Terminal and communication method

Abstract

A terminal according to the present invention comprises: a transmitter that, in a lower layer triggered mobility (LTM) preparation phase, transmits an inter-RAT measurement report in a first radio access technology (RAT) to a second base station of a second RAT; and a receiver that receives a physical downlink control channel (PDCCH) order of a random access channel (RACH) from the second base station. The transmitter transmits a RACH preamble to a first base station of the first RAT. In an LTM execution phase, the transmitter transmits a layer 1 measurement report in the first RAT to the second base station, and the receiver receives a cell switching command from the second base station.

Description

Terminal and Communication Method

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

[0002] In 3GPP (registered trademark) (3rd Generation Partnership Project), in order to achieve further increase in system capacity, further increase in data transmission rate, further reduction in latency in a radio section, and the like, studies are progressing on a radio communication scheme called 5G or NR (New Radio) (hereinafter, this radio communication scheme is referred to as "5G" or "NR"). In 5G, various radio technologies are being studied to satisfy the requirement that the delay in the radio section be 1 ms or less while achieving a throughput of 10 Gbps or more.

[0003] In NR, a network architecture including 5GC (5G Core Network) corresponding to EPC (Evolved Packet Core), which is a core network in the LTE (Long Term Evolution) network architecture, and NG-RAN (Next Generation - Radio Access Network) corresponding to E-UTRAN (Evolved Universal Terrestrial Radio Access Network), which is RAN (Radio Access Network) in the LTE network architecture, is being studied (for example, Non-Patent Document 1).

[0004] Furthermore, various requirements are being studied for the next-generation 6G. For example, the requirements include ultra broadband communication, mission critical communication, ultra massive connection, universal coverage, intelligent connection, ubiquitous sensing, and the like.

[0005] To meet these requirements, the new concept aims for extensibility (e.g., making it more effective for future use), ease of operation, customizability (e.g., making it easier to operate), and sustainability (e.g., cost reduction, a more robust configuration, and resilience). Furthermore, guaranteed communication, ensuring a minimum level of performance at all times, is being considered.

[0006] Furthermore, to enhance mobility, functional enhancements are expected to be made to support cases where inter-Central Unit (CU) LTM (Lower Layer Triggered Mobility) and DC (Dual Connectivity) are performed while maintaining LTM (for example, Non-Patent Document 2).

[0007] 3GPP TS 23.501 V18.7.0 (2024-09)3GPP TSG-RAN Meeting #101 RP-232618, Bengaluru, India, 11-15 September 2023

[0008] With the introduction of 6G, the method for performing inter-RAT-LTM from 6G-RAN nodes to 5G-RAN nodes, or from 5G-RAN nodes to 6G-RAN nodes, was unclear.

[0009] This invention has been made in view of the above points, and aims to implement InterRAT (Radio Access Technology) LTM (Lower layer Triggered Mobility).

[0010] According to the disclosed technology, a terminal is provided that, in the Lower Layer Triggered Mobility (LTM) preparation phase, includes a transmitting unit that transmits an inter-RAT measurement report from a first RAT (Radio Access Technology) to a second base station of a second RAT, and a receiving unit that receives a PDCCH (Physical Downlink Control Channel) order for a Random Access Channel (RACH) from the second base station, wherein the transmitting unit transmits a RACH preamble to the first base station of the first RAT, and in the LTM execution phase, the transmitting unit transmits a Layer 1 measurement report from the first RAT to the second base station, and the receiving unit receives a cell switching command from the second base station.

[0011] According to the disclosed technology, it is possible to perform InterRAT (Radio Access Technology) LTM (Lower layer Triggered Mobility).

[0012] This is a diagram illustrating an example of a communication system. This is a diagram illustrating an example of a communication system in a roaming environment. This is a sequence diagram illustrating an example (1) of an NG-based inter-RAT-LTM in an embodiment of the present invention. This is a sequence diagram illustrating an example (2) of an NG-based inter-RAT-LTM in an embodiment of the present invention. This is a sequence diagram illustrating an example (1) of an Xn-based inter-RAT-LTM in an embodiment of the present invention. This is a sequence diagram illustrating an example (2) of an Xn-based inter-RAT-LTM in an embodiment of the present invention. This is a diagram illustrating an example of the functional configuration of a base station 10 and a network node 30 in an embodiment of the present invention. This is a diagram illustrating an example of the functional configuration of a terminal 20 in an embodiment of the present invention. This is a diagram illustrating an example of the hardware configuration of a base station 10 and a terminal 20 in an embodiment of the present invention. This is a diagram illustrating an example of the configuration of a vehicle 2001 in an embodiment of the present invention.

[0013] Embodiments of the present invention will be described below with reference to the drawings. Note that the embodiments described below are examples, and the embodiments to which the present invention is applied are not limited to those described below.

[0014] In the operation of the wireless communication system according to the embodiments of the present invention, existing technologies may be used as appropriate. However, such existing technologies include, for example, existing LTE, but are not limited to existing LTE. Furthermore, the term "LTE" as used herein has a broad meaning that includes LTE-Advanced, LTE-Advanced and later technologies (e.g., NR), or wireless LAN (Local Area Network), unless otherwise specified.

[0015] Furthermore, in the embodiments of the present invention, "configuring" wireless parameters means that predetermined values ​​are pre-configured, or that wireless parameters notified from the network node 30 or terminal 20 are configured.

[0016] Figure 1 is a diagram illustrating an example of a communication system. As shown in Figure 1, the communication system consists of a terminal 20 (UE) and multiple network nodes 30. Hereafter, one network node 30 will be assumed to correspond to each function, but one network node 30 may implement multiple functions, or multiple network nodes 30 may implement one function. Also, the "connection" described below may be a logical connection or a physical connection.

[0017] The RAN (Radio Access Network) is a network node 30 having wireless access functionality, which may include a base station 10, and is connected to a UE, AMF (Access and Mobility Management Function), and 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 interconnected with the DN (Data Network) and having functions such as a PDU (Protocol Data Unit) session point to the outside, packet routing and forwarding, and user plane QoS (Quality of Service) handling. The UPF and DN constitute a network slice. In the wireless communication network in the embodiment of the present invention, multiple network slices are constructed.

[0018] AMF is connected to 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). AMF, SMF, NSSF, NEF, NRF, UDM, AUSF, PCF, and AF are network nodes 30 that are interconnected via interfaces based on their respective services: Namf, Nsmf, Nnssf, Nnef, Nnrf, Nudm, Nausf, Npcf, and Naf.

[0019] The SMF is a network node 30 that has functions such as session management, IP (Internet Protocol) address allocation and management for UEs, DHCP (Dynamic Host Configuration Protocol) functionality, ARP (Address Resolution Protocol) proxy, and roaming functionality. The NEF is a network node 30 that has the function of notifying other NFs (Network Functions) of capabilities and events. The NSSF is a network node 30 that has functions such as selecting the network slice to which the UE connects, determining the allowed NSSAI (Network Slice Selection Assistance Information), determining the NSSAI to be set, and determining the AMF set to which the UE connects. The PCF is a network node 30 that has the function of controlling network policies. The AF is a network node 30 that has the function of controlling application servers. The NRF is a network node 30 that has the 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 the UDR (User Data Repository) that holds the said data.

[0020] Figure 2 is a diagram illustrating an example of a communication system in a roaming environment. As shown in Figure 2, the network consists of a terminal 20 (UE) and multiple network nodes 30. Hereafter, one network node 30 will be assigned to each function, but one network node 30 may implement multiple functions, or multiple network nodes 30 may implement one function. Also, the "connection" described below may be a logical connection or a physical connection.

[0021] The RAN is a network node 30 having wireless access functionality and is connected to the UE, AMF, and 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 interconnected with the DN, having functions such as external PDU session point, packet routing and forwarding, and user plane QoS handling. The UPF and DN constitute a network slice. In the wireless communication network according to the embodiment of the present invention, multiple network slices are constructed.

[0022] AMF is connected to UE, RAN, SMF, NSSF, NEF, NRF, UDM, AUSF, PCF, AF, and SEPP (Security Edge Protection Proxy). AMF, SMF, NSSF, NEF, NRF, UDM, AUSF, PCF, and AF are network nodes 30 that are interconnected via interfaces based on their respective services: Namf, Nsmf, Nnssf, Nnef, Nnrf, Nudm, Nausf, Npcf, and Naf.

[0023] SMF is a network node 30 that has functions such as session management, IP address allocation and management for UEs, DHCP functionality, ARP proxy, and roaming functionality. NEF is a network node 30 that has the function of notifying other NFs of capabilities and events. NSSF is a network node 30 that has functions such as selecting the network slice to which the UE connects, determining which NSSAIs are allowed, determining which NSSAIs are configured, and determining which AMF set the UE connects to. PCF is a network node 30 that has the function of controlling network policies. AF is a network node 30 that has the function of controlling application servers. NRF is a network node 30 that has the function of discovering NF instances that provide services. SEPP is an opaque proxy that filters control plane messages between PLMNs (Public Land Mobile Networks). In Figure 2, vSEPP is the SEPP in the visited network, and hSEPP is the SEPP in the home network.

[0024] As shown in Figure 2, the UE is in a roaming environment connected to the RAN and AMF in the Visited PLMN. The Visited PLMN and Home PLMN are connected via vSEPP and hSEPP. The UE can communicate with the UDM of the Home PLMN, for example, via the AMF of the Visited PLMN.

[0025] Furthermore, in an NG-RAN (Next Generation Radio Access Network), a gNB, which is a RAN node, may have an architecture separated into gNB-CU (Central Unit) and gNB-DU (Distributed Unit). One gNB-CU may accommodate multiple gNB-DUs, and one gNB-DU may accommodate multiple cells.

[0026] To enhance mobility, it is expected that LTM will be supported from the initial release of 6G. When 6G is introduced, a switchover will occur between 5G-RAT and 6G-RAT, requiring an inter-RAT handover, i.e., a handover from 6G to 5G or from 5G to 6G.

[0027] In the initial release of 6G, localized 6G cell coverage is expected, and frequent switching to 5G cells is anticipated. To improve the user experience, low-interruption-time inter-RAT handovers are required.

[0028] Therefore, the UE may specify a method for implementing inter-RAT-LTM from a 6G-RAN node to a 5G-RAN node, or from a 5G-RAN node to a 6G-RAN node.

[0029] The NG-based InterRAT-LTM may be executed as follows. Details are explained in Figures 3 and 4.

[0030] When handing over from a 5G base station to a 6G base station, some or all of the following steps 1)-6) may be performed. Note that L1 (Layer 1) and / or L3 (Layer 3) will also be referred to as L1 / L3.

[0031] 1) In the LTM preparation phase, the UE may provide the 5G base station with an L1 / L3 inter-RAT measurement report (including 6G L1 / L3 cell / beam measurement results).

[0032] 2) During the LTM Execution phase, the UE may provide the 5G base station with an L1 measurement report including the 6G cell ID, beam ID, cell SSBRI (SS / PBCH Block Resource Indicator), beam (SSB or CSI-RS) quality (RSRP (Reference Signal Received Power), RSRQ (Reference Signal Received Quality), SINR (Signal-to-Interference plus Noise Ratio)), and cell quality (RSRP, RSRQ, SINR).

[0033] 3) During the LTM execution phase, the 5G base station may send a cell switch command (including target 6G cell config ID, cell TA value, cell RACH resource, cell TCI state ID / UL TCI state ID) to the UE.

[0034] 4) In the LTM preparation phase, for signaling exchange between 5GC and 6GC (6G Core network), 5GC may send intersignaling between 5GC and 6GC (Inter 5GC and 6GC signaling (containing Source NG-RAN Node to Target NG-RAN Node Transparent Container (LTM info setup))) to 6GC, which includes a transparent container containing LTM information setup from the source NG-RAN note to the target NG-RAN.

[0035] 5) In the LTM execution phase, for signaling exchange between 5GC and 6GC, 5GC may send intersignaling (inter 5GC and 6GC signaling (containing cell switch notification (Cell ID, TCI state ID, TA value, Tag ID pointer))) from 5GC to 6GC, including a cell switch notification containing the cell ID, TCI state ID, TA value, and tag ID pointer.

[0036] 6) During the LTM early sync phase, the 6GC may transmit intersignaling information between the 5GC and 6GC (TA info transfer (6G cell ID, TA value, preamble index, RA-RNTI, source gNB DU ID, Tag ID pointer)) to the 5GC.

[0037] When handing over from a 6G base station to a 5G base station, some or all of the following steps 1)-6) may be performed. Note that L1 and / or L3 will also be referred to as L1 / L3.

[0038] 1) In the LTM preparation phase, the UE may provide the 6G base station with an L1 / L3 inter-RAT measurement report (including 5G L1 / L3 cell / beam measurement results).

[0039] 2) During the LTM execution phase, the UE may provide the 6G base station with an L1 measurement report including the 5G cell ID, beam ID, cell SSBRI (SS / PBCH Block Resource Indicator), beam (SSB or CSI-RS) quality (RSRP (Reference Signal Received Power), RSRQ (Reference Signal Received Quality), SINR (Signal-to-Interference plus Noise Ratio)), and cell quality (RSRP, RSRQ, SINR).

[0040] 3) During the LTM execution phase, the 6G base station may send a cell switch command (including target 6G cell config ID, cell TA value, cell RACH resource, cell TCI state ID / UL TCI state ID) to the UE.

[0041] 4) In the LTM preparation phase, for signaling exchange between 6GC and 5GC, 6GC may send intersignaling between 5GC and 6GC (Inter 5GC and 6GC signaling (containing Source NG-RAN Node to Target NG-RAN Node Transparent Container (LTM info setup))) to 5GC, which includes a transparent container containing LTM information setup from the source NG-RAN note to the target NG-RAN.

[0042] 5) In the LTM execution phase, for signaling exchange between 6GC and 5GC, inter-signaling between 5GC and 6GC (Inter 5GC and 6GC signaling (containing cell switch notification (Cell ID, TCI state ID, TA value, Tag ID pointer))) including a cell switch notification containing a cell ID, a TCI state ID, a TA value and a Tag ID pointer may be transmitted from 6GC to 5GC.

[0043] 6) In the LTM early sync phase, inter-signaling between 5GC and 6GC (Inter 5GC and 6GC signaling (TA info transfer (5G cell ID, TA value, preamble index, RA-RNTI, source gNB DU ID, Tag ID pointer))) containing a 5G cell ID, a TA value, a preamble index, a source gNB-DU-ID and a Tag ID pointer may be transmitted from 5GC to 6GC.

[0044] Figure 3 is a sequence diagram for explaining example (1) of NG-based inter-RAT-LTM in the embodiment of the present invention. The 5G base station and the 6G base station may be CUs, or may be DUs.

[0045] In step S101, the UE transmits an L1 / L3 inter-RAT measurement report (L1 / L3 inter-RAT measurement reporting (6G L1 / L3 cell / beam measurement results)) containing 6G L1 / L3 cell and / or beam measurement results to the source 5G base station.

[0046] In step S102, the UE transmits, to the 5GC, a handover request including a transparent container containing LTM configuration information from the source NG-RAN node to the target NG-RAN node (HO required(Source NG-RAN Node to Target NG-RAN Node Transparent Container(LTM info setup))).

[0047] In step S103, the 5GC transmits, to the 6GC, inter-signaling between 5GC and 6GC including a transparent container containing LTM configuration information from the source NG-RAN node to the target NG-RAN node (Inter 5GC and 6GC signaling (containing Source NG-RAN Node to Target NG-RAN Node Transparent Container(LTM info setup )).

[0048] In step S104, the 6GC transmits, to the target 6G base station, a handover request including a transparent container containing LTM configuration information from the source NG-RAN node to the target NG-RAN node (HO request (Source NG-RAN Node to Target NG-RAN Node Transparent Container(LTM info setup))).

[0049] In step S105, the target 6G base station transmits, to the 6GC, a handover request acknowledgment including a transparent container from the target NG-RAN node to the source NG-RAN node (HO request Ack(Target NG-RAN Node to Source NG-RAN Node Transparent Container)).

[0050] In step S106, 6GC transmits an intersignaling signal between 5GC and 6GC (containing a transparent container from the target NG-RAN node to the source NG-RAN node) to 5GC.

[0051] In step S107, the 5GC sends a handover command (HO command (Target NG-RAN Node to Source NG-RAN Node Transparent Container(SSB info, cell config info, complete candidate config indicator, LTM CFRA resource config, LTM CFRA resource config for SUL))) from the target NG-RAN node to the source NG-RAN node to the source 5G base station. The transparent container may include SSB information, cell configuration information, a complete candidate config indicator, LTM-CFRA resource configuration, and LTM-CFRA resource configuration for SUL.

[0052] In step S108, the source 5G base station sends an RRC Reconfiguration to the UE. In step S109, the UE sends an RRC Reconfiguration Complete to the source 5G base station. In step S110, the source 5G base station sends a RACH PDCCH (Physical Downlink Control Channel) order including the 6G cell ID to the UE. In step S111, the UE sends a RACH preamble to the target 6G base station. The RACH PDCCH order is instruction information for the RACH preamble sent from the UE, and may be, for example, a DCI containing information about the RACH preamble.

[0053] In step S112, the target 6G base station transfers TA information (TA info transfer (6G cell ID, TA value, preamble index, RA-RNTI, source gNB-DU ID, Tag ID pointer)) to the 6GC. This TA information may include the 6G cell ID, TA value, preamble index, RA-RNTI, source gNB-DU-ID, and tag ID pointer.

[0054] In step S113, 6GC transmits intersignaling information between 5GC and 6GC, including TA information (TA info transfer (6G cell ID, TA value, preamble index, RA-RNTI, source gNB DU ID, Tag ID pointer)), to 5GC.

[0055] In step S114, the 5GC transmits TA information (TA info transfer (6G cell ID, TA value, preamble index, RA-RNTI, source gNB DU ID, Tag ID pointer)) to the source 5G base station.

[0056] In step S115, the UE transmits an L1 measurement report (including 6G cell ID, beam ID, cell SSBRI, beam (SSB or CSI-RS) quality (RSRP, RSRQ, SINR), cell quality (RSRP, RSRQ, SINR)) to the source 5G base station. The L1 measurement report may include the 6G cell ID, beam ID, cell SSBRI, SSB or CSI-RS beam quality (RSRP, RSRQ, SINR), and cell quality (RSRP, RSRQ, SINR).

[0057] In step S116, the source 5G base station sends a cell switch command (including target 6G cell config ID, cell TA value, cell RACH resource, cell TCI state ID / UL TCI state ID) to the UE. The cell switch command may include the target 6G cell config ID, cell TA value, cell RACH resource, cell TCI state ID, and UL-TCI state ID.

[0058] In step S117, the source 5G base station sends a cell switch notification (6G Cell ID, TCI state ID, TA value, Tag ID pointer) to the 5GC. The cell switch notification may include the 6G cell ID, TCI state ID, TA value, and tag ID pointer.

[0059] In step S118, 5GC transmits an intersignaling (Inter 5GC and 6GC signaling) between 5GC and 6GC, including a cell switching notification, to 6GC.

[0060] In step S119, the 6GC sends a cell switching notification to the target 6G base station. In step S120, the UE sends an RRC reconfiguration complete notification to the target 6G base station. Through these steps, the UE performs a handover from the source 5G base station to the target 6G base station.

[0061] Figure 4 is a sequence diagram illustrating an example (2) of the NG-based interframe RAT-LTM in an embodiment of the present invention. The 5G base station and 6G base station may be a CU or a DU.

[0062] In step S201, the UE transmits an L1 / L3 inter-RAT measurement report (5G L1 / L3 cell / beam measurement results) to the source 6G base station, which includes 5G L1 / L3 cell and / or beam measurement results.

[0063] In step S202, the UE sends a handover request (HO required(Source NG-RAN Node to Target NG-RAN Node Transparent Container(LTM info setup))) to the 5GC, which includes a transparent container containing LTM configuration information from the source NG-RAN node to the target NG-RAN node.

[0064] In step S203, 6GC sends an intersignaling signal (containing Source NG-RAN Node to Target NG-RAN Node Transparent Container (LTM info setup)) between 5GC and 6GC to 5GC, which includes a transparent container containing LTM setup information from the source NG-RAN node to the target NG-RAN node.

[0065] In step S204, the 5GC sends a handover request (HO request (Source NG-RAN Node to Target NG-RAN Node Transparent Container(LTM info setup))) containing a transparent container with LTM configuration information from the source NG-RAN node to the target NG-RAN node to the target 5G base station.

[0066] In step S205, the target 5G base station sends a handover request acknowledgment (HO request Ack (Target NG-RAN Node to Source NG-RAN Node Transparent Container)) containing a transparent container from the target NG-RAN node to the source NG-RAN node to the 5GC.

[0067] In step S206, 5GC transmits an intersignaling signal between 5GC and 6GC (containing a transparent container from the target NG-RAN node to the source NG-RAN node) to 6GC.

[0068] In step S207, the 6GC sends a handover command (HO command (Target NG-RAN Node to Source NG-RAN Node Transparent Container(SSB info, cell config info, complete candidate config indicator, LTM CFRA resource config, LTM CFRA resource config for SUL))) from the target NG-RAN node to the source NG-RAN node to the source 6G base station. The transparent container may include SSB information, cell configuration information, a complete candidate config indicator, LTM-CFRA resource configuration, and LTM-CFRA resource configuration for SUL.

[0069] In step S208, the source 6G base station sends RRCReconfiguraion to the UE. In step S209, the UE sends RRCReconfiguraionComplete to the source 6G base station. In step S210, the source 6G base station sends the RACH PDCCH order, including the 5G cell ID, to the UE. In step S211, the UE sends the RACH preamble to the target 5G base station.

[0070] In step S212, the target 5G base station transfers TA information (TA info transfer (6G cell ID, TA value, preamble index, RA-RNTI, source gNB-DU ID, Tag ID pointer)) to the 5GC. This TA information may include the 5G cell ID, TA value, preamble index, RA-RNTI, source gNB-DU-ID, and tag ID pointer.

[0071] In step S213, 5GC transmits intersignaling information between 5GC and 6GC to 6GC, including TA information (TA info transfer (5G cell ID, TA value, preamble index, RA-RNTI, source gNB DU ID, Tag ID pointer)).

[0072] In step S214, 6GC transmits TA information (TA info transfer (5G cell ID, TA value, preamble index, RA-RNTI, source gNB DU ID, Tag ID pointer)) to the source 5G base station.

[0073] In step S215, the UE transmits an L1 measurement report (including 5G cell ID, beam ID, cell SSBRI, beam (SSB or CSI-RS) quality (RSRP, RSRQ, SINR, cell quality (RSRP, RSRQ, SINR)) to the source 6G base station. The L1 measurement report may include the 5G cell ID, beam ID, cell SSBRI, SSB or CSI-RS beam quality (RSRP, RSRQ, SINR), and cell quality (RSRP, RSRQ, SINR).

[0074] In step S216, the source 6G base station sends a cell switch command (including target 5G cell config ID, cell TA value, cell RACH resource, cell TCI state ID / UL TCI state ID) to the UE. The cell switch command may include the target 5G cell config ID, cell TA value, cell RACH resource, cell TCI state ID, and UL-TCI state ID.

[0075] In step S217, the source 6G base station sends a cell switch notification (5G Cell ID, TCI state ID, TA value, Tag ID pointer) to the 6GC. The cell switch notification may include the 5G cell ID, TCI state ID, TA value, and tag ID pointer.

[0076] In step S218, 6GC transmits an intersignaling (Inter 5GC and 6GC signaling) between 5GC and 6GC, including a cell switching notification, to 5GC.

[0077] In step S219, the 5GC sends a cell switching notification to the target 5G base station. In step S220, the UE sends an RRC Reconfiguration Complete notification to the target 5G base station. Through these steps, the UE performs a handover from the source 6G base station to the target 5G base station.

[0078] Alternatively, the Xn-based inter-RAT-LTM may be executed as follows. Details are explained in Figures 5 and 6.

[0079] When handing over from a 5G base station to a 6G base station, some or all of the following steps 1)-8) may be performed. Note that L1 and / or L3 will also be referred to as L1 / L3.

[0080] 1) In the LTM preparation phase, the UE may provide the 5G base station with an L1 / L3 inter-RAT measurement report (including 6G L1 / L3 cell / beam measurement results).

[0081] 2) The source 5G base station may send a handover request (LTM info setup) containing LTM configuration information to the candidate 6G base station.

[0082] 3) A Handover request Ack(LTM config(SSB info, cell config info, complete candidate config indicator, LTM CFRA resource config, LTM CFRA resource config for SUL)) may be sent from the candidate 6G base station to the source 5G base station. The Handover request Ack may include an LTM configuration, which includes SSB information, cell configuration information, a complete candidate config indicator, LTM-CFRA resource configuration, and LTM-CFRA resource configuration for SUL.

[0083] 4) The source 5G base station may send an LTM configuration update message to the candidate 6G base station.

[0084] 5) A candidate 6G base station may send an LTM configuration update acknowledgment message to a 5G base station.

[0085] 6) In the LTM early sync phase, a candidate 6G base station may transmit TA information transfer (6G cell ID, TA value, preamble index, RA-RNTI, source gNB-DU ID, Tag ID pointer) to a 5G base station. The TA information transfer may include the 6G cell ID, TA value, preamble index, RA-RNTI, source gNB-DU-ID, and tag ID pointer.

[0086] 7) In the LTM Execution phase, the UE may provide an L1 measurement report (including 6G cell ID, beam ID, cell SSBRI, beam (SSB or CSI-RS) quality (RSRP, RSRQ, SINR, cell quality (RSRP, RSRQ, SINR)) to the source 5G base station. The L1 measurement report may include 6G cell ID, beam ID, cell SSBRI, SSB or CSI-RS beam quality (RSRP, RSRQ, SINR), and cell quality (RSRP, RSRQ, SINR).

[0087] 8) During the LTM execution phase, the 5G base station may send a cell switch command (including target 6G cell config ID, cell TA value, cell RACH resource, cell TCI state ID / UL TCI state ID) to the UE. The cell switch command may include the target 6G cell config ID, cell TA value, cell RACH resource, cell TCI state ID, and UL-TCI state ID.

[0088] When handing over from a 6G base station to a 5G base station, some or all of the following 1)-8) may be performed.

[0089] 1) In the LTM preparation phase, the UE may provide the 6G base station with an L1 / L3 inter-RAT measurement report (including 5G L1 / L3 cell / beam measurement results).

[0090] 2) The source 6G base station may send a handover request (LTM info setup) containing LTM configuration information to the candidate 5G base station.

[0091] 3) A Handover request Ack(LTM config(SSB info, cell config info, complete candidate config indicator, LTM CFRA resource config, LTM CFRA resource config for SUL)) may be sent from the candidate 5G base station to the source 6G base station. The Handover request Ack may include LTM configuration, which includes SSB information, cell configuration information, a complete candidate config indicator, LTM-CFRA resource configuration, and LTM-CFRA resource configuration for SUL.

[0092] 4) The source 6G base station may send an LTM configuration update message to the candidate 5G base station.

[0093] 5) A candidate 5G base station may send an LTM configuration update acknowledgment message to the 6G base station.

[0094] 6) In the LTM early sync phase, candidate 5G base stations may transmit TA information transfer (5G cell ID, TA value, preamble index, RA-RNTI, source gNB-DU ID, Tag ID pointer) to 6G base stations. The TA information transfer may include the 6G cell ID, TA value, preamble index, RA-RNTI, source gNB-DU-ID, and tag ID pointer.

[0095] 7) In the LTM Execution phase, the UE may provide an L1 measurement report (including 5G cell ID, beam ID, cell SSBRI, beam (SSB or CSI-RS) quality (RSRP, RSRQ, SINR), cell quality (RSRP, RSRQ, SINR)) to the source 6G base station. The L1 measurement report may include 5G cell ID, beam ID, cell SSBRI, SSB or CSI-RS beam quality (RSRP, RSRQ, SINR), and cell quality (RSRP, RSRQ, SINR).

[0096] 8) During the LTM execution phase, the 6G base station may send a cell switch command (including target 5G cell config ID, cell TA value, cell RACH resource, cell TCI state ID / UL TCI state ID) to the UE. The cell switch command may include the target 5G cell config ID, cell TA value, cell RACH resource, cell TCI state ID, and UL-TCI state ID.

[0097] Figure 5 is a sequence diagram illustrating an example (1) of the Xn-based interRAT-LTM in an embodiment of the present invention.

[0098] In step S301, the UE transmits an L1 / L3 inter-RAT measurement report (including 6G L1 / L3 cell / beam measurement results) to the 5G base station.

[0099] In step S302, the source 5G base station sends a handover request (LTM info setup) containing LTM configuration information to the candidate 6G base station.

[0100] In step S303, the candidate 6G base station sends a Handover request Ack (LTM config(SSB info, cell config info, complete candidate config indicator, LTM CFRA resource config, LTM CFRA resource config for SUL)) to the source 5G base station. The Handover request Ack may include SSB information, cell configuration information, a complete candidate configuration indicator, LTM-CFRA resource configuration, and LTM-CFRA resource configuration for SUL.

[0101] In step S304, the source 5G base station sends an LTM configuration update to the candidate 6G base station. In step S305, the candidate 6G base station sends an LTM configuration update acknowledgment to the source 5G base station.

[0102] In step S306, the source 5G base station sends RRCReconfiguration to the UE. In step S307, the UE sends RRCReconfigurationComplete to the source 5G base station. In step S308, the source 5G base station sends PDCCH ordered RACH to the UE. In step S309, the UE sends the RACH preamble to the candidate 6G base station.

[0103] In step S310, the candidate 6G base station transmits TA information transfer (TA info transfer (6G cell ID, TA value, preamble index, RA-RNTI, source gNB-DU ID, Tag ID pointer)) to the source 5G base station. This TA information transfer may include the 6G cell ID, TA value, preamble index, RA-RNTI, source gNB-DU-ID, and tag ID pointer.

[0104] In step S311, the UE transmits an L1 measurement report (including 6G cell ID, Scell ​​beam ID, Scell ​​SSBRI, beam (SSB or CSI-RS) quality (RSRP, RSRQ), SINR, cell quality (RSRP, RSRQ, SINR)) to the source 5G base station. The L1 measurement report may include the 6G cell ID, beam ID, cell SSBRI, SSB or CSI-RS beam quality (RSRP, RSRQ, SINR), and cell quality (RSRP, RSRQ, SINR).

[0105] In step S312, the source 5G base station makes an LTM cell switch decision.

[0106] In step S313, the source 5G base station sends a cell switch command (including 6G target config ID, cell TA value, cell RACH resource, cell TCI state ID / UL TCI state ID) to the UE. The cell switch command may include the target 5G cell configuration ID, cell TA value, cell RACH resource, cell TCI state ID, and UL-TCI state ID.

[0107] In step S314, the source 5G base station transmits a cell switching notification to the candidate 6G base station. The cell switching notification may include the cell ID and the TCI status ID.

[0108] In step S315, the candidate 6G base station transmits a Handover success message to the source 5G base station.

[0109] In step S316, the core network performs user data forwarding to the candidate 6G base station and the source 5G base station.

[0110] In step S317, the UE transmits RRC RecongurationComplete to the candidate 6G base station. Through these steps, the UE performs a handover from the source 5G base station to the candidate 6G base station.

[0111] Figure 6 is a sequence diagram illustrating an example (2) of the Xn-based interRAT-LTM in an embodiment of the present invention.

[0112] In step S401, the UE transmits an L1 / L3 inter-RAT measurement report (including 5G L1 / L3 cell / beam measurement results) to the 6G base station.

[0113] In step S402, the source 6G base station sends a handover request (LTM info setup) containing LTM configuration information to the candidate 5G base station.

[0114] In step S403, the candidate 5G base station sends a Handover request Ack (LTM config(SSB info, cell config info, complete candidate config indicator, LTM CFRA resource config, LTM CFRA resource config for SUL)) to the source 6G base station. The Handover request Ack may include SSB information, cell configuration information, a complete candidate configuration indicator, LTM-CFRA resource configuration, and LTM-CFRA resource configuration for SUL.

[0115] In step S404, the source 6G base station sends an LTM configuration update to the candidate 5G base station. In step S405, the candidate 5G base station sends an LTM configuration update acknowledgment to the source 6G base station.

[0116] In step S406, the source 6G base station sends RRCReconfiguration to the UE. In step S407, the UE sends RRCReconfigurationComplete to the source 6G base station. In step S408, the source 6G base station sends PDCCH ordered RACH to the UE. In step S409, the UE sends the RACH preamble to the candidate 5G base station.

[0117] In step S410, the candidate 5G base station transmits TA information transfer (TA info transfer (5G cell ID, TA value, preamble index, RA-RNTI, source gNB-DU ID, Tag ID pointer)) to the source 6G base station. This TA information transfer may include the 5G cell ID, TA value, preamble index, RA-RNTI, source gNB-DU-ID, and tag ID pointer.

[0118] In step S411, the UE transmits an L1 measurement report (including 5G cell ID, Scell ​​beam ID, Scell ​​SSBRI, beam (SSB or CSI-RS) quality (RSRP, RSRQ), SINR, cell quality (RSRP, RSRQ, SINR)) to the source 6G base station. The L1 measurement report may include the 5G cell ID, beam ID, cell SSBRI, SSB or CSI-RS beam quality (RSRP, RSRQ, SINR), and cell quality (RSRP, RSRQ, SINR).

[0119] In step S412, the source 6G base station makes an LTM cell switch decision.

[0120] In step S413, the source 6G base station sends a cell switch command (including 5G target config ID, cell TA value, cell RACH resource, cell TCI state ID / UL TCI state ID) to the UE. The cell switch command may include the target 6G cell configuration ID, cell TA value, cell RACH resource, cell TCI state ID, and UL-TCI state ID.

[0121] In step S414, the source 6G base station transmits a cell switching notification to the candidate 5G base station. The cell switching notification may include the cell ID and the TCI status ID.

[0122] In step S415, the candidate 5G base station transmits a Handover success message to the source 6G base station.

[0123] In step S416, the core network performs user data forwarding to the candidate 5G base station and the source 6G base station.

[0124] In step S417, the UE transmits RRC RecongurationComplete to the candidate 5G base station. Through these steps, the UE performs a handover from the source 6G base station to the target 5G base station.

[0125] As a result of the above operation, when 6G is introduced, it will be possible to perform inter-RAT LTM with minimal downtime when switching between 5G-RAT and 6G-RAT, which is expected to contribute to a smooth transition from 6G to 5G.

[0126] In other words, it can perform InterRAT (Radio Access Technology) LTM (Lower Layer Triggered Mobility).

[0127] (Device Configuration) Next, an example of the functional configuration of the base station 10, network node 30, and terminal 20 that perform the processing and operations described above will be explained. The base station 10, network node 30, and terminal 20 include the functions to perform the embodiments described above. However, the base station 10, network node 30, and terminal 20 may each be equipped with only some of the functions in the embodiments.

[0128] <Base Station 10 and Network Node 30> Figure 7 shows an example of the functional configuration of a base station 10 and a network node 30. As shown in Figure 7, 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 Figure 7 is merely an example. Any functional classification and functional unit names are acceptable as long as they enable the operation according to the embodiment of the present invention. The network node 30 may have the same functional configuration as the base station 10. Furthermore, a network node 30 having multiple different functions on the system architecture may be composed of multiple network nodes 30 separated by function.

[0129] The transmitting unit 110 includes the function of generating a signal to be transmitted to the terminal 20 or other network node 30 and transmitting the signal by wire or wireless. The receiving unit 120 includes the function of receiving various signals transmitted from the terminal 20 or other network node 30 and obtaining information from the received signal, for example, information from a higher layer. A communication unit including the transmitting unit 110 and the receiving unit 120 may be configured.

[0130] The setting unit 130 stores pre-configured setting information and various setting information to be transmitted to the terminal 20 in a storage device, and reads it from the storage device as needed. The contents of the setting information include, for example, information related to LTM.

[0131] The control unit 140 performs processing related to the LTM, as described in the embodiment. The control unit 140 also performs processing related to communication with the terminal 20. The signal transmission function in the control unit 140 may be included in the transmission unit 110, and the signal reception function in the control unit 140 may be included in the reception unit 120.

[0132] <Terminal 20> Figure 8 is a diagram showing an example of the functional configuration of terminal 20. As shown in Figure 8, 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 Figure 8 is merely an example. The functional classifications and names of the functional units can be anything as long as they can perform the operations according to the embodiment of the present invention. In addition, the communication device that becomes the resource holder 20 may have a functional configuration similar to that of terminal 20.

[0133] The transmitting unit 210 creates a transmission signal from the transmission data and transmits the transmission signal wirelessly. The receiving unit 220 wirelessly receives various signals and obtains signals from higher layers from the received physical layer signals. The receiving unit 220 also has the function of receiving NR-PSS, NR-SSS, NR-PBCH, DL / UL control signals or reference signals transmitted from the network node 30. A communication unit including the transmitting unit 210 and the receiving unit 220 may be configured.

[0134] The configuration unit 230 stores various configuration information received from the network node 30 by the receiving unit 220 in its storage device and reads it from the storage device as needed. The configuration unit 230 also stores pre-configured configuration information. The contents of the configuration information include, for example, information related to LTM.

[0135] The control unit 240 performs processing related to LTM as described in the embodiment. The signal transmission function in the control unit 240 may be included in the transmission unit 210, and the signal reception function in the control unit 240 may be included in the reception unit 220.

[0136] (Hardware Configuration) The block diagrams (Figures 7 and 8) used in the description of the above embodiments show functional units. These functional blocks (components) are realized by any combination of at least one of hardware and software. Furthermore, the method of realizing each functional block is not particularly limited. That is, each functional block may be realized using one device that is physically or logically coupled, or it may be realized using two or more physically or logically separated devices that are directly or indirectly connected (for example, using wired or wireless connections). A functional block may be realized by combining the one device or the multiple devices with software.

[0137] Functions include, but are not limited to, judgment, decision, determination, calculation, calculation, processing, derivation, investigation, exploration, confirmation, reception, transmission, output, access, resolution, selection, selection, establishment, comparison, assumption, expectation, assumption, broadcasting, notifying, communicating, forwarding, configuring, reconfiguring, allocating (mapping), and assigning. For example, a functional block (configuration part) that enables transmission is called a transmitting unit or transmitter. In all cases, as mentioned above, the method of implementation is not particularly limited.

[0138] For example, the network node 30, terminal 20, etc. in one embodiment of the present disclosure may function as a computer that processes the wireless communication method of the present disclosure. Figure 9 is a diagram showing an example of the hardware configuration of a base station 10 and terminal 20 according to one embodiment of the present disclosure. The network node 30 may have the same hardware configuration as the base station 10. The above-mentioned base station 10 and 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.

[0139] In the following explanation, the term "device" can be read as "circuit," "device," "unit," etc. The hardware configuration of the base station 10 and terminal 20 may include one or more of the devices shown in the figure, or it may be configured without some of the devices.

[0140] Each function in the base station 10 and terminal 20 is realized by loading predetermined software (programs) onto hardware such as the processor 1001 and storage device 1002, which allows the processor 1001 to perform calculations, control communication by the communication device 1004, and control at least one of data reading and writing in the storage device 1002 and auxiliary storage device 1003.

[0141] The processor 1001 controls the entire computer, for example, by running an operating system. The processor 1001 may consist of a central processing unit (CPU) that includes interfaces with peripheral devices, control devices, arithmetic units, registers, etc. For example, the control unit 140, control unit 240, etc., described above may be implemented by the processor 1001.

[0142] Furthermore, the processor 1001 reads programs (program code), software modules, or data from at least one of the auxiliary storage device 1003 and the communication device 1004 into the storage device 1002, and executes various processes accordingly. The program used is one that causes the computer to execute at least a part of the operations described in the above embodiment. For example, the control unit 140 of the base station 10 shown in Figure 7 may be implemented by a control program stored in the storage device 1002 and operated by the processor 1001. Also, for example, the control unit 240 of the terminal 20 shown in Figure 8 may be implemented by a control program stored in the storage device 1002 and operated by the processor 1001. Although the above-described processes have been explained as being executed by one processor 1001, they may be executed simultaneously or sequentially by two or more processors 1001. The processor 1001 may be implemented by one or more chips. The program may also be transmitted from the network via a telecommunications line.

[0143] The storage device 1002 is a computer-readable recording medium and may consist of at least one of the following: ROM (Read Only Memory), EPROM (Erasable Programmable ROM), EEPROM (Electrically Erasable Programmable ROM), RAM (Random Access Memory), etc. The storage device 1002 may also be called a register, cache, main memory, etc. The storage device 1002 can store executable programs (program code), software modules, etc., for implementing a communication method according to one embodiment of the present disclosure.

[0144] The auxiliary storage device 1003 is a computer-readable recording medium and may consist of at least one of the following: an optical disc 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 multipurpose disk, a Blu-ray® disk), a smart card, flash memory (e.g., a card, a stick, a key drive), a floppy® disk, a magnetic strip, etc. The above-mentioned storage medium may also be a database, server, or other suitable medium that includes at least one of the storage device 1002 and the auxiliary storage device 1003.

[0145] The communication device 1004 is hardware (transmitting / receiving device) for communicating between computers via at least one of a wired network and a wireless network, and is also referred to as a network device, network controller, network card, communication module, etc. The communication device 1004 may be configured to include, for example, a high-frequency switch, duplexer, filter, frequency synthesizer, etc., in order to implement at least one of frequency division duplex (FDD) and time division duplex (TDD). For example, the transmitting and receiving antenna, amplifier section, transmitting and receiving section, transmission path interface, etc., may be implemented by the communication device 1004. The transmitting and receiving section may be implemented in a physically or logically separated manner, with a transmitting section and a receiving section.

[0146] The input device 1005 is an input device that accepts input from an external source (e.g., a keyboard, mouse, microphone, switch, button, sensor, etc.). The output device 1006 is an output device that outputs to an external source (e.g., a display, speaker, LED lamp, etc.). The input device 1005 and the output device 1006 may be configured as an integrated unit (e.g., a touch panel).

[0147] 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 different buses may be configured for each device.

[0148] Furthermore, the base station 10 and terminal 20 may be configured to include hardware such as a microprocessor, a digital signal processor (DSP), an ASIC (Application Specific Integrated Circuit), a PLD (Programmable Logic Device), and an FPGA (Field Programmable Gate Array), and some or all of each functional block may be realized by such hardware. For example, the processor 1001 may be implemented using at least one of these hardware components.

[0149] Figure 10 shows an example of the configuration of vehicle 2001. As shown in Figure 10, 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 this disclosure may be applied to a communication device mounted on vehicle 2001, for example, to the communication module 2013.

[0150] The drive unit 2002 consists of, for example, 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, which is operated by the user.

[0151] The electronic control unit 2010 consists of a microprocessor 2031, memory (ROM, RAM) 2032, and communication ports (IO ports) 2033. Signals from various sensors 2021 to 2029 installed in the vehicle 2001 are input to the electronic control unit 2010. The electronic control unit 2010 may also be called an ECU (Electronic Control Unit).

[0152] Signals from various sensors 2021 to 2029 include current signals from current sensor 2021 for sensing motor current, front and rear wheel rotation speed signals acquired by rotation speed sensor 2022, front and rear wheel air pressure signals acquired by air pressure sensor 2023, vehicle speed signals acquired by vehicle speed sensor 2024, acceleration signals acquired by acceleration sensor 2025, accelerator pedal depression signals acquired by accelerator pedal sensor 2029, brake pedal depression signals acquired by brake pedal sensor 2026, shift lever operation signals acquired by shift lever sensor 2027, and detection signals acquired by object detection sensor 2028 for detecting obstacles, vehicles, pedestrians, etc.

[0153] The Information Service Unit 2012 consists of various devices for providing (outputting) various types of information such as driving information, traffic information, and entertainment information, including a car navigation system, audio system, speakers, television, and radio, and one or more ECUs that control these devices. The Information Service Unit 2012 uses information acquired from external devices via a communication module 2013, etc., to provide various multimedia information and multimedia services to the occupants of the vehicle 2001. The Information Service Unit 2012 may include input devices that accept input from the outside (e.g., keyboard, mouse, microphone, switch, button, sensor, touch panel, etc.) and output devices that perform output to the outside (e.g., display, speaker, LED lamp, touch panel, etc.).

[0154] The driver assistance system unit 2030 consists of various devices that provide functions to prevent accidents or reduce the driver's workload, such as millimeter-wave radar, LiDAR (Light Detection and Ranging), cameras, positioning locators (e.g., GNSS), map information (e.g., high-definition (HD) maps, autonomous vehicle (AV) maps), gyro systems (e.g., IMU (Inertial Measurement Unit), INS (Inertial Navigation System)), AI (Artificial Intelligence) chips, and AI processors, as well as one or more ECUs that control these devices. The driver assistance system unit 2030 also transmits and receives various information via the communication module 2013 to realize driver assistance functions or autonomous driving functions.

[0155] The communication module 2013 can communicate with the microprocessor 2031 and components of the vehicle 2001 via its communication port. For example, the communication module 2013 sends and receives data via the communication port 2033 between the drive unit 2002, steering unit 2003, accelerator pedal 2004, brake pedal 2005, shift lever 2006, front wheels 2007, rear wheels 2008, axle 2009, the microprocessor 2031 and memory (ROM, RAM) 2032 in the electronic control unit 2010, and sensors 2021-29 provided in the vehicle 2001.

[0156] 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 external devices. For example, it can send and receive various types of information with external devices 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 or a mobile station.

[0157] The communication module 2013 may transmit at least one of the following to an external device via wireless communication: signals from the various sensors 2021-2028 input to the electronic control unit 2010, information obtained based on said signals, and information based on input from an external source (user) obtained via the information service unit 2012. The electronic control unit 2010, the various sensors 2021-2028, the information service unit 2012, etc., may also be called input units that accept input. For example, the PUSCH transmitted by the communication module 2013 may include the information based on the above input.

[0158] The communication module 2013 receives various information (traffic information, signal information, inter-vehicle information, etc.) transmitted from an external device and displays it on the information service unit 2012 provided in the vehicle 2001. The information service unit 2012 may also be called an output unit, which outputs information (for example, outputs information to devices such as displays and speakers 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 the external device 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 2021-2029, etc., provided in the vehicle 2001.

[0159] (Summary of Embodiments) The terminal, base station, or network node of this embodiment may be configured as the communication device, terminal, base station, or network node described in the following sections. The following communication methods may also be implemented.

[0160] (Clause 1) A terminal comprising: a transmitting unit that transmits an inter-RAT measurement report of a first RAT (Radio Access Technology) to a second base station of a second RAT during the LTM (Lower layer Triggered Mobility) preparation phase; and a receiving unit that receives a RACH (Random Access Channel) PDCCH (Physical Downlink Control Channel) order from the second base station, wherein the transmitting unit transmits a RACH preamble to the first base station of the first RAT; during the LTM execution phase, the transmitting unit transmits a Layer 1 measurement report of the first RAT to the second base station; and the receiving unit receives a cell switching command from the second base station. (Clause 2) The terminal according to Clause 1, wherein the transmitting unit transmits the Layer 1 measurement report including the cell ID of the first RAT to the second base station. (Clause 3) The terminal according to Clause 1, wherein the receiving unit receives the cell switching command including the cell ID of the first RAT from the second base station. (Clause 4) The terminal according to Clause 1, wherein the first RAT is 5G and the second RAT is 6G. (Clause 5) The terminal according to Clause 1, wherein the first RAT is 6G and the second RAT is 5G. (Clause 6) A communication method in which, in the Lower Layer Triggered Mobility (LTM) preparation phase, the terminal performs the following steps: a procedure to transmit an inter-RAT measurement report of the first RAT (Radio Access Technology) to the second base station of the second RAT; a procedure to receive a PDCCH (Physical Downlink Control Channel) order of RACH (Random Access Channel) from the second base station; a procedure to transmit a RACH preamble to the first base station of the first RAT; and in the LTM execution phase, the transmitting unit performs the following steps: a procedure to transmit a Layer 1 measurement report of the first RAT to the second base station; and a procedure to receive a cell switching command from the second base station.

[0161] In any of the above configurations, Inter-RAT (Radio Access Technology) LTM (Lower layer Triggered Mobility) can be implemented. According to paragraphs 2 to 5, when 6G is introduced, it will be possible to implement Inter-RAT LTM with minimal downtime when switching between 5G-RAT and 6G-RAT, which is expected to contribute to a smooth transition from 6G to 5G.

[0162] (Supplement to Embodiments) Embodiments of the present invention have been described above, but the disclosed invention is not limited to such embodiments, and those skilled in the art will understand various modifications, alterations, alternatives, substitutions, etc. Specific numerical examples have been used to facilitate understanding of the invention, but 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, and matters described in two or more items may be combined as needed, and matters described in one item may be applied to matters described in another item (as long as they do not contradict each other). The boundaries of functional units or processing units in the functional block diagram do not necessarily correspond to the boundaries of physical parts. The operation of multiple functional units may be physically performed by one part, or the operation of one functional unit may be physically performed by multiple parts. The processing procedures described in the embodiments may be rearranged as long as they do not contradict each other. For the convenience of explaining the processing, the base station 10 and terminal 20 have been described using functional block diagrams, but such devices may be realized in hardware, software, or a combination thereof. The software operated by the processor of the base station 10 according to an embodiment of the present invention and the software operated by the processor of the terminal 20 according to an embodiment of the present invention may be stored in any suitable storage medium such as random access memory (RAM), flash memory, read-only memory (ROM), EPROM, EEPROM, register, hard disk (HDD), removable disk, CD-ROM, database, server, or other appropriate storage medium.

[0163] Furthermore, notification of information is not limited to the embodiments described herein and may be carried out by other means. For example, notification of information may be carried out by physical layer signaling (e.g., DCI (Downlink Control Information), UCI (Uplink Control Information)), upper layer signaling (e.g., RRC (Radio Resource Control) signaling, MAC (Medium Access Control) signaling), broadcast information (MIB (Master Information Block), SIB (System Information Block)), other signals, or combinations thereof. Also, RRC signaling may be called RRC messages, and may be, for example, RRC Connection Setup messages, RRC Connection Reconfiguration messages, etc.

[0164] Each aspect / embodiment described in this disclosure refers to LTE (Long Term Evolution), LTE-A (LTE-Advanced), 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 (where x is, for example, an integer or decimal)), 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 802.20 may apply to at least one system utilizing UWB (Ultra-WideBand), Bluetooth®, or other appropriate systems, and to next-generation systems extended, modified, created, or defined based thereon. Alternatively, multiple systems may be applied in combination (e.g., a combination of at least one of LTE and LTE-A with 5G).

[0165] The processing procedures, sequences, flowcharts, etc., of each aspect / embodiment described herein may be reordered, provided they are consistent with each other. For example, the methods described herein present various step elements in an exemplary order and are not limited to that specific order.

[0166] In this specification, specific operations performed by the base station 10 may, in some cases, be performed by its upper node. In a network consisting of one or more network nodes having a base station 10, it is clear that various operations performed for communication with the terminal 20 can be performed by the base station 10 and at least one of the other network nodes (for example, an MME or S-GW, but not limited to these). Although the above example illustrates the case where there is one other network node besides the base station 10, the other network node may be a combination of multiple other network nodes (for example, an MME and an S-GW).

[0167] The information or signals described in this disclosure may be output from a higher layer (or lower layer) to a lower layer (or higher layer). They may also be input and output via multiple network nodes.

[0168] Input and output information may be stored in a specific location (e.g., memory) or managed using a management table. Input and output information may be overwritten, updated, or appended to. Output information may be deleted. Input information may be transmitted to other devices.

[0169] The determination in this disclosure may be made by a value represented by one bit (0 or 1), by a Boolean value (true or false), or by a numerical comparison (for example, a comparison with a predetermined value).

[0170] Software should be broadly interpreted to mean instructions, instruction sets, code, code segments, program code, programs, subprograms, software modules, applications, software applications, software packages, routines, subroutines, objects, executable files, execution threads, procedures, functions, and so on, whether they are called software, firmware, middleware, microcode, hardware description languages, or by any other name.

[0171] Furthermore, software, instructions, information, etc., may be transmitted and received via a transmission medium. For example, if software is transmitted from a website, server, or other remote source using at least one of wired technology (such as coaxial cable, fiber optic cable, twisted pair, or digital subscriber line (DSL)) and wireless technology (such as infrared or microwave), then at least one of these wired and wireless technologies is included in the definition of a transmission medium.

[0172] The information, signals, etc. described in this disclosure may be represented using any of the various different techniques. For example, the data, instructions, commands, information, signals, bits, symbols, chips, etc. that may be referred to throughout the above description may be represented by voltage, current, electromagnetic waves, magnetic fields or magnetic particles, optical fields or photons, or any combination thereof.

[0173] In addition, terms used 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 the channel and symbol may be a signal (signaling). Also, a signal may be a message. Furthermore, a component carrier (CC) may be called a carrier frequency, cell, frequency carrier, etc.

[0174] The terms “system” and “network” as used in this disclosure are interchangeable.

[0175] Furthermore, the information, parameters, etc., described in this disclosure may be expressed using absolute values, relative values ​​from a given value, or other corresponding information. For example, wireless resources may be indicated by an index.

[0176] The names used for the parameters described above are not restrictive in any way. Furthermore, the formulas and other expressions using these parameters may differ from those expressly disclosed in this disclosure. Various channels (e.g., PUCCH, PDCCH, etc.) and information elements can be identified by any suitable name, and therefore, the various names assigned to these various channels and information elements are not restrictive in any way.

[0177] In this disclosure, terms such as "Base Station (BS)", "wireless base station", "base station equipment", "fixed station", "NodeB", "eNodeB (eNB)", "gNodeB (gNB)", "access point", "transmission point", "reception point", "transmission / reception point", "cell", "sector", "cell group", "carrier", and "component carrier" may be used interchangeably. Base stations may also be referred to by terms such as macrocell, small cell, femtocell, and picocell.

[0178] A base station can accommodate one or more (e.g., three) cells. If a base station accommodates multiple cells, the entire coverage area of ​​the base station can be divided into multiple smaller areas, each of which may also be provided with communication services by a base station subsystem (e.g., a Remote Radio Head (RRH)). The terms “cell” or “sector” refer to part or all of the coverage area of ​​at least one of the base station and / or base station subsystems that provide communication services in that coverage.

[0179] In this disclosure, the transmission of information by a base station to a terminal may be interpreted as the base station instructing the terminal to perform control or operation based on the information.

[0180] In this disclosure, terms such as "Mobile Station (MS)," "user terminal," "User Equipment (UE)," and "terminal" may be used interchangeably.

[0181] 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 several other appropriate terms.

[0182] At least one of the base station and the mobile station may be called a transmitting device, a receiving device, a communication device, etc. At least one of the base station and the mobile station may also be a device mounted on a mobile body, the mobile body itself, etc. The mobile body refers to a movable object, and its speed of movement is arbitrary. This also includes the case when the mobile body is stationary. The mobile body includes, but is not limited to, vehicles, transport vehicles, automobiles, motorcycles, bicycles, connected cars, excavators, bulldozers, wheel loaders, dump trucks, forklifts, trains, buses, handcarts, rickshaws, ships and other watercraft, airplanes, rockets, satellites, drones (registered trademark), multicopters, quadcopters, balloons, and items mounted on them. The mobile body may also be a mobile body that moves autonomously based on operation commands. It may be a vehicle (e.g., a car, an airplane, etc.), an unmanned mobile body (e.g., a drone, an autonomous vehicle, etc.), or a robot (manned or unmanned). Furthermore, at least one of the base station and the mobile station may include devices that do 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.

[0183] Furthermore, the term "base station" in this disclosure may be interpreted as "user terminal." For example, the various aspects / embodiments of this 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, D2D (Device-to-Device), V2X (Vehicle-to-Everything), etc.). In this case, the terminals 20 may have the functions that the base station 10 has. Also, terms such as "uplink" and "downlink" may be interpreted as terms corresponding to terminal-to-terminal communication (for example, "side"). For example, uplink channel, downlink channel, etc., may be interpreted as side channel.

[0184] Similarly, the term "user terminal" in this disclosure may be replaced with "base station." In this case, the base station may be configured to have the same functions as the user terminal described above.

[0185] As used in this disclosure, the terms “determining” and “determining” may encompass a wide variety of actions. “Determining” may include, for example, judging, calculating, computing, processing, deriving, investigating, looking up, searching, or inquiring (e.g., searching in a table, database, or other data structure), or ascertaining. “Determining” may also include receiving (e.g., receiving information), transmitting (e.g., sending information), inputting, outputting, or accessing (e.g., accessing data in memory). Furthermore, "judgment" and "decision" can include considering something as having been "judged" or "decided" after resolving, selecting, choosing, establishing, comparing, etc. In other words, "judgment" and "decision" can include considering something as having been "judged" or "decided" after some action. Also, "judgment (decision)" can be reinterpreted as "assuming," "expecting," or "considering."

[0186] The terms “connected,” “coupled,” or any variation thereof, mean 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” with each other. The coupling or connection between elements may be physical, logical, or a combination thereof. For example, “connection” may be reinterpreted as “access.” As used in this disclosure, two elements may be considered to be “connected” or “coupled” with each other using at least one of one or more wires, cables, and printed electrical connections, and, in some non-limiting and non-exclusive examples, electromagnetic energy having wavelengths in the radio frequency domain, microwave domain, and optical (both visible and invisible) domain.

[0187] The reference signal can also be abbreviated as RS (Reference Signal), and may be called a pilot depending on the applicable standard.

[0188] In this disclosure, the phrase "based on" does not mean "based solely on" unless otherwise specified. In other words, the phrase "based on" means both "based solely on" and "based at least on."

[0189] Any reference to elements using the designations “first,” “second,” etc., as used in this disclosure does not generally limit the quantity or order of those elements. These designations may be used in this disclosure as a convenient way to distinguish between two or more elements. Accordingly, references to the first and second elements do not imply that only two elements may be employed, or that the first element must precede the second element in any way.

[0190] In the configuration of each of the above devices, "means" may be replaced with "part," "circuit," "device," etc.

[0191] Where the terms “include,” “including,” and variations thereof are used in this disclosure, these terms are intended to be inclusive, as is the term “comprising.” Furthermore, the term “or” as used in this disclosure is not intended to mean exclusive OR.

[0192] In this disclosure, if articles are added through translation, such as a, an, and the in English, this disclosure may include the fact that the noun following these articles is plural.

[0193] In this 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 "combine" may be interpreted similarly to "different."

[0194] Each aspect / embodiment described in this disclosure may be used individually, in combination, or switched between as needed during implementation. Furthermore, notification of specific information (e.g., notification that "X is") is not limited to explicit notification, but may also be implicit (e.g., by not providing such notification).

[0195] Although the present disclosure has been described in detail above, it will be 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 intent and scope of the present disclosure as defined by the claims. Therefore, the descriptions in the present disclosure are illustrative and not intended to be restrictive in any way.

[0196] 10 Base station 110 Transmitter 120 Receiver 130 Setting unit 140 Control unit 20 Terminal 210 Transmitter 220 Receiver 230 Setting unit 240 Control unit 30 Network node 1001 Processor 1002 Storage device 1003 Auxiliary storage device 1004 Communication device 1005 Input device 1006 Output device

Claims

1. A terminal comprising: a transmitting unit that transmits an inter-RAT measurement report from a first RAT (Radio Access Technology) to a second base station of a second RAT during the LTM (Lower layer Triggered Mobility) preparation phase; and a receiving unit that receives a RACH (Random Access Channel) PDCCH (Physical Downlink Control Channel) order from the second base station, wherein the transmitting unit transmits a RACH preamble to the first base station of the first RAT; and during the LTM execution phase, the transmitting unit transmits a Layer 1 measurement report from the first RAT to the second base station; and the receiving unit receives a cell switching command from the second base station.

2. The terminal according to claim 1, wherein the transmitting unit transmits the Layer 1 measurement report, including the cell ID of the first RAT, to the second base station.

3. The terminal according to claim 1, wherein the receiving unit receives the cell switching command, which includes the cell ID of the first RAT, from the second base station.

4. The terminal according to claim 1, wherein the first RAT is 5G and the second RAT is 6G.

5. The terminal according to claim 1, wherein the first RAT is 6G and the second RAT is 5G.

6. A communication method in which a terminal performs the following steps during the Lower Layer Triggered Mobility (LTM) preparation phase: transmitting an inter-RAT measurement report from the first RAT (Radio Access Technology) to the second base station of the second RAT; receiving a PDCCH (Physical Downlink Control Channel) order for the Random Access Channel (RACH) from the second base station; transmitting a RACH preamble to the first base station of the first RAT; and during the LTM execution phase: transmitting a Layer 1 measurement report from the first RAT to the second base station; and receiving a cell switching command from the second base station.

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