A method for establishing cross-layer links in a multi-layer low-orbit satellite network

Abstract

The present invention belongs to the field of satellite communications, and relates to a method for establishing a cross-layer link in a multi-layer low-orbit satellite network. The method includes partitioning the space where the satellite network is located to form a grid using virtual positions, selecting the middle node of the upper constellation in the grid as the active link establishment node to establish a cross-layer link, and reducing the superposition effect of nodes in different layers in the partition; starting from the factors affecting the on-off of the cross-layer link, the inter-satellite orbit and cross-layer link changes and node resources are characterized; a cross-layer node motion model and a node and link resource model are constructed, and a reliable link utility function is constructed with the signal-to-noise ratio, node cache, and link duration as decision variables, and the node with the largest node and link resource utility value is selected to establish a link with the active link establishment node. The present invention establishes a reliable cross-layer link in a multi-layer low-orbit satellite network, realizes cross-layer reliable communication of a multi-layer network, increases the diversity of data packet transmission paths, reduces data packet transmission delay, and improves network communication performance.

Description

Technical Field

[0001] The present invention relates to the field of satellite network communications, and in particular to a method for establishing a cross-layer link in a multi-layer low-orbit satellite network. Background Art

[0002] With the widespread application of mobile networks and the rapid development of aerospace technology, satellite networks have become an important part of communication networks. In recent years, low-orbit satellite networks have developed towards large-scale, multi-layer orbital plane deployment. They have relatively low transmission delay and link loss, and can more efficiently build a global continuous coverage network. Many multi-layer low-orbit satellite constellations such as Starlink, Kuiper, and OneWeb have been launched, providing wide-area low-latency communications for applications such as emergency communications and remote areas. The cross-layer inter-orbit links formed between satellites in different orbital planes increase the transmission efficiency of the network and reduce the number of transmission hops to optimize latency. However, in multi-layer low-orbit satellite networks, due to factors such as the relative motion of satellite nodes between orbits and the occlusion of satellites in the middle layer, cross-layer inter-orbit links are prone to interruption. For example, a link interruption occurs because the relative motion speed of the nodes at both ends of the link is too large and the distance between the nodes exceeds the transmission range of each other. In addition, limited resource conditions of satellite nodes and links can also lead to frequent link interruptions. For example, the cache queue of a node will change with the time-varying data flow in the network. When the remaining cache queue of the receiving node is insufficient to store and process the received data packets, the node forwarding fails. When the link is affected by fading, the received signal strength of the receiving node is too low, resulting in link interruption. Therefore, in the multi-layer low-orbit satellite network scenario, the relative motion of the constellation, the size of the node, and the complexity of the channel environment all increase the probability of cross-layer link interruption, resulting in discontinuous data transmission, increased latency and packet loss rate. It can be seen that in order to reduce satellite network communication latency and improve network reliability, the dynamic problem of cross-layer inter-orbit links must be solved.

[0003] At present, the research on cross-layer links in multi-layer LEO satellite networks is in its infancy. Due to the complexity of multi-layer LEO satellite networks, researchers focus on physical conditions when establishing cross-layer links, that is, the physical properties of nodes such as link distance and angular velocity, but lack consideration of factors such as space environment and data packet congestion during communication. There is a problem of failure of cross-layer inter-orbit links; in addition, when selecting link establishment nodes, the existing methods consider global satellite nodes and judge the link establishment conditions for all satellite nodes, which increases the complexity of the link establishment method. Therefore, there is a need for an effective method for establishing cross-layer links in multi-layer low-orbit satellite networks, which can simplify the structure of multi-layer satellite networks while improving the reliability of cross-layer links to ensure high-reliability and low-latency cross-layer data transmission. Summary of the invention

[0004] In order to solve the above problems, the present invention provides a method for establishing a cross-layer link in a multi-layer low-orbit satellite network, comprising the following steps:

[0005] S1. The satellite network is partitioned into a grid according to the virtual position of the satellite, and the central node of the upper constellation in the grid is selected as the active link establishment node;

[0006] S2: Link communication distance, relative angular velocity, and elevation angle are used as physical conditions that affect cross-layer link connectivity and as node selection constraints.

[0007] S3, taking the link transmission signal-to-noise ratio, node cache queue, and link duration as resource conditions that affect the cross-layer link disconnection, and conducting analysis and modeling;

[0008] S4. Use a multi-attribute decision-making model to model the various parameters of node resources as a node utility evaluation function, calculate the weight value of each node parameter, and select the node with the largest utility value from the candidate nodes to establish a reliable cross-layer link with the active link-building node.

[0009] Beneficial effects of the present invention:

[0010] The present invention proposes a method for establishing a cross-layer link in a multi-layer low-orbit satellite network. The use of cross-layer links in wide-area data packet transmission can reduce the transmission delay by reducing the number of relay nodes, and reduce the probability of routing interruption by increasing the transmission path and the quality of cross-layer links, thereby ensuring reliable data transmission. The present invention also uses a game method based on the correlation coefficient method and the information entropy weight method to calculate the three parameter attributes, and finds consistency for different weights of parameter indicators to ensure that the decision result is more accurate, making the final link establishment result more reliable. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 It is a communication scenario diagram of a multi-layer satellite network of the present invention;

[0012] Figure 2 It is a flow chart of a method for establishing a cross-layer link in a multi-layer low-orbit satellite network according to the present invention;

[0013] Figure 3 is the virtual location partition map of the present invention;

[0014] Figure 4 This is a satellite relative motion relationship diagram described in the present invention. DETAILED DESCRIPTION

[0015] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0016] Multi-layer LEO satellite network scenario Figure 1 As shown, satellite networks have a wide range of applications in many fields due to their global coverage. For example, they provide access to core network services for remote areas, provide emergency communication services for post-disaster areas, and provide low-latency and high-reliability communication services at sea.

[0017] like Figure 2 The figure shows a flow chart of the overall solution for establishing a cross-layer link in a multi-layer low-orbit satellite network, which specifically includes the following steps:

[0018] S1: The satellite network is partitioned into a grid according to the virtual position of the satellite, and the upper constellation center node in the grid is selected as the active link establishment node;

[0019] Due to the large scale of nodes in satellite networks and the frequent disconnection of cross-layer links, the satellite network architecture is complex and the link establishment algorithm is highly complex. Therefore, this paper uses the concept of virtual location to reduce the number of cross-layer links in the network without affecting the use of cross-layer links worldwide. Figure 3 As shown, the virtual position divides the entire satellite network into grids with equal sizes, and uses the high-orbit satellite closest to the center of the grid position as the active link-building satellite to establish cross-layer links with satellites at different altitude layers.

[0020] S2: Link communication distance, relative angular velocity, and elevation angle are used as physical conditions that affect cross-layer link connectivity and as node selection constraints.

[0021] In a multi-layer low-orbit satellite network, the nodes at both ends of the inter-layer orbital link belong to orbital layers of different heights. The link distance, node relative speed, and node relative angle will change highly dynamically, resulting in frequent on-off of the inter-layer orbital link. Therefore, before selecting the link building node, it is necessary to fully characterize the motion characteristics of the satellite node. Figure 4 As shown, in the embodiment of the present invention, starting from visibility, relative angular velocity and elevation angle, these three physical conditions are modeled as constraint conditions for selecting the chain building nodes in the following text.

[0022] S3: Link transmission signal-to-noise ratio, node cache queue, and link duration are used as resource conditions that affect cross-layer link connectivity and are analyzed and modeled;

[0023] In a multi-layer LEO satellite network scenario, the on-off of cross-layer inter-orbit links is also affected by node and link resource limitations. First, from the node perspective, the signal-to-noise ratio (SNR) of the receiving node needs to be greater than the receiving threshold to ensure that the receiving node can successfully receive the data transmitted by the sending node; secondly, the network node needs to have sufficient cache queue length to store and forward the received data; finally, from the link perspective, in order to ensure the stability of the network architecture, links with long duration should be selected as cross-layer inter-orbit links as much as possible. Therefore, the present invention models the SNR, cache queue length, and link duration.

[0024] S4: Use the multi-attribute decision-making model to model the various parameters of node resources as the node utility evaluation function, calculate the weight value of each node parameter, and select the node with the largest utility value from the candidate nodes to establish a reliable cross-layer link with the active link-building node.

[0025] In step S2: the three physical parameters of communication distance, relative angular velocity and elevation angle are modeled and the formula for describing the physical constraints of the cross-layer node pair is:

[0026] U p =U pd ×U pw ×U pe

[0027] Among them, U pd is the visibility constraint, U pw is the relative angular velocity constraint, U pe is the elevation angle constraint. p =1 indicates that the node pair meets the physical conditions for link building, U p =0 means that the node pair does not meet the physical conditions for link establishment.

[0028] Furthermore, the visibility constraints of nodes i and j are expressed as:

[0029]

[0030] Among them, d ij is the link distance between node i and node j; d i and d j are the communication radius of node i and node j respectively.

[0031] Furthermore, the communication radius d of the satellite node is expressed as:

[0032]

[0033] Among them, R E is the radius of the earth; h is the orbital height of the satellite node; h* is the height of the Earth's thermosphere.

[0034] The relative angular velocity constraint between nodes i and j is expressed as:

[0035]

[0036] Among them, w ij is the relative steering angle between node i and node j in unit time; w m is the maximum steering angle per unit time, that is, the maximum relative angular velocity.

[0037] Furthermore, the relative turning angle of the node pair per unit time is:

[0038]

[0039] in, is the orbit height h and the Earth radius R E sum; is the relative speed between node i and node j.

[0040] The relative elevation angle constraint between nodes i and j is expressed as:

[0041]

[0042] The relative elevation angle is El, which is defined as the projection of node i on the orbital sphere where node j is located and the sum of l ij The angle between the lines is:

[0043]

[0044] Among them, v p =s2-(s1·s2)s1 / ||s1|| 2 is the position formula of two satellite nodes, s i (x i ,y i ,z i ) and s j (x j ,y j ,z j ) are the position coordinates of node i and node j in the geocentric coordinate system.

[0045] In step S3, the cross-layer link SNR is expressed as:

[0046]

[0047] Among them, P t represents the transmitted signal power; γ represents the link loss factor; N ijis Gaussian white noise with variance σ; |h ij | 2 Follows a noncentral chi-square distribution.

[0048] Furthermore, link l ij The probability that the link is unavailable when the SNR between them is less than the interruption threshold can be expressed as:

[0049]

[0050] In step S3, the probability that the node cache queue state of node j is less than the maximum cache queue length F at time t1 can be expressed as:

[0051]

[0052] Where a is the length of the cache queue used by node j at time t0; the arrival process of the data packet received by node j follows the Poisson distribution, and the arrival rate is λ; the probability of node j processing the data packet and successfully sending it follows the binomial distribution, and the probability of the node failing to successfully send the data packet is p e .

[0053] In step S3, the link duration can be expressed as:

[0054]

[0055] Among them, D ij The relative speed of node j The movement distance of the movement into the communication range of node i; is the relative speed Model.

[0056] The node reliability utility function characterized by multi-attribute decision making is expressed as:

[0057]

[0058] s1U p (v i )=1

[0059]

[0060]

[0061] Among them, U(v i ) represents the total utility function value of node i; Represents node v i The signal-to-noise ratio constraint condition; Represents node v i The node cache queue constraints; Indicates link lij The link duration constraint of Indicates the weight of the signal-to-noise ratio among all attributes; Indicates the weight of the node cache queue in all attributes; represents the weight of link duration in all attributes; constraint C1 indicates that the target node pair needs to meet its physical motion conditions; constraint C2 indicates that the utility value of the link and the utility value of the decision attribute should be between [0,1]; constraint C3 indicates that the sum of all attribute weights is 1.

[0062] Weight allocation is the key to ensuring the effectiveness of the utility function. If an attribute has almost no difference on all links, it means that the attribute has little impact on the decision-making process and should be given a smaller weight. If an attribute can cause a large deviation in the attribute values ​​of all links, it means that it plays an important role in decision-making and sorting, and needs to be given a larger weight.

[0063] In some embodiments, conventional multi-attribute decision weight allocation methods in the prior art, such as hierarchical analysis method, principal component analysis method, deviation maximization method, information entropy method, etc., can be used to assign weights to the node reliability utility function, so as to accurately characterize the parameter attributes of each link transmission signal-to-noise ratio, node cache queue, and link duration, and improve the reliability of cross-layer links.

[0064] In some preferred embodiments, the present invention uses a game theory method to calculate the three parameter attributes, and seeks consistency for different weights of parameter indicators to ensure that the decision result is more accurate. The specific steps include:

[0065] A game method based on the correlation coefficient method and the information entropy weight method is used to determine the parameter attributes of the link transmission signal-to-noise ratio, the node cache queue, and the link duration; the correlation coefficient is defined according to the influence of each attribute on the decision-making scheme, and the correlation coefficient is used to assign weights to each parameter attribute, and the weight of each parameter attribute is obtained using the correlation coefficient method; the information entropy weight method is used to obtain the weight of each parameter attribute; a mixed strategy is performed on the attribute weights obtained using the correlation coefficient method and the attribute weights obtained using the information entropy weight method; the equilibrium point is selected through game theory, and the Lagrangian function is constructed to calculate the final attribute weight.

[0066] To further illustrate the above embodiment, the above process of the present invention may also include the following process:

[0067] Step 1: Normalize the decision matrix;

[0068] Step 2: Determine the players, strategy space, and benefit function. The players are subjective weighting method and information entropy weighting method; the strategy space is the weight set, W = W1 × W2; the benefit function is the proportion of the two methods u = {α, β}, where α, β∈[0,1], α+β=1.

[0069] Step 3: Use the correlation coefficient method to determine the weight of the decision attribute:

[0070] Define the correlation coefficient based on the impact of the attribute parameters on the overall solution, and use the correlation coefficient to weight the attribute parameters:

[0071] The correlation coefficient is used to determine the importance of parameter attributes to the overall solution. If the correlation coefficient is high, it means that deleting the attribute will have a significant impact on the decision, and the attribute is given a high weight.

[0072] The overall program evaluation value is:

[0073] Remove attributes After that, the overall scheme evaluation value is:

[0074] Parameter properties The correlation coefficient with the overall solution is:

[0075] in is the average utility of m candidate cross-layer links;

[0076] Parameter properties The weight calculation formula is:

[0077] The weights obtained by the correlation coefficient method are:

[0078] Step 4: Use the information entropy weight method to determine the weight of the decision attribute:

[0079] Scheme for attribute parameters The evaluation is:

[0080] The information entropy of attribute parameters is

[0081] The information deviation is:

[0082] Then the relevant parameter weights can be expressed as:

[0083] The weights obtained by the information entropy weighting method are:

[0084] Step 4: Two weighting methods mixed strategy:

[0085] Step 5: Find the equilibrium point through game selection and construct the Lagrangian function: Solve the optimal weights, that is, determine α and β to maximize the Lagrangian function;

[0086] Step 5: Take partial derivatives of the Lagrangian function to determine α and β.

[0087] Step 6: Determine the optimal weight W = αW1 + βW2.

[0088] This embodiment considers a game method combining the correlation coefficient method and the information entropy weight method to assign more accurate weights to the link transmission signal-to-noise ratio, node cache queue, and link duration. The correlation coefficient weighting method can reflect the importance of a single attribute parameter to the overall decision, and the information entropy weighting method can reflect the difference between each attribute parameter. If used alone, there will be a large difference from the actual importance of each indicator. Through the game method, the optimal balance point is found between the two weighting methods to obtain the optimal weight.

[0089] This embodiment considers multiple attributes to solve the problem of establishing satellite links. When transmitting wide-area data packets, cross-layer links are used to reduce transmission delays by reducing the number of relay nodes, and to reduce the probability of routing interruptions by increasing the quality of transmission paths and cross-layer links, thereby ensuring reliable data transmission. The preferred embodiment of the present invention determines the weight of each attribute by using the correlation coefficient weighting method and the information entropy weighting method to game each other, so that the weighting result is more reasonable.

[0090] A person skilled in the art can understand that all or part of the steps in the various methods of the above embodiments can be completed by instructing the relevant hardware through a program, and the program can be stored in a computer-readable storage medium, which can include: ROM, RAM, disk or CD, etc.

[0091] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for establishing a cross-layer link in a multi-layer low-orbit satellite network, characterized in that: The following steps are involved: S1. The satellite network is partitioned into a grid according to the virtual position of the satellite, and the central node of the upper constellation in the grid is selected as the active link establishment node; S2: Link communication distance, relative angular velocity, and elevation angle are used as physical conditions that affect cross-layer link connectivity and as node selection constraints. S3, taking the link transmission signal-to-noise ratio, node cache queue, and link duration as resource conditions that affect the cross-layer link disconnection, and conducting analysis and modeling; S4. Use the multi-attribute decision-making model to model the various parameters of node resources and use it as a node utility evaluation function to calculate the weight value of each node parameter, and select the node with the largest utility value from the candidate nodes to establish a reliable cross-layer link with the active link-building node; The node utility evaluation function obtained by modeling using the multi-attribute decision-making model is expressed as: s.t.C1 U p (v i )=1 Among them, U(v i ) represents node v i The total utility function value of Represents node v i The signal-to-noise ratio constraint condition; Represents node v i The node cache queue constraints; Indicates link l ij The link duration constraint of Indicates the weight of the signal-to-noise ratio among all attributes; Indicates the weight of the node cache queue in all attributes; Indicates the weight of link duration in all attributes; Constraint C1 indicates that the target node pair needs to meet its physical motion conditions; Constraint C2 indicates that the utility value of the link and the utility value of the decision attribute should be between [0,1]; Constraint C3 indicates that the sum of all attribute weights is 1; The calculation method of the weight of each attribute includes using a game method based on the correlation coefficient method and the information entropy weight method to determine the parameter attributes of the link transmission signal-to-noise ratio, the node cache queue, and the link duration; defining the correlation coefficient according to the influence of each attribute on the decision-making scheme, and using the correlation coefficient to weight each parameter attribute, and using the correlation coefficient method to obtain the weight of each parameter attribute; using the information entropy weight method to obtain the weight of each parameter attribute; using a mixed strategy for the attribute weights obtained using the correlation coefficient method and the attribute weights obtained using the information entropy weight method; selecting the equilibrium point through game theory, constructing a Lagrangian function to calculate the final attribute weight.

2. The method for establishing a cross-layer link in a multi-layer low-orbit satellite network according to claim 1, characterized in that: The step S1 includes: dividing the entire space where the satellite orbit is located into a number of cubes, namely, space grids; each grid includes a plurality of satellite nodes at different heights, and the heights of the satellite nodes can be distinguished according to the coordinate values ​​of the satellite nodes in the grid in the earth coordinate system; and selecting the central node of the high-level orbit in the grid as the active link establishment node.

3. The method for establishing a cross-layer link in a multi-layer low-orbit satellite network according to claim 1, characterized in that: The link communication distance is one of the physical conditions that affect the connection and disconnection of cross-layer links. Its formula is expressed as follows: Among them, d ij Represents satellite node v i and satellite node v j The link communication distance between i (x i ,y i ,z i ) and s j (x j ,y j ,z j ) is the satellite node v i and satellite node v j The coordinates of the position in the geocentric coordinate system.

4. The method for establishing a cross-layer link in a multi-layer low-orbit satellite network according to claim 1, characterized in that: As one of the physical conditions that affect the connection and disconnection of cross-layer links, the relative angular velocity is the relative steering angle per unit time, and its formula is expressed as follows: Among them, w ij is the satellite node v per unit time i and satellite node v j The relative steering angle; Indicates the distance from the center of the earth to the satellite node v j The distance Indicates the distance from the center of the earth to the satellite node v i distance; For satellite node v i and satellite node v j relative speed.

5. The method for establishing a cross-layer link in a multi-layer low-orbit satellite network according to claim 1, characterized in that: The elevation angle is one of the physical conditions that affect link connectivity, and its formula is expressed as: Among them, v p =s j -(s i ·s j )s i / ||s i || 2 For two satellite nodes v i and satellite node v j The position of ij is the link communication distance between satellite node i and satellite node j, s i and j are the position coordinates of node i and node j in the geocentric coordinate system.

6. The method for establishing a cross-layer link in a multi-layer low-orbit satellite network according to claim 1, characterized in that: When the link transmission signal-to-noise ratio SNR is used as a resource condition affecting the connection and disconnection of the cross-layer link, the following includes: if the link transmission signal-to-noise ratio SNR is less than the interruption threshold s m The probability of causing link unavailability is expressed as: in, h ij represents the link loss factor from satellite node i to satellite node j; d ij represents the link communication distance between satellite node i and satellite node j; γ represents the path loss index generated by the signal propagation in space; P t Indicates the transmission power of the transmitter; N ij It means that the variance is The additive Gaussian white noise is G, which represents the signal gain and N0, which represents the power spectral density of the noise.

7. The method for establishing a cross-layer link in a multi-layer low-orbit satellite network according to claim 1, characterized in that: The node cache queue as a resource condition affecting the cross-layer link disconnection includes: if the node cache queue state of the satellite node at time t1 is less than the maximum cache queue length F, the probability is: P b (t)=p(a+x-y≤F)=∑f X (x,λΔt)f Y (y,a+x) Among them, a is the length of the cache queue used by the node at time t0; x is the number of data packets received by the node within Δt time. The data packet arrival process of the satellite node follows the Poisson distribution with an arrival rate of λ; y is the number of data packets successfully processed by the node within Δt time. The probability of successful data packet transmission follows the binomial distribution.

8. The method for establishing a cross-layer link in a multi-layer low-orbit satellite network according to claim 1, characterized in that: When the link duration is used as a resource condition affecting the inter-layer link disconnection, the calculation formula of the link duration is expressed as: Among them, D ij is the movement distance of satellite node j within the communication range of satellite node i, is the relative speed from satellite node i to satellite node j Model.

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