Network node and communication method

Abstract

To configure LTM (Lower layer Triggered Mobility) between each base station.SOLUTION: A network node has a control unit that performs LTM (Lower layer Triggered Mobility) preparation between a terminal, a first network node, and a second network node, a receiving unit that receives Xn (Network interface between NG-RAN nodes) early state transfer from the first network node, and a transmission unit that transmits the Xn early state transfer to the second network node, and the receiving unit receives early user data from the first network node, and the transmission unit transmits the early user data to the second network node.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a network node in a communication system and a communication method. [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 the LTM configuration, there may be cases where there is no Xn (Network interface between NG-RAN nodes) interface between candidate BSs (Base stations). In such cases, the LTM configuration must also be synchronized.

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

[0008] According to the disclosed technology, there is provided a network node including: a control unit that performs LTM (Lower layer Triggered Mobility) preparation between a terminal, a first network node, and a second network node; a receiving unit that receives Xn (Network interface between NG-RAN nodes) early state transfer from the first network node; and a transmitting unit that transmits the Xn early state transfer to the second network node, wherein the receiving unit receives early user data from the first network node and the transmitting unit transmits the early user data to the second network node. [Effects of the Invention]

[0009] According to the disclosed technology, LTM (Lower layer Triggered Mobility) can be set between base stations. [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 diagram illustrating an example of an Xn interface between BSs. [Figure 4] FIG. 10 is a diagram illustrating an example of an LTM. [Figure 5] FIG. 1 is a sequence diagram illustrating an example (1) of inter-CU-LTM according to an embodiment of the present invention. [Figure 6] FIG. 10 is a sequence diagram illustrating an example (2) of inter-CU-LTM according to an embodiment of the present invention. [Figure 7] FIG. 10 is a sequence diagram illustrating an example (3) of inter-CU-LTM according to an embodiment of the present invention. [Figure 8] FIG. 10 is a sequence diagram illustrating an example (4) of inter-CU-LTM according to an embodiment of the present invention. [Figure 9] FIG. 10 is a sequence diagram illustrating an example (5) of inter-CU-LTM according to an embodiment of the present invention. [Figure 10] FIG. 10 is a sequence diagram illustrating an example (6) of inter-CU-LTM according to an embodiment of the present invention. [Figure 11] 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 12] 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 13] 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. 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] Figure 3 is a diagram illustrating an example of an Xn interface between BSs. In the deployment scenario shown in Figure 3, the Xn interfaces between candidate BSs for subsequent LTM are not fully meshed. Since there are no Xn interfaces between BS-B and BS-E, and between BS-C and BS-D, coverage continuity cannot be maintained between BS-B and BS-E, and between BS-C and BS-D.

[0027] The handover cancel message may be used by the source BS to release resources reserved for the LTM candidate cell of the candidate BS. A new procedure may be introduced for BS-initiated LTM cancellation. An XnAP (Application) Class 2 procedure, LTM cell switch notification, may be introduced on the Xn interface to transfer the target cell ID and target TCI state from the source CU to the target CU. To support continuous LTM, the LTM configuration update procedure may be reused to establish association with the UE between the new source BS and other candidate BSs after each inter-CULTM cell switch. The Xn interface is not limited to an interface between NG-RAN nodes, and may be replaced by an interface between network nodes.

[0028] Fig. 4 is a diagram for explaining an example of LTM. As shown in Fig. 4, when the source BS is BS#1, Xn interfaces are established between the source BS and all candidate BSs, but among candidate BSs for which some Xn interfaces are not established, after a cell switch is performed to one of the BSs, Xn signaling related to LTM cannot be transmitted to the other BS. In the deployment scenario shown in Fig. 4, BS#1 has Xn interfaces with BS#2, BS#3, and BS#4. On the other hand, there is no Xn interface between BS#2 or BS#3 and BS#4.

[0029] As an example, in FIG. 4, the situation is as follows: When the UE was in the coverage area of ​​BS#1, an LTM was set with BS#2, BS#3, and BS#4 as candidates. ·The UE performed cell switching from BS#1 to BS#2 and from BS#2 to BS#4. Xn interfaces are established between BS#1 and BS#2, BS#3, and BS#4. · Xn interfaces are not established between BS#4 and BS#2 and BS#3.

[0030] The problems that arise in this situation are: After the UE moves from BS#1 to BS#2, BS#2 must send an XnAP-LTM Configuration Update message to BS#3 and BS#4 to notify them of the change in source BS, but BS#2 cannot send this message to BS#4. When BS#4 decides to cancel LTM while the UE is in the coverage area of ​​BS#2, it sends an XnAP-LTM Cancel message to BS#2, and BS#2 must send an LTM Cancel message (or LTM Configuration Update message) to BS1 and BS#3, but BS#4 cannot send this message to BS#2. When BS#2 instructs the UE to switch cells to BS#4, it must send an XnAP Cell Switch Notification and an XnAP Handover Success message to BS#4, but BS#2 cannot send these to BS#4.

[0031] The solution shown in Fig. 4 above is proposed, but it may be applied to cases where the number of BSs configured for LTM is other than four.

[0032] Solution 1: A procedure may be defined for when BS#2 signals to BS#4 for which the Xn interface has not been established.

[0033] The base station operation may be as follows. The following XnAP signaling or new signaling may be subject to new definition: Early Status Transfer Early / Late data forwarding Cell Switch Notification Handover Success LTM Configuration Update / Acknowledge / Failure TA Information Transfer LTM Cancel

[0034] The sending node operation may be as follows: BS#2 may send signaling via BS#1 to BS#4, which has not yet established an Xn interface.

[0035] The receiving node operation may be as follows: ·When BS#1 receives signaling from BS#2, it may forward the signaling to BS#4. ·When BS#4 discards the LTM configuration of a candidate cell set in a cell under its control, LTM cancellation (option 1) or LTM configuration update (option 2) may be used.

[0036] The common actions may be: Action A: When BS#2 signals to BS#4 via BS#1, the message sent to BS#1 may explicitly notify that BS#4 is the target. Operation B: When BS#2 signals to BS#4 via BS#1, in the preparation phase, BS#2 may notify BS#1 that it does not have an Xn interface with BS#4. Also, when BS#1 receives a message from BS#2, BS#2 may forward the message to BS#4, with which BS#2 does not have an Xn interface.

[0037] Solution 2: A procedure may be defined for the case where BS#2 suppresses the execution of LTM operation for BS#4, which does not have an Xn interface established. The following F1AP message may include a notification of whether or not the BS has an Xn interface with the BS to which each candidate cell belongs. For example, the notification may be included in the LTM configuration mapping list. F1 Setup Request / Response (Alt0) gNB-DU Configuration Update / Acknowledge (Alt0) UE Context Setup Request / Response (Alt1) UE Context Modification Request / Response (Alt1) CU-DU Cell Switch Notification (Alt2)

[0038] Solution 3: A procedure may be defined in which BS#1 decides to set up LTM only when all BSs have established Xn interfaces with each other.

[0039] Alt1: In the following XnAP procedure, the BS may notify information about the BS with which the BS has established an Xn interface (e.g., Global BS ID). Xn Setup NG-RAN node Configuration Update

[0040] Alt2: When a BS decides to configure an LTM, it may configure only BSs that have mutual Xn interfaces as candidate BSs.

[0041] Alt3: In the following XnAP procedure, when a BS is requested to configure LTM, if the list of candidate BSs includes a BS that has not established an Xn interface, the BS may respond with information about the BS (e.g., Global BS ID) and a denial of the LTM configuration. Handover Request LTM Configuration Update

[0042] Figure 5 is a sequence diagram for explaining an example (1) of inter-CU-LTM in an embodiment of the present invention. In the BS deployment scenario in Figure 5, as in Figure 4, it is assumed that there are Xn interfaces between BS#1 and BS#2, BS#3, and BS#4, and there are no Xn interfaces between BS#2 or BS#3 and BS#4. Note that Figure 5 is a sequence for applying the above solution 1.

[0043] In step S101, the UE, BS#1, BS#2, BS#3, and BS#4 perform LTM preparation or previous cell switch. In step S102, the UE camps on BS#2.

[0044] In step S103, BS#2CU transmits an Xn Early Status Transfer to BS#1CU. In step S104, BS#1CU transmits the Xn Early Status Transfer to BS#2CU. In step S105, BS#1CU transmits the Xn Early Status Transfer to BS#4CU.

[0045] In step S106, BS#2CU transmits early user data to BS#1CU. In step S107, BS#1CU transmits the early user data to BS#2CU. In step S108, BS#1CU transmits the early user data to BS#4CU.

[0046] In step S109, the UE transmits L1 measurements to BS#2DU. In step S110, BS#2DU makes an LTM decision. In step S111, BS#2DU transmits a MAC-CE Cell Switch Command (switch to BS#4) to the UE.

[0047] In step S112, BS#2DU sends an F1APDU-CU Cell Switch Notification to BS#2CU. In step S113, BS#2CU sends an XnAP Cell Switch Notification to BS#1CU. In step S114, BS#1CU sends an XnAP Cell Switch Notification to BS#4CU. In step S115, BS#4CU sends an F1APCU-DU Cell Switch Notification to BS#4DU.

[0048] In step S116, the UE switches to BS#4. In step S117, BS#4CU transmits XnAP Handover Success to BS#1CU. In step S118, BS#1CU transmits XnAP Handover Success to BS#2CU.

[0049] In step S119, BS#2CU transmits an XnAP SN Status Transfer to BS#1CU. In step S120, BS#1CU transmits an XnAP SN Status Transfer to BS#4CU.

[0050] In step S121, BS#2CU transmits DL user data to BS#1CU. In step S122, BS#1CU transmits DL user data to BS#4CU.

[0051] In step S123, BS#4CU transmits an XnAPLTM configuration update (XnAP LTM Configuration Update) to BS#1CU. In step S124, BS#1CU transmits an XnAPLTM configuration update (XnAP LTM Configuration Update) to BS#3CU.

[0052] In step S125, BS#3CU transmits an XnAPLTM configuration update acknowledgement (XnAP LTM Configuration Update Acknowledge) to BS#1CU. In step S126, BS#1CU transmits an XnAPLTM configuration update acknowledgement (XnAP LTM Configuration Update Acknowledge) to BS#4CU.

[0053] 6 is a sequence diagram for explaining an example (2) of inter-CU-LTM in the embodiment of the present invention. In the BS deployment scenario in FIG. 6, it is assumed that an Xn interface exists between each BS.

[0054] In step S201, the UE, BS#1, BS#2, BS#3, and BS#4 perform LTM preparation or previous cell switch. In step S202, the UE camps on BS#2.

[0055] In steps S203, S204, and S205, BS#2CU transmits an Xn Early Status Transfer to BS#1CU, BS#3CU, and BS#4CU. In steps S206, S207, and S208, BS#2CU transmits an Xn Early Status Transfer to BS#1CU, BS#3CU, and BS#4CU.

[0056] In step S209, the UE transmits L1 measurements to BS#2DU. In step S210, BS#2DU makes an LTM decision. In step S211, BS#2DU transmits a MAC-CE Cell Switch Command (switch to BS#4) to the UE.

[0057] In step S212, BS#2DU transmits an F1APDU-CU Cell Switch Notification to BS#2CU. In step S213, BS#2CU transmits an XnAP Cell Switch Notification to BS#4CU. In step S214, BS#4CU transmits an F1APCU-DU Cell Switch Notification to BS#4DU.

[0058] In step S215, the UE switches to BS#4. In step S216, BS#4CU transmits XnAP Handover Success to BS#2CU. In step S217, BS#2CU transmits XnAP SN Status Transfer to BS#4CU.

[0059] In step S218, BS#2CU transmits DL user data to BS#4CU. In step S219, BS#4CU transmits an XnAP LTM Configuration Update to BS#2CU. In step S220, BS#2CU transmits an XnAP LTM Configuration Update Acknowledge to BS#4CU.

[0060] Figure 7 is a sequence diagram for explaining an example (3) of inter-CU-LTM in an embodiment of the present invention. In the BS deployment scenario in Figure 5, as in Figure 4, it is assumed that there are Xn interfaces between BS#1 and BS#2, BS#3, and BS#4, and there are no Xn interfaces between BS#2 or BS#3 and BS#4. Note that Figure 7 is a sequence for applying the above solution 1.

[0061] In step S301, the UE, BS#1, BS#2, BS#3, and BS#4 perform LTM preparation or previous cell switch. In step S302, the UE camps on BS#2. In step S303, BS#4 decides to cancel LTM.

[0062] Option 1 will be explained below. In step S304, BS#4CU sends an XnAPLTM Cancel (XnAP LTM Cancel) to BS#1CU. In step S305, BS#1CU sends an XnAPLTM Cancel (XnAP LTM Cancel) to BS#2CU. In step S306, BS#1CU sends an XnAPLTM Cancel (XnAP LTM Cancel) to BS#3CU.

[0063] Option 2 will be described below. In step S307, BS#4CU sends an XnAPLTM configuration update (XnAP LTM Configuration Update) to BS#1CU. In step S308, BS#1CU sends an XnAPLTM configuration update (XnAP LTM Configuration Update) to BS#2CU. In step S309, BS#1CU sends an XnAPLTM configuration update (XnAP LTM Configuration Update) to BS#3CU.

[0064] Option 3 will be described below. In step S310, BS#3CU sends an XnAPLTM configuration update acknowledgement (XnAP LTM Configuration Update Acknowledge) to BS#1CU. In step S311, BS#2CU sends an XnAPLTM configuration update acknowledgement (XnAP LTM Configuration Update Acknowledge) to BS#1CU. In step S312, BS#1CU sends an XnAPLTM configuration update acknowledgement (XnAP LTM Configuration Update Acknowledge) to BS#4CU.

[0065] Figure 8 is a sequence diagram for explaining an example (4) of inter-CU-LTM in an embodiment of the present invention. In the BS deployment scenario in Figure 8, it is assumed that an Xn interface exists between each BS. Note that Figure 8 is a sequence for applying the above solution 2.

[0066] In step S401, the UE, BS#1, BS#2, BS#3, and BS#4 perform LTM preparation or previous cell switch. In step S402, the UE camps on BS#2. In step S403, BS#4 decides to cancel LTM.

[0067] The following describes option 1. In step S404, BS#4CU transmits an XnAPLTM cancel (XnAP LTM Cancel) to BS#2CU.

[0068] The following describes option 2. In step S405, BS#4CU transmits an XnAP LTM configuration update to BS#2CU.

[0069] The following describes option 3. In step S406, BS#2CU transmits an XnAP LTM Configuration Update Acknowledge to BS#4CU.

[0070] Fig. 9 is a sequence diagram for explaining an example (5) of inter-CU-LTM in an embodiment of the present invention. In the BS deployment scenario in Fig. 9, as in Fig. 4, it is assumed that Xn interfaces exist between BS#1 and BS#2, BS#3, and BS#4, and that no Xn interface exists between BS#2 or BS#3 and BS#4.

[0071] In step S501, the UE, BS#1, BS#2, BS#3, and BS#4 perform F1 connection establishment or configuration update. In step S502, the BS#1CU and DU, the BS#2CU and DU, the BS#3CU and DU, and the BS#4CU and DU each perform F1AP F1 Setup / BS-DU Configuration Update. Note that steps S501 and S502 may be referred to as an F1 setup phase.

[0072] In step S503, the UE, BS#1, BS#2, BS#3, and BS#4 establish an F1 connection or perform LTM preparation. In step S504, the BS#1CU and DU, the BS#2CU and DU, the BS#3CU and DU, and the BS#4CU and DU each perform F1AP F1 UE Context Setup / Modification. In step S505, the UE camps on BS#1. Note that steps S503, S504, and S505 may be referred to as an F1 preparation phase.

[0073] In step S506, the UE transmits L1 measurements to BS#1DU. In step S507, BS#1DU makes an LTM decision. In step S508, BS#1DU transmits a MAC-CE Cell Switch Command (switch to BS#2) to the UE.

[0074] In step S509, BS#1DU transmits an F1APDU-CU Cell Switch Notification to BS#1CU. In step S510, BS#1CU transmits an XnAP Cell Switch Notification to BS#2CU. In step S511, BS#2CU transmits an F1APCU-DU Cell Switch Notification to BS#2DU. In step S512, the UE switches to BS#2. Note that steps S506 to S512 may be referred to as the execution phase.

[0075] In step S513, the UE transmits L1 measurements to the BS#2DU. In step S514, the BS#2DU does not make an LTM decision to the BS#4.

[0076] Fig. 10 is a sequence diagram for explaining an example (6) of inter-CU-LTM in an embodiment of the present invention. In the BS deployment scenario in Fig. 10, as in Fig. 4, it is assumed that there are Xn interfaces between BS#1 and BS#2, BS#3, and BS#4, and there are no Xn interfaces between BS#2 or BS#3 and BS#4. Note that Fig. 10 is a sequence for applying the above solution 3.

[0077] In step S601, the UE, BS#1, BS#2, BS#3, and BS#4 perform an Xn connection establishment or configuration update. In steps S602, S603, and S604, the BS#1CU sends an XnAP Xn Setup / NG-RAN node Configuration Update to the BS#2CU, BS#3CU, and BS#4CU, respectively.

[0078] In step S605, BS#1CU decides on the LTM configuration (LTM Configuration Decision). In step S606, BS#1CU sends an XnAP handover request / LTM configuration update request to BS#2CU. In step S607, BS#1CU sends an XnAP handover request / LTM configuration update request to BS#3CU. On the other hand, in step S608, BS#1CU does not send an XnAP handover request / LTM configuration update request to BS#4CU. Note that steps S601 to S608 may be managed by the source BS.

[0079] In step S609, BS#2CU transmits an XnAP handover request acknowledgement / LTM configuration update request acknowledgement (XnAP Handover Request Ack / LTM Configuration Update Request Ack) to BS#1CU. In step S610, BS#3CU transmits an XnAP handover request acknowledgement / LTM configuration update request acknowledgement (XnAP Handover Request Ack / LTM Configuration Update Request Ack) to BS#1CU.

[0080] In step S611, BS#4CU transmits an XnAP handover preparation failure / LTM configuration update failure to BS#1CU. Note that steps S609 to S611 may be managed by the source BS.

[0081] 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.

[0082] According to the above-described embodiment, even if there is no Xn interface between the BSs that are LTM candidate BSs, it is possible to appropriately perform LTM-related settings in all BSs.

[0083] That is, LTM (Lower layer Triggered Mobility) can be set between each base station.

[0084] (Device configuration) Next, 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 will be described. 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 have only a part of the functions of the embodiments. Below, the base station 10 and terminal 20 will be described as examples, but the network node 30 may also have similar functions.

[0085] <Base station 10> Fig. 11 is a diagram showing an example of the functional configuration of the base station 10 according to the embodiment of the present invention. As shown in Fig. 11, 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. 11 is merely an example. The functional divisions and names of the functional units may be any names as long as they can perform the operations according to the embodiment of the present invention. The transmitting unit 110 and the receiving unit 120 may be collectively referred to as a communication unit.

[0086] The transmitter 110 includes a function of generating a signal to be transmitted to the terminal 20 and transmitting the signal wirelessly. The transmitter 110 also transmits setting information, instructions, notifications, etc. related to a low-power wake-up signal to the terminal 20. The transmitter 110 also transmits notifications related to switching of monitoring operations to the terminal. The receiver 120 includes a function of receiving various signals transmitted from the terminal 20 and acquiring, for example, information of higher layers from the received signals. The transmitter 110 also has a function of transmitting PSS, SSS, PBCH, DL / UL control signals, etc. to the terminal 20. The receiver 120 also receives inter-network node messages from other network nodes.

[0087] The setting unit 130 stores preset setting information and various setting information to be transmitted to the terminal 20. The content of the setting information is, for example, information related to the operations described in the embodiments.

[0088] The control unit 140 controls settings, instructions, and notifications related to the operations described in the embodiments. 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.

[0089] <Terminal 20> Fig. 12 is a diagram showing an example of the functional configuration of terminal 20 in an embodiment of the present invention. As shown in Fig. 12, 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. 12 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. Transmitting unit 210 and receiving unit 220 may be collectively referred to as a communication unit.

[0090] The transmitter 210 creates a transmission signal from transmission data and transmits the transmission signal wirelessly. The transmitter 210 also transmits capability information related to the low-power wake-up signal to the base station 10. 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 PSS, SSS, PBCH, DL / UL / SL control signals, etc. transmitted from the base station 10. The receiver 220 also receives paging notification information and configuration information, instructions, and notifications related to the low-power wake-up signal from the base station 10. For example, the receiver 220 receives a low-power wake-up signal from the base station 10. The setting unit 230 stores various configuration information received by the receiver 220 from the base station 10. The setting unit 230 also stores pre-configured configuration information. The content of the configuration information is, for example, information related to the operations described in the embodiments.

[0091] As described in the embodiments, the control unit 240 controls settings, instructions, and notifications related to the operations described in the embodiments. A functional unit related to signal transmission in the control unit 240 may be included in the transmitting unit 210, and a functional unit related to signal reception in the control unit 240 may be included in the receiving unit 220.

[0092] (Hardware configuration) The block diagrams (FIGS. 11 and 12) used to explain the above embodiments show functional blocks. These functional blocks (components) are realized by hardware, software, or a combination of these. Furthermore, the method for realizing each functional block is not particularly limited. That is, each functional block may be realized by using one device that is physically or logically coupled, or may be realized by 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 one device or the multiple devices with software.

[0093] For example, a base station, a terminal, a network node, 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. 13 is a diagram illustrating an example of the hardware configuration of a base station and a terminal according to an embodiment of the present disclosure. The above-described base station 10 and terminal 20 may be physically configured as a computer device including a processor 1001, a memory 1002, a storage 1003, a communication device 1004, an input device 1005, an output device 1006, a bus 1007, etc.

[0094] In the present disclosure, the term "apparatus" may be interchangeable with any two terms selected from a set of terms such as circuit, device, unit, module, chip, means, etc. The hardware configurations of the base station 10 and the terminal 20 may be configured to include one or more of the devices shown in the drawings, or may be configured to exclude some of the devices.

[0095] 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, memory 1002, etc., so that the processor 1001 performs calculations, controls communication by the communication device 1004, and controls the reading, writing, or both reading and writing of data in the memory 1002 and storage 1003.

[0096] The processor 1001, for example, runs an operating system to control the entire computer. 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, a baseband signal processing unit, a call processing unit, etc. may be realized by the processor 1001. Although only one processor 1001 is shown in the figure, there may be multiple processors.

[0097] The processor 1001 also reads programs (program codes), software modules, data, etc. from the storage 1003, the communication device 1004, or both the storage 1003 and the communication device 1004 into the memory 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 401 of the terminal 20 may be implemented by a control program stored in the memory 1002 and running on the processor 1001, and similar implementations may be made for other functional blocks. While the above-described various processes have been described as being executed by a single 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, or may be provided to the computer via the communication device 1004, for example.

[0098] The present disclosure also provides a computer program product including a computer program, which may implement the steps of the methods described in the above embodiments when the computer program is executed by a computer (e.g., the processor 1001).

[0099] The memory 1002 is a computer-readable recording medium and may be configured, for example, as a read-only memory (ROM), an erasable programmable ROM (EPROM), an electrically erasable programmable ROM (EEPROM), a random access memory (RAM), or a combination of at least two of these. The memory 1002 may also be called a register, a cache, a main memory (primary storage device), or the like. The memory 1002 can store executable programs (program codes), software modules, and the like for implementing a wireless communication method according to an embodiment of the present disclosure.

[0100] Storage 1003 is a computer-readable recording medium, and may be, for example, 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, or a combination of at least two of these. Storage 1003 may also be referred to as an auxiliary storage device. The above-mentioned storage medium may be, for example, memory 1002, storage 1003, or a database, server, or other appropriate medium including both memory 1002 and storage 1003.

[0101] The communication device 1004 is hardware (transmitting / receiving device) for communicating between computers via a wired network, a wireless network, or both wired and wireless networks, 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, or a combination of at least two of these. For example, a transmitting / receiving antenna, an amplifier unit, a transmitting / receiving unit, or a transmission path interface may be realized by the communication device 1004. The transmitting / receiving unit may be implemented as a transmitting unit and a receiving unit that are physically or logically separated.

[0102] The input device 1005 is an input device that accepts input from the outside (for example, a keyboard, a mouse, a microphone, a switch, a button, a sensor, or a combination of at least two of these). The output device 1006 is an output device that outputs to the outside (for example, a display, a speaker, an LED lamp, or a combination of at least two of these). The input device 1005 and the output device 1006 may be integrated into one device (for example, a touch panel).

[0103] Furthermore, each device, such as the processor 1001 and the memory 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.

[0104] 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), a field programmable gate array (FPGA), a graphics processing unit (GPU), a neural processing unit (NPU), or a combination of at least two of these, 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.

[0105] <Configuration of this embodiment> (Section 1) a control unit that performs LTM (Lower layer Triggered Mobility) preparation between a terminal, a first network node, and a second network node; a receiver for receiving an Xn (Network interface between NG-RAN nodes) early state transfer from the first network node; a transmitter for transmitting the Xn early state transfer to the second network node; the receiving unit receives early user data from the first network node; The transmitting unit is a network node that transmits the early user data to the second network node. (Section 2) 2. The network node of claim 1, wherein there is no Xn interface between the first network node and the second network node. (Section 3) The receiving unit receives an XnAP (Xn Application) cell switch notification from the first network node; 2. The network node of claim 1, wherein the transmitter transmits the XnAP cell switch notification to the second network node. (Section 4) The receiving unit receives an XnAP (Xn Application) handover success from the second network node; 2. The network node of claim 1, wherein the sending unit sends the XnAP handover success to the first network node. (Section 5) The receiving unit receives an Xn (Xn Application) APLTM configuration update from the second network node; 2. The network node of claim 1, wherein the sending unit sends the XnAPL™ configuration update to a third network node. (Section 6) A procedure for performing a Lower Layer Triggered Mobility (LTM) preparation between a terminal, a first network node, and a second network node; receiving an Xn (Network interface between NG-RAN nodes) early state transfer from the first network node; sending the Xn early state transfer to the second network node; receiving early user data from the first network node; and transmitting the early user data to the second network node.

[0106] Any of the above configurations allows for setting up LTM (Lower layer Triggered Mobility) between base stations. Furthermore, according to paragraphs 2 to 5, even if there is no Xn interface between BSs that are LTM candidate BSs, LTM-related settings can be appropriately performed in all BSs.

[0107] (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.

[0108] The aspects / embodiments described in the present disclosure may be categorized as Long Term Evolution (LTE), LTE-Advanced (LTE-A), International Mobile Telecommunications-Advanced (IMT-Advanced), 4th generation mobile communication system (4G), 5th generation mobile communication system (5G), 5G-Advanced (5G-A), 6th generation mobile communication system (6G), xth generation mobile communication system (x is, for example, an integer or a decimal number)), Future Radio Access (FRA), New Radio (NR), New radio access (NX), Future generation radio access (FX), Open Radio Access Network (O-RAN), Wideband Code Division Multiple Access (W-CDMA) (registered trademark), Global System for Mobile communications (GSM) (registered trademark), CDMA2000, Ultra Mobile Broadband (UMB), Institute of Electrical and Electronics Engineers (IEEE) Engineers) 802.11, IEEE802.11x (where x is any character string such as b, a, g, n, ac, ax, be, or bn, and when x=n it is called Wi-Fi4, when x=ac it is called Wi-Fi5, when x=ax it is called Wi-Fi6 or Wi-Fi6E, when x=be it is Wi-Fi7, and when x=bn it is called Wi-Fi8, etc. Wi-Fi is a registered trademark.), IEEE802.16 (WiMAX (registered trademark), IEEE802.20, UWB (Ultra-Wide Band), Bluetooth (registered trademark), network virtualization technology (e.g., NFV (Network Function Virtualization), SFC (Service Function Chaining), SDN (Software Defined Networking)), or LPWA (Low Power Wide Area). Furthermore, each aspect / embodiment described in the present disclosure may be applied to a system based on a combination of at least two of these technologies. Furthermore, "based on" naturally refers not only to a system that uses the technology, but also to a system that uses an extension or modification of the technology.

[0109] In the present disclosure, any two terms selected from a set of terms such as "base station (BS)", "radio base station", "fixed station (fixed station)", "NodeB", "eNodeB (eNB)", "gNodeB (gNB)", "access point (AP)", "transmission point (TP)", "reception point (RP)", "transmission / reception point (TRP)", "radio unit (RU)", "remote unit (RU)", "control unit (CU)", "distributed unit (DU)", "remote radio head (RRH)", "node", "gateway", "terrestrial base station", "stratospheric base station", "unmanned aerial vehicle", "high altitude platform station (HAPS)", "airborne platform", "panel", "cell", "radio access network (RAN)", and "network" may be used interchangeably.

[0110] Each cell accommodated by a base station may be referred to by terms such as a macro cell, a small cell, a femto cell, a pico cell, a serving cell, or a super cell. In the present disclosure, any two terms selected from a set of terms such as "cell," "sector," "cell group," "carrier," "component carrier," "cluster," "bandwidth part (BWP)," and "carrier bandwidth" may be used interchangeably.

[0111] In the present disclosure, any two terms selected from the set of terms such as "Mobile Station (MS)", "user terminal", "User Equipment (UE)", "Device", "Module" and "Terminal" may be used interchangeably.

[0112] A terminal may be referred to 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, router (e.g., home router, mobile router, etc.), TCU (Telematics Control Unit), or some other suitable terminology.

[0113] The base station and the terminal may each be composed of one or more devices. The devices constituting at least a portion of the base station and the terminal may be called a transmitting device, a receiving device, a communication device, etc. Note that the devices constituting at least a portion of the base station and the terminal may be, for example, an object itself, such as a vehicle, a transport vehicle, an automobile, a motorcycle, a bicycle, a connected car, an excavator, a bulldozer, a wheel loader, a dump truck, a forklift, a train, a bus, a handcar, a rickshaw, a ship and other watercraft, an airplane, a rocket, an unmanned aerial vehicle, a stratospheric base station (e.g., a High Altitude Platform Station (HAPS)), an artificial satellite (e.g., a Low Earth Orbit (LEO) satellite, a Medium Earth Orbit (MEO) satellite, a Geostationary Earth Orbit (GEO) satellite), a drone (registered trademark), a multicopter, a quadcopter, a balloon, or an Internet of Things (IoT) device (e.g., a smart meter, a sensor), or may include, but are not limited to, an object or device mounted on the object. Furthermore, the object may be a moving object (hereinafter referred to as a "moving object"; this does not exclude the case where the moving object is in a stationary state where it is not moving), or may be a fixedly positioned object (hereinafter referred to as a "non-moving object").

[0114] Furthermore, a base station in the present disclosure may be read as a 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 terminal is replaced with communication between multiple terminals (which may be called, for example, D2D (Device-to-Device) or V2X (Vehicle-to-Everything)) or communication of a non-terrestrial network (NTN). In this case, the terminal 20 may be configured to have at least some of the functions of the base station 10 described above. Furthermore, terms such as "uplink" and "downlink" may be read as terms corresponding to communication between terminals (for example, "sidelink") or terms corresponding to NTN (for example, feeder link or service link). For example, an uplink channel or a downlink channel may be read as a sidelink channel.

[0115] The present disclosure is also applicable to cases where at least some of the devices constituting the base station and the terminal operate outside the earth (for example, in the atmosphere or outer space).

[0116] In addition, the term "terminal" in the present disclosure may be read as "base station." In this case, the base station 10 may be configured to have the functions of the terminal 20 described above.

[0117] 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) and 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) and System Information Block (SIB))), other signals, or a combination of at least two of these. Note that the physical layer signaling may be referred to as Layer 1 (L1) control information. The MAC signaling may be referred to as a MAC Control Element (CE) or a MAC Protocol Data Unit (PDU), for example. Furthermore, the RRC signaling may be referred to as an RRC message or an information element (IE) in the RRC message. The RRC message may be, for example, a message used for controlling an RRC connection (for example, setup, reconfiguration, establishment, reestablishment, release, or resume), mobility, a measurement report, or notification of a terminal's capabilities, or may be an information element within the message. Furthermore, notification of information may be explicit or implicit. Note that explicit notification of certain information means notification of the certain information itself, and implicit notification of certain information may mean notification of information other than the certain information, or may mean that the certain information is considered to have been notified when a certain condition is satisfied.Furthermore, notification of information may include not only notification between the same layers of different devices (e.g., between a lower layer or an upper layer of the base station 10 and the terminal 20) but also notification between different layers in the same or different devices (e.g., between a lower layer and an upper layer in the base station 10 or the terminal 20). Furthermore, notification of information from one device to another device may be performed via one or more devices. Regarding any information (e.g., a variable, a constant, a parameter, a setting) described in the present disclosure, even if not specifically stated in the above embodiments, information indicating / specifying (or related to) the any information (value) may be notified from any first device (e.g., a terminal / base station) to any second device (e.g., a base station / terminal).

[0118] The order of the procedures, sequences, flowcharts, etc. of each aspect / embodiment described in this disclosure 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.

[0119] In the present disclosure, a specific operation described as being performed by a base station may be performed by its upper node or by some of its upper nodes (e.g., CU, RU, or DU, etc.) in some cases. It is clear that various operations performed for communication with a terminal in a RAN or core network may be performed by at least some of the base station and other network nodes other than the base station. The other network node may be one node or a combination of multiple nodes. The network node is, for example, a node provided in various core networks such as EPC (Evolved Packet Core) and 5GC (5G Core Network), and provides one or more network functions (NF: Network Functions), but is not limited to this.

[0120] Furthermore, in the present disclosure, the operation of "a terminal receives information from a base station" accompanies the operation of "the base station transmits the information to the terminal," "the base station generates the information," or both. Similarly, the operation of "a terminal transmits information to a base station" accompanies the operation of "the base station receives the information from the terminal." Furthermore, the operation of "a terminal is configured to ..." or "configure UE to ..." may include the operation of "a base station transmits configuration information regarding the configuration of the terminal" and the operation of "a terminal configures a predetermined operation based on the configuration information."

[0121] Each aspect / embodiment described in the present disclosure may be used alone, in combination, or switched depending on the implementation.

[0122] The present disclosure has been described above, but it is for illustrative purposes only, and the present invention is not limited to the aspects / embodiments described in the present disclosure. The present disclosure can be implemented in modified and altered forms without departing from the spirit of the invention. The present disclosure and its modifications and alterations are included in the scope of the present invention and its equivalents.

[0123] 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.

[0124] The radio resource may be defined by a combination of resource units in one or more domains, such as the time domain, the frequency domain, the spatial domain, the code domain, and the power domain.

[0125] For example, resources in the time domain may be defined by one or more time units. The one or more time units may include, but are not limited to, a radio frame, a subframe, a slot, a symbol, a transmission time interval (TTI), or a combination of at least two of these. The time unit may be a fixed-length time unit independent of numerology, a variable-length time unit dependent on numerology, or both. Examples of fixed-length time units include, but are not limited to, a subframe consisting of one or more slots and a radio frame including multiple subframes. Examples of variable-length time units include, but are not limited to, a symbol and a slot including a fixed number of symbols. A certain time unit may be divided into shorter time units. Examples of shorter time units include, but are not limited to, a minislot consisting of fewer symbols than the number of symbols constituting a slot. The above-described time units may include, for example, time units used as units for scheduling, link adaptation, etc. Furthermore, any time unit in the present disclosure may be read as another time unit.

[0126] Numerology is a parameter that defines the physical layer structure, and may be a parameter based on at least one of subcarrier spacing (SCS), symbol length, cyclic prefix length, and sampling time, for example.

[0127] Resources in the frequency domain may be defined, for example, by one or more frequency units. The one or more frequency units may include, for example, subcarriers, resource blocks (RBs), bandwidth parts (BWPs), carrier bandwidths, or a combination of at least two of these, but the terminology of the frequency units is not limited to these. The number of subcarriers included in a frequency unit may be a fixed number regardless of numerology, or may be a variable number that changes depending on numerology. For example, an RB is composed of a predetermined number of consecutive subcarriers in the frequency domain, and the number of subcarriers included in the RB may be the same regardless of numerology, for example, 12, but is not limited to this. A BWP may be composed of, for example, one or more consecutive RBs within a certain carrier bandwidth, but is not limited to this. One or more BWPs may be configured within one carrier for terminal 20, and at least one of the BWPs may be activated. Any frequency unit in the present disclosure may be interchangeable with another frequency unit.

[0128] Furthermore, resources in both the time domain and the frequency domain may be defined by one or more time / frequency units each consisting of a time unit and a frequency unit, such as, but not limited to, a resource element (RE) consisting of one symbol and one subcarrier, a resource element group (REG) consisting of a predetermined number of REs, or a control resource set (CORESET) consisting of a predetermined number of symbols and a predetermined number of RBs.

[0129] Furthermore, resources in the spatial domain may be defined, for example, by one or more spatial units, including, but not limited to, a beam, a layer of MIMO (Multi-Input Multi-Output), an antenna port, or a combination of at least two of these.

[0130] Furthermore, the resources in the code domain may be defined by one or more code units, such as, but not limited to, a cyclic shift (CS), an orthogonal cover code (OCC), or a combination thereof.

[0131] 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.

[0132] The "means" in the configuration of each of the above devices may be replaced with "part," "circuit," "device," etc. [Explanation of symbols]

[0133] 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 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 a Lower Layer Triggered Mobility (LTM) preparation between a terminal, a first network node, and a second network node; a receiver for receiving an Xn (Network interface between NG-RAN nodes) early state transfer from the first network node; a transmitter configured to transmit the Xn early state transfer to the second network node; the receiving unit receives early user data from the first network node; The transmitting unit is a network node that transmits the early user data to the second network node.

2. 2. The network node of claim 1, wherein there is no Xn interface between the first network node and the second network node.

3. The receiving unit receives an Xn Application (XnAP) cell switch notification from the first network node; The network node according to claim 1 , wherein the transmitter transmits the XnAP cell switching notification to the second network node.

4. The receiving unit receives an Xn Application (XnAP) handover success from the second network node; The network node according to claim 1 , wherein the transmitter transmits the XnAP handover success to the first network node.

5. The receiving unit receives an Xn (Xn Application) APLTM setting update from the second network node; The network node of claim 1 , wherein the transmitter transmits the XnAPLTM configuration update to a third network node.

6. performing a Lower layer Triggered Mobility (LTM) preparation between a terminal, a first network node, and a second network node; receiving an Xn (Network interface between NG-RAN nodes) early state transfer from the first network node; sending the Xn early state transfer to the second network node; receiving early user data from the first network node; and transmitting the early user data to the second network node.

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