Mobile communication system, network device, terminal device, comunication method and computer program

Abstract

A mobile communication system comprising two radio access networks of different generations to which terminals can simultaneously connect comprises an SM node that, when a terminal requests "MG-DualSteer," which is "DualSteer" implemented by a combination of the two radio access networks of different generations, is capable of establishing a session using a "DS-capable NW," which is a mobile core network supporting "DualSteer," and a "DS-incapable NW," which is a mobile core network not supporting "DualSteer" to which the terminal is connected or can connect, and that selects a "DS-capable GW," which is a gateway at each site of the "DS-capable NW."

Description

Mobile communication systems, network devices, terminal devices, communication methods, and computer programs

[0001] The present invention relates to a mobile communication system, a network device, a terminal device, a communication method, and a computer program. This application claims priority to Japanese Patent Application No. 2024-224095, filed in Japan on December 19, 2024, the contents of which are incorporated herein by reference.

[0002] Conventionally, the fifth-generation mobile communication system (5G system) standardized by "3GPP (registered trademark) (3rd Generation Partnership Project)" is known (see, for example, Non-Patent Documents 1 and 2). Figure 6 is a diagram showing the schematic architecture of a 5G system. In Figure 6, the 5G system consists of UE (User Equipment), RAN (Radio Access Network), CN (Core Network) UPF (User Plane Function), and various NF (Network Function) of the CN's control plane (C-plane). Examples of NFs of the CN's C-plane include AMF (Access and Mobility Management Function), SMF (Session Management Function), PCF (Policy Control Function), UDM (Unified Data Management), and UDR (Unified Data Repository).

[0003] Here, the logical communication path established between the UE and the CN (UPF) for the UE to use the mobile communication service is referred to as a "session". Also, the session established between the UE and the CN (UPF) using multiple radio paths is referred to as a "multi-access session". In Non-Patent Documents 1 and 2, "Multi-access PDU (Packet Data Unit) Session" (hereinafter referred to as "MA PDU Session") is defined as an example of a multi-access session. The UE establishes a "MA PDU Session" with the CN (UPF) using a radio path via the RAN, which is "3gpp access", and a radio path via a wireless LAN (Local Area Network) such as "Wi-Fi (registered trademark)", which is "non-3gpp access". "3gpp access" is an access network defined by 3GPP. "non-3gpp access" is an access network other than "3gpp access". The UE uses its "MA PDU Session" to send and receive data with a DN (Data Network), such as the Internet, outside the 5GC (CN of the 5G system). By using the "MA PDU Session", the UE can obtain the effect of improving communication quality, such as expanding the communication bandwidth, reducing communication delay, and ensuring communication path redundancy.

[0004] Also, Non-Patent Document 3 describes an implementation case of "DualSteer (DS)" (see, for example, Figure 6.1.13.2-1: "DualSteer solution based on ATSSS and using an external access path"). In "DualSteer (DS)", the communication device simultaneously connects to two "3gpp accesses" and establishes a multi-access session with the UPF.

[0005] The proposed implementation of DS described in Non-Patent Document 3 involves notifying the communication device of the UPF's MultiPath TCP (Transmission Control Protocol: MPTCP) proxy address, and the communication device setting the MPTCP proxy address as the destination IP (Internet Protocol) address of the uplink traffic on the first PLMN (Public Land Mobile Network) side. This enables communication between the communication device and the proxy on the second PLMN without impacting the first PLMN.

[0006] 3GPP, TS 23.501, V18.2.0, 2023-063GPP, TS 23.502, V18.2.0, 2023-063GPP, TR 23.700-54, V1.1.0, 2024-09

[0007] By using DS to simultaneously utilize different generations of RANs, communication devices can achieve performance improvements through multi-access communication. Furthermore, it eliminates the need for coordination control between different generations of RANs, as required by conventional multi-access communication technologies such as ENDC (E-UTRA NR Dual Connectivity; a wireless connection method that uses both 4G and 5G), thus offering significant advantages from an investment perspective.

[0008] Furthermore, making the DS described in Non-Patent Document 3 available in combination with "DS-capable networks; mobile core networks that support DS" and "DS-incapable networks; mobile core networks that do not support DS" will contribute to further reducing capital investment in the network.

[0009] However, the proposed implementation of DS described in Non-Patent Document 3 had the problem that the communication delay on the DS-incapable network side could become very large.

[0010] (Problem 1) For example, suppose that a 5G gateway (GW) and a 6G (sixth generation) GW exist at base A on the Sea of ​​Japan side of the Tohoku region, and a 4G GW and a 6G GW exist at base B on the Pacific side of the Tohoku region, and that a DS can be configured with a 5G and 6G pair or a 4G and 6G pair. In this case, if the 6G C-plane determines the anchor GW to be paired with the 6G GW without considering bases A and B where the candidate 5G GW and 4G GW exist, it may determine a GW located at a different base than the 6G GW as the anchor GW (for example, determining the 4G GW at base B as the anchor GW for the 6G GW at base A), which could lead to significant communication delay.

[0011] (Problem 2) For example, with the conventional uniform method of assigning proxy IP addresses (IP addresses of the GW terminating the DS), depending on the combination of generations of GWs that make up the DS, there is a possibility that the communication path will be significantly rerouted, which will lead to increased communication delay.

[0012] This invention was made in consideration of these circumstances, and its purpose is to realize an appropriate communication path when a communication device is simultaneously connected to two "3GPP access" systems of different generations.

[0013] One aspect of the present invention is a mobile communication system comprising two wireless access networks of different generations to which a terminal can connect simultaneously, and comprising a Session Management (SM) node that selects a DS-capable GW, which is the gateway to each location of a DS-capable NW, capable of establishing a session using a DS-capable NW, which is a mobile core network that supports DualSteer, and a DS-incapable NW, which is a mobile core network that does not support DualSteer, to which the terminal is currently connected or could connect. One aspect of the present invention is a mobile communication system in which the SM node has the function of identifying the generation of the "DS-incapable NW" wireless access network to which the terminal is connected, and the instance of the "DS-incapable GW" which is the gateway to the "DS-incapable NW", from at least one of the existing PLMN identifier, RAT, cell ID, and "Access Type" included in the other access NW identification information that can identify other wireless access networks to which the terminal is connected or can connect, other than the wireless access network to which the terminal has sent a network registration request.One aspect of the present invention is a mobile communication system in which the selected "DS-capable GW" determines an IP address that can realize the optimal communication path from the "DS-incapable NW" that is paired with the "MG-DualSteer" of the terminal to the "DS-capable GW" from at least one of the following pieces of information: an "MG-DualSteer" rule for the "DS-capable GW", other access network identification information that can identify other wireless access networks that the terminal is connected to or can connect to other than the wireless access network from which the terminal has sent a network registration request, and "MG-DualSteer capability" indicating that the terminal supports "MG-DualSteer", and the determined IP address is used as a proxy IP address for the "DS-incapable NW". One aspect of the present invention is a mobile communication system in which the SM node has a database that can identify a "DS-incapable NW" to which the terminal is connected or can connect from other access NW identification information that can identify other wireless access networks to which the terminal is connected or can connect, other than the wireless access network to which the terminal has sent a network registration request. One aspect of the present invention is a mobile communication system in which the terminal includes other access NW identification information that can identify other wireless access networks to which the terminal is connected or can connect, other than the wireless access network to which the terminal has sent a network registration request, in the network registration request. One aspect of the present invention is a mobile communication system in which the terminal includes other access NW identification information that can identify other wireless access networks to which the terminal is connected or can connect, other than the wireless access network to which the terminal has sent a network registration request, in the network registration information update request. One aspect of the present invention is a mobile communication system in which the terminal includes other access NW identification information that can identify other wireless access networks to which the terminal is connected or can connect, other than the wireless access network to which the terminal has sent a network registration request, in the session establishment request.One aspect of the present invention is a mobile communication system in which the terminal sets the "Request Type" of the session establishment request to "MG-DualSteer". Another aspect of the present invention is a mobile communication system in which the terminal manages a proxy IP address for "DS-incapable NW" as an IP address for uplink communication of "DS-incapable NW", and uses the said proxy IP address for "DS-incapable NW" as the destination IP address for traffic destined for "DS-incapable NW". Another aspect of the present invention is a mobile communication system in which the terminal further comprises a node that manages other access network identification information capable of identifying other wireless access networks that are connected to or can be connected to, other than the wireless access network from which the terminal has sent a network registration request.

[0014] One aspect of the present invention is a network device for a mobile communication system that includes two wireless access networks of different generations to which a terminal can connect simultaneously, and when the terminal requests "MG-DualSteer," which is "DualSteer" implemented with a combination of two wireless access networks of different generations, the network device selects a "DS-capable GW," which is a gateway at each location of the "DS-capable NW," capable of establishing a session using a "DS-capable NW," which is a mobile core network that supports "DualSteer," and a "DS-incapable NW," which is a mobile core network that does not support "DualSteer" to which the terminal is currently connected or could connect.

[0015] One aspect of the present invention is a terminal device in a mobile communication system comprising two wireless access networks of different generations to which the terminal device can simultaneously connect, wherein the terminal device includes in its network registration request other access network identification information that can identify other wireless access networks to which it is connected or can connect, other than the wireless access network to which it has sent a network registration request.

[0016] One aspect of the present invention is a communication method performed by a mobile communication system having two different generation wireless access networks to which a terminal can connect simultaneously, wherein when the terminal requests "MG-DualSteer," which is a "DualSteer" implemented with a combination of two different generation wireless access networks, the communication method selects a "DS-capable GW," which is a gateway at each location of the "DS-capable NW," capable of establishing a session using a "DS-capable NW," which is a mobile core network that supports "DualSteer," and a "DS-incapable NW," which is a mobile core network that does not support "DualSteer" to which the terminal is currently connected or can connect.

[0017] One aspect of the present invention is a computer program for a mobile communication system equipped with two different generation wireless access networks to which a terminal can connect simultaneously, which causes the computer to execute the step of selecting a "DS-capable GW" which is a gateway at each location of a "DS-capable NW" that can establish a session using a "DS-capable NW", which is a mobile core network that supports "DualSteer", and a "DS-incapable NW", which is a mobile core network that the terminal is currently connected to or can connect to, when the terminal requests "MG-DualSteer", which is "DualSteer" implemented with a combination of two different generation wireless access networks.

[0018] According to the present invention, when a communication device connects to two "3GPP access" systems of different generations simultaneously, it is possible to achieve an appropriate communication path.

[0019] This figure shows a schematic configuration example of a mobile communication system according to one embodiment. This figure shows a configuration example of "DS-capable C-plane" and "DS-incapable C-plane" according to one embodiment. This figure shows an example of the procedure of a communication method according to one embodiment. This figure shows an example of the procedure of a communication method according to one embodiment. This figure shows an example of the procedure of a communication method according to one embodiment. This figure shows a schematic architecture of a 5G system.

[0020] Embodiments of the present invention will be described below with reference to the drawings.

[0021] In this embodiment, a communication device that communicates with other devices is referred to as a "terminal device" (sometimes simply called a terminal). The terminal may be a "UE" as defined in 3GPP.

[0022] This embodiment proposes a method for a terminal to implement DualSteer (DS) using a combination of two different generations of "3gpp access". This DS is referred to as "MG-DualSteer (Multi-Generation DualSteer)". The session established for MG-DualSteer is referred to as "MG-DualSteer Session".

[0023] In this embodiment, a mobile core network that supports DS is referred to as "DS-capable NW," and a mobile core network that does not support DS is referred to as "DS-incapable NW." If the DS-capable NW is, for example, 6G, then the DS-incapable NW is a different generation from 6G, such as 5G, 4G, 3G, ... or 7G, 8G, ... Therefore, "DS-capable xxx" and "DS-incapable xxx" can be said to be information that identifies the generation of the network.

[0024] In this embodiment, the gateway (GW) of the "DS-capable NW" operates as a proxy for the MG-DualSteer. In the mobile network section, the gateway of the "DS-capable NW" and the terminal communicate using the MG-DualSteer. The terminal and the "Remote Host (RH)" on the internet communicate using normal single-path communication such as TCP / UDP. For example, the gateway in 5G is a UPF. The gateway of the mobile core network refers to the network device (node) that serves as the connection point between the "Data Network (DN)" and the mobile core network.

[0025] Figure 1 is a diagram showing a schematic configuration example of the mobile communication system 1 according to this embodiment. Figure 1 shows the architecture of "MG-DualSteer Session" according to this embodiment.

[0026] The mobile communication system 1 includes a "DS-capable NW" 20 and a "DS-incapable NW" 30.

[0027] The "DS-capable NW" 20 comprises a wireless access network (NG (Next Generation)-RAN 21), a C-plane ("DS-capable C-plane" 22), and a gateway ("DS-capable GW" 23). The "DS-capable GW" 23 may be present at each location of the "DS-capable NW" 20.

[0028] The "DS-incapable NW" 30 comprises a wireless access network (Legacy-RAN 31), a C-plane ("DS-incapable C-plane" 32), and a gateway ("DS-incapable GW" 33). The "DS-incapable NW" 30 may be present at each of its locations.

[0029] In Figure 1, terminal 10 connects simultaneously to the "DS-capable NW" 20 and the "DS-incapable NW" 30 and performs MG-DualSteer. In this MG-DualSteer, terminal 10 establishes an "MG-DualSteer Session" with the "DS-capable GW" 23. This allows terminal 10 to use the DS with the combination of the "DS-capable NW" 20 and the "DS-incapable NW" 30. Terminal 10 sends and receives data to and from RH 50 on DN 40 via the "DS-capable GW" 23.

[0030] Figure 2 shows an example configuration of the "DS-capable C-plane" 22 and "DS-incapable C-plane" 32 according to this embodiment. In Figure 2, the "DS-capable C-plane" 22 and "DS-incapable C-plane" 32 include an AM (Access and Mobility) node 101, an SM (Session Management) node 102, a user management node 103, and a policy control node 104. Each node is connected to the others so as to be able to communicate with each other. There may be multiple SM nodes 102.

[0031] AM node 101 supports 5G AMF. SM node 102 supports 5G SMF. User management node 103 supports 5G UDM or UDR. Policy control node 104 supports 5G PCF.

[0032] The functions of AM node 101, SM node 102, user management node 103, and policy control node 104 may be configured as a single node in any combination. For example, the functions of AM node 101 and SM node 102 may be configured as a single node. For example, in the case of 4G, the MME (Mobility Management Entity) corresponds to AM node 101 and SM node 102, and the HSS (Home Subscriber Server) corresponds to user management node 103.

[0033] Furthermore, the AM node 101, SM node 102, user management node 103, and policy control node 104 may be functionally divided as desired. For example, the AM node 101 may be functionally divided into an Access node and a Mobility node.

[0034] Furthermore, the "DS-capable C-plane" 22 and the "DS-incapable C-plane" 32 may further include nodes having any other functions besides the AM node 101, SM node 102, user management node 103, and policy control node 104.

[0035] The AM node 101, SM node 102, user management node 103, and policy control node 104 may each be implemented as independent physical servers (information processing devices), or multiple nodes may be implemented on a single physical server. For example, multiple nodes may coexist and be deployed as software on a single physical server.

[0036] Next, the communication method according to this embodiment will be described with reference to Figures 3-5. Figures 3-5 show an example of the procedure of the communication method according to this embodiment.

[0037] [Registration process to "DS-capable NW" for MG-DualSteer] The registration process to "DS-capable NW" 20 for MG-DualSteer will be explained with reference to Figure 3.

[0038] (Step S1) Terminal 10 sends a network (NW) registration request to the AM node 101 ("DS-capable AM ​​node" 22_101) of the "DS-capable C-plane" 22. This NW registration request may include the following parameters 1-1 and 1-2.

[0039] <Parameter 1-1; Other Access Network Identification Information> Other Access Network Identification Information is information that allows terminal 10 to identify other RANs that it is connected to or can connect to, other than the RAN from which it sent the NW registration request. Other Access Network Identification Information includes identifiers of other networks that can be uniquely identified by the "DS-capable NW" 20. These identifiers of other networks may be existing PLMN (Public Land Mobile Network) identifiers, RAT (Radio Access Type), cell identifiers (cell IDs), "Access Type," etc., or combinations of these. Other Access Network Identification Information may be in list format. An example of a list format for Other Access Network Identification Information is "NW list = { [ ID = 0, PLMN = xxx, RAT Type = NR, Cell ID = yyy ], [ID = 1, PLMN = zzz, RAT Type = LTE, Cell ID = aaa ]}".

[0040] <Parameter 1-2; "MG-DualSteer capability"> "MG-DualSteer capability" is information indicating that terminal 10 supports MG-DualSteer. "MG-DualSteer capability" may be in list format. "MG-DualSteer capability" may include information such as protocols supported by terminal 10, "Steering modes" supported by terminal 10, and simultaneous transmission capability. Examples of protocols supported by terminal 10 include MPTCP, MPQUIC, and ATSSS-LL. "Steering mode" is information indicating the traffic transmission mode, such as Active-standby and Smallest-delay. Simultaneous transmission capability information indicates whether terminal 10 can use two "3gpp access" simultaneously.

[0041] (Step S2) The "DS-capable AM node" 22_101 receives the NW registration request transmitted from the terminal 10. If the received NW registration request contains other access NW specific information or "MG-DualSteer capability", the "DS-capable AM node" 22_101 saves the other access NW specific information and "MG-DualSteer capability" contained in the NW registration request (Step S2a).

[0042] In addition, the user management node 103 of the "DS-capable C-plane" 22 (the "DS-capable user management node" 22_103) may save the other access NW specific information and "MG-DualSteer capability" contained in the NW registration request. In this case, the "DS-capable AM node" 22_101 transmits the other access NW specific information and "MG-DualSteer capability" contained in the NW registration request to the "DS-capable user management node" 22_103 (Step S2b-1). The "DS-capable user management node" 22_103 saves the other access NW specific information and "MG-DualSteer capability" received from the "DS-capable AM node" 22_101 (Step S2b-2).

[0043] As a result, the other access NW specific information and "MG-DualSteer capability" contained in the NW registration request of the terminal 10 are saved by the "DS-capable AM node" 22_101 or the "DS-capable user management node" 22_103. Note that both the "DS-capable AM node" 22_101 and the "DS-capable user management node" 22_103 may save the other access NW specific information and "MG-DualSteer capability" contained in the NW registration request of the terminal 10.

[0044] Note that any conventional procedures may be executed between Step S1 and Step S2, or before and after them.

[0045] [NW Registration Information Update Process for MG-DualSteer] The NW registration information update process for MG-DualSteer will be described with reference to FIG. 4. Here, the terminal 10 is already connected to the "DS-capable NW" 20.

[0046] (Step S11) When the terminal 10 establishes a connection with another "3gpp access" different from the connected "DS-capable NW" 20, the terminal 10 sends a NW registration information update request to the "DS-capable AM node" 22_101. This NW registration information update request includes other access NW identification information by the terminal 10. Note that the NW registration information update request may be sent from the terminal 10 at any timing.

[0047] (Step S12) The "DS-capable AM node" 22_101 receives the NW registration information update request sent from the terminal 10. When the other access NW identification information is included in the received NW registration information update request, the "DS-capable AM node" 22_101 stores the other access NW identification information included in the NW registration information update request (Step S12a).

[0048] Note that the "DS-capable user management node" 22_103 may store the other access NW identification information included in the NW registration information update request. In this case, the "DS-capable AM node" 22_101 sends the other access NW identification information included in the NW registration information update request to the "DS-capable user management node" 22_103 (Step S12b-1). The "DS-capable user management node" 22_103 stores the other access NW identification information received from the "DS-capable AM node" 22_101 (Step S12b-2).

[0049] As a result, the "DS-capable AM ​​node" 22_101 or the "DS-capable user management node" 22_103 saves the other access network specific information included in the network registration information update request of terminal 10. Alternatively, both the "DS-capable AM ​​node" 22_101 and the "DS-capable user management node" 22_103 may be configured to save the other access network specific information included in the network registration information update request of terminal 10.

[0050] In addition, any conventional procedure may be performed between step S11 and step S12, or before or after them.

[0051] [MG-DualSteer Session Establishment Procedure] The MG-DualSteer Session establishment procedure will be explained with reference to Figure 5.

[0052] (Step S21) Terminal 10 sends a session establishment request to the "DS-capable AM ​​node" 22_101. At this time, terminal 10 may include other access network specific information and "MG-DualSteer capability" in the session establishment request. Terminal 10 also sets "MG-DualSteer" as the "Request Type" to be included in the session establishment request. When the "Request Type" to be included in the session establishment request is "MG-DualSteer", it indicates that the session establishment request is a request for an "MG-DualSteer Session".

[0053] Furthermore, the session establishment request may be indicated as an "MG-DualSteer Session" request by including at least one of "other access network identification information" and "MG-DualSteer capability" in the session establishment request.

[0054] Alternatively, a new "MG-DualSteer Session" establishment request may be created as a message distinct from a normal session establishment request. The procedure for the "MG-DualSteer Session" establishment request may be the same as for a normal session establishment request.

[0055] Alternatively, the session establishment request may be indicated as an "MG-DualSteer Session" request by setting "DualSteer" as the "Request Type" to be included in the session establishment request and combining it with parameters other than "Request Type" (for example, other access network identification information or "MG-DualSteer capability").

[0056] (Step S22) The "DS-capable AM ​​node" 22_101 receives a Session establishment request sent from terminal 10 (hereinafter referred to as target terminal 10) and recognizes that the received Session establishment request is an "MG-DualSteer Session" request. If the Session establishment request from target terminal 10 includes other access network identification information and "MG-DualSteer capability", the process proceeds to step S22-3.

[0057] If the session establishment request from the target terminal 10 does not include the other access network identification information and the "MG-DualSteer capability", the "DS-capable AM ​​node" 22_101 checks whether it has stored the other access network identification information and the "MG-DualSteer capability" for the target terminal 10 (step S22-1). If, as a result of this check, the "DS-capable AM ​​node" 22_101 has stored the other access network identification information and the "MG-DualSteer capability" for the target terminal 10, the process proceeds to step S22-3.

[0058] On the other hand, if the "DS-capable AM ​​node" 22_101 does not store the other access network identification information and "MG-DualSteer capability" of the target terminal 10, it queries the "DS-capable user management node" 22_103 for the other access network identification information and "MG-DualSteer capability" of the target terminal 10, and obtains the other access network identification information and "MG-DualSteer capability" of the target terminal 10 from the "DS-capable user management node" 22_103 (step S22-2). After this, the process proceeds to step S22-3.

[0059] The "DS-capable user management node" 22_103 selects a "DS-capable SM node" 22_102 from among the SM nodes 102 ("DS-capable SM nodes" 22_102) of the "DS-capable C-plane" 22 that satisfies the MG-DualSteer requirements for the target terminal 10, based on the other access network identification information of the target terminal 10 and the "MG-DualSteer capability".

[0060] (Step S23) The "DS-capable AM ​​node" 22_101 sends a session establishment request to the selected "DS-capable SM node" 22_102, along with the other access network identification information of the target terminal 10 and the "MG-DualSteer capability". The "DS-capable SM node" 22_102 receives the session establishment request from the "DS-capable AM ​​node" 22_101, along with the other access network identification information of the target terminal 10 and the "MG-DualSteer capability".

[0061] (Step S24) The "DS-capable SM node" 22_102 compares the information of the target terminal 10 managed by the "DS-capable user management node" 22_103 with the other access network identification information of the target terminal 10 and the "MG-DualSteer capability" to determine whether the target terminal 10 can use MG-DualSteer. If the result of this determination indicates that the target terminal 10 can use MG-DualSteer, the process proceeds to step S25. On the other hand, if the target terminal 10 cannot use MG-DualSteer, the session establishment request from the target terminal 10 is rejected, and the process shown in Figure 5 is terminated.

[0062] (Step S25) The "DS-capable SM node" 22_102 transmits information regarding the "MG-DualSteer capability" of the target terminal 10, as well as the "DS-capable NW" 20 and "DS-incapable NW" 30, to the policy control node 104 of the "DS-capable C-plane" 22 ("DS-capable policy control node" 22_104), and queries the MG-DualSteer rules for the target terminal 10.

[0063] The "DS-capable policy control node" 22_104 determines the MG-DualSteer rule for the target terminal 10. The MG-DualSteer rule for the target terminal 10 specifies how the target terminal 10 and the "DS-capable GW" 23 distribute traffic to two RANs of different generations, NG-RAN 21 and Legacy-RAN 31. Note that the content of the MG-DualSteer rule may differ between the target terminal 10 (uplink communication) and the "DS-capable GW" 23 (downlink communication).

[0064] The "DS-capable policy control node" 22_104 responds to the "DS-capable SM node" 22_102 with the MG-DualSteer rule for the determined target terminal 10.

[0065] Alternatively, the "DS-capable policy control node" 22_104 may respond to the "DS-capable SM node" 22_102 with instructions (MG-DualSteer rule instruction information) for determining the MG-DualSteer rule for the target terminal 10, and the "DS-capable SM node" 22_102 may determine the MG-DualSteer rule for the target terminal 10 based on the said MG-DualSteer rule instruction information.

[0066] (Step S26) The "DS-capable SM node" 22_102 recognizes the "DS-incapable NW" 30 to which the target terminal 10 is currently connected or can connect, based on the other access network identification information of the target terminal 10. The "DS-capable SM node" 22_102 may also have a database that can identify the "DS-incapable NW" 30 to which the target terminal 10 is currently connected or can connect, based on the other access network identification information of the target terminal 10.

[0067] The "DS-capable SM node" 22_102 selects the "DS-capable GW" 23 from among the "DS-capable GWs" 23 at each location of the "DS-capable NW" 20 that minimizes the communication delay between the target terminals 10 via the recognized "DS-incapable NW" 30. This solves the aforementioned problem 1. Examples 1 and 2 of the method for selecting the "DS-capable GW" 23 are shown below.

[0068] <Example 1 of how to select a "DS-capable GW"> If the candidate "DS-capable GW" 23 exists at both sites A and B, and the "DS-incapable NW" 30 exists at site A, then the "DS-capable GW" 23 at site A is selected.

[0069] <Example 2 of how to select a "DS-capable GW"> If the specific information of other access networks is provided in the list format described above, in addition to the "DS-capable GW" 23, the recommended "Legacy-RAN 31 generation" is also determined. For example, suppose a 4G "DS-capable GW" 23 exists at site A, a 5G "DS-capable GW" 23 exists at site B, and a 6G "DS-capable GW" 23 exists at site C. In this case, the expected delay in communication between site C and site A is compared with the expected delay in communication between site C and site B, and the appropriate "DS-capable GW" 23 and the appropriate "DS-incapable NW" 30 are selected based on the results of this comparison.

[0070] Furthermore, the "DS-capable SM node" 22_102 is configured to have the function of identifying the RAN generation of the "DS-incapable NW" 30 and the instance of the "DS-incapable GW" 33 from the information of the parameters when the other access network identification information is indicated by existing PLMN identifiers, RATs, cell IDs, "Access Type", or combinations thereof.

[0071] (Step S27) The "DS-capable SM node" 22_102 forwards the session establishment request received from the "DS-capable AM ​​node" 22_101 in step S23 to the selected "DS-capable GW" 23 (step S27-1). At this time, the following information (1), (2), and (3) may also be included in the transmission: (1) MG-DualSteer rules for the "DS-capable GW" 23 obtained in step S25 (2) Other access network identification information for the target terminal 10 (3) "MG-DualSteer capability" of the target terminal 10

[0072] Based on the session establishment request received from the DS-capable SM node 22_102 and the above information (1), (2), and (3), the DS-capable GW 23 determines an IP address that can realize the optimal communication path (for example, a communication path with the lowest latency) from the DS-incapable NW 30 which is paired with the MG-DualSteer of the target terminal 10 to itself, the DS-capable GW 23, and responds to the DS-capable SM node 22_102 with the determined IP address as a proxy IP address for the DS-incapable NW (step S27-2). This solves the above-mentioned problem 2.

[0073] (Step S28) The "DS-capable SM node" 22_102 responds to the "DS-capable AM ​​node" 22_101 that it has accepted the request for "MG-DualSteer Session". In this response, the "DS-capable SM node" 22_102 sends tunnel information necessary for establishing a tunnel between the NG-RAN 21 of the "DS-capable NW" 20 and the "DS-capable GW" 23 to the "DS-capable AM ​​node" 22_101. This tunnel information is the same as before. The "DS-capable SM node" 22_102 also sends the MG-DualSteer rule for the target terminal 10 obtained in step S25, and the proxy IP address for the "DS-incapable NW" responded to from the "DS-capable GW" 23 in step S27-2 to the "DS-capable AM ​​node" 22_101. The proxy IP address for "DS-incapable NW" is the IP address that the target terminal 10 uses as the destination address for uplink communication to "DS-incapable NW" 30.

[0074] (Step S29) The "DS-capable AM ​​node" 22_101 transmits the tunnel information received in response from the "DS-capable SM node" 22_102 to the NG-RAN 21.

[0075] (Step S30) The "DS-capable AM ​​node" 22_101 responds to the target terminal 10 with the MG-DualSteer rule and the proxy IP address for the "DS-incapable NW" that were responded to from the "DS-capable SM node" 22_102, as well as the MG-DualSteer session establishment completion instruction information. The target terminal 10 receives the response from the "DS-capable AM ​​node" 22_101. The target terminal 10 saves the received proxy IP address for the "DS-incapable NW" to be used as the destination IP address for uplink communication of the "DS-incapable NW" 30. The target terminal 10 uses the saved proxy IP address for the "DS-incapable NW" as the destination IP address for traffic destined for the "DS-incapable NW".

[0076] According to the embodiment described above, when terminal 10 connects to two "3gpp access" systems of different generations simultaneously, an appropriate communication path can be realized.

[0077] Furthermore, this will enable improvements in overall service quality, such as in mobile communication systems, and will contribute to Goal 9 of the United Nations-led Sustainable Development Goals (SDGs): "Build resilient infrastructure, promote sustainable industrialization and foster innovation."

[0078] Although embodiments of the present invention have been described in detail above with reference to the drawings, the specific configuration is not limited to these embodiments, and design modifications and the like are also included within the scope of the gist of the present invention.

[0079] Alternatively, computer programs for realizing the functions of each of the above-mentioned devices may be recorded on a computer-readable recording medium, and the programs recorded on this recording medium may be loaded into a computer system and executed. The term "computer system" here may include hardware such as an operating system and peripheral devices. Furthermore, "computer-readable recording medium" refers to writable non-volatile memory such as flexible disks, magneto-optical disks, ROMs, and flash memory, portable media such as DVDs (Digital Versatile Discs), and storage devices such as hard disks built into a computer system.

[0080] Furthermore, "computer-readable recording media" includes volatile memory (e.g., DRAM (Dynamic Random Access Memory)) within a computer system that acts as a server or client when a program is transmitted via a network such as the Internet or a communication line such as a telephone line, which retains the program for a certain period of time. In addition, the above program may be transmitted from the computer system that stores the program in a storage device, etc., to another computer system via a transmission medium or by transmission waves within the transmission medium. Here, the "transmission medium" for transmitting the program refers to a medium that has the function of transmitting information, such as a network such as the Internet or a communication line such as a telephone line. Furthermore, the above program may be for the purpose of realizing a part of the above-mentioned functions. In addition, it may be a so-called differential file (differential program) that can realize the above-mentioned functions in combination with a program already recorded in the computer system.

[0081] According to the present invention, an appropriate communication path can be realized when a communication device connects to two different generations of "3GPP access" simultaneously.

[0082] 1...Mobile communication system, 10...Terminal device, 20...DS-capable NW, 21...NG-RAN, 22...DS-capable C-plane, 23...DS-capable GW, 30...DS-incapable NW, 31...Legacy-RAN, 32...DS-incapable C-plane, 33...DS-incapable GW, 40...Data Network, 50...Remote Host, 101...AM node, 102...SM node, 103...User management node, 104...Policy control node

Claims

1. A mobile communication system comprising two wireless access networks of different generations to which a terminal can connect simultaneously, wherein when the terminal requests "MG-DualSteer," which is a "DualSteer" implemented using a combination of two wireless access networks of different generations, the system includes a Session Management (SM) node that selects a "DS-capable GW," which is the gateway to each location of the "DS-capable NW," capable of establishing a session using a "DS-capable NW," which is a mobile core network that supports "DualSteer," and a "DS-incapable NW," which is a mobile core network that the terminal is currently connected to or could connect to, and does not support "DualSteer." 2. The mobile communication system according to claim 1, wherein the SM node has a function to identify the generation of the "DS-incapable NW" wireless access network to which the terminal is connected or can connect, and the instance of the "DS-incapable GW" which is the gateway to the "DS-incapable NW", from at least one of the existing PLMN identifier, RAT, cell ID, and "Access Type" included in the other access NW identification information that can identify other wireless access networks to which the terminal is connected or can connect, other than the wireless access network to which the terminal has sent a network registration request.

3. The selected "DS-capable GW" determines an IP address that enables the optimal communication path from the "DS-incapable NW" that is paired with the "MG-DualSteer" of the terminal to the "DS-capable GW" based on at least one of the following pieces of information: an "MG-DualSteer" rule for the "DS-capable GW", other access network identification information that can identify other wireless access networks that the terminal is connected to or can connect to other than the wireless access network from which the terminal has sent a network registration request, and "MG-DualSteer capability" indicating that the terminal supports "MG-DualSteer", and the determined IP address is used as a proxy IP address for the "DS-incapable NW", the mobile communication system according to claim 1.

4. The mobile communication system according to claim 1, wherein the SM node includes a database that can identify a "DS-incapable NW" to which the terminal is connected or can connect from other access network identification information that can identify other wireless access networks to which the terminal is connected or can connect, other than the wireless access network to which the terminal has sent a network registration request.

5. The mobile communication system according to any one of claims 1 to 4, wherein the terminal includes in the network registration request other access network identification information that can identify other wireless access networks that it is connected to or can connect to, other than the wireless access network to which it has sent the network registration request.

6. The mobile communication system according to any one of claims 1 to 4, wherein the terminal includes in the network registration information update request other access network identification information that can identify other wireless access networks that it is currently connected to or can connect to, other than the wireless access network from which it sent the network registration request.

7. The mobile communication system according to any one of claims 1 to 4, wherein the terminal includes in the session establishment request other access network identification information that can identify other wireless access networks that it is connected to or can connect to, other than the wireless access network from which it sent the network registration request.

8. The mobile communication system according to claim 7, wherein the terminal sets the "Request Type" of the session establishment request to "MG-DualSteer".

9. The mobile communication system according to any one of claims 1 to 4, wherein the terminal manages a proxy IP address for the "DS-incapable NW" as an IP address for uplink communication of the "DS-incapable NW", and uses the said proxy IP address for the "DS-incapable NW" as the destination IP address for traffic destined for the "DS-incapable NW".

10. The mobile communication system according to any one of claims 1 to 4, further comprising a node that manages other access network identification information capable of identifying other wireless access networks that are connected to or can be connected to, other than the wireless access network from which the terminal transmitted a network registration request.

11. A network device for a mobile communication system that includes two wireless access networks of different generations to which a terminal can connect simultaneously, wherein when the terminal requests "MG-DualSteer," which is a "DualSteer" implemented using a combination of two wireless access networks of different generations, the network device selects a "DS-capable GW," which is a gateway at each location of the "DS-capable NW," capable of establishing a session using a "DS-capable NW," which is a mobile core network that supports "DualSteer," and a "DS-incapable NW," which is a mobile core network that the terminal is currently connected to or could connect to, and does not support "DualSteer." 12. A terminal device in a mobile communication system that includes two wireless access networks of different generations to which the terminal device can simultaneously connect, wherein the terminal device includes in its network registration request other access network identification information that can identify other wireless access networks to which it is connected or can connect, other than the wireless access network to which it has sent a network registration request.

13. A communication method performed by a mobile communication system having two wireless access networks of different generations to which a terminal can connect simultaneously, wherein when the terminal requests "MG-DualSteer," which is "DualSteer" implemented with a combination of two wireless access networks of different generations, the communication method selects a "DS-capable GW," which is a gateway at each location of the "DS-capable NW," capable of establishing a session using a "DS-capable NW," which is a mobile core network that supports "DualSteer," and a "DS-incapable NW," which is a mobile core network that does not support "DualSteer" and to which the terminal is currently connected or can connect.

14. A computer program for causing a computer in a mobile communication system equipped with two different generation wireless access networks to which a terminal can connect simultaneously to execute the following steps: When the terminal requests "MG-DualSteer," which is a "DualSteer" implemented using a combination of two different generation wireless access networks, the computer program selects a "DS-capable GW," which is a gateway at each location of a "DS-capable NW," a mobile core network that supports "DualSteer," and a "DS-incapable NW," a mobile core network that does not support "DualSteer," to which the terminal is currently connected or could connect.

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