Method and apparatus for providing time synchronization in wireless communication system

Abstract

The present disclosure relates to a 5th-Generation (5G) or 6th-Generation (6G) communication system for supporting higher data transmission rates. A method for providing time synchronization in a wireless communication system is provided. The method includes receiving, by a user equipment (UE), a reference identification (ID) from a base station based on time synchronization state information received by the base station from a network entity, and receiving, by the UE, time synchronization state information from the base station via radio resource control (RRC) signaling.

Description

Technical Field

[0001] The present disclosure relates to a method and apparatus for providing time synchronization in a wireless communication system. Background Art

[0002] Fifth-generation (5G) mobile communication technology defines a wide frequency band to enable fast transmission speeds and new services, and can be implemented in "sub-6 GHz" frequencies below 6 GHz, such as 3.5 gigahertz (GHz), and in ultra-high frequency bands called millimeter waves (mmWave), such as 28 GHz and 39 GHz, "above 6 GHz." Furthermore, in order to achieve transmission speeds 50 times faster than 5G mobile communication technology and ultra-low latency reduced by one-tenth, the sixth-generation (6G) mobile communication technology, referred to as "Beyond 5G Systems (5GS)," is being considered for implementation in the terahertz (THz) frequency band (e.g., 95 GHz to 3 THz).

[0003] In the early stages of 5G mobile communication technology, standardization is underway on the following: beamforming and massive multiple-input multiple-output (MIMO) to mitigate propagation path loss and increase propagation range in the ultra-high frequency band; support for various basic parameter sets for efficient use of ultra-high frequency resources (e.g., operation with multiple subcarrier spacings); dynamic operation of time slot formats; initial access technology to support multi-beam transmission and broadband; definition and operation of the BandWidth Part (BWP); new channel codecs such as Low Density Parity Check (LDPC) codes for large-scale data transmission and polar codes for highly reliable transmission of control information; L2 preprocessing; and network slicing to provide dedicated networks dedicated to specific services in order to meet performance requirements and support services for enhanced Mobile BroadBand (eMBB), Ultra Reliable Low Latency Communications (URLLC), and massive Machine-Type Communications (mMTC).

[0004] Currently, discussions are underway on improvements and performance enhancements to initial 5G mobile communication technologies, taking into account the services they are intended to support, and physical layer standardization is underway for technologies such as: Vehicle-to-everything (V2X), for assisting driving determination of autonomous vehicles and enhancing user convenience based on positioning and status information transmitted from voice over new radio (VoNR); New Radio Unlicensed (NR-U), for system operation matching various regulatory requirements; New Radio (NR) User Equipment (UE) energy saving; Non-Terrestrial Network (NTN), which is direct communication between UE and satellite for securing coverage in areas where communication with terrestrial networks is not possible; and positioning technology.

[0005] Also being standardized are radio interface architectures / protocols for the following technologies: Industrial Internet of Things (IIoT), to support new services through connectivity and convergence with other industries; Integrated Access and Backhaul (IAB), to provide nodes for extending the network service area by supporting access links and radio backhaul links; enhanced mobility, including conditional handover and Dual Active Protocol Stack (DAPS) handover; a two-step random access channel (RACH) for NR, to simplify the random access procedure; and system architecture / service areas for 5G baseline architecture (e.g., service-based architecture or service-based interface), to combine Network Functions Virtualization (NFV) and Software-Defined Networking (SDN) technologies; and Mobile Edge Computing (MEC), to receive services based on the UE's location.

[0006] As 5G mobile communication systems are commercialized, a surge in the number of connected devices will be connected to the communication network, leading to the expected need for enhanced functionality and performance of 5G mobile communication systems and the integrated operation of connected devices. To this end, new research will be conducted on: extended reality (XR) to effectively support augmented reality (AR), virtual reality (VR), and mixed reality (MR); 5G performance enhancement and complexity reduction using artificial intelligence (AI) and machine learning (ML); support for AI services; support for metaverse services; and drone communications.

[0007] Furthermore, the development of such 5G mobile communication systems may serve as a foundation for: multi-antenna transmission technologies (such as new waveforms for ensuring coverage in the terahertz band for 6G mobile communication, Full Dimensional MIMO (FD-MIMO), array antennas, and massive antennas); full-duplex technologies for enhancing the frequency efficiency and system networks of 6G mobile communication technologies; metamaterial-based lenses and antennas for enhancing the coverage of terahertz band signals; high-dimensional spatial multiplexing using orbital angular momentum (OAM); reconfigurable intelligent surfaces (RIS); AI-based communication technologies for achieving system optimization by using satellites and artificial intelligence (AI) from the design step and embedding end-to-end AI support functions; and next-generation distributed computing technologies for implementing services with complexity that exceeds the operational capability limits of UEs through ultra-high-performance communication and computing resources.

[0008] The above information is presented as background information only to assist with an understanding of the present disclosure. No determination has been made, and no assertion is made, as to whether any of the above might be applicable as prior art with respect to the present disclosure. Summary of the Invention

[0009] Solution to the problem

[0010] A method is needed for providing a synchronization status to a user equipment (UE) while providing coverage conditions when a fifth generation (5G) system becomes a synchronization source to provide a time synchronization service to the UE.

[0011] An idle UE moves between base stations in the same Registration Area (RA) without separate signaling, but ensures that the synchronization conditions are the same in the RA.

[0012] Aspects of the present disclosure are to address at least the above-mentioned problems and / or disadvantages and to provide at least the advantages described below. Therefore, one aspect of the present disclosure is to provide a method and apparatus for providing time synchronization between UEs in a wireless communication system.

[0013] Another aspect of the present disclosure is to provide a method and apparatus for providing a synchronization status to a UE when providing time synchronization between wireless UEs using a synchronization range condition in a wireless communication system.

[0014] Additional aspects will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the presented embodiments.

[0015] According to one aspect of the present disclosure, a method for providing time synchronization in a wireless communication system is provided. The method includes receiving, by a user equipment (UE), a reference identification (ID) from the base station based on time synchronization status information received by the base station from a network entity, and receiving, by the UE, the time synchronization status information from the base station via radio resource control (RRC) signaling.

[0016] According to another aspect of the present disclosure, a method for providing time synchronization in a wireless communication system is provided. The method includes receiving, by a base station, time synchronization status information from a network entity, transmitting, by the base station, a reference identification (ID) to a user equipment (UE) based on the time synchronization status information, and transmitting, by the base station, the time synchronization status information to the UE via radio resource control (RRC) signaling.

[0017] According to another aspect of the present disclosure, a user equipment (UE) for providing time synchronization in a wireless communication system is provided. The UE includes a transceiver and at least one processor, the at least one processor being coupled to the transceiver and configured to: receive a reference identification (ID) from the base station based on time synchronization status information received by the base station from a network entity, and receive the time synchronization status information from the base station via radio resource control (RRC) signaling.

[0018] According to another aspect of the present disclosure, a base station for providing time synchronization in a wireless communication system is provided. The base station includes a transceiver and at least one processor, the at least one processor being coupled to the transceiver and configured to: receive time synchronization status information from a network entity; send a reference identification (ID) by the base station to a user equipment (UE) based on the time synchronization status information; and send the time synchronization status information to the UE via radio resource control (RRC) signaling.

[0019] Other aspects, advantages, and salient features of the present disclosure will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the accompanying drawings, discloses various embodiments of the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The above and other aspects, features and advantages of certain embodiments of the present disclosure will become more apparent through the following description in conjunction with the accompanying drawings, in which:

[0021] Figure 1 A method for transmitting a synchronization status to a user equipment (UE) when providing a fifth generation system (5GS) synchronization service over a third generation partnership project (3GPP) communication network according to an embodiment of the present disclosure is shown;

[0022] Figure 2 A handover scenario of an idle UE between registration areas (RAs) or within a RA according to an embodiment of the present disclosure is shown;

[0023] Figure 3a and Figure 3b A scenario according to various embodiments of the present disclosure is shown, where the synchronization status needs to be updated when the synchronization coverage condition changes when handing over an idle UE in RA;

[0024] Figure 4 A process of transmitting synchronization status to an idle UE using a system information block (SIB) when time synchronization is provided through a 3GPP communication network according to an embodiment of the present disclosure is shown;

[0025] Figure 5a and Figure 5b A scenario is shown in which an idle UE performs a synchronization status update when identifying a synchronization status according to various embodiments of the present disclosure;

[0026] Figure 6 FIG2 shows an operation of a UE performing handover in the same synchronization range according to an embodiment of the present disclosure;

[0027] Figure 7 1. The embodiment of the present disclosure shows an operation of a UE performing handover to another synchronization range;

[0028] Figure 8 The present invention shows an operation of performing synchronization status update of a UE in the same synchronization range according to an embodiment of the present disclosure; and

[0029] Figure 9 is a block diagram illustrating a device according to an embodiment of the present disclosure.

[0030] The same reference numerals are used throughout the drawings to denote the same elements. DETAILED DESCRIPTION

[0031] The following description, with reference to the accompanying drawings, is provided to assist in a comprehensive understanding of the various embodiments of the present disclosure as defined by the claims and their equivalents. It includes various specific details to assist in understanding, but these details are to be considered as exemplary only. Therefore, those skilled in the art will recognize that various changes and modifications may be made to the various embodiments described herein without departing from the scope and spirit of the present disclosure. Furthermore, descriptions of well-known functions and configurations may be omitted for clarity and conciseness.

[0032] The terms and words used in the following description and claims are not limited to the bibliographical meanings, but are merely used by the inventor to enable a clear and consistent understanding of the present disclosure. Therefore, it should be apparent to those skilled in the art that the following description of various embodiments of the present disclosure is provided for illustration purposes only and not for the purpose of limiting the present disclosure as defined by the appended claims and their equivalents.

[0033] It will be understood that the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to "a component surface" includes reference to one or more of such surfaces.

[0034] The advantages and features of the present disclosure and the methods for achieving the same can be understood by referring to the embodiments described below in conjunction with the accompanying drawings. However, the present disclosure is not limited to the embodiments disclosed herein and various modifications may be made thereto. The embodiments disclosed herein are provided solely to inform those skilled in the art of the scope of the present disclosure. The present disclosure is defined solely by the appended claims. Throughout the specification, the same reference numerals represent the same elements.

[0035] It should be understood that the blocks in each flowchart and combinations of flowcharts may be executed by one or more computer programs comprising instructions. One or more programs may be stored in a single memory or divided among multiple memories.

[0036] In addition, each block can represent a module, segment or portion of a code comprising one or more executable instructions for performing a specified logical function. In addition, it should also be noted that in some alternative embodiments of the present disclosure, the functions mentioned in the blocks can occur in different orders. For example, depending on the corresponding functions, two blocks shown in succession can be executed substantially simultaneously or in reverse order.

[0037] As used herein, the term "unit" refers to a software element or a hardware element, such as a field programmable gate array (FPGA) or an application-specific integrated circuit (ASIC). A unit performs a function. However, a "unit" is not limited to software or hardware. A "unit" can be configured in an addressable storage medium, or can be configured to execute one or more processors. Thus, as an example, a "unit" includes elements such as software elements, object-oriented software elements, class elements, and task elements, processes, functions, properties, procedures, subroutines, program code segments, drivers, firmware, microcode, circuits, data, databases, data architectures, tables, arrays, and variables. The functions provided within components and "units" can be combined into a smaller number of components and "units," or further divided into additional components and "units." In addition, components and "units" can be implemented to execute one or more central processing units (CPUs) in a secure multimedia card or device. According to embodiments of the present disclosure, a "unit" can include one or more processors.

[0038] The functions in the claims may be processed by a processor or a combination of processors. A processor or a combination of processors is a circuit that performs processing and includes circuits such as a CPU, a microprocessor unit (MPU), an access point (AP), a CP, a system on a chip (SoC), or an integrated circuit (IC).

[0039] As used herein, each of phrases such as “A or B,” “at least one of A and B,” “at least one of A or B,” “A, B or C,” “at least one of A, B and C,” and “at least one of A, B or C” may include all possible combinations of items listed together in the corresponding one phrase. As used herein, terms such as “first” and “second” or “first” and “second” may be used to simply distinguish a corresponding component from another component and do not limit the components in other respects (e.g., importance or order).

[0040] As used herein, for ease of description, terms used to identify access nodes, terms representing network entities, terms representing messages, terms representing interfaces between network entities, and terms representing various pieces of identification information are provided as examples. Therefore, the present disclosure is not limited to these terms, and these terms may be replaced with other terms representing objects having equivalent technical meanings.

[0041] In the present disclosure, a base station (BS) is a network entity that allocates resources to a UE and can communicate with the UE, and may be at least one of an eNode B, a Node B, a gNB, a radio access network (RAN), an access network (AN), a RAN node, an integrated access / backhaul (IAB) node, a radio access unit, a base station controller, a node on a network, and a transmission reception point (TRP). A user equipment (UE) may be at least one of a terminal capable of performing a communication function, a mobile station (MS), a cellular phone, a smart phone, a computer, and a multimedia system.

[0042] For ease of description, this document uses terms and names defined in the latest 3GPP 5G and NR standards, which are current communication standards. However, the present disclosure is not limited by these terms and names and is equally applicable to wireless communication networks that conform to other standards. More specifically, the present disclosure can be applied to 3GPP GS / NR (5th generation mobile communication standards).

[0043] When using applications such as smart grids, accurate time synchronization between UEs is required. Synchronization services may be provided only in a specific area. Outside of this area, synchronization services may not be required, or different types of synchronization services may be required.

[0044] Furthermore, factory automation requires accurate time synchronization between UEs. Applications that share audio and video also require accurate time synchronization between UEs. Financial applications also require time synchronization. For example, stock trading applications require accurate time synchronization between trading UEs to buy and sell stocks.

[0045] In the present disclosure, network technology may refer to standards defined by the International Telecommunication Union (ITU) or 3GPP (e.g., TS 23.501, TS 23.502, TS 23.503, etc.), and components included in the network architecture described below may refer to physical entities or may refer to software that performs various functions or hardware combined with software.

[0046] 3GPP standards standardize the 5G network system architecture and procedures. Mobile network operators can offer a variety of services in 5G networks. To provide each service, mobile network operators need to meet different service requirements (e.g., latency, communication range, data rate, bandwidth, reliability, etc.). To this end, 5G systems can support network slicing (or network slicing), and traffic from different network slices can be handled by different PDU sessions. A PDU session refers to the association between a data network that provides PDU connectivity services and a UE. Network slicing can be understood as a technology for logically configuring a network with a collection of network functions (NFs) to support various services with different characteristics (such as broadband communication services, massive IoT, V2X, or other mission-critical services), and for separating different network slices. Therefore, even if a communication failure occurs in one network slice, it will not affect communication in other network slices, thereby ensuring stable communication services. To this end, mobile network operators can configure network slices and allocate network resources suitable for specific services to each network slice or to each collection of network slices. Network resources can refer to network functions (NFs), logical resources provided by NFs, or radio resource allocations of base stations. For example, a mobile network operator can configure network slice A for providing mobile broadband services, network slice B for providing vehicle communication services, and network slice C for providing IoT services. In other words, the 5G system can effectively provide corresponding services to UEs through dedicated network slices suitable for the characteristics of each service.

[0047] In the accompanying drawings, reference numerals N1, N2, N3, ..., Nxxx indicate known interfaces between network functions in the 5G system. The 3GPP system defines conceptual links connecting NFs in the 5G system as reference points. The following describes reference points included in the 5G system structure as examples.

[0048] -N1: Reference point between UE and Access and Mobility Management Function (AMF)

[0049] -N2: Reference point between base station (R)AN and AMF

[0050] -N3: Reference point between the base station ((R)AN) and the user plane function (UPF)

[0051] -N4: Reference point between Session Management Function (SMF) and UPF

[0052] -N5: Reference point between Policy Control Function (PCF) and Application Function (AF)

[0053] -N6: Reference point between UPF and data network (DN)

[0054] -N7: Reference point between SMF and PCF

[0055] -N8: Reference point between User Data Management (UDM) and AMF

[0056] -N9: Reference point between two core UPFs

[0057] -N10: Reference point between UDM and SMF

[0058] -N11: Reference point between AMF and SMF

[0059] The 5G system may include the 5G core network (5GC), base stations, and user equipment (UE). The 5GC may include the Advanced Mobile Function (AMF) (AMF), which manages UE mobility; the Advanced Mobile Function (SMF), which manages sessions; the User Public Function (UPF), which connects to the data network (DN) and transmits data; the Network Exposure Function (NEF), which externally transmits and receives events and capabilities occurring in the 5G system; the Personalized Network Function (PCF), which provides policy control for network operators; and the User Data Management (UDM), which manages data such as subscriber data and policy control data. The Access Control (AF), which provides application services, may communicate with the 5GC. The AMF is a network entity responsible for managing UE access and mobility. The AMF performs network functions such as UE registration, connection, reachability, mobility management, access identification, authentication, and mobility event generation. The SMF manages protocol data unit (PDU) sessions for the UE. For example, the SMF performs session management functions such as establishing, modifying, or releasing sessions and maintaining tunnels between the UPF and base stations; allocating and managing UE Internet Protocol (IP) addresses; and selecting and controlling the user plane. The UPF performs data processing functions, such as delivering data sent by the UE to a DN (a network that is an external network) or delivering data received from a DN to the UE. Furthermore, the UPF performs network functions such as acting as an anchor point between radio access technologies (RATs), providing connections to PDU sessions and AFs, packet routing and forwarding, packet inspection, application of user plane policies, and creation of traffic usage reports or buffering. The PCF manages operator policy information for providing services in the 5G system, and the UDM performs functions such as generating authentication information for 3GPP security, managing a list of NFs supporting the UE, and managing subscription information. The Unified Data Repository (UDR) stores and provides subscription information managed by the UDM, structured data for exposure, and application data related to the NEF or services. During the UE registration procedure, the UE sends identification information regarding the requested network slice (requested single network slice selection assistance information (S-NSSAI)) to the AMF. Based on the requested S-NSSAI and subscriber information, the AMF provides the UE with information regarding the network slices available to the UE (allowed NSSAI). In order to send and receive data to and from a specific data network (DN) through allowed slices (allowed NSSAI), the UE may select one of the allowed slices, request a data network name (DNN) of the network slice selected from the allowed network slices to generate a PDU session, and send and receive data through the generated PDU session. Figure 1 、 Figure 2 、 Figure 3a 、 Figure 3b 、 Figure 4 、 Figure 5a 、 Figure 5b and Figures 6 to 8 In the embodiment of the present invention, the basic functions of network entities (such as NEF, UDM145, UPF 140, PCF 135, SMF 130, AMF 125, (R)AN 120 and DN 160) are the same as the above basic functions.

[0060] Figure 1 The principle for transmitting synchronization status to UE when providing 5GS synchronization service through 3GPP communication network according to an embodiment of the present disclosure is shown.

[0061] refer to Figure 1 , the 5G system can provide synchronization services to the UE at the request of the application function (AF) 255. The 5G system interoperates with the external AF 255 through the time-sensitive communication and time synchronization function (TSCTSF) / network exposure function (NEF) 250. In this case, the TSCTSF / NEF 250 can exchange management information with the network-side TSN translator (NW-TT) 141 and the device 105-side TSN translator (DS-TT) 111. The NW-TT 141 can periodically generate synchronization (sync) messages for synchronization and send time information to the DS-TT 111.

[0062] The TSCTSF / NEF 150 can interwork with the session management function (SMF) 130, the access and mobility management function (AMF) 125, the policy control function (PCF) 135, and the unified data management (UDM) / user data repository (UDR) to transmit information about the 5G system to the external AF 155 or apply requests from the external AF 155 to the 5G system. More specifically, the TSCTSF / NEF 150 can store information required by the UDR and transmit updated information to the UDM / UDR or the policy control function (PCF) 135 through a notification procedure. This method may be referred to as a non-access stratum (NAS)-based method.

[0063] The request from the AF 155 may be transmitted to the radio access network (RAN) 120 of the 5G system, and the RAN 120 may support time synchronization between UEs by adjusting the radio resource control (RRC) or system information block (SIB). The RAN 120 may use parameters to control the synchronization function. This method may be referred to as an access stratum (AS)-based method.

[0064] Within a range that satisfies accuracy requirements, RAN 120 may increase the frequency of transmitting RRC / SIBs to transmit time information. The base station may adjust the accuracy of time synchronization by adjusting the period of time during which messages used to measure the delay time between a specific UE and the base station are exchanged via RRC to accurately measure the delay time. Furthermore, the base station may adjust the frequency with which time information is included in SIBs broadcast to all UEs and transmitted, thereby adjusting time synchronization accuracy.

[0065] Although the AF 155's request is based on either NAS or AS, the AF 155 does not know internal state information about the 5G system, such as the supportable synchronization accuracy, the number of corresponding UEs, and the status of the corresponding UEs (idle / active). Therefore, although the AF 1500 makes a request based on NAS, 5G system synchronization should be handled based on AS. Furthermore, although the AF 155 makes a request based on AS, 5G system synchronization should be handled based on NAS. Alternatively, although the AF 155 makes a request based on NAS or AS, both AS-based and NAS-based 5G system synchronization can be handled.

[0066] Figure 2 2 is a diagram illustrating a handover scenario of an idle UE between RAs or within a RA according to an embodiment of the present disclosure.

[0067] refer to Figure 2 In this example, cells 1, 2, 3, and 4 211 to 214 are included in one registration area (RA) 210, and cells 5, 6, 7, and 8 221 to 224 are included in another RA 220. In this case, when UE 110-1 in the RRC_Idle state moves from cell 2 212 to cell 3 213, the movement is within the same RA 210, and therefore no separate signaling occurs. As another example, when UE 110-1 in the RRC_Idle state moves from cell 4 214 to cell 5 221, the movement is between different RAs (i.e., from RA1 210 to RA2 220), and therefore UE 110-2 changes its state to RRC_Connected and performs registration update signaling. In this case, the AMF (i.e., AMF 125-1 or AMF 125-2) may be changed, or the same AMF may be used. When no separate traffic occurs within a predetermined time, UE 110 - 2 changed to RRC_Connected may change back to the RRC_Idle state.

[0068] Figure 3a and Figure 3bA scenario is shown in which the synchronization status needs to be updated when the synchronization coverage condition changes when handing over an idle UE in a RA according to various embodiments of the present disclosure.

[0069] refer to Figure 3a and Figure 3b The coverage conditions for NAS / AS-based synchronization requests or UDM synchronization service subscriptions for AFs can differ from the coverage conditions for RAs. For example, when the coverage condition for a synchronization request is Cell List A, the handover area (RA) for a UE in idle state can be Cell List B. Furthermore, for example, when synchronization status change input from the RAN / core network (CN) / operations, administration, and management (OAM) is provided to the TSCTSF, the changed coverage condition can be Cell List C, and the handover area (RA) for a UE in idle state can be Cell List B. The UE can identify the synchronization error budget, synchronization source type, and synchronization source accuracy information included in the synchronization status and proceed to determine whether the conditions required by the UE's application are met. If the 5G system's synchronization service does not meet the requirements, other synchronization services (such as other GPS-based synchronization services or wired synchronization services) can be used to support the application's needs. If the 5G system's synchronization service does not meet the requirements and no alternative service is available, the application can be instructed to stop running, or running applications can be rendered as if they were still in use despite performance differences.

[0070] refer to Figure 3a , UE 110-1 in the RRC_Idle state moves from cell 1 211 to cell 2 212. In this case, since cell 1 211 and cell 2 212 provide synchronization #1 310 in the same synchronization state, no separate synchronization state update signaling is required, and UE 110-1 continues to maintain the RRC_Idle state. In addition, since cell 1 211 and cell 2 212 belong to the same RA 210, no separate signaling for handover is required, and UE 110-1 continues to maintain the RRC_Idle state.

[0071] refer to Figure 3bUE 110-1, which is in the RRC_Idle state, moves from cell 2 212 to cell 3 213. In this case, since cell 2 212 and cell 3 213 belong to the same RA 210, separate signaling for handover is not required, and UE 110-1 can continue to maintain the RRC_Idle state. However, cell 2 212 and cell 3 213 each have Sync #1 310 and Sync #2 320 in different synchronization states. Therefore, Sync #2 320 in the synchronization state of cell 3 213 should be transmitted to UE 110-1. To this end, UE 110-2 changes to the RRC_Connected state to perform a synchronization state update via RRC.

[0072] Figure 4 A process of transmitting a synchronization status to an idle UE using an SIB when time synchronization is provided through a 3GPP communication network according to an embodiment of the present disclosure is shown.

[0073] refer to Figure 4 , the 5G system includes a reference identifier (ID) indicating a synchronization status update in the SIB for each cell, broadcasts the reference ID, and transmits the reference ID to the UE. When a UE 110 in the RRC_Idle state moves between cells, the UE 110 can simply refer to the reference ID in the synchronization status broadcast in the SIB. If the value is the same as the value previously known to the UE, the UE 110 does not need to perform a separate synchronization status update. Conversely, if the value is different from the value previously known to the UE, the UE 110 performs synchronization status update signaling to identify the new synchronization status.

[0074] Figure 5a and Figure 5b A scenario is shown in which an idle UE performs a synchronization status update when identifying a synchronization status according to various embodiments of the present disclosure.

[0075] refer to Figure 5a When UE 110-1 in the RRC_Idle state moves from cell 1 211 to cell 2 212, UE 110-1 does not need to perform separate signaling for handover because cell 1 211 and cell 2 212 belong to the same RA 210. Furthermore, when cell 1 211 and cell 2 212 have Sync#1 310 in the same synchronization state, cell 1 211 and cell 2 212 broadcast the same reference ID via the SIB. Therefore, since UE 110-1 receives the same reference ID from cell 2 212 as from cell 1 211, UE 110-1 does not need to perform separate signaling for synchronization status update.

[0076] refer to Figure 5bWhen UE 110-1 in the RRC_Idle state moves from cell 2 212 to cell 3 213, UE 110-1 does not need to perform separate signaling for handover because cell 2 212 and cell 3 213 belong to the same RA 210. Furthermore, when cell 2 212 and cell 3 213 have Sync#1 310 and Sync#2 320, respectively, in different synchronization states, cell 2 212 and cell 3 213 broadcast different reference IDs via the SIB. Therefore, since UE 110-1 receives a different reference ID from cell 3 213 than from cell 2 212, UE 110-1 performs separate signaling for synchronization status update.

[0077] Figure 6 An operation of a UE performing handover in the same synchronization range according to an embodiment of the present disclosure is shown.

[0078] refer to Figure 6 In operation 600, UE 110 sends a UE registration. The UE registration includes UE capabilities, which indicate that the synchronization service of the 5G system can be supported. In addition, the UE registration may include the cell ID or RAN ID, or TA ID and SAID where the UE 110 is located. The RAN ID, TA ID or SA ID can be derived from the cell ID. The UE registration is transmitted to the UDR / UDM 145 via the AMF 125. The UDM 145 can identify whether the UE 110 has a service subscription for receiving the 5G system synchronization service. The service subscription information may include information about the UE 110, requirements (such as synchronization error limit), and coverage conditions.

[0079] In operation 601, the AF 255 may send a 5GS synchronization request for a target UE to the TSCTSF / NEF 250. This request includes the required synchronization accuracy as a synchronization error budget. Furthermore, the coverage to which the synchronization service is to be applied may be referred to as a location or range. The target UE may be represented by a UE ID list, a group ID, or a data network name (DNN) / single network slice selection assistance information (S-NSSAI).

[0080] In operation 602, the TSC TSF / NEF 250 may request the AMF 125 to notify the target UE of location and range information. In this case, the location / range may be converted into a RAN ID, TA ID, SA ID, cell ID, etc. that may be known in 3GPP and may be used.

[0081] In operation 603, the AMF 125 may notify the TSC TSF / AMF 250 of location and range information about the corresponding UE 110.

[0082] In operation 604 , the TSCTSF / NEF 250 may report the location and range of the corresponding UE 110 to the AF 255 .

[0083] In operation 604a, the AF 255 may determine whether the location information about the UE 110 satisfies the requirement.

[0084] In operation 604b, AF 255 may send a 5GS synchronization request for UE 110 to TSCTSF / NEF 250.

[0085] In operation 605 , the TSCTSF / NEF 250 may determine whether the location information about the UE 110 satisfies requirements.

[0086] In operation 606, TSCTSF / NEF 250 may receive a synchronization status change from RAN / CN / OAM and determine whether to update the synchronization status. An input requesting a synchronization status change in the RAN may occur due to congestion in a specific area, or an input requesting a synchronization status change may occur from the CN to TSCTSF / NEF 250, thereby updating the synchronization status of UE 110 via a report from UPF 140 following interaction between UE 110 and UPF 140. Furthermore, when OAM detects a status anomaly, such as in the RAN or CN, an input requesting a synchronization status change may be generated from OAM to TSCTSF / NEF 250, causing OAM to request a synchronization status change. TSCTSF / NEF 250 may determine whether to update the synchronization status by interpreting these inputs.

[0087] In operation 606 a , the TSCTSF / NEF 250 may inform the AF 255 of the current synchronization state by reflecting the changed synchronization state of the UE 110 .

[0088] In operation 607, the TSCTSF / NEF 250 may transmit a 5GS synchronization request for the UE 110 to the PCF 135. In this case, the request transmitted from the TSCTSF / NEF 250 to the PCF 135 may include the required synchronization accuracy as a synchronization error budget. The scope to which the synchronization service should be applied may also be specified based on location or range. In this case, a reference ID (e.g., reference ID #1) may be included as information indicating the time or event at which the synchronization status was transmitted.

[0089] In operation 608, PCF 135 may transmit a 5GS synchronization request for UE 110 that meets the location or range conditions to AMF 125. In this case, the request transmitted from PCF 135 to AMF 125 may include the required synchronization accuracy as a synchronization error budget. The range in which the synchronization service should be applied may also be specified based on the location or range. In this case, a reference ID (e.g., reference ID #1) may be included as information indicating the time or event at which the synchronization status was transmitted. This reference ID may be received from TSCTSF 250 or generated by PCF 135.

[0090] In operation 608a, the AMF 125 may determine whether the location information about the UE 110 satisfies the requirements.

[0091] In operation 609, AMF 125 requests at least one gNB to apply synchronization accuracy to UE 110 that meets the conditions. In this case, the request may include a synchronization error budget. In this case, the request may be sent simultaneously to all gNBs corresponding to the range conditions, namely gNB1 123 and gNB2 126. In this case, a reference ID (e.g., reference ID #1) may be included as information indicating the time or event at which the synchronization status was transmitted. This reference ID may be received from TSCTSF 250 or generated by PCF 135.

[0092] In operation 609, each of the gNBs 120 and 125 may increase / decrease a system information block (SIB) broadcast period based on the synchronization error budget information transmitted from the 5GC, or may increase / decrease a delay time measurement period between the gNB and the UE to meet the time synchronization accuracy requirement of the UE to measure a radio resource control (RRC) timing advance (TA) value with each UE.

[0093] In addition, each gNB 120 or 125 may store a reference ID (e.g., reference ID #1) indicating the time or event at which the synchronization status information received from the AMF 125 was received, or may directly generate and store a reference ID based on the time at which the synchronization status information was received. Furthermore, each gNB 120 or 125 may include the reference ID in the SIB and periodically broadcast it. Each gNB 120 or 125 may allow gNBs with the same synchronization status to have the same group ID, generate a reference ID including the group ID, include the reference ID in the SIB, and periodically broadcast the reference ID.

[0094] In operation 610, UE 110 receives an SIB from gNB1 123 where it resides. In this case, UE 110 recognizes that reference ID #1 included in the SIB is a new value. UE 110 may store multiple latest reference IDs and then use them for comparison.

[0095] In operation 611, UE 110 performs RRC signaling with gNB1 123 to receive detailed synchronization status. UE 110 stores Reference ID #1, which is the reference ID of the most recently performed synchronization status update. Thereafter, when there is no traffic for a predetermined period of time, UE 110 switches to the RRC_Idle state and moves to gNB2 126.

[0096] In operation 612, UE 110 receives the SIB from gNB2 126 on which it resides. In this case, since reference ID #1 included in the SIB is the same value as the previously stored value, UE 110 does not perform a separate synchronization status update.

[0097] Figure 7 An operation when a UE is handed over to another synchronization range according to an embodiment of the present disclosure is shown.

[0098] refer to Figure 7 In operation 701, the AF 255 may send a 5GS synchronization request for a target UE to the TSCTSF / NEF 250. The request may include the required synchronization accuracy as a synchronization error budget. The scope to which the synchronization service should be applied may also be specified based on location or range. The target UE may be represented by a UE ID list, group ID, or DNN / S-NSSAI.

[0099] In operation 702, the TSC TSF / NEF 250 may request the AMF 125 to notify the target UE of location and range information. In this case, the location / range may be converted into a RAN ID, TA ID, SA ID, cell ID, etc. that may be known in 3GPP and may be used.

[0100] In operation 703, the AMF 125 may notify the TSC TSF / AMF 250 of location and range information about the corresponding UE 110.

[0101] In operation 704 , the TSCTSF / NEF 250 may report the location and range of the corresponding UE 110 to the AF 255 .

[0102] In operation 704a, the AF 255 may determine whether the location information about the UE 110 satisfies the requirement.

[0103] In operation 704b, AF 255 may send a 5GS synchronization request for UE 110 to TSCTSF / NEF 250.

[0104] In operation 705 , the TSCTSF / NEF 250 may determine whether the location information about the UE 110 satisfies requirements.

[0105] In operation 706 , the TSCTSF / NEF 250 may receive a synchronization status change from the RAN / CN / OAM and determine whether to update the synchronization status.

[0106] In operation 706a, the TSCTSF / NEF 250 may notify the AF 255 of the current synchronization state by reflecting the changed synchronization state of the UE 110. An input to change the synchronization state in the RAN may occur due to congestion in a specific area, or an input to change the synchronization state may occur from the CN to the TSCTSF / NEF 250 to update the synchronization state of the UE 110 through a report from the UPF 140 after interaction between the UE 110 and the UPF 140. Furthermore, when the OAM detects a state abnormality, such as in the RAN or CN, an input to change the synchronization state may be generated from the OAM to the TSCTSF / NEF 250, causing the OAM to request a synchronization state change. The TSCTSF / NEF 250 may determine whether to update the synchronization state by understanding these inputs.

[0107] In operation 707, the TSCTSF / NEF 250 may transmit a 5GS synchronization request for the UE 110 to the PCF 135. In this case, the request transmitted from the TSCTSF / NEF 250 to the PCF 135 may include the required synchronization accuracy as a synchronization error budget. The scope to which the synchronization service should be applied may also be specified based on location or range. In this case, a reference ID (e.g., reference ID #2) may be included as information indicating the time or event at which the synchronization status was transmitted.

[0108] In operation 708, PCF 135 may transmit to AMF 125 a 5GS synchronization request for a UE that meets the location or range conditions. In this case, the request transmitted from PCF 135 to AMF 125 may include the required synchronization accuracy as a synchronization error budget. The range in which the synchronization service should be applied may also be specified based on the location or range. In this case, a reference ID (e.g., reference ID #2) may be included as information indicating the time or event at which the synchronization status was transmitted. This reference ID may be received from TSCTSF 250 or generated by PCF 135.

[0109] In operation 708a, the AMF 125 may determine whether the location information about the UE 110 satisfies the requirements.

[0110] In operation 709, AMF 125 requests at least one gNB to apply synchronization accuracy to UE 110 that meets the conditions. In this case, the request may include a synchronization error budget. In this case, the request may be sent to all gNBs corresponding to the scope conditions, namely, gNB2 126 and gNB3 127. In this case, a reference ID (e.g., reference ID #2) may be included as information indicating the time or event at which the synchronization status was transmitted. This reference ID may be received from TSCTSF 250 or generated by PCF 135.

[0111] In operation 709, each of the gNBs 125 and 127 may increase / decrease a system information block (SIB) broadcast period based on the synchronization error budget information transmitted from the 5GC, or may increase / decrease a delay time measurement period between the gNB and the UE to meet the time synchronization accuracy requirement of the UE to measure a radio resource control (RRC) timing advance (TA) value with each UE.

[0112] In addition, each gNB 125 or 127 may store a reference ID (e.g., reference ID #2) indicating the time or event at which the synchronization status information received from the AMF 125 was received, or may directly generate and store a reference ID based on the time at which the synchronization status information was received. Furthermore, each gNB 125 or 127 may include the reference ID in the SIB and periodically broadcast it. Each gNB 125 or 127 may allow gNBs with the same synchronization status to have the same group ID, generate a reference ID including the group ID, include the reference ID in the SIB, and periodically broadcast the reference ID.

[0113] In operation 710, UE 110 receives an SIB from gNB3 127, where it resides. In this case, UE 110 recognizes that Reference ID #2 included in the SIB is a new value and prepares to perform synchronization status update signaling by switching to the RRC_connected state. Previously, whenever UE 110 received an SIB including Reference ID #1 from gNB2 126, UE 110 determined that the Reference ID included in the SIB was the same as the previously stored Reference ID and remained in the RRC_Idle state without performing a separate synchronization status update. In this state, it moved to the area of gNB3 127. UE 110 can store multiple latest Reference IDs and then use them for comparison.

[0114] In operation 711, UE 110 performs RRC signaling with gNB3 127 to receive detailed synchronization status. UE 110 stores reference ID #2, which is the reference ID of the most recently performed synchronization status update. Thereafter, when there is no traffic for a predetermined period of time, UE 110 switches to the RRC_Idle state and moves to gNB2 126.

[0115] Figure 8 The operation of the UE performing synchronization status update in the same synchronization range according to an embodiment of the present disclosure is shown.

[0116] refer to Figure 8 In operation 801, the AF 255 may send a 5GS synchronization request for a target UE to the TSCTSF / NEF 250. The request may include the required synchronization accuracy as a synchronization error budget. The scope to which the synchronization service should be applied may also be specified based on location or range. The target UE may be represented by a UE ID list, group ID, or DNN / S-NSSAI.

[0117] In operation 802, the TSC TSF / NEF 250 may request the AMF 125 to notify the target UE of location and range information. In this case, the location / range may be converted into a RAN ID, TA ID, SA ID, cell ID, etc. that may be known in 3GPP and may be used.

[0118] In operation 803, the AMF 125 may notify the TSC TSF / AMF 250 of location and range information about the corresponding UE 110.

[0119] In operation 804 , the TSCTSF / NEF 250 may report the location and range of the corresponding UE 110 to the AF 255 .

[0120] In operation 804a, the AF 255 may determine whether the location information about the UE 110 satisfies the requirement.

[0121] In operation 804b, AF 255 may send a 5GS synchronization request for UE 110 to TSCTSF / NEF 250.

[0122] In operation 805 , the TSCTSF / NEF 250 may determine whether the location information about the UE 110 satisfies requirements.

[0123] In operation 806, TSCTSF / NEF 250 may receive a synchronization status change from RAN / CN / OAM and determine whether to update the synchronization status. An input to change the synchronization status in the RAN may occur due to congestion in a specific area, or an input to change the synchronization status from the CN to TSCTSF / NEF 250 may occur, thereby updating the synchronization status of UE 110 via a report from UPF 140 following interaction between UE 110 and UPF 140. Furthermore, when OAM detects a status abnormality, such as in the RAN or CN, an input to change the synchronization status from OAM to TSCTSF / NEF 250 may be generated, causing OAM to request a synchronization status change. TSCTSF / NEF 250 can determine whether to update the synchronization status by understanding these inputs.

[0124] In operation 806 a , the TSCTSF / NEF 250 may inform the AF 255 of the current synchronization state by reflecting the changed synchronization state of the UE 110 .

[0125] In operation 807, the TSCTSF / NEF 250 may transmit a 5GS synchronization request for the UE 110 to the PCF 135. In this case, the request transmitted from the TSCTSF / NEF 250 to the PCF 135 may include the required synchronization accuracy as a synchronization error budget. The scope to which the synchronization service should be applied may also be specified based on location or range. In this case, a reference ID (e.g., reference ID #3) may be included as information indicating the time or event at which the synchronization status was transmitted.

[0126] In operation 808, the PCF 135 may transmit to the AMF 125 a 5GS synchronization request for the UE that meets the location or range conditions. In this case, the request transmitted from the PCF 135 to the AMF 125 may include the required synchronization accuracy as a synchronization error budget. The range in which the synchronization service should be applied may also be specified based on the location or range. In this case, a reference ID (e.g., reference ID #3) may be included as information indicating the time or event at which the synchronization status was transmitted. This reference ID may be received from the TSCTSF 250 or may be generated by the PCF 135.

[0127] In operation 808a, the AMF 125 may determine whether the location information about the UE 110 satisfies the requirements.

[0128] In operation 809, the AMF 125 requests at least one gNB to apply synchronization accuracy to the UE 110 that meets the conditions. In this case, the request may include a synchronization error budget. In this case, the request may be sent to all gNBs corresponding to the scope conditions, i.e., to gNB3 127. In this case, a reference ID (e.g., reference ID #3) may be included as information indicating the time or event at which the synchronization status was transmitted. This reference ID may be received from the TSCTSF 250 or generated by the PCF 135.

[0129] In operation 809, each gNB 127 may increase / decrease a system information block (SIB) broadcast period based on synchronization error budget information transmitted from the 5GC, or may increase / decrease a delay time measurement period between the gNB and the UE to meet the time synchronization accuracy requirement of the UE to measure a radio resource control (RRC) timing advance (TA) value with each UE.

[0130] In addition, each gNB 127 may store a reference ID (e.g., reference ID #3) indicating the time or event at which the synchronization status information received from the AMF 125 was received, or may directly generate and store a reference ID based on the time at which the synchronization status information was received. Furthermore, each gNB 127 may include the reference ID in the SIB and periodically broadcast it. Each gNB 127 may allow gNBs with the same synchronization status to have the same group ID, generate a reference ID including the group ID, include the reference ID in the SIB, and periodically broadcast the reference ID.

[0131] In operation 810, UE 110 receives an SIB from gNB3 127, where it resides. In this case, UE 110 recognizes that Reference ID #3 included in the SIB is a new value and prepares to perform synchronization status update signaling by switching to the RRC_connected state. Previously, whenever UE 110 received an SIB including Reference ID #2 from gNB3 127, UE 110 determined that the Reference ID included in the SIB was the same as the previously stored Reference ID and remained in the RRC_Idle state without performing a separate synchronization status update. In this state, UE 110 remained in the area of gNB3 127. UE 110 can store multiple latest Reference IDs and then use them for comparison.

[0132] In operation 811, UE 110 performs RRC signaling with gNB3 127 to receive detailed synchronization status. UE 110 stores reference ID #3, which is the reference ID of the most recently performed synchronization status update. Thereafter, when there is no traffic for a predetermined period of time, UE 110 switches to the RRC_Idle state.

[0133] According to the above-mentioned embodiments of the present disclosure, when the 5G system becomes a synchronization source and provides a synchronization status to the UE to provide a synchronization service to the UE, the 5G system can perform separate signaling when the synchronization status changes, regardless of whether the idle UE moves between base stations in the same RA, so that the UE can receive a detailed synchronization status.

[0134] Figure 9 is a diagram illustrating a configuration of a network entity in a wireless communication system according to an embodiment of the present disclosure.

[0135] refer to Figure 9 , the network entities can be such as combined Figure 1 、 Figure 2 、 Figure 3a 、 Figure 3b 、 Figure 4 、 Figure 5a 、 Figure 5b and Figures 6 to 8 One of the network entities of AF, TSCTSF, NEF, UDM, PCF, SMF, AMF, UPF, (R)AN, UE and DN described in the embodiment.

[0136] Figure 9 The network entity may include a processor 910, a transceiver 920, and a memory 930. The processor 910, the transceiver 920, and the memory 930 of the network entity may be combined with the above Figure 1 、 Figure 2 、 Figure 3a 、 Figure 3b 、 Figure 4 、 Figure 5a 、 Figure 5b and Figures 6 to 8 The network entity communication method described in the embodiments operates according to the embodiment. However, the components of the network entity are not limited thereto. For example, the network entity may include more or fewer components than those described above. The processor 910, transceiver 920, and memory 930 may be implemented in the form of a single chip.

[0137] The transceiver 920 collectively refers to a receiver of a network entity and a transmitter of a network entity, and may send and receive signals to / from a UE or another network entity. The sent / received signal may include at least one of control information and data. To this end, the transceiver 920 may include a wired / wireless transceiver and may include various components for sending / receiving signals. The transceiver 920 may receive a signal through a predetermined communication interface, output the signal to the processor 910, and transmit a signal output from the processor 910. Further, the transceiver 920 may receive a communication signal and output it to the processor 910, and transmit the signal output from the processor 910 to the UE or another network entity through the network. The memory 930 may store data according to Figure 1 、 Figure 2 、 Figure 3a 、 Figure 3b 、 Figure 4 、 Figure 5a 、 Figure 5b and Figures 6 to 8 The program and data necessary for the operation of at least one of the embodiments of the network entity. In addition, the memory 930 may store control information or data included in the signal obtained by the network entity. The memory 925 may include a storage medium such as a read-only memory (ROM), a random access memory (RAM), a hard disk, a compact disc read-only memory (CD-ROM) and a digital versatile disk (DVD) or a combination of storage media. In addition, the processor 910 may control a series of processes so that the network entity can operate according to Figure 1 、 Figure 2 、 Figure 3a 、 Figure 3b 、 Figure 4 、 Figure 5a 、 Figure 5b and Figures 6 to 8 The processor 910 may include at least one processor.

[0138] The methods according to the embodiments described in the specification or claims of the present disclosure may be implemented in hardware, software, or a combination of hardware and software.

[0139] When implemented in software, a computer-readable storage medium storing one or more programs (software modules) may be provided. The one or more programs stored in the computer-readable storage medium are configured to be executed by one or more processors in an electronic device. The one or more programs include instructions that enable the electronic device to perform the methods according to the embodiments described in the specification or claims of this disclosure.

[0140] Programs (software modules or software) may be stored in random access memory, nonvolatile memory including flash memory, read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), magnetic disk storage, compact disc ROM, digital versatile disk (DVD), or other types of optical storage devices, or magnetic tape cartridges. Alternatively, the program may be stored in a memory comprising a combination of all or some of these. Each memory component may include multiple memories.

[0141] The program may be stored in an attachable storage device that is accessible via a communication network, such as the Internet, an intranet, a local area network (LAN), a wide area network (WLAN), a storage area network (SAN), or a combination thereof. The storage device may be connected to a device executing embodiments of the present disclosure via an external port. A separate storage device on a communication network may be connected to a device executing embodiments of the present disclosure.

[0142] In the above-described specific embodiments of the present disclosure, components included in the present disclosure are presented in either singular or plural form, depending on the specific embodiment being proposed. However, the singular or plural form is selected to be sufficient for the context suggested for ease of description, and the present disclosure is not limited to singular or plural components. As used herein, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

[0143] While the present disclosure has been shown and described with reference to various embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present disclosure as defined by the appended claims and their equivalents.

Claims

1. A method for providing time synchronization in a wireless communication system, the method comprising: Receiving, by a user equipment (UE), a reference identification (ID) from a base station based on time synchronization status information received by the base station from a network entity; and The time synchronization status information is received by the UE from the base station via radio resource control (RRC) signaling.

2. The method according to claim 1, wherein The time synchronization status information includes a synchronization error budget.

3. The method according to claim 1, wherein The reference ID contains information about the event.

4. The method according to claim 1, wherein The reference ID is broadcast via the System Information Block (SIB).

5. The method according to claim 1, further comprising: The received reference ID is compared by the UE with the stored reference ID.

6. The method according to claim 1, further comprising: In case the UE determines that the received reference ID is changed, the UE is connected to a network.

7. A method for providing time synchronization in a wireless communication system, the method comprising: Receiving, by the base station, time synchronization status information from the network entity; Based on the time synchronization state information, the base station sends a reference identification (ID) to a user equipment (UE); and The time synchronization status information is sent by the base station to the UE via radio resource control (RRC) signaling.

8. The method according to claim 7, wherein: The time synchronization status information includes a synchronization error budget.

9. The method according to claim 7, wherein: The reference ID contains information about the event.

10. The method according to claim 7, wherein: The reference ID is broadcast via the System Information Block (SIB).

11. A user equipment (UE) for providing time synchronization in a wireless communication system, the UE comprising: transceiver; and at least one processor coupled to the transceiver and configured to: receiving a reference identification (ID) from the base station based on time synchronization status information received by the base station from a network entity, and The time synchronization status information is received from the base station via radio resource control (RRC) signaling.

12. The UE according to claim 11, wherein: The time synchronization status information includes a synchronization error budget.

13. The UE according to claim 11, wherein: The reference ID contains information about the event, The reference ID is broadcast via a system information block (SIB).

14. The UE according to claim 11, wherein: The processor is further configured to: Comparing the received reference ID with the stored reference ID, and Connecting to a network if the UE determines that the received reference ID is changed.

15. A base station for providing time synchronization in a wireless communication system, the base station comprising: transceiver; and at least one processor coupled to the transceiver and configured to: Receive time synchronization status information from network entities, Based on the time synchronization status information, the base station sends a reference identification (ID) to a user equipment (UE), and The time synchronization status information is sent to the UE via radio resource control (RRC) signaling.

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