Method and apparatus for managing ue context information in non-terrestrial network

Abstract

A method and apparatus for operating terminal context information required for a procedure to resume an RRC connection between a terminal and a satellite in a non-terrestrial network are disclosed. The method of a satellite for operating terminal context information includes the steps of determining whether to transfer previously stored terminal context (UE context) information; transferring said terminal context information to a core network based on the determination that said terminal context information should be transferred; receiving a terminal context release command from said core network; and removing said terminal context information based on said terminal context release command.

Description

Technology Field

[0001] The present disclosure relates to communication technology for satellite-based non-terrestrial networks, and more specifically, to a method and apparatus for operating terminal context (UE context) information required for a Radio Resource Control (RRC) resumption procedure between a terminal (UE, user equipment) and a satellite in a satellite-based non-terrestrial network. Background Technology

[0002] Communication networks can be classified into terrestrial networks and non-terrestrial networks. Non-terrestrial networks may be referred to as NTN (non-terrestrial network). In terrestrial networks, communication services for terminals (UE, user equipment) can be provided by base stations located on the ground. In non-terrestrial networks, communication services for terminals can be provided by base stations located off-ground (e.g., satellites, UAVs (unmanned aerial vehicles), drones, etc.). Communication in terrestrial and non-terrestrial networks can be performed based on NR (New Radio) communication technology.

[0003] In satellite-based non-ground networks, satellites can be classified into low earth orbit (LEO), medium earth orbit (MEO), or geostationary orbit (GEO) satellites based on their operating orbits. LEO and MEO satellites may be non-geostationary satellites. Additionally, satellites may be transparent satellites operating in bypass mode between a ground base station and a terminal, or regenerative satellites equipped with all or part of the functions of a ground base station.

[0004] In a terrestrial network or a satellite-based non-terrestrial network, a terminal may have one of the following states: RRC (Radio Resource Control) idle (RRC_IDLE), RRC connected (RRC_CONNECTED), or RRC inactive (RRC_INACTIVE). For example, the terminal may be in an RRC connected state with a base station (e.g., a terrestrial base station or a regenerative satellite equipped with base station functions), and may transition to the RRC inactive state if no signal or data transmission is performed with the base station for a certain period of time while in the RRC connected state. The RRC inactive state may be a state in which radio resources between the terminal and the base station are temporarily released or suspended. In the RRC inactive state, terminal context (UE context) information may be stored and maintained at the base station, and terminal information may be stored and maintained at the base station or the core network.

[0005] A terminal in an RRC-inactive state can transmit a message to the base station requesting the resumption of the RRC connection, and can transition to an RRC-connected state by resuming the connection with the base station. However, in a non-terrestrial network based on regenerative satellites, multiple regenerative satellites move at high speeds along Earth's orbit; therefore, if the terminal's RRC-inactive state persists for a long time—that is, if a long period elapses until the terminal's request to resume the RRC connection is executed—the regenerative satellite storing the terminal context information may move far away from the terminal, which may cause the resumption of the RRC connection between the terminal and the regenerative satellite to fail. Consequently, the terminal may transition from the RRC-inactive state to an RRC-idle state or perform the RRC connection procedure again with a new regenerative satellite. In this case, the terminal must re-perform the initial connection procedure with the new regenerative satellite, which may lead to issues such as increased service provision time or degraded service quality. The problem to be solved

[0006] The objective of the present disclosure to solve the above-mentioned problem is to provide a method and apparatus for operating terminal context information required for a procedure to resume RRC connection between a terminal and a satellite in a satellite-based non-terrestrial network. means of solving the problem

[0007] A method for a satellite for operating terminal context information according to the present disclosure for achieving the above objective may include: a step of determining whether to transfer previously stored terminal context (UE context) information; a step of transferring said terminal context information to a core network based on the determination that said terminal context information should be transferred; a step of receiving a terminal context release command from said core network; and a step of removing said terminal context information based on said terminal context release command.

[0008] The step of determining whether to transfer the above may include: a step of predicting a disconnection point of at least one of the interface between the satellite and the core network or the inter-satellite link (ISL) based interface of adjacent satellites based on orbital movement information; and a step of determining the transfer of the terminal context information when the time remaining until the predicted disconnection point is less than a threshold.

[0009] The step of predicting the disconnection time may include predicting the disconnection time based on the fact that the terminal has switched from an RRC (radio resource control) connected state to an RRC disabled state.

[0010] The step of transferring the terminal context information to the core network may include the step of transmitting a terminal context transfer message containing the terminal context information to the core network.

[0011] A method for a satellite for operating terminal context information according to the present disclosure for achieving the above objective may include: receiving a radio resource control (RRC) connection resume request message from a terminal; attempting to request terminal context information from a previous serving satellite based on the RRC connection resume request message; determining whether the request for terminal context information has failed; requesting the terminal context information from a core network based on the determination that the request for terminal context information has failed; receiving the terminal context information from the core network; resuming the RRC connection with the terminal based on the terminal context information; and transmitting a route change request message to the core network.

[0012] The step of determining whether the above failure has occurred may include determining the failure of the terminal context information request based on at least one of failing to receive a response message for the terminal context information request from the terminal's previous serving satellite within a preset time, or detecting the release of the interface through the inter-satellite link (ISL) with the previous serving satellite.

[0013] The step of requesting the terminal context information may include the step of transmitting a terminal information lookup message containing the terminal context information request to the core network. The terminal information lookup message may be a message defined in an extended form by adding an information element (IE) related to the terminal context information to the Next Generation Application Protocol (NGAP).

[0014] The step of receiving the terminal context information may include the step of receiving a terminal information transfer message containing the terminal context information from the core network. The terminal information transfer message may be a message defined in an extended form by adding information elements related to the terminal context information to the NGAP.

[0015] The method of the satellite may further include the step of receiving a RAN (radio access network) paging request message from the core network; and the step of broadcasting a paging message to a cell area of ​​the satellite based on the RAN paging request message.

[0016] The above RRC resumption request message may be received from the terminal after the terminal's previous serving satellite has transferred the terminal context information to the core network based on the result of predicting the disconnection time of at least one of the interface with the core network or the interface with the satellite.

[0017] A satellite for operating terminal context information according to the present disclosure to achieve the above objective may include at least one processor. The at least one processor may cause the satellite to receive a radio resource control (RRC) connection resume request message from a terminal, attempt to request terminal context information from a previous serving satellite based on the RRC connection resume request message, determine whether the request for terminal context information has failed, and based on the determination that the request for terminal context information has failed, request the terminal context information from a core network, receive the terminal context information from the core network, resume the RRC connection with the terminal based on the terminal context information, and transmit a route change request message to the core network.

[0018] To determine whether the above failure has occurred, the at least one processor may cause the satellite to determine the failure of the terminal context information request based on at least one of the following: the satellite failing to receive a response message for the terminal context information request from the terminal's previous serving satellite within a preset time, or detecting the release of the interface through the inter-satellite link (ISL) with the previous serving satellite.

[0019] To request the terminal context information, the at least one processor may cause the satellite to transmit a terminal information lookup message, which includes a request for terminal context information, to the core network. The terminal information lookup message may be a message defined in an extended form by adding an information element (IE) related to the terminal context information to the Next Generation Application Protocol (NGAP).

[0020] To receive the terminal context information, the at least one processor may cause the satellite to receive a terminal information transfer message containing the terminal context information from the core network. The terminal information transfer message may be a message defined in an extended form by adding information elements related to the terminal context information to the NGAP.

[0021] The above at least one processor may further cause the satellite to receive a RAN (radio access network) paging request message from the core network and, based on the RAN paging request message, broadcast a paging message to the cell area of ​​the satellite.

[0022] The above RRC resumption request message may be received from the terminal after the terminal's previous serving satellite has transferred the terminal context information to the core network based on the result of predicting the disconnection time of at least one of the interface with the core network or the interface with the satellite. Effects of the invention

[0023] According to the present disclosure, in a non-terrestrial network, the previous serving satellite of a terminal can transfer stored terminal context information to the core network based on the result of predicting the time of interface disconnection with the core network or another satellite. Accordingly, the new serving satellite can obtain terminal context information from the core network in response to the terminal's request to resume connection and resume the RRC connection with the terminal. Thus, service continuity can be ensured by minimizing service interruption to the terminal in the non-terrestrial network. Brief explanation of the drawing

[0024] FIG. 1 is a diagram showing an embodiment of a non-ground network. Figure 2 is a diagram showing another embodiment of a non-ground network. FIG. 3 is a block diagram showing an example of a communication node of a non-terrestrial network. FIG. 4 is a flowchart illustrating an example of an RRC connection resumption operation between a ground base station and a terminal in a ground network. FIG. 5 is a flowchart illustrating an example of an RRC connection setup operation between a ground base station and a terminal in a ground network. FIG. 6 is a conceptual diagram illustrating an example of an RRC connection resumption operation between a satellite and a terminal in a non-terrestrial network. FIG. 7 is a flowchart illustrating an example of an operation in which a satellite transfers terminal context information in a non-terrestrial network. FIG. 8 is a flowchart illustrating an example of an RRC connection resumption operation between a satellite and a terminal in a non-terrestrial network. FIG. 9 is a flowchart illustrating another embodiment of the operation to resume the RRC connection between a satellite and a terminal in a non-terrestrial network. Specific details for implementing the invention

[0025] The present disclosure is capable of various modifications and may have various embodiments, and specific embodiments are illustrated in the drawings and described in detail. However, this is not intended to limit the present disclosure to specific embodiments, and it should be understood that it includes all modifications, equivalents, and substitutions that fall within the spirit and scope of the present disclosure.

[0026] Terms such as "first," "second," etc., may be used to describe various components, but said components should not be limited by said terms. Such terms are used solely for the purpose of distinguishing one component from another. For example, without departing from the scope of the present disclosure, the first component may be named the second component, and similarly, the second component may be named the first component. The term "and / or" includes a combination of a plurality of related described items or any of a plurality of related described items.

[0027] When it is stated that one component is "connected" or "connected" to another component, it should be understood that while it may be directly connected or connected to that other component, there may also be other components in between. On the other hand, when it is stated that one component is "directly connected" or "directly connected" to another component, it should be understood that there are no other components in between.

[0028] The terms used in this disclosure are used merely to describe specific embodiments and are not intended to limit this disclosure. The singular expression includes the plural expression unless the context clearly indicates otherwise. In this disclosure, terms such as “comprising” or “having” are intended to specify the existence of the features, numbers, steps, actions, components, parts, or combinations thereof described in the specification, and should be understood as not precluding the existence or addition of one or more other features, numbers, steps, actions, components, parts, or combinations thereof.

[0029] Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as generally understood by those skilled in the art to which this disclosure pertains. Terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant technology, and should not be interpreted in an ideal or overly formal sense unless explicitly defined in this disclosure.

[0030] A communication network to which embodiments according to the present disclosure are applied will be described. The communication network may be a non-terrestrial network (NTN), a 4G communication network (e.g., a long-term evolution (LTE) communication network), a 5G communication network (e.g., a new radio (NR) communication network), a B5G mobile communication network (e.g., a 6G mobile communication network), etc. 4G communication networks and 5G communication networks may be classified as terrestrial networks.

[0031] In an embodiment, "an operation (e.g., a transmission operation) being set in a communication node" may mean that "setting information for said operation (e.g., an information element, a parameter)" and / or "information directing the execution of said operation" is signaled to said communication node. In other words, "an operation (e.g., a transmission operation) being set in a communication node" may mean that said communication node receives "setting information for said operation (e.g., an information element, a parameter)" and / or "information directing the execution of said operation." "An information element (e.g., a parameter) being set in a communication node" may mean that said information element is signaled to said communication node (e.g., said communication node receiving said information element). The signaling may be at least one of SI (system information) signaling (e.g., transmission of SIB (system information block) and / or MIB (master information block)), RRC (radio resource control) signaling (e.g., transmission of RRC parameters and / or upper layer parameters), MAC CE (control element) signaling, or PHY signaling (e.g., transmission of DCI (downlink control information), UCI (uplink control information), and / or SCI (sidelink control information).

[0032] In the present disclosure, even when a method performed at a first communication node among the communication nodes (e.g., transmission or reception of a signal) is described, the corresponding second communication node may perform a method corresponding to the method performed at the first communication node (e.g., reception or transmission of a signal). For example, when the operation of a terminal is described, the base station corresponding to the terminal may perform an operation corresponding to the operation of the terminal. Conversely, when the operation of a base station is described, the terminal corresponding to the base station may perform an operation corresponding to the operation of the base station. Furthermore, when the operation of a first terminal is described, the second terminal corresponding to the first terminal may perform an operation corresponding to the operation of the first terminal. Conversely, when the operation of a second terminal is described, the first terminal corresponding to the second terminal may perform an operation corresponding to the operation of the second terminal.

[0033] In the present disclosure, a phrase containing "~ case (e.g., when ~)" may be expressed as a phrase containing "~ based on (e.g., based on ~)" or a phrase containing "~ in response to (e.g., in response to ~)". In other words, a phrase containing "~ case" may be interpreted as identical or similar to a phrase containing "~ based on" or a phrase containing "~ in response to".

[0034] Throughout the specification, the term "terminal" may refer to a mobile station, mobile terminal, subscriber station, portable subscriber station, user equipment, access terminal, etc., and may include all or part of the functions of a terminal, mobile station, mobile terminal, subscriber station, portable subscriber station, user equipment, access terminal, etc.

[0035] Here, a desktop computer, laptop computer, tablet PC, wireless phone, mobile phone, smartphone, smart watch, smart glass, e-book reader, PMP (portable multimedia player), portable game console, navigation device, digital camera, DMB (digital multimedia broadcasting) player, digital audio recorder, digital audio player, digital picture recorder, digital picture player, digital video recorder, digital video player, etc., capable of communicating with a terminal can be used.

[0036] Throughout the specification, the term "base station" may refer to an access point, a radio access station, a node B, an evolved node B, a base transceiver station, a mobile multihop relay (MMR)-BS, etc., and may include all or part of the functions of a base station, access point, radio access station, node B, eNodeB, base transceiver station, MMR-BS, etc.

[0037] Hereinafter, preferred embodiments of the present disclosure will be described in more detail with reference to the attached drawings. In order to facilitate an overall understanding of the present disclosure, the same reference numerals are used for identical components in the drawings, and redundant descriptions of identical components are omitted.

[0038] FIG. 1 is a diagram showing an embodiment of a non-ground network.

[0039] Referring to FIG. 1, the non-ground network (100) of the present embodiment may be a communication network based on at least one satellite (110). The non-ground network (100) may include a satellite (110), a communication node (120), a gateway (130), a data network (140), etc. The non-ground network (100) of FIG. 1 may be a non-ground network based on a transparent payload.

[0040] The satellite (110) can operate as a non-ground base station in a non-ground network. Such a satellite (110) may be a low earth orbit (LEO) satellite, a medium earth orbit (MEO) satellite, a geostationary earth orbit (GEO) satellite, a high elliptical orbit (HEO) satellite, or an unmanned aircraft system (UAS) platform. A UAS platform may include a high altitude platform station (HAPS).

[0041] The communication node (120) may include a communication node located on the ground and a communication node located off the ground. The communication node located on the ground may be a UE (user equipment) or a terminal, etc. The communication node located off the ground may be an airplane or a drone, etc.

[0042] A service link may be established between the satellite (110) and the communication node (120). The service link may be a radio link. The satellite (110) may provide communication services to the communication node (120) using one or more beams. The shape of the beam footprint of the satellite (110) may be elliptical. One of the beam footprints of the satellite (110) may have a range of 500 to 1,000 km, and multiple communication nodes (120) may be located within one beam footprint.

[0043] A communication node (120) can perform downlink or uplink communication with a satellite (110) using LTE technology or NR technology. Communication between the satellite (110) and the communication node (120) can be performed using an NR-Uu interface. If dual connectivity (DC) is supported, the communication node (120) can be connected not only to the satellite (110) but also to another base station (e.g., a base station supporting LTE or NR functions), and can perform DC operations based on technology defined in the LTE or NR specifications.

[0044] The gateway (130) may be located on the ground, and a feeder link may be established between the satellite (110) and the gateway (130). The feeder link may be a wireless link. The gateway (130) may be referred to as a non-terrestrial network (NTN) gateway. Communication between the satellite (110) and the gateway (130) may be performed based on an NR-Uu interface or a satellite radio interface (SRI). The gateway (130) may be connected to a data network (140).

[0045] A core network may exist between the gateway (130) and the data network (140). In this case, the gateway (130) may be connected to the core network, and the core network may be connected to the data network (140). The core network may support NR technology. For example, the core network may include an access and mobility management function (AMF), a user plane function (UPF), a session management function (SMF), etc. Communication between the gateway (130) and the core network may be performed based on an NG-C / U interface.

[0046] Alternatively, a ground base station and a core network may exist between the gateway (130) and the data network (140). In this case, the gateway (130) may be connected to the ground base station, the ground base station may be connected to the core network, and the core network may be connected to the data network (140). The ground base station and the core network may support NR technology. Communication between the gateway (130) and the ground base station may be performed based on an NR-Uu interface, and communication between the ground base station and the core network may be performed based on an NG-C / U interface.

[0047] Figure 2 is a diagram showing another embodiment of a non-ground network.

[0048] Referring to FIG. 2, the non-ground network (200) of the present embodiment may be a communication network based on a plurality of satellites (211, 212). The non-ground network (200) may include a first satellite (211), a second satellite (212), a communication node (220), a gateway (230), a data network (240), etc.

[0049] The non-ground network (200) illustrated in FIG. 2 may be a non-ground network based on a regenerative payload. For example, each of the first satellite (211) and the second satellite (212) may perform a regenerative operation on a payload received from another entity constituting the non-ground network (200), such as a communication node (220) or a gateway (230), and may transmit the regenerated payload. Here, the regenerative operation may be a demodulation operation, a decoding operation, a re-coding operation, a re-modulation operation, or a filtering operation.

[0050] The first satellite (211) and the second satellite (212) may be LEO satellites, MEO satellites, GEO satellites, HEO satellites, or UAS platforms. The UAS platform may include HAPS. The first satellite (211) may be connected to the second satellite (212), and an inter-satellite link (ISL) may be established between the first satellite (311) and the second satellite (212). The ISL may operate in a radio frequency (RF) band or an optical band. The ISL may be set optionally.

[0051] The communication node (220) may include a communication node located on the ground and a communication node located off the ground. The communication node located on the ground may be a UE (user equipment) or a terminal, etc. The communication node located off the ground may be an airplane or a drone, etc.

[0052] A service link may be established between the first satellite (211) and the communication node (220). The service link may be a radio link. The first satellite (211) may provide communication services to the communication node (220) using one or more beams. The shape of the reception range of the beam of the first satellite (211) may be elliptical.

[0053] The communication node (220) can perform downlink communication or uplink communication with the first satellite (211) using LTE technology or NR technology. Communication between the first satellite (211) and the communication node (220) can be performed using an NR-Uu interface. If DC is supported, the communication node (220) can be connected to the first satellite (211) as well as other base stations that support LTE or NR functions, and can perform DC operations based on technology defined in the LTE or NR specifications.

[0054] The gateway (230) may be located on the ground. A feeder link may be established between the first satellite (211) and the gateway (230) or between the second satellite (212) and the gateway (230). The feeder link may be a wireless link. If an ISL is not established between the first satellite (211) and the second satellite (212), a feeder link between the first satellite (211) and the gateway (230) may be established mandatorily. Communication between the first satellite (211) and the second satellite (212), respectively, and the gateway (230) may be performed based on an NR-Uu interface or SRI.

[0055] A core network may exist between the gateway (230) and the data network (240). In this case, the gateway (230) may be connected to the core network, and the core network may be connected to the data network (240). The core network may support NR technology. For example, the core network may include an access and mobility management function (AMF), a user plane function (UPF), a session management function (SMF), etc. Communication between the gateway (230) and the core network may be performed based on an NG-C / U interface.

[0056] Alternatively, a ground base station and a core network may exist between the gateway (230) and the data network (240). In this case, the gateway (230) may be connected to the ground base station, the ground base station may be connected to the core network, and the core network may be connected to the data network (240). The ground base station and the core network may support NR technology. Communication between the gateway (230) and the ground base station may be performed based on an NR-Uu interface, and communication between the ground base station and the core network may be performed based on an NG-C / U interface.

[0057] FIG. 3 is a block diagram showing an example of a communication node of a non-terrestrial network.

[0058] Referring to FIG. 3, the communication node (300) may include at least one processor (310), a memory (320), and a transceiver (330) that is connected to a network to perform communication. Additionally, the communication node (300) may further include an input interface device (340), an output interface device (350), a storage device (360), etc. Each component included in the communication node (300) may be connected by a bus (370) to communicate with one another.

[0059] However, each component included in the communication node (300) may be connected via individual interfaces or individual buses centered around the processor (310), rather than via a common bus (370). For example, the processor (310) may be connected via a dedicated interface to at least one of a memory (320), a transmission / reception device (330), an input interface device (340), an output interface device (350), or a storage device (360).

[0060] The processor (310) can execute a program command stored in at least one of memory (320) or storage device (360). The processor (310) may mean a central processing unit (CPU), a graphics processing unit (GPU), or a dedicated processor on which the methods according to embodiments of the present disclosure are performed.

[0061] Each of the memory (320) and the storage device (360) may be composed of at least one of a volatile storage medium or a non-volatile storage medium. For example, the memory (320) may be composed of at least one of read-only memory (ROM) or random access memory (RAM).

[0062] FIG. 4 is a flowchart illustrating an example of an RRC connection resumption operation between a ground base station and a terminal in a ground network.

[0063] Referring to FIG. 4, the ground network may include a terminal, ground base station #1 (hereinafter, the first ground base station), ground base station #2 (hereinafter, the second ground base station), and a core network. The first ground base station may be the terminal's current serving base station, and the second ground base station may be the terminal's previous serving base station. The core network may include an access and mobility management function for the terminal, for example, an Access and Mobility Management Function (AMF).

[0064] The terminal may be in an RRC-connected state (RRC_CONNECTED) with the second ground base station. The second ground base station may generate and maintain terminal context (UE context) information for the terminal and establish a control plane connection with a core network (e.g., AMF). The terminal context information may be terminal-specific control information for maintaining communication services between the base station and the terminal. For example, the terminal context information may include at least one of terminal identification information, security information, wireless resource configuration information, or mobility and access management information.

[0065] If the second ground base station does not transmit or receive signals or data with the terminal for a certain period of time, it may transmit a message for disconnecting the RRC connection to the terminal, for example, an RRC release (RRCRelease) message (S411). The RRC release message may include suspendConfig information.

[0066] The terminal may transition from an RRC connected state to an RRC disabled state (RRC_INACTIVE) based on an RRC release received from the second ground base station (S412). The RRC disabled state may mean a state in which the wireless resources established between the terminal and the serving base station are temporarily released or the use of said resources is stopped. Unlike the RRC idle state (RRC_IDLE), the terminal context information stored at the serving base station may be maintained in the RRC disabled state, and said terminal context information may also be maintained between the serving base station and the core network.

[0067] In a terrestrial network, a terminal can move in a predetermined direction, and the serving base station may change depending on the terminal's location change. For example, if the terminal moves out of the cell area of ​​a second terrestrial base station and enters the cell area of ​​a first terrestrial base station, the terminal's serving base station may change from the second terrestrial base station to the first terrestrial base station.

[0068] A terminal in an RRC disabled state may send a message to the first ground base station to resume the RRC connection, for example, an RRC resumption request (RRCResumeRequest) message, in order to resume the RRC connection with the first ground base station (S420).

[0069] The first ground base station may transmit a terminal context request message to the second ground base station, which is the previous serving base station of the terminal, based on the received RRC resumption request message. For example, the first ground base station may transmit a terminal context lookup request (RETRIEVE UE CONTEXT REQUEST) message to the second ground base station (S431). The first ground base station may transmit the terminal context lookup request message to the second ground base station using the Xn interface (or X2 interface).

[0070] The second ground base station may transmit a response message containing context information of the terminal to the first ground base station in response to a received terminal context lookup request message. For example, the second ground base station may transmit a terminal context lookup response (RETRIEVE UE CONTEXT RESPONSE) message to the first ground base station (S432).

[0071] The first ground base station may transmit a message instructing the terminal to resume the RRC connection (RRCResume) based on the terminal context information included in the received terminal context lookup request message (S441). Based on the received RRC connection resume message, the terminal may perform an RRC connection procedure with the first ground base station and transition from an RRC disabled state to an RRC connected state (S442). The terminal may transmit an RRC connection resume completion (RRCResumeComplete) message to the first ground base station (S443). Through this, the RRC connection resumption procedure between the terminal and the first ground base station may be completed.

[0072] The first ground base station may transmit an Xn-U address indication message to the second ground base station (S450). The Xn-U address indication message may be a message used to establish or change a User Plane connection between base stations. In other words, even if the procedure to resume the RRC connection between the first ground base station and the terminal is completed, the core network may not recognize the change in the terminal's location and may transmit data about the terminal to the second ground base station, which is the previous serving base station. Therefore, the first ground base station may transmit an Xn-U address indication message containing its own receiving address information to the second ground base station to prevent data loss. Based on the received Xn-U address indication message, the second ground base station may forward data received from the core network to the first ground base station. According to an embodiment, the first ground base station may omit the transmission operation of the Xn-U address indication message.

[0073] The first ground base station may transmit a path switch request message to the core network (S461). Based on the received path switch request message, the core network may change the transmission path of data for the terminal (e.g., user plane path) from the second ground base station to the first ground base station. The core network may transmit a path switch response message to the first ground base station in response to the change in the data transmission path (S462).

[0074] Since the transmission path of terminal data in the core network has changed, the second ground base station does not need to maintain the previously stored terminal context information. Accordingly, the first ground base station can transmit a terminal context release (UE CONTEXT RELEASE) message to the second ground base station based on the received path change response message (S470). Based on the received terminal context release message, the second ground base station can remove the context information of the corresponding terminal and release the wireless resources allocated to the terminal.

[0075] FIG. 5 is a flowchart illustrating an example of an RRC connection setup operation between a ground base station and a terminal in a ground network.

[0076] Referring to FIG. 5, the terrestrial network may include a terminal, a terrestrial base station #1 (hereinafter, the first terrestrial base station), a terrestrial base station #2 (hereinafter, the second terrestrial base station), and a core network. The first terrestrial base station may be the terminal's current serving base station, and the second terrestrial base station may be the terminal's previous serving base station. The core network may include a connection and mobility management function for the terminal, for example, an AMF.

[0077] The terminal may be in an RRC-connected state (RRC_CONNECTED) with the second ground base station. The second ground base station may generate and maintain context (UE context) information of the terminal and establish a control plane connection with the core network. If no signal or data transmission or reception is performed with the terminal for a certain period of time, the second ground base station may send an RRC release (RRCRelease) message to the terminal to disconnect the RRC connection (S511).

[0078] The terminal can be switched from an RRC connected state to an RRC disabled state (RRC_INACTIVE) based on an RRC release received from the second ground base station (S512). In the terminal's RRC disabled state, terminal context information stored at the second ground base station can be maintained, and the corresponding terminal context information can be maintained between the second ground base station and the core network.

[0079] The terminal can move out of the cell area of ​​the second ground base station and into the cell area of ​​the first ground base station, and depending on this change in the terminal's location, the serving base station can be changed from the second ground base station to the first ground base station. The terminal, which is in an RRC disabled state, can send an RRC resumption request (RRCResumeRequest) message to the first ground base station to resume the RRC connection with the first ground base station (S520).

[0080] The first ground base station may transmit a terminal context request message, for example, a terminal context lookup request (RETRIEVE UE CONTEXT REQUEST) message to the second ground base station based on the received RRC resumption request message (S531). The first ground base station may transmit the terminal context lookup request message to the second ground base station using the Xn interface (or X2 interface).

[0081] The second ground base station may query the context information of the corresponding terminal based on a received terminal context lookup request message. The second ground base station may fail to query the context information of the corresponding terminal due to reasons such as a discrepancy in terminal identification information included in the received message or a failure in security verification (S532). In response to the failure to query the terminal context information, the second ground base station may transmit a "RETRIEVE UE CONTEXT FAILURE" message to the first ground base station (S533).

[0082] The first ground base station may send a message to the terminal to proceed with a new RRC connection procedure based on a received terminal context lookup failure message (S540). For example, the first ground base station may send an RRC Setup message to the terminal. Based on the received RRC Setup message, the terminal may perform a new RRC connection procedure with the first ground base station and / or the core network (S550). Upon completion of the RRC connection procedure, the terminal may transition from an RRC disabled state to an RRC connected state.

[0083] FIG. 6 is a conceptual diagram illustrating an example of an RRC connection resumption operation between a satellite and a terminal in a non-terrestrial network.

[0084] Referring to FIG. 6, the non-ground network may include a plurality of satellites (611, 612, 613) and a terminal (620). The plurality of satellites (611, 612, 613) may include a first satellite (611), a second satellite (612), and a third satellite (613), and each satellite may move at a high speed along the Earth's orbit. Each of the plurality of satellites (611, 612, 613) may be a regenerative satellite that includes all or part of the functions of a base station. Among the plurality of satellites (611, 612, 613), adjacent satellites may transmit and receive control information or data to and from each other based on an Xn interface established through an inter-satellite link (ISL).

[0085] The terminal (620) may receive an RRC release (RRCRelease) message from the first satellite (611) for disconnecting or stopping the RRC connection while in an RRC connected state (RRC_CONNECTED) with the first satellite (611), which is the serving base station. Based on the received RRC message, the terminal (620) may switch from the RRC connected state to the RRC disabled state (RRC_INACTIVE).

[0086] As described above, since each of the multiple satellites (611, 612, 613) moves at a high speed, the serving base station of the terminal (620) can be changed from the first satellite (611) to the third satellite (613) after time t has elapsed. The terminal (620) can send an RRC resumption request (RRCResumeRequest) message to the third satellite (613) to resume the RRC connection.

[0087] The third satellite (613) can transmit a Retriev UE Context Request message to the previous serving base station based on the received RRC resumption request message. Here, the third satellite (613) can transmit the Retriev UE Context Request message via ISL. However, in the non-terrestrial network of this embodiment, each of the multiple satellites (611, 612, 613) may maintain an ISL connection between adjacent satellites. Accordingly, the third satellite (613) may maintain an ISL connection with the second satellite (612), but as the physical distance from the first satellite (611) increases, the ISL connection may be disconnected, making direct communication with the first satellite (611) impossible. As a result, the third satellite (613) cannot obtain the terminal context information, and therefore the RRC resumption procedure between the terminal (620) and the third satellite (613) may fail.

[0088] The terminal (620) may be switched from an RRC disabled state to an RRC idle state (RRC_IDLE) due to a failure to resume the RRC connection with the third satellite (613). In this case, the terminal (620) must perform a new RRC connection procedure with the third satellite (613), so the service provision time may increase, making it difficult to guarantee service continuity, and service quality or satisfaction may be degraded.

[0089] FIG. 7 is a flowchart illustrating an example of an operation in which a satellite transfers terminal context information in a non-terrestrial network.

[0090] Referring to FIG. 7, the non-terrestrial network may include a terminal, a satellite, and a core network. The satellite may be a regenerative satellite that includes all or part of the functions of a base station. The core network may include an AMF for managing the connection and mobility of the terminal.

[0091] The terminal can maintain an RRC connection state (RRC_CONNECTED) through an RRC connection procedure with the satellite in the satellite's cell area (S710). The satellite can generate and maintain context (UE context) information of the terminal and establish a control plane connection with the core network. If no signal or data transmission or reception is performed with the terminal for a certain period of time, the satellite can send an RRC release (RRCRelease) message to the terminal to disconnect the RRC connection (S720). Based on the received RRC release message, the terminal can switch to an RRC inactive state (RRC_INACTIVE) (S730).

[0092] The satellite can determine whether to transfer stored terminal context information (S740). For example, the satellite can predict the time when the NG interface with the core network or the ISL-based Xn interface between satellites is disconnected based on orbital movement information. Based on the predicted time when the interface is disconnected, the satellite can decide to transfer the stored terminal context information to the core network. For example, if the time remaining until the time when the interface is disconnected is less than a preset threshold, the satellite can determine that the interface is about to be disconnected and decide to transfer the terminal context information.

[0093] When the transfer of terminal context information is determined, the satellite may transmit a message to transfer the context information of the corresponding terminal to the core network (S750). For example, the satellite may transmit the terminal context information to the core network using a terminal context transfer (UE CONTEXT TRANSFER) message. The core network may transmit a response message for the received terminal context information, for example, a terminal context transfer acknowledgment (UE CONTEXT TRANSFER ACK) message, to the satellite (S760). Here, the terminal context transfer message or the terminal context transfer acknowledgment message may be defined by extending a message defined in the existing Next Generation Application Protocol (NGAP), or may be defined as a new message.

[0094] After the transfer of terminal context information from the satellite is completed, the core network may transmit a terminal context release command (UE CONTEXT RELEASE COMMAND) message to the satellite (S770). Based on the received terminal context release command message, the satellite may remove the context information of the corresponding terminal and release the wireless resources allocated to the terminal. The satellite may transmit a terminal context release completion (UE CONTEXT RELEASE COMPLETE) message to the core network (S780).

[0095] FIG. 8 is a flowchart illustrating an example of an RRC connection resumption operation between a satellite and a terminal in a non-terrestrial network. The RRC connection resumption operation illustrated in FIG. 8 may represent a procedure performed when a terminal in an RRC inactive state (RRC_INACTIVE) transmits data to a satellite (MO, mobile originated).

[0096] Referring to FIG. 8, the non-terrestrial network may include a terminal, satellite #1 (hereinafter, the first satellite), satellite #2 (hereinafter, the second satellite), and a core network. Each of the first satellite and the second satellite may be a regenerative satellite that includes all or part of the functions of a base station. The first satellite may be a current serving base station, and the second satellite may be a previous serving base station. The core network may include a terminal access and mobility management function, for example, an Access and Mobility Management Function (AMF).

[0097] The terminal may be in an RRC-connected state with the second satellite (RRC_CONNECTED). The second satellite may generate and maintain terminal context (UE context) information for the terminal and establish a control plane connection with the core network. The terminal context information may be terminal-specific control information for maintaining communication services between the base station and the terminal. For example, the terminal context information may include at least one of terminal identification information, security information, wireless resource configuration information, or mobility and access management information.

[0098] If the second satellite does not transmit or receive signals or data with the terminal for a certain period of time, it may transmit an RRC release (RRCRelease) message to the terminal to disconnect the RRC connection (S811). The RRC release message may include suspendConfig information. Based on the received RRC release message, the terminal may switch from an RRC connected state to an RRC disabled state (RRC_INACTIVE) (S812).

[0099] The second satellite can determine whether to transfer the stored terminal context information. For example, the satellite can predict the time when the NG interface with the core network or the inter-satellite ISL-based Xn interface becomes disconnected based on orbital movement information. Based on the predicted time of interface disconnection, the satellite can decide to transfer the previously stored terminal context information to the core network. If the transfer of terminal context information is determined, the satellite can transmit the terminal context information to the core network using a Terminal Context Transfer (UE CONTEXT TRANSFER) message (S813). The core network can store the received terminal context information. This terminal context transfer operation of the second satellite may be the same as described above with reference to FIG. 7.

[0100] In a non-terrestrial network, the first satellite and the second satellite can each move in a certain direction based on orbital information. Depending on the change in the satellite's position, the serving base station for the terminal may change. For example, even if the terminal's location remains the same, the terminal's serving base station may change from the second satellite (previous serving base station) to the first satellite (current serving base station) due to changes in the cell area resulting from the movement of the first and second satellites.

[0101] A terminal in an RRC disabled state may request the first satellite to resume the RRC connection if there is an uplink (UL) signal or data to be transmitted to the satellite or core network. For example, the terminal may transmit an RRC resume request (RRCResumeRequest) message to the first satellite to resume the RRC connection (S820).

[0102] The first satellite may attempt to request terminal context information from the second satellite, which is the previous serving base station, based on the received RRC resumption request message. For example, the first satellite may transmit a Retriev UE Context Request message to the second satellite via the ISL (S831). Here, the ISL connection may be disconnected as the orbital distance between the first satellite and the second satellite increases. Consequently, the second satellite may not receive the Retriev UE Context Request message from the first satellite. The first satellite may determine the failure of the Retriev UE Context Information request based on the failure to receive a response message to the Retriev UE Context Request from the second satellite or the detection of an ISL disconnection (S832). Here, the failure of the first satellite to receive a response message may mean that the response message is not received within a preset time after transmitting the Retriev UE Context Request message to the second satellite.

[0103] The first satellite can request terminal context information from the core network through the NG interface. For example, the first satellite can transmit a RETRIEVE UE INFORMATION message containing a request for terminal context information to the core network (S841). The terminal information retrieval message can be defined in an extended form by adding information elements (IE) related to the terminal context to a message defined in the existing Next Generation Application Protocol (NGAP), or it can be defined as a new message.

[0104] The core network may transmit a response message containing context information of the corresponding terminal to the first satellite based on the received terminal information lookup message. For example, the core network may transmit a terminal information transfer (UE INFORMATION TRANSFER) message containing terminal context information to the first satellite (S842). The terminal information transfer message may be defined in an extended form by adding information elements (IE) related to the terminal context to a message defined in the existing Next Generation Application Protocol (NGAP), or it may be defined as a new message.

[0105] The first satellite may transmit a message instructing the terminal to resume the RRC connection (RRCResume) based on the terminal context information included in the received terminal information transfer message (S851). Based on the received RRC connection resumption message, the terminal may perform an RRC connection procedure with the first satellite and transition from an RRC disabled state to an RRC connected state (S852). The terminal may transmit an RRC connection resumption completion (RRCResumeComplete) message to the first satellite (S853). Through this, the RRC connection resumption procedure between the terminal and the first satellite may be completed.

[0106] The first satellite may transmit a path switch request message to the core network (S861). Based on the received path switch request message, the core network may change the transmission path of data for the terminal (e.g., user plane path) from the second satellite to the first satellite. The core network may transmit a path switch response message to the first satellite in response to the change in the data transmission path (S862).

[0107] FIG. 9 is a flowchart illustrating another embodiment of an RRC connection resumption operation between a satellite and a terminal in a non-terrestrial network. The RRC connection resumption operation illustrated in FIG. 9 may represent a procedure performed when the core network transmits data to a terminal in an RRC-inactive state (RRC_INACTIVE) (MT, mobile terminated).

[0108] Referring to FIG. 9, the non-terrestrial network may include a terminal, satellite #1 (hereinafter, the first satellite), satellite #2 (hereinafter, the second satellite), and a core network. Each of the first satellite and the second satellite may be a regenerative satellite that includes all or part of the functions of a base station. The first satellite may be a current serving base station, and the second satellite may be a previous serving base station. The core network may include an Access and Mobility Management Function (AMF) for managing the connection and mobility of the terminal.

[0109] The terminal may be in an RRC-connected state with the second satellite (RRC_CONNECTED). The second satellite may generate and maintain terminal context (UE context) information for the terminal and establish a control plane connection with the core network. The terminal context information may be terminal-specific control information for maintaining communication services between the base station and the terminal. For example, the terminal context information may include at least one of terminal identification information, security information, wireless resource configuration information, or mobility and access management information.

[0110] If the second satellite does not transmit or receive signals or data with the terminal for a certain period of time, it may transmit an RRC release (RRCRelease) message to the terminal to disconnect the RRC connection (S911). The RRC release message may include suspendConfig information. Based on the received RRC release message, the terminal may switch from an RRC connected state to an RRC disabled state (RRC_INACTIVE) (S912).

[0111] The second satellite can determine whether to transfer the stored terminal context information. For example, the satellite can predict the time when the NG interface with the core network or the inter-satellite ISL-based Xn interface becomes disconnected based on orbital movement information. Based on the predicted time of interface disconnection, the satellite can decide to transfer the previously stored terminal context information to the core network. If the transfer of terminal context information is determined, the satellite can transmit the terminal context information to the core network using a Terminal Context Transfer (UE CONTEXT TRANSFER) message (S913). The core network can store the received terminal context information. The terminal context transfer operation of the second satellite may be the same as described above with reference to FIG. 7.

[0112] In a non-terrestrial network, the first satellite and the second satellite can each move in a certain direction based on orbital information. Depending on the change in the satellite's position, the serving base station for the terminal may change. For example, even if the terminal's location remains the same, the terminal's serving base station may change from the second satellite (previous serving base station) to the first satellite (current serving base station) due to changes in the cell area resulting from the movement of the first and second satellites.

[0113] The core network may request paging from the terminal if there is a downlink (DL) signal or data to be transmitted to the terminal or satellite. For example, the core network may transmit a RAN (radio access network) paging request message to multiple satellites included in the RNA through an NG interface based on the terminal's RAN Notification Area (RNA) information (S921).

[0114] The first satellite can perform terminal paging in its cell area based on a received RAN paging request message. For example, the first satellite can broadcast a paging message to the cell area through the Uu interface based on a set paging occasion (PO) (S922).

[0115] A terminal in an RRC disabled state can check for a match based on the terminal identifier included in the received paging message. Based on the received paging message, the terminal can send an RRC resumption request (RRCResumeRequest) message to the first satellite to resume the RRC connection (S930).

[0116] The first satellite may attempt to request terminal context information from the second satellite, which is the previous serving base station, based on the received RRC resumption request message. For example, the first satellite may transmit a Retriev UE Context Request message to the second satellite via the ISL (S941). Here, the ISL connection may be disconnected as the orbital distance between the first satellite and the second satellite increases. Consequently, the second satellite may not receive the Retriev UE Context Request message from the first satellite. The first satellite may determine the failure of the Retriev UE Context Information request based on the failure to receive a response message to the Retriev UE Context Request from the second satellite or the detection of an ISL disconnection (S942). Here, the failure of the first satellite to receive a response message may mean that the response message is not received within a preset time after transmitting the Retriev UE Context Request message to the second satellite.

[0117] The first satellite can request terminal context information from the core network through the NG interface. For example, the first satellite can transmit a RETRIEVE UE INFORMATION message containing a request for terminal context information to the core network (S951). The terminal information retrieval message can be defined in an extended form by adding information elements (IE) related to the terminal context to a message defined in the existing NGAP (Next Generation Application Protocol), or it can be defined as a new message.

[0118] The core network may transmit a response message containing context information of the corresponding terminal to the first satellite based on the received terminal information lookup message. For example, the core network may transmit a terminal information transfer (UE INFORMATION TRANSFER) message containing terminal context information to the first satellite (S952). The terminal information transfer message may be defined in an extended form by adding information elements (IE) related to the terminal context to a message defined in the existing Next Generation Application Protocol (NGAP), or it may be defined as a new message.

[0119] The first satellite may transmit a message instructing the terminal to resume the RRC connection (RRCResume) based on the terminal context information included in the received terminal information transfer message (S961). Based on the received RRC connection resumption message, the terminal may perform an RRC connection procedure with the first satellite and transition from an RRC disabled state to an RRC connected state (S962). The terminal may transmit an RRC connection resumption completion (RRCResumeComplete) message to the first satellite (S963). Through this, the RRC connection resumption procedure between the terminal and the first satellite may be completed.

[0120] The first satellite may transmit a path switch request message to the core network (S971). Based on the received path switch request message, the core network may change the transmission path of data for the terminal (e.g., user plane path) from the second satellite to the first satellite. The core network may transmit a path switch response message to the first satellite in response to the change in the data transmission path (S972).

[0121] The operation of the method according to an embodiment of the present disclosure can be implemented as a computer-readable program or code on a computer-readable recording medium. A computer-readable recording medium includes all types of recording devices in which information that can be read by a computer system is stored. Additionally, the computer-readable recording medium may be distributed across networked computer systems, and the computer-readable program or code may be stored and executed in a distributed manner.

[0122] In addition, computer-readable recording media may include hardware devices specifically configured to store and execute program instructions, such as ROM, RAM, and flash memory. Program instructions may include machine code, such as that generated by a compiler, as well as high-level language code that can be executed by a computer using an interpreter, etc.

[0123] Some aspects of the present disclosure have been described in the context of a device, but may also be described according to a corresponding method, wherein a block or device corresponds to a method step or a feature of a method step. Similarly, aspects described in the context of a method may also be described according to a corresponding block or item or a feature of a corresponding device. Some or all of the method steps may be performed by (or using) a hardware device, such as, for example, a microprocessor, a programmable computer, or an electronic circuit. In some embodiments, at least one of the most important method steps may be performed by such a device.

[0124] In the embodiments, a programmable logic device (e.g., a field-programmable gate array) may be used to perform some or all of the functions of the methods described herein. In the embodiments, a field-programmable gate array may operate with a microprocessor to perform one of the methods described herein. Generally, it is preferable that the methods be performed by some hardware device.

[0125] Although the present disclosure has been described with reference to preferred embodiments, those skilled in the art will understand that various modifications and changes can be made to the present disclosure without departing from the spirit and scope of the present disclosure as set forth in the following claims.

Claims

Claim 1 A method of satellite comprising: a step of determining whether to transfer previously stored terminal context (UE context) information; a step of transferring said terminal context information to a core network based on the determination of said transfer of said terminal context information; a step of receiving a terminal context release command from said core network; and a step of removing said terminal context information based on said terminal context release command. Claim 2 A method of a satellite according to claim 1, wherein the step of determining whether to transfer comprises: a step of predicting a disconnection point of at least one of an interface between the satellite and the core network or an inter-satellite link (ISL) based interface between the satellite and a new serving satellite adjacent to the satellite based on orbital movement information; and a step of determining the transfer of the terminal context information when the time remaining until the predicted disconnection point is less than a threshold. Claim 3 A method of a satellite according to claim 2, wherein the step of predicting the disconnection time includes the step of predicting the disconnection time based on the fact that the terminal has switched from an RRC (radio resource control) connected state to an RRC disabled state. Claim 4 A method of a satellite according to claim 1, wherein the step of transferring the terminal context information to a core network comprises the step of transmitting a terminal context transfer message containing the terminal context information to the core network. Claim 5 A method of a satellite comprising: receiving a radio resource control (RRC) connection resume request message from a terminal; attempting to request terminal context information from a previous serving satellite based on the RRC connection resume request message; determining whether the request for terminal context information has failed; requesting the terminal context information from a core network based on the determination that the request for terminal context information has failed; receiving the terminal context information from the core network; resuming the RRC connection with the terminal based on the terminal context information; and transmitting a route change request message to the core network. Claim 6 A method of a satellite according to claim 5, wherein the step of determining whether there is a failure comprises determining the failure of the terminal context information request based on at least one of failing to receive a response message for the terminal context information request from the previous serving satellite of the terminal within a preset time or detecting the release of an interface through an inter-satellite link (ISL) with the previous serving satellite. Claim 7 A method of a satellite according to claim 5, wherein the step of requesting terminal context information includes the step of transmitting a terminal information lookup message including a request for terminal context information to the core network, and the terminal information lookup message is a message defined in an extended form by adding an information element (IE) related to the terminal context information to the Next Generation Application Protocol (NGAP). Claim 8 A method of a satellite according to claim 5, wherein the step of receiving terminal context information includes the step of receiving a terminal information transfer message containing the terminal context information from the core network, and the terminal information transfer message is a message defined in an extended form by adding information elements related to the terminal context information to the NGAP. Claim 9 A method of a satellite according to claim 5, further comprising: receiving a RAN (radio access network) paging request message from the core network; and broadcasting a paging message to a cell area of ​​the satellite based on the RAN paging request message. Claim 10 A method of a satellite according to claim 5, wherein the RRC resumption request message is received from the terminal after the terminal's previous serving satellite transfers the terminal context information to the core network based on the result of predicting the disconnection time of at least one of the interface with the core network or the interface with the satellite. Claim 11 A satellite comprising at least one processor, wherein the at least one processor causes the satellite to receive a radio resource control (RRC) connection resume request message from a terminal, attempt to request terminal context information from a previous serving satellite based on the RRC connection resume request message, determine whether the request for terminal context information fails, and based on the determination that the request for terminal context information failed, request the terminal context information from a core network, receive the terminal context information from the core network, resume the RRC connection with the terminal based on the terminal context information, and cause the satellite to transmit a route change request message to the core network. Claim 12 In claim 11, for determining whether the failure occurred, the at least one processor causes the satellite to determine the failure of the terminal context information request based on at least one of the following: the satellite fails to receive a response message for the terminal context information request from the terminal's previous serving satellite within a preset time, or detects the release of the interface through the inter-satellite link (ISL) with the previous serving satellite. Claim 13 In claim 11, to request the terminal context information, the at least one processor causes the satellite to transmit a terminal information lookup message including a request for terminal context information to the core network, and the terminal information lookup message is a message defined in an extended form by adding an information element (IE) related to the terminal context information to the Next Generation Application Protocol (NGAP). Claim 14 In claim 11, for receiving the terminal context information, the at least one processor causes the satellite to receive a terminal information transfer message including the terminal context information from the core network, and the terminal information transfer message is a message defined in an extended form by adding information elements related to the terminal context information to the NGAP. Claim 15 The satellite according to claim 11, wherein the at least one processor further causes the satellite to receive a RAN (radio access network) paging request message from the core network and, based on the RAN paging request message, broadcast a paging message to a cell area of ​​the satellite. Claim 16 In claim 11, the RRC resumption request message is received from the terminal after the terminal's previous serving satellite transfers the terminal context information to the core network based on the result of predicting the disconnection time of at least one of the interface with the core network or the interface with the satellite.

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