Urban private communication physical layer safety performance evaluation method based on ray tracing

Abstract

The invention discloses an urban environment private communication physical layer safety performance evaluation method based on ray tracing, which mainly solves the problem of inaccurate physical layer communication safety performance evaluation in the prior art, and the implementation scheme is as follows: extracting geometric features and electromagnetic material features of urban buildings; setting geographic information and electromagnetic information of a signal sender, a signal receiver and a signal eavesdropper; according to the building geometric feature and electromagnetic material feature data set and geographic information and electromagnetic information of a signal sender, a signal receiver and a signal eavesdropper, simulating and calculating a received power predicted value and a small-scale fading feature of each point of the receiver and the eavesdropper; simulation calculation is carried out on secrecy performance of the whole area under the scenes that noise is limited and noise and interference are considered on the basis of receiving power and small-scale fading characteristics, and the secrecy outage probability is obtained. The method can accurately predict the security performance of the physical layer of the private communication scene of the actual city environment under the condition that the channel state information of the eavesdropper is unknown, and can be used for optimizing the secrecy performance of the private communication of the city.

Description

Technical Field

[0001] The present invention belongs to the field of communication technology, and in particular relates to a method for evaluating the physical layer security performance of urban private communications, which can be used for evaluating and optimizing the confidentiality performance of urban private communications. Background Art

[0002] With the rapid adoption of wireless communication technology in modern life, unprecedented amounts of private information are transmitted in wireless media. Due to the unchangeable openness of wireless channels, communication security has become a critical issue. In order to protect wireless communications by exploiting the characteristics of wireless channels, physical layer security has been widely studied as a complement to traditional cryptographic techniques. Scholar Wyner introduced the eavesdropping channel system as a framework for physical layer security in his pioneering work and defined the confidentiality capacity as the maximum rate at which a message can be reliably sent to the intended recipient without being eavesdropped. Later, scholars Csiszár and This result was extended to broadcast channels with confidential messages. In recent years, many scholars have conducted extensive analysis on the physical layer security of various communication scenarios. However, due to idealized and unrealistic assumptions, most research in this field is theory-oriented. For example, many existing articles assume that the transmitter has perfect channel state information CSI to the intended receiver and eavesdropper. In practical applications, external eavesdroppers will naturally not cooperate with the transmitter to send CSI feedback, so it is difficult for the transmitter to obtain the eavesdropper's CSI. For example, many existing articles do not consider the actual real environment and radio wave propagation effects, equate path loss with the power of distance, and even do not consider shadow fading, resulting in the inability of existing theoretical analysis to be applied in practice.

[0003] The patent document with application number CN201811075144.8 discloses a physical layer security optimization method based on heterogeneous wireless transmission mode scheduling, which divides information transmission into three steps: data aggregation, transmission mode scheduling and data forwarding. According to whether the instantaneous eavesdropping channel state information can be obtained and the estimated probability of successful eavesdropping by the eavesdropper is evaluated, the corresponding transmission mode is adaptively designed to achieve the purpose of countering eavesdropping behavior and improving the confidentiality of information transmission. Since this method focuses on the scheduling planning of the network layer, that is, how to make corresponding response strategies after the channel state information of the eavesdropper is known, it is impossible to simulate and analyze the confidentiality of the current communication scenario when the channel state information of the eavesdropper is unknown. In addition, since the eavesdropper is unlikely to actively send the channel state information of the received signal to the private transmission party in actual private communication, this method is difficult to apply to the confrontation with eavesdroppers in actual urban environments.

[0004] Patent document with application number CN201310244665.2 discloses a method for predicting indoor three-dimensional wireless signals based on a ray tracing propagation model, which calculates the electromagnetic propagation characteristics of indoor signals by modeling the building hierarchically and solving the corresponding mapping relationship of antennas on each floor, and reduces the computational complexity based on the wireless propagation loss parameter database of building materials to achieve simplified calculation of indoor three-dimensional wireless signal ray tracing. Since this method focuses on the research of the electromagnetic calculation algorithm itself, and does not consider the security requirements and practical application value of private communications in actual urban environments, this method cannot directly provide assistance for the analysis of the confidentiality and security performance of actual communications. Summary of the invention

[0005] The purpose of the present invention is to address the deficiencies of the above-mentioned prior art and propose a method for evaluating the physical layer security performance of urban private communications based on ray tracing, so as to achieve accurate coverage prediction of the physical layer security performance of private communication scenarios in actual urban environments when the eavesdropper's channel state information is unknown.

[0006] The key technology of the present invention is to predict the received power of the locations where eavesdroppers may appear in the entire area based on the existing environmental modeling and electromagnetic modeling data, and then substitute it into the physical layer security calculation formula to obtain the confidentiality performance evaluation result of the specified area. The implementation steps include the following:

[0007] (1) Obtain building vector data and material electromagnetic medium parameters of a specified urban scene;

[0008] (2) Set the location information and electromagnetic information of the information sender, receiver and eavesdropper according to actual needs;

[0009] (3) According to the acquired modeling data and the set parameter information, the received power prediction result of each receiving point is obtained based on ray tracing simulation, and the small-scale fading characteristic parameters m and ω are fitted:

[0010] (3a) Setting up three configuration files with different formats and storing the geographic information and electromagnetic information required for simulation analysis;

[0011] (3b) Analyze all ray paths of the signal from the transmitter Tx to the receiver Rx;

[0012] (3c) Calculate the total electric field at each receiving point based on the ray path obtained by step (3b)

[0013] (3d) Convert the total electric field calculated in step (3c) into the received power P at each receiving point r and output it according to the format of the third configuration file;

[0014] (3e) Generate a small-scale fading simulation point set, simulate and obtain the received signal amplitude of each point, and fit the small-scale fading characteristic parameters m and ω;

[0015] (4) Substitute the received power P of each point obtained in step (3) r The small-scale fading characteristic parameters m and ω are substituted into the confidentiality interruption probability calculation formula of various communication scenarios to obtain the corresponding confidentiality performance prediction results.

[0016] (4a) The received power P at each point r Substitute the small-scale fading characteristic parameters m and ω into the confidentiality interruption probability calculation formula of the noise-limited communication scenario to calculate the confidentiality interruption probability P out1 ;

[0017] (4b) The formula for calculating the probability of confidentiality interruption in a general communication scenario with interference and noise is derived, where the received power P at each point is r Substitute the small-scale fading characteristic parameters m and ω into the formula to calculate the confidentiality interruption probability P out2 .

[0018] Compared with the prior art, the present invention has the following advantages:

[0019] Firstly, since the present invention obtains relatively accurate urban scene building vector data and material electromagnetic medium parameters, the received power calculated by the present invention is more accurate than that of the prior art.

[0020] Secondly, since the present invention adopts ray tracing simulation instead of actual measurement to obtain the received power, the cost of obtaining small-scale fading characteristic parameters of the present invention is lower than that of the prior art.

[0021] Thirdly, since the present invention calculates the confidentiality interruption probability by using the accurate receiving power obtained by ray tracing simulation, the confidentiality interruption probability calculated by the present invention is more accurate than the analysis result of the prior art which does not consider the actual environment.

[0022] Fourthly, since the present invention derives a calculation expression for the probability of confidentiality interruption in a general situation with interference and noise signals, it has a wider scope of application than the prior art. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a flow chart of the implementation of the present invention;

[0024] Figure 2 is a schematic diagram of an interface for obtaining building vector data in an embodiment of the present invention;

[0025] Figure 3 is a schematic diagram of building data results extracted in an embodiment of the present invention;

[0026] Figure 4 is a schematic diagram of the mirror image method used in an embodiment of the present invention;

[0027] Figure 5 is a ray tracing power coverage prediction result diagram in an embodiment of the present invention;

[0028] Figure 6 This is the received power result diagram of different frequency points obtained by actual measurement;

[0029] Figure 7 is a comparison result diagram of the received power obtained by simulation of the present invention and the actual measured value of the received power;

[0030] Figure 8 It is a diagram of the signal amplitude simulation and probability distribution fitting results under line-of-sight conditions of the present invention.

[0031] Fig. 9 It is a diagram of the signal amplitude simulation and probability distribution fitting results in the non-line-of-sight situation of the present invention;

[0032] Fig.10 This is a simulation result diagram of the confidentiality interruption probability assessment of the present invention in a Gaussian white noise restricted scenario.

[0033] Fig.11 This is a simulation result diagram of the confidentiality interruption probability assessment in a scenario where Gaussian white noise and interference signals coexist. DETAILED DESCRIPTION

[0034] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with embodiments.

[0035] This embodiment is aimed at establishing a scheme for physical layer security performance evaluation in an actual urban environment. It mainly sets the location information and electromagnetic information of the information sender, receiver and eavesdropper according to actual needs, calls the ray tracing algorithm through the acquired building vector data and material electromagnetic medium parameter data of the specified urban scene, and thus calculates the average receiving power of the receiving point set in the specified area, and then obtains the small-scale parameter characteristics of Nakagmi-m through ray tracing simulation fitting by means of small-area fine point set segmentation, constructs a receiving power probability distribution model, divides the communication scene into two parts according to the presence or absence of interference signals, and derives their confidentiality performance expressions respectively. Finally, the precise physical layer security performance index of the specified area is calculated based on the simulated receiving power data set and small-scale fading parameter data set.

[0036] Reference Figure 1 , the implementation steps of this embodiment include the following:

[0037] Step 1: Obtain building vector data and material electromagnetic medium parameters of a specified urban scene.

[0038] 1.1) Get building vector data:

[0039] Methods for obtaining building vector data include obtaining it from the open source map editing website OpenStreetMap, obtaining it from the map data platform Google Earth, and modeling based on laser point cloud scanning. This step uses but is not limited to obtaining it from the OpenStreetMap website. The OpenStreetMap, referred to as OSM, is an online map collaboration project. Its goal is to create a world map with free content that can be edited by everyone. OSM data is open source and can be freely downloaded and used. On OpenStreetMap, you can freely select locations of interest based on satellite maps to delineate points to form lines and polygons, and you can export the longitude and latitude coordinates of each point. Its specific interface is as follows: Figure 2 As shown. With the building attributes marked on the map, the longitude and latitude coordinates of the buildings in the specified area can be derived, and the final building projection can be obtained after processing. Figure 3 shown.

[0040] 1.2) Obtain material electromagnetic medium parameters:

[0041] Methods for obtaining electromagnetic dielectric parameters of materials include searching from ITU recommendations, actual measurements, etc. This step uses but is not limited to obtaining from ITU recommendations. ITU recommendations are a series of models and parameter databases developed and published by the International Telecommunication Union for the field of electronic information, covering almost all currently existing communication technologies including electromagnetic wave propagation and signal processing. By consulting ITU recommendations, one can quickly retrieve the magnetic permeability and dielectric constant of common materials in urban environments, such as building bricks and street trees.

[0042] Step 2: Set the location information and electromagnetic information of the information sender, receiver and eavesdropper according to actual needs.

[0043] The electromagnetic information includes antenna gain, signal wavelength, initial transmission power, initial transmission electric field, number of antennas and antenna pattern;

[0044] The geographical location refers to the latitude and longitude or relative coordinates of the current location of the transmitting source, the receiving party, or the eavesdropper.

[0045] The location information and electromagnetic information provided in this step include:

[0046] Set the geographical location of the transmitting source and the transmitting antenna gain G t , emission signal wavelength λ, initial power P t and the initial electric field E0, the number of transmitting antennas and the transmitting antenna pattern;

[0047] Set the receiving party’s geographical location and receiving antenna gain G r, the number of receiving antennas and the receiving antenna pattern;

[0048] Set the possible geographical location of the eavesdropper and the eavesdropping antenna gain G e , the number of eavesdropping antennas and the radiation pattern of eavesdropping antennas.

[0049] Step 3: According to the acquired modeling data and the set parameter information, the received power prediction result of each receiving point is obtained based on ray tracing simulation, and the small-scale fading characteristic parameters m and ω are fitted.

[0050] 3.1) Set up three configuration files with different formats and store the geographic information and electromagnetic information required for simulation analysis:

[0051] Set three configuration files with different formats, where the format of the first configuration file is "variable name + value", the format of the second configuration file is "longitude + latitude + altitude" or "relative coordinate X + relative coordinate Y + relative coordinate Z", and the format of the third configuration file is "longitude + latitude + altitude + received power" or "relative coordinate X + relative coordinate Y + relative coordinate Z + received power";

[0052] Set the ray limit number N+M+L, reflection weight N, diffraction weight M, and transmission weight L of the ray tracing algorithm, and write them together with the electromagnetic information set in step 2 into the first configuration file, and then write the position information set in step 2 into the second configuration file;

[0053] 3.2) Treat each building in the building vector data obtained in step 1 as a polygonal cylinder, store the coordinates and vertical height of each point on the horizontal plane polygon of each building, and combine the receiving point location information provided by the second configuration file to solve the direct, reflected, and diffraction paths in the process of starting from the transmitting point Tx and reaching each receiving point Rx:

[0054] 3.2.1) Direct ray path solution:

[0055] First, the line connecting the transmitting source Tx and the receiving point Rx is judged to be blocked by buildings:

[0056] If there is no obstruction, Tx and Rx meet the line-of-sight condition, and the line connecting Tx and Rx is the direct path.

[0057] If there is an obstruction, Tx and Rx meet the non-line-of-sight condition, and there is no direct path. The building plane that obstructs the line connecting Tx and Rx is screened out, and the reflection path of 3.2.2) and the diffraction path of 3.2.3) are solved;

[0058] 3.2.2) Solution of reflected ray path:

[0059] like Figure 4As shown in (a), the reflected ray path is solved by the following steps:

[0060] Summarize the planes of buildings that block the rays into a mirror plane set W, first determine the first-order mirror point Tx1 of Tx relative to its nearest mirror plane W1, then determine the second-order mirror point Tx2 of the first-order mirror point Tx1 relative to its nearest mirror plane W2, connect the emission source Tx with the first-order mirror point Tx1, and the intersection of the straight line and plane W1 is the first-order reflection point P1;

[0061] Connect the second-order mirror point Tx2 with the receiving point Rx, and the intersection of the straight line and plane W2 is the second-order reflection point P2;

[0062] By analogy, we get multiple-order reflection points Pn. Connect Tx, each-order reflection point Pn and Rx, and the resulting line is the reflection ray path.

[0063] 3.2.3) Diffraction ray path solution:

[0064] like Figure 4 As shown in (b), the transmitting source Tx is rotated around the vertical edge of the shielding plane W to form a hollow circle, and then the real position of the first-order diffraction point D is found on the vertical edge, so that the line connecting the receiving point Rx and D intersects with the boundary of the hollow circle. In this way, multiple-order diffraction points are obtained, and the transmitting source Tx, each order diffraction point and the receiving point Rx are connected. The obtained connecting line is the diffraction ray path;

[0065] 3.3) Analyze the following parameters required for electromagnetic calculations from the ray path obtained in step 3.2):

[0066] Record the total number of reflections n and diffractions m that occur when the ray travels from Tx to Rx;

[0067] Based on the elevation angle θ of the ray path relative to the transmitting antenna t and roll angle Extract the normalized directivity factor of the transmitting antenna

[0068] Based on the elevation angle θ of the ray path relative to the receiving antenna r and roll angle Extract the normalized directivity factor of the receiving antenna

[0069] 3.4) Calculate the dyadic reflection coefficient at the hth reflection according to the electromagnetic medium parameters of the material obtained in step (1) The calculation formula is as follows:

[0070]

[0071] in, They represent the unit vectors of the incident ray and the reflected ray in the ray basis coordinates under parallel polarization, They represent the unit vectors of the incident ray and the reflected ray in the ray basis coordinates under vertical polarization, represents the parallel polarization reflection coefficient, represents the vertical polarization reflection coefficient, represents the intrinsic impedance of the ith medium, μ i represents the magnetic permeability of the ith medium, ε i Represents the dielectric constant of the i-th medium, i=1,2.

[0072] 3.5) Calculate the dyadic diffraction coefficient at the jth diffraction according to the electromagnetic medium parameters of the material obtained in step (1)

[0073] Calculate the parallel polarization reflection coefficient D || :

[0074]

[0075] Calculate the vertical polarization reflection coefficient D ⊥ :

[0076]

[0077] Where n = θ e / π,θ e represents the outer angle of the diffraction wedge, k represents the wave number, β0 is the angle between the incident ray and the diffraction edge, represents the angle of incidence, represents the diffraction angle; F(·), a ± (·) represents two different transition functions, and their expressions are:

[0078]

[0079]

[0080] Where N ± is the smallest integer that satisfies the following equation:

[0081] L is the distance parameter, which is related to the type of wave and is shown as follows:

[0082]

[0083] According to the parallel polarization reflection coefficient D || and the vertical polarization reflection coefficient D ⊥ Calculate the dyadic diffraction coefficient

[0084]

[0085] in, They represent the unit vectors of the incident ray and the diffracted ray in the ray basis coordinates under parallel polarization, They represent the unit vectors of the incident ray and the diffracted ray in the ray basis coordinates under vertical polarization respectively.

[0086] 3.6) Calculate the diffusion factor A of the reflected field s1 and the diffusion factor A of the diffraction field s2 :

[0087]

[0088] Where r1 represents the distance from the incident point to the reflection point, and r2 represents the distance from the reflection point to the exit point;

[0089] s1 represents the distance from the incident point to the diffraction point, and s2 represents the distance from the diffraction point to the exit point.

[0090] 3.7) Calculate the electric field when the signal reaches the receiving antenna through the i-th ray

[0091] 3.7.1) Starting the electric field according to the transmission signal Calculate the radiation field from the emission point to the first node

[0092]

[0093] Where k is the wave number, r0 is the distance from the launch point to the first node, represents the normalized directivity coefficient of the transmitting antenna;

[0094] 3.7.2) According to the radiation field Calculate the electric field of the i-th ray path reaching the receiving antenna

[0095] If the ray path is a line-of-sight path, the first node is the receiving point, and the normalized directivity coefficient of the receiving antenna is The electric field of the i-th ray path reaching the receiving antenna is calculated as:

[0096]

[0097] If the ray path is a non-line-of-sight path, the electric field when the i-th ray path reaches the receiving point is:

[0098]

[0099] Where n is the total number of reflections, m is the total number of diffractions, and A sis the diffusion factor after reflection and diffraction, r q is the distance from the qth ray node to the q+1th node.

[0100] 3.8) The received electric field of each ray path The total electric field at the receiving point is obtained by superimposing the vectors

[0101]

[0102] Where I represents the total number of ray paths generated by the signal propagating from the transmitting point Tx to the receiving point Rx;

[0103] 3.9) The total electric field calculated in step 3.8) is Converted into the receiving power P of each receiving point r :

[0104]

[0105] Where P t is the antenna radiation power, G t and G r are the gains of the transmitting antenna and the receiving antenna respectively, and λ is the operating wavelength of the transmitting antenna;

[0106] 3.10) Generate a small-scale fading simulation point set, simulate the received signal amplitude of each point, and fit the small-scale fading characteristic parameters m and ω:

[0107] In order to analyze the signal attenuation in actual scenarios, the present invention defines a square with the position of each eavesdropper as the center for line-of-sight and non-line-of-sight scenarios, takes 10 times the wavelength of the transmitted signal as the side length of the square, divides 5000 points in the square at equal intervals as simulation points, and writes the position information of these points into the second configuration file;

[0108] Execute steps 3.3) to 3.9) again to simulate the received signal amplitude α of each simulation point at 2.4 GHz. Assuming that the received signal amplitude α conforms to the Nakagmi-m distribution, the Nakagmi-m distribution closest to the simulation data is obtained by least squares fitting. The shape parameter m and scale parameter ω are obtained from the distribution. The expression of the Nakagami-m distribution is as follows:

[0109]

[0110] Step 4: Substitute the received power P of each point obtained in step (3) r The small-scale fading characteristic parameters m and ω are substituted into the confidentiality interruption probability calculation formula of various communication scenarios to obtain the corresponding confidentiality performance prediction results.

[0111] 4.1) According to the received power P at each point r and small-scale fading characteristic parameters m and ω to calculate the confidentiality outage probability P out1 :

[0112] 4.1.1) Calculate the probability density of the signal-to-noise ratio of the receiving signal of the receiver Bob and the eavesdropper Eve and

[0113] Construct a A Alice, N, the transmitting end with antennas B The legal receiving end Bob and N antennas E The MIMO eavesdropping channel model consists of an eavesdropping end Eve with 1 antenna, and it is assumed that both the main channel Alice-Bob and the eavesdropping channel Alice-Eve experience quasi-static Nakagami-m fading with a fading parameter of m. When only Gaussian white noise is considered, the signal y received by the legitimate receiver B and the signal y received from the illegal eavesdropper Eve E Respectively expressed as:

[0114]

[0115] Where P0 represents the initial power of the message signal, Represents an information symbol with unit power, P0 is the transmission power, is the channel matrix from the transmitter Alice to the legitimate receiver Bob, represents Gaussian white noise with average power N0, is the channel matrix from the transmitter Alice to the legitimate receiver Bob, represents Gaussian white noise with average power N0;

[0116] Assume that the channels between different antennas are uncorrelated, and both the legitimate receiving end Bob and the eavesdropping end Eve use the maximum ratio combining technique to transmit the L AB =N A ×N B and L AE =N A ×N E The signal-to-noise ratio of the legitimate receiving end Bob is γ B and the signal-to-noise ratio γ of the eavesdropping end Eve E Respectively expressed as:

[0117]

[0118] in, and are the total signal power received by Bob and Eve respectively, and are the signal powers received by Bob and Eve on a diversity path respectively, and All satisfy the Gamma distribution;

[0119] Based on gamma B and γ E According to the probability density transformation formula of the composite variable, we can get γ B The probability density and γ E The probability density of is:

[0120]

[0121] Where m is the shape parameter obtained by step 3, ω B =P AB / N0 indicates the average power P of the message signal received by the legitimate receiving end Bob AB Ratio of the noise power N0,ω E =P AE / N0 represents the average power P of the message signal received by the eavesdropping end Eve AE The ratio of the noise power N0;

[0122] 4.1.2) Derived from step 4.1.1) and Calculate the probability of confidentiality interruption P out1 :

[0123]

[0124] 4.2) According to the received power P r The probability of confidentiality interruption P in the communication scenario with interference and noise is derived from the small-scale fading characteristic parameters m and ω out2 :

[0125] 4.2.1) Calculate the probability density of the signal-to-interference-to-noise ratio of the receiving signal of the receiver Bob and the eavesdropper Eve and

[0126]

[0127] First, for the eavesdropping channel model where other signals interfere with Bob and Eve, the signal y received by the legitimate receiver is B and the signal y received from the illegal eavesdropper Eve E Respectively expressed as:

[0128]

[0129] Among them, P I represents the initial power of the interference signal, and are the channel matrices between the interference signal source and Bob and Eve respectively;

[0130] Next, based on y B and E The expression of Bob’s signal-to-interference-noise ratio λ is derived B and Eve’s signal-to-interference-to-noise ratio λ E :

[0131]

[0132] Where, L IB =N I ×N B represents the diversity path from the interference signal to the legitimate receiver Bob, L IE =N I ×N E represents the diversity path from the interference signal to the eavesdropping end Eve, and Represent the total power of interference signal received at Bob and Eve respectively, and are the signal powers received by the interference signal source on a certain diversity path of Bob and Eve respectively;

[0133] Then, based on λ B and λ E The expression of λ is B The probability density of and λ E The probability density of

[0134] In the formula, ω IB =P IB / N0 indicates the average power P of the interference signal received by the legitimate receiving end Bob IB Ratio of the noise power N0,ω IE =P IE / N0 represents the average power P of the interference signal received by the eavesdropping end Eve IE Ratio to noise power N0, ω AB =P AB / N0 indicates the average power P of the message signal received by the legitimate receiving end Bob AB Ratio of the noise power N0,ω AE =P AE / N0 represents the average power P of the message signal received by the eavesdropping end Eve AE The ratio of the noise power N0;

[0135] 4.2.2) Derived from step 4.2.1) and Expression, calculate the probability of confidentiality interruption P out2 :

[0136]

[0137] Among them, C1, C2, C3, and C4 represent four different transition functions, and the calculation formulas are as follows:

[0138]

[0139] In the formula, R th Indicates the confidentiality interruption threshold. represents a binary MeijerG series;

[0140] 4.2.3) Set the confidentiality interruption threshold R p , the received power P of each point obtained according to step (3) r and the small-scale fading characteristic parameter m to calculate the confidentiality interruption probability P out2 , evaluate the security performance of the physical layer:

[0141] When the probability of confidentiality interruption P out2 Greater than R p When the number of messages leaks out, the probability of the message being leaked is high, and the sending of private information should be reduced or terminated at this time;

[0142] When the probability of confidentiality interruption P out2 Less than or equal to R p , the probability of information leakage is low, and normal private information communication can be carried out at this time. At this point, the security performance evaluation of the physical layer of urban private communications is completed.

[0143] The effect of the present invention can be further illustrated by the following simulation experiment:

[0144] 1. Simulation conditions

[0145] According to step one, the building vector data of Xidian University and the electromagnetic medium parameters of common materials are obtained, and according to step two, the location information and electromagnetic information of the information sender, receiver and eavesdropper are set.

[0146] 2. Simulation content

[0147] Simulation 1: Under the above simulation conditions, the coverage prediction simulation of the received signal power in the specified area is performed using steps 3.3) to 3.9) of the present invention. The results are as follows: Figure 5As shown, the horizontal and vertical axes represent the two-dimensional projection under the relative coordinate system, the unit is m, the gray-brown polygon represents the buildings in the area, the color represents the strength of the received power at the point, the yellow is the strongest and the blue is the weakest, the unit is dBm, the simulation data shows that the calculation method proposed in the present invention can take into account the direct radiation, reflection, and diffraction effects that occur in the process of electromagnetic wave propagation;

[0148] Simulation 2, measured the received power of continuous waves at 2GHz and 4GHz respectively, the results are as follows Figure 6 As shown, Figure 6 (a) shows the measured result at 2 GHz. Figure 6 (b) represents the measured result at 4 GHz. Under the above simulation conditions, the simulated values ​​of received power at 2 GHz and 4 GHz obtained by simulation in steps 3.3) to 3.9) of the present invention are compared with the measured data. The results are as follows: Figure 7 As shown, Figure 7 (a) is the comparison between the simulation value and the measured value of the continuous wave at 2GHz receiving power. Figure 7 (b) is the comparison result between the simulation value and the measured value of the continuous wave at 4GHz receiving power. Figure 7 The comparison results show that the root mean square error of the present invention is no more than 6.5dB, which has higher accuracy.

[0149] Simulation 3, under the above simulation conditions, the amplitude fluctuation of the received signal at each line-of-sight receiving point at 2.4 GHz frequency is simulated by using step 3.10) of the present invention. The results are as follows: Figure 8 As shown in (a), the small-scale fading characteristics under line-of-sight are fitted based on the amplitude fluctuation of the received signal and compared with the theoretical model. The results are shown in Figure 8 As shown in (b), Figure 8 It can be seen from the comparison results that the line-of-sight small-scale fading feature fitting method proposed in the present invention is consistent with the theoretical model.

[0150] Simulation 4: Under the above simulation conditions, the amplitude fluctuation of the received signal at each non-line-of-sight receiving point at 2.4 GHz frequency is simulated using step 3.10) of the present invention. The results are as follows: Fig. 9 As shown in (a), the small-scale fading characteristics under non-line-of-sight are fitted based on the amplitude fluctuation of the received signal, and compared with the theoretical model. The results are as follows Fig. 9 As shown in (b), Fig. 9 It can be seen from the comparison results that the non-line-of-sight small-scale fading feature fitting method proposed in the present invention is consistent with the theoretical model.

[0151] Simulation 5: Under the above simulation conditions, the confidentiality interruption probability P is calculated by simulation using step 4.1) of the present invention considering only the Gaussian white noise condition. out1 , the results are as follows Fig.10 As shown. Fig.10 (a) represents the number of antennas N of the transmitting source A Set to 1, the number of antennas at the receiver is N B Set to 1, the number of antennas of the eavesdropper is N E Set to 1 to keep the interruption threshold R confidential. th The prediction results of confidentiality outage probability when the value is set to 5 and the noise power N0 is set to -80dBm; Fig.10 (b) represents the number of antennas N of the transmitting source A Set to 1, the number of antennas at the receiver is N B Set to 1, the number of antennas of the eavesdropper is N E Set to 3, confidentiality interrupt threshold R th The prediction results of confidentiality outage probability when the value is set to 5 and the noise power N0 is set to -80dBm. Fig.10 The comparison results show that the increase in the number of antennas on the eavesdropping party will significantly increase the probability of confidentiality interruption.

[0152] Simulation 6: Under the above simulation conditions, the confidentiality interruption probability P of a general scenario considering Gaussian white noise and interference is obtained by simulation calculation using step 4.2) of the present invention. out2 , the results are as follows Fig.11 As shown. Among them:

[0153] Fig.11 (a) represents the number of antennas N of the transmitting source A Set to 3, the number of antennas at the receiver is N B Set to 3, the number of antennas of the eavesdropper is N E Set to 3, confidentiality interrupt threshold R th When the power of the interference signal is 0.1 times of the transmission signal power, the probability of confidentiality interruption in the specified area is 1, the noise power N0 is -80dBm, and the interference signal power is 0.1 times of the transmission signal power;

[0154] Fig.11 (b) represents the number of antennas N of the transmitting source A Set to 3, the number of antennas at the receiver is N B Set to 3, the number of antennas of the eavesdropper is N E Set to 3, confidentiality interrupt threshold R th The probability of confidentiality interruption in the specified area when the value is 1, the noise power N0 is -80dBm, and the interference signal power is 0.5 times the transmission signal power.

[0155] from Fig.11 The comparison results show that when the interference signal to the legitimate receiving end is greater than the interference to the eavesdropper, the probability of confidentiality interruption will increase significantly.

[0156] The above description is only a specific example of the present invention and does not constitute any limitation to the present invention. It is obvious that for professionals in this field, after understanding the content and principles of the present invention, they may make various modifications and changes in form and details without departing from the principles and structures of the present invention. However, these modifications and changes based on the ideas of the present invention are still within the scope of protection of the claims of the present invention.

[0157] It should be noted that the step numbers in the specification and claims of the present invention are only for a clear description of the implementation scheme of the present invention to facilitate understanding, and the order of the step numbers is not limited.

Claims

1. A method for evaluating the physical layer security performance of urban private communications based on ray tracing, characterized in that: These include: (1) Obtain building vector data and material electromagnetic medium parameters of a specified urban scene; (2) Set the location information and electromagnetic information of the information sender, receiver and eavesdropper according to actual needs; (3) According to the acquired modeling data and the set parameter information, the received power prediction result of each receiving point is obtained based on ray tracing simulation, and the small-scale fading characteristic parameters m and ω are fitted: (3a) Setting up three configuration files with different formats and storing the geographic information and electromagnetic information required for simulation analysis; (3b) Analyze all ray paths of the signal from the transmitter Tx to the receiver Rx; (3c) Calculate the total electric field at each receiving point based on the ray path obtained by step (3b) (3d) Convert the total electric field calculated in step (3c) into the received power P at each receiving point r and output it according to the format of the third configuration file; (3e) Generate a small-scale fading simulation point set, simulate and obtain the received signal amplitude of each point, and fit the small-scale fading characteristic parameters m and ω; (4) Substitute the received power P of each point obtained in step (3) r The small-scale fading characteristic parameters m and ω are substituted into the confidentiality interruption probability calculation formula of various communication scenarios to obtain the corresponding confidentiality performance prediction results. (4a) The received power P at each point r Substitute the small-scale fading characteristic parameters m and ω into the confidentiality interruption probability calculation formula of the noise-limited communication scenario to calculate the confidentiality interruption probability P out1 ; (4b) The formula for calculating the probability of confidentiality interruption in a general communication scenario with interference and noise is derived, where the received power P at each point is r Substitute the small-scale fading characteristic parameters m and ω into the formula to calculate the confidentiality interruption probability P out2 .

2. The method according to claim 1, characterized in that : In the step (1), the building vector data and material electromagnetic medium parameters of the specified urban scene are obtained by downloading the urban environment geometric feature modeling file from a domestic or foreign public map website, and obtaining the building vector data through parsing; and obtaining the material electromagnetic medium parameters by looking up a table in the ITU recommendation; In the step (2), the location information and electromagnetic information of the information sender, the receiver and the eavesdropper are set according to actual needs, which is to set the following information according to actual needs: Set the geographical location of the transmitting source and the transmitting antenna gain G t , emission signal wavelength λ, initial power P t and the initial electric field E0, the number of transmitting antennas and the transmitting antenna pattern; Set the receiving party’s geographical location and receiving antenna gain G r , the number of receiving antennas and the receiving antenna pattern; Set the possible geographical location of the eavesdropper and the eavesdropping antenna gain G e , the number of eavesdropping antennas and the radiation pattern of eavesdropping antennas. The geographical location refers to the latitude and longitude or relative coordinates of the current location of the transmitting source, the receiving party, or the eavesdropper.

3. The method according to claim 1, characterized in that Step (3a) sets three configuration files of different formats to store the geographic information and electromagnetic information required for simulation analysis. The implementation steps include the following: (3a1) setting three configuration files of different formats, wherein the format of the first configuration file is "variable name + value", the format of the second configuration file is "longitude + latitude + altitude" or "relative coordinate X + relative coordinate Y + relative coordinate Z", and the format of the third configuration file is "longitude + latitude + altitude + received power" or "relative coordinate X + relative coordinate Y + relative coordinate Z + received power"; (3a2) Setting the ray limit number N+M+L, reflection weight N, diffraction weight M, and transmission weight L of the ray tracing algorithm, and writing them together with the electromagnetic information set in step (2) into the first configuration file, and writing the position information set in step (2) into the second configuration file.

4. The method according to claim 1, characterized in that: Step (3b) analyzes all ray paths of the signal from the transmitter Tx to the receiver Rx, and the implementation steps include the following: (3b1) Treat each building in the building vector data obtained in step (1) as a polygonal cylinder, store the coordinates and vertical height of each point on the horizontal plane polygon of each building, and solve the direct, reflected, and diffracted paths from the transmitting point to each receiving point in combination with the receiving point location information provided by the second configuration file: (3b2) Direct ray path solution: First, determine whether the line connecting the transmitting source Tx and the receiving point Rx is blocked by buildings: If there is no obstruction, Tx and Rx meet the line-of-sight condition, and the line connecting Tx and Rx is the direct path. If there is occlusion, Tx and Rx meet the non-line-of-sight condition, and there is no direct path. Filter out the building planes that block the line connecting Tx and Rx, and execute steps (3b3) and (3b4): (3b3) Solution of reflected ray path: The building planes that block the rays are grouped into a mirror plane set W. First, determine the first-order mirror point Tx1 of Tx relative to its nearest mirror plane W1. Then determine the second-order mirror point Tx2 of the first-order mirror point Tx1 relative to its nearest mirror plane W2. Connect the transmitting source Tx with the first-order mirror point Tx1. The intersection of this straight line and plane W1 is the first-order reflection point P1. Connect the second-order mirror point Tx2 with the receiving point Rx. The intersection of this straight line and plane W2 is the second-order reflection point P2. In this way, multiple-order reflection points Pn are obtained. The line connecting Tx, each order reflection point, and Rx is the reflected ray path: (3b4) Solution of the diffraction ray path: Rotate the transmitting source Tx around the vertical edge of the shielding plane W to form a hollow circle, and then find the true position of the first-order diffraction point D on the vertical edge so that the line connecting the receiving point Rx and D intersects with the boundary of the hollow circle. Similarly, multiple-order diffraction points are obtained. The line connecting the transmitting source Tx, each order diffraction point, and the receiving point Rx is the diffraction ray path.

5. The method according to claim 1, characterized in that In step (3c), the total electric field at each receiving point is calculated The implementation steps include the following: (3c1) The total number of reflections n and diffraction m that occur in the process of the ray from Tx to Rx are obtained analytically. According to the elevation angle θ of the ray path relative to the transmitting antenna, t and roll angle Extract the normalized directivity factor of the transmitting antenna According to the elevation angle θ of the ray path relative to the receiving antenna r and roll angle Extract the normalized directivity factor of the receiving antenna (3c2) Calculate the dyadic reflection coefficient at the hth reflection based on the electromagnetic medium parameters of the material obtained in step (1) and the dyadic diffraction coefficient at the first diffraction Calculate the diffusion factor A of the reflected field based on the position information of each ray node s1 and the diffusion factor A of the diffraction field s2 ; (3c3) Read the initial electric field E0 of the emission signal in the first configuration file, and calculate the diffusion factor A according to the diffusion factor A. s The radiation field of the transmitted signal at the first node is calculated by the distance r0 from the transmitting source Tx to the first node. Calculate the receiving electric field from the transmitting source Tx to the receiving point Rx through the i-th ray path (3c4) The receiving electric field vectors of each ray path are superimposed to obtain the total electric field at the receiving point Where I represents the total number of ray paths generated by the signal propagating from the transmitting point Tx to the receiving point Rx, It represents the receiving electric field from the transmitting source Tx to the receiving point Rx through the i-th ray path.

6. The method according to claim 1, characterized in that In step (3d), the total electric field is converted into the received power of each receiving point, and the implementation steps include the following: (3d1) Read the first configuration file to obtain the initial power P of the transmitted signal t , Transmitting antenna gain G t , receiving antenna gain G r , emission signal wavelength λ, emission electric field initial intensity E0; (3d2) Using the parameters read in step (3d1) and the total received electric field obtained in step (3c) Calculate the receiving power P of each receiving point r ; Among them, G t represents the transmit antenna gain, G r represents the receiving antenna gain, λ represents the wavelength of the transmitted signal, E0 represents the scalar value of the initial intensity of the emission electric field, E total A scalar value representing the total received electric field.

7. The method according to claim 1, characterized in that: The step (3e) generates a small-scale fading simulation point set, simulates to obtain the received signal amplitude of each point, and fits the small-scale fading characteristic parameters m and ω. The implementation steps include the following: (3e1) A square is defined with the location of each eavesdropper as the center, and the side length of the square is 10 times the wavelength of the transmitted signal. N points are equally spaced in the square as simulation points, and the location information of these points is written into the second configuration file, where N ≥ 5000; (3e2) Re-execute steps (3b) to (3d) to obtain the received power and received signal amplitude of each simulation point, and fit the Nakagami-m distribution of the received signal amplitude based on the least squares method, and obtain the shape parameter m and scale parameter ω from the distribution. The step (3c2) calculates the dyadic reflection coefficient at the hth reflection The formula is as follows: in, They represent the unit vectors of the incident ray and the reflected ray in the ray basis coordinates under parallel polarization, They represent the unit vectors of the incident ray and the reflected ray in the ray basis coordinates under vertical polarization, represents the parallel polarization reflection coefficient, represents the vertical polarization reflection coefficient, represents the intrinsic impedance of the ith medium, μ i represents the magnetic permeability of the ith medium, ε i Represents the dielectric constant of the i-th medium, i=1,2.

8. The method according to claim 6, characterized in that The dyadic diffraction coefficient for the jth diffraction is calculated in step (3c2): The calculation steps include the following: (3c2a) Calculate the parallel polarization reflection coefficient D || : (3c2b) Calculate the vertical polarization reflection coefficient D ⊥ : Where n = θ e / π,θ e represents the outer angle of the diffraction wedge, k represents the wave number, β0 is the angle between the incident ray and the diffraction edge, represents the angle of incidence, represents the diffraction angle, F(·), a ± (·) represents two different transition functions, and L represents the distance parameter; (3c2c) According to the parallel polarization reflection coefficient D || and the vertical polarization reflection coefficient D ⊥ Calculate the dyadic diffraction coefficient in, They represent the unit vectors of the incident ray and the diffracted ray in the ray basis coordinates under parallel polarization, They represent the unit vectors of the incident ray and the diffracted ray in the ray basis coordinates under vertical polarization respectively.

9. The method according to claim 6, characterized in that: The diffusion factor A of the reflected field is calculated in step (3c2) s1 and the diffusion factor A of the diffraction field s2 , the formula is as follows: Where r1 represents the distance from the incident point to the reflection point, and r2 represents the distance from the reflection point to the exit point; s1 represents the distance from the incident point to the diffraction point, and s2 represents the distance from the diffraction point to the exit point. The step (3c3) calculates the radiation field of the transmitted signal at the first node and the receiving electric field from the transmitting source Tx through the i-th ray path to the receiving point Rx The formula is as follows: in, represents the initial value of the emitted electric field, r0 represents the distance from the emission point to the first ray node, k represents the wave number, represents the normalized directivity of the transmitting antenna, represents the dyadic reflection coefficient, represents the dyadic diffraction coefficient, r q Indicates the distance from the qth ray node to the q+1th node, A represents the normalized directivity of the receiving antenna, n represents the total number of reflections, and m represents the total number of diffractions; s Represents the diffusion factor. When calculating the reflection field, the diffusion factor is calculated as A s1 Substitute into the calculation, when calculating the diffraction field, the diffusion factor is A s2 Substitute into the calculation.

10. The method according to claim 1, characterized in that Step (4a) calculates the confidentiality interruption probability P in the noise-limited communication scenario out1 , the formula is as follows: Where m represents the shape parameter of the Nakagami-m distribution, ω B It indicates the signal-to-noise ratio of the message signal received by the receiver. ω E It represents the signal-to-noise ratio of the message signal received by the eavesdropper, L AB represents the product of the number of transmitting antennas and the number of receiving antennas, L AE represents the product of the number of transmitting antennas and the number of eavesdropping antennas, R th represents the confidentiality interruption threshold, Γ(·) represents the Gamma function, Indicates the number of combinations.

11. The method according to claim 1, characterized in that: Step (4b) derives the probability of confidentiality interruption P for a general communication scenario with interference and noise out2 The implementation steps include the following: (4b1) Derivation of the signal-to-interference-to-noise ratio λ of the message signal received by the receiver B The probability density P λB (x): According to the receiving power P of the message signal received by the receiver AB , Gaussian white noise N0, the power of the interference signal received by the receiver P IB , derived from the composite variable probability formula The probability density of The expression is as follows: Where m represents the shape parameter of the Nakagami-m distribution, ω IB It indicates the signal-to-noise ratio of the interference signal received by the receiver. ω AB Indicates the signal-to-noise ratio of the message signal received by the receiver, L IB represents the product of the number of interfering antennas and the number of receiving antennas, L AB Represents the product of the number of transmitting antennas and the number of receiving antennas, R th represents the confidentiality interruption threshold, Γ(·) represents the Gamma function, Indicates the number of combinations; (4b2) Derivation of the signal-to-interference-to-noise ratio λ of the message signal received by the eavesdropper E The cumulative probability density F λE (x): According to the receiving power P of the message signal received by the eavesdropper AE , Gaussian white noise N0, the power of the interference signal received by the receiver P IE , derived from the composite variable probability formula The cumulative probability density of The expression is as follows: Among them, ω AE represents the signal-to-noise ratio of the message signal received by the eavesdropper, ω IE It represents the signal-to-noise ratio of the interference signal received by the eavesdropper, L AE represents the product of the number of transmitting antennas and the number of eavesdropping antennas, L IE represents the product of the number of jamming antennas and the number of eavesdropping antennas; (4b3) Through the probability density and the cumulative probability density Derivation of confidentiality interruption probability P out2 The following calculation formula: Among them, C1, C2, C3, and C4 represent four different transition functions, and the calculation formula is as follows: Where m represents the shape parameter of the Nakagami-m distribution, ω AB Indicates the signal-to-noise ratio of the message signal received by the receiver, ω IE Represents the signal-to-noise ratio of the interference signal received by the eavesdropper, ω IB Indicates the signal-to-noise ratio of the interference signal received by the receiver, ω AE It represents the signal-to-noise ratio of the message signal received by the eavesdropper, L IB represents the product of the number of interfering antennas and the number of receiving antennas, L AE represents the product of the number of transmitting antennas and the number of eavesdropping antennas, L IE represents the product of the number of interference antennas and the number of eavesdropping antennas, R th represents the confidentiality interruption threshold, Γ(·) represents the Gamma function, Indicates the number of combinations. represents a binary MeijerG series.

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