Method for processing subsequent pscell change and addition configuration during mobile operation in next generation mobile communication system

Abstract

The present disclosure relates to a 5G communication or 6G communication system for supporting higher data transmission rates, and relates to a method and device for deleting a subsequent PSCell change and addition (SCPAC) configuration which is no longer valid when SCPAC configuration information previously received by a terminal is no longer valid.

Description

A method for handling continuous conditional PSCELL changes and additional configurations during mobile operation in next-generation mobile communication systems.

[0001] The present disclosure relates to the operation of a base station and a terminal in a mobile communication system. More specifically, the present disclosure relates to a method and device for a terminal to process settings related to continuous conditional PSCell addition and change. In particular, the present disclosure relates to a method for processing settings related to conditional PSCell addition and change during a mobile operation of a terminal.

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

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

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

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

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

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

[0008] As described above and with the development of mobile communication systems, various services have become available, and methods for effectively providing these services are required.

[0009] The present disclosure proposes a method and device for controlling the setting of subsequent conditional PSCell change and addition (SCPAC) to solve the above-described problems.

[0010] More specifically, a terminal can receive SCPAC configuration information from the network. If a handover (e.g., PCell change) occurs after the terminal has received SCPAC configuration information, the SCPAC configuration information previously received by the terminal may no longer be valid. The present disclosure proposes a method for deleting (or erasing) SCPAC configurations that are no longer valid.

[0011] Another object of the present disclosure is to propose a method for deleting (or clearing) SCPAC settings in a recovery operation using secondary cell group (SCG) change, or conditional handover (CHO).

[0012] Additionally, signaling procedures may be required depending on which entity on the network performs the release operation. If the release operation is not warranted, the terminal may perform unnecessary measurement and condition determination operations through invalid SCPAC settings. Another purpose of the present disclosure is to propose a method to address the problem of moving to an invalid target cell and applying settings in that cell.

[0013] The technical problems to be achieved in the embodiments of the present disclosure are not limited to the technical problems mentioned above, and other technical problems not mentioned can be clearly understood by a person having ordinary skill in the technical field to which the present disclosure belongs from the description below.

[0014] In order to solve the above problems, the present invention is characterized in that the method performed by a terminal (user equipment, UE) in a wireless communication system comprises the steps of: receiving, from a base station related to a source cell, first conditional reconfiguration information including subsequent conditional primary secondary cell group (SCG) cell (PSCell) addition or change (SCPAC) configuration information; deleting, when the terminal receives a message for cell change including second conditional reconfiguration information related to release of the SCPAC configuration information, the stored SCPAC configuration information based on the second conditional reconfiguration information related to release of the SCPAC configuration information; and performing a cell change to a target cell based on the message for cell change.

[0015] According to another embodiment of the present disclosure, a method performed by a base station associated with a source cell in a wireless communication system is characterized by comprising the steps of: transmitting, to a terminal, first conditional reconfiguration information including subsequent conditional primary secondary cell group (SCG) cell (PSCell) addition or change (SCPAC) configuration information; determining whether to change a cell; and, if it is determined to change a cell, transmitting, to the terminal, a message for cell change including second conditional reconfiguration information related to release of the SCPAC configuration information.

[0016] According to another embodiment of the present disclosure, a user equipment (UE) in a wireless communication system comprises: a transceiver for transmitting and receiving a signal; and a control unit, wherein the control unit receives, from a base station related to a source cell, first conditional reconfiguration information including subsequent conditional primary secondary cell group (SCG) cell (PSCell) addition or change (SCPAC) configuration information, and, when the UE receives a message for cell change including second conditional reconfiguration information related to release of the SCPAC configuration information, deletes the stored SCPAC configuration information based on the second conditional reconfiguration information related to release of the SCPAC configuration information, and performs a cell change to a target cell based on the message for cell change.

[0017] According to another embodiment of the present disclosure, in a wireless communication system, a base station related to a source cell comprises: a transceiver for transmitting and receiving a signal; and a control unit, wherein the control unit transmits, to a terminal, first conditional reconfiguration information including subsequent conditional PSCell addition or change (SCPAC) configuration information, determines whether to change a cell, and, when it is determined to change a cell, transmits, to the terminal, a message for cell change including second conditional reconfiguration information related to release of the SCPAC configuration information.

[0018] According to an embodiment of the present disclosure, a terminal can delete subsequent conditional PSCell addition and change (SCPAC) n settings. More specifically, the terminal can delete SCPAC-related settings along with a mobile operation instruction of the terminal. Accordingly, the terminal can avoid performing unnecessary SCPAC operations.

[0019] The effects that can be obtained from the present disclosure are not limited to the effects mentioned in the various embodiments, and other effects that are not mentioned can be clearly understood by a person having ordinary skill in the art to which the present disclosure belongs from the description below.

[0020] FIG. 1 is a diagram illustrating the structure of a long term evolution (LTE) system according to one embodiment of the present disclosure.

[0021] FIG. 2 is a diagram illustrating a wireless protocol structure of a long term evolution (LTE) system according to an embodiment of the present disclosure.

[0022] FIG. 3 is a diagram illustrating the structure of a next-generation mobile communication system according to an embodiment of the present disclosure.

[0023] FIG. 4 is a diagram illustrating a wireless protocol structure of a next-generation mobile communication system according to an embodiment of the present disclosure.

[0024] FIG. 5 is a block diagram illustrating the internal structure of a terminal according to an embodiment of the present disclosure.

[0025] FIG. 6 is a block diagram illustrating the structure of a new radio (NR) base station according to an embodiment of the present disclosure.

[0026] FIG. 7 is a diagram illustrating a method for canceling subsequent conditional PSCell addition and change in case of inter-MN handover according to an embodiment of the present disclosure.

[0027] FIG. 8a is a diagram illustrating a signal structure when a network transmits subsequent conditional PSCell addition and change (SCPAC) settings to a terminal according to an embodiment of the present disclosure.

[0028] FIG. 8b is a diagram illustrating a sequence in which a terminal according to the prior art applies a radio resource control (RRC) reset message.

[0029] FIG. 9 is a diagram illustrating a signal structure related to subsequent conditional PSCell addition and change (SCPAC) according to one embodiment of the present disclosure.

[0030] FIG. 10 is a flowchart illustrating a sequence of a subsequent conditional PSCell addition and change (SCPAC) setup release procedure in the case of inter master node (MN) handover according to one embodiment of the present disclosure.

[0031] FIG. 11 is a flowchart illustrating a sequence of a subsequent conditional PSCell addition and change (SCPAC) setup release procedure of an intra master node (MN) PCell handover procedure according to one embodiment of the present disclosure.

[0032] FIG. 12 is a flowchart illustrating a sequence of a subsequent conditional PSCell addition and change (SCPAC) configuration release procedure in a secondary cell group (SCG) release according to one embodiment of the present disclosure.

[0033] FIG. 13 is a flowchart illustrating a sequence of a subsequent conditional PSCell addition and change (SCPAC) setup release procedure in a conditional handover (CHO) recovery procedure according to one embodiment of the present disclosure.

[0034] The operating principles of the present invention will be described in detail below with reference to the attached drawings. In the following description of the present invention, detailed descriptions of known functions or components will be omitted if they are deemed to unnecessarily obscure the gist of the invention. Furthermore, the terms described below are defined based on their functions in the present invention and may vary depending on the intentions or practices of the user or operator. Therefore, their definitions should be based on the overall content of this specification.

[0035] The 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, and terms referring to various identification information are provided for convenience of explanation. Therefore, the present invention is not limited to the terms described below, and other terms referring to objects with equivalent technical meanings may be used.

[0036] Hereinafter, the base station is an entity that performs resource allocation of the terminal, and may be at least one of a gNode B, an eNode B, a Node B, a BS (Base Station), a wireless access unit, a base station controller, or a node on a network. The terminal may include a UE (User Equipment), an MS (Mobile Station), a cellular phone, a smartphone, a computer, or a multimedia system capable of performing a communication function. In the present disclosure, downlink (DL) refers to a wireless transmission path of a signal transmitted from a base station to a terminal, and uplink (UL) refers to a wireless transmission path of a signal transmitted from a terminal to a base station. In addition, although the LTE or LTE-A system may be described below as an example, the embodiments of the present disclosure may also be applied to other communication systems having similar technical backgrounds or channel types. For example, the 5th generation mobile communication technology (5G, new radio, NR) developed after LTE-A may be included in a system to which the embodiments of the present disclosure may be applied, and 5G below may also be a concept that includes existing LTE, LTE-A, and other similar services. Furthermore, the present disclosure may be applied to other communication systems with some modifications, as determined by a person skilled in the art, without significantly departing from the scope of the present disclosure. It will be appreciated that each block of the processing flow diagrams and combinations of the flow diagrams can be executed by computer program instructions.

[0037] These computer program instructions may be installed in a processor of a general-purpose computer, a special-purpose computer, or other programmable data processing apparatus, so that the instructions executed by the processor of the computer or other programmable data processing apparatus create means for performing the functions described in the flowchart block(s). These computer program instructions may also be stored in a computer-available or computer-readable memory that can be directed to a computer or other programmable data processing apparatus to implement functions in a particular manner, so that the instructions stored in the computer-available or computer-readable memory can produce an article of manufacture that includes instruction means for performing the functions described in the flowchart block(s). The computer program instructions may also be installed on a computer or other programmable data processing apparatus, so that a series of operational steps are performed on the computer or other programmable data processing apparatus to create a computer-implemented process, so that the instructions executing on the computer or other programmable data processing apparatus can provide steps for performing the functions described in the flowchart block(s).

[0038] Additionally, each block may represent a module, segment, or portion of code that contains one or more executable instructions for executing a specific logical function(s). It should also be noted that in some alternative implementation examples, the functions mentioned in the blocks may occur out of order. For example, two blocks shown in succession may in fact be executed substantially simultaneously, or the blocks may sometimes be executed in reverse order depending on the corresponding function. In this case, the term '~unit' used in the present embodiment means software or a hardware component such as an FPGA (Field Programmable Gate Array) or an ASIC (Application Specific Integrated Circuit), and the '~unit' may perform certain roles. However, the '~unit' is not limited to software or hardware. The '~unit' may be configured to be on an addressable storage medium and may be configured to execute one or more processors. Thus, as an example, the '~ unit' includes components such as software components, object-oriented software components, class components, and task components, processes, functions, attributes, procedures, subroutines, segments of program code, drivers, firmware, microcode, circuits, data, databases, data structures, tables, arrays, and variables. The functionality provided within the components and '~ units' may be combined into a smaller number of components and '~ units' or further separated into additional components and '~ units'. In addition, the components and '~ units' may be implemented to reproduce one or more CPUs within a device or a secure multimedia card. Also, in an embodiment, the '~ unit' may include one or more processors.

[0039] For convenience of explanation, the present invention uses terms and names defined in the 5GS and NR standards, which are standards defined by the 3rd Generation Partnership Project (3GPP) among the existing communication standards. However, the present invention is not limited to the above terms and names and can be equally applied to wireless communication networks that follow other standards. For example, the present invention can be applied to the 3GPP 5GS / NR (5th generation mobile communication standard).

[0040] FIG. 1 is a diagram illustrating the structure of a long term evolution (LTE) system according to one embodiment of the present disclosure.

[0041] Referring to FIG. 1, a wireless access network of a long term evolution (LTE) system as illustrated in FIG. 1 may be composed of next-generation base stations (Evolved Node Bs, hereinafter referred to as ENBs, Node Bs or base stations) (1-05, 1-10, 1-15, 1-20), a mobility management entity (MME) (1-25) and an S-GW (1-30, Serving-Gateway). A user equipment (UE or terminal) (1-35) may access an external network through the ENBs (1-05 to 1-20) and the S-GW (1-30).

[0042] In Fig. 1, ENBs (1-05 to 1-20) may correspond to existing Node Bs of a UMTS system. ENBs are connected to UEs (1-35) via a wireless channel and may perform more complex roles than existing Node Bs. In an LTE system, all user traffic, including real-time services such as VoIP (Voice over IP) via the Internet Protocol, can be serviced through a shared channel. Therefore, a device that collects status information such as the buffer status, available transmission power status, and channel status of UEs and performs scheduling is required, and ENBs (1-05 to 1-20) may be responsible for this. One ENB can typically control multiple cells. For example, in order to achieve a transmission rate of 100 Mbps, an LTE system may use, for example, Orthogonal Frequency Division Multiplexing (OFDM) as a wireless access technology in a 20 MHz bandwidth. Additionally, an adaptive modulation and coding (AMC) method can be applied, which determines the modulation scheme and channel coding rate according to the channel status of the terminal.

[0043] The S-GW (serving gateway, 1-30) is a device that provides data bearers and can create or remove data bearers under the control of the mobility management entity (MME, 1-25). The MME is a device responsible for various control functions as well as mobility management for terminals and can be connected to multiple base stations.

[0044] FIG. 2 is a diagram illustrating a wireless protocol structure of a long term evolution (LTE) system according to an embodiment of the present disclosure.

[0045] Referring to FIG. 2, the wireless protocol of the long term evolution (LTE) system may be composed of Packet Data Convergence Protocol (PDCP) (2-05, 2-40), Radio Link Control (RLC) (2-10, 2-35), and Medium Access Control (MAC) (2-15, 2-30) in the terminal and ENB, respectively.

[0046] Packet Data Convergence Protocol (PDCP) (2-05, 2-40) can handle operations such as IP header compression / decompression. The main functions of PDCP can be summarized as follows.

[0047] - Header compression and decompression (ROHC only)

[0048] - User data transfer function

[0049] - In-sequence delivery of upper layer PDUs at PDCP re-establishment procedure for RLC AM

[0050] - Order reordering function (For split bearers in DC (only support for RLC AM): PDCP PDU routing for transmission and PDCP PDU reordering for reception)

[0051] - Duplicate detection function (Duplicate detection of lower layer SDUs at PDCP re-establishment procedure for RLC AM)

[0052] - Retransmission function (Retransmission of PDCP SDUs at handover and, for split bearers in DC, of ​​PDCP PDUs at PDCP data-recovery procedure, for RLC AM)

[0053] - Encryption and decryption functions (Ciphering and deciphering)

[0054] - Timer-based SDU discard in uplink.

[0055] Radio Link Control (RLC) (2-10, 2-35) can perform ARQ operations, etc. by reconfiguring PDCP packet data units (PDUs) to an appropriate size. The main functions of RLC can be summarized as follows.

[0056] - Data transfer function (Transfer of upper layer PDUs)

[0057] - ARQ function (Error Correction through ARQ (only for AM data transfer))

[0058] - Concatenation, segmentation and reassembly of RLC SDUs (only for UM and AM data transfer)

[0059] - Re-segmentation of RLC data PDUs (only for AM data transfer)

[0060] - Reordering of RLC data PDUs (only for UM and AM data transfer)

[0061] - Duplicate detection (only for UM and AM data transfer)

[0062] - Error detection function (Protocol error detection (only for AM data transfer))

[0063] - RLC SDU discard function (RLC SDU discard (only for UM and AM data transfer))

[0064] - RLC re-establishment function

[0065] Medium Access Control (MAC) (2-15, 2-30) connects to multiple RLC layer devices configured in a single terminal and can perform operations of multiplexing RLC PDUs into MAC PDUs and demultiplexing RLC PDUs from MAC PDUs. The main functions of MAC can be summarized as follows.

[0066] - Mapping function (Mapping between logical channels and transport channels)

[0067] - Multiplexing and demultiplexing function (Multiplexing / demultiplexing of MAC SDUs belonging to one or different logical channels into / from transport blocks (TB) delivered to / from the physical layer on transport channels)

[0068] - Scheduling information reporting function

[0069] - HARQ function (Error correction through HARQ)

[0070] - Priority handling between logical channels of one UE

[0071] - Priority handling between UEs by means of dynamic scheduling

[0072] - MBMS service identification function

[0073] - Transport format selection function

[0074] - Padding function

[0075] The physical layer (2-20, 2-25) can perform the operation of channel coding and modulating upper layer data, converting it into OFDM symbols and transmitting it through a wireless channel, or demodulating and channel decoding OFDM symbols received through a wireless channel and transmitting them to a higher layer.

[0076] FIG. 3 is a diagram illustrating the structure of a next-generation mobile communication system according to an embodiment of the present disclosure.

[0077] Referring to FIG. 3, a wireless access network of a next-generation mobile communication system (hereinafter referred to as new radio (NR) or 5G) may be composed of a next-generation base station (New Radio Node B, hereinafter referred to as NR gNB or NR base station) (3-10) and a next-generation radio core network (New Radio Core Network, NR CN) (3-05). A next-generation radio user equipment (NR UE or terminal) (3-15) may access an external network through the NR gNB (3-10) and the NR CN (3-05).

[0078] In Fig. 3, the NR gNB (3-10) may correspond to an eNB (Evolved Node B) of an existing LTE system. The NR gNB is connected to an NR UE (3-15) via a wireless channel and may provide superior services than an existing Node B.

[0079] In next-generation mobile communication systems, all user traffic can be serviced through a shared channel. Therefore, a device is needed to collect status information, such as UE buffer status, available transmit power status, and channel status, and perform scheduling. This scheduling can be performed by an NR NB (3-10). A single NR gNB can control multiple cells.

[0080] In next-generation mobile communication systems, bandwidths exceeding the typical maximum bandwidth may be applied to achieve ultra-high-speed data transmission compared to conventional LTE. Furthermore, beamforming technology may be incorporated into orthogonal frequency division multiplexing (OFDM) as a wireless access technology.

[0081] Additionally, an adaptive modulation and coding (AMC) method that determines a modulation scheme and channel coding rate according to the channel status of the terminal may be applied.

[0082] A new radio core network (NR CN) (3-05) can perform functions such as mobility support, bearer setup, and quality of service (QoS) setup. The NR CN is a device that handles various control functions as well as mobility management for terminals and can be connected to multiple base stations. In addition, the next-generation mobile communication system can be interoperable with the LTE system, and the NR CN can be connected to a mobility management entity (MME) (3-25) via a network interface. The MME can be connected to an eNB (3-30), which is an LTE base station.

[0083] FIG. 4 is a diagram illustrating a wireless protocol structure of a next-generation mobile communication system according to an embodiment of the present disclosure.

[0084] Referring to FIG. 4, the wireless protocol of the next-generation mobile communication system may be composed of NR Service Data Adaptation Protocol (SDAP) (4-01, 4-45), NR Packet Data Convergence Protocol (NR PDCP) (4-05, 4-40), NR Radio Link Control (NR RLC) (4-10, 4-35), NR Medium Access Control (NR MAC) (4-15, 4-30), and NR PHY (4-20, 4-25) in the terminal and the NR base station, respectively.

[0085] The main functions of the NR Service Data Adaptation Protocol (NR SDAP) (4-01, 4-45) may include some of the following functions:

[0086] Transfer of user plane data

[0087] Mapping between a QoS flow and a DRB for both DL and UL

[0088] QoS flow ID marking function for both uplink and downlink (marking QoS flow ID in both DL and UL packets)

[0089] Ability to map relective QoS flow to data bearer for the UL SDAP PDUs (reflective QoS flow to DRB mapping for the UL SDAP PDUs).

[0090] For an SDAP layer device, a terminal can be configured by a Radio Resource Control (RRC) message for each PDCP layer device, per bearer, or per logical channel, whether to use the header of the SDAP layer device or whether to use the function of the SDAP layer device. When the SDAP header is configured, the terminal can instruct the terminal to update or reset the mapping information for the QoS flow and data bearer of the uplink and downlink by using a 1-bit indicator for reflecting the Non-Access Stratum (NAS) Quality of Service (QoS) in the SDAP header (NAS reflective QoS) and a 1-bit indicator for reflecting the Access Stratum (AS) QoS in the SDAP header. The SDAP header can include QoS flow ID information indicating QoS. The QoS information can be used as data processing priority, scheduling information, etc. to support a smooth service.

[0091] The main features of the NR Packet Data Convergence Protocol (NR PDCP) (4-05, 4-40) may include some of the following:

[0092] - Header compression and decompression (ROHC only)

[0093] - User data transfer function

[0094] - In-sequence delivery of upper layer PDUs

[0095] - Out-of-sequence delivery of upper layer PDUs

[0096] - PDCP PDU reordering for reception

[0097] - Duplicate detection of lower layer SDUs

[0098] - Retransmission function (Retransmission of PDCP SDUs)

[0099] - Encryption and decryption functions (Ciphering and deciphering)

[0100] - Timer-based SDU discard in uplink.

[0101] In the above, the reordering function of the NR PDCP device may refer to a function of reordering PDCP PDUs received from a lower layer in order based on a PDCP SN (sequence number). The reordering function of the NR PDCP device may include a function of transmitting data to an upper layer in the reordered order, or a function of transmitting data directly without considering the order, a function of recording lost PDCP PDUs by reordering the order, a function of reporting a status of lost PDCP PDUs to the transmitting side, and a function of requesting retransmission of lost PDCP PDUs.

[0102] The main functions of NR Radio Link Control (NR RLC)(4-10, 4-35) may include some of the following functions:

[0103] - Data transfer function (Transfer of upper layer PDUs)

[0104] - In-sequence delivery of upper layer PDUs

[0105] - Out-of-sequence delivery of upper layer PDUs

[0106] - ARQ function (Error Correction through ARQ)

[0107] - Concatenation, segmentation and reassembly of RLC SDUs

[0108] - Re-segmentation of RLC data PDUs

[0109] - Reordering of RLC data PDUs

[0110] - Duplicate detection function

[0111] - Protocol error detection

[0112] - RLC SDU discard function

[0113] - RLC re-establishment function

[0114] In the above, the in-sequence delivery function of the NR RLC device may refer to the function of sequentially delivering RLC SDUs received from the lower layer to the upper layer. If a single RLC SDU is originally received divided into multiple RLC SDUs, the in-sequence delivery function of the NR RLC device may include the function of reassembling and delivering them.

[0115] The in-sequence delivery function of the NR RLC device may include a function to reorder received RLC PDUs based on the RLC SN (sequence number) or PDCP SN (sequence number), a function to record lost RLC PDUs by reordering them, a function to report status of lost RLC PDUs to the transmitter, and a function to request retransmission of lost RLC PDUs.

[0116] The in-sequence delivery function of the NR RLC device may include a function to sequentially deliver only the RLC SDUs up to the lost RLC SDU to the upper layer when there is a lost RLC SDU.

[0117] The in-sequence delivery function of the NR RLC device may include a function to deliver to the upper layer in sequence all RLC SDUs received before a predetermined timer starts if there are lost RLC SDUs and a predetermined timer has expired.

[0118] The in-sequence delivery function of the NR RLC device may include a function to deliver all RLC SDUs received so far to the upper layer in order if a predetermined timer has expired, even if there are lost RLC SDUs.

[0119] An NR RLC device can process RLC PDUs in the order they are received and deliver them to an NR PDCP device, regardless of the order of the sequence number (out-of-sequence delivery).

[0120] When an NR RLC device receives a segment, it can receive segments that are stored in a buffer or will be received later, reconstruct them into a complete RLC PDU, and then transmit them to the NR PDCP device.

[0121] The NR RLC layer may not include concatenation functionality, and the functionality may be performed by the NR MAC layer or replaced by the multiplexing functionality of the NR MAC layer.

[0122] In the above, the out-of-sequence delivery function of the NR RLC device may refer to the function of directly delivering RLC SDUs received from a lower layer to an upper layer regardless of the order. The out-of-sequence delivery function of the NR RLC device may include the function of reassembling and delivering the RLC SDUs when an original RLC SDU is received fragmented into multiple RLC SDUs. The out-of-sequence delivery function of the NR RLC device may include the function of storing and arranging the RLC SN or PDCP SN of the received RLC PDUs to record the lost RLC PDUs.

[0123] NR Medium Access Control (NR MAC) (4-15, 4-30) can be connected to multiple NR RLC layer devices configured in one terminal, and the main functions of NR MAC can include some of the following functions.

[0124] - Mapping function (Mapping between logical channels and transport channels)

[0125] - Multiplexing / demultiplexing of MAC SDUs

[0126] - Scheduling information reporting function

[0127] - HARQ function (Error correction through HARQ)

[0128] - Priority handling between logical channels of one UE

[0129] - Priority handling between UEs by means of dynamic scheduling

[0130] - MBMS service identification function

[0131] - Transport format selection function

[0132] - Padding function

[0133] The NR physical layer (NR PHY layer) (4-20, 4-25) can perform operations such as channel coding and modulating upper layer data, converting it into OFDM symbols and transmitting it through a wireless channel, or demodulating and channel decoding OFDM symbols received through a wireless channel and transmitting them to a higher layer.

[0134] FIG. 5 is a block diagram illustrating the internal structure of a terminal according to an embodiment of the present disclosure.

[0135] Referring to the above drawing, the terminal may include an RF (Radio Frequency) processing unit (5-10), a baseband processing unit (5-20), a storage unit (5-30), and a control unit (5-40).

[0136] The RF processing unit (5-10) above can perform functions for transmitting and receiving signals through a wireless channel, such as signal band conversion and amplification. The RF processing unit (5-10) can up-convert a baseband signal provided from the baseband processing unit (5-20) into an RF band signal and transmit it through an antenna, and down-convert an RF band signal received through the antenna into a baseband signal. For example, the RF processing unit (5-10) can include a transmission filter, a reception filter, an amplifier, a mixer, an oscillator, a digital to analog convertor (DAC), an analog to digital convertor (ADC), etc. In the drawing, only one antenna is shown, but the terminal can be equipped with multiple antennas. In addition, the RF processing unit (5-10) can include multiple RF chains. Furthermore, the RF processing unit (5-10) can perform beamforming. For the above beamforming, the RF processing unit (5-10) can adjust the phase and size of each signal transmitted and received through multiple antennas or antenna elements. In addition, the RF processing unit can perform MIMO and can receive multiple layers when performing the MIMO operation.

[0137] The baseband processing unit (5-20) above can perform a conversion function between a baseband signal and a bit stream according to the physical layer specifications of the system. For example, when transmitting data, the baseband processing unit (5-20) can generate complex symbols by encoding and modulating a transmission bit stream. In addition, when receiving data, the baseband processing unit (5-20) can restore a reception bit stream by demodulating and decoding a baseband signal provided from the RF processing unit (5-10). For example, in the case of following the OFDM (orthogonal frequency division multiplexing) method, when transmitting data, the baseband processing unit (5-20) generates complex symbols by encoding and modulating a transmission bit stream, maps the complex symbols to subcarriers, and then configures OFDM symbols through an inverse fast Fourier transform (IFFT) operation and a cyclic prefix (CP) insertion. In addition, when receiving data, the baseband processing unit (5-20) divides the baseband signal provided from the RF processing unit (5-10) into OFDM symbol units, restores signals mapped to subcarriers through FFT (fast Fourier transform), and then restores the received bit string through demodulation and decoding.

[0138] The baseband processing unit (5-20) and the RF processing unit (5-10) can transmit and receive signals as described above. Accordingly, the baseband processing unit (5-20) and the RF processing unit (5-10) may be referred to as a transmitter, a receiver, a transceiver, or a communication unit. Furthermore, at least one of the baseband processing unit (5-20) and the RF processing unit (5-10) may include a plurality of communication modules to support a plurality of different wireless access technologies. In addition, at least one of the baseband processing unit (5-20) and the RF processing unit (5-10) may include different communication modules to process signals of different frequency bands. For example, the different wireless access technologies may include a wireless LAN (e.g., IEEE 802.11), a cellular network (e.g., LTE), etc. Additionally, the different frequency bands may include a super high frequency (SHF) (e.g., 2.NRHz, NRhz) band and a millimeter wave (mm wave) (e.g., 60GHz) band.

[0139] The storage unit (5-30) stores data such as basic programs, application programs, and setting information for the operation of the terminal. In particular, the storage unit (5-30) can store information related to a second access node that performs wireless communication using a second wireless access technology. In addition, the storage unit (5-30) provides the stored data at the request of the control unit (5-40).

[0140] The above control unit (5-40) controls the overall operations of the terminal. For example, the control unit (5-40) transmits and receives signals through the baseband processing unit (5-20) and the RF processing unit (5-10). In addition, the control unit (5-40) records and reads data in the storage unit (5-40). For this purpose, the control unit (5-40) may include at least one processor. For example, the control unit (5-40) may include a communication processor (CP) that performs control for communication and an application processor (AP) that controls upper layers such as application programs.

[0141] FIG. 6 is a block diagram illustrating the structure of a new radio (NR) base station according to one embodiment of the present disclosure.

[0142] As shown in the above drawing, the base station may include an RF (radio frequency) processing unit (6-10), a baseband processing unit (6-20), a backhaul communication unit (6-30), a storage unit (6-40), and a control unit (6-50).

[0143] The RF processing unit (6-10) above can perform functions for transmitting and receiving signals through a wireless channel, such as signal band conversion and amplification. The RF processing unit (6-10) up-converts the baseband signal provided from the baseband processing unit (6-20) into an RF band signal and transmits it through an antenna, and down-converts the RF band signal received through the antenna into a baseband signal. For example, the RF processing unit (6-10) may include a transmission filter, a reception filter, an amplifier, a mixer, an oscillator, a DAC, an ADC, etc. In the drawing, only one antenna is shown, but the first access node may have multiple antennas. In addition, the RF processing unit (6-10) may include multiple RF chains. Furthermore, the RF processing unit (6-10) may perform beamforming. For the above beamforming, the RF processing unit (6-10) can adjust the phase and size of each signal transmitted and received through multiple antennas or antenna elements. The RF processing unit can perform a downlink MIMO operation by transmitting one or more layers.

[0144] The baseband processing unit (6-20) above can perform a conversion function between a baseband signal and a bit stream according to the physical layer specifications of the first wireless access technology. For example, when transmitting data, the baseband processing unit (6-20) can generate complex symbols by encoding and modulating a transmission bit stream. In addition, when receiving data, the baseband processing unit (6-20) restores the reception bit stream by demodulating and decoding the baseband signal provided from the RF processing unit (6-10). For example, in the case of OFDM, when transmitting data, the baseband processing unit (6-20) can generate complex symbols by encoding and modulating a transmission bit stream, map the complex symbols to subcarriers, and then configure OFDM symbols through IFFT operation and CP insertion. In addition, when receiving data, the baseband processing unit (6-20) divides the baseband signal provided from the RF processing unit (6-10) into OFDM symbol units, restores the signals mapped to subcarriers through FFT operation, and then restores the received bit string through demodulation and decoding. The baseband processing unit (6-20) and the RF processing unit (6-10) transmit and receive signals as described above. Accordingly, the baseband processing unit (6-20) and the RF processing unit (6-10) may be referred to as a transmitter, a receiver, a transceiver, a communication unit, or a wireless communication unit.

[0145] The above backhaul communication unit (6-30) provides an interface for communicating with other nodes within the network. The above backhaul communication unit (6-30) can convert a bit string transmitted from the main base station to other nodes, such as auxiliary base stations or core networks, into a physical signal, and can also convert a physical signal received from the other nodes into a bit string.

[0146] The storage unit (6-40) can store data such as basic programs, application programs, and setting information for the operation of the main base station. In particular, the storage unit (6-40) can store information on bearers assigned to connected terminals, measurement results reported from connected terminals, and the like. In addition, the storage unit (6-40) can store information that serves as a judgment criterion for whether to provide or terminate multiple connections to a terminal. In addition, the storage unit (6-40) provides the stored data at the request of the control unit (6-50).

[0147] The control unit (6-50) controls the overall operations of the base station. For example, the control unit (6-50) transmits and receives signals through the baseband processing unit (6-20) and the RF processing unit (6-10) or through the backhaul communication unit (6-30). In addition, the control unit (6-50) records and reads data in the storage unit (6-40). For this purpose, the control unit (6-50) may include at least one processor.

[0148] The following terms and abbreviations may be used throughout the specification.

[0149] - Conditional PSCell addition and change: conditional PSCell addition (CPA) / conditional PSCell change (CPC)

[0150] - Subsequent conditional PSCell addition and change (SCPAC)

[0151] - Master node: master node (MN)

[0152] - Secondary node (SN)

[0153] - Master cell group: master cell group (MCG)

[0154] - Secondary cell group (SCG)

[0155] SCPAC background operation according to one embodiment of the present disclosure is as follows.

[0156] In a situation where a terminal configures a dual connection through a base station MN and a SN, the SN may request resource allocation for performing SCPAC to another SN (hereinafter referred to as a "candidate SN"). For this purpose, necessary information may be transmitted to the MN. This information may include information indicating at least one proposed candidate PSCell for each of the candidate SNs, measurement result information for the corresponding PSCell, and initial condition information for moving from the SN's current PSCell to the candidate PSCells.

[0157] The above MN can receive the above information from the S-SN and transmit the above information by applying the SNAddition procedure to each candidate SN.

[0158] Each candidate SN transmits its proposed candidate PSCell and measurement results for that cell. It can also transmit proposed candidate PSCell information for other candidate SNs.

[0159] Each candidate SN that receives this information can determine a PSCell to which SCPAC resources will be allocated from its proposed PSCells and include the information about that cell in the SNADDReqACK message to the MN. Furthermore, the SN can also convey condition information to be used when moving from the determined PSCell to other candidate PSCells.

[0160] The MN that has received the above information can link the target settings for the determined PSCells and the condition information required for moving from the target cell to another SCPAC candidate cell, and transmit this information to the terminal as SCPAC settings. This transmission of settings can be transmitted as an RRCReconfiguration message.

[0161] After receiving the above settings, the terminal can perform measurement and condition evaluation operations. Then, if certain conditions are met, it can move to the candidate PSCell. At this time, the SCPAC settings will remain in the terminal, and even after moving to the PSCell, the terminal can continue to perform SCPAC operations using the necessary condition information and target cell configuration information within the same SCPAC settings.

[0162] The problems with conventional technology are as follows:

[0163] When performing PCell change, SCG release, normal PSCell change, or CHO recovery operations on a terminal performing the SCPAC operation described above, there may be cases where the SCPAC configuration must be removed rather than maintained. When performing the mobility operation described above, the terminal must either delete the SCPAC configuration itself or the network must explicitly send (or give) a signal (or signaling) to delete the SCPAC configuration.

[0164] On the running RRC CR currently being discussed, the command to delete (or erase) the SCPAC configuration can be performed with condReconfigToRemoveList-r16 in the conditional Reconfiguration field. By indicating the conditional Reconfig Id of the target PSCell indicated as the SCPAC candidate cell in the IE, the target PSCell can be prevented from being configured as an SCPAC any longer.

[0165] However, the condReconfigToRemoveList-r16 exists in the conditional Reconfiguration field. The conditional Reconfiguration field cannot be included together when the RRCReconfiguration message includes the reconfigurationWithSync field of MCG or the reconfigurationWithSync field of SCG. That is, the conditionalReconfiguration field cannot be included in a command for handover (HO) or PSCell change of MCG or SCG. Accordingly, in order for the network to delete (or erase) the SCPAC configuration, the only methods are to issue a command to erase the SCPAC configuration before or after the RRCREconfiguration message indicating HO or PSCell change.

[0166] FIG. 7 is a diagram illustrating a method for canceling subsequent conditional PSCell addition and change in case of inter-MN handover according to an embodiment of the present disclosure.

[0167] Referring to Figure 7, in the case of inter-MN handover, it is a diagram illustrating a case where SCPAC is released before HO preparation or after that.

[0168] In the case of Fig. 7, it is assumed that there is an Inter-MN PCell change. After the source-master node (S-MN) and the source-secondary node (S-SN) establish (or configure) dual connection (or dual connectivity), if SCPAC settings are prepared, and after transmitting the SCPAC settings to the terminal, the S-MN can decide to handover (HO) to a specific target PCell.

[0169] More specifically, the terminal can set up dual connectivity (DC) with the S-MN and the S-SN (SN1), and the S-MN can transmit an RRCReconfiguration message including SCPAC configuration information to the terminal. Thereafter, the terminal can transmit an RRCReconfigurationcomplete message to the S-MN.

[0170] As in case A, there may be a case where the final admission control fails during the handover preparation process after the S-MN releases SCPAC (or SCPAC configuration). In this case, the UE may unnecessarily delete (or erase) the SCPAC configuration even though it cannot move to the target PCell, which may cause a problem in that SCPAC operation cannot be performed.

[0171] More specifically, the S-MN may transmit an RRCReconfiguration message including SCPAC configuration release information to the UE in order to release SCPAC (or SCPAC configuration). The UE may transmit an RRCReconfigcomplete message to the S-MN. Thereafter, the S-MN may prepare for handover to the T-MN, and during the process, the final admission control may fail.

[0172] Or, as in Case B, if admission is made after HO preparation, when the SCPAC release is performed, when the release command message is transmitted and the corresponding complete message is received, a link failure, etc. may occur. This may be a problem when it is assumed that the HO preparation procedure is an immediate operation up to the order of transmitting the HOcommand.

[0173] In particular, a timer may be started in the target master-node (T-MN) to measure the time from when the HO request ack is transmitted until the terminal connects to the T-MN. Since the timer is set to a relatively short time, the delay in transmitting other RRC messages and the resulting failure before transmitting the HO command may result in unnecessary time for maintaining allocated resources in the T-MN.

[0174] More specifically, the S-MN can transmit a handover request message (HO request message) to the T-MN. The T-MN can perform admission control, and if admission is permitted, the T-MN can then transmit a HO request acknowledgment message including a HO command to the S-MN.

[0175] Afterwards, the S-MN can transmit an RRCReconfiguration message including an SCPAC configuration release to the terminal, and the terminal can transmit an RRCReconfiguration complete message to the S-MN. During this process, a link failure, etc. may occur.

[0176] In this case, a timer may be run in the T-MN to measure until the terminal connects to the T-MN, and the delay time due to the RRCReconfiguration transmission failure may result in unnecessary time for maintaining allocated resources in the T-MN.

[0177] In another case, after the HO command, the T-MN can issue a command to release the SCPAC configuration. In this case, the UE performs the HO, connects to the target PCell, and maintains SCPAC until a separate RRCReconfiguration message containing the release command is received. Therefore, there is a problem that invalid SCPAC configurations are maintained for a period of time.

[0178] FIG. 8a is a diagram illustrating a signal structure when a network transmits subsequent conditional PSCell addition and change (SCPAC) settings to a terminal according to an embodiment of the present disclosure.

[0179] Referring to FIG. 8a, subsequent conditional PSCell addition and change (SCPAC) configuration (or configuration information, or configuration) may be conveyed via a radio resource control (RRC) reconfiguration message (e.g., RRCReconfiguration) in MN format. The RRC reconfiguration message may include (or have) a conditional Reconfiguration field. The conditional Reconfiguration field may be associated with at least one of the following information for one target PSCell.

[0180] - ID of the above setting (condReconfig Id),

[0181] - target PSCell configuration (condRRCReconfig),

[0182] - Condition information required to move to the target cell at the time of setting (initial cond)

[0183] - A collection of condition information lists for performing SCPAC, i.e., subsequent movement from another SCPAC candidate cell to the target PSCell (SCPAC configuration)

[0184] A terminal that receives the above information can evaluate the conditions within the SCPAC configuration when moving between SCPAC candidate cells, and can move to an SCPAC candidate cell that satisfies the conditions.

[0185] The release (or release) operation of an SCPAC configuration as referred to herein may include the release of all elements indicated by the ID. Alternatively, the release of an SCPAC configuration may also mean the release of only the subsequent movement condition list named SCPAC configuration.

[0186] When performing SCPAC release using the opt 1 and 2 methods mentioned in this specification, all elements indicated by ID are released, and all related information of the SCPAC candidate cell is erased. On the other hand, when only the list of subsequent movement conditions named SCPAC configuration is released, the configuration and initial conditions of the candidate cell may remain. In this case, there is a difference that the terminal can still perform a one-time conditional PCell change (CPC) or conditional PCell addition (CPA) operation.

[0187] FIG. 8b is a diagram illustrating a sequence in which a terminal according to the prior art applies a radio resource control (RRC) reset message.

[0188] Referring to FIG. 8b, the application of the RRCReconfiguration message indicating the HO command or PSCell change at the terminal may be as follows.

[0189] More specifically, when the terminal receives RRCReconfiguration,

[0190] - You can apply master cell group (MCG) settings (or apply reconfigWithSync).

[0191] - You can apply secondary cell group (SCG) settings (SCG configuration).

[0192] - Radio bearer settings (RB configuration) and measurement configuration settings (measConfig) can be applied.

[0193] - You can apply the settings of the Conditional Reconfiguration field.

[0194] - You can create an RRCReconfigurationComplete message and deliver it to the lower layer.

[0195] - Random access (RA) can be performed.

[0196] - If the MCG includes the reconfigurationWithSync field, the system information block 1 (SIB1) of the target PCell can be received (or read) to obtain the necessary information.

[0197] - If the MCG has a reconfigurationWithSync field, or if there is a conditional PSCell addition and change (CPAC) configuration and the SCG contains a reconfigurationWithSync field, all entry information in VarcondReconfig of the MCG and SCG are deleted (or erased). All elements of the measurement configuration for condition information associated with the above entry are deleted.

[0198] The above-described operation is a legacy operation that does not consider SCPAC. In the final step of SCPAC's running CR, which is to erase all entry information and delete (or erase) the measurement settings of the associated condition information, the entry and condition information associated with SCPAC are maintained without being erased.

[0199] According to one embodiment of the present disclosure, assuming that the above-mentioned selective release already exists as an operation of the terminal, we propose an operation in which the network additionally deletes (or erases) information on conditions associated with the remaining SCPAC config. More specifically, the method proposed in the present disclosure is as follows. If the removal of the SCPAC configuration is included together with a message instructing the performance of a mobility operation (e.g., a handover command and / or a PSCell change message), the terminal can operate ideally. Accordingly, for mobility cases, it is necessary to include the release of the SCPAC configuration in the RRC message instructing the mobility operation, and we propose a solution in the direction of resolving the current operational problems therefor.

[0200] Here, HO command may mean that the RRCReconfiguration message includes the reconfigurationWithSync field in the master cell group configuration. PSCell change message / command may mean that the RRCReconfiguration message includes the reconfigurationWithsync field in the secondary cell group configuration.

[0201] FIG. 9 is a diagram illustrating a signal structure related to subsequent conditional PSCell addition and change (SCPAC) according to one embodiment of the present disclosure.

[0202] The entry mentioned in the present disclosure may correspond to one of the condReconfigToAddMod IEs of the above drawing. In addition, among these entries, the subsequentCondReconfig IE referred to as the SCPAC setting includes only condition information used when performing SCPAC, and the condReconfigToAddMod including the subsequentCondReconfig IE is an entry that includes a candidate cell capable of performing SCPAC as a target cell.

[0203] subsequentCondReconfig may contain (or may exist) command IEs that can add or delete (or clear) specific condition information. For example, a command IE that can add specific condition information may be condExecutionCondToAddModList, and a command IE that can clear specific condition information may be condExecutionCondToReleaseList.

[0204] Opt 1. The HO command and / or the Pscell change command may include a Conditional Reconfiguration field. The conditional reconfiguration may include a release directive for the SCPAC configuration or a directive to release all remaining conditional reconfiguration entries.

[0205] Opt 2. The HOcommand and / or PSCell change command may include a release directive for SCPAC configuration or a directive to release all remaining conditional reconfiguration entries in areas other than the Conditional Reconfiguration field.

[0206] For Opt 1, the conditional Reconfiguration field included in the HO command and / or PSCell change command may include a command to release an entry for a specific target cell previously set to the terminal, i.e., an entry corresponding to a specific condReconfig Id, i.e., condReconfigToremovelist. This will be specifically described as Opt 1-1 and Opt 1-2 below.

[0207] Opt 1-1. In the above case, more specifically, the list (condReconfigToRemoveList) may include an entry indicated by a condReconfig Id assigned to a target cell used as an SCPAC candidate cell among entries for each target cell of the conditional reconfiguration set in the terminal. When this information is transmitted to the terminal, the terminal may perform an operation of applying the RRCReconfiguration (HO command and / or PSCell change command) and simultaneously delete (or erase) at least one or more of the information of the entry indicated by the corresponding id (e.g., initial condition, target PSCell configuration, list of condition information to be applied when moving from this target PSCell to another SCPAC candidate PSCell). In this case, the release may be performed on conditional Reconfiguration ids currently stored in the master cell group (MCG) and / or secondary cell group (SCG) Variable of the terminal.

[0208] Opt 1-2. In another embodiment, the condReconfigToremoveList should individually indicate the id of each entry, but instead of individually indicating the id of each entry, it can delete (or erase) all conditional reconfiguration setting information stored in the MCG and / or SCG UE variable of the current terminal through a single directive. In other words, it is a command to erase the settings corresponding to all remaining condReconfig Id without having to indicate the id.

[0209] In the case of the above opt 1, the configuration information on the conditional Reconfiguration variable of the terminal is deleted (or erased), and the measurement configuration information corresponding to the "conditions" of the condReconfig Ids to be deleted (or erased) must be additionally deleted (or erased). The above deletion (or erasing) operation is to delete (or erase) from the measConfiguration UE variable of the MCG and / or SCG maintained by the terminal. For the measid associated with each condReconfig id to be released, if the reportConfig constituting each corresponding measId is of the condition type of conditional mobility, the corresponding reportConfig is deleted (or erased). In addition, if the measObj constituting the measId is used only for the conditional purpose of conditional mobility, the corresponding measObj is also deleted (or erased). In addition, each measId can also be deleted (or erased).

[0210] In order to create the terminal signaling system of the aforementioned opt 1, a signaling system between the source-master node (S-MN) and the target-master node (T-MN) is also required.

[0211] For Opt 1, since the release indicator is included in the HO command, it must be included when the RRCReconfiguration message (HO command) is written by the target gNB, i.e., the central unit (CU) of the target PCell. Accordingly, the subject of writing is the T-MN, but the decision on this action can be made (or issued) by the S-MN and / or by the T-MN.

[0212] First, the T-MN can decide to release the SCPAC configuration. For example, if the HO Request message it received is from another S-MN, and / or if the T-MN has the SCPAC configuration stored (or has) in the current terminal and the context associated with other candidate SNs and can still use it, the T-MN can decide to release it.

[0213] Alternatively, the S-MN may directly instruct SCPAC configuration release. The S-MN may already recognize that the HO request message is being transmitted to a T-MN, i.e., an inter-MN. Therefore, when the S-MN itself transmits an HORequest message or an Xn message with an equivalent role to the T-MN, it may include an instruction to add an SCPAC release indication to the HO command. The T-MN, which has received the instruction to add the SCPAC release indication, may create (or write) an HO command by including the indications of opt 1-1 and 1-2 in the conditional Reconfiguration field when writing the HO command, and may then forward the HO command to the MN. Thereafter, the HO command may be delivered to the terminal, and the terminal may perform SCPAC config release.

[0214] In case of SCG change, the S-SN may include an instruction to T-SN to release SCPAC settings on SCG as needed in the Xn message requesting PSCell change (e.g., SNAddRequest message). After the T-SN receives the instruction to release SCPAC settings on SCG, the T-SN may include the instruction of opt 1-1,1-2 in the PSCell change command.

[0215] In case of intra-MN HO, intra-SN PSCell change, the indicator in the above Xn message is not required.

[0216] When including the above directive, in the case of opt 1-1, the condReconfig Id value of the release target may be included. When receiving the condReconfig Id value of the release target, the T-MN and / or SN may include the corresponding id in the release target and write the HO command and / or PSCell change command.

[0217] In case of Opt 1, if conditional Reconfiguration includes release indicators of opt 1-1, 1-2, the terminals support SCPAC, and can release only the SCPAC configuration (i.e., only the condReconfig Id associated with the SCPAC configuration).

[0218] For opt 1, the information contained in the conditional Reconfiguration field can only include condReconfigTorelease.

[0219] Other information may be included. For example, at least one of the following information may be included:

[0220] - attamptCondReconfig: In case of MCG failure, an instruction to select one of the CHO candidate PCells and perform CHO.

[0221] - condReconfigToAddModList: CHO / CPC target cell settings and condition information used at that time, condReconfig Id information

[0222] ■ Target spcell config entered for each ID above

[0223] ■ SCPAC config: List of conditions to be applied to the target cell of the above ID

[0224] - scpac-ReferenceConfiguration: Reference configuration that serves as the basis for setting the target cell of the SCPAC.

[0225] - servingSecurityCellSetId: ID assigned to each candidate PSCell required for SCPAC operation

[0226] - sk-counterconfiguration: sk-counter values ​​required for SCPAC operation.

[0227] When the above information is entered, the T-MN can perform addition, modification, and release on the current conditional Reconfiguration settings stored in the terminal.

[0228] The target of the above addition is a setting based on the target cell (target PCell / target PSCell) of the T-MN / SN compared to the settings currently stored in the terminal. In other words, these may be settings required when moving from the target cell to another PCell / PSCell.

[0229] For Opt 2, the HO command and / or PSCell change command may include an SCPAC configuration release directive outside the conditionalReconfiguration field or a directive to release all remaining conditional reconfiguration entries. This is described in detail in Opt 2-1 and Opt 2-2 below.

[0230] For Opt 2, there is no need to depend on the constraints of the conditional Reconfiguration field.

[0231] Opt 2-1. A 1-bit indicator may be included in the RRCReconfiguration field regardless of the MCG and / or SCG settings. When the terminal receives the indicator, it may perform at least one of the following actions.

[0232] - remove All the remaining entry or all the entry with the target cell configuration of SCPAC candidate cells in VarConditionalReconfig in either MCG or SCG or both MCG and SCG

[0233] - For each abovementioned entry's condition info (measId) of the MCG measConfig, and for each measId of the SCG mesaConfig,

[0234] ■ if the associated reportConfig has a reportType set to condTriggerConfig, remove the entry with the matching reportconfig Id from the reportConfig list within the VarMeasConfig

[0235] ■ If the associated measObjectId is only associated to a reportconfig with reporttype set to condTriggerConfig, remove the entry with the matching measObjectId from the measObjectList within the VarMeasConfig

[0236] ■ Remove the entry with the matching measId from the measIdList within VarMeasConfig

[0237] In the above case, instead of a 1-bit indication, a list of condReconfig Ids to be deleted (or erased) may be specified. A terminal that receives (or has received) the condReconfig Id to be deleted (or erased) can delete (or erase) the entry of the indicated id.

[0238] Opt 2-2. 1 bit indicator per each CG operation. That is, a separate indicator can be transmitted for each MCG and / or SCG. The UE receiving this can separately perform the following actions for the indicated CG: delete (or erase) all remaining entries in the UE variable or entries containing SCPAC settings, as in opt 2-1, or erase reportConfig, measObj, or measId in the measConfig variable. Accordingly, the location of the indicator can be included in each MCG and / or SCG cell group configuration in the RRCReconfiguration. Otherwise, it is necessary to distinguish between CGs.

[0239] - remove all the entry or all the entry with the target cell configuration of SCPAC candidate cells in VarConditionalReconfig in indicated CG

[0240] - For each abovementioned measId of the indicated CG's measConfig,

[0241] ■ if the associated reportConfig has a reportType set to condTriggerConfig, remove the entry with the matching reportconfig Id from the reportConfig list within the corresponding CG's VarMeasConfig

[0242] ■ If the associated measObjectId is only associated to a reportconfig with reporttype set to condTriggerConfig, remove the entry with the matching measObjectId from the measObjectList within the corresponding CG's VarMeasConfig

[0243] ■ Remove the entry with the matching measId from the measIdList within corresponding CG's VarMeasConfig

[0244] In the case of the above opt 2, as in opt 1, the target of deletion (or erasure) can be any condReconfig entry. Or, depending on the definition, it can be any condReconfiguration entry associated with SCPAC config.

[0245] In the above case, instead of a 1-bit indication, a list of condReconfig IDs to be deleted (or erased) may be specified. A terminal that receives (or has received) the above information can delete (or erase) the entry of the indicated ID.

[0246] For Opt 2 versus Opt 1, you can delete (or clear) conditional Reconfiguration settings, including SCPAC config, with a single directive. At the same time, you can also delete (or clear) measurement components used as associated conditions.

[0247] Similar to opt 1, either the S-MN or the T-MN can decide which node issues (or initiates) the release instruction. If the S-MN decides, or if the T-MN decides, the required Xn signals can be applied equally.

[0248] Also, instead of just deleting (or erasing) the SCPAC configuration, you can delete (or erase) all condReconfigs. If an id is given, you can delete (or erase) the condReconfigs corresponding to that id.

[0249] Alternatively, the release indicator and id may be included in the Xn message (or given). Upon receiving the message, the T-MN and / or T-SN may include the corresponding release information in the HO command, PSCell change command.

[0250] In case of intra-MN Pcell HO or intra-SN PSCell change, the above release indicator may be included without the Xn message.

[0251] Additionally, according to one embodiment of the present disclosure, only the SCPAC conditions associated with the entry may be deleted. More specifically, unlike the operation of deleting the entry associated with the SCPAC settings, an operation of deleting only the SCPAC conditions associated with the entry may be possible. In this case, the field / IE used is not condReconfigToRemove, but rather, by adding (or filling in) the IDs of the conditions existing in all terminals to the field for deleting conditions among the SCPAC settings in the entry (e.g., the condExecutionCondToReleaseList field), deleting all SCPAC condition information may mean deleting (or erasing) the entry that has the SCPAC settings.

[0252] This method can be an alternative to using condReconfigToReleaseList of opt 1. That is, if the condExecutionCondToReleaseList includes the IDs of all SCPAC condition information configured for the corresponding target PSCell in the subsequentCondReconfig field of the entries associated with each SCPAC configuration in the conditional Reconfiguration of the HO command and / or the PSCell change command, the terminal can delete (or erase) all conditions corresponding to the IDs. If there is no more condition information for the corresponding SCPAC operation, the terminal can erase the entry of the corresponding SCPAC configuration.

[0253] FIG. 10 is a flowchart illustrating a sequence of a subsequent conditional PSCell addition and change (SCPAC) setup release procedure in the case of inter master node (MN) handover according to one embodiment of the present disclosure.

[0254] Referring to Fig. 10, an example is shown for inter MN normal HO (PCell change).

[0255] First, the UE may be in a dual connection (or dual connectivity, DC) situation with the source-master node (S-MN) and the source-secondary node (S-SN). (MR DC configured) In a situation where the UE is configuring a dual connection through the base station MN and SN, it can perform subsequent conditional PSCell addition and change (SCPAC) preparation operations.

[0256] The above SCPAC preparation may include the following contents.

[0257] An SN (e.g., SN1) can request resource allocation for SCPAC to other SNs (which may be called "candidate SNs", e.g., SN2, SN3, ...). For this purpose, the S-SN can transmit necessary information to the MN. The necessary information may include information indicating proposed candidate PSCells for each of the candidate SNs, measurement result information for the corresponding PSCell, and initial condition information for moving from the SN's current PSCell to the candidate PSCells.

[0258] The MN can receive the above information from the S-SN and transmit the above information by applying the SNAddition procedure to each candidate SN.

[0259] Each candidate SN can transmit its proposed candidate PSCell and measurement results for that cell. It can also transmit proposed candidate PSCell information for other candidate SNs.

[0260] Each candidate SN that receives this information can determine a PSCell to which SCPAC resources will be allocated from its proposed PSCells and include the information about that cell in the SNADDReqACK message to the MN. Furthermore, the SN can also convey condition information to be used when moving from the determined PSCell to at least one other candidate PSCell.

[0261] The MN that has received the above information can link target settings for at least one PSCell determined above and condition information required for moving from the target cell to another SCPAC candidate cell, and can transmit the information to the terminal as SCPAC configuration.

[0262] The above series of procedures can be viewed as SCPAC preparation.

[0263] Thereafter, the S-MN can transmit SCPAC settings (SCAPC configuration) to the terminal via an RRCReconfiguration message. More specifically, the S-MN can transmit an RRCReconfiguration message including the SCPAC configuration to the terminal, and the terminal can transmit an RRCReconfigurationComplete message to the S-MN.

[0264] After receiving the SCPAC settings, the terminal can perform measurement and condition evaluation operations. Then, if certain conditions are met, the terminal can move to the corresponding candidate PSCell.

[0265] At this time, SCPAC settings can be maintained in the terminal. Even after moving to a PSCell, the terminal can continue to perform SCPAC operations using the necessary condition information and target cell configuration information within the same SCPAC settings.

[0266] Afterwards, the S-MN can decide to handover (HO) to a specific target PCell of the target-master node (T-MN). (HO determined)

[0267] The S-MN may transmit a handover request message (HO request message) to the T-MN. More specifically, as a preparatory action for the handover, the S-MN may transmit a HO request message to the T-MN. The HO request message may include and transmit at least one of the master cell group (MCG), secondary cell group (SCG) configuration (config), radio resource management (RRM) configuration, RRC context, and other various current configuration information currently set for the terminal.

[0268] Additionally, the S-MN may include an indicator indicating SCPAC release. This indicator may be included in the Xn field of the HandoverRequest message or in an RRC inter node message therein. The T-MN receiving the above message may include (or add) the SCPAC release indicator when generating (or writing) the HO command message. That is, in this case, the MN has decided to remove the SCPAC configuration.

[0269] Alternatively, the T-MN can decide to release itself. If the HO request message received by the T-MN is from a different gNB, the T-MN recognizes that the HO is an inter-MN HO and can decide to remove the SCPAC configuration and add (or append) the SCPAC release indicator directly.

[0270] In the above operation, the operation according to opt 1 and opt 2 may be as follows. First, in the case of opt 1, the conditional Reconfiguration field of the Ho command may include a release indicator (or appended) and a setting to remove components of the measurement configuration, i.e., conditional information linked to the SCPAC setting mentioned in opt 1, in the measurement configuration to be applied in the target PSCell. In the case of opt 2, the release indicator may be included in the HO command, but may be set outside the conditional Reconfiguration field.

[0271] The HO command thus generated (or created) can be transmitted to the S-MN. Thereafter, the S-MN can transmit the HO command to the terminal. More specifically, the T-MN can transmit an HO request acknowledgment message containing the HO command to the S-MN. Thereafter, the S-MN can transmit an RRCReconfiguration message containing the HO command to the terminal.

[0272] In the operation of applying the HO command received by the terminal, the steps of Fig. 8 can be applied. In the step of applying cond Reconfiguration, in case of opt 1, all entries of SCPAC config can be deleted (or erased) according to the release indicator, or the entry corresponding to the condReconfig Id indicated by the release indicator can be deleted (or erased). Additionally, elements of measConfig corresponding to the conditions associated with the above entries can be deleted (or erased) in the subsequent measConfig application step.

[0273] For Opt 2, since there is no existing conditional reconfiguration procedure, a new procedure can be added. Possibly, it can be performed in the order of the conditional reconfiguration procedure described above. Alternatively, it can be added before or at the very end, i.e., after the step of deleting all entries except those related to SCPAC settings in varCondReconfig of the MCG / SCG. (Or, it can be added.)

[0274] The terminal that receives the HO command can delete (or erase) the SCPAC configuration information within the conditional Reconfiguration in case of opt 1, and can also erase the meas configuration component associated with the SCPAC config according to the given measurement configuration.

[0275] For Opt 2, the terminal can see the release indicator and delete (or erase) the SCPAC configuration. In addition, the terminal can erase the meas configuration component associated with the SCPAC config without a separate measurement configuration instruction.

[0276] After the above operation, the terminal can perform random access while moving to the target PCell. (RACH operation)

[0277] After receiving (or having received) a UL grant from the target cell, the UE can terminate the handover procedure (or complete the HO) by sending an RRCReconfigurationComplete message to the target cell.

[0278] FIG. 11 is a flowchart illustrating a sequence of a subsequent conditional PSCell addition and change (SCPAC) setup release procedure of an intra master node (MN) PCell handover procedure according to one embodiment of the present disclosure.

[0279] More specifically, Fig. 11 is a diagram for explaining a case of PCell handover of an intra-master node (intra-MN). In the case of PCell handover of an intra-master node (intra-MN), the source-master node (S-MN) can determine on its own and, if necessary, add (or append) release indicators of opt 1 and / or opt 2 to create a HO command and transmit it to the terminal.

[0280] Referring to FIG. 11, first, the terminal may be in a dual connection (or dual connectivity, DC) situation with a source-master node (S-MN) and a source-secondary node (S-SN). (MR DC configured) In a situation where the terminal is configuring a dual connection through the base station MN and SN, it may perform a subsequent conditional PSCell addition and change (SCPAC) preparation operation.

[0281] The above SCPAC preparation may include the following contents.

[0282] An SN (e.g., SN1) can request resource allocation for SCPAC to other SNs (which may be called "candidate SNs", e.g., SN2, SN3, ...). For this purpose, it can transmit necessary information to the MN. The information may include information indicating proposed candidate PSCells for each of the candidate SNs, measurement result information for the corresponding PSCell, and initial condition information for moving from the SN's current PSCell to the candidate PSCells.

[0283] The MN can receive the above information from the S-SN and transmit the above information by applying the SNAddition procedure to each candidate SN.

[0284] Each candidate SN can transmit its proposed candidate PSCell and measurement results for that cell. It can also transmit proposed candidate PSCell information for other candidate SNs.

[0285] Each candidate SN that receives this information can determine a PSCell to which SCPAC resources will be allocated from its proposed PSCells and include the information about that cell in the SNADDReqACK message to the MN. Furthermore, the SN can also convey condition information to be used when moving from the determined PSCell to at least one other candidate PSCell.

[0286] The MN that has received the above information can link target settings for at least one PSCell determined above and condition information required for moving from the target cell to another SCPAC candidate cell, and can transmit the information to the terminal as SCPAC configuration.

[0287] The above series of procedures can be viewed as SCPAC preparation.

[0288] Thereafter, the S-MN can transmit SCPAC settings (SCAPC configuration) to the terminal via an RRCReconfiguration message. More specifically, the S-MN can transmit an RRCReconfiguration message including the SCPAC configuration to the terminal, and the terminal can transmit an RRCReconfigurationComplete message to the S-MN.

[0289] After receiving the SCPAC settings, the terminal can perform measurement and condition evaluation operations. Then, if certain conditions are met, the terminal can move to the corresponding candidate PSCell.

[0290] At this time, SCPAC settings can be maintained in the terminal. Even after moving to a PSCell, the terminal can continue to perform SCPAC operations using the necessary condition information and target cell configuration information within the same SCPAC settings.

[0291] Afterwards, the S-MN can decide on handover (HO). (HO determined)

[0292] The above S-MN can generate a handover command including a release indicator.

[0293] In the above operation, the operation according to opt 1 and opt 2 may be as follows. First, in the case of opt 1, the conditional Reconfiguration field of the Ho command may include a release indicator (or appended) and a setting to remove components of the measurement configuration, i.e., conditional information linked to the SCPAC setting mentioned in opt 1, in the measurement configuration to be applied in the target PSCell. In the case of opt 2, the release indicator may be included in the HO command, but may be set outside the conditional Reconfiguration field.

[0294] Thereafter, the S-MN can transmit a HO command including a release indicator to the terminal.

[0295] In the operation of applying the HO command received by the terminal, the steps of Fig. 8 can be applied. In the step of applying cond Reconfiguration, in case of opt 1, all entries of SCPAC config can be deleted (or erased) according to the release indicator, or the entry corresponding to the condReconfig Id indicated by the release indicator can be deleted (or erased). Additionally, elements of measConfig corresponding to the conditions associated with the above entries can be deleted (or erased) in the subsequent measConfig application step.

[0296] For Opt 2, since there is no existing conditional reconfiguration procedure, a new procedure can be added. Possibly, it can be performed in the order of the conditional reconfiguration procedure described above. Alternatively, it can be added before or at the very end, i.e., after the step of deleting all entries except those related to SCPAC settings in varCondReconfig of the MCG / SCG. (Or, it can be added.)

[0297] The terminal that receives the HO command can delete (or erase) the SCPAC configuration information within the conditional Reconfiguration in case of opt 1, and can also erase the meas configuration component associated with the SCPAC config according to the given measurement configuration.

[0298] For Opt 2, the terminal can see the release indicator and delete (or erase) the SCPAC configuration. In addition, the terminal can erase the meas configuration component associated with the SCPAC config without a separate measurement configuration instruction.

[0299] After the above operation, the terminal can perform random access while moving to the PCell of the intra-master node (intra-MN). (RACH operation)

[0300] After receiving (or having received) a UL grant from the target cell, the UE can terminate the handover procedure (or complete the HO) by sending an RRCReconfigurationComplete message to the target PCell of the intra-master node (intra-MN).

[0301] FIG. 12 is a flowchart illustrating a sequence of a subsequent conditional PSCell addition and change (SCPAC) configuration release procedure in a secondary cell group (SCG) release according to one embodiment of the present disclosure.

[0302] In the case of a secondary cell group (SCG) release, subsequent conditional PSCell addition and change (SCPA) configurations may be required even in the absence of an SCG. For example, a UE may perform a conditional PSCell addition (CPA), in which case SCPAC configurations may be used. In such cases, the UE needs to maintain (or retain) the corresponding configurations. This will be described in detail below.

[0303] Referring to FIG. 12, first, the terminal may be in a dual connection (or dual connectivity, DC) situation with a source-master node (S-MN) and a source-secondary node (S-SN). (MR DC configured) In a situation where the terminal is configuring a dual connection through the base station MN and SN, it may perform a subsequent conditional PSCell addition and change (SCPAC) preparation operation.

[0304] The above SCPAC preparation may include the following contents.

[0305] An SN (e.g., SN1) can request resource allocation for SCPAC to other SNs (which may be called "candidate SNs", e.g., SN2, SN3, ...). For this purpose, it can transmit necessary information to the MN. The information may include information indicating proposed candidate PSCells for each of the candidate SNs, measurement result information for the corresponding PSCell, and initial condition information for moving from the SN's current PSCell to the candidate PSCells.

[0306] The MN can receive the above information from the S-SN and transmit the above information by applying the SNAddition procedure to each candidate SN.

[0307] Each candidate SN can transmit its proposed candidate PSCell and measurement results for that cell. It can also transmit proposed candidate PSCell information for other candidate SNs.

[0308] Each candidate SN that receives this information can determine a PSCell to which SCPAC resources will be allocated from its proposed PSCells and include the information about that cell in the SNADDReqACK message to the MN. Furthermore, the SN can also convey condition information to be used when moving from the determined PSCell to at least one other candidate PSCell.

[0309] The MN that has received the above information can link target settings for at least one PSCell determined above and condition information required for moving from the target cell to another SCPAC candidate cell, and can transmit the information to the terminal as SCPAC configuration.

[0310] The above series of procedures can be viewed as SCPAC preparation.

[0311] Thereafter, the S-MN can transmit SCPAC settings (SCAPC configuration) to the terminal via an RRCReconfiguration message. More specifically, the S-MN can transmit an RRCReconfiguration message including the SCPAC configuration to the terminal, and the terminal can transmit an RRCReconfigurationComplete message to the S-MN.

[0312] After receiving the SCPAC settings, the terminal can perform measurement and condition evaluation operations. Then, if certain conditions are met, the terminal can move to the corresponding candidate PSCell.

[0313] At this time, SCPAC settings can be maintained in the terminal. Even after moving to a PSCell, the terminal can continue to perform SCPAC operations using the necessary condition information and target cell configuration information within the same SCPAC settings.

[0314] Afterwards, the S-MN can decide to release the secondary cell group (SCG). (SCG release determine)

[0315] The S-MN may transmit an RRCReconfiguration message including an indicator (or indicator) indicating MR-DC release and SCPAC release to the UE. More specifically, the MN may transmit the release indicator to the UE by using the method of opt 1 or opt 2 in the RRCReconfiguration including the SCG release indicator (or MR-DC release indicator). In this case, since there is currently no restriction on whether or not a conditional Reconfiguration message can be included in the RRCReconfiguration message indicating SCG release, there is no need to consider a separate network configuration restriction in the case of Opt 1.

[0316] When a terminal receives an RRCReconfiguration message indicating SCG release, the terminal can perform the following actions in the following order.

[0317] - You can delete (or erase) SCG measurement configurations except for measId, reportconfiguration, and measurement object specified by conditions in SCPAC settings in SCG meas configuration.

[0318] - In the conditionalReconfig variable of SCG, you can delete (or erase) all entries except the condReconfig entries that are linked to the SCPAC settings.

[0319] - In the conditionalReconfiguration variable of MCG, you can delete (or erase) all cond Reconfiguration entries that do not include reconfigurationWithSync in the MCG part settings, except for the condReconfig entries that are linked to the SCPAC settings.

[0320] In the case of Opt 1, in the conditional reconfiguration application operation of Fig. 8, among the SCPAC setting removal methods described above, the release method of Opt 1 can be performed. Thereafter, the above operation can be performed.

[0321] For Opt 2, after or before the above actions, the network must be able to (additionally) clear the condReconfig entry associated with the SCPAC settings, at its discretion.

[0322] In case of a normal PSCell change, according to the current running CR, all entries in the conditional Reconfig variable except for the SCPAC configuration link entries in the master cell group (MCG) and / or secondary cell group (SCG) are deleted, and also the reportconfig, measurement object, and measId information used in the conditions corresponding to the above entries can be deleted (or are set to be deleted) from the measurement configuration variable.

[0323] Accordingly, if the above reconfigurationWithSync is included in the SCG cell group configuration (and conditional PSCell addition (CPA) / conditional PScell ​​change (CPC) / SCPAC configuration has been previously configured), the release can be included in the above message using the opt 1 / opt 2 method and delivered to the terminal.

[0324] FIG. 13 is a flowchart illustrating a sequence of a subsequent conditional PSCell addition and change (SCPAC) setup release procedure in a conditional handover (CHO) recovery procedure according to one embodiment of the present disclosure.

[0325] For conditional handover (CHO) recovery, the basic operation is similar to PCell change.

[0326] However, the difference from PCell change is as follows. During the CHO preparation process for a CHO candidate cell, whether the CHO target cell is an inter-MN CHO is considered, and if it is an inter-MN CHO, a release indicator can be included and transmitted to the target MN. At this time, the HO Request message can contain the CHO preparation / initiation indicator along with the SCPAC release indicator. Of course, the ID of the cond Reconfig entry linked to the SCPAC config to be deleted can be included in the HO request message along with the release indicator, just like the method of opt 1 and 2.

[0327] The specific operations proposed in this disclosure are as follows.

[0328] First, the UE may be in a dual connection (or dual connectivity, DC) situation with the source-master node (S-MN) and the source-secondary node (S-SN). (MR DC configured) In a situation where the UE has configured a dual connection through the base station MN and SN, it can perform subsequent conditional PSCell addition and change (SCPAC) preparation operations.

[0329] The above SCPAC preparation may include the following contents.

[0330] An SN (e.g., SN1) can request resource allocation for SCPAC to other SNs (which may be called "candidate SNs", e.g., SN2, SN3, ...). For this purpose, the S-SN can transmit necessary information to the MN. The necessary information may include information indicating proposed candidate PSCells for each of the candidate SNs, measurement result information for the corresponding PSCell, and initial condition information for moving from the SN's current PSCell to the candidate PSCells.

[0331] The MN can receive the above information from the S-SN and transmit the above information by applying the SNAddition procedure to each candidate SN.

[0332] Each candidate SN can transmit its proposed candidate PSCell and measurement results for that cell. It can also transmit proposed candidate PSCell information for other candidate SNs.

[0333] Each candidate SN that receives this information can determine a PSCell to which SCPAC resources will be allocated from its proposed PSCells and include the information about that cell in the SNADDReqACK message to the MN. Furthermore, the SN can also convey condition information to be used when moving from the determined PSCell to at least one other candidate PSCell.

[0334] The MN that has received the above information can link target settings for at least one PSCell determined above and condition information required for moving from the target cell to another SCPAC candidate cell, and can transmit the information to the terminal as SCPAC configuration.

[0335] The above series of procedures can be viewed as SCPAC preparation.

[0336] Thereafter, the S-MN can transmit SCPAC settings (SCAPC configuration) to the terminal via an RRCReconfiguration message. More specifically, the S-MN can transmit an RRCReconfiguration message including the SCPAC configuration to the terminal, and the terminal can transmit an RRCReconfigurationComplete message to the S-MN.

[0337] After receiving the SCPAC settings, the terminal can perform measurement and condition evaluation operations. Then, if certain conditions are met, the terminal can move to the corresponding candidate PSCell.

[0338] At this time, SCPAC settings can be maintained in the terminal. Even after moving to a PSCell, the terminal can continue to perform SCPAC operations using the necessary condition information and target cell configuration information within the same SCPAC settings.

[0339] Afterwards, the S-MN can decide to handover (HO) to a specific target PCell of the target-master node (T-MN). (HO determined)

[0340] The S-MN may transmit a handover request message (HO request message) to the T-MN. More specifically, as a preparatory action for the handover, the S-MN may transmit a HO request message to the T-MN.

[0341] At this time, the CHO preparation / initiation directive can be transmitted along with the SCPAC release directive in the HO Request message. Of course, in the same way as in opt 1 and 2, the ID of the cond Reconfig entry associated with the specific SCPAC config to be deleted can be included in the HO request message along with the release directive.

[0342] More specifically, the behavior according to opt 1 and opt 2 may be as follows. First, in case of opt 1, the conditional Reconfiguration field of the HO request may include a release indicator, along with a setting to remove components of the measurement configuration, i.e., conditional information linked to the SCPAC setting mentioned in opt 1, from the measurement configuration to be applied in the target PSCell. In case of opt 2, the release indicator may be included in the HO request, but may be set outside the conditional Reconfiguration field.

[0343] A T-MN that receives an HO Request can perform admission control and generate a CHO command containing a release indicator. The CHO command can be identical to the target configuration and can be transmitted to the terminal.

[0344] The CHO command thus generated (or created) can be transmitted to the S-MN. Thereafter, the S-MN can transmit the CHO command to the terminal. More specifically, the T-MN can transmit a HO request acknowledgment message containing the CHO command to the S-MN. Thereafter, the S-MN can transmit an RRCReconfiguration message containing the CHO command to the terminal.

[0345] A terminal that receives a CHO configuration including the above information can store the CHO configuration. It can also perform measurement and evaluation on the condition information included in the configuration. Here, the CHO configuration is identical to the target configuration of the CHO, which can also be identical to the CHO command. The release directive refers to the release directive of the SCPAC configuration, and in this embodiment, it can be included in the CHO configuration or the CHO command.

[0346] If a failure occurs on the MCG, and the selected cell is one of the CHO candidate cells, the condReconfig entry related to SCPAC settings can be deleted in response to opt 1,2 while performing CHO with the selected cell.

[0347] More specifically, if the target configuration includes a release indicator, the terminal may delete (or erase) all entries of SCPAC config according to the release indicator, or delete (or erase) the entry corresponding to the condReconfig Id indicated by the release indicator. Additionally, elements of measConfig corresponding to the conditions associated with the above entries may be deleted (or erased) in a subsequent measConfig application step.

[0348] The terminal receiving the CHO command can delete (or erase) the SCPAC configuration information within the conditional Reconfiguration in case of opt 1, and can also erase the meas configuration component associated with the SCPAC config according to the given measurement configuration.

[0349] For Opt 2, the terminal can see the release indicator and delete (or erase) the SCPAC configuration. In addition, the terminal can erase the meas configuration component associated with the SCPAC config without a separate measurement configuration instruction.

[0350] After the above operation, the terminal can perform random access while moving to the T-MN. (RACH operation)

[0351] After receiving (or having received) a UL grant from the corresponding T-MN, the UE can terminate the conditional handover procedure (or finalize CHO) by sending an RRCReconfigurationComplete message to the target cell.

[0352] According to another embodiment of the present disclosure, in the case of the above failure, when the RRCReconfiguration message of the T-MN, i.e., when the terminal selects a candidate cell of the CHO during cell selection, the target cell configuration message (RRCReconfiguration) of the selected cell may not include a separate SCPAC configuration and a release indicator of related measurement components. In this case, the terminal may perform an operation of excluding the remaining conditional Reconfiguration configuration entries except for the SCPAC configuration from the MCG and / or SCG variable.

[0353] More specifically, the terminal can experience various MCG failures and perform an RRC Reestablishment operation. In this case, if it is set as a recovery indicator using CHO, the terminal can perform an operation of selecting a cell and applying the configuration of the candidate cell if the cell is one of the current CHO candidate cells of the terminal. At this time, among the conditional Reconfiguration entries (cond Reconfig Id, target spcell settings, condition information applied when moving to the target cell, SCPAC settings) stored in the conditional Reconfiguration terminal variables of the MCG and / or SCG of the terminal, entries that do not include SCPAC settings can be deleted (or deleted) in bulk. After that, by the method of opt 1 and / or opt 2, entries indicated by separate Ids can be deleted (or deleted) separately, and this Id can include the ID of the condReconfig entry linked to the SCPAC settings that the network wants to delete (or wants to delete) and can be transmitted to the terminal.

[0354] According to another embodiment of the present disclosure, there may be something related to updating securityCellSetId in a situation of Normal PSCell change.

[0355] When configuring SCPAC, the MN can pre-generate (or generate) multiple sk-counter values ​​and corresponding (or corresponding) security key values ​​for each SN of SCPAC candidate cells and transmit the values ​​for each securityCellSetID to all SNs. In addition, a list of counter values ​​for each SecurityCellSetID can also be configured for the UE. One securityCellSetID is assigned to each SCPAC candidate cell configuration, and the same ID value is assigned to each SN. Whenever the UE performs SCPAC, the UE can compare the securityCellSetId of the current PSCell with the securityCellSetID of the target PSCell, and if the comparison results are not the same, the first counter value associated with the securityCellSetID of the target PSCell is selected as the new counter value. Thereafter, the security key is updated based on the corresponding counter value. In this configuration situation, if the network wants to indicate a normal PSCell change, the following three cases can occur.

[0356] More specifically, the target PSCell may be case 1) not a PSCell served by an SN (SPCAC candidate SN) that is currently configured for SCPAC, case 2) served by an SN that is currently configured for SCPAC but is not one of the SCPAC candidate cells, or case 3) served by an SN that is currently configured for SCPAC and is also one of the SCPAC candidate cells.

[0357] If only a normal PSCell change to one of the SCPAC candidate cells is possible, i.e., the network has implementation constraints to always change (or be able to send) the target of a normal PSCell change to only one of the SCPAC candidate cells, then the above-described cases 1 and 2 do not occur. In this case, the network can still update the servingSecurityCellSetID by explicitly including the securityCellSetId value assigned to the SN to which the target PSCell belongs in the servingSecurityCellSetID field in the normal PSCell change command (i.e., when the RRCReconfiguration message in the MN format includes the reconfigurationwithsync field in the SCG configuration) and transmitting (or signaling) the servingSecurityCellSetID field to the UE. The UE receiving the signal can compare the servingSecurityCellSetID with the servingSecurityCellSetID it currently maintains, and if the comparison results are different, the UE updates the servingSecurityCellSetID variable with the received ID value. Additionally, the terminal can select the first counter value from the counter-security key list associated with the corresponding ID value and update and use the security parameter with the selected counter value.

[0358] If there is no restriction on the target PSCell of the normal PSCell change, case 1, case 2, and case 3 can all occur, and the operation of each case is explained.

[0359] In Case 1, the network can include a new sk-counter value in the normal PSCell change command. In this case, it refers to the shallowest level sk-counter field of RRCReconfiguration, not the conditional Reconfiguration field. The terminal that receives the counter value can use the value to update the security key. In addition, the terminal can release the SCPAC settings. At this time, the release of the SCPAC settings can be performed by the terminal itself or through a release indicator in the conditional Reconfiguration field of the normal PSCell change.

[0360] Case 2. The network may forward the securityCellSetID value assigned to the SN of the corresponding target PSCell through the servingSecurityCellSetID in the normal PSCell change command, or may include a new counter value in the shallowest field. If the terminal receives the new counter value, the terminal may use the value as the new counter and perform a security update. In addition, the terminal may clear the SCPAC configuration. The release may be performed by the terminal itself or through a release directive in the conditional Reconfiguration field of the normal PSCell change.

[0361] If a servingSecurityCellSetID is received, it can be compared with the currently stored servingSecurityCellSetID. If the comparison results are the same, the terminal can use (or write) the current counter value and security key as they are. If the comparison results are not the same, the ID can be updated to servingSecurityCellSetID, the first value in the list of counter values ​​associated with it can be written as the new counter, and the security update can be performed. In addition, the terminal can release the SCPAC configuration. At this time, the release can be performed by the terminal itself or through the release directive in the conditional Reconfiguration field of the normal PSCell change.

[0362] If neither a new counter value nor a securityCellSetID is passed to the normal PSCell change command, the terminal uses (or writes) the current counter value as is and maintains the currently stored servingSecurityCellSetId.

[0363] The above normal PSCell command includes an instruction to clear the SCPAC settings and / or the servingSecurityCellSetID of the target PSCell as a conditional Reconfiguration field. For the above operations, even if the reconfigurationWithSync field is included in the secondary Cell group of the normal PSCell change command, i.e., the RRCReconfiguration message in MN format, the conditional Reconfiguration field may be included in this RRCReconfiguration message.

[0364] For Case 3, the following options are possible.

[0365] Opt 1. The network may not signal the counter value in the shallowest field of the normal PSCell change command, and may include (or insert) the securityCellSetID value assigned to the SN of the corresponding target PSCell in servingSecurityCellSetID. In this case, the terminal may compare the received ID value with the existing servingSecurityCellSetID it has stored, and if the comparison result is the same, the currently used (or written) counter value is used (or written) as is, and a separate security key update is not performed. If the comparison result is that the received ID value is not the same as the existing servingSecurityCellSetID it has stored, the terminal may update the stored ID with the received ID. In addition, the terminal may perform a security key update using the counter value associated with the ID as the sk-counter.

[0366] If the above normal PSCell change command includes the SCPAC execution condition from / to the target PSCell and is transmitted to the terminal, the terminal can maintain the SCPAC configuration as is. However, if the SCPAC execution condition from / to the target PSCell is not included and transmitted (or if the SCPAC execution condition from / to the target PSCell is not transmitted to the terminal), the terminal can release the SCPAC configuration. The terminal can release it itself or through a release directive in the conditional Reconfiguration field of the normal PSCell change. In the case of the above option, if there is no counter value in the shallowest field and there is no separate value in servingSecurityCellSetID, the terminal can use (or write) the currently used (or written) counter value as is, and there may be no need to update servingSecurityCellSetID. In this case, the terminal can maintain the SCPAC configuration as is.

[0367] Opt 2. The network can signal a new counter value in the shallowest field of RRCReconfiguration in the normal PSCell change command. This value can be one of the values ​​assigned to each SN of each existing SCPAC candidate cell. The UE that receives this value can perform a security update using the corresponding counter value. The UE can find the securityCellSetID that includes the counter value (which can be the very first value) and store the corresponding ID as a new servingSecurityCellSetID. If the normal PSCell change command includes and transmits to the UE the SCPAC execution condition from / to the target PSCell, the UE can maintain the SCPAC configuration as is. However, if the normal PSCell change command does not include and transmit the SCPAC execution condition from / to the target PSCell (or if the SCPAC execution condition from / to the target PSCell is not transmitted to the UE), the UE can release the SCPAC configuration. Release can be done by the terminal itself or through a release directive in the conditional Reconfiguration field of a normal PSCell change.

[0368] Cases 1, 2, and 3 described above may be partially or completely acceptable. In each case, the network and terminal may perform actions corresponding to the corresponding case.

[0369] The methods according to the embodiments described in the claims or specification of the present invention may be implemented in the form of hardware, software, or a combination of hardware and software.

[0370] When implemented in software, a computer-readable storage medium storing one or more programs (software modules) may be provided. The one or more programs stored in the computer-readable storage medium are configured for execution by one or more processors within an electronic device. The one or more programs include instructions that cause the electronic device to execute methods according to the embodiments described in the claims or specification of the present invention.

[0371] These programs (software modules, software) may be stored in random access memory, non-volatile memory including flash memory, read only memory (ROM), electrically erasable programmable read only memory (EEPROM), magnetic disc storage device, compact disc ROM (CD-ROM), digital versatile discs (DVDs) or other forms of optical storage device, magnetic cassette. Or, they may be stored in a memory configured as a combination of some or all of these. In addition, each configuration memory may be included in multiple numbers.

[0372] Additionally, the program may be stored in an attachable storage device that is accessible via a communication network such as the Internet, an intranet, a local area network (LAN), a wide local area network (WLAN), a storage area network (SAN), or a combination thereof. Such a storage device may be connected to a device implementing an embodiment of the present invention via an external port. Additionally, a separate storage device on the communication network may be connected to a device implementing an embodiment of the present invention.

[0373] In the specific embodiments of the present invention described above, components included in the invention are expressed in the singular or plural form depending on the specific embodiment presented. However, the singular or plural expressions are selected to suit the presented situation for convenience of explanation, and the present invention is not limited to singular or plural components. Even components expressed in the plural form may be composed of singular elements, or even components expressed in the singular form may be composed of plural elements.

[0374] While the detailed description of the present invention has described specific embodiments, it is clear that various modifications are possible without departing from the scope of the present invention. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be defined not only by the scope of the following claims but also by equivalents thereof.

Claims

1. A method performed by a terminal (user equipment, UE) in a wireless communication system, A step of receiving first conditional reconfiguration information including subsequent conditional PSCell addition or change (SCPAC) configuration information from a base station associated with a source cell; When the terminal receives a message for cell change including second condition reset information related to the release of the SCPAC setting information, a step of deleting the stored SCPAC setting information based on the second condition reset information related to the release of the SCPAC setting information; and A method characterized by comprising a step of performing a cell change to a target cell based on the message for the above cell change.

2. In paragraph 1, A method characterized in that the message for the above cell change is a radio resource control (RRC) reset message including a reconfiguration with sync field related to a master cell group (MCG) or an RRC reset message including a reconfiguration with sync field related to an SCG.

3. In paragraph 1, The SCPAC configuration information includes a cell identifier (ID) of a candidate cell to which the SCPAC configuration information is applied and condition information for performing SCPAC operation with the candidate cell. A method characterized in that the second condition reset information related to the release of the SCPAC setting information includes an identifier of a candidate cell to which the SCPAC setting information is applied.

4. In paragraph 1, A method characterized in that, when the terminal receives a message related to the release of the SCG, the first condition reset information is deleted except for the SCPAC setting information.

5. A method performed by a base station associated with a source cell in a wireless communication system, A step of transmitting, to a terminal, first conditional reconfiguration information including subsequent conditional PSCell addition or change (SCPAC) configuration information; a step of determining whether a cell has changed; and A method characterized by comprising the step of transmitting a message for cell change including second condition reset information related to release of SCPAC setting information to the terminal when a cell change is decided.

6. In paragraph 5, A method characterized in that the message for the above cell change is a radio resource control (RRC) reset message including a reconfiguration with sync field related to a master cell group (MCG) or an RRC reset message including a reconfiguration with sync field related to an SCG.

7. In paragraph 5, The SCPAC configuration information includes a cell identifier (ID) of a candidate cell to which the SCPAC configuration information is applied and condition information for performing SCPAC operation with the candidate cell. A method characterized in that the second condition reset information related to the release of the SCPAC setting information includes an identifier of a candidate cell to which the SCPAC setting information is applied.

8. In paragraph 5, If it is decided to release the SCG of the above terminal, a step of transmitting a message related to the release of the SCG is included. A method characterized in that the message related to the release of the above SCG is related to the deletion of the first condition reset information excluding the SCPAC setting information.

9. In a terminal (user equipment, UE) in a wireless communication system, A transceiver for transmitting and receiving signals; and A control unit is included, wherein the control unit comprises: Receive first conditional reconfiguration information including subsequent conditional PSCell addition or change (SCPAC) configuration information from a base station associated with a source cell, When the terminal receives a message for cell change including second condition reset information related to the release of the SCPAC setting information, the SCPAC setting information stored based on the second condition reset information related to the release of the SCPAC setting information is deleted, and A terminal characterized in that it performs a cell change to a target cell based on the message for the above cell change.

10. In paragraph 9, A terminal characterized in that the message for the above cell change is a radio resource control (RRC) reset message including a reconfiguration with sync field related to a master cell group (MCG) or an RRC reset message including a reconfiguration with sync field related to an SCG.

11. In paragraph 9, The SCPAC configuration information includes a cell identifier (ID) of a candidate cell to which the SCPAC configuration information is applied and condition information for performing SCPAC operation with the candidate cell. A terminal characterized in that the second condition reset information related to the release of the SCPAC setting information includes an identifier of a candidate cell to which the SCPAC setting information is applied.

12. In paragraph 11, the control unit, A terminal characterized in that, when the terminal receives a message related to the release of the SCG, the terminal deletes the first condition reset information except for the SCPAC setting information.

13. In a base station related to a source cell in a wireless communication system, A transceiver for transmitting and receiving signals; and A control unit is included, wherein the control unit comprises: Transmitting first conditional reconfiguration information including subsequent conditional PSCell addition or change (SCPAC) configuration information to the terminal, Determines whether a cell changes, and A base station characterized in that, when a cell change is decided, a message for cell change including second condition reset information related to the release of the SCPAC setting information is transmitted to the terminal.

14. In paragraph 13, The message for the above cell change is a radio resource control (RRC) reset message including a reconfiguration with sync field related to a master cell group (MCG) or an RRC reset message including a reconfiguration with sync field related to an SCG. The above SCPAC configuration information includes a cell identifier (ID) of a candidate cell to which the SCPAC configuration information is applied and condition information for performing SCPAC operation with the candidate cell. A base station, characterized in that the second condition reset information related to the release of the SCPAC setting information includes an identifier of a candidate cell to which the SCPAC setting information is applied.

15. In paragraph 13, the control unit, If it is decided to release the SCG of the above terminal, a message related to the release of the SCG is transmitted, A base station characterized in that the message related to the release of the above SCG is related to the deletion of the first condition reset information excluding the SCPAC setting information.

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