Method and apparatus for rederiving cell reselection priority in slice-based cell reselection in next generation mobile communication system

Abstract

The present disclosure relates to a 5G or 6G communication system for supporting higher data rates. A method performed by a terminal performing slice-based cell reselection in a wireless communication system is provided. The method includes: obtaining information about a network slice access layer group (NSAG) from a non-access layer (NAS); identifying if a cell in the frequency supports at least one NSAG other than the NSAG in a case where the cell satisfies a cell reselection criterion and does not support the NSAG; and rederiving a reselection priority of the frequency based on a result of the identification.

Description

Technical Field

[0001] The present disclosure relates generally to mobile communication systems, and more particularly, to a method for re-deriving cell reselection priorities in slice-based cell reselection in a next generation mobile communication system. Background Art

[0002] 5G mobile communication technology defines a wide frequency band, making high transmission rates and new services possible, and can be implemented not only in "below 6 GHz" frequency bands such as 3.5 GHz, but also in "above 6 GHz" frequency bands called millimeter waves (mmWave) including 28 GHz and 39 GHz. In addition, it has been considered to implement 6G mobile communication technology (called Beyond 5G System) in the terahertz frequency band (e.g., 95 GHz to 3 THz frequency band) in order to achieve a transmission rate 50 times faster than 5G mobile communication technology and an ultra-low latency of one tenth of 5G.

[0003] At the beginning of the development of 5G mobile communication technology, in order to support services and meet performance requirements related to enhanced mobile broadband (eMBB), ultra-reliable and low-latency communication (URLLC), and massive machine type communication (mMTC), standardization is underway on the following technologies: beamforming and massive MIMO for mitigating radio wave path loss and increasing radio wave transmission distance in millimeter waves, support for parameter sets (e.g., operating multiple subcarrier intervals) for efficient utilization of millimeter wave resources and dynamic operation of time slot formats, initial access technology for supporting multi-beam transmission and broadband, definition and operation of BWP (bandwidth part), new channel coding methods such as LDPC (low-density parity check) codes for large-scale data transmission and polar codes for highly reliable transmission of control information, L2 preprocessing, and network slicing for providing dedicated networks dedicated to specific services.

[0004] Currently, in view of the services that 5G mobile communication technology will support, discussions are ongoing on improvements and performance enhancements of initial 5G mobile communication technology, and there is already physical layer standardization on technologies such as: V2X (Vehicle to Everything) for assisting driving determination of autonomous vehicles based on information about the location and status of the vehicle sent by the vehicle and for enhancing user convenience, NR-U (New Radio Unlicensed) for system operation in unlicensed frequency bands that complies with various regulatory requirements, NR UE power saving, NTN (Non-Terrestrial Network), which is UE-satellite direct communication for providing coverage in areas where communication with terrestrial networks is not available, and positioning.

[0005] In addition, in terms of air interface architecture / protocol, standardization is being carried out on technologies such as the Industrial Internet of Things (IIoT) for supporting new services through interworking and integration with other industries, IAB (Integrated Access and Backhaul) for providing nodes for network service area expansion by supporting wireless backhaul links and access links in an integrated manner, mobility enhancement including conditional handover and DAPS (Dual Active Protocol Stack) handover, and two-step random access (NR's 2-step RACH) for simplifying the random access procedure. In terms of system architecture / services, standardization is also being carried out on technologies such as the 5G baseline architecture (e.g., service-based architecture or service-based interface) for combining network function virtualization (NFV) and software defined network (SDN) technologies, and mobile edge computing (MEC) for receiving services based on UE location.

[0006] As 5G mobile communication systems are commercialized, the number of connected devices, which has been growing exponentially, will be connected to the communication network, and it is therefore expected that enhanced functions and performance of the 5G mobile communication system and integrated operations of the connected devices will be necessary. To this end, new research related to the following technologies is planned: extended reality (XR) for effectively supporting AR (augmented reality), VR (virtual reality), MR (mixed reality), etc., 5G performance improvement and complexity reduction by utilizing artificial intelligence (AI) and machine learning (ML), AI service support, metaverse service support, and drone communication.

[0007] Furthermore, such development of 5G mobile communication systems will serve as a foundation for developing not only new waveforms for providing coverage in the terahertz band for 6G mobile communication technology, multi-antenna transmission technologies (such as full-dimensional MIMO (FD-MIMO), array antennas, and massive antennas), metamaterial-based lenses and antennas for improving coverage of terahertz band signals, high-dimensional spatial multiplexing technologies using OAM (orbital angular momentum), and RIS (reconfigurable smart surfaces), but also full-duplex technologies for improving the frequency efficiency of 6G mobile communication technology and improving system networks, AI-based communication technologies for achieving system optimization by utilizing satellites and AI from the design stage and internalizing end-to-end AI support functions, and next-generation distributed computing technologies for achieving services with a complexity level that exceeds the operational capability limits of UEs by utilizing ultra-high performance communication and computing resources. Summary of the invention

[0008] Technical issues

[0009] A mobile communication system may be configured with a network that supports network slicing. That is, a single physical network may be configured and managed as logically separated network slices (hereinafter referred to as slices). A mobile communication service provider may provide dedicated networks dedicated to various services with different characteristics. Depending on the service characteristics, each network slice may have different types and quantities of required resources, and the mobile communication system may guarantee the resources required for each network slice. For example, control plane signaling may frequently appear in a network slice that provides voice phone services, for which a network slice may be configured with a dedicated network function (NF). Large-scale data services may frequently appear in a network slice that provides Internet data services, for which a network slice may be configured with a dedicated NF. In the 5G system defined by the Third Generation Partnership Project (3GPP), a network slice may be referred to as a single network slice selection assistance information (S-NSSAI), which consists of a slice / service type (SST) value and a slice distinguisher (SD) value. SST may represent the characteristics of services supported by a slice (such as eMBB, IoT, URLLC, and V2X). SD may be used as an additional identifier for a specific service referred to as SST.

[0010] The UE may access the mobile communication system to perform a registration process, during which the UE may send information about the slice to be used (hereinafter referred to as the requested NSSAI) to the mobile communication system. Such a requested NSSAI may include one or more S-NSSAI values. The mobile communication system may authenticate the UE's request, and when the authentication is successful, determine the network slice information available to the UE (hereinafter referred to as the allowed NSSAI). Such an allowed NSSAI may include one or more S-NSSAI values. The UE may receive the allowed NSSAI from the mobile communication system, may store the allowed NSSAI, and may use the allowed NSSAI in subsequent processes.

[0011] However, the prior art has deficiencies in handling such network slices in cell reselection. Therefore, there is a need in the art to consider the cell reselection process of network slices.

[0012] Technical Solution

[0013] According to one aspect of the present disclosure, a method performed by a terminal performing slice-based cell reselection in a wireless communication system is provided. The method includes: obtaining information about a network slice access layer group (NSAG) from a non-access layer (NAS); in the case where a cell in a frequency satisfies a cell reselection criterion and does not support NSAG, identifying whether the cell supports at least one NSAG other than the NSAG; and based on the result of the identification, re-deriving the reselection priority of the frequency.

[0014] According to another aspect of the present disclosure, a terminal for performing slice-based cell reselection in a wireless communication system is provided. The terminal includes a transceiver and a controller coupled to the transceiver. The controller is configured to obtain information about NSAG from NAS, identify whether the cell supports at least one NSAG other than the NSAG when the cell in the frequency meets the cell reselection criteria and does not support NSAG, and re-derive the reselection priority of the frequency based on the result of the identification.

[0015] Beneficial Effects

[0016] The present disclosure addresses at least the above-mentioned problems and / or disadvantages and provides at least the advantages described below.

[0017] Therefore, an aspect of the present disclosure is to provide a method and apparatus for effectively and efficiently performing cell reselection considering network slicing in a wireless communication system. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The above and other aspects, features and advantages of certain embodiments of the present disclosure will become more apparent from the following description in conjunction with the accompanying drawings, in which:

[0019] Figure 1 The structure of the LTE system according to the embodiment is shown;

[0020] Figure 2 A radio protocol structure in an LTE system according to an embodiment is shown;

[0021] Figure 3 shows the structure of a next generation mobile communication system according to an embodiment;

[0022] Figure 4 shows a radio protocol structure of a next generation mobile communication system according to an embodiment;

[0023] Figure 5 A process of receiving a configuration of a slice group and a slice group priority by a UE through an access and mobility management function (AMF) in a next generation mobile communication system according to an embodiment is shown;

[0024] Figure 6 It is shown that a UE supporting slice-based cell reselection in a next-generation mobile communication system according to an embodiment performs a slice-based cell reselection process;

[0025] Fig. 7A A UE that re-derives reselection priorities for supporting slice-based cell reselection in a next generation mobile communication system according to an embodiment is shown;

[0026] Figure 7BA UE that re-derives reselection priorities for supporting slice-based cell reselection in a next generation mobile communication system according to an embodiment is shown;

[0027] Fig. 8A A UE that re-derives reselection priorities for supporting slice-based cell reselection in a next generation mobile communication system according to an embodiment is shown;

[0028] Figure 8B A UE that re-derives reselection priorities for supporting slice-based cell reselection in a next generation mobile communication system according to an embodiment is shown;

[0029] Fig.9A A UE that re-derives reselection priorities for supporting slice-based cell reselection in a next generation mobile communication system according to an embodiment is shown;

[0030] Fig. 9B A UE that re-derives reselection priorities for supporting slice-based cell reselection in a next generation mobile communication system according to an embodiment is shown;

[0031] Fig.10 shows the internal structure of a UE according to an embodiment; and

[0032] Fig.11 The configuration of an NR base station according to an embodiment is shown. DETAILED DESCRIPTION

[0033] Embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. For the sake of clarity and conciseness, descriptions of well-known components and processing techniques are omitted.

[0034] In the accompanying drawings, some elements may be exaggerated, omitted or schematically shown. The size of each element does not completely reflect the actual size, and the same or corresponding elements are provided with the same reference numerals.

[0035] The present disclosure is not limited to the embodiments described below, but can be implemented in various forms. The embodiments are provided to fully disclose the present disclosure and inform those skilled in the art of the scope of the present disclosure. Throughout the specification, the same or similar reference numerals represent the same or similar elements.

[0036] Herein, the term "unit" refers to a software element or a hardware element that performs a predetermined function, such as a field programmable gate array (FPGA) or an application specific integrated circuit (ASIC). However, the unit is not always limited to software or hardware. The unit can be constructed to be stored in an addressable storage medium or to execute one or more processors. Therefore, the unit includes software elements, object-oriented software elements, class elements or task elements, processes, functions, attributes, programs, subroutines, program code segments, drivers, firmware, microcodes, circuits, data, databases, data structures, tables, arrays, and parameters. The elements and functions provided by the unit can be combined into smaller numbers of elements or units, or divided into larger numbers of elements or units. In addition, elements and units can be implemented as duplicating one or more central processing units (CPUs) in a device or a secure multimedia card.

[0037] The terms to be described below are defined in consideration of the functions of this document and may differ depending on the user, the user's intention or habit. Therefore, the definition of the terms should be made based on the contents of the entire specification.

[0038] In this article, for the convenience of description, the terms used to identify access nodes, refer to network entities, refer to messages, refer to interfaces between network entities, and refer to various identification information are used illustratively. Therefore, the present disclosure is not limited to the terms used below, and other terms referring to themes with equivalent technical meanings may be used.

[0039] For convenience of description, the terms and names defined in the 3rd Generation Partnership Project Long Term Evolution (3GPP LTE) specification will be used. However, the present disclosure is not limited to these terms and names and can be applied to systems conforming to other specifications in the same manner. Herein, the term eNB can be used interchangeably with the term gNB to refer to a base station.

[0040] Figure 1 The structure of an LTE system according to an embodiment is shown.

[0041] refer to Figure 1 , the radio access network of the LTE system includes next generation base stations (evolved node B, hereinafter referred to as ENB, node B or base station) 1-05, 1-10, 1-15 and 1-20, mobility management entity (MME) 1-25 and serving gateway (S-GW) 1-30. User equipment (hereinafter referred to as UE or terminal) 1-35 accesses the external network through ENB 1-05 to 1-20 and S-GW 1-30.

[0042] exist Figure 1In the LTE system, ENB 1-05 to 1-20 correspond to the existing Node B of the UMTS system. The ENB is connected to the UE 1-35 through a radio channel and performs a more complex role than the existing Node B. In the LTE system, because all user services, including real-time services such as Voice Over IP (VoIP) through the Internet Protocol, can be served through a shared channel, a device for scheduling by collecting status information such as the buffer status of the UE, the available transmission power status, the channel status, etc. is required, and the ENB 1-05 to 1-20 is responsible for this. One ENB usually controls multiple cells. For example, in order to achieve a transmission rate of 100Mbps, the LTE system uses orthogonal frequency division multiplexing (OFDM) as a radio access technology in a 20MHz bandwidth. In addition, an adaptive modulation and coding (AMC) scheme that determines the modulation scheme and the channel coding rate based on the channel state of the UE is applied. The S-GW 1-30 provides a data bearer and generates or removes a data bearer under the control of the MME 1-25, which controls various control functions and a mobility management function of the UE and is connected to a plurality of base stations.

[0043] Figure 2 A radio protocol structure in an LTE system according to an embodiment is shown.

[0044] refer to Figure 2 , the radio protocols of the LTE system include Packet Data Convergence Protocol (PDCP) 2-05 and 2-40, Radio Link Control (RLC) 2-10 and 2-35, and Medium Access Control (MAC) 2-15 and 2-30 in the UE and ENB respectively. PDCP 2-05 and 2-40 perform operations such as IP header compression / decompression. The main functions of PDCP include header compression and decompression (Robust Header Compression (ROHC) only), transmission of user data, in-order delivery of upper layer PDUs during PDCP reestablishment of RLC AM, for split bearers in DC (supporting RLC AM only): PDCP PDU routing for transmission and PDCP PDU reordering for reception, duplication detection of lower layer SDUs during PDCP reestablishment of RLC AM, retransmission of PDCP SDUs at handover for RLC AM and retransmission of PDCP PDUs during PDCP data recovery for split bearers in DC, encryption and decryption, and timer-based SDU discard in UL.

[0045] RLC 2-10 and 2-35 perform ARQ operations by reconfiguring PDCP packet data units (PDUs) to the appropriate size. The main functions of RLC include: delivery of upper layer PDUs; error correction through ARQ (only for AM data transmission); concatenation, segmentation and reassembly of RLC SDUs (only for UM and AM data transmission); resegmentation of RLC data PDUs (only for AM data transmission); reordering of RLC data PDUs (only for UM and AM data transmission); duplicate detection (only for UM and AM data transmission); protocol error detection (only for AM data transmission); RLC SDU discard (only for UM and AM data transmission); and RLC reconstruction.

[0046] MAC 2-15 and 2-30 are connected to several RLC layers configured in one UE, and perform operations of multiplexing RLC PDU into MAC PDU and demultiplexing RLC PDU from MAC PDU. The main functions of MAC include: mapping between logical channels and transport channels, multiplexing MAC SDUs belonging to one or different logical channels into transport blocks (TBs) delivered to the physical layer on the transport channel / demultiplexing MAC SDUs belonging to one or different logical channels according to transport blocks (TBs) delivered from the physical layer on the transport channel, scheduling information reporting, error correction through HARQ, priority processing between logical channels of one UE, priority processing between UEs with the help of dynamic scheduling, MBMS service identification, transport format selection and padding.

[0047] The physical layers 2-20 and 2-25 channel-code and modulate the upper layer data, create OFDM symbols and transmit the OFDM symbols through a radio channel, or demodulate and channel-decode OFDM symbols received through a radio channel and transmit the symbols to an upper layer.

[0048] Figure 3 A structure of a next generation mobile communication system according to an embodiment is shown.

[0049] refer to Figure 3 , the radio access network of the next generation mobile communication system (hereinafter referred to as NR or 5G) includes NRgNB or NR base station 3-10 and new radio core network (NR CN) 3-05. The new radio user equipment (hereinafter referred to as NR UE or terminal) 3-15 accesses the external network through NR gNB 3-10 and NR CN 3-05.

[0050] exist Figure 3In the present invention, NR gNB 3-10 corresponds to the eNB of the existing LTE system. NR gNB is connected to NR UE 3-15 through a radio channel and can provide services superior to those of the existing Node B. In the next generation mobile communication system, since all user services are served through a shared channel, a device for scheduling by collecting status information such as the buffer status of the UE, the available transmission power status, the channel status, etc. is required and is performed by NR NB 3-10. One NR gNB usually controls multiple cells. Compared with the current LTE, a bandwidth greater than or equal to the existing maximum bandwidth can be applied to achieve ultra-high-speed data transmission, and additional beamforming technology can be transplanted by using OFDM as a radio access technology. In addition, an AMC scheme for determining a modulation scheme and a channel coding rate according to the channel status of the UE is applied. NR CN 3-05 performs functions such as mobility support, bearer configuration, QoS configuration, and mobility management functions for the UE and is connected to multiple base stations. In addition, the next generation mobile communication system can be linked with the existing LTE system, and NR CN is connected to MME 3-25 through a network interface. MME is connected to the existing base station eNB 3-30.

[0051] Figure 4 A radio protocol structure of a next generation mobile communication system according to an embodiment is shown.

[0052] Reference Figure 4 The radio protocols of the next generation mobile communication system include NR Service Data Adaptation Protocol (NR SDAP) 4-01 and 4-45, NR PDCP 4-05 and 4-40, NR RLC 4-10 and 4-35, and NR MAC 4-15 and 4-30 in UE and NR base station respectively.

[0053] The main functions of NR SDAP 4-01 and 4-45 may include transmission of user plane data, mapping between QoS flows and DRBs for both DL and UL, marking of QoS flow IDs in both DL and UL packets, and reflective QoS flow to DRB mapping of UL SDAP PDU.

[0054] Regarding the SDAP layer, the UE may be configured with an RRC message to determine whether to use the SDAP layer header or the SDAP layer function for each PDCP layer, for each bearer or for each logical channel, and when the SDAP header is configured, the UE may use the 1-bit indicator (NAS reflected QoS) of the non-access layer (NAS) quality of service (QoS) reflection of the SDAP header and the 1-bit indicator (AS reflected QoS) of the AS QoS reflection to indicate that the UE updates or reconfigures the mapping information for UL and DL QoS flows and data bearers. The SDAP header may include QoS flow ID information indicating QoS. QoS information can be used as data processing priority, scheduling information, etc. to support smooth services.

[0055] The main functions of NR PDCP 4-05 and 4-40 may include: header compression and decompression (ROHC only), transmission of user data, in-order delivery of upper layer PDUs, out-of-order delivery of upper layer PDUs, PDCP PDU reordering for reception, duplicate detection of lower layer SDUs, retransmission of PDCP SDUs, ciphering and deciphering, and timer-based SDU discard in UL.

[0056] The reordering function of NR PDCP may refer to reordering the PDCP PDUs received from the lower layer in sequence based on the PDCP sequence number (SN), and may include the following functions: sending data to the upper layer in the rearranged order or directly sending the data without considering the order, recording the lost PDCP PDUs by rearranging the order, reporting the status of the lost PDCP PDUs to the transmitting side, and requesting retransmission of the lost PDCP PDUs.

[0057] The main functions of NR RLC 4-10 and 4-35 may include: transmission of upper layer PDUs; in-order delivery of upper layer PDUs; out-of-order delivery of upper layer PDUs; error correction through ARQ; concatenation, segmentation and reassembly of RLC SDUs; resegmentation of RLC data PDUs; reordering of RLC data PDUs; duplicate detection; protocol error detection; RLC SDU discard; and RLC reconstruction.

[0058] The ordered delivery of NR RLC refers to the sequential delivery of the RLC SDU received from the lower layer to the upper layer, which may include the following functions: when an initial RLC SDU is divided into several RLC SDUs and received, reassembling and delivering the divided RLC SDUs, rearranging the received RLC PDUs based on the RLC sequence number (SN) or the PDCP sequence number (SN), reordering and recording the lost RLC PDUs, reporting the status of the lost RLC PDUs to the sending side, requesting the retransmission of the lost RLC SDUs, when there is a lost RLC SDU, only transmitting the RLC SDUs before the lost RLC SDU to the upper layer in sequence, or if a predetermined timer has expired, even if there is a lost RLC SDU, all RLC SDUs received before the timer starts are delivered to the upper layer in sequence, or if the predetermined timer has expired, even if there is a lost RLC SDU, all RLC SDUs received so far are delivered to the upper layer in sequence. The RLC PDUs may be processed in the order in which they are received (regardless of the order of the sequence number and the sequence number, in the order of arrival) and delivered to the PDCP device out of order (out of order delivery), and in the case of segmentation, segments stored in a buffer or to be received later are received, reconstructed into a complete RLC PDU, processed, and sent to the PDCP device. The NR RLC layer may not include a cascading function, and this function may be performed by the NR MAC layer or replaced by a multiplexing function of the NR MAC layer.

[0059] The out-of-order delivery of the NR RLC device refers to directly delivering the RLC SDU received from the lower layer to the upper layer regardless of the order, and may include the following functions: reassembly and delivery when the original RLC SDU is divided into several RLC SDUs and received, storage of the RLC SN or PDCP SN of the received RLC PDU, arrangement of the order, and recording of lost RLC PDUs.

[0060] NR MAC 4-15 and 4-30 can be connected to several NR RLC layers configured in one UE, and the main functions of NR MAC can include: mapping between logical channels and transport channels, multiplexing / demultiplexing of MAC SDU, scheduling information reporting, error correction through HARQ, priority handling between logical channels of one UE, priority handling between UEs with the help of dynamic scheduling, MBMS service identification, transport format selection and padding.

[0061] The NR PHY layers 4-20 and 4-25 may channel encode and modulate upper layer data, create OFDM symbols, and transmit the OFDM symbols through a radio channel, or may demodulate and channel decode OFDM symbols received through a radio channel and transmit the symbols to an upper layer.

[0062] Figure 5 The following figure shows the process of UE receiving the configuration of slice group and slice group priority through AMF in the next generation mobile communication system.

[0063] A slice group according to the present disclosure may refer to one or more slices. A slice group may be referred to as a network slice AS group (NSAG). A UE supporting NSAG may receive NSAG information configured in a NAS message and a priority value of each NSAG through an AMF. NSAG information may be configured for each tracking area (TA), and the information may include at least one of an NSAG identifier (NSAG-Id) for identifying each NSAG, mapping information of which NSAG a particular slice belongs to, and a tracking area identifier (TAI) for each NSAG. When each TA uses the same NSAG identifier but includes different slices, the TAI may be included. For example, when the TAI is not included in a particular NSAG, it may indicate that the mapping of the same slice is applied to all TAs belonging to the registration area (RA) of the UE.

[0064] refer to Figure 5 In step 5-05, UE 5-01 may be in RRC_IDLE mode.

[0065] In step 5-10, the RRC idle mode UE 5-01 may perform a public land mobile network (PLMN) selection procedure.

[0066] In step 5-13, the RRC idle mode UE 5-01 can obtain the system information broadcast by the NR base station 5-02, and in step 5-15, can reside in a suitable NR cell through the cell selection or cell reselection process.

[0067] RRC idle mode UE 5-01 can perform an RRC connection establishment process with the resident cell. Specifically, in step 5-20, UE 5-01 can send an RRC connection establishment request message (RRCSetupRequest (RRC establishment request)) to the NR base station. In step 5-25, the NR base station 5-02 can send an RRC connection establishment message to UE 5-01. When receiving the RRC connection establishment message, UE 5-01 can apply the configuration information contained in the RRC connection establishment message and transition to RRC connection mode (RRC_CONNECTED (RRC_connection)) (5-26).

[0068] In step 5-30, UE 5-01 that has transitioned to RRC connection mode may send an RRC connection establishment completion message to NR base station 5-02. When the upper layer device provides one or more single network slice selection assistance information (S-NSSAI), UE 5-01 may include an s-NSSAI-List (s-NSSAI-list) with a value provided by the upper layer device in the RRC connection establishment completion message and send the message to the NR base station. The S-NSSAI-List includes one or more S-NSSAIs, and each S-NSSAI may include an SST (slice / service type) or an SST and an SST-SD (slice / service type and slice distinguisher), and the ASN.1 structure may be represented as shown in Table 1 below.

[0069]

Table 1

[0070]

[0071]

[0072] In step 5-30, UE 5-01 may include a NAS message (DedicatedNAS-Message) in an RRC connection setup complete message (RRCSetupComplete) and send it to the NR base station 5-02. For example, the NAS message may refer to a registration request message and may include information indicating that UE 5-01 supports NSAG or information indicating whether UE 5-01 supports NSAG.

[0073] In step 5-35, the NR base station 5-02 may forward the registration request message to the AMF 5-03.

[0074] In step 5-40, the Network Slice Selection Function (NSSF) 5-04 may select a network slice that can be supported by the 5G Core and deliver it to the AMF 5-03.

[0075] In step 5-45, the AMF 5-03 may include at least one of NSAG information of one or more N-SSAIs and priority information of each NSAG in the registration acceptance message and send it to the NR base station. The NSAG information may include at least one of TA and TAI, and

[0076] Mapping information indicating which NSAG one or more slices belong to and an identifier (NSAG-Id) of each NSAG. Up to 32 NSAGs can be configured for each PLMN, and the NSAG can be unique for each PLMN. This information can be configured for each TA.

[0077] NSAG information and NSAG priority information may also be provided in the UE configuration command message. In step 5-45, the registration accept message may include the allowed NSSAI and the unsupported NSSAI (target NSSAI) among the NSSAI requested by the UE 5-01, and send them to the NR base station. The message may also include an index of the RAT / frequency slice selection priority for each frequency / RAT (hereinafter referred to as the RFSP index).

[0078] In step 5-50, the NR base station 5-02 may send a DLInformationTransfer message to the UE 5-01. A registration acceptance message may be included in the message.

[0079] Figure 6 It is shown that a UE supporting slice-based cell reselection in a next-generation mobile communication system according to an embodiment performs a slice-based cell reselection process.

[0080] According to the present disclosure, the UE can support slice-based cell reselection in a normal camping state (when camping on a suitable cell). For example, the UE can perform a slice-based cell reselection process taking into account one or more NSAGs provided from the non-access stratum (NAS) and the priority of each NSAG.

[0081] refer to Figure 6 In step 6-05, UE 6-01 can establish an RRC connection with NR base station 6-02 and is in RRC connection mode (RRC_CONNECTED). Figure 5 In the above embodiment, the UE can configure NSAG information and priority information for each NSAG using NAS messages through the AMF.

[0082] In step 6-10, UE 6-01 may send a UE capability information message (UECapabilityInformation) to NR base station 6-02. The message may include the following indicator (sliceInfoforCellReselection).

[0083] An indicator indicating whether slice reselection information included in a system information block (hereinafter referred to as SIB) and / or an RRC connection release (RRC Release (RRC Release)) message is supported to perform slice-based cell reselection in RRC idle mode (RRC_IDLE) and RRC inactive mode (RRC_INACTIVE), indicating whether the UE supports slice reselection information in the SIB and / or on the RRC Release message for slice-based cell reselection in RRC_IDLE and RRC_INACTIVE modes.

[0084] In step 6-15, the NR base station 6-02 may send a RRCRelease message to the UE 6-01. The cell reselection priority configuration information may be included in the message. The cell reselection priority configuration information may include at least one of the frequency priority list of EUTRA (freqPriorityListEUTRA), the frequency priority list of NR (freqPriorityListNR), the t320 timer value, and the frequency priority list dedicated to slicing (freqPriorityListDedicatedSlicing).

[0085] FreqPriorityListEUTRA may include one or more FreqPriorityEUTRA (frequency priority EUTRA), and is a list that may include up to maxFreq (maximum frequency) (=8) FreqPriorityEUTRA. Each FreqPriorityEUTRA may include at least one of a reference radio frequency channel number (ARFCN-ValueEUTRA (ARFCN-value EUTRA)) indicating a carrier frequency, a cell reselection priority value (CellReselectionPriority (cell reselection priority)), and a cell reselection sub-priority value (cellReselectionSubPriority (cell reselection sub-priority)). The cell reselection priority value may be configured as an integer value from 0 to 7, and the cell reselection sub-priority value may be configured as a decimal value of one of 0.2, 0.4, 0.6, and 0.8. When the cell reselection priority value and the cell reselection sub-priority value are configured simultaneously for a specific carrier frequency, the UE may derive the cell reselection priority value by adding the two values. When only one of the cell reselection priority value and the cell reselection sub-priority value is configured for a specific carrier frequency, the UE may derive the cell reselection priority value by using the configured value.

[0086] FreqPriorityListNR may include one or more FreqPriorityNRs, and may include up to maxFreq (=8) FreqPriorityNRs in a list (depending on UE capabilities). FreqPriorityNR may include at least one of a reference radio frequency channel number (ARFCN-ValueNR (ARFCN-value NR)) indicating a carrier frequency, a cell reselection priority value (CellReselectionPriority), and a cell reselection sub-priority value (cellReselectionSubPriority). As described above, the UE may derive a cell reselection priority value for each NR carrier frequency. Herein, for convenience of description, the cell reselection priority information included in the list may be referred to as conventional cell reselection priority information.

[0087] The t320 timer value can be configured as one of 5 minutes, 10 minutes, 20 minutes, 30 minutes, 60 minutes, 120 minutes and 180 minutes. Of course, the value can also be configured as other values. The UE can perform a cell reselection evaluation process by driving the T320 timer with the configured timer value and applying the cell reselection priority configuration information received in the RRC connection release message. For example, until the T320 timer expires or stops, the UE can perform a cell reselection evaluation process by applying the cell reselection priority configuration information received in the RRC connection release message. If the timer value is not configured, the UE can perform a cell reselection evaluation process by applying the cell reselection priority configuration information until the cell reselection priority configuration information received in the RRC connection release message is deleted. When performing a cell reselection evaluation process by applying the cell reselection priority configuration information received in the RRC connection release message, the UE can ignore the cell reselection priority configuration information broadcast in the system information. The T320 timer and the above description can be commonly applied to traditional cell reselection priority information and slice cell reselection priority information.

[0088] FreqPriorityListDedicatedSlicing may include one or more FreqPriorityDedicatedSlicings, and may include up to maxFreq (=8) FreqPriorityDedicatedSlicings in a list (depending on UE capabilities). FreqPriorityDedicatedSlicing may include at least one of a reference radio frequency channel number (ARFCN-ValueNR) indicating a carrier frequency and a slice information list (SliceInfoListDedicated). SliceInfoListDedicated may include at least one of NSAG identification information (NSAG-IdentityInfo), a NSAG cell reselection priority value (nsag-CellReselectionPriority), and a NSAG cell reselection sub-priority value (nsag-CellReselectionSubPriority). The NSAG cell reselection priority value may be configured as an integer value in the same range as the above-mentioned cell reselection priority value, and the NSAG cell reselection sub-priority value may be configured as a decimal value in the same range as the above-mentioned cell reselection sub-priority value. NSAG-IdentityInfo may include at least one of an NSAG identifier (NSAG-ID) and a TA code (trackingAreaCode). For the NR carrier frequency included in each FreqPriorityDedicatedSlicing, the cell reselection priority value may be derived according to the above method. Herein, for the convenience of description, the cell reselection priority information included in the list may be referred to as slice cell reselection priority information.

[0089] In step 6-15, the NR base station 6-02 may send an RRC connection release message to the UE 6-01 without simultaneously including the slice cell reselection priority information and the traditional cell reselection priority information for the same NR frequency.

[0090] In step 6-20, upon receiving the RRCRelease message, UE 6-01 may transition to RRC idle mode or RRC inactive mode. Specifically, upon receiving the RRCRelease message including the suspended configuration information (suspendConfig), UE 6-01 may transition to RRC inactive mode, otherwise, UE 6-01 may transition to RRC idle mode.

[0091] In step 6-25, the UE 6-01 in the RRC idle mode or the RRC inactive mode may obtain system information. The system information may refer to a master information block (MIB) and a system information block 1 (SIB1).

[0092] In step 6-30, the UE 6-01 in RRC idle mode or RRC inactive mode can camp on a NR suitable cell by performing a cell selection process. The cell where the UE 6-01 camps can be called a serving cell.

[0093] Herein, based on the specification, a suitable cell can be defined when the conditions in the following Table 2 are met.

[0094]

Table 2

[0095]

[0096]

[0097] When the following expression is satisfied, the UE may determine that the cell selection criterion (S-criterion) is satisfied.

[0098] Srxlev>0 and Squal>0

[0099] in,

[0100] Srxlev=Q rxlevmeas -(Q rxlevmin +Q rxlevminoffset )-P compensation -Qoffset temp ,

[0101] Squal=Q qualmeas -(Q qualmin +Q qualminoffset )-Qoffset temp .

[0102] Definitions of these parameters are provided in the specification.

[0103] In step 6-35, the UE 6-01 in RRC idle mode or RRC inactive mode may obtain system information (e.g., SIB2, SIB3, SIB4, SIB5, and SIB16) including cell reselection information from the serving cell 6-02 in order to perform a cell reselection evaluation process. SIB2 may include information / parameters commonly applied by the UE 6-01 for reselection of NR intra-frequency, NR inter-frequency, and inter-RAT frequency cells, as well as NR intra-frequency cell reselection information in addition to information related to neighboring cells within the NR frequency. For example, SIB2 may include a cell reselection priority configuration information for a serving NR frequency (a frequency on which a cell currently resides). The cell reselection priority configuration information may refer to cellReselectionPriority and cellReselectionSubPriority. Specifically, cellReselectionPriority may contain an integer value (e.g., an integer value from 0 to 7), and cellReselectionSubPriority may contain a fractional value (e.g., one of 0.2, 0.4, 0.6, and 0.8). If both cellReselectionPriority and cellReselectionSubPriority are signaled, the UE may derive the cell reselection priority value by adding the two values. A larger cell reselection priority value indicates a higher priority. Specifically, the cell reselection configuration information broadcast in SIB2 may be as shown in Table 3 below.

[0104]

Table 3

[0105]

[0106]

[0107]

[0108] SIB3 may include neighboring cell information / parameters for UE to reselect NR intra-frequency cells. As an example, in SIB3, an NR intra-frequency cell list (intraFreqNeighCellList) for reselecting NR intra-frequency cells or a cell list (intraFreqBlackCellList) in which NR intra-frequency cell reselection is not allowed may be broadcast. Specifically, the information shown in Table 4 below may be broadcast in SIB3.

[0109]

Table 4

[0110]

[0111]

[0112] SIB4 may include information / parameters for UE to reselect NR inter-frequency cells. For example, one or more NR inter-frequency cells may be broadcast in SIB4, and one cell reselection priority configuration information for each NR inter-frequency cell may be broadcast. The cell reselection priority configuration information for each NR inter-frequency cell refers to the above description (e.g., mapped to cellReselectionPriority and / or cellReselectionSubPriority for each NR inter-frequency cell), but there is a feature of optionally broadcasting one cell reselection priority configuration information for each inter-frequency cell. Specifically, the information shown in Table 5 below may be broadcast in SIB4.

[0113]

Table 5

[0114]

[0115]

[0116]

[0117] SIB5 may include information / parameters for UE to reselect inter-RAT frequency cells. For example, one or more EUTRA frequencies may be broadcast in SIB5, and one cell reselection priority configuration information for each EUTRA frequency may be broadcast. The cell reselection priority configuration information for each EUTRA frequency refers to the above description (e.g., cellReselectionPriority and / or cellReselectionSubPriority mapped to each EUTRA frequency), but there is a feature of optionally broadcasting one cell reselection priority configuration information for each EUTRA frequency. Specifically, the information shown in Table 6 below may be broadcast in SIB5.

[0118]

Table 6

[0119]

[0120]

[0121] SIB16 may include information / parameters for UE to reselect slice-based cells. As an example, in SIB16, slice-based cell reselection priority information of NR frequencies on which UE can perform slice-based cell reselection among NR frequencies broadcast in SIB2 and SIB4 may be broadcast. Specifically, a slice information list (SliceInfoList) for each NR frequency capable of performing slice-based cell reselection may be broadcast. SliceInfoList includes one or more SliceInfo (slice information), and each SliceInfo may include at least one of nsag-IdentityInfo, nsag-CellReselectionPriority, nsag-CellReselectionSubPriority, and sliceCellList. Specifically, the information shown in Table 7 below may be broadcast in SIB16.

[0122]

Table 7

[0123]

[0124]

[0125] Herein, the cell reselection priority information broadcast in SIB2, SIB4 and SIB5 may be referred to as traditional cell reselection priority information, and the cell reselection priority information broadcast in SIB16 may be referred to as slice cell reselection priority configuration information (cellReselectionPriorities).

[0126] In step 6-40, UE 6-01 in RRC idle mode or RRC inactive mode can derive reselection priorities for slice-based cell reselection. When cellReselectionPriorities are configured in the RRC connection release message, the reselection priorities can be derived by applying the cellReselectionPriorities as described above. For example, UE 6-01 can ignore the reselection priorities broadcast in the system information. However, when the cellReselectionPriorities of the RRC connection release message are not applied as described above, UE 6-01 can derive the reselection priorities by applying the reselection priority information broadcast in the system information. Specifically, UE 6-01 can derive the reselection priorities according to the following predetermined rules.

[0127] A frequency that supports at least one prioritized NSAG received from the NAS has a higher reselection priority than a frequency that does not support any NSAG received from the NAS.

[0128] Frequencies supporting at least one NSAG provided by NAS are prioritized in order of the NAS-provided priority of the NSAG with the highest priority supported on the frequency. For example, when NSAG 1 and NSAG 2 are supported at a particular frequency, but the NSAG 1 priority value (provided by NAS) is 3 and the NSAG 2 priority value is 1, the corresponding frequencies may be prioritized according to the priority value of NSAG 1.

[0129] Among the frequencies (one or more) supporting the highest prioritized NSAGs with the same NAS provided priority, the frequencies are prioritized in the order of their highest nsag-CellReselectionPriority given to those NSAGs. For example, when frequency 1 supports NSAG 1 (NSAG 1 priority value is 2), frequency 2 supports NSAG 2 (NSAG 2 priority value is 2), the nsag-CellReselectionPriority of NSAG 1 in frequency 1 is broadcast as 3, and the nsag-CellReselectionPriority of NSAG 2 in frequency 2 is broadcast as 2, frequency 1 may be prioritized over frequency 2.

[0130] A frequency that supports a NSAG provided by NAS and indicates a nsag-CellReselectionPriority of the NSAG has a higher reselection priority than a frequency that supports the preferred NSAG but does not indicate a nsag-CellReselectionPriority of the NSAG. Alternatively, a frequency that supports a NSAG provided by NAS and indicates a nsag-CellReselectionPriority (greater than 0) and / or a nsag-CellReselectionSubPriority (greater than 0) has a higher reselection priority than a frequency that supports the preferred NSAG but does not indicate a nsag-CellReselectionPriority and / or a nsag-CellReselectionSubPriority of the NSAG.

[0131] Frequencies that do not support any NSAG provided by the NAS are prioritized in the order of their cellReselectionPriority and / or cellReselectionSubPriority.

[0132] The UE considers NR frequency to support all slices of NSAG if the following conditions are met.

[0133] The corresponding nsag-ID is indicated for the NR frequency and is valid for the current TA.

[0134] In step 6-45, the UE 6-01 in the RRC idle mode or the RRC inactive mode may perform frequency measurement for cell reselection by using the following measurement rules according to the cell reselection priority determined in step 6-40 in order to minimize battery consumption.

[0135] -When the reception level (Srxlev) of the serving cell is greater than the SIntraSearchP threshold and the reception quality (Squal) of the serving cell is greater than the SIntraSearchQ threshold (the serving cell satisfies Srxlev>SIntraSearchP and Squal>SIntraSearchQ), the UE may not perform NR intra-frequency measurement. Otherwise, the UE performs NR intra-frequency measurement.

[0136] For NR inter-frequencies or inter-RAT frequencies that have a higher reselection priority than the NR frequency of the current serving cell, the UE may perform measurements according to the specification.

[0137] For NR inter-frequencies with a reselection priority lower than or equal to the NR frequency of the current serving cell and inter-RAT frequencies with a reselection priority lower than the NR frequency of the current serving cell, if the reception level of the serving cell (Srxlev) is greater than the SnonIntraSearchP threshold and the reception quality of the serving cell (Squal) is greater than the SnonIntraSearchQ threshold (the serving cell satisfies Srxlev>SnonIntraSearchP and Squal>SnonIntraSearchQ), the UE may not perform measurement. Otherwise, the UE measures cells in the NR inter-frequencies with a reselection priority lower than or equal to the NR frequency, or measures cells in the inter-RAT frequencies with a reselection priority lower than the NR frequency.

[0138] The aforementioned thresholds (SintraSearchP, SintraSearchQ, SnonIntraSearchP, and SnonintraSearchQ) may be broadcast in the system information obtained in step 8-20.

[0139] In step 6-50, the UE 6-01 in RRC idle mode or RRC inactive state may determine to reselect a cell that meets the cell reselection criteria based on the measurement values ​​performed in step 6-45. Different criteria may be applied as cell reselection criteria according to the cell reselection priority. If multiple cells of different priorities meet the cell reselection criteria, cell reselection to a higher priority RAT / frequency may take precedence over a lower priority RAT / frequency. Specifically, the operation of the UE's reselection criteria for an inter-frequency / inter-RAT cell having a higher priority than the frequency of the current serving cell is as follows.

[0140] In the first operation, when SIB2 includes a threshold value of threshServingLowQ and is broadcasted, and 1 second has passed since the UE camped on the current serving cell, if the signal quality (Squal) of the inter-frequency / inter-RAT cell is greater than the threshold value Thresh during a specific time interval TreselectionRAT (TreselectionRAT), the UE shall be reconnected to the serving cell. X，HighQ (Threshold X，高Q )(During the time interval TreselectionRAT, Squal>Thresh X，HighQ ), the UE performs reselection to the corresponding inter-frequency / inter-RAT cell.

[0141] In the second operation, when the UE fails to perform the first operation, the UE performs the second operation. When 1 second has passed since the UE camped on the current serving cell, and the reception level (Srxlev) of the inter-frequency / inter-RAT cell of the specific time interval TreselectionRAT is greater than the threshold Thresh X，HighP (Threshold X，高P )(During the time interval TreselectionRAT-Srxlev>Thresh X，HighP ), the UE performs reselection to the corresponding inter-frequency / inter-RAT cell.

[0142] The UE determines the signal quality (Squal), reception level (Srxlev), threshold (Thresh X、HighQ , Thresh X、HighP ) and TreselectionRAT value, and performs the first operation or the second operation based on the signal quality (Squal), reception level (Srxlev), threshold (Thresh X、HighQ , Thresh X、HighP) and TreselectionRAT value to perform the first operation or the second operation. As an example, SIB4 includes Q qualmin Value or Q rxlevmin The UE determines the signal quality (Squal) or reception level (Srxlev) of the inter-frequency cell based on the value. If there are multiple cells in the NR frequency that meet the high cell reselection priority, the UE can reselect the highest ranked cell among the cells that meet the reselection criteria for the intra-frequency / inter-frequency cell, which has the same priority as the frequency of the current serving cell, as described in detail below.

[0143] In addition, for the reselection criteria of the intra-frequency / inter-frequency cell having the same priority as the frequency of the current serving cell, the UE performs a third operation. Specifically,

[0144] When the signal quality (Squal) and reception level (Srxlev) of the intra-frequency / inter-frequency cell are greater than 0, the ranking (rank) of each cell is derived based on the measurement value (RSRP) (the UE can perform ranking on all cells that meet the cell selection criterion S). The rankings of the serving cell and the neighboring cell are calculated by equations 1 and 2, respectively, as follows.

[0145] [Equation 1]

[0146] Rs=Qmeas,s+Qhyst

[0147] [Equation 2]

[0148] Rn=Qmeas,n-Qoffset

[0149] In equations 1 and 2, Qmeas,s is the RSRP measurement value of the serving cell, Qmeas,n is the RSRP measurement value of the neighboring cell, Qhyst is the hysteresis value of the serving cell, and Qoffset is the offset between the serving cell and the neighboring cell. SIB2 includes a Qhyst value, which is commonly used for intra-frequency / inter-frequency cell reselection. When intra-frequency cell reselection occurs, Qoffset is signaled for each cell, applied only to the indicated cell, and included in SIB3. When inter-frequency cell reselection occurs, Qoffset is signaled for each cell, applied only to the indicated cell, and included in SIB4. When the ranking of the neighboring cell obtained according to equation 2 is greater than the ranking of the serving cell (Rn>Rs), the best cell among the neighboring cells is reselected.

[0150] In addition, for the reselection criteria of the inter-frequency / inter-RAT cell with a lower priority than the frequency of the current serving cell, the UE performs the fourth operation. Specifically, when the threshold of threshServingLowQ is included and broadcasted in SIB2, and 1 second has passed since the UE camped on the current serving cell, if the signal quality (Sqaul) of the current serving cell is less than the threshold Thresh Serving,LowQ (Threshold 服务,低Q )(Squal <Thresh Serving,LowQ ), and during a specific time interval TreselectionRAT, the signal quality (Squal) of the inter-frequency / inter-RAT cell is greater than the threshold Thresh X LowQ -(Threshold X,低Q )(During the time interval TreselectionRAT, Squal>Thresh X,LowQ ), the UE performs reselection to the corresponding inter-frequency / inter-RAT cell.

[0151] In the fifth operation, when the UE fails to perform the fourth operation, the fifth operation is performed.

[0152] When 1 second has passed since the UE camped on the current serving cell, the reception level (Srxlev) of the current serving cell is less than the threshold Thresh Serving，LowP (Threshold 服务,低P )(Srxlev <Thresh Serving，LowP ), and during a specific time interval TreselectionRAT, the reception level (Srxlev) of the inter-frequency / inter-RAT cell is greater than the threshold Thresh X,LowQ (During the time interval TreselectionRAT, Srxlev>Thresh X，LowP (Threshold X,低P )), the UE performs reselection to the corresponding inter-frequency / inter-RAT cell.

[0153] Based on the threshold value (Thresh Serving,LowQ , Thresh Serving,LowP ) and the signal quality (Squal), reception level (Srxlev), threshold (Thresh X,LowQ , Thresh X,LowP ), TreselectionRAT to perform the fourth operation or the fifth operation of the inter-frequency cell of the UE, and based on the threshold value (Thresh Serving,LowQ , Thresh Serving,LowP), and the signal quality (Squal), reception level (Srxlev), threshold (Thresh X,LowQ , Thresh X,LowP ), TreselectionRAT to perform the fourth operation or the fifth operation of the inter-RAT cell of the UE. As an example, SIB4 includes Q qualmin Value or Q rxlevmin value, and based on this, derive the signal quality (Squal) or reception level (Srxlev) of the inter-frequency cell. If there are multiple cells in the NR frequency that meet the high cell reselection priority, the UE can reselect the highest ranked cell among the cells that meet the reselection criteria of the intra-frequency / inter-frequency cell, which has the same priority as the frequency of the current serving cell, as described in detail below. Of course, when a candidate cell is derived by satisfying the above conditions at a frequency with a higher priority or a lower priority than the frequency of the current serving cell, the UE can reselect the cell with the strongest signal strength in the corresponding frequency.

[0154] For a UE that performs slice-based cell reselection according to an embodiment of the present disclosure, it may be additionally determined whether a specific cell (e.g., the best cell or the highest ranked cell) that satisfies the cell reselection criteria in the above step 6-50 supports the corresponding NSAG on a specific frequency based on the reselection priority of the NSAG and frequency derived according to step 6-40. Specifically, if the corresponding nsag-ID is indicated for the NR frequency and is valid for the current TA, and the cell is listed in sliceAllowedCellListNR (if provided in the slice-specific cell reselection information used) or the cell is not listed in sliceExcludedCellListNR (if provided in the slice-specific cell reselection information used), or neither sliceAllowedCellListNR nor sliceExcludedCellListNR is configured in the slice-specific cell reselection information used, the UE considers all slices of the cell on the NR frequency that support NSAG.

[0155] If the best or highest ranked cell in a frequency satisfies the cell reselection criteria in 6-50 for cell reselection based on the NSAG and the reselection priorities for the frequency derived according to 6-40, but the cell does not support the NSAG as described above, the UE may re-derive the reselection priorities for the frequency according to 6-40 by considering the NSAG supported by the cell (rather than those of the corresponding NR frequency). The reselection priorities are used for a maximum of 300 seconds, or until new information of the NSAG and its priorities are received from the NAS. The UE may ensure that the above cell reselection criteria are met based on the newly derived priorities.

[0156] In step 6-55, the UE 6-01 in the RRC idle mode or RRC inactive state receives system information (e.g., MIB or SIB1) broadcast in the candidate target cell before finally reselecting the candidate target cell, and determines whether the reception level (Srxlev) and reception quality (Squal) of the candidate target cell satisfy the S-criteria expression disclosed above, i.e., Srxlev>0 and Squal>0 based on the received system information. When the S-criteria expression is satisfied and the candidate target cell is suitable, the UE can reselect the candidate target cell.

[0157] Fig. 7A A UE that re-derives reselection priorities for supporting slice-based cell reselection in a next generation mobile communication system according to an embodiment is shown, and

[0158] Figure 7B A UE that re-derives reselection priorities and supports slice-based cell reselection in a next generation mobile communication system according to an embodiment is shown.

[0159] refer to Fig. 7A and Figure 7B , a UE supporting slice-based cell reselection can configure an RRC connection with an NR base station and can be in RRC connected mode (RRC_CONNECTED) (7-05). Figure 6 In the embodiment, the UE can send a UE capability information message (UECapabilityInformation) to the NR base station, and the message includes information indicating support for slice-based cell reselection.

[0160] In steps 7-10, the UE may receive an RRCRelease message including cellReselectionPriorities from the NR base station. When the message includes a t320 value and the T320 timer is running, or when the message does not include a t320 value, the UE may perform a cell reselection evaluation procedure by applying the cellReselectionPriorities information. For example, the UE may ignore the cellReselectionPriorities information broadcast in the system information. When the message does not include the cellReselectionPriorities information, when the T320 timer expires, or when the cellReselectionPriorities is released, the UE may perform a cell reselection evaluation procedure by applying the cellReselectionPriorities information broadcast in the system information.

[0161] In step 7-15, the UE may transition to RRC_IDLE or RRC_INACTIVE mode. For example, when the RRC connection release message received in step 7-10 includes suspend configuration information (suspendConfig), the UE may transition to RRC inactive mode, otherwise transition to RRC idle mode.

[0162] In step 7-20, the UE may camp on a suitable cell of the NR to obtain system information including cell reselection information. The system information may refer to MIB, SIB1, SIB2, SIB3, SIB4, SIB5 and SIB16.

[0163] In step 7-25, for slice-based cell reselection, the UE may select a cell based on the Figure 6 The above embodiment in derives the reselection priority. For example, the UE may derive the reselection priority according to the following predetermined rule.

[0164] A frequency that supports at least one preferred NSAG received from the NAS has a higher reselection priority than a frequency that does not support any NSAG received from the NAS.

[0165] Frequencies supporting at least one NSAG provided by the NAS are prioritized in order of the NAS-provided priority of the NSAG with the highest priority supported on the frequency.

[0166] Among the frequencies (one or more) supporting the highest priority NSAGs with the same NAS-provided priority, the frequencies are prioritized in the order of their highest nsag-CellReselectionPriority or nsag-CellReselectionSubPriority given to these NSAGs, or the sum of their highest nsag-CellReselectionPriority and nsag-CellReselectionSubPriority.

[0167] Frequencies that support the NAS-provided NSAG and indicate the nsag-CellReselectionPriority (e.g., it is greater than 0) and / or the nsag-CellReselectionSubPriority (e.g., it is greater than 0) of the NSAG have a higher reselection priority than frequencies that support the preferred NSAG but do not indicate the nsag-CellReselectionPriority and / or the nsag-CellReselectionSubPriority of the NSAG.

[0168] Frequencies that do not support any NSAG provided by the NAS are prioritized in the order of their cellReselectionPriority or in the order of the sum of their cellReselectioPriority and cellReselectionSubPriority.

[0169] In step 7-30, the UE can use Figure 6 The frequency measurements are performed using the measurement rules described in .

[0170] In step 7-35, the UE may determine to reselect a cell that meets the cell reselection criteria. Figure 6 As shown, a specific cell (the best cell or the highest ranked cell) that meets the cell reselection criteria may be derived.

[0171] In step 7-40, the UE performing slice-based cell reselection may determine whether the best cell or the highest ranked cell in the frequency that meets the cell reselection criteria for cell reselection supports NSAG based on the reselection priority of the NSAG and the frequency derived according to step 7-25. If the corresponding nsag-ID is indicated for the NR frequency and is valid for the current TA; and the cell is listed in sliceAllowedCellListNR (if provided in the slice-specific cell reselection information used) or the cell is not listed in sliceExcludedCellListNR (if provided in the slice-specific cell reselection information used), or neither sliceAllowedCellListNR nor sliceExcludedCellListNR is configured in the slice-specific cell reselection information used, the UE may determine whether the best cell or the highest ranked cell supports NSAG by considering all slices in which the cells on the NR frequency support NSAG.

[0172] In step 7-45, when it is determined in step 7-40 that the best cell or the highest ranked cell supports NSAG, the UE performing slice-based cell reselection may reselect Figure 6 Suitable candidate target cells described in .

[0173] In step 7-50, when it is determined in step 7-40 that the best cell or the highest ranked cell does not support NSAG, the UE performing slice-based cell reselection can determine whether other NSAGs are supported in the cell according to the above conditions.

[0174] In step 7-55, when it is determined in step 7-50 that the best cell or the highest ranked cell supports other NSAGs, the UE performing slice-based cell reselection may re-derive the reselection priority by considering the NSAGs supported by the cell according to step 7-25. The re-derived reselection priority may be used for up to 300 seconds, or until new NSAG information and priority values ​​for each NSAG are received from NAS.

[0175] In step 7-60, when it is determined in step 7-50 that the best cell or the highest ranked cell does not support other NSAGs, the UE performing slice-based cell reselection may set the frequency in which the cell operates to the lowest priority. (The UE may consider this frequency to be lower than any network configured value. The re-derived reselection priority may be used for up to 300 seconds, or until new NSAG information and priority values ​​for each NSAG are received from the NAS.

[0176] Fig. 7A and Figure 7BAn embodiment in discloses a method for a UE performing slice-based reselection to re-derive a reselection priority for a corresponding frequency when a specific cell (best cell or highest ranked cell) in a frequency that satisfies a cell reselection criterion based on a reselection priority derived taking into account an NSAG does not support the NSAG. For example, when the corresponding cell does not support all NSAGs received from a NAS, the UE may set a first frequency in which the corresponding cell operates to a lowest reselection priority. As a result, when a cell operating in a different frequency (e.g., a second frequency) does not satisfy a series of conditions and is not subject to reselection, the UE may reselect a cell at a first frequency set to a lowest reselection priority. In this case, when set to the lowest reselection priority, the UE may not consider the NSAG for the corresponding first frequency. Alternatively, because the other best cell or highest ranked cell that satisfies the cell reselection criterion at a frequency (e.g., the first frequency) set to the lowest reselection priority by the UE may be a cell that supports the corresponding NSAG, the UE may consider the NSAG for the first frequency. That is, the following operations are performed by the UE.

[0177] For a UE performing slice-based cell reselection, if a specific cell in a frequency (the best cell or the highest ranked cell) meets the above criteria for cell reselection based on the reselection priorities for the NSAG and frequency derived according to the standard, but the cell does not support the NSAG but supports any other NSAG, the UE may re-derive the reselection priority for the frequency by considering the NSAGs supported by the cell according to the standard (instead of those of the corresponding NR frequency). Otherwise, the UE may consider the frequency to be lower than any network configured value. The reselection priority is used for a maximum of 300 seconds, or until new information of the NSAG and its priority is received from NAS. The UE may ensure that the above cell reselection criteria are met based on the newly derived priority.

[0178] Fig. 8A A UE that supports slice-based cell reselection and re-derives reselection priorities in a next generation mobile communication system according to an embodiment is shown, and Figure 8B A UE that re-derives reselection priorities and supports slice-based cell reselection in a next generation mobile communication system according to an embodiment is shown.

[0179] refer to Fig. 8A and Figure 8B , a UE supporting slice-based cell reselection may configure an RRC connection with an NR base station and may be in RRC connected mode (RRC_CONNECTED) (8-05). The UE may Figure 6The NR base station described in sends a UE capability information message (UECapabilityInformation), which contains information indicating support for slice-based cell reselection.

[0180] In steps 8-10, the UE may receive a RRCRelease message from the NR base station. Figure 6 The message may include cellReselectionPriorities. When the message includes cellReselectionPriorities information, and when the message includes a t320 value and the T320 timer is running, or when the message does not include a t320 value, the UE may perform a cell reselection evaluation procedure by applying the cellReselectionPriorities information. For example, the UE may ignore the cellReselectionPriorities information broadcast in the system information. When the message does not include the cellReselectionPriorities information, when the T320 timer expires, or when the cellReselectionPriorities is released, the UE may perform a cell reselection evaluation procedure by applying the cellReselectionPriorities information broadcast in the system information.

[0181] In step 8-15, the UE may transition to RRC_IDLE or RRC_INACTIVE mode. For example, when the RRC connection release message received in step 8-10 includes suspend configuration information (suspendConfig), the UE may transition to RRC inactive mode, otherwise transition to RRC idle mode.

[0182] In step 8-20, the UE may camp on a suitable cell of the NR to obtain system information containing cell reselection information. The system information may refer to MIB, SIB1, SIB2, SIB3, SIB4, SIB5 and SIB16.

[0183] In step 8-25, the UE may derive Figure 6 The reselection priority for slice-based cell reselection described in.

[0184] A frequency that supports at least one preferred NSAG received from the NAS has a higher reselection priority than a frequency that does not support any NSAG received from the NAS.

[0185] Frequencies supporting at least one NSAG provided by the NAS are prioritized in order of the NAS-provided priority of the NSAG with the highest priority supported on the frequency.

[0186] Among the frequencies (one or more) supporting the highest priority NSAGs with the same NAS provided priority, the frequencies are prioritized in the order of their highest nsag-CellReselectionPriority or nsag-CellReselectionSubPriority given to these NSAGs, or the sum of their highest nsag-CellReselectionPriority and nsag-CellReselectionSubPriority.

[0187] Frequencies that support the NAS-provided NSAG and indicate the nsag-CellReselectionPriority (e.g., it is greater than 0) and / or the nsag-CellReselectionSubPriority (e.g., it is greater than 0) of the NSAG have a higher reselection priority than frequencies that support the preferred NSAG but do not indicate the nsag-CellReselectionPriority and / or the nsag-CellReselectionSubPriority of the NSAG.

[0188] Frequencies that do not support any NSAG provided by the NAS are prioritized in the order of their cellReselectionPriority or in the order of the sum of their cellReselectioPriority and cellReselectionSubPriority.

[0189] In step 8-30, the UE can use Figure 6 The frequency measurements are performed using the measurement rules described in .

[0190] In step 8-35, the UE may determine to reselect a cell that meets the cell reselection criteria. Figure 6 As described above, a specific cell (the best cell or the highest ranked cell) that meets the cell reselection criteria may be derived.

[0191] In step 8-40, the UE performing slice-based cell reselection can determine whether the best cell or the highest ranked cell in the frequency that meets the cell reselection criteria for cell reselection supports NSAG based on the NSAG and the reselection priority of the frequency derived according to step 8-25. The UE can determine whether the best cell or the highest ranked cell supports NSAG according to the following conditions.

[0192] The UE considers that the cell on the NR frequency supports all slices of NSAG if

[0193] The corresponding nsag-ID is indicated for the NR frequency and is valid for the current TA; and

[0194] The cell is listed in sliceAllowedCellListNR (if provided in the slice specific cell reselection information in use) or the cell is not listed in sliceExcludedCellListNR (if provided in the slice specific cell reselection information in use), or

[0195] Neither sliceAllowedCellListNR nor sliceExcludedCellListNR is configured in the slice-specific cell reselection information used.

[0196] In step 8-45, when it is determined in step 8-40 that the best cell or the highest ranked cell supports NSAG, the UE performing slice-based cell reselection may reselect Figure 6 Suitable candidate target cells described in .

[0197] In step 8-50, when it is determined in step 8-40 that the best cell or the highest ranked cell does not support the NSAG, the UE performing slice-based cell reselection can determine whether other NSAGs are supported in the cell according to the above conditions.

[0198] In step 8-55, when it is determined in step 8-50 that the best cell or the highest ranked cell supports other NSAGs, the UE performing slice-based cell reselection may re-derive the reselection priority according to step 8-25 by considering the NSAGs supported by the cell. The re-derived reselection priority may be used for up to 300 seconds, or until new NSAG information and priority values ​​for each NSAG are received from the NAS.

[0199] In step 8-60, when it is determined in step 8-50 that the best cell or the highest ranked cell does not support other NSAGs, the UE performing the slice-based cell reselection may be set such that the priority of the frequency in which no cell operates is set. (The UE may re-derive the reselection priority of the frequency as no reselection priority). The re-derived reselection priority may be used for up to 300 seconds, or until new NSAG information and the priority value of each NSAG are received from the NAS. When the corresponding cell belongs to the serving frequency, the UE may set the corresponding frequency to the lowest reselection priority because other frequencies may be managed as frequencies with higher priorities.

[0200] Fig. 8A and Figure 8BA method is disclosed for re-deriving the reselection priority of the corresponding frequency by a UE performing slice-based reselection when a specific cell (best cell or highest ranked cell) in a frequency that satisfies a cell reselection criterion based on the reselection priority derived in consideration of an NSAG does not support the NSAG. For example, when the corresponding cell does not support all NSAGs received from a NAS, the UE has a feature of setting the reselection priority of a frequency in which no corresponding cell operates. Therefore, the UE has an advantage of being able to reselect a cell supporting NSAG through a different frequency. In connection with this, the operation of the UE can be expressed as follows.

[0201] For a UE performing slice-based cell reselection, if a specific cell in a frequency (the best cell or the highest ranked cell) meets the above criteria for cell reselection based on the reselection priorities for the NSAG and frequency derived according to the specification, but the cell does not support the NSAG and supports any other NSAG, the UE may re-derive the reselection priority for the frequency by considering the NSAG supported by the cell instead of those of the corresponding NR frequency. Otherwise, the UE may consider the frequency to be lower than any network configured value. The reselection priority is used for a maximum of 300 seconds, or until new information of the NSAG and its priority is received from NAS. The UE may ensure that the above cell reselection criteria are met based on the newly derived priority.

[0202] Fig.9A A UE that re-derives reselection priorities and supports slice-based cell reselection in a next generation mobile communication system according to an embodiment is shown. Fig. 9B A UE that re-derives reselection priorities and supports slice-based cell reselection in a next generation mobile communication system according to an embodiment is shown.

[0203] refer to Fig.9A and Fig. 9B In step 9-05, the UE supporting slice-based cell reselection may configure an RRC connection with the NR base station and may be in RRC connection mode (RRC_CONNECTED). The UE may send a UE capability information message (UECapabilityInformation) to the NR base station, which includes information indicating support for slice-based cell reselection.

[0204] In steps 9-10, the UE may receive a RRCRelease message from the NR base station. Figure 6The message may include cell reselection priority configuration information (interchangeably referred to as cellReselectionPriority or cellReselectionPriorities information). When the message includes a t320 value and the T320 timer is running, or when the message does not include a t320 value, the UE may perform a cell reselection evaluation procedure by applying the cellReselectionPriorities information. For example, the UE may ignore the cellReselectionPriorities information broadcast in the system information. When the message does not include the cellReselectionPriorities information, when the T320 timer expires, or when the cellReselectionPriorities information in the RRCRelease message is released, the UE may perform a cell reselection evaluation procedure by applying the cellReselectionPriorities broadcast in the system information.

[0205] In step 9-15, the UE may transition to RRC_IDLE or RRC_INACTIVE mode. For example, when the RRC connection release message received in step 9-10 includes suspend configuration information (suspendConfig), the UE may transition to RRC inactive mode, otherwise transition to RRC idle mode.

[0206] In step 9-20, the UE may camp on a suitable cell of the NR to obtain system information containing cell reselection information. The system information may refer to MIB, SIB1, SIB2, SIB3, SIB4, SIB5 and SIB16.

[0207] In step 9-25, the UE may derive Figure 6 The reselection priority for slice-based cell reselection described in.

[0208] A frequency that supports at least one preferred NSAG received from the NAS has a higher reselection priority than a frequency that does not support any NSAG received from the NAS.

[0209] Frequencies supporting at least one NSAG provided by the NAS are prioritized in order of the NAS-provided priority of the NSAG with the highest priority supported on the frequency.

[0210] Among the frequencies (one or more) supporting the highest priority NSAGs with the same NAS provided priority, the frequencies are prioritized in the order of their highest nsag-CellReselectionPriority or nsag-CellReselectionSubPriority given to these NSAGs, or the sum of their highest nsag-CellReselectionPriority and nsag-CellReselectionSubPriority.

[0211] Frequencies that support the NAS-provided NSAG and indicate the nsag-CellReselectionPriority (e.g., it is greater than 0) and / or the nsag-CellReselectionSubPriority (e.g., it is greater than 0) of the NSAG have a higher reselection priority than frequencies that support the preferred NSAG but do not indicate the nsag-CellReselectionPriority and / or the nsag-CellReselectionSubPriority of the NSAG.

[0212] Frequencies that do not support any NSAG provided by the NAS are prioritized in the order of their cellReselectionPriority or in the order of the sum of their cellReselectioPriority and cellReselectionSubPriority.

[0213] In step 9-30, the UE can use Figure 6 The frequency measurements are performed using the measurement rules described in .

[0214] In step 9-35, the UE may determine to reselect a cell that meets the cell reselection criteria. Figure 6 As described above, a specific cell (the best cell or the highest ranked cell) that meets the cell reselection criteria may be derived.

[0215] In step 9-40, the UE performing slice-based cell reselection may determine whether the best cell or the highest ranked cell in the frequency that meets the cell reselection criteria for cell reselection supports NSAG based on the NSAG and the reselection priority of the frequency derived according to step 9-25. If the corresponding nsag-ID is indicated for the NR frequency and is valid for the current TA; and the cell is listed in sliceAllowedCellListNR (if provided in the slice-specific cell reselection information used) or the cell is not listed in sliceExcludedCellListNR (if provided in the slice-specific cell reselection information used), or neither sliceAllowedCellListNR nor sliceExcludedCellListNR is configured in the slice-specific cell reselection information used, the UE may determine whether the best cell or the highest ranked cell supports NSAG by considering all slices in which the cells on the NR frequency support NSAG.

[0216] In step 9-45, when it is determined in step 9-40 that the best cell or the highest ranked cell supports NSAG, the UE performing slice-based cell reselection may reselect Figure 6 Suitable candidate target cells described in

[0217] In step 9-50, when it is determined in step 9-40 that the best cell or the highest ranked cell does not support the NSAG, the UE performing slice-based cell reselection can determine whether other NSAGs are supported in the cell according to the above conditions.

[0218] In step 9-55, when it is determined in step 9-50 that the best cell or the highest ranked cell supports other NSAGs, the UE performing slice-based cell reselection may re-derive the reselection priority by considering the NSAGs supported by the cell according to step 9-25. The re-derived reselection priority may be used for up to 300 seconds, or until new NSAG information and priority values ​​for each NSAG are received from NAS.

[0219] In step 9-60, when it is determined in step 9-50 that the best cell or the highest ranked cell does not support other NSAGs, the UE performing slice-based cell reselection considers that the frequency does not support all NSAGs provided from NAS, and derives the reselection priority of the frequency according to step 9-25. (According to step 9-25, the UE can re-derive the reselection priority of the frequency as if none of the NSAGs provided by NAS are supported). For example, the reselection priority of the frequency can be derived based on the traditional cell reselection priority. The re-derived reselection priority can be used for up to 300 seconds, or until new NSAG information and the priority value of each NSAG are received from NAS.

[0220] Fig.9A and Fig. 9B A method is disclosed for re-deriving the reselection priority of the corresponding frequency by a UE that performs slice-based reselection when a specific cell (best cell or highest ranked cell) in a frequency that satisfies a cell reselection criterion based on a reselection priority derived in consideration of an NSAG does not support the NSAG. For example, when the corresponding cell does not support all NSAGs received from a NAS, the UE may re-derive the reselection priority of the corresponding frequency based on conventional cell reselection priority information about the reselection priority of the frequency in which the corresponding cell operates. Therefore, the UE has the advantage of being able to reselect a cell in the corresponding frequency when cell reselection through other frequencies is not possible.

[0221] Relatedly, for a UE performing slice-based cell reselection, if a specific cell in a frequency (the best cell or the highest ranked cell) meets the above criteria for cell reselection based on the reselection priorities for the NSAG and frequency derived according to the specification, but the cell does not support NSAG but supports any other NSAG, the UE may re-derive the reselection priority for the frequency by considering the NSAGs supported by the cell according to the specification (rather than those of the corresponding NR frequency). Otherwise, the UE may consider the frequency to be lower than any network configured value. This reselection priority is used for a maximum of 300 seconds, or until new information of the NSAG and its priority is received from NAS. The UE may ensure that the above cell reselection criteria are met based on the newly derived priority.

[0222] Fig.10 The internal structure of the UE according to the embodiment is shown.

[0223] exist Fig.10 In the present invention, the UE includes a radio frequency (RF) processor 10-10, a baseband processor 10-20, a storage device 10-30, and a controller 10-40.

[0224] The RF processor 10-10 performs functions such as frequency band conversion and amplification of signals for transmitting and receiving signals through a radio channel. That is, the RF processor 10-10 up-converts the baseband signal provided by the baseband processor 10-20 into an RF band signal, transmits the RF band signal through an antenna, and down-converts the RF band signal received through the antenna into a baseband signal. For example, the RF processor 10-10 may include a transmission filter, a reception filter, an amplifier, a mixer, an oscillator, a digital-to-analog converter (DAC), an analog-to-digital converter (ADC), etc. Fig.10 In the embodiment, only one antenna is shown, but the UE may include multiple antennas. In addition, the RF processor 10-10 may include multiple RF chains and may perform beamforming. For beamforming, the RF processor 10-10 may adjust the phase and amplitude of each signal sent and received through multiple antennas or antenna elements. In addition, the RF processor 10-10 may perform MIMO and may receive multiple layers when performing MIMO operations.

[0225] The baseband processor 10-20 performs the conversion function between the baseband signal and the bit stream according to the physical layer specification of the system. For example, when sending data, the baseband processor 10-20 generates complex symbols by encoding and modulating the transmitted bit stream. In addition, when receiving data, the baseband processor 10-20 recovers the received bit stream by demodulating and decoding the baseband signal provided from the RF processor 10-10. For example, when following the OFDM scheme, when sending data, the baseband processor 10-20 generates complex symbols by encoding and modulating the transmitted bit stream, maps the complex symbols to subcarriers, and then configures OFDM symbols by inverse fast Fourier transform (IFFT) operation and cyclic prefix (CP) insertion. In addition, when receiving data, the baseband processor 10-20 divides the baseband signal provided by the RF processor 10-10 into OFDM symbol units, recovers the signal mapped to the subcarrier by fast Fourier transform (FFT) operation, and then recovers the received bit stream by demodulation and decoding.

[0226] The baseband processor 10-20 and the RF processor 10-10 send and receive signals as described above. Therefore, the baseband processor 10-20 and the RF processor 10-10 can be referred to as a transmitter, a receiver, a transceiver or a communicator. At least one of the baseband processor 10-20 and the RF processor 10-10 may include a plurality of communication modules to support a variety of different radio access technologies. In addition, at least one of the baseband processor 10-20 and the RF processor 10-10 may include different communication modules to process signals of different frequency bands. For example, different radio access technologies may include wireless LAN (e.g., IEEE 802.11), cellular networks (e.g., LTE), etc. Different frequency bands may include ultra-high frequency (SHF) (e.g., 2.5 GHz, 5 GHz) bands and millimeter wave (e.g., 60 GHz) bands.

[0227] The storage device 10-30 stores data such as basic programs, applications, and configuration information for the operation of the UE. Specifically, the storage device 10-30 may store information related to a second access node performing wireless communication by using a second radio access technology, and provide the stored data according to a request of the controller 10-40.

[0228] The controller 10-40 controls the overall operation of the UE. The controller 10-40 may include a multi-link processor 10-42. For example, the controller 10-40 sends and receives signals through the baseband processor 10-20 and the RF processor 10-10, writes data in the storage device 10-30, and reads data. To this end, the controller 10-40 may include at least one of a communication processor (CP) that controls communication and an application processor (AP) that controls an upper layer such as an application program.

[0229] Fig.11 The configuration of an NR base station according to an embodiment is shown.

[0230] exist Fig.11 In the present invention, the base station includes an RF processor 11-10, a baseband processor 11-20, a backhaul communicator 11-30, a storage device 11-40 and a controller 11-50.

[0231] The RF processor 11-10 performs functions such as frequency band conversion and amplification of signals for sending and receiving signals through a radio channel. That is, the RF processor 11-10 up-converts the baseband signal provided by the baseband processor 11-20 into an RF band signal, sends the RF band signal through an antenna, and down-converts the RF band signal received by the antenna into a baseband signal. The RF processor 11-10 may include a transmission filter, a reception filter, an amplifier, a mixer, an oscillator, a DAC, an ADC, etc. The first access node may include multiple antennas, and the RF processor 11-10 may include multiple RF chains and may perform beamforming. For beamforming, the RF processor 11-10 may adjust the phase and amplitude of each signal sent and received through multiple antennas or antenna elements. The RF processor may perform downlink MIMO operations by sending one or more layers.

[0232] The baseband processor 11-20 performs a conversion function between a baseband signal and a bit stream according to the physical layer specification of the first radio access technology. For example, when sending data, the baseband processor 11-20 generates complex symbols by encoding and modulating the transmitted bit stream. When receiving data, the baseband processor 11-20 recovers the received bit stream by demodulating and decoding the baseband signal provided from the RF processor 11-10. For example, when following the OFDM scheme and sending data, the baseband processor 11-20 generates complex symbols by encoding and modulating the transmitted bit stream, maps the complex symbols to subcarriers, and then configures OFDM symbols through IFFT operations and CP insertion. When receiving data, the baseband processor 11-20 divides the baseband signal provided by the RF processor 11-10 into OFDM symbol units, recovers the signal mapped to the subcarrier through FFT operations, and then recovers the received bit stream through demodulation and decoding. The baseband processor 11 - 20 and the RF processor 11 - 10 transmit and receive signals as described above, and may be referred to as a transmitter, a receiver, a transceiver, a communicator, or a wireless communicator.

[0233] The backhaul communicator 11-30 provides an interface for performing communication with other nodes in the network. That is, the backhaul communicator 11-30 converts a bit stream sent from the primary base station to the secondary base station or the core network into a physical signal, and converts a physical signal received from other nodes into a bit stream.

[0234] The storage device 11-40 stores data such as basic programs, application programs, and configuration information for the operation of the main base station. Specifically, the storage device 11-40 may store information about the bearer assigned to the accessed UE, measurement results reported from the accessed UE, etc. In addition, the storage device 11-40 may store information used as a criterion for determining whether to provide or stop multiple connections to the UE. In addition, the storage device 11-40 provides the stored data according to the request of the controller 11-50.

[0235] The controller 11-50 controls the overall operation of the master base station. The controller 11-50 may include a multi-link processor 11-52. For example, the controller 11-50 sends and receives signals through the baseband processor 11-20 and the RF processor 11-10 or through the backhaul communicator 11-30. In addition, the controller 11-50 writes data to the storage device 11-40 and reads the data. To this end, the controller 11-50 may include at least one processor.

[0236] Herein, each block and combination of blocks in the flowchart diagram can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device create equipment for implementing the functions specified in one or more blocks of the flowchart. These computer program instructions can also be stored in a computer-usable or computer-readable memory, which can instruct the computer or other programmable data processing device to operate in a particular manner, so that the instructions stored in the computer-usable or computer-readable memory produce a manufactured product including an instruction equipment for implementing the functions specified in one or more blocks of the flowchart. The computer program instructions can also be loaded onto a computer or other programmable data processing device, so that a series of operating steps are executed on a computer or other programmable device to produce a computer-implemented process, so that the instructions executed on the computer or other programmable device provide steps for implementing the functions specified in one or more blocks of the flowchart.

[0237] Each block of the flowchart diagram can represent a part, segment or module of code, which includes one or more executable instructions for realizing a specified logical function. In some alternative embodiments, the functions mentioned in the block may not occur in order. For example, two blocks shown in succession can actually be performed substantially simultaneously, or these blocks can sometimes be performed in reverse order, depending on the functions involved.

[0238] While the present disclosure has been described with reference to various embodiments, various changes may be made without departing from the spirit and scope of the present disclosure, which is defined not by the detailed description and embodiments but by the appended claims and their equivalents.

Claims

1. A method performed by a terminal for performing slice-based cell reselection in a wireless communication system, the method comprising: Obtain information about the Network Slice Access Stratum Group (NSAG) from the Non-Access Stratum (NAS); In the event that a cell in the frequency satisfies a cell reselection criterion and does not support the NSAG, identifying whether the cell supports at least one NSAG other than the NSAG; as well as Based on the result of the identification, the reselection priority of the frequency is re-derived.

2. The method according to claim 1, wherein: Re-deriving the reselection priority of the frequency further includes: In case that the cell supports the at least one NSAG other than the NSAG, the reselection priority of the frequency is re-derived by considering the at least one NSAG supported by the cell.

3. The method according to claim 1, wherein: Re-deriving the reselection priority of the frequency further includes: in case the cell does not support any NSAG other than the NSAG, re-deriving the reselection priority of the frequency as if at least one NSAG provided by NAS is not supported, and The frequency reselection priority is re-derived based on the cell reselection priority per frequency not used for the slice.

4. The method according to claim 1, wherein: The cell is the highest ranked cell in the frequency.

5. The method according to claim 1, wherein: The cell is the best cell in the frequency.

6. The method according to claim 1, wherein: The re-derived reselection priority of the frequency is used for a maximum of 300 seconds or until new information of at least one NSAG and at least one corresponding priority is received from the NAS.

7. The method according to claim 1, wherein: Whether the cell supports the NSAG is identified based on the following: the identifier and tracking area of ​​the NSAG provided by NAS; and At least one of the slice allowed cell list and the slice excluded cell list, if configured.

8. The method according to claim 1, wherein: Information about the NSAG is received from the Access and Mobility Function (AMF).

9. A terminal for performing slice-based cell reselection in a wireless communication system, the terminal comprising: Transceiver; and A controller is coupled to the transceiver and is configured to: Get information about the Network Slice Access Stratum Group (NSAG) from the Non-Access Stratum (NAS), In the event that a cell in the frequency satisfies a cell reselection criterion and does not support the NSAG, identifying whether the cell supports at least one NSAG other than the NSAG, and Based on the result of the identification, the reselection priority of the frequency is re-derived.

10. The terminal according to claim 9, wherein: The controller is also configured to: In case that the cell supports the at least one NSAG other than the NSAG, the reselection priority of the frequency is re-derived by considering the at least one NSAG supported by the cell.

11. The terminal according to claim 9, wherein: The controller is also configured to: in case the cell does not support any NSAG other than the NSAG, re-deriving the reselection priority of the frequency as if at least one NSAG provided by NAS is not supported, and The frequency reselection priority is re-derived based on the cell reselection priority per frequency not used for the slice.

12. The terminal according to claim 9, wherein: The cell is the highest ranked cell or base cell in the frequency.

13. The terminal according to claim 9, wherein: The re-derived reselection priority of the frequency is used for a maximum of 300 seconds or until new information of at least one NSAG and at least one corresponding priority is received from the NAS.

14. The terminal according to claim 9, wherein: Whether the cell supports the NSAG is identified based on the following: the identifier and tracking area of ​​the NSAG provided by NAS; and At least one of the slice allowed cell list and the slice excluded cell list, if configured.

15. The terminal according to claim 9, wherein: Information about the NSAG is received from the Access and Mobility Function (AMF).

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