Civil aviation traffic-oriented low earth orbit satellite network switching method and system

Abstract

The invention discloses a low earth orbit satellite network switching method and system for civil aviation traffic, and mainly solves the problem that the traditional switching algorithm does not consider the influence of a target switching satellite on inter-satellite routing, resulting in high service transmission delay. According to the scheme, the method comprises the following steps: predicting a coverage time period of a satellite to civil aviation flights in a set time period based on satellite topology and predictability of civil aviation flight routes; converting the satellite coverage time period into a switching directed graph of civil aviation flights; the routing hop count from the target switching satellite to the landing satellite is estimated, the communication elevation angle of the civil aircraft accessing the target switching satellite is calculated, the switching weight of the edges in the switching directed graph is calculated through the routing hop count and the communication elevation angle, and an updated switching directed graph is obtained; and calculating the optimal switching path of the civil aviation flight according to the switching weight in the updated switching directed graph. According to the method, the switching path can be arranged in advance for the civil aircraft, the switching success rate of the civil aircraft is improved, the service transmission delay is reduced, the communication efficiency and the user experience are improved, and the method can be used for optimizing transmission of civil aviation traffic services.

Description

Technical Field

[0001] The present invention belongs to the field of communication technology, and further relates to a low-orbit satellite network switching method and system, which can be used to optimize the transmission delay of civil aviation transportation services and the delay jitter caused by switching. Background Art

[0002] In recent years, with the rapid development of mobile Internet and the surge in user demand, communication networks have become an indispensable part of social life. Although 5G users have met the needs of most users, the construction of ground communication networks is restricted by terrain, and there is a problem of insufficient signal coverage in deserts, oceans, mountains and other areas. In addition, natural disasters are also prone to damage to ground communication network infrastructure, affecting the stability of communication services. In contrast, satellite networks have become an important part of the future 6G network with their global coverage capabilities. Low-orbit satellite networks LEO have developed rapidly in recent years and have the ability to provide global bandwidth services to meet diverse business needs. Typical LEO constellation projects include Starlink, OneWeb, etc., which have gradually achieved global broadband access. Compared with medium-orbit satellites MEO and geostationary orbit satellites GEO, LEO satellites have the advantages of low latency, low cost, and wide coverage, and play an important role in communications, meteorological monitoring, civil aviation communications and other fields.

[0003] At present, satellite communication systems widely use network architectures, including "space-based network", "space-star-ground network" and "space-net-ground network". The "space-net-ground network" architecture can give full play to the advantages of ground networks in data transmission and processing, while combining the wide-area coverage capabilities of satellite networks, effectively reducing the technical complexity and construction and operation costs of the system.

[0004] The topology of the LEO constellation is constantly changing due to the high-speed movement of low-orbit satellites, and the coverage area of ​​low-orbit satellites is relatively limited. Users may exceed the coverage of satellites due to their own or satellite movement. At this time, the communication connection needs to be switched to the next satellite within the coverage area. The core of inter-satellite switching is to ensure the smoothness of the switching process and the continuity of communication, to avoid data interruption and degradation of service quality. Civil aviation traffic has the characteristics of fast movement speed and predictable flight trajectory. The inter-satellite switching process is jointly affected by the high-speed relative movement of satellites and users, with high switching frequency and short window time. Compared with stationary users, the switching complexity is higher, and multiple satellites need to work together to meet high real-time and reliability requirements.

[0005] The inter-satellite switching algorithm proposed by Papapetrou E et al. emphasizes optimizing the switching performance with the longest remaining service time as the core. When the user selects the switching target, the satellite with the longest service time is given priority based on the predictability of the satellite network topology. By extending the communication time after the switch, the frequency of switching requests and the number of switches are effectively reduced, and the stability of the system is improved. ShenBai Zhang et al. use information entropy to weight factors such as channel quality, remaining service time, and the number of service users, and transform the multi-objective optimization problem into a single-objective optimization problem, aiming to optimize the user switching experience, reduce the number of switches, and balance the satellite switching load. These two algorithms are mainly aimed at ground stationary users or low-speed mobile users, and do not consider the switching complexity and real-time requirements brought about by the high-speed movement of users in civil aviation traffic switching scenarios.

[0006] In recent years, some graph-theory-based inter-satellite switching methods have been proposed, which optimize the switching decision by establishing a switching control graph model.

[0007] Zhaofeng Wu abstracted elements such as satellites, ground stations and user equipment as nodes in a graph, abstracted the connection relationships between them as edges in the graph, and used the minimum spanning tree algorithm in graph theory to calculate the optimal switching path in the switching control graph.

[0008] Lang Feng et al. proposed a LEO inter-satellite switching strategy based on weighted bipartite graph, which achieves maximum weight matching by improving the KuhnMunkres (KM) algorithm, optimizes communication quality and balances satellite network load.

[0009] The above inter-satellite switching strategies based on graph theory do not consider the impact of the target switching satellite on the inter-satellite routing. As the low-orbit satellite network is developing towards a giant constellation, the number of satellites is showing a significant growth trend. Selecting different switching satellites will affect the number of routing hops between the switching satellite and the landing satellite, resulting in extended service transmission time and low switching success rate. Summary of the invention

[0010] The purpose of the present invention is to address the deficiencies of the above-mentioned prior art and to propose a low-orbit satellite network switching method and system for civil aviation transportation, so as to reduce the service propagation delay of civil aviation flights and improve the switching success rate.

[0011] The technical solutions for achieving the purpose of the present invention include: a low-orbit satellite network switching method for civil aviation transportation and a low-orbit satellite network switching system for civil aviation transportation.

[0012] 1. A low-orbit satellite network switching method for civil aviation transportation, characterized in that it includes:

[0013] Predict the satellite coverage period for civil aviation flights within a set time period based on satellite topology and the predictability of civil aviation flight routes;

[0014] The satellite coverage time period is converted into a switching directed graph G of civil aviation flights, which includes a node V in the directed graph and an overlapping time of the coverage satellite period is converted into an edge E of the switching directed graph;

[0015] Estimate the number of routing hops h from the target switching satellite to the landing satellite c , calculate the communication angle e of the civil aircraft accessing the target switching satellite c , and use the routing hop count and communication angle to calculate the switching of any edge e in the directed graph df The switching weight cos t d,f , get the updated switching directed graph G′;

[0016] In the updated switching directed graph G′, according to the switching weight cos t d,f ,The shortest path algorithm is used to calculate the optimal switching path of civil aviation flights.

[0017] Further, the switching directed graph for converting the satellite coverage time period into a civil aviation flight includes:

[0018] Let G = {V, E} be the switching directed graph of civil aviation flights, where V represents the point set in the switching directed graph, and E represents the edge set in the switching directed graph;

[0019] For each satellite s in the satellite coverage set S c Transform to a node v in G c , v c ∈V;

[0020] Take the aircraft p as the virtual starting node v0 in the switching directed graph and add it to the node set V;

[0021] The overlapping time of satellite coverage periods is converted into the edges of the switching directed graph. For any pair of satellites (s d ,s f ), if two satellites s d and f The coverage time meets If the condition is met, then in the switching directed graph G, satellite s is established d and f Corresponding node v d and v f The undirected edge e between df , and add edge set E;

[0022] Determine the direction of switching the edges between nodes in a directed graph. For any edge e df, find the satellite s whose two endpoints correspond to in the set S d and f :

[0023] like In In this case, the edge df Direction v d Point to v f ;exist In this case, df Direction v f Point to v d ;

[0024] like In In this case, df Direction v d Point to v f ;exist In this case, df Direction v f Point to v d ;

[0025] In the switching directed graph, create a directed edge e between nodes v0 and v1 01 , the direction is v0 pointing to v1, and the converted civil aviation flight switching directed graph is obtained.

[0026] 2. A low-orbit satellite network switching system for civil aviation transportation, characterized by comprising:

[0027] The data management module is used to obtain the real-time satellite topology information and the route information of civil aviation flights. The real-time satellite topology information includes the real-time position information of each satellite and the start and end time of the satellite's coverage of the geographic grid; the route information of civil aviation flights includes the real-time position information of the flight and the flight speed and direction;

[0028] The satellite coverage and data calculation module is used to calculate the satellite coverage time period for civil aviation flights, the number of route hops from the target switching satellite to the landing satellite, and the communication angle of civil aviation aircraft accessing the target switching satellite based on the real-time satellite topology information and the route information of civil aviation flights output by the data management module;

[0029] A switching directed graph generation module is used to generate a switching directed graph of civil aviation flights according to the coverage time period of the satellite to the civil aviation flights output by the satellite coverage and data calculation module, and calculate the switching weight of the edge in the switching directed graph by using the number of route hops from the target switching satellite to the landing satellite and the communication angle of the civil aviation aircraft accessing the target switching satellite;

[0030] The switching path calculation and sending module is used to calculate the optimal switching path of the civil aviation flight according to the civil aviation flight switching directed graph output by the switching directed graph generation module, and send it to the corresponding switching target satellite.

[0031] Compared with the prior art, the present invention has the following advantages:

[0032] 1. The present invention arranges the switching path for civil aviation flights in advance within a future set time period according to the predicted information of satellite network topology and civil aviation flight routes, thereby avoiding the degradation of switching performance caused by the high relative moving speed between civil aviation flights and low-orbit satellites and improving the switching success rate.

[0033] 2. The present invention converts the satellite coverage time period of civil aviation flights into a directed switching graph of civil aviation flights, thus providing a mathematical model for optimizing switching decisions, facilitating the search for the optimal switching path in combination with a graph algorithm, thereby improving the real-time and accuracy of switching decisions, reducing the probability of switching failures, and improving the quality of communication services;

[0034] 3. The present invention takes into account the number of inter-satellite routing hops from the switching satellite to the landing satellite when calculating the switching weight of the switching directed graph edge, thereby optimizing the transmission path of civil aviation flight access switching satellite data in the satellite network, reducing service transmission delay, and thus improving communication efficiency and user experience. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a flow chart of the implementation of the low-orbit satellite network switching method for civil aviation transportation of the present invention;

[0036] Figure 2 is a coverage period diagram of satellites for civil aviation flights in the method of the present invention;

[0037] Figure 3 is the aircraft switching directed graph in the method of the present invention;

[0038] Figure 4 is the updated aircraft switching directed graph in the method of the present invention;

[0039] Figure 5 It is a block diagram of the low-orbit satellite network switching system for civil aviation transportation of the present invention. DETAILED DESCRIPTION

[0040] The embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0041] Embodiment 1: Low-orbit satellite network switching method for civil aviation transportation.

[0042] Reference Figure 1 The implementation steps of this example include the following:

[0043] Step 1: predict the satellite coverage period for civil aviation flights within a set time period based on satellite topology and the predictability of civil aviation flight routes.

[0044] In a low-orbit satellite network, satellites move regularly and periodically on a set orbit, so the real-time position information of satellites and the start and end time of satellite coverage of ground grids in the future can be predicted. In addition, the routes of civil aviation flights are planned in advance before take-off, and the prediction information can be used to predict the coverage period of satellites for civil aviation flights in a set time period, which includes the following implementation:

[0045] (1.1) Divide the time period T into n consecutive time slots, where T = (τ1, ..., τ k ,...,τ n ), τ k is the kth time slot, kv[1,n];

[0046] (1.2) The satellite divides the coverage mode into fixed beam coverage mode and staring beam coverage mode according to whether the beam direction is adjustable. In this example, the satellite adopts the staring beam coverage mode.

[0047] In the staring beam coverage mode, the satellite beam direction always points to the geographical grid that has been divided on the ground. n 、Number of satellites in a single orbit S n And the minimum number of satellite coverage N for each geographic grid sat Divide the global surface area into N a Geo rasters:

[0048]

[0049] (1.3) According to the flight trajectory of aircraft p, the geographical location of the aircraft in n consecutive time slots is obtained, and then according to the geographical location, the geographical grid set A to which the aircraft belongs in n consecutive time slots is obtained. k ,...,a n ), where a k For the aircraft at τ k The geographic grid of time slots, 1≤a k ≤N a ;

[0050] (1.4) According to the real-time position information of the satellite and the start and end time of the satellite's coverage of the geographic grid, the aircraft's position at any time slot τ is obtained. k Geographic grid a k The coverage satellites are sorted according to the starting coverage time of the geographic grid, and the coverage satellite set S of the aircraft in time period T is obtained:

[0051] S={s1,s2,…,s c ,…,s l}

[0052] Among them, s c represents the cth satellite covering the aircraft in the time period T, c = 1, 2, ..., l, l represents the number of satellites covering the aircraft in the time period T;

[0053] Each coverage satellite in the set S corresponds to a coverage period represents the starting time when the cth covering satellite in the set S covers the aircraft p, represents the end time of coverage of aircraft p by the cth covering satellite in the set S;

[0054] (1.5) Substitute the coverage period of each satellite in the set S The satellite coverage time period diagram of civil aviation flights in time period T is obtained by sequentially expressing them on the one-dimensional time axis, such as Figure 2 shown.

[0055] Step 2: Convert the satellite coverage time period into a switching directed graph G of civil aviation flights.

[0056] The nodes in the switching directed graph G represent the switching satellites that civil aviation flights may access during flight, and the edges represent the switching paths between satellites. Representing the switching satellites of civil aviation aircraft in the future as a directed graph can provide a mathematical model for optimizing switching decisions. Its implementation includes the following:

[0057] (2.1) Let G = {V, E} be the switching directed graph of civil aviation flights, where V represents the point set in the switching directed graph and E represents the edge set in the switching directed graph;

[0058] (2.2) For each satellite s in the satellite coverage set S c Transform to a node v in G c , v c ∈V;

[0059] In this example, Figure 2 Satellites s1…s7 are transformed into Figure 3 Nodes v1…v7 in

[0060] (2.3) Aircraft p is used as the virtual starting node v0 in the switching directed graph and added to the node set V;

[0061] In this example, Figure 3 A virtual starting node v0 is added to represent the aircraft p;

[0062] (2.4) The overlapping time of satellite coverage periods is converted into the edges of the switching directed graph. For any pair of satellites (s d ,s f ), if two satellites s d and f The coverage time meets If the condition is met, then in the switching directed graph G, satellite s is established d and f Corresponding node v d and v f The undirected edge e between df , and add edge set E;

[0063] For example, in Figure 2 The coverage start time of satellite s3 Less than the coverage end time of satellite s1 Satisfy the conditions Therefore Figure 3 In the example, we create an edge e between nodes v1 and v3. 13 ;

[0064] (2.5) Determine the direction of the edge between nodes in the switching directed graph. For any edge e df , find the satellite s whose two endpoints correspond to in the set S d and f :

[0065] like In In this case, the edge df Direction v d Point to v f ;exist In this case, df Direction v f Point to v d ;

[0066] For example, in Figure 2 The start time of coverage of satellite s1 and satellite s3 is different, that is, Because the initial coverage time of satellite s3 is greater than the initial coverage time of satellite s1, that is, Then edge e 13 The direction is from node v1 to node v3;

[0067] like In In this case, df Direction v d Point to v f ;exist In this case, df Direction v f Point to vd ;

[0068] For example, in Figure 2 The coverage start time of satellite s1 and satellite s2 is the same, that is, Because the coverage end time of satellite s2 is greater than the coverage end time of satellite s1, that is, Then edge e 12 The direction is from node v1 to node v2;

[0069] (2.6) In the switching directed graph, create a directed edge e between nodes v0 and v1. 01 , the direction is v0 pointing to v1, and the converted civil aviation flight switching directed graph is obtained, such as Figure 3 shown.

[0070] Step 3: Estimate the number of routing hops from the target switching satellite to the landing satellite.

[0071] Since the path delay of service transmission in the satellite network is most affected by the transmission distance, in the current typical low-orbit satellite network, the inter-satellite link distances between satellites are approximately the same, and the number of routing hops of the transmission path becomes the determining factor affecting the data transmission delay. Therefore, it is necessary to estimate the number of routing hops from the target switching satellite to the landing satellite. Its implementation includes the following:

[0072] (3.1) According to the low-orbit satellite network constellation topology, obtain the set of grounded satellites in the satellite network:

[0073] GW={g1,...,g j ,...,g m}

[0074] Among them, g j represents the jth landing satellite in the satellite network, j = 1, 2, ..., m, and m represents that there are m landing satellites in the satellite network;

[0075] (3.2) For any satellite s in the set S c , estimate the number of inter-satellite routing hops h(s) from the satellite to all the satellites in the satellite set GW. c ,g j ), we get the set H(s c ):

[0076] (3.2.1) Based on the direction of satellite movement, use the latitude of the satellite subsatellite point The target satellite s is calculated by the inclination angle θ of the satellite's orbit c and landing satellite j The phase angle u relative to the ascending node of the orbit:

[0077] When the satellite moves in ascending orbit,

[0078] When the satellite moves in descending orbit,

[0079] (3.2.2) Calculate the switching target satellite s according to the satellite movement direction c and landing satellite j The longitude difference ζ from the ascending node of the orbit:

[0080] When the satellite moves in ascending orbit, ζ=arctan(cosθtanu);

[0081] When the satellite moves in descending orbit, ζ=π+arctan(cosθtanu);

[0082] (3.2.3) According to the result of step (3.2.2), calculate the satellite s c With the landing satellite j The number of inter-orbit satellite routing hops h(s c ,g j ) h :

[0083]

[0084] Where Δλ represents s c With g j The longitude difference between c ) means s c The longitude difference between the ascending node and its orbit, ζ(g j ) represents g j The longitude difference between the ascending node and its orbit, ΔΩ, represents s c With g j The orbit angle difference, Round[] represents the rounding function;

[0085] (3.2.4) Based on the results of steps (3.2.1) and (3.2.3), calculate the satellite s c With the landing satellite j The number of satellite hops in the same orbit h(s c ,g j ) v :

[0086]

[0087] Among them, u c Indicates satellites c The phase angle relative to the ascending node of the orbit, u j Indicates the landing satellite g jThe phase angle relative to the ascending node of the orbit, Δf is the phase difference between adjacent orbital satellites caused by the phase factor, and ΔΦ represents the phase difference between adjacent satellites in the orbit;

[0088] (3.2.5) Estimate the value of each satellite s in the set S c The number of inter-satellite routing hops h(s) to all the landing satellites in the landing satellite set GW c ,g j ):

[0089] h(s c ,g j )=|h(s c ,g j ) h |+|h(s c ,g j ) v |;

[0090] (3.2.6) According to the result of step (3.2.5), we get satellite s c The inter-satellite routing hop count set H(s) to all the landing satellites in the landing satellite set GW c ):

[0091] H(s c )={h(s c ,g j )|g j ∈GW};

[0092] (3.3) For any satellite s in the set S c , select the set H(s c )The smallest h(s) c ,g j ) as the aircraft switches to satellites c The number of intersatellite routing hops for the subsequent service h c , and add it to the set H e middle:

[0093] H e ={h1,...,h c ,...,h l}

[0094] Wherein, c=1,2,...,l, l represents the number of satellites in the set S.

[0095] Step 4, calculate the initial communication elevation angle for the civil aircraft to access the target switching satellite.

[0096] The initial communication step angle of civil aircraft accessing the switching satellite will affect the quality of the communication link between the satellite and the switching satellite. If the initial communication step angle of the user accessing the switching satellite is large, the link communication quality is good; if the initial communication step angle of the user accessing the switching satellite is small, the link communication quality is poor. Therefore, the initial communication step angle needs to be included in the switching decision. The calculation formula is as follows:

[0097]

[0098] Among them, e c For aircraft p to access any satellite s in the set S c The initial communication angle e c , Indicates satellites c The longitude value of the subsatellite point, Indicates satellites c Latitude of the subsatellite point, LON p Indicates the longitude value of aircraft p, LAT p represents the latitude of the aircraft p, h represents the orbital height of the satellite, R e Represents the length of the Earth's radius.

[0099] Step 5: Calculate the switching weight of the switching directed graph edge using the routing hop count and the communication angle.

[0100] Traditional satellite switching algorithms usually only consider the initial communication angle of the terminal accessing the switching satellite when making switching decisions. In this example, when making switching decisions for civil aviation flights, the number of routing hops from the switching satellite to the landing satellite and the initial communication angle of the aircraft accessing the satellite are used as joint decision factors, which not only ensures the quality of the communication link between the aircraft and the switching satellite, but also reduces the transmission delay of the flight service. The switching weight calculation method of the switching directed graph edge is as follows:

[0101] (5.1) Calculate the switching of any edge e in the directed graph G df The switching weight cost d,f :

[0102]

[0103] Among them, h c Is the aircraft switching to satellites c The number of intersatellite routing hops for the subsequent service, h max With h min The set H e The maximum and minimum values ​​of all elements in e c Is the aircraft p access to the satellite s c The initial communication angle, e max With e minThey represent the maximum initial communication injection angle and the minimum initial communication injection angle of the satellite in the aircraft access set S, ω1 and ω2 represent the weight coefficients of the routing hops and the communication injection angle, respectively, which satisfy w1+w2=1. In this example, the values ​​of w1 and w2 are both 0.5;

[0104] (5.2) Substitute the switching weight cost calculated in step (5.1) d,f Mark it into the switching directed graph G, and get the updated switching directed graph G′, as Figure 4 shown.

[0105] Step 6: In the updated switching directed graph G′, use the Dijkstra algorithm to calculate the distance from the virtual initial node v0 to the last satellite node v in G′. l The shortest path is taken as the optimal switching path for aircraft p in time period T.

[0106] Existing shortest path algorithms for graphs include Dijkstra algorithm, Bellman-Ford algorithm, A * Algorithm and Floyd-Warshall algorithm. In this example, since the optimal path calculation of the switching directed graph is a single-source shortest path algorithm for a graph without negative edge weights, the Dijkstra algorithm is selected but not limited to perform the shortest path calculation of the switching directed graph. Its implementation includes the following:

[0107] (6.1) Initially, the nodes V in G′ are divided into two parts, namely the selected node set P and the remaining node set U. Suppose P only contains the source node v0, that is, P = {v0}; Suppose the remaining nodes except the source node v0 constitute U;

[0108] (6.2) Let the array d[v] be the shortest path length from node v0 to each node in the point set V. Initialize d[v0] = 0, indicating that the distance from node v0 to itself is 0; initialize d[v] = ∝, where v ≠ v0;

[0109] (6.3) Let the predecessor node array prev[v] be used to store the previous hop node of the shortest path from node v0 to each node in the point set V, and initialize prev[v] = None;

[0110] (6.4) Traverse all nodes v in set U f , if there is a path from node v0 to node v in G′ f The edge 0f , then update d[v f ]=cost 0,f , update prev[v f ]=v0; otherwise, d[v] and prev[v] are not updated;

[0111] (6.5) Select from the set U that satisfies the condition The node v t and compare it with the satellite node v l For comparison:

[0112] If v t =v l , it means find the path from node v0 to node v l The shortest path, execute step (6.7);

[0113] Otherwise, node v t Remove it from set U and add it to set P to obtain the current updated sets U and P, and execute step (6.6);

[0114] (6.6) Traverse all nodes v in the currently updated set U f , if there is a node v in G′ t To node v f The edge tf , and node v0 to node v f The distance d[v f ] satisfies the formula d[v f ]<d[v t ]+cost t,f , then update d[v f ]=d[v t ]+cost t,f , update prev[v f ]=v t , otherwise, do not update d[v] and prev[v], and return to step (6.5);

[0115] (6.7) Using the predecessor node array prev[v] from prev[v l ] Backtracking backwards, get node v0 to node v l The shortest path path.

[0116] In this example, Figure 4 In the updated switching directed graph G′, the Dijkstra algorithm is used to calculate the optimal switching path from the virtual starting node v0 to the last node v7, and the calculation result is s0→s2→s4→s5→s7.

[0117] Embodiment 2: Low-orbit satellite network switching system for civil aviation transportation.

[0118] Reference Figure 5 The system described in this example includes a data management module 1, a satellite coverage and data calculation module 2, a switching directed graph generation module 3, and a switching path calculation and delivery module 4. Its working principle is as follows:

[0119] The data management module 1 obtains the satellite real-time topology information including the real-time position of each satellite and the start and end time of the satellite coverage of the geographic grid and the civil aviation flight route information including the real-time position information of the flight and the flight speed and direction, and sends it to the satellite coverage and data calculation module 2; the satellite coverage and data calculation module 2 calculates the satellite coverage time period of the civil aviation flight, the number of routing hops from the target switching satellite to the landing satellite, and the communication angle of the civil aviation aircraft accessing the target switching satellite according to the satellite real-time topology information and the civil aviation flight route information sent by the data management module, and sends the calculation results to the switching directed graph generation module 3; The switching directed graph generation module 3 generates a switching directed graph of civil aviation flights according to the coverage time period of the satellite to the civil aviation flights sent by the satellite coverage and data calculation module, calculates the switching weights of the edges in the switching directed graph according to the number of routing hops from the target switching satellite to the landing satellite and the communication angle of the civil aircraft accessing the target switching satellite sent by the satellite coverage and data calculation module, and sends the generated switching directed graph to the switching path calculation and sending module 4; the switching path calculation and sending module 4 calculates the optimal switching path of the civil aviation flight according to the civil aviation flight switching directed graph sent by the switching directed graph generation module, and sends it to the corresponding switching target satellite.

[0120] The above descriptions are only two specific examples of the present invention and do not constitute any limitation to the present invention. Obviously, for professionals in this field, after understanding the content and principles of the present invention, it is possible to make various modifications and changes in form and details without departing from the principles and structures of the present invention. However, these modifications and changes based on the ideas of the present invention are still within the scope of protection of the claims of the present invention.

[0121] It should be noted that the step numbers in the specification and claims of the present invention are only for a clear description of the implementation scheme of the present invention to facilitate understanding, and the order of the step numbers is not limited.

Claims

1. A low-orbit satellite network switching method for civil aviation traffic, characterized in that: include: Predict the satellite coverage period for civil aviation flights within a set time period based on satellite topology and the predictability of civil aviation flight routes; The satellite coverage time period is converted into a switching directed graph G of civil aviation flights, which includes a node V in the directed graph and an overlapping time of the coverage satellite period is converted into an edge E of the switching directed graph; Estimate the number of routing hops h from the target switching satellite to the landing satellite c , calculate the communication angle e of the civil aircraft accessing the target switching satellite c , and use the routing hop count and communication angle to calculate the switching of any edge e in the directed graph df The switching weight cos t d,f , get the updated switching directed graph G′; In the updated switching directed graph G′, according to the switching weight cos t d,f ,The shortest path algorithm is used to calculate the optimal switching path of civil aviation flights.

2. The method according to claim 1, characterized in that: The method of predicting the satellite coverage period of civil aviation flights within a set time period based on the satellite topology and the predictability of civil aviation flight routes includes: 2a) Divide the time period T into n consecutive time slots, where T = (τ1, ..., τ k ,...,τ n ), τ k is the kth time slot, k∈[1,n]; 2b) According to the number of satellite orbits of the low-orbit satellite network O n 、Number of satellites in a single orbit S n And the minimum number of satellite coverage N for each geographic grid sat Divide the global surface area into N a Geo rasters: The longitude and latitude of each geographic grid center point are and λ i ,i=1,2,...,N a ; 2c) According to the flight trajectory of aircraft p, predict the geographic grid set A to which the aircraft belongs in n consecutive time slots = (a1, ..., a k ,...,a n ), where a k For the aircraft at τ k The geographic grid of time slots, 1≤a k ≤N a ; 2d) According to the predicted information of satellite network topology, obtain the aircraft at any time slot τ k Geographic grid a k The coverage satellites of the aircraft are sorted according to the coverage satellites, and the coverage satellite set S of the aircraft in time period T is obtained: S={s1,s2,…,s c ,…,s l } Among them, s c represents the cth satellite covering the aircraft in the time period T, c = 1, 2, ..., l, l represents the number of satellites covering the aircraft in the time period T; Each coverage satellite in the set S corresponds to a coverage period represents the starting time when the cth covering satellite in the set S covers the aircraft p, represents the end time of coverage of aircraft p by the cth covering satellite in the set S; 2e) According to the coverage period of each satellite in the set S Generate a time period diagram of satellite coverage of civil aviation flights within time period T.

3. The method according to claim 1, characterized in that: The switching directed graph for converting the satellite coverage time period into a civil aviation flight comprises: 3a) Let G = {V, E} be the switching directed graph of civil aviation flights, where V represents the point set in the switching directed graph and E represents the edge set in the switching directed graph; 3b) Cover each satellite s in the satellite coverage set S c Transform to a node v in G c , v c ∈V; 3c) Take aircraft p as the virtual starting node v0 in the switching directed graph and add it to the node set V; 3d) Convert the overlapping time of satellite coverage periods into the edges of a switching directed graph. For any pair of satellites (s d ,s f ), if two satellites s d and f The coverage time meets If the condition is met, then in the switching directed graph G, satellite s is established d and f Corresponding node v d and v f The undirected edge e between df , and add edge set E; 3e) Determine the direction of the edge between nodes in the switching directed graph. For any edge e df , find the satellite s whose two endpoints correspond to in the set S d and f : like In In this case, the edge df Direction v d Point to v f ;exist In this case, df Direction v f Point to v d ; like In In this case, df Direction v d Point to v f ;exist In this case, df Direction v f Point to v d ; 3f) In the switch directed graph, create a directed edge e between nodes v0 and v1 01 , the direction is v0 pointing to v1, and the converted civil aviation flight switching directed graph is obtained.

4. The method according to claim 1, characterized in that: The estimating the number of route hops from the target switching satellite to the landing satellite comprises: 4a) According to the low-orbit satellite network constellation topology, obtain the set of grounded satellites GW in the satellite network: GW{g1,...,g j ,...,g m }} Among them, g j represents the jth landing satellite in the satellite network, j = 1, 2, ..., m, and m represents that there are m landing satellites in the satellite network; 4b) For any satellite s in the set S c , estimate the number of inter-satellite routing hops h(s) from the satellite to all the satellites in the satellite set GW. c ,g j ), we get the set H(s c ): H(s c )={h(s c ,g j )|g j ∈GW}; 4c) For any satellite s in the set S c , select the set H(s c )The smallest h(s) c ,g j ) as the aircraft switches to satellites c The number of intersatellite routing hops for the subsequent service h c , and add it to the set H e middle: H e ={h1,...,h c ,...,h l } Wherein, c=1,2,...,l, l represents the number of satellites in the set S.

5. The method according to claim 4, characterized in that: In 4b), for any satellite s in the set S c , estimate the number of inter-satellite routing hops h(s) from the satellite to all the satellites in the satellite set GW. c ,g j ), which includes: (4b1) Based on the direction of satellite motion, use the latitude of the satellite subsatellite point The target satellite s is calculated by the inclination angle θ of the satellite's orbit c and landing satellite j The phase angle u relative to the ascending node of the orbit: When the satellite moves in ascending orbit, When the satellite moves in descending orbit, (4b2) Calculate the switching target satellite s according to the satellite movement direction c and landing satellite j The longitude difference ζ from the ascending node of the orbit: When the satellite moves in ascending orbit, ζ=arctan(cosθtanu); When the satellite moves in descending orbit, ζ=π+arctan(cosθtanu); (4b3) Based on the result of step (4b2), calculate the satellite s c With the landing satellite j The number of inter-orbit satellite routing hops h(s c ,g j ) h : Where Δλ represents s c With g j The longitude difference between c ) means s c The longitude difference between the ascending node and its orbit, ζ(g j ) represents g j The longitude difference between the ascending node and its orbit, ΔΩ, represents s c With g j The orbit angle difference, Round[] represents the rounding function; (4b4) Based on the results of steps (4b1) and (4b3), calculate the satellite s c With the landing satellite j The number of satellite hops in the same orbit h(s c ,g j ) v : Among them, u c Indicates satellites c The phase angle relative to the ascending node of the orbit, u j Indicates the landing satellite g j The phase angle relative to the ascending node of the orbit, Δf is the phase difference between adjacent orbital satellites caused by the phase factor, and ΔΦ represents the phase difference between adjacent satellites in the orbit; (4b5) Estimate the value of each satellite s in the set S c The number of inter-satellite routing hops h(s) to all the landing satellites in the landing satellite set GW c ,g j ): h(s c ,g j )=|h(s c ,g j ) h |+|h(s c ,g j ) v | 6. The method according to claim 1, characterized in that: The formula for calculating the initial communication elevation angle of the civil aircraft accessing the target switching satellite is as follows: Among them, e c For aircraft p to access any satellite s in the set S c The initial communication angle e c , Indicates satellites c The longitude value of the subsatellite point, Indicates satellites c Latitude of the subsatellite point, LON p Indicates the longitude value of aircraft p, LAT p represents the latitude of the aircraft p, h represents the orbital height of the satellite, R e Represents the length of the Earth's radius.

7. The method according to claim 1, characterized in that: The method of calculating the switching weight of the switching directed graph edge by using the routing hop count and the communication angle includes: 7a) Calculate the switching of any edge e in the directed graph G df The switching weight cos t d,c : Among them, h c Is the aircraft switching to satellites c The number of intersatellite routing hops for the subsequent service, h max With h min The set H e The maximum and minimum values ​​of all elements in e c Is the aircraft p access to the satellite s c The initial communication angle, e max With e min They represent the maximum initial communication bend angle and the minimum initial communication bend angle of the satellite in the aircraft access set S, ω1 and ω2 represent the weight coefficients of the routing hops and the communication bend angle, respectively, satisfying ω1+ω2=1; 7b) Substitute the switching weight cos t calculated in step 7a) d,f The mark is added to the switching directed graph G to obtain the updated switching directed graph G′.

8. The method according to claim 1, characterized in that: The shortest path algorithm is used to calculate the optimal switching path of civil aviation flights. In the updated switching directed graph G′, the Dijkstra algorithm is used to calculate the path from the virtual initial node v0 to the last satellite node v in G′. l The shortest path is taken as the optimal switching path for aircraft p in time period T.

9. The method according to claim 8, characterized in that: The Dijkstra algorithm is used to calculate the distance from the virtual initial node v0 to the last satellite node v in G′. l The shortest path includes: 8a) Initially, the nodes V in G′ are divided into two parts, namely the selected node set P and the remaining node set U. Suppose P only contains the source node v0, that is, P = {v0}; Suppose the remaining nodes except the source node v0 constitute U; 8b) Let array d[v] be the shortest path length from node v0 to each node in the point set V, initialize d[v0] = 0, indicating that the distance from node v0 to itself is 0; initialize d[v] = ∞, where v≠v0; 8c) Let the predecessor node array prev[v] be used to store the previous hop node of the shortest path from node v0 to each node in the point set V, and initialize prev[v] = None; 8d) Traverse all nodes v in set U f , if there exists a node v0 to node v in G′ f The edge 0f , then update d[v f ]=cost 0,f , update prev[v f ] = v0; 8e) Select from the set U that meets the condition The node v t and compare it with the satellite node v l For comparison: If v t =v l , it means find the path from node v0 to node v l Shortest path, execute step 8g); Otherwise, node v t Remove it from the set U and add it to the set P, and execute step 8f); 8f) Traverse all nodes v in set U f , if there is a node v in G′ t To node v f The edge tf , and node v0 to node v f The distance d[v f ] satisfies the formula d[v f ]<d[v t ]+cost t,f , then update d[v f ]=d[v t ]+cost t,f , update prev[v f ]=v t , return to step 8e); 8g) Use the predecessor node array prev[v] from prev[v l ] Backtracking backwards, get node v0 to node v l The shortest path path.

10. A low-orbit satellite network switching system for civil aviation transportation, characterized in that: include: The data management module is used to obtain the real-time satellite topology information and the route information of civil aviation flights. The real-time satellite topology information includes the real-time position information of each satellite and the start and end time of the satellite's coverage of the geographic grid; the route information of civil aviation flights includes the real-time position information of the flight and the flight speed and direction; The satellite coverage and data calculation module is used to calculate the satellite coverage time period for civil aviation flights, the number of route hops from the target switching satellite to the landing satellite, and the communication angle of civil aviation aircraft accessing the target switching satellite based on the real-time satellite topology information and the route information of civil aviation flights output by the data management module; A switching directed graph generation module is used to generate a switching directed graph of civil aviation flights according to the coverage time period of the satellite to the civil aviation flights output by the satellite coverage and data calculation module, and calculate the switching weight of the edge in the switching directed graph by using the number of route hops from the target switching satellite to the landing satellite and the communication angle of the civil aviation aircraft accessing the target switching satellite; The switching path calculation and sending module is used to calculate the optimal switching path of the civil aviation flight according to the civil aviation flight switching directed graph output by the switching directed graph generation module, and send it to the corresponding switching target satellite.

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