A Joint Secure and Stealth Communication Method and System Based on Rate Splitting

Abstract

A joint secure and covert communication method and system based on rate splitting provided by the present invention includes the following steps: calculating the secure communication rate of secure communication users; calculating the covert communication rate of covert communication users; calculating the power allocation coefficient corresponding to the base station under the conditions of satisfying secure communication, covert communication, and power limitation; the base station performs covert communication with the covert communication users in a pre-agreed time slot, and uses the obtained power allocation coefficient to transmit information to the covert communication users and the secure communication users; the present invention can reasonably and flexibly utilize the base station power resources, and significantly improves the system transmission rate compared with the scheme without rate splitting, thereby improving the frequency band utilization rate under the requirements of joint secure and covert communication.

Description

Technical Field

[0001] The present invention relates to the implementation of physical layer security transmission and covert communication, and particularly to a joint secrecy and covert communication method and system based on rate splitting. Background Art

[0002] With the rapid development of wireless communication, the security and privacy of wireless communication are becoming a key consideration for network operators, and wireless communication security has become the core problem that any communication system needs to face. Generally speaking, the security protection of wireless communication is realized based on the method of information encryption at a higher layer in network design, which assumes that the wireless computing ability of eavesdroppers is limited, so that they cannot discover the key assigned to legitimate users to decrypt confidential information.

[0003] Information-theoretic secrecy (ITS) is a promising wireless communication security technology, which does not involve information encryption, but realizes information security protection at the information transmission level. In some exploratory works, scholars have demonstrated that when the channel of the eavesdropper is a degraded version of the channel of the legitimate user, the sender and the receiver can achieve a rate that meets the information secrecy requirements. In addition, several technologies have proposed methods to achieve information-theoretic secrecy: transmit beamforming, antenna selection, cooperative technology, artificial noise-assisted transmission, using power-domain non-orthogonal multiple access (PD-NOMA), etc. The goal of information-theoretic secrecy is to ensure the security of confidential information sent to the target user. However, in many practical applications, such as military communication, simply protecting information security is far from enough. The communication parties also hope that the information is transmitted covertly, that is, the communication itself cannot be detected, which is the so-called covert communication; and currently, traditional secure communication cannot simultaneously achieve the problem of covert communication, resulting in communication security problems. Summary of the Invention

[0004] The purpose of the present invention is to provide a joint secrecy and covert communication method and system based on rate splitting, which solves the above-mentioned deficiencies in the prior art.

[0005] In order to achieve the above purpose, the technical solution adopted by the present invention is:

[0006] A joint secrecy and covert communication method based on rate splitting provided by the present invention is based on a set base station, secure communication users, covert communication users, virtual eavesdroppers, and virtual monitors, and includes the following steps:

[0007] Step 1, in the current time slot, the base station respectively obtains the channel state information and location information of the covert communication user, the secure communication user, and the virtual eavesdropper;

[0008] Step 2: Set the base station to perform covert communication with the covert communication user in a specific time slot, and the base station communicates with the secure communication user at the same time; outside the specific time slot, the base station sends messages to the secure communication user and does not send messages to the covert communication user, and then calculate the secure communication rate of the secure communication user.

[0009] Set the base station to send messages to the secure communication user and the covert communication user at the same time, and then calculate the secure communication rate of the secure communication user at this time.

[0010] Step 3: Construct the conditions for the establishment of covert communication, and then calculate the covert communication rate of the covert communication user.

[0011] Step 4: According to the covert communication rate of the covert communication user obtained in Step 3, calculate the corresponding power allocation coefficient of the base station under the conditions of satisfying secure communication, covert communication, and power limitation.

[0012] Step 5: The base station performs covert communication with the covert communication user in a pre-agreed time slot, and uses the power allocation coefficient obtained in Step 4 to transmit information to the covert communication user and the secure communication user.

[0013] Preferably, in Step 2, set the base station to perform covert communication with the covert communication user in a specific time slot, and the base station communicates with the secure communication user at the same time; outside the specific time slot, the base station sends messages to the secure communication user and does not send messages to the covert communication user, and then calculate the secure communication rate of the secure communication user. The specific method is:

[0014] Calculate the signal-to-noise ratios at the secure communication user and the virtual eavesdropper respectively.

[0015] Calculate the secure communication rate at the secure communication user according to the signal-to-noise ratios at the secure communication user and the virtual eavesdropper.

[0016] Preferably, in Step 2, set the base station to send messages to the secure communication user and the covert communication user at the same time, and then calculate the secure communication rate of the secure communication user at this time. The specific method is:

[0017] Set the base station to use the rate splitting strategy to send messages to the secure communication user and the covert communication user respectively.

[0018] Calculate the signal-to-noise ratios at the secure communication user, the virtual eavesdropper, and the virtual eavesdropper respectively.

[0019] Calculate the corresponding channel capacities according to the signal-to-noise ratios at the secure communication user, the virtual eavesdropper, and the virtual eavesdropper respectively.

[0020] Calculate the secure communication rate at the secure communication user according to the channel capacities at the secure communication user, the virtual eavesdropper, and the virtual eavesdropper.

[0021] Preferably, in step 3, the conditions for the establishment of covert communication are constructed, and then the covert communication rate of the covert communication user is calculated. The specific method is as follows:

[0022] Set the expression of the signal received at the eavesdropper.

[0023] Obtain the optimal decision rule that minimizes the detection error probability of the eavesdropper according to this expression.

[0024] Obtain the false alarm expression and the miss detection expression of the eavesdropper according to the obtained optimal decision rule that minimizes the detection error probability of the eavesdropper.

[0025] Obtain the expression of the index requirement for achieving covert communication between the base station and the covert communication user according to the false alarm expression and the miss detection expression of the eavesdropper.

[0026] Calculate the covert communication rate at the covert communication user according to this index requirement expression.

[0027] Preferably, in step 4, according to the covert communication rate of the covert communication user obtained in step 3, calculate the power allocation coefficient corresponding to the base station under the conditions of satisfying secure communication, covert communication, and power limitation. The specific method is as follows:

[0028] Set that the base station equally probably sends covert information to the covert communication user at each moment, and then obtain the average rate of the base station at each moment.

[0029] Obtain the optimization problem expression that maximizes the average rate under the constraints of power limitation, covert communication, and information security according to the obtained average rate of the base station at each moment.

[0030] Obtain the maximum transmission power of the base station according to the obtained optimization problem expression.

[0031] Obtain the power allocation coefficient corresponding to the maximum average rate according to the obtained maximum transmission power.

[0032] Preferably, in step 5, the base station uses the rate splitting strategy to transmit information to the covert communication user and the secure communication user.

[0033] Preferably, the rate splitting strategy is used to transmit information to the covert communication user and the secure communication user. The specific method is as follows:

[0034] Divide the information of the covert communication user and the secure communication user into a common part and a private part respectively.

[0035] Merge the information of the common part of the covert communication user and the secure communication user to obtain the common information.

[0036] Encode the information of the private parts of the covert communication user and the secure communication user separately;

[0037] Use the power allocation coefficient obtained in step 4 to send the obtained common information and the encoded private part information to the covert communication user and the secure communication user respectively.

[0038] A joint secure and covert communication system based on rate splitting, which can run the described method. The method is based on a set base station, secure communication users, covert communication users, virtual eavesdroppers, and virtual monitors, and includes:

[0039] An information acquisition unit, which is used for the base station to acquire the channel state information and location information of the covert communication user, the secure communication user, and the virtual eavesdropper respectively in the current time slot;

[0040] A secure communication rate calculation unit, which is used for the set base station to perform covert communication with the covert communication user in a specific time slot, and the base station communicates with the secure communication user at the same time; outside the specific time slot, the base station sends a message to the secure communication user and does not send a message to the covert communication user, then calculates the secure communication rate of the secure communication user;

[0041] If the set base station sends messages to the secure communication user and the covert communication user at the same time, then calculate the secure communication rate of the secure communication user at this time;

[0042] A covert communication rate calculation unit, which is used to construct the conditions for the establishment of covert communication, and then calculate the covert communication rate of the covert communication user;

[0043] A power allocation coefficient calculation unit, which is used to calculate the corresponding power allocation coefficient of the base station under the conditions of satisfying secure communication, covert communication, and power limitation according to the obtained covert communication rate of the covert communication user;

[0044] An information transmission unit, which is used for the base station to perform covert communication with the covert communication user in a pre-agreed time slot, and use the obtained power allocation coefficient to transmit information to the covert communication user and the secure communication user.

[0045] Compared with the prior art, the beneficial effects of the present invention are:

[0046] A joint secure and covert communication method based on rate splitting provided by the present invention adopts a rate splitting scheme and uses common information as interference against eavesdroppers and untrusted users to achieve the purposes of secure communication and covert communication. The adopted rate splitting scheme gives full play to the role of users with different requirements in information transmission in the current time slot. The signals of users with secure communication requirements interfere with eavesdroppers to support the covert communication requirements of another user. The signals of users with covert communication requirements interfere with eavesdroppers to support the secure communication requirements of another user, thereby improving the power utilization rate at the base station side.

[0047] By splitting and combining the information of legitimate users, it increases the difficulty for eavesdroppers to crack the information. And the base station selects to send covert information in different time slots, further increasing the difficulty for eavesdroppers to detect the covert information and enhancing the security performance of signal transmission.

[0048] In summary, the present invention uses the average rate as the evaluation index. By using the rate splitting strategy, it ensures the covert communication and secure communication of users. At the same time, by optimizing the power allocation coefficient, it maximizes the average information rate. Simulation experiments prove that the present invention can reasonably and flexibly utilize the base station power resources, and significantly improves the system transmission rate compared with the scheme without rate splitting, thereby improving the frequency band utilization rate under the requirements of joint secure and covert communication. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 is the joint secure and covert communication transmission model of the SIMO network involved in the present invention;

[0050] Figure 2 is the schematic diagram of the rate splitting strategy designed by the present invention.

[0051] Figure 3 is the simulation diagram of the average rate using the rate splitting strategy and not using the rate splitting strategy with the change of user distance.

[0052] Figure 4 is the simulation diagram of the average rate using the rate splitting strategy and not using the rate splitting strategy with the change of transmitter power. DETAILED DESCRIPTION OF THE INVENTION

[0053] The following further describes the present invention in detail with reference to the drawings.

[0054] A joint secure and covert communication method based on rate splitting provided by the present invention adopts a rate splitting scheme and uses common information as interference against eavesdroppers and untrusted users to achieve the purposes of secure communication and covert communication.

[0055] As Figure 1As shown, a joint secure and covert communication method based on rate splitting provided by the present invention sets that base station Alice simultaneously serves secure communication user Bob and covert communication user Carol. The base station is equipped with N antennas. At the same time, there is a virtual eavesdropper Eve in the base station attempting to intercept the message sent by base station Alice to secure communication user Bob, and a virtual monitor Willie attempting to detect whether base station Alice is sending a message to Carol. And all nodes in the network are only equipped with a single antenna.

[0056] Specifically, it includes the following steps:

[0057] In the first step, in the current time slot, base station Alice obtains the channel state information and location information of covert communication user Carol, secure communication user Bob, and virtual eavesdropper Eve through channel training;

[0058] In the second step, base station Alice selects a specific time slot to conduct covert communication with covert communication user Carol, and base station Alice always communicates with secure communication user Bob;

[0059] When base station Alice does not send covert information to covert communication user Carol outside the specific time slot, it only sends the information of secure communication user Bob; by calculating the signal-to-noise ratios at secure communication user Bob and virtual eavesdropper Eve, the respective channel capacities can be obtained, and by comparing them, the secure communication rate at secure communication user Bob can be obtained. Specifically:

[0060] S1, the signal expression sent by base station Alice is as follows:

[0061] x = P s S b = ρ s PS b Ψ0

[0062] Where P is the total transmitter power; Ψ0 means that base station Alice does not send a covert signal to covert communication user Carol; ρ s is the power allocation coefficient under the condition of Ψ0; S b is the information sent by base station Alice to secure communication user Bob; P s is the power for base station Alice to send information to secure communication user Bob.

[0063] S2, the signal-to-noise ratios at secure communication user Bob and virtual eavesdropper Eve can be expressed as follows:

[0064] γb = ρ s g b

[0065] γ e = ρ s g e

[0066]

[0067] where γ b is the initial signal-to-noise ratio of the legitimate communication user Bob; γ e is the signal-to-noise ratio at the virtual eavesdropper Eve; g m is the channel gain defined at point m in the system; h am is the channel fading coefficient from the base station Alice to point m, which follows a complex Gaussian distribution; d am is the distance from the base station Alice to point m; α is the path loss exponent; N m is the noise at point m,

[0068] S3. The secrecy communication rate at the legitimate communication user Bob can be expressed as follows:

[0069] R sec = [log2(1 + γ b ) - log2(1 + γ e )] +

[0070] where [x] + = max{x, 0};

[0071] Step 3. When the base station Alice sends the covert information to the covert communication user Carol and also sends a message to the legitimate communication user; assume that the base station Alice adopts the rate splitting strategy to send the information of the covert communication user Carol and the legitimate communication user Bob respectively, specifically:

[0072] S1. Divide the information of the two communication users into a common part and a private part respectively, that is, the information of both users has a common part and a private part;

[0073] S2. When the base station sends the information, merge the common parts of the two communication users into the common information W com , and encode this common information into the common information S com using the codebook shared by the two users. The private parts of the private information W p,b and W p,c are independently encoded into S b and S c . S com , S b and S c are sent to the legitimate communication user and the covert communication user respectively after linear precoding, and their expressions are as follows:

[0074] x = P com S com +P b S b +P c S c =ρ com PS com +ρ b PS b +ρ c PS c Ψ1

[0075] Among them, P is the total power of the transmitter; Ψ1 means that the base station Alice sends hidden information to the hidden communication user Carol; S com is the encoded public information; S b is the information encoded from the private information part of the secure communication user Bob; S c is the information encoded from the private information part of the hidden communication user Carol; ρ com ,ρ b ,ρ c ∈[0,1] and ρ com +ρ b +ρ c =1, ρ com is the power distribution coefficient of the transmitter for the public information under the condition of Ψ1; ρ b is the power distribution coefficient of the transmitter for the private information of the secure communication user Bob under the condition of Ψ1; ρ c is the power distribution coefficient of the transmitter for the private information of the hidden communication user Carol under the condition of Ψ1; P com is the power of the transmitter to transmit public information; P b is the power of the transmitter to transmit the private information of the secure communication user Bob; P c is the power of the transmitter to transmit the private information of the hidden communication user Carol;

[0076] S3. The hidden communication user Carol (secure communication user Bob) first regards the private information S b and S c as noise to decode the public information S com , and separates the part belonging to the hidden communication user Carol (secure communication user Bob) from the public information according to the strategy of the transmitter combining public information;

[0077] S4. The hidden communication user Carol and the secure communication user Bob use the successive interference cancellation technique (SIC) to remove the public information S decoded in S3 comRe-encode, pre-code and subtract from the received signal. Subsequently, the covert communication user Carol (the secure communication user Bob) will use S b (S c ) as an interference signal and decode S c (S b ). Finally, the covert communication user Carol and the secure communication user Bob respectively combine the parts of the common information that belong to themselves with the private information to obtain the complete information.

[0078] Step 4: By calculating the signal-to-noise ratios at the secure communication user Bob, the virtual eavesdropper Eve, and the covert communication user Carol, the respective channel capacities can be obtained, and the secure communication rate at the secure communication user Bob can be obtained. The specific steps are as follows:

[0079] S1. The expression for the signal received at the communication user is:

[0080]

[0081] where h am is the channel fading coefficient from the base station Alice to point m, which follows a complex Gaussian distribution; d am is the distance from the base station Alice to point m; α is the path loss exponent; N m is the noise at point m.

[0082] S2. To ensure that the common message can be decoded by each legitimate user, its actual transmission rate should satisfy the condition: where is the channel capacity of the common message and is defined by the following expression:

[0083]

[0084] where: is the channel capacity of the common information at the secure communication user Bob; is the channel capacity of the common information at the covert communication user Carol.

[0085] S3. For the virtual eavesdropper Eve, this condition should be satisfied, where represents the channel capacity of the common information between the base station Alice and the virtual eavesdropper Eve, so that the message W com cannot be decoded at the virtual eavesdropper Eve, and then W com can be used as its noise for interference. The expression is:

[0086]

[0087] The expressions for the signal-to-noise ratio of the common information at the covert communication user Carol, the secure communication user Bob, and the virtual eavesdropper Eve in S4 are as follows:

[0088]

[0089]

[0090]

[0091] S5. The covert communication user Carol and the secure communication user Bob can use SIC to cancel the interference of the common information. Therefore, the expressions for the signal-to-noise ratio of the private information at the covert communication user Carol, the secure communication user Bob, and the virtual eavesdropper Eve are as follows:

[0092]

[0093]

[0094]

[0095] Among them, is the channel gain defined at the m-th point in the system;

[0096] S6. Calculate the channel capacity of the private information at the secure communication user Bob and the virtual eavesdropper Eve. The expression is:

[0097]

[0098]

[0099] S7. Calculate the secure communication rates of the common information and the private information at the secure communication user Bob respectively. The expression is:

[0100]

[0101]

[0102] Among them, k is a constant representing the proportion of the common information belonging to the secure communication user Bob.

[0103] Step 5. By judging the received information power at the eavesdropper Willie, obtain the condition for the establishment of covert communication, and then obtain the covert communication rate. The specific steps are as follows:

[0104] S1. The expression of the signal received at the eavesdropper Willie is as follows:

[0105]

[0106] The ultimate goal of the monitoring party is to determine whether it is under the hypothesis Ψ0 or Ψ1. The optimal decision rule for minimizing the detection error probability of the monitoring party Willie can be written as: w whether it is under the hypothesis Ψ0 or Ψ1. The optimal decision rule for minimizing the detection error probability of the monitoring party Willie can be written as:

[0107]

[0108] where, is the total power received by Willie in each time slot; θ is the decision threshold of Willie. In the case of Ψ1, that is, when the base station Alice sends covert information to the covert communication user Carol, if Y w > θ, then Willie believes that there is a covert communication process; similarly, in the case of Ψ0, that is, when the base station Alice does not send covert information to the covert communication user Carol, if Y w < θ, then Willie believes that there is no covert communication process.

[0109] S2, for the convenience of calculation, define The expression is as follows:

[0110]

[0111] where h aw obeys the complex Gaussian distribution, then there is

[0112] S3, calculate The probability density of, which obeys the exponential distribution, and the expression is:

[0113]

[0114] where,

[0115] S4, Willie decides whether the base station Alice has sent information to the covert communication user Carol according to the signal power it receives. Assume that the events and respectively represent that the monitoring party believes that the base station Alice has not sent covert information to the covert communication user Carol and that the monitoring party believes that the base station Alice has sent covert information to the covert communication user Carol. The detection error probability is a commonly used indicator to measure the detection performance of the monitoring party, and it is composed of the sum of the false alarm probability and the miss probability. Among them, the false alarm probability is defined as the probability that the monitoring party Willie tends to in the case of Ψ0, and the miss probability is defined as the probability that Willie tends to in the case of Ψ1, and can be expressed by the formulas respectively as:

[0116]

[0117]

[0118] S5. In this paper, it is assumed that Ψ0 and Ψ1 have the same occurrence probability, that is, the probability that the transmitter base station Alice sends and does not send the covert information is the same. Under this assumption, the detection error probability of the eavesdropper can be expressed as

[0119]

[0120] S6. Let θ be the decision threshold of the eavesdropper Willie. Then the probability expressions for the false alarm and missed detection of the eavesdropper are as follows:

[0121]

[0122]

[0123] Specific calculations yield the expression as:

[0124]

[0125]

[0126]

[0127] S7. The index requirements for achieving covert communication between the base station Alice and the covert communication user Carol are obtained, and its expression is:

[0128] When n → ∞

[0129] S8. After meeting the covert communication index, the communication rates of the common information and the private information at the covert communication user Carol can be expressed as:

[0130]

[0131]

[0132] Step 6. Under the conditions of meeting the secure communication, covert communication, and power limitation, optimize the power allocation coefficient to obtain the maximum average rate. The specific steps are as follows:

[0133] S1. The base station Alice equally probably sends the covert information to the covert communication user Carol at each moment. Then the average rate expression at each moment is:

[0134]

[0135] S2. Maximize the average rate under the constraints of power limitation, covert communication, and information security. The optimization problem expression is as follows:

[0136]

[0137]

[0138]

[0139]

[0140]

[0141] 0 ≤ ρ com ≤ 1, 0 ≤ ρ b ≤ 1, 0 ≤ ρ c ≤ 1, ρ com + ρ b + ρ c =1

[0142] where is the minimum rate requirement for secure communication, is the minimum rate requirement for covert communication, is the minimum rate requirement for public information.

[0143] S3. The secrecy information rate R sec in the case of Ψ0. When g b > g e , it is a monotonically increasing function of ρ s . Therefore, to maximize the average rate, the base station Alice should transmit information at the maximum allowable transmission power in the case of Ψ0, so that ρ s =1. When ρ s =1, we can obtain: At this time the requirements for covert communication are always satisfied.

[0144] S4. Conduct a mathematical analysis of the optimization problem, analyze the monotonicity of with respect to ρ c , find the monotonic intervals of ρ c under different channel conditions, then traverse ρ b , find ρ b that satisfies the constraints according to the monotonicity for different ρ c , and finally find the power allocation coefficients ρ c ′ and ρ′ b corresponding to the maximum average rate.

[0145] Step 7: The base station Alice conducts covert communication with the covert communication user Carol in a pre-agreed time slot. Using the maximum average rate optimized in Step 6, it sends the information of the covert communication user Carol and the secure communication user Bob by adopting the rate splitting strategy. The specific steps are as follows:

[0146] S1, Divide the information of the covert communication user Carol and the secure communication user Bob into the common part (W com,c ,W com,b ) and the private part (W p,c ,W p,b ).

[0147] S2, Merge W com,b ,W com,c into the common message W com . This message is encoded into the common information S com using the codebook shared by the two users; Subsequently, the private information W p,b and W p,c are independently encoded as S b and S c . After linear precoding, the base station Alice uses the optimal power allocation coefficients ρ c ′ and ρ′ b obtained in Step 6 to send the information as shown in the following formula:

[0148] x = ρ′ com PS com + ρ′ b PS b + ρ′ c PS c

[0149] where ρ′ com = 1 - ρ′ b - ρ′ c .

[0150] Embodiment

[0151] The simulation experiment verifies the effectiveness and feasibility of the joint secure communication and covert communication of this patent. The parameters used in this embodiment are shown in the following table:

[0152]

[0153] Figure 3The computer simulation results of the method of the present invention are given and compared with the rateless splitting scheme. The simulation parameters are exactly the same under these two methods. In the figure, the abscissa represents the distance dab between the base station Alice and the secure communication user Bob, and the ordinate represents the system ergodic average rate. It can be seen from the figure that the method of the present invention is significantly superior to the other method at different transmission distances; when the distance between the transmitter base station Alice and the secure communication user Bob with secure communication requirements is relatively close, the average rate achieved by this scheme is greater.

[0154] Figure 4 The computer simulation results of the method of the present invention are given and compared with the rateless splitting scheme. The simulation parameters are exactly the same under these two methods. In the figure, the abscissa represents the transmitter power P, and the ordinate represents the system ergodic average rate. It can be seen from the figure that the method of the present invention is significantly superior to the other method at different transmitter powers; when the total power of the transmitter base station Alice is relatively small, under the requirements of secure communication and covert communication, the average rate achieved by this scheme is greater.

Claims

1. A joint secure and covert communication method based on rate splitting, characterized in that, The method is based on a set of base stations, secure communication users, covert communication users, virtual eavesdroppers, and virtual monitors, and includes the following steps: Step 1, at the current time slot, the base station respectively obtains the channel state information and location information of the covert communication user, the secure communication user, and the virtual eavesdropper; Step 2, it is set that the base station conducts covert communication with the covert communication user at a specific time slot, and the base station communicates with the secure communication user at the same time; outside the specific time slot, the base station sends a message to the secure communication user and does not send a message to the covert communication user, then calculate the secure communication rate of the secure communication user; It is set that the base station sends messages to both the secure communication user and the covert communication user at the same time, then calculate the secure communication rate of the secure communication user at this time; Step 3, construct the conditions for the establishment of covert communication, and then calculate the covert communication rate of the covert communication user; Step 4, according to the covert communication rate of the covert communication user obtained in Step 3, calculate the corresponding power allocation coefficient of the base station under the conditions of satisfying secure communication, covert communication, and power limitation; Step 5, the base station conducts covert communication with the covert communication user at a pre-agreed time slot, and uses the power allocation coefficient obtained in Step 4 to transmit information to the covert communication user and the secure communication user.

2. The joint secure and covert communication method based on rate splitting according to claim 1, wherein In Step 2, it is set that the base station conducts covert communication with the covert communication user at a specific time slot, and the base station communicates with the secure communication user at the same time; outside the specific time slot, the base station sends a message to the secure communication user and does not send a message to the covert communication user, then calculate the secure communication rate of the secure communication user. The specific method is: Calculate the signal-to-noise ratios at the secure communication user and the virtual eavesdropper respectively; Calculate the secure communication rate at the secure communication user according to the signal-to-noise ratios at the secure communication user and the virtual eavesdropper.

3. A joint secure and covert communication method based on rate splitting according to claim 1, characterized in that, In Step 2, it is set that the base station sends messages to both the secure communication user and the covert communication user at the same time, then calculate the secure communication rate of the secure communication user at this time. The specific method is: It is set that the base station uses the rate splitting strategy to send messages to the secure communication user and the covert communication user respectively; Calculate the signal-to-noise ratios at the secure communication user, the virtual eavesdropper, and the virtual monitor respectively; Calculate the corresponding channel capacities according to the signal-to-noise ratios at the secure communication user, the virtual eavesdropper, and the virtual monitor respectively; Calculate the secure communication rate at the secure communication user according to the channel capacities at the secure communication user, the virtual eavesdropper, and the virtual monitor.

4. A joint secure and covert communication method based on rate splitting according to claim 1, characterized in that In Step 3, construct the conditions for the establishment of covert communication, and then calculate the covert communication rate of the covert communication user. The specific method is: Set the expression of the signal received at the monitor; Obtain the optimal decision rule for minimizing the detection error probability of the monitor according to this expression; Obtain the false alarm expression and the missed detection expression of the monitor according to the obtained optimal decision rule for minimizing the detection error probability of the monitor; Obtain the expression of the index requirement for achieving covert communication between the base station and the covert communication user according to the false alarm expression and the missed detection expression of the monitor; Calculate the covert communication rate at the covert communication user according to this index requirement expression.

5. A joint secure and covert communication method based on rate splitting according to claim 1, characterized in that, In step 4, according to the covert communication rate of the covert communication user obtained in step 3, calculate the corresponding power allocation coefficient of the base station under the conditions of satisfying secure communication, covert communication, and power limitation. The specific method is as follows: Assume that the base station equally likely sends covert information to the covert communication user at each moment, and then obtain the average rate of the base station at each moment; According to the average rate of the base station obtained at each moment, obtain the expression of the optimization problem that maximizes the average rate under the constraints of power limitation, covert communication, and information security; According to the obtained expression of the optimization problem, obtain the maximum transmission power of the base station; According to the obtained maximum transmission power, obtain the power allocation coefficient corresponding to the maximum average rate.

6. A joint secure and covert communication method based on rate splitting according to claim 1, characterized in that In step 5, the base station uses the rate splitting strategy to transmit information to the covert communication user and the secure communication user.

7. A joint secure and covert communication method based on rate splitting according to claim 6, characterized in that, The method of using the rate splitting strategy to transmit information to the covert communication user and the secure communication user is as follows: Divide the information of the covert communication user and the secure communication user into a common part and a private part respectively; Merge the information of the common parts of the covert communication user and the secure communication user to obtain the common information; Encode the information of the private parts of the covert communication user and the secure communication user respectively; Use the power allocation coefficient obtained in step 4 to send the obtained common information and the encoded private part information to the covert communication user and the secure communication user respectively.

8. A joint secure and covert communication system based on rate splitting, characterized in that, This system can run the method described in any one of claims 1-7. This method is based on a set base station, secure communication user, covert communication user, virtual eavesdropper, and virtual monitor, and includes: An information acquisition unit, which is used for the base station to acquire the channel state information and location information of the covert communication user, the secure communication user, and the virtual eavesdropper respectively in the current time slot; A secure communication rate calculation unit, which is used for setting that the base station conducts covert communication with the covert communication user in a specific time slot, and the base station communicates with the secure communication user at the same time; outside the specific time slot, the base station sends a message to the secure communication user and does not send a message to the covert communication user, and then calculate the secure communication rate of the secure communication user; Set that the base station sends messages to the secure communication user and the covert communication user at the same time, and then calculate the secure communication rate of the secure communication user at this time; A covert communication rate calculation unit, which is used for constructing the conditions for the establishment of covert communication, and then calculating the covert communication rate of the covert communication user; A power allocation coefficient calculation unit, which is used for calculating the corresponding power allocation coefficient of the base station under the conditions of satisfying secure communication, covert communication, and power limitation according to the covert communication rate of the covert communication user obtained; An information transmission unit, which is used for the base station to conduct covert communication with the covert communication user in a pre-agreed time slot, and use the obtained power allocation coefficient to transmit information to the covert communication user and the secure communication user.

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