User terminal and communication control method

Abstract

To allow a user terminal to determine a SAN connection destination base station.SOLUTION: A user terminal includes a communication control unit that, when the user terminal establishes a "multi-access PDU session" using a first radio access network of a PPLMN to which the user terminal is already connected and a second radio access network of an SPLMN to which the user terminal is newly connected, identifies a second frequency available in the second radio access network included in a combination of frequencies available in the first radio access network and the second radio access network, and determines a connection destination base station of the second radio access network based on the identified second frequency.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a user terminal and a communication control method.

Background Art

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

[0003] Here, the logical communication path established between the UE and the CN (UPF) for the UE to use the mobile communication service is referred to as a "session". Also, the session established between the UE and the CN (UPF) using multiple radio paths is referred to as a "multi-access session". In Non-Patent Documents 1 and 2, "Multi-access PDU (Packet Data Unit) Session (hereinafter referred to as "MA PDU Session")" is defined as an example of a multi-access session. FIG. 6 is a diagram showing a configuration example of the "MA PDU Session". As shown in FIG. 6, the UE establishes a "MA PDU Session" with the CN (UPF) using a radio path via the RAN which is "3gpp access" and a radio path via a wireless LAN (Local Area Network) such as, for example, "Wi-Fi (registered trademark)" which is "non-3gpp access". "3gpp access" is an access network defined by 3GPP. "non-3gpp access" is an access network other than "3gpp access". The UE uses its "MA PDU Session" to transmit and receive data to and from a DN (Data Network), such as the Internet, outside the 5GC (the CN of the 5G system). By using the "MA PDU Session", the UE can obtain the effect of improving communication quality, such as expanding the communication bandwidth, reducing communication delay, and ensuring communication path redundancy.

[0004] Also, as communication methods in which one UE simultaneously uses a plurality of base stations that utilize different frequencies, DC (Dual Connectivity) and CA (Carrier aggregation) are known (see, for example, Non-Patent Document 3).

Prior Art Documents

Non-Patent Documents

[0005]

Non-Patent Document 1

Non-Patent Document 2

Non-Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0006] Generally, when a UE simultaneously uses a plurality of base stations that each use different frequencies, radio interference caused by intermodulation, harmonics, etc. may occur. In order to suppress performance degradation due to such radio interference, it is preferable that the frequencies of each RAN can be selected so as to be a combination of frequencies with less influence of interference. In conventional DC and CA, the "Master RAN" performed necessary information exchange and selected an appropriate combination of frequencies.

[0007] On the other hand, when a UE performs a multi-access session (MA PDU Session With two 3GPP Access) with a UPF using a plurality of radio paths via two RANs (3gpp access) respectively, the selection of the cell (base station) of the SAN (Secondary Access Network) can be considered to be performed by aggregating in the CN the frequency information used by the cell (base station) of the PAN (Primary Access Network) and the frequency information available to the UE. However, for that purpose, it is difficult to define the signaling between the CN and the RAN for the "MA PDU Session" in the standard specification because it requires a functional modification to the existing RAN base stations.

[0008] The present invention has been made in consideration of such circumstances, and its object is to enable a user terminal to determine the cell (base station) to which the SAN is connected.

Means for Solving the Problems

[0009] One aspect of the present invention is a user terminal of a mobile communication system including a core network connected to a plurality of radio access networks, the user terminal including: a frequency combination information storage unit that stores frequency combination information indicating a combination of frequencies available in a "Multi-access PDU Session"; a PLMN frequency information storage unit that stores PLMN frequency information indicating frequencies available in each PLMN (Public Land Mobile Network); and when establishing a "Multi-access PDU Session" between a first radio access network of a PPLMN (Primary PLMN) to which the user terminal is already connected and a second radio access network of an SPLMN (Secondary PLMN) to which the user terminal newly connects, based on the frequency combination information and the PLMN frequency information, a second frequency available in the second radio access network included in a combination of frequencies available in the first radio access network and the second radio access network is specified, and based on the specified second frequency, a communication control unit that determines a destination base station of the second radio access network. One aspect of the present invention is the user terminal described above, wherein the communication control unit restricts a second frequency available in the second radio access network according to a predetermined frequency restriction condition. One aspect of the present invention is the user terminal described above, wherein the communication control unit determines whether to restrict the second frequency available in the second radio access network based on information on an antenna used for connection to the first radio access network.

[0010] One aspect of the present invention is a communication control method executed by a user terminal of a mobile communication system including a core network connected to a plurality of radio access networks, the method including: a frequency combination information storage step of storing frequency combination information indicating a combination of frequencies available in a "Multi-access PDU Session" by the user terminal; a PLMN frequency information storage step of storing PLMN frequency information indicating frequencies available in each PLMN (Public Land Mobile Network); and when establishing a "Multi-access PDU Session" between a first radio access network of a PPLMN (Primary PLMN) to which the user terminal is already connected and a second radio access network of an SPLMN (Secondary PLMN) to be newly connected, based on the frequency combination information and the PLMN frequency information, identifying a second frequency available in the second radio access network included in a combination of frequencies available between the first radio access network and the second radio access network, and determining a connection destination base station of the second radio access network based on the identified second frequency.

Advantages of the Invention

[0011] According to the present invention, an effect is obtained that a user terminal can determine a cell (base station) to which a SAN is connected.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Embodiments for Carrying out the Invention

[0013] Hereinafter, embodiments 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 the first PLMN (Public Land Mobile Network). The first PLMN is a PLMN (PPLMN (Primary PLMN)) that manages the base stations of the PAN (Primary Access Network), which is the base station to which the UE 10 first connects. The RAN 30_2 is a candidate RAN of the second PLMN. The second PLMN is a PLMN (SPLMN (Secondary PLMN)) that manages the base stations of the SAN (Secondary Access Network), which is the base station to which the UE 10 connects next after the base station of the PAN.

[0014] 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 RAN 30 (30_1, 30_2) is connected to the UPF (User Plane Function) 60 of the CN (Core Network) of the mobile communication system 1. Hereinafter, when the RAN 30_1 and the RAN 30_2 are not particularly distinguished, they are referred to as RAN 30.

[0015] 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 be in the same PLMN, or they may not be. Also, all the RANs 30 (30_1, 30_2, 30_3, ···) are connected to the UPF 60 of the mobile communication system 1. Although only one UPF 60 is shown in FIG. 1, the mobile communication system 1 may include a plurality of UPFs 60, and one RAN 30 may be connected to one or more UPFs 60.

[0016] Also, the UE 10 can be connected to a wireless LAN 80 which is a "non-3gpp access". The wireless LAN 80 is connected to the UPF 60 of the mobile communication system 1. The wireless LAN 80 is an example of a wireless access network which is a "non-3gpp access".

[0017] The UPF 60 is connected to a DN (data network) such as the Internet etc. outside the CN of the mobile communication system 1.

[0018] 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 send and receive data with the DN using the established session. Also, 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 send and receive data with the DN using the established multi-access session.

[0019] In this embodiment, further, UE10 attempts to establish a multi-access session (MA PDU Session With two 3GPP Access) with UPF60 using a plurality of wireless paths via each of the plurality of RAN30s. The two "3gpp access" (base stations) for establishing the multi-access session are the base station of the PAN and the base station of the SAN. Here, in this embodiment, UE10 is enabled to determine the base station (cell) to which the SAN is connected.

[0020] 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, for example, a network device that realizes an NF corresponding to the AMF of the 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 the 5GC.

[0021] The AM control device 50 performs C-plane communication with UE10 and RAN30.

[0022] FIG. 2 is a diagram showing a schematic configuration of a UE according to this embodiment. In FIG. 2, UE10 includes a control unit 110, a storage unit 120, a communication unit 130, a display unit 140, and an operation unit 150.

[0023] The control unit 110 is a CPU (Central Processing Unit), and realizes various functions by calling and executing a program stored in the storage unit 120.

[0024] As its function, the control unit 110 includes a communication control unit 1110. The communication control unit 1110 is realized by the CPU executing a communication control program 1210 stored in the storage unit 120.

[0025] Note that FIG. 2 only shows the communication control unit 1110 regarding additional functions from the conventional UE10 as a function of the control unit 110. Similarly, as a program stored in the storage unit 120, only the communication control program 1210 regarding additional functions from the conventional UE10 is shown.

[0026] The storage unit 120 is composed of a storage medium, for example, an HDD (Hard Disk Drive), a flash memory, an EEPROM (Electrically Erasable Programmable Read Only Memory), a RAM (Random Access read / write Memory), a ROM (Read Only Memory), or any combination of these storage media. Various programs such as the communication control program 1210 executed by the control unit 110 (CPU) and various data are stored in the storage unit 120.

[0027] The communication unit 130 connects to the base station of the RAN30 and communicates wirelessly via the connected base station. Also, the communication unit 130 connects to the access point of the wireless LAN80 and communicates wirelessly via the connected access point.

[0028] 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. Or, the UE10 may be provided with a touch panel capable of both data input and data display.

[0029] The storage unit 120 stores SPLMN (Secondary PLMN) information 1202, TFCL (Technical Frequency Combination List) information 1203, and FPPP (Frequency party per PLMN) information 1204.

[0030] The SPLMN information 1202 is information indicating the candidate PLMNs of the second PLMN. The SPLMN information 1202 is provided, for example, from the CN of the mobile communication system 1. The SPLMN information 1202 may be, for example, information in a list format including a plurality of PLMNs. When a plurality of PLMNs are included in the SPLMN information 1202, a predetermined priority is set for each PLMN. Alternatively, the SPLMN information 1202 may be information in the form of a list of a plurality of PLMNs with priorities assigned to each PLMN.

[0031] The TFCL information 1203 is information (frequency combination information) indicating the combination of frequencies available for the UE10 in the "Multi-access PDU Session". The TFCL information 1203 is provided, for example, from the CN of the mobile communication system 1. The method for creating the TFCL information 1203 is, for example, to determine the combination of frequencies available for the UE10 in the "Multi-access PDU Session" by actual measurement, simulation, etc., and include the frequency combination of the result of this determination in the TFCL information 1203. Note that although the TFCL information 1203 is created in a list format as an example of this embodiment, the format is not limited as long as it is frequency combination information indicating the combination of frequencies available for the UE10 in the "Multi-access PDU Session".

[0032] The FPPP information 1204 is information (PLMN frequency information) indicating the frequencies available in each PLMN. The FPPP information 1204 is provided, for example, from the CN of the mobile communication system 1.

[0033] The communication control unit 1110 performs various communication controls of the UE10. The communication control unit 1110 according to this embodiment has a function of determining the cell (base station) of the SAN to which the UE10 is connected.

[0034] Fig. 3 is a diagram showing the schematic configuration of an AM control device according to this embodiment. The AM control device 50 shown in Fig. 3 is a device compatible with the 5GC AMF. In this embodiment, the AM control device 50 has, in addition to the functions of the 5GC AMF, an SPLMN control unit 501 as an additional part from the 5GC AMF. Note that Fig. 3 shows only the SPLMN control unit 501 added from the 5GC AMF as a function of the AM control device 50.

[0035] The SPLMN control unit 501 provides the SPLMN information 1202 to the UE 10. The SPLMN control unit 501 determines the SPLMN information 1202 appropriate for the UE 10.

[0036] In this embodiment, the AM control device 50 determines the SPLMN information 1202 of the UE 10, but this is not limiting. For example, the SPLMN information 1202 of the UE 10 may be determined by an SMF or a PCF.

[0037] Next, a communication control method according to this embodiment will be described with reference to Fig. 4. Fig. 4 is a flowchart showing an example of the procedure of the communication control method according to this embodiment. Hereinafter, a base station of a PAN may be referred to as a PAN cell. Similarly, a base station of a SAN may be referred to as a SAN cell.

[0038] (Step S1) The communication control unit 1110 of the UE 10 connects to a PAN cell, for example, when the UE 10 is powered on or airplane mode is turned off, performs network registration (NW registration) with the first PLMN (PPLMN) using the connected PAN cell, and establishes a PDU session with the RAN 30_1 of the first PLMN (PPLMN). The PAN cell may be, for example, a base station of the PLMN to which the UE 10 was previously connected, or a base station of a PLMN set as default in the UE 10. Here, for convenience of explanation, the PAN cell to which the UE 10 connects is PAN cell "n11" that uses frequency "n11". Therefore, the FPPP information 1204 related to the first PLMN (PPLMN) is {n11}.

[0039] (Step S2) The communication control unit 1110 of UE10 starts the establishment procedure of "MA PDU Session With two 3GPP Access". The trigger for the establishment of "MA PDU Session With two 3GPP Access" is not limited. As an example of the trigger for the establishment of "MA PDU Session With two 3GPP Access", it may be the case where a request for packet communication requiring a high level of reliability is notified from the upper layer.

[0040] (Step S3) The communication control unit 1110 of UE10 determines the second PLMN (SPLMN) based on the SPLMN information 1202. Here, for the sake of convenience of explanation, it is SPLMN "2".

[0041] (Step S4) The communication control unit 1110 of UE10 determines the frequency candidates of RAN30_2 (SAN) of SPLMN "2" as the frequency candidates of the SAN. Hereinafter, the method for determining the frequency candidates of the SAN will be described.

[0042] Here, for the sake of convenience of explanation, the TFCL information 1203 is {[n11, n21], [n11, n22], [n11, n32]}. Also, the FPPP information 1204 regarding SPLMN "2" is {n21, n22, n23}. The communication control unit 1110 selects the elements [n11, n21], [n11, n22] that include both the frequency "n11" of the PAN cell and the frequencies "n21", "n22" or "n23" of SPLMN "2" from the three elements [n11, n21], [n11, n22], [n11, n32] of the TFCL information 1203. Next, the communication control unit 1110 extracts the frequencies "n21" and "n22" that are the frequencies of SPLMN "2" from the selected two elements [n11, n21], [n11, n22]. The communication control unit 1110 determines the extracted frequencies "n21" and "n22" as the frequency candidates of RAN30_2 (SAN) of SPLMN "2".

[0043] (Step S5) The communication control unit 1110 of UE10 determines the destination frequency of RAN30_2 (SAN) of SPLMN "2" from the frequency candidates "n21" and "n22" of RAN30_2 (SAN) of SPLMN "2". Specifically, the communication control unit 1110 searches for each of the frequencies of the frequency candidates "n21" and "n22", and based on the result of the search, determines the frequency to actually attempt connection among the frequency candidates "n21" and "n22". The communication control unit 1110 connects to the SAN cell using the determined frequency.

[0044] Thereby, UE10 connects to the SAN cell, performs NW registration of the second PLMN (SPLMN) by the connected SAN cell, and establishes a PDU session by RAN30_2 of the second PLMN (SPLMN). After that, UE10 uses the PDU session by RAN30_1 of the first PLMN (PPLMN) and the PDU session by RAN30_2 of the second PLMN (SPLMN) to establish "MA PDU Session With two 3GPP Access".

[0045] Note that when determining the frequency candidates of the SAN, the communication control unit 1110 may limit the frequency candidates of the SAN according to a predetermined SAN frequency limitation condition. Examples of the SAN frequency limitation condition are given below.

[0046] (Example 1 of SAN frequency limitation condition) As a SAN frequency limitation condition, frequencies not used for "MA PDU Session With two 3GPP Access" are set in advance in UE10. In the above example, for example, the frequency "n21" is set in advance in UE10 as a frequency not used for "MA PDU Session With two 3GPP Access". Thereby, the communication control unit 1110 determines only the frequency "n22" among the frequencies "n21" and "n22" as the frequency candidates of RAN30_2 (SAN) of SPLMN "2".

[0047] (Example 2 of SAN frequency limitation condition) As a SAN frequency restriction condition, it is set in advance in the UE10 whether to restrict the frequencies available in the SAN cell based on the information of the antenna of the UE10 used for connection to the PAN cell. For example, as a SAN frequency restriction condition, when the number of antennas of the UE10 is 2, if the number of antennas used for connection to the PAN cell is 1, no restriction is imposed on the frequencies available in the SAN cell. On the other hand, when the number of antennas used for connection to the PAN cell is 2, a restriction is imposed on the frequencies available in the SAN cell. When the number of antennas used for connection to the PAN cell is 1, since there is one unused antenna, it is assumed that no restriction is imposed on the frequencies available in the SAN cell. On the other hand, when the number of antennas used for connection to the PAN cell is 2, since there is no unused antenna, a restriction is imposed on the frequencies available in the SAN cell. When there is no unused antenna, for example, the frequencies used in the SAN cell are restricted to the frequencies that can be shared with the PAN cell.

[0048] According to this embodiment, an effect that the UE10 can determine the cell (base station) that is the connection destination of the SAN can be obtained.

[0049] The above-described embodiment is applicable to mobile communication systems such as, for example, 5G systems, B5G (Beyond 5G) systems, and sixth-generation mobile communication systems (6G systems).

[0050] Note that, as a result, for example, since an improvement in the overall service quality in a mobile communication system can be realized, it is possible to contribute to Goal 9 of the Sustainable Development Goals (SDGs) led by the United Nations, "Build resilient infrastructure, promote sustainable industrialization, and foster innovation."

[0051] As described above, the embodiments of the present invention have been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and design changes and the like within the scope not departing from the gist of the present invention are also included.

[0052] Alternatively, a computer program for realizing the functions of each of the above-described devices may be recorded on a computer-readable recording medium, and the program recorded on this recording medium may be read into a computer system and executed. Here, the "computer system" may include hardware such as an OS and peripheral devices. Further, the "computer-readable recording medium" refers to a writable non-volatile memory such as a flexible disk, a magneto-optical disk, a ROM, a flash memory, a portable medium such as a DVD (Digital Versatile Disc), and a storage device such as a hard disk incorporated in a computer system.

[0053] Furthermore, the "computer-readable recording medium" also includes a volatile memory (for example, 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, and that holds the program for a certain period of time. Also, the above program may be transmitted from a computer system storing 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" for transmitting the program refers to a medium having a function of transmitting information, such as a network (communication network) such as the Internet or a communication line (communication wire) such as a telephone line. Also, the above program may be for realizing a part of the above-described functions. Further, it may be a so-called difference file (difference program) that can realize the above-described functions in combination with a program already recorded in a computer system.

Explanation of Reference Numerals

[0054] 1... Mobile communication system, 10... UE, 30... RAN, 50... AM control device, 60... UPF, 70... DN, 80... Wireless LAN, 110... Control unit, 120... Memory unit, 130... Communication unit, 140... Display unit, 150... Operation unit, 1110... Communication control unit, 501... SPLMN control unit

Claims

1. A user terminal of a mobile communication system including a core network connected to a plurality of radio access networks, a frequency combination information storage unit that stores frequency combination information indicating a combination of frequencies available in the “Multi-access PDU Session” for the user terminal, a PLMN frequency information storage unit that stores PLMN frequency information indicating frequencies available in each PLMN (Public Land Mobile Network), when establishing a “Multi-access PDU Session” between the first radio access network of the already connected PPLMN (Primary PLMN) and the second radio access network of the newly connected SPLMN (Secondary PLMN), based on the frequency combination information and the PLMN frequency information, identifying a second frequency available in the second radio access network included in the combination of frequencies available in the first radio access network and the second radio access network, a communication control unit that determines a base station to which the second radio access network is to be connected based on the identified second frequency, A user terminal comprising.

2. The communication control unit restricts a second frequency available in the second radio access network according to a predetermined frequency restriction condition, The user terminal according to claim 1.

3. The communication control unit determines whether to restrict the second frequency available in the second radio access network based on information on an antenna used for connection to the first radio access network, The user terminal according to claim 1.

4. A communication control method executed by a user terminal of a mobile communication system including a core network connected to a plurality of radio access networks, a frequency combination information storage step of storing frequency combination information indicating a combination of frequencies available in the “Multi-access PDU Session” for the user terminal, a PLMN frequency information storage step of storing PLMN frequency information indicating frequencies available in each PLMN (Public Land Mobile Network), When establishing a "Multi-access PDU Session" between the first wireless access network of the already connected PPLMN (Primary PLMN) and the second wireless access network of the newly connected SPLMN (Secondary PLMN), Based on the frequency combination information and the PLMN frequency information, identify a second frequency available in the second wireless access network included in the combination of available frequencies between the first wireless access network and the second wireless access network, A communication control step of determining a base station to which the second wireless access network is connected based on the identified second frequency, A communication control method including the above.

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