Communication system

Abstract

Provided is a robust communication network for preventing malfunction of edge computing in a communication system configured to allow a UE to connect to a plurality of networks simultaneously. This communication system is compatible with a fifth-generation radio access system and comprises: a plurality of networks each including a radio access network and a core network; and an edge application server connected to the networks to perform edge computing. When a communication terminal connected to one or more of the networks and communicating with the edge application server switches the destination network, switching of the edge application server with which the communication terminal communicates is also performed.

Description

communication systems

[0001] This application claims priority to Japanese Patent Application No. 2024-033313, filed on March 5, 2024, the contents of which are incorporated herein by reference.

[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. For example, a technology has been proposed in which a single terminal connects to multiple networks simultaneously to improve communication capacity and reliability (see Non-Patent Documents 30 and 31). Another technology has been proposed that reduces latency by introducing edge computing (see Non-Patent Documents 31 and 32).

[0055] 3GPP TS36.300 V18.0.03GPP TS38.300 V18.0.0 “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 V18.4.03GPP TS38.211 V18.1.03GPP TS38.212 V18.1.03GPP TS38.213 V18.1.03GPP TS38.214 V18.1.03GPP TS38.321 V18.0.03GPP TS38.322 V18.0.03GPP TS38.323 V18.0.03GPP TS37.324 V17.0.03GPP TS38.331 V18.0.03GPP TS38.401 V18.0.03GPP TS38.413 V18.0.03GPP TS37.340 V18.0.03GPP TS38.423 V18.0.03GPP TS38.305 V18.0.03GPP TS23.273 V18.4.03GPP TR23.703 V12.0.03GPP TS23.287 V18.2.03GPP TS23.303 V17.1.03GPP TS38.340 V18.0.03GPP SWS-2300493GPP TS23.502 V18.4.03GPP TS23.548 V18.4.0

[0056] Non-Patent Documents 31 and 32 do not disclose anything about the operation when a UE communicating with an Edge Application Server (EAS) connects to multiple networks. Therefore, for example, a discrepancy in recognition occurs between the UE and the communication system regarding whether or not the UE is connected to the EAS, which results in a malfunction of the communication system.

[0057] In view of the above-mentioned problems, one of the objectives of the present disclosure is to configure a communication system that allows a UE to connect to multiple networks simultaneously, and to provide a robust communication network that prevents malfunctions of edge computing.

[0058] In order to solve the above-mentioned problems and achieve the objectives, the present disclosure provides a communication system compatible with a fifth-generation wireless access system, including a plurality of networks, each including a wireless access network and a core network, and an edge application server for performing edge computing, connected to the network, wherein when a communication terminal connected to one or more of the networks and communicating with the edge application server switches the network to which it is connected, the edge application server with which the communication terminal communicates is also switched.

[0059] According to the present disclosure, it is possible to provide a robust communication network that prevents malfunctions of edge computing in a communication system configured so that a UE can be simultaneously connected to multiple networks.

[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] 13. It is an explanatory diagram showing the configuration of a radio frame used in an NR communication system. It is a block diagram showing the overall configuration of an NR communication system 210 discussed in 3GPP. It is a configuration diagram of DC by a base station connected to an NG core. It is a block diagram showing the configuration of a mobile terminal 202 shown in FIG. 2. It is a block diagram showing the configuration of a base station 213 shown in FIG. 2. It is a block diagram showing the configuration of a 5GC unit. It is a flowchart showing an overview from cell search to standby operation performed by a communication terminal (UE) in an NR communication system. It is a diagram showing an example of the configuration of a cell in an NR system. It is a connection configuration diagram showing an example of the connection configuration of a terminal in SL communication. It is a connection configuration diagram showing an example of the connection configuration of a base station that supports access / backhaul integration. It is a configuration diagram showing an example of edge computing in a communication system in which a UE is connected to multiple NWs, according to the first embodiment. It is a configuration diagram showing an example of EAS switching accompanying NW switching of a UE, according to the first embodiment. It is a sequence diagram showing an example of EAS switching operation accompanying NW switching, according to the first embodiment. It is a diagram of the first half of the sequence showing an example of procedure 1130 of FIG. 24 is a diagram showing the second half of a sequence illustrating an example of procedure 1130 of FIG. 13 . FIG. 24 is a sequence diagram showing an example of procedure 1150 of FIG. 13 . FIG. 24 is a sequence diagram showing another example of EAS switching operation accompanying NW switching for the first embodiment. FIG. 24 is a sequence diagram showing another example of EAS switching operation accompanying NW switching for the first embodiment. FIG. 24 is a configuration diagram showing an example of connecting to the same EAS after NW switching of a UE for the second embodiment. FIG. 24 is a sequence diagram showing an example of operation using the source EAS after NW switching for the second embodiment. FIG. 24 is a sequence diagram showing another example of operation using the source EAS after NW switching for the second embodiment. FIG. 24 is a configuration diagram showing an example of connecting to the same local anchor UPF and the same EAS after NW switching of a UE for a first variant of the second embodiment. FIG. 24 is a configuration diagram showing an example of connecting a different EAS to each branching NW for the third embodiment. FIG. 24 is a sequence diagram showing an example of operation of providing an EAS for each branching NW for the third embodiment.Fig. 25 is a diagram of the latter half of a sequence illustrating an example of procedure 2230 in Fig. 24. Fig. 26 is a configuration diagram illustrating an example in which branching destination networks are connected to the same EAS, according to the fourth embodiment. Fig. 27 is a sequence diagram illustrating an example of an operation in which the EAS connected to each branching destination network is common, according to the 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 control 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] Edge computing may be performed in a 3GPP mobile communication system. Edge computing may be performed in an Edge Application Server (EAS). In edge computing, part or all of application processing may be performed closer to the UE than the Data Network (DN). For example, a branching of a path between the UE and an anchor UPF (a UPF directly connected to the DN) may be performed. A local anchor UPF (see Non-Patent Document 32) may be provided at the branching destination. A connection between the UE and the EAS may be established via the local anchor UPF.

[0129] In a 3GPP mobile communication system, a UE may be connected to multiple NWs. The connection between the UE and the DN may be established via an anchor UPF. An anchor NW (a network having an anchor UPF, the same applies hereinafter) may be connected to one or more NWs connected to the UE. In this specification, a NW that does not have an anchor UPF is referred to as a non-anchor NW. Furthermore, a device constituting an anchor NW is referred to as an anchor NW device, and a device constituting a non-anchor NW is referred to as a non-anchor NW device.

[0130] However, non-patent documents 31 and 32 do not disclose anything about the operation when a UE communicating with an EAS connects to multiple networks. Therefore, for example, a discrepancy in recognition occurs between the UE and the communication system regarding whether or not the UE is connected to the EAS, which results in a malfunction of the communication system.

[0131] This embodiment discloses a method for solving the above-mentioned problems. Edge computing may be performed in a communication system in which a UE is connected to multiple networks. Fig. 11 is a configuration diagram showing an example in which edge computing is performed in a communication system in which a UE is connected to multiple networks. In the example shown in Fig. 11, the UE is connected to each of NW1090 (hereinafter, sometimes referred to as NW#1) and NW1091 (hereinafter, sometimes referred to as NW#2). In the example shown in FIG. 11 , base station #1, AMF #1, UPF #1, SMF #1, SEPP (Security Edge Protection Proxy: see Non-Patent Document 10) #1, PCF #1, UDM #1, anchor UPF, NEF (Network Exposure Function) #1, and local anchor UPF #1 all belong to NW1090, which is an anchor NW, and base station #2, AMF #2, UPF #2, SMF #2, SEPP #2, PCF #2, UDM #2, and NEF #2 all belong to NW1091. The anchor UPF is connected to the DN. The path between the UE and the DN branches from UPF #1 to the local anchor UPF #1, and the local anchor UPF #1 is connected to EAS #1. In the following description, a function or device belonging to the anchor NW may be referred to as "anchor XXX." For example, an AMF belonging to the anchor NW is referred to as an anchor AMF, and a base station belonging to the anchor NW is referred to as an anchor base station.

[0132] Multiple EASs may be provided in a network. For example, EASs corresponding to different applications may be provided. One or more EASs may be provided in one network, or may be provided in multiple networks, respectively. The EASs provided in each network may correspond to different applications. This, for example, can improve flexibility in edge computing.

[0133] The network to which the UE is connected may be switched. For example, the network used for transmission and reception between the UE and the DN may be switched from NW #1 to NW #2, or the network may be switched from NW #2 to NW #1, or the network may be switched to another network. This switching may be performed for part of the traffic. For example, when the UE performs communication related to application 1 via NW #1 and communication related to application 2 via NW #2, the path for communication related to application 2 may be switched to NW #1.

[0134] The following problem occurs in this switching: The above-mentioned Non-Patent Documents 31 and 32 do not disclose anything about the operation of network switching for a UE connected to an EAS, which may cause malfunctions related to edge computing in the communication system.

[0135] In this embodiment, a method for solving the above-mentioned problems is disclosed. In the following description, the NW to which the UE is connected before the NW to which the UE is connected is switched may be referred to as the source NW, and the NW to which the UE is connected after the NW is switched may be referred to as the destination NW. In addition, the base station to which the UE is connected before the NW to which the UE is connected is switched may be referred to as the source base station, and the base station to which the UE is connected after the NW is switched may be referred to as the destination base station.

[0136] In this embodiment, a new EAS is connected to the switching destination network. The new EAS may be different from the EAS connected to the switching source network.

[0137] FIG. 12 is a configuration diagram showing an example in which EAS switching is performed in conjunction with a UE network switching. In the example shown in FIG. 12 , an example is shown in which the network to which the UE is connected is switched from NW#1 to NW#2. Note that the EAS to which the UE connects after EAS switching in conjunction with a network switching may be referred to as a target EAS. In the example shown in FIG. 12 , the EAS to which the UE connects is switched from EAS#1 to EAS#2. The path between the UE and the DN in NW#2 branches from UPF#2 to the local anchor UPF#2, and the local anchor UPF#2 is connected to EAS#2. The UE connects to EAS#2 via UPF#2 and the local anchor UPF#2.

[0138] The EAS after NW switching (hereinafter may be referred to as switching destination EAS) may be determined by the NF of the switching destination NW. The NF of the switching destination NW may be, for example, an SMF (hereinafter may be referred to as switching destination SMF), an AMF, or a PCF. The NF of the switching destination NW may make the determination in response to a NW switching instruction from the NF of the switching source NW. The NF of the switching source NW may be, for example, an SMF (hereinafter may be referred to as switching source SMF) or an AMF. The NW switching may be determined by the NF of the switching source NW. The NF that determines the NW switching may be, for example, an SMF or an AMF.

[0139] The NF of the source network may notify the NF of the destination network of information about the EAS. For example, the information may be included in a network switching instruction and notified.

[0140] The information about the EAS may include information about the address (e.g., IP address) of the EAS, or information about the DN including the EAS (e.g., Data Network Access Identifier (see Non-Patent Document 11)). An NF (e.g., SMF) of the destination NW may use the information to determine the destination EAS. This enables, for example, the NF of the destination NW to quickly determine the destination EAS.

[0141] The UE and / or the NF of the target network may perform address discovery of the target EAS. The address discovery may be performed using, for example, the method disclosed in Section 6.2.3.2.2 or 6.2.3.2.3 of Non-Patent Document 32 (3GPP TS23.548).

[0142] The address search of the target EAS may not be performed. For example, when the UE and / or the NF of the target NW already knows the address of the target EAS, the search may not be performed. This allows, for example, NW switching to be performed quickly.

[0143] Even if the UE and / or the NF of the target network already knows the address of the target EAS, the address search of the target EAS may be performed. This makes it possible to detect, for example, that the path from the UE to the target EAS is out of service, thereby preventing a situation in which the UE cannot use the target EAS.

[0144] The UE may make a query to a Domain Name System (DNS). For example, the UE may make the query to an Edge Application Server Discovery Function (EASDF). The query may be, for example, a query to the target EAS. A PDU session may be established in the target network. The PDU session establishment may be, for example, a PDU session establishment for the UE to connect to the EASDF.

[0145] A PDU session may be established in the switching destination network, or a PDU session may be changed. The PDU session establishment / change may be a PDU session for performing edge computing in the switching destination network. For example, it may be the establishment / change of a PDU session used for transmitting and receiving data for edge computing.

[0146] A local anchor UPF (hereinafter, sometimes referred to as a target local anchor UPF) may be provided in the target NW. The target local anchor UPF may be a UPF connected to the target EAS. A connection may be established between the target local anchor UPF and the target EAS. A connection may be established between the UE and the target EAS.

[0147] A distinction may be made between data exchanged between the UE and the local anchor UPF and data exchanged between the UE and the anchor UPF, and this distinction may be made using PDU sessions or QoS flows.

[0148] The SMF may notify the UE of information regarding the distinction. The SMF may be the SMF of the target network or the SMF of the source network. The notification may be performed via the AMF or via the base station. For example, the notification may be performed using NAS signaling or RRC signaling. This allows the UE to quickly distinguish between data intended for EAS and data intended for DN, for example.

[0149] The information about this distinction may be notified from the SMF to the AMF, to the UPF, or to the base station, which may be an intermediate UPF, a local anchor UPF, or an anchor UPF, allowing, for example, routing of data for EAS and data for DN in the UPF.

[0150] The NF of the switching destination network may notify the NF of the switching source network of the completion of EAS switching. The NF may notify the NF of the switching source network of the completion of NW switching. The notification of the completion of EAS switching may be included in the notification of the completion of NW switching. The NF may be an SMF, an AMF, or a PCF.

[0151] The notification of the completion of EAS switching may be triggered by a notification of the completion of NW switching from the switching destination NW to the switching source NW. As another example, the notification of the completion of EAS switching may be triggered by the completion of PDU session establishment in the switched NW, or may be triggered by the completion of PDU session change in the switched NW.

[0152] The UE may switch the EAS to which uplink data is sent to the post-switching EAS upon the establishment of a PDU session and / or completion of the change in the target network.

[0153] The source EAS may continue to transmit downlink data to the UE. For example, the UE may continue to receive the downlink data even after the PDU session establishment and / or change in the target network is completed. This makes it possible to prevent, for example, the loss of downlink data from the EAS to the UE.

[0154] As another example, the source EAS may transfer data exchanged with the UE to the target EAS. The transfer may be performed, for example, via a DN. The transfer may be performed, for example, when the source network is released. This makes it possible to prevent data loss between the UE and the EAS during network switching.

[0155] The PDU session between the UE and the source network may be released or changed. The release / change may be triggered by a notification of completion of NW switching from the destination network or by a notification of completion of EAS switching.

[0156] The source EAS may stop sending downlink data to the UE when the PDU session with the source NW is released / changed.

[0157] Fig. 13 is a sequence diagram showing an example of EAS switching operation accompanying NW switching. In the example shown in Fig. 13, the connection destination of a UE is switched from NW#1, which is an anchor NW, to NW#2, which is a non-anchor NW. At the same time, the EAS to which the UE is connected is switched from EAS#1 to EAS#2. In the example shown in Fig. 13, the decision to switch the EAS is made by NW#2. In the example shown in Fig. 13, UPF#1, SMF#1, PCF#1, NEF#1, local anchor UPF#1, and anchor UPF belong to NW#1, and UPF#2, SMF#2, PCF#2, NEF#2, local anchor UPF#2, and UDM#2 belong to NW#2.

[0158] In steps ST1101 to ST1103 shown in Fig. 13, data is transmitted and received between the UE and EAS#1 via NW#1. Step ST1101 represents data transmission and reception between the UE and UPF#1, step ST1102 represents data transmission and reception between UPF#1 and local anchor UPF#1, and step ST1103 represents data transmission and reception between local anchor UPF#1 and EAS#1. Step ST1101 may be performed via base station#1.

[0159] In step ST1105 shown in Fig. 13 , SMF#1 detects QoS deterioration. In the example shown in Fig. 13 , SMF#1 detects QoS deterioration related to NW#1, for example, UPF#1. SMF#1 may detect the QoS deterioration using a QoS monitoring report from the anchor UPF, local anchor UPF#1, and / or UPF#1. For the detection, the QoS monitoring report from base station#1 may be used, or a QoS monitoring report from the UE may be provided and used.

[0160] In step ST1107 shown in Fig. 13, SMF#1 determines to switch the network that serves as the data path. In the example shown in Fig. 13, SMF#1 determines to switch the data path that passes through UPF#1 to the path that passes through UPF#2.

[0161] In steps ST1110 to ST1114 shown in FIG. 13 , a network switching notification is sent from SMF#1 to an AF (Application Function) via PCF#1 and NEF#1. Step ST1110 shows the notification from SMF#1 to PCF#1, step ST1112 shows the notification from PCF#1 to NEF#1, and step ST1114 shows the notification from NEF#1 to AF. The notification may include information about the EAS, information about the network switching (e.g., information about the source network and / or the destination network), or information about the reason for the network switching. The AF recognizes that the EAS switching will be performed in step ST1114.

[0162] In step ST1120 shown in FIG. 13 , SMF#1 instructs SMF#2 to switch the network. The instruction may use signaling of a PDU session establishment request or signaling of a PDU session modification request. The instruction may include information about the UE, information about the network switching (e.g., information about the source network and / or the destination network), information about the reason for the network switching (e.g., QoS deterioration), information about the anchor UPF, information about the PDU session, information about the QoS flow, information about the EAS (e.g., information about the address of the EAS and / or information about the DN including the EAS), or information requesting connection between NW#2 and the EAS. For example, the information about the EAS may include information requesting connection between NW#2 and the EAS.

[0163] The instruction may include information about QoS for each path. The path may include a path between the UE and the anchor UPF, or a path between the UE and the local anchor UPF #1. This allows, for example, the target network to quickly understand which path has a problem with QoS.

[0164] The instruction may include information about the QoS between each node. For example, the instruction may include information about the QoS between the UE and the local anchor UPF, information about the QoS between the base station and the local anchor UPF, or information about the QoS between the local anchor UPF and the anchor UPF. This allows, for example, the target network to quickly understand which node has a problem with the QoS between them.

[0165] The instruction may include information about network slicing (see Non-Patent Document 10). The information may include, for example, information about a slicing type. This makes it possible to configure the network slicing of the type in the destination network, and as a result, it is possible to ensure the QoS of the network after switching.

[0166] In procedure 1125 shown in FIG. 13 , an EAS address search is performed in NW #2. The address search may be performed, for example, using the method disclosed in Section 6.2.3.2.2 or 6.2.3.2.3 of 3GPP TS 23.548. In procedure 1125, a PDU session may be established. The PDU session may be established for the UE to connect to the EASDF. In the example shown in FIG. 13 , it is determined that EAS #2 is to be used in NW #2. In procedure 1125, a local anchor UPF #2 may be provided.

[0167] In procedure 1130 shown in Fig. 13, a connection establishment process with the UPF in NW #2 is performed. Procedure 1130 will be described below. Fig. 14 and Fig. 15 are sequence diagrams showing an example of procedure 1130 in Fig. 13. Fig. 14 shows the first half of the sequence, and Fig. 15 shows the second half of the sequence.

[0168] In step ST1201 shown in Fig. 14, SMF#2 selects a UPF. In the example shown in Fig. 14, SMF#2 selects UPF#2 and decides to use the UPF#2. The selection and / or decision of the local anchor UPF#2 may be performed in step ST1201.

[0169] In step ST1203 shown in FIG. 14 , a procedure for establishing a session management policy association is performed between SMF#2 and PCF#2. This procedure may be, for example, the procedure disclosed in clause 4.16.4 of non-patent document 31 (3GPP TS23.502). In step ST1203, a procedure for changing the session management policy association may be performed. The procedure for changing the session management policy association may be, for example, the procedure disclosed in clause 4.16.5 of non-patent document 31 (3GPP TS23.502).

[0170] In step ST1205 shown in FIG. 14 , SMF#2 requests UPF#2 to establish an N4 session. The request may include information regarding the distinction between data exchanged between the UE and the local anchor UPF and data exchanged between the UE and the anchor UPF. The information may include, for example, information regarding QoS. For example, the information may include information regarding the QoS flow to be routed to the local anchor UPF, or information regarding the QoS flow to be routed to the anchor UPF. UPF#2 establishes an N4 session triggered by step ST1205. In step ST1207, UPF#2 responds to step ST1205 to SMF#2. In steps ST1205 and ST1207, a request to change the N4 session and a response may be made.

[0171] In step ST1209 shown in FIG. 14 , SMF#2 requests local anchor UPF#2 to establish an N4 session. Step ST1209 is triggered by the local anchor UPF#2 to establish an N4 session. In step ST1209, a request for changing the N4 session may be made. Step ST1209 is triggered by the local anchor UPF#2 to establish an N4 session or to change the N4 session. In step ST1211, the local anchor UPF#2 responds to step ST1209 to SMF#2.

[0172] In step ST1215 shown in Fig. 14, SMF#2 requests SMF#1 to establish a connection between the intermediate UPF and the anchor UPF. In the example shown in Fig. 14, a request to establish a connection between UPF#2 and the anchor UPF may also be made.

[0173] In step ST1217 shown in FIG. 14 , SMF#1 requests the anchor UPF to change the N4 session. The request may include, for example, information about UPF#2, information about the UE, or PDU session identification information. The anchor UPF uses the information included in the request to establish a connection with UPF#2. In step ST1219, the anchor UPF responds to step ST1217 to SMF#1.

[0174] In step ST1221 shown in FIG. 14, SMF#1 notifies SMF#2 of the establishment of connection between the anchor UPF and the intermediate UPF. The notification may be made in response to the request in step ST1215.

[0175] In steps ST1223 and ST1224 shown in FIG. 14 , information required for establishing a PDU session of the UE is transmitted and received between SMF#2 and AMF#2. Information required for modifying a PDU session may also be transmitted and received. In step ST1223, an instruction to establish a PDU session may be sent from SMF#2 to AMF#2, or an instruction to modify a PDU session may be sent. The information may include information about the UE, information about the PDU session, information about the QoS flow, information about the UPF (e.g., UPF#2, local anchor UPF#2, and / or anchor UPF), or information about distinguishing between data intended for the local anchor UPF and data intended for the anchor UPF, as described above.

[0176] In step ST1226 shown in FIG. 14 , AMF#2 notifies base station#2 of a PDU session establishment request for the UE. The notification may also be a PDU session modification request. The notification may include the information included in step ST1223, or may include the above-mentioned information regarding the distinction between data intended for the local anchor UPF and data intended for the anchor UPF. In step ST1228, base station#2 notifies the UE of a PDU session establishment request. The notification may also be a PDU session modification request. RRC signaling, for example, RRC establishment signaling or RRC reconfiguration signaling may be used in step ST1228. The notification in step ST1228 may include the information included in step ST1226. For example, the above-mentioned information regarding the distinction between data intended for the local anchor UPF and data intended for the anchor UPF may be included. The UE may perform a PDU session establishment process or a PDU session modification process using the content of the notification in step ST1228.

[0177] In step ST1230 shown in FIG. 15 , the UE responds to step ST1228 to the base station #2. For the response, RRC signaling, for example, signaling of RRC establishment completion or signaling of RRC reconfiguration completion may be used. The UE may perform step ST1230 upon completion of the PDU establishment and / or PDU modification process. In step ST1232, the base station #2 responds to step ST1226 to the AMF #2. The response in step ST1232 may include N2 session management information.

[0178] In step ST1234 shown in FIG. 15 , AMF#2 notifies SMF#2 of the N2 session management information from base station#2. This notification may be performed, for example, using signaling of Nsmf_PDUSession_UpdateSMContext Request (see Non-Patent Document 31). In step ST1236, SMF#2 responds to step ST1234 to AMF#2. This response may be performed, for example, using signaling of Nsmf_PDUSession_UpdateSMContext Response (see Non-Patent Document 31).

[0179] In step ST1238 shown in Fig. 15, the SMF#2 requests the UPF#2 to change the N4 session. In step ST1240, the UPF#2 responds to step ST1238 to the SMF#2.

[0180] In step ST1242 shown in FIG. 15, the SMF#2 requests the local anchor UPF#2 to change the N4 session. In step ST1244, the local anchor UPF#2 sends a response to step ST1242 to the SMF#2.

[0181] 15 , a procedure for changing 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 4.16.5 of Non-Patent Document 31 (3GPP TS23.502).

[0182] Returning to the description of Fig. 13, in step ST1140 shown in Fig. 13, SMF #2 notifies SMF #1 of the completion of PDU session establishment and / or change. This response may be made as a response to step ST1120.

[0183] In procedure 1150 shown in Fig. 13, a PDU session is released in NW #1. A PDU session change may be performed in NW #1. Procedure 1150 will be described below. Fig. 16 is a sequence diagram showing an example of procedure 1150 in Fig. 13.

[0184] In step ST1301 shown in FIG. 16 , SMF#1 requests the anchor UPF to release the N4 session. A request to change the N4 session may also be made. The anchor UPF may release the N4 session or change the N4 session, triggered by step ST1301. In step ST1303, the anchor UPF responds to step ST1301 to SMF#1.

[0185] In step ST1305 shown in FIG. 16 , SMF#1 requests UPF#1 to release the N4 session. A request to change the N4 session may also be made. UPF#1 may release the N4 session or change the N4 session, triggered by step ST1305. In step ST1307, UPF#1 responds to step ST1305 to SMF#1.

[0186] In step ST1309 shown in FIG. 16 , SMF#1 requests local anchor UPF#1 to release the N4 session. A request to change the N4 session may also be made. The local anchor UPF#1 may release the N4 session or change the N4 session, triggered by step ST1309. In step ST1311, the local anchor UPF#1 responds to step ST1309 to SMF#1.

[0187] In steps ST1313 and ST1314 shown in FIG. 16 , information required for releasing a PDU session of a UE is transmitted and received between SMF#1 and AMF#1. Information required for modifying a PDU session may also be transmitted and received. In step ST1313, an instruction to release a PDU session may be issued from SMF#1 to AMF#1, or an instruction to modify a PDU session may be issued. The instruction may include the above-mentioned information. The information may include information about the UE, information about the PDU session, information about the QoS flow, or information about the UPF. The information may include information about the EAS.

[0188] In step ST1316 shown in FIG. 16 , AMF #1 notifies base station #1 of a PDU session release request for the UE. The notification may also be a PDU session modification request. The notification may include the information included in step ST1313. In step ST1318, base station #1 notifies the UE of a PDU session release request. The notification may also be a PDU session modification request. RRC signaling, for example, RRC release signaling or RRC reconfiguration signaling may be used in step ST1318. The notification in step ST1318 may include the information included in step ST1316. The UE may perform a PDU session release process or a PDU session modification process using the content of the notification in step ST1318.

[0189] In step ST1320 shown in Fig. 16 , the UE responds to step ST1318 to the base station #1. The response may be RRC signaling, for example, signaling indicating completion of RRC reconfiguration. In step ST1322, the base station #1 responds to step ST1316 to the AMF #1. The response in step ST1316 may include N2 session management information.

[0190] In step ST1324 shown in FIG. 16 , AMF#1 notifies SMF#1 of the N2 session management information from base station#1. This notification may be performed, for example, using signaling of Nsmf_PDUSession_UpdateSMContext Request (see Non-Patent Document 31). In step ST1326, SMF#1 responds to step ST1324 to AMF#1. This response may be performed, for example, using signaling of Nsmf_PDUSession_UpdateSMContext Response (see Non-Patent Document 31).

[0191] 16 , a procedure for terminating a session management policy association is performed between the SMF#1 and the PCF#1. This procedure may be, for example, the procedure disclosed in Section 4.16.6 of Non-Patent Document 31 (3GPP TS23.502).

[0192] Returning to the description of Fig. 13, in steps ST1151 to ST1153, data is transmitted and received between the UE and EAS#2 via NW#2. Step ST1151 represents data transmission and reception between the UE and UPF#2, step ST1152 represents data transmission and reception between UPF#2 and local anchor UPF#2, and step ST1153 represents data transmission and reception between local anchor UPF#2 and EAS#2. Step ST1151 may be performed via base station#2.

[0193] 13 shows an example in which a notification regarding NW switching is sent from the source SMF to the AF, but the notification from the source SMF to the AF may not be sent. For example, steps ST1110 to ST1114 in FIG. 13 may not be performed. This makes it possible to reduce the amount of processing in the source SMF, for example.

[0194] As another example, the AF may notify the NF of the destination network of information about the EAS. The NF may be, for example, the destination SMF. The notification from the AF to the destination SMF may be performed via the NEF and / or PCF of the destination network. The NF of the destination network may obtain information about the EAS using the notification.

[0195] The source NF (e.g., SMF) may not notify the destination NF (e.g., SMF) of information related to the source EAS (EAS before NW switching). For example, the NW switching instruction from the source NF (e.g., SMF) to the destination NF (e.g., SMF) may not include information related to the EAS. This, for example, makes it possible to reduce the size of signaling from the source NF to the destination NF. The source NF may notify the destination NF of information requesting connection between NW#2 and the EAS. This, for example, makes it possible to connect NW#2 and the EAS, and as a result, makes edge computing possible after the NW switching.

[0196] FIG. 17 is a sequence diagram showing another example of EAS switching operations accompanying NW switching. In the example shown in FIG. 17, the UE's connection destination is switched from NW#1, which is an anchor NW, to NW#2, which is a non-anchor NW. At the same time, the EAS to which the UE connects is switched from EAS#1 to EAS#2. In the example shown in FIG. 17, the decision to switch the EAS is made by NW#2. In the example shown in FIG. 17, UPF#1, SMF#1, PCF#1, NEF#1, local anchor UPF#1, and anchor UPF belong to NW#1, and base station#2, AMF#2, UPF#2, SMF#2, PCF#2, NEF#2, local anchor UPF#2, and UDM#2 belong to NW#2. In FIG. 17, processes similar to those in FIG. 13 are assigned the same numbers, and common descriptions will be omitted.

[0197] Steps ST1101 to ST1114 shown in FIG. 17 are the same as those in FIG.

[0198] 17, a NW switching notification is sent from the AF to the SMF#2 via the NEF#2 and PCF#2. Step ST1616 shows the notification from the AF to the NEF#2, step ST1617 shows the notification from the NEF#2 to the PCF#2, and step ST1618 shows the notification from the PCF#2 to the SMF#2. Steps ST1616 to ST1618 may include information related to the EAS or may include requirements related to latency.

[0199] In step ST1620 shown in Fig. 17, SMF#1 instructs SMF#2 to switch the network. Step ST1620 may be the same signaling as step ST1120 shown in Fig. 13. Step ST1620 may not include information about the EAS (e.g., information about the address of the EAS and / or the DN including the EAS). This makes it possible to reduce the size of the signaling in step ST1620, for example.

[0200] Procedure 1125 to step ST1153 shown in FIG. 17 are the same as those in FIG.

[0201] As another solution, the EAS decision may be made by an NF of the source network. The source NF may be, for example, an SMF, an AMF, or a PCF. The NF of the source network may decide to switch the EAS when a decision to switch the network in its own network is made.

[0202] The UE and / or the NF of the source network may perform address discovery of the target EAS. The address discovery may be performed using, for example, the method disclosed in Section 6.2.3.2.2 or 6.2.3.2.3 of Non-Patent Document 32 (3GPP TS23.548).

[0203] The UE may perform a DNS query. For example, the UE may perform the query to the EASDF. The query may be, for example, a query of the target EAS. A PDU session may be established in the source network. The PDU session establishment may be, for example, a PDU session establishment for the UE to connect to the EASDF.

[0204] The NF of the source network may notify the NF of the destination network of information about the EAS. For example, the information may be included in a network switching instruction and notified. The destination network may use the information to switch the EAS or to switch the network.

[0205] The information about the EAS may include information about the address (e.g., IP address) of the EAS, or information about the DN including the EAS (e.g., Data Network Access Identifier (see Non-Patent Document 11)). An NF (e.g., SMF) of the destination network may use the information to start a connection process to the destination EAS. This enables, for example, the NF of the destination network to quickly perform a switching process to the destination EAS.

[0206] A PDU session may be established in the target network, or a PDU session may be changed. The PDU session establishment / change may be similar to the above-described solution.

[0207] The NF of the switching destination network may notify the NF of the switching source network of the completion of EAS switching. The NF may notify the NF of the switching source network of the completion of NW switching. The notification of the completion of EAS switching may be included in the notification of the completion of NW switching. The NF may be an SMF, an AMF, or a PCF.

[0208] The PDU session between the UE and the source network may be released or modified. The release / modification may be performed in a manner similar to the above-mentioned solution.

[0209] FIG. 18 is a sequence diagram showing another example of EAS switching operations accompanying NW switching. In the example shown in FIG. 18, the UE's connection destination is switched from NW#1, which is an anchor NW, to NW#2, which is a non-anchor NW. At the same time, the EAS to which the UE connects is switched from EAS#1 to EAS#2. In the example shown in FIG. 18, the decision to switch the EAS is made by NW#1. In the example shown in FIG. 18, UPF#1, SMF#1, PCF#1, NEF#1, local anchor UPF#1, and anchor UPF belong to NW#1, and UPF#2, SMF#2, PCF#2, NEF#2, local anchor UPF#2, and UDM#2 belong to NW#2. In FIG. 18, the same processes as those in FIG. 13 are assigned the same numbers, and common descriptions will be omitted.

[0210] Steps ST1101 to ST1107 shown in FIG. 18 are the same as those in FIG.

[0211] In procedure 1725 shown in FIG. 18 , an EAS address search is performed in NW #1. The address search may be performed, for example, using the method disclosed in Section 6.2.3.2.2 or 6.2.3.2.3 of 3GPP TS 23.548. In procedure 1725, a PDU session may be established. The PDU session may be established for the UE to connect to the EASDF. In the example shown in FIG. 18 , it is determined that EAS #2 is to be used in NW #2. In procedure 1725, it may be determined that a local anchor UPF #2 is to be provided.

[0212] Steps ST1110 to ST1114 shown in FIG. 18 are the same as those in FIG.

[0213] In step ST1720 shown in FIG. 18 , SMF#1 instructs SMF#2 to switch the network. Step ST1720 may be the same signaling as step ST1120 shown in FIG. 13 . Step ST1720 may include information about the local anchor UPF (e.g., information about the local anchor UPF#2). This makes it possible to quickly establish a connection with the local anchor UPF#2 in NW#2, for example.

[0214] Steps ST1130 to ST1153 shown in FIG. 18 are the same as those in FIG.

[0215] The query to the DNS may be made by the NF of the source network. For example, the source SMF may make the query. The query may be made via the NF of the destination network or may be made directly. For example, the NF of the source network may request the NF of the destination network to make a query to the EASDF. The NF of the destination network may inquire about the address of the destination EAS from the EASDF of the destination network. As another example, the NF of the source network may inquire about the address of the destination EAS from the EASDF of the destination network. The EASDF of the destination network may inquire about the address of the destination EAS from the DNS. The NF of the source network may notify the UE of the address of the destination EAS. The UE may use this notification for network switching.

[0216] The NF of the target network may notify the AF of information about the target EAS. The NF may be, for example, an SMF, an AMF, or a PCF. The notification to the AF may be performed via the PCF or the NEF.

[0217] The information about the destination EAS may include information indicating that the destination EAS was not found, or information about the reason for this. The AF may, for example, use the information as a trigger to change the latency requirement required for the network. This makes it possible to perform edge computing in the destination network.

[0218] Although the present embodiment has disclosed NW switching from NW#1 to NW#2, it may also be applied to switching from NW#2 to NW#1.

[0219] According to the first embodiment, edge computing becomes possible even after NW switching, and malfunctions relating to edge computing in the communication system can be prevented.

[0220] Second Embodiment In the switching destination network, the same EAS as the EAS connected in the switching source network may be connected.

[0221] Fig. 19 is a configuration diagram showing an example in which a UE remains connected to the same EAS even after switching its network. In the example shown in Fig. 19, the network to which the UE is connected is switched from NW#1 to NW#2. In the example shown in Fig. 19, the EAS to which the UE is connected remains EAS#1. The path between the UE and the DN in NW#2 branches from UPF#2 to local anchor UPF#2, and the local anchor UPF#2 is connected to EAS#1. The UE connects to EAS#1 via UPF#2 and local anchor UPF#2.

[0222] The EAS after the NW switching may be determined by the NF of the post-switching NW. For example, the NF of the post-switching NW may determine that the EAS after the NW switching is the same as that before the NW switching. The EAS determination by the NF of the post-switching NW may be performed by the same method as the method disclosed in the first embodiment.

[0223] FIG. 20 is a sequence diagram showing an example of an operation using a source EAS after network switching. In the example shown in FIG. 20, a UE's connection destination is switched from NW#1, which is an anchor network, to NW#2, which is a non-anchor network. The EAS to which the UE connects remains EAS#1. In the example shown in FIG. 20, the decision to switch the EAS is made by NW#2. In the example shown in FIG. 20, base station#1, AMF#1, UPF#1, SMF#1, PCF#1, UDM#1, NEF#1, local anchor UPF#1, and anchor UPF belong to NW#1, and base station#2, AMF#2, UPF#2, SMF#2, PCF#2, NEF#2, local anchor UPF#2, and UDM#2 belong to NW#2. In FIG. 20, processes similar to those in FIG. 13 are assigned the same numbers, and common descriptions will be omitted.

[0224] Steps ST1101 to ST1120 in Fig. 20 are the same as those in Fig. 13. Information indicating that the EAS should be the same may be included in the request in step ST1120 shown in Fig. 20. This information may be included in the EAS-related information, for example.

[0225] In procedure 1925 in Fig. 20, an EAS address search is performed in NW #2. The address search may be performed, for example, using the method disclosed in Section 6.2.3.2.2 of Non-Patent Document 32 (3GPP TS23.548) or the method disclosed in Section 6.2.3.2.3 of the same. In procedure 1925, a PDU session establishment may be performed. The PDU session establishment may be, for example, a PDU session establishment for a UE to connect to the EASDF. In the example shown in Fig. 20, it is determined that EAS #1 is also used in NW #2.

[0226] Procedures 1130 to 1150 in FIG. 20 are the same as those in FIG.

[0227] In steps ST1151, ST1152, and ST1953 in Fig. 20, data is transmitted and received between the UE and EAS #1 via NW #2. Step ST1151 indicates data transmission and reception between the UE and UPF #2, step ST1152 indicates data transmission and reception between UPF #2 and local anchor UPF #2, and step ST1953 indicates data transmission and reception between local anchor UPF #2 and EAS #1. Step ST1151 may be performed via base station #2.

[0228] The EAS after the NW switching may be determined by the NF of the switching source NW. For example, the NF of the switching source NW may determine that the EAS after the NW switching is the same as that before the NW switching. The EAS determination by the NF of the switching source NW may be performed by the same method as the method disclosed in the first embodiment.

[0229] The local anchor UPF after the network switching may be determined in the source network or in the destination network. The NF of the source network may notify the NF of the destination network of information about the local anchor UPF. The NF may be, for example, an SMF, an AMF, or a PCF.

[0230]

[0073] Figure 21 is a sequence diagram showing another example of an operation using a source EAS after network switching. In the example shown in Figure 21, a UE's connection destination is switched from NW#1, which is an anchor network, to NW#2, which is a non-anchor network. The EAS to which the UE connects remains EAS#1. In the example shown in Figure 21, NW#1 decides not to switch the EAS. In the example shown in Figure 21, base station #1, AMF#1, UPF#1, SMF#1, PCF#1, UDM#1, NEF#1, local anchor UPF#1, and anchor UPF belong to NW#1, and base station #2, AMF#2, UPF#2, SMF#2, PCF#2, NEF#2, local anchor UPF#2, and UDM#2 belong to NW#2. In FIG. 21, the same processes as those in FIG. 13, FIG. 18, and FIG. 20 are denoted by the same numbers, and common explanations will be omitted.

[0231] Steps ST1101 to ST1114 shown in FIG. 21 are the same as those in FIG.

[0232] The local anchor UPF is determined in procedure 2025 shown in Fig. 21. In the example shown in Fig. 21, it is determined to use local anchor UPF #2. The local anchor UPF #2 may be determined by, for example, SMF #2.

[0233] Step ST1720 shown in FIG. 21 is the same as that in FIG.

[0234] Procedures 1130 to 1150 shown in Fig. 21 are the same as those in Fig. 13. Steps ST1151, ST1152, and ST1153 are the same as those in Fig. 20.

[0235] A priority may be set as to whether the destination EAS is the same as or different from the source EAS (EAS before the network switching). For example, priority may be given to making them the same. This makes it possible to avoid complexity in the EAS switching process. As another example, priority may be given to making the EASs different. This makes it possible to reduce latency in edge computing, for example.

[0236] The priority may be determined by an NF of the source NW. The NF may be, for example, an SMF, an AMF, or a PCF. As another example, the priority may be determined by an NF of the destination NW. The NF may be, for example, an SMF, an AMF, or a PCF. As another example, the priority may be determined by an AF. The AF may notify the priority to an NF of the source NW or may notify an NF of the destination NW. The source NF and / or the destination NF may be the same as described above. The AF may notify the priority via an NEF or via a PCF.

[0237] The priority may be notified in the source network. For example, the PCF may notify the priority to the SMF or the AMF. The same may be true in the destination network. This allows, for example, the SMF to understand the priority.

[0238] As another example, a condition may be set to determine whether the target EAS is the same as or different from the source EAS. The condition may be determined, for example, using a threshold. The condition may include, for example, a condition related to latency. The latency may include, for example, the latency from the UE to the local anchor UPF, the end-to-end latency (e.g., the latency from the UE to the EAS), the latency from the local anchor UPF to the EAS, the latency from an intermediate UPF (e.g., the UPF in FIG. 11, FIG. 12, or FIG. 19) to the EAS, or the latency from the UE to the intermediate UPF.

[0239] The NFs of the source network and / or the destination network may use the condition to determine whether the destination EAS should be the same as or different from the source EAS. The NFs may be, for example, SMFs, PCFs, or AMFs. For example, the SMF of the destination network may determine the EAS candidate as the destination EAS when the latency of the EAS candidate is less than or equal to the threshold. As another example, the SMF of the destination network may determine the destination EAS to be the same as the source EAS when the latency of the EAS candidate is greater than or equal to the threshold. This enables, for example, flexible EAS switching.

[0240] The condition may be determined by an NF of a source NW. The NF may be, for example, an SMF, an AMF, or a PCF. As another example, the condition may be determined by an NF of a destination NW. The NF may be, for example, an SMF, an AMF, or a PCF. As another example, the condition may be determined by an AF. The AF may notify the NF of the source NW or the NF of the destination NW of the condition. The source NF and / or the destination NF may be the same as those described above. The AF may notify the condition via an NEF or via a PCF.

[0241] The condition may be notified in the source network. For example, the PCF may notify the condition to the SMF or the AMF. The same may be done in the destination network. This allows, for example, the SMF to quickly grasp the condition.

[0242] According to the second embodiment, it is possible to quickly switch networks when edge computing is being performed.

[0243] Modification 1 of the Second Embodiment In the switching destination network, the mobile station may be connected to the same local anchor UPF as the local anchor UPF connected in the switching source network, or may be connected to the same EAS.

[0244] 22 is a configuration diagram showing an example in which a UE is connected to the same local anchor UPF and the same EAS even after switching its network. In the example shown in FIG. 22, the network to which the UE is connected is switched from NW#1 to NW#2. The EAS to which the UE is connected remains EAS#1. The path between the UE and the DN in NW#2 branches from UPF#2 to local anchor UPF#1. The UE connects to EAS#1 via UPF#2 and local anchor UPF#1.

[0245] The NF of the source network may notify the NF of the destination network of information about the local anchor UPF. The information may include, for example, information about the address of the local anchor UPF. The information may be included in, for example, a NW switching instruction notified from the NF of the source network to the NF of the destination network.

[0246] The NF of the target network may request the NF of the source network to establish a connection between the local anchor UPF and the intermediate UPF of NW#2. The request may be made, for example, as a request to establish an N4 session or as a request to change an N4 session. The NF of the source network may establish a connection between the local anchor UPF and the intermediate UPF of NW#2 in response to the notification.

[0247] According to the first modification, it is possible to improve the utilization efficiency of a network device, for example, a UPF.

[0248] Third Embodiment Traffic may be split. For example, some packets of the same data traffic may go through one network, and other packets may go through another network. In the traffic split, one PDU session may be split, or multiple PDU sessions may be established.

[0249] Edge computing may be performed in a communication system where traffic is branched. However, non-patent documents 31 and 32, which are related to edge computing, do not disclose the form of edge computing in the above case. As a result, for example, a misunderstanding may occur between the branching networks, which may cause malfunction of the communication system.

[0250] In this embodiment, a method for solving the above-mentioned problem is disclosed.

[0251] An EAS may be provided for each branched network.

[0252] Fig. 23 is a configuration diagram showing an example in which a different EAS is connected to each branching NW. In the example shown in Fig. 23, the NW to which a UE is connected branches into NW#1 and NW#2. The EAS to which the UE connects via NW#1 is EAS#1, and the EAS to which the UE connects via NW#2 is EAS#2. EAS#1 is connected to UPF#1 via local anchor UPF#1. EAS#2 is connected to UPF#2 via local anchor UPF#2.

[0253] FIG. 24 is a sequence diagram showing an example of an operation in which an EAS is provided for each branching NW. In the example shown in FIG. 24 , a UE's connection destination branches to NW#1, which is an anchor NW, and NW#2, which is a non-anchor NW. The UE connects to EAS#1 via UPF#1 and local anchor UPF#1, and connects to EAS#2 via UPF#2 and local anchor UPF#2. In the example shown in FIG. 24 , each NW determines its connection destination EAS. In the example shown in FIG. 24 , base station#1, AMF#1, UPF#1, SMF#1, PCF#1, UDM#1, NEF#1, local anchor UPF#1, and anchor UPF belong to NW#1, and base station#2, AMF#2, UPF#2, SMF#2, PCF#2, NEF#2, local anchor UPF#2, and UDM#2 belong to NW#2. In FIG. 24, the same processes as those in FIG. 13 are denoted by the same numbers, and common explanations will be omitted.

[0254] In procedure 2225 shown in FIG. 24 , an address search for an EAS in NW #1 is performed. The address search may be performed, for example, using the method disclosed in Section 6.2.3.2.2 or Section 6.2.3.2.3 of 3GPP TS 23.548. In procedure 2225, a PDU session may be established. The PDU session establishment may be, for example, a PDU session establishment for a UE to connect to an EASDF. In the example shown in FIG. 24 , it is determined that EAS #1 is to be used in NW #1. In procedure 2225, a local anchor UPF #1 may be provided.

[0255] In procedure 2230 shown in Fig. 24, a connection establishment process with the UPF in NW #1 is performed. Procedure 2230 will be described below. Fig. 25 and Fig. 26 are sequence diagrams showing an example of procedure 2230 in Fig. 24. Fig. 25 shows the first half of the sequence, and Fig. 26 shows the second half of the sequence.

[0256] In step ST2301 shown in Fig. 25 , SMF#1 selects a UPF. In the example shown in Fig. 25 , SMF#1 selects UPF#1 and decides to use the UPF#1. The selection and / or decision of the local anchor UPF#1 described above may be performed in step ST2301.

[0257] In Step ST2303 shown in FIG. 25 , a procedure for establishing a session management policy association is performed between SMF#1 and PCF#1. This procedure may be, for example, the procedure disclosed in clause 4.16.4 of Non-Patent Document 31 (3GPP TS 23.502). In Step ST2303, a procedure for changing the session management policy association may be performed. The procedure for changing the session management policy association may be, for example, the procedure disclosed in clause 4.16.5 of Non-Patent Document 31 (3GPP TS 23.502).

[0258] In step ST2305 shown in FIG. 25 , SMF#1 requests UPF#1 to establish an N4 session. Step ST2305 triggers UPF#1 to establish an N4 session. In step ST2307, UPF#1 responds to step ST2305 to SMF#1. In steps ST2305 and ST2307, a request to change the N4 session and a response to the request may be made.

[0259] In step ST2309 shown in FIG. 25 , SMF#1 requests local anchor UPF#1 to establish an N4 session. Step ST2309 is triggered by the local anchor UPF#1 to establish an N4 session. In step ST2309, a request for N4 session change may be made. Step ST2309 is triggered by the local anchor UPF#1 to establish an N4 session or to change an N4 session. In step ST2311, the local anchor UPF#1 responds to step ST2309 to SMF#1.

[0260] In Step ST2317 shown in FIG. 25 , SMF#1 requests the anchor UPF to establish an N4 session. A request for modifying an N4 session may also be made. The request may include, for example, information about UPF#1, information about the UE, or PDU session identification information. The anchor UPF establishes and / or modifies a connection with UPF#1 using the information included in the request. In Step ST2319, the anchor UPF responds to Step ST2317 to SMF#1.

[0261] In steps ST2323 and ST2324 shown in FIG. 25 , information required for establishing a PDU session of the UE is transmitted and received between SMF#1 and AMF#1. Information required for modifying a PDU session may also be transmitted and received. In step ST2323, an instruction to establish a PDU session may be sent from SMF#1 to AMF#1, or an instruction to modify a PDU session may be sent. The information may include information about the UE, information about the PDU session, information about the QoS flow, or information about the UPF (e.g., UPF#1, local anchor UPF#1, and / or anchor UPF).

[0262] In step ST2326 shown in FIG. 25 , AMF #1 notifies base station #1 of a PDU session establishment request for the UE. The notification may also be a PDU session modification request. The notification may include the information included in step ST2323. In step ST2328, base station #1 notifies the UE of a PDU session establishment request. The notification may also be a PDU session modification request. RRC signaling, for example, RRC establishment signaling or RRC reconfiguration signaling may be used in step ST2328. The notification in step ST2328 may include the information included in step ST2326. The UE may perform a PDU session establishment process or a PDU session modification process using the contents of the notification in step ST2328.

[0263] In Step ST2330 shown in Fig. 26, the UE responds to Step ST2328 shown in Fig. 25 to the base station #1. For the response, RRC signaling, for example, signaling of RRC establishment completion or signaling of RRC reconfiguration completion may be used. The UE may perform Step ST2330 upon completion of the PDU establishment and / or PDU modification process. In Step ST2332, the base station #1 responds to Step ST2326 shown in Fig. 25 to the AMF #1. The response in Step ST2326 may include N2 session management information.

[0264] In Step ST2334 shown in FIG. 26 , AMF#1 notifies SMF#1 of the N2 session management information from base station#2. This notification may be performed, for example, by using signaling of Nsmf_PDUSession_UpdateSMContext Request (see Non-Patent Document 31). In Step ST2336, SMF#1 responds to Step ST2334 to AMF#1. This response may be performed, for example, by using signaling of Nsmf_PDUSession_UpdateSMContext Response (see Non-Patent Document 31).

[0265] In step ST2338 shown in FIG. 26, the SMF#1 requests the UPF#1 to change the N4 session. In step ST2340, the UPF#1 responds to step ST2338 to the SMF#1.

[0266] In step ST2342 shown in FIG. 26, the SMF#1 requests the local anchor UPF#1 to change the N4 session. In step ST2344, the local anchor UPF#1 sends a response to step ST2342 to the SMF#1.

[0267] In Step ST2346 shown in FIG. 26 , the SMF#1 requests the anchor UPF to modify the N4 session. In Step ST2348, the anchor UPF sends a response to Step ST2346 to the SMF#1.

[0268] In Step ST2349 shown in FIG. 26 , a procedure for changing a session management policy association is performed between the SMF#1 and the PCF#1. This procedure may be, for example, the procedure disclosed in Section 4.16.5 of Non-Patent Document 31 (3GPP TS23.502).

[0269] Returning to the description of Fig. 24, steps ST1101 to ST1103 are the same as those in Fig. 13.

[0270] In step ST2207 shown in FIG. 24, SMF#1 determines to perform network branching.

[0271] In steps ST2210 to ST2214 shown in FIG. 24, a network branch notification is sent from SMF#1 to the AF via PCF#1 and NEF#1. Step ST2210 shows the notification from SMF#1 to PCF#1, step ST2212 shows the notification from PCF#1 to NEF#1, and step ST2214 shows the notification from NEF#1 to the AF. The notification may include information about the EAS, information about the network branch (e.g., information about the branch destination network), or information about the reason for the network branch. Step ST2214 triggers the AF to recognize that an EAS will be established in the branch destination network.

[0272] In step ST2220 shown in FIG. 24 , SMF#1 instructs SMF#2 to branch the network. The instruction may use signaling of a PDU session establishment request or signaling of a PDU session modification request. The instruction may include information about the UE, information about the network branch, information about the reason for the network branch (e.g., QoS deterioration), information about the PDU session, information about the QoS flow, or information about the EAS (e.g., the address of the EAS and / or information about the DN including the EAS).

[0273] Procedures ST1125 to ST1140 shown in Fig. 24 are the same as those in Fig. 13. In the example shown in Fig. 24, ST1140 may be performed as a response to ST2220.

[0274] Steps ST2301 to ST2303 shown in Fig. 24 are the same as steps ST1101 to ST1103, and steps ST1151 to ST1153 are the same as those in Fig. 13.

[0275] One of the networks may notify the AF of information related to the EAS. The NF may be, for example, an SMF. The notification from the SMF to the AF may be performed via the PCF and / or the NEF. For example, signaling similar to steps ST1110 to ST1114 shown in FIG. 17 may be used. The network switching notification of the signaling may be replaced with a network branching notification.

[0276] The AF may notify the NF of the other NW of information related to the EAS or information related to the latency requirement. The NF may be, for example, an SMF. The notification from the AF to the SMF may be performed via the NEF and / or PCF. For example, signaling similar to steps ST1616 to ST1618 shown in FIG. 17 may be used. The NW switching notification of the signaling may be replaced with a NW branching notification.

[0277] Coordination between EASs may be performed, and this coordination may be performed in the DN to which the EASs belong.

[0278] An NF of one NW may notify an NF of the other NW of information about the EAS to which the NW is connected. The NF may be an SMF, a PCF, or an AMF. The NF of the other NW may notify the EAS to which the NW is connected of the information. This allows, for example, smooth cooperation between EASs.

[0279] As another example, an NF of one NW may inquire of an NF of another NW about information regarding the EAS to which the other NW is connected. The other NF may, in response to the inquiry, notify the NF of the other NW of information regarding the EAS to which the own NW is connected. The NF of the one NW may notify the EAS to which the own NW is connected of the information. This may provide, for example, the same effect as described above.

[0280] The one NW may be, for example, an anchor NW or a non-anchor NW, and the other NW may be a non-anchor NW or an anchor NW.

[0281] As another example, coordination between EASs may be performed via the AF. Notification from the NF of the NW to the AF and / or notification from the AF to the NF of the NW may be performed via the PCF and / or the NEF.

[0282] The AF may notify one and / or both NFs of information about available EASs. The information may include information about latency requirements. The information may be transmitted as appropriate. The NFs of the NW may use the information to determine the EAS or change the EAS. Changing the EAS may be performed, for example, by EAS rediscovery (see Section 6.2 of Non-Patent Document 32) or EAS relocation (see Section 6.3 of Non-Patent Document 32). This allows, for example, flexible EAS selection in a communication system.

[0283] As another solution, only one of the networks may have EAS. The other network may not have EAS. For example, if the latency between the UE and the AF in the other network is small, the other network may not have EAS. As a configuration in which only one network has EAS, for example, a configuration similar to that shown in FIG. 11 may be used.

[0284] The UE may route uplink transmission data. For example, the UE may perform routing based on the buffer amount accumulated in the UE. For example, when the buffer amount is greater than or equal to a predetermined threshold, the UE may transmit data to either of the two NWs, or may transmit data to both NWs simultaneously. When the buffer amount is less than or equal to a predetermined threshold, the UE may transmit data to one of the NWs. The NW that is the destination of uplink data when the buffer amount is less than or equal to the predetermined threshold may be referred to as the main NW hereinafter. As another example, when the buffer amount is greater than or equal to a predetermined threshold, the UE may transmit data to a NW that is not the main NW, or when the buffer amount is less than or equal to a predetermined threshold, the UE may transmit data to the main NW.

[0285] The one of the networks may be an anchor network or a non-anchor network, which can improve flexibility in communication, for example.

[0286] The buffer amount may include the buffer amount of a lower layer. For example, it may include the buffer amount of the SDAP layer, the buffer amount of the PDCP layer, the buffer amount of the RLC layer, the buffer amount of the MAC layer or lower, the buffer amount of the PHY layer, or the above-mentioned multiple buffer amounts. This enables routing that takes into account the overall buffer amount of the UE, for example.

[0287] For the routing described above, the buffer amount for each PDU session or the buffer amount for each QoS flow may be used, which enables flexible routing for each traffic, for example.

[0288] A lower layer of the UE may notify the PDU layer of the buffer amount of the lower layer. The lower layer may be SDAP, PDCP, the RLC layer, or the MAC layer. The buffer amount may be the buffer amount per PDU session or per QoS flow. This allows, for example, the PDU layer to quickly grasp the buffer amount of the lower layer.

[0289] As another example, QoS may be used for routing. The QoS may include, for example, latency or data rate. For example, a UE may transmit data to a network with good QoS. This may ensure, for example, QoS for uplink communication.

[0290] The UE may perform QoS monitoring. The UE may perform the routing using the results of the QoS monitoring. The QoS monitored by the UE may include, for example, information about uplink and / or downlink packet delay, information about congestion, data rate, packet delay variance, information about round-trip packet delay, and information about uplink delay at the UE (e.g., the difference between the time when uplink data should be sent and the time when it is actually sent).

[0291] A threshold may be used in QoS-based routing. For example, if the QoS in one NW is better than or equal to a predetermined threshold, the NW may be continued to be used, or if the QoS is worse than or equal to a predetermined threshold, data may be transmitted to another NW. The one NW may be an anchor NW or a non-anchor NW. This makes it possible to ensure QoS in uplink transmission. Hysteresis may be provided to the threshold. This makes it possible to prevent, for example, frequent switching of the destination NW for uplink data.

[0292] Routing using QoS flows may be performed for each QoS flow. For example, a QoS flow requiring latency may be routed through a network with low latency, and a QoS flow requiring reliability may be routed through a network with high reliability. This makes it possible to ensure QoS for each QoS flow, for example.

[0293] The threshold may be determined by the PCF. For example, the threshold may be determined by the anchor PCF. The anchor PCF may notify the anchor SMF of the threshold. The anchor SMF may notify the UE of the threshold. The notification from the anchor SMF may be performed via the anchor AMF or the anchor base station.

[0294] As another example, the threshold may be determined by the SMF. For example, the anchor SMF may determine the threshold. The anchor SMF may determine the threshold using a policy notified by the anchor PCF. The anchor SMF may notify the UE of the threshold. The notification from the anchor SMF to the UE may be performed in the same manner as described above.

[0295] As another example, the threshold may be determined by an AMF, for example, an anchor AMF, or by a base station, for example, an anchor base station. The AMF and / or the base station may notify the threshold to the UE.

[0296] As another example, the threshold may be determined by a Network Data Analytics Function (NWDAF). This allows flexible threshold determination based on, for example, the status of the network. The NWDAF may notify the threshold to the UE. The notification may be performed via the AMF, via the base station, or directly to the UE.

[0297] As another example, information about the EAS may be used for routing. For example, the UE may transmit data to a network having the EAS, or may transmit data to a network having the EAS corresponding to the application of the data to be transmitted. This may reduce latency, for example.

[0298] As another example, information about a PDU set (see Non-Patent Document 10) may be used for routing. For example, UEs may transmit data of the same PDU set to the same NW.

[0299] One NW may notify the other NW of information about the PDU set. The notification may be included in, for example, a NW branch instruction from the one NW to the other NW.

[0300] PDU classification may be performed. The classification may be performed across PDU sessions. QoS may be used for the classification. One network may notify the other network of information regarding the classification. The notification may be included, for example, in a network branch instruction from one network to the other network.

[0301] As another example of routing, the above-mentioned PDU classification may be performed. PDUs that have been classified in the same way may be transmitted to the same network. This makes it possible to transmit related data across PDU sessions in the same network, thereby preventing malfunctions in the communication system.

[0302] According to the third embodiment, it is possible to prevent misunderstandings between networks, thereby preventing malfunctions of the communication system. In addition, it is possible to select an optimal EAS for each network, which in turn makes it possible to reduce latency in edge computing, for example.

[0303] Modification 1 of the Third Embodiment When branching of networks is eliminated and one network is used, the EAS used in the one network may be used. For example, the above-described method may be applied when EAS is used in both networks at branching destinations, or when EAS is used in one of the networks at branching destinations.

[0304] The EAS used in the network where the branching is eliminated may be used as is. For example, the method disclosed in the second embodiment may be used. This allows the EAS used in the network where the branching is eliminated to be used as is, for example.

[0305] A combination of the above methods may be used, for example, when multiple EAS systems are used in one and / or both networks, which may allow for greater flexibility in EAS configuration.

[0306] According to the first modification, even when the branching of the network is eliminated, the EAS can be continuously used.

[0307] Fourth Embodiment Each branched network may be connected to a common EAS.

[0308] 27 is a configuration diagram showing an example in which branching NWs are connected to the same EAS. In the example shown in FIG. 27, an example is shown in which the NW to which a UE is connected branches into NW#1 and NW#2. The EAS to which the UE connects via NW#1 and the EAS to which the UE connects via NW#1 are both EAS#1. EAS#1 is connected to UPF#1 via local anchor UPF#1, and to UPF#2 via local anchor UPF#2.

[0309] An NF of one of the branched networks (e.g., NW#1, hereinafter the same) may notify an NF of the other network (e.g., NW#2, hereinafter the same) of information about the EAS connected to NW#1. NW#2 may use this notification to connect to the EAS.

[0310] 28 is a sequence diagram showing an example of an operation in which each branching NW connects to a common EAS. In the example shown in FIG. 28, the UE's connection destination branches to NW#1, which is an anchor NW, and NW#2, which is a non-anchor NW. The UE connects to EAS#1 via UPF#1 and local anchor UPF#1, and also connects to the same EAS#1 via UPF#2 and local anchor UPF#2. In the example shown in FIG. 28, each NW determines the EAS to connect to. In the example shown in Figure 28, base station #1, AMF #1, UPF #1, SMF #1, PCF #1, UDM #1, NEF #1, local anchor UPF #1, and anchor UPF belong to NW #1, and base station #2, AMF #2, UPF #2, SMF #2, PCF #2, NEF #2, local anchor UPF #2, and UDM #2 belong to NW #2. In Figure 28, the same processes as those in Figures 13 and 24 are assigned the same numbers, and common descriptions will be omitted.

[0311] Procedures 2225 and 2230 shown in Fig. 28 are the same as those in Fig. 24. Steps ST1101 to ST1103 are the same as those in Fig. 13. Steps ST2207 to ST2214 are the same as those in Fig. 24.

[0312] In step ST2420 shown in FIG. 28 , SMF#1 instructs SMF#2 to branch the network. The instruction may use signaling of a PDU session establishment request or signaling of a PDU session modification request. The instruction may include information about the UE, information about the network branch, information about the reason for the network branch (e.g., QoS deterioration), information about the anchor UPF, information about the PDU session, information about the QoS flow, information about the EAS (e.g., information about the address of the EAS and / or information about the DN including the EAS), or information indicating that the same EAS as NW#1 is used.

[0313] The local anchor UPF is determined in procedure 2425 shown in Fig. 28. In the example shown in Fig. 28, it is determined that local anchor UPF #2 is used in NW #2.

[0314] Procedure 1130 to step ST1140 shown in FIG. 28 are the same as those in FIG.

[0315] Steps ST2301 to ST2303 shown in Fig. 28 are the same as steps ST1101 to ST1103, and steps ST1151 to ST1153 are the same as those in Fig. 13.

[0316] A priority may be set as to whether the EASs of both networks are the same or different. For example, priority may be given to making them the same. This may improve the utilization efficiency of the EASs, for example. As another example, priority may be given to making the EASs different. This may reduce the latency in edge computing, for example.

[0317] The priority may be determined by the NF of the anchor NW. The NF may be, for example, an SMF, an AMF, or a PCF. As another example, the priority may be determined by the NF of the non-anchor NW. The NF may be, for example, an SMF, an AMF, or a PCF. As another example, the priority may be determined by the AF. The AF may notify the NF of the anchor NW or the NF of the non-anchor NW of the priority. The NF of the anchor NW and / or the NF of the non-anchor NW may be the same as described above. The AF may notify the priority via the NEF or the PCF.

[0318] As another example, a condition may be set as to whether the EASs of both networks are the same or different. The condition may be determined using, for example, a threshold. The condition may include, for example, a condition related to latency. The latency may include, for example, the latency from the UE to the local anchor UPF, or end-to-end latency, for example, from the UE to the EAS, or from the local anchor UPF to the EAS, or from an intermediate UPF (e.g., the UPF in FIG. 11, FIG. 12, or FIG. 19) to the EAS, or from the UE to the intermediate UPF.

[0319] The NFs of the anchor network and / or the non-anchor network may use the condition to determine whether the target EAS should be the same as or different from the source EAS. The NFs may be, for example, SMFs, PCFs, or AMFs. For example, the SMF of the anchor network may determine the EAS candidate as the target EAS when the latency of the EAS candidate is less than or equal to the threshold. As another example, the SMF of the anchor network may determine the target EAS to be the same as the source EAS when the latency of the EAS candidate is greater than or equal to the threshold. This enables, for example, flexible EAS switching.

[0320] The condition may be determined by the NF of the anchor NW. The NF may be, for example, an SMF, an AMF, or a PCF. As another example, the condition may be determined by the NF of the non-anchor NW. The NF may be, for example, an SMF, an AMF, or a PCF. As another example, the condition may be determined by the AF. The AF may notify the NF of the anchor NW or the NF of the non-anchor NW of the condition. The NF of the anchor NW and / or the NF of the non-anchor NW may be the same as described above. The AF may notify the condition via the NEF or the PCF.

[0321] The uplink data from the UE may be routed using, for example, a method similar to that disclosed in the third embodiment.

[0322] The EAS may determine the conditions to be used for the routing (e.g., the thresholds disclosed in the third embodiment), and may notify the UE of the conditions. This allows, for example, flexible routing.

[0323] According to the fourth embodiment, for example, it is possible to improve the utilization efficiency of the EAS.

[0324] Variation 1 of the fourth embodiment: In a network branch, both networks may be connected to the same local anchor UPF or the same EAS. The connection configuration may be similar to the configuration shown in FIG. 22, for example.

[0325] An NF of one NW (e.g., NW#1) may notify an NF of the other NW (e.g., NW#2) of information about the local anchor UPF. The information may include, for example, information about the address of the local anchor UPF. The information may be included, for example, in an instruction for NW branching from NW#1 to NW#2.

[0326] The NF of NW#2 may request the NF of NW#1 to establish a connection between the local anchor UPF and the intermediate UPF of NW#2. The request may be made, for example, as a request for establishing an N4 session or a request for changing an N4 session. The NF of NW#1 may establish a connection between the local anchor UPF and the intermediate UPF of NW#2 in response to the notification.

[0327] According to the first modification, it is possible to improve the utilization efficiency of a network device, for example, a UPF.

[0328] Fifth embodiment: Relocation of the EAS may be performed. For example, when the QoS between the local anchor UPF connected to the EAS and the UE deteriorates, the EAS may be relocated.

[0329] The relocation of the EAS may be determined by the NF of the network or by the AMF, which may be an SMF, an AMF, or a PCF.

[0330] EAS rearrangement may be performed even when a UE is connected to multiple networks. However, non-patent documents 31 and 32, which relate to edge computing, do not disclose the operation when one of the networks decides to rearrange the EAS when the same EAS is used in multiple networks. This may cause, for example, a discrepancy in the recognition of the EAS between the two networks, which may result in malfunction of the communication system.

[0331] In this embodiment, a method for solving the above-mentioned problem is disclosed.

[0332] In the communication system according to this embodiment, EAS rearrangement is performed in both networks. The EAS to be rearranged may be common to both networks. The NF of one of the networks may decide the rearrangement of the EAS. The NF may be an SMF, an AMF, or a PCF.

[0333] The NF may notify the NF of the other NW of information regarding the relocation of the EAS. The NF of the other NW may be an SMF, an AMF, or a PCF. The information regarding the relocation of the EAS may include information regarding the address (e.g., IP address) of the EAS, or information regarding the DN including the EAS (e.g., Data Network Access Identifier (see Non-Patent Document 11)). The NF of the other NW may relocate the EAS of the other NW in response to the notification.

[0334] As another example, the EASs of the relocation destination may be different between the two networks. The NF of the other network may perform relocation to an EAS different from that of the one network, triggered by the notification.

[0335] A priority may be set as to whether the EAS at the relocation destination is the same or different. For example, priority may be given to making the EAS the same. This may avoid, for example, complexity in the EAS switching process. As another example, priority may be given to making the EAS different. This may reduce, for example, latency in edge computing.

[0336] The priority may be determined by an NF of the anchor NW. The NF may be, for example, an SMF, an AMF, or a PCF. As another example, the priority may be determined by an NF of a non-anchor NW. The NF may be, for example, an SMF, an AMF, or a PCF. As another example, the priority may be determined by an AF. The AF may notify the priority to an NF of the anchor NW or to an NF of a non-anchor NW. The NFs of the anchor NW and / or the non-anchor NW may be the same as those described above. The AF may notify the priority via an NEF or via a PCF.

[0337] As another example, a condition may be set as to whether the EAS of the relocation destination is the same or different. The condition may be determined, for example, using a threshold value. The condition may be similar to the condition disclosed in the second embodiment.

[0338] The NFs of the anchor NW and / or the non-anchor NW may use the condition to determine whether to keep the EAS of the relocation destination the same or different. The NFs may be, for example, SMFs, PCFs, or AMFs. For example, the SMF of the anchor NW may keep the EAS of the relocation destination the same when the latency related to the EAS of the relocation destination is less than or equal to the threshold. As another example, the SMF of the anchor NW may change the EAS of the relocation destination when the latency related to the EAS of the relocation destination is greater than or equal to the threshold. This enables, for example, flexible EAS switching.

[0339] The condition may be determined by the NF of the anchor NW. The NF may be, for example, an SMF, an AMF, or a PCF. As another example, the condition may be determined by the NF of the non-anchor NW. The NF may be, for example, an SMF, an AMF, or a PCF. As another example, the condition may be determined by the AF. The AF may notify the NF of the anchor NW or the NF of the non-anchor NW of the condition. The NF of the anchor NW and / or the NF of the non-anchor NW may be the same as described above. The AF may notify the condition via the NEF or the PCF.

[0340] Another solution is disclosed. Only one of the networks relocates the EAS. The network notifies the other network of information about the EAS relocation. The information may include information about the address (e.g., IP address) of the EAS, or information about the DN containing the EAS (e.g., Data Network Access Identifier (see Non-Patent Document 11)).

[0341] Information regarding the relocation of the EAS may be notified from an NF of one NW to an NF of the other NW, or may be notified via an AF. The information may include, for example, the reason for the relocation (e.g., UE mobility, QoS deterioration). The NF and / or AF of the other NW may use the information to understand the information regarding the relocation of the EAS.

[0342] According to the fifth embodiment, it is possible to prevent discrepancies in the recognition of EAS between both networks, and as a result, it is possible to prevent malfunctions in the communication system.

[0343] 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.

[0344] In this specification, a node may be a function.

[0345] 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.

[0346] In the present disclosure, a gNB may be an MCG or an SCG.

[0347] 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.

[0348] 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.

[0349] 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.

[0350] Various aspects of the present disclosure are summarized below as appendices.

[0351] (Supplementary Note 1) A communication system compatible with a fifth-generation wireless access system, comprising: a plurality of networks, each including a wireless access network and a core network; and an edge application server for performing edge computing, connected to the networks, wherein when a communication terminal connected to one or more of the networks and communicating with the edge application server switches a destination network, the communication system also switches the edge application server with which the communication terminal communicates. (Supplementary Note 2) The communication system according to Supplementary Note 1, wherein a network device constituting a destination network determines the edge application server to which the communication terminal will connect after switching the destination network. (Supplementary Note 3) The communication system according to Supplementary Note 1, wherein a network device constituting a source network determines the edge application server to which the communication terminal will connect after switching the destination network. (Supplementary Note 4) A communication system compatible with a fifth-generation wireless access system, comprising: a plurality of networks, each including a wireless access network and a core network; and an edge application server connected to the networks for performing edge computing, wherein when a communication terminal connected to one or more of the networks and communicating with the edge application server switches a connection destination network, the communication path between the communication terminal and the edge application server is switched to a path via the switching destination network without switching the edge application server with which the communication terminal communicates. (Supplementary Note 5) The communication system according to any one of Supplementary Notes 1 to 4, wherein when the communication terminal connects to a plurality of the networks simultaneously and branches traffic to each connected network, a data transmission path is established between the communication terminal and a plurality of edge application servers that are different for each connected network.(Supplementary Note 6) The communication system according to any one of Supplementary Notes 1 to 4, wherein, when the communication terminal is connected to a plurality of the networks simultaneously and branches traffic to each of the connected networks, a data transmission path is established between a common edge application server and the communication terminal via each of the networks to which the communication terminal is connected. (Supplementary Note 7) The communication system according to any one of Supplementary Notes 1 to 6, wherein, when a predetermined condition is satisfied, the edge application server to which the communication terminal is connected is relocated.

[0352] 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 beams, 752 cell.

Claims

1. A communications system compatible with a fifth-generation wireless access system, comprising: a plurality of networks, each including a wireless access network and a core network; and an edge application server for performing edge computing, connected to the networks; wherein, when a communications terminal connected to one or more of the networks and communicating with the edge application server switches the network to which it is connected, the edge application server with which the communications terminal communicates is also switched.

2. The communication system according to claim 1, wherein the edge application server to which the communication terminal connects after switching the destination network is determined by a network device constituting the destination network.

3. The communication system according to claim 1, wherein the edge application server to which the communication terminal connects after switching the destination network is determined by a network device constituting the source network.

4. A communications system compatible with a fifth-generation wireless access system, comprising: a plurality of networks, each including a wireless access network and a core network; and an edge application server for performing edge computing, connected to the networks; wherein, when a communications terminal connected to one or more of the networks and communicating with the edge application server switches the network to which it is connected, the edge application server with which the communications terminal communicates is not switched, but the communications path between the communications terminal and the edge application server is switched to a path via the network to which it is switched.

5. A communication system according to any one of claims 1 to 4, characterized in that when the communication terminal is connected to multiple networks simultaneously and branches traffic to each connected network, a data transmission path is established between the communication terminal and multiple edge application servers that are different for each connected network.

6. A communication system according to any one of claims 1 to 4, characterized in that when the communication terminal is connected to multiple networks simultaneously and branches traffic to each of the connected networks, a data transmission path is established between a common edge application server and the communication terminal via each of the networks to which the communication terminal is connected.

7. The communication system according to claim 1, wherein, when a predetermined condition is satisfied, the edge application server to which the communication terminal is connected is relocated.

Images