A zone-specific beamforming physical layer security transmission system and method

Abstract

The application provides a kind of fixed area beam forming physical layer security transmission system and method, it is related to wireless communication physical layer security field, it aims at solving the technical defects that traditional directional angle beam forming and rotating angle beam forming are easily intercepted signal by intelligent eavesdropping equipment due to existing fixed main lobe transmission track.The system includes baseband modulation module, frequency adjustment module and phased array module, by dividing phased array into multiple multi-frequency phased subarrays, transmitting multiple rotating sub-beams, effectively superimposing to form beam main lobe in the target receiving position small area, mutually canceling to form side lobe outside the target area;Combining frequency offset increment probability switching realizes side lobe randomization, for unknown eavesdropping position, crowd search algorithm is used to optimize frequency offset increment, for known eavesdropping position, block coordinate sinking linear approximation algorithm is used to optimize frequency offset increment.Eliminate the long distance transmission track of traditional beam main lobe, significantly improve the physical layer security performance of wireless communication system.

Description

Technical Field

[0001] This invention relates to the field of physical layer security technology in wireless communication, specifically to a fixed-area beamforming physical layer secure transmission system and method, applicable to millimeter-wave beam transmission scenarios requiring high security. Background Technology

[0002] Millimeter-wave massive beamforming technology is one of the core technologies of 6G systems. It uses a large array of antennas to transmit and receive wireless signals, controlling the convergence of these signals at a specific angle to form a main lobe, enabling directional signal transmission and improving communication efficiency. However, the main lobe transmission path of traditional directional beamforming is relatively stable, making it easy for unauthorized users to intercept signals and posing a physical layer security vulnerability.

[0003] To address this issue, existing technologies propose rotating beamforming technology for multi-frequency arrays. By adding a frequency fine-tuning module to a traditional phased array, the frequency of each branch of the antenna array undergoes a slight change, generating a beam that can rotate around the target receiving user. Through frequency fine-tuning, the beam rotates around the target user, avoiding the transmission beam main lobe from eavesdroppers in known locations.

[0004] However, regardless of whether it's directional or rotational beamforming, the spatial transmission trajectory of the main lobe always exists. With the increasing maturity of artificial intelligence technology, intelligent eavesdropping equipment can use AI to learn and judge the transmission trajectory of the main lobe, grasp the frequency control characteristics of the base station on the multi-frequency array, and continuously track the main lobe through multiple programmable eavesdropping terminals. Ultimately, this leads to the complete failure of the physical layer security performance of rotational beamforming. Current technology still cannot fundamentally solve the eavesdropping risks posed by the main lobe. Summary of the Invention

[0005] The purpose of this invention is to provide a physical layer secure transmission system and method for fixed-area beamforming, which solves the technical defects of traditional directional angle beamforming and rotation angle beamforming, which are easily intercepted by intelligent eavesdropping equipment due to the fixed main lobe transmission trajectory. By superimposing the target area of ​​multiple sub-beams to form a small-range main lobe, the long-distance transmission trajectory of the main lobe is eliminated. Combined with sidelobe randomization technology and frequency offset increment optimization strategy, it can achieve accurate anti-interception against known / unknown eavesdropping locations, and significantly improve the physical layer security rate of wireless communication systems.

[0006] To achieve the above objectives, the present invention provides a fixed-area beamforming physical layer secure transmission system, the system comprising: The baseband modulation module is used to modulate private information using quadrature components and then load it to a frequency of [frequency value missing]. On the carrier wave; A frequency adjustment module is used to fine-tune the frequency of L branches of the phased array. The frequency adjustment module includes an M-channel low-frequency oscillator, M M-to-1 random selector switches, a frequency equal-probability switching controller, and M N-channel frequency multipliers. The low-frequency oscillator outputs M frequencies respectively... , , and The low-frequency offset increment, the frequency equal probability switching controller outputs a frequency switching control vector, controls M M-to-1 random switching switches to randomly distribute the low-frequency signal to the output channel, realizing sidelobe randomization control, and L=MN, where L, M, and N are all integers greater than 1; The phased array module consists of L uniform linear antennas, and the L antennas are divided into M multi-frequency phased subarrays. ,m∈ Each subarray contains N antennas; used to transmit M rotating sub-beams, achieving superposition of sub-beams in the target area and cancellation in the non-target area.

[0007] Compared with existing technologies, the physical layer secure transmission system for fixed-area beamforming provided by this invention has the following beneficial effects: Through the collaborative design of the baseband modulation module, frequency adjustment module, and phased array module, it breaks through the technical defect of traditional directional or rotating beamforming, which is easily eavesdropped by smart devices due to the fixed main lobe transmission trajectory. The phased array is divided into M multi-frequency phased arrays and rotating sub-beams are emitted. By precisely superimposing the sub-beams in the target area, a main lobe focused on a small space is formed. In non-target areas, they cancel each other out to form compressed side lobes, completely eliminating long-distance main lobe transmission paths. At the same time, the frequency adjustment module outputs a control vector through a frequency equal probability switching controller, driving M M-to-1 random switching switches to randomly allocate M low-frequency offset increments, realizing randomized control of side lobes, converting side lobe leakage signals into artificial noise, and effectively suppressing eavesdroppers' analysis of the leakage signals.

[0008] The present invention also provides a method for secure transmission of physical layer beamforming in a fixed region, the method comprising the following steps: Step S1: After the private information is orthogonally modulated by the baseband modulation module, it is loaded onto the carrier frequency. superior; Step S2: Generate M frequencies using the low-frequency oscillator of the frequency adjustment module, respectively. , , and The low-frequency offset increment, after being randomly allocated by M M-to-1 random switching switches controlled by a frequency equal-probability switching controller, is then fine-tuned by M N-channel frequency multipliers on the N branches of the M subarrays of the phased array, so that the first... Subarrays The frequency of the nth branch satisfies , in, n , For the first Frequency offset increment of each subarray Where N is the carrier frequency, and N is the number of antennas in a single subarray; Step S3: The rotating sub-beams are emitted through the M sub-arrays of the phased array module. The phase control factor is used to make the sub-beams superimpose in the target area to form the main lobe and cancel each other out in the non-target area to form the side lobes. Step S4: Sidelobe randomization is achieved by switching frequency offset increments with equal probability, converting the sidelobe leakage signal into artificial noise; Step S5: Depending on whether the eavesdropping location information is known, select the corresponding optimization algorithm to adjust the frequency offset increment of each subarray to reduce sidelobe signal leakage. When the eavesdropping location information is unknown, the crowd search algorithm is used to minimize the sidelobe leakage peak. When the eavesdropping location information is known, the block coordinate sinking linear approximation algorithm is used to minimize the beam gain of the eavesdropping location.

[0009] Compared with the prior art, the fixed-area beamforming physical layer secure transmission method provided by the present invention has the same beneficial effects as the fixed-area beamforming physical layer secure transmission system provided by the above-mentioned technical solution, and will not be repeated here.

[0010] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings. Attached Figure Description

[0011] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0012] Figure 1 This diagram illustrates the safety hazards of the physical layer in existing angle beamforming technology. Figure 2 A schematic diagram of the structure of the fixed-area beamforming physical layer secure transmission system provided in an embodiment of the present invention is shown. Figure 3 (a) A schematic diagram of beamforming in a known eavesdropping location scenario provided in the present embodiment; Figure 3(b) shows a schematic diagram of traditional directional angle beamforming in a scenario where the eavesdropping location is known; Figure 4 This diagram illustrates the frequency offset increment equal probability switching beam sidelobe randomization structure provided in an embodiment of the present invention. Figure 5 (a) illustrates the target receiving location provided in an embodiment of the present invention. A diagram illustrating the target user constellations; Figure 5 (b) shows the eavesdropping location provided in an embodiment of the present invention. , A diagram illustrating the constellations of users who use side-lobes to eavesdrop; Figure 5 (c) The listening position provided by the embodiment of the present invention is shown. , A diagram illustrating the constellations of users who use side-lobes to eavesdrop; Figure 5 (d) illustrates the listening position provided by an embodiment of the present invention. , A diagram illustrating the constellations of users who use side-lobes to eavesdrop; Figure 6 This diagram illustrates the safe rate effect of fixed-area beamforming provided by an embodiment of the present invention. Figure 7 (a) shows a schematic diagram of a fixed-area beamforming in an unknown eavesdropping location scenario provided by an embodiment of the present invention; Figure 7 (b) shows a schematic diagram of traditional directional angle beamforming in a scenario where the eavesdropping location is unknown; Figure 8 A schematic diagram of the linear approximation process provided in an embodiment of the present invention is shown; Figure 9 (a) illustrates a known eavesdropping location provided by an embodiment of the present invention. Schematic diagram of directional safety rate profile; Figure 9 (b) illustrates the known eavesdropping locations provided by embodiments of the present invention. Schematic diagram of safe rate profile; Figure 10 A schematic diagram comparing the security and speed performance of BCDLA and SOA optimization provided in the embodiments of the present invention is shown. Detailed Implementation

[0013] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0014] In this embodiment, "multiple" refers to two or more. "And / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A alone, A and B simultaneously, or B alone. Words such as "exemplary" or "for example" are used to indicate examples, illustrations, or explanations, intended to present related concepts in a specific manner, and should not be construed as superior or more advantageous than other embodiments or designs.

[0015] Figure 1 This diagram illustrates a potential safety hazard in the physical layer of angle beamforming in the prior art. Figure 1 As shown, a multi-frequency array transmitting base station controls beam rotation according to certain rules. An eavesdropping agent uses artificial intelligence learning technology to learn the base station's frequency control strategy and controls multiple programmable eavesdropping terminals at various locations to conduct eavesdropping. This ensures that the eavesdropping terminals are always on the main lobe of the beam, thus rendering the physical layer security performance of the multi-frequency array's rotating beam ineffective. Therefore, regardless of whether it's directional or rotating beamforming, the transmission trajectory of the main lobe always exists, making it impossible to fundamentally solve the signal interception problem.

[0016] Example 1 Based on this, embodiments of the present invention provide a physical layer secure transmission system for fixed-area beamforming. Figure 2 This diagram illustrates the structure of a fixed-area beamforming physical layer secure transmission system provided in an embodiment of the present invention. Figure 4 A schematic diagram of the frequency offset increment equal probability switching beam sidelobe randomization structure provided in an embodiment of the present invention is shown. Figure 2 and Figure 4 As shown, the system includes: The baseband modulation module is used to apply in-phase and quadrature modulation (IQ modulation) to private information and then load it to a frequency of [frequency value missing]. On the carrier wave.

[0017] The frequency adjustment module is used to fine-tune the frequency of the L branches of the phased array. The frequency adjustment module includes an M-channel low-frequency oscillator, M M-to-1 random selector switches, a frequency equal-probability switching controller, and M N-channel frequency multipliers. The low-frequency oscillator outputs M frequencies respectively... , , and The low-frequency offset increment, the frequency equal probability switching controller outputs a frequency switching control vector, which controls M M-to-1 random switching switches to randomly distribute the low-frequency signal to the output channel, realizing sidelobe randomization control, and L=MN, where L, M, and N are all integers greater than 1. Subarray The transmission frequency difference between adjacent branches within the branch is The subarray The resulting rotatable beam satisfies: The local beamforming array factor satisfies: in, For the first Subarrays The formed rotatable beam This represents the frequency offset increment of the m-th subarray. For carrier frequency, The azimuth angle of the eavesdropper. The distance between the eavesdropper and the center of the array. The angle of the target receiving position. Distance to the target receiving location ， The spacing between adjacent antennas in a phased array. Where M is the speed of light, M is the total number of subarrays, and N is the number of antennas in a single subarray.

[0018] The M M-to-1 random switching switches of the frequency adjustment module satisfy the equal probability selection characteristic, and the probability distribution of the output frequency offset increment of the m-th M-to-1 random switching switch is as follows: , in, The phased array module consists of L uniform linear antennas, i.e. It consists of L branches, and the L antennas are divided into M multi-frequency phased arrays. ,m∈ Each subarray contains N antennas, satisfying L=MN, that is... Each subarray has 1 subarray One antenna is used to transmit M rotating sub-beams, which achieve superposition of sub-beams in the target area and cancellation in the non-target area.

[0019] Compared with the prior art, the physical layer secure transmission system for fixed-area beamforming provided by the embodiments of the present invention has the following beneficial effects: The present invention, through the collaborative design of the baseband modulation module, frequency adjustment module and phased array module, breaks through the technical defect of traditional directional or rotating beamforming, which is easily eavesdropped by smart devices due to the fixed main lobe transmission trajectory: the phased array is divided into M multi-frequency phased arrays and rotating sub-beams are emitted. The main lobe of the beam is focused in a small space by means of the precise superposition of the sub-beams in the target area. The side lobes are compressed and cancel each other out in the non-target area, thus completely eliminating the long-distance main lobe transmission path. Meanwhile, the frequency adjustment module outputs a control vector through a frequency equal probability switching controller, driving M M-to-1 random switching switches to randomly allocate M low-frequency offset increments, achieving sidelobe randomization control and converting sidelobe leakage signals into artificial noise, effectively suppressing eavesdroppers' analysis of the leakage signals. The system uses an L=MN array architecture compatible with traditional uniform linear antenna layouts, and the core components are all mature communication devices, requiring no reconstruction of new hardware. While ensuring stable communication for the target user, it significantly improves the physical layer's anti-eavesdropping capability, making it suitable for high-speed wireless communication scenarios with high security requirements such as millimeter waves.

[0020] This invention also provides a method for secure transmission at a physical layer using fixed-area beamforming. By controlling the rotating sub-beams emitted by multiple sub-arrays, the main lobe of the beam is effectively superimposed in a small region near the target receiving location, while side lobes cancel each other out outside the target region. The method includes the following steps: Step S1: After the private information is orthogonally modulated by the baseband modulation module, it is loaded onto the carrier frequency. superior; Step S2: Generate M frequencies using the low-frequency oscillator of the frequency adjustment module, respectively. , , and The low-frequency offset increment, after being randomly allocated by M M-to-1 random switching switches controlled by a frequency equal-probability switching controller, is then fine-tuned by M N-channel frequency multipliers on the N branches of the M subarrays of the phased array, so that the first... Subarrays The frequency of the nth branch satisfies: , in, n , For the first Frequency offset increment of each subarray Where N is the carrier frequency, and N is the number of antennas in a single subarray; Step S3: The rotating sub-beams are emitted through the M sub-arrays of the phased array module. The phase control factor is used to make the sub-beams superimpose in the target area to form the main lobe and cancel each other out in the non-target area to form the side lobes. Step S4: Sidelobe randomization is achieved by switching frequency offset increments with equal probability, converting the sidelobe leakage signal into artificial noise; Step S5: Depending on whether the eavesdropping location information is known, select the corresponding optimization algorithm to adjust the frequency offset increment of each subarray to reduce sidelobe signal leakage. When the eavesdropping location information is unknown, the crowd search algorithm is used to minimize the sidelobe leakage peak. When the eavesdropping location information is known, the block coordinate sinking linear approximation algorithm is used to minimize the beam gain of the eavesdropping location.

[0021] When the location of the eavesdropping is unknown, a crowd search algorithm is used to optimize the frequency offset increment. The optimization objective is to minimize the sidelobe leakage peak value. The optimization objective formula is: , in, Indicates the position of the beam's sidelobes. , For the maximum frequency offset increment, This is the local beamforming array factor.

[0022] When the location of the eavesdropping is known, a block coordinate sinking linear approximation algorithm is used to optimize the frequency offset increment. The optimization objective is to minimize the beam gain at the eavesdropping location, and the optimization objective formula is as follows: , , in, , subarray Beamforming coefficient, For angle-dependent phase coefficients, For distance-related phase coefficients, This represents the total angular phase coefficient of the subarray. This represents the total phase coefficient of the subarray distance. is the beamforming coefficient of the m-th subarray.

[0023] Example 2 I. Fixed-area beamforming technology.

[0024] (1) Fixed-area beamforming array factor.

[0025] Figure 2 In the middle, assuming the first Subarrays The frequency difference between adjacent branches within the same branch is , Then the subarray The The frequencies on the branch are: , (1) in, n , For the first Frequency offset increment of each subarray Where is the carrier frequency, and N is the number of antennas in a single subarray.

[0026] In angular distance space, from subarray The antenna to far-field receiving point ( The propagation distance of ) can be expressed as: , (2) From subarray The The antenna transmits signals from the center of the array to the far-field receiving point. The resulting phase difference can be approximately expressed as: , (3) Let the first Subarrays The corresponding channel vector is represented as: , (4) In equation (4), Represented as: , (5) The channel vector for fixed-area beamforming can then be expressed as: , (6) Assuming beam steering vector The local beamforming array factor is then expressed as: , (7) in, No. Subarrays The formed rotatable beam is represented as (8) As can be seen from equations (7) and (8), fixed-area beamforming is... Individual Beam Formed by superposition. It is a phase control factor, controlling The sub-beam in the target area Effective superposition forms the main lobe of the beam; the M sub-beams are controlled within the target area. The outer beams cancel each other out, forming side lobes of the beam.

[0027] Figure 3 This is a comparison diagram of fixed-area and directional angle beamforming. Figure 3 (a) is a local beamforming pattern, where the beam is only at the target location. The upper lobe forms the main lobe, while other regions are compressed side lobes. The eavesdropper receives the best signal quality only when they are in the same location as the target user. Figure 3 (b) is a traditional directional angle beamforming method, which has a transmission path for the main lobe of the beam and a target position. Even if it's just one point on the main lobe of the beam, an eavesdropper can intercept the signal simply by standing in the direction of the main lobe. This demonstrates that localized beamforming eliminates the long-distance trajectory of traditional beam transmission, forming the main lobe only within a small spatial area at the target location. This effectively solves the security risks associated with eavesdropping on the main lobe of traditional beamforming.

[0028] (2) Frequency offset increment equal probability switching beam sidelobe randomization technology.

[0029] According to formula (7), when , hour, =1, forming the main lobe of the beam; in Outside the target area, For complex numbers, the magnitude and phase are vectors of frequency offset increments. The value is related to the frequency offset increment. When the number and value of the frequency offset increment are fixed, adjusting the frequency offset increment added to each subarray can change the phase and magnitude of the sidelobe beam factor. This provides a basis for implementing the frequency offset increment equal probability switching beam sidelobe randomization technique.

[0030] Figure 5 In the middle, assuming , The carrier frequency is 60 GHz, and the frequency offset increment set is {-9 kHz, -8 kHz, -7 kHz, -6 kHz, -5 kHz, -4 kHz, -3 kHz, -2 kHz, -1 kHz, 0, 1 kHz, 2 kHz, 3 kHz, 4 kHz, 5 kHz, 6 kHz, 7 kHz, 8 kHz, 9 kHz}. The frequency offset increment corresponding to each transmitted symbol is selected using an equal-probability selection method, resulting in... Figure 5 (a) A schematic diagram of the target user constellation and Figure 5 (b) Figure 5 (c) Figure 5 (d) A constellation diagram showing the location of the sidelobe eavesdropping. Figure 5This indicates that each random adjustment of the frequency offset increment to the subarray position yields a clear constellation diagram for the target user, demonstrating that the target user's received signal is unaffected by frequency modulation. However, at the sidelobe positions, the received constellation diagram is chaotic, indicating that sidelobe leakage signals have become artificial noise.

[0031] exist Figure 4 In this process, the randomization of sidelobes in a fixed-area beamforming is achieved by M M-to-1 switches and a frequency-equal-probability switching controller. M low-frequency oscillators output M frequencies respectively... , , and The low-frequency offset increment, after being switched with equal probability by M M-to-1 switches, is sent to M N-channel frequency multipliers. The frequency equal-probability switching controller outputs a control vector to control the numbering of the signals connected to the M-to-1 switches. , , .when At that time, it represents the first The M-selector switch selects the first... The path signal is used as input.

[0032] No. The frequency selection model for the output signal of an M-to-1 switch is as follows: (9) because Let there be M non-independent but identically distributed random variables. It also contains the sum of M non-independent but identically distributed random variables. The probability distribution model is as follows: (10) The mathematical expectation is: (11) in, The frequency offset increment is The corresponding sub-beam array factor. For any , The probability distribution is as follows: (12) The mathematical expectation is: (13) therefore, and It is a non-independent but identically distributed random variable.

[0033] Beamforming factor The mathematical expectation is: (14) Beamforming factor variance ,and (15) (16) Beamforming factor The variance is expressed as: (17) Assume the transmitted signal is ,and The transmission power is The receiving end adopts a single With one antenna, any angle and distance The received signal is represented as follows: (18) The mean is 0 and the variance is Gaussian white noise, Path loss coefficient. Then the artificial noise power of the sidelobe randomization parameter is: (19) The signal-to-interference-plus-noise ratio at the sidelobe position is: (20) The signal-to-noise ratio for the target user is: (twenty one) System safe speed: , (twenty two) express hour, Assuming The safe rate can be expressed as: Assumption , , =500, The simulation results of the safe speed are shown in the figure. Figure 6 As shown, besides the target user location Except for the safe rate dropping to zero, the other sidelobe positions all maintain a high safe rate.

[0034] Algorithm explanation for each line of Algorithm 1: Line 1: Initialize antenna array parameters Line 2: Controls the number of transmitted symbols. Line 3: Randomly shuffle the sequence of numbers 1: M using the randperm function. Line 4: Controls the switch to toggle and outputs the frequency offset vector of this symbol transmission. Line 5: Array multi-frequency control, synthesizing directional beams and randomizing sidelobes. Line 6: A symbolic message is generated. Line 7: Determine if all symbols have been sent. If not, start the next loop from line 2.

[0035] (3) Frequency offset increment optimization of unknown eavesdropping location information Depending on whether the eavesdropping location is known, the appropriate optimization algorithm is selected to adjust the frequency offset increment of each subarray to reduce sidelobe signal leakage. If there are potential eavesdroppers with unknown locations, the frequency offset increment of each subarray can be optimized. This minimizes the peak value of sidelobe leakage, expressed as: , (twenty three) in, Indicates the position of the beam's sidelobes. , For the maximum frequency offset increment, This is the local beamforming array factor.

[0036] Synthetic beamforming array factor Location information With spectral offset increment vector And change. Solve. The process is very complex and difficult to solve directly. The Seeker Optimization Algorithm (SOA) is used to achieve an approximate optimal solution for the frequency offset increment vector that minimizes the maximum beam sidelobe peak value, as shown in Algorithm 2.

[0037] It is the particle position matrix, representing A potential frequency offset increment vector solution that satisfies equation (9). represent The search direction for a potential frequency offset increment vector solution. This represents the step size of the change in the incremental vector solution of each potential frequency offset. represent The individual position of the optimal frequency offset increment vector The optimal global position corresponds to the optimal frequency offset increment vector obtained during the search. The first line of the algorithm is about the parameters. , , , and Perform initialization. Line 4 is to gradually improve the search accuracy as the number of iterations increases, controlling the calculated weight value to decrease from 0.9 to 0.1.

[0038] The search space of SOA can be viewed as a gradient domain. By evaluating the searcher's own position, neighboring searchers' own positions, or historical positional changes, empirical gradients are used to guide the searcher's search direction. Line 5 of the algorithm is used to calculate the... The empirical gradient of each searcher is expressed as: , (twenty four) In equation (24), and A random number that is uniformly distributed between 0 and 1. This is a sign function, returning a result of -1, 0, or 1. The searcher uses three empirical gradients—preemptive behavior, self-interested behavior, and altruistic behavior—to evaluate its current or historical position, as well as the positions of its neighbors. Preemptive direction This means that searchers can preemptively change their search direction and predict and guide future behavior based on past actions, thus possessing a global guidance function. Self-interest direction. This indicates that searchers can use cognitive learning to reach their historical best position. Altruistic direction. This indicates that the searchers, through social learning and careful collaboration, have reached the globally optimal position together.

[0039] Line 6 is used to calculate the search. Searcher step size , is represented as: (25) and These refer to the location of the last searcher and from... A randomly selected location. It is a random number. This represents the input for fuzzy inference modeling, using the fuzzy rule "if the fitness value is small, then the step size is short", expressed as follows: (26) Represents the result after sorting by fitness value The The value of the searcher. and These represent the maximum and minimum member degrees of freedom, respectively. Lines 7-10 update the searcher's position. Lines 11-16 update the searcher's position. Update individual optimal position And the global free position g.

[0040] It is the fitness function of the value searcher, and it is the maximum sidelobe peak generated by the frequency offset increment vector.

[0041] Assuming the carrier frequency Transmission power Default noise power Default frequency offset increment limit , , Target angle Target distance . Figure 4 The diagram shows a comparison of the safe rates of fixed-area beamforming and traditional angle beamforming in scenarios with unknown location information. Figure 7 In (a), the SOA algorithm is used to find the optimized value of the frequency offset increment vector, and the resulting safe rate is obtained except at the target receiving position ( Outside of [location], it can maintain a very high value. At the target location ( On the other hand, the security rate drops to zero, at which point the eavesdropper and the target user completely overlap. Figure 7 (b) represents the safe rate corresponding to traditional angle beamforming, along... At different distances along the target angle, there exists a gap with a zero security rate. Therefore, local beamforming can eliminate the security problem of the traditional beam's main lobe being easily eavesdropped on.

[0042] (4) Optimization of frequency offset increment of known eavesdropping location information.

[0043] Assuming the location of the eavesdropper is known, the optimization objective of equation (23) can be simplified to finding an optimal frequency offset increment vector that minimizes the beam gain at the eavesdropping location. Furthermore, it can even create zero-gain sidelobes, resulting in a signal reception blind zone upstream of the known eavesdropping location. The optimization objective formula is: , (27) In equation (27), , subarray The beamforming coefficient.

[0044] Equation (27) contains a Frequency offset increment parameter at each position This is a non-convex and non-smooth parameter optimization problem, which is difficult to solve directly. We use the Block Coordinate Descent Linear Approximation (BCDLA) method to solve it.

[0045] Based on the fundamental principles of the BCD algorithm, assuming that in the... In this iteration, one element of the frequency offset increment vector in solving the optimal safe rate problem is obtained. Updated, expressed as follows (28) In equation (28), the definition is... It is a single variable block. Obviously, equation (28) is a typical convex optimization problem of a quadratic equation in one variable, and the optimal solution can be expressed as follows: (29) In equation (29), The representative function is in the interval The projection. and It is a function The minimum and maximum values.

[0046] Find After finding the optimal value, a linear approximation method is used to solve the problem. The value is obtained by solving the problem as follows: Figure 8 As shown.

[0047] like Figure 8 As shown, the horizontal axis represents frequency. The ordinate is a function .exist The constraints are arrive Between these points, the frequency values ​​corresponding to all positive and negative peaks are calculated. Then, based on the constraint of the optimized frequency offset increment, a suitable positive and negative peak frequency range is selected. The positive peak point is ( ). The negative peak point is ( Using these two peaks as the endpoints of the line, construct a linear equation to approximate the line. Function. Expressed as a formula: (30) According to the formula for linear approximation, the solution to equation (29) can be obtained as follows: (31) Figure 9The secure rate profile is obtained after optimizing the frequency offset increment of the fixed-area beamforming for known eavesdropping location information. The target receiving location is ( ). Figure 9 (a) The eavesdropper was in a confirmed situation. At various distances along the direction, the frequency offset increment parameter is optimized using the SOA algorithm to output the minimum beam sidelobes to the known eavesdropping location, resulting in a security rate that is close to the system's overall security rate. When the eavesdropping location approaches the target location, since zero sidelobes do not exist, only the sidelobes with the lowest gain can be output, leading to a decrease in the security rate. Figure 9 (b) The eavesdropper By eavesdropping at various known locations along the target's angle direction, one can also obtain and Figure 9 (a) Similar security rate.

[0048] Figure 10 The image compares the security rate performance of the BCDLA and SOA algorithms for optimizing the frequency offset increment parameters, with and without a known eavesdropping location. When the eavesdropping location is known, the frequency offset increment parameters can be optimized to transmit the lowest possible sidelobes, or even zero sidelobes, to that location. The security rate obtained after optimization using the BCDLA algorithm is close to the upper limit of the security rate. However, when the eavesdropping location is unknown, only the maximum peak value of the sidelobes can be minimized. Therefore, the security rate obtained after optimization using the SOA algorithm is generally lower than that obtained using the BCDLA algorithm.

[0049] Compared with the prior art, the fixed-area beamforming physical layer secure transmission method provided by the embodiments of the present invention has the following beneficial effects: 1. It eliminates the long-distance transmission trajectory of the main lobe in traditional beamforming technology, forming the main lobe of the beam only in a small area near the target receiving position, which greatly reduces the probability of eavesdroppers intercepting the signal.

[0050] 2. By implementing random switching control of sidelobes and combining it with a frequency offset incremental optimization algorithm, the risk of sidelobe signal leakage is further reduced, and the security performance of the physical layer is improved.

[0051] 3. Adaptive optimization algorithms are used for both known and unknown eavesdropping locations, taking into account the security needs of different application scenarios and making it highly applicable.

[0052] 4. The system architecture is compatible with traditional phased arrays, easy to implement in engineering, and can be directly applied to next-generation wireless communication systems such as 6G.

[0053] Furthermore, embodiments of the present invention also provide an electronic device, including a bus, a transceiver, a memory, a processor, and a computer program stored in the memory and executable on the processor. The transceiver, the memory, and the processor are respectively connected via the bus. When the computer program is executed by the processor, it implements the various processes of the above-described embodiment of a fixed-area beamforming physical layer secure transmission method and achieves the same technical effect. To avoid repetition, it will not be described again here.

[0054] Furthermore, this embodiment of the invention also provides a computer-readable storage medium storing a computer program thereon. When the computer program is executed by a processor, it implements the various processes of the above-described embodiment of a fixed-area beamforming physical layer secure transmission method and achieves the same technical effect. To avoid repetition, it will not be described again here.

[0055] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A fixed-area beamforming physical layer secure transmission system, characterized in that, include: The baseband modulation module is used to modulate private information using quadrature components and then load it to a frequency of [frequency value missing]. On the carrier wave; A frequency adjustment module is used to fine-tune the frequency of L branches of the phased array. The frequency adjustment module includes an M-channel low-frequency oscillator, M M-to-1 random selector switches, a frequency equal-probability switching controller, and M N-channel frequency multipliers. The low-frequency oscillator outputs M frequencies respectively... , , and The low-frequency offset increment, the frequency equal probability switching controller outputs a frequency switching control vector, controls M M-to-1 random switching switches to randomly distribute the low-frequency signal to the output channel, realizing sidelobe randomization control, and L=MN, where L, M, and N are all integers greater than 1; The phased array module consists of L uniform linear antennas, and the L antennas are divided into M multi-frequency phased subarrays. ,m∈ Each subarray contains N antennas; used to transmit M rotating sub-beams, achieving superposition of sub-beams in the target area and cancellation in the non-target area.

2. The fixed-area beamforming physical layer secure transmission system according to claim 1, characterized in that, No. Subarray The transmission frequency difference between adjacent branches within the branch is The subarray The resulting rotatable beam satisfies: The local beamforming array factor satisfies: in, For the first Subarrays The formed rotatable beam This represents the frequency offset increment of the m-th subarray. For carrier frequency, The azimuth of the eavesdropper. The distance between the eavesdropper and the center of the array. The angle of the target receiving position. Distance to the target receiving location ， The spacing between adjacent antennas in a phased array. Where M is the speed of light, M is the total number of subarrays, and N is the number of antennas in a single subarray.

3. A fixed-area beamforming physical layer secure transmission system according to claim 1, characterized in that, The M M-to-1 random switching switches of the frequency adjustment module satisfy the equal probability selection characteristic, and the probability distribution of the output frequency offset increment of the m-th M-to-1 random switching switch is as follows: , in for A non-independent but identically distributed random variable.

4. A method for secure transmission at the physical layer of a fixed-area beamforming system, characterized in that, Includes the following steps: Step S1: After the private information is orthogonally modulated by the baseband modulation module, it is loaded onto the carrier frequency. superior; Step S2: Generate M frequencies using the low-frequency oscillator of the frequency adjustment module, respectively. , , and The low-frequency offset increment, after being randomly allocated by M M-to-1 random switching switches controlled by a frequency equal-probability switching controller, is then fine-tuned by M N-channel frequency multipliers on the N branches of the M subarrays of the phased array, so that the first... Subarrays The frequency of the nth branch satisfies: ， in, n , For the first Frequency offset increment of each subarray Where N is the carrier frequency, and N is the number of antennas in a single subarray; Step S3: The rotating sub-beams are emitted through the M sub-arrays of the phased array module. The phase control factor is used to make the sub-beams superimpose in the target area to form the main lobe and cancel each other out in the non-target area to form the side lobes. Step S4: Sidelobe randomization is achieved by switching frequency offset increments with equal probability, converting the sidelobe leakage signal into artificial noise; Step S5: Depending on whether the eavesdropping location information is known, select the corresponding optimization algorithm to adjust the frequency offset increment of each subarray to reduce sidelobe signal leakage. When the eavesdropping location information is unknown, the crowd search algorithm is used to minimize the sidelobe leakage peak. When the eavesdropping location information is known, the block coordinate sinking linear approximation algorithm is used to minimize the beam gain of the eavesdropping location.

5. A method for secure transmission of physical layer beamforming in a fixed region according to claim 4, characterized in that, In step S5, when the eavesdropping location information is unknown, a crowd search algorithm is used to optimize the frequency offset increment. The optimization objective is to minimize the sidelobe leakage peak value, and the optimization objective formula is: , in, Indicates the position of the sidelobes of the beam. , For the largest frequency offset increment, This is the local beamforming array factor.

6. A method for secure transmission of physical layer beamforming in a fixed region according to claim 4, characterized in that, In step S5, when the eavesdropping location information is known, the frequency offset increment is optimized using a block coordinate sinking linear approximation algorithm. The optimization objective is to minimize the beam gain at the eavesdropping location, and the optimization objective formula is: ， ， in, , subarray Beamforming coefficient, For angle-dependent phase coefficients, For distance-related phase coefficients, This represents the total angular phase coefficient of the subarray. This represents the total phase coefficient of the subarray distance. is the beamforming coefficient of the m-th subarray.

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