Method and device for determining l1-based handover according to performance of serving cell in next generation mobile communication system

Abstract

The present invention provides a terminal, a base station, and a method for measuring a serving cell on the basis of an RRC message including information for configuring an s-measure to be performed in an LTM candidate cell and determining whether to measure an L1 channel of LTM candidate cells on the basis of a signal of the serving cell and configuration information.

Description

Method and device for determining L1-based handover based on serving cell performance in a next-generation mobile communication system

[0001] The present invention relates to the operation of a terminal and a base station in a mobile communication system. More specifically, the present invention relates to a method and device for determining L1-based handover based on serving cell performance.

[0002] 5G mobile communication technology defines a wide frequency band to enable fast transmission speeds and new services, and can be implemented not only in the sub-6GHz frequency band such as 3.5 gigahertz (3.5GHz), but also in the ultra-high frequency band called millimeter wave (mmWave) such as 28GHz and 39GHz ('Above 6GHz'). In addition, for 6G mobile communication technology, which is called the system after 5G communication (Beyond 5G), implementation in the terahertz band (for example, the 3 terahertz (3THz) band at 95GHz) is being considered to achieve a transmission speed that is 50 times faster than 5G mobile communication technology and an ultra-low latency time that is reduced to one-tenth.

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

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

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

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

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

[0008] The present disclosure allows a terminal, while currently receiving service from a serving cell via a specific beam, to measure and report a beam belonging to another cell, and, if the beam of a neighboring cell is improved, to be instructed to change cells to that cell via L1 / L2 signaling. In particular, if a Layer 1 measurement configuration for a target cell to be measured is provided, the terminal must always measure and report the corresponding measurement resource. However, if the performance of the current serving cell (PCell, PSCell) is sufficiently good, the base station may not instruct a cell change even if measurement reports are performed for the corresponding LTM (Layer 1 / Layer 2 triggered mobility) candidate cells. Therefore, a method for effectively reporting LTM Layer 1 measurements is needed.

[0009] The technical problems to be achieved in the embodiments of the present disclosure are not limited to the technical problems mentioned above, and other technical problems not mentioned can be clearly understood by a person having ordinary skill in the technical field to which the present disclosure belongs from the description below.

[0010] In order to solve these problems, the present disclosure provides a method performed by a terminal supporting Layer 1 (L1) / Layer 2 (L2) Triggered Mobility (LTM) of a wireless communication system, the method comprising: receiving, from a base station, a radio resource control (RRC) message including configuration information for setting s-measure to be performed in at least one LTM candidate cell; measuring a signal of a serving cell; and determining, based on the signal of the serving cell and the configuration information, whether to measure an L1 channel of the at least one LTM candidate cell.

[0011] In order to solve these problems, the present disclosure provides a method performed by a base station supporting Layer 1 (L1) / Layer 2 (L2) Triggered Mobility (LTM) of a wireless communication system, the method comprising the steps of: transmitting, to a terminal, a radio resource control (RRC) message including configuration information for setting s-measure to be performed in at least one LTM candidate cell; and receiving, based on a signal of a serving cell and the configuration information, a result of L1 channel measurement of at least one LTM candidate cell.

[0012] In order to solve these problems, the present disclosure provides a terminal supporting Layer 1 (L1) / Layer 2 (L2) Triggered Mobility (LTM) of a wireless communication system, comprising: a transceiver for transmitting and receiving signals; and a control unit, wherein the control unit receives, from a base station, a radio resource control (RRC) message including configuration information for setting s-measure to be performed in at least one LTM candidate cell, measures a signal of a serving cell, and determines, based on the signal of the serving cell and the configuration information, whether to measure an L1 channel of the at least one LTM candidate cell.

[0013] In order to solve these problems, the present disclosure provides a base station supporting Layer 1 (L1) / Layer 2 (L2) Triggered Mobility (LTM) of a wireless communication system, comprising: a transceiver for transmitting and receiving signals; and a control unit, wherein the control unit transmits, to a terminal, a radio resource control (RRC) message including configuration information for setting s-measure to be performed in at least one LTM candidate cell, and receives a result of L1 channel measurement of at least one LTM candidate cell based on a signal of a serving cell and the configuration information.

[0014] The proposed s-measure support in LTM enables more efficient LTM layer 1 measurements. More specifically, instead of always measuring the target cell, the terminal can be configured to measure only when the channel performance of the SpCell (PCell, PSCell) is worse than a certain threshold. This reduces the measurement complexity of the terminal, enables efficient layer 1 measurements, and provides mobility support.

[0015] The effects that can be obtained from the present disclosure are not limited to the effects mentioned in the various embodiments, and other effects that are not mentioned can be clearly understood by a person having ordinary skill in the art to which the present disclosure belongs from the description below.

[0016] FIG. 1a is a diagram illustrating the structure of a next-generation mobile communication system to which the present disclosure can be applied.

[0017] FIG. 1b is a diagram showing a wireless protocol structure of a next-generation mobile communication system to which the present disclosure can be applied.

[0018] FIG. 1c is a diagram illustrating the structure of another next-generation mobile communication system to which the present disclosure can be applied.

[0019] FIG. 1D is a diagram illustrating a method for changing a serving cell and beam to a target cell supporting Layer1 (L1) / Layer2 (L2) based cell change according to one embodiment of the present disclosure.

[0020] FIG. 1e is a diagram illustrating a method for performing measurement and reporting on an LTM candidate cell by applying s-measure in an intra-CU situation according to one embodiment of the present disclosure.

[0021] FIG. 1f is a diagram illustrating the operation of a terminal according to an embodiment of the present disclosure.

[0022] FIG. 1g is a diagram illustrating the operation of a base station in one embodiment of the present disclosure.

[0023] FIG. 1h is a block diagram illustrating the structure of a terminal according to an embodiment of the present disclosure.

[0024] FIG. 1i is a block diagram illustrating the structure of a base station according to one embodiment of the present disclosure.

[0025] Hereinafter, the operating principles of the present invention will be described in detail with reference to the attached drawings. In the following description of the present invention, if a detailed description of a related known function or configuration is judged to unnecessarily obscure the gist of the present invention, the detailed description thereof will be omitted. In addition, the terms described below are terms defined in consideration of the functions of the present invention, and these may vary depending on the intention or custom of the user or operator. Therefore, the definitions should be made based on the contents throughout this specification. Terms used in the following description, such as terms for identifying connection nodes, terms referring to network entities, terms referring to messages, terms referring to interfaces between network entities, and terms referring to various identification information, are examples for the convenience of explanation. Therefore, the present invention is not limited to the terms described below, and other terms referring to objects having equivalent technical meanings may be used.

[0026] Hereinafter, the base station is an entity that performs resource allocation of the terminal, and may be at least one of a gNode B, an eNode B, a Node B, a BS (Base Station), a wireless access unit, a base station controller, or a node on a network. The terminal may include a UE (User Equipment), an MS (Mobile Station), a cellular phone, a smartphone, a computer, or a multimedia system capable of performing a communication function. In the present disclosure, downlink (DL) refers to a wireless transmission path of a signal transmitted from a base station to a terminal, and uplink (UL) refers to a wireless transmission path of a signal transmitted from a terminal to a base station. In addition, although the LTE or LTE-A system may be described below as an example, the embodiments of the present disclosure may also be applied to other communication systems having similar technical backgrounds or channel types. For example, the 5th generation mobile communication technology (5G, new radio, NR) developed after LTE-A may be included in a system to which the embodiments of the present disclosure may be applied, and 5G below may also be a concept that includes existing LTE, LTE-A, and other similar services. Furthermore, the present disclosure may be applied to other communication systems with some modifications, as determined by a person skilled in the art, without significantly departing from the scope of the present disclosure. It will be appreciated that each block of the processing flow diagrams and combinations of the flow diagrams can be executed by computer program instructions.

[0027] These computer program instructions may be installed in a processor of a general-purpose computer, a special-purpose computer, or other programmable data processing apparatus, so that the instructions executed by the processor of the computer or other programmable data processing apparatus create means for performing the functions described in the flowchart block(s). These computer program instructions may also be stored in a computer-available or computer-readable memory that can be directed to a computer or other programmable data processing apparatus to implement functions in a particular manner, so that the instructions stored in the computer-available or computer-readable memory can produce an article of manufacture that includes instruction means for performing the functions described in the flowchart block(s). The computer program instructions may also be installed on a computer or other programmable data processing apparatus, so that a series of operational steps are performed on the computer or other programmable data processing apparatus to create a computer-implemented process, so that the instructions executing on the computer or other programmable data processing apparatus can provide steps for performing the functions described in the flowchart block(s).

[0028] Additionally, each block may represent a module, segment, or portion of code that contains one or more executable instructions for executing a specific logical function(s). It should also be noted that in some alternative implementation examples, the functions mentioned in the blocks may occur out of order. For example, two blocks shown in succession may in fact be executed substantially simultaneously, or the blocks may sometimes be executed in reverse order depending on the corresponding function. In this case, the term '~unit' used in the present embodiment means software or a hardware component such as an FPGA (Field Programmable Gate Array) or an ASIC (Application Specific Integrated Circuit), and the '~unit' may perform certain roles. However, the '~unit' is not limited to software or hardware. The '~unit' may be configured to be on an addressable storage medium and may be configured to execute one or more processors. Thus, as an example, the '~ unit' includes components such as software components, object-oriented software components, class components, and task components, processes, functions, attributes, procedures, subroutines, segments of program code, drivers, firmware, microcode, circuits, data, databases, data structures, tables, arrays, and variables. The functionality provided within the components and '~ units' may be combined into a smaller number of components and '~ units' or further separated into additional components and '~ units'. In addition, the components and '~ units' may be implemented to reproduce one or more CPUs within a device or a secure multimedia card. Also, in an embodiment, the '~ unit' may include one or more processors.

[0029] For convenience of explanation, 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 to these terms and names and can be equally applied to systems conforming to other standards.

[0030] FIG. 1a is a diagram illustrating the structure of a next-generation mobile communication system to which the present disclosure can be applied.

[0031] Referring to Fig. 1a, as illustrated, the wireless access network of the next-generation mobile communication system is composed of a next-generation base station (New Radio Node B, hereinafter referred to as NR NB, 1a-10) and a NR CN (New Radio Core Network, or NG CN: Next Generation Core Network, 1a-05). A user terminal (New Radio User Equipment, hereinafter referred to as NR UE or terminal, 1a-15) accesses an external network through the NR NB (1a-10) and the NR CN (1a-05).

[0032] In Fig. 1a, the NR NB (1a-10) corresponds to the eNB (Evolved Node B) of the existing LTE system. The NR NB is connected to the NR UE (1a-15) via a wireless channel and can provide a service superior to that of the existing Node B. In the next-generation mobile communication system, all user traffic is serviced through a shared channel, so a device that collects status information such as the buffer status of UEs, available transmission power status, and channel status and performs scheduling is required, and the NR NB (1a-10) is responsible for this. One NR NB typically controls multiple cells.

[0033] In order to implement ultra-high-speed data transmission compared to existing LTE, it can have a bandwidth that exceeds the existing maximum, and beamforming technology can be additionally grafted on Orthogonal Frequency Division Multiplexing (OFDM) as a wireless access technology. In addition, Adaptive Modulation & Coding (AMC) method, which determines the modulation scheme and channel coding rate according to the channel condition of the terminal, can be applied.

[0034] The NR CN (1a-05) performs functions such as mobility support, bearer setup, and quality of service (QoS) configuration. The NR CN is a device responsible for terminal mobility management as well as various control functions and is connected to multiple base stations. Furthermore, the next-generation mobile communication system can be interoperable with the existing LTE system, and the NR CN is connected to the mobility management entity (MME, 1a-25) via a network interface. The MME is connected to the existing base station, the eNB (1a-30).

[0035] FIG. 1b is a diagram showing a wireless protocol structure of a next-generation mobile communication system to which the present disclosure can be applied.

[0036] Referring to FIG. 1b, the wireless protocol of the next-generation mobile communication system is composed of NR SDAP (NR service data adaptation protocol, 1b-01, 1b-45), NR PDCP (NR packet data convergence protocol, 1b-05, 1b-40), NR RLC (NR radio link control, 1b-10, 1b-35), and NR MAC (NR medium access control, 1b-15, 1b-30) in the terminal and the new radio (NR) base station, respectively.

[0037] Key features of NR SDAP (1b-01, 1b-45) may include some of the following:

[0038] - Transfer of user plane data

[0039] - Mapping function between QoS flow and data bearer for both DL and UL

[0040] - Marking function of QoS flow ID for both uplink and downlink (marking QoS flow ID in both DL and UL packets)

[0041] - Ability to map relective QoS flow to data bearer for uplink SDAP PDUs (reflective QoS flow to DRB mapping for the UL SDAP PDUs).

[0042] For the above SDAP layer device, the terminal can be configured by RRC message for each PDCP layer device, each bearer, or each logical channel, whether to use the header of the SDAP layer device or whether to use the function of the SDAP layer device, and when the SDAP header is configured, the terminal can be instructed to update or reset the mapping information for the QoS flow and data bearer of the uplink and downlink with the NAS QoS reflection configuration 1-bit indicator (NAS reflective QoS) and the AS QoS reflection configuration 1-bit indicator (AS reflective QoS) of the SDAP header. The SDAP header can include QoS flow ID information indicating QoS. The QoS information can be used as data processing priority, scheduling information, etc. to support a smooth service.

[0043] The main functions of NR PDCP (1b-05, 1b-40) may include some of the following functions:

[0044] ● Header compression and decompression (ROHC only)

[0045] ● User data transfer function

[0046] ● In-sequence delivery of upper layer PDUs

[0047] ● Out-of-sequence delivery of upper layer PDUs

[0048] ● Reordering function (PDCP PDU reordering for reception)

[0049] ● Duplicate detection of lower layer SDUs

[0050] ● Retransmission function (Retransmission of PDCP SDUs)

[0051] ● Encryption and decryption functions (Ciphering and deciphering)

[0052] ● Timer-based SDU discard in uplink

[0053] The reordering function of the NR PDCP device above refers to a function of reordering PDCP PDUs received from a lower layer in order based on the PDCP SN (sequence number), and may include a function of transmitting data to an upper layer in the reordered order, or may include a function of transmitting data directly without considering the order, may include a function of recording lost PDCP PDUs by reordering the order, may include a function of reporting the status of lost PDCP PDUs to the transmitting side, and may include a function of requesting retransmission of lost PDCP PDUs.

[0054] The main functions of NR RLC (1b-10, 1b-35) may include some of the following functions:

[0055] ● Data transfer function (Transfer of upper layer PDUs)

[0056] ● In-sequence delivery of upper layer PDUs

[0057] ● Out-of-sequence delivery of upper layer PDUs

[0058] ● ARQ function (Error Correction through ARQ)

[0059] ● Concatenation, segmentation and reassembly of RLC SDUs

[0060] ● Re-segmentation of RLC data PDUs

[0061] ● Reordering of RLC data PDUs

[0062] ● Duplicate detection function

[0063] ● Error detection function (Protocol error detection)

[0064] ● RLC SDU discard function

[0065] ● RLC re-establishment function

[0066] The in-sequence delivery function of the NR RLC device above refers to the function of sequentially transmitting RLC SDUs received from a lower layer to an upper layer, and may include a function of reassembling and transmitting RLC SDUs when an RLC SDU is originally received divided into multiple RLC SDUs, may include a function of reordering received RLC PDUs based on RLC SN (sequence number) or PDCP SN (sequence number), may include a function of recording lost RLC PDUs by reordering the sequence, may include a function of reporting the status of lost RLC PDUs to the transmitting side, may include a function of requesting retransmission of lost RLC PDUs, may include a function of sequentially transmitting only RLC SDUs up to the lost RLC SDU to an upper layer when there is a lost RLC SDU, or may include a function of sequentially transmitting all RLC SDUs received before the timer starts when a predetermined timer expires even when there is a lost RLC SDU. Or, even if there are lost RLC SDUs, if a predetermined timer has expired, it may include a function to sequentially deliver all RLC SDUs received up to the upper layer. In addition, the RLC PDUs may be processed in the order they are received (in the order of arrival, regardless of the order of the sequence number) and delivered to the PDCP device out of sequence (out-of-sequence delivery). In the case of segments, the segments stored in the buffer or to be received later may be received, reconstructed into a single complete RLC PDU, processed, and then delivered to the PDCP device.The above NR RLC layer may not include a concatenation function, and the above function may be performed in the NR MAC layer or replaced with a multiplexing function of the NR MAC layer.

[0067] The out-of-sequence delivery function of the NR RLC device above refers to the function of directly delivering RLC SDUs received from a lower layer to an upper layer regardless of the order, and may include a function of reassembling and delivering RLC SDUs when an original RLC SDU is received divided into multiple RLC SDUs, and may include a function of storing the RLC SN or PDCP SN of received RLC PDUs and arranging the order to record lost RLC PDUs.

[0068] NR MAC (1b-15, 1b-30) can be connected to multiple NR RLC layer devices configured in one terminal, and the main functions of NR MAC can include some of the following functions.

[0069] ● Mapping function (Mapping between logical channels and transport channels)

[0070] ● Multiplexing / demultiplexing of MAC SDUs

[0071] ● Scheduling information reporting function

[0072] ● HARQ function (Error correction through HARQ)

[0073] ● Priority handling between logical channels of one UE

[0074] ● Priority handling between UEs by means of dynamic scheduling

[0075] ● MBMS service identification function

[0076] ● Transport format selection function

[0077] ● Padding function

[0078] The NR PHY layer (1b-20, 1b-25) can perform operations such as channel coding and modulating upper layer data, converting it into OFDM symbols and transmitting it over a wireless channel, or demodulating and channel decoding OFDM symbols received over a wireless channel and transmitting them to a higher layer.

[0079] FIG. 1c is a diagram illustrating the structure of another next-generation mobile communication system to which the present disclosure can be applied.

[0080] Referring to FIG. 1c, a cell served by an NR gNB (1c-05) operating on a beam basis may be composed of at least one Transmission Reception Point (TRP, 1c-10, 1c-15, 1c-20, 1c-25, 1c-30, 1c-35, 1c-40). The TRPs (1c-10 to 1c-40) represent blocks that separate some functions of transmitting and receiving physical signals from an existing NR base station (eNB) and are composed of multiple antennas. The NR gNB (1c-05) may be expressed as a CU (Central Unit) and the TRP may be expressed as a DU (Distributed Unit).

[0081] The functions of the above NR gNB (1c-05) and TRP can be configured by separating each layer in the PDCP / RLC / MAC / PHY layers such as 1c-45. That is, the TRP can perform the function of the corresponding layer with only the PHY layer (1c-15, 1c-25), the TRP can perform the functions of the corresponding layers with only the PHY layer and the MAC layer (1c-10, 1c-35, 1c-40), and the TRP can perform the functions of the corresponding layers with only the PHY layer, the MAC layer, and the RLC layer (1c-20, 1c-30).

[0082] In particular, TRP (1c-10~1c-40) can use beamforming technology to transmit and receive data by generating narrow beams in various directions using multiple transmit / receive antennas. User terminal (1c-50) can connect to NR gNB (1c-05) and external networks through TRP (1c-10~1c-40).

[0083] The above NR gNB (1c-05) collects status information such as buffer status, available transmission power status, and channel status of terminals to provide services to users, and schedules the information to support connections between the terminals and the core network (CN), particularly AMF / SMF (1c-50).

[0084] The TRP in the present invention is based on a structure (1c-15, 1c-25) that can perform the function of the corresponding layer with only the PHY layer.

[0085] FIG. 1D is a diagram illustrating a method for changing a serving cell and beam to a target cell that supports Layer 1 (L1) / Layer 2 (L2) based cell change according to one embodiment of the present disclosure.

[0086] Referring to FIG. 1d, this is a diagram illustrating a scenario in which a terminal transmits and receives data by changing a serving cell and beam to a transmission reception point (TRP) of a target cell that supports L1 / L2-based cell change, as an L1 / L2 triggered mobility (LTM) scenario applicable to the present disclosure. Although this diagram illustrates a case in which multiple cells (TRP1-Cell1, TRP2-Cell2; 1d-15, 1d-20) exist within one DU (Distributed unit, 1d-10), the scope of the present invention is not limited thereto. The overall content of the present invention can also be applied to an inter-DU case (each DU constitutes one TRP-Cell).

[0087] The terminal (1d-25) can receive common configuration information and dedicated configuration information for an LTM candidate cell (TRP 2-Cell 2, 1d-20) from the serving cell (1d-15) via RRC configuration information (1d-50). That is, overall RRC configuration information such as Cell group configuration (e.g., including ServingCellConfigCommon and ServingCellConfig, etc.) associated with ServingCellID or candidateCellID (cell ID associated with PCI), bearer configuration, and measurement configuration can be provided in advance.

[0088] The configuration information can be provided in the form of pre-configuration in the RRC configuration, and configuration information for multiple candidate cells can be transmitted.

[0089] In addition, the configuration is characterized by including all configuration information applied when the terminal moves to the corresponding cell (handover). All configuration information applied when moving to the corresponding cell (handover) may include cell configuration, bearer configuration, security key configuration, etc. In addition, along with the configuration, unified TCI state configuration for the candidate cell and configuration related to L1 measurement and report may be transmitted together.

[0090] In the following embodiments of the present disclosure, particularly in the above-described situation, when a terminal performs a handover by receiving a handover message to a target cell via LTM (L1 / L2 triggered mobility), the terminal automatically synchronizes (or synchronizes) uplink synchronization with the target cell. A detailed method will be described later in the following embodiments.

[0091] After the configuration for TRP 2-Cell 2 (1d-20) is provided to the serving cell 1 (1d-15) in an RRC connection state, the terminal (1d-25) can perform L1 measurement for the corresponding TRP 2-Cell 2 (1d-20) according to the configuration received in step 1d-55 and report the (measurement) result to the serving cell (Cell 1, 1d-15). The serving cell (Cell 1, 1d-15) can determine that a handover is necessary simultaneously with a beam change to a specific beam (TCI state 2, 1d-40) of TRP 2 (Cell 2, 1d-20) rather than the serving cell beam (TCI state 1, 1d-30) according to (or based on) the received measurement result. If it is determined that a handover is required simultaneously with a beam change to a specific beam (TCI state 2, 1d-40), the serving cell (Cell 1, 1d-15) may trigger a beam change and / or handover in step 1d-60 and instruct the terminal (1d-25) through L1 / L2 signaling. The terminal (1d-25) may perform a handover simultaneously with a beam change to TRP 2 (Cell 2, 1d-20) through the instruction and transmit and receive data through the TRP 2 (Cell 2, 1d-20). At this time, the terminal may apply the configuration information for the target cell to which the handover is to be performed, which was previously configured in step 1d-50. In this step, the terminal (1d-25) may perform a random access depending on whether uplink synchronization is required, or the random access to the target cell may be omitted. Detailed operations are described in the drawings below.

[0092] In the NR system, in the procedure where the terminal and the network perform measurements for RRM (Radio Resource Management) and report the results, there is an s-measure function to prevent unnecessary measurements and measurement reports of neighboring cells by the terminal. The s-measure function may refer to a function that performs measurements by considering the channel performance of the current serving special cell (PCell, PSCell).

[0093] The s-measure used throughout the present disclosure is an operation to not perform measurements on neighboring cells when the received signal received power (RSRP) of an NR SpCell is greater than a threshold value set in advance by RRC, and to start measurements on neighboring cells only when the RSRP of the NR SpCell is less than a threshold value set in advance by RRC. This is to avoid requesting unnecessary measurements to the UE since movement to a neighboring cell (handover and / or PSCell change) is not necessary when the channel performance of the current NR SpCell is sufficiently good. This can be configured with s-MeasureConfig in the MeasConfig IE, and one of the threshold settings of SSB-RSRP or CSI-RSRP can be provided.

[0094]

[0095]

[0096] This disclosure proposes a specific method for applying s-measure to LTM. More specifically, we propose a method for supporting s-measure by dividing the cases in which LTM operates into intra-CU and inter-CU scenarios. In particular, LTM can increase the burden on the terminal because it requires measurements on multiple LTM candidate cells in addition to the existing L3 measurements. To address this issue, the base station can adjust measurements on candidate cells by setting (or lowering) an appropriate threshold.

[0097] Additionally, since LTM is considered a mobility that takes into account the sensitive response of the serving cell signal quality due to the beam, a method that considers the stability of the s-measure operation on the time scale of L1 (e.g., filtering to average the L1 measurement value for s-measure judgment) may be required.

[0098] FIG. 1e is a diagram illustrating a method for performing measurement and reporting on an LTM candidate cell by applying s-measure in an intra-CU situation according to one embodiment of the present disclosure.

[0099] More specifically, FIG. 1e is a diagram illustrating the entire operation of performing measurement resources and reporting for LTM candidate cell(s) according to the channel status of the serving cell by applying s-measure when changing LTM cells in an intra-CU situation proposed in the present disclosure.

[0100] At step 1e-10, the terminal (user equipment, UE, 1e-01) can transmit L3 measurement information to source cell 1 (source cell-DU#1, 1e-02). (L3 Measurement report)

[0101] More specifically, the terminal (1e-01) in the RRC connection state can transmit and receive data with the source cell 1 (1e-02) and transmit the layer 3 measurement values ​​for the serving cell and neighboring cells to the source cell 1 (1e-02) according to the layer 3 (Layer3, L3) measurement and reporting set in step 1e-10. At this time, the actual measurement values ​​are transmitted to the base station's CU1 (1e-03). This is because the base station CU1 (1e-03) is responsible for processing radio resource control (RRC) messages and determining mobility.

[0102] At step 1e-15, the base station CU1 (1e-03) can determine LTM configuration information. (LTM configuration decision)

[0103] More specifically, at step 1e-15, the base station CU1 (1e-03) can determine which cells to request LTM configuration for based on the layer 3 measurement value report received from the terminal.

[0104] At step 1e-20, the base station CU1 (1e-03) can send an LTM configuration request to at least one LTM candidate surrounding cell (1e-04, 1e-05).

[0105] More specifically, the base station CU1 (1e-03) may transmit a message (e.g., a UE CONTEXT SETUP REQUEST message) requesting LTM configuration information to LTM candidate surrounding cells (1e-04, 1e-05) through the F1 interface, including a setting requesting LTM configuration.

[0106] Although the candidate cells are shown in the drawing as being linked to DUs, in reality, the candidate cells and DUs may be mapped 1:1, or multiple candidate cells may be included in one DU.

[0107] The message requesting the above LTM configuration information may request neighboring cells to be determined as LTM candidate cells, and at the same time request RRC configuration information to be applied when LTM is performed on the corresponding cell. That is, the message may convey at least one of the following information.

[0108] - Target candidate cell ID

[0109] - LTM configuration ID of the candidate cell

[0110] - LTM configuration ID mapping list (collected cell ID and LTM configuration ID mapping information)

[0111] - CSI resource configuration

[0112] - Source gNB-DU ID

[0113] - PRACH resources

[0114] - Request of lower layer configuration (to create a reference configuration)

[0115] At step 1e-25, the LTM candidate surrounding cells (1e-04, 1e-05) can transmit an LTM configuration information response message (LTM config response message) to the base station.

[0116] More specifically, the candidate neighboring cells (1e-04, 1e-05) that received the message requesting the configuration information for LTM in step 1e-20 can generate the configuration information of the candidate neighboring cells applied after LTM and a response to the requested information. Thereafter, in step 1e-25, each candidate neighboring cell (1e-04, 1e-05) can transmit the LTM configuration information response message to the base station CU1 (1e-03) by including (or including) it in the UE CONTEXT SETUP RESPONSE message. The message may include the following information.

[0117] - Lower layer configuration (TCI state settings, RACH settings, CSI report settings)

[0118] At step 1e-30, the base station CU1 (1e-03) can transmit (or forward) a UE CONTEXT MODIFICATION REQUEST message to the source cell 1 (1e-02).

[0119] The above UE CONTEXT MODIFICATION REQUEST message may include CSI report settings, RACH settings, and TCI state settings received from LTM candidate surrounding cells (1e-04, 1e-05).

[0120] At step 1e-35 thereafter, source cell 1 (1e-02) can transmit a UE CONTEXT MODIFICATION RESPONSE message to base station CU1 (1e-03).

[0121] The UE CONTEXT MODIFICATION RESPONSE message may convey updated lower layer configuration information of the source cell based on the information received in the above step. For example, the CSI report configuration of the source cell may be updated.

[0122] At step 1e-40, the CU1 (1e-03) can request an updated LTM configuration (LTM config request) to the LTM candidate surrounding cells (1e-04, 1e-05).

[0123] More specifically, if necessary at step 1e-40, the CU1 (1e-03) may forward a message requesting LTM configuration information to the LTM candidate neighboring cells (1e-04, 1e-05) through the F1 interface, including a configuration requesting an updated LTM configuration (e.g., a UE CONTEXT MODIFICATION REQUEST message).

[0124] The above message may include LTM-related configuration information in other candidate cells. Additionally, the message may also be accompanied by a reference configuration.

[0125] At step 1e-45, the LTM candidate peripheral cells (1e-04, 1e-05) can transmit an updated LTM config response message to the CU1 (1e-03).

[0126] More specifically, the candidate peripheral cells (1e-04, 1e-05) can transmit the updated LTM configuration information response message to the base station CU1 (1e-03) by including it in the UE CONTEXT MODIFICATION RESPONSE message. For example, the candidate peripheral cells (1e-04, 1e-05) can update and transmit the lower layer configuration information based on the provided (or acquired) reference configuration.

[0127] At step 1e-50, the source cell (1e-02) can receive the RRC message generated by the base station CU1 (1e-03) and transmit it to the terminal (1e-01).

[0128] The above RRC message is a message that stores (or includes) configuration information for surrounding candidate cells to which LTM is applied. The LTM candidate cell-specific configuration included in the message is a message that includes the configuration received from the LTM candidate cells in step 1e-45, the reference configuration, the LTM configuration (LTM-Config) including the CSI resource configuration, and the bearer configuration and Layer 3 measurement configuration for the LTM candidate cells generated by the base station.

[0129] Whether or not to set the s-measure proposed in this disclosure can also be determined and added at that stage and transmitted together with the RRCReconfiguration message.

[0130] Note that LTM, unlike the existing L3 mobility, is determined based on L1 measurements, not L3 measurements. Furthermore, LTM's L1 measurement resource configuration (CSI resource configuration: actually configured by referencing SSB resources) is configured outside of the LTM candidate cell configuration, and SSBs are provided as a CSI resource set for each candidate cell. See the ASN.1 signaling below.

[0131]

[0132] Additionally, the CSI report configuration is transmitted within the serving cell configuration for each serving cell. This follows the principle of providing related configuration within the cell receiving the L1 measurement report. That is, for an LTM candidate cell, the CSI report-related configuration can be transmitted by including it in the ServingCellConfig within the LTM candidate configuration.

[0133]

[0134]

[0135] The method of setting s-measure in LTM described above can be broadly divided into the following three methods.

[0136] 1. How to set s-measure above LTM-Config;

[0137] 2. How to set s-measure in LTM settings (LTM-Config) or LTM CSI resource settings;

[0138] 3. How to set s-measure in LTM CSI report settings

[0139] Additionally, while the LTM CSI resource currently supports L1 measurements for SSB, there is a possibility that settings for CSI-RS will be added in the future. Therefore, threshold settings for both RSs (SSB RSRP threshold, CSI-RS RSRP threshold) may be required, and can be set to values ​​independent of those set in L3 s-measure. This assumes that the methods for determining mobility by judging L3 and L1 measurements will be different.

[0140] Additionally, a method may be added to distinguish how to determine s-measrure depending on whether the LTM candidate cell to be measured is a serving cell.

[0141] For example, a threshold setting may be set to different values ​​depending on whether the LTM candidate cell is a serving cell or not, and an indicator (included in at least one of the LTM setting, the LTM candidate cell setting, or the LTM measurement reporting setting) may be included to indicate this. That is, if the LTM candidate cell is a serving cell, there is no problem in reporting the serving cell channel performance even if it is good, because the terminal may already be measuring the measurement value for the serving cell.

[0142] Moreover, even when the serving cell channel performance is good, the base station can instruct an LTM cell change based on the measurements received from the serving cell, which is an LTM candidate cell. This applies to the case of a roll change between the currently operating SpCell and the SCell, and does not require a significant burden on the base station to determine LTM measurements and cell changes.

[0143] Depending on how the signaling for setting s-measure is determined, the entity that sets and determines it can be the serving CU, the serving DU, or the LTM candidate cell (DU).

[0144] Hereinafter, we propose a method for applying Layer 1 s-measure to each LTM candidate cell / DU or to all candidate cells. For reference, the s-measure configuration signaling for LTM can be as follows.

[0145]

[0146] 1.Option 1: Set a common s-measure for all LTM candidate cells.

[0147] ● Advantages: Simple application of common settings to candidate cells, low signaling complexity

[0148] ● Signaling structure:

[0149] - Set a common s-measure that applies to all candidate cells within LTM-Config. In this case, the serving CU determines the setting.

[0150] - Set s-measure for each serving cell configuration where LTM CSI report configuration is provided. In this case, the configuration is determined for each serving cell (DU) and each candidate cell (DU).

[0151] ● Additional information: Filtering information that can be triggered based on how long the measurement information for SpCell (L1 measurement) remains below a given threshold (the filtering can be applied directly to the L1 measurement, or it can be applied by changing it to an average value (a time-weighted value of the measurements)).

[0152] - Number of applications (N): If the measurement value for SpCell is measured lower than the threshold (either continuously or discontinuously) for N or more times, measurements are performed on the surrounding cells; or

[0153] - Application time (T): If the measurement value for SpCell is measured lower than the threshold value for T time or longer, measurements are performed on surrounding cells.

[0154] ● Terminal operation

[0155] - When s-measure is set for LTM candidate cells, the terminal starts L1 measurement for all and / or indicated candidate cells and reports if the condition is satisfied.

[0156] 2.Option 2: Control s-measure for each LTM candidate cell (DU)

[0157] ● Advantage: Network can be managed efficiently because measurements can be controlled by candidate cell and DU.

[0158] ● Signaling structure:

[0159] - Provides a list of LTM candidate cells to which s-measure is applied and mapped within LTM-Config, and provides s-measure settings (including index and mapping information). In this case, the serving CU determines the settings.

[0160] - Set the s-measure for each candidate cell(s) to which the report applies within the LTM CSI report settings. In this case, the settings are determined for each serving cell (DU) and each candidate cell (DU).

[0161] - Provides s-measure settings within each LTM candidate cell configuration. This is a structure that includes the content transmitted from the source CU and DU in the candidate cell, and is determined by the serving CU or DU.

[0162] ● Additional information: Filtering information that can be triggered based on how long the measurement information for SpCell (L1 measurement) remains below a given threshold (the filtering can be applied directly to the L1 measurement, or it can be applied by changing it to an average value (a time-weighted value of the measurements)).

[0163] - Number of applications (N): If the measurement value for SpCell is measured lower than the threshold (either continuously or discontinuously) for N or more times, measurements are performed on the surrounding cells; or

[0164] - Application time (T): If the measurement value for SpCell is measured lower than the threshold value for T time or longer, measurements are performed on surrounding cells.

[0165] ● Terminal operation

[0166] - When s-measure is set for each LTM candidate cell, the terminal starts L1 measurement for the indicated candidate cells and reports if the condition is satisfied.

[0167] - After checking the s-measure instruction, apply the LTM CSI resource and report settings set for the cells that satisfy the settings.

[0168] The terminal (1e-01) that receives the RRC message at step 1e-50 can perform a procedure for decoding and processing the RRC message. The processing includes methods for ASN.1 decoding and validating the received message and storing and managing the configuration contents.

[0169] Thereafter, in step 1e-55, the terminal (1e-01) can check the SpCell (PCell or PSCell) measurement value and determine whether to perform measurement on LTM candidate cells based on the received s-measure configuration information. (check the serving cell quality and threshold for s-measure, determine measurement on candidates cells) In this step, the existing s-measure determines L3 measurement, but the present disclosure differs in that it determines whether to perform L1 measurement on cells to which LTM is applied.

[0170] At step 1e-60, the source cell (1e-02) can instruct the terminal (1e-01) to transmit a preamble for early TA.

[0171] At step 1e-65, the terminal (1e-01) can transmit a preamble for early TA to the corresponding LTM candidate cell (1e-04).

[0172] More specifically, if the terminal (1e-01) receives (or has received) an early TA (time advance) related setting for an LTM candidate cell in step 1e-50, and is instructed to transmit a preamble for early TA to an LTM candidate cell through a physical downlink control channel (PDCCH) from the source cell (1e-02) in step 1e-60, the terminal (1e-01) can transmit a preamble for early TA to the LTM candidate cell (1e-04) in step 1e-65 according to the pre-configured RACH preamble information for early TA.

[0173] At step 1e-70, the candidate target cell (1e-04) can transmit a valid TA value to the source CU (1e-03).

[0174] More specifically, the candidate target cell (1e-04) can calculate the TA of the terminal through the preamble received from the terminal, and can transmit a valid TA value to the source CU (1e-03) through a DU-CU TA INFORMATION TRANSFER message.

[0175] At step 1e-75, the source CU (1e-03) can transmit the TA information received from the target cell to the source cell / DU (1e-02) by including it in the CU-DU TA INFORMATION TRANSFER message.

[0176] Thereafter, the terminal (1e-01) performs L1 and L3 channel measurement and / or measurement report according to the setting information in steps 1e-80 and 1e-85, and the source cell / DU (1e-02) can trigger LTM based on the L1 measurement report of the terminal received.

[0177] At step 1e-90, the source cell / DU (1e-02) can instruct handover to the LTM target cell via the LTM cell switch MAC CE.

[0178] When the LTM cell switch instruction is transmitted to the terminal, the terminal applies the settings for the target cell in step 1e-95 and initiates the handover procedure, and in step 1e-100, a timer for L1 / L2 handover can be started. The timer may include a T304 timer set for each LTM candidate cell.

[0179] At step 1e-105, the source cell / DU (1e-02) transmits a DU-CU CELL SWITCH NOTIFICATION message to the source CU (1e-03) that includes information notifying that LTM has been triggered. The information notifying that LTM has been triggered may include at least one of an LTM target cell ID and a TCI state ID.

[0180] At step 1e-110, a CU-DU CELL SWITCH NOTIFICATION message containing information indicating that LTM has been triggered is transmitted from the source CU (1e-03) to the target cell (1e-04). The information indicating that the LTM has been triggered may include at least one of an LTM target cell ID and a TCI state ID.

[0181] At step 1e-115, the terminal (1e-01) can perform random access if there is no valid TA in the target cell (1e-04).

[0182] However, if TA information is included in the LTM cell switch MAC CE at step 1e-90 or if valid TA information for the target cell is known through terminal-based TA, the terminal can skip the random access procedure and perform UL data transmission directly to the target cell. In this case, the LTM handover may be completed when DCI addressed to C-RNTI is received from the base station.

[0183] At step 1e-120, the terminal (1e-01) can transmit and receive data in the corresponding cell after handover is completed.

[0184] The overall operation of applying s-measure to LTM cell change proposed in this disclosure can also be applied to LTM cell change in an inter-CU situation.

[0185] Although not shown in the drawing, the LTM setup preparation procedure for this (1e-15 to 1e-45 of this drawing based on intra-CU) may include an LTM setup request and response procedure via the Xn interface with the inter CU. For example, the HO request message (HandoverPreparationInformation) or a new Xn message may be used as the LTM setup request and response between CUs, and a response thereto may also be performed correspondingly. That is, the HO Command message (HandoverCommand) or a new Xn message may be used.

[0186] In this case, each CU can perform the existing LTM configuration request and response procedure for the DUs within the CU, and can pass the collected configuration to the source CU by including it in the HO Command message (HandoverCommand) or a new Xn message.

[0187] In all cases, the s-measure is determined by the source CU as the default. However, if the specific signaling of Option 2 (controlling the s-measure per LTM candidate cell (DU)) is to be supported, an indicator is transmitted to the inter-CU indicating whether to apply the s-measure so that it can be included in the LTM configuration within the inter-CU or included in the LTM candidate cell configuration.

[0188] FIG. 1f is a diagram illustrating the operation of a terminal according to an embodiment of the present disclosure.

[0189] More specifically, FIG. 1f is a diagram illustrating the overall terminal operation when applied to embodiments of the present disclosure and supports s-measure in LTM.

[0190] In step 1f-05, a connected UE can receive an LTM configuration from a serving cell via an RRC reconfiguration message (e.g., an RRCReconfiguration message). The LTM configuration can include at least one of an LTM candidate cell configuration, an LTM CSI resource configuration, and an LTM CSI report configuration.

[0191] In particular, the RRC configuration may include configuration information that instructs the LTM candidate cells proposed in the present disclosure to perform s-measure. That is, the LTM s-measure configuration may be included to determine whether to perform L1 measurement on all LTM candidate cells or specific LTM candidate cells. For detailed configuration methods and contents, refer to the contents of the aforementioned Drawing 1e.

[0192] In addition, although the RRC configuration information was omitted beforehand, the terminal has received basic RRC configuration from the base station and can perform an operation of reporting layer 3 measurement values ​​for neighboring cells. In particular, the LTM candidate cell configuration information received in the above step is characterized in that it is transmitted with a delta configuration applied based on the configuration for one reference cell.

[0193] The terminal can know the reference cell and the configuration information for the reference cell by instructing it in the RRC configuration. At this time, since the configuration for neighboring cells other than the reference cell is transmitted (or received incorrectly) only the parts that are different from the reference cell, the signaling overhead is small. The terminal can decode the received configuration for neighboring cells based on the configuration of the reference cell at that stage and store and manage the actually applied configuration (i.e., the operation of saving the configuration that is delta-configured based on the reference cell as the full configuration by referring to the reference cell configuration) in a separate buffer and list.

[0194] Alternatively, rather than decoding the received settings based on the reference cell and storing and managing the settings that are actually applied, the received RRC settings can be stored and managed directly in a buffer. If the settings for surrounding cells are decoded based on the reference cell at this stage and stored as the settings that are actually applied, handovers for the corresponding cells can be applied immediately when an actual LTM cell change is indicated, which has the advantage of eliminating additional delays.

[0195] In step 1f-10, the terminal can determine whether to perform L1 channel measurement for LTM candidate cells based on signal measurement of the serving cell and s-measure settings while maintaining a connection state with the serving cell.

[0196] At this time, whether to perform L1 channel measurement on LTM candidate cells is determined based on the provided RRC settings, and may be applied to all LTM candidate cells or some LTM candidate cells, depending on the base station settings. Additionally, if the serving cell is an LTM candidate cell, whether to perform s-measure measurement may be determined through separate signaling.

[0197] In step 1f-15, the terminal can determine whether the channel performance of the measured serving SpCell (PCell or PSCell) is greater than a preset s-measure threshold.

[0198] In step 1f-20, if the measured channel performance of the serving SpCell (PCell or PSCell) is greater than the preset s-measure threshold, the terminal maintains the connection to the current serving cell and does not perform L1 measurement and reporting on the LTM candidate cells. In this case, the base station determines that there is no need to change cells to LTM candidate cells because the channel measurement value of the serving SpCell is sufficiently good.

[0199] However, if one of the serving cells, the SCell, is configured as an LTM candidate cell, LTM L1 channel measurements and / or reporting may be performed for the SCell, depending on the base station configuration. In this case, the base station may instruct a change of LTM cell based on the measurement values ​​of the serving SCell, even if the channel measurements of the serving SpCell are sufficiently good.

[0200] In step 1f-25, if the channel performance of the serving SpCell (PCell or PSCell) measured is less than a preset s-measure threshold, the terminal may perform LTM L1 channel measurement on all LTM candidate cells or some LTM candidate cells according to the LTM s-measure configuration, and may perform LTM L1 measurement reporting according to the LTM L1 channel reporting conditions.

[0201] In step 1f-30, the terminal can receive an LTM cell change MAC CE indicating an LTM cell change from the base station based on the measurement result transmitted in step 1f-25.

[0202] In step 1f-35, handover or PSCell change is performed according to the method determined according to the operation in this embodiment.

[0203] Afterwards, the terminal can determine and perform LTM handover.

[0204] More specifically, when the LTM cell change is successfully performed and the handover is successful, the settings for the corresponding target cell that the terminal has received and stored for the handover method to be performed are also applied, and the terminal can connect to the corresponding cell and transmit and receive data using the indicated beam.

[0205] FIG. 1g is a diagram illustrating the operation of a base station according to one embodiment of the present disclosure.

[0206] In step 1g-05, the base station receives L3 measurement reports from the terminal, and based on the terminal's measurements of surrounding frequencies and cells, it can determine whether the terminal requires handover and which cells are candidate cells for handover.

[0207] In step 1g-10, the base station can request LTM configuration information from surrounding cells and receive responses from the cells.

[0208] When requesting LTM configuration information, the configuration request can be made to a candidate cell of an intra CU through the F1 interface, and if an LTM candidate cell exists in an inter CU, the request can be made through the Xn interface.

[0209] At this stage, RRC configuration information based on delta configuration can be received from neighboring cells, and the base station can inform neighboring cells of the reference cell and its settings. Thereafter, based on the reference cell settings, LTM configuration information for other neighboring cells can be received. Although not shown in this drawing, settings related to L3 measurement settings and basic RRC settings are provided prior to this stage.

[0210] In step 1g-15, the base station can determine the LTM configuration including the surrounding cell configuration information received in the step.

[0211] At this time, the base station may determine whether to apply the LTM s-measure proposed in the present disclosure and include this in the configuration information. For detailed signaling methods, refer to Drawing 1e of the present invention.

[0212] Additionally, in the case of CU, when it is decided to apply s-measure in the source CU, when requesting LTM setup to another CU via Xn interface (1g-10), information requesting that s-measure be included in the LTM setup may be included.

[0213] Another embodiment of the present disclosure may be to always determine and set the s-measure in the source CU.

[0214] In step 1g-20, the base station transmits an RRC configuration message containing the LTM configuration generated in step 1g-15 to the connected terminal. As previously described, the RRC configuration may include LTM configuration and LTM s-measure configuration.

[0215] Specifically, signaling may vary depending on the type of LTM candidate cells to which the LTM s-measure proposed in this disclosure is applied.

[0216] Afterwards, in step 1g-25, the base station can receive reports on L1 and L3 measurement values ​​from the terminal. At this time, the L1 measurement value may be a neighboring cell (non-serving cell) that supports L1 / L2-based mobility. The serving cell can determine whether to change the beam of the terminal and whether to perform a handover / LTM cell change based on the received measurement results. If it is determined that a change to a specific beam of a neighboring cell is necessary rather than a specific beam of the serving cell, the base station can transmit an LTM cell change MAC CE to the terminal in step 1g-30, and instruct an LTM cell change (or LTM handover).

[0217] FIG. 1h is a block diagram illustrating the structure of a terminal according to an embodiment of the present disclosure.

[0218] Referring to FIG. 1h, the terminal may include an RF (Radio Frequency) processing unit (1h-10), a baseband processing unit (1h-20), a storage unit (1h-30), and a control unit (1h-40).

[0219] The RF processing unit (1h-10) above can perform functions for transmitting and receiving signals through a wireless channel, such as signal band conversion and amplification. That is, the RF processing unit (1h-10) up-converts the baseband signal provided from the baseband processing unit (1h-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 (1h-10) can include a transmission filter, a reception filter, an amplifier, a mixer, an oscillator, a digital to analog convertor (DAC), an analog to digital convertor (ADC), etc.

[0220] In the above drawing, only one antenna is shown, but the terminal may have multiple antennas.

[0221] Additionally, the RF processing unit (1h-10) may include multiple RF chains.

[0222] Furthermore, the RF processing unit (1h-10) can perform beamforming. For the beamforming, the RF processing unit (1h-10) can adjust the phase and size of each signal transmitted and received through multiple antennas or antenna elements. In addition, the RF processing unit can perform MIMO, and can receive multiple layers when performing the MIMO operation.

[0223] The baseband processing unit (1h-20) above can perform a conversion function between baseband signals and bit streams according to the physical layer specifications of the system. For example, when transmitting data, the baseband processing unit (1h-20) generates complex symbols by encoding and modulating the transmission bit stream.

[0224] In addition, when receiving data, the baseband processing unit (1h-20) restores the reception bit stream by demodulating and decoding the baseband signal provided from the RF processing unit (1h-10). For example, in the case of OFDM (orthogonal frequency division multiplexing) method, when transmitting data, the baseband processing unit (1h-20) generates complex symbols by encoding and modulating the transmission bit stream, maps the complex symbols to subcarriers, and then configures OFDM symbols by performing an inverse fast Fourier transform (IFFT) operation and inserting a cyclic prefix (CP).

[0225] In addition, when receiving data, the baseband processing unit (1h-20) divides the baseband signal provided from the RF processing unit (1h-10) into OFDM symbol units, restores signals mapped to subcarriers through FFT (fast Fourier transform) operation, and then restores the received bit string through demodulation and decoding.

[0226] The baseband processing unit (1h-20) and the RF processing unit (1h-10) transmit and receive signals as described above. Accordingly, the baseband processing unit (1h-20) and the RF processing unit (1h-10) may be referred to as a transmitting unit, a receiving unit, a transceiver unit, or a communication unit.

[0227] Furthermore, at least one of the baseband processing unit (1h-20) and the RF processing unit (1h-10) may include a plurality of communication modules to support a plurality of different wireless access technologies. In addition, at least one of the baseband processing unit (1h-20) and the RF processing unit (1h-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), a cellular network (e.g., LTE), etc. In addition, the different frequency bands may include a super high frequency (SHF) (e.g., 2.NRHz, NRhz) band, a millimeter wave (mm wave) (e.g., 60GHz) band.

[0228] The storage unit (1h-30) can store data such as basic programs, application programs, and setting information for the operation of the terminal. In particular, the storage unit (1h-30) can store information related to a second access node that performs wireless communication using a second wireless access technology. In addition, the storage unit (1h-30) provides the stored data at the request of the control unit (1h-40).

[0229] The control unit (1h-40) can control the overall operations of the terminal. For example, the control unit (1h-40) transmits and receives signals through the baseband processing unit (1h-20) and the RF processing unit (1h-10). In addition, the control unit (1h-40) records and reads data in the storage unit (1h-40). For this purpose, the control unit (1h-40) can include at least one processor. For example, the control unit (1h-40) can include a communication processor (CP) that performs control for communication and an application processor (AP) that controls upper layers such as application programs.

[0230] FIG. 1i is a block diagram illustrating the structure of a base station according to one embodiment of the present disclosure.

[0231] As shown in the above drawing, the base station may be configured to include an RF processing unit (1i-10), a baseband processing unit (1i-20), a backhaul communication unit (1i-30), a storage unit (1i-40), and a control unit (1i-50).

[0232] The RF processing unit (1i-10) can perform functions for transmitting and receiving signals through a wireless channel, such as signal band conversion and amplification. That is, the RF processing unit (1i-10) up-converts the baseband signal provided from the baseband processing unit (1i-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 (1i-10) can include a transmission filter, a reception filter, an amplifier, a mixer, an oscillator, a DAC, an ADC, etc.

[0233] In the above drawing, only one antenna is shown, but the first access node may have multiple antennas.

[0234] In addition, the RF processing unit (1i-10) may include multiple RF chains. Furthermore, the RF processing unit (1i-10) may perform beamforming. For the beamforming, the RF processing unit (1i-10) may adjust the phase and magnitude of each signal transmitted and received through multiple antennas or antenna elements. The RF processing unit may perform a downlink MIMO operation by transmitting one or more layers.

[0235] The baseband processing unit (1i-20) above can perform a conversion function between baseband signals and bit streams according to the physical layer specifications of the first wireless access technology. For example, when transmitting data, the baseband processing unit (1i-20) generates complex symbols by encoding and modulating the transmission bit stream.

[0236] In addition, when receiving data, the baseband processing unit (1i-20) restores the reception bit stream by demodulating and decoding the baseband signal provided from the RF processing unit (1i-10). For example, in the case of OFDM, when transmitting data, the baseband processing unit (1i-20) generates complex symbols by encoding and modulating the transmission bit stream, maps the complex symbols to subcarriers, and then configures OFDM symbols through IFFT operation and CP insertion.

[0237] In addition, when receiving data, the baseband processing unit (1i-20) divides the baseband signal provided from the RF processing unit (1i-10) into OFDM symbol units, restores signals mapped to subcarriers through FFT operation, and then restores the received bit string through demodulation and decoding.

[0238] The baseband processing unit (1i-20) and the RF processing unit (1i-10) transmit and receive signals as described above. Accordingly, the baseband processing unit (1i-20) and the RF processing unit (1i-10) may be referred to as a transmitter, a receiver, a transceiver, a communication unit, or a wireless communication unit.

[0239] The above backhaul communication unit (1i-30) can provide an interface for performing communication with other nodes within the network. That is, the backhaul communication unit (1i-30) converts a bit string transmitted from the main base station to another node, such as an auxiliary base station or core network, into a physical signal, and converts a physical signal received from the other node into a bit string.

[0240] The storage unit (1i-40) can store data such as basic programs, application programs, and setting information for the operation of the main base station. In particular, the storage unit (1i-40) can store information on bearers assigned to connected terminals, measurement results reported from connected terminals, and the like. In addition, the storage unit (1i-40) can store information that serves as a judgment criterion for whether to provide or terminate multiple connections to a terminal. In addition, the storage unit (1i-40) provides the stored data at the request of the control unit (1i-50).

[0241] The control unit (1i-50) can control the overall operations of the base station. For example, the control unit (1i-50) transmits and receives signals through the baseband processing unit (1i-20) and the RF processing unit (1i-10) or through the backhaul communication unit (1i-30). In addition, the control unit (1i-50) records and reads data in the storage unit (1i-40). For this purpose, the control unit (1i-50) can include at least one processor.

[0242] The 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.

[0243] When implemented in software, a computer-readable storage medium storing one or more programs (software modules) may be provided. The one or more programs stored in the computer-readable storage medium are configured for execution by one or more processors within an electronic device. The one or more programs include instructions that cause the electronic device to execute methods according to the embodiments described in the claims or specification of the present invention.

[0244] These programs (software modules, software) may be stored in random access memory, non-volatile memory including flash memory, read only memory (ROM), electrically erasable programmable read only memory (EEPROM), magnetic disc storage device, compact disc ROM (CD-ROM), digital versatile discs (DVDs) or other forms of optical storage device, magnetic cassette. Or, they may be stored in a memory configured as a combination of some or all of these. In addition, each configuration memory may be included in multiple numbers.

[0245] Additionally, the program may be stored in an attachable storage device that is accessible via a communication network such as the Internet, an intranet, a local area network (LAN), a wide local area network (WLAN), a storage area network (SAN), or a combination thereof. Such a storage device may be connected to a device implementing an embodiment of the present invention via an external port. Additionally, a separate storage device on the communication network may be connected to a device implementing an embodiment of the present invention.

[0246] In the specific embodiments of the present invention described above, components included in the invention are expressed in the singular or plural form depending on the specific embodiment presented. However, the singular or plural expressions are selected to suit the presented situation for convenience of explanation, and the present invention is not limited to singular or plural components. Even components expressed in the plural form may be composed of singular elements, or even components expressed in the singular form may be composed of plural elements.

[0247] While the detailed description of the present invention has described specific embodiments, it is clear that various modifications are possible without departing from 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 not only by the scope of the following claims but also by equivalents thereof.

Claims

1. A method performed by a terminal supporting Layer 1 (L1) / Layer 2 (L2) Triggered Mobility (LTM) of a wireless communication system, A step of receiving a radio resource control (RRC) message from a base station including configuration information for performing s-measure in at least one LTM candidate cell; a step of measuring the signal of the serving cell; and A method characterized by comprising a step of determining whether to measure an L1 channel of at least one LTM candidate cell based on a signal of the serving cell and the configuration information.

2. In paragraph 1, The above setting information sets s-measurement information that is commonly applied to at least one or more LTM candidate cells, or A method characterized in that the above setting information sets s-measurement information applied to each of the at least one LTM candidate cells.

3. In the second paragraph, the step of determining whether to measure the L1 channel is as follows: If the signal of the serving cell is less than the s-measurement threshold, it is decided to measure the L1 channel for at least one candidate cell, A method characterized in that if the signal of the serving cell is greater than the s-measurement threshold, it is decided not to measure the L1 channel for at least one candidate cell.

4. In paragraph 2, A method characterized in that the above s-measurement information is either synchronization signal block (SSB) received signal received power (RSRP) information or channel state information (RSRP) information.

5. A method performed by a base station supporting Layer 1 (L1) / Layer 2 (L2) Triggered Mobility (LTM) of a wireless communication system, A step of transmitting a radio resource control (RRC) message including configuration information for setting up to perform s-measure on at least one LTM candidate cell to the terminal; and A method characterized by comprising the step of receiving a result of L1 channel measurement of at least one LTM candidate cell based on a signal of a serving cell and the above configuration information.

6. In paragraph 1, The above setting information sets s-measurement information that is commonly applied to at least one or more LTM candidate cells, or A method characterized in that the above setting information sets s-measurement information applied to each of the at least one LTM candidate cells.

7. In paragraph 6, A method characterized in that the result of L1 channel measurement for at least one candidate cell is received when the signal of the serving cell is less than the s-measurement threshold.

8. In paragraph 6, A method characterized in that the above s-measurement information is one of synchronization signal block (SSB) received signal received power (RSRP) information or channel state information (RSRP) information.

9. In a terminal supporting Layer 1 (L1) / Layer 2 (L2) Triggered Mobility (LTM) of a wireless communication system, A transceiver for transmitting and receiving signals; and A control unit is included, wherein the control unit comprises: Receive a radio resource control (RRC) message from a base station including configuration information for performing s-measure on at least one LTM candidate cell, Measure the signal of the serving cell, A terminal characterized in that it determines whether to measure an L1 channel of at least one LTM candidate cell based on a signal of the serving cell and the configuration information.

10. In paragraph 9, The above setting information sets s-measurement information that is commonly applied to at least one or more LTM candidate cells, or A terminal characterized in that the above setting information sets s-measurement information applicable to each of the at least one LTM candidate cells.

11. In paragraph 10, the control unit, If the signal of the serving cell is less than the s-measurement threshold, it is decided to measure the L1 channel for at least one candidate cell, A terminal characterized in that it is determined not to measure the L1 channel for at least one candidate cell if the signal of the serving cell is greater than the s-measurement threshold.

12. In paragraph 10, A terminal characterized in that the above s-measurement information is either synchronization signal block (SSB) received signal received power (RSRP) information or channel state information (RSRP) information.

13. In a base station supporting Layer 1 (L1) / Layer 2 (L2) Triggered Mobility (LTM) of a wireless communication system, A transceiver for transmitting and receiving signals; and A control unit is included, wherein the control unit comprises: Transmitting a radio resource control (RRC) message including configuration information for performing s-measure on at least one LTM candidate cell to the terminal, A base station characterized by receiving the results of L1 channel measurement of at least one LTM candidate cell based on a signal of a serving cell and the above configuration information.

14. In paragraph 13, The above setting information sets s-measurement information that is commonly applied to at least one or more LTM candidate cells, or A base station, characterized in that the above setting information sets s-measurement information applicable to each of the at least one LTM candidate cells.

15. In paragraph 14, If the signal of the serving cell is less than the s-measurement threshold, the result of L1 channel measurement is received for at least one candidate cell, A base station, characterized in that the above s-measurement information is either synchronization signal block (SSB) received signal received power (RSRP) information or channel state information (RSRP) information.

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