A Fast Rerouting Method for Satellite Network Topology Changes

Abstract

This invention provides a fast rerouting method for satellite network topology changes, belonging to the field of satellite communication network technology. Based on the Floyd-Warshall algorithm, and addressing the dynamic changes in inter-satellite links in satellite networks, an incremental routing update algorithm is proposed to locally update path information when a new link is established. A decremental routing update algorithm is also proposed, which utilizes the regular characteristics of inter-satellite links to locally update only the affected shortest distance path when inter-orbit or intra-orbit links are interrupted, avoiding global route recalculation. The algorithm of this invention quickly determines alternative paths when satellite network topology changes abruptly. Through an efficient local update mechanism, it significantly reduces the computational load of routing updates and can be effectively integrated with shortest path algorithms to enhance the stability and transmission performance of satellite networks.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of satellite network communication, and particularly relates to a high-efficiency and fast re-routing method for satellite network topology changes. BACKGROUND

[0002] With the continuous growth of global communication demand, satellite networks have become an important part of future communication infrastructure. Among them, low earth orbit (LEO) satellite constellation greatly enhances global network coverage and data transmission capacity. In particular, with the development of laser communication technology, inter-satellite links (ISLs) play a crucial role in satellite network construction. ISLs not only provide low latency and high data transmission rates for efficient communication, but also provide flexibility and reliability for complex network architecture. However, due to factors such as space environment, laser alignment, network attacks, etc., the topology of satellite networks is prone to frequent changes due to link failures or recoveries.

[0003] In LEO satellite networks, efficient routing is crucial to minimize end-to-end delay and ensure high communication quality. Shortest distance path (SDP) based routing algorithms are widely used in satellite networks to minimize the ISL distance between the source ground station and the target ground station, thereby reducing data transmission delay. In order to solve the computational complexity problem of routing selection, satellite networks are usually divided into multiple time slots, and each time slot assumes a static topology structure, and classic algorithms such as Dijkstra and Floyd-Warshall are used for routing decisions. Among them, the Floyd-Warshall algorithm provides an efficient and general way to solve the shortest path problem, and is particularly suitable for handling all-pair shortest path computation requirements. However, existing algorithms are difficult to quickly adapt to frequent and unpredictable topology changes. As the network size expands, each link failure or recovery requires forwarding update information between hundreds of satellites, which may cause temporary traffic interruption or loops for several seconds until the network converges. Such interruptions will increase computational overhead and delay, reducing user service quality.

[0004] Efficient re-routing algorithms are crucial for timely restoring communication and improving the resilience of satellite networks when the topology changes. Current research on satellite network re-routing algorithms is still very limited. Some research has pre-computed re-routing paths by satellites with abundant computing resources, and distributed routing rules to satellites with stronger forwarding capabilities. However, this method only maintains backup paths and does not effectively reduce computational overhead. Another research has considered the predictability of time-varying topology to minimize routing convergence time during ISL switching, but this research does not fully address unexpected link interruption problems. In addition, some research has analyzed the unique topological characteristics exhibited by LEO satellite constellations and the SDP mode of satellite constellations, but does not address the re-routing requirements when links fail.

[0005] Therefore, in view of the frequent change of LEO satellite network topology, developing a re-routing algorithm capable of quickly adapting and efficiently recovering communication has become the focus and difficulty of current research. SUMMARY

[0006] The application aims to solve the above technical problems, and proposes a high-efficiency and fast re-routing (RFR) method for satellite network topology change for LEO satellite networks adopting Walker constellation configuration. The method is based on Floyd-Warshall algorithm, and calculates the SDP between all satellite pairs in the satellite network. The network topology characteristics are fully utilized: the intra-orbit link distance is basically equal, the inter-orbit link distance changes regularly with the satellite phase, the link distance near the equator is the largest, and gradually decreases with the increase of latitude. The method can effectively deal with the problems of high computational overhead and slow routing convergence caused by dynamic changes of satellite network topology, and significantly improves the network performance.

[0007] The technical solution of the application is as follows:

[0008] A fast re-routing method for satellite network topology change, characterized in that it includes the following cases:

[0009] I. Incremental routing update method for new link establishment in satellite network, including the following steps:

[0010] S1.1 define and initialize a distance matrix D for storing the shortest path distance between all satellite node pairs, and define and initialize a predecessor matrix P for storing the information of the first satellite node to be reached to reach each destination satellite;

[0011] S1.2 traverse all satellite pairs to judge whether there is a shorter path through the new link, which is based on the following conditions:

[0012] For each pair of satellites i and j, check whether there is a new link u-v through which the path length from satellite i to satellite v to satellite j is less than the shortest path length from satellite i to satellite j stored in the distance matrix D;

[0013] If the above conditions are met, mark the satellite pair as an affected satellite pair;

[0014] S1.3 locally update the affected satellite pairs, and the update content includes:

[0015] - Recalculate and update the shortest path distance between the corresponding satellite pairs in the distance matrix D according to the new link;

[0016] - update the predecessor node information in the predecessor matrix P for the corresponding satellite pairs to reflect the shortest paths through the new link;

[0017] II. A reduced update method for satellite network after intra-orbit link deletion, comprising steps of:

[0018] S2.1 define the minimum hop path (MHP) as the path with the least number of hops between the source satellite s and the destination satellite d, and determine the MHP region, which contains all such paths, wherein the intra-orbit hops and the inter-orbit hops of each path are the same;

[0019] S2.2 traverse all satellite pairs to detect whether the original shortest path passes through the deleted intra-orbit link, if any satellite pair passes through, it indicates that the routing information of the satellite pair needs to be updated, otherwise no update is needed;

[0020] S2.3 when the source and destination satellites passing through the deleted intra-orbit link are in the same orbit, then select an alternative path, which relies on inter-orbit links to bypass and increases two hops, while ensuring that the alternative path passes through the parallel edges adjacent to the interrupted link to optimize communication delay; when the source and destination satellites passing through the deleted intra-orbit link are not in the same orbit, then select different alternative paths according to whether the link deletion occurs before or after the cross-plane jump, and ensure that the alternative path passes through the edges parallel and adjacent to the deleted link in the MHP region;

[0021] S2.4 update the distance matrix and the predecessor matrix to reflect the new shortest path and the predecessor node information.

[0022] III. A reduced update method for satellite network after inter-orbit link deletion, comprising steps of:

[0023] S3.1 traverse all satellite pairs to detect whether the original shortest path passes through the deleted inter-orbit link, if any satellite pair passes through, it indicates that the routing information of the satellite pair needs to be updated, otherwise no update is needed;

[0024] S3.2 when the intra-orbit numbers of the source satellite and the destination satellite passing through the deleted link are the same, if the original inter-orbit link distance is the smallest, the alternative path only bypasses near the deleted link, and then returns to the original path quickly; if the original inter-orbit link distance is not the smallest, then the inter-orbit link parallel and adjacent to the deleted link must be shorter, and the alternative path will make a one-hop orbit from the source satellite, then perform a series of shorter inter-orbit jumps, and finally return in the destination satellite orbit.

[0025] S3.3 update the distance matrix and the predecessor matrix to reflect the new shortest path and the predecessor node information.

[0026] Preferably, the step S2.2 detects whether the original shortest path passes through the deleted inter-orbit link, with the specific condition that the original path first passes through satellite u and then satellite v, where v is the next satellite or the previous satellite of u in the orbit direction, and if the condition is met and the link u-v is the deleted inter-orbit link, it indicates that the satellite pair (i, j) passes through the link.

[0027] Preferably, in the step S2.3, when the source and destination satellites passing through the deleted inter-orbit link are in the same orbit, the alternative path first routes along the original orbit, then makes the shortest cross-plane jump before reaching the interrupted link; after crossing to the adjacent orbit, the data stream continues to route along the orbit until it passes through the adjacent parallel edge of the interrupted link; then the shortest inter-orbit link before reaching the destination satellite is selected to return to the original orbit, and finally reaches the destination satellite.

[0028] At this time, the shortest path will pass through the adjacent parallel edge of e=(u, v, w), and the distance between the satellite pairs is d1 or d2,

[0029] d1 = dist[i][u w ]+w w +dist[v w ][j]

[0030] d2 = dist[i][u e ]+w e +dist[v e ][j]

[0031] In a special case, when the difference between the intra-orbit numbers of the source and destination satellites is equal to , the alternative path will route in the opposite direction of the original path without detouring the inter-orbit link, and the distance between the satellite pairs is d3,

[0032] d3 = dist[i][j s ]+dist[j s ][j].

[0033] Preferably, in S2.3, when the source and destination satellites of the deleted inter-orbit link are not in the same orbit, if the link deletion occurs before the cross-plane hop, the alternative path will cross to the adjacent orbit to bypass the interrupted link before reaching the interrupted link, i.e. the alternative path will make a cross-plane hop at satellite u, and then return to the original path along the adjacent orbit; if the link deletion occurs after the cross-plane hop, the alternative path will route along the second-to-last orbit plane of the original path, make a last cross-plane hop after passing through the parallel edge adjacent to the deleted link, and finally reach the destination satellite. At this time, the alternative path will pass through the edge e' = (u', v', w') in the MHP area which is parallel and adjacent to the deleted link. The distance between the satellite pairs is d1 or d2.

[0034] Preferably, in S3.1, the original shortest path is detected to pass through the deleted inter-orbit link, and the specific condition is that the original path first passes through satellite u and then passes through satellite v, where v is the satellite with the same intra-orbit number as u on the adjacent orbit. If this condition is met and the link u-v is the deleted inter-orbit link, it indicates that the satellite pair (i, j) passes through this link.

[0035] Preferably, in S3.2, when the intra-orbit numbers of the source and destination satellites of the deleted inter-orbit link are the same, if the original inter-orbit link distance is the smallest, the alternative path only detours near the deleted link and then quickly returns to the original path; if the original inter-orbit link distance is not the smallest, the alternative path will first make a jump along the orbit from the source satellite, then perform a series of shorter inter-orbit jumps, and finally return to the orbit at the destination satellite.

[0036] At this time, the alternative path will pass through the parallel edge adjacent to e = (u, v, w), and the distance between the satellite pairs is d4 or d5

[0037] d4 = dist[i][u n ]+w n +dist[v n ][j]

[0038] d5 = dist[i][u s ]+w s +dist[v s ][j]

[0039] In a special case, when the difference between the orbit numbers of the source and destination satellites is equal to , the alternative path will route in the opposite direction of the original path, and the distance between the satellite pairs is d6

[0040] d6 = dist[i][j e ]+dist[j e ][j]

[0041] Preferably, when the intra-orbital numbers of the source and destination satellites of the deleted inter-orbital link are different, the alternative path passes through a link in the MHP region parallel and adjacent to the deleted link, and the distance between the satellite pairs is d4 or d5.

[0042] Compared with the prior art, the technical effects of the present application are as follows:

[0043] When the topology of the satellite network changes due to the interruption or reconstruction of the inter-satellite link, only the routing information of the affected satellite pairs needs to be updated locally, and the shortest path can be quickly identified. Compared with the traditional Floyd-Warshall routing algorithm, the calculation overhead and routing update time are significantly improved. BRIEF DESCRIPTION OF DRAWINGS

[0044] Figure 1 is a schematic diagram of the distance of the inter-orbital link changing with the phase of the satellite.

[0045] Figure 2 is a parameter diagram of a real constellation.

[0046] Figure 3 is a schematic diagram of an MHP region.

[0047] Figure 4 is a schematic diagram of rerouting after intra-orbital link deletion (the source and destination satellites are in the same orbit).

[0048] Figure 5 is a schematic diagram of rerouting after intra-orbital link deletion (the source and destination satellites are not in the same orbit).

[0049] Figure 6 is a flowchart of the incremental routing update algorithm after intra-orbital link deletion.

[0050] Figure 7 is a schematic diagram of rerouting after inter-orbital link deletion (the intra-orbital numbers of the source and destination satellites are the same).

[0051] Figure 8 is a schematic diagram of rerouting after inter-orbital link deletion (the intra-orbital numbers of the source and destination satellites are different).

[0052] Figure 9 is a flowchart of the incremental routing update algorithm after inter-orbital link deletion.

[0053] Figure 10 is a comparison diagram of routing update time when a single link changes.

[0054] Figure 11 is a comparison diagram of routing update time under different link failure rates.

[0055] Figure 12is the error map of the rerouting path when the inter-orbit link is deleted. DETAILED DESCRIPTION

[0056] The application is further explained below in conjunction with the accompanying drawings and examples, but should not be limited by them.

[0057] In a LEO (Low Earth Orbit) satellite network with Walker constellation configuration, satellites in the same orbital plane usually maintain a relatively fixed phase difference. The phase difference refers to the position difference of a satellite on its orbit relative to a certain reference point, which is cyclic within the orbital period. Due to the stability of this phase difference, the distance between adjacent satellites in the same orbital plane also remains essentially unchanged. This means that, ignoring the slight influence of factors such as the shape of the Earth and atmospheric drag, the intra-orbit link (i.e. the connection between satellites in the same orbital plane) can be considered equal in distance. Unlike intra-orbit links, inter-orbit links (i.e. links between different orbital planes) are affected by various factors, including orbital inclination (the angle between the orbital plane and the equatorial plane), phase difference between orbital planes, and difference in right ascension of the ascending node (RAAN, i.e. the angle between the intersection of the orbital plane and the equatorial plane and the vernal equinox). As shown in FIG. 1, the distance of the inter-orbit link between different orbital planes varies with the instantaneous phase μ of the satellite. The satellite phase ranges from [0, 2π], and the distance of the inter-orbit link is largest near the equator and gradually decreases with increasing latitude. Figure 1

[0058] §1.1. When new links are added to the satellite network, the distance between some satellite pairs may be shortened. For the topology changes caused by the establishment of new links in the satellite network, an incremental routing update algorithm for link addition is proposed, the core idea of which is to only update the satellite pairs affected by the new link locally, rather than recalculating the shortest paths of the entire network. Specifically, it includes the following contents:

[0059] §1.1.1. Network model and data structure: a LEO satellite network based on Walker constellation configuration, consisting of N×M satellites distributed on multiple circular orbits, where N represents the number of orbital planes and M represents the number of satellites on each orbit. Figure 2 Some real constellation parameters are shown. Starting from the orbital plane with the smallest RAAN, the position of each orbit is identified; within each orbit, the satellites are numbered in the direction of movement along the orbit, starting from the position with the smallest perigee parameter to specify the position of each satellite. Satellites are numbered according to their orbital plane and in-orbit number order. The number of satellite y in orbit x is defined as sat x,y ​= x-m + y. To efficiently manage and query the shortest path between satellites, a distance matrix D and a predecessor matrix P are introduced. Matrix D stores the shortest path distance between all pairs of satellite nodes, and the distance between satellite i and satellite j is denoted as dist[i][j]. Matrix P stores the satellite node that is first reached when traveling from satellite i to satellite j, which is helpful for accurate shortest path positioning, and P[i][j] denotes the satellite that satellite i first reaches when traveling to satellite j.

[0060] §1.1.2. Detecting affected satellite pairs: When a new link e = (u, v, w) is built in the satellite network, all satellite pairs are traversed to check whether there is a shorter path through the new link. Assuming that the path first passes through u and then through v, if the following conditions are met

[0061] dist[i][u] + w + dist[v][j] < dist[i][j]

[0062] then the routing information for these satellite pairs needs to be updated.

[0063] §1.1.3. Local update: The affected satellite pairs are locally updated, and the shortest path distance is updated as follows:

[0064] dist[i][j] = dist[i][u] + w + dist[v][j]

[0065] The predecessor matrix P is updated as:

[0066] P[i][j] = u if j == v else P[v][j]

[0067] The routing information for other unaffected satellite pairs does not need to be updated.

[0068] §1.2. When an intraplanar link e = (u, v, w) in the satellite network is interrupted or fails, it will cause the shortest path distance between some satellite pairs to increase. For the topology change of the intraplanar link interruption in the satellite network, a decremental routing update algorithm for intraplanar link deletion is proposed, which includes the following contents:

[0069] §1.2.1. As Figure 3As shown in LEO satellite networks, the Minimum Hop Path (MHP) refers to the path with the least number of hops between the source satellite s and the destination satellite d, and the MHP region includes all such paths. For the "+Grid" topology of Walker constellation, the intra-orbit hops and inter-orbit hops of each path in the MHP region are the same. The shortest distance between satellites is the sum of all inter-orbit link distances and intra-orbit link distances. Since the intra-orbit link distance is almost constant, the SDP is mainly determined by the inter-orbit link distance. The general form of the SDP between the source and destination satellites on different orbits and with different intra-orbit numbers is defined as follows: the path starts from the source satellite, first routes along the orbit plane, then makes a few shortest inter-orbit consecutive hops, and finally reaches the destination satellite along the orbit plane where the destination satellite is located. This structure means that the inter-orbit link on the current shortest path is the shortest link available in the MHP region. To facilitate the design of the algorithm, the relative positions of the following satellite nodes are defined with satellite u as an example. u n is the next satellite in the direction of orbit motion, u s is the previous satellite. In the reference direction of increasing RAAN, the satellites with the same orbit number in the clockwise and counterclockwise directions are denoted as u e and u w .

[0070] §1.2.2. Traverse all satellite pairs to detect whether the original shortest path passes through the deleted intra-orbit link e = (u, v, w), assuming that the original path first passes through u and then v (v = u s ), if the following conditions are met

[0071] dist[i][j] == dist[i][u] + w + dist[v][j]

[0072] then it indicates that the satellite pair (i, j) passes through the link, and the routing information needs to be updated; otherwise, no update is needed.

[0073] §1.2.3. When the source and destination satellites passing through the deleted intra-orbit link are on the same orbit, the alternative path needs to rely on the inter-orbit link to detour. In this case, the SDP will increase by two hops. As shown in Figure 4 , since the shortest path distance is mainly affected by the inter-orbit link, and the inter-orbit link has monotonicity, the alternative path will first route along the original orbit, then make the shortest cross-plane jump before reaching the interrupted link; after crossing to the adjacent orbit, the data flow will continue to route along the orbit until it passes through the adjacent parallel edge of the interrupted link; then select the shortest inter-orbit link before reaching the destination satellite to return to the original orbit, and finally reach the destination satellite. At this time, the shortest path will pass through the adjacent parallel edge of e = (u, v, w), and the distance between the satellite pairs may be d1 or d2,

[0074] d1 = dist[i][u w ]+w w +dist[v w ][j]

[0075] d2 = dist[i][u e ]+w e +dist[v e ][j]

[0076] In special cases, when the difference between the orbital indices of the source and destination satellites is equal to , the alternative path is routed in the opposite direction of the original path without detouring the inter-orbital link, and the distance between the pair of satellites can be d3,

[0077] d3 = dist[i][j s ]+dist[j s ][j]

[0078] The minimum d k is chosen as the alternative path, and dist[i][j] and P[i][j] are updated

[0079] dist[i][j] = d k

[0080]

[0081] §1.2.4. When the source and destination satellites of the deleted intra-orbital link are not in the same orbit, two cases can be distinguished. As shown in Figure 5 , if the link deletion occurs before the cross-plane hop, the alternative path must cross to the adjacent orbit before reaching the broken link to bypass it. Based on the monotonicity of the inter-orbital links and the analysis of the general pattern of SDP, the alternative path will make a cross-plane hop at satellite u and then return to the original path along the adjacent orbit. If the link deletion occurs after the cross-plane hop, the alternative path will route in the penultimate orbital plane of the original path, make a final cross-plane hop after passing the parallel edge adjacent to the deleted link, and finally reach the destination satellite. Regardless of whether the intra-orbital link deletion occurs before or after the cross-plane hop, the alternative path must traverse the edge e' = (u', v', w') in the MHP region that is parallel and adjacent to the deleted link, which can be e w = (u w , v w , w w ) or e e = (u e , v e , w e). This path selection ensures efficient routing under link disruption conditions, optimizing communication delay. dist[i][j] and P[i][j] are updated as

[0082] dist[i][j] = dist[i][u'] + w' + dist[v'][j]

[0083] P[i][j] = P[v'][j]

[0084] The algorithm flow of the above steps is shown in Figure 6 .

[0085] §1.3. When the inter-orbit link e = (u, v, w) is interrupted or failed, it will cause the distance of the shortest path between some satellite pairs to increase. For the case of topological changes caused by inter-orbit link interruption in satellite networks, a decremental routing update algorithm for inter-orbit link deletion is proposed, including the following contents:

[0086] §1.3.1. Traverse all satellite pairs to detect whether the original shortest path passes through the deleted inter-orbit link e = (u, v, w). Assume that the original path first passes through u, then v (v = u e ), if the following conditions

[0087] dist[i][j] = dist[i][u] + w + dist[v][j]

[0088] are met, it indicates that the satellite pair (i, j) passes through the link and the routing information needs to be updated; otherwise, no update is needed.

[0089] §1.3.2. When the intra-orbit numbers of the source satellite and the destination satellite passing through the deleted link are the same, the characteristics of MHP determine that the alternative path needs to use the parallel edges adjacent to the deleted link to detour, thereby increasing the number of two hops. As shown in Figure 7 , according to the monotonicity of inter-orbit links, if the original inter-orbit link distance is the smallest, the alternative path will only detour the deleted link at satellite u, and then quickly return to the original path; if the original inter-orbit link distance is not the smallest, then the inter-orbit link adjacent to the deleted link and parallel to it must be shorter, and the alternative path will make one intra-orbit hop from the source satellite, then perform a series of shorter inter-orbit hops, and finally return to the destination satellite orbit. At this time, the shortest path will pass through the parallel edges adjacent to e = (u, v, w), and the distance between the satellite pairs may be d4 or d5

[0090] d4 = dist[i][u n ] + w n + dist[v n ][j]

[0091] d5 = dist[i][us ]+w s +dist[v s ][j]

[0092] In special cases, when the difference between the orbit numbers of the source and destination satellites is equal to , the alternative path is routed in the opposite direction of the original path, and the distance between the satellite pairs can be d6

[0093] d6= dist[i][j e ]+dist[j e ][j]

[0094] The minimum d k is chosen as the alternative path, and dist[i][j] and P[i][j] are updated

[0095] dist[i][j] = d k

[0096]

[0097] §1.3.3. When the orbit numbers of the source and destination satellites through the deleted link are different, based on the analysis of the SDP general mode, the deleted inter-orbit link is the shortest link in the MHP region. As shown in Figure 8 , the links parallel and adjacent to the deleted link in the MHP region become suboptimal choices, and the possible distances of the alternative paths are d4or d5. The minimum d k is chosen as the alternative path, and dist[i][j] and P[i][j] are updated. This path selection ensures efficient routing under link interruption conditions and optimizes communication delay. The algorithm flow of the above steps is shown in Figure 9 .

[0098] Figure 10 It is shown that when a single link in the satellite network changes (such as adding or interrupting a link), the average routing update time of the RFR algorithm and the Floyd-Warshall algorithm will increase with the increase of the LEO constellation scale. The RFR algorithm has obvious advantages, and the average update time is greatly shortened. The Floyd-Warshall algorithm needs to be recalculated comprehensively for all satellite pairs, so the calculation cost is large. In contrast, the RFR algorithm only updates the affected satellite pairs, minimizes unnecessary calculations, and effectively determines the shortest alternative path. The RFR algorithm can handle frequent link changes with minimal computational cost, so it is particularly suitable for large-scale satellite networks that require rapid adjustment.

[0099] Figure 11The average routing update times of the RFR algorithm and the Floyd - Warshall algorithm under different link failure rates are compared. p represents the proportion of faulty links in the total number of links in the LEO constellation. As the link failure rate increases, the average routing update times of both the RFR algorithm and the Floyd - Warshall algorithm increase. When the topology changes, the Floyd - Warshall algorithm needs to traverse all nodes and edges in the graph. Therefore, for networks of the same scale, regardless of the link failure rate, its average update time is high. This also highlights the redundant computational overhead of this algorithm. In contrast, due to the adoption of a local update mechanism, the update time of RFR is greatly shortened.

[0100] The experimental results show that when the satellite network topology changes, using the Floyd - Warshall algorithm as the rerouting benchmark, the RFR algorithm can achieve a 100% path accuracy rate when adding links. In the case of intra - orbit link failures, the RFR algorithm can also maintain a 100% path accuracy rate. When inter - orbit links fail, there will be a slight path inaccuracy. This is because in the RFR algorithm, the alternative path passes through links that are parallel and adjacent to the faulty link. As Figure 1 shown, due to the symmetry of the inter - orbit links, link B is adjacent to link A. However, due to the discreteness of the ISLs, a symmetric link C (A < C < B) may exist on the opposite side. Figure 12 shows the rerouting path error rate and the maximum inter - orbit link deviation in the worst - case scenario (the shortest inter - orbit link is interrupted, affecting many paths), which is generally acceptable for the laser transmission speed.

Claims

1. A fast re-routing method for satellite network topology changes, characterized in that, The following cases are included: I. Incremental routing update method for new link establishment in satellite network, comprising steps of: S1.1 defining and initializing a distance matrix D for storing the shortest path distance between all pairs of satellite nodes; defining and initializing a predecessor matrix P for storing the satellite node information that first needs to be reached to reach each destination satellite; S1.2 traversing all satellite pairs to determine whether there is a shorter path through the new link, which is based on the following conditions: For each pair of satellites i and j, check whether there is a new link u-v through which the path length from satellite i to satellite j is shorter than the shortest path length currently stored in the distance matrix D from satellite i to satellite j; If the above condition is met, mark the satellite pair as an affected satellite pair; S1.3 performing local update on the affected satellite pair, including: - Recalculating and updating the shortest path distance between the corresponding satellite pairs in the distance matrix D according to the new link; - Updating the predecessor node information of the corresponding satellite pairs in the predecessor matrix P to reflect the shortest path through the new link; II. Decreasing routing update method after intra-orbit link deletion in satellite network, comprising steps of: S2.1 defining the minimum hop path MHP as the path with the least number of hops between the source satellite s and the destination satellite d, and determining the MHP region, which contains all such paths, wherein the intra-orbit hop number and the inter-orbit hop number of each path are the same; S2.2 traversing all satellite pairs to detect whether the original shortest path passes through the deleted intra-orbit link, if any satellite pair passes through, it indicates that the routing information of the satellite pair needs to be updated, otherwise it does not need to be updated; S2.3 when the source and destination satellites passing through the deleted intra-orbit link are in the same orbit, then the alternative path is selected, which relies on the inter-orbit link to bypass and increases two hops, while ensuring that the alternative path passes through the parallel edge adjacent to the interrupted link to optimize the communication delay; when the source and destination satellites passing through the deleted intra-orbit link are not in the same orbit, then different alternative paths are selected according to whether the link deletion occurs before or after the cross-plane jump, and the alternative path is ensured to pass through the edge parallel and adjacent to the deleted link in the MHP region; S2.4 updating the distance matrix and the predecessor matrix to reflect the new shortest path and the predecessor node information; III. Decreasing routing update method after inter-orbit link deletion in satellite network, comprising steps of: S3.1 traversing all satellite pairs to detect whether the original shortest path passes through the deleted inter-orbit link, if any satellite pair passes through, it indicates that the routing information of the satellite pair needs to be updated, otherwise it does not need to be updated; S3.2 when the intra-orbit numbers of the source satellite and the destination satellite passing through the deleted link are the same, if the original inter-orbit link distance is the smallest, the alternative path only bypasses the deleted link and then quickly returns to the original path; if the original inter-orbit link distance is not the smallest, then the inter-orbit link parallel and adjacent to the deleted link must be shorter, and the alternative path will perform a series of shorter inter-orbit jumps from the source satellite to the destination satellite. S3.3 update the distance matrix and predecessor matrix to reflect the new shortest path and predecessor node information.

2. The method for fast re-routing towards satellite network topology changes according to claim 1, characterized in that, The step S2.2 detects whether the original shortest path passes through the deleted inter-orbit link, and the specific condition is that the original path first passes through satellite u and then passes through satellite v, where v is the next satellite or the previous satellite of u in the orbit motion direction, and if the condition is met and the link u-v is the deleted inter-orbit link, it indicates that the satellite pair (i, j) passes through the link.

3. The method of claim 1, wherein, In the S2.3, when the source and destination satellites passing through the deleted inter-orbit link are on the same orbit, the alternative path first routes along the original orbit, then performs a shortest cross-plane jump before reaching the interrupted link; after crossing to the adjacent orbit, the data stream will continue to route along the orbit until passing through the parallel edge adjacent to the interrupted link; then the shortest inter-orbit link before reaching the destination satellite is selected to return to the original orbit, and finally reaches the destination satellite. The shortest path at this time will pass through the parallel edges adjacent to e = (u, v, w) and the distance between the pairs of satellites is di or d2, di = dist[i][u] + w + dist[v][j] w w w + dist[v][j]​​ d2 = dist[i][u e ]+w e +dist[v e ][j] In special cases, when the difference between the orbital numbers of the source and destination satellites is equal to when the difference between the orbital numbers of the source and destination satellites is equal to 1, the alternative path is routed in the opposite direction to the original path without circumventing the inter-orbital link, the distance between the satellite pairs being d3, M denoting the number of satellites in each orbit, d3 = dist[i][j s ]+ dist[j s ][j].

4. The method for fast re-routing towards satellite network topology changes according to claim 1, characterized in that, In the S2.3, when the source and destination satellites passing through the deleted inter-orbit link are not on the same orbit, if the link deletion occurs before the cross-plane jump, the alternative path will cross to the adjacent orbit before reaching the interrupted link to bypass the interrupted link, that is, the alternative path will perform a cross-plane jump at satellite u, and then return to the original path along the adjacent orbit; if the link deletion occurs after the cross-plane jump, the alternative path will route along the second last orbit plane of the original path, and after passing through the parallel edge adjacent to the deleted link, perform a last cross-plane jump to finally reach the destination satellite, at this time, the alternative path will pass through the edge e'=(u', v', w') parallel and adjacent to the deleted link in the MHP area, and the distance between the satellite pairs is d1 or d2.

5. The method for fast re-routing towards satellite network topology changes according to claim 1, characterized in that, The step S3.1 detects whether the original shortest path passes through the deleted inter-orbit link, and the specific condition is that the original path first passes through satellite u and then passes through satellite v, where v is the satellite with the same intra-orbit number on the adjacent orbit of u, and if the condition is met and the link u-v is the deleted inter-orbit link, it indicates that the satellite pair (i, j) passes through the link.

6. The method for fast re-routing towards satellite network topology changes according to claim 1, characterized in that, In the S3.2, when the intra-orbit numbers of the source and destination satellites passing through the deleted inter-orbit link are the same, if the original inter-orbit link distance is the smallest, the alternative path only detours near the deleted link and then quickly returns to the original path; if the original inter-orbit link distance is not the smallest, the alternative path will first jump along the orbit from the source satellite, then perform a series of shorter inter-orbit jumps, and finally return to the orbit at the destination satellite; At this time, the alternative path will pass through the parallel edge adjacent to e=(u, v, w), and the distance between the satellite pairs is d4 or d5: d4 = dist[i][u n ]+ w n + dist[v n ][j] d5 = dist[i][u s ]+ w s + dist[v s ][j] In special cases, when the difference between the orbital numbers of the source and destination satellites is equal to the alternative path is routed in the opposite direction to the original path, the distance between the satellite pairs is d6, and N represents the number of orbital planes. d6 = dist[i][j e ]+ dist[j e ][j].

7. The method for fast re-routing towards satellite network topology changes according to claim 1, characterized in that, In the S3.2, when the intra-orbit numbers of the source and destination satellites passing through the deleted inter-orbit link are different, the alternative path will pass through the link parallel and adjacent to the deleted link in the MHP area, and the distance between the satellite pairs is d4 or d5.

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