A NTN satellite communication fast switching method, system, device and medium

Abstract

The application provides a NTN satellite communication fast switching method, system, device and medium, comprising: a master cell base station identifies that a terminal supports a protocol extension function, and preconfigures a target cell base station as a secondary cell base station, so that all service bearers of the terminal are transmitted by the master and secondary cell base stations; the master cell base station triggers switching according to a terminal measurement result, and completes switching preparation through interface signaling to make the secondary cell base station preacquire a security key and preconfigure a signaling bearer; the master cell base station sends first reconfiguration signaling to instruct the terminal to migrate the signaling bearer and update the key step by step, and only the signaling bearer takes effect with a new key; the terminal sends reconfiguration completion signaling through the newly established signaling bearer of the secondary cell, and the secondary cell base station receives the reconfiguration completion signaling and executes path switching to upgrade to a new master cell base station. By using the above scheme, the switching time of NTN satellite communication is shortened, the service interruption risk in the switching process is reduced, and the execution efficiency of the switching process is improved.

Description

Technical Field

[0001] This application relates to the field of non-terrestrial network communication, and more specifically, to a method, system, device, and medium for fast switching of NTN satellite communication. Background Technology

[0002] Non-terrestrial network (NTN) satellite communication, as an important supplement to terrestrial mobile communication, has been incorporated into the 5G and subsequent mobile communication standards system by 3GPP R17 / R18. It can achieve wide-area coverage in remote areas, oceans, airspace, and other terrestrial communication blind spots, and is a core technology for building a seamless communication network across all domains. Due to the high-speed mobility of low-Earth orbit satellites, terminals need to frequently cross different satellite cells during communication. Cell handover technology directly determines the continuity and stability of terminal service transmission. The inherent characteristics of satellite-to-ground link transmission delay and large signal jitter place stringent requirements on the latency and interruption control of the handover process.

[0003] In the current NTN satellite communication system, cell handover directly adopts the conventional handover mechanism of terrestrial cellular networks defined by the 3GPP protocol. This mechanism takes measurement reporting as the trigger condition and completes standardized steps in sequence, such as handover decision, target cell context establishment, source cell service bearer release, target cell bearer reconstruction, security key update, and user plane path handover. During the handover process, the terminal maintains only a single cell communication connection and follows the handover logic of disconnecting before reconnecting throughout the process.

[0004] Due to the high latency characteristics of NTN satellite-to-ground transmission, the steps of releasing the source cell bearer and rebuilding the target cell bearer in the conventional ground handover mechanism will generate significant service transmission gaps. Furthermore, the bidirectional transmission of multiple rounds of signaling will further amplify the latency, resulting in a significant increase in the duration of terminal service interruptions. This makes it unsuitable for application scenarios with high service continuity requirements, such as high-definition video and emergency communications. Summary of the Invention

[0005] In view of this, the purpose of this application is to provide a method, system, device and medium for fast handover of NTN satellite communication, which effectively shortens the handover time of NTN satellite communication, reduces the risk of service interruption during the handover process and improves the execution efficiency of the handover process.

[0006] In a first aspect, embodiments of this application provide a fast handover method for NTN satellite communication, applied to an NTN satellite communication system, the system including a terminal, a primary cell base station, and a secondary cell base station; the method includes: After identifying that the terminal supports protocol extension functions, the primary cell base station pre-configures the target cell base station as the secondary cell base station of the terminal, and ensures that all service bearers of the terminal are transmitted through the primary cell base station and the secondary cell base station, while maintaining the established signaling bearers between the terminal and the primary cell base station. After the primary cell base station triggers a handover based on the measurement results reported by the terminal, it prepares for the handover with the secondary cell base station through interface signaling, so that the secondary cell base station can pre-acquire the security key and pre-configure the signaling bearer. The primary cell base station sends a first reconfiguration signaling to the terminal, instructing the terminal to migrate the established signaling bearer from the primary cell base station to the secondary cell base station, and to update the security key in a step-by-step manner, so that the migrated signaling bearer takes effect with the new security key, while the data bearer retains the original security key. The terminal sends reconfiguration completion signaling through the newly established signaling bearer of the secondary cell base station; After receiving the reconfiguration completion signaling, the secondary cell base station performs a path switch to upgrade to a new primary cell base station.

[0007] Optionally, the step-by-step updating of the security key includes: In the first phase, the new security key is applied to the signaling bearer migrated to the secondary cell base station, while the data bearer retains the original security key, which is the security key negotiated between the terminal and the primary cell base station when establishing a communication connection. In the second stage, after the secondary cell base station is upgraded to a new primary cell base station and the new primary cell base station completes the data switchover with the original primary cell base station, the new security key is made effective on the data carrier.

[0008] Optionally, the primary cell base station prepares for handover with the secondary cell base station via interface signaling, including: The primary cell base station sends a handover request signaling to the secondary cell base station. The handover request signaling carries a handover type identifier, a security key base field, and user plane configuration information for data bearer. After receiving the handover request signaling, the secondary cell base station pre-derives the new security key based on the security key base field, establishes a Packet Data Convergence Protocol (PDCP) entity for data bearer based on the user plane configuration information, and pre-configures the signaling bearer to be established. After completing the pre-assignment and pre-configuration, the secondary cell base station returns a handover confirmation signaling to the primary cell base station. The handover confirmation signaling carries the configuration information of the signaling bearer to be established.

[0009] Optionally, after the secondary cell base station performs a path handover to upgrade to a new primary cell base station, it further includes: The new primary cell base station sends a handover notification signaling to the original primary cell base station, triggering the original primary cell base station to be downgraded to a secondary cell base station, and performs data switching and sequence number (SN) status transmission. After receiving the SN status transmission message sent by the original primary cell base station, the new primary cell base station confirms that the data switchover is complete and sends a second reconfiguration signaling to the terminal, instructing the terminal to release the original primary cell base station and enable the data bearer to take effect with the new security key.

[0010] Optionally, the handover notification signaling is a newly defined interface signaling, using a signaling identifier ID reserved in the protocol, and the handover notification signaling includes: Terminal identifier, used to uniquely specify the terminal performing the handover; The SN status transmission request command is used to trigger the original primary cell base station to initiate the SN status transmission; A data handover identifier is used to instruct the original primary cell base station to perform the data handover.

[0011] Optionally, the main cell base station identifies that the terminal supports protocol extension functions, including: The primary cell base station receives capability information reported by the terminal, and the capability information carries extended fields. The primary cell base station parses the capability information, and when the extended field is parsed and the value of the extended field is true, it determines that the terminal supports the NRDC primary / secondary handover function in the NTN scenario.

[0012] Optionally, the method further includes a switch preparation exception handling step: If the primary cell base station does not receive the handover confirmation signaling from the secondary cell base station within a preset time period, the handover preparation is deemed to have failed. The primary cell base station sends a stop signaling message to the secondary cell base station to cancel the handover preparation and resume sending downlink data packets to the secondary cell base station; After receiving the abort signaling, the secondary cell base station releases the pre-allocated signaling bearer configuration, the pre-derived security key, and the established PDCP entity resources, and falls back to the normal dual-connection state before receiving the handover request signaling, without releasing the terminal's service bearer throughout the process.

[0013] Secondly, embodiments of this application provide an NTN satellite communication system, the system comprising a terminal, a primary cell base station, and a secondary cell base station: The primary cell base station is used to pre-configure the target cell base station as the secondary cell base station of the terminal after identifying that the terminal supports the protocol extension function, and to ensure that all service bearers of the terminal are transmitted through the primary cell base station and the secondary cell base station, and to maintain the established signaling bearers between the terminal and the primary cell base station. The primary cell base station is used to prepare for handover with the secondary cell base station via interface signaling after triggering the handover based on the measurement results reported by the terminal, so that the secondary cell base station can pre-acquire the security key and pre-configure the signaling bearer. The primary cell base station is used to send a first reconfiguration signaling to the terminal, instructing the terminal to migrate the established signaling bearer from the primary cell base station to the secondary cell base station, and to update the security key in a step-by-step manner, so that the migrated signaling bearer takes effect with the new security key, while the data bearer retains the original security key. The terminal is used to send reconfiguration completion signaling through the newly established signaling bearer of the secondary cell base station; The secondary cell base station is used to perform path switching to upgrade to a new primary cell base station after receiving the reconfiguration completion signaling.

[0014] Optionally, the terminal and the new primary cell base station are also used to perform operations related to the phased activation of the security key: The terminal is used to enable the new security key for the signaling bearer migrated to the secondary cell base station in the first phase, while the data bearer retains the original security key, which is the security key negotiated between the terminal and the primary cell base station when establishing a communication connection. The terminal is used in the second stage after the secondary cell base station is upgraded to a new primary cell base station and the new primary cell base station completes the data switchover with the original primary cell base station, to enable the new security key to take effect on the data carrier.

[0015] Optionally, the primary cell base station and the secondary cell base station are specifically used to perform handover preparation related operations: The primary cell base station is used to send a handover request signaling to the secondary cell base station. The handover request signaling carries a handover type identifier, a security key base field, and user plane configuration information for data bearer. The secondary cell base station is used to receive the handover request signaling, pre-derive the new security key based on the security key base field, establish a Packet Data Convergence Protocol (PDCP) entity for data bearer based on the user plane configuration information, and pre-configure the signaling bearer to be established. The secondary cell base station is used to return a handover confirmation signaling to the primary cell base station after completing the pre-assignment and pre-configuration. The handover confirmation signaling carries the configuration information of the signaling bearer to be established.

[0016] Optionally, the new primary cell base station, the original primary cell base station, and the terminal are also used to perform handover termination-related operations: The new primary cell base station is used to send a handover notification signaling to the original primary cell base station, triggering the original primary cell base station to be downgraded to a secondary cell base station, and performing data switching and sequence number (SN) status transmission. The new primary cell base station is used to receive the SN status transmission message sent by the original primary cell base station, confirm that the data switchover is complete, and send a second configuration signaling to the terminal to instruct the terminal to release the original primary cell base station and enable the data bearer to take effect with the new security key; The terminal is configured to receive the second reconfiguration signaling, release the original primary cell base station, and enable the data bearer to take effect with the new security key.

[0017] Optionally, the handover notification signaling is a newly defined interface signaling, using a signaling identifier ID reserved in the protocol, and the handover notification signaling includes: Terminal identifier, used to uniquely specify the terminal performing the handover; The SN status transmission request command is used to trigger the original primary cell base station to initiate the SN status transmission; A data handover identifier is used to instruct the original primary cell base station to perform the data handover.

[0018] Optionally, the main cell base station is specifically used to identify whether the terminal supports protocol extension functions: The main cell base station is used to receive capability information reported by the terminal, wherein the capability information carries extended fields; The primary cell base station is used to parse the capability information. When the extended field is parsed and the value of the extended field is true, it determines that the terminal supports the NRDC primary / secondary handover function in the NTN scenario.

[0019] Optionally, the primary cell base station and the secondary cell base station are also used to perform handover preparation anomaly handling related operations: The primary cell base station is configured to determine that the handover preparation has failed if it does not receive the handover confirmation signaling returned by the secondary cell base station within a preset time period. The primary cell base station is used to send a stop signaling message to the secondary cell base station to notify the cancellation of the handover preparation and to resume sending downlink data packets to the secondary cell base station. The secondary cell base station, upon receiving the abort signaling, releases the pre-allocated signaling bearer configuration, the pre-derived security key, and the established PDCP entity resources, and falls back to the normal dual-connection state before receiving the handover request signaling, without releasing the terminal's service bearer throughout the process.

[0020] Thirdly, embodiments of this application provide a computer device, including: a processor, a memory, and a bus. The memory stores machine-readable instructions executable by the processor. When the computer device is running, the processor communicates with the memory via the bus. When the machine-readable instructions are executed by the processor, the steps of the NTN satellite communication fast switching method described in any of the optional embodiments of the first aspect are performed.

[0021] Fourthly, embodiments of this application provide a computer-readable storage medium storing a computer program that, when executed by a processor, performs the steps of the NTN satellite communication fast handover method described in any of the optional embodiments of the first aspect.

[0022] The technical solution provided in this application includes, but is not limited to, the following beneficial effects: After identifying that the terminal supports protocol extension functions, the primary cell base station pre-configures the target cell base station as the secondary cell base station, so that all terminal service bearers are transmitted through the primary and secondary cell base stations, and the signaling bearers already established between the terminal and the primary cell base station are maintained. This avoids the reconstruction and release operations of service bearers during the handover process, eliminates the service transmission gap caused by bearer reconstruction from the process perspective, and ensures the continuous transmission of services during the handover process.

[0023] After the primary cell base station triggers the handover based on the terminal measurement results, it completes the handover preparation with the secondary cell base station through interface signaling. This enables the secondary cell base station to pre-acquire the security key and pre-configure the signaling bearer, eliminating the time-consuming steps of real-time key negotiation and new signaling bearer creation during the handover process. This shortens the overall handover preparation time and adapts to the high-latency transmission characteristics of NTN satellite communication.

[0024] The main cell base station sends the first reconfiguration signaling to the terminal, instructing the terminal to migrate the signaling bearer and update the security key in a step-by-step manner. Only the new security key is applied to the migrated signaling bearer, while the data bearer retains the original security key. This ensures the security of signaling transmission while avoiding data transmission interruption caused by a full key update, thus maintaining the stable transmission of user plane services.

[0025] The terminal sends reconfiguration completion signaling through the newly established signaling bearer of the secondary cell base station and completes signaling feedback based on the pre-configured signaling link. There is no need to rebuild the signaling transmission channel, which simplifies the signaling interaction process during handover and improves the response and execution speed of handover commands.

[0026] After receiving the reconfiguration completion signaling, the secondary cell base station performs path switching and upgrades to a new primary cell base station, omitting the redundant steps of cell access and context reconstruction in conventional handover, quickly completing cell role change and data path switching, and significantly reducing the overall handover time.

[0027] Through the coordinated implementation of the above steps, this application effectively shortens the handover time of NTN satellite communication, reduces the risk of service interruption during the handover process, improves the execution efficiency of the handover process, and can better adapt to the transmission characteristics of NTN satellite communication.

[0028] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings. Attached Figure Description

[0029] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 A flowchart of a fast handover method for NTN satellite communication provided in Embodiment 1 of this application is shown; Figure 2 A flowchart of a security key update method provided in Embodiment 1 of this application is shown; Figure 3 A flowchart of a switching preparation method provided in Embodiment 1 of this application is shown; Figure 4 A flowchart of a security key activation method provided in Embodiment 1 of this application is shown; Figure 5 A flowchart of a protocol extension function identification method provided in Embodiment 1 of this application is shown; Figure 6 A flowchart of a handover preparation exception handling method provided in Embodiment 1 of this application is shown; Figure 7 The signaling interaction flowchart of the NTN satellite communication fast handover method provided in Embodiment 1 of this application is shown; Figure 8 This paper shows a schematic diagram of the structure of an NTN satellite communication system provided in Embodiment 2 of this application; Figure 9 A schematic diagram of the structure of a computer device provided in Embodiment 3 of this application is shown. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely represents selected embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0032] Example 1 This application belongs to the field of wireless communication technology, specifically relating to handover technology in non-terrestrial network satellite communication, and is applicable to 5G and subsequent satellite communication systems under the 3GPP R17 / R18 NTN protocol architecture.

[0033] The existing NTN satellite communication handover directly follows the conventional 3GPP mechanism, which is not adapted to the high latency characteristics of satellites. Furthermore, NRDC (New Radio Dual Connectivity) dual connectivity does not support dynamic switching of primary and secondary roles, resulting in three major technical defects: excessive handover time, interruption of bearer reconstruction, and lack of support for role switching in the protocol.

[0034] The purpose of this application is to overcome the above-mentioned defects by partially extending the 3GPP protocol based on the dual connectivity feature of NRDC, thereby reducing handover service interruption time, reducing handover time consumption, improving success rate, being compatible with existing 5G NTN equipment, and facilitating engineering implementation.

[0035] This application's protocol extension follows three principles: compatibility with existing network element hardware with only software layer modifications, extension fields and signaling conforming to the 3GPP ASN.1 (Abstract Syntax Notation One) coding standard, and network elements that have not been upgraded can still operate according to the original protocol.

[0036] The terminal is a UE (User Equipment) that supports NRDC dual connectivity and the extended parsing function of the protocol in this application. The main cell base station is the source satellite gNB (next generation NodeB, 5G base station), and the auxiliary cell base station is the target satellite gNB. The main and auxiliary base stations are interconnected through XN (Xn Interface).

[0037] The system also includes 5G core network AMF (Access and Mobility Management Function) and UPF (User Plane Function) network elements, which are used to complete path switching and user plane data routing management. All network elements only require software upgrades and do not require hardware replacement.

[0038] To facilitate understanding of this application, the following is combined with... Figure 1 The flowchart illustrating the fast handover method for NTN satellite communication provided in Embodiment 1 of this application will be described in detail for Embodiment 1 of this application.

[0039] See Figure 1 As shown, Figure 1 A flowchart of a fast handover method for NTN satellite communication provided in Embodiment 1 of this application is shown. The method is applied to an NTN (Non-Terrestrial Networks) satellite communication system, which includes a terminal, a primary cell base station, and a secondary cell base station. The method includes steps S101-S105: S101: After identifying that the terminal supports the protocol extension function, the main cell base station pre-configures the target cell base station as the auxiliary cell base station of the terminal, and makes all service bearers of the terminal transmit together through the main cell base station and the auxiliary cell base station, and the terminal maintains the established signaling bearer with the main cell base station.

[0040] Specifically, the identification basis for the protocol extension function is the UE capability field NRDC_NTN_Switch_Capable in 3GPP TS (Technical Specification) 38.331, which is a Boolean field.

[0041] NRDC_NTN_Switch_Capable=True indicates that the terminal supports NRDC primary / secondary switching in NTN scenarios. If it is=False or not carried, it is not supported. Terminals that do not support it will be handled according to the original 3GPP regular switching procedure.

[0042] The target cell pre-selection needs to be completed by combining three dimensions of information: NTN satellite ephemeris orbit parameters, terminal real-time latitude and longitude location, and satellite cell coverage area.

[0043] The satellite ephemeris orbit parameters are updated periodically by the ground station, including the satellite's speed and direction of motion, and are used to predict the satellite's future coverage area.

[0044] The terminal has the ability to report its location autonomously, and assists the base station in pre-selecting the target cell by reporting its latitude and longitude coordinates.

[0045] The service bearer uses a split bearer mode for common transmission. All DRB (Data Radio Bearer) data bearers are transmitted synchronously in the primary and secondary cells. The terminal side uses a first-come, first-served mechanism to receive data, and duplicate data packets are discarded directly.

[0046] The signaling bearer that is maintained is the DRB, which is the signaling radio bearer that has been established between the terminal and the main cell base station, and it is not released during the entire handover process.

[0047] Uplink and downlink data will continue to be routed by the original primary cell before the path switch is completed, without affecting the continuity of service transmission.

[0048] S102: After the primary cell base station triggers the handover based on the measurement results reported by the terminal, it prepares for the handover with the secondary cell base station through interface signaling, so that the secondary cell base station can pre-acquire the security key and pre-configure the signaling bearer.

[0049] Specifically, the precondition for measurement is the A2 measurement event, where A2 is defined as the serving cell signal quality being below a threshold, which is used to trigger neighbor cell measurements.

[0050] The measurement results are the information reported by the terminal based on the A4+D2 combined measurement events. A4 indicates that the signal quality of the neighboring cell is higher than the threshold, and D2 indicates that the distance between the terminal and the cell is less than the threshold.

[0051] The interface signaling is the XN interface signaling based on the 3GPP TS 38.423 protocol extension, which includes handover request signaling and handover confirmation signaling.

[0052] The pre-acquired security key is a new AS (Access Stratum) layer security key Knew_AS pre-derived from the terminal root key KgNB, and the key derivation follows the 3GPP TS 33.501 protocol.

[0053] KgNB is the root key negotiated when the terminal establishes a connection with the original primary cell, and it is the basis for AS layer key derivation; Knew_AS is the new AS layer key derived during handover, used for encryption protection after handover.

[0054] The pre-configured signaling bearers are SRB1 and SRB2, which contain a complete set of configuration information including bearer identifier, resource configuration, and transmission link parameters.

[0055] The handover preparation omits the target cell context establishment and random access steps of conventional handover, and is completed by relying on the NRDC dual-connectivity context synchronization feature.

[0056] S103: The primary cell base station sends a first reconfiguration signaling to the terminal, instructing the terminal to migrate the established signaling bearer from the primary cell base station to the secondary cell base station, and to update the security key in a step-by-step manner, so that the migrated signaling bearer takes effect with the new security key, while the data bearer retains the original security key.

[0057] Specifically, the first configuration signaling is an RRC (Radio Resource Control) Reconfiguration signaling based on the 3GPP TS 38.331 protocol extension, which strictly follows the 3GPP ASN.1 coding standard, and all newly added extended fields are mandatory fields.

[0058] This signaling includes 5 dedicated extended fields, the complete definitions of which are as follows: 1. Handover Type Identifier: The field type is enumeration, the field attribute is required, and the value rule is NRDC_MN_SN_Switch / NRDC_MN_SN_Switch_Complete. Its function is to indicate that this reconfiguration is an NRDC primary and secondary cell handover in the NTN scenario (the former is the handover trigger stage, and the latter is the handover completion stage), an unconventional cell handover, or other NRDC operations.

[0059] 2. SRB Operation Identifier: The field type is bitmap (SIZE=2), the field attribute is required, and the value rule is bit0=1 (delete the original primary cell SRB1 / SRB2), bit1=1 (establish a new primary cell SRB1 / SRB2), with two fixed bits being 1. Its function is to instruct the UE to perform SRB bearer migration operation, and to ensure that the signaling link is uninterrupted by using the "build first, delete later" order.

[0060] 3. SRB Establishment Information: The field type is structured data, reusing the original SRB-ToAddModList structure. The field attributes are required, and the values ​​include the signaling bearer identifier, resource configuration, transmission link parameters, etc. of the new primary cell SRB1 / SRB2. The function is to provide the UE with complete configuration parameters for the establishment of the new primary cell SRB.

[0061] 4. Security Key Update Identifier: The field type is Boolean, the field attribute is required, the fixed value is True, and the function is to indicate to the UE to trigger the derivation and update of the AS layer security key.

[0062] 5. Key Validation Identifier: The field type is bitmap (SIZE=2), the field attribute is required, and the complete value rules include 4 combinations: bit0=0, bit1=0: SRB keeps the key unchanged, DRB temporarily uses the old key for the switch preparation phase; bit0=1, bit1=0: The new key for SRB activation, the old key for DRB temporary use, used for switching the trigger phase (used by the first configuration signaling). bit0=0, bit1=1: SRB retains the new key, DRB activates the new key, used to switch the end-of-phase (used by the second configuration signaling). bit0=1, bit1=1: New keys are applied to both SRB and DRB, and are used to make the full bearer key effective after the handover is completed; This field is designed to enable keys to take effect in stages, thus avoiding data transmission interruptions during the switching process.

[0063] The signaling bearer migration adopts a build-then-delete mode, first establishing the secondary cell-side SRB and then deleting the original primary cell-side SRB to ensure uninterrupted signaling links.

[0064] The terminal performs local reconfiguration using atomic operations. It takes effect once after the signaling is completely parsed, and if the parsing fails, the entire signaling is discarded.

[0065] S104: The terminal sends reconfiguration completion signaling through the newly established signaling bearer of the secondary cell base station.

[0066] Specifically, the reconfiguration completion signaling is RRC Reconfiguration Complete, which is sent through the newly established SRB1 bearer in the secondary cell to provide feedback on the local reconfiguration execution result of the terminal.

[0067] After the terminal completes key derivation, SRB migration, and configuration activation, it provides feedback through the new signaling link, ensuring normal transmission of services throughout the entire process.

[0068] S105: After receiving the reconfiguration completion signaling, the secondary cell base station performs a path switch to upgrade to a new primary cell base station.

[0069] Specifically, the path switch is a PathSwitch process based on the 3GPP TS 38.413 protocol, initiated by the new primary cell to the core network AMF / UPF.

[0070] The core network switches the user plane data transmission path from the original primary cell gNB to the secondary cell gNB, and the secondary cell is officially upgraded to the primary cell base station of the terminal.

[0071] The NG (Ng Interface) protocol has no new fields, only supplementary instructions on the adaptation of NRDC master-slave switching to path switching trigger conditions.

[0072] After the core network completes the path switch, it returns a confirmation signal, and the new primary cell is officially confirmed as the terminal master node.

[0073] In an optional implementation, see Figure 2 As shown, Figure 2 The flowchart of a security key update method provided in Embodiment 1 of this application is shown, wherein the security key update using a step-by-step activation method includes steps S201-S202: Specifically, the phased activation rule is based on the 3GPP TS 33.501 protocol extension, which is divided into two phases: SRB activation and DRB activation, to adapt to the high latency characteristics of NTN.

[0074] The phased activation process avoids business interruption caused by updating the key throughout the entire process, which is the core design of this application to ensure business continuity.

[0075] S201: In the first stage, the new security key is applied to the signaling bearer migrated to the secondary cell base station, while the data bearer retains the original security key, which is the security key negotiated between the terminal and the primary cell base station when establishing a communication connection.

[0076] Specifically, the first phase corresponds to the switching triggering process, and the new security key that takes effect is Knew_AS, which is only applied to SRB1 and SRB2 signaling bearers.

[0077] The data bearer DRB continues to use the old AS layer security key derived from KgNB, with the corresponding key validity flag bit0=1 and bit1=0, to ensure uninterrupted business data transmission.

[0078] The key update at this stage is completed locally between the terminal and the base station, without any additional satellite-to-ground signaling interaction, thus reducing latency overhead.

[0079] S202: In the second stage, after the auxiliary cell base station is upgraded to a new primary cell base station and the new primary cell base station completes the data switchover with the original primary cell base station, the new security key is made effective on the data carrier.

[0080] Specifically, the second phase corresponds to the handover process. After the data switchover is completed, the DRB key is updated, and the corresponding key validity identifier bit0=0 and bit1=1 are set according to the value rules.

[0081] In the case of low-Earth orbit satellites, the service interruption duration during this phase is ≤10ms, which is far superior to the second-level interruption of conventional handover.

[0082] After the full bearer key is updated, the communication security between the terminal and the new primary cell is fully guaranteed.

[0083] In an optional implementation, see Figure 3 As shown, Figure 3The flowchart illustrates a handover preparation method provided in Embodiment 1 of this application, wherein the primary cell base station performs handover preparation with the secondary cell base station via interface signaling, including steps S301-S303: Specifically, the handover preparation process relies on the NRDC dual-connection context synchronization feature, omitting the time-consuming steps of conventional handover.

[0084] S301: The primary cell base station sends a handover request signaling to the secondary cell base station. The handover request signaling carries a handover type identifier, a security key base field, and user plane configuration information for data bearer.

[0085] Specifically, the handover request signaling is the XN HandoverRequest signaling based on the 3GPP TS 38.423 protocol extension, and all newly added extended fields are mandatory.

[0086] This signaling includes three dedicated extended fields, the full definitions of which are as follows: 1. Switching type identifier: The field type is enumeration, the field attribute is required, the fixed value is XN_NRDC_MN_Switch, and the function is to indicate that this XN interface interaction is an NRDC primary / secondary switch, which is an unconventional cell switch.

[0087] 2. Security Key Basic Field: The field type is binary stream, reusing the original AS SecurityInformation structure. The field attribute is required, and the value content carries the UE root key (KgNB) and NCC (Next HopChaining Counter) parameters. Its function is to provide the basic key for the secondary cell to pre-derive the AS layer security key.

[0088] 3. Establish DRB-borne PDCP (Packet Data Convergence Protocol) information: The field type is structured data, reusing the original DRB-ToAddModList structure. The field attributes are required, and the values ​​contain configuration parameters such as PDCP of all DRBs. The function is to indicate the PDCP entity of the pre-configured DRB in the secondary cell.

[0089] S302: After receiving the handover request signaling, the secondary cell base station pre-derives the new security key based on the security key base field, establishes a PDCP entity for data bearer based on the user plane configuration information, and pre-configures the signaling bearer to be established.

[0090] Specifically, PDCP stands for Packet Data Convergence Protocol, which is a layer 2 structure of the 5G protocol stack and is responsible for data encryption, header compression, and sequential transmission.

[0091] The algorithm for pre-forwarded Knew_AS strictly follows the 3GPP TS 33.501 protocol, is completed only locally in the secondary cell, and is not sent to the terminal.

[0092] The PDCP entity establishment only reconstructs the layer 2 PDCP part. The underlying LC (Logical Channel), MAC (Media Access Control), and RLC (Radio Link Control) layers have been pre-established through dual connectivity, so there is no resource reconstruction delay.

[0093] The pre-configured SRB1 / SRB2 includes signaling bearer identifier, resource configuration, and a complete set of transmission link parameters.

[0094] S303: After completing the pre-assignment and pre-configuration, the secondary cell base station returns a handover confirmation signaling to the primary cell base station. The handover confirmation signaling carries the configuration information of the signaling bearer to be established.

[0095] Specifically, the handover confirmation signaling is the XNHandoverRequestAcknowledge signaling based on the 3GPP TS 38.423 protocol extension, and the newly added extended fields are mandatory.

[0096] This signaling adds one new mandatory exclusive field: New SRB Information. The field type is structured data, reusing the original SRB-ToAddModList structure. The field attribute is mandatory, and the value content includes the pre-configured complete parameters of SRB1 / SRB2 (identifier, resources, links, etc.). Its function is to provide the SRB configuration basis for constructing RRC reconfiguration signaling for the original primary cell.

[0097] After receiving the confirmation signaling, the primary cell parses and stores the SRB configuration, which is used to construct the RRC reconfiguration signaling.

[0098] In an optional implementation, see Figure 4 As shown, Figure 4 The flowchart of a security key activation method provided in Embodiment 1 of this application is shown. After the secondary cell base station performs a path handover to upgrade to a new primary cell base station, steps S401-S402 are further included: Specifically, this step, which completes the synchronization of primary and secondary roles, data switching, and final terminal configuration, is the core final step in the switchover process.

[0099] S401: The new primary cell base station sends a handover notification signaling to the original primary cell base station, triggering the original primary cell base station to be downgraded to a secondary cell base station, and performs data switching and SN (Sequence Number) status transmission.

[0100] The specific handover notification signaling is the newly added NRDCSwitchNotify signaling. The signaling ID follows the 3GPP TS38.413 standard signaling ID format, selects unused values ​​from the protocol reserved segment, and all fields are required.

[0101] This signaling contains four required fields, the complete definitions of which are as follows: 1. Message Type: The field type is signaling ID, the field format follows the 3GPP TS 38.413 standard signaling ID format, the value is the 3GPP protocol reserved segment value (avoiding used IDs), the field attribute is required, and the function is to indicate that the message type is NRDCSwitchNotify.

[0102] 2. Source NG-RAN node UE XnAPID: The field type is structured data, the field format follows the 3GPPTS 38.413 standard UEID format, the value is a unique identifier of the terminal, the field attribute is required, and the function is to uniquely specify the source terminal for this handover to ensure that the signaling matches the terminal.

[0103] 3. Target NG-RAN node UE XnAPID: The field type is structured data, the field format follows the 3GPPTS 38.413 standard UEID format, the value is a unique identifier of the terminal, the field attribute is required, and the function is to uniquely specify the target terminal for this handover to ensure that the signaling matches the terminal.

[0104] 4. DRB Data Switchover Identifier: The field type is Boolean, the field length is 1 bit, the fixed value is True, the field attribute is required, and the function is to instruct the original primary cell to perform full DRB bearer data switchover and switch the user plane data that has not been transmitted to the new primary cell.

[0105] SN stands for Data Bearer Transmission Sequence Number. SN status transmission is used to ensure that data transmission is orderly, without packet loss, and without out-of-order delivery.

[0106] After the original primary cell receives the signaling, its role is downgraded from MN (Master Node) to SN (Secondary Node), and service scheduling is stopped.

[0107] The data is switched to the original primary cell, which forwards all uncompleted user plane data packets to the new primary cell.

[0108] S402: After receiving the SN status transmission message sent by the original primary cell base station, the new primary cell base station confirms that the data switchover is complete, and sends a second reconfiguration signaling to the terminal, instructing the terminal to release the original primary cell base station and enable the data bearer to take effect with the new security key.

[0109] Specifically, the second reconfiguration signaling is an extended RRC reconfiguration signaling, which carries the switching type identifier NRDC_MN_SN_Switch_Complete, and configures the key activation identifier to bit0=0 and bit1=1, so that the SRB maintains the original new key and the DRB activates the new key, thus completing the key update of the entire bearer.

[0110] After receiving the signaling, the terminal deletes the radio resources and context configuration of the original primary cell, retaining only the communication connection with the new primary cell, and switches the DRB encryption key to Knew_AS, completing the entire configuration update. After completing the configuration update, the terminal sends an RRC reconfiguration completion signaling to the new primary cell base station.

[0111] After receiving the reconfiguration completion signaling from the terminal, the new primary cell base station sends a UEContextRelease signaling to the original primary cell to release the terminal context and resources. Upon receiving the UEContextRelease signaling, the original primary cell completes the release of the terminal's UE context and redundant resources, thus completing the handover process.

[0112] In an optional implementation, the handover notification signaling is a newly defined interface signaling that uses a signaling identifier ID reserved by the protocol. The handover notification signaling includes: a terminal identifier, used to uniquely specify the terminal performing the handover.

[0113] Specifically, the terminal identifier consists of two sets of structured UEIDs, with the format conforming to the 3GPP TS 38.413 standard, ensuring that the signaling accurately matches the terminal in this handover and eliminating the risk of mistransmission.

[0114] The SN status transmission request instruction is used to trigger the original primary cell base station to initiate the SN status transmission.

[0115] Specifically, this instruction is a built-in control field in the signaling system, which precisely triggers the original primary cell to transmit the DRB's SN status information to the new primary cell.

[0116] A data handover identifier is used to instruct the original primary cell base station to perform the data handover.

[0117] Specifically, the data switching flag is a 1-bit boolean type with a fixed value of True, which forces data switching across the entire DRB. This field attribute is mandatory.

[0118] In an optional implementation, see Figure 5 As shown, Figure 5 The flowchart illustrates a protocol extension function identification method provided in Embodiment 1 of this application, wherein the main cell base station identifies that the terminal supports protocol extension functions, including steps S501-S502: S501: The main cell base station receives the capability information reported by the terminal, and the capability information carries extended fields.

[0119] Specifically, the capability information is the UE Capability Information signaling, and the extended field is NRDC_NTN_Switch_Capable, which is newly added based on the 3GPP TS 38.331 protocol.

[0120] S502: The primary cell base station parses the capability information. When the extended field is parsed and the value of the extended field is true, it determines that the terminal supports the NRDC primary / secondary handover function in the NTN scenario.

[0121] Specifically, if the value is true (NRDC_NTN_Switch_Capable=True), the base station will enable the fast handover process of this application.

[0122] If the field is not parsed or its value is False, the base station uses the standard 3GPP handover mechanism and does not trigger a switch between primary and secondary roles.

[0123] In an optional implementation, see Figure 6 As shown, Figure 6 A flowchart of a handover preparation exception handling method provided in Embodiment 1 of this application is shown, wherein the method further includes handover preparation exception handling steps S601~S603: Specifically, the anomaly handling mechanism is adapted to the high latency and high jitter characteristics of the NTN satellite-to-ground link, and a dedicated timer and abort signaling have been added.

[0124] This mechanism ensures that service bearers are not released or services are not interrupted in the event of an anomaly, and can be rolled back and retried.

[0125] S601: If the primary cell base station does not receive the handover confirmation signaling returned by the secondary cell base station within a preset time period, it determines that the handover preparation has failed.

[0126] Specifically, the preset duration is controlled by the NTN dedicated long timer T_NRDC_XN_PREPARE, which adapts to a satellite-to-ground delay of 50ms for low Earth orbit and 250ms for high Earth orbit.

[0127] T_NRDC_XN_PREPARE is a new timer added in this invention, and its duration can be flexibly configured according to the satellite orbit type.

[0128] S602: The primary cell base station sends a stop signaling message to the secondary cell base station to notify the cancellation of the handover preparation and resumes sending downlink data packets to the secondary cell base station.

[0129] Specifically, the abort signaling is the newly added NRDCSwitchAbort signaling. The signaling ID follows the 3GPP TS 38.413 standard signaling ID format, selects unused values ​​from the protocol reserved segment, and all fields are required.

[0130] This signaling contains four required fields, the complete definitions of which are as follows: 1. Message Type: The field type is signaling ID, the field format follows the 3GPP TS 38.413 standard signaling ID format, the value is the 3GPP protocol reserved segment value, the identifier is NRDCSwitchAbort, the field attribute is required, and the function is to indicate that the message type is a switchover abort signaling.

[0131] 2. Source NG-RAN node UE XnAPID: The field type is structured data, the field format follows the 3GPPTS 38.413 standard UEID format, the value is a unique identifier of the terminal, the field attribute is required, and the function is to match the source terminal of this handover to ensure accurate signaling delivery.

[0132] 3. Target NG-RAN node UE XnAPID: The field type is structured data, the field format follows the 3GPPTS 38.413 standard UEID format, the value is a unique identifier of the terminal, the field attribute is mandatory, and the function is to match the target terminal of this handover to ensure accurate signaling delivery.

[0133] 4. Abort Cause: The field type is enumeration, the field attribute is required, and the values ​​include three types: timeout, configuration failure, and UE rejection. Its function is to identify the specific reason for the handover abort, which is convenient for locating abnormal scenarios.

[0134] The abort signaling carries the terminal identifier and the reason for abort, which helps the base station quickly locate the anomaly.

[0135] S603: After receiving the abort signaling, the secondary cell base station releases the pre-allocated signaling bearer configuration, the pre-derived security key, and the established PDCP entity resources, and falls back to the normal dual-connection state before receiving the handover request signaling, without releasing the terminal's service bearer throughout the process.

[0136] Specifically, the released resources include pre-configured SRB1 / SRB2, pre-derived Knew_AS, and PDCP entities for all DRBs.

[0137] After rollback, the primary and secondary dual-connection split bearer transmission state is maintained, and the service is uninterrupted. The base station can re-trigger the handover after a delay.

[0138] In an optional implementation, the method also includes an RRC reconfiguration exception handling mechanism.

[0139] Specifically, abnormal scenarios include UE parsing signaling failure and RRC reconfiguration completion signaling transmission failure.

[0140] When UE resolution fails, the RRC reconfiguration to the original primary cell fails, and the SRB deletion operation is not performed.

[0141] If the signaling fails to complete on the new SRB, it should be treated as a handover failure and a re-establishment process should be initiated.

[0142] In an optional implementation, this method also includes a mechanism for handling NRDCSwitchNotify signaling anomalies and data switching anomalies.

[0143] Specifically, when the NRDCSwitchNotify signaling is lost or times out, the new primary cell retains the MN role, while the original primary cell automatically downgrades to SN after its timer expires.

[0144] In the event of data switching failure / out-of-order delivery / packet loss, unacknowledged data packets are discarded directly without affecting already transmitted services.

[0145] See Figure 7 As shown, Figure 7 The diagram illustrates the signaling interaction flowchart of the NTN satellite communication fast handover method provided in Embodiment 1 of this application. The diagram involves four interacting entities: UE, original primary cell, original secondary cell / new primary cell, and core network. It fully demonstrates the entire process from access, measurement, handover preparation, reconfiguration to role downgrading and resource release. The flowchart is described below: 1. Initial Access Phase: The UE access process is consistent with the normal procedure. Whether the UE supports the handover scheme of this invention is determined through the UE capability extension fields. For supporting UEs, A2 measurement is configured. This phase completes terminal access and capability identification, laying the foundation for subsequent handover configuration.

[0146] 2. Measurement Reporting and Target Cell Preparation Phase: After the UE completes the actual measurement and meets the reporting conditions, it sends a measurement report to the original primary cell. After receiving the measurement report, the original primary cell selects the target cell based on ephemeris, UE location information, etc., completes the secondary cell addition configuration, and adds handover preparation configuration for the UE. The target cell is configured as a secondary cell in advance to realize split bearer transmission.

[0147] 3. Handover Decision and Preparation Phase: After the UE completes the actual measurement again and meets the reporting conditions, it sends a measurement report to the original primary cell; the original primary cell decides to handover, initiates handover preparation, stops sending downlink data packets to the target secondary cell, and sends an XN handover request (HANDOVER REQUEST) signaling carrying the extended structure to the original secondary cell / new primary cell.

[0148] 4. Target Cell Preparation Phase: After receiving the `HANDOVER REQUEST`, the primary / secondary cell / new primary cell calculates the update key, allocates SRB resources, and constructs the extended handover request ack. a. Suspend service scheduling in auxiliary cells; b. Establish SRB1 / 2 on the base station side; c. After sending the buffered uplink data packets, stop sending data packets to the main cell; d. Based on the PDCP information in the handover request, establish PDCP entities for all DRBs; After completing the preparation, reply to the original primary cell with an Xn handover ack (`HANDOVER REQUESTACKNOWLEDGE`) with an extended structure.

[0149] 5. First RRC reconfiguration phase: The original primary cell resolves the ACK and constructs a reconfiguration signaling with extended structure, sending the reconfiguration signaling with extended structure (`RRCReconfiguration`) to the UE; after receiving the signaling, the UE updates the key, creates a new SRB for the original secondary cell, deletes the SRB of the original primary cell, the SRB uses the new key, and the DRB still uses the old key, and then replies with the `RRCReconfigurationComplete` signaling to the original secondary cell / new primary cell.

[0150] 6. Path Switching and Role Notification Phase: After receiving `RRCReconfigurationComplete`, the primary / secondary cell / new primary cell sends a `PATH SWITCH REQUEST` signaling message to the core network, and the core network replies with `PATH SWITCH REQUEST ACKNOWLEDGE`; subsequently, the primary / secondary cell / new primary cell sends the newly added extended protocol message `NRDCSwitchNotify` to the primary primary cell to notify of role downgrading.

[0151] 7. Primary cell downgrade and SN status transmission phase: After receiving `NRDCSwitchNotify`, the primary cell is downgraded to a secondary cell, service scheduling is stopped, and data switching and SN status transmission (`SN STATUS TRANSFER`) are initiated to the primary secondary cell / new primary cell.

[0152] 8. Second RRC reconfiguration phase: After receiving the SN status transmission, the primary / secondary cell / new primary cell sends a reconfiguration (`RRCReconfiguration`) signaling with extended structure, instructing the UE to delete the primary cell and activate the new DRB key; after receiving the signaling, the UE deletes the primary cell, activates the new DRB key, and then replies with the `RRCReconfigurationComplete` signaling.

[0153] 9. Handover Completion and Resource Release Phase: After the primary / secondary cell / new primary cell completes the configuration, service scheduling begins, and a `UE Context Release` signaling is sent to the primary cell. The primary cell then releases the UE context, and the handover process is complete.

[0154] This flowchart fully presents the signaling interaction logic of the fast switching method of this application. All steps correspond to the aforementioned method flow. The core innovations, such as the newly added extended signaling, step-by-step key update, and main / auxiliary role swap, are all reflected in the flow.

[0155] This application, through the aforementioned rapid handover process for NTN satellite communication, achieves significant technical optimization and scenario adaptation, bringing four core beneficial effects. First, in low-Earth orbit satellite communication scenarios, it controls service interruption time to within 10ms, fundamentally solving the service interruption problem caused by bearer reconstruction in traditional handover, and fully meeting the high continuity service requirements such as high-definition video transmission and emergency communication. Second, it eliminates the time-consuming steps of traditional handover such as context establishment and random access, significantly reducing the number of signaling interactions between satellite and ground links, adapting to the high-latency link characteristics of NTN satellite communication, and effectively shortening the overall handover time. Third, it only involves partial extensions and supplements to existing 3GPP protocols, without requiring hardware modifications to existing network elements. Unupgraded network elements can still operate normally according to the original protocols, significantly reducing engineering deployment and network upgrade costs, and demonstrating good feasibility for implementation. Fourth, through standardized extended signaling, it simplifies the interaction logic between base stations and terminals, and between primary and secondary base stations, reducing the risk of abnormal signaling interactions caused by satellite-ground link jitter, and effectively improving the execution stability and operational efficiency of the handover process.

[0156] To support the implementation of the aforementioned fast handover scheme, this application has carried out targeted local modifications and adaptations to the five core 3GPP protocols. In the TS37.300 protocol, a new architecture definition for the NRDC primary / secondary role swapping in NTN scenarios is added, clarifying that this swapping operation only applies to satellite gNBs interconnected via the XN interface, while retaining the original core characteristics of NRDC dual connectivity. In the TS38.331 protocol, the RRC reconfiguration signaling structure is expanded, adding five dedicated fields and a new UE capability extension field, NRDC_NTN_Switch_Capable. In the TS38.423 protocol, the XN interface handover request and handover confirmation signaling are expanded, and two dedicated signaling words, NRDCSwitchNotify and NRDCSwitchAbort, are added. In the TS38.413 protocol, the triggering conditions for path switching are supplemented, incorporating NRDC primary / secondary switching into the triggering scenario of the PathSwitch process. In the TS33.501 protocol, a step-by-step activation rule for AS layer security keys is added, enabling phased key updates for SRB and DRB to ensure service continuity during the handover process.

[0157] This application uses 5G NTN low-Earth orbit satellite communication as a practical application scenario and designs a specific implementation method for a terminal to switch from satellite A to satellite B. After the terminal completes network registration on satellite A, the base station confirms its support for the protocol extension function of this application through capability identification, and then configures A2 measurement and A4+D2 combined measurement rules for the terminal. Satellite A adds satellite B as a secondary cell through the XN interface and configures split bearer for the terminal, enabling all types of services such as high-definition video, voice calls, and data transmission to be transmitted synchronously in both primary and secondary cells. After the handover is triggered, the system sequentially completes the entire process of XN interface handover preparation, RRC reconfiguration, core network path switching, primary / secondary role degradation, and resource release. Actual implementation results show that during the entire handover process, there is no lag in terminal services, no interruption in voice calls, and no packet loss in data transmission. The service interruption time does not exceed 10ms, which can fully meet the high continuity communication requirements of NTN satellite communication scenarios.

[0158] Example 2 See Figure 8 As shown, Figure 8 This paper presents a schematic diagram of an NTN satellite communication system according to Embodiment 2 of this application, wherein the system includes a terminal 801, a primary cell base station 802, and a secondary cell base station 803. The primary cell base station is used to pre-configure the target cell base station as the secondary cell base station of the terminal after identifying that the terminal supports the protocol extension function, and to ensure that all service bearers of the terminal are transmitted through the primary cell base station and the secondary cell base station, and to maintain the established signaling bearers between the terminal and the primary cell base station. The primary cell base station is used to prepare for handover with the secondary cell base station via interface signaling after triggering the handover based on the measurement results reported by the terminal, so that the secondary cell base station can pre-acquire the security key and pre-configure the signaling bearer. The primary cell base station is used to send a first reconfiguration signaling to the terminal, instructing the terminal to migrate the established signaling bearer from the primary cell base station to the secondary cell base station, and to update the security key in a step-by-step manner, so that the migrated signaling bearer takes effect with the new security key, while the data bearer retains the original security key. The terminal is used to send reconfiguration completion signaling through the newly established signaling bearer of the secondary cell base station; The secondary cell base station is used to perform path switching to upgrade to a new primary cell base station after receiving the reconfiguration completion signaling.

[0159] In an optional implementation, the terminal and the new primary cell base station are also used to perform operations related to the step-by-step activation of the security key: The terminal is used to enable the new security key for the signaling bearer migrated to the secondary cell base station in the first phase, while the data bearer retains the original security key, which is the security key negotiated between the terminal and the primary cell base station when establishing a communication connection. The terminal is used in the second stage after the secondary cell base station is upgraded to a new primary cell base station and the new primary cell base station completes the data switchover with the original primary cell base station, to enable the new security key to take effect on the data carrier.

[0160] In an optional implementation, the primary cell base station and the secondary cell base station are specifically used to perform handover preparation related operations: The primary cell base station is used to send a handover request signaling to the secondary cell base station. The handover request signaling carries a handover type identifier, a security key base field, and user plane configuration information for data bearer. The secondary cell base station is used to receive the handover request signaling, pre-derive the new security key based on the security key base field, establish a Packet Data Convergence Protocol (PDCP) entity for data bearer based on the user plane configuration information, and pre-configure the signaling bearer to be established. The secondary cell base station is used to return a handover confirmation signaling to the primary cell base station after completing the pre-assignment and pre-configuration. The handover confirmation signaling carries the configuration information of the signaling bearer to be established.

[0161] In an optional implementation, the new primary cell base station, the original primary cell base station, and the terminal are further configured to perform handover termination-related operations: The new primary cell base station is used to send a handover notification signaling to the original primary cell base station, triggering the original primary cell base station to be downgraded to a secondary cell base station, and performing data switching and sequence number (SN) status transmission. The new primary cell base station is used to receive the SN status transmission message sent by the original primary cell base station, confirm that the data switchover is complete, and send a second configuration signaling to the terminal to instruct the terminal to release the original primary cell base station and enable the data bearer to take effect with the new security key; The terminal is configured to receive the second reconfiguration signaling, release the original primary cell base station, and enable the data bearer to take effect with the new security key.

[0162] In an optional implementation, the handover notification signaling is a newly defined interface signaling, using a protocol-reserved signaling identifier ID, and the handover notification signaling includes: Terminal identifier, used to uniquely specify the terminal performing the handover; The SN status transmission request command is used to trigger the original primary cell base station to initiate the SN status transmission; A data handover identifier is used to instruct the original primary cell base station to perform the data handover.

[0163] In an optional implementation, the primary cell base station is specifically used to identify whether the terminal supports protocol extension functions: The main cell base station is used to receive capability information reported by the terminal, wherein the capability information carries extended fields; The primary cell base station is used to parse the capability information. When the extended field is parsed and the value of the extended field is true, it determines that the terminal supports the NRDC primary / secondary handover function in the NTN scenario.

[0164] In an optional implementation, the primary cell base station and the secondary cell base station are further configured to perform handover preparation anomaly handling related operations: The primary cell base station is configured to determine that the handover preparation has failed if it does not receive the handover confirmation signaling returned by the secondary cell base station within a preset time period. The primary cell base station is used to send a stop signaling message to the secondary cell base station to notify the cancellation of the handover preparation and to resume sending downlink data packets to the secondary cell base station. The secondary cell base station, upon receiving the abort signaling, releases the pre-allocated signaling bearer configuration, the pre-derived security key, and the established PDCP entity resources, and falls back to the normal dual-connection state before receiving the handover request signaling, without releasing the terminal's service bearer throughout the process.

[0165] Example 3 Based on the same application concept, see [link / reference] Figure 9 As shown, Figure 9 This illustration shows a structural schematic diagram of a computer device provided in Embodiment 3 of this application, wherein, as shown... Figure 9 As shown, the computer device 900 provided in Embodiment 3 of this application includes: The computer device 900 includes a processor 901, a memory 902, and a bus 903. The memory 902 stores machine-readable instructions that can be executed by the processor 901. When the computer device 900 is running, the processor 901 communicates with the memory 902 through the bus 903. When the machine-readable instructions are executed by the processor 901, the steps of the NTN satellite communication fast switching method shown in Embodiment 1 are performed.

[0166] Example 4 Based on the same concept, this application also provides a computer-readable storage medium storing a computer program, which, when executed by a processor, performs the steps of the NTN satellite communication fast handover method described in any of the above embodiments.

[0167] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working process of the system and apparatus described above can be referred to the corresponding process in the foregoing method embodiments, and will not be repeated here.

[0168] The computer program product for fast switching of NTN satellite communication provided in this application includes a computer-readable storage medium storing program code. The instructions included in the program code can be used to execute the methods described in the preceding method embodiments. For specific implementation, please refer to the method embodiments, which will not be repeated here.

[0169] The NTN satellite communication system provided in this application embodiment can be specific hardware on a device or software or firmware installed on the device. The system provided in this application embodiment has the same implementation principle and technical effects as the aforementioned method embodiment. For the sake of brevity, any parts not mentioned in the system embodiment can be referred to the corresponding content in the aforementioned method embodiment. Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working processes of the systems, systems, and units described above can all be referred to the corresponding processes in the above method embodiments, and will not be repeated here.

[0170] In the embodiments provided in this application, it should be understood that the disclosed systems and methods can be implemented in other ways. The system embodiments described above are merely illustrative. For example, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. Furthermore, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Additionally, the coupling or direct coupling or communication connection shown or discussed may be through some communication interfaces; the indirect coupling or communication connection between systems or units may be electrical, mechanical, or other forms.

[0171] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0172] In addition, the functional units in the embodiments provided in this application can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit.

[0173] If the aforementioned functions are implemented as software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, or a portion of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this application. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0174] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. In addition, the terms "first", "second", "third", etc. are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0175] Finally, it should be noted that the above-described embodiments are merely specific implementations of this application, used to illustrate the technical solutions of this application, and not to limit them. The protection scope of this application is not limited thereto. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that any person skilled in the art can still modify or easily conceive of changes to the technical solutions described in the foregoing embodiments, or make equivalent substitutions for some of the technical features, within the scope of the technology disclosed in this application; and these modifications, changes, or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application. All should be covered within the protection scope of this application. Therefore, the protection scope of this application should be determined by the protection scope of the claims.

Claims

1. A fast handover method for NTN satellite communication, characterized in that, Applied to an NTN satellite communication system, the system comprising a terminal, a primary cell base station, and a secondary cell base station; the method includes: After identifying that the terminal supports protocol extension functions, the primary cell base station pre-configures the target cell base station as the secondary cell base station of the terminal, and ensures that all service bearers of the terminal are transmitted through the primary cell base station and the secondary cell base station, while maintaining the established signaling bearers between the terminal and the primary cell base station. After the primary cell base station triggers a handover based on the measurement results reported by the terminal, it prepares for the handover with the secondary cell base station through interface signaling, so that the secondary cell base station can pre-acquire the security key and pre-configure the signaling bearer. The primary cell base station sends a first reconfiguration signaling to the terminal, instructing the terminal to migrate the established signaling bearer from the primary cell base station to the secondary cell base station, and to update the security key in a step-by-step manner, so that the migrated signaling bearer takes effect with the new security key, while the data bearer retains the original security key. The terminal sends reconfiguration completion signaling through the newly established signaling bearer of the secondary cell base station; After receiving the reconfiguration completion signaling, the secondary cell base station performs a path switch to upgrade to a new primary cell base station; The step-by-step updating of the security key includes: In the first phase, the new security key is applied to the signaling bearer migrated to the secondary cell base station, while the data bearer retains the original security key, which is the security key negotiated between the terminal and the primary cell base station when establishing a communication connection. In the second stage, after the secondary cell base station is upgraded to a new primary cell base station and the new primary cell base station completes the data switchover with the original primary cell base station, the new security key is made effective on the data carrier.

2. The method according to claim 1, characterized in that, The primary cell base station prepares for handover with the secondary cell base station via interface signaling, including: The primary cell base station sends a handover request signaling to the secondary cell base station. The handover request signaling carries a handover type identifier, a security key base field, and user plane configuration information for data bearer. After receiving the handover request signaling, the secondary cell base station pre-derives the new security key based on the security key base field, establishes a Packet Data Convergence Protocol (PDCP) entity for data bearer based on the user plane configuration information, and pre-configures the signaling bearer to be established. After completing the pre-assignment and pre-configuration, the secondary cell base station returns a handover confirmation signaling to the primary cell base station. The handover confirmation signaling carries the configuration information of the signaling bearer to be established.

3. The method according to claim 1, characterized in that, After the secondary cell base station performs a path switch to upgrade to a new primary cell base station, it also includes: The new primary cell base station sends a handover notification signaling to the original primary cell base station, triggering the original primary cell base station to be downgraded to a secondary cell base station, and performs data switching and sequence number (SN) status transmission. After receiving the SN status transmission message sent by the original primary cell base station, the new primary cell base station confirms that the data switchover is complete and sends a second reconfiguration signaling to the terminal, instructing the terminal to release the original primary cell base station and enable the data bearer to take effect with the new security key.

4. The method according to claim 3, characterized in that, The handover notification signaling is a newly defined interface signaling, using a pre-reserved signaling identifier ID in the protocol. The handover notification signaling includes: Terminal identifier, used to uniquely specify the terminal performing the handover; The SN status transmission request command is used to trigger the original primary cell base station to initiate the SN status transmission; A data handover identifier is used to instruct the original primary cell base station to perform the data handover.

5. The method according to claim 1, characterized in that, The main cell base station identifies that the terminal supports protocol extension functions, including: The primary cell base station receives capability information reported by the terminal, and the capability information carries extended fields. The primary cell base station parses the capability information. When the extended field is parsed and the value of the extended field is true, it determines that the terminal supports the NR-DC primary / secondary handover function in the NTN scenario.

6. The method according to claim 2, characterized in that, The method also includes a switch preparation exception handling step: If the primary cell base station does not receive the handover confirmation signaling from the secondary cell base station within a preset time period, the handover preparation is deemed to have failed. The primary cell base station sends a stop signaling message to the secondary cell base station to cancel the handover preparation and resume sending downlink data packets to the secondary cell base station; After receiving the abort signaling, the secondary cell base station releases the pre-allocated signaling bearer configuration, the pre-derived security key, and the established PDCP entity resources, and falls back to the normal dual-connection state before receiving the handover request signaling, without releasing the terminal's service bearer throughout the process.

7. An NTN satellite communication system, characterized in that, The system includes a terminal, a primary cell base station, and a secondary cell base station: The primary cell base station is used to pre-configure the target cell base station as the secondary cell base station of the terminal after identifying that the terminal supports the protocol extension function, and to ensure that all service bearers of the terminal are transmitted through the primary cell base station and the secondary cell base station, and to maintain the established signaling bearers between the terminal and the primary cell base station. The primary cell base station is used to prepare for handover with the secondary cell base station via interface signaling after triggering the handover based on the measurement results reported by the terminal, so that the secondary cell base station can pre-acquire the security key and pre-configure the signaling bearer. The primary cell base station is used to send a first reconfiguration signaling to the terminal, instructing the terminal to migrate the established signaling bearer from the primary cell base station to the secondary cell base station, and to update the security key in a step-by-step manner, so that the migrated signaling bearer takes effect with the new security key, while the data bearer retains the original security key. The terminal is used to send reconfiguration completion signaling through the newly established signaling bearer of the secondary cell base station; The secondary cell base station is used to perform path switching to upgrade to a new primary cell base station after receiving the reconfiguration completion signaling; The step-by-step updating of the security key includes: In the first phase, the new security key is applied to the signaling bearer migrated to the secondary cell base station, while the data bearer retains the original security key, which is the security key negotiated between the terminal and the primary cell base station when establishing a communication connection. In the second stage, after the secondary cell base station is upgraded to a new primary cell base station and the new primary cell base station completes the data switchover with the original primary cell base station, the new security key is made effective on the data carrier.

8. A computer device, characterized in that, include: The computer device includes a processor, a memory, and a bus. The memory stores machine-readable instructions executable by the processor. When the computer device is running, the processor communicates with the memory via the bus. When the machine-readable instructions are executed by the processor, they perform the steps of the NTN satellite communication fast handover method as described in any one of claims 1 to 6.

9. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program that, when executed by a processor, performs the steps of the NTN satellite communication fast handover method as described in any one of claims 1 to 6.

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