System, method, and information processing device

Abstract

The present invention suppresses deterioration in wireless communication quality resulting from movement of a user terminal. This system comprises a plurality of network functions (NF). Each of the NFs executes the following: when user equipment (UE) moves from or moves to a first cell which is a cell in charge among one or more cells in which the UE is predicted to be present according to movement of the UE and which are included in first information that includes information regarding the one or more cells, acquires second information to be used for provision of wireless communication to the UE in advance of the movement of the UE from or to the first cell, on the basis of the first information; and, when the UE moves from or moves to the first cell, executes a first process pertaining to the provision of the wireless communication to the UE by using the second information without executing a process pertaining to the acquisition of the second information.

Description

System, method, and information processing device

[0001] The present disclosure relates to communication network systems.

[0002] It is disclosed that the predicted communication quality for a predicted movement route of a mobile terminal is obtained based on a predicted communication quality distribution in a communication area, and the timing for starting communication of the mobile terminal is determined based on the predicted communication quality (for example, Patent Document 1).

[0003] Japanese Patent Application Laid-Open No. 2021-197622

[0004] An object of the present disclosure is to provide a system, a method, and an information processing device that can suppress deterioration of wireless communication quality due to movement of a user terminal.

[0005] One aspect of the present disclosure is a system including a plurality of NFs (Network Functions) that perform the following: acquire, before the UE moves from or to the first cell, second information used to provide wireless communication to a UE (User Equipment) when the UE moves from or to a first cell that is a serving cell of the one or more cells, based on first information including information about one or more cells that the UE is predicted to be within as the UE moves; and, when the UE moves from or to the first cell, perform a first process related to providing wireless communication to the UE using the second information without performing a process related to acquiring the second information.

[0006] Another aspect of the present disclosure is a method including: an NF acquiring, based on first information including information regarding one or more cells in which the UE is predicted to be present as the UE moves, second information to be used in providing wireless communication to the UE when the UE moves from or to a first cell that is a serving cell among the one or more cells, before the UE moves from or to the first cell; and, when the UE moves from or to the first cell, performing a first process related to providing wireless communication to the UE using the second information without performing a process related to acquiring the second information.

[0007] One aspect of the present disclosure is an information processing device comprising a control unit that performs the following: acquires, based on first information including information regarding one or more cells that are predicted to be present in response to the movement of the UE, second information to be used in providing wireless communication to the UE when the UE moves from or to a first cell that is a serving cell among the one or more cells, before the UE moves from or to the first cell; and when the UE moves from or to the first cell, performs a first process related to providing wireless communication to the UE using the second information without performing a process related to acquiring the second information.

[0008] According to the present disclosure, it is possible to suppress deterioration of wireless communication quality due to movement of a user terminal.

[0009] FIG. 1 is a diagram illustrating an example of the architecture of a fifth-generation mobile communication system. FIG. 2 is a diagram illustrating processing in a communication system according to the first embodiment. FIG. 3 is a diagram illustrating handover scenario #1. FIG. 4 is a diagram illustrating handover scenario #2. FIG. 5 is a diagram illustrating handover scenario #3. FIG. 6 is a diagram illustrating handover scenario #4. FIG. 7 is a diagram illustrating an example of the hardware configuration of an information processing device capable of operating as each NF and AF in 5GC. FIG. 8 is a diagram illustrating an example of the functional configuration of an AF. FIG. 9 is a diagram illustrating an example of the functional configuration of an NEF. FIG. 10 is a diagram illustrating an example of the functional configuration of an AMF. FIG. 11 is a diagram illustrating an example of the functional configuration of an SMF. FIG. 12 is an example of a flowchart of processing related to a pre-configuration request of an AF. FIG. 13 is an example of a flowchart of processing related to pre-configuration of an NEF. FIG. 14 is an example of a flowchart of processing when a handover pre-configuration request is received by an AMF. FIG. 15 is an example of a flowchart of intra-region handover pre-configuration processing by an AMF. FIG. 16 is an example of a flowchart of an out-of-region handover pre-configuration process by an AMF. FIG. 17 is an example of a flowchart of a PDU session pre-configuration process by an AMF when a PDU session pre-configuration request is received. FIG. 18 is an example of a flowchart of a process by an SMF when a pre-configuration request is received. FIG. 19 is an example of a flowchart of a handover process or a PDU session establishment process by an NF. FIG. 20 is an example of a processing sequence from when route information is transmitted from a UE to when a pre-configuration request is transmitted to a current AMF. FIG. 21 is a diagram showing an example of a handover pre-configuration sequence in scenario #1. FIG. 22 is a diagram showing a PDU session pre-configuration sequence in scenario #1. FIG. 23 is a diagram showing an example of a handover sequence in scenario #1. FIG. 24 is a diagram showing an example of a PDU session establishment sequence for an application to be pre-configured in scenario #1. FIG. 25 is a diagram showing an example of a handover pre-configuration sequence in scenario #2. FIG. 26 is a diagram showing an example of a handover sequence in scenario #2.FIG. 27 is a diagram showing an example of a handover pre-configuration sequence in scenario #3. FIG. 28 is a diagram showing an example of a handover sequence in scenario #3. FIG. 29 is a diagram showing an example of a handover pre-configuration sequence in scenario #4. FIG. 30 is a diagram showing an example of a handover sequence in scenario #4. FIG. 31 is a diagram explaining processing in a communication system according to the second embodiment. FIG. 32 is an example of a flowchart of processing by an AF according to the second embodiment. FIG. 33 is an example of a flowchart of processing related to pre-configuration of an NEF according to the second embodiment. FIG. 34 is an example of a processing sequence from when a pre-configuration request is transmitted from an AF to when a pre-configuration request is transmitted to a current AMF according to the second embodiment. FIG. 35 is an example of a flowchart of processing related to pre-configuration of an NEF according to a modification of the second embodiment. FIG. 36 is an example of a processing sequence from when a pre-configuration request is transmitted from an AF to when a pre-configuration request is transmitted to a current AMF according to a modification of the second embodiment.

[0010] For example, when a mobile terminal such as an onboard device mounted on a vehicle moves to another cell, it takes time to configure the wireless communication settings of the network-side device for the destination cell, and communication quality may deteriorate when the destination cell is changed.

[0011] In one aspect of the present disclosure, a system is configured to preconfigure wireless communication for a user equipment (UE) in advance of the UE's movement based on information about one or more cells that the UE is expected to be in. When the UE moves to another cell, the system is configured to provide wireless communication services to the UE in the destination cell. This reduces the time required for processing related to system configuration associated with the UE's movement between cells, and allows wireless communication to continue without degradation in wireless communication quality due to the UE's movement between cells.

[0012] More specifically, one aspect of the present disclosure is a system including a plurality of NFs. The NFs acquire, based on first information including information about one or more cells where the UE is predicted to be present as the UE moves, second information to be used in providing wireless communication to the UE when the UE moves from or to a first cell that is a serving cell among the one or more cells, before the UE moves from or to the first cell. When the UE moves from or to the first cell, the NFs perform a first process related to providing wireless communication to the UE using the second information without performing a process related to acquiring the second information.

[0013] The system is, for example, a core network system of a mobile communication system of a generation after 5G (5th Generation). The NF is, for example, an instance that performs a predetermined function within the core network of the mobile communication system. The NF instance is realized, for example, by executing virtualized computing such as a container on an information processing device. The information processing device that implements the NF instance is, for example, a computer including a control unit. The control unit is, for example, a processor such as a CPU (Central Processing Unit) and a GPU (Graphics Processing Unit). When the system is a 5G core network system, the NF is, for example, an Access and Mobility Management Function (AMF) and a Session Management Function (SMF), etc. However, the NF is not limited to these.

[0014] The UE is, for example, a mobile terminal equipped with a wireless communication function, such as an in-vehicle device mounted in a vehicle, a smartphone, or a tablet terminal. The UE may also include a vehicle equipped with a wireless communication function. In addition to vehicles, the UE may also include moving objects such as ships, aircraft, and trains, and devices mounted on these moving objects.

[0015] The predetermined processing executed by the second NF to provide wireless communication services to the UE when the UE is located in each of the one or more cells in the future includes, for example, selecting an NF to be changed or added due to handover of the UE, storing configuration information related to wireless communication for the UE and transmitting it to another NF, etc. The configuration information related to wireless communication for the UE includes, for example, QoS configuration, radio resource allocation, network slice configuration, etc.

[0016] According to one aspect of the present disclosure, one or more second NFs currently providing wireless communication services to a UE are configured to provide wireless communication services to the UE when the UE is present in one or more cells included in the first information, in advance of the UE's movement. For example, when the UE moves into the coverage area of ​​another cell, one or more second NFs providing wireless communication services in the destination cell have already been configured for wireless communication with the UE. This makes it possible to suppress deterioration of wireless communication quality due to movement between cells.

[0017] In one aspect of the present disclosure, the plurality of NFs may store second information in a storage unit so as to indicate that the information is preconfigured. Storing the second information in the storage unit so as to indicate that the information is preconfigured may, for example, involve storing the second information together with information indicating that the information is preconfigured, or storing the configuration information in a storage area reserved for preconfiguration. The information indicating that the information is preconfigured may, for example, be identification information, a flag, a keyword, or a code of the preconfiguration. This may prevent the second information from conflicting with other configuration information, such as a context, held by the NF.

[0018] Furthermore, when multiple NFs transmit a request to another NF using the second information while the first process is being executed, the NFs may transmit the second information together with information indicating that the second information has been pre-configured, thereby notifying the other NFs that have received the request that the other NFs may hold information obtained regarding the request as the second information.

[0019] Furthermore, when a plurality of NFs receives a request accompanied by information indicating that the setting is pre-set from another NF while the first processing is being executed, the NFs may search the storage unit for the second information. In this way, when a request accompanied by information indicating that the setting is pre-set is received from another NF, the NFs can search the storage unit to detect the second information before executing a processing related to the request, which is a processing related to obtaining the second information, thereby preventing the processing from being executed.

[0020] Furthermore, the plurality of NFs may acquire the second information by executing a second process that is a part of the first process, which eliminates the need to execute the second process again when executing the first process, thereby reducing the time required to execute the first process.

[0021] In one aspect of the present disclosure, the system may further include a first NF. The first NF may acquire first information and transmit, to a second NF of the plurality of NFs, a first request requesting pre-configuration of wireless communication for the UE and the first information. The first NF may acquire the first information from route information held by the UE, or may acquire the first information from a Network Data Analytics Function (NWDAF). The plurality of NFs may acquire the second information in response to the second NF receiving the first request. For example, if the first NF transmits the first request upon detecting that the UE has started moving, the system can perform pre-configuration of wireless communication for the UE in real time in response to the UE's movement.

[0022] In one aspect of the present disclosure, the second NF may be an Access and Mobility Management Function (AMF) in charge of managing the mobility of the UE. In this case, the second NF may receive the first request and transmit a second request to a third NF that has at least one of the one or more cells included in the first information as its serving cell, requesting pre-configuration of wireless communication for the UE. Upon receiving the second request, the third NF may perform pre-configuration of wireless communication for the UE. This allows the third NF to perform pre-configuration of wireless communication for the UE, starting from the second NF.

[0023] Furthermore, when the first information includes a cell other than the cell served by the second NF, the second NF may, as a third NF, send a second request to an AMF serving a cell other than the cell served by the second NF included in the first information. As a result, even if the UE may move between AMF regions, pre-configuration of radio communication for the UE is also performed in an AMF including the destination cell in its region. Therefore, when the UE moves from a cell served by the AMF serving as the second NF to a cell served by the AMF serving as the third NF in the future, it is possible to shorten the time required for radio communication configuration for the UE in the system.

[0024] Furthermore, when the first information includes a cell other than the serving cell of the second NF, the second NF may acquire information about the third NF as part of the second information by selecting an AMF as the third NF from multiple NFs in the system based on the first information. When the UE moves from the serving cell of the second NF as the first cell to the serving cell of the third NF in the first information, the second NF may perform the handover process as the first process using the acquired information about the third NF without selecting an AMF. This can shorten the time required for handover from the serving cell of the second NF as the first cell to the serving cell of the third NF.

[0025] Furthermore, when one or more AMFs included in multiple NFs in the system receive the first request or the second request and the serving cells of one or more of their own AMFs included in the first information include a second cell other than the serving cell of a first SMF (Session Management Function) managing the first session established with the UE, the AMFs may transmit a third request to the first SMF and a second SMF that may manage the first session in the second cell, requesting pre-configuration of wireless communication for the UE. When the first SMF and the second SMF receive the third request, the first SMF and the second SMF may perform pre-configuration for handover of the first session. This allows the UE to continue communication using the first session with minimal degradation in communication quality when the UE moves to the serving cell of the first SMF and the serving cell of the second SMF in the future. The first session is, for example, a Packet Data Unit (PDU) session.

[0026] Furthermore, the one or more AMFs may select a second SMF from a plurality of NFs in the system based on the first information, and acquire information about the selected second SMF as one piece of second information. When the UE moves to the second cell, the one or more AMFs may perform the handover process as the first process using the information about the second SMF without selecting an SMF. This can shorten the time required for handover from a cell serving the first SMF to a cell serving the second SMF due to the movement of the UE.

[0027] Furthermore, when the first SMF receives the third request and the serving cells of one or more first SMFs included in the first information include a third cell other than the serving cell of the first UPF in which the first session is established, the first SMF may select a second UPF that may establish the first session in the third cell based on the first information, and acquire information about the selected second UPF as part of the second information. When the UE moves to the third cell, the first SMF may perform the handover process as the first process using information about the second UPF without selecting a UPF. This can shorten the time required for handover from the serving cell of the first UPF to the serving cell of the second UPF due to the movement of the UE.

[0028] Furthermore, when the second SMF receives the third request, it may select a third UPF that may establish the first session in the second cell based on the first information, and acquire information about the selected third UPF as part of the second information. When the UE moves to the second cell, the second SMF may perform the handover process as the first process using the information about the third UPF without selecting a UPF. This makes it possible to reduce the time required for handover from a cell served by the first SMF to a cell served by the second SMF due to the movement of the UE.

[0029] In one aspect of the present disclosure, when the second NF receives the first request, the second NF may, as a third NF, set at least one fourth cell among the one or more cells included in the first information as a serving cell, and may transmit a fourth request to a third SMF that may manage a second session when the UE requests establishment of the second session in the fourth cell, requesting pre-configuration of wireless communication for the UE. The second session is a PDU session that may be established in the future. When the third SMF receives the fourth request, the third SMF performs pre-configuration for the establishment of the second session for the UE. Therefore, when the UE requests establishment of the second session in the future while moving through one or more cells included in the first information, it is possible to reduce the time required for configuration for the establishment of the second session for the UE in the system.

[0030] Furthermore, the second NF may acquire information about the third SMF as part of the second information by selecting a third SMF from among multiple NFs in the system based on the first information. When a UE requests establishment of a second session in a fourth cell, the second NF may perform the first process for establishing the second session using the information about the third SMF without selecting an SMF. This can reduce the time required to establish the second session when a UE requests establishment of the second session in the fourth cell.

[0031] Furthermore, when the third SMF receives the fourth request, it may select a UPF that may establish the second session in the fourth cell based on the first information, and acquire information about the selected UPF as part of the second information. When the UE requests the establishment of the second session in the fourth cell, the third SMF may perform the process related to the establishment of the second session as the first process using the acquired information about the UPF without selecting a UPF. This makes it possible to shorten the time required to establish the second session when the UE requests the establishment of the second session in the fourth cell.

[0032] As another aspect, the present disclosure can be specified as a method in which multiple NFs execute the above process in the system. The method includes: an NF acquiring, before the UE moves from or to a first cell that is a serving cell among the one or more cells, second information used to provide wireless communication to the UE when the UE moves from or to a first cell, based on first information including information about one or more cells where the UE is predicted to be present as the UE moves; storing the second information in a storage unit; and, when the UE moves from or to the first cell, executing a first process related to providing wireless communication to the UE using the second information stored in the storage unit without executing a process related to acquiring the second information. Furthermore, as another aspect, the present disclosure can be specified as an information processing device corresponding to the NF, a program for causing a computer to execute the process of the information processing device, and a non-transitory computer-readable recording medium having the program recorded thereon.

[0033] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. The configurations of the following embodiments are examples, and the present disclosure is not limited to the configurations of the embodiments.

[0034] <First embodiment> Fig. 1 is a diagram showing an example of the architecture of a fifth-generation mobile communication system. The fifth-generation mobile communication network is hereinafter referred to as a 5G network. The 5G network has a 5G core network (5GC) and an access network ((R)AN). A UE (User Equipment) 50, a DN (Data Network), and an AF (Application Function) 1 are connected to the 5G network. The UE 50 is a terminal of a user (subscriber). The RAN (Radio Access Network) is an access network to the 5GC. The RAN includes a base station (gNB) as one of the nodes. Hereinafter, when simply referred to as RAN, it refers to a node within the RAN.

[0035] FIG. 1 shows some of the components included in 5GC. Also, in FIG. 1, the components according to the first embodiment are labeled with reference numerals. In 5G, the software that realizes network functions and the hardware on which the software runs are separated using hardware abstraction technology. This allows various network function software to run on common hardware resources, regardless of the configuration of each hardware product. FIG. 1 shows the network functions (NFs) included in 5GC. Each of the multiple NFs included in 5GC is realized by one or more computers (information processing devices) executing a program. However, a single computer may realize any two or more NFs.

[0036] The UPF (User Plane Function) performs routing, forwarding, packet inspection, and QoS processing of user packets. User packets are user plane packets that are transmitted and received by the UE 50.

[0037] The AMF (Access and Mobility Management Function) 7 accommodates the RAN and performs registration management, connection management, and mobility management of UEs in 5GC. The AMF 7 also relays messages between the SMF 6 and the UE 50.

[0038] The SMF (Session Management Function) 6 manages PDU (Protocol Data Unit) sessions, allocates and manages IP addresses to UEs, and selects and controls UPFs. PDU session management includes the establishment, modification, and release of PDU sessions. For example, when a policy is changed, a PDU session change occurs, and the QoS or policy change is applied to the UPF through the SMF 6. The PDU session is a virtual communication path for exchanging data between the UE 50 and the DN. The DN is a data network (cloud, Internet, etc.) external to 5GC.

[0039] The PCF (Policy Control Function) 5 manages, for example, access and mobility management policies, session management policies, and charging policies, and provides information about the policies to the AMF and SMF. The access and mobility policies include, for example, routing. The session management policies include QoS, filtering, and so on. For example, when information about a policy is registered, changed, or deleted in the UDR 4, the PCF 5 is notified, and the PCF 5 notifies the AMF 7 or the SMF 6.

[0040] The UDM (Unified Data Management) 2 manages subscriber information, authentication information, and the like related to subscribers who subscribe to the operator. The subscriber information includes, for example, access and mobility subscription data used for registering UE 50 and managing mobility, slice selection subscription data used for selecting a network slice, SMF selection subscription data used for selecting an SMF 6, session management subscription data used for establishing a PDU session, and energy related subscription data used for processing related to communication of UE 50. A network slice is a virtual network having specifications according to its application.

[0041] The UDR 4 stores and provides retrieval of data used by the UDM 2, PCF 5, and NEF 3. More specifically, the data held by the UDR 4 includes, for example, subscriber information, authentication information, and policy data.

[0042] The NEF 3 provides a function for securely disclosing capabilities and event information disclosed by network functions in the 5G system to external applications such as the AF 1. The NEF 3 also provides a function for receiving information from authorized external applications into the network. The AF 1 is an application server (external server) that provides auxiliary services other than those specified in the 5GC. In the first embodiment, the NEF 3 manages preconfiguration (PreConfiguration) related to wireless communication for the UE 50 in 5GC in advance of the movement of the UE 50. Details of the preconfiguration related to wireless communication for the UE 50 will be described later.

[0043] The NWDAF 8 provides, for example, analytical and statistical information within the network, and analytical and predictive information regarding the movement of the UE 50. The predictive information regarding the movement provided by the NWDAF 8 includes, for example, information regarding cells to which the UE may move.

[0044] The Edge Application Server Discovery Function (EASDF) mediates communication between the UE 50 and the DNS server. The EASDF discovers the EAS using the DNS server.

[0045] The NRF stores and manages information on NFs (e.g., AMF, SMF, UPF, etc.) within 5GC. In response to an inquiry about an NF to be used, the NRF can return multiple NF candidates to the inquiry source. The AUSF provides the function of UE authentication. The UDM holds subscriber contract information and authentication information for AKA authentication.

[0046] In 5GC, multiple NFs of the same type may be prepared. For example, one NF may be prepared for each data center (station). Also, one NF may be shared between data centers. Also, one data center may configure multiple NFs of the same type. The correspondence between NFs and data centers can be set as appropriate.

[0047] FIG. 2 is a diagram illustrating processing in the communication system 100 according to the first embodiment. The communication system 100 is, for example, a system in which a vehicle manufacturer provides communication and communication services to vehicles equipped with communication functions. The communication system 100 includes a 5GC 10, multiple RANs 20, and a UE 50. FIG. 2 illustrates some of the NFs included in the 5GC 10. The communication system 100 includes multiple UEs 50, but FIG. 2 illustrates one UE 50 as a representative.

[0048] In the communication system 100 according to the first embodiment, the UE 50 is a vehicle or an on-board device mounted on a vehicle. The on-board device is, for example, a data communication device (Data Communication Module) and a device having a wireless communication function such as a car navigation system. In the following description, it is assumed that the UE 50 is a data communication device mounted on a vehicle. In the first embodiment, it is assumed that the UE 50 has been registered with the 5GC 10 and has established at least one PDU session.

[0049] In the first embodiment, the communication system 100 provides a preconfiguration service. The preconfiguration service is a service that, in advance of the movement of the UE 50, performs preconfiguration of wireless communication for the UE 50 in one or more cells through which the planned movement route of the UE 50 passes in the 5CG 10. In the first embodiment, the preconfiguration service performs preconfiguration of handover in the 5CG 10 and preconfiguration of PDU session establishment that may occur in the future, assuming movement of the UE 50 along the planned movement route. This allows handover to be performed more smoothly when the UE 50 moves along the planned movement route. Furthermore, while the UE 50 is moving along the planned movement route, for example, if establishment of a PDU session is initiated for communication of a specific application, the PDU session can be established more smoothly and QoS settings can be applied, thereby providing a communication service with a quality suitable for the application.

[0050] In the first embodiment, AF 1 is an AF that provides a service of performing pre-configuration related to wireless communication for UE 50. AF 1 transmits a pre-configuration request to 5CG 10. The pre-configuration request transmitted by AF 1 is a request for requesting pre-configuration related to wireless communication for UE 50. In the first embodiment, identification information and route information of UE 50 are also transmitted together with the pre-configuration request. The route information of UE 50 is, for example, a route set in a car navigation system of UE 50. When the pre-configuration request is input from AF 1 to 5CG 10, pre-configuration related to wireless communication for UE 50 in 5CG 10 is started.

[0051] In the 5GC 10, the pre-configuration request sent from the AF 1 is received by the NEF 3. The NEF 3 converts the route information into cell transition information. The cell transition information is a list of information indicating cells arranged in route order. It can also be said that the cell transition information is a list of handover destination cells of the UE 50 arranged in the order in which the UE 50 will handover. The NEF 3 also identifies the AMF 7 that is currently in charge of managing access and mobility of the UE 50. The NEF 3 transmits to the AMF 7 a pre-configuration request requesting pre-configuration of wireless communication for the UE 50 and the cell transition information.

[0052] In the first embodiment, the starting point of pre-configuration related to radio communication for UE 50 in 5GC 10 is AMF 7 in charge of managing access and mobility of UE 50. NFs related to (I) pre-configuration related to handover and (II) pre-configuration related to establishment of PDU sessions are mainly AMF(s) and SMF(s). Therefore, in the first embodiment, pre-configuration is sequentially performed from the AMF 7 serving as the starting point to the AMF 7 and SMF 6 related to pre-configuration related to radio communication for UE 50. The reason why the AMF 7 in charge of managing access and mobility of UE 50 is used as the starting point is that the AMF 7 holds all the information about UE 50 used for (I) pre-configuration related to handover and (II) pre-configuration related to PDU sessions. One of the pieces of information about the UE 50 held by the AMF 7 is information indicating cooperation between NFs, such as an SM context ID, a UE policy association ID, an AM policy association ID, and an SM policy association ID.

[0053] Hereinafter, preconfiguration related to radio communication for UE 50 will also be simply referred to as preconfiguration. (I) Preconfiguration related to handover will be simply referred to as handover preconfiguration. (II) Preconfiguration related to establishment of a PDU session will be simply referred to as PDU session preconfiguration. Furthermore, one or more NFs related to the preconfiguration will be referred to as related NFs.

[0054] In the first embodiment, in the (I) handover pre-configuration and (II) PDU session pre-configuration procedures in the 5GC 10, the following processes are performed as pre-configuration processes in each related NF: (A) NF selection process performed in the handover procedure and PDU session establishment procedure; (B) Association establishment process between related NFs established in the handover procedure; (C) Storing process of information acquired by the processes of (A) and (B) as pre-configuration information.

[0055] The AMF 7 and the related NFs that have received the pre-configuration request each perform the above steps (A) to (C). As a result, when handover or / and PDU session establishment is performed while the UE 50 is moving on the route, the related NFs have performed the pre-configuration process, so that handover or / and PDU session establishment can be performed more quickly.

[0056] 3, 4, 5, and 6 are examples of handover scenarios in the first embodiment. FIG. 3 is a diagram showing handover scenario #1. Handover scenario #1 is a scenario in which the entire path from the origin to the destination of UE 50 is included within the region of one AMF 7. In scenario #1, a handover between RANs occurs. Hereinafter, the NF and RAN responsible for processing related to UE 50 at the origin or departure point are referred to as the current NF and current RAN, respectively. The NF and RAN scheduled to be responsible for processing related to UE 50 at the destination of UE 50 are referred to as the future NF and future RAN, respectively. The AMF region is set on a cell-by-cell or TA-by-TA basis. Therefore, a cell within an AMF region can also be referred to as an AMF's serving cell.

[0057] In scenario #1, there is no replacement, addition, or release of the AMF and SMF responsible for processing the UE 50. In scenario #1, a pre-configuration request is sent from the current AMF 7A to the current SMF 6A. The pre-configuration request is sent to the current SMF 6A because changes occur in established PDU sessions due to handover.

[0058] 4 is a diagram showing handover scenario #2. Handover scenario #2 is a scenario in which the route from the origin to the destination of UE 50 spans the regions of two AMFs 7A and 7B. In scenario #2, the route is assumed to be within the service area of ​​SMF 6A. In scenario #2, an inter-RAN handover occurs, and a replacement from AMF 7A to AMF 7B occurs when moving from the region of current AMF 7A to the region of future AMF 7B. In scenario #2, a pre-configuration request is sent from current AMF 7A to current SMF 6A as well as from current AMF 7A to future AMF 7B. Hereinafter, the region of the current AMF will be referred to as the current region. The region of the future AMF will be referred to as the future region. The service area of ​​the SMF is set in units of cells or TAs. Therefore, a cell in the service area of ​​the SMF can also be referred to as a cell served by the SMF.

[0059] 5 shows handover scenario #3. Handover scenario #3 is a scenario in which the path from the origin to the destination of UE 50 is included in the region of one AMF 7A but spans the service areas of two SMFs 6A and 6C. In scenario #3, an inter-RAN handover occurs, and an SMF 6C is inserted as an I-SMF (Intermediate-SMF) when moving from the service area of ​​the current SMF 6A to the service area of ​​the future SMF 6C. In scenario #2, a pre-configuration request is sent from the current AMF 7A to the current SMF 6A as well as from the current AMF 7A to the future SMF 6C.

[0060] 6 is a diagram showing handover scenario #4. Handover scenario #4 is a scenario in which the route from the origin to the destination of UE 50 spans the regions of two AMFs 7A and 7C and also spans the service areas of two SMFs 6A and 6D. In scenario #4, an inter-RAN handover occurs, an AMF replacement occurs when UE 50 moves from the region of current AMF 7A to the region of future AMF 7C, and SMF 6D as the I-SMF is replaced when UE 50 moves from the service area of ​​current SMF 6A to the service area of ​​future SMF 6D. In scenario #4, pre-configuration requests are sent from the current AMF 7A to the current SMF 6A, as well as from the current AMF 7A to the future AMF 7C and from the future AMF 7C to the future SMF 6D.

[0061] In Fig. 6, for convenience of explanation, the AMF region and the SMF service area are shown as if they are the same range. However, this is not limited to this, and the AMF region and the SMF service area may be set to different ranges independently. Also, the handover scenarios are not limited to scenarios #1 to #4. <Device Configuration>

[0062] 7 is a diagram showing an example of the hardware configuration of an information processing device capable of operating as each NF and AF 1 in the 5G core network 10. The information processing device 110 can be configured using an information processing device (computer) such as a personal computer (PC), a workstation (WS), or a server machine. The information processing device 110 may be a collection (cloud) of one or more computers. Note that the NF and AF 1 in the 5G core network may be devices equipped with electrical circuits such as a dedicated FPGA (Field-Programmable Gate Array) or ASIC (Application Specific Integrated Circuit) that execute the corresponding processing.

[0063] The information processing device 110 includes, as its hardware configuration, a processor 101, a memory 102, an auxiliary storage device 103, and a communication unit 104. The memory 102 and the auxiliary storage device 103 are computer-readable recording media. The processor 101, the auxiliary storage device 103, and the communication unit 104 are electrically connected by a bus.

[0064] The auxiliary storage device 103 stores programs used to operate as either each NF or AF 1 in the 5G core network, and data used by the processor 101 when executing each program. The auxiliary storage device 103 is, for example, an erasable programmable ROM (EPROM), a hard disk drive, or a solid state drive (SSD). Programs held in the auxiliary storage device 103 include, for example, an operating system (OS) and a control program for the corresponding NF or AF.

[0065] The memory 102 is a storage device that provides the processor 101 with a storage area and a working area for loading programs stored in the auxiliary storage device 103, and is used as a buffer. The memory 102 includes, for example, semiconductor memory such as a ROM (Read Only Memory) and a RAM (Random Access Memory).

[0066] The processor 101 loads into the memory 102 an OS stored in the auxiliary storage device 103 and a program related to either one of the NFs or AFs 1 in the 5G core network and executes the programs, thereby executing processing corresponding to each NF or AF 1 in the 5G core network. The processor 101 is, for example, a CPU or a DSP (Digital Signal Processor). The number of processors 101 is not limited to one, and multiple processors 101 may be provided.

[0067] The communication unit 104 is, for example, a network interface card (NIC), an optical line interface, etc. The communication unit 104 may be, for example, a wireless communication circuit that connects to a wireless network such as a wireless LAN. The hardware configuration of the information processing device 110 that realizes the functions of each NF and AF 1 in the 5G core network is not limited to that shown in FIG. 7 .

[0068] FIG. 8 is a diagram showing an example of the functional configuration of the AF 1. In FIG. 8, functional components according to the first embodiment are extracted from the functional configuration of the AF 1 and shown. The same applies to the functional configuration of each subsequent NF. The AF 1 includes a control unit 11 as a functional component. The AF 1 receives route information from the UE 50. For example, when one of multiple routes searched by a car navigation system is selected and an operation to start route guidance is input, the UE 50 transmits the set route information to the AF 1. The route information includes, for example, location information of a departure point, one or more points on the route, and a destination point in the order in which they are passed. The location information is, for example, latitude and longitude.

[0069] When the control unit 11 receives route information from the UE 50, it first transmits a QoS registration request to the NEF 3, requesting registration of QoS settings for the UE 50 for the application to be pre-configured, which is used when pre-configuring a PDU session. The QoS registration request also transmits identification information for the UE 50, identification information for the flow of the target application, and QoS setting information. The identification information for the UE 50 is, for example, a Subscription Permanent Identifier (SUPI). The identification information for the flow of the target application is, for example, a combination of a destination IP address, a source IP address, a destination port number, a source port number, and a protocol number, or an application ID. The QoS setting information includes, for example, priority, required delay, maximum burst size, maximum bit rate, guaranteed bit rate, and packet error rate. However, the QoS setting information is not limited to these.

[0070] Note that the identification information of the target application does not need to be transmitted if it is desired to set the same QoS for all PDU sessions of the UE 50. When the control unit 11 receives a response to the QoS registration request from the NEF 3, it transmits a pre-configuration request, the identification information of the UE 50, the route information, and the identification information of the target application to the NEF 3.

[0071] 9 is a diagram showing an example of the functional configuration of the NEF 3. The NEF 3 has, as its functional configuration, a control unit 31 and a geographic information conversion unit 32. When the control unit 31 receives a QoS registration request from the AF 1, it transmits the QoS registration request, identification information of the UE 50, identification information of the target application, and QoS setting information to the UDM 2, and requests registration from the UDM 2. When it receives a response to the request from the UDM 2, the control unit 31 transmits the response to the QoS registration request to the AF 1.

[0072] When the control unit 31 receives a pre-configuration request from the AF 1, it requests the geographic information conversion unit 32 to convert the route information received together with the pre-configuration request into cell transition information, and acquires the cell transition information. The NEF 3 identifies the AMF 7 (current AMF) responsible for managing the mobility of the UE 50. The NEF 3 identifies the current AMF by, for example, querying the UDM 2. The NEF 3 transmits a handover pre-configuration request, UE identification information, and cell transition information to the current AMF 7. Furthermore, if a PDU session has not been established for the target application, the NEF 3 transmits a PDU session pre-configuration request, UE identification information, cell transition information, and flow identification information of the target application to the current AMF 7. For example, whether the UE 50 has established a PDU session for the target application may be obtained by inquiring to the UDM 2, or the AF 1 may obtain information about the application in communication from the UE 50 and notify the NEF 3 of the information together with the pre-configuration request.

[0073] The geographic information conversion unit 32 converts the geographic area into a list of Tracking Areas (TAs), RAN nodes, and / or cell identification information. In the first embodiment, when route information is input from the control unit 31, the geographic information conversion unit 32 converts, for example, location information of the starting point, intermediate points, destination point, and multiple points on the route from the starting point to the destination included in the route information into cell identification information, arranges the information in order from the starting point to the destination, and converts the route information into cell transition information. However, the information included in the cell transition information is not limited to cell identification information, and may be a list of TAs or identification information of RAN nodes. The geographic information conversion unit 32 outputs the cell transition information to the control unit 31.

[0074] 10 is a diagram illustrating an example of the functional configuration of the AMF 7. The AMF 7 includes a control unit 71 and a configuration information storage unit 72 as functional components. The control unit 71 executes a handover pre-configuration process when a handover pre-configuration request is received from the NEF 3. The control unit 71 executes a PDU session pre-configuration process when a PDU session pre-configuration request is received from the NEF 3. In the first embodiment, the handover pre-configuration process and PDU session pre-configuration process of the AMF 7 are similar to some of the processes executed by the AMF in the handover procedure and the PDU session establishment procedure, respectively. However, they differ in that information indicating pre-configuration is also transmitted along with messages exchanged with other NFs.

[0075] The handover pre-configuration process is divided into a process for within the region of the AMF 7 and a process for outside the region of the AMF 7. In the handover pre-configuration process, a handover pre-configuration request, which is a pre-configuration request for handover, is used.

[0076] In the intra-region handover pre-configuration process, the control unit 71 sends a pre-configuration request to the SMF (current SMF) responsible for managing the currently established PDU session, prompting the selection of a UPF associated with the handover. Furthermore, the control unit 71 determines whether an I-SMF (Intermediate-SMF) has been inserted, replaced, or removed for the currently established PDU session based on the cell transition information. When the control unit 71 determines the insertion, replacement, or removal of an I-SMF, it performs the corresponding processing with the corresponding I-SMF, as disclosed in the 3GPP standard. For example, when the addition or replacement of an I-SMF is determined, the control unit 71 selects a new I-SMF (future SMF) and sends a handover pre-configuration request to the selected future SMF to prompt the establishment of an association and the selection of a UPF. If it is determined that the I-SMF is to be released, the control unit 71 identifies the SMF that manages the I-SMF, transmits a handover pre-setting request, and establishes an association.

[0077] The out-of-region handover pre-configuration process is executed when the route of the UE 50 spans the region of another AMF 7. In the out-of-region handover pre-configuration process, the control unit 71 selects another AMF (future AMF) that is likely to be in charge of mobility management in the destination cell of the UE 50 based on the cell transition information, and transmits a pre-configuration request to the future AMF.

[0078] In the PDU session pre-configuration process, the control unit 71 selects an SMF 6 (future AMF) that will manage the new PDU session when a new PDU session is established for the UE 50 in the future. The control unit 71 transmits a PDU session pre-configuration request, which is a pre-configuration request for the PDU session, to the selected future AMF.

[0079] When the control unit 71 receives a pre-configuration request from another AMF 7, it executes a handover pre-configuration process within the region as a future AMF. Furthermore, the control unit 71 stores information acquired in the handover pre-configuration process and the PDU session pre-configuration process in the configuration information storage unit 72. Hereinafter, with respect to the AMF 7, the handover pre-configuration process and the PDU session pre-configuration process may be collectively referred to as the pre-configuration process. Hereinafter, the information acquired through the execution of the handover pre-configuration process and the PDU session pre-configuration process is also referred to as pre-configuration information.

[0080] When the control unit 71 receives a handover request or a PDU session establishment request, it refers to the preset information stored in the setting information storage unit 72. If there is corresponding preset information, the control unit 71 uses the preset information to perform the subsequent handover process or PDU session establishment process.

[0081] The setting information storage unit 72 is, for example, a part of the storage area of ​​the auxiliary storage device 103 of the information processing device 110 in which the AMF 7 is implemented. The setting information storage unit 72 stores the preset information acquired by the control unit 71 through execution of the preset processing, with the preset information being clearly indicated as preset information. For example, the preset information may be clearly indicated as preset information by being stored in a storage area or file prepared for preset information. Alternatively, the preset information may be clearly indicated as preset information by being stored in the setting information storage unit 72 together with information indicating that the information is "preset." The information indicating that the information is "preset" may be, for example, a preset ID, a flag, a code, or a keyword.

[0082] 10 shows an example in which preconfiguration information is stored in a storage area prepared for preconfiguration information in the configuration information storage unit 72. In the example shown in FIG. 10, preconfiguration information is stored for each identification information (UE ID) of UE 50. Furthermore, preconfiguration information is stored for each preconfiguration ID. The preconfiguration ID is uniquely assigned to each preconfiguration request by, for example, NEF 3. The preconfiguration information identified by the preconfiguration ID includes preconfiguration information obtained through the handover preconfiguration process and preconfiguration information obtained through the PDU session preconfiguration process. The preconfiguration information obtained through the handover preconfiguration process is hereinafter referred to as handover preconfiguration information. The preconfiguration information obtained through the PDU session preconfiguration process is hereinafter referred to as PDU session preconfiguration information.

[0083] The handover preconfiguration information includes, for example, a target RAN ID and PDU session-specific information for each PDU session. The RAN ID may be a cell ID or a RAN node ID. The PDU session-specific information includes a PDU session ID, an SMF ID that has established an SM association with the AMF 7, an SM context ID, and the like. The SM context ID is identification information assigned by the SMF to identify the SM association between the AMF and the SMF for the PDU session. In addition, if the target RAN is a cell outside the region of the AMF 7, the PDU session-specific information includes a target AMF ID, which is the ID of the AMF selected as the future AMF. Furthermore, if the target RAN is a cell outside the service area of ​​the SMF responsible for managing the PDU session, the ID of the selected SMF is included. The PDU session-specific information in the handover preconfiguration information is maintained for each established PDU session.

[0084] The PDU session pre-configuration information includes QoS flow-oriented information. The QoS flow-oriented information includes, for example, QoS flow identification information, the SMF ID of the SMF selected to manage the PDU session corresponding to the QoS flow, and the SM context ID in the SMF. The QoS flow identification information is the flow identification information of the target application sent from AF 1 together with the QS registration request. The QoS flow identification information includes, for example, the destination IP address, the source IP address, the destination port number, the source port number, and the protocol number.

[0085] Note that the SMF ID included in the pre-configuration information obtained through the handover pre-configuration process is the SMF responsible for managing the established PDU session, while the SMF ID included in the PDU session pre-configuration information is the SMF responsible for managing the PDU session that may be established in the future (i.e., not yet established). Note that the information included in the pre-configuration information held by the AMF shown in Figure 10 is an example. The information included in the pre-configuration information held by the AMF is not limited to the example shown in Figure 10.

[0086] For example, when a handover request is received, the control unit 71 searches the setting information storage unit 72 using the UE ID, target RAN ID, and PDU session ID of the handover request as keys. If handover pre-configuration information that matches the search key exists, the control unit 71 performs the subsequent handover processing using the handover pre-configuration information.

[0087] For example, when a PDU session establishment request is received, the control unit 71 searches the setting information storage unit 72 using the UE ID included in the PDU session establishment request as a key in the setting information storage unit 72. If PDU session pre-configuration information that matches the search key exists, the control unit 71 performs the subsequent PDU session establishment process using the PDU session pre-configuration information.

[0088] FIG. 11 is a diagram illustrating an example of the functional configuration of the SMF 6. The SMF 6 includes a control unit 61 as a functional component. When the control unit 61 receives a handover pre-configuration request from the SMF 6, it selects a UPF to which an established PDU session in the handover target cell is assigned as a handover pre-configuration process. When the control unit 61 receives a PDU session pre-configuration request from the SMF 6, it performs, as a PDU session pre-configuration process, NF selection and policy information acquisition processes, which are processes executed by the SMF in the PDU session establishment procedure. The control unit 61 also stores information acquired through the pre-configuration process in the configuration information storage unit 62. When the control unit 61 receives a handover request or a PDU session establishment request, it refers to the pre-configuration information stored in the configuration information storage unit 62. If there is corresponding pre-configuration information, the control unit 61 uses the pre-configuration information to perform the subsequent handover process or PDU session establishment process.

[0089] The setting information storage unit 62 is, for example, a part of the storage area of ​​the auxiliary storage device 103 of the information processing device 110 in which the SMF 6 is implemented. The setting information DB 62 stores the pre-setting information acquired by the control unit 61 through execution of the pre-setting process, with the information clearly marked as pre-setting.

[0090] 11, preset information is held for each identification information of UE 50. Furthermore, preset information is held for each preset ID. The preset information identified by the preset ID includes handover preset information and PDU session preset information.

[0091] The handover preconfiguration information includes, for example, a target RAN ID and PDU session-specific information for each PDU session. The PDU session-specific information includes, for example, a PDU session ID, an AMF ID that has established an SM association for the PDU session, an SM context ID, an old SMF ID, and a selected UPF ID. The PDU session-specific information in the handover preconfiguration information is retained for each established PDU session whose management is assigned to the SMF at the time of the preconfiguration request. The AMF that has established an SM association is the AMF that sent the handover preconfiguration request.

[0092] The PDU session pre-configuration information includes QoS flow-oriented information. The QoS flow-oriented information includes, for example, QoS flow identification information, the AMF ID establishing the SM association, the SM context ID, the ID of the selected PCF assigned policy management for the PDU session of the target application, the SM policy association ID, the selected UPF ID, and QoS information. The QoS information includes QoS configuration information transmitted from the AF 1 together with the QoS registration request. Note that the information included in the pre-configuration information held by the SMF 6 shown in FIG. 11 is an example. The information included in the pre-configuration information held by the SMF 6 is not limited to the example shown in FIG. 11.

[0093] For example, when a handover request is received from the AMF, the control unit 61 searches the configuration information storage unit 62 using the UE ID, preconfigured ID, target RAN ID, and PDU session ID received together with the handover request as keys in the configuration information storage unit 62. If handover preconfiguration information matching the search key exists, the control unit 61 performs the subsequent handover process using the handover preconfiguration information.

[0094] For example, when a PDU session establishment request is received, the control unit 61 searches the configuration information storage unit 62 using the UE ID, preconfiguration ID, and SM context ID received together with the PDU session establishment request as keys. If PDU session preconfiguration information matching the search key exists, the control unit 61 performs the subsequent PDU session establishment process using the PDU session preconfiguration information. Note that the preconfiguration information held by the SMF 6 is not limited to the information shown in FIG. 11, and information received from other NFs through the preconfiguration process may also be held. Note that the functional configurations of each NF shown in FIGS. 8 to 11 are only examples, and the functional configurations of each NF are not limited to the functional configurations shown in FIGS. 8 to 11.

[0095] <Processing Flow> Fig. 12 is an example of a flowchart of processing related to a pre-setting request of AF1. The processing shown in Fig. 12 is repeatedly executed at a predetermined cycle. The processing shown in Fig. 12 is executed by the CPU 101 of the information processing device 110 in which an instance of AF1 is implemented. However, for convenience of explanation, AF1 or the functional components of AF1 will be described as the main processing. Furthermore, when AF1 is described as the main processing in the explanation of the flowchart, it is assumed that the control unit of AF1 is in charge of the processing. The same applies to the flowcharts from Fig. 12 onwards.

[0096] In OP11, the AF 1 determines whether or not route information has been received from the UE 50. If route information has been received from the UE 50 (OP11: YES), the process proceeds to OP12. If route information has not been received from the UE 50 (OP11: NO), the process shown in Fig. 12 ends. Along with the route information, information on the application currently in communication is also received from the UE 50.

[0097] At OP12, the AF 1 transmits a QoS registration request for the target application to the NEF 3. Along with the QoS registration request, for example, identification information of the UE 50, flow identification information of the target application, and QoS setting information are also transmitted.

[0098] In OP13, the AF 1 determines whether or not a response to the QoS registration request has been received. If a response to the QoS registration request has been received (OP13: YES), the processing proceeds to OP14. The AF 1 remains in a standby state until a response to the QoS registration request is received (OP13: NO).

[0099] At OP14, the AF 1 sends a pre-configuration request to the NEF 3. Along with the pre-configuration request, identification information of the UE 50, route information, flow identification information of the target application, and information indicating whether the UE 50 has already established a PUD session of the target application are also sent.

[0100] In OP15, the AF 1 determines whether or not a response to the pre-setting request has been received. If a response to the pre-setting request has been received (OP15: YES), the processing shown in Fig. 12 ends. The AF 1 remains in a standby state until a response to the pre-setting request has been received (OP15: NO).

[0101] Fig. 13 is an example of a flowchart of processing related to pre-setting of the NEF 3. The processing shown in Fig. 13 is repeatedly executed at a predetermined cycle. In OP21, the NEF 3 determines whether or not a pre-setting request has been received from the AF 1. If a pre-setting request has been received from the AF 1 (OP21: YES), the processing proceeds to OP22. If a pre-setting request has not been received from the AF 1 (OP21: NO), the processing shown in Fig. 13 ends.

[0102] In OP22, the NEF 3 (geographic information conversion unit 32) converts the route information into cell transition information. In OP23, the NEF 3 queries the UDM 2 to identify an AMF that manages the mobility of the UE 50 as a target for pre-configuration. In OP24, the NEF 3 transmits a handover pre-configuration request to the identified AMF. The pre-configuration ID, identification information of the UE 50, and cell transition information are also transmitted together with the handover pre-configuration request. If multiple AMFs are identified in OP23, the handover pre-configuration request is transmitted to each AMF.

[0103] In OP25, the NEF 3 determines whether a PDU session for the target application has been established. For example, the determination in OP25 is made based on information indicating whether the UE 50 has established a PDU session for the target application, which is received together with the pre-configuration request from the AF 1. If a PDU session for the target application has been established (OP25: YES), the process proceeds to OP27. If a PDU session for the target application has not been established (OP25: NO), the process proceeds to OP26.

[0104] In OP26, the NEF 3 sends a PDU session pre-configuration request to the AMF identified in OP23. The PDU session pre-configuration request also includes the pre-configuration ID, the identification information of the UE 50, the cell transition information, and the flow identification information of the application to be pre-configured.

[0105] In OP27, the NEF 3 determines whether or not a response to the handover and PDU session pre-configuration request has been received. If a response to the pre-configuration request has been received (OP27: YES), the process proceeds to OP28. If a response to the pre-configuration request has been received (OP27: NO), the NEF 3 enters a standby state. In OP28, the NEF 3 transmits a response to the pre-configuration request to the AF 1. Then, the process shown in FIG. 13 ends.

[0106] Fig. 14 is an example of a flowchart of processing by the AMF 7 when a handover preset request is received. The processing shown in Fig. 14 is repeatedly executed at a predetermined period. In OP31, the AMF 7 determines whether or not a handover preset request has been received from the NEF 3. If a handover preset request has been received (OP31: YES), the processing of OP32 and OP33 is started. The processing of OP32 and OP33 is performed in parallel. If a handover preset request has not been received (OP31: NO), the processing proceeds to OP38A.

[0107] The processes of OP32 to OP37 are processes that are executed when the AMF 7 is the current AMF and receives a pre-configuration request from the NEF 3. In OP32, the AMF 7 executes an intra-region handover process. In OP33, the AMF 7 executes an out-of-region handover process. The intra-region handover process and the out-of-region handover process will be described in detail later.

[0108] In OP35, the AMF 7 determines whether or not all of the processes from OP32 to OP33 have been completed. If all of the processes from OP32 to OP33 have been completed (OP35: YES), the process proceeds to OP36. The AMF 7 remains in a standby state until all of the processes from OP32 to OP34 have been completed (OP35: NO).

[0109] In OP36, the AMF 7 stores the handover pre-configuration information in the configuration information storage unit 72. In OP37, the AMF 7 transmits a response to the handover pre-configuration request to the NEF 3. After that, the process illustrated in Fig. 14 ends.

[0110] The processes in OP38A to OP38D are processes when the AMF 7 is selected as a future AMF. In OP38A, the AMF 7 determines whether or not a pre-configuration request has been received from the AMF. When a pre-configuration request has been received from the AMF (OP38A: YES), the process proceeds to OP38B. When a pre-configuration request has not been received from the AMF (OP38B: NO), the process illustrated in FIG. 14 ends.

[0111] In OP38B, the AMF 7 executes an intra-region handover process. In OP38C, the AMF 7 stores the pre-configuration information in the configuration information storage unit 72. In OP38D, the AMF 7 transmits a response to the pre-configuration request to the AMF that is the source of the pre-configuration request received in OP38. After that, the process illustrated in Fig. 14 ends.

[0112] Figure 15 is an example of a flowchart of an intra-region handover pre-configuration process. The process shown in Figure 15 is a process executed in OP32 of Figure 14. In the process shown in Figure 15, AMF 7 corresponds to the current AMF. The process in Figure 15 is performed for each PDU session being established for UE 50. The PDU session that is the target of the process is referred to as the target PDU session. Therefore, in Figure 15, the current SMF is the SMF that is in charge of processing the target PDU session.

[0113] In OP321, the AMF 7 determines whether or not there is a future RAN in the region, based on the cell transition information. The future RAN is a RAN corresponding to a cell included in the cell transition information and in which the UE 50 is not currently located. If there is a future RAN in the region (OP321: YES), the processing proceeds to OP322 and OP324. If there is no future RAN in the region (OP321: NO), the processing illustrated in Fig. 15 ends, and the processing proceeds to OP35 in Fig. 14 .

[0114] The processes from OP322 to OP323 and the processes from OP324 to OP327 are executed in parallel. The processes from OP322 to OP323 are processes for the current SMF. In OP322, the AMF 7 transmits a handover pre-configuration request to the current SMF. The ID of the UE 50, the pre-configuration ID, cell transition information, and the ID of the PDU session to be handed over are also transmitted together with the handover pre-configuration request.

[0115] In OP323, the AMF 7 determines whether or not a response to the handover pre-configuration request has been received from the current SMF. If a response to the handover pre-configuration request has been received from the current SMF (OP323: YES), the processing for the current SMF for the target PDU session is terminated. The AMF 7 remains in a standby state until a response to the handover pre-configuration request is received from the current SMF (OP323: NO).

[0116] The processing from OP324 to OP327 is processing related to the future SMF. In OP324, the AMF 7 determines whether or not the cell transition information includes a cell outside the service area of ​​the current SMF. If the cell transition information includes a cell outside the service area of ​​the current SMF (OP324: YES), the processing proceeds to OP325. If the cell transition information does not include a cell outside the service area of ​​the current SMF (OP324: NO), the processing related to the future SMF for the target PDU session ends.

[0117] In OP325, the AMF 7 selects a future SMF whose service area includes a cell outside the service area of ​​the current SMF included in the cell transition information. The AMF 7 queries the NRF for candidate AMFs according to, for example, the 3GPP standard, and selects a future SMF from the list of candidate SMFs, taking into consideration the future RAN, the service area of ​​the SMF, the processing load of the SMF, etc. In OP326, the AMF 7 transmits a handover pre-configuration request to the SMF selected as the future SMF. The ID of the UE 50, the pre-configuration ID, the cell transition information, the PDU session ID to be handovered, and the target RAN ID in the case of handover to a cell within the service area of ​​the future SMF are also transmitted together with the handover pre-configuration request.

[0118] In OP327, the AMF 7 determines whether or not a response to the handover pre-configuration request has been received. If a response to the handover pre-configuration request has been received (OP327: YES), the process for the future SMF for the target PDU session is terminated. The AMF 7 remains in a standby state until a response to the handover pre-configuration request is received (OP327: NO). When the process for the current SMF and the process for the future SMF for all established PDU sessions are terminated, the process shown in Fig. 15 is terminated, and the process proceeds to OP35 in Fig. 14.

[0119] Fig. 16 is an example of a flowchart of an out-of-region handover pre-configuration process of the AMF 7. The process illustrated in Fig. 16 is a process executed in OP33 of Fig. 14. In the process illustrated in Fig. 16, the AMF 7 is a current AMF.

[0120] In OP331, the AMF 7 determines whether or not the cell transition information includes a cell outside the region. If the cell transition information includes a cell outside the region (OP331: YES), the process proceeds to OP332. If the cell transition information does not include a cell outside the region (OP331: NO), the process illustrated in Fig. 16 ends.

[0121] In OP332, the AMF 7 selects a future AMF. The AMF 7 queries the NRF for candidate AMFs according to, for example, the 3GPP standard, and selects, from the list of candidate AMFs, an AMF whose region includes a cell outside the region included in the cell transition information as the future AMF. For multiple AMFs other than the current AMF, if the cell transition information includes a cell within the region, the multiple AMFs are selected as future AMFs. In OP333, the AMF 7 transmits a handover pre-configuration request to the future AMF selected in OP332. The ID of the UE 50, the pre-configuration ID, the cell transition information, and the PDU session ID of the handover target are also transmitted together with the handover pre-configuration request.

[0122] In OP334, the AMF 7 determines whether or not a handover pre-configuration request has been received from all future AMFs. If a handover pre-configuration request has been received from all future AMFs (OP334: YES), the process illustrated in Fig. 16 ends, and the process proceeds to OP35 in Fig. 14. The AMF 7 remains in a standby state until a handover pre-configuration request has been received from all future AMFs (OP334: NO).

[0123] 17 is an example of a flowchart of a PDU session pre-configuration process when an AMF receives a PDU session pre-configuration request. In the process shown in FIG. 17, AMF 7 is the current AMF.

[0124] In OP341, the AMF 7 determines whether or not a PDU session pre-establishment request has been received from the NEF 3. When a PDU session pre-establishment request has been received (OP341: YES), the processing proceeds to OP342. When a PDU session for the target application has not yet been established (OP341: NO), the processing shown in Fig. 17 ends.

[0125] In OP342, the AMF 7 selects a future SMF that will be in charge of the PDU session of the target application. The AMF 7 queries the NRF for candidate SMFs, for example, according to the 3GPP standard, and selects a future SMF from the list of candidate SMFs. In OP343, the AMF 7 sends a PDU session establishment request to the future SMF. The ID of the UE 50, the pre-configuration ID, cell transition information, and flow identification information of the target application are also sent together with the PDU session pre-configuration request.

[0126] In OP344, the AMF 7 determines whether or not a response to the PDU session pre-configuration request has been received from the future SMF. If a response to the PDU session pre-configuration request has been received from the future SMF (OP334: YES), the processing proceeds to OP345. The AMF 7 remains in a standby state until a response to the PDU session pre-configuration request is received from the future SMF (OP334: NO).

[0127] In OP345, the AMF 7 stores the PDU session pre-configuration information in the configuration information storage unit 72. In OP346, the AMF 7 transmits a response to the PDU session pre-configuration request to the NEF 3. After that, the processing shown in Fig. 17 ends.

[0128] Fig. 18 is an example of a flowchart of processing performed by the SMF 6 when a pre-configuration request is received. The processing shown in Fig. 18 is repeatedly executed at a predetermined cycle. In OP41, the SMF 6 determines whether or not a pre-configuration request has been received from the AMF. If a pre-configuration request has been received from the AMF (OP41: YES), the processing proceeds to OP42. If a pre-configuration request has not been received from the AMF (OP41: NO), the processing proceeds to OP46.

[0129] The processes from OP42 to OP45 are processes performed when a handover pre-configuration request is received. In OP42, the SMF 6 determines whether to select a UPF. If it is determined that a UPF selection is to be performed (OP42: YES), the process proceeds to OP43. If it is determined that a UPF selection is not to be performed (OP42: NO), the process proceeds to OP44. In OP43, the SMF 6 selects a UPF. The SMF 6 inquires about UPF candidates from the NRF, for example, and selects a UPF whose service area includes the future cell included in the cell transition information from a list of candidate UPFs.

[0130] For example, when the SMF 6 does not hold information about the PDU session to be handover received together with the pre-configuration request, i.e., when a session with the UPF that has established the PDU session to be handover is not established, the SMF 6 determines to select a UPF (OP42: YES) and selects a PDU for establishing the PDU session to be handover (OP43). For example, when the SMF 6 is selected as an I-SMF (future SMF) by the AMF 7 and receives a handover pre-configuration request from the AMF 7, the SMF 6 will not hold information about the PDU session to be handover.

[0131] Furthermore, for example, even when the SMF 6 holds information about the PDU session to be handover received together with the pre-configuration request, it determines to select a UPF in the following cases: In a local breakout or redundant configuration, when the cell transition information includes a transition from a cell within the service area of ​​the I-UPF currently connected to the RAN to a cell outside the service area, the SMF 6 determines to select a UPF during handover from a cell within the service area of ​​the I-UPF (Intermediate UPF) currently connected to the RAN to a cell outside the service area (OP42: YES), and selects a new I-UPF (OP43).

[0132] For example, when the SMF 6 holds information about the PDU session to be handovered received together with the pre-configuration request and the cell transition information does not include a transition from a cell within the service area of ​​the UPF currently connected to the RAN to a cell outside the service area, it is determined not to perform UPF selection (OP42: NO).

[0133] In OP44, the SMF 6 stores, as handover pre-configuration information, information about the UPF selected in OP43, a target RAN ID when the UPF is selected, and the like, in the configuration information storage unit 62. In OP45, the SMF 6 transmits a response to the handover pre-configuration request to the AMF. After that, the process illustrated in FIG. 18 ends.

[0134] In OP46, the SMF 6 determines whether or not a PDU session pre-configuration request has been received from the AMF. If a PDU session pre-configuration request has been received (OP46: YES), the process proceeds to OP47. If a PDU session pre-configuration request has not been received (OP46: NO), the process shown in FIG. 18 ends.

[0135] The processes from OP47 to OP49 are processes performed when a PDU session pre-configuration request is received. In OP47, the SMF 6 selects a UPF to which a PDU session to be newly established in the future will be assigned and acquires policy rules including QoS information. The SMF 6 selects a UPF whose service area includes a cell included in the cell transition information in accordance with the 3GPP standard. If the target application is to be transferred to an edge server, the SMF 6 selects, for example, a UL CL (Uplink Classifier) ​​and a UPF as a PDU session anchor connected to a local DN. In OP48, the SMF 6 stores, for example, information about the selected UPF as PDU session pre-configuration information in the configuration information storage unit 62. In OP49, the SMF 6 transmits a response to the PDU session pre-configuration request to the AMF. After that, the process illustrated in FIG. 18 ends.

[0136] 19 is an example of a flowchart of a handover process or a PDU session establishment process of an NF. In the first embodiment, the NFs that are the subjects of the process in FIG. 19 are, for example, an AMF and an SMF.

[0137] In OP51, the NF determines whether or not a handover request or a PDU session request has been received. If a handover request or a PDU session request has been received (OP51: YES), the processing proceeds to OP52. If a handover request or a PDU session request has not been received (OP51: NO), the processing shown in Fig. 19 ends. If a handover request has been received, the processing from OP52 onwards is processing for handover. If a PDU session request has been received, the processing from OP52 onwards is processing for the PDU session.

[0138] In OP52, the NF determines whether or not there is corresponding information in the preconfigured information. When a handover request is received, the NF determines whether or not there is corresponding information in the handover pre-information. When a PDU session establishment request is received, the NF determines whether or not there is corresponding information in the PDU session pre-information. If there is corresponding information in the preconfigured information (OP52: YES), the processing proceeds to OP53. If there is no corresponding information in the preconfigured information (OP52: NO), the processing proceeds to OP6. In OP56, the NF performs processing when a handover request or PDU session request specified in the 3GPP standard is received. Thereafter, the processing shown in FIG. 19 ends.

[0139] In OP53, the NF reflects pre-configured information corresponding to the handover request or PDU session request in the context information. In OP54, an appropriate request corresponding to the handover request or PDU session request is transmitted to the selected NF included in the pre-configured information. In OP55, the NF executes subsequent processing in the handover procedure or PDU session establishment procedure specified in the 3GPP standard. Thereafter, the processing shown in FIG. 19 ends. Note that the processing shown in FIGS. 12 to 19 is an example and can be modified as appropriate depending on the embodiment.

[0140] 20 shows an example of a processing sequence from when route information is transmitted from UE 50 to when a pre-configuration request is transmitted to the current AMF. In the example shown in FIG. 20, UE 50 is registered in the region of the current AMF 7A, and at least one PDU session has been established under the management of the current SMF 6A.

[0141] In S11, for example, when a route is set in a car navigation system by a vehicle occupant, the UE 50 transmits route information and information on the application currently communicating to the AF 1. In S12, when the AF 1 receives the route information and the like from the UE 50 (OP11: YES in FIG. 12 ), the AF 1 transmits a QoS registration request to the NEF 3 to request the NEF 10 to set a QoS for the application to be pre-configured (OP12 in FIG. 12 ). The QoS registration request is transmitted using, for example, an Nnef_AF_Request_QoS_Create request message. Identification information of the UE 50, identification information of the flow of the application to be pre-configured, and QoS setting information are also transmitted together with the Nnef_AF_Request_QoS_Create request message. However, the Nnef_AF_Request_QoS_Create request message uses a GPSI (Generic Public Subscription Identifier) ​​as identification information of the UE 50.

[0142] In S13, when the NEF 3 receives the Nnef_AF_Request_QoS_Create request message, it acquires the SUPI corresponding to the GPSI of the UE 50 from the UDM 2. Thereafter, the AF 1 uses the SUPI as identification information of the UE 50.

[0143] In S14, the NEF 3 transmits a Nudr_DM_Create request to the UDR 4 requesting registration of QoS information for the UE 50. As a result, the QoS information of the target application for the UE 50 is registered in the UDR 4. The QoS information is registered as "Policy Data". A response is transmitted from the UDR 4 to the NEF 3. In S15, upon receiving the response from the UDR 4, the NEF 3 transmits an Nnef_AF_Request_QoS_Create response message to the AF 1. The AF 1 receives the Nnef_AF_Request_QoS_Create response message (OP13 in FIG. 12 : YES).

[0144] In S16, since the policy data for UE 50 has been updated in S14, UDR 4 transmits a Nudr_DM_Notify message notifying the update of the policy data and the update contents (flow identification information and QoS information of the target application) to PCF 5. PCF 5 receives the QoS information of the target application for UE 50 via the Nudr_DM_Notify message.

[0145] In S17, the PCF 5 identifies the current SMF 6A that manages the PDU session of the target application, and starts a procedure for changing the SM policy association with the current SMF 6A. Through the procedure for changing the SM policy association, the PCF 5 notifies the current SMF 6A of the QoS information of the target application for the UE 50.

[0146] In S18, the current SMF 6A initiates an N4 session modification procedure with the UPF to which the PDU session of the target application is allocated, and notifies the UE 50 of the QoS information of the target application through this procedure.

[0147] In S19, the current SMF 6A sends the QoS information of the target application for UE 50 to the current RAN along with a Namf_Communication_N1N2MessageTransfer message to the current AMF 7A. The current SMF 6A that has received the Namf_Communication_N1N2MessageTransfer message transfers the QoS information of the target application for UE 50 to the current RAN using an N2 message. As a result, the QoS information of the target application for UE 50 is reflected in the PCF 5, the current SMF 6A, and the current RAN that are currently responsible for the PDU session of the target application.

[0148] In S21, the AF 1 sends a pre-configuration request to the NEF 3. Along with the pre-configuration request, a pre-configuration ID, identification information of the UE 50, route information, flow identification information of the target application, and information indicating whether the UE 50 has already established a PDU session for the target application are also sent (OP14 in FIG. 12). The pre-configuration ID is used to identify the pre-configuration request. The NEF 3 receives the pre-configuration request (OP21 in FIG. 13: YES).

[0149] In S22, the NEF 3 converts the route information received together with the pre-configuration request into cell transition information (OP22 in FIG. 13 ). In S23, the NEF 3 identifies the current AMF 7A to be configured (OP23 in FIG. 13 ). In S24, the NEF 3 transmits a handover pre-configuration request to the current AMF 7A (OP24 in FIG. 13 ). The NEF 3 transmits the pre-configuration ID, identification information of the UE 50, and cell transition information together with the handover pre-configuration request.

[0150] If a PDU session for the target application has not been established, the process of S25 is executed. In S25, since the UE 50 has not established a PDU session for the target application (OP25: NO in FIG. 13), the NEF 3 transmits a PDU session pre-configuration request to the current AMF 7A (OP26 in FIG. 13). Together with the PDU session pre-configuration request, the NEF 3 transmits the pre-configuration ID, identification information of the UE 50, cell transition information, and flow identification information of the target application.

[0151] 21 is a diagram showing an example of a handover pre-configuration sequence in scenario #1. Scenario #1 is a scenario in which the route of UE 50 falls within the region of current AMF 7A and the service area of ​​current SMF 6A. Therefore, one or more cells included in the cell transition information are cells that are included in the region of current AMF 7A and also in the service area of ​​current SMF 6A. Also, in FIG. 21 , it is assumed that the cell transition information, i.e., the planned movement route of UE 50, does not include movement from a cell within the service area of ​​the UPF currently connected to the RAN to a cell outside the service area.

[0152] The sequence illustrated in Fig. 21 is a continuation of the sequence illustrated in Fig. 20. S100 is the same process as S24 in Fig. 20. In S100, the current AMF 7A receives a preconfiguration request, a preconfiguration ID, identification information of the UE 50, and cell transition information from the NEF 3 (OP31 in Fig. 14 : YES).

[0153] In scenario #1, handover outside the region of the current AMF 7A does not occur, so the current AMF 7A performs an intra-region handover pre-configuration process (OP32 in FIG. 14) and a PDU session pre-configuration process (FIG. 17). The sequence from S111 to S115 is a handover pre-configuration sequence within the current region in scenario #1.

[0154] In S111, the current AMF 7A identifies the current SMF 6A. The current AMF 7A holds information about each established PDU session in the UE context for the UE 50. The information about the PDU session held by the AMF 7A includes the ID of the SMF managing the PDU session. The current AMF 7A identifies the SMF included in the information about the PDU session as the current SMF 6A. In the example shown in FIG. 21 , it is assumed that one SMF is identified as the current SMF 6A. However, this is not limited to this, and there may be multiple SMFs identified as the current SMF 6A.

[0155] In S112, the current AMF 7A transmits a handover pre-configuration request to the current SMF 6A (OP321: YES, OP322 in FIG. 15 ). Together with the handover pre-configuration request, for example, the ID of the UE 50, the pre-configuration ID, cell transition information, and the ID of the PDU session to be handovered are also transmitted.

[0156] The handover pre-configuration request is transmitted using, for example, an Nsmf_PDUSession_UpdateSMContext request message. For example, information indicating that the request is a handover pre-configuration request may be included in the Nsmf_PDUSession_UpdateSMContext request message. The information indicating that the request is a handover pre-configuration request may be, for example, a keyword, a code, or a flag. The Nsmf_PDUSession_UpdateSMContext request message may also include, as a format, a target RAN ID and a PDU session ID to be handovered. Cell transition information may be included in the Nsmf_PDUSession_UpdateSMContext request message as the target RAN. The Nsmf_PDUSession_UpdateSMContext request message also includes an SM context ID that identifies the SM association with the current SMF 6A. The SM context ID is included in information about the PDU session in the UE context for the UE 50 in the current AMF 7A. Note that the message used to transmit the handover pre-configuration request is not limited to the Nsmf_PDUSession_UpdateSMContext request message. The current SMF 6A receives the handover pre-configuration request (OP41 in FIG. 18: YES).

[0157] In S113, the current SMF 6A holds information about the PDU session to be handover-targeted. In scenario #1, the cell transition information does not include transition from a cell within the service area of ​​the UPF currently connected to the RAN to a cell outside the service area. Therefore, the current SMF 6A does not select a UPF for the PDU session to be handover-targeted (OP42: NO in FIG. 18 ).

[0158] In S114, the current SMF 6A stores the information received in S112 and the execution result of the process of S113 together with the preset ID as handover preset information (OP44 in FIG. 18 ). For example, for each active PDU session, the current SMF 6A stores the PDU session ID, the SM context ID included in the Nsmf_PDUSession_UpdateSMContext request message received in S112, and the ID of the current AMF 7A corresponding to the SM context ID, together with one or more cell IDs and preset IDs included in the cell transition information as target RAN IDs, in the configuration information storage unit 62 as handover preset information for the UE 50 (see FIG. 11 ).

[0159] In S115, the current SMF 6A transmits a response to the handover pre-configuration request (OP45 in FIG. 18 ). Along with the response to the handover pre-configuration request, the pre-configuration ID, the target RAN ID(s) (future cell included in the cell transition information) in which the handover pre-configuration information is stored, and the PDU session ID are also transmitted. The response to the handover pre-configuration request is transmitted, for example, by using an Nsmf_PDUSession_UpdateSMContext response message, including information indicating that it is a response to the handover pre-configuration request. The Nsmf_PDUSession_UpdateSMContext response message also includes an SM context ID. The current AMF 7A receives the response to the handover pre-configuration request (OP323 in FIG. 15 : YES).

[0160] In S116, the current AMF 7A stores the information received in S100 and S115 together with the preset ID as handover preset information (OP36 in FIG. 14 ). For example, for each PDU session included in the Nsmf_PDUSession_UpdateSMContext response message received in S115, the current AMF 7A stores the PDU session ID, the SM context ID included in the Nsmf_PDUSession_UpdateSMContext response message received in S115, and the ID of the current SMF 6A corresponding to the SM context ID, together with the cell ID and preset ID included in the cell transition information as the target RAN ID, in the configuration information storage unit 72 as handover preset information for the UE 50 (see FIG. 10 ).

[0161] In S117, the current AMF 7A transmits a response to the handover pre-configuration request to the NEF 3 (OP37 in FIG. 14 ). The ID and the pre-configuration ID of the UE 50 are also transmitted together with the response to the handover pre-configuration request. The NEF 3 receives the response to the pre-configuration request (OP27 in FIG. 13 : YES). The handover pre-configuration sequence in FIG. 21 completes the handover pre-configuration in the 5CG 10 in scenario #1.

[0162] 22 shows a PDU session pre-configuration sequence in scenario #1. The PDU session pre-configuration sequence is executed when the current AMF 7A receives a PDU session pre-configuration request from the NEF 3 (FIG. 17, OP341: YES).

[0163] In S121, when the current AMF 7A receives a PDU session establishment request for the target application in the current region in the future, it selects an SMF 6B to which management of the PDU session will be assigned (OP342 in FIG. 17). For example, the AMF 7A queries the NRF to obtain a list of candidate SMFs, and selects a future SMF 6B from the list based on the cell transition information.

[0164] In S122, the current AMF 7A transmits a PDU session pre-configuration request to the selected SMF 6B (OP343 in FIG. 17 ). The identification information of the UE 50, the pre-configuration ID, and cell transition information may also be transmitted together with the PDU session pre-configuration request. The PDU session pre-configuration request is transmitted, for example, in an Nsmf_PDUSession_CreateSMContext request message, including information indicating that the request is a PDU session pre-configuration request. The information indicating that the request is a PDU session pre-configuration request is, for example, a keyword, a code, or a flag. In addition to the above information, the Nsmf_PDUSession_CreateSMContext request message includes, as one piece of information, the current location of the UE 50, the ID of the current AMF 7A, etc. The SMF 6B receives the PDU session pre-establishment request (OP46 in FIG. 18: YES) and issues an SM context ID for the received Nsmf_PDUSession_CreateSMContext request message.

[0165] In S123, the SMF 6B transmits a Nudm_SDM_Get message to the UDM 2 to request subscribe data of the UE 50. The processing of S123 is processing for acquiring information used for UPF selection and policy data acquisition (OP47 in FIG. 18 ). In S124, the UDM 2 transmits the subscribe data of the UE 50 together with a Nudm_SDM_Get response message to the SMF 6B. The SMF 6B receives the subscribe data of the UE 50. The subscribe data of the UE 50 acquired in S124 is session management subscribe data. The session management subscribe data includes, for example, authentication information and the like.

[0166] In S125, the SMF 6B selects a PCF 5 that manages a policy for a PDU session to be established in response to a PDU session establishment request that will be newly generated in the future. The SMF 6B, for example, inquires of the NRF about candidate PCFs and selects the PCF 5 from among the candidate PCFs. The PCF 5 may be the same PCF as that of the existing PDU session.

[0167] In S126, the SMF 6B sends an Npcf_SMPolicyControl_Create request message to the PCF 5 to request the creation of a new SM policy association with the PCF 5 for the UE 50. The Npcf_SMPolicyControl_Create request message includes, as part of the information, identification information of the UE 50, a PDU session ID, etc. However, in FIG. 22, since a PDU session establishment request accompanying the start of communication of the target application has not yet occurred, the PDU session ID remains undetermined or uses a value indicating that it has been pre-set. Upon receiving the Npcf_SMPolicyControl_Create request message, the PCF 5 creates an SM policy association with the SMF 6B for the UE 50 and issues an SM policy association ID.

[0168] In S127, the PCF 5 transmits a Nudr_DM_Query request message to the UDR 4 requesting policy information for the UE 50. In S128, the UDR 4 transmits the policy information of the UE 50 together with a Nudr_DM_Query response message to the PCF 5. The policy information of the UE 50 also includes QoS information of the target application registered in the UDR 4 in S14 of Fig. 20. The PCF 5 receives the policy information of the UE 50 together with the Nudr_DM_Query response message, and stores it in association with the SM policy association ID with the SMF 6B.

[0169] In S129, the PCF 5 transmits an Npcf_SMPolicyControl_Create response to the SMF 6B. The Npcf_SMPolicyControl_Create response includes, for example, an SM policy association ID with the PCF 5, policy information about the UE 50, and the like. The policy information about the UE 50 includes, as one piece of information, a default PCC rule used for subsequent UPF selection, QoS information of the target application, and the like. The SMF 6B receives the Npcf_SMPolicyControl_Create response.

[0170] In S130, the SMF 6B selects a UPF to which a PDU session establishment request for the target application will be assigned in the future when the SMF 6B receives the PDU session establishment request based on the default PCC rule. At this time, if the target application is a target of edge computing, for example, a UPF operating as a UL CL and a UPF operating as a PSA may be selected as the UPF. Information indicating that the target application is a target of edge computing is included in the policy information for the UE 50 received in S129.

[0171] In S131, the SMF 6B sends an Npcf_SMPolicyControl_Update request message to the PCF 5, requesting the creation of a PCC rule for the target application. The Npcf_SMPolicyControl_Update request message includes, for example, an SM association ID as one piece of information. In S132, the PCF 5 receives the Npcf_SMPolicyControl_Update request message and determines a policy for the UE 50 based on the policy information. At this time, a PCC rule for the target application is also created. In S133, the PCF 5 sends an Npcf_SMPolicyControl_Update response message to the SMF 6B. The Npcf_SMPolicyControl_Update response message includes, for example, an SM association ID and a PCC rule for the target application as one piece of information. The SMF 6B receives the Npcf_SMPolicyControl_Update response message. This completes the PDU session pre-setting process in the SMF 6B (OP47 in FIG. 18).

[0172] In S134, the SMF 6B stores the information on the PCF 5 selected in S125, the information on the UPF selected in S130, and the information received in S122, S124, S129, and S133 together with the preset ID as PDU session preset information (OP48 in FIG. 18 ). For example, for each target application, the SMF 6B stores the QoS flow identification information (flow identification information of the target application), the SM context ID issued in response to the Nsmf_PDUSession_CreateSMContext request message received in S122, the ID of the current AMF 7A corresponding to the SM context, the SM policy association ID included in the Npcf_SMPolicyControl_Update response message received in S131, the ID of the selected PCF 5, the ID of the selected UPF, and QoS information, together with a pre-configuration ID, in the configuration information storage unit 62 as PDU session pre-configuration information for the UE 50 (see FIG. 11 ).

[0173] In S135, the SMF 6B transmits a response to the PDU session pre-configuration request to the current AMF 7A (OP49 in FIG. 18). The UE identification information and pre-configuration ID are also transmitted together with the response to the PDU session pre-configuration request. The response to the PDU session pre-configuration request is transmitted, for example, in an Nsmf_PDUSession_CreateSMContext response message, including information indicating that it is a response to the PDU session pre-configuration request. The Nsmf_PDUSession_CreateSMContext response message includes, for example, the SM context ID issued by the SMF 6B as one piece of information. The current AMF 7A receives the response to the PDU session pre-configuration request (OP344: YES in FIG. 17).

[0174] In S136, the current AMF 7A stores information about the SMF 6B selected in S121 and the information received in S100 and S135 of Fig. 21 together with the preset ID as PDU session preset information (OP345 in Fig. 17). For example, the current AMF 7A stores, for each target application, QoS flow identification information (flow identification information of the target application), the ID of the selected SMF 6B, and the SM context ID included in the Nsmf_PDUSession_CreateSMContext response message received in S135 together with the preset ID in the configuration information storage unit 72 as PDU session preset information for the UE 50 (see Fig. 10).

[0175] In S137, the current AMF 7A transmits a response to the pre-configuration request to the NEF 3 (OP346 in FIG. 17 ). The NEF 3 receives the response to the pre-configuration request (OP27: YES in FIG. 13 ). Through the PDU session pre-configuration sequence in FIG. 22 , the PDU session pre-configuration in the 5CG 10 in Scenario #1 is completed.

[0176] Fig. 23 is a diagram showing an example of a handover sequence in scenario #1. Fig. 23 is based on the premise that the pre-setting sequence from Fig. 20 to Fig. 22 has been completed in the 5CG 10. It is also assumed that the UE 50 is moving on a route based on the route information notified in S11 of Fig. 20.

[0177] When UE 50 moves near the boundary between the source RAN and the target RAN, it detects a handover and transmits a handover request, which is received by the source RAN and a handover preparation process is performed between the source RAN and the target RAN (see, for example, steps 1-8 of TS38.300 Fig. 9.2.3.2.1-1).

[0178] In S151, the target RAN sends an N2 Path Switch request message including a handover request to the current AMF 7A. The N2 Path Switch request message includes, as part of the information, identification information of the UE 50, the target RAN ID, and a list of PDU sessions to be handed over. The current AMF 7A receives the N2 Path Switch request message including the handover request.

[0179] In S152, the current AMF 7A searches for handover pre-configuration information using the identification information of the UE 50, the target RAN ID, and the ID of the PDU session to be handed over, which are included in the N2 Path Switch request message received in S151, as keys, and detects the handover pre-configuration information stored in S116 of FIG. 21 as the search result.

[0180] In S153, the current AMF 7A sends an Nsmf_PDUSession_UpdateSMContext request message to the SMF 6A included in the handover preset information detected in S152. The Nsmf_PDUSession_UpdateSMContext request message includes identification information of the UE 50, a handover request, a target RAN ID, and the SM context ID and PDU session ID included in the handover preset information detected in S152. In addition, a preset ID corresponding to the handover preset information detected in S152 is also sent together with the Nsmf_PDUSession_UpdateSMContext request message. The SMF 6A receives the Nsmf_PDUSession_UpdateSMContext request message.

[0181] In S154, the SMF 6A searches for handover preset information using the identification information of the UE 50, the preset ID, the target RAN ID, and the PDU session ID included in the Nsmf_PDUSession_UpdateSMContext request message received in S153 as keys, and detects the handover preset information stored in S114 of Fig. 21 as the search result. In the example shown in Fig. 23, UPF selection was not performed in S113 of Fig. 21, and the detected handover preset information does not include information about the selected UPF. Therefore, in Fig. 23, the SMF 6A does not determine whether to perform UPF selection and does not select a UPF.

[0182] In S155, the SMF 6A performs, for example, an N4 session modification process in step 3-5 of Fig. 4.9.1.2.2-1 of 3GPP TS23.502 for the selected UPF based on the handover pre-configuration information detected in S154, thereby switching the PDU session established between the source RAN and the UPF to a PDU session between the target RAN and the UPF.

[0183] In S156, the SMF 6A sends an Nsmf_PDUSession_UpdateSMContext response message including information indicating the success of the handover to the current AMF 7A. The current AMF 7A receives the Nsmf_PDUSession_UpdateSMContext response message. In S157, the current AMF 7A sends an Ack message in response to the N2 Path Switch Request including information indicating the success of the handover to the target RAN. Thereafter, the target RAN notifies the source RAN and the UE 50 of the success of the handover.

[0184] In the handover sequence in Scenario #1 shown in Fig. 23, since the SMF 6A has already determined in the pre-configuration process not to select a UPF to allocate the PDU session to be handed over, the SMF 6A does not determine whether to perform UPF selection in S154. This can shorten the time required for handover and further shorten the time of communication interruption due to handover.

[0185] Furthermore, in scenario #1, if local breakout is configured for one of the established PDU sessions, for example, by edge computing, and a cell outside the service area of ​​the I-UPF operating as the UL CL is included in the cell transition information (OP42: YES in FIG. 18 ), the current SMF 6A selects a new I-UPF and PSA (PDU Session Anchor) in pre-configuration S113 in FIG. 21 (OP43 in FIG. 18 ). In this case, when the UE 50 performs a handover from a cell within the service area of ​​the I-UPF to a cell outside the service area of ​​the I-UPF, the current SMF 6A holds handover pre-configuration information including information on the selected I-UPF, and therefore performs a session establishment process related to handover between the selected I-UPF included in the handover pre-configuration information and the PSA without performing a process for selecting a new I-UPF. This allows, for example, even when local breakout is set, to reduce the time required for handover and further shorten the time of momentary communication interruption due to handover.

[0186] 24 is a diagram showing an example of a sequence for establishing a PDU session for a pre-configured application in scenario #1. The premise of the example in FIG. 24 is the same as the example in FIG. 23. In S171, UE 50 transmits a PDU session establishment request for a pre-configured application. The PDU session establishment request includes, as one piece of information, identification information of UE 50 and a PDU session ID. The current AMF 7A receives the PDU session establishment request from UE 50.

[0187] In S172, the current AMF 7A searches for PDU session pre-configuration information using the identification information of the UE 50 included in the PDU session establishment request received in S171 as a key, and detects the handover pre-configuration information stored in S136 of Fig. 22 as the search result. Since the handover pre-configuration information includes information on the SMF 6B selected in S121 of Fig. 22, the AMF 7A does not perform SMF selection in Fig. 24.

[0188] In S173, the current AMF 7A sends an Nsmf_PDUSession_CreateSMContext request message to the SMF 6B included in the PDU session pre-configuration information detected in S172. The Nsmf_PDUSession_CreateSMContext request message includes a PDU session establishment request, the identification information of the UE 50 and the PDU session ID included in the PDU session establishment request received in S171, and the SM context ID included in the PDU session pre-configuration information detected in S172. In addition, the pre-configuration ID corresponding to the PDU session pre-configuration information detected in S172 is also sent together with the Nsmf_PDUSession_CreateSMContext request message. The SMF 6B receives the Nsmf_PDUSession_CreateSMContext request message.

[0189] In S174, the SMF 6B searches for PDU session pre-configuration information using the identification information, pre-configuration ID, and SM context ID of UE 50 included in the Nsmf_PDUSession_CreateSMContext request message received in S173 as keys, and detects the PDU session pre-configuration information stored in S134 of Fig. 22 as a result of the search. The PDU session pre-configuration information includes, for example, subscription data for UE 50 acquired in S123 and S124 of Fig. 22, information on the PCF selected in S125 of Fig. 22, information on the UPF selected in S130 of Fig. 22, the SM policy association ID received in S129, and flow identification information and QoS information of the target application received in S133. Therefore, the SMF 6B does not acquire subscription data for UE 50 in Fig. 24. The SMF 6B reflects the PDU session advance information in the context information of the UE 50.

[0190] In S175, the SMF 6B transmits an Nsmf_PDUSession_CreateSMContext response message to the current AMF 7A. The Nsmf_PDUSession_CreateSMContext response message includes an SM context ID as one piece of information. A pre-configured ID is also transmitted together with the Nsmf_PDUSession_CreateSMContext response message. The current AMF 7A receives the Nsmf_PDUSession_CreateSMContext response message. In addition, the current AMF 7A may reflect PDU session pre-information corresponding to the received SM context ID in the context information of the UE 50.

[0191] In S176, secondary authentication is performed for UE 50 (see 4.3.2.2.1 step 6 of TS23.502). In S177, since the PDU session pre-configuration information includes information on the PCF selected in S125 of Fig. 22, the SM policy association ID received in S129, the flow identification information and QoS information of the target application received in S133, etc., SMF 6B does not select a PCF, does not establish a PCF selection and SM association with PCF 5, does not obtain QoS information from PCF 5, etc.

[0192] In S178, the SMF 6B does not select a UPF because the PDU session pre-configuration information includes information about the UPF selected in S130 of FIG. 22.

[0193] In S179, the SMF 6B performs a procedure to change the SM policy association with the selected PCF 5 included in the PDU session pre-configuration information and notifies the PDU session ID. As a result, the PCF 5 obtains the PDU session ID corresponding to the SM policy association ID issued in S131 of Fig. 22 and updates the SM policy association information. In S180, the SMF 6B performs a procedure to establish an N4 session with the selected UPF included in the PDU session pre-configuration information.

[0194] In S181, the SMF 6B sends a Namf_Communication_N1N2MessageTransfer message to the current AMF 7A. The Namf_Communication_N1N2MessageTransfer message includes, as one piece of information, an acceptance of the establishment of the PDU session, flow identification information and QoS information of the target application included in the PDU session pre-configuration information, etc. The current AMF 7A receives the Namf_Communication_N1N2MessageTransfer message and notifies the RAN and UE 50 of, for example, the acceptance of the establishment of the PDU session, and the flow identification information and QoS information of the target application.

[0195] In the sequence of establishing a PDU session in scenario #1 shown in Figure 24, in the pre-configuration process, the current AMF 7A has selected the SMF 6B that will manage a new PDU session that will be generated in the future, and the SMF 6B has acquired subscription data for the UE 50, selected a PCF and a UPF, and acquired flow identification information and QoS information of the target application from the PCF. As a result, in the sequence shown in Figure 24, the SMF selection process in S172, the acquisition of information from the UDM in S174, the selection of a PCF and the acquisition of a policy in S177, and the UPF selection in S178 are not performed. This reduces the time required for the procedure of establishing a PDU session, and enables the UE 50 to more quickly perform communication of the target application to which an appropriate QoS is applied.

[0196] 25 is a diagram showing an example of a handover pre-configuration sequence in scenario #2. Scenario #2 is a scenario in which the route of UE 50 does not fall within the region of the current AMF 7A and extends to the region of another AMF, resulting in AMF replacement. On the other hand, in scenario #2, the route of UE 50 falls within the service area of ​​the current SMF 6A. Therefore, the cell transition information includes cells included in the region of the current AMF 7A and cells not included in the region of the current AMF 7A. Furthermore, one or more cells included in the cell transition information are cells included in the service area of ​​the current SMF 6A. Also, in FIG. 25, it is assumed that the cell transition information, i.e., the planned movement route of UE 50, does not include movement from a cell within the service area of ​​the UPF currently connected to the RAN to a cell outside the service area.

[0197] The sequence illustrated in Fig. 25 is a continuation of the sequence illustrated in Fig. 20. S200 is the same process as S24 in Fig. 20, and the current AMF 7A receives a handover pre-configuration request, identification information of the UE 50, a pre-configured ID, and cell transition information from the NEF 3 (OP31 in Fig. 14: YES).

[0198] In scenario #2, the cell transition information includes a cell outside the region of the current AMF 7A, and therefore the current AMF 7A performs an intra-region handover pre-configuration process (OP32 in FIG. 14 ) and an out-of-region handover pre-configuration process (OP33 in FIG. 14 ).

[0199] In S211, for handover between cells within the region of the current AMF 7A included in the cell transition information, a handover pre-configuration sequence within the region of the current AMF 7A is executed, similar to S111-S116 of Scenario #1.

[0200] The sequence from S212 to S219 is a handover pre-configuration sequence for a handover from a cell within the region of the current AMF 7A to a cell outside the region of the current AMF 7A, which is included in the cell transition information, and a handover between cells outside the region of the current AMF 7A, i.e., a handover pre-configuration sequence for a handover outside the region of the current AMF 7A. In S212, the current AMF 7A selects a future AMF 7B (OP332 in FIG. 16 ). The current AMF 7A, for example, queries the NRF to acquire future AMF candidates and selects the future AMF 7B from among the candidates based on the cell transition information. As the future AMF 7B, an AMF whose region includes a cell outside the region of the current AMF 7A included in the cell transition information is selected.

[0201] In S213, the current AMF 7A transmits a handover pre-configuration request to the future AMF 7B (OP333 in FIG. 16 ). A pre-configuration ID and cell transition information are also transmitted together with the handover pre-configuration request. The handover pre-configuration request is transmitted, for example, by including information indicating that it is a handover pre-configuration request in a Namf_Communication_CreateUEContext request message. The Namf_Communication_CreateUEContext request message includes, as one piece of information, a UE context for the UE 50 held by the current AMF 7A, a target cell ID, and the like. The ID of a cell outside the region of the current AMF 7A in the cell transition information may be included as the target cell ID in the Namf_Communication_CreateUEContext request message as the target cell. The UE context for the UE 50 also includes, for example, the IDs of the active PDU sessions, the SM context ID for each PDU session, and the ID of the SMF responsible for managing the PDU session. The future AMF 7B receives a handover pre-configuration request (OP38A in FIG. 14: YES).

[0202] In S214, the future AMF 7B transmits a handover pre-configuration request to the SMF 6A included in the Namf_Communication_CreateUEContext request message received in S213 (OP38B in FIG. 14 , OP322 in FIG. 15 ). A pre-configuration ID and cell transition information may be transmitted together with the handover pre-configuration request. The handover pre-configuration request is transmitted, for example, in an Nsmf_PDUSession_UpdateSMContext request message including information indicating that it is a handover pre-configuration request. The Nsmf_PDUSession_UpdateSMContext request message includes, as pieces of information, the ID of the UE 50, the target cell ID, the SM context ID included in the Namf_Communication_CreateUEContext request message, and the ID of the future AMF 7B as the target AMF. In the Nsmf_PDUSession_UpdateSMContext request message, the ID of a cell outside the region of the current AMF 7A in the cell transition information may be included as the target cell ID. If the Namf_Communication_CreateUEContext request message received in S213 includes IDs of multiple active PDU sessions, an Nsmf_PDUSession_UpdateSMContext request message is sent to the SMF corresponding to each PDU session. The SMF 6A receives the handover pre-configuration request (OP41: YES in FIG. 18 ).

[0203] In S215, the SMF 6A holds information about the PDU session to be handover-targeted. In scenario #2, the cell transition information does not include a transition from a cell within the service area of ​​the UPF currently connected to the RAN to a cell outside the service area, so no UPF is selected for the PDU session to be handover-targeted (OP42: NO in FIG. 18 ).

[0204] In S216, the SMF 6A stores the information etc. received in S214 as handover pre-configuration information together with the pre-configuration ID received in S214 (OP44 in FIG. 18 ). For example, for each active PDU session, the SMF 6A stores the PDU session ID, the SM context ID included in the Nsmf_PDUSession_UpdateSMContext request message received in S214, and the ID of the future AMF 7B corresponding to the SM context, together with the cell ID in the region of the future AMF 7B and the pre-configuration ID included in the cell transition information as the target RAN ID, in the configuration information storage unit 62 as handover pre-configuration information for the UE 50 (see FIG. 11 ).

[0205] In S217, the SMF 6A transmits a response to the handover pre-configuration request to the future AMF 7B (OP45 in FIG. 18 ). The pre-configuration ID is also transmitted together with the response to the handover pre-configuration request. The response to the handover pre-configuration request is transmitted, for example, in an Nsmf_PDUSession_UpdateSMContext response message, including information indicating that it is a response to the handover pre-configuration request. The Nsmf_PDUSession_UpdateSMContext response message includes, as pieces of information, the SM context ID, the ID of the PDU session for which handover pre-configuration has been performed, and the like. The future AMF 7B receives the response to the handover pre-configuration request (OP323 in FIG. 15 : YES).

[0206] In S218, the future AMF 7B stores the information received in S213 and S217 together with the preset ID as handover preset information (OP38C in FIG. 14 ). For example, for each PDU session included in the Nsmf_PDUSession_UpdateSMContext response message received in S217, the future AMF 7B stores the PDU session ID, the SM context ID included in the Nsmf_PDUSession_UpdateSMContext response message received in S217, and the ID of the SMF 6A corresponding to the SM context ID, together with the ID of the cell in the region of the future AMF 7B included in the cell transition information as the target RAN ID and the preset ID, in the configuration information storage unit 72 as handover preset information for the UE 50 (see FIG. 10 ).

[0207] In S219, the future AMF 7B transmits a response to the handover pre-configuration request to the current AMF 7A (OP38D in FIG. 14 ). The pre-configuration ID is also transmitted together with the response to the handover pre-configuration request. The response to the handover pre-configuration request is transmitted, for example, by including information indicating that it is a response to the handover pre-configuration request in a Namf_Communication_CreateUEContext response message. The Namf_Communication_CreateUEContext response message includes, for example, the ID of the future AMF 7B as the target AMF as one piece of information. The current AMF 7A receives the response to the handover pre-configuration request (OP334 in FIG. 16 : YES).

[0208] In S220, the current AMF 7A stores the information received in S219 and the information on the future AMF 7B selected in S212 together with the preset ID as handover preset information (OP36 in FIG. 14 ). For example, for each PDU session included in the Nsmf_PDUSession_UpdateSMContext response message received in S219, the current AMF 7A stores the PDU session ID, the SM context ID included in the Nsmf_PDUSession_UpdateSMContext response message received in S115, the ID of the current SMF 6A corresponding to the SM context ID, and the ID of the future AMF 7B as the target AMF ID selected in S212 in the configuration information storage unit 72 as handover pre-configuration information for the UE 50, together with the ID of the cell in the region of the future AMF 7B included in the cell transition information as the target RAN ID and the pre-configuration ID (see FIG. 10 ).

[0209] In S221, the current AMF 7A transmits a response to the handover pre-configuration request to the NEF 3 (OP37 in FIG. 14 ). The NEF 3 receives the response to the handover pre-configuration request (OP27 in FIG. 13 : YES).

[0210] If a PDU session for the application to be pre-configured has not yet been established, the PDU session pre-configuration sequence is also executed in scenario #2. The PDU session pre-configuration sequence in scenario #2 is the same as the PDU session pre-configuration sequence in scenario #1 shown in FIG.

[0211] Fig. 26 is a diagram showing an example of a handover sequence in scenario #2. The premise of Fig. 26 is the same as that of Fig. 23. Fig. 26 describes a handover sequence when UE 50 moves from a cell in a region of current AMF 7A to a cell in a region of future AMF 7B. Therefore, in Fig. 26, the target RAN is a cell in a region of future AMF 7B to which UE 50 transitions from a cell in a region of current AMF 7A. In Fig. 26, the current AMF 7A in Fig. 25 is referred to as the source AMF 7A, and the future AMF 7B is referred to as the target AMF 7B.

[0212] In S251, the source RAN determines handover based on the field strength of the received signal from the source RAN and the field strength from the target RAN included in a measurement report from the UE 50, and transmits a Handover Required message to the source AMF 7A. The Handover Required message includes, as part of the information, identification information of the UE 50 and the target RAN ID. The source AMF 7A receives the Handover Required message from the source RAN.

[0213] In S252, the source AMF 7A searches for handover pre-configuration information in the configuration information storage unit 72 using the identification information of the UE 50 and the target RAN ID included in the Handover Required message as keys, and detects, for example, the handover pre-configuration information stored in S220 of Fig. 25 as the corresponding handover pre-configuration information. The detected handover pre-configuration information includes the PDU session ID and the ID of the selected target AMF 7B (see Fig. 10). Therefore, in S252, the source AMF 7A does not select a target AMF.

[0214] In S253, the source AMF 7A sends a Namf_Communication_CreateUEContext request message including information indicating a handover request to the target AMF 7B. The Namf_Communication_CreateUEContext request message includes, as one piece of information, a UE context for the UE 50 held by the source AMF 7A, a target RAN ID, etc. In the example shown in FIG. 26 , the target RAN ID is the ID of a cell in the region of the future AMF 7B to which the UE 50 will transition from a cell in the region of the current AMF 7A. The UE context for the UE 50 also includes, for example, IDs of active PDU sessions, SM context IDs for each PDU session, and the ID of the SMF responsible for managing the PDU session. A pre-configured ID is also sent together with the Namf_Communication_CreateUEContext request message. The target AMF 7B receives the Namf_Communication_CreateUEContext request message.

[0215] In S254, the target AMF 7B searches the handover pre-configuration information in the configuration information storage unit 72 using the ID of the UE 50, the target cell ID, the pre-configuration ID, and the PDU session ID received together with the Namf_Communication_CreateUEContext request message as keys, and detects the handover pre-configuration information stored in S218 of Fig. 25 as the corresponding handover pre-configuration information. The detected handover pre-configuration information includes, for example, an SMF ID, an SM context ID, etc. (see Fig. 10). The target AMF 7B confirms that the information included in the handover pre-configuration information matches the information received together with the Namf_Communication_CreateUEContext request message.

[0216] The target AMF 7B transmits an Nsmf_PDUSession_UpdateSMContext request message including information indicating a handover request to the SMF 6A. The Nsmf_PDUSession_UpdateSMContext request message includes, as part of the information, the ID of the UE 50, the target RAN ID, the SM context ID, and the ID of the target AMF 7B, which are included in the Namf_Communication_CreateUEContext request message. The pre-configured ID received together with the Namf_Communication_CreateUEContext request message is also transmitted together with the Nsmf_PDUSession_UpdateSMContext request message. The SMF 6A receives the Nsmf_PDUSession_UpdateSMContext request message.

[0217] In S255, the SMF 6A searches for handover pre-configuration information in the configuration information storage unit 72 using the ID of the UE 50, the pre-configuration ID, the PDU session ID, and the target RAN ID received together with the Nsmf_PDUSession_UpdateSMContext request message as keys, and detects the handover pre-configuration information stored in S216 of Fig. 25 as the corresponding handover pre-configuration information. The detected handover pre-configuration information does not include information on the selected UPF because UPF selection was not performed in S215 of Fig. 25. Therefore, in S255, the SMF 6A does not determine whether to perform UPF selection or not, and does not select a UPF.

[0218] In S256, the SMF 6A performs the N4 session change procedure, for example, steps 6a-6b of Fig. 4.9.1.3.2-1 of 3GPP TS23.502, with the UPF to which the target PDU session is currently assigned. This prepares the UPF to establish a PDU session with the target RAN.

[0219] In S257, the SMF 6A sends an Nsmf_PDUSession_UpdateSMContext response message to the target AMF 7B. The Nsmf_PDUSession_UpdateSMContext response message includes information about the PDU session with the target RAN in the UPF. The target AMF 7B receives the Nsmf_PDUSession_UpdateSMContext response message.

[0220] In S258, the target AMF 7B sends a Handover Request message to the target RAN. The Handover Request message is a message requesting the target RAN to prepare for handover. Thereafter, the handover sequence proceeds in accordance with the 3GPP standard. In S259, a Handover Request Acknowledge message is sent from the target RAN to the target AMF 7B, and information about the PDU session with the UPF in the target RAN is transmitted.

[0221] In S260, the target AMF 7B transfers the information about the PDU session with the UPF in the target RAN received in S259 to the SMF 6A using an Nsmf_PDUSession_UpdateSMContext request message. In S261, the SMF 6A performs an N4 session modification procedure with the UPF. This notifies the UPF of the information about the PDU session with the UPF in the target RAN. In S262, the SMF 6A completes the UPF configuration and sends an Nsmf_PDUSession_UpdateSMContext response message to the target AMF 7B.

[0222] In S263, the target AMF 7B sends a Namf_Communication_CreateUEContext response message to the source AMF 7A in response to the Namf_Communication_CreateUEContext request message in S253. This completes the preparation for handover within the 5GC 10. In S264, the source AMF 7A sends a Handover Command message to the source RAN to notify that the preparation for handover within the 5GC 10 has been completed. Thereafter, the handover sequence is executed in accordance with the handover execution procedure disclosed in 4.9.1.3.3 of 3GPP TS23.502, for example.

[0223] In the sequence of handover between AMF regions in scenario #2 shown in Figure 26, the source AMF 7A has already selected the target AMF 7B in the pre-configuration process, so AMF selection is not performed in S252. Also, the SMF 6A has already selected a UPF to allocate the PDU session to be handed over, so UPF selection is not performed in S255. As a result, even when the UE 50 moves as in scenario #2, the pre-configuration process can shorten the time required for handover between AMF regions, and the time of communication interruption due to handover can be further shortened.

[0224] Also, like scenario #1, scenario #2 can also support a configuration including an I-UPF such as local breakout. For example, when UE 50 moves out of the service area of ​​the I-UPF due to movement from a cell in the region of source AMF 7A to a cell in the target AMF 7B (OP42: YES in FIG. 18 ), the SMF 6 selects a new I-UPF and PSA in pre-configuration S215 in FIG. 25 (OP43 in FIG. 18 ). When handover occurs due to movement from a cell in the region of source AMF 7A to a cell in the target AMF 7B, the SMF 6A holds handover pre-configuration information including information on the selected I-UPF, and therefore performs a session establishment process related to handover between the selected I-UPF included in the handover pre-configuration information and the PSA without performing a process for selecting a new I-UPF.

[0225] 27 is a diagram showing an example of a handover pre-configuration sequence in scenario #3. Scenario #3 is a scenario in which the route of UE 50 falls within the region of the current AMF 7A, so no AMF replacement occurs, but it does not fall within the service area of ​​the current SMF 6A, so insertion, replacement, and removal of an I-SMF occur. Therefore, the cell transition information in scenario #3 includes cells included in the service area of ​​the current SMF 6A and cells not included in the service area of ​​the current SMF 6A. Note that all cells included in the cell transition information in scenario #3 are cells included in the service area of ​​the current AMF 7A.

[0226] The sequence illustrated in Fig. 27 is a continuation of the sequence illustrated in Fig. 20. S300 is the same process as S24 in Fig. 20, and the current AMF 7A receives a handover pre-configuration request, identification information of the UE 50, a pre-configured ID, and cell transition information from the NEF 3 (OP31 in Fig. 14: YES).

[0227] In scenario #3, since the cell transition information does not include a cell outside the region of the current AMF 7A, the current AMF 7A performs an intra-region handover pre-configuration process (OP32 in FIG. 14 ). In S311, for a handover between cells within the region of the current AMF 7A included in the cell transition information, a handover pre-configuration sequence within the region of the current AMF 7A is executed, similar to S111-S116 in scenario #1.

[0228] The sequence from S312 to S319 is a handover pre-configuration sequence for handover from a cell in the service area of ​​the current SMF 6A to a cell outside the service area of ​​the current SMF 6A, which is included in the cell transition information. In S312, the current AMF 7A selects a future SMF and selects SMF 6C as the future SMF (OP325 in FIG. 15 ) because the cell transition information includes a transition to a cell outside the service area of ​​the current SMF 6A (OP324 in FIG. 15 : YES). The current AMF 7A acquires SMF candidates by, for example, querying the NRF, and selects, from the candidates, an SMF whose service area includes a cell outside the service area of ​​the SMF 6A, which is included in the cell transition information.

[0229] In S313, the current AMF 7A transmits a handover pre-configuration request to the selected future SMF 6C (OP326 in FIG. 15 ). Along with the handover pre-configuration request, for example, a pre-configuration ID, cell transition information, and an ID of a PDU session to be handed over are also transmitted.

[0230] The handover pre-configuration request is transmitted using an Nsmf_PDUSession_CreateSMContext request message, for example, including information indicating that it is a handover pre-configuration request. The Nsmf_PDUSession_CreateSMContext request message also includes a target RAN ID, a PDU session ID to be handovered, an SM context ID, and the ID of the current SMF 6A. Cell transition information may be included in the Nsmf_PDUSession_CreateSMContext request message as the target RAN. The SM context ID included in the Nsmf_PDUSession_CreateSMContext request message is the SM context ID associated with the PDU session to be handovered in the context information of the UE 50 held by the current AMF 7A. The ID of the current SMF 6A included in the Nsmf_PDUSession_CreateSMContext request message is the SMF ID associated with the PDU session to be handed over in the context information of the UE 50 held by the current AMF 7A. The future SMF 6C receives the handover pre-configuration request (OP41 in FIG. 18 : YES).

[0231] In S314, the future SMF 6C determines to perform UPF selection because it does not hold information about the PDU session to be handovered (OP42: YES in FIG. 18 ). In S315, the future SMF 6C transmits an Nsmf_PDUSession_Context request message to the current SMF 6A included in the Nsmf_PDUSession_CreateSMContext request message received in S313. The Nsmf_PDUSession_Context request message includes the SM context ID included in the Nsmf_PDUSession_CreateSMContext request message received in S313, and is a message requesting an SM context corresponding to the SM context ID. In S316, the current SMF 6A receives the Nsmf_PDUSession_Context request message and transmits an Nsmf_PDUSession_Context response message including the SM context corresponding to the specified SM context ID to the future SMF 6C.

[0232] In S317, the future SMF 6C selects a UPF for the PDU session to be handed over (OP43 in FIG. 18).

[0233] In S318, the future SMF 6C stores the information received in S313 and S316 and the execution result of the process in S317 as handover preset information together with the preset ID (OP44 in FIG. 18). For example, the future SMF 6C stores, for each PDU session, the PDU session ID, the SM context ID and the ID of the current SMF 6A as the old SMF ID included in the Nsmf_PDUSession_CreateSMContext request message received in S313, the ID of the current AMF 7A corresponding to the SM context ID, and the ID of the UPF selected in S317 as the selected SMF ID, together with the ID and preset ID of the cell in the service area of ​​the future SMF 6C to which transition is made from the cell in the service area of ​​the current SMF 6A in the cell transition information as the target RAN ID in the configuration information storage unit 62 as handover preset configuration information for the UE 50 (see FIG. 11 ).

[0234] In S319, the future SMF 6C transmits a response to the handover pre-configuration request to the current AMF 7A (OP45 in FIG. 18 ). Along with the response to the handover pre-configuration request, the pre-configuration ID, the target RAN ID(s) (a cell in the service area of ​​the future SMF 6C included in the cell transition information) in which the handover pre-configuration information is stored, and the PDU session ID are also transmitted. The response to the handover pre-configuration request is transmitted by using an Nsmf_PDUSession_CreateSMContext response message, for example, including information indicating that it is a response to the handover pre-configuration request. The Nsmf_PDUSession_CreateSMContext response message also includes an SM context ID. The current AMF 7A receives the response to the handover pre-configuration request (OP327 in FIG. 15 : YES).

[0235] In S320, the current AMF 7A stores the information received in S300 and S319 together with the preset ID as handover preset information (OP36 in FIG. 14 ). For example, the current AMF 7A stores, for each PDU session included in the Nsmf_PDUSession_CreateSMContext response message received in S319, the PDU session ID, the SM context ID, and the ID of the future SMF 6C as handover preset information for the UE 50 in the configuration information storage unit 72 together with the ID and preset ID of the cell in the service area of ​​the future SMF 6C included in the cell transition information as the target RAN ID (see FIG. 10 ).

[0236] In S321, the current AMF 7A transmits a response to the handover pre-configuration request to the NEF 3 (OP37 in FIG. 14 ). The ID and pre-configuration ID of the UE 50 are also transmitted together with the response to the handover pre-configuration request. The NEF 3 receives the response to the pre-configuration request (OP27 in FIG. 13 : YES). The handover pre-configuration sequence in FIG. 27 completes the handover pre-configuration in the 5CG 10 in scenario #3.

[0237] FIG. 28 is a diagram showing an example of a handover sequence in scenario #3. FIG. 28 assumes that the pre-configuration sequences of FIG. 20 and FIG. 27 have been completed in the 5CG 10. It is also assumed that the UE 50 is moving on a route based on the route information notified in S11 of FIG. 20. FIG. 28 describes a handover sequence when the UE 50 moves from a cell within the service area of ​​the current SMF 6A to a cell outside the service area of ​​the current SMF 6A. However, both cells are cells within the region of the current AMF 7A. It is also assumed that the current SMF 6A is the main SMF that manages the target PDU session and is not an I-SMF.

[0238] In the example of Figure 28, the current SMF 6A is not an I-SMF, so an I-SMF is added by handover when UE 50 moves from a cell within the service area of ​​the current SMF 6A to a cell outside the service area of ​​the current SMF 6A. In the example of Figure 28, the target RAN is a cell outside the region of the current SMF 6A to which UE 50 transitions from a cell within the region of the current SMF 6A in the cell transition information. In Figure 28, the current SMF 6A in Figure 27 is referred to as the source SMF 6A, and the future SMF 6C is referred to as the target SMF 6C.

[0239] In S351, the target RAN transmits an N2 Path Switch request message corresponding to a handover request to the current AMF 7A. The N2 Path Switch request message includes, as one piece of information, identification information of the UE 50, the target RAN ID, and a list of PDU sessions to be handed over. The current AMF 7A receives the N2 Path Switch request message.

[0240] In S352, the current AMF 7A searches for handover pre-configuration information using the identification information of the UE 50, the target RAN ID, and the ID of the PDU session to be handed over, which are included in the N2 Path Switch request message received in S351, as keys, and detects the handover pre-configuration information stored in S320 of Fig. 27 as the search result. The detected handover pre-configuration information includes the pre-configuration ID, the SM context ID, and the ID of the target SMF 6C as the selected SMF ID (see Fig. 10). Therefore, in S352, the current AMF 7A does not perform SMF selection.

[0241] In S353, the current AMF 7A transmits an Nsmf_PDUSession_CreateSMContext request message to the target SMF 6C included in the handover pre-configuration information detected in S352. The Nsmf_PDUSession_CreateSMContext request message includes identification information of the UE 50, information indicating a handover request, the target RAN ID, the SM context ID and PDU session ID included in the handover pre-configuration information detected in S152, and the ID of the source SMF 6A as the old SMF ID. The ID of the source SMF 6A as the old SMF ID is the SMF ID associated with the PDU session to be handover in the context information of the UE 50 held by the current AMF 7A. Also sent together with the Nsmf_PDUSession_CreateSMContext request message is the preset ID corresponding to the handover preset information detected in S352. The target SMF 6C receives the Nsmf_PDUSession_CreateSMContext request message.

[0242] In S354, the target SMF 6C searches for handover pre-configuration information in the configuration information storage unit 62 using the identification information of the UE 50, the pre-configuration ID, the target RAN ID, and the PDU session ID included in the Nsmf_PDUSession_CreateSMContext request message received in S353 as keys, and detects the handover pre-configuration information stored in S318 of Fig. 27 as the search result. In the example shown in Fig. 28, the detected handover pre-configuration information includes the ID of the source SMF 6A as the old SMF ID and the selected UPF ID. Therefore, in Fig. 28, the target SMF 6C does not determine whether to perform UPF selection and does not select a UPF.

[0243] In S355, the target SMF 6C performs an N4 session establishment procedure with the selected UPF (I-UPF) included in the handover pre-configuration information detected in S354, thereby preparing the I-UPF for establishing a PDU session with the target RAN.

[0244] In S356, the target SMF 6C sends an Nsmf_PDUSession_Create request message to the source SMF 6A, requesting the creation of a PDU session. The Nsmf_PDUSession_Create request message includes, as part of the information, the ID of the UE 50, the SM context ID, and the PDU session ID. The source SMF 6A receives the Nsmf_PDUSession_Create request message.

[0245] In S357, the source SMF 6A performs an N4 session modification procedure for the PSA UPF of the PDU session corresponding to the PDU session ID included in the Nsmf_PDUSession_Create request message. This prepares the PSA UPF to establish a PDU session with the I-UPF. In S358, the source SMF 6A sends an Nsmf_PDUSession_Create response message to the target SMF 6C. The Nsmf_PDUSession_Create response message includes information about the PDU session with the I-UPF in the PSA.

[0246] In S359, the target SMF 6C notifies the I-UPF of information about the PDU session between the I-UPF and the PSA UPF, which is included in the Nsmf_PDUSession_Create response message, and performs the N4 session change procedure. This prepares the I-UPF to establish a PDU session with the PSA UPF.

[0247] In S360, the target SMF 6C sends an Nsmf_PDUSession_CreateSMContext response message including information indicating preparation for establishing a PDU session to the current AMF 7A. The current AMF 7A receives the Nsmf_PDUSession_CreateSMContext response message. In S361, the current AMF 7A sends an Ack message in response to the N2 Path Switch request to the transmitting target RAN, notifying it of preparation for handover in 5GC. After that, the target RAN notifies the source RAN and the UE 50 of preparation for handover, and the handover is performed.

[0248] In the handover sequence in scenario #3 shown in Figure 28, the selection of an I-SMF by the current AMF 7A in S352, the selection of a UPF by the target SMF 6C in S354, and the acquisition of an SM context from the source SMF 6A have already been executed in the handover pre-configuration sequence in Figure 27, and are skipped in the handover sequence in Figure 28. This makes it possible to shorten the time required for handover, even in a handover in which the service area of ​​the SMF is changed, as in scenario #3, and further shorten the time of a momentary interruption in communication due to handover.

[0249] In Figure 28, a sequence for adding an I-SMF in association with a handover in which the service area of ​​the SMF is changed is described, taking as an example a case in which there is no I-SMF other than the current SMF (source SMF) 6A, and the current SMF 6A is the SMF that was initially responsible for managing the target PDU session. Not limited to this, even if the current SMF is an I-SMF, the handover pre-configuration sequence in Figure 27 is executed, thereby making it possible to shorten the time required for the handover sequence in which the service area of ​​the SMF is subsequently changed. The SMF that was initially responsible for managing the target PDU session is hereinafter referred to as the original SMF.

[0250] For example, when the current SMF is an I-SMF, a handover that changes the service area of ​​the SMF may result in the I-SMF being released or replaced. The case in which the I-SMF is released is when the current SMF is an I-SMF and the target cell is a cell within the service area of ​​the original SMF. The case in which the I-SMF is replaced is when the current SMF is an I-SMF and the target cell is a cell within the service area of ​​an SMF other than the original SMF.

[0251] In the case where the I-SMF is released, the original SMF is selected as the future SMF in S312 of Figure 27 in the pre-configuration, and the PSA UPF managed by the SMF is selected in S317 of Figure 27. Thereafter, when a handover occurs that changes the service area of ​​the SMF, management of the target PDU session is transferred to the original SMF as the future SMF, and at the same time, the path of the PDU session is changed to a path that reaches the pre-selected PSA UPF without passing through the I-UPF managed by the I-SMF. Then, the I-UPF and the I-SMF that manages the I-UPF are released. In this series of sequences, for example, processes such as selecting the original SMF as the future SMF and selecting the PSA UPF as the UPF to which the target PDU session is assigned within the service area of ​​the original SMF are not performed.

[0252] In the case where the I-SMF is replaced, in the pre-configuration, in S312 of Figure 27, an SMF whose service area includes a target cell other than the original SMF is selected as the future SMF, and in S317 of Figure 27, a UPF managed by the SMF is selected. Thereafter, when a handover occurs that changes the service area of ​​the SMF, the I-SMF on which the target PDU session is established is switched to the SMF selected as the future SMF, and at the same time, the I-UPF of the PDU session path is switched to the I-UPF selected in the pre-configuration sequence. In this series of sequences, for example, the process of selecting the future SMF and the process of selecting the UPF to which the target PDU session is assigned within the service area of ​​the future SMF are not performed.

[0253] Also, in scenario #3, for example, the handover pre-configuration sequence shown in Figure 27 can be applied to local breakout such as edge computing. For example, in the case where the above-mentioned I-SMF is added or replaced, a UL CL UPF and a PSA UPF in the service area of ​​the future I-SMF are selected in S317 of Figure 27. In this case, when UE 50 performs a handover from a cell in the service area of ​​the current SMF to a cell in the service area of ​​the future I-SMF, the future I-SMF holds handover pre-configuration information including information on the selected I-UPF (UL CL and PSA). Therefore, a session establishment process related to handover is performed between the selected UL CL and PSA included in the handover pre-configuration information without performing a process of selecting a new I-UPF. As a result, even in scenario #3, for example, even when local breakout is set, the time required for handover can be shortened, and the time of communication interruption due to handover can be further shortened. Note that in scenario #3, the PDU session pre-setting sequence and PDU session establishment sequence are the same as in scenario #1.

[0254] 29 is a diagram showing an example of a handover pre-configuration sequence in scenario #4. Scenario #4 is a scenario in which the route of UE 50 is neither within the region of the current AMF 7A nor within the service area of ​​the current SMF 6A. Therefore, scenario #4 is a scenario in which AMF replacement and I-SMF insertion, replacement, or removal occur. Therefore, the cell transition information in scenario #4 includes cells within the region of the current AMF 7A and cells outside the region of the current AMF 7A, as well as cells within the service area of ​​the current SMF 6A and cells outside the service area of ​​the current SMF 6A. In addition, in the cell transition information in scenario #4, it is assumed that transition from a cell within the service area of ​​the current SMF 6A to a cell outside the service area of ​​the current SMF 6A occurs outside the region of the current AMF 7A.

[0255] The sequence illustrated in Fig. 29 is a continuation of the sequence illustrated in Fig. 20. S400 is the same process as S24 in Fig. 20, and the current AMF 7A receives a handover pre-configuration request, identification information of the UE 50, a pre-configured ID, and cell transition information from the NEF 3 (OP31 in Fig. 14: YES).

[0256] In S411, for handover between cells within the region of the current AMF 7A included in the cell transition information, a sequence similar to S111-S116 of scenario #1 is executed. Also, for handover from a cell within the region of the current AMF 7A included in the cell transition information to a cell outside the region of the current AMF 7A included in the cell transition information, a sequence similar to S212-S218 of scenario #2 is executed. It is assumed that AMF 7C is selected as a future AMF in S411.

[0257] The sequence from S412 to S422 is a handover pre-configuration sequence for handover from a cell in the service area of ​​the current SMF 6A to a cell outside the service area of ​​the current SMF 6A, within the region of the future AMF 7C, which is included in the cell transition information. In S412, since the cell transition information includes a transition to a cell outside the service area of ​​the current SMF 6A (YES in OP324 in FIG. 15 ), the future AMF 7C selects a future SMF and selects SMF 6D as the future SMF (OP325 in FIG. 15 ).

[0258] The processes from S413 to S420 are the same as the processes from S313 to S320 in scenario #3, except that the current AMF 7A is replaced with the future AMF 7C and the future SMF 6B is replaced with the future SMF 6D. In S413, the future AMF 7C transmits a handover pre-configuration request to the selected future SMF 6D by using an Nsmf_PDUSession_CreateSMContext request message (OP326 in FIG. 15 ).

[0259] In S414, the future SMF 6D determines to perform UPF selection because it does not hold information about the PDU session to be handed over (OP42 in FIG. 18 : YES). In S415, the future SMF 6D transmits an Nsmf_PDUSession_Context request message to the current SMF 6A. In S416, the current SMF 6A receives the Nsmf_PDUSession_Context request message and transmits an Nsmf_PDUSession_Context response message to the future SMF 6D, including the SM context corresponding to the specified SM context ID.

[0260] In S417, the future SMF 6D selects a UPF for the PDU session to be handover (OP43 in FIG. 18 ). In S418, the future SMF 6D stores the information received in S413 and S416 and the execution result of the processing of S417 as handover preset information together with the preset ID (OP44 in FIG. 18 ). For example, the future SMF 6D stores, for each PDU session, a PDU session ID, an SM context ID, the ID of the current SMF 6A as the old SMF ID, the ID of the future AMF 7C corresponding to the SM context ID, and the ID of the UPF selected in S417 as the selected SMF ID, together with the ID and preset ID of the cell in the service area of ​​the future SMF 6D to which transition is made from the cell in the service area of ​​the current SMF 6A in the cell transition information as the target RAN ID in the configuration information storage unit 62 as handover preset information for the UE 50 (see FIG. 11 ).

[0261] In S419, the future SMF 6D sends a response to the handover pre-configuration request to the future AMF 7C by using an Nsmf_PDUSession_CreateSMContext response message (OP45 in FIG. 18 ). In S420, the future AMF 7C stores the information received in S319 together with the pre-configuration ID as handover pre-configuration information (OP38C in FIG. 14 ). For example, the future AMF 7C stores, for each PDU session, the PDU session ID, the SM context ID, and the ID of the future SMF 6D as handover pre-configuration information for the UE 50 in the configuration information storage unit 72 together with the ID of the cell in the service area of ​​the future SMF 6D and the pre-configuration ID included in the cell transition information as the target RAN ID (see FIG. 10 ).

[0262] In S421, the future AMF 7C transmits a response to the handover pre-configuration request by using a Namf_Communication_CreateUEContext response message to the current AMF 7A (OP38D in FIG. 14 ). In S422, the current AMF 7A stores the information received in S421 together with the pre-configuration ID as handover pre-configuration information (OP36 in FIG. 14 ). For example, the current AMF 7A stores, for each PDU session, the PDU session ID, the SM context ID, the ID of the current SMF 6A corresponding to the SM context ID, and the ID of the future AMF 7C as the target AMF ID, together with the ID of the cell in the region of the future AMF 7C included in the cell transition information as the target RAN ID and the preset ID, in the configuration information storage unit 72 as handover preset information for the UE 50 (see FIG. 10 ).

[0263] In S423, the current AMF 7A transmits a response to the handover pre-configuration request to the NEF 3 (OP37 in FIG. 14 ). The NEF 3 receives the response to the handover pre-configuration request (OP25 in FIG. 13 : YES). Through the handover pre-configuration sequence in FIG. 29 , the handover pre-configuration in the 5CG 10 in scenario #4 is completed.

[0264] FIG. 30 is a diagram showing an example of a handover sequence in scenario #4. FIG. 30 assumes that the pre-configuration sequences of FIG. 20 and FIG. 29 have been completed in the 5CG 10. It is also assumed that the UE 50 is moving on a route based on the route information notified in S11 of FIG. 20. In FIG. 30, it is assumed that the cell located at the boundary of the region of the current AMF 7A and the cell located at the boundary of the service area of ​​the current SMF 6A are the same cell, and when the UE 50 moves from a cell in the region of the current AMF 7A to a cell in the region of the current AMF 7A, a transition from a cell in the service area of ​​the current SMF 6A to a cell outside the service area of ​​the current SMF 6A also occurs.

[0265] In the example of Fig. 30, it is assumed that the current SMF 6A is an I-SMF. It is also assumed that the cell outside the service area of ​​the current SMF 6A, which is the destination of movement from a cell within the service area of ​​the current SMF 6A, is not a cell within the service area of ​​the original SMF 6E. Therefore, in the example of Fig. 30, the I-SMF is replaced by a handover when moving from a cell within the service area of ​​the current SMF 6A to a cell outside the service area of ​​the current SMF 6A.

[0266] In the example of Figure 30, the target RAN is a cell outside the region of the current AMF 7A to which UE 50 transitions from a cell within the region of the current AMF 7A in the cell transition information, and is a cell outside the region of the current SMF 6A to which UE 50 transitions from a cell within the region of the current SMF 6A. In Figure 30, the current AMF 7A in Figure 29 is referred to as the source AMF 7A, the future AMF 7C is referred to as the target AMF 7C, the current SMF 6A is referred to as the source SMF 6A, and the future SMF 6D is referred to as the target SMF 6D.

[0267] In S451, the target RAN sends a Handover Required message corresponding to a handover request to the source AMF 7A. The Handover Required message includes, as part of the information, identification information of the UE 50 and a target RAN ID. The source AMF 7A receives the Handover Required message.

[0268] In S452, the source AMF 7A searches for handover pre-configuration information in the configuration information storage unit 72 using the identification information of the UE 50 and the target RAN ID included in the Handover Required message as keys, and detects, for example, the handover pre-configuration information stored in S422 of Fig. 29 as the corresponding handover pre-configuration information. The detected handover pre-configuration information includes the PDU session ID and the ID of the selected target AMF 7C (see Fig. 10). Therefore, in S452, the source AMF 7A does not select a target AMF.

[0269] In S453, the source AMF 7A sends a Namf_Communication_CreateUEContext request message including information indicating a handover request to the target AMF 7C. The Namf_Communication_CreateUEContext request message includes, as one piece of information, a UE context for the UE 50 held by the source AMF 7A, a target RAN ID, etc. In the example shown in FIG. 30 , the target RAN ID is the ID of a cell in the region of the future AMF 7C to which the UE 50 transitions from a cell in the region of the current AMF 7A. The UE context for the UE 50 also includes, for example, a PDU session ID, an SM context ID for each PDU session, and the ID of the SMF responsible for managing the PDU session. A preconfigured ID is also sent together with the Namf_Communication_CreateUEContext request message. The target AMF 7C receives the Namf_Communication_CreateUEContext request message.

[0270] In S454, the target AMF 7C searches for handover pre-configuration information in the configuration information storage unit 72 using the ID of the UE 50, the target cell ID, the pre-configuration ID, and the PDU session ID received together with the Namf_Communication_CreateUEContext request message as keys, and detects the handover pre-configuration information stored in S420 of Fig. 29 as the corresponding handover pre-configuration information. The detected handover pre-configuration information includes the pre-configuration ID, the SM context ID, and the ID of the target SMF 6D as the selected SMF ID (see Fig. 10). Therefore, in S454, the target MF 7C does not perform SMF selection.

[0271] In S455, the target AMF 7C transmits an Nsmf_PDUSession_CreateSMContext request message to the target SMF 6D included in the handover pre-configuration information detected in S454. The Nsmf_PDUSession_CreateSMContext request message includes identification information of the UE 50, information indicating the handover request, the target RAN ID, the SM context ID and PDU session ID included in the handover pre-configuration information detected in S454, and the ID of the source SMF 6A as the old SMF ID. The ID of the source SMF 6A as the old SMF ID is the SMF ID associated with the PDU session to be handed over in the context information of the UE 50 received by the target AMF 7C from the source AMF 7A in S453. Also sent together with the Nsmf_PDUSession_CreateSMContext request message is a preset ID corresponding to the handover preset information detected in S454. The target SMF 6D receives the Nsmf_PDUSession_CreateSMContext request message.

[0272] In S456, the target SMF 6D searches for handover pre-configuration information in the configuration information storage unit 62 using the identification information of the UE 50, the pre-configuration ID, the target RAN ID, and the PDU session ID included in the Nsmf_PDUSession_CreateSMContext request message received in S455 as keys, and detects the handover pre-configuration information stored in S418 of Fig. 29 as the search result. In the example shown in Fig. 30, the detected handover pre-configuration information includes the ID of the source SMF 6A as the old SMF ID and the selected UPF ID. Therefore, in Fig. 30, the target SMF 6D does not determine whether to perform UPF selection and does not select a UPF. The detected handover pre-configuration information also includes the SM context in the source SMF 6A acquired in S416 of Fig. 29.

[0273] In S457, the target SMF 6D performs an N4 session establishment procedure with the selected UPF (target I-UPF) included in the handover pre-configuration information detected in S456. The target SMF 6D notifies the target I-UPF of information about the PDU session with the PSA, and the target I-UPF prepares to establish a PDU session with the PSA. The information about the PDU session with the PSA is included in the SM context detected in S456. In addition, the target I-UPF prepares to establish a PDU session with the target RAN.

[0274] At S458, the target SMF 6D sends a Nsmf_PDUSession_CreateSMContext response message to the target AMF 7A. The Nsmf_PDUSession_CreateSMContext response message includes information about the PDU session between the target I-UPF and the target RAN.

[0275] At S459, the target AMF 7C sends a Handover Request message to the target RAN. The Handover Request message is a message requesting the target RAN to prepare for handover. At S460, the target RAN sends a Handover Request Acknowledge message to the target AMF 7C indicating acceptance of the handover in the target RAN.

[0276] In S461, the target AMF 7C sends an Nsmf_PDUSession_UpdateSMContext request message including information indicating acceptance of the handover in the target RAN to the target SMF 6D. The Nsmf_PDUSession_UpdateSMContext request message includes configuration information of the PDU session in the target RAN.

[0277] In S462, the target SMF 6D performs an N4 session modification procedure with the target I-UPF. In S462, the target I-UPF is notified of the PDU session configuration information in the target RAN. In addition, the target I-UPF prepares for indirect forwarding between the source I-UPF and the target I-UPF to forward data from the UE 50 generated during handover from the source RAN to the target RAN.

[0278] In S463, the target SMF 6D sends an Nsmf_PDUSession_UpdateSMContext request message to the source SMF 6A. The Nsmf_PDUSession_UpdateSMContext request message sent in S463 includes information about indirect forwarding between the source I-UPF and the target I-UPF. In S464, the source SMF 6A performs an N4 session modification procedure with the source I-UPF. In S464, the source I-UPF is notified of information about indirect forwarding, and the source I-UPF prepares for indirect forwarding with the target I-UPF.

[0279] In S465, the source SMF 6A sends an Nsmf_PDUSession_UpdateSMContext response message to the target SMF 6D to notify that the indirect forwarding configuration has been completed. In S466, the target SMF 6D sends an Nsmf_PDUSession_UpdateSMContext response message to the target AMF 7C in response to the Nsmf_PDUSession_UpdateSMContext request message received in S461. The Nsmf_PDUSession_UpdateSMContext response message includes information about indirect forwarding to notify the source RAN.

[0280] In S467, the target AMF 7C transmits a Namf_Communication_CreateUEContext response message to the Namf_Communication_CreateUEContext request message received in S453 to the source AMF 7A. The Namf_Communication_CreateUEContext response message includes information about indirect forwarding to notify the source RAN.

[0281] In S468, the source AMF 7A sends a Handover Command message to the source RAN to notify it that preparation for handover within the 5GC 10 has been completed. At the same time, information about indirect forwarding is also notified to the source RAN. After that, the handover sequence is executed in accordance with the handover execution procedure disclosed in 4.23.7.3.3 of 3GPP TS23.502, for example.

[0282] In the handover sequence in scenario #4 shown in Figure 30, the selection of the target AMF by the source AMF 7A in S452, the selection of the target SMF by the target AMF 7C in S454, the selection of the UPF by the target SMF 6D in S456, and the acquisition of the SM context from the source SMF 6A have already been performed in the handover pre-configuration sequence in Figure 29, and are skipped in the handover sequence in Figure 30. This makes it possible to shorten the time required for handover and further shorten the time of communication interruption due to handover, even in a handover in which the SMF service area changes along with the change of the AMF region, as in scenario #4.

[0283] 30 has been described as an example in which the current SMF (source SMF) 6A is an I-SMF, and the handover destination cell is a cell within the service area of ​​another SMF other than the original SMF, so that the I-SMF is replaced with a new I-SMF. This is not limited to this, and the time required for the handover sequence can also be shortened in the same way as in the example shown in FIG. 30 in cases in which the current SMF is an I-SMF, the handover destination cell is a cell within the service area of ​​the original SMF, so that the I-SMF is released, and in cases in which the current SMF is the original SMF, and the handover destination cell is a cell within the service area of ​​another SMF, so that an I-SMF is added.

[0284] Also in scenario #4, for example, when local breakout such as edge computing is configured, the handover pre-configuration sequence shown in Figure 29 can be applied, as in scenario #3. Note that in scenario #4, the PDU session pre-configuration sequence and PDU session establishment sequence are the same as in scenario #1.

[0285] <Effects of the First Embodiment> In the first embodiment, the time required for handover and PDU session establishment can be shortened by pre-setting the 5GC 10 in advance of the movement route of the UE 50. This can shorten the time for communication interruption due to handover and reduce degradation in communication quality. In addition, the time required for PDU session establishment can be shortened, allowing the UE 50 to start communication through the PDU session more quickly. Furthermore, since QoS is set in advance for a predetermined application, communication related to the application can be started more quickly with communication quality appropriate for the UE 50.

[0286] <Second embodiment> In the second embodiment, cell transition information of the UE 50 is acquired by utilizing the UE mobility prediction function of the NWDAF 8. In the second embodiment, descriptions common to the first embodiment will be omitted. In the second embodiment, the hardware configuration and functional configuration of each NF are the same as those in the first embodiment.

[0287] 31 is a diagram illustrating processing in a communication system 100B according to the second embodiment. In the second embodiment, the AF 1 transmits a pre-configuration request for the UE 50 to the 5CG 10. However, unlike the first embodiment, the AF 1 does not transmit route information for the UE 50. Also, in the second embodiment, the AF 1 does not need to transmit a pre-configuration request for the UE 50 every time a route is configured in the UE 50.

[0288] Upon receiving the pre-configuration request, the NEF 3 starts monitoring the movement of the UE 50, and when it detects that the UE 50 has started moving, it acquires movement prediction information of the UE 50 from the NWDAF 8. The movement prediction information of the UE 50 acquired from the NWDAF 8 includes, for example, identification information of cells in which the UE 50 may be located during a predetermined period, in order of time slots. The NEF 3 transmits the movement prediction information acquired from the NEF 8 as cell transition information to the AMF 1 together with the handover pre-configuration request.

[0289] 32 is an example of a flowchart of the process of AF 1 in the second embodiment. The process shown in FIG. 32 is repeatedly executed at a predetermined cycle. In the second embodiment, it is assumed that AF 1 receives location information from UE 50 at a predetermined cycle.

[0290] In OP61, the AF 1 determines whether or not the UE 50 has started moving. The start of movement of the UE 50 is detected, for example, by a change in the position of the UE 50. If the UE 50 has started moving (OP61: YES), the processing proceeds to OP62. If the UE 50 has not started moving (OP61: NO), the processing shown in Fig. 32 ends.

[0291] In OP62, the AF 1 transmits a pre-configuration request to the NEF 3. The identification information of the UE 50 is also transmitted together with the pre-configuration request. In OP63, the AF 1 determines whether or not a response to the pre-configuration request has been received. If a response to the pre-configuration request has been received (OP63: YES), the processing proceeds to OP64. If a response to the pre-configuration request has not been received (OP63: NO), the AF 1 enters a standby state.

[0292] In OP64, the AF 1 determines whether or not the movement of the UE 50 has ended. The end of the movement of the UE 50 is detected, for example, when the location information of the UE 50 does not change for a predetermined time. If the movement of the UE 50 has ended (OP64: YES), the processing proceeds to OP65. If the movement of the UE 50 has not ended (OP64: NO), the AF 1 enters a standby state.

[0293] In OP65, the AF 1 notifies the NEF 3 of the end of the movement of the UE 50. After that, the process shown in Fig. 32 ends.

[0294] Fig. 33 is an example of a flowchart of processing related to pre-setting of the NEF 3 according to the second embodiment. The processing shown in Fig. 33 is repeatedly executed at a predetermined cycle. In OP71, the NEF 3 determines whether or not a pre-setting request has been received from the AF 1. If a pre-setting request has been received from the AF 1 (OP71: YES), the processing proceeds to OP72. If a pre-setting request has not been received from the AF 1 (OP71: NO), the processing shown in Fig. 33 ends.

[0295] In OP72, the NEF 3 starts monitoring the location of the UE 50. Specifically, the NEF 3 registers notification of the serving cell of the UE 50 with the AMF 7, and periodically acquires the serving cell of the UE 50.

[0296] In OP73, the NEF 3 inquires of the NWDAF 8 and acquires movement prediction information of the UE 50. In OP74, the NEF 3 executes the processes of OP23 to OP27 in Fig. 13 using the movement prediction information acquired from the NWDAF 8 as cell transition information. As a result, pre-settings related to wireless communication for the UE 50 in the 5CG 10 are performed.

[0297] In OP75, the NEF 3 determines whether or not the UE 50 has moved out of the cell included in the cell transition information, based on the notification of the serving cell of the UE 50 from the AMF 7. If the UE 50 has moved out of the cell included in the cell transition information (OP75: YES), the processing proceeds to OP73, and is executed again from obtaining movement prediction information of the UE 50. If the UE 50 has not moved out of the cell included in the cell transition information (OP75: NO), the processing proceeds to OP76.

[0298] In OP76, the NEF 3 determines whether or not the movement of the UE 50 has ended. The NEF 3 detects the end of the movement of the UE 50 by receiving a notification of the end of the movement of the UE 50 from the AF 1. If the movement of the UE 50 has ended (OP76: YES), the processing proceeds to OP77. If the movement of the UE 50 has not ended (OP76: NO), the processing proceeds to OP75. In OP77, the NEF 3 ends the location monitoring of the UE 50. Specifically, the NEF 3 transmits a message to the AMF 7 to cancel the registration of notification of the serving cell of the UE 50. Then, the processing shown in FIG. 33 ends.

[0299] 34 shows an example of a processing sequence from when a pre-configuration request is transmitted from AF 1 to when the pre-configuration request is transmitted to the current AMF in the second embodiment. In the example shown in FIG. 34, it is assumed that UE 50 has been registered in the region of current AMF 7A and one PDU session has been established under the management of current SMF 6A. It is also assumed that the QoS configuration sequence for the target application (S12 to S18 in FIG. 20) has been executed.

[0300] In S501, the AF 1 detects that the UE 50 has started to move from the location information of the UE 50 that is periodically received. In S502, the AF 1 transmits a pre-configuration request to the NEF 3. The identification information of the UE 50 is transmitted together with the pre-configuration request transmitted in S501. The NEF 3 receives the pre-configuration request ( FIG. 33 , OP71: YES).

[0301] In S511, the NEF 3 transmits a Namf_EventExposure_Subscribe request message to the AMF 7 in which the UE 50 is registered, for registering notification of the serving cell of the UE 50. The AMF 7 in which the UE 50 is registered is identified, for example, by making an inquiry to the UDM 2. The Namf_EventExposure_Subscribe request message includes "Location Reporting" as the target event ID and the ID of the UE 50 as the target UE ID. In S512, the AMF 7 transmits a Namf_EventExposure_Subscribe response message to the NEF 3. As a result, the serving cell of the UE 50 is notified from the AMF 7 to the NEF 3 periodically at a predetermined cycle, and the NEF 3 starts monitoring the location of the UE 50 (OP72 in FIG. 33 ).

[0302] In S513, the NEF 3 transmits an Nnwdaf_AnalyticsInfo_Request message requesting movement prediction information of the UE 50 to the NWDAF 8. The Nnwdaf_AnalyticsInfo_Request message includes "UE Mobility" as the Analytics ID and the ID of the UE 50 as the target UE ID. In S514, the NWDAF 8 transmits an Nnwdaf_AnalyticsInfo_Request response message including the movement prediction information of the UE 50 to the NEF 3. The NEF 3 acquires the movement prediction information of the UE 50 (OP73 in FIG. 33 ).

[0303] In S515, the NEF 3 identifies the current AMF 7A to be configured (OP74 in FIG. 33 ). In S516, the NEF 3 transmits a handover pre-configuration request to the current AMF 7A (OP74 in FIG. 33 ). The NEF 3 transmits the pre-configuration ID, identification information of the UE 50, and cell transition information together with the handover pre-configuration request.

[0304] In S521, the AMF 7 notifies, at a predetermined period, the cell in which the UE 50 is located. When it is detected that the UE 50 has moved out of the cell included in the cell change information, the sequence starts again from S513.

[0305] According to the second embodiment, by utilizing the UE movement prediction function of the NWDAF 8, even if route information of the UE 50 cannot be obtained, it is possible to perform pre-configuration regarding wireless communication for the UE 50 in the 5GC 10 in advance of the movement of the UE 50.

[0306] <Modification of Second Embodiment> In the second embodiment, the AF 1 acquires location information of the UE 50 from the UE 50, detects when the UE 50 starts moving, and transmits a pre-configuration request to the NEF 3. Instead, in a modification of the second embodiment, the NEF 3 periodically acquires location information of the UE 50 from the NWDAF 8 and detects when the UE 50 starts moving. In the modification of the second embodiment, descriptions common to the second embodiment will be omitted. In the modification of the second embodiment, the AF 1 does not detect when the UE 50 starts moving or when it stops moving, but transmits a pre-configuration request to the NEF 3.

[0307] Fig. 35 is an example of a flowchart of a process related to pre-configuration of the NEF 3 according to a modification of the second embodiment. The process shown in Fig. 35 is started when the NEF 3 receives a pre-configuration request from the AF 1. The process shown in Fig. 35 is stopped, for example, when an instruction to stop the pre-configuration process is received from the AF 1.

[0308] When the NEF 3 receives a pre-configuration request from the AF 1 (OP81: YES), the process proceeds to OP82. In OP82, the NEF 3 registers periodic notification of the location information of the UE 50 with the NWDAF 8. Thereafter, the NEF 3 periodically acquires the location information of the UE 50 from the NWDAF 8. The location information of the UE 50 acquired from the NWDAF 8 is indicated by, for example, latitude and longitude. The location information of the UE 50 acquired from the NWDAF 8 may also include the serving cell of the UE 50.

[0309] In OP83, the NEF 3 determines whether the UE 50 has started to move, based on the location information of the UE 50. For example, when there is a change in the location information of the UE 50, the start of movement of the UE 50 is detected. When the UE 50 has started to move (OP83: YES), the processing proceeds to OP84. The NEF 3 remains in a standby state until the UE 50 starts to move (OP83: NO).

[0310] In OP84, the NEF 3 acquires movement prediction information of the UE 50 from the NWDAF 8, and in OP85, executes the processes from OP23 to OP27 in FIG. 13 using the movement prediction information as cell transition information.

[0311] In OP86, the NEF 3 determines whether the UE 50 has moved out of the cell included in the cell transition information, based on the location information of the UE 50 periodically notified by the NWDAF 8. If the UE 50 has moved out of the cell included in the cell transition information (OP86: YES), the processing proceeds to OP84, and is executed again from obtaining movement prediction information of the UE 50. If the UE 50 has not moved out of the cell included in the cell transition information (OP86: NO), the processing proceeds to OP87.

[0312] In OP87, the NEF 3 determines whether or not the movement of the UE 50 has ended, based on the location information of the UE 50 periodically notified from the NWDAF 8. If the movement of the UE 50 has ended (OP87: YES), the processing proceeds to OP83. If the movement of the UE 50 has not ended (OP87: NO), the processing proceeds to OP86.

[0313] 36 illustrates an example of a processing sequence from when a pre-configuration request is transmitted from AF 1 to when the pre-configuration request is transmitted to the current AMF in a modified example of the second embodiment. The premise of the example illustrated in FIG. 36 is the same as the example illustrated in FIG. 34.

[0314] In S601, the AF 1 transmits a pre-configuration request to the NEF 3 together with the identification information of the UE 50. The NEF 3 receives the pre-configuration request ( FIG. 34 , OP81: YES).

[0315] In S602, the NEF 3 transmits an Nnwdaf_AnalyticsSubscription_Subscribe request message to the NWDAF 8, requesting periodic notification of the location information of the UE 50 (OP82 in FIG. 35 ). The Nnwdaf_AnalyticsSubscription_Subscribe request message includes "UE Mobility" as the target Analytics ID and identification information of the UE 50 as the target UE ID. In S603, the NWDAF 8 transmits an Nnwdaf_AnalyticsSubscription_Subscribe response message to the NEF 3. As a result, the NWDAF 8 periodically notifies the NEF 3 of the location information of the UE 50 at a predetermined cycle, and the NEF 3 starts monitoring the location of the UE 50.

[0316] In S604, the NWDAF 8 transmits an Nnwdaf_AnalyticsSubscription_Notify message to the NEF 3 to notify the NEF 3 of the location information of the UE 50. The Nnwdaf_AnalyticsSubscription_Notify message includes the location information of the UE 50. Thereafter, the NWDAF 8 notifies the NEF 3 of the location information of the UE 50 at predetermined intervals.

[0317] In S611, the UE 50 starts moving, and the NEF 3 detects the start of movement of the UE 50 based on the location information of the UE 50 notified from the NWDAF 8 (OP83 in FIG. 35 : YES). In S612, the NEF 3 transmits an Nnwdaf_AnalyticsInfo_Request message requesting movement prediction information of the UE 50 to the NWDAF 8. The Nnwdaf_AnalyticsInfo_Request message includes "UE Mobility" as the Analytics ID and the ID of the UE 50 as the target UE ID. In S613, the NWDAF 8 transmits an Nnwdaf_AnalyticsInfo_Request response message including the movement prediction information of the UE 50 to the NEF 3. The NEF 3 acquires the movement prediction information of the UE 50 (OP84 in FIG. 35 ).

[0318] In S614, the NEF 3 identifies the current AMF 7A to be configured (OP85 in FIG. 35 ). In S615, the NEF 3 transmits a handover pre-configuration request to the current AMF 7A (OP85 in FIG. 35 ). The NEF 3 transmits the pre-configuration ID, identification information of the UE 50, and cell transition information together with the handover pre-configuration request.

[0319] Thereafter, when the NEF 3 detects, based on the location information of the UE 50 notified from the NWDAF 8, that the UE 50 has moved out of the cell included in the cell transition information (OP86 in FIG. 35 : YES), the NEF 3 performs the process from S612.

[0320] According to the modified example of the second embodiment, by utilizing the UE movement statistics function of the NWDAF 8, it is possible to pre-configure the UE 50 without the UE 50 periodically notifying the location information of the UE 50, and it is possible to reduce the wireless communication with the AF 1.

[0321] In a modification of the second embodiment, the location information and movement prediction information of the UE 50 are acquired from the NWDAF 8 by different messages (see S604 and S613). This is not limiting, and the location information and movement prediction information of the UE 50 can be acquired from the NWDAF 8 by the same message. In this case, the movement prediction information, together with the location information of the UE 50, is periodically notified from the NWDAF 8 to the NEF 3 by an Nnwdaf_AnalyticsSubscription_Notify message. In this case, the NEF 3 may detect that the UE 50 has deviated from the cell transition information by detecting a change in the content of the movement prediction information that is periodically notified (OP86 in FIG. 35 ).

[0322] Other Embodiments The above-described embodiment is merely an example, and the present disclosure can be implemented with appropriate modifications within the scope of the gist thereof.

[0323] In the first and second embodiments, the NEF 3 has a function of controlling pre-configuration related to wireless communication for the UE 50 in the 5GC 10. Without being limited to this, a new NF may have a function of controlling pre-configuration. The new NF receives a pre-configuration request and cell transition information through the NEF 3, identifies the AMF that manages the UE 50, and sends a pre-configuration request to the AMF.

[0324] In the first and second embodiments, existing messages (Nsmf_PDUSession_Create / UpdateSMContext, Namf_Commnication_CreateUEContext) in the 3GPP standard are used for transmitting pre-configuration requests and responses between an AMF and an SMF and between AMFs, but are not limited to this. New messages for pre-configuration may be used for transmitting pre-configuration requests and responses between an AMF and an SMF and between AMFs.

[0325] In the first and second embodiments, the QoS setting for a specific application may be performed before the UE 50 starts moving, regardless of the timing at which the pre-setting request is transmitted.

[0326] In the first and second embodiments, handover pre-configuration may be performed only when UE 50 is establishing a PDU session for a predetermined application. The predetermined application is, for example, an application that transmits and receives large amounts of data and requires low latency, such as a metaverse application. Whether UE 50 is establishing a PDU session for the target application can be obtained, for example, by NEF 3 querying UDM 2. NEF 3 may send a handover pre-configuration request to the current AMF when UE 50 is establishing a PDU session for the predetermined application, and may decide not to perform handover pre-configuration when UE 50 is not establishing a PDU session for the predetermined application.

[0327] In the first and second embodiments, the QoS of a specific application is configured in accordance with the handover pre-configuration and the PDU session pre-configuration, but in addition to this, a network slice selection policy may also be configured.

[0328] In the first and second embodiments, the pre-configuration information held by each NF may be deleted from each NF when triggered by the expiration of a timer, reflection in a context, or receipt of a response to a pre-configuration request.

[0329] In the first and second embodiments, the NEF 3 sends a pre-configuration request to the current AMF, but is not limited to this. The NEF 4 may perform, for example, AMF selection, SMF selection, and UPF selection performed in Figures 21, 22, 25, 27, and 29, and notify each AMF and each SMF of the selection result together with the pre-configuration request. Information used for these NF selections may be collected, for example, from the UDM 2, the NWDAF 8, and each NF.

[0330] Although the first and second embodiments have been described assuming a 5G system, the present invention is not limited to this. The techniques described in the first and second embodiments may be applied to, for example, systems of mobile communication methods of 5G and later generations.

[0331] The processes and means described in this disclosure can be freely combined and implemented as long as no technical contradiction occurs.

[0332] Furthermore, a process described as being performed by one device may be shared and executed by multiple devices. Alternatively, a process described as being performed by different devices may be executed by a single device. In a computer system, the hardware configuration (server configuration) by which each function is realized can be flexibly changed.

[0333] The present disclosure can also be realized by supplying a computer program that implements the functions described in the above embodiments to a computer, and having one or more processors in the computer read and execute the program. Such a computer program may be provided to the computer on a non-transitory computer-readable storage medium connectable to the computer's system bus or via a network. Non-transitory computer-readable storage media include, for example, any type of disk, such as a magnetic disk (e.g., a floppy disk, a hard disk drive (HDD), etc.), an optical disk (e.g., a CD-ROM, a DVD disk, a Blu-ray disk), a read-only memory (ROM), a random access memory (RAM), an EPROM, an EEPROM, a magnetic card, a flash memory, an optical card, or any type of medium suitable for storing electronic instructions.

[0334] DESCRIPTION OF SYMBOLS 1 AF 2 UDM 3 NEF 4 UDR 5 PCF 6 SMF 7 AMF 8 NWDAF 10 5G core 11, 31, 61, 71 Control unit 32 Geographic information conversion unit 50 UE 62, 72 Setting information storage unit 100 Communication system 101 Processor 102 Memory 103 Auxiliary storage device 104 Communication unit 110 Information processing device

Claims

1. A system comprising a plurality of NFs (Network Functions) that perform the following operations: acquire, before the UE moves from or to a first cell, second information to be used in providing wireless communication to the UE when the UE moves from or to a first cell that is a serving cell among the one or more cells, based on first information including information about one or more cells that the UE is predicted to be in as the UE moves; and when the UE moves from or to the first cell, perform a first process related to providing wireless communication to the UE using the second information without performing a process related to acquiring the second information.

2. The system according to claim 1, wherein the plurality of NFs further executes storing the second information in a storage unit so as to be designated as a pre-setting.

3. The system according to claim 2, wherein when the plurality of NFs send a request to another NF using the second information while the first process is being executed, the plurality of NFs send the request together with information indicating that the request has been pre-configured.

4. The system according to claim 3, wherein the plurality of NFs, when receiving a request accompanied by information indicating that the information is pre-configured from another NF while executing the first process, search the storage unit for the second information.

5. The system according to claim 1, wherein the plurality of NFs acquire the second information by executing a second process that is part of the first process.

6. The system described in claim 1, further comprising a first NF that performs the following: acquiring the first information; and transmitting a first request requesting pre-configuration of wireless communication for the UE and the first information to a second NF among the plurality of NFs; wherein the plurality of NFs acquire the second information in response to the second NF receiving the first request.

7. The system according to claim 6, wherein the first NF acquires the first information from route information held by the UE.

8. The system according to claim 6, wherein the first NF acquires the first information from a Network Data Analytics Function (NWDAF).

9. The system described in claim 6, wherein the second NF is an AMF (Access and Mobility Management Function) in charge of managing the mobility of the UE, and performs the following: receiving the first request; and transmitting a second request to a third NF that has as its serving cell at least one of the one or more cells included in the first information, requesting pre-configuration of wireless communication for the UE; and when the third NF receives the second request, performs pre-configuration of wireless communication for the UE.

10. The system according to claim 9, wherein the second NF, when the first information includes a cell other than a cell served by the second NF, transmits the second request as the third NF to an AMF that is responsible for a cell other than a cell served by the second NF included in the first information.

11. The system described in claim 10, wherein the second NF, when the first information includes a cell other than the cell served by the second NF, acquires information about the third NF as one of the second information by selecting an AMF as the third NF from the multiple NFs based on the first information, and when the UE moves from the cell served by the second NF as the first cell to the cell served by the AMF as the third NF, performs the handover processing as the first processing using the acquired information about the third NF without selecting an AMF.

12. The system according to claim 9, wherein one or more AMFs included in the plurality of NFs, when receiving the first request or the second request and when the serving cells of one or more of their own AMFs included in the first information include a second cell other than the serving cell of a first SMF (Session Management Function) managing a first session established with the UE, transmit a third request to the first SMF and a second SMF that may manage the first session in the second cell, requesting pre-configuration related to wireless communication for the UE; and when the first SMF and the second SMF receive the third request, perform pre-configuration related to handover of the first session.

13. The system described in claim 12, wherein the one or more AMFs: select the second SMF from the plurality of NFs based on the first information, thereby acquiring information about the selected second SMF as one of the second information; and when the UE moves to the second cell as the first cell, executes the handover processing as the first processing using the acquired information about the second SMF without selecting an SMF.

14. The system described in claim 12, wherein the first SMF, when receiving the third request and when the serving cells of one or more of the first SMFs included in the first information include a third cell other than the serving cell of the first UPF with which the first session is being established, selects a second UPF with which the first session may be established in the third cell based on the first information, thereby acquiring information about the selected second UPF as part of the second information, and when the UE moves to the third cell as the first cell, performs the handover process as the first process using the acquired information about the second UPF without selecting a UPF.

15. The system described in claim 12, wherein the second SMF, when receiving the third request, selects a third UPF with which the first session may be established in the second cell based on the first information, thereby acquiring information about the selected third UPF as one of the second information, and when the UE moves to the second cell as the first cell, performs the handover process as the first process using the acquired information about the third UPF without selecting a UPF.

16. The system described in claim 9, wherein the second NF, when receiving the first request, as the third NF, sets at least one fourth cell among the one or more cells included in the first information as a serving cell, and transmits a fourth request requesting pre-configuration of wireless communication for the UE to a third SMF that may manage the second session when the UE requests establishment of the second session in the fourth cell; and the third SMF, when receiving the fourth request, performs pre-configuration for the UE regarding the establishment of the second session.

17. The system described in claim 16, wherein the second NF selects the third SMF from among the plurality of NFs based on the first information, thereby acquiring information about the third SMF as one of the second information, and when the UE requests establishment of the second session in the fourth cell, performs the process related to the establishment of the second session as the first process using the information about the third SMF without selecting the SMF.

18. The system described in claim 16, wherein the third SMF, when receiving the fourth request, selects a UPF with which the second session may be established in the fourth cell based on the first information, thereby obtaining information about the selected UPF as one of the second information, and when the UE requests establishment of the second session in the fourth cell, performs the first process for establishing the second session using the information about the UPF without selecting a UPF.

19. A method comprising: an NF (Network Function) acquiring, before the UE moves from or to the first cell, second information to be used in providing wireless communication to the UE when the UE moves from or to a first cell that is a serving cell among the one or more cells, based on first information including information about one or more cells in which the UE is predicted to be present as the UE moves; and, when the UE moves from or to the first cell, performing a first process related to providing wireless communication to the UE using the second information without performing a process related to acquiring the second information.

20. An information processing device comprising: a control unit that performs the following operations: acquires, before the UE moves from or to the first cell, second information used to provide wireless communication to the UE when the UE moves from or to a first cell that is a serving cell among the one or more cells, based on first information including information about one or more cells that the UE is predicted to be within as the UE moves; and when the UE moves from or to the first cell, performs a first process related to providing wireless communication to the UE using the second information without performing a process related to acquiring the second information.

Images