Network device, user terminal, communication method, and computer program

Abstract

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. The network device includes: a measurement information acquisition unit for acquiring measurement information indicating the communication quality of each of the plurality of radio access networks; and a multi-access session configuration determination unit for determining, from among the plurality of radio access networks, a radio access network to be used for a multi-access session established between a user terminal and the core network on the basis of the measurement information.

Description

Network device, user terminal, communication method and computer program

[0001] The present invention relates to a network device, a user terminal, a communication method, and a computer program.This application claims priority to Japanese Patent Application No. 2023-183153, filed on October 25, 2023, the contents of which are incorporated herein by reference.

[0002] Conventionally, a fifth-generation mobile communication system (5G system) standardized by "3GPP (registered trademark) (3rd Generation Partnership Project)" has been known (see, for example, Non-Patent Documents 1 and 2). FIG. 9 is a diagram showing a schematic architecture of a 5G system. In FIG. 9, the 5G system is composed of a UE (User Equipment, user terminal), a RAN (Radio Access Network), a UPF (User Plane Function) of a CN (Core Network), and various NFs (Network Functions) of the CN control plane (C-plane). Examples of NFs of the CN C-plane include an AMF (Access and Mobility Management Function), an SMF (Session Management Function), and a UDM (Unified Data Management).

[0003] Here, a logical communication path established between a UE and a CN (UPF) to use a mobile communication service is referred to as a "session." A session established between a UE and a CN (UPF) using multiple wireless paths is referred to as 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. Figure 10 is a diagram showing an example configuration of an "MA PDU Session." As shown in Figure 10, a UE establishes an "MA PDU Session" with a CN (UPF) using a "3GPP access" wireless path via a RAN and a "non-3GPP access" wireless path via a wireless LAN (Local Area Network) such as Wi-Fi (registered trademark). "3GPP access" refers to an access network specified by 3GPP. "Non-3GPP access" refers to an access network other than "3GPP access." The UE uses the "MA PDU Session" to send and receive data between 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 improve communication quality by expanding the communication bandwidth, reducing communication delays, and ensuring redundancy in the communication path.

[0004] Furthermore, Non-Patent Documents 1 and 2 specify a steering mode as a policy indicating how traffic related to a UE is transmitted when a "MA PDU Session" is established. The steering mode is notified from the CN to the UE when a "MA PDU Session" is established. The steering modes (1) to (5) specified in Non-Patent Documents 1 and 2 are shown below.

[0005] (1) "Active-Standby" In "Active-Standby," traffic is basically transmitted to the "Active" access network, and when the "Active" access network becomes unavailable, it switches to the "Standby" access network. After that, when the "Active" access network becomes available again, it switches back to the "Active" access network.

[0006] (2) "Smallest Delay" "Smallest Delay" transmits traffic to the access network with the smallest RTT (Round Trip Time). The UE and UPF can measure the RTT of "3GPP access" and "non-3GPP access". If one access network becomes unavailable, all traffic is transmitted through the other available access network. "Smallest Delay" is only applicable to "non-GBR SDF".

[0007] (3) "Load-Balancing" "Load-Balancing" is a mode used when distributing traffic across two sessions. Percentage information is set to indicate the percentage of transmission for each session. If one access network becomes unavailable, the other access network operates as if its percentage was set to 100%. "Load-Balancing" is only applicable to "non-GBR" traffic.

[0008] (4) "Priority-based" "Priority-based" is a mode used when distributing traffic between two sessions. All traffic is transmitted over the access network with the higher priority until the access network with the higher priority is determined to be "congested." In the event of congestion, traffic is also transmitted over the access network with the lower priority. The determination of congestion depends on the UE and the implementation of the UPF. If one access network becomes unavailable, all traffic is transmitted over the other access network. "Priority-based" is only applicable to "non-GBR" traffic.

[0009] (5) "Redundant" When both access networks are available, traffic is transmitted redundantly through both access networks. "Primary access" information may be provided to the UE and UPF by the "ATSSS rule" and "N4 rule." "Primary access" may be "3GPP access" or "non-3GPP access." When "Primary access" information is provided, the UE and UPF transmit all traffic through "Primary access" and transmit redundant traffic through other access networks. In redundancy, how much data the UE and UPF duplicate depends on the implementation. When "Primary Access" information is not provided, the UE and UPF always duplicate all data and transmit it through both access networks.

[0010] 11 shows a configuration example of DC (Dual Connectivity). DC is a technology that realizes broadband by simultaneously using two sets (master and secondary) of RUs (Radio Units) and DUs (Distributed Units) in the UE to transmit user plane data between the UE and the UPF via a CU (Central Unit) (see, for example, Non-Patent Document 3).

[0011] 3GPP, TS 23.501, V18.2.0, 2023-063GPP, TS 23.502, V18.2.0, 2023-063GPP, TS 36.300, V17.0.0, 2022-03

[0012] In the next generation 5G (Beyond 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) of communication for each 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 communication and ultra-low latency is limited.

[0013] Therefore, if a multi-access session can be established as shown in Figure 12 using two arbitrarily selected "3GPP access" 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.

[0014] In the conventional multi-access session establishment procedure, the SMF identifies the access networks available for the multi-access session by checking the network registration information indicating the access networks to which the UE is registered, and then performs the session establishment process based on the identification result. However, when the UE is registered with two "3GPP access"s and one "non-3GPP access", there is a problem that it is not possible to determine an appropriate multi-access session configuration.

[0015] In addition, since the conventional DC is implemented by closed control in the RAN domain, it is implemented regardless of the configuration of the multi-access session established between the UE and the CN (UPF). This causes the following problems.

[0016] FIG. 13 shows an example of the configuration of a multi-access session. The multi-access session shown in FIG. 13 is composed of a first session SesA and a second session SesB. The first session SesA transmits data between the UE and the UPF via the DC using a first wireless path dcA_1 "RU1-DU1-CU1" and a second wireless path dcA_2 "RU2-DU2-CU2-CU1." The second session SesB uses only one wireless path "RU2-DU2-CU2."

[0017] In the configuration of the multi-access session in Fig. 13, if DC is used when the multi-access session is used in the steering mode "Redundant", it may happen that both the original data and the duplicated data are transmitted over the wireless path "RU2-DU2-CU2". If both the original data and the duplicated data are transmitted over the wireless path "RU2-DU2-CU2", the purpose of the steering mode "Redundant", traffic redundancy, is not fully achieved.

[0018] Furthermore, in the configuration of the multi-access session in Figure 13, if DC is used when the multi-access session is used in the steering mode "Load-Balancing", there is a possibility that traffic will not be distributed to each session SesA, SesB in the desired proportions.

[0019] As mentioned above, there are various problems associated with conventional multi-access sessions.

[0020] The present invention has been made in consideration of the above circumstances, and an object of the present invention is to appropriately configure a multi-access session.

[0021] One aspect of the present invention is a network device provided in a core network in a mobile communication system having a core network connected to multiple radio access networks, the network device comprising: a measurement information acquisition unit that acquires measurement information indicating the communication quality of each of the multiple radio access networks; and a multi-access session configuration determination unit that determines, based on the measurement information, a radio access network from the multiple radio access networks to be used for a multi-access session established by a user terminal with the core network.

[0022] One aspect of the present invention is a network device provided in a core network in a mobile communication system having a core network connected to multiple radio access networks, the network device comprising: a multi-access session priority information storage unit that stores multi-access session priority information indicating the priority of a radio access network to be used for a multi-access session established by a user terminal with the core network; and a multi-access session configuration determination unit that determines a radio access network to be used for the multi-access session from among the multiple radio access networks based on the multi-access session priority information.

[0023] In one aspect of the present invention, the network device further comprises a multi-access session configuration identification unit that identifies a configuration of a multi-access session to be established between the user terminal and the core network based on multi-access session configuration capability information indicating which combination of radio access networks among the plurality of radio access networks the user terminal is capable of establishing a multi-access session with and NW registration information indicating a radio access network among the plurality of radio access networks in which the user terminal is registered, and the multi-access session configuration determination unit determines a radio access network corresponding to the identification result of the multi-access session configuration.In another aspect of the present invention, the network device further comprises a multi-access session configuration determination unit that, when the NW registration information indicates that the user terminal is registered in two or more radio access networks, executes a session establishment process to establish a session using a second or subsequent radio access network to be used for the multi-access session.

[0024] One aspect of the present invention is a user terminal of a mobile communication system having a core network connected to multiple radio access networks, the user terminal comprising: a multi-access session configuration capability information storage unit that stores multi-access session configuration capability information indicating which combination of radio access networks among the multiple radio access networks the user terminal has the capability to establish a multi-access session with; and a multi-access session control unit that notifies the core network of the multi-access session configuration capability information.

[0025] One aspect of the present invention is a user terminal of a mobile communication system having a core network connected to multiple radio access networks, the user terminal comprising: a multi-access session priority information storage unit that stores multi-access session priority information indicating the priority of the radio access network to be used for a multi-access session established by the user terminal with the core network; and a multi-access session control unit that notifies the core network of the multi-access session priority information.

[0026] One aspect of the present invention is a network device provided in a core network in a mobile communication system having a core network connected to multiple radio access networks, the network device comprising: a multi-access session priority information management unit that manages multi-access session priority information indicating the priority of a radio access network to be used for a multi-access session established by a user terminal with the core network, and provides the multi-access session priority information to a network device that has a multi-access session configuration determination unit that determines a radio access network to be used for the multi-access session from among the multiple radio access networks based on the multi-access session priority information.

[0027] One aspect of the present invention is a communication method executed by a network device provided in a core network in a mobile communication system having the core network connected to multiple radio access networks, the communication method including: a measurement information acquisition step of acquiring measurement information indicating the communication quality of each of the multiple radio access networks; and a multi-access session configuration determination step of determining, based on the measurement information, a radio access network from the multiple radio access networks to be used for a multi-access session established by a user terminal with the core network.

[0028] One aspect of the present invention is a communication method executed by a network device provided in a core network in a mobile communication system having the core network connected to multiple radio access networks, the communication method including: a multi-access session priority information storage step of storing multi-access session priority information indicating the priority of the radio access network to be used for a multi-access session established by a user terminal with the core network in a multi-access session priority information storage unit; and a multi-access session configuration determination step of determining a radio access network to be used for the multi-access session from among the multiple radio access networks based on the multi-access session priority information.

[0029] One aspect of the present invention is a computer program for causing a computer of a network device provided in a mobile communication system having a core network connected to multiple radio access networks to execute a measurement information acquisition step of acquiring measurement information indicating the communication quality of each of the multiple radio access networks, and a multi-access session configuration determination step of determining, based on the measurement information, a radio access network from the multiple radio access networks to be used for a multi-access session established by a user terminal with the core network.

[0030] One aspect of the present invention is a computer program for causing a computer of a network device provided in a core network in a mobile communication system connected to a plurality of radio access networks to execute a multi-access session priority information storage step of storing multi-access session priority information indicating the priority of a radio access network to be used for a multi-access session established by a user terminal with the core network in a multi-access session priority information storage unit, and a multi-access session configuration determination step of determining a radio access network to be used for the multi-access session from among the plurality of radio access networks based on the multi-access session priority information.

[0031] One aspect of the present invention is a computer program for causing a computer of a user terminal of a mobile communication system having a core network connected to multiple radio access networks to execute a multi-access session configuration capability information storage step of storing multi-access session configuration capability information in a multi-access session configuration capability information storage unit, the multi-access session configuration capability information indicating which combination of radio access networks the user terminal has the capability to establish a multi-access session with, and a multi-access session control step of notifying the core network of the multi-access session configuration capability information.

[0032] One aspect of the present invention is a computer program for causing a computer of a user terminal of a mobile communication system having a core network connected to multiple radio access networks to execute a multi-access session priority information storage step of storing multi-access session priority information indicating the priority of a radio access network to be used for a multi-access session established by the user terminal with the core network in a multi-access session priority information storage unit, and a multi-access session control step of notifying the core network of the multi-access session priority information.

[0033] One aspect of the present invention is a computer program for causing a computer of a network device provided in the core network in a mobile communication system having a core network connected to multiple radio access networks to execute a multi-access session priority information management step of managing multi-access session priority information indicating the priority of a radio access network to be used for a multi-access session established by a user terminal with the core network, and providing the multi-access session priority information to a network device having a multi-access session configuration determination unit that determines a radio access network to be used for the multi-access session from among the multiple radio access networks based on the multi-access session priority information.

[0034] According to the present invention, it is possible to obtain an effect that a multi-access session can be appropriately configured.

[0035] 1 is a block diagram showing an example of the configuration of a mobile communication system according to an embodiment. FIG. 2 is a diagram showing a schematic configuration of a user terminal (UE) according to an embodiment. FIG. 3 is a diagram showing an example of the configuration of a multi-access session information management table according to an embodiment. FIG. 4 is a diagram showing a schematic configuration of a session control device according to an embodiment. FIG. 5 is a diagram showing a schematic configuration of a subscriber information management device according to an embodiment. FIG. 6 is a diagram showing a schematic configuration of a base station device according to an embodiment. FIG. 7 is a sequence diagram showing the overall flow of a communication method according to an embodiment. FIG. 8 is a diagram showing an example of a multi-access session configuration identification method according to an embodiment. FIG. 9 is a diagram showing a schematic architecture of a conventional 5G system. FIG. 10 is a diagram showing an example of the configuration of a "MA PDU Session". FIG. 11 is a diagram showing an example of the configuration of DC (Dual Connectivity). FIG. 12 is a diagram showing an example of the configuration of a multi-access session.

[0036] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing an example of the configuration of a mobile communication system according to one embodiment. In FIG. 1, a UE (user terminal) 10 can be connected to a RAN (radio access network) 30 (30_1, 30_2) that is "3gpp access." Examples of the RAN 30 include a base station (4G base station) of a fourth-generation mobile communication system (4G system) and a base station (5G base station) of a 5G system.

[0037] 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 different PLMNs (i.e., different communication carriers). The RANs 30 (30_1, 30_2) are connected to a UPF (User Plane Function) 60 of a CN (Core Network) of the mobile communication system 1.

[0038] Hereinafter, when there is no need to distinguish between RAN 30_1 and RAN 30_2, they will be referred to as RAN 30. Furthermore, the CN of the mobile communication system 1 may be simply referred to as CN. Furthermore, the UPF 60 of the CN of the mobile communication system 1 may be simply referred to as UPF 60.

[0039] 1 shows only two RANs 30 (30_1, 30_2), 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 of the RANs 30 (30_1, 30_2, 30_3, ...) may or may not be the same PLMN. Furthermore, all of the RANs 30 (30_1, 30_2, 30_3, ...) are connected to the UPF 60.

[0040] The UE 10 can also connect to a wireless LAN 80 that is "non-3GPP access." The wireless LAN 80 is connected to the UPF 60. The wireless LAN 80 is an example of a wireless access network that is "non-3GPP access."

[0041] The UPF 60 is connected to a DN (data network) outside the CN, such as the Internet.

[0042] 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. In addition, the UE 10 can 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.

[0043] In this embodiment, the UE 10 is further intended to be able to establish a multi-access session with the UPF 60 using multiple wireless paths via multiple RANs 30. Two "3GPP accesses" for establishing the multi-access session can be appropriately selected. Furthermore, when the UE 10 is registered with two "3GPP accesses" and one "non-3GPP access," an appropriate multi-access session configuration can be determined.

[0044] In addition, in this embodiment, the UE 10 can use DC (Dual Connectivity). Therefore, there is a possibility that the multi-access session will not be effectively used due to DC. Therefore, in this embodiment, it is intended to effectively use the multi-access session.

[0045] 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 a 5G system). The AM control device 50 performs C-plane communication between the UE 10 and the RAN 30. In addition, the AM control device 50 performs communication on the C-plane of the CN with the session control device 51.

[0046] The session control device 51 is a network device that realizes one NF of the C-plane of the mobile communication system 1. The session control device 51 is a network device that realizes an NF corresponding to the SMF of 5GC (CN of the 5G system), for example. However, in this embodiment, the session control device 51 is a network device that realizes a new additional NF in addition to the SMF of 5GC.

[0047] The session control device 51 performs communication on the C-plane with the UPF 60. The session control device 51 also performs communication on the C-plane of the CN with the subscriber information management device 52.

[0048] 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.

[0049] The control unit 110 is a CPU (Central Processing Unit) that calls and executes programs stored in the storage unit 120 to realize various functions.

[0050] The control unit 110 includes, as one of its functions, a multi-access session control unit 1111. The multi-access session control unit 1111 is realized by the CPU executing a multi-access session control program 1210 stored in the storage unit 120.

[0051] 2 shows only a multi-access session control unit 1111 added from the conventional UE 10 as a function of the control unit 110. Similarly, only a multi-access session control program 1210 added from the conventional UE 10 as a program stored in the storage unit 120.

[0052] The storage unit 120 is configured by a storage medium, such as a hard disk drive (HDD), flash memory, electrically erasable programmable read-only memory (EEPROM), random access read / write memory (RAM), read-only memory (ROM), or any combination of these storage media. The storage unit 120 stores various programs, such as a multi-access session control program 1210 executed by the control unit 110 (CPU), and various data.

[0053] 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.

[0054] The display unit 140 includes a display element such as a liquid crystal display or an organic electroluminescence (EL) display, and displays display data output from the control unit 110. The operation unit 150 is configured with an input device such as a numeric keypad, and inputs data in response to user operations. Alternatively, the UE 10 may include a touch panel that can both input and display data.

[0055] The storage unit 120 stores a multi-access session information management table 1220. Fig. 3 is a diagram showing an example of the configuration of the multi-access session information management table according to this embodiment. In Fig. 3, the multi-access session information management table 1220 is a table that stores multi-access session configuration capability information and multi-access session priority information.

[0056] The multi-access session configuration capability information is information indicating which combination of radio access networks the UE 10 has the capability to establish a multi-access session with among a plurality of radio access networks (RANs 30_1, 30_2, and wireless LAN 80). The multi-access session configuration capability information is set in the UE 10 in advance.

[0057] The multi-access session priority information is information indicating the priority of a radio access network used for a multi-access session established between the UE 10 and the CN (UPF 60). The multi-access session priority information is set in the UE 10 in advance.

[0058] The multi-access session control unit 1111 has a function of notifying the CN of multi-access session configuration capability information stored in the multi-access session information management table 1220. The multi-access session control unit 1111 has a function of notifying the CN of multi-access session priority information stored in the multi-access session information management table 1220.

[0059] 4 is a diagram showing a schematic configuration of a session control device according to this embodiment. The session control device 51 shown in FIG. 4 is a device corresponding to the 5GC SMF. In this embodiment, the session control device 51 includes, in addition to the functions of the 5GC SMF, a multi-access session configuration identification unit 511, a multi-access session configuration determination unit 512, a multi-access session DC control information transmission unit 513, a measurement information acquisition unit 514, and a multi-access session priority information storage unit 515, which are added from the 5GC SMF. Note that FIG. 4 shows only the multi-access session configuration identification unit 511, the multi-access session configuration determination unit 512, the multi-access session DC control information transmission unit 513, the measurement information acquisition unit 514, and the multi-access session priority information storage unit 515, which are added from the 5GC SMF, as the functions of the session control device 51.

[0060] The functions of the session control device 51 are realized by the session control device 51 including computer hardware such as a CPU and memory, and the CPU executing a computer program stored in the memory. The session control device 51 may be configured using a general-purpose computer device, or may be configured as a dedicated hardware device. For example, the session control device 51 may be configured using a server computer connected to a communication network. The functions of the session control device 51 may also be realized by cloud computing. The session control device 51 may also be realized by a single computer, or the functions of the session control device 51 may be distributed across multiple computers.

[0061] The multi-access session configuration identification unit 511 identifies the configuration of the multi-access session that the UE 10 will establish with the CN (UPF 60) based on the multi-access session configuration capability information notified from the UE 10 and the network registration information (NW registration information) indicating the wireless access network in which the UE 10 is registered among multiple wireless access networks (RAN 30_1, 30_2, wireless LAN 80).

[0062] The multi-access session configuration determination unit 512 determines a radio access network to be used for the multi-access session that the UE 10 will establish with the CN (UPF 60) from among a plurality of radio access networks (RANs 30_1, 30_2, and wireless LAN 80). For example, the multi-access session configuration determination unit 512 determines a radio access network to be used for the multi-access session that the UE 10 will establish with the CN (UPF 60) based on measurement information indicating the communication quality of each of the plurality of radio access networks (RANs 30_1, 30_2, and wireless LAN 80). The measurement information is acquired by the measurement information acquisition unit 514. For example, the multi-access session configuration determination unit 512 determines a radio access network to be used for the multi-access session that the UE 10 will establish with the CN (UPF 60) based on multi-access session priority information.

[0063] When the multi-access session established by the UE 10 with the CN (UPF 60) satisfies a specific multi-access session condition, the multi-access session DC control information transmission unit 513 transmits DC control information for the multi-access session indicating a combination of base stations that prohibit DC for the UE 10 to a base station of a radio access network to which the UE 10 is connected. Specifically, the multi-access session DC control information transmission unit 513 transmits DC control information for the multi-access session for the UE 10 when the multi-access session established by the UE 10 with the CN (UPF 60) uses multiple "3gpp access".

[0064] Further, the multi-access session DC control information transmission unit 513 controls transmission of multi-access session DC control information for the UE 10 based on a steering mode indicating a policy of the multi-access session for the UE 10. As an example of control of transmission of multi-access session DC control information according to this embodiment, the multi-access session DC control information transmission unit 513 transmits multi-access session DC control information for the UE 10 when the steering mode of the UE 10 is a specific mode in a case where the multi-access session established between the UE 10 and the CN (UPF 60) uses multiple "3gpp accesses". Specifically, the multi-access session DC control information transmission unit 513 transmits multi-access session DC control information for the UE 10 when the steering mode of the UE 10 is "Load-Balancing" or "Redundant" in a case where the multi-access session established between the UE 10 and the CN (UPF 60) uses multiple "3gpp accesses".

[0065] The measurement information acquisition unit 514 acquires measurement information indicating the communication quality of each of the multiple wireless access networks (RANs 30_1, 30_2, and wireless LAN 80). The communication quality is, for example, throughput, RTT, packet loss rate, etc. The measurement function is possessed by, for example, the UPF in a 5G system. As an example of this embodiment, the UPF 60 has the measurement function, and the measurement information acquisition unit 514 acquires the measurement information from the UPF 60.

[0066] The multi-access session priority information storage unit 515 stores multi-access session priority information of the UE 10. The multi-access session priority information is provided from the subscriber information management device 52 or the UE 10. Alternatively, the multi-access session priority information may be set in advance in the session control device 51 as a value unique to each communication carrier (PLMN).

[0067] Fig. 5 is a diagram showing a schematic configuration of a subscriber information management device according to this embodiment. The subscriber information management device 52 shown in Fig. 5 is a device compatible with the 5GC UDM. In this embodiment, the subscriber information management device 52 includes, in addition to the functions of the 5GC UDM, a multi-access session priority information management unit 521 as an additional part from the 5GC UDM. Note that Fig. 5 shows only the multi-access session priority information management unit 521 added from the 5GC UDM as a function of the subscriber information management device 52.

[0068] Each function of the subscriber information management device 52 is realized by the subscriber information management device 52 including computer hardware such as a CPU and memory, and the CPU executing a computer program stored in the memory. The subscriber information management device 52 may be configured using a general-purpose computer device or a dedicated hardware device. For example, the subscriber information management device 52 may be configured using a server computer connected to a communications network. Each function of the subscriber information management device 52 may be realized by cloud computing. The subscriber information management device 52 may be realized by a single computer, or the functions of the subscriber information management device 52 may be distributed across multiple computers.

[0069] The multi-access session priority information management unit 521 manages and stores multi-access session priority information for each UE 10. The multi-access session priority information management unit 521 has a function of providing the session control unit 51 with the multi-access session priority information of each UE 10.

[0070] Fig. 6 is a diagram showing a schematic configuration of a base station device according to this embodiment. The base station device 30bs shown in Fig. 6 is a base station device corresponding to the RAN 30, which is "3GPP access." Hereinafter, the base station device 30bs may be referred to as the base station 30bs.

[0071] In this embodiment, the base station 30bs includes, in addition to the functions of a "3GPP access" base station (for example, a 4G base station or a 5G base station), a multi-access session DC control information storage unit 302 as an additional part from the "3GPP access" base station. The base station 30bs also makes modifications to the DC control unit 301, which is one function of the "3GPP access" base station. Note that FIG. 6 shows only the DC control unit 301 and the multi-access session DC control information storage unit 302 added from the "3GPP access" base station as functions of the base station 30bs.

[0072] The multi-access session DC control information storage unit 302 stores the multi-access session DC control information for each UE 10. The multi-access session DC control information is notified for each UE 10 from the session control device 51 (multi-access session DC control information transmission unit 513).

[0073] The DC control unit 301 controls the DC of the UE 10 connected to its own base station 30bs. The DC control unit 301 controls the DC of the UE 10 that is the DC control target based on the DC control information for the multi-access session of the UE 10 that is the DC control target stored in the DC control information storage unit 302. Specifically, the DC control unit 301 controls the DC of the UE 10 that is the DC control target in the "combination of base stations that prohibit DC" indicated in the DC control information for the multi-access session of the UE 10 that is the DC control target so as not to perform DC.

[0074] Next, a communication method according to this embodiment will be described with reference to Fig. 7. Fig. 7 is a sequence diagram showing the overall flow of the communication method according to this embodiment.

[0075] The UE 10 is connected to a base station (BS) 30bs_1 of a first PLMN with which the UE 10 has completed network registration (NW registration).

[0076] (Step S1) The multi-access session control unit 1111 of the UE 10 transmits a multi-access session establishment request to the AM control device 50 via the base station 30bs_1. At this time, the multi-access session control unit 1111 includes multi-access session configuration capability information from the multi-access session information management table 1220 in the multi-access session establishment request transmitted to the AM control device 50. Furthermore, the multi-access session control unit 1111 may include multi-access session priority information from the multi-access session information management table 1220 in the multi-access session establishment request.

[0077] (Step S2) The AM control device 50 selects a session control device 51 that will execute the session establishment process in response to the multi-access session establishment request (including the multi-access session configuration capability information) received from the UE 10, and transfers the multi-access session establishment request (including the multi-access session configuration capability information) together with network registration information (NW registration information) to the selected session control device 51. The NW registration information is information that indicates all "3GPP access" and "non-3GPP access" networks to which the UE 10 has been registered. The AM control device 50 manages the status of NW registration for each UE 10.

[0078] (Step S3) The session control device 51 receives the NW registration information and the multi-access session establishment request (including the multi-access session configuration capability information) transmitted from the AM control device 50. Based on the received NW registration information and multi-access session configuration capability information, the multi-access session configuration identification unit 511 of the session control device 51 identifies the configuration of the multi-access session that the UE 10 that has made the multi-access session establishment request (requestor UE 10) will establish with the CN (UPF 60).

[0079] Here, a multi-access session configuration identification method according to this embodiment will be described. Fig. 8 is a diagram showing an example of the multi-access session configuration identification method according to this embodiment. Fig. 8 shows multi-access session configurations corresponding to each combination of NW registration information and multi-access session configuration capability information. The multi-access session configuration identification method shown in Fig. 8 is set in advance in the multi-access session configuration identification unit 511. The multi-access session configuration identification unit 511 identifies the multi-access session configuration corresponding to the NW registration information and the multi-access session configuration capability information for the requesting UE 10 according to the multi-access session configuration identification method of Fig. 8.

[0080] In the multi-access session configuration identification method of FIG. 8 , in the case of a combination of NW registration information “one 3gpp & one non-3gpp (one “3gpp access” and one “non-3gpp access”)” and multi-access session configuration capability information “3gpp+ non-3gpp (a multi-access session can be configured by a combination of “3gpp access” and “non-3gpp access”),” the multi-access session configuration is “3gpp+ non-3gpp (a combination of “3gpp access” and “non-3gpp access”).” In addition, in the case of a combination of NW registration information "one 3gpp & one non-3gpp" and multi-access session configuration capability information "3gpp+non-3gpp&3gpp+3gpp (a multi-access session can be configured with either the combination of "3gpp access" and "non-3gpp access", or the combination of "3gpp access" and "3gpp access")," the multi-access session configuration is "3gpp+non-3gpp (a combination of "3gpp access" and "non-3gpp access")."

[0081] In addition, in the case of a combination of NW registration information "two 3gpp (two '3gpp access')" and multi-access session configuration capability information "3gpp+3gpp (a multi-access session can be configured by combining '3gpp access' and '3gpp access')," the multi-access session configuration is "3gpp+3gpp (a combination of '3gpp access' and '3gpp access')." In addition, in the case of a combination of NW registration information "two 3gpp" and multi-access session configuration capability information "3gpp+non-3gpp&3gpp+3gpp," the multi-access session configuration is "3gpp+3gpp."

[0082] In addition, when the NW registration information "two 3gpp & one non-3gpp (two '3gpp access' and one 'non-3gpp access')" is combined with the multi-access session configuration capability information "3gpp + non-3gpp", the multi-access session configuration is "3gpp + non-3gpp". In addition, when the NW registration information "two 3gpp & one non-3gpp" is combined with the multi-access session configuration capability information "3gpp + 3gpp", the multi-access session configuration is "3gpp + 3gpp".

[0083] In the multi-access session configuration identification method of FIG. 8, the cases where the multi-access session configuration is "session established only on the 3GPP side" and "determined based on measurement information or priority information" will be described later.

[0084] The multi-access session configuration determination unit 512 of the session control device 51 determines a radio access network for the multi-access session configuration of the requesting UE 10 identified by the multi-access session configuration identification unit 511 (the identification result of the multi-access session configuration).

[0085] (Step S4) The multi-access session configuration determination unit 512 determines a steering mode indicating how traffic is transmitted between multiple sessions of the multi-access session, with respect to the multi-access session configuration of the requesting UE 10. Examples of the steering mode according to this embodiment include steering modes (1) to (5) defined in Non-Patent Documents 1 and 2.

[0086] (Steps S5 and S6) The multi-access session configuration determination unit 512 executes a session establishment process for the multi-access session configuration of the requesting UE 10. In one example of this session establishment process, the multi-access session configuration determination unit 512 establishes a session (first session) on the radio access network to which the requesting UE 10 has transmitted the multi-access session establishment request. At this time, the multi-access session configuration determination unit 512 transmits to the requesting UE 10 a set of information necessary for multi-access session control, including steering mode information indicating the steering mode determined in step S4 (step S6). The multi-access session configuration determination unit 512 also transmits the set of information to the gateway device (UPF 60) (not shown).

[0087] After the first session is established, if the requestor UE 10 has already been registered in the second wireless access network based on the NW registration information of the requestor UE 10, the multi-access session configuration determination unit 512 establishes a session (second session) in the second wireless access network in the same manner as the first session. In the session establishment process, for example, tunnel information is exchanged between the base station and the gateway device.

[0088] Here, in the multi-access session configuration identification method of Figure 8 described above, we will explain the case of the multi-access session configuration "session established only on the 3GPP side" corresponding to the combination of NW registration information "one 3GPP & one non-3GPP" and multi-access session configuration capability information "3GPP + 3GPP", and the combination of NW registration information "two 3GPP" and multi-access session configuration capability information "3GPP + non-3GPP".

[0089] In this embodiment, similar to the conventional "MA PDU Session," the UE 10 can issue a multi-access session establishment request while registered with only one of the radio access networks, either one "3GPP access" or one "non-3GPP access." At this time, the CN determines various information necessary for the multi-access session (e.g., the Internet Protocol (IP) address to be provided to the UE 10, CN-side proxy information, etc.), and establishes a session for the UE 10 only in the "3GPP access" in which the UE 10 is registered. As soon as the UE 10 completes network registration with the other unregistered radio access network, the UE 10 immediately issues a session establishment request in the radio access network in which the network registration has been completed. In this session establishment request, the UE 10 presents the same session ID as the session already established as a multi-access session. As a result, the CN recognizes that the session establishment request from the UE 10, in which the session ID is presented, is a request to establish a session to be used for the multi-access session of the UE 10. Conventionally, the steering mode is notified from the CN to the UE when the "MA PDU Session" is established. In this embodiment, the CN notifies the UE 10 of the steering mode when at least the second session is established.

[0090] In addition, in the above-described multi-access session configuration identification method of FIG. 8 , a case of a multi-access session configuration "determined by measurement information or priority information" corresponding to the combination of NW registration information "two 3GPP & one non-3GPP" and multi-access session configuration capability information "3GPP+non-3GPP&3GPP+3GPP" will be described. In this case, a multi-access session can be formed with either "3GPP+3GPP" or "3GPP+non-3GPP". Below, the cases of the multi-access session configuration "determined by measurement information" and the multi-access session configuration "determined by priority information" will be described respectively. The session control device 51 is configured in advance to use either "determined by measurement information" or "determined by priority information".

[0091] In the multi-access session configuration "determined based on measurement information", the multi-access session configuration determination unit 512 determines the radio access network to be used for the multi-access session of the requesting UE 10 from two "3GPP accesses" and one "non-3GPP access" based on the measurement information acquired by the measurement information acquisition unit 514. For example, the multi-access session configuration determination unit 512 compares the measurement information of the two "3GPP accesses" and one "non-3GPP access" and determines the radio access network to be used for the multi-access session of the requesting UE 10 based on the result of the comparison.

[0092] In the multi-access session configuration "determined by priority information" mode, the multi-access session configuration determination unit 512 determines the radio access network to be used for the multi-access session of the requesting UE 10 from among two "3GPP access" and one "non-3GPP access" based on the multi-access session priority information stored in the multi-access session priority information storage unit 515.

[0093] (Step S7) When the multi-access session of the requesting UE 10 satisfies a specific multi-access session condition, the multi-access session DC control information transmission unit 513 of the session control device 51 transmits the multi-access session DC control information for the requesting UE 10 to the base station of the radio access network to which the requesting UE 10 is connected.

[0094] The DC control information for the multi-access session for the request source UE 10 is information indicating a combination of base stations that prohibit DC for the request source UE 10. The combination of base stations that prohibit DC for the request source UE 10 is a combination of base stations of a radio access network that can be used for the multi-access session of the request source UE 10. For example, the DC control information for the multi-access session for the request source UE 10 is information indicating a combination of all base stations to which the request source UE 10 is connected in a radio access network that can be used for the multi-access session of the request source UE 10.

[0095] An example of a specific multi-access session condition according to this embodiment is that the multi-access session uses multiple "3gpp access"s and the steering mode is a specific mode, and further, the specific steering mode is "Load-Balancing" or "Redundant."

[0096] For example, when the multi-access session of the request source UE 10 uses multiple "3gpp access" and the steering mode is "Load-Balancing" or "Redundant", the multi-access session DC control information transmission unit 513 transmits the multi-access session DC control information for the request source UE 10 to the base station of the radio access network to which the request source UE 10 connects. The base station receives the multi-access session DC control information and associates the received multi-access session DC control information with the identifier of the request source UE 10 and stores it in the multi-access session DC control information storage unit 302.

[0097] (Step S8) The base station of the radio access network to which the requesting UE 10 is connected controls the DC of the requesting UE 10 so that it does not perform DC in the "combination of base stations that prohibit DC" indicated in the DC control information for the multi-access session stored in the DC control information storage unit 302.

[0098] According to the above-described embodiment, it is possible to obtain the effect that a multi-access session can be appropriately configured.

[0099] According to the above-described embodiment, the DC of the UE 10 can be controlled according to the multi-access session of the UE 10.

[0100] According to the above-described embodiment, it is possible to obtain the effect that multi-access sessions can be effectively utilized.

[0101] The above-described embodiment is applicable to mobile communication systems such as 5G systems, B5G systems, and 6G systems.

[0102] This will enable, for example, improvements to the overall service quality of mobile communication systems, thereby contributing to Goal 9 of the United Nations-led Sustainable Development Goals (SDGs), which is to "Build resilient infrastructure, promote sustainable industrialization and foster innovation."

[0103] 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 are also included within the scope that does not deviate from the gist of the present invention.

[0104] Furthermore, a computer program for implementing the functions of each of the above-described devices may be recorded on a computer-readable recording medium, and the program recorded on the recording medium may be read and executed by a computer system. Note that the term "computer system" may also include hardware such as an OS and peripheral devices. Furthermore, the term "computer-readable recording medium" refers to a flexible disk, a magneto-optical disk, a ROM, a writable nonvolatile memory such as a flash memory, a portable medium such as a DVD (Digital Versatile Disc), or a storage device such as a hard disk built into a computer system.

[0105] Furthermore, the term "computer-readable recording medium" also includes a storage medium that stores a program for a certain period of time, such as a volatile memory (e.g., a dynamic random access memory (DRAM)) within a computer system that serves as a server or client when the program is transmitted via a network such as the Internet or a communication line such as a telephone line. The program may also 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 transmission waves within the transmission medium. Here, the "transmission medium" that transmits the program refers to a medium that has the 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 program may also be a program that realizes part of the aforementioned functions. Furthermore, the program may be a so-called differential file (differential program) that can realize the aforementioned functions in combination with a program already stored in the computer system.

[0106] According to the present invention, it is possible to appropriately configure a multi-access session.

[0107] 1...mobile communication system, 10...UE, 30...RAN, 50...AM control device, 51...session control device, 52...contractor information management device, 60...UPF, 70...DN, 80...wireless LAN, 110...control unit, 120...storage unit, 130...communication unit, 140...display unit, 150...operation unit, 1111...multi-access session control unit, 1210...multi-access session control program, 1220...multi-access session information management table, 511...multi-access session configuration identification unit, 512...multi-access session configuration determination unit, 513...multi-access session DC control information transmission unit, 514...measurement information acquisition unit, 515...multi-access session priority information storage unit, 521...multi-access session priority information management unit, 30bs...base station device, 301...DC control unit, 302...multi-access session DC control information storage unit

Claims

1. 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: a measurement information acquisition unit that acquires measurement information indicating communication quality of each of the multiple radio access networks; and a multi-access session configuration determination unit that determines, based on the measurement information, from the multiple radio access networks, a radio access network to be used for a multi-access session established by a user terminal between the core network and the multiple radio access networks.

2. A network device provided in a core network in a mobile communication system having a core network connected to multiple radio access networks, the network device comprising: a multi-access session priority information storage unit that stores multi-access session priority information indicating the priority of a radio access network to be used for a multi-access session established by a user terminal between the core network; and a multi-access session configuration determination unit that determines a radio access network to be used for the multi-access session from among the multiple radio access networks based on the multi-access session priority information.

3. A network device as described in any one of claims 1 or 2, further comprising a multi-access session configuration identification unit that identifies a configuration of a multi-access session to be established between the user terminal and the core network based on multi-access session configuration capability information indicating which combination of radio access networks among the plurality of radio access networks the user terminal has the capability of establishing a multi-access session with and NW registration information indicating which radio access network among the plurality of radio access networks in which the user terminal is registered, and the multi-access session configuration determination unit determines a radio access network for the identification result of the multi-access session configuration.

4. The network device according to claim 3, wherein the multi-access session configuration determination unit executes a session establishment process for establishing a session using a second or subsequent radio access network to be used for the multi-access session when the NW registration information indicates that the user terminal is registered in two or more radio access networks.

5. A user terminal of a mobile communication system having a core network connected to a plurality of radio access networks, comprising: a multi-access session configuration capability information storage unit that stores multi-access session configuration capability information indicating which combination of radio access networks among the plurality of radio access networks the user terminal has the capability of establishing a multi-access session with; and a multi-access session control unit that notifies the core network of the multi-access session configuration capability information.

6. A user terminal of a mobile communication system having a core network connected to multiple radio access networks, comprising: a multi-access session priority information storage unit that stores multi-access session priority information indicating the priority of a radio access network to be used for a multi-access session established by the user terminal between the core network; and a multi-access session control unit that notifies the core network of the multi-access session priority information.

7. A network device provided in a core network in a mobile communication system having a core network connected to a plurality of radio access networks, the network device comprising: a multi-access session priority information management unit that manages multi-access session priority information indicating the priority of a radio access network to be used for a multi-access session established between a user terminal and the core network, and provides the multi-access session priority information to a network device having a multi-access session configuration determination unit that determines a radio access network to be used for the multi-access session from among the plurality of radio access networks based on the multi-access session priority information.

8. A communication method executed by a network device in a core network in a mobile communication system having a core network connected to a plurality of radio access networks, the communication method comprising: a measurement information acquisition step of acquiring measurement information indicating communication quality of each of the plurality of radio access networks; and a multi-access session configuration determination step of determining, based on the measurement information, from the plurality of radio access networks, a radio access network to be used for a multi-access session established between a user terminal and the core network.

9. A communication method executed by a network device provided in a core network in a mobile communication system having a core network connected to a plurality of radio access networks, the communication method comprising: a multi-access session priority information storage step of storing multi-access session priority information indicating the priority of a radio access network to be used for a multi-access session established between a user terminal and the core network in a multi-access session priority information storage unit; and a multi-access session configuration determination step of determining a radio access network to be used for the multi-access session from among the plurality of radio access networks based on the multi-access session priority information.

10. A computer program for causing a computer of a network device provided in a core network in a mobile communications system connected to a plurality of radio access networks to execute: a measurement information acquisition step for acquiring measurement information indicating communication quality of each of the plurality of radio access networks; and a multi-access session configuration determination step for determining, based on the measurement information, from the plurality of radio access networks, a radio access network to be used for a multi-access session established between a user terminal and the core network.

11. A computer program for causing a computer of a network device provided in a core network in a mobile communication system connected to a plurality of radio access networks to execute the following steps: a multi-access session priority information storage step of storing multi-access session priority information indicating the priority of a radio access network to be used for a multi-access session established between a user terminal and the core network in a multi-access session priority information storage unit; and a multi-access session configuration determination step of determining a radio access network to be used for the multi-access session from among the plurality of radio access networks based on the multi-access session priority information.

12. A computer program for causing a computer of a user terminal of a mobile communication system having a core network connected to multiple radio access networks to execute: a multi-access session configuration capability information storage step of storing multi-access session configuration capability information indicating which combination of radio access networks among the multiple radio access networks the user terminal has the capability of establishing a multi-access session with in a multi-access session configuration capability information storage unit; and a multi-access session control step of notifying the core network of the multi-access session configuration capability information.

13. A computer program for causing a computer of a user terminal of a mobile communication system having a core network connected to multiple radio access networks to execute the following steps: a multi-access session priority information storage step of storing multi-access session priority information indicating the priority of a radio access network to be used for a multi-access session established between the user terminal and the core network in a multi-access session priority information storage unit; and a multi-access session control step of notifying the core network of the multi-access session priority information.

14. A computer program for causing a computer of a network device provided in a core network in a mobile communication system connected to multiple radio access networks to execute a multi-access session priority information management step of managing multi-access session priority information indicating the priority of a radio access network to be used for a multi-access session established between a user terminal and the core network, and providing the multi-access session priority information to a network device provided with a multi-access session configuration determination unit that determines a radio access network to be used for the multi-access session from among the multiple radio access networks based on the multi-access session priority information.

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