Method and apparatus for measuring csi-rs for supporting ltm in wireless communication system

Abstract

The present disclosure relates to a 5G or 6G communication system for supporting higher data transmission rates.

Description

Method and apparatus for measuring CSI-RS to support LTM in a wireless communication system

[0001] The present disclosure relates to a wireless communication system, and more specifically to a method and apparatus for measuring CSI-RS for LTM support.

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

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

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

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

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

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

[0008] The disclosed embodiments aim to provide an apparatus and method capable of effectively providing services in a mobile communication system.

[0009] According to one embodiment of the present disclosure, a method performed by a terminal of a wireless communication system comprises: receiving configuration information for an LTM including information regarding a plurality of semi-persistent CSI-RS resources for at least one LTM candidate cell; storing the configuration information for the LTM; the method may further include: receiving a MAC CE that activates at least one CSI-RS resource set corresponding to the at least one LTM candidate cell among the CSI-RS resource sets including the plurality of semi-persistent CSI-RS resources; measuring a channel state using the activated at least one CSI-RS resource set; reporting information regarding the measured channel state; receiving a MAC CE that indicates a TCI state for the at least one LTM candidate cell; receiving a MAC CE that indicates LTM cell switching; performing cell switching to a target cell based on the MAC CE that indicates LTM cell switching; and deactivating some of the activated at least one CSI-RS resource set after performing LTM cell switching.

[0010] The step of deactivating some of the activated at least one CSI-RS resource set after performing the above LTM cell switching may be to deactivate at least one activated CSI-RS resource set corresponding to at least one LTM candidate cell, excluding the target cell among the activated at least one CSI-RS resource set.

[0011] The configuration information for the above LTM may include at least one of information indicating the type of CSI-RS, CSI-RS resource set information, identification information of the CSI-RS included in the CSI-RS resource set, and identification information of at least one LTM candidate cell corresponding to the CSI-RS resource.

[0012] At least one of the information indicating the type of the CSI-RS, the CSI-RS resource set information, the identification information of the CSI-RS included in the CSI-RS resource set, and the identification information of at least one LTM candidate cell corresponding to the CSI-RS resource may be included in an RRC message containing LTM-CSI-ResourceConfig.

[0013] A MAC CE that activates the at least one set of CSI-RS resources corresponding to the at least one LTM candidate cell may include information indicating the activation and deactivation of the set of at least one CSI-RS resources corresponding to the at least one LTM candidate cell, identification information indicating the set of at least one CSI-RS resources corresponding to the at least one LTM candidate cell, and TCI state information corresponding to the set of at least one CSI-RS resources corresponding to the at least one LTM candidate cell.

[0014] According to one embodiment of the present disclosure, a method performed by a base station of a wireless communication system comprises: transmitting configuration information for an LTM including information regarding a plurality of semi-persistent CSI-RS resources for at least one LTM candidate cell; transmitting a MAC CE that activates at least one CSI-RS resource set corresponding to the at least one LTM candidate cell among the CSI-RS resource sets including the plurality of semi-persistent CSI-RS resources; receiving information regarding a channel state measured using the activated at least one CSI-RS resource set; transmitting a MAC CE that indicates a TCI state for the at least one LTM candidate cell; and transmitting a MAC CE that indicates performing LTM cell switching to a target cell, wherein after performing LTM cell switching, some of the activated CSI-RS resource sets may be deactivated.

[0015] Some CSI-RS resource sets that are deactivated after the above LTM cell switching are performed may include at least one activated CSI-RS resource set corresponding to at least one LTM candidate cell excluding the target cell.

[0016] The configuration information for the above LTM may include at least one of information indicating the type of CSI-RS, CSI-RS resource set information, identification information of the CSI-RS included in the CSI-RS resource set, and identification information of at least one LTM candidate cell corresponding to the CSI-RS resource.

[0017] At least one of the information indicating the type of the CSI-RS, the CSI-RS resource set information, the identification information of the CSI-RS included in the CSI-RS resource set, and the identification information of at least one LTM candidate cell corresponding to the CSI-RS resource may be included in an RRC message containing LTM-CSI-ResourceConfig.

[0018] A MAC CE that activates the at least one set of CSI-RS resources corresponding to the at least one LTM candidate cell may include information indicating the activation and deactivation of the set of at least one CSI-RS resources corresponding to the at least one LTM candidate cell, identification information indicating the set of at least one CSI-RS resources corresponding to the at least one LTM candidate cell, and TCI state information corresponding to the set of at least one CSI-RS resources corresponding to the at least one LTM candidate cell.

[0019] In a terminal of a wireless communication system, the terminal comprises at least one transceiver; and at least one processor coupled to the at least one transceiver, wherein the at least one processor receives configuration information for an LTM including information regarding a plurality of semi-persistent CSI-RS resources for at least one LTM candidate cell, stores the configuration information for the LTM, receives a MAC CE that activates at least one CSI-RS resource set corresponding to the at least one LTM candidate cell among the CSI-RS resource sets including the plurality of semi-persistent CSI-RS resources, measures a channel state using the activated at least one CSI-RS resource set, reports information regarding the measured channel state, receives a MAC CE that indicates a TCI state for the at least one LTM candidate cell, receives a MAC CE that indicates LTM cell switching, performs cell switching to a target cell based on the MAC CE that indicates LTM cell switching, and can deactivate some of the activated at least one CSI-RS resource set after performing LTM cell switching.

[0020] The above at least one processor can disable at least one activated CSI-RS resource set corresponding to at least one LTM candidate cell, excluding the target cell among the at least one activated CSI-RS resource set.

[0021] A MAC CE that activates the at least one set of CSI-RS resources corresponding to the at least one LTM candidate cell may include information indicating the activation and deactivation of the set of at least one CSI-RS resources corresponding to the at least one LTM candidate cell, identification information indicating the set of at least one CSI-RS resources corresponding to the at least one LTM candidate cell, and TCI state information corresponding to the set of at least one CSI-RS resources corresponding to the at least one LTM candidate cell.

[0022] In a base station of a wireless communication system, the base station comprises at least one transceiver and at least one processor coupled to the at least one transceiver, and the at least one processor transmits configuration information for an LTM including information regarding a plurality of semi-persistent CSI-RS resources for at least one LTM candidate cell, transmits a MAC CE that activates at least one CSI-RS resource set corresponding to the at least one LTM candidate cell among the sets of CSI-RS resources including the plurality of semi-persistent CSI-RS resources, receives information regarding a channel state measured using the activated at least one CSI-RS resource set, transmits a MAC CE that indicates a TCI state for the at least one LTM candidate cell, transmits a MAC CE that indicates the performance of LTM cell switching to a target cell, and after the performance of LTM cell switching, some of the activated at least one CSI-RS resource sets may be deactivated.

[0023] Some CSI-RS resource sets that are deactivated after the above LTM cell switching are performed may include at least one activated CSI-RS resource set corresponding to at least one LTM candidate cell excluding the target cell.

[0024] The disclosed embodiments provide an apparatus and method capable of effectively providing services in a mobile communication system.

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

[0026] FIG. 1b is a diagram showing the wireless protocol structure of a next-generation mobile communication system according to one embodiment of the present disclosure.

[0027] FIG. 1c is a drawing illustrating the structure of another next-generation mobile communication system according to one embodiment of the present disclosure.

[0028] FIG. 1d is a diagram illustrating a scenario in which a terminal according to one embodiment of the present disclosure transmits and receives data through the beam of a TRP (transmission / reception point) of a surrounding cell that supports beam changing based on L1 / L2 while maintaining a connection state with a serving cell.

[0029] FIG. 1e is a diagram illustrating a scenario in which a terminal according to one embodiment of the present disclosure changes a serving cell and a beam to a TRP of a cell that supports L1 / L2-based beam changing to transmit and receive data.

[0030] FIG. 1f is a diagram illustrating the overall operation for supporting continuous LTM operation based on semi-persistent CSI-RS resource measurement reporting according to one embodiment of the present disclosure.

[0031] FIG. 1g is a diagram illustrating a MAC CE structure for enabling and deactivating semi-persistent CSI-RS resources in an LTM according to one embodiment of the present disclosure.

[0032] FIG. 1h is a diagram illustrating the overall terminal operation for supporting continuous LTM operation based on semi-persistent CSI-RS resource measurement reporting according to one embodiment of the present disclosure.

[0033] FIG. 1i is a drawing illustrating base station operation according to one embodiment of the present disclosure.

[0034] FIG. 1j is a block diagram illustrating the internal structure of a terminal according to one embodiment of the present disclosure.

[0035] FIG. 1k is a block diagram showing the configuration of a base station according to one embodiment of the present disclosure.

[0036] The operating principle of the present invention will be described in detail below with reference to the attached drawings. In describing the present invention below, if it is determined that a detailed description of related known functions or configurations may unnecessarily obscure the essence of the present invention, such detailed description will be omitted. Furthermore, the terms described below are defined considering their functions in the present invention, and these may vary depending on the intentions or conventions of the user or operator. Therefore, such definitions should be based on the content throughout this specification. Terms used in the following description to identify connection nodes, terms referring to network entities, terms referring to messages, terms referring to interfaces between network entities, terms referring to various identification information, etc., are provided as examples for the convenience of explanation. Accordingly, the present invention is not limited to the terms described below, and other terms referring to objects having equivalent technical meanings may be used.

[0037] 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.

[0038] 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.

[0039] 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).

[0040] 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.

[0041] For the convenience of the following explanation, the present invention uses terms and names defined in the 5GS and NR specifications, which are standards defined by the 3GPP (The 3rd Generation Partnership Project) organization among existing communication standards. However, the present invention is not limited by the above terms and names and can be applied in the same way to wireless communication networks according to other standards. For example, the present invention can be applied to 3GPP 5GS / NR (5th generation mobile communication standard).

[0042] The present disclosure describes a determination based on Layer 1-based measurements when L1 / L2 triggered mobility (LTM; L1 / L2-based mobility) is performed at a terminal, and for this purpose, SSB measurements and CSI-RS resource measurements for LTM candidate cells are supported. In particular, operations that enable the measurement of semi-persistent CSI-RS resources should be supported, and detailed operations to support this in continuous LTM are considered.

[0043] As the terminal operation proposed in the present invention, which enables the measurement and reporting of semi-persistent CSI-RS resources in a continuous LTM, is realized, a procedure for measuring and reporting semi-persistent CSI-RS resources in a continuous LTM is created without separate RRC and MAC CE signaling even after the terminal has performed a cell change.

[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, 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 or gNB, 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) can correspond 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 superior service compared to the existing Node B. In the next-generation mobile communication system, since all user traffic can be serviced through a shared channel, a device is required to collect status information such as the buffer status, available transmission power status, and channel status of the UEs and perform scheduling, and the NR NB (1a-10) can handle this. A single NR NB can control multiple cells. To achieve ultra-high-speed data transmission compared to existing LTE, it can have a maximum bandwidth greater than the existing maximum bandwidth, and beamforming technology can be additionally used by using Orthogonal Frequency Division Multiplexing (hereinafter referred to as OFDM) as the wireless access technology. Additionally, the NR NB (1a-10) can apply an Adaptive Modulation & Coding (AMC) method to determine the modulation scheme and channel coding rate according to the channel conditions of the terminal. The NR CN (1a-05) can perform functions such as mobility support, bearer configuration, and QoS configuration. The NR CN (1a-05) is a device responsible for various control functions as well as mobility management functions for the terminal, and can be connected to multiple base stations. Furthermore, the next-generation mobile communication system can be interoperable with the existing LTE system, and the NR CN (1a-05) can be connected to the MME (1a-25) via a network interface. The MME can be connected to the existing base station eNB (1a-30).

[0047] FIG. 1b is a diagram showing the wireless protocol structure of a next-generation mobile communication system according to one embodiment of the present disclosure.

[0048] Referring to FIG. 1b, the wireless protocol of the next-generation mobile communication system may include NR SDAP (1b-01, 1b-45), NR PDCP (1b-05, 1b-40), NR RLC (1b-10, 1b-35), NR MAC (1b-15, 1b-30), and NR PHY (1b-20, 1b-25) at the terminal and the NR base station, respectively. Of course, the wireless protocol of the next-generation mobile communication system may include more or fewer layers than the configuration shown in FIG. 1b.

[0049] According to one embodiment of the present disclosure, the main functions of the NR SDAP (1b-01, 1b-45) may include some of the following functions, provided that they are not limited to the examples below.

[0050] - User data transfer function (transfer of user plane data)

[0051] - Mapping function between a QoS flow and a DRB for both DL and UL for uplink and downlink

[0052] - Marking QoS flow ID for uplink and downlink (marking QoS flow ID in both DL and UL packets)

[0053] - Function to map reflective QoS flow to data bearers for uplink SDAP PDUs (reflective QoS flow to DRB mapping for the UL SDAP PDUs).

[0054] For SDAP layer devices, the terminal may receive a radio resource control (RRC) message indicating whether to use the SDAP layer device header or the SDAP layer device functions 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 NAS reflective QoS and AS reflective QoS indicators in the SDAP header. The SDAP header may include QoS flow ID information indicating QoS. The QoS information may be used for data processing priorities, scheduling information, etc., to support seamless service.

[0055] According to one embodiment of the present disclosure, the main functions of the NR PDCP (1b-05, 1b-40) may include some of the following functions. Of course, it is not limited to the following examples.

[0056] - Header compression and decompression features (ROHC only)

[0057] - User data transfer function (Transfer of user data)

[0058] - Sequential delivery function (In-sequence delivery of upper layer PDUs)

[0059] - Out-of-sequence delivery of upper layer PDUs

[0060] - Reordering function (PDCP PDU reordering for reception)

[0061] - Duplicate detection function (Duplicate detection of lower layer SDUs)

[0062] - Retransmission of PDCP SDUs

[0063] - Encryption and decryption functions (Ciphering and deciphering)

[0064] - Timer-based SDU discard in uplink.

[0065] The reordering function of the NR PDCP device may include a function to reorder PDCP PDUs received from the lower layer in order based on the PDCP SN (sequence number), a function to transmit data to the upper layer in the reordered order, a function to transmit immediately without considering the order, a function to record lost PDCP PDUs by reordering, a function to report the status of lost PDCP PDUs to the transmitting side, and a function to request retransmission of lost PDCP PDUs.

[0066] According to one embodiment of the present disclosure, the main functions of the NR RLC (1b-10, 1b-35) may include some of the following functions. Of course, it is not limited to the following examples.

[0067] - Data transfer function (Transfer of upper layer PDUs)

[0068] - Sequential delivery function (In-sequence delivery of upper layer PDUs)

[0069] - Out-of-sequence delivery of upper layer PDUs

[0070] - ARQ function (Error Correction through ARQ)

[0071] - Concatenation, segmentation, and reassembly functions of RLC SDUs

[0072] - Re-segmentation function (Re-segmentation of RLC data PDUs)

[0073] - Reordering function (Reordering of RLC data PDUs)

[0074] - Duplicate detection

[0075] - Error detection function (Protocol error detection)

[0076] - RLC SDU discard function

[0077] RLC re-establishment function

[0078] The in-sequence delivery function of an NR RLC device may include the function of delivering RLC SDUs received from a lower layer to an upper layer in order, the function of reassembling and delivering them if a single RLC SDU is received split into multiple RLC SDUs, the function of rearranging received RLC PDUs based on the RLC SN (sequence number) or PDCP SN (sequence number), the function of recording lost RLC PDUs after rearranging the order, the function of reporting the status of lost RLC PDUs to the transmitting side, and the function of requesting retransmission of lost RLC PDUs. Furthermore, if there are lost RLC SDUs, it may include the function of delivering only the RLC SDUs prior to the lost RLC SDU to the upper layer in order, or the function of delivering all RLC SDUs received before the timer started to the upper layer in order if a predetermined timer has expired even if there are lost RLC SDUs, or the function of delivering all RLC SDUs received so far if a predetermined timer has expired even if there are lost RLC SDUs It may include a function to deliver all RLC SDUs to the upper layer in order. Additionally, the NR RLC device may process RLC PDUs in the order they are received (regardless of the order of sequence numbers, but in the order of arrival) and deliver them to the PDCP device out of order (out-of-sequence delivery); 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 NR RLC layer may not include a concatenation function, and this function may be performed by the NR MAC layer or replaced by the multiplexing function of the NR MAC layer.

[0079] The out-of-sequence delivery function of the NR RLC device may include a function to deliver RLC SDUs received from a lower layer directly to an upper layer regardless of order, a function to reassemble and deliver them when an original RLC SDU is received divided into multiple RLC SDUs, and a function to store the RLC SN or PDCP SN of the received RLC PDUs and sort the order to record the lost RLC PDUs.

[0080] According to one embodiment of the present disclosure, an NR MAC (1b-15, 1b-30) may be connected to multiple NR RLC layer devices configured in a terminal, and the main functions of the NR MAC may include some of the following functions. Of course, it is not limited to the following examples.

[0081] - Mapping function (Mapping between logical channels and transport channels)

[0082] - Multiplexing and demultiplexing functions (Multiplexing / demultiplexing of MAC SDUs)

[0083] - Scheduling information reporting function

[0084] - HARQ function (Error correction through HARQ)

[0085] - Priority handling between logical channels of one UE

[0086] - Priority handling between UEs by means of dynamic scheduling

[0087] - MBMS service identification function

[0088] - Transport format selection function

[0089] - Padding

[0090] According to one embodiment of the present disclosure, the NR PHY layer (1b-20, 1b-25) can perform the operation of channel coding and modulating upper layer data, making it into an OFDM symbol and transmitting it to a wireless channel, or demodulating and channel decoding the OFDM symbol received through the wireless channel and transmitting it to an upper layer.

[0091] FIG. 1c is a drawing illustrating the structure of another next-generation mobile communication system according to one embodiment of the present disclosure.

[0092] Referring to FIG. 1c, a cell serviced by a beam-based NR gNB (1c-05) may be composed of multiple TRPs (Transmission Reception Points, 1c-10, 1c-15, 1c-20, 1c-25, 1c-30, 1c-35, 1c-40). The TRPs (1c-10 to 1c-40) represent blocks from which some functions of transmitting and receiving physical signals from an existing NR base station (eNB) have been separated, and may include multiple antennas. The NR gNB (1c-05) may also be represented as a CU (Central Unit), and the TRP as a DU (Distributed Unit). The functions of the NR gNB (1c-05) and the TRPs can be implemented by separating each layer at the PDCP / RLC / MAC / PHY layer, such as 1c-45. That is, some of the TRPs in FIG. 1c (1c-15, 1c-25) may perform the functions of the corresponding layer using only the PHY layer, some of the TRPs in FIG. 1c (1c-10, 1c-35, 1c-40) may perform the functions of the corresponding layers using only the PHY layer and the MAC layer, and some of the TRPs in FIG. 1c (1c-20, 1c-30) may perform the functions of the corresponding layers using only the PHY layer, the MAC layer, and the RLC layer. In particular, TRPs (1c-10~1c-40) may use beamforming technology to transmit and receive data by generating narrow beams in multiple directions using multiple transmitting and receiving antennas. A user terminal (1c-50) can connect to an NR gNB (1c-05) and an external network through the TRPs (1c-10~1c-40). NR gNB (1c-05) can support a connection between the terminals and the core network (CN), particularly AMF / SMF (1c-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 users.

[0093] For convenience of explanation, the TRP of the present disclosure is described based on a structure (1c-15, 1c-25) capable of performing the functions of a layer using only a PHY layer. Of course, it is not limited to the above examples, and a TRP including a PHY layer and a MAC layer, or a PHY layer, a MAC layer, and an RLC layer is also included in the embodiments of the present disclosure.

[0094] FIG. 1d is a diagram illustrating a scenario in which a terminal transmits and receives data through the beam of a TRP (transmission / reception point) of a surrounding cell that supports beam changing based on L1 / L2 while maintaining a connection state with a serving cell, according to one embodiment of the present disclosure.

[0095] FIG. 1d describes a case where multiple cells (TRP1-Cell1, TRP2-Cell2; 1d-10, 1d-15) exist within a single DU (Distributed unit, 1d-05), but the embodiments of the present disclosure are also applicable to inter-DU cases (each DU constitutes a single TRP-Cell). Furthermore, throughout 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 the PCI different from the serving cell.

[0096] It is assumed that the existing terminal beam change procedure (1d-45) starts with the terminal (1d-20) transmitting and receiving data in a connected state through the TRP 1 (1d-10) of the serving cell 1, and is set to the optimal beam, TCI state 1 (1d-25, 1d-30). The terminal (1d-20) can receive instructions for setting information for L3 channel measurement (RRM; radio resource management) for an additional cell (TRP 2-Cell 2, 1d-15) that has a different physical cell ID (PCI) from the serving cell through RRC setting information from the serving cell (1d-10), and can perform an L3 measurement operation (1d-46) for the corresponding frequency and cell. Subsequently, the serving cell (TRP 1-Cell 1, 1d-10) may direct a handover to the corresponding cell (TRP 2-Cell 2, 1d-15) based on the reported measurement value (1d-47), and after the handover is completed, additional RRC configuration information may be transmitted to the terminal (1d-20) via TRP 2-Cell 2 (1d-15) (1d-48). The RRC configuration information may include UL / DL configuration information in the corresponding cell, L1 measurement related settings (CSI-RS measurement and reporting), and in particular, TCI state configuration information for PDCCH and PDSCH channels. The terminal performs an L1 measurement according to the settings (1d-49), and the base station may update the TCI state through L1 / L2 signaling according to the measurement report (1d-50). Through L1 / L2 signaling for updating the TCI state, the optimal beam, TCI state 2 (1d-40), can be indicated to the terminal (1d-20). According to one embodiment of the present disclosure, the serving cell may be Cell 1 prior to handover, and Cell 2 may be the serving cell after handover. That is, many procedures and time are required even after handover until the optimal beam is indicated.

[0097] Unlike the existing terminal beam change procedure (1d-45), the improved beam change technique (1d-55) of the present disclosure is as follows. The terminal can refer to and transmit the beam setting associated with an additional cell (TRP 2-Cell 2, 1d-15) with a different PCI from the serving cell through RRC setting information (1d-56) from the serving cell (1d-10). The part that associates the beam setting associated with the additional cell (TRP 2-Cell 2, 1d-15) with a different PCI from the serving cell, i.e., the TCI state corresponding to TRP2, may apply a method of associating and indicating a new cell ID (Physical cell ID, PCI; additionalPCI-r17) as follows.

[0098]

[0099] 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 configured as either Joint UL / DL mode or separate UL / DL mode.

[0100]

[0101] 1. Joint UL / DL Mode: Configures UL and DL to share the same TCI settings (in PDSCH-Config)

[0102]

[0103] 2. Separate UL / DL Mode: The UL and DL provide their own TCI settings. The TCI state for the DL follows the settings in dl-OrJoint-TCIStateList-r17 (in PDSCH-Config), and the TCI state for the UL follows ul-TCI-StateList-r17 (in BWP-UplinkDedicated).

[0104]

[0105] After the setting for TRP 2-Cell 2 is provided in the RRC connection state to serving cell 1, the terminal can perform an L1 measurement for the TRP 2-Cell 2 according to the setting and report the result to the serving cell (Cell 1, 1d-10) (1d-57). If the serving cell determines that a change to a specific beam (TCI state 2, 1d-35, 1d-40) of TRP 2 (Cell 2, 1d-15) is necessary based on the measurement result, it triggers a beam change and instructs the terminal via L1 / L2 signaling (1d-58). Through the instruction, the terminal can change the beam to the specific beam (TCI state 2, 1d-40) of TRP 2 (Cell 2, 1d-15) and perform physical channel setting and upper layer setting operations associated with the set beam. From this stage, the terminal remains connected to the serving cell (Cell 1, 1d-10), but performs data transmission and reception using the channel link of TRP 2 (Cell 2, 1d-15) (receiving PDCCH / PDSCH, transmitting PUCCH / PUSCH). That is, transmission and reception for the common control channel are performed through the serving cell (Cell 1, 1d-10). Subsequently, the terminal performs L3 measurement operations according to the measurement settings configured in the independent serving cell (1d-59), receives a handover command message from the serving base station (Cell 1), and can perform a serving cell change to Cell 2 (1d-60). Through the enhanced beam changing technique (1d-55) of the present disclosure, the terminal performs data transmission and reception with a specific TRP 2 of Cell 2 that supports L1 / L2-based mobility while connected to the serving cell, and can continue to use the beam even after the handover.

[0106] Additionally, the RRC settings regarding the settings and operations related to the L1 measurement and report in step 1d-57 of the present disclosure are described in more detail below. Furthermore, the description of the L1 measurement and report in step 1d-57 may also be applied to other embodiments of the present disclosure, and additional details of the following embodiments may be further performed.

[0107] 1. L1 measurement settings (configured within CSI-ResourceConfig and ServingCellConfig in IE)

[0108] - CSI-RS / SSB resources and resource pools requiring measurement (nzp-CSI-RS, csi-IM, csi-SSB)

[0109] - Configuration of CSI-RS / SSB resources requiring measurement (aperiodic, semi-persistent) and triggering settings

[0110] - 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).

[0111]

[0112]

[0113] 2. L1 report settings (configured within the serving cell, ServingCellConfig, configured within IE)

[0114] - Report Type: Periodic Report, Semi-periodic Report with PUCCH, Semi-periodic Report with PUSCH, Aperiodic Report with PUSCH

[0115] - Report quantity

[0116] - Other settings required for reporting

[0117] FIG. 1e is a diagram illustrating a scenario in which a terminal transmits and receives data by changing the serving cell and beam to the TRP of a cell that supports L1 / L2-based beam changing, according to one embodiment of the present disclosure. Although FIG. describes a case where multiple cells (TRP1-Cell1, TRP2-Cell2; 1e-10, 1e-15, 1e-40, 1e-45) exist within a single DU (Distributed unit, 1e-05, 1e-35), the embodiments of the present disclosure can also be applied to inter-DU within an intra-CU (each DU constitutes a single TRP-Cell).

[0118] Unlike the conventional terminal beam changing procedure (1d-45, 1d-55) described in FIG. 1d, the enhanced beam changing technique (1e-25, 1e-75) described in FIG. 1e is as follows.

[0119] 1. Example 1 (1e-25): After performing inter-cell beam management (change) operation, perform L1 / L2 handover

[0120] 2. Example 2 (1e-75): Perform L1 / L2 handover immediately

[0121] First, to explain the overall operation of Embodiment 1, the terminal can receive common configuration and dedicated configuration information for an additional cell (TRP 2-Cell 2, 1e-15) with a different PCI from the serving cell (1e-10) through RRC configuration information (1e-26). That is, configuration information corresponding to ServingCellID or candidateCellID (cell ID associated with PCI), ServingCellConfigCommon, and ServingCellConfig may be provided in advance. The common configuration and dedicated configuration information may be provided in the form of pre-configuration in the RRC configuration and may include configuration information for multiple cells. In addition, the configuration may include all configuration information (cell configuration, bearer configuration, security key configuration, etc.) that is applied when the terminal moves to the corresponding cell (handover). Furthermore, the common configuration and dedicated configuration include enhanced configurations by referring to the unified TCI state configuration and L1 measurement and report-related configurations described in step 1d-56. For example, enhanced unified TCI state settings and L1 measurement and report settings for continuous LTM may be included, but are not limited to the above examples. Details regarding the settings related to the unified TCI state settings and L1 measurement and report are described in detail in the drawings of the present invention below.

[0122] After the setting for TRP 2-Cell 2 (1e-15) is provided in the RRC connection state to serving cell 1, the terminal performs an L1 measurement for the TRP 2-Cell 2 (1e-15) according to the setting received in step 1e-27 and reports the result to the serving cell (Cell 1, 1e-10). If the serving cell determines that a change to a specific beam (TCI state 2, 1e-40) of TRP 2 (Cell 2, 1e-15) is necessary from the serving cell beam (TCI state 1, 1e-25) based on the measurement result, it may trigger a beam change in step 1e-28 and instruct the terminal via L1 / L2 signaling. Based on instructions via L1 / L2 signaling, the terminal performs a beam change to TRP 2 (Cell 2, 1e-15) and transmits and receives data through TRP 2 (Cell 2, 1e-15). At this time, no serving cell change occurs, and the terminal remains connected to the serving cell (Cell 1, 1e-10) via RRC. Subsequently, the terminal performs an L1 measurement for TRP 2-Cell 2 (1e-15) (1e-29) and reports the result to the serving cell (Cell 1, 1e-10). If the L1 measurement reported by the terminal satisfies the triggering condition for a handover to TRP 2-Cell 2 (1e-15) (detailed operation is described below), the serving cell (Cell 1, 1e-10) instructs the terminal to perform a handover (1e-30). This instruction may be an L1 / L2 message. In other words, MAC CE may include an indicator that directs a handover.

[0123] To describe the overall operation of Example 2, the terminal can receive common configuration and dedicated configuration information for an additional cell (TRP 2-Cell 2, 1e-45) that has a different PCI from the serving cell (1e-40) through RRC configuration information (1e-76). That is, ServingCellID or candidateCellID (cell ID associated with PCI), and configuration information corresponding to the candidate LTM cell may be provided in advance. Configuration information corresponding to the candidate LTM cell 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 corresponding to the candidate LTM cell may include all configuration information (cell configuration, bearer configuration, channel measurement configuration, etc.) that is applied when the terminal moves to the corresponding cell (handover). Furthermore, in the configuration corresponding to the candidate LTM cell, the unified TCI state configuration and settings related to L1 measurement and report described in step 1d-56 may be modified and included to support consecutive LTMs. The L1 measurement, report, and TCI state settings applied to the present invention are explained in detail below.

[0124] After the configuration for TRP 2-Cell 2 (1e-45) is provided in the RRC connection state to serving cell 1, the terminal performs an L1 measurement for the corresponding TRP 2-Cell 2 (1e-45) according to the configuration received in step 1e-77 and reports the result to the serving cell (Cell 1, 1e-40). If the serving cell determines that a beam change from the serving cell beam (TCI state 1, 1e-45) to a specific beam (TCI state 2, 1e-70) of TRP 2 (Cell 2, 1e-45) and a handover are required based on the measurement result, it triggers the beam change and handover in step 1e-78 and instructs the terminal via L1 / L2 signaling. The terminal performs a handover simultaneously with changing the beam to TRP 2 (Cell 2, 1e-15) via the corresponding instruction, and transmits and receives data through TRP 2 (Cell 2, 1e-15). At this time, the terminal applies the configuration information for the target cell where the handover is performed, which was pre-configured in step 1e-76. Depending on whether uplink synchronization is required in this step, the terminal may perform random access, or random access to the target cell may be omitted. The detailed operation is explained in the drawings below.

[0125] As described above, a detailed method for setting the unified TCI state and L1 measurement and report for candidate cells surrounding an LTM to support the continuous LTM proposed in this disclosure is explained. As illustrated in Figure 1d, in conventional inter-cell beam management (ICBM), L1 measurement resource settings for cells requiring measurement can be 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.

[0126] Detailed settings for L1 measurement and reporting settings for LTM can be provided as L1 measurement resource settings applied to LTM candidate cells as follows. To this end, it may be necessary to share and determine L1 measurement resources and reporting settings for LTM among LTM candidate cells during the preprocessing stage, which will be described later. The following examples are explained with reference to the settings below.

[0127] 1. L1 measurement resource configuration (configured within LTM-CSI-ResourceConfig and LTM-Config)

[0128] - CSI Resource configuration index exists to specify CSI resource settings (LTM-CSI-ResourceConfigId-r18)

[0129] - CSI resource set containing CSI-RS or SSB resources requiring measurement

[0130] - A single CSI resource set can be multiple SSB resources or CSI-RS resources existing within an LTM candidate cell.

[0131] 2. L1 report settings (configured within LTM-Config)

[0132] - CSI Report configuration index exists to specify CSI reporting settings (LTM-CSI-ReportConfig-r18)

[0133] - Report Type: Periodic Report, Semi-periodic Report with PUCCH, Semi-periodic Report with PUSCH, Aperiodic Report with PUSCH

[0134] - Report Content (Number of reporting cells, number of reporting resources, etc.)

[0135]

[0136]

[0137]

[0138]

[0139] The present disclosure proposes a method for setting L1 measurement information for surrounding candidate cells for LTM to support subsequent LTM (subsequent L1 / L2 triggered mobility), and a method for setting a terminal to report the set L1 measurement information. In particular, it describes detailed information and the overall procedure for enabling / disabling semi-persistent CSI-RS resources, setting and reporting the corresponding L1 measurement information.

[0140] FIG. 1f illustrates an overall operation for supporting continuous LTM operations based on semi-persistent CSI-RS resource measurement reporting according to one embodiment of the present disclosure. FIG. 1f illustrates an overall operation with L1 measurement resources and reporting settings applied to support continuous L1 / L2-based handover (LTM) operations in cells within different CUs.

[0141] A terminal (1f-01) in an RRC connection state can transmit and receive data with source cell 1 (1f-02) and, according to the layer 3 measurement and reporting set in step 1f-10, transmit layer 3 measurement values ​​for the serving cell and surrounding cells to the source base station (1f-03). At this time, the layer 3 measurement values ​​can be transmitted to the base station's CU (1f-03). This is because the base station CU (1f-03) is responsible for processing RRC messages and determining mobility.

[0142] The base station CU (1f-03) can generate a message (e.g., UE Context Setup Request or UE Context Modification Request) requesting configuration information for L1 / L2-based handover to the intra-CU LTM candidate surrounding cells (1f-04, 1f-05) in step 1f-15 and transmit it to the F1 interface based on the measurement report received from the terminal. Although candidate cells are shown in association with DUs in FIG. 1f, in reality, candidate cells and DUs may be mapped 1:1, or multiple candidate cells may be included in a single DU. Additionally, the message requesting configuration information for L1 / L2-based handover may be a UE context request message, a UE context modification request message, etc., or a new F1 message. The message requesting configuration information for L1 / L2-based handover may include a procedure to notify surrounding cells that the cell has been determined as an L1 / L2-based handover candidate cell, and simultaneously request RRC configuration information that is applied when an L1 / L2-based handover is performed to that cell. That is, it may include information requesting L1 measurement resources and reporting settings for LTM candidate cells. The information that may be included in the message requesting configuration information for L1 / L2-based handover is as follows, but is not limited to the examples below.

[0143] 1. Configuration information applicable to LTM and conditional LTM (Information to be displayed when issuing the cell switch command MAC CE instruction to the candidate cell that made the LTM decision.)

[0144] - LTM candidate ID

[0145] - Mapping information between the LTM candidate ID and the corresponding cell ID

[0146] - Beam information to be used for each candidate (TCI state)

[0147] -- 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.

[0148] - RACH preamble index

[0149] - SSB index: An index of the SSB (synchronization signal block) used to determine the RACH occasion in each candidate cell, which can represent the occasion of the RACH preamble of the CFRA (contention-free RA).

[0150] 2. Pre-configuration procedures for LTM and conditional LTM

[0151] - CSI resource request information for each candidate cell (requests for CSI-RS resources or SSB resources)

[0152] -- This may be requested during the pre-configuration preprocessing section for LTM candidate cells.

[0153] --- Indicator for whether the request is for initial preparation, e.g., initiation, or for a modification request after the initial one

[0154] -- 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.

[0155] -- If CSI resource information is received from candidate cells using the corresponding request information, the CSI resource settings of each candidate cell below may be transmitted instead of the request. In other words, a CSI resource setting preprocessing procedure is required in at least 2 steps.

[0156] In addition, it is possible to decide whether to request CSI-RS resources or SSB resources for each target candidate cell.

[0157] - 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.

[0158] -- Provides L1 measurement settings for LTM delivered by the corresponding candidate cell based on CSI resource request information

[0159] -- Depending on the CSI-RS or SSB resource request from each target cell, one of the two resource configurations or both resource configurations can be delivered.

[0160] Information indicating the configuration of semi-persistent CSI-RS resources and whether the resources are enabled or disabled can be transmitted, and the source cell signals whether the semi-persistent CSI-RS resources for the terminal are enabled based on this information.

[0161] - CSI report configuration considering the CSI resources of each candidate cell

[0162] -- When a candidate DU creates CSI report configuration information and transmits it to a CU, the CSI report configuration 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 CSI report configuration information may not be transmitted separately but may be included within the target cell configuration (RRCReconfiguration).

[0163] 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.

[0164] -- Event-based L1 measurement reporting

[0165] You can define and use Best beam's L1-RSRP-based events.

[0166] For example, the following events can be introduced. That is, events are defined by comparing the serving cell beam with the surrounding cell beam, and L1 filtering values ​​such as threshold, beam offset, hysteresis, and time to trigger (TTT) can be introduced.

[0167] *Event LTM2: Beam of serving cell becomes worse than absolute threshold;

[0168] *Event LTM3: Beam of candidate cell becomes amount of offset better than beam of serving cell;

[0169] *Event LTM4: Beam of candidate cell becomes better than absolute threshold;

[0170] *Event LTM5: Beam of serving cell becomes worse than absolute threshold1 AND Beam of candidate cell becomes better than another absolute threshold2.

[0171] Events can also be used for conditions that trigger conditional LTM. Alternatively, in addition to a single beam, events through multiple beams or events based on cell-level measurements estimated through multiple beams may be added.

[0172] The condition for triggering the conditional LTM is determined by coordination between the serving CU and the LTM candidate DU in step 1f-15, and the serving CU can confirm the event condition for triggering the LTM provided by the LTM candidate cell and the L1 filtering value and transmit them to the terminal.

[0173] --- Information regarding the application of L3-based event conditions (conditions used in conditional handovers)

[0174] - RACH configuration and lower layer setting information to be used in the relevant concerned cell

[0175] -- This information can be transmitted from the candidate DU to the CU, written as the settings required for RACH execution within the target cell configuration of the concerned cell, the lower layer settings to be applied when moving to the cell, and / or reference settings including them, and later transmitted to the terminal.

[0176] --In particular, some of the RACH settings can be used to include RACH preamble index, Mask, and occasion determination information in the cell switch command MAC CE described above.

[0177] --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.

[0178] Although it is illustrated as one step in the 1f-15 steps in the diagram, it may be performed in multiple steps. That is, LTM-related settings may be requested for each LTM candidate cell, the settings organized from the source cell may be transmitted once again, and then the necessary LTM settings may be determined and transmitted to the source cell.

[0179] In particular, this disclosure describes detailed operations regarding the configuration of semi-persistent CSI-RS resources and whether said resources remain applicable even after a cell change, in relation to L1 measurement resource configuration and reporting configuration.

[0180] Additionally, the base station CU (1f-03) can generate a message (Handover Request or a new message) requesting configuration information for LTM from the target base station (CU2; 1f-06) in step 1f-20 for an LTM candidate cell configuration request for an LTM surrounding cell (1f-07) of the inter-CU based on a measurement report received from the terminal, and transmit it to the X2 interface.

[0181] Subsequently, in step 1f-25, the target base station (CU2; 1f-06) can generate a message (UE Context Setup Request or UE Context Modification Request) requesting configuration information for LTM cell modification for an LTM candidate cell (1f-07) belonging to the CU, transmit it to the F1 interface, and receive a message (UE Context Setup Response or UE Context Modification Response) responding with configuration information for LTM. This procedure is similar to the LTM configuration preprocessing procedure of FIG. 1f-15.

[0182] Subsequently, in step 1f-30, the target base station (CU2; 1f-06) can generate a message (Handover Response or a new response message) to the source base station (CU; 1f-03) via the X2 interface, including the LTM candidate configuration information transmitted by the LTM candidate cell (1f-07) belonging to the CU. The content that can be newly added to the LTM configuration request message via the X2 interface in step 1f-30 is summarized as follows. Of course, it is not limited to the examples below.

[0183] - Indicator for LTM execution

[0184] -- Additionally, an indicator indicating whether the request is for initial preparation, e.g., initiation, or a modification request after the initial one.

[0185] - Terminal ID

[0186] - Source CU and / or Source DU ID, and / or Source DU's TNL address (e.g., IP address)

[0187] - ID of the requesting candidate cell (PCI or NR CGI with NR ARFCN)

[0188] - Candidate cell's LTM configuration ID (If accepted, the source DU can use the LTM config ID when cell switching to the target cell.)

[0189] - LTM configuration ID mapping list: Information to inform the candidate DU of the mapping relationships between the candidate DU's currently available LTM configurations and its cells when delivered to the candidate DU.

[0190] -- Opt 1. The candidate cell list may be a list of candidate cells operated by all candidate CUs for the terminal, and

[0191] -- Opt 2. It may be a list containing only candidate cells operated by the source CU that transmits the HO request message.

[0192] - Request information for CSI resource configuration for LTM L1 measurement

[0193] -- The CSI resource request is omitted, and configuration information for CSI resources being transmitted by all currently configured candidate cells may be conveyed.

[0194] -- SSB or CSI-RS resource request

[0195] You can request only one of the two resources, or you can request both resources.

[0196] --- Request regarding whether to allow semi-persistent CSI-RS resource configuration in the case of CSI-RS resources, and related configuration information (resource and activation status)

[0197] - An indicator requesting PRACH resource information for target candidate cells

[0198] - An indicator requesting a lower layer setting for target candidate cells

[0199] In addition to the information mentioned above, information previously used in HO request messages may also be included, as explained in Table 1 below. Of course, it is not limited to the examples below.

[0200] Source NG-RAN node UE XnAP ID referenceNG-RAN node UE XnAP ID9.2.3.16Allocated at the source NG-RAN nodeCause9.2.3.2Target Cell Global ID9.2.3.25Includes either an E-UTRA CGI or an NR CGIGUAMI9.2.3.24UE Context Information>NG-C UE associated Signalling referenceAMF UE NGAP ID9.2.3.26Allocated at the AMF on the source NG-C connection.>Signalling TNL association address at source NG-C sideCP Transport Layer Information9.2.3.31This IE indicates the AMF's IP address of the SCTP association used at the source NG-C interface instance.NOTE: If no UE TNLA binding exists at the source NG-RAN node, the source NG-RAN node indicates the TNL association address it would have selected if it would have had to create a UE TNLA binding.>UE Security Capabilities9.2.3.49>AS Security Information9.2.3.50>Index to RAT / Frequency Selection Priority9.2.3.23>UE Aggregate Maximum Bit Rate9.2.3.17>PDU Session Resources To Be Setup List9.2.1.1Similar to NG-C signalling, containing UL tunnel information per PDU Session Resource;and in addition, the source side QoS flow ↔DRB mapping>RRC ContextOCTET STRINGEither includes theHandoverPreparationInformationmessage as defined in subclause 10.2.2. of TS 36.331

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

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

[0010] , if the target NG-RAN node is a gNB.>Location Reporting Information9.2.3.47Includes the necessary parameters for location reporting.>Mobility Restriction List9.2.3.53>5GC Mobility Restriction List Container9.2.3.100>NR UE Sidelink Aggregate Maximum Bit Rate9.2.3.107This IE applies only if the UE is authorized for NR V2X services.>LTE UE Sidelink Aggregate Maximum Bit Rate9.2.3.108This IE applies only if the UE is authorized for LTE V2X services.>ManagementBasedMDT PLMN ListMDT PLMN List9.2.3.133>UE Radio Capability ID9.2.3.138>MBS Session Information List9.2.1.36>5G ProSe UE PC5 Aggregate Maximum Bit RateNR UE Sidelink Aggregate Maximum Bit Rate9.2.3.107This IE applies only if the UE is authorized for 5G ProSe services.>UE Slice Maximum Bit Rate List9.2.3.167>NR A2X UE PC5 Aggregate Maximum Bit RateNR UE Sidelink Aggregate Maximum Bit Rate9.2.3.107This IE applies only if the UE is authorized for NR A2X services.>LTE A2X UE PC5 Aggregate Maximum Bit RateLTE UE Sidelink Aggregate Maximum Bit Rate 9.2.3.108This IE applies only if the UE is authorized for LTE A2X services.Trace Activation9.2.3.55Masked IMEISV9.2.3.32UE History Information9.2.3.64UE Context Reference at the S-NG-RAN node>Global NG-RAN Node ID9.2.2.3>S-NG-RAN node UE XnAP IDNG-RAN node UE XnAP ID9.2.3.16.

[0201] Subsequently, in step 1f-35, the source base station (1f-02) may trigger the procedures 1f-15 (transmitting the finally determined CSI resource settings to LTM candidate cells within the CU and requesting and responding to LTM-related settings) and 1f-20 (transmitting the finally determined CSI resource settings to LTM candidate cells within another CU and requesting LTM-related settings) based on the information of LTM-related candidate cells received from the target base station (1f-06). In addition, in response to this, the procedure 1f-30 (receiving LTM-related settings based on the finally transmitted CSI resource settings from LTM candidate cells within another CU) may be performed.

[0202] In step 1f-40, the source base station (1f-02) can collect all LTM-related settings received from LTM candidate cells and store them in an RRCReconfiguration message that is transmitted to the terminal, and transmit the corresponding RRC setting information to the terminal. That is, pre-configuration information for LTM candidate cells can be transmitted to the terminal. At this time, the source base station CU (1f-03) can transmit the source cell's setting information and separate reference cell configuration information. In the present invention, the reference cell configuration information may include L1 measurement resource settings for continuous LTM, in particular CSI-RS resource settings (including semi-persisetent CSI-RS resources) and reporting settings.

[0203] In particular, the configuration for the above-mentioned semi-persisetent CSI-RS resource can be transmitted in the following structure. Of course, it is not limited to the following example.

[0204] 1. Method for configuring resources first: Provide resource configurations within each LTM candidate cell configuration.

[0205] - Option 1-1: Provide CSI-RS resource configuration information directly within the LTM candidate configuration

[0206] i) CSI-RS resource configuration index

[0207] ii) CSI-RS Resource Type: Periodic, Semi-persistent

[0208] iii) CSI-RS resource set list: Each set is provided with an index of CSI-RS resources to which the same settings apply and common settings. Here, if multiple CSI-RS resources are indicated within a CSI-RS resource set, the same settings apply to those resources, and if the index of the CSI-RS resource set is used to activate semi-persistent CSI-RS resources, all semi-persistent CSI-RS resources within that CSI-RS resource set can be activated.

[0209] - Option 1-2: Provide CSI-RS resource configuration information within LTM-TCI-Info in the LTM candidate configuration, and provide resource and TCI state information together.

[0210] i) CSI-RS resource configuration index

[0211] ii) CSI-RS Resource Type: Periodic, Semi-persistent

[0212] iii) CSI-RS Resource Set List: Each set provides an index of CSI-RS resources to which the same settings apply, as well as common settings.

[0213] For reference, the signaling of Method Option 1-1 of the first resource configuration method is described below. In the case of Option 1-2, the location of the relevant settings in the underlined section below may change to within LTM-TCI-Info. Since the first configuration method includes CSI-RS resource settings within each candidate cell setting, the terminal may need to pre-decode the settings for the candidate cells to enable the terminal to measure the corresponding resource in the serving cell. However, because the settings are included within the candidate cells, separate coordination between candidate cells may not be required. Of course, it is not limited to the above examples.

[0214]

[0215] 2. Second resource configuration method: Provide resource settings within LTM-CSI-ResourceConfig inside LTM-Config so that they apply to all LTM candidate cells.

[0216] i) Candidate cell index with CSI-RS resource configured

[0217] ii) CSI-RS resource configuration index

[0218] iii) CSI-RS Resource Type: Periodic, Semi-persistent

[0219] iv) CSI-RS Resource Set List: Each set provides an index of CSI-RS resources to which the same settings apply, as well as common settings.

[0220] For reference, the signaling of the second resource configuration method is described below. Since the CSI-RS resource settings of all candidate cells are configured to be common, the terminal can measure the corresponding resource without the serving cell having to decode the settings for a specific candidate cell in advance. Instead, the source cell must provide the corresponding settings after coordination between the candidate cells and the source cell.

[0221]

[0222] In addition, CSI report settings that can be linked with CSI-RS resources can be configured only within an sPCell, and CSI-RS resources can be linked with any type of LTM L1 report settings. That is, they can be applied to periodic L1 reports via UCI, event-based L1 measurement reports, and measurement data for conditional LTM. If linked to measurements for conditional LTM (CLTM), the base station can configure valid resources within the intra-CU to link with the CLTM conditions. Alternatively, when applying to CLTM, the CU ID can be additionally applied to the settings of candidate cells and resources to determine whether to apply semi-persistent CSI-RS resources.

[0223] Additionally, according to one embodiment of the present disclosure, an operation regarding whether a semi-persistent CSI-RS resource activated in a serving cell is maintained or released after an LTM cell change can be configured. That is, the base station may add an indicator that directs the operation according to the configuration. As will be explained in the embodiments below, the detailed operation regarding whether the semi-persistent CSI-RS resource is maintained or released after an LTM cell change may be determined in advance and performed as a single operation without separate configuration.

[0224] A terminal that receives an RRC message in step 1f-45 may perform a procedure to decode and process the RRC message. According to one embodiment of the present disclosure, processing includes ASN.1 decoding of the received message, validation, and a method for storing and managing configuration details. Additionally, the terminal may store LTM configuration information for each candidate cell decoded in step 1f-45 as complete configuration information in the terminal's buffer (memory), and simultaneously store the received reference cell configuration information in the terminal's buffer (memory) as well, and manage it for future use. Furthermore, according to one embodiment of the present disclosure, the reference cell configuration information may be omitted from the RRC message (or configuration information for each LTM candidate cell) in step 1f-40. In this case, the terminal recognizes that there is no reference cell configuration information and may determine and store the configuration information for the received LTM target candidate cells as complete configuration information. At this time, the reference cell configuration information may not be stored separately (it operates as empty). That is, delta configuration is not applied. In addition, L1 measurement resources and reporting configuration information for continuous LTM can be transmitted via RRC messages.

[0225] In this disclosure, channel measurement and reporting for semi-persistent CSI-RS resources are primarily directed, but separately, other forms of L1 channel measurement reporting may be established and the terminal may perform them. Although omitted in FIG. 1f, existing L1 measurement and reporting procedures may be added. In step 1f-50, the base station transmits a MAC CE to the terminal instructing the activation of specific semi-persistent CSI-RS resources so that the terminal can measure the L1 resources. The MAC CE instructing the activation / deactivation of semi-persistent CSI-RS resources is described in more detail in FIG. 1g. Based on this, although omitted in FIG. 1f, in step 1f-50, the base station may instruct the terminal to a TCI state as a unified TCI state activation MAC CE to indicate the optimal beam to be used in the corresponding serving cell. This can be used by the terminal to synchronize the downlink to the indicated candidate cell.

[0226] In step 1f-55, the terminal measures the semi-persistent CSI-RS resource that is activated according to the settings, and if there is a CSI report setting associated with the semi-persistent CSI-RS resource, the terminal evaluates the L1 measurement result according to the settings. In step 1f-60, the terminal reports the L1 measurement result to the base station based on the L1 measurement report result measured and evaluated in step 1f-55. As described above, any form of L1 measurement reporting method (UCI or MAC CE) associated with the semi-persistent CSI-RS resource may be used.

[0227] A source base station that receives an L1 measurement report from a terminal may refer to the L1 measurement value and instruct the terminal to change LTM cells in step 1f-65. In step 1f-65, MAC CE containing a handover indicator may be used for L1 / L2 signaling. If there is a need for RACH-less LTM prior to step 1f-65, a procedure for acquiring a TA for the corresponding target cell may be added. For LTM, the source cell makes the final decision and does not transmit the L1 measurement value to the base station; instead, the source cell independently decides on the handover based on measurement criteria (threshold and measurement range) for making handover decisions for each candidate surrounding cell received from the previous base station, and accordingly transmits L1 / L2 signaling to the terminal. Subsequently, the LTM decision information may be transmitted to the CU.

[0228] When an L1 / L2 handover instruction is delivered to the terminal, the terminal may start the handover procedure in step 1f-70 and start a timer for the L1 / L2 handover. The timer may be a newly configured timer for the LTM for each LTM candidate cell, or an existing T304 timer may be reused.

[0229] In step 1f-75, the terminal can apply the settings for the target cell to which L1 / L2 handover is applied, that is, it can replace the current settings with the complete setting information of the designated LTM target cell that was previously stored in the terminal. This may be one of the LTM candidate surrounding cell settings received in advance in step 1f-40 and may be a setting stored in the terminal.

[0230] Depending on the settings applied in step 1f-80, the terminal may perform random access to the corresponding target cell if random access is required, and if random access is not instructed or is not required (if uplink synchronization has already been performed or matched), the random access procedure may be omitted.

[0231] In step 1f-85, the terminal can perform a handover completion procedure with the target cell. The handover completion procedure may be a handover completion procedure for the LTM. It is a process of delivering an RRCReconfiugrationComplete message to the RRC message configured by the target cell, and the actual handover completion is determined by the end of the random access process.

[0232] In step 1f-90, the target cell (DU, 1f-04) that receives the handover completion message can transmit the received message to the base station CU (1f-03). At this time, the handover completion message received through the F1 interface can be transmitted as is, or the message can be newly processed and transmitted based on the received information.

[0233] Afterwards, in step 1f-195, the base station CU (1f-03) can transmit information about the completion of the handover to the source cell (1f-02) and instruct it to release the terminal context.

[0234] Additionally, as described in step 1f-100, embodiments of the present disclosure may support subsequent LTM operations. This means that the LTM configuration information (configuration for target candidate cells and reference cell configuration information, etc.) received by the terminal in step 1f-40 is stored in the terminal as is, and the terminal may continue to perform the LTM procedure unless the LTM configuration information is changed, released, or added through a separate RRC configuration. If it is necessary to update the reference cell configuration information, new RRC configuration information is transmitted to the terminal to perform this. That is, the procedure described in this drawing may be triggered again to be performed.

[0235] In addition, in step 1f-100, to support the subsequent LTM operation primarily proposed in this invention, an operation regarding whether the semi-persistent CSI-RS resource is activated or deactivated even after an LTM cell change occurs may be applied. The detailed operation is described in FIG. 1h.

[0236] FIG. 1g illustrates a MAC CE structure for enabling and disabling semi-persistent CSI-RS resources in an LTM according to an embodiment of the present disclosure. In particular, the present disclosure is characterized by enabling semi-persistent CSI-RS resources in a source cell and determining whether the enabled resources are maintained even after an LTM cell change. FIG. 1g proposes a MAC CE structure for enabling / disabling semi-persistent CSI-RS resources for this purpose. Furthermore, the MAC CE for enabling / disabling semi-persistent CSI-RS resources proposed in the present disclosure is a newly introduced MAC CE exclusively for LTMs, and may be used separately by assigning a new LCID or eLCID. Of course, it is not limited to the above examples.

[0237] In particular, the configuration information for the semi-persistent CSI-RS resource proposed in FIG. 1g is described in detail in FIG. 1f, and the content and configuration used described in FIG. 1f can be applied to the explanation of MAC CE signaling for enabling / disabling the semi-persistent CSI-RS resource. In particular, depending on which semi-persistent CSI-RS resource index is indicated, the present invention proposes two methods.

[0238] 1. Method for indicating a first semi-persistent CSI-RS resource: A method for indicating the index of a semi-persistent CSI-RS resource set. FIG. 1g illustrates that a single semi-persistent CSI-RS resource set is included within a MAC CE, but multiple semi-persistent CSI-RS resource sets may be included. In this case, activation / deactivation calls to the A / D field for each set may be signaled independently.

[0239] - A / D Field (1g-05): Enable and disable indication information regarding whether the terminal can measure semi-persistent CSI-RS resources included in the semi-persistent CSI-RS resource set indicated below. For example, if indicated as 1, it indicates the enablement of the corresponding resource, and if indicated as 0, it indicates the disablement of the corresponding resource. (The opposite signaling may also be used.)

[0240] - Semi-persistent CSI-RS resource set index field (1g-10): A semi-persistent CSI-RS resource set index applied to LTM candidate cells for LTM, which can be mapped to the example LTM-NZP-CSI-RS-ResourceConfigId or NZP-CSI-RS-ResourceSetId in the above RRC configuration. Alternatively, it may be defined as a CSI-RS resource set index.

[0241] - TCI state index (1g-15, 1g-20): Indicates which beam information (TCI state) is associated with the actual resource for multiple semi-persistent CSI-RS resources existing within the semi-persistent CSI-RS resource set specified in 1g-10 above. The corresponding TCI state information may be associated with the information configured in ltm-TCI-Info within each candidate cell's configuration. Refer to the ASN.1 signaling for LTM-TCI-Info-r18 below.

[0242] 2. Second Method for Indicating Semi-Persistent CSI-RS Resources: A Method for Indicating the Index of Semi-Persistent CSI-RS Resources

[0243] - A / D Field (1g-25, 1g-35): Enable and disable indication information regarding whether the terminal can measure semi-persistent CSI-RS resources included within the semi-persistent CSI-RS resource set indicated below. For example, if indicated as 1, it indicates the enablement of the corresponding resource, and if indicated as 0, it indicates the disablement of the corresponding resource. (The opposite signaling may also be used.)

[0244] - semi-persistent CSI-RS resource index field (1g-30, 1g-40): A semi-persistent CSI-RS resource index applied to LTM candidate cells for LTM, which can be mapped to the NZP-CSI-RS-ResourceId of the example in the RRC setting above. In this case, it is characterized by indicating multiple semi-persistent CSI-RS resources existing within the same semi-persistent CSI-RS resource set.

[0245] - TCI state index (1g-45, 1g-50): Indicates which beam information (TCI state) is associated with the actual resource for the semi-persistent CSI-RS resources specified above. The corresponding TCI state information is associated with the information configured in ltm-TCI-Info within each candidate cell's configuration. Refer to ASN.1 for LTM-TCI-Info-r18 below.

[0246]

[0247] FIG. 1h is a diagram illustrating the overall terminal operation for supporting continuous LTM operation based on semi-persistent CSI-RS resource measurement reporting according to one embodiment of the present disclosure.

[0248] In step 1h-05, the connected terminal can receive configuration information from surrounding cells and LTM-related settings that are applied after L1 / L2-based movement is instructed via an RRC reset message from the serving cell. For detailed configuration methods and content, refer to the contents of Figure 1f. In particular, the present disclosure features measurement and reporting of semi-persistent CSI-RS resources, and includes detailed operations and related settings below.

[0249] In step 1h-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 storing a delta-configured setting based on the reference cell as a complete configuration by referring to the reference cell settings) in a separate buffer and list. Alternatively, the terminal may not decode the received settings based on the reference cell to store and manage the settings that are actually applied, but instead store and manage the received RRC settings as they are in the buffer. As described in Figure 1f, if the reference cell settings are omitted when received, the terminal recognizes that there is no reference cell setting information and determines the setting information for the received LTM target candidate cells as complete setting information and stores it. In particular, in the present disclosure, LTM-related settings are provided in that step, and specifically, they may include candidate cell settings for LTM, settings for L1 resources requiring measurement, and reporting settings. The terminal can decode the L1 resource settings and reporting settings, store them in the terminal buffer, and manage them.

[0250] In step 1h-15, the terminal receives a Semi-persistent CSI-RS resource activation MAC CE from the base station for measuring Semi-persistent CSI-RS resources. Based on the resources and beam information associated with the resources indicated in the MAC CE, the terminal performs the measurement of the corresponding Semi-persistent CSI-RS resources and can report the measurement result value to the base station according to the LTM measurement reporting setting associated with the resources. Refer to the detailed parameter description of the MAC CE in Fig. 1h. Here, if the terminal does not receive a separate deactivation instruction for the Semi-persistent CSI-RS resource measurement for which it was instructed to activate from the source cell, the terminal can continue to perform measurement and reporting for the resources.

[0251] In step 1h-20, the terminal receives a MAC CE with a TCI state instruction for an LTM candidate cell from the base station and can perform downlink synchronization with the candidate cell according to the TCI state instruction. The terminal can use the beam corresponding to the received TCI state.

[0252] In step 1h-25, the terminal may receive an LTM cell change MAC CE from the base station instructing a cell change to a specific LTM candidate cell.

[0253] According to the information indicated within the relevant MAC CE, the terminal may perform a cell change in step 1h-30. The relevant MAC CE may include TA information of the target cell where the terminal performed the RACH-less cell change, or settings related to random access.

[0254] As previously explained, if a cell change of step 1h-35 is performed without receiving a separate deactivation instruction for a Semi-persistent CSI-RS resource measurement that was instructed to be activated from the source cell, one of the following actions may be performed as an action regarding how to operate after the cell change for the Semi-persistent CSI-RS resource that was instructed to be activated from the previous source cell.

[0255] 1. 1. Method 1: A method for a terminal to automatically stop measuring and reporting on semi-persistent CSI-RS resources instructed to be activated in the previous source cell without separate instructions after a cell change.

[0256] (UE stops to measure the activated semi-persistent CSI-RS resources after cell switch)

[0257] - This is characterized by the fact that semi-persistent CSI-RS resources activated in the previous source cell are invalid based on the operation in which the cell changes during continuous LTM operation.

[0258] - The terminal needs to release the Semi-persistent CSI-RS resources activated for this purpose after a cell change.

[0259] - If you want to enable the Semi-persistent CSI-RS resource in the target cell, instruct the resource to be enabled in a separate Semi-persistent CSI-RS resource enable / disable MAC CE after changing cells.

[0260] - To do this, the source cell and each LTM candidate cell must exchange information that the corresponding resource has been deactivated.

[0261] After the terminal changes cells, signaling is added (to the F1 / Xn message) to transmit an indicator to all LTM candidate cells that a successful LTM cell change has been completed. This is to allow the target cell to transmit the enable / disable status of semi-persistent CSI-RS resources to candidate cells and to transmit the new enable / disable status of those resources back to the terminal.

[0262] That is, the target cell can request the enable / disable status from the LTM candidate cell to which the semi-persistent CSI-RS resource belongs, and receive the enable / disable status from that candidate cell. To this end, signaling related to the request and response for the enable / disable status of the semi-persistent CSI-RS resource may be added via F1 / Xn messages.

[0263] (The success of LTM cell switch indication is provided to all candidate cells in order that candidate cell could provide the state of SP CSI-RS resources again after cell switch. Some new indication could be added in F1 / Xn message.)

[0264] - Alternatively, transmit a MAC CE that immediately reactivates the Semi-persistent CSI-RS resource that was instructed to be activated in the previous cell immediately after a cell change occurs in the target cell.

[0265] 2. Method 2: A method for a terminal to automatically continue measuring and reporting on semi-persistent CSI-RS resources instructed to be activated in the previous source cell without separate instructions after a cell change.

[0266] (UE continues to measure the activated semi-persistent CSI-RS resources after cell switch)

[0267] - This is a valid method because the source cell has already received the enable / disable status of the Semi-persistent CSI-RS resource from the LTM candidate cell to which the resource is being delivered, and this means that unless a separate request is made from the source cell or the target cell, the LTM candidate cell will continue to transmit the resource according to the assigned settings.

[0268] - It is characterized by the fact that a semi-persistent CSI-RS resource, which was instructed to be activated in the previous source cell, remains valid in successive LTM operations in the absence of a separate deactivation instruction.

[0269] In other words, there is no need to share the state of semi-persistent CSI-RS resources after a cell change between the source cell and LTM candidate cells, and the terminal only needs to measure the resources according to explicit MAC CE instructions.

[0270] To achieve this, it is necessary for the Semi-persistent CSI-RS resource measurement information, in accordance with the instructions of the Semi-persistent CSI-RS resource activation MAC CE directed by the source cell, to be maintained at the terminal without being released even after a cell change.

[0271] Alternatively, the Semi-persistent CSI-RS resource measurement information may be configured as RRC so that it is not released from the terminal even after a cell change, but is retained only in specific LTM candidate cells. For example, it may be configured to be retained within cells in an Intra-CU or only within cells in the same DU. Additionally, instead of the above configuration, the operation may be defined to be retained within cells in an Intra-CU or only within cells in the same DU.

[0272] 3. Method 3: A method in which, after a cell change, the terminal automatically continues to measure and report resources for the target cell among the semi-persistent CSI-RS resources instructed to be activated in the previous source cell, while stopping the measurement and reporting of resources for LTM candidate cells other than the target cell, without separate instructions.

[0273] (UE stop to measure the activated semi-persistent CSI-RS resources of the candidate cells (ie other than target cell) after cell switch. UE continues to measure the activated semi-persistent CSI-RS resources of the target cell after cell switch)

[0274] - This is characterized by handling semi-persistent CSI-RS resources transmitted from the target cell and other non-target LTM candidate cells differently among the LTM candidate cells.

[0275] - Alternatively, among the semi-persistent CSI-RS resources instructed to be activated in the previous source cell in a manner contrary to this method, the semi-persistent CSI-RS resources for LTM candidate cells other than the target cell may continue to perform measurements and reporting, while measurements and reporting for resources for LTM candidate cells other than the target cell may be discontinued.

[0276] In step 1h-40, if the terminal receives a MAC CE (Semi-persistent CSI-RS resource enable / disable MAC CE) from the target cell after the cell change that instructs deactivation for a specific Semi-persistent CSI-RS resource or a set of Semi-persistent CSI-RS resources, it stops L1 measurement for the instructed Semi-persistent CSI-RS resource and set of Semi-persistent CSI-RS resources.

[0277] FIG. 1i is a drawing illustrating base station operation according to one embodiment of the present disclosure.

[0278] In step 1i-05, the base station receives L3 measurement reports from the terminal and, based on the terminal's measurements regarding surrounding frequencies and cells, can determine whether the terminal requires a handover and which cells are handover candidate cells.

[0279] In step 1i-10, the base station may request configuration information for L1 / L2-based handover from surrounding cells and receive responses from those cells. In step 1i-10, the base station transmits configuration information for the current source cell and reference cell configuration information together to the surrounding cells, and may receive RRC configuration information from surrounding cells and LTM candidate cells, where delta configuration is applied based on the reference cell configuration information. Additionally, in step 1i-10, inter-node coordination for L1 measurement resources and reporting settings proposed in the present invention may be performed. The procedure described in detail in Fig. 1f is included in this step, and in particular, includes determining L1 measurement resources and reporting settings within intra-CU and inter-CU. Furthermore, configuration information for the semi-persistent CSI-RS resources of the present disclosure and request and response information regarding the activation / deactivation status of said resources may be exchanged. Although omitted in Fig. 1i, prior to this step, settings related to L3 measurement settings and basic RRC settings are provided.

[0280] In step 1i-15, an RRC configuration message generated including the surrounding cell configuration information and L1 measurement resource / reporting settings received in step 1i-10 can be transmitted to the terminal in a connected state. That is, configuration information from the surrounding cell that is applied after L1 / L2-based movement is instructed via the RRC reset message from the serving cell can be transmitted. Additionally, in step 1i-15, the serving cell can instruct the terminal to enable a specific Semi-persistent CSI-RS resource based on the activation / deactivation status of the Semi-persistent CSI-RS resource received from the surrounding LTM candidate cell by transmitting a Semi-persistent CSI-RS resource activation / deactivation MAC CE. Detailed configuration methods and contents are described in detail in Figure 1f.

[0281] Subsequently, in step 1i-20, the base station may instruct L1 measurement reports via RRC or L1 / L2 signaling in various ways according to the L1 measurements and reports it wishes to configure and trigger. Refer to the foregoing for details on the method. In step 1i-20, reports regarding L1 and L3 measurement values ​​are received from the terminal, and in particular, L1 measurement reports can be received via UCI and MAC CE. The L1 measurement report may be a measurement report associated with the semi-persistent CSI-RS resource that has been instructed to be activated.

[0282] In steps 1i-25, the base station (source cell) may transmit an LTM cell change MAC CE to the terminal, instructing the terminal to change cells to a specific LTM candidate LTM cell based on L1 measurement information received from the terminal. In particular, in steps 1i-25, the operation between the base station, the source cell, and the LTM candidate cells varies depending on how to handle the Semi-persistent CSI-RS resources that were active in the previous source cell. This description corresponds to the description in FIG. 1h.

[0283] Subsequently, upon receiving a handover completion message from the target cell in step 1i-30, it is confirmed that the LTM operation has been successfully completed. Accordingly, in step 1i-35, the previous source cell may be notified of the handover completion and a request may be made to release the terminal context. Additionally, if a handover failure report message containing information that the handover failed is received, a message indicating that the terminal attempted to reconnect to the cell after the handover failure may be received. The handover failure report message may be a UEInformationResponse or another uplink RRC message. It may also be reported via a new MAC CE or uplink control signal (UCI; uplink control information). The information included in the above handover failure report message may include the following information. Of course, it is not limited to the examples below.

[0284] - An indicator that the handover failed due to an LTM failure

[0285] - Target cell information where LTM attempt failed: LTM cell configuration index or actual cell index (PCI; Physical Cell Index) information

[0286] The source base station can know that the LTM attempt failed and fell back to the cell through the handover failure message report.

[0287] In particular, after changing to a target cell, a measurement result for a semi-persistent CSI-RS resource can be received from a terminal according to the method for processing semi-persistent CSI-RS resources after a cell change of the present disclosure. Alternatively, a semi-persistent CSI-RS resource activation / deactivation MAC CE can be additionally transmitted to the terminal to indicate the status of the semi-persistent CSI-RS resource and subsequent operation can be performed.

[0288] FIG. 1j is a block diagram illustrating the internal structure of a terminal to which the present invention is applied.

[0289] Referring to Fig. 1j, the terminal includes an RF (Radio Frequency) processing unit (1j-10), a baseband processing unit (1j-20), a storage unit (1j-30), and a control unit (1j-40).

[0290] According to one embodiment of the present disclosure, the RF processing unit (1j-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 (1j-10) can up-convert a baseband signal provided by the baseband processing unit (1j-20) into an RF band signal and transmit it through an antenna, and down-convert an RF band signal received through an antenna into a baseband signal. For example, the RF processing unit (1j-10) may include a transmission filter, a reception filter, an amplifier, a mixer, an oscillator, a DAC (digital to analog converter), an ADC (analog to digital converter), etc. Although only one antenna is shown in FIG. 1j, the terminal may be equipped with a plurality of antennas. In addition, the RF processing unit (1j-10) may include a plurality of RF chains. Furthermore, the RF processing unit (1j-10) may perform beamforming. For beamforming, the RF processing unit (1j-10) can adjust the phase and magnitude of each of the signals transmitted and received through multiple antennas or antenna elements. Additionally, the RF processing unit can perform MIMO and can receive multiple layers when performing MIMO operation.

[0291] According to one embodiment of the present disclosure, the baseband processing unit (1j-20) can perform a conversion function between a baseband signal and a bit sequence according to the physical layer specifications of the system. For example, when transmitting data, the baseband processing unit (1j-20) can generate complex symbols by encoding and modulating the transmitted bit sequence. Additionally, when receiving data, the baseband processing unit (1j-20) restores the received bit sequence by demodulating and decoding the baseband signal provided by the RF processing unit (1j-10). For example, in the case of following the orthogonal frequency division multiplexing (OFDM) method, when transmitting data, the baseband processing unit (1j-20) can generate complex symbols by encoding and modulating the transmitted bit sequence, map the complex symbols to subcarriers, and then construct OFDM symbols through inverse fast Fourier transform (IFFT) operations and cyclic prefix (CP) insertion. Additionally, upon receiving data, the baseband processing unit (1j-20) can divide the baseband signal provided by the RF processing unit (1j-10) into OFDM symbol units, restore the signals mapped to subcarriers through a fast Fourier transform (FFT) operation, and then restore the received bit sequence through demodulation and decoding.

[0292] The baseband processing unit (1j-20) and the RF processing unit (1j-10) transmit and receive signals as described above. Accordingly, the baseband processing unit (1j-20) and the RF processing unit (1j-10) may be referred to as a transmitting unit, a receiving unit, a transmitting and receiving unit, or a communication unit. Furthermore, at least one of the baseband processing unit (1j-20) and the RF processing unit (1j-10) may include a plurality of communication modules to support a plurality of different wireless access technologies. Additionally, at least one of the baseband processing unit (1j-20) and the RF processing unit (1j-10) may include different communication modules to process signals of different frequency bands. For example, different wireless access technologies may include wireless LAN (e.g., IEEE 802.11), cellular network (e.g., LTE), etc. In addition, different frequency bands may include super high frequency (SHF) bands (e.g., 2 NRHz, NRHz) and millimeter wave (e.g., 60 GHz) bands.

[0293] According to one embodiment of the present disclosure, the storage unit (1j-30) stores data such as a basic program, an application program, and setting information for the operation of the terminal. In particular, the storage unit (1j-30) may store information related to a second connection node that performs wireless communication using a second wireless connection technology. Additionally, the storage unit (1j-30) may provide the stored data upon a request from the control unit (1j-40).

[0294] According to one embodiment of the present disclosure, a control unit (1j-40) can control the overall operations of the terminal. For example, the control unit (1j-40) can transmit and receive signals through a baseband processing unit (1j-20) and an RF processing unit (1j-10). Additionally, the control unit (1j-40) writes and reads data to and from a storage unit (1j-40). To this end, the control unit (1j-40) may include at least one processor. For example, the control unit (1j-40) may include a communication processor (CP) that performs control for communication and an application processor (AP) that controls upper layers such as applications.

[0295] FIG. 1k is a block diagram showing the configuration of a base station according to one embodiment of the present disclosure.

[0296] As illustrated in FIG. 1k, the base station may be configured to include an RF processing unit (1k-10), a baseband processing unit (1k-20), a backhaul communication unit (1k-30), a storage unit (1k-40), and a control unit (1k-50).

[0297] The RF processing unit (1k-10) performs functions for transmitting and receiving signals through a wireless channel, such as signal band conversion and amplification. That is, the RF processing unit (1k-10) upconverts a baseband signal provided by the baseband processing unit (1k-20) into an RF band signal, transmits it through an antenna, and downconverts the RF band signal received through the antenna into a baseband signal. For example, the RF processing unit (1k-10) may include a transmit filter, a receive filter, an amplifier, a mixer, an oscillator, a DAC, an ADC, etc. Although only one antenna is shown in FIG. 1k, the first connection node may be equipped with multiple antennas. Additionally, the RF processing unit (1k-10) may include multiple RF chains. Furthermore, the RF processing unit (1k-10) may perform beamforming. For beamforming, the RF processing unit (1k-10) may adjust the phase and magnitude of each of the signals transmitted and received through multiple antennas or antenna elements. The RF processing unit can perform down-to-down MIMO operation by transmitting one or more layers.

[0298] The baseband processing unit (1k-20) can perform a conversion function between a baseband signal and a bit sequence according to the physical layer specifications of the first wireless access technology. For example, when transmitting data, the baseband processing unit (1k-20) can generate complex symbols by encoding and modulating the transmitted bit sequence. Additionally, when receiving data, the baseband processing unit (1k-20) can restore the received bit sequence by demodulating and decoding the baseband signal provided by the RF processing unit (1k-10). For example, in the case of following the OFDM method, when transmitting data, the baseband processing unit (1k-20) can generate complex symbols by encoding and modulating the transmitted bit sequence, map the complex symbols to subcarriers, and then construct OFDM symbols through IFFT operation and CP insertion. Additionally, upon receiving data, the baseband processing unit (1k-20) can divide the baseband signal provided by the RF processing unit (1k-10) into OFDM symbol units, restore the signals mapped to subcarriers through FFT operations, and then restore the received bit sequence through demodulation and decoding. The baseband processing unit (1k-20) and the RF processing unit (1k-10) can transmit and receive signals as described above. Accordingly, the baseband processing unit (1k-20) and the RF processing unit (1k-10) may be referred to as a transmitting unit, a receiving unit, a transmitting and receiving unit, a communication unit, or a wireless communication unit.

[0299] The backhaul communication unit (1k-30) can provide an interface for communicating with other nodes within the network. That is, the backhaul communication unit (1k-30) can convert 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 can convert a physical signal received from another node into a bit sequence.

[0300] The storage unit (1k-40) can store data such as basic programs, application programs, and configuration information for the operation of the main station. In particular, the storage unit (1k-40) can store information regarding bearers assigned to connected terminals, measurement results reported from connected terminals, etc. Additionally, the storage unit (1k-40) can store information that serves as a criterion for determining whether to provide or disconnect multiple connections to the terminals. Furthermore, the storage unit (1k-40) can provide the stored data upon a request from the control unit (1k-50).

[0301] According to one embodiment of the present disclosure, the control unit (1k-50) can control the overall operations of the main station. For example, the control unit (1k-50) can transmit and receive signals through the baseband processing unit (1k-20) and the RF processing unit (1k-10) or through the backhaul communication unit (1k-30). Additionally, the control unit (1k-50) writes and reads data to and from the storage unit (1k-40). To this end, the control unit (1k-50) may include at least one processor.

[0302] 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.

[0303] 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.

[0304] Such programs (software modules, software) may be stored in random access memory, non-volatile memory including flash memory, ROM (Read Only Memory), Electrically Erasable Programmable Read Only Memory (EEPROM), magnetic disc storage devices, Compact Disc-ROM (CD-ROM), Digital Versatile Discs (DVDs), or other forms of optical storage devices, magnetic cassettes. Alternatively, they may be stored in memory composed of some or all of these. Additionally, each constituent memory may include multiple units.

[0305] 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.

[0306] 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.

[0307] 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 of a wireless communication system, wherein the method comprises: A step of receiving configuration information for an LTM including information regarding multiple semi-persistent CSI-RS resources for at least one LTM candidate cell; A step of storing configuration information for the above LTM; A step of receiving a MAC CE that activates at least one CSI-RS resource set corresponding to at least one LTM candidate cell among the CSI-RS resource sets including the plurality of semi-persistent CSI-RS resources; A step of measuring the channel state using at least one activated CSI-RS resource set; A step of reporting information regarding the above-mentioned measured channel status; A step of receiving a MAC CE indicating a TCI state for at least one LTM candidate cell; A step of receiving a MAC CE instructing the execution of LTM cell switching; A step of performing cell switching to a target cell based on a MAC CE instructing the performance of the above LTM cell switching; and A method comprising the step of deactivating some of the at least one set of activated CSI-RS resources after performing the above LTM cell switching.

2. In Paragraph 1, The step of deactivating some of the at least one set of activated CSI-RS resources after performing the above LTM cell switching is A method of deactivating at least one activated CSI-RS resource set corresponding to at least one LTM candidate cell, excluding the target cell among at least one activated CSI-RS resource set.

3. In Paragraph 1, The configuration information for the above LTM is, A method comprising at least one of information indicating the type of CSI-RS, information on a CSI-RS resource set, identification information of a CSI-RS included in the CSI-RS resource set, and identification information of at least one LTM candidate cell corresponding to the CSI-RS resource.

4. In Paragraph 3, A method in which at least one of information indicating the type of the CSI-RS, information on the CSI-RS resource set, identification information of the CSI-RS included in the CSI-RS resource set, and identification information of at least one LTM candidate cell corresponding to the CSI-RS resource is included in an RRC message containing LTM-CSI-ResourceConfig.

5. In Paragraph 1, A MAC CE that activates the at least one CSI-RS resource set corresponding to the at least one LTM candidate cell, Information indicating the activation and deactivation of at least one set of CSI-RS resources corresponding to the above at least one LTM candidate cell, Identification information indicating a set of at least one CSI-RS resources corresponding to at least one LTM candidate cell, and A method comprising TCI state information corresponding to a set of at least one CSI-RS resources corresponding to at least one LTM candidate cell.

6. In a method performed by a base station of a wireless communication system, the method comprises: A step of transmitting configuration information for an LTM including information regarding multiple semi-persistent CSI-RS resources for at least one LTM candidate cell; A step of transmitting a MAC CE that activates at least one CSI-RS resource set corresponding to at least one LTM candidate cell among the CSI-RS resource sets including the plurality of semi-persistent CSI-RS resources; A step of receiving information regarding the channel state measured using at least one activated CSI-RS resource set; The step of transmitting a MAC CE indicating a TCI state for at least one LTM candidate cell; and The method includes the step of transmitting a MAC CE instructing the performance of LTM cell switching to a target cell, and A method in which some of the at least one activated CSI-RS resource set is deactivated after the above LTM cell switching is performed.

7. In Paragraph 6, Some sets of CSI-RS resources that are disabled after the above LTM cell switching is, A method comprising at least one set of activated CSI-RS resources corresponding to at least one LTM candidate cell, excluding the target cell.

8. In Paragraph 6, The configuration information for the above LTM is, A method comprising at least one of information indicating the type of CSI-RS, information on a CSI-RS resource set, identification information of a CSI-RS included in the CSI-RS resource set, and identification information of at least one LTM candidate cell corresponding to the CSI-RS resource.

9. In Paragraph 8, A method in which at least one of information indicating the type of the CSI-RS, information on the CSI-RS resource set, identification information of the CSI-RS included in the CSI-RS resource set, and identification information of at least one LTM candidate cell corresponding to the CSI-RS resource is included in an RRC message containing LTM-CSI-ResourceConfig.

10. In Paragraph 6, A MAC CE that activates the at least one CSI-RS resource set corresponding to the at least one LTM candidate cell, Information indicating the activation and deactivation of at least one set of CSI-RS resources corresponding to the above at least one LTM candidate cell, Identification information indicating a set of at least one CSI-RS resources corresponding to at least one LTM candidate cell, and A method comprising TCI state information corresponding to a set of at least one CSI-RS resources corresponding to at least one LTM candidate cell.

11. In a terminal of a wireless communication system, the terminal, At least one transceiver; and It includes at least one processor coupled to the above-mentioned at least one transceiver, and the at least one processor, Receive configuration information for an LTM including information regarding multiple semi-persistent CSI-RS resources for at least one LTM candidate cell, and Stores configuration information for the above LTM, and Receiving a MAC CE that activates at least one CSI-RS resource set corresponding to at least one LTM candidate cell among the CSI-RS resource sets including the plurality of semi-persistent CSI-RS resources, and Measure the channel state using at least one set of activated CSI-RS resources, and Report information regarding the above-mentioned measured channel status, and Receiving a MAC CE indicating the TCI state for at least one LTM candidate cell, and Received a MAC CE instructing the execution of LTM cell switching, Cell switching to a target cell is performed based on the MAC CE instructing the above LTM cell switching to be performed, and A terminal that disables some of the at least one set of CSI-RS resources activated after performing the above LTM cell switching.

12. In Paragraph 11, The above-mentioned at least one processor is, A terminal that disables at least one activated CSI-RS resource set corresponding to at least one LTM candidate cell, excluding the target cell among the at least one activated CSI-RS resource set.

13. In Paragraph 11, A MAC CE that activates the at least one CSI-RS resource set corresponding to the at least one LTM candidate cell, Information indicating the activation and deactivation of at least one set of CSI-RS resources corresponding to the above at least one LTM candidate cell, Identification information indicating a set of at least one CSI-RS resources corresponding to at least one LTM candidate cell, and A terminal comprising TCI state information corresponding to a set of at least one CSI-RS resources corresponding to at least one LTM candidate cell.

14. In a base station of a wireless communication system, the base station, At least one transceiver, and It includes at least one processor coupled to the above-mentioned at least one transceiver, and the at least one processor, Transmitting configuration information for an LTM including information regarding multiple semi-persistent CSI-RS resources for at least one LTM candidate cell, and Transmitting a MAC CE that activates at least one CSI-RS resource set corresponding to at least one LTM candidate cell among the CSI-RS resource sets including the plurality of semi-persistent CSI-RS resources, and Receive information regarding the channel state measured using at least one activated CSI-RS resource set, and Transmitting a MAC CE indicating the TCI state for at least one LTM candidate cell, and Transmit a MAC CE instructing the execution of LTM cell switching to the target cell, and A base station in which some of the CSI-RS resource sets among the at least one activated CSI-RS resource set are deactivated after the above LTM cell switching is performed.

15. In Paragraph 14, Some sets of CSI-RS resources that are disabled after the above LTM cell switching is, A base station comprising at least one set of activated CSI-RS resources corresponding to at least one LTM candidate cell, excluding the target cell.

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