Security Assurance Method, System and Terminal for Drone-Assisted Ground Satellite Communication

Abstract

The present invention belongs to the field of wireless communication technology, and discloses a security guarantee method, system and terminal for unmanned aerial vehicle (UAV)-assisted ground satellite communication. A ground satellite communication network G2SN model with eavesdroppers is constructed; based on the ground satellite communication network G2SN model with eavesdroppers, four channel models including ground link, low-altitude link, high-altitude link and direct link are analyzed; the eavesdropping probability is used as an index to measure the eavesdropping risk in G2SN, and the security performance of G2SN under the aerial assistance scheme is analyzed; the link connectivity is introduced as an index to evaluate the transmission reliability, and the reliable performance of G2SN under the aerial assistance scheme is analyzed. The present invention proposes an aerial assistance scheme to protect the confidential information transmission in G2SN. In the face of a secret ground eavesdropper, the UAV acts as an auxiliary device between the ground user and the satellite, which can alleviate the information leakage of legitimate users; at the same time, the connectivity is introduced to analyze the reliability of the scheme.

Description

Technical Field

[0001] The present invention belongs to the technical field of wireless communication, and particularly relates to a security guarantee method, system and terminal for drone-assisted ground satellite communication. Background Art

[0002] Currently, with the rapid spread of ground-to-satellite communication networks (G2SN), how to ensure feasible and reliable transmission in the network has become an increasingly important issue. On the one hand, due to the openness and broadcast nature of the wireless channel, it is difficult for G2SN to avoid the leakage of confidential information, resulting in serious enemy eavesdropping. And in G2SN, long transmission distances and masking effects will both lead to significant path losses. Therefore, signals must be transmitted at high power to resist severe attenuation. However, high transmission power will increase the eavesdropping risk of G2SN. On the other hand, traditional cryptographic encryption is not applicable to G2SN. In G2SN, a large number of distributed users will bring unforeseen challenges in key distribution and management. Moreover, encryption usually underestimates the computing power of illegal users, and with the improvement of computing power, information leakage is a serious problem.

[0003] Physical layer security, as a supplement to cryptographic encryption, has been used to provide promising security solutions for G2SN. Physical layer security can protect confidential information without being limited by computing power. For example, friendly jamming is a popular physical layer security method in G2SN, and the jamming signal can be transmitted by the transmitter to prevent eavesdropping. Recently, unmanned aerial vehicles (UAVs) have attracted more and more attention due to their flexibility and mobility, and many studies consider using UAVs to achieve friendly jamming to support secure and reliable communication. However, in most existing studies, when the jamming signal is sent to interfere with the eavesdropper, the quality of legitimate transmission will inevitably be weakened. Especially for large networks with secret eavesdroppers, it is much more difficult to accurately send the jamming signal to the eavesdropper. Therefore, there is an urgent need to design a new security guarantee method for drone-assisted ground satellite communication.

[0004] Through the above analysis, the problems and defects of the existing technology are as follows:

[0005] 1. A large number of distributed users in traditional encryption methods will bring unforeseen challenges in key distribution and management. Moreover, encryption usually underestimates the computing power of illegal users, and with the improvement of computing power, information leakage is a serious problem.

[0006] 2. When the satellite communicates with the ground, in order to increase the intensity of the signal received by the ground, the transmission power is inevitably increased, resulting in an increased risk of channel eavesdropping. It is easier for ground eavesdroppers to receive the communication information in the system.

[0007] 3. When using a physical layer security jammer for friendly jamming, while the jammer emits a jamming signal to interfere with the eavesdropper, the quality of legitimate transmission will also be interfered; for a large network with secret eavesdroppers, the jammer cannot accurately emit a jamming signal to the eavesdropper, resulting in a decrease in the throughput of legitimate transmission. Summary of the Invention

[0008] In view of the problems existing in the prior art, the present invention provides a security guarantee method, system and terminal for UAV-assisted ground satellite communication.

[0009] The present invention proposes an air-assisted scheme to protect the confidential information transmission in G2SN. Facing secret ground eavesdroppers, the UAV acts as an auxiliary device between the ground user and the satellite to alleviate the information leakage of legitimate users. The present invention introduces the eavesdropping probability as a measure of the eavesdropping risk in the G2SN scenario with eavesdroppers. At the same time, the connectivity is also introduced to analyze the reliability of the scheme.

[0010] The present invention is implemented as follows. A security guarantee method for UAV-assisted ground satellite communication, the security guarantee method for UAV-assisted ground satellite communication includes: constructing an eavesdropping G2SN model; based on the eavesdropping G2SN model, analyzing four channel models including the ground link, low-altitude link, high-altitude link and direct link; respectively analyzing the security performance and reliable performance of G2SN under the air-assisted scheme.

[0011] Further, the security guarantee method for UAV-assisted ground satellite communication includes the following steps:

[0012] Step 1, construct a ground satellite communication network G2SN model with eavesdroppers;

[0013] Step 2, based on the ground satellite communication network G2SN model with eavesdroppers, analyze four channel models including the ground link, low-altitude link, high-altitude link and direct link;

[0014] Step 3, use the eavesdropping probability as an index to measure the eavesdropping risk in G2SN, and analyze the security performance of G2SN under the air-assisted scheme;

[0015] Step 4, introduce link connectivity as an index to evaluate the transmission reliability, and analyze the reliable performance of G2SN under the air-assisted scheme.

[0016] Furthermore, the ground satellite communication network G2SN model with eavesdroppers in step 1 consists of four parts: ground users, eavesdroppers, UAVs, and satellites. Ground users communicate with satellites through legitimate links. Eavesdroppers randomly appear around ground users and eavesdrop on the confidential information between ground users and satellites.

[0017] In the G2SN model, ground users are distributed on the horizontal plane according to a homogeneous Poisson point process with density λ g and communicate with satellites through legitimate links. The satellite is located at a fixed height H s ; eavesdroppers randomly appear around ground users, eavesdrop on the confidential information between ground users and satellites, and the exact positions of eavesdroppers are unknown to the UAVs. Multiple UAVs are randomly deployed in the air at height H u , similar to ground users, they follow a homogeneous Poisson point process with density λ u . The confidential information of ground users can first be transmitted to UAVs with relatively low power, and then the air-assisted devices continue to forward the information to satellites. In addition, the proposed scheme in the present invention uses directional antennas on UAVs and satellites to reduce information leakage in the direction of eavesdroppers, so that jammers can effectively perform friendly jamming and reduce the impact on the channels of legitimate users. It should be noted that considering that ground nodes (i.e., ground users and eavesdroppers) need to send or receive signals uniformly in all directions, omnidirectional antennas are deployed on ground nodes in the G2SN model to achieve maximum coverage.

[0018] Furthermore, based on the ground satellite communication network G2SN model with eavesdroppers in step 2, the analysis of four channel models including ground links, low-altitude links, high-altitude links, and direct links is as follows:

[0019] (1) Ground link / low-altitude link: The ground link refers to the transmission link between ground nodes; the ground link from the ground user to the eavesdropper is denoted as g = {ge}, and the low-altitude link used for transmission between ground nodes and the UAV swarm is denoted as l = {gu, ue}; when both types of links suffer from path loss and Rayleigh fading, the received power is expressed as:

[0020]

[0021] where P g,l is the transmission power, l g,l represents the transmission distance between two nodes, h g,l is the channel coefficient following an exponential distribution with an average value of 1 / μ g,l , α g,l represents the path loss factor; G {g,u} is the gain of the transmitting antenna, G {e,u}is the gain of the receiving antenna; for all ground nodes G equipped with omnidirectional antennas g and G e is the gain of the omnidirectional antenna. Let G g = G e = 1; The keyhole model is used to describe the directional antenna, which consists of a main lobe and a side lobe; for the UAV, the antenna gain G in the low-altitude link u is expressed as the main lobe receiving / transmitting and the side lobe receiving / transmitting The antenna gains of the main lobe and the side lobe are represented by G m and G b respectively, and follow the following relationship:

[0022]

[0023] where θ m represents the beam width of the main lobe, and the combined beam width of the side lobe / back lobe is 2π - θ m .

[0024] (2) High-altitude link: The high-altitude link refers to the transmission link between the UAV and the satellite. The high-altitude link is hardly affected by obstacles; the signal is only subject to path loss. The satellite received power is expressed as:

[0025]

[0026] where P us is the transmission power of the UAV, G u is the transmission antenna gain of the UAV, G s is the receiving antenna gain of the satellite; l us represents the distance between the UAV and the satellite, and α us is the path loss factor.

[0027] (3) Direct link: The transmission link between the legitimate ground user and the satellite is described as the direct link, denoted by d = {gs}; the direct link is described as the link from GU3 and GU5 to the satellite, and the independent and identically distributed Shadowed-Rician fading is used to simulate the direct link. The power received by the satellite is:

[0028]

[0029] where l d is the distance of the direct link, α d = 2 represents the instantaneous free space loss; h d is the channel coefficient. Since the parameter m of the fading severity is an arbitrary integer in the range [0, ∞), the probability density function of h d is expressed as:

[0030]

[0031] Among them, Ω and 2ρ represent the average power of the line-of-sight link and the multipath component respectively; 1F1(a, b, c) is a confluent hypergeometric function, rewritten as:

[0032]

[0033] Furthermore, using the eavesdropping probability as an indicator to measure the eavesdropping risk in G2SN, the analysis of the security performance of G2SN under the air-assisted scheme includes:

[0034] The eavesdropping probability is defined as the probability that the eavesdropper receives and decodes the confidential information. After the signal is transmitted from the ground user, it reaches the satellite through the air-assisted device. Using The eavesdropping probability of the ground link is expressed as follows:

[0035]

[0036] Among them, γ e is the signal-to-noise ratio threshold at the eavesdropper, l g is the distance between the eavesdropper and the ground user, l max is the maximum eavesdropping range, and σ 2 is the Gaussian white noise.

[0037] Specify the received power threshold of the eavesdropper as η e , and the maximum eavesdropping range is expressed as:

[0038]

[0039] The eavesdropper can only obtain the signals sent by legitimate users that appear within the maximum eavesdropping range l max . The eavesdropper can successfully decode the confidential information only when the received SINR is greater than the threshold γ e . Therefore, the eavesdropping probability of the ground eavesdropping link is expressed and derived as:

[0040]

[0041] Among them, represents the probability of the event, represents the expected value, I g represents the interference from other users, is the Laplace transform of the cumulative interference from other ground users, calculated as:

[0042]

[0043] Among them, is a set of other interfering users, (a) Based on the characteristics of the probability generating function: l g The PDF of is expressed as:

[0044]

[0045] Low-altitude link The eavesdropping probability of is calculated as:

[0046]

[0047] where l ue is the distance of the low-altitude eavesdropping link. l ue The value range of is [H u , l max' , where l max' is the maximum eavesdropping range of the low-altitude eavesdropping link. At the same time, there is expression, represents the antenna gain of the sidelobe of the UAV.

[0048] According to the preliminary result of the eavesdropping probability, the eavesdropping probability of the air-assisted scheme is calculated as as follows:

[0049]

[0050] Furthermore, introducing link connectivity as an index to evaluate transmission reliability in step four, the reliable performance analysis of G2SN under the air-assisted scheme includes:

[0051] Link connectivity is introduced as an index to evaluate transmission reliability and is defined as the probability of successfully establishing a legitimate link, indicating the probability that a legitimate user can receive and decode confidential information.

[0052] In the air-assisted scheme, there are two types of transmission links, including low-altitude links and high-altitude links. The link connectivity of the air-assisted scheme is calculated using where represent the connectivity of the low-altitude link and the high-altitude link respectively, is expressed as:

[0053]

[0054] where, The cumulative interference received by the UAV from other users can be divided into main lobe interference and sidelobe interference and represent respectively The Laplace transform of is derived as follows:

[0055]

[0056] where 2F1(a, b, c) is the Gaussian hypergeometric function; calculate the maximum transmission distance from the interfering user to the UAV η u is the received power threshold of the UAV, The Laplace transform of

[0057]

[0058] where l min = H u (tan 2 (θ u / 2)+1) 1 / 2 represents the minimum interference distance of the UAV sidelobe.

[0059] For the connectivity of the high-altitude link is calculated as follows:

[0060]

[0061] where γ s is the SINR threshold of the satellite; the distance between the UAV and the projection of the satellite on the air platform is represented by d us ; I us and I gs are the cumulative interferences of the UAV and the ground user on the satellite respectively. I us is represented as:

[0062]

[0063] where l js represents the distance between the jth UAV and the satellite, is the probability that the interfering UAV appears in the main lobe coverage area of satellite A s and is calculated as:

[0064]

[0065] where x is the number of UAVs appearing in the main lobe coverage area of the satellite,

[0066] For the cumulative interference of the ground user I gs the probability distribution function of the satellite received power is given as follows:

[0067]

[0068] Among them, is the average free space path loss of the interference signal; Let A I be represented as the interference area, and the cumulative interference I gs is expressed as:

[0069]

[0070] By adjusting the antenna beamwidth θ at the UAV u' and θ at the satellite s achieve

[0071] Another object of the present invention is to provide a security guarantee system for UAV-assisted ground satellite communication applying the security guarantee method for UAV-assisted ground satellite communication, and the security guarantee system for UAV-assisted ground satellite communication includes:

[0072] G2SN model construction module, which is used to construct a ground satellite communication network G2SN model with eavesdroppers;

[0073] Channel model analysis module, which is used to analyze four channel models including ground link, low-altitude link, high-altitude link and direct link based on the ground satellite communication network G2SN model with eavesdroppers;

[0074] Security performance analysis module, which is used to analyze the security performance of G2SN under the air-assisted scheme by using the eavesdropping probability as an index to measure the eavesdropping risk in G2SN;

[0075] Reliable performance analysis module, which is used to analyze the reliable performance of G2SN under the air-assisted scheme by introducing link connectivity as an index to evaluate transmission reliability.

[0076] Another object of the present invention is to provide a computer device, which includes a memory and a processor, and the memory stores a computer program. When the computer program is executed by the processor, the processor executes the steps of the security guarantee method for UAV-assisted ground satellite communication.

[0077] Another object of the present invention is to provide a computer-readable storage medium, which stores a computer program. When the computer program is executed by a processor, the processor executes the steps of the security guarantee method for UAV-assisted ground satellite communication.

[0078] Another object of the present invention is to provide an information data processing terminal, which is used to implement the security guarantee system for UAV-assisted ground satellite communication.

[0079] Combined with the above technical solutions and the technical problems solved, the advantages and positive effects of the technical solution to be protected by the present invention are as follows:

[0080] First, in view of the technical problems existing in the above-mentioned prior art and the difficulty of solving this problem, closely combined with the technical solution to be protected by the present invention and the results and data in the R & D process, etc., analyze in detail and deeply how the technical solution of the present invention solves the technical problems and the creative technical effects brought after solving the problems. The specific description is as follows:

[0081] In traditional encryption methods, a large number of distributed users will bring unforeseeable challenges in key distribution and management. In response to this, the present invention uses the physical layer security method to solve this problem.

[0082] As a supplement to cryptographic encryption, physical layer security has been used to provide a promising security solution for G2SN. Physical layer security can protect confidential information without being limited by computing power. Friendly jamming is a popular physical layer security method in G2SN. The jamming signal can be transmitted by the transmitter to prevent eavesdropping. However, in most existing studies, when the jamming signal is sent to interfere with the eavesdropper, the quality of legitimate transmission is inevitably weakened. The present invention adds a drone as an aerial auxiliary device to relay the satellite-to-ground signal in the traditional G2SN model. The confidential information of the ground user can first be transmitted to the UAV with relatively low power, and then the aerial auxiliary device continues to forward the information to the satellite, avoiding the satellite directly transmitting communication signals to the ground node with high power and reducing the risk of being eavesdropped.

[0083] In addition, using the drone as an aerial auxiliary device also effectively improves the connection probability between the satellite and the ground user in the case of the existence of an eavesdropper in the G2SN model and improves the channel insertion transmission quality in the traditional G2SN model.

[0084] The present invention proposes an aerial assistance scheme to protect the transmission of confidential information in G2SN, and proves through a series of simulation results that this scheme can effectively alleviate the information leakage of legitimate users in the face of secret ground eavesdroppers. The present invention proposes an aerial assistance scheme to protect the transmission of confidential information in the ground satellite communication network. The main advantages of this scheme are:

[0085] 1. In the face of secret ground eavesdroppers, the drone acts as an auxiliary device between the ground user and the satellite, which can reduce the risk of the confidential information of legitimate users being eavesdropped and at the same time ensure the communication quality of legitimate users in G2SN.

[0086] 2. The present invention uses directional antennas at the drone and the satellite transmitter to reduce the information leakage in the direction of the eavesdropper.

[0087] 3. By introducing the eavesdropping probability, for a ground-satellite communication network with eavesdroppers, the eavesdropping probability can serve as an effective measure of the eavesdropping risk. Meanwhile, connectivity is also introduced to analyze the reliability of the scheme.

[0088] 4. Through comparison with non-protection schemes, the effectiveness of the air-assisted scheme in preventing eavesdropping is fully verified. In addition, in the case of a dense user population, the scheme proposed by the invention can provide relatively high connectivity.

[0089] 5. The invention discusses the performance of the air-assisted scheme under different parameter settings and provides useful deployment insights. In most channel states, the air-assisted scheme can significantly reduce the eavesdropping probability.

[0090] Second, considering the technical solution as a whole or from the perspective of the product, the technical effects and advantages of the technical solution to be protected by the invention (the advantages of the mobility of the UAV, reducing the eavesdropping probability, increasing the connection probability and thus improving the throughput) are specifically described as follows:

[0091] The invention proposes an air-assisted scheme to protect the transmission of confidential information in G2SN. In the scheme, the mobility and easy deployment advantages of the UAV are utilized as an air-assisted device for auxiliary communication. The UAV used in the invention can be used to relay the information between the satellite and the ground users. The confidential information of the ground users can first be transmitted to the UAV at a relatively low power, and then the air-assisted device continues to forward the information to the satellite, avoiding the satellite directly transmitting communication signals to the ground nodes at high power and reducing the risk of being eavesdropped.

[0092] The invention uses the eavesdropping probability as an index to measure the eavesdropping risk in G2SN and further derives a closed-form expression of this index in the scheme proposed by the invention. The eavesdropping probability is defined as the probability that the eavesdropper receives and decodes the confidential information.

[0093] The invention introduces link connectivity (connection probability) as an index to evaluate the transmission reliability, which is defined as the probability of successfully establishing a legitimate link, that is, the probability that legitimate users can receive and decode the confidential information.

[0094] The eavesdropping probability and the connectivity of the link as evaluation indexes of the system fully verify the effectiveness of the air-assisted scheme proposed by the invention in preventing eavesdropping compared with the non-assisted scheme. And, in the case of a dense user population, the scheme proposed by the invention can provide relatively high connectivity

[0095] Third, as an auxiliary evidence of the creativity of the claims of the invention, it is also reflected in the following important aspects:

[0096] (1) The technical solution of the invention fills the domestic and foreign industry technical gaps:

[0097] As a supplement to cryptographic encryption, physical layer security can protect confidential information without being limited by computing power. Friendly jamming is a popular physical layer security method in G2SN. The jamming signal can be transmitted by the transmitter to prevent eavesdropping. However, in most existing studies, when the jamming signal is sent to interfere with the eavesdropper, the quality of legitimate transmission is inevitably weakened. The old schemes cannot well reduce the eavesdropping risk while ensuring the communication quality of G2SN. In the present invention, a drone is added as an aerial auxiliary device to relay the satellite-to-ground signal in the traditional G2SN model. The confidential information of the ground user can first be transmitted to the UAV at a relatively low power, and then the aerial auxiliary device continues to forward the information to the satellite, avoiding the satellite directly transmitting communication signals to the ground node at high power and reducing the risk of being eavesdropped. In addition, using the drone as an aerial auxiliary device also effectively improves the connection probability between the satellite and the ground user in the presence of an eavesdropper in the G2SN model and improves the channel transmission quality in the traditional G2SN model.

[0098] (2) The technical solution of the present invention solves the technical problems that people have been eager to solve but have never succeeded in:

[0099] In physical layer security, friendly jamming is a popular physical layer security method in G2SN. The jamming signal can be transmitted by the transmitter to prevent eavesdropping. However, in most existing studies, when the jamming signal is sent to interfere with the eavesdropper, the quality of legitimate transmission is inevitably weakened. The old schemes cannot well reduce the eavesdropping risk while ensuring the communication quality of G2SN.

[0100] The aerial auxiliary scheme proposed by the present invention for protecting the transmission of confidential information in G2SN uses a drone as an aerial auxiliary device to relay the satellite-to-ground signal. The confidential information of the ground user can first be transmitted to the UAV at a relatively low power, and then the aerial auxiliary device continues to forward the information to the satellite. The scheme proposed by the present invention can effectively reduce the eavesdropping risk while ensuring the communication quality of G2SN. BRIEF DESCRIPTION OF THE DRAWINGS

[0101] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required to be used in the embodiments of the present invention. Obviously, the following described drawings are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0102] Figure 1 It is a flowchart of the security guarantee method for drone-assisted ground satellite communication provided by the embodiments of the present invention;

[0103] Figure 2 It is the system model diagram of the air-assisted scheme of G2SN provided by the embodiment of the present invention;

[0104] Figure 3 It is the diagram showing the influence of the ground user density on the eavesdropping probability under different schemes provided by the embodiment of the present invention;

[0105] Figure 4 It is the diagram showing the influence of the ground user density on the connection probability under different schemes provided by the embodiment of the present invention;

[0106] Figure 5 It is the diagram showing the influence of the UAV swarm density on the eavesdropping probability under different path loss factors provided by the embodiment of the present invention;

[0107] Figure 6 It is the diagram showing the influence of the antenna beam width of the UAV on the eavesdropping probability under different UAV swarm densities provided by the embodiment of the present invention;

[0108] Figure 7 It is the diagram showing the influence of the UAV deployment altitude on the eavesdropping probability under different UAV swarm densities provided by the embodiment of the present invention. Detailed implementation manners

[0109] In order to make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the following further elaborates the present invention in detail with reference to embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0110] Aiming at the problems existing in the prior art, the present invention provides a security guarantee method, system and terminal for UAV-assisted ground satellite communication, which will be described in detail below with reference to the accompanying drawings.

[0111] I. Explanation of the embodiment. This part is an explanatory embodiment that expands and explains the technical solution of the claim in order to enable those skilled in the art to fully understand how the present invention is specifically implemented.

[0112] As Figure 1 shown, the security guarantee method for UAV-assisted ground satellite communication provided by the embodiment of the present invention includes the following steps:

[0113] S101, constructing a ground satellite communication network G2SN model with an eavesdropper;

[0114] S102, analyzing four channel models including the ground link, low-altitude link, high-altitude link and direct link based on the ground satellite communication network G2SN model with an eavesdropper;

[0115] S103. Use the eavesdropping probability as an indicator to measure the eavesdropping risk in G2SN, and analyze the security performance of G2SN under the air-assisted scheme;

[0116] S104. Introduce link connectivity as an indicator to evaluate transmission reliability, and analyze the reliability of G2SN under the air-assisted scheme.

[0117] As a preferred embodiment, the security guarantee method for drone-assisted ground satellite communication provided by the embodiments of the present invention specifically includes the following steps:

[0118] Step 1: Establish a ground satellite communication network with an eavesdropper. The G2SN network consists of four parts: ground users, eavesdroppers, drones, and satellites. Among them, the ground users communicate with the satellites through legitimate links. The eavesdroppers randomly appear around the ground users and eavesdrop on the confidential information between the ground users and the satellites.

[0119] Step 2: Propose an air-assisted scheme to reduce information leakage in G2SN. In the scheme of the present invention, multiple UAVs are randomly deployed in the air, similar to ground users. The confidential information of the ground users can first be transmitted to the UAVs with relatively low power, and then the air assistants continue to forward the information to the satellites. Directional antennas are used on both the UAVs and the satellites to reduce information leakage in the direction of the eavesdroppers; at the same time, considering that the ground nodes (i.e., ground users and eavesdroppers) need to transmit and receive signals uniformly in all directions, omnidirectional antennas are deployed on them to achieve maximum coverage.

[0120] Step 3: Aim to analyze the security performance of G2SN under the air-assisted scheme. Specifically, use the eavesdropping probability as an indicator to measure the eavesdropping risk in G2SN, and further derive the closed-form expression of this indicator in the scheme proposed by the present invention. The eavesdropping probability is defined as the probability that the eavesdropper receives and decodes the confidential information.

[0121] Step 4: Focus on discussing the reliability of G2SN under the air-assisted scheme. Specifically, link connectivity is introduced as an indicator to evaluate transmission reliability, which is defined as the probability of successfully establishing a legitimate link, that is, the probability that legitimate users can receive and decode the confidential information.

[0122] The present invention proposes an air-assisted scheme to protect the transmission of confidential information in G2SN, and a series of simulation results prove that this scheme can effectively alleviate the information leakage of legitimate users in the face of secret ground eavesdroppers. For the convenience of describing the specific implementation method, the model background is introduced first.

[0123] In the present invention, the present invention considers an eavesdropping G2SN model as shown in Figure 2 where the ground users follow a density of λ gThe homogeneous Poisson point process is distributed on the horizontal plane and communicates with the satellite through legitimate links. Here, the present invention assumes that the satellite is located at a fixed height H s . In addition, eavesdroppers randomly appear around the ground users and eavesdrop on the confidential information between the ground users and the satellite. It is worth mentioning that the exact positions of the eavesdroppers are unknown.

[0124] The present invention proposes an air-assisted scheme to reduce information leakage in G2SN. In the proposed scheme of the present invention, multiple UAVs are randomly deployed in the air at a height of H u , similar to the ground users, the swarm of UAVs follows a homogeneous Poisson point process with a density of λ u .

[0125] The confidential information of the ground users can first be transmitted to the UAVs with relatively low power, and then the air assistants continue to forward the information to the satellite. In addition, the present invention uses directional antennas on both the UAVs and the satellite to reduce information leakage in the direction where the eavesdroppers are located. It should be noted that considering that the ground nodes (i.e., ground users and eavesdroppers) need to transmit and receive signals uniformly in all directions, omnidirectional antennas are deployed on them to achieve maximum coverage.

[0126] Based on Figure 2 the network model in, the present invention further summarizes four channel models, including the ground link, the low-altitude link, the high-altitude link, and the direct link, which are specifically introduced as follows:

[0127] 1) Ground link / Low-altitude link: The ground link refers to the transmission link between ground nodes. In particular, the present invention represents the ground link from the ground user to the eavesdropper as g = {ge} (such as Figure 2 from GU5 to E3 in). Similarly, the low-altitude link for transmission between the ground nodes and the swarm of UAVs (e.g., between GU1, E1, and U1) is represented by l = {gu, ue}. In the present invention, it is assumed that both types of links suffer from path loss and Rayleigh fading, and the received power is further expressed as:

[0128]

[0129] where, P g,l is the transmission power, l g,l represents the transmission distance between two nodes, h g,l is the channel coefficient that follows an exponential distribution with an average value of 1 / μ g,l , α g,l represents the path loss factor. In addition, G {g,u} is the gain of the transmitting antenna, and G {e,u} is the gain of the receiving antenna. Specifically, for all ground nodes equipped with omnidirectional antennas, G g and Ge is the gain of the omnidirectional antenna. Let G g = G e = 1;. In contrast, to simplify the theoretical analysis, the present invention uses the keyhole model to describe the directional antenna, which consists of a main lobe and a side lobe. Therefore, for the UAV, the antenna gain G u in the low-altitude link can be expressed as (main lobe reception / transmission) and (side lobe reception / transmission). In particular, the antenna gains of the main lobe and the side lobe (denoted by G m and G b ) follow the following relationship:

[0130]

[0131] where θ m represents the beam width of the main lobe, and the combined beam width of the side lobe / back lobe is 2π - θ m .

[0132] 2) High-altitude link: The high-altitude link refers to the transmission link between the UAV and the satellite (as Figure 2 shown, from U1 and U2 to the satellite). Different from the low-altitude link, the high-altitude link is hardly affected by obstacles. The signal is only subject to path loss, so the satellite received power can be expressed as:

[0133]

[0134] where P us is the transmission power of the UAV, G u is the transmission antenna gain of the UAV, G s is the receiving antenna gain of the satellite. In addition, l us represents the distance between the UAV and the satellite, and α us is the path loss factor.

[0135] 3) Direct link: The transmission link between the legitimate ground user and the satellite is described as the direct link, which can be represented by d = {gs}. In particular, in Figure 2 , the direct link is described as the link from GU3 and GU5 to the satellite. To represent a real channel, the present invention uses independent and identically distributed Shadowed-Rician fading to simulate the direct link. In this case, the power received by the satellite is:

[0136]

[0137] where l d is the distance of the direct link, α d = 2 represents the instantaneous free space loss. In addition, hd is the channel coefficient. Since the parameter m representing the severity of fading is an arbitrary integer in the range [0, ∞), the probability density function of h d is expressed as:

[0138]

[0139] where Ω and 2ρ represent the average power of the line-of-sight (Los) link and the multipath components, respectively. In addition, 1F1(a, b, c) is a confluent hypergeometric function, which can be further rewritten as:

[0140]

[0141] Next, the security performance analysis is carried out. The present invention focuses on analyzing the security performance of G2SN under the air-assisted scheme. Specifically, the present invention uses the eavesdropping probability as an index to measure the eavesdropping risk in G2SN, and further derives a closed-form expression of this index in the scheme of the present invention. It should be noted that the eavesdropping probability is defined as the probability that the eavesdropper receives and decodes the confidential information.

[0142] In the scheme of the present invention, after the signal is transmitted from the ground user, it first passes through the air-assisted device and then reaches the satellite. However, both of these two steps face the threat of confidential information leakage. In particular, due to the full coverage of the omnidirectional antenna, the eavesdropper can eavesdrop on the transmitted signal through the ground link. When the UAV forwards the signal to the satellite through the directional antenna, the information leaked by the sidelobe can also be obtained by the eavesdropper through the low-altitude link.

[0143] Let denote the eavesdropping probability of the ground link, which is expressed as follows:

[0144]

[0145] where γ e is the signal-to-noise ratio threshold at the eavesdropper, l g is the distance between the eavesdropper and the ground user, l max is the maximum eavesdropping range, and σ 2 is the Gaussian white noise.

[0146] Proof: Considering the limitation of the component sensitivity, the received power threshold of the eavesdropper is specified as η e . Then the maximum eavesdropping range can be expressed as:

[0147]

[0148] It should be noted that the eavesdropper can only obtain the signals sent by the legitimate users that appear within the maximum eavesdropping range l max Moreover, the eavesdropper can only decode the signal when the received SINR is greater than the threshold γe The confidential information can be successfully decoded only when... Therefore, the eavesdropping probability of the ground eavesdropping link can be expressed as and further derived as:

[0149]

[0150] where, represents the probability of an event, represents the expected value, I g represents the interference from other users, is the Laplace transform of the cumulative interference from other ground users and can be calculated as:

[0151]

[0152] where, is the set of other interfering users, (a) Based on the properties of the probability generating function: In addition, the PDF of l g can be expressed as:

[0153]

[0154] Therefore, as shown in Equation (7), the final expression of... can be obtained by inserting Equation (11) and Equation (10) into Equation (9).

[0155] Following a similar derivation process in the proof, the eavesdropping probability of the low-altitude link can be calculated as:

[0156]

[0157] where, l ue is the distance of the low-altitude eavesdropping link. The value range of l ue is [H u , l max' , where l max' is the maximum eavesdropping range of the low-altitude eavesdropping link. At the same time, there is expressed as, represents the antenna gain of the side lobe of the UAV.

[0158] According to the preliminary results of the eavesdropping probability, the eavesdropping probability of the air-assisted scheme can be calculated as as follows:

[0159]

[0160] The present invention also focuses on the reliability of G2SN under the aerial assistance scheme. Specifically, link connectivity is introduced as an index to evaluate transmission reliability, which is defined as the probability of successfully establishing a legitimate link, that is, the probability that a legitimate user can receive and decode the confidential information.

[0161] In the aerial assistance scheme, there are two types of transmission links, including low-altitude links and high-altitude links. Therefore, the link connectivity of the aerial assistance scheme can be calculated using , where respectively represent the connectivity of the low-altitude link and the high-altitude link connectivity. According to a similar derivation process of Equation (9), can be expressed as:

[0162]

[0163] where, The cumulative interference received by the UAV from other users can be divided into main lobe interference and side lobe interference and respectively represent and the Laplace transforms of. Referring to Equation (10), it can be derived as:

[0164]

[0165] where 2F1(a,b,c) is the Gaussian hypergeometric function. Using the same method shown in Equation (8), the maximum transmission distance from the interfering user to the UAV can be calculated by the following formula η u is the received power threshold of the UAV. Subsequently, the Laplace transform of can be expressed as:

[0166]

[0167] where, l min = H u (tan 2 (θ u / 2)+1) 1 / 2 represents the minimum interference distance of the UAV side lobe.

[0168] In addition, for the connectivity of the high-altitude link , it can be calculated as follows:

[0169]

[0170] where, γ s is the SINR threshold of the satellite. The distance between the UAV and the projection of the satellite on the aerial platform is denoted as dus denote \(I\) us and \(I\) gs are the cumulative interferences of the UAV and the ground user on the satellite respectively. In particular, \(I\) us can be expressed as:

[0171]

[0172] where \(l\) js denotes the distance between the \(j\)-th UAV and the satellite, is the probability that the interfering UAV appears in the main lobe coverage area of satellite \(A\) s and can be calculated as:

[0173]

[0174] where \(x\) is the number of UAVs appearing in the main lobe coverage area of the satellite,

[0175] Different from the derivation of \(I\) us for the cumulative interference of the ground user \(I\) gs first, the probability distribution function of the satellite received power is given, referring to Equations (4) and (5), as follows:

[0176]

[0177] where, is the average free space path loss of the interfering signal. The present invention defines \(A\) I as the interference area. Then, the cumulative interference \(I\) gs can be expressed as:

[0178]

[0179] It is worth mentioning that both the satellite and the aerial assistance device can narrow the antenna beamwidth to increase the main lobe gain. On the one hand, when other parameters are fixed, the increase in antenna gain can reduce the large path loss caused by the long transmission link, thus generating a relatively high received power on the satellite. On the other hand, the cumulative interference of the UAVs and ground users distributed within the main lobe coverage area of the antenna can be reduced as the antenna beamwidth decreases. Therefore, the security guarantee system for UAV-assisted ground satellite communication provided by the embodiments of the present invention can be realized by adjusting the antenna beamwidth \(\theta\) u' at the UAV and \(\theta\) s at the satellite

[0180] The security guarantee system for UAV-assisted ground satellite communication provided by the embodiments of the present invention includes:

[0181] a G2SN model construction module, configured to construct a ground satellite communication network G2SN model with eavesdroppers;

[0182] A channel model analysis module, which is used to analyze four channel models including the ground link, low-altitude link, high-altitude link, and direct link based on the ground-satellite communication network G2SN model with an eavesdropper present;

[0183] A security performance analysis module, which is used to analyze the security performance of G2SN under the air-assisted scheme by using the eavesdropping probability as an index to measure the eavesdropping risk in G2SN;

[0184] A reliability performance analysis module, which is used to analyze the reliability performance of G2SN under the air-assisted scheme by introducing link connectivity as an index to evaluate transmission reliability.

[0185] II. Application embodiments. In order to prove the creativity and technical value of the technical solution of the present invention, this part is an application embodiment of the technical solution of the claims on specific products or related technologies.

[0186] The application of the present invention is directed to a low-earth orbit satellite communication system. It aims to solve the problems of poor communication quality of G2SN in low-earth orbit satellite communication and high risk of eavesdropping on the confidential information of legitimate users.

[0187] Low-earth orbit satellite communication can solve broadband communication problems in remote areas, oceans, space, deserts, mountains, etc. that cannot be solved by terrestrial mobile communication. However, due to the very large path loss between the satellite and the ground terminal, atmospheric absorption loss (such as rain fade, etc.), if the transmission rate is to be increased, the transmit power and the ground user antenna aperture need to be increased. As a result, the two key indicators of the spectrum utilization efficiency and energy consumption per bit of satellite communication are still not high, and due to the increase in the satellite's transmit power, the transmission of confidential information in G2SN faces a great risk of being eavesdropped.

[0188] Currently, the secure transmission of low-earth orbit satellite communication mainly relies on upper-layer security protocols, but traditional key schemes can be cracked with sufficient computing power. Currently, friendly jamming using physical layer security is popular to address this problem, but friendly jamming will also reduce the channel quality of legitimate users while reducing the channel quality of eavesdroppers, resulting in a decrease in the overall throughput of G2SN.

[0189] In response to the above scenario, for the air-assisted scheme proposed by the present invention to protect the transmission of confidential information in G2SN, an unmanned aerial vehicle (UAV) is used as an air-assisted device to relay the signal from the satellite to the ground. The confidential information of the ground user can first be transmitted to the UAV with relatively low power, and then the air-assisted device continues to forward the information to the satellite. The scheme proposed by the present invention can effectively reduce the eavesdropping risk while ensuring the communication quality of G2SN.

[0190] III. Evidence of the effects related to the embodiments. Some positive effects have been achieved during the research and development or use of the embodiments of the present invention, and it indeed has great advantages compared with the prior art. The following content will be described in combination with the data, charts, etc. in the test process.

[0191] Finally, the present invention gives numerical results to verify the effectiveness of the proposed solution. First, the parameter settings of the present invention are introduced. Then, the present invention discusses the performance of G2SN under the air-assisted scheme, namely the eavesdropping probability and link connectivity. In addition, the present invention also analyzes the influence of main parameters such as the density of UAVs, the antenna beam width of UAVs, and the deployment height of UAVs.

[0192] First, the parameter settings are introduced. To reflect the actual situation, the present invention sets the deployment height of satellite H s to 200 km. Correspondingly, the antenna beam width of satellite θ s is π / 180. When the legitimate user on the ground communicates directly with the satellite, its transmit power is set to P gs = 40 W to resist the high attenuation of the signal. In addition, the channel parameters of the direct link are set to (m, ρ, Ω) = (2, 0.251, 0.279), and the Gaussian white noise is σ 2 = 45 dBm. For the air-assisted scheme, the UAV deployment height is set to H u = 750 m. In the low-altitude link, the transmit power of the ground user is 1 W. While in the high-altitude link, the transmit power of the UAV is P us = 30 W, and the antenna beam width of the UAV is set to θ u' = π / 12. The SINR thresholds of the UAV and the eavesdropper are respectively set to γ u = 10 -3 , γ e = 10 -3 . Note that the densities of the ground users and UAVs mentioned in the present invention are in square meters.

[0193] Next, the performance analysis and simulation results of the present invention are discussed. In Figure 3 and Figure 4 , the performance of G2NS under the air-assisted and non-protected schemes is jointly studied. The marked symbols represent the simulation results, while the theoretical results are represented by curves. First, it can be found from the figure that the theoretical results match the simulation results, verifying the accuracy of the theoretical model of the present invention. As Figure 3 shown, the eavesdropping probability increases with the increase of the ground user density λ g , and finally reaches 1. Compared with the non-protected scheme, it is easy to find that the proposed solution of the present invention can significantly reduce the eavesdropping probability, especially when the density λ g is in [10 -6 , 10 -4within the range of. In addition, as Figure 4 shows, when there are a large number of users in G2SN, the air-assisted scheme can also provide more reliable transmission than the non-protected scheme. Therefore, the scheme proposed by the present invention can achieve remarkable effects in protecting the information transmission in G2SN.

[0194] Further analyze the influence of the main parameters on the eavesdropping probability, such as Figure 5 , Figure 6 , Figure 7 the density, antenna beam width, and deployment height of the UAVs in Figure 5 shows the influence of the change in the density of UAVs' λ ue under different path loss factors α u on the eavesdropping probability . As Figure 5 shows, when α ue = 3, the curve first rises and then gradually flattens as λ u increases. In contrast, the value is nearly stable and α ue = 2. In addition, in a relatively poor channel state (i.e., α ue = 4), no matter how the density λ u changes, it is more difficult for the eavesdropper to eavesdrop on the confidential information. Therefore, in most channel states, the air-assisted scheme can significantly reduce the eavesdropping probability.

[0195] In Figure 6 , the present invention analyzes the influence of the receiving antenna beam width θ u at the UAV on the eavesdropping probability u under different densities λ of different UAV groups. As Figure 6 shows, the curve rises as θ u increases. In addition, the u value under a lower density λ of the UAV group (i.e., λ u = 10 -8 ) is much smaller than that at a higher density because the data transmission of more users may lead to a greater risk of information leakage. When λ u increases from 10 -7 to 10 -6 , the increment is particularly obvious. It is worth mentioning that no matter how the density of the UAV group changes, the air-assisted scheme can reduce the eavesdropping probability by narrowing the receiving antenna beam width at the UAV, especially when there are a large number of UAVs distributed in G2SN. This method is still effective.

[0196] Figure 7 shows different Hu Eavesdropping probability at a certain value It can be observed that when the density of the UAV swarm in the network is low (i.e., λu = 10 -7 ), it is hardly affected by the deployment height H u . However, when the density λ of the UAV swarm u increases, the eavesdropper has more opportunities to eavesdrop on legitimate communications. In addition, the eavesdropping probability can be reduced as much as possible by adjusting the deployment height of the UAVs. It should be noted that when λ u = 10 -6 , as H u increases from 1000m to 3000m, the value decreases significantly instead. Therefore, when a large number of UAVs are deployed on an aerial platform, the transmission security can be ensured by increasing the deployment height of the UAVs.

[0197] It should be noted that the embodiments of the present invention can be implemented by hardware, software, or a combination of software and hardware. The hardware part can be implemented using dedicated logic; the software part can be stored in a memory and executed by a suitable instruction execution system, such as a microprocessor or dedicated design hardware. Those of ordinary skill in the art can understand that the above devices and methods can be implemented using computer-executable instructions and / or included in processor control code, for example, such code is provided on a carrier medium such as a disk, CD, or DVD-ROM, a programmable memory such as a read-only memory (firmware), or a data carrier such as an optical or electronic signal carrier. The devices and modules of the present invention can be implemented by hardware circuits of programmable hardware devices such as very large scale integrated circuits or gate arrays, semiconductors such as logic chips, transistors, etc., or programmable logic devices such as field programmable gate arrays, programmable logic devices, etc., can also be implemented by software executed by various types of processors, or can be implemented by a combination of the above hardware circuits and software such as firmware.

[0198] The above is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any modification, equivalent replacement, and improvement made within the spirit and principle of the present invention by those skilled in the art within the technical scope disclosed by the present invention shall be covered by the protection scope of the present invention.

Claims

1. A security guarantee method for drone-assisted ground satellite communication, characterized in that, The security guarantee method for the UAV-assisted ground satellite communication includes the following steps: Step 1, construct a ground satellite communication network G2SN model with eavesdroppers; Step 2, based on the ground satellite communication network G2SN model with eavesdroppers, analyze four channel models including the ground link, low-altitude link, high-altitude link, and direct link; Step 3, use the eavesdropping probability as an indicator to measure the eavesdropping risk in G2SN, and analyze the security performance of G2SN under the air-assisted scheme; Step 4, introduce link connectivity as an indicator to evaluate the transmission reliability, and analyze the reliable performance of G2SN under the air-assisted scheme; The use of the eavesdropping probability as an indicator to measure the eavesdropping risk in G2SN in Step 3 and the analysis of the security performance of G2SN under the air-assisted scheme include: The eavesdropping probability is defined as the probability that an eavesdropper receives and decodes the confidential information; after the signal is transmitted from the ground user, it reaches the satellite through the air-assisted device; the eavesdropping probability of the ground link denoted by is expressed as follows: Among them, γ e is the signal-to-noise ratio threshold at the eavesdropper, l g is the distance between the eavesdropper and the ground user, l max is the maximum eavesdropping range, σ 2 is the Gaussian white noise; Specify the received power threshold of the eavesdropping device as η e , and the maximum eavesdropping range is expressed as: An eavesdropper can only intercept signals sent by legitimate users within the maximum eavesdropping range \(l\). max The eavesdropper can only successfully decode the confidential information when the received SINR is greater than the threshold \(\gamma\). e Therefore, the eavesdropping probability of the ground eavesdropping link is expressed and derived as follows: Among them, represents the probability of an event, represents the expected value, I g represents the interference from other users, is the Laplace transform of the cumulative interference from other terrestrial users, calculated as: Among them, is a set of other interfering users. (a) Based on the characteristics of the probability generating function: l g The PDF representation of is: Low-altitude link The wiretapping probability calculation is as follows: where, l ue is the distance of the low-altitude eavesdropping link; the value range of l ue is [H u , l max′ , where l max′ is the maximum eavesdropping range of the low-altitude eavesdropping link; meanwhile, there is expressed as indicating the antenna gain of the side lobe of the UAV; Based on the preliminary results of the eavesdropping probability, the air-assisted scheme has its eavesdropping probability calculated as shown below: The introduction of link connectivity as an indicator to evaluate the transmission reliability in Step 4 and the analysis of the reliable performance of G2SN under the air-assisted scheme include: Link connectivity is introduced as an indicator to evaluate the transmission reliability, which is defined as the probability of successfully establishing a legitimate link, representing the probability that a legitimate user can receive and decode confidential information; In the air-assisted solution, there are two types of transmission links, including a low-altitude link and a high-altitude link; the air-assisted solution has its link connectivity calculated using , where represent the connectivity of the low-altitude link and the high-altitude link respectively, and is expressed as: Among them, The cumulative interference received by the UAV from other users can be divided into main lobe interference and side lobe interference and respectively represent and The Laplace transform of, which is deduced as: where 2F1(a, b, c) is the Gaussian hypergeometric function; calculate the maximum transmission distance from the interfering user to the UAV η u is the received power threshold of the UAV, The Laplace transform of is expressed as: where, l min = H u (tan 2 (θ u / 2) + 1) 1 / 2 represents the minimum interference distance of the UAV sidelobe; For high-altitude links The connectivity is calculated as follows: Among them, γ s is the SINR threshold of the satellite; the distance between the UAV and the projection of the satellite on the air platform is represented by d us ; I us and I gs are the cumulative interferences of the UAV and the ground user on the satellite respectively. Express I us as: where \(l\) js represents the distance between the \(j\)-th UAV and the satellite, and \(\rho\) is the probability that the interfering UAV appears in the main lobe coverage area of satellite \(A\), s which is calculated as: where x is the number of drones that appear in the main lobe coverage area of the satellite For the ground user I gs Regarding the cumulative interference, the probability distribution function of the satellite received power is given as follows: wherein, is the average free space path loss of the interference signal; A I is represented as the interference region, and the cumulative interference I gs is expressed as: By adjusting the antenna beamwidth θ at the drone u′ and θ at the satellite s achieve 2. The security guarantee method for drone-assisted ground satellite communication according to claim 1, characterized in that The ground satellite communication network G2SN model with eavesdroppers in Step 1 consists of four parts: ground users, eavesdroppers, UAVs, and satellites. Ground users communicate with satellites through legitimate links. Eavesdroppers randomly appear around ground users and eavesdrop on the confidential information between ground users and satellites; In the G2SN model, ground users are distributed on the horizontal plane according to a homogeneous Poisson point process with density λ g and communicate with the satellite through legitimate links, and the satellite is located at a fixed height H s ; eavesdroppers randomly appear around ground users and eavesdrop on the confidential information between ground users and the satellite.

3. The security guarantee method for drone-assisted ground satellite communication according to claim 1, wherein The analysis of the four channel models including the ground link, low-altitude link, high-altitude link, and direct link based on the ground satellite communication network G2SN model with eavesdroppers in Step 2 includes: (1) Ground link / low-altitude link: The ground link refers to the transmission link between ground nodes; the ground link from the ground user to the eavesdropper is represented as g = {ge}, and the low-altitude link for transmission between ground nodes and the UAV swarm is represented as l = {gu,ue}; when both types of links suffer from path loss and Rayleigh fading, and the received power is expressed as: Among them, P g,l is the transmission power, l g,l represents the transmission distance between two nodes, h g,l is the channel coefficient that follows an exponential distribution with an average value of 1 / μ g,l , α g,l represents the path loss factor; G {g,u} is the gain of the transmitting antenna, G {e,u} is the gain of the receiving antenna; for all ground nodes equipped with omnidirectional antennas, set G g = G e = 1; the keyhole model is adopted to describe the directional antenna, and the antenna consists of a main lobe and a side lobe; for the UAV, the antenna gain G u in the low-altitude link is expressed as the main lobe reception / transmission and the side lobe reception / transmission The antenna gains of the main lobe and the side lobe are represented by G m and G b respectively, and follow the following relationship: where θ m represents the beam width of the main lobe, and the beam width of the combined side lobe / back lobe is 2π - θ m ; (2) High-altitude link: The high-altitude link refers to the transmission link between the UAV and the satellite. The high-altitude link is hardly affected by obstacles; the signal is only affected by path loss, and the satellite received power is expressed as: Among them, P us is the transmission power of the UAV, G u is the transmitting antenna gain of the UAV, G s is the receiving antenna gain of the satellite; l us represents the distance between the UAV and the satellite, α us is the path loss factor; (3) Direct link: The transmission link between the legitimate ground user and the satellite is described as the direct link, represented as d = {gs}; the direct link is described as the link from GU3 and GU5 to the satellite, and the independent and identically distributed Shadowed-Rician fading is used to simulate the direct link, and the power received by the satellite is: where l d is the distance of the direct link, and α d = 2 represents the instantaneous free space loss; h d is the channel coefficient; since the parameter m for the fading severity is an arbitrary integer in the range [0, ∞), the probability density function of h d is expressed as: where, Ω and 2ρ respectively represent the average power of the line-of-sight link and the multipath component; 1F1(a,b,c) is a confluent hypergeometric function, rewritten as:

4. A security guarantee system for unmanned aerial vehicle (UAV)-assisted ground satellite communication applying the security guarantee method for UAV-assisted ground satellite communication according to any one of claims 1 to 3, characterized in that, The security guarantee system for the UAV-assisted ground satellite communication includes: A G2SN model construction module for constructing a ground satellite communication network G2SN model with eavesdroppers; A channel model analysis module for analyzing four channel models including the ground link, low-altitude link, high-altitude link, and direct link based on the ground satellite communication network G2SN model with eavesdroppers; A security performance analysis module, which is used to analyze the security performance of G2SN under the air-assisted scheme by using the eavesdropping probability as an index to measure the eavesdropping risk in G2SN; A reliability performance analysis module, which is used to analyze the reliability performance of G2SN under the air-assisted scheme by introducing link connectivity as an index to evaluate transmission reliability.

5. A computer device, characterized in that, The computer device includes a memory and a processor. When the computer program stored in the memory is executed by the processor, the processor is caused to execute the steps of the security guarantee method for unmanned aerial vehicle-assisted ground satellite communication according to any one of claims 1 to 3.

6. A computer-readable storage medium stores a computer program. When the computer program is executed by a processor, the processor is caused to execute the steps of the security guarantee method for unmanned aerial vehicle-assisted ground satellite communication according to any one of claims 1 to 3.

7. An information data processing terminal, characterized in that, The information data processing terminal is used to implement the security guarantee system for unmanned aerial vehicle-assisted ground satellite communication according to claim 4.

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