Covert communication method and apparatus, and device and storage medium

Abstract

Disclosed in the present invention are a covert communication method and apparatus, and a device and a storage medium The method comprises: solving an optimization problem of maximizing the signal-to-noise ratio of a received signal at a receiving device under covertness constraints and power constraints, in order to obtain a precoding matrix and a pre-sending power; adjusting a sending power at which a sending device transmits a sending signal to a relay device, such that the sending power is equal to the pre-sending power; on the basis of the precoding matrix, amplifying the sending signal to obtain an amplified signal; and sending the amplified signal to the receiving device. The present invention maximizes the signal-to-noise ratio at a legitimate receiving device, thereby significantly improving the signal transmission efficiency and the overall communication quality, and also further enhancing the security of covert communications.

Description

A covert communication method, device, equipment and storage medium TECHNICAL FIELD

[0001] The present application relates to the field of covert communication, and in particular to a covert communication method, device, equipment and storage medium. BACKGROUND

[0002] Covert communication refers to a communication method that hides communication content or behavior to avoid third parties from detecting the existence of communication or the transmission of content. This method is often used in military, intelligence, commercial secrets and other occasions that require high confidentiality and security. The main purpose of covert communication is to hide the existence or content of communication, ensuring that no one except the communicating parties can perceive the occurrence of communication. In covert communication technology, a common method is to add artificial noise to increase the uncertainty of the communication behavior for external listeners (wardens). This method hides information in artificial noise, making it difficult for third parties to detect the existence of communication or understand the transmitted content. For example, hiding communication signals in the radio frequency spectrum is a way to achieve covert communication. In the Internet of Things (IoT) scenario, communication between devices may involve user privacy information. Using covert communication technology can help protect this information from being stolen or leaked during transmission. In addition, device communication in the Internet of Things system may face malicious eavesdropping or attacks, and covert communication technology can enhance the concealment of device-to-device communication, reducing the risk of being discovered by attackers, thereby improving the security of the entire system.

[0003] In covert communication, using relay nodes can enhance the security and concealment of communication. Relay nodes forward and interfere with signals to increase the complexity of the communication path and the difficulty of being monitored. For example, direct communication between a sending user Alice and a legitimate receiving user Bob may be easily monitored, but by using relay nodes to forward, the direct communication path between them can be hidden, making it difficult for listeners to track. The relay receives information from the sending user Alice and re-sends it to Bob, thereby hiding the traces of direct communication. In addition, the relay can also generate interference signals to confuse the receiver and increase the difficulty of analyzing the communication content for the listener.

[0004] First, the security performance of existing covert communication is limited, and the concealment performance between legitimate users cannot support the security requirements of covert communication in actual scenarios. Second, traditional methods rely too much on instantaneous channel information of the listener's channel, but in actual applications, the instantaneous channel information of the listener is often difficult to obtain or predict. Third, the excessive pursuit of security in existing technologies results in a too low signal-to-noise ratio at the receiving device, affecting the overall transmission efficiency and communication quality. SUMMARY

[0005] The embodiment of the present application provides a covert communication method, device, equipment and storage medium, adjusts the precoding matrix of a relay and adjusts the sending power of a sending device, maximizes the signal-to-noise ratio of a receiving device, and thus improves the transmission efficiency of a signal and overall communication quality.

[0006] To achieve the above object, a first aspect of the embodiment of the present application provides a covert communication method, comprising:

[0007] Solving an optimization problem of maximizing the signal-to-noise ratio of a receiving device under the constraints of concealment and power, obtaining a precoding matrix and a pre-sending power;

[0008] Adjusting the sending power of a sending device to a relay device to send a sending signal, so that the sending power is equal to the pre-sending power;

[0009] Amplifying the sending signal according to the precoding matrix to obtain an amplified signal;

[0010] Sending the amplified signal to a receiving device.

[0011] In a possible implementation manner of the first aspect, before solving the optimization problem of maximizing the signal-to-noise ratio of a receiving device under the constraints of concealment and power, the method comprises:

[0012] Determining the false alarm rate and the missing detection rate of a monitoring device according to the detection signal power of the monitoring device;

[0013] Determining the minimum detection error probability of the monitoring device according to the false alarm rate and the missing detection rate;

[0014] Determining the concealment constraint according to the minimum detection error probability;

[0015] Determining the power constraint according to the device information of a relay device.

[0016] In a possible implementation manner of the first aspect, the concealment constraint comprises: t ln t-(t+1)ln(t+1)=lnε;

[0017] wherein, is a semi-positive definite matrix with a rank of 1, N r is the number of antennas of a relay device, is the artificial noise of a sending device when a relay device sends a signal, is the maximum sending power of a sending device, P a is the sending power of a sending device, and ε is a concealment parameter, is the artificial noise of a sending device when a relay device sends a signal, is The non-zero characteristic matrix, It is a solution to the t-parameter equation t ln t-(t+1)ln(t+1)=lnε.

[0018] In one possible implementation of the first aspect, the power constraint includes: X i ≥0, i∈{1,2,…,N r}; Rank(X i )=1,i∈{1,2,…,N r};

[0019] in, and X i P is a positive semi-definite matrix with rank 1. a It is the transmission power of the transmitting device, t ar N is the signal transmission time spent by the transmitting device when transmitting a signal. r It refers to the number of antennas in the relay equipment. It is the maximum transmission power of the transmitting device. This is the maximum transmission power of the relay device. It is artificial noise generated by the relay equipment when the transmitting equipment sends signals.

[0020] In one possible implementation of the first aspect, solving the optimization problem of maximizing the signal-to-noise ratio of the received signal at the receiving device under concealment and power constraints to obtain the precoding matrix and pretransmit power specifically includes:

[0021] The optimization problem of maximizing the signal-to-noise ratio of the received signal at the receiving device under concealment and power constraints is transformed by Dinkelbach transformation to obtain the transform optimization problem.

[0022] Based on the transformation optimization problem, determine the fixed variables and the optimization variables;

[0023] The process is repeated multiple times until the change in the optimization variable is less than a preset threshold or the iteration count is met. The solution to the transformation optimization problem is then used as the values ​​of the precoding matrix and the pretransmission power.

[0024] In one possible implementation of the first aspect, before amplifying the transmitted signal according to the precoding matrix to obtain the amplified signal, the following steps are included:

[0025] The number of antennas in the relay device is adjusted according to the precoding matrix.

[0026] A second aspect of this application provides a covert communication device, comprising:

[0027] a problem solving module, configured to solve an optimization problem of maximizing a signal-to-noise ratio of a received signal at a receiving device under concealment constraints and power constraints, to obtain a precoding matrix and a pre-transmission power;

[0028] a power adjusting module, configured to adjust a transmission power of a transmitting device for transmitting a sending signal to a relay device, so that the transmission power is equal to the pre-transmission power;

[0029] a signal amplifying module, configured to amplify the sending signal according to the precoding matrix, to obtain an amplified signal;

[0030] a signal sending module, configured to send the amplified signal to the receiving device.

[0031] In a possible implementation of the second aspect, the method further includes:

[0032] a first determining module, configured to determine a false alarm rate and a missed detection rate of the monitoring device according to a detected signal power of the monitoring device;

[0033] a second determining module, configured to determine a minimum detection error probability of the monitoring device according to the false alarm rate and the missed detection rate;

[0034] a third determining module, configured to determine the concealment constraints according to the minimum detection error probability;

[0035] a fourth determining module, configured to determine the power constraints according to device information of the relay device.

[0036] A third aspect of the embodiments of the present application provides a terminal device, including a processor and a memory, the memory is used for storing a computer program, the computer program is executed by the processor to implement a kind of concealment communication method as described above.

[0037] A fourth aspect of the embodiments of the present application provides a computer readable storage medium, the computer program is executed by processor to implement a kind of concealment communication method as described above.

[0038] Compared with the prior art, the embodiment of the present application provides a covert communication method, device, equipment and storage medium, which uses analysis of channel statistical distribution information of a listener to design concealment constraints and power constraints, reduces the dependence on instantaneous channel information which is difficult to predict or obtain, and improves the practical applicability and robustness of the method. In optimizing the relay precoding matrix and the transmission power, the optimization problem of maximizing the received signal signal-to-noise ratio at the receiving device under the concealment constraints and the power constraints is solved, and the precoding matrix of the relay device and the transmission power of the transmitting device are adjusted according to the solution, so that the problem of not maximizing the signal-to-noise ratio of the legal receiving user in the prior art is solved. This optimization can significantly improve the transmission efficiency and overall communication quality of the signal, and further enhance the security of covert communication. BRIEF DESCRIPTION OF DRAWINGS

[0039] Fig. 1 is a flowchart of a covert communication method provided by an embodiment of the present application;

[0040] Fig. 2 is a structural diagram of a covert communication system provided by an embodiment of the present application;

[0041] Fig. 3 is a diagram showing the influence of the number of relay antennas on the proposed algorithm and the random precoding matrix method in terms of SNR;

[0042] Fig. 4 is a diagram showing the relationship between the maximum transmission power of the transmitting device and the analyzed system communication interruption probability;

[0043] Fig. 5 is a diagram showing the relationship between the maximum transmission power of the transmitting device and the analyzed minimum detection error probability. DETAILED DESCRIPTION

[0044] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0045] Please refer to Fig. 1, the embodiment of the present application provides a covert communication method, comprising:

[0046] S10, solving the optimization problem of maximizing the received signal signal-to-noise ratio at the receiving device under the concealment constraints and the power constraints, obtaining the precoding matrix and the pre-transmission power.

[0047] S11, adjusting the transmission power of the transmitting device to the relay device for transmitting the sending signal, so that the transmission power is equal to the pre-transmission power.

[0048] S12, amplifying the sending signal according to the precoding matrix to obtain an amplified signal.

[0049] S13, sending the amplified signal to a receiving device.

[0050] At this stage of S10, a complex mathematical optimization problem needs to be solved. The goal is to maximize the signal-to-noise ratio at the receiving end under the constraints of concealment and power. This usually requires the use of numerical optimization methods, such as gradient descent, Lagrange multiplier method, or Dinkelbach transformation method. The original nonlinear fractional optimization problem can be converted into a series of parameterized convex optimization problems through Dinkelbach transformation. The parameter is updated iteratively, and each iteration is based on the results of the previous iteration to improve the optimization variables. Iteration continues until the convergence criterion is met (i.e., the change in optimization variables is less than a pre-set threshold or the maximum number of iterations is reached).

[0051] Precoding matrix: used to adjust the signal processing of the relay device, so that the sending signal can better match the channel characteristics when passing through the relay device, thereby improving the signal-to-noise ratio at the receiving end.

[0052] Pre-transmission power: the optimal power level that the sending device should use to maximize the signal-to-noise ratio at the receiving end while meeting the concealment requirements.

[0053] After determining the pre-transmission power, the sending device adjusts its transmission power to ensure that the actual transmission power equals the pre-transmission power obtained in the optimization process. In S12, the relay device processes the signal received from the sending device according to the precoding matrix. The precoding matrix is used to adjust the amplitude and phase of the signal, so that the signal can more effectively combat interference and improve the signal-to-noise ratio at the receiving end after being forwarded by the relay device. In S13, the relay device forwards the processed signal to the receiving device. At this time, the signal received by the receiving device has been optimized, improving the signal-to-noise ratio and enhancing the security and communication quality of covert communication.

[0054] In summary, the above-mentioned scheme optimizes the covert communication system by adjusting the transmission power and using the precoding matrix. Through this method, communication efficiency can be improved while ensuring concealment.

[0055] Exemplarily, before solving the optimization problem of maximizing the signal-to-noise ratio of the received signal at the receiving device under the constraints of concealment and power, it includes:

[0056] According to the detection signal power of the monitoring device, the false alarm rate and the missed detection rate of the monitoring device are determined.

[0057] According to the false alarm rate and the missed detection rate, the minimum detection error probability of the monitoring device is determined.

[0058] determine the concealment constraint according to the minimum detection error probability;

[0059] determine the power constraint according to the device information of the relay device.

[0060] Referring to FIG. 2, the determination and solution process of the optimization problem are introduced below with the sending device as a sending user Alice, the monitoring device as a monitoring user Willie, and the receiving device as a receiving user Bob.

[0061] In FIG. 2, a multi-antenna relay is introduced between the Internet of Things source A and the Internet of Things sink B to assist in covert communication, where the multi-antenna relay adopts a half-duplex mode. The covert communication from A to B is divided into two stages, the first stage is that A sends a signal to the relay R, and the second stage is that the multi-antenna relay R amplifies and sends the signal to B through a precoding matrix. In addition, when A chooses not to send a signal, the relay will send some AN to confuse Willie (W) to increase the uncertainty of the detection of the monitor W.

[0062] Alice, the relay, Willie, and Bob are denoted as a, r, w, and b, respectively. The channels between Alice-relay, relay-Bob, Alice-Willie, and Willie-Bob are denoted as h aw and Because Willie is an enemy, he only knows the statistical distribution information about the channel, that is, in and In the latter two, only the distribution information is currently known, and a specific value that satisfies the distribution can be obtained based on the former two.

[0063] It should be noted that Nr is the number of antennas at the relay, h_ar represents the channel parameter from Alice to the relay, h_rb represents the channel parameter from the relay to Bob, h_aw represents the channel parameter from Alice to the monitoring user, and h_rw represents the channel parameter from the relay to the monitoring user.

[0064] The relay device is in a half-duplex mode and adopts an amplify-and-forward relay protocol, and the number of antennas of the relay device is N r The half-duplex relay forwarding is divided into two stages. Specifically, in the first stage, when Alice sends a signal, the signal received by the relay device is where P a is the power transmitted by Alice, x is the signal sent by Alice, and satisfies is the additive white Gaussian noise (AWGN) at the relay. In the second stage, the relay amplifies and forwards the signal to Bob through a precoding matrix The received signal is amplified and transmitted to Bob, so the signal received by Bob is where is the AWGN at Bob. The signal-to-noise ratio of the received signal at Bob is expressed as:

[0065] Let where H ar is a rank-1 semi-definite matrix, which is spectrally decomposed in ascending order of eigenvalues, and where U ar satisfies is a unitary matrix, S ar is a diagonal matrix with only the last row and last column element non-zero, denoted as t ar . Let where the i-th column of matrix Q is denoted as q i , i = 1, …, N r . Then the signal-to-noise ratio of Bob can be rewritten as:

[0066] where X i is a rank-1 semi-definite matrix. Finally, in the present invention, the power of the retransmitted signal of the relay can be expressed as:

[0067] The listener Willie is detecting in the above two stages. denotes the assumption that Alice does not send a signal, denotes the assumption that Alice sends a signal. When Alice does not send a signal, the relay sends some artificial noise to interfere with Willie in order to increase the uncertainty of the listener's detection. Therefore, the signal detected by Willie in the first stage is:

[0068] where is the AWGN at Willie in the first stage, satisfies is the artificial noise sent by the relay in the first stage. At this time, the power of the artificial noise sent by the relay is:

[0069] The signal detected by Willie in the second stage is:

[0070] where is the AWGN at Willie in the second stage, is the artificial noise sent by the relay in the second stage. It is noted that when Willie detects the same signal power in the second phase regardless of the assumption, so the second phase relay can design the power of the artificial noise to be sent to achieve perfect covert communication, and the present application only needs to consider the first phase. Willie makes a judgment according to the detected signal and the pre-set threshold value γ , wherein represents that Willie thinks that Alice sends a signal to Bob, represents that Willie thinks that Alice does not send a signal to Bob. The signal power detected by Willie in the first phase is:

[0071] Based on this, the false alarm rate of Willie is calculated:

[0072] wherein is the non-zero eigenvalue of the semi-positive definite matrix X i of rank 1. The missed detection rate of Willie is:

[0073] Therefore, the error detection probability of Willie is:

[0074] Therefore, the optimal detection threshold value set by Willie is and the minimum detection error probability is wherein Since the monotonicity of ξ with respect to γ is not clear, the minimum ξ is either taken at the two end points or taken at the stationary point. Therefore, the minimum detection error probability of Willie is represented as:

[0075] wherein is the stationary point satisfying In order to ensure the covertness of transmission, there is ξ*>1-ε, wherein ε is a covertness parameter. At this time, there are three cases, specifically,

[0076] a. When , there is ξ (1) =p>1, so only the second and third cases need to be considered.

[0077] b. When , there is According to ξ (2) >1-ε, there is

[0078] c. When , there is ​Where t>0 or t<-1. When t<-1, ξ(3)>1, and when t>0, it can be known from the expression of t that

[0079] By ξ (3) ≥1-ε, there are Where is the solution of the equation t ln t-(t+1)ln(t+1)=lnε.

[0080] Exemplarily, in combination with the above two cases of b and c, the concealment constraint comprises: t ln t-(t+1)ln(t+1)=lnε;

[0081] Where, is a semi-definite matrix of rank 1, N r is the number of antennas of the relay device, is the artificial noise of the relay device when sending a signal, is the maximum transmission power of the sending device, P a is the transmission power of the sending device, and ε is a concealment parameter, is the artificial noise of the sending device when the relay device sends a signal, is a non-zero eigenmatrix of X is the solution of the t parameter equation t ln t-(t+1)ln(t+1)=lnε.

[0082] Exemplarily, the power constraint comprises: X i ≥0,i∈{1,2,…,N r}; Rank(X i )=1,i∈{1,2,…,N r};

[0083] Where, and X i is a semi-definite matrix of rank 1, P a is the transmission power of the sending device, t ar is the signal transmission time spent by the sending device when sending a signal, N r is the number of antennas of the relay device, is the maximum transmission power of the sending device, is the maximum transmission power of the relay device, is the artificial noise of the relay device when the sending device sends a signal.

[0084] The optimization problem is expressed as follows:

[0085] For example, solving the optimization problem of maximizing the signal-to-noise ratio of the received signal at the receiving device under concealment and power constraints to obtain the precoding matrix and pretransmit power specifically includes:

[0086] The optimization problem of maximizing the signal-to-noise ratio of the received signal at the receiving device under concealment and power constraints is transformed by Dinkelbach transformation to obtain the transform optimization problem.

[0087] Based on the transformation optimization problem, determine the fixed variables and the optimization variables;

[0088] The process is repeated multiple times until the change in the optimization variable is less than a preset threshold or the iteration count is met. The solution to the transformation optimization problem is then used as the values ​​of the precoding matrix and the pretransmission power.

[0089] Since the optimization problem is a fractional optimization problem, we first use the Dinkelbach transform to change the objective function by introducing a variable μ. Furthermore, the constraint that the matrix rank is 1 is about the optimization variable X. i Non-convex constraints, therefore, introducing a variable η transforms the constraint into in It is a given feasible solution. It is a matrix Maximum eigenvalue, This is the eigenvector associated with the largest eigenvalue. To make the variable η approach 0, a penalty term -τη is added to the objective function, where the parameter τ is a given, very large parameter. Therefore, the optimization problem is rewritten as:

[0090] The optimization problem involves four optimization variables that are coupled together. Note that when the variable {P} is fixed... a ,μ}, optimization problem P1 with respect to the remaining optimization variables {X} i The problem is a convex optimization problem, which can be solved using the CVX toolbox in MATLAB to obtain the current optimal value. Where t is the iteration index. When the optimization variable is fixed... With P a As the objective function increases, the objective function also increases. Note that according to the constraints...

[0091] therefore

[0092] When given Optimize variable μ according to expression

[0093] Update.

[0094] The iteration is performed according to the above steps until or t > t max .

[0095] Further, the outage probability δ of the transmission from Alice to Bob can be analyzed ab When C < R, the transmission is interrupted, where C = log2(l + SNR) is the channel capacity from Alice to Bob, and R is the pre-set transmission rate from Alice to Bob. The analytical expression for the outage probability is calculated as

[0096] where Δ = 2 R -1.

[0097] Exemplarily, before the amplifying the sending signal according to the precoding matrix to obtain an amplified signal, the method comprises:

[0098] Adjusting the number of antennas of the relay device according to the precoding matrix.

[0099] The relay device processes the signal received from the sending device according to the precoding matrix. The precoding matrix is used to adjust the amplitude and phase of the signal, so that the signal can more effectively combat interference and improve the signal-to-noise ratio at the receiving end after being forwarded by the relay device.

[0100] In some cases, the precoding matrix not only adjusts the signal, but also may instruct the relay device to adjust its antenna configuration. For example, if the precoding matrix indicates that fewer antennas can be used to transmit the signal more effectively, the relay device may reduce the number of antennas it is using. This adjustment can reduce the complexity of the signal, reduce interference, and improve the signal-to-noise ratio at the receiving end.

[0101] Suppose the relay device is initially configured with Nr antennas, and the precoding matrix indicates that fewer antennas can be used (for example, M < Nr antennas can achieve better communication results. In this case, the relay device can adjust its antenna configuration and use only M antennas to forward the signal.

[0102] Figure 2 is a graph of the influence of the number of relay antennas on the proposed covert communication method and the random precoding matrix method in terms of SNR in the MATLAB simulation environment of the present application. As expected, the SNR of the proposed covert communication method and the random precoding matrix method both increase with the number of antennas, because more antennas can make the design of the precoding matrix more flexible. Obviously, the proposed algorithm is superior to all benchmark schemes.

[0103] FIG. 3 is a plot of Alice's maximum transmit power versus the analyzed system outage probability. As can be seen from the plot, the analyzed outage probability agrees well with the simulation results, proving the derived analytical expression. In addition, as the transmission power at Alice increases, the transmission outage probability decreases, because a larger power can make the SNR of the received signal at Bob larger, i.e., the data transmission rate from Alice to Bob is larger, effectively reducing the outage probability. Furthermore, as the number of antennas increases, the probability of transmission outage decreases. This is because the relay can take advantage of the gain brought by the multi-antenna system to design the precoding matrix, thus reducing the probability of transmission outage.

[0104] FIG. 4 is a plot of Alice's maximum transmit power versus the analyzed minimum detection error probability. As can be seen from the plot, as Alice's transmit power increases, the minimum detection error probability at Willie decreases. This is because as Alice's transmit power increases, Willie can better distinguish the AN and Alice's signal according to the detected signal power. Therefore, although the transmission power has a positive impact on the performance of covert communication, in order to guarantee the covertness constraint, the transmission power should not be too large. In addition, as the number of relay antennas increases, the minimum detection error probability increases significantly. This phenomenon shows that arranging more antennas at the relay can effectively mitigate the impact of higher transmit power on the minimum detection error probability.

[0105] In one simulation, the distance from Alice to the relay and the distance from the relay to Bob were both set to 20 meters, while the distance from Alice to Willie and the distance from the relay to Willie were both set to 30 meters. In addition, a path loss model was used to describe the characteristics of the wireless fading link in the system, where the path loss constant β0at the reference distance was set to -40 dBm, the path loss exponent a was 2, and the noise power at the relay, Bob, and Willie was set to -90 dBm. The concealment parameter ∈ was set to 0.1. In addition, the number of antennas at the relay N_r was set to 4 if not specified. The maximum transmit power of the relay P_r^max was 25 dBm, the maximum transmit power of Alice P_a^max was 20 dBm, and the initial transmit power of Alice P_a^((0)) was 10 dBm.

[0106] Compared with the prior art, the embodiment of the present application provides a covert communication method, device, equipment and storage medium, which uses analysis of channel statistical distribution information of a listener to design concealment constraints and power constraints, reduces the dependence on instantaneous channel information which is difficult to predict or obtain, and improves the practical applicability and robustness of the method. In optimizing the relay precoding matrix and the transmission power, the optimization problem of maximizing the received signal signal-to-noise ratio at the receiving device under the concealment constraints and the power constraints is solved, and the precoding matrix of the relay device and the transmission power of the transmitting device are adjusted according to the solution, so that the problem that the signal-to-noise ratio of the legal receiving user cannot be maximized in the prior art is solved. This optimization can significantly improve the transmission efficiency of the signal and the overall communication quality, and further enhance the security of the covert communication.

[0107] An embodiment of the present application provides a covert communication device, which comprises a problem solving module, a power adjusting module, a signal amplifying module and a signal transmitting module.

[0108] The problem solving module is used for solving an optimization problem of maximizing the received signal signal-to-noise ratio at the receiving device under concealment constraints and power constraints, to obtain a precoding matrix and a pre-transmission power.

[0109] The power adjusting module is used for adjusting the transmission power of the transmitting device for transmitting a transmission signal to the relay device, so that the transmission power is equal to the pre-transmission power.

[0110] The signal amplifying module is used for amplifying the transmission signal according to the precoding matrix to obtain an amplified signal.

[0111] The signal transmitting module is used for transmitting the amplified signal to the receiving device.

[0112] Exemplarily, the device further comprises:

[0113] The first determining module is used for determining the false alarm rate and the missed detection rate of the monitoring device according to the detection signal power of the monitoring device.

[0114] The second determining module is used for determining the minimum detection error probability of the monitoring device according to the false alarm rate and the missed detection rate.

[0115] The third determining module is used for determining the concealment constraints according to the minimum detection error probability.

[0116] The fourth determining module is used for determining the power constraints according to the device information of the relay device.

[0117] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working process of the system described above can refer to the corresponding process in the foregoing method embodiments, which will not be repeated here.

[0118] Compared with the prior art, the embodiment of the present application provides a covert communication device, which uses analysis of channel statistical distribution information of a listener to design concealment constraints and power constraints, reduces dependence on instantaneous channel information that is difficult to predict or obtain, and improves practical applicability and robustness of the method. In optimizing the relay precoding matrix and the transmission power, by solving an optimization problem of maximizing the received signal-to-noise ratio at the receiving device under the concealment constraints and the power constraints, the precoding matrix of the relay device and the transmission power of the sending user Alice are adjusted according to the solution, and the present application solves the problem that the prior art fails to maximize the signal-to-noise ratio of the legal receiving user. This optimization can significantly improve the transmission efficiency of the signal and the overall communication quality, and further enhance the security of covert communication.

[0119] An embodiment of the present application provides a terminal device, including a processor and a memory, the memory is used to store a computer program, the computer program is executed by the processor to realize a covert communication method as described above.

[0120] An embodiment of the present application provides a computer readable storage medium, the computer program is executed by the processor to realize a covert communication method as described above.

[0121] The computer device can be a smart phone, a tablet computer, a desktop computer, a cloud server and the like. The computer device can include but is not limited to a processor and a memory. Those skilled in the art can understand that the figure is only an example of the computer device, and does not constitute a limitation on the computer device, and can include more or fewer components than the figure, or combine certain components, or different components, for example, can also include an input / output device, a network access device and the like.

[0122] The processor can be a central processing unit (CPU), and the processor can also be other general-purpose processors, digital signal processors (DSP), application specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor can be a microprocessor or the processor can also be any conventional processor.

[0123] The memory can be an internal storage unit of the computer device in some embodiments, for example, a hard disk or a memory of the computer device. The memory can also be an external storage device of the computer device in other embodiments, for example, a plug-in hard disk, a smart media card (SMC), a secure digital (SD) card, a flash card, and the like. Further, the memory can include both the internal storage unit and the external storage device of the computer device. The memory is used to store an operating system, an application program, a boot loader, data, and other programs, for example, program codes of the computer program, and the like. The memory can also be used to temporarily store data that has been output or is to be output.

[0124] The computer program product provided in the embodiments of the present application, when running on the computer device, causes the computer device to execute the steps in the above-mentioned various method embodiments.

[0125] In the several embodiments provided in the present application, it can be understood that each block in the flowchart or block diagram can represent a module, a segment or a portion of code, which includes one or more executable instructions for implementing the specified logic function. It should also be noted that in some alternative implementations, the functions noted in the blocks can occur in a different order than that noted in the figure. For example, two blocks noted in succession can in fact be executed substantially concurrently or in the opposite order, depending on the functions involved.

[0126] The functions, if implemented in the form of software function modules and sold or used as independent products, can be stored in a computer readable storage medium. Based on such an understanding, the technical solutions of the present application, essentially or in part, or parts of the technical solutions can be embodied in the form of a software product. The computer software product is stored in a storage medium, and includes a plurality of instructions for causing a computer device to perform all or part of the steps of the methods described in the various embodiments of the present application. The aforementioned storage medium includes: a U disk, a mobile hard disk, a read-only memory (ROM, Read-Only Memory), a random access memory (RAM, Random Access Memory), a magnetic disk or an optical disk, and the like.

[0127] The above is the preferred embodiment of the present application, it should be pointed out that, for those skilled in the art, without departing from the principles of the present application, can also make a number of improvements and refinements, these improvements and refinements are also considered to be within the scope of the present application.

Claims

1. A method of covert communication, characterized by, The method comprises the following steps: Solving an optimization problem of maximizing a signal-to-noise ratio of a received signal at a receiving device under a concealment constraint and a power constraint to obtain a precoding matrix and a pre-transmission power; Adjusting a transmission power of a sending device for transmitting a sending signal to a relay device, so that the transmission power is equal to the pre-transmission power; Amplifying the sending signal according to the precoding matrix to obtain an amplified signal; Transmitting the amplified signal to the receiving device.

2. The method of claim 1, wherein Before the step of solving the optimization problem of maximizing the signal-to-noise ratio of the received signal at the receiving device under the concealment constraint and the power constraint, the method further comprises the following steps: Determining a false alarm rate and a missed detection rate of a monitoring device according to a detected signal power of the monitoring device; Determining a minimum detection error probability of the monitoring device according to the false alarm rate and the missed detection rate; Determining the concealment constraint according to the minimum detection error probability; Determining the power constraint according to device information of the relay device.

3. The method of claim 2, wherein The concealment constraint includes: t ln t - (t + 1) ln (t + 1) = ln ε; wherein is a semi-definite matrix of rank 1, N r is the number of antennas of the relay device, is artificial noise of the relay device when transmitting a signal, is the maximum transmission power of the transmitting device, P a is the transmission power of the transmitting device, ε is the stealthiness parameter, is an artificial noise sent by the transmitting device when the signal is sent by the relaying device, is nonzero feature matrix of the t is a solution of a t-parameter equation t ln t-(t+1)ln(t+1)=lnε.

4. The method of claim 2, wherein The power constraints include: X i ≥ 0, i ∈ {1, 2, …, N r}; Rank(X i ) = 1, i ∈ {1, 2, …, N r}. wherein, and X i is a semi-positive definite matrix of rank 1, P a is the transmission power of the transmitting device, t ar is the signal transmission time spent by the transmitting device in transmitting the signal, N r is the number of antennas of the relay device, is the maximum transmission power of the transmitting device, is the maximum transmission power of the relay device, The artificial noise is a noise generated by the relay device when the sending device transmits the sending signal.

5. The method of claim 1, wherein The step of solving the optimization problem of maximizing the signal-to-noise ratio of the received signal at the receiving device under the concealment constraint and the power constraint to obtain the precoding matrix and the pre-transmission power specifically comprises the following steps: Performing Dinkelbach transformation on the optimization problem of maximizing the signal-to-noise ratio of the received signal at the receiving device under the concealment constraint and the power constraint to obtain a transformed optimization problem; Determining a fixed variable and an optimization variable according to the transformed optimization problem; Performing multiple iterations until a change value of the optimization variable is less than a preset threshold or an iteration number index is met, and taking a solution of the transformed optimization problem as a value of the precoding matrix and the pre-transmission power.

6. The method of claim 1, wherein Before the step of amplifying the sending signal according to the precoding matrix to obtain the amplified signal, the method further comprises the following step: Adjusting a number of antennas of the relay device according to the precoding matrix.

7. A covert communications device, characterized by The method comprises the following steps: A problem solving module is configured to solve an optimization problem of maximizing a signal-to-noise ratio of a received signal at a receiving device under a concealment constraint and a power constraint to obtain a precoding matrix and a pre-transmission power; A power adjusting module is configured to adjust a transmission power of a sending device for transmitting a sending signal to a relay device, so that the transmission power is equal to the pre-transmission power; A signal amplifying module is configured to amplify the sending signal according to the precoding matrix to obtain an amplified signal; A signal transmitting module is configured to transmit the amplified signal to the receiving device.

8. The covert communications apparatus of claim 7, wherein, The method further comprises the following steps: A first determining module is configured to determine a false alarm rate and a missed detection rate of a monitoring device according to a detected signal power of the monitoring device; A second determining module is configured to determine a minimum detection error probability of the monitoring device according to the false alarm rate and the missed detection rate; A third determining module is configured to determine the concealment constraint according to the minimum detection error probability; A fourth determining module is configured to determine the power constraint according to device information of the relay device.

9. A terminal device, comprising: The method comprises a processor and a memory, wherein the memory is configured to store a computer program, and the computer program is configured to be executed by the processor to implement the method according to any one of claims 1 to 6.

10. A computer-readable storage medium, characterized in that, The computer program is stored in the computer readable medium and is executed by the processor to implement the covert communication method according to any one of claims 1 to 6.

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