A method and device for countering perception and communication eavesdropping in a STAR-RIS-assisted ISAC system

Abstract

The present invention discloses a method and apparatus for countering perception and communication eavesdropping in a STAR-RIS-assisted ISAC system. The method comprises the following steps: establishing a STAR-RIS-assisted ISAC system model; constructing a target optimization problem with the communication beam, perception beam, and the transmission / reflection coefficients of the STAR-RIS as optimization variables, with the goal of maximizing the confidentiality rate of the communication end; and solving the target optimization problem using an alternating optimization algorithm based on successive convex approximation and penalized dual decomposition. The present invention divides the reflection and transmission ends of the STAR-RIS into a perception region and a communication region, while simultaneously considering both the communication security and perception security of the STAR-RIS-assisted ISAC system. By utilizing an alternating optimization algorithm based on successive convex approximation and penalized dual decomposition, the communication beam, perception beam, and the transmission / reflection coefficients of the STAR-RIS-assisted ISAC system are optimized to maximize the security rate of the communication end, while ensuring both the performance and perception security of the perception end, thereby ensuring the security of the STAR-RIS-assisted ISAC system.

Description

Technical Field

[0001] The present invention relates to the field of wireless communication technology, and in particular to a method and device for countering perception and communication eavesdropping in a STAR-RIS-assisted ISAC system. Background Art

[0002] Due to the rapid growth of connected devices and mobile services, spectrum resources are becoming increasingly scarce. Traditionally, most commercial communications systems have operated primarily in frequency bands below 6 GHz, coexisting peacefully with radar sensing systems used for applications such as air traffic control and weather observation. However, with the increasing demand for wireless connectivity, wireless communications are beginning to expand to higher frequencies, such as millimeter wave, terahertz, and even visible light bands. This has led to increasingly severe frequency overlap with existing radar sensing systems. Continuing to develop communications and radar sensing systems using traditional independent design approaches will result in significant mutual interference. Therefore, a joint design approach is urgently needed to reduce interference and improve spectrum efficiency by achieving spectrum sharing and technical compatibility. Furthermore, with advances in digital communications technology and developments in fields such as massive MIMO (multiple-input, multiple-output), millimeter wave communications, and terahertz technology, the boundaries between communications and radar are gradually blurring, enabling a better integration of the two, enabling resource sharing not only at the software level but also at the hardware level. Looking ahead, high hopes are placed on sixth-generation (6G) mobile communication networks. They must not only provide ultra-high-speed data services but also support high-precision wireless sensing capabilities, which are crucial for promoting the development of smart cities and the application of telematics. Against this backdrop, Integrated Sensor and Communication (ISAC) has become a key focus in current 6G technology research and development.

[0003] Integrated Communication and Awareness (ISAC) is a novel information processing technology that achieves synergistic improvements in perception and communication capabilities by sharing hardware resources and information flows, significantly improving the system's spectrum efficiency, hardware utilization efficiency, and overall information processing performance. The core of this technology lies in the flexible reuse of time-frequency resources, the multifunctional integration of hardware platforms, and the joint optimization design at the airport and protocol levels. The goal is to build a unified framework that can efficiently perform both data transmission and environmental awareness tasks. The essence of ISAC lies in its dual-functionality: seamlessly integrating communication and perception capabilities within the same system architecture, enabling them to complement and enhance each other. While ISAC demonstrates great potential, its practical application has encountered a number of challenges. Specifically, the performance of ISAC systems is highly dependent on the specific propagation environment. In particular, high-frequency signal transmission suffers from significant path loss and weak signal strength in non-line-of-sight (NLOS) paths. Furthermore, line-of-sight paths are susceptible to obstruction by surrounding objects. These factors collectively lead to limited coverage and numerous blind spots.

[0004] As an emerging technology, smart metasurfaces (RIS) offer innovative solutions to the challenges of integrated sensing, communication, and communication (ISAC) technology by integrating multiple low-cost passive components into an artificial surface. The core of RIS lies in its intelligent controller, which can dynamically adjust the phase response of each component to precisely manipulate the propagation path of wireless signals. This breaks through the limitations of traditional wireless propagation environments and enables customized propagation environments to suit specific system requirements. However, traditional RIS only reflect signals, limiting their service range to the 180-degree half-plane between the base station and the RIS, resulting in coverage blind spots. To overcome this limitation, the transmissive-reflective dual-function reconfigurable smart surface (STAR-RIS) has emerged. It not only reflects but also transmits signals, achieving 360-degree coverage. The unique feature of STAR-RIS is its ability to simultaneously process both the transmission and reflection of the incident signal, providing service to users located in front of and behind it, greatly enhancing the system's flexibility and coverage capabilities. The integration of STAR-RIS technology and ISAC concept can not only significantly expand the coverage of the system and improve communication and perception performance, but also effectively reduce deployment costs and operating power consumption, open up new development paths for wireless communication and sensing fields, and bring more innovation opportunities.

[0005] At the same time, STAR-RIS's full spatial coverage and the broadcast nature of its channels also make it easy for signals to be eavesdropped. How to ensure the security of the ISAC system while improving its communication and perception capabilities with STAR-RIS is a crucial issue.

[0006] Current research has explored some security designs for STAR-RIS-assisted ISAC systems. For example, consider the possibility of an active eavesdropper on either the communication or sensing side of a STAR-RIS-assisted ISAC system. Furthermore, some researchers consider the possibility that the sensing user on the STAR-RIS sensing side could be a potential eavesdropper, potentially eavesdropping on the communication user's information. However, in practical applications, due to perception errors and limited detection resolution, the target's position cannot always be perfectly determined. For example, given N antennas arranged in a uniform linear structure with half-wavelength spacing, the angular resolution is approximately 2 / N (in rad), meaning that targets within this angular interval cannot be individually detected. When the target's position can only be roughly sensed within a certain angular region, a wider beam must be directed toward that region to avoid missing the target. However, focusing the beam on a single spatial region inevitably increases the risk of information leakage, necessitating robust and secure waveform design.

[0007] However, there are technologies that have begun to study the perceived security of traditional ISACs, but no researchers have considered the perceived security of SATR-RIS-assisted ISAC systems. Summary of the Invention

[0008] In order to overcome the deficiencies of the prior art, the present invention provides a method for countering perception and communication eavesdropping in a STAR-RIS assisted ISAC system, a corresponding device, an electronic device, and a computer-readable storage medium.

[0009] The technical solution of the present invention to solve the above technical problems is:

[0010] A method for countering perception and communication eavesdropping in a STAR-RIS-assisted ISAC system includes the following steps:

[0011] Step S1: Establishing the STAR-RIS assisted ISAC system model;

[0012] Step S2: maximizing the confidentiality rate of the communication end is the optimization goal, and the communication beam, sensing beam, and STAR-RIS transmission / reflection coefficients are used as optimization variables to construct a target optimization problem;

[0013] Step S3: Using an alternating optimization algorithm of successive convex approximation and penalized dual decomposition to solve the target optimization problem.

[0014] As a preferred solution of the present invention, in step S1, the STAR-RIS assisted ISAC system model consists of an ISAC base station, a STAR-RIS with N elements, a single-antenna communication user, a single-antenna communication eavesdropper, a single-antenna sensing target and a single-antenna sensing eavesdropper; wherein, the antenna array of the ISAC base station adopts a uniform linear array arrangement; the array of the elements of the STAR-RIS adopts a uniform planar array arrangement; the ISAC base station simultaneously sends communication signals and sensing signals, and the communication signals can be used to assist sensing.

[0015] As a preferred solution of the present invention, in step S2, by optimizing the communication beam w c ,, sensing beam w s and the transmission / reflection coefficient θ of STAR-RIS t ,θ r , maximize the confidentiality rate of the communication end; among them,

[0016] The target optimization problem is:

[0017]

[0018] Where: (1a) represents the transmit power constraint of the ISAC base station; (1b) and (1c) represent the amplitude constraint and phase shift constraint of the coupled STAR-RIS, respectively; (1d) and (1e) represent the gain constraints at the sensing target and sensing eavesdropper, respectively; P t Indicates the maximum transmission power of the ISAC base station; R c represents the confidentiality rate at the communication user; β n,t ,β n,r and φ n,t ,φ n,r are the amplitude and phase shift of the reflection coefficient and transmission coefficient of the coupled phase-shifted STAR-RIS, respectively; P s represents the beam gain at the sensing target; P s,e represents the beam gain at the sensing eavesdropper, τ s ,τ s,e Respectively represent the set thresholds;

[0019] Among them, the confidentiality rate R at the communication user c The calculation formula is:

[0020]

[0021] Among them, the beam gain P at the sensing target s and the beam gain P at the eavesdropper s,e They are:

[0022]

[0023] Where: G represents the channel gain from the ISAC base station to STAR-RIS; h s ,h s,e They represent the channel gains from SATR-RIS to the sensing target and the sensing eavesdropper respectively; represents the Gaussian white noise variance at the communication user and the communication eavesdropper.

[0024] As a preferred solution of the present invention, in step S3, the algorithm of penalty dual decomposition is adopted, by introducing auxiliary variables Dual variable λ t ,λ r and penalty parameter ρ, we get the augmented Lagrangian problem of the original problem:

[0025]

[0026] Then the augmented Lagrangian problem is decomposed into three sub-problems, which are: c ,w s}Sub-problem 1: Regarding the variable {θ t ,θ r}Subproblem 2 and about variables , and solve subproblems 1, 2, and 3 respectively.

[0027] As a preferred embodiment of the present invention, regarding the variable {w c ,w s The first sub-problem of} is a non-convex problem, and its solution process is:

[0028] The augmented Lagrangian problem can be rewritten as:

[0029]

[0030] Based on the successive convex approximation SCA method, we introduce auxiliary variables {p, q, t} to obtain:

[0031]

[0032] Based on the successive convex approximation (SCA) method, Taylor expansion is performed on the non-convex variables of Equations (8b), (8c), (8d), and (8e):

[0033]

[0034] Where: μ = h H ΘG represents the total channel gain from STAR-RIS to the communication user, and the set {w c (m), w s(m), t(m)} are the values of the variables in the mth iteration. Since the problem is convex with respect to the variables, CVX is used to solve it, and the optimal solution is obtained through multiple rounds of iteration.

[0035] As a preferred embodiment of the present invention, regarding {θ t ,θ r The second sub-problem of} is a non-convex problem, and its solution process is:

[0036] The augmented Lagrangian problem can be rewritten as:

[0037]

[0038] Based on the successive convex approximation SCA method, we introduce auxiliary variables {a, b, l} to obtain:

[0039]

[0040] Based on the successive convex approximation (SCA) method, Taylor expansion is performed on the non-convex part variables of equations (11a), (11b), (11c), and (11d):

[0041]

[0042] Where: v = diag (h H )G represents the partial channel gain from STAR-RIS to the user, and the set {θ t (m),θ r (m), l(m)} is the value of the variable in the mth iteration. Since the problem is convex with respect to the variable, CVX is used to solve it, and the optimal solution is obtained through multiple rounds of iteration.

[0043] As a preferred embodiment of the present invention, The solution process of sub-problem 3 is:

[0044] The augmented Lagrangian problem can be rewritten as:

[0045]

[0046] Where: η i =-θ i +ρλ i ;

[0047] Expanding formula (13), the original problem can be equivalently transformed into:

[0048]

[0049] Sub-problem 3 is further divided into the amplitude Sub-problem 4 and about phase shift Sub-problem 5: Assume

[0050] Among them, the amplitude The fourth sub-problem is:

[0051]

[0052] set up For the nth element, equation (15) can be transformed into:

[0053]

[0054] Get the optimal amplitude solution:

[0055]

[0056] Among them, the phase shift The fifth sub-problem is:

[0057]

[0058] Through formula (6c), we can get:

[0059]

[0060] Then formula (18) is:

[0061]

[0062] Therefore, the minimum phase shift solution is obtained:

[0063]

[0064] Right now:

[0065]

[0066] A device for countering perception and communication eavesdropping in a STAR-RIS-assisted ISAC system, comprising:

[0067] Model building module: used to build the STAR-RIS assisted ISAC system model;

[0068] Objective function construction module: used to construct an objective optimization problem with the goal of maximizing the confidentiality rate of the communication end, using the communication beam, sensing beam, and STAR-RIS transmission / reflection coefficients as optimization variables;

[0069] Alternating optimization module; used to maximize the system's confidentiality rate while ensuring perceived security by continuously iteratively optimizing variables, dual variables, and penalty parameters.

[0070] An electronic device includes a central processing unit and a memory, wherein the central processing unit is used to call and run a computer program stored in the memory to execute the steps of the method for countering perception and communication eavesdropping in the STAR-RIS assisted ISAC system.

[0071] A computer-readable storage medium stores a computer program implemented by the method for countering perception and communication eavesdropping in the STAR-RIS assisted ISAC system in the form of computer-readable instructions. When the computer program is called and executed by a computer, the steps included in the corresponding method are executed.

[0072] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0073] 1. The method for countering perception and communication eavesdropping in a STAR-RIS-assisted ISAC system of the present invention divides the reflection and transmission ends of the STAR-RIS into a perception area and a communication area, while simultaneously considering the communication security and perception security of the STAR-RIS-assisted ISAC system. By utilizing an alternating optimization algorithm based on successive convex approximation and penalized dual decomposition, while ensuring the performance and security of the perception end, the communication beam, perception beam, and transmission / reflection coefficients of the STAR-RIS-assisted ISAC system are optimized to maximize the security rate of the communication end, thereby ensuring the security of the STAR-RIS-assisted ISAC system.

[0074] 2. The method for countering perception and communication eavesdropping in a STAR-RIS-assisted ISAC system of the present invention incorporates perception constraints into the STAR-RIS-assisted ISAC system model and solves the constructed target optimization problem using an alternating optimization algorithm based on successive convex approximation and penalized dual decomposition, thereby obtaining optimal communication beams, perception beams, and STAR-RIS transmission / reflection coefficients. By adopting the optimal communication beams, perception beams, and STAR-RIS transmission / reflection coefficients, even if a perceptive eavesdropper is present in the STAR-RIS-assisted ISAC system model, the amount of information eavesdropped can be minimized, or even approximately reduced to zero, thereby achieving communication security performance close to that in the absence of a perceptive eavesdropper. BRIEF DESCRIPTION OF THE DRAWINGS

[0075] Figure 1 Schematic diagram of the method for countering perception and communication eavesdropping in the STAR-RIS assisted ISAC system of the present invention.

[0076] Figure 2 Schematic diagram of the STAR-RIS assisted ISAC system model in the present invention.

[0077] Figure 3This is a curve diagram showing how the confidentiality rate changes with power during the simulation process.

[0078] Figure 4 This is a curve diagram showing how the confidentiality rate changes with the threshold value during the simulation process.

[0079] Figure 5 This is a structural block diagram of the device for countering perception and communication eavesdropping in the STAR-RIS assisted ISAC system of the present invention.

[0080] Figure 6 Schematic diagram of the structure of the computer device of the present invention. DETAILED DESCRIPTION

[0081] The following describes embodiments of the present invention in detail, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended only to explain the present invention and are not to be construed as limiting the present invention.

[0082] It will be understood by those skilled in the art that, unless expressly stated otherwise, the singular forms "a", "an", "said" and "the" used herein may also include the plural forms. It should be further understood that the term "comprising" used in the description of the present invention refers to the presence of the features, integers, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or groups thereof. It should be understood that when we refer to an element as being "connected" or "coupled" to another element, it may be directly connected or coupled to the other element, or there may be intermediate elements. In addition, "connected" or "coupled" as used herein may include wireless connections or wireless couplings. The term "and / or" used herein includes all or any units and all combinations of one or more associated listed items.

[0083] It will be understood by those skilled in the art that, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by those skilled in the art in the art to which the present invention belongs. It should also be understood that terms such as those defined in common dictionaries should be understood to have meanings consistent with their meanings in the context of the prior art and will not be interpreted in an idealized or overly formal sense unless specifically defined as herein.

[0084] It will be understood by those skilled in the art that the terms "client," "terminal," and "terminal device" as used herein include both devices that are wireless signal receivers, i.e., devices that only have wireless signal receivers without transmission capabilities, and devices that have receiving and transmitting hardware capable of two-way communication over a two-way communication link. Such devices may include: cellular or other communication devices such as personal computers and tablet computers, which have single-line displays, multi-line displays, or cellular or other communication devices without multi-line displays; PCS (Personal Communications Service), which may combine voice, data processing, fax, and / or data communication capabilities; PDA (Personal Digital Assistant), which may include a radio frequency receiver, a pager, Internet / Intranet access, a web browser, a notepad, a calendar, and / or a GPS (Global Positioning System) receiver; and conventional laptop and / or palmtop computers or other devices, which have and / or include a radio frequency receiver. As used herein, the terms "client," "terminal," or "terminal device" may be portable, transportable, or installed in a vehicle (air, sea, and / or land), or may be adapted and / or configured to operate locally and / or in a distributed manner at any other location on Earth and / or in space. As used herein, the terms "client," "terminal," or "terminal device" may also refer to a communication terminal, an Internet terminal, or a music / video playback terminal, such as a PDA, an MID (Mobile Internet Device), and / or a mobile phone with music / video playback capabilities, or may include a smart TV, a set-top box, or other device.

[0085] The hardware referred to by the names "server", "client", "service node", etc. in this invention is essentially an electronic device with capabilities equivalent to those of a personal computer. It is a hardware device that has the necessary components revealed by the von Neumann principle, such as a central processing unit (including an arithmetic unit and a controller), a memory, an input device, and an output device. Computer programs are stored in its memory, and the central processing unit loads the programs stored in the external memory into the internal memory for execution, executes the instructions in the programs, and interacts with the input and output devices to complete specific functions.

[0086] It should be noted that the concept of "server" in this invention can similarly be extended to encompass server clusters. Based on network deployment principles understood by those skilled in the art, the servers described should be logically divided. Physically, these servers can be independent but accessible via interfaces, or integrated into a single physical computer or computer cluster. Those skilled in the art should understand this flexibility, and it should not constrain the implementation of the network deployment method of this invention.

[0087] Unless expressly specified otherwise, one or more technical features of the present invention may be deployed on a server for implementation and accessed by a client through a remote call to obtain an online service interface provided by the server, or may be directly deployed and run on a client for implementation.

[0088] Unless expressly specified otherwise, the neural network models referenced or may be referenced in the present invention may be deployed on a remote server and remotely called on the client, or may be deployed on a client with sufficient device capabilities and directly called. In some embodiments, when it runs on the client, its corresponding intelligence may be obtained through transfer learning so as to reduce the requirements for the client's hardware operating resources and avoid excessive occupation of the client's hardware operating resources.

[0089] Unless expressly specified otherwise, the various data involved in the present invention may be stored remotely on a server or on a local terminal device, as long as they are suitable for being called by the technical solution of the present invention.

[0090] Those skilled in the art should understand that, although the various methods of the present invention are described based on the same concepts and thus exhibit commonality, unless otherwise specified, these methods can be independently implemented. Similarly, the various embodiments disclosed herein are all based on the same inventive concept. Therefore, concepts expressed in the same manner, as well as concepts expressed differently but appropriately modified for convenience, should be understood as equivalent.

[0091] Unless expressly stated to be mutually exclusive, the various embodiments disclosed herein may combine the relevant technical features of the various embodiments to flexibly construct new embodiments, as long as such combination does not deviate from the inventive spirit of the present invention and can meet the needs of the prior art or address certain deficiencies in the prior art. Persons skilled in the art should be aware of such flexibility.

[0092] See also Figure 1-Figure 2 The method for countering perception and communication eavesdropping in the STAR-RIS assisted ISAC system of the present invention comprises the following steps:

[0093] Step S1: Establishing a STAR-RIS-assisted ISAC system model;

[0094] In this embodiment, the STAR-RIS assisted ISAC system model consists of an ISAC base station, a STAR-RIS with N elements, a single-antenna communication user, a single-antenna communication eavesdropper, a single-antenna sensing target, and a single-antenna sensing eavesdropper; wherein, the antenna array of the ISAC base station adopts a uniform linear array arrangement; the array of elements in the STAR-RIS adopts a uniform planar array arrangement; the ISAC base station simultaneously sends communication signals and sensing signals, and the communication signals can be used to assist sensing.

[0095] Step S2: maximizing the confidentiality rate of the communication end is the optimization goal, and the communication beam, sensing beam, and transmission / reflection coefficients are used as optimization variables to construct a target optimization problem;

[0096] By optimizing the communication beam w c ,, sensing beam w s and the transmission / reflection coefficient θ of STAR-RIS t ,θ r , while ensuring that the perceived target is at the lower threshold and the perceived eavesdropper is at the upper threshold, maximize the confidentiality rate of the communication end; therefore, the target optimization problem constructed is:

[0097]

[0098] Where: (1a) represents the transmit power constraint of the ISAC base station; (1b) and (1c) represent the amplitude constraint and phase shift constraint of the coupled STAR-RIS, respectively; (1d) and (1e) represent the gain constraints at the sensing target and sensing eavesdropper, respectively; P t Indicates the maximum transmission power of the ISAC base station; R c represents the confidentiality rate at the communication user; β n,t ,β n,r and φ n,t ,φ n,r are the amplitude and phase shift of the coupled phase-shifted STAR-RIS reflection and transmission coefficients, respectively; P s represents the beam gain at the sensing target; P s,e represents the beam gain at the sensing eavesdropper, τ s ,τ s,e Respectively represent the set thresholds;

[0099] Among them, the confidentiality rate R at the communication user c The calculation formula is:

[0100]

[0101] Among them, the beam gain P at the sensing targets and the beam gain P at the eavesdropper s,e They are:

[0102]

[0103] Where: G represents the channel gain from the ISAC base station to STAR-RIS; h s ,h s,e They represent the channel gains from SATR-RIS to the sensing target and the sensing eavesdropper respectively; represents the Gaussian white noise variance at the communication user and the communication eavesdropper.

[0104] Step S3: Using an alternating optimization algorithm of successive convex approximation (SCA) and penalized dual decomposition (PDD) to solve the target optimization problem, the algorithm uses successive convex approximation (SCA) to iterate the variables of problem 1 and subproblem 2 internally to obtain a high-quality solution. At the same time, the three subproblems are continuously optimized alternately, while the dual variables and penalty parameters are continuously updated externally to obtain a solution to the original problem. This maximizes the system's confidentiality rate while ensuring perceptual security.

[0105] First, the penalized dual decomposition (PDD) algorithm is used to introduce auxiliary variables Dual variable λ t ,λ r and penalty parameter ρ, we get the augmented Lagrangian problem of the original problem:

[0106]

[0107] Next, the augmented Lagrangian problem is decomposed into three sub-problems: c ,w s}Sub-problem 1: Regarding the variable {θ t ,θ r}Subproblem 2 and about variables , and solve subproblems 1, 2, and 3 respectively.

[0108] Among them, regarding the variable {w c ,w s The first sub-problem of} is a non-convex problem, and its solution process is:

[0109] (1) Rewrite the augmented Lagrangian problem as follows:

[0110]

[0111] (2) Based on the successive convex approximation SCA method, the following auxiliary variables {p, q, t} can be introduced:

[0112]

[0113] (3) Based on the successive convex approximation (SCA) method, Taylor expansion is performed on the non-convex part variables of equations (8b), (8c), (8d), and (8e):

[0114]

[0115] Where: μ = h H ΘG represents the total channel gain from STAR-RIS to the communication user, and the set {w c (m), w s (m), t(m)} are the values of the variables in the mth iteration. This problem is convex with respect to the variables and can be solved using CVX. By performing multiple rounds of iteration on the variables, a higher quality solution can be obtained.

[0116] Among them, about {θ t ,θ r The second sub-problem of} is a non-convex problem, and its solution process is:

[0117] (1) Rewrite the augmented Lagrangian problem as follows:

[0118]

[0119] (2) Based on the successive convex approximation SCA method, the following auxiliary variables {a, b, l} can be introduced:

[0120]

[0121] (3) Based on the successive convex approximation (SCA) method, Taylor expansion is performed on the non-convex part variables of equations (11a), (11b), (11c), and (11d):

[0122]

[0123] Where: v = diag (h H )G represents the partial channel gain from STAR-RIS to the communication user, and the set {θ t (m),θ r (m), l(m)} is the value of the variable in the mth iteration. Since the problem is convex for the variables {a, b, l}, CVX is used to solve it, and a higher quality solution is obtained by iterating the variables for multiple rounds.

[0124] Among them, about The solution process of sub-problem 3 is:

[0125] The augmented Lagrangian problem can be rewritten as:

[0126]

[0127] Where: η i =-θ i +ρλ i ;

[0128] Expanding formula (13), the original problem can be equivalently transformed into:

[0129]

[0130] Sub-problem 3 is further divided into the amplitude Sub-problem 4 and about phase shift Sub-problem 5: Assume

[0131] Among them, the amplitude The fourth sub-problem is:

[0132]

[0133] set up For the nth element, equation (15) can be transformed into:

[0134]

[0135] Get the optimal amplitude solution:

[0136]

[0137] Among them, the phase shift The fifth sub-problem is:

[0138]

[0139] Through formula (6c), we can get:

[0140]

[0141] Then formula (18) is:

[0142]

[0143] Therefore, the minimum phase shift solution is:

[0144]

[0145] Right now:

[0146]

[0147] Finally, the process of the entire alternating optimization algorithm is as follows:

[0148] 1) Initialize the auxiliary variables, dual variables, penalty parameters, reduction factor c, and threshold γ.

[0149] 2) By solving sub-problem 1 and iterating the variables for multiple rounds, the optimal {w c ,w s}, solve subproblem 2 and iterate the variables for multiple rounds to obtain the optimal {θ t ,θ r}, by solving subproblems 4 and 5, we get the optimal Until the objective function converges;

[0150] 3) Calculation If δ≤γ, update the dual variable Otherwise, update the penalty parameter ρ = cρ;

[0151] 4) v = 0.9δ;

[0152] 5) Until δ converges.

[0153] See also Figure 3 and Figure 4 ,By comparing three cases of different number of STAR-RIS components, no aware eavesdropper, and random phase shift, the ,performance of the scheme of the present invention is verified through ,simulation;

[0154] In the simulation, the following parameters are used: M = 8, N = 40, Pt = 1W, σ k =σ k,e =σ s =σ s,e =-110dB, τ s =-91dB,τ s,e =-130dB, for easy observation, normalization is required. Γ s,e =-20dB, the large-scale fading of the channel is modeled as: d0 is the unit distance, set to 1, α is the path loss factor, all set to 2.2; the channel model from STAR-RIS to four users is:

[0155]

[0156] Figure 3 The dynamic relationship between confidentiality rate and maximum power is vividly demonstrated.

[0157] It is revealed that as the power P tWith the increase of , the confidentiality rate values show a steady upward trend. Among them, in this scheme, the scheme with N=50 STAR-RIS components shows a significant performance advantage compared with the scheme with N=40. It can be concluded that increasing the number of STAR-RIS components can effectively improve the system's degree of freedom and thus optimize the overall performance.

[0158] In low-power transmission ranges, traditional eavesdropper-unaware schemes perform better in terms of communication confidentiality. This is primarily due to the reduced need for beamforming in these low-power transmission ranges, allowing them to focus more on communication confidentiality. However, as power levels increase, this performance advantage gradually diminishes, and the gap between the two schemes narrows. This trend reflects the inevitable need to allocate more resources to the communication area to meet the increasing gain requirements while maintaining sensing performance.

[0159] In addition, the random phase STAR-RIS scheme exhibits the weakest communication confidentiality rate in the entire comparison, which shows that the transmission / reflection beamforming strategy of the present invention plays a key role in enhancing the confidentiality performance of the studied network.

[0160] Figure 4 The changes in confidentiality rate under different predetermined thresholds are shown.

[0161] As the threshold increases, the communication confidentiality of all schemes decreases because more gain is allocated to the sensing target area. The gap between this scheme and the scheme with no perceived eavesdropper widens with increasing threshold, demonstrating the importance of beamforming capabilities in the STAR-RIS sensing area. The scheme with N = 50 outperforms the scheme with N = 40, while the random phase shift scheme performs the worst, highlighting the critical role of a carefully designed beamforming strategy.

[0162] Based on any embodiment of the present invention, please refer to Figure 5 Another embodiment of the present invention further provides an apparatus for a method of countering perception and communication eavesdropping in a STAR-RIS-assisted ISAC system, comprising a model building module, an objective function construction module, and an alternating optimization module. The model building module is used to construct a STAR-RIS-assisted ISAC system model; the objective function construction module is used to construct a target optimization problem with maximizing the confidentiality rate of the communication end as the optimization objective, and with the communication beam, the perception beam, and the transmission / reflection coefficient of the STAR-RIS as optimization variables; and the alternating optimization module is used to maximize the confidentiality rate of the system while ensuring perception security by continuously iterating optimization variables, dual variables, and penalty parameters.

[0163] The present invention considers the communication security and perception security of the STAR-RIS-assisted ISAC system; by utilizing an alternating optimization algorithm based on successive convex approximation and penalized dual decomposition, under the premise of ensuring the performance and security of the perception end, the communication beam, perception beam and transmission / reflection coefficient of STAR-RIS in the STAR-RIS-assisted ISAC system are optimized to maximize the security rate of the communication end, thereby ensuring the security of the STAR-RIS-assisted ISAC system.

[0164] Based on any embodiment of the present invention, please refer to Figure 6 Another embodiment of the present invention further provides an electronic device, which can be implemented by a computer device, such as Figure 6 As shown, a schematic diagram of the internal structure of a computer device. The computer device includes a processor, a computer-readable storage medium, a memory, and a network interface connected via a system bus. The computer-readable storage medium of the computer device stores an operating system, a database, and computer-readable instructions. The database may store a control information sequence. When the computer-readable instructions are executed by the processor, the processor may implement a method for countering perception and communication eavesdropping in a STAR-RIS-assisted ISAC system. The processor of the computer device is used to provide computing and control capabilities to support the operation of the entire computer device. The memory of the computer device may store computer-readable instructions. When the computer-readable instructions are executed by the processor, the processor may execute the method for countering perception and communication eavesdropping in the STAR-RIS-assisted ISAC system of the present invention. The network interface of the computer device is used to connect and communicate with a terminal. Those skilled in the art will understand that Figure 6 The structure shown in the figure is merely a block diagram of a portion of the structure related to the solution of the present invention and does not constitute a limitation on the computer device to which the solution of the present invention is applied. The specific computer device may include more or fewer components than shown in the figure, or combine certain components, or have a different component arrangement.

[0165] In this embodiment, the processor is used to execute Figure 5 The memory stores the program code and various data required to execute the specific functions of each module in the STAR-RIS-assisted ISAC system. The network interface is used to transmit data between user terminals or servers. The memory in this embodiment stores the program code and data required to execute all modules / submodules in the device for countering perception and communication eavesdropping in the STAR-RIS-assisted ISAC system of the present invention. The server can call the server's program code and data to execute the functions of all submodules.

[0166] The present invention also provides a storage medium storing computer-readable instructions. When the computer-readable instructions are executed by one or more processors, the one or more processors execute the steps of the method for countering perception and communication eavesdropping in the STAR-RIS assisted ISAC system described in any embodiment of the present invention.

[0167] The present invention also provides a computer program product, including a computer program / instruction, which, when executed by one or more processors, implements the steps of the method for countering perception and communication eavesdropping in the STAR-RIS assisted ISAC system described in any embodiment of the present invention.

[0168] Those skilled in the art will appreciate that all or part of the processes in the above-described method embodiments of the present invention can be implemented by instructing related hardware through a computer program. The computer program can be stored in a computer-readable storage medium. When the program is executed, it can include the processes in the above-described method embodiments. The aforementioned storage medium can be a computer-readable storage medium such as a magnetic disk, an optical disk, a read-only memory (ROM), or a random access memory (RAM).

[0169] The above is a preferred embodiment of the present invention, but the embodiment of the present invention is not limited to the above content. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. A method for countering perception and communication eavesdropping in a STAR-RIS-assisted ISAC system, characterized in that: The following steps are involved: Step S1: Establishing a STAR-RIS-assisted ISAC system model; the STAR-RIS-assisted ISAC system model consists of an ISAC base station, a STAR-RIS with N elements, a single-antenna communication user, a single-antenna communication eavesdropper, a single-antenna sensing target, and a single-antenna sensing eavesdropper; wherein the antenna array of the ISAC base station adopts a uniform linear array arrangement; the array of the STAR-RIS elements adopts a uniform planar array arrangement; the ISAC base station simultaneously transmits communication signals and sensing signals, and the communication signals can be used to assist sensing; Step S2: To maximize the confidentiality rate of the communication user, the communication beam w c ,, sensing beam w s , and the transmission / reflection coefficient θ of STAR-RIS t ,θ r To optimize the variables, construct the target optimization problem, where By optimizing the communication beam w c ,, sensing beam w s , and the transmission / reflection coefficient θ of STAR-RIS t ,θ r , maximize the confidentiality rate of communication users; where, The target optimization problem is: s.t.||w c || 2 +||w s || 2 ≤P t ,(1a) R s ≥τ s ,(1d) R s,e ≤τ s,e ,(1e) Where: (1a) represents the transmit power constraint of the ISAC base station; (1b) and (1c) represent the amplitude constraint and phase shift constraint of the coupled STAR-RIS, respectively; (1d) and (1e) represent the gain constraints at the sensing target and sensing eavesdropper, respectively; P t Indicates the maximum transmission power of the ISAC base station; R c represents the confidentiality rate at the communication user; β n,t ,β n,r are the transmission coefficient amplitude and reflection coefficient amplitude of the coupled phase-shifted STAR-RIS; φ n,t ,φ n,r are the phase shifts of the transmission coefficient and reflection coefficient of the coupled phase-shifted STAR-RIS; P s represents the beam gain at the sensing target; P s,e represents the beam gain at the sensing eavesdropper, τ s ,τ s,e Respectively represent the set thresholds; Among them, the confidentiality rate R at the communication user c The calculation formula is: Among them, the beam gain P at the sensing target s and the beam gain P at the eavesdropper s,e They are: Where: G represents the channel gain from the ISAC base station to STAR-RIS; h s ,h s,e They represent the channel gains from SATR-RIS to the sensing target and the sensing eavesdropper respectively; represents the Gaussian white noise variance at the communication user and the communication eavesdropper; Step S3: using an alternating optimization algorithm of successive convex approximation and penalized dual decomposition to solve the target optimization problem; The algorithm of penalty dual decomposition is adopted, by introducing auxiliary variables Dual variable λ t ,λ r and penalty parameter ρ, we get the augmented Lagrangian problem of the target optimization problem: s.t.||w c || 2 +||w s || 2 ≤P t ,(6a) P s ≥τ s ,(6d) Ρ s,e ≤τ s,e ,(6e) Then the augmented Lagrangian problem is decomposed into three sub-problems, which are: c ,w s }Sub-problem 1: Regarding the variable {θ t ,θ r }Subproblem 2 and about variables , and solve subproblems 1, 2, and 3 respectively.

2. A device for countering the method of sensing and communication eavesdropping in a STAR-RIS-assisted ISAC system according to claim 1, characterized in that: include: Model building module: used to build the STAR-RIS assisted ISAC system model; Objective function construction module: used to construct an objective optimization problem with the goal of maximizing the confidentiality rate of communication users, using the communication beam, sensing beam, and STAR-RIS transmission / reflection coefficients as optimization variables; Alternating optimization module; It is used to maximize the system's confidentiality rate while ensuring perceived security by continuously iteratively optimizing variables, dual variables, and penalty parameters.

3. An electronic device comprising a central processing unit and a memory, characterized in that: The central processing unit is configured to call and run a computer program stored in the memory to execute the steps of the method for countering perception and communication eavesdropping in a STAR-RIS assisted ISAC system as claimed in claim 1.

4. A computer-readable storage medium, characterized in that It stores a computer program implemented by the method for countering perception and communication eavesdropping in the STAR-RIS assisted ISAC system according to claim 1 in the form of computer-readable instructions. When the computer program is called and executed by a computer, the steps included in the corresponding method are executed.

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