WO2023188025A1

WO2023188025A1 - Communication device, base station, communication method, and non-transitory computer readable medium

Info

Publication number: WO2023188025A1
Application number: PCT/JP2022/015610
Authority: WO
Inventors: 拓也庄司
Original assignee: 日本電気株式会社
Priority date: 2022-03-29
Filing date: 2022-03-29
Publication date: 2023-10-05

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

Communication devices, base stations, communication methods, and non-transitory computer-readable media

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 a part of the network managed by a telecommunications carrier, the effects of the failure may spread to the entire network, causing the entire network to become congested. When the entire network becomes congested, the network becomes unable 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 communication carriers and use communication services provided by other communication carriers.

Patent Document 1 discloses a process in which a base station that receives a connection request from a terminal to a network selects a network to which the terminal connects. For example, the base station identifies the network corresponding to the terminal and selects the identified network as the network to which the terminal connects.

Japanese Patent Application Publication No. 2016-144106

If 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. There is a problem in that communication services cannot be provided separately.

In view of the above-mentioned problems, one of the objects of the present disclosure is to provide a communication device, a base station, and a base station capable of providing communication services by distinguishing terminals that temporarily use a network and/or base stations to which they are temporarily connected. An object of the present invention is to provide a communication method and a non-transitory computer-readable medium.

A communication device according to a first aspect of the present disclosure is a communication device that configures a first Public Land Mobile Network (PLMN), and after temporarily connecting with a base station, the communication device connects to a base station from a communication terminal via the base station. a communication unit that receives a request message requesting establishment of a session with a second data network available in the second PLMN; the first PLMN and the second PLMN are different from each other.

A base station according to a second aspect of the present disclosure includes a communication unit that receives a notification message indicating that it is in a congestion state from a second communication device that configures a second PLMN, and a communication unit that receives the notification message after receiving the notification message. , a control unit that starts processing for establishing a connection with a first communication device constituting the 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), in which a communication terminal a request message requesting the establishment of a session with a second data network available at a second PLMN from, via said base station, and after receiving said request message, a request message requesting establishment of a session with a second data network available at the first PLMN; establishing a session between a first data network and the communication terminal, and the first PLMN and the second PLMN are different.

A program according to a fourth aspect of the present disclosure is a program that is caused to be executed by a computer that is a communication device that constitutes a first Public Land Mobile Network (PLMN), and is a program that causes a computer, which is a communication device that constitutes a first Public Land Mobile Network (PLMN), to execute a communication terminal. a request message requesting establishment of a session with a second data network available at a second PLMN, different from the first PLMN and the second PLMN, from the base station; After receiving the request message, the computer is caused to establish a session between a first data network available in a first PLMN and the communication terminal.

According to the present disclosure, there is provided a communication device, a base station, a communication method, and a non-transitory computer-readable medium that can provide communication services by distinguishing terminals that temporarily use a network and/or temporarily connected base stations. can be provided.

1 is a configuration diagram of a communication device according to a first embodiment; FIG. 7 is a flowchart of session establishment processing executed in the communication device according to the first embodiment. 1 is a configuration diagram of a base station according to Embodiment 1. FIG. 5 is a flowchart of connection establishment processing executed in the base station according to the first embodiment. FIG. 2 is a configuration diagram of a communication system according to a second embodiment. FIG. 7 is a diagram showing the flow of processing when congestion occurs in the AMF according to the second embodiment. 7 is a diagram showing the flow of Registration processing according to Embodiment 2. FIG. FIG. 7 is a diagram showing the flow of PDU session establishment processing according to the second embodiment. FIG. 7 is a diagram showing the flow of Registration processing according to Embodiment 3; FIG. 2 is a configuration diagram of a communication device, a base station, a gNB, and an AMF according to each embodiment.

(Embodiment 1)
Embodiments of the present disclosure will be described below with reference to the drawings. A configuration example of the communication device 10 according to the first embodiment will be described using FIG. 1. The communication device 10 may be software or a module that operates by a processor executing a program stored in a memory. The communication device 10 may be, for example, a node device that configures 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 telecommunications carrier to provide telecommunications services. PLMN consists of "MCC" (Mobile Country Code), which represents the country/region represented by a three-digit number, and "MNC" (Mobile Network Code), which represents the operator by a two- to three-digit number (depending on the country). ) is expressed as a 5- to 6-digit number. In the following description, the communication device 10 will be described as a communication device forming a first PLMN.

The communication device 10 has a communication section 11 and a control section 12. The communication unit 11 and the control unit 12 may be software or modules whose processing is executed by a processor executing a program stored in a memory. Alternatively, the communication unit 11 and the control unit 12 may be hardware such as a circuit or a chip.

After temporarily connecting with the base station 20, the communication unit 11 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. Receive. The base station 20 may be a base station that constitutes a first PLMN. The base station 20 may be a base station that constitutes a second PLMN.

The communication unit 11 temporarily connecting with 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 be a state in which a logical line is set up between the communication device 10 and the base station 20. For example, a state in which a connection is established may be a state in which 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 be a state in which association is performed between the communication device 10 and the base station 20 using a protocol in the transport layer. A state in which a connection is established means, for example, that the setup of the NG (Next Generation) interface between AMF (Access and Mobility management Function) and gNB (gNode B) in 5G is completed, and communication using an application protocol is completed. It may be possible to do so.

When the 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. The message may be referred to as, for example, C (Control)-Plane data or control data.

The state where a connection is temporarily established may be, for example, maintaining the establishment of a connection for a predetermined period of time, and canceling the connection after the predetermined period has elapsed. Resolving a connection may also be referred to as severing the connection. The connection may be canceled autonomously after a predetermined period has elapsed, or may be canceled by a maintenance person or the like operating the communication device 10 or the base station 20. Thereby, when the base station 20 is different from the PLMN of the communication device 10, the processing load on the PLMN of the communication device 10 can be managed.

The data network may be, for example, a network that includes a server device in which data used by the user is stored, or a server device that the user wishes to access. A network having a server device may also be referred to as a network to which the server device is connected.

The second PLMN is a different network 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, and the second PLMN includes the second data network. It may be a configuration.

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

After receiving the request message, the control unit 12 establishes a session between the first data network available in the first PLMN and the communication terminal. Since the communication device 10 is a communication device constituting the first PLMN, the control unit 12 does not establish a session between the second data network available in the second PLMN and the communication terminal. Alternatively, if the control unit 12 does not manage the second data network or does not recognize the existence of the second data network, the control unit 12 establishes a session between the second data network and the communication terminal. Can not do it. 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 the temporarily connected base station 20, the control unit 12 connects the first data network available in the first PLMN instead of the second data network. Establish a session with the communication terminal. That is, when the control unit 12 receives a request message from a communication terminal via a constantly connected base station, the control unit 12 sends a message to the communication terminal rejecting the process of establishing a session between the second data network and the communication terminal. You can also send it to A base station that is always connected refers to a base station that maintains connection unless a failure occurs in the base station or the communication device 10, or unless it is necessary to disconnect the base station and the communication device 10 due to maintenance work. It may also be a base station.

Next, a flowchart of session establishment processing executed in the communication device 10 according to the first embodiment will be described using FIG. 2. First, after temporarily connecting with the base station 20, the communication unit 11 sends a request from the communication terminal via the base station 20 to establish a session with a second data network available in the second PLMN. A message is received (S11). Next, the control unit 12 establishes a session between the communication terminal and the first data network that can be used in the first PLMN instead of the second data network (S12).

Next, a configuration example of the base station 20 according to the first embodiment will be described using FIG. 3. Base station 20 may be a computer device whose processor operates by executing a program stored in memory. The base station 20 performs wireless communication with communication terminals according to a predetermined communication standard. The communication standard is, for example, a communication standard defined in the 3rd Generation Partnership Project (3GPP), and may be a wireless communication standard called 5G, for example.

The base station 20 has a communication section 21 and a control section 22. The communication unit 21 and the control unit 22 may be software or modules whose processing is executed by a processor executing a program stored in a memory. Alternatively, the communication section 21 and the control section 22 may be hardware such as a circuit or a chip.

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

After receiving the notification message, the control unit 22 starts processing to establish a connection with the first communication device forming the first PLMN. It is assumed that the base station 20 is always connected to the communication devices forming the second PLMN. When the base station 20 receives a notification message indicating the congestion state from the communication device forming the second PLMN, it temporarily connects to the communication device 10 forming the first PLMN. Thereby, communication terminals connected to the PLMN via the base station 20 can 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 maintain the connection with the communication device constituting the second PLMN. , may start a connection with the communication device 10.

Next, a flowchart of a connection establishment process executed at the base station 20 according to the first embodiment will be described using FIG. 4. First, the communication unit 21 receives a notification message indicating a congestion state from a communication device forming the second PLMN (S21). Next, after receiving the notification message, the control unit 22 starts processing to establish a connection with the communication device 10 that constitutes 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 establishment of a session with the data network via the temporarily connected base station 20. That is, a session is temporarily established with the first data network for the communication terminal that uses the first PLMN. As a result, the communication device 10 provides a communication service to the communication terminal that has sent the request message to the first PLMN due to the fact that the second PLMN is not available, and A data network can be used.

(Embodiment 2)
Next, a configuration example of the communication system according to the second embodiment will be described using FIG. 5.
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. Further, a DN (Data Network) 50 is available via the 5GC-NW 40, and a DN 70 is available via the 5GC-NW 60. UE (User Equipment) 81 is located in a communication area formed by gNB 31 and performs wireless communication with gNB 31. DN70 corresponds to the first data network in the first embodiment, and DN50 corresponds to the second data network. For example, it is assumed that 5GC-NW40 is included in PLMN_A, and 5GC-NW60 is included in PLMN_B. PLMN_A is, for example, a network managed by carrier A, and PLMN_B is a network managed by 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.

The gNBs 31 to 33 are base stations that support 5G and New Radio (NR) as wireless communication standards. The

gNBs

31 and 32 are always connected to the 5GC-NW 40, and when the 5GC-NW 40 becomes congested, the connection destination is temporarily switched to the 5GC-NW 60. In other words, when the 5GC-NW 40 becomes congested, the

gNBs

31 and 32 save the data that was being transmitted and received with the 5GC-NW 40 to the 5GC-NW 60. The

gNBs

31 and 32 may temporarily switch the connection destination to the 5GC-NW 60 even if a failure occurs in the 5GC-NW 40. The

gNBs

31 and 32 may be base stations that are managed in association with the MCC and MNC of the communication carrier A, for example. Furthermore, the gNB 33 may be a base station that is managed in association with, for example, the MCC and MNC of the communication carrier B.

The UE 81 communicates with the DN 50 via the gNB 31 and the 5GC-NW 40 when the 5GC-NW 40 is not in a congestion state but in a normal state. In other words, the UE 81 establishes a session in the gNB 31 and the 5GC-NW 40 and communicates with the DN 50. The session established between the gNB 31 and the 5GC-NW 40 may be a PDU (Protocol Data Unit) session. UE is used as a general term for communication terminals in 3GPP. The UE may be, for example, a smartphone terminal, a tablet terminal, an IoT (Internet of Things) terminal, or the like.

The 5GC-NW 40 includes an AMF (Access and Mobility management Function) entity 41 (hereinafter referred to as AMF 41), an SMF (Session Management Function) entity 42 (hereinafter referred to as SMF 42), and a UDM (Unified Data Management) entity 43 (hereinafter referred to as SMF 42). UDM43), PCF (Policy Control Function) entity 44 (hereinafter referred to as PCF44), AUSF (Authentication Server Function) 45 (hereinafter referred to as AUSF45), and UPF (User Plane Function) entity 46 (hereinafter referred to as UPF46). ).

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

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, the AMF 61, SMF 62, UDM 63, PCF 64, and UPF 65 have functions necessary to temporarily connect with the gNBs 31 to 33. The AMF 61 corresponds to the communication device 10 in FIG.

5GC-NW40 and 5GC-NW60 are connected. For example, 5GC-NW40 and 5GC-NW40 may be connected via a SEPP (Security Edge Protection Proxy) (not shown) placed in 5GC-NW40 and SEPP placed in 5GC-NW60. Alternatively, 5GC-NW40 and 5GC-NW40 may be connected without going through SEPP. SEPP is used for interconnection of PLMNs, and performs filtering of messages transmitted between PLMNs.

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

First, when the AMF 41 detects that it is in a congestion state, it transmits a congestion notification message to the gNB 31 to notify that it is in a congestion state (S21).

Next, upon receiving the congestion notification message, the gNB 31 transmits an NG setup request message to the AMF 61 (S22). The gNB 31 may predetermine to establish a new connection with the AMF 61 when the AMF 41 becomes congested. Alternatively, information about the AMF that establishes a new connection may be included in the congestion notification message. For example, if the congestion notification message includes information about the AMF 61, the gNB 31 may decide to establish a connection with the AMF 61.

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.

The gNB 31 may cancel the connection with the AMF 41 before transmitting the NG setup request message or after receiving the NG setup response message. Alternatively, the gNB 31 may cancel the connection with the AMF 41 after transmitting the NG setup request message and before receiving the NG setup response message.

Furthermore, the gNB 31 may set a parameter indicating that a temporary connection establishment with the AMF 61 is requested in the NG setup request message. The gNB 31 may further set a parameter indicating that the cause of temporarily requesting establishment of a connection with the AMF 61 is that the AMF 41 is in a congested state. For example, the gNB 31 may indicate that the AMF that the gNB 31 always connects to is the AMF 41 and that it temporarily connects to the AMF 61 by setting the ID indicating PLMN_A in the NG setup request message. Upon receiving the NG setup request message, the AMF 61 may manage that the gNB 31 is a gNB that is constantly connected to a PLMN different from PLMN_B. In other words, the AMF 61 may manage the gNB 31 as a gNB that is temporarily connected to the AMF 61. For example, the AMF 61 may manage that the gNB 31 is a gNB that is constantly connected to a PLMN different from PLMN_B using a flag indicating whether the gNB is a gNB that is always connected to a PLMN different from PLMN_B.

The AMF 61 transmits an NG setup response message to the gNB 31 when it is permitted to temporarily establish a connection with the gNB 31. When the AMF 61 receives an NG setup request message including a parameter indicating that a temporary connection establishment with the AMF 61 is requested, the AMF 61 may uniformly permit establishment of the connection. Alternatively, if the AMF 61 has previously managed the PLMN ID included in the NG setup request message as a PLMN that temporarily permits connection establishment, it may permit connection establishment. Note that when temporarily permitting the establishment of a connection, a predetermined timer may be used to manage each permitted connection. If the timer expires, a temporary connection may be released. According to this, it becomes possible to prevent temporary connections from being maintained continuously, and it becomes possible to manage the load caused by temporary connections.

Next, the flow of the Registration process according to the second embodiment will be explained using FIG. 7. The Registration process in FIG. 7 will be explained from Figure 4.2.2.2.2-1:Registration procedure in 3GPP TS 23.502 V17.3.0 (2021-12) with reference to the parts necessary for explaining the present disclosure. Further, the Registration process in FIG. 7 is executed after the gNB 31 establishes a connection with the AMF 61 in FIG.

First, the UE 81 transmits a Registration Request message to the gNB 31 (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 SUCI (Subscription Concealed Identifier) or SUPI (Subscription Permanent Identifier), which is identification information of the UE 81. Furthermore, the Registration Request message may include identification information of the network slice that the UE 81 desires to use. It is assumed that the 5GC-NW 40 has the subscriber data and authentication data of the UE 81. That is, the UE 81 temporarily registers with the 5GC-NW 60.

Next, gNB31 selects AMF (S32). Here, the gNB 31 selects the AMF 61 with which the connection has been established. Next, the gNB 31 transmits the Registration Request message received in step S31 to the AMF 61 (S33).

Next, the AMF 61 selects the AUSF to perform authentication processing for the UE 81 (S34). The AMF 61 may select the AUSF 45 by, for example, inquiring an NRF (Network Repository Function) entity (hereinafter referred to as NRF) using the MCC and MNC included in the SUCI. SUCI consists of MCC, MNC, and 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 may manage information regarding the node devices or functions that constitute the 5GC-NW40 and the 5GC-NW60, and may provide the managed information in response to inquiries.

Next, the AMF 61, AUSF 45, and UDM 43 each cooperate to perform authentication processing regarding the UE 81 (S35).

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

Next, the AMF 61 transmits a request message to the UDM 43 to call the Nudm_SDM_Get service in the UDM 43, and receives a response message containing subscriber data regarding the UE 81 (S37). AMF61 may transmit a request message to UDM43 via AMF41.

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. When the AMF 61 selects the PCF 44, the policy in the 5GC-NW 40 may be applied to the UE 81.

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 PLMN_B network.

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

By executing the Registration process in FIG. 7, the UE 81 is registered with the AMF 61.

Next, the flow of the PDU session establishment process according to the second embodiment will be described using FIG. 8. The process of establishing a PDU session regarding the UE 81 is based on the premise that the Registration process of the UE 81 in the 5GC-NW 60 has been completed.

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 DN50 as the DN that the UE 81 desires to use.

Next, the AMF 61 selects an SMF that manages the session regarding the UE 81 (S52). The AMF 61 may select an SMF in consideration of the DN used by the UE 81. For example, the AMF 61 may select an SMF that can establish a session regarding the DN used by the UE 81.

Here, in step S51, the AMF 61 receives a NAS message containing DN50 as the DN that the UE 81 desires to use. However, the DN to which the 5GC-NW 60 to which the AMF 61 is installed can connect is DN70. Therefore, the AMF 61 selects the SMF 62 that can establish a session regarding the DN 70 instead of the DN 50 that the UE 81 desires to use. In other words, the AMF 61 replaces DN50 with DN70 and selects the SMF 62 in consideration of DN70.

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

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

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 information necessary to establish a PDU session regarding the UE 81, for example. Specifically, the information necessary to establish a PDU session regarding the UE 81 may be an IP address assigned to the UE 81.

Next, the UPF 66 transmits an N4_Session Establishment/Modification Response message to the SMF 62 as a response to the N4_Session Establishment/Modification Request message (S57).

Next, the SMF 62 transmits a request message to call the Namf_Communication_N1N2Message Transfer service in the AMF 61 to the AMF 61 (S58). The request message may include, for example, a PDU Session ID.

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

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

By executing the PDU session establishment process in FIG. 8, a PDU session is established between the UE 81 and the UPF 66, and the UE 81 is able to transmit and receive U-Plane data with the DN 70 via the UPF 66. becomes.

As explained above, the gNB 31 can temporarily establish a connection with the AMF 61 in the 5GC-NW 60 when the 5GC-NW 40 becomes congested. Further, the UE 81 is registered with the AMF 61 by performing a registration process with the AMF 61, and can further establish a PDU session with the UPF 66. Thereby, the UE 81 can transmit and receive U-Plane data to and from the DN 70. That is, the UE 81 can transmit and receive U-Plane data via the 5GC-NW 60 when the 5GC-NW 40 is in a congested state.

Furthermore, in the Registration process, the AMF 61 can perform billing processing and the like regarding the UE 81 in the 5GC-NW 40 by accessing the UDM 43.

(Embodiment 3)
Next, the flow of Registration processing according to the third embodiment will be explained using FIG. 9. Steps S41-S43 are the same as steps S31-S33 in FIG. 7, so their explanation will be omitted.

Next, the AMF 61 selects the 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 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, the DN 50. Alternatively, when the AMF 61 receives a Registration Request message from the gNB 31 managed as a gNB temporarily connected to the AMF 61, the AMF 61 may select the AUSF 65 as the predetermined AUSF. For example, a case will be described in which a parameter indicating that a temporary connection establishment with the AMF 61 is requested is included in the NG setup request message received from the gNB 31. In such a case, the AMF 61 may select the AUSF 65 when receiving the Registration Request message from the gNB 31.

Next, the AMF 61, AUSF 65, and UDM 63 cooperate to perform authentication processing regarding the UE 81 (S45). The authentication process for the UE 81 may be simpler than the authentication process for the UE that has transmitted the Registration Request message via the gNB 33 that is constantly connected to the AMF 61, for example. For example, the authentication process for the UE 81 may be performed with a smaller amount of calculation than the authentication process for the UE that has transmitted the Registration Request message via the gNB 33. Alternatively, in the authentication process regarding the UE 81, an encryption key for encrypting data regarding the UE 81 may not be generated. Alternatively, in a case where registration of all UEs to be temporarily registered is permitted, the authentication process itself in step S45 may not be performed. Alternatively, a predetermined encryption key may be used. Alternatively, a common key may be used for UEs that have temporarily registered. The encryption key may be generated, for example, by using predetermined input values (for example, all 0s) as input values necessary for generation.

Next, the AMF 61 selects UDM (S46). Here, the AMF 61 may select the UDM 63 when the UE 81 corresponds to a UE that temporarily registers. For example, the AMF 61 may select the UDM 63 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 the AMF 61. Alternatively, the AMF 61 may select the UDM 63 as the predetermined UDM if the Registration Request message includes information on a data network that is not available in the 5GC-NW 60, for example, the DN 50. Alternatively, when the AMF 61 receives a Registration Request message from the gNB 31 managed as a gNB temporarily connected to the AMF 61, the AMF 61 may select the UDM 63 as the predetermined UDM. For example, a case will be described in which a parameter indicating that a temporary connection establishment with the AMF 61 is requested is included in the NG setup request message received from the gNB 31. In such a case, the AMF 61 may select the UDM 63 when receiving the Registration Request message from the gNB 31.

The AMF 61 may select the UDM using the same selection criteria as the selection criteria used when selecting the AUSF in step S44. Further, when the AMF 61 selects the AUSF 65 in step S44 because the UE 81 corresponds to the UE to be temporarily registered, the AMF 61 may select the UDM 63 associated with the AUSF 65 in advance in step S46.

Next, the AMF 61 transmits a request message to the UDM 63 to call the Nudm_SDM_Get service in the UDM 63, and receives a response message containing subscriber data regarding the UE 81 (S37). The subscriber data regarding the UE 81 managed by the UDM 63 may be subscriber data associated with the UE temporarily registered in the 5GC-NW 60. For example, the subscriber data regarding the UE 81 managed by the UDM 63 may include temporary identification information assigned to the UE temporarily registered with the 5GC-NW 60.

Next, the AMF 61 selects the 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 if the Registration Request message includes a PLMN ID indicating PLMN_A or a PLMN ID indicating a PLMN different from the AMF 61. Alternatively, the AMF 61 may select the PCF 64 as the predetermined PCF if the Registration Request message includes information on a data network that is not available in the 5GC-NW 60, for example, the DN 50. Alternatively, when the AMF 61 receives a Registration Request message from the gNB 31 managed as a gNB temporarily connected to the AMF 61, the AMF 61 may select the PCF 64 as the predetermined PCF. For example, a case will be described in which a parameter indicating that a temporary connection establishment with the AMF 61 is requested is included in the NG setup request message received from the gNB 31. In such a case, the AMF 61 may select the PCF 64 when receiving the Registration Request message from the gNB 31.

The AMF 61 may select the PCF using the same selection criteria as the selection criteria used when selecting the AUSF in step S44. Further, when the AMF 61 selects the AUSF 65 in step S44 because the UE 81 corresponds to the UE to be temporarily registered, the AMF 61 may select the PCF 64 associated with the AUSF 65 in advance in step S46.

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 PLMN_B network.

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

As explained above, by executing the Registration process according to the third embodiment, the AMF 61 can select the AUSF 65, UDM 63, and PCF 64 arranged in the 5GC-NW 60. This makes it possible to reduce the processing load on the 5GC-NW 40 that is in a congested state. Furthermore, in the 5GC-NW 60, authentication processing for temporarily registered UEs is executed more simply than authentication processing executed for normal UEs. Thereby, many UEs that were registered in PLMN_A can be registered in PLMN_B.

(Embodiment 4)
Next, the flow of data processing 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, it transmits a message to the gNB 31 notifying that it has recovered from the congestion state. When the gNB 31 receives a message notifying that it has recovered from the congestion state, it may cancel the connection with the AMF 61 and establish a connection with the AMF 41. When gNB31 cancels the connection with AMF61, UE81 transmits a Registration Request message to AMF41 via gNB31. Furthermore, as the connection between the gNB 31 and the AMF 61 is terminated, the PDU session regarding the UE 81 is also disconnected. Therefore, the UE 81 establishes a PDU session in the 5GC-NW 40.

When the AMF 41 simultaneously notifies all gNBs that can establish connections with the AMF 41 with a message notifying that it has recovered from the congestion state, Registration Request messages are concentrated in the AMF 41 in a short period of time. As a result, the AMF 41 may become congested again. Therefore, for example, all gNBs that can establish a connection with the AMF 41 may be divided into several groups, and a message notifying that the congestion state has been recovered may be sent to each group at a time difference. This can prevent Registration Request messages from concentrating on the AMF 41 in a short period of time.

Alternatively, when temporarily registering the UE 81, the AMF 61 may cancel the registration of the UE 81 after a predetermined period has elapsed. Specifically, the AMF 61 may set a timer for each UE that is temporarily registered, and manage the registration period given to the UE.

Each deregistered UE sends a Registration Request message to the gNB 31. At this time, the gNB 31 receives a message from the AMF 41 notifying that it has recovered from the congestion state, and if it has established a connection with the AMF 41, it sends a Registration Request message to the AMF 41. Further, if the gNB 31 has not received a message from the AMF 41 notifying that the congestion state has been recovered, the gNB 31 transmits a Registration Request message to the AMF 61.

As explained above, by providing a time difference in the 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.

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 the communication device 10 etc.) described in the above embodiment. Referring to FIG. 10, the communication device 10 and the like include a network interface 1201, a processor 1202, and a memory 1203. Network interface 1201 may be used to communicate with network nodes. 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 software (computer program) from the memory 1203 and executes it, thereby performing the processing of the communication device 10 and the like described using the flowchart in the above embodiment. Processor 1202 may be, for example, a microprocessor, MPU, or CPU. Processor 1202 may include multiple processors.

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

In the example of FIG. 10, memory 1203 is used to store software modules. By reading these software module groups from the memory 1203 and executing them, the processor 1202 can perform the processing of the communication device 10 and the like described in the above-described embodiments.

As described using FIG. 10, each of the processors included in the communication device 10, etc. in the above-described embodiments executes one or more programs including a group of instructions for causing a computer to execute the algorithm described using the drawings. Execute.

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

Note that the technical idea shown in the present disclosure is not limited to the above embodiments, and can be modified as appropriate without departing from the spirit.

Part or all of the above embodiments may be described as in the following additional notes, but are not limited to the following.
(Additional note 1)
A communication device constituting a first Public Land Mobile Network (PLMN),
a communication unit that receives a request message requesting establishment of a session with a second data network available in a second PLMN from a communication terminal via the base station after temporarily connecting with the base station;
a control unit that establishes a session between a first data network available in a first PLMN and the communication terminal after receiving the request message;
A communication device in which the first PLMN and the second PLMN are different.
(Additional note 2)
The control unit includes:
If the request message is sent from the base station after temporarily permitting the connection with the base station that was connected to the second PLMN, the communication between the first data network and the communication terminal The communication device according to supplementary note 1, which establishes a session between.
(Additional note 3)
The control unit includes:
When information indicating that the connection destination of the base station will be temporarily changed from the second PLMN to the first PLMN is notified from the base station, the connection with the base station is temporarily changed. The communication devices described in Appendix 2 are permitted.
(Additional note 4)
The control unit includes:
The communication device according to appendix 3, wherein the communication device temporarily permits connection with the base station when information identifying the second PLMN is notified as the information.
(Appendix 5)
The control unit includes:
5. The communication device according to any one of Supplementary Notes 1 to 4, wherein subscriber information of the communication terminal is acquired from a management device constituting the second PLMN in the registration process regarding the communication terminal.
(Appendix 6)
The control unit includes:
The communication device according to appendix 5, wherein the communication device specifies the management device when the communication terminal requests to use the second data network in the registration process.
(Appendix 7)
The control unit includes:
In the registration process regarding the communication terminal, when the use of the second data network is requested, a second registration process is executed, and the second registration process uses the first data network. 5. The communication device according to any one of Supplementary Notes 1 to 4, which is different from the first registration process performed on a communication terminal that requests to do so.
(Appendix 8)
The control unit includes:
The communication device according to supplementary note 7, wherein the second registration process is executed so that a load in the second registration process is less than 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 forming the second PLMN;
A base station comprising: a control unit that starts processing for establishing a connection with a first communication device constituting a first PLMN after receiving the notification message.
(Appendix 10)
The control unit includes:
According to appendix 9, when a registration request message is received from a communication terminal corresponding to the second PLMN after establishing a connection with the first communication device, the registration request message is sent to the first communication device. Base station listed.
(Appendix 11)
A communication method executed in a communication device constituting a first Public Land Mobile Network (PLMN), comprising:
After temporarily connecting with a base station, receiving 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;
establishing a session between a first data network available in a first PLMN and the communication terminal after receiving the request message;
A communication method in which the first PLMN and the second PLMN are different.
(Appendix 12)
In establishing a session between the first data network and the communication terminal,
If the request message is sent from the base station after temporarily permitting the connection with the base station that was connected to the second PLMN, the communication between the first data network and the communication terminal The communication method according to supplementary note 11, which establishes a session between.
(Appendix 13)
Before receiving said request message,
When information indicating that the connection destination of the base station will be temporarily changed from the second PLMN to the first PLMN is notified from the base station, the connection with the base station is temporarily changed. The communication method described in Appendix 12 is permitted.
(Appendix 14)
The communication method according to appendix 13, wherein connection with the base station is temporarily permitted when information identifying the second PLMN is notified as the information.
(Appendix 15)
After temporarily connecting with the base station,
15. The communication method according to any one of appendices 11 to 14, wherein, in the registration process regarding the communication terminal, subscriber information of the communication terminal is acquired from a management device constituting the second PLMN.
(Appendix 16)
After temporarily connecting with the base station,
16. The communication method according to appendix 15, wherein the management device is identified when the communication terminal requests to use the second data network in the registration process.
(Appendix 17)
After temporarily connecting with the base station,
In the registration process regarding the communication terminal, when the use of the second data network is requested, a second registration process is executed, and the second registration process uses the first data network. 15. The communication method according to any one of Supplementary Notes 11 to 14, which is different from the first registration process performed on a communication terminal that requests to do so.
(Appendix 18)
18. The communication method according to appendix 17, wherein the second registration process is executed so that the load on the second registration process is less than the load on the first registration process.
(Appendix 19)
A communication method executed at a base station, the method comprising:
receiving a notification message indicating a congestion state from a second communication device configuring the second PLMN;
A communication method, wherein after receiving the notification message, a process for establishing a connection with a first communication device constituting a first PLMN is started.
(Additional note 20)
If a registration request message is received from a communication terminal corresponding to the second PLMN after establishing a connection with the first communication device, the registration request message is sent to the first communication device, according to appendix 19. Communication method described.
(Additional note 21)
A non-transitory computer-readable medium storing a program executed by a computer that is a communication device constituting a first Public Land Mobile Network (PLMN),
After temporarily connecting with the base station, receiving a request message from the communication terminal via the base station requesting the establishment of a session with a second data network available in the second PLMN; PLMN and the second PLMN are different from each other.
a non-transitory computer storing a program that causes the computer to execute, after receiving the request message, establishing a session between a first data network available in a first PLMN and the communication terminal; readable medium.
(Additional note 22)
In establishing a session between the first data network and the communication terminal,
If the request message is sent from the base station after temporarily permitting the connection with the base station that was connected to the second PLMN, the communication between the first data network and the communication terminal 22. The non-transitory computer-readable medium of clause 21 for establishing a session between.
(Additional note 23)
Before receiving said request message,
When information indicating that the connection destination of the base station will be temporarily changed from the second PLMN to the first PLMN is notified from the base station, the connection with the base station is temporarily changed. Non-transitory computer-readable media as described in Clause 22.
(Additional note 24)
24. The non-transitory computer-readable medium according to attachment 23, wherein the non-transitory computer-readable medium temporarily permits connection with the base station when information identifying the second PLMN is notified as the information.
(Additional note 25)
After temporarily connecting with the base station,
25. The non-transitory computer-readable medium according to any one of appendices 21 to 24, wherein subscriber information of the communication terminal is acquired from a management device constituting the second PLMN in the registration process regarding the communication terminal.
(Additional note 26)
After temporarily connecting with the base station,
26. The non-transitory computer-readable medium according to appendix 25, which identifies the management device when the communication terminal requests to use the second data network in the registration process.
(Additional note 27)
After temporarily connecting with the base station,
In the registration process regarding the communication terminal, when the use of the second data network is requested, a second registration process is executed, and the second registration process uses the first data network. 25. The non-transitory computer-readable medium according to any one of appendices 21 to 24, which is different from the first registration process performed on a communication terminal that requests to do so.
(Additional note 28)
28. The non-transitory computer-readable medium according to attachment 27, wherein the second registration process is executed so that a load on the second registration process is reduced compared to a load on the first registration process.
(Additional note 29)
A non-transitory computer-readable medium storing a program to be executed by a computer serving as a base station,
receiving a notification message indicating a congestion state from a second communication device configuring the second PLMN;
A non-transitory computer-readable medium that initiates a process of establishing a connection with a first communication device constituting a first PLMN after receiving the notification message.
(Additional note 30)
If a registration request message is received from a communication terminal corresponding to the second PLMN after establishing a connection with the first communication device, the registration request message is sent to the first communication device, according to appendix 29. non-transitory computer-readable medium as described.

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
50DN
60 5GC-NW
61 AMF
62 SMF
63 UDM
64 PCF
65 AUSF
66 UPF
70DN
81 U.E.

Claims

A communication device constituting a first Public Land Mobile Network (PLMN),
a communication unit that receives a request message requesting establishment of a session with a second data network available in a second PLMN from a communication terminal via the base station after temporarily connecting with the base station;
a control unit that establishes a session between a first data network available in a first PLMN and the communication terminal after receiving the request message;
A communication device in which the first PLMN and the second PLMN are different.
The control unit includes:
If the request message is sent from the base station after temporarily permitting the connection with the base station that was connected to the second PLMN, the communication between the first data network and the communication terminal The communication device according to claim 1, wherein the communication device establishes a session between users.
The control unit includes:
When information indicating that the connection destination of the base station will be temporarily changed from the second PLMN to the first PLMN is notified from the base station, the connection with the base station is temporarily changed. The communication device according to claim 2, wherein the communication device allows.
The control unit includes:
4. The communication device according to claim 3, wherein when information identifying the second PLMN is notified as the information, connection with the base station is temporarily permitted.
The control unit includes:
5. The communication device according to claim 1, wherein subscriber information of the communication terminal is acquired from a management device constituting the second PLMN in the registration process regarding the communication terminal.
The control unit includes:
6. The communication device according to claim 5, wherein the communication device specifies the management device when the communication terminal requests to use the second data network in the registration process.
The control unit includes:
In the registration process regarding the communication terminal, when the use of the second data network is requested, a second registration process is executed, and the second registration process uses the first data network. The communication device according to any one of claims 1 to 4, wherein the communication device is different from the first registration process performed on a communication terminal requesting the communication terminal.
The control unit includes:
The communication device according to claim 7, wherein the second registration process is executed so that the load on the second registration process is reduced compared to the load on the first registration process.
a communication unit that receives a notification message indicating a congestion state from a second communication device forming the second PLMN;
A base station comprising: a control unit that starts processing for establishing a connection with a first communication device constituting a first PLMN after receiving the notification message.
The control unit includes:
10. When a registration request message is received from a communication terminal corresponding to the second PLMN after establishing a connection with the first communication device, the registration request message is sent to the first communication device. Base station described in.
A communication method executed in a communication device constituting a first Public Land Mobile Network (PLMN), comprising:
After temporarily connecting with a base station, receiving 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;
establishing a session between a first data network available in a first PLMN and the communication terminal after receiving the request message;
A communication method in which the first PLMN and the second PLMN are different.
In establishing a session between the first data network and the communication terminal,
If the request message is sent from the base station after temporarily permitting the connection with the base station that was connected to the second PLMN, the communication between the first data network and the communication terminal The communication method according to claim 11, wherein the communication method establishes a session between the two parties.
Before receiving said request message,
When information indicating that the connection destination of the base station will be temporarily changed from the second PLMN to the first PLMN is notified from the base station, the connection with the base station is temporarily changed. The communication method according to claim 12, wherein the communication method is permitted.
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.
After temporarily connecting with the base station,
15. The communication method according to claim 11, wherein, in the registration process regarding the communication terminal, subscriber information of the communication terminal is acquired from a management device constituting the second PLMN.
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 to use the second data network in the registration process.
After temporarily connecting with the base station,
In the registration process regarding the communication terminal, when the use of the second data network is requested, a second registration process is executed, and the second registration process uses the first data network. The communication method according to any one of claims 11 to 14, which is different from the first registration process performed on a communication terminal requesting the communication.
18. The communication method according to claim 17, wherein the second registration process is executed so that the load on the second registration process is less than the load on the first registration process.
A communication method executed at a base station, the method comprising:
receiving a notification message indicating a congestion state from a second communication device configuring the second PLMN;
A communication method, wherein after receiving the notification message, a process for establishing a connection with a first communication device constituting a first PLMN is started.
19. When a registration request message is received from a communication terminal corresponding to the second PLMN after establishing a connection with the first communication device, the registration request message is sent to the first communication device. Communication methods described in.
A non-transitory computer-readable medium storing a program executed by a computer that is a communication device constituting a first Public Land Mobile Network (PLMN),
After temporarily connecting with the base station, receiving a request message from the communication terminal via the base station requesting the establishment of a session with a second data network available in the second PLMN; PLMN and the second PLMN are different from each other.
a non-transitory computer storing a program that causes the computer to execute, after receiving the request message, establishing a session between a first data network available in a first PLMN and the communication terminal; readable medium.
In establishing a session between the first data network and the communication terminal,
If the request message is sent from the base station after temporarily permitting the connection with the base station that was connected to the second PLMN, the communication between the first data network and the communication terminal 22. The non-transitory computer-readable medium of claim 21, wherein the non-transitory computer-readable medium establishes a session between users.
Before receiving said request message,
When information indicating that the connection destination of the base station will be temporarily changed from the second PLMN to the first PLMN is notified from the base station, the connection with the base station is temporarily changed. 23. The non-transitory computer readable medium of claim 22.
The non-transitory computer-readable medium according to claim 23, wherein when information identifying the second PLMN is notified as the information, connection with the base station is temporarily permitted.
After temporarily connecting with the base station,
The non-transitory computer-readable medium according to any one of claims 21 to 24, wherein in the registration process regarding the communication terminal, subscriber information of the communication terminal is acquired from a management device constituting the second PLMN. .
After temporarily connecting with the base station,
26. The non-transitory computer-readable medium of claim 25, wherein the non-transitory computer-readable medium identifies the management device when requested by the communication terminal to utilize the second data network in the registration process.
After temporarily connecting with the base station,
In the registration process regarding the communication terminal, when the use of the second data network is requested, a second registration process is executed, and the second registration process uses the first data network. 25. The non-transitory computer-readable medium of any one of claims 21-24, wherein the non-transitory computer-readable medium is different from the first registration process performed on a communication terminal requesting to do so.
28. The non-transitory computer-readable medium according to claim 27, wherein the second registration process is executed so that the load on the second registration process is less than the load on the first registration process.
A non-transitory computer-readable medium storing a program to be executed by a computer serving as a base station,
receiving a notification message indicating a congestion state from a second communication device configuring the second PLMN;
A non-transitory computer-readable medium that initiates a process of establishing a connection with a first communication device constituting a first PLMN after receiving the notification message.
29. When a registration request message is received from a communication terminal corresponding to the second PLMN after establishing a connection with the first communication device, the registration request message is sent to the first communication device. non-transitory computer-readable medium as described in .