Method and apparatus for optimizing conditional pscell addition and change in wireless communication system

Abstract

The present disclosure relates to a 5th-Generation (5G) or 6th-Generation (6G) communication system for supporting higher data rates. A method for optimizing conditional primary-secondary cell (PSCell) addition / change (CPAC) in a communication system and an apparatus capable of performing the same are provided. The methods include methods for reporting successfully completed (C) PAC related information and CPAC failure related information.

Description

Technical Field

[0001] The present disclosure relates to the operation of user equipment and base stations in a mobile communication system. More specifically, the present disclosure relates to a method for optimizing conditional primary and secondary cell (PSCell) addition and change (CPAC) in a communication system and an apparatus capable of performing the method. Background Art

[0002] The fifth generation (5G) mobile communication technology defines a wide frequency band so that high transmission rates and new services are possible, and can be realized not only in the "6 gigahertz (GHz) below" frequency band such as 3.5 GHz, but also in the "6 GHz above" frequency band called millimeter wave (mmWave) including 28 GHz and 39 GHz. In addition, the implementation of the sixth generation (6G) mobile communication technology (called super 5G system) in the terahertz frequency band (for example, the 95 GHz to 3 terahertz (THz) frequency band) has been considered in order to achieve a transmission rate fifty times faster than that of 5G mobile communication technology and an ultra-low latency one-tenth of that of 5G.

[0003] In the initial stage of 5G mobile communication technology, in order to support services and meet performance requirements related to enhanced mobile broadband (eMBB), ultra-reliable and low-latency communication (URLLC), and massive machine type communication (mMTC), there has been ongoing standardization on the following: beamforming and massive multiple-input multiple-output (MIMO) for mitigating radio wave path loss and increasing radio wave transmission distance in mmWave, parameter sets for dynamic operation of efficient utilization of mmWave resources and time slot formats (e.g., operating multiple subcarrier spacings), initial access technology for supporting multi-beam transmission and broadband, definition and operation of bandwidth parts (BWPs), new channel coding methods such as low-density parity-check (LDPC) codes for large-capacity data transmission and polar codes for highly reliable transmission of control information, L2 preprocessing, and network slicing for providing dedicated networks dedicated to specific services.

[0004] Currently, in view of the services supported by the 5G mobile communication technology, discussions are ongoing on the improvement and performance enhancement of the initial 5G mobile communication technology, and there is already physical layer standardization on technologies such as V2X (Vehicle to Everything) for assisting driving decisions made by an autonomous vehicle based on information about the position and status of the vehicle transmitted by the vehicle and for enhancing user convenience, NR-U (New Radio Unlicensed) for system operation intended to comply with various regulatory-related requirements in unlicensed bands, NR UE power saving, non-terrestrial network (NTN) (which is UE-satellite direct communication for providing coverage in areas where communication with terrestrial networks is unavailable), and positioning.

[0005] In addition, there is ongoing standardization of air interface architecture / protocol aspects of technologies such as Industrial Internet of Things (IIoT) for supporting new services through interworking and convergence with other industries, IAB (Integrated Access and Backhaul) for providing nodes for network service area extension by supporting wireless backhaul links and access links in an integrated manner, mobility enhancements including conditional handover and DAPS (Dual Active Protocol Stack) handover, and two-step random access (two-step RACH for NR) for simplifying the random access procedure. Standardization is also ongoing on the 5G baseline architecture (e.g., service-based architecture or service-based interface) for combining network function virtualization (NFV) and software defined network (SDN) technologies, and system architecture / services for mobile edge computing (MEC) for receiving services based on UE location.

[0006] As 5G mobile communication systems are commercialized, the number of connected devices, which has been growing exponentially, will be connected to the communication network, and it is therefore expected that enhanced functions and performance of the 5G mobile communication systems and the integrated operation of connected devices will be necessary. To this end, new research related to extended reality (XR) is arranged for effectively supporting augmented reality (AR), virtual reality (VR), etc. (XR = AR + VR + mixed reality (MR)), 5G performance improvement and complexity reduction by utilizing artificial intelligence (AI) and machine learning (ML), AI service support, metaverse service support, and drone communication.

[0007] Furthermore, such developments in 5G mobile communication systems will serve as a foundation not only for the development of new waveforms that provide terahertz band coverage for 6G mobile communication technology, multi-antenna transmission technologies such as full-dimensional MIMO (FD-MIMO), array antennas, and massive antennas, metamaterial-based lenses and antennas for improving terahertz band signal coverage, high-dimensional spatial multiplexing technologies using OAM (orbital angular momentum), and RIS (reconfigurable smart surfaces), but also for the development of full-duplex technologies that increase the frequency efficiency of 6G mobile communication technology and improve system networks, AI-based communication technologies for achieving system optimization by leveraging satellites and AI (artificial intelligence) from the design stage and internalizing end-to-end AI support functions, and next-generation distributed computing technologies for achieving services at a complexity level that exceeds the operational capability limits of UEs by utilizing ultra-high-performance communication and computing resources.

[0008] Recently, methods for triggering conditional PSCell addition or PSCell change operations in 3rd Generation Partnership Project (3GPP) communication technology are being studied. For example, if a configured condition is met, a PSCell addition (PA) or PSCell change (PC) operation is performed. These are respectively referred to as conditional PSCell addition (CPA) and conditional PSCell change (CPC), and both of them are collectively referred to as conditional PSCell addition and change (CPAC).

[0009] The above information is presented as background information only to assist with an understanding of the present disclosure. No determination has been made, and no assertion is made, as to whether any of the above might be applicable as prior art with respect to the present disclosure. Summary of the invention

[0010] Technical issues

[0011] Aspects of the present disclosure are to address at least the above-mentioned problems and / or disadvantages and to provide at least the advantages described below.

[0012]

[0013] Accordingly, one aspect of the present disclosure is to provide improved processes for the above-mentioned Conditional PSCell Addition (CPA), Conditional PSCell Change (CPC), and Conditional PSCell Addition and Change (CPAC).

[0013] Another aspect of the present disclosure is to provide a method and apparatus for reporting a successful CAP or CPC when the CPA or CPC is successfully performed.

[0014] Additional aspects will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the presented embodiments.

[0015] Solution to the problem

[0016] According to one aspect of the present disclosure, a method performed by a user equipment (UE) supporting dual connectivity in a wireless communication system is provided. The method includes: receiving a radio resource control (RRC) message from a first base station associated with a primary cell group (MCG), the RRC message including first configuration information about a primary secondary cell (PSCell) change associated with a secondary cell group (SCG) and second configuration information about a successful PSCell change report (SPR), performing a PSCell change based on the first configuration information, identifying whether the PSCell change satisfies at least one condition for triggering an SPR based on the second configuration information, and sending the SPR to the first base station if at least one condition for triggering the SPR is satisfied.

[0017] According to another aspect of the present disclosure, a method performed by a first base station associated with a primary cell group (MCG) in a wireless communication system is provided. The method includes: obtaining a radio resource control (RRC) message, the RRC message including first configuration information about a primary secondary cell (PSCell) change associated with a secondary cell group (SGC) and second configuration information about a successful PSCell change report (SPR), sending the RRC message including the first configuration information and the second configuration information to a user equipment (UE), and receiving the SPR from the UE if at least one condition for triggering the SPR is met.

[0018] According to another aspect of the present disclosure, a user equipment (UE) supporting dual connectivity in a wireless communication system is provided. The UE includes a transceiver configured to send and receive signals, and at least one processor, the at least one processor is coupled to the transceiver and is configured to receive a radio resource control (RRC) message from a first base station associated with a primary cell group (MCG), the RRC message including first configuration information about a primary secondary cell (PSCell) change associated with a secondary cell group (SCG) and second configuration information about a successful PSCell change report (SPR), perform a PSCell change based on the first configuration information, identify whether the PSCell change satisfies at least one condition for triggering an SPR based on the second configuration information, and send the SPR to the first base station if at least one condition for triggering the SPR is satisfied.

[0019] According to another aspect of the present disclosure, a first base station associated with a primary cell group (MCG) in a wireless communication system is provided. The first base station includes a transceiver configured to send and receive signals, and at least one processor coupled to the transceiver, and the at least one processor is configured to obtain a radio resource control (RRC) message, the RRC message including first configuration information about a primary secondary cell (PSCell) change associated with a secondary cell group (SGC) and second configuration information about a successful PSCell change report (SPR), send the RRC message including the first configuration information and the second configuration information to a user equipment (UE), and receive the SPR from the UE if at least one condition for triggering the SPR is met.

[0020] Advantageous Effects of the Invention

[0021] According to the present disclosure, user equipment of a wireless communication system may report CPAC-related information.

[0022] More specifically, the user equipment can report the successfully completed CPAC related information and the CPAC failure related information to the base station in the wireless communication system, so that the base station can identify the information about the successfully completed CPAC. In addition, the base station can use the completed CPAC related information and the CPAC failure related information to determine the optimal parameter configuration value for wireless communication with the user equipment.

[0023] Other aspects, advantages, and salient features of the present disclosure will become apparent to those skilled in the art from the following detailed description which, in conjunction with the accompanying drawings, discloses various embodiments of the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The above and other aspects, features and advantages of certain embodiments of the present disclosure will become more apparent through the following description in conjunction with the accompanying drawings, in which:

[0025] FIG. 1a is a schematic diagram showing a structure of a next generation mobile communication system according to an embodiment of the present disclosure;

[0026] FIG1 b is a flow chart illustrating a (conditional) PSCell addition and change process according to an embodiment of the present disclosure;

[0027] FIG. 1c is a flow chart illustrating a process of reporting information related to successfully completed (conditional) PSCell additions and changes according to an embodiment of the present disclosure;

[0028] FIG1d is a flow chart illustrating user equipment operations for reporting information related to successfully completed (conditional) PSCell additions and changes according to an embodiment of the present disclosure;

[0029] FIG. 1e is a flow chart illustrating base station operations for reporting information related to successfully completed (conditional) PSCell additions and changes according to an embodiment of the present disclosure;

[0030] FIG. 1f is a flow chart illustrating a process of reporting information related to successfully completed (conditional) PSCell additions and changes in a dual connectivity environment according to an embodiment of the present disclosure;

[0031] FIG1g is a flowchart showing a process of reporting SCGFailureInformation (SCG failure information) according to an embodiment of the present disclosure;

[0032] 1h is a flow chart illustrating a process of reporting information related to failure of conditional PSCell addition and change according to an embodiment of the present disclosure;

[0033] FIG. 1i is a flow chart illustrating a user equipment operation of reporting information related to a failure of a conditional PSCell addition and change according to an embodiment of the present disclosure;

[0034] FIG1j is a flow chart illustrating base station operations for reporting information related to failure of conditional PSCell addition and change according to an embodiment of the present disclosure;

[0035] FIG. 1k is a block diagram showing an internal structure of a user equipment according to an embodiment of the present disclosure; and

[0036] FIG. 11 is a block diagram showing the structure of a base station according to an embodiment of the present disclosure.

[0037] Throughout the drawings, it should be noted that like reference numbers are used to depict the same or similar elements, features, and structures. DETAILED DESCRIPTION

[0038] The following description with reference to the accompanying drawings is provided to assist in a comprehensive understanding of the various embodiments of the present disclosure as defined by the claims and their equivalents. It includes various specific details to assist in understanding, but these details are considered to be exemplary only. Therefore, it will be appreciated by those of ordinary skill in the art that various changes and modifications may be made to the various embodiments described herein without departing from the scope and spirit of the present disclosure. In addition, for the sake of clarity and conciseness, descriptions of well-known functions and structures may be omitted.

[0039] The terms and words used in the following description and claims are not limited to the bibliographical meanings, but are merely used by the inventor to enable a clear and consistent understanding of the present disclosure. Therefore, it will be apparent to those skilled in the art that the following description of various embodiments of the present disclosure is provided for illustrative purposes only and not for the purpose of limiting the present disclosure as defined by the appended claims and their equivalents.

[0040] It should be understood that the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to "a component surface" includes reference to one or more of such surfaces.

[0041] For the same reason, in the accompanying drawings, some elements may be exaggerated, omitted or schematically shown. In addition, the size of each element does not fully reflect the actual size. In the accompanying drawings, the same or corresponding elements are provided with the same reference numerals.

[0042] By referring to the embodiments described in detail below in conjunction with the accompanying drawings, the advantages and features of the present disclosure and the ways to achieve them will be apparent. However, the present disclosure is not limited to the embodiments set forth below, but can be implemented in various different forms. The following embodiments are provided only to fully disclose the present disclosure and inform those skilled in the art of the scope of the present disclosure, and the present disclosure is limited only by the scope of the attached claims. Throughout the specification, the same or similar reference numerals represent the same or similar elements.

[0043] In this article, it will be understood that each box of the flowchart diagram and the combination of boxes in the flowchart diagram can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device create a device for implementing the function specified in one or more flowchart boxes. These computer program instructions can also be stored in a computer-usable or computer-readable memory, which can instruct the computer or other programmable data processing device to act in a specific way, so that the instructions stored in the computer-usable or computer-readable memory produce an article of instruction device including the function specified in the flowchart box or multiple boxes. The computer program instructions can also be loaded on a computer or other programmable data processing device so that a series of operating steps are performed on the computer or other programmable device to produce a computer-implemented process, so that the instructions executed on the computer or other programmable device provide steps for implementing the functions specified in one or more flowchart boxes.

[0044] In addition, each box of the flowchart diagram may represent a module, fragment or portion of code, which includes one or more executable instructions for implementing the specified logical function. It should also be noted that in some alternative embodiments, the functions marked in the box may not occur in order. For example, two boxes shown in succession can actually be executed substantially simultaneously, or these boxes can sometimes be executed in reverse order, depending on the functions involved.

[0045] As used herein, "unit" refers to a software element or hardware element that performs a predetermined function, such as a field programmable gate array (FPGA) or an application specific integrated circuit (ASIC). However, "unit" does not always have a meaning limited to software or hardware. "Unit" can be constructed to be stored in an addressable storage medium or to execute one or more processors. Therefore, "unit" includes, for example, software elements, object-oriented software elements, class elements or task elements, processes, functions, attributes, procedures, subroutines, program code segments, drivers, firmware, microcodes, circuits, data, databases, data structures, tables, arrays, and parameters. The elements and functions provided by the "unit" can be combined into a smaller number of elements or "units", or divided into a larger number of elements or "units". In addition, elements and "units" can be implemented as one or more central processing units (CPUs) in a reproduction device or a secure multimedia card.

[0046] In the following description of the present disclosure, a detailed description of known functions or configurations incorporated herein will be omitted when it is determined that the description may make the subject matter of the present disclosure unnecessarily unclear. Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings.

[0047] FIG. 1a is a diagram illustrating a structure of a next generation mobile communication system according to an embodiment of the present disclosure.

[0048] Referring to Figure 1a, the radio access network of the next generation mobile communication system (new radio, NR) includes a next generation base station (new radio node B, hereinafter referred to as gNB) 1a-10 and an access and mobility management function (AMF) 1a-05 (new radio core network), as shown in the figure. User equipment (new radio user equipment, hereinafter referred to as NR UE or user equipment) 1a-15 accesses an external network through the gNB 1a-10 and the AMF 1a-05.

[0049] Referring to FIG. 1a, gNB corresponds to an evolved Node B (eNB) in an existing long term evolution (LTE) system. The gNB can be connected to an NR UE through a radio channel and can provide a better service than the existing Node B (1a-20). Since all user services are served through a shared channel in the next generation mobile communication system, it is necessary for the device to perform scheduling by collecting status information such as the buffer status of the UE, the available transmission power status, the channel status, etc., and gNB 1a-10 is used to do so. One gNB generally controls a plurality of cells. In order to achieve high-speed data transmission compared with the existing LTE, it can have an existing maximum bandwidth or more, and can further apply beamforming technology by adopting orthogonal frequency division multiplexing (hereinafter referred to as OFDM) as a radio access technology. In addition, an adaptive modulation and coding (hereinafter referred to as AMC) method for determining a modulation scheme and a channel coding rate according to the channel status of the user equipment is applied.

[0050] AMF 1a-05 performs functions such as mobility support, bearer configuration, quality of service (QoS) configuration, etc. AMF is a device that performs various control functions and mobility management functions of user equipment, and is connected to multiple base stations. In addition, the next generation mobile communication system can interwork with the existing LTE system, and AMF is connected to the mobility management entity (MME) 1a-25 through a network interface. MME is connected to eNB 1a-30, which is an existing base station.

[0051] A user equipment supporting LTE-NR dual connectivity (EN-DC) can send and receive data while maintaining connections with both the eNB and the gNB (1a-35).

[0052] FIG. 1 b is a flow chart illustrating a (conditional) PSCell addition and change process according to an embodiment of the present disclosure.

[0053] 1b , in order to increase the maximum data rate of a user equipment in a mobile communication system such as Long Term Evolution (LTE) or New Radio (NR) , a dual connectivity (DC) technology for simultaneously transmitting and receiving data to and from two base stations may be configured for the user equipment.

[0054] The master node (MN) 1b-10 indicates a base station that provides a primary cell (PCell), and the secondary node (SN) 1b-15 indicates a base station that provides a PSCell. The PCell is a reference cell of a primary cell group (MCG) that provides a physical uplink control channel (PUCCH) and determines mobility, and the PSCell also provides a PUCCH and is a reference cell of a secondary cell group (SCG). The MCG represents a set of service cells provided by the MN, and the SCG represents a set of service cells provided by the SN. Therefore, the PCell and the PSCell must be configured in the MCG and the SCG, respectively.

[0055] Configuration of SCG for user equipment is performed by a PSCell Addition (PA) operation. In addition, the PSCell can be changed, which is performed by a PSCell Change (PC) operation. Rel-17NR has introduced a method for triggering PSCell Addition or PSCell Change operations based on conditions. For example, if the configured conditions are met, a PA or PC operation is performed. These are respectively referred to as Conditional PSCell Addition (CPA) and Conditional PSCell Change (CPC), and both of them are collectively referred to as Conditional PSCell Addition and Change (CPAC).

[0056] In order to configure the (C)PAC, in operation 1b-20, the MN 1b-10 needs to coordinate on configuration with a predetermined SN (source SN and / or target SN) 1b-17 (1b-20). For example, in the case of a (C)PC, coordination with the target SN 1b-17 is required. Coordination indicates an operation of exchanging information for configuring related configuration information together with a request for an operation.

[0057] After completing the coordination, in operation 1b-25, MN 1b-10 sends an RRCReconfiguration message including a ReconfigurationWithSync information element (IE) to the user equipment 1b-05 (1b-25). The ReconfigurationWithSyncSCG IE includes configuration information required to perform PAC. In the case of CPAC, a ConditionalReconfiguration IE is included in the RRCReconfiguration message instead of the ReconfigurationWithSync IE. Up to two conditions can be configured for CPAC, and the conditions are as follows.

[0058] CondEvent A3: Conditional reconfiguration candidate becomes better than the offset of PCell / PSCell

[0059] CondEvent A4: Conditional reconfiguration candidate becomes better than absolute threshold

[0060] CondEvent A5: PCell / PSCell becomes worse than absolute threshold 1, and conditional reconfiguration candidate becomes better than another absolute threshold 2

[0061] If two conditions are configured, the user equipment performs the CPAC operation only when both configured conditions are met.

[0062] When receiving the RRCReconfiguration message including the ReconfigurationWithSyncSCG IE in the case of PAC, and when the configured condition is met in the case of CPAC, the user equipment drives a predetermined timer T304. If the (C)PAC operation is not successfully completed until the timer expires, the user equipment regards it as a (C)PAC failure. If the random access to the SN is successfully completed, the (C)PAC operation is considered to be successfully completed, and the user equipment terminates the timer T304.

[0063] In operation 1b-30, if the (C)PAC operation also requires reconfiguration with the MN 1b-10, a random access operation (1b-30) with the MN 1b-10 may be required.

[0064] In operation 1b-35, upon receiving the RRCReconfiguration message, the user equipment 1b-05 sends an RRCReconfigurationComplete message to the MN 1b-10 (1b-35).

[0065] In operation 1b-40, the user equipment 1b-05 performs a random access operation on a new SN for (C)PAC operation (1b-40).

[0066] FIG. 1 c is a flow chart illustrating a process of reporting information related to successfully completed (conditional) PSCell additions and changes according to an embodiment of the present disclosure.

[0067] Referring to FIG. 1c, an embodiment of the present disclosure proposes a method in which a user equipment stores and reports information about successful completion of a (C)PAC. Even a successfully completed (C)PAC process may need to be improved. To this end, identifying information about a successfully completed (C)PAC by a base station may be useful for finding an optimal parameter configuration value. In this embodiment, the reporting operation will be referred to as a successful (C)PAC report (or SPR).

[0068] In operation 1c-20, the user equipment (UE) 1c-05 reports its own capability information to the master node (MN) 1c-10 (1c-20). The capability information may include an indicator indicating whether the user equipment supports successful conditional PSCell add and change reporting (successful CPAC reporting).

[0069] In order to configure (C)PAC, in operation 1c-25, the MN needs to coordinate configuration with the SN (source SN and / or target SN) 1c-17 (1c-25). At this time, coordination for configuring configuration information related to a successful CPAC report is also required.

[0070] In operation 1c-30, after completing the coordination, MN 1c-10 sends an RRCReconfiguration message including ReconfigurationWithSync IE (including ConditionalReconfiguration IE in the case of CPAC) and OtherConfig IE to the user equipment 1c-05 (1c-30). ReconfigurationWithSync IE includes configuration information necessary for performing PAC. OtherConfig IE includes configuration information required for performing successful CPAC reporting.

[0071] Although storing and reporting information about all successfully completed (C)PAC operations through successful CPAC reporting increases user equipment complexity and signaling overhead, the usefulness may not be greatly improved. It may be more sensible to trigger successful CPAC reporting only for difficult successful (C)PAC operations, rather than always triggering successful CPAC reporting. Therefore, the configuration information of successful CPAC reporting contained in the OtherConfig IE may include information about the conditions that trigger the reporting operation.

[0072] The above conditions may include storing and reporting information related to all successfully completed (C)PACs. In addition, a condition that the timer T304 exceeds a certain threshold may be considered.

[0073] The network can configure a specific threshold for the user equipment. The specific threshold can be configured as a specific ratio of the configured T304 value (e.g., 20%, 40%, 60%, 80%, etc.). If timer T304 is driven during (C)PAC operation, and if a time period corresponding to a specific ratio (e.g., 20%, 40%, 60%, 80%, etc.) or more has passed, the user equipment triggers a successful CPAC report. For example, if the configured T304 value is 1000ms and if the ratio is configured to 80%, the time when the T304 value reaches 800ms is the time to trigger a successful CPAC report. Alternatively, the specific threshold can be configured as an absolute value in ms. In order to determine the specific threshold, the MN may need to coordinate with the new (or source) SN or the target SN.

[0074] In an embodiment of the present disclosure, the newly added SN (or PSCell) 1c-15 determines a specific threshold value in the case of (conditional) PSCell addition and sends it to the MN 1c-10, and the target SN (or target PSCell) 1c-17 determines a specific threshold value in the case of (conditional) PSCell change and sends it to the MN 1c-10. The MN 1c-10 receiving the specific threshold value includes the configuration information in the OtherConfig IE and sends it to the user equipment 1c-05.

[0075] In addition, the following other conditions may also be considered, and if at least one of the following conditions is met, the user device 1c-05 may trigger a successful CPAC report.

[0076] Whether an MCG failure (ie, MN Radio Link Failure (RLF)) occurs during (C)PAC operation.

[0077] When the timer T310 is driven for the PCell during the (C)PAC operation, and if a time period corresponding to a specific ratio (e.g., 20%, 40%, 60%, 80%, etc.) or more has passed. In this case, the specific ratio is determined by the PCell, and the MN 1c-10 includes the specific ratio in the OtherConfig IE and transmits it to the user equipment 1c-05.

[0078] When the timer T312 is driven for the PCell during the (C)PAC operation, and if a period of time corresponding to a specific ratio (e.g., 20%, 40%, 60%, 80%, etc.) or longer has passed. In this case, the specific ratio is determined by the PCell, and the MN 1c-10 includes the specific ratio in the OtherConfig IE and transmits it to the user equipment 1c-05.

[0079] When the timer T310 is driven for the source PSCell during the (C) PC operation, and if a time period corresponding to a specific ratio (e.g., 20%, 40%, 60%, 80%, etc.) or more has passed. In this case, the specific ratio is determined by the source PSCell, and the configuration information is included in the OtherConfig IE via the MN and then transmitted to the user equipment.

[0080] When the timer T312 is driven for the source PSCell during the (C) PC operation, and if a time period corresponding to a specific ratio (e.g., 20%, 40%, 60%, 80%, etc.) or more has passed. In this case, the specific ratio is determined by the source PSCell, and the configuration information is included in the OtherConfig IE via the MN and then transmitted to the user equipment.

[0081] In operation 1c-35, the user equipment 1c-05 performs random access to the newly added PSCell in case of (conditional) PSCell addition, and performs random access to the target PSCell in case of (conditional) PSCell change (1c-35).

[0082] The user equipment 1c-05 determines whether the configured conditions are met based on the configuration information of the successful CPAC report. If the configured conditions are met, a successful CPAC report is triggered.

[0083] At this time, in operation 1c-40, when the CPAC operation is successfully completed, the user device 1c-05 stores the predetermined information related to the CPAC operation (1c-40). The predetermined information is as follows.

[0084] -PCell information, i.e., PCell identifier (ID) (i.e., Cell Global Identity (CGI) or Physical Cell ID (PCI)), cell-level and beam-level PCell measurement results, and whether RLF occurs in (C)PAC

[0085] - Source PSCell information, i.e., source PSCell ID (i.e., CGI or PCI) and cell-level and beam-level source PSCell measurements

[0086] - Target PSCell information, i.e., target PSCell ID (i.e., CGI or PCI) and cell-level and beam-level target PSCell measurements

[0087] -Cell-level and beam-level neighboring cell measurement results

[0088] -PSCell change type information, e.g., MN initiated or SN initiated, normal or conditional, and PSCell addition or change

[0089] - In the case of CPAC, the configured condition information, the executed condition information and the list of candidate target PSCell IDs (CGI or PCI)

[0090] -In the case of CPAC, information about an indicator indicating whether the measured neighboring cell is a candidate target PSCell

[0091] - Time information from the time the latest (C)PAC configuration information is received to the time the PSCell addition or change is completed

[0092] - In the case of CPAC, time information from the time when CPAC was performed as the most recent condition was satisfied to the time when PSCell addition or change was completed

[0093] -Time during which UP data transmission in the SN is suspended during CPAC operation. Time from the arrival of the last Packet Data Convergence Protocol (PDCP) Protocol Data Unit (PDU) in the source PSCell until the arrival of the first PDCP PDU in the target PSCell in case of (conditional) PSCell change. Time from the reception of the most recent PSCell add configuration until the arrival of the first PDCP PDU in the new PSCell in case of (conditional) PSCell addition.

[0094] - Indicator information indicating whether an inter-master node handover has occurred with a PSCell change

[0095] -Location information of the user's device

[0096] - Information related to random access, for example, (some of) the information contained in the related art ra-InformationCommon; and

[0097] - Information about the currently registered Public Land Mobile Network (RPLMN) (or the PLMN selected by the user equipment Network Attachment Storage (NAS)). This information is used to perform a PLMN check before reporting the stored information to the base station.

[0098] The user equipment storing the above information(s) may report the content of the stored successful CPAC report to the network through a predetermined RRC procedure.

[0099] The user equipment may report the information to the base station through the UE information process. The user equipment determines whether the PLMN information stored with the information is the same as the RPLMN of the current user equipment. If they are the same, in operation 1c-45, the user equipment 1c-05 includes a feasibility indicator indicating that the user equipment 1c-05 stores the content of the successful CPAC report in a predetermined RRC message (e.g., RRCReestablishmentComplete, RRCsetupComplete, RRCResumeComplete, or RRCReconfigurationComplete) and sends it to the base station 1c-10 (1c-45). In operation 1c-50, upon receiving the indicator information, the base station 1c-10 may use a UEInformationRequest message to request a report on the information (1c-50).

[0100] In operation 1c-55, upon receiving the request, the user equipment 1c-05 sends a successful CPAC report to the base station 1c-10 (1c-55) using a UEInformationResponse message.

[0101] The user equipment 1c-05 can use the SCGFailureInformation message to send a successful CPAC report to the base station 1c-10. Although the SCGFailureInformation message is used according to the related art to report only SCG failure related information, in an embodiment of the present disclosure, it can be extended to report successfully completed CPAC related information.

[0102] After CPAC is successfully completed, the user equipment 1c-05 can include (some) content of the successful CPAC report in the SCGFailureInformation message and send it to the MN or SN. At this time, a new indicator indicating a successful CPAC report is configured in the failureType field included in the SCGFailureInformation message.

[0103] The user equipment 1c-05 may send a successful CPAC report to the base station using the MCGFailureInformation message. More specifically, if a successful CPAC report is triggered due to the satisfaction of a specific condition, the MCG cannot perform the report. For example, if a successful CPAC report is triggered due to the satisfaction of the following conditions:

[0104] - Whether an MCG failure (i.e., MN RLF) occurred during the (C)PAC operation;

[0105] - When the timer T310 is driven for the PCell during the (C)PAC operation, and if a time period corresponding to a specific ratio or more has elapsed;

[0106] -When the timer T312 is driven for the PCell during the (C)PAC operation, and if a time period corresponding to a specific ratio or more has elapsed,

[0107] The user equipment cannot report to the MN. Instead, the user equipment can include (some) content of the successful CPAC report in the MCGFailureInformation message and send it to the SN. At this time, a new indicator indicating a successful CPAC report is configured in the failureType field included in the MCGFailureInformation message.

[0108] FIG. 1 d is a flow diagram illustrating user equipment operations for reporting information related to successfully completed (conditional) PSCell additions and changes according to an embodiment of the present disclosure.

[0109] 1d, in operation 1d-05, the user equipment reports its own capability information to the master node (MN) (send UE capabilities). The capability information may include an indicator indicating whether the user equipment supports successful CPAC reporting.

[0110] In operation 1d-10, the user equipment may receive an RRCReconfiguration message (ReceiveRRCReconfiguration). The user equipment receives an RRCReconfiguration message including a ReconfigurationWithSync IE (or ConditionalReconfiguration IE) and an OtherConfig IE. The ReconfigurationWithSync IE or ConditionalReconfiguration IE includes configuration information required to perform a CPAC operation, and the OtherConfig IE includes configuration information required to perform a successful CPAC reporting operation.

[0111] In operation 1d-15, the user equipment performs a random access procedure to a predetermined PSCell (initiates a random access procedure to a target PSCell).

[0112] In operation 1d-20, if at least one of the conditions contained in the successful CPAC report operation configuration information is met during the random access procedure, the user equipment stores the content of the successful CPAC report (records information about the successful PSCell addition / change).

[0113] In operation 1d-25, the user equipment includes a feasibility indicator, which indicates that the user equipment stores the content of the successful CPAC report in a predetermined RRC message and sends it to the base station (sending the feasibility indicator via the RRC message).

[0114] In operation 1d-30, the user equipment receives a UEInformationRequest message including an indicator requesting a report on information from the base station (receives a retrieval request through the UEInformationRequest).

[0115] In operation 1d-35, the user equipment sends a successful CPAC report to the base station using a UEInformationResponse message (the recorded information about the successful PSCell addition / change is sent via the UEInformationResponse).

[0116] FIG. 1 e is a flow diagram illustrating base station operations for reporting information related to successfully completed (conditional) PSCell additions and changes according to an embodiment of the present disclosure.

[0117] 1e , in operation 1e-05 , the base station receives capability information of the corresponding user equipment from the user equipment (receive UE capability).

[0118] In operation 1e-10, the base station performs coordination with a predetermined SN to establish a (C)PAC and a successful CPAC report (coordinating PSCell addition / change with SN).

[0119] In operation 1e-15, the base station sends an RRCReconfiguration message (SendRRCReconfiguration) including configuration information of a predetermined (C)PAC and a successful CPAC report to the user equipment.

[0120] In operation 1e-20, the base station recognizes that the (C)PAC operation has been successfully completed (recognizes successful PSCell addition / change).

[0121] In operation 1e-25, the base station receives a predetermined RRC message including a feasibility indicator from the user equipment, the feasibility indicator indicating that the content of the successful CPAC report is stored (the feasibility indicator is received via the RRC message).

[0122] In operation 1e-30, the base station transmits a UEInformationRequest message including an indicator requesting a report on information to the user equipment (sending a retrieval request via UEInformationRequest).

[0123] In operation 1e-35, the base station receives a UEInformationResponse message including a successful CPAC report from the user equipment (receiving recorded information about successful PSCell addition / change via UEInformationResponse).

[0124] FIG. 1f is a flow chart illustrating a process of reporting information related to successfully completed (conditional) PSCell additions and changes in a dual connectivity environment according to an embodiment of the present disclosure.

[0125] Referring to FIG. 1f, in order to increase the maximum data rate of a user equipment in a mobile communication system such as Long Term Evolution (LTE) or New Radio (NR), a dual connectivity technology (DC) for simultaneously transmitting and receiving data to and from two base stations may be configured for the user equipment. In this case, the case where the MN is LTE and the SN is NR is referred to as EN-DC.

[0126] Embodiments of the present disclosure propose a method for performing (C)PAC and successful CPAC reporting in an EN-DC scenario.

[0127] In operation 1f-20, the user equipment 1f-05 reports its own capability information to the LTE MN 1f-10 (1f-20). The capability information may include an indicator indicating whether the user equipment 1f-05 supports successful CPAC reporting in EN-DC.

[0128] In operation 1f-25, in order to configure (C)PAC, MN 1f-10 needs to coordinate configuration with a predetermined NR SN (source SN and / or target SN) 1f-17 (1f-25). At this time, coordination for configuring configuration information related to a successful CPAC report is also required.

[0129] In operation 1f-30, after completing the coordination, the MN sends an RRCConnectionReconfiguration message including ReconfigurationWithSync IE (ConditionalReconfiguration IE in the case of CPAC) and OtherConfig IE to the user equipment (1f-30). At this time, the IE is included in the nr-SecondaryCellGroupConfig IE of the RRCConnectionReconfiguration message. The ReconfigurationWithSync IE includes the configuration information necessary to perform PAC. In the case of CPAC, the ConditionalReconfiguration IE is included in the RRCConnectionReconfiguration message instead of the ReconfigurationWithSync IE. As conditions for CPAC, in addition to the above conditions, the following two conditions can be further considered.

[0130] Condition B1: Conditional reconfiguration candidate becomes better than the absolute threshold

[0131] Condition B2: PCell becomes worse than absolute threshold 1, and conditional reconfiguration candidate becomes better than another absolute threshold 2

[0132] If two conditions are configured, the user equipment performs the CPAC operation only when both configured conditions are met.

[0133] The OtherConfig IE includes the configuration information required to perform a successful CPAC report. Although storing and reporting information about all successfully completed (C)PAC operations through successful CPAC reporting increases user equipment complexity and signaling overhead, the usefulness may not be greatly improved. It may be wiser to trigger successful CPAC reporting only for difficult successful (C)PAC operations, rather than always triggering successful CPAC reporting. Therefore, the configuration information for successful CPAC reporting included in the OtherConfig IE may include information about the conditions for triggering the reporting operation. The conditions have been described above.

[0134] In operation 1f-35, the user equipment 1f-05 performs random access to the newly added PSCell 1f-15 in case of (conditional) PSCell addition, and performs random access to the target PSCell 1f-17 in case of (conditional) PSCell change (1f-35).

[0135] The user equipment 1f-05 determines whether the configured conditions are met based on the configuration information of the successful CPAC report. If the configured conditions are met, a successful CPAC report is triggered. At this time, in operation 1f-40, when the CPAC operation is successfully completed, the user equipment 1f-05 stores the predetermined information related to the CPAC operation (1f-40). The predetermined information has been described above, but since the service cell belonging to the MCG is LTE, the beam-level measurement results are excluded.

[0136] The user equipment 1f-05 storing (some) information may report the content of the stored successful CPAC report to the network via a predetermined RRC procedure.

[0137] The user equipment 1f-05 can report the information to the base station through the UE information process. The user equipment 1f-05 determines whether the PLMN information stored together with the information is the same as the RPLMN of the current user equipment.

[0138] If they are the same, in operation 1f-45, the user equipment 1f-05 includes a feasibility indicator indicating that the user equipment stores the content of the successful CPAC report in a predetermined RRC message (e.g., RRCConnectionReestablishmentComplete, RRCConnectionSetupComplete, RRCConnectionResumeComplete, or RRCConnectionReconfigurationComplete) and sends it to the base station 1f-10 (1f-45).

[0139] In operation 1f - 50 , upon receiving the indicator information, the base station 1f - 10 may request a report on the information using a UEInformationRequest message ( 1f - 50 ).

[0140] In operation 1f-55, upon receiving the request, the user equipment 1f-05 sends a successful CPAC report to the base station 1f-10 (1f-55) using a UEInformationResponse message.

[0141] A successful CPAC report can be reported to the NR cell as well as to LTE. In this case, the successful CPAC report can be stored in a container and reported to the NR cell via a predetermined RRC message. The introduction of the container is due to the fact that the NR cell may not be able to decode the successful CPAC report because it is configured for LTE encoding. The successful CPAC report received by the NR cell may need to be forwarded to the LTE cell associated with the report. To this end, the ID information (CGI) of the LTE PCell for which the successful CPAC report is configured can also be reported to the NR. At this time, the cell ID information is not included in the container and is configured as NR encoding so that the NR cell can interpret it.

[0142] FIG. 1g is a flowchart illustrating a process of reporting SCGFailureInformation according to an embodiment of the present disclosure.

[0143] 1g, in operation 1g-15, the user equipment (UE) 1g-05 may send an RRC reconfiguration message to the base station (gNB) 1g-10. Thereafter, in operation 1g-20, the base station (gNB) 1g-10 receiving the RRC reconfiguration message may send an SCGFailureInformation message to the user equipment 1g-05.

[0144] The SCGFailureInformation message is used by the user equipment 1g-05 for the purpose of notifying the NR MN 1g-10 or LTE MN (in EN-DC environment) of the SCG failure. The message includes failureType information indicating the type of SCG failure, ID information of the previous PSCell and the failed PSCell, cell measurement information, user equipment location information, information related to the random access attempt to the PSCell, and the elapsed time information after the failure until the SCGFailureInformation message is sent.

[0145] In EN-DC, the SCGFailureInformationNR message including the content is reported to the LTE MN.

[0146] An embodiment of the present disclosure proposes a method, wherein when CPAC fails, the user equipment includes information related to CPAC in an SCGFailureInformation message and reports it to the base station.

[0147] FIG. 1 h is a flow chart illustrating a process of reporting information related to failure of conditional PSCell addition and change according to an embodiment of the present disclosure.

[0148] 1h, in operation 1h-20, the user equipment 1h-05 reports its own capability information to the master node (MN) 1h-10 (1h-20). The capability information may include an indicator indicating whether the user equipment 1h-05 can report information related to failure of conditional PSCell addition and change (CPAC).

[0149] In operation 1h-25, in order to configure CPAC, the MN 1h-10 needs coordination for configuration with the SN (source SN and / or target SN) 1h-15 (1h-25).

[0150] At operation 1h-30, after completing the coordination, the MN 1h-10 sends an RRCReconfiguration message including the ConditionalReconfiguration IE and the OtherConfig IE to the user equipment 1h-05 (1h-30).

[0151] The ConditionalReconfiguration IE includes configuration information necessary to perform CPAC. The OtherConfigIE may include an indicator indicating a CPAC failure report. Alternatively, when a CPAC failure occurs, a user device capable of reporting a CPAC failure may always have to send an SCGFailureInformation message containing information related to the failure.

[0152] In operation 1h-35, when the condition configured in the ConditionalReconfiguration IE is satisfied, the user equipment 1h-05 performs a CPAC operation on a predetermined PSCell (1h-35).

[0153] At this time, in operation 1h-40, the user equipment 1h-05 drives the timer T304 (1h-40).

[0154] In operation 1h-45, the user equipment 1h-05 performs random access to the newly added PSCell in case of conditional PSCell addition, and performs random access to the target PSCell in case of conditional PSCell change (1h-45).

[0155] In operation 1h-50, if timer T304 expires before random access is successfully completed (1h-50), then in operation 1h-55, the user equipment 1h-05 determines that CPAC has failed and stores the following information related to the CPAC operation (1h-55). At this time, the information contained in the SCGFailureInformation of the above-mentioned prior art is also stored.

[0156] - An indicator that CPAC has failed or a new code point in the failureType field

[0157] -Configuration condition information and execution condition information

[0158] - The ID information (CGI or PCI) of the PCell for which CPAC is configured, and the cell-level / beam-level cell measurement results

[0159] - List of candidate target PSCell IDs (CGI or PCI), and cell-level / beam-level cell measurement results

[0160] -Indicator information indicating whether the measured neighboring cell is a candidate target PSCell

[0161] - Time information from the time the latest CPAC configuration information is received to the time the PSCell addition or change is completed

[0162] - Time information from the time when CPAC is executed to meet the latest condition to the time when PSCell addition or change is completed

[0163] -Time when UP data transmission is suspended in the SN. Time from the arrival of the last PDCP PDU in the source PSCell until the arrival of the first PDCP PDU in the target PSCell in case of (conditional) PSCell change. Time from the reception of the most recent PSCell add configuration until the arrival of the first PDCP PDU in the new PSCell in case of (conditional) PSCell addition.

[0164] -Indicator indicating whether to suspend MCG transmission in case of CPAC failure

[0165] In operation 1h-60, the user equipment 1h-05 transmits information to the base station 1h-10 (1h-60) using the SCGFailureInformation message.

[0166] If the MCG transmission is temporarily suspended, the SCGFailureInformation message cannot be sent. Therefore, in the above situation, in operation 1h-65, the user equipment 1h-05 can include (some) CPAC-related storage information in the RLF report and report it to the base station 1h-10 (1h-65).

[0167] The base station 1h-10 receiving the information will use the information to optimize the CPAC configuration information. For example, the base station can identify the cause of the failure from the information and readjust the configuration value of the condition for executing CPAC.

[0168] FIG. 1i is a flowchart illustrating a user equipment operation of reporting information related to a failure of a conditional PSCell addition and change according to an embodiment of the present disclosure.

[0169] 1i, in operation 1i-05, the user equipment reports its own capability information to the base station. The capability information may include an indicator (Send UE Capability) indicating whether the user equipment is capable of reporting information related to CPAC failure.

[0170] In operation 1i-10, the user equipment receives an RRCReconfiguration message including CPAC configuration information (receive RRCReconfiguration).

[0171] In operation 1i-15, if the configuration conditions are met, the user equipment performs a CPAC operation (initiates a CPAC process).

[0172] In operation 1i-20, the user equipment recognizes that the CPAC operation has failed (recognizes CPACP failure).

[0173] In operation 1i-25, the user equipment stores the information related to the above-mentioned CPAC (records information related to CPAC failure).

[0174] In operation 1i-30, the user equipment sends SCGFailureInformation including information related to CPAC (sends a SCGFailureInformation message to the MN).

[0175] FIG. 1j is a flow chart illustrating base station operations for reporting information related to failure of conditional PSCell addition and change according to an embodiment of the present disclosure.

[0176] 1j , in operation 1j - 05 , the base station receives user equipment capability information from the user equipment (receive UE capability).

[0177] In operation 1j-10, the base station performs coordination with a predetermined PCell to perform CPAC (coordination with SN for PSCell addition / change).

[0178] In operation 1j-15, the base station sends an RRCReconfiguration message including CPAC configuration information to the user equipment (sending RRCReconfiguration).

[0179] In operation 1j-20, the base station receives a SCGFailureInformation message including information related to CPAC failure from the user equipment (receives a SCGFailureInformation message including information related to CPAC failure).

[0180] FIG. 1k is a block diagram illustrating an internal structure of a user equipment according to an embodiment of the present disclosure.

[0181] 1k , the user equipment includes a radio frequency (RF) processor 1k-10, a baseband processor 1k-20, a storage device 1k-30, a controller 1k-40, and a multi-connection processor 1k-42.

[0182] The RF processor 1k-10 performs functions for sending and receiving signals through wireless channels, such as frequency band conversion and amplification of signals. For example, the RF processor 1k-10 converts the baseband signal provided by the baseband processor 1k-20 into an RF band signal, transmits the RF band signal through an antenna, and converts the RF band signal received by the antenna into a baseband signal. For example, the RF processor 1k-10 may include a transmit filter, a receive filter, an amplifier, a mixer, an oscillator, a digital-to-analog converter (DAC), an analog-to-digital converter (ADC), and the like. Although only one antenna is shown in the accompanying drawings, the user equipment may include multiple antennas. In addition, the RF processor 1k-10 may include multiple RF chains. In addition, the RF processor 1k-10 may perform beamforming. For beamforming, the RF processor 1k-10 may adjust the phase and size of each signal sent and received through multiple antennas or antenna elements. In addition, the RF processor may perform MIMO and receive multiple layers when performing MIMO operations.

[0183] The baseband processor 1k-20 performs the conversion function between the baseband signal and the bit stream according to the physical layer standard of the system. For example, when sending data, the baseband processor 1k-20 generates complex symbols by encoding and modulating the transmission bit stream. In addition, when receiving data, the baseband processor 1k-20 demodulates and decodes the baseband signal provided from the RF processor 1k-10, thereby recovering the received bit stream. For example, in the case of orthogonal frequency division multiplexing (OFDM), when sending data, the baseband processor 1k-20 encodes and modulates the transmission bit stream to generate complex symbols, and configures OFDM symbols through inverse fast Fourier transform (IFFT) operation and cyclic prefix (CP) insertion after mapping the complex symbols to subcarriers. In addition, when receiving data, the baseband processor 1k-20 divides the baseband signal provided by the RF processor 1k-10 into OFDM symbol units, recovers the signal mapped to the subcarrier through a fast Fourier transform (FFT) operation, and then recovers the received bit stream through demodulation and decoding.

[0184] The baseband processor 1k-20 and the RF processor 1k-10 send and receive signals as described above. Therefore, the baseband processor 1k-20 and the RF processor 1k-10 may be referred to as a transmitter, a receiver, a transceiver, or a communication unit. In addition, at least one of the baseband processor 1k-20 and the RF processor 1k-10 may include multiple communication modules to support a variety of different wireless access technologies. In addition, at least one of the baseband processor 1k-20 and the RF processor 1k-10 may include different communication modules to process signals in different frequency bands. For example, different wireless access technologies may include a wireless local area network (LAN) (e.g., Institute of Electrical and Electronics Engineers (IEEE) 802.11), a cellular network (e.g., LTE), and the like. In addition, different frequency bands may include super high frequency (SHF) (e.g., 2.nHz or nHz) bands and millimeter (mm) wave (e.g., 60GHz) bands.

[0185] The storage device 1k-30 stores basic programs, applications, and data for operating the user equipment, such as configuration information, etc. More specifically, the storage device 1k-30 may store information related to a second access node that performs wireless communication using a second wireless access technology. In addition, the storage device 1k-30 provides stored data according to a request from the controller 1k-40.

[0186] The controller 1k-40 controls the overall operation of the user equipment. For example, the controller 1k-40 sends and receives signals through the baseband processor 1k-20 and the RF processor 1k-10. In addition, the controller 1k-40 writes data to the storage device 1k-30 and reads data from the storage device 1k-30. To this end, the controller 1k-40 may include at least one processor. For example, the controller 1k-40 may include a communication processor (CP) that performs communication control and an application processor (AP) that controls an upper layer (such as an application).

[0187] FIG. 11 is a block diagram showing the structure of a base station according to an embodiment of the present disclosure.

[0188] 11 , the base station is configured to include an RF processor 11 - 10, a baseband processor 11 - 20, a backhaul communication unit 11 - 30, a storage device 11 - 40, a controller 11 - 50, and a multi-connection processor 11 - 52.

[0189] The RF processor 11-10 performs functions for sending and receiving signals through a wireless channel, such as frequency band conversion and signal amplification. For example, the RF processor 11-10 converts the baseband signal provided by the baseband processor 11-20 into an RF band signal, transmits the RF band signal through an antenna, and converts the RF band signal received by the antenna into a baseband signal. For example, the RF processor 11-10 may include a transmit filter, a receive filter, an amplifier, a mixer, an oscillator, a DAC, an ADC, etc. Although only one antenna is shown in the accompanying drawings, the first connection mode may include multiple antennas. In addition, the RF processor 11-10 may include multiple RF chains. In addition, the RF processor 11-10 may perform beamforming. For beamforming, the RF processor 11-10 may adjust the phase and size of each signal sent and received by multiple antennas or antenna elements. In addition, the RF processor may perform downlink MIMO operations by sending one or more layers.

[0190] The baseband processor 11-20 performs a conversion function between a baseband signal and a bit stream according to the physical layer standard of the first wireless connection technology. For example, when sending data, the baseband processor 11-20 generates complex symbols by encoding and modulating the transmission bit stream. In addition, when receiving data, the baseband processor 11-20 demodulates and decodes the baseband signal provided from the RF processor 11-10, thereby recovering the received bit stream. For example, in the case of OFDM, when sending data, the baseband processor 11-20 encodes and modulates the transmission bit stream to generate complex symbols, and configures OFDM symbols by IFFT operation and CP insertion after mapping the complex symbols to subcarriers. In addition, when receiving data, the baseband processor 11-20 divides the baseband signal provided by the RF processor 11-10 into OFDM symbol units, recovers the signal mapped to the subcarrier by FFT operation, and then recovers the received bit stream by demodulation and decoding. The baseband processor 11-20 and the RF processor 11-10 send and receive signals as described above. Therefore, the baseband processor 1l-20 and the RF processor 1l-10 can be referred to as a transmitter, a receiver, a transceiver, a communication unit, or a wireless communication unit.

[0191] The backhaul communication unit 11-30 provides an interface for communicating with other nodes in the network. For example, the backhaul communication unit 11-30 converts a bit stream sent from the master base station to another node (e.g., a secondary base station, a core network, etc.) into a physical signal, and converts a physical signal received from other nodes into a bit stream.

[0192] The storage device 11-40 stores basic programs, application programs, and data such as configuration information for the operation of the main base station. More specifically, the storage device 11-40 may store information about bearers allocated to connected user equipment, measurement results reported from connected user equipment, and the like. In addition, the storage device 11-40 may store information as a criterion for determining whether to provide or stop multiple connections to user equipment. In addition, the storage device 11-40 provides the stored data according to a request from the controller 11-50.

[0193] The controller 11-50 controls the overall operation of the main base station. For example, the controller 11-50 sends and receives signals through the baseband processor 11-20 and the RF processor 11-10 or through the backhaul communication unit 11-30. In addition, the controller 11-50 writes data to the storage device 11-40 and reads data from the storage device 11-40. To this end, the controller 11-50 may include at least one processor.

[0194] While the present disclosure has been shown and described with reference to various embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present disclosure as defined by the appended claims and their equivalents.

Claims

1. A method performed by a user equipment (UE) supporting dual connectivity in a wireless communication system, the method include: receiving a radio resource control (RRC) message from a first base station associated with a primary cell group (MCG), the RRC message including first configuration information regarding a primary secondary cell (PSCell) change associated with a secondary cell group (SCG) and second configuration information regarding a successful PSCell change report (SPR); Performing a PSCell change based on the first configuration information; identifying whether the PSCell change satisfies at least one condition for triggering the SPR based on the second configuration information; as well as In a case where the at least one condition for triggering the SPR is met, the SPR is sent to the first base station.

2. The method according to claim 1, in, The at least one condition for triggering the SPR includes at least one of the following conditions: a first condition indicating that the T304 timer exceeds a first threshold, a second condition indicating that the T310 timer exceeds a second threshold, and a third condition indicating that the T312 timer exceeds a third threshold, Among them, SPR includes: At least one source PSCell information, Target PSCell information, time information between the reception of the second configuration information and the execution of the PS cell change to the target cell, or Information associated with random access, The source PSCell information includes at least one of a source PSCell identifier (ID) of the source PSCell and a measurement result, and The target PSCell information includes at least one of a target PSCell identifier (ID) and a measurement result of the target PSCell.

3. The method according to claim 1, further comprising: include: A UE capability information message is sent to the first base station, where the UE capability information message includes an indicator indicating whether the UE supports SPR.

4. The method according to claim 1, wherein the SPR is sent include: receiving a UE information request message from the first base station; as well as Based on the UE information request message, a UE information response message including the SPR is sent to the first base station.

5. A method performed by a first base station associated with a master cell group (MCG) in a wireless communication system, the method include: obtaining a radio resource control (RRC) message including first configuration information regarding a primary secondary cell (PSCell) change associated with a secondary cell group (SGC) and second configuration information regarding a successful PSCell change report (SPR); Sending an RRC message including first configuration information and second configuration information to a user equipment (UE); and In case at least one condition for triggering the SPR is satisfied, the SPR is received from the UE.

6. The method according to claim 5, in, The at least one condition for triggering the SPR includes at least one of the following conditions: a first condition indicating that the T304 timer exceeds a first threshold, a second condition indicating that the T310 timer exceeds a second threshold, and a third condition indicating that the T312 timer exceeds a third threshold, Among them, SPR includes: At least one source PSCell information and target PSCell information, time information between the reception of the second configuration information and the execution of the PSCell change to the target cell, or Information associated with random access, The source PSCell information includes at least one of a source PSCell identifier (ID) of the source PSCell and a measurement result, and The target PSCell information includes at least one of a target PSCell identifier (ID) and a measurement result of the target PSCell.

7. The method according to claim 5, further comprising: include: A UE capability information message is received from a UE, the UE capability information message including an indicator indicating whether the UE supports SPR.

8. The method according to claim 5, wherein receiving the SPR further include: Sending a UE information request message to the UE; as well as Based on the UE Information Request message, a UE Information Response message including the SPR is received from the UE.

9. A user equipment (UE) supporting dual connectivity in a wireless communication system, the UE include: a transceiver configured to transmit and receive signals; and At least one processor coupled to the transceiver and configured to: receiving a radio resource control (RRC) message from a first base station associated with a primary cell group (MCG), the RRC message including first configuration information regarding a primary secondary cell (PSCell) change associated with a secondary cell group (SCG) and second configuration information regarding a successful PSCell change report (SPR), Performing a PSCell change based on the first configuration information, identifying whether the PSCell change satisfies at least one condition for triggering the SPR based on the second configuration information; as well as In a case where the at least one condition for triggering the SPR is met, the SPR is sent to the first base station.

10. The UE according to claim 9, in, The at least one condition for triggering the SPR includes at least one of the following conditions: a first condition indicating that the T304 timer exceeds a first threshold, a second condition indicating that the T310 timer exceeds a second threshold, and a third condition indicating that the T312 timer exceeds a third threshold, Among them, SPR includes: At least one source PSCell information and target PSCell information, time information between the reception of the second configuration information and the execution of the PS cell change to the target cell, or Information associated with random access, The source PSCell information includes at least one of a source PSCell identifier (ID) of the source PSCell and a measurement result, and The target PSCell information includes at least one of a target PSCell identifier (ID) and a measurement result of the target PSCell.

11. The UE according to claim 9, wherein the at least one processor is further configured to: A UE capability information message is sent to the first base station, where the UE capability information message includes an indicator indicating whether the UE supports SPR.

12. The UE according to claim 9, wherein the at least one processor is further configured to: receiving a UE information request message from the first base station; and Based on the UE information request message, a UE information response message including the SPR is sent to the first base station.

13. A first base station associated with a master cell group (MCG) in a wireless communication system, the first base station include: a transceiver configured to transmit and receive signals; and At least one processor coupled to the transceiver and configured to: obtaining a radio resource control (RRC) message including first configuration information regarding a primary secondary cell (PSCell) change associated with a secondary cell group (SGC) and second configuration information regarding a successful PSCell change report (SPR), Sending an RRC message including first configuration information and second configuration information to a user equipment (UE); and In case at least one condition for triggering the SPR is satisfied, the SPR is received from the UE.

14. The first base station according to claim 13, in, The at least one condition for triggering the SPR includes at least one of the following conditions: a first condition indicating that the T304 timer exceeds a first threshold, a second condition indicating that the T310 timer exceeds a second threshold, and a third condition indicating that the T312 timer exceeds a third threshold, Among them, SPR includes: At least one source PSCell information and target PSCell information, time information between the reception of the second configuration information and the execution of the PS cell change to the target cell, or Information associated with random access, The source PSCell information includes at least one of a source PSCell identifier (ID) of the source PSCell and a measurement result, and The target PSCell information includes at least one of a target PSCell identifier (ID) of the target PSCell and a measurement result.

15. The first base station of claim 13, wherein the at least one processor is further configured to: receiving a UE capability information message from the UE, the UE capability information message including an indicator indicating whether the UE supports SPR, Sending a UE information request message to the UE; Based on the UE Information Request message, a UE Information Response message including the SPR is received from the UE.

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