Communication system

Abstract

This communication system includes a plurality of networks including a radio access network and a core network, wherein: an anchor network to which a communication terminal is connected determines, on the basis of information relating to the communication quality between the communication terminal and a data network, whether it is necessary to add a network for the communication terminal to connect to, and selects an additional network if it is necessary to add a network for the communication terminal to connect to; and the network selected as the additional network by the anchor network executes registration processing for connecting to the communication terminal.

Description

communication systems

[0001] The present disclosure relates to wireless communication technology.

[0002] The 3rd Generation Partnership Project (3GPP), a standardization organization for mobile communication systems, is considering a fifth-generation (hereinafter sometimes referred to as "5G") wireless access system as a successor to Long Term Evolution (LTE) and Long Term Evolution Advanced (LTE-A), one of the fourth-generation wireless access systems (see Non-Patent Document 1) (for example, Non-Patent Document 2). The technology for the wireless section of 5G is called "New Radio Access Technology" ("New Radio" is abbreviated as "NR"). The NR system is being studied based on the LTE system and the LTE-A system.

[0003] For example, in Europe, an organization called METIS has compiled 5G requirements (see Non-Patent Document 3). The requirements for a 5G wireless access system are that it must have 1000 times the system capacity, 100 times the data transmission speed, one-fifth the data processing delay, and 100 times the number of simultaneous connections of communication terminals compared to an LTE system, while also achieving further reductions in power consumption and cost reductions for the equipment (see Non-Patent Document 3).

[0004] In order to meet such demands, 3GPP is currently studying 5G standards (see Non-Patent Documents 4 to 23).

[0005] The NR access method uses OFDM (Orthogonal Frequency Division Multiplexing) in the downlink direction and OFDM and DFT-s-OFDM (Discrete Fourier Transform-spread-OFDM) in the uplink direction. Also, like LTE and LTE-A, the 5G system does not include circuit switching and is only a packet communication method.

[0006] NR allows the use of higher frequencies than LTE in order to improve transmission speeds and reduce processing delays.

[0007] In NR, which may use higher frequencies than LTE, cell coverage is ensured by forming a narrow beam-shaped transmission and reception range (beam forming) and changing the direction of the beam (beam sweeping).

[0008] The decisions made by 3GPP regarding the frame structure in an NR system, as described in Non-Patent Document 1 (Chapter 5), are explained using Figure 1. Figure 1 is an explanatory diagram showing the structure of a radio frame used in an NR communication system. In Figure 1, one radio frame is 10 ms. The radio frame is divided into 10 equally sized subframes. The NR frame structure supports one or more numerologies, i.e., one or more subcarrier spacings (SCSs). In NR, one subframe is 1 ms long, and one slot consists of 14 symbols, regardless of the subcarrier spacing. Furthermore, the number of slots included in one subframe is one when the subcarrier spacing is 15 kHz, and the number of slots at other subcarrier spacings increases in proportion to the subcarrier spacing (see Non-Patent Document 11 (3GPP TS38.211)).

[0009] 3GPP's decisions regarding channel configuration in NR systems are described in Non-Patent Document 2 (Chapter 5) and Non-Patent Document 11.

[0010] A physical broadcast channel (PBCH) is a channel for downlink transmission from a base station device (hereinafter sometimes simply referred to as a "base station") to a communication terminal device (hereinafter sometimes referred to as a "communication terminal" or "terminal") such as a mobile terminal device (hereinafter sometimes simply referred to as a "mobile terminal"). The PBCH is transmitted together with a downlink synchronization signal.

[0011] Downlink synchronization signals in NR include a primary synchronization signal (P-SS) and a secondary synchronization signal (S-SS). Synchronization signals are transmitted from base stations as synchronization signal bursts (hereinafter sometimes referred to as SS bursts) at predetermined intervals and for a predetermined duration. SS bursts are composed of synchronization signal blocks (hereinafter sometimes referred to as SS blocks) for each beam of the base station.

[0012] The base station transmits the SS block of each beam by changing the beam during the duration of the SS burst. The SS block consists of the P-SS, S-SS, and PBCH.

[0013] The Physical Downlink Control Channel (PDCCH) is a channel for downlink transmission from a base station to a communication terminal. The PDCCH carries downlink control information (DCI). The DCI includes resource allocation information for a Downlink Shared Channel (DL-SCH), which is one of the transport channels described below, resource allocation information for a Paging Channel (PCH), which is one of the transport channels described below, and Hybrid Automatic Repeat reQuest (HARQ) information related to the DL-SCH. The DCI may also include an uplink scheduling grant. The DCI may also include an acknowledgement (Ack) / negative acknowledgement (Nack), which is a response signal to the uplink transmission. In addition, in order to flexibly switch between DL and UL within a slot, the DCI may include a slot format indication (SFI). The PDCCH or the DCI is also called an L1 / L2 control signal.

[0014] In NR, a time-frequency region that is a candidate for including a PDCCH is provided. This region is called a control resource set (CORESET). A communication terminal monitors the CORESET and acquires a PDCCH.

[0015] The Physical Downlink Shared Channel (PDSCH) is a channel for downlink transmission from a base station to a communication terminal. The Downlink Shared Channel (DL-SCH), which is a transport channel, and the PCH, which is a transport channel, are mapped to the PDSCH.

[0016] The Physical Uplink Control Channel (PUCCH) is a channel for uplink transmission from a communication terminal to a base station. The PUCCH carries uplink control information (UCI). The UCI includes Ack / Nack, which is a response signal to a downlink transmission, CSI (Channel State Information), a scheduling request (SR), and the like. The CSI is composed of a Rank Indicator (RI), a Precoding Matrix Indicator (PMI), and a CQI (Channel Quality Indicator) report. The RI is rank information of a channel matrix in MIMO (Multiple Input Multiple Output). The PMI is information on a precoding weight matrix used in MIMO. The CQI is quality information indicating the quality of received data or the quality of a communication path. The UCI may be carried by the PUSCH, which will be described later. The PUCCH or UCI is also called an L1 / L2 control signal.

[0017] The Physical Uplink Shared Channel (PUSCH) is a channel for uplink transmission from a communication terminal to a base station. The Uplink Shared Channel (UL-SCH), which is one of the transport channels, is mapped to the PUSCH.

[0018] A physical random access channel (PRACH) is a channel for uplink transmission from a communication terminal to a base station. The PRACH carries a random access preamble.

[0019] A downlink reference signal (RS) is a known symbol in an NR communication system. The following four types of downlink reference signals are defined: a demodulation reference signal (DM-RS), which is a UE-specific reference signal, a phase tracking reference signal (PT-RS), a positioning reference signal (PRS), and a channel state information reference signal (CSI-RS). Measurements of the physical layer of a communication terminal include reference signal received power (RSRP) measurement and reference signal received quality (RSRQ) measurement.

[0020] Similarly, the uplink reference signal is a known symbol in an NR communication system. The following three types of uplink reference signals are defined: a data demodulation reference signal (DM-RS), a phase tracking reference signal (PT-RS), and a sounding reference signal (SRS).

[0021] The transport channels described in Non-Patent Document 2 (Chapter 5) will be described below. Among the downlink transport channels, a broadcast channel (BCH) is broadcast to the entire coverage of the base station (cell). The BCH is mapped to a physical broadcast channel (PBCH).

[0022] Retransmission control using HARQ is applied to the Downlink Shared Channel (DL-SCH). The DL-SCH can be broadcast to the entire coverage of the base station (cell). The DL-SCH supports dynamic or semi-static resource allocation. Semi-static resource allocation is also called semi-persistent scheduling. The DL-SCH supports discontinuous reception (DRX) in communication terminals to reduce power consumption of the communication terminals. The DL-SCH is mapped to the Physical Downlink Shared Channel (PDSCH).

[0023] The Paging Channel (PCH) supports DRX of communication terminals to enable low power consumption of the communication terminals. The PCH is required to broadcast to the entire coverage of the base station (cell). The PCH is mapped to physical resources such as the Physical Downlink Shared Channel (PDSCH) that can be dynamically used for traffic.

[0024] Among the uplink transport channels, the uplink shared channel (UL-SCH) is subject to retransmission control using HARQ. The UL-SCH supports dynamic or semi-static resource allocation. Semi-static resource allocation is also called configured grant. The UL-SCH is mapped to the physical uplink shared channel (PUSCH).

[0025] The Random Access Channel (RACH) is limited to control information, has a risk of collision, and is mapped to the Physical Random Access Channel (PRACH).

[0026] The following describes HARQ. HARQ is a technology that improves the communication quality of a transmission path by combining Automatic Repeat reQuest (ARQ) and Forward Error Correction. HARQ has the advantage that error correction functions effectively through retransmission even for transmission paths whose communication quality varies. In particular, by combining the reception result of the initial transmission and the reception result of the retransmission when retransmitting, it is possible to obtain further quality improvement.

[0027] An example of a retransmission method will be described below. If the receiving side is unable to decode the received data correctly, in other words, if a CRC (Cyclic Redundancy Check) error occurs (CRC=NG), the receiving side will send a "Nack" to the transmitting side. The transmitting side, having received the "Nack", will retransmit the data. If the receiving side is able to decode the received data correctly, in other words, if no CRC error occurs (CRC=OK), the receiving side will send an "Ack" to the transmitting side. The transmitting side, having received the "Ack", will send the next data.

[0028] Another example of a retransmission method will be described. If a CRC error occurs on the receiving side, the receiving side requests a retransmission from the transmitting side. The retransmission request is made by toggling an NDI (New Data Indicator). The transmitting side, upon receiving the retransmission request, retransmits the data. If no CRC error occurs on the receiving side, no retransmission request is made. If the transmitting side does not receive a retransmission request for a predetermined period of time, it assumes that no CRC error occurred on the receiving side.

[0029] The logical channels described in Non-Patent Document 1 (Chapter 6) are explained below. The Broadcast Control Channel (BCCH) is a downlink channel for broadcasting system control information. The BCCH, which is a logical channel, is mapped to the broadcast channel (BCH) or the downlink shared channel (DL-SCH), which are transport channels.

[0030] The Paging Control Channel (PCCH) is a downlink channel for transmitting paging information and changes to system information. The PCCH, which is a logical channel, is mapped to the Paging Channel (PCH), which is a transport channel.

[0031] The Common Control Channel (CCCH) is a channel for transmitting control information between a communication terminal and a base station. The CCCH is used when the communication terminal does not have an RRC connection with the network. In the downlink direction, the CCCH is mapped to the Downlink Shared Channel (DL-SCH), which is a transport channel. In the uplink direction, the CCCH is mapped to the Uplink Shared Channel (UL-SCH), which is a transport channel.

[0032] A Dedicated Control Channel (DCCH) is a channel that transmits dedicated control information between a communication terminal and a network in a one-to-one relationship. The DCCH is used when the communication terminal has an RRC connection with the network. The DCCH is mapped to an uplink shared channel (UL-SCH) in the uplink and to a downlink shared channel (DL-SCH) in the downlink.

[0033] A Dedicated Traffic Channel (DTCH) is a point-to-point communication channel for transmitting user information to a communication terminal. DTCH exists in both uplink and downlink. In uplink, DTCH is mapped to an uplink shared channel (UL-SCH) and in downlink, it is mapped to a downlink shared channel (DL-SCH).

[0034] The location of a communication terminal is tracked in units of an area consisting of one or more cells. Location tracking is performed to track the location of the communication terminal even when it is in standby mode and to call the communication terminal, in other words, to enable the communication terminal to receive calls. The area for tracking the location of this communication terminal is called a Tracking Area (TA).

[0035] In NR, paging of communication terminals within a range that is smaller than a tracking area is supported. This range is called a RAN Notification Area (RNA). Paging of communication terminals in the RRC_INACTIVE state, which will be described later, is performed within this range.

[0036] In NR, in order to support wide frequency bandwidths (transmission bandwidths), carrier aggregation (CA) is being considered, which aggregates (also referred to as "aggregation") two or more component carriers (CCs). CA is described in Non-Patent Document 1.

[0037] When CA is configured, a communication terminal (UE) has only one RRC connection with the network (NW). In the RRC connection, one serving cell provides NAS (Non-Access Stratum) mobility information and security input. This cell is called a primary cell (PCell). Depending on the UE's capabilities, a secondary cell (SCell) is configured to form a serving cell set together with the PCell. A serving cell set consisting of one PCell and one or more SCells is configured for one UE.

[0038] In addition, in 3GPP, in order to further increase communication capacity, there is a dual connectivity (abbreviated as DC) in which a UE connects to two base stations to communicate. DC is described in Non-Patent Documents 1 and 22.

[0039] Of the base stations performing dual connectivity (DC), one may be referred to as a "master base station (Master Node: MN)" and the other as a "secondary base station (Secondary Node: SN)." Serving cells configured by the master base station may be collectively referred to as a master cell group (MCG), and serving cells configured by secondary base stations may be collectively referred to as a secondary cell group (SCG). In DC, the primary cell in the MCG or SCG is referred to as a special cell (SpCell or SPCell). The special cell in the MCG is referred to as a PCell, and the special cell in the SCG is referred to as a primary SCG cell (PSCell).

[0040] In addition, in NR, the base station pre-sets a portion of the carrier frequency band (hereinafter sometimes referred to as the Bandwidth Part (BWP)) for the UE, and the UE transmits and receives data to and from the base station using this BWP, thereby reducing power consumption in the UE.

[0041] Additionally, 3GPP is considering supporting services (or applications) using side link (SL) communication (also referred to as PC5 communication) in both the Evolved Packet System (EPS) (described later) and the 5G core system (see Non-Patent Documents 1, 2, 26 to 28). SL communication involves communication between terminals. Services using SL communication include, for example, vehicle-to-everything (V2X) services and proximity services. In SL communication, not only direct communication between terminals but also communication between a UE and a network via a relay has been proposed (see Non-Patent Documents 26 and 28).

[0042] The physical channels used for SL (see Non-Patent Documents 2 and 11) are as follows: The physical sidelink broadcast channel (PSBCH) carries information related to the system and synchronization and is transmitted from the UE.

[0043] The physical sidelink control channel (PSCCH) carries control information from the UE for sidelink and V2X sidelink communications.

[0044] The physical sidelink shared channel (PSSCH) carries data from the UE for sidelink and V2X sidelink communications.

[0045] The physical sidelink feedback channel (PSFCH) carries HARQ feedback on the sidelink from a UE that received a PSSCH transmission to the UE that transmitted the PSSCH.

[0046] The transport channel used for SL (see Non-Patent Document 1) will be described. The sidelink broadcast channel (SL-BCH) has a predetermined transport format and is mapped to the PSBCH, which is a physical channel.

[0047] The Sidelink Shared Channel (SL-SCH) supports broadcast transmissions. The SL-SCH supports both UE autonomous resource selection and base station scheduled resource allocation. UE autonomous resource selection involves a collision risk, whereas when the UE is allocated dedicated resources by the base station, there is no collision. The SL-SCH also supports dynamic link adaptation by changing transmit power, modulation, and coding. The SL-SCH is mapped to the PSSCH, which is a physical channel.

[0048] The logical channels used for SL (see Non-Patent Document 2) will be described. The Sidelink Broadcast Control Channel (SBCCH) is a sidelink channel for broadcasting sidelink system information from one UE to other UEs. The SBCCH is mapped to the SL-BCH, which is a transport channel.

[0049] The Sidelink Traffic Channel (STCH) is a point-to-multipoint traffic channel for transmitting user information from one UE to other UEs. The STCH is used only by UEs with sidelink communication capability and UEs with V2X sidelink communication capability. Point-to-point communication between two sidelink-capable UEs is also realized by the STCH. The STCH is mapped to the SL-SCH, a transport channel.

[0050] The Sidelink Control Channel (SCCH) is a control channel for transmitting control information from one UE to another UE. The SCCH is mapped to the SL-SCH, which is a transport channel.

[0051] In LTE, only broadcast was supported for SL communication. In NR, support for unicast and groupcast as SL communication in addition to broadcast is being considered (see Non-Patent Document 27 (3GPP TS23.287)).

[0052] In unicast communication and groupcast communication in SL, HARQ feedback (Ack / Nack), CSI reporting, etc. are supported.

[0053] In addition, 3GPP is considering integrated access and backhaul (IAB), which performs both the access link between a UE and a base station and the backhaul link between base stations wirelessly (see Non-Patent Documents 2, 20, and 29).

[0054] Several new technologies have been proposed for mobile communication systems, such as a technology that allows a single terminal to connect to multiple networks simultaneously to improve communication capacity and reliability (see Non-Patent Documents 30 and 31).

[0055] 3GPP TS36.300 V17.3.03GPP TS38.300 V17.3.0 “Scenarios, requirements and KPIs for 5G mobile and wireless system”, ICT-317669-METIS / D1.13GPP TR23.799 V14.0.03GPP TR38.801 V14.0.03GPP TR38.802 V14.2.03GPP TR38.804 V14.0.03GPP TR38.912 V16.0.03GPP RP-1721153GPP TS23.501 V18.0.03GPP TS38.211 V17.4.03GPP TS38.212 V17.4.03GPP TS38.213 V17.4.03GPP TS38.214 V17.4.03GPP TS38.321 V17.3.03GPP TS38.322 V17.2.03GPP TS38.323 V17.3.03GPP TS37.324 V17.0.03GPP TS38.331 V17.3.03GPP TS38.401 V17.3.03GPP TS38.413 V17.3.03GPP TS37.340 V17.3.03GPP TS38.423 V17.3.03GPP TS38.305 V17.3.03GPP TS23.273 V18.0.03GPP TR23.703 V12.0.03GPP TS23.287 V17.5.03GPP TS23.303 V17.0.03GPP TS38.340 V17.3.03GPP SWS-2300493GPP TS23.502 V18.2.0

[0056] In a mobile communication system, a UE may be connected to multiple networks. When the UE connects to multiple networks, a network to which the UE is connected may be added. However, no specific process for adding a network is disclosed. As a result, a connection with multiple networks cannot be established, which causes problems such as an inability to improve communication capacity and reliability.

[0057] In view of the above-mentioned problems, one of the objectives of the present disclosure is to improve communication capacity and reliability in a communication network by adding a network to which a UE is connected.

[0058] The communication system disclosed herein is a communication system compatible with a fifth-generation wireless access system, and includes multiple networks including a wireless access network and a core network. An anchor network, which is a network to which a communication terminal is connected and has a user plane function that directly connects to a data network to which the communication terminal sends and receives data, determines whether or not it is necessary to add a network to which the communication terminal connects based on information regarding the communication quality between the communication terminal and the data network, and if it is necessary to add a network to which the communication terminal connects, selects an additional network. The network selected as the additional network by the anchor network performs a registration process to connect to the communication terminal.

[0059] According to the present disclosure, a communication system can be obtained that can improve communication capacity and reliability in a communication network by adding a network to which a UE is connected.

[0060] The objects, features, aspects, and advantages of the present disclosure will become more apparent from the following detailed description and the accompanying drawings.

[0061] 1 is an explanatory diagram showing the configuration of a radio frame used in an NR communication system. FIG. 2 is a block diagram showing the overall configuration of an NR communication system 210 being discussed in 3GPP. FIG. 3 is a configuration diagram of DC by a base station connected to an NG core. FIG. 4 is a block diagram showing the configuration of a mobile terminal 202 shown in FIG. 2. FIG. 5 is a block diagram showing the configuration of a base station 213 shown in FIG. 2. FIG. 6 is a block diagram showing the configuration of a 5GC unit. FIG. 7 is a flowchart showing an overview of operations from cell search to standby operations performed by a communication terminal (UE) in an NR communication system. FIG. 8 is a diagram showing an example of a cell configuration in an NR system. FIG. 9 is a connection configuration diagram showing an example of a connection configuration of a terminal in SL communication. FIG. 10 is a connection configuration diagram showing an example of a connection configuration of a base station that supports access / backhaul integration. FIG. 11 is a sequence diagram showing an example of operations until an SMF decides to add a connection NW for a UE, according to a first embodiment. FIG. 12 is a sequence diagram showing another example of operations until an SMF decides to add a connection NW for a UE, according to a first embodiment. FIG. 13 is a sequence diagram showing another example of operations until an SMF decides to add a connection NW for a UE, according to a first embodiment. 10 is a diagram of the second half of a sequence illustrating an example of a registration process and a PDU session establishment process between a UE and an additional target NW according to a first embodiment. FIG. 11 is a diagram of the first half of a sequence illustrating an example of an operation of releasing a NW connected to a UE according to a second embodiment. FIG. 12 is a diagram of the second half of a sequence illustrating an example of an operation of releasing a NW connected to a UE according to a second embodiment. FIG. 13 is a sequence diagram illustrating another example of an operation of releasing a NW connected to a UE according to a second embodiment. FIG. 14 is a diagram of the first half of a sequence illustrating another example of an operation of releasing a NW connected to a UE according to a second embodiment. FIG. 15 is a diagram of the second half of a sequence illustrating another example of an operation of releasing a NW connected to a UE according to a fourth embodiment. FIG. 16 is a diagram of another example of a network configuration in which a plurality of anchor UPFs exist according to a fourth embodiment.

[0062] Embodiment 1. Figure 2 is a block diagram showing the overall configuration of an NR communication system 210 being discussed in 3GPP. Figure 2 will be explained. The radio access network is called an NG-RAN (Next Generation Radio Access Network) 211. A mobile terminal device (hereinafter referred to as a "mobile terminal (User Equipment: UE)") 202, which is a communication terminal device, is capable of wireless communication with a base station device (hereinafter referred to as an "NR base station (NG-RAN NodeB: gNB)") 213, and transmits and receives signals via wireless communication. The NG-RAN 211 is composed of one or more NR base stations 213.

[0063] Here, the term "communication terminal device" includes not only mobile terminal devices such as mobile cell phone terminal devices, but also stationary devices such as sensors. In the following description, the term "communication terminal device" may be simply referred to as a "communication terminal."

[0064] An access stratum (AS) protocol is terminated between the UE 202 and the NG-RAN 211. Examples of AS protocols include radio resource control (RRC), service data adaptation protocol (SDAP), packet data convergence protocol (PDCP), radio link control (RLC), medium access control (MAC), and physical layer (PHY). RRC is used in the control plane (hereinafter sometimes referred to as the C-plane, C-Plane, or CP), SDAP is used in the user plane (hereinafter sometimes referred to as the U-plane, U-Plane, or UP), and PDCP, MAC, RLC, and PHY are used in both the C-plane and the U-plane.

[0065] The control protocol RRC (Radio Resource Control) between the UE 202 and the NR base station 213 performs broadcasting, paging, RRC connection management, etc. The states of the NR base station 213 and the UE 202 in RRC include RRC_IDLE, RRC_CONNECTED, and RRC_INACTIVE.

[0066] In RRC_IDLE, PLMN (Public Land Mobile Network) selection, system information (SI) broadcast, paging, cell re-selection, mobility, etc. are performed. In RRC_CONNECTED, the mobile terminal has an RRC connection and can transmit and receive data with the network. In addition, in RRC_CONNECTED, handover (HO), measurement of neighbor cells, etc. are performed. In RRC_INACTIVE, the connection between the 5G core unit 214 and the NR base station 213 is maintained, and system information (SI) broadcast, paging, cell re-selection, mobility, etc. are performed.

[0067] The gNB 213 is connected to a 5G core unit (hereinafter sometimes referred to as the "5GC unit") 214, which includes an Access and Mobility Management Function (AMF), a Session Management Function (SMF), or a User Plane Function (UPF), via an NG interface. Control information and / or user data is communicated between the gNB 213 and the 5GC unit 214. The NG interface is a collective term for the N2 interface between the gNB 213 and the AMF 220, the N3 interface between the gNB 213 and the UPF 221, the N11 interface between the AMF 220 and the SMF 222, and the N4 interface between the UPF 221 and the SMF 222. Multiple 5GC units 214 may be connected to one gNB 213. The gNBs 213 are connected via an Xn interface, and control information and / or user data are communicated between the gNBs 213.

[0068] The 5GC unit 214 is a higher-level device, specifically a higher-level node, and controls the connection between the NR base station 213 and the mobile terminal (UE) 202, distributes paging signals to one or more NR base stations (gNB) 213 and / or LTE base stations (E-UTRAN NodeB: eNB), and performs other functions. The 5GC unit 214 also performs mobility control in the idle state. The 5GC unit 214 manages the tracking area list when the mobile terminal 202 is in the idle state, in the inactive state, and in the active state. The 5GC unit 214 initiates a paging protocol by transmitting a paging message to a cell belonging to the tracking area in which the mobile terminal 202 is registered.

[0069] The gNB 213 may configure one or more cells. When one gNB 213 configures multiple cells, each cell is configured to be able to communicate with the UE 202.

[0070] The gNB 213 may be divided into a central unit (hereinafter, sometimes referred to as CU) 215 and a distributed unit (hereinafter, sometimes referred to as DU) 216. One CU 215 is configured within the gNB 213. One or more DUs 216 are configured within the gNB 213. One DU 216 configures one or more cells. The CU 215 is connected to the DU 216 via an F1 interface, and control information and / or user data is communicated between the CU 215 and the DU 216. The F1 interface consists of an F1-C interface and an F1-U interface. The CU 215 is responsible for the functions of the RRC, SDAP, and PDCP protocols, and the DU 216 is responsible for the functions of the RLC, MAC, and PHY protocols. One or more TRPs (Transmission Reception Points) 219 may be connected to the DU 216. The TRP 219 transmits and receives radio signals to and from the UE.

[0071] The CU 215 may be divided into a C-plane CU (CU-C) 217 ​​and a U-plane CU (CU-U) 218. One CU-C 217 is configured within the CU 215. One or more CU-Us 218 are configured within the CU 215. The CU-C 217 is connected to the CU-U 218 via an E1 interface, and control information is communicated between the CU-C 217 and the CU-U 218. The CU-C 217 is connected to the DU 216 via an F1-C interface, and control information is communicated between the CU-C 217 and the DU 216. The CU-U 218 is connected to the DU 216 via an F1-U interface, and user data is communicated between the CU-U 218 and the DU 216.

[0072] In a 5G communication system, a Unified Data Management (UDM) function and a Policy Control Function (PCF) described in Non-Patent Document 10 (3GPP TS23.501) may be included. The UDM and / or PCF may be included in the 5GC unit 214 in FIG. 2 .

[0073] In a 5G communication system, a Location Management Function (LMF) described in Non-Patent Document 24 (3GPP TS 38.305) may be provided. The LMF may be connected to a base station via an AMF as disclosed in Non-Patent Document 25 (3GPP TS 23.273).

[0074] A 5G communication system may include a Non-3GPP Interworking Function (N3IWF) described in Non-Patent Document 10 (3GPP TS23.501). The N3IWF may terminate an Access Network (AN) between the UE and the N3IWF in non-3GPP access between the UE and the N3IWF.

[0075] FIG. 3 is a diagram showing a DC (dual connectivity) configuration connected to an NG core. In FIG. 3, solid lines indicate U-Plane connections, and dashed lines indicate C-Plane connections. In FIG. 3, the master base station 240-1 may be a gNB or an eNB. Furthermore, the secondary base station 240-2 may be a gNB or an eNB. For example, in FIG. 3, a DC configuration in which the master base station 240-1 is a gNB and the secondary base station 240-2 is an eNB may be referred to as NG-EN-DC. In FIG. 3, an example is shown in which the U-Plane connection between the 5GC unit 214 and the secondary base station 240-2 is performed via the master base station 240-1, but it may also be performed directly between the 5GC unit 214 and the secondary base station 240-2. 3, an EPC (Evolved Packet Core), which is a core network connected to the LTE system and the LTE-A system, may be connected to the master base station 240-1 instead of the 5GC unit 214. A U-Plane connection may be directly established between the EPC and the secondary base station 240-2.

[0076] FIG. 4 is a block diagram showing the configuration of mobile terminal 202 shown in FIG. 2. The transmission process of mobile terminal 202 shown in FIG. 4 will be described. First, control data from control unit 310 and user data from application unit 302 are sent to protocol processing unit 301. Buffering of the control data and user data may be performed. Buffers for the control data and user data may be provided in control unit 310, application unit 302, or protocol processing unit 301. Protocol processing unit 301 performs protocol processing such as SDAP, PDCP, RLC, and MAC, for example, determining a destination base station in DC, and adding a header for each protocol. The protocol-processed data is passed to encoder unit 304, where it is subjected to encoding such as error correction. Some data may be output directly from protocol processing unit 301 to modulation unit 305 without being encoded. The data encoded by encoder unit 304 is modulated by modulation unit 305. Precoding in MIMO may be performed by modulation unit 305. The modulated data is converted into a baseband signal, and then output to frequency conversion section 306, where it is converted into a radio transmission frequency. Then, the transmission signal is transmitted from antennas 307-1 to 307-4 to base station 213. Although the example in FIG. 4 shows a case where the number of antennas is four, the number of antennas is not limited to four.

[0077] Furthermore, the reception process of the mobile terminal 202 is performed as follows. Radio signals from the base station 213 are received by the antennas 307-1 to 307-4. The received signals are converted from a radio reception frequency to a baseband signal by the frequency conversion unit 306, and demodulated by the demodulation unit 308. The demodulation unit 308 may also perform weight calculation and multiplication processing. The demodulated data is passed to the decoder unit 309, where decoding processes such as error correction are performed. The decoded data is passed to the protocol processing unit 301, where protocol processing such as MAC, RLC, PDCP, and SDAP is performed, for example, operations such as removing headers in each protocol. Of the data that has undergone protocol processing, the control data is passed to the control unit 310, and the user data is passed to the application unit 302.

[0078] A series of processes in the mobile terminal 202 is controlled by a control unit 310. Therefore, the control unit 310 is also connected to each of the units 302, 304 to 309, although this is omitted in FIG.

[0079] Each unit of the mobile terminal 202, such as the control unit 310, protocol processing unit 301, encoder unit 304, and decoder unit 309, is implemented by a processing circuit including, for example, a processor and memory. For example, the control unit 310 is implemented by a processor executing a program describing a series of processes performed by the mobile terminal 202. The program describing the series of processes performed by the mobile terminal 202 is stored in memory. Examples of memory include non-volatile or volatile semiconductor memory such as RAM (Random Access Memory), ROM (Read Only Memory), and flash memory. Each unit of the mobile terminal 202, such as the control unit 310, protocol processing unit 301, encoder unit 304, and decoder unit 309, may be implemented by a dedicated processing circuit such as an FPGA (Field Programmable Gate Array), an ASIC (Application Specific Integrated Circuit), or a DSP (Digital Signal Processor). In FIG. 4, the number of antennas used by the mobile terminal 202 for transmission and the number of antennas used for reception may be the same or different.

[0080] 5 is a block diagram showing the configuration of the base station 213 shown in FIG. 2. The transmission process of the base station 213 shown in FIG. 5 will be described. The EPC communication unit 401 transmits and receives data between the base station 213 and the EPC. The 5GC communication unit 412 transmits and receives data between the base station 213 and the 5GC (such as the 5GC unit 214). The other base station communication unit 402 transmits and receives data with other base stations. The EPC communication unit 401, the 5GC communication unit 412, and the other base station communication unit 402 each exchange information with the protocol processing unit 403. Control data from the control unit 411, and user data and control data from the EPC communication unit 401, the 5GC communication unit 412, and the other base station communication unit 402 are sent to the protocol processing unit 403. Buffering of the control data and user data may be performed. Buffers for control data and user data may be provided in the control unit 411, the EPC communication unit 401, the 5GC communication unit 412, or the other base station communication unit 402.

[0081] The protocol processing unit 403 performs protocol processing such as SDAP, PDCP, RLC, MAC, etc., such as routing transmission data in DC, etc., and adding headers for each protocol. The protocol-processed data is passed to the encoder unit 405, where it is subjected to encoding processing such as error correction. Some data may be output directly from the protocol processing unit 403 to the modulation unit 406 without being encoded. Data may also be sent from the protocol processing unit 403 to the other base station communication unit 402. For example, in DC, data sent from the 5GC communication unit 412 or the EPC communication unit 401 may be sent to another base station, such as a secondary base station, via the other base station communication unit 402. The encoded data is modulated by the modulation unit 406. The modulation unit 406 may also perform MIMO precoding. The modulated data is converted into a baseband signal, and then output to the frequency conversion unit 407, where it is converted into a radio transmission frequency. Thereafter, the transmission signals are transmitted from antennas 408-1 to 408-4 to one or more mobile terminals 202. Although the number of antennas is four in the example shown in Fig. 5, the number of antennas is not limited to four.

[0082] Furthermore, the reception process of the base station 213 is performed as follows. Radio signals from one or more mobile terminals 202 are received by antennas 408-1 to 408-4. The received signals are converted from a radio reception frequency to a baseband signal by a frequency conversion unit 407, and demodulated by a demodulation unit 409. The demodulated data is passed to a decoder unit 410, where decoding processes such as error correction are performed. The decoded data is passed to a protocol processing unit 403, where protocol processes such as MAC, RLC, PDCP, and SDAP are performed, for example, operations such as removing headers in each protocol. Of the data that has undergone protocol processing, control data is passed to the control unit 411, 5GC communication unit 412, EPC communication unit 401, or other base station communication unit 402, and user data is passed to the 5GC communication unit 412, EPC communication unit 401, or other base station communication unit 402. Data sent from the other base station communication unit 402 may be sent to the 5GC communication unit 412 or the EPC communication unit 401. The data may be, for example, uplink data sent to the 5GC communication unit 412 or the EPC communication unit 401 via another base station in DC.

[0083] A series of processes in the base station 213 is controlled by a control unit 411. Therefore, the control unit 411 is also connected to each of the units 401, 402, 405 to 410, and 412, although this is omitted in FIG.

[0084] Each unit of the base station 213, for example, the control unit 411, the protocol processing unit 403, the 5GC communication unit 412, the EPC communication unit 401, the other base station communication unit 402, the encoder unit 405, and the decoder unit 410, is realized by a processing circuit including a processor and a memory, or a dedicated processing circuit such as an FPGA, an ASIC, or a DSP, similar to the above-mentioned mobile terminal 202. In Fig. 5, the number of antennas used by the base station 213 for transmission and the number of antennas used for reception may be the same or different.

[0085] As an example of the configuration of the CU 215 shown in Fig. 2, a configuration in which a DU communication unit is provided is sometimes used, excluding the encoder unit 405, modulation unit 406, frequency conversion unit 407, antennas 408-1 to 408-4, demodulation unit 409, and decoder unit 410 shown in Fig. 5. The DU communication unit is connected to a protocol processing unit 403. The protocol processing unit 403 in the CU 215 performs protocol processing such as PDCP and SDAP.

[0086] As an example of the configuration of the DU 216 shown in Fig. 2, a configuration in which a CU communication unit is provided may be used, excluding the EPC communication unit 401, other base station communication unit 402, and 5GC communication unit 412 shown in Fig. 5. The CU communication unit is connected to a protocol processing unit 403. The protocol processing unit 403 in the DU 216 performs protocol processing such as PHY, MAC, and RLC.

[0087] FIG. 6 is a block diagram showing the configuration of the 5GC unit. FIG. 6 shows the configuration of the 5GC unit 214 shown in FIG. 2 described above. FIG. 6 shows a case where the 5GC unit 214 shown in FIG. 2 includes an AMF configuration, an SMF configuration, and a UPF configuration. In the example shown in FIG. 6, the AMF may have the function of the control plane control unit 525, the SMF may have the function of the session management unit 527, and the UPF may have the functions of the user plane communication unit 523 and the Data Network communication unit 521. The Data Network communication unit 521 transmits and receives data between the 5GC unit 214 and the Data Network. The base station communication unit 522 transmits and receives data via the NG interface between the 5GC unit 214 and the base station 213. User data sent from the Data Network is passed from the Data Network communication unit 521 to the base station communication unit 522 via the user plane communication unit 523, and then transmitted to one or more base stations 213. User data sent from the base station 213 is passed from the base station communication unit 522 to the Data Network communication unit 521 via the user plane communication unit 523, and then transmitted to the Data Network.

[0088] The control data sent from the base station 213 is passed from the base station communication unit 522 to the control plane control unit 525. The control plane control unit 525 may pass the control data to the session management unit 527. The control data may be sent from the Data Network. The control data sent from the Data Network may be sent from the Data Network communication unit 521 to the session management unit 527 via the user plane communication unit 523. The session management unit 527 may send the control data to the control plane control unit 525.

[0089] The user plane communication unit 523 includes a PDU processing unit 523-1, a mobility anchoring unit 523-2, etc., and performs general processing for the user plane (hereinafter sometimes referred to as U-Plane). The PDU processing unit 523-1 processes data packets, for example, transmitting and receiving packets to and from the Data Network communication unit 521, and transmitting and receiving packets to and from the base station communication unit 522. The mobility anchoring unit 523-2 is responsible for anchoring the data path during UE mobility.

[0090] The session management unit 527 manages the PDU session established between the UE and the UPF. The session management unit 527 includes a PDU session control unit 527-1, a UE IP address allocation unit 527-2, etc. The PDU session control unit 527-1 manages the PDU session between the mobile terminal 202 and the 5GC unit 214. The UE IP address allocation unit 527-2 assigns an IP address to the mobile terminal 202, etc.

[0091] The control plane control unit 525 includes a NAS security unit 525-1, an idle state mobility management unit 525-2, etc., and performs overall processing for the control plane (hereinafter sometimes referred to as the C-Plane). The NAS security unit 525-1 performs security for NAS (Non-Access Stratum) messages, etc. The idle state mobility management unit 525-2 performs mobility management in the standby state (idle state: also referred to as RRC_IDLE state or simply idle), generation and control of paging signals in the standby state, addition, deletion, update, search, tracking area list management, etc. for one or more mobile terminals 202 under its control.

[0092] A series of processes of the 5GC unit 214 is controlled by a control unit 526. Therefore, although the control unit 526 is omitted in Fig. 6, it is connected to each unit 521 to 523, 525, and 527. Like the control unit 310 of the mobile terminal 202 described above, each unit of the 5GC unit 214 is realized by, for example, a processing circuit configured to include a processor and memory, or a dedicated processing circuit such as an FPGA, ASIC, or DSP.

[0093] Next, an example of a cell search method in a communication system is shown. Fig. 7 is a flowchart showing an outline of the process from cell search to standby operation performed by a communication terminal (UE) in an NR communication system. When the communication terminal starts a cell search, in step ST601, it synchronizes slot timing and frame timing using a primary synchronization signal (P-SS) and a secondary synchronization signal (S-SS) transmitted from a surrounding base station.

[0094] P-SS and S-SS are collectively called a synchronization signal (SS). A synchronization code is assigned to the synchronization signal (SS) in one-to-one correspondence with a PCI (Physical Cell Identifier) ​​assigned to each cell. 1008 different PCIs are being considered. A communication terminal synchronizes using these 1008 different PCIs and detects (identifies) the PCI of the synchronized cell.

[0095] In step ST602, the communication terminal receives the PBCH for the next synchronized cell. A master information block (MIB) including cell configuration information is mapped to the BCCH on the PBCH. Therefore, the MIB can be obtained by receiving the PBCH and obtaining the BCCH. Examples of MIB information include a system frame number (SFN), scheduling information for system information block (SIB) 1, subcarrier spacing for SIB1 and the like, and information on the DM-RS position.

[0096] Furthermore, the communication terminal acquires an SS block identifier from the PBCH. A part of the bit string of the SS block identifier is included in the MIB. The remaining bit string is included in an identifier used to generate a sequence of DM-RS associated with the PBCH. The communication terminal acquires the SS block identifier using the MIB included in the PBCH and the sequence of DM-RS associated with the PBCH.

[0097] Next, in step ST603, the communication terminal measures the received power of the SS block.

[0098] Next, in step ST604, the communication terminal selects the cell with the best reception quality, for example, the cell with the highest reception power, that is, the best cell, from among the one or more cells detected up to step ST603. The communication terminal also selects the beam with the best reception quality, for example, the beam with the highest reception power of the SS block, that is, the best beam. The reception power of the SS block for each SS block identifier is used, for example, to select the best beam.

[0099] Next, in step ST605, the communication terminal receives DL-SCH based on the scheduling information of SIB1 included in the MIB, and obtains SIB (System Information Block) 1 in the broadcast information BCCH. SIB1 includes information on access to the cell, cell configuration information, and scheduling information of other SIBs (SIBk: k is an integer greater than or equal to 2). SIB1 also includes a tracking area code (TAC).

[0100] Next, in step ST606, the communication terminal compares the TAC of SIB1 received in step ST605 with the TAC portion of the tracking area identity (TAI) in the tracking area list already held by the communication terminal. The tracking area list is also called a TAI list. The TAI is identification information for identifying a tracking area, and is composed of an MCC (Mobile Country Code), an MNC (Mobile Network Code), and a TAC (Tracking Area Code). The MCC is a country code. The MNC is a network code. The TAC is a tracking area code number.

[0101] If the comparison in step ST606 shows that the TAC received in step ST605 is the same as the TAC included in the tracking area list, the communication terminal enters standby mode in the cell. If the comparison shows that the TAC received in step ST605 is not included in the tracking area list, the communication terminal requests a core network (EPC) including an MME and the like to change the tracking area through the cell in order to perform a Tracking Area Update (TAU).

[0102] An apparatus constituting a core network (hereinafter sometimes referred to as a "core network apparatus") updates the tracking area list based on the identification number (e.g., UE-ID) of a communication terminal sent from the communication terminal together with a TAU request signal. The core network apparatus transmits the updated tracking area list to the communication terminal. The communication terminal rewrites (updates) the TAC list held by the communication terminal based on the received tracking area list. Thereafter, the communication terminal enters standby mode in the cell.

[0103] Next, examples of random access methods in a communication system are shown. Four-step random access and two-step random access are used for random access. For each of the four-step and two-step random access methods, there is contention-based random access, i.e., random access in which timing collisions with other mobile terminals may occur, and contention-free random access.

[0104] An example of a collision-based four-step random access method is shown below. In the first step, the mobile terminal transmits a random access preamble to the base station. The random access preamble may be selected by the mobile terminal from a predetermined range, or may be individually assigned to the mobile terminal and notified by the base station.

[0105] In the second step, the base station transmits a random access response to the mobile terminal, which includes uplink scheduling information used in the third step, a terminal identifier used in the uplink transmission in the third step, and the like.

[0106] In the third step, the mobile terminal performs uplink transmission to the base station. The mobile terminal uses the information acquired in the second step for uplink transmission. In the fourth step, the base station notifies the mobile terminal whether or not the collision has been resolved. If the mobile terminal is notified that there is no collision, it ends the random access process. If the mobile terminal is notified that there is a collision, it starts the process over from the first step.

[0107] The contention-free four-step random access method differs from the contention-based four-step random access method in the following points: Prior to the first step, the base station pre-assigns a random access preamble and uplink scheduling to the mobile terminal, and the notification of whether or not contention has been resolved in the fourth step is not required.

[0108] An example of a collision-based two-step random access method is shown below. In the first step, the mobile terminal transmits a random access preamble and performs uplink transmission to the base station. In the second step, the base station notifies the mobile terminal whether there is a collision. If the mobile terminal is notified that there is no collision, it terminates the random access process. If the mobile terminal is notified that there is a collision, it restarts the process from the first step.

[0109] The contention-free two-step random access method differs from the contention-based two-step random access method in the following points: prior to the first step, the base station pre-assigns a random access preamble and uplink scheduling to the mobile terminal, and in the second step, the base station transmits a random access response to the mobile terminal.

[0110] FIG. 8 shows an example of a cell configuration in NR. In an NR cell, narrow beams are formed and transmitted in different directions. In the example shown in FIG. 8, at certain times, base station 750 transmits and receives signals to and from a mobile terminal using beam 751-1. At other times, base station 750 transmits and receives signals to and from a mobile terminal using beam 751-2. In a similar manner, base station 750 transmits and receives signals to and from a mobile terminal using one or more of beams 751-3 to 751-8. In this way, base station 750 forms a wide-area cell 752.

[0111] 8 shows an example in which the number of beams used by the base station 750 is 8, but the number of beams may be different from 8. Also, in the example shown in FIG. 8, the number of beams used simultaneously by the base station 750 is 1, but it may be multiple.

[0112] The concept of Quasi-CoLocation (QCL) is used to identify beams (see Non-Patent Document 14 (3GPP TS38.214)). That is, the beam is identified by information indicating which reference signal (e.g., SS block, CSI-RS) the beam can be considered to be the same as. The information may include types of information regarding the aspects of the beams that can be considered to be the same, such as Doppler shift, Doppler shift spread, mean delay, mean delay spread, and spatial Rx parameters (see Non-Patent Document 14 (3GPP TS38.214)).

[0113] In 3GPP, a side link (SL) is supported for D2D (Device to Device) communication and V2V (Vehicle to Vehicle) communication (see Non-Patent Document 1 and Non-Patent Document 16). The SL is defined by the PC5 interface.

[0114] In order to support unicast and groupcast in addition to broadcast in SL communication, support for PC5-S signaling is being considered (see Non-Patent Document 27 (3GPP TS23.287)). For example, PC5-S signaling is implemented to establish a link for implementing SL, i.e., PC5 communication. The link is implemented in the V2X layer and is also called a Layer 2 link.

[0115] Furthermore, support for RRC signaling in SL communication is being considered (see Non-Patent Document 27 (3GPP TS23.287)). RRC signaling in SL communication is also referred to as PC5 RRC signaling. For example, it has been proposed to notify UE capabilities between UEs performing PC5 communication, or to notify AS layer settings for performing V2X communication using PC5 communication.

[0116] An example of a connection configuration of mobile terminals in SL communication is shown in Fig. 9. In the example shown in Fig. 9, UE 805 and UE 806 exist within the coverage 803 of base station 801. UL / DL communication 807 is performed between base station 801 and UE 805. UL / DL communication 808 is performed between base station 801 and UE 806. SL communication 810 is performed between UE 805 and UE 806. UE 811 and UE 812 exist outside the coverage 803. SL communication 814 is performed between UE 805 and UE 811. In addition, SL communication 816 is performed between UE 811 and UE 812.

[0117] As an example of communication between a UE and a NW via a relay in SL communication, a UE 805 shown in FIG. 9 relays communication between a UE 811 and a base station 801.

[0118] A configuration similar to that shown in FIG. 4 may be used for a UE that performs relaying. The relaying process in the UE will be described using FIG. 4. The relaying process by UE 805 in communication from UE 811 to base station 801 will be described. A radio signal from UE 811 is received by antennas 307-1 to 307-4. The received signal is converted from a radio reception frequency to a baseband signal by frequency conversion unit 306, and demodulated by demodulation unit 308. Weight calculation and multiplication processing may also be performed by demodulation unit 308. The demodulated data is passed to decoder unit 309, where decoding processing such as error correction is performed. The decoded data is passed to protocol processing unit 301, where protocol processing such as MAC and RLC used for communication with UE 811 is performed, such as removing headers in each protocol. Protocol processing such as RLC and MAC used for communication with base station 801 is also performed, such as adding headers in each protocol. Protocol processing of PDCP and SDAP may be performed in protocol processing unit 301 of UE 811. The protocol-processed data is passed to encoder unit 304, where encoding such as error correction is performed. Some data may be output directly from protocol processing unit 301 to modulation unit 305 without being encoded. The data encoded by encoder unit 304 is modulated by modulation unit 305. Precoding in MIMO may be performed by modulation unit 305. The modulated data is converted into a baseband signal, and then output to frequency conversion unit 306, where it is converted into a radio transmission frequency. Thereafter, a transmission signal is transmitted to base station 801 from antennas 307-1 to 307-4.

[0119] In the above, an example of relaying by UE 805 in communication from UE 811 to base station 801 has been shown, but similar processing is also used in relaying communication from base station 801 to UE 811.

[0120] 5G base stations can support integrated access and backhaul (IAB) (see Non-Patent Documents 2 and 20). A base station supporting IAB (hereinafter sometimes referred to as an IAB base station) is composed of an IAB donor CU, which is a CU of the base station operating as an IAB donor that provides IAB functions, an IAB donor DU, which is a DU of the base station operating as an IAB donor, and an IAB node connected to the IAB donor DU and to a UE via a radio interface. An F1 interface is provided between the IAB node and the IAB donor CU (see Non-Patent Document 2).

[0121] An example of IAB base station connections is shown in Figure 10. IAB donor CU 901 is connected to IAB donor DU 902. IAB node 903 is connected to IAB donor DU 902 using a wireless interface. IAB node 903 is connected to IAB node 904 using a wireless interface. In other words, IAB nodes may be connected in cascade. UE 905 is connected to IAB node 904 using a wireless interface. UE 906 may be connected to IAB node 903 using a wireless interface, and UE 907 may be connected to IAB donor DU 902 using a wireless interface. Multiple IAB donor DUs 902 may be connected to an IAB donor CU 901, multiple IAB nodes 903 may be connected to an IAB donor DU 902, and multiple IAB nodes 904 may be connected to an IAB node 903.

[0122] A BAP (Backhaul Adaptation Protocol) layer is provided in the connection between the IAB donor DU and the IAB node and in the connection between the IAB nodes (see Non-Patent Document 29). The BAP layer performs operations such as routing received data to the IAB donor DU and / or the IAB node, and mapping to an RLC channel (see Non-Patent Document 29).

[0123] As an example of the configuration of the IAB donor CU, a configuration similar to that of CU 215 is used.

[0124] An example of the configuration of the IAB donor DU is the same as that of the DU 216. The protocol processing unit of the IAB donor DU performs BAP layer processing, such as adding a BAP header to downstream data, routing to an IAB node, and removing the BAP header from upstream data.

[0125] As an example of the configuration of an IAB node, a configuration excluding the EPC communication unit 401, other base station communication unit 402, and 5GC communication unit 412 shown in Figure 5 may be used.

[0126] The transmission and reception processing at the IAB node will be described using FIGS. 5 and 10 . The transmission and reception processing at the IAB node 903 in communication between the IAB donor CU 901 and the UE 905 will be described. In uplink communication from the UE 905 to the IAB donor CU 901, a radio signal from the IAB node 904 is received by the antenna 408 (some or all of the antennas 408-1 to 408-4). The received signal is converted from a radio reception frequency to a baseband signal by the frequency conversion unit 407, and demodulated by the demodulation unit 409. The demodulated data is passed to the decoder unit 410, where decoding processing such as error correction is performed. The decoded data is passed to the protocol processing unit 403, where protocol processing such as MAC and RLC used for communication with the IAB node 904 is performed, such as removing headers in each protocol. In addition, routing to the IAB donor DU 902 is performed using a BAP header, and protocol processing such as RLC and MAC used for communication with the IAB donor DU 902, such as adding headers for each protocol, is performed. The protocol-processed data is passed to the encoder unit 405, where it is subjected to encoding processing such as error correction. Some data may be output directly from the protocol processing unit 403 to the modulation unit 406 without being encoded. The encoded data is modulated by the modulation unit 406. The modulation unit 406 may also perform precoding in MIMO. The modulated data is converted into a baseband signal, and then output to the frequency conversion unit 407, where it is converted into a radio transmission frequency. Then, a transmission signal is transmitted to the IAB donor DU 902 from antennas 408-1 to 408-4. Similar processing is performed in downlink communication from the IAB donor CU 901 to the UE 905.

[0127] The IAB node 904 also performs the same transmission and reception processing as the IAB node 903. The protocol processing unit 403 of the IAB node 903 performs BAP layer processing, such as adding a BAP header and routing to the IAB node 904 in upstream communication, and removing the BAP header in downstream communication.

[0128] In a 3GPP mobile communication system, a UE may be connected to multiple NWs. The connection between the UE and a data network (DN) may be established via an anchor UPF (a UPF directly connected to the DN). The anchor NW (a network having an anchor UPF, hereinafter the same) may be connected to one or more of the NWs connected to the UE.

[0129] When a UE connects to multiple networks, a network may be added to connect to the UE. However, no specific process for adding a network is disclosed. As a result, connections to multiple networks cannot be established, and problems such as inability to ensure communication capacity and reliability arise.

[0130] In this embodiment, a method for solving the above-mentioned problems is disclosed.

[0131] In this embodiment, the anchor NW determines whether to add a network. For example, the SMF of the anchor NW may make this determination. By having the SMF of the anchor NW make this determination, for example, it becomes possible to determine whether to add a network using the data communication status of the U-plane, and it becomes possible to quickly execute a network addition instruction from the SMF to the UPF.

[0132] The SMF of the anchor NW may request information used to determine NW addition from the UE. The request from the SMF of the anchor NW to the UE may be made via the AMF of the anchor NW. The UE may notify the SMF of the anchor NW of the information. The notification from the UE may be made via the AMF of the anchor NW. The above notification may be made, for example, using the C-plane.

[0133] The SMF of the anchor NW may request the above-mentioned information from an entity of the additional candidate NW. The request may be made, for example, via a SEPP (Security Edge Protection Proxy; see Non-Patent Document 10). The request may be made via the SEPPs of both the anchor NW and the additional candidate NW, or via the SEPP of one of the NWs. The entity of the additional candidate NW may be an SMF or a UPF. The entity of the additional candidate NW may notify the SMF of the anchor NW of the above-mentioned information. The notification may be made, for example, via a SEPP. The notification may be made via the SEPPs of both the anchor NW and the additional candidate NW. This allows, for example, the SMF of the anchor NW to obtain the above-mentioned information of other NWs, thereby making it possible to appropriately select an additional NW.

[0134] The SMF of the anchor NW may obtain information about other NWs. For example, the SMF may inquire about information about other NWs from an entity in the anchor NW. The entity in the anchor NW may be, for example, a NW Exposure Function (NEF) (see Non-Patent Document 10) or a NW Repository Function (NRF) (see Non-Patent Document 10). The entity in the anchor NW may notify the SMF about information about other NWs. The information may include information about the NW, for example, information identifying the NW, or information about the address of the NW, for example, an IP address. The address may include, for example, the address of the SEPP of the NW. The SMF may use the information about the other NWs to determine candidate NWs to add.

[0135] Information on Quality of Service (QoS) or Quality of Experience (QoE) may be used to determine whether to add a network. QoS may include, for example, information on communication capacity, communication speed, latency, or data error rate. QoE may include, for example, information on audio skipping rate, or video skipping rate.

[0136] The following (1) to (9) are disclosed as examples of information used to determine whether to add a network.

[0137] (1) Information regarding the QoS / QoE that can be supported by the local network.

[0138] (2) Information regarding the measurement results of QoS / QoE in the local network.

[0139] (3) Information about the QoS / QoE that can be supported by other networks.

[0140] (4) Information regarding QoS / QoE measurement results in other networks.

[0141] (5) Information regarding the QoS / QoE required for the service.

[0142] (6) Information regarding the load of the local network.

[0143] (7) Information regarding the load of other networks.

[0144] (8) Information about the network to which the UE can connect.

[0145] (9) A combination of the above (1) to (8).

[0146] The above (1) makes it possible to prevent the selection of a network with excessive QoS, for example, and as a result, it is possible to improve the efficiency of the communication system.

[0147] The above (2) makes it possible to grasp, for example, the QoS / QoE that should actually be supported in the additional network, and as a result, it becomes possible to prevent the selection of a network with excessive QoS, thereby achieving the same effect as described above.

[0148] The above-mentioned (3) enables, for example, the anchor NW to appropriately select a NW to be added. The same applies to the above-mentioned (4) and (5).

[0149] The above-mentioned (6) may be, for example, a load in the core network. The load may be, for example, a load of data traffic volume or a control processing load. The load may be, for example, a load of the UPF, a load of the AMF, or a load of the SMF.

[0150] As another example, the above (6) may be the load on the base station. The load may be, for example, the load of the data traffic volume or the control processing load.

[0151] The above (6) may include information about the device. The device may be, for example, a core network (e.g., AMF, SMF, UPF) or a base station.

[0152] The above-mentioned (6) makes it possible to avoid situations where, for example, there is no room for load and a predetermined QoS cannot be met.

[0153] The above-mentioned (7) may be, for example, the same information as the above-mentioned (6), thereby obtaining, for example, the same effect as the above-mentioned (6).

[0154] The above (8) may be, for example, information about a network in which the UE can be registered, or information about a cell in which the UE can be located and / or a network to which a base station belongs. The above (8) makes it possible, for example, for the anchor network to prevent the UE from selecting a network to which it cannot connect.

[0155] The decision to add a network may be made when the UE is in an RRC_Connected state, an RRC_Inactive state, or an RRC_Idle state. This allows, for example, the anchor network to quickly add a network.

[0156] The UE may measure QoS and / or QoE. The measurement may be triggered by an instruction from a core network device, by an instruction from an application, or by the UE itself. The core network device may be, for example, a core network device of an anchor network. The core network device of an anchor network may be, for example, an SMF of the anchor network or an AMF of the anchor network. The SMF may issue the instruction via the AMF.

[0157] The UE may report the measurement result. The UE may report the measurement result to a core network device or to an application. The core network device may be, for example, a core network device of an anchor network. The core network device of an anchor network may be, for example, an AMF of the anchor network. The AMF may notify the measurement result to an SMF of the network.

[0158] The report from the UE may be triggered by a request from the core network device, or may be periodically reported. The core network device may notify the UE of information regarding the reporting period. For example, NAS signaling may be used for the notification. The notification may include information regarding the QoS / QoE to be measured or information regarding the network to be measured. The UE may use the information to perform measurements or report the measurement results.

[0159] 11 is a sequence diagram showing an example of the operation until the SMF decides to add a connection network for the UE. In the example shown in FIG. 11, base station #1, AMF #1, UPF #1, SMF #1, PCF #1, UDM #1, and anchor UPF all belong to NW #1, and base station #2, AMF #2, UPF #2, SMF #2, PCF #2, and UDM #2 all belong to NW #2. In the example shown in FIG. 11, the UE is connected to NW #1. In the example shown in FIG. 11, SMF #1 uses information about QoS to decide to add a connection network for the UE.

[0160] Steps ST1105 to ST1108 shown in Fig. 11 show data transmission and reception between a UE and a DN (Data Network). The data transmission and reception shown in steps ST1105 to ST1108 is performed via base station #1, UPF #1, and anchor UPF. Step ST1105 shows data transmission and reception between the UE and base station #1, step ST1106 shows data transmission and reception between base station #1 and UPF #1, step ST1107 shows data transmission and reception between UPF #1 and anchor UPF, and step ST1108 shows data transmission and reception between the anchor UPF and DN.

[0161] In steps ST1110 and ST1112 shown in FIG. 11 , SMF#1 requests information about QoS from the UE. The request is made via AMF#1. Step ST1110 shows the request from SMF#1 to AMF#1, and step ST1112 shows the request from AMF#1 to the UE. NAS signaling may be used in step ST1112. Step ST1110 may include information for identifying the UE (e.g., a UE identifier). AMF#1 can use this information to identify the UE to which the request is made. Steps ST1110 and ST1112 may include information about the QoS requested by SMF#1. In the example shown in FIG. 11 , SMF#1 requests the UE's requested QoS and QoS measurement results for the service. Steps ST1110 and ST1112 may include information about the QoS type. The type-related information may include, for example, information about communication capacity, information about latency, or information about data error rate.

[0162] In steps ST1114 and ST1116 shown in FIG. 11 , the UE notifies SMF#1 of information related to QoS. The notification is performed via AMF#1. Step ST1114 shows the notification from the UE to AMF#1, and step ST1116 shows the notification from AMF#1 to SMF#1. NAS signaling may be used in step ST1114. Step ST1116 may include information for identifying the UE (e.g., a UE identifier). SMF#1 can use this information to identify the UE that has sent the notification. Steps ST1114 and ST1116 may include information related to the QoS notified by the UE. In the example shown in FIG. 11 , the UE notifies SMF#1 of the requested QoS and QoS measurement results for its own service. Steps ST1114 and ST1116 may include information related to the QoS type. The type-related information may include, for example, information on communication capacity, information on latency, or information on a data error rate. SMF#1 acquires information on QoS by using step ST1116.

[0163] In step ST1118 shown in FIG. 11 , SMF#1 requests information about QoS from SMF#2. The request may be made via the SEPPs of NW#1 and NW#2. Step ST1118 may include information for identifying the NW. SMF#2 can use this information to determine that step ST1118 is a request to its own NW. Step ST1118 may also include information about the QoS requested by SMF#1. In the example shown in FIG. 11 , SMF#1 requests information about QoS that can be supported in NW#2 from SMF#2. Step ST1118 may include information about the type of QoS. The information about the type may include, for example, information about communication capacity, information about latency, or information about a data error rate.

[0164] In step ST1120 shown in FIG. 11 , SMF#2 notifies SMF#1 of information related to QoS. The notification may be made via the SEPPs of NW#2 and NW#1. Step ST1120 may include information for identifying the NW. SMF#1 can determine that step ST1120 is a notification from NW#2 using this information. Step ST1120 may also include information related to the QoS notified by SMF#2. In the example shown in FIG. 11 , SMF#2 notifies SMF#1 of information related to QoS that can be supported in NW#2. Step ST1120 may include information related to the type of QoS. The information related to the type may include, for example, information related to communication capacity, information related to latency, or information related to a data error rate. SMF#1 acquires information related to QoS using step ST1120.

[0165] 11 may be performed between multiple networks. This allows, for example, SMF#1 to acquire information about the QoS of multiple networks, and as a result, to determine a more appropriate network addition destination from among the multiple networks.

[0166] In step ST1125 shown in Fig. 11, SMF#1 decides to add a network to which the UE is connected. In the example shown in Fig. 11, SMF#1 decides to add NW#2.

[0167] 11 shows an example in which information about QoS is requested and notified, but information about QoE may also be requested and notified. The request for and notification of information about QoE may be performed in a similar manner to the request for and notification of information about QoS. For example, the request for and notification of information about QoE may be performed between the UE and the UE.

[0168] The SMF of the anchor network may request the above information from the UPF of the anchor network. The UPF may notify the SMF of the above information. This may reduce the amount of signaling between the communication network and the UE, thereby improving communication efficiency.

[0169] 12 is a sequence diagram showing another example of the operation until the SMF decides to add a UE connection NW. In the example shown in Figure 12, an example is shown in which SMF #1 requests information about QoS from UPF #1. In the example shown in Figure 12, the same process as in Figure 11 is assigned the same step number, and common explanations will be omitted.

[0170] Steps ST1105 to ST1108 shown in FIG. 12 are the same as those in FIG.

[0171] In step ST1210 shown in FIG. 12 , SMF#1 requests information about QoS from UPF#1. Step ST1210 may include information for identifying the UE (e.g., a UE identifier). UPF#1 can use this information to identify the target UE. Step ST1210 may also include information about the QoS requested by SMF#1. In the example shown in FIG. 12 , SMF#1 requests the UPF#1 to provide the requested QoS and QoS measurement results for the service of the UE. Step ST1210 may also include information about the QoS type. The type-related information may include, for example, information about communication capacity, information about latency, or information about a data error rate.

[0172] In step ST1216 shown in FIG. 12 , UPF#1 notifies SMF#1 of information related to QoS. Step ST1216 may include information for identifying the UE (e.g., a UE identifier). SMF#1 can use this information to identify the target UE. Step ST1216 may also include information related to the QoS notified by UPF#1. In the example shown in FIG. 12 , UPF#1 notifies SMF#1 of the requested QoS of the service of the UE and the QoS measurement results. Step ST1216 may also include information related to the QoS type. The information related to the type may include, for example, information related to communication capacity, information related to latency, or information related to a data error rate. SMF#1 acquires information related to QoS using step ST1216.

[0173] Steps ST1118 to ST1125 shown in FIG. 12 are the same as those in FIG.

[0174] Although FIG. 12 shows an example in which information related to QoS is requested and notified, information related to QoE may also be requested and notified.

[0175] The above-mentioned measurement result report from the UE may be triggered by satisfying a predetermined condition. The predetermined condition may be determined by a standard, or may be notified to the UE by a core network device of the anchor network and / or an application.

[0176] As examples of the predetermined conditions, the following (A) to (G) are disclosed.

[0177] (A) The measured QoS / QoE parameters are below or equal to a predetermined threshold.

[0178] (B) The measured QoS / QoE parameters are above or equal to a predetermined threshold.

[0179] (C) The measured QoS / QoE parameters are less than or equal to the supportable QoS / QoE.

[0180] (D) The measured QoS / QoE parameters are greater than or equal to the supportable QoS / QoE.

[0181] (E) The measured QoS / QoE parameters are less than or equal to the requested QoS / QoE.

[0182] (F) The measured QoS / QoE parameters are greater than or equal to the requested QoS / QoE.

[0183] (G) A combination of (A) to (F) above.

[0184] An offset may be provided in the above (A) to (F). For example, in (A), the condition may be satisfied when the measured QoS / QoE parameters are less than or equal to a value obtained by subtracting the offset from a predetermined threshold, or when the measured QoS / QoE parameters are less than or equal to a value obtained by adding the offset to a predetermined threshold. The same may be true for (B) to (F). This allows flexible condition determination in a communication system, for example.

[0185] The SMF may notify the UE of the offset value. The notification may be performed via the AMF. The notification from the AMF to the UE may be performed, for example, using NAS signaling.

[0186] A UE may request the addition of a network. For example, the UE may request the addition of a network to an SMF. The request may be made via an AMF. The request may include information on QoS. For example, the request may include information on the requested QoS of the service of the UE itself, or information on QoS measurement results in the UE itself. The SMF may decide to add a network in response to the request.

[0187] A UE capability for connection to multiple networks may be provided. The UE may notify information about the capability to a base station or to an AMF. The base station may be a base station of an anchor network or a base station of a non-anchor network. The AMF may be an AMF of an anchor network or an AMF of a non-anchor network. The base station and / or the AMF may notify information about the capability to an SMF. The notification from the base station to the SMF may be performed via the AMF. The SMF may use the information to determine whether to add a network to which the UE is connected.

[0188] As examples of the aforementioned UE capabilities, the following (a) to (i) are disclosed.

[0189] (a) Information regarding whether or not connections to multiple networks are possible.

[0190] (b) Information regarding whether registration to multiple networks is possible.

[0191] (c) Information about the number of RRC states held simultaneously.

[0192] (d) Information about the number of CM (Connection Management) states held simultaneously.

[0193] (e) Information regarding the number of RM (Registration Management) states held simultaneously.

[0194] (f) Information regarding the maximum transmission capacity and / or maximum transmission rate of the UE.

[0195] (g) Information about packet latency within the UE.

[0196] (h) Information about the network to which the UE can connect.

[0197] (i) A combination of (a) to (h) above.

[0198] The above (a) makes it possible to prevent the core network device from making unnecessary network addition decisions, for example, when a UE cannot connect to multiple networks, thereby improving the efficiency of controlling the communication network.

[0199] The above (b) makes it possible to prevent unnecessary registration processing in the communication system, for example, when a UE cannot be registered to multiple networks, thereby improving the efficiency of controlling the communication networks.

[0200] The above-mentioned (c) may be, for example, information regarding whether or not a plurality of RRC states can be present. The above-mentioned (c) makes it possible to prevent, for example, a discrepancy in recognition regarding the RRC state of the UE between the UE and the core network device, thereby making it possible to prevent malfunctions in the communication system.

[0201] The above (d) may be, for example, information on whether or not a plurality of CM states can be present. The above (d) makes it possible to prevent, for example, discrepancies in the recognition of the CM state of the UE between the UE and the core network device, thereby preventing malfunctions in the communication system.

[0202] The above (e) may be, for example, information on whether or not a plurality of RM states can be present. The above (e) can prevent, for example, discrepancies in the recognition of the RM states of the UE between the UE and the core network device, thereby preventing malfunctions in the communication system.

[0203] The above (f) enables, for example, the core network device to properly determine the additional network required to satisfy the UE's QoS.

[0204] The above-mentioned (g) can provide the same effect as the above-mentioned (f), for example.

[0205] The above (h) enables, for example, a core network device to prevent a UE from selecting a network to which it cannot connect as an additional network.

[0206] 13 is a sequence diagram showing another example of the operation until the SMF decides to add a connection NW for the UE. In the example shown in Figure 13, an example is shown in which the UE requests the SMF #1 to add a connection NW. In the example shown in Figure 13, the same process as in Figure 11 is assigned the same step number, and common explanations will be omitted.

[0207] In steps ST1310 and ST1312 shown in FIG. 13, the UE requests SMF#1 to add a connected network. The request is made via AMF#1. Step ST1310 shows the request from the UE to AMF#1, and step ST1312 shows the request from AMF#1 to SMF#1. NAS signaling may be used in step ST1310. Step ST1312 may include information for identifying the UE (e.g., a UE identifier). SMF#1 can use this information to identify the UE that has sent the notification. Steps ST1310 and ST1312 may include information about QoS. In the example shown in FIG. 13, the UE notifies SMF#1 of the requested QoS and QoS measurement results for its own service. Steps ST1310 and ST1312 may include information about the QoS type. The type-related information may include, for example, information on communication capacity, information on latency, or information on a data error rate. The SMF#1 acquires information on QoS by using step ST1312.

[0208] Steps ST1118 to ST1125 shown in FIG. 13 are the same as those in FIG.

[0209] Although FIG. 13 shows an example in which information about QoS is included in the request for network addition, information about QoE may also be included.

[0210] As another example of the determination of network addition, the AMF may determine the network addition. For example, the AMF of the anchor network may make the determination. This can avoid, for example, complexity related to UE state management.

[0211] The anchor NW may request the target NW to connect to the UE. The request may be made by the SMF of the anchor NW. The request may be made to the SMF of the target NW. The target NW may start the process of adding the UE's connected NW in response to the request.

[0212] The request may include information regarding the addition of the UE's connection NW. This allows, for example, the addition target NW to quickly understand that the request is for the addition of the UE's connection NW. The request may include information regarding the anchor UPF. This allows, for example, the addition target NW to quickly perform connection processing with the anchor NW.

[0213] The SMF of the anchor network may instruct the UE to add a connection network. The instruction may include information about the additional network.

[0214] The UE may request the addition target network to register the UE. The request may be triggered by an instruction from the SMF of the anchor network. The instruction may include information indicating the addition of a connecting network or information about the anchor network.

[0215] The UE may request the anchor NW to add another NW. The request may include information regarding the reason. The information regarding the reason may be, for example, information indicating that the UE cannot connect to the NW to be added, or information indicating that the UE cannot connect to a base station belonging to the NW to be added. As another example, the UE may notify the anchor NW that it cannot connect to the NW to be added. The notification from the UE to the anchor NW may be made to the AMF. The AMF may forward the notification to the SMF. The SMF may reselect the NW to be added based on the notification. This may enable the UE to connect to the reselected NW, for example.

[0216] The target network to be added may perform a registration process for the UE. The registration process may be performed, for example, in response to a registration request from the UE. The registration process may be similar to the process disclosed in Section 4.2.2.2.2 of Non-Patent Document 31.

[0217] The target network to be added may establish a PDU session with the UE. The PDU session establishment process may be similar to the process disclosed in Section 4.3.2.2.1 of Non-Patent Document 31, for example.

[0218] The target network to be added may respond to the above-mentioned request to the anchor network. The response may be made by the SMF of the target network to be added. The response may be made to the SMF of the anchor network. The response may include information about the target network to be added, information about the PDU session to be established in the target network to be added, or information about the UPF of the target network to be added.

[0219] The SMF of the anchor NW may request the anchor UPF to establish a connection with the UPF of the NW to be added. The request may include information about the UPF of the NW to be added, or information about data to be forwarded to the UPF of the NW to be added (e.g., information about QoS flows). The anchor UPF may initiate a connection with the UPF of the NW to be added. This connection initiation operation may be triggered by a request from the SMF of the anchor NW.

[0220] A PDU session may be established in the additional NW. A connection between the anchor UPF and the UPF of the additional NW may be established when the PDU session is established.

[0221] 14 and 15 are sequence diagrams showing an example of a registration process and a PDU session establishment process between a UE and an addition target NW. Fig. 14 shows the first half of the sequence, and Fig. 15 shows the second half of the sequence. In the examples shown in Fig. 14 and 15, the same processes as in Fig. 11 are assigned the same step numbers, and common explanations are omitted.

[0222] Step ST1125 shown in FIG. 14 is the same as that in FIG.

[0223] In step ST1430 shown in FIG. 14, SMF#1 requests SMF#2 to generate a PDU session. The request may be a request to register the UE to NW#2. The request may include information about the UE, information indicating the addition of a network to which the UE is connected, information about the anchor UPF, information about the anchor network, or information about the UE's subscription to its own network. Step ST1430 triggers SMF#2 to start the operation of registering the UE to its own network.

[0224] In step ST1435 shown in FIG. 14 , SMF#1 instructs AMF#1 to add a connection NW for the UE. The instruction may include information about the UE, or may include information about the additional NW for the UE. AMF#1 uses step ST1435 to identify the UE related to the addition of the connection NW. In step ST1437, AMF#1 instructs the UE to add a connection NW. The instruction may include information about the connection NW. For example, NAS signaling may be used for the instruction. The UE may start a registration operation to NW#2 in response to the instruction. For example, the UE may start a connection to a cell belonging to NW#2 in response to the instruction.

[0225] In step ST1440 shown in Fig. 14, a registration process is performed between the UE and NW #2. This process may be the same as the process disclosed in section 4.2.2.2.2 of Non-Patent Document 31 (3GPP TS23.502), for example. The signaling of a registration request from the UE to the AMF #2 may include information about adding a network, or may include information about a network to which the UE is currently connected. In the example shown in Fig. 14, the signaling of a registration request from the UE to the AMF #2 may include information about NW #1.

[0226] In step ST1445 shown in FIG. 14, authentication / authorization of the PDU session is performed between the UE and NW#2.

[0227] In Step ST1447 shown in Fig. 14, the SMF#2 selects a PCF. In Step ST1449, a procedure for establishing a session management policy association is performed between the SMF#2 and the PCF#2. This procedure may be, for example, the procedure disclosed in Section 4.16.4 of Non-Patent Document 31 (3GPP TS23.502).

[0228] In Step ST1451 shown in Fig. 14, SMF#2 selects a UPF. In Step ST1453, a procedure for modifying a session management policy association is performed between SMF#2 and PCF#2. This procedure may be, for example, the procedure disclosed in Section 4.16.5.1 of Non-Patent Document 31 (3GPP TS23.502).

[0229] In step ST1455 shown in Fig. 14, SMF#2 requests UPF#2 to establish an N4 session. UPF#2 establishes the N4 session in response to step ST1455. In step ST1457, UPF#2 responds to the request of step ST1455 to SMF#2.

[0230] 14, SMF#2 sends a response to step ST1430 to SMF#1. The response may include information about the UPF used in NW#2, or information about the PDU session used in NW#2, for example, information used to identify the PDU session.

[0231] In step ST1461 shown in FIG. 14, SMF#1 requests the anchor UPF to establish a connection with UPF#2. The request may include information about the UE, information about UPF#2, or information about the PDU session used in NW#2. The anchor UPF establishes a connection with UPF#2 in response to the request. In step ST1463 shown in FIG. 14 and step ST1464 shown in FIG. 15, downlink data from the DN is forwarded to UPF#2. Step ST1463 shows data forwarding from the DN to the anchor UPF, and step ST1464 shows data forwarding from the anchor UPF to UPF#2. In step ST1465, the anchor UPF notifies SMF#1 of the establishment of a connection with UPF#2. This notification may be made in response to step ST1461.

[0232] The data transfer in step ST1464 shown in FIG. 15 may be triggered by an instruction from SMF#1 to the anchor UPF. The instruction may be, for example, an instruction to start (activate) data transfer. This enables, for example, flexible control of data transfer.

[0233] The SMF#1 may instruct the anchor UPF to deactivate data transfer, and the anchor UPF may deactivate data transfer in response to the instruction. This allows flexible control of data transfer, for example.

[0234] The SMF#1 may notify the anchor UPF of information regarding data processing. The information may be, for example, an instruction to start and / or stop forwarding, or information regarding the data path. The information regarding the data path may be, for example, information indicating that the data passes through both the anchor NW and the target NW to be added, information indicating forwarding to the target NW to be added, information indicating that the data passes through the anchor NW, or information regarding data duplication as disclosed in the fifth embodiment described below. This enables, for example, flexible control of data forwarding.

[0235] In steps ST1466 and ST1467 shown in Figure 15, information required to establish an N1 interface and an N2 interface is transmitted and received between SMF#2 and AMF#2. Step ST1466 represents message transmission from SMF#2 to AMF#2, and step ST1467 represents message transmission from AMF#2 to SMF#2.

[0236] In step ST1469 shown in FIG. 15 , AMF#2 notifies base station#2 of a PDU session establishment request to the UE. In step ST1470, base station#2 notifies the UE of the PDU session establishment request. Step ST1469 may include a NAS signaling message to the UE. Step ST1470 may include a NAS signaling message from AMF#2. Signaling of the N2 interface may be used in step ST1469. RRC signaling, for example, signaling of RRC reconfiguration may be used in step ST1470. The UE establishes a PDU session using step ST1470.

[0237] In step ST1472 shown in FIG. 15 , the UE notifies base station #2 of the completion of establishment of the PDU session. In step ST1473, base station #2 notifies AMF #2 of the completion of establishment of the PDU session of the UE. Step ST1472 may include a NAS signaling message to AMF #2. Step ST1473 may include a NAS signaling message from the UE or may include session management information in base station #2. RRC signaling, for example, signaling indicating completion of RRC reconfiguration, may be used in step ST1472. Signaling of the N2 interface may be used in step ST1473.

[0238] In step ST1480 shown in FIG. 15 , AMF#2 requests SMF#2 to update the PDU session information. In the request, session management information from base station #2 is notified. In step ST1482, SMF#2 requests UPF#2 to update the PDU session information. UPF#2 updates the PDU session information using step ST1482. In step ST1484, UPF#2 notifies SMF#2 that the PDU session information has been updated. In step ST1486, SMF#2 notifies AMF#2 that the PDU session information has been updated. Step ST1486 may be performed in response to step ST1480.

[0239] In steps ST1488 and ST1489 shown in FIG. 15, downlink data is transmitted from UPF #2 to the UE. Step ST1488 indicates downlink data transmission from UPF #2 to base station #2, and step ST1489 indicates downlink data transmission from base station #2 to the UE. The downlink data may include the downlink data of step ST1464. Steps ST1488 and ST1489 may be performed upon completion of the PDU session information update performed in conjunction with step ST1482.

[0240] In steps ST1495 to ST1498 shown in Fig. 15, uplink data transmission is performed from the UE to the DN via NW #2. Step ST1495 shows uplink data transmission from the UE to base station #2, step ST1496 shows uplink data transmission from base station #2 to UPF #2, step ST1497 shows uplink data transmission from UPF #2 to the anchor UPF, and step ST1498 shows uplink data transmission from the anchor UPF to the DN.

[0241] A service request may be made between the UE and the additional network. The service request may be initiated by the UE or the additional network. This allows, for example, quick resumption of communication even if communication between the UE and the additional network is once interrupted.

[0242] According to the first embodiment, it becomes possible to add a connection network for the UE, thereby realizing improvements in communication capacity and reliability.

[0243] Second Embodiment In this embodiment, a method for releasing an added network is disclosed.

[0244] The UE requests the AMF of the additional NW to deregister the additional NW. The request may include information indicating that only the additional NW is to be released. The request may be made using, for example, NAS signaling.

[0245] The AMF of the additional network may request the SMF of the local network to deregister the UE. The request may include information indicating that only the additional network is being released.

[0246] The SMF of the additional NW may request the UPF of the additional NW to release resources. The UPF releases the resources of the additional NW in response to the request.

[0247] The SMF of the additional NW may notify the SMF of the anchor NW of the release of the additional NW. The SMF of the anchor NW may request the anchor UPF to release the connection with the UPF of the additional NW upon receiving the notification. The anchor UPF may also release the connection with the UPF of the additional NW upon receiving the notification.

[0248] 16 and 17 are sequence diagrams showing an example of the operation of releasing a NW connected to a UE. FIG. 16 shows the first half of the sequence, and FIG. 17 shows the second half of the sequence. In the examples shown in FIGS. 16 and 17, deregistration is performed between the UE and NW#2. In the examples shown in FIGS. 16 and 17, the UE requests deregistration from NW#2.

[0249] In step ST1505 shown in FIG. 16 , the UE requests deregistration from AMF#2. The request may include information indicating deregistration of NW#2, or may include information indicating that registration with NW#1 will continue. In step ST1506, AMF#2 requests SMF#2 to release the UE's PDU session. The request may be a request for deregistration of the UE from NW#2. The request may include information indicating deregistration of NW#2, or may include information indicating that registration with NW#1 will continue. This allows, for example, SMF#2 to quickly understand that it is necessary to release only the resources of UPF#2.

[0250] In step ST1508 shown in FIG. 16 , SMF#2 requests UPF#2 to release the PDU session. This request may be a request to release resources of UPF#2 related to the PDU session. UPF#2 may release the PDU session or release the resources of UPF#2, triggered by step ST1508. In step ST1510, UPF#2 responds to the request to SMF#2.

[0251] In step ST1512 shown in FIG. 16 , SMF#2 requests SMF#1 to release the connection between the anchor UPF and UPF#2. The request may be a request to release resources related to communication with UPF#2 in the anchor UPF. In step ST1514, SMF#1 requests the anchor UPF to release the connection with UPF#2. The request may be a request to release resources related to communication with UPF#2. The anchor UPF may release the connection with UPF#2, or may release resources related to communication with UPF#2 in its own UPF, triggered by step ST1514. In step ST1516, the anchor UPF responds to the request to SMF#1. In step ST1518, SMF#1 responds to step ST1512 to SMF#2.

[0252] In step ST1520 shown in FIG. 17, SMF#2 responds to AMF#2 to the UE's PDU session release request.

[0253] In Step ST1522 shown in Fig. 17, a procedure for terminating session management policy association is performed between SMF#2 and PCF#2. This procedure may be, for example, the procedure disclosed in Section 4.16.6 of Non-Patent Document 31. In Steps ST1524 and ST1525, UE deregistration is performed between SMF#2 and UDM#2. Step ST1524 is signaling transmission from SMF#2 to UDM#2, and Step ST1525 is signaling transmission from UDM#2 to SMF#2.

[0254] In Step ST1527 shown in FIG. 17 , an access and mobility (AM) policy association termination procedure is performed between AMF#2 and UPF#2. This procedure may be, for example, the procedure disclosed in section 4.16.3.2 of Non-Patent Document 31. In Step ST1529, a UE policy association termination procedure is performed between AMF#2 and UPF#2. This procedure may be, for example, the procedure disclosed in section 4.16.13.2 of Non-Patent Document 31.

[0255] In step ST1533 shown in FIG. 17 , AMF#2 notifies the UE that it has accepted the deregistration. This notification may be performed using, for example, NAS signaling. In steps ST1535 and ST1537, the signaling connection is released between AMF#2, base station#2, and the UE. Step ST1535 indicates the release of the signaling connection between AMF#2 and base station#2, and step ST1537 indicates the release of the signaling connection between base station#2 and the UE. Step ST1537 may use RRC signaling, for example, RRC release signaling.

[0256] The UE may include information about the desired RRC state after deregistration in a request for deregistration to the anchor NW. The AMF of the anchor NW may notify the SMF of its own NW of the information. The SMF may notify the SMF of the NW to be deregistered of the information. The SMF of the NW to be deregistered may notify the AMF of its own NW of the information. The AMF of the NW to be deregistered may notify the UE of information about the RRC state after deregistration. The information about the RRC state may be included in a notification of deregistration acceptance from the AMF to be deregistered to the UE. The UE may use the information about the RRC state to configure its own UE's RRC state.

[0257] As another example, the base station of the NW to be deregistered may notify the UE of the RRC state after deregistration. The AMF of the NW to be deregistered may notify the base station of the information regarding the RRC state. RRC signaling may be used for the notification from the base station to the UE. The RRC signaling may be, for example, RRC reconfiguration signaling, RRC interruption signaling, or RRC release signaling. The signaling used for the notification from the base station to the UE may be determined depending on the RRC state the UE should be in.

[0258] As another example, the UE may request the AMF of the anchor network to deregister the additional network. The request may include information about the network to be deregistered. The AMF may request the SMF of the anchor network to deregister the additional network.

[0259] The SMF of the anchor NW may request the anchor UPF to release the connection with the UPF of the additional NW. The anchor UPF may release the connection with the UPF of the additional NW in response to the request.

[0260] The SMF of the anchor network instructs the SMF of the additional network to deregister the additional network. The instruction may include information about the UE. The SMF of the additional network may perform a deregistration process of the UE from the additional network in response to the instruction.

[0261] Fig. 18 is a sequence diagram showing another example of the operation of releasing a NW connected to a UE. In the example shown in Fig. 18, deregistration is performed between the UE and NW #2. The example shown in Fig. 18 shows a case where a UE requests deregistration from NW #1, which is an anchor NW. In the example shown in Fig. 18, the same step numbers are assigned to processes similar to those in Fig. 16 and Fig. 17, and common explanations will be omitted.

[0262] In Step ST1605 shown in FIG. 18 , the UE requests deregistration from AMF#1. The request may include information indicating deregistration of NW#2, or may include information indicating that registration with NW#1 will continue. In Step ST1606, AMF#1 requests SMF#1 to release the UE's PDU session. The request may be a request for deregistration of the UE from NW#2. The request may include information indicating deregistration of NW#2, or may include information indicating that registration with NW#1 will continue. This allows SMF#1 to quickly understand that it is necessary to release only the resources of UPF#2. In Step ST1607, SMF#1 requests deregistration from SMF#2. The request requests release of the UE's PDU session. The request may include the same information as in Step ST1606.

[0263] Steps ST1508 to ST1529 shown in Fig. 18 are the same as those in Fig. 16 and Fig. 17. SMF#1 may perform the process of step ST1514 upon step ST1606.

[0264] In step ST1630 shown in FIG. 18 , SMF#2 sends a response to step ST1607 to SMF#1. In step ST1631, SMF#1 sends a response to step ST1606 to AMF#1. In step ST1632, AMF#1 sends a response to step ST1605 to the UE.

[0265] Steps ST1535 and ST1537 shown in FIG. 18 are the same as those in FIG.

[0266] As another example, the anchor NW may decide to deregister the UE from the additional NW. For example, the decision may be made by the AMF of the anchor NW.

[0267] The AMF of the anchor network may instruct the SMF of its own network to deregister the UE from the additional network. The SMF may request the anchor UPF to release the connection with the UPF of the additional network. The anchor UPF may release the connection with the UPF of the additional network in response to the request.

[0268] The SMF of the anchor network may instruct the SMF of the additional network to deregister the UE from the additional network. The SMF of the additional network may use the instruction to perform a deregistration process of the UE from the additional network.

[0269] Figure 19 is a sequence diagram showing another example of the operation of releasing a NW connected to a UE. In the example shown in Figure 19, deregistration is performed between the UE and NW #2. In the example shown in Figure 19, AMF #1 decides to deregister the UE from NW #2. In the example shown in Figure 19, the same step numbers are assigned to processes similar to those in Figures 16 to 18, and common descriptions will be omitted.

[0270] In Step ST1705 shown in Fig. 19 , AMF#1 requests deregistration of the UE. The request may include information on the NW to be deregistered, or may include information on the NW to maintain registration. In the example shown in Fig. 19 , information on NW#2 as the NW to be deregistered may be included.

[0271] Steps ST1606 and ST1607 shown in FIG. 19 are the same as those in FIG.

[0272] Steps ST1508 to ST1529 shown in Fig. 19 are the same as those in Fig. 16 and Fig. 17. SMF#1 may perform the process of step ST1514 upon step ST1606.

[0273] Steps ST1630 and ST1631 shown in FIG. 19 are the same as those in FIG.

[0274] In Step ST1733 shown in FIG. 19 , the UE notifies the AMF#1 of the acceptance of the deregistration. The notification may be made as a response to Step ST1705. The notification may be made by using NAS signaling, for example.

[0275] Steps ST1535 and ST1537 shown in FIG. 19 are the same as those in FIG.

[0276] As another example, the additional NW may decide to deregister the UE. For example, the decision may be made by an AMF of the additional NW.

[0277] The AMF of the additional NW may request the UE to deregister from NW #2. The AMF of the additional NW may instruct the SMF of its own NW to deregister the UE from the additional NW. The SMF may perform a UE deregistration process in response to the instruction.

[0278] The SMF of the additional NW may notify the SMF of the anchor NW of the release of the additional NW. The SMF of the anchor NW may request the anchor UPF to release the connection with the UPF of the additional NW upon receiving the notification. The anchor UPF may also release the connection with the UPF of the additional NW upon receiving the notification.

[0279] 20 and 21 are sequence diagrams showing another example of the operation of releasing a NW connected to a UE. FIG. 20 shows the first half of the sequence, and FIG. 21 shows the second half of the sequence. In the example shown in FIGS. 20 and 21, deregistration is performed between the UE and NW#2. In the example shown in FIGS. 20 and 21, AMF#2 requests deregistration from the UE. In the example shown in FIGS. 20 and 21, the same processes as those in FIGS. 16 to 18 are assigned the same step numbers, and common descriptions will be omitted.

[0280] In Step ST1805 shown in Fig. 20 , the AMF#2 requests the UE to deregister. The request may include information indicating deregistration of the NW#2, or information indicating that registration with the NW#1 will continue. The request may be made by using, for example, NAS signaling.

[0281] Steps ST1506 to ST1529 shown in FIGS. 20 and 21 are the same as those in FIGS.

[0282] In Step ST1833 shown in FIG. 21 , the UE notifies the AMF#2 of the acceptance of the deregistration. The notification may be performed using, for example, NAS signaling.

[0283] Steps ST1535 and ST1537 shown in FIG. 21 are the same as those in FIG.

[0284] A PDU session may be released. For example, only a PDU session may be released. The release of the PDU session may be, for example, a release of a PDU session in an additional NW.

[0285] The UPF of the additional NW may forward data to the anchor UPF. The data may be, for example, downlink data. The data may be, for example, data that has not yet been transmitted to the UE. The forwarding may be triggered, for example, by a resource release request from the SMF of the additional NW for its own UPF. The anchor UPF may forward the data to the UPF of the anchor NW. The UPF of the anchor NW may transmit the data to the UE via the base station. This makes it possible to prevent data loss due to, for example, deregistration of the additional NW.

[0286] The UE may transmit data to the anchor NW. The data may be, for example, uplink data. The data may be, for example, data that has not yet been transmitted to the additional NW. The transmission from the UE to the anchor NW may be triggered by the release of the additional NW, for example, signaling of deregistration from the additional NW, or may be triggered by the release of a signaling connection with the additional NW. This makes it possible to prevent data loss due to, for example, deregistration of the additional NW.

[0287] A connection release between the UE and the additional NW may be performed. The connection release may be performed before deregistration of the UE. The connection release may be determined by the anchor NW. For example, the SMF of the anchor NW may make the decision. The SMF of the anchor NW may instruct the SMF of the additional NW to release the connection of the additional NW. As another example, the decision may be made by the additional NW. For example, the SMF of the additional NW may make the decision. The SMF of the additional NW may request the SMF of the anchor NW to release the connection of the additional NW.

[0288] Deregistration between the UE and the additional network may be triggered by the aforementioned connection release.

[0289] According to the second embodiment, it becomes possible to release the connection NW when the QoS of the communication service is excessive, and as a result, it becomes possible to improve the efficiency of the communication system.

[0290] Modification 1 of the Second Embodiment: The registration of both the anchor network and the additional network may be cancelled.

[0291] The UE may request the anchor NW to deregister both NWs. The request may be made to the AMF of the anchor NW. The AMF of the anchor NW may request the SMF of its own NW to deregister both NWs. For the request, for example, the same signaling as in step ST1606 of FIG. 18 may be used. The SMF of the anchor NW may deregister the UE from its own NW in response to the request. For the deregistration, for example, the method disclosed in Section 4.2.2.3.2 of Non-Patent Document 31 may be used.

[0292] The SMF of the anchor network may request the SMF of the non-anchor network to deregister the UE. For this request, for example, signaling similar to that in step ST1607 of FIG. 18 may be used.

[0293] The SMF of the non-anchor network may deregister the UE from its own network. For example, the method disclosed in Section 4.2.2.3.2 of Non-Patent Document 31 may be used for the deregistration.

[0294] The SMF of the anchor network may instruct the anchor UPF to release resources related to communication with the UE. The instruction may include information about the anchor network, information about the non-anchor network, or information about both networks. The anchor UPF may use the information to release resources related to communication with the UE.

[0295] The SMF of the non-anchor NW may notify the SMF of the anchor NW of a response to the deregistration request. For this notification, the same process as in step ST1630 in FIG. 18 may be performed. The SMF of the anchor NW may notify the AMF of its own NW of a response to the deregistration request. For this notification, the same signaling as in step ST1631 in FIG. 18 may be used.

[0296] Another solution will be disclosed. The anchor network may decide to deregister the UE from both networks. As the operation of deregistration from both networks decided by the anchor network, for example, a combination of the process disclosed in Section 4.2.2.3.3 of Non-Patent Document 31 and the process disclosed in the second embodiment (for example, the process shown in FIG. 19 ) may be used.

[0297] According to this first modification, the process of releasing the UE from the network can be quickly executed.

[0298] Third embodiment The added network may be switched.

[0299] The switching may be performed, for example, by a combination of the deletion of the additional network disclosed in the second embodiment and the addition of the network disclosed in the first embodiment.

[0300] The anchor NW may determine the switching. For example, the anchor NW may request the UE to switch the NW. The request may include information on the NW to be deregistered, or information on the NW to be newly registered. The switching operation may be performed by, for example, a combination of the deletion of the additional NW disclosed in the second embodiment and the addition of the NW disclosed in the first embodiment.

[0301] The AMF of the anchor NW may request the SMF of the anchor NW to perform the switching. The request may include information about the NW to be deregistered, information about the NW to be newly registered, or information about the UE. The SMF of the anchor NW may request deregistration from the NW to be deregistered. The NW to be deregistered may deregister the UE from its own NW in response to the request. The deregistration operation may be the same as, for example, the method disclosed in the second embodiment. The SMF of the anchor NW may request registration of the UE from the NW to be added. The NW to be added may register the UE to its own NW in response to the request. The registration operation may be the same as, for example, the method disclosed in the first embodiment.

[0302] As another example, the UE may request the switchover. The UE may make the request to the anchor NW. The UE may make the request to, for example, the AMF of the anchor NW. For example, the UE may request the anchor NW to switch the NW. The request may include information about the NW to be deregistered, or may include information about the NW to be newly registered. The switchover operation may be, for example, the same as described above.

[0303] Data may be transferred. The data may be, for example, data that has not yet been transmitted to the UE. For example, data may be transferred from the UPF of the NW to be deregistered to the anchor UPF, or data may be transferred from the anchor UPF to the UPF of the NW to be added. Data transfer from the UPF of the NW to be deregistered to the anchor UPF may be performed, for example, in the same manner as in the second embodiment. Data transfer from the anchor UPF to the UPF of the NW to be added may be performed, for example, when a connection between the anchor UPF and the UPF of the NW to be added is established.

[0304] Another example of data transfer may be data that has not yet been transmitted from the UE to the deregistered network. For example, data may be transferred from the UE to the anchor network, or data may be transferred from the UE to the target network. The data transfer may be performed in the same manner as in the second embodiment, for example.

[0305] According to the third embodiment, even if QoS cannot be ensured in an added network, for example, the network can be switched to another network, and as a result, QoS can be ensured in the communication system.

[0306] Fourth Embodiment There may be a plurality of anchor UPFs. For example, a plurality of networks to which a UE is connected may each have an anchor UPF.

[0307] 22 is a diagram illustrating an example of a network configuration in which a plurality of anchor UPFs exist. In the example illustrated in FIG. 22, NW#1 and NW#2 each have an anchor UPF.

[0308] In communication from a DN to a UE, the anchor UPF of each network may be switched in the DN. For example, in FIG. 22, the DN may switch the route to via anchor UPF #2 when data to the UE via anchor UPF #1 fails to be delivered.

[0309] As another example, one or more of the networks to which the UE connects may each have multiple anchor UPFs.

[0310] 23 is a diagram illustrating another example of a network configuration in which multiple anchor UPFs exist. In the example illustrated in Fig. 23, NW#1 has two anchor UPFs (Anchor UPF#1-1, #1-2), and NW#2 has one anchor UPF (Anchor UPF#2).

[0311] The SMF may decide to add an anchor UPF. The SMF may be an SMF of the anchor network or an SMF of a non-anchor network. For example, the SMF of the network to which the UPF to be added belongs may make the decision. The SMF may instruct the anchor UPF to be added to configure resources as the anchor UPF. The UPF may be configured as the anchor UPF in response to the instruction.

[0312] The SMF may decide to delete the anchor UPF. The SMF may be an SMF of the anchor network or an SMF of a non-anchor network. For example, the SMF of the network to which the UPF to be added belongs may make the decision. The SMF may instruct the anchor UPF to be added to release its resources as the anchor UPF. The UPF may release its resources as the anchor UPF in response to the instruction.

[0313] The switching of the anchor UPF may be determined by the SMF, and may be performed, for example, as a combination of adding and deleting the anchor UPF.

[0314] A resource change may be performed as the anchor UPF. The resource change may be to add an anchoring function for predetermined data to an existing anchor UPF, to delete an anchoring function for predetermined data from an existing anchor UPF, or to change the path of predetermined data (e.g., the UPF through which data passes) for the existing anchor UPF. The resource change may be determined by an SMF. The SMF may be an SMF of the anchor NW or an SMF of a non-anchor NW. For example, the SMF of the NW to which the UPF to be added belongs may make the decision. The SMF may instruct the anchor UPF to change the resources. The UPF may change the resources in response to the instruction.

[0315] A connection may be established between the anchor UPF and a UPF of another NW. In the example shown in FIG. 22, anchor UPF #1 and UPF #2 may be connected, or anchor UPF #2 and UPF #1 may be connected. As another example, in FIG. 23, anchor UPF #1-1 and anchor UPF #1-2 may be connected to UPF #2, respectively, or anchor UPF #2 may be connected to UPF #1-1 and UPF #1-2, respectively. As a result, even if, for example, the anchor UPF of one NW and the UPF of the other NW both fail, the DN can communicate with the UE via the anchor UPF of the other NW and the UPF of the other NW, thereby improving the reliability of communication.

[0316] According to the fourth embodiment, even when a failure occurs in one anchor UPF, communication between the UE and the DN is possible, and as a result, the reliability of the communication system can be improved.

[0317] Fifth Embodiment In communication using a plurality of networks, data may be duplicated. For example, each duplicated piece of data may be transmitted and received via a different network.

[0318] The transmitting device may duplicate the data. The transmitting device may add information to the duplicated data to identify the duplication. The information may be, for example, a sequence number or a timestamp. The transmitting device may transmit each of the duplicated data to each NW.

[0319] The receiving device may detect duplicate data and may delete duplicately received data. For example, the receiving device may use only the earliest received data and delete any duplicate data received after that. The receiving device may use the above information to detect duplicate data.

[0320] The transmitting device may be, for example, a UPF. The UPF may be, for example, an anchor UPF. As another example, a new entity may be provided to replicate the data. For example, the anchor UPF may transmit each of the replicated data to the UPF of each NW.

[0321] As another example, the transmitting device may be a UE, which may perform data duplication in a PDU layer, or a new layer may be provided and perform data duplication in the new layer, which may be, for example, a PDU layer opposite to the anchor UPF.

[0322] The receiving device may be, for example, a UE, which may perform the detection and / or elimination of duplicate data in, for example, the PDU layer, or a new layer may be provided in which the detection and / or elimination of duplicate data is performed.

[0323] Alternatively, the receiving device may be, for example, a UPF, which may be, for example, an anchor UPF, or a new entity may be provided that performs the detection and / or removal of duplicate data.

[0324] The data replication may be configured by the AMF. The AMF may be, for example, the AMF of the anchor NW. The AMF may instruct the UE to configure data replication. The instruction may include information about data related to replication, for example, information about QoS flows. The instruction from the AMF to the UE may be performed, for example, using NAS signaling. The UE may configure data replication or start data replication in response to the instruction.

[0325] The AMF may instruct the SMF of its own network to configure data replication. The instruction may include information about data related to the replication, for example, information about QoS flows. The SMF may configure data replication for the UPF. The UPF may be, for example, an anchor UPF. As another example, the SMF may configure data replication for the new entity that performs data replication. The configuration from the SMF to the UPF and / or the entity may include information about data related to the replication, for example, information about QoS flows. The UPF and / or the entity may start data replication in response to the configuration.

[0326] The AMF may decide to release the data replication configuration. The release operation may be performed, for example, in the same manner as the operation of setting up data replication.

[0327] Activation / deactivation of data replication may be performed. The activation / deactivation may be determined by an AMF. The AMF may be, for example, an AMF of an anchor NW. The activation / deactivation operation may be performed in the same manner as, for example, the operation of setting up data replication.

[0328] As another example, the AMF that determines the activation / deactivation of data replication may be an AMF of a non-anchor NW. The AMF may notify the SMF of its own NW of information regarding the activation / deactivation of data replication. The SMF may notify the SMF of the anchor NW of information regarding the activation / deactivation of data replication. The SMF of the anchor NW may instruct the anchor UPF to activate / deactivate data replication.

[0329] The SMF of the anchor NW may notify the AMF of the anchor NW of information regarding activation / deactivation of data replication. This allows, for example, the AMF of the anchor NW to understand the activation / deactivation of data replication determined by the AMF of the non-anchor NW, thereby preventing discrepancies regarding data replication between the AMF of the anchor NW and the AMF of the non-anchor NW, and thus preventing malfunctions in the communication system.

[0330] This fifth embodiment makes it possible to improve the reliability of communication between the UE and the UPF.

[0331] In the present disclosure, signaling between different networks may be performed via SEPP (see Non-Patent Document 10), which makes it possible to ensure security in the signaling, for example.

[0332] In the present disclosure, the Inter PLMN User Plane Security (IPUPS) function (see Non-Patent Document 10) may be used for transferring user data between different networks. This makes it possible to ensure security in transferring user data, for example.

[0333] Transmission and reception between a base station and a CN node (excluding the AMF) may be performed via the AMF. Alternatively, transmission and reception between a base station and a CN node (excluding the AMF) may be performed without the AMF. By not using the AMF, the amount of signaling can be reduced and the load on the AMF can be reduced.

[0334] In this specification, a node may be a function.

[0335] In the communication system according to the present disclosure, one or more cells are configured in one gNB. In the present disclosure, although it is described as a gNB or a cell, it may be a gNB or a cell unless otherwise specified.

[0336] In the present disclosure, a gNB may be an MCG or an SCG.

[0337] The above-described embodiments and their modifications are merely examples, and the embodiments and their modifications can be freely combined. Furthermore, any of the components of the embodiments and their modifications can be modified or omitted as appropriate.

[0338] For example, in the above-described embodiments and their modifications, a slot is an example of a time unit for communication in a fifth-generation communication system. A slot may be a scheduling unit. In the above-described embodiments and their modifications, processing described as being performed in slot units may be performed in TTI units, subframe units, subslot units, or minislot units.

[0339] For example, the methods disclosed in the above-described embodiments and their modifications may be applied to the IAB, to communications between an IAB donor and an IAB node, or to processing using a Uu in the IAB.

[0340] Various aspects of the present disclosure are summarized below as appendices.

[0341] (Supplementary Note 1) A communication system compatible with a fifth-generation wireless access system, comprising a plurality of networks including a wireless access network and a core network, wherein an anchor network, to which a communication terminal is connected and which has a user plane function for directly connecting to a data network to which the communication terminal transmits and receives data, determines whether or not it is necessary to add a network to which the communication terminal connects based on information about communication quality between the communication terminal and the data network, and selects an additional network if it is necessary to add a network to which the communication terminal connects, and the network selected as the additional network by the anchor network performs registration processing for connecting to the communication terminal. (Supplementary Note 2) The communication system according to Supplementary Note 1, characterized in that when the communication terminal, which is connected to a plurality of networks, decides to deregister from one of the connected networks that does not correspond to the anchor network, the network to be deregistered accepts a deregistration request to its own network from the communication terminal, and performs processing for releasing the connection with the anchor network and for deregistering the communication terminal. (Supplementary Note 3) The communication system described in Supplementary Note 1, characterized in that when the communication terminal connected to multiple networks decides to deregister from one of the networks that does not correspond to the anchor network, the anchor network accepts a network deregistration request from the communication terminal and executes processing to release the connection with the network to be deregistered, and the network to be deregistered executes processing to deregister the communication terminal in response to the request from the anchor network.(Supplementary Note 4) The communications system according to Supplementary Note 1, wherein the anchor network decides to deregister the communications terminal from the networks other than its own network, requests the communications terminal to deregister from the network to be deregistered, and performs processing to release the connection with the network to be deregistered, and the network to be deregistered performs processing to deregister the communications terminal in response to the request from the anchor network. (Supplementary Note 5) The communications system according to Supplementary Note 1, wherein a network to which the communications terminal is connected that is not the anchor network decides to deregister the communications terminal from its own network, requests the communications terminal to deregister from its own network, and performs processing to release the connection with the anchor network and to deregister the communications terminal. (Supplementary Note 6) The communications system according to Supplementary Note 3, wherein the anchor network further performs processing to release the connection with the communications terminal when it receives a further request to deregister from its own network from the communications terminal. (Supplementary Note 7) The communication system according to any one of Supplements 2 to 5, wherein, after the network to be deregistered executes processing to deregister the communication terminal, the network different from the network to be registered executes registration processing to connect to the communication terminal. (Supplementary Note 8) The communication system according to any one of Supplements 1 to 7, wherein the network selected as the additional network by the anchor network has a user plane function that directly connects to the data network to which the communication terminal transmits and receives data. (Supplementary Note 9) The communication system according to any one of Supplements 1 to 8, wherein a user plane function of the anchor network that directly connects to the data network copies data from the data network, and the anchor network and the network connected to the communication terminal each transmit the same data obtained by the copy processing by the user plane function.

[0342] 202 Communication terminal device (mobile terminal), 210 Communication system, 213, 240-1, 240-2, 750 Base station device (NR base station, base station), 214 5G core unit, 215 Central unit, 216 Distributed unit, 217 Central unit for control plane, 218 Central unit for user plane, 219 TRP, 301, 403 Protocol processing unit, 302 Application unit, 304, 405 Encoder unit, 305, 406 Modulation unit, 306, 407 Frequency conversion unit, 307-1 to 307-4, 408-1 to 408-4 Antenna, 308, 409 Demodulation unit, 309, 410 Decoder unit, 310, 411, 526 Control unit, 401 EPC communication unit, 402 Other base station communication unit, 412 5GC communication unit, 521 Data Network communication unit, 522 base station communication unit, 523 user plane communication unit, 523-1 PDU processing unit, 523-2 mobility anchoring unit, 525 control plane control unit, 525-1 NAS security unit, 525-2 idle state mobility management unit, 527 session management unit, 527-1 PDU session control unit, 527-2 UE IP address allocation unit, 751-1 to 751-8 beam, 752 cell, 1100 learning device, 1110, 1210 data acquisition unit, 1120 model generation unit, 1121 reward calculation unit, 1122 function update unit, 1130 learned model storage unit, 1200 inference device, 1220 inference unit.

Claims

1. A communication system compatible with fifth-generation wireless access systems, It includes multiple networks, including wireless access networks and core networks. An anchor network, which is a network to which a communication terminal is connected and which has user-plane functionality and is directly connected to the data network to which the communication terminal sends and receives data, determines whether or not it is necessary to add a network to which the communication terminal is connected, and if it is necessary to add a network to which the communication terminal is connected, it selects an additional network, based on information regarding the communication quality between the communication terminal and the data network. The network selected as the additional network by the anchor network performs a registration process to connect to the communication terminal. A communication system characterized by the following features.

2. If a communication terminal connected to multiple networks decides to deregister a network that is not the anchor network among the networks to which it is connected, The network to be deregistered receives a deregistration request from the communication terminal and executes a process to release the connection with the anchor network, and a process to deregister the communication terminal. The communication system according to feature 1.

3. If a communication terminal connected to multiple networks decides to unregister from one of the connected networks that does not correspond to the anchor network, The anchor network receives a network deregistration request from the communication terminal and executes a process to release the connection with the network to be deregistered. The network to be deregistered executes a process to deregister the communication terminal in response to a request from the anchor network. The communication system according to feature 1.

4. The anchor network decides to unregister the communication terminal from a network other than its own network, requests the communication terminal to unregister from the network to be unregistered, and executes a process to release the connection with the network to be unregistered. The network to be deregistered executes a process to deregister the communication terminal in response to a request from the anchor network. The communication system according to feature 1.

5. Among the networks to which the communication terminal is connected, the network that does not correspond to the anchor network decides to unregister the communication terminal from its own network, requests the communication terminal to unregister from its own network, and executes a process to release the connection with the anchor network, and a process to unregister the communication terminal. The communication system according to feature 1.

6. If the anchor network receives a further request from the communication terminal to unregister from its own network, it will further perform a process to release the connection with the communication terminal. The communication system according to claim 3.

7. After the network to be deregistered performs the process to deregister the communication terminal, the network selected as the additional network performs the registration process to connect with the communication terminal. The communication system according to any one of claims 2 to 5.

8. The network selected as the additional network by the anchor network has a user-plane function that directly connects to the data network to which the communication terminal sends and receives data. The communication system according to feature 1.

9. The user-plane function of the anchor network, which is directly connected to the data network, replicates data from the data network. Each of the anchor network and the network connected to the communication terminal transmits the same data obtained by the replication process performed by the user-plane function. The communication system according to feature 1.

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