CN113114336A

CN113114336A - Method and device for determining switching threshold in low-earth-orbit satellite communication network

Info

Publication number: CN113114336A
Application number: CN202110297540.0A
Authority: CN
Inventors: 林文亮; 邓中亮; 王珂; 贺轶烈; 于晓艺; 刘浩; 樊亮亮; 谷磊; 李中国; 孔祥灃
Original assignee: Beijing University of Posts and Telecommunications
Current assignee: Beijing University of Posts and Telecommunications
Priority date: 2021-03-19
Filing date: 2021-03-19
Publication date: 2021-07-13
Anticipated expiration: 2041-03-19
Also published as: CN113114336B

Abstract

The embodiment of the invention provides a method and a device for determining a switching threshold in a low earth orbit satellite communication network, which are applied to the technical field of communication and can comprise the following steps: determining a plurality of influence factors which can influence a handover threshold in a low-orbit satellite communication network; constructing a relation graph corresponding to a plurality of influence factors; respectively taking an influence factor as a variable node, adding a switching variable node corresponding to a switching threshold in a relation graph, and establishing an incidence relation between the variable node directly related to the switching variable node and the switching variable node; determining factor nodes of the variable nodes aiming at each variable node, wherein the factor nodes are used for representing the influence degree of the variable nodes on the nodes with the incidence relation with the variable nodes; adding factor nodes in the relation graph to obtain a factor graph corresponding to a plurality of influence factors; and determining the optimal state variable estimation value based on the factor graph, and taking the optimal state variable estimation value as a switching threshold. The accuracy of determining the switching threshold can be improved.

Description

Method and device for determining switching threshold in low-earth-orbit satellite communication network

Technical Field

The invention relates to the technical field of communication, in particular to a method and a device for determining a switching threshold in low-earth-orbit satellite communication.

Background

The fifth Generation mobile communication technology (5th-Generation, 5G) has solved the problem of large bandwidth, low latency, high reliability, and high concurrency of information interaction, and one of the important research points of the sixth Generation mobile communication technology (6th-Generation, 6G) is how to extend such high performance communication capability from local to the full space, such as the earth surface and the air. Because base stations cannot be built in the air, the ocean, the desert, the forest and the like or the cost of building the base stations is too high, the adoption of the satellite is an important way for realizing efficient communication in the area under the coverage of the base stations. While low earth orbit satellite communications are an important element of enabling communications via satellites.

In the low earth orbit satellite communication network, a multi-satellite global coverage and single-satellite multi-beam multiplexing mode is adopted, so that a ground surface user can keep continuous communication by switching between satellites and beams with a satellite internet. For example, at time 1, a user node (a node used by a surface user) accesses a satellite node 1, and the satellite node 1 provides service for the user node; at time 2, the user node is not within the service range of the satellite node 1, or the service quality provided by the satellite node 1 for the user node 1 is poor, and the like, at this time, the satellite node accessed by the user node needs to be switched, that is, the satellite node providing service for the user node is switched, for example, the satellite node accessed by the user node is switched from the satellite node 1 to the satellite node 2, and the satellite node 2 provides service for the user node. The satellite node may provide a service to the user node by transmitting a beam, which may be understood as switching a beam accessed by the user node, that is, switching a beam providing a service to the user node.

And in the process of switching, switching is carried out according to the switching threshold, and if the switching threshold is met, switching is carried out. It will be appreciated that the handover threshold represents a handover threshold for a satellite node or beam accessed by the user node.

In the existing mode, power can be used as a decision threshold, a user node measures a signal transmitted by a satellite node, and switching decision is carried out according to the strength of the signal power. However, the power distribution from the beam to the ground of the low earth orbit satellite communication network is uniform, the power difference from the center of the beam to the edge of the beam is about 3dB, and if the power is used as a decision threshold, the false switching is easily caused.

Disclosure of Invention

The embodiment of the invention aims to provide a method and a device for determining a switching threshold in a low-earth-orbit satellite communication network, so as to improve the accuracy of determining the switching threshold. The specific technical scheme is as follows:

in a first aspect, an embodiment of the present invention provides a method for determining a handover threshold in a low earth orbit satellite communication network, including:

determining a plurality of influence factors which can influence a handover threshold in a low-orbit satellite communication network;

constructing a relation graph corresponding to a plurality of influence factors, wherein the relation graph comprises an incidence relation existing in the plurality of influence factors;

respectively taking an influence factor as a variable node, adding a switching variable node corresponding to a switching threshold in the relation graph, and establishing an association relation between the variable node directly related to the switching variable node and the switching variable node;

determining factor nodes of the variable nodes aiming at each variable node, wherein the factor nodes are used for representing the influence degree of the variable nodes on the nodes with the incidence relation with the variable nodes;

adding the factor nodes in the relation graph to obtain a factor graph corresponding to a plurality of influence factors;

and determining the optimal state variable estimation value based on the factor graph, and taking the optimal state variable estimation value as a switching threshold.

Optionally, the method further includes:

for each variable node, determining the direct access degree of the variable node and a switching variable node, wherein the direct access degree represents the cascade relation of the access degrees of the variable node and other nodes and the access degree weighted sum taking the variable node as a factor cluster center;

sorting the direct access degree of each variable node, grading each variable node according to a sorting result, and determining an associated weight corresponding to each variable node according to the graded grades;

determining tensor combinations based on the association relationship among the variable nodes, the association relationship between the variable nodes directly associated with the switched variable nodes and the switched variable nodes, and the association weight corresponding to each variable node;

and when the influence factors corresponding to one or more variable nodes in each variable node change, updating the tensor combination based on the changed influence factors, and if the closeness degree of the updated tensor combination and the tensor combination before updating is lower than the preset closeness degree, reconstructing a factor graph.

Optionally, the determining a tensor combination based on an association relationship among the variable nodes, an association relationship between the variable node having an association relationship directly with the switched variable node and the switched variable node, and an association weight corresponding to each variable node includes:

taking the variable nodes in association relation with the switching variable nodes and the association relation of the switching variable nodes as basis vectors in the tensor, and taking the association weights corresponding to the variable nodes in association relation with the switching variable nodes as components on the corresponding basis vectors respectively; and taking the association relation existing among the variable nodes as an auxiliary vector in the tensor, and respectively determining the components on the corresponding auxiliary vector based on the association weight corresponding to the variable nodes to obtain the tensor combination.

Optionally, after determining the direct access degree between the variable node and the switching variable node, the method further includes:

taking the variable node with the direct access degree larger than a preset threshold value as a passive protection node;

if the proximity degree of the updated tensor combination and the tensor combination before updating is lower than the preset proximity degree, reconstructing a factor graph, including:

and traversing all the passive protection nodes in sequence, and if the proximity degree of the updated tensor combination corresponding to one passive protection node and the tensor combination before updating is lower than the preset proximity, reconstructing a factor graph.

Optionally, for a passive protection node, determining a tensor combination based on an association relationship existing between variable nodes, an association relationship existing between a variable node directly having an association relationship with the switched variable node and the switched variable node, and an association weight corresponding to each variable node includes:

taking the association relation between the passive protection node having the association relation with the switching variable node and the switching variable node as a basis vector in a tensor, and taking the association weight corresponding to the passive protection node having the association relation directly with the switching variable node as a component on the corresponding basis vector to obtain a tensor combination;

updating the tensor combination based on the changed influence factors comprises the following steps:

and re-determining the basis vectors and the components corresponding to the passive protection nodes based on the changed influence factors to obtain the updated update tensor combination.

Optionally, the reconstruction factor graph includes:

exchanging the incidence relation between the passive protection node and the switching variable node with the incidence relation between the lower variable node and the switching transformation node;

calculating the combination of the exchanged base vectors and the components corresponding to the base vectors to obtain a new tensor combination;

if the closeness degree between the new tensor combination and the old tensor combination is higher than the preset closeness degree, the association relationship exchange between the base vector and the lower variable node is continued until the closeness degree between the new tensor combination and the old tensor combination is higher than the preset closeness degree, the exchange is stopped, and the association relationship between the variable nodes when the exchange is stopped and the association relationship between the variable nodes and the switching variable node are used as a reconstruction relationship graph;

and obtaining a reconstruction factor graph based on the reconstruction relation graph.

Optionally, the determining an optimal estimated value of the state variable based on the factor graph includes:

based on the factor graph, by formula X^MAP＝argmax[Φ(X)]＝argmaxΠ_i[Φ_i(X_j)]Determining the optimal estimated value of the state variable;

wherein, X^MAPFor the optimum estimated value of the state variable, phi (X) is pi_i[Φ_i(X_j)]I represents the number of factor nodes in the factor graph, j represents the number of variable nodes in the factor graph,

h_i(X_j) Representing the value of the measurement function, z_iRepresenting the actual measurement.

Optionally, the Φ (X) includes a first factor node f (X) of the variable node directly associated with the switching variable node_k1) And a second factor node g (X) of a variable node generating an association relation with other variable nodes_k2)；

For each variable node, determining a factor node of the variable node includes:

for the variable nodes directly associated with the switching variable nodes, the formula f (X) is used_k1)＝L(Z_k1-h(X_k1) Determining a first factor node of a variable node directly associated with the switching variable node;

wherein, f (X)_k1) Is a first factor node, X, of a variable node directly associated with said switched variable node_k1Is an estimate of the handover threshold, h (X)_k1) Is a measurement function, Z, obtained based on the fitting of variable nodes having direct association with the switched variable nodes_k1Is the actual measurement value of the influencing factor k1 corresponding to the variable node directly having the incidence relation with the switching variable node, and L (-) is a cost function;

for variable nodes generating incidence relation to other variable nodes, the formula g (X) is used_k2)＝d(Z_k2-h(X_k2) Determining a second factor node of the variable nodes generating incidence relation to other variable nodes;

wherein g (X)_k2) Second factor nodes, X, of variable nodes for generating associations to other variable nodes_k2Is an estimate of a variable node that generates an association relationship with other variable nodes, h (X)_k2) Is based on a measurement function, Z, of variable nodes which generates an association relationship with other variable nodes_k2Is the actual measurement value of the influencing factor k2 corresponding to the variable node generating the association relation with other variable nodes, and d (-) is the cost function.

Optionally, the influencing factors include orbit, satellite, bias, atmospheric attenuation, channel, topography, location, doppler multipath, traffic, user, relative distance, and relative position.

In a second aspect, an embodiment of the present invention provides an apparatus for determining a handover threshold in a low earth orbit satellite communication network, including:

the system comprises a first determining module, a second determining module and a switching module, wherein the first determining module is used for determining a plurality of influence factors which can influence a switching threshold in a low-orbit satellite communication network;

the construction module is used for constructing a relationship graph corresponding to a plurality of influence factors, and the relationship graph comprises an incidence relation existing in the plurality of influence factors;

a first adding module, configured to take an influence factor as a variable node, and add a switching variable node corresponding to a switching threshold in the relationship graph;

the establishment module is used for establishing an incidence relation between variable nodes directly related to the switching variable nodes and the switching variable nodes;

the second determining module is used for determining factor nodes of the variable nodes aiming at each variable node, and the factor nodes are used for representing the influence degree of the variable nodes on the nodes with the incidence relation with the variable nodes;

a second adding module, configured to add the factor node in the relationship graph to obtain a factor graph corresponding to a plurality of influence factors;

and the third determining module is used for determining the optimal state variable estimation value based on the factor graph and taking the optimal state variable estimation value as a switching threshold.

Optionally, the apparatus further comprises:

the fourth determining module is used for determining direct access degrees of the variable nodes and the switching variable nodes aiming at each variable node, wherein the direct access degrees represent the cascade relation of the access degrees of the variable nodes and other nodes and the access degree weighted sum taking the variable nodes as the factor cluster center;

the classification module is used for sequencing the direct access degree of each variable node, classifying each variable node according to a sequencing result, and determining the associated weight corresponding to each variable node according to the classified grade;

a fifth determining module, configured to determine a tensor combination based on an association relationship existing among the variable nodes, an association relationship existing between the variable node having an association relationship directly with the switched variable node and the switched variable node, and an association weight corresponding to each variable node;

the updating module is used for updating the tensor combination based on the changed influence factors when the influence factors corresponding to one or more variable nodes in each variable node change;

and the reconstruction module is used for reconstructing the factor graph if the closeness degree of the updated tensor combination and the tensor combination before updating is lower than the preset closeness degree.

Optionally, the fifth determining module is specifically configured to use an association relationship between a variable node having an association relationship with a switching variable node and the switching variable node as a basis vector in a tensor, and use association weights corresponding to the variable nodes having an association relationship with the switching variable node as components on corresponding basis vectors respectively; and taking the association relation existing among the variable nodes as an auxiliary vector in the tensor, and respectively determining the components on the corresponding auxiliary vector based on the association weight corresponding to the variable nodes to obtain the tensor combination.

Optionally, the reconfiguration module is specifically configured to, after determining a direct access degree between the variable node and the switching variable node, use the variable node whose direct access degree is greater than a preset threshold as a passive protection node; and traversing all the passive protection nodes in sequence, and if the proximity degree of the updated tensor combination corresponding to one passive protection node and the tensor combination before updating is lower than the preset proximity, reconstructing a factor graph.

The embodiment of the invention also provides electronic equipment which comprises a processor, a communication interface, a memory and a communication bus, wherein the processor, the communication interface and the memory are communicated with each other through the communication bus.

A memory for storing a computer program;

a processor, configured to implement the method steps of the first aspect in the foregoing embodiments when executing a program stored in the memory.

In yet another aspect of the present invention, there is also provided a computer-readable storage medium having stored therein a computer program which, when executed by a processor, implements the method steps of the first aspect described above.

In a further aspect of the present invention, there is also provided a computer program product comprising instructions which, when run on a computer, cause the computer to perform the method steps of the first aspect described above.

The embodiment of the invention has the following beneficial effects:

the method and the device for determining the switching threshold in the low-orbit satellite communication network can determine a plurality of influence factors which can influence the switching threshold in the low-orbit satellite communication network; constructing a relation graph corresponding to the plurality of influence factors, wherein the relation graph comprises an incidence relation existing in the plurality of influence factors; respectively taking an influence factor as a variable node, adding a switching variable node corresponding to a switching threshold in a relation graph, and establishing an incidence relation between the variable node directly related to the switching variable node and the switching variable node; determining factor nodes of the variable nodes aiming at each variable node, wherein the factor nodes are used for representing the influence degree of the variable nodes on the nodes with the incidence relation with the variable nodes; adding factor nodes in the relation graph to obtain a factor graph corresponding to a plurality of influence factors; and determining the optimal state variable estimation value based on the factor graph, and taking the optimal state variable estimation value as a switching threshold. In the embodiment of the invention, a plurality of influence factors which can influence the switching threshold in the low-orbit satellite communication network are considered, different mutual relations exist among the multi-level and multi-factor factors, a multi-level and multi-factor switching threshold factor graph is constructed, an important basis is provided for accurately analyzing the multi-level and multi-factor, and the accuracy of determining the switching threshold can be improved based on variable nodes corresponding to the plurality of influence factors and the factor graph constructed by switching the variable nodes.

Of course, not all of the above advantages need be achieved in the practice of any one product or method of the present invention.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art that other embodiments can be obtained by using the drawings without creative efforts.

Fig. 1 is a flowchart of a method for determining a handover threshold in a low earth orbit satellite communication network according to an embodiment of the present invention;

FIG. 2 is a diagram illustrating handover threshold factor relationships in an embodiment of the present invention;

FIG. 3 is a schematic diagram of a relationship graph constructed in an embodiment of the invention;

FIG. 4 is a diagram illustrating a factor graph reconstruction process according to an embodiment of the present invention;

FIG. 5 is another schematic diagram of the factor graph reconstruction process according to the embodiment of the present invention;

fig. 6 is another flowchart of a method for determining a handover threshold in a low earth orbit satellite communication network according to an embodiment of the present invention;

FIG. 7 is a diagram illustrating a reconstructed factor graph according to an embodiment of the present invention;

fig. 8 is a schematic structural diagram of an apparatus for determining a handover threshold in a low-earth orbit satellite communication network according to an embodiment of the present invention;

fig. 9 is a schematic structural diagram of an apparatus for determining a handover threshold in a low-earth orbit satellite communication network according to an embodiment of the present invention;

fig. 10 is a schematic structural diagram of an electronic device according to an embodiment of the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived from the embodiments given herein by one of ordinary skill in the art, are within the scope of the invention.

And a single factor is used as a switching judgment threshold, and the terminal judges whether the terminal is kept in the original network or switched to another network according to the relative change of the value of a certain factor in different signal sources. In a low-orbit satellite scene, the difference of signal power distribution in a wave beam is small, and only power is adopted as a judgment threshold, so that frequent switching processing and error switching are easily caused; only ephemeris is used as a decision threshold, and the method cannot adapt to signal changes of cities and the like due to complex shielding of the earth surface environment, and is easy to cause switching delay and call drop; only the channel quality is adopted as a decision threshold, complex signal processing is needed to calculate the channel quality condition, the complexity is high, and the processing is delayed. Therefore, the switching decision threshold of single factor is not suitable for the development requirement of the low orbit satellite internet.

Unlike high orbit satellites, the relative movement speed between a satellite node and a user node of a low orbit satellite communication network is high, and therefore switching is frequent. Secondly, the power distribution from the wave beam of the low earth orbit satellite internet to the ground is uniform, the power difference from the center of the wave beam to the edge of the wave beam is about 3dB generally, and if the power is adopted as a judgment threshold, the false switching is easy to cause, or the switching fails due to the switching delay. In fact, the handover factors affecting the low earth orbit satellite communication network are complex and various, including the received power of the signal reaching the ground, the relative position of the satellite and the user terminal, the environment of the user terminal, and so on, wherein each factor includes a plurality of correlation factors, and the correlation relationships among the correlation factors are aliased and staggered. Rapid position changes will cause drastic changes in the correlation factors and relationships that rely on the above factors to construct the switching threshold. If the low-orbit satellite internet switching influence factors and the mutual relation of the low-orbit satellite internet switching influence factors can be accurately described, the low-orbit satellite internet switching threshold model is constructed, and the satellite internet switching efficiency can be effectively improved.

The embodiment of the invention considers a plurality of influence factors influencing switching in a low-orbit satellite communication network, constructs a factor graph based on the plurality of influence factors and determines the switching threshold based on the factor graph. And representing the relation of each influence factor and the relation of the influence factors and the switching threshold through a factor graph, and determining the switching threshold. Therefore, the accuracy of determining the switching threshold can be improved. In addition, considering that the relative movement speed between the satellite node and the user node in the low-orbit satellite communication network is high, the switching is frequent, and the node is possible to change rapidly, the embodiment of the invention can reconstruct the factor graph rapidly based on the change, and further determine the switching threshold rapidly based on the change.

On one hand, the embodiment of the invention can solve the problems of multiple influence factors and multiple layers of switching thresholds under the low-orbit satellite internet and the determination of the switching thresholds under the condition of rapid change of the factors. The invention constructs the switching threshold factor graph of the multi-level and multi-factor by introducing the factor graph, and provides an important basis for accurately analyzing the multi-level and multi-factor.

On the other hand, the terminal, such as the relative state change of the user node and the satellite node is large, the difference of the influence factors is large under different scenes, and a switching threshold factor graph constructed according to the characteristics of a certain scene is not suitable for a new scene because a certain factor changes rapidly under another scene. For example, when the terminal rapidly enters a heavily-shaded space from an open place in an emergency scene, the decision threshold needs to be rapidly switched from a factor graph with the terminal position as a main factor graph to a factor graph with the channel state as a main factor graph. The invention describes the factor weight relation of the switching threshold through a tensor theory and carries out rapid reconstruction on the factor graph of the switching threshold under the factor association mutation.

The method for determining the handover threshold in the low earth orbit satellite communication network provided by the embodiment of the invention is explained in detail below.

The embodiment of the invention provides a method for determining a switching threshold in a low earth orbit satellite communication network, which comprises the following steps:

constructing a relation graph corresponding to the plurality of influence factors, wherein the relation graph comprises an incidence relation existing in the plurality of influence factors;

respectively taking an influence factor as a variable node, adding a switching variable node corresponding to a switching threshold in a relation graph, and establishing an incidence relation between the variable node directly related to the switching variable node and the switching variable node;

adding factor nodes in the relation graph to obtain a factor graph corresponding to a plurality of influence factors;

In the embodiment of the invention, a plurality of influence factors which can influence the switching threshold in the low-orbit satellite communication network are considered, different mutual relations exist among the multi-level and multi-factor factors, a multi-level and multi-factor switching threshold factor graph is constructed, an important basis is provided for accurately analyzing the multi-level and multi-factor, and the accuracy of determining the switching threshold can be improved based on variable nodes corresponding to the plurality of influence factors and the factor graph constructed by switching the variable nodes.

Fig. 1 is a flowchart of a method for determining a handover threshold in a low earth orbit satellite communication network according to an embodiment of the present invention. Referring to fig. 1, may include:

s101, determining a plurality of influence factors which can influence a handover threshold in a low-orbit satellite communication network.

The influencing factors may include orbit, orbital, satellite, bias, atmospheric attenuation, channel, terrain, location, doppler multipath, traffic, user, relative distance, relative location, and the like.

The plurality of influencing factors influencing the handover threshold may also be understood as influencing factors influencing the handover procedure in the low earth orbit satellite communication network.

And S102, constructing a corresponding relation graph of a plurality of influence factors.

The relationship graph includes an associative relationship existing among a plurality of influencing factors.

When a new relational graph is created, the incidence relation needs to be established among all the influencing factors.

Fig. 2 is a description diagram of handover threshold factor relationship, and a corresponding relationship diagram is constructed in combination with fig. 2.

Based on the above-mentioned multiple influence factors, each factor node expands outward, finds a node directly related to it and establishes an association relationship, and the constructed relationship graph is shown in fig. 3.

The blocks in fig. 3 indicate the influencing factors to be considered in the determination process of the handover threshold in the low earth orbit satellite communication network, and the arrow indicates the influence relationship between one influencing factor and another influencing factor.

The respective influencing factors are defined as follows: relative distance node is represented by variable V_distanceRepresenting the relative position node by a vector V_locations＝[P_longitude1，P_longitude2，P_latitude1，P_latitude2，P_height]Representing the position node by a vector V_location＝[P_longitude1，P_latitude1]Representing the landform node by V_land＝[P_land，P_feature]Indicating that the Doppler multipath node is represented by V_fading＝[P_doppler，P_multipath]Indicating that the user node is V_user＝[P_longitude1，P_latitude1，P_traffic]Indicating that the service node is represented by V_trafficThe satellite nodes are represented by vectors V_satellite＝[P_offset，P_orbit，P_position]Deviation node by vector V_offsetIndicating that the rail position node is formed by vector V_positionRepresenting the orbital nodes by vectors V_orbitRepresenting the channel node by a vector V_channel＝[P_doppler，P_multipath，P_estimate，P_distance]Indicating that atmospheric attenuation is represented by vector V_decayIndicating that the CSI (Channel State Information) node is represented by vector V_csiAnd (4) showing.

Wherein, P_longitude1And P_latitude1Longitude and latitude information, P, respectively representing the location of the mobile terminal_longitude2、P_latitude2And P_heightRespectively representing longitude, latitude and altitude information of the satellite terminal; p_featureCharacteristics of the terrain where the mobile terminal is located, including reflection and shielding conditions, P_landRepresenting the type of the landform of the position where the mobile terminal is located; p in Doppler multipath node_multipathRepresenting a multipath parameter, P_dopplerRepresenting a doppler shift parameter; t in the user node represents the service type of the current mobile terminal; p in satellite node_offsetRepresenting deviations, P, caused by changes in satellite attitude_positionIndicating the position of the satellite in the orbit,track node P_orbitRepresenting orbit information of the satellite after orbit determination; p_estimateRepresenting channel estimation information, P_distanceIndicating distance information of the satellite terminal and the mobile terminal.

The satellite terminal can be understood as a satellite node, and the mobile terminal can be understood as a user node.

S103, respectively taking an influence factor as a variable node, adding a switching variable node corresponding to a switching threshold in the relation graph, and establishing an association relation between the variable node directly related to the switching variable node and the switching variable node.

And adding a switching variable node, and converting the original relational graph in the two-dimensional plane into the relational graph in the three-dimensional space.

And S104, determining factor nodes of the variable nodes aiming at the variable nodes.

The factor nodes are used for representing the influence degree of the variable nodes on the nodes with the incidence relation with the variable nodes.

And S105, adding factor nodes in the relation graph to obtain a factor graph corresponding to a plurality of influence factors.

The factor graph is built in a three-dimensional space, while the relationship graph is built in a two-dimensional plane. The relationship graph is the basis of a factor graph, which is formed by adding factor nodes to the relationship graph.

And S106, determining the optimal state variable estimation value based on the factor graph, and taking the optimal state variable estimation value as a switching threshold.

Specifically, the method may include: based on the factor graph, by the formula X^MAP＝argmax[Φ(X)]＝argmaxΠ_i[Φ_i(X_j)]And determining the optimal estimation value of the state variable.

Phi (X) includes a first factor node f (X) of variable nodes directly associated with the switching variable node_k1) And a second factor node g (X) of a variable node generating an association relation with other variable nodes_k2)；

For each variable node, determining a factor node of the variable node, including:

for variable nodes directly associated with the switching variable nodes, the formula f (X) is used_k1)＝L(Z_k1-h(X_k1) Determining a first factor node of a variable node directly associated with a switching variable node;

wherein, f (X)_k1) Is the first factor node, X, of a variable node directly associated with a switched variable node_k1Is an estimate of the handover threshold, h (X)_k1) Is a measurement function, Z, obtained based on the fitting of variable nodes having direct association with the switched variable nodes_k1Is the actual measurement value of the influencing factor k1 corresponding to the variable node directly having the incidence relation with the switching variable node, and L (-) is the cost function;

The handover threshold may be understood as a handover threshold for performing a handover of a satellite node or beam accessed by the user node. The user node accesses a satellite node or a beam, the satellite node provides service to the user node through the beam, and the handover can be understood as the handover of the beam providing service to the user node.

Specifically, when the handover is to be performed, the handover state value at the current time is compared with the handover threshold, and the handover is performed based on the comparison result, and the handover may be performed when the handover state value is higher than the handover threshold, or may be performed when the handover state value is lower than the handover threshold.

On the basis of improving the accuracy of determining the switching threshold based on the factor graph, the embodiment of the invention considers that the relative motion between a user node and a satellite node in the low-orbit satellite communication network is fast and the switching is frequent, and the invention describes the factor weight relationship of the switching threshold through a tensor theory, and carries out fast reconstruction on the factor graph of the switching threshold under factor association mutation so as to re-determine the switching threshold based on the influence factor of transformation based on the fast reconstruction factor graph and adapt to the determination of the switching threshold under fast change.

In summary, the fast reconstruction process of the embodiment of the present invention mainly includes two parts, which are respectively a factor graph reconstruction process and a switching threshold of the low earth orbit satellite internet designed based on the proposed factor graph reconstruction. The idea of factor graph reconstruction is to construct a tensor association vector representing the association relationship of the variation factors, determine the association change degree of the variation factors and the main nodes by using the association vector, and realize the quick association of the main factor nodes and the variation factors and the relationship, thereby realizing the reconstruction of the factor graph and solving the problem of quick reconstruction of the switching threshold factor graph under the condition of factor mutation. Based on factor graph reconstruction, the switching threshold is used as a main factor node, the channel state and the relative position are used as passive protection nodes, and the switching threshold setting of factors such as the satellite state, the channel state, the user state and the like is completed. The main process is as follows:

(1) the factor graph reconstruction process mainly comprises four steps of unified factor importance construction, switching factor association degree analysis, tensor-based factor association mutation processing, new factor graph reconstruction and the like. The process is shown in fig. 4, and referring to fig. 4, the process may include:

first, unity factor importance is constructed. Importance evaluation δ of construction of factor graph_iI is equal to 0, M is (self-entrance/exit degree N)_iI ∈ 0.. M, forming a factor cluster g_k＝(F_k，X_k，E_k) Setting an independent factor decision threshold N_tRemoving e association relation between factor clusters with close entrance and exit degrees_i，j，F_kRepresents a factor cluster g_kFactor node in, X_kRepresents a factor cluster g_kVariable node of (1), E_kRepresents a factor cluster g_kThe associated edge of (1).

Secondly, the method comprises the following steps: and analyzing the relevance of the switching factors. Taking the switching threshold as a main factor node, and setting a switching factor correlation degree judgment threshold N_handoverThe direct access degree of the node is the cascade relation e of the factor and the access degrees of other nodes_h+1，jAnd taking the node as the weighted sum of the entrance and exit of the factor cluster center. And sequencing according to the size of the direct access degree, setting the association weights of different nodes, and defining the factor of the high direct access degree as a passive protection node.

Then: tensor-based factors associate mutation processing. And describing the association relationship among the factors by adopting a tensor, setting the association relationship between the factors and the main factor nodes as a basis vector, setting the association relationship with other nodes as an auxiliary vector, resetting the basis vector according to the magnitude of direct connection and exit when the factor graph has sudden change, and recalculating the combination of the basis vector and the components in the new factor graph.

Also: and (5) reconstructing a new factor graph. When the factors and relationships of the factor graph change, the master node remains unchanged, while nodes that do not change also remain unchanged. And judging whether the changed node is associated with the master node or not by the changed node, preferentially comparing whether the combination of the basis vector and the component in the passive protection node factor cluster is close to the old combination or not, if so, directly establishing a new association relationship between the factor cluster of the passive node and the master node, and updating the tensor. And if the difference between the combination of the basis vector and the component and the old combination is large, the node is recurred to a lower node, the closeness degree of the combination of the basis vector and the component and the old combination in the factor cluster of the node is calculated, and the tensor is updated. And if the lower node still does not meet the condition, the lower node is pushed forward downwards according to the rule. Thereby forming a new factor graph. As shown in fig. 5.

(2) And designing the switching threshold of the low-orbit satellite Internet based on the proposed factor graph reconstruction.

And according to the factor graph reconstruction process, taking the switching threshold as a main factor node. And calculating the self-entrance degree of each node. Analyzing the incidence relation between different factors and switching factors, determining the direct access degrees of the different factors and the switching factors, sorting the current direct access degrees, setting the incidence weights of the different factors, defining the factor with high direct access degree as a passive protection node, wherein the passive protection node can comprise the relative distance (rDis) between a satellite and a user, reference signal power (RSRP), reference signal quality (RSRQ), service quality requirement (Qos), factor access degree of Busy occupancy (Busy percentage) of a cell and the like according to the design requirement of a satellite internet, and correlating the secondary factors of the passive protection nodes. And each factor is associated with a switching main factor node, a tensor is adopted to construct a mutually associated vector set, the association relation between the factor and the main factor node is set as a base vector, and the association relation between the factor and other nodes is set as an auxiliary vector. And when the original switching factor graph changes, judging the size of the tensor vector and the direct access degree, and pushing down a new switching factor graph according to the tensor vector.

The following describes the factor graph reconstruction and the process of determining the switching threshold based on the factor graph reconstruction in the embodiment of the present invention in detail.

Referring to fig. 6, an embodiment of the present invention may further include:

s601, determining the direct access degree of the variable nodes and the switching variable nodes aiming at each variable node.

The direct access degree represents the cascade relation of the access degrees of the variable node and other nodes and the weighted sum of the access degrees with the variable node as the center of the factor cluster.

S602, sorting the direct access degree of each variable node, grading each variable node according to the sorting result, and determining the associated weight corresponding to each variable node according to the graded grades.

One variable node corresponds to one associated weight.

S603, tensor combination is determined based on the incidence relation among the variable nodes, the incidence relation between the variable nodes directly having the incidence relation with the switched variable nodes and the switched variable nodes, and the incidence weight corresponding to the variable nodes.

Taking the variable nodes with incidence relation with the switching variable nodes and the incidence relation of the switching variable nodes as basis vectors in the tensor, and respectively taking the incidence weights corresponding to the variable nodes with incidence relation with the switching variable nodes as components on the corresponding basis vectors; and taking the association relation existing among the variable nodes as an auxiliary vector in the tensor, and respectively determining the components on the corresponding auxiliary vector based on the association weight corresponding to the variable nodes to obtain the tensor combination.

The association weight corresponds to one variable node, and in the embodiment of the invention, the association weights of two variable nodes related to the component are added to obtain the component value.

S604, when the influence factors corresponding to one or more variable nodes in each variable node change, the tensor combination is updated based on the changed influence factors, and if the closeness degree of the updated tensor combination and the tensor combination before updating is lower than the preset closeness degree, a factor graph is reconstructed.

After determining the direct access degree of the variable node and the switching variable node, the method may further include:

and taking the variable node with the direct connection access degree larger than a preset threshold value as a passive protection node.

If the proximity of the updated tensor combination and the tensor combination before updating is lower than the preset proximity, reconstructing a factor graph, including:

For a passive protection node, determining a tensor combination based on an incidence relation existing among variable nodes, an incidence relation existing between the variable nodes directly existing in the incidence relation with a switching variable node and the switching variable node, and an incidence weight corresponding to each variable node, wherein the tensor combination comprises the following steps:

and respectively taking the association relationship between the passive protection node having the association relationship with the switching variable node and the switching variable node as a basis vector in the tensor, and taking the association weight corresponding to the passive protection node having the association relationship with the switching variable node directly as a component on the corresponding basis vector to obtain a tensor combination.

Updating the tensor combination based on the changed influencing factors may include: and re-determining the basis vectors and the components corresponding to the passive protection nodes based on the changed influence factors to obtain the updated update tensor combination. When a variable node changes, the total basis vectors and components are definitely changed, and then in order to determine how to update, the combination of the basis vectors and the components inside the factor cluster under which passive protection node is found is different from the original combination inside the factor cluster by a large difference from the several passive protection nodes of the largest block.

Reconstructing the factor graph may include:

exchanging the association relationship between the passive protection node and the switching variable node and the association relationship between the lower variable node and the switching transformation node (as in fig. 5, the original main factor node is connected with the node 1, and then the main factor node is connected with the node 4 in the left graph); calculating the combination of the exchanged base vectors and the components corresponding to the base vectors to obtain a new tensor combination; if the closeness degree between the new tensor combination and the old tensor combination is higher than the preset closeness degree, the association relationship exchange between the base vector and the lower variable node is continued until the closeness degree between the new tensor combination and the old tensor combination is higher than the preset closeness degree, the exchange is stopped, and the association relationship between the variable nodes when the exchange is stopped and the association relationship between the variable nodes and the switching variable node are used as a reconstruction relationship graph; and obtaining a reconstruction factor graph based on the reconstruction relation graph.

The embodiment of the invention can realize factor graph reconstruction under the condition that the incidence relation between the factors is mutated. The problem of determining the switching threshold of the satellite internet under the conditions of uniform power distribution and large environmental change is solved.

In an alternative embodiment, if a factor graph model already exists when a factor graph is reconstructed, the factor nodes and the switching variable nodes of the old factor graph need to be deleted first, and the factor graph in the three-dimensional space is converted into a relationship graph in the two-dimensional plane. The factor cluster is defined to include any variable nodes with association relation, and the variable nodes are all influence factors related to the switching threshold. If the degree of access of the two factor clusters is less than the judgment threshold N of the independent factor_tAnd if the in-out degrees of the two factor clusters are close, the mutual association relationship between the two factor clusters is removed, so that the reconstruction of a subsequent factor graph is facilitated.

After the relational graph is established, switching variable nodes are added, and the relational graph in the original two-dimensional plane is converted into the relational graph in the three-dimensional space. And simultaneously, determining the direct access degree of each variable node according to the incidence relation between the switching variable node and each variable node. And dividing all variable nodes into a plurality of levels according to the height of the direct access degree, and endowing different associated weights, wherein the variable node with the highest direct access degree is set as a passive protection node.

According to the relationship graph in the three-dimensional space obtained in the above steps, the association relationship between the switching variable node and the variable node is set as a base vector in the tensor, the association weight is set as a component on the base vector, the association relationship between the variable nodes is set as an auxiliary vector, and the association weight is set as a component on the auxiliary vector. If some variable nodes are changed drastically at the current moment, correspondingly, the association relation related to the variable nodes is also changed, that is, the basis vector and the auxiliary vector in the tensor are changed.

After the change of the basis vector and the auxiliary vector of the tensor, the components in the tensor should also change accordingly. And if the combination sum of the base vector and the component of the passive protection node after updating is similar to the old combination, considering that the factor cluster where the passive protection node is located does not have violent change, and continuously traversing other passive protection nodes. If the difference between the new combination and the old combination of a certain passive protection node is large, the factor cluster where the passive protection node is located is considered to be changed violently, and needs to be reconstructed. In the factor cluster, the association relationship between the passive protection node and the switching variable node and the association relationship between the lower-level variable node are exchanged, namely two basis vectors are exchanged, the combination of the basis vector and the component at each moment is calculated, and if the difference between the new combination and the old combination is still large, the basis vectors continue to be exchanged with the association relationship between the lower-level variable node. When the new combination approaches the old combination, the basis vectors stop traversing and replace the associations there. And completing the process, completing the establishment of a new relation graph, and then constructing a new factor graph. In the new relationship graph, a factor node is inserted between every two interrelated variable nodes, as shown in fig. 7.

In fig. 7, the ellipses are represented as factor nodes. Each factor node is a local function after factorization, and the incidence relation between two variable nodes is represented in the embodiment of the invention.

The expression of the factor node of the variable node directly connected with the switching variable node is f (X)_k)＝L(Z_k-h(X_k)). Wherein, X_kIs an estimate of the switching threshold variable, h (-) is a measurement function of each variable node, Z_kIs the actual measurement of each influencing factor, and L (-) is the set cost function.

Similarly, the factor node expression between variable nodes can be expressed as: g (X)_k)＝d(Z_k-h(X_k) Wherein, X)_kIs an estimated value of each variable node, h (-) is a measure of each variable nodeFunction, Z_kIs the actual measurement of each influencing factor, and d (-) is the set cost function.

Under the assumption of a gaussian noise model, the cost function can be generally defined as:

wherein: h is_i(X_i) For each parameter measurement function, the variable representing the switching state is taken as X_iPredicted measured values of the respective parameters; z is a radical of_iIs the actual measurement.

And estimating the size of the switching state variable of the mobile terminal at the current moment according to the established factor graph model. In particular, in the factor graph, for a given measurement value Z (where Z is P)_longitude1、P_latitudde1、P_longitude2、P_latitudde2、P_height、P_feature、P_multipath、P_doppler、P_position、P_offset、P_position、P_orbit、P_estimate、P_distanceThe most common estimation method is maximum a posteriori probability estimation, whose principle is to maximize the post-density p (X | Z) of the state variable X given the measured value Z, i.e.:

X^MAP＝argmax(X|Z)

whereas for any factor graph, the MAP (maximum a posteriori probability estimate) inference comes down to maximizing the product of all factors:

in the above formula, the function Φ (X) is Π_i[Φ_i(X_j)]Which is a global function, can be decomposed into the product of all factors. And X^MAPFor the optimal estimation of the state variables, the formula means: when X is equal to X^MAPThen, the function phi (X) is obtainedThe maximum a posteriori probability estimation is achieved. In the estimation process, the improved cost function is substituted into the above formula, since h_i(X_i) Generally, the switching state variable is a nonlinear function, and the scale of a factor graph is not large in the invention, so that an initial value can be set, and the switching state variable can be estimated by a Gaussian-Newton iteration method.

Corresponding to the method for determining a handover threshold in a low earth orbit satellite communication network provided in the foregoing embodiment, an embodiment of the present invention provides an apparatus for determining a handover threshold in a low earth orbit satellite communication network, as shown in fig. 8, where the method may include:

a first determining module 801, configured to determine a plurality of influencing factors that may influence a handover threshold in a low-earth orbit satellite communication network;

a building module 802, configured to build a relationship graph corresponding to the multiple influence factors, where the relationship graph includes an association relationship existing in the multiple influence factors;

a first adding module 803, configured to use one influence factor as a variable node, and add a switching variable node corresponding to a switching threshold in the relationship graph;

an establishing module 804, configured to establish an association relationship between a variable node directly related to a switching variable node and the switching variable node;

a second determining module 805, configured to determine, for each variable node, a factor node of the variable node, where the factor node is used to characterize an influence degree of the variable node on a node having an association relationship with the variable node;

a second adding module 806, configured to add factor nodes in the relationship graph to obtain a factor graph corresponding to the multiple influencing factors;

a third determining module 807, configured to determine an optimal state variable estimation value based on the factor graph, and use the optimal state variable estimation value as a handover threshold.

Optionally, as shown in fig. 9, the apparatus further includes:

a fourth determining module 901, configured to determine, for each variable node, a direct access degree between the variable node and a handover variable node, where the direct access degree represents a cascade relationship between access degrees of the variable node and other nodes and a weighted sum of access degrees of the variable node serving as a factor cluster center;

a ranking module 902, configured to rank direct access degrees of the variable nodes, rank the variable nodes according to a ranking result, and determine association weights corresponding to the variable nodes according to the ranked levels;

a fifth determining module 903, configured to determine a tensor combination based on an association relationship existing among the variable nodes, an association relationship existing between the variable node having an association relationship directly with the switched variable node and the switched variable node, and an association weight corresponding to each variable node;

an updating module 904, configured to update the tensor combination based on changed influence factors when the influence factors corresponding to one or more variable nodes in each variable node change;

a reconstructing module 905, configured to reconstruct the factor graph if a proximity of the updated tensor combination and the tensor combination before updating is lower than a preset proximity.

Optionally, the fifth determining module 903 is specifically configured to use an association relationship between a variable node having an association relationship with a switching variable node and the switching variable node as a basis vector in a tensor, and use association weights corresponding to the variable nodes having an association relationship with the switching variable node as components on corresponding basis vectors respectively; and taking the association relation existing among the variable nodes as an auxiliary vector in the tensor, and respectively determining the components on the corresponding auxiliary vector based on the association weight corresponding to the variable nodes to obtain the tensor combination.

Optionally, the reconfiguration module 905 is specifically configured to, after determining a direct access degree between a variable node and a switching variable node, use the variable node whose direct access degree is greater than a preset threshold as a passive protection node; and traversing all the passive protection nodes in sequence, and if the proximity degree of the updated tensor combination corresponding to one passive protection node and the tensor combination before updating is lower than the preset proximity, reconstructing a factor graph.

Optionally, the fifth determining module 903 is specifically configured to use an association relationship between a passive protection node having an association relationship with a switching variable node and the switching variable node as a basis vector in a tensor, and use association weights corresponding to the passive protection node having the association relationship with the switching variable node directly as components on corresponding basis vectors to obtain a tensor combination;

the updating module 904 is specifically configured to re-determine the basis vectors and components corresponding to the passive protection nodes based on the changed influence factors, so as to obtain an updated update tensor combination.

Optionally, the reconfiguration module 905 is specifically configured to exchange an association relationship between the passive protection node and the switching variable node and an association relationship between the lower level variable node and the switching transformation node; calculating the combination of the exchanged base vectors and the components corresponding to the base vectors to obtain a new tensor combination; if the closeness degree between the new tensor combination and the old tensor combination is higher than the preset closeness degree, the association relationship exchange between the base vector and the lower variable node is continued until the closeness degree between the new tensor combination and the old tensor combination is higher than the preset closeness degree, the exchange is stopped, and the association relationship between the variable nodes when the exchange is stopped and the association relationship between the variable nodes and the switching variable node are used as a reconstruction relationship graph; and obtaining a reconstruction factor graph based on the reconstruction relation graph.

An optional third determining module 807, in particular for determining the value of the factor graph by the formula X^MAP＝argmax[Φ(X)]＝argmaxΠ_i[Φ_i(X_j)]Determining a switching threshold;

Optionally, phi (X) bagFirst factor node f (X) including variable nodes directly associated with switching variable nodes_k1) And a second factor node g (X) of a variable node generating an association relation with other variable nodes_k2)；

A second determining module 805, specifically configured to determine, for a variable node directly associated with a switched variable node, a formula f (X)_k1)＝L(Z_k1-h(X_k1) Determining a first factor node of a variable node directly associated with a switching variable node;

Optionally, the influencing factors include orbit, orbital, satellite, bias, atmospheric attenuation, channel, topography, location, doppler multipath, traffic, user, relative distance, and relative position.

The embodiment of the present invention further provides an electronic device, as shown in fig. 10, including a processor 1001, a communication interface 1002, a memory 1003 and a communication bus 1004, where the processor 1001, the communication interface 1002 and the memory 1003 complete mutual communication through the communication bus 1004.

A memory 1003 for storing a computer program;

the processor 1001 is configured to implement the method steps of the method for determining the handover threshold in the low earth orbit satellite communication network in the foregoing embodiment when executing the program stored in the memory 1003.

The communication bus mentioned in the electronic device may be a Peripheral Component Interconnect (PCI) bus, an Extended Industry Standard Architecture (EISA) bus, or the like. The communication bus may be divided into an address bus, a data bus, a control bus, etc. For ease of illustration, only one thick line is shown, but this does not mean that there is only one bus or one type of bus.

The communication interface is used for communication between the electronic equipment and other equipment.

The Memory may include a Random Access Memory (RAM) or a Non-Volatile Memory (NVM), such as at least one disk Memory. Optionally, the memory may also be at least one memory device located remotely from the processor.

The Processor may be a general-purpose Processor, including a Central Processing Unit (CPU), a Network Processor (NP), and the like; but also Digital Signal Processors (DSPs), Application Specific Integrated Circuits (ASICs), Field Programmable Gate Arrays (FPGAs) or other Programmable logic devices, discrete Gate or transistor logic devices, discrete hardware components.

In a further embodiment of the present invention, a computer-readable storage medium is further provided, in which a computer program is stored, and the computer program, when being executed by a processor, implements the method steps of the method for determining a handover threshold in a low-earth orbit satellite communication network in the foregoing embodiment.

In a further embodiment of the present invention, there is also provided a computer program product comprising instructions which, when run on a computer, cause the computer to perform the method steps of the method for determining a handover threshold in a low earth orbit satellite communication network of the above embodiment.

In the above embodiments, the implementation may be wholly or partially realized by software, hardware, firmware, or any combination thereof. When implemented in software, may be implemented in whole or in part in the form of a computer program product. The computer program product includes one or more computer instructions. When loaded and executed on a computer, cause the processes or functions described in accordance with the embodiments of the invention to occur, in whole or in part. The computer may be a general purpose computer, a special purpose computer, a network of computers, or other programmable device. The computer instructions may be stored in a computer readable storage medium or transmitted from one computer readable storage medium to another, for example, from one website site, computer, server, or data center to another website site, computer, server, or data center via wired (e.g., coaxial cable, fiber optic, Digital Subscriber Line (DSL)) or wireless (e.g., infrared, wireless, microwave, etc.). The computer-readable storage medium can be any available medium that can be accessed by a computer or a data storage device, such as a server, a data center, etc., that incorporates one or more of the available media. The usable medium may be a magnetic medium (e.g., floppy Disk, hard Disk, magnetic tape), an optical medium (e.g., DVD), or a semiconductor medium (e.g., Solid State Disk (SSD)), among others.

It is noted that, herein, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.

All the embodiments in the present specification are described in a related manner, and the same and similar parts among the embodiments may be referred to each other, and each embodiment focuses on the differences from the other embodiments. In particular, for the apparatus, the device, the computer-readable storage medium, and the computer program product embodiments, since they are substantially similar to the method embodiments, the description is relatively simple, and in relation to the description, reference may be made to some of the description of the method embodiments.

The above description is only for the preferred embodiment of the present invention, and is not intended to limit the scope of the present invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention shall fall within the protection scope of the present invention.

Claims

1. A method for determining a handover threshold in a low earth orbit satellite communication network, comprising:

2. The method of claim 1, further comprising:

3. The method according to claim 2, wherein the determining a tensor combination based on the association relationship existing among the variable nodes, the association relationship existing between the variable node directly associated with the switching variable node and the switching variable node, and the association weight corresponding to each variable node comprises:

4. The method of claim 2, wherein after the determining the direct ingress and egress of the variable node to a handover variable node, the method further comprises:

5. The method of claim 4, wherein for a passive protection node, determining a tensor combination based on the association relationship existing between the variable nodes, the association relationship existing between the variable nodes directly associated with the switched variable node and the switched variable node, and the association weight corresponding to each variable node comprises:

6. The method of claim 5, wherein reconstructing the factor graph comprises:

7. The method of claim 1, wherein determining an optimal state variable estimate based on the factor graph comprises:

based on the factor graph, by formula X^MAP＝argmax[Φ(X)]＝argmax∏_i[Φ_i(X_j)]Determining the optimal estimated value of the state variable;

wherein, X^MAPFor the optimum estimated value of the state variable, phi (X) is ^ pi_i[Φ_i(X_j)]I represents the number of factor nodes in the factor graph, j represents the number of variable nodes in the factor graph,

h_i(X_j) Representing a measurement functionValue z_iRepresenting the actual measurement.

8. The method of claim 7, wherein Φ (X) comprises a first factor node f (X) of a variable node directly associated with the switch variable node_k1) And a second factor node g (X) of a variable node generating an association relation with other variable nodes_k2)；

9. The method of any one of claims 1 to 8, wherein the influencing factors include orbit, orbital, satellite, bias, atmospheric attenuation, channel, topography, location, Doppler multipath, traffic, user, relative distance and relative position.

10. An apparatus for determining a handoff threshold in a low earth orbit satellite communication network, comprising: