Base station and network node

Abstract

This base station comprises: a transmission unit that transmits, to a destination base station, a message that requests the execution of a handover and includes information indicating that the cause is satellite movement; and a control unit that starts a timer for detecting the elapse of a time limit that is set for the handover due to satellite movement and extends from the transmission of the message to the reception of a response to the message.

Description

Base Stations and Network Nodes

[0001] The present invention relates to base stations and network nodes in communication systems.

[0002] 3GPP (registered trademark) (3rd Generation Partnership Project) is currently studying a wireless communication system called 5G or NR (New Radio) (hereinafter, the wireless communication system will be referred to as "5G" or "NR") in order to achieve a larger system capacity, a higher data transmission speed, and a lower latency in wireless sections. Various wireless technologies are being studied for 5G to meet the requirements of achieving a throughput of 10 Gbps or more while keeping latency in wireless sections to 1 ms or less.

[0003] In NR, a network architecture including 5GC (5G Core Network) corresponding to EPC (Evolved Packet Core), which is the core network in the network architecture of LTE (Long Term Evolution), and NG-RAN (Next Generation - Radio Access Network) corresponding to E-UTRAN (Evolved Universal Terrestrial Radio Access Network), which is the RAN (Radio Access Network) in the network architecture of LTE, is being considered (for example, Non-Patent Document 1).

[0004] Furthermore, as an IMS (IP Multimedia Subsystem) architecture that supports the data channel capabilities of terminals, specifications for an IMS data channel network are being studied (see, for example, Non-Patent Document 2). In the IMS data channel network, a Data Channel Signalling Function (DCSF) having a signaling function, a Media Function (MF) having a media-related function, and a Data Channel Application Server (DCAS) that is an application server are arranged on both the calling and called sides.

[0005] Furthermore, in 3GPP Rel-19, in order to realize IMS voice terminal-satellite-terminal communication (UE-satellite-UE communication), reducing the impact on existing specifications when deploying 5GC network functions and IMS components on satellites is an issue (see, for example, Non-Patent Document 3). Here, terminal-satellite-terminal communication refers to terminal-to-terminal communication under routing that keeps user plane traffic within the satellite. The types of satellites handled include geostationary satellites (GEO), low Earth orbit satellites (LEO), and medium Earth orbit satellites (MEO). Furthermore, for low Earth orbit satellites and medium Earth orbit satellites, satellite constellations can be formed without using inter-satellite links (ISLs) or using inter-satellite links.

[0006] 3GPP TS 23.501 V18.4.0 (2023-12) 3GPP TS 23.228 V18.4.0 (2023-12) 3GPP TR 23.700-29 V0.2.0 (2023-11) 3GPP TS 38.331 V17.7.0 (2024-01) 3GPP TS 29.244 V18.4.0 (2024-01)

[0007] In terminal-satellite-terminal communications, for example, when a satellite constellation is formed using inter-satellite links in low-earth-orbit satellites, communication devices such as base stations, user plane functions, and IMS access gateways are deployed on each satellite. Each satellite moves over time. The network nodes deployed on each satellite sequentially connect with terminals and network nodes in specific areas on the ground.

[0008] In this case, network nodes deployed on satellites and network nodes deployed on the ground must be able to discover and select communication partners, and data and voice communications must continue even when the satellite is moving.

[0009] The present invention has been made in view of the above points, and aims to provide a communication technology that enables communication between a communication device deployed on a satellite and a communication device deployed on the ground in a wireless communication system while continuing data communication and voice communication even when the satellite is moving.

[0010] According to the disclosed technology, a base station is provided that has a transmitting unit that transmits a message requesting the execution of a handover to a destination base station, the message including information indicating that the handover is caused by satellite movement, and a control unit that activates a timer that detects the expiration of a time limit set in a handover caused by satellite movement, from the transmission of the message to the reception of a response to the message.

[0011] According to the disclosed technology, it is possible to provide a communication technology that enables a communication device deployed on a satellite and a communication device deployed on the ground in a wireless communication system to communicate with each other while continuing data communication and voice communication even when the satellite moves and switching occurs.

[0012] FIG. 1 is a diagram for explaining an example of a communication system. FIG. 1 is a diagram for explaining an example of a communication system in a roaming environment. FIG. 1 is a diagram for explaining an example of an IMS data channel network. FIG. 2 is a diagram showing an example of a first sequence diagram in an embodiment of the present invention. FIG. 3 is a diagram showing an example of a second sequence diagram in an embodiment of the present invention. FIG. 4 is a diagram showing an example of a third sequence diagram in an embodiment of the present invention. FIG. 5 is a diagram showing an example of a fifth sequence diagram in an embodiment of the present invention. FIG. 6 is a diagram showing an example of a sixth sequence diagram in an embodiment of the present invention. FIG. 7 is a diagram showing an example of a seventh sequence diagram in an embodiment of the present invention. FIG. 8 is a diagram showing an example of an eighth sequence diagram in an embodiment of the present invention. FIG. 1 is a diagram showing an example of the functional configuration of a base station 10 and a network node 30 in an embodiment of the present invention. FIG. 2 is a diagram showing an example of the functional configuration of a terminal 20 in an embodiment of the present invention. FIG. 3 is a diagram showing an example of the hardware configuration of a base station 10, a terminal 20, and a network node 30 in an embodiment of the present invention. FIG. 4 is a diagram showing an example of the configuration of a vehicle 2001 in an embodiment of the present invention.

[0013] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Note that the embodiment described below is an example, and the embodiment to which the present invention is applied is not limited to the following embodiment.

[0014] In the operation of the wireless communication system according to the embodiment of the present invention, existing technology is used as appropriate. However, the existing technology is, for example, the existing LTE, but is not limited to the existing LTE. Furthermore, the term "LTE" used in this specification has a broad meaning including LTE-Advanced, and systems subsequent to LTE-Advanced (e.g., NR), or wireless LAN (Local Area Network), unless otherwise specified.

[0015] Furthermore, in the embodiments of the present invention, "configuring" radio parameters and the like may mean that predetermined values ​​are pre-configured, or that radio parameters notified from the network node 30 or the terminal 20 are set.

[0016] Fig. 1 is a diagram illustrating an example of a communication system. As shown in Fig. 1, the communication system is composed of a UE, which is a terminal 20, and multiple network nodes 30. Hereinafter, it is assumed that one network node 30 corresponds to each function, but multiple functions may be realized by one network node 30, or multiple network nodes 30 may realize one function. Furthermore, the "connection" described below may be a logical connection or a physical connection.

[0017] The RAN (Radio Access Network) is a network node 30 having a radio access function, which may include a base station 10, and is connected to a UE, an AMF (Access and Mobility Management Function), and a UPF (User Plane Function). The AMF is a network node 30 having functions such as terminating the RAN interface, terminating the NAS (Non-Access Stratum), registering management, connecting management, reachability management, and terminal mobility management. The UPF is a network node 30 having functions related to processing user plane data, such as a PDU (Protocol Data Unit) session point to the outside that interconnects with the DN (Data Network), packet routing and forwarding, and user plane Quality of Service (QoS) handling. The UPF and the DN constitute a network slice. In the wireless communication network according to the embodiment of the present invention, multiple network slices are constructed.

[0018] The AMF is connected to the UE, RAN, SMF (Session Management function), NSSF (Network Slice Selection Function), NEF (Network Exposure Function), NRF (Network Repository Function), UDM (Unified Data Management), AUSF (Authentication Server Function), PCF (Policy Control Function), and AF (Application Function). The AMF, SMF, NSSF, NEF, NRF, UDM, AUSF, PCF, and AF are network nodes 30 that are mutually connected via interfaces based on their respective services, Namf, Nsmf, Nnssf, Nnef, Nnrf, Nudm, Nausf, Npcf, and Naf.

[0019] The SMF is a network node 30 having functions such as session management, UE IP (Internet Protocol) address allocation and management, DHCP (Dynamic Host Configuration Protocol) function, ARP (Address Resolution Protocol) proxy, and roaming function. The NEF is a network node 30 having a function of notifying other NFs (Network Functions) of capabilities and events. The NSSF is a network node 30 having functions such as selecting a network slice to which a UE connects, determining an allowed NSSAI (Network Slice Selection Assistance Information), determining an NSSAI to be set, and determining an AMF set to which a UE connects. The PCF is a network node 30 having a function of controlling network policies. The AF is a network node 30 having a function of controlling application servers. The NRF is a network node 30 having a function of discovering NF instances that provide services. The UDM is a network node 30 that manages subscriber data and authentication data. The UDM is connected to a UDR (User Data Repository) that stores the data.

[0020] Fig. 2 is a diagram illustrating an example of a communication system in a roaming environment. As shown in Fig. 2, the network is composed of a UE, which is a terminal 20, and multiple network nodes 30. Hereinafter, it is assumed that one network node 30 corresponds to each function, but multiple functions may be realized by one network node 30, or multiple network nodes 30 may realize one function. Furthermore, the "connection" described below may be a logical connection or a physical connection.

[0021] The RAN is a network node 30 having a radio access function, and is connected to the UE, the AMF, and the UPF. The AMF is a network node 30 having functions such as RAN interface termination, NAS termination, registration management, connection management, reachability management, and mobility management. The UPF is a network node 30 having functions such as a PDU session point to the outside that interconnects with the DN, packet routing and forwarding, and user plane QoS handling. The UPF and the DN constitute a network slice. In the wireless communication network according to the embodiment of the present invention, multiple network slices are constructed.

[0022] The AMF is connected to the UE, RAN, SMF, NSSF, NEF, NRF, UDM, AUSF, PCF, AF, and SEPP (Security Edge Protection Proxy). The AMF, SMF, NSSF, NEF, NRF, UDM, AUSF, PCF, and AF are network nodes 30 that are interconnected via respective service-based interfaces, Namf, Nsmf, Nnssf, Nnef, Nnrf, Nudm, Nausf, Npcf, and Naf.

[0023] The SMF is a network node 30 having functions such as session management, UE IP address allocation and management, DHCP function, ARP proxy, and roaming function. The NEF is a network node 30 having a function of notifying other NFs of capabilities and events. The NSSF is a network node 30 having functions such as selecting a network slice to which a UE connects, determining an allowed NSSAI, determining a configured NSSAI, and determining an AMF set to which a UE connects. The PCF is a network node 30 having a function of controlling network policies. The AF is a network node 30 having a function of controlling application servers. The NRF is a network node 30 having a function of discovering NF instances that provide services. The SEPP is a non-transparent proxy that filters control plane messages between PLMNs (Public Land Mobile Networks). The vSEPP shown in FIG. 2 is a SEPP in the visited network, and the hSEPP is a SEPP in the home network.

[0024] As shown in Figure 2, a UE is in a roaming environment connected to a RAN and an AMF in a Visited PLMN (VPLMN). The VPLMN and a Home PLMN (HPLMN) are connected via a vSEPP and an hSEPP. The UE can communicate with a UDM in the HPLMN via the AMF in the VPLMN, for example.

[0025] Fig. 3 is a diagram illustrating an example of an IMS data channel network. As shown in Fig. 3, the IMS data channel network is configured with a terminal 20 (UE) and multiple network nodes 30 in each of an originating network and a terminating network. Hereinafter, it is assumed that one network node 30 corresponds to each function, but multiple functions may be realized by one network node 30, or multiple network nodes 30 may realize one function. Furthermore, the "connection" described below may be a logical connection or a physical connection. The network node 30 has, for example, the following functions described in Non-Patent Document 2:

[0026] The IMS-AGW (Access Gateway) is a network node 30 having a gateway function between the UE and the IMS network, a function related to access processing for voice communication, and the like.

[0027] A P-CSCF (Proxy-Call Session Control Function) is a network node 30 that has a proxy function between the UE and the IMS network, an access control function for voice communication, and the like.

[0028] The S-CSCF (Serving-Call Session Control Function) is a network node 30 having functions related to session control for the UE.

[0029] The I-CSCF (Interrogate-Call Session Control Function) is a connection point on the destination network side between networks (e.g., between the source network side and the destination network side) in the IMS network, and is a network node 30 that has, for example, the function of forwarding a received SIP request to the S-CSCF of its own network.

[0030] An IMS AS (IP Multimedia Subsystem Application Server) is a network node 30 in an IMS network that has functions such as communicating with a DCSF for event notification and receiving data channel control instructions from the DCSF to communicate with an MF. The IMS AS also receives a communication termination point registration request from a DCSF (Data Channel Signalling Function), converts the received registration request into a SIP Register, and sends it to a Serving-Call Session Control Function (S-CSCF). The IMS AS also converts a data channel establishment request received from the DCSF into a SIP INVITE and sends it to the S-CSCF.

[0031] The DCSF (Data Channel Signaling Function) is a network node 30 that has functions such as receiving an event report from the IMS-AS and determining whether to allow the provision of a data channel service, managing the bootstrap data channel, and performing HTTP web server functions.

[0032] An MF (Media Function) is a network node 30 in an IMS network that has functions such as media resource management and forwarding of data channel media traffic. The MF processes media between a DCAS (Data Channel Application Server), which is a communication termination point, and a destination termination point based on configuration information received from a DCSF. The MF may also be called a DCMF (Data Channel Media Function). The MF may also be called an MRF (Multimedia Resource Function).

[0033] A DCAS (Data Channel Application Server) is a network node 30 having functions such as a communication termination point for media and signaling in the IMS network.

[0034] (Example) In a wireless communication system, a procedure will be described for enabling communication between a communication device deployed on a satellite and a communication device deployed on the ground while continuing data communication and voice communication even when switching occurs due to the movement of the satellite.

[0035] In this embodiment, it is assumed that a plurality of low-earth orbit satellites (LEOs) equipped with base stations, UPFs, and IMS AGWs form a satellite constellation using inter-satellite links (ISLs). A satellite base station GW 30C, a satellite UPF GW 30D, and a satellite IMS AGW GW 30E are deployed on the ground as satellite GWs, communicating with the base stations, UPFs, and IMS AGWs deployed in the LEOs, respectively. The base station 10, the terminal 20, and the network nodes 30 (30A, 30B, etc.) may also be referred to as communication devices.

[0036] The satellite base station GW30C performs communication with the base station 10 and communication with the AMF 30F based on the interface between the base station 10 and the AMF 30F. That is, the satellite base station GW30C behaves as the AMF 30F with respect to the base station 10, and as the base station 10 with respect to the AMF 30F.

[0037] The satellite UPF GW 30D communicates with the UPF 30A and the SMF 30G based on the interface between the UPF 30A and the SMF 30G. That is, the satellite UPF GW 30D behaves as the SMF 30G with respect to the UPF 30A, and as the UPF 30A with respect to the SMF 30G.

[0038] The satellite IMS AGW GW30E communicates with the IMS AGW 30B and the P-CSCF 30J based on the interface between the IMS AGW 30B and the P-CSCF 30J. That is, the satellite IMS AGW GW30E behaves as the P-CSCF 30J with respect to the IMS AGW 30B, and as the IMS AGW 30B with respect to the P-CSCF 30J.

[0039] Furthermore, the satellite GW and terminal 20 connect to different LEOs depending on the time based on the satellite ephemeris. Here, the satellite ephemeris is information indicating the relationship between the position in the satellite orbit and the time.

[0040] In addition, an inter-satellite communication network function (NF) 300 is installed in the LEO. The inter-satellite communication network function (NF) performs processing related to communications in the ISL between satellites.

[0041] The satellite communications operator prepares mainly the base station 10, UPF 30A, IMS AGW 30B, and inter-satellite coordination NF 30O deployed in the LEO, and the satellite GW deployed on the ground, as dedicated equipment for satellite constellation communications.

[0042] Meanwhile, mobile carriers prepare mainly the AMF30F, SMF30G, PCF30H, P-CSCF30J, S-CSCF30K, and HSS30L, which are network nodes deployed on the ground, as satellite constellation utilization equipment. Here, the AMF30F, SMF30G, and P-CSCF30J recognize the satellite base station GW30C, satellite UPF GW30D, and satellite IMS AGW GW30E, respectively, as devices representing the satellite constellation. In other words, since the processing other than that related to this recognition is the same as the existing specifications, the impact on the existing specifications when deploying network nodes on satellites is reduced.

[0043] The following describes, using sequence diagrams, the procedures when a satellite (LEO) connected to a communication device deployed on the ground moves. Here, a base station 10A, a UPF 30M, an IMS AGW 30N, and an inter-satellite cooperation NF 30O are deployed in the source LEO, and a base station 10B, a UPF 30P, an IMS AGW 30Q, and an inter-satellite cooperation NF 30R are deployed in the destination LEO. Requests, responses, notifications, and the like transmitted and received in the procedures described below may be referred to as messages (e.g., request messages). For details of existing specifications related to messages transmitted and received in the sequence diagrams, see Non-Patent Document 4 and Non-Patent Document 5, etc.

[0044] 4 is a diagram showing an example of a first sequence diagram according to an embodiment of the present invention. The processing of each step in FIG. 4 will now be described.

[0045] S501: In the source LEO, uplink user plane data (hereinafter referred to as UL user data) is being transmitted on the route from the terminal 20 to the base station 10A and on the route from the base station 10A to the UPF 30M. Also, downlink user plane data (hereinafter referred to as DL user data) is being transmitted on the route from the base station 10A to the terminal 20 and on the route from the UPF 30M to the base station 10A.

[0046] S502: The base station 10A transmits a request message (handover request) requesting a handover to the base station 10B. The request message includes a PDU session identifier and information indicating that the cause of the handover is a satellite movement cause. By including the cause in the request message, it is possible to execute a different handover (such as a handover including a UPF switching process). Here, the base station 10A may select the destination base station 10B using a list created based on the satellite ephemeris. For example, the base station 10A selects the base station 10B to connect to at the current time based on a list indicating the relationship between a connectable time period (specified by, for example, a start time and an end time) and a connectable base station candidate.

[0047] S503: The base station 10A starts a timer that detects whether the time limit for receiving a response to the request sent in S502 has expired (timeout). The time limit for the timer to detect the timeout may be set to, for example, a time limit longer than that for a normal handover, in order to limit the time when the cause of the handover is a satellite movement cause.

[0048] S504: The base station 10B transmits a notification message notifying the event to the inter-satellite cooperation NF 30R. The notification message includes information indicating that a request for handover due to satellite movement has been received and a PDU session identifier.

[0049] S505: The inter-satellite cooperation NF 30R transmits a notification message notifying the event to the base station 10B. The notification message includes information indicating the start of UPF switching.

[0050] S506: The base station 10B stores context information including UPF side termination point information at the time of UL user data transmission in its own device, and then waits until an event related to UPF switching starts. For example, the base station 10B sets the value of UL NG-U UP TNL Information in the Handover Request Transfer included in the request message received in S502 as the UPF side termination point information.

[0051] S507: The inter-satellite cooperation NF30R transmits to the UPF 30P a first request message related to UL user data and a second request message related to DL user data as request messages (PFCP Session Establishment requests) requesting establishment of a path for transferring UL user data and DL user data between UPFs. The first request message and the second request message include setting information related to a packet detection rule (PDR) and setting information related to a forwarding action rule (FAR). The setting information related to the PDR in the first request message includes information requesting allocation of an identifier (UL Tunnel Endpoint Identification (TEID)) related to a termination point at which the UL user data is received in the UPF 30P. The setting information related to the PDR in the second request message includes information requesting allocation of an identifier (DL TEID) related to a termination point at which the DL user data is received in the UPF 30P. The setting information related to the FAR in the first request message includes information indicating that buffering is set to ON.

[0052] S508: The UPF 30P transmits a first response message related to UL user data and a second response message related to DL user data to the inter-satellite cooperation NF 30R as response messages (PFCP Session Establishment responses) to the request message received in S507. The first response message includes an identifier (UL TEID) related to the termination point for UL user data in the destination UPF 30P as setting information related to the PDR. The second response message includes an identifier (DL TEID) related to the termination point for DL ​​user data in the destination UPF 30P as setting information related to the PDR.

[0053] S509: The inter-satellite cooperation NF 30R transmits a request message (UL / DL forwarding path setting request) to the inter-satellite cooperation NF 30O, requesting execution of setting related to the forwarding paths of UL user data and DL user data. The request message includes the UL TEID of the UPF 30P that is the moving destination, the DL TEID of the UPF 30P that is the moving destination, setting information related to the PDR, and a PDU session identifier. Here, the setting information related to the PDR is information (null information) that does not include any information to be set.

[0054] S510: The inter-satellite cooperation NF 30O transmits to the UPF 30M a first request message related to UL user data and a second request message related to DL user data as request messages (PFCP Session Establishment requests) requesting establishment of a path for transferring UL user data and DL user data between UPFs. The first request message includes configuration information related to the PDR and configuration information related to the FAR. Here, the configuration information related to the PDR is information (null information) that does not include any information to be set. The configuration information related to the FAR includes the UL TEID of the UPF 30P that is the destination of the movement. The second request message includes configuration information related to the PDR and configuration information related to the FAR. Here, the configuration information related to the PDR is information (null information) that does not include any information to be set. The configuration information related to the FAR includes the DL TEID of the UPF 30P that is the destination of the movement.

[0055] S511: The UPF 30M transmits, to the inter-satellite cooperation NF 30O, a first response message related to the UL user data and a second response message related to the DL user data as response messages (PFCP Session Establishment responses) to the request message received in S510.

[0056] S512: The inter-satellite cooperation NF 30O transmits a response message (UL / DL forwarding path setting response) to the request message received in S509 to the inter-satellite cooperation NF 30R.

[0057] S513: As a result of the processing from S507 to S512 being executed, route information for UL and DL user data is set on the route from UPF 30M to UPF 30P. However, since setting information related to PDR is not set on this route, transmission of UL user data and DL user data is not executed, and only transmission of UL user data and DL user data described in S501 is executed.

[0058] The process following S513 will be described. Fig. 5 is a diagram showing an example of a second sequence diagram according to an embodiment of the present invention. The process of each step in Fig. 5 will be described.

[0059] S521: The inter-satellite cooperation NF 30R transmits a request message (RAN-oriented UPF context acquisition request) requesting acquisition of UPF context information for the RAN (base station) to the inter-satellite cooperation NF 30O. The request message includes an identifier of the PDU session.

[0060] S522: The inter-satellite cooperation NF 30O transmits to the UPF 30M a first request message related to UL user data and a second request message related to DL user data as request messages (PFCP context acquisition requests) requesting acquisition of UPF context information for the RAN (base station). The first request message includes the identifier of the PDU session received in S521 and requests acquisition of context information related to the UL user data associated with the identifier. The identifier may be an F-SEID (Fully Qualified-Session Endpoint Identification) that indicates the path between the source UPF 30M and the source base station 10A. The second request message includes the identifier of the PDU session received in S521 and requests acquisition of context information related to the DL user data associated with the identifier. The identifier may be an F-SEID that indicates the path between the source UPF 30M and the source base station 10A.

[0061] S523: The UPF 30M transmits a first response message related to UL user data and a second response message related to DL user data to the inter-satellite cooperation NF 30O as response messages (PFCP context acquisition responses) to the request message received in S522. The first response message includes context information related to the route between the source UPF 30M and the source base station 10A related to the UL user data. The second response message includes context information related to the route between the source UPF 30M and the source base station 10A related to the DL user data.

[0062] S524: The inter-satellite cooperation NF 30O transmits a response message (UPF context acquisition response for RAN) to the inter-satellite cooperation NF 30R in response to the request message received in S521. The response message includes the context information received in S523 as context information held by the source UPF 30M for the identifier of the PDU session included in the request message.

[0063] S525: The inter-satellite cooperation NF 30R transmits a request message (PFCP context setting request) to the UPF 30P requesting the setting of context information. A first request message related to UL user data and a second request message related to DL user data are transmitted. The first request message includes context information related to the route between the source UPF 30M and the source base station 10A related to UL user data, and a PDU session identifier. The second request message includes context information related to the route between the source UPF 30M and the source base station 10A related to DL user data, setting information related to a PDR indicating that input packets (user data) will not be accepted (entrance blocking), and a PDU session identifier.

[0064] S526: The UPF 30P sets the context information received in S525 (context information acquired from the UPF 30M) and starts processing related to user data based on the context information. Here, due to the setting information related to the PDR indicating entrance closure received in S525, packet detection processing is temporarily stopped for DL ​​user data.

[0065] S527: The UPF 30P transmits, to the inter-satellite cooperation NF 30R, a first response message related to the UL user data and a second response message related to the DL user data as response messages (PFCP context setting responses) to the request message received in S525.

[0066] S528: The inter-satellite cooperation NF 30R transmits a request message (UL / DL forwarding path update request) to the inter-satellite cooperation NF 30O, requesting update of settings related to the forwarding paths of UL user data and DL user data. The request message includes, as setting information related to the PDR of UL user data, a request to set the UL TEID associated with the identifier of the PDU session and already transmitted to the source base station 10A, i.e., the setting value of the PDR set in the UPF 30M to detect UL user data from the source base station 10A, in the PDR in the UPF 30M for the forwarding path of UL user data between UPFs, and also includes information indicating the interface (N6) between the UPF and the DN as setting information related to the PDR of DL user data.

[0067] S529: The inter-satellite cooperation NF 30O transmits to the UPF 30M a first request message related to UL user data and a second request message related to DL user data as request messages (PFCP Session Modification request) requesting an update of the settings of paths for transferring UL user data and DL user data between UPFs. The first request message includes setting information related to a PDR as a transfer path for UL user data between UPFs. Here, the setting information related to the PDR is a request to set the setting value of the PDR set for detecting UL user data from the base station 10A in the PDR for the transfer path for UL user data between UPFs. The second request message includes setting information related to a PDR in which information indicating the interface (N6) between the UPF and the DN is set as a transfer path for DL ​​user data between UPFs.

[0068] S530: The UPF 30M executes settings related to the transfer of UL user data and DL user data based on the setting information related to the PDR received in S529.

[0069] S531: The UPF 30M starts transferring the UL and DL user data to the destination UPF 30P.

[0070] S532: The UPF 30M transmits, to the inter-satellite cooperation NF 30O, a first response message related to the UL user data and a second response message related to the DL user data as response messages (PFCP Session Modification response) to the request message received in S529.

[0071] S533: The inter-satellite cooperation NF 30O transmits a response message (UL / DL forwarding path update response) to the request message received in S528 to the inter-satellite cooperation NF 30R.

[0072] S534: As a result of the processing of S521 to S533 being executed, UL user data transmission is executed on the route from the terminal 20 to the base station 10A and on the route from the base station 10A to the UPF 30M, but DL user data transmission is not executed on the route from the base station 10A to the terminal 20 and on the route from the UPF 30M to the base station 10A. Also, UL and DL user data transmission is executed from the UPF 30M to the UPF 30P, but the UPF 30P buffers the received UL and DL user data. Also, a route between the base station 10A and the UPF 30P is set within the UPF 30P, but UL user data transmission is not executed because the route is not set in the base station 10A, and DL user data transmission is not executed because input blocking is set.

[0073] The process following S534 will be described. Fig. 6 is a diagram showing an example of a third sequence diagram according to an embodiment of the present invention. The process of each step in Fig. 6 will be described.

[0074] S541: The inter-satellite cooperation NF 30R transmits a notification message to the base station 10B to notify the base station 10B of the event. The notification message includes information indicating that the UPF switching (switching from the source UPF 30M to the destination UPF 30P) has been completed, and an identifier (Fully-qualified TEID (F-TEID)) indicating the termination point in the UPF 30P after the switching. The value of the identifier is set to "aa" (F-TEID=aa).

[0075] S542: The base station 10B changes the termination point information of the destination of the UL user data, which was set in the base station 10B based on the value of the UL NG-U UP TNL Information in the Handover Request Transfer included in the handover request received from the source base station 10A in S502, to the value (aa) of the identifier (F-TEID) acquired in S541.

[0076] S543: The base station 10B transmits to the base station 10A a response message (Handover Request Acknowledge) in response to the request message received in S502.

[0077] S544: The base station 10A transmits to the terminal 20 a request message (RRCReconfiguration (=Handover Command)) requesting the execution of handover.

[0078] S545: The base station 10A transmits a message (SN status transfer) related to the status of the sequence number (SN) to the base station 10B. The message includes the status of the sequence number of the GTP-U (GPRS (General Packet Radio Service) Tunnel Protocol - User Plane) in the UL (UL GTP-U SN status).

[0079] S546: As a result of the processing from S541 to S545 being executed, routes for DL ​​user data are set between UPF 30M and base station 10A and between base station 10A and base station 10B, but transmission of DL user data is not executed on these routes.

[0080] S547: The terminal 20 transmits a message (RRCReconfigurationComplete) notifying the base station 10B of the confirmation of the handover.

[0081] S548: The base station 10B confirms that the context information included in the message received in S502 includes information indicating satellite movement cause.

[0082] S549: Even after the processes of S547 and S548 are executed, DL user data transmission is not executed on the route between the UPF 30M and the base station 10A, and between the base station 10A and the base station 10B. Furthermore, UL user data transmission is not executed on the route from the base station 10A to the UPF 30M. Meanwhile, UL user data transmission is executed on the route between the terminal 20 and the base station 10B, and between the base station 10B and the UPF 30P, but buffering of the UL user data is set in the UPF 30P. Furthermore, a route for DL ​​user data is set between the base station 10B and the terminal 20, but transmission is not executed.

[0083] The process following S549 will be described. Fig. 7 is a diagram showing an example of a fourth sequence diagram according to an embodiment of the present invention. The process of each step in Fig. 7 will be described.

[0084] S551: The base station 10B transmits a notification message notifying an event to the inter-satellite link NF 30R. The notification message includes information indicating that the handover confirmation (received in S547) has been received, and the value (bb) of DL NG-U UP TNL Information, which is termination point information on the own device side when receiving DL user data.

[0085] S552: In order to avoid duplication of IP addresses, the inter-satellite cooperation NF 30R decides to start data transmission and reception at the destination UPF 30P after releasing the source UPF 30M.

[0086] S553: ​​The inter-satellite cooperation NF 30R transmits a request message (UPF resource release request) requesting the release of UPF resources to the inter-satellite cooperation NF 30O. The request message includes information indicating a request for the status of the GTP-U sequence number (DL GTP-U SN status) in DL user data transfer between UPFs.

[0087] S554: The inter-satellite cooperation NF 30O transmits a first request message, a second request message, a third request message, and a fourth request message to the UPM 30M as request messages (PFCP Session Deletion requests) requesting the release of UPF resources. The first request message requests the release of UPF resources related to UL user data transfer between the UPF 30M and the UPF 30P. The second request message includes information indicating a request for the release of UPF resources related to DL user data transfer between the UPF 30M and the UPF 30P, and information indicating a request for the status of the GTP-U sequence number in DL (DL GTP-U SN status). The third request message requests the release of UPF resources related to UL user data transfer between the UPF 30M and the base station 10A. The fourth request message requests the release of UPF resources related to DL user data transfer between the UPF 30M and the base station 10A.

[0088] S555: The UPM 30M transmits a first response message, a second response message, a third response message, and a fourth response message to the inter-satellite cooperation NF 300 as response messages (PFCP Session Deletion responses) to the request message received in S554. The second response message includes the status of the GTP-U sequence number in DL (DL GTP-U SN status).

[0089] S556: The inter-satellite cooperation NF 30O transmits a response message (UPF resource release response) to the request message received in S553 to the inter-satellite cooperation NF 30R. The response message includes the status of the GTP-U sequence number in DL user transfer between UPFs (DL GTP-U SN status).

[0090] S557: The inter-satellite link NF 30R transmits to the UPF 30P a request message (PFCP Session Modification request) requesting update of the setting of the path for transferring DL user data to the base station 10B. The request message includes, as setting information for DL, setting information related to the FAR including the termination identifier (TEID (= bb)) set by the destination base station 10B, and information indicating that the status of the GTP-U sequence number in DL (DL GTP-U SN status) is to be updated.

[0091] S558: The UPF 30P transmits a response message (PFCP Session Modification response) to the request message received in S557 to the inter-satellite cooperation NF 30R.

[0092] S559: Even after the processes of S551 to S558 are executed, the base station 10A still retains the DL user data transfer settings for the route from UPF 30M to base station 10B via base station 10A. However, DL user data transfer is not actually executed. Also, since the settings in UPF 30M have been deleted, transmission of UL and DL user data on the route from UPF 30M to UPF 30P is not executed. Also, since the settings in UPF 30P have been changed, a route for transmitting DL user data from UPF 30P to the terminal 20 via base station 10B rather than base station 10A has been established.

[0093] The process following S559 will be described. Fig. 8 is a diagram showing an example of a fifth sequence diagram according to an embodiment of the present invention. The process of each step in Fig. 8 will be described.

[0094] S561: The inter-satellite cooperation NF 30R transmits a request message (IMS AGW context acquisition / switching request) requesting acquisition of context information in the IMS AGW and switching of the IMS AGW to the inter-satellite cooperation NF 30O. The request message includes a PDU session identifier.

[0095] S562: The inter-satellite cooperation NF 300 transmits the request message (IMS AGW context acquisition / switching request) received in S561 to the IMS AGW 30N.

[0096] S563: The IMS AGW 30N transmits a response message (IMS AGW context acquisition / switching response) to the request message received in S562 to the inter-satellite cooperation NF 300. The response message includes context information in the IMS AGW 30N.

[0097] S564: The inter-satellite cooperation NF 300 transmits a response message (IMS AGW context acquisition / switching response) to the request message received in S562 to the inter-satellite cooperation NF 30R. The response message includes context information in the IMS AGW 30N.

[0098] S565: The inter-satellite cooperation NF 30R transmits a request message (IMS AGW context setting request) requesting the setting of context information to the IMS AGW 30Q. The request message includes the context information in the IMS AGW 30N received in S564 and the identifier of the PDU session.

[0099] S566: The IMS AGW 30Q transmits a response message (IMS AGW context setting response) to the request message received in S565 to the inter-satellite cooperation NF 30R.

[0100] S567: The inter-satellite cooperation NF 30R transmits a first request message, a second request message, and a third request message to the UPF 30P as request messages (PFCP Session Modification requests) requesting updates regarding the setting of a path for transferring DL user data to the base station 10B and the setting of paths for transferring UL user data and DL user data between UPFs. The first request message includes setting information related to a PDR indicating the release of the entrance blockage of the path for transferring DL user data to the base station 10B. The second request message includes information indicating the release of buffering for UL user data transferred between UPFs. The third request message includes information indicating the release of buffering for DL ​​user data transferred between UPFs.

[0101] S568: The UPF 30P receives the first response message, the second response message, and the third response message from the inter-satellite cooperation NF 30R as response messages (PFCP Session Modification responses) to the request message received in S567.

[0102] S569: In the processing of S567 to S568, the entrance blockage and buffering in UPF 30P are released, and transmission of DL user data is now performed on the route from UPF 30P to base station 10B and on the route from base station 10B to terminal 20.

[0103] The process following S569 will be described. Fig. 9 is a diagram showing an example of a sixth sequence diagram according to an embodiment of the present invention. The process of each step in Fig. 9 will be described.

[0104] S571: The base station 10B transmits a request message (Path Switch request) requesting path switching to the satellite base station GW 30C. The request message includes information indicating switching to the base station 10B, but does not include information related to the user plane.

[0105] S572: The satellite base station GW 30C transmits to the base station 10B a response message (Path Switch response, Path Switch Request Acknowledge) in response to the request message received in S571.

[0106] S573: The base station 10B transmits a request message (UE Context release) to the base station 10A to request the release of the context of the terminal 20.

[0107] S574: The inter-satellite cooperation NF 30R transmits to the UPF 30P a first request message for the UL and a second request message for the DL as request messages (PFCP Session Deletion request) requesting the release of resources held for transferring UL user data and DL user data between UPFs.

[0108] S575: The UPF 30P transmits to the inter-satellite cooperation NF 30R, as response messages (PFCP Session Deletion responses) to the request message received in S574, a first response message for UL and a second response message for DL.

[0109] S576: By executing the processes from S571 to S575, all settings before the handover in the base station 10A and the UPF 30M are deleted. Also, all settings for transferring UL user data and DL user data between the UPFs in the UPF 30M and the UPF 30P are deleted. That is, as settings after the handover, UL user data can be transmitted on the route from the terminal 20 to the base station 10B and on the route from the base station 10B to the UPF 30P, and DL user data can be transmitted on the route from the base station 10B to the terminal 20 and on the route from the UPF 30P to the base station 10B.

[0110] The process following S576 will be described. Fig. 10 is a diagram showing an example of a seventh sequence diagram according to an embodiment of the present invention. The process of each step in Fig. 10 will be described.

[0111] S581: The inter-satellite cooperation NF 30R transmits a request message (Path Switch request) related to path switching to the satellite UPF GW 30D. The request message includes information indicating a change of UPF (from UPF 30M to UPF 30P).

[0112] S582: The satellite UPF GW 30D transmits a response message (Path Switch response) to the request message received in S581 to the inter-satellite cooperation NF 30R.

[0113] S583: The inter-satellite cooperation NF 30R transmits a request message (Path Switch request) related to path switching to the satellite IMS AGW GW 30E. The request message includes information indicating a change of the IMS AGW (from the IMS AGW 30N to the IMS AGW 30Q).

[0114] S584: The satellite IMS AGW GW30E transmits a response message (Path Switch response) to the request message received in S583 to the inter-satellite cooperation NF30R.

[0115] Next, a procedure will be described for when a satellite (LEO) connected to a ground-based communication device moves while the terminal 20 is in idle mode. Fig. 11 is a diagram showing an example of an eighth sequence diagram according to an embodiment of the present invention. The processing of each step in Fig. 11 will be described below.

[0116] S601: The UPM 30M is in a preservation state (a state in which the connection with the base station 10A is open) in which the connection with the base station 10A is open for the session of the terminal 20.

[0117] S602: The inter-satellite cooperation NF 30O determines to execute processing to move from the source LEO to the destination LEO in the preservation state, based on information on the time period in which the satellite is connectable, which is generated by the satellite ephemeris. Here, the inter-satellite cooperation NF 30O may select the destination LEO (or the inter-satellite cooperation NF 30R in the destination LEO) by using a list created based on the satellite ephemeris. For example, the inter-satellite cooperation NF 30O selects the LEO (or the inter-satellite cooperation NF in the destination LEO) to connect to at the current time, based on a list indicating the relationship between the connectable time period (specified by, for example, a start time and an end time) and the connectable destination LEO (or the inter-satellite cooperation NF in the destination LEO) candidates.

[0118] S603: The inter-satellite cooperation NF 300 transmits a request message (PFCP context acquisition request) requesting acquisition of a context to the UPF 30M. The request message includes information indicating that all terminals in the UPF 30M's preservation state are the target (non-UE) and information indicating UPF switching.

[0119] S604: The UPF 30M transmits a response message (PFCP context acquisition response) to the request message received in S603 to the inter-satellite cooperation NF 300. The response message includes context information held by the UPF 30.

[0120] S605: The UPF 30M deactivates (invalidates) the context information that the UPF 30M has.

[0121] S606: The inter-satellite cooperation NF 300 transmits a request message (UPF context setting request for RAN) requesting the setting of context information to the inter-satellite cooperation NF 30R. The request message includes the context information received in S604.

[0122] S607: The inter-satellite cooperation NF 30R transmits a request message (PFCP context setting request) requesting the setting of context information to the UPF 30P. The request message includes the context information received in S606.

[0123] S608: The UPF 30P transmits a response message (PFCP context setting response) to the request message received in S607 to the inter-satellite cooperation NF 30R.

[0124] S609: The UPF 30P sets the context information received in S608 (context information acquired from the UPF 30M) and starts processing related to the user data based on the context information.

[0125] S610: The UPF 30P enters a preservation state in which the connection with the base station is released for the session of the terminal 20.

[0126] S611: The inter-satellite cooperation NF 30R transmits a response message (UPF context setting response for RAN) to the inter-satellite cooperation NF 30O in response to the request message received in S606.

[0127] S612: The inter-satellite cooperation NF 30O transmits a request message (PFCP Session Deletion request) to the UPF 30M to request the release of UPF resources.

[0128] S613: The UPF 30M receives a response message (PFCP Session Deletion response) in response to the request message received in S612 from the inter-satellite cooperation NF 300.

[0129] S614: The inter-satellite cooperation NF 30R transmits a request message (Path Switch request) requesting path switching to the satellite UPF GW 30D.

[0130] S615: The satellite UPF GW 30D transmits a response message (Path Switch response, Path Switch Request Acknowledge) to the inter-satellite cooperation NF 30R in response to the request message received in S614.

[0131] According to the above-described embodiment, in a wireless communication system, a communication device deployed on a satellite and a communication device deployed on the ground can communicate with each other while continuing data communication and voice communication, even when switching occurs due to the movement of the satellite.

[0132] In the above-described embodiment, the inter-satellite cooperation NF 30R can complete the route switching from the source UPF 30M to the destination UPF 30P by executing the following process.

[0133] First, in S507-S512, the inter-satellite cooperation NF30R determines to set an inlet block that does not accept input packets and a buffering that holds output packets on a first route for transferring uplink user plane data and downlink user plane data from the source UPF 30M to the destination UPF 30P, and transmits a message for setting a transfer route including the settings related to the inlet block and the settings related to the buffering on the first route.

[0134] Also, in S525, the inter-satellite cooperation NF30R transmits a message to set the context information held by the UPF 30M in the UPF 30P and to set an entrance closure in the second route for transferring downlink user plane data from the UPF 30P to the source base station 10A.

[0135] In addition, in S528, the inter-satellite link NF30R transmits a message to release the entrance blockage in the first route.

[0136] In addition, in S553, the inter-satellite cooperation NF 30R transmits a message for releasing the resources of the UPF 30M.

[0137] Also, in S557, the inter-satellite cooperation NF 30R transmits a message for changing the transfer of downlink user plane data to the source base station 10A in the UPF 30P to the transfer of downlink user plane data to the destination base station 10B.

[0138] In addition, in S567, the inter-satellite link NF30R transmits a message to release the entrance blockage in the second route.

[0139] In addition, in S567, the inter-satellite link NF30R transmits a message to release buffering in the first route.

[0140] By executing the above process, the inter-satellite cooperation NF 30R recognizes that the route switching from the UPF 30M to the UPF 30P has been completed.

[0141] (Device Configuration) Next, a description will be given of an example of the functional configuration of the base station 10, network node 30, and terminal 20 that perform the processes and operations described above. The base station 10, network node 30, and terminal 20 include functions for performing the above-described embodiments. However, the base station 10, network node 30, and terminal 20 may each include only a part of the functions of the embodiments.

[0142] <Base Station 10 and Network Node 30> Fig. 12 is a diagram showing an example of the functional configuration of the base station 10 and the network node 30. As shown in Fig. 12, the base station 10 has a transmitting unit 110, a receiving unit 120, a setting unit 130, and a control unit 140. The functional configuration shown in Fig. 12 is merely an example. As long as the operations according to the embodiment of the present invention can be performed, the names of the functional divisions and functional units may be any. Note that the network node 30 may have the same functional configuration as the base station 10. Furthermore, a network node 30 having multiple different functions in the system architecture may be composed of multiple network nodes 30 separated by function.

[0143] The transmitter 110 includes a function of generating a signal to be transmitted to the terminal 20 or another network node 30 and transmitting the signal by wire or wirelessly. The receiver 120 includes a function of receiving various signals transmitted from the terminal 20 or another network node 30 and acquiring, for example, information of a higher layer from the received signal. A communication unit including the transmitter 110 and the receiver 120 may be configured.

[0144] The setting unit 130 stores in a storage device preset setting information and various setting information to be transmitted to the terminal 20, and reads out from the storage device as needed. The content of the setting information is, for example, information related to a communication path in the IMS data channel network.

[0145] As described in the embodiments, the control unit 140 performs processing to enable communication between the communication device deployed on the satellite and the communication device deployed on the ground. The control unit 140 also performs processing related to communication with the terminal 20. The function unit related to signal transmission in the control unit 140 may be included in the transmitting unit 110, and the function unit related to signal reception in the control unit 140 may be included in the receiving unit 120.

[0146] <Terminal 20> Fig. 13 is a diagram showing an example of the functional configuration of the terminal 20. As shown in Fig. 13, the terminal 20 has a transmitting unit 210, a receiving unit 220, a setting unit 230, and a control unit 240. The functional configuration shown in Fig. 13 is merely an example. As long as the operations related to the embodiment of the present invention can be performed, the names of the functional divisions and functional units may be any. In addition, the communication device that becomes the resource holder 20 may have the same functional configuration as the terminal 20.

[0147] The transmitter 210 creates a transmission signal from transmission data and transmits the transmission signal wirelessly. The receiver 220 receives various signals wirelessly and acquires higher layer signals from the received physical layer signals. The receiver 220 also has a function of receiving control signals, reference signals, etc. transmitted from the network node 30. A communication unit including the transmitter 210 and the receiver 220 may be configured.

[0148] The setting unit 230 stores various pieces of setting information received from the network node 30 by the receiving unit 220 in a storage device and reads them from the storage device as needed. The setting unit 230 also stores setting information that is set in advance. The content of the setting information is, for example, information related to communication paths in the IMS network.

[0149] As described in the embodiments, the control unit 240 performs processing to enable communication between the communication device deployed on the satellite and the communication device deployed on the ground. The function unit related to signal transmission in the control unit 240 may be included in the transmitting unit 210, and the function unit related to signal reception in the control unit 240 may be included in the receiving unit 220.

[0150] (Hardware Configuration) The block diagrams (FIGS. 12 and 13) used to explain the above embodiments show functional blocks. These functional blocks (components) are realized by any combination of at least one of hardware and software. Furthermore, the method for realizing each functional block is not particularly limited. That is, each functional block may be realized using a single device that is physically or logically coupled, or may be realized using two or more physically or logically separated devices that are directly or indirectly connected (for example, using wires, wirelessly, etc.) and these multiple devices. The functional block may be realized by combining software with the single device or the multiple devices.

[0151] Functions include, but are not limited to, judgment, determination, assessment, calculation, computation, processing, derivation, investigation, search, confirmation, reception, transmission, output, access, resolution, selection, selection, establishment, comparison, assumption, expectation, consideration, broadcasting, notifying, communicating, forwarding, configuring, reconfiguring, allocating, mapping, and assignment. For example, a functional block (component) that performs transmission is called a transmitting unit or transmitter. As mentioned above, there are no particular limitations on how these functions are implemented.

[0152] For example, the base station 10, the network node 30, the terminal 20, etc. according to an embodiment of the present disclosure may function as a computer that performs processing of the wireless communication method of the present disclosure. Fig. 14 is a diagram illustrating an example of the hardware configuration of the base station 10 and the terminal 20 according to an embodiment of the present disclosure. The network node 30 may have the same hardware configuration as the base station 10. The above-described base station 10 and the terminal 20 may be physically configured as a computer device including a processor 1001, a storage device 1002, an auxiliary storage device 1003, a communication device 1004, an input device 1005, an output device 1006, a bus 1007, etc.

[0153] In the following description, the term "apparatus" can be interpreted as a circuit, a device, a unit, etc. The hardware configuration of the base station 10 and the terminal 20 may be configured to include one or more of the apparatuses shown in the drawings, or may be configured to exclude some of the apparatuses.

[0154] Each function in the base station 10 and the terminal 20 is realized by loading specified software (programs) onto hardware such as the processor 1001, the memory device 1002, etc., so that the processor 1001 performs calculations, controls communication by the communication device 1004, and controls at least one of reading and writing data in the memory device 1002 and the auxiliary memory device 1003.

[0155] The processor 1001 controls the entire computer by running, for example, an operating system. The processor 1001 may be configured as a central processing unit (CPU) including an interface with peripheral devices, a control device, an arithmetic unit, a register, etc. For example, the above-mentioned control unit 140, control unit 240, etc. may be realized by the processor 1001.

[0156] Furthermore, the processor 1001 reads programs (program codes), software modules, data, etc. from at least one of the auxiliary storage device 1003 and the communication device 1004 into the storage device 1002 and executes various processes in accordance with the programs. The programs used are those that cause a computer to execute at least some of the operations described in the above-described embodiments. For example, the control unit 140 of the base station 10 shown in FIG. 12 may be implemented by a control program stored in the storage device 1002 and running on the processor 1001. Furthermore, for example, the control unit 240 of the terminal 20 shown in FIG. 13 may be implemented by a control program stored in the storage device 1002 and running on the processor 1001. While the above-described various processes have been described as being executed by one processor 1001, they may also be executed simultaneously or sequentially by two or more processors 1001. The processor 1001 may be implemented by one or more chips. The programs may also be transmitted from a network via a telecommunications line.

[0157] The storage device 1002 is a computer-readable recording medium and may be configured, for example, by at least one of a read-only memory (ROM), an erasable programmable read-only memory (EPROM), an electrically erasable programmable read-only memory (EEPROM), a random access memory (RAM), etc. The storage device 1002 may also be called a register, a cache, a main memory, etc. The storage device 1002 can store executable programs (program codes), software modules, etc. for implementing a communication method according to an embodiment of the present disclosure.

[0158] The secondary storage device 1003 is a computer-readable recording medium, and may be, for example, at least one of an optical disk such as a CD-ROM (Compact Disc ROM), a hard disk drive, a flexible disk, a magneto-optical disk (e.g., a compact disk, a digital versatile disk, a Blu-ray (registered trademark) disk), a smart card, a flash memory (e.g., a card, a stick, a key drive), a floppy (registered trademark) disk, a magnetic strip, etc. The above-mentioned storage medium may be, for example, a database, a server, or other appropriate medium including at least one of the storage device 1002 and the secondary storage device 1003.

[0159] The communication device 1004 is hardware (transmission / reception device) for communicating between computers via at least one of a wired network and a wireless network, and is also referred to as, for example, a network device, a network controller, a network card, a communication module, etc. The communication device 1004 may be configured to include a high-frequency switch, a duplexer, a filter, a frequency synthesizer, etc. to realize at least one of frequency division duplex (FDD) and time division duplex (TDD). For example, a transmission / reception antenna, an amplifier unit, a transmission / reception unit, a transmission path interface, etc. may be realized by the communication device 1004. The transmission / reception unit may be implemented as a transmission unit and a reception unit that are physically or logically separated.

[0160] The input device 1005 is an input device (e.g., a keyboard, a mouse, a microphone, a switch, a button, a sensor, etc.) that receives input from the outside. The output device 1006 is an output device (e.g., a display, a speaker, an LED lamp, etc.) that outputs to the outside. Note that the input device 1005 and the output device 1006 may be integrated into one device (e.g., a touch panel).

[0161] Furthermore, each device such as the processor 1001 and the storage device 1002 is connected by a bus 1007 for communicating information. The bus 1007 may be configured using a single bus, or may be configured using different buses between each device.

[0162] Furthermore, the base station 10 and the terminal 20 may be configured to include hardware such as a microprocessor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a programmable logic device (PLD), or a field programmable gate array (FPGA), and some or all of the functional blocks may be realized by the hardware. For example, the processor 1001 may be implemented using at least one of these pieces of hardware.

[0163] Fig. 15 shows an example configuration of a vehicle 2001. As shown in Fig. 15, the vehicle 2001 includes a drive unit 2002, a steering unit 2003, an accelerator pedal 2004, a brake pedal 2005, a shift lever 2006, front wheels 2007, rear wheels 2008, an axle 2009, an electronic control unit 2010, various sensors 2021 to 2029, an information service unit 2012, and a communication module 2013. Each aspect / embodiment described in the present disclosure may be applied to a communication device mounted on the vehicle 2001, and may be applied to the communication module 2013, for example.

[0164] The drive unit 2002 is configured, for example, by an engine, a motor, or a hybrid of an engine and a motor. The steering unit 2003 includes at least a steering wheel (also called a handle) and is configured to steer at least one of the front wheels and the rear wheels based on the operation of the steering wheel operated by the user.

[0165] The electronic control unit 2010 is composed of a microprocessor 2031, a memory (ROM, RAM) 2032, and a communication port (IO port) 2033. Signals are input to the electronic control unit 2010 from various sensors 2021 to 2029 provided in the vehicle 2001. The electronic control unit 2010 may also be called an ECU (Electronic Control Unit).

[0166] The signals from the various sensors 2021 to 2029 include a current signal from a current sensor 2021 that senses the current of the motor, a rotation speed signal of the front and rear wheels obtained by a rotation speed sensor 2022, an air pressure signal of the front and rear wheels obtained by an air pressure sensor 2023, a vehicle speed signal obtained by a vehicle speed sensor 2024, an acceleration signal obtained by an acceleration sensor 2025, an accelerator pedal depression amount signal obtained by an accelerator pedal sensor 2029, a brake pedal depression amount signal obtained by a brake pedal sensor 2026, a shift lever operation signal obtained by a shift lever sensor 2027, and a detection signal for detecting obstacles, vehicles, pedestrians, etc. obtained by an object detection sensor 2028.

[0167] The information service unit 2012 is composed of various devices, such as a car navigation system, an audio system, speakers, a television, and a radio, for providing (outputting) various types of information, such as driving information, traffic information, and entertainment information, and one or more ECUs for controlling these devices. The information service unit 2012 uses information acquired from external devices via the communication module 2013 or the like to provide various types of multimedia information and multimedia services to the occupants of the vehicle 2001. The information service unit 2012 may include input devices (e.g., a keyboard, a mouse, a microphone, a switch, a button, a sensor, a touch panel, etc.) that accept input from the outside, and may also include output devices (e.g., a display, a speaker, an LED lamp, a touch panel, etc.) that output information to the outside.

[0168] The driving assistance system unit 2030 is composed of various devices that provide functions for preventing accidents and reducing the driving burden on the driver, such as millimeter-wave radar, LiDAR (Light Detection and Ranging), cameras, positioning locators (e.g., GNSS, etc.), map information (e.g., high-definition (HD) maps, autonomous vehicle (AV) maps, etc.), gyro systems (e.g., IMU (Inertial Measurement Unit), INS (Inertial Navigation System), etc.), AI (Artificial Intelligence) chips, and AI processors, as well as one or more ECUs that control these devices. In addition, the driving assistance system unit 2030 transmits and receives various information via the communication module 2013 to realize the driving assistance function or the autonomous driving function.

[0169] The communication module 2013 can communicate with the microprocessor 2031 and components of the vehicle 2001 via the communication port. For example, the communication module 2013 transmits and receives data via the communication port 2033 to and from the drive unit 2002, steering unit 2003, accelerator pedal 2004, brake pedal 2005, shift lever 2006, front wheels 2007, rear wheels 2008, axle 2009, microprocessor 2031 and memory (ROM, RAM) 2032 in the electronic control unit 2010, and sensors 2021 to 29, which are provided in the vehicle 2001.

[0170] The communication module 2013 is a communication device that can be controlled by the microprocessor 2031 of the electronic control unit 2010 and can communicate with an external device. For example, it transmits and receives various information to and from the external device via wireless communication. The communication module 2013 may be located either inside or outside the electronic control unit 2010. The external device may be, for example, a base station, a mobile station, or the like.

[0171] The communication module 2013 may transmit at least one of signals from the above-mentioned various sensors 2021-2028 input to the electronic control unit 2010, information obtained based on the signals, and information based on input from the outside (user) obtained via the information service unit 2012 to an external device via wireless communication. The electronic control unit 2010, the various sensors 2021-2028, the information service unit 2012, etc. may be referred to as input units that accept input. For example, the PUSCH transmitted by the communication module 2013 may include information based on the above-mentioned input.

[0172] The communication module 2013 receives various information (traffic information, traffic signal information, vehicle-to-vehicle information, etc.) transmitted from external devices and displays it on an information service unit 2012 provided in the vehicle 2001. The information service unit 2012 may be called an output unit that outputs information (for example, outputs information to a device such as a display or speaker based on the PDSCH (or data / information decoded from the PDSCH) received by the communication module 2013). The communication module 2013 also stores the various information received from external devices in a memory 2032 that can be used by the microprocessor 2031. Based on the information stored in the memory 2032, the microprocessor 2031 may control the drive unit 2002, steering unit 2003, accelerator pedal 2004, brake pedal 2005, shift lever 2006, front wheels 2007, rear wheels 2008, axles 2009, sensors 2021 to 2029, etc. provided in the vehicle 2001.

[0173] <Additional Notes> (Additional Item 1) A base station comprising: a transmitter that transmits a message requesting the execution of a handover, the message including information indicating that the handover is caused by satellite mobility, to a destination base station; and a controller that starts a timer that detects the expiration of a time limit that is set in a handover caused by satellite mobility, from the transmission of the message to the reception of a response to the message. (Additional Item 2) A base station comprising: a receiver that receives, from a source base station, a first message requesting the execution of a handover, the first message including information indicating that the handover is caused by satellite mobility and a session identifier; and a controller that stores context information that includes first termination point information on the user plane function side when transmitting uplink user plane data, the first termination point information corresponding to the session identifier, from a network node, and the controller that updates the first termination point information included in the context information to the second termination point information. (Supplementary Item 3) A base station having: a receiving unit that receives, from a source base station, a message requesting execution of handover, including information indicating that the cause is satellite movement, and receives, from a terminal, a message notifying confirmation of the handover; and a transmitting unit that transmits, to a network node, termination point information on the own device side when downlink user plane data is received.(Supplementary clause 4) A mobile station comprising: a control unit that determines to set an ingress block that does not accept input packets and a buffer that holds output packets in a first path for forwarding uplink user plane data and downlink user plane data from a first network node having a user plane data function of a source network to a second network node having a user plane data function of a destination network; and a transmission unit that transmits a message for setting a forwarding path including a setting related to the ingress block and a setting related to the buffering in the first path, wherein the transmission unit transmits a message for setting context information possessed by the first network node in the second network node and for setting an ingress block in a second path for forwarding downlink user plane data from the second network node to a source base station, the transmission unit transmits a message for releasing the ingress block in the first path, the transmission unit transmits a message for releasing resources of the first network node, and the transmission unit transmits a message for changing, in the second network node, forwarding of downlink user plane data to the source base station to forwarding of downlink user plane data to a destination base station, The network node according to claim 4, wherein the transmitter transmits a message to unblock an entrance on the second route, the transmitter transmits a message to unblock buffering on the first route, and the controller recognizes that route switching from the first network node to the second network node has been completed. (Supplementary Item 5) The network node according to Supplementary Item 4, wherein the transmitter transmits a message to a third network node after the route switching has been completed, the message including information related to the route switching.(Supplementary Item 6) A network node comprising: a control unit that decides to execute satellite switching based on information regarding a time period when the satellite is connectable; a receiving unit that receives a first message including context information including information related to user plane data from a first network node having a user plane data function of a source satellite, the first network node being in a state where the connection with the base station is open; and a transmitting unit that transmits a message to a second network node of a destination satellite, requesting setting of the context information.

[0174] Any of Supplementary Items 1 to 6 can provide a communication technology that enables a communication device deployed on a satellite and a communication device deployed on the ground in a wireless communication system to communicate with each other while continuing data communication and voice communication, even when switching occurs due to the movement of the satellite.

[0175] (Supplementary Notes on the Embodiments) Although the embodiments of the present invention have been described above, the disclosed invention is not limited to such embodiments, and those skilled in the art will understand various modifications, alterations, alternatives, and substitutions. While specific numerical examples have been used to facilitate understanding of the invention, unless otherwise specified, these numerical values ​​are merely examples, and any appropriate values ​​may be used. The division of items in the above description is not essential to the present invention; matters described in two or more items may be used in combination as needed, and matters described in one item may apply to matters described in another item (as long as there is no contradiction). Boundaries between functional units or processing units in functional block diagrams do not necessarily correspond to boundaries between physical components. The operations of multiple functional units may be performed by a single physical component, or the operations of a single functional unit may be performed by multiple physical components. The order of processing steps described in the embodiments may be reversed as long as there is no contradiction. For convenience of processing description, the base station 10 and terminal 20 have been described using functional block diagrams, but such devices may be realized by hardware, software, or a combination thereof. The software operated by the processor of the base station 10 in accordance with an embodiment of the present invention and the software operated by the processor of the terminal 20 in accordance with an embodiment of the present invention may each be stored in random access memory (RAM), flash memory, read-only memory (ROM), EPROM, EEPROM, register, hard disk (HDD), removable disk, CD-ROM, database, server, or any other suitable storage medium.

[0176] Furthermore, the notification of information is not limited to the aspects / embodiments described in the present disclosure, and may be performed using other methods. For example, the notification of information may be performed by physical layer signaling (e.g., Downlink Control Information (DCI), Uplink Control Information (UCI)), higher layer signaling (e.g., Radio Resource Control (RRC) signaling, Medium Access Control (MAC) signaling), broadcast information (Master Information Block (MIB), System Information Block (SIB)), other signals, or a combination thereof. Furthermore, the RRC signaling may be referred to as an RRC message, and may be, for example, an RRC Connection Setup message, an RRC Connection Reconfiguration message, or the like.

[0177] Each aspect / embodiment described in the present disclosure may be implemented using any of the following standards: LTE (Long Term Evolution), LTE-Advanced (LTE-A), SUPER 3G, IMT-Advanced, 4G (4th generation mobile communication system), 5G (5th generation mobile communication system), 6th generation mobile communication system (6G), xth generation mobile communication system (xG) (xG (x is, for example, an integer or a decimal number)), FRA (Future Radio Access), NR (new Radio), New radio access (NX), Future generation radio access (FX), W-CDMA (registered trademark), GSM (registered trademark), CDMA2000, UMB (Ultra Mobile Broadband), IEEE 802.11 (Wi-Fi (registered trademark)), IEEE 802.16 (WiMAX (registered trademark)), IEEE 802.17 (WiMAX (registered trademark)), IEEE 802.19 (WiMAX (registered trademark)), IEEE 802.20 (WiMAX (registered trademark)), IEEE 802.21 (Wi-Fi (registered trademark)), IEEE 802.22 (WiMAX (registered trademark)), IEEE 802.23 (WiMAX (registered trademark)), IEEE 802.24 (WiMAX (registered trademark)), IEEE 802.25 (WiMAX (registered trademark)), IEEE 802.26 (WiMAX (registered trademark)), IEEE 802.27 (WiMAX (registered trademark)), IEEE 802.28 (WiMAX (registered trademark)), IEEE 802.29 (WiMAX (registered trademark)), IEEE 802.30 (WiMAX (registered trademark)), IEEE 802.31 (Wi-Fi (registered trademark)), IEEE 802.32 (WiMAX (registered trademark)), IEEE 802.33 (WiMAX (registered trademark)), IEEE 802.34 ( The present invention may be applied to at least one of systems using 802.20, UWB (Ultra-Wide Band), Bluetooth (registered trademark), or other suitable systems, and next-generation systems that are extended, modified, created, or defined based on these systems. The present invention may also be applied to a combination of multiple systems (e.g., a combination of LTE and / or LTE-A with 5G).

[0178] The order of the procedures, sequences, flowcharts, etc. of each aspect / embodiment described herein may be rearranged unless it is consistent. For example, the methods described in this disclosure present elements of various steps using an example order and are not limited to the particular order presented.

[0179] In this specification, a specific operation described as being performed by the base station 10 may be performed by its upper node in some cases. In a network consisting of one or more network nodes having the base station 10, it is clear that various operations performed for communication with the terminal 20 may be performed by at least one of the base station 10 and another network node other than the base station 10 (such as, but not limited to, an MME or an S-GW). Although the above example illustrates a case where there is one other network node other than the base station 10, the other network node may be a combination of multiple other network nodes (such as an MME and an S-GW).

[0180] The information, signals, etc. described in the present disclosure may be output from a higher layer (or a lower layer) to a lower layer (or a higher layer), or may be input / output via multiple network nodes.

[0181] Input and output information may be stored in a specific location (for example, memory) or may be managed using a management table. Input and output information may be overwritten, updated, or added to. Output information may be deleted. Input information may be sent to another device.

[0182] In the present disclosure, the determination may be made based on a value represented by one bit (0 or 1), a Boolean value (true or false), or a numerical comparison (e.g., comparison with a predetermined value).

[0183] Software shall be construed broadly to mean instructions, instruction sets, code, code segments, program code, programs, subprograms, software modules, applications, software applications, software packages, routines, subroutines, objects, executable files, threads of execution, procedures, functions, etc., whether referred to as software, firmware, middleware, microcode, hardware description language, or otherwise.

[0184] Software, instructions, information, etc. may also be transmitted or received over a transmission medium. For example, if software is transmitted from a website, server, or other remote source using wired technologies (such as coaxial cable, fiber optic cable, twisted pair, Digital Subscriber Line (DSL)), and / or wireless technologies (such as infrared, microwave), then these wired and / or wireless technologies are included within the definition of transmission media.

[0185] The information, signals, etc. described in this disclosure may be represented using any of a variety of different technologies. For example, data, instructions, commands, information, signals, bits, symbols, chips, etc. that may be referred to throughout the above description may be represented by voltages, currents, electromagnetic waves, magnetic fields or magnetic particles, optical fields or photons, or any combination thereof.

[0186] Note that terms described in this disclosure and terms necessary for understanding this disclosure may be replaced with terms having the same or similar meanings. For example, at least one of a channel and a symbol may be a signal (signaling). Furthermore, a signal may be a message. Furthermore, a component carrier (CC) may be called a carrier frequency, a cell, a frequency carrier, etc.

[0187] As used in this disclosure, the terms "system" and "network" are used interchangeably.

[0188] Furthermore, the information, parameters, etc. described in the present disclosure may be expressed using absolute values, may be expressed using relative values ​​from a predetermined value, or may be expressed using other corresponding information. For example, a radio resource may be indicated by an index.

[0189] The names used for the above-described parameters are not intended to be limiting in any way. Furthermore, the mathematical expressions using these parameters may differ from those explicitly disclosed in this disclosure. The various channels (e.g., PUCCH, PDCCH, etc.) and information elements may be identified by any suitable names, and therefore the various names assigned to these various channels and information elements are not intended to be limiting in any way.

[0190] In the present disclosure, terms such as "base station (BS)," "radio base station," "base station device," "fixed station," "NodeB," "eNodeB (eNB)," "gNodeB (gNB)," "access point," "transmission point," "reception point," "transmission / reception point," "cell," "sector," "cell group," "carrier," and "component carrier" may be used interchangeably. A base station may also be referred to by terms such as a macrocell, a small cell, a femtocell, and a picocell.

[0191] A base station can accommodate one or more (e.g., three) cells. When a base station accommodates multiple cells, the overall coverage area of ​​the base station can be partitioned into multiple smaller areas, and each smaller area can also be provided with communication services by a base station subsystem (e.g., a small indoor base station (RRH: Remote Radio Head)). The terms "cell" or "sector" refer to part or all of the coverage area of ​​a base station and / or base station subsystem that provides communication services within that coverage.

[0192] In the present disclosure, the base station transmitting information to a terminal may be interpreted as the base station instructing the terminal to control or operate based on the information.

[0193] In this disclosure, the terms "Mobile Station (MS)," "user terminal," "User Equipment (UE)," "terminal," and the like may be used interchangeably.

[0194] A mobile station may also be referred to by those skilled in the art as a subscriber station, mobile unit, subscriber unit, wireless unit, remote unit, mobile device, wireless device, wireless communication device, remote device, mobile subscriber station, access terminal, mobile terminal, wireless terminal, remote terminal, handset, user agent, mobile client, client, or some other suitable terminology.

[0195] At least one of the base station and the mobile station may be referred to as a transmitting device, a receiving device, a communication device, etc. At least one of the base station and the mobile station may be a device mounted on a mobile object, the mobile object itself, etc. The mobile object refers to a movable object, and may move at any speed. Naturally, this also includes cases where the mobile object is stationary. Examples of the mobile object include, but are not limited to, vehicles, transport vehicles, automobiles, motorcycles, bicycles, connected cars, excavators, bulldozers, wheel loaders, dump trucks, forklifts, trains, buses, handcars, rickshaws, ships and other watercraft, airplanes, rockets, satellites, drones (registered trademark), multicopters, quadcopters, balloons, and objects mounted thereon. The mobile object may also be a mobile object that moves autonomously based on an operational command. It may be a vehicle (e.g., a car, an airplane, etc.), an unmanned mobile object (e.g., a drone, an autonomous vehicle, etc.), or a robot (manned or unmanned). At least one of the base station and the mobile station may be a device that does not necessarily move during communication operations. For example, at least one of the base station and the mobile station may be an IoT (Internet of Things) device such as a sensor.

[0196] Furthermore, a base station in the present disclosure may be read as a user terminal. For example, the aspects / embodiments of the present disclosure may be applied to a configuration in which communication between a base station and a user terminal is replaced with communication between multiple terminals 20 (which may be called, for example, Device-to-Device (D2D) or Vehicle-to-Everything (V2X)). In this case, the terminal 20 may be configured to have the functions of the base station 10 described above. Furthermore, terms such as "uplink" and "downlink" may be read as terms corresponding to terminal-to-terminal communication (for example, "side"). For example, terms such as an uplink channel and a downlink channel may be read as a side channel.

[0197] Similarly, the user terminal in the present disclosure may be read as a base station, in which case the base station may be configured to have the functions of the user terminal described above.

[0198] As used in this disclosure, the terms "determining" and "determining" may encompass a wide variety of actions. "Determining" and "determining" may include, for example, judging, calculating, computing, processing, deriving, investigating, looking up, searching, inquiring (e.g., searching in a table, database, or other data structure), ascertaining, and the like. "Determining" and "determining" may also include receiving (e.g., receiving information), transmitting (e.g., sending information), input, output, accessing (e.g., accessing data in memory), and the like. Furthermore, "judgment" and "decision" can include regarding resolving, selecting, choosing, establishing, comparing, etc. as having been "judged" or "decided." In other words, "judgment" and "decision" can include regarding some action as having been "judged" or "decided." Furthermore, "judgment (decision)" can be interpreted as "assuming," "expecting," "considering," etc.

[0199] The terms "connected," "coupled," or any variation thereof, refer to any direct or indirect connection or coupling between two or more elements, and may include the presence of one or more intermediate elements between two elements that are "connected" or "coupled" to each other. The coupling or connection between elements may be physical, logical, or a combination thereof. For example, "connected" may be read as "access." As used in this disclosure, two elements may be considered to be "connected" or "coupled" to each other using one or more wires, cables, and / or printed electrical connections, as well as electromagnetic energy having wavelengths in the radio frequency range, microwave range, and optical (both visible and invisible) range, as some non-limiting and non-exhaustive examples.

[0200] The reference signal may be abbreviated as RS (Reference Signal) or may be called a pilot depending on the applicable standard.

[0201] As used in this disclosure, the phrase "based on" does not mean "based only on," unless expressly stated otherwise. In other words, the phrase "based on" means both "based only on" and "based at least on."

[0202] As used in this disclosure, any reference to an element using a designation such as "first," "second," etc. does not generally limit the quantity or order of those elements. These designations may be used in this disclosure as a convenient method of distinguishing between two or more elements. Thus, a reference to a first and a second element does not imply that only two elements may be employed or that the first element must in some way precede the second element.

[0203] The "means" in the configuration of each of the above devices may be replaced with "part," "circuit," "device," etc.

[0204] When the terms "include," "including," and variations thereof are used in this disclosure, these terms are intended to be inclusive, similar to the term "comprising." Furthermore, when the term "or" is used in this disclosure, it is not intended to be an exclusive or.

[0205] In this disclosure, where articles are added by translation, such as a, an, and the in English, the disclosure may include that the nouns following these articles are in the plural form.

[0206] In the present disclosure, the term "A and B are different" may mean "A and B are different from each other." The term may also mean "A and B are each different from C." Terms such as "separate" and "coupled" may also be interpreted in the same way as "different."

[0207] The aspects / embodiments described in this disclosure may be used alone, in combination, or switched depending on the implementation. Notification of predetermined information (e.g., notification that "X is true") is not limited to explicit notification, but may be implicit (e.g., not notifying the predetermined information).

[0208] Although the present disclosure has been described in detail above, it is clear to those skilled in the art that the present disclosure is not limited to the embodiments described herein. The present disclosure can be implemented in modified and altered forms without departing from the spirit and scope of the present disclosure as defined by the claims. Therefore, the description of the present disclosure is intended to be illustrative and does not have any limiting meaning on the present disclosure.

[0209] 10 Base station 110 Transmitter 120 Receiver 130 Setting unit 140 Control unit 20 Terminal 210 Transmitter 220 Receiver 230 Setting unit 240 Control unit 30 Network node 1001 Processor 1002 Storage device 1003 Auxiliary storage device 1004 Communication device 1005 Input device 1006 Output device 2001 Vehicle 2002 Drive unit 2003 Steering unit 2004 Accelerator pedal 2005 Brake pedal 2006 Shift lever 2007 Front wheels 2008 Rear wheels 2009 Axle 2010 Electronic control unit 2012 Information service unit 2013 Communication module 2021 Current sensor 2022 RPM sensor 2023 Tire pressure sensor 2024 Vehicle speed sensor 2025 Acceleration sensor 2026 Brake pedal sensor 2027 Shift lever sensor 2028 Object detection sensor 2029 Accelerator pedal sensor 2030 Driving assistance system unit 2031 Microprocessor 2032 Memory (ROM, RAM) 2033 Communication port (IO port)

Claims

1. A base station having: a transmitter that transmits a message requesting execution of handover to a destination base station, the message including information indicating that the handover is caused by satellite movement; and a controller that starts a timer that detects the expiration of a time limit set in a handover caused by satellite movement, from the transmission of the message to the reception of a response to the message.

2. A base station comprising: a receiver that receives, from a source base station, a first message requesting execution of handover, the first message including information indicating that the handover is caused by satellite movement and a session identifier; and a controller that stores context information including first termination point information on the user plane function side when transmitting uplink user plane data, wherein the receiver receives, from a network node, a second message including second termination point information on the user plane function side when transmitting uplink user plane data, the second termination point information corresponding to the session identifier; and the controller updates the first termination point information included in the context information to the second termination point information.

3. A base station having: a receiving unit that receives a message from a source base station requesting the execution of a handover, including information indicating that the handover is caused by satellite movement, and receives a message from the terminal notifying confirmation of the handover; and a transmitting unit that transmits termination point information on the device's side when receiving downlink user plane data to a network node.

4. A mobile station comprising: a control unit that determines to set an ingress block that does not accept input packets and a buffer that holds output packets on a first route for forwarding uplink user plane data and downlink user plane data from a first network node having a user plane data function of a source network to a second network node having a user plane data function of a destination network; and a transmission unit that transmits a message for setting a forwarding route, the ingress block setting and the buffering setting on the first route, wherein the transmission unit transmits a message for setting context information possessed by the first network node on the second network node and for setting an ingress block on a second route for forwarding downlink user plane data from the second network node to a source base station, the transmission unit transmits a message for releasing the ingress block on the first route, the transmission unit transmits a message for releasing resources of the first network node, and the transmission unit transmits a message for changing, in the second network node, forwarding of downlink user plane data to the source base station to forwarding downlink user plane data to a destination base station, A network node, wherein the transmitter transmits a message to release an entrance block on the second route, the transmitter transmits a message to release buffering on the first route, and the controller recognizes that route switching from the first network node to the second network node has been completed.

5. The network node according to claim 4, wherein the transmitter transmits a message including information related to the route switching to a third network node after the route switching is completed.

6. A network node comprising: a control unit that decides to execute satellite switching based on information regarding a time period when the satellite is connectable; a receiving unit that receives a first message including context information including information related to user plane data from a first network node having a user plane data function of a source satellite, the first network node being in a state where the connection with the base station is open; and a transmitting unit that transmits a message to a second network node of a destination satellite requesting the setting of the context information.

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