Handover method and related device

Abstract

A handover method includes, when a base station is a single base station on a satellite and the satellite performs a feeder link handover, the base station performing a handover procedure by simultaneously acting as a source radio access network (RAN) node and a target RAN node. This enables a regenerative satellite payload to implement a feeder link handover.

Description

Technical Field

[0001] This application relates to the field of wireless communication, and more specifically, to a switching method and related equipment. Background Technology

[0002] In cellular wireless communication systems developed under the Third Generation Partnership Project (3GPP), user equipment (UE) connects to the radio access network (RAN) via a radio link. The RAN comprises a set of base stations (BSs) that provide radio links to UEs located within their covered cells and also provide an interface to the core network (CN), which provides overall network control. The RAN and CN each perform their respective functions related to the overall network. The so-called 4G Long Term Evolution (LTE) system, namely the Evolved Universal Mobile Communications System Regional Radio Access Network (E-UTRAN), was developed for mobile access networks, where one or more macro cells are supported by base stations called eNodeBs or eNBs (evolved NodeBs). The so-called 5G or new radio (NR) system, evolving from LTE, supports one or more cells by base stations called gNBs. 6G cellular systems are the upcoming generation of wireless communication technology, designed to replace current 5G networks.

[0003] The concept of transparent mode satellite access has been introduced to facilitate the integration of satellite components with EPS and 5GS architectures. This approach assumes that the satellite acts solely as a transmission channel, forwarding signals without performing any processing. The NG-RAN supported by the satellite resides on the ground. The satellite functions as a remote unit, completely transparent to 3GPP protocols.

[0004] The regenerative satellite payloads are designed to directly embed ground base stations (gNBs) and / or 5G core network functions into the satellite. This capability brings several value-added services to users, such as supporting reduced latency on the user plane and control plane, and enabling ISL communications. For network operations, these regenerative payloads offer greater flexibility in deploying space-segment-related ground segment or NTN gateways.

[0005] Figure 1 A schematic diagram of a non-terrestrial network (NTN) is shown. It should be noted that... Figure 1The NTN payload will transparently forward the radio protocol received by the UE (via the serving link) to the NTN gateway (via the feeder link) and vice versa. In this case, such as Figure 2 As shown, the protocol running on the feeder link is NR Uu, meaning that in this case, the satellite payload performs frequency conversion and RF amplification in both the uplink and downlink directions. The satellite forwards the NR-Uu radio interface from the feeder link (between the NTN gateway and the satellite) to the service link (between the satellite and the UE), and vice versa.

[0006] The satellite radio interface (SRI) on the feeder link is NR-Uu. In other words, the satellite does not terminate NR-Uu.

[0007] The scenario for regenerating payloads is quite different, such as Figure 3 As shown, the SRI on the feeder link between the NTN gateway (GW) and the satellite is the transmission link between the NTN GW and the satellite, with an NG interface.

[0008] Section 16.14.4 of TS 38.300 outlines the feeder link handover procedure in transparent payload scenarios. The NTN control function determines the timing of the feeder link handover between the two gNBs. During feeder link handover, the transmission of the affected UE's context between the two gNBs is achieved through NG-based or Xn-based handover, depending on the gNB implementation and the configuration information provided to the gNB by the NTN control function. A diagram illustrating the NTN control function is provided below. Figure 4 .

[0009] The NTN control function controls the radio resources (NTN payload and NTN gateway) of onboard (or unmanned) vehicles and the NTN infrastructure. It provides control data, such as satellite ephemeris information, to the non-NTN infrastructure gNB functions. Providing NTN control data to the gNB is not within the scope of 3GPP.

[0010] However, the situation changes in the case of regenerated payloads, where the gNB is deployed directly on the satellite, causing the NG-AP at the satellite to terminate. Figure 5 This shows that before and after the feeder link switch, the regenerable satellite payload was served by the same AMF. In this case, both feeder links are connected to the same AMF, but through different NTN GWs. Figure 5As shown, this configuration faces challenges due to satellite movement, which could lead to the loss of feeder link connectivity with the NTN gateway. In this scenario, the feeder link may need to be switched from NTN GW1 to NTN GW2 when a Low Earth Orbit (LEO) satellite leaves the coverage area of ​​NTN GW1.

[0011] This contrasts with transparent load scenarios, where the gNB is typically located on the ground, alongside the NTN GW. In such scenarios, switching in the feeder link only affects the Uu interface, while the NG-AP and N3 interfaces remain unaffected.

[0012] In addition, such as Figure 6 As shown, the switching of feeder links in the regenerated payload may cause changes in AMF, where AMF1 is connected to NTN GW1 and AMF2 is connected to NTN GW2.

[0013] The payload on a satellite may consist of multiple gNBs. It's also possible that a satellite carries only one gNB. In this case, it can be beneficial for the two AMFs to exchange information about the satellites that may be involved during NG setup and / or AMF configuration updates, such as a list of satellites connected to the AMF, the ID of each satellite in the list, a list of cells carrying the gNB, and the satellite's ephemeris data.

[0014] Existing solutions and processes are insufficient to support feeder link switching in regenerated payload scenarios.

[0015] In regeneration scenarios, the existing handover process is also insufficient because the serving cell and gNB continuously cover the area where the UE is located, thus preventing handover from being triggered.

[0016] Therefore, adopting the current 3GPP process or the transparent payload satellite 5GC integration process cannot solve the feeder link switching problem in the regenerative payload scenario. Summary of the Invention

[0017] In a first aspect, some embodiments of this application provide a handover method, including performing a handover process by acting as both a source radio access network (RAN) node and a target RAN node when the base station is a single base station on a satellite and the satellite is undergoing feeder link handover.

[0018] In a second aspect, some embodiments of this application provide a communication device including a processor configured to invoke and execute program instructions stored in a memory to perform any of the methods described above. Attached Figure Description

[0019] To more clearly illustrate the embodiments of this application or related technologies, the accompanying drawings described in the embodiments will be briefly introduced below. Obviously, these drawings are only some embodiments of this application, and those skilled in the art can obtain other drawings based on these drawings without incurring additional costs.

[0020] Figure 1 This is a schematic diagram illustrating a Non-Terrestrial Network (NTN).

[0021] Figure 2 This is a schematic diagram illustrating that the satellite payload transmitted between the satellite and the NTN gateway is a transparent payload.

[0022] Figure 3 This is a schematic diagram showing that the satellite payload between the satellite and the NTN gateway is a regenerative payload.

[0023] Figure 4 This is a schematic diagram illustrating the architecture of an NTN infrastructure that includes NTN control functions.

[0024] Figure 5 This is a schematic diagram of the first scenario, in which the onboard gNB continuously covers the area where the UE is located with an adjustable beam, but the feeder link is switched from NTN GW1 to NTN GW2.

[0025] Figure 6 This is a schematic diagram of the second scenario, in which the onboard gNB continuously covers the area where the UE is located with an adjustable beam, but the feeder link is switched from NTN GW1 to NTN GW2.

[0026] Figure 7 This is a flowchart of a switching method according to an embodiment of this application.

[0027] Figure 8 This is a schematic diagram of a registration process triggered by feeder link switching according to an embodiment of this application.

[0028] Figure 9 This is a schematic diagram of Xn-based switching to support feeder link switching according to an embodiment of this application.

[0029] Figure 10 This is a schematic diagram of a placeholder for N2-based switching according to an embodiment of this application.

[0030] Figure 11 This is a schematic diagram of a TNL-based association solution according to an embodiment of this application. Detailed Implementation

[0031] The embodiments of this disclosure will be described in detail below with reference to the accompanying drawings, including technical content, structural features, achieved objectives, and effects. Specifically, the terminology used in the embodiments of this application is only used to describe the purpose of specific embodiments and is not intended to limit the scope of this disclosure.

[0032] In this document, combinations such as “at least one of A, B or C”, “one or more of A, B or C”, “at least one of A, B and C”, “one or more of A, B and C” or “A, B and / or C” may be only A, only B, only C, A and B, A and C, B and C, or A, B and C, where any combination may contain one or more members of A, B or C.

[0033] The following table lists some abbreviations that may be used in some embodiments of this application:

[0034] This disclosure provides the following solutions to support feeder link switching for onboard gNB or NG-RAN in 5G and satellite convergence.

[0035] A UE configuration update has been introduced to support feeder link switching.

[0036] The feeder link handover-triggered registration process provides a method for enabling the gNB to establish a connection with the new AMF, whereby a feeder link handover triggers a registration process. This article outlines the detailed steps of this process and focuses on the specific interactions between the UE, gNB, and AMF.

[0037] The UE learns of feeder link switching in multiple ways, including information pre-stored in the USIM, updates to user equipment configuration parameters via NAS signaling, and information from NTN control functions.

[0038] The post-registration process following AMF change and AN release outlines the procedures that may involve AN release. This release is triggered by predefined events such as feeder link switching or unavailability.

[0039] The adaptation for N2-based handover between NG-RAN nodes for feeder link switching covers the adaptation of standard handover procedures for scenarios involving feeder link switching, especially in satellite-based gNB mobile scenarios.

[0040] Conditional Handover (CHO) triggered by feeder link handover focuses on the UE performing a conditional handover when the feeder link handover conditions are met. This includes the process of the gNB notifying the UE that the feeder link is unavailable, and subsequent steps performed in accordance with relevant technical specifications.

[0041] Load rebalancing between AMFs during feeder link switching reveals a method for managing TNL associations using an AMF configuration update process, facilitating feeder link switching. This method includes strategies for dynamically adding or removing TNL associations during switching, as well as strategies for assigning weighting factors to transitions.

[0042] The feeder switching process for a single-board onboard gNB covers a specific scenario where the satellite carries only one gNB, detailing how the gNB simultaneously plays the role of source and target during the switching process.

[0043] Managing TNL associations in feeder link switching scenarios involves the signaling process between the gNB and AMF used to manage TNL associations during feeder link switching, including specific details of the TNLA removal and update procedures.

[0044] Figure 7 This is a flowchart of a handover method according to an embodiment of this application. Method 100 includes the following steps. In step 110, when the base station (e.g., gNB) is a single base station on a satellite and the satellite is undergoing feeder link handover, the base station performs the handover procedure by simultaneously acting as both a source RAN node and a target RAN node. This method enables feeder link handover of the regenerated satellite payload.

[0045] In some embodiments, the handover process may result in changes to the access and mobility management function (AMF) associated with the new non-terrestrial network (NTN) gateway (GW). In one embodiment, the method may further include a handover decision made by the base station based on the feeder link state. In one example, the handover process may be an Xn-based handover process. In another example, the handover process may be an N2-based handover process.

[0046] In some embodiments, the handover procedure may be a conditional handover (CHO) procedure. In one embodiment, the method may further include notifying the user equipment (UE) of a CHO configuration, which includes execution conditions and the configuration of CHO candidate cells. Execution conditions may include feeder link unavailability and the requirement for different AMFs being met. In some embodiments, the method may further include determining the need for different AMFs based on satellite control data. In one embodiment, the CHO configuration is notified to the UE via a radio resource control (RRC) message.

[0047] In some embodiments, the method may further include: notifying the UE to initiate a registration process due to a feeder link switch; and receiving a registration request message from the UE and forwarding the registration request message to a new AMF, wherein the registration request message includes the feeder link switch situation. In one embodiment, the registration request message indicates a registration type triggered by a feeder link switch. In one embodiment, the registration request message indicates a registration reason in a sub-element of the registration type. In one embodiment, the UE obtains feeder link switch information through one of the following: information pre-stored in a non-volatile memory in a universal subscriber identity module (USIM) or mobile equipment (ME); updates to UE configuration parameters; or information from an NTN control function or a specific module in an NTN GW.

[0048] In some embodiments, the AMF used before and after the feeder link handover is the same. In one embodiment, transport network layer (TNL) associations are added or removed in one or more of the following ways: a TNL association on the source NTN GW is removed, and a new TNL association is added on the target NTN GW; while maintaining the same association, the local and remote IP addresses in the association are changed; and a rebalancing weight factor is assigned to the TNL associations (TNLAssociations, TNLAs) on the source NTN GW and the target NTN GW. In one embodiment, the AMF used before and after the feeder link handover is different. In one embodiment, the method may further include: sending a signal to the source AMF to prepare for the feeder link handover; receiving a removal list of transport network layer (TNL) associations (TNLAs) or an updated list of AMF TNLAs with weight factors from the source AMF; and updating the weight factors of the AMF-TNLAs in the updated list provided by the source AMF, or removing TNLAs based on the removal list. In one embodiment, the method may further include: sending a signal to a target AMF to prepare for feeder link switching; receiving an add list of transport network layer (TNL) associations (TNLAs) or an updated list of AMF TNLAs with weight factors from the target AMF; and updating the weight factors of the AMF TNLAs in the updated list provided by the target AMF, or adding TNLAs based on the add list.

[0049] For the registration process triggered by feeder link switching: In this method, feeder link switching triggers a registration process, enabling the gNB to establish a connection with the new AMF. Figure 8 The registration process triggered by feeder link handover is described in detail. The process begins in step 0, where the UE is notified to initiate the registration process due to feeder link handover.

[0050] The UE obtains feeder link switching information through various methods: (a) Information pre-stored in non-volatile memory in the USIM or ME.

[0051] (b) Update of UE configuration parameters. The 5GS in the PLMN can update UE parameters via NAS signaling. For example, the AMF may send feeder link switching information to the UE, enabling the HPLMMN to securely and dynamically reconfigure the UE configuration parameters stored on the USIM and ME.

[0052] (c) Information from NTN control functions or specific modules in the NTN GW. The AMF that predicts the handover start time may send a NAS UE configuration update command, prompting the UE to initiate re-registration with the new AMF.

[0053] In steps 1 and 2, the registration request message is forwarded to the new AMF, including the reason being feeder link switching.

[0054] The registration type can be a new type, such as registration triggered by a feeder link switch. Alternatively, it can be indicated as a sub-element of an existing registration type in the registration reason.

[0055] Select a new AMF as described in Clause 6.3.5 of TS 23.501.

[0056] After registration, the AN release may be performed locally by the AMF or RAN as specified in Clause 4.2.6 of TS 23.502. In the event of loss of NG-AP signaling connection due to a (R)AN or AMF failure, this release is performed locally by the AMF or (R)AN, without relying on the signaling indicated between the (R)AN and AMF. The AN release will disable all UP connections of the UE.

[0057] Factors that may trigger AN release include feeder link switching or feeder link unavailability.

[0058] Regarding the switching method: When the UE is in connected mode, Xn-based, N2-based, or conditional handovers may be initiated due to feeder link handover. However, feeder link handover scenarios require special consideration due to the unique challenges posed by satellite-based gNB mobility and feeder link handover.

[0059] Specifically, the N2-based handover procedure between NG-RAN nodes can be applied to intra-NG-RAN handover in regenerative systems. For example, when a single gNB on a satellite performs a feeder link handover, it may enter the coverage area of ​​a new AMF. In this case, the gNB acts as both the source and destination NG-RAN node, facilitating the handover, thereby causing a change in the AMF associated with the new NTN gateway.

[0060] Figure 9 This demonstrates the call flow for an Xn-based handover triggered by a feeder link switch. With only one onboard gNB, that gNB acts as both the source and destination gNB in ​​the handover process. The handover decision is made by the source gNB based on the feeder link's state. When the feeder link begins switching to another NTN gateway, the single onboard gNB assumes the dual role of source and destination gNB to initiate handover preparation. It then follows the Xn-based handover process defined in Clause 4.9.1.2 of TS 23.502.

[0061] same, Figure 10 This describes the call flow for an NG-based handover driven by a feeder link switch when there is only one onboard gNB. In this configuration, the onboard gNB acts as both the source and destination for the handover. The handover decision is again made by the source gNB and is influenced by the feeder link status. When the feeder link switches to a different NTN gateway, the onboard gNB simultaneously acts as both the source and destination to begin handover preparation. Subsequently, the gNB follows the flow outlined in Section 4.9.1.3 of TS 23.502 for N2-based handover.

[0062] For UE-triggered CHO due to feeder link switching: Conditional Handover (CHO) refers to a handover performed by the UE when one or more handover execution conditions are met.

[0063] The feeder link status is sent to the UE as a CHO configuration. The UE begins to evaluate the execution conditions of the CHO candidate cell and executes the CHO if the execution conditions are met.

[0064] Once the gNB receives a notification that the feeder link is unavailable, the gNB on the satellite will decide to use CHO to perform a handover based on the feeder link unavailable status information.

[0065] Unless otherwise stated in this disclosure, the CHO driven by the feeder link switching follows the general procedure specified in Clauses 9.2.3.4 and 16.14.3.2.2 of TS 38.300.

[0066] In step 6 of clause 9.2.3.4.2 of TS 38.300, the source gNB notifies the UE by sending an RRC reconfiguration containing the CHO configuration, where the CHO configuration includes the CHO candidate cell configuration generated by each CHO candidate cell and the execution conditions generated by the source cell. In addition to the execution conditions specified in clauses 9.2.3.4.1 and 16.14.3.2.2 of TS 38.300 and relevant clauses in TS 38.331, the execution conditions may also include the conditions of feeder link unavailability and the fulfillment of requirements for different AMFs.

[0067] For example, based on satellite control data (such as ephemeris information), the gNB can determine that a different AMF is required. The gNB may notify the UE via RRC messages or other means that a conditional handover triggered by a feeder link switch is required.

[0068] If there is only one gNB on the satellite, that gNB will simultaneously act as both the source gNB and the target gNB to perform these conditional handover procedures.

[0069] For feeder link switching achieved through load rebalancing between AMFs: The AMF configuration update process can be used to manage TNL associations, thereby facilitating feeder link switching.

[0070] When a feeder link switchover is triggered, or before a feeder link is interrupted, the gNB node and the AMF have exchanged configuration data. During these interactions, the AMF provides the gNB with information about the TNL association set to be established, the weight factor of each TNL association within the AMF, and the weight factor of each AMF name within the AMF set.

[0071] When the same AMF is used before and after the switchover, since each gNB node / AMF pair can be configured with multiple TNL endpoints, the AMF can dynamically add or remove TNL associations using one or more of the following methods. - Request to remove the TNL association on the source NTN GW and add a new TNL association on the target NTN GW.

[0072] - Keep the association unchanged when you change the local and remote IP addresses in this association.

[0073] - Assign rebalancing weight factors to TNLA on the source and target NTN GW.

[0074] If the source AMF and target AMF belong to the same AMF set, and there is an opportunity to balance network load during the transition period of a soft handover, a strategy of assigning different weight factors to TNL associations can be adopted to move subscribers to the target AMF. In this case, the source AMF and target AMF provide the gNB with information about the set of TNL associations to be established, as well as the weight factor of each TNL association (e.g., 0 TNL associations for the source AMF and 100 TNL associations for the target AMF).

[0075] If different AMFs are used before and after the switch, Figure 11 A possible call flow is provided to support this scenario.

[0076] In step 1, the gNB sends relevant satellite information (such as satellite ID and ephemeris data) during NG setup or RAN configuration updates.

[0077] In step 2, when configuring TNL associations (TNLAs), the source AMF may consider the satellite information obtained in step 1 and send these associations to the gNB, for example, by specifying TNLAs to the removal list and / or AMFTNLAs to the weighted update list.

[0078] An AMF configuration update may be initiated to provide the gNB AMF TNLA to the removal list, as this AMF may have TNLA associations serving other gNBs that cannot be removed.

[0079] After step 2, if a hard handover occurs, the gNB can initiate the deletion of the TNLA provided by the source AMF in step 2 or update the TNLA weight factor provided by the source AMF in step 2.

[0080] In the third step, the gNB sends a signal to the target AMF to prepare for feeder link switching, for example, by using the RAN configuration update procedure.

[0081] gNB sends a signal to AMF2 via RAN configuration updates or other means to trigger AMF2 to provide AMFTNLA to the add list.

[0082] In step 4, the target AMF provides TNLA to the add list and / or provides AMF TNLA to the update list with weighting factors.

[0083] In the case of a soft handover, the gNB will create a new TNLA or update the TNLA information and remove the TNLA from the source AMF.

[0084] It is worth noting that for hard feeder link switching, the onboard gNB can only connect to one NTN gateway at any given time; while for soft feeder link switching, the onboard gNB can connect to both the source NTN gateway and the target NTN gateway simultaneously within a given time period.

[0085] This invention supports feeder link handover between regenerative payload satellites and core networks (such as 5GC). Without the proposed procedure, the UE cannot connect to the target AMF, and the target AMF cannot obtain the UE's context, resulting in unnecessary signaling overhead and additional power consumption for the UE. These factors lead to prolonged service outages and a degraded overall user experience.

[0086] Updating UE configurations based on network changes can improve UE performance and user experience.

[0087] Adjusting the switching procedure for feeder link switching can minimize UE service interruptions and ensure smooth connectivity.

[0088] Conditional Handover (CHO), triggered by feeder link switching, allows UEs to actively participate in handover decisions, thereby improving network efficiency and user satisfaction.

[0089] During the handover process, load balancing between AMFs can improve network efficiency, thereby directly improving UE performance and quality of service.

[0090] Embodiments of this application also provide a computer-readable storage medium for storing a computer program. This computer-readable storage medium enables a computer to execute the corresponding processes implemented in each method of the embodiments of this application. For the sake of brevity, further details are omitted here.

[0091] Embodiments of this application also provide a computer program product including computer program instructions. This computer program product enables a computer to execute the corresponding processes implemented in each method of the embodiments of this application. For the sake of brevity, further details are omitted here.

[0092] Embodiments of this application also provide a computer program. This computer program enables a computer to execute the corresponding processes implemented in each method of the embodiments of this application. For the sake of brevity, details are not repeated herein.

[0093] Those skilled in the art will understand that information and signals can be represented using a variety of different techniques and methods. For example, data, instructions, commands, information, signals, bits, symbols, and chips that may be referenced in the foregoing description can be represented by voltage, current, electromagnetic waves, magnetic fields or magnetic particles, optical fields or optical particles, or any combination thereof.

[0094] Furthermore, those skilled in the art will understand that the various exemplary logic blocks, modules, circuits, and algorithm steps described in conjunction with the embodiments disclosed herein can be implemented as electronic hardware, computer software, or a combination of both. To clearly illustrate this interchangeability between hardware and software, the various exemplary components, blocks, modules, circuits, and steps have been generally described above in terms of their functionality. Whether these functions are implemented as hardware or software depends on the specific application and the design constraints imposed on the overall system. Those skilled in the art can implement the described functions in different ways for each specific application, but these implementation decisions should not be construed as departing from the scope of the invention.

[0095] The methods, sequences, and / or algorithms described in conjunction with the embodiments disclosed herein may be embodied directly in hardware, in software modules executed by a processor, or a combination of both. The software modules may reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disks, removable disks, CD-ROMs, or any other form of storage medium known in the art. An exemplary storage medium is coupled to a processor such that the processor can read information from and write information to the storage medium. Alternatively, the storage medium may be part of the processor.

[0096] It should be understood that any “non-transient” embodiments disclosed herein do not exclude any physical storage medium, but only exclude the interpretation of such medium as a transient propagating signal.

[0097] The elements and components of this invention can be implemented physically, functionally, and logically in any suitable manner. In fact, these functions can be implemented as a single unit, multiple units, or as part of other functional units. Although the invention has been described in conjunction with certain embodiments, it is not intended to be limited to the specific forms set forth herein. Rather, the scope of the invention is defined only by the appended claims. Furthermore, although a feature may appear to be described in conjunction with a particular embodiment, those skilled in the art will recognize that various features of the described embodiments can be combined together according to the invention. In the claims, the word "comprising" does not exclude the presence of other elements or steps.

[0098] Furthermore, although means, elements, or method steps are listed separately, they may also be implemented by, for example, a single unit or processor. Additionally, while individual features may be included in different claims, these features may be advantageously combined, and inclusion in different claims does not imply that the combination of features is infeasible and / or lacks advantage. Similarly, inclusion of a feature in one class of claims does not imply limitation to that class, but rather indicates that the feature is equally applicable to other appropriate claim classes.

[0099] Furthermore, the order of features in the claims does not imply that these features must be performed in a specific order. In particular, the order of steps in a method claim does not imply that these steps must be performed in this order. On the contrary, these steps can be performed in any suitable order. Moreover, singular references do not exclude plural meanings. Therefore, references to "an," "first," "second," etc., do not exclude plural meanings.

[0100] While preferred embodiments of this application have been described in detail, various modifications and alterations can be made thereto by those skilled in the art. Therefore, the embodiments of this application are described in an illustrative rather than restrictive sense. This application is not limited to the specific forms shown, and all modifications and alterations that maintain the spirit and scope of this application fall within the scope defined by the appended claims.

Claims

1. A switching method, comprising: When the base station is a single base station on a satellite and the satellite is performing a feeder link handover, the base station performs the handover procedure by simultaneously acting as a source radio access network (RAN) node and a target RAN node.

2. The method according to claim 1, wherein, The handover process results in changes to the Access and Mobility Management Functions (AMF) associated with the new non-terrestrial network NTN gateway GW.

3. The method according to claim 1, further comprising: The base station makes a handover decision based on the feeder link status.

4. The method according to claim 1, wherein the switching process is a switching process based on Xn.

5. The method according to claim 1, wherein the switching process is a switching process based on N2.

6. The method according to claim 1, wherein the switching process is a condition-switching CHO process.

7. The method according to claim 6, further comprising: The User Equipment (UE) is notified of the CHO configuration, which includes the execution conditions and the configuration of the CHO candidate cells.

8. The method of claim 7, wherein the execution conditions include feeder link unavailable and the requirements for different AMFs being met.

9. The method according to claim 7, further comprising: Based on satellite control data, different AMFs are required.

10. The method according to claim 7, wherein, The CHO configuration is notified to the UE via a Radio Resource Control (RRC) message.

11. The method of claim 1, further comprising: Due to the feeder link switching, the UE is notified to initiate the registration process; and The UE receives a registration request message and forwards the registration request message to a new AMF, wherein the registration request message includes the case of feeder link switching.

12. The method of claim 11, wherein the registration request message indicates a registration type triggered by feeder link switching.

13. The method according to claim 11, wherein, The registration request message indicates the registration reason in the sub-element of the registration type.

14. The method according to claim 11, wherein, The UE obtains feeder link switching information through one of the following methods: Information pre-stored in the non-volatile memory of the Universal User Identification Module (USIM) or the Mobile Equipment (ME); Update UE configuration parameters; Information from NTN control functions or specific modules in the NTN GW.

15. The method of claim 1, wherein the AMF used before and after the feeder link switching is the same.

16. The method according to claim 15, wherein, Transport Network Layer (TNL) associations can be added or removed in one or more of the following ways: The TNL association on the source NTN GW is removed, and the new TNL association is added to the target NTN GW; While maintaining the same association, change the local and remote IP addresses in this association; and A rebalancing weighting factor was assigned to the TNL association TNLA on the source NTN GW and the target NTN GW.

17. The method of claim 1, wherein the AMF used before and after the feeder link switching is different.

18. The method of claim 17, further comprising: Send a signal to the source AMF to prepare for the feeder link switch; Receive a removal list of transport network layer TNL associated with TNLA or an AMF TNLA update list with weight factors from the source AMF; and Update the weight factor of AMF TNLA in the update list provided by the source AMF, or remove TNLA based on the removal list.

19. The method of claim 17, further comprising: Send a signal to the target AMF to prepare for the feeder link switch; Receive an add list of transport network layer TNL associated with TNLA or an AMF TNLA update list with weight factors from the target AMF; and Update the weight factor of AMF TNLA in the updated list provided by the target AMF, or add TNLA based on the added list.

20. A communication device comprising a processor configured to invoke and execute program instructions stored in a memory to perform the method of any one of claims 1 to 20.

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