JP7385608B2 - Registration method and system for registering communication devices owned by others in the core system by relaying them - Google Patents

Description

The present invention relates to a technology for coordinating different core systems in a mobile communication network.

Common to both 5G (5th Generation) and 4G (4th Generation) standards, a mobile communication network system conceptually consists of a user terminal (UE (User Equipment)), an access network (Access Network), and a core system. It consists of

The user terminal is a device connectable to a mobile communication network, and has a SIM (Subscriber Identity Module) inserted therein. The SIM stores a subscriber identification number IMSI (International Mobile Subscriber Identity) and an authentication key that are different for each user. On the other hand, a device can access data stored in a SIM using an API (Application Programming Interface) (for example, see Non-Patent Document 3). The user terminal is generally the user's own property since the user will be inserting a SIM based on his or her contract.

In the case of a mobile communication network, an access network (AN) is composed of a large number of base stations (eNBs, gNBs, access points) that can communicate with user terminals via radio. The AN transfers data packets between user terminals and the core system. Regarding AN, NR (New Radio) is defined in 5GC (5G Core) (for example, see Non-Patent Document 1), and LTE (Long Term Evolution) is defined in EPC (Evolved Packet Core) of 4GC (4G Core). (For example, see Non-Patent Document 2).

The core system controls user terminals and ANs and provides communication services to users. In the core system, a physical user plane network device group is arranged on a virtualization platform of a logical control plane network device group. The 5G standard is an expansion of the EPC of the 4G standard, and the technical specifications of CUPS (Control and User Plane Separation) have been inherited.

In recent years, services have been considered that allow users to operate communication devices owned by others as if they were their own devices. For example, in the case of a car, travel plan information created by a user's own user terminal and setting information set in a user's own navigation system (for example, user's preferred driving operation information such as speed and how to apply the brakes) are It can be reflected in the navigation system of a rental car owned by someone else.
As described above, there is a need for technology that allows users to continue their own service experience and improve user convenience even when using communication devices owned by others.

In contrast, conventional technology has been developed to link a self-owned SIM card device placed externally with a communication device owned by another person in order to enable the user to use the communication device owned by another person under the user's own communication contract. (For example, see Non-Patent Document 4). According to this technology, a user can connect to a mobile communication network to which he has contracted without inserting his own SIM into a communication device owned by someone else.

There is also an OAuth technology that authorizes a user's communication contract, such as billing and device settings, from a communication device owned by another person to a mobile communication network with which the user has subscribed. OAuth allows multiple web service applications to cooperate without the user himself/herself entering authentication information (ID (IDentifier) and password).

3GPP TS 23.501 “System Architecture for the 5G System” 3GPP TS 23.401 “General Packet Radio Service (GPRS) enhancements for Evolved Universal Terrestrial Radio Access Network (E-UTRAN) access” 3GPP TS 31.101 “UICC-terminal interface; Physical and logical characteristics” Development of portable SIM to create new services “https://www.nttdocomo.co.jp/binary/pdf/corporate/technology/rd/technical_journal/bn/vol22_4/vol22_4_005jp.pdf”

However, according to the technology described in Non-Patent Document 4 mentioned above, only one communication device can be linked, so if the communication device owned by another person is under contract with the other person, the user's own There is a restriction that it is not possible to use communication services based on the contract.
Furthermore, according to the OAuth technology described above, when using a communication device owned by someone else using a user terminal owned by the user, the user does not have to enter authentication information directly or indirectly into the communication device. be. Such an operation not only reduces convenience for the user, but also risks leaving the user's authentication information on a communication device owned by another person. This also creates a security risk that the authentication information may be misused by a third party.

In response to this, the inventors of the present application considered whether it would be possible to immediately use a communication device owned by another person without the user having to input authentication information himself/herself. In particular, we wondered if it would be possible to ensure the same security as a self-owned user terminal, so that even if a communication device owned by someone else is relayed, the user's authentication information will not remain on the communication device.
In addition, the inventors of the present application considered that it would be necessary to charge the user himself/herself even if a communication device owned by another person is relayed.

Therefore, the present invention aims to provide a registration method and system in which a communication device owned by another person can be relayed and registered in a core system from a user terminal owned by the user without inputting authentication information by the user himself/herself. purpose.

According to the present invention, there is provided a registration method in which a first user terminal registers with a first core system via a second user terminal and a second core system,
a first step in which the first user terminal sends a message including a registration request for the first core system to the second user terminal;
a second step in which the second user terminal determines a link ID for the first user terminal that is the source of the received message, and sends a message including the registration request and the link ID to the second core system; ,
A third step in which the second core system associates and stores the link ID with the second user terminal that is the source of the received message, and transfers the message including the registration request to the first core system. and,
a fourth step in which the first core system stores the link ID in association with the second core system that is the source of the received message, and processes the registration request from the first user terminal;
a fifth step in which the first core system responds to the second core system a message including the registration response and the link ID;
a sixth step in which the second core system forwards the message including the registration response and the link ID to the second user terminal based on the link ID included in the received message;
a seventh step in which the second user terminal forwards the message including the registration response to the first user terminal based on the link ID included in the received message;
It is characterized by having the following.

According to another embodiment of the registration method of the present invention,
The first user terminal is connected to the second user terminal by tethering or near field communication,
the second user terminal communicates with the mobility management server of the second core system;
It is also preferred that the second mobility management server of the second core system communicates with the first mobility management server of the first core system.

According to another embodiment of the registration method of the present invention,
For the third step, the second core system further includes the identification number of the second user terminal in the message containing the registration request and forwards it to the first core system;
For the fourth step, the first core system extracts the identification number of the first user terminal by processing the registration request;
For the fifth step, the first core system responds to the second core system by including the identification number of the first user terminal and the identification number of the second user terminal in a message including the registration response and the link ID. death,
Regarding the sixth step, the second core system links and manages the identification number of the first user terminal and the identification number of the second user terminal, and the second core system manages the identification number of the first user terminal and the second user terminal, and It is also preferable to perform billing processing on the user of the user terminal.

According to another embodiment of the registration method of the present invention,
In the case of 5GC (5th Generation Core network), it is also preferable that the mobility management server is AMF (Access and Mobility management Function).

According to another embodiment of the registration method of the present invention,
Regarding the first step, if GUTI (Globally Unique Temporary UE Identity) is described in the registration request included in the message sent by the first user terminal, then regarding the fifth step, the first core system registers It is also preferable to reply with a message describing GUTI in response.

According to another embodiment of the registration method of the present invention,
Regarding the first step, if SUCI (Subscription Concealed Identifier) is described in the registration request included in the message sent by the first user terminal,
Regarding the fourth step, the first core system performs an authentication sequence with the first user terminal via the second core system and the second user terminal, and then, regarding the fifth step, the first core system performs an authentication sequence with the first user terminal via the second core system and the second user terminal. It is also preferable that the core system No. 1 sends back a message describing GUTI in the registration response.

According to another embodiment of the registration method of the present invention,
Regarding the authentication sequence executed in the fourth step,
The first core system obtains an authentication context based on SUCI from the authentication processing server,
the first core system sends a message including the authentication context and the link ID to the second core system;
a second core system forwards a message including an authentication context and a link ID to a second user terminal based on a link ID included in the received message;
the second user terminal forwards a message including the authentication context and the link ID to the first user terminal based on the link ID included in the received request message;
the first user terminal transmits a message including an authentication response for the first core system to the second user terminal;
The second user terminal identifies a link ID based on the first user terminal that received the message, and transmits a message including the authentication request and the link ID to the second core system,
The second core system identifies a link ID based on the second user terminal that is the source of the received message, and forwards the message including the authentication request to the first core system;
It is also preferable that the first core system identifies the link ID for the second core system that is the source of the received message, and processes the authentication request from the first user terminal with the authentication server. .

According to another embodiment of the registration method of the present invention,
In the case of 4GC (4th Generation Core network), it is also preferable that the mobility management server is MME (Mobility Management Entity).

According to the present invention, a system in which a first user terminal registers with the first core system via the second user terminal and the second core system,
The first user terminal is
transmitting a message including a registration request for the first core system to a second user terminal;
The second user terminal is
determining a link ID for the first user terminal that is the source of the message received from the first user terminal, and transmitting a message including the registration request and the link ID to the second core system;
forwarding the message including the registration response to the first user terminal based on the link ID included in the message received from the second core system;
The second core system is
storing a link ID in association with the second user terminal that is the source of the message received from the second user terminal, and forwarding the message including the registration request to the first core system;
forwarding the message including the registration response and the link ID to a second user terminal based on the link ID included in the message received from the first core system;
The first core system is
storing a link ID in association with the second core system that is the source of the message received from the second core system, and processing a registration request from the first user terminal;
The second core system is characterized in that a message including a registration response and a link ID is sent as a response to the second core system.

According to the registration method and system of the present invention, a communication device owned by another person can be relayed from a user terminal owned by the user and registered in the core system without the user himself/herself inputting authentication information.

FIG. 1 is a system configuration diagram in the present invention. It is a sequence diagram in this invention. FIG. 3 is a sequence diagram of authentication in the present invention. FIG. 2 is a sequence diagram illustrating billing processing in a communication device owned by another person and a core system.

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a system configuration diagram according to the present invention.

According to FIG. 1, it is configured by user terminal #1 (first user terminal), communication device #2 (second user terminal), and two core systems #1 and #2.
Here, it is assumed that the user terminal #1 owned by the user has a contract with the communication carrier of the core system #1, and its authentication information is managed. On the other hand, it is assumed that communication device #2 owned by another person has a contract with the communication carrier of core system #2, and its authentication information is managed. According to general existing technology, user terminal #1 cannot communicate with core system #2 that is a different contract partner.

According to the present invention, user terminal #1 is connected to communication device #2 by tethering or short-range communication.
In the case of tethering, communication device #2 functions as an access point for a wireless LAN (Local Area Network), and user terminal #1 connects to communication device #2 via the wireless LAN.
In the case of short-range communication, user terminal #1 establishes a connection after pairing with communication device #2 using, for example, Bluetooth (registered trademark). Alternatively, Prose (Proximity Service), which is D2D (Device to Device) communication of 3GPP (Third Generation Partnership Project), may be used. Furthermore, it may be directly connected using a USB (Universal Serial Bus) cable.

According to FIG. 1, the communication device #2 can connect to the AN (access network) 32 wirelessly or by wire and communicate with the mobility management server of the core system #2. Further, communication between the carriers is also possible between the mobility management server of core system #2 and the mobility management server of core system #1.

Here, the core systems include 5GC and 4GC. According to FIG. 1, 5GC is explained as an example.

In the case of 5GC, AMF and SMF are arranged as control plane network devices.
The AMF (Access and Mobility Management Function) communicates with the UE (User Equipment) via a base station (gNB) located in the AN, and functions as a mobility management server (registration management and connection management) for the UE. Further, the AMF acquires subscriber information from an AUSF (AUthentication Server Function) that cooperates with the UDM (Unified Data Management) of the subscriber server.
The SMF (Session Management Function) controls and manages user plane network devices to manage sessions under the control of the AMF.
A UPF (User Plane Function) serving as a user plane network device establishes a data communication path and is responsible for routing management and transfer processing of user packets.

Furthermore, in the case of 4GC, an MME (Mobility Management Entity) is arranged as a mobility management server.

According to FIG. 1, which is an example of 5GC, AMF#1 of core system #1 can accommodate user terminal #1, and AMF#2 of core system #2 can accommodate communication device #2. be.
According to the present invention, the registration sequence between user terminal #1 and core system #1 can be performed through the connection between communication device #2 and core system #2.
Thereby, user terminal #1 can register with core system #1 via communication device #2 and core system #2, and can use the contracted communication service by itself.

FIG. 2 is a sequence diagram in the present invention.

User terminal #1 may already be "registered in core system #1" via another network, or may be "unregistered in core system #1." If it has been registered, there is no need to execute the authentication sequence as shown in FIG. On the other hand, if it is unregistered, an authentication sequence is executed as shown in FIG. 3, which will be described later.
Furthermore, communication device #2 has already been registered with AMF #2 of core system #2 via base station #2, and a connection has been established between communication device #2 and core system #2. shall be.

According to FIG. 2, user terminal #1 and communication device #2 are connected by tethering or short-range communication. The user may operate user terminal #1 to connect to communication device #2, or conversely may operate communication device #2 to connect to user terminal #1.
At this time, as a feature of the present invention, the user does not need to input his or her own authentication information (ID and password) based on the communication service usage contract.

(S1) First, user terminal #1 transmits a message (user cooperation Uplink message) including a "registration request" to core system #1 to communication device #2.
The “registration request” is a Registration Request in the communication protocol 5G-NAS (Non-Access-Stratum) between the UE and 5GC. User terminal #1 transmits a message including this registration request in the payload to communication device #2. The payload type of the message is given a "user collaboration" identifier, and is recognized as a user collaboration Uplink message.
Message (user cooperation, registration request [SUCI/GUTI])

When user terminal #1 is “registered in core system #1”, the registration request includes the GUTI (Globally Unique Temporary UE Identity) (and S-TMSI) already assigned to user terminal #1. In 5G, instead of IMSI, a random value TMSI (Temporary Mobile Subscriber Identity), which is temporarily used to prevent tracking, is used.

If "not registered in core system #1", the registration request includes SUCI (Subscription Concealed Identifier) as a user identifier. SUCI is a system used to hide SUPI (SUbscription Permanent ID), which corresponds to 4G-LTE IMSI in subscriber identification.
It is randomly encrypted using the network operator's public key. By not transmitting SUPI in clear text, leakage of identifiers between endpoints in mobile communication networks is avoided. Incidentally, the identification number SUPI corresponding to IMSI is registered in the SIM.

(S2) When communication device #2 receives a message including a registration request (user cooperation Uplink message), communication device #2 determines and stores the "link ID" for user terminal #1. The link ID may be, for example, a short-range communication link layer ID or a wireless LAN MAC-ID.

Communication device #2 then transmits a message including the registration request and link ID to core system #2 via AN32. This message is transmitted as a NAS-MM signal containing "user cooperation" in the payload (NAS-MM Uplink message).
Message (user cooperation, registration request [SUCI/GUTI], link ID)
If an S-TMSI is included in the registration request, that S-TMSI will be the destination of the message.

(S3) The user cooperation Uplink message sent from communication device #2 is received by AMF #2 of core system #2.
AMF#2 of core system #2 stores the link ID in association with the communication device #1 that is the source of the received message.
Then, AMF#2 of core system #2 transfers a message (NAS-MM Uplink message) including the registration request to AMF#1 of core system #1.
Message (user cooperation, registration request [SUCI/GUTI], link ID)
Note that if the NAS-MM Uplink message does not include the destination GUTI, it is transferred to the default AMF#1 that is preset for each communication carrier based on the subscriber type.

(S4) AMF#1 of core system #1 stores the link ID in association with AMF#2 of core system #2, which is the source of the received message.
AMF#1 of core system #1 then processes the registration request from user terminal #1.

Here, if GUTI is described in the registration request, user terminal #1 has already been authenticated, so the process moves to S5.
On the other hand, if SUCI is written in the registration request, user terminal #1 executes an authentication sequence because it has not yet been authenticated. The authentication sequence will be described later with reference to FIG.

(S5) AMF#1 of core system #1 responds to AMF#2 of core system #2 with a message including the registration response and link ID.
Message (user cooperation, registration response [GUTI], link ID)

(S6) AMF#2 of core system #2 transfers a message (NAS-MM Downlink message) including the registration response and link ID to communication device #2 based on the link ID included in the received message.
Message (user cooperation, registration response [GUTI], link ID)
Note that AMF#2 of core system #2 stores UE#2-SUPI and UE#1-SUPI that are user-cooperated.

(S7) Communication device #2 transfers a message including a registration response (user cooperation Downlink message) to user terminal #1 based on the link ID included in the received message.
Message (user cooperation, registration response [GUTI])

Finally, user terminal #1 is able to receive the registration response via communication device #2 and core system #2, becomes registered with core system #1, and is unable to store the GUTI. can.

According to the above sequence, if GUTI is described in the registration request included in the message sent by user terminal #1 for S1, AMF#1 of core system #1 will write GUTI in the registration response for S5. Reply with the written message.
On the other hand, for S1, if SUCI is described in the registration request included in the message sent by user terminal #1, for S4, AMF #1 of core system #1 will Execute the authentication sequence with user terminal #1 via . Then, regarding S5, AMF#1 of core system #1 returns a message describing GUTI in the registration response.

FIG. 3 is a sequence diagram of authentication in the present invention.

(S41) AMF#1 requests an authentication context based on SUCI from the authentication server AUSF. AUSF requests subscriber information using SUPI as a key from UDM. In response, the UDM responds with subscriber information to the AUSF. Then, AUSF responds to AMF#1 with an authentication context including the NW authentication Vector. Note that when AMF#1 executes re-authentication, AMF#1 executes 3GPP-AKA (Authentication and Key Agreement) authentication with AUSF.
(S42) AMF#1 transmits a message including the authentication request and link ID to AMF#2 based on the link ID.
Message (UE#2-SUPI, authentication request [NW authentication Vector], link ID)
(S43) AMF#2 transfers the received message to communication device #2 based on the link ID.
Message (authentication request [NW authentication Vector], link ID)
(S44) Communication device #2 transfers the received message to user terminal #1 based on the link ID.
Message (Authentication request [NW authentication Vector])
(S45) User terminal #1 generates an authentication response including the UE authentication Vector based on the NW authentication Vector of the authentication request. Then, user terminal #1 transmits a message including the authentication response to communication device #2.
Message (Authentication Response [UE Authentication Vector])
(S46) Communication device #2 identifies the link ID based on user terminal #1 that is the source of the received message, and transfers the message to AMF #2 of core system #2 based on the link ID.
Message (authentication response [UE authentication Vector], link ID)
(S47) AMF#2 of core system #2 specifies the link ID based on communication device #2 that is the source of the received message, and transfers the message to AMF#1 of core system #1 based on the link ID.
Message (UE#2-SUPI, authentication response [UE authentication Vector], link ID)
(S48) AMF#1 transmits the UE authentication Vector to the AUSF. AUSF determines whether or not authentication is possible as a result of collating the authentication data, and responds with the result to AMF#1. Here, if the authentication is successful, the SUPI of user terminal #1 is responded. In contrast, AMF#1 stores its SUPI.
Through S41 to S48, a sequence for determining a NAS (Non-Access Stratum) security algorithm is executed between user terminal #1 and core system #1. In the subsequent sequence, messages between user terminal #1 and core system #1 are encrypted.

FIG. 4 is a sequence diagram showing billing processing in a communication device owned by another party and a core system.

According to FIG. 2 described above, a registration/authentication sequence is shown from user terminal #1 via communication device #2 owned by another person and core system #2. Thereafter, the user terminal #1 becomes capable of data communication via the communication device #2 owned by another person and the core system #2.
At this time, core system #2 needs to manage user terminal #1 in association with communication device #2 owned by another person, and charge user terminal #1 for data communication in communication device #2.

According to FIG. 4, compared to FIG. 2, S3 to S6 are different as follows.
(S3) AMF#2 of core system #2 further includes SUPI (UE#2-SUPI) of communication device #2 in the message including the registration request (NAS-MM Uplink message), and sends the AMF of core system #1 Transfer to #1. As mentioned above, SUPI is a terminal identification number that corresponds to IMSI.
Message (user cooperation, registration request, link ID, UE#2-SUPI)

(S4) AMF#1 of core system #1 further stores UE#2-SUPI in association with AMF#2 and link ID of core system #2. Further, AMF #1 of core system #1 processes a registration request from user terminal #1. At this time, UE#1-SUPI is identified by SUCI or GUTI.

(S5) AMF#1 of core system #1 responds to AMF#2 of core system #2 with a message including the registration response and link ID, and further includes UE#2-SUPI and UE#1-SUPI. .
Message (user cooperation, registration response, link ID, UE#2-SUPI, UE#1-SUPI)

(S6) AMF#2 of core system #2 links and manages UE#2-SUPI and UE#1-SUPI, which are user cooperation, based on the received message.
Then, within the core system #2, it is possible to charge the user terminal #1 for data communication in the communication device #2 owned by another person. Note that if the carrier of core system #1 and the carrier of core system #2 are different, charges can be charged to user terminal #1 by settling the bill between the carriers.

As described above in detail, according to the registration method and system of the present invention, users can access the core system by relaying communication devices owned by others from their own user terminals without inputting authentication information themselves. Can be registered.

According to the present invention, there is no need for the user to input authentication information (user ID and password) between user terminals (between user terminal #1 and communication device #2), and inter-terminal cooperation can be achieved through a simple procedure. can be executed immediately. For the user, the communication device #2 owned by someone else can be used like the user terminal #1 owned by the user.

Here, according to the present invention, it becomes possible for the communication device #2 connected to the user terminal #1 to read SUCI, GUTI, and S-TMSI as information related to the user terminal #1. However, SUCI is an encrypted ID, and GUTI and S-TMSI are temporary IDs assigned by AMF#1. Therefore, user terminal #1 and its owner cannot be specified. Furthermore, since the 3GPP-AKA authentication sequence is applied, the authentication key is not disclosed to communication device #2. Furthermore, even if communication device #2 collects each control signal during signal relay, it cannot operate in imitation of user terminal #1.

Furthermore, as a result of this, for example, ``users can relay communication devices owned by others and register them in the core system from their own user terminals without having to enter authentication information themselves.'' It will be possible to contribute to Goal 9 of the Sustainable Development Goals (SDGs): ``Build resilient infrastructure, promote sustainable industrialization, and expand innovation.''

Regarding the various embodiments of the present invention described above, various changes, modifications, and omissions within the scope of the technical idea and viewpoint of the present invention can be easily made by those skilled in the art. The above description is merely an example and is not intended to be limiting in any way. The invention is limited only by the claims and their equivalents.

1 Mobile communication core system 11 User terminal, first user terminal 12 Communication device, second user terminal 21 First core system 211 AMF
212 SMF
213 UPF
214 AUSF
215 UDM
22 Second Core System 221 AMF
222 SMF
223 UPF
3 AN, access network

Claims (9)

A registration method in which a first user terminal registers with a first core system via a second user terminal and a second core system, the method comprising:
a first step in which the first user terminal sends a message including a registration request for the first core system to the second user terminal;
A second user terminal determines a link ID (IDentifier) for the first user terminal that is the source of the received message, and sends a message including the registration request and the link ID to the second core system. and the steps of
A third step in which the second core system associates and stores the link ID with the second user terminal that is the source of the received message, and transfers the message including the registration request to the first core system. and,
a fourth step in which the first core system stores the link ID in association with the second core system that is the source of the received message, and processes the registration request from the first user terminal;
a fifth step in which the first core system responds to the second core system a message including the registration response and the link ID;
a sixth step in which the second core system forwards the message including the registration response and the link ID to the second user terminal based on the link ID included in the received message;
a seventh step in which the second user terminal forwards the message including the registration response to the first user terminal based on the link ID included in the received message;
A registration method characterized by having the following. The first user terminal is connected to the second user terminal by tethering or near field communication,
the second user terminal communicates with the mobility management server of the second core system;
2. The registration method according to claim 1, wherein the second mobility management server of the second core system communicates with the first mobility management server of the first core system. For the third step, the second core system further includes the identification number of the second user terminal in the message containing the registration request and forwards it to the first core system;
For the fourth step, the first core system extracts the identification number of the first user terminal by processing the registration request;
For the fifth step, the first core system responds to the second core system by including the identification number of the first user terminal and the identification number of the second user terminal in a message including the registration response and the link ID. death,
Regarding the sixth step, the second core system links and manages the identification number of the first user terminal and the identification number of the second user terminal, and the second core system manages the identification number of the first user terminal and the second user terminal, and 3. The registration method according to claim 1, further comprising performing billing processing on the user of the user terminal. 4. The registration method according to claim 1, wherein in the case of 5GC (5th Generation Core network), the mobility management server is AMF (Access and Mobility management Function). Regarding the first step, if GUTI (Globally Unique Temporary UE Identity) is described in the registration request included in the message sent by the first user terminal, then regarding the fifth step, the first core system registers 5. The registration method according to claim 4, wherein a message describing GUTI is returned as a response. Regarding the first step, if SUCI (Subscription Concealed Identifier) is described in the registration request included in the message sent by the first user terminal,
Regarding the fourth step, the first core system performs an authentication sequence with the first user terminal via the second core system and the second user terminal, and then, regarding the fifth step, the first core system performs an authentication sequence with the first user terminal via the second core system and the second user terminal. 5. The registration method according to claim 4, wherein the first core system returns a message describing GUTI as a registration response. Regarding the authentication sequence executed in the fourth step,
The first core system obtains an authentication context based on SUCI from the authentication processing server,
the first core system sends a message including the authentication context and the link ID to the second core system;
a second core system forwards a message including an authentication context and a link ID to a second user terminal based on a link ID included in the received message;
the second user terminal forwards the message including the authentication context to the first user terminal based on the link ID included in the received message;
the first user terminal transmits a message including an authentication response for the first core system to the second user terminal;
The second user terminal identifies a link ID based on the first user terminal that received the message, and sends a message including the authentication response and the link ID to the second core system;
The second core system identifies a link ID based on the second user terminal that is the source of the received message, and forwards the message including the authentication response to the first core system;
The first core system specifies a link ID for the second core system that is the source of the received message, and processes the authentication response from the first user terminal with the authentication server. 7. The registration method according to claim 6. 4. The registration method according to claim 1, wherein in the case of a 4GC (4th Generation Core network), the mobility management server is an MME (Mobility Management Entity). A system in which a first user terminal registers with the first core system via a second user terminal and a second core system,
The first user terminal is
transmitting a message including a registration request for the first core system to a second user terminal;
The second user terminal is
determining a link ID for the first user terminal that is the source of the message received from the first user terminal, and transmitting a message including the registration request and the link ID to the second core system;
forwarding the message including the registration response to the first user terminal based on the link ID included in the message received from the second core system;
The second core system is
storing a link ID in association with the second user terminal that is the source of the message received from the second user terminal, and forwarding the message including the registration request to the first core system;
forwarding the message including the registration response and the link ID to a second user terminal based on the link ID included in the message received from the first core system;
The first core system is
storing a link ID in association with the second core system that is the source of the message received from the second core system, and processing a registration request from the first user terminal;
A system that responds to a second core system with a message including a registration response and a link ID.

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