Base station and communication method

Abstract

To appropriately control LTM (Lower layer Triggered Mobility).SOLUTION: A base station includes a control unit that executes LTM (Lower layer Triggered Mobility) preparation for a certain terminal, and a receiving unit that receives a cell switching notification from another base station, the control unit executes cell switching for the terminal, the receiving unit receives RRC (Radio resource control) reconfiguration completion from the terminal, and further includes a transmission unit that transmits a path switching notification and a cause of the path switching notification to an AMF (Access and Mobility Management Function).SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a base station and a communication method in a communication system. [Background technology]

[0002] 3GPP (registered trademark) (3rd Generation Partnership Project) is currently studying a wireless communication system called 5G or NR (New Radio) (hereinafter, this wireless communication system will be referred to as "5G" or "NR") in order to achieve even larger system capacity, even faster data transmission speeds, and even lower latency in wireless sections. Various wireless technologies are being studied for 5G to meet the requirements of achieving a throughput of 10 Gbps or more while reducing latency in wireless sections to 1 ms or less.

[0003] In NR, a network architecture is being considered that includes 5GC (5G Core Network), which corresponds to EPC (Evolved Packet Core), which is the core network in the network architecture of LTE (Long Term Evolution), and NG-RAN (Next Generation - Radio Access Network), which corresponds to E-UTRAN (Evolved Universal Terrestrial Radio Access Network), which is the RAN (Radio Access Network) in the network architecture of LTE (e.g., Non-Patent Document 1).

[0004] In addition, Release 19 is expected to include enhanced mobility features, such as inter-CU (inter-Central Unit) LTM (Lower layer Triggered Mobility) and functionality expansion to support cases where LTM is performed while maintaining DC (Dual connectivity) (see, for example, Non-Patent Document 2). [Prior art documents] [Non-patent literature]

[0005] [Non-Patent Document 1] 3GPP TS 23.501 V18.7.0 (2024-09) [Non-patent document 2] 3GPP TSG-RAN Meeting #101 RP-232618, Bengaluru, India, 11-15 September 2023 [Non-patent document 3] 3GPP TS 38.401 V18.3.0 (2024-09) Summary of the Invention [Problem to be solved by the invention]

[0006] In LTM, the AMF (Access and Mobility Management Function) cannot determine whether the path switching procedure is triggered for inter-gNB-LTM or by other legacy functions.

[0007] The present invention has been made in view of the above points, and has as its object to appropriately control LTM (Lower layer Triggered Mobility). [Means for solving the problem]

[0008] According to the disclosed technology, there is provided a base station having a control unit that performs LTM (Lower layer Triggered Mobility) preparation for a terminal, and a receiving unit that receives a cell switch notification from another base station, wherein the control unit performs cell switch for the terminal, the receiving unit receives RRC (Radio resource control) reconfiguration completion from the terminal, and further has a transmitting unit that transmits a path switch notification and a cause of the path switch notification to an AMF (Access and Mobility Management Function). [Effects of the Invention]

[0009] According to the disclosed technology, it is possible to appropriately control LTM (Lower layer Triggered Mobility). [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a diagram illustrating an example of a communication system. [Figure 2] FIG. 1 is a diagram illustrating an example of a communication system in a roaming environment. [Figure 3] FIG. 10 is a sequence diagram illustrating an example (1) of inter-DU-LTM. [Figure 4] FIG. 10 is a sequence diagram illustrating an example (2) of inter-DU-LTM. [Figure 5] A sequence diagram for explaining an example of inter gNB-LTM in an embodiment of the present invention. [Figure 6] 2 is a diagram illustrating an example of a functional configuration of a base station 10 and a network node 30 according to an embodiment of the present invention. [Figure 7] FIG. 2 is a diagram illustrating an example of a functional configuration of a terminal 20 according to the embodiment of the present invention. [Figure 8] 1 is a diagram illustrating an example of a hardware configuration of a base station 10 and a terminal 20 according to an embodiment of the present invention. [Figure 9] FIG. 2 is a diagram showing an example of the configuration of a vehicle 2001 according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Note that the embodiment described below is an example, and the embodiment to which the present invention is applied is not limited to the following embodiment.

[0012] In the operation of the wireless communication system according to the embodiment of the present invention, existing technologies are used as appropriate. However, the existing technologies are, for example, but not limited to, the existing LTE. Furthermore, the term "LTE" used in this specification has a broad meaning including LTE-Advanced, a system subsequent to LTE-Advanced (e.g., NR), or a wireless LAN (Local Area Network), unless otherwise specified.

[0013] Furthermore, in the embodiments of the present invention, when radio parameters etc. are "configured," it may mean that predetermined values ​​are pre-configured, or that radio parameters notified from the network node 30 or the terminal 20 are set.

[0014] Fig. 1 is a diagram illustrating an example of a communication system. As shown in Fig. 1, the communication system is composed of a UE, which is a terminal 20, and multiple network nodes 30. Hereinafter, it is assumed that one network node 30 corresponds to each function, but multiple functions may be realized by one network node 30, or multiple network nodes 30 may realize one function. Furthermore, the "connection" described below may be a logical connection or a physical connection.

[0015] The RAN (Radio Access Network) is a network node 30 having a radio access function, which may include a base station 10, and is connected to a UE, an AMF (Access and Mobility Management Function), and a UPF (User plane function). The AMF is a network node 30 having functions such as terminating the RAN interface, terminating the NAS (Non-Access Stratum), and performing registration management, connection management, reachability management, and mobility management. The UPF is a network node 30 having functions such as a PDU (Protocol Data Unit) session point to the outside that interconnects with a DN (Data Network), packet routing and forwarding, and user plane QoS (Quality of Service) handling. The UPF and the DN constitute a network slice. In the wireless communication network according to the embodiment of the present invention, multiple network slices are constructed.

[0016] The AMF is connected to the UE, RAN, SMF (Session Management function), NSSF (Network Slice Selection Function), NEF (Network Exposure Function), NRF (Network Repository Function), UDM (Unified Data Management), AUSF (Authentication Server Function), PCF (Policy Control Function), and AF (Application Function). The AMF, SMF, NSSF, NEF, NRF, UDM, AUSF, PCF, and AF are network nodes 30 that are interconnected via interfaces based on their respective services: Namf, Nsmf, Nnssf, Nnef, Nnrf, Nudm, Nausf, Npcf, and Naf.

[0017] The SMF is a network node 30 that has functions such as session management, UE IP (Internet Protocol) address allocation and management, DHCP (Dynamic Host Configuration Protocol) function, ARP (Address Resolution Protocol) proxy, and roaming function. The NEF is a network node 30 that has a function of notifying other NFs (Network Functions) of capabilities and events. The NSSF is a network node 30 that has functions such as selecting a network slice to which a UE connects, determining allowed NSSAIs (Network Slice Selection Assistance Information), determining the NSSAI to be configured, and determining the AMF set to which the UE connects. The PCF is a network node 30 that has a function of controlling network policies. The AF is a network node 30 that has a function of controlling application servers. The NRF is a network node 30 that has a function of discovering NF instances that provide services. The UDM is a network node 30 that manages subscriber data and authentication data. The UDM is connected to a UDR (User Data Repository) that stores the data.

[0018] Fig. 2 is a diagram illustrating an example of a communication system in a roaming environment. As shown in Fig. 2, the network is composed of a UE, which is a terminal 20, and multiple network nodes 30. Hereinafter, it is assumed that one network node 30 corresponds to each function, but multiple functions may be realized by one network node 30, or multiple network nodes 30 may realize one function. Furthermore, the "connection" described below may be a logical connection or a physical connection.

[0019] The RAN is a network node 30 having a radio access function, and is connected to the UE, the AMF, and the UPF. The AMF is a network node 30 having functions such as RAN interface termination, NAS termination, registration management, connection management, reachability management, and mobility management. The UPF is a network node 30 having functions such as a PDU session point to the outside that interconnects with the DN, packet routing and forwarding, and user plane QoS handling. The UPF and the DN constitute a network slice. In the wireless communication network according to the embodiment of the present invention, multiple network slices are constructed.

[0020] The AMF is connected to the UE, RAN, SMF, NSSF, NEF, NRF, UDM, AUSF, PCF, AF, and SEPP (Security Edge Protection Proxy). The AMF, SMF, NSSF, NEF, NRF, UDM, AUSF, PCF, and AF are network nodes 30 that are interconnected via their respective service-based interfaces, Namf, Nsmf, Nnssf, Nnef, Nnrf, Nudm, Nausf, Npcf, and Naf.

[0021] The SMF is a network node 30 having functions such as session management, UE IP address allocation and management, DHCP function, ARP proxy, and roaming function. The NEF is a network node 30 having a function of notifying other NFs of capabilities and events. The NSSF is a network node 30 having functions such as selecting a network slice to which a UE connects, determining an allowed NSSAI, determining an NSSAI to be configured, and determining an AMF set to which a UE connects. The PCF is a network node 30 having a function of controlling network policies. The AF is a network node 30 having a function of controlling application servers. The NRF is a network node 30 having a function of discovering NF instances that provide services. The SEPP is a non-transparent proxy that filters control plane messages between PLMNs (Public Land Mobile Networks). The vSEPP shown in Figure 2 is the SEPP in the visited network, and the hSEPP is the SEPP in the home network.

[0022] As shown in Figure 2, a UE is in a roaming environment connected to a RAN and an AMF in a Visited PLMN (VPLMN). The VPLMN and a Home PLMN (HPLMN) are connected via a vSEPP and an hSEPP. The UE can communicate with a UDM in the HPLMN via the AMF in the VPLMN, for example.

[0023] In addition, in an NG-RAN (Next Generation Radio Access Network), a gNB, which is a RAN node, may have an architecture separated into a gNB-CU (Central Unit) and a gNB-DU (Distributed Unit). One gNB-CU may accommodate multiple gNB-DUs, and one gNB-DU may accommodate multiple cells.

[0024] To enhance mobility, functional extensions are being considered to support inter-CU-LTM, cases where LTM is performed while maintaining DC, and LTM where the UE performs cell switching on its own device (conditional LTM).

[0025] In conventional LTM, the network triggers cell switching. Only intra-CU-LTM in non-DC mode and intra-SN PSCell LTM without MN involvement in DC mode were supported.

[0026] Here, in the conditional LTM, signaling between BSs is not defined. Therefore, F1 signaling used in the conditional LTM in general may be defined as described below.

[0027] 3 is a sequence diagram for explaining an example (1) of inter-DU-LTM (see Non-Patent Document 3). In step S101, the UE and source DU, and the source DU and CU transmit and receive user data. In step S102, Layer 3 measurement control and reporting are performed.

[0028] In step S103, the CU determines the LTM configuration. In step S104, the CU sends a UE context setup request to the candidate DU. In step S105, the candidate DU sends a UE context setup response to the CU. In step S106, the CU sends a UE context modification request to the source DU. In step S107, the source DU sends a UE context modification response to the CU.

[0029] In step S108, the CU may send a UE context modification request to the candidate DU. In step S109, the candidate DU may send a UE context modification response to the CU. In step S110, the CU sends a DL RRC message transfer including RRCReconfiguration to the source DU. In step S111, the source DU sends RRCReconfiguration to the UE. In step S112, the UE sends RRCReconfigurationComplete to the source DU. In step S113, the source DU sends a UL RRC message transfer including RRCReconfigurationComplete to the CU.

[0030] In step S114, the UE may perform early TA acquisition. In step S115, the candidate DU may forward the TA information to the CU. In step S116, the CU may forward the TA information to the source DU.

[0031] 4 is a sequence diagram for explaining an example (2) of inter-DU-LTM. In step S117, the UE transmits an L1 measurement report to the source DU. In step S118, the source DU determines an LTM cell switch. In step S119, the source DU transmits a cell switch command to the UE.

[0032] In step S120, the source DU sends a cell switch notification including the target cell ID and the TCI state ID to the CU. In step S121, the CU sends a cell switch notification including the target cell ID and the TCI state ID to the candidate DU. In step S122, the source DU may send a DL data delivery status to the CU.

[0033] In step S123, the DU detects UE access. In step S124, the candidate DU sends an access status including the target cell ID to the CU. In step S125, the UE sends an RRCReconfigurationComplete to the candidate DU. In step S126, the candidate DU sends an UL RRC message transfer including an RRCReconfigurationComplete to the CU.

[0034] In step S127, the CU may send a UE context release command to the source DU, causing the provisioning cell to be released. In step S128, the source DU may send a UE context release to the CU. In step S129, the UE and candidate DU, and the candidate DU and CU transmit and receive user data.

[0035] Note that steps S103 to S112 may be called LTM preparation.

[0036] Here, in LTM, the AMF (Access and Mobility Management Function) cannot determine whether the path switching procedure is triggered for inter-gNB-LTM or by other legacy functions.

[0037] Whether vertical key derivation or horizontal key derivation is performed depends on whether the AMF generates new NH parameters. However, in the case of vertical key derivation, RRC Reconfiguration may not be avoided. Since the inter-gNB-LTM, which the RAN assumes as subsequent LTM, is no longer continuous, the mobility control intended by the RAN may not be performed.

[0038] Therefore, in the case of inter-CU-LTM, when the CU sends an NGAP message (e.g., a path switching request) to the AMF, the CU may also notify that the procedure was triggered in the case of inter-CU-LTM. The AMF that receives the notification may return a response message without including an NH parameter so that horizontal key derivation is performed so that RRCReconfiguration does not occur in consecutive LTMs. Note that the key derived by horizontal key derivation or vertical key derivation may be a key applied to communication between a terminal executing LTM and a base station.

[0039] 5 is a sequence diagram illustrating an example of inter-gNB-LTM according to an embodiment of the present invention. In step S201, LTM preparation is performed. In step S202, the UE transmits an L1 measurement report to BS#1. BS#1 transmits a MAC-CE cell switch command including a target cell and beam to the UE. In step S204, BS#1 transmits a cell switch notification to BS#2.

[0040] In step S205, the UE, BS#1, and BS#2 perform cell switching. In step S206, the UE transmits an RRCReconfigurationComplete to BS#2.

[0041] In step S207, BS#1, BS#2, and AMF execute a path switching procedure. When BS#2 triggers the path switching procedure, it may notify the AMF that the path switching procedure is due to an LTM cell switch. Upon receiving the notification, the AMF may cause the RAN to perform horizontal key derivation by not generating and transmitting new NH parameters.

[0042] If vertical key derivation is performed, there is a high possibility that RRC Reconfiguration from BS#2 to the UE shown in step S208 will occur. Therefore, by not performing vertical key derivation, the occurrence of RRC Reconfiguration may be avoided.

[0043] When the BS triggers an NG procedure, it may notify the AMF in the NG message that the NG procedure is triggered by an LTM cell switch. The notification may be included in an existing NG message such as a path switch request, or may be sent in a new NG message. The notification may include some or all of information indicating whether the NG procedure is triggered by an LTM cell switch, and information related to the target BS, target DU, and target cell.

[0044] Note that class 1 procedures are procedures that use response messages including success and / or failure. Class 2 procedures are procedures that do not use response messages. Both class 1 and class 2 procedures may be used for the Xn interface or the F1 interface.

[0045] According to the above-described embodiment, when LTM is executed, the AMF receives notification of the cause of the path switching procedure from the BS, and performs horizontal key derivation without vertical key derivation, thereby enabling continuous LTM in the RAN to be executed smoothly.

[0046] In other words, LTM (Lower layer Triggered Mobility) can be appropriately controlled.

[0047] (Device configuration) Next, a description will be given of examples of functional configurations of the base station 10, network node 30, and terminal 20 that perform the processes and operations described above. The base station 10, network node 30, and terminal 20 include functions for performing the above-described embodiments. However, the base station 10, network node 30, and terminal 20 may each include only a part of the functions of the embodiments.

[0048] <Base Station 10 and Network Node 30> FIG. 6 is a diagram showing an example of the functional configuration of the base station 10 and the network node 30. As shown in FIG. 6, the base station 10 has a transmitting unit 110, a receiving unit 120, a setting unit 130, and a control unit 140. The functional configuration shown in FIG. 6 is merely an example. As long as the operations according to the embodiment of the present invention can be performed, the names of the functional divisions and functional units may be any. Note that the network node 30 may have the same functional configuration as the base station 10. Furthermore, a network node 30 having multiple different functions in the system architecture may be composed of multiple network nodes 30 separated by function.

[0049] The transmitter 110 includes a function of generating a signal to be transmitted to the terminal 20 or another network node 30, and transmitting the signal by wire or wirelessly. The receiver 120 includes a function of receiving various signals transmitted from the terminal 20 or another network node 30, and acquiring, for example, information of a higher layer from the received signal. A communication unit including the transmitter 110 and the receiver 120 may be configured.

[0050] The setting unit 130 stores in a storage device setting information that is set in advance and various setting information to be transmitted to the terminal 20, and reads out from the storage device as needed. The content of the setting information is, for example, information related to LTM.

[0051] The control unit 140 performs processing related to LTM as described in the embodiment. The control unit 140 also performs processing related to communication with the terminal 20. The function unit related to signal transmission in the control unit 140 may be included in the transmitting unit 110, and the function unit related to signal reception in the control unit 140 may be included in the receiving unit 120.

[0052] <Terminal 20> FIG. 7 is a diagram showing an example of the functional configuration of terminal 20. As shown in FIG. 7, terminal 20 has a transmitting unit 210, a receiving unit 220, a setting unit 230, and a control unit 240. The functional configuration shown in FIG. 7 is merely an example. As long as the operations according to the embodiment of the present invention can be performed, the names of the functional divisions and functional units may be any. In addition, a communication device that becomes resource holder 20 may have the same functional configuration as terminal 20.

[0053] The transmitter 210 creates a transmission signal from transmission data and transmits the transmission signal wirelessly. The receiver 220 receives various signals wirelessly and acquires higher layer signals from the received physical layer signals. The receiver 220 also has a function of receiving NR-PSS, NR-SSS, NR-PBCH, DL / UL control signals, reference signals, and the like transmitted from the network node 30. A communication unit including the transmitter 210 and the receiver 220 may be configured.

[0054] The setting unit 230 stores various setting information received from the network node 30 by the receiving unit 220 in a storage device and reads it out from the storage device as needed. The setting unit 230 also stores setting information that is set in advance. The content of the setting information is, for example, information related to LTM.

[0055] The control unit 240 performs processing related to LTM as described in the embodiment. The function unit related to signal transmission in the control unit 240 may be included in the transmitting unit 210, and the function unit related to signal reception in the control unit 240 may be included in the receiving unit 220.

[0056] (Hardware configuration) The block diagrams (FIGS. 6 and 7) used to explain the above embodiments show functional blocks. These functional blocks (components) are realized by any combination of at least one of hardware and software. Furthermore, the method for realizing each functional block is not particularly limited. That is, each functional block may be realized using a single device that is physically or logically coupled, or may be realized using two or more physically or logically separated devices that are connected directly or indirectly (for example, by wire, wirelessly, etc.) and these multiple devices. The functional block may be realized by combining the single device or the multiple devices with software.

[0057] Functions include, but are not limited to, judgment, determination, judgment, calculation, computation, processing, derivation, investigation, search, confirmation, reception, transmission, output, access, resolution, selection, election, establishment, comparison, assumption, expectation, consideration, broadcasting, notifying, communicating, forwarding, configuring, reconfiguring, allocation, mapping, and assignment. For example, a functional block (component) that performs transmission is called a transmitting unit or transmitter. As mentioned above, there are no particular limitations on how these functions are implemented.

[0058] For example, the network node 30, the terminal 20, etc. according to an embodiment of the present disclosure may function as a computer that performs processing of the wireless communication method of the present disclosure. Fig. 8 is a diagram illustrating an example of the hardware configuration of the base station 10 and the terminal 20 according to an embodiment of the present disclosure. The network node 30 may have the same hardware configuration as the base station 10. The above-described base station 10 and the terminal 20 may be physically configured as a computer device including a processor 1001, a storage device 1002, an auxiliary storage device 1003, a communication device 1004, an input device 1005, an output device 1006, a bus 1007, etc.

[0059] In the following description, the term "apparatus" can be read as a circuit, a device, a unit, etc. The hardware configuration of the base station 10 and the terminal 20 may be configured to include one or more of the apparatuses shown in the drawings, or may be configured to exclude some of the apparatuses.

[0060] Each function in the base station 10 and the terminal 20 is realized by loading predetermined software (programs) onto hardware such as the processor 1001, the memory device 1002, etc., so that the processor 1001 performs calculations, controls communication by the communication device 1004, and controls at least one of reading and writing data in the memory device 1002 and the auxiliary memory device 1003.

[0061] The processor 1001 controls the entire computer by running, for example, an operating system. The processor 1001 may be configured as a central processing unit (CPU) including an interface with peripheral devices, a control device, an arithmetic unit, a register, etc. For example, the above-mentioned control unit 140, control unit 240, etc. may be realized by the processor 1001.

[0062] Furthermore, the processor 1001 reads programs (program codes), software modules, data, etc. from at least one of the auxiliary storage device 1003 and the communication device 1004 into the storage device 1002, and executes various processes in accordance with the programs. The programs used are those that cause a computer to execute at least some of the operations described in the above-described embodiments. For example, the control unit 140 of the base station 10 shown in FIG. 6 may be implemented by a control program stored in the storage device 1002 and running on the processor 1001. Furthermore, for example, the control unit 240 of the terminal 20 shown in FIG. 7 may be implemented by a control program stored in the storage device 1002 and running on the processor 1001. While the above-described various processes have been described as being executed by one processor 1001, they may also be executed simultaneously or sequentially by two or more processors 1001. The processor 1001 may be implemented by one or more chips. The programs may be transmitted from a network via a telecommunications line.

[0063] The storage device 1002 is a computer-readable recording medium and may be configured, for example, by at least one of a read-only memory (ROM), an erasable programmable ROM (EPROM), an electrically erasable programmable ROM (EEPROM), a random access memory (RAM), etc. The storage device 1002 may also be called a register, a cache, a main memory, etc. The storage device 1002 can store executable programs (program codes), software modules, etc. for implementing a communication method according to an embodiment of the present disclosure.

[0064] The secondary storage device 1003 is a computer-readable recording medium, and may be, for example, at least one of an optical disk such as a CD-ROM (Compact Disc ROM), a hard disk drive, a flexible disk, a magneto-optical disk (e.g., a compact disk, a digital versatile disk, a Blu-ray disc), a smart card, a flash memory (e.g., a card, a stick, a key drive), a floppy disk, a magnetic strip, etc. The above-mentioned storage medium may be, for example, a database, a server, or other suitable medium including at least one of the storage device 1002 and the secondary storage device 1003.

[0065] The communication device 1004 is hardware (transmission / reception device) for communicating between computers via at least one of a wired network and a wireless network, and is also referred to as, for example, a network device, a network controller, a network card, or a communication module. The communication device 1004 may be configured to include a high-frequency switch, a duplexer, a filter, a frequency synthesizer, etc. to realize at least one of frequency division duplex (FDD) and time division duplex (TDD). For example, a transmission / reception antenna, an amplifier unit, a transmission / reception unit, a transmission path interface, etc. may be realized by the communication device 1004. The transmission / reception unit may be implemented as a transmission unit and a reception unit that are physically or logically separated.

[0066] The input device 1005 is an input device (for example, a keyboard, a mouse, a microphone, a switch, a button, a sensor, etc.) that receives input from the outside. The output device 1006 is an output device (for example, a display, a speaker, an LED lamp, etc.) that performs output to the outside. Note that the input device 1005 and the output device 1006 may be integrated into one device (for example, a touch panel).

[0067] Furthermore, each device such as the processor 1001 and the storage device 1002 is connected by a bus 1007 for communicating information. The bus 1007 may be configured using a single bus, or may be configured using different buses between each device.

[0068] Furthermore, base station 10 and terminal 20 may be configured to include hardware such as a microprocessor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a programmable logic device (PLD), or a field programmable gate array (FPGA), and some or all of the functional blocks may be realized by the hardware. For example, processor 1001 may be implemented using at least one of these pieces of hardware.

[0069] Fig. 9 shows an example configuration of a vehicle 2001. As shown in Fig. 9, the vehicle 2001 includes a drive unit 2002, a steering unit 2003, an accelerator pedal 2004, a brake pedal 2005, a shift lever 2006, front wheels 2007, rear wheels 2008, an axle 2009, an electronic control unit 2010, various sensors 2021 to 2029, an information service unit 2012, and a communication module 2013. Each aspect / embodiment described in the present disclosure may be applied to a communication device mounted on the vehicle 2001, and may be applied to the communication module 2013, for example.

[0070] The drive unit 2002 is configured, for example, by an engine, a motor, or a hybrid of an engine and a motor. The steering unit 2003 includes at least a steering wheel (also called a handle), and is configured to steer at least one of the front wheels and the rear wheels based on the operation of the steering wheel operated by the user.

[0071] The electronic control unit 2010 is composed of a microprocessor 2031, a memory (ROM, RAM) 2032, and a communication port (IO port) 2033. Signals are input to the electronic control unit 2010 from various sensors 2021 to 2029 provided in the vehicle 2001. The electronic control unit 2010 may also be called an ECU (Electronic Control Unit).

[0072] The signals from the various sensors 2021 to 2029 include a current signal from a current sensor 2021 that senses the current of the motor, a rotation speed signal of the front and rear wheels obtained by a rotation speed sensor 2022, an air pressure signal of the front and rear wheels obtained by an air pressure sensor 2023, a vehicle speed signal obtained by a vehicle speed sensor 2024, an acceleration signal obtained by an acceleration sensor 2025, an accelerator pedal depression amount signal obtained by an accelerator pedal sensor 2029, a brake pedal depression amount signal obtained by a brake pedal sensor 2026, a shift lever operation signal obtained by a shift lever sensor 2027, and a detection signal for detecting obstacles, vehicles, pedestrians, etc. obtained by an object detection sensor 2028.

[0073] The information service unit 2012 is composed of various devices, such as a car navigation system, an audio system, speakers, a television, and a radio, for providing (outputting) various types of information, such as driving information, traffic information, and entertainment information, and one or more ECUs for controlling these devices. The information service unit 2012 uses information acquired from external devices via the communication module 2013 or the like to provide various types of multimedia information and multimedia services to the occupants of the vehicle 2001. The information service unit 2012 may include input devices (e.g., a keyboard, a mouse, a microphone, a switch, a button, a sensor, a touch panel, etc.) that accept input from the outside, and may also include output devices (e.g., a display, a speaker, an LED lamp, a touch panel, etc.) that output information to the outside.

[0074] The driving assistance system unit 2030 is composed of various devices that provide functions for preventing accidents and reducing the driver's driving burden, such as a millimeter-wave radar, a LiDAR (Light Detection and Ranging), a camera, a positioning locator (e.g., GNSS, etc.), map information (e.g., high-definition (HD) map, autonomous vehicle (AV) map, etc.), a gyro system (e.g., an IMU (Inertial Measurement Unit), an INS (Inertial Navigation System), etc.), an AI (Artificial Intelligence) chip, and an AI processor, as well as one or more ECUs that control these devices. The driving assistance system unit 2030 also transmits and receives various information via the communication module 2013 to realize the driving assistance function or the autonomous driving function.

[0075] The communication module 2013 can communicate with the microprocessor 2031 and components of the vehicle 2001 via the communication port. For example, the communication module 2013 transmits and receives data via the communication port 2033 to and from the drive unit 2002, steering unit 2003, accelerator pedal 2004, brake pedal 2005, shift lever 2006, front wheels 2007, rear wheels 2008, axle 2009, microprocessor 2031 and memory (ROM, RAM) 2032 in the electronic control unit 2010, and sensors 2021 to 29, which are provided in the vehicle 2001.

[0076] The communication module 2013 is a communication device that can be controlled by the microprocessor 2031 of the electronic control unit 2010 and can communicate with an external device. For example, it transmits and receives various information to and from the external device via wireless communication. The communication module 2013 may be located either inside or outside the electronic control unit 2010. The external device may be, for example, a base station, a mobile station, or the like.

[0077] The communication module 2013 may transmit at least one of signals from the above-mentioned various sensors 2021-2028 input to the electronic control unit 2010, information obtained based on the signals, and information based on input from the outside (user) obtained via the information service unit 2012 to an external device via wireless communication. The electronic control unit 2010, the various sensors 2021-2028, the information service unit 2012, etc. may be referred to as input units that accept input. For example, the PUSCH transmitted by the communication module 2013 may include information based on the above-mentioned input.

[0078] The communication module 2013 receives various information (traffic information, traffic signal information, vehicle distance information, etc.) transmitted from external devices and displays it on an information service unit 2012 provided in the vehicle 2001. The information service unit 2012 may be called an output unit that outputs information (for example, outputs information to a device such as a display or speaker based on the PDSCH (or data / information decoded from the PDSCH) received by the communication module 2013). The communication module 2013 also stores the various information received from external devices in a memory 2032 that can be used by the microprocessor 2031. Based on the information stored in the memory 2032, the microprocessor 2031 may control the drive unit 2002, steering unit 2003, accelerator pedal 2004, brake pedal 2005, shift lever 2006, front wheels 2007, rear wheels 2008, axles 2009, sensors 2021 to 2029, etc. provided in the vehicle 2001.

[0079] (Summary of the embodiment) As described above, according to an embodiment of the present invention, there is provided a base station having a control unit that executes LTM (Lower layer Triggered Mobility) preparation for a terminal, and a receiving unit that receives a cell switch notification from another base station, wherein the control unit executes cell switch for the terminal, the receiving unit receives RRC (Radio resource control) reconfiguration completion from the terminal, and further has a transmitting unit that transmits a path switch notification and a cause of the path switch notification to an AMF (Access and Mobility Management Function).

[0080] With the above configuration, when LTM is executed, the AMF receives a notification of the cause of the path switching procedure from the BS, and performs horizontal key derivation without vertical key derivation, thereby smoothly executing continuous LTM in the RAN. In other words, LTM (Lower layer Triggered Mobility) can be appropriately controlled.

[0081] The transmitter may transmit the path switch notification and information indicating that the cause of the path switch notification is LTM to the AMF. With this configuration, when LTM is executed, the AMF receives a notification of the cause of the path switch procedure from the BS, and performs horizontal key derivation without vertical key derivation, thereby enabling smooth execution of continuous LTM in the RAN.

[0082] The control unit may perform horizontal key derivation for a key related to communication with the terminal in LTM. With this configuration, when LTM is executed, the AMF receives a notification of a cause of a path switching procedure from a BS and performs horizontal key derivation without vertical key derivation, thereby enabling smooth execution of continuous LTM in the RAN.

[0083] The control unit may not perform vertical key derivation for a key related to communication with the terminal in LTM. With this configuration, when LTM is executed, the AMF receives a notification of a cause of a path switching procedure from the BS, and performs horizontal key derivation without vertical key derivation, thereby enabling smooth execution of continuous LTM in the RAN.

[0084] The transmitter may not need to send an RRC reconfiguration to the terminal after the path switching. With this configuration, when the LTM is executed, the AMF receives a notification of the cause of the path switching procedure from the BS, and performs horizontal key derivation without vertical key derivation, thereby enabling smooth execution of continuous LTM in the RAN.

[0085] Furthermore, according to an embodiment of the present invention, there is provided a communication method in which a base station executes the following procedures: a procedure of performing LTM (Lower layer Triggered Mobility) preparation for a terminal; a procedure of receiving a cell switch notification from another base station; a procedure of performing cell switch for the terminal; a procedure of receiving RRC (Radio resource control) reconfiguration completion from the terminal; and a procedure of transmitting a path switch notification and a cause of the path switch notification to an AMF (Access and Mobility Management Function).

[0086] With the above configuration, when LTM is executed, the AMF receives a notification of the cause of the path switching procedure from the BS, and performs horizontal key derivation without vertical key derivation, thereby smoothly executing continuous LTM in the RAN. In other words, LTM (Lower layer Triggered Mobility) can be appropriately controlled.

[0087] (Supplementary explanation of the embodiment) Although the embodiments of the present invention have been described above, the disclosed invention is not limited to such embodiments, and those skilled in the art will understand various modifications, alterations, alternatives, and substitutions. While specific numerical examples have been used to facilitate understanding of the invention, unless otherwise specified, these numerical values ​​are merely examples, and any appropriate values ​​may be used. The division of items in the above description is not essential to the present invention; two or more items may be combined as needed, and items described in one item may apply to items described in another item (unless inconsistent). The boundaries between functional units or processing units in the functional block diagram do not necessarily correspond to the boundaries between physical components. The operations of multiple functional units may be performed by a single physical component, or the operations of a single functional unit may be performed by multiple physical components. The order of the processing steps described in the embodiments may be reversed as long as there is no contradiction. For convenience of processing description, the base station 10 and terminal 20 have been described using functional block diagrams. However, such devices may be implemented using hardware, software, or a combination thereof. The software operated by the processor of the base station 10 in accordance with an embodiment of the present invention and the software operated by the processor of the terminal 20 in accordance with an embodiment of the present invention may each be stored in random access memory (RAM), flash memory, read-only memory (ROM), EPROM, EEPROM, registers, hard disk (HDD), removable disk, CD-ROM, database, server or any other suitable storage medium.

[0088] Furthermore, the notification of information is not limited to the aspects / embodiments described in the present disclosure, and may be performed using other methods. For example, the notification of information may be performed by physical layer signaling (e.g., Downlink Control Information (DCI), Uplink Control Information (UCI)), higher layer signaling (e.g., Radio Resource Control (RRC) signaling, Medium Access Control (MAC) signaling), broadcast information (Master Information Block (MIB), System Information Block (SIB)), other signals, or a combination thereof. Furthermore, the RRC signaling may be referred to as an RRC message, and may be, for example, an RRC Connection Setup message, an RRC Connection Reconfiguration message, or the like.

[0089] Each aspect / embodiment described in the present disclosure may be any of the following: LTE (Long Term Evolution), LTE-Advanced (LTE-A), SUPER 3G, IMT-Advanced, 4G (4th generation mobile communication system), 5G (5th generation mobile communication system), 6th generation mobile communication system (6G), xth generation mobile communication system (xG) (xG (x is, for example, an integer or decimal number)), FRA (Future Radio Access), NR (new Radio), New radio access (NX), Future generation radio access (FX), W-CDMA (registered trademark), GSM (registered trademark), CDMA2000, UMB (Ultra Mobile Broadband), IEEE 802.11 (Wi-Fi (registered trademark)), IEEE 802.16 (WiMAX (registered trademark)), IEEE The present invention may be applied to at least one of systems using 802.20, UWB (Ultra-Wideband), Bluetooth (registered trademark), or other appropriate systems, and next-generation systems that are extended, modified, created, or defined based on these systems. The present invention may also be applied to a combination of multiple systems (e.g., a combination of at least one of LTE and LTE-A with 5G).

[0090] The order of the procedures, sequences, flowcharts, etc. of each aspect / embodiment described herein may be changed unless it is consistent. For example, the methods described in this disclosure present elements of various steps using an example order and are not limited to the particular order presented.

[0091] In this specification, a specific operation that is described as being performed by the base station 10 may also be performed by its upper node in some cases. In a network consisting of one or more network nodes having the base station 10, it is clear that various operations performed for communication with the terminal 20 may be performed by at least one of the base station 10 and another network node other than the base station 10 (such as, but not limited to, an MME or an S-GW). Although the above example illustrates a case where there is one other network node other than the base station 10, the other network node may be a combination of multiple other network nodes (such as an MME and an S-GW).

[0092] The information or signals described in the present disclosure may be output from a higher layer (or a lower layer) to a lower layer (or a higher layer), or may be input / output via multiple network nodes.

[0093] Input and output information may be stored in a specific location (for example, memory) or may be managed using a management table. Input and output information may be overwritten, updated, or added to. Output information may be deleted. Input information may be sent to another device.

[0094] In the present disclosure, the determination may be made based on a value represented by one bit (0 or 1), a Boolean value (true or false), or a numerical comparison (e.g., comparison with a predetermined value).

[0095] Software shall be construed broadly to mean instructions, instruction sets, code, code segments, program code, programs, subprograms, software modules, applications, software applications, software packages, routines, subroutines, objects, executable files, threads of execution, procedures, functions, etc., whether referred to as software, firmware, middleware, microcode, hardware description language, or otherwise.

[0096] Software, instructions, information, etc. may also be transmitted or received over a transmission medium. For example, if software is transmitted from a website, server, or other remote source using wired technologies (such as coaxial cable, fiber optic cable, twisted pair, Digital Subscriber Line (DSL)), and / or wireless technologies (such as infrared, microwave), then these wired and / or wireless technologies are included within the definition of transmission media.

[0097] The information, signals, etc. described in this disclosure may be represented using any of a variety of different technologies. For example, data, instructions, commands, information, signals, bits, symbols, chips, etc. that may be referred to throughout the above description may be represented by voltages, currents, electromagnetic waves, magnetic fields or magnetic particles, optical fields or photons, or any combination thereof.

[0098] Note that terms explained in this disclosure and terms necessary for understanding this disclosure may be replaced with terms having the same or similar meanings. For example, at least one of a channel and a symbol may be a signal (signaling). Furthermore, a signal may be a message. Furthermore, a component carrier (CC) may be called a carrier frequency, a cell, a frequency carrier, etc.

[0099] As used in this disclosure, the terms "system" and "network" are used interchangeably.

[0100] Furthermore, the information, parameters, etc. described in the present disclosure may be expressed using absolute values, may be expressed using relative values ​​from a predetermined value, or may be expressed using other corresponding information. For example, a radio resource may be indicated by an index.

[0101] The names used for the above-described parameters are not intended to be limiting in any way. Furthermore, the mathematical expressions using these parameters may differ from those explicitly disclosed in this disclosure. The various channels (e.g., PUCCH, PDCCH, etc.) and information elements may be identified by any suitable names, and therefore the various names assigned to these various channels and information elements are not intended to be limiting in any way.

[0102] In the present disclosure, terms such as "base station (BS)," "radio base station," "base station device," "fixed station," "NodeB," "eNodeB (eNB)," "gNodeB (gNB)," "access point," "transmission point," "reception point," "transmission / reception point," "cell," "sector," "cell group," "carrier," and "component carrier" may be used interchangeably. Base stations may also be referred to by terms such as macrocell, small cell, femtocell, and picocell.

[0103] A base station can accommodate one or more (e.g., three) cells. When a base station accommodates multiple cells, the overall coverage area of ​​the base station can be divided into multiple smaller areas, and each smaller area can be provided with communication service by a base station subsystem (e.g., a small indoor base station (RRH: Remote Radio Head)). The term "cell" or "sector" refers to a part or the entire coverage area of ​​a base station and / or base station subsystem that provides communication service within that coverage.

[0104] In the present disclosure, the base station transmitting information to a terminal may be interpreted as the base station instructing the terminal to control or operate based on the information.

[0105] In this disclosure, the terms "Mobile Station (MS)," "user terminal," "User Equipment (UE)," "terminal," etc. may be used interchangeably.

[0106] A mobile station may also be referred to by those skilled in the art as a subscriber station, mobile unit, subscriber unit, wireless unit, remote unit, mobile device, wireless device, wireless communication device, remote device, mobile subscriber station, access terminal, mobile terminal, wireless terminal, remote terminal, handset, user agent, mobile client, client, or some other suitable terminology.

[0107] At least one of the base station and the mobile station may be referred to as a transmitting device, a receiving device, a communication device, etc. At least one of the base station and the mobile station may be a device mounted on a mobile object, the mobile object itself, etc. The mobile object refers to a movable object, and may move at any speed. Naturally, this also includes cases where the mobile object is stationary. Examples of the mobile object include, but are not limited to, vehicles, transport vehicles, automobiles, motorcycles, bicycles, connected cars, excavators, bulldozers, wheel loaders, dump trucks, forklifts, trains, buses, handcars, rickshaws, ships and other watercraft, airplanes, rockets, satellites, drones (registered trademark), multicopters, quadcopters, balloons, and objects mounted thereon. The mobile object may also be a mobile object that moves autonomously based on an operational command. It may be a vehicle (e.g., a car, an airplane, etc.), an unmanned mobile object (e.g., a drone, an autonomous vehicle, etc.), or a robot (manned or unmanned). At least one of the base station and the mobile station may be a device that does not necessarily move during communication operations. For example, at least one of the base station and the mobile station may be an IoT (Internet of Things) device such as a sensor.

[0108] Furthermore, a base station in the present disclosure may be read as a user terminal. For example, the aspects / embodiments of the present disclosure may be applied to a configuration in which communication between a base station and a user terminal is replaced with communication between a plurality of terminals 20 (which may be called, for example, D2D (Device-to-Device) or V2X (Vehicle-to-Everything)). In this case, the terminal 20 may be configured to have the functions of the base station 10 described above. Furthermore, terms such as "uplink" and "downlink" may be read as terms corresponding to terminal-to-terminal communication (for example, "side"). For example, terms such as an uplink channel and a downlink channel may be read as a side channel.

[0109] Similarly, the user terminal in the present disclosure may be read as a base station, in which case the base station may be configured to have the functions of the user terminal described above.

[0110] As used in this disclosure, the terms "determining" and "determining" may encompass a wide variety of actions. "Determining" and "determining" may include, for example, judging, calculating, computing, processing, deriving, investigating, looking up, searching, inquiring (e.g., searching in a table, database, or other data structure), ascertaining, and the like. "Determining" and "determining" may also include receiving (e.g., receiving information), transmitting (e.g., sending information), input, output, accessing (e.g., accessing data in memory), and the like. Furthermore, "judgment" and "decision" can include regarding resolving, selecting, choosing, establishing, comparing, etc. as having been "judged" or "decided." In other words, "judgment" and "decision" can include regarding some action as having been "judged" or "decided." Furthermore, "judgment (decision)" can be interpreted as "assuming," "expecting," "considering," etc.

[0111] The terms "connected," "coupled," or any variation thereof, refer to any direct or indirect connection or coupling between two or more elements, and may include the presence of one or more intermediate elements between two elements that are "connected" or "coupled" to each other. The coupling or connection between elements may be physical, logical, or a combination thereof. For example, "connected" may be read as "access." As used in this disclosure, two elements may be considered to be "connected" or "coupled" to each other using one or more wires, cables, and / or printed electrical connections, as well as electromagnetic energy having wavelengths in the radio frequency range, microwave range, and optical (both visible and invisible) range, as some non-limiting and non-exhaustive examples.

[0112] The reference signal may be abbreviated as RS (Reference Signal) or may be called a pilot depending on the applicable standard.

[0113] As used in this disclosure, the phrase "based on" does not mean "based only on," unless expressly stated otherwise. In other words, the phrase "based on" means both "based only on" and "based at least on."

[0114] As used in this disclosure, any reference to an element using a designation such as "first," "second," etc. does not generally limit the quantity or order of those elements. These designations may be used in this disclosure as a convenient method of distinguishing between two or more elements. Thus, a reference to a first and a second element does not imply that only two elements may be employed or that the first element must in some way precede the second element.

[0115] The "means" in the configuration of each of the above devices may be replaced with "part," "circuit," "device," etc.

[0116] When used in this disclosure, the terms "include," "including," and variations thereof are intended to be inclusive, similar to the term "comprising." Furthermore, when used in this disclosure, the term "or" is not intended to be an exclusive or.

[0117] In this disclosure, where articles are added by translation, such as a, an, and the in English, the disclosure may include that the nouns following these articles are in the plural form.

[0118] In the present disclosure, the term "A and B are different" may mean "A and B are different from each other." The term may also mean "A and B are each different from C." Terms such as "separate" and "coupled" may also be interpreted in the same way as "different."

[0119] Each aspect / embodiment described in this disclosure may be used alone, in combination, or switched depending on the implementation. Furthermore, notification of predetermined information (e.g., notification that "X is true") is not limited to being done explicitly, but may be done implicitly (e.g., by not notifying the predetermined information).

[0120] Although the present disclosure has been described in detail above, it is clear to those skilled in the art that the present disclosure is not limited to the embodiments described herein. The present disclosure can be implemented in modified and altered forms without departing from the spirit and scope of the present disclosure as defined by the claims. Therefore, the description of the present disclosure is intended to be illustrative and does not have any limiting meaning on the present disclosure. [Explanation of symbols]

[0121] 10 base station 110 Transmitter 120 Receiver 130 Setting section 140 Control Unit 20 terminals 210 Transmitter 220 Receiving unit 230 Setting Section 240 Control Unit 30 network nodes 1001 processor 1002 Storage device 1003 Auxiliary storage device 1004 Communication equipment 1005 Input Device 1006 Output Device

Claims

1. A control unit that performs LTM (Lower layer Triggered Mobility) preparation for a terminal; a receiving unit that receives a cell switching notification from another base station; The control unit performs cell switching of the terminal, The receiving unit receives an RRC (Radio resource control) reconfiguration completion from the terminal, The base station further includes a transmitter that transmits a path switching notification and a cause of the path switching notification to an Access and Mobility Management Function (AMF).

2. The base station according to claim 1, wherein the transmitting unit transmits the path switching notification and information indicating that the cause of the path switching notification is LTM to the AMF.

3. The base station according to claim 1 , wherein the control unit performs horizontal key derivation for a key related to communication with the terminal in the LTM.

4. The base station according to claim 1 , wherein the control unit does not perform vertical key derivation on a key related to communication with the terminal in LTM.

5. The base station according to claim 1 , wherein the transmission unit does not transmit an RRC reconfiguration to the terminal after a path switch.

6. A procedure for performing LTM (Lower layer Triggered Mobility) preparation for a terminal; receiving a cell switch notification from another base station; A procedure for performing cell switching of the terminal; receiving a radio resource control (RRC) reconfiguration completion from the terminal; A communication method in which a base station executes a procedure of transmitting a path switching notification and a cause of the path switching notification to an AMF (Access and Mobility Management Function).

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