Satellite switching method and system for NTN high and low orbit fusion network

Abstract

The invention discloses a satellite switching method and system for an NTN high and low orbit fusion network, and the method comprises the steps: S1, UE obtains the position of the UE through a GNSS, reports the position to a source satellite, and obtains a candidate satellite list which is allowed to be accessed and measurement configuration from the source satellite; s2, the UE starts measurement after receiving the candidate satellite list, and updates the candidate satellite list according to a measurement result; s3, the UE measures all satellites in the updated candidate satellite list; and sorting the low earth orbit satellites and the geostationary orbit satellites meeting the conditions according to the measurement result and the candidate satellite information, and switching the satellites according to the sorting result. The method has the characteristics that the success rate and the communication continuity of UE conditional switching are improved, the switching decision delay and the signaling interaction load are dynamically reduced, and the cooperative advantages of LEO low time delay and GEO wide coverage are fully exerted.

Description

Technical Field

[0001] The present invention relates to the field of satellite communication, and in particular, to a satellite handover method and system for an NTN high and low orbit integrated network. Background Art

[0002] A Non-Terrestrial Network (NTN) is a network that uses non-terrestrial communication infrastructures such as satellites to achieve global communication coverage, and has advantages such as a large coverage area and a long communication distance. The coverage radius of an NTN cell can reach dozens to hundreds of kilometers, and usually the following two schemes are used.

[0003] 1) Earth fixed cell scheme: It refers to an NTN scheme in which a satellite cell is fixed at a certain geographical location on the earth for a certain period of time. The continuous service duration of this scheme is related to the satellite orbit altitude and the minimum elevation angle, and can reach from several minutes to dozens of minutes.

[0004] 2) Earth moving cell scheme: It refers to an NTN scheme in which a satellite cell continuously moves on the earth's surface. The beam footprint of the satellite cell sweeps across the ground, and the coverage position of the cell will move with the movement of the satellite. The continuous service duration of this scheme is related to the satellite orbit altitude and the beam coverage diameter, and can reach from several seconds to dozens of seconds.

[0005] The 3rd Generation Partnership Project (3GPP) Rel-17 defines the basic process of mobility management in the connected state of NTN. The network issues measurement configuration and reporting configuration to the UE (User Equipment), and the UE reports the measurement report after completing the measurement. The network decides whether to perform a handover based on the measurement report, and the reporting forms include periodic triggering and event-based triggering. At the same time, since the NTN cell is covered by a satellite, the signal strength at the cell center and the signal strength at the cell edge only have a small difference, that is, for an NTN cell, there is no obvious near-far effect. Therefore, in 3GPP 5G NTN, for a terminal in the connected state, conditional handover can be mainly relied on to complete handover across cells.

[0006] The basic principle of Conditional Handover (CHO) is that the network pre-configures information related to neighboring cells and handover thresholds in advance. When the UE meets the handover conditions, it can perform a handover without reporting measurements and receiving handover commands from the network, which can reduce the situation of failed handover due to receiving handover command failures, increase the handover success rate, and reduce handover signaling. In Rel-17 NTN, two new CHO triggering conditions based on time period and based on terminal location are added. However, the triggering conditions based on time period or based on terminal location need to be configured together with a triggering condition based on signal quality measurement that has been used by a terrestrial network. The triggering condition based on time period (also known as T1 event) is defined as: CHO can only be performed during a certain period related to "the time when the satellite corresponding to the candidate target cell flies over the terminal". The CHO triggering condition based on terminal location (also known as D1 event) is defined as: the distance between the terminal and the ground fixed reference point of the serving cell becomes greater than the corresponding threshold, and the distance between the terminal and the ground fixed reference point of the candidate target cell becomes less than the corresponding threshold.

[0007] In the high and low orbit integrated network, Low Earth Orbit (LEO) satellites and Geostationary Earth Orbit (GEO) satellites jointly form the NTN network. Since the orbital altitude of GEO satellites is about 35,786 kilometers, this will lead to a large propagation delay and path loss in the satellite-ground link. At the same time, although GEO satellites have a wide coverage area and can serve a large number of UEs simultaneously, it is difficult to dynamically adjust the system load distribution according to the user distribution, especially in a multi-user environment where the remaining available resources of the system will be more scarce. Due to its relatively close distance to the ground, LEO satellites have a small propagation delay, but due to their fast movement, the link between the user terminal and the satellite may need to be switched frequently during the communication process.

[0008] For UEs, different UEs use different services. Referring to the description of service delay tolerance in ITU-T G.1010 (International Telecommunication Union. Recommendation ITU-R G.1010: End-user multimedia QoS categories[R]. Geneva: ITU, 2001.), services are divided into four levels. Different levels of services will be processed differently according to the maximum delay tolerance. Services with different delay tolerances have different requirements for target satellites, as shown in Table 1 specifically.

[0009] In the CHO process defined in the existing protocol, the source satellite (i.e., the source base station and the satellite, with the base station deployed on the satellite) sends CHO requests to multiple candidate satellites (base stations and satellites), and the candidate satellites (base stations and satellites) send CHO responses to the source satellite. After receiving the responses from the candidate satellites, the source satellite issues a candidate cell list to the UE. Thereafter, it no longer knows the situation of the candidate satellites, does not update the list for the UE, and does not control the handover direction of the UE.

[0010] Within a period of time after the source satellite issues a candidate satellite list to the UE, the UE cannot know whether the channel conditions and ephemeris information of the candidate satellites have changed at the current moment and how they have changed; at the same time, the source satellite does not control the UE to select a target satellite, increasing the risk of the UE's failed handover attempt. For example, the candidate satellite has reached its maximum throughput and cannot access new UEs, but is still selected by the UE as the target satellite and attempts to handover and access.

[0011] At the same time, there is currently a lack of a standardized method for the UE to select a target satellite in a high-low orbit integrated network. For how the UE selects a suitable target satellite, multiple factors affecting the quality of service (QoS) of the UE in the connected state need to be considered, including: the measured RSRQ (Reference Signal Receiving Quality) specified by 3GPP, the distance from the UE to the satellite beam center, the satellite service duration, the communication delay affecting QoS, the satellite load situation, etc. The most suitable target satellite is selected from them for handover. Summary of the Invention

[0012] The technical problem to be solved by the embodiments of the present invention is to provide a satellite handover method and system for an NTN high-low orbit integrated network to solve the problems of lagging update of candidate satellite information, lack of comprehensive multi-factor decision-making, and insufficient adaptation of high-low orbit satellite characteristics.

[0013] To solve the above technical problems, the embodiments of the present invention propose a satellite handover method for an NTN high-low orbit integrated network, including: Step S1: After the UE establishes a connection with the source satellite, it obtains its own position through GNSS and reports it to the source satellite, and obtains a list of candidate satellites allowed to access and measurement configuration from the source satellite; Step S2: After the UE receives the candidate satellite list, it starts measurement and updates the candidate satellite list according to the measurement results; Step S3: The UE measures all satellites in the updated candidate satellite list; sorts the low Earth orbit satellites and geostationary orbit satellites that meet the conditions according to the measurement results and candidate satellite information, and switches satellites according to the sorting results.

[0014] Accordingly, an embodiment of the present invention further provides a satellite handover system for an NTN high and low orbit integrated network, including: Reporting and acquisition module: After the UE establishes a connection with the source satellite, it obtains its own position through GNSS and reports it to the source satellite, and obtains a list of candidate satellites allowed to access and measurement configuration from the source satellite; Measurement update module: The UE starts to measure after receiving the list of candidate satellites, and updates the list of candidate satellites according to the measurement results; Sorting and handover module: The UE measures all satellites in the updated list of candidate satellites; sorts the low Earth orbit satellites and geostationary orbit satellites that meet the conditions according to the measurement results and candidate satellite information, and switches satellites according to the sorting results.

[0015] The beneficial effects of the present invention are as follows: 1) Improve the handover success rate and QoS (Quality of Service) guarantee: The present invention dynamically updates the list of candidate satellites, avoids the UE from attempting to access unavailable or overloaded satellites, reduces the probability of handover failure; combines the entropy weight method for multi-factor optimization sorting to ensure that the load, delay and signal quality of the selected satellite meet the service requirements, and improves communication continuity.

[0016] 2) Enhance the adaptability of high and low orbit networks: In view of the short-term service of LEO satellites and the high delay characteristics of GEO satellites, the present invention adopts a service level differentiation strategy, preferentially selects LEO satellites for delay-sensitive services, and flexibly utilizes the wide coverage advantage of GEO for non-sensitive services to optimize resource utilization.

[0017] 3) Reduce signaling overhead and decision delay: The objective weight calculation based on the entropy weight method in the present invention reduces the complexity of manual configuration, and the dynamic sorting mechanism reduces the repeated measurement of the UE and the signaling interaction with the satellite, shortening the handover decision time, which is suitable for the high-dynamic scenario of satellite networks. Description of the Drawings

[0018] Figure 1 is a flowchart of the satellite handover method for the NTN high and low orbit integrated network according to the embodiment of the present invention.

[0019] Figure 2 is a flowchart of the UE measurement according to the embodiment of the present invention.

[0020] Figure 3 is a CHO handover flowchart for switching to a LEO satellite according to the embodiment of the present invention. Detailed Embodiments

[0021] It should be noted that, without conflict, the embodiments in the present application and the features in the embodiments may be combined with each other. The present invention will be further described in detail below with reference to the drawings and specific embodiments.

[0022] In the embodiments of the present invention, if there are directional indications (such as up, down, left, right, front, back...), they are only used to explain the relative positional relationship, movement conditions, etc. between components in a certain specific posture (as shown in the drawings). If this specific posture changes, the directional indications will also change accordingly.

[0023] In addition, in the present invention, the descriptions such as "first" and "second" are only for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one such feature.

[0024] Please refer to Figures 1 to 3 , the satellite handover method for the NTN high and low orbit integration network in the embodiments of the present invention includes steps S1 to S3.

[0025] Step S1, candidate satellite list setting stage: After the UE establishes a stable connection with the source satellite, it obtains its own position through GNSS and reports it to the source satellite, and obtains the candidate satellite list allowed to access and the measurement configuration from the source satellite.

[0026] As an implementation manner, the source satellite divides the service levels of each UE connected to the source satellite according to the service level standard according to the used service, and presets candidate satellites for each UE.

[0027] The source satellite informs the candidate satellites of the position, movement direction and service level of the UE, applies for the access of the UE to the candidate satellites. After obtaining the confirmation of the candidate satellites, the source satellite collects and collates the confirmation situations of all candidate satellites, and issues the candidate satellite list allowed to access and the measurement configuration to the UE. The measurement configuration includes measurement trigger conditions and measurement thresholds.

[0028] Step S2, UE measurement stage: 1) The UE starts to measure after receiving the candidate satellite list and updates the candidate satellite list according to the measurement results.

[0029] a. The UE obtains GNSS (Global Navigation Satellite System) information to predict its own movement trajectory and position coordinates in the next period of time. Combining the signal quality currently measured, it calculates the ideal signal quality of each candidate satellite in the next period of time and filters out the satellites that do not meet the signal quality threshold; b. By obtaining the candidate satellite ephemeris and beam center information, it predicts the beam center position of the candidate satellite after a period of time, calculates the distance between the UE and the beam center of the candidate satellite after a period of time, and filters out the satellites that exceed the distance threshold; c. Organize and update to obtain a candidate satellite list that meets its own requirements.

[0030] 2) Meanwhile, the UE further updates its candidate satellite list by obtaining the real-time broadcast of the candidate satellite changes from the source satellite.

[0031] a. The source satellite regularly shares the UE's location information with all candidate satellites. By obtaining the UE's location information, the candidate satellites monitor the UE in combination with the UE service level received previously to determine whether the UE can switch. For example, the candidate satellite reaches the maximum throughput and cannot accept new UEs; the available bandwidth of the candidate satellite decreases, and the service types that can be carried change; the moving directions of the UE and the candidate satellite are opposite, and they are moving away from each other.

[0032] b. When the above changes occur, the candidate satellites send the situation after the change to the source satellite. The source satellite broadcasts the ephemeris information, remaining available channels, acceptable UE service types for admission, and remaining service duration of each candidate satellite in the broadcast message; c. The UE deletes and updates its candidate satellite list according to the broadcast information of the source satellite to ensure that the candidate satellites are always in an accessible state and avoid the situation of failed handover access.

[0033] Please refer to Figure 2 , and the specific process is as follows: The UE obtains the measurement configuration and candidate satellite list sent by the source satellite; The UE performs measurements to obtain the signal quality at the current moment t; The UE obtains GNSS information to get the location, moving direction, and speed information at the current moment. Combining the signal quality at the current moment, it predicts and calculates the ideal signal quality RSRQ(t + Δt)_ideal of each candidate satellite in the next period of time Δt, that is, at the moment t + Δt, and determines whether RSRQ(t + Δt)_ideal ≥ the preset signal quality threshold. If not, the satellite is discarded; if so, the beam is put into the candidate satellite list; The UE obtains the ephemeris and beam center information of each candidate satellite in the candidate satellite list, predicts and calculates the distance d(t + Δt)_ideal from the UE to the beam center of each candidate satellite, and determines whether d(t + Δt)_ideal is less than the preset distance threshold. If not, the satellite is discarded; if so, the beam is put into the candidate satellite list; The UE organizes and updates the candidate satellite list; The UE further updates the candidate satellite list according to the candidate satellite information broadcast by the source satellite.

[0034] Step S3, handover decision stage: The UE measures all the satellites in the updated candidate satellite list; sorts the low Earth orbit satellites and geostationary orbit satellites that meet the conditions according to the measurement results and candidate satellite information, and switches to the most suitable satellite according to the sorting results.

[0035] As an implementation manner, a. The UE judges its own service level. If the service has a low tolerance for delay, proceed to the next step; if the tolerance for delay is high, calculate and sort the weights of GEO satellites and LEO satellites according to parameters such as communication delay and satellite load. b. For the UE with low tolerance for delay, sort the remaining LEO satellites in the order of RSRQ, the distance from the UE to the satellite beam center, and the remaining service duration of the satellite. c. The UE performs measurements periodically. When the candidate satellite list is updated in step S2, the updated list needs to be sorted again. When a handover occurs, the UE preferentially initiates a handover to the satellite ranked first.

[0036] As an implementation manner, the method for sorting GEO satellites and LEO satellites is as follows: Step S31, candidate satellite parameter acquisition and preprocessing: The collected and sorted parameters include: communication delay D , in milliseconds (ms); satellite load L , in percentage (%); reference signal received quality (RSRQ), in decibels (dB); the distance from the UE to the satellite beam center R , in kilometers (km); satellite service duration T , in seconds (s) Perform standardization processing on the parameters: Positive indicators (RSRQ, service duration T ): ; Negative indicators (communication delay D, load L, distance R): ; Among them, x ij is the value of the i th parameter of the j th satellite, and min( x j ), max( x j ) are the minimum and maximum values of the j th parameter among all candidate satellites.

[0037] Step S32, calculate the information entropy of each parameter: Calculate the probability distribution for the standardized parameters: (If z ij = 0, it is corrected to 10 -6 to avoid calculation errors); Calculate the information entropy of each parameter e j : ; Among them, n is the total number of candidate satellites, e j ∈ [0, 1]; is the probability distribution of the i th satellite's j th parameter after normalization.

[0038] Step S33, dynamically determine the parameter weights: Calculate the objective weights of each parameter according to the information entropy: ; Among them m = 5, corresponding to five parameters: communication delay, load, RSRQ, distance, and service duration.

[0039] Step S34, calculate the comprehensive score and sort: Calculate the weighted comprehensive score for each candidate satellite: ; According to S i Sort the candidate satellites from high to low, and select the satellite with the highest score as the primary service node.

[0040] The present invention can be directly applied to the UE in the NTN high and low orbit integrated network. The CHO handover process of the UE switching from the source satellite to the LEO satellite is as Figure 3 shown.

[0041] The satellite handover system for the NTN high and low orbit integrated network in the embodiment of the present invention includes: Reporting and acquisition module: After the UE establishes a connection with the source satellite, it obtains its own position through GNSS and reports it to the source satellite, and obtains a list of candidate satellites allowed to access and measurement configurations from the source satellite; Measurement update module: After the UE receives the list of candidate satellites, it starts to measure and updates the list of candidate satellites according to the measurement results; Sorting and handover module: The UE measures all the satellites in the updated list of candidate satellites; sorts the low Earth orbit satellites and geostationary orbit satellites that meet the conditions according to the measurement results and candidate satellite information, and switches the satellite according to the sorting results.

[0042] As an implementation manner, the source satellite divides the services of each UE connected to the source satellite according to the service level standard according to the used services, and presets candidate satellites for each UE; the source satellite notifies the candidate satellites of the position, moving direction, and service level of the UE, applies for UE access to the candidate satellites, and after obtaining the confirmation of the candidate satellites, the source satellite collects and sorts out the confirmation situations of all candidate satellites, and issues a list of candidate satellites allowed to access and measurement configurations to the UE, where the measurement configurations include measurement trigger conditions and measurement thresholds.

[0043] As an implementation manner, the measurement update module updates the candidate satellite list according to the following steps: The UE obtains the issued measurement configurations and candidate satellite list from the source satellite; The UE performs measurements and measures the signal quality at the current moment; The UE obtains GNSS information to obtain the position, moving direction, and speed information at the current moment, combines the signal quality at the current moment, predicts and calculates the ideal signal quality of each candidate satellite in the candidate satellite list in a future period of time, and eliminates the satellites that do not meet the signal quality threshold; The UE obtains the ephemeris and beam center information of each candidate satellite in the candidate satellite list, predicts the beam center position of the candidate satellites after a future period of time, calculates the distance between the UE and the beam centers of each candidate satellite after a future period of time, and eliminates the satellites that exceed the preset distance threshold; The UE sorts out and updates the candidate satellite list; The UE further updates the candidate satellite list according to the broadcast candidate satellite information of the source satellite.

[0044] As an implementation manner, the measurement update module further updates the candidate satellite list according to the following steps: The source satellite regularly shares the position information of the UE with all candidate satellites, and the candidate satellites judge whether the UE can be switched according to the UE position information. If there is a change, the candidate satellites send the situation after the change to the source satellite; The source satellite broadcasts the ephemeris information, remaining available channels, acceptable UE service types, and remaining service duration of each candidate satellite in the broadcast message; The UE deletes and updates its own candidate satellite list according to the broadcast information of the source satellite to ensure that the candidate satellites are always in an accessible state and avoid the situation of failed handover access.

[0045] As an implementation manner, the sorting and handover module judges the own service level of the UE. If the delay tolerance is high, it calculates and sorts the low Earth orbit satellites and geostationary orbit satellites according to the communication delay and satellite load conditions; If the service has low tolerance for latency, for UEs with low latency tolerance, the remaining low Earth orbit satellites are sorted in the order of reference signal reception quality, the distance from the UE to the satellite beam center, and the remaining satellite service duration; Periodic measurements are performed. When the candidate satellite list is updated, the updated candidate satellite list is re-sorted; when a handover occurs, the handover is initiated to the satellite ranked first.

[0046] As an implementation, the sorting and handover module sorts the low Earth orbit satellites and geostationary orbit satellites according to the following steps: Collection and preprocessing of candidate satellite parameters: Collect candidate satellite parameters, where the candidate satellite parameters include: communication latency D , in milliseconds; satellite load L , in percentage; reference signal reception quality, in decibels; the distance from the UE to the satellite beam center R , in kilometers; satellite service duration T , in seconds; Process the reference signal reception quality and satellite service duration T According to the following formula: ; Process the communication latency D, satellite load L, and the distance R from the UE to the satellite beam center according to the following formula: ; where, x ij is the value of the i th item of the j th satellite, min( x j ), max( x j ) are the minimum and maximum values of the j th item of all candidate satellites, is the i th satellite's j th parameter after normalization; Calculate the information entropy of each parameter: Calculate the probability distribution of each parameter after normalization : ; Calculate the information entropy of each parameter e j : ; where, n is the total number of candidate satellites, i ∈ n, e j ∈ [0,1]; Dynamically determine parameter weights: Calculate the objective weights of each parameter according to information entropy: ; where m = 5, corresponding to five parameters: communication delay D, satellite load L, reference signal receiving quality, distance R from the UE to the satellite beam center, and satellite service duration T Five parameters; Calculate the comprehensive score and sort: Calculate the weighted comprehensive score for each candidate satellite: ; According to S i Sort the candidate satellites from high to low, and select the satellite with the highest score as the primary service node.

[0047] Through real-time information interaction between the source satellite (with a base station deployed on the satellite) and candidate space-based access points represented by, for example, Low Earth Orbit (LEO) satellites or Geostationary Earth Orbit (GEO) satellites, this invention periodically obtains satellite load, remaining service duration, and beam coverage changes, realizes dynamic update of the candidate list, and has a candidate list optimization mechanism for the user equipment (UE) to autonomously predict future signal quality and distance changes. Combining Global Navigation Satellite System (GNSS) trajectory prediction and satellite ephemeris data, it dynamically calculates the ideal Reference Signal Receiving Quality (RSRQ) values and beam center distance change trends of each candidate satellite in the future period, and real-time screens satellites that meet the signal quality threshold and distance constraints, thereby more accurately screening candidate satellites and avoiding the UE from switching to inaccessible or resource-insufficient satellites. At the same time, considering five key parameters: communication delay, satellite load, RSRQ, distance from the UE to the beam center, and service duration, it dynamically calculates the objective weights of each parameter using the entropy weight method, generates a comprehensive score and sorts, so as to achieve the global optimal selection of high and low orbit satellites. In addition, according to the UE service delay tolerance (ITU-T G.1010 standard), it adopts a differentiated handover strategy driven by service levels. For delay-sensitive services, it preferentially selects low-delay LEO satellites (sorted by RSRQ, distance, and service duration), while for delay-tolerant services, it combines the entropy weight method score to evenly select LEO or GEO satellites. This invention has the characteristics of improving the success rate and communication continuity of conditional handover of the UE, dynamically reducing handover decision delay and signaling interaction load, and giving full play to the collaborative advantages of low delay of LEO and wide coverage of GEO.

[0048] Although embodiments of the present invention have been shown and described, those of ordinary skill in the art will appreciate that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A satellite handover method for an NTN high-low orbit integrated network, characterized in that, including: Step S1: After establishing a connection with the source satellite, the UE obtains its own location through GNSS and reports it to the source satellite, and obtains a list of candidate satellites allowed to access and measurement configurations from the source satellite; Step S2: After receiving the list of candidate satellites, the UE starts measurements and updates the list of candidate satellites according to the measurement results; Step S3: The UE measures all satellites in the updated list of candidate satellites; sorts the low Earth orbit satellites and geostationary orbit satellites that meet the conditions according to the measurement results and candidate satellite information, and switches satellites according to the sorting results.

2. The satellite handover method for NTN high and low orbit integrated network according to claim 1, characterized in that In Step S1, the source satellite divides the service levels of each UE connected to the source satellite according to the service level standard according to the used services, and presets candidate satellites for each UE; The source satellite informs the candidate satellites of the location, moving direction and service level of the UE, applies for UE access to the candidate satellites, and after obtaining the confirmation of the candidate satellites, the source satellite collects and collates the confirmation situations of all candidate satellites, and issues a list of candidate satellites allowed to access and measurement configurations to the UE, and the measurement configuration includes a measurement trigger condition and a measurement threshold.

3. The satellite handover method for the NTN high and low orbit integrated network according to claim 1, wherein, In Step S2, the list of candidate satellites is updated according to the following steps: The UE obtains the issued measurement configuration and the list of candidate satellites from the source satellite; The UE performs measurements and measures the signal quality at the current moment; The UE obtains GNSS information to obtain the location, moving direction and speed information at the current moment, combines the signal quality at the current moment, predicts and calculates the ideal signal quality of each candidate satellite in the list of candidate satellites in the future period of time, and eliminates the satellites that do not meet the signal quality threshold; The UE obtains the ephemeris and beam center information of each candidate satellite in the list of candidate satellites, predicts the beam center position of the candidate satellite after a future period of time, calculates the distance between the UE and the beam center of each candidate satellite after a future period of time, and eliminates the satellites that exceed the preset distance threshold; The UE collates and updates the list of candidate satellites; The UE further updates the list of candidate satellites according to the broadcast candidate satellite information of the source satellite.

4. The satellite handover method for NTN high and low orbit integrated network according to claim 3, wherein, In Step S2, the list of candidate satellites is further updated according to the following steps: The source satellite regularly shares the location information of the UE with all candidate satellites, and the candidate satellites judge whether the UE can switch based on the UE location information. If there is a change, the candidate satellites send the situation after the change to the source satellite; The source satellite broadcasts the ephemeris information, remaining available channels, acceptable UE service types, and remaining service duration of each candidate satellite in the broadcast message; The UE deletes and updates its own list of candidate satellites according to the broadcast information of the source satellite, ensuring that the candidate satellites are always in an accessible state and avoiding the situation of failed handover access.

5. The satellite handover method for NTN high and low orbit integrated network according to claim 1, wherein In Step S3, the UE judges its own service level. If the delay tolerance is high, the low Earth orbit satellites and geostationary orbit satellites are weighted and sorted according to the communication delay and satellite load conditions; If the service has a low delay tolerance, for UEs with a low delay tolerance, the remaining low Earth orbit satellites are sorted in the order of reference signal reception quality, distance from the UE to the satellite beam center, and remaining service duration of the satellite; The UE performs measurements periodically. When the candidate satellite list is updated, the updated candidate satellite list is re - sorted; When a handover occurs, the UE first initiates a handover to the satellite ranked first.

6. The satellite handover method for the NTN high and low orbit integrated network according to claim 5, wherein In step S3, the low - Earth - orbit satellites and geostationary orbit satellites are sorted according to the following steps: Step S31, Candidate Satellite Parameter Acquisition and Preprocessing: Collect candidate satellite parameters, where the candidate satellite parameters include: communication delay D , in milliseconds; satellite load L , in percentage; reference signal reception quality, in decibels; distance from the UE to the satellite beam center R , in kilometers; satellite service duration T , in seconds; Standardize the parameters: For the reference signal reception quality and satellite service duration T Process according to the following formula: ； Process the communication delay D, satellite load L, and the distance R from the UE to the satellite beam center according to the following formula: ； Among them, x ij is the i th parameter value of the j th satellite, min( x j ), max( x j ) are the minimum and maximum values of the j th parameter among all candidate satellites, is the i th satellite's j th parameter after standardization; Step S32, calculate the information entropy of each parameter: Calculate the probability distribution of each parameter after standardization : ; Calculate the information entropy of each parameter e j : ; Among them, n is the total number of candidate satellites, i ∈ n, e j ∈ [0, 1]; Step S33, dynamically determine the parameter weights: Calculate the objective weights of each parameter according to information entropy: ; Among them m = 5, corresponding to five parameters: communication delay D, satellite load L, reference signal reception quality, distance R from the UE to the satellite beam center, and satellite service duration T Five parameters; Step S34, calculate the comprehensive score and sort: Calculate the weighted comprehensive score for each candidate satellite: ; According to S i Sort the candidate satellites from high to low, and select the satellite with the highest score as the primary service node.

7. A satellite handover system for an NTN high-low orbit integrated network, characterized in that, Including: Reporting and acquisition module: After the UE establishes a connection with the source satellite, it obtains its own position through GNSS and reports it to the source satellite, and obtains the candidate satellite list allowed to access and the measurement configuration from the source satellite; Measurement update module: The UE starts to measure after receiving the candidate satellite list and updates the candidate satellite list according to the measurement results; Sorting and handover module: The UE measures all the satellites in the updated candidate satellite list; sorts the low - Earth - orbit satellites and geostationary orbit satellites that meet the conditions according to the measurement results and candidate satellite information, and switches satellites according to the sorting results.

8. The satellite handover system for the NTN high and low orbit integrated network according to claim 7, wherein The measurement update module updates the candidate satellite list according to the following steps: The UE obtains the measurement configuration and candidate satellite list sent by the source satellite; The UE performs measurements and measures the signal quality at the current moment; The UE obtains GNSS information to get the position, moving direction and speed information at the current moment. Combining with the signal quality at the current moment, it predicts and calculates the ideal signal quality of each candidate satellite in the candidate satellite list in the next period of time, and eliminates the satellites that do not meet the signal quality threshold; The UE obtains the ephemeris and beam center information of each candidate satellite in the candidate satellite list, predicts the beam center position of the candidate satellite after a period of time in the future, calculates the distance between the UE and the beam center of each candidate satellite after a period of time in the future, and eliminates the satellites that exceed the preset distance threshold; The UE sorts and updates the candidate satellite list; The UE further updates the candidate satellite list according to the candidate satellite information broadcast by the source satellite.

9. The satellite handover system for the NTN high and low orbit integrated network according to claim 7, characterized in that, The sorting and handover module judges the service level of the UE itself. If the delay tolerance is high, it calculates the weights and sorts the low - Earth - orbit satellites and geostationary orbit satellites according to the communication delay and satellite load conditions; If the service has a low delay tolerance, for the UE with a low delay tolerance, the remaining low - Earth - orbit satellites are sorted in the order of reference signal reception quality, the distance from the UE to the satellite beam center, and the remaining service duration of the satellite; Perform periodic measurements. When the candidate satellite list is updated, the updated candidate satellite list is re - sorted; When a handover occurs, first initiate a handover to the satellite ranked first.

10. The satellite handover system for the NTN high and low orbit integrated network according to claim 9, wherein, The sorting and handover module sorts the low - Earth - orbit satellites and geostationary orbit satellites according to the following steps: Candidate satellite parameter acquisition and preprocessing: Collect candidate satellite parameters, where the candidate satellite parameters include: communication delay D , in milliseconds; satellite load L , in percentage; reference signal reception quality, in decibels; distance from the UE to the satellite beam center R , in kilometers; satellite service duration T , in seconds. For the reference signal reception quality and satellite service duration T Process according to the following formula: ； Process the communication delay D, satellite load L, and the distance R from the UE to the satellite beam center according to the following formula: ； Among them, x ij is the i th parameter value of the j th satellite, min( x j ), max( x j ) are the minimum and maximum values of the j th parameter among all candidate satellites, is the i th satellite's j th parameter after standardization processing; Calculate the information entropy of each parameter: Calculate the probability distribution of each parameter after standardization : ; Calculate the information entropy of each parameter e j : ; Among them, n is the total number of candidate satellites, i ∈ n, e j ∈ [0, 1]; Dynamically determine the parameter weights: Calculate the objective weights of each parameter according to information entropy: ; Among them m = 5, corresponding to five parameters: communication delay D, satellite load L, reference signal reception quality, distance R from the UE to the satellite beam center, and satellite service duration T Five parameters; Calculate the comprehensive score and sort: Calculate the weighted comprehensive score for each candidate satellite: ; According to S i Sort the candidate satellites from high to low, and select the satellite with the highest score as the primary service node.

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