A wireless sensing covert communication based on broadcast beacon

Abstract

The present invention discloses a wireless sensing covert communication based on broadcast beacons, comprising the following steps: (1) a covert communication sender sends a radar signal and receives an echo; (2) based on the echo of the radar signal, a rough estimation of the CSI between the covert communication detector and the covert communication sender is performed; (3) beacon signal beamforming; (4) accurate CSI information between the covert communication detector and the sender is obtained based on the signal echo; (5) the beacon signal and the covert communication dual-function signal are jointly optimized; (6) the transmission power of the next frame is optimized in real time in each time frame to achieve the target requirements of wireless sensing covert communication; the present invention improves the reliability and concealment of covert communication.

Description

Technical Field

[0001] The present invention relates to the field of communication technology, and in particular to wireless sensing covert communication based on broadcast beacons. Background Art

[0002] Wireless covert communication is a special communication method that focuses on concealment. It has important application prospects in complex confrontation environments and scenarios with extremely high security requirements. In order to maximize the transmission rate of wireless covert communication while ensuring the concealment and security of communication, it is necessary to use beamforming methods to optimize the transmission power of the signal.

[0003] In order to solve the beamforming optimization problem in covert communication, there is usually a high reliance on the channel state information (CSI) of the communication scenario. The channel CSI between the covert communication sender and receiver can be obtained through the uplink communication protocol, while the covert communication detector usually does not cooperate with the covert communication sender to obtain CSI information; the power optimization of dual-function waveforms in the current existing ISAC covert communication is based on the established assumption that the detector has prior knowledge of the channel CSI, but there is no clear description of the method for obtaining this prior knowledge and the threshold of the perceived signal. This also leads to problems such as low efficiency and missing key steps in the power optimization of dual-function waveforms in the existing ISAC covert communication. Summary of the invention

[0004] Purpose of the invention: The purpose of the present invention is to provide a wireless sensing covert communication based on broadcast beacons, combining ISAC technology and covert communication technology, to obtain the channel CSI of the detecting party during covert communication, and to solve the power optimization problem of dual-function waveform in ISAC covert communication while ensuring concealment.

[0005] Technical solution: The wireless sensing covert communication based on broadcast beacon described in the present invention includes the following steps:

[0006] (1) The covert communication sender sends a radar signal and receives the echo;

[0007] (2) Based on the radar signal echo, a rough estimate of the CSI between the covert communication detector and the covert communication sender is made;

[0008] (3) Beacon signal beamforming;

[0009] (4) Obtain accurate CSI information between the covert communication detector and the sender based on the signal echo;

[0010] (5) Jointly optimize the dual-function signals of beacon signal and covert communication;

[0011] (6) In each time frame, the transmission power of the next frame is optimized in real time to achieve the goal of wireless sensing covert communication.

[0012] Furthermore, step (1) includes the following steps:

[0013] (11) The sender of covert communication imitates the legitimate beacon broadcast signal of the network equipment in the area, and broadcasts the current beacon as a radar signal with reference to the corresponding frequency;

[0014] (12) The sender of covert communication receives the echo of the transmitted radar signal.

[0015] Furthermore, step (3) includes the following steps:

[0016] (31) Modeling communication scenarios;

[0017] (32) The zero-forcing method is used for power optimization to maximize the signal echo of the covert communication detection party.

[0018] Furthermore, in step (4), the signal echo is used to perform channel estimation in each time frame, and the power of the next time frame is optimized to achieve an accurate estimation of the channel CSI, and silence is maintained between the two beacon signals.

[0019] Furthermore, in step (5), beamforming technology is used to maximize the radar reflection signal while ensuring that the covert communication rate meets the threshold.

[0020] Furthermore, in step (6), the signal echo is used to perform channel estimation in each time frame, and the power of the next time frame is optimized to achieve accurate estimation of the channel CSI; wherein the beacon signal is sent with reference to the corresponding transmission frequency, and the covert communication signal is always in the transmission state.

[0021] The wireless sensing covert communication system based on broadcast beacon described in the present invention comprises:

[0022] Transmitting module: used for covert communication where the sender sends radar signals and receives echoes;

[0023] Estimation module: used to roughly estimate the CSI between the covert communication detector and the covert communication sender based on the echo of the radar signal;

[0024] Beamforming module: used for beacon signal beamforming;

[0025] CSI information module: used to obtain accurate CSI information between the covert communication detector and the sender based on signal echo;

[0026] Joint optimization module: used to jointly optimize the dual-function signals of beacon signal and covert communication;

[0027] Real-time optimization module: used to optimize the transmission power of the next frame in real time in each time frame to achieve the target requirements of wireless perception covert communication.

[0028] An electronic device described in the present invention includes a memory, a processor, and a computer program stored in the memory and executable on the processor. When the computer program is loaded into the processor, any one of the wireless sensing covert communications based on broadcast beacons is implemented.

[0029] A storage medium described in the present invention stores a computer program, and when the computer program is executed by a processor, it implements any one of the wireless sensing covert communications based on broadcast beacons.

[0030] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: Based on the ISAC technology, the channel CSI between the covert communication detector and the covert communication sender is accurately estimated. In addition, the beamforming technology is used to design the dual-function waveform of covert communication and channel perception, and the signal reflection echo is maximized on the basis of meeting the covert communication rate requirements. Finally, the real-time and accurate estimation of the channel CSI is achieved, and the transmission power is optimized in real time according to the accurate CSI, thereby improving the reliability and concealment of covert communication. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is the application scenario of the present invention;

[0032] Figure 2 is a flow chart of the present invention;

[0033] Figure 3 This is the operation process of the wireless sensing covert communication system of the present invention when no covert communication is performed;

[0034] Figure 4 This is the operation process of the wireless sensing covert communication system at the covert communication moment of the present invention. DETAILED DESCRIPTION

[0035] The technical solution of the present invention is further described below in conjunction with the accompanying drawings.

[0036] like Figure 1As shown, an embodiment of the present invention provides a wireless perception covert communication based on broadcast beacons, which mainly includes two sub-scenarios. In sub-scenario 1, before the covert communication starts, the covert communication sender uses a sending device to broadcast a beacon signal. Usually a legal signal is used, such as a Beacon signal of Bluetooth or an AP beacon signal of WiFi. Using the signal echo of the transmitted beacon signal, the ISAC technology is used to sense the channel between the detection party and the sender. This scenario only involves the beamforming of one signal, the beacon signal. In sub-scenario 2, based on the perception of the channel CSI information between the detection party and the sender, the covert communication signal and the beacon signal can be beamformed simultaneously, such as Figure 2 As shown, the following steps are included:

[0037] (1) The covert communication sender sends a radar signal and receives the echo; the following steps are included:

[0038] (11) The sender of covert communication imitates the legitimate beacon broadcast signal of the network equipment in the area, and broadcasts the current beacon as a radar signal with reference to the corresponding frequency;

[0039] (12) The sender of covert communication receives the echo of the transmitted radar signal.

[0040] (2) Based on the radar signal echo, a rough estimate of the CSI between the covert communication detector and the covert communication sender is made;

[0041] (3) Beacon signal beamforming: Specifically: Model the communication scenario; Use zero-forcing to optimize power and maximize the signal echo of the covert communication detector.

[0042] (4) Obtain accurate CSI information between the covert communication detector and the sender based on the signal echo. The signal flow in each time slot is as follows: Figure 3 As shown in the figure, the signal echo is used to perform channel estimation in each time frame, and the power of the next time frame is optimized to achieve accurate estimation of the channel CSI, and silence is maintained between the two beacon signals.

[0043] (5) Jointly optimize the dual-function signals of beacon signal and covert communication; use beamforming technology to maximize the radar reflection signal while ensuring that the covert communication rate meets the threshold.

[0044] (6) In each time frame, the transmission power of the next frame is optimized in real time to achieve the goal of wireless sensing covert communication. The signal flow in each time slot is as follows: Figure 4As shown, the signal echo is used to estimate the channel in each time frame, and the power of the next time frame is optimized to achieve accurate estimation of the channel CSI. The beacon signal is sent with reference to the corresponding transmission frequency, and the covert communication signal remains in the transmission state.

[0045] The beamforming of the beacon signal and the covert communication signal includes the following steps:

[0046] (S1) Problem Modeling

[0047] When the radar only sends a detection signal without sending a communication signal, the signal reflected from the target can be written as:

[0048] (1.1);

[0049] in, represents the path loss coefficient, Indicates that the radar is only sending detection signals. The beamforming vector of is the noise received by the radar. is the radar detection signal in the present invention, which can be any common continuous broadcast signal such as a Bluetooth Beacon signal or a WIFI AP broadcast signal. Without loss of generality, the present invention assumes that , radar receiving channel In the present invention, the channel between the sender and the covert communication detection party) can be expressed as , represents the azimuth of the target (the detection party in this invention), represents the transmission steering vector. At the same time, assuming ,in Represents the receiving guidance vector. According to the existing ISAC communication papers, we can know the parameter and can be estimated from the received signal.

[0050] By detecting the signal Estimate the channel coefficient between the covert communication sender and the detector After that, send a hidden message Since the transmitted signal is omnidirectional, the covert communication sender can receive two types of echoes: the detection signal and the communication signal.

[0051] Considering that the covert communication receiver and sender can share channel CSI information, the covert communication sender can completely eliminate the signal echo from the covert communication receiver. The echo received by the covert communication sender is only from the covert communication detector, so the echo signal received by the covert communication party can be expressed as

[0052] (1.2);

[0053] in, is the covert transmission signal in the present invention, is the beamforming power vector for concealed information. Without loss of generality, the present invention assumes . is the Gaussian noise in the environment received by the radar.

[0054] (S2) Radar performance analysis

[0055] In order to characterize the performance of radar detection, mutual information can be used as a performance characterization indicator.

[0056] (1.3);

[0057] In the present invention, there are two situations for receiving the reflected signal of the radar:

[0058] A No covert communication time

[0059] Combined with formula (1.1), the moment when the concealed signal is not transmitted can be given. The mutual information of the radar signal in the present invention is:

[0060] (1.4);

[0061] B. Covert communication time

[0062] Combined with the above formula (1.2), the time of sending the concealed signal can be given. The mutual information expression of the radar signal in the present invention is:

[0063] (1.5);

[0064] (S3) Covert Communication Performance Analysis

[0065] Similarly, the Shannon formula can be used to characterize the transmission rate of covert communication, which can be expressed as:

[0066] (1.6);

[0067] (S4) Concealment performance analysis

[0068] Based on the general theory of hypothesis testing, the tester usually conducts the following binary hypothesis test:

[0069] (1.7);

[0070] Among them, H0 is the null hypothesis and H1 is the alternative hypothesis. is the ambient Gaussian noise at the covert communication detection party. Based on the above formula, the likelihood function expression at the time H0 and H1 can be given as:

[0071] (1.8);

[0072] (1.9);

[0073] In covert communication, KL divergence is usually used to characterize the concealment index, which can be expressed as:

[0074] (1.10);

[0075] in, , Represents an infinitesimal number. Based on the above background, the communication targets of the two main processes in the present invention can be modeled.

[0076] (S5) Problem statement

[0077] When no covert communication is performed, the radar detection signal is simply transmitted. The goal is to maximize the mutual information of the radar reflection signal to estimate the channel coefficient between the covert communication party and the covert communication detection party. The objective function can be expressed as:

[0078] (1.11);

[0079] In the above formula, is the total transmission power of the concealed communication device. This is a simple single-constraint optimization problem that can be solved directly using the zero-forcing method.

[0080] When performing covert communication, it is necessary to send radar detection signals and covert communication signals at the same time. The goal is to maximize the detection performance of radar detection signals on the basis of satisfying the covert communication transmission rate and concealment constraints. Its objective function can be expressed as:

[0081] (1.12);

[0082] In the above formula, is the threshold of covert communication transmission rate.

[0083] (S6) Convex Optimization Problem

[0084] In order to solve problem (1.12), the concealment constraint can be reconstructed first. That is, if we want the signal power accepted by the detection party to be infinitesimal, we can reconstruct the original concealment constraint as follows:

[0085] (1.13);

[0086] Then, we can introduce auxiliary variables , refactoring the original problem (1.12) into:

[0087] (1.14);

[0088] Using the semidefinite relaxation method to relax the problem, we can obtain:

[0089] (1.15);

[0090] By combining equation (1.15) and constraining By relaxing, the original problem (1.14) can be reformulated as:

[0091] (1.16);

[0092] It should be noted that for any value , problem (1.16) is a convex semidefinite problem. Given the convexity of the problem, we can Under the given value, the optimal value is solved by testing its feasibility (i.e. verifying whether the constraints are met).

[0093] In order to optimize the transmission power vector and To solve the problem, a binary step-by-step search algorithm is designed in the present invention, and the specific process is as follows:

[0094] C1, set the target search interval , and step accuracy .in, , A slightly larger value, the specific value and total power related.

[0095] C2, when At this moment, go to step C3, otherwise go to step C6.

[0096] C3, solve the middle value of the interval .if Now, use the CVX toolbox to solve the problem. If the constraints in problem (1.16) can be met, go to step C4, otherwise go to step C5.

[0097] C4, then the power factor is retained and , and adjust the interval boundaries , proceed to step C2.

[0098] C5, set step boundaries, , proceed to step C2.

[0099] C6, output optimal power vector and .

[0100] Using the above algorithm, the optimal power vector parameters for covert communication and radar transmission can be output.

[0101] The embodiment of the present invention further provides a wireless sensing covert communication system based on broadcast beacons, comprising:

[0102] Transmitting module: used for covert communication where the sender sends radar signals and receives echoes;

[0103] Estimation module: used to roughly estimate the CSI between the covert communication detector and the covert communication sender based on the echo of the radar signal;

[0104] Beamforming module: used for beacon signal beamforming;

[0105] CSI information module: used to obtain accurate CSI information between the covert communication detector and the sender based on signal echo;

[0106] Joint optimization module: used to jointly optimize the dual-function signals of beacon signal and covert communication;

[0107] Real-time optimization module: used to optimize the transmission power of the next frame in real time in each time frame to achieve the target requirements of wireless perception covert communication.

[0108] An embodiment of the present invention also provides an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the computer program is loaded into the processor, any one of the wireless sensing covert communications based on broadcast beacons is implemented.

[0109] An embodiment of the present invention further provides a storage medium storing a computer program, wherein the computer program, when executed by a processor, implements any one of the wireless sensing covert communications based on broadcast beacons.

Claims

1. A wireless sensing covert communication based on broadcast beacon, characterized in that: The following steps are involved: (1) The covert communication sender sends a radar signal and receives the echo; the following steps are included: (11) The sender of covert communication imitates the legitimate beacon broadcast signal of the network equipment in the area, and broadcasts the current beacon as a radar signal with reference to the corresponding frequency; (12) The sender of covert communication receives the echo of the radar signal sent; (2) Based on the radar signal echo, a rough estimate of the CSI between the covert communication detector and the covert communication sender is made; (3) Beacon signal beamforming; comprising the following steps: (31) Modeling communication scenarios; (32) Use zero-forcing method to optimize power and maximize the signal echo of the covert communication detection party; (4) Obtain accurate CSI information between the covert communication detector and the sender based on the signal echo; wherein, the signal echo is used to estimate the channel in each time frame, and the power of the next time frame is optimized to achieve the final accurate estimation of the channel CSI, and silence is maintained between the two beacon signals; (5) Jointly optimize the dual-function signals of beacon signal and covert communication; use beamforming technology to maximize the radar reflection signal while ensuring that the covert communication rate meets the threshold; (6) In each time frame, the transmission power of the next frame is optimized in real time to achieve the goal of wireless perception covert communication; wherein, the signal echo is used to estimate the channel in each time frame, and the power of the next time frame is optimized to achieve accurate estimation of the channel CSI; wherein, the transmission of the beacon signal refers to the corresponding transmission frequency, and the covert communication signal is always in the transmission state.

2. A wireless sensing covert communication system based on broadcast beacons, characterized in that: include: Transmitting module: used for the covert communication sender to send radar signals and receive echoes; the details are as follows: the covert communication sender imitates the legitimate beacon broadcast signal of the network device in the area, and broadcasts the current beacon as a radar signal with reference to the corresponding frequency; the covert communication sender receives the echo of the sent radar signal; Estimation module: used to roughly estimate the CSI between the covert communication detector and the covert communication sender based on the echo of the radar signal; Beamforming module: used for beacon signal beamforming; specifically: modeling the communication scenario; using zero-forcing method for power optimization to maximize the signal echo of the covert communication detection party; CSI information module: used to obtain accurate CSI information between the covert communication detector and the sender based on the signal echo; wherein, the signal echo is used to perform channel estimation in each time frame, and the power of the next time frame is optimized to achieve the final accurate estimation of the channel CSI, and silence is maintained between the two beacon signals; Joint optimization module: used to jointly optimize the dual-function signals of beacon signal and covert communication; using beamforming technology to maximize the radar reflection signal while ensuring that the covert communication rate meets the threshold; Real-time optimization module: used to optimize the transmission power of the next frame in real time in each time frame to achieve the target requirements of wireless perception covert communication; wherein, the signal echo is used to estimate the channel in each time frame, and the power of the next time frame is optimized to achieve accurate estimation of the channel CSI; wherein, the transmission of the beacon signal refers to the corresponding transmission frequency, and the covert communication signal is always in the transmission state.

3. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that: When the computer program is loaded into a processor, the wireless-aware covert communication based on broadcast beacons according to claim 1 is implemented.

4. A storage medium storing a computer program, characterized in that: When the computer program is executed by a processor, the wireless-aware covert communication based on broadcast beacons according to claim 1 is implemented.

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