Network node and communication method

Abstract

A network node according to the present invention has a reception unit that receives a random access channel preamble from a terminal in a dual connectivity (DC) state, a control unit that calculates a timing advance (TA) value on the basis of the random access channel preamble, and a transmission unit that transmits a message that includes at least the TA value to a master node (MN) or a source secondary node (SN) via a target SN central unit (CU). The control unit executes lower layer triggered mobility (LTM) for the terminal as having executed early UL synchronization on the basis of the TA value.

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 define signaling related to LTM (Lower layer Triggered Mobility) in order to enhance mobility.

[0008] According to the disclosed technology, a network node is provided that includes, in a DC (Dual connectivity) state, a receiving unit that receives a random access channel preamble from a terminal, a control unit that calculates a TA (Timing Advance) value based on the random access channel preamble, and a transmitting unit that transmits a message including at least the TA value to a MN (Master Node) or a source SN via a target SN (Secondary Node)-CU (Central Unit), wherein the control unit executes LTM (Lower layer Triggered Mobility) of the terminal that has executed early UL synchronization based on the TA value.

[0009] According to the disclosed technology, signaling related to LTM (Lower layer Triggered Mobility) can be defined 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. FIG. 1 is a diagram for explaining an example of a system 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. FIG. 1 is a sequence diagram for explaining an example of an LTM in an embodiment of the present invention. FIG. 1 is a sequence diagram for explaining an example of an LTM in an embodiment of the present invention. FIG. 1 is a diagram for explaining an example of an LTM in an embodiment of the present invention. FIG. 1 is a diagram for explaining an example of an LTM in an embodiment of the present invention. A diagram showing an example of the functional configuration of a base station 10 and a network node 30 in an embodiment of the present invention. A diagram showing an example of the functional configuration of a terminal 20 in an embodiment of the present invention. A diagram showing an example of the hardware configuration of a base station 10 and a terminal 20 in an embodiment of the present invention. A diagram showing an example of the configuration of a vehicle 2001 in an embodiment of the present invention.

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

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

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

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

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

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

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

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

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

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

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

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

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

[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] 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.

[0028] FIG. 4 is a diagram illustrating an example of a system according to an embodiment of the present invention. FIG. 4 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.

[0029] 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 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.

[0030] When early UL synchronization is performed, the target gNB may notify the source gNB of the calculated TA (Timing Advance) value. For example, the following cases 1)-3) may be assumed.

[0031] Case 1) When the candidate configuration is configured in a non-DC state with an inter-gNB, as shown in Figure 3. Case 2) When the candidate configuration is configured with multiple candidate SNs and a single MN, as shown in Figure 4. Case 3) When the candidate configuration is configured with multiple candidate MNs and a single SN, as shown in Figure 5.

[0032] After the target DU receives the RACH preamble and sends the calculated TA value to the target CU via F1 signaling, the target CU may forward the TA value to the source CU via Xn signaling.

[0033] The target DU may determine the destination to send the above TA value from the RACH settings for early UL sync received from the source gNB during the preparation phase and the ID of the source gNB or source DU.

[0034] The target DU may send the DU-CU TA Information Transfer of the F1AP, including the ID of the source gNB.

[0035] The above information may be sent in an independent IE (Information Element), in a container, or included in some kind of list.

[0036] The above Xn or F1 message may be sent in the following cases 1) to 5). Any of the following cases may be either NW triggered LTM or UE triggered LTM.

[0037] 1) In the non-DC state interCU LTM of case 1) above, when the target gNB notifies the source gNB of the TA value. 2) In the DC state interCU LTM of case 2) above, when the target SN notifies the source SN or MN of the TA value. 3) In the DC state interCU LTM of case 2) above, when the source SN notifies the MN of the TA value. 4) In the DC state interCU LTM of case 2) above, when the MN notifies the source SN of the TA value. 5) In the DC state interCU LTM of case 3) above, when the target MN notifies the source MN of the TA value.

[0038] Information regarding the TA value may be sent from the original source DU or source gNB to the new source DU or source gNB in ​​an F1 or Xn message when an LTM cell switch is performed and the target DU or target gNB becomes the source DU or source gNB in ​​a subsequent LTM.

[0039] Table 1 shows an example of the IE included in the above Xn or F1 message.

[0040]

[0041] 6 is a sequence diagram illustrating an example of LTM in an embodiment of the present invention. In step S101, the system performs preparation. This preparation may be preparation for LTM. In step S102, the system enables DL synchronization and TCI (Transmission Configuration Indication) states. Execution of step S102 may be optional.

[0042] In step S103, the source DU sends a PDCCH order to the UE. In step S104, the UE sends a RACH preamble to the target DU. In step S105, the target DU calculates the TA.

[0043] In step S106, the target DU sends a message (TA info Transfer) including information on the TA value to the target CU. In step S107, the target CU sends a message including information on the TA value to the source CU. In step S108, the source CU sends a message including information on the TA value to the source DU. In step S109, the UE performs LTM cell switch to move from the source SN-DU to the target SN-DU.

[0044] 7 is a sequence diagram illustrating an example of LTM in an embodiment of the present invention. In step S201, the UE receives a PDCCH order. In step S202, the UE transmits a RACH preamble to the target SN-DU. In step S203, the target SN-DU calculates the TA. In step S204, the target SN-DU transmits a message (TA info transfer) including information related to the TA to the target SN-CU.

[0045] In step S211, the target SN-CU sends a message including information related to the TA to the MN-CU. In step S212, the MN-CU sends a message including information related to the TA to the MN-DU. Steps S211 and S212 show a procedure initiated by the MN and in which the message is sent to the MN.

[0046] In step S221, the target SN-CU sends a message including information related to the TA to the source SN-CU. In step S222, the source SN-CU sends a message including information related to the TA to the source SN-DU. Steps S221 and S222 show a procedure initiated by the SN and in which the message is sent to the SN.

[0047] In step S231, the target SN-CU sends a message including information related to the TA to the MN-CU. In step S232, the MN-CU sends a message including information related to the TA to the source SN-CU. In step S233, the source SN-CU sends a message including information related to the TA to the source SN-DU. Steps S231 to S233 show a procedure initiated by the SN, in which the message is sent to the SN via the MN.

[0048] In step S241, the target SN-CU sends a message including information related to the TA to the source SN-CU. In step S242, the source SN-CU sends a message including information related to the TA to the MN-CU. In step S243, the MN-CU sends a message including information related to the TA to the MN-DU. Steps S241 to S243 show a procedure initiated by the MN, in which the message is sent to the MN via the SN.

[0049] After the message including the information related to the TA shown in FIG. 7 is transmitted and UL synchronization is performed, the LTM cell switch may be performed.

[0050] 8 is a sequence diagram illustrating an example of LTM in an embodiment of the present invention. In step S301, the system performs preparation. This preparation may be preparation for LTM. In step S302, the system enables DL synchronization and TCI (Transmission Configuration Indication) states. Execution of step S302 may be optional.

[0051] In step S303, the source MN-DU sends a PDCCH order to the UE. In step S304, the UE sends a RACH preamble to the target MN-DU. In step S305, the target DU calculates the TA and sends a message (TA info Transfer) containing information about the TA value to the target MN-CU.

[0052] In step S306, the target MN-CU sends a message including information on the TA value to the source MN-CU. In step S307, the source MN-CU sends a message including information on the TA value to the source MN-DU. In step S308, the UE performs an LTM cell switch to move from the source MN-DU to the target MN-DU.

[0053] In addition, in Figures 6, 7 and 8, the UE may perform early UL synchronization using the TA value included in the message including information related to the TA value, and perform LTM cell switching.

[0054] Here, when the source SN determines to perform early UL synchronization to a candidate cell based on the L1 measurement result, if it cannot instruct the UE to transmit a RACH preamble directly by a PDCCH indication, it may instruct the UE via the MN. For example, as shown in Figure 4, case 2) above, a case may be considered in which candidate configuration is configured with multiple candidate SNs and a single MN.

[0055] When a node that has decided to perform early UL synchronization instructs a UE to transmit a RACH via a PDCCH indication via another node, the node may transmit an early UL synchronization request via Xn or F1. The early UL synchronization request may be a class 1 or class 2 message, or may be transmitted in an existing message (e.g., UE Context Modification) or a new message.

[0056] Specifically, the above instruction may include the following information, and may also include other information necessary for transmitting the PDCCH instruction. Alternatively, the PDCCH instruction to be instructed to the UE for transmission may itself be sent as a container. The following information may be sent in the form of an independent IE or included in some list.

[0057] Target Config ID or target LTM Config ID Target Cell ID RA Preamble index SSB index CSI-RS index PRACH Mask index Source gNB-DU ID Source gNB ID Master or Secondary-NG-RAN node UE ID

[0058] Table 2 shows an example of IEs included in the above early UL synchronization request.

[0059]

[0060] 9 is a sequence diagram illustrating an example of LTM in an embodiment of the present invention. In step S401, the system performs preparation. This preparation may be preparation for LTM. In step S402, the system enables DL synchronization and TCI (Transmission Configuration Indication) states. Execution of step S402 may be optional.

[0061] In step S403, the UE transmits the L1 measurement results to the source SN-DU. In step S404, the source SN-DU determines to perform early UL synchronization based on the received L1 measurement results. In step S405, the source SN-DU transmits an early UL synchronization request to the MN-CU. This transmission may be via the source SN-CU.

[0062] In step S406, the MN-CU sends the early UL synchronization request to the MN-DU. In step S407, the MN-DU sends a PDCCH order to the UE based on the early UL synchronization request. Steps S403 to S407 show the early UL synchronization procedure. In step S408, the UE performs an LTM cell switch to move from the source SN-DU to the target SN-DU.

[0063] For example, after step S407, the sequence shown in FIG. 7 may be executed.

[0064] According to the above embodiment, in the inter-CU LTM, when early UL synchronization is performed by PDCCH ordered RACH, the source DU can know the TA value. Also, in the inter-SN LTM during DC, even if the SN cannot directly instruct the UE to perform early UL synchronization, it can instruct the UE to perform early UL synchronization via the MN.

[0065] That is, to enhance mobility, signaling related to LTM (Lower layer Triggered Mobility) can be defined.

[0066] (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.

[0067] <Base Station 10 and Network Node 30> Fig. 10 is a diagram showing an example of the functional configuration of the base station 10 and the network node 30. As shown in Fig. 10, the base station 10 has a transmitting unit 110, a receiving unit 120, a setting unit 130, and a control unit 140. The functional configuration shown in Fig. 10 is merely an example. As long as the operations according to the embodiment of the present invention can be performed, the names of the functional divisions and functional units may be any. Note that the network node 30 may have the same functional configuration as the base station 10. Furthermore, a network node 30 having multiple different functions in the system architecture may be composed of multiple network nodes 30 separated by function.

[0068] 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.

[0069] 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.

[0070] 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.

[0071] <Terminal 20> Fig. 11 is a diagram showing an example of the functional configuration of the terminal 20. As shown in Fig. 11, the terminal 20 has a transmitting unit 210, a receiving unit 220, a setting unit 230, and a control unit 240. The functional configuration shown in Fig. 11 is merely an example. 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.

[0072] 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.

[0073] 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.

[0074] 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.

[0075] (Hardware Configuration) The block diagrams (FIGS. 10 and 11) used to explain the above embodiments show functional blocks. These functional blocks (components) are realized by any combination of at least one of hardware and software. Furthermore, the method for realizing each functional block is not particularly limited. That is, each functional block may be realized using a single device that is physically or logically coupled, or may be realized using two or more physically or logically separated devices that are directly or indirectly connected (for example, using wires, wirelessly, etc.) and these multiple devices. The functional block may be realized by combining software with the single device or the multiple devices.

[0076] 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.

[0077] For example, the network node 30, the terminal 20, etc. according to an embodiment of the present disclosure may function as a computer that performs processing of the wireless communication method of the present disclosure. Fig. 12 is a diagram illustrating an example of the hardware configuration of the base station 10 and the terminal 20 according to an embodiment of the present disclosure. The network node 30 may have the same hardware configuration as the base station 10. The above-described base station 10 and the terminal 20 may be physically configured as a computer device including a processor 1001, a storage device 1002, an auxiliary storage device 1003, a communication device 1004, an input device 1005, an output device 1006, a bus 1007, etc.

[0078] 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.

[0079] 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.

[0080] 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.

[0081] The processor 1001 also reads programs (program codes), software modules, data, etc. from at least one of the auxiliary storage device 1003 and the communication device 1004 into the storage device 1002 and executes various processes in accordance with the programs. The programs used are those that cause a computer to execute at least some of the operations described in the above-described embodiments. For example, the control unit 140 of the base station 10 shown in FIG. 10 may be implemented by a control program stored in the storage device 1002 and running on the processor 1001. Furthermore, for example, the control unit 240 of the terminal 20 shown in FIG. 11 may be implemented by a control program stored in the storage device 1002 and running on the processor 1001. While the above-described various processes have been described as being executed by one processor 1001, they may also be executed simultaneously or sequentially by two or more processors 1001. The processor 1001 may be implemented by one or more chips. The programs may also be transmitted from a network via a telecommunications line.

[0082] 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.

[0083] 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.

[0084] 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.

[0085] 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).

[0086] 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.

[0087] 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.

[0088] Fig. 13 shows an example configuration of a vehicle 2001. As shown in Fig. 13, the vehicle 2001 includes a drive unit 2002, a steering unit 2003, an accelerator pedal 2004, a brake pedal 2005, a shift lever 2006, front wheels 2007, rear wheels 2008, an axle 2009, an electronic control unit 2010, various sensors 2021 to 2029, an information service unit 2012, and a communication module 2013. Each aspect / embodiment described in the present disclosure may be applied to a communication device mounted on the vehicle 2001, and may be applied to the communication module 2013, for example.

[0089] 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.

[0090] 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).

[0091] 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.

[0092] 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.

[0093] 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.

[0094] 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.

[0095] 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.

[0096] 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.

[0097] 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.

[0098] (Summary of Embodiments) As described above, according to the embodiments of the present invention, there is provided a network node that includes, in a DC (Dual connectivity) state, a receiver that receives a random access channel preamble from a terminal, a controller that calculates a TA (Timing Advance) value based on the random access channel preamble, and a transmitter that transmits a message including at least the TA value to a MN (Master Node) or a source SN via a target SN (Secondary Node)-CU (Central Unit), wherein the controller executes LTM (Lower layer Triggered Mobility) of the terminal that has executed early UL synchronization based on the TA value.

[0099] With the above configuration, in inter-CU LTM, when early UL synchronization is achieved by a PDCCH ordered RACH, the source DU can know the TA value. That is, to enhance mobility, signaling related to lower layer triggered mobility (LTM) can be specified.

[0100] The controller may include a candidate cell ID in the message. With this configuration, in inter-CU LTM, when early UL synchronization is achieved by a PDCCH ordered RACH, the source DU can know the TA value.

[0101] The controller may include an ID of the source base station in the message. With this configuration, in inter-CU LTM, when early UL synchronization is achieved by a PDCCH ordered RACH, the source DU can know the TA value.

[0102] Furthermore, according to an embodiment of the present invention, there is provided a network node that includes, in a DC (Dual connectivity) state, a receiver that receives Layer 1 measurement results from a terminal, a controller that determines to perform early UL (Uplink) synchronization based on the Layer 1 measurement results, and a transmitter that transmits a message to a MN (Master Node) requesting to perform early UL synchronization, wherein the controller executes Lower layer Triggered Mobility (LTM) of the terminal for which early UL synchronization has been performed.

[0103] With the above configuration, in the inter-SN LTM in DC, even if the SN cannot directly instruct the UE to perform early UL synchronization, it is possible to instruct the UE to perform early UL synchronization via the MN. That is, to enhance mobility, it is possible to specify signaling related to LTM (Lower layer Triggered Mobility).

[0104] The control unit may include an LTM setting ID in the message. With this configuration, in inter-SN LTM in DC, even if the SN cannot directly instruct the UE to perform early UL synchronization (early UL sync), it can instruct the UE to perform early UL synchronization via the MN.

[0105] Furthermore, according to an embodiment of the present invention, there is provided a communication method in which a network node performs the following procedures in a DC (Dual connectivity) state: receiving a random access channel preamble from a terminal; calculating a TA (Timing Advance) value based on the random access channel preamble; transmitting a message including at least the TA value to a MN (Master Node) or a source SN via a target SN (Secondary Node)-CU (Central Unit); and performing LTM (Lower layer Triggered Mobility) of the terminal that has performed early UL synchronization based on the TA value.

[0106] With the above configuration, in inter-CU LTM, when early UL synchronization is achieved by a PDCCH ordered RACH, the source DU can know the TA value. That is, to enhance mobility, signaling related to lower layer triggered mobility (LTM) can be specified.

[0107] (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.

[0108] 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.

[0109] 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).

[0110] 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.

[0111] 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).

[0112] 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.

[0113] Input and output information may be stored in a specific location (for example, memory) or may be managed using a management table. Input and output information may be overwritten, updated, or added to. Output information may be deleted. Input information may be sent to another device.

[0114] In the present disclosure, the determination may be made based on a value represented by one bit (0 or 1), a Boolean value (true or false), or a numerical comparison (e.g., comparison with a predetermined value).

[0115] 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.

[0116] 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.

[0117] 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.

[0118] 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.

[0119] As used in this disclosure, the terms "system" and "network" are used interchangeably.

[0120] 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.

[0121] 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.

[0122] 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.

[0123] 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.

[0124] 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.

[0125] In this disclosure, the terms "Mobile Station (MS)," "user terminal," "User Equipment (UE)," "terminal," and the like may be used interchangeably.

[0126] 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.

[0127] 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.

[0128] 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.

[0129] 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.

[0130] 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.

[0131] 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.

[0132] The reference signal may be abbreviated as RS (Reference Signal) or may be called a pilot depending on the applicable standard.

[0133] 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."

[0134] 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.

[0135] The "means" in the configuration of each of the above devices may be replaced with "part," "circuit," "device," etc.

[0136] 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.

[0137] 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.

[0138] 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."

[0139] 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).

[0140] 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.

[0141] 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 receiving unit that receives a random access channel preamble from a terminal in a DC (Dual connectivity) state; a control unit that calculates a TA (Timing Advance) value based on the random access channel preamble; and a transmitting unit that transmits a message including at least the TA value to a MN (Master Node) or a source SN via a target SN (Secondary Node)-CU (Central Unit), wherein the control unit is a network node that performs LTM (Lower layer Triggered Mobility) of the terminal that has performed early UL synchronization based on the TA value.

2. The network node according to claim 1, wherein the control unit includes a candidate cell ID in the message.

3. The network node according to claim 1, wherein the control unit includes an ID of a source base station in the message.

4. A network node having: a receiver that receives Layer 1 measurement results from a terminal in a DC (Dual connectivity) state; a controller that determines to perform early UL (Uplink) synchronization based on the Layer 1 measurement results; and a transmitter that transmits a message to an MN (Master Node) requesting that early UL synchronization be performed, wherein the controller is a network node that performs LTM (Lower layer Triggered Mobility) for the terminal for which early UL synchronization has been performed.

5. The network node according to claim 4, wherein the control unit includes an LTM setting ID in the message.

6. A communication method in which a network node performs the following procedures in a DC (Dual connectivity) state: receiving a random access channel preamble from a terminal; calculating a TA (Timing Advance) value based on the random access channel preamble; transmitting a message including at least the TA value to a MN (Master Node) or a source SN via a target SN (Secondary Node)-CU (Central Unit); and performing LTM (Lower layer Triggered Mobility) of the terminal that has performed early UL synchronization based on the TA value.

Images