Relay satellite position optimization method and system based on satellite covert communication

Abstract

The invention discloses a relay satellite position optimization method and system based on satellite covert communication, and the method comprises the following steps: (1) constructing a covert communication model in a satellite covert communication system, the covert communication model comprises a relay satellite, a transmitting base station which is located on the ground and transmits signals to the relay satellite, a receiving base station which is located on the ground and receives the signals through the relay satellite and transmits interference signals to interfere with the detection satellite, and a monitoring satellite which monitors the signals of the relay satellite and transmits interference signals to interfere with the receiving base station. (2) constructing a minimum total error detection probability calculation model of a monitoring satellite in the satellite covert communication system; (3) establishing a relay satellite position optimization model which takes the maximum covert communication rate as a target and takes the condition that the minimum total error detection probability of the monitoring satellite is greater than or equal to a preset threshold value as a constraint condition; and (4) solving the relay satellite position optimization model to obtain the optimal position of the relay satellite. According to the invention, the concealment and the communication rate can be improved.

Description

Technical Field

[0001] The present invention relates to satellite communication technology, and in particular to a method and system for optimizing the position of a relay satellite based on satellite covert communication. Background Art

[0002] With the rapid development of communication technology, 6G technology with the vision of "global coverage, full spectrum, full application, and strong security" is being studied in depth. It will expand from ground communication to an integrated communication network of air, land, and sea by integrating satellite communication, drone communication, ground ultra-dense communication network, maritime communication, underwater communication, and underground communication. The satellite communication system is an advanced communication system that uses artificial earth satellites located in the earth's orbit as relay stations to realize information transmission and exchange between different ground stations or user terminals. Satellite communication can make up for the shortcomings of ground communication in 6G in terms of coverage and ensure that the signal can cover every corner of the world. However, in the complex and changeable space electromagnetic environment, satellite communication faces many severe security threats.

[0003] Satellite covert communication technology ensures the concealment and security of information during transmission, and can achieve safe and reliable information transmission. It can be used for covert communication between specific parties or through relay satellite nodes. In the covert communication between two parties, that is, point-to-point communication, the sender and the receiver use advanced encryption technology and special signal modulation methods to ensure that the information is difficult to detect and crack in the satellite channel. For example, when one party needs to transmit sensitive information to a specific other party, satellite covert communication technology can highly encrypt the information and transmit it directly to the other party through a satellite link to achieve secure point-to-point communication. When the relay satellite node participates, the sender first transmits the information to the relay satellite, and the relay satellite uses special signal processing and encryption technology to process the information before forwarding it. For example, in some application scenarios for transmitting encrypted information, the information is first transmitted to the relay satellite through a satellite link. After the relay satellite performs encryption and modulation, the information is accurately forwarded to the ground receiving station to achieve a secure communication link. However, the current satellite covert communication technology is still not concealed enough, and the communication rate is limited. Summary of the invention

[0004] In view of the problems existing in the prior art, the object of the present invention is to provide a method and system for optimizing the position of a relay satellite based on satellite covert communication, which can improve concealment and communication rate.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions: The method for optimizing the position of a relay satellite based on satellite covert communication comprises the following steps: (1) Constructing a covert communication model in a satellite covert communication system, wherein the covert communication model includes a relay satellite, a transmitting base station located on the ground transmitting signals to the relay satellite, a receiving base station located on the ground receiving signals through the relay satellite and sending interference signals to interfere with the detection satellite, and a monitoring satellite monitoring the relay satellite signal and sending interference signals to interfere with the receiving base station; (2) Construct a calculation model for the minimum total false detection probability of monitoring satellites in the satellite covert communication system, specifically: , In the formula, represents the minimum total false detection probability of the monitoring satellite, H de represents the channel coefficient from the relay satellite to the monitoring satellite, It represents the channel coefficient of information transmission when the distance is 1 km. Indicates the signal transmission power of the relay satellite, Indicates the interference signal transmission power of the receiving base station, express The exponential parameter of the exponential distribution, H be represents the channel coefficient from the receiving base station to the monitoring satellite, Indicates the distance between the relay satellite and the monitoring satellite. , Respectively represent the polar coordinates of the relay satellite and the monitoring satellite, Respectively represent the polar diameter and polar angle in the polar coordinates of the relay satellite, They represent the polar diameter and polar angle in the polar coordinates of the monitoring satellite respectively; (3) establishing a relay satellite position optimization model based on the minimum total false detection probability calculation model of the monitoring satellite, wherein the relay satellite position optimization model aims to maximize the covert communication rate and takes the minimum total false detection probability of the monitoring satellite as greater than or equal to a preset threshold as a constraint; (4) Solve the relay satellite position optimization model to obtain the optimal position of the relay satellite.

[0006] A relay satellite position optimization system based on satellite covert communication, comprising: A satellite covert communication model construction module is used to construct a covert communication model in a satellite covert communication system, wherein the covert communication model includes a relay satellite, a transmitting base station located on the ground for transmitting signals to the relay satellite, a receiving base station located on the ground for receiving signals through the relay satellite and sending interference signals to interfere with the detection satellite, and a monitoring satellite for monitoring the relay satellite signal and sending interference signals to interfere with the receiving base station; The minimum total false detection probability calculation model construction module is used to construct the minimum total false detection probability calculation model for monitoring satellites in the satellite covert communication system, specifically: , In the formula, represents the minimum total false detection probability of the monitoring satellite, H de represents the channel coefficient from the relay satellite to the monitoring satellite, It represents the channel coefficient of information transmission when the distance is 1 km. Indicates the signal transmission power of the relay satellite, Indicates the interference signal transmission power of the receiving base station, express The exponential parameter of the exponential distribution, H be represents the channel coefficient from the receiving base station to the monitoring satellite, Indicates the distance between the relay satellite and the monitoring satellite. , Respectively represent the polar coordinates of the relay satellite and the monitoring satellite, Respectively represent the polar diameter and polar angle in the polar coordinates of the relay satellite, They represent the polar diameter and polar angle in the polar coordinates of the monitoring satellite respectively; A relay satellite position optimization model building module is used to establish a relay satellite position optimization model according to a minimum total false detection probability calculation model of a monitoring satellite, wherein the relay satellite position optimization model takes the maximum covert communication rate as a goal and takes the minimum total false detection probability of the monitoring satellite being greater than or equal to a preset threshold as a constraint condition; The model solving module is used to solve the relay satellite position optimization model to obtain the optimal position of the relay satellite.

[0007] Compared with the prior art, the present invention has the following beneficial effects: the present invention is the first to attempt to improve the covert communication rate by optimizing the relative position of relay satellites. During the communication process, the security threat factor of monitoring satellites is fully considered, and a targeted optimization strategy is formulated. Compared with traditional satellite communication methods, the present invention can effectively solve the problem of insufficient concealment and the negative impact of unreasonable relay satellite positions on communication rates, significantly improve concealment and communication rates, and provide a strong guarantee for the security and efficiency of satellite communications. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 It is a flow chart of a method for optimizing the position of a relay satellite based on satellite covert communication provided by an embodiment of the present invention; Figure 2 is a schematic diagram of a scenario of a satellite covert communication system provided by an embodiment of the present invention; Figure 3 is a covert communication model diagram of a satellite covert communication system provided by an embodiment of the present invention; Figure 4 It is a flowchart of the process of deriving the expression of the concealed communication rate provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0009] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0010] Embodiment 1 of the present invention provides a method for optimizing the position of a relay satellite based on satellite covert communication, such as Figure 1 As shown, the following steps are included: (1) Construct a covert communication model in a satellite covert communication system.

[0011] Among them, Figure 2 and Figure 3 As shown, the covert communication model includes a relay satellite (named Dave), a transmitting base station (named Alice) located on the ground that transmits signals to the relay satellite, a receiving base station (named Bob) located on the ground that receives signals through the relay satellite and sends interference signals to interfere with the detection satellite, and a monitoring satellite (named Eve) that monitors the relay satellite signal and sends interference signals to interfere with the receiving base station.

[0012] Alice is a ground base station located on the equator of the earth, and it attempts to communicate with another ground base station Bob. During the communication, Alice will first pass the information to Dave. Since the information sent by Alice to the relay satellite is a covert communication based on environmental noise, the equivalent interference level with the relay satellite is very low, so this process will not interfere with the monitoring of the monitor.

[0013] Bob is a ground base station in full-duplex mode and located at the equator of the earth. In the system, Bob is responsible for receiving messages sent by Alice and transmitted by Dave. At the same time, Bob also sends interference signals, specifically artificial noise, to interfere with Eve's monitoring. During the communication process, Bob will generate a certain degree of self-interference to himself. Bob's position The polar coordinates are expressed as: , are the polar diameter and polar angle in Bob's polar coordinates respectively.

[0014] Dave is an artificial satellite located in geosynchronous orbit and acts as a relay node in the entire communication system. When Dave receives information from Alice, it accurately transmits the information to Bob, ensuring the transmission of information between different nodes. Dave's location The polar coordinates are expressed as: , are the polar diameter and polar angle in Dave's polar coordinates respectively.

[0015] Eve is a satellite in full-duplex mode and located in geosynchronous orbit. It plays the role of a monitor in the entire communication system. Eve tries to monitor any information from Dave and sends out interference signals, specifically artificial noise, to interfere with Bob's reception of information. At the same time, Alice will also generate a certain degree of self-interference. Eve's position L e Expressed in polar coordinates: L e =( ), are the polar diameter and polar angle in Bob's polar coordinates respectively.

[0016] (2) Construct a calculation model for the minimum total false detection probability of monitoring satellites in the satellite covert communication system.

[0017] The derivation process of the minimum total false detection probability calculation model is as follows.

[0018] First, through the binary hypothesis method, write the expression of the information received by the monitoring satellite Eve in two cases: whether the relay satellite Dave transmits information to the receiving base station Bob or not: , Where Y e (i) indicates the i-th information received by the monitoring satellite Eve, This means that the relay satellite Dave does not send a signal to the receiving base station Bob, and Another situation is shown in which the relay satellite Dave sends a signal to the receiving base station Bob. represents the signal transmission power of the relay satellite Dave, and P e They respectively represent the interference signal transmission power of the receiving base station Bob and the detection satellite Eve, that is, the artificial noise power. Represents the signal Dave sends to Alice, represents the artificial noise transmitted by Bob, S e (i) represents the artificial noise emitted by Eve. be represents the channel coefficient from the receiving base station to the monitoring satellite, H de represents the channel coefficient from the relay satellite to the monitoring satellite. The self-interference channel coefficient of Eve is recorded as H ee . is Eve’s self-interference coefficient. e (i) is the additive white Gaussian noise at Eve’s location, and , is the noise variance.

[0019] Secondly, the total false detection probability of the monitoring satellite Eve in the system is listed.

[0020] List the channel gains from the relay satellite Dave to the receiving base station Bob and the monitoring satellite Eve : , in: , It represents the channel coefficient of information transmission when the distance is 1 km, L db , L de They represent the distances from the relay satellite Dave to the receiving base station Bob and the monitoring satellite Eve respectively.

[0021] List the false alarm probability and missed detection probability of the monitoring satellite Eve. The false alarm probability means that Dave is not communicating covertly with Bob at present, but due to the interference of artificial noise, the monitoring result reaches the monitoring threshold of the monitoring satellite. , which leads to false detection. On the contrary, the missed detection probability indicates that there is a covert communication between Dave and Bob, but because the detection threshold is not reached , which was ignored during the monitoring process. The false alarm probability can be obtained by expressing the information received by the monitoring satellite Eve and the probability of missed detection It can be expressed as: , The obedience index parameter is exponential distribution, then the false alarm probability can be and the probability of missed detection Further transformed into: , The total false alarm probability of monitoring satellite Eve is obtained by the false alarm probability and missed detection probability. : , Finally, the minimum total false detection probability of monitoring satellite Eve is obtained from the monotonicity of the function: The calculation model is: .

[0022] (3) A relay satellite position optimization model is established based on the minimum total false detection probability calculation model of the monitoring satellite.

[0023] The relay satellite position optimization model aims at maximizing the concealed communication rate and takes the minimum total false detection probability of the monitoring satellite as being greater than or equal to a preset threshold as a constraint condition.

[0024] The derivation process of the expression of covert communication rate is as follows: Figure 4As shown, the details are as follows: First, write down the communication interruption probability constraints: , is the probability of communication interruption, is a number that approaches 0 in the range (0,1).

[0025] Next, write the information expression received by the receiving base station Bob: , in, It represents the i-th information received by the receiving base station, and the self-interference channel coefficient of the receiving base station Bob is recorded as , is the self-interference coefficient of the receiving base station Bob. In this embodiment, it is considered that the receiving base station Bob is not affected by the self-interference, that is, , Defined as the channel coefficient from the relay satellite Dave to the receiving base station Bob, H eb Represents the channel coefficient from the monitoring satellite Eve to the receiving base station Bob. is the additive white Gaussian noise at Bob's location, and , is the noise variance at Bob’s location.

[0026] Next, list the channel capacity from the relay satellite Dave to Bob: The expression of (taking the bandwidth as 1000Hz): , Finally, combined with Shannon's second theorem, we can see that when the communication rate of the channel exceeds the channel capacity, reliable communication cannot be achieved, that is, the following formula: , Channel capacity Substituting the expression into the above formula, we can get the covert communication rate from the relay satellite to the receiving base station. for: , Combined with the minimum total error detection probability expression, the relay satellite position optimization model is constructed as follows: , .

[0027] For Eve, the hope is to minimize On the contrary, in order to achieve covert communication, the goal of this embodiment is to maximize this probability and make it as close to 1 as possible. Therefore, in the above constraints, is a number that approaches 0 in the range (0,1). is the preset threshold.

[0028] (4) Solve the relay satellite position optimization model to obtain the optimal position of the relay satellite.

[0029] The goal of this embodiment is to achieve the maximum concealed communication rate. Substitute the calculation formula into the constraint conditions and analyze it in combination with the system. The receiving base station Bob is located on the polar axis of the equatorial plane, that is, , while the relay satellite Dave and the monitoring satellite Eve are both located in the geosynchronous satellite orbit, that is, The further transformed expression can be obtained as: , , Combined with the constraints, the calculation expression for the optimal position of the relay satellite Dave is: , , In the formula, is an intermediate variable.

[0030] Embodiment 2 of the present invention provides a relay satellite position optimization system based on satellite covert communication, including: A satellite covert communication model construction module is used to construct a covert communication model in a satellite covert communication system, wherein the covert communication model includes a relay satellite, a transmitting base station located on the ground for transmitting signals to the relay satellite, a receiving base station located on the ground for receiving signals through the relay satellite and sending interference signals to interfere with the detection satellite, and a monitoring satellite for monitoring the relay satellite signal and sending interference signals to interfere with the receiving base station; The minimum total false detection probability calculation model construction module is used to construct the minimum total false detection probability calculation model for monitoring satellites in the satellite covert communication system, specifically: , In the formula, represents the minimum total false detection probability of the monitoring satellite, H de represents the channel coefficient from the relay satellite to the monitoring satellite, It represents the channel coefficient of information transmission when the distance is 1 km. Indicates the signal transmission power of the relay satellite, Indicates the interference signal transmission power of the receiving base station, express The exponential parameter of the exponential distribution, H be represents the channel coefficient from the receiving base station to the monitoring satellite, Indicates the distance between the relay satellite and the monitoring satellite. , Respectively represent the polar coordinates of the relay satellite and the monitoring satellite, Respectively represent the polar diameter and polar angle in the polar coordinates of the relay satellite, They represent the polar diameter and polar angle in the polar coordinates of the monitoring satellite respectively; A relay satellite position optimization model building module is used to establish a relay satellite position optimization model according to a minimum total false detection probability calculation model of a monitoring satellite, wherein the relay satellite position optimization model takes the maximum covert communication rate as a goal and takes the minimum total false detection probability of the monitoring satellite being greater than or equal to a preset threshold as a constraint condition; The model solving module is used to solve the relay satellite position optimization model to obtain the optimal position of the relay satellite.

[0031] The relay satellite position optimization model is specifically as follows: , , In the formula, represents the covert communication rate from the relay satellite to the receiving base station, is the preset threshold, Represents a number that approaches 0 in the range (0,1).

[0032] The calculation formula of the covert communication rate is specifically:

[0033] , In the formula, represents the covert communication rate from the relay satellite to the receiving base station, represents the channel coefficient from the relay satellite to the receiving base station, Represents the signal transmission power of the relay satellite, P e Indicates the interference signal transmission power of the monitoring satellite, represents the noise power variance at the receiving base station location, express The exponential parameter of the exponential distribution, H eb represents the channel coefficient from the monitoring satellite to the receiving base station, is a number that approaches 0 in the range (0,1).

[0034] The model solving module is specifically used to convert the relay satellite position optimization model into the following simplified model, and then solve it to obtain the optimal position of the relay satellite: , , In the formula, Represents the polar diameter in the polar coordinates of the receiving base station, and the solved The optimal value of is output as the optimal position of the relay satellite.

[0035] Among them, the optimal position calculation formula of the relay satellite is: , , In the formula, is an intermediate variable.

[0036] This system is used to implement the method of embodiment 1, and has the same technical effect as the method of embodiment 1. If the reference method description is not fully specified, it will not be repeated.

[0037] It should be understood that the above embodiments and descriptions only describe the principles, main features and advantages of the present invention. Without departing from the spirit and scope of the present invention, the present invention may be subject to various changes and improvements, and these changes and improvements all fall within the scope of protection of the present invention.

Claims

1. A method for optimizing the position of a relay satellite based on satellite covert communication, characterized in that: The steps include: (1) Constructing a covert communication model in a satellite covert communication system, wherein the covert communication model includes a relay satellite, a transmitting base station located on the ground transmitting signals to the relay satellite, a receiving base station located on the ground receiving signals through the relay satellite and sending interference signals to interfere with the detection satellite, and a monitoring satellite monitoring the relay satellite signal and sending interference signals to interfere with the receiving base station; (2) Construct a calculation model for the minimum total false detection probability of monitoring satellites in the satellite covert communication system, specifically: ， In the formula, represents the minimum total false detection probability of the monitoring satellite, H de represents the channel coefficient from the relay satellite to the monitoring satellite, It represents the channel coefficient of information transmission when the distance is 1 km. Indicates the signal transmission power of the relay satellite, Indicates the interference signal transmission power of the receiving base station, express The exponential parameter of the exponential distribution, H be represents the channel coefficient from the receiving base station to the monitoring satellite, Indicates the distance between the relay satellite and the monitoring satellite. , Respectively represent the polar coordinates of the relay satellite and the monitoring satellite, Respectively represent the polar diameter and polar angle in the polar coordinates of the relay satellite, They represent the polar diameter and polar angle in the polar coordinates of the monitoring satellite respectively; (3) establishing a relay satellite position optimization model based on the minimum total false detection probability calculation model of the monitoring satellite, wherein the relay satellite position optimization model aims to maximize the covert communication rate and takes the minimum total false detection probability of the monitoring satellite as greater than or equal to a preset threshold as a constraint; (4) Solve the relay satellite position optimization model to obtain the optimal position of the relay satellite.

2. The method for optimizing the position of relay satellites based on satellite covert communication according to claim 1, characterized in that: The relay satellite position optimization model is specifically as follows: , , In the formula, represents the covert communication rate from the relay satellite to the receiving base station, is the preset threshold, Represents a number that approaches 0 in the range (0,1).

3. The method for optimizing the position of relay satellites based on satellite covert communication according to claim 2, characterized in that: The calculation formula of the covert communication rate is specifically: , In the formula, represents the covert communication rate from the relay satellite to the receiving base station, represents the channel coefficient from the relay satellite to the receiving base station, Represents the signal transmission power of the relay satellite, P e Indicates the interference signal transmission power of the monitoring satellite, represents the noise power variance at the receiving base station location, express The exponential parameter of the exponential distribution, H eb represents the channel coefficient from the monitoring satellite to the receiving base station, is a number that approaches 0 in the range (0,1).

4. The method for optimizing the position of relay satellites based on satellite covert communication according to claim 3, characterized in that: Step (4) specifically includes: The relay satellite position optimization model is converted into the following simplified model and then solved to obtain the optimal position of the relay satellite: , , In the formula, Represents the polar diameter in the polar coordinates of the receiving base station, and the solved The optimal value of is output as the optimal position of the relay satellite.

5. The method for optimizing the position of relay satellites based on satellite covert communication according to claim 4, characterized in that: The calculation formula for the optimal position of the relay satellite is: ， ， In the formula, is an intermediate variable.

6. A relay satellite position optimization system based on satellite covert communication, characterized in that: include: A satellite covert communication model construction module is used to construct a covert communication model in a satellite covert communication system, wherein the covert communication model includes a relay satellite, a transmitting base station located on the ground for transmitting signals to the relay satellite, a receiving base station located on the ground for receiving signals through the relay satellite and sending interference signals to interfere with the detection satellite, and a monitoring satellite for monitoring the relay satellite signal and sending interference signals to interfere with the receiving base station; The minimum total false detection probability calculation model construction module is used to construct the minimum total false detection probability calculation model for monitoring satellites in the satellite covert communication system, specifically: , In the formula, represents the minimum total false detection probability of the monitoring satellite, H de represents the channel coefficient from the relay satellite to the monitoring satellite, It represents the channel coefficient of information transmission when the distance is 1 km. Indicates the signal transmission power of the relay satellite, Indicates the interference signal transmission power of the receiving base station, express The exponential parameter of the exponential distribution, H be represents the channel coefficient from the receiving base station to the monitoring satellite, Indicates the distance between the relay satellite and the monitoring satellite. , Respectively represent the polar coordinates of the relay satellite and the monitoring satellite, Respectively represent the polar diameter and polar angle in the polar coordinates of the relay satellite, They represent the polar diameter and polar angle in the polar coordinates of the monitoring satellite respectively; A relay satellite position optimization model building module is used to establish a relay satellite position optimization model according to a minimum total false detection probability calculation model of a monitoring satellite, wherein the relay satellite position optimization model takes the maximum covert communication rate as a goal and takes the minimum total false detection probability of the monitoring satellite being greater than or equal to a preset threshold as a constraint condition; The model solving module is used to solve the relay satellite position optimization model to obtain the optimal position of the relay satellite.

7. The relay satellite position optimization system based on satellite covert communication according to claim 6 is characterized in that: The relay satellite position optimization model is specifically as follows: , , In the formula, represents the covert communication rate from the relay satellite to the receiving base station, is the preset threshold, Represents a number that approaches 0 in the range (0,1).

8. The relay satellite position optimization system based on satellite covert communication according to claim 7 is characterized in that: The calculation formula of the covert communication rate is specifically: , In the formula, represents the covert communication rate from the relay satellite to the receiving base station, represents the channel coefficient from the relay satellite to the receiving base station, Represents the signal transmission power of the relay satellite, P e Indicates the interference signal transmission power of the monitoring satellite, represents the noise power variance at the receiving base station location, express The exponential parameter of the exponential distribution, H eb represents the channel coefficient from the monitoring satellite to the receiving base station, is a number that approaches 0 in the range (0,1).

9. The relay satellite position optimization system based on satellite covert communication according to claim 8, characterized in that: The model solving module is specifically used to convert the relay satellite position optimization model into the following simplified model, and then solve it to obtain the optimal position of the relay satellite: , , In the formula, Represents the polar diameter in the polar coordinates of the receiving base station, and the solved The optimal value of is output as the optimal position of the relay satellite.

10. The relay satellite position optimization system based on satellite covert communication according to claim 9, characterized in that: The optimal position calculation formula for the relay satellite is: ， ， In the formula, is an intermediate variable.

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