Method and apparatus for supporting mobility on basis of layer 1 / layer 2 signaling based on CSI-RS measurement

Abstract

The present disclosure relates to a 5G or 6G communication system for supporting a higher data transmission rate. The present disclosure relates to a method and an apparatus for supporting mobility on the basis of layer 1 / layer 2 signaling based on CSI-RS measurement.

Description

CSI-RS Measurement-Based Layer 1 / Layer 2 Signaling-Based Mobility Support Method and Device

[0001] The present invention relates to the operation of a base station, a terminal, and a core network in a mobile communication system. More specifically, the present invention relates to a CSI-RS measurement-based Layer 1 / Layer 2 signaling-based mobility support method and apparatus.

[0002] 5G mobile communication technology defines a wide frequency band to enable fast transmission speeds and new services, and can be implemented not only in frequency bands below 6 GHz ('Sub 6 GHz'), such as 3.5 gigahertz (3.5 GHz), but also in ultra-high frequency bands called millimeter waves (mmWave), such as 28 GHz and 39 GHz ('Above 6 GHz'). In addition, for 6G mobile communication technology, which is referred to as a system beyond 5G, implementation in the terahertz band (e.g., the 3 terahertz (3 THz) band at 95 GHz) is being considered to achieve transmission speeds 50 times faster and ultra-low latency reduced to one-tenth compared to 5G mobile communication technology.

[0003] In the early stages of 5G mobile communication technology, aiming to satisfy service support and performance requirements for enhanced Mobile BroadBand (eMBB), Ultra-Reliable Low-Latency Communications (URLLC), and massive Machine-Type Communications (mMTC), technologies such as beamforming and Massive MIMO to mitigate path loss and increase transmission distance in ultra-high frequency bands, support for various numerologies (such as the operation of multiple subcarrier spacings) and dynamic operation of slot formats for the efficient utilization of ultra-high frequency resources, initial access techniques to support multi-beam transmission and broadband, definition and operation of Band-Width Parts (BWP), Low Density Parity Check (LDPC) codes for high-volume data transmission, new channel coding methods such as Polar Codes for the reliable transmission of control information, and L2 pre-processing (L2 Standardization has been carried out for pre-processing, network slicing which provides a dedicated network specialized for specific services, and other methods.

[0004] Currently, discussions are underway to improve and enhance the performance of the initial 5G mobile communication technology, taking into account the services that the 5G mobile communication technology was intended to support. Additionally, standardization of the physical layer is in progress for technologies such as V2X (Vehicle-to-Everything), which helps autonomous vehicles make driving decisions and enhance user convenience based on their own location and status information transmitted by the vehicle; NR-U (New Radio Unlicensed), which aims for system operation in unlicensed bands to comply with various regulatory requirements; NR terminal low power consumption technology (UE Power Saving); Non-Terrestrial Network (NTN), which is direct terminal-satellite communication for securing coverage in areas where communication with the terrestrial network is impossible; and positioning.

[0005] In addition, standardization is underway in the field of wireless interface architecture / protocols for technologies such as the Industrial Internet of Things (IIoT) for supporting new services through linkage and convergence with other industries, Integrated Access and Backhaul (IAB) which provides nodes for expanding network service areas by integrating wireless backhaul links and access links, Mobility Enhancement including Conditional Handover and Dual Active Protocol Stack (DAPS) Handover, and 2-step Random Access (2-step RACH for NR) which simplifies random access procedures. Standardization is also underway in the field of system architecture / services for 5G baseline architectures (e.g., Service based Architecture, Service based Interface) for incorporating Network Functions Virtualization (NFV) and Software-Defined Networking (SDN) technologies, and Mobile Edge Computing (MEC), which provides services based on the location of the terminal.

[0006] When such 5G mobile communication systems are commercialized, connected devices, which are increasing explosively, will be connected to communication networks. Accordingly, it is expected that there will be a need to enhance the functionality and performance of 5G mobile communication systems and to integrate the operation of connected devices. To this end, new research is planned to be conducted on 5G performance improvement and complexity reduction, support for AI services, support for metaverse services, and drone communication using eXtended Reality (XR), Artificial Intelligence (AI), and Machine Learning (ML) to efficiently support Augmented Reality (AR), Virtual Reality (VR), and Mixed Reality (MR).

[0007] Furthermore, the advancement of these 5G mobile communication systems encompasses multi-antenna transmission technologies such as new waveforms, Full Dimensional MIMO (FD-MIMO), array antennas, and large-scale antennas to guarantee coverage in the terahertz band of 6G mobile communication technology; metamaterial-based lenses and antennas; high-dimensional spatial multiplexing technology using Orbital Angular Momentum (OAM); and Reconfigurable Intelligent Surface (RIS) technology to improve terahertz band signal coverage; as well as full-duplex technology for enhancing frequency efficiency and system networks in 6G mobile communication technology; AI-based communication technologies that realize system optimization by utilizing satellites and Artificial Intelligence (AI) from the design stage and internalizing end-to-end AI support functions; and the realization of services of complexity exceeding the limits of terminal computing capabilities by utilizing ultra-high-performance communication and computing resources. It could serve as a foundation for the development of next-generation distributed computing technologies.

[0008] As a result of the aforementioned developments and advancements in mobile communication systems, it has become possible to provide a variety of services, and thus measures to effectively provide these services are required.

[0009] One embodiment of the present invention aims to provide a method for utilizing the Channel State Information (CSI)-Reference Signal (RS) among several Layer 1 measurement values ​​that serve as the basis or standard for performing a handover (LTM: L1 / L2 Triggered Mobility) of a terminal based on Layer 1 / Layer 2 signaling in a mobile communication system.

[0010] Specifically, one embodiment of the present invention aims to provide information and a method for exchanging between base stations and between a base station and a terminal to set / report CSI-RS as one of periodic, semi-persistent, and aperiodic types.

[0011] The technical problems to be solved by the present invention are not limited to those mentioned above, and other unmentioned technical problems may be considered by those skilled in the art from the various embodiments of the present disclosure described below.

[0012] A method performed by a first base station of a wireless communication system according to an embodiment of the present invention for solving the above-mentioned problems may include: receiving a first message from a second base station associated with the transmission of resource setting information for LTM (layer 1 / layer 2 triggered mobility) measurement; and transmitting a second message to the second base station that includes resource setting information of a CSI-RS (channel status information reference signal) for the LTM measurement.

[0013] According to an embodiment, the resource setting information of the CSI-RS for the LTM measurement may include at least one of a periodic CSI-RS resource setting or a semi-persistent CSI-RS resource setting.

[0014] According to an embodiment, the first message may include at least one of a UE (user equipment) context setup request message, a UE context modification request message, or a handover request message.

[0015] According to an embodiment, the second message may include at least one of a UE context setup response message, a UE context modification response message, or a handover request acknowledgment message.

[0016] According to an embodiment, the first base station may include at least one of a gNB-DU (distributed unit) or a target base station.

[0017] According to an embodiment, the second base station may include at least one of a gNB-CU (centralized unit) or a source base station.

[0018] In addition, a method performed by a terminal of a wireless communication system according to an embodiment of the present invention for solving the above-mentioned problems may include: receiving a message from a second base station containing resource information for CSI-RS-based LTM measurement determined based on resource setting information of CSI-RS (channel status information reference signal) for LTM (layer 1 / layer 2 triggered mobility) measurement set by a first base station; and transmitting L1 (layer 1) measurement information based on the resource information for CSI-RS-based LTM measurement to the first base station.

[0019] According to an embodiment, the resource setting information of the CSI-RS for the LTM measurement set by the first base station may include at least one of a periodic CSI-RS resource setting or a semi-persistent CSI-RS resource setting.

[0020] According to an embodiment, the message may be a radio resource control (RRC) reconfiguration message.

[0021] In addition, a first base station of a wireless communication system according to an embodiment of the present invention for solving the above-mentioned problems may include: a transceiver; and a control unit connected to the transceiver, receiving a first message from a second base station associated with the transmission of resource setting information for LTM (layer 1 / layer 2 triggered mobility) measurement, and transmitting a second message to the second base station that includes an LTM setting containing resource setting information of a CSI-RS (channel status information reference signal) for the LTM measurement.

[0022] In addition, a terminal of a wireless communication system according to an embodiment of the present invention for solving the above-mentioned problems may include: a transceiver; and a control unit connected to the transceiver, receiving from a second base station a message containing resource information for CSI-RS-based LTM measurement determined based on resource setting information of CSI-RS (channel status information reference signal) for LTM (layer 1 / layer 2 triggered mobility) measurement set by a first base station, and transmitting L1 (layer 1) measurement information based on the resource information for CSI-RS-based LTM measurement to the first base station.

[0023] One embodiment of the present invention can provide a method for utilizing Channel State Information (CSI)-Reference Signal (RS) among several Layer 1 measurement values ​​that serve as the basis or standard for performing a handover (LTM: L1 / L2 Triggered Mobility) of a terminal based on Layer 1 / Layer 2 signaling in a mobile communication system.

[0024] Specifically, one embodiment of the present invention may provide information and a method for exchanging between base stations and between a base station and a terminal to set / report CSI-RS as one of periodic, semi-persistent, and aperiodic types.

[0025] The effects obtainable in the present disclosure are not limited to those mentioned in the various embodiments, and other unmentioned effects will be clearly understood by those skilled in the art to which the present disclosure pertains from the description below.

[0026] FIG. 1 is a drawing illustrating an example of a next-generation mobile communication system structure according to one embodiment of the present invention.

[0027] FIG. 2 is a signal flow diagram in the process (Intra-DU LTM) in which a terminal according to an embodiment of the present invention performs cell movement within one DU in a separated base station based on Layer 1 / Layer 2 signaling.

[0028] FIG. 3 is a signal flow diagram in the process (Inter-DU LTM) in which a terminal according to an embodiment of the present invention performs cell movement from the DU to which the currently serving cell belongs to another DU in a separated base station based on Layer 1 / Layer 2 signaling.

[0029] FIG. 4 is a signal flow diagram in the process (Inter-CU LTM) in which a terminal according to an embodiment of the present invention performs cell movement from a base station (or gNB-CU) to which the current serving cell belongs to another base station (or gNB-CU) based on Layer 1 / Layer 2 signaling in a separated or non-separated base station.

[0030] FIGS. 5a, FIGS. 5b, FIGS. 5c, FIGS. 5d, and FIGS. 5e are examples of messages including an Information Element (IE) that includes Layer 1 measurement value information, such as SSB and CSI-RS setting information, which are to be measured by the terminals exemplified in FIG. 2 (Intra-DU LTM) and FIG. 3 (Inter-DU LTM) according to an embodiment of the present invention.

[0031] FIGS. 6a, FIGS. 6b, FIGS. 6c, and FIGS. 6d are examples of messages including an Information Element (IE) that includes Layer 1 measurement value information, such as SSB and CSI-RS setting information, which is to be measured by the terminal exemplified in FIG. 4 (Inter-CU LTM) according to an embodiment of the present invention.

[0032] FIG. 7 is a flowchart illustrating a procedure for activating or deactivating and reporting the measurement value when a terminal according to an embodiment of the present invention is configured to measure a Layer 1 measurement using CSI-RS after undergoing the LTM preparation process described in FIG. 2, 3, and 4.

[0033] FIG. 8 is a flowchart of activating, deactivating, or changing the reporting settings of measurement values ​​in a situation where CSI-RS is already set as a Layer 1 measurement in an Inter-gNB or Inter-CU LTM according to an embodiment of the present invention.

[0034] FIG. 9 is a block diagram showing an example of the configuration of a RAN Node according to one embodiment of the present invention.

[0035] FIG. 10 is a block diagram illustrating an example of the structure of a terminal according to one embodiment of the present invention.

[0036] The operating principle of the present invention will be described in detail below with reference to the attached drawings. In describing the present invention below, specific descriptions of related known functions or configurations will be omitted if it is determined that such detailed descriptions would unnecessarily obscure the essence of the invention. Furthermore, the terms described below are defined considering their functions in the present invention, and these may vary depending on the intentions or conventions of the user or operator. Therefore, their definitions should be based on the content throughout this specification.

[0037] Terms used in the following description to identify connection nodes, terms referring to network entities, terms referring to messages, terms referring to interfaces between network entities, terms referring to various identification information, etc., are examples provided for the convenience of explanation. Accordingly, the present invention is not limited to the terms described below, and other terms referring to objects having equivalent technical meanings may be used.

[0038] Hereinafter, a base station is an entity that performs resource allocation for terminals and may be at least one of a gNode B, eNode B, Node B, BS (Base Station), radio access unit, base station controller, or a node on a network. A terminal may include a UE (User Equipment), MS (Mobile Station), cellular phone, smartphone, computer, or a multimedia system capable of performing communication functions. In this disclosure, a downlink (DL) refers to a wireless transmission path of a signal transmitted by a base station to a terminal, and an uplink (UL) refers to a wireless transmission path of a signal transmitted by a terminal to a base station. Furthermore, while an LTE or LTE-A system may be described as an example below, embodiments of this disclosure may be applied to other communication systems having similar technical backgrounds or channel types. For example, 5th generation mobile communication technology (5G, new radio, NR) developed after LTE-A may be included in a system to which embodiments of this disclosure can be applied, and the 5G below may be a concept that includes existing LTE, LTE-A, and other similar services. Furthermore, the present disclosure may be applied to other communication systems with some modifications made at the discretion of a person with skilled technical knowledge, without departing significantly from the scope of the present disclosure. In this case, it will be understood that each block of the process flow diagrams and combinations of the flow diagrams may be executed by computer program instructions.

[0039] Since these computer program instructions can be loaded onto the processor of a general-purpose computer, a computer for special purposes, or other programmable data processing equipment, the instructions executed through the processor of the computer or other programmable data processing equipment create means for performing the functions described in the flowchart block(s). Since these computer program instructions can also be stored in computer-available or computer-readable memory that can be directed toward the computer or other programmable data processing equipment to implement functions in a specific way, the instructions stored in computer-available or computer-readable memory can also produce a manufactured item containing means of instruction for performing the functions described in the flowchart block(s). Since the computer program instructions can also be loaded onto the computer or other programmable data processing equipment, the instructions that perform a series of operation steps on the computer or other programmable data processing equipment to create a computer-executable process can also provide steps for performing the functions described in the flowchart block(s).

[0040] Additionally, each block may represent a module, segment, or part of code containing one or more executable instructions for executing a specific logical function(s). Also, it should be noted that in some alternative execution examples, the functions mentioned in the blocks may occur out of order. For example, two blocks described in succession may actually be executed substantially simultaneously, or the blocks may be executed in reverse order depending on the corresponding function. In this case, the term "part" as used in this embodiment refers to software or hardware components such as a Field Programmable Gate Array (FPGA) or an Application Specific Integrated Circuit (ASIC), and the "part" may perform certain roles. However, the meaning of "part" is not limited to software or hardware. The "part" may be configured to reside in an addressable storage medium or configured to run one or more processors. Accordingly, as an example, 'part' includes components such as software components, object-oriented software components, class components, and task components, as well as processes, functions, attributes, procedures, subroutines, segments of program code, drivers, firmware, microcode, circuits, data, databases, data structures, tables, arrays, and variables. The functions provided within the components and 'parts' may be combined into a smaller number of components and 'parts' or further separated into additional components and 'parts'. Furthermore, the components and 'parts' may be implemented to utilize one or more CPUs within a device or secure multimedia card. Additionally, in an embodiment, 'part' may include one or more processors.

[0041] For the convenience of the following explanation, the present invention uses terms and names defined in the LTE (3rd Generation Partnership Project Long Term Evolution), 5GS, and NR specifications, which are standards defined by the 3GPP (The 3rd Generation Partnership Project) organization among currently existing communication standards. However, the present invention is not limited by the above terms and names and can be applied in the same way to systems conforming to other standards. For example, the present invention can be applied to 3GPP 5GS / NR (5th generation mobile communication standard).

[0042] FIG. 1 is a drawing illustrating an example of a next-generation mobile communication system structure according to an embodiment of the present invention. That is, FIG. 1 is a drawing illustrating an example of a next-generation mobile communication system structure to which embodiments of the present disclosure can be applied.

[0043] Referring to FIG. 1, the RAN Node (1-100, 1-200) specified in this structure may refer to a mobile communication base station, such as an LTE eNB or NR gNB, connected to a mobile communication Core Network (Core Network, CN, Core Network), such as an EPC (Evolved Packet Core) or a 5GC (5G Core Network) (1-400). Additionally, the RAN Node (1-100, 1-200) may be divided into a CU (Centralized Unit) and a DU (Distributed Unit), and the CU may be further divided into a CU-CP (Control Plane) and a CU-UP (User Plane). Referring to FIG. 1, the RAN Node (1-100) may refer to a Source RAN Node, and the RAN Node (1-200) may refer to a Target RAN Node.

[0044] According to one embodiment, a single RAN Node (1-100, 1-200) may each be composed of one or more CU-CPs, one or more CU-UPs, and one or more DUs (1-110, 1-120). Additionally, the CU-CPs, CU-UPs, and DUs constituting a single RAN Node (1-100, 1-200) may be configured together. For example, a single RAN Node (1-100, 1-200) may be composed of a CU in which a CU-CP and a CU-UP are implemented together, and a DU. In another embodiment, a single RAN Node (1-100, 1-200) may have a CU-CP and a DU implemented together, and a CU-UP configured separately. In another embodiment, a single RAN Node (1-100, 1-200) may be configured in the form of an integrated base station in which CU-CP, CU-UP, and DU are implemented together. A single RAN Node may be configured in any other combination other than the example described above.

[0045] According to one embodiment, the CU and the DU can support their respective base station functions separately. For example, the CU may support the RRC (radio resource control) / PDCP (packet data convergence protocol) layer, and the DU may support the RLC (radio link control) / MAC (medium access control) / PHY (physical) / RF (radio frequency) layer. Additionally, the CU and the DU may be connected through an interface between internal base station functions, such as a W1 interface or an F1 interface.

[0046] According to one embodiment, the CU can be divided into CU-CP and CU-UP. For example, the CU-CP may support an RRC / PDCP (for RRC) layer, and the CU-UP may support a PDCP (for user data transmission) layer, and the CU-CP and CU-UP may be connected through an interface between internal base station functions such as an E1 interface.

[0047] According to one embodiment, base stations may be constructed in an integrated or separated structure, enabling connections between integrated base stations, between separated base stations, and between an integrated base station and a separated base station. RAN Nodes may be connected via an inter-base station interface such as an X2 interface or an Xn interface. Additionally, RAN Nodes and Core networks may be connected via a base station-Core network interface such as an S1 interface or an NG interface. The technology proposed in this disclosure may be applied when a terminal (1-300) moves within a cell (Intra-DU) within a single DU at a separated base station, or when moving from DU 1 (1-110) to DU 2 (1-120) (Inter-DU). Alternatively, it may be applied when a handover occurs between base stations when the terminal (1-300) moves to a Target RAN Node (1-200) while connected to a Source RAN Node (1-100), regardless of whether it is an integrated base station or a separated base station.

[0048] FIG. 2 is a signal flow diagram in the process (Intra-DU LTM) in which a terminal according to an embodiment of the present invention performs cell movement within one DU in a separated base station based on Layer 1 / Layer 2 signaling.

[0049] Referring to FIG. 2, in step 205, the terminal (UE) (201) is connected to the separate base station gNB-DU (202) and gNB-CU (203) to transmit and receive user packets (downlink / uplink user data) through the 5GC (204).

[0050] In step 207, the terminal (201) can perform (control) Layer 3 measurement based on signals transmitted by base stations according to information set by base stations (202, 203), and transmit (report) the measurement information to the gNB-DU (20).

[0051] In step 207, the gNB-DU (202), having received Layer 3 measurement information from the terminal (201), transmits this to the gNB-CU (203), and in step 210, the gNB-CU (203) can determine whether to set up a handover (LTM: L1 / L2 Triggered Mobility) based on Layer 1 / Layer 2 signaling for the terminal (201). If the gNB-CU (203) decides to perform a handover based on Layer 1 / Layer 2 signaling, the gNB-CU (203) can determine a candidate target cell for which the terminal (201) can perform a handover and gNBs containing said candidate target cell (determining LTM candidates). This embodiment relates to a Layer 1 / Layer 2 signaling-based handover situation in an intra-DU situation, where all candidate target cells are under the management of a gNB-DU (202) to which the terminal (201) is connected.

[0052] The gNB-CU (203) can send a UE CONTEXT MODIFICATION REQUEST message to each gNB-DU (202) containing the target cell determined in step 210 to set up a handover based on Layer 1 / Layer 2 signaling in step 215. If there are multiple candidate target cells, the message (215) can be sent multiple times, and each message can be distinguished by cell ID information. The UE CONTEXT MODIFICATION REQUEST message may include an indicator such as an LTM (L1 / L2 Triggered Mobility) Indicator indicating that it is for setting up a handover based on Layer 1 / Layer 2 signaling, and information for setting up the LTM.

[0053] Upon receiving the UE CONTEXT MODIFICATION REQUEST message, the gNB-DU (202) determines whether to accept the handover setting based on Layer 1 / Layer 2 signaling in step 220, and if it decides to accept it, it can send the UE CONTEXT MODIFICATION RESPONSE message to the gNB-CU (203). The message may include RRC setting values ​​related to the cell that decided to accept it and Layer 1 measurement value information that the terminal (201) must measure. The Layer 1 measurement value information that the terminal (201) must measure may be at least one of the SSB (Synchronization Signal Block) and the CSI (Channel State Information)-RS (Reference Signal) set for the terminal (201), and may be both. This content is described in detail along with the message in FIGS. 5a to 5e.

[0054] At this time, as described above, if there are multiple target cells, the message corresponding to step 220 may also be transmitted multiple times.

[0055] The gNB-CU (203), having exchanged information with all candidate target cells, can send a message (UE CONTEXT MODIFICATION REQUEST) containing Layer 1 measurement information related to the target cell included as the final candidate to the gNB-DU (202) in step 225. The Layer 1 measurement value included in the message (225) can be an SSB or a CSI-RS, or both.

[0056] The gNB-DU (202) that receives the message transmitted in step 225 above can generate a lower layer RRC, put it in the UE CONTEXT MODIFICATION RESPONSE, and transmit it to the gNB-CU (203) in step 230. This operation is to generate Layer 1 measurement value information related to the candidate cell when performing a handover based on Layer 1 / Layer 2 signaling based on the serving cell to which the current terminal (201) is connected, and this information can be included in the RRC of step 230.

[0057] Based on the lower layer RRC value received from gNB-DU (202), gNB-CU (203) can generate an RRCReconfiguration message to be transmitted to the terminal (201), put it in a DL RRC TRANSFER MESSAGE, and transmit it to gNB-DU (202) in step 235.

[0058] gNB-DU (202) can transmit the received RRCReconfiguration message to the terminal (201) at step 240. In response to this, the terminal (201) can transmit an RRCReconfigurationComplete message to the gNB-DU (202) at step 245, and the message can be finally delivered to the gNB-CU (203) in the form of a UL RRC TRANSFER MESSAGE at step 250.

[0059] After going through the process described above, the preparation process for Layer 1 / Layer 2 signaling-based handover is completed.

[0060] After completing the preparation process, the terminal (201) can report (transmit) Layer 1 measurement information to the gNB-DU (202) at step 255 according to the setting value in the process described above.

[0061] When the gNB-DU (202) receives Layer 1 measurement information from the terminal (201) and determines that a specific condition for LTM is satisfied (step 260, LTM cell switch determination), the gNB-DU (202) can perform LTM by instructing the terminal (201) to move to a cell by specifying a target cell in step 265 (cell switch command).

[0062] FIG. 3 is a signal flow diagram in the process (Inter-DU LTM) in which a terminal according to an embodiment of the present invention performs cell movement from the DU to which the currently serving cell belongs to another DU in a separated base station based on Layer 1 / Layer 2 signaling.

[0063] Referring to FIG. 3, in step 307, the terminal (301) is connected to a separated base station Source gNB-DU (302, hereinafter S-DU) and a gNB-CU (304, hereinafter CU), and can transmit and receive user packets through the 5GC (305).

[0064] In step 309, the terminal (301) can perform Layer 3 measurement based on signals transmitted by base stations according to information set by base stations (302, 304), and transmit the measurement information to the S-DU (source gNB-DU) (302).

[0065] In step 309, the S-DU (302) that receives Layer 3 measurement information from the terminal (301) transmits it to the CU (gNB-CU) (304), and in step 310, the CU (304) can determine whether to set up a handover (LTM: L1 / L2 Triggered Mobility) based on Layer 1 / Layer 2 signaling for the terminal (301). If the gNB-CU (304) decides to perform a handover based on Layer 1 / Layer 2 signaling, the gNB-CU (304) can determine a candidate target cell for which the terminal (301) can perform a handover and gNBs containing said candidate target cell. This embodiment relates to a Layer 1 / Layer 2 signaling-based handover situation in an inter-DU situation, that is, a situation where the candidate target cell is under the management of a Candidate gNB-DU (303, hereinafter C-DU) rather than the S-DU (302) to which the terminal (301) is connected.

[0066] The gNB-CU (304) can send a UE CONTEXT SETUP REQUEST message to the C-DU (303) containing the target cell determined in step 310 to set up a handover based on Layer 1 / Layer 2 signaling in step 315. If there are multiple candidate target cells, the message (315) can be sent multiple times, and each message can be distinguished by cell ID information. The UE CONTEXT SETUP REQUEST message may include an indicator such as an LTM (L1 / L2 Triggered Mobility) Indicator indicating that the handover is to be set up based on Layer 1 / Layer 2 signaling, and information for setting up the LTM.

[0067] Upon receiving the UE CONTEXT SETUP REQUEST message, the C-DU (303) determines whether to accept the handover setting based on Layer 1 / Layer 2 signaling in step 320, and if it decides to accept it, it can send the UE CONTEXT SETUP RESPONSE message to the gNB-CU (304). The message may include RRC setting values ​​related to the cell that decided to accept it and Layer 1 measurement value information that the terminal (301) must measure. The Layer 1 measurement value information that the terminal (301) must measure may be at least one of the SSB (Synchronization Signal Block) and the CSI (Channel State Information)-RS (Reference Signal) set for the terminal (301), or both. This content is discussed in detail along with the message in FIGS. 5a to 5e, just as with the intra-DU situation in FIG. 2.

[0068] At this time, as described above, if there are multiple target cells, the message corresponding to step 320 may also be transmitted multiple times.

[0069] The gNB-CU (304), having exchanged information with all candidate target cells, can send a message (UE CONTEXT MODIFICATION REQUEST) containing Layer 1 measurement information related to the target cell included as the final candidate to the S-DU (302) in step 325. The Layer 1 measurement value included in the message (325) can be an SSB or a CSI-RS, or both.

[0070] The S-DU (302) that receives the message transmitted in step 325 above can generate a lower layer RRC, put it in the UE CONTEXT MODIFICATION RESPONSE, and transmit it to the gNB-CU (304) in step 330. This operation is to generate Layer 1 measurement value information related to the candidate cell when performing a handover based on Layer 1 / Layer 2 signaling based on the serving cell to which the current terminal (301) is connected, and this information can be included in the RRC of step 330.

[0071] Based on the lower layer RRC value received from the S-DU (302), the gNB-CU (304) can generate an RRCReconfiguration message to be transmitted to the terminal (301), put it in a DL RRC TRANSFER MESSAGE, and transmit it to the S-DU (302) in step 335.

[0072] S-DU (302) can transmit the received RRCReconfiguration message to the terminal (301) at step 340. In response to this, the terminal (301) can transmit an RRCReconfigurationComplete message to S-DU (302) at step 345, and the message can be finally delivered to gNB-CU (304) in the form of a UL RRC TRANSFER MESSAGE at step 350.

[0073] After going through the process described above, the preparation process for Layer 1 / Layer 2 signaling-based handover is completed.

[0074] After completing the preparation process, the terminal (301) can report (transmit) Layer 1 measurement information to the S-DU (302) at step 355 according to the setting value in the process described above.

[0075] When the gNB-DU (302) receives Layer 1 measurement information from the terminal (301), if it determines that a specific condition for LTM is satisfied (step 360), it can perform LTM by instructing the terminal (301) to move to a cell by designating a target cell in step 365.

[0076] FIG. 4 is a signal flow diagram in the process (Inter-CU LTM) in which a terminal according to an embodiment of the present invention performs cell movement from a base station (or gNB-CU) to which the current serving cell belongs to another base station (or gNB-CU) based on Layer 1 / Layer 2 signaling in a separated or non-separated base station.

[0077] Referring to FIG. 4, in step 405, the terminal (401) is connected to the base station Source gNB (402, hereinafter S-gNB) and can transmit and receive user packets through the 5GC (404).

[0078] In step 407, the terminal (401) can perform Layer 3 measurement based on signals transmitted by base stations according to information set by the base station (S-gNB) (402), and transmit the measurement information to the S-gNB (402).

[0079] In step 407, the S-gNB (402) that receives Layer 3 measurement information from the terminal (10) can decide in step 410 whether to set up a handover (LTM: L1 / L2 Triggered Mobility) based on Layer 1 / Layer 2 signaling for the terminal (401). If it is decided to perform a handover based on Layer 1 / Layer 2 signaling, the S-gNB (402) can determine a candidate target cell where the terminal (401) can perform a handover and gNBs containing said candidate target cell. This embodiment relates to a Layer 1 / Layer 2 signaling-based handover situation in an inter-gNB (or inter-CU) situation where the candidate target cell is under the management of a Candidate gNB (candidate gNB-CU) (403, hereinafter C-gNB), rather than the S-gNB (402) to which the terminal (401) is currently connected.

[0080] S-gNB (402) can send a HANDOVER REQUEST message to C-gNB (403) containing the target cell determined in step 410 to set up a handover based on Layer 1 / Layer 2 signaling in step 415. If there are multiple candidate target cells, the message (415) may be sent multiple times, and each message may be distinguished by cell ID information. The HANDOVER REQUEST message may include an indicator such as an LTM (L1 / L2 Triggered Mobility) Indicator indicating that the handover is to be set up based on Layer 1 / Layer 2 signaling, and information for setting up the LTM.

[0081] Upon receiving the HANDOVER REQUEST message, the C-gNB (403) determines whether to accept the handover setting based on Layer 1 / Layer 2 signaling in step 420, and if it decides to accept it, it can send a HANDOVER REQUEST ACKNOWLEDGE message to the S-gNB (402). The message may include RRC setting values ​​related to the cell that decided to accept and Layer 1 measurement value information that the terminal (401) must measure. The Layer 1 measurement value information that the terminal (401) must measure may be at least one of the SSB (Synchronization Signal Block) and the CSI (Channel State Information)-RS (Reference Signal) set for the terminal (401), or both. This content is discussed in detail along with the message in FIGS. 6a to 6d, just as in the intra-DU situation of FIG. 2 and the inter-DU situation of FIG. 3.

[0082] At this time, as described above, if there are multiple target cells, the message corresponding to step 420 may also be transmitted multiple times.

[0083] The S-gNB (402), having exchanged information with all candidate target cells, can send a message (LTM CONFIGURATION UPDATE) containing Layer 1 measurement information related to the target cell included as the final candidate to the C-gNB (403) in step 425. The Layer 1 measurement value included in the message (425) can be an SSB or a CSI-RS, or both.

[0084] The C-gNB (403) that receives the message transmitted in step 425 above can generate an RRC, put it in the LTM CONFIGURATION UPDATE ACKNOWLEDGE, and transmit it to the S-gNB (402) in step 430. This operation is to generate Layer 1 measurement value information related to the candidate cell when performing a handover based on Layer 1 / Layer 2 signaling based on the serving cell to which the current terminal (401) is connected, and this information can be included in the RRC of step 430.

[0085] S-gNB (402) can generate an RRCReconfiguration message to be delivered to the terminal (401) and transmit it to the terminal (401) in step 435. In response to this, the terminal (401) can transmit an RRCReconfigurationComplete message to S-gNB (402) in step 440.

[0086] After going through the process described above, the preparation process for Layer 1 / Layer 2 signaling-based handover is completed.

[0087] After completing the preparation process, the terminal (401) can report Layer 1 measurement information to the S-gNB (402) in step 445 according to the setting value in the process described above.

[0088] When the S-gNB (402) receives Layer 1 measurement information from the terminal (401), if it determines that specific conditions for LTM are satisfied (step 450), it can perform LTM by instructing the terminal (401) to move to a cell by designating a target cell in step 455.

[0089] FIGS. 5a, FIGS. 5b, FIGS. 5c, FIGS. 5d, and FIGS. 5e are examples of messages including an Information Element (IE) that includes Layer 1 measurement value information, such as SSB and CSI-RS setting information, which are to be measured by the terminals exemplified in FIG. 2 (Intra-DU LTM) and FIG. 3 (Inter-DU LTM) according to an embodiment of the present invention.

[0090] Referring to FIGS. 5a, 5b, 5c, 5d, and 5e, the UE CONTEXT SETUP REQUEST (510) message is a message transmitted by the gNB-CU to the candidate gNB-DU during the Inter-DU LTM preparation process, and may include (configuration) information including the SSB or CSI-RS, or both, that the candidate cells collected so far have configured for the terminal. The SSB and CSI-RS information may exist simultaneously within the CSI Resource Configuration IE of 513, or may exist in the form of a newly defined CSI-RS Resource Configuration (515) under the CSI Resource Configuration (513) for SSB information. When using CSI-RS as a measurement value, one of three types can be selected, as indicated by the CSI-RS type (517) included in the CSI Resource Configuration (513) or CSI-RS Resource Configuration (515). If configured as a Periodic type, the terminal can continuously measure the corresponding CSI-RS periodically. In the case of the Semi-Persistent type, the CSI-RS resource is pre-configured, but the terminal does not measure the value until a separate instruction (e.g., MAC CE) is received from the base station. Once the instruction is received, the terminal can begin measurement according to the period provided by the base station, just as in the Periodic type. When configured as the Aperiodic type, the CSI-RS resource is also pre-configured as in the Semi-Persistent case, but the terminal performs measurement only upon receiving a separate instruction from the base station; unlike the two types described above, however, the measurement is performed only once.

[0091] Upon receiving the UE CONTEXT SETUP REQUEST (510), the gNB-DU can send the Layer 1 measurement value associated with the cell to the gNB-CU in the UE CONTEXT SETUP RESPONSE message (530). At this time, the Layer 1 measurement value can be an SSB, a CSI-RS, or both. If only SSB is to be used, only the SSB information (533) is included and sent; if only CSI-RS is to be used, the CSI-RS information (535) and CSI-RS type (537) are included and sent. These values ​​represent the CSI-RS resource and its type, and the specific details are identical to those in the UE CONTEXT SETUP REQUEST message (510). When only CSI-RS is used, the message in 533 is included, but this information may be ignored, and the details are described in the Semantic description within the message. When the use of both SSB and CSI-RS measurement values ​​is allowed, the description may be ignored.

[0092] The UE CONTEXT MODIFICATION REQUEST (520) message is used to change existing values ​​in both the Inter-DU LTM and Intra-DU LTM, or to change the values ​​transmitted by the gNB-CU to the candidate gNB-DU during the Intra-DU LTM preparation process. It may include (configuration) information containing the SSB or CSI-RS, or both, that the candidate cells collected so far have configured for the terminal. The SSB and CSI-RS information may exist simultaneously within the CSI Resource Configuration IE of 10a, or may exist in the form of a newly defined CSI-RS Resource Configuration (515) under the CSI Resource Configuration (513) for SSB information. When using CSI-RS as a measurement value, one of three types can be selected, as indicated by the CSI-RS type (517) included in the CSI Resource Configuration (10a) or CSI-RS Resource Configuration (515). If configured as a Periodic type, the terminal can continuously measure the corresponding CSI-RS periodically. In the case of the Semi-Persistent type, the CSI-RS resource is pre-configured, but the terminal does not measure the value until a separate instruction (e.g., MAC CE) is received from the base station. Once the instruction is received, the terminal can begin measurement according to the period provided by the base station, just as in the Periodic type. When configured as the Aperiodic type, the CSI-RS resource is also pre-configured as in the Semi-Persistent case, but the terminal performs measurement only upon receiving a separate instruction from the base station; unlike the two types described above, however, the measurement is performed only once.

[0093] Upon receiving the UE CONTEXT MODIFICATION REQUEST (520), the gNB-DU can send the UE CONTEXT MODIFICATION RESPONSE message (540) to the gNB-CU containing the Layer 1 measurement value associated with the cell. At this time, the Layer 1 measurement value can be an SSB, a CSI-RS, or both. If only SSB is to be used, only the SSB information (533) is included and sent; if only CSI-RS is to be used, the CSI-RS information (535) and CSI-RS type (537) are included and sent. These values ​​represent the CSI-RS resource and its type, and the specific details are identical to those in the UE CONTEXT SETUP REQUEST message (520). If only CSI-RS is used, the message 30a is included, but this information may be ignored, and the details are described in the Semantic description within the message. When the use of both SSB and CSI-RS measurement values ​​is permitted, the description may be ignored.

[0094] FIGS. 6a, FIGS. 6b, FIGS. 6c, and FIGS. 6d are examples of messages including an Information Element (IE) that includes Layer 1 measurement value information, such as SSB and CSI-RS setting information, which is to be measured by the terminal exemplified in FIG. 4 (Inter-CU LTM) according to an embodiment of the present invention.

[0095] Referring to FIGS. 6a, 6b, 6c, and 6d, the HANDOVER REQUEST MESSAGE (610) is a message transmitted from the Source gNB to the Candidate gNB during the Inter-gNB or Inter-CU LTM preparation process, and may include (configuration) information including the SSB or CSI-RS, or both, that the candidate cells collected so far have configured for the terminal. The SSB and CSI-RS information may exist simultaneously within the CSI Resource Configuration IE of 613, or may exist in the form of a newly defined CSI-RS Resource Configuration (619, 615) under the CSI Resource Configuration (613) for SSB information. When using CSI-RS as a measurement value, one of three types can be selected, such as the CSI-RS type (650) included in the CSI Resource Configuration (613) or CSI-RS Resource Configuration (619). If configured as a Periodic type, the terminal can continuously measure the corresponding CSI-RS periodically. In the case of the Semi-Persistent type, the CSI-RS resource is pre-configured, but the terminal does not measure the value until a separate instruction (e.g., MAC CE) is received from the base station. Once the instruction is received, the terminal can begin measurement according to the period provided by the base station, just as in the Periodic type. When configured as the Aperiodic type, the CSI-RS resource is also pre-configured as in the Semi-Persistent case, but the terminal performs measurement only upon receiving a separate instruction from the base station; unlike the two types described above, however, the measurement is performed only once.A HANDOVER REQUEST MESSAGE (610) includes an LTM information request IE, and the LTM information request IE may include a CSI Resource Configuration (613), a CSI-RS Resource Configuration (619, 615), etc.

[0096] Upon receiving the HANDOVER REQUEST (610), the gNB can send the HANDOVER REQUEST ACKNOWLEDGE message (630) containing the Layer 1 measurement value associated with the cell to the gNB-CU. At this time, the Layer 1 measurement value can be an SSB, a CSI-RS, or both. If only the SSB is to be used, only the SSB information (633) is included and sent; if only the CSI-RS is to be used, the CSI resource configuration (635) and the CSI-RS resource configuration (637) can be included and sent. These values ​​represent the CSI-RS resources and their types, and the specific details are identical to those in the HANDOVER REQUEST message (610). When both the SSB and CSI-RS measurement values ​​are to be used, 633, 635, and 637 can all be included and sent. The HANDOVER REQUEST ACKNOWLEDGE message (630) includes an LTM information response IE, and the LTM information response IE may include SSB information (633), CSI resource configuration (635), CSI-RS resource configuration (637), etc.

[0097] The LTM CONFIGURATION UPDATE (620) message is used to change existing values ​​or to send a message from the Source gNB to the Candidate gNB during the Inter-gNB or Inter-CU LTM preparation process. It may include (configuration) information containing the SSB or CSI-RS, or both, that the candidate cells collected so far have configured for the terminal. The SSB and CSI-RS information may exist simultaneously within the CSI Resource Configuration IE of 613, or may exist in the form of a newly defined CSI-RS Resource Configuration (619, 615) under the CSI Resource Configuration (613) for SSB information. When using CSI-RS as a measurement value, one of three types can be selected, as indicated by the CSI-RS type (650) included in the CSI Resource Configuration (613) or CSI-RS Resource Configuration (619). If configured as a Periodic type, the terminal can continuously measure the corresponding CSI-RS periodically. In the case of the Semi-Persistent type, the CSI-RS resource is pre-configured, but the terminal does not measure the value until a separate instruction (e.g., MAC CE) is received from the base station. Once the instruction is received, the terminal can begin measurement according to the period provided by the base station, just as in the Periodic type. When configured as the Aperiodic type, the CSI-RS resource is also pre-configured as in the Semi-Persistent case, but the terminal performs measurement only upon receiving a separate instruction from the base station; unlike the two types described above, however, the measurement is performed only once.The LTM CONFIGURATION UPDATE (620) message includes an LTM information request IE, and the LTM information request IE may include a CSI Resource Configuration (613), a CSI-RS Resource Configuration (619, 915), etc.

[0098] Upon receiving the LTM CONFIGURATION UPDATE (620), the gNB can send the LTM CONFIGURATION UPDATE ACKNOWLEDGE message (640) containing the Layer 1 measurement value associated with the cell to the gNB-CU. At this time, the Layer 1 measurement value can be an SSB, a CSI-RS, or both. If only SSB is to be used, only the SSB information (633) is included and sent; if only CSI-RS is to be used, the CSI resource configuration (635) and CSI-RS resource configuration (637) can be included and sent. These values ​​represent the CSI-RS resource and its type, and the specific details are identical to those in the LTM CONFIGURATION UPDATE message (620). When both SSB and CSI-RS measurement values ​​are to be used, 633, 635, and 637 can all be included and sent. The LTM CONFIGURATION UPDATE ACKNOWLEDGE message (640) includes an LTM information response IE, and the LTM information response IE may include SSB information (633), CSI resource configuration (635), CSI-RS resource configuration (637), etc.

[0099] FIG. 7 is a flowchart illustrating a procedure for activating or deactivating and reporting the measurement value when a terminal according to an embodiment of the present invention is configured to measure a Layer 1 measurement using CSI-RS after undergoing the LTM preparation process described in FIG. 2, 3, and 4.

[0100] As described above in FIGS. 5 and 6, CSI-RS can be set to three types: periodic, semi-static, and transient. When the type is set to periodic, the transmission and measurement of CSI-RS occur immediately, but in the case of semi-static and transient types, the transmission of CSI-RS occurs only after receiving an activation or deactivation signal from the base station (via methods such as MAC CE) after the setting value is transmitted to the terminal. Also, in the case of reporting the result value, it can be set to three types—periodic, semi-static, and transient—just like the three types for setting CSI-RS resources, and activation or deactivation can also be set via methods such as MAC CE from the base station.

[0101] To do this, a new IE (790) called CSI-RS Information must be defined and the information inserted into a new message or an existing message so that it can be exchanged between or within base stations.

[0102] Referring to FIG. 7, the CSI-RS Information IE (790) may consist of a part (791) for setting the CSI-RS Resource and a part (795) for reporting the measurement value, and both parts may have Trigger (792, 796), Period (793, 797), and Time offset (794, 798) as components. The Trigger (792, 796) may have three values: activate, deactivate, and once. When the CSI-RS is set to semi-static, the Resource and reporting can be activated or deactivated using the activate and deactivate values, and the value once is for use once when the CSI-RS is set to aperiodic. The Period (793, 797) is a value that is meaningful only when the Trigger is activated, and indicates how often the corresponding CSI-RS signal should be transmitted and the measurement value reported. Finally, time offset(794, 798) indicates how long after receiving the signal the CSI-RS signal or the result value should be transmitted, and this is a correction value that can be set by taking into account the delay between base stations and between a base station and a terminal.

[0103] The flowchart for the transmission of CSI-RS Information IE (790) is as follows.

[0104] Referring to FIG. 7, in the flowchart of the Inter-DU LTM including the case of Intra-DU, as in step 705, the entity that can activate, deactivate, or change the reporting settings of the measurement value (deactivate / deactivate CSI-RS resource / report) may be the Source gNB-DU (702).

[0105] If a gNB-DU (702) or cell currently communicating with a terminal (701) wishes to enable or disable the CSI-RS Resource or measurement value reporting of a candidate cell (candidate gNB-DU) (703), the source gNB-DU (702) may first transmit a message containing CSI-RS Information indicating the relevant information to the gNB-CU (704) in step 710. In step 715, the gNB-CU (704) transmits the relevant information to the candidate gNB-DU (703) to enable the configuration related to the CSI-RS resource. At the same time, in step 720, the source gNB-DU (702) may also enable or disable the CSI-RS Resource or enable or disable the measurement value reporting by signaling the terminal (701) through MAC CE, etc. The above steps 710 and 720 may occur simultaneously, or step 720 may occur before step 710.

[0106] In step 710, when the Source gNB-DU (702) transmits the CSI-RS Information IE, it may use existing Class 1 messages as they are (e.g., UE CONTEXT MODIFICATION REQUEST / RESPONSE messages) or existing Class 2 messages as they are (e.g., UL RRC MESSAGE TRANSFER). Alternatively, it may use a method of defining a new Class 2 message (e.g., DU-CU CSI-RS INFORMATION TRANSFER). In step 715, as in the example in step 710, it may use existing Class 1 messages as they are (e.g., UE CONTEXT MODIFICATION REQUEST / RESPONSE messages) or existing Class 2 messages as they are (e.g., DL RRC MESSAGE TRANSFER). Alternatively, it may use a method of defining a new Class 2 message (e.g., CU-DU CSI-RS INFORMATION TRANSFER).

[0107] Next, as in step 730, the entity that changes the measurement reporting cycle of the CSI-RS Resource or terminal (701) may be a candidate cell (candidate gNB-DU) (703).

[0108] In this case, at step 740, the Candidate gNB-DU (703) can first transmit a message containing CSI-RS Information IE to the gNB-CU (704). Then, at step 745, the gNB-CU (704) can transmit this to the source gNB-DU (702). At step 750, the Source gNB-DU (702) can finally operate by transmitting a new setting value to the terminal (701) using methods such as MAC CE.

[0109] As described above, when transmitting the CSI-RS Information IE in step 740, existing Class 1 messages may be used as they are (e.g., UE CONTEXT MODIFICATION REQUEST / RESPONSE messages) or existing Class 2 messages (e.g., UL RRC MESSAGE TRANSFER). Alternatively, a method of defining a new Class 2 message (e.g., DU-CU CSI-RS INFORMATION TRANSFER) may be used. In step 745, as in the example in step 740, existing Class 1 messages may be used as they are (e.g., UE CONTEXT MODIFICATION REQUEST / RESPONSE messages) or existing Class 2 messages (e.g., DL RRC MESSAGE TRANSFER). Alternatively, a method of defining a new Class 2 message (e.g., CU-DU CSI-RS INFORMATION TRANSFER) may be used.

[0110] Finally, the entity that changes the measurement reporting cycle of the current cell or candidate cell's CSI-RS Resource or terminal (701), as in step 760, may be the gNB-CU (704).

[0111] In this case, in steps 770 and 775, the gNB-CU (704) can transmit a message containing CSI-RS Information IE to the source gNB-DU (702) and candidate gNB-DU (703). Then, in step 780, the Source gNB-DU (20) can finally transmit a new setting value to the terminal (701) using a method such as MAC CE. Steps 770 and 377520 may be performed sequentially or simultaneously.

[0112] When delivering CSI-RS Information IE in steps 770 and 775, existing Class 1 messages may be used as they are (e.g., UE CONTEXT MODIFICATION REQUEST / RESPONSE message) or existing Class 2 messages may be used as they are (e.g., DL RRC MESSAGE TRANSFER). Alternatively, a method of defining a new Class 2 message (e.g., CU-DU CSI-RS INFORMATION TRANSFER) may be used.

[0113] The first operation of steps 705 to 720, the second operation of steps 730 to 750, and the third operation of steps 760 to 780 may refer to separate embodiments.

[0114] FIG. 8 is a flowchart of activating, deactivating, or changing the reporting settings of measurement values ​​in a situation where CSI-RS is already set as a Layer 1 measurement in an Inter-gNB or Inter-CU LTM according to an embodiment of the present invention.

[0115] The IE transmitted between base stations in Fig. 8 may be the same as the CSI-RS Information IE (790 in Fig. 7) described in Fig. 7. Therefore, a detailed explanation thereof will be omitted.

[0116] In step 810, the Source gNB (802) may decide to enable or disable the CSI-RS resources of the Candidate gNB (803).

[0117] And in step 815, the Source gNB (802) can transmit the relevant information, CSI-RS Information IE, to the Candidate gNB (803). Simultaneously with or sequentially with step 815, in step 820, the Source gNB (802) can transmit the configuration value and report-related information to the terminal (801) via MAC CE, etc. The candidate gNB (803) that receives the message transmitted in step 815 can apply the configuration value. At this time, the message used to transmit the CSI-RS Information IE may be an existing Class 1 message (e.g., HANDOVER REQUEST / ACKNWOLEDGE or LTM CONFIGURATION UPDATE / ACKNOWOLEDGE) or an existing Class 2 message (e.g., RRC TRANSFER). Or it may be a newly defined Class 2 message (e.g., LTM CSI-RS INFORMATION TRANSFER).

[0118] Next, in step 830, the Candidate gNB (803) may decide to enable or disable the CSI-RS resources of the candidate cell or the cell to which the current base station is connected.

[0119] In step 835, the Candidate gNB (803) can transmit the relevant information, CSI-RS Information IE, to the Source gNB (802). Upon receiving the message (information) in step 835, the Source gNB (802) can transmit the configuration value and report-related information to the terminal (801) via MAC CE, etc., in step 840. At this time, the message used to transmit the CSI-RS Information IE may be an existing Class 1 message (e.g., HANDOVER REQUEST / ACKNWOLEDGE or LTM CONFIGURATION UPDATE / ACKNOWOLEDGE) or an existing Class 2 message (e.g., RRC TRANSFER). Alternatively, it may be a newly defined Class 2 message (e.g., LTM CSI-RS INFORMATION TRANSFER).

[0120] The first operation of steps 810 to 820 and the second operation of steps 830 to 840 may refer to separate embodiments.

[0121] FIG. 9 is a block diagram showing an example of the configuration of a RAN Node according to one embodiment of the present invention.

[0122] Referring to FIG. 9, a RAN Node (base station) may be configured to include an RF processing unit (910), a baseband processing unit (920), a backhaul communication unit (930), a storage unit (940), a control unit (950), etc. If the RAN Node is separated into a CU (Central Unit) and a DU (Distributed Unit), blocks other than those included in FIG. 9 may also be configured. For example, the RF processing unit (910) and the baseband processing unit (920) may be configured to include a control unit, a storage unit, and a backhaul communication unit for communication with the CU in the DU, and for example, the backhaul communication unit (930) may be configured to include a control unit, a storage unit, and a backhaul communication unit for communication with the DU in the CU.

[0123] The RF processing unit (910) performs functions for transmitting and receiving signals through a wireless channel, such as signal band conversion and amplification. The RF processing unit (910) upconverts the baseband signal provided by the baseband processing unit (920) into an RF band signal, transmits it through an antenna, and downconverts the RF band signal received through the antenna into a baseband signal. For example, the RF processing unit (910) may include a transmit filter, a receive filter, an amplifier, a mixer, an oscillator, a DAC, an ADC, etc. Although only one antenna is shown in the drawing, the RAN Node may be equipped with multiple antennas. Additionally, the RF processing unit (910) may include multiple RF chains. Furthermore, the RF processing unit (910) may perform beamforming. For beamforming, the RF processing unit (910) may adjust the phase and magnitude of each of the signals transmitted and received through multiple antennas or antenna elements. The above RF processing unit can perform down-to-down MIMO operation by transmitting one or more layers.

[0124] The baseband processing unit (920) performs a conversion function between a baseband signal and a bit sequence according to the physical layer specifications of the first wireless access technology. For example, when transmitting data, the baseband processing unit (920) generates complex symbols by encoding and modulating the transmitted bit sequence. Additionally, when receiving data, the baseband processing unit (920) restores the received bit sequence by demodulating and decoding the baseband signal provided by the RF processing unit (910). For example, in the case of an OFDM method, when transmitting data, the baseband processing unit (920) generates complex symbols by encoding and modulating the transmitted bit sequence, maps the complex symbols to subcarriers, and then constructs OFDM symbols through IFFT operation and CP insertion. Additionally, upon receiving data, the baseband processing unit (920) divides the baseband signal provided by the RF processing unit (910) into OFDM symbol units, restores the signals mapped to subcarriers through FFT operations, and then restores the received bit sequence through demodulation and decoding. The baseband processing unit (920) and the RF processing unit (910) transmit and receive signals as described above. Accordingly, the baseband processing unit (920) and the RF processing unit (910) may be referred to as a transmitting unit, a receiving unit, a transmitting and receiving unit, a communication unit, or a wireless communication unit.

[0125] The backhaul communication unit (930) provides an interface for communicating with other nodes within the network. The backhaul communication unit (930) converts a bit sequence transmitted from a RAN Node to another node, such as an auxiliary base station, a main base station, a core network, etc., into a physical signal, and converts a physical signal received from the other node into a bit sequence.

[0126] The storage unit (940) stores data such as basic programs, application programs, and configuration information for the operation of the RAN Node. In particular, the storage unit (940) can store information regarding bearers assigned to connected terminals, measurement results reported from connected terminals, etc. Additionally, the storage unit (940) can store information serving as a criterion for determining whether to provide or disconnect multiple connections to the terminals. Furthermore, the storage unit (940) provides the stored data upon a request from the control unit (950).

[0127] The control unit (950) controls the overall operations of the RAN Node. For example, the control unit (950) transmits and receives signals through the baseband processing unit (920) and the RF processing unit (910) or through the backhaul communication unit (930). Additionally, the control unit (950) writes and reads data to and from the storage unit (940). To this end, the control unit (950) may include at least one processor.

[0128] FIG. 10 is a block diagram illustrating an example of the structure of a terminal according to one embodiment of the present invention.

[0129] Referring to FIG. 10, the terminal (UE) may include an RF (Radio Frequency) processing unit (1010), a baseband processing unit (1020), a storage unit (1030), a control unit (1040), etc.

[0130] The RF processing unit (1010) performs functions for transmitting and receiving signals through a wireless channel, such as signal band conversion and amplification. The RF processing unit (1010) up-converts the baseband signal provided by the baseband processing unit (1020) into an RF band signal and transmits it through an antenna, and down-converts the RF band signal received through the antenna into a baseband signal. For example, the RF processing unit (1010) may include a transmission filter, a reception filter, an amplifier, a mixer, an oscillator, a DAC (digital to analog converter), an ADC (analog to digital converter), etc. Although only one antenna is shown in the drawing, the terminal may be equipped with multiple antennas. Additionally, the RF processing unit (1010) may include multiple RF chains. Furthermore, the RF processing unit (1010) may perform beamforming. For the above beamforming, the RF processing unit (1010) can adjust the phase and magnitude of each of the signals transmitted and received through a plurality of antennas or antenna elements. In addition, the RF processing unit can perform MIMO and can receive multiple layers when performing MIMO operation.

[0131] The baseband processing unit (1020) performs a conversion function between a baseband signal and a bit sequence according to the physical layer specifications of the system. For example, when transmitting data, the baseband processing unit (1020) generates complex symbols by encoding and modulating the transmitted bit sequence. Additionally, when receiving data, the baseband processing unit (1020) restores the received bit sequence by demodulating and decoding the baseband signal provided by the RF processing unit (1010). For example, in the case of following the OFDM (orthogonal frequency division multiplexing) method, when transmitting data, the baseband processing unit (1020) generates complex symbols by encoding and modulating the transmitted bit sequence, maps the complex symbols to subcarriers, and then constructs OFDM symbols through IFFT (inverse fast Fourier transform) operation and CP (cyclic prefix) insertion. Additionally, upon receiving data, the baseband processing unit (1020) divides the baseband signal provided by the RF processing unit (1010) into OFDM symbol units, restores the signals mapped to subcarriers through a fast Fourier transform (FFT), and then restores the received bit sequence through demodulation and decoding.

[0132] The baseband processing unit (1020) and the RF processing unit (1010) transmit and receive signals as described above. Accordingly, the baseband processing unit (1020) and the RF processing unit (1010) may be referred to as a transmitting unit, a receiving unit, a transmitting and receiving unit, or a communication unit. Furthermore, at least one of the baseband processing unit (1020) and the RF processing unit (1010) may include a plurality of communication modules to support a plurality of different wireless access technologies. Additionally, at least one of the baseband processing unit (1020) and the RF processing unit (1010) may include different communication modules to process signals of different frequency bands. For example, the different wireless access technologies may include wireless LAN (e.g., IEEE 802.11), cellular network (e.g., LTE), etc. In addition, the above different frequency bands may include super high frequency (SHF) bands (e.g., 2 NRHz, NRHz) and millimeter wave (e.g., 60 GHz) bands.

[0133] The storage unit (1030) stores data such as basic programs, application programs, and setting information for the operation of the terminal. Additionally, the storage unit (1030) provides the stored data upon the request of the control unit (1040).

[0134] The control unit (1040) controls the overall operations of the terminal. For example, the control unit (1040) transmits and receives signals through the baseband processing unit (1020) and the RF processing unit (1010). Additionally, the control unit (1040) writes and reads data to and from the storage unit (1030). To this end, the control unit (1040) may include at least one processor. For example, the control unit (1040) may include a communication processor (CP) that performs control for communication and an application processor (AP) that controls upper layers such as applications.

[0135] When implemented in software, a computer-readable storage medium may be provided for storing one or more programs (software modules). One or more programs stored in the computer-readable storage medium are configured for execution by one or more processors within an electronic device. One or more programs include instructions that cause the electronic device to execute methods according to embodiments described in the claims or specification of the present invention.

[0136] Such programs (software modules, software) may be stored in random access memory, non-volatile memory including flash memory, ROM (Read Only Memory), Electrically Erasable Programmable Read Only Memory (EEPROM), magnetic disc storage devices, Compact Disc-ROM (CD-ROM), Digital Versatile Discs (DVDs), or other forms of optical storage devices, magnetic cassettes. Alternatively, they may be stored in memory composed of some or all of these. Additionally, each constituent memory may include multiple units.

[0137] In addition, the above program may be stored on an attachable storage device that can be accessed via a communication network such as the Internet, Intranet, Local Area Network (LAN), Wide LAN (WLAN), or Storage Area Network (SAN), or a combination thereof. Such a storage device may be connected to a device performing an embodiment of the present invention through an external port. Additionally, a separate storage device on a communication network may be connected to a device performing an embodiment of the present invention.

[0138] In the specific embodiments of the present invention described above, the components included in the invention are expressed in a singular or plural form according to the specific embodiments presented. However, the singular or plural expression is selected to suit the situation presented for convenience of explanation, and the present invention is not limited to singular or plural components; even if a component is expressed in the plural form, it may be composed in the singular form, or even if a component is expressed in the singular form, it may be composed in the plural form.

[0139] Meanwhile, although specific embodiments have been described in the detailed description of the present invention, it is understood that various modifications are possible within the scope of the present invention. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be defined by the claims set forth below as well as equivalents thereof.

Claims

1. A method performed by a first base station of a wireless communication system, A step of receiving a first message from a second base station associated with the transmission of resource configuration information for LTM (layer 1 / layer 2 triggered mobility) measurement; and A method comprising the step of transmitting a second message to the second base station, the message including resource setting information of a CSI-RS (channel status information reference signal) for the above LTM measurement.

2. In Paragraph 1, A method characterized in that the resource setting information of the CSI-RS for the above LTM measurement includes at least one of periodic CSI-RS resource setting or semi-persistent CSI-RS resource setting.

3. In Paragraph 1, The first message above includes at least one of a UE (user equipment) context setup request message, a UE context modification request message, or a handover request message, and A method characterized in that the second message includes at least one of a UE context setup response message, a UE context modification response message, or a handover request acknowledgment message.

4. In Paragraph 1, The first base station includes at least one of a gNB-DU (distributed unit) or a target base station, and A method characterized in that the second base station includes at least one of a gNB-CU (centralized unit) or a source base station.

5. A method performed by a terminal of a wireless communication system, A step of receiving from a second base station a message including resource information for CSI-RS-based LTM measurement determined based on resource setting information of CSI-RS (channel status information reference signal) for LTM (layer 1 / layer 2 triggered mobility) measurement set by a first base station; and A method comprising the step of transmitting L1 (layer 1) measurement information based on resource information for the above CSI-RS-based LTM measurement to the first base station.

6. In Paragraph 5, A method characterized in that the resource setting information of the CSI-RS for the LTM measurement set by the first base station comprises at least one of a periodic CSI-RS resource setting or a semi-persistent CSI-RS resource setting.

7. In Paragraph 5, A method characterized in that the above message is a radio resource control (RRC) reconfiguration message.

8. In Paragraph 5, The first base station includes at least one of a gNB-DU (distributed unit) or a target base station, and A method characterized in that the second base station includes at least one of a gNB-CU (centralized unit) or a source base station.

9. In the first base station of a wireless communication system, Transmitter / receiver; and Connected to the above-mentioned transmitting and receiving unit, Receive a first message from a second base station associated with the transmission of resource configuration information for LTM (layer 1 / layer 2 triggered mobility) measurement, and A first base station comprising a control unit that transmits to the second base station a second message containing an LTM setting that includes resource setting information of a CSI-RS (channel status information reference signal) for the above LTM measurement.

10. In Paragraph 9, A first base station characterized in that the resource setting information of the CSI-RS for the above LTM measurement includes at least one of periodic CSI-RS resource setting or semi-persistent CSI-RS resource setting.

11. In Paragraph 9, The first message above includes at least one of a UE (user equipment) context setup request message, a UE context modification request message, or a handover request message, and A first base station characterized in that the second message includes at least one of a UE context setup response message, a UE context modification response message, or a handover request acknowledgment message.

12. In Paragraph 9, The first base station includes at least one of a gNB-DU (distributed unit) or a target base station, and The first base station is characterized by including at least one of a gNB-CU (centralized unit) or a source base station.

13. In a terminal of a wireless communication system, Transmitter / receiver; and Connected to the above-mentioned transmitting and receiving unit, Receiving a message from a second base station containing resource information for CSI-RS-based LTM measurement determined based on resource setting information of CSI-RS (channel status information reference signal) for LTM (layer 1 / layer 2 triggered mobility) measurement set by a first base station, and A terminal comprising a control unit that transmits L1 (layer 1) measurement information based on resource information for the above CSI-RS-based LTM measurement to the first base station.

14. In Paragraph 13, A terminal characterized in that the resource setting information for the CSI-RS for the LTM measurement set by the first base station includes at least one of a periodic CSI-RS resource setting or a semi-persistent CSI-RS resource setting.

15. In Paragraph 13, The above message is an RRC (radio resource control) reconfiguration message, and The first base station includes at least one of a gNB-DU (distributed unit) or a target base station, and A terminal characterized in that the second base station includes at least one of a gNB-CU (centralized unit) or a source base station.

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