Patent Description:
In order to meet the demand for wireless data traffic that is on an increasing trend after commercialization of 4th-generation (<NUM>) communication systems, efforts have been made to develop improved 5th-generation (<NUM>) or pre-<NUM> communication system. For this reason, the <NUM> or pre-<NUM> communication system is also called a beyond <NUM> network communication system or a post long-term evolution (LTE) system. In order to achieve a high data rate, implementation of a <NUM> communication system in an ultrahigh frequency (mmWave) band (e.g., like a <NUM> band) has been considered. In order to mitigate a path loss of radio waves and to increase a transfer distance of the radio waves in the ultrahigh frequency band, technologies of beamforming, massive multiple input, multiple output (MIMO), full dimension MIMO (FD-MIMO), array antennas, analog beamforming, and large-scale antennas for the <NUM> communication system have been discussed. Furthermore, for system network improvement, in the <NUM> communication system, development of technologies such as an evolved small cell, an advanced small cell, a cloud radio access network (cloud RAN), an ultra-dense network, device to device communication (D2D), a wireless backhaul, a moving network, cooperative communication, coordinated multi-points (CoMP), and reception interference cancellation has been made. In addition, hybrid frequency shift keying (FSK) and quadrature amplitude modulation (QAM) modulation (FQAM) and sliding window superposition coding (SWSC), which correspond to advanced coding modulation (ACM) systems, and filter bank multicarrier (FBMC), non-orthogonal multiple access (NOMA) and sparse code multiple access (SCMA), which correspond to advanced access technology, have been developed in the <NUM> system.

On the other hand, the Internet, which is a human centered connectivity network where human beings generate and consume information, is now evolving to the Internet of things (IoT) network where distributed entities, such as things, exchange and process information. The Internet of everything (IoE), which is a combination of the IoT technology and big data processing technology through connection with a cloud server, has emerged. As technology elements, such as a sensing technology, wired/wireless communication and a network infrastructure, a service interface technology, and a security technology, have been demanded for IoT implementation, technologies such as a sensor network for machine-to-machine (M2M) connection, M2M communication, machine type communication (MTC), and so forth have been recently researched. Such an IoT environment may provide intelligent internet technology (IT) services that create a new value to human life by collecting and analyzing data generated among connected things. The IoT may be applied to a variety of fields including smart homes, smart buildings, smart cities, smart cars or connected cars, smart grid, health care, smart appliances and advanced medical services through convergence and combination between the existing information technology (IT) and various industries.

Accordingly, various attempts have been made to apply the <NUM> communication system to IoT networks. For example, technologies of a sensor network, M2M communication, and MTC have been implemented by techniques for beamforming, MIMO, and array antennas, which correspond to the <NUM> communication technology. As the big data processing technology as described above, application of a cloud radio access network (cloud RAN) would be an example of convergence between the <NUM> technology and the IoT technology.

<NPL>, aims to avoid the dependency of NGC on EPC for interworking. "<NPL>, provides study on architecture for next generation system. "<NPL>, discusses General Packet Radio Service (GPRS) enhancements for Evolved Universal Terrestrial Radio Access Network.

Aspects of the present disclosure are to address at least the above-mentioned problems and/or disadvantages and to provide at least the advantages described below. Accordingly, an aspect of the present disclosure is to provide a method in which a mobile communication provider provides interworking between a 4th-generation (<NUM>) mobile communication system and a 5th-generation (<NUM>) mobile communication system to a terminal capable of using both the <NUM> mobile communication system and the <NUM> mobile communication system, provides a negotiation procedure and negotiation information on whether the terminal can use the <NUM> and the <NUM> between the terminal and a network in order to provide continuous internet protocol (IP) connectivity to the terminal, and sets a network (that is, a gateway) for <NUM>-<NUM> interworking in the terminal based on the negotiation procedure and the negotiation information.

In accordance with an aspect of the present disclosure, a method for connecting to a network by a terminal in a mobile communication system wherein a first communication network and a second communication network are operable is provided. The method includes transmitting, to a mobility management function, information on supportable communication network for the terminal and an attach request message including a packet data unit (PDU) session request, receiving an internet protocol (IP) address allocated based on the information on supportable communication network and an attach accept message including a PDU session response, and connecting to a network based on the IP address.

In accordance with another aspect of the present disclosure, a method for allocating a network by a mobility management function in a mobile communication system wherein a first communication network and a second communication network are operable is provided. The method includes receiving, from a terminal information on supportable communication network for the terminal and an attach request message including a packet data unit (PDU) session request, selecting a session management function (SMF) which allocates an internet protocol (IP) address to the terminal based on the information on supportable communication network, receiving, from the selected SMF, a PDU session response message including an allocated IP address, and transmitting, to the terminal an attach accept message including the PDU session response message.

In accordance with still another aspect of the present disclosure, a method for allocating a network by a session management function (SMF) in a mobile communication system wherein a first communication network and a second communication network are operable is provided. The method includes receiving, from a mobility management function, a packet data unit (PDU) session request message including information on supportable communication network for a terminal, establishing a PDU session based on the information on supportable communication network and determining an internet protocol (IP) address to be allocated to a terminal, and transmitting, to the mobility management function, a PDU session response message including the IP address.

In accordance with yet another aspect of the present disclosure, a terminal of a mobile communication system wherein a first communication network and a second communication network are operable is provided. The terminal includes a terminal transceiver configured to transmit, to a mobility management function, information on supportable communication network for the terminal and an attach request message including a packet data unit (PDU) session request and to receive an internet protocol (IP) address allocated based on the information on supportable communication network and an attach accept message including a PDU session response, and a terminal controller configured to connect to a network based on the IP address.

In accordance with yet another aspect of the present disclosure, a mobility management function of a mobile communication system where a first communication network and a second communication network are operable is provided. The mobility management function includes a mobility management function transceiver configured to receive, from a terminal, information on supportable communication network for the terminal and an attach request message including a packet data unit (PDU) session request, receive, from a session management function (SMF), a PDU session response message including an allocated IP address, and transmit, to the terminal, an attach accept message including the PDU session response message, and a mobility management function controller configured to select a SMF, which allocates an IP address to the terminal, based on the information on supportable communication network.

In accordance with yet another aspect of the present disclosure, a session management function (SMF) of a mobile communication system wherein a first communication network and a second communication network are operable is provided. The SMF includes a SMF transceiver configured to receive, from a mobility management function, a packet data unit (PDU) session request message including information on supportable communication network for a terminal and transmit, to the mobility management function a PDU session response message including an IP address, and a SMF controller configured to establish a PDU session based on the information on supportable communication network, and determine an IP address to be allocated to the terminal.

According to the aspects of the present disclosure, a service provider operating both the <NUM> mobile communication system and the <NUM> mobile communication system and a terminal using both the <NUM> mobile communication system and the <NUM> mobile communication system can exchange information necessary for mutual <NUM>-<NUM> interworking, thereby providing the same IP connectivity service between the <NUM> mobile communication system and the <NUM> mobile communication system.

The following description with reference to the accompanying drawings is provided to assist in a comprehensive understanding of various embodiments of the present disclosure as defined by the claims.

In detailed description of embodiments of the present disclosure, a radio access network (RAN), and a new RAN (NR) and a packet core next generation core (NG core), which are core networks, will be mainly described, 5th-generation (<NUM>) network standard of these networks being defined by the <NUM>rd generation partnership project (3GPP). However, the subject matter of the present disclosure can be applied to other communication systems having similar technical backgrounds through slight modification without largely departing from the scope of the present disclosure, and this will be possible through the judgment of those skilled in the art in the technical field of the present disclosure.

Hereinafter, for the convenience of description, terms and names defined in the 3GPP Long-Term Evolution (LTE) standard may be partially used. However, the present disclosure is not limited by the terms and names and can also be applied to systems conforming to other standards in the same manner.

Entities used in the present disclosure will be described as follows.

A terminal user equipment (UE) is connected to a radio access network (RAN) and connects to a mobility management function of a core network device of <NUM>. In the present disclosure, the mobility management function may be replaced with a common control network function (CCNF), wherein the CCNF performs terminal authentication together with the mobility management function. The mobility management function or the CCNF including the same routes a session-related message for a terminal to a session management function (SMF). The CCNF is connected to the SMF, wherein the SMF is connected to a network to allocate resources to be provided to the terminal, thereby establishing a tunnel for transmitting data between a base station and the network. In the present disclosure, a device called the mobility management function may represent a core network device including the mobility management function, that is, the CCNF or a device that receives a network attached storage (NAS) message of a terminal having another name. For the purpose of convenience, in the present disclosure, it is called the mobility management function.

A network slice instance represents a service provided by a network including the CCNF, the SMF, and a user plane function (UPF). For example, when a mobile communication provider supports a wideband communication service, the mobile communication provider defines a network service satisfying requirements for the wideband communication, configures the network service as a network slice instance, and provides the service. When the mobile communication provider supports an IoT service, the mobile communication provider defines a network service satisfying requirements for the IoT service, configures the network service as a network slice instance for IoT, and provides the service.

<NUM> represents <NUM>th generation mobile communication and includes a radio access network (RAN) technology called LTE and a core network technology called an evolved packet core (EPC). <NUM> represents <NUM>th generation mobile communication. A RAN technology of the <NUM> is called next generation RAN (NG-RAN) and a core network technology is called next generation core (NG-core). A mobile communication provider can provide both the <NUM> and the <NUM>. A terminal can use both the <NUM> and the <NUM> when it has both a <NUM> modem and a <NUM> modem. A terminal capable of using both the <NUM> and the <NUM> can use the <NUM> in an area, where only the <NUM> service is possible, while using the <NUM> in an area, where the <NUM> service is possible, according to a service coverage provided by the mobile communication provider. In order to allow one terminal to use services by changing two types of mobile communication systems, interworking between the <NUM> network and the <NUM> network is required. To this end, the <NUM> core network and the <NUM> core network should cooperate with each other. The present disclosure provides a method in which a terminal capable of using both the <NUM> and the <NUM> negotiates with a <NUM> core network regarding whether the terminal can use both the <NUM> and the <NUM>, the <NUM> core network and the <NUM> core network allocate one IP address to the terminal according to the negotiation result, and both systems establish a session in order to continuously provide IP connectivity.

First embodiment - <FIG> is a diagram illustrating a method in which a terminal connects to a network, negotiates regarding whether <NUM> and <NUM> services are available and simultaneously establishes a packet data unit (PDU) session according to the negotiation, according to an embodiment of the present disclosure.

Referring to <FIG>, a terminal has Capability capable of using both the <NUM> and the <NUM>. The terminal connects to the <NUM> network and performs an Attach procedure with the <NUM> core network in order to use a mobile communication service. The Attach procedure is performed between the terminal and the mobility management function.

That is, the Capability may represent whether the terminal <NUM> can perform the <NUM>-<NUM> interworking, has the <NUM> radio capability or the <NUM> radio capability, supports the <NUM> and prefers the <NUM>, or prefers the <NUM> and supports the <NUM>. The terminal <NUM> may prefer the <NUM> service in an area where both the <NUM> and the <NUM> are possible, or prefers the <NUM> but may connect to the <NUM> network because only the <NUM> is provided in a current area. In the former case, the terminal <NUM> may transfer the capability representing the <NUM> supported and <NUM> preferred. In the latter case, the terminal <NUM> may transfer the capability representing the <NUM> preferred and <NUM> supported.

For connecting to a packet data network, the terminal <NUM> may put a PDU Session Request, which is a session management (SM) message, into the Attach Request message, and transmit the Attach Request message. The terminal <NUM> may put the Capability, which represents that the terminal <NUM> can use both the <NUM> and the <NUM>, into the PDU session request. Alternatively, since the terminal <NUM> desires to establish connectivity to the packet data network in which the terminal <NUM> can use both the <NUM> and the <NUM>, the terminal <NUM> puts a name of the Packet Data Network for supporting the <NUM>-<NUM> interworking, such as an access point name (APN) and a data network name (DNN), into the PDU session request message. This is transferred to a session management function (SMF) <NUM> through operation <NUM>, and the SMF <NUM> may check the APN or the DNN to recognize that the terminal <NUM> uses both the <NUM> and the <NUM> and establish a PDU session enabling the <NUM>-<NUM> interworking in the terminal <NUM>.

Even though the terminal <NUM> does not put the Capability into the SM message, a mobility management function <NUM> may inform the SMF <NUM> of the fact that the terminal <NUM> uses both the <NUM> and the <NUM> through the fourth procedure (SM message forwarding) at operation S125.

Even though the terminal <NUM> does not put the Capability into the SM message and does not input the APN or the DNN for the <NUM>-<NUM> interworking, the SMF <NUM> may check subscription information of the terminal <NUM> acquired after the sixth procedure at operation S130, check the <NUM>-<NUM> interworking Capability from the subscription information, and establish a PDU session for the <NUM>-<NUM> interworking Capability.

The mobility management function (MMF) having received the Attach request message may check the Capability information of the terminal <NUM> and recognize that the terminal <NUM> can use both the <NUM> and <NUM> services at operation S115. The mobility management function <NUM> performs a procedure for checking a server <NUM> (a server storing user subscription information) and the subscription information of the terminal <NUM>. Through this procedure, the mobility management function <NUM> may check that the terminal <NUM> can use both the <NUM> and <NUM> services in a corresponding mobile communication network. This may be checked by comparing Capability of the terminal <NUM> acquired from the server <NUM> with the Capability of the terminal <NUM> acquired in the first procedure. Alternatively, the mobility management function <NUM> may transfer the Capability of the terminal <NUM> to the server <NUM>, and the server <NUM> may perform a permission procedure and then transfer a response for the permission procedure to the mobility management function <NUM>.

After performing the operation, the mobility management function <NUM> may perform a Network Slice Instance Selection procedure in order to allocate a Network Slice Instance to the terminal <NUM>. In this case, the mobility management function <NUM> may perform Network Slice Instance Selection in consideration of whether the terminal <NUM> uses both the <NUM> and <NUM> services checked in the above procedure. That is, the mobility management function <NUM> may select a Network Slice Instance supporting the <NUM>-<NUM> interworking and allocate the Network Slice Instance to the terminal <NUM>.

The mobility management function <NUM> performs a procedure for selecting the session management function (SMF) <NUM> in order to transfer the SM message received in the first procedure to the SMF <NUM> at operation S120. In this case, in consideration of whether the terminal <NUM> can use both the <NUM> and <NUM> services acquired in the Attach procedure, the mobility management function <NUM> selects the SMF <NUM> enabling the <NUM>-<NUM> interworking. The SMF <NUM> may be a SMF <NUM> belonging to a specific Network Slice Instance.

The mobility management function <NUM> transfers the PDU session request sent by the terminal <NUM> to the selected SMF <NUM> at operation S <NUM>. In this case, the mobility management function <NUM> may transfer whether the terminal <NUM> can use both the <NUM> and the <NUM> (the <NUM>-<NUM> interworking Capability) acquired through the Attach procedure to the selected SMF <NUM> together with the PDU session request. The mobility management function <NUM> may transfer this as a part of the Subscription information of the terminal <NUM> or as an explicit IE.

After receiving the message, the SMF <NUM> may negotiate with the server <NUM> in order to acquire subscription information for the terminal <NUM> at operation S130. This procedure may be omitted, and in this case, the mobility management function <NUM> may transfer the subscription information of the terminal <NUM> acquired in the Attach procedure to the session management function <NUM> through the fourth procedure.

The SMF <NUM> may check the <NUM>-<NUM> interworking Capability included in the PDU Session Request message sent by the terminal <NUM>, the APN/the DNN included in the PDU Session Request message, the '<NUM>-<NUM> interworking Capability of the terminal <NUM>' included in the message including the PDU Session Request message sent by the MMF, or the <NUM>-<NUM> interworking Capability in the subscription information of the terminal <NUM> sent by the mobility management function <NUM>, thereby judging that it is necessary to establish a PDU session required for the <NUM>-<NUM> interworking in the terminal <NUM>. After the judgment procedure, the SMF <NUM> selects a network <NUM> which is used in both a <NUM> system and a <NUM> system. Since IP connectivity of the terminal <NUM> is provided through the network <NUM>, the terminal <NUM> can use a Packet Data Network service with one IP address in the <NUM> system and the <NUM> system. When there occurs a change between the <NUM> system and the <NUM> system, since the IP address is continuously anchored through the network <NUM>, the terminal <NUM> can use a continuous Packet Data Network service. In the <NUM> system, the user plane function (UPF) is considered like a packet data network gateway (P-GW). In another example, the SMF may perform a domain name system (DNS) query based on the APN or the DNN value for the <NUM>-<NUM> interworking sent by the terminal <NUM>, thereby acquiring an IP address of a corresponding UPF.

The session management function (SMF) <NUM> having selected the network <NUM> performs a procedure for establishing a PDU session for the terminal <NUM> in the network <NUM> at operation S <NUM>. This is called PDU session Establishment in the present disclosure. This message may include the <NUM>-<NUM> interworking Capability of the terminal <NUM>.

After establishing the PDU session enabling the <NUM>-<NUM> interworking for the terminal <NUM>, the SMF <NUM> generates a response (e.g., a PDU session response) for the PDU Session Request, which is the SM message sent by the terminal <NUM>, and transfers the response to the mobility management function <NUM> at operation S <NUM>. In this case, the SMF <NUM> may transfer the IP address of the network <NUM> for the PDU session established to the terminal <NUM> to the mobility management function <NUM>. The mobility management function <NUM> preserves this information as a Context of the terminal <NUM> and updates the information to the server <NUM>, and the server <NUM> may store the IP address of the network <NUM> provided to the terminal <NUM>, so that the <NUM> system and the <NUM> system can check the IP address of the network <NUM> included in subscription information later, and always allocate the network <NUM> to the terminal <NUM> to maintain continuity of IP connectivity. In another example, the SMF <NUM> may directly update the IP address of the network <NUM> to the server <NUM>.

The mobility management function <NUM> puts the PDU session response message received through the seventh procedure into an Attach Accept serving as a response MM message for the first message, and transfers the Attach Accept to the terminal <NUM> at operation S145. The mobility management function <NUM> puts Capability information indicating that the terminal <NUM> can use both the <NUM> and <NUM> services into the MM message, thereby representing that the terminal <NUM> uses both the <NUM> and <NUM> services. This may have the type as described in the first procedure. This is not limited to the name of the Attach Accept and represents all messages indicating a response for the first message.

The terminal <NUM> may judge the establishment of the PDU session enabling the <NUM>-<NUM> interworking through the information included in the PDU session response. The information may be an IE representing the <NUM>-<NUM> interworking Capability, or an IE including an APN or DNN value requested in order to use the <NUM>-<NUM> interworking service.

Second embodiment - <FIG> is a diagram illustrating a method in which a terminal connects to a network, negotiates regarding whether <NUM> and <NUM> services are available and simultaneously establishes a PDU session according to the negotiation, according to an embodiment of the present disclosure.

Even though the terminal <NUM> does not put the Capability into the SM message, the mobility management function <NUM> may inform the SMF <NUM> of the fact that the terminal <NUM> uses both the <NUM> and the <NUM> through the fifth and sixth procedures.

Even though the terminal <NUM> does not put the Capability into the SM message and does not input the APN or the DNN for the <NUM>-<NUM> interworking, the SMF <NUM> may check subscription information of the terminal <NUM> acquired after the sixth procedure, check the <NUM>-<NUM> interworking Capability from the subscription information, and establish a PDU session for the <NUM>-<NUM> interworking Capability.

The mobility management function <NUM> performs a procedure for selecting the SMF <NUM> in order to transfer the SM message received in the fourth procedure to the SMF <NUM> at operation S230. In this case, in consideration of whether the terminal <NUM> can use both the <NUM> and the <NUM> acquired in the Attach procedure, the mobility management function <NUM> selects the SMF <NUM> enabling the <NUM>-<NUM> interworking. This may be the SMF <NUM> belonging to a specific Network Slice Instance.

The mobility management function <NUM> transfers the PDU session request sent by the terminal <NUM> to the selected SMF <NUM> at operation S235. In this case, the mobility management function <NUM> may transfer whether the terminal <NUM> can use both the <NUM> and the <NUM> (that is, the <NUM>-<NUM> interworking Capability) acquired through the Attach procedure to the SMF <NUM> together with the PDU session request.

After receiving the message, the SMF <NUM> may negotiate with the server <NUM> in order to acquire subscription information for the terminal <NUM> at operation S240. This procedure may be omitted, and in this case, the mobility management function <NUM> may transfer the subscription information of the terminal <NUM> acquired in the Attach procedure to the SMF <NUM> through the sixth procedure.

The SMF <NUM> may check the <NUM>-<NUM> interworking Capability included in the PDU Session Request message sent by the terminal <NUM>, the APN/the DNN included in the PDU Session Request message, the '<NUM>-<NUM> interworking Capability of the terminal <NUM>' included in the message including the PDU Session Request message sent by the MMF, or the <NUM>-<NUM> interworking Capability in the subscription information of the terminal <NUM> sent by the mobility management function <NUM>, thereby judging that it is necessary to establish a PDU session required for the <NUM>-<NUM> interworking in the terminal <NUM>. After the judgment procedure, the SMF selects a network <NUM> which is used in both a <NUM> system and a <NUM> system. Since IP connectivity of the terminal <NUM> is provided through the network <NUM>, the terminal <NUM> can use a Packet Data Network service with one IP address in the <NUM> system and the <NUM> system. When there occurs a change between the <NUM> system and the <NUM> system, since the IP address is continuously anchored through the network <NUM>, the terminal <NUM> can use a continuous Packet Data Network service. In the <NUM> system, the network <NUM> is considered like a P-GW. In another example, the session management function (SMF) <NUM> may perform a domain name system (DNS) query based on the APN or the DNN value for the <NUM>-<NUM> interworking sent by the terminal <NUM>, thereby acquiring an IP address of a corresponding UPF.

The SMF <NUM> having selected the network <NUM> performs a procedure for establishing a PDU session for the terminal <NUM> in the network <NUM> at operation S245. This is called PDU session Establishment in the present disclosure. This message may include the <NUM>-<NUM> interworking Capability of the terminal <NUM>.

After establishing the PDU session enabling the <NUM>-<NUM> interworking for the terminal <NUM>, the SMF <NUM> generates a response (e.g., a PDU session response) for the PDU Session Request, which is the SM message sent by the terminal <NUM>, and transfers the response to the mobility management function <NUM> at operation S250. In this case, the SMF <NUM> may transfer the IP address of the network <NUM> for the PDU session established to the terminal <NUM> to the mobility management function <NUM>. The mobility management function <NUM> preserves this information as a Context of the terminal <NUM> and updates the information to the server <NUM>, and the server <NUM> may store the IP address of the network <NUM> provided to the terminal <NUM>, so that the <NUM> system and the <NUM> system can check the IP address of the network <NUM> included in subscription information later, and always allocate the network <NUM> to the terminal <NUM> to maintain continuity of IP connectivity. In another example, the SMF <NUM> may directly update the IP address of the network <NUM> to the server <NUM>.

The mobility management function <NUM> transfers the PDU session response message received through the ninth procedure to the terminal <NUM> at operation S255. The terminal <NUM> may judge the establishment of the PDU session enabling the <NUM>-<NUM> interworking through the information included in the PDU session response. The information may be an IE representing the <NUM>-<NUM> interworking Capability, or an IE including an APN or DNN value requested in order to use the <NUM>-<NUM> interworking service.

It should be noted that the scope of the present disclosure is not limited to the names of the devices constituting the present disclosure. For example, the mobility management function <NUM> according to the present disclosure may include an access and mobility management function (AMF) that performs the same operations, the SMF <NUM> according to the present disclosure may include a SMF, and the server <NUM> according to the present disclosure may include a user data respository (UDR).

<FIG> is a diagram illustrating a structure of a terminal according to an aspect of the present disclosure.

Referring to <FIG>, a structure of a terminal <NUM> according to the present disclosure may include a terminal transceiver <NUM> that transmits applicable communication network information and an attach request message with a PDU session request to a mobility management function and receives an IP address allocated based on the applicable communication network information and an attach accept message with a PDU session response, and a terminal controller <NUM> that connects to a network based on the IP address.

<FIG> is a diagram illustrating a structure of a mobile management function according to an aspect of the present disclosure. Referring to <FIG>, a structure of a mobility management function <NUM> according to the present disclosure may include a mobility management function transceiver <NUM> that receives the applicable communication network information and the attach request message with a PDU session request from the terminal, receives a PDU session response message with an allocated IP address from a SMF, and transmits an attach accept message with the PDU session response message to the terminal, and a mobility management function controller <NUM> that selects a SMF, which allocates an IP address to the terminal, based on the applicable communication network information.

Claim 1:
A method performed by a terminal (<NUM>, <NUM>, <NUM>) in a <NUM> network of a mobile communication system, the method comprising:
transmitting, to an entity in the <NUM> network of a mobile communication system that implements the mobility management function (<NUM>, <NUM>, <NUM>), an attach request including capability information representing that the terminal supports both a <NUM> and the <NUM> networks and a protocol data unit, PDU, session request including access point name, APN, information for supporting the <NUM>-<NUM> interworking.