Method and apparatus for supporting handover request in wireless communication system

Abstract

The present disclosure is to support a handover request in a wireless communication system. A method of a target master node (MN) may comprise the steps of: receiving at least one first message related to a conditional handover request of a terminal from a source MN of the terminal; transmitting a second message related to an SN addition request to a first SN among candidate target SNs for the terminal; and receiving a third message related to the SN addition request from the first SN, wherein the second message includes at least one of a list of candidate target primary cells (PCells) determined for the first SN among candidate target PCells requested by the source MN for conditional handover, and information related to the number of candidate primary secondary cells (PSCells) allowed for configuration thereof, and the third message includes information related to candidate PSCell configuration prepared by the first SN on the basis of the second message.

Description

Method and device for supporting handover requests in a wireless communication system

[0001] The following description relates to a wireless communication system, and more particularly, to a method and apparatus for supporting a conditional handover request in a wireless communication system.

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

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

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

[0005] The present disclosure relates to a device and method for supporting multiple conditional handover (CHO) requests in a wireless communication system.

[0006] The present disclosure relates to a device and method for supporting multiple conditional handover requests (CHO requests) using a single conditional primary secondary cell (PSCell) addition (CPA) procedure in a wireless communication system.

[0007] The present disclosure relates to a device and method for requesting conditional PSCell addition to at least one candidate target secondary node (SN) based on a plurality of conditional handover requests in a wireless communication system.

[0008] The present disclosure relates to a device and method for providing a list of candidate target PCells determined for at least one candidate target SN in a wireless communication system.

[0009] The present disclosure relates to a device and method for providing information related to an allowed number of candidate PSCell configurations to at least one candidate target SN in a wireless communication system.

[0010] The present disclosure relates to a device and method for limiting the number of candidate PSCell configurations to be prepared by at least one candidate target SN in a wireless communication system.

[0011] The present disclosure relates to a device and method for preparing at least one candidate PSCell configuration based on an allowed number of candidate PSCell configurations in a wireless communication system.

[0012] The present disclosure relates to a device and method for transmitting at least one candidate PSCell configuration prepared based on an allowed number of candidate PSCell configurations in a wireless communication system.

[0013] The present disclosure relates to a device and method for transmitting information indicating a relationship between at least one prepared candidate PSCell configuration and a candidate target PCell 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, the method includes the steps of receiving at least one first message related to a conditional handover request of the terminal from a source MN (master node) of the terminal, transmitting a second message related to an SN addition request to a first SN among candidate target secondary nodes (SNs) for the terminal, and receiving a third message related to the SN addition request from the first SN, wherein the second message includes at least one of a list of candidate target PCells (primary cells) determined for the first SN among candidate target PCells (primary cells) requested by the source MN for conditional handover, or information related to an allowed number for candidate primary secondary cell (PSCell) configuration, and the third message may include information related to a candidate PSCell configuration prepared by the first SN based on the second message.

[0016] As an example of the present disclosure, the method includes the steps of receiving a second message related to an SN addition request from a target MN (master node) of a terminal, and transmitting a third message related to the SN addition request to the target MN, wherein the second message includes at least one of a list of candidate target PCells (primary cells) determined for a first SN among candidate target PCells (primary cells) requested by a source MN for conditional handover, or information related to an allowed number for candidate primary secondary cell (PSCell) configuration, and the third message may include information related to a candidate PSCell configuration prepared by the first SN based on the second message.

[0017] As an example of the present disclosure, a device includes a transceiver, and a processor connected to the transceiver, wherein the processor receives at least one first message related to a conditional handover request of the terminal from a source MN (master node) of the terminal, transmits a second message related to an SN addition request to a first SN among candidate target SNs for the terminal, and receives a third message related to the SN addition request from the first SN, wherein the second message includes at least one of a list of candidate target PCells (primary cells) determined for the first SN among candidate target PCells (primary cells) requested by the source MN for conditional handover, or information related to an allowed number for candidate primary secondary cell (PSCell) configuration, and the third message may include information related to a candidate PSCell configuration prepared by the first SN based on the second message.

[0018] As an example of the present disclosure, a device includes a transceiver and a processor connected to the transceiver, the processor controls to receive a second message related to an SN addition request from a target MN (master node) of a terminal, and to transmit a third message related to the SN addition request to the target MN, the second message including at least one of a list of candidate target PCells (primary cells) determined for a first SN among candidate target PCells (primary cells) requested by a source MN for a conditional handover, or information related to an allowed number for candidate primary secondary cell (PSCell) configuration, and the third message may include information related to a candidate PSCell configuration prepared by the first SN based on the second message.

[0019] As an example of the present disclosure, a communication device includes at least one processor, and at least one memory connected to the at least one processor and storing instructions that direct operations when executed by the at least one processor, the operations including: receiving at least one first message related to a conditional handover request of the terminal from a source master node (MN) of the terminal; transmitting a second message related to an SN addition request to a first SN among candidate target SNs for the terminal; and receiving a third message related to the SN addition request from the first SN, wherein the second message includes at least one of a list of candidate target PCells (primary cells) determined for the first SN among candidate target PCells requested by the source MN for conditional handover, or information related to an allowed number for a candidate primary secondary cell (PSCell) configuration, and the third message may include information related to a candidate PSCell configuration prepared by the first SN based on the second message.

[0020] As an example of the present disclosure, a non-transitory computer-readable medium storing at least one instruction, wherein the at least one instruction, when executed by at least one processor, causes a communication device to perform operations, the operations including: receiving at least one first message related to a conditional handover request of the terminal from a source master node (MN) of the terminal; transmitting a second message related to an SN addition request to a first SN among candidate target SNs for the terminal; and receiving a third message related to the SN addition request from the first SN, wherein the second message includes at least one of a list of candidate target PCells (primary cells) determined for the first SN among candidate target PCells (primary cells) requested by the source MN for a conditional handover, or information related to an allowed number for candidate primary secondary cell (PSCell) configuration, and wherein the third message includes information related to a list of candidate target PCells prepared by the first SN based on the second message. It may contain information related to the candidate PSCell configuration.

[0021] The above-described aspects of the present disclosure are only some of the preferred embodiments of the present disclosure, and various embodiments reflecting the technical features of the present disclosure can be derived and understood by a person having ordinary skill in the art based on the detailed description of the present disclosure to be described below.

[0022] The following effects may be achieved by embodiments based on the present disclosure.

[0023] The present disclosure can support multiple conditional handover requests in a wireless communication system.

[0024] 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.

[0025] 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.

[0026] Figure 1 illustrates an example of a communication system applicable to the present disclosure.

[0027] FIG. 2 illustrates an example of a user equipment (UE) applicable to the present disclosure.

[0028] 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.

[0029] FIG. 4 illustrates an example of a general architecture of a 5G (5th generation) system applicable to the present disclosure.

[0030] Figures 5a and 5b illustrate a conditional handover procedure with a secondary node.

[0031] FIGS. 6A and 6B illustrate examples of a procedure for supporting multiple conditional handover requests according to an embodiment of the present disclosure.

[0032] FIG. 7 illustrates an example of a procedure for receiving PSCell configuration information according to an embodiment of the present disclosure.

[0033] FIG. 8 illustrates an example of a procedure for transmitting PSCell configuration information according to an embodiment of the present disclosure.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] 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).

[0040] 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.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] 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.

[0045] 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.

[0046] 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).

[0047] 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.

[0048] 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.

[0049] 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.

[0050] Hereinafter, this specification is described based on the terms defined above.

[0051] 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).

[0052] 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.

[0053]

[0054] Communication system applicable to the present disclosure

[0055] 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.

[0056] 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.

[0057] Figure 1 illustrates an example of a communication system applied to the present disclosure.

[0058] 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.

[0059] 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).

[0060] 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.

[0061] Figure 2 illustrates an example of a UE applicable to the present disclosure.

[0062] 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).

[0063] 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).

[0064] 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.

[0065] 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.

[0066] 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).

[0067] 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).

[0068] 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.

[0069] 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).

[0070] 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.

[0071] 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.

[0072] 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.

[0073] 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.

[0074] 5G system architecture applicable to the present disclosure

[0075] 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.

[0076] 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.

[0077] - 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).

[0078] 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.

[0079] 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).

[0080] 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.

[0081] 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.

[0082] 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.

[0083] 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).

[0084] The UPF acts as a boundary between the next generation RAN (NG-RAN) and the core network, and is an element that maintains the data path between the gNB and the SMF. In addition, the UPF acts as a mobility anchor point when the UE moves across the area served by the gNB. The UPF can perform the function of handling PDUs. For mobility within the NG-RAN (e.g., NG-RAN defined after 3GPP Release-15), the UPF can route packets. In addition, the UPF can also act as an anchor point for mobility with other 3GPP networks (e.g., RAN defined before 3GPP Release-15), such as UTRAN (UMTS (universal mobile telecommunications system) terrestrial radio access network), E-UTRAN (evolved-UTRAN), or GERAN (GSM (global system for mobile communication) / EDGE (enhanced data rates for global evolution) radio access network). A UPF may correspond to the termination point of a data interface toward a data network.

[0085] 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).

[0086] 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.

[0087] 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.

[0088] Figure 3 illustrates an example of functional separation of NG-RAN and 5GC (5th generation core) applicable to the present disclosure.

[0089] 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.

[0090] The UPF node functions as a gateway through which user data is transmitted and received.

[0091] The authentication server function (AUSF) authenticates and manages UEs. The Network Slice Selection Function (NSSF) is a node for network slicing, as described below.

[0092] The network exposure function (NEF) provides a mechanism to securely expose the services and functions of the 5G core.

[0093]

[0094] 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.

[0095] 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.

[0096] 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.

[0097] 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.

[0098] 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.

[0099]

[0100] Specific embodiments of the present disclosure

[0101] The present disclosure relates to a device and method for supporting a conditional handover (CHO) request in a wireless communication system. Specifically, the present disclosure relates to a device and method for supporting multiple conditional handover requests (CHO requests) using a single conditional primary secondary cell (PSCell) addition (CPA) procedure in a wireless communication system.

[0102]

[0103] In the present disclosure, a conditional handover (CHO) includes a handover that is executed only when an execution condition is met, and a conditional primary secondary cell addition (CPA) procedure includes a PSCell addition procedure that is executed only when a PSCell addition execution condition is met.

[0104] A master cell group (MCG) is a group of serving cells associated with a master node (MN) in multi-radio dual connectivity (MR-DC), including a primary cell (PCell) and optionally one or more secondary cells (SCells). The master node is a radio access node that provides control plane connectivity to a core network in MR-DC, and may include at least one of a master eNB of E-UTRA-NR dual connectivity (EN-DC), a master ng-eNB of NG-RAN E-UTRA-NR dual connectivity (NGEN-DC), or a master gNB of NR-NR dual connectivity (NR-DC) and NR-E-UTRA dual connectivity (NE-DC). The PCell is a basic cell of the master cell group.

[0105] A secondary cell group (SCG) is a group of serving cells associated with a secondary node (SN) in an MR-DC, including a PSCell and optionally one or more SCells. A secondary node is a radio access node without control plane connectivity to a core network in an MR-DC, and can provide additional resources to a UE. A secondary node may include at least one of a secondary en-gNB of an EN-DC, a secondary ng-eNB of an NE-DC, or a secondary gNB of an NR-DC and an NGEN-DC. A PSCell is a primary cell of a secondary cell group.

[0106] According to the Network Mobility Improvement Work Item (WI) of Rel-18, the following was documented to extend Conditional Handover (CHO) using the NR-DC architecture defined in Rel-17.

[0107] ---------------------------------------------------------------------

[0108] 3. Justification

[0109] 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.

[0110] 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.

[0111] 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.

[0112] 4. Objective

[0113] 4.1 SI or core part WI or testing part WI purpose

[0114] The detailed objectives of the research item are as follows:

[0115] 1. Define the mechanism and procedure of L1 / L2-based inter-cell mobility to reduce mobility delay:

[0116] - Configuration and maintenance of multiple candidate cells to enable rapid application of settings to candidate cells [RAN2, RAN3]

[0117] o Dynamic switching mechanism between candidate serving cells (including SpCell and SCell) for potentially applicable scenarios based on L1 / L2 signaling [RAN2, RAN1]

[0118] o L1 improvements for inter-cell beam management, including L1 measurements and reporting, and beam indications [RAN1, RAN2]

[0119] - Note 1: Early RAN2 engagement is needed, including the possibility of further clarifying the interactions between this bullet and previous bullets.

[0120] - Note 2: Only SSB-based L1 measurements are supported in this release.

[0121] o Timing advance management [RAN1, RAN2]

[0122] o CU-DU interface signaling to support L1 / L2 mobility, if required [RAN3]

[0123] Note 3: If there are specific improvements to FR2, this is not ruled out.

[0124] Note 4: L1 / L2 based inter-cell mobility procedures are applicable to the following scenarios:

[0125] - In standalone mode, CA, and NR-DC cases where there is a change in serving cell within a CG, MCG is given priority.

[0126] - For intra-DU cases and intra-CU inter-DU cases (applicable to standalone mode and CA; no new RAN interfaces are expected)

[0127] - Both within and between frequencies

[0128] - Both FR1 and FR2

[0129] - Source and target cells may or may not be synchronized.

[0130] 2. Definition of NR-DC mechanisms and procedures using selective activation of cell groups (at least for SCG) through L3 enhancements:

[0131] o Allow subsequent cell group changes after CG change without restarting and resetting CPC / CPA [RAN2, RAN3, RAN4]

[0132] Note 5: To minimize the workload of RAN2, an integrated RRC modeling approach for Objectives 1 and 2 may be considered.

[0133] 3. For CHO containing target MCG and target SCG in NR-DC [RAN3]:

[0134] o Define data forwarding optimization; and

[0135] o Define a solution to avoid unnecessary signal exchange between the source MN and the target SN, if necessary.

[0136] 4. CHO definition including target MCG and candidate SCG for CPC / CPA in NR-DC [RAN3, RAN2]:

[0137] o CHO containing target MCG and target SCG is used as the reference.

[0138] 5. Define RRM core requirements for the following as needed [RAN4]:

[0139] o L1 / L2 based inter-cell mobility

[0140] o Enhanced CHO settings covered in the research item

[0141] 6. Define RF requirements to cover L1 / L2 based mobility across frequencies as needed [RAN4].

[0142] 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]

[0143] o Availability and validation of IDLE / INACTIVE mode measurement results to be reported [RAN4]; and

[0144] o Define the relevant RRM requirements [RAN4];

[0145] o Define the corresponding signaling support based on RAN4 results, if required [RAN2].

[0146] Note 6: RAN4 will commence work in collaboration with RAN2 at an appropriate time.

[0147] Note 7: R4-2220415 provides a baseline for future work in RAN4.

[0148] 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.

[0149] ---------------------------------------------------------------------

[0150] That is, in a conditional handover of Rel-17 with NR-DC, each candidate PCell configuration (e.g., MCG configuration) can be associated with one SCG configuration. Therefore, when a conditional handover is executed for a specific target PCell, the SCG configuration associated with that target PCell configuration can be used for NR-DC operation with that selected target PCell. This is documented in Section 10.19 of TS 37.340, which defines inter-master node conditional handover (inter-MN CHO).

[0151] Figures 5a and 5b illustrate a conditional handover procedure with a secondary node. Figure 5 is similar to Figure 10.19.2-1 of TS 37.340 Section 10.19.2. As illustrated in Figures 5a and 5b, during a conditional handover procedure using NR-DC, different SNs may be selected or the same SN may be maintained based on how the corresponding SCG configuration for each candidate target PCell is prepared.

[0152] In Rel-18, research is underway to extend this architecture to allow UEs to conditionally select a PSCell from among multiple pre-configured PSCells, similar to conditional handover. The selected PSCells can be referred to as candidate SCGs. The goal of this research is to leverage the existing CPA mechanism of Rel-17 and combine it with CHO.

[0153] Although more than one candidate PSCell configuration can be prepared for each PCell requested for a conditional handover, according to Rel-17 conditional handover using NR-DC, at most one SCG configuration can be associated with each PCell requested for a conditional handover. In Rel-17, the target MN was allowed to trigger separate SN addition procedures for the same SN. For example, for each received parallel conditional handover request with different PCells, the target MN was allowed to trigger separate SN addition procedures for the same SN. Furthermore, depending on the target MN implementation, only one SN addition procedure was allowed for the SN, and the same CG-Config was used for all parallel conditional handover requests. Alternatively, a combination of the two approaches described above is also possible.

[0154] The former approach makes sense, for example, when the PDU sessions or DRBs requested to be established at the source are different for different PCells in parallel conditional handover requests from the source.

[0155] On the other hand, the latter approach makes sense even when the PDU sessions or DRBs requested to be established at the source are identical for different PCells in parallel conditional handover requests from the source. In this case, a single SN addition procedure is sufficient to prepare only one SCG configuration for the same SN and combine it with multiple conditional handover requests. This approach can also be applied to Rel-18 conditional handovers with candidate SCGs. That is, it can also be applied to conditional handover procedures that utilize CPA instead of the traditional SN addition procedure.

[0156] The latter approach is more suitable for intra-master node conditional handover (intra-MN CHO) scenarios, where conditional handovers are prepared within the same master node. For example, it is more suitable for the scenario in Figures 5a and 5b where the source MN and target MN are merged into a single MN. In this case, parallel SN addition procedures for the same SN for other candidate target PCells are likely not required.

[0157] While both approaches are permitted in Rel-17, the second approach, which utilizes a single CPA procedure instead of parallel CPA for candidate target SNs, cannot accommodate multiple conditional handover requests. Furthermore, it is unclear how this approach will work in Rel-18 with candidate SCGs.

[0158] Therefore, the present disclosure proposes mechanisms to support multiple conditional handover requests (CHO requests) from a target MN using a single conditional PSCell addition (CPA) procedure for each candidate target SN during handover preparation in Rel-18 with a configuration of candidate SCGs for the UE.

[0159]

[0160] Embodiments of the present disclosure propose a procedure for supporting multiple conditional handover requests from a target mobile node (MN) using a single CPA procedure for each candidate target SN. Embodiments of the present disclosure can be applied when preparing for a conditional handover in Rel-18 with the configuration of candidate SCGs for a UE.

[0161] FIGS. 6A and 6B illustrate examples of a procedure for supporting multiple conditional handover requests according to an embodiment of the present disclosure. Specifically, FIGS. 6A and 6B illustrate examples of a procedure for supporting multiple conditional handover requests using a single CPA procedure in a Rel-18 conditional handover with candidate SCGs.

[0162] Referring to FIGS. 6A and 6B , in step S601, a source MN (620) transmits multiple handover request messages to a target MN (630). Specifically, the source MN (620) determines a conditional handover for the UE based on the measurement results obtained from the UE (610). The source MN (620) determines candidate target PCells suitable for the conditional handover of the UE, and initiates a handover preparation procedure by transmitting handover request messages for each of the candidate target PCells to the target MN (630) to which the candidate target PCells belong. Depending on the selected candidate target PCells, the handover preparation procedure may be triggered in parallel for each target MN, or may be triggered for one or more target MNs. Each handover request message may include, for each candidate target PCell, the maximum number of conditional reconfigurations (condReconfig) allowed to be prepared by the requested target MN.

[0163] In step S603, the target MN (630) determines at least one candidate target SN for which to prepare a CPA for the UE. If a conditional handover request message for multiple PCells currently in service is received from the source MN (620), the target MN (630) may determine the multiple PCells as candidate target PCells for the conditional handover of the UE. The target MN (630) may perform admission control for the candidate target PCells for which the conditional handover has been requested, and determine at least one candidate target SN for which to prepare a CPA for the candidate target PCells.

[0164] In step S605, the target MN (630) transmits an SN addition request message to at least one candidate target SN (640-1, 640-2). When at least one candidate target SN (640-1, 640-2) is determined, the target MN (630) may initiate a CPA procedure for at least one candidate target SN (640-1, 640-2) by transmitting an SN addition request message to each of the determined at least one candidate target SN (640-1, 640-2). The SN addition request message is a request message for conditional PSCell addition and may be referred to as a CPA request message. The CPA request message may include a list of candidate target PCells determined for the candidate target SN among the candidate target PCells requested from the source MN for conditional handover. The candidate target PCells requested from the source MN may include PCells corresponding to handover request messages received from the source MN. The CPA request message may further include the total number of PSCell configurations allowed to be prepared by each candidate target SN for the list of candidate target PCells. The total number of allowed PSCell configurations may be determined based on the maximum number of conditional reconfigurations for each candidate target PCell indicated by the source MN in step S601. Alternatively, the CPA request message may include the number of allowed PSCell configurations for each PCell to be prepared by each candidate target SN. The number of allowed PSCell configurations for each PCell may be determined based on the maximum number of allowed conditional reconfigurations indicated by the source MN for each candidate target PCell for which a conditional handover is requested in step S601.

[0165] In step S607, at least one candidate target SN (640-1, 640-2) transmits an SN addition request confirmation message to the target MN (630). At least one candidate target SN (640-1, 640-2) that has received the CPA request message performs admission control on candidate PSCells and prepares candidate PSCell configurations. At this time, the number of candidate PSCell configurations prepared does not exceed the number allowed by the CPA request message. For example, the number of candidate PSCell configurations prepared for the list of candidate target PCells in each of at least one candidate target SN (640-1, 640-2) may be limited so as not to exceed the total number of allowed candidate PSCell configurations. In one embodiment, the number of prepared candidate PSCell configurations may be limited per PCell. For example, if a restriction per PCell is requested by the target MN (630), the number of candidate PSCell configurations prepared for each candidate target PCell in each of at least one candidate target SN (640-1, 640-2) may be restricted so as not to exceed the maximum number of candidate PSCell configurations allowed for each candidate target PCell. At least one candidate target SN (640-1, 640-2) provides the target MN (630) with a list of CG-Configs including information related to each prepared candidate PSCell configuration. That is, at least one candidate target SN (640-1, 640-2) transmits an SN addition request confirmation message including the list of CG-Configs to the target MN (630). The SN addition request confirmation message may be a response message to the CPA request message.The SN Addition Request Confirmation message may further include information on how each prepared CG-Config for each selected candidate PSCell is associated with which of the candidate target PCells in the list of candidate target PCells indicated by the CPA Request message.

[0166] In step S609, the target MN (630) transmits an Xn-U address indication message to at least one candidate target SN (640-1, 640-2). If SN terminated bearers using MCG resources are prepared, the target MN (630) can provide Xn-U DL (downlink) TNL (transport network layer) information using a subsequent Xn-U address indication message. That is, the subsequent Xn-U address indication message can include Xn-U DL TNL information.

[0167] In step S611, the target MN (630) transmits a handover request confirmation message to the source MN (620). Based on the candidate PSCell configurations prepared by at least one candidate target SN (640-1, 640-2) and the association of each candidate PSCell configuration with a specific candidate target PCell among the candidate target PCells requested for conditional handover from the source MN (620), the target MN (630) transmits a message approving the handover request for each candidate target PCell to the source MN (620). At this time, the message approving the handover request may include a handover request confirmation message as a response message to the handover request message. Each handover request confirmation message may include information to be transmitted to the UE (610) for performing a conditional handover of Rel-18 with candidate SCGs. For example, each handover request confirmation message may include information related to an MCG configuration for the corresponding candidate target PCell and information related to at least one SCG configuration for at least one prepared candidate PSCell associated therewith.

[0168] In step S613, the source MN (620) transmits an RRC reconfiguration message to the UE (610). The RRC reconfiguration message may include an MN RRC reconfiguration* message and an SN RRC reconfiguration** message. The source MN (620) may generate an RRC reconfiguration message including a conditional reconfiguration. At this time, the RRC reconfiguration message may be generated based on information related to the MCG configuration and / or the SCG configuration conveyed through the handover request confirmation message received in step S611. For example, the handover request confirmation message received in step S611 may include a list of RRC reconfiguration* messages and associated execution conditions, and each RRC reconfiguration* message may include information related to the MCG configuration. Each RRC reconfiguration** message received from at least one candidate target SN in step S611 may include information related to the SCG configuration. In step S615, the UE (610) transmits an RRC reconfiguration complete message to the source MN (620). The UE (610) may store the conditional handover with information related to the configuration of candidate SCGs received in step S613 and respond to the source MN (620) using an RRC reconfiguration complete message.

[0169] At step S617, step 7 and / or subsequent steps defined in clause 10.19 of TS 37.340 may be performed. For example, step 7 (e.g., random access procedure) and subsequent steps of Figure 10.19.2-1 of clause 10.19 of TS 37.340 may be performed.

[0170]

[0171] As described above, the present disclosure proposes a method and apparatus for supporting conditional handover with conditional PSCell settings in a network system.

[0172] A target master node (MN) may receive at least one conditional handover request message for at least one candidate target PCell within the target MN of the UE from a source NG-RAN node that serves the UE. In this case, the target MN may determine to add at least one candidate PSCell configuration for the UE using at least one adjacent candidate target SN, and initiate a conditional PSCell addition procedure for the candidate target SN.

[0173] A conditional PSCell addition procedure for a corresponding candidate target SN can be initiated by sending a CPA request message to the corresponding candidate target SN. The CPA request message can include an SN addition request message. The SN addition request message can include at least one of a list of candidate target PCells determined for the candidate target SN among candidate target PCells requested from a source NG-RAN node for conditional handover, or information related to an allowed number of candidate PSCell configurations. The information related to the allowed number of candidate PSCell configurations can include at least one of a total number of PSCell configurations allowed to be prepared by the candidate target SN for the list of candidate target PCells, or a maximum number of PSCell configurations allowed for each PCell to be prepared by the candidate target SN.

[0174] A candidate target SN may receive a CPA request message for initiating a CPA procedure from a target MN. In this case, the candidate target SN may perform admission control for at least one candidate PSCell and prepare at least one candidate PSCell configuration. Here, the number of at least one candidate PSCell configuration prepared by the candidate target SN does not exceed the total number of PSCell configurations allowed by the target MN. Here, the total number of PSCell configurations allowed by the MN may be the total number of allowed PSCell configurations included in the CPA request message. If the CPA request message includes the maximum number of allowed PSCell configurations for each PCell, the number of candidate PSCell configurations prepared by the candidate target SN for each candidate PCell may be limited so as not to exceed the maximum number of allowed PSCell configurations for each candidate PCell.

[0175] A candidate target SN may send a response message to a CPA request to the target MN. The response message to the CPA request may include an SN addition request confirmation message. The SN addition request confirmation message may include at least one of a list of all candidate PSCell configurations prepared by the candidate target SN for the UE, or information on how each prepared candidate PSCell configuration is associated with which candidate target PCell among the list of candidate target PCells provided by the target MN.

[0176]

[0177] FIG. 7 illustrates an example of a procedure for receiving PSCell configuration information according to an embodiment of the present disclosure. FIG. 7 illustrates a method performed by a first node, which is a target MN of a terminal.

[0178] Referring to FIG. 7, in step S701, the first node receives a first message related to a conditional handover request. The first node may receive the first message related to the conditional handover request of the terminal from the source MN of the terminal. The first message may include a conditional handover request message. The first message may be received for each candidate target PCell for the conditional handover of the terminal. For example, if multiple candidate target PCells suitable for the conditional handover of the terminal belong to the first node, the first node may receive conditional handover request messages for each of the multiple candidate target PCells. Each conditional handover request message for each candidate target PCell may include information related to the maximum number of conditional reconfigurations that the first node is allowed to prepare for the corresponding candidate target PCell.

[0179] In step S703, the first node transmits a second message related to an SN addition request to the candidate target SN. The first node may determine at least one candidate target SN including the first SN as at least one candidate target SN for the terminal, and transmit a second message related to the SN addition request to each of the at least one candidate target SN. The second message may be a CPA request message and may include an SN addition request message. The second message may include at least one of a list of candidate target PCells determined for the candidate target SN among the candidate target PCells requested from the source MN for conditional handover, or information related to an allowed number for candidate PSCell configurations. The candidate target PCells requested from the source MN may include PCells corresponding to the first message. The information related to the allowed number for candidate PSCell configurations may include at least one of a total number of allowed candidate PSCell configurations for the list of candidate target PCells, or a maximum number of allowed PSCell configurations for each PCell. Information regarding the allowed number of candidate PSCell configurations may be determined based on the maximum number of allowed conditional resets included in the first message.

[0180] In step S705, the first node receives a third message related to confirmation of an SN addition request. The first node may receive the third message from the candidate target SN as a response message to the second message. The third message, as a response message to the CPA request, may include an SN addition request confirmation message. The third message may include information related to a candidate PSCell configuration prepared by the candidate target SN based on the second message. Specifically, the third message may include information related to the configuration of a prepared candidate PSCell corresponding to each of the candidate target PCells determined for the candidate target SN. The number of prepared candidate PSCell configurations may be limited so as not to exceed the allowed number of candidate PSCell configurations. The third message may further include information indicating an association between each prepared candidate PSCell configuration and the candidate target PCell. For example, the third message may further include information indicating how each prepared candidate PSCell configuration is associated with which candidate target PCell in the list of candidate target PCells provided by the first node to the corresponding candidate SN.

[0181] In one embodiment, the first node may include a target MN as described with reference to FIGS. 6A and 6B . The first node may further perform at least one operation of the target MN as described with reference to FIGS. 6A and 6B .

[0182]

[0183] FIG. 8 illustrates an example of a procedure for transmitting PSCell configuration information according to an embodiment of the present disclosure. FIG. 8 illustrates a method performed by a second node, which is a candidate target SN of a terminal.

[0184] Referring to FIG. 8, in step S801, the second node receives a second message related to an SN addition request. The second message is a CPA request message and may include an SN addition request message. The second message may be received from the first node, which is a target MN. The second message may include at least one of a list of candidate target PCells determined for the second node, which is a candidate target SN, or information related to an allowed number of candidate PSCell configurations. The information related to the allowed number of candidate PSCell configurations may include at least one of a total number of allowed candidate PSCell configurations for the list of candidate target PCells, or a maximum number of allowed PSCell configurations for each PCell.

[0185] In step S803, the second node transmits a third message related to the SN addition request confirmation. The second node may send the third message to the first node, which is the target MN, as a response message to the second message. The third message, as a response message to the CPA request, may include an SN addition request confirmation message. The third message may include information related to the configuration of prepared candidate PSCells corresponding to each of the candidate target PCells determined for the second node, which is the corresponding candidate SN. The number of prepared candidate PSCell configurations may be limited so as not to exceed the allowed number of candidate PSCell configurations. The third message may further include information regarding how each prepared candidate PSCell configuration is associated with which candidate target PCell among the list of candidate target PCells provided by the first node.

[0186] In one embodiment, the second node may include a candidate target SN as described with reference to FIGS. 6A and 6B . The second node may further perform at least one operation of the candidate target SN as described with reference to FIGS. 6A and 6B .

[0187]

[0188] 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).

[0189] 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.

[0190] 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.

[0191] 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.

[0192] Additionally, embodiments of the present disclosure can be applied to various applications such as autonomous vehicles and drones.

Claims

1. In the method, A step of receiving at least one first message related to a conditional handover request of the terminal from a source MN (master node) of the terminal; A step of transmitting a second message related to a request for adding an SN to a first SN among candidate target SNs (secondary nodes) for the terminal; and A step of receiving a third message related to an SN addition request from the first SN, The second message includes at least one of a list of candidate target PCells (primary cells) requested by the source MN for conditional handover, determined for the first SN, or information related to the number allowed for candidate PSCell (primary secondary cell) configuration. A method wherein the third message includes information related to a candidate PSCell configuration prepared by the first SN based on the second message.

2. In claim 1, A method in which information related to the number allowed for the above candidate PSCell configurations includes at least one of the total number of PSCell configurations allowed to be prepared by the first SN for the list of the determined candidate target PCells, or the maximum number of PSCell configurations allowed for each PCell to be prepared by the first SN.

3. In claim 1, A method wherein at least one of the total number of allowed PSCell configurations or the maximum number of allowed PSCell configurations for each PCell is determined based on the maximum number of allowed conditional resets included in the first message.

4. In claim 1, A method in which the third message includes at least one of information indicating a relationship between candidate PSCell settings prepared by the first SN or candidate target PCells determined for the first SN and the prepared candidate PSCell settings.

5. In claim 4, A method in which the number of the above prepared candidate PSCell settings is limited by the number allowed for the above candidate PSCell settings.

6. In claim 5, A method in which the number of the above-mentioned prepared candidate PSCell configurations is limited by the total number of allowed PSCell configurations for the list of the above-mentioned determined candidate target PCells.

7. In claim 5, The number of the above prepared candidate PSCell settings is limited by the maximum number of PSCell settings allowed for each candidate target PCell.

8. In claim 4, A method further comprising the step of transmitting at least one fourth message to the source MN based on the association between the prepared candidate PSCell settings and the candidate target PCells determined for the first SN.

9. In claim 1, A method wherein the second message includes a message requesting addition of a conditional PSCell.

10. In claim 1, The step of receiving at least one first message comprises: A step of receiving a plurality of first messages corresponding to each of a plurality of candidate target PCells from the source MN, A method in which the candidate target PCells requested by the above source MN include the plurality of candidate target PCells.

11. In the method, A step of receiving a second message related to a request for adding an SN from a target MN (master node) of the terminal; and A step of transmitting a third message related to a request for adding a SN (secondary node) to the target MN, The second message includes at least one of a list of candidate target PCells (primary cells) requested by the source MN for conditional handover, determined for the first SN, or information related to the number allowed for candidate PSCell (primary secondary cell) configuration. A method wherein the third message includes information related to a candidate PSCell configuration prepared by the first SN based on the second message.

12. In the device, Transmitter and receiver; and A processor connected to the above transmitter and receiver is included, The above processor, Receive at least one first message related to a conditional handover request of the terminal from the source MN (master node) of the terminal, Transmitting a second message related to a request for adding an SN to the first SN (secondary node) among the candidate target SNs for the above terminal, Control to receive a third message related to an SN addition request from the above first SN, The second message includes at least one of a list of candidate target PCells (primary cells) requested by the source MN for conditional handover, determined for the first SN, or information related to the number allowed for candidate PSCell (primary secondary cell) configuration. A device wherein the third message includes information related to a candidate PSCell configuration prepared by the first SN based on the second message.

13. In the device, Transmitter and receiver; and A processor connected to the above transmitter and receiver is included, The above processor, Receive a second message related to a request to add a SN (secondary node) from the target MN (master node) of the terminal, Control to transmit a third message related to a request for adding an SN to the above target MN, The second message includes at least one of a list of candidate target PCells (primary cells) requested by the source MN for conditional handover, determined for the first SN, or information related to the number allowed for candidate PSCell (primary secondary cell) configuration. A device wherein the third message includes information related to a candidate PSCell configuration prepared by the first SN based on the second message.

14. In communication devices, At least one processor; At least one memory connected to said at least one processor and storing instructions that direct operations when executed by said at least one processor, The above actions are, A step of receiving at least one first message related to a conditional handover request of the terminal from a source MN (master node) of the terminal; A step of transmitting a second message related to a request for adding an SN to a first SN among candidate target SNs (secondary nodes) for the terminal; and A step of receiving a third message related to an SN addition request from the first SN, The second message includes at least one of a list of candidate target PCells (primary cells) requested by the source MN for conditional handover, determined for the first SN, or information related to the number allowed for candidate PSCell (primary secondary cell) configuration. A communication device, wherein the third message includes information related to a candidate PSCell configuration prepared by the first SN based on the second message.

15. In a non-transitory computer-readable medium storing at least one instruction, wherein said at least one instruction, when executed by at least one processor, causes the communication device to perform operations; The above actions are, A step of receiving at least one first message related to a conditional handover request of the terminal from a source MN (master node) of the terminal; A step of transmitting a second message related to a request for adding an SN to a first SN among candidate target SNs (secondary nodes) for the terminal; and A step of receiving a third message related to an SN addition request from the first SN, The second message includes at least one of a list of candidate target PCells (primary cells) requested by the source MN for conditional handover, determined for the first SN, or information related to the number allowed for candidate PSCell (primary secondary cell) configuration. A computer-readable medium, wherein the third message includes information related to a candidate PSCell configuration prepared by the first SN based on the second message.

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