JP7754288B2 - Communication device, communication method, and program - Google Patents

Description

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

If a failure occurs in part of a network managed by a telecommunications carrier, the impact of the failure can spread to the entire network, causing the entire network to become congested. If the entire network becomes congested, the network will no longer be able to provide communication services to all communication terminals requesting communication services. In such cases, network configurations are being considered that allow communication terminals to select networks managed by other telecommunications carriers and use communication services provided by those other carriers.

Patent document 1 discloses the process by which a base station that receives a network connection request from a terminal selects a network to which the terminal will connect. For example, the base station identifies a network that corresponds to the terminal and selects the identified network as the network to which the terminal will connect.

JP 2016-144106 A

When the entire network becomes congested, it is expected that communication terminals will temporarily use networks managed by other telecommunications carriers. However, Patent Document 1 does not clearly describe how communication services are provided to terminals that temporarily use the network, which poses the problem of not being able to distinguish between terminals that temporarily use the network and/or base stations that are temporarily connected to provide communication services.

In view of the above-mentioned problems, one of the objectives of the present disclosure is to provide a communication device, base station, communication method, and 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.

A communication device according to a first aspect of the present disclosure is a communication device constituting 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.

A base station according to a second aspect of the present disclosure comprises 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, initiates processing to establish a connection with a first communication device that constitutes a first PLMN.

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.

A program according to a fourth aspect of the present disclosure is a program executed by a computer that is a communication device constituting a first Public Land Mobile Network (PLMN), and causes the computer to: after temporarily connecting to a base station, receive 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, 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.

The present disclosure provides a communication device, base station, communication method, and 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.

FIG. 1 is a configuration diagram of a communication device according to a first embodiment; 10 is a flowchart of a session establishment process executed in the communication device according to the first embodiment; FIG. 2 is a configuration diagram of a base station according to the first embodiment; 10 is a flowchart of a connection establishment process executed in the base station according to the first embodiment; FIG. 10 is a configuration diagram of a communication system according to a second embodiment. FIG. 10 is a diagram showing the processing flow when congestion occurs in the AMF according to the second embodiment. FIG. 10 is a diagram showing the flow of registration processing according to the second embodiment. A diagram showing the flow of the PDU session establishment process in embodiment 2. FIG. 10 is a diagram showing the flow of registration processing according to the third embodiment. This is a configuration diagram of a communication device, base station, gNB, and AMF for each embodiment.

(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 as a five- to six-digit number that combines a "Mobile Country Code" (MCC), which indicates a country or region and a "Mobile Network Code" (MNC), which indicates a carrier and is represented by a three-digit number (varies by country). In the following description, the communication device 10 will be described as a communication device that constitutes a first PLMN.

The communication device 10 has a communication unit 11 and a control unit 12. The communication unit 11 and the control unit 12 may be software or modules that perform processing when a processor executes a program stored in memory. Alternatively, the communication unit 11 and the control unit 12 may be hardware such as a circuit or chip.

After temporarily connecting to base station 20, communication unit 11 receives a request message from the communication terminal via base station 20 requesting the establishment of a session with a second data network available in the 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.

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

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 send and receive messages via the established connection. A message may be referred to as, for example, C (Control)-Plane data or control data.

The state in which a connection is temporarily established may mean, for example, maintaining the connection established for a predetermined period and then releasing the connection after the predetermined period has elapsed. Releasing the connection may also be described as disconnecting the connection. The connection may be released autonomously after the predetermined period has elapsed, or may be released by a maintenance worker operating the communication device 10 or base station 20. This makes it possible to manage the processing load in the PLMN of the communication device 10 when the base station 20 is different from the PLMN of the communication device 10.

A data network may be, for example, a network that has a server device on which data used by a user is stored, or a server device that a user wishes to access. A network that has a server device may also be referred to as a network to which a server device is connected.

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.

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

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, it 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.

When the control unit 12 receives a request message from the communication terminal via a 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 a message to the communication terminal rejecting the process of establishing a session between the second data network and the communication terminal. A 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.

Next, a flowchart of the session establishment process executed in the communication device 10 according to the first embodiment will be described with reference to Figure 2. First, the communication unit 11 temporarily connects to the base station 20, and then receives a request message from the communication terminal via the base station 20 requesting the 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).

Next, an example configuration of the base station 20 according to the first embodiment will be described using Figure 3. The base station 20 may be a computer device that operates when a processor executes 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 known as 5G.

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 whose processing is performed by a processor executing a program stored in memory. Alternatively, the communication unit 21 and the control unit 22 may be hardware such as a circuit or chip.

The communication unit 21 receives a notification message indicating a congestion state from a communication device that constitutes the second PLMN. If the communication device is in a congested state, the communication terminal may not be able to receive communication services from the communication device in the congested state.

After receiving the notification message, the control unit 22 begins processing to establish a connection with the first communication device that constitutes the first PLMN. Assume that the base station 20 is constantly connected to the communication device that constitutes the second PLMN. When the base station 20 receives a notification message from the communication device that constitutes the second PLMN indicating a congestion state, the base station 20 temporarily connects to the communication device 10 that constitutes 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 that constitutes the second PLMN and initiate a connection with the communication device 10, or may initiate a connection with the communication device 10 while maintaining the connection with the communication device that constitutes the second PLMN.

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

As described above, the communication device 10 establishes a session between the first data network and a communication terminal that requests the establishment of a session with the data network via the temporarily connected base station 20. In other words, a session with the first data network is established for a communication terminal that temporarily uses the first PLMN. As a result, the communication device 10 can provide communication services to a communication terminal that has sent 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.

(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. Also, 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 the 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. Assume that 5GC-NW 40 is included in PLMN_A, for example, and 5GC-NW 60 is included in PLMN_B. PLMN_A is, for example, a network managed by a communication carrier A, and PLMN_B is a network managed by a communication carrier B. PLMN_B corresponds to the first PLMN in the first embodiment, and PLMN_A corresponds to the second PLMN in the first embodiment.

gNBs 31 to 33 are base stations that support 5G and New Radio (NR) as wireless communication standards. gNBs 31 to 32 are always connected to 5GC-NW40, and if 5GC-NW40 becomes congested, they temporarily switch their connection to 5GC-NW60. In other words, if 5GC-NW40 becomes congested, gNBs 31 to 32 evacuate data that was being transmitted and received between 5GC-NW40 and 5GC-NW60. gNBs 31 to 32 may also temporarily switch their connection to 5GC-NW60 if a failure occurs in 5GC-NW40. gNBs 31 and 32 may be base stations that are managed in association with the MCC and MNC of telecommunications carrier A, for example. gNB33 may also be a base station that is linked to and managed by, for example, the MCC and MNC of telecommunications operator B.

When the 5GC-NW40 is not in a congested state and is 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 between the gNB31 and the 5GC-NW40 and communicates with the DN50. The session established between 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, etc.

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).

AMF41 performs mobility management for UEs. SMF42 performs session management for UEs. A session indicates a logical or virtual communication path for carrying U (User)-Plane data sent or received by the UE. UPF46 relays U-Plane data. UDM43 manages subscriber data for UEs. PCF44 manages or controls policies applied to the PLMN including 5GC-NW40. AUSF45 performs authentication processing for UEs.

5GC-NW60 has AMF61, SMF62, UDM63, PCF64, and UPF65. AMF61, SMF62, UDM63, PCF64, AUSF65, and UPF66 basically perform the same functions and operations as AMF41, SMF42, UDM43, PCF44, AUSF45, and UPF46. Furthermore, AMF61, SMF62, UDM63, PCF64, and UPF65 have the functions necessary for temporary connection with gNB31-33. AMF61 corresponds to communication device 10 in Figure 1.

The 5GC-NW40 and the 5GC-NW60 are connected. For example, the 5GC-NW40 and the 5GC-NW40 may be connected via a SEPP (Security Edge Protection Proxy) (not shown) located in the 5GC-NW40 and a SEPP located in the 5GC-NW60. Alternatively, the 5GC-NW40 and the 5GC-NW40 may be connected without going through a SEPP. The SEPP is used to interconnect PLMNs and performs functions such as filtering of messages transmitted between PLMNs.

Next, using Figure 6, we will explain the processing flow when congestion occurs in AMF41 in embodiment 2. In Figure 6, it is assumed that gNB31 has established a connection with AMF41.

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).

Next, upon receiving the congestion notification message, gNB31 sends an NG setup request message to AMF61 (S22). gNB31 may predetermine that a new connection will be established with AMF61 if AMF41 becomes congested. Alternatively, information about the AMF with which a new connection will be established may be included in the congestion notification message. For example, if information about AMF61 is included in the congestion notification message, gNB31 may decide to establish a connection with AMF61.

AMF61 sends an NG setup response message to gNB31 as a response message to the NG setup request message (S23). This establishes a connection between gNB31 and AMF61.

gNB31 may terminate the connection with AMF41 before sending the NG setup request message or after receiving the NG setup response message. Alternatively, gNB31 may terminate the connection with AMF41 after sending the NG setup request message but before receiving the NG setup response message.

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

When AMF61 permits the establishment of a temporary connection with gNB31, it sends 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 temporary connection establishment 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 manage the load caused by temporary connections.

Next, the flow of the registration process for embodiment 2 will be explained using Figure 7. The registration process in Figure 7 will be explained by referring to Figure 4.2.2.2.2-1: Registration procedure in 3GPP TS 23.502 V17.3.0 (2021-12) and the parts necessary for explaining this disclosure. In addition, the registration process in Figure 7 is executed after gNB31 establishes a connection with AMF61 in Figure 6.

First, UE81 sends 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 SUPI (Subscription Permanent Identifier), which are identification information for UE81. Furthermore, the Registration Request message may include identification information for the network slice that UE81 wishes to use. It is assumed that the subscriber data and authentication data for UE81 are held by 5GC-NW40. In other words, UE81 temporarily registers with 5GC-NW60.

Next, gNB31 selects an AMF (S32). Here, gNB31 selects AMF61 with which it has established a connection. Next, gNB31 sends the Registration Request message received in step S31 to AMF61 (S33).

Next, AMF61 selects an AUSF to perform authentication processing for UE81 (S34). AMF61 may select AUSF45, for example, by querying an NRF (Network Repository Function) entity (hereinafter referred to as NRF) using the MCC and MNC included in the SUCI. SUCI consists of an MCC, MNC, and an encrypted MSIN (Mobile Subscriber Identification Number). The MCC and MNC of the SUCI transmitted from UE81 are associated with 5GC-NW40. The NRF may manage information related to the node devices or functions constituting 5GC-NW40 and 5GC-NW60, and provide the information it manages in response to a query.

Next, AMF61, AUSF45, and UDM43 work together to perform authentication processing for UE81 (S35).

Next, AMF61 selects a UDM (S36). AMF61 may select a UDM43 by querying the NRF using the MCC and MNC included in the SUCI.

Next, AMF61 sends a request message to UDM43 to invoke the Nudm_SDM_Get service in UDM43 and receives a response message including subscriber data for UE81 (S37). AMF61 may send the request message to UDM43 via AMF41.

Next, AMF61 selects a PCF (S38). AMF61 may determine the PCF44 by querying the NRF using the MCC and MNC included in the SUCI. By AMF61 selecting the PCF44, policies in the 5GC-NW40 may be applied to UE81.

Next, AMF61 establishes an AM Policy Association with PCF44 (S39). By establishing the AM Policy Association, a predetermined policy is applied to UE81. This makes it possible to apply policy management in PLMN_A while using the PLMN_B network.

Next, AMF61 sends a Registration Accept message to UE81 in response to the Registration Request message (S40). The Registration Accept message may include an NSSAI (Network Slice Selection Assistance Information) (Allowed NSSAI) indicating the network slice allowed for UE81. A network slice is a division of a physical network into multiple logical networks according to different service requirements. An NSSAI is a set of S (Single)-NSSAIs that identify a network slice. For example, for a UE81 that is temporarily registered via gNB31, AMF61 may notify UE81 of an NSSAI indicating the 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, to prevent congestion. For example, the network slice specified for the temporarily registered UE may be a slice that restricts communications with large amounts of data 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.

By executing the Registration process in Figure 7, UE81 is registered to AMF61.

Next, the flow of the PDU session establishment process for embodiment 2 will be explained using Figure 8. The PDU session establishment process for UE81 is based on the premise that the registration process for UE81 in 5GC-NW60 has been completed.

First, UE81 sends a NAS (Non Access Stratum) message including a PDU Session Establishment Request to AMF61 (S51). The NAS message may include a DN (UE Requested DNN) that UE81 wishes to use. UE81 uses 5GC-NW40 if the 5GC-NW40 is not in a congested state. Therefore, the NAS message may include DN50 as the DN that UE81 wishes to use.

Next, AMF61 selects an SMF to manage a session related to UE81 (S52). AMF61 may select an SMF taking into account the DN used by UE81. For example, AMF61 may select an SMF that can establish a session related to the DN used by UE81.

Here, in step S51, AMF61 receives a NAS message including DN50 as the DN that UE81 wishes to use. However, the DN to which the 5GC-NW60 in which AMF61 is located can connect is DN70. Therefore, AMF61 selects SMF62, which can establish a session related to DN70, instead of DN50 that UE81 wishes to use. In other words, AMF61 replaces DN50 with DN70 and selects SMF62 taking DN70 into consideration.

Next, AMF61 sends a request message to SMF62 to invoke the Nsmf_PDUSession_CreateSMContext service in SMF62 (S53). The request message may include, for example, a DNN indicating DN70. Next, SMF62 sends a response message to AMF61 in response to the request message to invoke the Nsmf_PDUSession_CreateSMContext service (S54).

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 the UPF that can connect to DN 70.

Next, SMF62 sends an N4_Session Establishment/Modification Request message to UPF66 (S56). The N4_Session Establishment/Modification Request message may include, for example, information necessary to establish a PDU session for UE81. Specifically, the information necessary to establish a PDU session for UE81 may be an IP address to be assigned to UE81.

Next, UPF66 sends an N4_Session Establishment/Modification Response message to SMF62 in response to the N4_Session Establishment/Modification Request message (S57).

Next, SMF62 sends a request message to AMF61 to invoke the Namf_Communication_N1N2Message Transfer service in AMF61 (S58). The request message may include, for example, a PDU Session ID.

Next, AMF61 sends a NAS message to gNB31 to execute the N2 PDU Session Request (S59). The NAS message may include, for example, a PDU Session ID and information for notifying UE81 that establishment of a PDU session is permitted.

Next, gNB31 sends a NAS message to UE81 to perform AN-specific resource setup (S60). The NAS message may include, for example, a PDU Session ID and information for notifying UE81 that establishment of a PDU session is permitted.

By executing the PDU session establishment process in Figure 8, a PDU session is established between UE81 and UPF66, and UE81 becomes able to send and receive U-Plane data between DN70 via UPF66.

As described above, gNB31 can temporarily establish a connection with AMF61 in 5GC-NW60 when 5GC-NW40 becomes congested. UE81 is also registered with AMF61 by performing registration processing with AMF61, and can further establish a PDU session with UPF66. This allows UE81 to send and receive U-Plane data with DN70. In other words, when 5GC-NW40 becomes congested, UE81 can send and receive U-Plane data via 5GC-NW60.

In addition, during the registration process, AMF61 accesses UDM43, thereby enabling billing processes and the like for UE81 to be performed in 5GC-NW40.

(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 a description thereof will be omitted.

Next, AMF61 selects an AUSF to perform authentication processing for UE81 (S44). Here, AMF61 may select AUSF65 if UE81 corresponds to a UE that temporarily registers. For example, AMF61 may select AUSF65 as the predetermined AUSF if 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 AUSF65 as the predetermined AUSF if the Registration Request message includes information on a data network that is not available in 5GC-NW60, such as DN50. Alternatively, AMF61 may select AUSF65 as the predetermined AUSF if 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 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, when the AMF 61 receives a Registration Request message from the gNB 31, it may select the AUSF 65.

Next, AMF61, AUSF65, and UDM63 cooperate to perform authentication processing for UE81 (S45). The authentication processing for UE81 may be simpler than, for example, the authentication processing for a UE that has transmitted a Registration Request message via gNB33, which is always connected to AMF61. For example, the authentication processing for UE81 may require less computational effort than the authentication processing for a UE that has transmitted a Registration Request message via gNB33. Alternatively, the authentication processing for UE81 may not involve the generation of an encryption key for encrypting data related to UE81. Alternatively, if registration of all UEs is permitted for UEs that are temporarily registered, the authentication processing in step S45 may not be performed. Alternatively, a predetermined encryption key may be used. Alternatively, a key common to all 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.

Next, AMF61 selects a UDM (S46). Here, AMF61 may select UDM63 if UE81 corresponds to a UE that temporarily registers. For example, AMF61 may select UDM63 as the predetermined UDM if 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 if the Registration Request message includes information on a data network that is not available in 5GC-NW60, such as DN50. Alternatively, AMF61 may select UDM63 as the predetermined UDM if 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 in which a parameter indicating a request to temporarily establish a connection with AMF 61 is included in the NG setup request message received from gNB 31. In such a case, when AMF 61 receives a Registration Request message from gNB 31, AMF 61 may select UDM 63.

AMF61 may select a UDM using the same selection criteria as those used to select an AUSF in step S44. Furthermore, if AMF61 selects AUSF65 in step S44 because UE81 is a UE that will temporarily register, AMF61 may select a UDM63 that has been previously associated with AUSF65 in step S46.

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 on 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 on 5GC-NW60.

Next, AMF61 selects a PCF (S48). Here, AMF61 may select PCF64 if UE81 corresponds to a UE that temporarily registers. For example, AMF61 may select PCF64 as the predetermined PCF if 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 PCF64 as the predetermined PCF if the Registration Request message includes information on a data network that is not available in 5GC-NW60, such as DN50. Alternatively, AMF61 may select PCF64 as the predetermined PCF if 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 in which 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 PCF64 when receiving a Registration Request message from gNB31.

AMF61 may select a PCF using the same selection criteria as those used to select an AUSF in step S44. Furthermore, if AMF61 selects AUSF65 in step S44 because UE81 is a UE that will temporarily register, AMF61 may select a PCF64 that has been previously associated with AUSF65 in step S46.

Next, AMF61 establishes an AM Policy Association with PCF64 (S49). By establishing the AM Policy Association, a predetermined policy is applied to UE81. This makes it possible to apply policy management in PLMN_A while using the PLMN_B network.

Next, AMF61 sends a Registration Accept message to UE81 in response to the Registration Request message (S50). The Registration Accept message may include an NSSAI (Network Slice Selection Assistance Information) (Allowed NSSAI) indicating the network slice allowed for UE81. A network slice is a division of a physical network into multiple logical networks according to different service requirements. An NSSAI is a set of S (Single)-NSSAIs that identify network slices. For example, for a UE81 that is temporarily registered via gNB31, AMF61 may notify UE81 of an NSSAI indicating the 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 telecommunications operator different from the telecommunications operator that manages 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 defined 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 defined 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 defined 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 of the UE may be managed as a Rejected NSSAI from an Allowed NSSAI. The predetermined period may be managed by a timer by the AMF for each slice.

As described above, by performing the registration process according to embodiment 3, AMF61 can select AUSF65, UDM63, and PCF64 located in 5GC-NW60. This reduces the processing burden on 5GC-NW40, which is in a congested state. Furthermore, in 5GC-NW60, authentication processing for UEs to be temporarily registered is performed more simply than the authentication processing performed for normal UEs. This allows many UEs that were registered in PLMN_A to be registered in PLMN_B.

(Embodiment 4)
Next, the flow of data processing after the AMF41 recovers from the congestion state according to the fourth embodiment will be described. When the AMF41 recovers from the congestion state, it transmits a message to the gNB31 notifying that it has recovered from the congestion state. When the gNB31 receives the message notifying that it has recovered from the congestion state, it may terminate the connection with the AMF61 and establish a connection with the AMF41. When the gNB31 terminates the connection with the AMF61, the UE81 transmits a Registration Request message to the AMF41 via the gNB31. Furthermore, as the connection between the gNB31 and the AMF61 is terminated, the PDU session for the UE81 is also disconnected. Therefore, the UE81 establishes a PDU session in the 5GC-NW40.

If AMF41 simultaneously notifies all gNBs that can establish a connection with AMF41 of a message notifying that it has recovered from the congestion state, Registration Request messages will be concentrated at AMF41 in a short period of time. As a result, AMF41 may again become congested. Therefore, for example, all gNBs that can establish a connection with 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 at AMF41 in a short period of time.

Alternatively, when AMF61 temporarily registers UE81, it may deregister UE81 after a predetermined period has elapsed. Specifically, AMF61 may set a timer for each UE to be temporarily registered and manage the registration period given to the UE.

Each deregistered UE sends a Registration Request message to gNB31. At this time, if gNB31 receives a message from AMF41 notifying that it has recovered from the congestion state and has established a connection with AMF41, it sends a Registration Request message to AMF41. Also, if gNB31 does not receive a message from AMF41 notifying that it has recovered from the congestion state, it sends a Registration Request message to AMF61.

As explained above, by setting a time difference between Registration Request messages sent to AMF41 that has recovered from a congested state, it is possible to prevent Registration Request messages from concentrating on AMF41. As a result, it is possible to prevent AMF41 from becoming congested again.

Figure 10 is a block diagram showing an example configuration 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 Figure 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) compliant with the IEEE 802.3 series. IEEE stands for Institute of Electrical and Electronics Engineers.

The processor 1202 reads and executes software (computer programs) from the memory 1203 to perform the processing of the communication device 10, etc., 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.

Memory 1203 is composed of a combination of volatile memory and non-volatile memory. Memory 1203 may also include storage located remotely from processor 1202. In this case, processor 1202 may access memory 1203 via an I/O (Input/Output) interface not shown.

In the example of Figure 10, memory 1203 is used to store a group of software modules. The processor 1202 reads and executes these software modules from memory 1203, thereby performing processing of the communication device 10, etc., described in the above-mentioned embodiment.

As explained using Figure 10, each of the processors possessed by the communication device 10, etc. in the above-mentioned embodiments executes one or more programs including a set of instructions for causing a computer to perform the algorithm explained using the drawings.

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.

Note that the technical ideas presented in this disclosure are not limited to the above-described embodiments and can be modified as appropriate within the scope of the intent.

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.
(Appendix 2)
The control unit
2. The communication device according to 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 a 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 to 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 to the base station.
(Appendix 5)
The control unit
5. The communication device according to claim 1, 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 6)
The control unit
6. 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.
(Appendix 7)
The control unit
A communication device 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
The base station 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;
A communication method in which the first PLMN and the second PLMN are different.
(Appendix 12)
When establishing a session between the first data network and the communication terminal,
12. The communication method according to claim 11, wherein a session between the first data network and the communication terminal is established 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 to 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, further comprising identifying the management device when the communication terminal requests the use of the second data network in the registration process.
(Appendix 17)
After temporarily connecting with the base station,
A communication method 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 in which, after receiving the notification message, a process of establishing a connection with a first communication device constituting a first PLMN is started.
(Appendix 20)
20. The communication method described in claim 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 transmitted 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 execute the following: after receiving the request message, establish a session between the communication terminal and a first data network available in a first PLMN.
(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 to the base station.
(Appendix 24)
24. The non-transitory computer-readable medium of claim 23, wherein if the information is notified, the connection with the base station is temporarily permitted.
(Appendix 25)
After temporarily connecting with the base station,
25. The non-transitory computer-readable medium of any one of Supplementary Notes 21 to 24, wherein, in a registration process for the communication terminal, subscriber information for 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, wherein the management device is identified 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 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;
A non-transitory computer-readable medium that initiates a process of establishing a connection with a first communication device that constitutes a first PLMN after receiving the notification message.
(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.

10 Communication device 11 Communication unit 12 Control unit 20 Base station 21 Communication unit 22 Control unit 31 gNB
32 gNB
33 gNB
40 5GC-NW
41 AMF
42 SMF
43 UDM
44 PCF
45 AUSF
46 UPF
50 DN
60 5GC-NW
61 AMF
62 SMF
63 UDM
64 PCF
65 AUSF
66 UPF
70 DN
81 UE

Claims (10)

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. 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. 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. 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. 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. 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. 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. 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. 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. 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.