Communication device, communication method, and program

Abstract

The purpose of the present invention is to provide a communication device which can provide a communication service by differentiating terminals temporarily using a network. A communication device (10) according to the present disclosure constitutes a first public land mobile network (PLMN), the communication device (10) comprising: a communication unit (11) that, after temporarily being connected with a base station (20), receives, from a communication terminal via the base station (20), a request message for requesting establishment of a session with a second data network available in a second PLMN; and a control unit (12) that, after the request message is received, establishes a session between the communication terminal and a first data network available in the first PLMN.

Description

[Technical Field]

[0001] The present disclosure relates to a communication device, a base station, a communication method, and a non-transitory computer-readable medium. [Background technology]

[0002] When a failure occurs in a part of a network managed by a telecommunications carrier, the impact of the failure spreads to the entire network, and the entire network may become congested. When the entire network becomes congested, the network will be unable to provide communication services to all communication terminals requesting communication services. In such a case, a network configuration is being considered that allows communication terminals to select a network managed by another telecommunications carrier and use the communication services provided by that other telecommunications carrier.

[0003] Patent Document 1 discloses a process in which a base station that receives a connection request from a terminal selects a network to which the terminal will connect. For example, the base station identifies a network corresponding to the terminal and selects the identified network as the network to which the terminal will connect. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-144106 Summary of the Invention [Problem to be solved by the invention]

[0005] When the entire network becomes congested, it is assumed that communication terminals will temporarily use networks managed by other communication carriers. However, Patent Document 1 does not clearly describe a method for providing communication services to terminals that temporarily use the network, which poses a problem in that it is not possible to provide communication services by distinguishing between terminals that temporarily use the network and / or base stations that are temporarily connected.

[0006] In view of the above-mentioned problems, one of the objects of the present disclosure is to provide a communication device, a base station, a communication method, and a non-transitory computer-readable medium that can provide communication services by distinguishing between terminals that temporarily use a network and / or base stations that are temporarily connected. [Means for solving the problem]

[0007] A communication device according to a first aspect of the present disclosure is a communication device that constitutes a first Public Land Mobile Network (PLMN), and includes: a communication unit that, after temporarily connecting to a base station, receives a request message from a communication terminal via the base station, requesting the establishment of a session with a second data network available in a second PLMN; and a control unit that, after receiving the request message, establishes a session between the communication terminal and a first data network available in the first PLMN, wherein the first PLMN and the second PLMN are different.

[0008] A base station according to a second aspect of the present disclosure includes a communication unit that receives a notification message indicating a congestion state from a second communication device that constitutes a second PLMN, and a control unit that, after receiving the notification message, starts a process of establishing a connection with a first communication device that constitutes a first PLMN.

[0009] A communication method according to a third aspect of the present disclosure is a communication method executed in a communication device constituting a first Public Land Mobile Network (PLMN), which, after temporarily connecting to a base station, receives a request message from a communication terminal via the base station requesting the establishment of a session with a second data network available in a second PLMN, and after receiving the request message, establishes a session between the communication terminal and a first data network available in a first PLMN, the first PLMN and the second PLMN being different.

[0010] A program according to a fourth aspect of the present disclosure is a program to be executed by a computer that is a communication device constituting a first Public Land Mobile Network (PLMN), and causes the computer to execute the following: after temporarily connecting to a base station, receive a request message from a communication terminal via the base station requesting establishment of a session with a second data network available in a second PLMN; and, after receiving the request message, establish a session between the communication terminal and a first data network available in the first PLMN, which is different from the first PLMN and the second PLMN. [Effects of the Invention]

[0011] The present disclosure provides a communication device, a base station, a communication method, and a non-transitory computer-readable medium that can provide communication services by distinguishing between terminals that temporarily use a network and / or base stations that are temporarily connected. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a configuration diagram of a communication device according to a first embodiment. [Figure 2] 10 is a flowchart of a session establishment process executed in the communication device according to the first embodiment; [Figure 3] FIG. 2 is a configuration diagram of a base station according to the first embodiment. [Figure 4] 10 is a flowchart of a connection establishment process executed in the base station according to the first embodiment. [Figure 5] FIG. 10 is a configuration diagram of a communication system according to a second embodiment. [Figure 6] FIG. 10 is a diagram showing the processing flow when congestion occurs in the AMF according to the second embodiment. [Figure 7] FIG. 10 is a diagram showing the flow of registration processing according to the second embodiment. [Figure 8] A diagram showing the flow of the PDU session establishment process in embodiment 2. [Figure 9] FIG. 11 is a diagram showing the flow of registration processing according to the third embodiment. [Figure 10] This is a configuration diagram of a communication device, a base station, a gNB, and an AMF for each embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0013] (Embodiment 1) Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. An example configuration of a communication device 10 according to a first embodiment will be described with reference to FIG. 1. The communication device 10 may be software or a module that operates when a processor executes a program stored in a memory. The communication device 10 may be, for example, a node device that constitutes a communication network. The communication network may be, for example, a PLMN (Public Land Mobile Network). A PLMN is a network established and / or operated by a communication carrier to provide communication services. A PLMN is expressed by a five- to six-digit number that combines a "Mobile Country Code" (MCC) that indicates a country or region expressed as a three-digit number, and an "MNC" (Mobile Network Code) that indicates a carrier as a two- to three-digit number (varies depending on the country). In the following description, the communication device 10 will be described as a communication device that constitutes a first PLMN.

[0014] The communication device 10 includes a communication unit 11 and a control unit 12. The communication unit 11 and the control unit 12 may be software or modules that are executed by a processor executing a program stored in a memory, or may be hardware such as a circuit or a chip.

[0015] After temporarily connecting to base station 20, communication unit 11 receives a request message from the communication terminal via base station 20 requesting establishment of a session with a second data network available in a second PLMN. Base station 20 may be a base station constituting a first PLMN. Base station 20 may be a base station constituting a second PLMN.

[0016] The communication unit 11 temporarily connecting to the base station 20 may mean that the communication unit 11 temporarily establishes a connection with the base station 20. The state in which the connection is established may mean that a logical line is set between the communication device 10 and the base station 20. For example, the state in which the connection is established may mean that setting of a logical line using a protocol such as SCTP (Stream Control Transmission Protocol) or TCP (Transmission Control Protocol) is completed. In other words, the state in which the connection is established may mean that association is performed between the communication device 10 and the base station 20 using a protocol in the transport layer. The state in which the connection is established may mean, for example, that setup of a Next Generation (NG) interface between an Access and Mobility management Function (AMF) and a gNode B (gNB) in 5G is completed and communication using an application protocol is possible.

[0017] When a connection between the communication device 10 and the base station 20 is established, the communication device 10 and the base station 20 can transmit and receive messages via the established connection. The messages may be referred to as, for example, C (Control)-Plane data or control data.

[0018] The state in which a connection is temporarily established may mean, for example, maintaining the connection established for a predetermined period and releasing the connection after the predetermined period has elapsed. Releasing the connection may be rephrased as disconnecting the connection. The connection may be released autonomously after the predetermined period has elapsed, or may be released by a maintenance person or the like operating the communication device 10 or the base station 20. This allows the processing load in the PLMN of the communication device 10 to be managed when the base station 20 is different from the PLMN of the communication device 10.

[0019] The data network may be, for example, a network having a server device in which data used by a user is stored, or a server device that a user wishes to access. A network having a server device may be rephrased as a network to which a server device is connected.

[0020] The second PLMN is a network different from the first PLMN. The second data network available in the second PLMN may be a configuration in which the second data network is connected to the second PLMN, or a configuration in which the second PLMN includes the second data network.

[0021] A session indicates a logical or virtual communication path for carrying U-Plane (User) data transmitted or received by a communication terminal. U-Plane data may also be referred to as user data.

[0022] After receiving the request message, the control unit 12 establishes a session between the communication terminal and a first data network available in the first PLMN. Because the communication device 10 is a communication device that constitutes the first PLMN, the control unit 12 does not establish a session between the communication terminal and a second data network available in the second PLMN. Alternatively, if the control unit 12 does not manage the second data network or is not aware of the existence of the second data network, the control unit 12 cannot establish a session between the second data network and the communication terminal. In this case, the control unit 12 establishes a session between the first data network and the communication terminal instead of establishing a session between the second data network and the communication terminal.

[0023] When the control unit 12 receives a request message from the communication terminal via the temporarily connected base station 20, it establishes a session between the communication terminal and a first data network available in the first PLMN instead of the second data network. In other words, when the control unit 12 receives a request message from the communication terminal via a permanently connected base station, it may send to the communication terminal a message refusing to establish a session between the second data network and the communication terminal. The permanently connected base station may be a base station that maintains a connection except as long as no failure occurs in the base station or the communication device 10, or when it is necessary to disconnect the connection between the base station and the communication device 10 due to maintenance work.

[0024] Next, a flowchart of a session establishment process executed in the communication device 10 according to the first embodiment will be described with reference to Fig. 2. First, the communication unit 11, after temporarily connecting to the base station 20, receives a request message from the communication terminal via the base station 20 requesting establishment of a session with a second data network available in the second PLMN (S11). Next, the control unit 12 establishes a session between the communication terminal and a first data network available in the first PLMN instead of the second data network (S12).

[0025] Next, a configuration example of the base station 20 according to the first embodiment will be described with reference to Fig. 3. The base station 20 may be a computer device operated by a processor executing a program stored in a memory. The base station 20 performs wireless communication with a communication terminal in accordance with a predetermined communication standard. The communication standard may be, for example, a communication standard defined by the 3rd Generation Partnership Project (3GPP), such as a wireless communication standard called 5G.

[0026] The base station 20 has a communication unit 21 and a control unit 22. The communication unit 21 and the control unit 22 may be software or modules that perform processing by a processor executing a program stored in a memory, or may be hardware such as a circuit or a chip.

[0027] The communication unit 21 receives a notification message indicating a congestion state from a communication device constituting the second PLMN. When the communication device is in a congestion state, the communication terminal may not be able to receive communication services from the communication device in the congestion state.

[0028] After receiving the notification message, the control unit 22 starts processing to establish a connection with the first communication device constituting the first PLMN. Assume that the base station 20 has always been connected to the communication device constituting the second PLMN. When the base station 20 receives a notification message indicating a congestion state from the communication device constituting the second PLMN, the base station 20 temporarily connects to the communication device 10 constituting the first PLMN. This allows communication terminals connected to the PLMN via the base station 20 to continue to receive communication services. The control unit 22 may terminate the connection with the communication device constituting the second PLMN and start a connection with the communication device 10, or may start a connection with the communication device 10 while maintaining the connection with the communication device constituting the second PLMN.

[0029] Next, a flowchart of a connection establishment process executed in base station 20 according to the first embodiment will be described with reference to Fig. 4. First, communication unit 21 receives a notification message indicating a congestion state from a communication device constituting a second PLMN (S21). Next, after receiving the notification message, control unit 22 starts a process of establishing a connection with communication device 10 constituting a first PLMN (S22).

[0030] As described above, communication device 10 establishes a session between a communication terminal that requests the establishment of a session with a data network and the first data network via temporarily connected base station 20. That is, a session is established between the communication terminal that temporarily uses the first PLMN and the first data network. In this way, communication device 10 can provide communication services to a communication terminal that has transmitted a request message to the first PLMN because it is unable to use the second PLMN, allowing the communication terminal to use the first data network.

[0031] (Embodiment 2) Next, a configuration example of a communication system according to the second embodiment will be described with reference to FIG. In the communication system of FIG. 5, gNB (gNode B) 31 and gNB 32 are always connected to 5GC (5th Generation Core)-NW (Network) 40, and gNB 33 is always connected to 5GC-NW 60. In addition, DN (Data Network) 50 is available via 5GC-NW 40, and DN 70 is available via 5GC-NW 60. UE (User Equipment) 81 is located in a communication area formed by gNB 31 and performs wireless communication with gNB 31. DN 70 corresponds to the first data network in the first embodiment, and DN 50 corresponds to the second data network. It is assumed that 5GC-NW 40 is included in PLMN_A, for example, and 5GC-NW 60 is included in PLMN_B. It is assumed that PLMN_A is a network managed by communication carrier A, for example, and PLMN_B is a network managed by communication carrier B, for example. PLMN_B corresponds to the first PLMN in the first embodiment, and PLMN_A corresponds to the second PLMN in the first embodiment.

[0032] The gNBs 31 to 33 are base stations that support 5G and New Radio (NR) as wireless communication standards. The gNBs 31 to 32 are always connected to the 5GC-NW 40, and temporarily switch their connection to the 5GC-NW 60 when the 5GC-NW 40 becomes congested. In other words, when the 5GC-NW 40 becomes congested, the gNBs 31 to 32 evacuate data that was being transmitted and received between the 5GC-NW 40 and the 5GC-NW 60. The gNBs 31 and 32 may also temporarily switch their connection to the 5GC-NW 60 when a failure occurs in the 5GC-NW 40. The gNBs 31 and 32 may be, for example, base stations that are linked to and managed by the MCC and MNC of a telecommunications carrier A. The gNB 33 may also be, for example, a base station that is linked to and managed by the MCC and MNC of a telecommunications carrier B.

[0033] When the 5GC-NW40 is not in a congested state but in a normal state, the UE81 communicates with the DN50 via the gNB31 and the 5GC-NW40. In other words, the UE81 establishes a session in the gNB31 and the 5GC-NW40 and communicates with the DN50. The session established in the gNB31 and the 5GC-NW40 may be a PDU (Protocol Data Unit) session. The term "UE" is used in 3GPP as a general term for a communication terminal. The UE may be, for example, a smartphone terminal, a tablet terminal, an IoT (Internet of Things) terminal, or the like.

[0034] The 5GC-NW40 has an AMF (Access and Mobility management Function) entity 41 (hereinafter referred to as AMF41), an SMF (Session Management Function) entity 42 (hereinafter referred to as SMF42), a UDM (Unified Data Management) entity 43 (hereinafter referred to as UDM43), a PCF (Policy Control Function) entity 44 (hereinafter referred to as PCF44), an AUSF (Authentication Server Function) 45 (hereinafter referred to as AUSF45), and a UPF (User Plane Function) entity 46 (hereinafter referred to as UPF46).

[0035] The AMF 41 performs mobility management for the UE. The SMF 42 performs session management for the UE. A session indicates a logical or virtual communication path for carrying U (User)-Plane data sent or received by the UE. The UPF 46 relays U-Plane data. The UDM 43 manages subscriber data for the UE. The PCF 44 manages or controls policies applied to the PLMN including the 5GC-NW 40. The AUSF 45 performs authentication processing for the UE.

[0036] The 5GC-NW 60 has an AMF 61, an SMF 62, an UDM 63, a PCF 64, and an UPF 65. The AMF 61, the SMF 62, the UDM 63, the PCF 64, the AUSF 65, and the UPF 66 basically perform the same functions and operations as the AMF 41, the SMF 42, the UDM 43, the PCF 44, the AUSF 45, and the UPF 46. Furthermore, the AMF 61, the SMF 62, the UDM 63, the PCF 64, and the UPF 65 have functions necessary for temporarily connecting to the gNBs 31 to 33. The AMF 61 corresponds to the communication device 10 in FIG. 1.

[0037] The 5GC-NW40 and the 5GC-NW60 are connected to each other. For example, the 5GC-NW40 and the 5GC-NW40 may be connected to each other via a Security Edge Protection Proxy (SEPP) (not shown) arranged in the 5GC-NW40 and a SEPP arranged in the 5GC-NW60. Alternatively, the 5GC-NW40 and the 5GC-NW40 may be connected to each other without going through a SEPP. The SEPP is used for interconnecting PLMNs, and performs filtering of messages transmitted between PLMNs.

[0038] Next, a processing flow when congestion occurs in the AMF 41 according to the second embodiment will be described with reference to Fig. 6. In Fig. 6, it is assumed that the gNB 31 has established a connection with the AMF 41.

[0039] First, when AMF41 detects that a congestion state has occurred, it sends a congestion notification message to gNB31 notifying that a congestion state has occurred (S21).

[0040] Next, upon receiving the congestion notification message, the gNB 31 sends an NG setup request message to the AMF 61 (S22). The gNB 31 may predetermine that a new connection will be established with the AMF 61 when the AMF 41 is in a congested state. Alternatively, information about the AMF to establish a new connection may be included in the congestion notification message. For example, if information about the AMF 61 is included in the congestion notification message, the gNB 31 may decide to establish a connection with the AMF 61.

[0041] The AMF 61 transmits an NG setup response message to the gNB 31 as a response message to the NG setup request message (S23). This establishes a connection between the gNB 31 and the AMF 61.

[0042] The gNB 31 may terminate the connection with the AMF 41 before sending the NG setup request message or after receiving the NG setup response message. Alternatively, the gNB 31 may terminate the connection with the AMF 41 after sending the NG setup request message but before receiving the NG setup response message.

[0043] Furthermore, the gNB31 may set a parameter in the NG setup request message indicating that it requests the establishment of a connection with the AMF61 temporarily. The gNB31 may further set a parameter indicating that the cause of the request for the temporary establishment of a connection with the AMF61 is that the AMF41 has entered a congestion state. For example, the gNB31 may indicate that the AMF to which the gNB31 is always connected is the AMF41 and that the gNB31 will be temporarily connected to the AMF61 by setting an ID indicating PLMN_A in the NG setup request message. Upon receiving the NG setup request message, the AMF61 may manage that the gNB31 is always connected to a PLMN different from PLMN_B. In other words, the AMF61 may manage the gNB31 as a gNB that temporarily connects to the AMF61. For example, the AMF61 may manage that the gNB31 is always connected to a PLMN different from PLMN_B by using a flag indicating whether the gNB31 is always connected to a PLMN different from PLMN_B.

[0044] When AMF61 permits the establishment of a temporary connection with gNB31, it transmits an NG setup response message to gNB31. When AMF61 receives an NG setup request message including a parameter indicating a request to temporarily establish a connection with AMF61, AMF61 may uniformly permit the establishment of the connection. Alternatively, AMF61 may permit the establishment of the connection if it has previously managed the PLMN ID included in the NG setup request message as a PLMN for which the establishment of a temporary connection is permitted. Note that when permitting the establishment of a temporary connection, management may be performed using a predetermined timer for each permitted connection. When the timer expires, the temporary connection may be terminated. This makes it possible to prevent temporary connections from being maintained, and to manage the load caused by temporary connections.

[0045] Next, the flow of the registration process according to the second embodiment will be described with reference to Figure 7. The registration process in Figure 7 will be described with reference to Figure 4.2.2.2.2-1: Registration procedure in 3GPP TS 23.502 V17.3.0 (2021-12) and parts necessary for the explanation of the present disclosure. In addition, the registration process in Figure 7 is executed after the gNB 31 in Figure 6 establishes a connection with the AMF 61.

[0046] First, UE81 transmits a Registration Request message to gNB31 (S31). The Registration Request message may include a PLMN ID indicating PLMN_A and / or a DNN (Data Network Name) indicating DN50. Furthermore, the Registration Request message may include a SUCI (Subscription Concealed Identifier) ​​or a SUPI (Subscription Permanent Identifier), which are identification information of UE81. Furthermore, the Registration Request message may include identification information of a network slice that UE81 wishes to use. It is assumed that the 5GC-NW40 has subscriber data and authentication data of UE81. In other words, UE81 temporarily registers with 5GC-NW60.

[0047] Next, gNB 31 selects an AMF (S32). Here, gNB 31 selects AMF 61 with which a connection has been established. Next, gNB 31 transmits the Registration Request message received in step S31 to AMF 61 (S33).

[0048] Next, the AMF 61 selects an AUSF to perform authentication processing for the UE 81 (S34). The AMF 61 may select the AUSF 45 by, for example, querying an NRF (Network Repository Function) entity (hereinafter referred to as NRF) using the MCC and MNC included in the SUCI. The SUCI is composed of an MCC, an MNC, and an encrypted MSIN (Mobile Subscriber Identification Number). The MCC and MNC of the SUCI transmitted from the UE 81 are associated with the 5GC-NW 40. The NRF manages information related to the node devices or functions constituting the 5GC-NW 40 and the 5GC-NW 60, and may provide the managed information in response to a query.

[0049] Next, the AMF 61, the AUSF 45, and the UDM 43 cooperate with each other to perform authentication processing for the UE 81 (S35).

[0050] Next, the AMF 61 selects a UDM (S36). The AMF 61 may select a UDM 43 by querying the NRF using the MCC and MNC included in the SUCI.

[0051] Next, the AMF 61 sends a request message to the UDM 43 to invoke the Nudm_SDM_Get service in the UDM 43, and receives a response message including subscriber data for the UE 81 (S37). The AMF 61 may send the request message to the UDM 43 via the AMF 41.

[0052] Next, the AMF 61 selects a PCF (S38). The AMF 61 may determine the PCF 44 by querying the NRF using the MCC and MNC included in the SUCI. By the AMF 61 selecting the PCF 44, a policy in the 5GC-NW 40 may be applied to the UE 81.

[0053] Next, the AMF 61 establishes an AM Policy Association with the PCF 44 (S39). By establishing the AM Policy Association, a predetermined policy is applied to the UE 81. This makes it possible to apply policy management in PLMN_A while using the network of PLMN_B.

[0054] Next, the AMF 61 transmits a Registration Accept message to the UE 81 in response to the Registration Request message (S40). The Registration Accept message may include Network Slice Selection Assistance Information (NSSAI) (Allowed NSSAI) indicating a network slice allowed for the UE 81. A network slice is a division of a physical network into multiple logical networks according to different service requirements. The NSSAI is a set of S (Single)-NSSAIs that identify a network slice. For example, for a UE 81 that is temporarily registered via the gNB 31, the AMF 61 may notify the UE 81 of an NSSAI indicating a network slice specified for the temporarily registered UE. For example, the network slice specified for the temporarily registered UE may be a slice that allows only specific communication services, such as emergency communications, public safety communications, and vehicle-to-vehicle communications, in order to prevent congestion. For example, the network slice specified for the temporarily registered UE may be a slice that restricts communications with a large amount of data in order to prevent congestion. For example, a network slice specified for a temporarily registered UE may be a slice that can be used only for a predetermined period to prevent congestion. For example, after the predetermined period has elapsed, the UE may be managed as a Rejected NSSAI instead of an Allowed NSSAI. The predetermined period may be managed by a timer for each slice by the AMF.

[0055] By executing the registration process in FIG. 7, the UE 81 is registered with the AMF 61.

[0056] Next, a flow of a process for establishing a PDU session according to the second embodiment will be described with reference to Fig. 8. The process for establishing a PDU session for the UE 81 is premised on the completion of the registration process of the UE 81 in the 5GC-NW 60.

[0057] First, the UE 81 transmits a NAS (Non Access Stratum) message including a PDU Session Establishment Request to the AMF 61 (S51). The NAS message may include a DN (UE Requested DNN) that the UE 81 wishes to use. The UE 81 uses the 5GC-NW 40 when the 5GC-NW 40 is not in a congested state. Therefore, the NAS message may include the DN 50 as the DN that the UE 81 wishes to use.

[0058] Next, AMF 61 selects an SMF that manages a session related to UE 81 (S52). AMF 61 may select an SMF taking into consideration the DN used by UE 81. For example, AMF 61 may select an SMF that can establish a session related to the DN used by UE 81.

[0059] Here, in step S51, AMF 61 receives a NAS message including DN50 as the DN that UE 81 wishes to use. However, the DN that 5GC-NW 60 in which AMF 61 is located can connect to is DN70. Therefore, AMF 61 selects SMF 62 that can establish a session regarding DN70 instead of DN50 that UE 81 wishes to use. In other words, AMF 61 replaces DN50 with DN70 and selects SMF 62 taking DN70 into consideration.

[0060] Next, AMF 61 transmits to SMF 62 a request message for invoking the Nsmf_PDUSession_CreateSMContext service in SMF 62 (S53). The request message may include, for example, a DNN indicating DN 70. Next, SMF 62 transmits to AMF 61 a response message in response to the request message for invoking the Nsmf_PDUSession_CreateSMContext service (S54).

[0061] Next, SMF 62 selects a UPF. For example, SMF 62 may select UPF 66 based on the DNN indicating DN 70. That is, SMF 62 may select UPF 66 as a UPF that can connect to DN 70.

[0062] Next, the SMF 62 transmits an N4_Session Establishment / Modification Request message to the UPF 66 (S56). The N4_Session Establishment / Modification Request message may include, for example, information necessary to establish a PDU session for the UE 81. Specifically, the information necessary to establish a PDU session for the UE 81 may be an IP address to be assigned to the UE 81.

[0063] Next, UPF 66 transmits an N4_Session Establishment / Modification Response message to SMF 62 in response to the N4_Session Establishment / Modification Request message (S57).

[0064] Next, the SMF 62 sends a request message to the AMF 61 to invoke the Namf_Communication_N1N2Message Transfer service in the AMF 61 (S58). The request message may include, for example, a PDU Session ID.

[0065] Next, the AMF 61 transmits an NAS message for executing an N2 PDU Session Request to the gNB 31 (S59). The NAS message may include, for example, a PDU Session ID and information for notifying the UE 81 that establishment of a PDU session is permitted.

[0066] Next, the gNB 31 transmits an NAS message for executing AN-specific resource setup to the UE 81 (S60). The NAS message may include, for example, a PDU Session ID and information for notifying the UE 81 that establishment of the PDU session is permitted.

[0067] By executing the PDU session establishment process in Figure 8, a PDU session is established between the UE 81 and the UPF 66, and the UE 81 becomes able to send and receive U-Plane data between the DN 70 via the UPF 66.

[0068] As described above, when the 5GC-NW40 is in a congested state, the gNB31 can temporarily establish a connection with the AMF61 in the 5GC-NW60. Also, the UE81 is registered with the AMF61 by performing a registration process with the AMF61, and can further establish a PDU session with the UPF66. This enables the UE81 to transmit and receive U-Plane data with the DN70. In other words, when the 5GC-NW40 is in a congested state, the UE81 can transmit and receive U-Plane data via the 5GC-NW60.

[0069] In addition, during the registration process, AMF61 can access UDM43 to perform billing processes and the like for UE81 in 5GC-NW40.

[0070] (Embodiment 3) Next, the flow of the registration process according to the third embodiment will be described with reference to Fig. 9. Steps S41 to S43 are the same as steps S31 to S33 in Fig. 7, and therefore the description thereof will be omitted.

[0071] Next, the AMF 61 selects an AUSF to perform authentication processing for the UE 81 (S44). Here, the AMF 61 may select the AUSF 65 when the UE 81 corresponds to a UE that temporarily registers. For example, the AMF 61 may select the AUSF 65 as the predetermined AUSF when the Registration Request message includes a PLMN ID indicating PLMN_A or a PLMN ID indicating a PLMN different from that of the AMF 61. Alternatively, the AMF 61 may select the AUSF 65 as the predetermined AUSF when the Registration Request message includes information on a data network that is not available in the 5GC-NW 60, for example, information on DN50. Alternatively, the AMF 61 may select the AUSF 65 as the predetermined AUSF when it receives a Registration Request message from the gNB 31 that it manages as a gNB temporarily connected to the AMF 61. For example, a case will be described in which a parameter indicating a request to temporarily establish a connection with the AMF 61 is included in the NG setup request message received from the gNB 31. In such a case, AMF61 may select AUSF65 when it receives a Registration Request message from gNB31.

[0072] Next, the AMF 61, the AUSF 65, and the UDM 63 cooperate to perform authentication processing for the UE 81 (S45). The authentication processing for the UE 81 may be simpler than, for example, authentication processing for a UE that has transmitted a Registration Request message via the gNB 33 that is always connected to the AMF 61. For example, the authentication processing for the UE 81 may be processing with a smaller amount of calculations than authentication processing for a UE that has transmitted a Registration Request message via the gNB 33. Alternatively, the authentication processing for the UE 81 may not involve generation of an encryption key for encrypting data related to the UE 81. Alternatively, when registration of all UEs is permitted for UEs that are temporarily registered, the authentication processing itself in step S45 may not be performed. Alternatively, a predetermined encryption key may be used. Alternatively, a key common to UEs that have temporarily registered may be used. The encryption key may be generated, for example, by using predetermined values ​​(e.g., all 0s) as input values ​​required for generation.

[0073] Next, AMF61 selects a UDM (S46). Here, AMF61 may select UDM63 when UE81 corresponds to a UE that temporarily registers. For example, AMF61 may select UDM63 as the predetermined UDM when the Registration Request message includes a PLMN ID indicating PLMN_A or a PLMN ID indicating a PLMN different from that of AMF61. Alternatively, AMF61 may select UDM63 as the predetermined UDM when the Registration Request message includes information of a data network that is not available in 5GC-NW60, such as DN50. Alternatively, AMF61 may select UDM63 as the predetermined UDM when it receives a Registration Request message from gNB31 that it manages as a gNB temporarily connected to AMF61. For example, a case will be described where a parameter indicating a request to temporarily establish a connection with AMF61 is included in the NG setup request message received from gNB31. In such a case, AMF61 may select UDM63 when it receives a Registration Request message from gNB31.

[0074] The AMF 61 may select a UDM using the same selection criteria as those used when selecting the AUSF in step S44. Furthermore, if the AMF 61 selects the AUSF 65 in step S44 because the UE 81 corresponds to a UE to be temporarily registered, the AMF 61 may select the UDM 63 previously associated with the AUSF 65 in step S46.

[0075] Next, AMF61 sends a request message to UDM63 to invoke the Nudm_SDM_Get service in UDM63, and receives a response message including subscriber data for UE81 (S37). The subscriber data for UE81 managed by UDM63 may be subscriber data associated with a UE that is temporarily registered with 5GC-NW60. For example, the subscriber data for UE81 managed by UDM63 may include temporary identification information assigned to a UE that is temporarily registered with 5GC-NW60.

[0076] Next, the AMF 61 selects a PCF (S48). Here, the AMF 61 may select the PCF 64 when the UE 81 corresponds to a UE that temporarily registers. For example, the AMF 61 may select the PCF 64 as the predetermined PCF when the Registration Request message includes a PLMN ID indicating PLMN_A or a PLMN ID indicating a PLMN different from that of the AMF 61. Alternatively, the AMF 61 may select the PCF 64 as the predetermined PCF when the Registration Request message includes information of a data network that is not available in the 5GC-NW 60, for example, information of the DN 50. Alternatively, the AMF 61 may select the PCF 64 as the predetermined PCF when it receives a Registration Request message from the gNB 31 that it manages as a gNB temporarily connected to the AMF 61. For example, a case will be described in which a parameter indicating a request to temporarily establish a connection with the AMF 61 is included in the NG setup request message received from the gNB 31. In such a case, AMF61 may select PCF64 when it receives a Registration Request message from gNB31.

[0077] The AMF 61 may select a PCF using the same selection criteria as those used when selecting an AUSF in step S44. Furthermore, if the AMF 61 selects the AUSF 65 in step S44 because the UE 81 corresponds to a UE for which temporary registration is to be performed, the AMF 61 may select the PCF 64 previously associated with the AUSF 65 in step S46.

[0078] Next, the AMF 61 establishes an AM Policy Association with the PCF 64 (S49). By establishing the AM Policy Association, a predetermined policy is applied to the UE 81. This makes it possible to apply policy management in PLMN_A while using the network of PLMN_B.

[0079] Next, the AMF 61 transmits a Registration Accept message to the UE 81 in response to the Registration Request message (S50). The Registration Accept message may include Network Slice Selection Assistance Information (NSSAI) (Allowed NSSAI) indicating a network slice allowed for the UE 81. A network slice is a division of a physical network into multiple logical networks according to different service requirements. The NSSAI is a set of S (Single)-NSSAIs that identify network slices. For example, for a UE 81 that is temporarily registered via the gNB 31, the AMF 61 may notify the UE 81 of an NSSAI indicating a network slice specified for the temporarily registered UE. The network slice specified for the temporarily registered UE may be a network slice that can allow registration from a UE that has a contract with a communication carrier different from the communication carrier that manages the PLMN_B. Furthermore, the network slice specified for the temporarily registered UE may be a network slice with limited usage time or a network slice with a more limited available bandwidth than usual. For example, the network slice specified for a temporarily registered UE may be a slice that allows only specific communication services, such as emergency communications, public safety communications, and vehicle-to-vehicle communications, in order to prevent congestion. For example, the network slice specified for a temporarily registered UE may be a slice that restricts communications with large amounts of data in order to prevent congestion. For example, the network slice specified for a temporarily registered UE may be a slice that is usable only for a predetermined period in order to prevent congestion. For example, after the predetermined period has elapsed, the NSSAI may be managed as a Rejected NSSAI from an Allowed NSSAI for the UE. The predetermined period may be managed by a timer by the AMF for each slice.

[0080] As described above, by executing the registration process according to the third embodiment, the AMF 61 can select the AUSF 65, the UDM 63, and the PCF 64 arranged in the 5GC-NW 60. This can reduce the processing load on the 5GC-NW 40, which is in a congested state. Furthermore, the 5GC-NW 60 executes an authentication process for a UE to be temporarily registered in a simpler manner than the authentication process executed for a normal UE. This allows many UEs that were registered in PLMN_A to be registered in PLMN_B.

[0081] (Fourth embodiment) Next, a data processing flow after the AMF 41 recovers from the congestion state according to the fourth embodiment will be described. When the AMF 41 recovers from the congestion state, the AMF 41 transmits a message to the gNB 31 notifying that the AMF 41 has recovered from the congestion state. When the gNB 31 receives the message notifying that the AMF 41 has recovered from the congestion state, the gNB 31 may terminate the connection with the AMF 61 and establish a connection with the AMF 41. When the gNB 31 terminates the connection with the AMF 61, the UE 81 transmits a Registration Request message to the AMF 41 via the gNB 31. Furthermore, as the connection between the gNB 31 and the AMF 61 is terminated, the PDU session related to the UE 81 is also disconnected. Therefore, the UE 81 establishes a PDU session in the 5GC-NW 40.

[0082] If the AMF41 simultaneously notifies all gNBs that can establish a connection with the AMF41 of a message notifying that it has recovered from the congestion state, Registration Request messages will be concentrated in the AMF41 in a short period of time. As a result, the AMF41 may become congested again. Therefore, for example, all gNBs that can establish a connection with the AMF41 may be divided into several groups, and messages notifying that it has recovered from the congestion state may be sent to each group at different times. This makes it possible to prevent Registration Request messages from being concentrated in the AMF41 in a short period of time.

[0083] Alternatively, when AMF 61 temporarily registers UE 81, AMF 61 may cancel the registration of UE 81 after a predetermined period has elapsed. Specifically, AMF 61 may set a timer for each UE to be temporarily registered and manage the registration period given to the UE.

[0084] Each deregistered UE sends a Registration Request message to gNB 31. At this time, if gNB 31 receives a message from AMF 41 notifying that it has recovered from the congestion state and has established a connection with AMF 41, it sends a Registration Request message to AMF 41. Furthermore, if gNB 31 does not receive a message from AMF 41 notifying that it has recovered from the congestion state, it sends a Registration Request message to AMF 61.

[0085] As described above, by providing a time difference between Registration Request messages sent to the AMF 41 that has recovered from the congestion state, it is possible to prevent Registration Request messages from concentrating on the AMF 41. As a result, it is possible to prevent the AMF 41 from becoming congested again.

[0086] FIG. 10 is a block diagram showing a configuration example of the communication device 10, base station 20, gNB 31, AMF 41, and AMF 61 (hereinafter referred to as communication device 10, etc.) described in the above-mentioned embodiment. Referring to FIG. 10, the communication device 10, etc. includes a network interface 1201, a processor 1202, and a memory 1203. The network interface 1201 may be used to communicate with a network node. The network interface 1201 may include, for example, a network interface card (NIC) that complies with the IEEE 802.3 series. IEEE stands for Institute of Electrical and Electronics Engineers.

[0087] The processor 1202 reads and executes software (computer programs) from the memory 1203 to perform the processes of the communication device 10 and the like described using flowcharts in the above-described embodiments. The processor 1202 may be, for example, a microprocessor, an MPU, or a CPU. The processor 1202 may include multiple processors.

[0088] The memory 1203 is configured by a combination of volatile memory and non-volatile memory. The memory 1203 may include storage located remotely from the processor 1202. In this case, the processor 1202 may access the memory 1203 via an I / O (Input / Output) interface (not shown).

[0089] 10, the memory 1203 is used to store software modules. The processor 1202 reads and executes these software modules from the memory 1203, thereby performing the processing of the communication device 10 and the like described in the above-described embodiment.

[0090] As explained using FIG. 10, each of the processors of the communication device 10 etc. in the above-described embodiment executes one or more programs including a group of instructions for causing a computer to perform the algorithm explained using the drawings.

[0091] In the above examples, the program includes instructions (or software code) that, when loaded into a computer, cause the computer to perform one or more functions described in the embodiments. The program may be stored on a non-transitory computer-readable medium or a tangible storage medium. By way of example and not limitation, computer-readable medium or tangible storage medium includes random-access memory (RAM), read-only memory (ROM), flash memory, solid-state drive (SSD) or other memory technology, CD-ROM, digital versatile disc (DVD), Blu-ray® disc or other optical disk storage, magnetic cassette, magnetic tape, magnetic disk storage or other magnetic storage device. The program may also be transmitted on a transitory computer-readable medium or communication medium. By way of example and not limitation, transitory computer-readable medium or communication medium includes electrical, optical, acoustic, or other forms of propagated signals.

[0092] The technical ideas shown in the present disclosure are not limited to the above-described embodiments, and can be modified as appropriate within the scope of the gist thereof.

[0093] Some or all of the above-described embodiments can be described as, but are not limited to, the following supplementary notes. (Appendix 1) A communication device constituting a first Public Land Mobile Network (PLMN), a communication unit configured to receive, after temporarily connecting to a base station, a request message from the communication terminal via the base station requesting establishment of a session with a second data network available in a second PLMN; a control unit for establishing a session between the communication terminal and a first data network available in a first PLMN after receiving the request message; The first PLMN and the second PLMN are different communications devices. (Appendix 2) The control unit 2. The communication device of claim 1, wherein the communication device establishes a session between the first data network and the communication terminal when the request message is sent from the base station after temporarily permitting connection to the base station that was connected to the second PLMN. (Appendix 3) The control unit 3. The communication device according to claim 2, wherein when the base station notifies the communication device of information indicating that the connection destination of the base station is temporarily changed from the second PLMN to the first PLMN, the communication device temporarily permits connection with the base station. (Appendix 4) The control unit 4. The communication device according to claim 3, wherein when information identifying the second PLMN is notified as the information, the communication device temporarily permits connection with the base station. (Appendix 5) The control unit 5. The communication device according to claim 1, wherein, in a registration process relating to the communication terminal, subscriber information of the communication terminal is obtained from a management device that constitutes the second PLMN. (Appendix 6) The control unit 6. The communication device according to claim 5, wherein the communication device identifies the management device when the communication terminal requests use of the second data network in the registration process. (Appendix 7) The control unit A communication device as described in any one of Appendices 1 to 4, wherein, in a registration process for the communication terminal, when a request is made to use the second data network, a second registration process is executed, and the second registration process is different from a first registration process executed for a communication terminal requesting to use the first data network. (Appendix 8) The control unit 8. The communication device according to claim 7, wherein the second registration process is performed so that a load in the second registration process is reduced compared to a load in the first registration process. (Appendix 9) a communication unit that receives a notification message indicating a congestion state from a second communication device that constitutes a second PLMN; a control unit that, after receiving the notification message, starts a process of establishing a connection with a first communication device that constitutes a first PLMN. (Appendix 10) The control unit A base station as described in Supplementary Note 9, wherein after establishing a connection with the first communication device, if a registration request message is received from a communication terminal corresponding to the second PLMN, the base station transmits the registration request message to the first communication device. (Appendix 11) A communication method executed in a communication device constituting a first Public Land Mobile Network (PLMN), comprising: receiving, after temporarily connecting with a base station, a request message from the communications terminal via the base station requesting establishment of a session with a second data network available in a second PLMN; establishing a session between the communications terminal and a first data network available in a first PLMN after receiving the request message; The first PLMN and the second PLMN have different communication methods. (Appendix 12) When establishing a session between the first data network and the communication terminal, 12. The communication method of claim 11, wherein a session is established between the first data network and the communication terminal when the request message is sent from the base station after temporarily permitting connection to the base station that was connected to the second PLMN. (Appendix 13) before receiving the request message, 13. The communication method according to claim 12, wherein when the base station notifies the mobile station of information indicating that the connection destination of the base station is temporarily changed from the second PLMN to the first PLMN, the mobile station temporarily permits connection with the base station. (Appendix 14) 14. The communication method according to claim 13, wherein, when information identifying the second PLMN is notified as the information, connection with the base station is temporarily permitted. (Appendix 15) After temporarily connecting with the base station, 15. The communication method according to any one of claims 11 to 14, wherein in the registration process for the communication terminal, subscriber information of the communication terminal is obtained from a management device that constitutes the second PLMN. (Appendix 16) After temporarily connecting with the base station, 16. The communication method according to claim 15, wherein the management device is identified when the communication terminal requests use of the second data network in the registration process. (Appendix 17) After temporarily connecting with the base station, A communication method as described in any one of Appendices 11 to 14, wherein in the registration process for the communication terminal, when a request is made to use the second data network, a second registration process is executed, and the second registration process is different from the first registration process executed for the communication terminal requesting to use the first data network. (Appendix 18) 18. The communication method according to claim 17, wherein the second registration process is executed so that a load in the second registration process is reduced compared to a load in the first registration process. (Appendix 19) 1. A communication method performed in a base station, comprising: receiving a notification message indicating a congestion state from a second communication device constituting a second PLMN; A communication method, wherein after receiving the notification message, a process of establishing a connection with a first communication device constituting a first PLMN is started. (Appendix 20) A communication method as described in Appendix 19, wherein, after establishing a connection with the first communication device, if a registration request message is received from a communication terminal corresponding to the second PLMN, the registration request message is sent to the first communication device. (Appendix 21) A non-transitory computer-readable medium storing a program to be executed by a computer that is a communication device constituting a first Public Land Mobile Network (PLMN), receiving, after temporarily connecting with a base station, from a communications terminal via the base station a request message requesting establishment of a session with a second data network available in a second PLMN, the first PLMN and the second PLMN being different; a non-transitory computer-readable medium having stored thereon a program that causes a computer to establish a session between the communication terminal and a first data network available in a first PLMN after receiving the request message. (Appendix 22) When establishing a session between the first data network and the communication terminal, 22. The non-transitory computer-readable medium of claim 21, wherein the session between the first data network and the communications terminal is established if the request message is sent from the base station after temporarily allowing a connection with the base station that was connected to the second PLMN. (Appendix 23) before receiving the request message, 23. The non-transitory computer-readable medium of claim 22, wherein when the base station notifies the mobile station of information indicating that the base station's connection destination is temporarily changed from the second PLMN to the first PLMN, the mobile station temporarily allows connection with the base station. (Appendix 24) 24. The non-transitory computer-readable medium of claim 23, wherein if the information notified is information identifying the second PLMN, connection with the base station is temporarily permitted. (Appendix 25) After temporarily connecting with the base station, A non-transitory computer-readable medium described in any one of Supplementary Notes 21 to 24, wherein in a registration process for the communication terminal, subscriber information of the communication terminal is obtained from a management device that constitutes the second PLMN. (Appendix 26) After temporarily connecting with the base station, 26. The non-transitory computer-readable medium of claim 25, which identifies the management device when the communication terminal requests use of the second data network in the registration process. (Appendix 27) After temporarily connecting with the base station, A non-transitory computer-readable medium as described in any one of Appendices 21 to 24, wherein in a registration process for the communication terminal, when a request is made to use the second data network, a second registration process is executed, and the second registration process is different from a first registration process executed for a communication terminal requesting to use the first data network. (Appendix 28) 28. The non-transitory computer-readable medium of claim 27, wherein the second registration process is executed so as to reduce the load of the second registration process compared to the load of the first registration process. (Appendix 29) A non-transitory computer-readable medium storing a program to be executed by a computer that is a base station, receiving a notification message indicating a congestion state from a second communication device constituting a second PLMN; and a non-transitory computer-readable medium that, after receiving the notification message, initiates a process of establishing a connection with a first communication device that constitutes a first PLMN. (Appendix 30) 30. The non-transitory computer-readable medium of claim 29, wherein after establishing a connection with the first communication device, if a registration request message is received from a communication terminal corresponding to the second PLMN, the registration request message is sent to the first communication device. [Explanation of symbols]

[0094] 10. Communications equipment 11 Communications Department 12 Control Unit 20 base station 21 Communications Department 22 Control Unit 31 gNB 32 gNB 33 gNB 40 5GC-NW 41 AMF 42 SMF 43 UDM 44 PCF 45 AUSF 46 UPF 50DN 60 5GC-NW 61 AMF 62 SMF 63 UDM 64 PCF 65 AUSF 66 UPF 70DN 81UE

Claims

1. A communication device constituting a first Public Land Mobile Network (PLMN), a communication unit for receiving a request message from a communication terminal via a base station requesting the establishment of a session with a second data network available in a second PLMN; a control unit that, after receiving the request message, establishes a session between the communication terminal and a first data network available in the first PLMN if the first PLMN and the second PLMN have previously agreed on connection establishment; The first PLMN and the second PLMN are different.

2. The control unit 2. The communication device according to claim 1, wherein the session between the first data network and the communication terminal is established when the request message is transmitted from the base station after temporarily permitting connection to the base station that was connected to the second PLMN.

3. The control unit 3. The communication device according to claim 2, wherein when the base station notifies the communication device of information indicating that a connection destination of the base station is temporarily changed from the second PLMN to the first PLMN, the communication device temporarily permits connection to the base station.

4. The control unit The communication device according to claim 3 , wherein when information identifying the second PLMN is notified as the information, the communication device temporarily permits connection to the base station.

5. The control unit The communication device according to claim 1 , wherein in the registration process for the communication terminal, subscriber information of the communication terminal is acquired from a management device that constitutes the second PLMN.

6. The control unit The communication device according to claim 5 , wherein the management device is identified when the communication terminal requests the use of the second data network in the registration process.

7. The control unit 5. A communication device according to claim 1, wherein, in a registration process for the communication terminal, when a request is made to use the second data network, a second registration process is executed, and the second registration process is different from a first registration process executed for a communication terminal requesting to use the first data network.

8. The control unit The communication device according to claim 7 , wherein the second registration process is executed so that a load in the second registration process is reduced compared to a load in the first registration process.

9. A communication method executed in a communication device constituting a first Public Land Mobile Network (PLMN), comprising: receiving a request message from the communications terminal via the base station requesting establishment of a session with a second data network available in a second PLMN; if the first PLMN and the second PLMN have previously agreed on connection establishment, after receiving the request message, establishing a session between the communication terminal and a first data network available in the first PLMN; A communication method in which the first PLMN and the second PLMN are different.

10. A program to be executed by a computer that is a communication device constituting a first Public Land Mobile Network (PLMN), receiving a request message from a communications terminal via a base station requesting establishment of a session with a second data network available in a second PLMN, the first PLMN and the second PLMN being different; a program that causes a computer to execute the following: if the first PLMN and the second PLMN have previously agreed on connection establishment, after receiving the request message, establish a session between the communication terminal and a first data network available in the first PLMN.

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