Base station and communication method

Abstract

A terminal according to the present invention comprises: a control unit that determines whether or not to execute continuous mobility with a Lower layer Triggered Mobility (LTM) related to a certain terminal; a transmission unit that transmits a message requesting information related to security to a Central Unit (CU); and a reception unit that receives a message including the information related to security from the CU. The transmission unit transmits a Cell Switch Command (CSC) including the information related to security to the terminal.

Description

Base station and communication method

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

[0002] 3GPP (registered trademark) (3rd Generation Partnership Project) is currently studying a wireless communication system called 5G or NR (New Radio) (hereinafter, the wireless communication system will be referred to as "5G" or "NR") in order to achieve a larger system capacity, a higher data transmission speed, and a 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 keeping latency in wireless sections to 1 ms or less.

[0003] In NR, a network architecture including 5GC (5G Core Network) corresponding 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) corresponding to E-UTRAN (Evolved Universal Terrestrial Radio Access Network), which is the RAN (Radio Access Network) in the network architecture of LTE, is being considered (for example, 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 functional extensions to support cases where LTM is performed while maintaining DC (Dual connectivity) (e.g., Non-Patent Document 2).

[0005] 3GPP TS 23.501 V18.4.0 (2023-12)3GPP TSG-RAN Meeting #101 RP-232618, Bengaluru, India, 11-15 September 20233GPP TS 33.501 V18.4.0 (2023-12)3GPP TS 38.473 V18.0.0 (2023-12)3GPP TS 38.413 V18.0.0 (2023-12)3GPP TS 38.331 V18.0.0 (2023-12)

[0006] Functional extensions to support subsequent mobility in lower layer triggered mobility (LTM) or conditional handover are being considered. For example, a secondary node (SN) change during dual connectivity (DC) has been supported in the past. However, when supporting subsequent mobility, problems related to security key updates are expected to occur.

[0007] The present invention has been made in view of the above points, and has as its object to perform security key updates during subsequent mobility.

[0008] According to the disclosed technology, a base station is provided that has a control unit that decides to execute continuous mobility using LTM (Lower layer Triggered Mobility) for a certain terminal, a transmission unit that transmits a message requesting security-related information to a CU (Central Unit), and a reception unit that receives a message including the security-related information from the CU, wherein the transmission unit transmits a CSC (Cell Switch Command) including the security-related information to the terminal.

[0009] The disclosed technique allows security key updates to be performed during subsequent mobility.

[0010] FIG. 1 is a diagram for explaining an example of a communication system. FIG. 1 is a diagram for explaining an example of a communication system in a roaming environment. FIG. 2 is a diagram for explaining an example of key update in an embodiment of the present invention. FIG. 3 is a sequence diagram for explaining example (1) of handover in an embodiment of the present invention. FIG. 4 is a sequence diagram for explaining example (2) of handover in an embodiment of the present invention. FIG. 5 is a sequence diagram for explaining example (3) of handover in an embodiment of the present invention. FIG. 6 is a sequence diagram for explaining example (4) of handover in an embodiment of the present invention. FIG. 7 is a diagram for explaining an example of key update in an embodiment of the present invention. FIG. 8 is a sequence diagram for explaining example (5) of handover in an embodiment of the present invention. FIG. 9 is a diagram showing an example of the functional configuration of a base station 10 and a network node 30 in an embodiment of the present invention. FIG. 10 is a diagram showing an example of the functional configuration of a terminal 20 in an embodiment of the present invention. FIG. 11 is a diagram showing an example of the hardware configuration of a base station 10 and a terminal 20 in an embodiment of the present invention. FIG. 12 is a diagram showing an example of the configuration of a vehicle 2001 in an embodiment of the present 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 technology is used as appropriate. However, the existing technology is, for example, the existing LTE, but is not limited to the existing LTE. Furthermore, the term "LTE" used in this specification has a broad meaning including LTE-Advanced, and systems subsequent to LTE-Advanced (e.g., NR), or wireless LAN (Local Area Network), unless otherwise specified.

[0013] Furthermore, in the embodiments of the present invention, "configuring" radio parameters and the like 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), 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 mutually connected 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 having 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 having a function of notifying other NFs (Network Functions) 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 (Network Slice Selection Assistance Information), determining an NSSAI to be set, 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 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 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 a configured NSSAI, 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 FIG. 2 is a SEPP in the visited network, and the hSEPP is a 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. F1AP (F1 Application Protocol) may be used for signaling between the gNB-DU and the gNB-CU (see Non-Patent Document 4).

[0024] Functional extensions to support subsequent mobility in LTM (Lower layer Triggered Mobility), conditional handover, and the like are being considered. For example, conventionally, a change of SN (Secondary Node) during DC (Dual connectivity) has been supported. On the other hand, when supporting continuous mobility, problems related to security key updates are expected to occur. Therefore, in this embodiment, an operation related to security key updates in continuous mobility is proposed.

[0025] Here, the K_gNB in ​​the gNB must be refreshed. However, due to forward security, there are specifications that do not allow security keys to be set in the UE in advance (see Non-Patent Document 3). It is not possible to pre-calculate the future K_gNB, NH (Next Hop parameter), and NCC (Next Hop Chaining Counter parameter) pairs.

[0026] There are three methods for calculating K_gNB, as shown in 1)-3) below (see Non-Patent Document 3).

[0027] 1) Horizontal key derivation This may be possible when K_AMF is not updated. It may be calculable without additional parameters. If it can be updated between cell switches, an indication of the number of updates may be required.

[0028] 2) Vertical key derivation This may be possible when K_AMF is not updated. NH and K_gNB may be updated with an increment of NCC.

[0029] 3) K_AMF Update This may be performed when K_AMF is updated. A pair of {NH, NCC} may be sent to the gNB and UE. Only the first {NH, NCC} is configured in the gNB and UE from the AMF. Note that {NH, NCC} may or may not be reconfigured in the UE during vertical key derivation.

[0030] Based on the above calculation method of K_gNB, horizontal key derivation is possible in subsequent inter-CU LTM. Also, in subsequent inter-CU LTM, vertical key derivation is possible when NCC is incremented by 1, and is possible if incremented by 2 or more with notification. Note that K_AMF may be a parameter used for K_gNB derivation.

[0031] 3 is a diagram for explaining an example of key refresh in an embodiment of the present invention. As shown in FIG. 3, K_gNB is refreshed by horizontal key derivation or vertical key derivation.

[0032] Horizontal key derivation is performed based on K_gNB, PCI (Physical Cell Identifier), and DL frequency. In horizontal key derivation, it is necessary to determine how many times to perform key updates.

[0033] Vertical key derivation is performed based on the NH, PCI and DL frequencies. It is necessary to decide which NCC to use in the vertical key derivation.

[0034] Fig. 4 is a sequence diagram for explaining an example (1) of handover in an embodiment of the present invention, showing an example of legacy L3 HO (Hand Over) or CHO (Conditional HO).

[0035] In step S100, gNB #1 and gNB #2 perform handover preparation (HO Preparation). In step S101, gNB #1 sends an RRCReconfiguration message including an information element MasterKeyUpdate for updating K_gNB to the UE. The RRCReconfiguration message including the information element MasterKeyUpdate is sent from the gNB to the UE when every handover is performed. In step S102, the UE sends an RRCReconfigurationComplete message to gNB #1.

[0036] In step S103, the UE, gNB #1, and gNB #2 execute handover (HO Execution) and update the master key, i.e., K_gNB (Master Key Update). The UE updates K_gNB based on the information element MasterKeyUpdate set by gNB #1 immediately before the handover. In step S104, the UE sends the message RRCReconfigurationComplete to gNB #2.

[0037] Steps S100 to S104 correspond to an initial handover.

[0038] Subsequently, in step S105, gNB #2 and gNB #3 perform handover preparation (HO Preparation). In step S106, gNB #2 sends to the UE an RRCReconfiguration message including the information element MasterKeyUpdate for updating K_gNB. The RRCReconfiguration message including the information element MasterKeyUpdate is sent from the gNB to the UE when every handover is executed. In step S107, the UE sends an RRCReconfigurationComplete message to gNB #2.

[0039] In step S108, the UE, gNB #2, and gNB #3 execute handover (HO Execution) and update the master key, i.e., K_gNB (Master Key Update). The UE updates K_gNB based on the information element MasterKeyUpdate set by gNB #2 immediately before the handover. In step S109, the UE sends a message RRCReconfigurationComplete to gNB #1.

[0040] Steps S105 to S109 correspond to subsequent handover.

[0041] Fig. 5 is a sequence diagram for explaining an example (2) of handover in the embodiment of the present invention, showing an example of inter CU-LTM (Lower layer Triggered Mobility).

[0042] In step S201, the UE, gNB #1, gNB #2, and gNB #3 perform LTM preparation. In step S202 included in the LTM preparation, gNB #1 sends a message RRCReconfiguration including LTM settings to the UE. In step S203 included in the LTM preparation, the UE sends a message RRCReconfigurationComplete to gNB #1.

[0043] In step S204, gNB #1 transmits a CSC (Cell Switch Command) including information indicating the target cell and beam to the UE via MAC-CE. In step S205, cell switching is executed (Cell Switch Execution). Here, the master key, i.e., K_gNB, may be updated using the information element MasterKeyUpdate included in the message RRCReconfiguration received by the UE in step S202 (Master Key Update). In step S206, the UE transmits a message RRCReconfigurationComplete to gNB #2. The CSC is a command in which the source gNB-DU notifies the UE of the target cell and target beam via MAC-CE and instructs cell switching.

[0044] Steps S201 to S206 correspond to an initial handover.

[0045] The LTM preparation in step S207 is not performed. In continuous LTM, LTM preparation is not performed after the initial LTM cell switch. The message RRCReconfiguration is not sent from the gNB to the UE. In addition, the information element MasterKeyUpdate is used during the initial LTM cell switch.

[0046] In step S208, gNB #2 transmits a CSC (Cell Switch Command) including information indicating the target cell and beam to the UE via MAC-CE. In step S209, cell switching is executed (Cell Switch Execution). As described above, the information element MasterKeyUpdate is used during initial LTM cell switching, so the UE cannot use the information element MasterKeyUpdate and may update K_gNB using other methods. In step S210, the UE transmits a message RRCReconfigurationComplete to gNB #3.

[0047] Steps S208 to S210 correspond to subsequent handover.

[0048] Fig. 6 is a sequence diagram for explaining an example (3) of handover in the embodiment of the present invention, showing an example of inter-CU-LTM (Lower layer Triggered Mobility).

[0049] In step S301, the UE, gNB #1, and gNB #2 perform LTM preparation. In step S302 included in the LTM preparation, gNB #1 sends a message RRCReconfiguration including LTM settings to the UE. The message RRCReconfiguration may include the information element MasterKeyUpdate shown below.

[0050] MasterKeyUpdate ::= SEQUENCE { keySetChangeIndicator BOOLEAN, nextHopChainingCount NextHopChainingCount, nas-Container OCTET STRING OPTIONAL, -- Cond securityNASC ...}

[0051] In step S303 included in the LTM preparation, the UE transmits a message RRCReconfigurationComplete to gNB #1. In step S304, gNB #1 transmits a CSC (Cell Switch Command) including information indicating the target cell and beam to the UE via MAC-CE. In step S305, cell switching is executed (Cell Switch Execution).

[0052] Here, the UE may update the master key, i.e., K_gNB, using the information element MasterKeyUpdate included in the message RRCReconfiguration received by the UE in step S302 (Master Key Update). In step S306, the UE sends a message RRCReconfigurationComplete to gNB #2.

[0053] The LTM preparation in step S307 is not performed. In continuous LTM, LTM preparation is not performed after the initial LTM cell switch. The message RRCReconfiguration is not sent from the gNB to the UE. In addition, the information element MasterKeyUpdate is used during the initial LTM cell switch.

[0054] In step S308, gNB #1 transmits a CSC (Cell Switch Command) including information indicating the target cell and beam to the UE via MAC-CE. The CSC may be the MAC-CE shown in Table 1.

[0055]

[0056] In step S309, cell switching is executed (Cell Switch Execution). Here, as shown in Table 1, CSC includes the number of vertical key refreshes and the number of horizontal key refreshes. In step S309, the UE can update K_gNB based on the number of vertical key refreshes and the number of horizontal key refreshes. In step S310, the UE sends a message RRCReconfigurationComplete to gNB #3.

[0057] Fig. 7 is a sequence diagram for explaining an example (4) of handover in the embodiment of the present invention, showing an example of inter CU-LTM (Lower layer Triggered Mobility).

[0058] In step S401, the UE, gNB #1, gNB #2, gNB #3, and AMF perform LTM preparation. In step S402 included in the LTM preparation, gNB #1 sends a message RRCReconfiguration including LTM settings to the UE. The message RRCReconfiguration may include an information element MasterKeyUpdate for updating K_gNB.

[0059] In steps S403 and S404 included in the LTM preparation, gNB #1 sends an LTM request including a MasterKeyUpdate generation request to gNB #2 and gNB #3. In step S405 included in the LTM preparation, the UE sends the message RRCReconfigurationComplete to gNB #1.

[0060] In step S406, gNB #1 transmits a CSC (Cell Switch Command) including information indicating the target cell and beam to the UE via MAC-CE. In step S407, gNB #1 transmits a Cell Switch Notification to gNB #2. In step S408, cell switching is executed (Cell Switch Execution).

[0061] Here, the UE may update the master key, i.e., K_gNB, using the information element MasterKeyUpdate included in the message RRCReconfiguration received by the UE in step S402 (Master Key Update). In step S409, the UE sends a message RRCReconfigurationComplete to gNB #2.

[0062] In step S410, gNB #2 and AMF perform a security key update procedure like a path switch update. In step S411, gNB #2 and gNB #3 transmit and receive security update signaling. In step S412, gNB #2 and gNB #3 transmit and receive security update signaling. Steps S410 to S412 are performed by Xn or NG signaling.

[0063] In step S413, gNB #2 transmits a CSC (Cell Switch Command) including information indicating the target cell and beam via MAC-CE to the UE. The CSC may be the MAC-CE shown in Table 1, or may include information that enables K_gNB to be updated.

[0064] In step S414, cell switching is executed (Cell Switch Execution). Here, in step S414, the UE can update K_gNB based on the information for updating K_gNB acquired together with the CSC. In step S415, the UE sends a message RRCReconfigurationComplete to gNB #3.

[0065] In inter-CU-LTM, the network may send a security key update instruction to the UE, and the CU may send security key update information to the DU. The CU may also obtain or generate security key update information for the next cell switch.

[0066] Here, if the CU manages the security of the gNB and cell switching is decided by the DU and instructed to the UE (e.g., continuous LTM), cell switching may be triggered before the DU obtains security-related information.

[0067] Therefore, when the CU manages the security of the gNB and cell switching is decided by the DU and instructed to the UE (e.g., continuous LTM), CU-DU signaling may be specified as shown below in 1)-3).

[0068] 1) The DU may be configured in advance by the CU, OAM (Operations, Administration, Maintenance) or O-RAN node (SMO (Service Management and Orchestration), RIC (RAN Intelligent Controller)), etc., to determine whether or not security key updates are required for cell switching targeting each candidate setting, each candidate cell, and each candidate beam.

[0069] 2) When a security key update is required, it may be explicitly or implicitly configured that a security key update is always required when switching to a cell belonging to a gNB other than the serving gNB.

[0070] 3) The settings in 1) and 2) above may be set during or before LTM preparation, or may be set from a CU, OAM, or O-RAN node (SMO or RIC) at any time during the LTM procedure.

[0071] The DU may operate as shown in 1) and 2) below.

[0072] 1) When the DU makes a cell switching decision (determination of target cell and beam, timing to start cell switching, etc.) based on the L1 measurement report received from the UE, if a security key update is required for cell switching to the target, the DU may wait to send the CSC until it receives security-related information to be sent to the UE from the CU, or may stop sending the CSC.

[0073] 2) In the above 1), when cell switching targets a candidate that does not require security key updating, such as when the target belongs to the same gNB as the serving one, the DU may send a CSC without waiting to receive security-related information.

[0074] When each DU performs an LTM decision as a serving DU and sends a CSC to the UE, it may determine whether a security key update is required in a cell switch targeting each candidate configuration, each candidate cell, and each candidate beam based on the configuration previously received from the CU.

[0075] 8 is a diagram illustrating an example of key updating in an embodiment of the present invention. The configuration received in advance from the CU may be a list of all candidate configurations, candidate cells, candidate beams, and IDs (SecIDs) for distinguishing security classifications associated with the candidates, as shown in FIG.

[0076] When each DU performs an LTM decision as a serving DU and sends a CSC to the UE, it may compare the SecID associated with the configuration currently applied to the UE with the SecID associated with the candidate configuration, candidate cell, and candidate beam selected as the target, and determine that if the SecIDs are the same, no security key update is required, and if they are different, a security key update is required.

[0077] In the example shown in Figure 8, when CU #0 switches from cell #0 to cell #2, the DU may determine that security key update is not required because the SecIDs are the same, 0. When CU #1 switches from cell #3 to cell #5, the DU may determine that security key update is required because the SecIDs are different, even though the cells belong to the same CU #1. When CU #0 switches from cell #0 to cell #6 of CU #2, the DU may determine that security key update is required because the SecIDs are different.

[0078] The settings received in advance from the CU may be set in the DU from an OAM or O-RAN node (SMO or RIC), etc.

[0079] 9 is a sequence diagram for explaining a handover example (5) according to an embodiment of the present invention. In step S501, LTM preparation is performed. In the LTM preparation, security-related information to be set in the UE for initial cell switching is prepared.

[0080] In step S502, the UE transmits an L1 measurement report to the DU belonging to CU#0. In step S503, the DU belonging to CU#0 makes an LTM decision. In step S504, the DU belonging to CU#0 transmits a CSC to the UE.

[0081] In step S505, cell switching to CU#1 is performed. Based on pre-configured security-related information, the UE performs security key update to perform cell switching.

[0082] In step S506, after the cell switching is completed, CU #1, which has become the serving CU for the successive cell switching, prepares security-related information for the next cell switching with CU #2, which is a candidate CU, and the AMF.

[0083] In step S507, the UE transmits an L1 measurement report to the DU belonging to CU#1. In step S508, the DU belonging to CU#0 makes an LTM decision. Process A including steps S507 and S508 illustrates an example in which the next cell switching trigger occurs before CU#1 transmits the acquired security-related information to the DU.

[0084] In step S509, the DU belonging to CU #1 transmits a security related info request message to CU #1. In step S510, CU #1 transmits a security related information message to the DU belonging to CU #1. Process B including steps S509 and S510 shows an example in which, when a target requiring a security key update is selected based on a previous setting in the DU, cell switching is triggered after waiting until security related information is received from the CU.

[0085] In step S511, the DU belonging to CU#1 transmits a CSC including a security update command to the UE. In step S512, cell switching to CU#2 is performed. The UE performs security key update based on the security-related information received in the CSC, and cell switching is performed.

[0086] The DU may receive security related information required for the next cell switch for each candidate configuration, cell and beam, for example by means of the Information Element (IE) shown in Table 2. Based on this IE, the DU may determine the security related information to be included in the CSC.

[0087]

[0088] As shown in Table 2, the security key refresh may indicate no update required, a horizontal key refresh, or a vertical key refresh. The NCC may indicate the number of NCC increments. The number of horizontal key derivations may indicate the number of horizontal key updates. The number of key derivations may indicate the number of NCC increments or the number of horizontal key updates.

[0089] The security-related information may be received from the CU to which the DU belongs, or from an OAM or O-RAN node (SMO or RIC), etc. The security-related information may be provided in response to a request from the DU, or may be unilaterally notified to the DU from another node. The security-related information may be transmitted by F1 signaling transmitted for each UE or candidate configuration and cell, or may be transmitted for each DU to provide a list of security-related information corresponding to each candidate. The security-related information may be transmitted in an F1 message such as UE Context Setup or UE Context Modification, or similar content may be transmitted over the O-RAN interface (O1, E2, A1, etc.).

[0090] In the UE Context Setup or UE Context Modification procedure transmitted in CU-DU signaling for LTM candidate preparation, which is performed in the LTM preparation phase, the IE shown in Table 3 may indicate whether each candidate cell is an inter-CU or intra-CU from the perspective of each candidate gNB and DU.

[0091]

[0092] As shown in Table 3, information in which an LTM configuration ID and a notification indicating whether or not the device is an inter-CU candidate (Inter-CU Candidate indication) are associated may be notified by the IE.

[0093] A DU that receives the IE may automatically determine that security key update is required when switching to the selected target cell if the selected target cell is a candidate cell for inter-CU.

[0094] A DU that receives the IE may automatically determine that security key update is not required when switching to the selected target cell if the selected target cell is a candidate cell for intra-CU.

[0095] This IE may be sent in an F1 message such as UE Context Setup or UE Context Modification, or similar content may be sent over the O-RAN interface (O1, E2, A1, etc.).

[0096] In the UE Context Setup or UE Context Modification procedure transmitted in CU-DU signaling for LTM candidate preparation, which is performed in the LTM preparation phase, a list of the IDs of the gNBs to which each candidate cell belongs may be indicated by the IE shown in Table 4.

[0097]

[0098] As shown in Table 4, information associating the LTM configuration ID (LTM Configuration ID) with the gNB ID (gNB ID) may be notified by the IE.

[0099] A DU that receives the IE may automatically determine that a security key update is required when switching to a selected target cell if the ID of the gNB associated with the selected target cell is different from the ID of the gNB associated with the currently configured candidate cell.

[0100] The DU that receives the IE may automatically determine that no security key update is required when switching to the selected target cell if the ID of the gNB associated with the selected target cell is the same as the ID of the gNB associated with the currently configured candidate cell.

[0101] This IE may be sent in an F1 message such as UE Context Setup or UE Context Modification, or similar content may be sent over the O-RAN interface (O1, E2, A1, etc.).

[0102] In the UE Context Setup or UE Context Modification procedure sent in CU-DU signaling for LTM candidate preparation, which is performed in the LTM preparation phase, the SecID associated with each candidate cell may be indicated by the IE shown in Table 5.

[0103]

[0104] As shown in Table 5, information in which an LTM configuration ID and an LTM security ID are associated with each other may be notified by the IE.

[0105] A DU that receives this IE may automatically determine that a security key update is required upon cell switching to a selected target cell if the SecID associated with the selected target cell is different from the SecID associated with the currently configured candidate cell.

[0106] A DU that receives the IE may automatically determine that no security key update is required when switching to the selected target cell if the SecID associated with the selected target cell is identical to the SecID associated with the currently configured candidate cell.

[0107] This IE may be sent in an F1 message such as UE Context Setup or UE Context Modification, or similar content may be sent over the O-RAN interface (O1, E2, A1, etc.).

[0108] According to the above-described embodiment, in mobility such as subsequent inter-CU mobility in which the DU decides to switch cells and instructs the UE to do so, it is possible to appropriately instruct the UE to perform security update operations.

[0109] That is, security key updates can be performed during subsequent mobility.

[0110] (Device Configuration) Next, a description will be given of an example of the functional configuration 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.

[0111] <Base Station 10 and Network Node 30> Fig. 10 is a diagram showing an example of the functional configuration of the base station 10 and the network node 30. As shown in Fig. 10, 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. 10 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.

[0112] 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.

[0113] The setting unit 130 stores in a storage device preset setting information 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.

[0114] 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.

[0115] <Terminal 20> Fig. 11 is a diagram showing an example of the functional configuration of the terminal 20. As shown in Fig. 11, the 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. 11 is merely an example. As long as the operations related 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 a resource holder 20 may have the same functional configuration as the terminal 20.

[0116] 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.

[0117] 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 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.

[0118] 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.

[0119] (Hardware Configuration) The block diagrams (FIGS. 10 and 11) 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 directly or indirectly connected (for example, using wires, wirelessly, etc.) and these multiple devices. The functional block may be realized by combining software with the single device or the multiple devices.

[0120] Functions include, but are not limited to, judgment, determination, assessment, calculation, computation, processing, derivation, investigation, search, confirmation, reception, transmission, output, access, resolution, selection, selection, establishment, comparison, assumption, expectation, consideration, broadcasting, notifying, communicating, forwarding, configuring, reconfiguring, allocating, 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.

[0121] 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. 12 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.

[0122] In the following description, the term "apparatus" can be interpreted 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.

[0123] Each function in the base station 10 and the terminal 20 is realized by loading specified 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.

[0124] 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.

[0125] The processor 1001 also 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. 10 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. 11 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 also be transmitted from a network via a telecommunications line.

[0126] 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 read-only memory (EPROM), an electrically erasable programmable read-only memory (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.

[0127] 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 (registered trademark) disk), a smart card, a flash memory (e.g., a card, a stick, a key drive), a floppy (registered trademark) disk, a magnetic strip, etc. The above-mentioned storage medium may be, for example, a database, a server, or other appropriate medium including at least one of the storage device 1002 and the secondary storage device 1003.

[0128] 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, a communication module, etc. 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.

[0129] The input device 1005 is an input device (e.g., 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 (e.g., a display, a speaker, an LED lamp, etc.) that outputs to the outside. Note that the input device 1005 and the output device 1006 may be integrated into one device (e.g., a touch panel).

[0130] 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.

[0131] Furthermore, the base station 10 and the 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, the processor 1001 may be implemented using at least one of these pieces of hardware.

[0132] Fig. 13 shows an example configuration of a vehicle 2001. As shown in Fig. 13, 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.

[0133] 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.

[0134] 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).

[0135] 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.

[0136] 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.

[0137] The driving assistance system unit 2030 is composed of various devices that provide functions for preventing accidents and reducing the driving burden on the driver, such as millimeter-wave radar, LiDAR (Light Detection and Ranging), cameras, positioning locators (e.g., GNSS, etc.), map information (e.g., high-definition (HD) maps, autonomous vehicle (AV) maps, etc.), gyro systems (e.g., IMU (Inertial Measurement Unit), INS (Inertial Navigation System), etc.), AI (Artificial Intelligence) chips, and AI processors, as well as one or more ECUs that control these devices. In addition, the driving assistance system unit 2030 transmits and receives various information via the communication module 2013 to realize the driving assistance function or the autonomous driving function.

[0138] 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.

[0139] 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.

[0140] 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.

[0141] The communication module 2013 receives various information (traffic information, traffic signal information, vehicle-to-vehicle 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.

[0142] (Summary of embodiment) As described above, according to an embodiment of the present invention, a base station is provided that includes a control unit that determines to execute continuous mobility by LTM (Lower layer Triggered Mobility) for a certain terminal, a transmission unit that transmits a message requesting security-related information to a CU (Central Unit), and a reception unit that receives a message including the security-related information from the CU, wherein the transmission unit transmits a CSC (Cell Switch Command) including the security-related information to the terminal.

[0143] With the above configuration, in mobility in which the DU determines cell switching and instructs the UE to switch cells, such as subsequent inter-CU mobility, it is possible to appropriately instruct the UE to perform security update operations. That is, it is possible to perform security key updates during subsequent mobility.

[0144] The control unit may not transmit the CSC until the control unit receives the security information. With this configuration, in mobility in which a DU determines a cell switch and instructs the UE to switch cells, such as subsequent mobility, it is possible to appropriately instruct the UE to perform a security update operation.

[0145] The control unit may determine whether a security key update is necessary after a cell change based on the security information. With this configuration, in mobility in which a DU determines a cell change and instructs the UE to change the cell, such as subsequent mobility, it is possible to appropriately instruct the UE to perform a security update operation.

[0146] The controller may determine, for each candidate LTM configuration, whether a security key update is required after a cell switch, based on the security-related information. With this configuration, it is possible to appropriately instruct a UE to perform a security update operation in mobility in which a DU determines a cell switch and instructs the UE to perform a cell switch, such as subsequent mobility.

[0147] The control unit may determine whether a security key update is necessary after a cell switch based on information indicating whether the cell is an inter-CU associated with a candidate LTM configuration, an ID of a base station, or a security ID, which is included in the security-related information. With this configuration, it is possible to appropriately instruct the UE to perform a security update operation in mobility in which a DU determines a cell switch and instructs the UE to perform a cell switch, such as subsequent mobility.

[0148] 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 deciding to perform continuous mobility using LTM (Lower layer Triggered Mobility) for a certain terminal; a procedure of sending a message requesting security-related information to a CU (Central Unit); a procedure of receiving a message including the security-related information from the CU; and a procedure of sending a CSC (Cell Switch Command) including the security-related information to the terminal.

[0149] With the above configuration, in mobility in which the DU determines cell switching and instructs the UE to switch cells, such as subsequent inter-CU mobility, it is possible to appropriately instruct the UE to perform security update operations. That is, it is possible to perform security key updates during subsequent mobility.

[0150] (Supplementary Notes on the Embodiments) 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; matters described in two or more items may be used in combination as needed, and matters described in one item may apply to matters described in another item (as long as there is no contradiction). Boundaries between functional units or processing units in functional block diagrams do not necessarily correspond to 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 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, but such devices may be realized by 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, register, hard disk (HDD), removable disk, CD-ROM, database, server, or any other suitable storage medium.

[0151] 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.

[0152] Each aspect / embodiment described in the present disclosure may be implemented using any of the following standards: 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 a 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 802.17 (WiMAX (registered trademark)), IEEE 802.19 (WiMAX (registered trademark)), IEEE 802.20 (WiMAX (registered trademark)), IEEE 802.21 (Wi-Fi (registered trademark)), IEEE 802.22 (WiMAX (registered trademark)), IEEE 802.23 (WiMAX (registered trademark)), IEEE 802.24 (WiMAX (registered trademark)), IEEE 802.25 (WiMAX (registered trademark)), IEEE 802.26 (WiMAX (registered trademark)), IEEE 802.27 (WiMAX (registered trademark)), IEEE 802.28 (WiMAX (registered trademark)), IEEE 802.29 (WiMAX (registered trademark)), IEEE 802.30 (WiMAX (registered trademark)), IEEE 802.31 (Wi-Fi (registered trademark)), IEEE 802.32 (WiMAX (registered trademark)), IEEE 802.33 (WiMAX (registered trademark)), IEEE 802.34 ( The present invention may be applied to at least one of systems using 802.20, UWB (Ultra-Wide Band), Bluetooth (registered trademark), or other suitable 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 LTE and / or LTE-A with 5G).

[0153] The order of the procedures, sequences, flowcharts, etc. of each aspect / embodiment described herein may be rearranged 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.

[0154] In this specification, a specific operation described as being performed by the base station 10 may 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).

[0155] The information, signals, etc. 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.

[0156] 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 transmitted to another device.

[0157] In the present disclosure, the determination may be made by a value represented by one bit (0 or 1), by a Boolean value (true or false), or by a comparison of numerical values ​​(e.g., comparison with a predetermined value).

[0158] 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.

[0159] 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.

[0160] 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.

[0161] Note that terms described 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.

[0162] As used in this disclosure, the terms "system" and "network" are used interchangeably.

[0163] 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.

[0164] 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.

[0165] 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. A base station may also be referred to by terms such as a macrocell, a small cell, a femtocell, and a picocell.

[0166] 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 partitioned into multiple smaller areas, and each smaller area can also be provided with communication services by a base station subsystem (e.g., a small indoor base station (RRH: Remote Radio Head)). The terms "cell" or "sector" refer to part or all of the coverage area of ​​a base station and / or base station subsystem that provides communication services within that coverage.

[0167] 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.

[0168] In this disclosure, the terms "Mobile Station (MS)," "user terminal," "User Equipment (UE)," "terminal," and the like may be used interchangeably.

[0169] 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.

[0170] 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.

[0171] 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 multiple terminals 20 (which may be called, for example, Device-to-Device (D2D) or Vehicle-to-Everything (V2X)). 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.

[0172] 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.

[0173] 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.

[0174] 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.

[0175] The reference signal may be abbreviated as RS (Reference Signal) or may be called a pilot depending on the applicable standard.

[0176] 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."

[0177] 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.

[0178] The "means" in the configuration of each of the above devices may be replaced with "part," "circuit," "device," etc.

[0179] When the terms "include," "including," and variations thereof are used in this disclosure, these terms are intended to be inclusive, similar to the term "comprising." Furthermore, when the term "or" is used in this disclosure, it is not intended to be an exclusive or.

[0180] 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.

[0181] 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."

[0182] The aspects / embodiments described in this disclosure may be used alone, in combination, or switched depending on the implementation. Notification of predetermined information (e.g., notification that "X is true") is not limited to explicit notification, but may be implicit (e.g., not notifying the predetermined information).

[0183] 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.

[0184] REFERENCE SIGNS LIST 10 Base station 110 Transmitter 120 Receiver 130 Setting unit 140 Controller 20 Terminal 210 Transmitter 220 Receiver 230 Setting unit 240 Controller 30 Network node 1001 Processor 1002 Storage device 1003 Auxiliary storage device 1004 Communication device 1005 Input device 1006 Output device

Claims

1. A base station having a control unit that determines to perform continuous mobility using LTM (Lower layer Triggered Mobility) for a certain terminal, a transmission unit that transmits a message requesting security-related information to a CU (Central Unit), and a reception unit that receives a message including the security-related information from the CU, wherein the transmission unit transmits a CSC (Cell Switch Command) including the security-related information to the terminal.

2. The base station according to claim 1, wherein the control unit does not transmit the CSC until the security-related information is received.

3. The base station according to claim 1, wherein the control unit determines whether or not a security key update is required after cell switching based on the security-related information.

4. The base station according to claim 1, wherein the control unit determines, for each candidate LTM setting, whether or not a security key update is required after cell switching, based on the security-related information.

5. The base station of claim 1, wherein the control unit determines whether a security key update is required after cell switching based on information indicating whether the LTM setting is an inter-CU, the base station ID, or the security ID, which is included in the security-related information and is associated with the candidate LTM setting.

6. A communication method in which a base station executes the following procedures: determining to perform continuous mobility using LTM (Lower layer Triggered Mobility) for a certain terminal; transmitting a message requesting security-related information to a CU (Central Unit); receiving a message including the security-related information from the CU; and transmitting a CSC (Cell Switch Command) including the security-related information to the terminal.

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