe rate for each user is ,in ; Therefore, this security communication system needs to solve the following optimization problems: Formula (5a) Formula (5b) Formula (5c) Formula (5e) Formula (5d) Formula (5e) in .

3. The STAR-RIS-assisted secure communication method against cooperative multi-eavesdropping according to claim 2, characterized in that: Step S2 specifically includes: Perform a first-order Taylor expansion on the rates of legitimate users and eavesdroppers, and at the fixed point Everywhere and The lower and upper bounds of Formula (6) Formula (7) in Formula (8) Formula (9) Formula (10) Formula (11) Formula (12) Formula (13) Formula (14) To take the real part; convert the optimization objective into , at this time the optimization objective is still non-convex, and the auxiliary variable is further introduced and ,have to The upper bound of Formula (15) in Formula (16) Formula (17) Formula (18) at this time It is a quadratic function divided by a linear function, which is a convex function; In order to smooth the objective function, ignore , and transforms the problem of optimizing the beamforming vector into Formula (19a) Formula (19b) Formula (19c) The above problem is a convex problem and is solved using the CVX toolkit.

4. The STAR-RIS-assisted secure communication method against cooperative multi-eavesdropping according to claim 3, characterized in that: Step S3 specifically includes: For the non-convex constraints (5c) and (5d), they are equivalent to ; and the non-convex constraint (5e) is equivalent to Formula (20) Introducing slack variables , relax the feasible domain to Formula (21) Formula (22) Formula (23) Formula (24) The constraint (22) is still non-convex, and further at the fixed point Perform a first-order Taylor expansion on the left side of equation (22), and we get Formula (25) By introducing the penalty term To approximate the original constraint, the subproblem of optimizing the transflection coefficient is transformed into Formula (26a) Formula (26b) After each iteration, optimization Need to update later , that is, The iteration used ,in , and then continue to optimize , until Less than the target accuracy.

5. A computer device comprising a memory and a processor, wherein the memory stores a computer program, wherein: When the computer program is executed by the processor, the processor is caused to perform the steps of the method according to any one of claims 1 to 4.

6. A computer-readable storage medium storing a computer program, characterized in that: When the computer program is executed by a processor, the processor is caused to perform the steps of the method according to any one of claims 1 to 4.

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