Low earth orbit satellite mobile network and handover method for satellites thereof

Abstract

Disclosed in the present invention is a handover method for satellite base stations of a low earth orbit satellite mobile network. The method comprises: a source satellite base station being connected to a UE sending a handover request to a target satellite base station; upon receiving the handover request, the target satellite base station performing handover preparation, and sending handover acknowledgement to the source satellite base station, and the source satellite base station receiving the handover acknowledgement; the source satellite base station notifying the UE connected thereto of a handover decision, the UE disconnecting from the source satellite base station and establishing a new RRC connection with the target satellite base station; and the source satellite base station and the target satellite base station transmitting synchronous data. The handover preparation comprises pre-allocating channel resources. By means of a rapid handover method introduced into a satellite mobile network, the present invention calculates the position of a satellite on the basis of ephemeris, so as to predict the occurrence of handover on a user side, thereby significantly reducing handover latency for users in this scenario.

Description

A Low Earth Orbit Satellite Mobile Network and Its Satellite Handover Method Technical Field

[0001] This invention belongs to the field of satellite mobile communication technology, and specifically relates to a low Earth orbit satellite mobile network and its satellite handover method. Background Technology

[0002] Low Earth Orbit (LEO) satellite mobile networks are a technology that provides communication services by deploying multiple satellites in low Earth orbit. Satellite mobile networks integrate satellite and mobile networks to form a unified sky-ground network architecture. Due to the large-scale deployment of LEO satellites, ground-based user equipment can enjoy globally covered, low-latency, and high-bandwidth mobile network services. LEO satellite networks can complement and integrate with traditional terrestrial networks to provide more robust and resilient communication services.

[0003] In mobile communication networks, handover is the process by which a terminal (UE) switches from the channel used by its original station (cell) to a more suitable channel for information transmission at a new station (cell) during service information transmission. However, in satellite mobile communication networks, handover differs from terrestrial networks in two main ways. First, due to the high-speed movement of LEO satellites, terrestrial UEs frequently experience handovers; second, the distance between the terminal and the core network may be longer than in terrestrial networks. This results in significantly longer transmission and handover delays in satellite mobile networks, greatly impacting the user's service experience.

[0004] Summary of the Invention

[0005] One embodiment of this disclosure provides a low Earth orbit satellite mobile network, comprising a source satellite base station, a target satellite base station, and a UE. The satellite base stations of this network employ a fast handover method under a low Earth orbit satellite mobile network, which includes the following steps:

[0006] The source satellite base station connected to the UE sends a handover request to the target satellite base station;

[0007] After receiving the handover request, the target satellite base station prepares for the handover and sends a handover confirmation to the source satellite base station, which then receives the handover confirmation.

[0008] The source satellite base station notifies the UE connected to it of the handover decision in progress, and the UE then disconnects from the source satellite base station and establishes a new RRC connection with the target satellite base station.

[0009] The source satellite base station and the target satellite base station transmit synchronized data. Attached Figure Description

[0010] The above and other objects, features, and advantages of exemplary embodiments of the present invention will become readily apparent from the following detailed description taken in conjunction with the accompanying drawings. Several embodiments of the invention are illustrated in the drawings by way of example and not limitation, wherein:

[0011] Figure 1 shows the latency measurement results of existing satellite mobile networks.

[0012] Figure 2 is a schematic diagram of fast handover signaling in one embodiment of the present invention.

[0013] Figure 3 shows the switching delay measurement results according to one embodiment of the present invention.

[0014] Figure 4 shows the application-level latency performance according to one embodiment of the present invention.

[0015] Figure 5 shows the predicted velocity of the access satellite according to one embodiment of the present invention.

[0016] Figure 6 shows the probability of satellite abnormal handover occurring according to one of the embodiments of the present invention. Detailed Implementation

[0017] According to one or more embodiments, a fast handover method for low Earth orbit satellite mobile networks is provided. This method aims to solve the problems of prolonged handover time and frequent handovers in existing mobile satellite networks.

[0018] The technical solution disclosed herein comprises two parts: a fast handover signaling process and a core network synchronization algorithm based on ephemeris data. Among them,

[0019] Compared to traditional handover signaling procedures, the fast handover signaling process uses ephemeris information to predict the UE's access satellite, avoiding the time-consuming control signaling interactions between the satellite-to-ground connection and the core network, thus significantly reducing handover latency. Furthermore,

[0020] The core network synchronization mechanism based on ephemeris ensures synchronization with the access network even without interaction with the access network, thus guaranteeing the smooth operation of the downlink.

[0021] The fast handover signaling process in this embodiment includes the following steps:

[0022] S101, the source satellite base station connected to the UE predicts the target satellite base station for handover through ephemeris information and sends a handover request to the target satellite base station;

[0023] S102, after receiving the handover request, the target satellite base station prepares for the handover and sends a handover confirmation to the source satellite base station, which receives the handover confirmation.

[0024] S103, the source satellite base station notifies the UE connected to it of the handover decision in progress, and the UE disconnects from the source satellite base station and establishes a new RRC connection with the target satellite base station;

[0025] S104, the source satellite base station and the target satellite base station transmit synchronization data.

[0026] This disclosure introduces a fast handover method in satellite mobile networks, which calculates satellite positions based on ephemeris data to predict handover events on the user side, thereby greatly reducing handover latency in this scenario.

[0027] According to one or more embodiments, a fast handover method for low Earth orbit satellite mobile networks, as shown in Figure 2, illustrates a fast signaling handover procedure. The handover procedure proposed in this disclosure begins with a handover decision. The handover is triggered by the source S-gNB (source satellite base station), which also selects the target S-gNB (target satellite base station) to which it will be handed over. The specific steps of the handover process are as follows.

[0028] Step 1: Corresponding to Step 1 in Figure 2, the source S-gNB notifies the target S-gNB of the handover decision, that is, the user connection will be switched from the source S-gNB to the target S-gNB;

[0029] Step 2: The target S-gNB prepares for the handover, for example, by pre-allocating channel resources, as shown in the decision control process in Figure 2. Then, the target S-gNB sends a handover confirmation message to the source S-gNB, as shown in Step 2 of Figure 2. After the source S-gNB receives the confirmation, the handover preparation is complete. It should be noted that from this point onwards, the connection between the core network and the UE is broken, and the user begins to experience a link unavailability period.

[0030] Step 3: The third step can be further divided into two parallel operations. One is that the source S-gNB notifies the UE of the handover decision, then the UE disconnects from the source S-gNB and establishes a new RRC connection with the target S-gNB, corresponding to steps 3.a.1 and 3.a.2 in Figure 2. The other is that the source S-gNB and the target S-gNB transmit relevant synchronization information, including the base station sequence number (SN) and the user data to be transmitted (as shown in step 3.b of Figure 2). The data to be transmitted here includes user data packets that should have been sent by the source base station during the disconnection period. The base station sequence number is an identifier for the base station.

[0031] Meanwhile, the synchronization algorithm within the UPF proactively modifies the downlink direction by predicting user handover, sending user data that should have been sent to the source S-gNB to the target S-gNB. This process is implemented in the standard process by steps 4-9 in Figure 2.

[0032] Step 4: Finally, notify the source S-gNB to release resources (Figure 2, Step 10). Once this is done, the switchover process is complete.

[0033] Therefore, to compare the solution of this application with existing standards, steps 1-10 in Figure 2 illustrate the standard handover process specified by the 3GPP 5G standards organization, which is the handover process currently used on the ground.

[0034] Step 1: The source satellite base station sends a handover request to the target satellite base station;

[0035] Step 2: The target satellite base station sends a handover request confirmation back to the source satellite base station;

[0036] Step 3 includes two sub-steps, one of which is...

[0037] 3.a.1 The source satellite base station sends an RRC reconnection request to the user equipment;

[0038] 3.a.2, The user equipment sends an RRC reconnection confirmation back to the source satellite base station;

[0039] Another sub-step, 3.b, involves the source satellite base station sending the SN status to the target satellite base station;

[0040] Step 4: The target satellite base station sends a path switching request to the AMF;

[0041] Step 5: The AMF forwards the path switching request to the SMF;

[0042] Step 6: SMF sends a bearer modification request to UPF;

[0043] Step 7: The UPF modifies the downlink and sends a bearer modification request reply back to the SMF;

[0044] Step 8: The SMF sends a path switching request to the AMF for forwarding confirmation;

[0045] Step 9: The AMF sends a path switching request confirmation to the target satellite base station;

[0046] Step 10: The target satellite base station sends a session release to the source satellite base station.

[0047] Here, AMF, SMF, and UPF are three functional entities in the 5G communication network, collectively forming part of the 5G core network and responsible for implementing different network functions. Specifically: AMF (Access and Mobility Management Function): This entity in the 5G core network is responsible for access control and mobility management of User Equipment (UE). It handles UE registration, deregistration, connection establishment, session management, and decisions during mobility processes such as handover and paging. AMF is also responsible for establishing and maintaining the UE's security context, including encryption and authentication processes. AMF manages PDU sessions (Packet Data Unit sessions), which are logical channels used for data transmission in the 5G network. SMF (Session Management Function): This function manages the UE's PDU sessions, including session establishment, modification, and release. SMF enforces policy rules, determining data flow routing and Quality of Service (QoS). SMF is also responsible for session billing and permission control, ensuring that the services used by users conform to their subscribed tariff plans.

[0048] UPF (User Plane Function) is the entity in the 5G core network responsible for forwarding user data. It processes data traffic from the UE and forwards it to the correct destination, such as the internet or a specific service network, according to the instructions of the SMF. The UPF also enforces data flow policies, such as traffic filtering and routing. The UPF is responsible for implementing the QoS rules defined by the SMF, ensuring that different types of traffic are transmitted according to priority and quality of service requirements.

[0049] However, directly applying the above communication process to satellite networks results in significant transmission delays. Specifically, this is because steps 4 and 9 involve inter-satellite communication in satellite networks, leading to substantial delays. This embodiment optimizes and avoids inter-satellite interaction during handover, specifically steps 4-9 in Figure 2, thereby shortening handover delays and ensuring service continuity for users.

[0050] Therefore, this embodiment of the disclosure shares with existing standards the handover decision process between user equipment and source satellite base station, the decision control process of target satellite base station, and the resource release process of source satellite base station, while a synchronization algorithm is designed in UPF.

[0051] The fast signaling handover process for low Earth orbit satellite mobile networks proposed in this disclosure includes the following embodiments:

[0052] Step 1: The source satellite base station sends a handover request to the target satellite base station;

[0053] Step 2: The target satellite base station sends a handover request confirmation back to the source satellite base station;

[0054] Step 3 includes two sub-steps, one of which is...

[0055] 3.a.1 The source satellite base station sends an RRC reconnection request to the user equipment;

[0056] 3.a.2, The user equipment sends an RRC reconnection confirmation back to the source satellite base station;

[0057] Another step,

[0058] 3.b, The source satellite base station sends the SN status to the target satellite base station;

[0059] Step 4: The target satellite base station sends a session release instruction to the source satellite base station.

[0060] Meanwhile, the UPF includes a synchronization algorithm to ensure that the operation of the entire system is not affected and normal switching is achieved even without steps 4-9. The pseudocode representation of this synchronization algorithm is given below.

[0061] The pseudocode above describes a synchronization algorithm for the User Plane Function (UPF). UPF is part of the 5G network architecture and is responsible for handling user data forwarding. This synchronization algorithm includes:

[0062] 1. `Initialize T,R`: Initializes two variables, T and R. T represents the time point when the prediction has been completed, while R represents the user-access satellite relationship stored by the algorithm.

[0063] 2. `while True do`: Starts an infinite loop, which means the algorithm will continue to run.

[0064] 3. `if current time>T then PERIODIC UPDATE(T+Δt)`: If the current time exceeds the time recorded in variable T, then call the `PERIODIC UPDATE` function and pass T plus a time interval Δt.

[0065] 4. `if localization of u change then UPDATE UE(u,T)`: If the location of user u changes, the `UPDATE UE` function is called, passing in the user identifier u and the current time T.

[0066] 5-13. The following section defines two procedures: `PERIODIC UPDATE` and `UPDATE UE`:

[0067] -`PERIODIC UPDATE(t)`: This is a periodic update process that takes a time parameter t.

[0068] 6. `Get At from R`: Retrieves the user's location information At at the current time from R.

[0069] 7. `Based on At, predict At+Δt according`: Based on the current user location information At, predict the location information at the next time point At+Δt.

[0070] 8. `According to At and At+Δt, get Tp with binary search`: Based on the current and predicted position information, use a binary search algorithm to obtain Tp, which is the time when user u switches between two points in time.

[0071] 9. `Wait until t, update R`: Wait until time t, then update R.

[0072] 10. `T = t`: Updates the current time T to the passed-in time parameter t.

[0073] 11. `UPDATE UE(u,t)`: This is a process for updating the user equipment (UE), receiving the user identifier u and the time parameter t.

[0074] 12. `Calculate At[u],At+Δt[u],and Tp[u]`: Calculates the user's location information at the current time and the next time, as well as the parameter Tp related to user u.

[0075] 13. `Update R`: Update R, the synchronization algorithm for the User-Access Satellite Relationship (UPF), is primarily responsible for handling periodic updates in the user plane function and updates due to changes in user location. It involves time management, location prediction, parameter calculation, and updating routing information.

[0076] The handover scheme proposed in this disclosure differs from existing communication standard handover processes in that it avoids the existing control signaling transmission steps between the RAN and the core network, which cause significant delays in mobile satellite networks. Therefore, this disclosure proposes a synchronization algorithm at the core network end, enabling synchronization with the RAN even without interaction. The synchronization algorithm between the RAN and the core network utilizes the predictable trajectory of LEO satellites, which is also a key aspect of this disclosure's scheme.

[0077] However, achieving this synchronization without requiring control signaling interaction between the RAN and the core network is a highly complex task. For example, a limited prediction frequency can lead to unacceptable handover delays. Furthermore, performing prediction operations on a large number of ground-based UEs places a significant computational burden on the UPF.

[0078] The most fundamental problem in achieving synchronization without control signaling interaction is predicting the UE's access satellite at the core network end. The performance of this prediction is affected by two factors: relative location and weather. This information is available at the core network. The former can be obtained based on the UE's location and the predictable trajectory of the satellite, while the latter can be obtained from the Internet. By utilizing this information and the UE's access policy, the UE's access satellite can be accurately determined at the core network.

[0079] After acquiring the UE's access satellites, the next problem is the asynchrony caused by coarse-grained prediction. Predicting the user's access satellites at a point in time and within a fixed time interval Δt is a straightforward approach. However, this mechanism cannot bypass the asynchrony between the RAN and the core network, leading to additional latency during handover. Due to the computational complexity of prediction, Δt is typically on the order of hundreds of milliseconds, so this additional latency can severely impact the entire handover process.

[0080] As a solution, this disclosure considers a mechanism for predicting user access to satellites simultaneously at two time points, which can resolve the aforementioned asynchrony problem. A detailed description follows.

[0081] Assume t0 and t1 = t0 + Δt are two consecutive time points in time where the UPF performs prediction. Let U refer to all UEs served by the UPF, and use... Let represent the set of satellites accessed by all users U at time t. By appropriately choosing Δt, it is ensured that for each UE u∈U, at most one handover is triggered between t0 and t1. Therefore, by comparing... and —The satellite access of user u at times t0 and t1 can determine whether a handover will be triggered between t0 and t1.

[0082] If a handover is to be triggered, the UPF needs to predict the accurate handover trigger time to minimize the duration of asynchrony between the RAN and the core network. To avoid any additional latency, the predicted handover trigger time T... p It should fall between the handover trigger and handover completion in the RAN. To achieve this, a simple and efficient binary search method can be used to determine this time point.

[0083] Based on the above discussion, this disclosure proposes a core network synchronization algorithm based on ephemeris, as shown in the pseudocode above. Specifically, T is first defined as the last time point after the periodic update is completed. p A predicted set of handover trigger times for each UE. The calculation results include... and T p All are stored in table R. In subsequent discussions, we will... The access satellite, referred to as u, will The next access satellite is called u. The synchronization algorithm proposed here considers two update scenarios based on the cause of the update.

[0084] Reason 1: Periodic updates caused by satellite motion. Because LEO satellites travel at high speeds, the synchronization algorithm iteratively updates periodically with a period of Δt. The following explanation uses a periodic update of T+Δt as an example. First, we obtain the update times of all UEs from R from T+Δt to... The satellite is accessed at the location, and then the predicted trajectory of the LEO satellite is used to predict T+2Δt. The location is accessible via satellite. According to... and The difference between them is used to calculate the predicted handover trigger time T using a binary search algorithm. p A set. Specifically, for those with different and For each UE u, we calculate its associated access satellite at the midpoint of time, T+1.5Δt, halving the prediction error of the access time. This process is repeated iteratively until the error is less than the time required for the RAN handover process. To avoid premature updates, we update table R when time reaches T+Δt.

[0085] Reason 2: Updates caused by the UE. When the location of UE u changes, possibly due to registration, deregistration, or relocation, the algorithm will also update UE u. At this time, the synchronization algorithm updates table R. and T p .

[0086] In summary, the fast handover method for low Earth orbit satellite mobile networks disclosed herein redesigns the handover signaling process to avoid interaction between the core network and the RAN. This design needs to address the synchronization issue between the core network and the RAN.

[0087] Regarding the synchronization problem between the core network and the RAN, since this disclosure avoids control signaling interaction between the core network and the RAN, measures are needed to solve the synchronization problem. This disclosure proposes a fine-grained synchronization algorithm that utilizes the predictable trajectory of satellites and weather information to accurately predict the handover trigger time by making predictions at two time points without interacting with the RAN, using methods such as binary search.

[0088] Traditional direct prediction methods consider all satellites in the constellation for each user equipment (UE) to predict access satellites, which generates enormous computational pressure. To address this issue, this disclosure leverages satellite access strategies and the unique spatial distribution of LEO satellites to significantly reduce the number of UEs and satellites required for prediction. By reducing computational pressure, it avoids situations that could potentially paralyze the core network.

[0089] In summary, the embodiments disclosed herein effectively reduce handover latency in mobile satellite networks and improve overall performance by redesigning the handover signaling process, introducing fine-grained synchronization algorithms, and utilizing satellite access strategies and spatial distribution. Figure 1 shows the latency measurement results of existing satellite mobile networks, including latency measurements for two currently relatively well-deployed commercial constellations, Starlink and Kuiper. The specific measurements include: terminal-to-base station latency, inter-base station latency, and base station-to-core network latency.

[0090] Figure 3 illustrates the system-level simulation results of this invention. The simulation compares the latency of different handover strategies using different access satellite selection policies and constellations to demonstrate the impact of these metrics. Here, NTN refers to the standard handover procedure specified in 5G NTN; NTN-GS refers to a handover procedure assisted by nearby ground stations, which utilizes ground stations near LEO satellites to record handover information, thus eliminating the need to transmit handover control signaling to the core network and reducing handover latency; NTN-SMN refers to a handover procedure assisted by a nearby space network (SMN). This strategy is similar to the NTN-GS handover scheme, where the satellite simultaneously acts as both the access network and the core network. This also reduces handover latency.

[0091] It can be observed that the handover scheme proposed in this disclosure outperforms the other three handover schemes in terms of latency. More specifically, as shown in Figure 3a, the average handover latency based on the proposed scheme is 20.87ms, significantly shorter than the handover latency based on the NTN strategy (250ms). Simultaneously, its handover latency is also much lower than the other two optimized handover schemes (NTN-GS and NTN-SMN), at 153ms and 158.5ms respectively. Figures 3a and 3b illustrate the handover latency using different access satellite selection strategies. It can be seen that without optimizing the access satellite selection process, the average handover latency increases by approximately 6.1 times compared to the proposed handover scheme. This means that the simple and effective optimal access satellite selection scheme proposed during the handover process can significantly reduce handover latency. This performance improvement can be attributed to the reduced transmission latency between satellites when they are in the same direction among satellite constellations. Since onboard base stations need to exchange information, information transmission between satellites is unavoidable. Similar performance was also observed under other satellite selection strategies.

[0092] Finally, this disclosure evaluates the performance of the proposed handover scheme under different satellite constellations, including Starlink and Kuiper. First, it can be seen that the proposed handover strategy outperforms the other three handover schemes regardless of the satellite constellation, as shown in Figures 3a and 3e. This is because the proposed handover scheme primarily utilizes the predictable orbital trajectories of low-Earth orbit satellites to reduce handover latency, and is therefore constellation-independent. Second, the handover latency difference between the Starlink and Kuiper satellite constellations is small (averaging approximately 10%), mainly due to differences in constellation configurations such as inter-satellite and intra-satellite distances and satellite altitudes. Third, this disclosure observes a slight difference in handover latency when using different access satellite selection strategies within the Kuiper satellite constellation, which can be verified by comparing Figures 3e and 3f.

[0093] Figure 4 illustrates the application-level latency performance of this invention. Compared to 5G NTN handover strategies, the handover scheme based on this disclosure reduces latency by 89%. Furthermore, in the case of TCP streams, compared to 5G NTN handover, the handover scheme based on this invention reduces latency by 33%, as shown in Figure 4a. This is because handover affects user-level performance; significant handover latency increases the latency of user-level applications, thereby reducing overall performance.

[0094] Meanwhile, in the case of TCP streams, the limited performance improvement is due to the three-way handshake mechanism, which incurs significant time overhead, exacerbated by the long propagation delay between satellites. To illustrate this further, experiments were conducted to investigate the ping process in mobile satellite networks. As shown in Figure 4b, the stall time during link recovery can be divided into two steps:

[0095] First, the user terminal connects to the target base station. Second, after a period of time, the connection between the user and the server is restored.

[0096] The proposed handover scheme can significantly reduce the time delay of the first step, i.e., the time required for link recovery. However, the overhead of the second step is mainly caused by inter-satellite latency, which is beyond the scope of this invention, thus limiting the performance improvement in terms of latency.

[0097] As shown in Figure 5, this disclosure studies the performance of the fast satellite access prediction algorithm under different numbers of users. The time overhead of using the consistent access strategy is much lower than that of the flexible strategy because the number of handovers under the consistent access strategy is much smaller than that under the flexible strategy. Meanwhile, the computation time increases with the number of users.

[0098] Based on the deployment of existing commercial mega-constellations, a single ground station serves an average of around 10,000 users. With 10,000 users, the computation time using a commercial laptop is approximately 2 seconds, within the handover time requirements. Some predict that the number of users in future satellite networks will increase significantly, thus exacerbating the computational burden on ground stations. However, this challenge can actually be easily overcome by equipping ground stations with higher-performance hardware.

[0099] Furthermore, this disclosure assesses the impact of user mobility (e.g., users moving at different speeds in active and inactive scenarios) on handover performance. Deviations between user mobility and satellite orbit predictions can lead to inaccurate predictions of satellite access for the terminal; this disclosure defines this situation as "abnormal handover."

[0100] As shown in Figure 6, for active ground users, the probability of an "abnormal handover" is very low. For users on high-speed airplanes, the probability is approximately 10⁻⁶; at walking speeds, the probability is on the order of one in a million, which can be considered negligible. On the other hand, for users who are moving at high speeds and inactive for extended periods, the likelihood of triggering an "abnormal handover" is relatively high. For example, after 10 minutes of inactivity, users on airplanes have an 18% probability of experiencing an abnormal handover, while users traveling on high-speed trains have a 7% probability. In fact, the latency cost of such an abnormal handover is equivalent to the time overhead of a standard 5G NTN handover. Therefore, in these cases, the abnormal handover scheme can be considered as a standard 5G NTN handover.

[0101] It should be understood that in the embodiments of the present invention, the term "and / or" is merely a description of the relationship between associated objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Furthermore, the character " / " in this document generally indicates that the preceding and following associated objects have an "or" relationship.

[0102] It is worth noting that although the spirit and principles of this invention have been described with reference to several specific embodiments, it should be understood that this invention is not limited to the disclosed specific embodiments, and the division of aspects does not imply that the features in these aspects cannot be combined; such division is merely for the convenience of description. This invention is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

Claims

1. A method for handover of satellite base stations in a low Earth orbit satellite mobile network, characterized in that, Includes the following steps: S101, The source satellite base station connected to the UE sends a handover request to the target satellite base station; S102, after receiving the handover request, the target satellite base station prepares for the handover and sends a handover confirmation to the source satellite base station, which receives the handover confirmation. S103, the source satellite base station notifies the UE connected to it of the handover decision in progress, and the UE disconnects from the source satellite base station and establishes a new RRC connection with the target satellite base station; S104, the source satellite base station and the target satellite base station transmit synchronization data.

2. The method according to claim 1, characterized in that, In step S102, the handover preparation includes pre-allocating channel resources.

3. The method according to claim 1, characterized in that, The method for predicting or determining the target satellite base station is to consider the relative position of the target satellite base station relative to the source satellite base station, and / or weather factors.

4. The method according to claim 3, characterized in that, The relative position of the target satellite base station to the source satellite base station is calculated using the position of the UE and / or the predicted trajectory of the satellite base station.

5. The method according to claim 3, characterized in that, The weather information was obtained from the Internet.

6. The method according to claim 3, characterized in that, The target satellite base station is continuously predicted or determined at preset time intervals.

7. A low Earth orbit satellite mobile network, characterized in that, The satellite mobile network includes a source satellite base station, a target satellite base station, and a UE, and the base station handover of the network is performed as described in claim 1.

8. A satellite base station for a low Earth orbit satellite mobile network, characterized in that, The satellite base station is connected to the UE and serves as the source satellite base station. The method for switching the source satellite base station is as described in claim 1.

9. A UE for a low Earth orbit satellite mobile network, characterized in that, The UE is connected to the source satellite base station, and the handover method of the source satellite base station is as described in claim 1.

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