Method and apparatus for selecting beam when performing event-based layer 1 measurement in next generation mobile communication system

Abstract

The present disclosure relates to a 5G or 6G communication system for supporting a higher data transmission rate. Disclosed are a method and an apparatus for configuring layer 1 measurement and reporting on the basis of an event when L1 / L2 triggered mobility (LTM) is performed.

Description

Method and apparatus for selecting a beam when performing event-based LAYER 1 measurements in a next-generation mobile communication system

[0001] The present disclosure relates to a method and apparatus for setting up event-based Layer 1 measurement and reporting when performing LTM (L1 / L2 triggered mobility).

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

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

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

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

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

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

[0008] Meanwhile, in such next-generation mobile communication systems, LTM (layer 1 / layer 2 triggered mobility) operations are applied in which mobility is determined based on Layer 1-based measurements, and in particular, methods to support event-based Layer 1 measurement and reporting are being discussed.

[0009] Accordingly, one objective of the present disclosure is to propose detailed operations for setting up event-based Layer 1 measurement and reporting.

[0010] In addition, one objective of the present disclosure is to propose a method for determining the beam to be the subject of such operation when performing beam-based signal strength comparison and beam-based reporting therefrom.

[0011] A method of a terminal in a wireless communication system according to an example of the present disclosure for solving the above-mentioned problems comprises: receiving a radio resource control (RRC) message containing layer 1 / layer 2 triggered mobility (LTM) setting information from a source cell of a base station, wherein the LTM setting information includes information on at least one candidate cell and information on resource setting for LTM measurement; measuring a beam for the source cell and a beam for the candidate cell when the report on the LTM measurement is set based on an event; and transmitting the result of the measurement to the base station when it is determined that the event is satisfied based on the result of the measurement, wherein the reference signal (RS) type of the beam for the candidate cell is identified as a synchronization signal block (SSB) or a channel state information (CSI-RS) based on the information on resource setting, and the RS type of the beam for the source cell may be the same as the RS type for the candidate cell.

[0012] In addition, in a wireless communication system according to one example of the present disclosure, a terminal comprises: a transceiver; and a control unit that controls the transceiver to receive a radio resource control (RRC) message including layer 1 / layer 2 triggered mobility (LTM) setting information from a source cell of a base station, wherein the LTM setting information includes information on at least one candidate cell and information on resource setting for LTM measurement, wherein when a report on the LTM measurement is set on an event basis, the beam for the source cell and the beam for the candidate cell are measured, and when it is determined that the event is satisfied based on the result of the measurement, the transceiver is controlled to transmit the result of the measurement to the base station, wherein the reference signal (RS) type of the beam for the candidate cell is identified as a synchronization signal block (SSB) or a channel state information (CSI-RS) based on the information on resource setting, and the RS type of the beam for the source cell may be the same as the RS type for the candidate cell.

[0013] According to the present disclosure, as a beam selection method for setting event-based Layer 1 measurement and reporting is specified, it becomes possible to set LTM event-based measurement and reporting on a terminal, and thereby a procedure for more accurately triggering LTM can be defined.

[0014] FIG. 1 is a drawing illustrating the structure of a next-generation mobile communication system to which the present disclosure applies.

[0015] FIG. 2 is a diagram showing the wireless protocol structure of a next-generation mobile communication system that can be applied to the present disclosure.

[0016] FIG. 3 is a drawing illustrating the structure of another next-generation mobile communication system that can be applied to the present disclosure.

[0017] FIG. 4 is a diagram illustrating a scenario in which a terminal transmits and receives data through the beam of a TRP (transmission / reception point) of a surrounding cell that supports beam changing based on L1 / L2 while maintaining a connection state with a serving cell, according to an example of the present disclosure.

[0018] FIG. 5a is a diagram illustrating a scenario in which a terminal according to an example of the present disclosure changes the serving cell and beam to the TRP of a cell that supports L1 / L2-based beam changing to transmit and receive data.

[0019] FIG. 5b is a diagram illustrating a scenario in which a terminal according to an example of the present disclosure changes the serving cell and beam to the TRP of a cell that supports L1 / L2-based beam changing to transmit and receive data.

[0020] FIG. 6 is a diagram illustrating the procedure for applying a unified TCI state and the unified TCI state MAC CE in an NR system according to one example of the present disclosure.

[0021] FIG. 7a is a diagram illustrating the overall operation including a beam crystal for performing event-based Layer 1 measurement reporting in an LTM according to one example of the present disclosure.

[0022] FIG. 7b is a diagram illustrating the overall operation including a beam crystal to perform event-based Layer 1 measurement reporting in an LTM according to one example of the present disclosure.

[0023] FIG. 8 is a diagram illustrating the overall terminal operation of performing LTM based on an event-based Layer 1 measurement report according to an example of the present disclosure.

[0024] FIG. 9 is a drawing illustrating base station operation applied to embodiments of the present disclosure.

[0025] FIG. 10 is a block diagram illustrating the internal structure of a terminal according to one example of the present disclosure.

[0026] FIG. 11 is a block diagram showing the configuration of a base station according to one example of the present disclosure.

[0027] The operating principle of the present invention will be described in detail below with reference to the attached drawings. In describing the present invention below, if it is determined that a detailed description of related known functions or configurations may unnecessarily obscure the essence of the present invention, such detailed description will be omitted. Furthermore, the terms described below are defined considering their functions in the present invention, and these may vary depending on the intentions or conventions of the user or operator. Therefore, such definitions should be based on the content throughout this specification. Terms used in the following description to identify connection nodes, terms referring to network entities, terms referring to messages, terms referring to interfaces between network entities, terms referring to various identification information, etc., are provided as examples for the convenience of explanation. Accordingly, the present invention is not limited to the terms described below, and other terms referring to objects having equivalent technical meanings may be used.

[0028] For convenience of explanation below, the present invention uses terms and names defined in the 3GPP LTE (3rd Generation Partnership Project Long Term Evolution) standard. However, the present invention is not limited by the above terms and names and can be applied in the same way to systems conforming to other standards.

[0029] FIG. 1 is a drawing illustrating the structure of a next-generation mobile communication system to which the present disclosure applies.

[0030] Referring to FIG. 1, as illustrated, the wireless access network of a next-generation mobile communication system consists of a next-generation base station (New Radio Node B, hereinafter 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 NR UE or terminal, 1a-15) connects to an external network through the NR NB (1a-10) and the NR CN (1a-05).

[0031] In FIG. 1, 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 superior service compared to the existing Node B. In next-generation mobile communication systems, since all user traffic is serviced through a shared channel, a device is required to collect status information such as the buffer status, available transmission power status, and channel status of the UEs and perform scheduling, and this is handled by the NR NB (1a-10). A single NR NB typically controls multiple cells. The NR NB (1a-10) according to the present disclosure can have a maximum bandwidth greater than that of existing LTE (long term evolution) to achieve ultra-high-speed data transmission, and can additionally incorporate beamforming technology by using Orthogonal Frequency Division Multiplexing (hereinafter referred to as OFDM) as a wireless access technology. In addition, the NR NB (1a-10) according to the present disclosure applies an Adaptive Modulation & Coding (hereinafter referred to as AMC) method that determines a modulation scheme and a channel coding rate according to the channel conditions of the terminal.

[0032] The NR CN (1a-05) performs functions such as mobility support, bearer configuration, and QoS (quality of service) configuration. The NR CN (1a-05) is a device responsible for various control functions as well as mobility management functions for terminals, and is connected to multiple base stations. In addition, the next-generation mobile communication system can be interoperable with existing LTE systems, and the NR CN (1a-05) is connected to the MME (mobility management entity, 1a-25) via a network interface. The MME (1a-25) is connected to the existing base station eNB (1a-30).

[0033] FIG. 2 is a diagram showing the wireless protocol structure of a next-generation mobile communication system that can be applied to the present disclosure.

[0034] Referring to FIG. 2, the wireless protocol of the next-generation mobile communication system consists 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), and NR MAC (medium access control, 1b-15, 1b-30) at the terminal and the NR base station, respectively.

[0035] The main functions of NR SDAP (1b-01, 1b-45) may include some of the following functions.

[0036] - User data transfer function (transfer of user plane data)

[0037] - Mapping function between a QoS flow and a DRB for both DL and UL for uplink and downlink

[0038] - Marking QoS flow ID for uplink and downlink (marking QoS flow ID in both DL and UL packets)

[0039] - Function to map reflective QoS flow to the data bearer for the uplink SDAP PDUs (protocol data unit).

[0040] Regarding the SDAP layer device, the terminal may receive a radio resource control (RRC) message indicating whether to use the header of the SDAP layer device or the functions of the SDAP layer device for each PDCP layer device, bearer, or logical channel. If the SDAP header is configured, the terminal may be instructed to update or reset the mapping information for the QoS flow of the uplink and downlink and the data bearer using the 1-bit indicator for the NAS (non-access stratum) QoS (quality of service) reflection setting (NAS reflective QoS) and the 1-bit indicator for the AS (access stratum) QoS reflection setting (AS reflective QoS) of the SDAP header. The SDAP header may include QoS flow ID (identity) information indicating QoS. The QoS information may be used for data processing priority, scheduling information, etc., to support smooth service.

[0041] The main functions of NR PDCP (1b-05, 1b-40) may include some of the following functions.

[0042] ● Header compression and decompression features (ROHC only)

[0043] ● User data transfer function (Transfer of user data)

[0044] ● Sequential delivery function (In-sequence delivery of upper layer PDUs)

[0045] ● Out-of-sequence delivery of upper layer PDUs

[0046] ● Reordering function (PDCP PDU reordering for reception)

[0047] ● Duplicate detection function (Duplicate detection of lower layer SDUs)

[0048] ● Retransmission of PDCP SDUs

[0049] ● Encryption and decryption functions (Ciphering and deciphering)

[0050] ● Timer-based SDU discard in uplink.

[0051] In the above, the reordering function of the NR PDCP device refers to a function of reordering PDCP PDUs (protocol data units) received from the lower layer in order based on the PDCP SN (sequence number), and may include a function of transmitting data to the upper layer in the reordered order, or may include a function of transmitting immediately without considering the order, may include a function of recording lost PDCP PDUs by reordering, 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.

[0052] The main functions of NR RLC(1b-10, 1b-35) may include some of the following functions.

[0053] ● Data transfer function (Transfer of upper layer PDUs)

[0054] ● Sequential delivery function (In-sequence delivery of upper layer PDUs)

[0055] ● Out-of-sequence delivery of upper layer PDUs

[0056] ● ARQ Function (Error Correction through ARQ)

[0057] ● Concatenation, segmentation, and reassembly functions of RLC SDUs

[0058] ● Re-segmentation of RLC data PDUs

[0059] ● Reordering function (Reordering of RLC data PDUs)

[0060] ● Duplicate detection

[0061] ● Error detection function (Protocol error detection)

[0062] ● RLC SDU discard function

[0063] ● RLC re-establishment function

[0064] In the above, the in-sequence delivery function of the NR RLC device refers to the function of delivering RLC SDUs (service data units) received from a lower layer to an upper layer in sequence. It may include a function to reassemble and deliver them if a single RLC SDU is received divided into multiple RLC SDUs; a function to rearrange received RLC PDUs based on an RLC SN (sequence number) or PDCP SN (sequence number); a function to record lost RLC PDUs after rearranging the order; a function to report the status of lost RLC PDUs to the transmitting side; a function to request retransmission of lost RLC PDUs; a function to deliver only the RLC SDUs prior to the lost RLC SDU to the upper layer in sequence if there is a lost RLC SDU; or a function to deliver all RLC SDUs received before the timer started to the upper layer in sequence if a predetermined timer has expired, even if there is a lost RLC SDU. It may include a function to deliver all RLC SDUs received up to that point to the upper layer in order once a predetermined timer has expired, even if there are any lost RLC SDUs. Additionally, the RLC PDUs may be processed in the order they are received (regardless of the order of sequence numbers, but in the order of arrival) and delivered to the PDCP device out of order (out-of-sequence delivery). In the case of segments, segments stored in a buffer or to be received later may be received, reconstructed into a 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 the multiplexing function of the NR MAC layer.

[0065] In the above, the out-of-sequence delivery function of the NR RLC device refers to a function of delivering RLC SDUs received from a lower layer directly to an upper layer regardless of order. It may include a function of reassembling and delivering them when a single RLC SDU is received divided into multiple RLC SDUs, and may include a function of storing the RLC SN or PDCP SN of the received RLC PDUs and sorting the order to record the lost RLC PDUs.

[0066] The NR MAC (1b-15, 1b-30) can be connected to multiple NR RLC layer devices configured in a terminal, and the main functions of the NR MAC may include some of the following functions.

[0067] ● Mapping function (Mapping between logical channels and transport channels)

[0068] ● Multiplexing and demultiplexing of MAC SDUs

[0069] ● Scheduling information reporting function

[0070] ● HARQ function (Error correction through HARQ)

[0071] ● Priority handling between logical channels of one UE

[0072] ● Priority handling between UEs by means of dynamic scheduling

[0073] ● MBMS service identification

[0074] ● Transport format selection function

[0075] ● Padding

[0076] The NR PHY layer (1b-20, 1b-25) can perform the operation of channel coding and modulating upper layer data, creating OFDM symbols and transmitting them to the wireless channel, or demodulating OFDM symbols received through the wireless channel and channel decoding them to transmit them to the upper layer.

[0077] FIG. 3 is a drawing illustrating the structure of another next-generation mobile communication system that can be applied to the present disclosure.

[0078] Referring to FIG. 3, the cell serviced by the beam-based NR gNB (1c-05) can be composed of multiple TRPs (Transmission Reception Points, 1c-10, 1c-15, 1c-20, 1c-25, 1c-30, 1c-35, 1c-40). The TRPs (1c-10 to 1c-40) represent blocks from which some functions of transmitting and receiving physical signals from an existing NR base station (eNB) have been separated, and they are composed of multiple antennas. Here, the NR gNB (1c-05) can be represented as a CU (Central Unit), and the TRPs (1c-10 to 1c-40) can also be represented as a DU (Distributed Unit). The functions of the above NR gNB (1c-05) and TRP (1c-10 to 1c-40) can be configured by separating each layer from the PDCP / RLC / MAC / PHY layers, such as 1c-45. That is, TRP (1c-15, 1c-25) can perform the functions of the corresponding layer using only the PHY layer, TRP (1c-10, 1c-35, 1c-40) can perform the functions of the corresponding layers using only the PHY layer and the MAC layer, and TRP (1c-20, 1c-30) can perform the functions of the corresponding layers using only the PHY layer, the MAC layer, and the RLC layer. In particular, TRP (1c-10 to 1c-40) can use beamforming technology to transmit and receive data by generating narrow beams in multiple directions using multiple transmitting and receiving antennas.

[0079] The user terminal (1c-50) connects to the NR gNB (1c-05) and the external network through the TRP (1c-10 to 1c-40). The NR gNB (1c-05) collects status information such as the buffer status, available transmission power status, and channel status of the terminals to schedule them in order to provide services to the users, thereby supporting the connection between the terminals and the core network (CN), particularly the AMF / SMF (1c-50).

[0080] The TRP in the present disclosure is based on a structure (1c-15, 1c-25) that can perform the functions of the corresponding layer using only the PHY layer.

[0081] FIG. 4 is a diagram illustrating a scenario for inter-cell beam management referenced in the present disclosure, in which a terminal transmits and receives data through the beam of a TRP (transmission / reception point) of a neighboring cell that supports beam changing based on L1 / L2 while maintaining a connection state with a serving cell.

[0082] In this drawing, the case in which multiple cells (TRP1-Cell1, TRP2-Cell2; 1d-10, 1d-15) exist within a single DU (Distributed unit, 1d-05) is described as an example, but the general content of this disclosure is also applicable to inter-DU cases (each DU constitutes a single TRP-Cell). Furthermore, for convenience of explanation, in the following disclosure, non-serving cells (TRP 2, Cell 2) that support L1 / L2-based mobility (beam change and serving cell change) will be described interchangeably as neighbor cells, non-serving cells, and additional cells with a physical cell identity (PCI) different from the serving cell.

[0083] In the existing terminal beam change procedure (1d-45), the terminal (1d-20) is transmitting and receiving data in a connected state through the TRP 1 (1d-10) of serving cell 1, and may be set to the optimal beam, the transmission configuration indicator (TCI) state 1 (1d-25, 1d-30). At this stage, the terminal (1d-20) may receive instructions for setting information for L3 channel measurement (RRM; radio resource management) for an additional cell (TRP 2-Cell 2, 1d-15) that has a different PCI from the serving cell through RRC setting information from the serving cell (1d-10), and performs an L3 measurement operation (1d-46) for the corresponding frequency and cell. Afterward, the serving cell (TRP 1-Cell 1, 1d-10) may direct a handover to the corresponding cell (TRP 2-Cell 2, 1d-15) based on the reported measurement value (1d-47), and after the handover is completed, additional RRC configuration information may be transmitted to the terminal (1d-20) via TRP 2-Cell 2 (1d-15) (1d-48). The RRC configuration information may include UL (uplink) / DL (downlink) configuration information in the corresponding cell, L1 measurement related settings (CSI-RS (channel state information - reference signal) measurement and reporting), and in particular, may include TCI state configuration information for the PDCCH (physical downlink control channel) and PDSCH (physical downlink shared channel) channels. The terminal performs an 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-40), can be directed to the terminal (1d-20).At this stage, Cell 1 (1d-10) is the serving cell until handover, and Cell 2 (1d-15) becomes the serving cell after handover. In other words, even after handover, many procedures and time are required until the optimal beam is directed to the terminal.

[0084] Unlike the existing terminal beam change procedure (1d-45) described above, the improved beam change technique (1d-55) considered in this disclosure is as follows. Serving cell 1 (1d-10) can be transmitted to the terminal (1d-20) by referring to the beam setting associated with an additional cell (TRP 2-Cell 2, 1d-15) with a different PCI from the serving cell through RRC setting information (1d-56). The beam setting, that is, associating the TCI state corresponding to TRP 2 with the additional cell (TRP 2-Cell 2, 1d-15) with a different PCI from the serving cell 1 (1d-10), is applied by a method of associating a new cell ID (Physical cell ID, PCI; additionalPCI-r17) with the corresponding TCI state as shown in [Table 1] below.

[0085]

[0086] In addition, for beam management between the cells, a unified TCI state framework as shown in [Table 2] below is applied. The unified TCI state framework applies a common TCI state framework to the uplink and downlink, and to the common channel and dedicated channel, and can be set to one of the Joint UL / DL mode as shown in [Table 3] or the separate UL / DL mode as shown in [Table 4].

[0087]

[0088]

[0089]

[0090] After the configuration for TRP 2-Cell 2 (1d-15) is provided in the RRC connection state to serving cell 1 (1d-10), the terminal (1d-20) performs an L1 measurement for the corresponding TRP 2-Cell 2 (1d-15) according to the configuration and reports the result to serving cell 1 (Cell 1, 1d-10) (1d-57). If serving cell 1 (1d-10) determines that a change to a specific beam (TCI state 2, 1d-35, 1d-40) of TRP 2 (Cell 2, 1d-15) is necessary from the serving cell beam (TCI state 1, 1d-25, 1d-30) based on the measurement result, it triggers a beam change and instructs the terminal (1d-20) via L1 / L2 signaling (1d-58). The terminal (1d-20) changes the beam to a specific beam (TCI state 2, 1d-40) of TRP 2 (Cell 2, 1d-15) through the corresponding instruction, and performs physical channel setup and upper layer setup operations associated with the set beam. From this stage, the terminal (1d-20) remains connected to the serving cell (Cell 1, 1d-10), but performs data transmission and reception using the channel link of TRP 2 (Cell 2, 1d-15) (receiving PDCCH / PDSCH, transmitting PUCCH / PUSCH). That is, transmission and reception for the common control channel are performed through the serving cell 1 (Cell 1, 1d-10). Afterward, the terminal (1d-20) performs an L3 measurement operation according to the measurement settings set in an independent serving cell (1d-59), receives a handover command message from the serving base station (Cell 1, 1d-10), and can perform a serving cell change to Cell 2 (1d-15) (1d-60). Through this technique (1d-55), the terminal (1d-20) performs data transmission and reception with a specific TRP 2 of Cell 2 (1d-15) that supports L1 / L2-based mobility while connected to the serving cell, and can continue to use the beam even after the handover.

[0091] For reference, the RRC settings regarding the settings and operations related to L1 measurement and report in step 1d-57 above are described in [Table 5]-[Table 6] and below. These contents are basically applied to the following embodiments of the present invention, and enhancement techniques may be added in future embodiments.

[0092] 1. L1 measurement settings (configured within CSI-ResourceConfig, ServingCellConfig, or IE)

[0093] - CSI-RS / SSB (synchronization signal block) resources and resource pools (nzp-CSI-RS, csi-IM, csi-SSB) requiring measurement

[0094] - Configuration of CSI-RS / SSB resources requiring measurement (aperiodic, semi-persistent) and triggering settings

[0095] - When a CSI-RS resource references an SSB resource, additional PCI information is provided to enable L1 measurement from neighboring cells (up to 7 additional neighboring cells (PCI) can be added from a single serving cell).

[0096]

[0097]

[0098] 2. L1 report settings (configured within the serving cell, ServingCellConfig, configured within IE)

[0099] - Report Type: Periodic reporting, semi-periodic reporting via PUCCH (physical uplink control channel), semi-periodic reporting via PUSCH (physical uplink shared channel), aperiodic reporting via PUSCH (periodic, semi-persistent for PUCCH, semi-persistent for PUSCH, aperiodic)

[0100] - Report quantity

[0101] - Other settings required for reporting

[0102] FIGS. 5A and 5B illustrate embodiments considered in the present disclosure, illustrating a scenario in which a terminal changes the serving cell and beam to a TRP of a cell that supports L1 / L2-based beam changing to transmit and receive data. FIGS. 5A and 5B describe a case where multiple cells (TRP1-Cell1, TRP2-Cell2; 1e-10, 1e-15, 1e-40, 1e-45) exist within a single DU (Distributed unit, 1e-05, 1e-35), but the overall content of the present disclosure is also applicable to inter-DU within an intra-CU (each DU constitutes a single TRP-Cell).

[0103] Unlike the conventional terminal beam changing procedure (1d-45, 1d-55) described in Fig. 4, the improved beam changing technique (1e-25, 1e-75) considered in these embodiments is as follows.

[0104] Example 1 (1e-25): After performing inter-cell beam management (change) operation, perform L1 / L2 handover

[0105] Example 2 (1e-75): Perform L1 / L2 handover immediately

[0106] First, referring to FIG. 5a, the overall operation of Embodiment 1 is described as follows: the terminal (1e-20) can receive common configuration and dedicated configuration information for an additional cell (TRP 2-Cell 2, 1e-15) that has 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 to the terminal (1e-20) in advance. The configuration information can be provided in the form of pre-configuration in the RRC configuration and may include configuration information for multiple cells. Furthermore, the configuration is characterized by including all configuration information (cell configuration, bearer configuration, security key configuration, etc.) that is applied when the terminal moves to the corresponding cell (handover). In addition, the setting includes an enhanced setting by referring to the unified TCI state setting and L1 measurement and report settings described in step 1d-56. More specifically, the enhanced unified TCI state setting and L1 measurement and report settings for continuous LTM are included, which will be explained in more detail in the drawings below of the present disclosure.

[0107] After the setting for TRP 2-Cell 2 (1e-15) is provided in the RRC connection state to serving cell 1 (1e-10), the terminal (1e-20) performs an L1 measurement for the corresponding TRP 2-Cell 2 (1e-15) in step 1e-27 according to the received setting and reports the result to serving cell 1 (Cell 1, 1e-10). If serving cell 1 (1e-10) determines that a change from the serving cell beam (TCI state 1, 1e-25) to a specific beam (TCI state 2, 1e-40) of TRP 2 (Cell 2, 1e-15) is necessary based on the measurement result, it triggers a beam change in step 1e-28 and instructs the terminal (1e-20) to change the beam through L1 / L2 signaling. The terminal (1e-20) performs a beam change to TRP 2 (Cell 2, 1e-15) through the corresponding instruction and transmits and receives data through the TRP 2 (Cell 2, 1e-15). At this time, no serving cell change occurs, and the terminal (1e-20) remains connected to the serving cell (Cell 1, 1e-10) via RRC. Subsequently, the terminal (1e-20) performs an L1 measurement for TRP 2-Cell 2 (1e-15) and reports the result to the serving cell (Cell 1, 1e-10). If the L1 measurement reported by the terminal (1e-20) satisfies the triggering condition for a handover to TRP 2-Cell 2 (1e-15) (detailed operation is described in detail below), the serving cell (Cell 1, 1e-10) instructs the terminal to perform a handover. The instruction in question can be an L1 / L2 message. That is, the MAC CE (control element) may contain an instruction directing a handover.

[0108] Referring to FIG. 5b, the overall operation of Embodiment 2 is described as follows: the terminal (1e-50) can receive common and dedicated configuration information for an additional cell (TRP 2-Cell 2, 1e-45) that has a different PCI from the serving cell (1e-40) through RRC configuration information from the serving cell (1e-40) (1e-76). That is, the ServingCellID or candidateCellID (cell ID associated with PCI), and configuration information corresponding to the corresponding 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. Furthermore, the configuration is characterized by including all configuration information (cell configuration, bearer configuration, channel measurement configuration, etc.) that is applied when the terminal moves to the corresponding cell (handover). In addition, the configuration includes the unified TCI state configuration and settings related to L1 measurement and report described in step 1d-56, modified to support consecutive LTMs. The L1 measurement, report, and TCI state settings applicable to the present disclosure are described in detail below.

[0109] After the setting for TRP 2-Cell 2 (1e-45) is provided while RRC is connected to serving cell 1 (1e-40), the terminal (1e-50) performs an L1 measurement for the corresponding TRP 2-Cell 2 (1e-45) in step 1e-77 according to the received setting and reports the result to the serving cell (Cell 1, 1e-40). If the serving cell (1e-40) determines that a beam change from the serving cell beam (TCI state 1, 1e-45) to a specific beam (TCI state 2, 1e-70) of TRP 2 (Cell 2, 1e-45) and a handover are required based on the measurement result, it triggers the beam change and handover in step 1e-78 and instructs the terminal (1e-50) to perform the beam change and handover through L1 / L2 signaling. The terminal (1e-50) performs a handover simultaneously with changing the beam to TRP 2 (Cell 2, 1e-15) via the corresponding instruction, and performs data transmission and reception through the TRP 2 (Cell 2, 1e-15). At this time, the terminal (1e-50) applies the configuration information for the target cell where the handover is performed, which was pre-configured in step 1e-76. Depending on whether uplink synchronization is required in that step, the terminal (1e-50) may perform random access to the target cell, or may omit the random access procedure for the target cell. More detailed operations regarding this are described in the drawings below.

[0110] The present disclosure proposes a detailed method for setting the unified TCI state and L1 measurement and report for candidate cells surrounding an LTM to support continuous LTM. As described in detail in FIG. 4, in conventional inter-cell beam management (ICBM), L1 measurement resource settings for cells requiring measurement are provided through the CSI-ResourceConfig within the ServingCellConfig IE included in the serving cell settings. In particular, to indicate resources for surrounding cells, the PCI of the cell where the corresponding L1 measurement resource is set can be indicated in servingAdditionalPCIList.

[0111] Detailed settings for L1 measurement and reporting settings for LTM are provided as L1 measurement resource settings applied to LTM candidate cells as shown in [Table 7]–[Table 10] below. To this end, it is necessary to share and determine L1 measurement resources and reporting settings for LTM among LTM candidate cells during the preprocessing stage. The entire procedure for L1 measurement and reporting settings for LTM will be described together in the following examples.

[0112]

[0113]

[0114]

[0115]

[0116] The present disclosure proposes a method for setting L1 measurement information for surrounding candidate cells for LTM to support subsequent LTM (subsequent L1 / L2 triggered mobility), and a method for setting a terminal to report a measurement based on the set L1 measurement information. The method for setting event-based L1 measurement information and reporting based thereon is described in detail, and in particular, details regarding which beam is measured and used as a comparison target for event L1 measurement are explained.

[0117] FIG. 6 is a diagram illustrating the procedure for applying the unified TCI state and the unified TCI state MAC CE in the NR system referenced in this disclosure. In this figure, specific examples are used to explain how the unified TCI state operates functionally.

[0118] A terminal in an RRC connection state performs data transmission and reception with a base station (serving cell, for example, PCell (primary cell)) and, in order to change to the optimal beam, performs a Layer 1 channel measurement according to the base station settings and reports the result of the measurement to the base station. The base station checks the Layer 1 channel measurement value reported by the terminal, determines which beam is best for the terminal at present, and can instruct the terminal to change to that beam. Below, we will explain the procedure for instructing the terminal to the optimal beam through the unified TCI framework.

[0119] Although omitted from the drawings, a base station according to one example of the present disclosure may set a unified TCI state for a terminal through RRC settings. The unified TCI state here may be set as either the Joint UL / DL mode (setting so that the UL and DL share the same TCI settings (in PDSCH-Config)) as described in [Table 3] or the Separate UL / DL mode (setting so that the UL and DL each provide their own TCI settings. The TCI state for the DL follows the settings in dl-OrJoint-TCIStateList-r17 (in PDSCH-Config), and the TCI state for the UL follows ul-TCI-StateList-r17 in BWP-UplinkDedicated) as described in [Table 4].

[0120] For reference, the beam directed in the unified TCI state may be directed to the TCI state in a cell where the serving cell and PCI are different. Here, the cell where the serving cell and PCI are different may be based on the method in which the cell where the PCI is different is associated with the corresponding TCI state, as described in [Table 2].

[0121] In step 1f-05, the base station may instruct the terminal to activate one or more TCI states through a unified TCI state activation / deactivation MAC CE. As also illustrated in FIG. 6, the MAC CE may indicate multiple TCI states indicated per serving cell and UL / DL BWP (bandwidth part). Here, the P field is an indicator indicating whether the indicated unified TCI state is indicated separately for uplink / downlink. Refer to the following description.

[0122] - Pi: This field indicates whether each TCI codepoint has multiple TCI states or single TCI state. If Pi field is set to 1, it indicates that ith TCI codepoint includes the DL TCI state and the UL TCI state. If Pi field is set to 0, it indicates that ith TCI codepoint includes only the DL / joint TCI state or the UL TCI state. The codepoint to which a TCI state is mapped is determined by its ordinal position among all the TCI state ID fields;

[0123] In step 1f-10, the base station instructs the terminal via downlink control information (DCI) a single unified TCI state to be actually applied. For reference, if only one TCI state code point was transmitted from the MAC CE in step 1f-05, the terminal activates the corresponding TCI state without receiving the DCI. The above DCI may schedule the downlink PDSCH (physical downlink shared channel) or may instruct only the beam without PDSCH scheduling. That is, if the DCI schedules the downlink PDSCH, PDSCH transmission is involved as in step 1f-15, and if the DCI does not schedule the downlink PDSCH, step 1f-15 may be omitted without separate PDSCH transmission.

[0124] Subsequently, in step 1f-20, the terminal transmits an ACK signal to the base station via PUCCH, indicating that the DCI or PDSCH received from the base station has been successfully received. In practice, after transmitting the ACK signal via PUCCH, the terminal waits for a Beam Application Time (BAT; 1f-25) and, in the first slot (1f-40), applies the specified unified TCI state to all channels (PDCCH / PDSCH / PUCCH / PUSCH) of the uplink and downlink. As illustrated in FIG. 6, the terminal continues to use the previously used TCI state until the specified unified TCI state is applied (1f-35). Then, for all subsequent channel transmissions (1f-40, 1f-45), a new beam is applied with activation indicated by the unified TCI state (1f-50).

[0125] The above description explains the application of the unified TCI state when only one TRP exists in a cell; however, it is also possible to support cases where multiple TRPs are configured in a cell and the TCI state applied to those TRPs is indicated. This can be supported through the Enhanced Unified TCI state activation / deactivation MAC CE in Figure 1f-50. That is, the two beams indicated in a cell may represent the TCI state activated at TRP1 and TRP2, respectively, of that cell. Here, the F field is an indicator representing whether the indicated unified TCI state consists of one or two elements. Refer to the following description regarding this. For reference, the present disclosure describes the Enhanced Unified TCI state activation / deactivation MAC CE where the joint UL / DL TCI state is applied.

[0126] - Fi,j: This field indicates for the TCI state ID fields associated with the codepoint i of the DCI Transmission Configuration Indication field whether the j-th joint TCI state is present or not, where j=1, 2. If Fi,j field is set to 1, it indicates the j-th joint TCI state for codepoint i is present. If Fi,j field is set to 0, it indicates the j-th joint TCI state for codepoint i is absent. The codepoint to which a TCI state is mapped is determined by its ordinal position among all the TCI state ID fields;

[0127] As described above, when multiple unified TCI states are indicated by MAC CE, the corresponding activated beam is applied to all channels after BAT; however, since the TCI state activated may differ for each channel in reality, signaling is provided to indicate the beam activated for each channel in various ways. In this regard, refer to [Table 11] below regarding the method of selecting TCI states per channel. For example, in the case of PDCCH, for each CORESET (control resource set), the beam of the TCI state used for receiving the corresponding PDCCH is indicated by RRC signaling. If two TCI states are indicated in a single cell in step 1f-50, and the first of the two TCI states is actually used in the PDCCH, the first TCI state is set in the RRC settings to indicate it.

[0128] Channel / signalTCI selection schemePDCCHRRC config. (1 st / 2 nd / both / non) per CORESETPDSCH by DCI format 1_1 / 1_2Determining by TCI selection field in the DCIPDSCH by DCI format 1_0RRC config. (1 st / 2 nd / both)DG, Type-2 CG PUSCH by DCI format 0_1 / 0_2Determining by SRS resource set indicator in the DCIDG, Type-2 CG PUSCH by DCI format 0_0Applying 1 st indicated TCI stateType-1 CG PUSCHRRC config. (1 st / 2 nd / both) per Type-1 CG configPUCCHRRC config. (1 st / 2 nd / both) per PUCCH resource / resource groupAP CSI-RS for CSI / BMRRC config. (1 st / 2 nd ) per CSI-RS resource or per resource setP / SP / AP SRS for CB / NCB / AS & AP SRS for BMRRC config. (1 st / 2 nd ) per SRS resource set

[0129] In the following embodiments of the present disclosure, a specific method is proposed to determine which beam serves as the reference beam and to perform beam evaluation when LTM event-based L1 channel measurement and reporting are performed based on the unified TCI state described in FIG. 6, particularly when evaluating events for a beam. For detailed operation, refer to the following embodiments.

[0130] FIGS. 7a and 7b illustrate an overall operation including a beam determination for performing event-based Layer 1 measurement reporting in LTM as an embodiment of the present disclosure. In this figure, an overall operation is illustrated with L1 measurement resources and reporting settings applied to support continuous L1 / L2-based handover (LTM) operations in cells within different CUs.

[0131] Referring to FIG. 7a, the terminal (1g-01) in an RRC connection state performs data transmission and reception with source cell 1 (1g-02), and then transmits layer 3 measurement values ​​for the serving cell and surrounding cells to the source base station (1g-03) (1g-10) according to the configured layer 3 measurement and report. 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 processing RRC messages and determining mobility.

[0132] Based on the measurement report received from the terminal (1g-01), the base station CU (1g-03) generates a message (UE Context Setup Request or UE Context Modification Request) requesting configuration information for L1 / L2-based handover from the intra-CU's LTM candidate surrounding cells (1g-04, 1g-05) and transmits it to the F1 interface (1g-15). Although candidate cells are shown in association with DUs in FIG. 7a, in reality, candidate cells and DUs can be mapped 1:1, or multiple candidate cells can be mapped to be included in a single DU. Additionally, the message requesting configuration information for L1 / L2-based handover may be a UE context request message, a UE context modification request message, etc., or alternatively, a new F1 message. The message requesting configuration information for the L1 / L2-based handover described above may include a procedure for notifying neighboring cells that a cell has been determined as a candidate cell for the L1 / L2-based handover, and simultaneously requesting RRC configuration information applicable when the L1 / L2-based handover is performed to that cell. That is, the requesting message may include information requesting L1 measurement resources and reporting settings for the LTM candidate cells proposed in this disclosure. The information that may be included in the message is summarized as follows.

[0133] 1. Configuration information applicable to LTM and conditional LTM (information to be displayed when issuing the cell switch command MAC CE instruction to the candidate cell that made the LTM decision)

[0134] - LTM candidate ID

[0135] - Mapping information between the LTM candidate ID and the corresponding cell ID

[0136] - Beam information (TCI state) to be used by each candidate

[0137] ■ In this case, the beam to be used may refer to a beam linked to a RACH occasion when performing DL and / or UL synchronization and / or RACH (random access channel) procedures, and / or a beam to be used for the first UL data transmission. If necessary, an indicator corresponding to each case may be provided to perform a cell switch.

[0138] - RACH preamble index

[0139] - SSB index: An index of the SSB used to determine the RACH occasion in each candidate cell, which may represent the occasion for transmitting the RACH preamble of CFRA (contention-free random access).

[0140] 2. Pre-configuration procedures for LTM and conditional LTM

[0141] - CSI resource request information for each candidate cell (requests for CSI-RS resources or SSB resources)

[0142] ■ It may be requested during the pre-configuration preprocessing section for LTM candidate cells.

[0143] ◆ Indicator for whether the request is for initial preparation, e.g., initiation, or for a modification request after the initial one

[0144] ■ In particular, when the relevant request information is included, lower layer configuration information and CSI report configuration information in this message may not be transmitted.

[0145] ■ If CSI resource information is received from candidate cells using the corresponding request information, the CSI resource settings of each of the following candidate cells may be transmitted instead of the request. In other words, a CSI resource setting preprocessing procedure is required in at least 2 steps.

[0146] In addition, it is possible to decide whether to request CSI-RS resources or SSB resources for each target candidate cell.

[0147] - CSI resource settings for each candidate cell (necessary when transmitting L1 measurement settings as source DU to the terminal), may include individual resource settings and setting IDs for each cell, CSI resource settings for LTM, may use the same CSI resources as the conditional LTM, but may also explicitly distinguish and transmit the CSI resources for the conditional LTM.

[0148] ■ Based on the above CSI resource request information, provide L1 measurement settings for LTM transmitted from the corresponding candidate cell.

[0149] ■ Depending on the request for CSI-RS or SSB resources from each target cell, one of the two resource configurations or both resource configurations can be delivered.

[0150] - CSI report configuration considering the CSI resources of each of the above candidate cells

[0151] The purpose of this is that when a candidate DU creates the above information and transmits it to a CU, this information can be used as the CSI report configuration within the target cell configuration (RRCReconfiguration) of the relevant concerned cell (i.e., target cell) generated by the CU. Additionally, the information may not be transmitted separately but may be included within the target cell configuration (RRCReconfiguration) and transmitted.

[0152] ■ In other words, if the 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 intended to be included in the target cell configuration for subsequent LTM without providing separate L1 settings.

[0153] ■ Event-based L1 measurement reporting

[0154] You can define and use L1-RSRP (reference signal received power) based events of the best beam.

[0155] ◆ For example, the following events may be introduced. That is, events are defined by comparing the serving cell beam and the surrounding cell beam, and L1 filtering values ​​such as threshold, beam offset, hysteresis, and time to trigger (TTT) may be introduced.

[0156] - Event A1beam: Beam of serving cell becomes better than absolute threshold;

[0157] - Event A2beam: Beam of serving cell becomes worse than absolute threshold;

[0158] - Event A3beam: Beam of candidate cell becomes amount of offset better than beam of serving cell;

[0159] - Event A4beam: Beam of candidate cell becomes better than absolute threshold;

[0160] - Event A5beam: Beam of serving cell becomes worse than absolute threshold1 AND Beam of candidate cell becomes better than another absolute threshold2.

[0161] The above event may also be used in conditions that trigger a conditional LTM. Alternatively, in addition to a single beam, events through multiple beams or events through cell-level measurements estimated through multiple beams may be added.

[0162] The above conditions are determined by coordination between the serving CU and the LTM candidate DU in step 1g-15, and the serving CU can determine the event conditions and L1 filtering values ​​that trigger the LTM provided by the LTM candidate cell and transmit them to the terminal.

[0163] - RACH configuration and lower layer setting information to be used in the concerned cell

[0164] ■ These information can be transmitted from the above candidate DU to the CU, written as settings required for performing the RACH procedure within the target cell configuration of the concerned cell, lower layer settings to be applied when moving to the cell, and / or reference settings including them, and later transmitted to the terminal.

[0165] ■ In particular, some of the RACH settings can be used to include RACH preamble index, Mask, and occasion determination information in the cell switch command MAC CE described above.

[0166] ■ Settings may be applied simultaneously to both LTM and Conditional LTM, but resources dedicated to Conditional LTM may also be configured separately.

[0167] Meanwhile, although step 1g-15 in Fig. 7a is depicted as a single signaling procedure, the step may include multiple signaling procedures. That is, LTM-related settings may be requested from each LTM candidate cell, the settings obtained in response to the request may be organized at the source cell and transmitted to each LTM candidate cell, and then the necessary LTM settings may be transmitted from each LTM candidate cell to the source cell. A detailed procedure is described below.

[0168] 1. Step 1: Request L1 measurement resource configuration from LTM candidate cells (request SSB or CSI-RS resources)

[0169] 2. Step 2: LTM candidate cells respond by setting up L1 measurement resources and transmit them to the source base station CU (1g-03) (SSB or CSI-RS resource request). This procedure can be transmitted to the source base station via the F1 interface as a UE Context Setup Response message.

[0170] 3. Step 3: The source base station CU (1g-03) transmits L1 measurement resource settings for continuous LTM support to each candidate cell through the L1 measurement resource settings for each collected candidate cell. This procedure can be transmitted to the source base station via the F1 interface as a UE Context Modification Request message.

[0171] 4. Step 4: The source base station CU (1g-03) requests L1 measurement report setup from LTM candidate cells and receives the measurement report setup. This procedure can be transmitted to the source base station via the F1 interface as a UE Context Modification Response message.

[0172] 5. Step 5: Deliver LTM-related settings to the terminal. The source base station collects all LTM-related settings received from LTM candidate cells, stores them in an RRCReconfiguration message delivered to the terminal, and transmits the corresponding RRC setting information to the terminal. That is, pre-configuration information for the LTM candidate cells is delivered to the terminal.

[0173] Hereinafter, regarding the Event-based L1 measurement reporting proposed in the embodiments of the present disclosure, we will explain in more detail which beam is used as the source cell beam and which beam is used as the measured beam of the LTM candidate cell.

[0174] Referring again to FIG. 7a, the base station CU (1g-03) generates a message (Handover Request or new message) requesting configuration information for LTM from the target base station (CU2; 1g-06) in step 1g-20 to request LTM candidate cell configuration information for the LTM surrounding cell (1g-07) of the inter-CU based on the measurement report received from the terminal (1g-01), and transmits it to the X2 interface.

[0175] Subsequently, in step 1g-25, the target base station (CU2; 1g-06) generates a message (UE Context Setup Request or UE Context Modification Request) requesting configuration information for LTM cell modification for an LTM candidate cell (1g-07) belonging to the CU (1g-06), transmits it to the F1 interface, and receives a response message (UE Context Setup Response or UE Context Modification Response) to the requesting message containing configuration information for LTM. This procedure is similar to the LTM configuration preprocessing procedure of step 1g-15 described above.

[0176] Subsequently, in the 1g-30 step, the target base station (CU2; 1g-06) generates a message (Handover Response or a new response message) to the source base station (CU; 1g-03) via the X2 interface, including the LTM candidate configuration information transmitted by the LTM candidate cell (1g-07) belonging to the CU (1g-06). The content that can be newly added to the LTM configuration request message through the X2 interface in the 1g-30 step is summarized as follows.

[0177] - Indicator for LTM execution

[0178] Additionally, an indicator indicating whether the request is for initial preparation, e.g., initiation, or for modification after the initial request.

[0179] - Device ID

[0180] - Source CU and / or Source DU ID, and / or Source DU's TNL (Transport Network Layer) address (e.g., IP (Internet Protocol) address)

[0181] - ID of the requesting candidate cell (PCI or NR (new radio) CGI (cell global identity) with NR ARFCN (absolute radio frequency channel number))

[0182] - LTM configuration ID of this candidate cell (if accepted, it can be used when the source DU cell switches to the target cell with the LTM config ID)

[0183] - LTM configuration ID mapping list: Information to inform the candidate DU of the mapping relationships between the candidate DU's currently available LTM configurations and its cells when delivered to the candidate DU.

[0184] ■ Opt 1. The above candidate cell list may be a list of candidate cells operated by all candidate CUs for the terminal in question, and

[0185] ■ Opt 2. It may be a list containing only candidate cells operated by the source CU that transmits the HO request message.

[0186] - Request information for CSI resource configuration for LTM L1 measurement

[0187] ■ CSI resource requests are omitted, and configuration information for CSI resources being transmitted by all currently configured candidate cells may be transmitted.

[0188] ■ Request SSB or CSI-RS resources

[0189] You can request only one of the two resources, or you can request both resources.

[0190] - An indicator requesting PRACH (physical random access channel) resource information for target candidate cells

[0191] - An indicator requesting a lower layer setting for target candidate cells

[0192] Of course, in addition to the information above, information used in existing HO request messages, as shown in [Table 12] below, can also be included in the LTM configuration request message through the X2 interface.

[0193] Source NG-RAN node UE XnAP ID referenceNG-RAN node UE XnAP ID9.2.3.16Allocated at the source NG-RAN nodeCause9.2.3.2Target Cell Global ID9.2.3.25Includes either an E-UTRA CGI or an NR CGIGUAMI9.2.3.24UE Context Information>NG-C UE associated Signalling referenceAMF UE NGAP ID9.2.3.26Allocated at the AMF on the source NG-C connection.>Signalling TNL association address at source NG-C sideCP Transport Layer Information9.2.3.31This IE indicates the AMF's IP address of the SCTP association used at the source NG-C interface instance.NOTE: If no UE TNLA binding exists at the source NG-RAN node, the source NG-RAN node indicates the TNL association address it would have selected if it would have had to create a UE TNLA binding.>UE Security Capabilities9.2.3.49>AS Security Information9.2.3.50>Index to RAT / Frequency Selection Priority9.2.3.23>UE Aggregate Maximum Bit Rate9.2.3.17>PDU Session Resources To Be Setup List9.2.1.1Similar to NG-C signalling, containing UL tunnel information per PDU Session Resource;and in addition, the source side QoS flow ⇔ DRB mapping>RRC ContextOCTET STRINGEither includes theHandoverPreparationInformationmessage as defined in subclause 10.2.2. of TS 36.331

[0014] , or theHandoverPreparationInformation-NBmessage as defined in subclause 10.6.2 of TS 36.331

[0014] , if the target NG-RAN node is an ng-eNB,or theHandoverPreparationInformationmessage as defined in subclause 11.2.2 of TS 38.331

[0010] , if the target NG-RAN node is a gNB.>Location Reporting Information9.2.3.47Includes the necessary parameters for location reporting>Mobility Restriction List9.2.3.53>5GC Mobility Restriction List Container9.2.3.100>NR UE Sidelink Aggregate Maximum Bit Rate9.2.3.107This IE applies only if the UE is authorized for NR V2X services.>LTE UE Sidelink Aggregate Maximum Bit Rate9.2.3.108This IE applies only if the UE is authorized for LTE V2X services.>ManagementBasedMDT PLMN ListMDT PLMN List9.2.3.133>UE Radio Capability ID9.2.3.138>MBS Session Information List9.2.1.36>5G ProSe UE PC5 Aggregate Maximum Bit RateNR UE Sidelink Aggregate Maximum Bit Rate9.2.3.107This IE applies only if the UE is authorized for 5G ProSe services.>UE Slice Maximum Bit Rate List9.2.3.167>NR A2X UE PC5 Aggregate Maximum Bit RateNR UE Sidelink Aggregate Maximum Bit Rate9.2.3.107This IE applies only if the UE is authorized for NR A2X services.>LTE A2X UE PC5 Aggregate Maximum Bit RateLTE UE Sidelink Aggregate Maximum Bit Rate9.2.3.108This IE applies only if the UE is authorized for LTE A2X services.Trace Activation9.2.3.55Masked IMEISV9.2.3.32UE History Information9.2.3.64UE Context Reference at the S-NG-RAN node>Global NG-RAN Node ID9.2.2.3>S-NG-RAN node UE XnAP IDNG-RAN node UE XnAP ID9.2.3.16.

[0194] Subsequently, in step 1g-35, the source base station (1g-02) can trigger the procedures 1g-15 (transmitting the finally determined CSI resource settings to LTM candidate cells within the CU and requesting and responding to LTM-related settings) and 1g-20 (transmitting the finally determined CSI resource settings to LTM candidate cells within another CU and requesting LTM-related settings) again based on the information of LTM-related candidate cells received from the target base station (1g-06). In addition, in response to this, the procedure 1g-30 (receiving LTM-related settings based on the finally transmitted CSI resource settings from LTM candidate cells within another CU) can be performed.

[0195] In step 1g-40, the source base station (1g-02) aggregates all LTM-related settings received from LTM candidate cells and generates an RRC message to be included in the RRC message (RRCReconfiguration message), and transmits the generated RRC message to the terminal (1g-02). That is, through this procedure, pre-configuration information for LTM candidate cells is transmitted to the terminal (1g-01). At this time, the source base station CU (1g-03) can transmit the source cell configuration information and separate reference cell configuration information together in the RRC message to the terminal (1g-01).

[0196] According to one example of the present disclosure, the reference cell setting information may include L1 measurement resource settings for continuous LTM. In the message transmitted at that step, settings related to how to apply the beam (TCI state) used when performing an LTM L1 measurement event with an LTM candidate cell from the source cell, as proposed in the present disclosure, may be added. Additionally, when applying filtering to L1 measurement values ​​used for L1 measurement and evaluation, an implementation L1 filtering value (a filter that averages N L1 measurement values ​​(L1-RSRP) over time) may be used, or L1 filtering may be applied after applying L3 filtering (a value obtained by weighted averaging L3 filtered values ​​over time) for each beam, and settings including instructions for this may be added to the RRC message of the above step.

[0197] Below, we will describe the issues of the beam determination methods used for L1 measurement reporting based on LTM events proposed in this disclosure and explain the measures to resolve them.

[0198] 1. Problem 1:

[0199] A. According to the unified TCI state structure described in Figure 6 above, the beams indicated by the Unified TCI state activation / deactivation MAC CE are applied simultaneously to all channels (PDCCH / PDSCH / PUCCH / PUSCH) after BAT. However, if multiple beams are indicated by the MAC CE, the actual channels are separately specified to determine which beam among the indicated TCI states is applied according to each channel. In this regard, refer to [Table 11] above regarding the method of selecting the TCI state per channel. That is, different beams may be indicated for each channel.

[0200] B. Accordingly, in event-based LTM channel measurement, a beam serving as the standard for channel evaluation is required in the current source cell, and for the beams of LTM candidate cells, beams explicitly provided by L1 measurement resources can be the beams to be measured.

[0201] C. Determine which beam is currently in the source cell.

[0202] D. Solution

[0203] i. Option 1: Among the beams indicated as the unified TCI state in the current source cell, the beam used for PDCCH is defined as the beam from the current source cell and used for event-based L1 measurement evaluation.

[0204] ii. Option 2: Among the beams indicated as the unified TCI state in the current source cell, the beam used for PDSCH is defined as the beam from the current source cell and used for event-based L1 measurement evaluation.

[0205] iii. Option 3: Among the beams indicated as the unified TCI state in the current source cell, the beam used for PUCCH is defined as the beam from the current source cell and used for event-based L1 measurement evaluation.

[0206] iv. Option 4: Among the beams indicated as the unified TCI state in the current source cell, the beam used for PUSCH is defined as the beam in the current source cell and used for event-based L1 measurement evaluation.

[0207] v. Option 5: Uses RRC settings to specify which channel among the beams indicated by the unified TCI state in the current source cell should be applied as the beam from the current source cell, and is used for event-based L1 measurement evaluation.

[0208] vi. Option 6: If there is a beam used for PDSCH among the beams designated as the unified TCI state in the source cell, that beam is defined as the beam in the current source cell and used for event-based L1 measurement evaluation. Conversely, if there is no beam used for PDSCH among the beams designated as the unified TCI state in the source cell, the beam to which PDCCH is applied is defined as the beam in the current source cell and used for event-based L1 measurement evaluation (in this step, the same method may be applied to PUCCH and PUSCH in place of PDCCH and PDSCH, respectively).

[0209] vii. Option 7: Define the best beam with the highest signal strength among the beams indicated by the unified TCI state from the current source cell as the beam from the current source cell and use it for event-based L1 measurement evaluation.

[0210] 2. Problem 2:

[0211] A. If event-based LTM L1 measurement and channel reporting and multiple TRP settings are provided simultaneously, in particular, the beam applied to the multiple TRPs may be indicated as an enhanced unified TCI state-activated MAC CE. For a detailed explanation regarding this, refer to section 1f-50 of Fig. 6 described above. This problem may occur simultaneously with the above-mentioned problem 1, in which case the solutions proposed above and the solutions proposed below are applied simultaneously.

[0212] B. As described in 1f-50 of Fig. 6, when TCI state activation for multiple TRPs is indicated by MAC CE, the terminal applies the beam indicated after BAT to all channels. However, in practice, the beam used per channel may use some or all of the beams indicated by MAC CE through different methods.

[0213] C. In LTM event-based L1 channel measurement and evaluation, when multiple beams are indicated as the current beam, a procedure to identify it is necessary because it is impossible to determine which beam is actually the source cell beam used in the LTM event-based L1 channel measurement and evaluation.

[0214] D. Solution

[0215] i. Enhanced unified TCI state activation: Always use the first TCI state among the TCI states indicated by MAC CE (the beam used in TRP1).

[0216] ii. Explicitly specify which beam is used among the two TCI states (first or second) through RRC settings

[0217] iii. Among the beams indicated by the Enhanced Unified TCI state, the best beam with the highest signal strength is defined as the beam from the current source cell and used for event-based L1 measurement evaluation.

[0218] 3. Problem 3:

[0219] A. If the measurement resource types of the beam directed by the source cell and the beam set in the LTM candidate cell differ for event-based LTM L1 measurement and channel reporting and evaluation—for example, if one beam directs an SSB resource and the other directs a CSI-RS resource—the difference in measurement resource types may result in a difference in the L1-RSRP level. In particular, since the TCI state directed by the source cell can dynamically change to MAC CE and DCI depending on the current channel state in the source cell, if the beams of the LTM candidate cell are set to two types, SSB and CSI-RS, a difference in resource types may occur between the reference cell and the cell to be measured.

[0220] B. Solution

[0221] i. Option 1: A method in which the base station always sets two types of RS (SSB and CSI-RS) simultaneously for event-based L1 measurement resource configuration in LTM candidate cells, and determines the beam type and index of the LTM candidate cell based on the RS type of the source cell. Alternatively, a method in which both types of RS are set for a single cell for the same purpose. For example, a beam list configured with SSB and a beam list configured with CSI-RS resources in Cell 1 are provided independently. Through this, resources for all LTM candidate cells can be compared.

[0222] ii. Option 2: A method in which the base station sets only RS of the same type (SSB or CSI-RS) for each LTM candidate cell, and the source cell determines the beam type and index of the LTM candidate cell based on the specified RS type. For example, if SSB resources are set for Cell 1 and Cell 2, and CSI-RS resources are set for Cell 3 and Cell 4 as measurement beams, the terminal measures only resources of the same type as the resource type of the beam specified in the current source cell. Through this, measurement and reporting are not performed for LTM candidate cells with different types. In this case, the LTM event-based L1 measurement report MAC CE or a new MAC CE can report to the base station that there are no measurable beams of the same type for a specific cell. At this time, beam reporting for the current source cell can also be performed.

[0223] iii. Option 3: Since measurement comparison is not possible due to a difference at the L1-RSRP level when receiving SSB resources and CSI-RS resources, if SSB resources and CSI-RS resources are simultaneously provided as measurement resources for each LTM candidate cell or all candidate cells, the received L1-RSRP offset values ​​of the SSB resources and CSI-RS resources are transmitted to the terminal. Based on this offset information, the terminal can perform L1 measurement evaluation and reporting by correcting by the offset amount when measuring other types of L1 measurement resources, even if the types are different. In this case, when adding a measurement report value in the LTM event-based L1 measurement reporting MAC CE, an indicator may be added to indicate that the value is an offset-corrected value.

[0224] In all of the above options, information indicating what the source cell beam type and target cell beam type were when reporting measurements in the LTM event-based L1 measurement report MAC CE may be added.

[0225] The reference cell configuration information transmitted by the source base station CU (1g-03) to each candidate cell (1g-04, 1g-05) above may be a common configuration that can be applied to multiple target candidate cells in order to reduce signaling overhead when target candidate cells provide configuration information for LTM. This may be a measurement configuration, a bearer configuration, or, in the case of cells belonging to the same CellGroup, configurations configured at the CellGroup level (e.g., MAC-CellGroupConfig, RLC bearer configuration, SCell configuration, etc.). Alternatively, if the source base station CU (1g-03) has a procedure to roughly know or know the configuration information for each candidate cell (1g-04, 1g-05, 1g-07), the reference cell configuration may be determined through a separate procedure to obtain the reference cell configuration information. The purpose of the source base station CU (1g-03) transmitting the reference cell settings to each candidate cell (1g-04, 1g-05, 1g-07) is to allow each candidate cell to transmit only the setting information added to the reference cell settings to the source base station CU (1g-03), so that a delta configuration (a method of configuring a complete setting by applying settings added on top of the reference cell settings, or a method of configuring a complete setting by applying settings over the reference cell settings in the target cell) can be applied. This is then transmitted to the terminal as is, which has the effect of reducing the signaling overhead of the RRC message transmitted to the terminal. Additionally, when the source base station CU (1g-03) transmits the reference cell settings to each candidate cell (1g-04, 1g-05, 1g-07), this can be omitted, and in this case, the candidate cell settings are provided as complete RRC settings.

[0226] As described above, in step 1g-40, the source cell (1g-02) receives an RRC message generated by the base station CU (1g-03) based on configuration information received from each candidate cell, and transmits it to the terminal (1g-01). The RRC message contains configuration information for surrounding candidate cells to which L1 / L2-based handover (LTM) is applied. The RRC message includes a configuration indicating which TCI state will become the reference beam of the source cell, particularly regarding the LTM event-based L1 measurement report proposed in this disclosure, and L1 resources of the target cell to be measured.

[0227] Referring to FIG. 7b, in step 1g-45, the terminal (1g-01) that receives the RRC message performs a procedure to decode and process the RRC message. The processing includes ASN.1 decoding of the received message, validation, and a method for storing and managing the configuration content. Additionally, the terminal (1g-03) stores the LTM configuration information for each candidate cell decoded in this step as complete configuration information in the terminal's buffer (memory), and simultaneously stores the received reference cell configuration information in the terminal's buffer (memory) as well, and manages it for subsequent operations. Meanwhile, 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 terminal (1g-01) determines that the reference cell configuration information is not present in the RRC message, determines the configuration information for the received LTM target candidate cells as complete configuration information, and stores it in memory. At this time, the reference cell configuration information is not stored separately (operates as empty). In other words, delta configuration is not applied. Additionally, the above RRC message includes L1 measurement resources and reporting configuration information for continuous LTM. For detailed configuration, refer to the descriptions above in this disclosure.

[0228] Although the present disclosure primarily deals with event-based L1 channel measurement and reporting being directed, other forms of L1 channel measurement reporting may be set separately, and the terminal may perform operations based thereon. Although omitted in the drawings, existing L1 measurement and reporting procedures may be added to the operations according to an example of the present disclosure. Based on this, in step 1g-50, the base station (1g-02) directs the terminal (1g-01) to a TCI state to direct the optimal beam used in the corresponding serving cell as a unified TCI state activation MAC CE.

[0229] The terminal (1g-01) that receives this performs an event-based L1 resource measurement and evaluation step considered by the terminal in step 1g-50, and when the execution conditions for a specific event are satisfied, transmits an L1 measurement report to the base station (1g-02) through an event-based L1 measurement MAC CE in step 1g-55.

[0230] Upon receiving this, the source base station (1g-02) refers to the corresponding L1 measurement value and transmits a command to the terminal (1g-01) in step 1g-60 to instruct the LTM cell change. In the above step, a MAC CE including a handover indicator may be used as the L1 / L2 signaling. If there is a need for a RACH-less LTM prior to this step, a procedure for obtaining a TA for the corresponding target cell may be added. The source cell makes the final decision on the LTM and does not transmit the L1 measurement value to the CU base station (1g-03). The source cell (1g-02) independently decides on the handover based on the measurement criteria (threshold and measurement range) for making a handover decision for each candidate surrounding cell received from the previous base station, and accordingly transmits the L1 / L2 signaling to the terminal (1g-01). Subsequently, the source cell (1g-02) transmits the LTM decision information to the CU base station (1g-03).

[0231] When an L1 / L2 handover instruction is transmitted to the terminal (1g-01), the terminal (1g-01) starts the handover procedure in step 1g-65 and starts a timer for the L1 / L2 handover. The timer may be a newly set timer for the LTM, or an existing T304 timer may be reused.

[0232] In step 1g-70, the terminal (1g-01) applies the settings for the target cell to which L1 / L2 handover is applied. That is, the current settings of the terminal (1g-01) are replaced with the complete setting information of the indicated LTM target cell that was previously stored in the terminal (1g-01). This is one of the LTM candidate surrounding cell settings received in advance in step 1g-40 and is a setting stored in the terminal (1g-01).

[0233] According to the settings applied in step 1g-75, the terminal (1g-01) performs random access if random access is required for the corresponding target cell, and skips the random access procedure if random access is not instructed or is not required (if uplink synchronization has already been performed or matched).

[0234] In step 1g-80, the terminal (1g-01) performs a handover completion procedure with the target cell. The completion procedure may be a handover completion procedure for the LTM. This procedure is a process of delivering an RRCReconfiugrationComplete message to the RRC message, which is the configuration of the target cell, and the actual handover completion is determined by the end of the random access process.

[0235] In step 1g-95, the target cell (DU, 1g-04) that receives the handover completion message can transmit the received message to the CU base station (1g-03). At this time, the target cell (1g-04) can transmit the handover completion message received through the F1 interface to the CU base station (1g-03) as is, or it can transmit the message to the CU base station (1g-03) after processing it based on the received information.

[0236] Afterwards, in step 1g-100, the CU base station (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.

[0237] In addition, as described in step 1g-105, the embodiment of the present invention supports a subsequent LTM operation. This means that the LTM configuration information (settings for target candidate cells and reference cell configuration information, etc.) received by the terminal (1g-01) in step 1g-40 is stored in the terminal as is, and the terminal continues to perform the LTM procedure unless the LTM configuration information is changed, released, or added through a separate RRC setting. If it is necessary to update the reference cell configuration information, new RRC configuration information is delivered to the terminal to perform this. That is, the procedure described in relation to updating the reference cell configuration information in this drawing can be triggered again to be performed.

[0238] In summary, when the terminal (1g-01) receives reference cell setting information in step 1g-40, it stores it in the terminal buffer, and if there is no update to the separate setting, it continues to use the setting as reference cell setting information even after LTM execution (step 1g-70) (i.e., applies the reference cell setting and LTM candidate setting values ​​stored in the successive LTM). In addition, if the terminal (1g-01) does not receive reference cell setting information in the RRC connection state in step 1g-40, it may store the reference cell setting as empty according to the terminal operation option described above, or store the setting information for the source cell (PCell) that received the LTM setting information as reference cell setting information.

[0239] FIG. 8 is a diagram illustrating the overall terminal operation applied to embodiments of the present disclosure and performing L1 / L2-based handover. In particular, the terminal operation of the present disclosure is characterized by a method of performing L1 measurement and reporting according to L1 measurement resources and reporting settings for continuous LTM operation.

[0240] In step 1h-05, the terminal in the connected state can receive configuration information from surrounding cells that is applied after L1 / L2-based movement is instructed via an RRC reset message from the serving cell. For detailed configuration methods and content, refer to the details described in FIGS. 7a and 7b. Additionally, although omitted, the terminal has received basic RRC configuration from the base station prior to the RRC configuration information and performs the operation of reporting layer 3 measurements for surrounding cells to the base station based on this. In particular, the configuration information from LTM candidate cells that is applied after L1 / L2-based movement is instructed received in step 1h-05 is characterized by being transmitted with a delta configuration applied based on the configuration of a single reference cell. In particular, the present disclosure considers how the reference beam applied to the current source cell and the beam to be measured in the LTM candidate cell are configured and instructed for LTM event-based L1 resource measurement and reporting, and some proposed configurations may be provided in the RRC message of this step.

[0241] In step 1h-10, the terminal can decode the settings for LTM candidate cells received from the base station based on the settings of the reference cell, and store and manage the complete settings that are actually applied (i.e., the operation of storing a delta-configured setting based on the reference cell as a complete configuration by referring to the reference cell settings) in a separate buffer and list. Alternatively, the terminal according to an example of the present disclosure may not decode the received settings based on the reference cell and store and manage the settings that are actually applied, but may store and manage the received RRC settings as they are in the buffer. As described in FIGS. 7a and 7b, the terminal according to an example of the present disclosure recognizes that there is no reference cell setting information when the reference cell settings are omitted in the setting information received from the base station, and determines and stores the setting information for the received LTM target candidate cells as complete setting information. In particular, in the present disclosure, LTM-related settings are provided in the corresponding step, and more specifically, candidate cell settings for LTM and settings for L1 resources requiring measurement are included in the information provided in the corresponding step. The terminal can decode the settings, store them in the terminal buffer, and then manage them.

[0242] In step 1h-15, the terminal is instructed on the TCI state applied to the source cell via MAC CE from the base station. The method proposed in this disclosure may be applied to determine the source cell beam used for actual event-based L1 measurement evaluation among the beams indicated in the MAC CE, and the terminal determines the beam accordingly.

[0243] Subsequently, in step 1h-20, while maintaining the connection with the cell, an L1 measurement is performed using an SSB or CSI-RS resource associated with a candidate surrounding cell. Additionally, the measurement results are reported to the serving cell according to a pre-configured L1 measurement reporting setting method. In this step, the present disclosure considers that an event-based LTM L1 resource reporting setting is applied.

[0244] That is, if the LTM L1 channel measurement report event set in step 1h-25 is satisfied, the terminal may report to the base station via MAC CE including the relevant measurement value in step 1h-30. The MAC CE may include the following information.

[0245] - Event ID Information

[0246] - Beam performance (RSRP) and beam resource information (SSB or CSI-RS index) measured at the current source cell

[0247] - Beam performance (RSRP) and beam resource information (SSB or CSI-RS index) in LTM candidate cells that satisfied the event

[0248] - If configured to report multiple best beams, N best beam reports and beam resource information (SSB or CSI-RS index) depending on the setting

[0249] Additionally, information indicating the difference in resource types between the source cell and the target cell described above may be reported. Refer to the previously mentioned details regarding this.

[0250] The serving cell can determine whether to change the terminal's beam and hand over based on the received measurement results, and if it is determined that a change to a specific beam of a surrounding cell is necessary rather than a specific beam of the serving cell, it instructs the terminal to hand over and change the beam through L1 / L2 signaling in step 1h-35.

[0251] In step 1h-25, if the event-based LTM measurement report event is not satisfied, the terminal can continue to perform the corresponding L1 measurement and evaluation.

[0252] FIG. 9 is a drawing illustrating base station operation applied to embodiments of the present disclosure.

[0253] In step 1i-05, the base station receives L3 measurement reports from the terminal and, based on the terminal's measurements regarding surrounding frequencies and cells, determines whether the terminal requires a handover and which cells are handover candidate cells.

[0254] In step 1i-10, the base station requests configuration information for L1 / L2-based handover from neighboring cells and receives responses from those cells. In this step, the base station transmits configuration information for the current source cell and reference cell configuration information together to the neighboring cells, and receives RRC configuration information from the neighboring cells and LTM candidate cells, to which delta configuration is applied based on the reference cell configuration information. Additionally, in this step, inter-node coordination for L1 measurement resources and reporting settings proposed in this disclosure is performed. The procedure described in detail in FIGS. 7a and 7b is included in this step, and in particular, includes determining L1 measurement resources and reporting settings within intra-CU and inter-CU. Although omitted from the description in this figure, settings related to L3 measurement settings and basic RRC settings are provided prior to this step.

[0255] In step 1i-15, an RRC configuration message is transmitted to the terminal in the connected state, including the surrounding cell configuration information and L1 measurement resource / reporting settings received in step 1i-10. That is, configuration information from the surrounding cell that is applied after L1 / L2-based movement is instructed via an RRC reset message from the serving cell is transmitted in this step. Detailed configuration methods and contents are described in detail in FIGS. 6, 7a, and 7b.

[0256] Subsequently, in step 1i-20, the base station may direct L1 measurement reporting in various ways via RRC or L1 / L2 signaling according to the L1 measurement and reporting that it wishes to configure and trigger. For detailed methods, refer to the invention above. Reports regarding L1 and L3 measurement values ​​are received from a terminal, and the present disclosure considers the case where an event-based L1 measurement report MAC CE is received from the terminal in that step. In this case, the L1 measurement value may be a non-serving cell that supports L1 / L2-based mobility.

[0257] The serving cell can determine whether to change the terminal's beam and perform a handover based on the received measurement results. If it is determined that a change to a specific beam of a neighboring cell is necessary rather than the serving cell's specific beam, the serving cell instructs the terminal's LTM handover via L1 / L2 signaling in step 1i-25. The above L1 / L2 signaling may be MAC CE and includes information instructing a change to a specific beam of a neighboring cell. Additionally, an existing handover via an RRC message may also be independently performed and instructed in that step. This can occur because the base station and the serving cell independently determine the LTM and Layer 3 handover.

[0258] Subsequently, upon receiving a handover completion message from the terminal in step 1i-35, it is confirmed that the corresponding LTM operation has been successfully completed; accordingly, the previous source cell is notified of the handover completion, and the release of the terminal context is requested. Additionally, if a handover failure report message containing information that the handover failed is received, a message is received indicating that the terminal attempted to reconnect to the cell after the handover failure. The handover failure report message may be a UEInformationResponse message or another uplink RRC message. Furthermore, this may be reported via a new MAC CE or uplink control signal (UCI; uplink control information). The information included in the handover failure report message may include the following information.

[0259] - An indicator that the handover failed due to an LTM failure

[0260] - Target cell information where LTM was attempted but failed: LTM cell configuration index or actual cell index (PCI; Physical Cell Index) information

[0261] - The source base station can know that the LTM attempt failed and fell back to the cell through the handover failure message report.

[0262] FIG. 10 is a block diagram illustrating the internal structure of a terminal according to one example of the present disclosure.

[0263] Referring to FIG. 10, a terminal according to one example of the present disclosure includes 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).

[0264] 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 by 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 DAC (digital to analog converter), an ADC (analog to digital converter), etc. Although only one antenna is shown in the drawing, the terminal may be equipped with multiple antennas. 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 magnitude of each of the signals transmitted and received through a plurality of antennas or antenna elements. In addition, the RF processing unit can perform MIMO and can receive multiple layers when performing MIMO operation.

[0265] The baseband processing unit (1j-20) performs a conversion function between a baseband signal and a bit sequence according to the physical layer specifications of the system. For example, when transmitting data, the baseband processing unit (1j-20) generates complex symbols by encoding and modulating the transmitted bit sequence. Additionally, when receiving data, the baseband processing unit (1j-20) restores the received bit sequence by demodulating and decoding the baseband signal provided by 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 the transmitted bit sequence, maps the complex symbols to subcarriers, and then constructs OFDM symbols through IFFT (inverse fast Fourier transform) operation and CP (cyclic prefix) insertion. Additionally, upon receiving data, the baseband processing unit (1j-20) divides the baseband signal provided by the RF processing unit (1j-10) into OFDM symbol units, restores the signals mapped to subcarriers through a fast Fourier transform (FFT) operation, and then restores the received bit sequence through demodulation and decoding.

[0266] 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 transmitting unit, a receiving unit, a transmitting and receiving unit, 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. Additionally, 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 wireless LAN (e.g., IEEE 802.11), cellular network (e.g., LTE), etc. In addition, the above different frequency bands may include super high frequency (SHF) bands (e.g., 2 NRHz, NRHz) and millimeter wave (e.g., 60 GHz) bands.

[0267] The storage unit (1j-30) stores data such as basic programs, application programs, and configuration information for the operation of the terminal. In particular, the storage unit (1j-30) can store information related to a second connection node that performs wireless communication using a second wireless connection technology. Additionally, the storage unit (1j-30) provides the stored data upon the request of the control unit (1j-40).

[0268] The control unit (1j-40) controls the overall operations of the terminal. 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). Additionally, the control unit (1j-40) writes and reads data to and from the storage unit (1j-30). To this end, 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 applications.

[0269] FIG. 11 is a block diagram showing the configuration of a base station according to one example of the present disclosure.

[0270] Referring to FIG. 11, a base station according to one example of the present disclosure is configured to 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).

[0271] 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 by 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 transmit filter, a receive filter, an amplifier, a mixer, an oscillator, a DAC, an ADC, etc. Although only one antenna is shown in the drawing, the first connection node may be equipped with multiple antennas. Additionally, 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 of the signals transmitted and received through a plurality of antennas or antenna elements. The RF processing unit can perform down-to-down MIMO operation by transmitting one or more layers.

[0272] The baseband processing unit (1k-20) performs a conversion function between a baseband signal and a bit sequence according to the physical layer specifications of the first wireless access technology. For example, when transmitting data, the baseband processing unit (1k-20) generates complex symbols by encoding and modulating the transmitted bit sequence. Additionally, when receiving data, the baseband processing unit (1k-20) restores the received bit sequence by demodulating and decoding the baseband signal provided by the RF processing unit (1k-10). For example, in the case of following the OFDM method, when transmitting data, the baseband processing unit (1k-20) generates complex symbols by encoding and modulating the transmitted bit sequence, maps the complex symbols to subcarriers, and then constructs OFDM symbols through IFFT operation and CP insertion. Additionally, upon receiving data, the baseband processing unit (1k-20) divides the baseband signal provided by the RF processing unit (1k-10) into OFDM symbol units, restores the signals mapped to subcarriers through FFT operations, and then restores the received bit sequence through demodulation and decoding. The baseband processing unit (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 transmitting unit, a receiving unit, a transmitting and receiving unit, a communication unit, or a wireless communication unit.

[0273] The 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 sequence transmitted from the main base station to another node, e.g., an auxiliary base station, a core network, etc., into a physical signal, and converts a physical signal received from the other node into a bit sequence.

[0274] The storage unit (1k-40) stores data such as basic programs, application programs, and configuration information for the operation of the main station. In particular, the storage unit (1k-40) can store information regarding bearers assigned to connected terminals, measurement results reported from connected terminals, etc. Additionally, the storage unit (1k-40) can store information serving as a criterion for determining whether to provide or disconnect multiple connections to the terminals. Furthermore, the storage unit (1k-40) provides the stored data upon the request of the control unit (1k-50).

[0275] The control unit (1k-50) controls the overall operations of the main station. 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). Additionally, the control unit (1k-50) writes and reads data to and from the storage unit (1k-40). To this end, the control unit (1k-50) may include at least one processor.

[0276] Methods according to the embodiments described in the claims or specification of the present disclosure may be implemented in the form of hardware, software, or a combination of hardware and software.

[0277] When implemented in software, a computer-readable storage medium may be provided for storing one or more programs (software modules). One or more programs stored in the computer-readable storage medium are configured for execution by one or more processors within an electronic device. One or more programs include instructions that cause the electronic device to execute methods according to embodiments described in the claims or specification of the present invention.

[0278] Such programs (software modules, software) may be stored in random access memory, non-volatile memory including flash memory, ROM (Read Only Memory), EEPROM (Electrically Erasable Programmable Read Only Memory), magnetic disc storage devices, CD-ROM (Compact Disc-ROM), Digital Versatile Discs (DVDs), or other forms of optical storage devices, magnetic cassettes. Alternatively, they may be stored in memory composed of some or all of these. Additionally, each constituent memory may include multiple units.

[0279] In addition, the above program may be stored on an attachable storage device that can be accessed via a communication network such as the Internet, Intranet, Local Area Network (LAN), Wide LAN (WLAN), or Storage Area Network (SAN), or a combination thereof. Such a storage device may be connected to a device performing an embodiment of the present invention through an external port. Additionally, a separate storage device on a communication network may be connected to a device performing an embodiment of the present invention.

[0280] In the specific embodiments of the present disclosure described above, the components included in the invention are expressed in a singular or plural form according to the specific embodiments presented. However, the singular or plural expression is selected to suit the situation presented for convenience of explanation, and the present invention is not limited to singular or plural components; even if a component is expressed in the plural form, it may be composed in the singular form, or even if a component is expressed in the singular form, it may be composed in the plural form.

[0281] Meanwhile, although specific embodiments have been described in the detailed description of the present disclosure, it is understood that various modifications are possible within the scope of the present invention. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be defined by the claims set forth below as well as equivalents thereof.

Claims

1. In a method of a terminal in a wireless communication system, A step of receiving a radio resource control (RRC) message containing layer 1 / layer 2 triggered mobility (LTM) setting information from a source cell of a base station—the LTM setting information includes information about at least one candidate cell and information about resource settings for LTM measurement—; When the reporting for the above LTM measurement is set to event-based, the step of measuring the beam for the source cell and the beam for the candidate cell; and If it is determined that an event is satisfied based on the result of the above measurement, the method includes the step of transmitting the result of the measurement to the base station. The type of the beam's reference signal (RS) for the above candidate cell is identified as an SSB (synchronization signal block) or CSI-RS (channel state information - reference signal) based on information regarding the resource configuration, and A method of a terminal characterized in that the RS type of the beam for the source cell is the same as the RS type for the candidate cell.

2. In Paragraph 1, The method further includes the step of receiving TCI (transmission configuration indicator) status information from the base station that indicates a beam for the source cell. A method of a terminal characterized in that the beam for the source cell is determined based on the TCI status information.

3. In Paragraph 2, A method of a terminal characterized in that, when a plurality of TRPs (transmission and reception points) are set in the serving cell, the beam for the source cell is determined as the beam with the best signal strength among the beams indicated by the TCI status information.

4. In Paragraph 3, The above plurality of TRPs includes a first TRP and a second TRP, and A method of a terminal characterized in that the beam with the best signal strength is selected from among the beam for the first TRP and the beam for the second TRP.

5. In paragraph 1, the above event is, A method of a terminal characterized by including an event in which the beam intensity for the source cell is measured to be smaller than a preset threshold, an event in which the beam intensity for the candidate cell is larger than the beam intensity for the serving cell by an offset, an event in which the beam intensity for the candidate cell is measured to be larger than the preset threshold, or an event in which the beam intensity for the serving cell is smaller than a first threshold and the beam intensity for the candidate cell is measured to be larger than a second threshold.

6. In Paragraph 1, A step of receiving an LTM cell switch command MAC (medium access control) CE (control element) from the base station, which includes information instructing the configuration of the candidate cell; and The method further includes the step of performing cell switching to the above candidate cell, A method of a terminal characterized in that the setting of the above candidate cell is applied in the above candidate cell after the cell switching.

7. In Paragraph 1, A method of a terminal characterized in that the beam for the source cell is determined to be either a beam for PDSCH (physical downlink control channel) reception or a beam for PDCCH (physical downlink control channel) reception.

8. In a terminal of a wireless communication system, Transmitter / receiver; and The control unit controls the transceiver to receive a radio resource control (RRC) message containing layer 1 / layer 2 triggered mobility (LTM) setting information from a source cell of a base station, wherein the LTM setting information includes information on at least one candidate cell and information on resource setting for LTM measurement; when reporting on the LTM measurement is set to be event-based, measures a beam for the source cell and a beam for the candidate cell; and when it is determined that an event is satisfied based on the result of the measurement, controls the transceiver to transmit the result of the measurement to the base station. The type of the beam's reference signal (RS) for the above candidate cell is identified as an SSB (synchronization signal block) or CSI-RS (channel state information - reference signal) based on information regarding the resource configuration, and A terminal characterized in that the RS type of the beam for the source cell is the same as the RS type for the candidate cell.

9. In Paragraph 8, The above control unit controls the transceiver to receive TCI (transmission configuration indicator) status information indicating a beam for the source cell from the base station, and A terminal characterized in that the beam for the source cell is determined based on the TCI status information.

10. In Paragraph 9, A terminal characterized in that, when a plurality of TRPs (transmission and reception points) are set in the serving cell, the control unit determines the beam for the source cell as the beam with the best signal strength among the beams indicated by the TCI status information.

11. In Paragraph 9, The above plurality of TRPs includes a first TRP and a second TRP, and The terminal is characterized by the above control unit selecting the beam with the best signal strength among the beam for the first TRP and the beam for the second TRP.

12. In Paragraph 8, the above event is, A terminal characterized by including an event in which the beam intensity for the source cell is measured to be smaller than a preset threshold, an event in which the beam intensity for the candidate cell is larger than the beam intensity for the serving cell by an offset, an event in which the beam intensity for the candidate cell is measured to be larger than the preset threshold, or an event in which the beam intensity for the serving cell is smaller than a first threshold and the beam intensity for the candidate cell is measured to be larger than a second threshold.

13. In Paragraph 8, The control unit controls the transceiver to receive an LTM cell switch command MAC (medium access control) CE (control element) containing information instructing the setting of the candidate cell from the base station, and performs cell switching to the candidate cell. A terminal characterized in that the setting of the above candidate cell is applied in the above candidate cell after the above cell switching.

14. In Paragraph 8, A terminal characterized in that the beam for the source cell is determined to be either a beam for PDSCH (physical downlink control channel) reception or a beam for PDCCH (physical downlink control channel) reception.

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