Cross-domain relay selection and routing forwarding method for double-layer low-orbit constellation

Abstract

The invention discloses a cross-domain relay selection and routing forwarding method for a double-layer low-orbit constellation, which comprises the following steps of: constructing a resident relay satellite cluster, and strictly isolating inter-domain link state change signaling caused by high-speed movement of satellites in the cluster, thereby avoiding invalid topology perception of nodes of the whole network, and improving the reliability of the relay selection and routing forwarding. And the cross-domain routing signaling overhead and the convergence time are greatly reduced. On the basis, satellites in the cluster serve as cross-domain relay nodes, cross-domain routing forwarding is conducted on double-layer satellite network cross-domain routing through the resident relay satellite cluster, nodes outside the cluster can transmit cross-domain traffic to the relay cluster of the domain only through default routing, an on-satellite routing decision-making mechanism is greatly simplified, and the routing efficiency is improved. And the reliability and efficiency of whole network communication are improved.

Description

A method for cross-domain relay selection and routing forwarding for a two-layer low-Earth orbit constellation Technical Field

[0001] This invention belongs to the field of satellite communication technology, and specifically relates to a cross-domain relay selection and routing method for a two-layer low-Earth orbit constellation. Background Technology

[0002] As the core architecture of the next-generation integrated space-ground communication network, a dual-layer low-Earth orbit (LEO) satellite constellation can achieve seamless global coverage and highly reliable communication services through the coordination of satellites at different orbital altitudes and inclinations. In a dual-layer constellation, the high-speed motion of satellites in different orbital layers leads to drastic dynamic changes in inter-domain topology and frequent connection / disconnection of inter-satellite links. Simultaneously, cross-domain traffic exhibits high burstiness and high dynamism, placing stringent demands on the real-time performance, reliability, and resource utilization of cross-domain routing. Traditional BGP-based cross-domain methods do not fully consider the orbital dynamics of dual-layer constellations, resulting in problems such as high control signaling overhead, slow route convergence, and high cross-domain communication interruption rates. Furthermore, relay node selection strategies lack coordinated optimization of link persistence, load balancing, and service QoS, making them unsuitable for the high-speed dynamic scenarios of dual-layer LEO constellations and becoming a core bottleneck restricting the large-scale commercial application of dual-layer constellations.

[0003] A search revealed that typical existing technical solutions mainly include: 1. The paper "Efficient Optimization-based Routing Strategies for Large-Scale Multi-Layer LEO Satellite Networks" by Frank Yeong-Sung Lin et al. addresses the dynamic routing challenge of multi-layer LEO satellite networks. It uses end-to-end latency, link reliability, and path hop count as hard constraints, and sets minimizing average latency as the QoS objective. It employs a two-stage method combining Lagrange relaxation (LR) and heuristic algorithms to find the optimal solution. Furthermore, the method explicitly supports calculating K non-intersecting paths for each communication requirement. This fundamentally improves the system's fault tolerance from "single-point vulnerability" to "tolerance of K-1 failures," directly addressing service interruptions caused by frequent inter-satellite link switching in LEO networks and significantly enhancing service continuity. However, the method proposed in this paper primarily focuses on QoS guarantees for the data plane and does not consider the impact of control plane overhead on QoS in multi-layer LEO satellite networks.

[0004] 2. The paper "A Border Gateway Protocol LRA-BGP for Integrated Satellite-terrestrial Networks" by Jinhu Zang et al. addresses the high overhead caused by frequent switching of eBGP routers between terrestrial and satellite networks. Based on previously announced historical information of terrestrial autonomous systems, it avoids re-announcing previously announced historical information each time a satellite eBGP switch occurs, thus reducing the high overhead caused by the dynamism of satellite-terrestrial BGP. However, this method has only been verified in small-scale satellite networks, and its application in large-scale constellations with interconnection between multiple constellations and ground stations still needs to be verified. Furthermore, this method only addresses the interconnection between terrestrial and satellite networks and does not consider the signaling issues caused by interconnection between multiple satellite layers.

[0005] 3. In their paper "PH-BGP: A Proactive Hierarchical Border Gateway Protocol Routing Scheme and System in Ultra-Dense LEO Satellite Network," Yuze Liu et al. proposed the Proactive Hierarchical Border Gateway Protocol (PH-BGP) to address the high overhead and slow convergence issues of traditional BGP when applied to ultra-dense LEO satellite networks. Its core improvements are twofold: by introducing a new iBGP_PATH path attribute, satellites are divided into boundary, backbone, and non-backbone areas, and new route propagation and loop prevention rules are formulated, significantly reducing the number of iBGP connections and control message overhead within the network; leveraging the predictability of satellite orbits, time frames are pre-divided and handover opportunities are identified, proactively updating key routing entries before the satellite-to-ground station link switchover, transforming passive response into proactive prevention, thereby reducing routing convergence delays and packet loss caused by frequent handovers. However, this paper primarily focuses on cross-domain interconnection between satellite and terrestrial networks. Since terrestrial networks are static while satellite networks are dynamic, the improvements to BGP are not applicable to cross-domain interconnection of satellite networks.

[0006] Therefore, most existing satellite cross-domain routing solutions focus on cross-domain strategies between satellite networks and terrestrial networks, or concentrate on load balancing of the data plane of cross-domain LEO constellations. Existing research rarely considers the issue of stable and reliable cross-domain routing connections in two-layer LEO satellite networks, or how to reduce cross-domain routing control signaling distribution overhead and cross-domain routing convergence time. Summary of the Invention

[0007] In order to overcome the shortcomings of the prior art, the present invention aims to provide a cross-domain relay selection and routing method for dual-layer LEO constellations, so as to solve at least one of the problems of high control signaling overhead, slow route convergence, and poor cross-domain communication reliability caused by frequent relay node switching in the cross-domain routing scenario of existing dual-layer LEO constellations.

[0008] To achieve the above objectives, the technical solution adopted by this invention is: a method for cross-domain relay selection and routing forwarding for a two-layer low-Earth orbit constellation. This method constructs a resident relay satellite cluster, isolating signaling caused by inter-domain link status changes due to high-speed satellite motion within the cluster. Satellites within the cluster serve as cross-domain relay nodes, and cross-domain routing in the two-layer satellite network is performed through this resident relay satellite cluster. Specifically, one resident relay satellite cluster is defined as a cluster. The resident relay satellite clusters of Layer 1 and Layer 2 are defined as Cluster 1 and Cluster 2, respectively. Based on the {longitude, latitude, altitude} triplet generated during constellation initialization, suitable satellites are added to the cluster as relay satellites. The cluster selection satisfies the following condition: the number of links between clusters... Satisfy in each time slot , To ensure the reliability of cross-domain communication, the following minimum link number constraints must be met: satellites in cluster 1 and satellites in cluster 2 must meet visibility conditions to establish inter-layer links; each satellite in each cluster can establish at most one inter-layer link; the number of satellites in a cluster should be as small as possible to minimize the overhead of announcement signaling; the number of inter-cluster link switchings should be as small as possible, with each switching representing one message propagation.

[0009] In one embodiment, the constellation initialization is implemented as follows: Determine the parameters of the dual-layer low-Earth orbit satellite constellation, including orbital altitude, orbital inclination, number of orbital planes, number of satellites per orbit, and phase factor. Input these parameters into STK software to generate the 24-hour orbital trajectories of the two domain satellite constellations. Set a time interval to export the {longitude, latitude, altitude} triples of each satellite in each time slot. Constellation initialization is complete. Within the time interval, the longitude, latitude, and altitude of the satellites remain unchanged. This time interval is called a time slot. In this invention, the time interval is set to 30 seconds, with 24 hours in a day, totaling 2880 time slots.

[0010] In one embodiment, the relay satellite selection method is as follows: Step 1, input the original ephemeris data (longitude, latitude, altitude) of all satellites within the selected orbital plane of the dual-layer low-Earth orbit constellation throughout the entire simulation period, and set physical constraints, with the target parameters being... And the target size of the resident relay satellite constellations in Layer 1 and Layer 2, i.e., the window size. and Step 2: Pre-calculate the global visibility matrix and global lifetime matrix between orbital planes; Step 3: Apply a fixed-length matrix to the candidate orbital planes in layers 1 and 2. and The detection window requires that relay satellites selected into the same resident relay satellite cluster be a strictly adjacent set of continuous nodes in the physical orbital space; the sliding window is traversed, and each traversal selects two different satellites in the orbital plane as the starting point of the two sliding windows; based on the list of continuous satellite indices covered by the current sliding window, the dimension of [missing information] is extracted from the global visibility matrix and the global lifetime matrix. Step 4: Evaluate the performance of the selected relay satellites within the sliding window and update the globally optimal window starting point combination; Step 5: If all starting point pair combinations have been traversed, output the optimal starting point combination. The selected relay satellite is... as the starting node satellites and as the starting node 1 satellite, of which The satellites form a cluster, the said The satellites form a cluster of two.

[0011] In one embodiment, the candidate orbital planes are the two orbital planes with the closest right ascension of the ascending node among all orbits of the two-layer low-Earth orbit satellites, and the normal vectors of the two orbital planes are respectively: The angle between the two orbital planes is defined as: Distance between the two orbital planes for: ;in, , These are the inclination angles of track plane one and track plane two, respectively. , These are the radii of orbital plane one and orbital plane two, respectively. , These are the right ascensions of the ascending nodes of orbital plane 1 and orbital plane 2, respectively.

[0012] In one embodiment, step 2 involves converting the satellite coordinates within the selected orbit from a latitude, longitude, and altitude coordinate system to a geocentric, Earth-fixed coordinate system, traversing all time slots and satellite pairs, and generating a time-varying global visibility matrix for the entire network by calculating Euclidean distances and performing Earth occlusion line-of-sight checks. Using dynamic programming, the number of remaining visible time slots for any pair of visible satellites at any given time is calculated by working backward from the last time slot, thus obtaining the global lifetime matrix. .

[0013] In one embodiment, step 3 uses modulo operations to achieve a smooth transition between the beginning and end of the window, as follows: For windows containing... The orbital plane of the satellites will exceed the range when the starting satellite of the sliding window is selected as the satellite at the end of its orbit. The index is redirected back to the starting point of the orbital plane, and the selected layer-level orbital plane is traversed with a step size of 1. Available starting points and selected level 2 orbital planes There are 1 available starting point, and the traversal dimension is 1. .

[0014] In one embodiment, step 4, the evaluation method is as follows: Step 4.1, for the local visibility submatrix and local lifetime submatrix extracted in step 3, initialize the cumulative link switching count of the current window combination in the entire time slot to zero, the minimum number of links established in the entire cycle to infinity, and initialize an empty set of established inter-layer links; with a step size of 1, evaluate the entire simulation cycle. Iterate through each time slot; in any time slot traversal For each pair of link nodes in the inter-layer link set established in the time slot, the visibility is queried in the local visibility submatrix of the current time slot. If it is visible, the pair of links will continue to be retained in the time slot. If the link is not visible, it is removed from the set of established inter-layer links, and the cumulative link switching count is also recorded. Add one; Step 4.2, determine whether the total number of links in the currently established inter-layer link set is less than 1. If so, extract the local indices of the established Layer 1 nodes and Layer 2 nodes from the currently established inter-layer link set, and retrieve all candidate link pairs between all nodes without established inter-layer links in the current time slot slice of the local visibility sub-matrix; in the local lifetime sub-matrix of the current time slot, read the corresponding remaining visibility duration values ​​of all the above candidate link pairs, and select the candidate link pair with the largest value to add to the established inter-layer link set; repeat the new link retrieval and addition process until the total number of links in the current established inter-layer link set reaches [value missing]. Step 4.3: Extract the minimum number of established links for the entire cycle of the current sliding window combination, and determine whether it is greater than or equal to the minimum number of established links for the entire cycle of the current sliding window combination. If so, compare the cumulative number of link switching for that combination. Minimum number of switches in the global history recorded ,like ,renew And combine the globally optimal window starting points. The record is updated to the current starting point combination. .

[0015] In one embodiment, the cross-domain routing of the dual-layer satellite network is achieved through cross-domain routing forwarding via the resident relay satellite cluster. The implementation method is as follows: Step 1, the non-relay node at the source end generates a cross-domain routing data packet and performs a gateway query to obtain the default gateway node information, selecting the relay node with the lowest routing cost within the domain as the default route; Step 2, the non-relay node, according to the internal gateway protocol, sends the cross-domain routing data packet through several hops to a relay node in the resident relay satellite cluster of the local domain; Step 3, the relay node receiving the cross-domain routing data packet performs a status check to confirm whether it is currently a gateway node. If not, the relay node forwards the data packet to the current gateway node in the cluster through intra-domain routing; if yes, proceed to the next step; Step 4, the gateway node of the local domain, according to its maintained cross-domain routing table, forwards the cross-domain routing data packet directly to the gateway node of the target domain through the established inter-satellite cross-domain link; Step 5, after receiving the cross-domain routing data packet, the gateway node of the peer domain queries its intra-domain routing table and forwards the data packet hop-by-hop to the final destination node within that domain through the intra-domain routing protocol, completing the communication.

[0016] Compared with existing technologies, the beneficial effects of this invention are as follows: This invention abandons the relay selection mode that relies on instantaneous link states and innovatively combines orbital dynamics characteristics to construct a permanent relay satellite cluster. This fundamentally solves the problems of rampant network-wide signaling announcements and delayed routing convergence caused by frequent inter-domain link disconnections in existing technologies. Existing technologies suffer from high cross-domain communication interruption rates and high on-board routing decision-making complexity because they do not fully consider constellation motion patterns. In contrast, this invention strictly restricts routing announcements for link changes to within the relay cluster, which significantly reduces control signaling overhead and routing convergence time. It also ensures continuous connectivity of cross-domain links through persistence-first link establishment rules, while allowing nodes outside the cluster to be unaware of global topology changes, significantly simplifying the on-board routing decision-making process. This invention achieves breakthroughs over existing technologies in signaling efficiency, communication reliability, and on-board resource utilization. Attached Figure Description

[0017] Figure 1 is a schematic diagram of a permanent relay satellite constellation.

[0018] Figure 2 is a schematic diagram of the process for selecting cross-domain relays using the sliding window method.

[0019] Figure 3 is a schematic diagram of the orbital planes of the two satellites.

[0020] Figure 4 is a schematic diagram of the cross-domain routing process of the present invention. Detailed Implementation

[0021] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings and examples.

[0022] Existing cross-domain routing protocols mostly use BGP. In a two-layer satellite network scenario, inter-domain links frequently connect and disconnect due to the high-speed movement of satellites, leading to a proliferation of network-wide routing announcements and explosive signaling overhead. Meanwhile, non-relay nodes need to be aware of topology changes across the entire domain, resulting in massive routing tables and high decision-making latency. To address this, this invention proposes a cross-domain relay selection and forwarding method for two-layer low-Earth orbit constellations. By constructing a permanent cross-domain routing relay satellite cluster, routing announcements regarding inter-domain link changes are strictly limited to within the cluster, significantly reducing the scope of signaling announcements, greatly improving route convergence speed, and reducing control overhead. Simultaneously, based on orbital dynamics characteristics and link establishment rules, a relay cluster capable of long-term link establishment is selected. Non-cluster nodes only need to forward cross-domain traffic to their local relay cluster to complete cross-domain forwarding, enhancing the stability and service adaptability of cross-domain routing.

[0023] For cross-domain interconnection scenarios involving two-layer low-Earth orbit constellations, the core objective of this invention is to construct a resident relay satellite cluster. This limits the scope of cross-domain routing signaling announcements and strictly isolates signaling related to inter-domain link status changes caused by high-speed satellite motion within the cluster. This avoids invalid topology awareness across the entire network, significantly reducing cross-domain routing signaling overhead and convergence time. Based on this, the invention uses satellites within the cluster as cross-domain relay nodes. Cross-domain routing in the two-layer satellite network is forwarded through this resident relay satellite cluster. Nodes outside the cluster can simply rely on default routes to relay cross-domain traffic to their local relay cluster, greatly simplifying the on-board routing decision-making mechanism and improving the reliability and efficiency of the entire network communication. The specific implementation method of this invention is as follows: 1. Constellation initialization: Determine the parameters of the dual-layer low-Earth orbit satellite constellation, including orbital altitude, orbital inclination, number of orbital planes, number of satellites per orbit, and phase factor. Input the above parameters into STK software to generate the 24-hour operating trajectory of the two domain satellite constellations, and export the latitude, longitude, and altitude of each satellite at 30-second intervals (each satellite has 2880 {longitude, latitude, altitude} triplets). Constellation initialization is completed.

[0024] 2. Selecting Relay Satellites for Each Layer to Form a Permanent Relay Satellite Cluster: In this invention, a permanent relay satellite cluster is referred to as a cluster, and one permanent relay satellite cluster is called a cluster. The permanent relay satellite clusters of Layer 1 and Layer 2 are defined as Cluster 1 and Cluster 2, respectively. As shown in Figure 1, Domain 1 refers to all satellites of Layer 1, and Domain 2 refers to all satellites of Layer 2. Some satellites of Domain 1 (red satellites in the figure) form Cluster 1, and some satellites of Domain 2 (red satellites in the figure) form Cluster 2. It can be seen that the link connection between Cluster 1 and Cluster 2 (Domain 1 and Domain 2) will change over time, but overall, the connection between the two still exists. This invention adds suitable satellites to the cluster as relay satellites based on the {longitude, latitude, altitude} triple generated during constellation initialization. To ensure reliable inter-domain transmission and reduce signaling overhead, the cluster selection satisfies the following condition: the number of links between the two clusters. Satisfy in every time slot , To ensure the reliability of cross-domain communication, the following minimum link number constraints must be met: two cluster satellites (i.e., satellites in cluster 1 and satellites in cluster 2) must meet visibility conditions to establish an inter-layer link; each satellite in each cluster can establish at most one inter-layer link; the number of satellites in a cluster should be as small as possible, because a smaller number means less notification signaling overhead; the number of inter-cluster link switchings should be as small as possible, as each switching represents a message propagation.

[0025] Since all inter-layer links in this invention are established at satellite nodes within a cluster, inter-cluster links here are actually equivalent to inter-layer links.

[0026] Based on this, the present invention proposes a method for selecting relay satellites, the technical process of which is shown in Figure 2. To facilitate the explanation of the calculation process, the present invention selects the orbit with the closest right ascension to the ascending node, as shown in Figure 3. The orbital plane inclination, radius, and right ascension of the ascending node are respectively... , and In the geocentric inertial coordinate system, the normal vectors of the two orbital planes are as follows: (1) The angle between the two orbital planes is defined as: (2) Distance between the two orbital planes for For orbits with similar right ascension of ascending nodes, it is easier to satisfy the shortest chain establishment distance constraint.

[0027] Based on this, to optimally construct cluster nodes, this invention combines the characteristics of orbital closed loops and introduces a spatial sliding window mechanism to force the continuity of relay nodes in physical location; simultaneously, based on a dynamically programmed pre-calculated global lifetime matrix, a deterministic lifetime-first greedy link-building rule is adopted to absolutely minimize the number of cross-domain link switching between clusters, ensuring continuous and stable connectivity throughout the entire lifecycle. The specific selection steps for cross-domain relay nodes are as follows: Step 1: Parameter input.

[0028] The original ephemeris data (latitude, longitude, and altitude) of all satellites within the selected orbital plane of the dual-layer low-Earth orbit constellation are input throughout the entire simulation period, and physical constraints such as the maximum allowable link establishment distance and Earth radius are set. Simultaneously, this invention establishes the core search target parameters, namely the target size of the resident relay satellite clusters in Layer 1 and Layer 2 (i.e., the lengths of sliding window 1 and sliding window 2). and ), and the minimum number of links that must be met to ensure the reliability of cross-domain communication. .

[0029] Step 2: Pre-calculate the global visibility matrix between orbital planes and global lifetime matrix .

[0030] This invention transforms the satellite coordinates within the selected orbit from a latitude, longitude, and altitude coordinate system to a geocentric, Earth-fixed coordinate system, and traverses all time slots and satellite pairs. By calculating Euclidean distances and performing Earth occlusion line-of-sight checks, it generates a network-wide time-varying visibility matrix, i.e., a global visibility matrix. Based on this, using the idea of ​​dynamic programming, starting from the last time slot and proceeding backwards, the number of future visible time slots for any visible satellite pair at any given time is calculated, thus obtaining the global lifetime matrix. .

[0031] In this step, a satellite pair is defined as follows: Assuming that the first orbital plane of the first layer of satellites contains 9 satellites, numbered 1 to 9, and the first orbital plane of the second layer of satellites contains 10 satellites, numbered 1 to 10, then (1,1), (1,2), (1,3), ... (1,10), ..., (9,10) are all satellite pairs. The first number in the parentheses is the satellite number in the first layer of satellite network, and the second number is the satellite number in the second layer of satellite network.

[0032] Global visibility matrix This represents the visibility between all satellite pairs within the selected orbital plane, with dimensions of [dimension value missing]. The element is either 0 or 1, for example This represents the visibility between the i-th satellite in satellite layer 1 and the j-th satellite in satellite layer 2 in the t-th time slot (t>=1 and t<=2880). If the value is 0, it means that these two satellites are not visible in this time slot; if it is 1, it means that these two satellites are visible in this time slot. (Global lifetime matrix) This is the link lifetime matrix between all satellites in Layer 1 and all satellites in Layer 2, representing the link duration, with dimensions of [missing information]. , of which elements Representative satellite and satellite At any moment The established link can also maintain a certain number of time slots.

[0033] Step 3: Sliding window traversal, each traversal selects two different satellites in the orbital plane as the starting point of the two sliding windows.

[0034] This invention applies a fixed length to the candidate track surfaces of layers one and two, respectively. and The detection window mandates that satellites selected for the same relay cluster must be strictly adjacent, continuous nodes in their physical orbital space. The sliding window then iterates through the space, selecting two different satellites within the same orbital plane as the starting points for each sliding window.

[0035] This invention takes into account the closed-loop characteristics of satellite orbits and employs modulo operations to achieve a smooth transition between the beginning and end of the window. For example, when a certain orbital plane contains... When there are multiple satellites, and the starting satellite of the sliding window is selected as the satellite at the end of its orbit, the modulo operation will automatically include satellites exceeding the limit. The indexes are redirected back to the starting point of the orbital plane (e.g., index 1, index 2, etc.), thus mapping the ring topology of the satellite network at the data level and avoiding boundary overflow. Based on this physical mapping, the selected layer-one orbital plane is traversed with a step size of 1. One available starting point (i.e., starting point s1, where s1 is the initial satellite node number of the sliding window) and the selected Layer 2 orbital plane There are one available starting point (i.e., starting point s2, where s2 is the number of the starting satellite node in the second sliding window), therefore the traversal dimension is... ,in and These represent the number of satellites in orbital plane one and orbital plane two, respectively. This method directly extracts the satellites of dimension [dimension value missing] from the pre-calculated global visibility matrix and global lifetime matrix in step two, based on the specific continuous satellite index list covered by the current sliding window. The local visibility submatrix and local lifetime submatrix are defined. Continuous satellite indices refer to satellite indices that are consecutive. For example, if the current orbital satellite indices are 1, 2, 3, 4, 5, and the sliding window length is 3, then only consecutive satellite indices can be included, such as 1, 2, 3; 2, 3, 4; 3, 4, 5; 4, 5, 1; 5, 1, 2.

[0036] In this invention, satellites are layered according to their altitude. The altitudes of the first and second layers are different, and each low-Earth orbit (LEO) satellite layer contains multiple orbital planes. For example, the first layer of satellites has 12 orbits with right ascensions of the ascending node of 0°, 30°, 60°, ..., 330°; the second layer of satellites has 6 orbital planes with right ascensions of the ascending node of 0°, 30°, ..., 150°. Then (1,1), (2,2), (3,3), ..., (6,6) can all be considered as candidate orbital planes. The first number in parentheses is the orbital plane number of the first layer of satellites, and the second number is the orbital plane number of the second layer of satellites.

[0037] Step 4: Performance evaluation of the selected relay satellite within the sliding window.

[0038] Step 4.1, Switch count statistics.

[0039] For the local visibility submatrix and local lifetime submatrix extracted in step three, initialize the cumulative link switching count of the current window combination across all time slots to zero, the minimum number of links established across the entire cycle to infinity, and initialize an empty set of established inter-layer links. Use a step size of 1 for the entire cycle. Iterate through each time slot. In any time slot First, a visibility check is performed on the set of established inter-layer links left over from the previous time slot. Specifically, this involves traversing... The time slot has established an index for each pair of link nodes in the inter-layer link set, in the current time slot. The visibility is queried in the local visibility submatrix. If visible, the corresponding link pair is retained in the time slot. If the link is not visible, it is removed from the set of established inter-layer links, and the cumulative link switching count is also recorded. Add one.

[0040] Taking a dual-layer low-Earth orbit constellation consisting of Layer 1 (containing 12 orbital planes, 9 satellites per orbit) and Layer 2 (containing 6 orbital planes, 10 satellites per orbit) as an example. Assume the sliding window length for the relay satellite cluster in Layer 1 is 5, and the sliding window length for the relay satellite cluster in Layer 2 is 6; set the minimum required to establish... Consider an inter-layer link. Assume that orbital plane 1 is selected as the candidate orbital plane for layer 1, and orbital plane 1 is selected as the candidate orbital plane for layer 2. Assume that the sliding window of layer 1 is now... The indexes for the inner satellites are 9, 1, 2, 3, 4, and the sliding window is located within layer two. The satellite indices are 1, 2, 3, 4, 5, 6.

[0041] Now, extract the visibility submatrix and link lifetime submatrix between the five stars (9, 1, 2, 3, 4) in orbital plane 1 of layer 1 and the six stars (1, 2, 3, 4, 5, 6) in orbital plane 1 of layer 2. Let H be the number of link switching, and initialize it to 0. Let E(t) be the set of established inter-layer links, where t>=1 and t<=2880. This set represents the set of established inter-layer links in time slot t. The elements in this set are (i, j), where i represents a satellite in sliding window 1 and j represents a satellite in sliding window 2. Assume that the current time slot is 100, and assume that satellite 9 in sliding window 1 and satellite 1 in sliding window 2 are visible in time slot 100, and satellite 1 in window 1 and satellite 2 in window 2 are visible (by querying the visibility submatrix). Then E(100) contains two elements: (9, 1) and (1, 2). If we traverse to time slot 101, (9, 1) becomes invisible and (1, 2) becomes visible due to the relative motion of the satellites. Then E(101) will remove (9, 1) and contain only one element (1, 2), and the link switching count H of this window combination will be incremented by 1.

[0042] The entire cycle refers to the ephemeris of all satellites in one day. For example, if the time interval is 30 seconds, the entire cycle is one day and the number of time slots is 2880.

[0043] Step 4.2, add new links.

[0044] Determine if the total number of links in the currently established inter-layer link set is less than [a certain value]. If the condition is met, extract the local indices of the established Layer 1 nodes and Layer 2 nodes from the currently established inter-layer link set, and then use the current time slot of the local visibility submatrix extracted in step three. Within the slice, retrieve all candidate link pairs between all nodes that have not established inter-layer links. In the current time slot... In the local lifetime submatrix, the remaining visible duration values ​​of all candidate link pairs are read, and the candidate link pair with the largest value is added to the established inter-layer link set. This new link retrieval and addition process is repeated until the total number of links in the current established inter-layer link set reaches [value missing]. Until, or until there are no available unoccupied candidate link pairs.

[0045] Based on the embodiment in step 4.1, determine whether the number of established inter-layer links in the current time slot is greater than or equal to... For example, E(100) satisfies this condition. Since two inter-layer links are established in time slot 100, no operation is required in this step. Continue to traverse the time slots directly to E(101). However, E(101) does not meet the minimum number of links condition, so it is necessary to supplement the links: extract the candidate nodes that have not yet established a link. For example, if there is only the link (1,2), then the candidate nodes include 9, 2, 3, 4 in sliding window 1 and 1, 3, 4, 5, 6 in sliding window 2. Query the visibility relationship between these candidate nodes in the visibility submatrix. Assuming that the current (2,3), (4,5), and (4,6) node pairs are visible, then they constitute candidate node pairs. Subsequently, in the current time slot 101, the link lifetime submatrix between the aforementioned candidate node pairs is queried. For example, the lifetime of (2,3) is 20, the lifetime of (4,5) is 15, and the lifetime of (4,6) is 21. Then, link (4,6) is added and added to E(101). At this time, E(101) contains two links (1,2) and (4,6), satisfying the condition that the number of links is greater than 1. Condition: The link replenishment process is complete.

[0046] Step 4.3: Perform conditional judgment and update the optimal solution for the global performance of the current sliding window combination.

[0047] Extract the minimum number of established links for the entire cycle of this combination, and determine whether it is greater than or equal to the preset minimum link number constraint. If the result is true, further compare the cumulative number of link handovers for this combination. Minimum number of handovers recorded globally by the system .like ,renew And combine the globally optimal window starting points. The record is updated to the current starting point combination. .

[0048] Based on the embodiment in step 4.2, after completing the traversal of all 2880 time slots in the full cycle, the minimum number of links contained in E(t) within the 2880 time slots is extracted from the combination of window W1 (containing satellites 9, 1, 2, 3, 4) and window W2 (containing satellites 1, 2, 3, 4, 5, 6), where t>=1 and t<=2880. If the number of inter-layer links contained in any time slot E(t) is less than... Skip this step if the number of inter-layer links established across all time slots is greater than or equal to Compare whether the number of handovers H of the sliding window satellite combination within the entire time slot is less than the minimum number of handovers recorded by the system. Assuming the previously recorded The total number of handovers for this sliding window satellite combination is 10. Since 10 < 15, the minimum number of handovers recorded by the system is updated to 10. And the optimal window combination is recorded as satellite 9, 1, 2, 3, 4 in orbital plane 1 of satellite layer 1 and satellite 1, 2, 3, 4, 5, 6 in orbital plane 1 of satellite layer 2.

[0049] Step 5: Process termination check.

[0050] If all starting point pairs have been traversed, end the process and output the optimal starting point combination. The selected relay satellite node is the one that... as the starting node satellites and as the starting node 1 satellite, of which The satellites form a cluster, the said The satellites form a cluster of two.

[0051] 3. Routing based on resident relay satellite constellations.

[0052] After obtaining the relay cluster node through the above method, the cross-domain routing process of the present invention is shown in Figure 4: Step 1: Generate cross-domain routing data packets and query the gateway.

[0053] The non-cluster node (non-relay node) at the source end generates cross-domain routing data packets, extracts the destination address of the data packets, queries the routing table maintained by this node within the domain, triggers the default cross-domain forwarding rule, obtains the corresponding default gateway node information, and the non-relay node at the source end selects the relay node with the lowest routing cost within the domain as the default route.

[0054] Step 2: Forward within the domain to the relay cluster.

[0055] Based on the internal gateway protocol, the non-relay node sends cross-domain routing data packets through intra-domain routing addressing to a relay node in the local resident relay satellite cluster after several hops.

[0056] Step 3: Relay node identity verification and intra-cluster forwarding.

[0057] When a relay node receives a cross-domain routing data packet, it performs a status check to confirm whether it is currently a gateway node (i.e., whether it holds an active inter-domain link directly connected to the target domain). If the check is negative, the relay node forwards the data packet to the current gateway node within the cluster via intra-domain routing; if the check is positive, it proceeds directly to the next step.

[0058] Step 4: Cross-domain routing forwarding.

[0059] The gateway node of this domain, based on its maintained cross-domain routing table, forwards cross-domain routing data packets directly to the gateway node of the peer domain (target domain) through the established inter-satellite cross-domain links.

[0060] Step 5: Forward within the peer domain.

[0061] After receiving a cross-domain routing data packet, the peer domain gateway node extracts the cross-domain routing information and queries the routing table within its own domain. Finally, the peer domain gateway node forwards the data packet hop-by-hop to the final destination node within that domain using the intra-domain routing protocol, thus completing the communication.

[0062] Based on the above core principles of this invention, any routing method that, in a two- or multi-layer low-Earth orbit constellation network interconnection scenario, constructs a permanent cross-domain relay satellite cluster by selecting specific nodes and strictly limits the cross-domain routing signaling announcements caused by high-frequency dynamic switching of inter-domain links to synchronization between nodes within the cluster, so that non-cluster nodes only need to maintain their own domain topology and default gateway routes to complete cross-domain data forwarding, falls within the protection scope of this invention.

[0063] Based on the above core principles of this invention, any method or system that utilizes the physical closed-loop characteristics of the orbital plane to apply spatial sliding window constraints to ensure the physical continuity of candidate nodes during the selection process of such cross-domain relay clusters, and combines the time-varying visibility matrix of the entire network with the remaining continuous visibility duration (i.e., lifetime matrix) to perform lifetime-priority deterministic link establishment deduction, with the goal of minimizing the number of cross-domain link switching times within the entire network cycle and satisfying the minimum number of link establishment constraints, thereby establishing the optimal resident relay node cluster, falls within the protection scope of this invention.

Claims

1. A method for cross-domain relay selection and routing forwarding for a two-layer low-Earth orbit constellation, characterized in that, A permanent relay satellite cluster is constructed to isolate the signaling caused by inter-domain link status changes due to high-speed satellite movement within the cluster. Satellites within the cluster act as cross-domain relay nodes, and cross-domain routing in the two-layer satellite network is forwarded through this permanent relay satellite cluster. Each permanent relay satellite cluster is defined as a cluster. The permanent relay satellite clusters at layers one and two are defined as Cluster One and Cluster Two, respectively. Based on the {longitude, latitude, altitude} triplet generated during constellation initialization, suitable satellites are added to the clusters as relay satellites. The selection of clusters satisfies the following condition: the number of inter-cluster links. Satisfy in each time slot ， To ensure the reliability of cross-domain communication, the following minimum link number constraints must be met: satellites in cluster 1 and satellites in cluster 2 must meet visibility conditions to establish inter-layer links; each satellite in each cluster can establish at most one inter-layer link; the number of satellites in a cluster should be as small as possible to minimize the overhead of announcement signaling; the number of inter-cluster link switchings should be as small as possible, with each switching representing one message propagation.

2. The method for cross-domain relay selection and routing forwarding for a two-layer low-Earth orbit constellation according to claim 1, characterized in that, The constellation initialization is implemented as follows: Determine the parameters of the dual-layer low-Earth orbit satellite constellation, including orbital altitude, orbital inclination, number of orbital planes, number of satellites per orbit, and phase factor. Input the above parameters into STK software to generate the 24-hour operating trajectories of the two domain satellite constellations. Set the time interval to export the {longitude, latitude, altitude} triplet for each satellite in each time slot. The constellation initialization is completed. During the time interval, the longitude, latitude, and altitude of the satellites remain unchanged.

3. The method for cross-domain relay selection and routing forwarding for a two-layer low-Earth orbit constellation according to claim 1, characterized in that, The method for selecting relay satellites is as follows: Step 1, input the original ephemeris data (longitude, latitude, altitude) of all satellites within the selected orbital plane of the dual-layer low-Earth orbit constellation throughout the entire simulation period, and set physical constraints. The target parameters for the search are... And the target size of the resident relay satellite constellations in Layer 1 and Layer 2, i.e., the window size. and Step 2: Pre-calculate the global visibility matrix and global lifetime matrix between orbital planes; Step 3: Apply a fixed-length matrix to the candidate orbital planes in layers 1 and 2. and The detection window requires that relay satellites selected into the same resident relay satellite cluster be a strictly adjacent set of consecutive nodes in the physical orbital space; the sliding window traversal selects two different satellites in the orbital plane as the starting point of the two sliding windows in each traversal. Based on the continuous satellite index list covered by the current sliding window, extract the dimension from the global visibility matrix and global lifetime matrix. Step 4: Evaluate the performance of the selected relay satellites within the sliding window and update the globally optimal window starting point combination; Step 5: If all starting point pair combinations have been traversed, output the optimal starting point combination. The selected relay satellite is... as the starting node satellites and as the starting node 1 satellite, of which The satellites form a cluster, the said The satellites form a cluster of two.

4. The method for cross-domain relay selection and routing forwarding for a two-layer low-Earth orbit constellation according to claim 3, characterized in that, The candidate orbital plane is the orbital plane with the closest right ascension of the ascending node among all orbits of the two low-Earth orbit satellites. The normal vectors of the two orbital planes are as follows: The angle between the two orbital planes is defined as: Distance between the two orbital planes for: ;in, 、 These are the inclination angles of track plane one and track plane two, respectively. 、 These are the radii of orbital plane one and orbital plane two, respectively. 、 These are the right ascensions of the ascending nodes of orbital plane 1 and orbital plane 2, respectively.

5. The method for cross-domain relay selection and routing forwarding for a two-layer low-Earth orbit constellation according to claim 3, characterized in that, Step 2 involves converting the satellite coordinates within the selected orbit from a latitude, longitude, and altitude coordinate system to a geocentric, Earth-fixed coordinate system. It then iterates through all time slots and satellite pairs, calculating Euclidean distances and performing Earth occlusion line-of-sight checks to generate a time-varying global visibility matrix for the entire network. Using dynamic programming, the number of remaining visible time slots for any pair of visible satellites at any given time is calculated by working backward from the last time slot, thus obtaining the global lifetime matrix. 。 6. The method for cross-domain relay selection and routing forwarding for a two-layer low-Earth orbit constellation according to claim 3, characterized in that, Step 3 uses modulo operations to achieve a smooth transition between the beginning and end of the window, as follows: For windows containing... The orbital plane of the satellites will exceed the range when the starting satellite of the sliding window is selected as the satellite at the end of its orbit. The index is redirected back to the starting point of the orbital plane, and the selected layer-level orbital plane is traversed with a step size of 1. Available starting points and selected level 2 orbital planes There are 1 available starting point, and the traversal dimension is 1. 。 7. The method for cross-domain relay selection and routing forwarding for a two-layer low-Earth orbit constellation according to claim 3, characterized in that, The evaluation method for step 4 is as follows: Step 4.1, for the local visibility submatrix and local lifetime submatrix extracted in step 3, initialize the cumulative link switching count of the current window combination in the entire time slot to zero, the minimum number of links established in the entire cycle to infinity, and initialize an empty set of established inter-layer links; with a step size of 1, evaluate the entire simulation cycle. Iterate through each time slot; in any time slot traversal For each pair of link nodes in the inter-layer link set established in the time slot, the visibility is queried in the local visibility submatrix of the current time slot. If it is visible, the pair of links will continue to be retained in the time slot. The set of established inter-layer links; If not visible, remove the link pair from the set of established inter-layer links, and simultaneously increase the cumulative link switching count. Add one; Step 4.2, determine whether the total number of links in the currently established inter-layer link set is less than 1. If so, extract the local indices of the established Layer 1 nodes and Layer 2 nodes from the currently established inter-layer link set, and retrieve all candidate link pairs between all nodes without established inter-layer links in the current time slot slice of the local visibility sub-matrix; in the local lifetime sub-matrix of the current time slot, read the corresponding remaining visibility duration values ​​of all the above candidate link pairs, and select the candidate link pair with the largest value to add to the established inter-layer link set; repeat the new link retrieval and addition process until the total number of links in the current established inter-layer link set reaches [value missing]. Until there are no available unoccupied candidate link pairs; Step 4.3: Extract the minimum number of established links for the entire cycle of the current sliding window combination, and determine whether it is greater than or equal to... If so, compare the cumulative number of link switching for that combination. Minimum number of switches in the global history recorded ,like ,renew And combine the globally optimal window starting points. The record is updated to the current starting point combination. 。 8. The method for cross-domain relay selection and routing forwarding for a two-layer low-Earth orbit constellation according to any one of claims 1 to 7, characterized in that, The cross-domain routing of the dual-layer satellite network is achieved through cross-domain routing forwarding via the resident relay satellite cluster. The implementation method is as follows: Step 1, the non-relay node at the source end generates cross-domain routing data packets and performs a gateway query to obtain the default gateway node information, selecting the relay node with the lowest routing cost within the domain as the default route; Step 2, the non-relay node, according to the internal gateway protocol, sends the cross-domain routing data packets through several hops to a relay node in the resident relay satellite cluster of the local domain; Step 3, the relay node receiving the cross-domain routing data packets performs a status check to confirm whether it is currently a gateway node. If not, the relay node forwards the data packets to the current gateway node in the cluster through intra-domain routing; if yes, proceed to the next step; Step 4, the gateway node of the local domain, according to its maintained cross-domain routing table, forwards the cross-domain routing data packets directly to the gateway node of the target domain through the established inter-satellite cross-domain link; Step 5, after receiving the cross-domain routing data packets, the gateway node of the peer domain queries its intra-domain routing table and forwards the data packets hop-by-hop to the final destination node within that domain through the intra-domain routing protocol, completing the communication.

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