Terminal equipment, base station equipment, and communication systems

Abstract

We provide technology that enables reliability assurance and maintenance of TSC (Total System Standard). [Solution] The terminal device is configured to switch between a configuration in which the terminal device uses one network path and a configuration in which the terminal device uses multiple network paths, and the terminal device is configured to receive first information regarding the switching from the base station device, and the first information includes information regarding the assurance of QoS (Quality of Service).

Description

Technical Field

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

Background Art

[0002] In the 3GPP (3rd Generation Partnership Project), which is a standardization organization for mobile communication systems, the radio section is called Long Term Evolution (LTE), and the overall system configuration including the core network and the radio access network (hereinafter collectively referred to as the network) is being studied for a communication method called System Architecture Evolution (SAE) (for example, Non-Patent Documents 1 to 5). This communication method is also called a 3.9G (3.9 Generation) system.

[0003] As the access method of LTE, OFDM (Orthogonal Frequency Division Multiplexing) is used in the downlink direction, and SC-FDMA (Single Carrier Frequency Division Multiple Access) is used in the uplink direction. Also, different from W-CDMA (Wideband Code Division Multiple Access), LTE does not include circuit switching and is only a packet communication method.

[0004] The decisions made by 3GPP regarding the frame structure in LTE systems, as described in Non-Patent Document 1 (Chapter 5), will be explained using Figure 1. Figure 1 is an explanatory diagram showing the structure of a radio frame used in an LTE communication system. In Figure 1, one radio frame is 10ms. A radio frame is divided into 10 subframes of equal size. Each subframe is divided into two slots of equal size. Downlink synchronization signals are included in the 1st and 6th subframes of each radio frame. The synchronization signals consist of a primary synchronization signal (P-SS) and a secondary synchronization signal (S-SS).

[0005] The 3GPP's decisions regarding channel configuration in LTE systems are described in Non-Patent Document 1 (Chapter 5). It is assumed that the same channel configuration as non-CSG cells will be used in CSG (Closed Subscriber Group) cells.

[0006] The Physical Broadcast Channel (PBCH) is a channel used for downlink transmission from base station equipment (hereinafter sometimes simply referred to as "base station") to communication terminal equipment (hereinafter sometimes simply referred to as "mobile terminal") and other such devices. A PBCH transport block is mapped to four subframes within a 40ms interval. There is no explicit signaling at 40ms timing.

[0007] The Physical Control Format Indicator Channel (PCFICH) is a channel used for downlink transmission from the base station to the communication terminal. The PCFICH notifies the communication terminal of the number of OFDM (Orthogonal Frequency Division Multiplexing) symbols to be used for PDCCHs. The PCFICH is transmitted for each subframe.

[0008] The Physical Downlink Control Channel (PDCCH) is the channel used for downlink transmission from the base station to the communication terminal. The PDCCH notifies resource allocation information for the Downlink Shared Channel (DL-SCH), one of the transport channels described later, resource allocation information for the Paging Channel (PCH), another transport channel described later, and HARQ (Hybrid Automatic Repeat reQuest) information related to the DL-SCH. The PDCCH carries the Uplink Scheduling Grant. The PDCCH also carries Ack (Acknowledgement) / Nack (Negative Acknowledgement), which are response signals to uplink transmissions. The PDCCH is also called the L1 / L2 control signal.

[0009] The Physical Downlink Shared Channel (PDSCH) is a channel used for downlink transmission from a base station to a communication terminal. The PDSCH is mapped to the Downlink Shared Channel (DL-SCH), which is a transport channel, and the PCH, which is also a transport channel.

[0010] A physical multicast channel (PMCH) is a channel used for downlink transmission from a base station to a communication terminal. A multicast channel (MCH), which is a transport channel, is mapped to the PMCH.

[0011] The Physical Uplink Control Channel (PUCCH) is the channel used for uplink transmission from the communication terminal to the base station. The PUCCH carries the Ack / Nack response signal for downlink transmission. The PUCCH also carries Channel State Information (CSI). The CSI consists of the Rank Indicator (RI), Precoding Matrix Indicator (PMI), and Channel Quality Indicator (CQI) report. RI is the rank information of the channel matrix in MIMO. PMI is information of the precoding weight matrix used in MIMO. CQI is quality information indicating the quality of the received data or the quality of the communication channel. The PUCCH also carries a Scheduling Request (SR).

[0012] The Physical Uplink Shared Channel (PUSCH) is a channel used 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.

[0013] The Physical Hybrid ARQ Indicator Channel (PHICH) is the channel used for downlink transmission from the base station to the communication terminal. PHICH carries the Ack / Nack, which is the response signal to uplink transmissions. The Physical Random Access Channel (PRACH) is the channel used for uplink transmission from the communication terminal to the base station. PRACH carries the random access preamble.

[0014] The downlink reference signal (RS) is a well-known symbol in LTE communication systems. Five types of downlink reference signals are defined: Cell-specific Reference Signal (CRS), MBSFN Reference Signal, UE-specific Reference Signal (UE-specific), Demodulation Reference Signal (DM-RS), Positioning Reference Signal (PRS), and Channel State Information Reference Signal (CSI-RS). One measurement of the physical layer of a communication terminal is the Reference Signal Received Power (RSRP).

[0015] Similarly, the uplink reference signals are also known symbols for LTE communication systems. Two types of uplink reference signals are defined: the Demodulation Reference Signal (DM-RS) and the Sounding Reference Signal (SRS).

[0016] This section explains the transport channel described in Non-Patent Document 1 (Chapter 5). Of the downlink transport channels, the Broadcast Channel (BCH) broadcasts to the entire coverage of the base station (cell). The BCH is mapped to the Physical Broadcast Channel (PBCH).

[0017] Downlink Shared Channels (DL-SCH) are subject to retransmission control using HARQ (Hybrid ARQ). DL-SCH can broadcast to the entire coverage of a base station (cell). DL-SCH supports dynamic or semi-static resource allocation. Semi-static resource allocation is also called persistent scheduling. DL-SCH supports discontinuous reception (DRX) for communication terminals to reduce power consumption. DL-SCH is mapped to Physical Downlink Shared Channels (PDSCH).

[0018] Paging Channels (PCHs) support DRX for communication terminals to enable low power consumption for those terminals. PCHs are required to broadcast across the entire coverage of a base station (cell). PCHs are mapped to physical resources, such as Physical Downlink Shared Channels (PDSCHs), which are dynamically available for traffic.

[0019] Multicast channels (MCHs) are used for broadcasting across the entire coverage of a base station (cell). MCHs support SFN synthesis of MBMS (Multimedia Broadcast Multicast Service) services (MTCH and MCCH) in multi-cell transmission. MCHs support quasi-static resource allocation. MCHs are mapped to PMCHs.

[0020] Among the uplink transport channels, the Uplink Shared Channel (UL-SCH) is subject to retransmission control using HARQ (Hybrid ARQ). UL-SCH supports dynamic or semi-static resource allocation. UL-SCH is mapped to the Physical Uplink Shared Channel (PUSCH).

[0021] Random Access Channels (RACHs) are limited to control information. RACHs carry a risk of collisions. RACHs are mapped to Physical Random Access Channels (PRACHs).

[0022] This section explains 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 works effectively through retransmission even on transmission paths where the communication quality changes. In particular, it is possible to achieve further quality improvement by combining the reception results of the initial transmission and the retransmission during retransmission.

[0023] Here is an example of how to retransmit data. If the receiving side is unable to correctly decode the received data, in other words, if a CRC (Cyclic Redundancy Check) error occurs (CRC=NG), the receiving side sends "Nack" to the sending side. Upon receiving "Nack," the sending side retransmits the data. If the receiving side is able to correctly decode the received data, in other words, if no CRC error occurs (CRC=OK), the receiving side sends "Ack" to the sending side. Upon receiving "Ack," the sending side sends the next data.

[0024] This section explains the logical channel described in Non-Patent Document 1 (Chapter 6). The Broadcast Control Channel (BCCH) is a downstream channel for broadcast system control information. The BCCH, being a logical channel, is mapped to the broadcast channel (BCH), which is a transport channel, or to the downstream shared channel (DL-SCH).

[0025] The Paging Control Channel (PCCH) is a downlink channel used to transmit changes to paging information and system information. The PCCH is used when the network does not know the cell location of a communication terminal. As a logical channel, the PCCH is mapped to the Paging Channel (PCH), which is a transport channel.

[0026] The Common Control Channel (CCCH) is a channel for transmit control information between a communication terminal and a base station. The CCCH is used when a communication terminal does not have an RRC connection with the network. In the downlink direction, the CCCH is mapped to the downlink common channel (DL-SCH), which is a transport channel. In the uplink direction, the CCCH is mapped to the uplink common channel (UL-SCH), which is a transport channel.

[0027] A Multicast Control Channel (MCCH) is a downlink channel for one-to-many transmission. MCCHs are used to transmit MBMS control information for one or more MCCHs from the network to communication terminals. MCCHs are only used by communication terminals receiving MBMS. MCCHs are mapped to the Multicast Channel (MCH), which is the transport channel.

[0028] The Dedicated Control Channel (DCCH) is a channel that transmits dedicated control information between a communication terminal and a network on a one-to-one basis. The DCCH is used when the communication terminal is in an RRC connection. The DCCH is mapped to the UL-SCH in the uplink and to the DL-SCH in the downlink.

[0029] The Dedicated Traffic Channel (DTCH) is a channel for one-to-one communication to an individual communication terminal for the transmission of user information. The DTCH exists in both the uplink and the downlink. The DTCH is mapped to the UL-SCH in the uplink and to the DL-SCH in the downlink.

[0030] The Multicast Traffic Channel (MTCH) is a downlink channel for the transmission of traffic data from the network to a communication terminal. The MTCH is a channel used only for communication terminals during MBMS reception. The MTCH is mapped to the Multicast Channel (MCH).

[0031] CGI refers to the Cell Global Identifier. ECGI refers to the E-UTRAN Cell Global Identifier. In LTE, LTE-A (Long Term Evolution Advanced) to be described later, and UMTS (Universal Mobile Telecommunication System), a Closed Subscriber Group (CSG) cell is introduced.

[0032] Location tracking of communication terminals is performed in units of areas consisting of one or more cells. Location tracking is performed to track the location of communication terminals even when they are in standby mode, and to enable them to be called, in other words, to allow them to receive calls. This area used for location tracking of communication terminals is called the tracking area.

[0033] Furthermore, 3GPP is working on the Long Term Evolution Advanced (LTE-A) standard as Release 10 (see Non-Patent Documents 3 and 4). LTE-A is based on the LTE wireless communication method and incorporates several new technologies.

[0034] In LTE-A systems, carrier aggregation (CA), which involves aggregating two or more component carriers (CCs) to support wider transmission bandwidths up to 100 MHz, is being considered. CA is described in Non-Patent Document 1.

[0035] When a CA is configured, the UE has a single RRC connection to the network (NW). In the RRC connection, one serving cell provides NAS mobility information and security inputs. This cell is called the Primary Cell (PCell). On the downlink, the carrier corresponding to the PCell is the Downlink Primary Component Carrier (DL PCC). On the uplink, the carrier corresponding to the PCell is the Uplink Primary Component Carrier (UL PCC).

[0036] Depending on the capabilities of the UE, secondary cells (SCells) are configured to form a set of serving cells together with PCells. On the downlink, the carrier corresponding to the SCell is the Downlink Secondary Component Carrier (DL SCC). On the uplink, the carrier corresponding to the SCell is the Uplink Secondary Component Carrier (UL SCC).

[0037] A set of serving cells consisting of one PCell and one or more SCells is configured for a single UE.

[0038] Furthermore, new technologies in LTE-A include technologies that support wider bandwidths (Wider bandwidth extension) and technologies such as Coordinated Multiple Point transmission and reception (CoMP). The CoMP technology being considered by 3GPP for LTE-A is described in Non-Patent Document 1.

[0039] Furthermore, 3GPP is considering using small eNBs (sometimes referred to as "small-scale base station equipment") that constitute small cells to cope with the enormous traffic of the future. For example, technologies are being considered to increase communication capacity by improving frequency utilization efficiency by installing a large number of small eNBs to constitute a large number of small cells. Specifically, this includes dual connectivity (DC), in which a UE connects to and communicates with two eNBs. DC is described in Non-Patent Document 1.

[0040] In some cases, among eNBs that perform dual connectivity (DC), one is called the "master eNB (abbreviated as MeNB)" and the other is called the "secondary eNB (abbreviated as SeNB)".

[0041] Mobile network traffic is on the rise, and communication speeds are also increasing. Further speed increases are expected once LTE and LTE-A are fully operational.

[0042] Furthermore, in response to the increasing sophistication of mobile communications, a fifth-generation (sometimes referred to as "5G") wireless access system is being considered, with the goal of launching services after 2020. For example, in Europe, the METIS organization has compiled the requirements for 5G (see Non-Patent Document 5).

[0043] In 5G wireless access systems, the requirements include achieving 1000 times the system capacity, 100 times the data transmission speed, one-tenth (1 / 10) the data processing delay, and 100 times the number of simultaneous connections for communication terminals compared to LTE systems, while also achieving further reductions in power consumption and equipment costs.

[0044] To meet these requirements, 3GPP is working on the 5G standard as Release 15 (see Non-Patent Documents 6-18). The technology for the wireless portion of 5G is called "New Radio Access Technology" ("New Radio" is abbreviated as "NR").

[0045] The NR system is being developed based on the LTE system and LTE-A system, but the following changes and additions have been made compared to the LTE system and LTE-A system.

[0046] For NR access, OFDM is used for the downstream direction, and OFDM and DFT-s-OFDM (DFT-spread-OFDM) are used for the upstream direction.

[0047] NR allows for the use of higher frequencies compared to LTE, in order to improve transmission speed and reduce processing delays.

[0048] In NR (Noise Reduction), cell coverage is ensured by forming a narrow beam-shaped transmission and reception range (beamforming) and changing the direction of the beam (beam sweeping).

[0049] In NR's frame configuration, various subcarrier intervals, i.e., various numerologies, are supported. In NR, regardless of the numerology, one subframe is 1 millisecond, and one slot consists of 14 symbols. Furthermore, the number of slots contained in one subframe is one for a numerology with a subcarrier interval of 15 kHz, and increases proportionally with the subcarrier interval for other numerologies (see Non-Patent Document 13 (TS38.211 V15.7.0)).

[0050] In NR, the downlink synchronization signal is transmitted from the base station as a synchronization signal burst (SS burst) at a predetermined period and for a predetermined duration. The SS burst consists of a synchronization signal block (SS block) for each beam of the base station. The base station transmits the SS block for each beam, changing beams within the duration of the SS burst. The SS block consists of P-SS, S-SS, and PBCH.

[0051] In noise reduction (NR), the effect of phase noise is reduced by adding a Phase Tracking Reference Signal (PTRS) as the downstream reference signal. Similarly, a PTRS is also added to the upstream reference signal.

[0052] In NR, Slot Format Indication (SFI) information has been added to the PDCCH to allow for flexible switching between DL / UL within a slot.

[0053] Furthermore, in NR, a portion of the carrier frequency band (sometimes referred to as the Bandwidth Part (BWP)) is pre-configured by the base station for the UE, and the UE performs transmission and reception with the base station in the BWP, thereby reducing the power consumption of the UE.

[0054] 3GPP is considering several data center configurations, including a data center with LTE and NR base stations connected to an EPC, a data center with NR base stations connected to a 5G core system, and a data center with LTE and NR base stations connected to a 5G core system (see Non-Patent Documents 12, 16, and 19).

[0055] Furthermore, 3GPP is considering several new technologies. For example, they are exploring technologies to ensure reliability by providing redundancy in communication paths (hereinafter sometimes referred to as redundant paths) (see Non-Patent Document 20 (TR23.725)). [Prior art documents] [Non-patent literature]

[0056] [Non-Patent Document 1] 3GPP TS 36.300 V15.7.0 [Non-Patent Document 2] 3GPP S1-083461 [Non-Patent Document 3] 3GPP TR 36.814 V9.2.0 [Non-Patent Document 4] 3GPP TR 36.912 V15.0.0 [Non-Patent Document 5] "Scenarios, requirements and KPIs for 5G mobile and wireless system", ICT-317669-METIS / D1.1

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[0057] 3GPP is considering ways to improve communication reliability by providing redundant communication paths (see Non-Patent Documents 20 and 21). However, no method has been disclosed to prevent communication failures in the remaining redundant paths if a communication failure occurs in one redundant path. As a result, there is a possibility of communication failures occurring in any of the redundant paths, which leads to the problem of not being able to ensure communication reliability. In addition, this leads to the problem of time-sensitive communication (TSC) being impaired.

[0058] In view of the above-mentioned problems, one of the objectives of the present invention is to provide a technology that enables the assurance of reliability and the maintenance of TSC. [Means for solving the problem]

[0059] The terminal device of the present invention is configured to switch between a configuration in which the terminal device uses one network path and a configuration in which the terminal device uses multiple network paths, and the terminal device is configured to receive first information relating to the switching from a base station device, and the first information includes information relating to ensuring QoS (Quality of Service).

[0060] The base station device of the present invention is a base station device in a communication system comprising a terminal device and a base station device that performs wireless communication with the terminal device, wherein the terminal device is configured to switch between a configuration in which the terminal device uses one network path and a configuration in which the terminal device uses multiple network paths, and the base station device is configured to transmit first information relating to the switching to the terminal device, wherein the first information includes information relating to ensuring QoS (Quality of Service).

[0061] The present invention relates to a communication system comprising a terminal device, wherein the terminal device is configured to switch between a configuration in which the terminal device uses one network path and a configuration in which the terminal device uses multiple network paths, and the terminal device is configured to receive first information relating to the switching from a base station device, wherein the first information includes information relating to ensuring QoS (Quality of Service). [Effects of the Invention]

[0062] According to the present invention, it becomes possible to ensure reliability and maintain TSC (Total System Standard).

[0063] The object, features, aspects, and advantages of the present invention will become more apparent from the following detailed description and accompanying drawings. [Brief explanation of the drawing]

[0064] [Figure 1] This is an explanatory diagram showing the configuration of wireless frames used in LTE communication systems. [Figure 2] This block diagram shows the overall configuration of the LTE communication system 200 as discussed in 3GPP. [Figure 3] This is a block diagram showing the overall configuration of the NR communication system 210 as discussed in 3GPP. [Figure 4] This is a diagram illustrating the configuration of a data center using eNBs and gNBs connected to the EPC. [Figure 5] This is a diagram showing the configuration of the DC using gNB connected to the NG core. [Figure 6] This is a diagram showing the configuration of the DC with eNBs and gNBs connected to the NG core. [Figure 7] This is a diagram showing the configuration of the DC with eNBs and gNBs connected to the NG core. [Figure 8] Figure 2 is a block diagram showing the configuration of the mobile terminal 202. [Figure 9] Figure 2 is a block diagram showing the configuration of base station 203. [Figure 10] This block diagram shows the configuration of MME. [Figure 11] This is a block diagram showing the configuration of 5GC. [Figure 12] This is a flowchart illustrating the general process from cell search to standby operation performed by a communication terminal (UE) in an LTE communication system. [Figure 13] This figure shows an example of a cell configuration in an NR system. [Figure 14] This is a sequence diagram illustrating the establishment of communication using redundant paths with multiple UEs in Embodiment 1. [Figure 15] This is a sequence diagram illustrating the establishment of communication using redundant paths with multiple UEs in Embodiment 1. [Figure 16] This is a sequence diagram illustrating the establishment of communication using redundant paths with multiple UEs in Embodiment 1. [Figure 17] This sequence diagram for Embodiment 1 shows the operation of suppressing a handover in another redundant path and the operation of releasing that suppression when a handover occurs in one redundant path. [Figure 18] This sequence diagram for Embodiment 1 shows the operation of suppressing a handover in another redundant path and the operation of releasing that suppression when a handover occurs in one redundant path. [Figure 19]This sequence diagram for Embodiment 1 shows the operation of suppressing a handover in another redundant path and the operation of releasing that suppression when a handover occurs in one redundant path. [Figure 20] This is a sequence diagram illustrating a modified example of Embodiment 1, showing the operation of canceling a handover on another redundant path and initiating a handover in response to a communication failure on one redundant path. [Figure 21] This is a sequence diagram illustrating a modified example of Embodiment 1, showing the operation of canceling a handover on another redundant path and initiating a handover in response to a communication failure on one redundant path. [Figure 22] The second embodiment is a sequence diagram showing how a UE using a redundant path via a DC maintains the security key of the secondary base station before and after a master base station handover. [Figure 23] The second embodiment is a sequence diagram showing how a UE using a redundant path via a DC maintains the security key of the secondary base station before and after a master base station handover. [Figure 24] The second embodiment is a sequence diagram showing the operation in which a UE using a redundant path provided by a DC changes the security key of a secondary base station prior to a handover of the master base station. [Figure 25] The second embodiment is a sequence diagram showing the operation in which a UE using a redundant path provided by a DC changes the security key of a secondary base station prior to a handover of the master base station. [Figure 26] This sequence diagram shows a first example of operation in which communication with a secondary base station is continued after an MCG failure, according to a modified example 1 of Embodiment 2. [Figure 27] This sequence diagram shows a second example of operation in which communication with a secondary base station is continued after an MCG failure, according to a modified example 1 of Embodiment 2. [Modes for carrying out the invention]

[0065] Embodiment 1. Figure 2 is a block diagram showing the overall configuration of the LTE communication system 200 being discussed in 3GPP. Figure 2 will be explained below. The radio access network is called E-UTRAN (Evolved Universal Terrestrial Radio Access Network) 201. The mobile terminal equipment (hereinafter referred to as "User Equipment: UE") 202, which is a communication terminal device, can communicate wirelessly with the base station equipment (hereinafter referred to as "Base Station (E-UTRAN NodeB: eNB)") 203 and transmits and receives signals wirelessly.

[0066] Here, "communication terminal equipment" includes not only mobile terminal equipment such as portable mobile phone terminals, but also stationary devices such as sensors. In the following explanation, "communication terminal equipment" may sometimes be simply referred to as "communication terminal."

[0067] If the control protocol for the mobile terminal 202, such as RRC (Radio Resource Control), and the user plane (hereinafter sometimes referred to as U-Plane), such as PDCP (Packet Data Convergence Protocol), RLC (Radio Link Control), MAC (Medium Access Control), and PHY (Physical layer), are terminated at base station 203, then E-UTRAN is composed of one or more base stations 203.

[0068] The control protocol RRC (Radio Resource Control) between the mobile terminal 202 and the base station 203 performs functions such as broadcasting, paging, and RRC connection management. The states of the base station 203 and the mobile terminal 202 in RRC are RRC_IDLE and RRC_CONNECTED.

[0069] In RRC_IDLE mode, tasks such as PLMN (Public Land Mobile Network) selection, System Information (SI) notification, paging, cell re-selection, and mobility are performed. In RRC_CONNECTED mode, mobile terminals have an RRC connection and can send and receive data with the network. In RRC_CONNECTED mode, tasks such as handover (HO) and neighbor cell measurement are also performed.

[0070] Base station 203 consists of one or more eNB207 units. The system, comprising the core network EPC (Evolved Packet Core) and the wireless access network E-UTRAN201, is called EPS (Evolved Packet System). The EPC and E-UTRAN201 are sometimes collectively referred to as the "network."

[0071] The eNB207 is connected via an S1 interface to a Mobility Management Entity (MME), or a Serving Gateway (S-GW), or an MME / S-GW unit (hereinafter sometimes referred to as "MME unit") 204 that includes both an MME and an S-GW, and control information is communicated between the eNB207 and the MME unit 204. Multiple MME units 204 may be connected to a single eNB207. The eNB207s are connected to each other via an X2 interface, and control information is communicated between the eNB207s.

[0072] The MME unit 204 controls the connection between the higher-level device, specifically the higher-level node, which is the base station eNB 207, and the mobile terminal (UE) 202. The MME unit 204 constitutes the core network EPC. The base station 203 constitutes the E-UTRAN 201.

[0073] The base station 203 may constitute one cell or multiple cells. Each cell has a predetermined range called coverage, which is the range within which it can communicate with the mobile terminal 202, and wireless communication is performed with the mobile terminal 202 within that coverage. When one base station 203 constitutes multiple cells, each cell is configured to communicate with the mobile terminal 202.

[0074] Figure 3 is a block diagram showing the overall configuration of the 5G communication system 210 being discussed in 3GPP. Figure 3 will now be explained. The radio access network is called NG-RAN (Next Generation Radio Access Network) 211. UE 202 can communicate wirelessly with NR base station equipment (hereinafter referred to as "NR base station (NG-RAN NodeB: gNB)") 213 and transmits and receives signals wirelessly. The core network is called the 5G Core (5GC).

[0075] If the control protocol for UE202, such as RRC (Radio Resource Control), and the user plane (hereinafter sometimes referred to as U-Plane), such as SDAP (Service Data Adaptation Protocol), PDCP (Packet Data Convergence Protocol), RLC (Radio Link Control), MAC (Medium Access Control), and PHY (Physical layer), are terminated at the NR base station 213, then the NG-RAN is composed of one or more NR base stations 213.

[0076] The functionality of the Radio Resource Control (RRC) control protocol between UE202 and NR base station 213 is the same as in LTE. The states of NR base station 213 and UE202 in RRC are RRC_IDLE, RRC_CONNECTED, and RRC_INACTIVE.

[0077] RRC_IDLE and RRC_CONNECTED are the same as in the LTE system. RRC_INACTIVE means that the connection between the 5G core and NR base station 213 is maintained while system information (SI) broadcasting, paging, cell re-selection, and mobility are performed.

[0078] The gNB217 is connected via an NG interface to an Access and Mobility Management Function (AMF), a Session Management Function (SMF), or a User Plane Function (UPF), or an AMF / SMF / UPF unit (hereinafter sometimes referred to as the "5GC unit") 214 that includes AMF, SMF, and UPF. Control information and / or user data are communicated between the gNB217 and the 5GC unit 214. The NG interface is a collective term for the N2 interface between the gNB217 and AMF, the N3 interface between the gNB217 and UPF, the N11 interface between AMF and SMF, and the N4 interface between UPF and SMF. Multiple 5GC units 214 may be connected to a single gNB217. The gNB217s are connected to each other via an Xn interface, and control information and / or user data are communicated between them.

[0079] Like base station 203, NR base station 213 may also consist of one or more cells. When one NR base station 213 consists of multiple cells, each cell is configured to communicate with UE 202.

[0080] The gNB217 may be divided into a Central Unit (CU) 218 ​​and a Distributed Unit (DU) 219. One CU218 is configured within the gNB217. One or more DU219s are configured within the gNB217. The CU218 is connected to the DU219 via an F1 interface, and control information and / or user data are communicated between the CU218 and the DU219.

[0081] In a 5G communication system, the Unified Data Management (UDM) function and Policy Control Function (PCF) described in Non-Patent Document 24 (3GPP TS23.501 V16.2.0) may be included. The UDM and / or PCF may be included in the 5GC section in Figure 3.

[0082] In a 5G communication system, the Non-3GPP Interworking Function (N3IWF) described in Non-Patent Document 24 (3GPP TS23.501 V16.2.0) may be included. In non-3GPP access between the UE and the N3IWF, the Access Network (AN) may be terminated between the UE and the UE.

[0083] Figure 4 shows the configuration of a DC with eNBs and gNBs connected to the EPC. In Figure 4, solid lines indicate U-Plane connections, and dashed lines indicate C-Plane connections. In Figure 4, eNB223-1 acts as the master base station, and gNB224-2 acts as the secondary base station (this DC configuration is sometimes referred to as EN-DC). Figure 4 shows an example where the U-Plane connection between the MME unit 204 and gNB224-2 is made via eNB223-1, but it may also be made directly between the MME unit 204 and gNB224-2.

[0084] Figure 5 shows the configuration of a DC with gNBs connected to the NG core. In Figure 5, solid lines indicate U-Plane connections, and dashed lines indicate C-Plane connections. In Figure 5, gNB224-1 acts as the master base station, and gNB224-2 acts as the secondary base station (this DC configuration is sometimes referred to as NR-DC). Figure 5 shows an example where the U-Plane connection between 5GC unit 214 and gNB224-2 is made via gNB224-1, but it may also be made directly between 5GC unit 214 and gNB224-2.

[0085] Figure 6 shows the configuration of a DC with eNBs and gNBs connected to the NG core. In Figure 6, solid lines indicate U-Plane connections, and dashed lines indicate C-Plane connections. In Figure 6, eNB226-1 acts as the master base station, and gNB224-2 acts as the secondary base station (this DC configuration is sometimes referred to as NG-EN-DC). Figure 6 shows an example where the U-Plane connection between 5GC unit 214 and gNB224-2 is made via eNB226-1, but it may also be made directly between 5GC unit 214 and gNB224-2.

[0086] Figure 7 shows another configuration of a DC with eNBs and gNBs connected to the NG core. In Figure 7, solid lines indicate U-Plane connections, and dashed lines indicate C-Plane connections. In Figure 7, gNB224-1 acts as the master base station, and eNB226-2 acts as the secondary base station (this DC configuration is sometimes referred to as NE-DC). Figure 7 shows an example where the U-Plane connection between 5GC unit 214 and eNB226-2 is made via gNB224-1, but it may also be made directly between 5GC unit 214 and eNB226-2.

[0087] Figure 8 is a block diagram showing the configuration of the mobile terminal 202 shown in Figure 2. The transmission process of the mobile terminal 202 shown in Figure 8 will now be explained. First, control data from the protocol processing unit 301 and user data from the application unit 302 are stored in the transmission data buffer unit 303. The data stored in the transmission data buffer unit 303 is passed to the encoder unit 304, where encoding processing such as error correction is performed. There may be data that is output directly from the transmission data buffer unit 303 to the modulation unit 305 without undergoing encoding processing. The data encoded by the encoder unit 304 is then modulated in the modulation unit 305. Precoding in MIMO may be performed in the modulation unit 305. The modulated data is converted into a baseband signal, then output to the frequency conversion unit 306, where it is converted to a wireless transmission frequency. After that, the transmission signal is sent from antennas 307-1 to 307-4 to the base station 203. Figure 8 illustrates the case where there are four antennas, but the number of antennas is not limited to four.

[0088] Furthermore, the reception processing of the mobile terminal 202 is performed as follows: A radio signal from the base station 203 is received by antennas 307-1 to 307-4. The received signal is converted from the radio reception frequency to a baseband signal by the frequency conversion unit 306, and demodulation processing is performed by the demodulation unit 308. Weight calculation and multiplication processing may also be performed in the demodulation unit 308. The demodulated data is passed to the decoder unit 309, where decoding processing such as error correction is performed. Of the decoded data, the control data is passed to the protocol processing unit 301, and the user data is passed to the application unit 302. The series of processes of the mobile terminal 202 are controlled by the control unit 310. Therefore, although the control unit 310 is omitted in Figure 8, it is connected to each of the units 301 to 309. In Figure 8, 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.

[0089] Figure 9 is a block diagram showing the configuration of the base station 203 shown in Figure 2. The transmission process of the base station 203 shown in Figure 9 will now be explained. The EPC communication unit 401 transmits and receives data between the base station 203 and the EPC (MME unit 204, etc.). The 5GC communication unit 412 transmits and receives data between the base station 203 and the 5GC (5GC unit 214, etc.). 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 protocol processing unit 403, as well as 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 stored in the transmission data buffer unit 404.

[0090] The data stored in the transmission data buffer unit 404 is passed to the encoder unit 405, where it undergoes encoding processing such as error correction. Some data may be output directly from the transmission data buffer unit 404 to the modulation unit 406 without undergoing encoding processing. The encoded data is then modulated in the modulation unit 406. Precoding in MIMO may be performed in the modulation unit 406. The modulated data is converted to a baseband signal, then output to the frequency conversion unit 407, where it is converted to a wireless transmission frequency. Subsequently, the transmission signal is sent from antennas 408-1 to 408-4 to one or more mobile terminals 202. Figure 9 illustrates the case with four antennas, but the number of antennas is not limited to four.

[0091] Furthermore, the reception processing of the base station 203 is performed as follows: A radio signal from one or more mobile terminals 202 is received by the antenna 408. The received signal is converted from the radio reception frequency to a baseband signal by the frequency conversion unit 407, and demodulation processing is performed by the demodulation unit 409. The demodulated data is passed to the decoder unit 410, where decoding processing such as error correction is performed. Of the decoded data, the control data is passed to the protocol processing unit 403, the 5GC communication unit 412, the EPC communication unit 401, or the other base station communication unit 402, while the user data is passed to the 5GC communication unit 412, the EPC communication unit 401, and the other base station communication unit 402. The series of processes of the base station 203 are controlled by the control unit 411. Therefore, although the control unit 411 is omitted in Figure 9, it is connected to each of the units 401 to 410. In Figure 9, the number of antennas used by the base station 203 for transmission and the number of antennas used for reception may be the same or different.

[0092] Figure 9 is a block diagram showing the configuration of base station 203, but base station 213 may have a similar configuration. Also, in Figures 8 and 9, the number of antennas on mobile terminal 202 and base station 203 may be the same or different.

[0093] Figure 10 is a block diagram showing the configuration of the MME. Figure 10 shows the configuration of the MME204a included in the MME unit 204 shown in Figure 2 above. The PDN GW communication unit 501 transmits and receives data between the MME204a and the PDN GW. The base station communication unit 502 transmits and receives data between the MME204a and the base station 203 via the S1 interface. If the data received from the PDN GW is user data, the user data is passed from the PDN GW communication unit 501 to the base station communication unit 502 via the user-plane communication unit 503 and transmitted to one or more base stations 203. If the data received from the base station 203 is user data, the user data is passed from the base station communication unit 502 to the PDN GW communication unit 501 via the user-plane communication unit 503 and transmitted to the PDN GW.

[0094] If the data received from the PDN GW is control data, the control data is passed from the PDN GW communication unit 501 to the control plane control unit 505. If the data received from the base station 203 is control data, the control data is passed from the base station communication unit 502 to the control plane control unit 505.

[0095] The control plane control unit 505 includes the NAS security unit 505-1, the SAE bearer control unit 505-2, and the idle state mobility management unit 505-3, and performs all processing for the control plane (hereinafter sometimes referred to as C-Plane). The NAS security unit 505-1 performs security for NAS (Non-Access Stratum) messages, etc. The SAE bearer control unit 505-2 performs management of SAE (System Architecture Evolution) bearers, etc. The idle state mobility management unit 505-3 performs mobility management in the standby state (also referred to as LTE-IDLE state or simply idle), generation and control of paging signals in the standby state, addition, deletion, updating, searching, and tracking area list management for one or more mobile terminals 202 under its umbrella.

[0096] The MME204a distributes paging signals to one or more base stations 203. The MME204a also performs mobility control in the idle state. The MME204a manages the tracking area list when the mobile terminal is in the idle state and when it is in the active state. The MME204a initiates the paging protocol by sending paging messages to cells belonging to the registered tracking area of ​​the UE. The management of the CSG, CSG ID, and whitelist of the eNB207 connected to the MME204a may be performed by the idle state mobility management unit 505-3.

[0097] Figure 11 is a block diagram showing the configuration of the 5GC. Figure 11 shows the configuration of the 5GC unit 214 shown in Figure 3. Figure 11 shows the case where the 5GC unit 214 shown in Figure 5 includes the configurations of AMF, SMF, and UPF. 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 S1 interface between the 5GC unit 214 and the base station 203, and / or the NG interface between the 5GC unit 214 and the base station 213. If the data received from the Data Network is user data, the user data is passed from the Data Network communication unit 521 to the base station communication unit 522 via the user-plane communication unit 523, and transmitted to one or more base stations 203 and / or base station 213. If the data received from base station 203 and / or base station 213 is user data, the user data is passed from base station communication unit 522 to Data Network communication unit 521 via user plane communication unit 523 and transmitted to the Data Network.

[0098] If the data received from the Data Network is control data, the control data is passed 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 passes the control data to the control-plane control unit 525. If the data received from base station 203 and / or base station 213 is control data, the control data is passed from base station communication unit 522 to the control-plane control unit 525. The control-plane control unit 525 passes the control data to the session management unit 527.

[0099] The control plane control unit 525 includes the NAS security unit 525-1, the PDU session control unit 525-2, and the idle state mobility management unit 525-3, and performs all processing for the control plane (hereinafter sometimes referred to as C-Plane). The NAS security unit 525-1 performs security for NAS (Non-Access Stratum) messages, etc. The PDU session control unit 525-2 manages PDU sessions between the mobile terminal 202 and the 5GC unit 214, etc. The idle state mobility management unit 525-3 performs mobility management in the standby state (also referred to as RRC_IDLE state or simply idle), generation and control of paging signals in the standby state, addition, deletion, updating, searching, and tracking area list management for one or more mobile terminals 202 under its umbrella.

[0100] The 5GC unit 214 distributes paging signals to one or more base stations 203 and / or base station 213. 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 is in the idle state, inactive state, and active state. The 5GC unit 214 initiates the paging protocol by sending a paging message to a cell belonging to the tracking area where the UE is registered.

[0101] Next, an example of a cell search method in a communication system is shown. Figure 12 is a flowchart illustrating the process from cell search to standby operation performed by a communication terminal (UE) in an LTE communication system. When the communication terminal starts a cell search, in step ST601, it synchronizes the slot timing and frame timing using the first synchronization signal (P-SS) and the second synchronization signal (S-SS) transmitted from the surrounding base station.

[0102] P-SS and S-SS together are called the Synchronization Signal (SS). Each PCI assigned to a cell has a synchronization code that corresponds one-to-one with that PCI. 504 different PCI combinations are being considered. These 504 PCI combinations are used for synchronization, and the PCI of the synchronized cell is detected (identified).

[0103] Next, for the synchronized cell, step ST602 detects the cell-specific reference signal (CRS), which is a reference signal (RS) transmitted from the base station to each cell, and measures the received power (RSRP) of the RS. The reference signal (RS) uses a code that corresponds one-to-one with the PCI. By correlating with this code, it is possible to isolate it from other cells. By deriving the code for the RS of the cell from the PCI identified in step ST601, it becomes possible to detect the RS and measure the received power of the RS.

[0104] Next, in step ST603, from among the one or more cells detected up to step ST602, the cell with the best RS reception quality, for example, the cell with the highest RS reception power, i.e., the best cell, is selected.

[0105] Next, in step ST604, the PBCH of the best cell is received to obtain the broadcast information, which is the BCCH. The BCCH on the PBCH is mapped to the MIB (Master Information Block), which contains cell configuration information. Therefore, by receiving the PBCH and obtaining the BCCH, the MIB can be obtained. MIB information includes, for example, the DL (downlink) system bandwidth (also called transmission bandwidth configuration: dl-bandwidth), the number of transmitting antennas, and the SFN (System Frame Number).

[0106] Next, in step ST605, the DL-SCH of the cell is received based on the cell configuration information of the MIB, and SIB (System Information Block) 1 is obtained from the broadcast information BCCH. SIB1 contains information about accessing the cell, information about cell selection, and scheduling information for other SIBs (SIBk; an integer k ≥ 2). SIB1 also contains the Tracking Area Code (TAC).

[0107] Next, in step ST606, the communication terminal compares the TAC of the 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 the TAI list. TAI is identification information for identifying a tracking area and consists of MCC (Mobile Country Code), MNC (Mobile Network Code), and TAC (Tracking Area Code). MCC is the country code. MNC is the network code. TAC is the code number of the tracking area.

[0108] If, as a result of the comparison in step ST606, the TAC received in step ST605 is the same as a TAC included in the tracking area list, the communication terminal enters a waiting state in that cell. If, after comparison, the TAC received in step ST605 is not included in the tracking area list, the communication terminal requests a change in the tracking area through that cell to the Core Network (EPC), which includes the MME, etc., in order to perform a Tracking Area Update (TAU).

[0109] In the example shown in Figure 12, an example of the operation from cell search to standby in the LTE system is shown. However, in the NR system, in step ST603, the best beam may be selected in addition to the best cell. Also in the NR system, in step ST604, beam information, such as a beam identifier, may be obtained. Also in the NR system, in step ST604, scheduling information for the Remaining Minimum SI (RMSI) may be obtained. In the NR system, in step ST605, the RMSI may be received.

[0110] The devices constituting the core network (sometimes referred to as "core network devices") update the tracking area list based on the identification number (UE-ID, etc.) of the communication terminal sent from the communication terminal along with the TAU request signal. The core network devices send the updated tracking area list to the communication terminal. The communication terminal rewrites (updates) its TAC list based on the received tracking area list. After that, the communication terminal enters a waiting state in that cell.

[0111] The proliferation of smartphones and tablet devices has led to an explosive increase in cellular wireless communication traffic, raising concerns about a shortage of wireless resources worldwide. To address this, efforts are being made to improve frequency utilization efficiency by reducing the number of cells and promoting spatial separation.

[0112] In conventional cell configurations, cells composed of eNBs have relatively wide coverage. Traditionally, cells are configured to cover a certain area through the relatively wide coverage of multiple cells composed of multiple eNBs.

[0113] When subdivided into smaller cells, the cells composed of eNBs have narrower coverage than cells composed of conventional eNBs. Therefore, as before, a larger number of subdivided eNBs are needed to cover a given area compared to conventional eNBs.

[0114] In the following explanation, cells with relatively high coverage, such as those composed of conventional eNBs, will be referred to as "macrocells," and the eNBs that make up macrocells will be referred to as "macro eNBs." Similarly, cells with relatively low coverage, such as those that have been resized into smaller cells, will be referred to as "small cells," and the eNBs that make up small cells will be referred to as "small eNBs."

[0115] Macro eNB may be, for example, a "Wide Area Base Station" as described in Non-Patent Document 7.

[0116] A small eNB may be, for example, a low-power node, a local area node, or a hotspot. Alternatively, a small eNB may be a pico eNB constituting a picocell, a femto eNB constituting a femtocell, a HeNB, an RRH (Remote Radio Head), an RRU (Remote Radio Unit), an RRE (Remote Radio Equipment), or an RN (Relay Node). Furthermore, a small eNB may be a "Local Area Base Station" or "Home Base Station" as described in Non-Patent Document 7.

[0117] Figure 13 shows an example of a cell configuration in NR. In an NR cell, a narrow beam is formed and transmitted by changing its direction. In the example shown in Figure 13, base station 750 uses beam 751-1 to transmit and receive with a mobile terminal at a certain time. At other times, base station 750 uses beam 751-2 to transmit and receive with a mobile terminal. Similarly, base station 750 uses one or more of beams 751-3 to 751-8 to transmit and receive with a mobile terminal. In this way, base station 750 configures a wide-area cell.

[0118] Figure 13 shows an example where the base station 750 uses eight beams, but the number of beams may be different from eight. Also, in the example shown in Figure 13, the base station 750 uses one beam simultaneously, but it may use multiple beams.

[0119] In communication using redundant paths, the same data may be transmitted and received through each path. The transmitting host may duplicate the data and send it to each device on each path. The receiving host may keep one of the data received from the transmitting host and delete the others. The transmitting host may be a host connected to a DN (Data Network) or a host connected to an UE. The receiving host may be a host connected to an UE or a host connected to a DN.

[0120] Communication using redundant paths may involve one UE or multiple UEs.

[0121] In a redundant path configuration using multiple UEs, each UE may be connected to a different base station. Each base station may be connected to a different UPF. Each UPF may be connected to the same DN or to different DNs. Each base station may be connected to the same AMF or to different AMFs. Each UPF may be connected to the same SMF or to different SMFs. In this redundant path configuration, a PDU session may be established between each UE and each UPF.

[0122] A redundant path configuration using multiple UEs may be used in the transmission and reception of small data (Non-Patent Document 9 (TR38.804)). For example, in uplink communication, multiple paths may be provided for transmitting data from the UE to the DN via the base station, AMF, SMF, and UPF. As another example, the same may be applied to the path for transmitting data from the DN to the UE via the UPF, SMF, AMF, and base station in downlink communication. In the foregoing, the base stations in each path may be different from each other. The same may be applied to the AMF, SMF, and UPF. This makes it possible to improve reliability in small data transmission and reception, for example.

[0123] In redundant communication using multiple UEs, the following problem arises: If communication is interrupted on one path, and UEs on the remaining paths become mobile, communication will stop on all redundant paths. As a result, the reliability of communication cannot be ensured, and Time Sensitive Communication (TSC) cannot be achieved.

[0124] This first embodiment discloses a method for solving the aforementioned problems.

[0125] The base station will not perform UE mobility if communication is not possible via other redundant paths. As another example, in the aforementioned case, the base station may not release or suspend the RRC connection with the UE.

[0126] The aforementioned inability to communicate may occur when a UE on another redundant path is in mobility, when a UE on another redundant path is not RRC_CONNECTED and / or CM_CONNECTED, when the power to any NW device on another redundant path is lost, when a UE on another redundant path detects an RLF (Radio Link Failure) and / or a beam failure, when a communication failure occurs between the base station and the core network and / or in the core network on another redundant path, or in any combination of the above. The aforementioned communication failure between the base station and the core network may be a communication failure between the base station and the AMF (e.g., a communication failure on the N2 interface), or a communication failure between the base station and the UPF (e.g., a communication failure on the N3 interface). The aforementioned communication interruption in the core network may be a communication interruption between UPF and SMF (e.g., a communication interruption on the N4 interface), a communication interruption between UPF and DN (e.g., a communication interruption on the N6 interface), a communication interruption between UPFs (e.g., a communication interruption on the N9 interface), a communication interruption between AMF and SMF (e.g., a communication interruption on the N11 interface), or a combination of the above.

[0127] As mentioned above, a base station on a redundant route where communication is not possible (hereinafter sometimes referred to as a communication-disrupted redundant route) notifies a base station on another redundant route (hereinafter sometimes referred to as a non-communication-disrupted redundant route) that it is unable to communicate with the UE on its own route. This information may include, for example, information about the redundant route described below, or it may include the reason why communication is not possible. This information about the redundant route may include, for example, the identifier of the route, information about the UE on the route, information about the base station on the route, information about the UPF on the route, information about the PDU session on the route, or a combination of the above. The reasons for the inability to communicate may include, for example, that the UE on another redundant path is in mobility, that the UE on another redundant path is not RRC_CONNECTED and / or CM_CONNECTED, that the power to each NW device on another redundant path has been lost, that the UE on another redundant path has detected RLF (Radio Link Failure) and / or Beam Failure, that a communication outage has occurred between the base station and the core network and / or that a communication outage has occurred in the core network on another redundant path, or a combination of the above.

[0128] A base station on a communication-disruption-redundant path may notify via the AMF that it is unable to communicate with the UE on its own path. The AMF may notify a base station on a non-communication-disruption-redundant path of this information. This notification from the AMF to a base station on a non-communication-disruption-redundant path may be made via the AMF on the non-communication-disruption-redundant path. As another example, a base station on a communication-disruption-redundant path may notify a base station on a communication-disruption-redundant path of this information via the AMF on the non-communication-disruption-redundant path.

[0129] A base station on a non-communication-disruption redundant path may use this information to refrain from performing mobility (e.g., handover) of the UE connected to it, or it may not release the RRC connection with the UE, or it may not suspend the connection.

[0130] A new signaling mechanism may be introduced for instructing the cessation of measurement reporting. This signaling mechanism may include, for example, information indicating the measurement to be stopped (e.g., a Measurement Object). This allows, for example, the UE to quickly identify the Measurement Objects for which measurement reporting should be stopped. The signaling mechanism may be, for example, an RRC signaling mechanism. This allows, for example, the base station to notify the UE of a greater amount of information. As another example, the signaling mechanism may be a MAC signaling mechanism. This allows, for example, the base station to quickly instruct the UE to stop measurement reporting. As yet another example, the signaling mechanism may be an L1 / L2 signaling mechanism. This allows, for example, the base station to even more quickly instruct the UE to stop measurement reporting.

[0131] A base station on another path may instruct a UE connected to its base station to stop reporting measurement data. This instruction may use, for example, the newly established signaling described above, or existing signaling. The base station may, triggered by this information, instruct the UE to stop reporting measurement data. The UE may, triggered by this instruction, stop transmitting measurement data to the base station. The measurement data may be event-triggered measurement data as disclosed in Non-Patent Document 22 (TS38.331) and / or Non-Patent Document 23 (TS36.331). This makes it possible, for example, to suppress measurement data from the UE during UE mobility suppression. As a result, the amount of signaling between the base station and the UE can be reduced.

[0132] As another example, a base station on a communication interruption redundancy path may release the measurement settings for the UE connected to its base station. These measurement settings may be event-triggered measurement settings as disclosed, for example, in Non-Patent Document 22 (TS38.331) and / or Non-Patent Document 23 (TS36.331). The base station may release the settings using RRC signaling, MAC signaling, or L1 / L2 signaling. The UE may release the measurement settings for its UE using the signaling of the release. This can, for example, reduce memory usage at the base station and / or the UE.

[0133] A base station on a redundant path that is unable to communicate may notify base stations on other paths that communication with the UE on its own path has been restored. This information indicating that communication has been restored may, for example, indicate that the UE's mobility is complete, or indicate that the UE has returned to RRC_CONNECTED. The base station on other paths may use this information to enable the UE connected to its own base station to perform mobility (e.g., handover), release the UE's RRC connection, or suspend it.

[0134] A new signaling mechanism may be introduced for instructing the start or restart of measurement reporting. This signaling mechanism may include, for example, information indicating the measurement to which reporting should be started or restarted (e.g., a measurement object). This allows, for example, the UE to quickly identify the measurement object for which measurement reporting should be restarted. The signaling mechanism may be, for example, an RRC signaling mechanism. This allows, for example, the base station to notify the UE of a large amount of information. As another example, the signaling mechanism may be a MAC signaling mechanism. This allows, for example, the base station to quickly instruct the UE to restart measurement reporting. As yet another example, the signaling mechanism may be an L1 / L2 signaling mechanism. This allows, for example, the base station to even more quickly instruct the UE to restart measurement reporting.

[0135] The base station may instruct the UE to resume measurement reporting. This instruction may use, for example, the newly established signaling described above, or the existing signaling. The base station may instruct the UE to resume measurement reporting using information indicating that communication between the UE and base stations on other redundant paths has been restored. The UE may then resume sending measurement reports to the base station. This can, for example, improve the stability of the communication quality on the redundant paths.

[0136] The signaling used to instruct the cessation of measurement reporting and the signaling used to instruct the start or restart of measurement reporting may be the same signaling. For example, the signaling may include information indicating the cessation of measurement reporting, information about the measurement subject to the cessation of measurement reporting (e.g., a measurement object), information indicating the start or restart of measurement reporting, or information about the measurement subject to the start or restart of measurement reporting (e.g., a measurement object). This can reduce the number of additional signaling types, for example. As a result, it becomes possible to reduce the complexity of adding functionality related to stopping / restarting measurement reporting in the communication system.

[0137] As another example, a base station on a communication interruption redundancy path may reconfigure the measurement settings for the UE connected to its base station. The aforementioned reconfiguration may occur when the base station releases the measurement settings for the UE. The aforementioned reconfiguration may differ from the settings before release. The measurement settings may be event-triggered measurement settings as disclosed, for example, in Non-Patent Document 22 (TS38.331) and / or Non-Patent Document 23 (TS36.331). The base station may perform the setting using, for example, RRC signaling. The UE may use the signaling of the release to reconfigure the measurement settings for its own UE. This allows for, for example, increased flexibility in measurement settings.

[0138] A base station may have different start / stop conditions for measurement reporting for UEs using a redundant configuration and for UEs not using a redundant configuration. The measurement report may be, for example, an event-triggered measurement report as disclosed in Non-Patent Document 22 (TS38.331) and / or Non-Patent Document 23 (TS36.331). The base station may perform the operation of differentiating the start / stop conditions by, for example, differentiating the start / stop thresholds. The base station may use, for example, the information described in (1) below as redundant path information to determine whether to differentiate the start / stop conditions.

[0139] A base station may, for example, relax the start / stop conditions for measurement reporting for UEs using a redundant configuration compared to the start / stop conditions for UEs not using a redundant configuration. This allows for handover before communication quality deteriorates, for example, compared to cases without a redundant configuration. As a result, it becomes possible to prevent link failure in the redundant configuration due to deterioration in communication quality while handover is being suppressed in the redundant configuration.

[0140] As another example, a base station may set stricter start / stop conditions for measurement reporting for UEs using a redundant configuration than for UEs not using a redundant configuration. This can, for example, reduce the frequency of handovers and, as a result, improve communication efficiency.

[0141] Before detecting RLF in a UE using a redundant path, a base station may notify base stations on other redundant paths that its own UE is likely to experience RLF, or that it will not be able to receive uplink signals from its own UE for a predetermined time. This notification may be made via AMF. For example, a base station may make this notification if it will not be able to receive uplink signals from the UE for a predetermined time. Base stations on other redundant paths may use this notification to suppress UE handover or to suppress measurement reporting to the UE. This makes it possible to prevent the own redundant path from experiencing RLF or beam failure after a handover has started on the other redundant path. As a result, it is possible to prevent both communication paths from being interrupted.

[0142] The predetermined time may be determined by a standard. For example, the predetermined time may be set to be shorter than the TSC period. Alternatively, the base station may determine the predetermined time. For example, the base station may determine the predetermined time to be shorter than the TSC period. The base station may notify the UE of the predetermined time quasi-statically, for example using RRC signaling. This allows for improved reliability in notifying the predetermined time, for example. Alternatively, the base station may notify the UE of the predetermined time dynamically, for example using MAC signaling. This allows for faster notification of the predetermined time, for example. Alternatively, the base station may notify the predetermined time using L1 / L2 signaling. This allows for even faster notification of the predetermined time, for example.

[0143] The aforementioned base station may, upon receiving an uplink signal from the UE, notify other base stations on the redundant path that communication with its UE has been restored. This notification may be made via the AMF. The base station may make this notification, for example, when it sends information to a base station on the redundant path indicating that it will not be able to receive an uplink signal from the UE for a predetermined time. The base station on the redundant path may use this notification to release the handover suppression for the UE, or to release the suppression of measurement reporting to the UE. This makes it possible to prevent, for example, a situation in which the UE is unable to hand over on the other redundant path after the communication path with the UE has been restored.

[0144] The UE may notify the base station of information regarding redundant routes. For example, the UE may notify the base station of this information using RRC signaling. The base station may forward this information to the AMF. For example, the base station may forward this information to the AMF using signaling on the N2 interface. As another example, the UE may notify the AMF of this information. The UE may forward this information to the AMF using NAS signaling.

[0145] Examples of information regarding redundant paths are disclosed below (1) to (17).

[0146] (1) Information regarding whether or not communication is using redundant paths.

[0147] (2) Information regarding the configuration of redundant paths.

[0148] (3) Information regarding the number of redundant paths in the sending and receiving hosts.

[0149] (4) Identifier of the redundant route used by the UE.

[0150] (5) Identifier of the UE. Examples include (5-1) to (5-5) below.

[0151] (5-1) The IMSI (International Mobile Subscriber Identity) of the user's UE.

[0152] (5-2) The UE's MSISDN (Mobile Subscriber Integrated Services Digital Network Number).

[0153] (5-3) 5G-S-TMSI (5G S-Temporary Mobile Subscription Identifier) ​​of the user's own UE.

[0154] (5-4) The UE-ID of your own UE.

[0155] (5-5) The combinations of (5-1) to (5-4) mentioned above.

[0156] (6) Information regarding combinations of redundant paths.

[0157] (7) Identifier of another redundant path.

[0158] (8) Identifiers of UEs on other redundant paths. Examples include (8-1) to (8-5) below.

[0159] (8-1) The IMSI (International Mobile Subscriber Identity) of the UE on another redundant path.

[0160] (8-2) The MSISDN (Mobile Subscriber Integrated Services Digital Network Number) of the UE on another redundant path.

[0161] (8-3) 5G-S-TMSI (5G S-Temporary Mobile Subscription Identifier) ​​of UEs on other redundant paths.

[0162] (8-4) The UE-ID of the UE on the other redundant path.

[0163] (8-5) The combinations of (8-1) to (8-4) mentioned above.

[0164] (9) Information regarding base stations connected in the redundant path.

[0165] (10) Information regarding AMFs connected in the redundant path.

[0166] (11) Information regarding UPFs connected in the redundant path.

[0167] (12) Information regarding SMFs connected in the redundant path.

[0168] (13) Information regarding base stations connected via other redundant paths.

[0169] (14) Information regarding AMFs connected via other redundant paths.

[0170] (15) Information regarding UPFs connected via other redundant paths.

[0171] (16) Information regarding SMFs connected via other redundant paths.

[0172] (17) A combination of the above (1) to (16).

[0173] The information in (1) above may, for example, be information indicating whether the UE configures redundant communication. The NW device may use this information to configure measurement settings for the UE. This makes it possible to reduce the number of mobility events for UEs that configure redundant paths, and as a result, it becomes possible to reduce the number of communication interruptions due to mobility.

[0174] The information in (2) above may, for example, indicate that redundant paths are configured by each of multiple UEs being connected to different base stations and UPFs; or it may indicate that redundant paths are configured by one UE being connected to multiple base stations and multiple UPFs; or it may indicate that redundant paths are configured by one UE being connected to one base station and one or more UPFs. A UE may maintain information about the configurations it can take as UE capabilities or in a SIM. The core network equipment may use the information in (2) above to determine the redundant configuration of the UEs. This makes it possible to configure an optimal redundant path between transmitting and receiving hosts, for example, depending on the communication environment.

[0175] The redundant paths mentioned in (3) above may be, for example, two or three or more. The network device may use this information to query other networks for information about other redundant paths. This allows the network device to query for information about other redundant paths as many times as needed. As a result, the signaling efficiency in the communication system can be improved.

[0176] The information in (4) above may be represented, for example, by a sequence of numbers starting from 0 or 1, by a flag using a bitmap, or by any other form. The NW device may use this information to determine whether a signaling signal (e.g., a query) from another NW device relates to its own redundant path. This can improve signaling efficiency in a communication system, for example.

[0177] As the information in (5) above, for example, the information in (5-1) and / or (5-2) may be used. This makes it possible to identify UEs on other paths even when the NW (e.g., PLMN) used in each redundant path is different, and as a result, complexity in controlling redundant paths can be avoided. As another example, the information in (5-3) and / or (5-4) may be used. This makes it possible to quickly identify UEs. The information in (5) above may include information about the type of identifier. This makes it possible for the NW device to quickly grasp the type of identifier, and as a result, processing in the communication system can be executed quickly.

[0178] The information in (6) above may, for example, be an identifier that identifies a pair of redundant paths. This allows, for example, a network device to quickly identify redundant paths that are paired with its own redundant path. As another example, identifiers of UEs that constitute a pair of redundant paths may be used, for example, the aforementioned (5-1), (5-2), (8-1), (8-2), or any combination thereof. This will, for example, produce the same effect as described above.

[0179] The information in (7) above may be the same as the information in (4) above. This can, for example, produce the same effect as in (4) above.

[0180] The information in (8) above may be the same as the information in (5) above. This will produce the same effect as in (5) above, for example.

[0181] The information in (9) above may be, for example, a gNB-ID disclosed in Non-Patent Document 16 (TS38.300), an NR cell global ID, a global gNB-ID, or the network address of the base station (e.g., an IP address).

[0182] A base station may notify each device on the other redundant paths of the information (9) relating to its own redundant path. This notification may include the information (5) described above. This notification may be made by the AMF or the SMF. Each device on the other redundant paths, for example, a base station on another redundant path, may reject a connection request from the UE by using the fact that the information (9) refers to its own base station and that the UE attempting to connect is the UE indicated in the information (5). This prevents, for example, a decrease in redundancy due to the duplication of base stations on multiple redundant paths.

[0183] The information in (10) above may be, for example, the AMF Name disclosed in Non-Patent Document 16 (TS38.300), the GUAMI (Globally Unique AMF Identifier) ​​disclosed in Non-Patent Document 24 (TS23.501), or the network address of the AMF (e.g., IP address). Alternatively, the information in (10) above may be, for example, an identifier consisting of one or more of the AMF Region ID, AMF Set ID, and AMF Pointer disclosed in Non-Patent Document 24.

[0184] A base station may notify each device on other redundant routes of the information (10) concerning its own redundant route. This notification may be made by an AMF or an SMF. Each device on other redundant routes, for example, a base station on another redundant route, may be connected to the same AMF as the information (10). This makes it possible to efficiently perform communication using redundant routes, for example. As another example, the base station on another redundant route may be connected to a different AMF than the information (10). This makes it possible to improve the redundancy in a C-plane, for example, and as a result improve the robustness of the communication system.

[0185] The information in (11) above may be, for example, a UPF ID disclosed in Non-Patent Document 25 (TS23.502), or the network address of the UPF (e.g., an IP address).

[0186] The base station may notify each device on the other redundant paths of the information (11) concerning its own redundant path. This notification may be made by the AMF or by the SMF. Each device on the other redundant paths, for example, the SMF on the other redundant path, may restrict the UPF used in its own SMF's redundant path. For example, the SMF may not connect to the UPF included in the information. This prevents, for example, a decrease in redundancy due to overlapping UPFs in multiple redundant paths.

[0187] The information in (12) above may be, for example, the SMF ID disclosed in Non-Patent Document 25 (TS23.502), or the network address of the base station (e.g., IP address).

[0188] The base station may notify each device on the other redundant paths of the information (12) concerning its own redundant path. This notification may be made by the AMF or the SMF. Each device on the other redundant paths, for example, the AMF of the other redundant path, may be connected to the same SMF as the information (12). This allows for efficient control of communication using the redundant path, for example. As another example, the AMF may be connected to a different SMF than the information (12). This allows for improved redundancy in the C-plane, for example, and as a result, improved robustness of the communication system.

[0189] The information in (13) above may be the same as the information in (9) above, for example. The UE may use the information in (13) above to determine the destination base station. This makes it possible to prevent a decrease in redundancy due to the duplication of base stations in multiple redundant paths, for example.

[0190] The information in (14) above may be the same as the information in (10) above, for example. The base station may use the information in (14) above to determine the AMF to which the UE will connect on the N1 interface. For example, the base station may determine the AMF to which the UE will connect to be the same AMF as in (14) above. This makes it possible to efficiently perform communication using redundant paths, for example. As another example, the base station may determine the AMF to which the UE will connect to be a different AMF from the one in (14) above. This makes it possible to improve the redundancy in the C-plane, for example, and as a result improve the robustness of the communication system.

[0191] The information in (15) above may be the same as the information in (11) above, for example. The SMF may use the information in (15) above to restrict the UPFs used in its redundant paths, for example, by not connecting to the UPFs included in the information. This makes it possible to prevent a decrease in redundancy due to UPFs overlapping in multiple redundant paths.

[0192] The information in (16) above may be the same as the information in (12) above, for example. The AMF may be connected to the same SMF as the information in (16) above. This makes it possible to efficiently control communication using redundant paths, for example. As another example, the AMF may be connected to a different SMF than the information in (16). This makes it possible to improve redundancy in the C-plane, for example, and as a result improve the robustness of the communication system.

[0193] The information described in (1) to (8) above may, for example, be included in the UE capabilities or in the UE's SIM.

[0194] The UE may notify the network of this redundant route information during registration. The UE may notify the base station, for example. For example, the UE may include this information in the signaling of the Registration Request. As another example, the UE may notify the information when establishing a PDU session. As yet another example, the UE may notify the information when making a service request. As yet another example, the UE may notify the information when establishing a connection with the AMF. For example, the UE may notify the AMF.

[0195] The base station may use this information to determine the AMF to which the UE is connected. The AMF may use this information to determine the SMF. The SMF may use this information to determine the UPF to which the UE is connected. The determination of the AMF, SMF, and / or UPF may be performed in the NW registration procedure, the PDU session establishment procedure, or the service request procedure. This reduces the possibility of changes to the AMF, SMF, and / or UPF after their determination, for example. As a result, the amount of signaling caused by procedures in the communication system can be reduced.

[0196] Another example of determining the AMF, SMF, and / or UPF is the existence of a default destination AMF, SMF, and / or UPF. Information regarding the default destination may be held, for example, by the UE, the base station, the AMF, or the SMF. For example, a base station may have a default destination AMF, an AMF may have a default destination SMF, and an SMF may have a default destination UPF. Each of the aforementioned devices may use information about redundant paths to re-determine the destination AMF, SMF, and / or UPF. This can, for example, avoid complexity in the communication system.

[0197] Another example of information regarding redundant routes is that network equipment may derive information regarding redundant routes. The aforementioned network equipment may be a base station, an AMF, an SMF, or a UDM. For example, the AMF may notify the base station or the SMF of the derived information. Another example is that the UDM may notify the AMF or the SMF of the derived information. The AMF may notify the base station or the SMF of the information derived by the UDM. This can, for example, reduce the amount of signaling between the UE and the base station.

[0198] As another example, the notification of redundant route information from the UE and the derivation of such information by the NW device may be used in combination. For example, the UE may notify the NW device of (1) to (8) or a combination thereof, which have been disclosed as examples of redundant route information. The aforementioned information (8) notified from the UE to the NW device may be, for example, (8-1) and / or (8-2). The NW device may use the information from the UE to derive (8) to (16) or a combination thereof, which have been disclosed as examples of redundant route information. The aforementioned information (8) derived by the NW device may be, for example, (8-3) and / or (8-4). This makes it possible to reduce the amount of signaling between the UE and the base station while reducing the processing load on the NW device.

[0199] The base station may acquire information about other redundant routes. The information acquired by the base station may be, for example, (8) to (16) disclosed above as examples of information about redundant routes, or a combination thereof. The base station may use this information, for example, information about base stations used in other redundant routes, to switch the base station to which a UE on its own redundant route is connected, or to select a base station to which the UE will be handed over. For example, when determining the handover destination for a UE on its own redundant route, the base station may exclude base stations currently in use on other redundant routes from the handover destinations. This makes it possible, for example, for UEs on multiple redundant routes to connect to different base stations, thereby improving the robustness of the redundant routes.

[0200] A base station may request the information from the AMF. The base station may make the request by, for example, using the information disclosed as an example of information regarding redundant routes in (1) as being true. The base station may include in the request a portion of the information regarding redundant routes, for example, (1) to (8) or a combination thereof, which were disclosed above as examples of information regarding redundant routes. The AMF may derive the information using the request. The AMF may notify the base station of the information in response to the request. This makes it possible to reduce the amount of processing required for the base station to derive the information, for example.

[0201] The AMF may request the UDM for the information. The AMF may make the request, for example, by using the information disclosed in (1) as an example of information regarding a redundant route as fact. The AMF may include in the request a portion of the information regarding a redundant route, for example, (8-1) and / or (8-2) disclosed above as examples of information regarding a redundant route. The UDM may use the information from the AMF to derive information regarding a redundant route. For example, the UDM may use the information in (8-1) and / or (8-2) provided by the AMF to derive information about an AMF connected on another redundant route, for example, the identifier of that AMF. The UDM may notify the AMF of the derived information. The AMF may use the information to request information about other redundant routes from an AMF on another redundant route. The AMF on another redundant route may use the request to derive information about its own redundant route to which the AMF is connected, for example, the base station used by that redundant route. The AMF on another redundant route may notify the AMF of the derived information. The AMF may also notify the base station of the information it has received. This allows network equipment on the local redundant path to obtain information about the other redundant path, even if the AMF used on the other redundant path is different from its own AMF.

[0202] The base station may request this information when the UE registers with the network. For example, the base station may request this information upon receiving a Registration Request signaling from the UE. The base station may also include this request in the Registration Request signaling it sends to the AMF. The AMF may request this information when the UE registers with the network. For example, the AMF may request this information upon receiving a Registration Request signaling from the base station.

[0203] As another example, a base station may request this information when a UE makes a service request. For example, a base station may request this information upon receiving a Service Request signaling from a UE. The AMF may request this information when a UE registers with the network. A base station may include this request in the Service Request signaling it sends to the AMF. The AMF may request this information when a UE makes a service request. For example, the AMF may request this information upon receiving a Service Request signaling from a base station.

[0204] As another example, the AMF may request this information when the UE establishes a PDU session. For instance, the AMF may request this information upon receiving a PDU Session Establishment Request from the UE.

[0205] UEs, base stations, AMFs, and / or SMFs may notify network equipment on other redundant paths of information about their own redundant path. The information notified by the UEs, base stations, AMFs, and / or SMFs may be some or all of (1) to (17) disclosed above as examples of information about redundant paths (e.g., (1) to (6), (9) to (12), or a combination thereof). The notification of such information may be made by the AMF or the SMF. Network equipment on other redundant paths may use this information to determine or switch the base stations, UPFs, AMFs, and / or SMFs to connect to on their own redundant path. For example, network equipment on other redundant paths may exclude the base stations and / or UPFs included in the information to determine the base stations and / or UPFs to use on their own redundant path. This allows, for example, UEs on multiple redundant paths to connect to different base stations and / or UPFs, thereby improving the robustness of the redundant paths.

[0206] For example, during a UE handover, the UE may be unable to connect to a base station on a redundant path other than its own redundant path. The base station may notify the source base station that it is rejecting the UE's handover request. This rejection may be done, for example, using HANDOVER PREPARATION FAILURE signaling. The rejection may include a reason. This reason may include, for example, information indicating that the UE is already connected to another redundant path.

[0207] As another example, during cell selection and / or cell reselection by a UE, the UE may be unable to connect to a base station on a redundant path different from its own redundant path. The base station may notify the UE that it cannot connect to it during random access processing with the UE. This notification may be given, for example, using random access message 4 or message 2. The notification may include a reason, which may include information indicating that it is already connected to another UE on a redundant path.

[0208] As another example, in a UE handover, a base station that has become the new destination of a UE on another redundant path may instruct the other connected UE to perform a handover. The base station may give this instruction to the other connected UE using RRC signaling, for example, RRCReconfiguration. The instruction may include a reason, which may include information indicating that the UE is already connected to another redundant path.

[0209] A base station may decide whether to refuse a UE handover to its own base station or to instruct a connected UE to handover. The base station may make this decision, for example, using measurement reports from each UE. The mobile base station may notify the base station of the UE's measurement report. The base station may request the mobile base station to provide the UE's measurement report. This can, for example, improve the stability of communication quality on both redundant paths.

[0210] When configuring measurement settings for the UE, a base station may set base stations or cells that can be connected on its own redundant path as the base station or cell to be measured, or as the base station or cell to be reported the measurement results for. The aforementioned base stations or cells that can be connected on its own redundant path may, for example, be base stations or cells that are not used on other redundant paths. This prevents, for example, a decrease in redundancy due to the duplication of base stations on multiple redundant paths. As another example, base stations or cells used on other redundant paths may be included in the base stations or cells that can be connected on its own redundant path. This allows, for example, a handover to be possible even if no candidate handover destination base stations can be found on its own redundant path other than base stations used on other redundant paths. As a result, the stability of communication quality on both redundant paths can be improved.

[0211] Another example of setting up measurement from base stations to UEs is that base stations or cells that cannot be connected to the self-redundant path may be excluded from the base stations or cells to be measured, or from the base stations or cells to which measurement results are reported. This can reduce the amount of signaling involved in the measurement setting, for example, when the number of connectable base stations or cells is small. The aforementioned base stations or cells that cannot be connected to the self-redundant path may be, for example, base stations or cells used in other redundant paths.

[0212] Notifications from the UE, base station, AMF, and / or SMF to network devices on other redundant paths may be made via the UE-side host or via inter-UE communication (e.g., sidelink). As another example, the notification may be made via the base station, for example, via the Xn interface. As yet another example, the notification may be made via the AMF, for example, via the base station, AMF, and base stations on other redundant paths, or via an inter-AMF interface. An inter-AMF interface may be provided. As yet another example, the notification may be made via the SMF, for example, using an inter-SMF interface. As yet another example, the notification may be made from the AMF via the SMF on other redundant paths. As yet another example, the notification may be made via the UPF or via the DN. The notification may be a notification of information indicating that communication with the UE on the local path is unavailable, a notification of information indicating that communication with the UE on the local path has been restored, or a notification of information regarding redundant paths.

[0213] A base station may individually notify or broadcast to a UE information about cells or base stations that the UE cannot connect to (e.g., a blacklist of cells or base stations). This broadcast may be made, for example, using system information. The base station may use information about redundant paths notified from other redundant paths to construct information about cells that the UE cannot connect to. The base station may include information about UEs that cannot connect to a cell, such as the UE's identifier, in the information it notifies or broadcasts to the UE. The UE may use this information to connect to the base station. This allows the UE to quickly identify cells that it cannot connect to.

[0214] A base station may notify or broadcast to the UE information regarding redundant routes that include its base station. This information may include redundant routes to which the base station can connect. This broadcast may be made, for example, using system information. This information may include, for example, information about the reliability group to which the base station includes (see Non-Patent Document 24 (TS23.501)), or information (1) to (17) regarding redundant routes to which the base station includes, or a combination thereof. The UE may use this information to connect to a base station. For example, the UE may connect to a base station if it is connectable on its redundant route. This allows the UE to quickly identify connectable base stations.

[0215] Figures 14-16 are sequence diagrams showing the establishment of communication using redundant paths with multiple UEs. Figures 14-16 are connected at the boundary lines BL1415 and BL1516. Figures 14-16 show the case where two redundant paths are used, with UE#1, base station#1, AMF#1, UPF#1, and SMF#1 used in one redundant path (which may be referred to as redundant path #1 below), and UE#2, base station#2, AMF#2, UPF#2, and SMF#2 used in the other redundant path (which may be referred to as redundant path #2 below), and where different UE#1 and UE#2 are connected to base station#1 and base station#2 respectively on the terminal side host and used for communication with the network side host. Note that in Figures 14-16, "base station#1" and "base station#2" are denoted as "BS#1" and "BS#2". Figures 14-16 show the establishment of PDU sessions in UE#1 and UE#2.

[0216] In step ST1401 shown in Figure 14, UE#1 requests AMF#1 to establish a PDU session. This request may include information about redundant paths using UE#1 and / or UE#2.

[0217] In procedure 1402, shown in Figure 14, a PDU session is established.

[0218] In step ST1403 shown in Figure 14, AMF#1 performs SMF selection. In step ST1405, AMF#1 requests SMF#1 to create a PDU session. In step ST1407, SMF#1 queries and retrieves subscriber information from UDM#1. In step ST1409, SMF#1 notifies AMF#1 of the response to the PDU session creation request. In step ST1411, authentication / authorization of the PDU session takes place.

[0219] In step ST1413 shown in Figure 14, SMF#1 selects the PCF to use for connecting with UE#1. In step ST1415, session management policy-related information is established between SMF#1 and PCF#1. In step ST1417, SMF#1 selects the UPF to use for communication with UE#1. In step ST1418, session management policy-related information may be modified between SMF#1 and PCF#1. In step ST1418, for example, SMF#1 may send information about the IP address assigned to the UE to PCF#1. In step ST1419 shown in Figure 15, SMF#1 requests N4 session establishment from UPF#1. In step ST1421, UPF#1 notifies SMF#1 of its response to the request in step ST1419.

[0220] In step ST1423 shown in Figure 15, SMF#1 and AMF#1 exchange RAN parameters derived in the core network. In step ST1425, AMF#1 sends a PDU session request on the N2 interface to base station#1. The request in step ST1425 may include the parameters exchanged in step ST1423. In step ST1427, base station#1 sends a RAN configuration request to UE#1. This request may include a response to the PDU session establishment request. Step ST1427 may be performed, for example, using RRCReconfiguration signaling. In step ST1429, base station#1 notifies AMF#1 of the response to the PDU session request on the N2 interface.

[0221] In step ST1431 shown in Figure 15, UE#1 sends the first uplink data to UPF#1.

[0222] In step ST1433 shown in Figure 15, AMF#1 may request SMF#1 to update the PDU session. This request may include session management information received from base station #1.

[0223] In step ST1435 shown in Figure 15, SMF#1 may request an N4 session modification from UPF#1. In step ST1437, UPF#1 may respond to the N4 session modification request from SMF#1.

[0224] In step ST1439 shown in Figure 16, UPF#1 sends the first downlink data to UE#1.

[0225] In step ST1441 shown in Figure 16, SMF#1 may notify AMF#1 of its response to the request to update the PDU session.

[0226] In steps ST1443 and ST1444 shown in Figure 16, SMF#1 notifies UE#1 of the IPv6 router advertisement via UPF#1.

[0227] In step ST1450 shown in Figure 16, AMF#1 notifies AMF#2 of information regarding redundant route #1. This notification may be, for example, a notification regarding the PDU session of redundant route #1. A new signaling may be established for use in this notification. This information may include the information (1) to (17) disclosed as information regarding the redundant route. In step ST1452, AMF#2 may forward this information to base station #2. In step ST1454, base station #2 may forward this information to UE#2.

[0228] In step ST1456 shown in Figure 16, UE#2 requests AMF#2 to establish a PDU session. This request may include information about redundant paths using UE#1 and / or UE#2.

[0229] In procedure 1460, shown in Figure 16, the same processing as in procedure 1402 is performed.

[0230] In step ST1470 shown in Figure 16, AMF#2 notifies AMF#1 of information regarding redundant route #2. This notification may be similar to, for example, the notification in step ST1450. This information may include the information (1) to (17) disclosed as information regarding the redundant route. In step ST1472, AMF#1 may forward this information to base station #1. In step ST1474, base station #1 may forward this information to UE#1.

[0231] Figures 14 to 16 show a case where AMF#1 used in redundant path #1 is different from AMF#2 used in redundant path #2, but the same AMF may also be used. This can, for example, avoid complexity in controlling redundant paths #1 and #2.

[0232] Figures 14 to 16 show the case where information regarding redundant route #1 from AMF#1 is notified to base station #2 via AMF#2. However, AMF#1 may also notify base station #2 directly. This would allow for, for example, rapid notification regarding redundant routes.

[0233] Figures 14 to 16 show the case where AMF#1 notifies information about redundant path #1, but base station #1 may also notify this information. Base station #1 may notify AMF#2, or base station #2 via AMF#2, or base station #2 directly. This can improve the flexibility of the communication system, for example.

[0234] Figures 17-19 illustrate the operation to suppress and release the handover of UE#2 using redundant path #2 when UE#1 on redundant path #1 performs a handover. Figures 17-19 are connected at the boundary lines BL1718 and BL1819. Figures 17-19 show the case where UE#1 performs a handover from base station #1-1 to base station #1-2. Note that in Figures 17-19, "base station #1-1", "base station #1-2", and "base station #2" are denoted as "BS#1-1", "BS#1-2", and "BS#2".

[0235] In steps ST1501 and ST1502 shown in Figure 17, user data is transmitted and received between UPF#1 and UE#1. Step ST1501 represents data transmission and reception between UE#1 and base station #1-1, and step ST1502 represents data transmission and reception between base station #1-1 and UPF#1.

[0236] In step ST1504 shown in Figure 17, AMF#1 notifies base station #1-1 of mobility control information. In step ST1506, base station #1-1 notifies UE#1 of measurement control information, and UE#1 uses this control information to perform a measurement and sends a measurement report to base station #1-1. In step ST1510, base station #1-1 decides to hand over UE#1 to base station #1-2.

[0237] In step ST1512 shown in Figure 17, base station #1-1 notifies AMF#1 that UE#1 will perform a handover. This notification may include the information (1) to (17) disclosed in Embodiment 1 as information regarding redundant routes. Base station #1-1 may determine whether UE#1 is using redundant routes based on whether or not the notification in step ST1512 is given. In step ST1514, AMF#1 forwards the information from step ST1512 to AMF#2. In step ST1516, AMF#2 forwards the information from step ST1512 to base station #2.

[0238] In procedure 1520, shown by the dashed line in Figure 17, handover decision suppression is performed by base station #2 and measurement report suppression is performed by UE #2.

[0239] In step ST1522 shown in Figure 17, base station #2 suppresses the handover of UE#2. This instruction may also be given using step ST1516. In step ST1524, base station #2 instructs UE#2 to suppress the measurement report. This instruction may also be given using RRC signaling, for example, RRCReconfiguration. In step ST1526, UE#2 suppresses the measurement report.

[0240] In step ST1530 shown in Figure 17, base station #1-1 sends a handover request for UE#1 to base station #1-2. In step ST1532, base station #1-2 performs admission control for UE#1. In step ST1534, base station #1-2 sends an acknowledgment to base station #1-1 regarding the handover request.

[0241] In step ST1536 shown in Figure 17, a handover between base station #1-1 and UE#1 is initiated. In step ST1536, base station #1-1 instructs UE#1 to perform a handover. This instruction may be performed, for example, using RRCReconfiguration. In step ST1538, UE#1 uses this instruction to release the connection with the cell of base station #1-1 and synchronize with the cell of base station #1-2.

[0242] In step ST1540 shown in Figure 17, base station #1-1 forwards the status of the sequence number of the packets transmitted and received with UE#1 to base station #1-2. In steps ST1542 and ST1543 shown in Figure 18, base station #1-1 forwards the user data received from UPF#1 to base station #1-2. Step ST1542 indicates the transmission of user data from UPF#1 to base station #1-1, and step ST1543 indicates the transfer of user data from base station #1-1 to base station #1-2. In step ST1545, base station #1-2 holds the data from ST1543.

[0243] In step ST1550 shown in Figure 18, UE#1 notifies base station #1-2 that the handover is complete. In steps ST1552 and ST1553, data transmission and reception between UE#1 and UPF#1 takes place via base station #1-2. Step ST1552 shows the uplink data transmission between UE#1 and base station #1-2 and the downlink data transmission held in step ST1543, and step ST1553 shows the uplink data transmission from base station #1-2 to UPF#1.

[0244] In step ST1555 shown in Figure 18, base station #1-2 requests a path switching from AMF#1. In step ST1557, UPF#1 switches the route to UE#1 from base station #1-1 to base station #1-2. In step ST1559, UPF#1 sends an end marker packet to base station #1-1. In step ST1560, base station #1-1 forwards the end marker packet to base station #1-2. Packets after the end marker packet are transmitted and received between UPF#1 and base station #1-2 in step ST1562.

[0245] In step ST1565 shown in Figure 18, AMF#1 sends an acknowledgment of the path switching request to base station #1-2. In step ST1567, base station #1-2 instructs base station #1-1 to release the UE context. Base station #1-1 uses this instruction to release the UE context of UE#1.

[0246] In procedure 1570, shown by the dashed line in Figure 19, UE#1 notifies that the handover is complete, base station#2 resumes the handover decision, and UE#2 resumes the measurement report.

[0247] In step ST1572 shown in Figure 19, base stations #1-2 notify AMF#1 that the handover of UE#1 is complete. In step ST1574, AMF#1 notifies AMF#2 that the handover of UE#1 is complete. In step ST1576, AMF#2 notifies base station #2 that the handover of UE#1 is complete.

[0248] In Procedure 1577, shown by the dashed line in Figure 19, the handover decision by base station #2 and the measurement report by UE #2 are resumed.

[0249] In step ST1578 shown in Figure 19, base station #2 releases handover suppression for UE#2. This release may also be performed using step ST1576. In step ST1580, base station #2 notifies UE#2 of the release of measurement report suppression. This notification may be performed using RRC signaling, for example, RRC Reconfiguration. In step ST1582, UE#2 releases measurement report suppression.

[0250] The AMF may determine or arbitrate the base stations and / or UPFs to which UEs on multiple redundant paths connect. A base station may request the AMF to determine or arbitrate the base stations to which UEs on multiple redundant paths connect. A base station may make such a request when it receives a connection request (e.g., signaling for RRC establishment) from a UE on one of the multiple redundant paths. Alternatively, a base station may make such a request when it receives a connection request from a UE on another redundant path while connected to a UE on one redundant path. The base station may include in the request information about the redundant path used by the UE. The AMF may make such determination or arbitrate using, for example, some or all of the information disclosed as such information about redundant paths in (1) to (17) (e.g., (5), (8), (9), and / or (13)). As another example, an SMF may request the AMF to determine or arbitrate the UPF to which UEs on multiple redundant paths connect. The SMF may include in the request information about the redundant path used by the UE. The AMF may make the decision or arbitration using, for example, some or all of the information (1) to (17) disclosed as information relating to redundant paths (e.g., (5), (8), (11), and / or (15)). The decision or arbitration may be made, for example, when the same AMF is used in multiple redundant paths. The AMF may, for example, prioritize the UE that first made a connection request to its AMF.

[0251] The AMF may notify the base station of information regarding preferred UEs or information regarding non-preferred UEs. The base station may use the notification to establish a connection with a preferred UE or to reject a connection request from a non-preferred UE. The non-preferred UE may use the rejection notification to attempt to establish a connection with another base station. As another example, the AMF may notify the SMF of information regarding preferred UEs or to notify the SMF of information regarding non-preferred UEs. The SMF may use the notification to determine the UPF to be used by a preferred UE or to re-determine the UPF to be used by a non-preferred UE.

[0252] As another example, a base station may determine which base station a UE on multiple redundant paths will connect to. The base station may make this determination using, for example, some or all of the information disclosed as redundant path information (1) to (17) (e.g., (5), (8), (9), and / or (13)). The base station may, for example, prioritize the UE that was connected to it first.

[0253] As another example, the SMF may determine the UPF to which UEs on multiple redundant paths connect. The SMF may make this determination using, for example, the information disclosed in (5), (8), (11), and / or (15) as information relating to redundant paths. This determination may be made, for example, when the same SMF is used on multiple redundant paths.

[0254] As another example, an AMF may query other AMFs for information about the base stations and / or UPFs to which UEs on multiple redundant paths are connected. Other AMFs may notify the AMF of information about the base stations, SMFs and / or UPFs to which UEs on multiple redundant paths are connected. The AMF may use this notification to determine the base stations, SMFs and / or UPFs to which its subordinate UEs are connected.

[0255] As another example, the SMF may query other SMFs for information about the UPF to which UEs on multiple redundant paths are connected. Another SMF may notify the SMF of information about the UPF to which UEs on multiple redundant paths are connected. The SMF may use the notification to determine the UPF to which the subordinate UEs are connected.

[0256] As another example, priorities may be set for multiple redundant paths. For example, a primary redundant path and a secondary redundant path may be provided. The priorities may be given statically. For example, the priorities may be stored in the UE's SIM. As another example, the NW device, such as the AMF, may determine the priorities, or the base station may determine the priorities.

[0257] Regarding handovers on multiple redundant paths, the handover that starts earlier may be prioritized. The base station may notify other base stations on other redundant paths of information about the UE's handover. The notification may be made via the AMF.

[0258] As another example, regarding handovers on multiple redundant paths, the handover that starts earlier may be prioritized. The base station may notify other base stations on other redundant paths of information about the UE's handover. The notification may be made via the AMF.

[0259] As another example, it may be assumed that the handover of the UE on the primary redundant path is prioritized over the handover of the UE on the secondary redundant path.

[0260] In the first embodiment disclosed, the notification of information regarding the redundant path to the devices of other redundant paths may be performed契机として when there is a change in the devices of the redundant path, for example, a switch of the base station, AMF, SMF, and / or UPF. This notification may be performed by the base station, the AMF, or the SMF. As a result, for example, information regarding the devices used in each redundant path can be shared between the redundant paths. As a result, it is possible to prevent a decrease in redundancy due to using the same devices in multiple redundant paths.

[0261] According to the first embodiment, it is possible to suppress handover in other redundant paths while communication is not possible in a certain redundant path. As a result, it is possible to prevent communication interruption in all redundant paths.

[0262] Modification Example 1 of Embodiment 1. After a handover occurs in a certain redundant path, if RLF, beam failure, communication interruption between the base station and the core network, power-off of each device in the NW of other redundant paths, and / or communication interruption between core networks occur in other redundant paths, communication interruption occurs in any redundant path, and as a result, there is a problem that reliability cannot be ensured.

[0263] In this modification example 1, a method for solving the above problem is disclosed.

[0264] The base station executing the handover procedure cancels the handover.

[0265] A base station on a communication-disruption-redundant path notifies a base station on a non-communication-disruption-redundant path of information regarding the communication disruption. This information may be similar to, for example, the information disclosed in Embodiment 1 indicating that communication with the UE on its own path is not possible. A base station on a communication-disruption-redundant path may also notify a base station on a non-communication-disruption-redundant path of information regarding its own redundant path. This information may be the information (1) to (17) disclosed in Embodiment 1 as examples of information regarding a redundant path. A base station on a non-communication-disruption-redundant path may be a pre-mobile base station for the connected UE.

[0266] A base station on a non-communication-disruption redundant path uses information from a base station on a communication-disruption redundant path to determine whether or not to cancel the handover. The base station then notifies the destination base station of the handover cancellation. This notification of handover cancellation from the base station may also be made when a handover request is notified to the destination base station.

[0267] The handover cancellation notification from the base station to the destination base station may include a reason. This reason may be, for example, information regarding a communication failure on another redundant path. The destination base station may use this reason to retain, for example, information about the UE involved in the handover. This allows for faster processing, for example, when resuming the handover to the destination base station. As another example, information about the UE involved in the handover may be released. This allows for, for example, a reduction in memory usage at the destination base station.

[0268] A base station on a non-disruption redundant path may suppress handovers. The base station may instruct the UE to suppress measurement reports. The UE may use this instruction to suppress measurement reports. The aforementioned actions at the base station and / or UE may be triggered by receiving information about a communication failure from a base station on a disruption redundant path. The handover suppression and measurement report suppression may be the same as in Embodiment 1. This can, for example, reduce power consumption at the UE and reduce the amount of signaling at the interface between the UE and the base station.

[0269] As another example, a UE on a non-disruption redundant path may continue to send measurement reports to the base station. The base station may ignore these measurement reports. This can, for example, avoid complexity in the communication system.

[0270] A base station on a communication-disruption-redundant path may notify a base station on a non-communication-disruption-redundant path of information regarding recovery from a communication disruption. A base station on a communication-disruption-redundant path may notify a base station on a non-communication-disruption-redundant path of information regarding its own redundant path. This information may be some or all of the information disclosed in (1) to (17) as examples of information regarding redundant paths in Embodiment 1. A base station on a non-communication-disruption-redundant path may be a pre-mobile base station for the connected UE.

[0271] A base station on a non-disruption redundant path may release handover suppression. The base station may instruct the UE to release measurement report suppression. The UE may use this instruction to release measurement report suppression. The aforementioned actions at the base station and / or UE may be triggered by receiving information from the base station on the disruption redundant path regarding recovery from a communication disruption. The release of handover suppression and measurement report suppression may be the same as in Embodiment 1. This allows, for example, the UE to quickly resume measurement.

[0272] As another example, the base station may resume receiving the measurement report. This resumption process may apply, for example, to the aforementioned example where the base station ignores the measurement report. This can, for example, avoid complexity in the communication system.

[0273] A base station on a non-disrupted redundant path may initiate a handover using information from a base station on the disrupted redundant path. This base station may select the original destination base station as the new destination base station, or it may select a different base station. This allows, for example, the original base station to select a base station with good communication quality with the UE as the new destination base station. As a result, the communication quality between the base station and the UE can be maintained.

[0274] A base station on a non-disrupted redundant path may choose not to cancel the UE's handover if the UE's handover procedure has progressed to a predetermined step. In other words, it may continue the UE's handover. This can, for example, avoid complexity in the communication system.

[0275] The aforementioned predetermined step may be, for example, a step in which the base station transmits a handover instruction to the UE. This eliminates the need for the base station to transmit a handover cancellation to the UE, and as a result, signaling between the UE and the base station can be reduced.

[0276] As another example, the predetermined step described above may be, for example, a predetermined time elapsed after the base station transmits a handover instruction to the UE. The predetermined time may be statically determined by the standard. Alternatively, the predetermined time may be determined by the base station and individually notified or broadcast to the UE. The base station may notify the predetermined time via RRC signaling. For example, the base station may notify the predetermined time by including it in the handover instruction to the UE. This can reduce the amount of signaling between the UE and the base station, for example. As another example, the base station may notify the predetermined time using MAC signaling. This can enable the base station to notify the predetermined time more quickly, for example. As yet another example, the base station may notify the time using L1 / L2 signaling. This can enable the base station to notify the time even more quickly, for example.

[0277] A base station may instruct a UE to cancel a handover. The base station may notify the UE of this instruction, for example, before a predetermined time has elapsed after the base station has sent the handover instruction to the UE. The base station may notify the cancellation instruction via RRC signaling. This can improve the reliability of the notification of the cancellation instruction, for example. As another example, the base station may notify the instruction using MAC signaling. This can enable the base station to notify the instruction more quickly, for example. As yet another example, the base station may notify the instruction using L1 / L2 signaling. This can enable the base station to notify the instruction even more quickly, for example.

[0278] The UE may use the handover cancellation instruction to cancel the handover process to the destination base station. The UE may also continue the connection with the source base station.

[0279] The handover of the UE on the non-disrupted redundant path may continue. This continuation may occur, for example, after a predetermined time has elapsed since the base station sent a handover instruction to the UE. The originating base station may transfer downlink data to the destination base station.

[0280] The UE may maintain synchronization with the source base station until the elapse of the predetermined time, or may receive a synchronization signal from the target base station. After the elapse of the predetermined time, the UE may start connection processing with the target base station. The connection processing may be reception of a synchronization signal or random access processing.

[0281] The handover instruction from the source base station to the UE may include information regarding a beam available at the target base station. The information may be, for example, an identifier of the beam or information regarding the timing at which the beam is transmitted. The handover instruction may include information regarding the position of the target base station. The UE may use the information to start a connection with the target base station. Thereby, for example, the UE can quickly connect to the target base station, and as a result, the time during which communication is unavailable can be shortened.

[0282] In the connection from the UE to the target base station, two-step random access may be performed. The source base station may instruct the target base station to perform two-step random access processing. The source base station may also instruct the UE to perform two-step random access processing. The instruction from the source base station to the UE may be included, for example, in the handover instruction to the UE. The UE may use the instruction to perform two-step random access with the target base station. Thereby, for example, the UE can quickly connect to the target base station, and as a result, the time during which communication is unavailable can be shortened.

[0283] Figures 20 and 21 show the operation to cancel the handover on redundant path #1 in response to a communication failure of UE#2 on redundant path #2, and the operation to initiate the handover on redundant path #1 in response to the recovery of communication from UE#2. Figures 20 and 21 are connected at the boundary line BL2021. Figures 20 and 21 show the case where UE#1 hands over from base station #1-1 to base station #1-2. Note that in Figures 20 and 21, "base station #1-1", "base station #1-2", and "base station #2" are denoted as "BS#1-1", "BS#1-2", and "BS#2". In Figures 20 and 21, the same step numbers are used for processes similar to those in Figures 17 and 19, and common explanations are omitted.

[0284] Steps ST1501 to ST1532 in Figure 20 are the same as in Figure 17.

[0285] In step ST1634 in Figure 20, UE#2 detects the RLF. In step ST1636, base station #2 detects that an RLF has occurred in UE#2. Base station #2 may detect the RLF in UE#2 by, for example, not being able to receive a signal from UE#2, such as a reference signal.

[0286] In step ST1638 in Figure 20, base station #2 notifies AMF #2 that UE #2 has become RLF. In step ST1640, AMF #2 forwards the notification to AMF #1. In step ST1642, AMF #1 forwards the notification to base station #1-1. Base station #1-1 uses step ST1642 to decide to cancel the handover for UE #1.

[0287] In procedure 1643 shown in Figure 21, the same processing as in procedure 1520 shown in Figure 17 is performed for base station #1-1 and UE#1.

[0288] Step ST1534 in Figure 21 is the same as in Figure 17. In step ST1645, base station #1-1 notifies base station #1-2 of the cancellation of the handover for UE#1. The notification in step ST1645 may also include information regarding the RLF for UE#2.

[0289] In step ST1650 in Figure 21, the connection between UE#2 and base station#2 is restored. In step ST1652, base station#2 notifies AMF#2 that the connection with UE#2 has been restored. In step ST1654, AMF#2 forwards the notification to AMF#1. In step ST1656, AMF#1 forwards the notification to base station#1-1.

[0290] Procedure 1577 in Figure 21 is the same as in Figure 19. In Procedure 1577, the handover decision by base station #1-1 and the measurement report by UE #1 are resumed.

[0291] In step ST1660 shown in Figure 21, the handover of UE#1 from base station #1-1 to base station #1-2 is initiated. The processing in step ST1660 may be the same as that in steps ST1530 to ST1565.

[0292] Procedure 1570, shown in Figure 21, is the same as that shown in Figure 19.

[0293] Similar to Embodiment 1, the base station may have different start / stop conditions for measurement reporting for UEs using a redundant configuration and for UEs not using a redundant configuration. For example, by relaxing the start / stop conditions for measurement reporting for UEs using a redundant configuration compared to those for UEs not using a redundant configuration, handover becomes possible before communication quality deteriorates. As a result, it becomes possible to prevent link disconnection of the redundant configuration due to deterioration of communication quality while handover of the redundant configuration is being suppressed. As another example, by making the start / stop conditions for measurement reporting for UEs using a redundant configuration stricter than those for UEs not using a redundant configuration, the frequency of handover can be reduced, and as a result, communication efficiency can be improved.

[0294] This modified version 1 allows the handover procedure to be canceled even if a communication failure occurs on a redundant path after the handover procedure has started. As a result, communication failures on all redundant paths can be prevented.

[0295] Embodiment 2. In a redundant path configuration using a single UE, the UE may be connected to multiple base stations or to a single base station.

[0296] In a redundant path configuration where one UE connects to multiple base stations, the UE may configure multi-connectivity with multiple base stations. These multiple base stations may be two, three, or more. For example, when the UE connects to two base stations, the UE may configure dual connectivity (DC) with the two base stations.

[0297] In a redundant path configuration where one UE connects to multiple base stations, each base station may connect to a different UPF. Different PDU sessions may be established between the UE and each UPF via each base station. Each UPF may connect to a different SMF or to the same SMF. Each UPF may connect to the same DN or to different DNs.

[0298] The configuration of redundant routes connecting one UE to multiple base stations may be performed, for example, during DC establishment. This configuration may also be performed when the UE uses redundant routes for communication. This configuration may be performed using UE capabilities or by base station determination. This configuration may be performed, for example, by signaling a request for the addition of a secondary base station from the master base station to the secondary base station. This configuration may include, for example, some and all of (1) to (17) disclosed as information regarding the redundant configuration in Embodiment 1. This allows, for example, the secondary base station to quickly obtain information regarding the configuration of redundant routes, and as a result, can quickly perform the configuration of redundant routes.

[0299] Notification of the configuration of redundant routes connecting one UE to multiple base stations may be sent from the master base station to the UE, or from a secondary base station to the UE. The notification may include information indicating the use of redundant routes. The UE may use this information to configure the redundant routes. This allows the UE to quickly identify whether the DC uses redundant routes or a normal DC, and as a result, the DC establishment process can be performed quickly.

[0300] A redundant path configuration in which one UE connects to multiple base stations may be used in the transmission and reception of small data (Non-Patent Literature 9 (TR38.804)). For example, in uplink communication, a path may be provided for transmitting data from the UE to the DN via the master base station, AMF, SMF, and UPF, and a path may be provided for transmitting data from the UE to the DN via the secondary base station, master base station, AMF, SMF, and UPF. As another example, in downlink communication, a path may be provided for transmitting data from the DN to the UE via the UPF, SMF, AMF, and master base station, and a path may be provided for transmitting data from the DN to the UE via the UPF, SMF, AMF, master base station, and secondary base station. This makes it possible to improve reliability in small data transmission and reception, for example.

[0301] As described above, the following problem arises: The security key (S-KgNB) of the secondary base station is derived by the master base station. When the master base station performs a handover, the S-KgNB switches, resulting in a period of communication interruption for both the master and secondary base stations.

[0302] This second embodiment discloses a method for solving the aforementioned problems.

[0303] The security key of the secondary base station is not changed before and after the master base station handover. The destination master base station may continue to use the security key of the secondary base station before the handover. The source master base station may notify the destination master base station of information regarding the security key of the secondary base station. This information may include the value of the security key of the secondary base station, or it may include information indicating that the security key of the secondary base station should be maintained. The source master base station may include this information in the signaling of the Handover Request and notify the destination master base station of it.

[0304] The source master base station may notify the destination master base station of information that the UE is configured in a redundant route by including this information in the signaling of the handover request. This information may be, for example, some or all of the redundant route information disclosed in Embodiment 1. For example, (2) of the redundant route information disclosed in Embodiment 1 may be information indicating the configuration of a redundant route in which one UE connects to multiple base stations. The destination master base station may use this information to understand that the UE is configured in a redundant route. The destination master base station may use this information to decide to continue using the security key of the secondary base station before the handover. This allows the destination master base station to make the aforementioned decision quickly, and as a result, the master base station to perform the handover process quickly.

[0305] The originating master base station may decide whether or not to execute the notification to the destination master base station based on whether the UE uses redundant routes for communication. This makes it possible to avoid, for example, the increased complexity of handover operations in UEs that do not use redundant routes.

[0306] The security key of the secondary base station may be changed after the master base station handover. This avoids, for example, the complexity of managing security keys after a handover.

[0307] A secondary base station may notify the other base station of a change in its security key. This can, for example, improve the communication rate of user data at the master base station after the handover. Alternatively, the master base station after the handover may notify the secondary base station of a change in its security key. This can, for example, enable the use of a base station with good radio wave conditions immediately after the handover, thereby improving the reliability of signaling.

[0308] Figures 22 and 23 are sequence diagrams showing how a UE using a redundant path provided by a DC maintains the security key of the secondary base station before and after a master base station handover. Figures 22 and 23 are connected at the boundary line BL2223. Figures 22 and 23 show an example where the master base station switches from S-MN to T-MN while the secondary base station (SN) remains unchanged.

[0309] In step ST1705 shown in Figure 22, S-MN notifies T-MN of a handover request. S-MN may include in the notification information indicating that the secondary base station will not be changed. S-MN may also include in the notification information indicating that the security key of the secondary base station will be maintained. If the UE is communicating using a redundant path, S-MN may maintain the security key of the secondary base station. T-MN may use the information included in the notification in step ST1705 to either keep the SN the same as the secondary base station after the handover, or to maintain the security key of the secondary base station.

[0310] In step ST1707 shown in Figure 22, T-MN requests SN to add a secondary base station. T-MN may include in the request the security key of the secondary base station before the handover, or information indicating that the security key of the secondary base station will be retained. In step ST1709, SN notifies T-MN of an acknowledgment of the request to add a secondary base station. In step ST1711, T-MN notifies S-MN of an acknowledgment of the handover request in step ST1705.

[0311] In step ST1713 shown in Figure 22, S-MN requests SN to release the secondary base station. In step ST1715, SN notifies S-MN of an acknowledgment of step ST1713.

[0312] In step ST1720 shown in Figure 22, S-MN notifies the UE of an instruction to switch the master base station to T-MN. S-MN may include in the notification information indicating that it will maintain the security key of the secondary base station. Using the information contained in the notification in step ST1720, the UE releases the connection with S-MN and establishes downlink synchronization with T-MN. Using the information contained in the notification in step ST1720, the UE maintains the SCG bearer.

[0313] In step ST1725 shown in Figure 22, the UE and T-MN perform random access processing to establish uplink synchronization between the UE and T-MN. In step ST1727, the UE notifies T-MN that the master base station switchover is complete. In step ST1729, T-MN notifies SN that the secondary base station reconfiguration is complete.

[0314] In step ST1731 shown in Figure 23, S-MN forwards the status of the sequence number of the packets transmitted and received with UE to T-MN. In steps ST1733 and ST1734, S-MN forwards the user data received from UPF to T-MN. Step ST1733 indicates the transmission of user data from UPF to S-MN, and step ST1734 indicates the transfer of user data from S-MN to T-MN.

[0315] In step ST1735 shown in Figure 23, T-MN notifies AMF of a path switching request. In step ST1737, the bearer for data transmission and reception between AMF and UPF is changed between AMF and UPF. In step ST1739, the downlink data path from UPF to the master base station switches from S-MN to T-MN. In step ST1741, AMF notifies T-MN of an acknowledgment of step ST1735.

[0316] In step ST1743 shown in Figure 23, T-MN instructs S-MN to release the UE context. S-MN uses this instruction to release the UE context. In step ST1745, S-MN instructs SN to release the UE context related to S-MN. SN uses this instruction to release the UE context.

[0317] After the master base station switchover is complete, the security key of the secondary base station may be changed. In step ST1750 shown in Figure 23, the T-MN derives the new security key of the secondary base station. In step ST1752, the T-MN notifies the SN of the change in the security key of the secondary base station. In step ST1754, the SN notifies the UE of the change in the security key of the secondary base station. This notification may be made, for example, using RRCReconfiguration. This notification may be made, for example, using a signaling bearer (e.g., SRB3) between the SN and the UE. In step ST1756, the UE notifies the SN that the change in the security key of the secondary base station is complete. This notification may be made, for example, using RRCReconfigurationComplete. This notification may be made, for example, using a signaling bearer (e.g., SRB3) between the SN and the UE. In step ST1758, SN notifies T-MN of an acknowledgment of step ST1752.

[0318] Figures 22 and 23 show an example where the SN notifies the secondary base station of a security key change; however, the T-MN may also notify the secondary base station of a security key change. This allows, for example, signaling to the UE using the T-MN, which has a good radio environment with the UE immediately after handover. As a result, the reliability of signaling can be improved.

[0319] Another solution is disclosed: Change the security key of the secondary base station prior to the handover of the master base station. The destination master base station may derive the changed security key of the secondary base station.

[0320] The destination master base station may notify the secondary base station of the changed security key. This notification may be included, for example, in a Secondary Base Station Addition Request (SN Addition Request) from the destination master base station to the secondary base station.

[0321] A secondary base station may notify the UE of its changed security key. This notification from the secondary base station to the UE may be included, for example, in an RRC reconfiguration. The secondary base station may also make this notification to the UE in response to an SN Addition Request from the destination master base station. The RRC reconfiguration signaling may include information regarding the reason. This reason information may include information regarding a master base station switchover, for example, a change in the secondary base station security key prior to the master base station switchover. This allows the UE to know that a master base station switchover is occurring, and as a result, enables smooth handover processing in the communication system.

[0322] As another example, the originating master base station may notify the UE of a change in the security key of the secondary base station. The destination master base station may then notify the originating master base station of the changed security key of the secondary base station. This can, for example, improve the communication rate of user data between the secondary base station and the UE.

[0323] The UE may use the notification to change the security key for the secondary base station. The UE may also notify the secondary base station that the security key change is complete. This notification from the UE may be included, for example, in RRCReconfigurationComplete. Alternatively, the UE may notify the originating master base station that the security key change is complete.

[0324] The secondary base station may notify the destination master base station that the security key change at the UE is complete. This notification may be included, for example, in the signaling of a Secondary Base Station Addition Request Acknowledgment (SN Addition Request Acknowledgment). Upon receiving this notification, the destination master base station may notify the source master base station of a Handover Request Acknowledgment. Upon receiving this notification, the source master base station may release the secondary base station. Upon releasing the secondary base station, the source master base station may instruct the UE to perform a handover.

[0325] Figures 24 and 25 illustrate the operation in which a UE using a redundant path provided by a DC changes the security key of a secondary base station prior to a master base station handover. Figures 24 and 25 are connected at the boundary line BL2425. Figures 24 and 25 show an example in which the master base station switches from S-MN to T-MN while the secondary base station (SN) remains unchanged. In Figures 24 and 25, the same steps as in Figures 22 and 23 are given the same step numbers, and common explanations are omitted.

[0326] Step ST1705, shown in Figure 24, is the same as in Figure 22.

[0327] In step ST1806 shown in Figure 24, T-MN derives the security key for the secondary base station. In step ST1807, T-MN requests SN to add a secondary base station. T-MN notifies SN of the request, including the security key derived in step ST1806.

[0328] Steps ST1809 and ST1811 shown in Figure 24 are the same processes as steps ST1754 and ST1756 in Figure 23.

[0329] Steps ST1709 shown in Figure 24 to ST1745 shown in Figure 25 are the same as those in Figures 22 and 23.

[0330] Figures 24 and 25 show an example where the SN notifies the secondary base station of a security key change, but the S-MN may also notify the secondary base station of a security key change. This would, for example, allow for an improvement in the communication rate of user data at the SN.

[0331] The security key of the secondary base station may be switchable between changing it before or after the handover. This switch may be determined, for example, by the source master base station. The source master base station may make this determination using, for example, the communication quality (e.g., radio quality) between its own base station and the UE. For example, the source master base station may change the security key of the secondary base station after the handover if the radio quality with the UE deteriorates rapidly. As another example, the source master base station may change the security key of the secondary base station before the handover if the deterioration of radio quality with the UE is gradual. This allows for a quick handover in cases of rapid radio quality deterioration, and as a result, communication quality between the UE and the base station can be maintained.

[0332] The source master base station may notify the destination master base station of the determination result. This notification may be included, for example, in the signaling of a handover request from the source master base station to the destination master base station. The destination master base station may use this notification to determine the timing for deriving the security key of the secondary base station. The destination master base station may derive the security key at that timing. This makes it possible to improve the efficiency of the process related to deriving the security key of the secondary base station at the destination master base station, for example.

[0333] As another example, the destination master base station may determine the switchover. The destination master base station may make this determination using, for example, the security key of the secondary base station derived by the source master base station. For example, if the security key derived by the source master base station is in use by any UE connected to the destination master base station, the security key of the secondary base station may be changed before the handover. As yet another example, if the security key derived by the source master base station is not in use by any UE connected to the destination master base station, the security key of the secondary base station may be changed after the handover. This makes it possible to prevent duplication of security keys between UEs, and as a result, the possibility of misreception at the UE can be reduced.

[0334] The source master base station may notify the destination master base station of the security key. This notification may be included, for example, in the signaling of a handover request from the source master base station to the destination master base station.

[0335] The operation disclosed in Embodiment 2 may also be applied to UEs using redundant routes. The master base station may use (1) to (17) disclosed in Embodiment 1 as information regarding redundant routes to determine whether the security key in the UE can be maintained. This allows, for example, the continued use of conventional UEs in the communication system, and as a result, complexity in the communication system can be avoided.

[0336] This second embodiment makes it possible to prevent communication interruptions between the secondary base station and the UE during master base station handover. As a result, reliability can be improved.

[0337] Modification 1 of Embodiment 2. Even in the event of an MCG failure, the connection with the secondary base station is released. As a result, a problem occurs where communication between the UE and the network equipment is interrupted.

[0338] This modified example 1 discloses a method for solving the aforementioned problem.

[0339] In the event of an MCG failure, data transmission and reception between the SN and the MCG may be enabled. If communication using a redundant path is being performed, data transmission and reception between the SN and the MCG may be enabled only between the SN and the MCG in the event of an MCG failure. Data transmission and reception between the SN and the MCG may be, for example, data transmission and reception using an SCG bearer.

[0340] The setting that enables data transmission and reception between the SN and the MCG in the event of an MCG failure may be performed, for example, when the DC is established. This setting may also be performed when the UE uses redundant paths for communication. This setting may be performed using UE capabilities or by the base station's decision.

[0341] The UE may notify a secondary base station of information regarding an MCG failure. The secondary base station may forward this information to the master base station. The master base station may use this information to perform actions related to restoring connectivity with the UE, such as transmitting a reference signal to the UE. This allows the UE to recover quickly from an MCG failure.

[0342] Figure 26 is a sequence diagram showing a first example of operation to continue communication with a secondary base station after an MCG failure. In Figure 26, the UE communicates using a path through the MN and UPF#1, and a path through the SN and UPF#2. Figure 26 shows an example of the UE re-establishing connection with the same MN after an MCG failure.

[0343] In steps ST1905 and ST1906 shown in Figure 26, user data is transmitted and received between the UE and UPF#1. Step ST1905 shows the transmission and reception of user data between the UE and MN, and step ST1906 shows the transmission and reception of user data between the MN and UPF#1. In steps ST1908 and ST1909, user data is transmitted and received between the UE and UPF#2. Step ST1908 shows the transmission and reception of user data between the UE and SN, and step ST1909 shows the transmission and reception of user data between the SN and UPF#2.

[0344] In step ST1911 shown in Figure 26, the UE detects an MCG failure. In steps ST1913 and ST1914, the UE maintains communication with UPF#2 via SN. Steps ST1913 and ST1914 are the same as steps ST1908 and ST1909, respectively.

[0345] In step ST1916 shown in Figure 26, the UE may notify the SN that an MCG failure has occurred. This notification may be made, for example, using RRC signaling. This notification may also be made, for example, using a signaling bearer (e.g., SRB3) between the SN and the UE. In step ST1918, the SN may notify the MN that an MCG failure has occurred in the UE. In step ST1920, the MN transmits a synchronization signal to the UE. The MN may execute step ST1920 upon receiving step ST1918.

[0346] In step ST1921 shown in Figure 26, the UE sends a PRACH to the MN. In step ST1923, the MN sends a Random Access Response (RAR) to the UE.

[0347] In step ST1925 shown in Figure 26, the UE requests the MN to start up the RRC. This request may use RRC signaling, for example, the RRC setup request (RRCSetupRequest) from Non-Patent Literature 22 (TS38.331). In step ST1927, the MN instructs the UE to start up the RRC. This instruction may use RRC signaling, for example, the RRC setup (RRCSetup) from Non-Patent Literature 22 (TS38.331).

[0348] In step ST1929 shown in Figure 26, the UE notifies the MN that the RRC startup is complete. This notification may use RRC signaling, such as RRCSetupComplete as described in Non-Patent Document 22 (TS38.331).

[0349] In step ST1931 shown in Figure 26, MN notifies SN of the UE's recovery from the MCG failure. In steps ST1935 and ST1936, user data is transmitted and received between the UE and UPF#1. Steps ST1935 and ST1936 are the same as steps ST1905 and ST1906, respectively. In steps ST1938 and ST1939, user data is transmitted and received between the UE and UPF#2. Steps ST1938 and ST1939 are the same as steps ST1908 and ST1909, respectively.

[0350] After detecting an MCG failure, the UE may reconnect to a different master base station than the one used for detection.

[0351] The UE may exclude secondary base stations from the list of candidates for the master base station to reconnect. This allows, for example, redundancy to be maintained in redundant paths.

[0352] Figure 27 is a sequence diagram showing a second example of operation to continue communication with a secondary base station after an MCG failure. In Figure 27, the UE communicates using a path through MN#1 and UPF#1, and a path through SN and UPF#2. Figure 27 shows an example of the UE re-establishing connection with MN#2 after an MCG failure. In Figure 27, the same steps as in Figure 26 are given the same step numbers, and common explanations are omitted.

[0353] Steps ST1905 to ST1920 shown in Figure 27 are the same as those in Figure 26.

[0354] In step ST2020 shown in Figure 27, MN#2 transmits a synchronization signal to UE. In the example shown in Figure 27, UE decides to reconnect to MN#2 using the reception results from steps ST1920 and ST2020.

[0355] In steps ST2021 to ST2025 shown in Figure 27, the same operations as in steps ST1921 to ST1925 in Figure 26 are performed between the UE and MN#2. The RRC startup request in step ST2025 may include information regarding an MCG failure. This information may include, for example, information indicating recovery from an MCG failure, or information regarding the base station that experienced the MCG failure.

[0356] In step ST2026 shown in Figure 27, MN#2 requests a UE context from MN#1. MN#2 may also use the information regarding the MCG failure included in the RRC startup request in step ST2025 to request a UE context from MN#1. In step ST2027, MN#1 notifies MN#2 of the UE context.

[0357] In steps ST1927 to ST1929 shown in Figure 27, the same operations as in steps ST1927 to ST1929 in Figure 26 are performed between UE and MN#2. In step ST2031 shown in Figure 27, the same operations as in step ST1931 in Figure 26 are performed between MN#2 and SN.

[0358] In step ST2033 shown in Figure 27, MN#2 requests MN#1 to release the UE context. MN#1 releases the UE context in response to the request in step ST2033.

[0359] In cases where data transmission and reception with the SCG is enabled during an MCG failure, the UE's RRC state may remain RRC_CONNECTED. Alternatively, the UE's RRC state may transition to RRC_INACTIVE or to RRC_IDLE.

[0360] The operation disclosed in this modified example 1 may also be applied to UEs using redundant paths. For example, a secondary base station may use (1) to (17) disclosed in Embodiment 1 as information regarding redundant paths to determine whether communication with the UE can continue after MCG failure detection. This allows, for example, the continued use of the conventional UE in the communication system, and as a result, complexity in the communication system can be avoided.

[0361] The method disclosed in Modification 1 may be used when the power supply to each NW device on the master base station side is lost, or when a communication interruption occurs between the master base station and the core network (e.g., UPF), and / or when a communication interruption occurs in the core network (e.g., UPF and SMF). This will provide, for example, the same effects as described above.

[0362] This modified version 1 enables data transmission and reception using a secondary base station even in the event of an MCG failure, thereby enabling the maintenance of the TSC.

[0363] Embodiment 3. In a redundant path configuration where one UE connects to one base station, the base station may connect to one UPF or to multiple UPFs. In the redundant path configuration, there may be one PDU session. The PDU session may include multiple N3 tunnels.

[0364] A redundant path configuration in which one UE connects to one base station may be used in the transmission and reception of small data (Non-Patent Literature 9 (TR38.804)). For example, in uplink communication, multiple N2 interfaces, multiple N11 interfaces, multiple N4 interfaces, and / or multiple N9 interfaces may be used in the path from the UE to the DN via the base station, AMF, SMF, and UPF. Multiple N9 interfaces may be used, for example, when the path to the DN has multiple UPFs. This makes it possible to improve reliability in small data transmission and reception, for example.

[0365] Furthermore, the redundant path configuration disclosed in Embodiment 1, in which each of the multiple UEs is connected to a different base station, may be used, or the redundant path configuration disclosed in Embodiment 2, in which one UE is connected to multiple base stations, may be used.

[0366] As described above, the following problems arise: namely, changes in propagation conditions and network load conditions may make it difficult to maintain reliability and / or TSC with the current redundant path configuration. However, the switching of the redundant path configuration is not disclosed. As a result, the redundant path configuration cannot be switched, and the problem arises where reliability and / or TSC cannot be maintained.

[0367] This third embodiment discloses a method for solving the aforementioned problems.

[0368] This enables switching from a redundant route configuration where one UE connects to one base station to a redundant route configuration where one UE connects to multiple base stations. This switching may be performed using the addition of a secondary base station (SN Addition), PDU session establishment, and PDU session modification. For example, in the redundant route configuration switching procedure, the addition of a secondary base station (SN Addition), PDU session establishment, and PDU session modification may be performed in this order. Alternatively, the addition of a secondary base station, PDU session establishment, and PDU session modification may be performed simultaneously. Alternatively, the addition of a secondary base station, PDU session establishment, and PDU session modification may be performed simultaneously.

[0369] The base station may decide to switch to a redundant route configuration. The base station may decide to switch to a redundant route configuration using measurement reports from the UE, information on the QoS of communication between the base station and the UPF, and / or information on the QoS of inter-base station backhaul communication. Information on the QoS of communication between the base station and the UPF may include, for example, information on the transmission rate, information on latency, and information on packet loss rate. Information on the QoS of inter-base station backhaul communication may include, for example, information on the communication medium (e.g., wired, wireless), and information similar to that of the QoS of communication between the base station and the UPF. By the base station deciding to switch to a redundant route configuration, it becomes possible to switch to a redundant route configuration in order to quickly reflect changes in the communication environment between the UE and the base station and / or between the base station and the UPF.

[0370] A base station may acquire the aforementioned information regarding the QoS of communication between its own base station and the UPF. For example, a base station may acquire this information by monitoring communication between its own base station and the UPF. A base station may also acquire the aforementioned information regarding the QoS of inter-base station backhaul communication. For example, a base station may acquire this information by monitoring backhaul communication between its own base station and other base stations. A base station may use the acquired information to determine redundant route configuration switching. This makes it possible, for example, to reduce the amount of signaling required to notify the information.

[0371] The base station may notify the AMF of information regarding the redundancy route configuration switchover. The AMF may notify the SMF of this information. The base station may include in this information information regarding the reason for the redundancy route configuration switchover. This reason may be, for example, a QoS-related reason for the wireless communication path (e.g., the communication path between the UE and the base station), a QoS-related reason for the wired communication path (e.g., the communication path between the base station and the UPF), or a QoS-related reason for the inter-base station backhaul. The SMF may use this information to determine which UPF to add in conjunction with the redundancy route configuration switchover. This makes it possible, for example, to ensure QoS in the communication system after the redundancy route configuration switchover.

[0372] As another example, the AMF may decide on a redundant route configuration switchover. The AMF may decide on a redundant route configuration switchover using information similar to that used by the base station as described above. The AMF may request this information from the base station. The base station may notify the AMF of this information. The AMF may notify the base station of information regarding the redundant route configuration switchover. The base station may use this information to perform actions related to adding a secondary base station to the UE. The AMF may notify the SMF of this information. The SMF may use this information to determine which UPFs to add in conjunction with the redundant route configuration switchover. By the AMF deciding on a redundant route configuration switchover, control in the communication system can be easily performed, for example.

[0373] As another example, the SMF may decide on a redundant route configuration switchover. The SMF may decide on a redundant route configuration switchover using information similar to that used by the base station as described above. The SMF may request this information from the base station via the AMF. The base station may notify the SMF of this information via the AMF. The SMF may notify the AMF of information regarding the redundant route configuration switchover. The AMF may notify the base station of this information. The base station may use this information to perform actions related to adding a secondary base station to the UE. The SMF may use this information to determine the UPF to be added in conjunction with the redundant route configuration switchover. By the SMF deciding on a redundant route configuration switchover, for example, it becomes possible to quickly determine the UPF to be used in the redundant route, and as a result, the redundant route configuration can be switched over quickly.

[0374] A new signaling method may be provided for notifying the aforementioned information regarding the QoS of communication between the base station and the UPF. This signaling method may be, for example, a signaling method on the N3 interface, a signaling method on the N4 interface, a signaling method notified between the base station and the SMF via the AMF, a signaling method notified between the UPF and the base station via the SMF and AMF, a signaling method notified between the UPF and the AMF via the SMF, a signaling method notified between the UPF and the AMF via the base station, or a signaling method notified between the UPF and the SMF via the base station and AMF. This makes it possible to avoid, for example, the complexity of the communication system design caused by the notification of such information.

[0375] The UPF may acquire the aforementioned information regarding the QoS of communication between the base station and the UPF. For example, the UPF may acquire this information by monitoring communication between the base station and itself. The UPF may notify the base station, the AMF, or the SMF of the acquired information. Notification of this information from the UPF to the base station may be done directly using the N3 interface, or via the SMF and AMF. Notification of this information from the UPF to the AMF may be done via the SMF or via the base station. Notification of this information from the UPF to the SMF may be done directly using the N4 interface, or via the UPF and AMF. As a result, for example, the base station does not need to acquire this information, and as a result, the processing load at the base station can be reduced.

[0376] In switching redundant routing configurations, a secondary base station may be added. The addition of a secondary base station may be performed, for example, using the procedure disclosed in Section 10.2.2 of Non-Patent Document 12 (TS37.340). The base station before the redundant routing configuration switchover may be the modified master base station. The request to add a secondary base station, notified from the base station to the secondary base station, may include information indicating the reason. The reason may be, for example, a change in the redundant configuration, or the reason for the change in the redundant configuration (e.g., ensuring QoS in the wireless section and / or ensuring QoS in the wired section). The secondary base station may use the notification to set up an SCG bearer with the UE. This allows for rapid switching of redundant routing configurations in, for example, the communication system.

[0377] The additional secondary base station may, for example, be a base station in the same reliability group as the master base station. This allows for, for example, rapid switching of redundant routing configurations. As another example, the additional secondary base station may be a base station in a different reliability group than the master base station. This allows for, for example, increased flexibility in switching redundant routing configurations.

[0378] The base station may notify the UE of information regarding redundant route configuration switching. This information may be notified, for example, by being included in an instruction from the base station to the UE to add a secondary base station. This information may also be included, for example, as the reason for the instruction. This instruction from the base station to the UE may be made using RRC signaling (e.g., RRC Reconfiguration). This information may include information regarding the reason for the redundant route configuration switching. The reason for the redundant route configuration switching may be, for example, ensuring QoS in the wireless section and / or ensuring QoS in the wired section. The UE may use the information regarding the redundant route configuration switching to request the AMF to add a PDU session. This allows, for example, to quickly execute the redundant route configuration switching procedure.

[0379] During the switching of redundant path configurations, a PDU session may be established. The establishment of the PDU session may be performed, for example, using the procedure disclosed in section 4.3.2.2.1 of Non-Patent Document 25 (TS23.502). The newly established PDU session may be, for example, a PDU session that passes through the secondary base station.

[0380] The base station may request the UE to initiate the PDU session establishment procedure. This request may be made, for example, using RRC signaling. The RRC signaling used in this request may be the same as, for example, the RRC signaling for the base station to instruct the UE to add a secondary base station, or it may be a different RRC signaling. The UE may use this request to request the AMF to establish a PDU session. This enables, for example, rapid switching of redundant route configurations in the communication system.

[0381] As another example, the AMF may invoke the PDU session establishment procedure. The AMF may invoke the PDU session establishment procedure even without a PDU session establishment request from the UE, for example, as disclosed in section 4.3.2.2.1 of Non-Patent Document 25 (TS23.502). The AMF may invoke the PDU session establishment procedure upon completion of the procedure for adding a secondary base station. This enables, for example, rapid switching of redundant route configurations in a communication system.

[0382] In switching redundant path configurations, a PDU session modification may be performed. The PDU session modification may be performed, for example, using the procedure disclosed in section 4.3.3.2 of Non-Patent Document 25 (TS23.502). The PDU session modification may be, for example, an operation that releases information regarding the N3 tunnel and / or QoS flow through the PDU session provided on the secondary base station side from the PDU session provided on the master base station side.

[0383] This third embodiment makes it possible to maintain reliability and / or TSC even when propagation conditions and network load conditions change.

[0384] Modification 1 of Embodiment 3. Embodiment 3 disclosed a switching from a redundant path configuration in which one UE is connected to one base station to a redundant path configuration in which one UE is connected to multiple base stations. This Modification 1 discloses a switching from a redundant path configuration in which one UE is connected to multiple base stations to a redundant path configuration in which one UE is connected to one base station.

[0385] Switching from a redundant route configuration where one UE connects to multiple base stations to a redundant route configuration where one UE connects to one base station may be performed using PDU session modification, PDU session release, and secondary base station release. For example, in the redundant route configuration switching procedure, PDU session modification, PDU session release, and secondary base station release may be performed in this order. Alternatively, PDU session modification and PDU session release may be performed simultaneously, followed by secondary base station release. Alternatively, PDU session modification may be performed, followed by PDU session release and secondary base station release simultaneously. Alternatively, PDU session modification, PDU session release, and secondary base station release may be performed simultaneously.

[0386] Similar to Embodiment 3, the redundancy route configuration switchover may be determined by the base station, the AMF, or the SMF. The determination may include measurement reports from the UE, information regarding the QoS of communication between the base station and the UPF, and / or information regarding the QoS of inter-base station backhaul communication. The aforementioned information may be the same as in Embodiment 3. Similar to Embodiment 3, the base station may acquire the information, or the base station may notify the AMF of the information. The notification of information regarding the redundancy route configuration switchover may also be the same as in Embodiment 3.

[0387] During the switching of redundant path configurations, a PDU session modification may be performed. The PDU session modification may be performed, for example, using the procedure disclosed in section 4.3.3.2 of Non-Patent Document 25 (TS23.502). The PDU session modification may be, for example, an operation to add information regarding the N3 tunnel and / or QoS flow through the PDU session provided on the secondary base station side to the PDU session provided on the master base station side.

[0388] The base station may notify the AMF of a PDU session change request. The AMF may notify the SMF of a PDU session change request. The aforementioned notification may include information indicating the reason. The reason may be, for example, a change in the redundancy configuration, or the reason for the change in the redundancy configuration (e.g., ensuring QoS in the wireless section and / or ensuring QoS in the wired section). The SMF may use the notification to take action regarding the release of the PDU session, for example, to prepare for the release of the PDU session. This enables, for example, a rapid switching of redundant routing configurations in the communication system.

[0389] During the switching of redundant route configurations, PDU sessions may be released. The release of PDU sessions may be performed, for example, using the procedure disclosed in Section 4.3.4.2 of Non-Patent Document 25 (TS23.502). The PDU sessions to be released may be, for example, PDU sessions that pass through the secondary base station.

[0390] During the switching of a redundant route configuration, the secondary base station may be released. The release of the secondary base station may be performed, for example, using the procedure disclosed in Section 10.4.2 of Non-Patent Document 12 (TS37.340).

[0391] The base station may notify the UE of information regarding the redundancy route configuration switchover. This information may be notified, for example, by being included in a secondary base station release instruction notified from the base station to the UE. This information may be included, for example, as the reason for the instruction. This instruction from the base station to the UE may be made using RRC signaling (e.g., RRC Reconfiguration). This information may include information regarding the reason for the redundancy route configuration switchover. The reason for the redundancy route configuration switchover may, for example, ensure QoS in the radio section and / or ensure QoS in the wired section. The UE may use the information regarding the redundancy route configuration switchover to release the secondary base station or make a bearer configuration change (e.g., change from an SCG bearer to a bearer that goes through the base station after the redundancy route configuration switchover). This allows for, for example, rapid execution of the redundancy route configuration switchover procedure.

[0392] The method disclosed in Modification 1 may be used when the power supply to each NW device on the secondary base station side is lost, or when a communication interruption occurs between the secondary base station and the core network (e.g., UPF), and / or when a communication interruption occurs in the core network (e.g., UPF and SMF). This will provide, for example, the same effects as described above.

[0393] This modified example 1 makes it possible to maintain reliability and / or TSC even when propagation conditions and network load conditions change.

[0394] Embodiment 4. In communication systems requiring low latency, the base station and UPF may be configured as a single device. For example, the gNB-CU-UP and UPF disclosed in Non-Patent Document 26 (TS38.401) may be a single device (hereinafter sometimes referred to as an integrated UPF). Other base stations may be connected to the integrated UPF.

[0395] As mentioned above, the following problems arise: The latency of C-plane signaling still persists. Furthermore, the use of C-plane for sending and receiving small data is being considered. This results in the problem that latency cannot be reduced for small data.

[0396] This fourth embodiment discloses a method for solving the aforementioned problems.

[0397] The base station and AMF are configured in a single device. For example, the gNB-CU-CP and AMF are configured in a single device (hereinafter sometimes referred to as the integrated AMF). Other base stations may be connected to the integrated AMF.

[0398] The integrated AMF may include functionality related to SMF. This could, for example, reduce the time required for procedures related to PDU sessions.

[0399] The integrated AMF may also include functionality related to UPF. This could, for example, reduce the time required to transmit small data from the C-plane to the U-plane.

[0400] An integrated AMF may inform or individually notify a UE that it is an integrated AMF. This notification may be made, for example, using system information. The UE may use this information to recognize that the base station it intends to connect to is an integrated AMF. For example, the UE may use this information to prioritize connecting to the integrated AMF over other cells. The aforementioned UE may be, for example, an UE that requires low-latency communication. The UE may use information on QoS supported by its UE to decide whether to prioritize the connection. This makes it possible to prevent congestion caused by many other UEs connecting to the integrated AMF, and as a result, latency can be reduced.

[0401] An integrated UPF may broadcast and / or individually notify the UE that it is an integrated UPF. The UE may use this information to recognize that the base station it intends to connect to is an integrated UPF. For example, the UE may use this information to prioritize connecting to the integrated UPF over other cells. The aforementioned UE may be, for example, an UE that requires low-latency communication. The UE may use information on QoS supported by its UE to decide whether to prioritize the connection. This makes it possible to prevent congestion caused by many other UEs connecting to the integrated UPF, and as a result, reduces U-plane latency.

[0402] Priority may be established between the integrated AMF and the integrated UPF. The UE may use information about the QoS supported by the UE to decide which to connect to first, the integrated AMF or the integrated UPF. For example, if the data size requiring low-latency communication is small and the frequency of such data transmission is low, the UE may prioritize connecting to the integrated AMF. As another example, if the data requiring low-latency communication is large or the frequency of such data transmission is high, the UE may prioritize connecting to the integrated UPF. This allows for, for example, ensuring QoS in the UE's communications.

[0403] This fourth embodiment makes it possible to reduce the latency of C-plane signaling, and as a result, it is possible to reduce the latency in sending and receiving small data.

[0404] The embodiments and their variations described above are merely illustrative examples of the present invention, and within the scope of the present invention, these embodiments and their variations can be freely combined. Furthermore, any component of each embodiment and its variation can be appropriately modified or omitted.

[0405] For example, in the embodiments and their modifications described above, a subframe is an example of a time unit for communication in a fifth-generation base station communication system. It may also be a scheduling unit. In the embodiments and their modifications described above, the processing described as being performed in subframe units may also be performed in TTI units, slot units, sub-slot units, or mini-slot units.

[0406] Although the present invention has been described in detail, the above description is illustrative in all respects and the invention is not limited thereto. It is understood that countless modifications not illustrated can be envisioned without falling outside the scope of the invention. [Explanation of Symbols]

[0407] 200, 210 Communication systems, 202 Communication terminal equipment, 203 Base station equipment.

Claims

1. A terminal device, The terminal device is configured to switch between a configuration in which the terminal device uses one network path and a configuration in which the terminal device uses multiple network paths. The terminal device is configured to receive first information regarding the switching from the base station device. The first information mentioned above includes information regarding the assurance of Quality of Service (QoS), Terminal device.

2. The aforementioned terminal device is configured to communicate with a UPF (User Plane Function), Second information regarding QoS in the aforementioned communication is obtained by the UPF. The terminal device according to claim 1.

3. The second information includes information regarding the transmission rate, The terminal device according to claim 2.

4. The second information includes information regarding the packet loss rate. The terminal device according to claim 2.

5. The UPF is configured to transmit the acquired second information to the SMF (Session Management Function) via the N4 interface. The terminal device according to claim 2.

6. The terminal device is configured to communicate with the UPF (User Plane Function) via the base station device. Second information regarding QoS in the aforementioned communication is acquired by the base station equipment. The terminal device according to claim 1.

7. The second information includes information about latency, The terminal device according to claim 6.

8. A communication system comprising a terminal device and a base station device that performs wireless communication with the terminal device, wherein the base station device is: The terminal device is configured to switch between a configuration in which the terminal device uses one network path and a configuration in which the terminal device uses multiple network paths. The base station device is configured to transmit the first information relating to the switching to the terminal device. The first information mentioned above includes information regarding the assurance of Quality of Service (QoS), Base station equipment.

9. A communication system equipped with terminal devices, The terminal device is configured to switch between a configuration in which the terminal device uses one network path and a configuration in which the terminal device uses multiple network paths. The terminal device is configured to receive first information regarding the switching from the base station device. The first information mentioned above includes information regarding the assurance of Quality of Service (QoS), Communication system.

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