Network node and communication method

Abstract

A network node according to the present invention comprises: a reception unit that receives, from another network node, a message requesting Lower Layer Triggered Mobility (LTM); a control unit that determines which cells will be LTM candidates; and a transmission unit that transmits a UE context setup request to a subordinate distributed unit (DU) on the basis of the determination. The reception unit receives a UE context setup response from the DU, and the transmission unit transmits a response to the message to the other network node.

Description

Network node and communication method

[0001] The present invention relates to a network node in a communication system and a communication method.

[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 2023

[0006] Currently, only intra-CU LTM during non-DC and intra-SN PSCell LTM (Intra Secondary Node Primary Secondary Cell LTM) during DC without involving the MN (Master Node) are supported. On the other hand, signaling between base stations in LTM during inter-CU or DC is not specified.

[0007] The present invention has been made in view of the above points, and aims to expand the scope of application of LTM (Lower layer Triggered Mobility) in order to enhance mobility.

[0008] According to the disclosed technology, a network node is provided that includes a receiver that receives a message requesting LTM (Lower layer Triggered Mobility) from another network node, a controller that determines which cell to select as an LTM candidate, and a transmitter that transmits a UE context setup request to a subordinate DU (Distributed Unit) based on the determination, wherein the receiver receives a UE context setup response from the DU and the transmitter transmits a response to the message to the other network node.

[0009] According to the disclosed technology, the scope of application of LTM (Lower layer Triggered Mobility) can be expanded to enhance 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. 1 is a diagram for explaining an example of a system in an embodiment of the present invention. A sequence diagram for explaining an example of LTM in an embodiment of the present invention. FIG. 1 is a diagram for explaining an example of a system in an embodiment of the present invention. A sequence diagram for explaining an example of LTM in an embodiment of the present invention. A sequence diagram for explaining an example of LTM in an embodiment of the present invention. A sequence diagram for explaining an example of LTM in an embodiment of the present invention. A diagram for explaining an example of a system in an embodiment of the present invention. A sequence diagram for explaining an example of LTM in an embodiment of the present invention. A diagram for explaining an example of a system in an embodiment of the present invention. A sequence diagram for explaining an example of LTM in an embodiment of the present invention. A diagram for explaining an example of a system in an embodiment of the present invention. A sequence diagram for explaining an example of LTM in an embodiment of the present invention. A diagram illustrating an example of a functional configuration of a base station 10 and a network node 30 in an embodiment of the present invention. A diagram illustrating an example of a functional configuration of a terminal 20 in an embodiment of the present invention. A diagram illustrating an example of a hardware configuration of a base station 10 and a terminal 20 in an embodiment of the present invention. A diagram illustrating an example of a 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.

[0024] In Release 19, mobility enhancements are expected to include functional extensions to support inter-CU (inter-Central Unit) LTM (Lower layer Triggered Mobility) and cases where LTM is performed while maintaining DC (Dual connectivity) (e.g., Non-Patent Document 2).

[0025] Currently, only intra-CU LTM during non-DC and intra-SN PSCell LTM (Intra Secondary Node Primary Secondary Cell LTM) during DC without involving the MN (Master Node) are supported. On the other hand, signaling between base stations during inter-CU or DC is not specified.

[0026] Therefore, the Xn signaling used in inter-CU LTM in general and the Xn signaling between MN and SN in LTM during DC may be defined as follows.

[0027] In Release 18 InterDU-LTM, the CU was required to obtain the following information from the DU:

[0028] ・List of SSB index / CSI-RS index (obtained outside the LTM procedure) ・Target candidate cell ID ・Target candidate LTM configuration ID ・LTM configuration ID mapping list (list of all candidate cell IDs and configuration IDs) ・CSI resource configuration (list of cell IDs and SSB / CSI-RS sets) ・PRACH resource (for early RACH (early random access channel)) ・Lower layer reference configuration ・Lower layer configuration (including CSI report configuration)

[0029] Therefore, the following operations 1)-4) may be performed.

[0030] 1) Inter-CU LTM target preparation: In Release 18, the CU may obtain information from the target gNB that it obtained from the DU via F1 signaling.

[0031] 2) DC Case 1 (SN-DU Switching) LTM Preparation Procedures for setting up LTM in the MN initiated and SN initiated cases may be defined.

[0032] 3) DC Case 2 (MN-DU Switching) LTM Preparation In order to maintain DC with the SN even after the MN is changed, the candidate MN may add the SN in advance during LTM target preparation.

[0033] 4) Conditional LTM Preparation In addition to the above, settings for conditional LTM such as execution conditions may be generated.

[0034] FIG. 3 is a diagram illustrating an example of a system according to an embodiment of the present invention. FIG. 3 illustrates inter-CU LTM in a non-DC state. A UE moves from a source CU and source DU to a target CU and target DU. Connections between CUs are made via XnAP, and between CUs and DUs via F1AP. Other candidate DUs may belong to the source CU and target CU.

[0035] The information required for the source CU to generate an RRCReconfiguration for LTM may be as follows:

[0036] ・List of SSB index / CSI-RS index ・Target candidate cell ID ・LTM configuration ID mapping list (list of all candidate cell IDs and configuration IDs) ・CSI resource configuration (list of cell IDs and SSB / CSI-RS sets) ・PRACH resource configuration (for early RACH) ・TCI state configuration ・SSB Information ・Lower layer reference configuration ・Lower layer configuration (including CSI report configuration)

[0037] Among the above, the information that the source CU needs to signal to obtain may be the following:

[0038] ・Target candidate cell ID ・PRACH resource configuration (for early RACH) ・CSI resource configuration (list of cell IDs and SSB / CSI-RS sets) ・TCI state configuration ・SSB Information ・Lower layer reference configuration ・Lower layer configuration (including CSI report configuration)

[0039] Of the above, the information that may be acquired either by the source CU or the target CU may be as follows: target candidate cell ID > May be determined as such PRACH resource configuration (for early RACH) > May be determined as such whether to perform early RACH CSI resource configuration (list of cell ID and SSB / CSI-RS set) > May be determined as such Lower layer reference configuration > May be determined as which one to generate

[0040] For intra-CU candidates, the source CU may generate the following information by itself: List of SSB index / CSI-RS index Target candidate cell ID LTM configuration ID mapping list (list of all candidate cell IDs and configuration IDs) CSI resource configuration (list of cell IDs and SSB / CSI-RS sets)

[0041] For intra-CU candidates, the source CU may include the following information in the F1 signaling instruction: target candidate cell ID, CSI resource configuration (list of cell IDs and SSB / CSI-RS sets), whether to perform early RACH / UE-based TA measurements, and which DU generates the reference configuration.

[0042] For intra-CU candidates, the source CU may obtain the following information through F1 signaling: PRACH resource configuration (for early RACH), TCI state configuration, SSB information, lower layer reference configuration, and lower layer configuration (including CSI report configuration).

[0043] Option 1: When the source CU indicates acquisition of all, the information on the candidates under the target CU may be as follows.

[0044] The information that the source CU can generate itself may be the following: List of SSB index / CSI-RS index Target candidate cell ID LTM configuration ID mapping list (list of all candidate cell IDs and configuration IDs) CSI resource configuration (list of cell IDs and SSB / CSI-RS sets)

[0045] The information that the source CU includes in the Xn signaling instruction may be: target candidate cell ID, CSI resource configuration (list of cell IDs and SSB / CSI-RS sets), whether to perform early RACH / UE-based TA measurements, and which DU generates the reference configuration.

[0046] The information that the source CU obtains through Xn signaling may be: PRACH resource configuration (for early RACH), TCI state configuration, SSB information, Lower layer reference configuration, and Lower layer configuration (including CSI report configuration).

[0047] Option 2: When the target CU instructs acquisition in response to a request from the source CU, the information about the candidates under the target CU may be as follows:

[0048] The information that the source CU can generate by itself may be the following: List of SSB index / CSI-RS index Target candidate cell ID LTM configuration ID mapping list (list of all candidate cell IDs and configuration IDs) CSI resource configuration (list of cell IDs and SSB / CSI-RS sets)

[0049] The information included in the Xn signaling instruction by the source CU may be the following: - That the LTM has been initiated - The upper limit of the number of candidates that the target CU can generate - Whether the target CU will generate a reference configuration

[0050] The information determined by the target CU may be the following: target candidate cell ID; CSI resource configuration (list of cell IDs and SSB / CSI-RS sets); whether to perform early RACH / UE-based TA measurements; which DU generates the reference configuration

[0051] The information that the source CU obtains through Xn signaling may be: PRACH resource configuration (for early RACH), TCI state configuration, SSB information, Lower layer reference configuration, and Lower layer configuration (including CSI report configuration).

[0052] 4 is a sequence diagram illustrating an example of LTM according to an embodiment of the present invention. In step S101, the source CU makes an LTM initiation decision. In step S101, the source CU may decide on the following instruction items and include them in an LTM request or LTM update.

[0053] Whether to perform LTM Whether to include cells under the target CU in LTM candidates Which cells to set as LTM candidates CSI resource configuration Whether to perform early RACH and / or UE-based TA measurements may be determined for each target cell or target CU The target DU or target CU may be determined for the node that generates the reference configuration

[0054] In step S102, the source CU sends a UE Context Setup for the other candidate to the source DU. In step S103, the source DU sends a response to the source CU. In step S104, the source CU sends an LTM Request to the target CU.

[0055] In step S105, the target CU executes a configuration decision. In step S105, the target CU may decide on the following instruction items and issue instructions to the subordinate DUs.

[0056] Which cells are candidates for LTM? CSI resource configuration Whether to perform early RACH and / or UE-based TA measurements may be determined for each target cell. The target DU may be determined for the node that generates the reference configuration.

[0057] In step S106, the target CU sends a UE Context Setup Request to the target DU. In step S107, the target DU sends a UE Context Setup Response to the target CU. In step S108, the target CU sends an LTM Request Ack to the source CU. The target CU may return information obtained as a result of preparing the candidate cells under its control in steps S106 and S107 to the source CU.

[0058] In step S109, the source CU sends a source-oriented UE context modification (UE Context Mod) to the source DU, and in step S110, the source DU sends a response to the source CU.

[0059] In step S111, the source CU sends an LTM Update to the target CU. In step S112, the target CU sends a UE Context Setup Request to the target DU. In step S113, the target DU sends a UE Context Setup Response to the target CU. In step S114, the target CU sends an LTM Update Ack to the source CU. In step S115, the source CU sends an RRCReconfiguration to the UE.

[0060] The following information may be included in the LTM request or LTM update message: - Indicator for whether to trigger LTM - Target candidate cell ID - Source cell ID - LTM configuration ID - Other candidates list (a list of the following information for all candidates) - Cell ID - LTM configuration ID - Node ID - Lower layer configuration - RACH configuration - TCI state configuration list - Indicator for requesting generation of lower layer reference configuration - Lower layer reference configuration - CSI resource configuration (list of cell ID / configuration ID and SSB / CSI-RS set) - Indicator for requesting generation of RACH configuration for early RACH - Indicator for requesting use of UE based TA measurements or generation of configuration for that purpose - Node ID

[0061] The message may contain only one piece of the above information, or multiple pieces of information as a list. The above information may be included as an independent Information Element (IE), or may be included in some kind of list.

[0062] The LTM request or LTM update message may be an existing Xn message (eg, Handover Request) or a new message.

[0063] The node ID may be the ID of the source and / or target gNB / CU / DU in Xn and / or F1 (e.g. gNB-DU UE F1AP ID), or the ID of the node itself (e.g. Source gNB-DU ID, Global gNB ID).

[0064] Table 1 shows examples of information elements included in an LTM request or LTM update message.

[0065]

[0066] The LTM request confirm or LTM update confirm message may contain the following information:

[0067] - Indicator to reject the LTM trigger (may be sent in the LTM Preparation Failure message) - Accepted Target candidate cell ID - Accepted LTM configuration ID - Indicator to request generation of Lower layer reference configuration - Lower layer reference configuration - Indication whether the Lower layer configuration is full or delta - Accepted CSI resource configuration (list of cell ID / configuration ID and SSB / CSI-RS set) - Accepted SSB index or CSI-RS index - SSB Information / CSI-RS Information (list of information required to identify SSB or CSI-RS) - RACH configuration for early RACH - Indication or configuration for UE based TA measurements - Node ID

[0068] The above information may be included in a message only once, or multiple pieces of information may be included as a list. The above information may be included as an independent IE or may be included in some kind of list.

[0069] The LTM request acknowledgement or LTM update acknowledgement message may be an existing Xn message (eg, Handover Request Ack) or a new message.

[0070] The node ID may be the ID of the source and / or target gNB / CU / DU in Xn and / or F1 (e.g. gNB-DU UE F1AP ID), or the ID of the node itself (e.g. Source gNB-DU ID, Global gNB ID).

[0071] Table 2 shows examples of information elements included in the LTM request confirm or LTM update confirm message.

[0072]

[0073] The UE Context Setup, UE Context Modification Request, or Response message may include the ID of the source and / or target gNB, CU, or DU in Xn and / or F1 (e.g., gNB-DU UE F1AP ID), or may include the ID of the node itself (e.g., Source gNB-DU ID, Global gNB ID).

[0074] The above information may be included in a message only once, or multiple information may be included as a list. The above information may be included as an independent IE or may be included in some kind of list. The above information may be sent in another existing F1 message or in a new message.

[0075] Table 3 shows examples of information elements included in F1 signaling of a UE Context Setup, UE Context Modification Request, or Response message.

[0076]

[0077] FIG. 5 is a diagram illustrating an example of a system according to an embodiment of the present invention. FIG. 5 illustrates an inter-CU LTM in DC state. A UE moves from a source SN-CU and source SN-DU to a target SN-CU and target SN-DU. Other candidate DUs may belong to the source SN-CU and target SN-CU.

[0078] 6 is a sequence diagram illustrating an example of LTM in an embodiment of the present invention. In step S201, the MN-CU makes an LTM initiation decision. In step S201, the MN-CU may decide on the following instruction items and include them in an LTM request or LTM update to the SN:

[0079] Whether to perform LTM Whether to include cells under the target SN in LTM candidates Which cells to set as LTM candidates CSI resource configuration Whether to perform early RACH and / or UE-based TA measurements may be determined for each target cell or target CU The target DU or target CU may be determined for the node that generates the reference configuration

[0080] In step S202, the MN-CU sends a UE Context Setup for the other candidate to the MN-DU. In step S203, the MN-DU sends a response to the MN-CU. In step S204, the MN-CU sends an SN LTM Request to the target SN-CU (T-SN CU).

[0081] In step S205, the target SN-CU makes a configuration decision, and may decide on the following instruction items and issue instructions to the subordinate DUs:

[0082] Which cells are candidates for LTM? CSI resource configuration Whether to perform early RACH and / or UE-based TA measurements may be determined for each target cell. The target DU may be determined for the node that generates the reference configuration.

[0083] In step S206, the target SN-CU sends a UE Context Setup Request to the target SN-DU. In step S207, the target SN-DU sends a UE Context Setup Response to the target SN-CU. In step S208, the target SN-CU sends an SN LTM Request Ack to the MN-CU. The target SN-CU may return information obtained as a result of preparing the candidate cells under its control in steps S206 and S207 to the MN-CU.

[0084] In step S209, the MN-CU sends a source-directed UE Context Modification to the MN-DU, and in step S210, the MN-DU sends a UE Context Modification Response to the MN-CU.

[0085] In step S211, the MN-CU sends an SN LTM Update to the target SN-CU. In step S212, the target SN-CU sends a UE Context Setup Modification to the target SN-DU. In step S213, the target SN-DU sends a UE Context Modification Response to the target CU. In step S214, the target SN-CU sends an SN LTM Update Ack to the MN-CU.

[0086] The MN may perform the same preparation procedure for the source SN as for the target SN. In step S215, the MN-CU sends an SN LTM Update to the source SN-CU. In step S216, the source SN-CU sends an SN LTM Request Ack to the MN-CU. In step S217a, the MN-CU sends an RRC Reconfiguration to the UE. Alternatively, in step S217b, the source SN may send an RRC Reconfiguration to the UE. That is, the RRC Reconfiguration to the UE may be generated and sent by the MN or the source SN.

[0087] 7 is a sequence diagram illustrating an example of LTM according to an embodiment of the present invention. In step S301, the MN-CU makes an LTM initiation decision. In step S301, the MN-CU may decide on the following instruction items and include them in an LTM request or LTM update to the SN:

[0088] Whether to perform LTM Whether to include cells under the target SN in LTM candidates Which cells to set as LTM candidates CSI resource configuration Whether to perform early RACH and / or UE-based TA measurements may be determined for each target cell or target CU The target DU or target CU may be determined for the node that generates the reference configuration

[0089] In step S302, the MN-CU sends a UE Context Setup for the other candidate to the MN-DU. In step S303, the MN-DU sends a response to the MN-CU. In step S204, the MN-CU sends an SN LTM Request to the source SN-CU (S-SN CU).

[0090] In step S305, the source SN may execute a procedure similar to the preparation phase of inter-CU LTM in non-DC mode for the target SN. The result of the preparation phase may be included in an SN LTM request acknowledgement and transmitted to the MN. In step S306, the source SN-CU transmits an SN LTM request acknowledgement (SN LTM Request Ack) to the MN-CU.

[0091] The MN may perform the same preparation procedure for the source SN as for the target SN. In step S307a, the MN-CU sends an RRCReconfiguration to the UE. Alternatively, in step S307b, the source SN may send an RRCReconfiguration to the UE. That is, the RRCReconfiguration to the UE may be generated and sent by the MN or the source SN.

[0092] 8 is a sequence diagram illustrating an example of LTM in an embodiment of the present invention. In step S401, the source SN-CU makes an LTM initiation decision. In step S401, the source SN-CU may decide on the following instructions and include them in the SN LTM Required for the MN:

[0093] Whether to perform LTM Whether to include cells under the target SN in LTM candidates Which cells to set as LTM candidates CSI resource configuration Whether to perform early RACH and / or UE-based TA measurements may be determined for each target cell or target CU The target DU or target CU may be determined for the node that generates the reference configuration

[0094] In step S402, the source SN-CU sends an SN LTM Required to the MN-CU.

[0095] In step S403, the MN may perform the same procedure as in Figure 6 or 7. The result of the procedure may be sent to the source SN in an SN LTM mandatory confirmation.

[0096] In step S403, the MN-CU makes a configuration decision, which may include determining the following instruction items and issuing instructions to the subordinate DU, source SN, and / or target SN:

[0097] Which cells are candidates for LTM? CSI resource configuration Whether to perform early RACH and / or UE-based TA measurements may be determined for each target cell. The target DU may be determined for the node that generates the reference configuration.

[0098] In step S404, the MN-CU sends an SN LTM Required Ack to the source SN-CU. Note that in the procedure of FIG. 6 executed in FIG. 8, step S215 may be regarded as step S404, in which case step S216 may be omitted. When the procedure of FIG. 6 is executed in FIG. 8, step S404 may be omitted or may be executed before step S403.

[0099] The MN may perform the same preparation procedure for the source SN as for the target SN. In step S405a, the MN-CU sends an RRCReconfiguration to the UE. Alternatively, in step S405b, the source SN may send an RRCReconfiguration to the UE. That is, the RRCReconfiguration to the UE may be generated and sent by the MN or the source SN.

[0100] 9 is a sequence diagram illustrating an example of LTM in an embodiment of the present invention. In step S501, the source SN-CU makes an LTM initiation decision. In step S501, the source SN-CU may decide on the following instructions and include them in the SN LTM Required for the MN:

[0101] Whether to perform LTM Whether to include cells under the target SN in LTM candidates Which cells to set as LTM candidates CSI resource configuration Whether to perform early RACH and / or UE-based TA measurements may be determined for each target cell or target CU The target DU or target CU may be determined for the node that generates the reference configuration

[0102] In step S502, the source SN may execute a procedure for the target SN similar to the preparation phase of the inter-CU LTM in the non-DC state. The result of the preparation phase may be included in an SN LTM Required and sent to the MN. In step S503, the source SN-CU sends an SN LTM Required to the MN-CU. In step S504, the MN-CU sends an SN LTM Required Ack to the source SN-CU.

[0103] The MN may perform the same preparation procedure for the source SN as for the target SN. In step S505a, the MN-CU sends an RRCReconfiguration to the UE. Alternatively, in step S505b, the source SN may send an RRCReconfiguration to the UE. That is, the RRCReconfiguration to the UE may be generated and sent by the MN or the source SN.

[0104] The above-mentioned LTM Request and LTM Update messages may be replaced with SN LTM Request, SN LTM Update, and SN LTM Required. That is, the IEs included in the above-mentioned LTM Request and LTM Update messages may be included in SN LTM Request, SN LTM Update, and SN LTM Required.

[0105] The above-mentioned LTM request confirm and LTM update confirm messages may be replaced with SN LTM request confirm, SN LTM update confirm, and SN LTM required confirm. That is, the IEs included in the above-mentioned LTM request confirm and LTM update confirm messages may be included in SN LTM request confirm, SN LTM update confirm, and SN LTM required confirm.

[0106] The SN LTM Request, SN LTM Update, and SN LTM Mandatory Confirm may include an RRCReconfiguration, which includes the lower layer configuration of the MN.

[0107] The LTM update confirmation, SN LTM request confirmation, and SN LTM mandatory may include RRCReconfiguration, which includes lower layer configuration of SN.

[0108] The SN LTM Request, SN LTM Update, SN LTM Request Confirm, and SN LTM Update Confirm messages may be existing Xn messages (eg, SN Addition Request) or new messages.

[0109] The node ID may be the ID of the source and / or target gNB / CU / DU in Xn and / or F1 (e.g. gNB-DU UE F1AP ID), or the ID of the node itself (e.g. Source gNB-DU ID, Global gNB ID). The node ID may also be the ID of the source or target MN or SN in Xn (e.g. M-NG-RAN node UE XnAP ID).

[0110] The UE Context Setup, UE Context Modification or UE Context Response message may contain the ID of the source and / or target gNB / CU / DU in Xn and / or F1 (e.g. gNB-DU UE F1AP ID), or the ID of the node itself (e.g. Source gNB-DU ID, Global gNB ID), and may further contain the ID of the source or target MN or SN in Xn (e.g. M-NG-RAN node UE XnAP ID).

[0111] In addition to the above, the ID of the source or target MN or SN in Xn (e.g., M-NG-RAN node UE XnAP ID) may also be included.

[0112] The above information may be included in a message only once, or multiple information may be included as a list. The above information may be included as an independent IE or may be included in some kind of list. The above information may be sent in another existing F1 message or in a new message.

[0113] FIG. 10 is a diagram illustrating an example of a system according to an embodiment of the present invention. FIG. 10 illustrates an inter-CU LTM in DC state. A UE moves from a source MN-CU and source MN-DU to a target MN-CU and target MN-DU. Other candidate DUs may belong to the source MN-CU and target MN-CU.

[0114] 11 is a sequence diagram illustrating an example of LTM in an embodiment of the present invention. In step S601, the source MN-CU makes an LTM initiation decision. In step S601, the source MN-CU may decide on the following instruction items and include them in an LTM request or LTM update.

[0115] Whether to perform LTM Whether to include cells under the target SN in LTM candidates Which cells to set as LTM candidates CSI resource configuration Whether to perform early RACH and / or UE-based TA measurements may be determined for each target cell or target CU The target DU or target CU may be determined for the node that generates the reference configuration

[0116] In step S602, the source MN-CU sends a UE Context Setup for the other candidate to the source MN-DU. In step S603, the source MN-DU sends a UE Context Setup Response to the MN-CU. In step S604, the source MN-CU sends an LTM Request to the target MN-CU (T-MN CU).

[0117] In step S605, the target MN-CU makes a configuration decision, which may include determining the following instruction items and issuing instructions to the subordinate DUs:

[0118] Which cells are candidates for LTM? CSI resource configuration Whether to perform early RACH and / or UE-based TA measurements may be determined for each target cell. The target DU may be determined for the node that generates the reference configuration.

[0119] In step S606, the target MN-CU sends a UE Context Setup Request to the target MN-DU. In step S607, the target MN-DU sends a UE Context Setup Response to the target MN-CU. In step S608, the target MN-CU sends an SN LTM request confirmation to the SN-CU. The target MN-CU may send information obtained as a result of preparing the candidate cells under its control in steps S606 and S607 to the SN-CU.

[0120] In step S609, the SN-CU sends an SN LTM request acknowledgement (SN LTM Request Ack) to the target MN-CU. In step S610, the target MN-CU sends an LTM request acknowledgement (LTM Request Ack) to the source MN-CU. In step S611, the source MN-CU sends a UE Context Setup Modification to the source MN-DU. In step S612, the source MN-DU sends a UE Context Modification Response to the source MN-CU.

[0121] In step S613, the source MN-CU sends an LTM Update to the target MN-CU. In step S614, the target MN-CU sends a UE Context Setup Modification to the target MN-DU. In step S615, the target MN-DU sends a UE Context Modification Response to the target MN-CU. The target MN may receive information about the SN in which the source MN is currently running DC, and may perform preparations for DC establishment with the SN.

[0122] In step S616, the target MN-CU sends an LTM Update Ack to the source MN-CU, and in step S617, the source MN-CU sends an RRCReconfiguration to the UE.

[0123] The LTM Request and LTM Update may include the source SN node ID. The SN LTM Request, SN LTM Update, and SN LTM Mandatory Confirm may include an RRCReconfiguration containing lower layer configuration for the MN. The LTM Update Confirm, SN LTM Request Confirm, and SN LTM Mandatory may include an RRCReconfiguration containing lower layer configuration for the SN.

[0124] The SN LTM Request, SN LTM Update, SN LTM Request Confirm, and SN LTM Update Confirm messages may be existing Xn messages (eg, SN Addition Request) or new messages.

[0125] The UE Context Setup, UE Context Modification or UE Context Response message may contain the ID of the source and / or target gNB / CU / DU in Xn and / or F1 (e.g. gNB-DU UE F1AP ID), or the ID of the node itself (e.g. Source gNB-DU ID, Global gNB ID), and may further contain the ID of the source or target MN or SN in Xn (e.g. M-NG-RAN node UE XnAP ID).

[0126] The above information may be included in a message only once, or multiple information may be included as a list. The above information may be included as an independent IE or may be included in some kind of list. The above information may be sent in another existing F1 message or in a new message.

[0127] FIG. 12 is a diagram illustrating an example of a system according to an embodiment of the present invention. FIG. 12 illustrates inter-CU LTM in a non-DC state. A UE moves from a source CU and source DU to a target CU and target DU. Connections between CUs are made via XnAP, and between CUs and DUs via F1AP. Other candidate DUs may belong to the source CU and target CU.

[0128] 13 is a sequence diagram illustrating an example of LTM according to an embodiment of the present invention. In step S701, the source CU makes an LTM initiation decision. In step S701, the source CU may decide on the following instruction items and include them in an LTM request or LTM update.

[0129] Lower layer settings of source cells and candidate cells under the source CU Execution conditions determined by the source CU

[0130] In step S702, the source CU sends a UE Context Setup for the other candidate to the source DU. In step S703, the source DU sends a response to the source CU. In step S704, the source CU sends an LTM Request to the target CU.

[0131] In step S705, the target CU performs a configuration decision. In step S705, the target CU or a subordinate DU may determine execution conditions for conditional LTM of subordinate candidate cells. The execution conditions may include execution conditions for initial LTM cell switching and execution conditions for continuous LTM and a list of corresponding candidate IDs. The execution conditions may be determined by the source CU, a subordinate DU of the source CU, the target CU, or a subordinate DU of the target CU.

[0132] In step S706, the target CU sends a UE Context Setup Request to the target DU. In step S707, the target DU sends a UE Context Setup Response to the target CU. In step S708, the target CU sends an LTM Request Ack to the source CU.

[0133] In step S709, the source CU sends a source-oriented UE context modification (UE Context Mod) to the source DU, and in step S710, the source DU sends a response to the source CU.

[0134] In step S711, the source CU sends an LTM Update to the target CU. In step S712, the target CU sends a UE Context Setup Request to the target DU. In step S713, the target DU sends a UE Context Setup Response to the target CU. In step S714, the target CU sends an LTM Update Ack to the source CU. In step S715, the source CU sends an RRCReconfiguration to the UE.

[0135] In addition to the information shown in Table 1 or Table 2, the LTM request, LTM request confirmation, LTM update, or LTM update confirmation may include an execution condition for conditional LTM for each candidate cell.

[0136] The execution conditions may include an execution condition for an initial LTM cell switch, and an execution condition for subsequent LTM and a list of corresponding candidate IDs.

[0137] The above information may be included as a separate IE, sent as a container, or included in some list. The above message may be an existing Xn message (e.g., Handover Request Ack) or a new message.

[0138] Table 4 is an example of an IE indicating execution conditions.

[0139]

[0140] In addition to the information shown in Table 3, the UE context setup, UE context modification, or UE context response message may include an execution condition for conditional LTM for each candidate cell.

[0141] The execution conditions may include an execution condition for an initial LTM cell switch, and an execution condition for subsequent LTM and a list of corresponding candidate IDs.

[0142] The above information may be included as a separate IE, sent as a container, or included in some list. The above message may be an existing F1 message (e.g., UE Context Setup Response) or a new message.

[0143] Table 5 is an example of an IE indicating execution conditions.

[0144]

[0145] According to the above embodiment, inter-CU LTM and LTM during DC or conditional LTM can be configured for the UE.

[0146] That is, in order to enhance mobility, the scope of application of LTM (Lower layer Triggered Mobility) can be expanded.

[0147] (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.

[0148] <Base Station 10 and Network Node 30> Fig. 14 is a diagram showing an example of the functional configuration of the base station 10 and the network node 30. As shown in Fig. 14, 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. 14 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.

[0149] 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.

[0150] 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.

[0151] 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.

[0152] <Terminal 20> Fig. 15 is a diagram showing an example of the functional configuration of the terminal 20. As shown in Fig. 15, 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. 15 is merely an example. The names of the functional divisions and functional units may be any as long as they can perform the operations related to the embodiment of the present invention.

[0153] 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.

[0154] 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.

[0155] 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.

[0156] (Hardware Configuration) The block diagrams (FIGS. 14 and 15) used to explain the above embodiments show functional blocks. These functional blocks (components) are realized by any combination of at least one of hardware and software. Furthermore, the method for realizing each functional block is not particularly limited. That is, each functional block may be realized using a single device that is physically or logically coupled, or may be realized using two or more physically or logically separated devices that are connected directly or indirectly (for example, 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.

[0157] 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.

[0158] 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. 16 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.

[0159] 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.

[0160] 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.

[0161] 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.

[0162] Furthermore, the processor 1001 reads programs (program codes), software modules, data, etc. from at least one of the auxiliary storage device 1003 and the communication device 1004 into the storage device 1002 and executes various processes in accordance with the programs. The programs used are those that cause a computer to execute at least some of the operations described in the above-described embodiments. For example, the control unit 140 of the base station 10 shown in FIG. 14 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. 15 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.

[0163] 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.

[0164] 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.

[0165] 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.

[0166] 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).

[0167] 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.

[0168] 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.

[0169] Fig. 17 shows an example configuration of a vehicle 2001. As shown in Fig. 17, 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.

[0170] 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.

[0171] 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).

[0172] 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.

[0173] 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.

[0174] 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.

[0175] 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.

[0176] 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.

[0177] 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.

[0178] 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.

[0179] (Summary of embodiment) As described above, according to the embodiment of the present invention, there is provided a network node including: a receiver that receives a message requesting LTM (Lower layer Triggered Mobility) from another network node; a controller that determines which cell should be an LTM candidate; and a transmitter that transmits a UE context setup request to a subordinate DU (Distributed Unit) based on the determination, wherein the receiver receives a UE context setup response from the DU, and the transmitter transmits a response to the message to the other network node.

[0180] With the above configuration, it is possible to configure inter-CU LTM, LTM in DC, or conditional LTM for the UE. That is, to enhance mobility, it is possible to expand the application range of LTM (Lower layer Triggered Mobility).

[0181] The control unit may include information related to lower layer configuration in the response. With this configuration, inter-CU LTM, LTM in DC, or conditional LTM can be configured for the UE.

[0182] The controller may include an ID of the source base station or the target base station in the UE context setup request. This configuration allows the UE to be configured with inter-CU LTM, LTM in DC, or conditional LTM.

[0183] The controller may determine whether to execute an early random access channel for each target cell. This configuration allows the UE to be configured with inter-CU LTM and LTM during DC, or conditional LTM.

[0184] The control unit may determine an execution condition for the conditional LTM and include the execution condition in the response or the UE context setup request. With this configuration, it is possible to set inter-CU LTM and LTM in DC, or conditional LTM, in the UE.

[0185] Furthermore, according to an embodiment of the present invention, there is provided a communication method in which a network node executes the following procedures: receiving a message requesting LTM (Lower layer Triggered Mobility) from another network node; determining which cell to select as an LTM candidate; transmitting a UE context setup request to a subordinate DU (Distributed Unit) based on the determination; receiving a UE context setup response from the DU; and transmitting a response to the message to the other network node.

[0186] With the above configuration, it is possible to configure inter-CU LTM, LTM in DC, or conditional LTM for the UE. That is, to enhance mobility, it is possible to expand the application range of LTM (Lower layer Triggered Mobility).

[0187] (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.

[0188] 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.

[0189] 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).

[0190] 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.

[0191] 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).

[0192] 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.

[0193] 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.

[0194] 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).

[0195] 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.

[0196] 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.

[0197] 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.

[0198] 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.

[0199] As used in this disclosure, the terms "system" and "network" are used interchangeably.

[0200] 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.

[0201] 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.

[0202] 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.

[0203] 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.

[0204] 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.

[0205] In this disclosure, the terms "Mobile Station (MS)," "user terminal," "User Equipment (UE)," "terminal," and the like may be used interchangeably.

[0206] 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.

[0207] 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.

[0208] 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.

[0209] 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.

[0210] 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.

[0211] 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.

[0212] The reference signal may be abbreviated as RS (Reference Signal) or may be called a pilot depending on the applicable standard.

[0213] 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."

[0214] 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.

[0215] The "means" in the configuration of each of the above devices may be replaced with "part," "circuit," "device," etc.

[0216] 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.

[0217] 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.

[0218] 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."

[0219] 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).

[0220] 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.

[0221] 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 network node having a receiver that receives a message requesting LTM (Lower layer Triggered Mobility) from another network node, a controller that determines which cell to select as an LTM candidate, and a transmitter that transmits a UE context setup request to a subordinate DU (Distributed Unit) based on the determination, wherein the receiver receives a UE context setup response from the DU, and the transmitter transmits a response to the message to the other network node.

2. The network node according to claim 1, wherein the control unit includes information relating to lower layer settings in the response.

3. The network node according to claim 1, wherein the control unit includes an ID of a source base station or a target base station in the UE context setup request.

4. The network node according to claim 1, wherein the control unit determines for each target cell whether to execute an early random access channel.

5. The network node according to claim 1, wherein the control unit determines an execution condition for the conditional LTM and includes the execution condition in the response or the UE context setup request.

6. A communication method in which a network node performs the following steps: receiving a message requesting LTM (Lower layer Triggered Mobility) from another network node; determining which cell to select as an LTM candidate; sending a UE context setup request to a subordinate DU (Distributed Unit) based on the determination; receiving a UE context setup response from the DU; and sending a response to the message to the other network node.

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