Mobile communication system, user terminal, network device, network registration method, and computer program

Abstract

To expand a service area of multipath communication.SOLUTION: A user terminal includes an SPLMN information storage unit that stores SPLMN (Secondary PLMN) information indicating one or more PLMNs (Public Land Mobile Networks) as candidates for the second or subsequent registration of the user terminal and the priority of each of the multiple PLMNs, and a network registration control unit that transmits a network registration request to a base station of the radio access network of the PLMN as the second or subsequent registration target of the user terminal on the basis of the SPLMN information.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a mobile communication system, a user terminal, a network device, a network registration method, and a computer program. [Background technology]

[0002] Conventionally, a fifth generation mobile communication system (5G system) standardized by "3GPP (registered trademark) (3rd Generation Partnership Project)" is known (for example, see Non-Patent Documents 1 and 2). FIG. 10 is a diagram showing a schematic architecture of a 5G system. In FIG. 10, the 5G system is composed of a UE (User Equipment), a RAN (Radio Access Network), a UPF (User Plane Function) of a CN (Core Network), and various NFs (Network Functions) of a control plane (Control plane: C-plane) of the CN. Examples of NFs of the C-plane of the CN include an AMF (Access and Mobility Management Function) and an SMF (Session Management Function).

[0003] Here, a logical communication path that the UE establishes with the CN (UPF) to use a mobile communication service is called a "session". A session that the UE establishes with the CN (UPF) using multiple wireless paths is called a "multi-access session". Non-Patent Documents 1 and 2 specify a "Multi-access PDU Session (hereinafter, referred to as an "MA PDU Session")" as an example of a multi-access session. FIG. 11 is a diagram showing a configuration example of an "MA PDU Session". As shown in FIG. 11, the UE establishes an "MA PDU Session" with the CN (UPF) using a wireless path via a RAN, which is "3gpp access", and a wireless 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 specified by 3GPP. "Non-3gpp access" is an access network other than "3gpp access". The UE uses the "MA PDU Session" to send and receive data between DN (Data Network), such as the Internet, outside the 5GC (CN of the 5G system). By using the "MA PDU Session", the UE can improve communication quality by expanding the communication band, reducing communication delays, and ensuring redundancy of the communication path.

[0004] In addition, the UE takes either the "Single Registration mode" or the "Dual Registration mode" as the network registration mode (NW registration mode). The Dual Registration mode is a NW registration mode specified to realize mobility between 5GC and EPC (Evolved Packet Core), which is the core network of the fourth generation mobile communication system (4G system). A UE operating in the Dual Registration mode simultaneously registers with two networks, "5G system base station (5G base station), 5GC" and "4G system base station (4G base station), EPC" on "3gpp access". This allows the UE to realize movement while continuing communication, for example, when moving from the coverage of the 5G system to the coverage of the 4G system. [Prior art documents] [Non-patent literature]

[0005] [Non-Patent Document 1] 3GPP, TS 23.501, V18.2.0, 2023-06 [Non-Patent Document 2] 3GPP, TS 23.502, V18.2.0, 2023-06 Summary of the Invention [Problem to be solved by the invention]

[0006] In the next generation B5G (Beyond 5G) system after the 5G system and the sixth generation mobile communication system (6G system), multipath communication can be utilized as a means for achieving service requirements such as ultra-high capacity (100 Gbps class) and ultra-low latency (1 ms or less) for one user. However, the "MA PDU Session" described in Non-Patent Documents 1 and 2 as a multi-access session for realizing multipath communication is limited to a combination of "one 3gpp access (e.g., 5G base station)" and "one non-3gpp access (e.g., wireless LAN)", and therefore the service area of ​​multipath communication in which a UE can realize ultra-high capacity and ultra-low latency communication is small.

[0007] Therefore, if a multi-access session can be established using two arbitrarily selected "3gpp access" (base stations) without limiting the PLMN (Public Land Mobile Network) (i.e., without limiting the communication carrier that manages the base station to which the UE is connected), the service area of ​​multipath communication will be significantly expanded, allowing many users to enjoy the benefits of multipath communication, such as ultra-high capacity communication and ultra-low latency.

[0008] However, in the "Dual Registration mode", a conventional UE cannot simultaneously register to two networks, "5G system base station (5G base station), 5GC" and "4G system base station (4G base station), EPC" on "3gpp access", after performing the first network registration to a certain PLMN (first PLMN), select the next PLMN (the same or different PLMN (second PLMN) from the first PLMN) and perform the second network registration to the selected second PLMN. For this reason, the two "3gpp access" (base stations) for establishing a multi-access session are limited, making it difficult to expand the service area of ​​multipath communication.

[0009] The present invention has been made in consideration of the above circumstances, and has an object to expand the service area of ​​multipath communication. [Means for solving the problem]

[0010] One aspect of the present invention is a mobile communications system comprising a core network connected to multiple radio access networks, in which a user terminal comprises an SPLMN information storage unit that stores SPLMN (Secondary PLMN) information indicating one or more PLMNs (Public Land Mobile Networks) as candidates for the user terminal to register as a second or subsequent time and the priority of each of the multiple PLMNs, and a network registration control unit that transmits a network registration request to a base station of the radio access network of the PLMN as the second or subsequent time registration target of the user terminal based on the SPLMN information, and the core network comprises a network device that provides the SPLMN information to the user terminal. One aspect of the present invention is a mobile communications system in which the user terminal further comprises a network registration mode information storage unit that stores network registration mode information indicating a "Single Registration Mode" in which the user terminal performs a single network registration on "3gpp access" or a "Dual Registration Mode" in which the user terminal can perform two network registrations on "3gpp access", a network registration trigger information storage unit that stores network registration trigger information indicating a timing for performing a second or subsequent network registration when the user terminal operates in "Dual Registration Mode", and a PLMN selection mode information storage unit that stores PLMN selection mode information for determining whether the user terminal operates in "Single PLMN Mode" in which the user terminal connects to two base stations of a single PLMN, or "Dual PLMN Mode" in which the user terminal connects to a total of two base stations, one in each of different PLMNs, and the network registration control unit controls execution of the network registration request based on the network registration mode information, the network registration trigger information, and the PLMN selection mode information. One aspect of the present invention is a mobile communications system, wherein the "Dual Registration Mode" in the above mobile communications system includes a "Dual Registration Mode for multi-path communication" in which the combination of PLMNs to be registered can be arbitrarily selected. One aspect of the present invention is a mobile communications system in which, in the above-mentioned mobile communications system, the network device provides the SPLMN information to the user terminal when the network registration request includes information indicating the "Dual Registration Mode". One aspect of the present invention is a mobile communications system in which, in the above-mentioned mobile communications system, the network registration control unit changes the network registration mode information, the network registration trigger information, the PLMN selection mode information, or the SPLMN information when a specified change condition is satisfied.

[0011] One aspect of the present invention is a user terminal of a mobile communications system having a core network connected to multiple radio access networks, the user terminal comprising: an SPLMN information storage unit that stores SPLMN (Secondary PLMN) information indicating one or more PLMNs (Public Land Mobile Networks) as candidates for the user terminal to register as a second or subsequent registration and the priority of each of the multiple PLMNs; and a network registration control unit that transmits a network registration request to a base station of the radio access network of the PLMN as the second or subsequent registration target of the user terminal based on the SPLMN information.

[0012] One aspect of the present invention is a network device provided in a core network in a mobile communications system having a core network connected to multiple radio access networks, the network device comprising an SPLMN control unit that provides a user terminal with SPLMN (Secondary PLMN) information indicating one or more PLMNs (Public Land Mobile Networks) as candidates for the user terminal to register as a second or subsequent time, and the priority of each of the multiple PLMNs.

[0013] One aspect of the present invention is a network registration method in a mobile communications system having a core network connected to multiple radio access networks, the network registration method including an SPLMN control step in which a network device in the core network provides a user terminal with SPLMN (Secondary PLMN) information indicating one or more PLMNs (Public Land Mobile Networks) as candidates for the user terminal to register as a second or subsequent time and the priority of each of the multiple PLMNs; an SPLMN information storage step in which the user terminal stores the SPLMN information in an SPLMN information storage unit; and a network registration control step in which the user terminal transmits a network registration request to a base station of the radio access network of the PLMN as the second or subsequent time registration target for the user terminal based on the SPLMN information.

[0014] One aspect of the present invention is a computer program for causing a computer of a user terminal of a mobile communications system having a core network connected to multiple radio access networks to execute an SPLMN information storage step of storing, in an SPLMN information storage unit, SPLMN (Secondary PLMN) information indicating one or more PLMNs (Public Land Mobile Networks) as candidates for the user terminal to register as a second or subsequent registration and the priority of each of the multiple PLMNs, and a network registration control step of transmitting a network registration request to a base station of the radio access network of the PLMN as the second or subsequent registration target of the user terminal based on the SPLMN information. One aspect of the present invention is a computer program for causing a computer of a network device in a mobile communications system having a core network connected to multiple radio access networks to execute an SPLMN control step of providing a user terminal with SPLMN (Secondary PLMN) information indicating one or more PLMNs (Public Land Mobile Networks) as candidates for the user terminal to register as a second or subsequent time, and the priority of each of the multiple PLMNs. Effect of the Invention

[0015] According to the present invention, it is possible to obtain an effect that the service area of ​​multipath communication can be expanded. [Brief description of the drawings]

[0016] [Figure 1] 1 is a block diagram showing a configuration example of a mobile communication system according to an embodiment. [Diagram 2] FIG. 1 is a diagram showing a schematic configuration of a user equipment (UE) according to an embodiment. [Diagram 3] FIG. 11 is a diagram illustrating an example of a configuration of a network registration management table according to an embodiment. [Figure 4] A figure showing an example of the configuration of a list of multiple PLMNs having priority information in one embodiment. [Diagram 5] 1 is a diagram showing a schematic configuration of an AM (Access and Mobility) control device according to an embodiment; [Figure 6] FIG. 2 is a sequence diagram showing an overall flow of a network registration method according to an embodiment. [Figure 7] FIG. 2 is a sequence diagram showing an overall flow of a network registration method according to an embodiment. [Figure 8] 1 is a flowchart illustrating an example of a procedure of a network registration control method according to an embodiment. [Figure 9] 1 is a flowchart illustrating an example of a procedure of a network registration control method according to an embodiment. [Figure 10] FIG. 1 is a diagram showing a schematic architecture of a conventional 5G system. [Figure 11] A diagram showing an example of the configuration of a conventional "MA PDU Session." DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a configuration example of a mobile communication system according to an embodiment. In FIG. 1, a UE (user equipment) 10 can be connected to a RAN (radio access network) 30 (30_1, 30_2) which is "3gpp access". The RAN 30_1 is a RAN of a first PLMN. The RAN 30_2 is a RAN of a second PLMN. The first PLMN and the second PLMN may be the same PLMN (i.e., the same communication carrier) or may be different PLMNs (i.e., different communication carriers). The RAN 30 (30_1, 30_2) is connected to a UPF (user plane function) 60 of a CN (core network) of a mobile communication system 1. Hereinafter, the RAN 30_1 and the RAN 30_2 are referred to as RAN 30 when there is no particular distinction between them.

[0018] Although only two RANs 30 (30_1, 30_2) are shown in FIG. 1, the mobile communication system 1 may include three or more RANs 30 (30_1, 30_2, 30_3,...) connected to the UPF 60, and the UE 10 may be connectable to three or more RANs 30 (30_1, 30_2, 30_3,...). In this case, all the RANs 30 (30_1, 30_2, 30_3,...) may or may not be the same PLMN. Furthermore, all the RANs 30 (30_1, 30_2, 30_3,...) are connected to the UPF 60 of the CN of the mobile communication system 1.

[0019] Furthermore, the UE 10 is connectable to a wireless LAN 80 which is a "non-3gpp access". The wireless LAN 80 is connected to a UPF 60 of a CN of the mobile communication system 1. The wireless LAN 80 is an example of a wireless access network which is a "non-3gpp access".

[0020] The UPF 60 is connected to a DN (data network) such as the Internet outside the CN of the mobile communication system 1.

[0021] The UE 10 can establish a session with the UPF 60 using a wireless path via the RAN 30 or the wireless LAN 80, and can transmit and receive data to and from the DN using the established session. The UE 10 can also establish a multi-access session with the UPF 60 using a wireless path via the RAN 30 and a wireless path via the wireless LAN 80, and can transmit and receive data to and from the DN using the established multi-access session.

[0022] In this embodiment, the UE 10 is further intended to be able to establish a multi-access session with the UPF 60 using a plurality of radio paths via each of a plurality of RANs 30. Also, two "3gpp access" (base stations) for establishing the multi-access session are appropriately selected. To this end, the UE 10 is made capable of selecting a next PLMN (a PLMN (second PLMN) that is the same as or different from the first PLMN) after making an initial network registration with a first PLMN, and making a second network registration with the selected second PLMN.

[0023] The AM (Access and Mobility) control device 50 is a network device that realizes one NF (network function) of the control plane (C-plane) of the mobile communication system 1. The AM control device 50 is a network device that realizes an NF corresponding to the AMF of, for example, 5GC (CN of the 5G system). However, in this embodiment, the AM control device 50 is a network device that realizes a new additional NF in addition to the AMF of 5GC.

[0024] The AM control device 50 performs C-plane communication between the UE 10 and the RAN 30.

[0025] 2 is a diagram showing a schematic configuration of a UE according to this embodiment. In FIG. 2, the UE 10 includes a control unit 110, a storage unit 120, a communication unit 130, a display unit 140, and an operation unit 150.

[0026] The control unit 110 is a CPU (Central Processing Unit), and realizes various functions by calling and executing programs stored in the storage unit 120 .

[0027] The control unit 110 includes, as one of its functions, a network registration control unit (NW registration control unit) 1101. The NW registration control unit 1101 is realized by the CPU executing a NW registration control program 1201 stored in the storage unit 120.

[0028] 2 shows only a conventional NW registration control unit 1101 for additional NW registration from UE 10 as a function of the control unit 110. Similarly, as a program stored in the storage unit 120, only a conventional NW registration control program 1201 for additional NW registration from UE 10 is shown.

[0029] The storage unit 120 is configured by a storage medium, for example, a hard disk drive (HDD), a flash memory, an electrically erasable programmable read only memory (EEPROM), a random access read / write memory (RAM), a read only memory (ROM), or any combination of these storage media. The storage unit 120 stores various programs such as a NW registration control program 1201 executed by the control unit 110 (CPU) and various data.

[0030] The communication unit 130 connects to a base station of the RAN 30 and performs wireless communication via the connected base station. The communication unit 130 also connects to an access point of the wireless LAN 80 and performs wireless communication via the connected access point.

[0031] The display unit 140 includes a display element such as a liquid crystal display or an organic EL (Electro Luminescence), and displays the display data output from the control unit 110. The operation unit 150 is composed of an input device such as a numeric keypad, and performs data input according to the user's operation. Alternatively, the UE 10 may be provided with a touch panel capable of both data input and data display.

[0032] The storage unit 120 stores a network registration management table (NW registration management table) 1202. FIG. 3 is a diagram showing a configuration example of the NW registration management table according to the present embodiment. In FIG. 3, the NW registration management table 1202 is a table that stores network registration mode (NW registration mode) information, network registration trigger (NW registration trigger) information, PLMN selection mode information, and SPLMN (Secondary PLMN) information.

[0033] <NW registration mode information> The NW registration mode information is information indicating the NW registration mode. There are the following three NW registration modes according to the present embodiment.

[0034] [Single Registration Mode] Single Registration Mode is a mode in which the UE 10 performs a single network registration on "3gpp access".

[0035] [Dual Registration Mode for mobility] "Dual Registration Mode for mobility" is a mode in which the UE 10 can perform two network registrations on "3gpp access". However, the registration destinations are limited to "5G base station, 5GC" and "4G base station, EPC". "Dual Registration Mode for mobility" is used, for example, for the purpose of ensuring the continuity of communication when the UE 10 leaves the coverage of the 5G system.

[0036] [Dual Registration Mode for multi-path communication] "Dual Registration Mode for multi-path communication" is a mode in which UE 10 can register with two networks on "3gpp access". In "Dual Registration Mode for multi-path communication", the combination of PLMNs to which the UE 10 registers can be selected arbitrarily. However, restrictions may be imposed by business contracts with PLMNs. "Dual Registration Mode for multi-path communication" is used, for example, in communications that simultaneously use two registered networks.

[0037] The NW registration mode information indicates any one of "Single Registration Mode", "Dual Registration Mode for mobility", or "Dual Registration Mode for multi-path communication".

[0038] The NW registration mode indicated by the NW registration mode information stored in the NW registration management table 1202 may be referred to as the NW registration mode of UE 10. Storing the NW registration mode information in the NW registration management table 1202 may be referred to as the NW registration mode of UE 10 being set. Changing the NW registration mode information in the NW registration management table 1202 may be referred to as the NW registration mode of UE 10 being changed. For example, storing the NW registration mode information "Dual Registration Mode for mobility" in the NW registration management table 1202 may be referred to as the NW registration mode of UE 10 becoming "Dual Registration Mode for mobility" or UE 10 becoming "Dual Registration Mode for mobility".

[0039] In addition, "Dual Registration Mode for mobility" and "Dual Registration Mode for multi-path communication" may be collectively referred to as "Dual Registration Mode". Therefore, when UE10 is said to be in "Dual Registration Mode", it means that the NW registration mode of UE10 is "Dual Registration Mode for mobility" or "Dual Registration Mode for multi-path communication".

[0040] Note that in all of "Single Registration Mode", "Dual Registration Mode for mobility", and "Dual Registration Mode for multi-path communication", for example, a session on "3gpp access" can be established while coexisting with a session on "non-3gpp access" such as Wireless LAN80, etc., to configure a multi-access session.

[0041] <NW registration trigger information> The NW registration trigger information is information indicating an NW registration trigger. The NW registration trigger is the timing at which the second network registration is executed when UE10 operates in "Dual Registration Mode". Here, UE10 according to this embodiment performs network registration for the previously connected PLMN (the first PLMN) upon power-on (power ON) or in-flight mode OFF (in-flight mode OFF). Therefore, the NW registration trigger information is information indicating the timing at which UE10 performs network registration for the next (second) PLMN (the second PLMN) in a state where UE10 has already registered with the first PLMN (the first PLMN).

[0042] There are the following two NW registration triggers according to this embodiment.

[0043] [Initial] In the case where the NW registration mode of the UE 10 becomes "Dual Registration Mode" at Initial, the UE 10 immediately executes the second network registration. In addition, when the NW registration mode is already "Dual Registration Mode" when the UE 10 is powered on or the airplane mode is turned off, the second network registration is immediately executed as soon as the network registration for the first PLMN is completed. Also, when the NW registration trigger information is changed to Initial by a user operation or the like and the UE 10 is operating in "Dual Registration Mode", the UE 10 terminal immediately executes the second network registration. When it is not possible to observe the radio waves of all the PLMNs included in the SPLMN information (details will be described later), the UE 10 connects to the base station of the PLMN for which radio waves can be observed as soon as the radio waves can be observed and immediately executes the second network registration.

[0044] [NW triggered] In NW triggered, the UE 10 executes the second network registration triggered by a notification of a registration instruction from the network. In addition, when a notification of a registration instruction from the network is received and it is not possible to observe the radio waves of all the PLMNs included in the SPLMN information, the UE 10 changes the NW registration trigger information to Initial. Then, after the completion of the second network registration, or triggered by the power-off (power OFF) or airplane mode on (airplane mode ON) of the UE 10, the NW registration trigger information is returned to NW triggered.

[0045] The NW registration trigger information indicates either "Initial" or "NW triggered".

[0046] <PLMN selection mode information> The PLMN selection mode information is information indicating the PLMN selection mode. There are the following three PLMN selection modes.

[0047] [Single PLMN Mode] Single PLMN Mode is a mode in which the UE10 is connected to two base stations of a single PLMN. The UE10 performs a second network registration for the base station of the first PLMN to which it is already connected.

[0048] [Dual PLMN Mode] Dual PLMN Mode is a mode in which the UE10 is connected to a total of two base stations, one from each of different PLMNs. The UE10 performs a second network registration for the base station of the second PLMN different from the first PLMN to which it is already connected.

[0049] [Single and Dual PLMN Mode] Single and Dual PLMN Mode is a mode in which the UE10 operates in either Single PLMN Mode or Dual PLMN Mode according to the radio conditions. In Single and Dual PLMN Mode, a priority is set between Single PLMN Mode and Dual PLMN Mode. If the UE10 cannot connect to two base stations in the mode with the higher priority between Single PLMN Mode and Dual PLMN Mode, it operates in the other mode.

[0050] The PLMN selection mode information indicates any one of "Single PLMN Mode", "Dual PLMN Mode", or "Single and Dual PLMN Mode".

[0051] <SPLMN information> The SPLMN information is information provided by the CN of the mobile communication system 1 and indicates PLMNs that are candidates for registration destinations for the second network registration. The SPLMN information may be, for example, information in the form of a list including a plurality of PLMNs. When the SPLMN information includes a plurality of PLMNs, a predetermined priority is set for each PLMN. Alternatively, the SPLMN information may be a list of a plurality of PLMNs having priority information. FIG. 4 is a diagram showing an example of the configuration of a list of a plurality of PLMNs having priority information.

[0052] The NW registration control unit 1101 executes a network registration process based on the NW registration management table 1202. The network registration process causes the UE 10 to be registered in the network.

[0053] The NW registration control unit 1101 changes the "NW registration mode information", "NW registration trigger information", "PLMN selection mode information", and "SPLMN information" when a predetermined change condition is satisfied. For example, the NW registration control unit 1101 changes the "NW registration mode information", "NW registration trigger information", "PLMN selection mode information", and "SPLMN information" in accordance with an input from outside the UE 10, such as a user operation or an information notification from the CN of the mobile communication system 1. For example, the NW registration control unit 1101 changes the "NW registration mode information" when a predetermined application is started. For example, the NW registration control unit 1101 changes the NW registration mode information from "Single Registration Mode" to "Dual Registration Mode" when an application using multipath communication is started.

[0054] Fig. 5 is a diagram showing a schematic configuration of the AM control device according to this embodiment. The AM control device 50 shown in Fig. 5 is a device corresponding to the AMF of 5GC. In this embodiment, the AM control device 50 further includes an SPLMN control unit 501 as an additional part from the AMF of 5GC in addition to the functions of the AMF of 5GC. Note that Fig. 5 shows only the SPLMN control unit 501 added from the AMF of 5GC as a function of the AM control device 50.

[0055] The SPLMN control unit 501 provides SPLMN information to the UE 10. The SPLMN control unit 501 determines appropriate SPLMN information for the UE 10.

[0056] Next, a network registration method according to this embodiment will be described.

[0057] The overall flow of the network registration method according to this embodiment will be described with reference to Figures 6 and 7. Figures 6 and 7 are sequence diagrams showing the overall flow of the network registration method according to this embodiment. Here, a case will be described where UE 10 is in "Dual Registration Mode" when UE 10 is powered on or airplane mode is off.

[0058] [First network registration stage] The first network registration stage will be described with reference to Fig. 6. The first network registration stage is a stage in which the UE 10 performs network registration with the previously connected PLMN (first PLMN) when the UE 10 is powered on or the airplane mode is turned off.

[0059] (Step S11) When the UE 10 is powered on or the airplane mode is turned off, the NW registration control unit 1101 of the UE 10 connects to the base station (BS) 30bs_1 of the first PLMN, which is the "Registered PLMN (previously connected PLMN)", and transmits a network registration request (NW registration request) to the connected base station 30bs_1. At this time, when the UE 10 is in "Dual Registration Mode", the NW registration control unit 1101 includes the NW registration mode information ("Dual Registration Mode for mobility" or "Dual Registration Mode for multi-path communication") of the NW registration management table 1202 in the NW registration request to be transmitted to the base station 30bs_1. Furthermore, the NW registration control unit 1101 may include the PLMN selection mode information of the NW registration management table 1202 in the NW registration request. Also, the NW registration control unit 1101 may transmit the SPLMN information of the NW registration management table 1202 to the base station 30bs_1.

[0060] (Step S12) Based on its own forwarding setting, the base station 30bs_1 forwards the NW registration request received from the UE 10 to the AM control device 50. Here, the NW registration request includes NW registration mode information.

[0061] (Step S13) The AM control device 50 performs network registration of the UE 10 in the first PLMN based on the NW registration request (including NW registration mode information) received from the base station 30bs_1.

[0062] (Step S14) The SPLMN control unit 501 of the AM control device 50 determines the SPLMN information to be provided to the UE 10 based on the NW registration mode information ("Dual Registration Mode for mobility" or "Dual Registration Mode for multi-path communication") included in the NW registration request received from the base station 30bs_1. The SPLMN information determination methods (A-1) and (A-2) are described below.

[0063] (A-1) When the NW registration mode information included in the NW registration request is “Dual Registration Mode for multi-path communication”. When the PLMN selection mode information included in the NW registration request is “Single PLMN Mode”, the SPLMN control unit 501 determines that there is no SPLMN information to be provided to the UE 10. When the PLMN selection mode information included in the NW registration request is not "Single PLMN Mode" (i.e., when it is "Dual PLMN Mode" or "Single and Dual PLMN Mode"), the SPLMN control unit 501 selects a PLMN appropriate for the UE 10, and sets the selected PLMN as the SPLMN information to be provided to the UE 10. One example of a method for selecting a PLMN appropriate for the UE 10 is to check the subscriber information and operator-specific setting information of the UE 10, and select a PLMN that can configure a multi-access session with the PLMN from which the UE 10 has sent the NW registration request, based on the checked information (e.g., business contract constraints, etc.). When the PLMN selection mode information is not included in the NW registration request, the SPLMN control unit 501 performs a predetermined determination. For example, when the PLMN selection mode information is not included in the NW registration request, the SPLMN control unit 501 may perform the same determination as when the PLMN selection mode information included in the NW registration request is not "Single PLMN Mode".

[0064] (A-2) When the NW registration mode information included in the NW registration request is “Dual Registration Mode for mobility”. When the base station through which the NW registration request is sent from UE10 is a 4G base station, the PLMN of the 5G system is set in the SPLMN information to be provided to UE10. When the base station through which the NW registration request is sent from UE10 is a 5G base station, the PLMN of the 4G system is set in the SPLMN information to be provided to UE10.

[0065] Note that the SPLMN control unit 501 does not have to judge the SPLMN information as described above when a predetermined judgment omission condition is satisfied, instead of making the judgment on the SPLMN information every time a NW registration request in the Dual Registration mode is received from the UE 10. One example of the judgment omission condition is to record the update date and time of the SPLMN information for each UE 10, and not judge the SPLMN information if the time elapsed since the update date and time of the SPLMN information is within a period set by the operator (e.g., 24 hours).

[0066] The SPLMN control unit 501 stores the SPLMN information to be provided to the UE 10 in the AM control device 50. The SPLMN control unit 501 may associate the terminal identifier and the serving area identifier of the UE 10 with the SPLMN information to be provided to the UE 10.

[0067] In addition, if the PLMN selection mode information is "Single PLMN Mode" or there is no PLMN to be set in the SPLMN information, the SPLMN control unit 501 records information indicating that there is no SPLMN information to be provided to the UE 10 in the AM control device 50.

[0068] (Step S15) The AM control device 50 transmits a response to the NW registration request to the base station 30bs_1. The AM control device 50 includes in the response the SPLMN information to be provided to the UE 10. However, if there is no SPLMN information to be provided to the UE 10, the response does not include the SPLMN information.

[0069] In addition, the AM control device 50 records the SPLMN information that has been provided to UE 10 in the past, and does not need to send SPLMN information to UE 10 to which it has already been provided, and further does not need to judge the SPLMN information in step S14.

[0070] (Step S16) The base station 30bs_1 transfers the response to the NW registration request received from the AM control device 50 to the UE 10.

[0071] (Step S17) When the SPLMN information is included in the response to the NW registration request received from the base station 30bs_1, the UE 10 stores the SPLMN information in the NW registration management table 1202.

[0072] [Second network registration stage] The second network registration stage will be described with reference to Fig. 7. The second network registration stage is a stage in which the UE 10, which has already been network registered with a first PLMN (first PLMN), performs network registration with a next (second) PLMN (second PLMN).

[0073] (Step S30) NW registration control unit 1101 of UE 10 attempts to connect to the second PLMN. Methods (B-1) and (B-2) of attempting to connect to the second PLMN will be described below.

[0074] (B-1) The NW registration mode of UE 10 is "Dual Registration Mode" and the NW registration trigger is "Initial". The NW registration control unit 1101 attempts to connect to a base station of each PLMN in order of priority from the PLMN with the highest priority among the PLMNs included in the SPLMN information of the NW registration management table 1202. Specifically, the NW registration control unit 1101 first determines whether radio waves of the highest priority PLMN_A can be observed. As a result, if radio waves of the highest priority PLMN_A can be observed, the NW registration control unit 1101 connects the UE 10 to the base station of the highest priority PLMN_A. On the other hand, if radio waves of the highest priority PLMN_A cannot be observed, the NW registration control unit 1101 determines whether radio waves of the next highest priority PLMN_B can be observed, and if they can be observed, connects the UE 10 to the base station of PLMN_B, while if they cannot be observed, determines whether radio waves of the next highest priority PLMN_C can be observed. This procedure is repeated any number of times until the UE 10 connects to a base station of any PLMN included in the SPLMN information. When the UE 10 connects to a base station of any PLMN included in the SPLMN information, the procedure proceeds to step S31.

[0075] (B-2) The NW registration mode of UE 10 is “Dual Registration Mode” and the NW registration trigger is “NW triggered”. When the NW registration control unit 1101 receives a notification of a registration instruction from the network, it attempts to connect to a base station of a PLMN included in the SPLMN information in the same procedure as (B-1) above. An example of a registration instruction from the network is when the UE 10 executes a session establishment process on the network of the first PLMN where the UE 10 first registered, and the CN (e.g., the AM control device) includes the registration instruction in the information that responds to the UE 10. If the UE 10 fails to connect to the base stations of all the PLMNs included in the SPLMN information, the NW registration control unit 1101 changes the NW registration trigger information in the NW registration management table 1202 to "Initial". Thereby, the NW registration control unit 1101 repeats the procedure of (B-1) above any number of times until the UE 10 connects to a base station of any PLMN included in the SPLMN information. When the UE 10 connects to a base station of any PLMN included in the SPLMN information, the process proceeds to step S31.

[0076] The base station of the PLMN to which the UE 10 connects in step S30 is the base station 30bs_2 of the second PLMN.

[0077] (Step S31) The NW registration control unit 1101 transmits a NW registration request to the base station 30bs_2 of the second PLMN connected in step S30. In the network registration to this second PLMN (second PLMN), even if the NW registration mode of the UE 10 is "Dual Registration Mode", the NW registration request does not include NW registration mode information.

[0078] (Step S32) Based on its own forwarding setting, the base station 30bs_2 forwards the NW registration request received from the UE 10 to the AM control device 50. This NW registration request does not include NW registration mode information.

[0079] (Step S33) The AM control device 50 performs network registration of the UE 10 in the second PLMN based on the NW registration request (without NW registration mode information) received from the base station 30bs_2. Here, since the NW registration request received from the base station 30bs_2 does not include NW registration mode information, the AM control device 50 does not execute the determination of the SPLMN information (step S14 in FIG. 6).

[0080] (Step S34) The AM control device 50 transmits a response to the NW registration request to the base station 30bs_1. The response does not include the SPLMN information to be provided to the UE 10.

[0081] (Step S35) The base station 30bs_1 transfers the response to the NW registration request received from the AM control device 50 to the UE 10.

[0082] Next, a NW registration control operation of the UE 10 according to this embodiment will be described with reference to Fig. 8 and Fig. 9. Fig. 8 and Fig. 9 are flowcharts showing an example of the procedure of a NW registration control method according to this embodiment.

[0083] The UE 10 starts the NW registration control process in FIG. 8 and FIG. 9 when the UE 10 is powered on or the airplane mode is turned off.

[0084] (Step S101) UE 10 determines its own NW registration mode. As a result, if it is "Dual Registration Mode", the process proceeds to step S102, and if it is Single Registration Mode, the process proceeds to step S121 in FIG.

[0085] (Step S102) The UE 10 connects to the base station 30bs_1 of the first PLMN, which is a "Registered PLMN", and transmits a NW registration request to the connected base station 30bs_1. This NW registration request includes the NW registration mode information ("Dual Registration Mode for mobility" or "Dual Registration Mode for multi-path communication") of the NW registration management table 1202. Furthermore, the PLMN selection mode information of the NW registration management table 1202 may be included in the NW registration request.

[0086] (Step S103) UE 10 receives a response to the NW registration request, and determines whether the received response includes SPLMN information. If the response includes SPLMN information (step S103, YES), the process proceeds to step S104. On the other hand, if the response does not include SPLMN information (step S103, NO), the process proceeds to step S105.

[0087] (Step S104) UE 10 stores in NW registration management table 1202 the SPLMN information included in the response to the NW registration request.

[0088] (Step S105) UE 10 determines its own NW registration trigger. If the result is Initial, the process proceeds to step S106, and if the result is NW triggered, the process proceeds to step S107.

[0089] (Step S106) Based on the SPLMN information in the NW registration management table 1202, the UE 10 attempts to connect to a base station of the PLMN (second PLMN candidate) included in the SPLMN information. This attempt method is the above-mentioned (B-1). The UE 10 transmits a NW registration request without NW registration mode information to the connected base station 30bs_2. After this, the processing of Figs. 8 and 9 is terminated.

[0090] (Step S107) UE 10 determines whether or not there is a registration instruction from the network. As a result, if there is a registration instruction from the network, the process proceeds to step S108. On the other hand, if there is no registration instruction from the network, the process returns to step S107 and waits for a registration instruction from the network.

[0091] (Step S108) UE 10 attempts to connect to a base station of a PLMN (second PLMN candidate) included in the SPLMN information, based on the SPLMN information in the NW registration management table 1202. This attempt method is the above-mentioned (B-2).

[0092] (Step S109) UE 10 determines whether or not connection to the second PLMN candidate base station has been successful. As a result, if connection has been successful, the process proceeds to step S110, and if connection has not been successful, the process proceeds to step S111.

[0093] (Step S110) The UE 10 transmits a NW registration request without NW registration mode information to the connected base station 30bs_2 of the second PLMN. After that, the process of Figs. 8 and 9 is terminated.

[0094] (Step S111) UE 10 changes the NW registration trigger information in NW registration management table 1202 to "Initial." After that, the processing in Figs. 8 and 9 ends.

[0095] (Step S121, FIG. 9) The UE 10 connects to the base station 30bs_1 of the first PLMN, which is a "Registered PLMN", and transmits a NW registration request without NW registration mode information to the connected base station 30bs_1.

[0096] (Step S122) UE 10 determines whether or not a predetermined change condition related to the NW registration mode is satisfied. One example of the change condition is when an application using multipath communication is started. Another example of the change condition is when the NW registration mode is changed to "Dual Registration Mode" by a user operation. If the change condition is satisfied (step S122, YES), the process proceeds to step S123, and if not, the process remains at step S122.

[0097] (Step S123) UE 10 changes the NW registration mode information in NW registration management table 1202 to "Dual Registration Mode". If an application using multi-path communication is started, the NW registration mode information is changed to "Dual Registration Mode for multi-path communication". If the NW registration mode setting is changed by a user operation, the NW registration mode information is changed to "Dual Registration Mode for mobility" or "Dual Registration Mode for multi-path communication" according to the specification by the user operation.

[0098] (Step S124) The UE 10 transmits a NW registration update request to the base station 30bs_1 of the first PLMN that has already been registered in the network. This NW registration update request corresponds to the NW registration request in step S102. Therefore, the NW registration update request includes the NW registration mode information ("Dual Registration Mode for mobility" or "Dual Registration Mode for multi-path communication") in the NW registration management table 1202, similar to the NW registration request in step S102. Furthermore, the NW registration update request may include the PLMN selection mode information in the NW registration management table 1202. After this, the process proceeds to step S103 in FIG. 8.

[0099] The NW registration update request is transferred to the AM control device 50 via the base station 30bs_1 of the first PLMN, similarly to steps S11-S12 in the first network registration stage in Fig. 6 described above. After that, the same processing as steps S13-S17 in the first network registration stage in Fig. 6 described above is executed. That is, processing is executed in which the "NW registration request" is replaced with a "NW registration update request" in the above-mentioned steps S13-S17.

[0100] In the 5G system, network registration requests and network registration update requests are carried out through a procedure called "Registration."

[0101] According to the above-described embodiment, the UE 10 can perform the first network registration to the first PLMN, and then select a next PLMN (a PLMN (second PLMN) that is the same as or different from the first PLMN) and perform the second network registration to the selected second PLMN. This allows the UE 10 to establish a multi-access session with the UPF 60 using multiple wireless paths via each of the multiple RANs 30. In addition, it becomes possible to appropriately select two "3gpp access" (base stations) for establishing the multi-access session.

[0102] According to the above-described embodiment, the freedom of selection of two "3gpp access" (base stations) for establishing a multi-access session is increased, thereby achieving the effect of expanding the service area of ​​multi-path communication.

[0103] In the above embodiment, the UE 10 transmits a network registration request to a base station of the RAN 30 of the second PLMN based on the SPLMN information, but the present invention is not limited to this. The UE 10 may transmit a network registration request to a base station of the RAN 30 of the third or subsequent PLMN based on the SPLMN information. Therefore, the SPLMN information may be information indicating one or more PLMNs that are candidates for the UE 10 to be registered as the second or subsequent PLMNs and the priority of each of the multiple PLMNs. The NW registration control unit 1101 may transmit a network registration request to a base station of the RAN 30 of the second or subsequent PLMN based on the SPLMN information.

[0104] Furthermore, the above-described embodiments are applicable to mobile communication systems such as 5G systems, B5G systems, and 6G systems.

[0105] This will, for example, make it possible to improve the overall service quality of mobile communications systems, thereby contributing to Goal 9 of the United Nations' Sustainable Development Goals (SDGs), which is to "build resilient infrastructure, promote sustainable industrialization and foster innovation."

[0106] Although an embodiment of the present invention has been described in detail above with reference to the drawings, the specific configuration is not limited to this embodiment, and design changes and the like that do not deviate from the gist of the present invention are also included.

[0107] Also, a computer program for implementing the functions of each of the above-mentioned devices may be recorded on a computer-readable recording medium, and the program recorded on the recording medium may be read into a computer system and executed. Note that the "computer system" referred to here may include hardware such as an OS and peripheral devices. Also, the "computer-readable recording medium" refers to a flexible disk, a magneto-optical disk, a ROM, a writable non-volatile memory such as a flash memory, a portable medium such as a DVD (Digital Versatile Disc), and a storage device such as a hard disk built into a computer system.

[0108] Furthermore, the term "computer-readable recording medium" includes a memory that holds a program for a certain period of time, such as a volatile memory (e.g., DRAM (Dynamic Random Access Memory)) inside a computer system that becomes a server or a client when a program is transmitted via a network such as the Internet or a communication line such as a telephone line. The above-mentioned program may be transmitted from a computer system that stores the program in a storage device or the like to another computer system via a transmission medium, or by a transmission wave in the transmission medium. Here, the "transmission medium" that transmits the program refers to a medium that has a function of transmitting information, such as a network (communication network) such as the Internet or a communication line (communication line) such as a telephone line. The above-mentioned program may be a program for realizing part of the above-mentioned functions. Furthermore, the above-mentioned function may be realized in combination with a program already recorded in the computer system, that is, a so-called difference file (difference program). [Explanation of symbols]

[0109] 1...mobile communication system, 10...UE, 30...RAN, 50...AM control device, 60...UPF, 70...DN, 80...wireless LAN, 110...control unit, 120...storage unit, 130...communication unit, 140...display unit, 150...operation unit, 1101...network registration control unit, 1201...network registration control program, 1202...network registration management table, 501...SPLMN control unit

Claims

1. A mobile communication system comprising a core network connected to a plurality of radio access networks, The user terminal is an SPLMN information storage unit that stores SPLMN (Secondary PLMN) information indicating one or more PLMNs (Public Land Mobile Networks) that are candidates for second or subsequent registration of the user terminal and a priority of each of the plurality of PLMNs; a network registration control unit that transmits a network registration request to a base station of the radio access network of a second or subsequent registration destination PLMN of the user terminal based on the SPLMN information, the core network comprises a network device that provides the SPLMN information to the user terminal; Mobile communication system.

2. The user terminal, a network registration mode information storage unit that stores network registration mode information indicating a "Single Registration Mode" in which the user terminal performs a single network registration on "3gpp access" or a "Dual Registration Mode" in which the user terminal can perform two network registrations on "3gpp access"; a network registration trigger information storage unit configured to store network registration trigger information indicating a timing for performing a second or subsequent network registration when the user terminal operates in "Dual Registration Mode"; and a PLMN selection mode information storage unit that stores PLMN selection mode information for determining whether the user terminal operates in a "Single PLMN Mode" in which the user terminal connects to two base stations of a single PLMN, or in a "Dual PLMN Mode" in which the user terminal connects to a total of two base stations, one in each of different PLMNs; The network registration control unit controls execution of the network registration request based on the network registration mode information, the network registration trigger information, and the PLMN selection mode information. The mobile communication system according to claim 1.

3. The "Dual Registration Mode" includes "Dual Registration Mode for multi-path communication" in which a combination of PLMNs to be registered can be arbitrarily selected. The mobile communication system according to claim 2.

4. the network device provides the SPLMN information to the user terminal when the network registration request includes information indicating the "Dual Registration Mode." The mobile communication system according to claim 2.

5. the network registration control unit changes the network registration mode information, the network registration trigger information, the PLMN selection mode information, or the SPLMN information when a predetermined change condition is satisfied. The mobile communication system according to claim 2.

6. A user terminal of a mobile communication system including a core network connected to a plurality of radio access networks, an SPLMN information storage unit that stores SPLMN (Secondary PLMN) information indicating one or more PLMNs (Public Land Mobile Networks) that are candidates for second or subsequent registration of the user terminal and a priority of each of the plurality of PLMNs; a network registration control unit that transmits a network registration request to a base station of the radio access network of a second or subsequent registration destination PLMN of the user terminal based on the SPLMN information; A user terminal comprising:

7. A network device provided in a core network in a mobile communication system including a core network connected to a plurality of radio access networks, comprising: an SPLMN control unit that provides a user terminal with SPLMN (Secondary PLMN) information indicating one or more PLMNs (Public Land Mobile Networks) that are candidates for the second or subsequent registration of the user terminal and a priority of each of the multiple PLMNs; A network device comprising:

8. A network registration method in a mobile communication system having a core network connected to a plurality of radio access networks, comprising: an SPLMN control step in which a network device in the core network provides, to a user terminal, SPLMN (Secondary PLMN) information indicating one or more PLMNs (Public Land Mobile Networks) as candidates for the second or subsequent registration of the user terminal and a priority of each of the multiple PLMNs; an SPLMN information storage step of the user terminal storing the SPLMN information in an SPLMN information storage unit; a network registration control step of transmitting a network registration request to a base station of the radio access network of a PLMN in which the user terminal is to be registered as a second or subsequent registration destination, based on the SPLMN information; A network registration method including:

9. A computer of a user terminal of a mobile communication system having a core network connected to a plurality of radio access networks, an SPLMN information storage step of storing, in an SPLMN information storage unit, SPLMN (Secondary PLMN) information indicating one or more PLMNs (Public Land Mobile Networks) as candidates for second or subsequent registration of the user terminal and priorities of each of the plurality of PLMNs; a network registration control step of transmitting a network registration request to a base station of the radio access network of a second or subsequent registration destination PLMN of the user terminal based on the SPLMN information; A computer program for executing the above.

10. In a mobile communication system having a core network connected to a plurality of radio access networks, a computer of a network device provided in the core network, a SPLMN control step of providing, to a user terminal, secondary PLMN (SPLMN) information indicating one or more PLMNs (Public Land Mobile Networks) as candidates for second or subsequent registration of the user terminal and a priority of each of the plurality of PLMNs; A computer program for executing the above.

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