Method and apparatus related to security during continuous pscell change or addition operation in next-generation mobile communication

Abstract

The present disclosure relates to a 5G or 6G communication system for supporting higher data transfer rates. The present disclosure relates to a method and an apparatus wherein, when a terminal performs a PSCell change and moves to a previously configured subsequent conditional PSCell addition and change (SCPAC) candidate cell, an SCPAC configuration is used as it is.

Description

Method and device for security in continuous PSCELL change addition operation in next-generation mobile communication

[0001] The present invention relates to the operation of a terminal in a mobile communication system. Specifically, when a terminal performs a pscell (primary secondary cell) change and moves to a previously configured SCPAC (subsequent conditional pcell addition and change) candidate cell, the SCPAC configuration is used as is.

[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] When a terminal performs a pscell change, if the target cell is a SCPAC (subsequent conditional pscell addition and change) candidate cell, if the pscell change signal does not include current security-related parameters, the terminal cannot update to the security parameters included in the SCPAC configuration.

[0010] An embodiment of the present invention aims to provide a method for using SCPAC settings as they are when a terminal performs a pscell change and moves to a previously set SCPAC candidate cell.

[0011] The technical problems to be achieved in the present invention 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 invention belongs from the description below.

[0012] In order to solve the above problem, according to an embodiment of the present invention, a method performed by a terminal of a wireless communication system comprises the steps of: receiving, from a master node, a first message including SCPAC (subsequent conditional pscell (primary secondary cell) addition and change) configuration information for at least one candidate secondary node, the first message including information related to a security parameter assigned to a pscell (primary secondary cell) of at least one candidate secondary node when dual connectivity (DC) is established with a master node and a first secondary node; receiving, from the master node, a second message including SCG (secondary cell group) configuration information for changing a secondary node to a pscell of a second secondary node among the at least one candidate secondary node; applying the SCG configuration information; and performing a random access procedure with the second secondary node, wherein the second message may include information related to a security parameter assigned to the pscell of the second secondary node.

[0013] According to an embodiment, the information associated with the security parameters assigned to the pscell of the second secondary node may be included in conditional reconfiguration information.

[0014] In some embodiments, the SCG configuration information may include ReconfigurationWithSync information.

[0015] Depending on the embodiment, the first message or the second message may include a radio resource control (RRC) reconfiguration message.

[0016] According to an embodiment, the information associated with the security parameters assigned to the pscell of the second secondary node may include a securityCellSetId.

[0017] In order to solve the above problem, according to an embodiment of the present invention, a method performed by a master node of a wireless communication system comprises the steps of: when dual connectivity (DC) is set for a terminal with the master node and a first secondary node, transmitting a first message including SCPAC (subsequent conditional pscell (primary secondary cell) addition and change) configuration information for at least one candidate secondary node, the first message including information related to a security parameter assigned to a pscell (primary secondary cell) of at least one candidate secondary node, to the terminal; transmitting a request message for a secondary node change to a pscell of a second secondary node among the at least one candidate secondary node; receiving a response message from the second secondary node including SCG (secondary cell group) configuration information for the secondary node change; And a step of transmitting a second message including the SCG setting information to the terminal, wherein the second message may include information associated with a security parameter assigned to the pscell of the second secondary node.

[0018] In order to solve the above-described problem, a terminal of a wireless communication system according to an embodiment of the present invention comprises: a transceiver; And a control unit connected to the transceiver and configured to receive, from the master node, a first message including SCPAC (subsequent conditional pscell (primary secondary cell) addition and change) configuration information for at least one candidate secondary node, the first message including information related to security parameters assigned to the pscell (primary secondary cell) of at least one candidate secondary node, when dual connectivity (DC) is established with the master node and the first secondary node, and to receive, from the master node, a second message including SCG (secondary cell group) configuration information for changing the secondary node of the second secondary node among the at least one candidate secondary node to the pscell, and to apply the SCG configuration information and perform a random access procedure with the second secondary node, wherein the second message may include information related to security parameters assigned to the pscell of the second secondary node.

[0019] In order to solve the above-described problem, a master node of a wireless communication system according to an embodiment of the present invention comprises: a transceiver; And a control unit connected to the transceiver, and configured to transmit a first message including SCPAC (subsequent conditional pscell (primary secondary cell) addition and change) configuration information for at least one candidate secondary node, including information related to a security parameter assigned to a pscell (primary secondary cell) of at least one candidate secondary node, to the terminal when dual connectivity (DC) is set with the master node and the first secondary node, and transmit a request message for a secondary node change to a pscell of a second secondary node among the at least one candidate secondary node, and receive a response message including secondary cell group (SCG) configuration information for the secondary node change from the second secondary node, and transmit a second message including the SCG configuration information to the terminal, wherein the second message includes a security parameter assigned to the pscell of the second secondary node. It may contain information associated with the parameters.

[0020] According to one embodiment of the present invention, any terminal may additionally directly perform a pscell change command when it receives settings for continuous conditional pscell changes and additional operations.

[0021] The effects that can be obtained from the present invention are not limited to the effects mentioned above, and other effects not mentioned can be clearly understood by a person having ordinary skill in the art to which the present disclosure pertains from the description below.

[0022] FIG. 1 is a diagram illustrating the structure of an LTE system according to one embodiment of the present invention.

[0023] FIG. 2 is a diagram illustrating a wireless protocol structure of an LTE system according to an embodiment of the present invention.

[0024] FIG. 3 is a diagram illustrating the structure of a next-generation mobile communication system according to an embodiment of the present invention.

[0025] FIG. 4 is a diagram showing a wireless protocol structure of a next-generation mobile communication system according to an embodiment of the present invention.

[0026] FIG. 5 is a block diagram illustrating the structure of a terminal according to an embodiment of the present invention.

[0027] Figure 6 is a block diagram showing the configuration of a base station according to one embodiment of the present invention.

[0028] FIG. 7 and FIG. 8 are diagrams illustrating examples of SCPAC configuration information and conditional reconfiguration information.

[0029] Figure 9 illustrates an example of a problem that may occur in the case of SN initiated normal pscell change.

[0030] Figure 10 illustrates an example of a problem that may occur in the case of MN initiated normal pscell change.

[0031] FIG. 11 illustrates an example of operation in the case of SN initiated normal pscell change according to one embodiment of the present invention.

[0032] FIG. 12 illustrates another example of operation in the case of SN initiated normal pscell change according to one embodiment of the present invention.

[0033] FIG. 13 is a diagram illustrating an example of a case in which securityCellSetId is included in a location unrelated to a conditional Reconfiguration field according to an embodiment of the present invention.

[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 an LTE system according to one embodiment of the present invention.

[0041] Referring to FIG. 1, the wireless access network of the LTE system may be composed of next-generation base stations (Evolved Node Bs, hereinafter 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 a more complex role 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 buffer status, available transmission power status, and channel status of UEs (1-35) and performs scheduling is required, and ENBs (1-05 to 1-20) may be responsible for this. One ENB (1-05 to 1-20) 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. In addition, the LTE system can apply an adaptive modulation and coding (AMC) method that determines a modulation scheme and a channel coding rate according to the channel condition of the terminal (1-35). The S-GW (1-30) is a device that provides a data bearer and can create or remove a data bearer according to the control of the MME (1-25). The MME (1-25) is a device that is responsible for various control functions as well as mobility management functions for the terminal (1-35) and can be connected to multiple base stations (1-05 to 1-20).

[0043] FIG. 2 is a diagram illustrating a wireless protocol structure of an LTE system according to an embodiment of the present invention.

[0044] Referring to FIG. 2, the wireless protocol of the 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.

[0045] PDCP (2-05, 2-40) can handle operations such as IP header compression / decompression. The main functions of PDCP (2-05, 2-40) can be summarized as follows.

[0046] - Header compression and decompression (ROHC only)

[0047] - User data transfer function

[0048] - In-sequence delivery of upper layer PDUs at PDCP re-establishment procedure for RLC AM

[0049] - Order reordering function (For split bearers in DC (only support for RLC AM): PDCP PDU routing for transmission and PDCP PDU reordering for reception)

[0050] - Duplicate detection function (Duplicate detection of lower layer SDUs at PDCP re-establishment procedure for RLC AM)

[0051] - 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)

[0052] - Encryption and decryption functions (Ciphering and deciphering)

[0053] - Timer-based SDU discard in uplink.

[0054] 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 (2-10, 2-35) can be summarized as follows.

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

[0056] - ARQ function (Error Correction through ARQ (only for AM data transfer))

[0057] - Concatenation, segmentation and reassembly of RLC SDUs (only for UM and AM data transfer)

[0058] - Re-segmentation of RLC data PDUs (only for AM data transfer)

[0059] - Reordering of RLC data PDUs (only for UM and AM data transfer)

[0060] - Duplicate detection (only for UM and AM data transfer)

[0061] - Error detection function (Protocol error detection (only for AM data transfer))

[0062] - RLC SDU discard function (RLC SDU discard (only for UM and AM data transfer))

[0063] - RLC re-establishment function

[0064] MAC(2-15, 2-30) is connected to multiple RLC layer devices configured in a single terminal, and can perform the operation of multiplexing RLC PDUs into MAC PDUs and demultiplexing RLC PDUs from MAC PDUs. The main functions of MAC(2-15, 2-30) can be summarized as follows.

[0065] - Mapping function (Mapping between logical channels and transport channels)

[0066] - 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)

[0067] - Scheduling information reporting function

[0068] - HARQ function (Error correction through HARQ)

[0069] - Priority handling between logical channels of one UE

[0070] - Priority handling between UEs by means of dynamic scheduling

[0071] - MBMS service identification function

[0072] - Transport format selection function

[0073] - Padding function

[0074] 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.

[0075] FIG. 3 is a diagram illustrating the structure of a next-generation mobile communication system according to an embodiment of the present invention.

[0076] Referring to FIG. 3, a wireless access network of a next-generation mobile communication system (hereinafter referred to as 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 (New 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).

[0077] In Fig. 3, the NR gNB (3-10) may correspond to the eNB (Evolved Node B) of the existing LTE system. The NR gNB (3-10) is connected to the NR UE (3-15) via a wireless channel (radio access, 3-20) and may provide a service superior to that of the existing Node B. In the next-generation mobile communication system, all user traffic may be serviced through a shared channel. Therefore, a device that collects status information such as buffer status, available transmission power status, and channel status of the UEs (3-15) and performs scheduling is required, and the scheduling may be performed by the NR NB (3-10). One NR gNB (3-10) may control multiple cells. In the next-generation mobile communication system, in order to implement ultra-high-speed data transmission compared to the general LTE, a bandwidth greater than the general maximum bandwidth may be applied. In addition, in the next-generation mobile communication system, beamforming technology can be additionally incorporated with orthogonal frequency division multiplexing (OFDM) as a wireless access technology. In addition, in the next-generation mobile communication system, an adaptive modulation and coding (AMC) method that determines a modulation scheme and a channel coding rate according to the channel condition of the terminal (3-15) can be applied. The NR CN (3-05) can perform functions such as mobility support, bearer setup, and QoS setup. The NR CN (3-05) is a device that is responsible for various control functions as well as mobility management functions for the terminal (3-15) and can be connected to multiple base stations (3-10). In addition, the next-generation mobile communication system can also be linked with the LTE system, and the NR CN (3-05) can be connected to the MME (3-25) through a network interface.MME (3-25) can be connected to eNB (3-30), which is an LTE base station.

[0078] FIG. 4 is a diagram showing a wireless protocol structure of a next-generation mobile communication system according to an embodiment of the present invention.

[0079] Referring to FIG. 4, the wireless protocol of the next-generation mobile communication system consists of NR Service Data Adaptation Protocol (SDAP) (4-01, 4-45), NR PDCP (4-05, 4-40), NR RLC (4-10, 4-35), NR MAC (4-15, 4-30), and NR PHY (4-20, 4-25) in the terminal and NR base station, respectively.

[0080] Key features of NR SDAP (4-01, 4-45) may include some of the following:

[0081] - Transfer of user plane data

[0082] - Mapping function between QoS flow and data bearer for both DL and UL

[0083] - QoS flow ID marking function for uplink and downlink (marking QoS flow ID in both DL and UL packets)

[0084] - Ability to map relective QoS flow to data bearer for uplink SDAP PDUs (reflective QoS flow to DRB mapping for the UL SDAP PDUs).

[0085] 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.

[0086] The main functions of NR PDCP (4-05, 4-40) may include some of the following functions:

[0087] - Header compression and decompression (ROHC only)

[0088] - User data transfer function

[0089] - In-sequence delivery of upper layer PDUs

[0090] - Out-of-sequence delivery of upper layer PDUs

[0091] - PDCP PDU reordering for reception

[0092] - Duplicate detection of lower layer SDUs

[0093] - Retransmission function (Retransmission of PDCP SDUs)

[0094] - Encryption and decryption functions (Ciphering and deciphering)

[0095] - Timer-based SDU discard in uplink.

[0096] 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.

[0097] The main functions of NR RLC(4-10, 4-35) may include some of the following functions:

[0098] - Data transfer function (Transfer of upper layer PDUs)

[0099] - In-sequence delivery of upper layer PDUs

[0100] - Out-of-sequence delivery of upper layer PDUs

[0101] - ARQ function (Error Correction through ARQ)

[0102] - Concatenation, segmentation and reassembly of RLC SDUs

[0103] - Re-segmentation of RLC data PDUs

[0104] - Reordering of RLC data PDUs

[0105] - Duplicate detection function

[0106] - Protocol error detection

[0107] - RLC SDU discard function

[0108] - RLC re-establishment function

[0109] 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.

[0110] 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.

[0111] 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.

[0112] 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.

[0113] 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.

[0114] 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).

[0115] 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.

[0116] 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.

[0117] 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.

[0118] 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.

[0119] - Mapping function (Mapping between logical channels and transport channels)

[0120] - Multiplexing / demultiplexing of MAC SDUs

[0121] - Scheduling information reporting function

[0122] - HARQ function (Error correction through HARQ)

[0123] - Priority handling between logical channels of one UE

[0124] - Priority handling between UEs by means of dynamic scheduling

[0125] - MBMS service identification function

[0126] - Transport format selection function

[0127] - Padding function

[0128] The 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.

[0129] FIG. 5 is a block diagram illustrating the structure of a terminal according to an embodiment of the present invention.

[0130] Referring to FIG. 5, 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).

[0131] The RF processing unit (5-10) performs functions for transmitting and receiving signals through a wireless channel, such as signal band conversion and amplification. The RF processing unit (5-10) up-converts the baseband signal provided from the baseband processing unit (5-20) 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 (5-10) may 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 Fig. 5, only one antenna is illustrated, but the terminal may be equipped with multiple antennas. In addition, the RF processing unit (5-10) may include multiple RF chains. Furthermore, the RF processing unit (5-10) may 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 (5-10) can perform MIMO and can receive multiple layers when performing the MIMO operation.

[0132] The baseband processing unit (5-20) above performs 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) generates complex symbols by encoding and modulating a transmission bit stream. In addition, when receiving data, the baseband processing unit (5-20) restores the reception bit stream by demodulating and decoding the 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.

[0133] The baseband processing unit (5-20) and the RF processing unit (5-10) 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.

[0134] The above storage unit (5-30) can store data such as basic programs, application programs, and setting information for the operation of the terminal. In addition, the storage unit (5-30) provides the stored data at the request of the control unit (5-40).

[0135] 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) can record and read 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.

[0136] Figure 6 is a block diagram showing the configuration of a base station according to one embodiment of the present invention.

[0137] Referring to FIG. 6, the base station is configured to include an RF 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).

[0138] The RF processing unit (6-10) performs 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. Although only one antenna is illustrated in FIG. 6, the base station 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 beamforming, the RF processing unit (6-10) may adjust the phase and magnitude of each signal transmitted and received through multiple antennas or antenna elements. The above RF processing unit (6-10) can perform a downlink MIMO operation by transmitting one or more layers.

[0139] The baseband processing unit (6-20) above performs a conversion function between a baseband signal and a bit stream according to the physical layer specifications of the wireless access technology. For example, when transmitting data, the baseband processing unit (6-20) generates 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) generates complex symbols by encoding and modulating a transmission bit stream, maps the complex symbols to subcarriers, and then configures 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.

[0140] 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) converts a bit string transmitted from the base station to other nodes, such as auxiliary base stations and core networks, into a physical signal, and converts a physical signal received from the other nodes into a bit string.

[0141] The storage unit (6-40) can store data such as basic programs, application programs, and configuration information for the operation of the 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 basis for determining whether to provide or terminate multiple connections to a terminal. In addition, the storage unit (6-40) can provide stored data at the request of the control unit (6-50).

[0142] 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) can record and read data in the storage unit (6-40). For this purpose, the control unit (6-50) may include at least one processor.

[0143] Looking at the background operation of SCPAC (subsequent conditional pscell addition and change), it can be as follows.

[0144] When a terminal configures a dual connection (DC) through a base station MN (master node) and a SN (secondary node), the SN can request resource allocation for SCPAC to another SN (called a candidate SN). To this end, the SN can transmit necessary information to the MN. This information can include information indicating proposed candidate PSCells (primary secondary cells) for each of the candidate SNs, measurement result information for the PSCells, and initial condition information for moving from the SN's current PSCell to the candidate PSCells.

[0145] The MN can receive the above information from the S-SN (source SN) and transmit the above information by applying the SN Addition procedure to each candidate SN.

[0146] Each candidate SN may transmit its proposed candidate pscell and measurement result information of the cell to the MN and / or the S-SN and / or other candidate SNs. In addition, each candidate SN may also transmit proposed candidate pscell information for other candidate SNs to the S-SN or the MN.

[0147] Upon receiving this information, each candidate SN can determine a pscell to which SCPAC resources will be allocated from its proposed pscells and forward the information about that cell to the MN by including it in the SNADDReqACK (SN addition request acknowledgment) message. Furthermore, the SN can also forward to the MN information on conditions to be used when moving from the determined pscell to other candidate pscells.

[0148] The MN that has received the above information can link the target settings for the determined pscells and the condition information required when 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 (RRC (radio resource control) Reconfiguration message, RRC reset message).

[0149] After receiving the above settings, the terminal can perform measurement and condition evaluation operations. Then, if certain conditions are met, the terminal will move to the candidate PSCell. At this time, the SCPAC settings will remain in the terminal, and even after PSCell movement, the terminal can continue to perform SCPAC operations using the necessary condition information and target cell configuration information within the same SCPAC settings.

[0150] FIG. 7 and FIG. 8 are diagrams illustrating examples of SCPAC configuration information and conditional reconfiguration information.

[0151] Figure 7 shows an example of the SCPAC setting signal structure on the current running CR.

[0152] Referring to Fig. 7, the RRCReconfiguration message in MN format or the RRCReconfiguration message in SN format may include a conditionalReconfiguration field. The conditional Reconfiguration field may include settings for various conditional movements. Among the information, scpac-ReferenceConfiguration may be included in relation to SCPAC operation. In addition, the conditional Reconfiguration field may include servingSecurityCellSetId and sk-counterConfiguration.

[0153] scpac-ReferenceConfiguration is the reference configuration of the target cell of SCPAC, and servingSecurityCellSetId is the ID corresponding to the security parameter of the pscell when receiving the initial SCPAC configuration, and is used when updating one of the values ​​in the list of sk-counter values ​​mapped to each ID in sk-counterConfiguration to sk-counter.

[0154] Additionally, Fig. 8 shows a condReconfigToAddMod list. The IE (information element) included here shows configuration information required to move to each candidate target cell. Information of one target cell is linked to the condReconfigToAddMod IE. In relation to SCPAC, one target cell configuration (i.e., candidate target pscell configuration) may include condReconfig Id of one condReconfigToAddMod, conditions required to move to the corresponding target cell, condition information (subsequentCondReconfig IE) to be used when moving to this target cell from other SCPAC candidate cells when performing SCPAC to the corresponding target cell, cell Id (securitycellsetid) required to obtain the sk-counter value of the corresponding target cell, an indicator (scpac-ConfigComplete) indicating whether the configuration is complete, etc. in the condReconfigToAddMod list.

[0155] According to the above information, when the terminal first receives the SCPAC settings, it stores the servingSecurityCellSet Id of the current pscell in its variable. After this, if the conditions for moving from the current pscell to another SCPAC candidate cell are satisfied according to the SCPAC settings, the terminal compares the securityCellSetId of the candidate cell with the servingSecurityCellSet Id stored in its variable. If they are the same, a separate security update is not performed. If they are different, the securityCellSetId of the target pscell can be stored in the servingSecurityCellSet variable of the terminal. In addition, the terminal can perform a security update by applying the first sk-counter value of the sk-counter value list corresponding to this id.

[0156] A network may assign the same securityCellSetId to pscells within the same SN and may assign different securityCellSetIds to different SNs.

[0157] However, if the network issues a pscell change command directly, rather than a normal pscell change (i.e., a pscell change that satisfies SCPAC conditions), then in the case of an inter-SN pscell change, a security update may need to be performed by applying a different sk-counter compared to the current pscell. In addition, if the target of the normal pscell change is one of the candidate target cells that previously transmitted SCPAC settings to the terminal, if the security parameters assigned to the target cell are used as is, unnecessary signaling between MN / SN is eliminated. Accordingly, when a normal pscell change is made, if the securityCellSetId value is included in the signal message and transmitted, the terminal does not perform SCPAC, but when moving to the target pscell, the servingSecurityCellSetId stored in the variable of the current terminal is compared with the securityCellSetId included in the pscell change command. If they are the same, a separate security update operation is not performed when the pscell change is made. If they are different, the securityCellSetId of the target cell is stored in the servingSecurityCellSetId variable of the terminal variable, and the corresponding sk-counter value is applied to perform a security update.

[0158] However, the pscell change signal cannot include a conditional reconfiguration field. This is a restriction to prevent conditional mobility configuration based on the target cell when a pcell or pscell change occurs.

[0159] 다음은 현재 RRC 스펙 상의 conditional Reconfiguration 필드의 설명이다.

[0160] Configuration of candidate target SpCell(s) and execution condition(s) for conditional handover, conditional PSCell addition or conditional PSCell change. The field is absent if any DAPS bearer is configured or if the masterCellGroup includes ReconfigurationWithSync or if the sl-L2RemoteUE-Config or sl-L2RelayUE-Config is configured. For conditional PSCell change, the field is absent if the secondaryCellGroup includes ReconfigurationWithSync. The RRCReconfiguration message contained in DLInformationTransferMRDC cannot contain the field conditionalReconfiguration for conditional PSCell change of for conditional PSCell addition.

[0161] The above constraint assumes that in R16 / 17, only one of CHO (conditional handover) or CPAC (CPA (conditional pscell addition) and CPC (conditional pscell change)) can be configured for the UE, and in case of CPAC, it indicates that if the MN RRCReconfiguration indicates a pscell change (reconfigurationWithSync) of the SCG, the conditional Reconfiguration field cannot be included.

[0162] Figure 9 illustrates an example of a problem that may occur in the case of an SN initiated normal pscell change.

[0163] Referring to FIG. 9, in step 910, a terminal (901) may set up MR (multi radio) DC (dual connectivity) with an S-MN (source master node) (MN) (902), an S-SN (SN1) (903), and an S-SN (SN2) (904). In addition, in step 915, SCPAC may be prepared for the S-MN (902), S-SN (SN1) (903), SN2 (904), and SN3 (905). In step 920, the terminal (901) may receive an RRC message (e.g., an RRC reconfiguration message) including SPCPAC configuration information from the S-MN (902). In step 925, the terminal (901) may transmit a response message (e.g., an RRC reconfiguration complete message) to the MN (902). The SCPAC configuration information may include a securityCellSetid for each candidate pscell. The terminal can store the initial servingSecurityCellSetid in its own variable.

[0164] After the terminal (901) receives the SCPAC settings, at step 930, the S-SN (SN1) (903) may want to perform a normal pscell change to one of the SCPAC candidate cells on SN3 (905). In this case, the S-SN (903) may request a pscell change to the target cell of SN3 (905) through an SN change required message (SN change request message) to MN (902). At steps 940 and 950, the MN (902) may request a resource reservation for the corresponding target cell by exchanging SN ADD (addition) Req (request) (SN addition request) / SN ADD REqACK (request acknowledgement) (SN addition request response) messages with SN3 (905). Accordingly, at step 945, the SN3 (905) may create an SN RRCReconfiguration message (SCG configuration, SCG config). And SN3 (905) can include the sk-counter value inside the SCG configuration. And the SCG config can be included in the SN ADD REQ ack message and transmitted to MN (902) at step 950.

[0165] The MN (902) receives the above SN RRCReconfiguration message, and in step 955, the MN (902) can create an RRCReconfiguration message in MN format and transmit (transmit) it to the terminal (901). The RRC reconfiguration message can include reconfigWithSync in SCG config.

[0166] And in step 960, the terminal (901) can apply the pscell change according to the RRC reconfiguration, and in step 965, can transmit a response message (e.g., RRC reconfiguration complete message) to MN (902) in response. In step 970, the MN (902) can transmit an SN change confirm message to SN1 (902), and in step 975, the MN (902) can transmit an SN reconfiguration complete message to SN3 (905). Accordingly, in step 980, the SN3 (905) and the terminal (901) can perform a RACH procedure (random access procedure).

[0167] Meanwhile, the terminal (901) that receives the SN RRCReconfiguration message (included in the MN RRCReconfiguration message) performs a pscell change, and if an sk-counter is included, can perform a security key update based on the corresponding counter value. However, since the configuration information for the pscell change cannot include a separate securityCellSet Id value, the terminal cannot update the Var (variable) ServingSecurityCellSetId value and cannot identify the sk-counter value in the SCPAC configuration accordingly. Instead, the security key update can be performed with the sk-counter value included in the SCG config. However, since the variable is not updated, the terminal (901) cannot perform a security update when performing a subsequent SCPAC operation, and thus, cannot operate SCPAC.

[0168] Figure 10 illustrates an example of a problem that may occur in the case of an MN initiated normal pscell change.

[0169] In the case of Fig. 10, this is the case of a pscell change initiated by MN. In this case, the same problem as described in Fig. 9 above may occur.

[0170] Referring to FIG. 10, in step 1010, a terminal (1001) may set up MR (multi radio) DC (dual connectivity) with an S-MN (MN) (1002), an S-SN (SN1) (1002), and an S-SN (SN2) (1004). In addition, in step 1015, SCPAC may be prepared for the S-MN (1002), S-SN (SN1) (1003), SN2 (1004), and SN3 (1005). In step 1020, the terminal (1001) may receive an RRC message (e.g., an RRC reconfiguration message) including SPCPAC configuration information from the S-MN (1002). In step 1025, the terminal (1001) may transmit a response message (e.g., an RRC reconfiguration complete message) to the MN (1002). The SCPAC configuration information may include a securityCellSetid for each candidate pscell. The terminal (1001) can store the initial servingSecurityCellSetid in its variable.

[0171] After the terminal (1001) receives the SCPAC setting, the S-MN (1002) may want to perform a normal pscell change to one of the SCPAC candidate cells on SN3 (1005) at step 1030. In this case, the S-MN (1002) may request a resource reservation for the corresponding target cell by exchanging SN ADD Req / SN ADD REqACK messages with SN3 (1005) at steps 1035 to 1045. Accordingly, the SN3 (1005) may create an SN RRCReconfiguration message (SCG configuration) at step 1040. The SN3 (1005) may include an sk-counter value within the SCG configuration. The SN3 (1005) may transmit the SCG configuration to the MN (1002) at step 1045.

[0172] The MN (1002) receives the above SN RRCReconfiguration message, and in step 1050, the MN (1002) can create an RRCReconfiguration message in MN format and transmit (transmit) it to the terminal (1001). The RRC reconfiguration message can include reconfigWithSync in SCG config.

[0173] And in step 1055, the terminal (1001) can apply the pscell change, and in response to the pscell change, can transmit a response message (e.g., RRC reconfiguration complete message) to the MN (1002) in step 1060. In step 1065, the MN (1002) can transmit an SN change confirm message to the SN1 (1003), and in step 1070, the MN (1002) can transmit an SN reconfiguration complete message to the SN3 (1005). Accordingly, in step 1080, the SN3 (1005) and the terminal (1001) can perform the RACH procedure.

[0174] Meanwhile, the terminal (1001) that receives the SN RRCReconfiguration message performs a pscell change, and if an sk-counter is included, can perform a security key update based on the corresponding counter value. However, since the configuration information for the pscell change cannot include a separate securityCellSet Id value, the terminal (1001) cannot update the Var ServingSecurityCellSetId value and cannot identify the sk-counter value in the SCPAC configuration accordingly. Instead, a security key update can be performed with the sk-counter value in the SCG config. However, since the variable is not updated, the terminal (1001) cannot perform a security update when performing a subsequent SCPAC operation, and thus, cannot operate SCPAC.

[0175] Accordingly, in the present invention,

[0176] As Issue 1, in case of normal pscell change, as a signaling method of security parameter,

[0177] Opt(option) 1: Allow adding a conditional Reconfiguration field to the Pscell change command / signal, and adding the corresponding securityCellSetId value to that field;

[0178] Opt 2: How to add the securityCellSetId value as a separate value independent of the conditional Reconfiguration field in the Pscell change command / signal, and

[0179] Opt 3: Instead of using SecurityCellSetId, we propose a method where the network directly adds the sk-counter value and includes it in the Pscell change command / signal.

[0180] Additionally, as issue 2, if additional CPA is performed, it is suggested to update the terminal's security key.

[0181] In the case of normal pscell change, let's look at the signaling method of security parameters.

[0182] Opt 1. After the S-SN makes a decision for an inter-SN pscell change, the S-SN can request a pscell change (via an SN ADD Req message) to the SN of the target pscell (T-SN, target SN) through the MN. The T-SN that receives the request can create an SCG configuration, i.e., SN RRCReconfiguration, and include a reconfigurationWithSync field in the SCG configuration. The SN RRCReconfiguration can be delivered to the MN via an SN ADD REQ ACK message. Then, the MN recognizes that the SN has performed change preparation for the target pscell, and if the target pscell is currently set as an SCPAC candidate cell for the terminal, the MN RRCReconfiguration can include a conditional Reconfiguration field, include a securityCellSet Id value assigned to the target pscell in the SCPAC configuration, and indicate it as a value for normal pscell change.

[0183] Accordingly, the constraints on the configuration of the existing conditionalReconfiguration field should be removed. That is, for CPAC, SCG, MN RRCReconfiguration with reconfigurationWithSync should be able to include the conditionalReconfiguration field, and in this case, it should only include the securityCellSetId value that was assigned to the existing SCPAC configuration in the target pscell of the normal pscell change, rather than other fields.

[0184] The terminal that has received the above information can perform pscell change while applying the MN RRCReconfiguration message. In addition, considering that the MN RRCReconfiguration message includes a reconfigurationWithSync field in SCG, and that the MN RRCReconfiguration message includes a conditional Reconfiguration field, and that this field includes the securityCellSetId value for the target pscell, the terminal compares the securityCellSetId value with the message that the terminal currently stores in Var ServingSecurityCellSetId, and if they are the same, a separate security key update is not performed. If they are different, the value stored in var ServingSecurityCellSetId is replaced with the indicated securityCellSetId value of the target pscell, and the first value among the sk-counter list linked to the Id is selected and a security key update is performed with that value.

[0185] FIG. 11 illustrates an example of operation in the case of SN initiated normal pscell change according to one embodiment of the present invention.

[0186] Referring to FIG. 11, in step 1110, a terminal (1101) may set up MR (multi radio) DC (dual connectivity) with an S-MN (MN) (1102), an S-SN (SN1) (1103), and an S-SN (SN2) (1104). In addition, in step 1115, SCPAC may be prepared for the S-MN (1102), S-SN (SN1) (1103), SN2 (1104), and SN3 (1105). In step 1120, the terminal (1101) may receive an RRC message (e.g., an RRC reconfiguration message) including SPCPAC configuration information from the S-MN (1102). In step 1125, the terminal (1101) may transmit a response message (e.g., an RRC reconfiguration complete message) to the MN (1102). The SCPAC configuration information may include a securityCellSetid for each candidate pscell. The terminal (1101) can store the initial servingSecurityCellSetid in a variable.

[0187] After the terminal (1101) receives the SCPAC setting, at step 1130, the S-SN (SN1) (1103) may want to perform a normal pscell change to one of the SCPAC candidate cells on SN3 (T-SN) (1105). In this case, at step 1135, the S-SN (1103) may request a pscell change to the target cell of SN3 (1105) through an SN change required message to MN (1102). At steps 1140 and 1150, the MN (1102) may request a resource reservation for the corresponding target cell by exchanging SN ADD (addition) Req (request) / SN ADD REqACK (request acknowledgment) messages with SN3 (1105). Accordingly, at step 1145, the SN3 (1105) may create an SN RRCReconfiguration message (SCG configuration). At this time, SN RRCReconfiguration may include an SCG config field having a reconfigurationWithSync field. The SCG configuration may be included in an SN ADD REQ ack message and transmitted to MN (1102) at step 1150.

[0188] At step 1155, if the MN (1102) recognizes that the SN (1105) has performed change preparation for the target pscell, and if the target pscell is currently set as an SCPAC candidate cell for the terminal (1101), the MN (1102) may include a conditional Reconfiguration field in the MN RRCReconfiguration, include the securityCellSet Id value assigned to the target pscell in the SCPAC setting, and indicate it as a value for normal pscell change purposes. Then, the MN (1102) may transmit an MN RRC reconfiguration message to the terminal (1101).

[0189] And in step 1160, the terminal (1101) can apply the pscell change, and in step 1165, can transmit a response message (e.g., RRC reconfiguration complete message) to the MN (1102) in response. In step 1170, the MN (1102) can transmit an SN change confirm message to the SN1 (1102), and in step 1175, the MN (1102) can transmit an SN reconfiguration complete message to the SN3 (1105). Accordingly, in step 1180, the SN3 (1105) and the terminal (1101) can perform the RACH procedure.

[0190] In this case, the terminal (1101) can perform a pscell change while applying the MN RRCReconfiguration message. In addition, considering that the SCG config included in the MN RRCReconfiguration message includes a reconfigurationWithSync field, and that the MN RRCReconfiguration message includes a conditional Reconfiguration field, and that this field includes a securityCellSetId value for the target pscell, the terminal (1101) compares the securityCellSetId value with the message that the terminal (1101) currently stores in Var ServingSecurityCellSetId, and if they are the same, a separate security key update is not performed. If they are different, the value stored in var ServingSecurityCellSetId is replaced with the indicated securityCellSetId value of the target pscell, and the first value among the sk-counter list linked to the corresponding Id is selected and a security key update is performed with that value.

[0191] According to an embodiment, in case of MN initiated normal pscell change, the same operation as SN initiated normal pscell change may be performed. That is, MN (1102) may also include a conditionalReconfiguration field in MN RRCReconfiguration including SCG config with reconfigWithSync at step 1155, and may include the securityCellSetId in the SCPAC configuration previously assigned to the target pscell in that field and indicate it for normal pscell change.

[0192] In this case, what is different from the SN initiated normal pscell change is that the MN (1102) determines the normal pscell change and performs the SN ADD procedure to the corresponding T-SN (1105). That is, steps 1130 to 1135 may not be performed. That is, after the terminal (1101) receives the SCPAC setting in step 1120, the S-MN (1102) may want to perform a normal pscell change to one of the SCPAC candidate cells on SN3 (1105). In this case, the S-MN (1002) may request a resource reservation for the corresponding target cell by exchanging SN ADD Req / SN ADD REqACK messages with SN3 (1005). The transmission and reception operation of the SN ADD Req / SN ADD REqACK message may be similar to the operation of steps 1140 to 1150, and a detailed description thereof will be omitted.

[0193] In another signaling embodiment, if the MN RRCReconfiguration message includes SCG with reconfigurationWithSync, but 1) does not include a conditional Reconfiguration field and does not indicate a separate sk-counter value, or 2) includes a conditional Reconfiguration field but does not include the securityCellSetId of the target pscell and does not indicate a separate sk-counter value, the terminal (1101) performs a pscell change, and it can be considered that there is an indication that there is no change in the separate securitycellset Id. Accordingly, the terminal (1101) may not update the Var ServingSecurityCellSetId value, nor may it perform a security key update operation accordingly.

[0194] During operation of the terminal (1101) of Opt 1, if the terminal (1101) selects a new sk-counter value of the terminal (1101) through the newly received securityCellSetId compared to the existing one, the newly selected sk-counter value can be included in the MN RRCReconfigurationComplete message and transmitted to the MN (1102) (step 1165). In addition to the existing conditional Reconfiguration performance, i.e., the new selection of the sk-counter value due to the SCPAC performance, the operation of including a new sk-counter value selection due to the change of the securityCellSetId in the case of a normal pscell change can be additionally included in the MN RRCReconfigurationComplete message.

[0195] The following may be relevant TPs:

[0196] ● Action 2. For making feasible this, based on the received servingSecurityCellSetId, UE will update the security keys. In this time, including the new selected sk-counter value should be included in MN format RRCReconfigurationComplete msg. So the current CR's condition should be modified as:

[0197] 2> if theRRCReconfigurationmessage includes themrdc-SecondaryCellGroupConfigwithmrdc-SecondaryCellGroupset toeutra-SCG:

[0198] 3> include in theeutra-SCG-Responsethe E-UTRARRCConnectionReconfigurationCompletemessage in accordance with TS 36.331

[0010] clause 5.3.5.3;

[0199] 2> if theRRCReconfigurationmessage includes themrdc-SecondaryCellGroupConfigwithmrdc-SecondaryCellGroupset tonr-SCG:

[0200] 3> include in thenr-SCG-Responsethe SCGRRCReconfigurationCompletemessage;

[0201] 3> if theRRCReconfigurationmessage is applied due to conditional reconfiguration execution or due to the normal change of Pscell and theRRCReconfigurationmessage does not include thereconfigurationWithSyncin themasterCellGroup:

[0202] 4> include in theselectedCondRRCReconfigthecondReconfigIdfor the selected cell of conditional reconfiguration execution;

[0203] 4> if a newsk-Countervalue has been selected due to the conditional reconfiguration execution for subsequent CPAC or due to the change of the received ServingCellSetId (or due to the normal change of Pscell etc):

[0204] 5> include in theselectedSK-Counterthe selectedsk-Countervalue;

[0205] The terminal may need to update Var servingSecuritycellSetId not only when performing the existing conditional reconfiguration, but also when, during a normal pscell change, the relevant securityCellSetId differs from the existing Var servingSecurityCellSetId value. Accordingly, an update may be required, as shown in the red section below.

[0206] ● Action 3. Counter value update condition also should be modified by adding this case.

[0207] 1> if theRRCReconfigurationis applied due to a conditional reconfiguration execution in accordance with 5.3.5.13.5 and thesecurityCellSetIdis included in the entry inVarConditionalReconfigcontaining theRRCReconfigurationmessage or the RRCReconfiguration message includes conditionalReconfiguration with the servingSecurityCellSetId:

[0208] 2> ifservingSecurityCellSetIdis not included withinVarServingSecurityCellSetID, or

[0209] 2> if the value of thesecurityCellSetIdor received servingSecurityCellSetId is not equal to the value ofservingSecurityCellSetIdwithinVarServingSecurityCellSetID:

[0210] 3> consider the first unusedsk-Countervalue in thesk-CounterListassociated with thesecurityCellSetIdwithin theVarConditionalReconfigas the selectedsk-Countervalue, and perform security key update procedure as specified in 5.3.5.7;

[0211] 3> if the currentVarServingSecurityCellSetIDincludesservingSecurityCellSetId:

[0212] 4> replace the value ofservingSecurityCellSetIdwithinVarServingSecurityCellSetIDwith the value ofsecurityCellSetIdassociated with the selected cell;

[0213] 3> else:

[0214] 4> store theservingSecurityCellSetIdwithinVarServingSecurityCellSetIDwith the value ofsecurityCellSetIdassociated with the selected cell;

[0215] FIG. 12 illustrates another example of operation in the case of SN initiated normal pscell change according to one embodiment of the present invention.

[0216] Figure 12 illustrates an example of the case of no securityCellSetId described above.

[0217] Referring to FIG. 12, in step 1210, a terminal (1201) can set up MR (multi radio) DC (dual connectivity) with an S-MN (MN) (1202), an S-SN (1203), and an S-SN (1205). In addition, in step 1215, SCPAC can be prepared for S-MN (1202), S-SN (SN1) (1203), SN2 (1204), and SN3 (1205). In step 1220, the terminal (1201) can receive an RRC message (e.g., an RRC reconfiguration message) including SPCPAC configuration information from the S-MN (1202). In step 1225, the terminal (1201) can transmit a response message (e.g., an RRC reconfiguration complete message) to the MN (1202). The SCPAC configuration information can include a securityCellSetid for each candidate pscell. The terminal (1201) can store the initial servingSecurityCellSetid in a variable.

[0218] After the terminal (1201) receives the SCPAC settings, at step 1230, the S-SN (SN1) (1203) may want to perform a normal pscell change to one of the SCPAC candidate cells on SN3 (T-SN) (1205). In this case, at step 1235, the S-SN (1203) may request a pscell change to the target cell of SN3 (1205) through an SN change required message to MN (1202). At steps 1240 and 1250, the MN (1202) may request a resource reservation for the corresponding target cell by exchanging SN ADD (addition) Req (request) / SN ADD REqACK (request acknowledgment) messages with SN3 (1205). Accordingly, at step 1245, the SN3 (1205) may create an SN RRCReconfiguration message (SCG configuration). At this time, SN RRCReconfiguration may include an SCG config field having a reconfigurationWithSync field. And SN3 (1203) may transmit the SCG configuration to MN (1202) at step 1250.

[0219] At step 1255, the MN (1201) recognizes that the SN (1205) has performed change preparation for the target pscell, and if the target pscell is currently configured as an SCPAC candidate cell for the terminal (1201), the MN (1201) may include a conditional Reconfiguration field in the MN RRCReconfiguration. At this time, the MN (1202) receives the SN ADD Req ACK message at step 1250, recognizes the prepared target pscell from the T-SN (1205), and if it has the same Id value as the source pscell in terms of the securityCellSetId transmitted in the previous SCPAC configuration, the terminal (1201) may recognize that there is no need for a separate security key update, and may not include a separate securityCellSetId in the MN RRCReconfiguration. Then, the MN (1202) may transmit an MN RRC reconfiguration message to the terminal (1201). Accordingly, the terminal (1201) does not need to include the selected sk-counter value in the MN RRCReconfigurationComplete message.

[0220] Then, the terminal (1201) can apply the pscell change at step 1260, and send a response message (e.g., an RRC reconfiguration complete message) to the MN (1202) in response at step 1265. At step 1270, the MN (1202) can send an SN change confirm message to the SN1 (1203), and at step 1275, the MN (1202) can send an SN reconfiguration complete message to the SN3 (1205). Accordingly, the SN3 (1205) and the terminal (1201) can perform the RACH procedure at step 1280.

[0221] In this case, the terminal (1201) can perform a pscell change while applying the MN RRCReconfiguration message. In this case, if the MN RRCReconfiguration message includes SCG with reconfigurationWithSync, includes a conditional Reconfiguration field, does not include the securityCellSetId of the target pscell, and does not indicate a separate sk-counter value, the terminal (1201) can perform a pscell change and identify that there is no change in the separate securitycellset Id. Accordingly, the terminal (1201) may not update the Var ServingSecurityCellSetId value and may not perform a security key update operation accordingly.

[0222] According to an embodiment, in the case of a MN initiated normal pscell change, the same operation may be performed as in the case of a SN initiated normal pscell change. Since a specific description thereof is similar to the embodiment described in FIGS. 10 and 11 above, a detailed description thereof will be omitted.

[0223] Method 2 of Issue 1 is to signal the terminal by including the securityCellSetId value outside of conditionalReconfiguration. In this case, a new IE indicating the securityCellSetId is required.

[0224] In this case, there may be two cases: either the MN determines the value, or the S-SN determines it. As for the method for the MN to determine, as will be exemplarily explained in FIG. 10, if the MN recognizes the success of resource allocation for the target pscell from the T-SN, and if the target pscell is one of the candidate cells of the existing SCPAC, the securityCellSetId value allocated to it may be included in the MN RRCReconfiguration. In another case, the securityCellSetId value may be included in the SN RRCReconfiguration including reconfigurationWithSync message. In this case, the MN may determine the securityCellSetId value and transmit it to the T-SN, and the T-SN that receives the value may include it in the SN RRCReconfiguration including reconfigurationWithSync message, and transmit it again to the MN, and finally, the MN may include the received SN RRCReconfiguration in the MN RRCReconfiguration and transmit it to the terminal. In this case, the MN can include the securityCellSetId value in the SN ADD REQ message and transmit it to the T-SN.

[0225] The terminal receiving the above information can perform the same operation as in opt 1. Therefore, a detailed description thereof may be omitted here, and those skilled in the art will be able to easily infer and apply the related operation based on the description in the above-described embodiment.

[0226] Meanwhile, in this case, actions 2 and 3 may also be required in opt 1.

[0227] FIG. 13 is a diagram illustrating an example of a case in which securityCellSetId is included in a location unrelated to a conditional Reconfiguration field according to an embodiment of the present invention.

[0228] Referring to FIG. 13, in step 1310, a terminal (1301) can set up MR (multi radio) DC (dual connectivity) with an S-MN (MN) (1302), an S-SN (SN1) (1303), and an S-SN (SN2) (1304). In addition, in step 1315, SCPAC can be prepared for the S-MN (1302), S-SN (SN1) (1303), SN2 (1304), and SN3 (1305). In step 1320, the terminal (1301) can receive an RRC message (e.g., an RRC reconfiguration message) including SPCPAC configuration information from the S-MN (1302). In step 1325, the terminal (1301) can transmit a response message (e.g., an RRC reconfiguration complete message) to the MN (1302). The SCPAC configuration information can include a securityCellSetid for each candidate pscell. The terminal (1301) can store the initial servingSecurityCellSetid in a variable.

[0229] After the terminal (1301) receives the SCPAC settings, at step 1330, the S-SN (SN1) (1303) may want to perform a normal pscell change to one of the SCPAC candidate cells on SN3 (T-SN) (1305). In this case, at step 1335, the S-SN (1303) may request a pscell change to the target cell of SN3 (1305) through an SN change required message to MN (1302). At steps 1340 and 1350, the MN (1302) may request a resource reservation for the corresponding target cell by exchanging SN ADD (addition) Req (request) / SN ADD REqACK (request acknowledgment) messages with SN3 (1305). Accordingly, at step 1345, the SN3 (1305) may create an SN RRCReconfiguration message (SCG configuration). At this time, depending on the embodiment, the securityCellSetId value may be included in the SN RRCReconfiguration including reconfigurationWithSync message. In this case, the MN (1302) can determine the securityCellSetId value and transmit it to the T-SN (1305), and the T-SN (1305) that receives the value can include it in the SN RRCReconfiguration including reconfigurationWithSync message and transmit it again to the MN (1302), and finally, the MN (1302) can include the received SN RRCReconfiguration in the MN RRCReconfiguration and transmit it to the terminal (1301) at step 1350. In this case, the MN (1302) can include the securityCellSetId value in the SN ADD REQ message and transmit it to the T-SN (1305).

[0230] According to an embodiment, at step 1355, if MN (1302) recognizes the success of resource allocation for a target pscell from T-SN (SN3) (1305), and if the target pscell is one of the candidate cells of the existing SCPAC, the securityCellSetId value allocated to it may be included in MN RRCReconfiguration. Then, MN (1302) may transmit an MN RRC reconfiguration message to UE (1301).

[0231] And in step 1360, the terminal (1301) can apply the pscell change, and in step 1365, can transmit a response message (e.g., RRC reconfiguration complete message) to the MN (1302) in response. In step 1370, the MN (1302) can transmit an SN change confirm message to the SN1 (1303), and in step 1375, the MN (1302) can transmit an SN reconfiguration complete message to the SN3 (1303). Accordingly, in step 1380, the SN3 (1305) and the terminal (1301) can perform the RACH procedure.

[0232] In this case, the terminal (1301) can perform a pscell change while applying the MN RRCReconfiguration message. In addition, considering that the securityCellSetId value for the target pscell is included, the terminal (1301) compares the securityCellSetId value with the message that the terminal (1301) currently stores in Var ServingSecurityCellSetId, and if they are the same, a separate security key update is not performed. If they are different, the value stored in var ServingSecurityCellSetId is replaced with the indicated securityCellSetId value of the target pscell, and the first value among the sk-counter list linked to the securityCellSetId is selected and a security key update is performed with that value.

[0233] According to an embodiment, in the case of a MN initiated normal pscell change, the same operation may be performed as in the case of a SN initiated normal pscell change. Since a specific description thereof is similar to the embodiment described in FIGS. 10 and 11 above, a detailed description thereof will be omitted.

[0234] Both Opt 1 and Opt 2 are expressed as securityCellSetId, but from the target pscell perspective, servingSecurityCellSetId can mean the same thing and the term is not limited.

[0235] For Opt 3, the MN or T-SN includes the sk-counter value to be used instead of the securityCellSetId value in the MN RRCReconfiguration and transmits it to the UE. In this case, the UE does not perform the update process by comparing the Var ServingSecurityCellSetId required for SCPAC configuration with the securityCellSetId of the target cell. Accordingly, since the Var value is not guaranteed to be updated, the SCPAC operation cannot be performed properly thereafter. Accordingly, when the UE receives the MN RRCReconfiguration including SN RRCREconfiguration with reconfigurationWithSync, and in that case, if the sk-count value is received in the SN RRCReconfiguration, the UE applies the sk-counter value, performs the corresponding security key update operation, and can erase all information related to the SCPAC configuration. The erased target may include at least one of the following:

[0236] - In Var conditional Reconfiguration, the condReconfigToAddMod entry associated with the SCPAC configuration

[0237] - Delete the measurement id, reportConfig, and measObjects of the conditions referred to as condition information in the above entry from Var measConfig.

[0238] -Var servingSecurityCellSetId

[0239] Additionally, the terminal may ignore the terminal variable update operation corresponding to action 2 / 3 on opt 1, 2.

[0240] For Issue 2, this is a proposal for the behavior of updating CPA-related security settings given the SCPAC settings.

[0241] There are cases where an SCG release is performed by the network or due to other requirements when the SCPAC configuration of the terminal has already been received. In this case, since there is no longer a serving pscell, the Var servingSecurityCellSetId that was maintained can be deleted. However, the terminal still maintains the candidate target pscell configuration within the SCPAC configuration and the conditions that must be satisfied when adding the pscell. Therefore, if one of the conditions is satisfied, a CPA to add the target pscell will be performed. Since the securityCellSetId of the target pscell also exists, the sk-counter value associated with the securityCellSetId can be selected to perform a security key update.

[0242] It should be noted that the aforementioned configuration diagrams, examples of control / data signal transmission methods, examples of operational procedures, and configuration diagrams are not intended to limit the scope of the present disclosure. That is, not all components, entities, or operational steps described in the embodiments of the present disclosure should be construed as essential components for implementing the disclosure, and implementations may be made within a scope that does not detract from the essence of the disclosure even if only some components are included. Furthermore, each embodiment may be combined and operated as needed. For example, parts of the methods proposed in the present disclosure may be combined to operate network entities and terminals.

[0243] The operations of the base station or terminal described above can be realized by providing a memory device storing the corresponding program code in any component within the base station or terminal device. That is, the control unit of the base station or terminal device can execute the operations described above by reading and executing the program code stored in the memory device using a processor or CPU (Central Processing Unit).

[0244] The various components and modules of the entity, base station or terminal device described in this specification may be operated using hardware circuits, such as logic circuits based on complementary metal oxide semiconductors, firmware, software and / or hardware and firmware and / or software embedded in a machine-readable medium. For example, various electrical structures and methods may be implemented using electrical circuits such as transistors, logic gates and application-specific semiconductors.

[0245] 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.

[0246] 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.

[0247] 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.

[0248] 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.

[0249] 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.

[0250] Meanwhile, while the detailed description of the present invention has described specific embodiments, it goes without saying 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 determined not only by the scope of the following claims but also by equivalents of the scope of the claims. In other words, it will be apparent to those skilled in the art that other modifications based on the technical idea of ​​the present disclosure are possible. In addition, each of the above embodiments can be combined and operated with each other as needed. For example, parts of the methods proposed in the present disclosure can be combined with each other to operate a base station and a terminal. In addition, although the above embodiments have been presented based on a 5G, NR system, other modifications based on the technical idea of ​​the above embodiments can be implemented with other systems such as LTE, LTE-A, and LTE-A-Pro systems.

Claims

1. A method performed by a terminal of a wireless communication system, When a dual connectivity (DC) is established between a master node and a first secondary node, a step of receiving a first message including SCPAC (subsequent conditional pscell (primary secondary cell) addition and change) configuration information for at least one candidate secondary node, the first message including information associated with security parameters assigned to a pscell (primary secondary cell) of at least one candidate secondary node, from the master node; A step of receiving a second message from the master node, the second message including secondary cell group (SCG) configuration information for changing the secondary node of the second secondary node among the at least one candidate secondary node to a pscell; A step of applying the above SCG setting information; and Comprising a step of performing a random access procedure with the second secondary node, A method characterized in that the second message includes information associated with security parameters assigned to the pscell of the second secondary node.

2. In paragraph 1, The information associated with the security parameters assigned to the pscell of the second secondary node is included in the conditional reconfiguration information, A method characterized in that the above SCG configuration information includes ReconfigurationWithSync information.

3. In paragraph 1, A method, characterized in that the first message or the second message includes a radio resource control (RRC) reconfiguration message.

4. In paragraph 1, A method characterized in that the information associated with the security parameters assigned to the pscell of the second secondary node includes a securityCellSetId.

5. A method performed by a master node of a wireless communication system, A step of transmitting, to the terminal, a first message including SCPAC (subsequent conditional pscell (primary secondary cell) addition and change) configuration information for at least one candidate secondary node, the first message including information related to a security parameter assigned to a pscell (primary secondary cell) of at least one candidate secondary node, when dual connectivity (DC) is established with the master node and the first secondary node; A step of transmitting a request message for changing the secondary node of at least one candidate secondary node to a pscell of the second secondary node to the second secondary node; A step of receiving a response message including SCG (secondary cell group) setting information for changing the secondary node from the second secondary node; and Comprising a step of transmitting a second message including the above SCG setting information to the terminal, A method characterized in that the second message includes information associated with security parameters assigned to the pscell of the second secondary node.

6. In paragraph 5, The information associated with the security parameters assigned to the pscell of the second secondary node is included in the conditional reconfiguration information, A method characterized in that the above SCG configuration information includes ReconfigurationWithSync information.

7. In paragraph 5, A method, characterized in that the first message or the second message includes a radio resource control (RRC) reconfiguration message.

8. In paragraph 5, A method characterized in that the information associated with the security parameters assigned to the pscell of the second secondary node includes a securityCellSetId.

9. In the terminal of a wireless communication system, Transmitter and receiver; and Connected to the above transmitter and receiver, When a dual connectivity (DC) is established between a master node and a first secondary node, a first message including SCPAC (subsequent conditional pscell (primary secondary cell) addition and change) configuration information for at least one candidate secondary node is received from the master node, the first message including information related to security parameters assigned to the pscell (primary secondary cell) of the at least one candidate secondary node, Receiving a second message from the master node, which includes SCG (secondary cell group) configuration information for changing the secondary node of the second secondary node among the at least one candidate secondary node to a pscell, Apply the above SCG setting information, Including the second secondary node and a control unit performing a random access procedure, A terminal characterized in that the second message includes information associated with security parameters assigned to the pscell of the second secondary node.

10. In paragraph 9, The information associated with the security parameters assigned to the pscell of the second secondary node is included in the conditional reconfiguration information, A terminal characterized in that the above SCG configuration information includes ReconfigurationWithSync information.

11. In paragraph 9, A terminal, characterized in that the first message or the second message includes an RRC (radio resource control) reconfiguration message.

12. In paragraph 8, A terminal characterized in that the information associated with the security parameters allocated to the pscell of the second secondary node includes a securityCellSetId.

13. In the master node of a wireless communication system, Transmitter and receiver; and Connected to the above transmitter and receiver, When dual connectivity (DC) is established with the master node and the first secondary node in the terminal, a first message including SCPAC (subsequent conditional pscell (primary secondary cell) addition and change) configuration information for at least one candidate secondary node, which includes information related to security parameters allocated to the pscell (primary secondary cell) of at least one candidate secondary node, is transmitted to the terminal, Transmitting a request message for changing the secondary node of at least one candidate secondary node to a PScell ​​of the second secondary node to the second secondary node, Receive a response message from the second secondary node, which includes SCG (secondary cell group) setting information for changing the secondary node, A control unit for transmitting a second message including the above SCG setting information to the terminal, A master node, characterized in that the second message includes information associated with security parameters assigned to the pscell of the second secondary node.

14. In paragraph 13, The information associated with the security parameters assigned to the pscell of the second secondary node is included in the conditional reconfiguration information, A master node, characterized in that the above SCG configuration information includes ReconfigurationWithSync information.

15. In paragraph 13, The first message or the second message includes a radio resource control (RRC) reconfiguration message, A master node, characterized in that the information associated with the security parameters assigned to the pscell of the second secondary node includes a securityCellSetId.

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