On-board autonomous routing method and system using the operating rules of low-orbit satellite constellations

Abstract

The present invention discloses an on-board autonomous routing method and system using the operation law of a low-orbit satellite constellation. First, the satellite equipment is powered on so that the satellite obtains a constellation topology rule set, and then a corresponding routing table is calculated according to the topology table. When the satellite moves to a north latitude disconnected link area, a topology calibration rule table is used for calibration, a currently used routing table is selected from a routing table set, and subsequent routing tables are enabled in sequence according to time slices. Link monitoring is performed by periodically detecting the link status with all its adjacent satellites. If the link status changes, a link status indication packet is generated, and the packet is diffused to other nodes in the entire network. The satellite that receives the link status indication packet updates all topology tables and routing tables related to the link. Finally, when the satellite passes over a gateway station located on the ground, a connection is established with the gateway station. At this time, the satellite identity is changed to a grounded satellite, and satellite-to-ground service transmission is realized.

Description

Technical Field

[0001] The present invention relates to the field of wireless network communication technology, and in particular to an on-board autonomous routing method and system utilizing the operating rules of a low-orbit satellite constellation. Background Art

[0002] Because the number of LEO satellite networks is large, the orbital period is short, the network topology changes rapidly, the coverage area is small, and frequent link switching is required, so routing selection has always been one of the problems that LEO satellite systems need to solve. According to the periodic time virtualization scheme of satellite network operation, the satellite network operation cycle is divided into a series of time slices. In each time slice, the network topology is considered to be fixed. By continuously injecting the topology, the satellite obtains the topology table. The change of topology occurs at the switching point between time slices. In this way, the shortest path algorithm can be used to find the optimal path according to the topology in the time slice, so this type of algorithm generally has a low latency. This type of algorithm was first proposed by Werner. The algorithm first discretizes the network structure into N time slices, converts the dynamic topology into N periodically recurring static virtual topologies, and then calculates the optimal path in N time slices. Grounder et al. define the network topology of the satellite system at a specific moment as a "snapshot". In order to reduce the storage pressure caused by too many snapshots, the program storage model is used to store the routing table to save storage space. However, the routing algorithm based on topology snapshots has the following problems:

[0003] (1) The topology changes are not combined with the actual operation rules of the satellite, resulting in errors between the actual topology of the satellite and the topology snapshot, causing packet loss.

[0004] (2) The original solution required ground calculations and reporting at regular intervals, which resulted in huge overhead.

[0005] (3) Relying on the ground station to transmit the signal to each satellite. If the transmission link fails, the routing information transmitted on the ground will become invalid and new instructions cannot be transmitted, resulting in network paralysis. Summary of the invention

[0006] In order to solve the problems of packet loss caused by the prior art not combining topology changes with the actual operation rules of satellites, and the huge overhead caused by relying on ground stations and frequent route switching, the present invention studies the operation rules of low-orbit satellites, and invents a method for accurately obtaining topology according to the movement rules of low-orbit satellites, thereby realizing autonomous routing on low-orbit satellites to achieve service transmission.

[0007] In order to achieve the above object, the present invention adopts the following technical scheme:

[0008] An on-board autonomous routing method utilizing the operating rules of a low-orbit satellite constellation comprises the following steps:

[0009] Step S100: The satellite equipment is powered on, the satellite power-on process is executed, and a constellation topology rule set is obtained. in; The duration for each topology table to take effect. G is N different topology tables of satellite network changes within a satellite return period. i (E,V i ) indicates that the i-th topology table consists of E satellites and V i The links consist of is the topology calibration rule table, c i Recorded topology G i (E,V i ) corresponding to the more accurate satellite number;

[0010] Step S200: according to the constellation topology rule set Topology table collection For each topology table, calculate the topology table set The corresponding routing table set

[0011] Step S300: according to the constellation topology rule set Topology calibration rules table The topology table used by the satellite is calibrated with satellite dimension information, and the routing table set Select the currently used routing table in the topology calibration, and then set the constellation topology rules according to the constellation topology rules. The duration for each topology table to take effect Perform topology switching;

[0012] Step S400: Each satellite periodically detects the link status with all its neighboring satellites based on the currently used topology table. If the link status changes, a link status indication packet is generated and diffused to other nodes in the entire network. The satellite that receives the link status indication packet updates the topology table set. All topology tables and routing tables related to the link status;

[0013] Step S500: When a satellite passes over a gateway station located on the ground, it establishes a connection with the gateway station. At this time, the satellite identity is changed to a landing satellite, the connection holding time is calculated, and the connection holding time, satellite address and gateway station address information are combined into a landing satellite information indication group, and the landing satellite information indication group is diffused to other nodes in the entire network;

[0014] Step S600, the satellites receiving the landing satellite information indication group update the locally maintained landing satellite catalog;

[0015] Step S700, when a satellite needs to relay a packet whose destination address is a gateway station, it queries the landing satellite table maintained by itself to determine the address of a satellite that can land and is currently connected to the ground station, and then uses the found landing satellite address as the destination address to query the corresponding entry in the routing table to relay and forward the data.

[0016] Furthermore, the specific method of the satellite power-on process in step S100 is:

[0017] Step S101, read the first power-on flag to determine whether it is the first power-on. If it is not the first power-on, go to step S102; if it is the first power-on, set the first power-on flag to no and go to step S104;

[0018] Step S102: The satellite that is not powered on for the first time sends a current constellation topology rule application packet to other satellites around it through all its intersatellite transmitters, and starts a timer to wait for a topology reply packet; the satellite that receives the application packet sends a topology reply packet to the satellite that is not powered on for the first time, and the packet contains a constellation topology rule set. If the timer times out and no topology reply packet is received, the process returns to step S102;

[0019] Step S103: After the satellite that is not powered on for the first time receives the topology reply packet, it records The information in the message cancels the timer and ends the satellite power-on process;

[0020] Step S104: Calculate the constellation topology rule set according to the constellation operation rule End the satellite power-on process.

[0021] Furthermore, the calculation method of the constellation topology rule set in step S100 adopts the following steps:

[0022] Step S110, initialize i=1, select a satellite j from the satellite set as the initial satellite, and record Init=j. According to the constellation operation law, the satellite regression period is obtained. Where H is the orbital altitude, G is the gravitational constant, M is the mass of the Earth, and r is the orbital radius; the satellite regression period is the time it takes for the satellite to orbit the Earth and return to its initial latitude position;

[0023] Step S120: When the j-satellite moves from the orbit raising direction to the latitude in the northern hemisphere disconnection zone, the satellite numbers of all the satellites with the same latitude as the j-satellite in the orbit raising direction are calculated, and the j-satellite and the numbers of these satellites are recorded in the topology calibration rule table c. i The northern hemisphere disconnection zone is the area where the satellite closes the intersatellite links with different orbits in the area above the Arctic Circle when it moves from the middle and low latitudes to the northern hemisphere, and only retains the intersatellite links with the same orbit;

[0024] Step S130, according to the satellite link establishment rules, in the case of the current satellite position snapshot, calculate the satellite network connection topology map and record it in G i (E,V i );

[0025] Step S140, calculate all the The angle difference between the satellite in the broken link and the latitude in the broken link direction, and the value with the smallest absolute value of the angle difference Δω is selected min , and assign the satellite number to j;

[0026] Step S150, calculate the topology graph G i Duration of validity And record this value in middle;

[0027] Step S160: If j is on the ascending track and equal to Init, the algorithm ends and outputs Otherwise, push all satellites forward in their respective directions of motion by Δω min , if the satellite j is located at the latitude of the broken link area in the ascending direction of the northern hemisphere at this time, go to step S120, otherwise go to step S170;

[0028] Step S170, let i=i+1, Go to step S130.

[0029] Furthermore, in step S200, the Dijkstra algorithm is used to calculate the topology table set The corresponding routing table set

[0030] The topology calibration rule table described in step S300 Contains the topological period and enabled satellite number. Every time the satellite moves to the disconnection zone in the northern hemisphere, the topological calibration rule table is queried. Calibrate the currently used topology table and then perform the topology switching steps, according to The subsequent topology tables are enabled in sequence at the time t recorded in .

[0031] Further, in step S400, the satellite periodically detects the link status with all its neighboring satellites, diffuses the link status indication packet, and updates the routing table using the following steps:

[0032] Step S401, periodically detecting the link status adopts the Hello mechanism, each node periodically sends HELLO packets on each channel, a node can periodically receive the HELLO packets sent by the four nodes, and periodically send HELLO packets to the four nodes; if a HELLO packet sent by a certain node is not received in several HELLO cycles, it is determined that the link between the nodes is faulty, and the node sets the link status to bidirectional interruption; link fault detection corresponds to the topology table, and the link status at this time is determined according to the link information in the topology table. When the link exists in the topology table but the link monitoring does not find the existence of this link, a link fault occurs;

[0033] Step S402, when a link failure occurs, the two end nodes of the faulty link use the link status indication packet, i.e., the SOP packet, to send the fault information to other nodes in the whole network in the form of flooding. The SOP packet carries the information number and the source node ID. The diffusion stage adopts the basic method of unidirectional flooding for transmission. Each node that receives the SOP packet first replies a receiving response to the receiving port, and then determines whether it is a new SOP packet according to the information number and the source node ID in the SOP packet. If it is a new SOP packet, the topology table is updated according to the new SOP packet, and the new SOP packet is forwarded to other ports; if not, the original SOP packet is discarded;

[0034] In step S403, all nodes in the network update the faulty links in the topology to obtain a new routing table, and then continue to periodically enable the routing table at the corresponding time; if there is no link failure, no update is performed; each node maintains two routing tables, an initial routing table, that is, the routing table calculated after the satellite obtains the initial topology information and there is no link failure; and a current routing table, that is, after a link failure occurs, the link information is updated to calculate a new routing table.

[0035] Furthermore, the landing satellite in step S500 is a satellite that completes satellite-to-ground service transmission. When the satellite establishes a feeder link connection with the gateway station, the satellite is a landing satellite.

[0036] The landing satellite table in step S600 includes the table entry number, the available gateway station number, the available landing satellite number, the remaining available time of the feeder link, the link quality level and the link load.

[0037] An on-board autonomous routing system utilizing the operating rules of a satellite constellation, comprising:

[0038] Satellite power-on module, used to power on satellite equipment, execute satellite power-on process, and obtain constellation topology rule set in; The duration for each topology table to take effect. G is N different topology tables of satellite network changes within a satellite return period. i (E,V i ) indicates that the i-th topology table consists of E satellites and V i The links consist of is the topology calibration rule table, c i Recorded topology G i (E,V i ) corresponding to the more accurate satellite number;

[0039] Routing table acquisition module, used to collect Topology table collection For each topology table, calculate the topology table set The corresponding routing table set

[0040] Routing table calibration module, used to calibrate the topology rules according to the constellation Topology calibration rules table The topology table used by the satellite is calibrated with satellite dimension information, and the routing table set Select the currently used routing table in the topology calibration, and then set the constellation topology rules according to the constellation topology rules. The duration for each topology table to take effect Perform topology switching;

[0041] The routing table update module is used to enable each satellite to periodically detect the link status with all its neighboring satellites according to the currently used topology table. If the link status changes, a link status indication packet is generated and diffused to other nodes in the entire network. The satellite that receives the link status indication packet updates the topology table set. All topology tables and routing tables related to the link status;

[0042] Landing satellite information indication packet diffusion module: used to establish a connection with the gateway station when the satellite passes over the ground. At this time, the satellite identity is changed to a landing satellite, the connection holding time is calculated, and the connection holding time, satellite address and gateway station address information are combined into a landing satellite information indication packet, and the landing satellite information indication packet is diffused to other nodes in the entire network;

[0043] Locally maintained landing star catalog update module: used for updating the locally maintained landing star catalog of satellites receiving the landing star information indication group;

[0044] The service transmission module is used to query the landing satellite table maintained by itself to determine the address of the satellite that can land and is currently connected to the ground station when a satellite needs to relay and forward a packet whose destination address is a gateway station. Then, the corresponding entry in the routing table is queried according to the found landing satellite address as the destination address to relay and forward the data.

[0045] Furthermore, the specific method of the satellite power-on process in the satellite power-on module is:

[0046] Step S101, read the first power-on flag to determine whether it is the first power-on. If it is not the first power-on, go to step S102; if it is the first power-on, set the first power-on flag to no and go to step S104;

[0047] Step S102: The satellite that is not powered on for the first time sends a current constellation topology rule application packet to other satellites around it through all its intersatellite transmitters, and starts a timer to wait for a topology reply packet; the satellite that receives the application packet sends a topology reply packet to the satellite that is not powered on for the first time, and the packet contains a constellation topology rule set. If the timer times out and no topology reply packet is received, the process returns to step S102;

[0048] Step S103: After the satellite that is not powered on for the first time receives the topology reply packet, it records The information in the message cancels the timer and ends the satellite power-on process;

[0049] Step S104: Calculate the constellation topology rule set according to the constellation operation rule End the satellite power-on process;

[0050] The calculation method of the constellation topology rule set in the satellite power-on module adopts the following steps:

[0051] Step S110, initialize i=1, select a satellite j from the satellite set as the initial satellite, and record Init=j. According to the constellation operation law, the satellite regression period is obtained. Where H is the orbital altitude, G is the gravitational constant, M is the mass of the Earth, and r is the orbital radius; the satellite regression period is the time it takes for the satellite to orbit the Earth and return to its initial latitude position;

[0052] Step S120: When the j-satellite moves from the orbit raising direction to the latitude in the northern hemisphere disconnection zone, the satellite numbers of all the satellites with the same latitude as the j-satellite in the orbit raising direction are calculated, and the j-satellite and the numbers of these satellites are recorded in the topology calibration rule table c. i The northern hemisphere disconnection zone is the area where the satellite closes the intersatellite links with different orbits in the area above the Arctic Circle when it moves from the middle and low latitudes to the northern hemisphere, and only retains the intersatellite links with the same orbit;

[0053] Step S130, according to the satellite link establishment rules, in the case of the current satellite position snapshot, calculate the satellite network connection topology map and record it in G i (E,V i );

[0054] Step S140, calculate all the The angle difference between the satellite in the broken link and the latitude in the broken link direction, and the value with the smallest absolute value of the angle difference Δω is selected min , and assign the satellite number to j;

[0055] Step S150, calculate the topology graph G i Duration of validity And record this value in middle;

[0056] Step S160: If j is on the ascending track and equal to Init, the algorithm ends and outputs Otherwise, push all satellites forward in their respective directions of motion by Δω min , if the satellite j is located at the latitude of the broken link area in the ascending direction of the northern hemisphere at this time, go to step S120, otherwise go to step S170;

[0057] Step S170, let i=i+1, Go to step S130.

[0058] Furthermore, the routing table acquisition module uses Dijkstra algorithm to calculate the topology table set The corresponding routing table set

[0059] The topology calibration rule table in the routing table calibration module Contains the topological period and enabled satellite number. Every time the satellite moves to the disconnection zone in the northern hemisphere, the topological calibration rule table is queried. Calibrate the currently used topology table and then perform the topology switching steps, according to The time t recorded in the above table enables the subsequent topology tables in turn;

[0060] The landing satellite in the locally maintained landing satellite list update module is a satellite that completes satellite-to-ground service transmission. When a satellite establishes a feeder link connection with a gateway station, the satellite is a landing satellite;

[0061] The landing satellite table in the service transmission module includes the table entry number, the available gateway station number, the available landing satellite number, the remaining available time of the feeder link, the link quality level and the link load.

[0062] Furthermore, in the routing table update module, the satellite periodically detects the link status with all its neighboring satellites, diffuses the link status indication packet, and updates the routing table using the following steps:

[0063] Step S401, periodically detecting the link status adopts the Hello mechanism, each node periodically sends HELLO packets on each channel, a node can periodically receive the HELLO packets sent by the four nodes, and periodically send HELLO packets to the four nodes; if a HELLO packet sent by a certain node is not received in several HELLO cycles, it is determined that the link between the nodes is faulty, and the node sets the link status to bidirectional interruption; link fault detection corresponds to the topology table, and the link status at this time is determined according to the link information in the topology table. When the link exists in the topology table but the link monitoring does not find the existence of this link, a link fault occurs;

[0064] Step S402, when a link failure occurs, the two end nodes of the faulty link use the link status indication packet, i.e., the SOP packet, to send the fault information to other nodes in the whole network in the form of flooding. The SOP packet carries the information number and the source node ID. The diffusion stage adopts the basic method of unidirectional flooding for transmission. Each node that receives the SOP packet first replies a receiving response to the receiving port, and then determines whether it is a new SOP packet according to the information number and the source node ID in the SOP packet. If it is a new SOP packet, the topology table is updated according to the new SOP packet, and the new SOP packet is forwarded to other ports; if not, the original SOP packet is discarded;

[0065] In step S403, all nodes in the network update the faulty links in the topology to obtain a new routing table, and then continue to periodically enable the routing table at the corresponding time; if there is no link failure, no update is performed; each node maintains two routing tables, an initial routing table, that is, the routing table calculated after the satellite obtains the initial topology information and there is no link failure; and a current routing table, that is, after a link failure occurs, the link information is updated to calculate a new routing table.

[0066] Compared with the prior art, the present invention has the following beneficial technical effects:

[0067] First, the actual operation rules of satellites and topological changes are combined with the operation rules of low-orbit satellite constellations to ensure that there are no structural changes in the topology within the calculated time interval.

[0068] Second, there is no need to periodically upload topology, which reduces overhead and enables autonomous on-board routing without the involvement of a ground control center.

[0069] Third, combined with link fault detection, routing self-recovery can be achieved, avoiding the failure of routing information on the ground due to link failure, which in turn causes network paralysis caused by the satellite network's inability to receive ground routing update paths.

[0070] Fourth, combined with the operation rules of the low-orbit satellite constellation, a landing satellite table is designed separately to avoid frequent changes in topology and routing tables when the satellite-to-ground link changes irregularly. Autonomous routing on the satellite is achieved, and the gateway does not appear in the routing table, which solves the problem of frequent routing switching in the previous satellite-to-ground link with routing tables. BRIEF DESCRIPTION OF THE DRAWINGS

[0071] The drawings in the specification are used to provide further understanding of the present invention and constitute a part of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0072] Figure 1 is a flow chart of an embodiment of the present invention;

[0073] Figure 2 is a network connection change relationship topology diagram of an embodiment of the present invention;

[0074] Figure 3 is a schematic diagram of topology change rule simulation of an embodiment of the present invention;

[0075] Figure 4 It is a SOP package processing flow chart;

[0076] Figure 5 It is a comparison chart of simulation results of the algorithm of the present invention and the snapshot routing algorithm. DETAILED DESCRIPTION

[0077] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0078] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0079] An on-board autonomous routing method using the operating rules of a low-orbit satellite constellation. The technical ideas are as follows:

[0080] First, the satellite equipment is powered on so that the satellite can obtain the constellation topology rule set, which includes the duration of each topology, the topology table and the topology calibration rule table. Then, the corresponding routing table is calculated according to the topology table; when the satellite moves to the north latitude disconnection zone, the topology calibration rule table is used for calibration, the currently used routing table is selected from the routing table set, and the subsequent routing tables are enabled in sequence according to the time slice. The north latitude disconnection zone refers to the satellite moving from the middle and low latitudes to the northern hemisphere, and the inter-satellite links of different orbits are closed in the area above the Arctic Circle, and only the inter-satellite links of the same orbit are retained.

[0081] Furthermore, the present invention performs link monitoring by periodically detecting the link status of all its neighboring satellites. If the link status changes, a link status indication packet is generated and diffused to other nodes in the entire network. The satellite that receives the link status indication packet updates all topology tables and routing tables related to the link.

[0082] Finally, when the satellite passes over a gateway station on the ground, it establishes a connection with the gateway station. At this time, the satellite's identity is transformed into a landed satellite, realizing satellite-to-ground business transmission.

[0083] Reference Figure 1 , the implementation steps of the present invention are further described.

[0084] The low-orbit LEO satellite network of the present invention is composed of 72 low-orbit LEO satellites, with 12 satellites distributed on each orbital plane, evenly distributed on 6 orbital planes. Each low-orbit LEO satellite is built on a satellite orbit with an altitude of 1175km from the ground and an inclination of 86.5°.

[0085] First, the satellite equipment is powered on, the satellite power-on process is executed, and the constellation topology rule set is obtained.

[0086] When the first satellite in the first orbit is powered on, read the first power-on flag to determine whether it is the first power-on. If it is not the first power-on, send the current constellation topology rule application packet to the second satellite in the first orbit and the 0th satellite in the first orbit through all intersatellite transmitters equipped by itself, and start the timer to wait for the topology reply packet. The timer is set to 60s. If the timer times out and no topology reply packet is received, repeat this step; if the second satellite in the first orbit receives the application packet, send a topology reply packet to the first satellite in the first orbit, and the packet contains the constellation topology rule set At this time, after the first satellite in the first orbit receives the topology reply packet, it records The information in the message box cancels the timer and ends the satellite power-on process.

[0087] If the first satellite in the first orbit is powered on for the first time, the constellation topology rule set is calculated according to the constellation operation rules. Calculate the constellation topology rule set based on the constellation operation rules End the satellite power-on process.

[0088] Reference Figure 2 , get the constellation topology rule set The calculation method and topology switching process.

[0089] According to the zodiac cycle Where H = 1175m, G = 6.67×10 -11 , M = 5.965 × 10 24 , we get T = 108.8 minutes, which is the regression period of the satellite operation.

[0090] exist Figure 2 At time T1, some satellites such as S63 enter the polar circle. At this time, S63 is located in the north latitude break zone, and the north latitude break zone in the embodiment is 63° north latitude. Select satellite S63 as the initial satellite, calculate the satellite numbers of all satellites with the same latitude as S63 in the ascending direction, and record S63 satellite and these satellite numbers in the calibration rule table In the equation, C1 = {S63, S43, S23}, Calibration rule table in the embodiment The current routing table is calibrated when the S63 satellite moves to 63°N. At this time, the satellite moving into the polar circle disconnects the inter-orbit link connection with the adjacent satellite in the polar circle, that is, S63 disconnects the inter-orbit connection with S6. Under the current satellite position snapshot, the satellite network connection topology is calculated and recorded. In Calculate all rules that are not currently in the calibration set The angular difference between the satellite and the latitude of the broken link area, and the value with the smallest absolute value of the angular difference Δω is selected min =5.25°, the duration of topology G1 taking effect Where T is the satellite return period of 108.8 minutes, and this value is recorded in In Push all satellites forward in their respective directions of motion by Δω min Enter T2 moment.

[0091] T2 is the next moment when a satellite such as S53 leaves the polar circle. Calculate the satellite numbers of all satellites with the same latitude as S53 in the ascending direction, and record S53 and these satellite numbers in the verification rule table. In the equation, C2 = {S53, S33, S13}, At this time, the satellite moving outside the polar circle re-establishes the inter-orbit connection with the adjacent satellite, that is, S53 reconnects with S65. Under the current satellite position snapshot, the satellite network connection topology is calculated and recorded. In Calculate all rules that are not currently in the calibration set The angular difference between the satellite and the latitude of the broken link area, and the value with the smallest absolute value of the angular difference Δω is selected min = 6°, the duration of topology G2 taking effect And record this value in In Push all satellites forward in their respective directions of motion by Δω min Enter T3 moment.

[0092] T3 is the next moment when a satellite such as S51 enters the polar circle. Calculate the numbers of all satellites with the same latitude as S51 in the ascending direction, and record S51 and these satellite numbers in the verification rule table. In the equation, G3 = {S51, S31, S11}, At this time, the satellite moving into the polar circle disconnects the inter-orbit link connection with the adjacent satellite in the polar circle, that is, S51 and S63 disconnect the inter-orbit connection. Under the current satellite position snapshot, the satellite network connection topology is calculated and recorded. In Calculate all rules that are not currently in the calibration set The angular difference between the satellite and the latitude of the broken link area, and the value with the smallest absolute value of the angular difference Δω is selected min =12.75°, calculate the duration of topology G3 taking effect And record this value in In Push all satellites forward in their respective directions of motion by Δω min Enter T4 moment.

[0093] T4 is the next moment when a satellite such as S64 leaves the polar circle. Calculate the numbers of all satellites with the same latitude as S64 in the ascending direction, and record S64 and these satellite numbers in the verification rule table. In the example, C4 = {S64, S44, S24}, At this time, the satellite moving outside the polar circle re-establishes the inter-orbit connection with the adjacent satellite, that is, S64 reconnects with S5. Under the current satellite position snapshot, the satellite network connection topology is calculated and recorded. In Calculate all rules that are not currently in the calibration set The angular difference between the satellite and the latitude of the broken link area, and the value with the smallest absolute value of the angular difference Δω is selected min = 6°, calculate the duration of topology G4 taking effect And record this value in In Push all satellites forward in their respective directions of motion by Δω min Enter the next moment. Similarly, if S63 is in the north latitude disconnection zone again, the program ends and the output is

[0094] When the S63 satellite moves to 63° north latitude, the topology calibration rule table is queried. Calibrate the currently used topology table and then perform the topology switching steps, according to The time t recorded in the topology table is used to enable the subsequent topology tables in sequence. The topology calibration rule table includes the topology period and the enabled satellite number. The topology calibration rule table is shown in Table 1.

[0095] Table 1 Topology calibration rules table

[0096]

[0097]

[0098] It can be found that there is a certain regularity in the constellation topological connection relationship: from time T1, the satellite moves 5.25° to time T2, from time T2, the satellite moves 6° to time T3, from time T3, the satellite moves 12.75° to time T4, from time T4, it moves 6° to the next time, and so on. The change interval of the constellation connection relationship alternates between the time difference Δt1 when the satellite moves 5.25°, the time difference Δt2 when the satellite moves 6°, the time difference Δt3 of 12.75°, and the time difference Δt4 of 6°.

[0099] By counting the events in the satellite's northern latitude disconnection zone and the time of occurrence of these events within a satellite's regression cycle, the statistical results are as follows: Figure 3 As shown, it can be seen that at any moment, four events occurred at the same time, and the event composed of these four events was recorded as a combined event. In one satellite operation cycle, 48 such combined events occurred, and the time difference of the combined events had a certain regularity, and the time difference of occurrence alternated between 231s, 109s, 95s and 109s. From the above analysis, it can be concluded that in each satellite operation cycle, the satellite network is divided into time slices with non-equal intervals in the time dimension. The time slice interval alternates between 231s, 109s, 95s and 109s, and there are 48 time slices in one cycle. Record the topology table of 72 low-orbit LEO satellites in 48 time slices. Table 2 is the topology table of the fourth time slice. According to the above calculation, each topology table of the topology table set in the constellation topology set is obtained, and the corresponding routing table set is calculated.

[0100] Table 2 Topology table of the fourth time slice

[0101]

[0102] The first satellite in the second orbit of the low-orbit LEO satellite network and its neighboring satellites related to the satellite are selected to further illustrate the autonomous update process after a link failure occurs.

[0103] The neighbor satellites associated with the first satellite in the second orbit are the second satellite in the second orbit, the 12th satellite in the second orbit, the second satellite in the third orbit, and the first satellite in the first orbit. The first satellite in the second orbit sends HELLO packets to neighbor satellites every 2 seconds. In the 10-second time interval, the first satellite in the second orbit only receives hello packets from three satellites, namely, the second satellite in the second orbit, the 12th satellite in the second orbit, and the second satellite in the third orbit. It is determined that the intersatellite links between the first satellite in the second orbit and these three neighbor satellites are normal, and the first satellite in the first orbit that has not received the hello packet is determined to have a fault in the intersatellite link with the first satellite in the second orbit. In the last 10-second time interval, the intersatellite link status between the first satellite in the second orbit and all neighbor satellites was normal.

[0104] Compare the intersatellite link status of the first satellite in the second orbit in this 10s time interval with that in the previous 10s time interval. It is found that the intersatellite link status between the first satellite in the second orbit and the first satellite in the first orbit is different twice. It is thus determined that the intersatellite link status between the first satellite in the second orbit and the first satellite in the first orbit has changed. At this time, the first satellite in the second orbit needs to set the link status of the first satellite in the first orbit to bidirectional interruption. The first satellite in the second orbit updates its own topology table and recalculates the route associated with the link.

[0105] Since the intersatellite link between the first satellite in the second orbit and the first satellite in the first orbit is faulty, the first satellite in the second orbit sends the faulty intersatellite link information to the second satellite in the second orbit, the twelfth satellite in the second orbit, the second satellite in the third orbit and the first satellite in the first orbit respectively by sending SOP packet flooding.

[0106] The second satellite in the second orbit forwards the received faulty intersatellite link information to the third satellite in the second orbit, the first satellite in the second orbit, the third satellite in the third orbit, and the second satellite in the first orbit. The 12th satellite in the second orbit forwards the received faulty intersatellite link information to the first satellite in the second orbit, the 11th satellite in the second orbit, the first satellite in the third orbit, and the 12th satellite in the first orbit. The second satellite in the third orbit forwards the received faulty intersatellite link information to the third satellite in the third orbit, the first satellite in the third orbit, the third satellite in the fourth orbit, and the second satellite in the second orbit. The first satellite in the first orbit forwards the received faulty intersatellite link information to the first satellite in the first orbit, the 12th satellite in the first orbit, and the first satellite in the second orbit.

[0107] The satellite that receives the SOP packet updates all the topology tables and routing tables related to the link. That is, the second satellite in the second orbit receives the SOP packet, checks the topology table and finds that link No. 21 has a link failure, updates the faulty link in the original topology, and recalculates the routing table. Table 3 and Table 4 are the topology table and routing table before the second satellite in the second orbit is updated, and Table 5 and Table 6 are the topology table and routing table after the second satellite in the second orbit is updated. Other satellites in the entire network that receive SOP packets also use the same method to update the routing table. After that, the routing table at the corresponding time will continue to be enabled according to the cycle, without repeated calculation. If there is no link failure, no update will be made to the original topology table. The SOP packet processing flow is as follows: Figure 4 shown.

[0108] Table 3 Topology table of the second satellite in the second orbit before update

[0109]

[0110] Table 4 Routing table before the second satellite in the second orbit is updated

[0111] Time slice information (8 bits) Destination node (8bit) Next hop egress port (8 bits) 15 9 12

[0112] Table 5 Topology table after the second satellite in the second orbit is updated

[0113]

[0114] Table 6 Routing table after the second satellite in the second orbit is updated

[0115] Time slice information (8 bits) Destination node (8bit) Next hop egress port (8 bits) 30 9 3

[0116] The fifth satellite in the first orbit of the low-orbit LEO satellite network is selected to further explain the process of landing services.

[0117] In the embodiment of the present invention, there are four gateway stations. They are gateway station 1, gateway station 2, gateway station 3, and gateway station 4. When the fifth satellite in the first orbit passes over the gateway station 1 located on the ground, it establishes a connection with the gateway station 1. At this time, the satellite identity is changed to a grounded satellite, and the connection maintenance time is calculated. The connection maintenance time, the satellite address, and the signal gateway station address information are combined into a grounded satellite information indication group, and the group is diffused to other satellites in the entire network; when the third satellite in the second orbit passes over the gateway station 2 located on the ground, it establishes a connection with the gateway station 2. At this time, the satellite identity is changed to a grounded satellite, and the connection maintenance time is calculated. The connection maintenance time, the satellite address, and the signal gateway station address information are combined into a grounded satellite information indication group, and the group is diffused to other satellites in the entire network; when the first satellite in the third orbit passes over the When the second satellite in the fourth orbit passes over the gateway station 4 on the ground, it establishes a connection with the gateway station 4. At this time, the satellite identity is changed to a landing satellite, the connection maintenance time is calculated, and the connection maintenance time, the satellite address, and the signal gateway address information are combined into a landing satellite information indication group, and the group is diffused to other satellites in the entire network; when the second satellite in the fourth orbit passes over the gateway station 4 on the ground, it establishes a connection with the gateway station 4. At this time, the satellite identity is changed to a landing satellite, the connection maintenance time is calculated, and the connection maintenance time, the satellite address, and the signal gateway address information are combined into a landing satellite information indication group, and the group is diffused to other satellites in the entire network; after receiving the status notification message of the landing satellite, the instant table items of the available landing satellites are established and maintained locally.

[0118] When the landing service of the 5th satellite in the second orbit is triggered and arrives at the gateway station 1, the gateway station 1 is used as the input condition to query the locally maintained landing satellite table. At this time, the 5th landing satellite in the first orbit is written into the destination address, and the best landing link is selected according to the longest available time, the best feeder link quality, load balancing and other strategies. Then, the routing entry of the 5th landing satellite in the first orbit in the inter-satellite routing table is queried and forwarded according to the next hop in the routing table. Table 7 shows the available landing satellite table entry of the 5th satellite in the second orbit, and Table 8 shows the corresponding routing table.

[0119] Table 7 List of available landing satellites for the 5th satellite in the second orbit

[0120]

[0121] Table 8 corresponding routing table

[0122] Time slice information (8 bits) Destination node (8bit) Next hop egress port (8 bits) 220 4 9

[0123] According to the method of the present invention, the simulation results of the algorithm of the present invention and the snapshot routing algorithm are as follows: Figure 5 As shown in the figure, it can be seen that on-board autonomous routing can ensure that there is no packet loss during the switching process, while the snapshot routing algorithm cannot ensure no packet loss.

[0124] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit its protection scope. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the field should understand that after reading the present invention, those skilled in the art can still make various changes, modifications or equivalent substitutions to the specific implementation methods of the invention, but these changes, modifications or equivalent substitutions are all within the protection scope of the pending claims of the invention.

Claims

1. An on-board autonomous routing method using the operating rules of a low-orbit satellite constellation, characterized in that: The following steps are involved: Step S100: The satellite equipment is powered on, the satellite power-on process is executed, and a constellation topology rule set is obtained. in; The duration for each topology table to take effect. G is N different topology tables of satellite network changes within a satellite return period. i (E,V i ) indicates that the i-th topology table consists of E satellites and V i The links consist of is the topology calibration rule table, c i Recorded topology G i (E,V i ) corresponding to the more accurate satellite number; Among them, the specific method of the satellite power-on process is: Step S101, read the first power-on flag to determine whether it is the first power-on. If it is not the first power-on, go to step S102; if it is the first power-on, set the first power-on flag to no and go to step S104; Step S102: The satellite that is not powered on for the first time sends a current constellation topology rule application packet to other satellites around it through all its intersatellite transmitters, and starts a timer to wait for a topology reply packet; the satellite that receives the application packet sends a topology reply packet to the satellite that is not powered on for the first time, and the packet contains a constellation topology rule set. If the timer times out and no topology reply packet is received, the process returns to step S102; Step S103: After the satellite that is not powered on for the first time receives the topology reply packet, it records The information in the message cancels the timer and ends the satellite power-on process; Step S104: Calculate the constellation topology rule set according to the constellation operation rule End the satellite power-on process; Step S200: according to the constellation topology rule set Topology table collection For each topology table, calculate the topology table set Corresponding routing table set Step S300: according to the constellation topology rule set Topology calibration rules table The topology table used by the satellite is calibrated with satellite dimension information, and the routing table set Select the currently used routing table in the topology calibration, and then set the constellation topology rules according to the constellation topology rules. The duration for each topology table to take effect Perform topology switching; Step S400: Each satellite periodically detects the link status with all its neighboring satellites based on the currently used topology table. If the link status changes, a link status indication packet is generated and diffused to other nodes in the entire network. The satellite that receives the link status indication packet updates the topology table set. All topology tables and routing tables related to the link status; Step S500: When a satellite passes over a gateway station located on the ground, it establishes a connection with the gateway station. At this time, the satellite identity is changed to a landing satellite, the connection holding time is calculated, and the connection holding time, satellite address and gateway station address information are combined into a landing satellite information indication group, and the landing satellite information indication group is diffused to other nodes in the entire network; Step S600, the satellites receiving the landing satellite information indication group update the locally maintained landing satellite catalog; Step S700, when a satellite needs to relay a packet whose destination address is a gateway station, it queries the landing satellite table maintained by itself to determine the address of a satellite that can land and is currently connected to the ground station, and then uses the found landing satellite address as the destination address to query the corresponding entry in the routing table to relay and forward the data.

2. The on-board autonomous routing method using the operating rules of a low-orbit satellite constellation according to claim 1, characterized in that: The calculation method of the constellation topology rule set in step S100 adopts the following steps: Step S110, initialize i=1, select a satellite j from the satellite set as the initial satellite, and record Init=j. According to the constellation operation law, the satellite regression period is obtained. Where H is the orbital altitude, G is the gravitational constant, M is the mass of the Earth, and r is the orbital radius; the satellite regression period is the time it takes for the satellite to orbit the Earth and return to its initial latitude position; Step S120: When the j-satellite moves from the orbit raising direction to the latitude in the northern hemisphere disconnection zone, the satellite numbers of all the satellites with the same latitude as the j-satellite in the orbit raising direction are calculated, and the j-satellite and the numbers of these satellites are recorded in the topology calibration rule table c. i The northern hemisphere disconnection zone is the area where the satellite closes the intersatellite links with different orbits in the area above the Arctic Circle when it moves from the middle and low latitudes to the northern hemisphere, and only retains the intersatellite links with the same orbit; Step S130, according to the satellite link establishment rules, in the case of the current satellite position snapshot, calculate the satellite network connection topology map and record it in G i (E,V i ); Step S140, calculate all the The angle difference between the satellite in the broken link and the latitude in the broken link direction, and the value with the smallest absolute value of the angle difference Δω is selected min , and assign the satellite number to j; Step S150, calculate the topology graph G i Duration of validity And record this value in middle; Step S160: If j is on the ascending track and equal to Init, the algorithm ends and outputs Otherwise, push all satellites forward in their respective directions of motion by Δω min , if the satellite j is located at the latitude of the broken link area in the ascending direction of the northern hemisphere at this time, go to step S120, otherwise go to step S170; Step S170, let i=i+1, Go to step S130.

3. The on-board autonomous routing method using the operating rules of a low-orbit satellite constellation according to claim 1, characterized in that: In step S200, Dijkstra algorithm is used to calculate the topology table set Corresponding routing table set The topology calibration rule table described in step S300 Contains the topological period and enabled satellite number. Every time the satellite moves to the disconnection zone in the northern hemisphere, the topological calibration rule table is queried. Calibrate the currently used topology table and then perform the topology switching steps, according to The subsequent topology tables are enabled in sequence at the time t recorded in .

4. The on-board autonomous routing method using the operating rules of a low-orbit satellite constellation according to claim 1, characterized in that: Step S400: The satellite periodically detects the link status with all its neighboring satellites, diffuses the link status indication packet, and updates the routing table using the following steps: Step S401, periodically detecting the link status adopts the Hello mechanism, each node periodically sends HELLO packets on each channel, a node can periodically receive the HELLO packets sent by the four nodes, and periodically send HELLO packets to the four nodes; if a HELLO packet sent by a certain node is not received in several HELLO cycles, it is determined that the link between the nodes is faulty, and the node sets the link status to bidirectional interruption; link fault detection corresponds to the topology table, and the link status at this time is determined according to the link information in the topology table. When the link exists in the topology table but the link monitoring does not find the existence of this link, a link fault occurs; Step S402, when a link failure occurs, the two end nodes of the faulty link use the link status indication packet, i.e., the SOP packet, to send the fault information to other nodes in the whole network in the form of flooding. The SOP packet carries the information number and the source node ID. The diffusion stage adopts the basic method of unidirectional flooding for transmission. Each node that receives the SOP packet first replies a receiving response to the receiving port, and then determines whether it is a new SOP packet according to the information number and the source node ID in the SOP packet. If it is a new SOP packet, the topology table is updated according to the new SOP packet, and the new SOP packet is forwarded to other ports; if not, the original SOP packet is discarded; In step S403, all nodes in the network update the faulty links in the topology to obtain a new routing table, and then continue to periodically enable the routing table at the corresponding time; if there is no link failure, no update is performed; each node maintains two routing tables, an initial routing table, that is, the routing table calculated after the satellite obtains the initial topology information and there is no link failure; and a current routing table, that is, after a link failure occurs, the link information is updated to calculate a new routing table.

5. The on-board autonomous routing method using the operating rules of a low-orbit satellite constellation according to claim 1, characterized in that: The grounded satellite in step S500 is a satellite that completes satellite-to-ground service transmission. When a satellite establishes a feeder link connection with a gateway station, the satellite is a grounded satellite. The landing satellite table in step S600 includes table entry numbers, available gateway station numbers, available landing satellite numbers, remaining available time of the feeder link, link quality level, and link load.

6. An on-board autonomous routing system utilizing the operating rules of a satellite constellation, characterized in that: include: Satellite power-on module, used to power on satellite equipment, execute satellite power-on process, and obtain constellation topology rule set in; The duration for each topology table to take effect. G is N different topology tables of satellite network changes within a satellite return period. i (E,V i ) indicates that the i-th topology table consists of E satellites and V i The links consist of is the topology calibration rule table, c i Recorded topology G i (E,V i ) corresponding to the more accurate satellite number; Among them, the specific method of the satellite power-on process is: Step S101, read the first power-on flag to determine whether it is the first power-on. If it is not the first power-on, go to step S102; if it is the first power-on, set the first power-on flag to no and go to step S104; Step S102: The satellite that is not powered on for the first time sends a current constellation topology rule application packet to other satellites around it through all its intersatellite transmitters, and starts a timer to wait for a topology reply packet; the satellite that receives the application packet sends a topology reply packet to the satellite that is not powered on for the first time, and the packet contains a constellation topology rule set. If the timer times out and no topology reply packet is received, the process returns to step S102; Step S103: After the satellite that is not powered on for the first time receives the topology reply packet, it records The information in the message cancels the timer and ends the satellite power-on process; Step S104: Calculate the constellation topology rule set according to the constellation operation rule End the satellite power-on process; Routing table acquisition module, used to collect Topology table collection For each topology table, calculate the topology table set Corresponding routing table set Routing table calibration module, used to calibrate the topology rules according to the constellation Topology calibration rules table The topology table used by the satellite is calibrated with satellite dimension information, and the routing table set Select the currently used routing table in the topology calibration, and then set the constellation topology rules according to the constellation topology rules. The duration for each topology table to take effect Perform topology switching; The routing table update module is used to enable each satellite to periodically detect the link status with all its neighboring satellites according to the currently used topology table. If the link status changes, a link status indication packet is generated and diffused to other nodes in the entire network. The satellite that receives the link status indication packet updates the topology table set. All topology tables and routing tables related to the link status; Landing satellite information indication packet diffusion module: used to establish a connection with the gateway station when the satellite passes over the ground. At this time, the satellite identity is changed to a landing satellite, the connection holding time is calculated, and the connection holding time, satellite address and gateway station address information are combined into a landing satellite information indication packet, and the landing satellite information indication packet is diffused to other nodes in the entire network; Locally maintained landing star catalog update module: used for updating the locally maintained landing star catalog of satellites receiving the landing star information indication group; The service transmission module is used to query the landing satellite table maintained by itself to determine the address of the satellite that can land and is currently connected to the ground station when a satellite needs to relay and forward a packet whose destination address is a gateway station. Then, the corresponding entry in the routing table is queried according to the found landing satellite address as the destination address to relay and forward the data.

7. The on-board autonomous routing system using the satellite constellation operation law according to claim 6, characterized in that: The calculation method of the constellation topology rule set in the satellite power-on module adopts the following steps: Step S110, initialize i=1, select a satellite j from the satellite set as the initial satellite, and record Init=j. According to the constellation operation law, the satellite regression period is obtained. Where H is the orbital altitude, G is the gravitational constant, M is the mass of the Earth, and r is the orbital radius; the satellite regression period is the time it takes for the satellite to orbit the Earth and return to its initial latitude position; Step S120: When the j-satellite moves from the orbit raising direction to the latitude in the northern hemisphere disconnection zone, the satellite numbers of all the satellites with the same latitude as the j-satellite in the orbit raising direction are calculated, and the j-satellite and the numbers of these satellites are recorded in the topology calibration rule table c. i The northern hemisphere disconnection zone is the area where the satellite closes the intersatellite links with different orbits in the area above the Arctic Circle when it moves from the middle and low latitudes to the northern hemisphere, and only retains the intersatellite links with the same orbit; Step S130, according to the satellite link establishment rules, in the case of the current satellite position snapshot, calculate the satellite network connection topology map and record it in G i (E,V i ); Step S140, calculate all the The angle difference between the satellite in the broken link and the latitude in the broken link direction, and the value with the smallest absolute value of the angle difference Δω is selected min , and assign the satellite number to j; Step S150, calculate the topology graph G i Duration of validity And record this value in middle; Step S160: If j is on the ascending track and equal to Init, the algorithm ends and outputs Otherwise, push all satellites forward in their respective directions of motion by Δω min , if the satellite j is located at the latitude of the broken link area in the ascending direction of the northern hemisphere at this time, go to step S120, otherwise go to step S170; Step S170, let i=i+1, Go to step S130.

8. The on-board autonomous routing system using the satellite constellation operation law according to claim 6, characterized in that: The routing table acquisition module uses Dijkstra algorithm to calculate the topology table set Corresponding routing table set The topology calibration rule table in the routing table calibration module Contains the topological period and enabled satellite number. Every time the satellite moves to the disconnection zone in the northern hemisphere, the topological calibration rule table is queried. Calibrate the currently used topology table and then perform the topology switching steps, according to The time t recorded in the above table enables the subsequent topology tables in turn; The landing satellite in the locally maintained landing satellite list update module is a satellite that completes satellite-to-ground service transmission. When a satellite establishes a feeder link connection with a gateway station, the satellite is a landing satellite; The landing satellite table in the service transmission module includes the table entry number, the available gateway station number, the available landing satellite number, the remaining available time of the feeder link, the link quality level and the link load.

9. The on-board autonomous routing system using the satellite constellation operation law according to claim 6, characterized in that: In the routing table update module, the satellite periodically detects the link status with all its neighboring satellites, diffuses the link status indication packet, and updates the routing table using the following steps: Step S401, periodically detecting the link status adopts the Hello mechanism, each node periodically sends HELLO packets on each channel, a node can periodically receive the HELLO packets sent by the four nodes, and periodically send HELLO packets to the four nodes; if a HELLO packet sent by a certain node is not received in several HELLO cycles, it is determined that the link between the nodes is faulty, and the node sets the link status to bidirectional interruption; link fault detection corresponds to the topology table, and the link status at this time is determined according to the link information in the topology table. When the link exists in the topology table but the link monitoring does not find the existence of this link, a link fault occurs; Step S402, when a link failure occurs, the two end nodes of the faulty link use the link status indication packet, i.e., the SOP packet, to send the fault information to other nodes in the whole network in the form of flooding. The SOP packet carries the information number and the source node ID. The diffusion stage adopts the basic method of unidirectional flooding for transmission. Each node that receives the SOP packet first replies a receiving response to the receiving port, and then determines whether it is a new SOP packet according to the information number and the source node ID in the SOP packet. If it is a new SOP packet, the topology table is updated according to the new SOP packet, and the new SOP packet is forwarded to other ports; if not, the original SOP packet is discarded; In step S403, all nodes in the network update the faulty links in the topology to obtain a new routing table, and then continue to periodically enable the routing table at the corresponding time; if there is no link failure, no update is performed; each node maintains two routing tables, an initial routing table, that is, the routing table calculated after the satellite obtains the initial topology information and there is no link failure; and a current routing table, that is, after a link failure occurs, the link information is updated to calculate a new routing table.

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