Method and apparatus for performing channel measurement in wireless communication system

Abstract

The present disclosure relates to a 5G or 6G communication system for supporting a higher data transmission rate. An operation method of a UE, according to an embodiment of the present disclosure, comprises the steps of: receiving, from a base station, Layer 1 measurement resource configuration information for Layer 1 / Layer2 triggered mobility (LTM) candidate cells within an intra-central unit (CU) or inter-CU, wherein the Layer 1 measurement resource configuration information includes information related to the configuration of channel state information (CSI)-reference signal (RS) resources; and transmitting, to the base station, a Layer 1 measurement report on the basis of the Layer 1 measurement resource configuration information for the LTM candidate cells.

Description

Method and device for performing channel measurement in a wireless communication system

[0001] The present disclosure relates to operations of a terminal and a base station in a wireless communication system, and more particularly, to a method and apparatus for performing channel measurement for LTM through CSI-RS resources in a next-generation mobile communication system.

[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 the sub-6GHz frequency band such as 3.5 gigahertz (3.5GHz), but also in the ultra-high frequency band called millimeter wave (mmWave) such as 28GHz and 39GHz ('Above 6GHz'). In addition, for 6G mobile communication technology, which is called the system after 5G communication (Beyond 5G), implementation in the terahertz band (for example, the 3 terahertz (3THz) band at 95GHz) is being considered to achieve a transmission speed that is 50 times faster than 5G mobile communication technology and an ultra-low latency time that is reduced to one-tenth.

[0003] In the early stages of 5G mobile communication technology, the goal is to support services and satisfy performance requirements for enhanced Mobile Broadband (eMBB), Ultra-Reliable Low-Latency Communications (URLLC), and massive Machine-Type Communications (mMTC). These include beamforming and massive MIMO to mitigate path loss of radio waves in ultra-high frequency bands and increase the transmission distance of radio waves, support for various numerologies (such as operation of multiple subcarrier intervals) and dynamic operation of slot formats for efficient use of ultra-high frequency resources, initial access technology to support multi-beam transmission and wideband, definition and operation of BWP (Bidth Part), new channel coding methods such as LDPC (Low Density Parity Check) codes for large-capacity data transmission and Polar Code for reliable transmission of control information, and L2 pre-processing (L2). Standardization has been made for network slicing, which provides dedicated networks specialized for specific services, and pre-processing.

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

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

[0006] Once these 5G mobile communication systems are commercialized, an explosive increase in connected devices will be connected to the communication network, necessitating enhanced functionality and performance of 5G mobile communication systems and integrated operation of these connected devices. To this end, new research will be conducted on improving 5G performance and reducing complexity, supporting AI services, supporting metaverse services, and drone communications by utilizing eXtended Reality (XR), Artificial Intelligence (AI), and Machine Learning (ML) to efficiently support Augmented Reality (AR), Virtual Reality (VR), and Mixed Reality (MR).

[0007] In addition, the development of these 5G mobile communication systems includes new waveforms to ensure coverage in the terahertz band of 6G mobile communication technology, multi-antenna transmission technologies such as Full Dimensional MIMO (FD-MIMO), Array Antenna, and Large Scale Antenna, metamaterial-based lenses and antennas to improve the coverage of terahertz band signals, high-dimensional spatial multiplexing technology using Orbital Angular Momentum (OAM), Reconfigurable Intelligent Surface (RIS) technology, as well as full duplex technology to improve the frequency efficiency and system network of 6G mobile communication technology, satellite, AI (Artificial Intelligence) from the design stage and AI-based communication technology that realizes system optimization by internalizing end-to-end AI support functions, and ultra-high-performance communication and computing resources to provide services with complexity that exceeds the limits of terminal computing capabilities. It can serve as a basis for the development of next-generation distributed computing technologies that can be realized by utilizing them.

[0008] In a wireless communication system according to one embodiment, a method of a user equipment (UE) is provided. The method of the UE may include: receiving an RRC (Radio Resource Control) message from a base station; performing measurement on CSI-RS resources of one or more LTM candidate cells; and transmitting, to the base station, a Layer 1 measurement report on the one or more LTM candidate cells. According to one embodiment, the RRC message may include information related to configuration of CSI-RS (Channel State Information-Reference Signal) resources of one or more LTM (Layer 1 / Layer 2 Triggered Mobility) candidate cells and configuration information related to a Layer 1 measurement report on the one or more LTM candidate cells.

[0009] In one embodiment, one or more LTM candidate cells may be comprised of cells belonging to an intra-CU (Central Unit).

[0010] In one embodiment, one or more LTM candidate cells may be comprised of cells belonging to an inter-CU.

[0011] According to one embodiment, the method of the UE may further include the step of setting a type of CSI-RS-based Layer 1 measurement report for one or more LTM candidate cells to at least one of periodic; semi-persist; or aperiodic, based on configuration information related to the Layer 1 measurement report.

[0012] According to one embodiment, the method of the UE may further include the step of receiving, from a base station, a Medium Access Control Control Element (MAC CE) or Downlink Control Information (DCI), which indicates activation or deactivation of a semi-persist type Layer 1 measurement report or an aperiodic type Layer 1 measurement report.

[0013] According to one embodiment, the method of the UE may further include the step of receiving, from a base station, Layer 1 / Layer 2 signaling including a beam switching instruction or a handover instruction based on a CSI-RS based Layer 1 measurement report.

[0014] In a wireless communication system according to one embodiment, a method of a base station is provided. The method of the base station may include the steps of: transmitting an RRC (Radio Resource Control) message to a UE (User Equipment); receiving, from the UE, a Layer 1 measurement report for one or more LTM candidate cells; and determining, based on the Layer 1 measurement report for the one or more LTM candidate cells, whether to indicate beam switching or handover. According to one embodiment, the RRC message may include information related to configuration of a CSI-RS (Channel State Information-Reference Signal) resource of one or more LTM (Layer 1 / Layer 2 Triggered Mobility) candidate cells and configuration information related to a Layer 1 measurement report for the one or more LTM candidate cells.

[0015] According to one embodiment, a method of a base station may further include: collecting information about CSI-RS resources from one or more LTM candidate cells within an intra-CU via an F1 interface; configuring information related to CSI-RS resource configuration based on the collected information and transmitting the information to one or more LTM candidate cells within the intra-CU; and receiving, from one or more LTM candidate cells within the intra-CU, a Layer 1 measurement report related configuration together with cell configuration information.

[0016] According to one embodiment, a method of a base station may further include: collecting information about CSI-RS resources from one or more LTM candidate cells within an inter-CU via an X2 interface; configuring information related to CSI-RS resource configuration based on the collected information and transmitting the information to one or more LTM candidate cells within the inter-CU; and receiving, from one or more LTM candidate cells within the inter-CU, a Layer 1 measurement report related configuration together with cell configuration information.

[0017] According to one embodiment, based on configuration information related to Layer 1 measurement reporting, the type of CSI-RS-based Layer 1 measurement reporting for one or more LTM candidate cells may be set to at least one of periodic; semi-persist; or aperiodic.

[0018] According to one embodiment, the method of the base station may further include the step of transmitting, to the UE, a Medium Access Control Control Element (MAC CE) or Downlink Control Information (DCI), which instructs activation or deactivation of a semi-persist type Layer 1 measurement report or an aperiodic type Layer 1 measurement report.

[0019] In a wireless communication system according to one embodiment, a user equipment (UE) is provided. The UE may include a memory storing one or more commands and at least one processor. The at least one processor may cause the UE to perform the following operations by executing one or more commands stored in the memory. The following operations may include operations of: receiving an RRC (Radio Resource Control) message from a base station; performing measurement on CSI-RS resources of one or more LTM candidate cells; and transmitting, to the base station, a Layer 1 measurement report for the one or more LTM candidate cells. According to one embodiment, the RRC message may include information related to configuration of CSI-RS (Channel State Information-Reference Signal) resources of one or more LTM (Layer 1 / Layer 2 Triggered Mobility) candidate cells and configuration information related to a Layer 1 measurement report for the one or more LTM candidate cells.

[0020] In a wireless communication system according to one embodiment, a base station is provided. The base station may include a memory storing one or more commands and at least one processor. The at least one processor may cause the base station to perform the following operations by executing one or more commands stored in the memory. The following operations may include: transmitting an RRC (Radio Resource Control) message to a UE (User Equipment); receiving, from the UE, a Layer 1 measurement report for one or more LTM candidate cells; and determining whether to indicate beam switching or handover based on the Layer 1 measurement report for the one or more LTM candidate cells. According to one embodiment, the RRC message may include information related to configuration of a CSI-RS (Channel State Information-Reference Signal) resource of one or more LTM (Layer 1 / Layer 2 Triggered Mobility) candidate cells and configuration information related to a Layer 1 measurement report for the one or more LTM candidate cells.

[0021] According to one embodiment, at least one processor may cause the base station to further perform the following operations by executing one or more instructions stored in a memory. The following operations may include: collecting information about CSI-RS resources from one or more LTM candidate cells within the intra-CU via the F1 interface; configuring information related to CSI-RS resource configuration based on the collected information and transmitting the information to one or more LTM candidate cells within the intra-CU; and receiving Layer 1 measurement report related configuration together with cell configuration information from one or more LTM candidate cells within the intra-CU.

[0022] According to one embodiment, at least one processor may cause the base station to further perform the following operations by executing one or more instructions stored in a memory. The following operations may include: collecting information about CSI-RS resources from one or more LTM candidate cells within the Inter-CU via an X2 interface; configuring information related to CSI-RS resource configuration based on the collected information and transmitting the information to one or more LTM candidate cells within the Inter-CU; and receiving, from one or more LTM candidate cells within the Inter-CU, a Layer 1 measurement report related configuration together with cell configuration information.

[0023] FIG. 1a is a diagram illustrating the structure of a next-generation mobile communication system according to an embodiment of the present disclosure.

[0024] FIG. 1b is a diagram illustrating a wireless protocol structure of a next-generation mobile communication system according to an embodiment of the present disclosure.

[0025] FIG. 1c is a diagram illustrating the structure of a next-generation mobile communication system according to an embodiment of the present disclosure.

[0026] FIG. 1D is a diagram for explaining a method for managing inter-cell beams according to an embodiment of the present disclosure, in which a terminal transmits and receives data through a beam of a TRP (transmission / reception point) of a neighboring cell that supports beam change based on L1 / L2 while maintaining a connection state with a serving cell.

[0027] FIG. 1e is a diagram for explaining a method for a terminal to transmit and receive data by changing a serving cell and beam to a TRP of a cell that supports L1 / L2-based beam change according to an embodiment of the present disclosure.

[0028] FIGS. 1fa and 1fb are diagrams illustrating a method for applying CSI-RS-based L1 measurement resources and reporting settings to support continuous L1 / L2-based handover (LTM) operations in cells within the same CU, according to one embodiment of the present disclosure.

[0029] FIG. 1ga and FIG. 1gb are diagrams illustrating a method for applying CSI-RS based L1 measurement resources and reporting configurations to support continuous L1 / L2 based handover (LTM) operations in cells within different CUs, according to one embodiment of the present disclosure.

[0030] FIG. 1h is a flowchart illustrating an operation of a terminal performing L1 / L2-based beam change and handover according to one embodiment of the present disclosure.

[0031] FIG. 1i is a flowchart illustrating the operation of a base station according to one embodiment of the present disclosure.

[0032] FIG. 1j is a block diagram illustrating the structure of a terminal according to one embodiment of the present disclosure.

[0033] FIG. 1k is a block diagram illustrating the structure of a base station according to one embodiment of the present disclosure.

[0034] The operating principles of the present invention are described in detail below with reference to the attached drawings. In the following description of the present invention, detailed descriptions of known functions or components will be omitted if they are deemed to unnecessarily obscure the gist of the invention.

[0035] In describing the embodiments of this disclosure, descriptions of technical details that are well-known in the technical field to which this disclosure pertains and are not directly related to this disclosure will be omitted. This is to avoid obscuring the gist of this disclosure by omitting unnecessary explanations and to convey it more clearly. Furthermore, the terms described below are defined based on their functions in this disclosure and may vary depending on the intent or custom of the user or operator. Therefore, their definitions should be based on the contents throughout this specification.

[0036] For the same reason, some components in the attached drawings are exaggerated, omitted, or schematically depicted. Furthermore, the dimensions of each component do not entirely reflect its actual size. Identical or corresponding components in each drawing are assigned the same reference numbers.

[0037] The advantages and features of the present disclosure, and methods for achieving them, will become clearer with reference to the embodiments described below in detail with the accompanying drawings. However, the present disclosure is not limited to the embodiments disclosed below and may be implemented in various different forms. These embodiments are provided solely to ensure that the disclosure is complete and to fully inform those skilled in the art of the scope of the disclosure, and the present disclosure is defined only by the scope of the claims. Like reference numerals designate like elements throughout the disclosure.

[0038] At this time, it will be understood that each block of the processing flow diagrams and combinations of the flow diagrams can be performed by computer program instructions. These computer program instructions can be installed in a processor of a general-purpose computer, a special-purpose computer, or other programmable data processing equipment, so that the instructions executed by the processor of the computer or other programmable data processing equipment create a means for performing the functions described in the flow diagram block(s). These computer program instructions can also be stored in a computer-available or computer-readable memory that can direct a computer or other programmable data processing equipment to implement the functions in a specific manner, so that the instructions stored in the computer-available or computer-readable memory can also produce a manufactured item that includes an instruction means for performing the functions described in the flow diagram block(s). Since the computer program instructions may be installed on a computer or other programmable data processing device, a series of operational steps may be performed on the computer or other programmable data processing device to create a computer-executable process, and the instructions that cause the computer or other programmable data processing device to perform the steps for performing the functions described in the flowchart block(s) may also provide steps for performing the functions described in the flowchart block(s).

[0039] Additionally, each block may represent a module, segment, or portion of code that contains one or more executable instructions for performing a specific logical function(s). It should also be noted that in some alternative implementation examples, the functions described in the blocks may occur out of order. For example, two blocks depicted in succession may actually be executed substantially concurrently, or the blocks may sometimes be executed in reverse order, depending on their respective functions.

[0040] Here, the term '~ unit' used in the present embodiment means a software or hardware component such as an FPGA or ASIC, and the '~ unit' performs certain roles. However, the '~ unit' is not limited to software or hardware. The '~ unit' may be configured to be on an addressable storage medium and may be configured to play one or more processors. Accordingly, as an example, the '~ unit' includes components such as software components, object-oriented software components, class components, and task components, processes, functions, properties, 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 '~ units' may be combined into a smaller number of components and '~ units' or further separated into additional components and '~ units'. Additionally, components and '~parts' may be implemented to regenerate one or more CPUs within a device or secure multimedia card.

[0041] The terms described below are terms defined in consideration of their functions in the present invention, and may vary depending on the intentions or customs of users and operators. Therefore, their definitions should be based on the contents throughout this specification. Terms used in the following description, such as terms for identifying connection nodes, terms for referring to network entities, terms for referring to messages, terms for referring to interfaces between network entities, and terms for referring to various identification information, are examples for convenience of explanation. Therefore, the present invention is not limited to the terms described below, and other terms for referring to objects with equivalent technical meanings may be used.

[0042] Hereinafter, the base station is an entity that performs resource allocation of the terminal, and may be at least one of a gNode B, an eNode B, a Node B, a BS (Base Station), a wireless access unit, a base station controller, or a node on a network. The terminal may include a UE (User Equipment), an MS (Mobile Station), a cellular phone, a smartphone, a computer, or a multimedia system capable of performing a communication function. In the present disclosure, downlink (DL) refers to a wireless transmission path of a signal transmitted from a base station to a terminal, and uplink (UL) refers to a wireless transmission path of a signal transmitted from a terminal to a base station. In addition, although the LTE or LTE-A system may be described below as an example, the embodiments of the present disclosure may also be applied to other communication systems having similar technical backgrounds or channel types. For example, the 5th generation mobile communication technology (5G, new radio, NR) or the 5G advanced system developed after LTE-A may be included in a system to which the embodiments of the present disclosure may be applied, and 5G below may also be a concept that includes existing LTE, LTE-A, and other similar services.

[0043] For convenience of explanation, the present invention uses terms and names defined in the 3rd Generation Partnership Project Long Term Evolution (3GPP) standard or NR (new radio) standard. However, the present invention is not limited to the above terms and names and can be equally applied to systems conforming to other standards. For example, the present invention can be applied to the 3GPP 5GS / NR (5th generation mobile communications standard) or the 3GPP 5G advanced standard.

[0044] The present disclosure enables a terminal, while currently receiving service from a serving cell through a specific beam, to measure and report a beam belonging to another cell, so that if the beam of a neighboring cell is better, a cell change to that cell can be performed. Currently, the terminal can only perform measurements on SSB resources transmitted from neighboring cells within the same CU (Central Unit) as Layer 1 measurements for LTM (L1 / L2 triggered mobility). That is, the serving cell transfers L1 measurement resources for LTM to the terminal between LTM candidate cells through the LTM procedure. However, there is a need for CSI-RS resource support to flexibly adjust LTM L1 measurement resources, rather than SSB resources, for each serving cell and / or each terminal.

[0045] According to the CSI-RS based LTM layer 1 measurement and reporting method proposed in the present disclosure, the terminal can support continuous L1 / L2 signaling-based handover operation to neighboring cells through layer 1 based beam measurement by determining a handover operation through beam measurement and beam measurement referring to CSI-RS resources from a cell other than the serving cell, and the base station can provide more flexible LTM L1 measurement resources to the terminal compared to L1 measurement through existing SSB resources. In addition, the present disclosure proposes an overall operation supporting LTM L1 measurement through CSI-RS in inter-CU scenarios as well as intra-CU scenarios.

[0046] FIG. 1a is a diagram illustrating the structure of a next-generation mobile communication system according to an embodiment of the present disclosure.

[0047] Referring to FIG. 1a, the wireless access network of the next-generation mobile communication system is composed of a next-generation base station (New Radio Node B, hereinafter referred to as NR NB, 1a-10) and an NR CN (New Radio Core Network, or NG CN: Next Generation Core Network, 1a-05). A user terminal (New Radio User Equipment, hereinafter referred to as NR UE or terminal, 1a-15) accesses an external network through the NR NB (1a-10) and the NR CN (1a-05). The NR NB (1a-10) may also be referred to as an NR gNB.

[0048] In Fig. 1a, the NR NB (1a-10) corresponds to the eNB (Evolved Node B) of the existing LTE system. The NR NB (1a-10) is connected to the NR UE (1a-15) via a wireless channel and can provide a service that is superior to the existing eNB. In the next-generation mobile communication system, since all user traffic is serviced through a shared channel, a device that collects status information such as the buffer status of UEs, available transmission power status, and channel status and performs scheduling is required, and the NR NB (1a-10) is in charge of this. One NR NB (1a-10) typically controls multiple cells. In order to implement ultra-high-speed data transmission compared to the existing LTE, it can have a bandwidth higher than the existing maximum, and beamforming technology can be additionally grafted using the orthogonal frequency division multiplexing (OFDM) method as a wireless access technology. In addition, it applies the Adaptive Modulation & Coding (AMC) method that determines the modulation scheme and channel coding rate according to the channel status of the terminal. NR CN (1a-05) performs functions such as mobility support, bearer setup, and QoS setup. NR CN (1a-05) is a device that handles various control functions as well as mobility management functions for the terminal and is connected to multiple base stations. In addition, the next-generation mobile communication system can also be linked with the existing LTE system, and NR CN (1a-05) is connected to MME (1a-25) through a network interface. MME (1a-25) is connected to eNB (1a-30), which is an existing base station.

[0049] FIG. 1b is a diagram illustrating a wireless protocol structure of a next-generation mobile communication system according to an embodiment of the present disclosure.

[0050] Referring to FIG. 1b, the wireless protocol of the next-generation mobile communication system is composed of NR SDAP (Service Data Adaptation Protocol) (1b-01, 1b-45), NR PDCP (Packet Data Convergence Protocol) (1b-05, 1b-40), NR RLC (Radio Link Control) (1b-10, 1b-35), NR MAC (Medium Access Control) (1b-15, 1b-30), and NR PHY (Physical Layer) layers (1b-20, 1b-25) in the terminal and NR base station, respectively.

[0051] Key features of NR SDAP (1b-01, 1b-45) may include some of the following:

[0052] - Transfer of user plane data

[0053] - Mapping function between QoS flow and data bearer for both DL and UL

[0054] - Marking function of QoS flow ID for both uplink and downlink (marking QoS flow ID in both DL and UL packets)

[0055] - Ability to map relective QoS flow to data bearer for uplink SDAP PDUs (reflective QoS flow to DRB mapping for the UL SDAP PDUs).

[0056] For the above SDAP layer device, the terminal can be configured by an RRC (Radio Resource Control) message for each PDCP layer device, each bearer, or each logical channel, whether to use the header of the SDAP layer device or whether to use the function of the SDAP layer device, and when the SDAP header is configured, the terminal can be instructed to update or reset the mapping information for the QoS flow and data bearer of the uplink and downlink with a 1-bit indicator for NAS QoS reflection configuration (NAS reflective QoS) and a 1-bit indicator for AS QoS reflection configuration (AS reflective QoS) of the SDAP header. The SDAP header can include QoS flow ID information indicating QoS. The QoS information can be used as data processing priority, scheduling information, etc. to support smooth service.

[0057] The main functions of NR PDCP (1b-05, 1b-40) may include some of the following functions:

[0058] - Header compression and decompression (ROHC only)

[0059] - User data transfer function

[0060] - In-sequence delivery of upper layer PDUs

[0061] - Out-of-sequence delivery of upper layer PDUs

[0062] - PDCP PDU reordering for reception

[0063] - Duplicate detection of lower layer SDUs

[0064] - Retransmission function (Retransmission of PDCP SDUs)

[0065] - Encryption and decryption functions (Ciphering and deciphering)

[0066] - Timer-based SDU discard in uplink.

[0067] The reordering function of the NR PDCP device above refers to a function of reordering PDCP PDUs received from a lower layer in order based on the PDCP SN (sequence number), and may include a function of transmitting data to an upper layer in the reordered order, or may include a function of transmitting data directly without considering the order, may include a function of recording lost PDCP PDUs by reordering the order, may include a function of reporting the status of lost PDCP PDUs to the transmitting side, and may include a function of requesting retransmission of lost PDCP PDUs.

[0068] The main functions of NR RLC (1b-10, 1b-35) may include some of the following functions:

[0069] - Data transfer function (Transfer of upper layer PDUs)

[0070] - In-sequence delivery of upper layer PDUs

[0071] - Out-of-sequence delivery of upper layer PDUs

[0072] - ARQ function (Error Correction through ARQ)

[0073] - Concatenation, segmentation and reassembly of RLC SDUs

[0074] - Re-segmentation of RLC data PDUs

[0075] - Reordering of RLC data PDUs

[0076] - Duplicate detection function

[0077] - Protocol error detection

[0078] - RLC SDU discard function

[0079] - RLC re-establishment function

[0080] The in-sequence delivery function of the NR RLC device above refers to the function of sequentially transmitting RLC SDUs received from a lower layer to an upper layer, and may include a function of reassembling and transmitting RLC SDUs when an RLC SDU is originally received divided into multiple RLC SDUs, may include a function of reordering received RLC PDUs based on RLC SN (sequence number) or PDCP SN (sequence number), may include a function of recording lost RLC PDUs by reordering the sequence, may include a function of reporting the status of lost RLC PDUs to the transmitting side, may include a function of requesting retransmission of lost RLC PDUs, may include a function of sequentially transmitting only RLC SDUs up to the lost RLC SDU to an upper layer when there is a lost RLC SDU, or may include a function of sequentially transmitting all RLC SDUs received before the timer starts when a predetermined timer expires even when there is a lost RLC SDU. Or, even if there are lost RLC SDUs, if a predetermined timer has expired, it may include a function to sequentially deliver all RLC SDUs received up to the upper layer. In addition, the RLC PDUs may be processed in the order they are received (in the order of arrival, regardless of the order of the sequence number) and delivered to the PDCP device out of sequence (out-of-sequence delivery). In the case of segments, the segments stored in the buffer or to be received later may be received, reconstructed into a single complete RLC PDU, processed, and then delivered to the PDCP device.The above NR RLC layer may not include a concatenation function, and the function may be performed in the NR MAC layer or replaced with a multiplexing function of the NR MAC layer.

[0081] The out-of-sequence delivery function of the NR RLC device mentioned above refers to the function of directly delivering RLC SDUs received from a lower layer to an upper layer regardless of the order, and may include a function of reassembling and delivering RLC SDUs when one RLC SDU is received divided into multiple RLC SDUs, and may include a function of storing and arranging the RLC SN or PDCP SN of received RLC PDUs to record lost RLC PDUs.

[0082] NR MAC (1b-15, 1b-30) can be connected to multiple NR RLC layer devices configured in one terminal, and the main functions of NR MAC can include some of the following functions.

[0083] - Mapping function (Mapping between logical channels and transport channels)

[0084] - Multiplexing / demultiplexing of MAC SDUs

[0085] ? Scheduling information reporting function

[0086] - HARQ function (Error correction through HARQ)

[0087] - Priority handling between logical channels of one UE

[0088] - Priority handling between UEs by means of dynamic scheduling

[0089] - MBMS service identification function

[0090] - Transport format selection function

[0091] - Padding function

[0092] The NR PHY layer (1b-20, 1b-25) can perform operations such as channel coding and modulating upper layer data, converting it into OFDM symbols and transmitting it over a wireless channel, or demodulating and channel decoding OFDM symbols received over a wireless channel and transmitting them to a higher layer.

[0093] FIG. 1c is a diagram illustrating the structure of a next-generation mobile communication system according to an embodiment of the present disclosure.

[0094] Referring to FIG. 1c, a cell served by an NR gNB (1c-05) operating on a beam basis may be composed of multiple Transmission Reception Points (TRPs, 1c-10, 1c-15, 1c-20, 1c-25, 1c-30, 1c-35, 1c-40). The TRPs (1c-10 to 1c-40) represent blocks that separate some functions of transmitting and receiving physical signals from an existing NR base station (gNB) and are composed of multiple antennas. The NR gNB (1c-05) may be expressed as a CU (Central Unit) and the TRP may be expressed as a DU (Distributed Unit). The functions of the NR gNB (1c-05) and the TRP may be configured by separating each layer in the PDCP / RLC / MAC / PHY layers such as 1c-45. That is, the TRP can perform the function of the corresponding layer with only the PHY layer (1c-15, 1c-25), the TRP can perform the functions of the corresponding layers with only the PHY layer and the MAC layer (1c-10, 1c-35, 1c-40), and the TRP can perform the functions of the corresponding layers with only the PHY layer, the MAC layer, and the RLC layer (1c-20, 1c-30). In particular, the TRPs (1c-10 to 1c-40) can use beamforming technology to transmit and receive data by generating narrow beams in multiple directions using multiple transmit / receive antennas. The user terminal (1c-50) connects to the NR gNB (1c-05) and the external network through the TRPs (1c-10 to 1c-40). The above NR gNB (1c-05) collects and schedules status information such as buffer status, available transmission power status, and channel status of terminals to provide services to users, thereby supporting connections between the terminals and the core network (CN), particularly the Access and Mobility Management Function (AMF) / Session Management Function (SMF) (1c-60).

[0095] For convenience of explanation below, the TRP of the present disclosure is explained assuming a structure (1c-15, 1c-25) that can perform the functions of the corresponding layer with only the PHY layer.

[0096] FIG. 1D is a diagram for explaining a method for managing inter-cell beams according to an embodiment of the present disclosure, in which a terminal transmits and receives data through a beam of a TRP (transmission / reception point) of a neighboring cell that supports beam change based on L1 / L2 while maintaining a connection state with a serving cell.

[0097] Referring to FIG. 1d, although FIG. 1d describes a case where multiple cells (TRP1-Cell1 (1d-10), TRP2-Cell2 (1d-15)) exist within one DU (Distributed unit, 1d-05), the overall content of the present disclosure can also be applied to the inter-DU case (where each DU constitutes one TRP-Cell). In addition, in the present disclosure, a non-serving cell that supports L1 / L2-based mobility (beam change and serving cell change) (e.g., TRP 2, Cell 2 (1d-15)) is referred to as a neighbor cell, a non-serving cell, an additional cell with the PCI (Physical Cell Identifier) ​​different from the serving cell, etc.

[0098] The existing terminal beam change procedure (1d-45) may be such that the terminal (1d-20) is transmitting and receiving data in a connected state through TRP 1 (1d-10) of serving cell 1, and may be set to the optimal beam, TCI (Transmission Configuration Indicator) state 1 (1d-25, 1d-30). At this stage, the terminal may receive configuration information for L3 channel measurement (RRM; radio resource management) for an additional cell (TRP 2-Cell 2, 1d-15) having a different PCI from the serving cell through RRC configuration information from the serving cell (1d-10), and performs L3 measurement operation (1d-46) for the corresponding frequency and cell. Afterwards, the serving cell (TRP 1-Cell 1, 1d-10) can instruct a handover to the corresponding cell (TRP 2-Cell 2, 1d-15) based on the reported measurement value (1d-47), and the handover is completed, and additional RRC configuration information can be transmitted (1d-48) to the terminal (1d-20) via TRP 2-Cell 2 (1d-15). The RRC configuration information may include UL / DL configuration information in the corresponding cell, L1 measurement-related settings (CSI-RS measurement and reporting), and in particular, TCI state configuration information for PDCCH and PDSCH channels. The terminal performs L1 measurement according to the settings (1d-49), and the base station updates the TCI state through L1 / L2 signaling according to the measurement report (1d-50). Here, the optimal beam, TCI state 2 (1d-35, 1d-40), may be indicated. At this stage, before the handover, the serving cell is Cell 1, and after the handover, Cell 2 becomes the serving cell. In other words, many procedures and time are required even after the handover until the optimal beam is indicated.

[0099] Unlike the existing terminal beam changing procedure (1d-45), the improved beam changing technique (1d-55) considered in the present disclosure is as follows.

[0100] The terminal can be instructed by the serving cell (1d-10) to refer to the beam setting associated with the additional cell (TRP 2-Cell 2, 1d-15) having a different PCI from the serving cell through RRC configuration information (1d-56). The beam setting associated with the additional cell (TRP 2-Cell 2, 1d-15) having a different PCI from the serving cell, i.e., the part that associates the TCI state corresponding to TRP2, can be instructed by associating a new cell ID (Physical cell ID, PCI; additionalPCI-r17) as shown in [Table 1] below.

[0101] [Table 1]

[0102]

[0103] Additionally, for beam management between the cells, a unified TCI state framework may be applied, for example, as shown in [Table 2] below. The unified TCI state framework applies a common TCI state framework to uplink and downlink, and common and dedicated channels, and can be set to either Joint UL / DL mode or separate UL / DL mode.

[0104] [Table 2]

[0105]

[0106] □ Joint UL / DL mode: Configure UL (Uplink) and DL (Downlink) to share the same TCI settings (in PDSCH-Config) (e.g., [Table 3])

[0107] [Table 3]

[0108]

[0109] □ Separate UL / DL mode: UL and DL each provide their own TCI configuration. The TCI state for DL ​​follows the configuration in dl-OrJoint-TCIStateList-r17 (in PDSCH-Config), and the TCI state for UL follows ul-TCI-StateList-r17 (in BWP-UplinkDedicated) (e.g., [Table 4]).

[0110] [Table 4]

[0111]

[0112] After the configuration for TRP 2-Cell 2 is provided in the RRC connection state to the serving cell 1, the terminal performs L1 measurement for the corresponding TRP 2-Cell 2 according to the configuration and reports the result to the serving cell (Cell 1, 1d-10) (1d-57). If the serving cell determines that a change to a specific beam (TCI state 2, 1d-35, 1d-40) of TRP 2 (Cell 2, 1d-15) is required from the serving cell beam (TCI state 1, 1d-25, 1d-30) based on the measurement result, it triggers the beam change and instructs the terminal through L1 / L2 signaling (1d-58). The terminal changes the beam to a specific beam (TCI state 2, 1d-40) of TRP 2 (Cell 2, 1d-15) through the instruction, and performs physical channel configuration and upper layer configuration operations related to the configured beam. From this step, the terminal remains connected to the serving cell (Cell 1, 1d-10), but performs data transmission and reception (PDCCH / PDSCH reception, PUCCH / PUSCH transmission) using the channel link of TRP 2 (Cell 2, 1d-15). That is, transmission and reception for the common control channel are performed through the serving cell (Cell 1, 1d-10). Thereafter, the terminal performs L3 measurement operations according to the measurement settings configured in the independent serving cell (1d-59), receives a handover command message from the serving base station (Cell 1), and can perform a serving cell change to Cell 2 (1d-60).

[0113] Through this technique (1d-55), the terminal performs data transmission and reception with a specific TRP 2 of Cell2 that supports L1 / L2-based mobility while connected to the serving cell, and can continuously use the beam even after handover.

[0114] For reference, the RRC settings for the L1 measurement and report related settings and operations in step 1d-57 above are described below. These details may also be applied to the following embodiments of the present disclosure, and further improved techniques may be added in future embodiments.

[0115] □ L1 measurement settings (configured in CSI-ResourceConfig, ServingCellConfig IE) (e.g., [Table 5])

[0116] - CSI-RS / SSB resources and resource pools requiring measurement (nzp-CSI-RS, csi-IM, csi-SSB)

[0117] - CSI-RS / SSB resource settings (aperiodic, semi-persistent) and triggering settings that require measurement

[0118] - When a CSI-RS resource references an SSB resource, additional PCI information is provided to enable L1 measurement from neighboring cells (up to 7 neighboring cells (PCI) can be added to a serving cell). (For example, [Table 6])

[0119] [Table 5]

[0120]

[0121] [Table 6]

[0122]

[0123] □ L1 report settings (set within ServingCellConfig IE within the serving cell)

[0124] - Report type: periodic report, semi-periodic report on PUCCH, semi-periodic report on PUSCH, aperiodic report on PUSCH (periodic, semi-persistent for PUCCH, semi-persistent for PUSCH, aperiodic)

[0125] - Report quantity

[0126] - Settings required for other reports

[0127] FIG. 1e is a diagram for explaining a method for a terminal to transmit and receive data by changing a serving cell and beam to a TRP of a cell that supports L1 / L2-based beam change according to an embodiment of the present disclosure.

[0128] Referring to FIG. 1e, although FIG. 1e describes a case where multiple cells (TRP1-Cell1, TRP2-Cell2; 1e-10, 1e-15, 1e-40, 1e-45) exist within one DU (Distributed unit, 1e-05, 1e-35), the overall content of the present disclosure can also be applied to the case of inter-DU (each DU constitutes one TRP-Cell) within an intra CU.

[0129] Compared to the existing terminal beam changing procedure (1d-45, 1d-55) described in FIG. 1d of the present disclosure, the improved beam changing technique (1e-25, 1e-75) considered in one embodiment of the present disclosure is as follows.

[0130] □ Example 1 (1e-25): After performing inter-cell beam management (change) operation, L1 / L2 handover is performed.

[0131] □ Example 2 (1e-75): Immediate L1 / L2 handover

[0132] First, the overall operation of Embodiment 1 (1e-25) will be described. The terminal can receive common configuration information and dedicated configuration information for an additional cell (TRP 2-Cell 2, 1e-15) with a different PCI from the serving cell (1e-10) through RRC configuration information (1e-26). That is, configuration information corresponding to ServingCellID or candidateCellID (cell ID associated with PCI), ServingCellConfigCommon, and ServingCellConfig can be provided in advance. The configuration information can be provided in the form of pre-configuration in the RRC configuration, and can include configuration information for multiple cells. In addition, the configuration can include all configuration information (cell configuration, bearer configuration, security key configuration, etc.) applied when the terminal moves to the corresponding cell (handover). In addition, the configuration can include enhanced configuration by referring to the unified TCI state configuration described in step 1d-56 of FIG. 1d and the configuration related to L1 measurement and report. In detail, it may include enhanced unified TCI state settings and L1 measurement and report settings for continuous LTM, which are described in detail below.

[0133] After the configuration for TRP 2-Cell 2 (1e-15) is provided in the RRC connection state to serving cell 1, the terminal can perform L1 measurement for the TRP 2-Cell 2 (1e-15) according to the configuration received in step 1e-26 and report the result to the serving cell (Cell 1, 1e-10) (1e-27).

[0134] If the serving cell determines that it needs to change to a specific beam (TCI state 2, 1e-40) of TRP 2 (Cell 2, 1e-15) rather than the serving cell beam (TCI state 1, 1e-25) based on the measurement results, it can trigger a beam change and instruct the terminal through L1 / L2 signaling at step 1e-28.

[0135] The terminal can perform a beam change to TRP 2 (Cell 2, 1e-15) through the instruction and transmit and receive data through the TRP 2 (Cell 2, 1e-15). At this time, the serving cell does not change and the terminal is still RRC connected to the serving cell (Cell 1, 1e-10). Afterwards, the terminal can still perform L1 measurement for TRP 2-Cell 2 (1e-15) and report the result to the serving cell (Cell 1, 1e-10) (1e-29).

[0136] The serving cell (Cell 1, 1e-10) can instruct the UE to perform a handover (1e-30) if the L1 measurement reported by the UE satisfies the triggering conditions for a handover (detailed operation is described below) to TRP 2-Cell 2 (1e-15). This instruction can be an L1 / L2 message. That is, the MAC CE can contain an instruction indicating a handover.

[0137] Hereinafter, the entire operation of Embodiment 2 (1e-75) will be described. The terminal can receive common configuration information and dedicated configuration information for an additional cell (TRP 2-Cell 2, 1e-45) with a different PCI from the serving cell (1e-40) through RRC configuration information (1e-76). That is, the ServingCellID or candidateCellID (cell ID associated with PCI) and configuration information corresponding to the candidate LTM cell may be provided in advance. The configuration information may be provided in the form of pre-configuration in the RRC configuration and may include configuration information for multiple cells. In addition, the configuration may include all configuration information (cell configuration, bearer configuration, channel measurement configuration, etc.) applied when the terminal moves to the cell (handover). In addition, the configuration may include the unified TCI state configuration described in step 1d-56 of FIG. 1d and the configuration related to L1 measurement and report, which may be modified to support continuous LTM. This will be described in detail below.

[0138] After the configuration for TRP 2-Cell 2 (1e-45) is provided in the RRC connection state to serving cell 1, the terminal can perform L1 measurement for the corresponding TRP 2-Cell 2 (1e-45) according to the configuration received in step 1e-76 and report the result to the serving cell (Cell 1, 1e-40) (1e-77).

[0139] If the serving cell determines that a handover is necessary simultaneously with a beam change to a specific beam (TCI state 2, 1e-70) of TRP 2 (Cell 2, 1e-45) rather than the serving cell beam (TCI state 1, 1e-45) based on the measurement results, the beam change and handover can be triggered in step 1e-78 and instructed to the UE through L1 / L2 signaling. The UE can perform a handover simultaneously with a beam change to TRP 2 (Cell 2, 1e-15) through the instruction and transmit and receive data through the TRP 2 (Cell 2, 1e-15). At this time, the UE can apply the configuration information for the target cell to which the handover is to be performed, which was previously configured in step 1e-76. In this step, the UE may perform a random access or may omit the random access to the target cell depending on whether uplink synchronization is required. The detailed operation is described below.

[0140] In the following, in particular, a detailed method for setting a unified TCI state and setting an L1 measurement and report for LTM peripheral candidate cells to support the continuous LTM proposed in the present disclosure as described above will be described.

[0141] As described in FIG. 1d of the present disclosure, in the existing ICBM (Inter cell beam management), L1 measurement resource settings for cells requiring measurement are provided in the CSI-ResourceConfig within the ServingCellConfig IE within the serving cell configuration. In particular, in order to indicate resources for neighboring cells, the PCI of the cell for which the corresponding L1 measurement resource is set can be indicated in the servingAdditionalPCIList.

[0142] Detailed settings for L1 measurement settings and reporting settings for LTM can be provided as L1 measurement resource settings applied to LTM candidate cells, as shown in [Table 7] below. To this end, an operation is required in the preprocessing step to share and determine L1 measurement resources and reporting settings for LTM between LTM candidate cells. The entire procedure is described in the following examples.

[0143] [Table 7]

[0144]

[0145]

[0146]

[0147] In the present disclosure, to support subsequent LTM (subsequent LTM; subsequent L1 / L2 triggered mobility), a method for setting L1 measurement information for neighboring candidate cells for LTM and a method for setting up a terminal to report the set L1 measurement information are proposed. In particular, a method for setting up CSI-RS resources for the above L1 measurement resources is proposed, and the overall operation is proposed for cases where the neighboring cells are cells within an intra-CU or inter-CU. In addition, a unified TCI state setting can be applied and set in the same manner to the location where the proposed L1 measurement resources are set.

[0148] FIGS. 1fa and 1fb are diagrams illustrating a method for applying CSI-RS-based L1 measurement resources and reporting settings to support continuous L1 / L2-based handover (LTM) operations in cells within the same CU, according to one embodiment of the present disclosure.

[0149] Referring to FIG. 1f, in step 1f-10, a terminal (1f-01) in an RRC connection state transmits and receives data with a source cell 1 (1f-02), and then transmits layer 3 measurement values ​​for the serving cell and surrounding cells to the source base station (1f-03) according to the configured layer 3 measurement and reporting. At this time, the actual measurement values ​​are transmitted to the base station CU (1f-03). This is because the base station CU (1f-03) is responsible for RRC message processing and determines mobility.

[0150] In step 1f-15, the base station CU (1f-03) generates a message (UE Context Setup Request or UE Context Modification Request) requesting setup information for L1 / L2-based handover to LTM candidate neighboring cells (1f-04, 1f-05) based on the measurement value report received from the terminal, and transmits the message to the F1 interface. In Fig. 1f, the candidate cell is shown in association with the DU, but in reality, the candidate cell and the DU may be mapped 1:1, or multiple candidate cells may be included in one DU.

[0151] In addition, the message requesting configuration information for the above L1 / L2-based handover may be a UE context setup request message, a UE context modification request message, or a new F1 message. The message requesting configuration information for the above L1 / L2-based handover may include a procedure for indicating to neighboring cells that the cell has been determined as a candidate cell for L1 / L2-based handover, and requesting RRC configuration information to be applied when L1 / L2-based handover is performed to the corresponding cell.

[0152] That is, the message requesting setup information for the L1 / L2-based handover may include information requesting L1 measurement resource and reporting setup for LTM candidate cells proposed in the present disclosure.

[0153] The information that can be included in the message and the information that can be included in the response message to the message are summarized below.

[0154] The information below can be used to construct messages for steps 1f-15, 1f-25, 1f-30 or 1f-30.

[0155] - LTM candidate ID

[0156] - Linkage information (mapping information) between LTM candidate ID and corresponding cell ID

[0157] - Beam information to be used for each candidate (TCI state)

[0158] ■ In this case, the meaning of use can mean a beam that is linked to a RACH occasion when performing DL and / or UL synchronization and / or RACH, and / or a beam to be used for the first UL data transmission. If necessary, a cell switch can be performed with an indicator for each case.

[0159] - RACH preamble index

[0160] - SSB index: This is the index of the SSB used to determine the RACH occasion in each candidate cell, and can mean the occasion of CFRA's RACH preamble.

[0161] The above-mentioned information may be displayed when issuing cell switch command MAC CE and / or DCI instructions to a candidate cell that has made an LTM decision.

[0162] - CSI resource request information for each candidate cell (request for CSI-RS resources or SSB resources)

[0163] ■ It can be requested in the pre-configuration preprocessing part for LTM candidate cells.

[0164] ◆ Indicator of whether the request is for initial preparation, eg, initiation, or subsequent to the initial request for modification.

[0165] ■ In particular, when the request information is included, lower layer configuration information and CSI report configuration information in this message may not be transmitted.

[0166] ■ If CSI resource information is received from candidate cells with the corresponding request information, the CSI resource settings of each candidate cell below may be transmitted instead of the request. In other words, a CSI resource setting preprocessing procedure of at least 2 steps is required.

[0167] ■ Additionally, it is possible to decide whether to request CSI-RS resources or SSB resources for each target candidate cell.

[0168] - CSI resource settings for each candidate cell (required when transmitting L1 measurement settings to the terminal as a source DU), individual resource settings and setting ID for each cell, or CSI resource settings for LTM

[0169] ■ Provides L1 measurement settings for LTM transmitted from the candidate cell based on the above CSI resource request information.

[0170] ■ Each target cell can transmit either one of the two resource settings or both resource settings depending on the CSI-RS resource or SSB resource request.

[0171] ■ For reference, in the present invention, the following two methods are possible for CSI resource request information and response.

[0172] ◆ Method 1: When a source cell requests CSI RS resources or SSB resources as L1 measurement resources to an LTM candidate cell, the target candidate cell always responds to the request by transmitting L1 measurement resources. This has the advantage of allowing the source cell (CU) to manage LTM L1 measurement resources and thus manage LTM between candidate cells.

[0173] ◆ Method 2: When a source cell requests CSI RS resources or SSB resources as L1 measurement resources to an LTM candidate cell, the target candidate cell has the final response authority to the request and provides the target candidate cell with the L1 measurement resources it desires. This allows the target cell to determine its own L1 resources based on its own circumstances, which has advantages such as load management.

[0174] ■ The above CSI resource request information and response may be transmitted to each candidate cell, but may be categorized into a separate list. Alternatively, it may be applied with the same constraints as serving cells set as DCs, not all cells.

[0175] - CSI report configuration considering the CSI resources of each candidate cell above

[0176] ■ The purpose of this is that when a candidate DU creates the above information and transmits it to the CU, this information can be used as the CSI report configuration within the target cell configuration (RRCReconfiguration) of the concerned cell (i.e., target cell) created by the CU. In addition, the information can be transmitted as included within the target cell configuration (RRCReconfiguration) rather than being transmitted separately.

[0177] ■ That is, when a terminal moves from another cell to this cell (concerned cell), it can be used as a CSI report configuration with that cell as the serving cell. It is used to include it in the target cell config without providing a separate L1 configuration for subsequent LTM.

[0178] - RACH configuration and lower layer setting information to be used in the concerned cell

[0179] ■ This information is transmitted from the candidate DU to the CU, and can be written as the settings required for performing RACH within the target cell configuration of the concerned cell, the lower layer settings to be applied when moving to the cell, and / or the reference settings including them, and can be transmitted to the terminal later.

[0180] ■ In particular, some of the RACH settings can be used to include RACH preamble index, Mask, and occasion decision information in the cell switch command MAC CE and / or DCI described above.

[0181] To summarize, the request for the L1 measurement resource and reporting settings can be performed for each candidate cell, and although it is shown as one procedure (step 1f-15) in FIG. 1f, the operation can include multiple procedures (steps 1f-15 and 1f-30 or multiple 1f-30 procedures).

[0182] An example of multiple procedures that can be performed to configure L1 measurement resources and reporting is as follows.

[0183] 1. Step 1 (1f-15): The source base station CU (1f-03) requests L1 measurement resource configuration to LTM candidate cells (request for SSB or CSI-RS resources).

[0184] 2. Step 2 (1f-20): LTM candidate cells requested from the source base station CU (1f-03) determine L1 measurement resource settings.

[0185] 3. Step 3 (1f-25): LTM candidate cells transmit L1 measurement resource configuration (SSB or CSI-RS resource configuration) to the source base station CU (1f-03) in response to the L1 measurement resource configuration request. This procedure can be transmitted to the source base station through the F1 interface as a UE Context Setup Response message.

[0186] 4. Step 4 (1f-30): The source base station CU (1f-03) transmits L1 measurement resource settings for continuous LTM support to each candidate cell based on the collected L1 measurement resource settings for each candidate cell. This procedure can be transmitted to the source base station via the F1 interface as a UE Context Modification Request message.

[0187] 5. Step 5 (1f-35): The source base station CU (1f-03) receives L1 measurement resource configuration from LTM candidate cells and L1 measurement report configuration from LTM candidate cells. This procedure can be transmitted to the source base station through the F1 interface as a UE Context Modification Response message.

[0188] Note that the above UE Context Setup / Modification related messages can also be used exclusively for CSI-RS requests and responses by introducing other messages. The present embodiment (Intra CU scenario) is characterized in that the above multiple procedures can be performed via the F1 interface.

[0189] 6. Step 6 (1f-40): The source base station CU (1f-03) transmits LTM-related settings to the terminal (1f-01). The source base station may configure an RRCReconfiguration message to be transmitted to the terminal by considering the LTM-related settings received from the LTM candidate cells, and transmit the RRC message to the terminal. In other words, pre-configuration information for the LTM candidate cells may be transmitted to the terminal.

[0190] In one embodiment, the source base station CU (1f-03) may transmit source cell configuration information and separate reference cell configuration information to candidate cells (1f-04, 1f-05) or the terminal (1f-01). The reference cell configuration information may include L1 measurement resource configuration for continuous LTM.

[0191] The reference cell configuration information that the source base station CU (1f-03) transmits to each candidate cell (1f-04, 1f-05) may be configuration information (common configuration) that can be commonly applied to multiple target candidate cells to reduce signaling overhead when the target candidate cells provide configuration information for LTM, and this may be a measurement configuration, a bearer configuration, or, if the cells belong to the same CellGroup, configurations set at the CellGroup level (e.g., MAC-CellGroupConfig, RLC bearer configuration, SCell configuration, etc.). Alternatively, if the source base station CU (1f-03) roughly knows or has a procedure for knowing the configuration information for each candidate cell (1f-04, 1f-05), the reference cell configuration may be determined through a separate procedure for obtaining the reference cell configuration information.

[0192] The purpose of the source base station CU (1f-03) transmitting the reference cell configuration to each candidate cell (1f-04, 1f-05) is to enable each candidate cell to transmit only the configuration information added based on the reference cell configuration to the source base station CU (1f-03) so that a delta configuration (a method of applying a configuration added on top of the reference cell configuration to configure a complete configuration or a method of overwriting the configuration in the target cell based on the reference cell configuration and then configuring a complete configuration) can be applied.

[0193] This has the effect of reducing the signaling of RRC messages transmitted to the terminal by being transmitted to the terminal as is.

[0194] Additionally, when the source base station CU (1f-03) transmits the reference cell configuration to each candidate cell (1f-04, 1f-05), it may be omitted, in which case the candidate cell configuration is provided as a complete RRC configuration.

[0195] In step 1f-40, the base station CU (1f-03) generates an RRC message based on the configuration information received from each candidate cell, and the source cell (1f-02) receives the message and transmits it to the terminal. The RRC message includes configuration information (Pre-Config1,…, Pre-ConfigN) for surrounding candidate cells to which L1 / L2-based handover (LTM) is applied. The Pre-Config included in the message may include the CellGroupConfig configuration received from the LTM candidate cells in step 1f-35, the bearer configuration for the LTM candidate cells generated by the base station, and the Layer 3 (Layer 3, L3) measurement configuration.

[0196] In step 1f-45, the terminal that received the RRC message performs a procedure for decoding and processing the RRC message. The processing includes ASN.1 (Abstract Syntax Notation One) decoding and validity determination of the received message, and a method for storing and managing the configuration contents. In addition, the terminal stores the LTM configuration information for each candidate cell decoded in this step as complete configuration information in the terminal's buffer (memory), and at the same time, the received reference cell configuration information can also be stored in the terminal's buffer (memory) and managed for the future.

[0197] The reference cell configuration information may be omitted from the RRC message (or configuration information for each LTM candidate cell) in step 1f-40. In this case, the UE recognizes that there is no reference cell configuration information and stores the configuration information for the received LTM target candidate cells as complete configuration information. At this time, the reference cell configuration information is not stored separately (operates as empty). That is, delta configuration is not applied. In addition, the message transmits L1 measurement resource and reporting configuration information for continuous LTM. For detailed configuration, refer to the above description of the present disclosure.

[0198] At step 1f-50, the base station may transmit a Medium Access Control Element (MAC CE) and / or Downlink Control Information (DCI) to the terminal to enable semi-persistent / aperiodic L1 reporting.

[0199] At step 1f-55, the terminal receiving this can perform L1 (layer 1) measurement and reporting for each candidate surrounding cell, and can perform semi-persistent L1 measurement reporting depending on the configuration.

[0200] In step 1f-60, the terminal may terminate semi-persistent L1 measurement reporting upon receiving a MAC CE and / or DCI that disables semi-persistent / aperiodic L1 reporting. Simultaneously, the terminal may perform L3 measurements and reporting according to the configuration in step 1f-65.

[0201] In step 1f-70, the source cell that received the L1 measurement report can make a handover decision based on the measurement value and instruct the UE to perform L1 / L2 handover. In this step, MAC CE and / or DCI including a handover indicator can be used as L1 / L2 signaling. LTM is a method in which the source cell makes the final decision and does not transmit the L1 measurement value to the base station. Instead, the source cell can decide on handover on its own based on measurement value criteria (threshold value and measurement value range) for making handover decisions for each candidate neighboring cell received from the previous base station and transmit L1 / L2 signaling to the UE accordingly. The source cell can then transmit the LTM decision information to the CU.

[0202] In step 1f-75, when an L1 / L2 handover instruction is transmitted to the terminal, the terminal may initiate the handover procedure and start a timer for L1 / L2 handover. The timer may be a newly configured timer for LTM, or an existing T304 timer may be reused.

[0203] In step 1f-80, the UE can apply the configuration for the target cell to which the L1 / L2 handover is applied. That is, the current configuration can be replaced with the complete configuration information of the designated LTM target cell previously stored in the UE. This can be one of the LTM candidate neighboring cell configurations received in advance in step 1f-40 and stored in the UE.

[0204] In step 1f-85, depending on the applicable settings, the terminal may perform random access to the target cell if random access is required. At this time, the terminal may skip the random access procedure if random access is not indicated or required (e.g., if uplink synchronization has already been performed or aligned).

[0205] In step 1f-90, the UE can perform a handover completion procedure with the target cell. This completion procedure may be a handover completion procedure for LTM. This procedure may vary depending on the method of indicating the handover completion. If the target cell configuration is received at the RRC message level, it may be a process of transmitting an RRCReconfigurationComplete message. However, if the cell-level or cell group-level configuration is received, a new handover completion indication message (a new RRC message or MAC CE and / or DCI) may replace this procedure.

[0206] Furthermore, since this scenario considers application to intra-CU, in step 1f-95, the target cell (DU, 1f-04) that received the handover completion message can forward the received message to the base station CU (1f-03). At this time, the handover completion message received via the F1 interface can be forwarded as is, or the message can be reprocessed and forwarded based on the received information.

[0207] At step 1f-100, the base station CU (1f-03) may transmit information about the completion of the handover to the source cell (1f-02) and instruct it to release the terminal context.

[0208] Additionally, as described in step 1f-105, the embodiments of the present disclosure can support subsequent LTM operations. This may mean that the LTM configuration information (configuration of target candidate cells and reference cell configuration information, etc.) received by the terminal in step 1f-40 is stored in the terminal as is, and the terminal continues to perform the LTM procedure unless the corresponding LTM configuration information is changed / released / added through a separate RRC configuration. If it is necessary to update the reference cell configuration information, this can be performed by transmitting new RRC configuration information to the terminal. That is, the procedure described in FIG. 1f can be triggered and performed again.

[0209] To summarize, if the terminal receives reference cell setting information in step 1f-40, it stores it in the terminal buffer and, if there is no update to a separate setting, can continue to use the setting as reference cell setting information even after performing LTM (step 1f-70) (i.e., apply the reference cell setting and LTM candidate setting values ​​stored in the successive LTM).

[0210] In addition, in step 1f-40, if the reference cell configuration information is not provided in the RRC connection state, the reference cell configuration can be saved as empty according to the terminal operation option described above, or the configuration information for the corresponding source cell (PCell) from which the LTM configuration information was received can be saved as the reference cell configuration information.

[0211] FIG. 1ga and FIG. 1b are diagrams illustrating a method for applying CSI-RS based L1 measurement resources and reporting configurations to support continuous L1 / L2 based handover (LTM) operations in cells within different CUs, according to one embodiment of the present disclosure.

[0212] Referring to Fig. 1g, the difference from the embodiment of Fig. 1f is that LTM candidate cells may not only exist within the same CU but may also exist within different CUs (inter-CUs). Therefore, the most important point to consider in the embodiment of Fig. 1g is that, in addition to the procedure for requesting and responding to configuration for LTM between a serving base station (CU) and an LTM candidate cell (DU) via the F1 interface of the embodiment of Fig. 1f, a procedure for requesting and responding to LTM configuration between a serving base station (CU) and a target base station (CU) via the X2 interface must be added. In addition, the present disclosure is characterized by requesting CSI-RS resources to LTM candidate cells belonging to a target base station (CU) for LTM L1 measurement, which is mainly considered, and receiving related CSI-RS resource configuration as a response.

[0213] In step 1g-10, a terminal (1g-01) in an RRC connection state transmits and receives data with source cell 1 (1g-02), and can transmit layer 3 measurement values ​​for the serving cell and surrounding cells to the source base station (1g-03) according to the configured layer 3 measurement and reporting. At this time, the actual measurement values ​​are transmitted to the base station CU (1g-03). This is because the base station CU (1g-03) is responsible for RRC message processing and determines mobility.

[0214] In step 1g-15, the base station CU (1g-03) can generate a message (UE Context Setup Request or UE Context Modification Request) requesting setup information for L1 / L2-based handover to the intra-CU's LTM candidate surrounding cells (1g-04, 1g-05) based on the measurement value report received from the terminal, and transmit the message to the F1 interface. For detailed procedures, refer to the procedures (steps 1f-15 to 1f-35) of the drawing 1f above, and any duplicate descriptions are omitted here.

[0215] At step 1g-20, the base station CU (1g-03) can generate a message (Handover Request or new message) requesting configuration information for L1 / L2-based handover to the target base station (CU2; 1g-06) for LTM candidate cell configuration for the LTM surrounding cell (1g-07) of the inter-CU based on the measurement value report received from the terminal, and transmit the message to the X2 interface.

[0216] In step 1g-25, the target base station (CU2; 1g-06) can generate a message (UE Context Setup Request or UE Context Modification Request) requesting configuration information for L1 / L2-based handover (LTM) for the LTM candidate cell (1g-07) belonging to the CU and transmit the message to the F1 interface. The target base station (CU2; 1g-06) can receive a message (UE Context Setup Response or UE Context Modification Response) responding with configuration information for L1 / L2-based handover from the LTM candidate cell (1g-07). The procedure is similar to the LTM configuration preprocessing procedure (steps 1f-15 to 1f-35) of FIG. 1f. In particular, the LTM-related configuration request and response of the message transmitted to the F1 interface refer to the contents described in FIG. 1f, and redundant description is omitted here.

[0217] At step 1g-30, the target base station (CU2; 1g-06) can generate a response message (Handover Response or new response message) including LTM candidate configuration information received from an LTM candidate cell (1g-07) belonging to the CU, and transmit the message to the source base station (CU; 1g-03) through the X2 interface.

[0218] The following summarizes the new content that can be added to the response message for the LTM setup request through the X2 interface of the above 1g-30 step.

[0219] - Instructions for performing LTM

[0220] ■ Additionally, an indicator of whether the request is for initial preparation, eg, initiation, or subsequent to the initial request for modification.

[0221] - Terminal ID

[0222] - Source CU and / or source DU ID, and / or TNL address (e.g., IP address) of the source DU

[0223] - ID of the requesting candidate cell (PCI or NR CGI with NR ARFCN)

[0224] - LTM configuration ID of this candidate cell (if accepted, the source DU can use this LTM config ID when switching cells to the target cell)

[0225] - LTM configuration ID mapping list: When delivered to a candidate DU, information to inform the candidate DU of the mapping relationship between the currently operable LTM settings and its cells.

[0226] ■ Opt 1. The above candidate cell list may be a list of candidate cells operated by all candidate CUs for the corresponding terminal, or

[0227] ■ Opt 2. It may be a list that includes only candidate cells operated by the source CU that transmits the HO request message.

[0228] - CSI resource setup request information for LTM L1 measurement

[0229] ■ CSI resource request may be omitted, and configuration information of CSI resources being transmitted by all currently configured candidate cells may be transmitted.

[0230] ■ Request for SSB or CSI-RS resources

[0231] ■ You can request only one of the two resources, or you can request both resources.

[0232] - An indicator requesting PRACH resource information for the target candidate cell.

[0233] - A directive requesting lower layer settings for target candidate cells.

[0234] Of course, in addition to the above information, information previously used in HO request messages may also be included. This can be seen in [Table 8] below.

[0235] [Table 8]

[0236]

[0237]

[0238] Additionally, the response message to the LTM setup request through the X2 interface of the above 1g-30 step may include LTM-related setup information of the LTM target cell within the corresponding CU.

[0239] - Includes CSI resource settings in response to requested CSI resources.

[0240] ■ Including resources in response to SSB or CSI-RS resource requests

[0241] ■ You can either respond and deliver only one of the two resources, or request both resources.

[0242] ■ Additionally, the base station may respond with the corresponding resource as requested, or the target cell may directly decide to include only one of the two resources.

[0243] - CSI reporting settings information

[0244] ■ If the CSI resource request is omitted and the configuration information of the CSI resources being transmitted by all currently configured candidate cells is transmitted, the CSI reporting settings that apply the settings are transmitted as is.

[0245] - RACH configuration and lower layer setting information to be used in the concerned cell

[0246] ■ This information is transmitted from the LTM candidate DU within the CU to the CU, and is written as the settings required for RACH execution within the target cell configuration of the concerned cell, the lower layer settings to be applied when moving to the cell, and / or the reference settings including them, and can be transmitted to the terminal later.

[0247] ■ In particular, some of the RACH settings can be used to include RACH preamble index, Mask, and occasion decision information in the cell switch command MAC CE and / or DCI described above.

[0248] ■ Beam information to be used for each candidate (TCI state)

[0249] ■ In this case, the meaning of use can mean a beam that is linked to a RACH occasion when performing DL and / or UL synchronization and / or RACH, and / or a beam to be used for the first UL data transmission. If necessary, an indicator for each case can be accompanied to perform a cell switch.

[0250] - In addition, the configuration information transmitted by DU can be configured as complete configuration information as configuration information applied after handover is completed.

[0251] At step 1g-35, the source base station (1g-02) may trigger procedures 1g-15 (transmitting the final determined CSI resource configuration to LTM candidate cells within a CU and requesting and responding to LTM-related configuration) and 1g-20 (transmitting the final determined CSI resource configuration to LTM candidate cells within another CU and requesting LTM-related configuration) based on the information on LTM-related candidate cells received from the target base station (1g-06). In addition, in response thereto, the source base station (1g-02) may perform procedure 1g-30 (receiving LTM-related configuration based on the final transmitted CSI resource configuration from LTM candidate cells within another CU).

[0252] In particular, the present disclosure assumes an operation of requesting and receiving CSI-RS resource configuration for LTM candidate cells within an inter-CU and then transmitting the configuration as an LTM L1 measurement resource to the UE. However, if the procedure is applied to all candidate cells within other CUs, complexity may increase. As an optimization method to prevent this, the procedure may be allowed only for specific CUs. A restriction may be included such that CSI RS resources may be requested only for allowed CUs, or CSI-RS resources may be requested only for candidate cells for which serving cells currently set as DCs exist in the standard document. Alternatively, CSI-RS resource request and response may not be supported for cells within an inter-CU, and LTM L1 resource configuration for SSB resources may be allowed.

[0253] In step 1g-40, the source base station (1g-02) may configure an RRCReconfiguration message to be transmitted to the terminal by considering LTM-related settings received from LTM candidate cells and transmit the corresponding RRC setting information to the terminal. In other words, pre-configuration information for LTM candidate cells may be transmitted to the terminal.

[0254] In one embodiment, a source base station CU (1g-03) may transmit configuration information of the source cell and separate reference cell configuration information to the terminal (1g-01) or candidate cells (1g-04, 1g-05, 1g-07). In the present disclosure, the reference cell configuration information may include L1 measurement resource configuration for continuous LTM.

[0255] The reference cell configuration information that the source base station CU (1g-03) transmits to each candidate cell (1g-04, 1g-05, 1g-07) may be configuration information (common configuration) that can be commonly applied to multiple target candidate cells to reduce signaling overhead when the target candidate cells provide configuration information for LTM, and this may be measurement configuration, bearer configuration, or, if the cells belong to the same CellGroup, configurations set at the CellGroup level (e.g., MAC-CellGroupConfig, RLC bearer configuration, SCell configuration, etc.). Alternatively, if the source base station CU (1g-03) roughly knows or has a procedure for knowing the configuration information for each candidate cell (1g-04, 1g-05, 1g-07), the reference cell configuration may be determined through a separate procedure for obtaining the reference cell configuration information.

[0256] The purpose of the source base station CU (1g-03) transmitting the reference cell configuration to each candidate cell (1g-04, 1g-05, 1g-07) is to enable each candidate cell to transmit only the configuration information added based on the reference cell configuration to the source base station CU (1g-03) so that a delta configuration (a method of applying a configuration added on top of the reference cell configuration to configure a complete configuration or a method of overwriting the configuration in the target cell based on the reference cell configuration and then configuring a complete configuration) can be applied.

[0257] This has the effect of reducing the signaling of RRC messages transmitted to the terminal by being transmitted to the terminal as is.

[0258] Additionally, when the source base station CU (1g-03) transmits the reference cell configuration to each candidate cell (1g-04, 1g-05, 1g-07), it may be omitted, in which case the candidate cell configuration is provided as a complete RRC configuration.

[0259] In step 1g-40, the base station CU (1g-03) can generate an RRC message based on configuration information received from each candidate cell, and the source cell (1g-02) can receive the message and transmit it to the terminal. The RRC message is a message including configuration information (Pre-Config1,…, Pre-ConfigN) for surrounding candidate cells to which L1 / L2-based handover (LTM) is applied. The Pre-Config included in the message can include CellGroupConfig configuration received from the LTM candidate cells in step 1g-35, bearer configuration for the LTM candidate cells generated by the base station, and Layer 3 (Layer 3, L3) measurement configuration.

[0260] In step 1g-45, the terminal that receives the RRC message can perform a procedure for decoding and processing the RRC message. The processing may include ASN.1 (Abstract Syntax Notation One) decoding and validity determination of the received message, and a method for storing and managing the configuration contents. In addition, the terminal can store the LTM configuration information for each candidate cell decoded in this step as complete configuration information in the terminal's buffer (memory), and at the same time, store the received reference cell configuration information in the terminal's buffer (memory) and manage it for the future.

[0261] The reference cell configuration information may be omitted from the RRC message (or configuration information for each LTM candidate cell) in step 1g-40. In this case, the UE recognizes that the reference cell configuration information is missing and stores the configuration information for the received LTM target candidate cells as complete configuration information. At this time, the reference cell configuration information is not stored separately (operates as empty). That is, delta configuration is not applied. In addition, the message transmits L1 measurement resource and reporting configuration information for continuous LTM. For detailed configuration, refer to the above description of the present disclosure.

[0262] In step 1g-50, the base station may transmit MAC CE and / or DCI to the terminal to enable semi-persistent / aperiodic L1 reporting.

[0263] At step 1g-55, the terminal can receive this and perform L1 (layer 1) measurement and reporting for each candidate surrounding cell, and can perform semi-persistent L1 measurement reporting depending on the configuration.

[0264] At step 1g-60, the terminal may terminate semi-persistent L1 measurement reporting when it receives MAC CE and / or DCI that disables semi-persistent / aperiodic L1 reporting.

[0265] At the same time, at 1g-65 stage, the terminal can also perform L3 measurements and reporting depending on the settings.

[0266] In step 1g-70, the source cell that received the L1 measurement report can make a handover decision based on the measurement value and instruct the UE to perform L1 / L2 handover. In this step, MAC CE and / or DCI including a handover indicator can be used as L1 / L2 signaling. In LTM, the source cell makes the final decision and does not transmit the L1 measurement value to the base station. Instead, the source cell determines the handover on its own based on the measurement value criteria (threshold and measurement value range) for making the handover decision for each candidate neighboring cell received from the previous base station and transmits L1 / L2 signaling to the UE accordingly. Thereafter, the LTM decision information is transmitted to the CU.

[0267] In step 1g-75, when an L1 / L2 handover instruction is transmitted to the UE, the UE may initiate a handover procedure and start a timer for L1 / L2 handover. The timer may be a newly configured timer for LTM, or an existing T304 timer may be reused.

[0268] In step 1g-80, the UE can apply the configuration for the target cell to which the L1 / L2 handover is applied. That is, the current configuration can be replaced with the complete configuration information of the designated LTM target cell previously stored in the UE. This is one of the LTM candidate neighboring cell configurations previously received in step 1g-40 and stored in the UE.

[0269] In step 1g-85, depending on the applicable settings, the terminal may perform random access to the target cell if random access is required. The terminal may skip the random access procedure if random access is not indicated or required (e.g., if uplink synchronization has already been performed or aligned).

[0270] In step 1g-90, the UE can perform a handover completion procedure with the target cell. This completion procedure may be a handover completion procedure for LTM. This procedure may vary depending on the method of indicating the handover completion. If the target cell configuration is received at the RRC message level, it may be a process of transmitting an RRCReconfigurationComplete message. However, if the cell-level or cell group-level configuration is received, a new handover completion indication message (a new RRC message or MAC CE and / or DCI) may replace this procedure.

[0271] Furthermore, since this scenario considers intra-CU application, the target cell (DU, 1g-04) that receives the handover completion message in step 1g-95 can forward the received message to the base station CU (1g-03). At this time, the handover completion message received via the F1 interface can be forwarded as is, or the message can be reprocessed and forwarded based on the received information.

[0272] At step 1g-100, the base station CU (1g-03) can transmit information about the completion of the handover to the source cell (1g-02) and instruct it to release the terminal context.

[0273] Furthermore, as described in step 1g-105, the embodiment of the present disclosure supports subsequent LTM operations. This may mean that the LTM configuration information (e.g., configuration for target candidate cells and reference cell configuration information) received by the terminal in step 1g-40 is stored in the terminal as is, and the terminal continues to perform the LTM procedure unless the corresponding LTM configuration information is changed / released / added through a separate RRC configuration. If it is necessary to update the reference cell configuration information, this is performed by transmitting new RRC configuration information to the terminal. In other words, the procedure described in FIG. 1g may be triggered and performed again.

[0274] To summarize, if the terminal receives reference cell setting information in step 1g-40, it stores it in the terminal buffer and, if there is no update to a separate setting, can continue to use the setting as reference cell setting information even after performing LTM (step 1g-70) (i.e., apply the reference cell setting and LTM candidate setting values ​​stored in successive LTMs).

[0275] In addition, in the 1g-40 step, if the reference cell configuration information is not provided in the RRC connection state, the reference cell configuration can be saved as empty according to the terminal operation option described above, or the configuration information for the corresponding source cell (PCell) from which the LTM configuration information was received can be saved as the reference cell configuration information.

[0276] FIG. 1h is a flowchart illustrating an operation of a terminal performing L1 / L2-based beam change and handover according to one embodiment of the present disclosure.

[0277] In particular, the terminal operation of the present disclosure is characterized by a method of performing L1 measurement and reporting according to L1 measurement resource and reporting settings for continuous LTM operation.

[0278] Referring to FIG. 1h, at step 1h-05, a terminal in a connected state can receive configuration information from a neighboring cell that is applied after L1 / L2-based movement is instructed through an RRC reconfiguration message from a serving cell.

[0279] For detailed setup methods and contents, refer to the contents of drawings 1f and 1g, and duplicate explanations are omitted here.

[0280] Also, although omitted in Figure 1h, the terminal has received basic RRC settings from the base station and performs an operation of reporting layer 3 measurement values ​​for surrounding cells.

[0281] In particular, the configuration information in the LTM candidate cell applied after the L1 / L2-based movement received in step 1h-05 is indicated is characterized in that the delta configuration is applied and transmitted based on the configuration for one reference cell. The terminal can know what the reference cell and the configuration information for the reference cell are, which is known in advance or indicated in the RRC configuration, and the configuration for surrounding cells other than the reference cell is transmitted based on the common reference cell configuration and the additional configurations that can be added to it, so the signaling overhead is low.

[0282] In the configuration of the above step, the terminal can receive configuration information related to resources and reporting for L1 measurement for LTM candidate cells. In particular, as described in FIGS. 1f and 1g, the present disclosure is characterized in that SSB and CSI-RS resources can be configured as L1 measurement resource settings for LTM candidate cells within an intra-CU or inter-CU, and the terminal can measure and report the corresponding L1 resources accordingly.

[0283] In step 1h-10, the terminal decodes the settings for the received LTM candidate cells based on the settings of the reference cell and stores and manages the complete settings that are actually applied (i.e., the settings that are delta-configured based on the reference cell are saved as complete configurations by referring to the reference cell settings) in a separate buffer and list. Alternatively, the terminal may store and manage the received RRC settings as they are in the buffer without decoding the received settings based on the reference cell and storing and managing the settings that are actually applied.

[0284] As described in the above drawing 1f, if the terminal receives the reference cell configuration information with the omitted reference cell configuration, the terminal recognizes that there is no reference cell configuration information and determines and stores the configuration information for the received LTM target candidate cells as complete configuration information. At this time, the reference cell configuration information is not stored separately (operates as empty). In other words, the delta configuration is not applied. The advantage of decoding the configuration for the surrounding cells based on the reference cell at this stage and storing the actually applied configuration is that when an actual L1 / L2-based handover is instructed, the handover for the corresponding cell can be applied immediately, so there is no additional delay time.

[0285] In step 1h-15, the terminal can perform L1 measurements using SSB or CSI-RS resources associated with candidate neighboring cells while maintaining a connection with the serving cell, and report the measurement results to the serving cell according to a preset L1 measurement reporting setting.

[0286] Target cells for which CSI-RS resources are configured may be configured separately from cells for which SSB resources are configured. Alternatively, L1 resource configurations provided by LTM candidate cells may be listed without distinction.

[0287] - Option 1: {1st LTM candidate cell SSB resource configuration, 2nd LTM candidate cell SSB resource configuration, …, Mth LTM candidate cell SSB resource configuration} + {M+1th LTM candidate cell CSI-RS resource configuration, M+2nd LTM candidate cell CSI-RS resource configuration, …, Nth LTM candidate cell CSI-RS resource configuration}

[0288] - Option 2: {Set 1st LTM candidate cell resource, Set 2nd LTM candidate cell resource, …, Set Nth LTM candidate cell resource}

[0289] At this stage, the base station can control L1 measurement resource reporting for LTM surrounding cells requiring measurement through RRC configuration and L1 / L2 signaling. The terminal performs L1 measurement resource reporting according to base station configuration and instructions.

[0290] Additionally, the terminal can measure surrounding cells independently of the operation according to the L3 measurement settings and report the measurement results to the base station according to the L3 measurement reporting settings.

[0291] In step 1h-20, the serving cell can determine whether to change the beam of the terminal and perform a handover based on the received measurement results, and if it is determined that a change to a specific beam of a neighboring cell is necessary rather than a specific beam of the serving cell, it instructs the terminal to perform a handover and a beam change through L1 / L2 signaling. In the present disclosure, the above L1 / L2 signaling is MAC CE and / or DCI, and all information instructing a specific beam of the neighboring cell and a serving cell change is instructed in the MAC CE and / or DCI (if the MAC CE and / or DCI indicates only one beam), or a plurality of specific beams of the LTM target cell are instructed in the MAC CE and / or DCI, and one of the plurality of beams of the activated neighboring cell can be selected in the MAC CE and / or DCI to instruct a handover.

[0292] In step 1h-25, the terminal can check whether the MAC CE and / or DCI signaling received in step 1h-15 indicates a handover, and can perform an LTM handover operation. If the received MAC CE and / or DCI indicates a handover (either the MAC CE itself indicates a handover, or the MAC CE activates multiple beams and indicates a handover by indicating one of the beams in the DCI), the terminal can perform a handover to the cell associated with the indicated TCI state.

[0293] In step 1h-30, if random access is successfully performed and handover is successful, the terminal can also apply the settings for the corresponding LTM target cell that were saved in step 1h-10. In step 1h-35, the terminal can maintain the previously saved LTM configuration information and reference cell configuration information. In step 1h-40, the terminal connects to the indicated LTM target cell, transmits and receives data using the indicated beam, performs channel measurement reporting according to the LTM configuration, and continues to perform continuous LTM operation.

[0294] If the LTM handover fails in step 1h-30, the UE can fallback to the previous source cell and attempt a connection in step 1h-45. To achieve this, the UE must maintain the configuration information for the source cell even if LTM is triggered. In addition, the LTM configuration information and reference cell configuration information for the LTM target cell are maintained even after the fallback to the source cell. This is to ensure that LTM can be triggered again according to the existing configuration. If the fallback to the source cell is not performed perfectly, the UE can enter the RRC Re-Establishment procedure and reselect cells that can be connected. If the cell found through cell reselection is one of the LTM candidate cells, the UE can attempt a connection by applying the preset RRC configuration for the cell. Thereafter, in step 1h-50, the UE generates a handover failure report message from the cell with which the connection was performed (source cell or target cell) and transmits it to the base station. The above handover failure report message may be a UEInformationResponse or another uplink RRC message. It may also be reported via a new MAC CE or uplink control information (UCI).

[0295] The information included in the above handover failure report message may include the following information:

[0296] - Indicator indicating that the handover failed due to LTM failure.

[0297] - Target cell information that failed when attempting LTM: LTM cell setup index or physical cell index (PCI) information

[0298] The source base station can report the handover failure message to inform that the LTM attempt failed and fellback to the corresponding cell. In addition, if the cell found through cell reselection after the RRC Re-Establishment procedure is not one of the LTM candidate cells, the UE can maintain the LTM configuration information and reference cell configuration information stored in that cell in step 1h-55. Alternatively, in this case, the UE can release the stored LTM-related configuration information and reference cell configuration information. Alternatively, the base station can explicitly specify the operation through configuration.

[0299] FIG. 1i is a flowchart illustrating the operation of a base station according to one embodiment of the present disclosure.

[0300] Referring to FIG. 1i, in step 1i-05, the base station receives an L3 measurement value report from the terminal, and based on the terminal's measurement values ​​for surrounding frequencies and cells, can determine whether the terminal requires handover and which cells are handover candidate cells.

[0301] In step 1i-10, the base station can send a request for configuration information for L1 / L2-based handover to neighboring cells and receive responses from the cells. In this step, the base station transmits configuration information for the current source cell and reference cell configuration information to neighboring cells, and receives RRC configuration information to which delta configuration is applied based on the reference cell configuration information from neighboring cells and LTM candidate cells.

[0302] Additionally, inter-node coordination for L1 measurement resource and reporting configuration proposed in this disclosure is performed in this step. The procedures detailed in FIGS. 1f and 1g may be included in this step, and in particular, may include determining L1 measurement resource and reporting configuration within intra-CU and inter-CU. Although not illustrated in FIG. 1i, settings related to L3 measurement configuration and basic RRC settings are provided to the terminal prior to this step.

[0303] In step 1i-15, the base station transmits to the connected terminal an RRC configuration message containing the neighboring cell configuration information and L1 measurement resource / reporting configuration information received in step 1i-10. That is, the base station transmits the configuration information in the neighboring cell that is applied after L1 / L2-based movement is indicated by an RRC reconfiguration message from the serving cell. For detailed configuration methods and contents, please refer to FIGS. 1f and 1g, and redundant descriptions will be omitted here.

[0304] In step 1i-20, the base station can instruct L1 measurement reporting in various ways, such as RRC or L1 / L2 signaling, depending on the L1 measurements and reports that the base station wants to configure and trigger. For detailed methods, refer to the disclosure above. The base station can receive reports on L1 and L3 measurement values ​​from the terminal, and the L1 measurement values ​​may be from a neighboring cell (non-serving cell) that supports L1 / L2-based mobility.

[0305] The serving cell can determine whether to change the beam of the terminal and whether to perform a handover based on the measurement results received. If it determines that a change to a specific beam of a neighboring cell is necessary rather than a specific beam of the serving cell, it can instruct an LTM handover of the terminal through L1 / L2 signaling in step 1i-25. The L1 / L2 signaling may be MAC CE and / or DCI, and may include information instructing a change to a specific beam of a neighboring cell.

[0306] Additionally, at this stage, the base station can independently direct existing handovers via RRC messages. This can occur because the base station and serving cell independently determine LTM and Layer 3 handovers.

[0307] In step 1i-35, when the base station receives a handover completion message from the terminal, it confirms that the corresponding LTM operation has been successfully completed, and accordingly, it can notify the previous source cell of the handover completion and request the terminal context to be released.

[0308] Additionally, when the base station receives a handover failure report message containing information that the handover has failed, it can receive a message indicating that the terminal has attempted to reconnect to the corresponding cell after the handover failure. The handover failure report message may be a UEInformationResponse or another uplink RRC message. Additionally, this may be reported via a new MAC CE or uplink control information (UCI). The information contained in the handover failure report message may include the following information.

[0309] - Indicator indicating that the handover failed due to LTM failure.

[0310] - Target cell information that failed when attempting LTM: LTM cell setup index or physical cell index (PCI) information

[0311] The source base station can report a handover failure message to indicate that the LTM attempt failed and fell back to that cell.

[0312] FIG. 1j is a block diagram illustrating the structure of a terminal (1j-00) according to one embodiment of the present disclosure.

[0313] Referring to FIG. 1j, a terminal (1j-00) according to an embodiment of the present disclosure may include an RF (Radio Frequency) processing unit (1j-10), a baseband processing unit (1j-20), a storage unit (1j-30), and a control unit (1j-40).

[0314] The RF processing unit (1j-10) performs functions for transmitting and receiving signals through a wireless channel, such as signal band conversion and amplification. That is, the RF processing unit (1j-10) up-converts the baseband signal provided from the baseband processing unit (1j-20) 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 (1j-10) may include a transmission filter, a reception filter, an amplifier, a mixer, an oscillator, a digital to analog convertor (DAC), an analog to digital convertor (ADC), etc. In the drawing, only one antenna is illustrated, but the terminal may be equipped with multiple antennas. In addition, the RF processing unit (1j-10) may include multiple RF chains. Furthermore, the RF processing unit (1j-10) may perform beamforming. For the above beamforming, the RF processing unit (1j-10) can adjust the phase and size of each signal transmitted and received through multiple antennas or antenna elements. In addition, the RF processing unit can perform MIMO and receive multiple layers when performing the MIMO operation.

[0315] The baseband processing unit (1j-20) performs a conversion function between a baseband signal and a bit stream according to the physical layer specifications of the system. For example, when transmitting data, the baseband processing unit (1j-20) generates complex symbols by encoding and modulating a transmission bit stream. In addition, when receiving data, the baseband processing unit (1j-20) restores the reception bit stream by demodulating and decoding the baseband signal provided from the RF processing unit (1j-10). For example, in the case of following the OFDM (orthogonal frequency division multiplexing) method, when transmitting data, the baseband processing unit (1j-20) generates complex symbols by encoding and modulating a transmission bit stream, maps the complex symbols to subcarriers, and then configures OFDM symbols by performing an inverse fast Fourier transform (IFFT) operation and inserting a cyclic prefix (CP). In addition, when receiving data, the baseband processing unit (1j-20) divides the baseband signal provided from the RF processing unit (1j-10) into OFDM symbol units, restores signals mapped to subcarriers through FFT (fast Fourier transform) operation, and then restores the received bit string through demodulation and decoding.

[0316] The baseband processing unit (1j-20) and the RF processing unit (1j-10) transmit and receive signals as described above. Accordingly, the baseband processing unit (1j-20) and the RF processing unit (1j-10) may be referred to as a transmitter, a receiver, a transceiver, or a communication unit. Furthermore, at least one of the baseband processing unit (1j-20) and the RF processing unit (1j-10) may include a plurality of communication modules to support a plurality of different wireless access technologies. In addition, at least one of the baseband processing unit (1j-20) and the RF processing unit (1j-10) may include different communication modules to process signals of different frequency bands. For example, the different wireless access technologies may include a wireless LAN (e.g., IEEE 802.11), a cellular network (e.g., LTE), etc. Additionally, the different frequency bands may include a super high frequency (SHF) (e.g., 2.NRHz, NRhz) band, a millimeter wave (mm wave) (e.g., 60GHz) band.

[0317] The storage unit (1j-30) stores data such as basic programs, application programs, and setting information for the operation of the terminal (1j-00). In particular, the storage unit (1j-30) can store information related to a second access node that performs wireless communication using a second wireless access technology. In addition, the storage unit (1j-30) provides the stored data upon request from the control unit (1j-40). The storage unit (1j-30) may be referred to as a memory.

[0318] The control unit (1j-40) controls the overall operations of the terminal (1j-00). For example, the control unit (1j-40) transmits and receives signals through the baseband processing unit (1j-20) and the RF processing unit (1j-10). In addition, the control unit (1j-40) records and reads data in the storage unit (1j-40). For this purpose, the control unit (1j-40) may include at least one processor. For example, the control unit (1j-40) may include a communication processor (CP) that performs control for communication and an application processor (AP) that controls upper layers such as application programs. The control unit (1j-40) may control the overall operations of the terminal (1j-00) according to the embodiments proposed in the present disclosure by executing one or more commands stored in the memory (1j-30).

[0319] At least one processor (1j-40) may include various processing circuits and / or multiple processors. For example, the term “processor” as used herein, including in the claims, may include various processing circuits, including at least one processor. One or more processors in at least one processor may be configured to perform various functions described herein, individually and / or collectively, in a distributed fashion. As used herein, “processor,” “at least one processor,” and “one or more processors” may be configured to perform multiple functions. However, these terms encompass, without limitation, situations where one processor performs some of the functions and other processor(s) perform other parts of the functions, and situations where a single processor may perform all of the functions. Furthermore, the at least one processor may include a combination of processors that perform various of the disclosed functions in a distributed manner. The at least one processor may execute program instructions to achieve or perform various functions.

[0320] In one embodiment, at least one processor (1j-40) may be a general-purpose processor, such as a CPU, AP, or DSP (Digital Signal Processor), a graphics-only processor, such as a GPU or VPU (Vision Processing Unit), or an AI-only processor, such as an NPU. For example, if one or more processors are AI-only processors, the AI-only processors may be designed with a hardware structure specialized for processing a specific AI model.

[0321] FIG. 1k is a block diagram illustrating the structure of a base station (1k-00) according to one embodiment of the present disclosure.

[0322] Referring to FIG. 1k, a base station (1k-00) according to an embodiment of the present disclosure may include an RF processing unit (1k-10), a baseband processing unit (1k-20), a backhaul communication unit (1k-30), a storage unit (1k-40), and a control unit (1k-50).

[0323] The RF processing unit (1k-10) performs functions for transmitting and receiving signals through a wireless channel, such as signal band conversion and amplification. That is, the RF processing unit (1k-10) up-converts the baseband signal provided from the baseband processing unit (1k-20) 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 (1k-10) may include a transmission filter, a reception filter, an amplifier, a mixer, an oscillator, a DAC, an ADC, etc. In the drawing, only one antenna is shown, but the first access node may have multiple antennas. In addition, the RF processing unit (1k-10) may include multiple RF chains. Furthermore, the RF processing unit (1k-10) may perform beamforming. For the above beamforming, the RF processing unit (1k-10) can adjust the phase and magnitude of each signal transmitted and received through multiple antennas or antenna elements. The RF processing unit can perform a downlink MIMO operation by transmitting one or more layers.

[0324] The baseband processing unit (1k-20) performs a conversion function between a baseband signal and a bit stream according to the physical layer specifications of the first wireless access technology. For example, when transmitting data, the baseband processing unit (1k-20) generates complex symbols by encoding and modulating a transmission bit stream. In addition, when receiving data, the baseband processing unit (1k-20) restores the reception bit stream by demodulating and decoding the baseband signal provided from the RF processing unit (1k-10). For example, in the case of OFDM, when transmitting data, the baseband processing unit (1k-20) generates complex symbols by encoding and modulating a transmission bit stream, maps the complex symbols to subcarriers, and then configures OFDM symbols through IFFT operation and CP insertion. In addition, when receiving data, the baseband processing unit (1k-20) divides the baseband signal provided from the RF processing unit (1k-10) into OFDM symbol units, restores the signals mapped to subcarriers through FFT operation, and then restores the received bit string through demodulation and decoding. The baseband processing unit (1k-20) and the RF processing unit (1k-10) transmit and receive signals as described above. Accordingly, the baseband processing unit (1k-20) and the RF processing unit (1k-10) may be referred to as a transmitter, a receiver, a transceiver, a communication unit, or a wireless communication unit.

[0325] The above backhaul communication unit (1k-30) provides an interface for communicating with other nodes within the network. That is, the backhaul communication unit (1k-30) converts a bit string transmitted from the main base station to another node, such as an auxiliary base station or core network, into a physical signal, and converts a physical signal received from the other node into a bit string.

[0326] The storage unit (1k-40) stores data such as basic programs, application programs, and setting information for the operation of the base station (1k-00). In particular, the storage unit (1k-40) can store information on bearers assigned to connected terminals, measurement results reported from connected terminals, and the like. In addition, the storage unit (1k-40) can store information that serves as a judgment criterion for whether to provide or terminate multiple connections to a terminal. In addition, the storage unit (1k-40) provides the stored data upon request from the control unit (1k-50). The storage unit (1k-40) can be referred to as a memory.

[0327] The control unit (1k-50) controls the overall operations of the base station (1k-00). For example, the control unit (1k-50) transmits and receives signals through the baseband processing unit (1k-20) and the RF processing unit (1k-10) or through the backhaul communication unit (1k-30). In addition, the control unit (1k-50) records and reads data in the storage unit (1k-40). For this purpose, the control unit (1k-50) may include at least one processor. The control unit (1k-50) may control the overall operations of the base station (1k-00) according to the embodiments proposed in the present disclosure by executing one or more commands stored in the memory (1k-40).

[0328] At least one processor (1k-50) may include various processing circuits and / or multiple processors. For example, the term “processor” as used herein, including in the claims, may include various processing circuits, including at least one processor. One or more processors in at least one processor may be configured to perform various functions described herein, individually and / or collectively, in a distributed fashion. As used herein, “processor,” “at least one processor,” and “one or more processors” may be configured to perform multiple functions. However, these terms encompass, without limitation, situations where one processor performs some of the functions and other processor(s) perform other parts of the functions, and situations where a single processor may perform all of the functions. Furthermore, at least one processor may include a combination of processors that perform various of the disclosed functions in a distributed manner. At least one processor may execute program instructions to achieve or perform various functions.

[0329] In one embodiment, at least one processor (1k-50) may be a general-purpose processor, such as a CPU, AP, or DSP (Digital Signal Processor), a graphics-only processor, such as a GPU or VPU (Vision Processing Unit), or an AI-only processor, such as an NPU. For example, if one or more processors are AI-only processors, the AI-only processor may be designed with a hardware structure specialized for processing a specific AI model.

[0330] Meanwhile, the embodiments of the present disclosure disclosed in this disclosure and the drawings are merely specific examples presented to easily explain the technical content of the present disclosure and aid in understanding of the present disclosure, and are not intended to limit the scope of the present disclosure. In other words, it will be apparent to those skilled in the art to which the present disclosure pertains that other modified examples based on the technical concepts of the present disclosure are possible.

[0331] Furthermore, the above embodiments may be combined and operated as needed. For example, parts of one embodiment of the present disclosure and parts of another embodiment may be combined to operate a base station and a terminal. Furthermore, the embodiments of the present disclosure are applicable to other communication systems, and other modifications based on the technical concepts of the embodiments may also be implemented. For example, the embodiments may be applied to LTE systems, 5G, NR systems, or 6G systems. Therefore, the scope of the present disclosure should not be limited to the described embodiments, but should be determined not only by the scope of the following claims but also by equivalents thereof.

[0332] A specific example for explaining an embodiment according to the present disclosure is only one combination of each criterion, method, detailed method, and operation, and through a combination of at least two or more techniques among the various techniques described, a terminal or base station can perform a channel measurement operation for LTM through CSI-RS resources in a next-generation mobile communication system. In addition, at this time, it can be performed according to a method determined through one or a combination of at least two or more of the above-described techniques. For example, it may be possible to perform a part of the operation of one embodiment in combination with a part of the operation of another embodiment.

[0333] A device-readable storage medium may be provided in the form of a non-transitory storage medium. Here, a 'non-transitory storage medium' means only that it is a tangible device and does not contain signals (e.g., electromagnetic waves), and this term does not distinguish between cases where data is permanently stored in the storage medium and cases where it is temporarily stored. For example, a 'non-transitory storage medium' may include a buffer in which data is temporarily stored. In one embodiment, the method according to various embodiments disclosed in the present document may be provided as a computer program product. The computer program product may be traded as a product between a seller and a buyer. The computer program product may be distributed in the form of a device-readable storage medium (e.g., a compact disc read only memory (CD-ROM)), or may be distributed online (e.g., by download or upload) through an application store or directly between two user devices (e.g., smartphones). In the case of online distribution, at least a portion of the computer program product (e.g., a downloadable app) may be temporarily stored or temporarily created in a device-readable storage medium, such as the memory of a manufacturer's server, an application store's server, or an intermediary server.

Claims

1. In a method of operating a UE (User Equipment) in a wireless communication system, A step of receiving an RRC (Radio Resource Control) message from a base station; wherein the RRC message includes information related to setting up CSI-RS (Channel State Information-Reference Signal) resources of one or more LTM (Layer 1 / Layer 2 Triggered Mobility) candidate cells and setting information related to Layer 1 measurement reporting for one or more LTM candidate cells. A step of performing measurements on CSI-RS resources of one or more LTM candidate cells; and A method comprising: transmitting, to the base station, a Layer 1 measurement report for one or more LTM candidate cells; 2. In the method of the first clause, the one or more LTM candidate cells are composed of cells belonging to an intra-CU (Central Unit).

3. In the method of the first clause, the one or more LTM candidate cells are composed of cells belonging to an inter-CU.

4. In the method of paragraph 1, A method further comprising: a step of setting the type of a CSI-RS-based Layer 1 measurement report for one or more LTM candidate cells to at least one of periodic; semi-persist; or aperiodic, based on configuration information related to the Layer 1 measurement report.

5. In the method of paragraph 1, A method further comprising: receiving, from the base station, a MAC CE (Medium Access Control Control Element) or DCI (Downlink Control Information), which indicates activation or deactivation of a semi-persist type Layer 1 measurement report or an aperiodic type Layer 1 measurement report.

6. In the method of paragraph 1, A method further comprising: receiving Layer 1 / Layer 2 signaling including a beam switching instruction or a handover instruction based on a CSI-RS-based Layer 1 measurement report from the base station.

7. In a method of operating a base station in a wireless communication system, A step of transmitting an RRC (Radio Resource Control) message to a UE (User equipment); the RRC message includes information related to setting up CSI-RS (Channel State Information-Reference Signal) resources of one or more LTM (Layer 1 / Layer 2 Triggered Mobility) candidate cells and setting information related to Layer 1 measurement reporting for one or more LTM candidate cells. A step of receiving a Layer 1 measurement report for one or more LTM candidate cells from the UE; and A method comprising: determining whether to instruct beam switching or handover based on Layer 1 measurement reports for one or more LTM candidate cells; 8. In the method of Article 7, A step of collecting information about CSI-RS resources from one or more LTM candidate cells within an intra-CU via an F1 interface; A step of configuring information related to the CSI-RS resource configuration based on the collected information and transmitting the information to one or more LTM candidate cells within the intra-CU; and A method further comprising: receiving Layer 1 measurement report related settings together with cell configuration information from one or more LTM candidate cells within the intra-CU.

9. In the method of Article 7, A step of collecting information about CSI-RS resources from one or more LTM candidate cells within an Inter-CU via an X2 interface; A step of configuring information related to the CSI-RS resource configuration based on the collected information and transmitting the information to one or more LTM candidate cells within the inter-CU; and A method further comprising: receiving Layer 1 measurement report related settings together with cell configuration information from one or more LTM candidate cells within the inter-CU.

10. In the method of Article 7, A method wherein, based on configuration information related to the Layer 1 measurement report, the type of the CSI-RS-based Layer 1 measurement report for one or more LTM candidate cells is set to at least one of periodic; semi-persist; or aperiodic.

11. In the method of Article 7, A method further comprising: a step of transmitting, to the UE, a MAC CE (Medium Access Control Control Element) or DCI (Downlink Control Information), which instructs activation or deactivation of a semi-persist type Layer 1 measurement report or an aperiodic type Layer 1 measurement report.

12. In a wireless communication system, in UE (User Equipment), memory for storing one or more instructions; and At least one processor; wherein the at least one processor performs the one or more instructions stored in the memory, thereby causing the UE to perform the following operations; wherein the following operations are: Receive an RRC (Radio Resource Control) message from a base station; wherein the RRC message includes information related to setting up CSI-RS (Channel State Information-Reference Signal) resources of one or more LTM (Layer 1 / Layer2 Triggered Mobility) candidate cells and setting information related to Layer 1 measurement reporting for one or more LTM candidate cells; Performing measurements on CSI-RS resources of one or more LTM candidate cells; and A UE transmitting a Layer 1 measurement report for one or more LTM candidate cells to the base station.

13. In a wireless communication system, at a base station, memory for storing one or more instructions; and At least one processor; wherein the at least one processor performs one or more instructions stored in the memory, thereby causing the base station to perform the following operations; wherein the following operations are: Transmitting an RRC (Radio Resource Control) message to a UE (User equipment); wherein the RRC message includes information related to setting up CSI-RS (Channel State Information-Reference Signal) resources of one or more LTM (Layer 1 / Layer 2 Triggered Mobility) candidate cells and setting information related to Layer 1 measurement reporting for one or more LTM candidate cells. Receive a Layer 1 measurement report for one or more LTM candidate cells from the UE; and A base station that determines whether to instruct beam switching or handover based on Layer 1 measurement reports for one or more of the LTM candidate cells.

14. In the base station of paragraph 13, the at least one processor causes the base station to perform the following operations by executing the one or more commands stored in the memory; and the following operations are: Through the F1 interface, collect information about CSI-RS resources from one or more LTM candidate cells within the intra-CU; Based on the collected information, information related to the CSI-RS resource configuration is configured and transmitted to one or more LTM candidate cells within the intra-CU; and A base station that receives Layer 1 measurement report related settings together with cell configuration information from one or more LTM candidate cells within the intra-CU.

15. In the base station of paragraph 13, the at least one processor causes the base station to perform the following operations by executing the one or more commands stored in the memory; and the following operations are: Collect information about CSI-RS resources from one or more LTM candidate cells within an Inter-CU via the X2 interface; Based on the collected information, information related to the CSI-RS resource configuration is configured and transmitted to one or more LTM candidate cells within the inter-CU; and A base station that receives Layer 1 measurement report related settings together with cell configuration information from one or more LTM candidate cells within the inter-CU.

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