Mobile covert communication system and method based on mobility and noise uncertainty

Abstract

The embodiment of the invention discloses a mobile covert communication system and method based on mobility and noise uncertainty. The system comprises a signal sender, a signal receiver and a monitoring party, the signal sending party and the monitoring party are provided with single antennas, the receiving party is provided with double antennas, and the signal sending party is used for randomly sending signals in the process of moving along a circular track at a constant speed; the signal receiver is used for receiving a signal in a static state and sending artificial noise of which the power is randomly changed at the same time; the monitoring party is used for detecting whether a communication transmission process exists between the signal sending party and the signal receiving party or not in a static state; the link between the signal sender and the signal receiver is a legal communication link, the link between the signal sender and the monitoring party is a detection link, and the link between the signal receiver and the monitoring party is an interference link.

Description

Technical Field

[0001] The present invention relates to the field of wireless communication technology, and in particular to a mobile covert communication system and method based on mobility and noise uncertainty. Background Art

[0002] Covert communication technology is a technology that can hide the existence of communication. This technology can use some technical means, such as collaborative interference, power control, random transmission, etc., to conceal the communication transmission process from potential malicious eavesdroppers, so as to ensure communication security.

[0003] Traditional wireless communication security methods such as cryptography technology and physical layer security transmission can only ensure that the transmission content is not stolen to a certain extent. However, with current wireless security transmission, once the transmission process is exposed, eavesdroppers can locate or conduct directional interference attacks through signals, causing the sender's location to be exposed or affecting the performance of secure transmission. Covert communication technology can hide the communication transmission process to address this problem, making the communication process undetectable by monitors, thereby providing a higher level of security.

[0004] Currently, a large number of covert communication studies are devoted to realizing positive rate covert transmission. The main method used is to use the inherent or artificial uncertainty of the system, such as noise uncertainty, channel uncertainty, time uncertainty, etc., to reduce the detection performance of the listener, thereby improving the covert communication performance. However, current research in this field focuses on the realization of covert communication between static nodes, that is, the communication nodes remain stationary during the communication process.

[0005] In fact, in actual scenarios, there are a large number of dynamic communication nodes, such as vehicle-to-vehicle communication, satellite-to-ground communication, vehicle-to-base station communication, etc., and the node mobility will cause changes in the channel model, distance, connectivity, etc. between nodes. These factors make the existing covert communication schemes unsuitable for covert transmission of mobile nodes. In the current research field, covert transmission schemes suitable for mobile nodes have not been studied. Summary of the invention

[0006] Based on this, it is necessary to propose a mobile covert communication system and method based on mobility and noise uncertainty to address the above problems.

[0007] The embodiment of the present invention provides a mobile covert communication system based on mobility and noise uncertainty, the system comprising: a signal sender, a signal receiver and a monitor;

[0008] The signal transmitter and the monitoring party are equipped with a single antenna, and the receiving party is equipped with a dual antenna;

[0009] The signal sender is used to randomly send signals in the process of moving at a uniform speed along a circular trajectory in full-duplex mode;

[0010] The signal receiver is used to receive the signal in a stationary state and send artificial noise with randomly changing power at the same time;

[0011] The monitoring party is used to detect whether there is a communication transmission process between the signal sender and the signal receiver in a static state;

[0012] The link between the signal sender and the signal receiver is a legitimate communication link, the link between the signal sender and the monitoring party is a detection link, and the link between the signal receiver and the monitoring party is an interference link.

[0013] In the above scheme, the signal receiver models the self-interference signal as having a mean of 0 and a variance of γ while receiving the signal. RSI A Gaussian distributed random variable.

[0014] In the above scheme, the moving trajectory of the signal sender is a circle, with an arbitrary point as the center and R as the radius, where R has a maximum value R_max.

[0015] In the above scheme, the artificial noise is sent by the signal receiver with randomly changing power, the power distribution is uniform, and the maximum value is P_max.

[0016] In the above scheme, the communication link channels between nodes are modeled using a double Rayleigh fading channel model, and the channel coefficients remain unchanged within a time slot and change randomly between time slots.

[0017] The embodiment of the present invention also provides a method for utilizing a mobile covert communication system based on mobility and noise uncertainty, comprising the following steps:

[0018] The signal sender moves along a fixed track and sends a covert signal;

[0019] The signal receiver sends artificial noise with randomly varying power while receiving the signal;

[0020] The monitoring party detects whether there is a communication transmission process by an energy detection method;

[0021] The covert communication performance is analyzed and optimized according to the detection results of the monitoring party to maximize the average covert transmission rate.

[0022] In the above scheme, the monitoring party detects whether there is a communication transmission process through an energy detection method, which specifically includes: the monitoring party continuously collects the received signals and calculates the average value Y of the energy of the received signals in each time slot w , using a binary hypothesis test to compare it with a pre-set threshold γ; if Yw <γ, indicating that there is no covert transmission between the signal sender and the signal receiver, represented by H0; if Y w >γ, indicating that there is covert transmission between the signal sender and the signal receiver, represented by H1;

[0023] According to the average value Y of the received signal energy in each time slot w Determine the false alarm probability and missed detection probability;

[0024] When the probability of the signal sending party sending or not sending information to the signal receiving party is equal, determining the detection error probability at the monitoring party according to the false alarm probability and the missed detection probability;

[0025] Determining an optimal detection threshold and a minimum detection error probability of the monitoring party;

[0026] An average minimum detection error probability of the monitoring party is determined.

[0027] In the above scheme, the average value Y of the received signal energy in each time slot is calculated w , specifically including: the kth signal y received by the monitoring party in a time slot w [k] is represented by:

[0028] where v b [k] is the artificial noise sent by the signal receiver, x a [k] is the signal sent by the signal sender, which satisfies Where k = 1, 2, ... n, which indicates the sequence number of the kth signal received by the monitoring party in a time slot. Yes b The conjugate of [k], is x a [k] conjugate, E() represents the mathematical expectation operation; P a is the signal transmission power of the signal sender, P b is the artificial noise transmission power of the signal receiver, γ is the path loss index; n w [k] is the ambient noise at the monitoring location;

[0029] according to Determine the mean value Y w ; where D1 and D0 represent the decisions of receiving H1 and H0 respectively.

[0030] In the above scheme, the average value Y of the energy of the received signal in each time slot is w Determine the false alarm probability and missed detection probability, including: Determine the false alarm probability, where

[0031] according to Determine the probability of missed detection, where d bw is the distance between the signal receiving party and the monitoring party and is known by the monitoring party.

[0032] In the above solution, the determination of the average minimum detection error probability of the monitoring party specifically includes: Determine, among which

[0033] The embodiments of the present invention have the following beneficial effects:

[0034] The mobile covert communication system of the present invention enables the signal sender to send signals while moving, and utilizes the full-duplex receiver to send artificial noise while receiving the signal to introduce uncertainty, and utilizes the node mobility and interference uncertainty to interfere with the signal detection performance of the monitor, thereby achieving a covert transmission rate greater than zero while satisfying the concealment constraint. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0036] in:

[0037] Figure 1 A network model diagram of a mobile covert communication system constructed for the present invention;

[0038] Figure 2 is a performance analysis flow chart of the present invention;

[0039] Figure 3 It is a flow chart of the detection error probability calculation in the present invention;

[0040] Figure 4 is a flow chart for calculating the average concealed transmission rate in the present invention;

[0041] Figure 5 is a relationship diagram between the detection error probability and the moving trajectory radius in the present invention;

[0042] Figure 6 is a relationship diagram between the transmission interruption probability and the moving trajectory radius in the present invention;

[0043] Figure 7 This is a relationship diagram between the concealed transmission rate and the maximum power of the interference signal in the present invention. DETAILED DESCRIPTION

[0044] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0045] Example 1

[0046] The embodiment of the present invention provides a mobile covert communication system based on mobility and noise uncertainty, such as Figure 1 As shown, the system includes: a signal sender, a signal receiver and a monitor;

[0047] The signal transmitter and the monitoring party are equipped with a single antenna, and the receiving party is equipped with a dual antenna;

[0048] The signal sender is used to randomly send signals in the process of moving at a uniform speed along a circular trajectory in full-duplex mode;

[0049] The signal receiver is used to receive the signal in a stationary state and send artificial noise with randomly changing power at the same time;

[0050] The monitoring party is used to detect whether there is a communication transmission process between the signal sender and the signal receiver in a static state;

[0051] The link between the signal sender and the signal receiver is a legitimate communication link, the link between the signal sender and the monitoring party is a detection link, and the link between the signal receiver and the monitoring party is an interference link.

[0052] In the present invention, the communication link channels between all nodes are modeled using a double Rayleigh fading channel model, and the channel coefficient remains unchanged within a time slot and changes randomly between time slots. The channel coefficient between node i and node j can be expressed as h ij , where i∈{a,b}, j∈{b,w}; a, b, w represent the signal sender, signal receiver and monitoring party respectively.

[0053] Since all communication link channels are modeled as double Rayleigh fading channels, |h ij | 2 The probability density function (PDF) of can be expressed as:

[0054]

[0055] Where K0 is the zero-order modified Bessel function of the second kind.

[0056] In the present invention, it is assumed that the monitoring party knows the instantaneous channel state information of its link, that is, h aw and h bw , and the signal sender and the signal receiver know the channel distribution information (Channel Distribution Information, CDI) of their respective channels; the environmental noise n at the node signal receiver and the monitoring party b 、n w They have a mean of zero and a variance of Gaussian white noise, that is

[0057] The received signal y at the kth time slot at the signal receiver b [k] can be expressed by the following formula:

[0058]

[0059] Among them I b is the self-interference signal at the signal receiving end. The present invention adopts the self-interference elimination technology at the signal receiving end. Therefore, the self-interference signal can be modeled as having a mean of 0 and a variance of γ RSI Gaussian distributed random variable, that is, I b ~CN(0,γ RSI ),and is the self-interference elimination coefficient.

[0060] In addition, P a , P b are the signal transmission powers of the signal sender and the signal receiver respectively, where P a is a fixed value and is known by other nodes, P b is a random variable with parameters The uniform distribution of can change randomly between different time slots, and its probability density function is:

[0061]

[0062] Due to the performance limitation of the equipment, the signal transmission power of the signal receiver has a maximum value Ω, that is,

[0063] In addition, the monitoring party knows the signal transmission power P of the signal receiving party b The distribution and probability density function of , but its exact value is unknown.

[0064] In addition, in formula (2), x a[k] is the signal sent by the signal sender, satisfying Where k = 1, 2, ... n, which indicates the sequence number of the kth signal received by the signal receiver in a time slot. is x a [k] conjugate, E() represents the mathematical expectation operation, γ is the path loss index, n b [k] is the ambient noise at the signal receiver.

[0065] In the present invention, the signal sender moves along a fixed circular trajectory, and the circular trajectory has M as the center and r as the radius.

[0066] Use d ij represents the distance between node i and node j, then the distance between the signal sender and the monitoring party can be expressed as:

[0067]

[0068] where d mw is the distance between M and the monitoring party, and due to the limitation of the mobility of the signal sender, r has a maximum value Δ, that is, r≤Δ.

[0069] Depend on Figure 1 It can be seen that the distance d between the signal sender and the monitoring party is aw ∈[d min ,d max ], where d min =d mw -r,d max =d mw +r. Let θ be the angle between the line connecting M and the signal sender and the line connecting M and the monitoring party. Since the signal sender will randomly send signals during the movement, the value of θ is random for the monitoring party at the moment when the signal sender sends the signal. Therefore, θ can be modeled as a random variable that obeys a uniform distribution. The parameter of the uniform distribution is 2π, and its probability density function can be expressed as:

[0070]

[0071] Example 2

[0072] The present invention utilizes the method of the mobile concealed communication system based on mobility and noise uncertainty of the above embodiment in a wireless communication network, such as Figure 2 As shown, the following steps:

[0073] Step 1: Model the mobile covert communication system, including scene modeling, mobile trajectory modeling, and channel modeling.

[0074] Step 2: Analyze the transmission performance of mobile covert communication. First, analyze the detection performance of the monitoring party and use it as a concealment constraint; second, analyze the transmission interruption probability of the legitimate communication parties (signal sender and signal receiver); finally, consider the concealment constraint and analyze the average covert transmission rate.

[0075] Specifically, step 2.1 analyzes the detection performance of the monitoring party, and the process is as follows Figure 3 shown.

[0076] (1) Design monitoring and detection methods.

[0077] In the present invention, the monitoring party uses energy detection to detect whether there is covert communication. In this method, the monitoring party will continuously collect the received signals and calculate the average value Y of the received signal energy in each time slot. w , and compare it with a pre-set threshold γ using a binary hypothesis test.

[0078] If Y w <γ, indicating that there is no covert transmission between the signal sender and the signal receiver, represented by H0; if Y w >γ, indicating that there is covert transmission between the signal sender and the signal receiver, represented by H1.

[0079] The specific process of using binary hypothesis testing to judge the signal is as follows:

[0080] Consider the kth signal y received by the monitoring party in a time slot w [k] is represented by:

[0081]

[0082] where v b [k] is the artificial noise sent by the signal receiver, x a [k] is the signal sent by the signal sender, which satisfies Where k = 1, 2, ... n, which indicates the sequence number of the kth signal received by the monitoring party in a time slot. Yes b The conjugate of [k], is x a [k] conjugate, E() represents the mathematical expectation operation; P a is the signal transmission power of the signal sender, P b is the artificial noise transmission power of the signal receiver, γ is the path loss index; n w [k] is the ambient noise at the monitoring location.

[0083] The monitoring party takes the average value Y of the signal energy received in each time slot wCompared with the pre-set detection threshold, it can be expressed by the following formula:

[0084]

[0085] Where D1 and D0 represent the decisions of receiving H1 and H0 respectively.

[0086] (2) Analyze the false alarm probability of the monitoring party and missed detection probability The monitoring party uses energy detection to determine whether the covert transmission signal exists. Two types of errors will occur in this process, namely false alarm error and missed detection error. The false alarm error means that the monitoring party makes the D1 decision under the H0 condition, and the missed detection error means that the monitoring party makes the D0 decision under the H1 condition.

[0087] When n→∞, according to the law of large numbers, the average energy value Y of the signal received by the monitoring party in a time slot is w as follows:

[0088]

[0089] in n w The variance of [k] is the ambient noise power at the monitoring location.

[0090] Calculate the false alarm probability and missed detection probability respectively.

[0091] The false alarm probability is:

[0092] in

[0093] The probability of missed detection is:

[0094] in d bw is the distance between the signal receiver and the monitoring party and is known to the monitoring party. Due to the complexity of the integral, it cannot be solved by the Newton-Leibniz formula, so the rectangular approximation method is used to obtain an approximate solution, and the result can be expressed by the following piecewise formula:

[0095] When ρ2≤ρ3,

[0096] When ρ2>ρ3,

[0097] The parameters involved are:

[0098]

[0099] (3) Analyze the minimum detection error probability and optimal detection threshold at the monitoring party.

[0100] When the probability of the signal sender sending or not sending information to the signal receiver is equal, the probability of detection error at the monitoring party can be expressed as ξ=α+β;

[0101] Since the signal sender cannot know the energy detection threshold of the monitoring party, in order to ensure reliable covert transmission between the communicating parties, it is necessary to analyze the covert transmission performance of the communicating parties under the worst case scenario, that is, the monitoring party can adopt the optimal detection threshold. Therefore, it is necessary to analyze the optimal detection threshold and the minimum detection error probability of the monitoring party.

[0102] The specific process is as follows:

[0103] The detection error probability at the monitoring party can be divided into two cases: ρ2≤ρ3 and ρ2>ρ3. Each case has multiple sub-cases, as follows:

[0104] Case 1: When ρ2≤ρ3, the false alarm rate is given by formula (9), and the missed detection rate is given by formula (11). In this case, according to the relationship between ρ5, ρ1 and ρ2, the detection error probability can be divided into the following three sub-cases:

[0105] Subcase 1.1, when ρ2<ρ5≤ρ3, the probability of detection error is as follows:

[0106]

[0107] in

[0108] When the detection threshold When , the derivative of the detection error probability ξ with respect to τ is

[0109] When the detection threshold τ∈[ρ2,ρ5], the derivative of the detection error probability ξ with respect to τ is

[0110] When the detection threshold τ∈[ρ5,ρ4], the derivative of the detection error probability ξ with respect to τ is

[0111] In summary, the optimal detection threshold τ in this case is * ∈[ρ2,ρ5], and τ * Substituting B1+D1, we can get the minimum detection error probability.

[0112] Subcase 1.2, when ρ1<ρ5≤ρ2, the probability of detection error is as follows:

[0113]

[0114] When the detection threshold When , the derivative of the detection error probability ξ with respect to τ is When the detection threshold τ∈[ρ5,ρ4], the derivative of the detection error probability ξ with respect to τ is In summary, the optimal detection threshold τ in this case * =ρ5, and τ * Substituting into A1, we can get the minimum detection error probability.

[0115] Subcase 1.3, when ρ5≤ρ1, the probability of detection error is as follows:

[0116]

[0117] In this case, the optimal detection threshold τ * ∈[ρ5,ρ1], the minimum detection error probability is 0.

[0118] Case 2: When ρ2>ρ3, the false alarm rate is given by formula (9), and the missed detection rate is given by formula (12). In this case, according to the relationship between ρ5 and ρ1, the detection error probability can be divided into the following two sub-cases:

[0119] Subcase 2.1: When ρ1<ρ5, the probability of detection error is as follows:

[0120]

[0121] in When the detection threshold When , the derivative of the detection error probability ξ with respect to τ is When the detection threshold τ∈[σ5,ρ4], the derivative of the detection error probability ξ with respect to τ

[0122] In summary, the optimal detection threshold τ in this case * =ρ5, and τ * Substituting into A1, we can get the minimum detection error probability.

[0123] Subcase 2.2: When ρ5≤ρ1, the probability of detection error is as follows:

[0124]

[0125] In this case, the optimal detection threshold τ * ∈[ρ5,ρ1], the minimum detection error probability is 0.

[0126] In summary, under the conditions of case 1 and case 2, the optimal detection threshold and minimum detection error probability of the monitoring party are:

[0127] Case 1: When ρ2≤ρ3

[0128]

[0129] in

[0130] Case 2: When ρ3<ρ2

[0131]

[0132] (4) Analyze the average minimum detection error probability at the monitoring party.

[0133] After obtaining the optimal detection threshold and minimum detection error probability at the monitoring party, it is necessary to further analyze the average minimum detection error probability at the monitoring party and use it as the concealment constraint of the communicating parties and introduce it into the subsequent analysis of the concealed transmission performance of the communicating parties.

[0134] The calculation process of the average minimum detection error probability at the monitoring party is as follows:

[0135]

[0136] in

[0137] Step 2.2: Analyze the covert transmission performance of both communicating parties. The process is as follows: Figure 4 shown.

[0138] (1) Analyze the probability of transmission interruption of the covert communication link between the two communicating parties.

[0139] According to formula (2), the signal to interference and noise ratio SINR at the receiving end is b It can be expressed by the following formula:

[0140]

[0141] in is the self-interference cancellation coefficient of the signal receiver. Therefore, the instantaneous channel capacity C of the link between the signal sender and the signal receiver can be expressed as C=log2(1+SINR b ), the transmission interruption probability δ of the link can be given by the following formula:

[0142]

[0143] in It is expressed by the following formula:

[0144]

[0145] Where K2 is the second-order modified Bessel function of the second kind.

[0146] (2) Analyze the average concealed transmission rate of the two communicating parties. Average concealed transmission rate is defined as the concealed transmission rate when no transmission interruption occurs, which can be expressed by the product of the ideal concealed transmission rate R and the probability of no transmission interruption, that is:

[0147]

[0148] Substituting formula (24) into formula (26) can obtain the average covert transmission rate of the communicating parties.

[0149] Step 3: Optimize the mobile covert communication transmission performance.

[0150] Specifically, an optimization problem is constructed to maximize the average covert transmission rate of both parties in communication by optimizing the moving trajectory radius r of the signal sender while satisfying the constraints. This problem can be expressed by the following formula:

[0151]

[0152] in is the maximum concealed transmission rate; the first constraint is the concealment constraint, where is the minimum average detection error probability, ε is the concealment coefficient, which is a sufficiently small positive number; the second constraint is the maximum value constraint of the trajectory radius r. Due to the limitation of the mobility of the signal sender, r has a maximum value Δ. The present invention searches for all r in the interval [0, Δ] through a search algorithm to obtain the optimal value r of r * , so that it can be maximized under the condition of satisfying the hidden constraints Get the maximum covert transmission rate

[0153] Experimental data

[0154] In order to verify the performance of the covert communication system proposed in the present invention, Monte Carlo simulation is used to conduct simulation experiments. The experimental results are as follows: Figures 5 to 7 As shown, the experimental simulation environment is as follows: All communication links in the experiment are double Rayleigh fading channels, and the environmental noise power at each node is Self-interference elimination coefficient The distance between each node is d bw =10m,d mw =21m, and the path loss exponent is γ=2.

[0155] Figure 5 is the power P at the signal transmitter aUnder different values, the detection error probability ξ of the monitoring party changes with the trajectory radius r of the signal sender. From the analysis result diagram, it can be seen that the simulation results are consistent with the theoretical analysis results, which verifies the accuracy of the approximate method used in the theoretical analysis. At the same time, the detection error probability ξ decreases to the minimum value in the interval [0,21] with the trajectory radius r, and then increases in the interval [21,40], where d mw =r is the minimum value. For different sender signal power P a , as P a As P decreases, the probability of detection error increases. a It can increase the detection error probability ξ of the monitoring party, and the value of the trajectory radius r will also affect the detection error probability. It should be avoided that r and d mw The values ​​of are consistent.

[0156] Figure 6 The figure shows the change of the transmission interruption probability δ between the two communicating parties with the radius r of the signal sender's trajectory when the ideal transmission rate R is different. The analysis result shows that the transmission interruption probability δ increases with the increase of the trajectory radius r, indicating that the larger the trajectory radius, the greater the transmission interruption probability; in addition, a higher ideal transmission rate will lead to a higher transmission interruption probability. Therefore, reducing the ideal transmission rate and the trajectory radius of the signal sender can reduce the transmission interruption probability of the two communicating parties.

[0157] Figure 7 is the average covert transmission rate of the two communicating parties when the signal sender's moving trajectory radius is different The maximum power of the interference signal at the signal receiver The analysis results show that the average hidden transmission rate along with The increase first remains at zero, then reaches a maximum value, and finally decreases toward zero. This is because when When it is small, the concealment constraint cannot be satisfied, resulting in the average concealed transmission rate remaining zero. Continue to increase until the concealment constraint is met, at which point the concealed transmission rate is the maximum average concealed transmission rate. As the radius of the moving trajectory r continues to increase, the impact of the interference signal on the covert communication increases, resulting in a continuous decrease in the average covert transmission rate. For different moving trajectory radii r, it can be seen from the figure that a larger r will increase the average covert transmission rate of the communicating parties. Bigger.

[0158] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0159] The above-mentioned embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the present application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the attached claims.

Claims

1. A mobile covert communication system based on mobility and noise uncertainty, characterized in that: The system comprises: a signal sending party, a signal receiving party and a monitoring party; The signal transmitter and the monitoring party are equipped with a single antenna, and the receiving party is equipped with a dual antenna; The signal sender is used to randomly send signals in the process of moving at a uniform speed along a circular trajectory in full-duplex mode; The signal receiver is used to receive the signal in a stationary state and send artificial noise with randomly changing power at the same time; The monitoring party is used to detect whether there is a communication transmission process between the signal sender and the signal receiver in a static state; The link between the signal sender and the signal receiver is a legitimate communication link, the link between the signal sender and the monitoring party is a detection link, and the link between the signal receiver and the monitoring party is an interference link.

2. The mobile covert communication system based on mobility and noise uncertainty according to claim 1 is characterized in that: When receiving the signal, the signal receiver models the self-interference signal as having a mean of 0 and a variance of γ RSI A Gaussian distributed random variable.

3. The mobile covert communication system based on mobility and noise uncertainty according to claim 1, characterized in that: The moving trajectory of the signal sender is a circle, with an arbitrary point as the center and R as the radius, where R has a maximum value R_max.

4. The mobile covert communication system based on mobility and noise uncertainty according to claim 3 is characterized in that: The artificial noise is sent by the signal receiver with randomly changing power, the power distribution is uniform, and the maximum value is P_max.

5. The mobile covert communication system based on mobility and noise uncertainty according to claim 4 is characterized in that: The communication link channels between nodes are modeled using a double Rayleigh fading channel model, where the channel coefficients remain constant within a time slot and vary randomly between time slots.

6. A method for utilizing the mobile covert communication system based on mobility and noise uncertainty according to any one of claims 1 to 5, characterized in that: The following steps are involved: The signal sender moves along a fixed track and sends a covert signal; The signal receiver sends artificial noise with randomly varying power while receiving the signal; The monitoring party detects whether there is a communication transmission process by an energy detection method; The covert communication performance is analyzed and optimized according to the detection results of the monitoring party to maximize the average covert transmission rate.

7. The method according to claim 6, characterized in that The monitoring party detects whether there is a communication transmission process through an energy detection method, specifically including: the monitoring party will continuously collect the received signals and calculate the average value Y of the received signal energy in each time slot w , using a binary hypothesis test to compare it with a pre-set threshold γ; if Y w <γ, indicating that there is no covert transmission between the signal sender and the signal receiver, represented by H0; if Y w >γ, indicating that there is covert transmission between the signal sender and the signal receiver, represented by H1; According to the average value Y of the received signal energy in each time slot w Determine the false alarm probability and missed detection probability; When the probability of the signal sending party sending or not sending information to the signal receiving party is equal, determining the detection error probability at the monitoring party according to the false alarm probability and the missed detection probability; Determining an optimal detection threshold and a minimum detection error probability of the monitoring party; An average minimum detection error probability of the monitoring party is determined.

8. The method according to claim 7, characterized in that The calculation of the average value Y of the received signal energy in each time slot w , specifically including: the kth signal y received by the monitoring party in a time slot w [k] is represented by: where v b [k] is the artificial noise sent by the signal receiver, x a [k] is the signal sent by the signal sender, which satisfies Where k = 1, 2, ... n, which indicates the sequence number of the kth signal received by the monitoring party in a time slot. Yes b The conjugate of [k], is x a [k] conjugate, E() represents the mathematical expectation operation; P a is the signal transmission power of the signal sender, P b is the artificial noise transmission power of the signal receiver, γ is the path loss index; n w [k] is the ambient noise at the monitoring location; according to Determine the mean value Y w ; where D1 and D0 represent the decisions of receiving H1 and H0 respectively.

9. The method according to claim 8, characterized in that The average value Y of the received signal energy in each time slot w Determine the false alarm probability and missed detection probability, including: Determine the false alarm probability, where according to Determine the probability of missed detection, where d bw is the distance between the signal receiving party and the monitoring party and is known by the monitoring party.

10. The method according to claim 9, characterized in that Determining the average minimum detection error probability of the monitoring party specifically includes: Determine, among which

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