Untrusted uav-assisted wireless secure covert communication method and system

Abstract

The application discloses an untrusted unmanned aerial vehicle (UAV) assisted wireless secure covert communication system and method. In the system, a source node wants to send secret information to a destination node, and a UAV relay serves as an auxiliary node between the source node and the destination node. The UAV relay is located in the sky at a height of H. The source node sends secret information to the destination node, and the sending includes first-hop transmission and second-hop transmission. In the first-hop transmission, an untrusted UAV is considered, the UAV forwards a message while stealing the secret message, an interference signal is continuously sent by the destination node, a safety constraint condition is calculated to adjust the height of the UAV. In the second-hop transmission, a detector judges whether transmission exists by detecting the transmission power of the UAV, and the destination node sends an interference signal to interfere with the detector and the UAV relay. When the untrusted UAV is used as a relay node to assist transmission, a security problem is caused. The safety constraint and the security constraint are used to improve the performance of the system, and the safety and the concealment required in the system transmission are met.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of wireless communication, and particularly relates to a method and system for wireless secure covert communication assisted by an untrusted unmanned aerial vehicle. BACKGROUND

[0002] In the past few decades, with the increasing demand for communication, modern communication technology has undergone several generations of innovation and development, greatly changing the way people communicate and largely alleviating people's demand for communication. Among them, wireless communication technology has developed rapidly in recent years. However, due to the broadcast nature of the wireless communication channel itself, environmental complexity and user random mobility, future wireless communication faces great challenges in improving communication reliability and data throughput. Therefore, for wireless communication networks, it is urgent to study reliable security enhancement mechanisms.

[0003] At present, the security scheme of various wireless communication networks still follows the high-layer encryption mechanism adopted by traditional wireless networks. Whether it is a cellular wireless network or other wireless communication networks, there are still many problems to be solved in the security of the information in communication, while wireless communication has unique advantages in physical layer security. Its channel characteristics and security mechanisms improve the reliability of information transmission, and cooperative and relay technologies can also enhance the physical layer security performance. However, the above technologies are often used to protect information from being stolen, and the transmission behavior itself has the risk of exposure.

[0004] The purpose of wireless covert communication is to prevent detection by the detector in a wireless transmission environment. Its main goal is to achieve the confidentiality, concealment and anti-interference of communication. Through the realization of the above goals, wireless covert communication can protect privacy, protect sensitive information, prevent eavesdropping and attacks. Common covert wireless communication models are shown in Figure 1 Figure 1 ​The model shown is a covert communication model in one-hop transmission, the source node sends information to the destination node, and a detector passively detects whether the source node has a communication behavior. The purpose of covert communication is to hide the communication behavior while maximizing the transmission rate. In existing covert communication research, it mainly includes single-hop relay system and two-hop relay system. The current covert communication research mostly analyzes the covert performance in various communication scenarios of single-hop and two-hop, including different channels, different noises, different power constraints, and different relays, and the covert performance includes maximizing the covert rate, minimizing the interruption probability, and maximizing the transmission power. For a fixed node system, there are certain limitations in deployment and power allocation. Therefore, in recent covert communication research, unmanned aerial vehicle nodes have been introduced, such as unmanned aerial vehicles as source nodes, relay nodes, destination nodes or detectors, and the performance of covert communication has been analyzed. However, the current covert communication research has not considered the case of using an untrusted unmanned aerial vehicle as a relay to assist transmission. In practical applications, users may use public unmanned aerial vehicles as relay nodes to serve them, and if the unmanned aerial vehicles themselves are untrusted, there will be a risk of leaking secret information. SUMMARY

[0005] In order to solve the problems in the prior art, the present application provides a wireless secure covert communication method and system assisted by an untrusted unmanned aerial vehicle, which uses an untrusted unmanned aerial vehicle relay and a full-duplex receiver as a destination node, effectively improves the covert communication rate and security of the system under the premise of meeting the covert constraint and security constraint.

[0006] In order to achieve the above purpose, the technical scheme adopted by the present application is: a wireless secure covert communication system assisted by an untrusted unmanned aerial vehicle, comprising a source node, an unmanned aerial vehicle relay, a destination node and a detector, the source node wants to send secret information to the destination node, the unmanned aerial vehicle relay serves as an auxiliary node between the source node and the destination node, the unmanned aerial vehicle relay is located in the sky at a height of H, the source node sends secret information to the destination node, the sending includes first-hop transmission and second-hop transmission; in the first-hop transmission, an untrusted unmanned aerial vehicle is considered, which forwards messages while stealing secret messages, the destination node continuously sends interference signals, and the height of the unmanned aerial vehicle is adjusted by calculating the security constraint condition; in the second-hop transmission, the detector judges whether the transmission exists by detecting the transmission power of the unmanned aerial vehicle, and the destination node sends interference signals to interfere with the detector and the unmanned aerial vehicle relay.

[0007] Further, the wireless channel in the system includes a data link, a detection link and an interference link, all of which use quasi-static Rayleigh fading to model the wireless channel, and the channel coefficient is constant in a time slot and changes independently between different time slots.

[0008] Further, in the communication process, the UAV relay provides a LOS link for the ground device; the channel between the destination node and the detector and the channel of the destination node itself are h bw and h bb , respectively, and the probability density function of h bw is: The channel noises used are all additive white Gaussian noises subject to It is assumed that the UAV relay knows h ua , h ub , and h uw , the destination node only knows h ub , and the detector only knows h uw .

[0009] Further, in the first stage, if the source node transmits covert information, the second stage is entered, and the UAV relay forwards a linearly scaled version of the information to the destination node, the linearly scaled version being a scalar G, and the value of G is determined according to a power constraint; the detector determines whether the source node transmits secret information by analyzing the forwarding signal of the UAV relay.

[0010] Further, the probability of error in the judgment of the detector on whether the source node transmits covert information is the sum of the false alarm probability P FA and the missed detection probability P MD ; the detector uses binary hypothesis testing to determine whether the source node transmits covert information, the false alarm probability being that the detector determines that covert transmission exists, actually it does not, and the missed detection probability being that the detector determines that covert transmission does not exist, actually it does, and the total test error probability of the detector is:

[0011]

[0012] The optimal detection threshold γ * of the detector is:

[0013]

[0014] The corresponding minimum detection error probability is:

[0015] .

[0016] Further, the covert constraint is:

[0017]

[0018] Substituting the value of ζ * , the range of the hovering height of the UAV can be obtained:

[0019]

[0020] where ζ *is the minimum detection error probability of the detector, ε is the concealment requirement value, H is the hovering height of the UAV relay, P u is the transmission power at the UAV relay, β is the wireless channel gain when the reference distance is 1 m, P J is the transmission power of the interference signal at the destination node, d w is the horizontal distance difference between the UAV relay and the detector.

[0021] Further, the difference between the channel rate C b stolen by the UAV relay and the channel rate C u at the receiving point destination node is defined as the safety rate C s , and a safety rate threshold R s is preset, when the safety rate C s is less than the preset threshold R s , the required safety rate is not reached, the transmission is immediately interrupted, and the safety rate of the entire transmission is as follows:

[0022]

[0023] wherein,

[0024]

[0025] is the symbol used to simplify C s , C s is the safety rate, C b is the receiving channel rate at the destination node, C u is the signal rate stolen by the UAV relay, P u is the transmission power at the UAV relay, P a is the transmission power at the source node, β is the wireless channel gain when the reference distance is 1 m, is the noise variance at the destination node, H is the hovering height of the UAV relay, is the noise variance at the UAV relay, d b is the horizontal distance difference between the UAV relay and the destination node, d a is the horizontal distance difference between the UAV relay and the source node, P J is the transmission power of the interference signal at the destination node,

[0026] The flight height of the UAV is controlled, and the hovering height H is in the range of: wherein, represents the highest hovering height of the UAV that meets the safety constraint condition.

[0027] Further, based on the safety constraint and the concealment constraint, the optimization problem of the system safety concealment rate is represented as:

[0028]

[0029] Among them, R b ζ is the received signal rate at the destination node. * P is the minimum probability of error in the tester, ε is the concealment requirement, and P is the minimum probability of error in the tester. u β is the transmit power at the UAV relay point, β is the channel gain when the UAV channel reference distance is 1m, and P is the transmit power at the UAV relay point. J It is the transmitted power of the interference signal at the destination node, d w P is the horizontal distance difference between the drone relay and the detector, H is the hovering height of the drone relay, H' is the maximum hovering height of the drone when the safety constraints are met, and P is the horizontal distance difference between the drone relay and the detector. max It is the maximum transmission power.

[0030] The maximum secure and covert transmission rate is obtained by solving the optimization problem using stochastic gradient descent.

[0031] This invention also provides a method for secure and covert wireless communication assisted by an untrusted drone. A source node sends secret information to a destination node, the transmission including a first-hop transmission and a second-hop transmission. In the first-hop transmission, an untrusted drone is considered, which steals the secret information while forwarding the message. The destination node continuously emits interference signals, and the drone's altitude is adjusted by calculating security constraints. In the second-hop transmission, a detector determines the existence of the transmission by detecting the drone's transmission power. The destination node emits interference signals to interfere with the detector and the drone relay. The drone relay hovering height... The scope is: ,in, The maximum hovering altitude of the UAV under the given safety constraints is represented by the maximum safe and covert transmission rate, which is obtained by solving an optimization problem:

[0032]

[0033] Among them, R b ζ is the received signal rate at the destination node. * P is the minimum probability of error in the tester, ε is the concealment requirement, and P is the minimum probability of error in the tester. u β is the transmit power at the UAV relay point, β is the channel gain when the UAV channel reference distance is 1m, and P is the transmit power at the UAV relay point. J It is the transmitted power of the interference signal at the destination node, d w P is the horizontal distance difference between the drone relay and the detector, H is the hovering height of the drone relay, H' is the maximum hovering height of the drone when the safety constraints are met, and P is the horizontal distance difference between the drone relay and the detector. max That is the maximum transmission power.

[0034] Compared with the prior art, the present application has at least the following beneficial effects: the present application ingeniously uses the security problem caused by the untrusted unmanned aerial vehicle as a relay node to assist transmission in a covert communication system, uses covert constraints and security constraints to improve the performance of the system, can maximize the interference of untrusted unmanned aerial vehicles and detectors, and meets the required security and concealment in system transmission. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 is a schematic diagram of a conventional covert communication model;

[0036] Figure 2 is a schematic diagram of a covert communication model of the present application;

[0037] Figure 3 is the change range of the total detection error probability of Willie with the detection threshold γ under different UAV transmission powers Pu;

[0038] Figure 4 is the maximum safe covert rate R b with the unmanned aerial vehicle hovering height H;

[0039] Figure 5 is the change of the covert rate of the system with the hovering height;

[0040] Figure 6 is the maximum safe covert rate R b with the change of the covert requirement ε. DETAILED DESCRIPTION

[0041] The present application provides a wireless secure covert communication system assisted by an untrusted unmanned aerial vehicle, comprising four roles of a source node, an unmanned aerial vehicle, a destination node and a detector, wherein the source node wants to send secret information to the destination node, but the distance between the two nodes is far, and the unmanned aerial vehicle is needed to assist in forwarding information. In the first hop transmission, an untrusted unmanned aerial vehicle is considered, which steals secret messages while forwarding messages. In order to solve this problem, the destination node continuously sends interference signals, and the height of the unmanned aerial vehicle is adjusted by calculating the security constraint condition, so as to ensure the security of the message in the transmission process. In the second hop transmission, the detector judges whether the transmission exists by detecting the transmission power of the unmanned aerial vehicle. In order to realize covert communication, the interference signal sent by the destination node is used to confuse the detector. For the above-mentioned scene, a theoretical model is constructed, the performance index is analyzed, and under the conditions of covert constraint and security constraint, the transmission power of the source node and the unmanned aerial vehicle is controlled and the hovering height of the unmanned aerial vehicle is adjusted, so that the safe covert rate is maximized. The simulation technology is used to verify the theoretical model, and the effectiveness of the wireless secure covert communication method and system assisted by the untrusted unmanned aerial vehicle of the present application is confirmed.

[0042] Fixed relay is located at a fixed node in the network, used for receiving and forwarding data, which plays a role in forwarding source node information, expanding the transmission range of the source node, saving the transmission resources of the source node, etc. in covert communication. However, the UAV can further improve the performance of covert communication due to its flexibility and rapid deployment. As a step forward in this direction, the present application explores the problem of secure covert communication assisted by an untrusted UAV, and constructs a model for maximizing the covert rate in a UAV relay system, as follows:

[0043] 1. A wireless two-hop transmission system composed of a source node, an untrusted UAV, a destination node and a detector is constructed, and the untrusted UAV is selected as the relay, and a full-duplex receiver is used as the destination node to ensure the security and security of the system.

[0044] 2. By designing a cooperative interference communication scheme, the optimal detection threshold of the detector γ * , the minimum detection error probability ζ * and the secure transmission rate Cs are analyzed under the condition that the detector is interfered by the interference signal transmitted by the destination node.

[0045] 3. According to the detection error probability of the detector and the security rate, two constraints, i.e. covert constraint and security constraint, are given, and under the given covert constraint and security constraint, the transmission power and the hovering height of the UAV are optimized, and the security covert rate of the whole system is explored by effective numerical search.

[0046] 4. The performance indicators obtained by simulation are analyzed, and the theoretical model is verified, which shows that the secure covert transmission performance in the untrusted UAV assisted transmission system as a relay.

[0047] The specific system model is described as follows:

[0048] 1. Communication scenario, reference Figure 2 The covert communication scenario model constructed by the present application includes a source node Alice, a UAV relay UAV, a destination node Bob and a detector Willie. The UAV is located at an altitude of H, and H is not fixed, and the rest of the devices are located on the ground. First, Alice intends to send secret information to Bob with the assistance of UAV relay, but there is a risk of UAV stealing secret information, UAV amplifies and forwards the received signal, while Willie tries to detect whether Alice has sent information by analyzing the transmission power of UAV, and Bob transmits interference signals to interfere with UAV and Willie while receiving signals. The transmission power of Alice P a and the transmission power of UAV P uNone of them can exceed the maximum power limit P max .

[0049] 2. Channel model, in this communication model, the channel has three uses, respectively, data link, detection link and interference link, all use quasi-static Rayleigh fading to model wireless channel, assuming that the channel coefficient is constant in a time slot, and changes independently between different time slots. In the communication process, UAV provides LOS link for ground equipment, so the channel fading coefficient from UAV to ground equipment can be expressed as h ui (i = a, w, b), the expression is as follows:

[0050]

[0051] Where, β represents the channel power gain when the reference distance is 1m, |h ui | 2 The channel between Bob and Willie and the channel of Bob himself are defined as h bw and h bb , respectively. The probability density function of h bw The channel noise we use is all additive white Gaussian noise obeying We assume that UAV knows h ua , h ub , h uw , Bob only knows h ub , and Willie only knows h uw .

[0052] 3. Communication process, the first stage of covert information transmission, that is, whether Alice sends covert information, if it sends covert information, then enter the second stage, that is, UAV forwards the linear scaled version of the received information to Bob, the linear scaled version takes G as a scalar, and the value of G is determined according to the power constraint. The detector Willie judges whether Alice sends secret information by analyzing the forwarding signal of UAV. In order to confuse Willie's detection, we use one of Bob's antennas to transmit interference information to achieve the purpose of transmitting covert information.

[0053] 4. Performance index,

[0054] (1) Willie's detection error probability, that is, the probability that Willie makes a wrong judgment on whether Alice transmits covert information, is equal to the false alarm probability P FA and the missed detection probability P MD ​The sum of the probabilities of false alarm and missed detection. Here, false alarm means that Willie decides H1 (Alice sent information), but in fact it is H0 (Alice did not send information). Missed detection means that Willie decides H0, but in fact it is H1.

[0055] (2) The secure covert rate, defined as the maximum transmission rate of the whole system under the realization of security and covertness.

[0056] The system performance analysis is as follows:

[0057] 1. Willie's detection mechanism, Willie makes a judgment on whether Alice sends covert information according to the received signal sent by UAV. Willie uses binary hypothesis testing, and uses zero hypothesis H0 to represent that Willie judges that Alice does not send information, and uses alternative hypothesis H1 to represent that Willie judges that Alice sends information. Two kinds of detection error probability, false alarm probability and missed detection probability. False alarm probability refers to the fact that Willie judges that there is covert transmission, but in fact there is no, and missed detection probability refers to the fact that Willie judges that there is no covert transmission, but in fact there is.

[0058] Based on the defined hypothesis, Willie receives the signal y W (i) is given by:

[0059]

[0060] Assuming different, the received signal is also different. Among them, PJ is the power of the interference signal xJ(i) sent by Bob, Pu is the power of the signal xu(i) forwarded by UAV, and nw(i) is the additive white Gaussian noise near Willie obeying the distribution .

[0061] The detection statistic of Willie, i.e. the average received power, is as follows:

[0062]

[0063] In order to minimize the total detection error probability of Willie, according to the Neyman-Pearson criterion, the optimal decision rule is:

[0064]

[0065] D0 and D1 represent the decisions made by Willie under the conditions that hypotheses H0 and H1 are true, respectively. γ is the detection threshold.

[0066] Therefore, the false alarm probability P FA and the missed detection probability P MD are:

[0067] Substitute the average received power of Willie into the above equation, the expressions of two detection error probabilities are as follows:

[0068]

[0069]

[0070] where, .

[0071] Thus, the total detection error probability of Willie is:

[0072]

[0073] When , the change range of ζ is not clear, so the first derivative is taken, and the first derivative is:

[0074]

[0075] The second derivative is:

[0076]

[0077] Therefore, the optimal detection threshold γ * of Willie is:

[0078]

[0079] The corresponding minimum detection error probability is:

[0080]

[0081] 2. Concealment performance constraint

[0082] According to the analysis of the detection performance of Willie, the concealment constraint is:

[0083]

[0084] Substitute the value of ζ * , the range of the hovering height of the UAV is:

[0085]

[0086] where, ζ * is the minimum detection error probability of Willie, ε is the concealment requirement value, H is the hovering height of the UAV, P u is the transmission power at the UAV, β is the wireless channel gain when the reference distance is 1 m, P J is the transmission power of the interference signal at Bob, dw is the horizontal distance difference between the UAV and Willie.

[0087] 3. Security constraint

[0088] In addition to the concealment constraint, the present application also defines a security constraint, which is the transmission security between the UAV and Bob. The channel rate C b at the receiving point Bob is defined as the difference between the signal rate C u stolen by the UAV and the signal rate C s stealed by Bob, and is defined as the security rate C s , and a security rate threshold R s is preset. When the security rate C s is less than the preset threshold R u , the required security rate is not reached, and the transmission is immediately interrupted.

[0089] According to the received signal y u (i) of the UAV, the received signal-to-noise ratio at the UAV is obtained as follows:

[0090]

[0091] The corresponding channel rate is:

[0092]

[0093] And the received signal y b (i) at Bob after self-interference filtering is represented as follows:

[0094]

[0095] Therefore, the received signal-to-noise ratio at Bob is obtained as follows:

[0096]

[0097] The corresponding channel rate is:

[0098]

[0099] Therefore, the security rate of the entire transmission is obtained as follows:

[0100]

[0101] Wherein,

[0102]

[0103] Since the safe transmission is defined as for a given safe transmission rate Rs, the transmission stops immediately when Cs < Rs, the required safe rate cannot be achieved. Therefore, it is necessary to control the flight height of the UAV to ensure transmission safety. Substituting the expression of Cs into, the range of hovering height is: wherein, represents the highest hovering height of the UAV that satisfies the safety constraint.

[0104] 4. Maximize the concealment rate

[0105] The object of the present application is to maximize the safe concealment transmission rate R b According to the two constraints, the optimization problem of the system safe concealment rate can be expressed as:

[0106]

[0107] Using the stochastic gradient descent to solve the optimization problem, the maximum safe concealment transmission rate can be obtained.

Claims

1. An untrusted unmanned aerial vehicle (UAV) assisted wireless secure covert communication system, comprising: The system includes a source node, a drone relay, a destination node, and a detector. The source node wants to send secret information to the destination node. The drone relay acts as an auxiliary node between the source and destination nodes, and is located at an altitude of H. The source node sends secret information to the destination node, and the sending includes a first-hop transmission and a second-hop transmission. In the first-hop transmission, there is an untrusted drone that steals the secret information while forwarding the message. It uses the destination node to continuously emit interference signals and adjusts the drone's altitude by calculating security constraints. In the second hop transmission, the detector judges whether the transmission exists by detecting the transmission power of the UAV, and the destination node sends an interference signal to interfere with the detector and the UAV relay; the wireless channel in the system includes a data link, a detection link and an interference link, all of which use quasi-static Rayleigh fading to model the wireless channel, and the channel coefficient is constant in a time slot and changes independently between different time slots; the false alarm probability P FA and the missed detection probability P MD of the detector for judging whether the source node transmits covert information; the detector uses binary hypothesis testing to judge whether the source node transmits covert information, the false alarm probability refers to that the detector judges that there is covert transmission, but in fact there is not, and the missed detection probability refers to that the detector judges that there is no covert transmission, but in fact there is, and the total test error probability of the detector is: in, The detection power threshold for the detector. , optimal detection threshold γ at the detector * is: The corresponding minimum detection error probability is: ； The hidden constraints are: Substituting the value of ζ * gives the range of hovering height of the UAV: wherein ζ * is the minimum detection error probability of the detector, ε is the concealment requirement value, H is the hovering height of the UAV relay, P u is the transmission power at the UAV relay, β is the channel gain when the reference distance of the UAV channel is 1 m, P J is the transmission power of the interference signal at the destination node, d w is the horizontal distance difference between the UAV relay and the detector. Channel rate C at the destination node of the receiving point b The difference between the signal rate C stolen by the UAV relay u The safety rate C is defined as s And a safety rate threshold R is preset s When the safety rate C s Is less than the set threshold R s Then the required safety rate is not reached, the transmission is immediately interrupted, and the safety rate of the whole transmission is as follows: in, It is used to simplify C s The symbol used, C s It is a safe speed, C b C is the received channel rate at the destination node. u It is the signal rate stolen by the drone relay, P a It is the transmit power at the source node. It is the noise variance at the destination node. It is the noise variance at the drone relay point, d b It is the horizontal distance difference between the UAV relay and the target node, d a It is the difference in horizontal distance between the drone relay and the source node. Controlling the drone's flight altitude and hovering altitude The scope is: ,in, This indicates the maximum hovering altitude of the drone under the condition of meeting safety constraints.

2. The untrusted drone-assisted wireless secure covert communication system according to claim 1, characterized in that, During communication, the UAV relay provides a LOS link to the ground equipment; the channel between the destination node and the detector, and the channel within the destination node itself, are h and h, respectively. bw and h bb h bw The probability density function is: All channel noise used is subject to Additive white Gaussian noise, assuming the UAV relay knows h ua h ub h uw The destination node only knows h ub The tester only knows h uw .

3. The untrusted drone-assisted wireless secure covert communication system according to claim 1, characterized in that, In the first stage, if the source node sends covert information, the second stage begins. The UAV relay forwards a linearly scaled version of the received information to the destination node. The linearly scaled version uses G as a scalar, and the value of G is determined based on power constraints. The detector determines whether the source node sent secret information by analyzing the forwarding signal of the UAV relay.

4. The untrusted drone-assisted wireless secure covert communication system according to claim 1, characterized in that, Based on security and concealment constraints, the optimization problem of the system's security concealment rate is expressed as: where R is the received signal rate at the destination node, P is the maximum transmission power, and b is the maximum transmission power, max is the maximum transmission power, The maximum secure and covert transmission rate is obtained by solving the optimization problem using stochastic gradient descent.

5. A method for secure and covert wireless communication assisted by an untrusted unmanned aerial vehicle (UAV), characterized in that, The source node sends secret information to the destination node. The sending includes a first hop transmission and a second hop transmission. In the first hop transmission, consider an untrusted drone that steals the secret information while forwarding the message. It uses the destination node to continuously send interference signals and adjusts the drone's altitude by calculating security constraints. In the second-hop transmission, the detector judges whether the transmission exists by detecting the transmission power of the UAV, and the destination node sends an interference signal to interfere with the detector and the UAV relay; the wireless channel includes a data link, a detection link and an interference link, all of which use quasi-static Rayleigh fading to model the wireless channel, and the channel coefficients are constant in a time slot and change independently between different time slots; the false alarm probability P FA and the missed detection probability P MD sum up the total error probability of the detector's test: in, The detection power threshold for the detector. optimal detection threshold γ at the detector * is: The corresponding minimum detection error probability is: ； Drone relay hovering altitude The scope is: ,in, The maximum hovering altitude of the UAV under the given safety constraints is represented by the maximum safe and covert transmission rate, which is obtained by solving an optimization problem: wherein R b is the received signal rate at the destination node, ζ * is the minimum inspection error probability of the detector, ε is the concealment requirement value, P u is the transmission power at the UAV relay, β is the channel gain when the channel reference distance of the UAV is 1 m, P J is the transmission power of the interference signal at the destination node, d w is the horizontal distance difference between the UAV relay and the detector, H is the hovering height of the UAV relay, P max is the maximum transmission power; The hidden constraints are: Substituting the value of ζ * gives the range of hovering heights of the UAV: Channel rate C at the destination node of the receiving point b The signal rate C stolen by the drone relay u The difference is defined as the safe rate C. s And a safe rate threshold R is preset. s When the safe rate C s Less than the set threshold R s If the required safe transmission rate is not met, the transmission is immediately interrupted. The safe transmission rate for the entire transmission is as follows: in, It is used to simplify C s The symbol used, C s It is a safe speed, C b C is the received channel rate at the destination node. u It is the signal rate stolen by the drone relay, P a It is the transmit power at the source node. It is the noise variance at the destination node. It is the noise variance at the drone relay point, d b It is the horizontal distance difference between the UAV relay and the target node, d a It is the difference in horizontal distance between the drone relay and the source node.

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