Early ta acquisition method and device for supporting conditional LTM without random access in next-generation mobile communication system

Abstract

The present disclosure relates to a 5G or 6G communication system capable of increasing the data transmission rate and maximizing the frequency efficiency. More specifically, disclosed is a method performed by a terminal in a wireless communication system. The method comprises the steps of: receiving, from a base station, an RRC reconfiguration message including configuration information about a candidate cell of conditional LTM (including information about the value of a timer, which is associated with the candidate cell and for identifying TA validity) and information about an execution condition of the conditional LTM; performing valuation on whether the execution condition of the conditional LTM is satisfied; receiving, from the base station, a MAC CE including information about a TA value of the candidate cell; and when the execution condition is satisfied and the timer is running, performing RACH-less conditional LTM cell change by applying the TA value.

Description

Method and apparatus for acquiring EARLY TA to support conditional LTM without random access in next-generation mobile communication systems

[0001] The present disclosure relates to terminal and base station operations in a wireless communication system (or, mobile communication system). Specifically, the present disclosure relates to a method for supporting conditional L1 / L2-based mobility (L1 / L2 triggered mobility, LTM).

[0002] 5G mobile communication technology defines wide frequency bands to enable fast transmission speeds and new services, and can be implemented not only in sub-6GHz bands such as 3.5 GHz ('Sub 6GHz') but also in ultra-high frequency bands known as millimeter wave (mmWave), such as 28GHz and 39GHz ('Above 6GHz'). Furthermore, for 6G mobile communication technology, which is referred to as a system beyond 5G, it is expected to become crucial to secure new frequency resources—including not only the 5G Sub 6GHz and ultra-high frequency bands but also the mid-frequency band (7-24 GHz), known as the Upper Mid band—and to efficiently utilize all available frequency resources as needed. This is necessary to handle the surge in data traffic driven by the spread of AI (artificial intelligence) technology and the increase in streaming services, and to improve user experience. To this end, reallocation, reuse, or sharing of existing frequency bands from 2G to 5G for 6G may also be considered. Separately, since the introduction of 5G, the telecommunications market has shown increasing interest in system operation efficiency, sustainability, and user experience improvement. Accordingly, not only are improvements in traditional communication performance, such as data transmission speed and latency, becoming increasingly important, but the introduction of new innovative technologies such as AI, reduction of operating costs, improvement of energy efficiency, expansion of service coverage, and introduction of new services are also becoming more critical.

[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 included beamforming and massive MIMO to mitigate path loss and increase propagation distance in ultra-high frequency bands; support for various numerologies (such as operating multiple subcarrier spacings) and dynamic operation of slot formats for the efficient utilization of ultra-high frequency resources; initial access technologies to support multi-beam transmission and broadband; definition and operation of band-width parts (BWPs); new channel coding methods such as low-density parity check (LDPC) codes for high-volume data transmission and polar codes for the reliable transmission of control information; L2 pre-processing; and networks providing dedicated networks specialized for specific services. Standardization of network slicing and the like has been carried out.

[0004] Since the early days of 5G mobile communication technology, discussions have been held regarding the improvement and enhancement of the initial technology, taking into account the services that 5G technology was intended to support. These include V2X (vehicle-to-everything), which assists autonomous vehicles in making driving decisions and enhances user convenience based on location and status information transmitted by vehicles; NR-U (new radio unlicensed), which aims for system operation compliant with various regulatory requirements in unlicensed bands; UE power saving technology for NR terminals; non-terrestrial network (NTN), a direct terminal-satellite communication for securing coverage in areas where communication with terrestrial networks is impossible; positioning; supporting NR operation up to 71 GHz; support of reduced capability NR devices for lower cost and complexity compared to general terminals; UE power saving enhancement for improved power management in preparation for the utilization of various terminal types; and sidelink enhancement. Evolution of redundancy technology (duplex enhancements) researching a new form of duplex method called subband non-overlapping full duplex (SBFD), network energy saving that maximizes idle periods during which base stations operate in maximum power saving mode and reduces power consumption,Physical layer standardization was conducted for technologies such as network-controlled repeaters, which have improved performance compared to existing repeaters by being equipped with the function of receiving and processing side control information from the network.

[0005] Furthermore, the standardization of Intelligent Factories (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 and access links; Mobility Enhancement technologies including Conditional Handover and Dual Active Protocol Stack (DAPS) Handover; 2-step Random Access for Non-Release (RACH for NR) to simplify random access procedures; multicast and broadcast; support for multi-USIM devices that provide services to users using information from two or more SIMs; sidelink relay, which provides relay-related functions to support connections between terminals at long distances and between terminals and networks; Small Data Transmission (SDT in an inactive state), which transmits small data or signaling in an inactive state without transitioning to a connection state; and Layer 1 / L2 Triggered Mobility (LTM) / Continuous Conditional Standardization of the wireless interface architecture / protocol layer for technologies such as mobility enhancements including subsequent conditional PSCell addition / change (SCAC) and conditional handover with candidate SCGs (CHO with candidate SCGs), and XR enhancements to support XR services in NR systems has also been carried out,Systems regarding 5G baseline architectures for integrating Network Functions Virtualization (NFV) and Software-Defined Networking (SDN) technologies (e.g., service-based architecture, service-based interface); Mobile Edge Computing (MEC), which provides services based on the terminal's location; Non-Public Networks (NPN), which are accessible only to authorized terminals for non-public purposes; Disaster Roaming, which supports the use of communication services through other carrier networks in the event of a telecommunications disaster; Proximity-Based Service via 5GS; Support for Uncrewed Aerial Vehicles (UAVs) to assist with remote identification, tracking, and authorization; Architecture enhancements to support XR and interactive media services; 5GS for supporting AI / ML (artificial intelligence / machine learning) services; and Advanced Mobile Edge Computing, which provides edge computing services on roaming networks. Standardization in the architecture / service fields also proceeded.

[0006] Currently, at the physical layer, standardization is underway for technologies such as beam prediction using AI / ML technology, CSI (channel state information) prediction for improved positioning accuracy, ultra-low power terminal technology using low-power wake-up receivers, technology for transmitting LTE (long term evolution) broadcasts to 5G networks, MIMO transmission technology using multiple base stations, and ambient IoT, which transmits data by acquiring power from an external source without a battery. At the wireless interface architecture / protocol layer, standardization is underway for supporting LTM scenarios between Central Units (CUs) and conditional LTM, supporting the same XR service simultaneously among multiple devices, improving and evolving NTN coverage, supporting mobility based on AI / ML, and relaying connections between terminals across multiple hops between terminals and networks. In addition, standardization is underway in the fields of system architecture and services regarding communication optimization methods for satellites, energy usage management and efficiency of 5G systems, user plane evolution based on SBI, Ambient IoT technology, data service provision methods in IMS (IP multimedia subsystem), and avatar communication services. Once 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 functions and performance of 5G mobile communication systems and to integrate the operation of connected devices.To this end, additional new research is planned to be conducted on eXtended Reality (XR) to efficiently support augmented reality (AR), virtual reality (VR), mixed reality (MR), 5G performance improvement and complexity reduction using AI / ML, support for AI services, support for metaverse services, and drone communication.

[0007] Furthermore, the advancement of these 5G mobile communication systems is expected to enhance 5G performance while serving as the foundation for the ultimate evolution into 6G. In the 6G era, the three major 5G services mentioned earlier—eMBB, URLLC, and mMTC—are expected to evolve and expand into immersive communication (IC), hyper-reliable and low-latency communication (HRLLC), and massive communication (MC), respectively. In addition, new services such as AI-integrated communication, integrated sensing and communication, and ubiquitous connectivity are planned to be additionally supported. Enhanced performance requirements compared to 5G are essential for these diverse 6G services, and standardization to define these requirements is currently underway.

[0008] As such, in order to satisfy the expanded services and enhanced performance requirements of 6G, it is expected that not only will existing communication performance be improved, but system operations will also be optimized and streamlined through the introduction of AI technology, improved energy efficiency, expanded coverage, and the application of next-generation security technology, and the development of sustainable communication technology will be essential.

[0009] To this end, AI internalization technology that applies the latest AI technology across all areas from the communication system design stage to development, management, and operation to realize improved communication performance and network automation and efficiency; technology to improve user perceived performance and network operational efficiency by reducing power consumption of networks and terminals; technology to reduce power consumption in core base station components such as RF (radio frequency) and modems, as well as in channel coding and signal modulation / demodulation transmission and reception processes; multi-antenna transmission technology (eXtreme MIMO, X-MIMO) utilizing large-scale antennas to overcome propagation path loss caused by higher frequencies compared to the 3.5GHz band of 5G communication and provide equivalent coverage; multi-base station-based transmission and reception technology (distributed MIMO, D-MIMO) to improve quality in cell boundary areas; sub-band non-overlapping full duplex (SBFD) technology for enhancing frequency efficiency and system networks; next-generation encryption technology (post-quantum cryptography, PQC) and zero trust architecture (ZTA) technology to strengthen 6G communication security; and initial connection delay and mobility delay Intensive research is planned to be conducted on minimization techniques, the design of hardware-friendly protocol structures for ultra-high-speed data processing, and the expanded application of integrity protection techniques.

[0010] In addition, research is planned on the structure of mobile communication systems (prevention of redundant functions, function simplification, etc.), the introduction of new planes for operator service provision, measures for protecting user privacy, immersive services, enhancement of network resiliency, network sharing technology, enhanced security technology (false base station, lower layer protection, etc.), and intent-based network operation and management.

[0011] As a result of the aforementioned developments and advancements in wireless communication systems, it has become possible to provide various services, and thus measures are required to facilitate the smooth provision of these services.

[0012] Meanwhile, in high-speed, high-frequency networks such as 5G, terminals often pass through cell boundaries quickly or the frequency environment changes rapidly, and in response, it is necessary to perform handovers quickly and accurately. Therefore, the concept of L1 / L2 triggered mobility (LTM) has been introduced to effectively guarantee terminal mobility based on information collected at the physical layer (layer-1) and data link layer (layer-2), and discussions are underway to reduce the time required to perform LTM operations or signaling overhead.

[0013] Accordingly, one objective of the present disclosure is to provide a method for supporting a random access-free conditional LTM (RACH-less conditional LTM) to reduce the interruption time caused by the operation of uplink synchronization with a target cell when a terminal performs conditional L1 / L2 triggered mobility (LTM; L1 / L2-based mobility).

[0014] In addition, one objective of the present disclosure is to provide a specific method for a terminal to acquire and handle a timing advance (TA) in a RACH-less conditional LTM to support an LTM without random access.

[0015] In addition, one objective of the present disclosure is to propose a structure of a new MAC (medium access control) CE (control element) used to transmit the TA value of a target cell to a terminal in order to support LTM without random access.

[0016] The technical problems to be solved in the various embodiments of the present disclosure are not limited to those mentioned above, and other unmentioned technical problems may be considered by those skilled in the art from the various embodiments of the present disclosure described below.

[0017] According to one example of the present disclosure for solving the above-mentioned problems, a method performed by a terminal in a wireless communication system may be provided. The method may include: receiving a radio resource control (RRC) reset message from a base station that includes configuration information for a candidate cell of a conditional LTM (layer 1 / layer 2 triggered mobility) and information on the execution conditions of the conditional LTM, wherein the configuration information includes information on the value of a timer for identifying the validity of a timing advance (TA), and the timer is associated with the candidate cell; evaluating whether the execution conditions of the conditional LTM are satisfied based on the information on the execution conditions of the conditional LTM; receiving a medium access control element (MAC CE) from the base station that includes information on the TA value of the candidate cell; checking whether the timer is running if the execution conditions are satisfied; and, if the timer is running, performing a random access channel (RACH)-less conditional LTM cell switch by applying the TA value.

[0018] According to one example of the present disclosure, a method performed by a base station in a wireless communication system may be provided. The method comprises the steps of: transmitting to a terminal a radio resource control (RRC) reset message including configuration information for a candidate cell of a conditional LTM (layer 1 / layer 2 triggered mobility) and information on an execution condition of the conditional LTM, wherein the configuration information includes information on a value of a timer for identifying a timing advance (TA) validity, and the timer is associated with the candidate cell; receiving from the candidate cell information on a TA value of the candidate cell; and transmitting to the terminal a medium access control element (MAC CE) including the information on the TA value; and, when the execution condition is satisfied and the timer is running, a random access channel (RACH)-less conditional LTM cell switch may be performed based on the TA value.

[0019] According to one example of the present disclosure, a terminal may be provided in a wireless communication system. The terminal comprises: a transceiver; and at least one processor connected to communicate with the transceiver; and connected to communicate with at least one processor, and the terminal may include: receiving a radio resource control (RRC) reset message from a base station that includes setting information for a candidate cell of a conditional LTM (layer 1 / layer 2 triggered mobility) and information on the execution condition of the conditional LTM; the setting information includes information on the value of a timer for identifying the validity of a timing advance (TA), and the timer is associated with the candidate cell; evaluating whether the execution condition of the conditional LTM is satisfied based on the information on the execution condition of the conditional LTM; receiving a medium access control element (MAC CE) from the base station that includes information on the TA value of the candidate cell; if the execution condition is satisfied, checking whether the timer is running; and if the timer is running, storing a command that causes a random access channel (RACH)-less conditional LTM cell switch to be performed by applying the TA value.

[0020] According to one example of the present disclosure, a base station may be provided in a wireless communication system. The base station comprises: a transceiver; and at least one processor connected to communicate with the transceiver; and connected to communicate with at least one processor, and the base station may include: a radio resource control (RRC) reset message including configuration information for a candidate cell of a conditional LTM (layer 1 / layer 2 triggered mobility) and information on the execution condition of the conditional LTM to a terminal, wherein the configuration information includes information on the value of a timer for identifying the validity of a timing advance (TA), the timer is associated with the candidate cell, receives information on the TA value of the candidate cell from the candidate cell, and a memory storing a command that causes the terminal to transmit a medium access control element (MAC CE) including the information on the TA value; and when the execution condition is satisfied and the timer is running, a random access channel (RACH)-less conditional LTM cell switch may be performed based on the TA value.

[0021] The various examples of the present disclosure described above are merely some of the preferred embodiments of the present disclosure, and various embodiments reflecting the technical features of the various examples of the present disclosure can be derived and understood by those skilled in the art based on the detailed description to be described below.

[0022] By using a method that supports RACH-less conditional LTM according to the example of the present disclosure, when a terminal performs conditional LTM, a random access operation that synchronizes uplink with a target cell can be omitted, thereby effectively reducing the interruption time during cell change.

[0023] The effects obtainable in the present disclosure are not limited to those mentioned in the various embodiments, and other unmentioned effects will be clearly understood by those skilled in the art to which the present disclosure pertains from the description below.

[0024] To more clearly explain the technical methods of the embodiments proposed in this disclosure, the drawings of the embodiments are briefly introduced. The following drawings are for reference only to the embodiments of this disclosure and are not intended to limit this disclosure.

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

[0026] FIG. 2 is a drawing illustrating the wireless protocol structure of a next-generation mobile communication system according to one embodiment of the present disclosure.

[0027] FIG. 3 is a drawing illustrating the structure of another next-generation mobile communication system according to one embodiment of the present disclosure.

[0028] FIG. 4 is a diagram illustrating a scenario for inter-cell beam management according to one embodiment of the disclosure, in which a terminal transmits and receives data through the beam of a TRP of a neighboring cell that supports beam changing based on L1 / L2 while maintaining a connection state with a serving cell.

[0029] FIG. 5 is a diagram illustrating a scenario in which a terminal according to one embodiment 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.

[0030] FIG. 6 is a diagram illustrating the overall operation for supporting conditional LTM operation in cells within the same CU according to one embodiment of the present disclosure.

[0031] FIG. 7 is a diagram illustrating the overall operation for supporting conditional LTM operation without random access in cells within the same CU according to one embodiment of the present disclosure.

[0032] FIG. 8 is a diagram illustrating a MAC CE structure that transmits the TA value of an LTM candidate cell obtained by a source cell to a terminal according to one embodiment of the present disclosure.

[0033] FIG. 9 is a diagram illustrating the overall terminal operation of performing a conditional LTM without random access according to one embodiment of the present disclosure.

[0034] FIG. 10 is a drawing illustrating base station operation according to one embodiment of the present disclosure.

[0035] FIG. 11 is a block diagram illustrating the internal structure of a terminal according to one embodiment of the present disclosure.

[0036] FIG. 12 is a block diagram illustrating the structure of a base station according to one embodiment of the present disclosure.

[0037] 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 might unnecessarily obscure the essence of the 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.

[0038] In the following description of the present invention, specific descriptions of related known functions or configurations will be omitted if it is determined that such detailed descriptions may unnecessarily obscure the essence of the invention. Embodiments of the present invention will be described below with reference to the attached drawings.

[0039] 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.

[0040] Hereinafter, a base station is an entity that performs resource allocation for terminals and may be at least one of a gNode B, eNode B, Node B, BS (Base Station), radio access unit, base station controller, or a node on a network. A terminal may include a UE (User Equipment), MS (Mobile Station), cellular phone, smartphone, computer, or a multimedia system capable of performing communication functions. In this disclosure, a downlink (DL) refers to a wireless transmission path of a signal transmitted by a base station to a terminal, and an uplink (UL) refers to a wireless transmission path of a signal transmitted by a terminal to a base station. Furthermore, while an LTE or LTE-A system may be described as an example below, embodiments of this disclosure may be applied to other communication systems having similar technical backgrounds or channel types. For example, 5th generation mobile communication technology (5G, new radio, NR) developed after LTE-A may be included in a system to which embodiments of this disclosure can be applied, and the 5G below may be a concept that includes existing LTE, LTE-A, and other similar services. Furthermore, the present disclosure may be applied to other communication systems with some modifications made at the discretion of a person with skilled technical knowledge, without departing significantly from the scope of the present disclosure. In this case, it will be understood that each block of the process flow diagrams and combinations of the flow diagrams may be executed by computer program instructions.

[0041] Since these computer program instructions can be loaded onto the processor of a general-purpose computer, a computer for special purposes, or other programmable data processing equipment, the instructions executed through the processor of the computer or other programmable data processing equipment create means for performing the functions described in the flowchart block(s). Since these computer program instructions can also be stored in computer-available or computer-readable memory that can be directed toward the computer or other programmable data processing equipment to implement functions in a specific way, the instructions stored in computer-available or computer-readable memory can also produce a manufactured item containing means of instruction for performing the functions described in the flowchart block(s). Since the computer program instructions can also be loaded onto the computer or other programmable data processing equipment, the instructions that perform a series of operation steps on the computer or other programmable data processing equipment to create a computer-executable process can also provide steps for performing the functions described in the flowchart block(s).

[0042] 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.

[0043] 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.

[0044] FIG. 1a is a drawing illustrating the structure of a next-generation mobile communication system according to one embodiment of the present disclosure.

[0045] Referring to FIG. 1a, as illustrated in FIG. 1a, the wireless access network of a next-generation mobile communication system may be composed 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) can connect to an external network through the NR NB (1a-10) and the NR CN (1a-05).

[0046] In FIG. 1a, the NR NB (1a-10) corresponds to the eNB (Evolved Node B) of the existing LTE (long term evolution) system. The NR NB is connected to the NR UE (1a-15) via a wireless channel and can provide the terminal with a service superior to that of the existing Node B. In the next-generation mobile communication system, since all user traffic is serviced through a shared channel, a device is required to collect state information such as the buffer status, available transmission power status, and channel status of the UEs to perform scheduling, and this is handled by the NR NB (1a-10). A single NR NB can typically control multiple cells. To achieve ultra-high-speed data transmission compared to existing LTE, it can have a maximum bandwidth greater than that of existing LTE, and beamforming technology can be additionally incorporated by using Orthogonal Frequency Division Multiplexing (hereinafter referred to as OFDM) as the wireless access technology. In addition, an Adaptive Modulation & Coding (hereinafter referred to as AMC) method is applied to determine the modulation scheme and channel coding rate according to the channel conditions of the terminal.

[0047] The NR CN (1a-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 terminals, and can be connected to multiple base stations. In addition, the next-generation mobile communication system can be interoperable with existing LTE systems, and the NR CN can be connected to the MME (mobility management entity, 1a-25) via a network interface. The MME can be connected to the existing base station eNB (1a-30).

[0048] FIG. 2 is a drawing illustrating the wireless protocol structure of a next-generation mobile communication system according to one embodiment of the present disclosure.

[0049] Referring to FIG. 2, the wireless protocol of the next-generation mobile communication system consists of NR SDAP (NR service data adaptation protocol, 2-01, 2-45), NR PDCP (NR packet data convergence protocol, 2-05, 2-40), NR RLC (NR radio link control, 2-10, 2-35), and NR MAC (NR medium access control, 2-15, 2-30) at the terminal and the NR (new radio) base station, respectively.

[0050] The main functions of NR SDAP (2-01, 2-45) may include some of the following functions.

[0051] - User data transfer function (transfer of user plane data)

[0052] - Mapping function between a QoS (quality of service) flow and a DRB (data radio bearer) for both DL and UL for uplink and downlink

[0053] - Marking QoS flow ID for uplink and downlink (marking QoS flow ID in both DL and UL packets)

[0054] - Function to map reflective QoS flow to the data bearer for uplink SDAP PDUs (packet data unit).

[0055] 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 uplink and downlink QoS flows and data bearers using the 1-bit indicators for NAS (non-access stratum) QoS reflection (NAS reflective QoS) and AS (access stratum) QoS reflection (AS reflective QoS) of the SDAP header. The SDAP header may include QoS flow ID information indicating QoS. The QoS information may be used for data processing priority, scheduling information, etc., to support smooth service.

[0056] The main functions of NR PDCP (2-05, 2-40) may include some of the following functions.

[0057] - Header compression and decompression features (ROHC only)

[0058] - User data transfer function (Transfer of user data)

[0059] - Sequential delivery function (In-sequence delivery of upper layer PDUs)

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

[0061] - Reordering function (PDCP PDU reordering for reception)

[0062] - Duplicate detection function (Duplicate detection of lower layer SDUs (service data units))

[0063] - Retransmission of PDCP SDUs

[0064] - Encryption and decryption functions (Ciphering and deciphering)

[0065] - Timer-based SDU discard in uplink.

[0066] In the above, the reordering function of the NR PDCP device refers to a function that reorders PDCP PDUs received from a lower layer in order based on the PDCP SN (sequence number), and may include a function that transmits data to an upper layer in the reordered order. Alternatively, the reordering function may include a function that transmits immediately without considering the order, a function that records lost PDCP PDUs by reordering, a function that reports the status of lost PDCP PDUs to the transmitting side, and a function that requests retransmission of lost PDCP PDUs.

[0067] The main functions of NR RLC(1b-10, 2-35) may include some of the following functions.

[0068] - Data transfer function (Transfer of upper layer PDUs)

[0069] - Sequential delivery function (In-sequence delivery of upper layer PDUs)

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

[0071] - ARQ function (Error Correction through ARQ (automatic repeat request))

[0072] - Concatenation, segmentation, and reassembly functions of RLC SDUs

[0073] - Re-segmentation function (Re-segmentation of RLC data PDUs)

[0074] - Reordering function (Reordering of RLC data PDUs)

[0075] - Duplicate detection

[0076] - Error detection function (Protocol error detection)

[0077] - RLC SDU discard function

[0078] RLC re-establishment function

[0079] In the above, the in-sequence delivery function of the NR RLC device refers to a function of delivering RLC SDUs received from a lower layer to an upper layer in order, and may include a function of reassembling and delivering them when a single RLC SDU is received divided into multiple RLC SDUs. Alternatively, the in-sequence delivery function may include a function of rearranging the received RLC PDUs based on an RLC SN (sequence number) or PDCP SN (sequence number), a function of recording lost RLC PDUs by rearranging the order, a function of reporting the status of lost RLC PDUs to the transmitting side, and a function of requesting retransmission of lost RLC PDUs. Alternatively, the above sequential delivery function may include a function to deliver only the RLC SDUs prior to the lost RLC SDU in order to the upper layer in the event that there is a lost RLC SDU, or a function to deliver all RLC SDUs received before the timer started in order to the upper layer if a predetermined timer has expired even if there is a lost RLC SDU, or a function to deliver all RLC SDUs received up to now in order to the upper layer if a predetermined timer has expired even if there is a lost RLC SDU. In addition, the NR RLC device may process RLC PDUs in the order they are received (regardless of the order of the sequence number, in the order of arrival) and deliver them to the PDCP device out of order (out-of-sequence delivery), and in the case of segments, it may receive segments stored in a buffer or to be received later, reconstruct them into a single complete RLC PDU, process them, and deliver them 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 by the multiplexing function of the NR MAC layer.

[0080] 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, and 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.

[0081] The NR MAC (2-15, 2-30) can be connected to multiple NR RLC layer devices configured in one terminal, and the main functions of the NR MAC may include some of the following functions.

[0082] - Mapping function (Mapping between logical channels and transport channels)

[0083] - Multiplexing and demultiplexing functions (Multiplexing / demultiplexing of MAC SDUs)

[0084] - Scheduling information reporting function

[0085] - HARQ function (Error correction through HARQ (hybrid automatic repeat request))

[0086] - Priority handling between logical channels of one UE

[0087] - Priority handling between UEs by means of dynamic scheduling

[0088] - MBMS service identification function (MBMS (multimedia broadcast / multicast service) service identification)

[0089] - Transport format selection function

[0090] - Padding

[0091] The NR PHY layer (2-20, 2-25) 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.

[0092] FIG. 3 is a drawing illustrating the structure of another next-generation mobile communication system according to one example of the present disclosure.

[0093] Referring to FIG. 3, the cell serviced by the beam-based NR gNB (3-05) can be composed of several TRPs (transmission reception points, 3-10, 3-15, 3-20, 3-25, 3-30, 3-35, 3-40).

[0094] TRP (3-10~3-40) represents a block from which some functions for transmitting and receiving physical signals from an existing NR base station (eNB) have been separated, and it is composed of multiple antennas. The NR gNB (3-05) can be represented as a CU (central unit), and the TRP as a DU (distributed unit). The functions of the NR gNB (3-05) and the TRP can be configured by separating each layer from the PDCP / RLC / MAC / PHY layers, such as 3-45. That is, the TRP can perform the functions of the corresponding layer using only the PHY layer (3-15, 3-25), the TRP can perform the functions of the corresponding layers using only the PHY layer and the MAC layer (3-10, 3-35, 3-40), and the TRP can perform the functions of the corresponding layers using only the PHY layer, the MAC layer, and the RLC layer (3-20, 3-30). In particular, TRP (3-10 to 3-40) can use beamforming technology to transmit and receive data by generating narrow beams in multiple directions using multiple transmitting and receiving antennas.

[0095] The user terminal (3-50) can connect to the NR gNB (3-05) and the external network through the TRP (3-10 to 3-40). The NR gNB (3-05) can support the connection between the terminals and the core network (CN), particularly the AMF / SMF (3-50), by collecting and scheduling status information such as the buffer status, available transmission power status, and channel status of the terminals to provide services to the users.

[0096] For convenience in the present disclosure, the TRP is assumed to have only a PHY layer and a structure (3-15, 3-25) capable of performing the functions of that layer, but this is merely an example and is not limited thereto, and the TRP may have the MAC layer, RLC layer, etc. described above.

[0097] FIG. 4 is a diagram illustrating a scenario for inter-cell beam management according to an embodiment of 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.

[0098] FIG. 4 describes a case where multiple cells (TRP1-Cell1, TRP2-Cell2; 4-10, 4-15) exist within a single DU (Distributed unit, 4-05), but the scope of the present invention is not limited thereto, and the general content of the present disclosure can also be applied to inter-DU cases (each DU constitutes a single TRP-Cell). Furthermore, in the present disclosure, non-serving cells (TRP 2, Cell 2) that support L1 / L2-based mobility (beam change and serving cell change) are referred to interchangeably as neighbor cells, non-serving cells, and additional cells with a physical cell ID (PCI) different from the serving cell.

[0099] In the existing terminal beam change procedure (4-45), the terminal (user equipment, UE, 4-20) is in a connected state and transmitting and receiving data through the TRP 1 (4-10) of serving cell 1, and may be set to the optimal beam, which is the transmission configuration indication (TCI) state 1 (4-25, 4-30). At this stage, the terminal may receive configuration information for L3 channel measurement (RRM; radio resource management) for an additional cell (TRP 2-Cell 2, 4-15) that has a different PCI from the serving cell through RRC configuration information (e.g., RRC configuration) from the serving cell (4-10), and at step 4-46, the terminal (4-20) may perform an L3 measurement operation (4-46) for the corresponding frequency and cell.

[0100] Subsequently, in step 4-47, the serving cell (TRP 1-Cell 1, 4-10) may direct a handover to the corresponding cell (TRP 2-Cell 2, 4-15) based on the reported measurement value (4-47), and in step 4-48, the handover is completed and additional RRC configuration information may be transmitted to the terminal (4-20) via TRP 2-Cell 2 (4-15) (4-48). The RRC configuration information (e.g., RRC reconfiguration) 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.

[0101] Subsequently, in step 4-49, the terminal (4-20) can perform an L1 measurement (4-49) according to the settings, and in step 4-50, the base station can update the TCI state through L1 / L2 signaling according to the measurement report (4-50). Here, the optimal beam, TCI state 2 (4-40), can be indicated. In this step, the serving cell is Cell 1 until handover, and Cell 2 becomes the serving cell after handover. That is, many procedures and time are required even after handover until the optimal beam is indicated.

[0102] Unlike the existing terminal beam change procedure (4-45) described above, the improved beam change technique (4-55) considered in the present invention is as follows. The terminal can refer to and transmit a beam setting associated with an additional cell (TRP 2-Cell 2, 4-15) with a different PCI from the serving cell through RRC setting information (4-56) (e.g., RRC Reconfiguration) from the serving cell (4-10). The part that associates the beam setting associated with the additional cell (TRP 2-Cell 2, 4-15) with a different PCI from the serving cell, i.e., the TCI state corresponding to TRP2, may be applied by associating a new cell ID (Physical cell ID, PCI; additionalPCI-r17) as shown in Table 1 below.

[0103]

[0104] In addition, a unified TCI state framework may be applied for beam management between the cells. 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 either Joint UL / DL mode or separate UL / DL mode as shown in Table 2.

[0105]

[0106] 1. Joint UL / DL Mode: Configures UL and DL to share the same TCI settings (in PDSCH-Config)

[0107] 2. Separate UL / DL Mode: 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) in Table 3, and the TCI state for the UL follows ul-TCI-StateList-r17 (in BWP-UplinkDedicated) in Table 4.

[0108]

[0109]

[0110] After the setting for TRP 2-Cell 2 is provided in the RRC connection state to serving cell 1, the terminal (4-20) can perform an L1 measurement for the TRP 2-Cell 2 according to the setting in step 4-57 and report the result to the serving cell (Cell 1, 4-10) (4-57).

[0111] If the serving cell (Cell 1, 4-10) determines, based on the measurement results, that a change to a specific beam (TCI state 2, 4-35, 4-40) of TRP 2 (Cell 2, 4-15) is necessary from the serving cell beam (TCI state 1, 4-25, 4-30), it can trigger a beam change and instruct the terminal (4-20) via L1 / L2 signaling (4-58). The terminal (4-20) can change the beam to the specific beam (TCI state 2, 4-40) of TRP 2 (Cell 2, 4-15) through the instruction and can perform physical channel setting and upper layer setting operations associated with the set beam. From that stage, the terminal (4-20) is connected to the serving cell (Cell 1, 4-10), but can perform data transmission and reception using the channel link of TRP 2 (Cell 2, 4-15) (receiving PDCCH / PDSCH, transmitting PUCCH / PUSCH). That is, transmission and reception for the common control channel can be performed through the serving cell (TRP 1, Cell 1, 4-10).

[0112] Subsequently, in step 4-59, the terminal (4-20) can perform an L3 measurement operation according to the measurement settings set in an independent serving cell (4-59), and in step 4-60, the terminal (4-20) can receive a handover command message from the serving base station (Cell 1) and perform a serving cell change to Cell 2 (4-60). Through this technique (4-55), the terminal performs data transmission and reception with a specific TRP 2 of Cell 2, which supports L1 / L2-based mobility while connected to the serving cell, and can continue to use the beam even after the handover.

[0113] For reference, the RRC settings regarding the settings and operations related to L1 measurement and report in the aforementioned steps 4-57 are described as follows. This content is basically applied to the following embodiments of the present invention, and enhancement techniques may be added in future embodiments.

[0114] 1. L1 measurement settings (configured within CSI-ResourceConfig in Table 5, ServingCellConfig within IE)

[0115] - CSI-RS / SSB resources and resource pools requiring measurement (nzp-CSI-RS, csi-IM, csi-SSB)

[0116] - Configuration of CSI-RS / SSB resources requiring measurement (aperiodic, semi-persistent) and triggering settings

[0117] - When a CSI-RS resource references an SSB resource, it provides additional PCI information to enable L1 measurements from neighboring cells (up to 7 additional neighboring cells (PCI) can be added from a single serving cell).

[0118]

[0119] 2. L1 report settings (configured within the serving cell, ServingCellConfig, configured within IE)

[0120] - Report Type: Periodic Report, Semi-periodic Report with PUCCH, Semi-periodic Report with PUSCH, Aperiodic Report with PUSCH

[0121] - Report quantity

[0122] - Other settings required for reporting

[0123] FIG. 5 is a diagram illustrating a scenario in which a terminal according to one embodiment of the present disclosure changes the serving cell and beam to the TRP (transmission / reception point) of a cell that supports L1 / L2-based beam changing to transmit and receive data.

[0124] FIG. 5 describes a case where multiple cells (TRP1-Cell1, TRP2-Cell2; 5-10, 5-15, 5-40, 5-45) exist within a single DU (Distributed unit, 5-05, 5-35), but the invention is not limited to the above-described case, and the overall content of the invention can also be applied to inter-DU within an intra-CU (each DU constitutes a single TRP-Cell).

[0125] Unlike the conventional terminal beam changing procedure (4-45, 4-55) described in FIG. 4, the improved beam changing technique (5-25, 5-75) disclosed in this embodiment is as follows.

[0126] 1. Example 1 (5-25): Perform L1 / L2 handover after performing inter-cell beam management (change) operation

[0127] 2. Example 2 (5-75): Perform L1 / L2 handover immediately

[0128] First, the entire operation of Example 1 is as follows.

[0129] In step 5-26, the terminal can receive common configuration and dedicated configuration information for additional cells (TRP 2-Cell 2, 5-15) that have different PCIs from the serving cell (5-10) through RRC configuration information (5-26). That is, configuration information corresponding to ServingCellID or candidateCellID (cell ID associated with PCI), ServingCellConfigCommon, and ServingCellConfig can be provided to the terminal 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. In addition, the configuration information may include all configuration information (cell configuration, bearer configuration, security key configuration, etc.) that is applied when the terminal moves to the corresponding cell (handover). Furthermore, the configuration information may include enhanced configurations by referring to the unified TCI state configuration and L1 measurement and report-related configurations described in step 4-56. For example, the configuration information may include enhanced unified TCI state settings and L1 measurement and report settings for continuous LTM, which will be explained in detail in the drawings to be described later in the present invention.

[0130] After the settings for TRP 2-Cell 2 (5-15) are provided in the RRC connection state to serving cell 1, in step 5-27, the terminal can perform an L1 measurement for the TRP 2-Cell 2 (5-15) according to the received settings and report the results to the serving cell (Cell 1, 5-10).

[0131] In step 5-28, if the serving cell (Cell 1, 5-10) determines, based on the measurement results, that a change to a specific beam (TCI state 2, 5-40) of TRP 2 (Cell 2, 5-15) is necessary rather than the serving cell beam (TCI state 1, 5-25), it may trigger a beam change and instruct the terminal (5-20) to do so via L1 / L2 signaling. The terminal (5-20) may perform a beam change to TRP 2 (Cell 2, 5-15) through the instruction and transmit and receive data through TRP 2 (Cell 2, 5-15). At this time, no serving cell change occurs, and the terminal remains connected to the serving cell (Cell 1, 5-10) via RRC.

[0132] Subsequently, in step 5-29, the terminal (5-20) can still perform an L1 measurement on TRP 2-Cell 2 (5-15) and report the result to the serving cell (Cell 1, 5-10).

[0133] In step 5-30, the serving cell (Cell 1, 5-10) may instruct the terminal to perform a handover if the L1 measurement reported by the terminal satisfies the triggering condition for a handover to TRP 2-Cell 2 (5-15) (detailed operation is described below). For example, the instruction may be an L1 / L2 message. That is, the MAC CE may contain an indicator instructing the handover.

[0134] The entire operation of Example 2 is as follows.

[0135] In step 5-76, the terminal can receive common configuration and dedicated configuration information for additional cells (TRP 2-Cell 2, 5-45) that have different PCIs from the serving cell (5-40) through RRC configuration information (5-76). That is, ServingCellID or candidateCellID (cell ID associated with PCI), and configuration information corresponding to the corresponding candidate LTM cell may be provided to the terminal in advance. The configuration information may be provided in the form of pre-configuration in the RRC configuration and may include configuration information for multiple cells. In addition, the configuration information may include all configuration information (cell configuration, bearer configuration, channel measurement configuration, etc.) that is applied when the terminal moves (handover) to the corresponding candidate LTM cell. Furthermore, the configuration information may include the unified TCI state configuration and L1 measurement and report related settings described in step 4-56, modified to support consecutive LTMs. For example, the configuration information may include L1 measurement and report settings modified to support continuous LTM, as well as unified TCI state settings, which are explained in detail below.

[0136] After the settings for TRP 2-Cell 2 (5-45) are provided in the RRC connection state to serving cell 1, in step 5-77, the terminal (5-50) can perform an L1 measurement for the TRP 2-Cell 2 (5-45) according to the received settings and report the results to the serving cell (Cell 1, 5-40).

[0137] In step 5-78, if the serving cell (Cell 1, 5-40) determines, based on the measurement results, that a handover is required simultaneously with a beam change to a specific beam (TCI state 2, 5-70) of TRP 2 (Cell 2, 5-45) rather than the serving cell beam (TCI state 1, 5-45), the serving cell may trigger the beam change and handover and instruct the terminal (5-50) to do so via L1 / L2 signaling. The terminal (5-50) may perform a handover simultaneously with a beam change to TRP 2 (Cell 2, 5-15) through the instruction and transmit and receive data through the TRP 2 (Cell 2, 5-15). At this time, the terminal applies the configuration information for the target cell where the handover is to be performed, which was pre-configured in step 5-76. Depending on whether uplink synchronization is required in this step, the terminal may perform random access, or random access to the target cell may be omitted. Detailed operation is explained in the drawings below.

[0138] Below, details regarding the unified TCI state settings and L1 measurement and report settings for candidate cells surrounding an LTM to support the continuous LTM proposed in this disclosure are disclosed. As illustrated in FIG. 4, in conventional inter-cell beam management (ICBM), L1 measurement resource settings for cells requiring measurement are provided in the CSI-ResourceConfig within the ServingCellConfig IE within 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 the servingAdditionalPCIList.

[0139] Detailed settings for L1 measurement and reporting settings for LTM are provided as L1 measurement resource settings applied to LTM candidate cells as follows. To this end, it is necessary to share and determine the L1 measurement resources and reporting settings for LTM among LTM candidate cells during the preprocessing stage. The entire procedure is explained together in the following examples. The following examples are explained by referring to the relevant settings.

[0140] 1. L1 measurement resource configuration (configured within LTM-CSI-ResourceConfig in Table 7 and LTM-Config in Table 6)

[0141] - CSI Resource configuration index exists to specify CSI resource settings (LTM-CSI-ResourceConfigId-r18)

[0142] - CSI resource set containing CSI-RS or SSB resources requiring measurement

[0143] - A single CSI resource set can be multiple SSB resources or CSI-RS resources existing within an LTM candidate cell.

[0144] 2. L1 report settings (configured within LTM-Config in Table 6)

[0145] - Existence of a CSI Report configuration index to specify CSI reporting settings (LTM-CSI-ReportConfig-r18 in Tables 8 and 9)

[0146] - Report Type: Periodic Report, Semi-periodic Report with PUCCH, Semi-periodic Report with PUSCH, Aperiodic Report with PUSCH

[0147] - Report Content (Number of reporting cells, number of reporting resources, etc.)

[0148]

[0149]

[0150]

[0151]

[0152]

[0153] The present disclosure proposes detailed operations for performing RACH-less cell changes instead of uplink synchronization operations during LTM execution to support RACH-less conditional LTM, and detailed operations for RACH-less operations for performing conditional LTM. In particular, key features of the RACH-less conditional LTM in the present disclosure include a method for obtaining a timing advance (TA) for LTM candidate cells in advance, a method for performing the first transmission after RACH-less conditional LTM, and a method for managing stored TA values.

[0154] FIG. 6 is a diagram illustrating the overall operation for supporting conditional LTM operation in cells within the same CU according to one example of the present disclosure.

[0155] Although not illustrated in FIG. 6, the terminal (6-01) in an RRC connection state is in a state where it can receive RRC settings from source cell 1 (6-02), and can receive Layer 3 measurements and reports for serving cells and surrounding cells (or LTM candidate cells) based on the RRC settings.

[0156] In steps 6-10, the terminal (6-01) in the RRC connection state performs data transmission and reception with source cell 1 (6-02) and can transmit Layer 3 measurements for the serving cell and surrounding cells to the source base station (6-03) according to the configured Layer 3 measurements and reports. At this time, the actual measurements can be transmitted to the CU (6-03) of the source base station. This is because the CU (6-03) of the source base station is responsible for processing RRC messages and determining the mobility of the terminal.

[0157] In step 6-15, the CU (6-03) of the source base station may generate a message (UE Context Setup Request or UE Context Modification Request) requesting configuration information for LTM from surrounding LTM candidate cells (6-04, 6-05, or LTM candidate cells) based on the measurement report received from the terminal, and transmit it through the F1 interface. Although candidate cells are illustrated in conjunction with DUs in FIG. 6, the illustrated content is not limited thereto; in reality, candidate cells and DUs may have a 1:1 mapping relationship, or multiple candidate cells may be included in a single DU. The message requesting configuration information for LTM may include a request regarding the determination of surrounding cells as LTM candidate cells, a request for conditional LTM, and a request for configuration information. That is, it may include a procedure for requesting RRC configuration information applied when an L1 / L2-based handover is performed to the corresponding cell. The information that may be included in the message requesting configuration information for LTM is summarized as 1 and 2 below. The following message content can be used as the composition of the messages in steps 6-15 and 6-35.

[0158] 1. Configuration information applicable to LTM and / or conditional LTM (Information to be displayed when issuing the cell switch command MAC CE instruction to the candidate cell that determined the LTM.)

[0159] - LTM candidate ID

[0160] - Mapping information between the LTM candidate ID and the corresponding cell ID

[0161] - Beam information to be used for each candidate (TCI state)

[0162] ■ In this case, the meaning of use may include a beam linked to the RACH occasion during DL and / or UL synchronization and / or RACH execution, 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.

[0163] - RACH preamble index

[0164] - SSB index: An index of the SSB used to determine the RACH occasion in each candidate cell, which can represent the occasion of the RACH preamble of CFRA.

[0165]

[0166] 2. Pre-configuration procedure for LTM and / or conditional LTM

[0167] - CSI resource request information for each candidate cell (requests for CSI-RS resources or SSB resources)

[0168] ■ It may be requested during the pre-configuration preprocessing section for LTM candidate cells.

[0169] ◆ Indicator for whether the request is for initial preparation, e.g., initiation, or for modification after the initial request

[0170] ■ 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.

[0171] ■ 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.

[0172] In addition, it is possible to decide whether to request CSI-RS resources or SSB resources for each target candidate cell.

[0173] - CSI resource settings for each candidate cell (necessary when transmitting L1 measurement settings as source DU to the terminal), individual resource settings per cell and setting IDs, CSI resource settings for LTM, may use the same CSI resources as conditional LTM, but may also be transmitted with explicit distinction for conditional LTM.

[0174] ■ Based on the above CSI resource request information, provide L1 measurement settings for LTM transmitted from the corresponding candidate cell.

[0175] ■ 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.

[0176] - CSI report configuration considering the CSI resources of each of the above candidate cells

[0177] 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) created by the CU. Additionally, the information may not be transmitted separately but may be included and transmitted within the target cell configuration (RRCReconfiguration).

[0178] ■ 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.

[0179] ■ Event-based L1 measurement reporting

[0180] You can define and use L1-RSRP-based events from Best beam.

[0181] ◆ For example, events such as those in Table 10 below can 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) can be introduced.

[0182] - Event LTM2: Beam of serving cell becomes worse than absolute threshold;- Event LTM3: Beam of candidate cell becomes amount of offset better than beam of serving cell;- Event LTM4: Beam of candidate cell becomes better than absolute threshold;- Event LTM5: Beam of serving cell becomes worse than absolute threshold1 AND Beam of candidate cell becomes better than another absolute threshold2.

[0183] 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.

[0184] The above conditions are determined by coordination between the serving CU and the LTM candidate DU in steps 6-15, and the serving CU can determine the event conditions that trigger the LTM provided by the LTM candidate cell and the L1 filtering values ​​and transmit them to the terminal.

[0185] - RACH configuration and lower layer setting information to be used in the relevant concerned cell

[0186] ■ This information can be transmitted from the above candidate DU to the CU, written as settings required for RACH execution 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.

[0187] ■ In particular, some of the RACH settings can be used to include information on determining the Rach preamble index, Mask, and occasion in the cell switch command MAC CE described above.

[0188] ■ It may be a setting that applies to both LTM and conditional LTM simultaneously, but resources dedicated to conditional LTM may also be configured separately.

[0189] In summary, the request for L1 measurement resources and reporting settings can be performed for each candidate cell, and although it is indicated in the diagram as a single procedure of steps 6-15, the steps can be applied to multiple procedures. For example, the multiple procedures that can be performed for L1 measurement resources and reporting settings are as follows.

[0190] 1. Step 1: The source base station CU (6-03) requests L1 measurement resource setup from LTM candidate cells (SSB or CSI-RS resource request)

[0191] 2. Step 2: LTM candidate cells respond by setting up L1 measurement resources and transmit them to the source base station CU (6-03) (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.

[0192] 3. Step 3: The source base station CU (6-03) transmits L1 measurement resource settings for continuous LTM and conditional LTM support to each candidate cell through 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.

[0193] 4. Step 4: The source base station CU (6-03) requests and receives L1 measurement report setup from LTM candidate cells. This procedure can be transmitted to the source base station via the F1 interface as a UE Context Modification Response message.

[0194] 5. Step 5 (6-20): The source base station CU (6-03) transmits LTM and conditional LTM related settings to the terminal. The source base station collects all LTM related settings received from LTM candidate cells and stores them in an RRCReconfiguration message transmitted to the terminal, and transmits the corresponding RRC setting information to the terminal. That is, pre-configuration information for LTM candidate cells can be transmitted to the terminal. In particular, regarding conditional LTM, it is characterized by matching and transmitting the execution condition (event-based L1 measurement report setting) with the RRC setting information of the target cell that is applied when executed.

[0195] At this time, the source base station CU (6-03) may transmit to each candidate cell (6-04, 6-05) information including the configuration information of the source cell and separate reference cell configuration information. The reference cell configuration information transmitted by the source base station CU (6-03) to each candidate cell (6-04, 6-05) may be a common configuration that can be applied to multiple target candidate cells to reduce signaling overhead when target candidate cells provide configuration information for LTM. This may be a measurement configuration, a bearer configuration, or, if the cells belong to the same CellGroup, configurations set at the CellGroup level (e.g., MAC-CellGroupConfig, RLC bearer configuration, SCell configuration, etc.). Alternatively, if the source base station CU (6-03) has a procedure to roughly know or know the configuration information for each candidate cell (6-04, 6-05), the reference cell configuration may be determined through a separate procedure to obtain such reference cell configuration information. The purpose of the source base station CU (6-03) transmitting the reference cell settings to each candidate cell (6-04, 6-05) is to ensure that each candidate cell transmits only the additional setting information based on the reference cell settings to the source base station CU (6-03), thereby enabling the application of 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). This is subsequently transmitted to the terminal (6-01) as is, thereby reducing the signaling of RRC messages transmitted to the terminal. Additionally, when the source base station CU (6-03) transmits the candidate cell settings to each candidate cell (6-04, 6-05), the reference cell settings may be omitted, and in this case, the candidate cell settings are provided as complete RRC settings.

[0196] In step 6-20, the source cell (6-02) can receive an RRC message generated by the base station CU (6-03) based on configuration information received from each candidate cell and transmit it to the terminal. In particular, regarding conditional LTM, it is characterized by matching the execution condition (event-based L1 measurement report setting) with the RRC configuration information of the target cell applied when executed and transmitting it to the terminal (6-01). The terminal (6-01) 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, validity determination, and methods for storing or managing the configuration content. Additionally, the terminal (6-01) can store the LTM configuration information for each candidate cell decoded in this step as complete configuration information in the terminal's buffer (memory), and at the same time, store the received reference cell configuration information together in the terminal's buffer (memory) and manage it for future use.

[0197] In step 6-25, the base station (6-03) can transmit downlink control information (DCI) that enables semi-persistent L1 report or aperiodic L1 report to the terminal (6-01).

[0198] In step 6-30, the terminal (6-01) can receive the MAC CE or the DCI and perform L1 (Layer 1) measurements and reports for each candidate surrounding cell, and can perform semi-persistent / aperiodic L1 measurements and reports depending on the settings. Subsequently, when the terminal (6-01) receives a MAC CE that disables semi-persistent L1 reports, it terminates semi-persistent L1 measurements and reports.

[0199] A terminal (6-01) that receives a conditional LTM setting from a base station in step 6-20 can evaluate an L1 measurement for the conditional LTM in step 6-35. That is, it checks the execution conditions for the set conditional LTM, and if the conditions are satisfied (if the event-based L1 measurement reporting conditions are satisfied), the terminal can determine a conditional LTM to an LTM candidate cell that satisfies the conditions. In FIG. 6, the operation of a conditional LTM that performs random access is described.

[0200] In step 6-40, the terminal (6-01) applies the RRC configuration information of the LTM candidate cell (the target cell where the conditional LTM is determined) configured in step 6-20, and can perform a random access procedure for the target cell (6-04) through the random access resources provided by the configuration. Through the random access, uplink and downlink synchronization can be achieved, and the handover procedure for the cell can be completed. That is, the random access procedure may be the conditional LTM completion procedure. The procedure may vary depending on the method of giving the handover completion instruction. For example, if the terminal (6-01) receives the configuration of the target cell at the RRC message level, it may be a process of transmitting an RRCReconfiugrationComplete message to the target cell (6-04) and receiving an ACK (acknowledgement) for it. As another example, if the terminal (6-01) receives the configuration at the cell level or cell group level, a new handover completion instruction message (a new RRC message or MAC CE) may replace the procedure. If the above handover is successful, data transmission and reception between the terminal and the corresponding target cell can be performed, and the RRC connection procedure service can be performed.

[0201] In addition, an embodiment of the present invention can support a subsequent conditional LTM operation. This means that the LTM setting information (settings for target candidate cells and reference cell setting information, etc.) received by the terminal (6-01) in step 6-20 is stored in the terminal as is, and the terminal continues to perform the conditional LTM procedure unless the LTM setting information is changed / released / added through a separate RRC setting. If it is necessary to update the reference cell setting information, new RRC setting information is transmitted to the terminal to perform this. That is, the procedure disclosed in FIG. 6 can be triggered again and performed.

[0202] In summary, when the terminal (6-01) receives reference cell setting information in step 6-20, it stores it in the terminal buffer, and if there is no update to a separate setting, it can continue to use the setting as reference cell setting information even after LTM execution (step 6-40) (i.e., the reference cell setting and conditional LTM candidate setting values ​​stored in consecutive conditional LTM can be applied).

[0203] If the conditional LTM procedure fails (step 6-45, e.g., RLF (radil link failure), random access failure, T304 timer completion, etc.), in step 6-50, the terminal (6-01) may maintain the previously configured LTM settings and fall back to the source cell. If the fallback to the source cell fails, the terminal (6-01) may perform an RRC re-establishment procedure, and if cell selection is performed, the terminal may apply the LTM settings and perform a connection procedure if the selected cell is an LTM candidate cell. In this case, only random access-based LTM operation may be supported.

[0204] FIG. 7 is a diagram illustrating the overall operation for supporting a random access-free conditional LTM operation (RACH-less conditional LTM) in cells within the same CU according to one example of the present disclosure.

[0205] This example may include a method for a terminal to obtain an early TA for a candidate cell for a RACH-less conditional LTM. More specifically, this example may include the terminal receiving information about the early TA for the candidate cell from a source cell via a new MAC CE. Any procedure in the example illustrated in FIG. 7 that overlaps with the content described in FIG. 6 may be replaced with the content of FIG. 6, and the description of said overlapping procedure may be omitted in FIG. 7.

[0206] Although not illustrated in FIG. 7, the terminal (7-01) in an RRC connection state is in a state where it can receive an RRC setting (or RRC setting message) from source cell 1 (7-02), and can receive Layer 3 measurements and reports for serving cells and surrounding cells (or LTM candidate cells) based on the RRC setting (or RRC setting message).

[0207] In steps 7-10, the terminal (7-01) in the RRC connection state performs data transmission and reception with source cell 1 (7-02) and can transmit Layer 3 measurements for the serving cell and surrounding cells to the source base station (7-03) according to the configured Layer 3 measurements and reports. At this time, the actual measurements are transmitted to the CU (7-03) of the source base station. This is because the CU (7-03) of the source base station is responsible for processing RRC messages and determining the mobility of the terminal.

[0208] In step 7-15, the CU (7-03) of the source base station may generate a message (UE Context Setup Request or UE Context Modification Request) requesting configuration information for LTM in step 7-15 to surrounding LTM candidate cells (7-04, 7-05, or LTM candidate cells) based on the measurement report received from the terminal, and transmit it through the F1 interface. Although candidate cells are depicted in association with DUs in the drawings, the details are not limited to what is depicted; in reality, candidate cells and DUs may be mapped 1:1, or multiple candidate cells may be included in a single DU. The message requesting configuration information for LTM may include a request regarding the determination of surrounding cells as LTM candidate cells, a request for conditional LTM, and a request for configuration information. That is, it may include a procedure for requesting RRC configuration information that is applied when an L1 / L2-based handover is performed to the cell. The information that may be included in the message requesting configuration information for LTM is summarized as 1 and 2 below. The following message content can be used as the composition of the messages in steps 7-15 and 7-35. Specific details regarding the information in 1 and 2 below are described in detail in 6-15 and 6-35 of FIG. 6.

[0209] 1. Configuration information applicable to LTM and / or conditional LTM

[0210] 2. Pre-configuration procedure for LTM and / or conditional LTM

[0211] Additionally, the content disclosed in 6-15 and 6-35 of FIG. 6 may be added as follows: the source base station (7-03) may request the LTM candidate DUs (7-04, 7-05) to request a conditional LTM without random access, that is, whether a random access resource for early TA (timing advance) or terminal-based TA acquisition is possible, and may receive a response thereto.

[0212] The source base station (7-03) can generate an RRC setting based on the response received from each LTM candidate DU (7-04, 7-05) and then determine the LTM operation.

[0213] In summary, the request for the L1 measurement resource and reporting settings can be performed for each candidate cell, and although it is indicated as a single procedure of steps 7-15 in the diagram, the steps can be applied to multiple procedures. For example, the multiple procedures that can be performed for L1 measurement resources and reporting, and RACH-less conditional LTM settings are as follows.

[0214] 1. Step 1: Request L1 measurement resource configuration from source base station CU(7-03)LTM candidate cells (request SSB or CSI-RS resources)

[0215] 2. Step 2: LTM candidate cells respond by setting up L1 measurement resources and transmit them to the source base station CU (7-03) (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.

[0216] 3. Step 3: The source base station CU (7-03) transmits L1 measurement resource settings for continuous LTM and RACH-less conditional LTM support to each candidate cell through L1 measurement resource settings for each collected candidate cell. This procedure may be transmitted to the source base station via the F1 interface as a UE Context Modification Request message. This step may include a request for early TA and / or UE-based TA related setting information for RACH-less conditional LTM.

[0217] 4. Step 4: The source base station CU (7-03) requests and receives L1 measurement report configuration settings from LTM candidate cells. This step may include configuration information related to early TA and / or UE-based TA for RACH-less conditional LTM. This procedure may be transmitted to the source base station via the F1 interface as a UE Context Modification Response message.

[0218] 5. Step 5 (7-20): The source base station CU (7-03) transmits LTM and conditional LTM related settings to the terminal. The source base station may collect all LTM related settings received from LTM candidate cells and store them in an RRCReconfiguration message transmitted to the terminal, and transmit the corresponding RRC setting information to the terminal. That is, pre-configuration information for LTM candidate cells may be transmitted to the terminal. In particular, regarding conditional LTM, it is characterized by matching and transmitting the execution condition (event-based L1 measurement report setting) with the RRC setting information of the target cell applied when executed. In addition, the present drawing is characterized by including early TA and / or UE-based TA related setting information for RACH-less conditional LTM.

[0219] At this time, the source base station CU (7-03) may transmit the source cell configuration information and / or separate reference cell configuration information to each candidate cell (7-04, 7-05). The reference cell configuration information transmitted by the source base station CU (7-03) to each candidate cell (7-04, 7-05) may be a common configuration that can be applied to multiple target candidate cells to reduce signaling overhead when target candidate cells provide configuration information for LTM. This may be a measurement configuration, a bearer configuration, or, if the cells belong to the same CellGroup, configurations set at the CellGroup level (e.g., MAC-CellGroupConfig, RLC bearer configuration, SCell configuration, etc.). Alternatively, if the source base station CU (7-03) has a procedure to roughly know or know the configuration information for each candidate cell (7-04, 7-05), the reference cell configuration may be determined through a separate procedure to obtain such reference cell configuration information. The purpose of the source base station CU (7-03) transmitting the reference cell settings to each candidate cell (7-04, 7-05) is to ensure that each candidate cell transmits only the additional setting information based on the reference cell settings to the source base station CU (7-03), thereby enabling the application of 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 overwriting the settings in the target cell based on the reference cell settings). This is subsequently transmitted to the terminal (7-01) as is, thereby reducing the signaling of RRC messages transmitted to the terminal. Additionally, when the source base station CU (7-03) transmits the candidate cell settings to each candidate cell (7-04, 7-05), the reference cell settings may be omitted; in this case, the candidate cell settings are provided as complete RRC settings.

[0220] In step 7-20, the source cell (7-02) can receive an RRC message generated by the base station CU (7-03) based on configuration information received from each candidate cell from the base station CU (7-03) and transmit it to the terminal. The terminal (7-01) that receives the RRC message can perform a procedure to decode and process the RRC message. The processing includes ASN.1 decoding and validity determination of the received message, and methods for storing or managing configuration content. Additionally, the terminal (7-01) can store the LTM configuration information for each candidate cell decoded in this step as complete configuration information in the terminal's buffer (memory), and at the same time, store the received reference cell configuration information in the terminal's buffer (memory) as well and manage it for the future.

[0221] Meanwhile, the present disclosure is characterized in that detailed settings for a RACH-less conditional LTM are included in the RRC message, and the relevant settings may be transmitted to the terminal in steps 7-20. As an example, the detailed settings for the RACH-less conditional LTM may include the following settings.

[0222] 1. RRC settings when RACH-less conditional LTM is applied

[0223] 2. Execution condition triggering RACH-less conditional LTM (event-based L1 measurement reporting settings, Bestbeam's L1-RSRP-based events described above, L1 filtering parameters described above)

[0224] 3. Settings for securing Early TA for RACH-less conditional LTM and / or CG settings

[0225] A. UE-based TA related settings

[0226] i. Provides LTM candidate cell information applied based on the UE-based TA terminal capability reported by the terminal.

[0227] ii. For example, add an indicator to the LTM candidate cell settings to specify a RACH-less conditional LTM, or provide cell information where UE-based TA is applied in the RACH-less conditional LTM above the LTM settings.

[0228] 1. Provide LTM candidate cell index in association with serving cell information (i.e., provide LTM candidate cell index to which UE-based TA can be applied per serving cell)

[0229] 2. Provides a group index that groups identical candidate cells to which UE-based TA applies, and if the group index is identical to the serving cell, UE-based TA is applied.

[0230] B. Early TA Related Settings

[0231] i. Setting up the Random Access Preamble (msg1) resource for Early TA per LTM candidate cell for Early TA.

[0232] C. Detailed Settings for RACH-less Conditional LTM Execution

[0233] i. Configured Grant (CG) Settings

[0234] 1. Allow the common use of resources used by the existing RACH-less LTM, or;

[0235] 2. Introduction of CG resource settings dedicated to RACH-less conditional LTM

[0236] 3. Frequency / time resources of the CG resource, period of the CG resource, number of repetitions or hold time for semi-static setting (e.g., using only resources up to the set time after the first valid resource), etc.

[0237] ii. TA Timer Settings

[0238] 1. In the Early TA procedure, this is a TA timer setting applied when the terminal acquires the TA after transmitting a preamble according to the PDCCH order and receiving signaling (MAC CE) containing the candidate cell's TA from the source cell in response to that transmission, and can be provided for each LTM candidate cell.

[0239] 2. Existing TA timer values ​​set for handover can be used commonly.

[0240] 3. Different setting values ​​can be provided for each LTM candidate cell (included in RRC settings or MAC CE)

[0241] In step 7-25, the base station (7-03) can transmit to the terminal (7-01) MAC CE that enables semi-persistent L1 report or DCI (downlink control information) that enables aperiodic L1 report.

[0242] In step 7-30, the terminal (7-01) receives this and can perform L1 (Layer 1) measurements and reports for each candidate surrounding cell, and can perform semi-persistent / aperiodic L1 measurements and reports depending on the settings. Subsequently, when the terminal (7-01) receives a MAC CE that disables semi-persistent L1 reports, it terminates semi-persistent L1 measurements and reports.

[0243] In step 7-35, the terminal (7-01) can report the measured L1 / L3 measurement values ​​to the base station according to the settings.

[0244] In step 7-40, the base station (7-03) may transmit a PDCCH order for obtaining an Early TA to the terminal based on a reported L1 or L3 measurement, and the PDCCH order may contain information including the index of an LTM candidate cell.

[0245] Subsequently, in step 7-45, the terminal (7-01) that receives the above PDCCH order transmits a preamble to the designated LTM candidate cell according to the preamble setting for the Early TA procedure configured for each LTM candidate cell. In particular, the PDCCH order in this step may include additional information to indicate that it is a conditional LTM, compared to the PDCCH order for early TA in the existing LTM. As will be explained in a later step, this is because a new MAC CE is introduced in response to the PDCCH order from the LTM candidate cell, and a procedure to transmit a TA to the target cell is added. In other words, the operation of the PDCCH order for the early TA procedure used in the existing LTM and the PDCCH order for the early TA procedure used in the conditional LTM are different. To distinguish this, the following two methods are possible.

[0246] 1. Introduce a new field within the PDCCH order to indicate that it is for the early TA procedure of the conditional LTM.

[0247] 2. Indicate that each LTM candidate cell setting is used for the early TA procedure of the conditional LTM through RRC settings (associated with the LTM candidate cell index, so the terminal can distinguish this when receiving the index as a PDCCH order). An example related to this is as follows.

[0248] A. Cell #1, Cell #2, Cell #3, Cell #4: legacy LTM

[0249] B. Cell #5, Cell #6, Cell #7, Cell #8: add the Conditional LTM indicator

[0250] Alternatively, the early TA procedure used for conditional LTM can be used without distinction from the existing LTM early TA procedure. This is because the base station already knows which candidate cells can have RACH-less conditional LTM applied.

[0251] In the early TA of the conventional LTM, the procedure from the terminal's perspective is completed due to the transmission of the terminal's preamble, and then it is determined whether the TA value is included in the LTM cell change MAC CE, and subsequent RACH-less LTM operations are performed. However, in the conditional LTM, particularly in the RACH-less conditional LTM operation, since the terminal triggers the LTM, the TA value cannot be received from the base station through the terminal (7-01) LTM cell change MAC CE. Therefore, in step 7-50, the LTM target cell (7-04) can calculate the TA through the preamble received from the terminal in step 7-45. Subsequently, in step 7-55, the LTM target cell (7-04) can transmit the calculated TA value to the source base station (7-03) via an F1 interface message. The operation can be performed for each candidate cell (7-04, 7-05), and the source base station (7-03) that receives it can transmit the information to the source cell (DU; 7-02) in step 7-60. Likewise, the TA information can also be transmitted via the F1 interface message.

[0252] In step 7-65, the source cell (DU; 7-02) may transmit a new MAC CE containing the target cell information and TA value to the terminal in order to transmit the terminal's TA information regarding the target cell received from the source base station (7-03) in step 7-60. Alternatively, the source cell (7-02) may modify and use the existing Timing Advance Command MAC CE and Absolute Timing Advance Command MAC CE. A detailed description of the MAC CE is further explained in FIG. 9. As an example, the MAC CE may include one or more target cells and TA information.

[0253] If, in step 7-65, the terminal receives a MAC CE from the source cell (DU; 7-02) and obtains a valid TA value for the cell, the terminal (7-01) can start (or operate) the TA timer in step 7-70. The timer operates according to the TA timer provided by the corresponding LTM candidate cell setting (a conditional LTM dedicated timer or a TA timer set to be applied to the corresponding target cell).

[0254] Additionally, in steps 7-75, the base station may transmit the Candidate cell TCI state activation / deactivation MAC CE based on L1 / L3 measurements received from the terminal. In this case, the terminal can perform the following two operations to perform downlink synchronization with the LTM candidate cell.

[0255] - Option 1: Candidate cell TCI state activation / deactivation. Use the beam of the candidate cell specified in the MAC CE as the beam for downlink synchronization and the first UL data transmission after cell change.

[0256] ■ In this case, downlink synchronization is performed on the corresponding beam, and UL data transmission can be used on a different beam. That is, for the first UL transmission, the best beam of the event that satisfies the actual conditional LTM can be used.

[0257] - Option 2: Even if a beam designated by the base station exists, downlink synchronization and the first UL data transmission can be performed based on the beam (best beam of the target cell) that satisfies the event when the conditional LTM is triggered.

[0258] This is because, although the actual base station directs the candidate cell's beam in the Candidate Cell TCI state activation / deactivation MAC CE based on measurements, the actual Conditional Long-Term Mechanism (LTM) occurs based on measurements at the terminal; therefore, the base station may not know the exact timing or which beam is best. In other words, the beam directed by the base station may not always be the best.

[0259] Alternatively, the terminal can update and use this only when the beam at the time of conditional LTM implementation is better than the beam instructed by the base station.

[0260] ■ Downlink synchronization is performed using the base station direct beam, and UL data transmission can be done using a different beam. That is, for the first UL transmission, the best beam of the event that satisfies the actual conditional LTM can be used.

[0261] If, while the configured TA timer is operating, an event triggering a conditional LTM in step 7-80 is satisfied and the conditional LTM is triggered, the terminal (7-01) can perform a RACH-less conditional LTM operation to the target cell that satisfies the condition without a separate L1 measurement report. The source cell beam used when the terminal evaluates the LTM conditional event in that step may be one of the following methods.

[0262] - Option 1: Use the TCI state specified from the source cell (via DCI or MAC CE; the beam used for receiving PDCCH or PDSCH).

[0263] - Option 2: Even if a beam designated by the base station exists, when the conditional LTM evaluates an event, use the source cell's best beam (or the best beam among the designated beams determined by the terminal's judgment) based on the terminal's own measurement.

[0264] At this stage, the terminal may obtain a TA through a UE-based TA operation and perform a RACH-less conditional LTM to the corresponding target cell. This means that if an LTM candidate cell, in which the event-based conditional LTM execution condition is satisfied according to the base station configuration, is a cell where a UE-based TA can be performed, the terminal can obtain an uplink TA through a downlink signal (e.g., DL RS) and perform a RACH-less conditional LTM by applying the value. Here, the cell where a UE-based TA can be performed may be a cell co-located with the serving cell, and a cell configuration that is possible in association with the serving cell is provided through the RRC configuration. Refer to the UE-based TA related configuration described above in FIG. 7-20.

[0265] That is, in step 7-85, the terminal (7-01) performs the transmission of a first MAC PDU containing an RRCReconfigurationComplete message for a pre-configured RRCReconfiguration for the target cell (LTM candidate cell) through a pre-configured initial transmission resource to the target cell (a CG resource configured based on RRC or a resource scheduled via Dynamic grant (DG) through PDCCH monitoring). As an example of a DG-based UL resource transmission method, the following method may be used.

[0266] - Option 1: If a TA value for conditional LTM is provided in each LTM candidate cell, resource settings for the first UL transmission are continuously provided to the corresponding terminal via the PDCCH addressed based on the C-RNTI provided in the conditional LTM candidate cell settings (PDCCH delivery cycle is adjusted according to the base station implementation).

[0267] - Option 2: If a TA value for the Conditional LTM is provided in each LTM candidate cell, and the applicable TCI state in the target cell is transmitted via the Candidate cell TCI state activation / deactivation MAC CE in that candidate cell, resource configuration for the first UL transmission is provided to the terminal only from resources associated with the previously specified TCI state (beam) via the PDCCH addressed based on the C-RNTI provided in the Conditional LTM candidate cell configuration. Similarly, after changing to that cell, the terminal performs PDCCH monitoring via the beam of that cell known through the Candidate cell TCI state activation / deactivation MAC CE, and obtains the UL grant.

[0268] In an LTM candidate cell, for the efficiency of DG resources, scheduling for DG resources is terminated when the TA timer of the terminal operating in the target cell expires. That is, the LTM candidate cell does not transmit PDCCH scheduling. If both DG and CG resources are configured, the terminal monitors for the faster resource.

[0269] The terminal may receive an ACK for the transmission of the first MAC PDU, and the ACK may include a DCI containing uplink or downlink scheduling information. The terminal may stop the running TA timer when the handover procedure to the target cell is completed (i.e., when the first MAC PDU is transmitted to the target cell and an ACK is received). However, if the running TA timer expires to a set value, the terminal considers the RACH-less handover operation to have failed and performs a different subsequent operation. For example, if the TA timer expires, the terminal may perform the operation of Method 1 or Method 2.

[0270] 1. Method 1: The terminal determines that there is a RACH-less conditional LTM failure and performs a random access-based LTM operation on the cell. If that operation also fails, it performs the conditional LTM failure procedure described below.

[0271] 2. Method 2: The terminal determines that there is a RACH-less conditional LTM failure and immediately performs the following conditional LTM failure procedure.

[0272] If the conditional LTM procedure fails (e.g., radio link failure, random access failure, T304 timer completion, etc.), the terminal can maintain the previously configured LTM settings and fall back to the source cell. If the fallback to the source cell fails, the terminal (6-01) can perform an RRC re-establishment procedure, and if cell selection is performed, the terminal can perform a connection procedure by applying the LTM settings if the selected cell is an LTM candidate cell. In this case, only random access-based LTM operation may be supported.

[0273] Below, the procedure for exchanging settings and information for an early TA applied to a RACH-less conditional LTM in steps 7-15 above between a source base station CU (7-03) and an LTM candidate cell is described in detail. In particular, the operation may be different depending on whether a RACH-less request for an existing LTM and a conditional LTM is provided simultaneously or if only one is requested separately.

[0274] - Situation 1: Source cell simultaneously provides RACH-less requests for existing LTM and conditional LTM

[0275] ■ The LTM candidate cell selects a TA method (existing RACH-less LTM method or conditional RACH-less LTM method), responds to the source cell, and applies the selected method to the terminal.

[0276] - Situation 2: The source cell provides only one of the RACH-less requests for the existing LTM and the conditional LTM.

[0277] ■ Apply the TA method requested by the LTM candidate cell (existing RACH-less LTM method or conditional RACH-less LTM method) to the terminal

[0278] In addition, when applying the above-mentioned conditional RACH-less LTM, conditional RACH-less LTM operation via a UE-based TA may be possible during the early TA procedure (particularly when a TA is received via MAC CE and the corresponding TA value is valid). That is, the early TA procedure and the UE-based TA procedure can be configured on the terminal simultaneously, and in this case, clear criteria are required for which action to perform. First, in both cases, the terminal possesses a valid TA value, and operation is possible regardless of which value is applied to execute the RACH-less conditional LTM. An example of the action performed by the terminal is as follows.

[0279] - Prioritize and execute TAs acquired through UE-based TA and Early TA procedures

[0280] ■ Increase the priority of UE-based TAs for application; or

[0281] ■ Apply the TA obtained through the Early TA process with higher priority.

[0282] - The above priority may also be transmitted by the base station to the terminal as a setting through RRC settings.

[0283] - Or, if you have TA through two methods, the terminal can take the average value and apply it.

[0284] - Or, if there are two methods to have TA, the terminal can select and apply one of them in terms of implementation.

[0285] - Example of priority action (when the Early TA procedure has high priority)

[0286] ■ When the terminal has TAs using two TA methods, apply the TA obtained through the Early TA.

[0287] ■ If you do not have a TA through Early TA but have a TA through UE-based TA, apply the TA through the UE-based TA.

[0288] ■ If the TA of the target cell is not obtained through both methods, perform random access (conditional LTM)

[0289] FIG. 8 is a diagram illustrating a MAC (medium access control) CE (control element) structure that transmits the TA (timing advance) value of an LTM (L1 / L2 triggered mobility) candidate cell acquired by a source cell to a terminal according to one embodiment of the present disclosure.

[0290] In FIG. 8, it is proposed that the MAC CE basically includes LTM candidate cell information and a valid TA value calculated based on the random access preamble transmitted by the terminal to the corresponding cell; in 8-05, a case is proposed where one LTM candidate cell information and TA value are included within a single MAC CE; and in 8-25 and 8-60, cases are proposed where multiple LTM candidate cell information and TA values ​​are included within a single MAC CE. In particular, in 8-60, the TA value of a specific LTM candidate cell may be indicated by a bitmap instead of a Target Config ID. Basically, the MAC CE that transmits the TA value of the LTM candidate cell acquired by the source cell to the terminal will be transmitted via a new downlink MAC CE and may be specified by a new LCID or eLCID. Alternatively, the existing Timing Advance Command MAC CE and Absolute Timing Advance Command MAC CE may be modified and used. In this case, an indicator indicating the target candidate cell may be added and used.

[0291] - R bit (8-10): reserved bit

[0292] - C bit (8-30, 8-45): A field used to indicate the presence of multiple target cell information and TAs. When set to 1, it indicates the existence of subsequent additional target cell information and TAs. When set to 0, it indicates that no additional target cell information or TAs exist.

[0293] - LTM Candidate Cell (Target Cell) Information (8-15, 8-35, 8-50): Target cell configuration Index

[0294] - LTM candidate cell (target cell) information (Di; 8-65): Target cell configuration bitmap. Instructions for the i-th cell

[0295] - Timing Advance Command (8-20, 8-40, 8-55): This can be transmitted using absolute value information or the difference information from the TA information in the current source cell, which is the TA information the terminal must apply in the corresponding target cell. It may indicate that there is no valid value (e.g., set to FFF) or represent the same value as the source cell (e.g., set to 0).

[0296] - Timing Advance Command (8-70): TA information applied to the i-th cell

[0297] - Timing Advance Command: This field indicates whether the TA is valid for the LTM target cell (i.e. the SpCell corresponding to the target configuration indicated by Target Configuration ID field). If the value of this field is set to FFF, this field indicates that no valid timing adjustment is available for the PTAG of the LTM target cell; otherwise, this field indicates the index value TA used to control the amount of timing adjustment that the MAC entity has to apply in TS 38.213 [6], and that the UE can skip the Random Access procedure for this LTM cell switch. If tag-Id-ptr is configured for the TCI state indicated by the UL TCI state ID field, if present, or by the TCI state ID field otherwise, in the LTM target cell and tag-Id-ptr is set to value n1, this field indicates the TA for the TAG indicated by the tag2-Id of the LTM target cell; otherwise, this field indicates the TA for the TAG indicated by the tag-id of the LTM target cell. The length of the field is 12 bits;

[0298] FIG. 9 is a diagram illustrating the overall terminal operation of performing a conditional LTM without random access according to one embodiment of the present disclosure.

[0299] In step 9-05, the terminal in the connection state can receive configuration information from a surrounding cell to which LTM is applied after L1 / L2-based mobility (LTM) is instructed via an RRC reset message from the serving cell. The detailed configuration method and content are the same as those described above in FIGS. 6 and 7. Additionally, although not shown in FIG. 9, prior to the RRC configuration information, the terminal has received basic RRC configuration from the base station and can perform an operation to report layer 3 measurements for surrounding cells. In particular, the configuration information from the LTM candidate cell to which LTM is applied after the LTM cell change received in step 9-05 is instructed or after conditional LTM is triggered is characterized by the fact that a delta configuration is applied based on the configuration of a reference cell and transmitted to the terminal.

[0300] The terminal can determine what the received reference cell and its configuration information are, whether known in advance or instructed by the RRC settings. In the case of configurations for surrounding cells other than the reference cell, signaling overhead is low because the reference cell settings are shared and additional settings that can be added to them are transmitted to the terminal.

[0301] In the configuration of step 9-05 above, the terminal may receive configuration information related to resources and reporting for L1 measurement for LTM candidate cells. In particular, the present disclosure is characterized by determining configuration information for RACH-less conditional LTM in step 9-05 through coordination between the source cell and the LTM candidate cells. In particular, the configuration information received by the terminal in step 9-05 may include configuration information related to whether early TA and UE-based TA are applied for RACH-less conditional LTM, event-based condition settings for conditional LTM, TA timer settings for RACH-less conditional LTM, and UL grant related settings when RACH-less conditional LTM is performed.

[0302] In steps 9-10, the terminal can decode the settings for the received LTM candidate cells based on the settings of the reference cell, and store and manage the complete settings that are actually applied (i.e., the operation of saving the delta-configured settings 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 may decode the received settings based on the reference cell and store and manage the received RRC settings as they are in the buffer without storing or managing the settings that are actually applied.

[0303] In steps 9-15, the terminal maintains a connection with the serving cell and performs L1 measurements configured with SSB or CSI-RS resources associated with candidate surrounding cells, and can report the measurement results to the serving cell according to a pre-configured L1 measurement reporting method. Target cells configured with CSI-RS resources may be provided with settings distinct from cells configured with SSB resources, or L1 resource settings provided by LTM candidate cells may be listed without distinction. Additionally, L1 measurement settings for existing LTM and conditional LTM may be applied commonly without separate distinction. However, for conditional LTM, event-based triggering conditions may be used for measurement reporting settings, which can be transmitted to the terminal in conjunction with the L1 measurement settings. In this step, L1 / L2-based semi-persistent / aperiodic L1 channel measurements may be instructed. In this step, the base station can control L1 measurement resource reporting for LTM surrounding cells requiring measurement through RRC settings and L1 / L2 signaling. The terminal performs L1 measurement resource reporting according to the base station settings and instructions. In addition, independently of the operation, surrounding cells are measured according to the L3 measurement settings, and the measurement results are reported to the base station according to the L3 measurement reporting settings.

[0304] In steps 9-20, if the serving cell determines, based on the received measurement results, that a terminal supporting RACH-less conditional LTM requires a RACH-less conditional LTM to a specific LTM candidate cell, it may transmit a PDCCH order containing the index of the corresponding LTM candidate cell and instruct the terminal to enter the early TA acquisition procedure for the RACH-less conditional LTM to the corresponding candidate cell. The PDCCH order may reuse the format used for the existing LTM, or it may be a new PDCCH order with an added field indicating that it is a conditional LTM. Upon receiving this, the terminal may transmit a pre-configured preamble to the corresponding candidate cell.

[0305] In steps 9-25, the terminal may receive a MAC CE containing LTM candidate cell information and a valid TA from the candidate cell via the source cell in response to the transmission of the random access preamble in the above steps. The MAC CE may be the MAC CE described in detail in FIG. 8. The terminal may start a TA timer the moment it obtains a valid TA. That is, while the timer is running, the terminal determines that the received TA value is valid.

[0306] Subsequently, in steps 9-30, the terminal checks (or determines) whether a conditional LTM is triggered (or whether a conditional LTM condition is satisfied) while the TA timer is running.

[0307] While the timer is running, if a conditional LTM is triggered based on the L1 measurement value, the terminal performs a RACH-less conditional LTM in step 9-35. That is, in step 9-40, the terminal can transmit the first MAC PDU containing the RRCReconfigurationComplete message to the target cell through a pre-configured UL grant resource (UL grant including CG and DG). If the terminal receives an ACK for the transmission (receipt of DCI including UL or DL ​​scheduling), it can be determined that the RACH-less conditional LTM operation is complete (9-40). Subsequently, the terminal performs data transmission and reception with the target cell.

[0308] On the other hand, if a conditional LTM is triggered based on an L1 measurement value after the TA timer expires, the terminal performs a RACH-based conditional LTM in steps 9-45.

[0309] FIG. 10 is a drawing illustrating base station operation according to one embodiment of the present disclosure.

[0310] In step 10-05, 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.

[0311] In step 10-10, the base station requests configuration information for RACH-less conditional LTM from surrounding cells and receives responses from those cells. In step 10-10, the base station may transmit configuration information for the current source cell and reference cell configuration information together to the surrounding cells, and may receive RRC configuration information where delta configuration is applied based on the reference cell configuration information from the surrounding cells and LTM candidate cells. The procedures described in detail in Figures 6 and 7 may be included in this step, and in particular, may include determining L1 measurement resources and reporting settings, securing early TA and UE-based TA for RACH-less conditional LTM, TA timers, and UL garnt settings. Although not shown in this figure, prior to this step, settings related to L3 measurement settings and basic RRC settings are provided to the terminal.

[0312] In steps 10-15, the base station transmits an RRC configuration message to the connected terminal, which includes the surrounding cell configuration information and L1 measurement resource / reporting settings received in step 10-10. That is, the base station can transmit to the terminal configuration information from the surrounding cell that is applied after L1 / L2-based mobility (LTM) is instructed via an RRC reset message from the serving cell. The specific configuration method, configuration information, and configuration details are described in detail in FIGS. 6 and 7.

[0313] Subsequently, in steps 10-20, the base station may instruct the terminal to report L1 measurements in various ways via RRC or L1 / L2 signaling according to the L1 measurements and reports for which configuration and triggering are desired. For details on the method, refer to the disclosure in FIG. 7. In steps 10-20, the base station receives reports of L1 and L3 measurements from the terminal, wherein the L1 measurement may be a non-serving cell that supports L1 / L2-based mobility (LTM).

[0314] The serving cell determines whether a RACH-less conditional LTM is applied based on the received measurement results, and in steps 10-25, transmits a PDCCH order for the RACH-less conditional LTM to the terminal to instruct the procedure for obtaining a TA for the RACH-less conditional LTM to the corresponding candidate cell.

[0315] In steps 10-30, the base station receives valid TA information for the terminal from the LTM candidate cell for the terminal that has delivered the random access preamble for the early TA to the candidate cells, and can deliver a TA MAC CE (see FIG. 8) containing the valid TA information and the information of the target candidate cell to the terminal. Additionally, in steps 10-30, the base station can notify the candidate cells via an F1 interface message that the TA MAC CE has been delivered to the terminal. This is because information is needed from the perspective of the target candidate cell regarding when the terminal receives the TA MAC CE and starts the TA timer. Through this, the target candidate cell can determine the period during which the delivered TA value is valid, and subsequently, depending on whether the TA value is valid, it can request the early TA procedure again or decide not to support the RACH-less conditional LTM operation any further.

[0316] Subsequently, when the base station receives a handover completion message from the target cell in steps 10-35, the base station confirms that the corresponding LTM operation has been successfully completed and accordingly releases the terminal context. On the other hand, if the base station receives a handover failure report message containing information that the handover failed in steps 10-40, the base station can determine that the terminal attempted to reconnect to the serving cell after the handover failure. The handover failure report message may be a UEInformationResponse or another uplink RRC message. Additionally, it 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.

[0317] - An indicator that the handover failed due to an LTM failure

[0318] - Target cell information where LTM attempt failed: LTM cell configuration index or actual cell index (PCI; Physical Cell Index) information

[0319] The source base station can know that the LTM attempt failed and fell back to the cell through the handover failure message report.

[0320] FIG. 11 is a block diagram illustrating the internal structure of a terminal according to one embodiment of the present disclosure.

[0321] Referring to the drawing above, the terminal includes an RF (Radio Frequency) processing unit (11-10), a baseband processing unit (11-20), a storage unit (11-30), and a control unit (11-40).

[0322] The RF processing unit (11-10) performs functions for transmitting and receiving signals through a wireless channel, such as signal band conversion and amplification. That is, the RF processing unit (11-10) up-converts the baseband signal provided by the baseband processing unit (11-20) 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 (11-10) 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 (11-10) may include multiple RF chains. Furthermore, the RF processing unit (11-10) may perform beamforming. For the above beamforming, the RF processing unit (11-10) 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.

[0323] The baseband processing unit (11-20) 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 (11-20) generates complex symbols by encoding and modulating the transmitted bit sequence. Additionally, when receiving data, the baseband processing unit (11-20) restores the received bit sequence by demodulating and decoding the baseband signal provided by the RF processing unit (11-10). For example, in the case of following the OFDM (orthogonal frequency division multiplexing) method, when transmitting data, the baseband processing unit (11-20) 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 (11-20) divides the baseband signal provided by the RF processing unit (11-10) 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.

[0324] The baseband processing unit (11-20) and the RF processing unit (11-10) transmit and receive signals as described above. Accordingly, the baseband processing unit (11-20) and the RF processing unit (11-10) 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 (11-20) and the RF processing unit (11-10) 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 (11-20) and the RF processing unit (11-10) 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.

[0325] The storage unit (11-30) stores data such as basic programs, application programs, and setting information for the operation of the terminal. In particular, the storage unit (11-30) can store information related to a second connection node that performs wireless communication using a second wireless connection technology. Additionally, the storage unit (11-30) provides the stored data upon the request of the control unit (11-40).

[0326] The control unit (11-40) controls the overall operations of the terminal. For example, the control unit (11-40) transmits and receives signals through the baseband processing unit (11-20) and the RF processing unit (11-10). Additionally, the control unit (11-40) writes and reads data to and from the storage unit (11-40). To this end, the control unit (11-40) may include at least one processor. For example, the control unit (11-40) may include a communication processor (CP) that performs control for communication and an application processor (AP) that controls upper layers such as applications.

[0327] FIG. 12 is a block diagram showing the configuration of a base station according to one embodiment of the present disclosure.

[0328] As illustrated in the drawing above, the base station is configured to include an RF processing unit (12-10), a baseband processing unit (12-20), a backhaul communication unit (12-30), a storage unit (12-40), and a control unit (12-50).

[0329] The RF processing unit (12-10) performs functions for transmitting and receiving signals through a wireless channel, such as signal band conversion and amplification. That is, the RF processing unit (12-10) upconverts the baseband signal provided by the baseband processing unit (12-20) into an RF band signal and 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 (12-10) may include a transmission filter, a reception 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. In addition, the RF processing unit (12-10) may include multiple RF chains. Furthermore, the RF processing unit (12-10) may perform beamforming. For the above beamforming, the RF processing unit (12-10) 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.

[0330] The baseband processing unit (12-20) 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 (12-20) generates complex symbols by encoding and modulating the transmitted bit sequence. Additionally, when receiving data, the baseband processing unit (12-20) restores the received bit sequence by demodulating and decoding the baseband signal provided by the RF processing unit (12-10). For example, in the case of following the OFDM method, when transmitting data, the baseband processing unit (12-20) 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 (12-20) divides the baseband signal provided by the RF processing unit (12-10) 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 (12-20) and the RF processing unit (12-10) transmit and receive signals as described above. Accordingly, the baseband processing unit (12-20) and the RF processing unit (12-10) may be referred to as a transmitting unit, a receiving unit, a transmitting and receiving unit, a communication unit, or a wireless communication unit.

[0331] The backhaul communication unit (12-30) provides an interface for communicating with other nodes within the network. That is, the backhaul communication unit (12-30) 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.

[0332] The storage unit (12-40) stores data such as basic programs, application programs, and configuration information for the operation of the main station. In particular, the storage unit (12-40) can store information regarding bearers assigned to connected terminals, measurement results reported from connected terminals, etc. Additionally, the storage unit (12-40) 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 (12-40) provides the stored data upon the request of the control unit (12-50).

[0333] The control unit (12-50) controls the overall operations of the main station. For example, the control unit (12-50) transmits and receives signals through the baseband processing unit (12-20) and the RF processing unit (12-10) or through the backhaul communication unit (12-30). Additionally, the control unit (12-50) writes and reads data to and from the storage unit (12-40). To this end, the control unit (10-50) may include at least one processor.

[0334] Methods according to the embodiments described in the claims or specification of the present invention may be implemented in the form of hardware, software, or a combination of hardware and software.

[0335] 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.

[0336] 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.

[0337] 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.

[0338] In the specific embodiments of the present invention described above, the components included in the invention are expressed in a singular or plural form according to the specific embodiments presented. However, the singular or plural expression is selected to suit the situation presented for convenience of explanation, and the present invention is not limited to singular or plural components; even if a component is expressed in the plural form, it may be composed in the singular form, or even if a component is expressed in the singular form, it may be composed in the plural form.

[0339] Meanwhile, although specific embodiments have been described in the detailed description of the present invention, it is understood that various modifications are possible within the scope of the present invention. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be defined by the claims set forth below as well as equivalents thereof.

Claims

1. A method performed by a terminal in a wireless communication system, A step of receiving a radio resource control (RRC) reset message from a base station, the message including configuration information for a candidate cell of a conditional LTM (layer 1 / layer 2 triggered mobility) and information regarding the execution conditions of the conditional LTM; wherein the configuration information includes information regarding the value of a timer for identifying the validity of a timing advance (TA), and the timer is associated with the candidate cell; A step of evaluating whether the execution condition of the conditional LTM is satisfied based on the information regarding the execution condition of the conditional LTM; A step of receiving a MAC CE (medium access control control element) containing information about the TA value of the candidate cell from the base station; When the above execution conditions are satisfied, a step of checking whether the timer is running; and A method of a terminal characterized by including the step of performing a RACH-less conditional LTM cell switch by applying the TA value when the above timer is running.

2. In Paragraph 1, The method further includes the step of performing a RACH-based conditional LTM cell change when the above timer expires, and The above MAC CE further includes information indicating the index of the LTM candidate setting for the above candidate cell, and A method of a terminal characterized in that the above timer is driven based on the reception of the above MAC CE.

3. In Paragraph 1, A step of receiving a PDCCH order from the base station; and The method further includes the step of transmitting a random access preamble to the candidate cell based on the PDCCH (physical downlink control channel) order. The above MAC CE is received based on the transmission of the above random access preamble, and A method of a terminal characterized in that the above-mentioned configuration information further includes information about a random access resource used for transmitting the above-mentioned random access preamble.

4. In Paragraph 1, The event corresponding to the above execution condition is satisfied when the quality of the first beam of the candidate cell is better than the quality of the second beam of the serving cell by an offset, or when the quality of the first beam is worse than the first absolute value and the quality of the second beam is greater than the second absolute value, and A method of a terminal characterized in that the second beam is indicated by the TCI (transmission configuration indicator) state of the serving cell.

5. In Paragraph 1, The method further includes the step of performing an uplink transmission to the above candidate cell through a CG (configured grant); The above uplink transmission includes the transmission of an RRC reset completion message, and The uplink transmission through the above CG is performed based on a beam corresponding to the beam of the candidate cell associated with the execution condition, and A method of a terminal characterized in that the above setting information further includes setting information for the above CG.

6. In a method performed by a base station in a wireless communication system, A step of transmitting a radio resource control (RRC) reset message to a terminal, the message including configuration information for a candidate cell of a conditional LTM (layer 1 / layer 2 triggered mobility) and information on the execution conditions of the conditional LTM; wherein the configuration information includes information on the value of a timer for identifying the validity of a timing advance (TA), and the timer is associated with the candidate cell; A step of receiving information about the TA value of the candidate cell from the candidate cell; and The method includes the step of transmitting a MAC CE (medium access control control element) containing information regarding the TA value to the terminal. A method of a base station characterized by performing a RACH-less conditional LTM cell switch based on the TA value when the above execution conditions are satisfied and the above timer is running.

7. In Paragraph 6, The method further includes the step of transmitting a PDCCH order to the above terminal, and The above TA value is received from the above candidate cell based on a random access preamble transmitted to the above candidate cell based on the PDCCH (physical downlink control channel) order, and The above configuration information further includes information regarding random access resources used for transmitting the above random access preamble, and When the above timer expires, a RACH-based conditional LTM cell change is performed, and The above MAC CE further includes information indicating the index of the LTM candidate setting for the above candidate cell, and The above timer is driven based on the reception of the above MAC CE, and The event corresponding to the above execution condition is satisfied when the quality of the first beam of the candidate cell is better than the quality of the second beam of the serving cell by an offset, or when the quality of the first beam is worse than the first absolute value and the quality of the second beam is greater than the second absolute value, and A method of a base station characterized in that the second beam is indicated by the transmission configuration indicator (TCI) state of the serving cell.

8. In Paragraph 6, The above conditional LTM is supported in the above base station inter-base station LTM, and The above candidate cell is included in the above base station, and The information regarding the above TA value is transmitted from the candidate cell of the base station to the serving cell of the base station, and The candidate cell of the above base station performs uplink reception through a configured grant (CG), and The above uplink reception includes the reception of an RRC reset completion message, and The uplink reception through the above CG is performed based on a beam corresponding to the beam of the candidate cell associated with the execution condition, and A method of a base station characterized by the above setting information further including setting information for the above CG.

9. In a terminal of a wireless communication system, Transceiver; At least one processor connected to communicate with the above transceiver; and Connected to communicate with at least one processor, and the terminal: Receive a radio resource control (RRC) reset message from a base station containing configuration information for a candidate cell of conditional LTM (layer 1 / layer 2 triggered mobility) and information on the execution conditions of said conditional LTM, wherein the configuration information includes information on the value of a timer for identifying the validity of a timing advance (TA), and said timer is associated with said candidate cell. Based on the information regarding the execution conditions of the above conditional LTM, an evaluation is performed to determine whether the execution conditions of the above conditional LTM are satisfied, and Receive a MAC CE (medium access control control element) containing information about the TA value of the candidate cell from the base station, and If the above execution condition is satisfied, check whether the above timer is running, and A terminal comprising: a memory storing a command that causes a RACH-less conditional LTM cell switch to be performed by applying the TA value when the above timer is running.

10. In Paragraph 9, The above command further causes the terminal to perform a RACH-based conditional LTM cell change when the timer expires, and The above MAC CE further includes information indicating the index of the LTM candidate setting for the above candidate cell, and A terminal characterized in that the above timer is driven based on the reception of the above MAC CE.

11. In Paragraph 9, The above command, the above terminal, Receive a PDCCH order from the above base station, and Further causing the above candidate cell to transmit a random access preamble based on the above PDCCH (physical downlink control channel) order, and The above MAC CE is received based on the transmission of the above random access preamble, and The above configuration information further includes information regarding random access resources used for transmitting the above random access preamble, and The event corresponding to the above execution condition is satisfied when the quality of the first beam of the candidate cell is better than the quality of the second beam of the serving cell by an offset, or when the quality of the first beam is worse than the first absolute value and the quality of the second beam is greater than the second absolute value, and A terminal characterized in that the second beam is indicated by the TCI (transmission configuration indicator) state of the serving cell.

12. In Paragraph 9, The above command further causes the terminal to perform an uplink transmission to the candidate cell via a configured grant (CG), and The above uplink transmission includes the transmission of an RRC reset completion message, and The uplink transmission through the above CG is performed based on a beam corresponding to the beam of the candidate cell associated with the execution condition, and A terminal characterized by the above setting information further including setting information for the above CG.

13. In a base station of a wireless communication system, Transceiver; At least one processor connected to communicate with the above transceiver; and Connected to communicate with at least one processor, and the base station: Transmit a radio resource control (RRC) reset message to a terminal, the message including configuration information for a candidate cell of a conditional LTM (layer 1 / layer 2 triggered mobility) and information on the execution conditions of said conditional LTM; wherein the configuration information includes information on the value of a timer for identifying the validity of a timing advance (TA), and said timer is associated with said candidate cell. From the above candidate cell, information regarding the TA value of the above candidate cell is received, and A memory storing a command that causes the terminal to transmit a MAC CE (medium access control control element) containing information regarding the TA value; A base station characterized by performing a RACH-less conditional LTM cell switch based on the TA value when the above execution conditions are satisfied and the above timer is running.

14. In Paragraph 13, The above command further causes the base station to transmit a PDCCH order to the terminal, and The above TA value is received from the above candidate cell based on a random access preamble transmitted to the above candidate cell based on the PDCCH (physical downlink control channel) order, and The above configuration information further includes information regarding random access resources used for transmitting the above random access preamble, and When the above timer expires, a RACH-based conditional LTM cell change is performed, and The above MAC CE further includes information indicating the index of the LTM candidate setting for the above candidate cell, and The above timer is driven based on the reception of the above MAC CE, and The event corresponding to the above execution condition is satisfied when the quality of the first beam of the candidate cell is better than the quality of the second beam of the serving cell by an offset, or when the quality of the first beam is worse than the first absolute value and the quality of the second beam is greater than the second absolute value, and A base station characterized in that the second beam is indicated by the TCI (transmission configuration indicator) state of the serving cell.

15. In Paragraph 13, The above conditional LTM is supported in the above base station inter-base station LTM, and The above candidate cell is included in the above base station, and The information regarding the above TA value is transmitted from the candidate cell of the base station to the serving cell of the base station, and The candidate cell of the above base station performs uplink reception through a configured grant (CG), and The above uplink reception includes the reception of an RRC reset completion message, and The uplink reception through the above CG is performed based on a beam corresponding to the beam of the candidate cell associated with the execution condition, and A base station characterized by the above setting information further including setting information for the above CG.

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