Signal security transmission method and transmission system

Abstract

The application provides a signal safety transmission method and a transmission system. The signal safety transmission method comprises the following steps: constructing a satellite-cell joint communication system, which comprises a satellite system and a cell system, and the satellite system and the cell system jointly provide services for users; based on the satellite-cell joint communication system, an optimization problem with a safety rate maximization as a target is established; the optimization problem with the safety rate maximization as the target is solved in two cases of diversity and multiplexing respectively, and an optimized safety transmission rate is obtained. According to the application, all users can simultaneously receive signals from the satellite system and the cell system, and the signals are safely transmitted in consideration of the two modes of diversity and multiplexing, so that more efficient and stable communication services are provided for the users.

Description

Technical Field

[0001] This invention relates to the field of communication technology, and in particular to a secure signal transmission method and transmission system. Background Technology

[0002] To achieve massive connectivity and meet ever-increasing data demands, fifth-generation (5G) mobile communication systems have proposed effective transmission technologies such as massive multiple-input multiple-output (MIMO) and non-orthogonal multiple access (NOMA). However, network access remains lacking in areas with no service coverage, such as oceans and remote mountainous regions. Satellite systems, with their wide coverage, can compensate for the shortcomings of terrestrial base station systems. Deeply integrating the superior access capabilities and mobility of terrestrial cellular mobile communication networks with the extensive coverage capabilities of satellite communication networks, leveraging the respective advantages of both, to achieve wide-area coverage and network interconnectivity, has become an important direction for 6G development. 6G can provide users worldwide with ubiquitous connectivity, high-quality services, and scalable networks, thereby enabling diverse applications. Summary of the Invention

[0003] This invention provides a secure signal transmission method and system to address the shortcomings of existing technologies where satellite systems only provide services to satellite users and cellular base stations only provide services to cellular users, failing to achieve true joint communication. This invention enables satellite systems and cellular systems to jointly provide services to users, thereby achieving secure signal transmission.

[0004] This invention provides a method for secure signal transmission, comprising the following steps:

[0005] Construct a satellite-cellular joint communication system, which includes satellite systems and cellular systems, and the satellite and cellular systems work together to provide services to users;

[0006] Based on a satellite-cellular joint communication system, an optimization problem is established with the goal of maximizing secure data rate.

[0007] In both diversity and multiplexing cases, the optimization problem aimed at maximizing the secure transmission rate is solved to obtain the optimized secure transmission rate.

[0008] According to a signal secure transmission method provided by the present invention, in the satellite-cellular joint communication system, the received signal y of a legitimate user k... k And the received signal y of the eavesdropper eve eve They are respectively:

[0009]

[0010]

[0011] In the formula, P sat,k w represents the power transmitted by the satellite to the legitimate user k. sat,k s represents the beamforming vector of a legitimate user k in a satellite system. sat,k P represents the signal sent by the satellite to the legitimate user k; i w represents the power transmitted from the ground base station to the legitimate user i. i s represents the beamforming vector of a legitimate user i in a cellular system. i This represents the signal sent by the ground base station to the legitimate user i; h k This represents the channel vector from the satellite to the legitimate user k. h k The conjugate transpose of the matrix, h eve This represents the channel vector from the satellite to the eavesdropper, eve. h eve The conjugate transpose of g; k This represents the channel vector from the ground base station to the legitimate user k. G represents k The conjugate transpose of the matrix, g eve This represents the channel vector from the ground base station to the eavesdropper, eve. G represents eve The conjugate transpose of n k This indicates that the mean is zero and the variance is... Gaussian additive white noise, n eve This indicates that the mean is zero and the variance is... Gaussian additive white noise; K represents the total number of legitimate users in the satellite-cellular joint communication system.

[0012] According to a signal secure transmission method provided by the present invention, the process of establishing an optimization problem with the objective of maximizing the secure rate is as follows:

[0013] Based on the physical layer security definition, the security rate of the satellite-cellular joint communication system is modeled as follows:

[0014]

[0015] In the formula, R sec To represent the safe rate, set an intermediate parameter x, let x = log2(1 + SINR) k )-log2(1+SINR eve ), [x] + =max(x,0); SINR k SINR represents the signal-to-interference-plus-noise ratio (SINR) of the kth legitimate user. eve This represents the signal-to-interference-plus-noise ratio (SIR) of the eavesdropper who launches an eavesdropping attack on the kth legitimate user.

[0016] To maximize the safe transmission rate, an optimization model is established with signal transmission power as a constraint:

[0017]

[0018] In the formula, Indicates the satellite's maximum transmission power. This indicates the maximum transmission power of the ground base station.

[0019] According to a signal secure transmission method provided by the present invention, in the diversity scenario, the signal s transmitted by the satellite to the legitimate user k sat,k The signal s sent by the ground base station to the legitimate user k k same.

[0020] According to the signal secure transmission method provided by the present invention, the process of obtaining the optimized secure transmission rate under the diversity condition is as follows:

[0021] Based on the received signal y of legitimate user k k And the received signal y of the eavesdropper eve eve The expression yields the received signal y of a legitimate user k in the diversity case. kd And the received signal y of the eavesdropper eve eved The expression;

[0022] Based on the received signal y of legitimate user k in the diversity case kd And the received signal y of the eavesdropper eve eved The expression yields the signal-to-noise ratio (SLNR) of the legitimate user k in the diversity case. kd ;

[0023]

[0024] In the formula, P k w represents the power transmitted from the ground base station to the legitimate user k. k G represents the beamforming vector of user k in a cellular system. i This represents the channel vector from the ground base station to the legitimate user i. G represents i The conjugate transpose of ;

[0025] Considering the case of equal power allocation, we establish an optimization problem in the case of diversity, with the objective of maximizing the signal-to-leakage-to-noise ratio;

[0026] The beamforming vector w for a legitimate user k in a cellular system k Beamforming vector w of legitimate user k in the satellite system sat,k Perform alternating optimization until |SLNR kd [i]-SLNRkd Optimization stops when [i-1]|≤ε, where ε represents the preset minimum value.

[0027] According to a signal secure transmission method provided by the present invention, the optimization problem in the diversity case, which aims to maximize the signal-to-leakage-to-noise ratio, is as follows:

[0028]

[0029] In the formula, variables satisfy and variable for Here, t is an introduced variable; tr() represents finding the trace of the matrix.

[0030] According to a signal secure transmission method provided by the present invention, in the multiplexing case, the signal s transmitted by the satellite to the legitimate user k sat,k The signal s sent by the ground base station to the legitimate user k k different.

[0031] According to a signal secure transmission method provided by the present invention, the process of obtaining an optimized secure transmission rate under the multiplexing condition is as follows:

[0032] Based on the received signal y of legitimate user k k And the received signal y of the eavesdropper eve eve The expression yields the received signal y of a valid user k under multiplexing conditions. km And the received signal y of the eavesdropper eve evem The expression;

[0033] Based on the received signal y of the legitimate user k under multiplexing conditions km And the received signal y of the eavesdropper eve evem The expression yields the signal-to-noise ratio (SLNR) of a valid user k under multiplexing conditions. km ;

[0034]

[0035] In the formula, P k w represents the power transmitted from the ground base station to the legitimate user k. k G represents the beamforming vector of a legitimate user k in a cellular system. i This represents the channel vector from the ground base station to the legitimate user i. G represents i The conjugate transpose of ;

[0036] Considering the case of equal power allocation, we establish an optimization problem under multiplexing conditions with the goal of maximizing the signal-to-leakage-to-noise ratio;

[0037] By introducing variables α and β, the optimization problem aimed at maximizing the signal-to-leakage-to-noise ratio in the case of reuse is divided into a primary problem and a secondary problem.

[0038] The main problem is solved using a binary search method. Then, the secondary problem is solved by fixing the variable α, resulting in the global optimal solution w for the optimization problem aimed at maximizing the signal-to-interference-plus-noise ratio in the reuse case. k and w sat,k .

[0039] According to a signal secure transmission method provided by the present invention, the optimization problem aimed at maximizing the signal-to-leakage-to-noise ratio in the multiplexing case is as follows:

[0040]

[0041] According to the signal secure transmission method provided by the present invention, the main problem is:

[0042]

[0043] The secondary problem is:

[0044]

[0045] In the formula, C1, C2, C3, and C4 all represent constraints;

[0046] The global optimal solution w for the optimization problem aimed at maximizing the signal-to-interference-plus-noise ratio in the multiplexing case. k and w sat,k They are respectively:

[0047]

[0048]

[0049] In the formula, eigenvector() represents the calculation of the eigenvector. Represents the channel compensation matrix Let I represent an N×K order complex matrix. N This represents an N-order identity matrix.

[0050] The present invention also provides a signal secure transmission system, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the program to implement any of the signal secure transmission methods described above.

[0051] This invention provides a signal security transmission method that, by setting up a satellite-cellular joint communication system, eliminates the distinction between satellite users and cellular users. The satellite system and cellular system in the satellite-cellular joint communication system jointly provide services to users, who can simultaneously receive signals from both systems. By establishing an optimization problem aimed at maximizing the security rate, and considering the security transmission problem of the system in both diversity and multiplexing scenarios, the invention optimizes the system's security rate using the concept of signal-to-leakage-to-noise ratio, making the information transmission of this communication system more reliable. Attached Figure Description

[0052] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0053] Figure 1 This is a schematic diagram of a space-ground fusion network model in existing technologies;

[0054] Figure 2 This is a flowchart illustrating the secure signal transmission method provided by the present invention;

[0055] Figure 3 This is a schematic diagram of a satellite-cellular joint communication system model in the signal secure transmission method provided by the present invention. Detailed Implementation

[0056] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0057] With the rapid development of 5G networks and the exploration of 6G networks, the integration of satellite communication and terrestrial cellular mobile communication has become an important development direction in the communications field. Satellite communication, with its wide coverage, minimal geographical limitations, and ability to achieve seamless global coverage, serves as a crucial supplement to terrestrial cellular mobile communication. Terrestrial cellular mobile communication, on the other hand, boasts low cost, high speed, large capacity, and high flexibility, providing essential support for satellite communication. The integration of the two can achieve a unified space-ground network architecture, offering more efficient, reliable, and intelligent communication services for various scenarios and businesses.

[0058] However, as Figure 1As shown, the existing STIN (Satellite Terrestrial Integrated Network) includes a satellite communication network and a terrestrial cellular mobile communication network. Among them, the satellite communication network is the primary network, and the terrestrial cellular mobile network is the secondary network.

[0059] Satellite communication systems using satellite communication networks include SAT (Satellite) and SU (Satellite User), and satellite users are vulnerable to eavesdropping attacks. Terrestrial cellular communication systems using terrestrial cellular communication networks include TBS (Terrestrial Base Station) and TU (Terrestrial User). To improve spectrum utilization, satellite systems and terrestrial cellular communication systems share spectrum.

[0060] To truly achieve joint communication between satellite communication systems and terrestrial cellular mobile communication systems, breaking down the existing primary and secondary system divisions and eliminating the distinction between satellite users and terrestrial users, this invention provides a satellite-cellular joint communication system. In this system, all users can simultaneously receive signals from both satellite and cellular systems, and the signals are transmitted using both diversity and multiplexing methods, thereby providing users with more efficient and stable communication services.

[0061] like Figure 2 As shown, the signal secure transmission method provided by the present invention includes the following steps:

[0062] S1, such as Figure 3 As shown, a satellite-cellular joint communication system is constructed, which includes a satellite system and a cellular system. The satellite system and the cellular system work together to provide services to users, meaning that users can receive both satellite signals and cellular signals simultaneously.

[0063] In satellite-cellular joint communication systems, it is necessary to maximize the secure transmission rate while ensuring secure link transmission. Furthermore, because satellite systems use TDMA multiple access and cellular systems use space division multiple access, providing services to more than one authorized user simultaneously, there is no mutual interference between authorized users when receiving signals transmitted from the satellite; however, when receiving signals transmitted from ground base stations, the interference problem between authorized users must also be considered.

[0064] The following section provides a detailed description of the downlink of the satellite-cellular joint communication system.

[0065] The satellite operates in the Ka-band. Assume the satellite is equipped with M transmitting antennas and generates M beams, while the ground base station is equipped with N antennas. Both legitimate users and eavesdroppers are equipped with a single antenna. Legitimate users are served jointly by the satellite and cellular systems and are vulnerable to eavesdropping attacks. To utilize spectrum resources more effectively, satellite systems typically employ frequency reuse technology, which can reduce interference between adjacent beams.

[0066] In this invention, the satellite uses TDMA multiple access, and the ground base station uses space division multiple access, simultaneously providing services to K users. The index of the set of valid users is...

[0067] Assume s sat,k The signal s is transmitted by the satellite to the legitimate user k. sat,k Satisfying the normalization condition E[|s sat,k | 2 ] = 1, where E[] represents the expected value of the calculation; P sat,k w is the power that the satellite transmits to legitimate user k. sat,k Let be the beamforming vector of a legitimate user k in the satellite system. The satellite signal passes through the beamforming vector. Modulated onto the antenna array, defined in, Describes an M×1 complex matrix. Represents the satellite beamforming vector w sat,k The conjugate transpose of . Meanwhile, the ground base station transmits signal s to legitimate user k using beamforming technology. k And signal s k Satisfying the normalization condition E[|s k 2 |] = 1; P k w is the power that the satellite transmits to legitimate user k. k Let be the beamforming vector of a legitimate user k in a cellular system, and define the beamforming matrix as follows: in, To represent an N×K complex matrix, define without loss of generality... Represents the beamforming vector w k The conjugate transpose of the matrix; then the received signal y of the legitimate user k. k And the received signal y of the eavesdropper eve eve They can be represented as follows:

[0068]

[0069]

[0070] In equations (1) and (2), This represents the channel vector from the satellite to the legitimate user k. This represents the channel vector from the satellite to the eavesdropper. This represents the channel vector from the ground base station to the legitimate user k. This represents the channel vector from the ground base station to the eavesdropper; n k This indicates that the mean is zero and the variance is... Gaussian additive white noise, n eve This indicates that the mean is zero and the variance is... Gaussian additive white noise; P i w represents the power transmitted from the ground base station to the legitimate user i. i s represents the beamforming vector of a legitimate user i in a cellular system. i This represents the signal sent by the ground base station to the legitimate user i.

[0071] S2. To improve the security of link transmission, an optimization problem is established with the goal of maximizing the secure rate. The process is as follows:

[0072] Based on the physical layer security definition, the secure rate of a satellite-cellular joint communication system is modeled as follows:

[0073]

[0074] In equation (3), R sec To represent the safe rate, set an intermediate parameter x, let x = log2(1 + SINR) k )-log2(1+SINR eve ), [x] + =max(x,0); SINR k SINR represents the signal-to-interference-plus-noise ratio (SINR) of the kth legitimate user. eve The signal-to-interference-plus-noise ratio (SIR) represents the signal-to-interference-plus-noise ratio (SNR) of the eavesdropper attempting to eavesdrop on the k-th legitimate user; K represents the total number of legitimate users in the satellite-cellular joint communication system.

[0075] With the goal of maximizing the safe transmission rate, an optimization model is established with signal transmission power as a constraint, namely:

[0076]

[0077] In equation (4), Indicates the satellite's maximum transmission power. This indicates the maximum transmission power of the ground base station.

[0078] S3. Solve the optimization problem with the objective of maximizing the secure transmission rate in both diversity and multiplexing cases to obtain the optimized secure transmission rate. The process is as follows:

[0079] In diversity mode, the satellite and ground base station send the same signal to the legitimate user to ensure that the legitimate user can receive it correctly, thereby enhancing the transmission reliability of the entire satellite-cellular joint communication system.

[0080] In diversity mode, the satellite transmits the signal s to the legitimate user k. sat,k The signal s sent by the ground base station to the legitimate user k k Same, i.e., s sat,k =s k Then, according to equation (1), the received signal y of the legitimate user k in the diversity case is obtained. kd And the received signal y of the eavesdropper eve eved They are respectively:

[0081]

[0082]

[0083] According to equations (5) and (6), the signal-to-interference-plus-noise ratio (SINR) of the received signal of legitimate user k can be calculated. k The signal-to-interference-plus-noise ratio (SINR) of the received signal from the eavesdropper Eve eve Represented as:

[0084]

[0085]

[0086] Since the expressions of Equations (7) and (8) regarding the signal-to-interference-plus-noise ratio are quite complex, it is difficult to directly solve the above optimization problem with the goal of maximizing the safe rate. Therefore, it is converted to solve the optimization problem using the signal-to-leakage-plus-noise ratio.

[0087] Sadek et al. proposed the concept of signal leakage, which refers to interference caused by a target user to other users. In physical layer security, this can be considered as a legitimate user leaking signals to other interfering users and eavesdroppers, thus leading to the leakage of confidential information. Based on this concept, SLNR is adopted. k The signal-to-noise ratio (SNR) of a legitimate user k is the ratio of the received signal power of user k to the signal power plus noise leaked to other interfering users and eavesdroppers.

[0088] In diversity scenarios, the signal-to-noise ratio (SLNR) of legitimate user k is... kd for:

[0089]

[0090] In equation (9), g i This represents the channel vector from the ground base station to the legitimate user i. G represents iThe conjugate transpose of .

[0091] Beamforming vector w for legitimate user k in the satellite system sat,k The beamforming vector w of a legitimate user k in a cellular system k These two variables are optimized using an alternating approach, that is, w is fixed first. sat,k Optimize w k ; then fix w k Optimize w sat,k ; until |SLNR k [i]-SLNR k Optimization stops when [i-1]|≤ε, where ε represents the preset minimum value.

[0092] First, fix w. sat,k Optimize w k The specific process is as follows:

[0093] Define the channel compensation matrix Let noise variance Equation (9) is equivalent to:

[0094]

[0095] Define variables make Here, t is an introduced variable.

[0096] Define variable R1, and let

[0097] Define variable R2, and let

[0098] Let t = 1, then equation (10) can be equivalently expressed as:

[0099]

[0100] Note

[0101] Define variables make in satisfy and

[0102] Due to constraints Since it is non-convex, we use SDR (Semi-definite Relaxation) to relax the constraint, where rank() represents the rank of the matrix.

[0103] Since t = 1, therefore for w k Constraints | wk | 2 =1 can be converted to a pair Constraints Here, tr() represents finding the trace of a matrix.

[0104] To simplify the problem, we consider the case of equal power allocation and establish an optimization problem with the objective of maximizing the signal-to-leakage-to-noise ratio, namely:

[0105]

[0106] By introducing an auxiliary variable α to solve the max-min problem in equation (12), the optimization problem of equation (12) is decomposed into a primary problem and a secondary problem.

[0107] The main problem is:

[0108]

[0109] In equation (13), This means that for any k, constraint C1 can be solved by performing a binary search on α. ​​First, initialize the lower bound α of the auxiliary variable α. l and upper bound α u Then let α = 1 / 2 (α l +α u Considering the non-convexity of constraint C1, two variables x and y are introduced, and variable substitution is used to transform the constraint C1. Replace with In constraint C1 Replace with

[0110] For a fixed α, introducing the variable β, the secondary problem can be expressed as:

[0111]

[0112] In equation (14), constraint C6 is non-convex. Therefore, it is necessary to transform this non-convex constraint into a convex constraint in order to solve the optimization problem. Consider using a first-order Taylor expansion. First, define the initial point of variable y as:

[0113]

[0114] Next, a first-order Taylor expansion is performed on constraint C6 at the initial point. Based on this method, the variable y is iterated n times to obtain the value y after n iterations. n :

[0115]

[0116] Applying the first-order Taylor expression to constraint C6, the transformed constraint (14) becomes:

[0117]

[0118] After the above transformation, the non-convex constraint condition is transformed into a convex constraint condition, and the optimization problem of equation (12) can be solved directly using the convex optimization toolkit CVX.

[0119] Generally speaking, since the constraints are not considered when solving the optimization problem of equation (12) using the convex optimization toolkit CVX, the constraints are not considered. Therefore, the solution obtained will no longer satisfy the condition. The constraints need to be reconstructed using Gaussian randomization to obtain the beamforming vector w. k The suboptimal solution is obtained through the following method:

[0120] Generate elements element Constitute vector e k θ i Let represent a random variable that follows a uniform distribution within the range [0, 2π].

[0121] right Perform eigenvalue decomposition Constructed Further optimization yielded Among them, U k Representing variables The characteristic matrix of , where ∑ represents a diagonal matrix.

[0122] Optimization yields w k After that, fix w k Optimize w using the same method sat,k The specific process is as follows:

[0123] Define variables make Here, t is an introduced variable.

[0124] Define variable R3, let

[0125] Define variable R4, let

[0126] Let t = 1, then equation (10) can be equivalently expressed as:

[0127]

[0128] Note

[0129] Define variables make in satisfy and

[0130] Due to constraints Since it is not convex, SDR is used to relax the constraint.

[0131] Since t = 1, therefore for w sat,k Constraints | w sat,k | 2 =1 can be converted to a pair Constraints

[0132] To simplify the problem, we consider the case of equal power allocation and establish an optimization problem with the objective of maximizing the signal-to-leakage-to-noise ratio, namely:

[0133]

[0134] By introducing an auxiliary variable α to solve the max-min problem in equation (12), the optimization problem of equation (12) is decomposed into a primary problem and a secondary problem.

[0135] The main problem is:

[0136]

[0137] In equation (20), constraint C1 can be solved by performing a binary search on α. ​​First, the lower bound α of the auxiliary variable α is initialized. l and upper bound α u Then let α = 1 / 2 (α l +α u Considering the non-convexity of constraint C1, two variables p and q are introduced, and variable substitution is used to change the constraint C1. Replace with In constraint C1 Replace with:

[0138] For a fixed α, introducing the variable β, the secondary problem can be expressed as:

[0139]

[0140] After the above transformation, the non-convex constraint condition is transformed into a convex constraint condition, and the optimization problem of equation (12) can be solved directly using the convex optimization toolkit CVX.

[0141] In general, the solution obtained from the relaxation problem described above will no longer satisfy... The constraints necessitate the reconstruction of the beamforming vector w using Gaussian randomization. sat,k The suboptimal solution is obtained through the following method:

[0142] Generate elements element Constitute vector e sat,k θ i Let represent a random variable that follows a uniform distribution within the range [0, 2π].

[0143] right Perform eigenvalue decomposition Constructed Further obtain Among them, U sat,k Representing variables The characteristic matrix of , where ∑ represents a diagonal matrix.

[0144] Then, the maximum SLNR is obtained by using an alternating optimization method. kd The final solution to the problem, which is the final optimized w. k and w sat,k .

[0145] In other words, the beamforming vector w of the legitimate user k in the satellite system is finally obtained through optimization. sat,k The beamforming vector w of a legitimate user k in a cellular system k Enabling the signal-to-noise ratio (SLNR) of legitimate user k kd Maximizing this solves the problem of maximizing safe speed.

[0146] In the case of reuse, where satellites and ground base stations send different signals to legitimate users, system resources can be fully utilized and signal transmission efficiency can be improved.

[0147] In the case of reuse, the satellite sends the signal s to the legitimate user k. sat,k The signal s sent by the ground base station to the legitimate user k k Different, i.e., s sat,k ≠s k Then, according to equation (1), the received signal y of user k is obtained. km And the received signal y of the eavesdropper eve evem They are respectively:

[0148]

[0149]

[0150] Signal-to-noise ratio (SLNR) of user k under multiplexing conditions km for:

[0151]

[0152] Define the channel compensation matrix Let noise variance I N Let N be the identity matrix, then equation (24) can be transformed into:

[0153]

[0154] Using the same optimization approach as in the diversity case, and considering the case of equal power allocation, we establish an optimization problem for the multiplexing case that aims to maximize the signal-to-leakage-to-noise ratio, namely:

[0155]

[0156] Introducing variables α and β, the optimization problem of equation (26) is decomposed into a primary problem and a secondary problem.

[0157] The main problem is:

[0158]

[0159] The secondary problem is:

[0160]

[0161] The main problem represented by equation (27) can be solved using a binary search method. Then, by fixing the variable α, we can solve the secondary problem. Observing the constraint C1, we can transform it into an eigenvalue problem and obtain the solution. The optimal solution is:

[0162]

[0163] Seeking The optimal solution is:

[0164]

[0165] In equations (29) and (30), eigenvector() means to calculate the eigenvector.

[0166] because and It is reversible; therefore, the global optimal solution w for the optimization problem aimed at maximizing the signal-to-interference-plus-noise ratio in the case of multiplexing can be directly obtained. k and w sat,k .

[0167] In other words, the beamforming vector w of the legitimate user k in the satellite system is finally obtained through optimization. sat,k The beamforming vector w of a legitimate user k in a cellular system kEnabling the signal-to-noise ratio (SLNR) of legitimate user k km Maximizing this solves the problem of maximizing safe speed.

[0168] In the signal secure transmission method provided by this invention, there is no longer a distinction between primary and secondary systems, nor between satellite users and cellular users. All users can simultaneously receive signals from both satellites and ground base stations, and all signals are considered useful signals. This approach can greatly improve the performance of satellite-cellular joint communication systems.

[0169] The signal security transmission method provided by this invention considers both diversity and multiplexing scenarios. In the diversity scenario, the same signal is transmitted to legitimate users via both satellite and ground base stations to ensure correct reception at the receiving end, thereby enhancing the transmission reliability of the entire satellite-cellular joint communication system. In the multiplexing scenario, different signals are transmitted to legitimate users via satellite and base stations. This approach fully utilizes system resources, thereby improving signal transmission efficiency.

[0170] For both diversity and multiplexing scenarios, considering the secure transmission problem of the satellite-cellular joint communication system, the security rate of the satellite-cellular joint communication system is optimized by using the concept of signal-to-leakage-to-noise ratio, so as to make the information transmission of the satellite-cellular joint communication system more reliable.

[0171] Based on the secure signal transmission method provided by this invention, this invention also provides a secure transmission device based on a satellite-cellular joint communication system, which includes a memory and a processor. The memory communicates with the processor through a communication bus, and the processor is configured to execute the secure signal transmission method in any embodiment of this invention based on the instructions stored in the memory.

[0172] Furthermore, the logical instructions in the aforementioned memory can be implemented as software functional units and sold or used as independent products, and can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art, or a part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of the present invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0173] On the other hand, the present invention also provides a computer program product, the computer program product comprising a computer program that can be stored on a non-transitory computer-readable storage medium, wherein when the computer program is executed by a processor, the computer is able to execute the signal secure transmission method provided by the above methods, the method comprising:

[0174] Construct a satellite-cellular joint communication system, which includes satellite systems and cellular systems. The satellite and cellular systems work together to provide services to users, meaning that users can receive both satellite signals and cellular signals simultaneously.

[0175] Based on a satellite-cellular joint communication system, an optimization problem is established with the goal of maximizing secure data rate.

[0176] In both diversity and multiplexing cases, the optimization problem aimed at maximizing the secure transmission rate is solved to obtain the optimized secure transmission rate.

[0177] In another aspect, the present invention also provides a non-transitory computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the signal secure transmission method provided by the methods described above, the method comprising:

[0178] Construct a satellite-cellular joint communication system, which includes satellite systems and cellular systems. The satellite and cellular systems work together to provide services to users, meaning that users can receive both satellite signals and cellular signals simultaneously.

[0179] Based on a satellite-cellular joint communication system, an optimization problem is established with the goal of maximizing secure data rate.

[0180] In both diversity and multiplexing cases, the optimization problem aimed at maximizing the secure transmission rate is solved to obtain the optimized secure transmission rate.

[0181] The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs. Those skilled in the art can understand and implement this without any creative effort.

[0182] Through the above description of the embodiments, those skilled in the art can clearly understand that each embodiment can be implemented by means of software plus necessary general-purpose hardware platforms, and of course, it can also be implemented by hardware. Based on this understanding, the above technical solutions, in essence or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, magnetic disk, optical disk, etc., and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute the methods described in the various embodiments or some parts of the embodiments.

[0183] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for secure signal transmission, characterized in that, Includes the following steps: A satellite-cellular joint communication system is constructed, comprising a satellite system and a cellular system, which jointly provide services to users; all users simultaneously receive signals from the satellite system and the cellular system. Based on a satellite-cellular joint communication system, an optimization problem is established with the goal of maximizing secure data rate. In both diversity and multiplexing cases, the optimization problem aimed at maximizing the secure transmission rate is solved to obtain the optimized secure transmission rate. In the case of diversity, the signal transmitted by the satellite system to the user is the same as the signal transmitted by the cellular system to the user; in the case of multiplexing, the signal transmitted by the satellite system to the user is different from the signal transmitted by the cellular system to the user; the separate solution includes, due to the complexity of the security rate expression, transforming the optimization problem with the goal of maximizing the security rate into an optimization problem that uses the signal-to-leakage-to-noise ratio to solve the optimization problem. We use the concept of signal-to-leakage-to-noise ratio (SNR) to establish and solve optimization problems with the objective of maximizing SNR in both diversity and multiplexing cases.

2. The signal secure transmission method according to claim 1, characterized in that, In the aforementioned satellite-cellular joint communication system, legitimate users Received signal and eavesdroppers Received signal They are respectively: ， ， In the formula, This indicates that the satellite is sent to legitimate users. power, This represents the beamforming vector of a legitimate user k in the satellite system. This indicates that the satellite is sent to legitimate users. The signal; This represents the power transmitted from the ground base station to the legitimate user i. This represents the beamforming vector of a legitimate user i in a cellular system. This represents the signal sent by the ground base station to the legitimate user i; Indicates satellite to legitimate users The channel vector, express The conjugate transpose of the matrix. Indicates satellite to eavesdropper The channel vector, express The conjugate transpose of ; Indicates the connection between the ground base station and the legitimate user. The channel vector, express The conjugate transpose of the matrix. Indicates the connection between ground base stations and eavesdroppers The channel vector, express The conjugate transpose of ; This indicates that the mean is zero and the variance is... Gaussian additive white noise This indicates that the mean is zero and the variance is... Gaussian additive white noise; K represents the total number of legitimate users in the satellite-cellular joint communication system.

3. The signal secure transmission method according to claim 2, characterized in that, The process of establishing the optimization problem with the objective of maximizing safe speed is as follows: Based on the physical layer security definition, the security rate of the satellite-cellular joint communication system is modeled as follows: ， In the formula, To represent the safe rate, set the intermediate parameter x, let , ; This represents the signal-to-interference-plus-noise ratio (SIR) of the k-th legitimate user. This represents the signal-to-interference-plus-noise ratio (SIR) of the eavesdropper who launches an eavesdropping attack on the kth legitimate user. To maximize the safe transmission rate, an optimization model is established with signal transmission power as a constraint: ， In the formula, Indicates the satellite's maximum transmission power. This indicates the maximum transmission power of the ground base station. This represents the beamforming vector of a legitimate user k in a cellular system.

4. The signal secure transmission method according to claim 2, characterized in that, In the diversity scenario, the signal transmitted by the satellite to the legitimate user k The signal sent by the ground base station to the legitimate user k same.

5. The signal secure transmission method according to claim 4, characterized in that, The process of obtaining the optimized secure transmission rate under the diversity condition is as follows: According to legitimate users Received signal and eavesdroppers Received signal The expression yields the received signal of a legitimate user k in the diversity case. And the signal received by the eavesdropper Eve The expression; According to the case of legitimate users in the episode segmentation Received signal and eavesdroppers Received signal The expression yields the legal users in the context of set division. signal-to-noise ratio ; ， In the formula, This represents the power transmitted from the ground base station to the legitimate user k. This represents the beamforming vector of a legitimate user k in a cellular system. Indicates the connection between the ground base station and the legitimate user. The channel vector, express The conjugate transpose of ; Considering the case of equal power allocation, we establish an optimization problem in the case of diversity, with the objective of maximizing the signal-to-leakage-to-noise ratio; Beamforming vector for legitimate user k in a cellular system Beamforming vector of legitimate user k in the satellite system Perform alternating optimization until... Optimization stops when the time is right, where, This represents the preset minimum value.

6. The signal secure transmission method according to claim 5, characterized in that, The optimization problem in the diversity case, which aims to maximize the signal-to-leakage-to-noise ratio, is as follows: ， In the formula, variables satisfy , and ,variable for ,in, , 、 Variables introduced; This indicates finding the trace of a matrix; This represents the rank of the matrix.

7. The signal secure transmission method according to claim 2, characterized in that, In the multiplexing scenario, the signal transmitted by the satellite to the legitimate user k The signal sent by the ground base station to the legitimate user k different.

8. The signal secure transmission method according to claim 7, characterized in that, The process of obtaining the optimized secure transmission rate under the aforementioned multiplexing condition is as follows: According to legitimate users Received signal and eavesdroppers Received signal The expression yields the received signal of a legitimate user k under multiplexing conditions. And the signal received by the eavesdropper Eve The expression; Based on the legitimate user under reuse conditions Received signal and eavesdroppers Received signal The expression yields the valid user in the reuse case. signal-to-noise ratio ; ， In the formula, This represents the power transmitted from the ground base station to the legitimate user k. This represents the beamforming vector of a legitimate user k in a cellular system. Indicates the connection between the ground base station and the legitimate user. The channel vector, express The conjugate transpose of ; Considering the case of equal power allocation, we establish an optimization problem under multiplexing conditions with the goal of maximizing the signal-to-leakage-to-noise ratio; By introducing variables and The optimization problem aimed at maximizing the signal-to-leakage-to-noise ratio under reuse conditions is divided into primary problem and secondary problem; The main problem is solved using a binary search method, and then the variables are fixed. Solving the secondary problem yields the global optimal solution to the optimization problem aimed at maximizing the signal-to-interference-plus-noise ratio (SINR) in the reuse case. and .

9. The signal secure transmission method according to claim 8, characterized in that, The optimization problem aimed at maximizing the signal-to-leakage-to-noise ratio in the case of reuse is as follows: 。 10. The signal secure transmission method according to claim 9, characterized in that, The main problem is: ， The secondary problem is: ， In the formula, C1, C2, C3, and C4 all represent constraints; The global optimal solution to the optimization problem aimed at maximizing the signal-to-interference-plus-noise ratio in the multiplexing case. and They are respectively: ， ， In the formula, eigenvector() represents the calculation of the eigenvector. Represents the channel compensation matrix , express A complex matrix of order 1. This represents an N-order identity matrix.

11. A secure signal transmission system, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the program, it implements the signal secure transmission method as described in any one of claims 1 to 10.

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