Device and method for transmitting small data in wireless communication system

Abstract

The present disclosure is for transmitting small data in a wireless communication system. A method performed by a first network node may comprise the steps of: transmitting a modification request message to a second network node; receiving, from the second network node, an acknowledgement message for the modification request; transmitting a radio resource control (RRC) connection release message to a terminal in order to change the state of the terminal to an RRC inactive state; receiving an activity notification message from the second network node; and transmitting a paging message to the terminal.

Description

Device and method for transmitting small data in a wireless communication system

[0001] The following description relates to a wireless communication system, and more particularly, to a device and method for transmitting small data in a wireless communication system.

[0002] Wireless access systems are widely deployed to provide various types of communication services, such as voice and data. Typically, wireless access systems are multiple access systems that support communications with multiple users by sharing available system resources (e.g., bandwidth, transmission power). Examples of multiple access systems include code division multiple access (CDMA), frequency division multiple access (FDMA), time division multiple access (TDMA), orthogonal frequency division multiple access (OFDMA), and single-carrier frequency division multiple access (SC-FDMA).

[0003] In particular, as numerous communication devices demand greater communication capacity, enhanced mobile broadband (eMBB) communication technologies are being proposed, improving upon existing radio access technology (RAT). Furthermore, massive machine type communications (mMTC), which connects multiple devices and objects to provide diverse services anytime and anywhere, as well as communication systems that consider reliability and latency-sensitive services / user equipment (UE), are being proposed. Various technological configurations are being proposed for these solutions.

[0004] The present disclosure relates to a device and method for effectively transmitting small data in a wireless communication system.

[0005] The present disclosure relates to a device and method for supporting small data transmission (SDT) for a terminal configured to have dual connectivity in a wireless communication system.

[0006] The present disclosure relates to a device and method for supporting SDT while a terminal is in an RRC (radio resource control) inactive state in a wireless communication system.

[0007] The present disclosure relates to a device and method for supporting SDT while maintaining a secondary cell group (SCG) of a terminal in a wireless communication system.

[0008] The present disclosure relates to a device and method for determining whether to operate SDT based on volume information of downlink (DL) SDT data in a wireless communication system.

[0009] The present disclosure relates to a device and method for transmitting a paging signal for SDT based on volume information of DL SDT data in a wireless communication system.

[0010] The present disclosure relates to a device and method for changing a secondary node (SN) for a terminal during SDT operation in a wireless communication system.

[0011] The present disclosure relates to a device and method for transmitting non-SDT data arriving at a network node during SDT operation in a wireless communication system.

[0012] The present disclosure relates to a device and method for completely resuming an RRC connection of a terminal based on non-SDT data arriving at a network node during an SDT operation in a wireless communication system.

[0013] The present disclosure relates to a device and method for terminating an SDT operation in a wireless communication system.

[0014] The present disclosure relates to a device and method for returning a terminal to an RRC inactive state based on a SDT termination request in a wireless communication system.

[0015] The technical objectives to be achieved in the present disclosure are not limited to those mentioned above, and other technical tasks not mentioned can be considered by a person having ordinary skill in the technical field to which the technical configuration of the present disclosure is applied from the embodiments of the present disclosure described below.

[0016] As an example of the present disclosure, a method performed by a first network node in a wireless communication system includes the steps of: transmitting a modification request message to a second network node; receiving a confirmation message for the modification request from the second network node; transmitting an RRC connection release message to the terminal to change the state of the terminal to an RRC inactive state; receiving an activity notification message from the second network node; and transmitting a paging message to the terminal based on the activity notification message, wherein the activity notification message includes information about downlink small data for the terminal that has arrived at the second network node, and the paging message can indicate legacy paging or paging for the downlink small data transmission (SDT) based on the information about the downlink small data.

[0017] As an example of the present disclosure, a method performed by a second network node in a wireless communication system further includes the steps of receiving a modification request message from a first network node, transmitting a confirmation message for the modification request to the second network node, transmitting an activity notification message to the first network node, resuming a bearer for small data transmission (SDT) at the request of the first network, and transmitting small data to the terminal through the resumed bearer, wherein the activity notification message may include information about downlink small data for the terminal that has arrived at the second network node.

[0018] As an example of the present disclosure, a method performed by a terminal in a wireless communication system may include the steps of receiving an RRC connection release message from a first network node, receiving a paging message for downlink small data transmission (SDT) from the first network node, performing a random access procedure for a second network node, transmitting an RRC resumption request message to the first network node, and receiving downlink small data from the second network node.

[0019] As an example of the present disclosure, in a wireless communication system, a first network node includes a transceiver and a processor connected to the transceiver, wherein the processor transmits a modification request message to a second network node, receives a confirmation message for the modification request from the second network node, transmits an RRC connection release message to the terminal to change the state of the terminal to an RRC (radio resource control) inactive state, receives an activity notification message from the second network node, and controls transmission of a paging message to the terminal based on the activity notification message, wherein the activity notification message includes information on downlink small data for the terminal that has arrived at the second network node, and the paging message can indicate legacy paging or paging for the downlink small data transmission (SDT) based on the information on the downlink small data.

[0020] As an example of the present disclosure, in a wireless communication system, a second network node includes a transceiver and a processor connected to the transceiver, wherein the processor receives a modification request message from a first network node, transmits a confirmation message for the modification request to the second network node, transmits an activity notification message to the first network node, resumes a bearer for small data transmission (SDT) at the request of the first network, and controls transmission of small data to the terminal through the resumed bearer, wherein the activity notification message may include information on downlink small data for the terminal that has arrived at the second network node.

[0021] As an example of the present disclosure, in a wireless communication system, a terminal includes a transceiver and a processor connected to the transceiver, wherein the processor is configured to receive an RRC connection release message from a first network node, receive a paging message for downlink small data transmission (SDT) from the first network node, perform a random access procedure for a second network node, transmit an RRC resumption request message to the first network node, and control the reception of downlink small data from the second network node.

[0022] As an example of the present disclosure, a communication device includes at least one processor, and at least one computer memory coupled to the at least one processor and storing instructions that, when executed by the at least one processor, direct operations, wherein the operations may include: receiving an RRC connection release message from a first network node; receiving a paging message for downlink small data transmission (SDT) from the first network node; performing a random access procedure for a second network node; transmitting an RRC resumption request message to the first network node; and receiving downlink small data from the second network node.

[0023] As an example of the present disclosure, a non-transitory computer-readable medium storing at least one instruction includes at least one instruction executable by a processor, wherein the at least one instruction can control a device to receive an RRC connection release message from a first network node, receive a paging message for downlink small data transmission (SDT) from the first network node, perform a random access procedure for a second network node, transmit an RRC resumption request message to the first network node, and receive downlink small data from the second network node.

[0024] The following effects may be achieved by embodiments based on the present disclosure.

[0025] The present disclosure can support small data transmission (SDT) for a terminal configured to have dual connectivity in a wireless communication system.

[0026] The effects that can be obtained from the embodiments of the present disclosure are not limited to the effects mentioned above, and other effects that are not mentioned can be clearly derived and understood by those skilled in the art to which the technical configuration of the present disclosure is applied, from the description of the embodiments of the present disclosure below. In other words, unintended effects that result from implementing the configuration described in the present disclosure can also be derived by those skilled in the art from the embodiments of the present disclosure.

[0027] The accompanying drawings are intended to aid in understanding the present disclosure and, together with detailed descriptions, may provide embodiments of the present disclosure. However, the technical features of the present disclosure are not limited to specific drawings, and the features disclosed in each drawing may be combined with each other to form new embodiments. Reference numerals in each drawing may indicate structural elements.

[0028] Figure 1 illustrates an example of a communication system applicable to the present disclosure.

[0029] FIG. 2 illustrates an example of a user equipment (UE) applicable to the present disclosure.

[0030] FIG. 3 illustrates an example of functional separation of a next generation radio access network (NG-RAN) and a 5th generation core (5GC) applicable to the present disclosure.

[0031] FIG. 4 illustrates an example of a general architecture of a 5G (5th generation) system applicable to the present disclosure.

[0032] Figures 5a and 5b illustrate examples of handover procedures between MNs regardless of whether SN changes are initiated by the MN.

[0033] Figure 6 illustrates an example of a successful procedure for preparing to add an S-NG-RAN node.

[0034] Figure 7 illustrates an example of a failure procedure for preparing to add an S-NG-RAN node.

[0035] Figure 8 illustrates an example of a procedure that supports activity notification of MR-DC.

[0036] FIG. 9a and FIG. 9b illustrate examples of a procedure for supporting DL SDT data arrival in an SN according to an embodiment of the present disclosure.

[0037] FIG. 10A and FIG. 10B illustrate examples of a procedure for changing an SN during SDT according to one embodiment of the present disclosure.

[0038] FIG. 11 illustrates an example of a procedure for supporting DL Non-SDT in an SN according to one embodiment of the present disclosure.

[0039] FIG. 12a and FIG. 12b illustrate examples of a procedure for changing an SN for DL ​​Non-SDT in an SN according to one embodiment of the present disclosure.

[0040] FIG. 13 illustrates an example of a procedure for supporting an SDT termination request of an SN according to one embodiment of the present disclosure.

[0041] FIG. 14a and FIG. 14b illustrate examples of a procedure for changing an SN when an SDT termination request of an SN is made according to one embodiment of the present disclosure.

[0042] FIG. 15 illustrates an example of a procedure for transmitting a paging message for DL ​​SDT according to one embodiment of the present disclosure.

[0043] FIG. 16 illustrates an example of a procedure for transmitting DL SDT according to one embodiment of the present disclosure.

[0044] FIG. 17 illustrates an example of a procedure for receiving a DL SDT according to one embodiment of the present disclosure.

[0045] The following embodiments combine components and features of the present disclosure in a predetermined form. Each component or feature may be considered optional unless explicitly stated otherwise. Each component or feature may be implemented without being combined with other components or features. Furthermore, some components and / or features may be combined to form embodiments of the present disclosure. The order of operations described in the embodiments of the present disclosure may be changed. Some components or features of one embodiment may be included in another embodiment or may be replaced with corresponding components or features of another embodiment.

[0046] In the description of the drawings, procedures or steps that may obscure the gist of the present disclosure are not described, and procedures or steps that can be understood by a person skilled in the art are also not described.

[0047] Throughout the specification, when a part is said to "comprising" or "including" a component, this does not mean that other components may be included, but rather that other components may be excluded, unless otherwise specifically stated. In addition, terms such as "...part," "...unit," and "module" described in the specification mean a unit that processes at least one function or operation, which may be implemented by hardware, software, or a combination of hardware and software. In addition, the words "a" or "an," "one," "the," and similar related words may be used in the context of describing the present disclosure (especially in the context of the claims below) to include both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context.

[0048] Embodiments of the present disclosure described herein focus on the data transmission and reception relationship between a base station and a mobile station. Here, the base station is understood as a terminal node of a network that directly communicates with the mobile station. Certain operations described herein as being performed by the base station may, in some cases, be performed by an upper node of the base station.

[0049] That is, in a network consisting of multiple network nodes including a base station, various operations performed for communication with a mobile station may be performed by the base station or other network nodes other than the base station. In this case, the term 'base station' may be replaced by terms such as fixed station, Node B, eNB (eNode B), gNB (gNode B), ng-eNB, advanced base station (ABS), or access point.

[0050] Additionally, in embodiments of the present disclosure, the term terminal may be replaced with terms such as user equipment (UE), mobile station (MS), subscriber station (SS), mobile subscriber station (MSS), mobile terminal, or advanced mobile station (AMS).

[0051] Additionally, a transmitter refers to a fixed and / or mobile node that provides data or voice services, and a receiver refers to a fixed and / or mobile node that receives data or voice services. Therefore, for uplink, a mobile station can be the transmitter, and a base station can be the receiver. Similarly, for downlink, a mobile station can be the receiver, and a base station can be the transmitter.

[0052] Embodiments of the present disclosure are wireless access systems such as IEEE 802.xx system, 3rd Generation Partnership Project (3GPP) system, 3GPP Long Term Evolution (LTE) system, 3GPP 5G (5 thgeneration) NR (New Radio) system and 3GPP2 system, and in particular, embodiments of the present disclosure may be supported by 3GPP TS (technical specification) 38.211, 3GPP TS 38.212, 3GPP TS 38.213, 3GPP TS 38.321 and 3GPP TS 38.331 documents.

[0053] Furthermore, the embodiments of the present disclosure can be applied to other wireless access systems and are not limited to the aforementioned systems. For example, they can also be applied to systems implemented after the 3GPP 5G NR system, and are not limited to a specific system.

[0054] That is, obvious steps or parts not described in the embodiments of the present disclosure can be explained by referring to the above documents. In addition, all terms disclosed in this document can be explained by the above standard documents.

[0055] Hereinafter, preferred embodiments according to the present disclosure will be described in detail with reference to the accompanying drawings. The detailed description set forth below, together with the accompanying drawings, is intended to illustrate exemplary embodiments of the present disclosure and is not intended to represent the only embodiments in which the technical configurations of the present disclosure may be implemented.

[0056] Additionally, specific terms used in the embodiments of the present disclosure are provided to aid in understanding the present disclosure, and the use of such specific terms may be changed to other forms without departing from the technical spirit of the present disclosure.

[0057] The following technology can be applied to various wireless access systems such as CDMA (code division multiple access), FDMA (frequency division multiple access), TDMA (time division multiple access), OFDMA (orthogonal frequency division multiple access), and SC-FDMA (single carrier frequency division multiple access).

[0058]

[0059] For clarity, the following description is based on a 3GPP communication system (e.g., LTE, NR, etc.), but the technical spirit of the present invention is not limited thereto. LTE may refer to technology after 3GPP TS 36.xxx Release 8. Specifically, LTE technology after 3GPP TS 36.xxx Release 10 may be referred to as LTE-A, and LTE technology after 3GPP TS 36.xxx Release 13 may be referred to as LTE-A pro. 3GPP NR may refer to technology after TS 38.xxx Release 15. 3GPP 6G may refer to technology after TS Release 17 and / or Release 18. "xxx" refers to a standard document detail number. LTE / NR / 6G may be collectively referred to as a 3GPP system.

[0060] For background information, terms, abbreviations, etc. used in this disclosure, reference may be made to standard documents published prior to the present invention. For example, reference may be made to the 36.xxx and 38.xxx standard documents.

[0061] For terms, abbreviations, and other background technologies that may be used in this document, please refer to the following standard documents published prior to this document. In particular, terms, abbreviations, and other background technologies related to LTE / EPS (Evolved Packet System) can refer to the 36.xxx series, 23.xxx series, and 24.xxx series, and terms, abbreviations, and other background technologies related to NR (new radio) / 5GS (5G system) can refer to the 38.xxx series, 23.xxx series, and 24.xxx series.

[0062] Hereinafter, this specification is described based on the terms defined above.

[0063] The three key requirement areas for 5G include (1) Enhanced Mobile Broadband (eMBB), (2) Massive Machine Type Communication (mMTC), and (3) Ultra-reliable and Low Latency Communications (URLLC).

[0064] Some use cases may require optimization across multiple domains, while others may focus on just one Key Performance Indicator (KPI). 5G supports these diverse use cases in a flexible and reliable manner.

[0065]

[0066] Communication system applicable to the present disclosure

[0067] Although not limited thereto, the various descriptions, functions, procedures, proposals, methods and / or operational flowcharts of the present disclosure disclosed in this document may be applied to various fields requiring wireless communication / connectivity (e.g., 5G) between devices.

[0068] Hereinafter, more specific examples will be provided with reference to the drawings. In the drawings / descriptions below, the same drawing reference numerals may represent identical or corresponding hardware blocks, software blocks, or functional blocks, unless otherwise described.

[0069] Figure 1 illustrates an example of a communication system applied to the present disclosure.

[0070] Referring to FIG. 1, a communication system (100) applied to the present disclosure includes a wireless device, a base station, and a network. Here, the wireless device refers to a device that performs communication using a wireless access technology (e.g., 5G NR, LTE) and may be referred to as a communication / wireless / 5G device. Although not limited thereto, the wireless device may include a robot (100a), a vehicle (100b-1, 100b-2), an XR (extended reality) device (100c), a hand-held device (100d), a home appliance (100e), an IoT (Internet of Things) device (100f), and an AI (artificial intelligence) device / server (100g). For example, the vehicle may include a vehicle equipped with a wireless communication function, an autonomous vehicle, a vehicle capable of performing vehicle-to-vehicle communication, etc. Here, the vehicles (100b-1, 100b-2) may include unmanned aerial vehicles (UAVs) (e.g., drones). The XR devices (100c) include augmented reality (AR) / virtual reality (VR) / mixed reality (MR) devices, and may be implemented in the form of head-mounted devices (HMDs), head-up displays (HUDs) installed in vehicles, televisions, smartphones, computers, wearable devices, home appliances, digital signage, vehicles, robots, etc. The portable devices (100d) may include smartphones, smart pads, wearable devices (e.g., smartwatches, smart glasses), computers (e.g., laptops, etc.), etc. The home appliances (100e) may include TVs, refrigerators, washing machines, etc. The IoT devices (100f) may include sensors, smart meters, etc. For example, the base station (120) and the network (130) may also be implemented as wireless devices, and a specific wireless device (120a) may act as a base station / network node to other wireless devices.

[0071] Wireless devices (100a to 100f) can be connected to a network (130) via a base station (120). AI technology can be applied to the wireless devices (100a to 100f), and the wireless devices (100a to 100f) can be connected to an AI server (100g) via a network (130). The network (130) can be configured using a 3G network, a 4G (e.g., LTE) network, a 5G (e.g., NR) network, etc. The wireless devices (100a to 100f) can communicate with each other via the base station (120) / network (130), but can also communicate directly (e.g., sidelink communication) without going through the base station (120) / network (130). For example, vehicles (100b-1, 100b-2) can communicate directly (e.g., V2V (vehicle to vehicle) / V2X (vehicle to everything) communication). In addition, IoT devices (100f) (e.g., sensors) can communicate directly with other IoT devices (e.g., sensors) or other wireless devices (100a to 100f).

[0072] Wireless communication / connection (150a, 150b, 150c) can be established between wireless devices (100a to 100f) / base stations (120), and base stations (120) / base stations (120). Here, the wireless communication / connection can be established through various wireless access technologies (e.g., 5G NR) such as uplink / downlink communication (150a), sidelink communication (150b) (or D2D communication), and base station-to-base station communication (150c) (e.g., relay, IAB (integrated access backhaul)). Through the wireless communication / connection (150a, 150b, 150c), the wireless device and base station / wireless device, and base stations and base stations can transmit / receive wireless signals to / from each other. For example, the wireless communication / connection (150a, 150b, 150c) can transmit / receive signals through various physical channels. To this end, based on various proposals of the present disclosure, at least some of various configuration information setting processes for transmitting / receiving wireless signals, various signal processing processes (e.g., channel encoding / decoding, modulation / demodulation, resource mapping / demapping, etc.), resource allocation processes, etc. may be performed.

[0073] Figure 2 illustrates an example of a UE applicable to the present disclosure.

[0074] Referring to FIG. 2, the UE (200) may include a processor (202), memory (204), a transceiver (206), one or more antennas (208), a power management module (241), a battery (242), a display (243), a keypad (244), a SIM (Subscriber Identification Module) card (245), a speaker (246), and a microphone (247).

[0075] The processor (202) may be configured to implement the descriptions, functions, procedures, proposals, methods, and / or flowcharts disclosed herein. The processor (202) may be configured to control one or more other components of the UE (200) to implement the descriptions, functions, procedures, proposals, methods, and / or flowcharts disclosed herein. A layer of a radio interface protocol may be implemented in the processor (202). The processor (202) may include an ASIC, other chipset, logic circuit, and / or data processing device. The processor (202) may be an application processor. The processor (202) may include at least one of a DSP, a CPU (Central Processing Unit), a GPU (Graphics Processing Unit), and a modem (modulator and demodulator).

[0076] Memory (204) is operatively coupled to the processor (202) and can store various information for operating the processor (202). Memory (204) may include ROM, RAM, flash memory, memory cards, storage media, and / or other storage devices. When the implementation is implemented in software, the techniques described herein may be implemented using modules (e.g., procedures, functions, etc.) that perform the descriptions, functions, procedures, suggestions, methods, and / or operational flowcharts disclosed herein. The modules may be stored in memory (204) and executed by the processor (202). Memory (204) may be implemented within the processor (202) or external to the processor (202), in which case it may be communicatively coupled to the processor (202) via various methods known in the art.

[0077] A transceiver (206) is operably coupled to the processor (202) and is capable of transmitting and / or receiving wireless signals. The transceiver (206) may include a transmitter and a receiver. The transceiver (206) may include baseband circuitry for processing radio frequency signals. The transceiver (206) may control one or more antennas (208) to transmit and / or receive wireless signals.

[0078] The power management module (241) can manage the power of the processor (202) and / or the transceiver (206). The battery (242) can supply power to the power management module (241).

[0079] The display (243) can output the results processed by the processor (202). The keypad (244) can receive input to be used by the processor (202). The keypad (244) can be displayed on the display (243).

[0080] A SIM card (245) is an integrated circuit that securely stores an International Mobile Subscriber Identity (IMSI) and associated keys, and can be used to identify and authenticate subscribers in mobile devices such as mobile phones and computers. Additionally, many SIM cards can store contact information.

[0081] The speaker (246) can output sound-related results processed by the processor (202). The microphone (247) can receive sound-related input to be used by the processor (202).

[0082] In implementations of this specification, a UE may operate as a transmitter in the uplink and as a receiver in the downlink. In implementations of this specification, a base station may operate as a receiver in the uplink and as a transmitter in the downlink. In this specification, a base station may be referred to as a Node B (Node B), an eNode B (eNB), or a gNB, and may not be limited to a specific form.

[0083] In addition, for example, the UE may be implemented in various forms depending on the use case / service. The UE may be composed of various components, devices / parts, and / or modules. For example, each UE may include a communication device, a control device, a memory device, and additional components. The communication device may include a communication circuit and a transceiver. For example, the communication circuit may include one or more processors and / or one or more memories. For example, the transceiver may include one or more transceivers and / or one or more antennas. The control device is electrically connected to the communication device, the memory device, and the additional components, and may control the overall operation of each UE. For example, the control device may control the electrical / mechanical operation of each UE based on a program / code / command / information stored in the memory device. The control device may transmit information stored in the memory device to an external device (e.g., another communication device) via the communication device via a wireless / wired interface, or may store information received from an external device (e.g., another communication device) via the communication device via a wireless / wired interface in the memory device.

[0084] Additional components may be configured in various ways depending on the type of UE. For example, the additional components may include at least one of a power unit / battery, an input / output (I / O) device (e.g., an audio I / O port, a video I / O port), a driving device, and a computing device. In addition, the UE is not limited thereto, and may be implemented in the form of a robot (100a in FIG. 1), a vehicle (100b-1 and 100b-2 in FIG. 1), an XR device (100c in FIG. 1), a portable device (100d in FIG. 1), a home appliance (100e in FIG. 1), an IoT device (100f in FIG. 1), a digital broadcasting terminal, a hologram device, a public safety device, an MTC device, a medical device, a fintech device (or a financial device), a security device, a climate / environmental device, an AI server / device (100g in FIG. 1), a base station (120 in FIG. 1), or a network node. UE can be used in mobile or fixed locations depending on the use case / service.

[0085] The various components, devices / parts, and / or modules of the UE may all be connected to each other via a wired interface, or at least some of them may be connected wirelessly via a communication device. In addition, each component, device / part, and / or module of the UE may further include one or more elements. For example, the control device may be configured by a set of one or more processors. For example, the control device may be configured by a set of a communication control processor, an application processor (AP), an electronic control unit (ECU), a graphics processing unit, and a memory control processor. As another example, the memory device may be configured by a random access memory (RAM), a dynamic random access memory (DRAM), a read-only memory (ROM), a flash memory, a volatile memory, a non-volatile memory, and / or a combination thereof.

[0086]

[0087] 5G system architecture applicable to the present disclosure

[0088] The 5G system is an advanced technology from the 4th generation LTE mobile communication technology. It supports new radio access technology (RAT: Radio Access Technology), extended LTE (eLTE) as an extended technology of LTE (Long Term Evolution), and non-3GPP (e.g., WLAN) access through the evolution or clean-state structure of the existing mobile communication network structure.

[0089] 5G systems are defined as service-based, and the interactions between network functions (NFs) within the architecture for 5G systems can be expressed in two ways as follows.

[0090] - Reference point representation: Represents the interaction between NF services within NFs described by a point-to-point reference point (e.g., N11) between two NFs (e.g., AMF and SMF).

[0091] Service-based representation: Network functions (e.g., AMF) within the control plane (CP) allow other authorized network functions to access their services. This representation also includes point-to-point reference points, if necessary.

[0092] 5GC (5G Core) can include various components, some of which include access and mobility management function (AMF), session management function (SMF), policy control function (PCF), user plane function (UPF), application function (AF), unified data management (UDM), and non-3GPP interworking function (N3IWF).

[0093] The UE connects to the data network via the UPF via the next-generation radio access network (NG-RAN) that includes the gNB. The UE can receive data services via untrusted non-3GPP access points, such as wireless local area networks (WLANs). To connect non-3GPP access points to the core network, an N3IWF may be deployed.

[0094] The N3IWF manages interworking between non-3GPP access and 5G systems. When a UE is connected to a non-3GPP access (e.g., WiFi, also known as IEEE 802.11), it can connect to a 5G system via the N3IWF. The N3IWF performs control signaling with the AMF and connects to the UPF via the N3 interface for data transmission.

[0095] AMF can manage access and mobility in 5G systems. It can also manage non-access stratum (NAS) security. It can also handle mobility in idle states.

[0096] The UPF functions as a gateway for transmitting and receiving user data. A UPF node can perform all or part of the user plane functions of a 4G mobile communications S-GW (serving gateway) and P-GW (packet data network gateway).

[0097] The UPF acts as a boundary between the next generation RAN (NG-RAN) and the core network, and is an element that maintains the data path between the gNB and the SMF. In addition, the UPF acts as a mobility anchor point when the UE moves across the area served by the gNB. The UPF can perform the function of handling PDUs. For mobility within the NG-RAN (e.g., NG-RAN defined after 3GPP Release-15), the UPF can route packets. In addition, the UPF can also act as an anchor point for mobility with other 3GPP networks (e.g., RAN defined before 3GPP Release-15), such as UTRAN (UMTS (universal mobile telecommunications system) terrestrial radio access network), E-UTRAN (evolved-UTRAN), or GERAN (GSM (global system for mobile communication) / EDGE (enhanced data rates for global evolution) radio access network). A UPF may correspond to the termination point of a data interface toward a data network.

[0098] The PCF is a node that controls the operator's policies. The AF is a server that provides various services to UEs. The UDM is a server that manages subscriber information, similar to the HSS (home subscriber server) of 4G mobile communications. The UDM (460) stores and manages subscriber information in a unified data repository (UDR).

[0099] The SMF can perform the function of assigning an IP (Internet protocol) address to the UE. In addition, the SMF can control the PDU (protocol data unit) session.

[0100] For convenience of explanation below, the drawing symbols for AMF, SMF, PCF, UPF, AF, UDM, N3IWF, gNB, or UE may be omitted, and operation may be performed by referring to the matters described in standard documents published prior to this document.

[0101] Figure 3 illustrates an example of functional separation of NG-RAN and 5GC (5th generation core) applicable to the present disclosure.

[0102] Referring to Figure 3, the UE connects to a data network (DN) via a next-generation RAN. The control plane function (CPF) node performs all or part of the functions of the mobility management entity (MME) of 4G mobile communications, and all or part of the control plane functions of the serving gateway (S-GW) and the PDN gateway (P-GW). The CPF node includes the AMF and the SMF.

[0103] The UPF node functions as a gateway through which user data is transmitted and received.

[0104] The authentication server function (AUSF) authenticates and manages UEs. The Network Slice Selection Function (NSSF) is a node for network slicing, as described below.

[0105] The network exposure function (NEF) provides a mechanism to securely expose the services and functions of the 5G core.

[0106] The reference points shown in Fig. 3 are as follows. N1 represents a reference point between the UE and the AMF. N2 represents a reference point between the (R)AN and the AMF. N3 represents a reference point between the (R)AN and the UPF. N4 represents a reference point between the SMF and the UPF. N5 represents a reference point between the PCF and the AF. N6 represents a reference point between the UPF and the DN. N7 represents a reference point between the SMF and the PCF. N8 represents a reference point between the UDM and the AMF. N9 represents a reference point between the UPFs. N10 represents a reference point between the UDM and the SMF. N11 represents a reference point between the AMF and the SMF. N12 represents a reference point between the AMF and the AUSF. N13 represents a reference point between the UDM and the AUSF. N14 represents a reference point between the AMFs. N15 represents a reference point between a PCF and an AMF in a non-roaming scenario, and a reference point between an AMF and a PCF of a visited network in a roaming scenario. N16 represents a reference point between SMFs. N22 represents a reference point between an AMF and an NSSF. N30 represents a reference point between a PCF and an NEF. N33 may represent a reference point between an AF and an NEF, and the entities and interfaces described above may be configured with reference to those described in standard documents published before this document. N58 represents a reference point between an AMF and an NSSAAF. N59 represents a reference point between a UDM and an NSSAAF. N80 represents a reference point between an AMF and an NSACF. N81 represents a reference point between an SMF and an NSACF.

[0107] The radio interface protocol is based on the 3GPP radio access network standard. Horizontally, the radio interface protocol consists of the physical layer, data link layer, and network layer. Vertically, it is divided into the user plane for data information transmission and the control plane for control signaling.

[0108] Protocol layers can be divided into L1 (layer-1), L2 (layer-2), and L3 (layer-3) based on the three lower layers of the open systems interconnection (OSI) standard model, which is widely known in communication systems.

[0109] Below, the present disclosure describes each layer of the wireless protocol. Figure 4 illustrates an example of a general architecture of a 5G (5th generation) system applicable to the present disclosure.

[0110] Referring to FIG. 4, the AS (access stratum) layer may include a physical (PHY) layer, a medium access control layer, a radio link control (RLC) layer, a packet data convergence protocol (PDCP) layer, and a radio resource control (RRC) layer, and operations based on each layer may be performed by referring to matters described in standard documents published prior to this document.

[0111]

[0112] In the TS 37.340 standard document, the definition of MR-DC can be described as follows:

[0113] ----------------------------------------------------------------

[0114] 10.7.2 MR-DC with 5GC

[0115] Inter-MN handover (with / without SN change) is used to transfer UE context data from a source MN to a target MN while the UE context is kept in one SN or moved to another SN. During an inter-MN handover, the target MN decides whether to keep or change the SN (or release the SN as described in Section 10.8). Only intra-RAT inter-MN handover is supported, regardless of SN change (e.g., no transition from NGEN-DC to NR-DC).

[0116] Figures 5a and 5b illustrate examples of handover procedures between MNs regardless of whether SN changes are initiated by the MN.

[0117] Note 1: For handover between master nodes without change of secondary node, the source SN and target SN shown in FIGS. 5a and 5b are the same nodes.

[0118] 1. The source MN initiates the handover procedure by initiating the Xn handover preparation procedure, which includes both MCG and SCG configuration. The source MN includes the source SN UE XnAP ID, SN ID, and the UE context of the source SN in the handover request message.

[0119] Note 2: The source MN can trigger an MN-initiated SN modification procedure (for the source SN) to retrieve the current SCG settings and allow provision of data forwarding related information prior to step 1.

[0120] 2. If the target MN decides to keep the UE context in the source SN, the target MN sends an SN add request to the SN, which includes the SN UE XnAP ID as a reference to the UE context of the SN established by the source MN. If the target MN decides to change the SN allowing delta setup, the target MN sends an SN add request to the target SN, which includes the UE context of the source SN established by the source MN. Otherwise, the target MN may send an SN add request to the target SN, which does not include the SN UE XnAP ID or the UE context of the source SN established by the source MN.

[0121] 3. The (target) SN responds with an SN addition request confirmation. The (target) SN may include an indication of full or delta RRC configuration.

[0122] Note 2a0: In a CHO using SCG configuration, it is up to the target MN implementation to ensure that the CG-Config provided by the (target) SN is available for all CHO preparations.

[0123] 3a. For SN termination bearers using MCG resources, the target MN provides Xn-U DL TNL address information in the Xn-U Address Indication message.

[0124] 4. The target MN may include the MN RRC reconfiguration message to be transmitted to the UE to perform the handover in the handover request acknowledge message and provide the forwarding address to the source MN. If the target side performs PDU session splitting during the handover procedure, two or more data forwarding addresses corresponding to each node are included in the handover request acknowledge message. If the target MN and SN decide to maintain the UE context in the SN in steps 2 and 3, the target MN indicates to the source MN that the UE context in the SN is maintained.

[0125] 5a / 5b. The source MN sends an SN release request message to the source SN, which includes the cause indicating MCG mobility. The source SN confirms the release request. If the source MN receives an indication from the target MN, it indicates to the source SN that the SN's UE context is maintained. If the SN includes an indication that the UE context is maintained, the SN maintains the UE context.

[0126] 5c. The source MN transmits data forwarding information to the (source) SN by sending an XN-U Address Indication message. If the PDU session is fragmented at the target side, more than one data forwarding address may be provided.

[0127] 6. The source MN triggers the UE to perform a handover and apply the new settings.

[0128] 7 / 8. The UE synchronizes with the target MN and responds with an MN RRC Reset Complete message.

[0129] 9. If bearers requiring SCG radio resources are configured, the UE synchronizes with the (target) SN.

[0130] Note 2a1: The order in which the UE performs the random access procedure to the MN (step 7) and the random access procedure to the SN (step 9) is not defined.

[0131] 10. If the RRC connection re-establishment procedure is successful, the target MN notifies the (target) SN through an SN re-establishment complete message.

[0132] 11a. The source SN sends a Secondary RAT Data Usage Report message to the source MN, containing the data volume received and delivered to the UE via NR / E-UTRA radio as described in Section 10.11.2.

[0133] Note 2a2: The order in which the source SN transmits the Secondary RAT Data Usage Report message and performs data transfer with the MN / target SN is not defined. The SN may transmit the report when transmission of the relevant QoS is suspended.

[0134] 11b. The source MN sends a Secondary RAT Report message to the AMF, providing information about the NR / E-UTRA resources used.

[0135] 12. For bearers using RLC AM, the source MN sends an SN status transfer message containing the SN status received from the source SN to the target MN, if necessary. If necessary, the target SN forwards the SN status to the target SN.

[0136] 13. Data forwarding occurs on the source side, if applicable. If the SN is maintained, data forwarding for SN-terminating bearers or QoS flows stored in the SN may be omitted.

[0137] 14-17. The target MN initiates the path switching procedure. If the target MN includes multiple DL TEIDs for a single PDU session in the path switching request message, multiple UL TEIDs in the UPF for the PDU session must be included in the path switching confirmation message if there is a TEID update in the UPF.

[0138] Note 3: If the UPF for the SN contains new UL TEIDs, the target MN performs the SN modification procedure initiated by the MN and provides it to the SN.

[0139] 18. The target MN initiates a UE context release procedure for the source MN.

[0140] 19. Upon receiving a UE context release message from the source MN, the (source) SN releases the C-plane resources associated with the UE context for the source MN. Any ongoing data transfer can continue. The SN does not release the UE context associated with the target MN if the SN release request message in step 5 includes a UE contest maintenance indication.

[0141] ----------------------------------------------------------------

[0142] Figure 6 illustrates an example of a successful procedure for preparing an S-NG-RAN node addition, and Figure 7 illustrates an example of a failed procedure for preparing an S-NG-RAN node addition. The S-NG-RAN node addition preparation is defined in the TS 38.423 specification document, and the definition is described as follows.

[0143] ----------------------------------------------------------------

[0144] 8.3.1. Preparing to Add S-NG-RAN Nodes

[0145] 8.3.1.1 General

[0146] The purpose of the S-NG-RAN node addition preparation procedure is to request the S-GN-RAN node to allocate resources for dual connectivity operation for a specific UE.

[0147] This procedure uses UE-related signaling.

[0148] 8.3.1.2 Successful operation

[0149] The M-NG-RAN node initiates the procedure by sending an S-NODE addition request message to the S-NG-RAN node.

[0150] When the M-NG-RAN node sends an S-NODE addition request message, timer TXn DCprep Start.

[0151] Resource allocation according to the values ​​of the Allocation and Retention Priority IE included in the QoS Flow Level QoS Parameters IE for each QoS flow shall follow the principles specified for the PDU Session Resource Establishment Procedure in TS 38.413 [5].

[0152] The S-NG-RAN node shall select an encryption algorithm based on the information in the UE Security Capabilities IE and the local preference list of AS encryption algorithms and apply the key indicated in the S-NG-RAN node Security Key IE as specified in TS 33.501

[0028] .

[0153] When the TSC Traffic Characteristics IE is included in the QoS flow of the S-NODE Addition Request message, the S-NG-RAN node shall behave identically to the NG-RAN node in the PDU session resource setup procedure specified in TS 38.413 [5].

[0154] When the Additional QoS Flow Information IE is included in the QoS flow of the S-NODE Addition Request message, the S-NG-RAN node shall behave identically to the NG-RAN node in the PDU session resource setup procedure specified in TS 38.413 [5].

[0155] For each GBR QoS flow, if the Alternative QoS Parameters Sets IE is included in the GBR QoS Flow Information IE, the S-NG-RAN node shall behave identically to the NG-RAN node in the PDU session resource setup procedure specified in TS 38.413 [5], if supported.

[0156] For each PDU session, if a Network Instance IE is included in the PDU Session Resources To Be Added List IE and the PDU Session Resource Setup Info - SN terminated IE is included in the PDU Session Resources To Be Added List IE and there is no Common Network Instance IE, the S-NG-RAN node shall use it when selecting transport network resources as specified in TS 23.501 [7], if supported.

[0157] For each GBR QoS flow, if the Offered GBR QoS Flow Information IE is included in the QoS Flows To Be Setup List IE contained in the PDU Session Resource Setup Info - SN terminated IE, the S-NG-RAN node may request the M-NG-RAN node to configure a DRB in which the corresponding QoS flow is mapped to an MCG resource.

[0158] For each PDU session, if the Non-GBR Resources Offered IE is included in the PDU Session Resources To Be Added List IE and is set to "true", the S-NG-RAN node may request the M-NG-RAN node to configure a DRB where the non-GBR QoS flows of the PDU session are mapped to MCG resources.

[0159] For each PDU session, if the PDU Session Resources To Be Added List IE contains a Common Network Instance IE in the PDU Session Resource Setup Info - SN terminated IE, the S-NG-RAN node shall use it when selecting transport network resources as specified in TS 23.501 [7], if supported.

[0160] Duplicate transmission:

[0161] - For each PDU session, if the Redundant UL NG-U UP TNL Information at UPF IE is included in the PDU Session Resource Setup Info - SN terminated IE, the S-NG-RAN node shall, if supported, use it as an uplink termination point for the user plane data of this PDU session for redundant transmission and shall include the DL NG-U UP TNL Information at NG-RAN IE in the PDU Session Resource Setup Response Info - SN terminated IE as described in TS 23.501 [7].

[0162] - For each PDU session, if a Redundant Common Network Instance IE is included in the PDU session resource configuration information - SN Termination IE, the S-NG-RAN node shall use it when selecting transport network resources for redundant transmission as specified in TS 23.501 [7], if supported.

[0163] - For each PDU session that contains a Redundant QoS Flow Indicator IE in the QoS Flows To Be Setup List IE included in the S-NODE Add Request message, the S-NG-RAN node shall store and use the Redundant QoS Flow Indicator IE, if supported, as specified in TS 23.501 [7].

[0164] - For each PDU session, if the Redundant PDU Session Information IE is included in the PDU Session Resource Setup Info - SN terminated IE of the S-NODE Add Request message, the S-NODE-RAN node shall store the received information in the UE context, if supported, and establish redundant user plane resources for that PDU session as specified in TS 23.501 [7].

[0165] - For each PDU session resource successfully established with a duplicate PDU Session Information IE included in the S-NODE Add Request message, the S-NG-RAN node shall include the Used RSN Information IE in the PDU Session Resource Setup Response Info - SN terminated IE of the S-NODE Add Request Acknowledge message, if supported. If the duplicate PDU Session Information IE includes a PDU Session Pair ID IE, the S-NG-RAN node may store it and use it to identify the paired PDU session.

[0166] If the S-NODE Addition Request message contains a Selected PLMN IE, the S-NG-RAN node may use it for RRM purposes.

[0167] If the S-NODE Addition Request message includes an Expected UE Behaviour IE, the S-NG-RAN node may store this information and use it to optimize resource allocation, if supported.

[0168] If the S-NODE Add Request message contains a Mobility Restriction List IE, the S-NG-RAN node stores this information, if supported, and uses it to select an appropriate SCG.

[0169] If the S-NODE Add Request message contains an index to the Index to RAT / Frequency Selection Priority IE, the S-NG-RAN node may use it for RRM purposes.

[0170] If the S-NG-RAN node is a gNB and the S-NODE ADD REQUEST message includes a PCell ID IE, the S-NG-RAN node shall search for a target NR cell among the NR neighbor cells of the specified PCell as specified in TS 37.340 [8].

[0171] If the S-NODE Add Request message includes an S-NG-RAN node PDU Session Aggregate Maximum Bit Rate IE, the S-NG-RAN node may use it for RRM purposes.

[0172] If the S-NODE ADD REQUEST message includes the MR-DC Resource Coordination Information IE, the S-NG-RAN node shall forward it to lower layers and may use it for resource coordination purposes with the M-NG-RAN node or to coordinate sidelink resources used by the M-NG-RAN node. The S-NG-RAN node shall consider the value of the received UL Coordination Information IE to be valid until it receives a new update of the IE for the same UE. The S-NG-RAN node shall consider the value of the received DL Coordination Information IE to be valid until it receives a new update of the IE for the same UE.

[0173] If the E-UTRA Coordination Assistance Information IE or the NR Coordination Assistance Information IE is included in the MR-DC Resource Coordination Information IE, the S-NG-RAN node uses that information, if supported, to determine additional coordination of resource utilization between the S-NG-RAN node and the M-NG-RAN node.

[0174] If the S-NODE Add Request message contains the NE-DC TDM Pattern IE, the S-NG-RAN node must forward it to lower layers for use as a single uplink transmission. The S-NG-RAN node must consider the value of the received NE-DC TDM Pattern IE valid until it receives a new IE update for the same UE.

[0175] If the S-NODE Add Request message includes a QoS Flow Mapping Indication IE, the S-NG-RAN node may consider that only uplink or downlink QoS flows are mapped to the DRB.

[0176] For each bearer for which PDCP entity allocation is requested at the S-NG-RAN node:

[0177] - The M-NG-RAN node may propose to apply downlink data forwarding by including a DL Forwarding IE within PDU Session Resource Setup Info - SN terminated IE of the S-NODE Addition Request message. For each bearer that it decides to accept, the S-NG-RAN node may indicate that it accepts the proposed downlink data forwarding for this bearer by including a DL Forwarding GTP Tunnel Endpoint IE in the PDU Session Resource Setup Response Info - SN terminated IE of the S-NODE Addition Request Acknowledge message.

[0178] - The S-NG-RAN node may indicate that it requests data forwarding of uplink packets to be performed for that bearer by including a UL Forwarding GTP Tunnel Endpoint IE for each bearer in the PDU Session Resource Setup Response Info - SN terminated IE.

[0179] - The M-NG-RAN node shall include an RLC Mode IE for each bearer offloaded from the M-NG-RAN node to the S-NG-RAN node in the DRBs to QoS Flow Mapping List IE within the PDU Session Resource Setup Info - SN terminated IE of the S-NODE Addition Request message, where the RLC Mode IE indicates the mode used by the M-NG-RAN for the DRB when hosted on the M-NG-RAN node.

[0180] For each bearer in the M-NG-RAN node, the PDCP entity:

[0181] - The M-NG-RAN node includes an RLC mode IE for each bearer in the DRBs To Be Setup List IE within the PDU Session Resource Setup Info - MN terminated IE of the S-NODE Add Request message, indicating that the RLC mode has been configured in the M-NG-RAN node, so the S-NG-RAN node must configure the same RLC mode for this MN terminated split bearer.

[0182] The M-NG-RAN node may also propose to apply UL data forwarding when offloading QoS flows for which forwarding is requested in sequence by including a UL Forwarding Proposal IE in the Data Forwarding and Offloading Info from source NG-RAN node IE in the PDU Session Resource Setup Info - MN terminated IE of the S-NODE Addition Request message. An S-NG-RAN node may indicate that it accepts the proposed forwarding by including a PDU Session Level UL Data Forwarding UP TNL Information IE in the Data Forwarding Info from target NG-RAN node IE within the PDU Session Resource Setup Response Info - SN terminated IE of the S-NODE Addition Request Confirmation message.

[0183] If the S-NODE Addition Request message includes the Masked IMEISV IE, the S-NG-RAN node shall use it to verify the UE's characteristics for further processing, if supported.

[0184] If the UE Radio Capability ID IE is included in the S-NODE Addition Request message, the S-NG-RAN node shall store this information in the UE context, if supported, and use it as defined in TS 23.501 [7] and TS 23.502

[0013] .

[0185] The S-NG-RAN node shall report the results for all requested PDU session resources to the M-NG-RAN node in the S-NODE Add Request Confirmation message in the following manner:

[0186] - The list of successfully established PDU session resources must be included in the PDU Session Resources Admitted To Be Added List IE.

[0187] - The list of PDU session resources for which establishment failed must be included in the PDU Session Resources Not Admitted List IE.

[0188] Upon receiving the S-NODE addition request confirmation message, the M-NG-RAN node sets the timer TXn DCprep must be stopped.

[0189] If the S-NODE Add Request Confirm message includes the MR-DC Resource Coordination Information IE, the M-NG-RAN node may use it for resource coordination with the S-NG-RAN node. The M-NG-RAN node shall consider the value of the received UL Coordination Information IE as valid until it receives a new update of the IE for the same UE. The M-NG-RAN node shall consider the value of the received DL Coordination Information IE as valid until it receives a new update of the IE for the same UE. If the E-UTRA Coordination Assistance Information IE or the NR Coordination Assistance Information IE is included in the MR-DC Resource Coordination Information IE, the M-NG-RAN node uses that information, if supported, to determine additional coordination of resource utilization between the M-NG-RAN node and the S-NG-RAN node.

[0190] The S-NG-RAN node may include a PDCP SN Length IE indicating the PDCP SN length for each bearer in the DRBs To Be Setup List IE of the S-NODE Add Request Confirmation message.

[0191] If the S-NG-RAN node UE XnAP ID IE (S-NG-RAN node UE XnAP ID IE) is included in the S-NODE addition request message, the S-NG-RAN node stores this information, if supported, and uses it as defined in TS 37.340 [8].

[0192] If the S-NODE Addition Request message contains a PDCP SN Length IE, the S-NG-RAN node stores this information, if supported, and uses it in the lower layer configuration of the relevant MN termination bearer.

[0193] If the S-NODE addition request message includes an SN Addition Trigger Indication IE, the S-NG-RAN node shall include an RRC config indication IE in the S-NODE addition request acknowledge message to inform the M-NG-RAN node whether the S-NG-RAN node has applied the full or delta configuration as specified in TS 37.340 [8].

[0194] If the S-NODE Add Request message contains an S-NG-RAN node Maximum Integrity Protected Data Rate Uplink IE or an S-NG-RAN node Maximum Integrity Protected Data Rate Downlink IE, the S-NG-RAN node shall use the received information when applying the maximum integrity protected data rate to the UE.

[0195] When a Security Indication IE is included in the PDU Session Resource Setup Info-SN terminated IE of an S-NODE Addition Request message, the behavior of the S-NG-RAN node shall be the same as specified for the same IE in the PDU Session Resources To Be Setup List IE of the handover preparation procedure for that PDU session, and the S-NG-RAN node shall include the Security Result IE in the PDU Session Resource Setup Response Info - SN terminated IE.

[0196] If the Security Result IE is included in the PDU Session Resource Setup Info - SN terminated IE of the S-NODE Add Request message,

[0197] The S-NG-RAN node may consider this information when deciding whether to perform user plane integrity protection or encryption for the DRB established for the relevant PDU session. However, if the Split Session Indicator IE is included in the PDU Session Resource Setup Info - SN terminated IE and is set to "Split", user plane integrity protection or encryption shall be performed based on the information in the Security Result IE.

[0198] An S-NG-RAN node may consider this information when deciding whether to perform user plane integrity protection or ciphering for a DRB established for that PDU session. However, if the Split Session Indicator IE is included in the PDU Session Resource Configuration Information - SN Termination IE and set to "Split", then it shall perform user plane integrity protection or ciphering based on the information in the Security Result IE. If the S-NG-RAN node is an ng-eNB, it shall reject any PDU session for which the Integrity Protection Indication IE is set to "required" as specified in TS 33.501

[0028] . If the S-NG-RAN node or M-NG-RAN node is an ng-eNB, the S-NG-RAN node shall act according to clause 6.10.4 of TS 33.501

[0028] for PDU sessions established with the Integrity Protection Indication IE set to "preferred".

[0199] An S-NG-RAN node may include the S-NODE's Location Information IE (Location Information at S-NODE IE) in the S-NODE addition request confirmation message if such information is available from the S-NG-RAN node (Location Information at S-NODE IE).

[0200] If the S-NODE reporting location information IE (Default DRB Allowed IE) set to "pscell" is included in the S-NODE addition request, the S-NG-RAN node shall start providing information about the UE's current location. If the S-NODE location information IE is included in the S-NODE addition request confirmation, the M-NG-RAN node shall store the included information, which may be forwarded to the AMF.

[0201] If the Default DRB Allowed IE is included in the PDU Session Resource Setup Info - SN terminated IE of the S-NODE Add Request message and is set to "true", the S-NG-RAN node can configure a default DRB for the PDU session.

[0202] If the S-NODE Add Request confirmation message includes the DRB IDs taken into use IE, the M-NG-RAN node shall operate as specified in TS 37.340 [8], if applicable.

[0203] If a Trace Activation IE has been previously received for this UE, it shall be included in the S-NODE Addition Request message. If the Trace Activation IE is included in the S-NODE Addition Request message, the S-NG-RAN node shall initiate the requested trace functionality as described in TS 32.422

[0023] , if supported.

[0204] If the S-NODE add request message includes the trace enable IE

[0205] - If the MDT Activation IE is set to “Immediate MDT and Tracking”, the S-NG-RAN node initiates the requested tracking session and MDT session as described in TS 32.422

[0023] , if supported.

[0206] - If the MDT Activation IE is set to “Immediate MDT only”, the S-NG-RAN node initiates the requested MDT session as described in TS 32.422

[0023] , if supported, and the S-NG-RAN node ignores the Interfaces To Trace IE and the Trace Depth IE.

[0207] - For MDT Location Information IE within MDT Configuration IE, S-NG-RAN node stores this information if supported and considers it in the requested MDT session.

[0208] - If the MDT Activation IE is set to “Immediate MDT only” and the Signaling based MDT PLMN List IE is included in the MDT Configuration IE, the S-NG-RAN node can use it to propagate the MDT configuration as described in TS 37.320

[0043] .

[0209] - For the Bluetooth Measurement Configuration IE within the MDT Configuration IE, the S-NG-RAN node shall consider it for MDT configuration as described in TS 37.320

[0043] , if supported.

[0210] - For the WLAN Measurement Configuration IE within the MDT Configuration IE, the S-NG-RAN node shall consider it for MDT configuration as described in TS 37.320

[0043] , if supported.

[0211] - For the Sensor Measurement Configuration IE within the MDT Configuration IE, the S-NG-RAN node shall consider it for MDT configuration as described in TS 37.320

[0043] .

[0212] - If the S-NG-RAN node is a gNB, at least the MDT Configuration-NR IE must exist, and if the S-NG-RAN node is a ng-eNB, at least the MDT Configuration-EUTRA IE must exist.

[0213] If the Requested Fast MCG recovery via SRB3 IE is set to "true" and included in the S-NODE Addition Request message and the S-NG-RAN node decides to configure fast MCG link recovery via SRB3 as specified in TS 37.340 [8], the S-NG-RAN node shall include the Available fast MCG recovery via SRB3 IE set to "true" in the S-NODE Addition Request Confirmation message, if supported.

[0214] If the QoS Monitoring Request IE is included in the QoS Flow Level QoS Parameters IE for a QoS flow included in the DRBs To Be Setup List IE of the PDU Session Resource Setup Info - MN terminated IE, the S-NG-RAN node shall use it to configure lower layers for delay measurement and QoS monitoring purposes as specified in TS 23.501 [7], if supported. If the QoS Monitoring Reporting Frequency IE is included in the QoS Flow Level QoS Parameters IE for a QoS flow included in the DRBs To Be Setup List IE of the PDU Session Resource Setup Info - MN terminated IE, the S-NG-RAN node shall use it for RAN partial delay reporting, if supported.

[0215] For each QoS flow successfully established at an S-NG-RAN node, if the QoS Monitoring Request IE is included in the QoS Flow Level QoS Parameters IE contained in the PDU Session Resource Setup Information - SN Termination IE, the S-NG-RAN node shall store this information and, if supported, perform delay measurement and QoS monitoring as specified in TS 23.501 [7]. If the QoS Monitoring Reporting Frequency IE is included in the QoS Flow Level QoS Parameters IE contained in the PDU Session Resource Setup Information - SN Termination IE, the S-NG-RAN node shall store this information and, if supported, use it for RAN partial delay reporting. If these QoS flows are included in the DRBs to be Established List IE of the PDU Session Resource Setup Response Information - SN Termination IE, the M-NG-RAN node shall use it to configure lower layers for the purposes of delay measurement and QoS monitoring, if supported. If the QoS Monitoring Reporting Frequency IE is included in the PDU Session Resource Setup Response Information - DRBs to be Set Up IE of the SN Termination IE, the M-NG-RAN node shall use it for RAN Partial Delay Reporting, if supported.

[0216] For each DRB configured as MN-Terminated Split Bearer / SCG Bearer, if the QoS Mapping Information IE is included in the DRB Allow List IE of the PDU Session Resource Setup Response Information - MN Termination IE of the S-NODE Add Request Confirmation message, the M-NG-RAN node shall use it, if supported, to set the DSCP and / or IPv6 Flow Label fields for downlink IP packets transmitted from the M-NG-RAN node to the S-NG-RAN node over the GTP tunnel specified in the UP Transport Layer Information IE.

[0217] If the Source NG-RAN Node ID IE is included in the S-NODE Add Request message, the S-NG-RAN node shall use it, if supported, to determine the availability of a direct data path with the specified source NG-RAN node, and if a direct data forwarding path is available, the S-NG-RAN node shall include a Direct Forwarding Path Availability IE in the S-NODE Add Request Confirm message.

[0218] For a given QoS flow, if the Source DL Forwarding IP Address IE or both, the Source DL Forwarding IP Address IE and the Source Node DL Forwarding IP Address IE, are included in the PDU Session Resource Setup Information - Data Forwarding and Offload Information in the Source NG-RAN Node IE of the SN Termination IE included in the S-NODE Addition Request message, the S-NG-RAN node shall store this information if supported and use it as part of the ACL feature configuration task if the ACL feature is deployed.

[0219] If the Source DL Forwarding IP Address IE for a given QoS Flow is included in the QoS Flows IE mapped to the DRB list of the PDU Session Resource Setup Response Information - SN Termination IE included in the S-NODE Add Request Confirmation message, the M-NG-RAN node, if supported, stores this information and uses it as part of the ACL functionality to identify the source TNL address for data forwarding when preparing for a subsequent handover (if the ACL functionality is deployed).

[0220] If a Management Based MDT PLMN List IE is included in the S-NODE Addition Request message, the S-NG-RAN node, if supported, stores the received information in the UE context and uses this information to allow subsequent UE selection for the Management Based MDT as defined in TS 32.422

[0023] .

[0221] Upon receiving an S-NODE addition request message, the S-NG-RAN node starts collecting SCG information, if supported, and continues collecting it while the UE remains in one of the cells.

[0222] If the UE History Information from the UE IE is included in the S-NODE Addition Request message, the S-NG-RAN node stores this information if supported.

[0223] When the PSCell Change History IE (PSCell Change History IE) set to "Report Full History" is included in the S-NODE Addition Request message, the S-NG-RAN node signals the M-NG-RAN node the latest SCG UE history information on each PSCell change using the S-NG-RAN node initiated S-NG-RAN node modification procedure, if supported.

[0224] If the IAB Node Indication IE is included in the S-NODE Addition Request message, the S-NG-RAN node considers dual connectivity operation to the IAB node to be requested, if supported. In addition:

[0225] - If the No PDU Session Indication IE is included in the S-NODE Addition Request message, the S-NG-RAN node, if supported, considers the UE as an IAB node with no PDU session active, ignores the PDU Session Resources To Be Added List IE, and takes no action with respect to PDU session establishment. The M-NG-RAN node then ignores the PDU Session Resources Admitted To Be Added List IE in the S-NODE Addition Request Confirmation message, if supported.

[0226] - If the F1-terminating IAB-donor Indicator IE is included in the S-NODE Addition Request message, the S-NG-RAN node shall assume that it will be the F1-terminating IAB-donor of the IAB node, if supported, and shall behave as described in TS 38.401 [2].

[0227] If the CHO Information SN Addition IE is included in the S-NODE Addition Request message, the S-NG-RAN node shall consider that the S-NG-RAN node addition preparation procedure is triggered as part of a conditional handover. The Source M-NG-RAN Node ID IE and the Source M-NG-RAN Node UE XnAP ID IE may be used to identify other active S-NG-RAN node addition preparations associated with this UE. If the Estimated Arrival Probability IE is included in the CHO Information SN Addition IE included in the S-NODE Addition Request message, the S-NG-RAN node may use this information to allocate required resources to the UE.

[0228] If the SCG Activation Request IE is included in the S-NODE Add Request message, the S-NG-RAN node may use it to configure SCG resources as specified in TS 37.340 [8] and, if supported, shall include the SCG Activation Status IE in the S-NODE Add Request Confirm message. If the SCG Activation Request IE in the S-NODE Add Request message is set to "SCG Activated", the S-NG-RAN node shall activate SCG resources, if supported, and set the SCG Activation Status IE in the S-NODE Add Request Confirm message to "SCG Activated".

[0229] If a Conditional PSCell Addition Information Request IE is included in the S-NODE addition request message, the S-NG-RAN node shall consider the request as CPAC-related as described in TS 37.340 [8], if supported. Therefore, the S-NG-RAN node shall include a Conditional PSCell Addition Acknowledge IE in the S-NODE addition request acknowledge message, if supported.

[0230] If the conditional PSCell additional information confirmation is included in the S-NODE additional request confirmation message, the M-NG-RAN node shall consider the designated PSCell selected by the target SN as a candidate PSCell for CPAC, if supported.

[0231] If CG-CandidateList is included in the S-NG-RAN node to M-NG-RAN node container IE of the S-NODE Addition Request Confirmation message, the M-NG-RAN node shall use it for CPAC purposes, if supported.

[0232] If the Estimated Arrival Probability IE is included in the Conditional PSCell Additional Information Request IE contained in the S-NODE Additional Request message, the candidate target S-NG-RAN node can use this information to allocate resources required for the incoming CPAC procedure.

[0233] If an S-NG-RAN node UE Slice Maximum Bit Rate IE for a particular S-NSSAI is included in the S-NODE Addition Request message, the S-NG-RAN node shall store and use the received S-NG-RAN node UE Slice Maximum Bit Rate for all PDU sessions associated with the S-NSSAI for that UE as defined in TS 23.501 [7], if supported.

[0234] Interaction with the S-NG-RAN node reconfiguration completion procedure:

[0235] If the S-NG-RAN node allows at least one PDU session resource, the S-NG-RAN node sends an S-NODE addition request confirmation message to the M-NG-RAN node, except for the CPAC request, when the timer TXn DCoverall . When receiving the S-NODE reconfiguration complete message, TXn DCoverall If this is running, timer TXn DCoveral l is stopped.

[0236] Interacting with activity notification procedures

[0237] Upon receiving an S-NODE Addition Request message containing a Desired Activity Notification Level IE, the S-NG-RAN node uses this information, if supported, to decide whether to trigger subsequent activation notification procedures based on the requested notification level.

[0238] 8.3.1.3 Unsuccessful Operations

[0239] If the S-NG-RAN node cannot accept any bearers or a failure occurs during the preparation of adding an S-NG-RAN node, the S-NG-RAN node sends an S-NODE Addition Request Reject message to the M-NG-RAN node with an appropriate cause value.

[0240] 8.3.1. Unsuccessful conditions

[0241] If an S-NG-RAN node receives an S-NODE addition request message that does not contain a PDU Session Resource To Be Added Item IE containing a PDU Session Resource Setup Information - SN Termination IE or a PDU Session Resource Setup Information - MN Termination IE, the S-NG-RAN node fails the S-NG-RAN node addition preparation procedure with an appropriate cause.

[0242] If the encryption support algorithms defined in the NR UE Security Capabilities IE (NR Encryption Algorithms IE) and the mandatory support of NEA0 in all UEs (TS 33.501

[0028] ) do not match the algorithms defined in the list of allowed encryption algorithms configured in the S-NG-RAN node (TS 33.501

[0028] ), the S-NG-RAN node rejects the procedure using an S-NODE Addition Request Reject message.

[0243] If the supported algorithms for integrity defined in the NR Integrity Protection Algorithms IE of the NR UE Security Capabilities IE do not match the algorithms defined in the S-NG-RAN node's list of allowed integrity protection algorithms (TS 33.501

[0028] ), the S-NG-RAN node shall reject the procedure using an S-NODE Add Request Reject message.

[0244] If an S-NG-RAN node receives an S-NODE Addition Request message containing a S-NG-RAN node UE XnAP ID IE that does not match an existing UE context with that ID, the S-NG-RAN node shall reject the procedure using an S-NODE Addition Request Reject message.

[0245] If an M-NG-RAN node receives an S-NODE Add Request Confirmation message containing a PDU Session ID value in the PDU Session Resources Admitted List IE and the PDU Session Resources Not Admitted List IE, the M-NG-RAN node considers the S-NG-RAN node resource setup for that PDU session to have failed.

[0246] If an S-NG-RAN node receives an S-NODE Add Request message containing a PDU Session Resource Configuration Information - SN Termination IE that includes a Split Session Indicator IE for a PDU session set to "Split", but does not include a Security Result IE and has either the Integrity Protection Indication IE or the Confidentiality Protection Indication IE set to "Preferred", it rejects the PDU session.

[0247] Interaction with the S-NG-RAN node release procedure initiated by the M-NG-RAN node:

[0248] If an M-NG-RAN node receives an S-NODE Add Request Confirm message that does not contain a PDU Session Resource Setup Response Information - SN Termination IE or a PDU Session Resource Setup Response Information - MN Termination IE in the PDU Session Resource Admitted To Be Added Item IE, the M-NG-RAN node triggers an M-NG-RAN node initiated S-NG-RAN node release procedure indicating an appropriate cause.

[0249] Timer TXn before the M-NG-RAN node receives the S-NODE addition request confirmation message DCprep If expires, the M-NG-RAN node considers the S-NG-RAN node addition preparation procedure as failed and triggers the M-NG-RAN node initiated S-NG-RAN node release procedure.

[0250] Interaction with the S-NG-RAN node reconfiguration completion and S-NG-RAN node decommissioning procedure initiated by the S-NG-RAN node:

[0251] Timer TXn before the S-NG-RAN node receives the S-NODE reconfiguration complete or S-NODE release request message. DCoverall Upon expiration, the S-NG-RAN node considers the requested RRC connection reconfiguration not applied by the UE and triggers an S-NG-RAN node release procedure initiated by the S-NG-RAN node.

[0252] -----------------------------------------------------------------------

[0253]

[0254] Specific embodiments of the present disclosure

[0255] The present disclosure relates to a device and method for transmitting small data in a wireless communication system. Specifically, the present disclosure relates to a device and method for supporting small data transmission (SDT) for a terminal configured to have dual connectivity in a wireless communication system using a secondary cell group (SCG).

[0256]

[0257] In 5G, NR inactive is designed to suspend access stratum (AS) operations while the UE remains connected to the core network (CN). Therefore, AS and data transmission can be immediately resumed without reestablishing the RRC connection. This is a lightweight approach to RRC idle and / or CN idle states, aimed at reducing connection latency and battery consumption.

[0258] The concept of inactivity can be extended to multi-radio dual connectivity (MR-DC), which can suspend and resume both the master cell group (MCG) and the secondary cell group (SCG). An exemplary flow for MR-DC using 5GC is illustrated in Figure 8. Figure 8 illustrates an example of a procedure supporting activity notification for MR-DC. This is identical to Figure 10.12.2-3 defined in Section 10.12.2 of the TS 37.340 standard.

[0259] The primary intent of the MR-DC activity notification support procedure, as illustrated in Figure 8, is to support non-mobile UEs that require infrequent, bursty data transmissions using the network. Although not explicitly illustrated in Figure 8, after Step 7, the master node (MN) triggers the UE to initiate connection resumption by transmitting a paging signal to the UE in accordance with Section 9.2.2.4.2 of TS 38.300. Subsequent steps for MCG and / or SCG resumption may then be performed.

[0260] Meanwhile, in Rel-17 and Rel-18, SDT is designed to allow small data transfers while remaining in an inactive state. For example, Rel-17 and Rel-18 are designed to support SDT without fully resuming the UE's RRC connection. In Rel-17, mobile-originated (MO) SDT is defined, and MO SDT is initiated when an SDT-capable UE sends a resume request to the network. Furthermore, MO SDT is terminated when the UE is indicated to the RRC idle or inactive state via RRC Release, or to the connected state via RRC resume or RRC setup. The initial UL SDT data or signaling is multiplexed using a resume request message, and multiple UL / DL SDT data exchanges may occur during the SDT session. In Rel-18, mobile-terminated (MT) SDT is defined, and MT SDT can be initiated by the network sending a paging message to the UE upon arrival of DL SDT data or signal.

[0261] Recent research suggests that SDT may be extended to DC in the future. If SDT is not supported by eNBs using EPC or ng-eNBs using 5GC, SDT can only be extended to EN-DC (E-UTRA-NR dual connectivity) or NR-NR dual connectivity (NR-DC). Currently, research on network mechanisms supporting SDT operations using SCG is still in the early stages. Accordingly, UEs configured for dual connectivity must release SCG when SDT is initiated.

[0262] Accordingly, the present disclosure proposes mechanisms that support both dual connectivity and SDT. In other words, the present disclosure proposes various embodiments that support SDT via SCG without forcibly releasing the SCG of a UE configured for dual connectivity.

[0263]

[0264] Example #1: Supporting DL SDT data arrival in SN

[0265] When it is decided to transition the UE's state to an inactive state, the master node (MN) may request the secondary node (SN) to suspend the lower layer. The SN may be configured or pre-configured based on at least one of information indicating whether the UE supports SCG SDT or bearer information for SDT. The bearer for SDT may also be determined and / or established by the SN.

[0266] The SN may provide the MN with some configuration information related to the SN's suspension. The MN may set or preset a threshold for the SDT data volume and provide the SN with the threshold for the SDT data volume. This is so that when the DL and / or UL SDT user data received by the SN via the SCG exceeds the threshold, the SN can notify the MN that the SDT user data has exceeded the threshold. The threshold for the SDT data volume may be set differently for the UL and DL. For example, the threshold for the UL SDT user data volume and the threshold for the DL SDT user data volume may be different. The threshold for the UL and / or DL ​​SDT data volume may be used by the MN to determine whether to fully resume the UE. If the SN cannot support the SCG SDT for the UE, the SN may reject the MN's request using a dedicated cause value.

[0267] When DL SDT user data arrives at the SN, the SN notifies the MN of the arrival of the DL SDT user data. The notification includes support information that helps the MN determine whether to trigger legacy paging or MT-SDT paging. For example, the support information may include DL SDT data volume information. The RAN paging message may include an indication of whether the DL SDT data has arrived at the SCG.

[0268] A UE that receives a RAN paging message initiates a resume request. If the RAN paging message is a paging message for SDT, the UE may transmit a resume request message containing UL SDT data or signaling. If the RAN paging message indicates the arrival of DL SDT data to the SCG, the UE may check the timing alignment with the resumed PSCell (primary SCG cell) and perform the RACH procedure as needed. The resume request message may include information on whether the resumed SCG is synchronized. The UE may be configured to transmit SCG cell measurement results using the resume request message. In addition, the UE may indicate whether there is pending UL SDT data to be transmitted via the SCG to help the MN decide to resume the SN.

[0269] If the MN decides to keep the same SN, the MN requests that SN to resume bearers only for SDT.

[0270] When UL SDT user data and / or DL ​​SDT user data larger than the SDT data volume threshold set by the MN arrives, the SN may notify the MN that UL SDT user data and / or DL ​​SDT user data larger than the set threshold has arrived.

[0271] When DL SDT user data or signaling arrives at the MN, and the MN decides to initiate SDT paging, the MN may request the SN to resume the bearer for SDT. At this time, the SN stops notifying the MN that DL SDT user data has arrived at the SN.

[0272] Figures 9a and 9b illustrate examples of a procedure for supporting the arrival of DL SDT data in an SN according to an embodiment of the present disclosure. Figures 9a and 9b illustrate the case where the MN decides to transition an SCG SDT capable UE to an inactive state while suspending the lower layer for SDT operations on the SN side. An SCG SDT capable UE refers to a UE that supports SDT via the SN's SCG.

[0273] Referring to FIGS. 9A and 9B, at step S901, the MN (920-1) decides to send the SCG SDT capable UE to an inactive state. That is, the MN (920-1) may decide to transition the UE supporting SDT via SCG to an inactive state.

[0274] In step S903, MN (920-1) transmits an SN modification request message to SN (920-2). The SN modification request message may include at least one of information requesting suspension of a lower layer, information indicating whether the UE is capable of SCG SDT, bearer information for SDT, or an SDT data volume threshold for subsequent notification. For example, MN (920-1) may use the SN modification request message to request SN to suspend a lower layer of the SN (e.g., SCG lower layer) for the UE. In addition, MN (920-1) may configure SN so that UE (910) is capable of performing SCG SDT and / or a bearer established in SN (920-2) is a target of SDT operations. In addition, MN (920-1) may configure SN to have an SDT data volume threshold. MN (920-1) can cause SN (920-2) to set an SDT data volume threshold so that SN (920-2) can notify MN (920-1) when the volume of DL SDT user data and / or UL SDT user data received via SCG exceeds the threshold. The SDT data volume threshold can be set to different values ​​for DL ​​SDT user data and UL SDT user data, respectively. That is, the SDT data volume threshold for DL ​​SDT user data and the SDT data volume threshold for UL SDT user data can be different. The SDT data volume threshold can be used by MN (920-1) to determine whether to fully resume the UE.

[0275] In step S905, the SN (920-2) transmits an SN modification request confirmation message to the MN (920-1). That is, the SN (920-2) may suspend the lower layer for the UE and transmit an SN modification request confirmation message including the SN's suspend configuration information for the UE to the MN. The suspend configuration information of the SN may include configuration information related to the suspend of the SCG managed by the SN. For example, the suspend configuration information of the SN may include at least one of configuration information required to transition the RRC connection state of the UE to the inactive state, or configuration information required when transitioning from the inactive state back to the connection resume state. If the SN (920-2) cannot support the SCG SDT for the UE, the SN (920-2) may reject the request of the MN (920-1) using a dedicated cause value. In other words, if the SN (920-2) cannot support SCG SDT for the UE, the SN Modification Request Confirmation message may include a cause value indicating that the SN (920-2) cannot support SCG SDT for the UE.

[0276] In step S907, MN (920-1) transmits an RRC release message to UE (910). The RRC release message may be an RRC connection release message. The RRC release message may include suspension configuration information. The suspension configuration information may include at least one of suspension configuration information of MN or suspension configuration information of SN obtained from SN (920-2). The suspension configuration information of MN may include at least one of configuration information required to switch the RRC connection state of UE (910) for MN (920-1) to inactive state, or MCG or SCG related configuration information required when switching back from inactive state to connection resume state.

[0277] In step S909, the UE (910) operates in an inactive state during a period of inactivity. The UE (910) that has received the RRC release message can be released from the inactive state based on the suspension configuration information included in the RRC release message.

[0278] At step S911, SN (920-2) receives DL SDT user data. That is, SN (920-2) can receive DL SDT user data from UPF (930) while the lower layer of SN is suspended and the terminal (910) is inactive. As DL SDT user data is received from UPF (930), the PSCell of SN (920-2) can be resumed.

[0279] At step S913, the SN (920-2) stores the DL SDT user data in a buffer, and at step S915, transmits an activity notification message to the MN (920-1) indicating the presence of the DL SDT user data. The activity notification may include information about the volume of the received DL SDT data. Additionally, the activity notification may include activity information for the UE. The activity information may indicate that user plane activity has been detected within the SCG resources managed by the SN (920-2).

[0280] At step S917, the MN (920-1) determines whether to trigger legacy RAN paging or SDT paging. The MN (920-1) may determine whether to trigger legacy RAN paging or SDT paging based on information about the received DL SDT data volume included in the activity notification. For example, if the received DL SDT data volume is less than or equal to a DL SDT data volume threshold, the MN (920-1) may determine SDT paging. On the other hand, if the received DL SDT data volume is greater than the DL SDT data volume threshold, the MN (920-1) may determine legacy RAN paging instead of SDT paging. The embodiments of FIGS. 9A and 9B are described assuming that SDT paging is determined.

[0281] At step S919, RAN paging is performed via the RAN (RAN notification area). MN (920-1) transmits a RAN paging message to UE (910). The RAN paging message may include information indicating that the SDT paging is due to the arrival of DL SDT data for the SCG.

[0282] At step S921, the UE (910) performs a random access procedure for the SN (920-2). If the received RAN paging message indicates the arrival of DL SDT data for the SCG, the UE (910) may check timing alignment with the resumed PSCell and, if necessary, perform a RACH. The resumed PSCell may be the cell of the SCG where the DL SDT data arrived.

[0283] In step S923, the UE (910) transmits an RRC Resume Request message. The RRC Resume Request message may be an RRC Connection Resume Request message. The RRC Resume Request message may include UL SDT data or signaling for the MCG. The RRC Resume Request message may include at least one of information indicating whether synchronization with the resumed SCG is achieved, SCG cell measurement results, or information indicating whether UL SDT data via the SCG is pending. This information may be used by the MN (920-1) to determine whether to resume the SN.

[0284] In step S925, MN (920-1) transmits the received UL SDT user data to UPF (930), and in step S927, MN (920-1) transmits the received UL SDT signal to AMF (940). That is, MN (920-1) transmits UL SDT user data and signaling for MCG included in the RRC resumption request message to UPF (930) and AMF (940), respectively.

[0285] At step S929, MN (920-1) transmits an SN modification request message to SN (920-2). The SN modification request message may request the resumption of bearers only for SDT. Here, MN (920-1) may determine whether to change the SN and decide to maintain the SN without changing it to another SN.

[0286] In step S931, SN (920-2) transmits an SN modification request confirmation message to MN (920-1). After resuming the bearer for the SDT, SN (920-2) may transmit an SN modification request confirmation message to MN (920-1) in response to the SN modification request message. Here, the bearer for the SDT may be a bearer established by the MN or the SN. For example, SN (920-2) may resume a bearer established based on bearer information for the SDT received from the MN, or a bearer established by SN (920-2) as the SDT bearer.

[0287] At step S933, SN (920-2) transmits buffered DL SDT user data to UE (910). At step S935, subsequent UL SDT user data and / or DL ​​SDT user data are transmitted and received between UE (910), MN (920-1), and / or SN (920-2). That is, UE (910) may transmit subsequent UL SDT user data to MN (920-1) and / or SN (920-2), and MN (920-1) and / or SN (920-2) may transmit subsequent DL SDT user data to UE (910).

[0288] At step S937, UL SDT user data larger than the UL SDT data volume threshold set in the SN (920-2) may arrive, or at step S939, DL SDT user data larger than the DL SDT data volume threshold set in the SN (920-2) may arrive. In this case, at step S941, the SN (920-2) may transmit an activity notification message to the MN (921-1) indicating that UL SDT user data and / or DL ​​SDT user data larger than the threshold have arrived.

[0289] In the embodiment set with reference to FIGS. 9A and 9B, the MN uses the SN modification request message to set at least one of the UE's SCG SDT capability, bearer information for the SDT, or SDT data volume threshold to the SN. However, at least one of the UE's SCG SDT capability, bearer information for the SDT, or SDT data volume threshold may be set before step S903 (e.g., at the time of SN addition). Alternatively, the bearer for the SDT may be determined by the SN.

[0290] In the embodiments described with reference to FIGS. 9A and 9B , the case where DL SDT user data or signaling arrives at the SN is described. However, DL SDT user data or signaling may also arrive at the MN. In this case, the MN may determine SDT paging and request the SN to resume the bearer for the SDT at a time earlier than step S929. At this time, the SN may stop notifying the MN that DL SDT user data has arrived at the SN.

[0291]

[0292] Example #2: Support for SN changes during SDT

[0293] Embodiment #2 is a modified embodiment of Embodiment #1, in which the MN changes the SN for the SDT of the UE. In Embodiment #2, when an SDT resumption request is received from the UE, the MN may decide to change the SN and perform UE reconfiguration based on the changed SN.

[0294] FIGS. 10A and 10B illustrate examples of a procedure for changing an SN during SDT according to one embodiment of the present disclosure. FIGS. 10A and 10B illustrate operations after a UE (1010) is paged and transmits an RRC resumption request, as in Embodiment #1. In other words, the procedures of FIGS. 10A and 10B may be performed after steps S901 to S923 of FIGS. 9A and 9B are performed.

[0295] Referring to FIGS. 10A and 10B , at step S1001, MN (1020-1) determines to change the SN. MN (1020-1) receives an RRC Resume Request message for SDT from UE (1010) and determines whether to change or maintain the SN for UE (1010) based on information included in the RRC Resume Request message (e.g., whether UE is synchronized to the resumed SCG, SCG cell measurement results reported by UE, etc.). For example, MN (1020-1) may determine whether to change the SN for UE (1010) to a new SN or to maintain the SN for UE (1010) for SDT of UE (1010) based on at least some information included in the RRC Resume Request message.

[0296] In step S1003, MN (1020-1) transmits an SN modification request message to SN (1020-2). By transmitting the SN modification request message to SN (1020-2), MN (1020-1) can request information about the current SCG configuration or forwarding proposals.

[0297] In step S1005, SN (1020-2) transmits an SN modification request confirmation message to MN (1020-1) in response to the SN modification request message. The SN modification request confirmation message may include current SCG settings or forwarding proposal information.

[0298] In step S1007, MN (1020-1) transmits an SN addition request message to new SN (1020-3). That is, MN (1020-1) transmits an SN addition request message to new SN (1020-3) to change the SN of UE (1010). The SN addition request message may include at least one of current SCG configuration information or information requesting the resumption of bearers only for SDT. For example, MN (1020-1) may request new SN (1020-3) to resume only bearers for SDT and suspend non-SDT bearers while establishing a new SN.

[0299] In step S1009, the new SN (1020-3) transmits an SN addition request confirmation message to the MN (1020-1). The SN addition request confirmation message may include SN RRC reconfiguration and forwarding TNLs (transport network layer address) information. The forwarding TNLs information may include TNLs information for data forwarding between the SN (1020-2) and the new SN (1020-3). If the new SN (1020-3) cannot support the SCG SDT for the UE (1010), the new SN (1020-3) may reject the MN's request using a dedicated cause value.

[0300] At step S1011, MN (1020-1) transmits an SN release request message to SN (1020-2), and at step S1013, SN (1020-2) transmits an SN release request confirmation message to MN (1020-1) as a response to the SN release request message. At step S1015, MN (1020-1) provides data forwarding and / or Xn-U address indication information to SN (1020-2). MN (1020-1) may forward TNLs information received from new SN (1020-3) to SN (1020-2) for data forwarding between SN (1020-2) and new SN (1020-3).

[0301] In step S1017, MN (1020-1) transmits an RRC reset message to UE (1010). The RRC reset message may be an RRC connection reset message. The RRC reset message may include SN RRC reset information.

[0302] In step S1019, the UE (1010) transmits an RRC reconfiguration complete message to the MN (1020-1), and in step S1021, the UE (1010) performs a random access procedure for the new SN (1020-3). The RRC reconfiguration complete message may be an RRC connection reconfiguration complete message and may include information indicating completion of the SN RRC reconfiguration. The UE (1010) performs configuration for the new SN based on the SN RRC reconfiguration information included in the RRC reconfiguration message, and then transmits the RRC reconfiguration complete message to the MN (1020-1).

[0303] At step S1023, MN (1020-1) forwards the SN RRC reconfiguration complete message received from UE (1010) to new SN (1020-3).

[0304] At step S1025, SN (1020-2) forwards DL SDT user data to new SN (1020-3), and new SN (1020-3) forwards DL SDT to UE (1010).

[0305] In the embodiment described with reference to FIGS. 10A and 10B, the description of the path switch procedure with AMF (1040) is omitted for brevity, but the path switch procedure must be performed from MN (1020-1) after step S1023. That is, the path switch procedure may be performed after step S1023, and step S1025 may be performed.

[0306]

[0307] Example #3: Supporting the arrival of DL non-SDT data in the SN

[0308] Embodiment #3 is a modified embodiment of Embodiment #1, in which the SN notifies the MN that DL non-SDT user data has arrived. In Embodiment #3, when DL non-SDT user data has arrived at the SN, the SN notifies the MN of the arrival of DL non-SDT user data, and the MN determines to terminate the SDT operation based on this. In this case, the UE and the SN are fully resumed.

[0309] FIG. 11 illustrates an example of a procedure for supporting DL Non-SDT in an SN according to one embodiment of the present disclosure. FIG. 11 assumes a situation in which the UE has resumed SDT, as in Example #1. In other words, the procedure of FIG. 11 below may be performed after steps S901 to S931 of FIGS. 9A and 9B have been performed.

[0310] Referring to FIG. 11, in step S1101, SN (1120-2) receives DL non-SDT user data. SN (1120-2) may receive DL non-SDT user data while UE (1110) is resumed for SDT, or while SDT user data is being transmitted to UE (1110).

[0311] In step S1103, SN (1120-2) stores DL non-SDT user data in a buffer, and in step S1105, transmits an activity notification message to MN (1120-1) indicating the presence of DL non-SDT user data. The activity notification may include information indicating that DL non-SDT data has been received.

[0312] At step S1107, MN (1120-1) determines whether to terminate SDT and fully resume the UE. MN (1120-1) may determine whether to terminate SDT and fully resume the UE based on information included in the activity notification, for example, information indicating that DL non-SDT user data has arrived.

[0313] In step S1109, MN (1120-1) transmits an SN modification request message to SN (1120-2). The SN modification request message may include information indicating resumption of the lower layer of the SN.

[0314] In step S1111, SN (1120-2) transmits an SN modification request confirmation message to MN (1120-1). The SN modification request confirmation message may include SN RRC reconfiguration information.

[0315] At step S1113, MN (1120-1) transmits an RRC resume message. The RRC resume message may be an RRC connection resume message and may include SN RRC reconfiguration information. At step S1115, UE (1110) transmits an RRC resume complete message to MN (1120-1). The RRC resume complete message may include information indicating that SN RRC reconfiguration has been completed. Accordingly, UE (1110) can be fully resumed.

[0316] At step S1117, MN (1120-1) transmits the SN RRC reconfiguration complete message received from UE (1110) to SN (1120-2).

[0317] At step S1119, SN (1120-2) transmits DL non-SDT user data to UE (1110). When SN RRC Reset Complete message is received, SN (1120-2) recognizes that UE (1110) is fully resumed and can transmit DL non-SDT user data to UE (1110).

[0318] In step S1121, subsequent UL user data and / or DL ​​user data are transmitted and received between the UE (1110), the MN (1120-1), and / or the SN (1120-2). That is, the UE (1110) can transmit subsequent UL user data to the MN (1120-1) and / or the SN (1120-2), and the MN (1120-1) and / or the SN (1120-2) can transmit subsequent DL user data to the UE (1110).

[0319] The embodiment described with reference to FIG. 11 describes a case where DL non-SDT user data arrives at the SN while the UE is in a state of resuming SDT. However, DL non-SDT user data or signaling may also arrive at the MN while the UE is in a state of resuming SDT. In this case, the MN may decide to terminate the SDT operation, and step S1109 and subsequent steps may be performed.

[0320]

[0321] Example #4: Support for SN change upon arrival of DL non-SDT data in SN

[0322] Embodiment #4 is a modified embodiment of Embodiments #2 and #3, in which the MN changes the SN for the UE's DL non-SDT and resets the UE based on the changed SN. In Embodiment #4, when DL non-SDT user data arrives at the SN, the MN can decide to terminate the SDT operation and change the SN. Embodiment #4, described below, can also be applied when DL non-SDT user data arrives at the MN.

[0323] FIGS. 12A and 12B illustrate examples of a procedure for changing an SN for DL ​​Non-SDT in an SN according to one embodiment of the present disclosure. FIGS. 12A and 12B assume a situation in which the UE resumes for SDT, as in Example #1. In other words, the procedures of FIGS. 12A and 12B may be performed after steps S901 to S931 of FIGS. 9A and 9B are performed.

[0324] Referring to FIGS. 12A and 12B, in step S1201, SN (1220-2) receives DL non-SDT user data. SN (1220-2) may receive DL non-SDT user data while UE (1210) is resumed for SDT, or while SDT user data is being transmitted to UE (1210).

[0325] In step S1203, SN (1220-2) stores DL non-SDT user data in a buffer, and in step S1205, transmits an activity notification message to MN (1220-1) indicating the presence of DL non-SDT user data. The activity notification may include information indicating that DL non-SDT data has been received.

[0326] At step S1207, MN (1220-1) decides to terminate SDT and fully resume the UE while changing the SN. MN (1220-1) may decide to terminate SDT and fully resume the UE while changing the SN based on information included in the activity notification, e.g., information indicating that DL non-SDT user data has arrived.

[0327] In step S1209, MN (1220-1) transmits an SN modification request message to SN (1220-2). By transmitting the SN modification request message to SN (1220-2), MN (1220-1) can request information about the current SCG configuration or forwarding proposals.

[0328] In step S1211, SN (1220-2) transmits an SN modification request confirmation message to MN (1220-1) in response to the SN modification request message. The SN modification request confirmation message may include current SCG settings or forwarding proposal information.

[0329] In step S1213, MN (1220-1) transmits an SN addition request message to new SN (1220-3). That is, MN (1220-1) transmits an SN addition request message to new SN (1220-3) to change the SN of UE (1210). The SN addition request message may include current SCG configuration information.

[0330] In step S1215, the new SN (1220-3) transmits an SN addition request confirmation message to the MN (1220-1). The SN addition request confirmation message may include SN RRC reconfiguration and forwarding TNLs information. The forwarding TNLs information may include TNLs information of the new SN for data forwarding between the SN (1220-2) and the new SN (1220-3).

[0331] At step S1217, MN (1220-1) transmits an SN release request message to SN (1220-2), and at step S1219, SN (1220-2) transmits an SN release request confirmation message to MN (1220-1) as a response to the SN release request message. At step S1221, MN (1220-1) provides data forwarding and / or Xn-U address indication information to SN (1220-2). MN (1220-1) may forward TNLs information received from new SN (1220-3) to SN (1220-2) for data forwarding between SN (1220-2) and new SN (1220-3).

[0332] In step S1223, MN (1220-1) transmits an RRC resume message. The RRC resume message may be an RRC connection resume message and may include SN RRC reconfiguration information. In step S1225, UE (1210) transmits an RRC resume complete message to MN (1220-1). The RRC resume complete message may include information indicating that SN RRC reconfiguration is complete. Accordingly, UE (1210) can be completely resumed. In step S1227, UE (1210) may perform a random access procedure for the new SN (1220-3).

[0333] At step S1229, MN (1220-1) forwards the SN RRC Reset Complete message received from UE (1210) to new SN (1220-3). At step S1231, SN (1220-2) forwards DL SDT user data to new SN (1220-3), and new SN (1220-3) forwards DL SDT to UE (1210). When the SN RRC Reset Complete message is received, new SN (1220-3) recognizes that UE (1210) is fully resumed and can forward DL non-SDT user data to UE (1210).

[0334] The embodiments described with reference to FIGS. 12A and 12B describe the case where DL non-SDT user data arrives at the SN while the UE is in a state of resuming SDT. However, DL non-SDT user data or signaling may also arrive at the MN while the UE is in a state of resuming SDT. In this case, the MN may decide to terminate the SDT operation, and steps S1209 and subsequent steps may be performed.

[0335]

[0336] Example #5: Supporting SDT Termination Requests in SN

[0337] Embodiment #5 is a modified embodiment of Embodiment #1, in which the SN requests termination of an ongoing SDT procedure. In Embodiment #5, if the SN requests termination of the SDT, the MN may decide to terminate the SDT operation and release the UE, thereby placing the UE in an inactive state.

[0338] FIG. 13 illustrates an example of a procedure for supporting an SDT termination request in an SN according to one embodiment of the present disclosure. FIG. 13 assumes a situation in which the UE has resumed SDT, as in Example #1. In other words, the procedure of FIG. 13 below may be performed after steps S901 through S931 of FIGS. 9A and 9B are performed.

[0339] Referring to FIG. 13, in step S1301, SN (1320-2) transmits an SDT termination request message to MN (1320-1). The SDT termination request message may include support information that is helpful in determining whether to terminate the SDT. For example, the SDT termination request message may include information indicating that the request is due to a wireless link problem, or information indicating that the request is due to a normal termination of the SDT session due to SN inactivity.

[0340] At step S1303, MN (1320-1) determines to release the UE to terminate SDT and return the UE to an inactive state. MN (1320-1) may determine to release the UE to terminate SDT and return the UE to an inactive state based on the support information included in the SDT termination request message.

[0341] In step S1305, MN (1320-1) transmits an SN modification request message to SN (1320-2). The SN modification request message may include information requesting the suspension of a lower layer. For example, MN (1320-1) may use the SN modification request message to request SN (1320-2) to suspend the lower layer of the SN.

[0342] In step S1307, SN (1320-2) transmits an SN modification request confirmation message to MN (1320-1). That is, SN (1320-2) can transmit an SN modification request confirmation message including SN suspension configuration information for UE to MN.

[0343] In step S1309, MN (1320-1) transmits an RRC release message to UE (1310). The RRC release message may be an RRC connection release message. The RRC release message may include suspension configuration information. The suspension configuration information may include at least one of suspension configuration information of MN or suspension configuration information of SN. UE (1310) that receives the RRC release message from MN (1320-1) may be switched to an inactive state.

[0344] In the embodiment described with reference to FIG. 13, the MN may decide to release the SN when the SDT ends. For example, the MN may decide to release the SN if the SDT termination request in step S1303 is due to a radio link problem. In this case, the MN may trigger an SN release request procedure to release the SN and perform an RRC re-establishment to release the UE and the SCG before sending an RRC release message to the UE to return the UE to an inactive state. During the SN release procedure, PDU sessions or DRBs established in the SN may be relocated to the MN and re-established in the UE. In this case, the DL SDT data stored in the SN may be forwarded to the MN before the RRC release message is sent to the UE, and may be transferred from the MN to the UE.

[0345] In the embodiment described with reference to FIG. 13, if the MN decides to completely resume the UE at step S1303, the steps after step S1107 of embodiment #3 may be performed after step S1303.

[0346]

[0347] Example #6: Support for SN change when SDT termination is requested from SN

[0348] Embodiment #6 is a modified embodiment of Embodiments #2 and #5, which terminates the SDT procedure and changes the SN. In Embodiment #6, when the MN receives a request to terminate the SDT from the SN, the MN may decide to terminate the SDT operation and, along with the SN change, release the UE and transition it to an inactive state.

[0349] FIGS. 14A and 14B illustrate examples of a procedure for changing an SN when an SN requests termination of SDT according to one embodiment of the present disclosure. FIGS. 14A and 14B assume a situation in which the UE resumes SDT, as in Example #1. In other words, the procedures of FIGS. 14A and 14B may be performed after steps S901 to S931 of FIGS. 9A and 9B are performed.

[0350] Referring to FIGS. 14A and 14B , in step S1401, SN (1420-2) transmits an SDT termination request message to MN (1420-1). The SDT termination request message may include support information that is helpful in determining whether to terminate the SDT. For example, the SDT termination request message may include information indicating that the request is due to a wireless link problem, or information indicating that the request is due to a normal termination of the SDT session due to SN inactivity.

[0351] At step S1403, MN (1420-1) determines to release the UE to terminate SDT and return the UE to an inactive state while changing the SN. MN (1420-1) may determine to release the UE to terminate SDT and return the UE to an inactive state while changing the SN based on the support information included in the SDT termination request message.

[0352] In step S1405, MN (1420-1) transmits an SN modification request message to SN (1420-2). MN (1420-1) can request current SCG configuration information by transmitting the SN modification request message to SN (1420-2).

[0353] In step S1407, SN (1420-2) transmits an SN modification request confirmation message to MN (1420-1) in response to the SN modification request message. The SN modification request confirmation message may include current SCG configuration information.

[0354] In step S1409, MN (1420-1) transmits an SN addition request message to new SN (1420-3). That is, MN (1420-1) transmits an SN addition request message to new SN (1420-3) to change the SN of UE (1410). The SN addition request message may include current SCG configuration information and lower layer suspension request information. The lower layer suspension request information may request suspension of the lower layer of the new SN while the new SN is being established.

[0355] In step S1411, the new SN (1420-3) transmits an SN addition request confirmation message to the MN (1420-1). The SN addition request confirmation message may include SN RRC reconfiguration information and SN suspension configuration information.

[0356] At step S1413, MN (1420-1) transmits an SN release request message to SN (1420-2), and at step S1415, SN (1420-2) transmits an SN release request confirmation message to MN (1420-1) as a response to the SN release request message. Through this, MN (1420-1) can release the existing SN (1420-2) for UE (1410).

[0357] At step S1417, MN (1420-1) transmits an RRC reset message to UE (1410). The RRC reset message may be an RRC connection reset message. The RRC reset message may include SN RRC reset information received from the new SN (1420-3).

[0358] At step S1419, the UE (1410) transmits an RRC reconfiguration complete message to the MN (1420-1), and at step S1421, the UE (1410) performs a random access procedure for the new SN (1420-3). The RRC reconfiguration complete message may be an RRC connection reconfiguration complete message and may include information indicating completion of the SN RRC reconfiguration. The UE (1410) performs configuration for the new SN (1420-3) based on the SN RRC reconfiguration information included in the RRC reconfiguration message, and then transmits the RRC reconfiguration complete message to the MN (1420-1).

[0359] At step S1423, MN (1420-1) forwards the SN RRC reconfiguration complete message received from UE (1410) to new SN (1420-3).

[0360] In step S1425, MN (1420-1) transmits an RRC release message to UE (1410). The RRC release message may be an RRC connection release message. The RRC release message may include suspension configuration information. The suspension configuration information may include at least one of suspension configuration information of the MN or suspension configuration information of a new SN. The UE (1410) that receives the RRC release message from MN (1420-1) may be switched to an inactive state.

[0361] In the embodiment described with reference to FIGS. 14a and 14b, if the MN decides to fully resume the UE, step S1113 of embodiment #3 and subsequent steps may be performed after step S1415.

[0362] As described above, the present disclosure proposes a method and apparatus for supporting SDT via dual connectivity in a network system. The network system of the present disclosure includes network nodes, i.e., MNs and SNs, interconnected via an X2 or Xn interface to serve UEs using dual connectivity.

[0363] In one embodiment, the MN may request the SN to configure at least one of whether the UE can perform SCG SDT, a bearer for SDT, or an SDT data volume threshold. Alternatively, the SN may determine and / or configure an SDT bearer for the UE's SCG SDT on its own. If the SN cannot support SCG SDT for the UE, the SN may reject the MN's request using a dedicated cause value. The SN may notify the MN when the DL SDT user data or UL SDT user data received via SCG exceeds the SDT data volume threshold.

[0364] In one embodiment, the MN may decide to put the UE in an inactive state and request the SN to suspend the lower layer. The SN may provide the MN with configuration information regarding the suspended portion. When DL SDT user data for the inactive UE arrives, the SN may notify the MN of this using an activity notification message. The activity notification message may include information related to the DL SDT user data. For example, the activity notification message may include DL SDT data volume information. The MN may determine whether to trigger legacy RAN paging or SDT paging based on the activity notification message. If SDT paging is determined to be triggered, the MN transmits a paging message including information indicating the arrival of DL SDT user data for the SCG. A UE that receives a paging message in an inactive state may initiate a resume request to the MN. The UE may check timing alignment with the resumed PSCell and, if necessary, perform a RACH procedure. A resume request message transmitted from the UE to the MN may include at least one of information indicating whether the resumed SCG is synchronized, SCG cell measurement results, or information indicating whether there is UL SDT data pending over the SCG.

[0365] In one embodiment, the MN may maintain the SN of the UE at the current SN or change it to a new SN. If the MN decides to maintain the SN of the UE, the MN may request that the SN be resumed only for the SCG SDT bearer. If the MN decides to change the SN of the UE, the MN may change the SN of the UE from the current SN to the new SN by performing an SN change procedure. The MN may configure the new SN so that only the SDT bearer is resumed and the non-SDT bearer is dropped during the configuration of the new SN. The SN may stop notifying the MN of the arrival of DL SDT user data via the SCG.

[0366] In one embodiment, the SN may notify the MN that DL non-SDT user data has arrived at the SN. If DL non-SDT user data has arrived at the SN, the MN may decide to terminate the ongoing SDT and completely resume the UE. At this time, the MN may maintain the SN of the UE at the current SN or change it to a new SN. If the MN decides to maintain the SN of the UE, the MN may request the SN to resume lower layers before sending the RRC resume message to the UE. If the MN decides to change the SN of the UE, the MN may change the SN of the UE from the current SN to the new SN by performing an SN change procedure before sending the RRC resume message to the UE.

[0367] In one embodiment, the SN may request the MN to terminate the SDT and provide the MN with information related to the SDT termination. The information related to the SDT termination may indicate a reason for the SDT termination, such as a normal termination of the SDT session due to a radio link problem or inactivity of the SN. Based on the SDT termination request from the SN, the MN may decide to terminate the ongoing SDT. At this time, the MN may maintain the SN of the UE at the current SN, change it to a new SN, or release the SN of the UE. If the MN decides to maintain the SN of the UE, the MN may request the SN to suspend or resume lower layers before returning the UE to the inactive state or before fully resuming the UE. The SN may provide the MN with information about the suspension configuration. If the MN decides to change the SN of the UE, the MN may change the SN of the UE from the current SN to the new SN by performing an SN change procedure before returning the UE to the inactive state or before fully resuming the UE. If the MN decides to release the SN of the UE, it may perform the SN release procedure before fully resuming the UE or sending the UE back to the inactive state.

[0368] As described in the embodiments described above, the present disclosure enables a network node to support small data transfer (SDT) for a UE configured to have dual connectivity, so that the SCG of the UE can be continued or changed for SDT operation without being forcibly released.

[0369]

[0370] FIG. 15 illustrates an example of a procedure for transmitting a paging message for a DL SDT according to one embodiment of the present disclosure. FIG. 15 illustrates a method performed by a first network node. The first network node may include an MN. For example, the first network node may be the MN described with reference to FIGS. 9A through 14B .

[0371] Referring to FIG. 15, in step S1501, the first network node controls the state of the second network node to a suspended state. The first network node determines the state of the terminal to be inactive and requests the second network node to suspend a lower layer. Here, the terminal may include a UE supporting SDT via SCG, and the second network node may include an SN. The terminal may be dually connected to the first network node and the second network node, and thus may receive services via the MCG managed by the first network node and / or the SCG by the second network node. The first network node may be interconnected with the second network node via an X2 or Xn interface. The first network node transmits a modification request message to the second network node to suspend a lower layer of the second network node for the terminal, and receives a modification request confirmation message from the second network node. The modification request message may include an SN modification request message. The modification request message may include at least one of information requesting suspension of a lower layer of the second network node, information indicating whether the terminal is capable of SCG SDT, bearer information for SDT, or an SDT data volume threshold for subsequent notification. The modification request confirmation message may include an SN modification request confirmation message. The SN modification request confirmation message may include suspension configuration information of the second network node. The suspension configuration information of the second network node may include configuration information for switching the RRC connection state of the terminal to an inactive state for the second network node.

[0372] In step S1503, the first network node transmits an RRC connection release message to the terminal. That is, the first network node transmits the RRC connection release message to the terminal to change the state of the terminal to an RRC inactive state. The RRC connection release message may include at least one of the suspension configuration information of the first network node or the suspension configuration information of the second network node. The suspension configuration information of the first network node may include configuration information for changing the RRC connection state of the terminal to the first network node to an inactive state.

[0373] In step S1505, the first network node receives an activity notification message from the second network node. The first network node receives the activity notification message from the second network node during a period of terminal inactivity. The activity notification message may include information about the volume of DL SDT data that has arrived at the second network node.

[0374] In step S1507, the first network node transmits a paging message to the terminal. The first network node may determine whether to trigger legacy RAN paging or SDT paging based on the activity notification message received from the second network node, and may transmit a paging message to the terminal based on the determination. For example, the first network node may determine whether to trigger legacy RAN paging or SDT paging based on the volume information of DL SDT data included in the activity notification message. If the volume information of the DL SDT data is less than or equal to an SDT data volume threshold, the first network node may determine to trigger SDT paging. On the other hand, if the volume information of the DL SDT data is greater than the SDT data volume threshold, the first network node may determine to trigger legacy RAN paging. The paging message transmitted to the terminal may include information indicating the triggered paging. For example, if SDT paging is triggered, the paging message may include information indicating SDT paging due to the arrival of DL SDT data for the SCG.

[0375] According to one embodiment, a first network node may receive an RRC resumption request message from a terminal that has received a paging message for SDT paging. The RRC resumption request message may include support information that helps the second network node determine whether to resume. For example, the RRC resumption request message may include at least one of information indicating whether the resumed SCG is synchronized, an SCG cell measurement result, or information indicating whether UL SDT data for the SCG is pending. In addition, the RRC resumption request message may further include UL SDT data or signaling for the MCG.

[0376] In one embodiment, a first network node that receives an RRC resumption request message may request a second network node to resume only the bearer for the SDT. For example, the first network node may transmit a modification request message to the second network node requesting the resumption of only the SDT bearer and receive a confirmation message in response. Accordingly, the bearer for the SDT is resumed at the second network node, and DL SDT user data may be transmitted to the terminal via the resumed bearer for the SDT.

[0377]

[0378] FIG. 16 illustrates an example of a procedure for transmitting a DL SDT according to one embodiment of the present disclosure. FIG. 16 illustrates a method performed by a second network node. The second network node may include an SN. For example, the second network node may be the SN described with reference to FIGS. 9A through 14B .

[0379] Referring to FIG. 16, in step S1601, the second network node is changed to a suspended state by the first network node. The second network node may receive a message from the first network node requesting suspension of a lower layer of the second network node for a terminal, and in response, may set the lower layer to a suspended state. Here, the first network node may include an MN, and the terminal may include a UE supporting SDT via SCG. The first network node may be interconnected with the second network node via an X2 or Xn interface. For example, the second network node receives a modification request message from the first network node, and transmits a modification request confirmation message to the first network node. The modification request message may include an SN modification request message. The modification request message may include at least one of information requesting suspension of a lower layer of the second network node, information indicating whether the terminal is capable of SCG SDT, bearer information for SDT, or an SDT data volume threshold for subsequent notification. The modification request confirmation message may include an SN modification request confirmation message. The SN modification request confirmation message may include the stop configuration information of the second network node.

[0380] At step S1603, the second network node detects DL SDT user data. The second network node may detect that DL SDT user data or signaling for the terminal arrives at the second network node during an inactivity period for the terminal.

[0381] In step S1605, the second network node transmits an activity notification message. The second network node may transmit the activity notification message to the first network node to notify the first network node that DL SDT user data or signaling for the terminal has arrived at the second network node. The activity notification message may include DL SDT data volume information. The DL SDT data volume information may indicate the volume of DL SDT user data that has arrived at the second network node.

[0382] In step S1607, the second network node resumes the bearer for the SDT. The second network node can resume the bearer for the SDT for the terminal based on the request of the first network node. Specifically, the second network node receives a modification request message from the first network node requesting to resume only the bearer for the SDT, and in response transmits a modification request confirmation message. The second network node can resume the bearer for the SDT of the terminal based on the modification request message requesting to resume only the bearer for the SDT. At this time, the second network node can resume the bearer established based on the bearer information for the SDT received in step S1601, or the bearer established by the second network node, as the SDT bearer.

[0383] At step S1609, the second network node transmits DL SDT user data to the terminal. The second network node can transmit DL SDT user data to the terminal via the resumed SDT bearer.

[0384]

[0385] Figure 17 illustrates an example of a procedure for receiving DL SDT according to one embodiment of the present disclosure. Figure 17 illustrates a method performed by a terminal. The terminal may include a UE supporting SDT via SCG. For example, the terminal may be a UE described with reference to Figures 9a to 14b.

[0386] Referring to Fig. 17, in step S1701, the terminal receives an RRC connection release message from the first network node. The RRC connection release message may include at least one of suspension configuration information of the first network node or suspension configuration information of the second network node. The suspension configuration information of the first network node may include configuration information for switching the RRC connection state between the terminal and the first network node to an inactive state, and the suspension configuration information of the second network node may include configuration information for switching the RRC connection state between the terminal and the second network node to an inactive state.

[0387] In step S1703, the terminal receives a paging message for SDT from the first network node. The paging message for SDT may include information indicating SDT paging due to the arrival of DL SDT data for SCG.

[0388] In step S1705, the terminal performs a random access procedure for the second network node. If a paging message for SDT is received, the terminal may perform a RACH procedure with the resumed PSCell to support SDT via the SCG. This allows the terminal to confirm timing alignment with the PSCell. Depending on the embodiment, the RACH procedure with the PSCell may be omitted. For example, if timing alignment with the PSCell has been performed, the RACH procedure may be omitted.

[0389] In step S1707, the terminal transmits an RRC resumption request message to the first network node. The RRC resumption request message may include at least one of information indicating whether the resumed SCG is synchronized, an SCG cell measurement result, or information indicating whether UL SDT data via the SCG is pending. This information may be used by the first network node to determine whether the second network node should be resumed and whether the second network node should be changed. In addition, the RRC resumption request message may include UL SDT data or signaling for the MCG.

[0390] In step S1709, the terminal receives DL SDT user data from the second network node. The terminal can receive DL SDT user data or signaling on the SCG managed by the second network node via the resumed SDT bearer of the second network node.

[0391]

[0392] It is clear that the examples of the proposed methods described above can also be considered as a type of proposed methods, as they can be included as one of the implementation methods of the present disclosure. Furthermore, the proposed methods described above can be implemented independently, but they can also be implemented in the form of a combination (or merge) of some of the proposed methods. Information regarding the applicability of the proposed methods (or information regarding the rules of the proposed methods) can be defined by a rule such that the base station notifies the terminal of the application of the proposed methods through a predefined signal (e.g., a physical layer signal or a higher layer signal).

[0393] The present disclosure may be embodied in other specific forms without departing from the technical ideas and essential features described herein. Therefore, the above detailed description should not be construed as limiting in all respects but rather as illustrative. The scope of the present disclosure should be determined by a reasonable interpretation of the appended claims, and all modifications within the equivalent scope of the present disclosure are intended to be included within the scope of the present disclosure. Furthermore, claims that do not explicitly cite each other in the claims may be combined to form embodiments or incorporated into new claims through post-filing amendments.

[0394] Embodiments of the present disclosure can be applied to various wireless access systems. Examples of various wireless access systems include the 3rd Generation Partnership Project (3GPP) or 3GPP2 systems.

[0395] The embodiments of the present disclosure can be applied not only to the various wireless access systems described above, but also to all technical fields that utilize these various wireless access systems. Furthermore, the proposed method can also be applied to mmWave and THz communication systems utilizing ultra-high frequency bands.

[0396] Additionally, embodiments of the present disclosure can be applied to various applications such as autonomous vehicles and drones.

Claims

1. A method performed by a first network node in a wireless communication system, A step of sending a modification request message to a second network node; A step of receiving a confirmation message for a modification request from the second network node; A step of transmitting an RRC connection release message to a terminal to change the status of the terminal to an RRC (radio resource control) inactive state; A step of receiving an activity notification message from the second network node; and A step of transmitting a paging message to the terminal based on the above activity notification message, The above activity notification message includes information about downlink small data for the terminal that has arrived at the second network node, The above paging message is a method for indicating legacy paging or paging for the downlink small data transmission (SDT) based on information about the downlink small data.

2. In claim 1, A method in which information about the above downlink small data includes volume information about the downlink small data for the terminal that has arrived at the second network node.

3. In claim 1, A method in which the above modification request message includes at least one of information requesting suspension of a lower layer of the second network node, information indicating whether the terminal supports small data transmission (SDT) through a secondary cell group (SCG), bearer information for SDT, or threshold information for SDT data volume.

4. In claim 3, A method further comprising the step of receiving a message from the second network node notifying that downlink small data having a volume greater than the threshold has arrived at the second network node.

5. In claim 1, A method in which a confirmation message for the above modification request includes at least one of the configuration information related to the suspension of the lower layer of the second network node.

6. In claim 1, When the paging message indicates paging for the downlink small data transmission, a step of receiving an RRC resumption request message from the terminal; and A method further comprising the step of requesting the second network node to resume a bearer for the small data transmission.

7. In claim 6, A method in which the RRC resumption request message includes at least one of: whether synchronization for the resumed SCG exists, an SCG cell measurement result, uplink SDT data for an MCG (master cell group), or the presence of pending uplink SDT data for the SCG.

8. In claim 6, A method further comprising a step of controlling the auxiliary node for dual connection of the terminal to be changed from the second network node to the third network node.

9. In claim 8, The step of controlling the change from the second network node to the third network node is: A step of requesting the third network node to resume the bearer for the small data transmission; and A method comprising the step of releasing the second network node.

10. In claim 1, A step of receiving a message indicating that data not corresponding to the downlink small data has arrived from the second network node; and A method further comprising the step of terminating the operation for transmitting the small data and controlling the RRC connection of the terminal to be completely resumed.

11. In claim 1, A step of receiving a message requesting termination of the small data transmission from the second network node; and A method further comprising the step of terminating the operation for transmitting the small data and controlling the state of the terminal to return to the RRC inactive state.

12. A method performed by a second network node in a wireless communication system, A step of receiving a modification request message from a first network node; A step of transmitting a confirmation message for a modification request to the second network node; A step of transmitting an activity notification message to the first network node; A step of resuming a bearer for small data transmission (SDT) at the request of the first network; and Further comprising a step of transmitting small data to the terminal through the resumed bearer, A method wherein the above activity notification message includes information about downlink small data for the terminal that has arrived at the second network node.

13. In claim 12, A method for stopping a lower layer of the second network node based on the above modification request message.

14. In a method performed by a terminal in a wireless communication system, A step of receiving an RRC connection release message from a first network node; A step of receiving a paging message for downlink small data transmission (SDT) from the first network node; A step of performing a random access procedure for a second network node; A step of transmitting an RRC resumption request message to the first network node; and A method comprising the step of receiving downlink small data from the second network node.

15. In a first network node in a wireless communication system, Transmitter and receiver; and A processor connected to the above transmitter and receiver is included, The above processor, Send a modification request message to the second network node, Receive a confirmation message for a modification request from the second network node, Transmit an RRC connection release message to the terminal to change the terminal's status to an RRC (radio resource control) inactive state, Receive an activity notification message from the second network node, Control to transmit a paging message to the terminal based on the above activity notification message, The above activity notification message includes information about downlink small data for the terminal that has arrived at the second network node, The paging message is a first network node that instructs legacy paging or paging for the downlink small data transmission (SDT) based on information about the downlink small data.

16. In a second network node in a wireless communication system, Transmitter and receiver; and A processor connected to the above transmitter and receiver is included, The above processor, Receive a modification request message from the first network node, Send a confirmation message for the modification request to the second network node, Send an activity notification message to the first network node, Resuming a bearer for small data transmission (SDT) at the request of the first network; Control to transmit small data to the terminal through the resumed bearer, The above activity notification message is a second network node that includes information about downlink small data for the terminal that has arrived at the second network node.

17. In a wireless communication system, at a terminal, Transmitter and receiver; and A processor connected to the above transmitter and receiver is included, The above processor, Receive an RRC connection release message from the first network node, Receive a paging message for downlink small data transmission (SDT) from the first network node, Performs a random access procedure for the second network node, Send an RRC resumption request message to the first network node, A terminal that controls to receive downlink small data from the second network node.

18. In communication devices, At least one processor; At least one computer memory connected to said at least one processor and storing instructions that direct operations when executed by said at least one processor, The above actions are, A step of receiving an RRC connection release message from a first network node; A step of receiving a paging message for downlink small data transmission (SDT) from the first network node; A step of performing a random access procedure for a second network node; A step of transmitting an RRC resumption request message to the first network node; and A communication device comprising a step of receiving downlink small data from the second network node.

19. In a non-transitory computer-readable medium storing at least one instruction, comprising at least one instruction executable by the processor, At least one of the above commands causes the device to: Receive an RRC connection release message from the first network node, Receive a paging message for downlink small data transmission (SDT) from the first network node, Performs a random access procedure for the second network node, Send an RRC resumption request message to the first network node, A computer-readable medium for controlling receiving downlink small data from the second network node.

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