Device and method for supporting inter-system mobility in wireless communication system

Abstract

The present disclosure is for supporting inter-system mobility in a wireless communication system. A method performed by a first network node of a first system comprises the steps in which: a handover required message for a terminal is received from a source base station; and, on the basis of the handover required message, the first network node transmits a forward relocation request message to a second network node of a second system, wherein the forward relocation request message may include at least one among second group identification information related to the access of a target cell, or information indicating whether the terminal belongs to the second group.

Description

Device and method for supporting mobility between systems in a wireless communication system

[0001] The following description relates to a wireless communication system, and to a device and method for supporting mobility between systems 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 supporting inter-system mobility in a wireless communication system.

[0005] The present disclosure relates to a device and method for supporting interworking of a closed access group (CAG) cell and a closed subscriber group (CSG) cell in a wireless communication system.

[0006] The present disclosure relates to a device and method for presetting information related to a CSG in an AMF for interworking between a CAG cell and a CSG cell in a wireless communication system.

[0007] The present disclosure relates to a device and method for supporting handover from 5GS to EPS based on information related to a CSG set in an AMF in a wireless communication system.

[0008] The present disclosure relates to a device and method for determining whether a handover target cell of a terminal is a CSG cell based on information related to a CSG set in an AMF in a wireless communication system.

[0009] The present disclosure relates to a device and method for transmitting CSG ID and CSG membership indication information of a target cell to an MME in a wireless communication system.

[0010] The present disclosure relates to a device and method for supporting handover from 5GS to EPS by using information related to CSG acquired based on automatic neighbor cell relation (ANR) in a wireless communication system.

[0011] The present disclosure relates to a device and method for supporting handover from 5GS to EPS using information related to CSG acquired based on configuration transfer signaling in a wireless communication system.

[0012] The present disclosure relates to a device and method for supporting handover from EPS to 5GS using an allowed CAG list in a wireless communication system.

[0013] The present disclosure relates to a device and method for acquiring subscriber information of a terminal to support handover from EPS to 5GS 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 a first network node of a first system receiving a handover required message for a terminal from a source base station, and the first network node transmitting a forward relocation request message to a second network node of a second system based on the handover required message, wherein the forward relocation request message may include at least one of second group identification information related to access of the target cell, or information indicating whether the terminal belongs to the second group.

[0016] As an example of the present disclosure, the method includes the steps of a second network node of a second system receiving a forward relocation request message from a first network node of a first system, and the second network node of the second system transmitting a handover request message for a terminal to a base station of the second system, wherein at least one of the forward relocation request message or the handover request message may include at least one of second group identification information related to access of the terminal to a handover target cell, or information indicating whether the terminal belongs to the second group.

[0017] As an example of the present disclosure, the method further includes the step of a first base station of a first system obtaining information related to a second group from a second base station of a second system, and the step of the first base station transmitting a handover required message for a terminal to a first network node, wherein the handover required message may include at least one of second group identification information related to access of a handover target cell of the terminal, or a cell access mode indicating whether the target cell is a hybrid cell.

[0018] As an example of the present disclosure, a device includes a transceiver and a processor connected to the transceiver, wherein the processor controls to receive a handover required message for a terminal from a source base station of a first system to which the device belongs, and to transmit a forward relocation request message to a second network node of a second system based on the handover required message, wherein the forward relocation request message may include at least one of second group identification information related to access of the target cell, or information indicating whether the terminal belongs to the second group.

[0019] As an example of the present disclosure, a device includes a transceiver and a processor connected to the transceiver, wherein the processor receives a forward relocation request message from a first network node of a first system and controls a base station of a second system to which the device belongs to transmit a handover request message for a terminal, wherein at least one of the forward relocation request message or the handover request message may include at least one of second group identification information related to access of a handover target cell of the terminal, or information indicating whether the terminal belongs to the second group.

[0020] As an example of the present disclosure, a device includes a transceiver and a processor connected to the transceiver, wherein the processor obtains information related to a second group from a second base station of a second system, and controls transmission of a handover required message for a terminal to a first network node of a first system to which the device belongs, wherein the handover required message may include at least one of second group identification information related to access of a handover target cell of the terminal, or a cell access mode indicating whether the target cell is a hybrid cell.

[0021] As an example of the present disclosure, a communication device includes at least one processor, and at least one memory storing instructions that, when executed by the at least one processor, direct operations, the operations including: a step of a first network node of a first system receiving a handover required message for a terminal from a source base station; and a step of the first network node transmitting a forward relocation request message to a second network node of a second system based on the handover required message, wherein the forward relocation request message may include at least one of second group identification information related to access of the target cell, or information indicating whether the terminal belongs to the second group.

[0022] As an example of the present disclosure, a non-transitory computer-readable medium stores at least one instruction, the at least one instruction being executable by a processor to control receiving a handover required message for a terminal from a source base station of a first system to which the device belongs, and transmitting a forward relocation request message to a second network node of a second system based on the handover required message, wherein the forward relocation request message may include at least one of second group identification information related to access of the target cell, or information indicating whether the terminal belongs to the second group.

[0023] The following effects may be achieved by embodiments based on the present disclosure.

[0024] The present disclosure can ensure service continuity in a wireless communication system.

[0025] 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.

[0026] 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.

[0027] Figure 1 illustrates an example of a communication system applicable to the present disclosure.

[0028] FIG. 2 illustrates an example of a user equipment (UE) applicable to the present disclosure.

[0029] 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.

[0030] FIG. 4 illustrates an example of a general architecture of a 5G (5th generation) system applicable to the present disclosure.

[0031] FIG. 5a and FIG. 5b illustrate examples of a handover procedure from 5GS to EPS according to one embodiment of the present disclosure.

[0032] FIG. 6A and FIG. 6B illustrate examples of mobility related procedures from 5GS to EPS according to one embodiment of the present disclosure.

[0033] FIG. 7 illustrates an example of a procedure for transmitting information related to a CSG without RAN influence according to one embodiment of the present disclosure.

[0034] FIG. 8 illustrates an example of a procedure for transmitting information related to a CSG based on RAN support according to one embodiment of the present disclosure.

[0035] FIG. 9a and FIG. 9b illustrate examples of mobility-related procedures from EPS to 5GS according to one embodiment of the present disclosure.

[0036] FIG. 10 illustrates an example of a procedure for transmitting allowed CAG information according to one embodiment of the present disclosure.

[0037] FIG. 11 illustrates an example of a procedure for transmitting information related to a CSG according to one embodiment of the present disclosure.

[0038] FIG. 12 illustrates an example of a procedure for receiving information related to a CSG according to one embodiment of the present disclosure.

[0039] FIG. 13 illustrates an example of transmitting information related to a CSG according to one embodiment of the present disclosure.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] 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.

[0045] 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).

[0046] 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.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] 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.

[0051] 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.

[0052] 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).

[0053] 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.

[0054] 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.

[0055] 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.

[0056] Hereinafter, this specification is described based on the terms defined above.

[0057] 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).

[0058] 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.

[0059] Communication system applicable to the present disclosure

[0060] 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.

[0061] 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.

[0062] Figure 1 illustrates an example of a communication system applied to the present disclosure.

[0063] 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.

[0064] 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).

[0065] 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.

[0066]

[0067] Figure 2 illustrates an example of a UE applicable to the present disclosure.

[0068] Referring to FIG. 2, the UE (200) may include a processor (102), memory (104), a transceiver (106), one or more antennas (108), a power management module (141), a battery (142), a display (143), a keypad (144), a SIM (Subscriber Identification Module) card (145), a speaker (146), and a microphone (147).

[0069] The processor (102) may be configured to implement the descriptions, functions, procedures, proposals, methods, and / or flowcharts disclosed herein. The processor (102) 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 (102). The processor (102) may include an ASIC, other chipset, logic circuit, and / or data processing device. The processor (102) may be an application processor. The processor (102) may include at least one of a DSP, a CPU (Central Processing Unit), a GPU (Graphics Processing Unit), and a modem (modulator and demodulator).

[0070] The memory (104) is operatively coupled to the processor (102) and can store various information for operating the processor (102). The memory (104) may include ROM, RAM, flash memory, a memory card, a storage medium, 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 the memory (14) and executed by the processor (102). The memory (104) may be implemented within the processor (102) or external to the processor (102), in which case it may be communicatively coupled to the processor (102) via various methods known in the art.

[0071] A transceiver (106) is operably coupled to the processor (102) and is capable of transmitting and / or receiving radio signals. The transceiver (106) may include a transmitter and a receiver. The transceiver (106) may include baseband circuitry for processing radio frequency signals. The transceiver (106) may control one or more antennas (108) to transmit and / or receive radio signals.

[0072] The power management module (141) can manage the power of the processor (102) and / or the transceiver (106). The battery (142) can supply power to the power management module (141).

[0073] The display (143) can output the results processed by the processor (102). The keypad (144) can receive input to be used by the processor (102). The keypad (144) can be displayed on the display (143).

[0074] A SIM card (145) 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, contact information can be stored on many SIM cards.

[0075] The speaker (146) can output sound-related results processed by the processor (102). The microphone (147) can receive sound-related input to be used by the processor (102).

[0076] 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.

[0077] 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.

[0078] 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.

[0079] 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.

[0080] 5G system architecture applicable to the present disclosure

[0081] 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.

[0082] 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.

[0083] - 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).

[0084] 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.

[0085] 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).

[0086] 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.

[0087] 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.

[0088] 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.

[0089] 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).

[0090] 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.

[0091] 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).

[0092] 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.

[0093] 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.

[0094] Figure 3 illustrates an example of functional separation of NG-RAN and 5GC (5th generation core) applicable to the present disclosure.

[0095] 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.

[0096] The UPF node functions as a gateway through which user data is transmitted and received.

[0097] The authentication server function (AUSF) authenticates and manages UEs. The Network Slice Selection Function (NSSF) is a node for network slicing, as described below.

[0098] The network exposure function (NEF) provides a mechanism to securely expose the services and functions of the 5G core.

[0099] 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.

[0100] 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.

[0101] 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.

[0102] 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.

[0103] 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.

[0104] Specific embodiments of the present disclosure

[0105] The present disclosure relates to a device and method for supporting inter-system handover in a wireless communication system. Specifically, the present disclosure relates to a device and method for interworking a CAG cell of a 5GS and a CSG cell of an EPS in a wireless communication system.

[0106] 3GPP is exploring ways to support femto cells in 5GS, under the theme of "Study on system aspects of 5G NR femto" in Rel-19. Specifically, the study is focused on the following objectives: The study document, "Study on system aspects of 5G NR femto" (SP-231797), defines the following objectives:

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

[0108] 4. Objective

[0109] The following aspects will be studied:

[0110] WT#1: Based on the RAN3 results, improve the overall architecture and enable functional and procedural changes required to support 5G NR femto deployments.

[0111] Note 1: It is anticipated that the need for potential architectural enhancements to support 5G NR femto deployments in RAN3 will be studied.

[0112] WT#2: A method to enable interaction between CAG and CSG cells.

[0113] Note 2: It is expected that the impact on EPC (e.g. MME), E-UTRAN and NG-RAN will be avoided.

[0114] Note 3: It is assumed that the existing CAG concept defined for PNI-NPN is reused for femto access control without affecting PNI-NPN.

[0115] WT#3: Study whether and how to support provisioning of subscribers who can access CAG cells and have access control managed by the CAG owner or authorized administrator.

[0116] Note 4: Ownership of the 5G NR Femto (or CAG or both) concepts and mechanisms will be defined in collaboration with SA3.

[0117] ---------------------------------------------------------------------

[0118] As mentioned above, 5GS uses a cell allocation group (CAG) to control access to femtocells. Accordingly, research is underway on how to link the cell subscriber group (CSG) used for access control to femtocells in 4GS with the CAG in 5GS. This disclosure presents a method to support this.

[0119] According to the prior art, access control to the CSG is performed by the MME. For example, when a UE attaches to the EPC and / or performs a tracking area update (TAU) through a CSG cell, the eNB notifies the MME of the identification information of the CSG cell (e.g., the CSG ID). The MME determines whether the UE is permitted to access the corresponding CSG cell based on the subscriber information of the UE and the identification information of the CSG cell, and notifies the eNB of information about the CSG membership status. Information about the CSG membership status may include a CSG membership indication indicating whether the UE is a CSG member. For example, the MME may notify the eNB of the UE's CSG membership indication information. Among the CSG cells, there are hybrid cells that can be accessed by both CSG members and non-CSG members. The MME can enable different policies to be applied to CSG members and non-CSG members in a hybrid cell by notifying the eNB whether the UE is a CSG member.

[0120] If the cell that the terminal has accessed is a CSG cell and not a hybrid cell, and the CSG ID of the cell that the terminal has accessed is not included in the subscriber information of the terminal, the MME may reject the registration (attach) request of the terminal. In addition, if the target cell is a CSG cell during the handover process, the handover required message transmitted from the source eNB to the MME includes the CSG ID and cell access mode (e.g., hybrid mode) of the target cell. The source MME verifies whether the terminal can receive service from the target cell based on the information included in the handover required message and the subscriber information of the terminal. Based on the verification result, the source MME decides whether to continue the handover of the terminal. That is, it verifies whether the subscriber information of the terminal includes the CSG ID of the target cell. At this time, if the subscriber information of the terminal does not include the CSG ID of the target cell and the target cell is not a hybrid cell, the source MME may reject the handover request of the source eNB.

[0121] Meanwhile, access control for CAG is performed by the gNB and AMF. For example, when a terminal performs initial registration or transitions from the connection management (CM)-IDLE state to the CM-CONNECTED state, the gNB transmits to the AMF a list of CAGs supported by the cell to which the terminal has connected. At this time, the AMF verifies whether the CAG ID included in the terminal's subscriber information exists in the list of CAGs supported by the cell to which the terminal has connected, based on the list of CAGs included in the terminal's subscriber information and the list of CAGs supported by the cell to which the terminal has connected from the gNB. If the CAG ID included in the terminal's subscriber information exists in the list of CAGs supported by the cell to which the terminal has connected, the AMF can process the terminal's request. On the other hand, if the CAG ID included in the terminal's subscriber information does not exist in the list of CAGs supported by the cell to which the terminal has connected, the AMF can reject the terminal's request.

[0122] On the other hand, the AMF notifies the gNB of a mobility restriction list including a list of allowed CAGs to prevent the UE from being moved to a disallowed CAG cell during a handover. When performing a handover, the gNB can compare at least one CAG ID supported by the target cell with the allowed CAG list of the UE, and determine whether to perform a handover to the target cell based on the comparison result. For example, if at least one supported CAG ID is included in the allowed CAG list of the UE, the gNB can determine the target cell as an allowed cell and control the UE to be handed over to the target cell.

[0123] As mentioned above, since the access control methods for CAG and CSG are different, additional functions need to be defined to link CAG and CSG.

[0124] Accordingly, the present disclosure proposes various embodiments for interworking CAG and CSG. The proposed embodiments may be configured to include at least one of the operations, configurations, and / or steps described below. Furthermore, at least two of the proposed embodiments may be combined with each other, or one embodiment may be used to complement at least one other embodiment. In the following, a terminal may include a user equipment (UE).

[0125] Example #1: Interworking Cells Without RAN Influence

[0126] Typically, when performing an inter-system handover from a gNB to an eNB or an inter-system handover from an eNB to a gNB, a target cell is selected without information about the CAG and / or CSG, and handover to the selected target cell is performed. The present disclosure proposes a method for interworking between a CAG cell and a CSG cell without changing the handover procedure at the base station level.

[0127] Example #1-1: Example of performing a handover from 5GC to EPC

[0128] When a handover occurs from 5GC to EPC, the AMF determines whether the target cell is a CSG cell. The AMF can determine whether the target cell is a CSG cell based on the tracking area identity (TAI) and global eNB ID information of the target cell. Alternatively, the AMF can obtain the target cell ID information included in the source-to-target transparent container received from the gNB and determine whether the target cell is a CSG cell based on the target cell ID.

[0129] For this purpose, information related to the CSG may be configured in the AMF. For example, the information related to the CSG may include at least one of an eNB ID supporting the CSG cell, a candidate cell ID supporting the CSG cell, or mapping information between the CSG and the CAG. The mapping information between the CSG and the CAG may include at least one of a CSG ID and a CAG ID mapped to each CSG ID, or a cell access mode.

[0130] According to one embodiment, the AMF can obtain the target cell ID included in the source-target transparent container only when the target cell is an eNB and the subscriber information of the terminal includes allowed CSG ID information. The subscriber information of the terminal may include CSG subscription data. For example, the CSG subscription data may include a list of CSG IDs that the terminal is allowed to use, i.e., an allowed CSG list. The AMF can determine whether the target cell is a CSG cell by comparing the target cell ID with information related to the CSG set in the AMF.

[0131] In one embodiment, when a handover of a UE occurs, given that the AMF knows the CAG list supported by the serving gNB, the AMF can infer a serving CAG ID based on the allowed CAG list of the UE and the CAG list supported by the serving gNB. For example, the AMF can infer which CAG ID is currently in use by comparing the allowed CAG list of the UE and the CAG list supported by the serving gNB. The AMF can directly receive the CAG list supported by the serving gNB from the serving gNB, or infer information about the CAG list supported by the serving gNB based on information included in an initial UE message received from the serving gNB. If a CSG ID mapped to the inferred serving CAG ID is included in information related to a CSG configured in the AMF, the AMF can decide to perform a handover to the corresponding CSG cell based on the corresponding CSG ID information. If the target cell is identified as a CSG cell, the AMF may transmit a forward relocation request message to the MME, which includes at least one of the target cell's CSG ID information or CSG membership indication. Upon receiving the forward relocation request message, the MME may transmit a message (e.g., a handover request message) including the CSG ID information and CSG membership indication to the target eNB. Through this, the UE may handover to the CSG cell.

[0132] Example #1-2: Example of performing a handover from EPC to 5GC

[0133] When a handover occurs from EPC to 5GC, the following actions can be taken:

[0134] When the source eNB sends a handover required message to the MME, the MME can send a forwarding relocation request message to the AMF based on the ID information of the target cell.

[0135] If the target cell is a CAG cell, the gNB can send a handover request acknowledge message to the AMF containing a list of CAGs supported by the target cell. The AMF can compare the list of CAGs supported by the target cell with the subscriber information of the UE to determine whether to release the UE's connection after the handover. Alternatively, the gNB can directly reject the UE's handover. That is, the gNB can receive a handover request message containing a list of allowed CAGs from the AMF and directly reject the UE's handover based on the list of allowed CAGs.

[0136] FIGS. 5A and 5B illustrate examples of a handover procedure from a 5GS to an EPS according to one embodiment of the present disclosure. Unless otherwise specified herein, the procedures of FIGS. 5A and 5B may essentially follow the handover procedure from a 5GS to an EPS using the N26 interface as defined in Section 4.11.1.2.1 of TS 23.502. For example, except for Step 3 in the procedures of FIGS. 5A and 5B, the remaining steps may follow the handover procedure from a 5GS to an EPS using the N26 interface as defined in Section 4.11.1.2.1 of TS 23.502.

[0137] Referring to FIGS. 5A and 5B , in step 0, UE (510) establishes a PDU session and QoS flow in 5GS. UE (510) can receive service through a femto cell. Femto cell supports CAG ID, and subscriber information of UE (510) can include allowed CAG ID supported by femto cell.

[0138] In step 1, the NG-RAN (530) determines that the UE (510) must be handed over to the E-UTRAN (520) and transmits a handover required message to the AMF (540). The handover required message may include a target eNB ID.

[0139] In steps 2a to 2c, the AMF (540) determines that the handover type is a handover to E-UTRAN (520) based on the target eNB ID and selects the MME (550). Steps 2a to 2c may be performed in the same manner as steps 2a to 2c of TS 23.502 clause 4.11.1.2.1.

[0140] In step 3, the AMF (540) transmits a forward relocation request message to the MME (550). At this time, the AMF (540) can recognize that the base station hands over the UE to the CSG cell based on at least one of information related to the CSG set in the AMF (540), subscriber information of the UE, target cell ID information, CAG ID information for the current serving cell, or target eNB ID and TAI information. Here, the information related to the CSG set in the AMF may include at least one of a cell ID of a candidate eNB cell available for handover, an eNB ID, a TAI, or mapping information of the CSG and CAG. The mapping information of the CSG and CAG may include at least one of a CSG ID and a CAG ID mapped to each CSG ID, or a cell access mode. If there is no mapping information of the CSG and CAG, the CSG ID value itself may become the CAG ID value. The subscriber information of the UE may include at least one of a list of allowed CSGs available to the UE, or a list of allowed CAGs. The target cell ID information may be the target cell ID information included in the source-target transparent container within the handover required message. Additionally, the target eNB ID and TAI information may be included in the handover required message.

[0141] The AMF (540) recognizes that the target cell is a CSG cell based on at least one piece of information as described above, and transmits a forwarding relocation request message including the CSG ID information and CSG membership indication of the target cell to the MME (550). According to one embodiment, the CSG membership indication may be included only when the target cell is a hybrid cell. If the CSG ID of the target cell is not included in the allowed CSG list in the subscriber information of the UE, the AMF (540) may transmit a handover preparation failure message to the gNB of the NG-RAN (530).

[0142] Steps 4 to 21 may be performed identically to steps 4 to 21 of TS 23.502 clause 4.11.1.2.1. For example, in step 6, the MME (540) transmits a handover request message to the target eNB of the E-UTRAN (520). At this time, the handover request message may include at least one of the CSG ID information of the target cell or the CSG membership indication. Through this, the UE can handover to the CSG cell.

[0143] Figures 6a and 6b illustrate examples of mobility-related procedures from 5GS to EPS according to one embodiment of the present disclosure. The procedures of Figures 6a and 6b may essentially follow the handover procedure from 5GS to EPS using the N26 interface as defined in Section 4.11.1.2.1 of TS 23.502. For example, the remaining steps in the procedures of Figures 6a and 6b, except for Step 3 below, may follow the handover procedure from 5GS to EPS using the N26 interface as defined in Section 4.11.1.2.1 of TS 23.502.

[0144] Before a procedure as illustrated in FIGS. 6A and 6B is triggered, information related to the CSG of candidate target eNB cells may be set in the AMF (640). For example, the information related to the CSG may include at least one of an eNB ID supporting the CSG cell, a candidate cell ID supporting the CSG cell, or mapping information of the CSG and CAG. The mapping information of the CSG and CAG may include at least one of a CSG ID and a CAG ID mapped to each CSG ID, or a cell access mode.

[0145] According to section 5.5.1.2.2 of TS 23.401, the target eNB of the E-UTRAN (620) must verify the CSG ID provided by the target MME (650). Therefore, in step 3, when the AMF (640) recognizes that the UE (610) is moving to the EPS, the AMF (640) can include necessary information (e.g., CSG ID) for CSG ID verification of the target eNB in ​​the Forward Relocation Request message. The AMF (640) can determine the CSG ID of the target cell and the necessary information to be included in the Forward Relocation Request message based on information related to the CSG set in the AMF (640). For example, the AMF (640) can determine whether the handover target cell of the UE (610) is a CSG cell based on the information set in the AMF and the UE subscriber information. If the handover target cell of the UE (610) is a CSG cell, the AMF (640) can transmit a forwarding relocation request message including the CSG ID and CSG membership indication of the target cell to the MME (650).

[0146] AMF (640) can check whether the target cell is a CSG cell allowed to the UE (610) based on subscriber information of UE (610) and the CSG ID of the target cell, and if it is a CSG cell not allowed, can stop the handover of UE (610). At this time, AMF (640) can transmit a handover preparation failure message to the gNB of NG-RAN (630).

[0147]

[0148] Figure 7 illustrates an example of a procedure for transmitting CSG-related information without RAN influence according to one embodiment of the present disclosure. Figure 7 illustrates a method performed by the AMF. Figure 7 may be performed when a handover occurs from 5GS to EPS.

[0149] Referring to FIG. 7, at step S701, the AMF receives a handover required message. The AMF may receive a handover required message from the source gNB, including at least one of a target eNB ID or a target cell ID from the NG-RAN.

[0150] In step S703, the AMF determines that the target cell is a CSG cell. The AMF may determine that the target cell is a CSG cell based on information related to a CSG preset in the AMF. The information related to the CSG may include at least one of a cell ID of a candidate eNB cell capable of handover, an eNB ID, a TAI, or mapping information of the CSG and CAG. The mapping information of the CSG and CAG may include at least one of a CSG ID and a CAG ID mapped to each CSG ID, or a cell access mode. For example, the AMF may determine whether the target cell is a CSG cell based on whether the target eNB ID included in the handover required message or the target cell ID is included in the information related to the CSG. The present disclosure assumes that the target cell is a CSG.

[0151] In step S705, the AMF determines whether the target cell is a hybrid cell. The AMF can determine whether the target cell is a hybrid cell based on the cell access mode in the information related to the CSG set in the AMF. In other words, the AMF can determine whether the target cell is a hybrid cell that supports both CSG members and non-CSG members based on the cell access mode in the information related to the CSG set.

[0152] If the target cell is a hybrid cell, in step S709, the AMF transmits a forwarding relocation request message. That is, if the target cell is a hybrid cell accessible to both CSG members and non-CSG members, the AMF transmits a forwarding relocation request message to the MME. At this time, the forwarding relocation request message may include the CSG ID and CSG membership indication of the target cell. The CSG membership indication may indicate whether the corresponding terminal is a CSG member. The reason why the forwarding relocation request message includes the CSG membership indication is because the policy applied to each terminal by the target base station may differ based on whether it is a CSG member.

[0153] If the target cell is not a hybrid cell, in step S707, the AMF determines whether the target cell is an allowed CSG cell. The AMF can determine whether the target cell corresponds to a CSG cell that the terminal is allowed to use based on the target cell ID and the subscriber information of the terminal. The subscriber information of the terminal may include at least one of an allowed CSG list or an allowed CAG list that the terminal can use. That is, the AMF can compare whether at least one CSG ID in the allowed CSG list is identical to the target cell ID. If at least one CSG ID in the allowed CSG list is identical to the target cell ID, the AMF can determine the target cell as an allowed CSG cell. On the other hand, if at least one CSG ID in the allowed CSG list is not identical to the target cell ID, the AMF can determine that the target cell is not an allowed CSG cell.

[0154] If the target cell is an authorized CSG cell, the AMF transmits a forwarding relocation request message in step S709. The AMF transmits the forwarding relocation request message including the CSG ID of the target cell to the MME. In one embodiment, the forwarding relocation request message may further include a CSG membership indication.

[0155] If the target cell is not an allowed CSG cell, the AMF transmits a handover preparation failure message in step S711. That is, if the target cell is not an allowed CSG cell, the AMF determines that the terminal cannot access the target cell and may interrupt the handover of the terminal by transmitting a handover preparation failure message to the NG-RAN. The handover preparation failure message may include a reason for the handover preparation failure or a reason for interrupting the handover.

[0156] In the embodiment described with reference to FIG. 7, the forward relocation request message may include at least one of the CSG ID or CSG membership indication of the target cell. In one embodiment, the CSG membership indication may be included in the forward relocation request message only when the target cell is a hybrid cell.

[0157] As described with reference to FIG. 7, the MME may receive a forwarding relocation request message from the AMF, which includes at least one of the CSG ID or CSG membership indication of the target cell. The MME may transmit a handover request message to the eNB, which includes at least one of the CSG ID or CSG membership indication of the target cell. Accordingly, the UE may handover from the 5GS to the CSG cell of the EPS.

[0158] Example #2: Interworking Method with RAN Support

[0159] When a handover from 5GS to EPS occurs and the target cell is a CSG cell, the source gNB may send a handover required message containing information about the CSG cell. To do this, the gNB must be aware of the CSG information of the target cell. The gNB and / or eNB may be aware of neighboring eNBs and / or gNBs based on automatic neighbor cell relationship (ANR). ANR is defined in clause 15.3.3 of TS 38.300 and / or clause 22.3.2a of TS 36.300. For example, the gNB and / or eNB may discover at least one neighboring cell based on operator configuration, OAM, and UE measurement reports, and may be aware of the presence of neighboring eNBs and / or gNBs based on the neighboring cells. Additionally, the gNB and / or eNB may recognize the surrounding eNB and / or gNB based on the ANR, and then exchange information about the surrounding eNB and / or gNB using a configuration transfer procedure. For example, the gNB and / or eNB may transmit CAG and / or CSG information (e.g., a CAG list, a CSG list, a cell access mode) of the cell it supports to the surrounding eNB and / or gNB using configuration transfer signaling, and may receive cell CAG and / or CSG information supported by the corresponding base station from the surrounding eNB and / or gNB. The configuration transfer procedure is as defined in clause 5.26 of TS 23.501 and / or clause 5.14 of TS 23.401.

[0160] If the CAG ID and CSG ID are mapped 1:1 and the CAG ID and CSG ID have the same value, the gNB and / or eNB may use only one of the CAG list or the CSG list, and may convert to the other list as needed.

[0161] The source gNB can determine whether the target cell is a CSG cell using information obtained based on the ANR and / or configuration transfer procedure as described above. If the target cell is a CSG cell, the source gNB can send a handover required message containing CSG information about the target cell to the AMF. The CSG information about the target cell can include at least one of a CSG ID and a cell access mode.

[0162] The AMF transmits a forwarding relocation request message to the MME based on the CSG information for the target cell. The forwarding relocation request message may include at least one of the CSG ID of the target cell or a CSG membership indication. The CSG membership indication may be based on CSG subscription data included in subscriber information. The CSG subscription data may include a list of CSG IDs that the UE is permitted to use. For example, the AMF may generate a CSG membership indication indicating whether the UE is a CSG member based on the CSG subscription data included in the subscriber information of the UE, and transmit the forwarding relocation request message including the generated CSG membership indication to the generating MME.

[0163] Before sending a forward relocation request message to the MME, the AMF can check whether the CSG ID of the target cell is included in the list of allowed CSG IDs in the CSG subscription data, and decide whether to continue the handover based on the check result. If the CSG ID of the target cell is not included in the list of allowed CSG IDs in the CSG subscription data, the AMF can decide to abort the handover. If the handover abort is decided, the AMF can send a handover preparation failure message to the source gNB. The handover preparation failure message can include a reason for aborting the handover. The reason for aborting the handover can indicate that the CSG ID of the target cell does not correspond to a CSG ID allowed to the UE.

[0164] FIG. 8 illustrates an example of a procedure for transmitting CSG-related information based on RAN support according to one embodiment of the present disclosure. FIG. 8 also illustrates an example of a procedure for linking a CSG cell and a CAG cell through RAN support when a handover occurs from 5GS to EPS.

[0165] Referring to FIG. 8, in step S801, the source gNB (830) determines whether the target cell is a CSG cell. The source gNB (830) can determine whether the handover target cell of the UE is a CSG cell based on information previously exchanged with neighboring eNBs and / or gNBs based on ANR. For example, the source gNB (830) can obtain CSG information and / or CAG information supported by each neighboring eNB and / or gNB in ​​advance based on configuration transfer signaling. The CSG information may include at least one of a CSG list including CSG IDs supported by the corresponding eNB, or a cell access mode of a CSG cell corresponding to each CSG ID. The CAG information may include a CAG list including CAG IDs supported by the corresponding gNB. The source gNB (830) can compare the ID of the handover target cell of the UE with the CSG list and / or CAG list supported by each neighboring eNB and / or gNB to determine whether the target cell is a CSG cell. The present disclosure assumes that the target cell is a CSG cell.

[0166] If the target cell is a CSG cell, the source gNB (830) transmits a handover required message to the AMF (840) in step S803. The handover required message may include at least one of the CSG ID of the target cell or the cell access mode. In other words, if the target cell is a CSG cell, the source gNB recognizes that the UE must be handed over from 5GS to EPS, and may transmit a handover required message including at least one of the CSG ID or the cell access mode of the target cell to the AMF (840) for interworking between the CAG cell and the CSG cell.

[0167] In step S805, the AMF (840) checks whether the CSG ID of the target cell is included in the allowed CSG list. The allowed CSG list is a list including the IDs of CSG cells that the terminal is allowed to use, and can be obtained from the CSG subscription data included in the subscriber information of the terminal. When a handover required message including at least one of the CSG ID of the target cell or the cell access mode is received from the source gNB (830), the AMF (840) can determine whether the CSG ID of the target cell is included in the allowed CSG list included in the subscriber information of the terminal.

[0168] If the CSG ID of the target cell is not included in the allowed CSG list, in step S807, the AMF (840) transmits a handover preparation failure message to the source gNB (830). That is, if the CSG ID of the target cell is not included in the allowed CSG list, the AMF (840) may determine that handover to the target cell, which is a CSG cell, is not possible. The AMF (840) may stop the handover of the terminal by sending the handover preparation failure message to the source gNB (830). At this time, the handover preparation failure message may include a handover stop reason. The handover stop reason may indicate that the CSG ID of the target cell is not included in the allowed CSG list of the terminal.

[0169] If the CSG ID of the target cell is included in the allowed CSG list, in step S809, the AMF (840) transmits a forwarding relocation request message. The forwarding relocation request message may include at least one of the CSG ID of the target cell or a CSG membership indication.

[0170] According to one embodiment, the MME (850) that receives the forwarding relocation request message may transmit a handover request message including the CSG ID of the target cell or the CSG membership indication of the UE to the target eNB that supports the target cell. Through this, the UE can handover to a CSG cell supported by the target eNB. Here, the CSG membership indication may be used by the eNB to determine a policy to be applied to the UE. For example, if the target cell is a hybrid cell, the UE may control different policies to be applied to CSG members and non-CSG members.

[0171] Example #3: Interaction between CAG cells and CSG cells based on mapping configuration information within the AMF.

[0172] The eNB and gNB may trigger a handover or redirection to a CAG cell or CSG cell based on at least one of ANR information or preset information in the RAN. At least one of candidate target eNB cells, a CSG ID associated with the target eNB cells, a CAG ID mapped to the CSG ID, or information indicating whether the target eNB cell is a hybrid cell may be configured in the AMF.

[0173] Figures 9a and 9b illustrate examples of mobility-related procedures from EPS to 5GS according to one embodiment of the present disclosure. The procedures of Figures 9a and 9b may essentially follow the handover procedure from EPS to 5GS using the N26 interface as defined in Section 4.11.1.2.2 of TS 23.502. For example, except for Step 9 below in the procedures of Figures 9a and 9b, the remaining steps may follow the handover procedure from EPS to 5GS using the N26 interface as defined in Section 4.11.1.2.2 of TS 23.502.

[0174] Referring to FIGS. 9A and 9B , in step 9, the target AMF (910-2) transmits a handover request message including an allowed CAG list to the NG-RAN (930). The target AMF (940-2) can check whether UE subscription data is stored in the target AMF (940-2). If the UE subscription data is stored, the target AMF (940-2) can obtain an allowed CAG list from the UE subscription data and transmit a handover request message including the obtained CAG list to the NG-RAN (930). The NG-RAN (930) can apply or enforce CAGs based on the allowed CAG list. On the other hand, if the target AMF (940-2) does not store UE subscription data, the target AMF (940-2) can search for UE subscription data in the UDM and include the allowed CAG list in the searched UE subscription data in the handover request message and transmit it to the NG-RAN (930).

[0175] The UE subscription data may also be obtained from the UDM by the initial AMF (940-1) rather than the target AMF (940-2). In this case, the remaining steps in the procedures of FIGS. 9A and 9B, except for the steps described below, may follow the handover procedure from EPS to 5GS using the N26 interface in section 4.11.1.2.2 of TS 23.502. For example, before the target AMF (940-2) sends the handover request message in step 9, the initial AMF (940-1) may retrieve the UE subscription data from the UDM after step 3 or after step 7. For example, the initial AMF (940-1) may obtain the UE subscription data from the UDM in parallel with steps 4 through 7 while performing steps 4 after receiving the forwarding relocation request message. If the initial AMF (940-1) had UE subscription data or obtained UE subscription data from the UDM, the initial AMF (940-1) may transmit a message including allowed CAG information (e.g., an allowed CAG list) based on the UE subscription data to the target AMF (940-2) in step 8a. The message including the allowed CAG information may include a Namf_Communication_RelocateUEContext Request message. According to one embodiment, if the forward relocation request message received from the MME (950) includes a CSG list or the target cell is a CAG cell, the initial AMF (940-1) may obtain the UE subscription data from the UDM. If the target AMF (940-2) receives the allowed CAG information from the initial AMF (940-1), the target AMF (940-2) may transmit a handover request message including the allowed CAG information to the NG-RAN (930) in step 9.

[0176] FIG. 10 illustrates an example of a procedure for transmitting allowed CAG information according to one embodiment of the present disclosure. FIG. 10 illustrates a method performed by the AMF. FIG. 10 may be performed when a handover occurs from EPS to 5GS.

[0177] Referring to FIG. 10, in step S1001, the AMF obtains subscription data of a terminal. The subscription data of the terminal may include an allowed CAG list indicating IDs of CAG cells that the terminal is allowed to use. The AMF, as a target AMF that manages or controls a handover target cell of the terminal, obtains subscription data of a terminal that requires handover. According to one embodiment, when a message related to a relocation UE context request for handover of the terminal (e.g., Namf_Communication_RelocateUEContext Request) is received from an initial AMF, the target AMF may check whether the subscription data of the corresponding terminal is stored in the target AMF. If the subscription data of the corresponding terminal is not stored in the target AMF, the target AMF may search for and obtain the subscription data of the terminal from the UDM. According to one embodiment, the target AMF may receive the subscription data of the terminal from the initial AMF. For example, the initial AMF may receive a forwarding relocation request message from the MME, and if the received forwarding relocation request message includes a CSG list or the target cell is identified as a CAG cell, the initial AMF may retrieve and obtain the subscription data of the terminal from the UDM, and transmit a message related to a relocation UE context request including the obtained subscription data of the terminal to the target AMF.

[0178] In step S1003, the AMF transmits a handover request message based on the terminal's subscription data. The AMF obtains the list of allowed CAGs included in the terminal's subscription data and transmits a handover request message containing the list of allowed CAGs to the NG-RAN. At this time, the NG-RAN can apply a CAG to the terminal based on the list of allowed CAGs included in the handover request message.

[0179] FIG. 11 illustrates an example of a procedure for transmitting information related to a CSG according to one embodiment of the present disclosure. FIG. 11 illustrates a method performed by a first network node of a first system. FIG. 11 may be performed when a handover occurs from the first system to a second system. For example, the first system may be a 5GS system, and the second system may be an EPS system. The first network node may include an AMF.

[0180] Referring to FIG. 11, in step S1101, a first network node receives a handover required message. When a terminal needs to be handed over from a base station of the first system to a base station of the second system, the first network node may receive a handover required message from the base station of the first system. According to one embodiment, the handover required message may include at least one of identification information of the target base station (e.g., an eNB ID) or identification information of the target cell (e.g., a target cell ID). According to one embodiment, the message may include at least one of a second group ID related to access to the target cell or cell access mode information indicating whether the target cell is in hybrid mode. The second group may include a CSG group as a group for restricting user access in the second system.

[0181] In step S1103, the first network node transmits a forward relocation request message. The first network node may transmit the forward relocation request message to the second network node of the second system for data path re-establishment and / or terminal context transfer. The first network node may transmit the forward relocation request message to the second network node of the second system based on a handover required message. For example, if the target cell is identified as a second group cell based on the handover required message, the first network node may transmit the forward relocation request message to the second network node of the second system, the forward relocation request message including at least one of a second group ID (e.g., CSG ID) of the target cell or second group member indication information (e.g., CSG group membership indication) indicating whether the corresponding terminal belongs to the second group. The forward relocation request message may further include identification information of a target base station managing the target cell.

[0182] According to one embodiment, the first network node may determine whether the target cell is a second group cell of the second system based on information set in the first network node and information included in a handover required message. The first network node may determine that the target cell is a second group cell based on information related to a second group preset in the first network node. The information related to the second group may include at least one of an ID of a candidate base station of the second system capable of handover, a cell ID of the candidate base station, a TAI of the cell, or mapping information of the second group and the first group. The first group may include a CAG as a group for restricting user access in the first system. The mapping information of the second group and the first group may include at least one of the second group ID and a first group ID mapped to the second group ID, or a cell access mode of the second group cell. The cell access mode of the second group cell may indicate whether the second group cell is a hybrid cell. For example, the first network node may determine whether the target cell is a second group cell based on whether the target base station identification information included in the handover required message or whether the target cell identification information is included in information related to a second group preset to the first network node. If the target cell is determined to be a second group cell, the first network node may transmit a forwarding relocation request message to the second network node of the second system.

[0183] In one embodiment, the first network node can confirm from the handover required message that the handover target cell of the terminal is a second group cell of the second system. Thereafter, the first network node can determine whether the target cell is a cell permitted to the terminal based on the second group ID of the target cell and the subscriber information of the terminal. If the target cell is a cell permitted to the terminal, the first network node can transmit a forwarding relocation request message to the second network node of the second system.

[0184] According to one embodiment, the first network node may further perform at least one operation of the AMF (540) of FIGS. 5A and 5B, the AMF (640) of FIGS. 6A and 6B, the AMF of FIG. 7, or the AMF of FIG. 8.

[0185] FIG. 12 illustrates an example of a procedure for receiving information related to a CSG according to one embodiment of the present disclosure. FIG. 12 illustrates a method performed by a second network node of a second system. FIG. 12 may be performed when a handover occurs from a first system to a second system. For example, the first system may be a 5GS system, and the second system may be an EPS system. The second network node may include an MME.

[0186] Referring to FIG. 12, in step S1201, a second network node receives a forward relocation request message. The second network node of the second system may receive the forward relocation request message from the first network of the first system. The forward relocation request message may include at least one of a second group ID indicating that the handover target cell of the terminal is a second group cell of the second system, or second group member indication information (e.g., a CSG group membership indication) indicating whether the terminal belongs to the second group. The forward relocation request message may further include identification information of a target base station managing the target cell. Here, the second group is a group for restricting user access in the second system and may include a CSG group.

[0187] In step S1203, the second network node transmits a handover request message. The second network node can identify a target base station based on the forwarding relocation request message and transmit a handover request message to the target base station. The handover request transmission message can include at least one of the second group ID received via the forwarding relocation request message or second group member indication information indicating whether the terminal belongs to the second group.

[0188] According to one embodiment, the second network node may further perform at least one operation of the MME (550) of FIGS. 5A and 5B, the MME (650) of FIGS. 6A and 6B, or the MME of FIG. 8.

[0189] Figure 13 illustrates an example of transmitting information related to a CSG according to one embodiment of the present disclosure. Figure 13 illustrates a method performed by a base station of a first system. Figure 13 may be performed when a handover occurs from the first system to a second system. For example, the first system may be a 5GS system, and the second system may be an EPS system. The base station may include a source gNB.

[0190] Referring to FIG. 13, in step S1301, the base station acquires group-related information related to access to each cell from at least one other base station. The base station can recognize at least one other base station located in the vicinity based on ANR, and exchange group-related information related to access to each cell with at least one other recognized base station using configuration transmission signaling. For example, the base station can transmit group-related information related to access to at least one cell supported by the base station to at least one other base station using configuration transmission signaling, and can receive group-related information related to access to at least one other cell supported by the base station from at least one other base station using configuration transmission signaling. The group-related information can include at least one of information related to a first group (e.g., CAG) of a first system, or information related to a second group (e.g., CSG) of a second system. The information related to the first group can include a first group list including first group identification information (e.g., CAG ID) supported by the corresponding base station (e.g., gNB). Information related to the second group may include at least one of a second group list including second group identification information (e.g., CSG ID) supported by the corresponding base station (e.g., eNB), or a cell access mode of a cell corresponding to each second group identification information.

[0191] In step S1303, the base station transmits a handover required message to the terminal. The base station detects that a handover of the terminal is required, and can use the identification information of the handover target cell of the terminal and group-related information related to access of each cell supported by at least one other base station to determine whether the target cell is a second group cell of the second system. If the target cell is a second group cell of the second system, the base station can transmit a handover required message to the first network node of the first system, the message including at least one of the second group identification information of the target cell or a cell access mode indicating whether the target cell is a hybrid cell.

[0192] According to one embodiment, the base station may further perform at least one operation of the source gNB (830) of FIG. 8.

[0193] 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).

[0194] 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.

[0195] 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.

[0196] 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.

[0197] Additionally, embodiments of the present disclosure can be applied to various applications such as autonomous vehicles and drones.

Claims

1. In terms of method, A step in which a first network node of a first system receives a handover requirement message for a terminal from a source base station; and A step of the first network node transmitting a forward relocation request message to the second network node of the second system based on the handover required message, A method wherein the above-described forwarding relocation request message includes at least one of identification information of a second group related to access of the target cell, or information indicating whether the terminal belongs to the second group.

2. In claim 1, The step of sending the above-mentioned forwarding relocation request message is: A step of determining, by the first network node of the first system, whether the handover target cell is a second group cell of the second system based on information set in the first network node and the handover required message, A method in which the above-mentioned forwarding relocation request message is transmitted based on the target cell being a second group cell of the second system.

3. In claim 2, The information set in the first network node includes at least one of an ID of a candidate base station of a second system capable of handover, a cell ID of the candidate base station, a TAI (tracking area identity) of the cell, or mapping information of a second group of the second system and a first group of the first system. A method wherein the mapping information comprises at least one of the second group ID and the first group ID mapped to the second group ID, or a cell access mode indicating whether the second group cell is a hybrid cell.

4. In claim 3, A method in which whether the handover target cell is a second group cell of the second system is determined based on whether at least one of the ID of the target base station or the ID of the target cell included in the handover required message is included in the set information.

5. In claim 3, The step of sending the above-mentioned forwarding relocation request message is: If the target cell is a second group cell of the second system, the method further includes a step of determining whether the target cell is an allowed cell for the terminal based on the second group ID of the target cell and the subscriber information of the terminal. If the target cell is a cell allowed to the terminal, the forwarding relocation request message is transmitted, A method in which a handover preparation failure message is transmitted from the first network node to the source base station when the target cell is not a cell allowed to the terminal.

6. In claim 3, The step of sending the above-mentioned forwarding relocation request message is: If the target cell is a second group cell of the second system, the step of determining whether the target cell is a hybrid cell based on a cell access mode of the target cell is further included. A method in which information indicating whether the terminal belongs to the second group is included in the forwarding relocation request message based on the target cell being a hybrid cell.

7. In claim 2, The first group above includes a closed access group (CAG), The second group is a method including a closed subscriber group (CSG).

8. In claim 1, A method wherein the handover required message includes at least one of second group identification information of the target cell, or a cell access mode indicating whether the target cell is a hybrid cell.

9. In the method, A step in which a second network node of a second system receives a forward relocation request message from a first network node of a first system; and A step of the second network node of the second system transmitting a handover request message for the terminal to the base station of the second system, A method wherein at least one of the above-described forwarding relocation request message or the above-described handover request message includes at least one of second group identification information related to access of the handover target cell of the terminal, or information indicating whether the terminal belongs to the second group.

10. In the method, A step in which a first base station of a first system obtains information related to a second group from a second base station of a second system; and The first base station further includes a step of transmitting a handover required message for the terminal to the first network node, A method wherein the handover required message includes at least one of second group identification information related to access to the handover target cell of the terminal, or a cell access mode indicating whether the target cell is a hybrid cell.

11. In claim 10, Information related to the second group is obtained through configuration transfer signaling with the second base station, A method wherein information related to the second group includes at least one of a group list of at least one cell supported by the second base station, or cell access mode information of the at least one cell.

12. In the device, Transmitter and receiver; and A processor connected to the transceiver, the processor comprising: Receives a handover required message for the terminal from a source base station of the first system to which the above device belongs, Control to transmit a forward relocation request message to the second network node of the second system based on the above handover requirement message, A device wherein the above-described forwarding relocation request message includes at least one of second group identification information related to access to the target cell, or information indicating whether the terminal belongs to the second group.

13. In the device, Transmitter and receiver; and A processor connected to the transceiver, the processor comprising: Receive a forward relocation request message from the first network node of the first system, Controls the transmission of a handover request message for the terminal to the base station of the second system to which the above device belongs, A device wherein at least one of the above-described forwarding relocation request message or the above-described handover request message includes at least one of second group identification information related to access of the handover target cell of the terminal, or information indicating whether the terminal belongs to the second group.

14. In the device, Transmitter and receiver; and A processor connected to the transceiver, the processor comprising: Obtain information related to the second group from the second base station of the second system, Controls the transmission of a handover required message to the first network node of the first system to which the above device belongs, A device in which the handover required message includes at least one of second group identification information related to access to the handover target cell of the terminal, or a cell access mode indicating whether the target cell is a hybrid cell.

15. In communication devices, At least one processor; At least one memory storing instructions that direct operations when executed by at least one processor; The above actions are, A step in which a first network node of a first system receives a handover required message for a terminal from a source base station; and A step of the first network node transmitting a forward relocation request message to the second network node of the second system based on the handover required message, A communication device wherein the above-mentioned forwarding relocation request message includes at least one of second group identification information related to access to the target cell, or information indicating whether the terminal belongs to the second group.

16. In a non-transitory computer-readable medium storing at least one instruction, At least one instruction executable by the processor, Receives a handover required message for the terminal from a source base station of the first system to which the above device belongs, Control to transmit a forward relocation request message to the second network node of the second system based on the above handover requirement message, A computer-readable medium wherein the above-mentioned forwarding relocation request message includes at least one of second group identification information related to access of the target cell, or information indicating whether the terminal belongs to the second group.

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