Method and device for conditional lower layer-based mobility for various services in next generation mobile communication system

Abstract

A method performed by a terminal in a wireless communication system according to an embodiment of the present disclosure may comprise the steps of: receiving configuration information for layer 1 / layer 2 triggered mobility (LTM), wherein the configuration information includes measurement object information and measurement identification information associated with a report configuration, and the report configuration includes information about an event related to an LTM execution condition; determining whether a candidate cell satisfies the event, on the basis of the configuration information and layer 3 (L3) measurement; and when the event is satisfied, performing an LTM cell switch procedure on the candidate cell, wherein the measurement identification information corresponds to an LTM configuration for each candidate cell.

Description

Conditional lower-layer based mobility method and device for various services in next-generation mobile communication systems

[0001] The present disclosure relates to the operation of a terminal in a mobile communication system. Specifically, it relates to a method for moving a terminal between cells and an apparatus for doing the same.

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

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

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

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

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

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

[0009] In conventional LTM (layer 1 / 2 triggered mobility), since conditional LTM (CLTM) related condition information is based on beam strength, the terminal determined whether the condition was satisfied solely through comparison based on beam strength. However, in order to implement operations required by various services, it is necessary to define various conditions for conditional LTM and update the criteria for determining whether the condition is satisfied.

[0010] A method performed by a terminal in a wireless communication system according to one embodiment of the present disclosure comprises the steps of receiving configuration information for LTM (layer 1 / layer 2 triggered mobility), wherein the configuration information includes measurement object information and measurement identification information associated with a report configuration, and wherein the report configuration includes information on an event associated with an LTM execution condition, and determining whether a candidate cell satisfies the event based on the configuration information and a L3 (layer 3) measurement, and, if the event is satisfied, performing an LTM cell switch procedure to the candidate cell, wherein the measurement identification information may correspond to an LTM configuration for each candidate cell.

[0011] In a wireless communication system according to one embodiment of the present disclosure, a terminal comprises at least one transceiver, at least one processor connected to communicate with the at least one transceiver, and a memory that stores a command to determine whether a candidate cell satisfies the event based on the setting information and L3 measurement, and to perform an LTM cell switch procedure to the candidate cell if the event is satisfied, wherein the terminal receives setting information for an LTM, the setting information includes measurement identification information associated with measurement target information and a reporting setting, the reporting setting includes information about an event associated with an LTM execution condition, and, if the event is satisfied, the terminal determines whether the event is satisfied and stores a command to perform an LTM cell switch procedure to the candidate cell. The measurement identification information may correspond to an LTM setting for each candidate cell.

[0012] A method performed by a base station in a wireless communication system according to one embodiment of the present disclosure comprises the steps of determining one or more candidate cells for an LTM, and transmitting to a terminal setting information for an LTM that includes measurement identification information corresponding to an LTM setting for each candidate cell, wherein the measurement identification information is associated with measurement target information and a reporting setting, and the reporting setting includes information about an event related to an LTM execution condition, and based on the setting information and L3 measurement, whether the event is satisfied for a candidate cell is determined, and if the event is satisfied, an LTM cell switching procedure to the candidate cell may be performed.

[0013] In a wireless communication system according to one embodiment of the present disclosure, a base station may include at least one transceiver, at least one processor connected to communicate with the at least one transceiver, and a memory connected to communicate with the at least one processor and capable of executing the at least one processor individually or in any combination thereof, wherein the base station determines one or more candidate cells for an LTM and transmits configuration information for an LTM, including measurement identification information corresponding to an LTM configuration for each candidate cell, to a terminal. Herein, the measurement identification information is associated with measurement target information and a reporting configuration, and the reporting configuration includes information regarding an event related to an LTM execution condition; based on the configuration information and L3 measurement, whether the event is satisfied for a candidate cell is determined, and if the event is satisfied, an LTM cell switch procedure to the candidate cell may be performed.

[0014] According to one embodiment of the present disclosure, a terminal can reduce the delay time during cell switching or handover by using a conditional LTM for operation for mobility in various vertical or various services in a wireless communication system.

[0015] Figure 1 illustrates the structure of a typical LTE (long-term evolution) system.

[0016] Figure 2 illustrates the wireless protocol structure of an LTE system.

[0017] FIG. 3 illustrates the structure of a next-generation mobile communication system according to one embodiment of the present disclosure.

[0018] FIG. 4 illustrates a wireless protocol structure of a next-generation mobile communication system according to one embodiment of the present disclosure.

[0019] FIG. 5 is a block diagram illustrating the internal structure of a terminal according to one embodiment of the present disclosure.

[0020] FIG. 6 is a block diagram showing the configuration of an NR base station according to one embodiment of the present disclosure.

[0021] Figure 7 illustrates the operation of measurement reporting through measurement settings at layer 3 (L3) in an NR communication system.

[0022] FIG. 8a illustrates a method for deriving L3-based cell signal strength and signaling cell-based signal conditions according to one embodiment of the present disclosure.

[0023] FIG. 8b illustrates a method for deriving L3-based cell signal strength and signaling cell-based signal conditions according to one embodiment of the present disclosure.

[0024] FIG. 9 illustrates another method for deriving layer 1 (L1)-based cell signal strength and signaling cell-based signal conditions according to one embodiment of the present disclosure.

[0025] FIG. 10 illustrates signaling between a terminal and a base station for performing CLTM according to one embodiment of the present disclosure.

[0026] The operating principles of the present disclosure will be described in detail below with reference to the attached drawings. In describing the present invention below, specific descriptions of related known functions or configurations will be omitted if it is determined that such detailed descriptions would unnecessarily obscure the essence of the invention. Furthermore, the terms described below are defined considering their functions in the present invention, and these may vary depending on the intentions or conventions of the user or operator. Therefore, their definitions should be based on the content throughout this specification.

[0027] Terms used in the following description to identify connection nodes, terms referring to network entities, terms referring to messages, terms referring to interfaces between network entities, terms referring to various identification information, etc., are examples provided for the convenience of explanation. Accordingly, the present invention is not limited to the terms described below, and other terms referring to objects having equivalent technical meanings may be used.

[0028] Hereinafter, the base station is an entity that performs resource allocation for terminals and may be at least one of a gNode B, eNode B, Node B, BS (Base Station), wireless access unit, base station controller, or a node on a network. The terminal may include a UE (User Equipment), MS (Mobile Station), cellular phone, smartphone, computer, or a multimedia system capable of performing communication functions. In the present disclosure, the downlink (DL) refers to the wireless transmission path of a signal transmitted by the base station to the terminal, and the uplink (UL) refers to the wireless transmission path of a signal transmitted by the terminal to the base station.

[0029] In addition, while LTE or LTE-A systems may be described below as examples, embodiments of the present disclosure may also be applied to other communication systems having similar technical backgrounds or channel types. For example, 5th generation mobile communication technology (5G, new radio, NR) developed after LTE-A may be included in a system to which embodiments of the present disclosure can be applied, and the 5G below may be a concept that includes existing LTE, LTE-A, and other similar services. Furthermore, the present disclosure may be applied to other communication systems with some modifications made at the discretion of a person with skilled technical knowledge, without significantly departing from the scope of the present disclosure.

[0030] At this time, it will be understood that each block of the process flow diagrams and combinations of the flow diagrams can be executed by computer program instructions. Since these computer program instructions can be loaded into the processor of a general-purpose computer, a special-purpose computer, or other programmable data processing equipment, the instructions executed through the processor of the computer or other programmable data processing equipment create means to perform the functions described in the flow diagram block(s). Since these computer program instructions can also be stored in computer-available or computer-readable memory that can be directed toward the computer or other programmable data processing equipment to implement the function in a specific way, the instructions stored in computer-available or computer-readable memory can also produce a manufactured item containing the means of instruction to perform the function described in the flow diagram block(s). Since computer program instructions can be loaded onto a computer or other programmable data processing equipment, instructions that perform a series of operation steps on the computer or other programmable data processing equipment to create a process executed by the computer can also provide steps for executing the functions described in the flowchart block(s).

[0031] Additionally, each block may represent a module, segment, or part of code containing one or more executable instructions for executing a specific logical function(s). Also, it should be noted that in some alternative execution examples, the functions mentioned in the blocks may occur out of order. For example, two blocks described in succession may actually be executed substantially simultaneously, or the blocks may be executed in reverse order depending on the corresponding function. In this case, the term "part" as used in this embodiment refers to software or hardware components such as a Field Programmable Gate Array (FPGA) or an Application Specific Integrated Circuit (ASIC), and the "part" may perform certain roles. However, the meaning of "part" is not limited to software or hardware. The "part" may be configured to reside in an addressable storage medium or configured to run one or more processors. Accordingly, as an example, 'part' includes components such as software components, object-oriented software components, class components, and task components, as well as processes, functions, attributes, procedures, subroutines, segments of program code, drivers, firmware, microcode, circuits, data, databases, data structures, tables, arrays, and variables. The functions provided within the components and 'parts' may be combined into a smaller number of components and 'parts' or further separated into additional components and 'parts'. Furthermore, the components and 'parts' may be implemented to utilize one or more CPUs within a device or secure multimedia card. Additionally, in an embodiment, 'part' may include one or more processors.

[0032] For the convenience of the following explanation, the present invention uses terms and names defined in the 5GS and NR specifications, which are standards defined by the 3GPP (The 3rd Generation Partnership Project) organization among existing communication standards. However, the present invention is not limited by the above terms and names and can be applied in the same way to wireless communication networks according to other standards. For example, the present invention can be applied to 3GPP 5GS / NR (5th generation mobile communication standard).

[0033] Figure 1 illustrates the structure of a typical LTE system.

[0034] Referring to FIG. 1, the wireless access network of an LTE system may be composed of a next-generation base station (Evolved Node B, hereinafter ENB, Node B or base station) (1-05, 1-10, 1-15, 1-20), a Mobility Management Entity (MME) (1-25), and an S-GW (1-30, Serving-Gateway). A user terminal (User Equipment, hereinafter UE or terminal) (1-35) can connect to an external network through the ENB (1-05 to 1-20) and the S-GW (1-30).

[0035] In FIG. 1, the ENB (1-05 to 1-20) can correspond to the existing Node B of the UMTS system. The ENB is connected to the UE (1-35) via a wireless channel and can perform more complex roles than the existing Node B. In an LTE system, all user traffic, including real-time services such as VoIP (Voice over IP) via the Internet Protocol, can be serviced through a shared channel. Therefore, a device is required to collect status information such as the buffer status, available transmission power status, and channel status of the UEs to perform scheduling, and this can be handled by the ENB (1-05 to 1-20). A single ENB can typically control multiple cells. For example, to achieve a transmission speed of 100 Mbps, the LTE system can use Orthogonal Frequency Division Multiplexing (OFDM) as a wireless access technology, for example, in a 20 MHz bandwidth. In addition, an Adaptive Modulation & Coding (AMC) method can be applied to determine the modulation scheme and channel coding rate according to the channel conditions of the terminal. The S-GW (1-30) is a device that provides a data bearer and can create or remove the data bearer under the control of the MME (1-25). The MME is a device that is responsible for various control functions as well as mobility management functions for the terminal and can be connected to multiple base stations.

[0036] Figure 2 illustrates the wireless protocol structure of an LTE system.

[0037] Referring to FIG. 2, the wireless protocol of the LTE system may consist of a Packet Data Convergence Protocol (PDCP) (2-05, 2-40), Radio Link Control (RLC) (2-10, 2-35), Medium Access Control (MAC) (2-15, 2-30), and a Physical Layer (PHY) (2-20, 2-25) at the terminal and ENB, respectively. PDCP can be responsible for operations such as IP header compression / decompression.

[0038] The main functions of PDCP(2-05, 2-40) can be summarized as follows.

[0039] - Header compression and decompression features (ROHC only)

[0040] - User data transfer function (Transfer of user data)

[0041] - Sequential delivery function (In-sequence delivery of upper layer PDUs at PDCP re-establishment procedure for RLC AM)

[0042] - Order reordering function (For split bearers in DC (only support for RLC AM): PDCP PDU routing for transmission and PDCP PDU reordering for reception)

[0043] - Duplicate detection function (Duplicate detection of lower layer SDUs at PDCP re-establishment procedure for RLC AM)

[0044] - Retransmission function (Retransmission of PDCP SDUs at handover and, for split bearers in DC, of ​​PDCP PDUs at PDCP data-recovery procedure, for RLC AM)

[0045] - Encryption and decryption functions (Ciphering and deciphering)

[0046] - Timer-based SDU discard in uplink.

[0047] Radio Link Control (RLC) (2-10, 2-35) can perform ARQ operations, etc., by reconfiguring PDCP Packet Data Units (PDUs) to an appropriate size. The main functions of RLC can be summarized as follows.

[0048] - Data transfer function (Transfer of upper layer PDUs)

[0049] - ARQ function (Error Correction through ARQ (only for AM data transfer))

[0050] - Concatenation, segmentation, and reassembly functions (Concatenation, segmentation, and reassembly of RLC SDUs (only for UM and AM data transfer))

[0051] - Re-segmentation function (Re-segmentation of RLC data PDUs (only for AM data transfer))

[0052] - Reordering function (Reordering of RLC data PDUs (only for UM and AM data transfer)

[0053] - Duplicate detection function (only for UM and AM data transfer)

[0054] - Error detection function (Protocol error detection (only for AM data transfer))

[0055] - RLC SDU deletion function (RLC SDU discard (only for UM and AM data transfer))

[0056] RLC re-establishment function

[0057] MAC (2-15, 2-30) is connected to multiple RLC layer devices configured in a terminal and can perform operations to multiplex RLC PDUs into MAC PDUs and demultiplex RLC PDUs from MAC PDUs. The main functions of MAC can be summarized as follows.

[0058] - Mapping function (Mapping between logical channels and transport channels)

[0059] - Multiplexing and demultiplexing function (Multiplexing / demultiplexing of MAC SDUs belonging to one or different logical channels into / from transport blocks (TB) delivered to / from the physical layer on transport channels)

[0060] - Scheduling information reporting function

[0061] - HARQ function (Error correction through HARQ)

[0062] - Priority handling between logical channels of one UE

[0063] - Priority handling between UEs by means of dynamic scheduling

[0064] - MBMS service identification function

[0065] - Transport format selection function

[0066] - Padding

[0067] The physical layer (2-20, 2-25) can perform the operation of channel coding and modulating upper layer data, making it into OFDM symbols and transmitting it to the wireless channel, or demodulating OFDM symbols received through the wireless channel and channel decoding them to transmit them to the upper layer.

[0068] FIG. 3 illustrates the structure of a next-generation mobile communication system according to one embodiment of the present disclosure.

[0069] Referring to FIG. 3, the wireless access network of a next-generation mobile communication system (hereinafter NR or 5G) may be composed of a next-generation base station (New Radio Node B, hereinafter NR gNB or NR base station) (3-10) and a next-generation wireless core network (New Radio Core Network, NR CN) (3-05). A next-generation wireless user terminal (New Radio User Equipment, NR UE or terminal) (3-15) can connect to an external network through the NR gNB (3-10) and the NR CN (3-05).

[0070] In FIG. 3, the NR gNB (3-10) can correspond to the eNB (Evolved Node B) of the existing LTE system. The NR gNB is connected to the NR UE (3-15) via a wireless channel and can provide superior service compared to the existing Node B. In the next-generation mobile communication system, all user traffic can be serviced through a shared channel. Therefore, a device is required to collect status information such as the buffer status, available transmission power status, and channel status of the UEs to perform scheduling, and the NR NB (3-10) can handle this scheduling. A single NR gNB can control multiple cells. In the next-generation mobile communication system, to achieve ultra-high-speed data transmission compared to standard LTE, a bandwidth exceeding the standard maximum bandwidth may be applied. Additionally, Orthogonal Frequency Division Multiplexing (OFDM) can be used as the wireless access technology, and beamforming technology can be additionally incorporated. In addition, an Adaptive Modulation & Coding (hereinafter AMC) method may be applied to determine the modulation scheme and channel coding rate according to the channel conditions of the terminal. The NR CN (3-05) can perform functions such as mobility support, bearer configuration, and QoS (quality of service) configuration. The NR CN is a device responsible for various control functions as well as mobility management functions for the terminal, and can be connected to multiple base stations. In addition, the next-generation mobile communication system can be interoperable with the LTE system, and the NR CN can be connected to the MME (3-25) via a network interface. The MME can be connected to the LTE base station eNB (3-30).

[0071] FIG. 4 illustrates the wireless protocol structure of a next-generation mobile communication system according to one embodiment of the present disclosure.

[0072] Referring to FIG. 4, the wireless protocol of the next-generation mobile communication system consists of the NR Service Data Adaptation Protocol (SDAP) (4-01, 4-45), NR PDCP (4-05, 4-40), NR RLC (4-10, 4-35), NR MAC (4-15, 4-30), and NR PHY (4-20, 4-25) at the terminal and the NR base station, respectively.

[0073] The main functions of NR SDAP (4-01, 4-45) may include some of the following functions.

[0074] - User data transfer function (transfer of user plane data)

[0075] - Mapping function between a QoS flow and a DRB for both DL and UL for uplink and downlink

[0076] - Marking QoS flow ID in both DL and UL packets for uplink and downlink

[0077] - Function to map reflective QoS flow to data bearers for uplink SDAP PDUs (reflective QoS flow to DRB mapping for the UL SDAP PDUs).

[0078] For SDAP layer devices, the terminal may receive a Radio Resource Control (RRC) message indicating whether to use the header of the SDAP layer device or to use the functions of the SDAP layer device for each PDCP layer device, for each bearer, or for each logical channel. If the SDAP header is configured, the terminal may be instructed to update or reset the mapping information for the uplink and downlink QoS flows and data bearers using the 1-bit NAS reflective QoS indicator and the 1-bit AS reflective QoS indicator of the SDAP header. The SDAP header may include QoS flow ID information indicating QoS. The QoS information may be used for data processing priorities, scheduling information, etc., to support seamless service.

[0079] The main functions of NR PDCP (4-05, 4-40) may include some of the following functions.

[0080] - Header compression and decompression features (ROHC only)

[0081] - User data transfer function (Transfer of user data)

[0082] - Sequential delivery function (In-sequence delivery of upper layer PDUs)

[0083] - Out-of-sequence delivery of upper layer PDUs

[0084] - Reordering function (PDCP PDU reordering for reception)

[0085] - Duplicate detection function (Duplicate detection of lower layer SDUs)

[0086] - Retransmission of PDCP SDUs

[0087] - Encryption and decryption functions (Ciphering and deciphering)

[0088] - Timer-based SDU discard in uplink.

[0089] In the above description, the reordering function of the NR PDCP device may refer to a function that reorders PDCP PDUs received from a lower layer in order based on the PDCP SN (sequence number). The reordering function of the NR PDCP device may include a function of transmitting data to an upper layer in the reordered order, or a function of transmitting it immediately without considering the order, a function of recording lost PDCP PDUs by reordering, a function of reporting the status of lost PDCP PDUs to the transmitting side, and a function of requesting retransmission of lost PDCP PDUs.

[0090] The main functions of NR RLC(4-10, 4-35) may include some of the following functions.

[0091] - Data transfer function (Transfer of upper layer PDUs)

[0092] - Sequential delivery function (In-sequence delivery of upper layer PDUs)

[0093] - Out-of-sequence delivery of upper layer PDUs

[0094] - ARQ function (Error Correction through ARQ)

[0095] - Concatenation, segmentation, and reassembly functions of RLC SDUs

[0096] - Re-segmentation function (Re-segmentation of RLC data PDUs)

[0097] - Reordering function (Reordering of RLC data PDUs)

[0098] - Duplicate detection

[0099] - Error detection function (Protocol error detection)

[0100] - RLC SDU discard function

[0101] RLC re-establishment function

[0102] In the above description, the in-sequence delivery function of the NR RLC device may refer to the function of delivering RLC SDUs received from a lower layer to an upper layer in sequence. In the case where a single RLC SDU is received divided into multiple RLC SDUs, the in-sequence delivery function of the NR RLC device may include the function of reassembling and delivering them.

[0103] The in-sequence delivery function of the NR RLC device may include 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 by rearranging the order, a function to report the status of lost RLC PDUs to the transmitting side, and a function to request retransmission of lost RLC PDUs.

[0104] The in-sequence delivery function of the NR RLC device may include a function that, in the event of a lost RLC SDU, delivers only the RLC SDUs prior to the lost RLC SDU in order to the upper layer.

[0105] The in-sequence delivery function of the NR RLC device may include a function to deliver all RLC SDUs received before the timer started to the upper layer in order, even if there are lost RLC SDUs, if a predetermined timer has expired.

[0106] The in-sequence delivery function of the NR RLC device may include a function to deliver all RLC SDUs received up to that point to the upper layer in order when a predetermined timer expires, even if there are lost RLC SDUs.

[0107] The NR RLC device can process RLC PDUs in the order they are received, regardless of the sequence number (out-of-sequence delivery), and deliver them to the NR PDCP device.

[0108] When an NR RLC device receives a segment, it can receive segments stored in a buffer or to be received later, reconstruct them into a complete RLC PDU, and then transmit it to an NR PDCP device.

[0109] The NR RLC layer may not include a concatenation function, and the function may be performed by the NR MAC layer or replaced by the multiplexing function of the NR MAC layer.

[0110] In the above description, the out-of-sequence delivery function of the NR RLC device may refer to a function of delivering RLC SDUs received from a lower layer directly to an upper layer regardless of order. The out-of-sequence delivery function of the NR RLC device may include a function of reassembling and delivering RLC SDUs when a single RLC SDU is received divided into multiple RLC SDUs. The out-of-sequence delivery function of the NR RLC device may include a function of storing the RLC SN or PDCP SN of the received RLC PDUs, sorting the order, and recording the lost RLC PDUs.

[0111] The NR MAC (4-15, 4-30) 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.

[0112] - Mapping function (Mapping between logical channels and transport channels)

[0113] - Multiplexing and demultiplexing functions (Multiplexing / demultiplexing of MAC SDUs)

[0114] - Scheduling information reporting function

[0115] - HARQ function (Error correction through HARQ)

[0116] - Priority handling between logical channels of one UE

[0117] - Priority handling between UEs by means of dynamic scheduling

[0118] - MBMS service identification function

[0119] - Transport format selection function

[0120] - Padding

[0121] The NR PHY layer (4-20, 4-25) 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.

[0122] FIG. 5 is a block diagram illustrating the structure of a terminal according to one embodiment of the present disclosure.

[0123] Referring to FIG. 5, the terminal may include an RF (Radio Frequency) processing unit (5-10), a baseband processing unit (5-20), a storage unit (5-30), and a control unit (5-40).

[0124] The RF processing unit (5-10) performs functions for transmitting and receiving signals through a wireless channel, such as signal band conversion and amplification. The RF processing unit (5-10) up-converts the baseband signal provided by the baseband processing unit (5-20) into an RF band signal, 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 (5-10) 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. Additionally, the RF processing unit (5-10) may include multiple RF chains. Furthermore, the RF processing unit (5-10) may perform beamforming. For the above beamforming, the RF processing unit (5-10) 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.

[0125] The baseband processing unit (5-20) 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 (5-20) generates complex symbols by encoding and modulating the transmitted bit sequence. Additionally, when receiving data, the baseband processing unit (5-20) restores the received bit sequence by demodulating and decoding the baseband signal provided by the RF processing unit (5-10). For example, in the case of following the OFDM (orthogonal frequency division multiplexing) method, when transmitting data, the baseband processing unit (5-20) 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 (5-20) divides the baseband signal provided by the RF processing unit (5-10) into OFDM symbol units, restores the signals mapped to subcarriers through a fast Fourier transform (FFT), and then restores the received bit sequence through demodulation and decoding.

[0126] The baseband processing unit (5-20) and the RF processing unit (5-10) transmit and receive signals as described above. Accordingly, the baseband processing unit (5-20) and the RF processing unit (5-10) 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 (5-20) and the RF processing unit (5-10) 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 (5-20) and the RF processing unit (5-10) 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.

[0127] The storage unit (5-30) stores data such as basic programs, application programs, and setting information for the operation of the terminal. In particular, the storage unit (5-30) can store information related to a second connection node that performs wireless communication using a second wireless connection technology. Additionally, the storage unit (5-30) provides the stored data upon request from the control unit (5-40).

[0128] The control unit (5-40) controls the overall operations of the terminal. For example, the control unit (5-40) can control terminal operations related to conditional layer 1 / 2 triggered mobility (CLTM) according to one embodiment of the present disclosure. For example, the control unit (5-40) transmits and receives signals through the baseband processing unit (5-20) and the RF processing unit (5-10). Additionally, the control unit (5-40) writes and reads data to and from the storage unit (5-40). To this end, the control unit (5-40) may include at least one processor. For example, the control unit (5-40) may include a communication processor (CP) that performs control for communication and an application processor (AP) that controls upper layers such as applications. For example, the control unit (5-40) may include a multiple connection processing unit (5-42).

[0129] FIG. 6 is a block diagram showing the configuration of an NR base station according to one embodiment of the present disclosure.

[0130] Referring to FIG. 6, the base station may include an RF processing unit (6-10), a baseband processing unit (6-20), a backhaul communication unit (6-30), a storage unit (6-40), and a control unit (6-50).

[0131] The RF processing unit (6-10) performs functions for transmitting and receiving signals through a wireless channel, such as signal band conversion and amplification. The RF processing unit (6-10) upconverts the baseband signal provided by the baseband processing unit (6-20) into an RF band signal, transmits it through an antenna, and downconverts the RF band signal received through the antenna into a baseband signal. For example, the RF processing unit (6-10) 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 (6-10) may include multiple RF chains. Furthermore, the RF processing unit (6-10) may perform beamforming. For beamforming, the RF processing unit (6-10) may adjust the phase and magnitude of each of the signals transmitted and received through multiple antennas or antenna elements. The above RF processing unit can perform down-to-down MIMO operation by transmitting one or more layers.

[0132] The baseband processing unit (6-20) 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 (6-20) generates complex symbols by encoding and modulating the transmitted bit sequence. Additionally, when receiving data, the baseband processing unit (6-20) restores the received bit sequence by demodulating and decoding the baseband signal provided by the RF processing unit (6-10). For example, in the case of following the OFDM method, when transmitting data, the baseband processing unit (6-20) 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 (6-20) divides the baseband signal provided by the RF processing unit (6-10) 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 (6-20) and the RF processing unit (6-10) transmit and receive signals as described above. Accordingly, the baseband processing unit (6-20) and the RF processing unit (6-10) may be referred to as a transmitting unit, a receiving unit, a transmitting and receiving unit, a communication unit, or a wireless communication unit.

[0133] The backhaul communication unit (6-30) provides an interface for communicating with other nodes within the network. The backhaul communication unit (6-30) converts a bit sequence transmitted from the main base station to other nodes, such as an auxiliary base station or a core network, into a physical signal, and converts a physical signal received from the other nodes into a bit sequence.

[0134] The storage unit (6-40) stores data such as basic programs, application programs, and configuration information for the operation of the main station. In particular, the storage unit (6-40) can store information regarding bearers assigned to connected terminals, measurement results reported from connected terminals, etc. Additionally, the storage unit (6-40) can store information that serves as a criterion for determining whether to provide multiple connections to the terminal or to disconnect them. Furthermore, the storage unit (6-40) provides the stored data upon the request of the control unit (6-50).

[0135] The control unit (6-50) controls the overall operations of the base station. For example, the control unit (6-50) can control base station operations related to the CLTM according to one embodiment of the present disclosure. For example, the control unit (6-50) transmits and receives signals through the baseband processing unit (6-20) and the RF processing unit (6-10) or through the backhaul communication unit (6-30). Additionally, the control unit (6-50) writes and reads data to and from the storage unit (6-40). To this end, the control unit (6-50) may include at least one processor. For example, the control unit (6-50) may include a multiple connection processing unit (6-52).

[0136] Figure 7 illustrates the operation of a measurement report (MR) through a measurement setting at layer 3 (L3) in an NR communication system.

[0137] Referring to FIG. 7, in operation 710, a measurement may be set up for the terminal. In operation 720, the terminal may determine whether a report configuration (e.g., reportConfig) includes (i) reportQuantityRS-Indexes, which represents measurement information per RS ​​index that the terminal must include in the measurement report, and (ii) maxNrofRS-IndexesToReport, which is the maximum number of RS indices to include in the measurement report. If the report configuration (e.g., reportConfig) does not include reportQuantityRS-Indexes or maxNrofRS-IndexesToReport, in operation 725, the terminal may derive cell-unit measurement results for the corresponding cell. If the report configuration (e.g., reportConfig) includes reportQuantityRS-Indexes and maxNrofRS-IndexesToReport, in operation 730, the terminal may derive beam-unit measurement values ​​for the indicated quantity for each serving cell. Additionally, in operation 740, the terminal can derive beam-unit measurements for the indicated quantity for each non-serving cell for the measID associated with the report configuration (e.g., reportConfig) (i.e., for the non-serving MO). In operation 750, a measurement report may be triggered. When a measurement report is triggered, in operation 760, the terminal can transmit to the base station the cell results and beam-unit measurements for each serving cell, including them in the measurement report. And / or, if the reportConfig triggering the MR includes reportAddNeighMeas, the terminal can transmit to the base station the cell measurement results and / or beam measurement results for the best non-serving cell in each serving MO, including them in the measurement report.And / or, for non-serving MO triggered MR, the terminal may include cell results and / or beam results for cells satisfying the event / cycle in the measurement report and transmit them to the base station.

[0138] As shown in FIG. 7, the basic measurement target is the signal strength per cell. And if necessary, if configured by the network, the terminal can measure the beam for the serving cell and include the beam measurement result in the MR, or include the beam result for the best neighbor cell in the MR, or include the cell result and beam result on the non-serving MO that triggered the MR in the MR and transmit the MR to the network. In this case, the terminal can include the measurement result value of the best beam within the maximum number set by the network and the index of the best beam in the MR and transmit it.

[0139] Meanwhile, the purpose of conventionally designed Layer 1 / 2 Triggered Mobility (LTM) is to enable immediate communication with a terminal in a target cell by indicating the target beam available for immediate use in that target cell along with the cell itself when determining the target cell. However, the terminal can perform LTM only after receiving a cell switch command signal from the network; if a frequency in the Frequency Range (FR) 2 and / or FR 3 band is used, momentary signal attenuation may occur, which may result in a failure to receive the cell switch command signal. To prevent the cell switch command signal itself from being transmitted to the terminal due to signal attenuation, a Conditional LTM (CLTM) may be introduced. In this case, when performing LTM to a specific cell, the terminal evaluates condition information pre-indicated by the network; if the condition is satisfied, it moves to the cell where the condition is satisfied and can immediately perform communication using the beam where the condition is satisfied.

[0140] The CLTMs being considered in Release 19 may be associated with layer 1 (L1) event-triggered CSI reports. The following events may be considered as L1 events, and L1-based CLTMs may be performed based on these L1 events. Event LTM 2 through Event LTM 5 represent examples of L1 events.

[0141] Event LTM2: Beam of serving cell becomes worse than absolute threshold;

[0142] Event LTM3: The beam of the candidate cell becomes better than the beam of the serving cell by an amount of offset.

[0143] Event LTM4: Beam of candidate cell becomes better than absolute threshold;

[0144] Event LTM5: Beam of serving cell becomes worse than absolute threshold 1 AND Beam of candidate cell becomes better than another absolute threshold 2.

[0145] All of the above events assume measurement and evaluation at the beam level. However, if CLTM is operated based on the above events, it is not possible to define which actual cell is the target cell, and only target beams satisfying the above events can be defined. However, in order to achieve the purpose of LTM while interoperating with various other services, the conditions of CLTM must be able to define target cells, and must be able to be combined with other conditions previously used in L3 RRM (radio resource management).

[0146] For example, when considering the service of a terminal via NTN, since the temporal and spatial movement of the satellite is already scheduled, the corresponding cell location may also be predetermined in time and space. A time window-based conditional handover has been introduced to account for cases where a terminal receiving the existing NTN service utilizes this scheduled cell location to move to another cell at a specific time without a separate handover (HO) command. In this case, a specified time window value is also considered as a condition, and a combination of that condition and a cell-to-cell signal-based condition can be assigned to the terminal. Similarly, in the case of CLTM, if considering the case based on the cell's predetermined temporal and spatial movement, the condition must first be checked using cell-based signal strength, and the beam-based condition can be considered together with it.

[0147] In addition to NTN, the same service scenario can be considered for cells formed by moving vehicles that travel along predefined routes, such as high-speed trains, mobile IABs, and V2X.

[0148] To satisfy the requirements of such CLTM, the present disclosure introduces new cell-based selection conditions regarding LTM CSI common info provided in LTM, namely information on candidate cells to perform measurements and evaluations for CLTM execution and beams to be considered in those cells, or without such information (e.g., in the case of L3-based CLTM), and additionally proposes the operation of CLTM through a combination of various types of cell-based selection conditions and beam-based selection conditions used in existing L3 RRM.

[0149] In this disclosure, a method using a combination of measurement objects (MOs) and report configurations used in L3 can be considered. This may be simpler than designing a new method for cell quality derivation and inter-cell signal comparison in L1.

[0150] In this case, the things to be considered may be (1) the method of defining cell signal strength, (2) the signal method of cell-based judgment conditions, and (3) the method of configuring final conditions. These will be explained in detail below.

[0151] (1) Method of defining cell signal strength (Cell quality derivation)

[0152] Opt. 1-1. Whether or not LTM CSI common info is configured from the network, the existing cell signal strength derivation method may be used. In this case, the terminal may perform measurements for the cell. Specifically, the terminal may derive cell signal strength values ​​using all beams detected based on the synchronization signal block (SSB) or channel state information reference signal (CSI-RS) transmitted by the cell.

[0153] For example, the average value of all measured beams can be used to derive the cell signal strength value.

[0154] Alternatively, if a specific threshold is set by the network, the terminal can select only beams above that threshold and derive a cell signal strength value using the average value of the signal strengths of those beams.

[0155] Alternatively, the number of beams to be used for deriving cell signal strength may be signaled to the terminal, and in this case, the terminal may select only the said number of beams in order of good signal strength and derive the cell signal strength value using the average value of the signal strength values ​​of the beams.

[0156] Alternatively, a threshold value and a maximum number of beams may be signaled to the terminal, and the terminal may select beams within the maximum number of beams in order of best among the beams exceeding the threshold value, and derive a cell signal strength value using the average value of the signal strengths of those beams. If the number of beams exceeding the threshold value is less than the maximum number of beams, only the beams exceeding the threshold value may be selected, and if the number of beams exceeding the threshold value is greater than the maximum number of beams, up to the maximum number of beams may be selected.

[0157] Opt. 1-2. The network can pre-configure beams to derive cell signal strength.

[0158] The configured beams may be specific beams of specific candidate cells given in LTM CSI common info.

[0159] For example, for the set beams, the cell signal strength can be derived using the average value of the signal strengths of all set beams.

[0160] Alternatively, for the configured beams, if a specific threshold is additionally set by the network, the terminal can select only the beams among the configured beams that are above that threshold and derive the cell signal strength using the average value of the signal strengths of those beams.

[0161] Alternatively, the number of beams to be used for deriving cell signal strength may be signaled to the terminal, and in this case, the terminal may select only the said number of beams in order of good signal strength among the set beams and derive the cell signal strength value using the average value of the signal strength values ​​of the beams.

[0162] Alternatively, a threshold value and a maximum number of beams may be signaled to the terminal together, and the terminal may determine the cell signal strength by selecting beams within the maximum number of beams in order of best among the beams that exceed the threshold value among the set beams, and using the average value of the signal strengths of those beams.

[0163] (2) Signal method of cell-based judgment conditions

[0164] FIGS. 8A and 8B illustrate a method for deriving L3-based cell signal strength and signaling cell-based signal conditions according to one embodiment of the present disclosure.

[0165] FIGS. 8A and 8B illustrate a method using the signal structure of L3 RRM. Referring to FIGS. 8A and 8B, the network can transmit common configuration information for CLTM (e.g., CLTM common config) and candidate configuration information required for each candidate cell (e.g., CLTM per candidate config) to the terminal via an RRC reconfiguration (e.g., RRCReconfiguration) message.

[0166] If the common configuration information does not include LTM CSI common info (e.g., ltm-CSI-ResourceConfig), the terminal can identify the measurement and evaluation target using only other information. In addition, the common configuration information may include information used in the existing LTM, such as configuration information used as a reference setting when the target cell is applied (e.g., ref config), list information of each candidate cell (e.g., ltm candidate release, ltm candidate addmod), and information of candidate cells that require an L2 reset when LTM is performed (e.g., ltm-servingcellNoResetID).

[0167] The configuration for each CLTM candidate cell may include the ID of the corresponding candidate cell configuration, the physical cell identity (PCI) of the corresponding candidate cell, an indicator (e.g., ConfigComplete) indicating whether the configuration is a delta or complete configuration when applied (e.g., ltm-TCIInfo), and the ID information of the beam mapped to the SSB of the corresponding candidate cell (e.g., ltm-TCIInfo). In addition, the configuration for each CLTM candidate cell may include condition information (e.g., condition info). This condition information may include a measurement and evaluation target and condition information to be evaluated based on that target. In this case, the measurement target is indicated in the measurement object (MO), and the condition information evaluated based on the corresponding candidate cell, i.e., event information, may be included in the report configuration (e.g., reportConfig). Furthermore, the measurement ID (measID) composed of this MO and reportConfig may be indicated in the configuration for each corresponding candidate cell.

[0168] Each MO constituting the measId given as a condition for the following options must be a cell that exists at the frequency of the MO for the candidate cell for which the measId is given as a condition.

[0169] Opt. 1 (810). MO may not contain separate CLTM candidate cell and / or beam information. Report Config may include CLTM event types.

[0170] The terminal can check the given measId as condition information for a specific candidate cell and check the MO and ReportConfig that constitute it. If the MO does not contain CLTM candidate cell and / or beam information, the terminal can derive the cell signal strength of the corresponding candidate cell based on the signal strengths of all detected beams. Additionally, the terminal can derive the cell signal strength using the method proposed in Opt. 1-1 of the method for defining cell signal strength (1) described above. Additionally, reportconfig may include event information based on cell signal strength. For example, in the case of condEventA3, if the candidate cell is better than the current serving cell by an offset, the terminal can determine that the event is satisfied. That is, the neighbor cell of each event may refer to the candidate cell indicated as a condition by the measId configured in the corresponding reportconfig. If all measIds indicated as conditions are satisfied, the corresponding candidate cell can be determined as the target cell for CLTM execution.

[0171] Opt. 2 (820). MO may include a specific CLTM candidate cell ID and / or beam information that is the target of measurement / evaluation in that cell. In this case, for a candidate cell indicated by a measId configured in this MO, the terminal can derive the cell signal strength using only the indicated beams. At this time, the terminal may use the Opt. 1-2 method of the cell signal strength definition method (1) described above. Based on the cell signal strength, the terminal can determine whether the event indicated in reportConfig is satisfied. If the event is satisfied for all of the indicated measIds, the terminal can determine the candidate cell as the target cell for CLTM execution.

[0172] Opt. 3 (830). If specific candidate cells and specific beams in those cells are specified as LTM CSI common info in the CLTM common setting, and measId is set as a condition in the candidate cell setting, the terminal may consider the beams of the candidate cells in the LTM CSI common info set above when deriving the signal strength of the candidate cell. At this time, the terminal may use the method of Opt. 1-2 of the method for defining cell signal strength (1) described above. The terminal may determine whether the event specified in reportConfig is satisfied based on the cell signal strength. If the event is satisfied for all of the specified measIds, the terminal may determine the candidate cell as the target cell for CLTM execution.

[0173] Opt. 4 (840). In addition to the operation of specifying beams among the above options, if the network provides the terminal with a beam-specific threshold (e.g., RSRP (reference signal received power) threshold, RSRQ (reference signal received quality) threshold, etc.), the terminal may consider only the beams with a signal strength greater than or equal to the threshold among all beams specified or detected in each option for deriving cell signal strength. Or, if the network specifies a maximum number of beams, the terminal may use only the best beams of the maximum number among all beams specified or detected in each option for deriving cell signal strength. The terminal may determine whether the event specified in reportConfig is satisfied based on the cell signal strength. If the event is satisfied for all of the specified measIds, the terminal may determine the candidate cell as the target cell for CLTM execution.

[0174] FIG. 9 illustrates another method for deriving L1-based cell signal strength and signaling cell-based signal conditions according to one embodiment of the present disclosure.

[0175] FIG. 9 illustrates a method of separately indicating on the L1 signal structure without using the L3 RRM signal structure. In this case, a separate MO is not signaled to the terminal, and the report configuration may not be signaled either. Referring to FIG. 9, the ID / index of each cell-specific beam of specific candidate cells is provided in the LTM common CSI info (e.g., ltm-CSI-ResourceConfig) within the CLTM common configuration, and in the CLTM per candidate configuration (e.g., CLTM per candidate config), each event can be directly referred to (e.g., condition info / event info) and signaled to the terminal. In this case, the event may be at least one of the cell-specific / beam-specific events proposed in the (3) final condition configuration method described later. The base station may set a single or multiple events simultaneously for the terminal. Subsequently, the configuration of the condition and the determination of whether the condition is satisfied may use the method proposed in the (3) final condition configuration method described later.

[0176] In such cases, one of the following options can be used to derive cell count.

[0177] Opt. 1 (910). Even if the beams of a specific candidate cell indicated in the LTM CSI common info are indicated, the terminal can derive the cell signal strength using all beams detected in the candidate cell. The terminal can also evaluate the indicated event for each candidate cell. Since the specific method is the same as Opt. 1 of the description for FIG. 8a, the description may be referenced.

[0178] Opt. 2 (920). The terminal can derive cell signal strength by considering only the beams of specific candidate cells indicated in the LTM CSI common info. The terminal can also evaluate the indicated event for each candidate cell. Since the specific method is the same as Opt. 2 of the description for FIG. 8a, the description may be referenced.

[0179] Opt. 3 (930). In addition to the above cases, when the LTM common setting of the network or each candidate setting signals to the terminal a threshold value for beam signal strength (e.g., RSRP threshold, RSRQ threshold, etc.) and / or a maximum number of beams to consider, the terminal may derive the cell signal strength for the candidate cell by using only the best beams among the given beams that are greater than or equal to the threshold value and / or less than or equal to the indicated maximum number.

[0180] For example, the method for deriving cell signal strength may refer to the description of the method for defining cell signal strength (1) described above. For example, the terminal may derive the cell signal strength as the average value of the beams considered.

[0181] (3) Method of constructing the final condition

[0182] When the above event is transmitted to the terminal, the terminal can determine a specific cell as the target cell by performing a signal-based evaluation for each candidate cell. However, since the actual purpose of the LTM is to determine the target beam of the target cell, an additional operation to determine the target beam in the target cell after comparing cells may be required.

[0183] Opt. 3-1. The terminal may first determine a target cell based on a cell-wise event of the signaling method of the cell-based determination condition (2) described above, and then determine a target beam from that target cell. Determining based on the overall signal strength of the cell rather than considering the beam is meaningful in that it provides a certain level of guaranteed signal quality over a long period of time when the terminal moves within the area of ​​that cell. In this case, the method for determining the target beam may have the following additional options.

[0184] Opt. 3-1-1. The terminal can determine the target beam in the cell in a terminal-implemented manner.

[0185] Opt. 3-1-2. If the network transmits a minimum threshold to the terminal, the terminal can select any beam among the beams having a signal strength greater than or equal to that threshold.

[0186] Opt. 3-1-3. The terminal may select the best beam in the corresponding target cell (e.g., the beam having the best / highest measured value of a specific RSRP, RSRQ, or RSSI (received signal strength indicator)). In this case, the point at which the best beam is determined may be the best beam at the time the corresponding target cell is determined, or it may be the best beam determined among all beams included in the cell signal determination after the signals of all beams have been measured.

[0187] Opt. 3-2. A target cell and a target beam within that cell can be determined based on a combination of cell-based events and beam-based events, that is, the simultaneous satisfaction of each event. In this case, measIds consisting of a report configuration including a cell-based determination event and a report configuration including a beam-based determination event can be simultaneously set as conditions in the settings for each candidate cell. Additionally, measIds containing event conditions for other services can also be indicated as conditions. If the terminal satisfies all events given by multiple measIds, it can determine the candidate cell satisfying the corresponding cell-based event as the target cell and determine the beam satisfying the corresponding beam-based event within that cell as the target beam.

[0188] For example, Event CLTM A3 (when the serving cell is better than the neighbor cell (this candidate cell) by an offset) and Event CLTM T1 can be configured as condition information for a single CLTM candidate cell. In this case, if a terminal is being served by a satellite cell of the NTN and switches to another cell at a specific time at the terminal's expected location, it determines whether the new cell is operational based on the signal strength of the entire cell. Furthermore, if the condition is satisfied that the beam in that cell is better than the serving beam in the current serving cell by an offset, the terminal can perform the CLTM. Through this method, the network can achieve the effect of indicating both cell quality and information on the optimal beam within that cell while moving multiple terminals without signal when a cell shifts within a large cell area of ​​the NTN. This operation reduces complexity as the number of terminals increases and minimizes collision effects when using resources due to RACH (random access channel).

[0189] Here, Event CLTM X is an event proposed in this disclosure for beam-based comparison and may be the following events. In the following beam-based events, neighbor may refer to a candidate cell to which this event is set.

[0190] Event CLTM1: Beam of serving cell becomes better than threshold;

[0191] Event CLTM2: Beam of serving cell becomes worse than absolute threshold;

[0192] Event CLTM3: Beam of candidate cell becomes amount of offset better than beam of serving cell / spcell (special cell);

[0193] Event CLTM4: Beam of candidate cell becomes better than absolute threshold;

[0194] Event CLTM5: Beam of serving cell / spcell becomes worse than absolute threshold1 AND Beam of candidate cell becomes better than another absolute threshold2.

[0195] Additionally, the events for cell-based comparison proposed in this disclosure include Event CLTM Ax, Event CLTM Bx, Event CLTM Dx, Event CLTM Tx, and Event CLTM AxHx.

[0196] Event CLTM A1: Serving becomes better than absolute threshold;

[0197] Event CLTM A2: Serving becomes worse than absolute threshold;

[0198] Event CLTM A3: Neighbor (candidate cell) becomes amount of offset better than Pcell (primary cell) / PSCell (primary SCG (secondary cell group) cell) by the amount of offset;

[0199] Event CLTM A4: Neighbour (candidate cell) becomes better than absolute threshold;

[0200] Event CLTM A5: PCell / PSCell becomes worse than absolute threshold1 AND Neighbour (candidate cell) / SCell becomes better than another absolute threshold2;

[0201] Event CLTM A6: Neighbor (candidate cell) becomes amount of offset better than SCell (secondary cell);

[0202] Event CLTM D1: Distance between UE and a reference location referenceLocation1 becomes larger than configured threshold distanceThreshFromReference1, and distance between UE and a reference location referenceLocation2 of a candidate cell becomes shorter than configured threshold distanceThreshFromReference2;

[0203] Event CLTM D2: The distance between the UE and the serving cell moving reference location determined based on movingReferenceLocation broadcast in SIB19 and its corresponding satellite ephemeris and epoch time becomes larger than the configured threshold distanceThreshFromReference1, and the distance between the UE and a moving reference location determined based on referenceLocation for the candidate cell in MO and its corresponding satellite ephemeris and epoch time becomes shorter than the configured threshold distanceThreshFromReference2;

[0204] Event CLTM T1: Time measured at UE becomes more than configured threshold t1-Threshold but is less than t1-Threshold + duration;

[0205] Event CLTM H1: Aerial UE altitude becomes higher than a threshold;

[0206] Event CLTM H2: Aerial UE altitude becomes lower than a threshold;

[0207] Event CLTM A3H1: Neighbour (candidate cell) becomes offset better than SpCell and the Aerial UE altitude becomes higher than a threshold;

[0208] Event CLTM A3H2: Neighbour (candidate cell) becomes offset better than SpCell and the Aerial UE altitude becomes lower than a threshold;

[0209] Event CLTM A4H1: Neighbour (candidate cell) becomes better than threshold1 and the Aerial UE altitude becomes higher than a threshold2;

[0210] Event CLTM A4H2: Neighbour (candidate cell) becomes better than threshold1 and the Aerial UE altitude becomes lower than a threshold2;

[0211] Event CLTM A5H1: SpCell becomes worse than threshold1 and neighbor (candidate cell) becomes better than threshold2 and the Aerial UE altitude becomes higher than a threshold3;

[0212] Event CLTM A5H2: SpCell becomes worse than threshold1 and neighbor (candidate cell) becomes better than threshold2 and the Aerial UE altitude becomes lower than a threshold3.

[0213] In another embodiment, for Events A3, A4, A5, D1, D2, and T1, since there is already a condition targeting a conditional reconfiguration candidate cell, for these events, the existing conditional reconfiguration event can be reused as a cell-based condition determination event of the CLTM. In this case, the target is not only conditional reconfiguration, but can also be included in the report Config as a condition of the CLTM candidate cell and configured as a measid in the configuration of the CLTM candidate cell to be configured for the terminal.

[0214] Opt. 3-3. When setting multiple conditions for a candidate cell, the network may transmit to the terminal the priority itself to be considered when each event is satisfied. In this case, the terminal may perform evaluations sequentially according to the priority associated with each event.

[0215] For example, the terminal determines whether the conditions of the event with the highest priority are satisfied, and if the conditions of the event with the highest priority are satisfied, it can determine whether the conditions of the event with the next highest priority are satisfied. If the conditions of the event with the highest priority are not satisfied, the terminal may not determine whether the conditions of the event with the next highest priority are satisfied. The terminal determines whether the conditions of the event are satisfied according to priority, and if the conditions of all events of all priorities are satisfied, it can select the target cell / target beam associated with the event.

[0216] For example, priorities can be set separately for beam-based events and cell-based events.

[0217] In the case of Opt. 3-1 above, the network can ensure the upper leveling of the average signal strength in the corresponding cell area by prioritizing the overall cell signal. However, in the case of Opt. 3-2, since the network can finely configure the usability of specific beams, if the serving of specific beams is dominant in a cell deployment situation, the network can enable detailed control of the beam signals by adding conditions to the signals of those beams.

[0218] FIG. 10 illustrates signaling between a terminal and a base station for performing CLTM according to one embodiment of the present disclosure.

[0219] Referring to Fig. 10, the terminal can maintain a connected (RRC_Connected) state.

[0220] In operation 1010, the terminal that previously received measurement settings from the network can send the measurement results to the serving base station.

[0221] In operation 1015, the base station that receives the report on the measurement results can determine the candidate cell for the CLTM and undergo the CLTM preparation process. The serving base station can receive the target cell configuration from the target cell base station while receiving the admission control result from the candidate base station operating the candidate cell. The serving base station can determine the conditions for the allowed candidate cell and transmit the condition-related information to the terminal. For example, in operation 1020, the serving base station can transmit to the terminal measurement configuration information consisting of an MO containing measurement target information for the CLTM, a reportConfig containing cell-by-cell and / or beam-by-beam decision event information based on the candidate cell, and a combination thereof, and can transmit to the terminal the measId added as a condition to the candidate cell configuration of the CLTM. In an embodiment using an L1-based signaling scheme (e.g., FIG. 9), instead of MO and reportConfig, each CLTM common setting may contain measurement target information (e.g., cell, beam), and condition information including cell-based and / or beam-based events to be considered in that cell may be instructed to the terminal in a candidate cell-specific CLTM setting. In this case, RRCReconfiguration or a corresponding RRC message may be used.

[0222] In operation 1030, the terminal can send a response to the RRCReconfiguration message (e.g., an RRC reconfiguration complete message) to the base station.

[0223] After receiving the above RRCReconfiguration message, in operation 1040, the terminal can start a measurement according to the MO included in the measurement settings. Additionally, the terminal can check the cell and / or beam-based condition information included in the reportConfig corresponding to the measId given to each CLTM candidate cell and evaluate whether the conditions are satisfied accordingly.

[0224] In operation 1050, if any of the conditions of the indicated candidate cells are satisfied, the terminal can determine the target cell that satisfies the condition and perform a handover or LTM cell switch to the determined target cell.

[0225] In operation 1060, the terminal can disconnect from the source cell and apply settings to the target cell.

[0226] If a RACH setting is given, the terminal can proceed with the RACH procedure in operation 1070.

[0227] If the RACH procedure is successfully completed, in operation 1080, the terminal may send an LTM cell switch complete message to the target cell. For example, this message may be an RRCReconfigurationComplete message. This message may include an indicator that the terminal has performed a move through the CLTM.

[0228] The base station of the target cell that receives the above LTM cell switch complete message can transmit CLTM instruction completion information to the source CU (centralized unit) regarding the execution of CLTM of the terminal.

[0229] 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.

[0230] 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.

[0231] Such programs (software modules, software) may be stored in random access memory, non-volatile memory including flash memory, ROM (Read Only Memory), Electrically Erasable Programmable Read Only Memory (EEPROM), magnetic disc storage devices, Compact Disc-ROM (CD-ROM), Digital Versatile Discs (DVDs), or other forms of optical storage devices, magnetic cassettes. Alternatively, they may be stored in memory composed of some or all of these. Additionally, each constituent memory may include multiple units.

[0232] 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.

[0233] 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 disclosure is not limited to singular or plural components; even if a component is expressed in the plural form, it may be composed of a singular form, or even if a component is expressed in the singular form, it may be composed of a plural form.

[0234] 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 disclosure. Therefore, the scope of the present disclosure should not be limited to the described embodiments, but should be defined by the claims set forth below as well as equivalents thereof.

Claims

1. A method performed by a terminal in a wireless communication system, A step of receiving configuration information for LTM (layer 1 / layer 2 triggered mobility), wherein the configuration information includes measurement object information and measurement identification information associated with a report configuration, and the report configuration includes information about an event associated with an LTM execution condition; A step of determining whether a candidate cell satisfies the event based on the above setting information and L3 (layer 3) measurement; and If the above event is satisfied, the step of performing an LTM cell switch procedure to the candidate cell is included. The above measurement identification information corresponds to the LTM setting for each candidate cell, a method.

2. In Paragraph 1, A method characterized by determining that the event is satisfied when the measurement result of the above candidate cell is better by an offset than the measurement result of PCell (primary cell) or PSCell (primary SCG cell).

3. In Paragraph 1, A method characterized by determining that the event is satisfied when PCell (primary cell) or PSCell (primary SCG cell) deteriorates below a first absolute threshold and the candidate cell improves above a second absolute threshold.

4. In claim 1, the step of determining whether the candidate cell satisfies the above event is: A step of measuring all SSB (synchronization signal block) or all CSI-RS (channel state information reference signal) received from the above candidate cell and calculating an average value; and A method characterized by including a step of determining whether the LTM execution condition related to the event is satisfied using the above average value.

5. In Paragraph 1, The method further includes the step of receiving at least one of information regarding a threshold value or information regarding a maximum number of beams, and The step of determining whether the above event is satisfied for a candidate cell is: A step of measuring all reference signals received from the above candidate cell; A step of selecting at least one beam among the beams corresponding to all reference signals based on at least one of the information regarding the threshold value or the information regarding the maximum number of beams; A step of deriving the signal strength of the candidate cell based on at least one selected beam; and A method characterized by including the step of determining whether the LTM execution condition associated with the event is satisfied based on the signal strength of the candidate cell.

6. In Paragraph 1, A method characterized by setting multiple events and the priority of each event through information regarding events related to LTM execution conditions within the above-mentioned reporting settings.

7. In a terminal of a wireless communication system, At least one transceiver; At least one processor connected to the above at least one transceiver so as to be able to communicate; and Connected to communicate with at least one processor and capable of executing individually or in any combination of the at least one processor, the terminal: Receives configuration information for LTM (layer 1 / layer 2 triggered mobility), said configuration information includes measurement object information and measurement identification information associated with a report configuration, and said report configuration includes information about events related to LTM execution conditions, and Based on the above configuration information and L3 (layer 3) measurement, it is determined whether the above event is satisfied for a candidate cell, and It includes a memory that stores a command to perform an LTM cell switch procedure to the candidate cell when the above event is satisfied, and The above measurement identification information is a terminal corresponding to the LTM setting for each candidate cell.

8. In Paragraph 7, A terminal characterized by determining that the event is satisfied when the measurement result of the above candidate cell is better by an offset than the measurement result of PCell (primary cell) or PSCell (primary SCG cell).

9. In Paragraph 7, A terminal characterized by determining that the event is satisfied when PCell (primary cell) or PSCell (primary SCG cell) deteriorates below a first absolute threshold and the candidate cell improves above a second absolute threshold.

10. In claim 7, the command is for determining whether the terminal satisfies the event with respect to the candidate cell: All SSBs (synchronization signal blocks) or all CSI-RSs (channel state information reference signals) received from the above candidate cell are measured to calculate an average value, and A terminal characterized by determining whether the LTM execution condition related to the event is satisfied using the above average value.

11. A terminal according to claim 7, wherein the command causes the terminal to further receive at least one of information regarding a threshold value or information regarding the maximum number of beams.

12. A method performed by a base station in a wireless communication system, A step of determining one or more candidate cells for LTM (layer 1 / layer 2 triggered mobility); and The method includes the step of transmitting setting information for an LTM to a terminal, the LTM including measurement identification information corresponding to the LTM setting for each candidate cell. The above measurement identification information is associated with measurement object information and report configuration, and The above reporting settings include information about events related to LTM execution conditions, and Based on the above configuration information and L3 (layer 3) measurement, it is determined whether the above event is satisfied for a candidate cell, and, A method in which, when the above event is satisfied, an LTM cell switch procedure to the candidate cell is performed.

13. In Paragraph 12, A method characterized by determining that the event is satisfied when the measurement result of the candidate cell is better by an offset than the measurement result of PCell (primary cell) or PSCell (primary SCG cell), or when PCell (primary cell) or PSCell (primary SCG cell) is worse than a first absolute threshold and the candidate cell is better than a second absolute threshold.

14. In Paragraph 12, A method characterized by setting multiple events and the priority of each event through information regarding events related to LTM execution conditions within the above-mentioned reporting settings.

15. In a base station of a wireless communication system, At least one transceiver; At least one processor connected to the above at least one transceiver so as to be able to communicate; and Connected to communicate with at least one processor and capable of executing individually or in any combination of the at least one processor, the base station: Determine one or more candidate cells for LTM (layer 1 / layer 2 triggered mobility), and It includes a memory that stores a command to transmit to a terminal setting information for an LTM, which includes measurement identification information corresponding to the LTM setting for each candidate cell, and The above measurement identification information is associated with measurement object information and report configuration, and The above reporting settings include information about events related to LTM execution conditions, and Based on the above configuration information and L3 (layer 3) measurement, it is determined whether the above event is satisfied for a candidate cell, and, A base station in which an LTM cell switch procedure to the candidate cell is performed when the above event is satisfied.

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