Apparatus and method for supporting data forwarding in wireless communication system

Abstract

The purpose of the present disclosure is to support data forwarding in a wireless communication system, and a method performed by a first network node may comprise the steps of: transmitting a secondary node (SN) addition request message to a second network node; and receiving an SN addition request confirmation message from the second network node.

Description

Device and method for supporting data forwarding in a wireless communication system

[0001] The following description relates to a wireless communication system, and more particularly, to a device and method for supporting data forwarding for a subsequent conditional primary secondary cell (PSCell) addition or change (CPAC) procedure 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 numerous 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 purposes.

[0004] The present disclosure relates to a device and method for efficiently supporting data forwarding in a wireless communication system.

[0005] The present disclosure relates to a device and method for supporting data forwarding for a subsequent conditional primary secondary cell (PSCell) addition or change (CPAC) procedure in a wireless communication system.

[0006] The present disclosure relates to a device and method for supporting subsequent CPAC without reconfiguration or re-initialization of CPAC settings in a wireless communication system.

[0007] The present disclosure relates to a device and method for obtaining information related to a data forwarding proposal from at least one candidate secondary node (SN) during a PSCell addition or change preparation step in a wireless communication system.

[0008] The present disclosure relates to a device and method for obtaining information related to a data forwarding proposal of a candidate SN using an SN addition procedure in a wireless communication system.

[0009] The present disclosure relates to a device and method for retrieving information related to a data forwarding proposal of a candidate SN using an SN addition request message in a wireless communication system.

[0010] The present disclosure relates to a device and method for transmitting an SN additional confirmation message including information related to a data forwarding proposal in a wireless communication system.

[0011] The present disclosure relates to a device and method for obtaining information related to a data forwarding proposal for at least one of a candidate SN initiated protocol data unit (PDU) session or data radio bearer (DRB) for a subsequent CPAC in a wireless communication system.

[0012] The present disclosure relates to a device and method in which information related to a data forwarding proposal obtained in advance from a candidate SN in a wireless communication system is used based on which the candidate SN is selected for access.

[0013] The present disclosure relates to a device and method for obtaining information related to forwarding TNLs (transport network layer addresses) allocated based on a data forwarding proposal of a candidate SN in a wireless communication system.

[0014] 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.

[0015] 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 an SN (secondary node) addition request message to a second network node, and receiving an SN addition request confirmation message from the second network node, wherein the SN addition request confirmation message may include information related to a data forwarding proposal of the second network node.

[0016] As an example of the present disclosure, a method performed by a second network node in a wireless communication system includes the steps of receiving an SN (secondary node) addition request message from a first network node, and transmitting an SN addition request confirmation message to the first network node, wherein the SN addition request confirmation message may include information related to a data forwarding proposal of the second network node.

[0017] 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 controls to transmit an SN (secondary node) addition request message to a second network node and to receive an SN addition request confirmation message from the second network node, wherein the SN addition request confirmation message may include information related to a data forwarding proposal of the second network node.

[0018] 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 an SN (secondary node) addition request message from a first network node and controls transmission of an SN addition request confirmation message to the first network node, wherein the SN addition request confirmation message may include information related to a data forwarding proposal of the second network node.

[0019] 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, the operations including: transmitting a secondary node (SN) addition request message to a second network node; and receiving an SN addition request confirmation message from the second network node, wherein the SN addition request confirmation message may include information related to a data forwarding proposal of the second network node.

[0020] 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, the at least one instruction controlling a device to transmit a second network secondary node (SN) addition request message and to receive an SN addition request confirmation message from the second network node, wherein the SN addition request confirmation message may include information related to a data forwarding proposal of the second network node.

[0021] The following effects may be achieved by embodiments based on the present disclosure.

[0022] The present disclosure can support subsequent CPAC (conditional PSCell addition or change) without reconfiguration or re-initialization of CPAC settings in a wireless communication system.

[0023] 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.

[0024] 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.

[0025] Figure 1 illustrates an example of a communication system applicable to the present disclosure.

[0026] FIG. 2 illustrates an example of a user equipment (UE) applicable to the present disclosure.

[0027] 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.

[0028] FIG. 4 illustrates an example of a general architecture of a 5G (5th generation) system applicable to the present disclosure.

[0029] Figures 5a and 5b illustrate examples of handover procedures between MNs regardless of whether SN changes are initiated by the MN.

[0030] Figure 6 illustrates an example of a successful procedure for preparing to add an S-NG-RAN node.

[0031] Figure 7 illustrates an example of a failure procedure for preparing to add an S-NG-RAN node.

[0032] FIGS. 8A and 8B illustrate examples of data forwarding support procedures for subsequent CPACs according to embodiments of the present disclosure.

[0033] FIG. 9 illustrates an example of a procedure for obtaining information related to a data forwarding proposal according to an embodiment of the present disclosure.

[0034] FIG. 10 illustrates an example of a procedure for transmitting information related to a data forwarding proposal according to an embodiment of the present disclosure.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] 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.

[0040] 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).

[0041] 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.

[0042] 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 th generation) 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.

[0043] 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.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] 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).

[0048]

[0049] 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.

[0050] 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.

[0051] 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.

[0052] Hereinafter, this specification is described based on the terms defined above.

[0053] 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).

[0054] 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.

[0055]

[0056] Communication system applicable to the present disclosure

[0057] 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.

[0058] 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.

[0059] Figure 1 illustrates an example of a communication system applied to the present disclosure.

[0060] 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.

[0061] 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).

[0062] 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.

[0063] Figure 2 illustrates an example of a UE applicable to the present disclosure.

[0064] 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).

[0065] 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).

[0066] 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.

[0067] 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.

[0068] 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).

[0069] 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).

[0070] 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.

[0071] 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).

[0072] 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.

[0073] 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.

[0074] 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.

[0075] 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.

[0076]

[0077] 5G system architecture applicable to the present disclosure

[0078] 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.

[0079] 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.

[0080] - 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).

[0081] 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.

[0082] 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).

[0083] 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.

[0084] 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.

[0085] 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.

[0086] 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).

[0087] The UPF acts as a boundary point 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.

[0088] 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).

[0089] 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.

[0090] 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.

[0091] Figure 3 illustrates an example of functional separation of NG-RAN and 5GC (5th generation core) applicable to the present disclosure.

[0092] 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.

[0093] The UPF node functions as a gateway through which user data is transmitted and received.

[0094] The authentication server function (AUSF) authenticates and manages UEs. The Network Slice Selection Function (NSSF) is a node for network slicing, as described below.

[0095] The network exposure function (NEF) provides a mechanism to securely expose the services and functions of the 5G core.

[0096]

[0097] 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.

[0098] 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.

[0099] 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.

[0100] 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.

[0101] 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.

[0102] In the TS 37.340 standard document, the MR-DC procedure is described as follows:

[0103] ----------------------------------------------------------------

[0104] 10.7.2 MR-DC (multi-radio dual connectivity) with 5GC

[0105] 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 (e.g., not switching from NGEN-DC to NR-DC) regardless of SN change.

[0106] Figures 5a and 5b illustrate examples of handover procedures between MNs regardless of whether SN changes are initiated by the MN.

[0107] 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.

[0108] 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.

[0109] Note 2: The source MN can trigger an MN-initiated SN modification procedure (for the source SN) to retrieve the current SCG configuration and allow provision of data forwarding related information prior to step 1.

[0110] 2. If the target MN decides to keep the UE context in the source SN, the target MN sends an SN addition 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 addition 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 addition 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.

[0111] 3. The (target) SN responds with an SN addition request confirmation. The (target) SN may include an indication of full or delta RRC configuration.

[0112] 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.

[0113] 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.

[0114] 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.

[0115] 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.

[0116] 5c. The source MN transmits data forwarding information by sending an XN-U Address Indication message to the (source) SN. If the PDU session is fragmented at the target side, more than one data forwarding address may be provided.

[0117] 6. The source MN triggers the UE to perform a handover and apply the new settings.

[0118] 7 / 8. The UE synchronizes with the target MN and responds with an MN RRC Reset Complete message.

[0119] 9. If bearers requiring SCG radio resources are configured, the UE synchronizes with the (target) SN.

[0120] 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.

[0121] 10. If the RRC connection re-establishment procedure is successful, the target MN notifies the (target) SN through an SN re-establishment complete message.

[0122] 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 over NR / E-UTRA radio as described in Section 10.11.2.

[0123] Note 2a2: The order in which the source SN sends the Secondary RAT Data Usage Report message and performs data forwarding with the MN / target SN is not defined. The SN may send the report when transmission of the relevant QoS is suspended.

[0124] 11b. The source MN sends a Secondary RAT Report message to the AMF, providing information about the NR / E-UTRA resources used.

[0125] 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.

[0126] 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.

[0127] 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.

[0128] 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.

[0129] 18. The target MN initiates a UE context release procedure for the source MN.

[0130] 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 forwarding 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.

[0131] ----------------------------------------------------------------

[0132] 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 is described as follows.

[0133] ----------------------------------------------------------------

[0134] 8.3.1. Preparing to Add S-NG-RAN Nodes

[0135] 8.3.1.1 General

[0136] 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.

[0137] This procedure uses UE-related signaling.

[0138] 8.3.1.2 Successful operation

[0139] The M-NG-RAN node initiates the procedure by sending an S-NODE addition request message to the S-NG-RAN node.

[0140] When the M-NG-RAN node sends an S-NODE addition request message, timer TXn DCprep Start.

[0141] 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].

[0142] 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] .

[0143] 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].

[0144] 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].

[0145] 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.

[0146] 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.

[0147] 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.

[0148] 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.

[0149] 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.

[0150] Duplicate transmission:

[0151] - 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].

[0152] - 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.

[0153] - 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].

[0154] - 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].

[0155] - 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.

[0156] If the S-NODE Addition Request message includes a Selected PLMN IE, the S-NG-RAN node may use it for RRM purposes.

[0157] 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.

[0158] 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.

[0159] 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.

[0160] 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].

[0161] 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.

[0162] 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.

[0163] 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.

[0164] 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.

[0165] 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.

[0166] For each bearer for which PDCP entity allocation is requested at the S-NG-RAN node:

[0167] - The M-NG-RAN node may propose to apply downlink data forwarding by including a DL forwarding IE in the 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.

[0168] - The S-NG-RAN node may indicate that it requests data forwarding of uplink packets to be performed for the corresponding bearer by including a UL Forwarding GTP Tunnel Endpoint IE for each bearer in the PDU Session Resource Setup Response Info - SN terminated IE.

[0169] - 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.

[0170] For each bearer in the M-NG-RAN node, the PDCP entity:

[0171] - 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.

[0172] The M-NG-RAN node may also propose to apply UL data forwarding when offloading QoS flows for which forwarding is requested in order 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. The 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 in the PDU Session Resource Setup Response Info - SN terminated IE of the S-NODE Addition Request Confirmation message.

[0173] 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.

[0174] 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] .

[0175] 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:

[0176] - The list of successfully established PDU session resources must be included in the PDU Session Resources Admitted To Be Added List IE.

[0177] - The list of PDU session resources for which establishment failed must be included in the PDU Session Resources Not Admitted List IE.

[0178] Upon receiving the S-NODE addition request confirmation message, the M-NG-RAN node sets the timer TXn DCprep must be stopped.

[0179] 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.

[0180] 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.

[0181] 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].

[0182] 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.

[0183] 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].

[0184] 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.

[0185] 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.

[0186] If the Security Result IE is included in the PDU Session Resource Setup Info - SN terminated IE of the S-NODE Addition Request message, the S-NG-RAN node may consider that information when deciding whether to perform user plane integrity protection or ciphering 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", the S-NG-RAN node shall perform user plane integrity protection or ciphering based on the information in the Security Result IE.

[0187] 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".

[0188] 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).

[0189] 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.

[0190] 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.

[0191] 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.

[0192] 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.

[0193] If the S-NODE add request message includes the trace enable IE

[0194] - 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.

[0195] - 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.

[0196] - 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.

[0197] - 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] .

[0198] - 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.

[0199] - 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.

[0200] - 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] .

[0201] - 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.

[0202] If the Requested Fast MCG recovery via SRB3 IE is 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.

[0203] 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.

[0204] 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 IE of the SN Termination IE, the M-NG-RAN node shall use it for RAN Partial Delay Reporting, if supported.

[0205] 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.

[0206] 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 to determine the availability of a direct data path with the specified source NG-RAN node, if supported, 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.

[0207] 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.

[0208] 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).

[0209] 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] .

[0210] 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.

[0211] 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.

[0212] 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.

[0213] 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:

[0214] - 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.

[0215] - 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].

[0216] 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.

[0217] 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".

[0218] 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.

[0219] If the Conditional PSCell Additional Information Confirmation is included in the S-NODE Addition 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.

[0220] 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.

[0221] 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.

[0222] 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.

[0223] Interaction with the S-NG-RAN node reconfiguration completion procedure:

[0224] 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.

[0225] Interacting with activity notification procedures

[0226] 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.

[0227] 8.3.1.3 Unsuccessful Operations

[0228] 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.

[0229] 8.3.1. Unsuccessful conditions

[0230] 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.

[0231] 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.

[0232] 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.

[0233] 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.

[0234] 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.

[0235] 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.

[0236] Interaction with the S-NG-RAN node release procedure initiated by the M-NG-RAN node:

[0237] 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.

[0238] 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.

[0239] Interaction with the S-NG-RAN node reconfiguration completion and S-NG-RAN node decommissioning procedure initiated by the S-NG-RAN node:

[0240] 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.

[0241] -----------------------------------------------------------------------

[0242]

[0243] Specific embodiments of the present disclosure

[0244] The present disclosure relates to a device and method for supporting data forwarding between network nodes in a wireless communication system. Specifically, the present disclosure relates to a device and method for supporting data forwarding for a subsequent conditional primary secondary cell (PSCell) addition or change (CPAC) procedure in a wireless communication system.

[0245]

[0246] According to the Network Mobility Improvement Work Item (WI) of Rel-18, to support subsequent CPACs without re-initialization or reconfiguration of CPAC configuration in the network, the following was documented:

[0247] ---------------------------------------------------------------------

[0248] 3. Justification

[0249] When a UE moves from one cell's coverage area to another, a serving cell change must occur. Currently, serving cell changes are triggered by L3 measurements, additional release of the secondary cell (SCell), synchronization for changing the primary cell (PCell) and primary secondary cell (PSCell), and RRC signaling trigger reset. In such cases, L2 (and L1) resets must be completed, resulting in longer delays, higher overhead, and longer downtime than beam switch mobility. The goal of improving L1 / L2 mobility is to enable serving cell changes via L1 / L2 signaling, thereby reducing delays, overhead, and downtime.

[0250] In Rel-17 conditional PSCell change (CPC) and / or conditional PSCell addition (CPA), a CPC / CPA-configured UE must release its CPC / CPA configuration upon completing random access to the target PSCell. Therefore, the UE does not have the opportunity to perform subsequent CPC / CPA operations without prior CPC / CPA reconfiguration and re-initialization in the network. This increases the delay and signaling overhead for cell changes, especially when SCGs are frequently changed during FR2 operation. Therefore, MR-DC, which selectively activates cell groups, aims to enable subsequent CPC / CPA operations after an SCG change without requiring the network to reconfigure and re-initialize CPC / CPA preparation. This reduces signaling overhead and downtime for SCG changes.

[0251] Currently, CHO and MR-DC cannot be configured simultaneously. This limits the usefulness of CHO and MR-DC when MR-DC is configured. If this has not been completed in Rel-17, a mechanism for configuring CHO and MR-DC simultaneously needs to be defined in Rel-18. However, this alone may not be sufficient to optimize MR-DC mobility, as the radio link quality of the conditionally configured PSCell may not be sufficiently good or the conditionally configured PSCell may not be the optimal candidate PSCell when the UE accesses the target PCell. This may impact UE throughput. To mitigate the impact on UE throughput, Rel-18 CHO+MR-DC may consider a CHO that includes a target MCG and multiple candidate SCGs for CPC / CPA.

[0252] 4. Objective

[0253] 4.1 SI or core part WI or testing part WI purpose

[0254] The detailed objectives of the research item are as follows:

[0255] 1. Define the mechanism and procedure of L1 / L2-based inter-cell mobility to reduce mobility delay:

[0256] - Configuration and maintenance of multiple candidate cells to enable rapid application of settings to candidate cells [RAN2, RAN3]

[0257] o Dynamic switching mechanism between candidate serving cells (including SpCell and SCell) for potentially applicable scenarios based on L1 / L2 signaling [RAN2, RAN1]

[0258] o L1 improvements for inter-cell beam management, including L1 measurements and reporting, and beam indications [RAN1, RAN2]

[0259] - Note 1: Early RAN2 engagement is needed, including the possibility of further clarifying the interactions between this bullet and previous bullets.

[0260] - Note 2: Only SSB-based L1 measurements are supported in this release.

[0261] o Timing advance management [RAN1, RAN2]

[0262] o CU-DU interface signaling to support L1 / L2 mobility, if required [RAN3]

[0263] Note 3: If there are specific improvements to FR2, this is not ruled out.

[0264] Note 4: L1 / L2 based inter-cell mobility procedures are applicable to the following scenarios:

[0265] - In standalone mode, CA, and NR-DC cases where there is a change in serving cell within a CG, MCG is given priority.

[0266] - For intra-DU cases and intra-CU inter-DU cases (applicable to standalone mode and CA; no new RAN interfaces are expected)

[0267] - Both within and between frequencies

[0268] - Both FR1 and FR2

[0269] - Source and target cells may or may not be synchronized.

[0270] 2. Definition of NR-DC mechanisms and procedures using selective activation of cell groups (at least for SCG) through L3 enhancements:

[0271] o Allow subsequent cell group changes after CG change without restarting and resetting CPC / CPA [RAN2, RAN3, RAN4]

[0272] Note 5: To minimize the workload of RAN2, an integrated RRC modeling approach for Objectives 1 and 2 may be considered.

[0273] 3. For CHO containing target MCG and target SCG in NR-DC [RAN3]:

[0274] o Define data forwarding optimization; and

[0275] o Define a solution to avoid unnecessary signal exchange between the source MN and the target SN, if necessary.

[0276] 4. CHO definition including target MCG and candidate SCG for CPC / CPA in NR-DC [RAN3, RAN2]:

[0277] o CHO containing target MCG and target SCG is used as the reference.

[0278] 5. Define RRM core requirements for the following as needed [RAN4]:

[0279] o L1 / L2 based inter-cell mobility

[0280] o Enhanced CHO settings covered in the research item

[0281] 6. Define RF requirements to cover L1 / L2 based mobility across frequencies as needed [RAN4].

[0282] 7. Study and define a method to reuse IDLE / INACTIVE mode measurement results reported after or during RRC connection establishment / resumption to improve SCell / SCG setup delay [RAN4, RAN2]

[0283] o Availability and validation of IDLE / INACTIVE mode measurement results to be reported [RAN4]; and

[0284] o Define the relevant RRM requirements [RAN4];

[0285] o Define the corresponding signaling support based on RAN4 results, if required [RAN2].

[0286] Note 6: RAN4 will commence work in collaboration with RAN2 at an appropriate time.

[0287] Note 7: R4-2220415 provides a baseline for future work in RAN4.

[0288] NOTE 8: Except for the above scenarios, improvements to IDLE / INACTIVE mode measurements and UE operation in IDLE / INACTIVE mode are not included in the scope.

[0289] ---------------------------------------------------------------------

[0290] As described above, CPAC configurations prepared on the network side and set in the UE are not used only once. That is, after CPAC is executed, the CPAC configurations can be reused for subsequent CPAC operations to reduce signaling overhead and interruption time for SCG changes in FR2.

[0291] However, simply reusing CPAC configurations raises new data forwarding issues. This is because the secondary node (SN) corresponding to the PSCell selected during the initial CPAC initiation of the UE becomes the new serving SN, and that SN acts as a source for data forwarding to at least one other candidate SN. In Rel-17, conditional configurations are used only once. That is, according to Rel-17, conditional configurations are disabled on both the UE and the network side during CPAC initiation. This means that from the network perspective, if early data forwarding is applied, only data forwarding from the serving node for the UE to the candidate target node(s) needs to be considered before initiation, and if late data forwarding is applied, only data forwarding to the selected target node needs to be considered. However, in subsequent CPACs currently under development for Rel-18, the PSCells selected during CPAC initiation may continue to change over time. Therefore, the network must not only forward data originating from one SN, but also handle forwarding of data originating from another SN at the next point in time.

[0292] In this case, reusing the same forwarding transport network layer addresses (TNLs) assigned by the MN and / or candidate SNs during CPAC preparation may cause the following problems:

[0293] (1) Starting with 4G LTE, the principle of data forwarding between network nodes is that, for downlink (DL), a source node proposes data forwarding, and the target node decides whether to accept it. During CPAC preparation, other candidate SNs can assign forwarding TNLs (e.g., target GTP-U TEID (GPRS Tunneling Protocol - User Plane Tunnel Endpoint Identifier) ​​and / or target IP address) based on the DL forwarding proposal of the source SN. After CPAC is executed and one of the candidate SNs other than the source SN becomes the new serving SN, if the new serving SN reuses the same forwarding TNLs for subsequent data forwarding operations, this principle is violated. This is because the TNLs were assigned based on the data forwarding proposal of the original source SN, not the data forwarding proposal of the new serving SN.

[0294] (2) Early data forwarding behavior may be problematic. For example, assume there are three SNs (e.g., a source SN, candidate SN1, and candidate SN2). Here, the source SN terminated data radio bearer (DRB) is admitted to candidate SN1 and candidate SN2 without any configuration change, and DRB-level data forwarding is accepted. If CPAC is successfully established in the UE, the source SN can perform early data forwarding to other candidate SNs for the corresponding DRB. After CPAC is executed, if candidate SN1 becomes the new serving SN, the new serving SN, candidate SN1, can perform early data forwarding to candidate SN2 for the corresponding DRB. If the same forwarding TNLs assigned by candidate SN2 for the corresponding DRB during the CPAC preparation phase are reused for the data forwarding operation of candidate SN1, which is the new serving SN, then it is possible that packets early forwarded from candidate SN1 may arrive at candidate SN2 together with some packets early forwarded from the source SN. Of course, the early data forwarding of the source SN will be interrupted when CPAC is executed and candidate SN1 becomes the new serving SN. However, packets early forwarded from the source SN before the interruption may arrive at candidate SN2 at a later time when candidate SN1 starts early data forwarding to candidate SN2 for the corresponding DRB. That is, DL PDCP SDUs with SNs assigned by the source SN and DL PDCP SDUs with SNs assigned by candidate SN1 may arrive on the same forwarding TNLs assigned by candidate SN2. At this time, packets forwarded from the source SN may be discarded, and packets forwarded from the new serving SN, candidate SN1, must not be discarded unless indicated by early status transfer of candidate SN1.However, candidate SN2 cannot know which packets arriving through the same forwarding TNLs were forwarded from the source SN and which were forwarded from candidate SN1. Candidate SN2 can also determine whether the packet was forwarded from the source SN or candidate SN1 by decoding the source IP address of the received forwarded packet and comparing it with the source IP address of the packet received at the source SN. However, in the current data forwarding operation, verifying the source of each forwarded packet is not considered at all, which may lead to a burden that increases the complexity of the implementation.

[0295] Accordingly, the present disclosure proposes mechanisms for performing data forwarding operations between candidate SNs in subsequent CPAC procedures. Specifically, the present disclosure proposes a method for enabling seamless early or late data forwarding operations between candidate SNs during subsequent CPAC procedures for a UE.

[0296]

[0297] Figures 8a and 8b illustrate examples of data forwarding support procedures for subsequent CPAC according to embodiments of the present disclosure. Figures 8a and 8b assume that a UE (810) executes CPAC and the serving SN changes from a source SN (S-SN) (820-2) to a candidate SN1 (C-SN) (820-3). The S-SN (820-2) may be referred to as the previous serving SN, and the C-SN1 (820-3) may be referred to as the new serving SN.

[0298] Referring to FIGS. 8A and 8B , in step S801, a subsequent CPAC preparation and UE configuration procedure initiated by an MN or SN may be performed. The subsequent CPAC preparation and UE configuration procedure may include an SN addition procedure and a UE reconfiguration procedure. In one embodiment, the subsequent CPAC preparation and UE configuration procedure may be configured similarly to the CPAC of Rel-17.

[0299] The preparation and UE setup procedures for subsequent CPACs initiated by the MN may include steps 1 to 4b of Figure 10.5.2-3 of TS 37.340. For example, a subsequent CPAC preparation and UE setup procedure initiated by the MN may include: step 1, where the MN sends an SN addition request message to at least one candidate SN; step 2, where the at least one candidate SN sends an SN addition request acknowledgement message to the MN; step 2a, where the MN provides an Xn-U address indication message including Xn-U DL TNL address information to the candidate SN for an SN terminated bearer using MCG resources; step 3, where the UE sends an RRC reconfiguration message including a conditional PSCell change (CPC) setup to the UE; step 4, where the UE applies the RRC reconfiguration message and sends an RRC reconfiguration complete message to the MN; and step 4a, where the MN informs the source SN that the CPC has been setup via the Xn-U address indication procedure.

[0300] In Steps 1 and 2, the MN initiates a conditional SN change by requesting candidate SNs to allocate resources for the UE via an SN addition procedure, and indicates that the request is for CPAC. In addition, the MN provides the candidate SNs with candidate cells recommended by the MN based on recent measurements for selecting and configuring SCG cells, and provides an upper bound on the number of PSCells that the candidate SN can prepare. The candidate SN determines a list of PSCells to be prepared within the list of candidate cells indicated by the MN, and for each prepared PSCell, the candidate SN determines other SCG SCells, and provides the MN with the new corresponding SCG radio resource configuration via an NR RRCReconfiguration** message included in the SN addition request confirmation message along with the prepared PSCell IDs. If data forwarding is required, the candidate SN provides the MN with a data forwarding address. The candidate SN includes a full or delta RRC configuration indication. At this time, the candidate SN can accept or reject each candidate cell listed in the measurement results indicated by the MN, but cannot set alternative candidates.

[0301] In step 3, the RRC Reconfiguration message transmitted to the UE includes the CPC configuration, i.e., a list of RRCReconfiguration* messages and their associated execution conditions. Each RRCReconfiguration* message includes the SCG configuration and possible MCG configuration of the RRCReconfiguration** message received from the candidate SN. The RRC Reconfiguration message may also include updated MCG configurations for the necessary conditional measurement configuration.

[0302] In step 4, the UE stores the CPC settings included in the RRC Reset message and sends an RRC Reset Complete message to the MN. If at least some of the settings included in the RRC Reset message cannot be complied with, the UE may perform a reset failure procedure.

[0303] In step 4a, the source SN may initiate early state transfer procedures and early data forwarding, and PDCP SDU delivery may occur during early data forwarding.

[0304] The preparation and UE setup procedures for subsequent CPACs initiated by SN may include steps 1 to 9b of Figure 10.5.2-4 of TS 37.340. For example, a subsequent CPAC preparation and UE setup procedure initiated by the SN may include: step 1, where the source SN requests an SN change to the MN; step 2, where the MN sends an SN addition request message to at least one candidate SN; step 3, where the at least one candidate SN sends an SN addition request acknowledgement message to the MN; step 3a, where the MN provides an Xn-U address indication message containing Xn-U DL TNL address information to the candidate SN for an SN termination bearer using MCG resources; step 4, where the MN sends an SN modification request message to the source SN; step 5, where the source SN sends an SN modification request acknowledgement message to the MN; step 6, where the UE sends an RRC reconfiguration message containing a conditional PSCell change (CPC) configuration to the UE; and step 7, where the UE applies the RRC reconfiguration message and sends an RRC reconfiguration complete message to the MN; and step 7, where the MN sends an SN change acknowledgement message to the source SN. The method may include step 8 of transmitting, step 9a of the source SN transmitting a message to the MN indicating that SN modification is required, and step 9b of the MN transmitting an RRC reconfiguration message to the UE.

[0305] In step 1, the source SN initiates a conditional SN change procedure by sending an SN change required message to the MN, which includes a CPC initiation indication. The SN change required message may include candidate node IDs, SCG configuration (for supporting delta configuration), measurement results for cells that are not CPC candidates, and a proposed PSCell candidate list recommended by the source SN. The proposed PSCell candidate list may include execution conditions, an upper limit on the number of PSCells that each candidate SN can prepare, and SCG measurement configurations for CPC (e.g., a measurement ID to be used for CPC).

[0306] In steps 2 and 3, the MN requests resource allocation for the UE to each candidate SN through the SN addition procedure, and indicates that the request is for CPAC. At this time, the SN addition request message may include the measurement results received from the source SN and the proposed PSCell candidate list. The candidate SN determines the PSCell list to prepare within the source proposed PSCell list, determines an SCG SCell for each prepared PSCell, and provides the MN with the new corresponding SCG radio resource configuration through the NR RRCReconfiguration** message included in the SN addition request confirmation message. If data forwarding is required, the candidate SN provides the MN with a data forwarding address. At this time, the candidate SN includes a full or delta RRC configuration indication and a list of prepared PSCell IDs for the MN. The candidate SN may accept or reject each candidate cell proposed by the source SN, but may not configure alternative candidates.

[0307] In steps 4 and 5, the MN may indicate the candidate PSCells accepted by each candidate SN to the source SN using the SN Modification Request message before configuring the UE. For example, if the candidate SN has not accepted all the candidate PSCells proposed by the source SN, the candidate PSCell information accepted by the candidate SN may be notified to the source SN. The source SN, upon receiving the SN Modification Request message, may provide the MN with updated measurement settings and / or contention conditions. Steps 4 and 5 may be omitted.

[0308] In step 6, the RRC Reconfiguration message transmitted to the UE includes the CPC configuration, i.e., a list of RRCReconfiguration* messages and their associated execution conditions. Each RRCReconfiguration* message includes the SCG configuration and possible MCG configuration of the RRCReconfiguration** message received from the candidate SN. The RRC Reconfiguration message may also include the NR RRCReconfiguration*** message generated by the source SN and the updated MCG configuration for the necessary conditional measurement configuration.

[0309] In step 7, the UE stores the CPC configuration included in the RRC reconfiguration message and sends an RRC reconfiguration complete message to the MN. The RRC reconfiguration complete message may include an NR RRCReconfigurationComplete*** message. If at least some of the configurations included in the RRC reconfiguration message cannot be complied with, the UE may perform a reconfiguration failure procedure. In step 8, the MN may use an SN change confirm message to inform the source SN of the SN RRCReconfigurationComplete*** message. If steps 4 and 5 are omitted, the SN change confirm message may include information related to the candidate PSCells accepted by each candidate SN. The MN sends the SN change confirm message to the source SN to indicate that the CPC is ready, in which case the source SN continues to provide user data to the UE. When early data forwarding is applicable, the MN informs the source SN of the data forwarding addresses received from the candidate SN(s), and the source SN can initiate early data forwarding with an early state transfer procedure, if applicable. PDCP SDU delivery can occur during early data forwarding. If multiple candidate SNs are prepared, the MN includes a list of target SN IDs and a list of data forwarding addresses for the source SN.

[0310] In steps 9a and 9b, the source SN may send an SN Modification Required message to the MN to trigger an update of the CPC execution conditions and / or the corresponding SCG measurement settings for the CPC. In this case, the MN may reset the UE.

[0311] After the subsequent CPAC preparation and UE configuration procedures initiated by the MN or SN as described above are performed, in step S803, the UE (810) transmits an RRC reconfiguration complete* message to the MN (820-1). The RRC reconfiguration complete message may include the SN identification information of the selected candidate PSCell and an SN RRC reconfiguration complete** message for the selected candidate PSCell. At this time, the candidate PSCell may be selected based on an execution condition for CPAC. Specifically, the UE (810) may check a plurality of candidate PSCells based on the CPAC configuration, and may check whether the CPAC execution condition for the plurality of candidate PSCells is satisfied. If the execution condition for any one of the plurality of candidate PSCells is satisfied, the UE (810) may select the corresponding candidate PSCell. The UE (810) may apply an RRC reset message corresponding to the selected candidate PSCell and transmit an SN RRC reset complete message corresponding to the selected candidate PSCell and an RRC reset complete message including SN identification information of the selected candidate PSCell to the MN (820-1).

[0312] In step S805, the UE (810) performs a random access procedure for C-SN1 (820-3) to which the selected PSCell belongs. That is, the UE (810) can perform synchronization with the selected PSCell.

[0313] At step S807, MN (820-1) confirms that CPAC has been performed for PSCell belonging to C-SN1 (820-3) of UE (810) based on the RRC Reset Complete message. At this time, MN (820-1) can recognize that C-SN1 (820-3) is a new serving SN. For example, MN (820-1) can confirm that C-SN1 (820-3) is selected as the new serving SN of UE (810) based on at least one of the SN identification information of the selected candidate PSCell included in the RRC Reset Complete message and the SN RRC Reset Complete message corresponding to the selected candidate PSCell.

[0314] In step S809, MN (820-1) transmits a data forwarding information request message to C-SN1 (820-3). The data forwarding information request message may include identification information of the selected PSCell. That is, MN (820-1) may transmit a message requesting information related to a data forwarding proposal to C-SN1 (820-3), the new serving SN to which the selected PSCell belongs.

[0315] In step S811, C-SN1 (820-3) transmits a data forwarding information response message to MN (820-1). The data forwarding information response message may include information related to a data forwarding proposal for C-SN1 terminated PDU sessions and / or DRBs (C-SNI terminated PDU sessions / DRBs). Here, the C-SN1 terminated PDU sessions and / or DRBs include data radio bearers for which PDCP is located in C-SN1 in the MR-DC. The information related to the data forwarding proposal may include at least one of information related to an uplink forwarding proposal and information related to a downlink forwarding proposal. For example, the information related to the data forwarding proposal may include information that C-SN1 (820-3) proposes uplink and / or downlink forwarding to another SN in case C-SN1 (820-3) operates as a new serving SN.

[0316] At step S813, MN (820-1) transmits a data forwarding request and update admission message to other SNs (e.g., S-SN (820-2) and C-SN2 (820-4)) based on information related to the data forwarding proposal received from C-SN1 (820-3). The data forwarding request and update admission message may include information related to the data forwarding proposal for MN-terminated PDU sessions and / or DRBs, and / or information related to the data forwarding proposal for C-SN1-terminated PDU sessions and / or DRBs.

[0317] At step S815, each of the S-SN (820-2) and the C-SN2 (820-4) transmits a data forwarding response message to the MN (820-1). The data forwarding response message may include information related to new forwarding TNLs allocated based on information related to the data forwarding proposal included in the data forwarding request and update acknowledge messages. Specifically, each of the S-SN (820-1) and the C-SN2 (820-3) may determine whether to accept the data forwarding proposal by considering information related to the data forwarding proposal for the MN-terminating PDU sessions and / or DRBs, or information related to the data forwarding proposal for the C-SN1-terminating PDU sessions and / or DRBs. When each of S-SN (820-1) and C-SN2 (820-3) accepts data forwarding, it may allocate forwarding TNLs for the corresponding PDU sessions and / or DRBs and transmit a data forwarding response message including information related to the allocated forwarding TNLs to MN (820-1). The information related to the forwarding TNLs may include at least one of a target GTP-U TEID (GPRS tunneling protocol - user plane tunnel endpoint identifier) ​​or a target IP address. According to one embodiment, if MN (820-1) knows in advance during the CPAC preparation phase that the prepared candidate PSCell of the corresponding SN did not allow the corresponding PDU sessions and / or DRBs, i.e., the PDU sessions and DRBs to which C-SN1 (820-3) proposed data forwarding, it may omit steps S813 and S815 for the corresponding SN. If there are PDU sessions or DRBs relocated to the MN during the CPAC preparation phase for prepared candidate PSCells of SNs other than C-SN1 and data forwarding for them is proposed by C-SN1, the MN may decide to accept and allocate the corresponding forwarding TNLs.On the other hand, for a prepared candidate PSCell belonging to a SN other than the new serving SN, C-SN1, if the PDU session and / or DRB is established in the MN and the selected PSCell is to be relocated to that SN during the CPAC preparation phase to serve the UE, the MN may generate a forwarding proposal and request data forwarding to that SN.

[0318] At step S817, MN (820-1) transmits an Xn-U address indication message to S-SN (820-2). The Xn-U address indication message may indicate the stop of early data forwarding and the start of late data forwarding to C-SN1 (820-3), which is a new serving SN. That is, MN (820-1) may stop the triggered early data forwarding in S-SN (820-2) by transmitting the Xn-U address indication to S-SN (820-2), and may transmit information related to forwarding TNLs previously assigned by C-SN1 (820-3) so that S-SN (820-2) may start late data forwarding to C-SN1 (820-3), which is selected as a new serving SN.

[0319] In step S819, the MN (820-1) provides information related to new forwarding TNLs allocated by the MN and / or at least one other SN to the new serving SN, C-SN1 (820-3). The MN (820-1) may provide the C-SN1 (820-3) with information related to new forwarding TNLs allocated by the MN and / or at least one other SN (e.g., S-SN (820-2) and C-SN2 (820-4)) for data forwarding of the C-SN1 (820-3) for PDU sessions and / or DRBs associated with the selected PSCell. The new forwarding TNLs may include forwarding TNLs allocated in the S-SN (820-2) and C-SN2 (820-4) based on the data forwarding proposal of the C-SN1 (820-3). At this time, MN (820-1) can transmit the RRC reconfiguration completion message of SCG received from UE (810) to C-SN1 (820-3). Here, the RRC reconfiguration completion message of SCG received from UE (810) may be an SN RRC reconfiguration completion message included in the RRC reconfiguration completion message received in step S803.

[0320] At step S821, S-SN (820-2) transmits an SN status transfer message to MN (820-1). MN (820) transmits the SN status transfer message to C-SN1 (820-3), which is a new serving SN.

[0321] In step S823, S-SN (820-2) initiates late data forwarding. Late data forwarding may be performed from S-SN (820-2) to C-SNI (820-3). For DRBs to which PDCP state preservation is applied, after C-SN1 (820-3) receives an SN state transfer message from S-SN (820-2), early data forwarding may occur from C-SN1 (830-3) to candidate PSCells in other SNs toward the forwarding TNLs received in step S819. DRBs to which PDCP state preservation is applied may include RLC UM (unacknowledge mode) / AM (acknowledge mode) DRBs to which early data forwarding is applied or RLC AM bearers in which early data forwarding is not performed.

[0322] In the embodiment described with reference to FIGS. 8A and 8B, steps S809 to S815 may be performed during the CPAC preparation procedure. In this case, the SN addition procedure or the SN modification procedure may be improved so that the MN retrieves data forwarding proposals for approved PDU sessions and / or DRBs for each candidate PSCell. The retrieved forwarding proposals may then be utilized when the candidate PSCell is selected for subsequent access. Alternatively, the SN addition procedure or the SN modification procedure may be improved so that it retrieves information related to at least one forwarding TNL to be utilized for subsequent CPAC operations when a candidate PSCell in another SN is selected for access.

[0323] In one embodiment, during steps S809 to S815, the MN may request PDU session modification for candidate PSCells other than the selected PSCell. In this case, the CPAC settings previously set for the UE may be updated and reset to suit the UE.

[0324] In one embodiment, when steps S809 and S811 are performed after CPAC execution, the SN modification procedure may be used to retrieve forwarding proposals from the selected PSCell. That is, the MN may retrieve allowed PDU sessions or DRBs for the selected PSCell using the SN modification procedure during the CPAC preparation procedure.

[0325] In one embodiment, when steps S813 and S815 are performed after CPAC execution, the SN modification procedure may be utilized and improved so that the MN requests data forwarding to candidate SNs other than the selected SN and retrieves information related to new forwarding TNLs. If a candidate SN other than the selected SN is excluded from the candidates for subsequent CPAC operations for the UE, in steps S813 and S815, the MN may perform a release procedure for SNs that do not require data forwarding requests using the SN release procedure.

[0326] According to one embodiment, the delivery of the RRC reconfiguration complete message of the UE SCG to the selected SN may be performed separately from step S819 using the legacy SN reconfiguration complete procedure.

[0327]

[0328] As described above, the present disclosure proposes a device and method for supporting a subsequent CPAC operation in a network system. According to one embodiment, the network system may include network nodes (e.g., an MN and at least one SN) interconnected via an X2 interface or an Xn interface to support a UE for a subsequent CPAC operation. According to one embodiment, a preparation procedure for a subsequent CPAC for the UE may be performed between the MN and at least one SN.

[0329] In one embodiment, the MN may retrieve data forwarding proposals from the candidate PSCell for PDU sessions or DRBs approved by the candidate PSCell. The retrieved data forwarding proposals may be used based on which PSCell is selected for future access by the UE. In one embodiment, the MN may request data forwarding from the candidate PSCell and provide the data forwarding proposal together with data forwarding proposals retrieved from at least one other candidate PSCell. In one embodiment, the MN may retrieve information related to forwarding TNLs from the candidate PSCell to be used for subsequent CPAC if another candidate PSCell is selected for access by the UE.

[0330] In one embodiment, after a candidate PSCell is selected for UE access, the MN may retrieve data forwarding proposals from the candidate PSCell. In another embodiment, after another candidate PSCell is selected for UE access, the MN may request data forwarding to the candidate PSCell. In another embodiment, after another candidate PSCell is selected for UE access, the MN may retrieve information related to forwarding TNLs from the candidate PSCell.

[0331] In one embodiment, the MN may request to modify the previous grant result toward at least one other candidate PSCell other than the PSCell selected for the UE's access, and may reset the CPAC settings previously set for the UE.

[0332] In one embodiment, the MN may optionally provide the UE with information regarding data forwarding TNLs allocated by at least one other candidate PSCell to the candidate PSCell selected for access. The data forwarding proposal of the selected PSCell may be considered.

[0333] According to one embodiment, the SN of the candidate PSCell selected for access of the UE may initiate early data forwarding toward at least one other candidate PSCell among the candidate SNs for DRBs to which PDCP state preservation is applied, after receiving an SN status transfer message from the previous serving PSCell. The DRBs to which PDCP state preservation is applied may include RLC UM / AM DRBs to which early data forwarding was previously applied, or RLC AM bearers if early data forwarding was not performed on the previous serving PSCell.

[0334]

[0335] Figure 9 illustrates an example of a procedure for obtaining information related to a data forwarding proposal according to an embodiment of the present disclosure. Figure 9 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 MN (820-1) described in Figures 8a and 8b.

[0336] Referring to FIG. 9, in step S901, a first network node transmits an SN addition request message. The first network node may transmit the SN addition request message to at least one second network node during a preparation phase for a subsequent CPAC. The second network node may be a candidate SN. The first network node may request at least one second network node to provide information related to a data forwarding proposal using the SN addition request message. The SN addition request message may be a message requesting resource allocation for a UE to at least one candidate SN and indicating that the request is for CPAC.

[0337] In step S903, the first network node receives an SN addition request acknowledge message. In response to the SN addition request message, the first network node may receive an SN addition request acknowledge message from at least one second network node. The SN addition request acknowledge message may include information related to a data forwarding proposal of a second network node that is a candidate SN for a subsequent CPAC. The information related to the data forwarding proposal of the second network node may include at least one of information related to an uplink forwarding proposal for second network node termination PDU sessions and / or DRBs or information related to a downlink forwarding proposal. Here, the second network node termination PDU sessions and / or DRBs include data radio bearers in which the PDCP is located in the second network node in the MR-DC. The information related to the data forwarding proposal of the second network node may be used for data forwarding when the PSCell of the second network node is selected for access of a terminal in the subsequent CPAC. That is, information related to the data forwarding proposal of the second network node can be utilized when the second network node becomes a new serving SN. For example, if the PSCell of the second network node satisfies the execution conditions set for the terminal, the PSCell of the second network node can be selected by the terminal. In this case, data forwarding can be performed based on information related to the data forwarding proposal of the second network node and information related to new forwarding TNLs of other network nodes allocated based on the information related to the data forwarding proposal.

[0338] According to one embodiment, the first network node may transmit information related to the data forwarding proposal of the candidate SN to other network nodes (e.g., the source SN and / or other candidate SNs), and obtain information related to new forwarding TNLs allocated based on the information related to the data forwarding proposal of the candidate SN from each of the other network nodes. The operation of obtaining information related to the new forwarding TNLs may be performed during the CPAC preparation phase, or may be performed after the CPAC preparation and UE configuration procedures are performed. The first network node may provide information related to the obtained new forwarding TNLs to the second network node.

[0339]

[0340] FIG. 10 illustrates an example of a procedure for transmitting information related to a data forwarding proposal according to an embodiment of the present disclosure. FIG. 10 illustrates a method performed by a second network node. The second network node may include a candidate SN. For example, the second network node may be candidate SN1 (820-3) described in FIGS. 8A and 8B .

[0341] Referring to FIG. 10, in step S1001, a second network node receives an SN addition request message. The second network node may receive an SN addition request message for preparation of a subsequent CPAC from a first network node. The first network node may be an MN. The SN addition request message may include a message requesting the provision of information related to a data forwarding proposal. The SN addition request message may be a message requesting resource allocation for the UE from at least one candidate SN and indicating that the request is for CPAC.

[0342] In step S1003, the second network node transmits an SN addition request confirmation message. In response to the SN addition request message, the second network node may transmit an SN addition request confirmation message to the first network node. The SN addition request confirmation message may include information related to a data forwarding proposal of the second network node for a subsequent CPAC. For example, the second network node may transmit the SN addition request confirmation message including information related to the forwarding proposal of the second network node to the first network node in preparation for a case where the PSCell of the second network node is selected for access of a terminal in the future by a subsequent CPAC. The information related to the data forwarding proposal may include at least one of information related to an uplink forwarding proposal or information related to a downlink forwarding proposal for the second network node's termination PDU sessions and / or DRBs. The information related to the data forwarding proposal of the second network node may be used when the second network node becomes a new serving SN. For example, if the PSCell of the second network node satisfies the execution conditions set for the terminal, the PSCell of the second network node may be selected by the terminal. At this time, data forwarding may be performed based on information related to the data forwarding proposal of the second network node and information related to new forwarding TNLs of other network nodes allocated based on the information related to the data forwarding proposal.

[0343] In one embodiment, the second network node may receive information from the first network node regarding new forwarding TNLs allocated by other network nodes. The new forwarding TNLs may be allocated based on information regarding the second network node's data forwarding proposal.

[0344]

[0345] 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).

[0346] 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.

[0347] 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.

[0348] 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.

[0349] 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 request message for adding a secondary node (SN) to a second network node; and A step of receiving an SN addition request confirmation message from the second network node, A method in which the above SN addition request confirmation message includes information related to a data forwarding proposal of the second network node.

2. In claim 1, A method in which information related to a data forwarding proposal of the second network node includes information proposing data forwarding for at least one of a second network node termination PDU (protocol data unit) session or a DRB (data radio bearer).

3. In claim 1, A method in which information related to a data forwarding proposal of the second network node is used based on which the second network node is selected for access.

4. In claim 1, A method in which information related to a data forwarding proposal of the second network node includes at least one of information related to a downlink forwarding proposal and information related to an uplink forwarding proposal.

5. In claim 1, The above SN addition request message is sent for subsequent conditional primary secondary cell (PSCell) addition or change (CPAC). The second network node, a method including a candidate SN.

6. In claim 1, A step of obtaining information related to at least one forwarding TNL (transport network layer address) based on information related to a data forwarding proposal of the second network node; and Further comprising a step of transmitting information related to at least one of the acquired forwarding TNLs to the second network node, A method wherein said at least one forwarding TNL is allocated based on information related to a data forwarding proposal of said second network node by at least one of said first network node or at least one other network node.

7. In claim 6, The step of obtaining information related to at least one forwarding TNL is: a step of transmitting information related to the data forwarding proposal of the second network node to at least one other network node; and A method comprising the step of receiving information related to forwarding TNLs allocated from at least one other network node.

8. In claim 1, The above SN addition request message includes information related to the candidate PSCell.

9. A method performed by a second network node in a wireless communication system, A step of receiving a SN (secondary node) addition request message from a first network node; and A step of transmitting an SN addition request confirmation message to the first network node, A method in which the above SN addition request confirmation message includes information related to a data forwarding proposal of the second network node.

10. In claim 9, Further comprising the step of receiving information related to at least one forwarding TNL (transport network layer address), A method wherein said at least one forwarding TNL is allocated based on information related to a data forwarding proposal of said second network node from at least one of said first network node or another network node.

11. 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 request message to add a secondary node (SN) to the second network node, Control to receive an SN addition request confirmation message from the second network node, The above SN addition request confirmation message is a first network node that includes information related to a data forwarding proposal of the second network node.

12. 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 request message to add a secondary node (SN) from the first network node, Control to send an SN addition request confirmation message to the first network node, The above SN addition request confirmation message is a second network node that includes information related to a data forwarding proposal of the second network node.

13. 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 sending a request message for adding a secondary node (SN) to a second network node; and A step of receiving an SN addition request confirmation message from the second network node, A communication device in which the above SN addition request confirmation message includes information related to a data forwarding proposal of the second network node.

14. 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: Send a request message to add a secondary node (SN) to the second network node, Control to receive an SN addition request confirmation message from the second network node, The above SN addition request confirmation message is a computer-readable medium including information related to a data forwarding proposal of the second network node.

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