A physical layer security transmission method and system based on intelligent reflective surface assistance

Abstract

The present invention discloses a physical layer secure transmission method and system assisted by intelligent reflective surfaces. The method comprises: obtaining the secure transmission rate from the base station to the legitimate user during the energy collection phase as a first secure transmission rate; obtaining the secure transmission rate from the base station to the legitimate user during the information reflection phase as a second secure transmission rate; constructing a system secure transmission rate maximization model based on the first and second secure transmission rates; solving for the optimal value when the second secure transmission rate is maximized based on the system secure transmission rate maximization model; and solving for the optimal value when the first secure transmission rate is maximized based on the optimal value when the second secure transmission rate is maximized. This invention can significantly improve the secure transmission rate of smart grid transmission systems.

Description

Technical Field

[0001] The present invention relates to a physical layer security transmission method and system based on intelligent reflective surface assistance, belonging to the technical field of power system communications. Background Art

[0002] The deep integration of the Energy Internet and 5G has driven the digital development of the power grid and enhanced its intelligence. An increasing number of emerging technologies are being incorporated into the development and transformation of smart grids. However, due to the open capabilities of 5G and the broadcast nature of wireless channels, information transmitted by base stations to legitimate users in smart grids is easily eavesdropped on by unauthorized users. Wireless communication security has become a critical issue. The large number of wireless devices with limited functionality within the power grid cannot support traditional encryption and decryption schemes, making encrypted communication impossible. Research has found that when the channel spaces of legitimate communication links and eavesdropping links are highly correlated, the secure transmission rate achievable by traditional physical layer security schemes is severely limited. Therefore, further improving the secure transmission rate of the system remains an unresolved issue.

[0003] Smart reflective surfaces are an emerging wireless communication technology widely used to improve the performance of wireless communication systems. Typically, a smart reflective surface consists of a large number of passive, reconfigurable reflective elements that control the reflection of incoming signals in specific directions, thereby intelligently controlling the propagation of electromagnetic waves. By adjusting the phase shift controllers on the smart reflective surface, the smart reflective surface can change the amplitude and phase information of the incoming signal, then focus the reflected beam toward the target user, leaving eavesdropping users with only weak sidelobe signals. Therefore, smart reflective surfaces can be used to enhance physical layer communication security and increase secure transmission rates.

[0004] Therefore, proposing a physical layer security transmission method based on the assistance of intelligent reflective surfaces is a current research direction. Summary of the Invention

[0005] The present invention aims to overcome the shortcomings of the prior art and provide a physical layer secure transmission method and system assisted by intelligent reflective surfaces, which can significantly improve the secure transmission rate of smart grid transmission systems. To achieve the above objectives, the present invention adopts the following technical solutions:

[0006] In a first aspect, the present invention provides a physical layer security transmission method based on the assistance of an intelligent reflective surface, wherein the intelligent reflective surface is deployed between a base station and a legitimate user, and the physical layer security transmission method includes:

[0007] Obtaining a secure transmission rate from the base station to the legitimate user during the energy collection phase as a first secure transmission rate;

[0008] Obtaining a secure transmission rate from the base station to the legitimate user during the information reflection phase as a second secure transmission rate;

[0009] Constructing a system security transmission rate maximization model based on the first security transmission rate and the second security transmission rate;

[0010] Based on the system security transmission rate maximization model, the optimal value of the second security transmission rate is obtained;

[0011] Based on the optimal value when the second safety transmission rate is maximized, the optimal value when the first safety transmission rate is maximized is obtained.

[0012] In combination with the first aspect, further, obtaining a secure transmission rate from the base station to a legitimate user during the energy collection phase includes:

[0013] In the energy collection phase, the smart reflective surface collects energy by receiving radio frequency signals from the base station, obtaining the signals received by the smart reflective surface and the energy collected by the smart reflective surface;

[0014] In the energy collection phase, the intelligent reflective surface does not reflect any signal from the base station. The legitimate user and the eavesdropper can only receive the direct signal from the base station. The received signals of the legitimate user and the eavesdropper are The transmission rates of the legitimate user and the eavesdropper in the energy harvesting phase are

[0015] During the energy collection phase, the secure transmission rate from the base station to the legitimate user is:

[0016]

[0017] In formula (1), The secure transmission rate from the base station to the legitimate user during the energy harvesting phase; [x] + =max(0,x).

[0018] In combination with the first aspect, further, obtaining a secure transmission rate from a base station to a legitimate user in the information reflection phase includes:

[0019] In the information reflection phase, the smart reflective surface uses previously collected energy to assist the base station in transmitting information to legitimate users. The power consumption generated by the smart reflective surface in reflecting information is preset to Nμ, where μ is the power consumption of each reflective element. This gives the energy constraint of the smart reflective surface.

[0020] The reflection phase matrix of the smart reflection surface is preset, and the mixed information received by the legitimate user and the eavesdropper from the direct link of the base station and the reflection link of the smart reflection surface are respectively The transmission rates of the legitimate user and eavesdropper information reflection phase are

[0021] During the information reflection phase, the secure transmission rate from the base station to the legitimate user is:

[0022]

[0023] In formula (2), is the secure transmission rate from the base station to the legitimate user during the information reflection phase; [x] + =max(0,x).

[0024] In combination with the first aspect, further, the construction of the system security transmission rate maximization model is:

[0025] By jointly optimizing the time t, the base station beamforming vector w1 during the energy collection phase, the base station beamforming vector w2 during the information reflection phase, and the reflection phase matrix of the smart reflective surface, we can obtain the maximum secure transmission rate of the system per unit time. The system secure transmission rate maximization model is expressed as follows:

[0026]

[0027] In formula (3), The secure transmission rate from the base station to the legitimate user during the energy collection phase; is the secure transmission rate from the base station to the legitimate user during the information reflection phase; η is the energy collection efficiency; t is the time; H ib is the downlink channel from the base station to the smart reflector; Nμ is the power consumption generated by the smart reflector reflecting information; q is the phase shift vector; n is the nth reflector element, and N is the total number of reflector elements; P max is the base station transmit power;

[0028] Since there is a problem of optimization variable coupling in the objective function and the constraints, the optimization variable coupling problem is solved by obtaining a suboptimal solution;

[0029] The system security transmission rate maximization model in the energy harvesting phase is expressed as follows:

[0030]

[0031] In formula (4), It is the channel between the legitimate user and the base station; is the variance of the Gaussian white noise distribution at the legitimate user; To eavesdrop on the channel between the user and the base station; is the variance of the Gaussian white noise distribution at the eavesdropping user;

[0032] Given time t optimization The model for maximizing the secure transmission rate from the base station to the legitimate user during the information reflection phase is expressed as follows:

[0033]

[0034] In formula (5), is the channel between the legitimate user and the smart reflective surface; Θ = diag(q) is the reflection phase matrix of the smart reflective surface, where q is the phase shift vector; It is the channel between the eavesdropper and the smart reflective surface;

[0035] Then the system security transmission rate maximization model P is re-expressed as P1:

[0036]

[0037] In formula (6), H ib P is the downlink channel from the base station to the smart reflector; max is the base station transmit power.

[0038] In combination with the first aspect, further, the solving to obtain the optimal value when the second secure transmission rate is maximized includes:

[0039] Given a phase shift vector q, optimize the beamforming vector w2 of the base station in the information reflection phase and obtain the optimal solution w2 * ;

[0040] According to the optimal solution w2 * , simplify the model of maximizing the secure transmission rate from base station to legitimate users in the information reflection phase;

[0041] The alternating optimization and fractional programming methods are used to solve the simplified model of maximizing the secure transmission rate from the base station to the legitimate user in the information reflection phase, and the optimal value of the second secure transmission rate is obtained.

[0042] In combination with the first aspect, further, the solving to obtain the optimal value when the first secure transmission rate is maximized includes:

[0043] Based on the optimal value when the second secure transmission rate is maximized, given time t, the continuous convex approximation algorithm and the semi-positive definite relaxation algorithm are used to optimize the base station beamforming vector w1 in the energy collection phase to obtain the optimal solution w1 * ;

[0044] According to the optimal solution w1 * Optimize time t and get the optimal value t * , substitute into the system security transmission rate maximization model P1, and obtain the optimal value when the first security transmission rate is maximized.

[0045] In a second aspect, the present invention provides a physical layer secure transmission system assisted by an intelligent reflective surface, comprising:

[0046] A first acquisition module is used to obtain a safe transmission rate from the base station to the legitimate user during the energy collection phase as a first safe transmission rate;

[0047] The second acquisition module is used to obtain the secure transmission rate from the base station to the legitimate user during the information reflection phase as the second secure transmission rate;

[0048] A construction module is used to construct a system security transmission rate maximization model according to the first security transmission rate and the second security transmission rate;

[0049] A first calculation module is used to solve the optimal value when the second security transmission rate is maximized based on the system security transmission rate maximization model;

[0050] The second calculation module is configured to obtain the optimal value when the first safety transmission rate is maximized based on the optimal value when the second safety transmission rate is maximized.

[0051] In a third aspect, the present invention provides a computing device, characterized in that it includes a processor and a storage medium;

[0052] The storage medium is used to store instructions;

[0053] The processor is configured to operate according to the instructions to execute the steps of the method of the first aspect.

[0054] In a fourth aspect, the present invention provides a computer-readable storage medium having a computer program stored thereon, wherein the program implements the steps of the method described in the first aspect when executed by a processor.

[0055] Compared with the prior art, the physical layer secure transmission method and system based on intelligent reflective surface assistance provided by the embodiments of the present invention have the following beneficial effects:

[0056] The intelligent reflective surface of the present invention is deployed between the base station and the legitimate user. In the smart grid, the information transmitted by the base station to the legitimate user is easily eavesdropped by illegal users due to the open capability of 5G and the broadcast characteristics of the wireless channel. The deployment of the intelligent reflective surface is used to improve the secure transmission rate of the system.

[0057] The present invention obtains the secure transmission rate from the base station to the legitimate user during the energy collection phase as the first secure transmission rate; obtains the secure transmission rate from the base station to the legitimate user during the information reflection phase as the second secure transmission rate. The present invention divides the intelligent reflective surface-assisted communication transmission into an energy collection phase and an information reflection phase. During the energy collection phase, the intelligent reflective surface collects energy from the radio frequency signal transmitted by the base station and stores the collected energy in a battery, while the legitimate user and the eavesdropper simultaneously receive information from the base station. During the information reflection phase, the intelligent reflective surface uses the collected energy to adjust the phase of the reflective element to enhance information transmission from the base station to the legitimate user and suppress information transmission from the base station to the eavesdropper.

[0058] The present invention constructs a system security transmission rate maximization model based on the first security transmission rate and the second security transmission rate; the present invention maximizes the system security transmission rate by jointly optimizing time allocation, two-stage beamforming vectors, and phase shift of the smart reflective surface;

[0059] The present invention is based on a system security transmission rate maximization model to solve the optimal value when the second security transmission rate is maximized. The present invention first uses alternating optimization and fractional programming methods to solve the security transmission rate maximization problem in the information transmission stage.

[0060] The present invention solves the optimal value when the first safe transmission rate is maximized based on the optimal value when the second safe transmission rate is maximized; the present invention then uses a continuous convex approximation algorithm and a semi-positive definite relaxation algorithm to solve the maximization of the safe transmission rate in the energy collection phase;

[0061] Compared with the physical layer security transmission method without the assistance of intelligent reflective surface and the physical layer security transmission method with random phase of intelligent reflective surface, the present invention can significantly improve the security transmission rate of the smart grid transmission system. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] Figure 1 This is a transmission model diagram of a physical layer security transmission method based on intelligent reflective surface assistance provided in the first embodiment of the present invention;

[0063] Figure 2 The relationship between the secure transmission rate of the smart grid transmission system and the reflected power of the base station in the physical layer secure transmission method based on the assistance of the smart reflective surface provided in the first embodiment of the present invention;

[0064] Figure 3 This is the relationship between the secure transmission rate of the smart grid transmission system and the number of reflective elements in a physical layer secure transmission method based on the assistance of a smart reflective surface provided in the first embodiment of the present invention. DETAILED DESCRIPTION

[0065] The present invention will be further described below in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention.

[0066] Example 1:

[0067] This embodiment of the present invention introduces a smart reflective surface as an auxiliary device. Deployed between the base station and legitimate users, the smart reflective surface improves the system's secure transmission rate. The entire transmission time slot is divided into an energy collection phase and an information reflection phase. During the energy collection phase, the smart reflective surface collects and stores energy from the base station, while transmitting power grid signals over wireless channels. During the information reflection phase, the collected energy is used to maintain the operation of the smart reflective surface, driving it to adjust the phase shift of its reflective elements to assist in the secure transmission of information from the base station to legitimate users, while simultaneously suppressing information transmitted to eavesdroppers.

[0068] The transmission model adopted in the embodiment of the present invention is as follows: Figure 1 As shown in Figure 2, the model consists of a base station with M antennas, a smart reflective surface composed of N reflective elements, a legitimate user, and an eavesdropper, where both the legitimate user and the eavesdropper have a single antenna. Assuming the smart reflective surface is an energy-constrained device, it uses an energy harvesting unit to harvest energy from the base station's transmitted signals to maintain its own operation and enhance the secure transmission performance from the base station to the legitimate user.

[0069] The downlink channel from the base station to the smart reflector is in represents an m×n complex matrix. The channel from the base station to the legal user is The channel from the base station to the eavesdropper is The channel from the intelligent reflector to the legitimate user is The channel from the smart reflective surface to the eavesdropper is The CSI of all channels is available in advance and fully functional.

[0070] In smart reflective surface-assisted communication transmission, the transmission process is divided into two phases: energy collection and information reflection. During time t, the energy collection phase occurs, where the smart reflective surface collects energy from the base station's RF signal and stores it in a battery. Meanwhile, legitimate users and eavesdroppers simultaneously receive information from the base station. During time 1-t, the information reflection phase occurs, where the smart reflective surface uses the collected energy to adjust the phase of its reflective elements, enhancing information transmission from the base station to legitimate users and suppressing information transmission from the base station to eavesdroppers.

[0071] An embodiment of the present invention provides a physical layer secure transmission method based on intelligent reflective surface assistance, including:

[0072] Obtaining a secure transmission rate from the base station to the legitimate user during the energy collection phase as a first secure transmission rate;

[0073] Obtaining a secure transmission rate from the base station to the legitimate user during the information reflection phase as a second secure transmission rate;

[0074] Constructing a system security transmission rate maximization model based on the first security transmission rate and the second security transmission rate;

[0075] Based on the system security transmission rate maximization model, the optimal value of the second security transmission rate is obtained;

[0076] Based on the optimal value when the second safety transmission rate is maximized, the optimal value when the first safety transmission rate is maximized is obtained.

[0077] The specific steps include:

[0078] Step 1: Obtain the secure transmission rate from the base station to the legitimate user during the energy collection phase as the first secure transmission rate.

[0079] In the energy collection phase, the smart reflective surface collects energy by receiving radio frequency signals from the base station. The signals received by the smart reflective surface are:

[0080] x=H ib w1s (1)

[0081] In formula (1), x is the signal received by the smart reflector, s is the unit power signal transmitted by the base station, w1 is the base station beamforming vector in the energy collection phase, And satisfy ||w1|| 2 ≤P max , P max is the base station transmission power; H ib It is the downlink channel from the base station to the smart reflector.

[0082] The energy E collected by the smart reflective surface is expressed as:

[0083] E=tη||H ib w1|| 2 (2)

[0084] In formula (2), η is the energy collection efficiency; t is the time.

[0085] During the energy collection phase, the smart reflective surface does not reflect any signal from the base station. Therefore, legitimate users and eavesdroppers can only receive direct signals from the base station. The corresponding received signals are expressed as follows:

[0086]

[0087] In formula (3), The receiving signal of the legitimate user in the energy harvesting phase; is the channel between the legitimate user and the base station; n u is the noise at the legitimate user, and satisfies is the variance of the Gaussian white noise distribution at the legitimate user; The received signal of the eavesdropper in the energy harvesting phase; is the channel between the eavesdropper and the base station; n e is the noise at the eavesdropper, and satisfies is the variance of the Gaussian white noise distribution at the eavesdropping user.

[0088] During the energy harvesting phase, the transmission rates of the legitimate user and the eavesdropper are:

[0089]

[0090] In formula (4), The transmission rate of legal users in the energy harvesting phase; is the eavesdropper transmission rate during the energy harvesting phase.

[0091] During the energy collection phase, the secure transmission rate from the base station to the legitimate user is:

[0092]

[0093] In formula (5), The secure transmission rate from the base station to the legitimate user during the energy harvesting phase; [x] + =max(0,x).

[0094] Step 2: Obtain the secure transmission rate from the base station to the legitimate user during the information reflection phase as the second secure transmission rate.

[0095] In the information reflection phase, the smart reflective surface uses the previously collected energy to assist the base station in transmitting information to legitimate users. The power consumption generated by the smart reflective surface in reflecting information is Nμ, where μ is the power consumption of each reflective element. The energy constraint of the smart reflective surface is:

[0096] tη||H ib w1|| 2 ≥(1-t)Nμ (6)

[0097] In formula (6), η is the energy collection efficiency; t is the time; H ib is the downlink channel from the base station to the smart reflector; w1 is the base station beamforming vector in the energy collection phase.

[0098] Let the reflection phase matrix of the smart reflector be expressed as Θ = diag(q), where q is the phase shift vector, satisfying q = [q1, ..., qN ], where θ n represents the phase of the nth reflective element, then the mixed information received by the legitimate user and the eavesdropper from the base station direct link and the smart reflective surface reflection link are:

[0099]

[0100] In formula (7), The receiving signal of the legitimate user in the information reflection phase; It is the channel between the legitimate user and the base station; It is the channel between the legitimate user and the smart reflective surface; The receiving signal of the eavesdropper in the information reflection phase; is the channel between the eavesdropper and the base station; is the channel between the eavesdropper and the smart reflective surface; w2 is the beamforming vector of the base station during the information reflection phase, And satisfy ||w2|| 2 ≤P max .

[0101] In the information reflection phase, the transmission rates of the legitimate user and the eavesdropper are:

[0102]

[0103] In formula (8), The transmission rate of legitimate users in the information reflection phase; is the eavesdropper transmission rate in the information reflection phase.

[0104] During the information reflection phase, the secure transmission rate from the base station to the legitimate user is:

[0105]

[0106] In formula (9), is the secure transmission rate from the base station to the legitimate user during the information reflection phase; [x] + =max(0,x).

[0107] Step 3: Based on the first safe transmission rate and the second safe transmission rate, a system safe transmission rate maximization model is constructed.

[0108] By jointly optimizing the time t, the base station beamforming vector w1 during the energy collection phase, the base station beamforming vector w2 during the information reflection phase, and the reflection phase matrix of the smart reflective surface, we can obtain the maximum secure transmission rate per unit time. The system secure transmission rate maximization model is expressed as follows:

[0109]

[0110] In formula (10), The secure transmission rate from the base station to the legitimate user during the energy collection phase; is the secure transmission rate from the base station to the legitimate user during the information reflection phase; η is the energy collection efficiency; t is the time; H ib is the downlink channel from the base station to the smart reflector; Nμ is the power consumption generated by the smart reflector reflecting information; q is the phase shift vector; n is the nth reflector element, and N is the total number of reflector elements; P max is the base station transmit power.

[0111] Since there is a coupling problem of optimization variables in the objective function and the constraints, it is a non-convex optimization problem and it is difficult to find its optimal solution. The coupling problem of optimization variables is solved by obtaining a suboptimal solution.

[0112] The system security transmission rate maximization model in the energy harvesting phase is expressed as follows:

[0113]

[0114] In formula (4), It is the channel between the legitimate user and the base station; is the variance of the Gaussian white noise distribution at the legitimate user; To eavesdrop on the channel between the user and the base station; is the variance of the Gaussian white noise distribution at the eavesdropping user.

[0115] Given time t optimization The model for maximizing the secure transmission rate from the base station to the legitimate user during the information reflection phase is expressed as follows:

[0116]

[0117] In formula (12), It is the channel between the legitimate user and the smart reflective surface; It is the channel between the eavesdropper and the smart reflective surface;

[0118] Then the system security transmission rate maximization model P is re-expressed as P1:

[0119]

[0120] In formula (13), H ib P is the downlink channel from the base station to the smart reflector; max is the base station transmit power.

[0121] Step 4: Based on the system security transmission rate maximization model, the optimal value when the second security transmission rate is maximized is obtained.

[0122] Since the problem P1 in step 3 is a non-convex optimization problem, it is difficult to obtain the optimal solution of the problem using convex optimization technology. Therefore, an iterative optimization algorithm is designed to solve it. Under the premise of given q, the optimization is w2 * , then according to the obtained w2 * Optimize q and repeat the above process to obtain the suboptimal solution to problem P1 in step 3.

[0123] Step 4.1: Given the phase shift vector q, optimize the beamforming vector w2 of the base station in the information reflection phase and obtain the optimal solution w2 * .

[0124] The formula for the maximum secure transmission rate in the information reflection phase is converted into the following form:

[0125]

[0126] In formula (14), w2 H is the beamforming vector of the base station. The optimal solution of formula (14) is:

[0127]

[0128] In formula (15), u max is the normalized eigenvector of the largest eigenvalue of the corresponding matrix.

[0129] Step 4.2: According to the optimal solution w2 * , simplify the secure transmission rate maximization model from base station to legitimate users in the information reflection phase.

[0130] According to the optimal solution w2 * ,make The model for maximizing the secure transmission rate from the base station to the legitimate user during the information reflection phase can be simplified as follows:

[0131]

[0132] In formula (16), q H is the eigenvector of the IRS phase shift, q n Expressed as where θ n represents the phase of the nth reflective element.

[0133] Step 4.3: Use alternating optimization and fractional programming to solve the simplified model of maximizing the secure transmission rate from the base station to the legitimate user in the information reflection phase, and obtain the optimal value when the second secure transmission rate is maximized.

[0134] Equation (16) belongs to the fractional programming problem, which can be transformed into the corresponding parameterized equation (17):

[0135]

[0136] In formula (17), γ is an auxiliary variable introduced, and γ≥0. The optimal target value of the parameterized formula (17) is expressed as ψ * (γ), for ease of handling, consider the upper limit objective function (18) of formula (16):

[0137]

[0138] In formula (18),

[0139] Where q is the value obtained in the previous iteration of the alternating algorithm, then the parameterized equation (17) can be simplified to equation (19):

[0140]

[0141] Because |q n |=1, we can get |q| 2 = N. In addition, it can be seen that when the phase shift q n and β n When equal, Get the maximum value, where β n is the nth value of β. Therefore, the optimal solution of the above formula (19) for a given γ is formula (20):

[0142]

[0143] Substituting equation (20) into parameterized equation (17), we obtain the optimal value formula (21) of parameterized equation (17):

[0144]

[0145] Obviously, * (γ) is a monotonically decreasing function with respect to γ, and ψ * (0)>0,ψ * (∞)<0. Then ψ * (γ)=0, there is a unique solution γ', which can be found by binary search. Finally, the optimal value q of formula (20) can be obtained * (γ').

[0146] Step 5: Based on the optimal value when the second safety transmission rate is maximized, the optimal value when the first safety transmission rate is maximized is obtained.

[0147] Obtain the optimal value of the maximum secure transmission rate in the information reflection phase After that, it is still necessary to continue to solve the non-convex problem through iterative optimization algorithm. Similarly, optimize w1 under the premise of given t, and then according to the obtained w1 * Optimize t and repeat the above process to obtain the suboptimal solution of P in step 3.

[0148] Step 5.1: Based on the optimal value when the second secure transmission rate is maximized, given time t, the base station beamforming vector w1 in the energy collection phase is optimized using the continuous convex approximation algorithm and the semi-positive definite relaxation algorithm to obtain the optimal solution w1 * .

[0149] Given t optimized w1, given the initial value of t is t', the system security transmission rate maximization model P1 is simplified to the following formula (22):

[0150]

[0151] Formula (22) is a non-convex optimization problem, and it is difficult to directly obtain its optimal solution. The key to solving Formula (22) is to obtain the objective function Based on this, the objective function is transformed into the following formula (23):

[0152]

[0153] In formula (23), is the initial value, And I N N× N The optimal value formula (21) in step 4 is transformed into the following formula (24):

[0154]

[0155] Due to the constraints of equation (24), the equation is still non-convex. By relaxing the rank 1 constraint through SDR, equation (23) can be solved using the convex optimization tool CVX, and then Gaussian randomization is used to obtain a rank 1 solution from the CVX result. The solution is make Substitute the updated value into the above formula (24) and iterate until convergence. Under the premise of a given time t, the optimal solution w1 of the above formula (24) can be obtained * .

[0156] Step 5.2: According to the optimal solution w1 * Optimize time t and get the optimal value t * , substitute into the system security transmission rate maximization model P1, and obtain the optimal value when the first security transmission rate is maximized.

[0157] According to the optimal solution w1 * ,make Then problem P1 can be simplified as:

[0158]

[0159] In the information reflection stage, the introduction of intelligent reflective surface can improve the system security transmission rate, so we can get Then Equation (25) is a monotonically decreasing function with respect to time t. When the constraint condition of Equation (25) takes the equal sign, the maximum value of the above equation can be obtained. Then the optimal value of time t is:

[0160]

[0161] In formula (26), t * is the optimal value at time t.

[0162] The algorithms for steps 4 and 5 are shown in Algorithm 1.

[0163]

[0164]

[0165]

[0166] This paper addresses the problem of information transmitted from base stations to legitimate users in smart grids being easily eavesdropped on by unauthorized users due to the open capabilities of 5G and the broadcast nature of wireless channels. It proposes a physical layer secure transmission method in smart grids, assisted by intelligent reflective surfaces. This method further improves the system's secure transmission rate at the physical layer.

[0167] The present invention proposes a physical layer security transmission method based on the assistance of smart reflective surfaces, in which the smart reflective surface first collects energy from the base station, and then uses the collected energy to assist the base station in transmitting information to legitimate users, while suppressing the information eavesdropped by eavesdropping users. The system security transmission rate is maximized by jointly optimizing time allocation, two-stage beamforming vectors, and the phase shift of the smart reflective surface. Due to the coupling of multiple variables in the above problem, the problem is non-convex and cannot be solved directly. To this end, an efficient iterative optimization algorithm is designed to obtain a high-precision suboptimal solution. The simulation results are shown in Figure 2. Figure 2 、 Figure 3 As shown, compared with the physical layer security transmission method without intelligent reflective surface assistance ( Figure 2 ) and physical layer security transmission method with random phase of smart reflector ( Figure 3 ), which can significantly improve the safe transmission rate of the smart grid transmission system.

[0168] Example 2:

[0169] An embodiment of the present invention provides a physical layer secure transmission system assisted by an intelligent reflective surface, including:

[0170] A first acquisition module is used to obtain a safe transmission rate from the base station to the legitimate user during the energy collection phase as a first safe transmission rate;

[0171] The second acquisition module is used to obtain the secure transmission rate from the base station to the legitimate user during the information reflection phase as the second secure transmission rate;

[0172] A construction module is used to construct a system security transmission rate maximization model according to the first security transmission rate and the second security transmission rate;

[0173] A first calculation module is used to solve the optimal value when the second security transmission rate is maximized based on the system security transmission rate maximization model;

[0174] The second calculation module is configured to obtain the optimal value when the first safety transmission rate is maximized based on the optimal value when the second safety transmission rate is maximized.

[0175] Example 3:

[0176] An embodiment of the present invention provides a computer device, including a processor and a storage medium;

[0177] The storage medium is used to store instructions;

[0178] The processor is configured to operate according to the instructions to execute the steps of the method described in embodiment 1.

[0179] Example 4:

[0180] An embodiment of the present invention further provides a computer-readable storage medium having a computer program stored thereon, which implements the steps of the method described in the first embodiment when the program is executed by a processor.

[0181] Those skilled in the art will appreciate that the embodiments of the present application can be provided as methods, systems, or computer program products. Therefore, the present application can adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment in combination with software and hardware. Moreover, the present application can adopt the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to magnetic disk storage, CD-ROM, optical storage, etc.) that contain computer-usable program code.

[0182] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the steps in the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0183] These computer program instructions may also be stored in a computer readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 a process or multiple processes and / or boxes Figure 1 The function specified in one or more boxes.

[0184] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operational steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing the instructions executed on the computer or other programmable device for implementing the process. Figure 1 a process or multiple processes and / or boxes Figure 1 The steps for the function specified in one or more boxes.

[0185] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A physical layer security transmission method based on intelligent reflective surface assistance, characterized in that: The intelligent reflective surface is deployed between a base station and a legitimate user, and the physical layer secure transmission method includes: Obtaining a secure transmission rate from the base station to the legitimate user during the energy collection phase as a first secure transmission rate; Obtaining a secure transmission rate from the base station to the legitimate user during the information reflection phase as a second secure transmission rate; According to the first safe transmission rate and the second safe transmission rate, a system safe transmission rate maximization model is constructed; wherein the system safe transmission rate maximization model is constructed as follows: By jointly optimizing the time t, the base station beamforming vector w1 during the energy collection phase, the base station beamforming vector w2 during the information reflection phase, and the reflection phase matrix of the smart reflective surface, we can obtain the maximum secure transmission rate of the system per unit time. The system secure transmission rate maximization model is expressed as follows: In formula (3), The secure transmission rate from the base station to the legitimate user during the energy collection phase; is the secure transmission rate from the base station to the legitimate user during the information reflection phase; η is the energy collection efficiency; t is the time; H ib is the downlink channel from the base station to the smart reflector; Nμ is the power consumption generated by the smart reflector reflecting information; q is the phase shift vector; n is the nth reflector element, and N is the total number of reflector elements; P max is the base station transmit power; Based on the system security transmission rate maximization model, the optimal value of the second security transmission rate is obtained; Based on the optimal value when the second safety transmission rate is maximized, the optimal value when the first safety transmission rate is maximized is obtained.

2. The physical layer security transmission method based on intelligent reflective surface assistance according to claim 1 is characterized in that: The obtaining of a secure transmission rate from a base station to a legitimate user during the energy collection phase includes: In the energy collection phase, the smart reflective surface collects energy by receiving radio frequency signals from the base station, obtaining the signals received by the smart reflective surface and the energy collected by the smart reflective surface; In the energy collection phase, the intelligent reflective surface does not reflect any signal from the base station. The legitimate user and the eavesdropper can only receive the direct signal from the base station. The received signals of the legitimate user and the eavesdropper are The transmission rates of the legitimate user and the eavesdropper in the energy harvesting phase are During the energy collection phase, the secure transmission rate from the base station to the legitimate user is: In formula (1), The secure transmission rate from the base station to the legitimate user during the energy harvesting phase; [x] + =max(0,x).

3. The physical layer security transmission method based on intelligent reflective surface assistance according to claim 1 is characterized in that: The secure transmission rate from the base station to the legitimate user in the information reflection phase is obtained, including: In the information reflection phase, the smart reflective surface uses previously collected energy to assist the base station in transmitting information to legitimate users. The power consumption generated by the smart reflective surface in reflecting information is preset to Nμ, where μ is the power consumption of each reflective element. This gives the energy constraint of the smart reflective surface. The reflection phase matrix of the smart reflection surface is preset, and the mixed information received by the legitimate user and the eavesdropper from the direct link of the base station and the reflection link of the smart reflection surface are respectively The transmission rates of the legitimate user and eavesdropper information reflection phase are During the information reflection phase, the secure transmission rate from the base station to the legitimate user is: In formula (2), is the secure transmission rate from the base station to the legitimate user during the information reflection phase; [x] + =max(0,x).

4. The physical layer security transmission method based on intelligent reflective surface assistance according to claim 1 is characterized in that: Since there is a problem of optimization variable coupling in the objective function and the constraints, the optimization variable coupling problem is solved by obtaining a suboptimal solution; The system security transmission rate maximization model in the energy harvesting phase is expressed as follows: In formula (4), It is the channel between the legitimate user and the base station; is the variance of the Gaussian white noise distribution at the legitimate user; To eavesdrop on the channel between the user and the base station; is the variance of the Gaussian white noise distribution at the eavesdropping user; Given time t optimization The model for maximizing the secure transmission rate from the base station to the legitimate user during the information reflection phase is expressed as follows: In formula (5), is the channel between the legitimate user and the smart reflective surface; Θ = diag(q) is the reflection phase matrix of the smart reflective surface, where q is the phase shift vector; It is the channel between the eavesdropper and the smart reflective surface; Then the system security transmission rate maximization model P is re-expressed as P1: In formula (6), H ib P is the downlink channel from the base station to the smart reflector; max is the base station transmit power.

5. The physical layer security transmission method based on intelligent reflective surface assistance according to claim 4 is characterized in that: The solving to obtain the optimal value when the second secure transmission rate is maximized includes: Given a phase shift vector q, optimize the beamforming vector w2 of the base station in the information reflection phase and obtain the optimal solution w2 * ; According to the optimal solution w2 * , simplify the model of maximizing the secure transmission rate from base station to legitimate users in the information reflection phase; The alternating optimization and fractional programming methods are used to solve the simplified model of maximizing the secure transmission rate from the base station to the legitimate user in the information reflection phase, and the optimal value of the second secure transmission rate is obtained.

6. The physical layer security transmission method based on intelligent reflective surface assistance according to claim 5 is characterized in that: The solving to obtain the optimal value when the first secure transmission rate is maximized includes: Based on the optimal value when the second secure transmission rate is maximized, given time t, the continuous convex approximation algorithm and the semi-positive definite relaxation algorithm are used to optimize the base station beamforming vector w1 in the energy collection phase to obtain the optimal solution w1 * ; According to the optimal solution w1 * Optimize time t and get the optimal value t * , substitute into the system security transmission rate maximization model P1, and obtain the optimal value when the first security transmission rate is maximized.

7. A physical layer security transmission system based on intelligent reflective surface assistance, characterized in that: include: A first acquisition module is used to obtain a safe transmission rate from the base station to the legitimate user during the energy collection phase as a first safe transmission rate; The second acquisition module is used to obtain the secure transmission rate from the base station to the legitimate user during the information reflection phase as the second secure transmission rate; A construction module is used to construct a system security transmission rate maximization model based on the first security transmission rate and the second security transmission rate; wherein the construction of the system security transmission rate maximization model is: By jointly optimizing the time t, the base station beamforming vector w1 during the energy collection phase, the base station beamforming vector w2 during the information reflection phase, and the reflection phase matrix of the smart reflective surface, we can obtain the maximum secure transmission rate of the system per unit time. The system secure transmission rate maximization model is expressed as follows: In formula (3), The secure transmission rate from the base station to the legitimate user during the energy collection phase; is the secure transmission rate from the base station to the legitimate user during the information reflection phase; η is the energy collection efficiency; t is the time; H ib is the downlink channel from the base station to the smart reflector; Nμ is the power consumption generated by the smart reflector reflecting information; q is the phase shift vector; n is the nth reflector element, and N is the total number of reflector elements; P max is the base station transmit power; A first calculation module is used to solve the optimal value when the second security transmission rate is maximized based on the system security transmission rate maximization model; The second calculation module is configured to obtain the optimal value when the first safety transmission rate is maximized based on the optimal value when the second safety transmission rate is maximized.

8. A computer device, characterized in that: including processor and storage medium; The storage medium is used to store instructions; The processor is configured to operate according to the instructions to execute the steps of the method according to any one of claims 1 to 6.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the program is executed by a processor, the steps of the method according to any one of claims 1 to 6 are implemented.

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