Method and apparatus for supporting resumption of terminal in wireless communication system

Abstract

The present disclosure relates to a 5G or 6G communication system for supporting a higher data transmission rate. In addition, the present disclosure relates to a method and an apparatus for fast connection resumption by using pre-configuration.

Description

Method and device for supporting terminal resumption in a wireless communication system

[0001] The present disclosure relates to base station and terminal operation in a mobile communication system. Additionally, the present disclosure relates to a method and apparatus for resuming connection of a terminal based on pre-configuration in a wireless communication system.

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

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

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

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

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

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

[0008] An embodiment of the present disclosure is capable of providing a method and apparatus for resuming connection of an enhanced terminal based on a pre-configuration in a wireless communication system.

[0009] An embodiment of the present disclosure provides a method for supporting a rapid connection between a terminal and a base station in the process of a terminal in an RRC (radio resource control) inactive state connecting to a base station in a mobile communication system. To this end, after the terminal selects a candidate cell and a base station while in an RRC connected state, it pre-configures terminal context information and RRC connection information for connection with the terminal at the base station supporting the candidate cell. Then, in the process of performing a resume connection to the candidate cell and base station where the RRC connection information is pre-configured after the terminal transitions to an RRC inactive state, the method enables the rapid completion of the RRC resume connection based on the pre-configured terminal context information and RRC connection configuration information.

[0010] The technical problems to be solved in the embodiments of the present invention are not limited to those mentioned above, and other technical problems not mentioned will be clearly understood by those skilled in the art to which the present invention belongs from the description below.

[0011] The present disclosure, for solving the above-mentioned problems, provides a method performed by a terminal in a wireless communication system comprising: receiving an RRC message from a serving cell containing configuration information of a candidate cell for a quick resume connection in a radio resource control (RRC) disabled state; maintaining the configuration information of the candidate cell for a quick resume connection in the RRC disabled state when the connection state of the terminal is switched from an RRC connected state to the RRC disabled state; determining a transition from the RRC disabled state to the RRC connected state; and performing an RRC resume procedure based on the configuration information of the candidate cell for a quick resume connection in the RRC disabled state when the terminal determines a transition from the RRC disabled state to the RRC connected state within the candidate cell.

[0012] Additionally, the present disclosure provides a method performed by a base station of a serving cell in a wireless communication system, comprising: determining a candidate cell for a quick resume connection in an RRC (radio resource control) disabled state based on measurement information received from a terminal in an RRC disabled state; obtaining configuration information of the candidate cell for a quick resume connection in the RRC disabled state; and transmitting an RRC message including the configuration information of the candidate cell for a quick resume connection in the RRC disabled state to the terminal in the RRC disabled state, wherein after transmitting the RRC message to the terminal, the terminal in the RRC disabled state switches to the RRC disabled state, and when the terminal in the RRC disabled state decides to switch to the RRC disabled state within the candidate cell, an RRC resumption procedure is performed based on the configuration information of the candidate cell for a quick resume connection in the RRC disabled state.

[0013] Additionally, the present disclosure provides a terminal of a wireless communication system comprising: a transceiver; and at least one processor connected to the transceiver, wherein the at least one processor receives an RRC message from a serving cell containing configuration information of a candidate cell for a quick resume connection in a radio resource control (RRC) disabled state, and when the connection state of the terminal is switched from an RRC connected state to an RRC disabled state, the processor maintains the configuration information of the candidate cell for a quick resume connection in the RRC disabled state, determines a transition from the RRC disabled state to the RRC connected state, and when the terminal determines a transition from the RRC disabled state to the RRC connected state within the candidate cell, controls the execution of an RRC resume procedure based on the configuration information of the candidate cell for a quick resume connection in the RRC disabled state.

[0014] Additionally, the present disclosure provides a base station of a serving cell of a wireless communication system comprising: a transceiver; and at least one processor connected to the transceiver; wherein the at least one processor determines a candidate cell for a quick resume connection in an RRC inactive state based on measurement information received from a terminal in an RRC (radio resource control) connection state, obtains configuration information of the candidate cell for a quick resume connection in the RRC inactive state, and controls the transmission of an RRC message including the configuration information of the candidate cell for a quick resume connection in the RRC inactive state to the terminal in the RRC connection state, and after transmitting the RRC message to the terminal, the terminal in the RRC connection state switches to the RRC inactive state, and when the terminal in the RRC inactive state decides to switch to the RRC connection state within the candidate cell, an RRC resumption procedure is performed based on the configuration information of the candidate cell for a quick resume connection in the RRC inactive state.

[0015] According to various embodiments of the present disclosure, an improved method for resuming a connection and an apparatus for performing the same can be provided.

[0016] In addition, according to various embodiments of the present disclosure, an improved resumption method for a terminal in an RRC disabled state based on a pre-configuration in a wireless communication system can be provided.

[0017] The effects obtainable in the present disclosure are not limited to those mentioned in the various embodiments, and other unmentioned effects will be clearly understood by those skilled in the art to which the present disclosure pertains from the description below.

[0018] FIG. 1 is a drawing illustrating an example of the structure of a mobile communication system to which embodiments of this disclosure can be applied.

[0019] FIG. 2 is a diagram illustrating an example of the structure of a mobile communication system using a detachable mobile communication base station to which embodiments of the present disclosure can be applied.

[0020] FIGS. 3A and 3B are drawings illustrating the setup and resumption process for a rapid resumption procedure according to one embodiment of the present disclosure.

[0021] FIG. 4 is a diagram illustrating the process of a terminal according to one embodiment of the present disclosure performing a resume connection to a base station of a cell that does not support a fast resume connection.

[0022] FIG. 5 is a diagram illustrating a process of performing a fast resume connection based on a paging procedure according to one embodiment of the present disclosure.

[0023] FIG. 6 is a diagram illustrating the process of performing a resume connection to a base station of a cell that does not support a fast resume connection after a paging procedure according to one embodiment of the present disclosure.

[0024] FIGS. 7A, 7B, and 7C are drawings illustrating a process of performing a fast resume when moving between cells within a separated base station according to one embodiment of the present disclosure.

[0025] FIGS. 8A and 8B are drawings illustrating a process of performing a connection to a cell that does not support a fast resume connection when moving between cells within a separated base station according to one embodiment of the present disclosure.

[0026] FIG. 9 is a diagram illustrating a process of performing a fast resume connection based on a paging procedure when moving between cells within a separated base station according to one embodiment of the present disclosure.

[0027] FIGS. 10A and 10B are drawings illustrating a process of performing a resume connection to a cell that does not support a fast resume connection after a paging procedure when moving between cells within a separated base station according to one embodiment of the present disclosure.

[0028] FIG. 11 is a diagram showing the configuration of a HANDOVER REQUEST message according to one embodiment of the present disclosure.

[0029] FIG. 12 is a diagram showing the configuration of a HADVER REQUEST ACKNOWLEDGE message according to one embodiment of the present disclosure.

[0030] FIG. 13 is a diagram showing the configuration of an RRC STATE TRANSITION NOTIFICATION message according to one embodiment of the present disclosure.

[0031] FIG. 14 is a diagram showing the configuration of a UE CONTEXT SETUP REQUEST message according to one embodiment of the present disclosure.

[0032] FIG. 15 is a diagram showing the configuration of a UE CONTEXT SETUP RESPONSE message according to one embodiment of the present disclosure.

[0033] FIG. 16 is a diagram showing the configuration of an RRC STATE TRANSITION NOTIFICATION message according to one embodiment of the present disclosure.

[0034] FIG. 17 is a diagram showing the configuration of a base station (RAN Node) according to one embodiment of the present disclosure.

[0035] FIG. 18 is a diagram showing the configuration of a terminal (UE) according to one embodiment of the present disclosure.

[0036] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the attached drawings. In this regard, it should be noted that identical components in the attached drawings are indicated by the same reference numerals whenever possible. Furthermore, detailed descriptions of known functions and configurations that may obscure the essence of the present invention will be omitted.

[0037] In describing the embodiments in this specification, technical details that are well known in the technical field to which the present invention belongs and are not directly related to the present invention are omitted. This is intended to convey the essence of the present invention more clearly without obscuring it by omitting unnecessary explanations.

[0038] For the same reason, some components in the attached drawings have been exaggerated, omitted, or schematically depicted. Additionally, the size of each component does not entirely reflect its actual dimensions. Identical or corresponding components in each drawing have been assigned the same reference numbers.

[0039] The advantages and features of the present invention and the methods for achieving them will become clear by referring to the embodiments described below in detail together with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below but can be implemented in various different forms. These embodiments are provided merely to ensure that the disclosure of the present invention is complete and to fully inform those skilled in the art of the scope of the invention, and the present invention is defined only by the scope of the claims. Throughout the specification, the same reference numerals refer to the same components.

[0040] At this time, it will be understood that each block of the process flow diagrams and combinations of the flow diagrams can be executed by computer program instructions. Since these computer program instructions can be loaded into the processor of a general-purpose computer, a special-purpose computer, or other programmable data processing equipment, the instructions executed through the processor of the computer or other programmable data processing equipment create means to perform the functions described in the flow diagram block(s). Since these computer program instructions can also be stored in computer-available or computer-readable memory that can be directed toward the computer or other programmable data processing equipment to implement the function in a specific way, the instructions stored in computer-available or computer-readable memory can also produce a manufactured item containing the means of instruction to perform the function described in the flow diagram block(s). Since computer program instructions can be loaded onto a computer or other programmable data processing equipment, instructions that perform a series of operation steps on the computer or other programmable data processing equipment to create a process executed by the computer can also provide steps for executing the functions described in the flowchart block(s).

[0041] Additionally, each block may represent a module, segment, or part of code containing one or more executable instructions for executing a specified logical function(s). It should also be noted that in some alternative execution examples, the functions mentioned in the blocks may occur out of order. For instance, two blocks described in succession may actually be executed substantially simultaneously, or the blocks may be executed in reverse order according to their corresponding functions.

[0042] In this embodiment, the term "part" refers to a software or hardware component, such as an FPGA or ASIC, and the "part" performs certain roles. However, the meaning of "part" is not limited to software or hardware. The "part" may be configured to reside in an addressable storage medium or configured to operate one or more processors. Accordingly, as an example, the "part" includes components such as software components, object-oriented software components, class components, and task components, as well as processes, functions, attributes, procedures, subroutines, segments of program code, drivers, firmware, microcode, circuits, data, databases, data structures, tables, arrays, and variables. The functions provided within the components and "parts" may be combined into a smaller number of components and "parts" or further separated into additional components and "parts." Furthermore, the components and "parts" may be implemented to operate one or more CPUs within a device or secure multimedia card.

[0043] Hereinafter, a base station is an entity that performs resource allocation for terminals and may be at least one of a Node B, BS (Base Station), eNB (eNode B), gNB (gNode B), RAN (radio access network) node, radio access unit, base station controller, or a node on a network. A terminal may include a UE (User Equipment), MS (Mobile Station), cellular phone, smartphone, computer, or a multimedia system capable of performing communication functions. Furthermore, the embodiments of the present disclosure may be applied to other communication systems having a technical background or channel type similar to the embodiments of the present disclosure described below. Additionally, the embodiments of the present disclosure may be applied to other communication systems through some modifications within the scope that does not significantly deviate from the scope of the present disclosure, at the judgment of a person with skilled technical knowledge. For example, 5th generation mobile communication technology (5G, new radio, NR) developed after LTE-A may be included therein, and the 5G below may be a concept that includes existing LTE, LTE-A, and other similar services. In addition, the present disclosure may be applied to other communication systems with some modifications made at the discretion of a person with skilled technical knowledge, without significantly departing from the scope of the present disclosure.

[0044] Terms used in the following description to identify connection nodes, terms referring to network entities or network functions (NFs), terms referring to messages, terms referring to interfaces between network entities, terms referring to various identification information, etc., are examples provided for the convenience of explanation. Accordingly, the present invention is not limited to the terms described below, and other terms referring to objects having equivalent technical meanings may be used.

[0045] For the convenience of the following explanation, some terms and names defined in the 3GPP (3rd generation partnership project) LTE (long term evolution) standards and / or 3GPP NR (new radio) standards may be used. However, the present invention is not limited by the above terms and names and can be applied in the same way to systems conforming to other standards.

[0046] In various embodiments of the present disclosure, setting information for a quick resume connection in an RRC inactive state, setting information for a quick resume connection in an RRC inactive state, setting for a quick resume connection in an RRC inactive state, setting for a quick resume connection in an RRC inactive state, etc., may be used with the same or similar meaning.

[0047] In addition, in various embodiments of the present disclosure, the previous serving base station, the previous serving (last serving) base station, the last serving base station, and the last serving RAN node correspond to the same entity. In addition, in various embodiments of the present disclosure, the new serving base station, the new serving (new serving) base station, the new serving base station, and the new serving RAN node correspond to the same entity. In addition, in various embodiments of the present disclosure, the serving base station, the serving base station, and the serving RAN node correspond to the same entity.

[0048] FIG. 1 is a drawing illustrating an example of the structure of a mobile communication system to which embodiments of this disclosure can be applied.

[0049] The RAN Node (20) specified in this structure can be a base station connected to the core network (CN: core network) (30), for example, a 4G eNB, a 5G gNB, a 6G base station, etc. The core network (30) can be an EPC (evolved packet core network), a 5GC (5G core network), a 6GC (6G core network), etc., and some entities or functions of the core network establish an interface connection with the RAN Node (20), for example, a 4G MME (mobility management entity) or a 5G AMF (access and mobility management function). The connection interface (70) between the RAN Node (20) and the core network (30) can be a 4G S1 interface, a 5G NG interface, a 6G NG interface, etc. A RAN Node (20) can be connected to an interface (70) that can communicate directly with another RAN Node, and the interface (80) between RAN Nodes can be a 4G X2 interface, a 5G Xn interface, a 6G Xn interface, etc. Additionally, a RAN Node (20) may not be connected to an interface for direct communication with another RAN Node, and if there is no interface directly connected between RAN Nodes, an interface connected to the core network (30) can be used.

[0050] FIG. 2 is a diagram illustrating an example of the structure of a mobile communication system using a detachable mobile communication base station to which embodiments of the present disclosure can be applied.

[0051] The RAN Node (20) specified in FIG. 2 may include a central unit (CU) (20-a) and a distributed unit (DU) (20-b). The central unit (20-a) may again include a CU-CP (central unit - control plane) that processes the radio resource control (RRC) layer and a CU-UP (central unit - user plane) for processing data packets from the terminal. In one embodiment, the RAN Node (20), which is a base station, may be composed of one CU (20-a) and one or more DUs (20-b) connected thereto, or may be composed of other combinations. The CU (20-a) and the DU (20-b) may support the respective base station functions separately. For example, the CU (20-a) may support the RRC layer that processes control signals to be transmitted to the terminal (10) and the PDCP (packet data convergence protocol) layer that processes data packets from the terminal. The DU (20-b) can support the RLC (radio link control) layer, MAC (medium access control) layer, and PHY (physical) layer, and can be responsible for communication with the terminal (10) in the wireless section. Depending on the base station functions supported by the RAN Node (20), the functions supported by the CU (20-a) and DU (20-b) constituting the RAN Node (20) may differ, and the names of each function or entity constituting the RAN Node (20) may differ. The interface (60) between the CU (20-a) and DU (20-b) within the RAN Node (20) may be a 4G W1 interface, a 5G F1 interface, a 6G F1 interface, etc.

[0052] The connection state between a terminal and a base station in a mobile communication system is defined by the RRC protocol, and the terminal's state is defined by the following three RRC states.

[0053] - RRC IDLE state: A state in which the terminal is not connected to the base station via RRC. During this time, the terminal detects the base station's incoming signal, monitors the paging channel to receive core network paging (CN Paging), obtains cell system information, and independently performs neighbor cell measurement and cell selection.

[0054] - RRC CONNECTED state: This is the state in which the terminal is RRC connected with the base station. The terminal transmits and receives data to and from the network through the base station, and performs handover between cells and base stations under the control of the base station based on the terminal's measurement result reports.

[0055] - RRC Inactive State: This is a state in which, after the terminal has entered the RRC Connected State with the base station, the RRC connection is disconnected, allowing the base station and the terminal to save some of the UE context information of the RRC Connected State, thereby enabling a fast RRC connection. Similar to the RRC IDLE State, the terminal detects the received signal from the base station and monitors the paging channel to receive CN Paging and RAN paging. It obtains cell system information and performs neighbor cell measurement and cell selection autonomously. Additionally, it checks the RAN-based notification area set by the network based on the cell system information, and if it moves out of the set RAN-based notification area, it performs a procedure to update the RAN-based notification area to the network.

[0056] Previously, for a terminal in the RRC inactive state, the last serving base station—the base station where the terminal transitioned from the RRC connected state to the RRC inactive state—stored the terminal context (UE context) information. Then, during the process of the RRC inactive terminal re-establishing an RRC connection with a base station to transition back to the RRC connected state, when the terminal transmits an RRC message for an RRC resume connection to the new serving base station, the new serving base station receives the terminal context (UE context) information from the last serving base station, configures the radio resources, and delivers them to the terminal via an RRC message to complete the resume procedure.

[0057] In the present invention, to ensure a rapid connection between the terminal and the base station during the process of a terminal in an RRC inactive state connecting to a base station, candidate cells and base stations are selected while the terminal is in an RRC connected state, and terminal context (UE context) information and RRC connection information for connection with the terminal are pre-configured. Furthermore, in the process of performing a resume connection to the candidate cells and base stations for which RRC connection information is pre-configured after the terminal transitions to an RRC inactive state, the RRC resume connection is performed based on the pre-configured terminal context (UE context) information and RRC connection configuration information. This allows the process of transmitting terminal context (UE context) information between base stations and the procedures required to configure wireless resources to be omitted, thereby enabling the terminal's resume connection procedure to be completed quickly. To this end, the method includes selecting candidate cells and base stations to pre-configure information for a fast resume connection in an RRC inactive state at a serving base station to which a terminal in an RRC connected state is connected, setting terminal context (UE context) information and RRC connection information for connection with the terminal in an RRC inactive state, releasing terminal context (UE context) information and RRC connection information for connection with the terminal in an RRC inactive state at a serving base station to which the terminal is connected, and transmitting configuration information for a fast resume connection to the candidate cells and base stations in an RRC inactive state to the terminal.In addition, the procedure includes a procedure for performing a fast resume connection when data or signaling messages to be transmitted occur at an RRC inactive state terminal, and a procedure for the RRC inactive state terminal to perform a fast resume connection after receiving a paging message following a paging procedure when data or signaling messages to be transmitted to an RRC inactive state terminal occur.

[0058] FIGS. 3A and 3B are drawings illustrating the setup and resumption process for a rapid resumption procedure according to an embodiment of the present disclosure. FIGS. 3A and FIGS. 3B are collectively referred to as FIG. 3.

[0059] Referring to FIG. 3, a signal flow for setting information to support a fast resume connection in an RRC inactive state to a terminal connected to a base station according to one embodiment, and after the terminal transitions from an RRC connected state to an RRC inactive state, user data or signal message to be transmitted by the terminal is generated, and the terminal performs a fast resume connection to a cell and base station where a fast resume connection in an RRC inactive state is set. The current serving RAN Node determines the surrounding candidate cell and RAN node while the terminal is in the RRC connected state, defines a handover procedure between base stations or a new procedure, performs a configuration procedure to support fast resume connection from the RRC inactive state to the candidate cell and RAN node, and also transmits configuration information for fast resume connection from the RRC inactive state to the terminal using an RRC message.

[0060] In step 100 of FIG. 3, the terminal (10) is connected to RAN Node 1 (20) and is in an RRC connected state. In step 110, the terminal (10) in the RRC connected state becomes capable of exchanging user data or signal messages with RAN Node 1 (20), and RAN Node 1 (20) operates as a serving RAN node for the terminal (10).

[0061] In step 200, the terminal (10) reports the surrounding signal measurement results to the RAN Node 1 (20) according to the signal measurement and reporting settings of the RAN Node 1 (20). In step 210, the RAN Node 1 (20), based on the measurement results reported by the terminal (10), determines whether the terminal (10) will set up a fast resume connection in the RRC inactive state and determines the candidate cell and base station (candidate cell / RAN node). In steps 220, 222, and 224, the RAN Node 1 (20) transmits a message to the RAN Node 2 (22), RAN Node 3 (24), and RAN Node 4 (26), respectively, containing information about the candidate cell or cells that will support the fast resume connection in the RRC inactive state of the terminal (10), and information related to the request for setting up a fast resume connection in the RRC inactive state. The above message may correspond to a message between base stations, for example, a handover request message or a new message, but is not limited thereto. RAN node 1 (20) transmits the above message to RAN Node 2 (22), RAN Node 3 (24) and RAN Node 4 (26), respectively, through a base station interface, for example, an Xn and / or 6G Xn interface. Information related to a request for a setup for a fast resume connection in an RRC inactive state may include timer information for maintaining and managing the setup for a fast resume connection in an RRC inactive state.RAN Node 2 (22), RAN Node 3 (24), and RAN Node 4 (26), upon receiving a request from RAN Node 1 (20) for a fast resume connection setup in an RRC inactive state for the terminal (10), determine whether to accept the fast resume connection setup in an RRC inactive state in steps 230, 232, and 234, respectively, and if accepted, allocate or reserve (reserve) context setup and resources for the terminal (10). The terminal context (UE context) information may be set based on the information included in the message transmitted by RAN Node 1 (20) in steps 220, 222, and 224.

[0062] RAN Node 2 (22) and RAN Node 3 (24), having accepted the fast resume connection setup in the RRC inactive state, may send a response message to RAN Node 1 (20) in steps 240 and 242. For example, the response message may be a Handover Request Acknowledge message or a new response message, but is not limited thereto. The response message may include an indicator that accepts the fast resume connection setup in the RRC inactive state (for example, setting the INACTIVE-PreConfiguration support IE (information element) to 'true'). Additionally, the response message may include configuration information for the fast resume connection in the RRC inactive state. Configuration information for a fast resume connection in the RRC inactive state may use the same configuration information for handover support, such as conditional handover (CHO) or LTM (L1 / L2 triggered mobility), which similarly pre-configures to support terminal handover in the RRC connected state, or may use separate configuration information only for a fast resume connection in the RRC inactive state. For example, the separate configuration information for a fast resume connection may be INACTIVEPreconfigurationInfo IE, but the name of the configuration information is not limited to this. On the other hand, RAN Node 4 (26), which rejects the fast resume connection configuration in the RRC inactive state, may send a response message to RAN Node 1 (20) in step 244.The above response message may include an indicator that rejects the fast resume connection setup in an RRC inactive state. For example, the indicator may be INACTIVE-PreConfiguration support IE, but the name of the indicator is not limited to this. The RAN Node 4 (26) may indicate the rejection of the fast resume connection by setting the value of the indicator to 'false'.

[0063] The procedures and messages for requesting and responding to fast resume connection setup in an RRC-inactive state using the inter-base station interfaces used in steps 220, 222, 224 and 240, 242, and 244 may use existing procedures and messages to support inter-base station handover, or may be supported by defining new inter-base station procedures and messages. When using handover procedures and messages, the requests and responses for fast resume connection setup in an RRC-inactive state may be supported simultaneously with supporting existing handover, or separately regardless of existing handover procedures.

[0064] RAN Node 1 (20), having received response messages from RAN Node 2 (22), RAN Node 3 (24), and RAN Node 4 (26) at steps 240, 242, and 244, respectively, can generate an RRC message containing configuration information for a fast resume connection in an RRC inactive state to be transmitted to the terminal (10) at step 250. If RAN Node 1 (20) supports a fast resume connection in an RRC inactive state, the configuration information for a fast resume connection in an RRC inactive state may also include configuration information for a fast resume connection in an RRC inactive state to RAN Node 1 (20). Then, RAN Node 1 (20) can transmit the configuration information for a fast resume connection in an RRC inactive state to the terminal (10) at step 260. The configuration information for a fast resume connection in an RRC inactive state may be, for example, INACTIVEPreConfiguration, but its name is not limited thereto. Configuration information for a fast resume connection in the above RRC inactive state may be included in an RRC message and transmitted to the terminal (10). For example, the RRC message may be an RRCReconfiguration message. In step 270, the terminal (10) may transmit an RRC response message to RAN Node 1 (20) in response to the RRC message received in step 260. For example, the RRC response message may be an RRCReconfigurationComplete message, but is not limited thereto.

[0065] Afterward, since there is no traffic transmitted or received between RAN Node 1 (20) and the terminal (10), RAN Node 1 (20) may decide to transition the RRC connection state of the terminal (10) to an RRC disabled state in step 300. In step 310, RAN Node 1 (20) may transmit an RRC message to the terminal (10) containing information for transitioning the terminal (10) to an RRC disabled state. For example, the information may be SuspendConfig information, and the RRC message may be an RRCRelease message. After receiving the RRC message in step 310 and transitioning to an RRC disabled state, the terminal (10) may continue to maintain configuration information for operation in the RRC disabled state in step 330 and may start a timer to maintain and manage the fast resume connection settings in the RRC disabled state. The timer information in step 330 may be included in the RRC message received from RAN Node 1 (20) in step 260.

[0066] If, in step 300, RAN Node 1 (20) decides to transition the RRC connection state of the terminal (10) to an RRC inactive state, in steps 320 and 322, RAN Node 1 (20) may transmit information indicating that the terminal's RRC state has changed to RAN Node 2 (22) and RAN Node 3 (24), respectively, which maintain a fast resume connection setting in the RRC inactive state (RRC INACTIVE state). For example, the information may be an RRC state IE, and the RRC state IE may be set to 'INACTIVE' to indicate that the terminal in the connection state has become inactive. The information may be transmitted via a message between base stations, and for example, the message between base stations may be an RRC State Transition Notification message, but is not limited thereto. The message notifying the RRC state information transmitted in steps 320 and 322 may include timer information for maintaining and managing a setting for a fast resume connection in the RRC inactive state.

[0067] And, if a handover method such as CHO or LTM is configured in steps 224 and 244, in step 324, RAN Node 1 (20) may send a message to RAN Node 3 (24), which is not configured for a fast resume connection in the RRC inactive state, to release the information and terminal context configured for CHO or LTM support. For example, the message may be a handover cancel message. If CHO or LTM is not configured on RAN Node 3 (24), the procedure in step 324 may not be used. And, in step 346, RAN Node 4 (26) releases or deletes all terminal context information.

[0068] After RAN Node 1 (20) decides to transition the RRC connection state of the terminal (10) to an RRC inactive state in step 300, or while sending messages to RAN Node 2 (22), RAN Node 3 (24), and RAN Node 4 (26) in steps 320, 322, and 324, RAN Node 1 (20) may maintain the terminal context information of the terminal (10) and the fast resume connection setup information in the RRC inactive state in step 340, and RAN Node 1 (20) may drive a timer to maintain and manage the fast resume connection setup in the RRC inactive state (RRC INACTIVE state). RAN Node 2 (22) and RAN Node 3 (24), having received a message containing information indicating that the terminal (10) has transitioned to an RRC inactive state from RAN Node 1 (20) in steps 320 and 324 respectively, maintain terminal context information and fast resume connection setup information in the RRC inactive state in steps 342 and 344 respectively, and RAN Node 1 (20) may also drive a timer to maintain and manage the fast resume connection setup in the RRC inactive state.

[0069] Subsequently, the terminal (10) can change the cell it can connect to. After the terminal (10) moves from the cell area belonging to RAN Node 1 (20) to the cell area belonging to RAN Node 2 (22) in step 400, if user data or a signaling message that needs to be transmitted occurs from the terminal (10) in step 500, the terminal (10) determines a method to attempt to resume connection to the cell where the terminal (10) is currently located in step 510. In the case of a cell configured to allow for a quick resume connection in an RRC inactive state in step 510, the terminal (10) can perform a procedure for a quick resume connection based on the configuration information for a quick resume connection in an RRC inactive state. In the case of a cell that is not configured to allow for a quick resume connection from an RRC inactive state, the terminal (10) can perform a procedure (e.g., an RRC Resume procedure) to transition from an existing RRC inactive state (RRC INACTIVE state) to an RRC connected state (RRC CONNECTED state).

[0070] In step 510, if the terminal (10) decides to perform a fast resume connection in an RRC inactive state, in step 520, the terminal (10) may perform a random access procedure in the RAN Node 2 (22) cell according to the configured information. Then, in step 530, if the terminal (10) completes the fast resume connection in an RRC inactive state to the RAN Node 2 (22), it transmits an RRC message to the RAN Node 2 (22) indicating the completion of the fast resume connection. For example, the RRC message may be an RRCReconfigurationComplete message.

[0071] RAN Node 2 (22), having received an RRC message from the terminal (10) that the fast resume connection in the RRC inactive state has been completed, may, at step 540, send a message to RAN Node 1 (20), which was the terminal's previous serving base station (last serving RAN node), to inform that the terminal has made a fast resume connection in the RRC inactive state. The message may be a message between base stations, for example, a handover success message or a message between new base stations. RAN Node 1 (20), having received from RAN Node 2 (22) that the terminal has made a fast resume connection in the RRC inactive state to RAN Node 2 (22), may, at step 600, send a message to RAN Node 3 (24), which has a fast resume connection in the RRC inactive state set up for the terminal (10), to instruct the establishment of a fast resume connection in the RRC inactive state and the release of the terminal context. The above message is a message between base stations, and may be, for example, a handover cancel message. Then, in steps 610 and 612, RAN Node 1 (20) and RAN Node 3 (24) release the fast resume connection setup information in the RRC inactive state and the terminal context that are stored and set for the terminal (10).

[0072] In steps 550 and 560, RAN Node 2 (22) informs the core network (30) that the path for transmitting data or signaling messages to the terminal (10) has been changed to RAN Node 2 (22), and if necessary, performs a path switch procedure to receive a new policy from the core network (30). Then, in step 570, RAN Node 2 (22) becomes capable of exchanging user data or signaling messages with the core network (30), and RAN Node 2 (22) operates as a new serving base station for the terminal (10).

[0073] According to one embodiment of FIG. 3, after setting information to support a fast resume connection in an RRC inactive state to a terminal connected to a base station in an RRC connected state (RRC CONNECTED state), at least one of the following methods may be used to release and manage the previously set information and terminal context (UE context) settings.

[0074] - After the last serving base station (RAN Node 1 (20) in the embodiment of FIG. 3) determines and RAN paging is performed, the base station where the terminal performs the resume connection releases or resets the information and terminal context to support a fast resume connection in an RRC inactive state.

[0075] - Releases fast resume connection configuration information and terminal context in an RRC inactive state based on timer settings and termination.

[0076] In OAM (Operation and Maintenance), a timer value is set at the base station, and the base station transmits the timer value to the terminal via an RRC message.

[0077] After the serving base station determines the timer value, it requests the candidate base station to configure a quick resume connection when RRC is disabled, or notifies the terminal of a change in its RRC state while transmitting the timer value along with it, and the serving base station transmits the timer value to the terminal via an RRC message.

[0078] After the candidate base station determines the timer value, it transmits the timer value along with configuration information for a fast resume connection when RRC is disabled to the serving base station, and the serving base station transmits the timer value to the terminal via an RRC message.

[0079] According to one embodiment of FIG. 3, in a method for setting information to support a fast resume connection in an RRC inactive state to a terminal in an RRC connected state connected to a base station, the method of transmitting setting information for a fast resume connection in an RRC inactive state to a terminal at a serving RAN node may utilize at least one of the following methods.

[0080] - The RRCReconfiguration message transmitted to the terminal includes configuration information (e.g., INACTIVEPreConfiguration) for a fast resume connection when the terminal is in an RRC-inactive state, and the terminal transmits an RRCReconfigurationComplete message to the base station upon establishing a fast resume connection.

[0081] - Use a new RRC message (e.g., RRCFastResumeRequest) that can be sent as an RRC message container within the RRCReconfiguration message transmitted to the terminal, and the new RRC message (e.g., RRCFastResumeRequest) includes configuration information for a fast resume connection when the terminal is in an RRC-inactive state (e.g., INACTIVEPreConfiguration), and the terminal transmits a new RRC response message (e.g., RRCFastResumeComplete) to the base station upon the fast resume connection.

[0082] - A new RRC message is transmitted to the terminal, for example, an RRCFastResumeRequest message, containing configuration information (for example, INACTIVEPreConfiguration) for a fast resume connection when the terminal is in an RRC-inactive state, and the terminal transmits a new RRC response message (for example, an RRCFastResumeComplete message) to the base station upon the fast resume connection.

[0083] - Use a new RRC message (e.g., RRCFastResumeRequest) that can be sent as an RRC message container within the RRCRelease message transmitted to the terminal to transition from an RRC connected state to an RRC disabled state; the new RRC message (e.g., RRCFastResumeRequest) includes configuration information (e.g., INACTIVEPreConfiguration) for a fast resume connection from the RRC disabled state, and the terminal transmits a new RRC response message (e.g., RRCFastResumeComplete) to the base station upon establishing a fast resume connection.

[0084] According to one embodiment of FIG. 3, in a method for setting information to support fast resume connection in an RRC inactive state to a terminal in an RRC connected state connected to a base station, a RAN-based Notification Area (RNA) may be determined by considering candidate cells and base stations that support fast resume connection at a serving base station. The RNA represents area information where the base station does not need to be notified of a cell change when the RRC inactive state terminal moves between cells, and an RRC message (e.g., an RRCR release message) that changes the state of the RRC connected state terminal to an RRC inactive state at the serving base station may include RAN-based Notification Area (RNA) information. When determining the RNA at the serving base station, at least one of the following methods may be used.

[0085] - Includes cells to support fast resume connection in the RRC inactive state at the RNA terminal

[0086] - After RNA determination, for cells not included in the RNA among those with fast resume connection configured in the terminal with RRC inactive, disable the fast resume connection configured in the terminal with RRC inactive.

[0087] -> Performs release of fast resume connection settings when RRC between base stations is disabled, and if the terminal is in a cell where a fast resume connection is established or is not included in the RNA received from the serving base station, automatically releases the fast resume connection setting in that cell.

[0088] -> After disabling the fast resume connection settings while RRC is disabled between base stations, reset the fast resume connection settings for the terminal at the serving base station, and then return the terminal to the RRC disabled state.

[0089] It should be noted that the operation of each step described in FIG. 3 above can be applied to the corresponding operation in the procedure of FIG. 4 to FIG. 10.

[0090] FIG. 4 is a diagram illustrating the process of a terminal according to one embodiment of the present disclosure performing a resume connection to a base station of a cell that does not support a fast resume connection.

[0091] Referring to FIG. 4, information is set to support a fast resume connection in an RRC-inactive state for a terminal connected to a base station, but the terminal performs a resume connection to a base station of a cell that does not support a fast resume connection. Refer to the description of FIG. 3 for the step corresponding to the procedure of FIG. 3 among the steps of FIG. 4.

[0092] Step 100 of FIG. 4 corresponds to the signal flow from Step 100 of FIG. 3 to Step 346, and the terminal (10) is in a state where it is connected to RAN Node 1 (20), and after receiving information to support a fast resume connection in an RRC inactive state, it transitions from an RRC connected state to an RRC inactive state.

[0093] Subsequently, the terminal changes the cell it can connect to, and in step 400, the terminal (10) moves from a cell area belonging to RAN Node 1 (20) to a cell area belonging to RAN Node 4 (26). Then, in step 500, when user data or signaling messages that need to be transmitted are generated from the terminal (10), in step 510, the terminal (10) determines a method to attempt to resume connection to the cell where the terminal (10) is currently located. In step 510, if the cell is configured to allow for a quick resume connection from an RRC inactive state, the terminal (10) can perform a procedure based on configuration information to allow for a quick resume connection from an RRC inactive state. In step 510, if the cell is not configured to allow for a quick resume connection from an RRC inactive state, the terminal (10) can perform a procedure to transition from the existing RRC inactive state to an RRC connected state (e.g., an RRC Resume procedure).

[0094] In step 510, if the terminal (10) decides to perform the existing resume connection in the RRC inactive state, in step 520, the terminal (10) performs a random access procedure in the RAN Node 4 (26) cell according to the configured information. Then, in step 530, the terminal (10) sends an RRC message (e.g., an RRCResumeRequest message) requesting the existing resume connection in the RRC inactive state to the RAN Node 4 (26).

[0095] RAN Node 4 (26), having received an RRC message requesting a resume connection from the terminal (10), transmits a message between base stations (e.g., a Retrieve UE Context Request message) requesting terminal context information to RAN Node 1 (20), which was the previous serving base station of the terminal (10), in step 540. RAN Node 1 (20), having received the request for terminal context information from RAN Node 4 (26), checks the terminal context information of the terminal (10) and then checks whether the request is valid. If it is valid, RAN Node 1 (20) transmits a response message (e.g., a Retrieve UE Context Response message) containing the terminal context information of the terminal (10) to RAN Node 4 (26) in step 550.

[0096] RAN Node 4 (26), having received terminal context information of the terminal (10) from RAN Node 1 (20), sends an RRC message (e.g., RRCResume message) to the terminal (10) to establish a resume connection in step 560. In step 570, the terminal (10) sends an RRC message (e.g., RRCResumeComplete message) to RAN Node 4 (26) to indicate that the resume connection has been completed.

[0097] In steps 580 and 590, RAN Node 4 (26) informs the core network (30) that the path for transmitting data or signaling messages with the terminal (10) has been changed to RAN Node 4 (26), and if necessary, performs a path switch procedure to receive a new policy from the core network (30). Then, in step 600, RAN Node 4 (26) becomes capable of exchanging user data or signaling messages with the core network (30), and RAN Node 4 (26) operates as a new serving base station.

[0098] In step 700, RAN Node 4 (26) sends a message between base stations (e.g., a UE Context Release message) to RAN Node 1 (20) indicating that the resume connection procedure of the terminal (10) is completed and that RAN Node 1 (20) may release the terminal context of the terminal (10). Upon receiving the message from RAN Node 4 (26) indicating that the terminal context of the terminal (10) may be released, RAN Node 1 (20) may send a message between base stations (e.g., a handover cancel message) in step 710 and step 712 to RAN Node 2 (22) and RAN Node 3 (24), respectively, which have a fast resume connection setup in an RRC inactive state for the terminal (10), to instruct them to set up a fast resume connection setup in an RRC inactive state and release the terminal context. Then, in steps 720, 722, and 724, RAN Node 1 (20), RAN Node 2 (22), and RAN Node 3 (24), respectively, release the fast resume connection setting information in the RRC inactive state and the terminal context that are stored and set for the terminal (10).

[0099] FIG. 5 is a diagram illustrating a process of performing a fast resume connection based on a paging procedure according to one embodiment of the present disclosure.

[0100] Referring to FIG. 5, after setting information to support a fast resume connection in an RRC inactive state to a terminal connected to a base station according to one embodiment, the terminal transitions from an RRC connected state to an RRC inactive state, and user data or signal messages to be transmitted from the network are generated, and after a paging procedure, the terminal performs a fast resume connection to the base station of the cell where the fast resume connection in an RRC inactive state is set.

[0101] Step 100 of FIG. 5 corresponds to the signal flow from Step 100 of FIG. 3 to Step 346, and the terminal (10) is in a state where it is connected to RAN Node 1 (20), and after receiving information to support a fast resume connection in an RRC inactive state, it transitions from an RRC connected state to an RRC inactive state.

[0102] Subsequently, the terminal changes the cell it can connect to, and in step 400, the terminal (10) moves from the cell area belonging to RAN Node 1 (20) to the cell area belonging to RAN Node 2 (22). In step 500, when user data or signaling messages that need to be transmitted from the network are generated and delivered to RAN Node 1 (20), in step 515, RAN Node 1 (20) attempts to send a paging message to the terminal. Also, in steps 520, 530, and 540, RAN Node 1 (20) sends a message for inter-base station paging requests to the surrounding base stations, RAN Node 2 (22), RAN Node 3 (24), and RAN Node 4 (26), respectively. RAN Node 2 (22), RAN Node 3 (24), and RAN Node 4 (26), having each received a message for a paging request between base stations from RAN Node 1 (20) in steps 525, 535, and 545, respectively, intend to send a paging message to a terminal in steps 525, 535, and 545.

[0103] When a terminal (10) that has moved to a cell area belonging to RAN Node 2 (22) receives a paging message transmitted by RAN Node 2 (22) in step 525, in step 600, the terminal (10) determines a method to attempt to resume connection to the cell where the terminal (10) is currently located. In step 600, if the cell is configured to allow for a quick resume connection from an RRC inactive state, a procedure based on configuration information to allow for a quick resume connection from an RRC inactive state can be performed, and if the cell is not configured to allow for a quick resume connection from an RRC inactive state, a procedure to transition from the existing RRC inactive state to an RRC connected state (for example, an RRC Resume procedure) is performed.

[0104] In step 600, if the terminal (10) decides to perform a fast resume connection in an RRC inactive state, the terminal (10) may perform a random access procedure in the RAN Node 2 (22) cell in step 610 according to the configured information. Then, in step 620, the terminal (10) sends an RRC message (e.g., an RRCReconfigurationComplete message) to the RAN Node 2 (22) to complete the fast resume connection in an RRC inactive state.

[0105] RAN Node 2 (22), having received an RRC message from the terminal (10) indicating that a fast resume connection in an RRC inactive state has been completed, transmits a base station message (e.g., Handover Success message or new base station message) to RAN Node 1 (20), which was the terminal's previous serving base station, in step 630 to inform that the terminal has made a fast resume connection in an RRC inactive state. RAN Node 1 (20), having received from RAN Node 2 (22) that the terminal has made a fast resume connection in an RRC inactive state to RAN Node 2 (22), transmits a base station message (e.g., SN Status Transfer message) containing information necessary for data forwarding to RAN Node 2 (22) in step 640 if necessary, and in step 645, RAN Node 1 (20) forwards the data to RAN Node 2 (22). RAN Node 1 (20), having received from RAN Node 2 (22) that the terminal has established a fast resume connection in an RRC inactive state to RAN Node 2 (22), transmits a message between base stations (e.g., a Handover Cancel message) to instruct RAN Node 3 (24), which has established a fast resume connection in an RRC inactive state for the terminal (10) in step 700, to release the fast resume connection in an RRC inactive state and the terminal context. Then, in steps 710 and 712, RAN Node 1 (20) and RAN Node 3 (24) each release the fast resume connection in an RRC inactive state information and the terminal context that they have stored and established for the terminal (10).

[0106] In steps 650 and 660, RAN Node 2 (22) informs the core network (30) that the path for transmitting data or signaling messages with the terminal (10) has been changed to RAN Node 2 (22), and if necessary, performs a path change procedure to receive a new policy from the core network (30). Then, in step 670, RAN Node 2 (22) becomes capable of exchanging user data or signaling messages with the core network (30), and RAN Node 2 (22) operates as a new serving base station.

[0107] FIG. 6 is a diagram illustrating the process of performing a resume connection to a base station of a cell that does not support a fast resume connection after a paging procedure according to one embodiment of the present disclosure.

[0108] Referring to FIG. 6, a procedure is described in which information is set to support a fast resume connection in an RRC inactive state for a terminal connected to a base station according to one embodiment, the terminal transitions from an RRC connected state to an RRC inactive state, user data or signal message to be transmitted from a network is generated, and after a paging procedure, the terminal performs a resume connection to a base station of a cell that does not support a fast resume connection.

[0109] Step 100 of FIG. 6 corresponds to the signal flow from Step 100 of FIG. 3 to Step 346, where the terminal (10) is connected to RAN Node 1 (20) and receives information to support a fast resume connection in an RRC inactive state, and then transitions from an RRC connected state to an RRC inactive state.

[0110] Subsequently, the terminal changes the cell it can connect to, and in step 400, the terminal (10) moves from the cell area belonging to RAN Node 1 (20) to the cell area belonging to RAN Node 4 (26). In step 500, when user data or signaling messages required for transmission in the network are generated and delivered to RAN Node 1 (20), in step 515, RAN Node 1 (20) attempts to send a paging message to the terminal. Additionally, in steps 520, 530, and 540, RAN Node 1 (20) sends messages for inter-base station paging requests to the surrounding base stations, RAN Node 2 (22), RAN Node 3 (24), and RAN Node 4 (26), respectively. RAN Node 2 (22), RAN Node 3 (24), and RAN Node 4 (26), having each received a message for a paging request between base stations from RAN Node 1 (20) in steps 525, 535, and 545, respectively, intend to send a paging message to a terminal in steps 525, 535, and 545, respectively.

[0111] When a terminal (10) that has moved to a cell area belonging to RAN Node 4 (26) receives a paging message transmitted by RAN Node 4 (26) in step 545, in step 600, the terminal (10) determines a method to attempt to resume connection to the cell where the terminal (10) is currently located. In step 600, if the cell is configured to allow for a quick resume connection from an RRC inactive state, a procedure based on configuration information to allow for a quick resume connection from an RRC inactive state can be performed, and if the cell is not configured to allow for a quick resume connection from an RRC inactive state, a procedure to transition from the existing RRC inactive state to an RRC connected state (for example, an RRC Resume procedure) is performed.

[0112] In step 600, if the terminal (10) decides to perform the existing resume connection in the RRC inactive state, the terminal (10) performs a random access procedure in the RAN Node 4 (26) cell in step 610 according to the configured information. Then, in step 620, the terminal (10) sends an RRC message (e.g., an RRCResumeRequest message) requesting the existing resume connection in the RRC inactive state to the RAN Node 4 (26).

[0113] RAN Node 4 (26), having received an RRC message requesting a resume connection from the terminal (10), transmits a base station-to-base station message (e.g., Retrieve UE Context Request message) requesting terminal context information to RAN Node 1 (20), which was the previous serving base station of the terminal (10), in step 630. RAN Node 1 (20), having received the request for terminal context information from RAN Node 4 (26), checks the terminal context information of the terminal (10) and then checks whether the request is valid. If it is valid, in step 640, RAN Node 1 (20) transmits a response message (e.g., Retrieve UE Context Response message) containing the terminal context information of the terminal (10) to RAN Node 4 (26).

[0114] RAN Node 4 (26), having received terminal context information of the terminal (10) from RAN Node 1 (20), sends an RRC message (e.g., RRCResume message) to the terminal (10) to establish a resume connection at step 650. At step 660, the terminal (10) sends an RRC message (e.g., RRCResumeComplete message) to RAN Node 4 (26) to indicate that the resume connection has been completed.

[0115] RAN Node 4 (26), having received an RRC message from the terminal (10) indicating that the resume connection has been completed, transmits a message between base stations (e.g., an address indication message) containing IP address information necessary for data forwarding to RAN Node 1 (20) in step 670 if necessary. RAN Node 1 (20), having received a message between base stations containing IP address information related to data forwarding from RAN Node 4 (26), transmits a message between base stations (e.g., an SN Status transfer message) containing information necessary for data forwarding to RAN Node 4 (26) in step 672 if necessary, and RAN Node 1 (20) forwards data to RAN Node 4 (26) in step 674.

[0116] In steps 680 and 690, RAN Node 4 (26) informs the core network (30) that the path for transmitting data or signaling messages with the terminal (10) has been changed to RAN Node 4 (26), and performs a path change procedure to receive a new policy from the core network (30) if necessary. Then, in step 700, RAN Node 4 (26) becomes capable of exchanging user data or signaling messages with the core network (30), and RAN Node 4 (26) operates as a new serving base station.

[0117] In step 800, RAN Node 4 (26) sends a message between base stations (e.g., UE Context Release message) to RAN Node 1 (20) indicating that the resume connection procedure of the terminal (10) is completed and that RAN Node 1 (20) may release the terminal context of the terminal (10). Upon receiving the message from RAN Node 4 (26) indicating that the terminal context of the terminal (10) may be released, RAN Node 1 (20) sends a message between base stations (e.g., handover cancel message) in steps 810 and 812 to RAN Node 2 (22) and RAN Node 3 (24), respectively, which have a fast resume connection setup in an RRC inactive state for the terminal (10), to instruct them to set up a fast resume connection setup in an RRC inactive state and release the terminal context. Then, in steps 820, 822, and 824, RAN Node 1 (20), RAN Node 2 (22), and RAN Node 3 (24), respectively, release the fast resume connection setting information in the RRC inactive state and the terminal context that are stored and set for the terminal (10).

[0118] FIGS. 7A, 7B, and 7C are drawings illustrating a process of performing a rapid resume when moving between cells within a separated base station according to an embodiment of the present disclosure. Hereinafter, FIGS. 7A, 7B, and 7C are collectively referred to as FIG. 7.

[0119] Referring to FIG. 7, when moving between cells within a base station in a separated base station structure according to one embodiment, there is a signal flow for setting information to support a fast resume connection in an RRC inactive state to a terminal connected to the base station in an RRC connection state, and a signal flow diagram for performing a fast resume connection to a cell and base station where a fast resume connection in an RRC inactive state is set, after the terminal transitions from an RRC connection state to an RRC inactive state, when user data or a signal message to be transmitted by the terminal is generated. The current serving base station determines a nearby candidate cell and DU (candidate cell / Distributed Unit) within the base station while the terminal is in an RRC connection state, defines a terminal context setup and modification procedure (UE Context Setup procedure or UE Context Modification procedure) or a new procedure between the CU (Central Unit) and DU (Distributed Unit) within the base station, performs a setup procedure to support fast resume connection from the RRC inactive state to the candidate cell and DU, and also transmits setup information for fast resume connection from the RRC inactive state to the terminal using an RRC message.

[0120] In step 100 of FIG. 7, the terminal (10) is connected to DU1 (20-b1) and operates in an RRC connected state (RRC CONNECTED state) so that it can exchange user data or exchange signal messages in step 110.

[0121] In step 200, when the terminal (10) reports the surrounding signal measurement results to the CU (20-a) through DU1 (20-b1) according to the signal measurement and reporting settings of the CU (20-a), in step 210, the CU (20-a) determines whether the terminal (10) will set up a fast resume connection in an RRC inactive state based on the measurement result report reported by the terminal (10), and determines the candidate cell and DU (candidate cell / DU). In step 210, the CU (20-a) can determine the candidate cell within the base station and simultaneously determine the candidate cell and base station (candidate cell / RAN Node) together with the cell of the surrounding base station, and the procedure between base stations refers to the operation of determining the candidate cell in the embodiment of FIG. 3.

[0122] In steps 220 and 222, the CU (20-a) may transmit a message to the DU2 (20-b2) and DU3 (20-b3), respectively, containing information about candidate cells or cells that support fast resume connection in an RRC-inactive state for the terminal (10), and information related to a setup request for fast resume connection in an RRC-inactive state. For example, the message may be a UE Context Setup / Modification Request message or a new message, but is not limited thereto. The message is a message between the CU and DU within the base station and may be transmitted from the CU (20-a) to the DU2 (20-b2) and / or DU3 (20-b3) via an inter-base station interface (e.g., F1 and 6G F1). DU2 (20-b2) and DU3 (20-b3), having received a request from CU (20-a) for a quick resume connection setup in the RRC inactive state for the terminal (10), determine whether to accept the quick resume connection setup in the RRC inactive state at each step 230 and step 232, and if accepted, allocate or reserve context setup and resources for the terminal (10). The terminal context information is set based on the information included in the message transmitted by CU (20-a) at steps 220 and 222.

[0123] DU2 (20-b2), having accepted the fast resume connection setup in the RRC inactive state, sends a response message to CU (20-a) in step 240. For example, the response message may be a UE Context Setup / Modification Response message or a new response message, but is not limited thereto. The response message may include an indicator that accepts the fast resume connection setup in the RRC inactive state. For example, the indicator may be INACTIVE-PreConfiguration support IE, and the indicator may be set to 'true' to indicate acceptance of the fast resume connection setup in the RRC inactive state. Additionally, the response message may include configuration information for the fast resume connection in the RRC inactive state. Configuration information for a fast resume connection in an RRC inactive state may use the same configuration information for handover support, such as CHO or LTM, which similarly pre-configures to support terminal handover in an RRC connected state, or may use separate configuration information (e.g., INACTIVEPreconfigurationInfo IE) only for a fast resume connection in an RRC inactive state. On the other hand, DU3 (20-b3), which rejects the fast resume connection configuration in an RRC inactive state, sends a response message to CU (20-a) in step 242. The response message may include an indicator rejecting the fast resume connection configuration in an RRC inactive state. For example, the indicator may be INACTIVE-PreConfiguration support IE, and the rejection of the fast resume connection configuration in an RRC inactive state may be indicated by setting the indicator to 'false'.

[0124] In step 250, the CU (20-a) may transmit a message to the DU1 (20-b1) to which the terminal is currently connected, which includes information regarding candidate cells or cells that support the fast resume connection in the RRC-inactive state for the terminal (10), and information related to a request for a setup for the fast resume connection in the RRC-inactive state. For example, the message may be a UE Context Modification Request message or a new message, but is not limited thereto. The message is a message between the CU and DU within the base station and may be transmitted from the CU (20-a) to the DU1 (20-b1) via an interface between base stations (for example, F1 and 6G F1). Upon receiving a request from the CU (20-a) for the setup of the fast resume connection in the RRC-inactive state for the terminal (10), the DU1 (20-b1) determines in step 260 whether to accept the setup for the fast resume connection in the RRC-inactive state, and if accepted, sets and stores the setup information for the fast resume connection in the RRC-inactive state for the terminal (10). Terminal context information is set based on the information included in the message transmitted by CU (20-a) in step 250.

[0125] DU1 (20-b1), having accepted the fast resume connection setting in the RRC inactive state, may send a response message to CU (20-a) in step 270. For example, the message may be a UE Context Modification Response message or a new response message, but is not limited thereto. The message may include an indicator that accepts the fast resume connection setting in the RRC inactive state, for example, the indicator may be INACTIVE-PreConfiguration support IE. The indicator may be set to 'true' to indicate acceptance of the fast resume connection setting in the RRC inactive state. Additionally, the message may include configuration information for the fast resume connection in the RRC inactive state. The configuration information for the fast resume connection in the RRC inactive state may use the same configuration information for handover support, such as CHO or LTM, which similarly pre-configure to support terminal handover in the RRC connection state, or may use separate configuration information only for the fast resume connection in the RRC inactive state. For example, the above separate configuration information may be INACTIVEPreconfigurationInfo IE, and the name of the configuration information is not limited thereto.

[0126] The procedures and messages for requesting and responding to fast resume connection setup in an RRC-inactive state using the inter-base station interfaces used in steps 220, 222, 250 and 240, 242, and 270 may be supported by using existing procedures and messages for setting or changing terminal context between the CU and DU within the base station, or by defining new procedures and messages between the CU and DU within the base station. When using existing procedures and messages for setting or changing terminal context between the CU and DU within the base station, the requests and responses for fast resume connection setup in an RRC-inactive state may be supported simultaneously with supporting existing inter-cell movement or handover of terminals, or separately regardless of existing inter-cell movement or handover procedures of terminals.

[0127] CU (20-a), having received response messages from DU1 (20-b1), DU2 (20-b2), and DU3 (20-b3) at steps 270, 240, and 242 respectively, generates an RRC message containing information for establishing a fast resume connection in an RRC-inactive state to be transmitted to the terminal (10) at step 300. The base station may determine a candidate cell within the base station and simultaneously determine a cell of a surrounding base station as a candidate cell and a base station (candidate cell / RAN Node). If a cell of a surrounding base station is determined as a candidate cell to support the establishment of a fast resume connection in an RRC-inactive state of the terminal, the information provided by the candidate cell of the surrounding candidate base station may be included together in the RRC message at step 300.

[0128] And, at step 310, CU (20-a) can transmit a message between CU and DU (e.g., DL RRC Message Transfer message) containing an RRC message (e.g., RRCReconfiguration message) containing fast resume connection configuration information (e.g., INACTIVEPreConfiguration) in an RRC inactive state to be transmitted to DU1 (20-b1) for terminal (10). At step 320, DU1 (20-b1) transmits an RRC message (e.g., RRCReconfiguration message) containing fast resume connection configuration information (e.g., INACTIVEPreConfiguration) in an RRC inactive state to terminal (10). At step 330, terminal (10) can transmit an RRC response message (e.g., RRCReconfigurationComplete message) to DU1 (20-b1). In step 340, DU1 (20-b1) includes the RRC response message transmitted by the terminal in a message between CU and DU (e.g., UL RRC Message Transfer message) and transmits it to CU (20-a).

[0129] Afterwards, when there is no traffic transmitted or received with the terminal (10), and the CU (20-a) decides in step 400 to transition the RRC connection state of the terminal (10) to an RRC inactive state, it generates an RRC message (e.g., an RRCR release message) containing information (e.g., SuspendConfig information) for transitioning the terminal (10) to an RRC inactive state. In step 410, the CU (20-a) transmits a message between the CU and the DU (e.g., a new RRC State Transition Notification message, a UE Context Modification Request message, or a UE Context Release Command message) to the DU1 (20-b1) containing information that the RRC state of the terminal has changed (e.g., setting the RRC state IE to 'INACTIVE'). In step 410, the message between the CU and the DU that the CU (20-a) transmits to the DU (20-b1) may include an RRC message (e.g., an RRCRelease message) containing information for transitioning to an RRC disabled state to be transmitted to the terminal (e.g., SuspendConfig information). In step 420, the DU1 (20-b1) transmits an RRC message (e.g., an RRCRelease message) containing information for transitioning to an RRC disabled state to be transmitted to the terminal (10) (e.g., SuspendConfig information). In step 450, the DU1 (20-b1) disconnects the connection with the terminal (10) and maintains the terminal context information and the quick resume connection setup information in the RRC disabled state.

[0130] After receiving the RRC message of step 420, the terminal (10) may continue to maintain configuration information for operation in the RRC inactive state in step 440, and may also drive a timer to maintain and manage the fast resume connection settings in the RRC inactive state. The timer information in step 420 may be included in the RRC message transmitted from the CU (20-a) in step 320.

[0131] In step 412, CU (20-a) transmits a message between CU and DU (e.g., a new RRC State Transition Notification message, a UE Context Modification Request message, or a UE Context Release Command message) containing information that the terminal's RRC state has changed (e.g., setting the RRC state IE to 'INACTIVE') to DU2 (20-b2), which maintains the fast resume connection setting in the RRC inactive state. Upon receiving the information that the terminal's RRC state has changed from CU (20-a), DU2 (20-b2) maintains context information and fast resume connection setting information in the RRC inactive state with the terminal (10) in step 452.

[0132] In step 430, CU (20-a) sends a message between CU and DU (e.g., UE Context Release Command message) instructing DU3 (20-b3), which does not support fast resume connection setup in an RRC inactive state, to release the terminal context information of the terminal (10), and in step 435, DU3 (20-b3) sends a response message (e.g., UE Context Release Complete message) to CU (20-a). Then, in step 460, DU3 (20-b3) can release and delete the terminal context information of the terminal (10).

[0133] A CU (20-a) that has completed the procedure to transition the terminal (10) from an RRC connected state to an RRC inactive state maintains the terminal context information of the terminal (10) and information related to the quick resume connection setting in the RRC inactive state, and the CU (20-a) may also drive a timer to maintain and manage the quick resume connection setting in the RRC inactive state.

[0134] Subsequently, the terminal can change the cell it can connect to. After the terminal (10) moves from the cell area belonging to DU1 (20-b1) to the cell area belonging to DU2 (20-b2) in step 500, if user data or a signaling message that needs to be transmitted occurs from the terminal (10) in step 600, the terminal (10) determines a method to attempt to resume connection to the cell where the terminal (10) is currently located in step 610. In step 610, if the cell is configured to allow for a quick resume connection from an RRC inactive state, a procedure based on configuration information to allow for a quick resume connection from an RRC inactive state can be performed, and if the cell is not configured to allow for a quick resume connection from an RRC inactive state, a procedure to transition from the existing RRC inactive state to an RRC connected state (for example, an RRC Resume procedure) is performed.

[0135] In step 610, if the terminal (10) decides to perform a fast resume connection in an RRC-inactive state, the terminal (10) may perform a random access procedure in the DU2 (20-b2) cell in step 620 according to the configured information. If the random access of the terminal (10) to the DU2 (20-b2) is successful, the DU2 (20-b2) transmits a message to the CU (20-a) to notify the terminal (10) of the access, and to this end, in step 630, the DU2 (20-b2) may transmit a message (e.g., Downlink Data Delivery Status (DDDS) message) to the CU (20-a) via a user plane interface (e.g., F1-U, 6G F1-U interface). In step 635, DU2 (20-b2) can send a signaling message between CU and DU (e.g., an Access Success message) to CU (20-a).

[0136] After the terminal (10) completes the random access procedure, at step 640, the terminal (10) sends an RRC message (e.g., RRCReconfigurationComplete message) to DU2 (20-b2) indicating that it has completed a fast resume connection in an RRC inactive state. At step 650, DU2 (20-b2) includes the RRC message sent by the terminal in a message between CU and DU (e.g., UL RRC Message Transfer message) and sends it to CU (20-a).

[0137] Upon receiving an RRC message from the terminal (10) indicating that a fast resume connection has been completed in the RRC inactive state, the CU (20-a) transmits a message between the CU and the DU (e.g., a new RRC State Transition Notification message or a UE Context Modification message) to the DU2 (20-b) to which the terminal (10) is connected in step 660, the message includes information indicating that the terminal's RRC state has changed (e.g., setting the RRC state IE to 'CONNECTED'). Then, in step 670, the terminal (10) becomes capable of exchanging user data or signal messages with the CN (30) through the DU2 (20-b2) and the CU (20-a).

[0138] CU (20-a), having received an RRC message from the terminal (10) indicating that a fast resume connection in an RRC inactive state has been completed, may send a message between CU and DU (e.g., a UE Context Release Command message) to instruct DU1 (20-b1), which has a fast resume connection in an RRC inactive state for the terminal (10) set up in step 700, to set up a fast resume connection in an RRC inactive state and release the terminal context. In step 710, DU2 (20-b2) sends a response message (e.g., a UE Context Release Complete message) to CU (20-a). Then, in step 720, DU2 (20-b2) may release and delete the fast resume connection in an RRC inactive state and terminal context information of the terminal (10).

[0139] According to one embodiment of FIG. 7, after setting information to support a fast resume connection in an RRC inactive state to an RRC connection state terminal connected to a base station, at least one of the following methods may be used to release and manage the previously set information and terminal context settings.

[0140] - After a decision by the CU within the base station and after performing RAN paging, release or reset the information and terminal context to support fast resume connection in an RRC disabled state.

[0141] - Releases fast resume connection configuration information and terminal context in an RRC inactive state based on timer settings and termination.

[0142] The OAM sets a timer value at the base station, and the base station transmits the timer value to the terminal via an RRC message.

[0143] After determining the timer value in the CU, it is transmitted to the terminal via an RRC message containing the timer value.

[0144] According to one embodiment of FIG. 7, in a method for setting information to support a fast resume connection in an RRC inactive state to a terminal connected to a base station, the base station may use at least one of the following methods for transmitting setting information for a fast resume connection in an RRC inactive state to the terminal.

[0145] - The RRCReconfiguration message transmitted to the terminal includes configuration information (e.g., INACTIVEPreConfiguration) for a fast resume connection when the terminal is in the RRC inactive state, and the terminal transmits an RRCReconfigurationComplete message to the base station upon establishing a fast resume connection.

[0146] - Use a new RRC message (e.g., RRCFastResumeRequest) that can be sent as an RRC message container within the RRCReconfiguration message transmitted to the terminal, and include configuration information (e.g., INACTIVEPreConfiguration) in the new RRC message (e.g., RRCFastResumeRequest) for a fast resume connection when the terminal is in an RRC-inactive state; and the terminal transmits a new RRC response message (e.g., RRCFastResumeComplete) to the base station upon the fast resume connection.

[0147] - A new RRC message (e.g., RRCFastResumeRequest message) is transmitted to the terminal, including configuration information (e.g., INACTIVEPreConfiguration) for a fast resume connection from the terminal's RRC inactive state (RRC INACTIVE state), and the terminal transmits a new RRC response message (e.g., RRCFastResumeComplete message) to the base station upon the fast resume connection.

[0148] - Use a new RRC message (e.g., RRCFastResumeRequest) that can be sent as an RRC message container within the RRCRelease message transmitted to the terminal to transition from an RRC connected state to an RRC disabled state; the new RRC message (e.g., RRCFastResumeRequest) includes configuration information (e.g., INACTIVEPreConfiguration) for a fast resume connection from the RRC disabled state, and the terminal transmits a new RRC response message (e.g., RRCFastResumeComplete) to the base station upon establishing a fast resume connection.

[0149] Among the operations of FIGS. 8 to 10, the operation corresponding to the operation described through FIG. 7 is described by referring to the explanation of FIG. 7.

[0150] FIG. 8 is a diagram illustrating a process of performing a connection to a cell that does not support a fast resume connection when moving between cells within a separated base station according to an embodiment of the present disclosure. Hereinafter, FIG. 8A and FIG. 8B are collectively referred to as FIG. 8.

[0151] Referring to FIG. 8, when moving between cells within a base station in a separated base station structure according to one embodiment, information is set to support a fast resume connection in an RRC inactive state (RRC INACTIVE state) for a terminal connected to the base station, but the process of the terminal performing a resume connection to a cell within the base station that does not support a fast resume connection is described.

[0152] Step 100 of FIG. 8 corresponds to the signal flow from Step 100 of FIG. 7 to Step 460, where the terminal (10) is connected to the base station via DU1 (20-b1), receives information to support a fast resume connection in an RRC inactive state, and then transitions from an RRC connected state to an RRC inactive state.

[0153] Subsequently, the terminal changes the cell it can connect to, and in step 500, the terminal (10) moves from the cell area belonging to DU1 (20-b1) to the cell area belonging to DU3 (20-b3). Then, in step 600, when user data or signaling messages that need to be transmitted occur from the terminal (10), in step 610, the terminal (10) determines a method to attempt to resume connection to the cell where the terminal (10) is currently located. In step 610, if the cell is configured to allow for a quick resume connection from an RRC inactive state, the terminal (10) can perform a procedure based on configuration information to allow for a quick resume connection from an RRC inactive state. If the cell is not configured to allow for a quick resume connection from an RRC inactive state, the terminal (10) performs a procedure to transition from the existing RRC inactive state to an RRC connected state (e.g., an RRC Resume procedure).

[0154] In step 610, if the terminal (10) decides to perform an existing resume connection in an RRC inactive state, in step 620, the terminal (10) performs a random access procedure in the DU3 (20-b3) cell according to the configured information. After the terminal (10) completes the random access procedure, in step 630, the terminal (10) transmits an RRC message (e.g., an RRCResumeRequest message) requesting an existing resume connection in an RRC inactive state to DU3 (20-b3). In step 640, DU3 (20-b3) includes the RRC message transmitted by the terminal in a message between the CU and DU (e.g., an Initial UL RRC Message Transfer message) and transmits it to the CU (20-a). Upon receiving an RRC message from the terminal (10) requesting an existing resume connection in an RRC inactive state, the CU (20-a) transmits a message between the CU and the DU (e.g., a UE Context Setup Request message) to the DU3 (20-b3) at step 650, requesting terminal context setup and resource allocation for a connection with the terminal. At step 660, if the DU3 (20-b3) can allow a connection with the terminal (10), it sets up the terminal context and allocates resources, and then transmits a response message (e.g., a UE Context Setup Response message) to the CU (20-a). After receiving information related to resource allocation for the terminal from the DU3 (20-b3), the CU (20-a) generates an RRC message (e.g., an RRCResume message) containing setup information for a resume connection to the terminal (10). In step 670, CU (20-a) transmits an RRC message containing configuration information for a resume connection to DU3 (20-b3) as a message between CU and DU (e.g., a DL RRC Message Transfer message). In step 680, DU3 (20-b3) transmits an RRC message containing resume connection configuration information to terminal (10).In step 690, the terminal (10) generates an RRC response message (e.g., an RRCResumeComplete message) indicating that the resume connection setup has been completed and transmits it to DU3 (20-b3). In step 700, DU3 (20-b3) transmits a message between CU and DU (e.g., a UL RRC Message Transfer message) containing the RRC message received from the terminal (10) to CU (20-a). When CU (20-a) receives the RRC response message from the terminal (10) indicating that the resume connection setup has been completed, in step 710, the terminal (10) becomes capable of exchanging user data or signal messages with CN (30) through DU3 (20-b3) and CU (20-a).

[0155] Upon receiving an RRC response message indicating that the resume connection setting transmitted from the terminal (10) has been completed, the CU (20-a) may, in steps 800 and 802, respectively, send a message between the CU and the DU (e.g., a UE Context Release Command message) to instruct the DU1 (20-b1) and DU2 (20-b2), which have a fast resume connection setting in an RRC inactive state for the terminal (10), to release the terminal context and the fast resume connection setting in an RRC inactive state. In steps 810 and 812, DU1 (20-b1) and DU2 (20-b2), respectively, may send a response message (e.g., a UE Context Release Complete message) to the CU (20-a). And, in steps 820 and 822, DU1 (20-b1) and DU2 (20-b2) can release and delete the fast resume connection setup and terminal context information in the RRC inactive state of the terminal (10).

[0156] FIG. 9 is a diagram illustrating a process of performing a fast resume connection based on a paging procedure when moving between cells within a separated base station according to one embodiment of the present disclosure.

[0157] Referring to FIG. 9, when moving between cells within a base station in a separated base station structure according to one embodiment, information is set to support a fast resume connection in an RRC inactive state for a terminal connected to the base station, and then the terminal transitions from an RRC connected state to an RRC inactive state, and user data or signal messages to be transmitted from the network are generated, and after a paging procedure, a process is described for the terminal to perform a fast resume connection to a cell within the base station where a fast resume connection in an RRC inactive state (RRC INACTIVE state) is set.

[0158] Step 100 of FIG. 9 corresponds to the signal flow from Step 100 of FIG. 7 to Step 460, where the terminal (10) is connected to the base station via DU1 (20-b1), receives information to support a fast resume connection in an RRC inactive state, and then transitions from an RRC connected state to an RRC inactive state.

[0159] Subsequently, the terminal changes the cell it can connect to, and in step 500, the terminal (10) moves from the cell area belonging to DU1 (20-b1) to the cell area belonging to DU2 (20-b3). In step 600, when user data or signaling messages that need to be transmitted from the network are generated and delivered to CU (20-a), in steps 610, 612, and 614, CU (20-a) transmits a message between CU and DU (e.g., a Paging message) to request paging from the terminal (10) to DU1 (20-b1), DU2 (20-b2), and DU3 (20-b3), respectively. DU1 (20-b1), DU2 (20-b2), and DU3 (20-b3), having received a paging request message from CU (20-a), each transmit a paging message to a terminal in steps 620, 622, and 624, respectively. When a terminal (10) that has moved to a cell area belonging to DU2 (20-b2) receives a paging message transmitted by DU2 (20-b2) in step 622, the terminal (10) determines a method to attempt to resume connection to the cell where the terminal (10) is currently located in step 700. In step 700, if the cell is configured to allow for a fast resume connection in an RRC inactive state, the terminal (10) can perform a procedure based on configuration information to allow for a fast resume connection in an RRC inactive state. In the case of a cell that is not configured to allow a quick resume connection from the RRC inactive state, the terminal (10) performs a procedure to transition from the existing RRC inactive state to the RRC connected state (for example, an RRC Resume procedure).

[0160] In step 700, if the terminal (10) decides to perform a fast resume connection in an RRC inactive state, in step 710, the terminal (10) may perform a random access procedure in the DU2 (20-b2) cell according to the set information. When the random access of the terminal (10) to the DU2 (20-b2) is successful, the DU2 (20-b2) transmits a message to the CU (20-a) to notify the access of the terminal (10). To do this, in step 720, the DU2 (20-b2) can transmit a message (e.g., Downlink Data Delivery Status (DDDS) message) to the CU (20-a) via a user plane interface (e.g., F1-U, 6G F1-U interface), and in step 725, the DU2 (20-b2) can transmit a signaling message between the CU and the DU (e.g., Access Success message) to the CU (20-a).

[0161] After the terminal (10) completes the random access procedure, in step 730, the terminal (10) transmits an RRC message (e.g., RRCReconfigurationComplete message) to DU2 (20-b2) indicating that a fast resume connection in an RRC inactive state has been completed. In step 740, DU2 (20-b2) includes the RRC message transmitted by the terminal in a message between CU and DU (e.g., UL RRC Message Transfer message) and transmits it to CU (20-a).

[0162] Upon receiving an RRC message from the terminal (10) indicating that a fast resume connection has been completed in an RRC inactive state, the CU (20-a) transmits a message between the CU and the DU (e.g., a new RRC State Transition Notification message or a UE Context Modification message) to the DU2 (20-b) to which the terminal (10) is connected at step 750, the message includes information indicating that the terminal (10) has changed its RRC state (e.g., setting the RRC state IE to 'CONNECTED'). Then, at step 760, the terminal (10) becomes capable of exchanging user data or signal messages with the CN (30) through the DU2 (20-b2) and the CU (20-a).

[0163] CU (20-a), having received an RRC message from the terminal (10) indicating that a fast resume connection in an RRC inactive state has been completed, can send a message between CU and DU (e.g., a UE Context Release Command message) to instruct DU1 (20-b1), which has a fast resume connection in an RRC inactive state for the terminal (10) set up in step 800, to set up a fast resume connection in an RRC inactive state and release the terminal context. In step 810, DU2 (20-b2) can send a response message (e.g., a UE Context Release Complete message) to CU (20-a). Then, in step 820, DU2 (20-b2) can release and delete the fast resume connection in an RRC inactive state and terminal context information of the terminal (10).

[0164] FIGS. 10A and FIGS. 10B are drawings illustrating a process of performing a resume connection to a cell that does not support a fast resume connection after a paging procedure when moving between cells within a separated base station according to an embodiment of the present disclosure. Hereinafter, FIGS. 10A and FIGS. 10B are collectively referred to as FIGS. 10.

[0165] Referring to FIG. 10, when moving between cells within a base station in a separated base station structure according to one embodiment, information is set to support a fast resume connection in an RRC inactive state for a terminal connected to the base station, the terminal transitions from an RRC connected state to an RRC inactive state, user data or signal messages to be transmitted from the network are generated, and after a paging procedure, the terminal performs a resume connection to a cell within the base station that does not support a fast resume connection.

[0166] Step 100 of FIG. 10 corresponds to the signal flow from Step 100 of FIG. 7 to Step 460, where the terminal (10) is connected to the base station via DU1 (20-b1), receives information to support a fast resume connection in an RRC inactive state, and then transitions from an RRC connected state to an RRC inactive state.

[0167] Subsequently, the terminal changes the cell it can connect to, and in step 500, the terminal (10) moves from the cell area belonging to DU1 (20-b1) to the cell area belonging to DU3 (20-b3). In step 600, when user data or signaling messages that need to be transmitted from the network are generated and delivered to CU (20-a), in steps 610, 612, and 614, CU (20-a) transmits a message between CU and DU (e.g., a Paging message) to request paging from the terminal (10) to DU1 (20-b1), DU2 (20-b2), and DU3 (20-b3), respectively. DU1 (20-b1), DU2 (20-b2), and DU3 (20-b3), having received a paging request message from CU (20-a), each transmit a paging message to a terminal in steps 620, 622, and 624, respectively. When a terminal (10) that has moved to a cell area belonging to DU2 (20-b2) receives a paging message transmitted by DU2 (20-b2) in step 622, the terminal (10) determines a method to attempt to resume connection to the cell where the terminal (10) is currently located in step 700. In step 700, if the cell is configured to allow for a fast resume connection in an RRC inactive state, the terminal (10) can perform a procedure based on configuration information to allow for a fast resume connection in an RRC inactive state. In the case of a cell that is not configured to allow for a quick resume connection from the RRC inactive state, the terminal (10) performs a procedure (e.g., an RRC Resume procedure) to transition from the existing RRC inactive state to the RRC connected state.

[0168] In step 700, if the terminal (10) decides to perform an existing resume connection in an RRC inactive state, the terminal (10) performs a random access procedure in the DU3 (20-b3) cell in step 710 according to the configured information. After the terminal (10) completes the random access procedure, in step 720, the terminal (10) transmits an RRC message (e.g., an RRCResumeRequest message) requesting an existing resume connection in an RRC inactive state to the DU3 (20-b3). In step 730, the DU3 (20-b3) includes the RRC message transmitted by the terminal in a message between the CU and the DU (e.g., an Initial UL RRC Message Transfer message) and transmits it to the CU (20-a). CU (20-a), having received an RRC message from terminal (10) requesting an existing resume connection in an RRC inactive state, may, at step 740, send a message between CU and DU (e.g., a UE Context Setup Request message) to DU3 (20-b3) requesting terminal context setup and resource allocation for a connection with the terminal. At step 750, if DU3 (20-b3) can allow a connection with the terminal (10), it sets up the terminal context and allocates resources, and then sends a response message (e.g., a UE Context Setup Response message) to CU (20-a). After receiving information related to resource allocation for the terminal from DU3 (20-b3), CU (20-a) may generate an RRC message (e.g., an RRCResume message) containing setup information for a resume connection to the terminal (10). In step 760, CU (20-a) can transmit an RRC message containing configuration information for a resume connection to DU3 (20-b3), a message between CU and DU (e.g., a DL RRC Message Transfer message). In step 770, DU3 (20-b3) can transmit an RRC message containing configuration information for a resume connection to the terminal (10).In step 780, the terminal (10) can generate an RRC response message (e.g., an RRCResumeComplete message) indicating that the resume connection setup has been completed and send it to DU3 (20-b3). In step 790, DU3 (20-b3) sends a message between CU and DU (e.g., a UL RRC Message Transfer message) containing the RRC message received from the terminal (10) to CU (20-a). When CU (20-a) receives the RRC response message indicating that the resume connection setup has been completed transmitted from the terminal (10), in step 800, the terminal (10) becomes capable of exchanging user data or signal messages with CU (20-a) through DU3 (20-b3).

[0169] Upon receiving an RRC response message indicating that the resume connection setting transmitted from the terminal (10) has been completed, the CU (20-a) may, in steps 900 and 902, respectively, send a message between the CU and the DU (e.g., a UE Context Release Command message) to instruct the DU1 (20-b1) and DU2 (20-b2), which have a fast resume connection setting in an RRC inactive state for the terminal (10), to release the terminal context and the fast resume connection setting in an RRC inactive state. In steps 910 and 912, DU1 (20-b1) and DU2 (20-b2), respectively, may send a response message (e.g., a UE Context Release Complete message) to the CU (20-a). And, in steps 920 and 922, DU1 (20-b1) and DU2 (20-b2) can release and delete the fast resume connection setup and terminal context information in the RRC inactive state of the terminal (10).

[0170] FIG. 11 is a diagram showing the configuration of a HANDOVER REQUEST message according to one embodiment of the present disclosure.

[0171] Referring to FIG. 11, an example of the configuration of a HANDOVER REQUEST message, which is an inter-base station message containing information about candidate cells or cells that support fast resume connection in an RRC-inactive state and information related to a configuration request for fast resume connection in an RRC-inactive state, is shown, which can be used in steps 220, 222, and 224 of FIG. 3, such as an X2 interface, an Xn interface, or a 6G Xn interface. The message of FIG. 11 may include other IE information in addition to the IE included in FIG. 11. As an example, the message name and IE name included in FIG. 11 may be used as different names for the same function, and the IE information included in FIG. 11 may be used for the purposes proposed in the present invention by including the IE (Information Element) included in FIG. 11 in other inter-base station messages or new inter-base station messages (for example, an INACTIVE PRECONFIGURATION REQUEST message) in addition to the HANDOVER REQUEST message.

[0172] The HANDOVER REQUEST message of FIG. 11 includes a Message Type IE used to distinguish message types. It may also include a Source RAN Node UE xxAP ID IE containing terminal identifier information from the base station (RAN Node) transmitting the HANDOVER REQUEST message. The HANDOVER REQUEST message may include a Target Cell Global ID IE containing candidate cell information that supports a fast resume connection when the terminal is in an RRC inactive state, and the Target Cell Global ID IE contains unique identifier information of the cell. The HANDOVER REQUEST message may include an INACTIVE Pre-Configuration Request IE, which is information requesting a fast resume connection setup for a terminal in an RRC inactive state. The INACTIVE Pre-Configuration Request IE may include an INACTIVE Pre-Configuration Trigger IE, which is an indicator including whether to initially request a fast resume connection setup for a terminal in an RRC inactive state or to request a change to pre-configured connection information. In addition, when the INACTIVE Pre-Configuration Trigger IE requests a change to the pre-configured connection information, it may include a Target RAN node UE xxAP ID that includes terminal identifier information from the referenced target base station (Target RAN Node).The INACTIVE Pre-Configuration Request IE may include a Candidate Cell List IE containing information on a list of candidate cells that will support fast resume connections for terminals in an RRC inactive state. The Candidate Cell List IE may include one or more Candidate Cell Global ID IEs, and the Candidate Cell Global ID IE includes unique identifier information for the cell. The Candidate Cell List IE may be used when establishing fast resume connections for terminals in an RRC inactive state for one or more cells in a single message, and when supporting configuration for only one cell, the cell information may be included only in the Target Cell Global ID IE included in the HANDOVER REQUEST message. The INACTIVE Pre-Configuration Request IE may include a Reference Configuration IE. The Reference Configuration IE may include an RRC message containing a reference configuration that serves as a reference when generating an RRC message containing fast resume connection settings for terminals in an RRC inactive state at a target or candidate base station, and may be used when creating an RRC message containing fast resume connection settings using a delta configuration method or similar during RRC message generation.The INACTIVE Pre-Configuration Request IE may include a Time to Keep IE containing timer time information that maintains the terminal's fast resume connection setup at the base station. The Time to Keep IE includes timer time information generated by the source base station, and the timer at the target or candidate base station may be activated after receiving a message containing information that the terminal has transitioned to an RRC inactive state, or after receiving a HANDOVER REQUEST message. The Time to Keep IE may be included as a single unit regardless of the cell, or a Time to Keep IE may be included per cell to have a different value for each cell.

[0173] FIG. 12 is a diagram showing the configuration of a HADVER REQUEST ACKNOWLEDGE message according to one embodiment of the present disclosure.

[0174] Referring to FIG. 12, an example of the configuration of a HANDOVER REQUEST ACKNOWLEDGE message is shown, which is an inter-base station message containing information about candidate cells or cells that support fast resume connection in an RRC-inactive state and information related to a response to a configuration request for fast resume connection in an RRC-inactive state, which can be used in steps 240, 242, and 244 of FIG. 3. The message of FIG. 12 may include other IE information in addition to the IE included in FIG. 12. As an example, the message name and IE name included in FIG. 12 may be used as different names for the same function, and the IE information included in FIG. 12 may be used for the purposes proposed in the present invention by including the IE included in FIG. 12 in other inter-base station messages or new inter-base station messages (for example, an INACTIVE PRECONFIGURATION ACKNOWLEDGE message) in addition to the HANDOVER REQUEST ACKNOWLEDGE message.

[0175] The HANDOVER REQUEST ACKNOWLEDGE message of FIG. 12 includes a Message Type IE used to distinguish message types. Additionally, it may include a Target RAN Node UE xxAP ID IE containing terminal identifier information of the base station transmitting the HANDOVER REQUEST ACKNOWLEDGE message, and a Source RAN Node UE xxAP ID IE containing terminal identifier information of the base station receiving the HANDOVER REQUEST ACKNOWLEDGE message. The HANDOVER REQUEST ACKNOWLEDGE message may include an INACTIVE Pre-Configuration Support IE containing information on whether it can support fast resume connection setup of a terminal in an RRC inactive state, and the HANDOVER REQUEST ACKNOWLEDGE message may include an INACTIVE Pre-Configuration Acknowledge IE, which is response information to a request for fast resume connection setup of a terminal in an RRC inactive state. INACTIVE Pre-Configuration Acknowledge IE may include an Acknowledged Cell List IE that includes cell list information containing fast resume connection setup information for a terminal in an RRC inactive state, and the Acknowledged Cell List IE may include one or more Requested Target Cell ID IEs, and the Requested Target Cell ID IE includes unique identifier information of cells that support the fast resume connection setup of the terminal among candidate cells that requested the fast resume connection setup of the terminal in an RRC inactive state from the source base station.The Acknowledged Cell List IE may include INACTIVE Pre-Configuration Information IE, and the INACTIVE Pre-Configuration Information IE may include fast resume connection setup information for a terminal in an RRC inactive state. The INACTIVE Pre-Configuration Information IE may be included for each cell, or a single INACTIVE Pre-Configuration Information IE may be included regardless of the cell. The Acknowledged Cell List IE may include Time to Keep IE, which includes timer time information for maintaining the terminal's fast resume connection setup at the base station, and may include timer time information generated by the target / candidate base station. The timer at the target or candidate base station may be activated after receiving a message containing information that the terminal has transitioned to an RRC inactive state, or after transmitting a HANDOVER REQUEST ACKNOWLEDGE message. The Time to Keep IE may be included to have different values ​​for each cell, or a single one may be included regardless of the cell.

[0176] FIG. 13 is a diagram showing the configuration of an RRC STATE TRANSITION NOTIFICATION message according to one embodiment of the present disclosure.

[0177] Referring to FIG. 13, an example of the configuration of an RRC STATE TRANSITION NOTIFICATION message, which is an inter-base station message containing RRC state change information of a terminal, is shown using an inter-base station interface (e.g., X2 interface, Xn interface, 6G Xn interface) that can be used in steps 320, 322, 324, and 540 of FIG. 3 and step 630 of FIG. 5. The message of FIG. 13 may include other IE information in addition to the IE included in FIG. 13. As an example, the message name and IE name included in FIG. 13 may be used as different names for the same function, and the IE information included in FIG. 13 may be used for the purposes proposed in the present invention by including the IE included in FIG. 13 in other inter-base station messages in addition to the new RRC STATE TRANSITION NOTIFICATION message.

[0178] The RRC STATE TRANSITION NOTIFICATION message of FIG. 13 includes a Message Type IE used to distinguish message types. It may also include a Source RAN Node UE xxAP ID IE containing terminal identifier information of the base station transmitting the RRC STATE TRANSITION NOTIFICATION message, and a Target RAN Node UE xxAP ID IE containing terminal identifier information of the base station receiving the RRC STATE TRANSITION NOTIFICATION message. The RRC STATE TRANSITION NOTIFICATION message may include an RRC State IE containing RRC state information of the terminal (e.g., RRC CONNECTED, RRC INACTIVE, RRC IDLE). The RRC STATE TRANSITION NOTIFICATION message may include a Time to Keep IE containing timer time information that maintains the terminal's fast resume connection setting at the base station, and may include timer time information generated by the source base station, and the timer at the target or candidate base station may be activated after receiving a message containing information that the terminal has transitioned to an RRC inactive state.

[0179] FIG. 14 is a diagram showing the configuration of a UE CONTEXT SETUP REQUEST message according to one embodiment of the present disclosure.

[0180] Referring to FIG. 14, an example of the configuration of a UE CONTEXT SETUP REQUEST message is shown, which is a message transmitted from a CU to a DU in a base station that includes information about candidate cells or cells that support fast resume connection in an RRC-inactive state and information related to a setup request for fast resume connection in an RRC-inactive state, which can be used in steps 220, 222, and 250 of FIG. 7 (e.g., W1 interface, F1 interface, 6G F1 interface). The message of FIG. 14 may include other IE information in addition to the IE included in FIG. 14. The message name and IE name included in FIG. 14 may be used as different names for the same function as one example, and the IE information included in FIG. 14 may be used for the purposes proposed in the present invention by including the IE included in FIG. 14 in a UE CONTEXT MODIFICATION REQUEST message or another inter-base station message or a new inter-base station message (for example, an INACTIVE PRECONFIGURATION REQUEST message) in addition to the UE CONTEXT SETUP REQUEST message.

[0181] The UE CONTEXT SETUP REQUEST message of FIG. 14 includes a Message Type IE used to distinguish message types. Additionally, it may include a CU UE xyAP ID IE containing terminal identifier information from the CU transmitting the UE CONTEXT SETUP REQUEST message, and a DU UE xyAP ID IE containing terminal identifier information from the DU. The UE CONTEXT SETUP REQUEST message may include a SpCell ID IE containing candidate cell information to support a fast resume connection when the terminal is in an RRC inactive state, and the SpCell ID IE includes unique identifier information of the cell. The UE CONTEXT SETUP REQUEST message may include an RRC-Container IE containing an RRC message transmitted by the CU to the terminal, and the DU transmits the RRC message received from the CU to the terminal. The UE CONTEXT SETUP REQUEST message may include an INACTIVE Pre-Configuration Request IE, which is information requesting the setup of a fast resume connection for a terminal in an RRC inactive state. The INACTIVE Pre-Configuration Request IE may include an INACTIVE Pre-Configuration Trigger IE, which is an indicator that includes whether to initially request a fast resume connection setup for a terminal in an RRC inactive state or to request a change to pre-configured connection information. In addition, if the INACTIVE Pre-Configuration Trigger IE requests a change to pre-configured connection information, it may include a Target DU UE xyAP ID that includes terminal identifier information from the referenced DU.The INACTIVE Pre-Configuration Request IE may include a Candidate Cell List IE containing candidate cell list information to support fast resume connections for terminals in an RRC inactive state, and the Candidate Cell List IE may include one or more Candidate Cell Global ID IEs, and the Candidate Cell Global ID IE contains unique identifier information of the cell. The Candidate Cell List IE may be used when establishing fast resume connections for terminals in an RRC inactive state for one or more cells with a single message, and when supporting configuration for only one cell, the cell information may be included only with the SpCell ID IE included in the UE CONTEXT SETUP REQUEST message. The INACTIVE Pre-Configuration Request IE may include a Reference Configuration IE, and the Reference Configuration IE may include an RRC message containing reference settings that serve as a reference when the DU generates an RRC message containing fast resume connection settings for terminals in an RRC inactive state, and may be used when creating an RRC message containing fast resume connection settings using a delta configuration method or similar when generating the RRC message. The INACTIVE Pre-Configuration Request IE may include a Lower Layer Reference Config Request IE that requests the CU to create and transmit information that serves as a reference setting when generating an RRC message containing fast resume connection settings for an RRC inactive terminal.

[0182] FIG. 15 is a diagram showing the configuration of a UE CONTEXT SETUP RESPONSE message according to one embodiment of the present disclosure.

[0183] Referring to FIG. 15, an example of the configuration of a UE CONTEXT SETUP RESPONSE message is shown, which is a message transmitted from the DU to the CU, containing information about candidate cells or cells that support fast resume connection in an RRC-inactive state and information related to a response to a setup request for fast resume connection in an RRC-inactive state, which can be used in steps 240, 242, and 270 of FIG. 7 between the CU and DU within the base station (e.g., W1 interface, F1 interface, 6G F1 interface). The message of FIG. 15 may include other IE information in addition to the IE included in FIG. 15. The message name and IE name included in FIG. 15 may be used as different names for the same function as one example, and the IE information included in FIG. 15 may be used for the purposes proposed in the present invention by including the IE included in FIG. 15 in the UE CONTEXT MODIFICATION RESPONSE message, other inter-base station messages, or new inter-base station messages (for example, INACTIVE PRECONFIGURATION RESPONSE message) in addition to the UE CONTEXT SETUP RESPONSE message.

[0184] The UE CONTEXT SETUP RESPONSE message of FIG. 15 includes a Message Type IE used to distinguish message types. Additionally, it may include a CU UE xyAP ID IE containing terminal identifier information of the CU receiving the UE CONTEXT SETUP RESPONSE message, and a DU UE xyAP ID IE containing terminal identifier information of the DU transmitting the UE CONTEXT SETUP RESPONSE message. The UE CONTEXT SETUP RESPONSE message may include an INACTIVE Pre-Configuration Support IE containing information on whether it can support fast resume connection setup of a terminal in an RRC inactive state, and the UE CONTEXT SETUP RESPONSE message may include an INACTIVE Pre-Configuration Response IE, which is response information to a request for fast resume connection setup of a terminal in an RRC inactive state. The INACTIVE Pre-Configuration Response IE may include an Acknowledged Cell List IE that includes cell list information containing fast resume connection configuration information for a terminal in an RRC inactive state, and the Acknowledged Cell List IE may include one or more Requested Target Cell ID IEs, and the Requested Target Cell ID IE includes unique identifier information of cells that support the fast resume connection configuration of the terminal among the candidate cells that requested the fast resume connection configuration of the terminal in an RRC inactive state from the CU.The Acknowledged Cell List IE may include INACTIVE Pre-Configuration Information IE, and the INACTIVE Pre-Configuration Information IE may include fast resume connection configuration information for terminals in an RRC inactive state. The INACTIVE Pre-Configuration Information IE may be included for each cell, or a single INACTIVE Pre-Configuration Information IE may be included regardless of the cell. When the CU is requested to create and transmit information that serves as a reference setting to be referenced when the DU creates an RRC message containing fast resume connection settings for terminals in an RRC inactive state, the INACTIVE Pre-Configuration Response IE may include a Reference Configuration Information IE that includes a reference setting to be referenced when creating an RRC message containing fast resume connection settings for terminals in an RRC inactive state.

[0185] FIG. 16 is a diagram showing the configuration of an RRC STATE TRANSITION NOTIFICATION message according to one embodiment of the present disclosure.

[0186] Referring to FIG. 16, an example of the configuration of an RRC STATE TRANSITION NOTIFICATION message is shown, which is a message transmitted from a CU to a DU containing information on the RRC state change of a terminal, through an interface between a CU and a DU within a base station (e.g., W1 interface, F1 interface, 6G F1 interface) that can be used in steps 410, 412, and 660 of FIG. 7 and step 750 of FIG. 9. The message of FIG. 16 may include other IE information in addition to the IE included in FIG. 16. As an example, the message name and IE name included in FIG. 16 may be used as different names for the same function, and the IE information included in FIG. 16 may be used for the purposes proposed in the present invention by including the IE included in FIG. 16 in other inter-base station messages, such as UE CONTEXT MODIFICATION REQUEST messages and UE CONTEXT RELEASE COMMAND messages, in addition to the new RRC STATE TRANSITION NOTIFICATION message.

[0187] The RRC STATE TRANSITION NOTIFICATION message of FIG. 16 includes a Message Type IE used to distinguish message types. Additionally, it may include a CU UE xyAP ID IE containing terminal identifier information of the CU transmitting the RRC STATE TRANSITION NOTIFICATION message, and a DU UE xyAP ID IE containing terminal identifier information of the DU receiving the RRC STATE TRANSITION NOTIFICATION message. The RRC STATE TRANSITION NOTIFICATION message may include an RRC State IE containing RRC status information of the terminal (e.g., RRC CONNECTED, RRC INACTIVE, RRC IDLE). The RRC STATE TRANSITION NOTIFICATION message may include an RRC-Container IE containing an RRC message transmitted by the CU to the terminal, and the DU transmits the RRC message received from the CU to the terminal. The RRC STATE TRANSITION NOTIFICATION message may include a UE Context Keep IE that includes an indicator instructing the DU to maintain terminal context and configuration information.

[0188] FIG. 17 is a diagram showing the configuration of a base station (RAN Node) according to one embodiment of the present disclosure.

[0189] As illustrated in the drawing above, the RAN Node is configured to include an RF processing unit (1710), a baseband processing unit (1720), a backhaul communication unit (1730), a storage unit (1740), and a control unit (1750). The control unit (1750) may further include a multiple connection processing unit (1752). If the RAN Node is separated into a CU and a DU, blocks other than those included in FIG. 17 may also be configured. For example, the RF processing unit (1710) and the baseband processing unit (1720) may be configured to include a control unit, a storage unit, and a backhaul communication unit for communication with the CU in the DU. For example, the backhaul communication unit (1730) may be configured to include a control unit, a storage unit, and a backhaul communication unit for communication with the DU in the CU. Additionally, the base station may be configured to include a transceiver unit and a control unit.

[0190] The RF processing unit (1710) performs functions for transmitting and receiving signals through a wireless channel, such as signal band conversion and amplification. The RF processing unit (1710) upconverts the baseband signal provided by the baseband processing unit (1720) into an RF band signal, transmits it through an antenna, and downconverts the RF band signal received through the antenna into a baseband signal. For example, the RF processing unit (1710) may include a transmit filter, a receive filter, an amplifier, a mixer, an oscillator, a DAC, an ADC, etc. Although only one antenna is shown in the drawing, the first connection node may be equipped with multiple antennas. Additionally, the RF processing unit (1710) may include multiple RF chains. Furthermore, the RF processing unit (1710) may perform beamforming. For beamforming, the RF processing unit (1710) may adjust the phase and magnitude of each of the signals transmitted and received through multiple antennas or antenna elements. The above RF processing unit (1710) can perform down-to-down MIMO operation by transmitting one or more layers.

[0191] The baseband processing unit (1720) performs a conversion function between a baseband signal and a bit sequence according to the physical layer specifications of the first wireless access technology. For example, when transmitting data, the baseband processing unit (1720) generates complex symbols by encoding and modulating the transmitted bit sequence. In addition, when receiving data, the baseband processing unit (1720) restores the received bit sequence by demodulating and decoding the baseband signal provided by the RF processing unit (10). For example, in the case of following the OFDM method, when transmitting data, the baseband processing unit (1720) generates complex symbols by encoding and modulating the transmitted bit sequence, maps the complex symbols to subcarriers, and then constructs OFDM symbols through IFFT operation and CP insertion. Additionally, upon receiving data, the baseband processing unit (1720) divides the baseband signal provided by the RF processing unit (1710) into OFDM symbol units, restores the signals mapped to subcarriers through FFT operations, and then restores the received bit sequence through demodulation and decoding. The baseband processing unit (1720) and the RF processing unit (1710) transmit and receive signals as described above. Accordingly, the baseband processing unit (1720) and the RF processing unit (1710) may be referred to as a transmitting unit, a receiving unit, a transmitting and receiving unit, a communication unit, or a wireless communication unit.

[0192] The backhaul communication unit (1730) provides an interface for communicating with other nodes within the network. The backhaul communication unit (1730) converts a bit sequence transmitted from the main RAN Node to other nodes, such as an auxiliary base station or a core network, into a physical signal, and converts a physical signal received from the other nodes into a bit sequence.

[0193] The storage unit (1740) stores data such as basic programs, application programs, and configuration information for the operation of the main RAN Node. In particular, the storage unit (1740) can store information regarding bearers assigned to connected terminals, measurement results reported from connected terminals, etc. Additionally, the storage unit (1740) can store information serving as a criterion for determining whether to provide or disconnect multiple connections to the terminals. Furthermore, the storage unit (1740) provides the stored data upon a request from the control unit (1750).

[0194] The control unit (1750) controls the overall operations of the RAN Node. For example, the control unit (1750) transmits and receives signals through the baseband processing unit (1720) and the RF processing unit (1710) or through the backhaul communication unit (1730). Additionally, the control unit (1750) writes and reads data to and from the storage unit (1740). To this end, the control unit (1750) may include at least one processor. Additionally, the control unit (1750) may be used to control the overall operations of the NCR.

[0195] FIG. 18 is a diagram showing the configuration of a terminal (UE) according to one embodiment of the present disclosure.

[0196] Referring to the drawing above, the terminal includes an RF (Radio Frequency) processing unit (1810), a baseband processing unit (1820), a storage unit (1830), and a control unit (1840). The control unit (1840) may further include a multiple connection processing unit (1842). Additionally, the terminal may be composed of a control unit and a transceiver unit.

[0197] The RF processing unit (1810) performs functions for transmitting and receiving signals through a wireless channel, such as signal band conversion and amplification. The RF processing unit (1810) up-converts the baseband signal provided by the baseband processing unit (1820) into an RF band signal, 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 (1810) may include a transmit filter, a receive filter, an amplifier, a mixer, an oscillator, a DAC (digital to analog converter), an ADC (analog to digital converter), etc. Although only one antenna is shown in the drawing, the terminal may be equipped with multiple antennas. Additionally, the RF processing unit (1810) may include multiple RF chains. Furthermore, the RF processing unit (1810) may perform beamforming. For the above beamforming, the RF processing unit (1810) can adjust the phase and magnitude of each of the signals transmitted and received through a plurality of antennas or antenna elements. In addition, the RF processing unit can perform MIMO and can receive multiple layers when performing MIMO operation.

[0198] The baseband processing unit (1820) performs a conversion function between a baseband signal and a bit sequence according to the physical layer specifications of the system. For example, when transmitting data, the baseband processing unit (1820) generates complex symbols by encoding and modulating the transmitted bit sequence. Additionally, when receiving data, the baseband processing unit (1820) restores the received bit sequence by demodulating and decoding the baseband signal provided by the RF processing unit (1810). For example, in the case of following the orthogonal frequency division multiplexing (OFDM) method, when transmitting data, the baseband processing unit (1820) generates complex symbols by encoding and modulating the transmitted bit sequence, maps the complex symbols to subcarriers, and then constructs OFDM symbols through inverse fast Fourier transform (IFFT) operations and cyclic prefix (CP) insertion. Additionally, upon receiving data, the baseband processing unit (1820) divides the baseband signal provided by the RF processing unit (1810) into OFDM symbol units, restores the signals mapped to subcarriers through a fast Fourier transform (FFT), and then restores the received bit sequence through demodulation and decoding.

[0199] The baseband processing unit (1820) and the RF processing unit (1810) transmit and receive signals as described above. Accordingly, the baseband processing unit (1820) and the RF processing unit (1810) may be referred to as a transmitting unit, a receiving unit, a transmitting and receiving unit, or a communication unit. Furthermore, at least one of the baseband processing unit (1820) and the RF processing unit (1810) may include a plurality of communication modules to support a plurality of different wireless access technologies. Additionally, at least one of the baseband processing unit (1820) and the RF processing unit (1810) may include different communication modules to process signals of different frequency bands. For example, the different wireless access technologies may include wireless LAN (e.g., IEEE 802.11), cellular network (e.g., LTE), etc. In addition, the above different frequency bands may include super high frequency (SHF) bands (e.g., 2 NRHz, NRHz) and millimeter wave (e.g., 60 GHz) bands.

[0200] The storage unit (1830) stores data such as a basic program, application program, and setting information for the operation of the NCR. Additionally, the storage unit (1830) provides the stored data upon request from the control unit (1840).

[0201] The control unit (1840) controls the overall operations of the NCR. For example, the control unit (1840) transmits and receives signals through the baseband processing unit (1820) and the RF processing unit (1810). Additionally, the control unit (1840) writes and reads data to and from the storage unit (1840). To this end, the control unit (1840) may include at least one processor. For example, the control unit (1840) may include a communication processor (CP) that performs control for communication and an application processor (AP) that controls upper layers such as applications.

[0202] It should be noted that the aforementioned configuration diagrams, exemplary diagrams of control / data signal transmission methods, exemplary diagrams of operation procedures, and configuration diagrams are not intended to limit the scope of the rights of the present disclosure. That is, all components, entities, or steps of operation described in the embodiments of the present disclosure should not be interpreted as essential components for the implementation of the disclosure, and may be implemented within a scope that does not impair the essence of the disclosure even if only some components are included. Furthermore, each embodiment may be combined with one another as needed. For example, parts of the methods proposed in the present disclosure may be combined with one another to operate network entities and terminals.

[0203] 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 the program code stored in the memory device using a processor or CPU (Central Processing Unit) and executing it.

[0204] Various components of entities, base stations, or terminal devices and modules described in this disclosure may be operated using hardware circuits, such as, for example, complementary metal oxide semiconductor-based logic circuits, firmware, software, and / or a combination of 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.

[0205] When implemented in software, a computer-readable storage medium may be provided for storing one or more programs (software modules). One or more programs stored in the computer-readable storage medium are configured for execution by one or more processors within an electronic device. One or more programs include instructions that cause the electronic device to execute methods according to the embodiments described in the claims or specification of this disclosure.

[0206] Such programs (software modules, software) may be stored in random access memory, non-volatile memory including flash memory, ROM (Read Only Memory), EEPROM (Electrically Erasable Programmable Read Only Memory), magnetic disc storage devices, CD-ROM (Compact Disc-ROM), Digital Versatile Discs (DVDs), or other forms of optical storage devices, magnetic cassettes. Alternatively, they may be stored in memory composed of some or all of these. Additionally, each constituent memory may include multiple units.

[0207] Additionally, the program may be stored on an attachable storage device accessible via a communication network such as the Internet, Intranet, Local Area Network (LAN), Wide LAN (WLAN), or Storage Area Network (SAN), or a combination thereof. Such a storage device may be connected to the device performing the embodiment of the present disclosure through an external port. Additionally, a separate storage device on the communication network may be connected to the device performing the embodiment of the present disclosure.

[0208] In the specific embodiments of the present disclosure described above, the components included in the present disclosure are expressed in a singular or plural form according to the specific embodiments presented. However, the singular or plural expression is selected to suit the situation presented for convenience of explanation, and the present disclosure is not limited to singular or plural components; even if a component is expressed in the plural, it may be composed of a singular form, and even if a component is expressed in the singular form, it may be composed of a plural form.

[0209] Meanwhile, the embodiments of the present disclosure disclosed in this specification and drawings are merely specific examples provided to facilitate the explanation of the technical content of the present disclosure and to aid in understanding the present disclosure, and are not intended to limit the scope of the present disclosure. That is, it is obvious to those skilled in the art that other variations based on the technical concept of the present disclosure are possible. Furthermore, each of the above embodiments may be combined and operated as needed. For example, parts of one embodiment of the present disclosure and another embodiment may be combined to operate a base station and a terminal. In addition, the embodiments of the present disclosure are applicable to other communication systems, and other variations based on the technical concept of the embodiments may also be implemented.

Claims

1. A method performed by a terminal in a wireless communication system, A step of receiving an RRC message from a serving cell containing configuration information of a candidate cell for a quick resume connection in a radio resource control (RRC) disabled state; When the connection state of the terminal switches from the RRC connection state to the RRC disabled state, the step of maintaining the configuration information of the candidate cell for a quick re-connection in the RRC disabled state; A step of determining a transition from the RRC disabled state to the RRC connected state; and A method comprising the step of, when the terminal determines a transition from the RRC disabled state to the RRC connected state within the candidate cell, performing an RRC resumption procedure based on the setting information of the candidate cell for a quick resumption connection from the RRC disabled state.

2. In Paragraph 1, A method further comprising the step of receiving RRC configuration information of the cell excluding the candidate cell for fast resumption connection in the RRC disabled state, based on a random access procedure for an RRC resumption procedure, if the terminal has determined a transition from the RRC disabled state to the RRC connected state within the cell excluding the candidate cell for fast resumption connection in the RRC disabled state.

3. In Paragraph 1, The setting information of the candidate cell for a quick resume connection in the above deactivated state is, Using the configuration information of CHO (conditional handover) or LTM (layer1 / layer2 triggered mobility) in the above RRC disabled state, or A method corresponding to one of the dedicated configuration information for a quick resumption connection in the above-mentioned disabled state.

4. In Paragraph 1, When the connection state of the terminal switches from the RRC connection state to the RRC disabled state, the method further includes the step of driving a timer to determine the validity of the setting information of the candidate cell for a quick re-connection in the RRC disabled state. The above RRC message is a method corresponding to an RRC reconfiguration message or an RRC release message.

5. A method performed by a base station of a serving cell in a wireless communication system, A step of determining a candidate cell for a quick resume connection from an RRC disabled state based on measurement information received from a terminal in an RRC (radio resource control) connection state; A step of obtaining configuration information of the candidate cell for a fast resumption connection in the above RRC disabled state; and The method includes the step of transmitting an RRC message containing the configuration information of the candidate cell for a fast resumption connection in the RRC disabled state to the terminal in the RRC connection state. A method in which, after transmitting the above RRC message to the terminal, the terminal in the RRC connection state switches to the RRC deactivation state, and when the terminal in the RRC deactivation state decides to switch to the RRC connection state within the candidate cell, an RRC resumption procedure is performed based on the configuration information of the candidate cell for a quick resumption connection in the RRC deactivation state.

6. In Paragraph 5, The configuration information of the candidate cell for fast re-connection in the above-mentioned inactive state corresponds to using the configuration information of CHO (conditional handover) or LTM (layer1 / layer2 triggered mobility) in the above-mentioned RRC inactive state, or to one of the dedicated configuration information for fast re-connection in the above-mentioned inactive state, and The above RRC message is a method corresponding to an RRC reconfiguration message or an RRC release message.

7. In Paragraph 5, If the terminal in the RRC connection state is instructed to switch to the RRC disabled state: A step of transmitting information indicating that the state of the terminal has changed to the candidate cell; and A method further comprising the step of driving a timer to determine the validity of the setting information of the candidate cell for a fast resumption connection in the above RRC disabled state.

8. In Paragraph 5, If the terminal determines a transition from the RRC disabled state to the RRC connected state within a cell excluding the candidate cell for a fast reconnection in the RRC disabled state, a method for obtaining RRC configuration information of the cell excluding the candidate cell for a fast reconnection in the RRC disabled state based on a random access procedure for an RRC reconnection procedure.

9. In a terminal of a wireless communication system, Transmitter / receiver; and It includes at least one processor connected to the above-mentioned transmitting and receiving unit, and The above-mentioned at least one processor is, Receive an RRC message from a serving cell containing configuration information for a candidate cell for a fast resume connection while RRC (radio resource control) is disabled, and When the connection status of the above terminal switches from the RRC connection status to the RRC disabled status, the above configuration information of the candidate cell for quick re-connection in the RRC disabled status is maintained, and Determine the transition from the above RRC disabled state to the above RRC connected state, and A terminal that, when the terminal determines a transition from the RRC disabled state to the RRC connected state within the candidate cell, controls the execution of an RRC resumption procedure based on the setting information of the candidate cell for a quick resumption connection from the RRC disabled state.

10. In Paragraph 9, The above-mentioned at least one processor is, A terminal that, if the terminal determines a transition from the RRC disabled state to the RRC connected state within a cell excluding the candidate cell for a fast reconnection in the RRC disabled state, controls the reception of RRC setting information of the cell excluding the candidate cell for a fast reconnection in the RRC disabled state based on a random access procedure for an RRC reconnection procedure.

11. In Paragraph 9, The setting information of the candidate cell for a quick resume connection in the above deactivated state is, Using the configuration information of CHO (conditional handover) or LTM (layer1 / layer2 triggered mobility) in the above RRC disabled state, or A terminal corresponding to one of the dedicated configuration information for a quick resumption connection in the above-mentioned deactivated state.

12. In Paragraph 9, When the connection state of the terminal switches from the RRC connection state to the RRC disabled state, the above at least one processor drives a timer to determine the validity of the configuration information of the candidate cell for a fast re-connection in the RRC disabled state, and The above RRC message is a method corresponding to an RRC reconfiguration message or an RRC release message.

13. In a base station of a serving cell of a wireless communication system, Transmitter / receiver; and It includes at least one processor connected to the above-mentioned transmitting and receiving unit, and The above-mentioned at least one processor is, Based on measurement information received from a terminal in an RRC (radio resource control) connection state, determine a candidate cell for a fast resume connection from an RRC disabled state, and Acquires configuration information of the candidate cell for a fast resume connection in the above RRC disabled state, and, Control to transmit an RRC message containing the configuration information of the candidate cell for a fast resumption connection in the above RRC disabled state to the terminal in the above RRC connection state, and A base station in which, after transmitting the above RRC message to the terminal, the terminal in the above RRC connection state switches to the above RRC deactivation state, and when the terminal in the above RRC deactivation state decides to switch to the above RRC connection state within the above candidate cell, an RRC resumption procedure is performed based on the above setting information of the above candidate cell for a quick resumption connection in the above RRC deactivation state.

14. In Paragraph 13, The configuration information of the candidate cell for fast re-connection in the above-mentioned inactive state corresponds to using the configuration information of CHO (conditional handover) or LTM (layer1 / layer2 triggered mobility) in the above-mentioned RRC inactive state, or to one of the dedicated configuration information for fast re-connection in the above-mentioned inactive state, and The above RRC message is a base station corresponding to an RRC reconfiguration message or an RRC release message.

15. In Paragraph 13, The above-mentioned at least one processor is, If the terminal in the RRC connection state is instructed to switch to the RRC disabled state: Transmit information indicating that the state of the above terminal has changed to the above candidate cell, and, A base station that drives a timer to determine the validity of the setting information of the candidate cell for a fast re-connection in the above RRC disabled state.

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