Method and apparatus for providing neighbor cell information in wireless communication system

Abstract

The present disclosure relates to a 5G or 6G communication system for supporting a higher data transmission rate. Specifically, the present disclosure relates to a method for a user equipment (UE) for obtaining first cell information (e.g., first ephemeris information) for a first cell (e.g., a serving cell) and second cell information (e.g., second ephemeris information) for one or more second cells (e.g., one or more neighboring cells). The second cell is a non-terrestrial network (NTN) cell. The method includes, in response to expiration of a first timer (e.g., T317) indicating that validity of previously acquired first cell information has expired, starting a second timer (e.g., T318 or a newly defined timer); attempting to acquire the first cell information and the second cell information during the period of the second timer; and when the second timer expires, if the first cell information is not successfully acquired, performing a Radio Link Failure (RLF) procedure regardless of whether the second cell information has been successfully acquired.

Description

TECHNICAL FIELD

[0001] The present disclosure relates generally to wireless communication systems, and more particularly, the present disclosure relates to methods and apparatuses for acquiring neighbor cell information in non-terrestrial networks (NTNs). For example, certain examples of the present disclosure provide one or more techniques for acquiring neighbor cell information in Third Generation Partnership Project (3GPP) Fifth Generation (5G) New Radio (NR) NTS. BACKGROUND

[0002] 5G mobile communication technologies define broadband wireless access technologies that enable implementation of high-speed and high-quality communication services based on wide frequency bands (e.g., 3 GHz to 60 GHz) and various infrastructure technologies (e.g., beamforming, massive multiple-input multiple-output (MIMO), full dimensional MIMO (FD-MIMO), array antennas, analog beamforming, and digital beamforming) using the wide frequency bands.

[0003] At the initial stage of 5G mobile communication technology development, beamforming, massive MIMO, and a large number of antennas are being considered to compensate for the path loss of radio waves in millimeter waves and to increase the distance of radio wave transmission. In addition, technologies such as V2X, NR-U, NR UE power saving, non-terrestrial networks (NTNs), and positioning are being considered to improve the performance of 5G mobile communication technologies.

[0004] Currently, in consideration of services to be supported by 5G mobile communication technologies, discussions are underway for improvement and performance enhancement of initial 5G mobile communication technologies, and physical layer standardization is also underway for technologies such as vehicle-to-everything (V2X) for assisting autonomous driving vehicles in making driving decisions based on position and state information transmitted by vehicles and improving user convenience, new radio unlicensed (NR-U) for system operation that satisfies various regulatory requirements in unlicensed bands, NR UE power saving, non-terrestrial networks (NTNs) for direct communication of UE-satellite for providing coverage in areas where ground communication is not available, and positioning technologies.

[0005] In addition, in the air interface architecture / protocol aspect, standardization efforts for the following technologies are ongoing: Industrial Internet of Things (IIoT) for support of new services based on interworking between 3GPP technologies and technologies from other industries such as industrial automation, vehicular, and aerospace; Integrated Access and Backhaul (IAB) for using the same radio interface for access and backhaul links to provide a flexible topology for the network service area expansion; Mobility Enhancements including Conditional Handover (CHO) and Dual Active Protocol Stack (DAPS) Handover; and two-step Random Access (2-step RACH for NR) for simplified random access procedure. In terms of system architecture / service aspect, standardization efforts are ongoing in: 5G baseline architecture including service- based architecture or service-based interface for network function virtualization (NFV) and software-defined networking (SDN) technology; and mobile edge computing (MEC) for receiving services based on UE location.

[0006] As 5G mobile communication systems are commercialized, a rapidly increasing number of connected devices will access the communication network, and thus, it will be necessary to support enhanced functionality and performance of the 5G mobile communication system and integrated operation of connected devices. To this end, new research in the following areas has been scheduled: extended reality (XR) for efficient support of augmented reality (AR), virtual reality (VR), mixed reality (MR), etc.; 5G performance improvement and complexity reduction through the use of artificial intelligence (AI) and machine learning (ML); AI service support; metaverse service support; and drone communication.

[0007] In addition, this development of 5G mobile communication systems will not only lay the foundation for the development of technologies for providing coverage in the terahertz bands for 6G mobile communication technology, but also for the development of technologies such as multi-antenna transmission techniques like full-dimensional MIMO (FD-MIMO), array antennas, and massive antennas; lenses and antennas based on metamaterials for improving coverage of terahertz-band signals; high-dimensional spatial multiplexing techniques using orbital angular momentum (OAM); and reconfigurable intelligent surfaces (RIS), full-duplex techniques for improving frequency efficiency of 6G mobile communication technologies and mitigating system latency, AI-based communication techniques that utilize satellites and artificial intelligence (AI) from the design stage and internalize end-to-end AI support functions to enable system optimization; and next-generation distributed computing techniques that utilize ultra-high-performance communication and computing resources to implement complex levels of services beyond the operational limits of UEs. SUMMARY

[0008] [Technical Problem]

[0009] The disclosure relates to a wireless communication system, and more particularly, the disclosure relates to a method and apparatus for providing neighbor cell information in a wireless communication system.

[0010] [Technical Solution]

[0011] In one embodiment of the disclosure, one or more techniques are provided for acquiring neighbor cell information in an NTN. For example, certain examples of the disclosure provide one or more techniques for acquiring neighbor cell information in a 3GPP 5G NR NTN. However, those skilled in the art will appreciate that the disclosure is not limited to these examples and can be applied to any suitable system or standard, such as one or more existing and / or next generation wireless communication systems or standards, including any existing or future versions of the same standard specification (e.g., 3GPP 5G).

[0012] The functions and other features of the various network entities disclosed herein can be applied to corresponding or equivalent entities or features in the same or any other suitable communication system or standard. A corresponding or equivalent entity or feature can be considered to be an entity or feature that performs the same or similar role, function, or purpose within a network. For example, the functions of an NG-RAN node (e.g., a base station or gNB) in the following examples can be applied to any other suitable type of entity that performs RAN functions. BRIEF DESCRIPTION OF DRAWINGS

[0013] Figure 1 An NTN architecture and scenarios are illustrated; Figure 2 Examples of ephemeris synchronization operation are illustrated; Figure 3 Example techniques are illustrated where T318 is continued after acquiring SIB31 if a new SIB is signaled; Figure 4 Example techniques are illustrated where a new timer (e.g., T3XX / T319) is started after T317 to acquire SIB31 and a new SIB; Figure 5 Example techniques are illustrated where a new timer (e.g., T3XX / T319) is started to acquire a new SIB; Figure 6 Example techniques are illustrated where a SIB validity period is included that triggers a new SIB acquisition at the next opportunity; Figure 7 Example techniques are illustrated where a new SIB is re-acquired at the next T318 opportunity after a failed attempt to acquire the new SIB; Figure 8 Example techniques are illustrated where SIB31 is autonomously acquired and T318 is not triggered (to acquire SIB31 and a new SIB); Figure 9 Example techniques are illustrated for signaling a UE capability to autonomously acquire SIB31 but not a new SIB; Figure 10A flowchart of an exemplary method for a UE to acquire first cell information (e.g., first ephemeris information) of a first cell (e.g., a serving cell) and second cell information (e.g., second ephemeris information) of one or more second cells (e.g., one or more neighboring cells), wherein the second cells are non-terrestrial network (NTN) cells; Figure 11 A block diagram of a network entity of an embodiment of the present disclosure; Figure 12 A block diagram of a terminal (or user equipment (UE)) of an embodiment of the present disclosure is shown; Figure 13 A block diagram of a base station of an embodiment of the present disclosure is shown; and Figure 14 A block diagram of a network entity of an embodiment of the present disclosure is shown. DETAILED DESCRIPTION

[0014] The following description of examples of the present disclosure, with reference to the drawings, is not intended to limit the scope of the invention as defined in the claims. The description includes various specific details in order to provide a thorough understanding. However, these details are merely examples. Accordingly, one of ordinary skill in the art will recognize that various changes and modifications of the examples described herein can be made without departing from the scope of the present invention.

[0015] The same or similar components can be identified with the same or similar reference numbers, although they can be shown in different drawings.

[0016] Detailed descriptions of technologies, structures, functions, operations or processes known in the art will be omitted for clarity and conciseness and to avoid obscuring the subject matter of the present invention.

[0017] The terms and words used herein are not limited to the bibliographical or standard meanings and are only used to enable a clear and consistent understanding of the present invention.

[0018] In the description of the specification and the claims, the words “comprise” “include” “contain” and variations thereof (such as “comprising” “including” “containing”) mean “including but not limited to,” and are not intended to (and will not) exclude other features, elements, components, integers, steps, processes, operations, functions, characteristics, attributes, and / or groups thereof.

[0019] In the description of the specification and the claims, the singular form (“a,” “an,” and “the”) covers the plural form unless the context requires otherwise. For example, reference to “an object” includes reference to one or more such objects.

[0020] In the description and claims of the application, expressions of the form "X for Y" (where Y is an action, process, operation, function, activity or step, and X is a means for carrying out the action, process, operation, function, activity or step) encompasses a special but non-exclusive adaptation of the means X for carrying out the action, process, operation, function, activity or step Y.

[0021] Features, elements, components, integers, steps, processes, operations, functions, attributes, properties, and / or combinations thereof described or disclosed in conjunction with a specific aspect, embodiment, example, or claim, are

[0022] Certain examples of the present disclosure are directed to at least partially addressing, handling, and / or mitigating at least one problem and / or disadvantage associated with the related art (e.g., at least one problem and / or disadvantage described herein). Certain examples of the present disclosure are directed to providing at least one advantage over the related art (e.g., at least one advantage described herein).

[0023] The invention is defined by the independent claims. Advantageous features are defined by the dependent claims. Embodiments or examples disclosed in the description and / or the drawings but not falling within the scope of the claims are to be interpreted as examples useful for understanding the invention.

[0024] Other aspects, advantages, and salient features of the application will become apparent to those skilled in the art from the following detailed description, which, taken in

[0025] Those skilled in the art will understand that the technology described herein can be used in any appropriate combination.

[0026] One of the areas currently being developed for 3GPP 5G wireless technology is support for non-terrestrial networks (NTN). NTN refers to a network that provides one or more nodes (e.g., Next Generation Radio Access Network (NG-RAN) nodes) by non-terrestrial infrastructure (e.g., satellites or High Altitude Platform Stations (HAPS)). Advantages of using NTN include: (i) extending coverage to areas where traditional terrestrial networks have limited or no coverage, such as remote areas; (ii) providing continuous coverage in situations where traditional terrestrial networks are inoperable, such as natural disasters; (iii) improving overall reliability, invulnerability, and capacity when used in conjunction with existing terrestrial networks. Figure 1 The 17th edition NTN architecture and scenarios are shown.

[0027] A satellite network implementing network nodes provides coverage through one or more radio beams forming a “footprint” on the Earth’s surface, which defines a coverage area or cell. An NTN cell can be Earth-Moving (i.e., moving over the Earth’s surface according to the satellite motion, e.g., in case of Low Earth Orbit (LEO) satellites), Earth-Fixed (i.e., a fixed area of the Earth’s surface, e.g., in case of Geostationary Equatorial Orbit (GEO) satellites), or Quasi-Earth-Fixed (i.e., a fixed area of the Earth’s surface, but only maintaining the area during the satellite pass).

[0028] Due to the motion of the satellites in non-geostationary orbits (e.g., LEO), the cells that can be observed by a UE also move (i.e., Earth-Moving cells). This results in the need for the UE to frequently handover from one cell to another, and this type of service handover occurs continuously. In view of this, mobility is one of the key issues in NR NTN and IoT NTN.

[0029] IoT NTN Overview

[0030] IoT NTN is a 3GPP Study and Work Item in 3GPP Release 17 (RP-202689, RAN#90, December 2020) to provide NTN access for Evolved Universal Terrestrial Radio Access Network (E-UTRAN) IoT devices, such as Narrow Band (NB)-IoT and Long Term Evolution Machine Type Communication (LTE-M), including enhanced Machine Type Communication (eMTC). As stated in 3GPP RP-202689, it is essential for many different industries to implement IoT operations in remote areas where cellular connectivity is weak or non-existent. The capabilities of NB-IoT and eMTC are well suited for many applications, but certain applications can require satellite connectivity to achieve coverage beyond the range of terrestrial deployments.

[0031] NR NTN is a work item in Release 17 to develop specifications that enable NR to operate over NTN (RP-211557, RAN#91-e, March 2021).

[0032] Following the work item in Release 17, work items for enhanced NR NTN (RP-220953, RAN#95-e, March 2022) and enhanced IoT NTN (RP-220979, RAN#95-e, March 2022) were carried out in Release 18.

[0033] NB-IoT and LTE-M Overview

[0034] NB-IoT is a 3GPP-defined network based on the fourth generation (4G) E-UTRAN, supporting ultra-low complexity devices with very narrow bandwidth, introduced in 3GPP Release 13. The application scenario for NB-IoT is to serve massive IoT applications, whose requirements include, for example, support for enhanced coverage, high energy-efficient operation, and massive devices. Some of the introduced features are as follows: - Support for enhanced coverage through low bandwidth and large number of repetitions.

[0035] - High energy-efficient operation through allowing user equipment (UE) to sleep for long time, relaxed requirements, and more efficient signaling with the cell.

[0036] LTE-M or eMTC is a 3GPP-defined network, an extension of 4G E-UTRAN, supporting low complexity devices with narrower bandwidth than normal LTE, and further simplified procedures. Similar to NB-IoT, its application scenario is to serve massive IoT, but with more features. Unlike NB-IoT, which is a brand new device type with major changes in the air interface, LTE-M inherits most of the features of normal LTE devices, but with some adaptations for reduced complexity.

[0037] NTN system information overview

[0038] Since NTN contains multiple NTN-specific information elements that are only needed when accessing an NTN cell, and since these information elements are relatively large, it is agreed that a new system information block (SIB) is needed.

[0039] In NR NTN, SIB19 contains information needed to access an NTN cell: -------------------------- 3GPP TS 38.331 V17.4.0-------------------------- – SIB19 SIB19 contains satellite assistance information for NTN access.

[0040] SIB19 information elements

[0041] -------------------------- 3GPP TS 38.331 V17.4.0--------------------------

[0042] In IoT NTN, SIB31 contains information needed to access an IoT NTN cell: -------------------------- 3GPP TS 36.331 V17.4.0-------------------------- - SystemInformationBlockType31 SystemInformationBlockType31 The information element contains satellite assistance information for the serving cell. SystemInformationBlockType31 Sent only in NTN cells.

[0043] SystemInformationBlockType31 information element

[0044] -------------------------- 3GPP TS 36.331 V17.4.0--------------------------

[0045] The system information contains the following: - Serving cell ephemeris elements. This allows the UE to compute the satellite position to perform Doppler and time pre-compensation. This information can be provided in two formats: o PVT format. Describes the (X, Y, Z) position as well as the velocity vector (vX, vY, vZ).

[0046] o Orbit parameters. Describes the orbital motion of the satellite and in turn used to infer the satellite position.

[0047] - TA common parameters. Provides common timing advance parameters used to compensate for feeder link delays. This signalling contains the following (occupies 57 bits in total): o Absolute TA common (23 bits).

[0048] o Drift of TA common, defining how TA common drifts, i.e. the first derivative of TA common (19 bits).

[0049] o Variation of TA common, defining how TA common varies, i.e. the second derivative of TA common (15 bits).

[0050] - Synchronization validity duration. Used to define the validity duration of ephemeris and TA common.

[0051] - Epoch time. Defines when the synchronization validity duration starts.

[0052] - k-Offset. Scheduling offset of timing relations in NTN.

[0053] - k-Mac. Scheduling offset used when downlink and uplink frame timing are not aligned.

[0054] - NR NTN specific information also includes (as part of 3GPP TS 38.331): o T-Service (sent over SIB3 in IoT NTN).

[0055] o Reference location and distance threshold. Used for location based measurement initiation in RRC IDLE and RRC CONNECTED state.

[0056] o Neighbor cell ephemeris. Used for IDLE state measurements.

[0057] NTN system information acquisition overview

[0058] Since ephemeris information is constantly changing due to the movement of NTN payload (such as satellites), it is necessary to ensure that the UE remains properly synchronized. Therefore, every time the UE connects to an eNB, it is necessary to read the system information (such as SIB19 or SIB31).

[0059] In IoT NTN, every time SIB31 is read, a timer (T317) associated with ephemeris elements is started. When T317 expires, the UE will no longer be considered in synchronization state and will need to reacquire SIB31 to maintain synchronization.

[0060] In IoT NTN, since IoT UEs (LTE-M and NB-IoT UEs) cannot acquire system information in connected state, the UE will tune away from the current frequency band and can not be paged during the reading of SIB31.

[0061] If an IoT NTN UE fails to read SIB31 within the configured duration timer (T318), the UE will perform a radio link failure (RLF), similar to other cases where RLF is performed. This operation can be seen in Figure 2 : Figure 2 (a) where SIB31 is working normally; Figure 2 (b) where the UE fails to read SIB31 during T318, then T318 expires and triggers RLF; In NR NTN, the UE needs to read SIB in time to ensure that the latest ephemeris is maintained (SIB19 in NR).

[0062] The T317 timer is different from the normal timers in RRC, it is not started upon reception of SIB31. This is because the ephemeris has an epoch time, which is the time reference point at which the ephemeris is defined. Therefore, the T317 timer is started from the epoch time, which can be before or after the reception of SIB31. This means that in UE implementation, the start value of the timer can be different from the value sent based on the ul-SyncValidityDuration field in SIB31.

[0063] Overview of NTN Ephemeris Format

[0064] There are three ways of signaling ephemeris in NTN: 1. PVT format, 2. Orbital Ephemeris Elements, and 3. TLE Ephemeris Elements (only for discontinuous coverage in IoT NTN).

[0065] PVT format

[0066] The PVT format sends the XYZ position and the velocity vector vXYZ. This can be seen from the following information element: -------------------------- 3GPP TS 36.331 V17.4.0-------------------------- - EphemerisStateVectors Ephemeris State Vectors IE provides satellite ephemeris in the format of position and velocity state vectors in ECEF coordinate system.

[0067] Ephemeris State Vectors Information Element

[0068] -------------------------- 3GPP TS 36.331 V17.4.0--------------------------

[0069] The position elements (X, Y, Z respectively) each take 26 bits, the velocity elements (vX, vY, vZ respectively) each take 18 bits, for a total of 132 bits.

[0070] Orbit Ephemeris format

[0071] The orbital ephemeris parameters (also known as Keplerian format) provide parameters that indicate how a celestial body moves in space, which can be used for precise synchronization and prediction of future positions of NTN payloads.

[0072] The orbital ephemeris elements are sent through the following elements (164 bits in total): - Semi-major axis (33 bits) - Eccentricity (20 bits) - Argument of perigee (28 bits) - Longitude of ascending node (28 bits) - Inclination (27 bits) - Mean anomaly (28 bits)

[0073] TLE orbit parameters

[0074] The TLE parameters are based on a two-line set of orbital elements (TLE), which is an industry-accepted data format for sending celestial body motion. While the PVT format and the orbital ephemeris format can be used for precise synchronization, the TLE parameters are mainly used for long-term prediction. For example, the TLE parameters can be used to accurately predict satellite transit times for up to several days in the future.

[0075] A full set of TLE parameters can take up more than 50 bytes of data, containing many fields that are not needed in 3GPP. Therefore, a simplified set of TLE parameters can be used, for example, based on the following parameters (189 bits in total): - Inclination (21 bits) - Argument of perigee (22 bits) - Longitude of ascending node (22 bits) - Mean anomaly (22 bits) - Eccentricity (24 bits) - Mean motion (34 bits) - B Value, sent through (i) fractional part (18 bits) and (ii) exponent part (5 bits) - Epoch start (21 bits) The above information is provided as background information only to assist with an understanding of the present disclosure. It has not been determined and is not claimed that any of the above can be used as prior art relevant to the present invention.

[0076] Certain examples of the present disclosure provide one or more techniques for acquiring neighbor cell information in an NTN. For example, certain examples of the present disclosure provide one or more techniques for acquiring neighbor cell information in a 3GPP 5G NR NTN. However, those skilled in the art will appreciate that the present application is not limited to these examples and can be applied to any suitable system or standard, such as one or more existing and / or next generation wireless communication systems or standards, including any existing or future versions of the same standard specification (e.g., 3GPP 5G).

[0077] The functions and other features of the various network entities disclosed herein can be applied to corresponding or equivalent entities or features in the same or any other suitable communication system or standard. A corresponding or equivalent entity or feature can be regarded as an entity or feature that performs the same or similar role, function, or purpose within a network. For example, the functions of an NG-RAN node (e.g., a base station or gNB) in the following examples can be applied to any other suitable type of entity that performs RAN functions.

[0078] A particular network entity can be implemented as a network element on a dedicated hardware, a software instance running on a dedicated hardware, and / or a virtualized function instantiated on a suitable platform (e.g., a cloud computing infrastructure).

[0079] Those skilled in the art will appreciate that the present application is not limited to the specific examples disclosed herein. For example: - The techniques disclosed herein are not limited to 3GPP 5G.

[0080] - One or more entities in the examples disclosed herein can be replaced by one or more alternative entities that perform equivalent or corresponding functions, procedures, or operations.

[0081] - One or more messages in the examples disclosed herein can be replaced by one or more alternative messages, signals, or other types of information carriers that convey equivalent or corresponding information.

[0082] - One or more other elements or entities can be added to the examples disclosed herein.

[0083] - One or more non-essential elements or entities can be omitted in certain examples.

[0084] - The functions, procedures, or operations of a particular entity in one example can be distributed among two or more separate entities in an alternative example.

[0085] - The functions, procedures, or operations of two or more separate entities in one example can be performed by a single entity in an alternative example.

[0086] - The information carried by a particular message in one example can be carried by two or more separate messages in an alternative example.

[0087] - Information carried by two or more separate messages in one example can be carried by a single message in an alternative example.

[0088] - In alternative examples, the order of execution of operations and / or the order of transmission of messages can be modified, if possible.

[0089] Certain examples of the present disclosure can take the form of apparatuses / devices / network entities configured to perform one or more defined network functions, and / or corresponding methods thereof. Certain examples of the present disclosure can take the form of a system (e.g., a network or wireless communication system) including one or more such apparatuses / devices / network entities, and / or corresponding methods thereof.

[0090] In 3GPP Release 17, ephemeris information was introduced for broadcast, which is essential for the UE to synchronize with the serving cell. Therefore, the concept of synchronization validity was introduced, i.e., ephemeris is considered valid for a certain duration defined by timer T317, and the UE is required to periodically re-acquire ephemeris within a period defined by timer T318.

[0091] In Release 18, neighbor cell assistance information including ephemeris information will be introduced for neighbor cell measurement. Similar to the synchronization with the serving cell, the neighbor cell assistance information also needs to be kept up-to-date, because the measurement quality will degrade if the UE is not synchronized with the cell being measured.

[0092] In the current 3GPP discussion, how to acquire the neighbor cell assistance information is being discussed, and it has been agreed that a new SIB will be introduced to broadcast this information. At the same time, how the UE acquires this new SIB is also being discussed, and it is proposed that the UE can acquire this new SIB during timer T318. In 3GPP R2-2306664, the following is proposed: Proposal 2 Agree to one of the following options - (9 / 13) Do not introduce a validity duration for SIBxx. It is up to the UE to decide when to acquire SIBxx, e.g., the UE can assume the validity duration of SIBxx is the same as the validity duration of the serving satellite, or rely on T318 (i.e., T318 of SIB31) in connected state.

[0093] - (2 / 13) Introduce an explicit validity duration for SIBxx. The absence of a validity duration means the validity duration of the serving satellite is applied. In connected state, the UE relies on T318 to acquire SIBxx. It is FFS which epoch time of which neighbor cell should be used to start the validity duration.

[0094] - (2 / 13) Mandate an explicit validity duration for SIBxx. In connected state, the UE relies on T318 to acquire SIBxx. It is FFS which epoch time of which neighbor cell should be used to start the validity duration.

[0095] However, there are still some open issues regarding how to acquire the new SIB: - One example is e.g. regarding T318 to be started after T317 expires. During T318, the UE shall try to acquire SIB31. However, if the UE succeeds in acquiring SIB31, T318 stops, which means there can be no time left to acquire the new SIB.

[0096] - Another example is: if a new validity time is introduced for the new SIB, how to define the start time of this timer.

[0097] Certain examples of the present disclosure provide one or more techniques for signaling neighbor cell information, such as neighbor cell assistance information.

[0098] Those skilled in the art will appreciate that ephemeris is not only applicable to satellite payloads, but can also be applicable to other platforms, such as High Altitude Platform Systems (HAPS). Thus, techniques mentioned herein with reference to “satellite ephemeris” can be applied not only to satellites, but also to any other suitable NTN platform and / or payload.

[0099] In the figures, T317 is shown to be started upon reception of SIB31. But this can be interpreted as T317 being started at the epoch time, which can be before or shortly after reception of SIB31.

[0100] The main use of the newly introduced SIB is to carry NTN neighbor cell assistance information. This neighbor cell assistance information can contain various information items, such as one or more of the following: ephemeris of the cell, satellite ID, timing advance common parameter, k-Offset, and k-Mac. In the present disclosure, references to “acquiring the new SIB”, “acquiring neighbor cell ephemeris”, “acquiring neighbor cell assistance information”, and the like can be considered as equivalent, referring to performing the same or similar UE actions, such as listening to, detecting, and decoding information in the new SIB.

[0101] Those skilled in the art will appreciate that the various techniques disclosed herein can be applied to: examples involving gNBs and / or NG-RAN; examples involving various related, newly defined, and / or existing signaling and / or messages, such as RRC, X2, Xn, S1, NG, and / or F1 signaling and / or messages; and / or examples involving various related network entities, such as MME, AMF, and the like.

[0102] Those skilled in the art will further appreciate that the various techniques disclosed herein can be applied to NR NTN.

[0103] Certain examples of the present disclosure provide a method for a user equipment (UE) for acquiring first cell information (e.g., first ephemeris information) for a first cell (e.g., a serving cell) and second cell information (e.g., second ephemeris information) for a second cell (e.g., a neighboring cell), wherein the second cell is a non-terrestrial network (NTN) cell, the method comprising: in response to expiration of a first timer (e.g., T317) indicating that a validity of previously acquired first cell information has expired, starting a second timer (e.g., T318 or a newly defined timer); attempting to acquire the first cell information and the second cell information during the second timer; and upon expiration of the second timer, performing a radio link failure (RLF) procedure if the first cell information has not been successfully acquired, regardless of whether the second cell information has been successfully acquired.

[0104] Certain examples of the present disclosure provide a method for a user equipment (UE) for acquiring first cell information (e.g., first ephemeris information) for a first cell (e.g., a serving cell) and second cell information (e.g., second ephemeris information) for a second cell (e.g., a neighboring cell), wherein the second cell is a non-terrestrial network (NTN) cell, the method comprising: in response to expiration of a first timer (e.g., T317) indicating that a validity of previously acquired first cell information has expired, starting a second timer (e.g., T318 or a newly defined timer); attempting to acquire the first cell information and the second cell information during the second timer; and upon expiration of the second timer, performing a radio link failure (RLF) procedure if the first cell information has not been successfully acquired, regardless of whether the second cell information has been successfully acquired.

[0105] In certain examples, the second timer can not be stopped upon successful acquisition of the first cell information.

[0106] In certain examples, the method can further comprise stopping the second timer upon successful acquisition of both the first cell information and the second cell information.

[0107] In certain examples, the method can further comprise determining whether the UE is capable of acquiring the second cell information.

[0108] In certain examples, if it is determined that the UE is capable of acquiring the second cell information, the UE can attempt to acquire the second cell information.

[0109] In certain examples, if it is determined that the UE is not capable of acquiring the second cell information, the method can further comprise stopping the second timer upon successful acquisition of the first cell information.

[0110] In certain examples, the UE can attempt to acquire the second cell information during the second timer only if a validity of previously acquired second cell information has expired.

[0111] In certain examples, the method can further include attempting to acquire the second cell information at a next opportunity during the second timer if the previously acquired validity of the second cell information has expired.

[0112] In certain examples: the second timer period can run at least partially after the first timer period; the second timer period can run at least partially before the first timer period; and / or the second timer period can run at least partially concurrently with the first timer period.

[0113] In certain examples, the first cell can be an NTN cell or a terrestrial network (TN) cell.

[0114] Certain examples of the present disclosure (e.g., a first example) provide a method for a user equipment (UE) for acquiring first cell information (e.g., first ephemeris information) for a first cell (e.g., a serving cell) and second cell information (e.g., second ephemeris information) for a second cell (e.g., a neighboring cell), wherein the second cell is a non-terrestrial network (NTN) cell, the method comprising: in response to expiration of a first timer (e.g., T317) indicating that a validity of previously acquired first cell information has expired, starting a second timer (e.g., T318 or a newly defined timer); attempting to acquire the first cell information and the second cell information during the second timer; and upon expiration of the second timer, performing a radio link failure (RLF) procedure based on whether the first and / or second cell information has been successfully acquired.

[0115] In certain examples (e.g., a second example according to the first example), the second timer can not be stopped when the first cell information is successfully acquired.

[0116] In certain examples (e.g., a third example according to the first or second example), upon expiration of the second timer, the RLF procedure is performed if the first cell information is not successfully acquired, regardless of whether the second cell information is successfully acquired.

[0117] In certain examples (e.g., a fourth example according to the first or second example), upon expiration of the second timer, the RLF procedure is performed if neither the first cell information nor the second cell information is successfully acquired.

[0118] In certain examples (e.g., a fifth example according to any of the first through fourth examples), the method can further include sending (e.g., in a RRC message) an indication (e.g., a flag) to a base station (e.g., a base station of the first cell) indicating that the second cell information was not successfully acquired if the second cell information was not successfully acquired. noNeighbourCellAssistance

[0119] ​In certain examples (such as a sixth example according to any of the first through fifth examples), the RLF procedure can be performed based on whether the second cell information is successfully acquired, according to network configuration.

[0120] In certain examples (such as a seventh example according to any of the first through sixth examples), the method can further include determining whether the UE has the capability to acquire the second cell information.

[0121] In certain examples (such as an eighth example according to the seventh example), the UE can attempt to acquire the second cell information if it is determined that the UE has the capability to acquire the second cell information.

[0122] In certain examples (such as a ninth example according to the seventh or eighth example), the second timer (such as selected from T318 or a newly defined timer) can be selected based on whether the UE has the capability to acquire the second cell information.

[0123] In certain examples (such as a tenth example according to any of the first through ninth examples), the UE can attempt to acquire the second cell information during the second timer only if the validity of the previously acquired second cell information has expired.

[0124] In certain examples (such as an eleventh example according to the tenth example), the validity duration of the second cell information can be longer (such as a multiple of) the validity duration of the first cell information.

[0125] In certain examples (such as a twelfth example according to any of the first through eleventh examples), the method can further include attempting to acquire the second cell information at a next opportunity within the second timer if the UE fails to acquire the second cell information during the second timer.

[0126] Certain examples (such as a thirteenth example) of the present disclosure provide a method for a user equipment (UE) for acquiring first cell information (such as first ephemeris information) of a first cell (such as a serving cell) and second cell information (such as second ephemeris information) of a second cell (such as a neighboring cell), wherein the second cell is a non-terrestrial network (NTN) cell, the method comprising: starting a second timer (such as T318) in response to expiration of a first timer (such as T317) indicating that a validity of previously acquired first cell information has expired; attempting to acquire the first cell information during the second timer; stopping the second timer if the first cell information is successfully acquired within the second timer; starting a third timer (such as a newly defined timer) in response to stopping the second timer; and attempting to acquire the second cell information during the third timer.

[0127] In certain examples (such as a fourteenth example according to the thirteenth example), the method can further include performing a radio link failure (RLF) procedure if the first cell information is not successfully acquired during the second timer.

[0128] In certain examples (such as a fifteenth example according to the thirteenth or the fourteenth example), the method can further include performing an RLF procedure if the second cell information is not successfully acquired during the third timer.

[0129] In certain examples (such as a sixteenth example according to any one of the first to the fifteenth examples), the second timer and / or the third timer can be configured by broadcast and / or dedicated configuration (such as by RRC).

[0130] In certain examples (such as a seventeenth example according to any one of the thirteenth to the sixteenth examples), the third timer can be started only when the validity of the previously acquired second cell information has expired, and the UE can attempt to acquire the second cell information during the third timer.

[0131] In certain examples (such as an eighteenth example according to the seventeenth example), the validity duration of the second cell information can be longer (such as a multiple of) the validity duration of the first cell information.

[0132] Certain examples (such as a nineteenth example) of the present disclosure provide a method for a user equipment (UE) for acquiring first cell information (such as first ephemeris information) of a first cell (such as a serving cell) and second cell information (such as second ephemeris information) of a second cell (such as a neighboring cell), wherein the second cell is a non-terrestrial network (NTN), the method comprising: attempting to acquire the first cell information during a second timer defined second timer duration; and attempting to acquire the second cell information during a third timer defined third timer duration; wherein the second timer duration and the third timer duration occur after expiration of a first timer defined first timer duration indicating that a validity of previously acquired first cell information has expired.

[0133] In certain examples (such as a twentieth example according to the nineteenth example), the second timer and the third timer can be the same timer (a single timer).

[0134] In certain examples (such as a twenty-first example according to the twentieth example), the single timer can be a timer T318 or a newly defined timer.

[0135] In certain examples (such as a twenty-second example according to the nineteenth example), the second timer can be different from the third timer.

[0136] In certain examples (such as a twenty-third example according to the twenty-second example), the second timer can be timer T318 and the third timer can be a newly defined timer.

[0137] In certain examples (such as a twenty-fourth example according to any of the first to twenty-third examples): the second timer period can run at least partly after the first timer period; the second timer period can run at least partly before the first timer period; and / or the second timer period can run at least partly concurrently with the first timer period.

[0138] In certain examples (such as a twenty-fifth example according to any of the first to twenty-fourth examples), the method can further comprise: performing a radio link failure (RLF) procedure based on whether the first and / or second cell information is successfully acquired.

[0139] In certain examples (such as a twenty-sixth example according to any of the first to twenty-fifth examples), the first cell can be an NTN cell or a terrestrial network (TN) cell.

[0140] Certain examples of the present disclosure provide a user equipment (UE) configured to perform a method according to any of the examples, aspects, embodiments and / or claims disclosed herein.

[0141] Certain examples of the present disclosure provide a network (or wireless communication system) comprising a base station and a UE according to any of the examples, aspects, embodiments and / or claims disclosed herein.

[0142] Certain examples of the present disclosure provide a computer program comprising instructions which, when the program is executed by a computer or processor, cause the computer or processor to carry out a method according to any of the examples, aspects, embodiments and / or claims disclosed herein.

[0143] Certain examples of the present disclosure provide a computer or processor readable data carrier having stored thereon a computer program according to any of the examples, aspects, embodiments and / or claims disclosed herein.

[0144] Various more detailed examples will now be described.

[0145] 1. Acquire new SIB during T318

[0146] According to existing characteristics, when attempting to acquire both a new SIB and SIB31 simultaneously during T318, there can be a problem that T318 is defined to stop as soon as SIB31 is acquired. This means that, unless the new SIB is acquired before SIB31, acquiring SIB31 can not allow acquiring the new SIB under the current condition. Therefore, in some examples, T318 will continue to run after acquiring SIB31 to acquire the new SIB. This scenario is detailed in Figure 3 and Example 1 below. In some examples, the condition for the timer to continue running can be based on one or more of the following: - if the UE has the capability to perform NTN neighbor cell measurements using ephemeris from the new SIB; - if the new SIB is broadcasted; - if configured by the network, e.g. dedicated identity in a broadcasted SIB (such as SIB31), or specifically configured.

[0147] In some examples, when T318 expires, the UE can perform a radio link failure (RLF) procedure. However, since the new SIB is not as important for the UE to maintain synchronization, it is not as useful for the UE to perform RLF based on not acquiring the new SIB. Therefore, in some examples, if T318 expires and the new SIB is not acquired, the UE will not perform RLF. In some examples, if T318 expires and SIB31 has been acquired, the UE will not perform RLF. Without this mechanism, the UE can unnecessarily perform RLF due to not acquiring the new SIB. Examples of this technique are further disclosed in Example 1 below. In some examples, if SIB31 is received during T318, the UE does not perform RLF, regardless of whether the new SIB is received before T318 expires.

[0148] In the above techniques, if the UE acquires the new SIB before acquiring SIB31 during T318, then if the UE does not acquire SIB31, the UE will wait for T318 to expire before triggering RLF.

[0149] In some examples, if acquiring the new SIB fails, the UE should not trigger RLF. In such scenarios, it can be indicated to the eNB that the new SIB is not acquired. For example, this can be reported in an RRC message such as a measurement report by an identity noNeighbourCellAssistance . Therefore, when the measurement report is triggered, the UE will include this identity to indicate that the new SIB is not acquired. In some examples, the missing of the neighbor cell assistance information can trigger a measurement report by itself. In this case, the UE can include all measurements performed before the measurement failed.

[0150] In certain examples, whether the UE should acquire new SIBs at T318 or in RRC connected state can be configured by the network. For example, this configuration can be useful if it is considered that the ephemeris of the neighboring cell does not change much and the UE only needs to acquire new SIBs once. As another example, when the UE is configured with conditional handover, it is configurable for the UE to perform RLF when it does not acquire new SIBs. The above options can be, for example, configured specifically. This is useful because a global configuration can be broadcast first and the above exceptions can be set by a dedicated configuration. In addition, there can be a capability report indicating that the UE is capable of acquiring new SIBs during T318.

[0151] 2. Acquiring new SIBs during a new timer (T3xx / T319)

[0152] In certain examples, a new timer is introduced to acquire both SIB31 and new SIBs. This new timer can be referred to as T3XX, or other suitable names such as T319, T318a, or T328. Those skilled in the art will understand that T3XX is a general name for a new unnamed timer, so it should not be confused with "T3XX" used as a general name for another new unnamed timer in other scenarios.

[0153] In certain examples, the new timer is configurable and only for UEs with the capability of acquiring new SIBs. The new timer can be started after T317. After the new timer expires, multiple scenarios can occur. For example, the UE can apply one or more of the following: (i) perform RLF only when SIB31 is not acquired; (ii) perform RLF when either SIB31 or new SIBs are not acquired; and (iii) perform RLF when neither SIB31 nor new SIBs are acquired. In certain examples, after both SIB31 and new SIBs are acquired, it is stopped. This applies to the previous three RLF conditions. Figure 4 An example of the new timer is shown. If T318 is also configured or broadcast, the UE can be configured to use this timer. This means that if the UE has the capability to perform neighbor cell measurements with the assistance of a neighbor cell and the UE is broadcasting new SIBs, the UE should use the new timer even if T318 has been broadcast.

[0154] In certain examples, when the T318 timer is stopped, the UE can start another timer that is dedicated to acquiring new SIBs, which is only used for new SIBs. This technical example is described in detail in Figure 5 and Example 2 of the description below. When T317 is started, it is started according to the epoch time indicated in SIB31.

[0155] In certain examples, this new timer can be broadcasted or dedicatedly configured via RRC (e.g., existing and / or newly defined signaling / messages). This timer can support both broadcast and dedicated configuration, or only dedicated configuration. An example of new timer defined as T319 is detailed in the specification example 4 below. In certain examples, there can be a separate capability for the new timer.

[0156] 3. New validity duration for new SIB

[0157] In certain examples, a new (separate) validity duration can be introduced for the new SIB. The advantage is that the validity duration for the new SIB can be longer than the validity duration for the serving cell (i.e., T317 and uplinkSyncValidityDuration). This can be of practical interest in certain scenarios because the requirement for tight synchronization when performing neighbor cell measurements can not be as stringent as compared to adjusting timing advance for uplink and downlink transmissions.

[0158] In certain examples, a validity duration can be defined for the new SIB. In certain embodiments, this validity duration can (only) indicate at which T318 occasion the UE should acquire the new SIB. This means that after the validity duration expires, the UE will wait until the next T318 occasion to acquire the new SIB. The validity duration thus configures the UE to acquire the new SIB at the next T318 occasion. An example of this technique is detailed in Figure 6 . According to this technique, the new SIB does not need to be attempted or acquired at every T318 occasion. When the new SIB is acquired at a T318 occasion, any of the above techniques related to how T318 should operate when reading the new SIB can be applied, e.g., (i) extend T318, and / or (ii) do not perform RLF if T318 expires.

[0159] In certain examples, the validity duration for the new SIB can be defined as a multiple of the validity duration in SIB31. In other examples, the validity duration for the new SIB can be defined as a fraction of the validity duration in SIB31. Those skilled in the art will appreciate that the validity duration for the new SIB can be defined in any suitable manner.

[0160] In certain examples, if the UE does not acquire the new SIB at a given (or current) T318 occasion, the UE will attempt to re-acquire the new SIB at the next T318 occasion (and thus not trigger RLF). An example of this technique is detailed in Figure 7 . Once the new SIB is acquired, the validity duration starts.

[0161] One issue with the validity duration is that there needs to be a point in time at which the timer is started. In Rel-17, for the uplink synchronization validity duration on the serving cell, the start of the validity duration is defined by a parameter called "epoch time", which is also the point in time at which the validity duration is defined to start. If a new validity duration is introduced for the new SIB, then the start of the validity duration needs to be defined.

[0162] In some examples, the start of the validity duration for the new SIB is the same as for the serving cell (i.e. the validity duration for SIB31). This can also be defined as the epoch time for the new SIB is the same as the epoch time for the serving cell, i.e. in SIB31 epochTime For example, this can be done if the UE acquires the new SIB at approximately the same time as it acquires SIB31.

[0163] In some examples, the start of the validity duration for the new SIB is different from the serving cell (i.e. the validity duration for SIB31) but not explicitly indicated. For example, the start of the validity duration for the new SIB can be offset by a certain time period with respect to the serving cell (i.e. in SIB31). In some examples, the time period can be a pre-configured time period.

[0164] In some examples, there can be a capability bit associated with the UE being capable of having a validity duration dedicated for the new SIB.

[0165] 4. Other embodiments

[0166] In some examples, when the UE is configured with a conditional handover, it needs to acquire the new SIB. This is important because when the UE is configured with a conditional handover, it can be more important to perform the handover.

[0167] As described earlier for the start and expiry conditions, the timer can also contain a stop condition. In some examples, for the timer described above, the UE can be configured to stop the timer for acquiring the new SIB when the new SIB and SIB31 are acquired at the same time. In the case where only the new SIB is acquired, the timer is stopped when the new SIB is acquired. After the timer is stopped, the UE can continue to transmit and receive data with the eNB. Furthermore, after the timer is stopped, the T317 timer can be started. In some examples, T317 can be restarted when T318 is stopped. In other examples, T318 can be started after SIB31 is acquired. In this case, there can be a slight overlap between T318 and T317 (i.e. this can happen when SIB31 is acquired but not the new SIB).

[0168] In some examples, if the new SIB (i.e. the neighbor cell assistance information) is invalid, the UE can be configured to not perform neighbor cell measurements. This is because if the measurements are performed when the UE is not synchronized with the neighbor cell, the network receives such measurement results and has no use of them. In this case, by not performing neighbor cell measurements, this also helps with power saving at the UE.

[0169] In some examples, when the neighbor cell assistance information in the new SIB is acquired, the lower layers can be instructed to perform measurements if needed.

[0170] In some examples, the UE can be configured to not report the measurement results of the neighbor cell if the neighbor cell assistance information is invalid.

[0171] In some examples, when the UE is configured with conditional handover, the UE can be provided with the neighbor cell assistance information in the new SIB.

[0172] In the 17th edition IoT NTN, when T318 is stopped because SIB31 has been acquired, the lower layers are instructed that the uplink synchronization has been restored. However, in some examples described herein, T318 can continue to run even though SIB31 has been acquired. To this end, in some examples, the uplink synchronization can still be restored even though T318 is continuing to run. In other examples, if a new timer (e.g. T319) is introduced, the uplink synchronization can still be restored even though the timer is still running when SIB31 is acquired. This technical example is described in detail in the following description examples 1 and 4.

[0173] In some examples, if the new SIB is considered very important and the UE cannot function without acquiring it, the UE can be configured to trigger RLF if the new SIB is not acquired. This is important for the network configuration in scenarios where the neighbor cell measurements are critical for the stable network operation (e.g. in scenarios where mobility is frequent). A new RLF cause value can be introduced at this time to inform the network of the failure cause. This can be defined as “unable to acquire new SIB”, “unable to acquire neighbor cell ephemeris”, “unable to acquire SIB during T318”, etc.

[0174] In some examples, if the network triggers this case, a radio link failure report (from the UE to the network) can be triggered. The radio link report can contain any suitable information about the failure, such as measurement results during the failure, failure time, location information related to the failure, failure cause, etc.

[0175] An example of a new RLF cause is described in the following description example 3. This example is a general scenario that can be triggered due to the inability to acquire SIB31 or a new SIB.

[0176] In some examples, if T318 expires, a new RLF cause can be introduced.

[0177] In some examples, if a new timer T319 is introduced, it may trigger an RLF once it expires, and a new RLF reason may be added.

[0178] In some examples, if the UE has the capability to acquire SIB31 in connected mode and continuously execute uplink and downlink procedures, then timer T317 will continuously update, and timer T318 will never start. See details for this example. Figure 8 A problem arises if the new SIB is large enough that it needs to be tuned out of the current frequency band during acquisition, thus preventing uplink and downlink procedures from being executed. In this case, the UE may not have the opportunity to acquire the new SIB. Therefore, in some examples, trusted ciphers notify the UE of the ability to autonomously acquire SIB31. This can be interpreted as the ability to autonomously acquire SIB31 but not the new SIB. Based on this, the network can, for example, notify the UE of the new SIB through a dedicated method. See the example of this procedure for details. Figure 9 .

[0179] In the various examples disclosed herein, reference may be made to obtaining second cell information (“second cell” may refer to “neighboring cell”), new SIBs, auxiliary information, and similar content. Such information / SIBs may, for example, contain ephemeris data. Those skilled in the art will understand that such information / SIBs may be associated with a single cell, or a group of one or more cells. For example, a UE may obtain a set of ephemeris elements for a group of cells (such as multiple neighboring cells).

[0180] Figure 10 This is an exemplary method flowchart for a UE to obtain first cell information (such as first ephemeris information) of a first cell (such as serving cell) and second cell information (such as second ephemeris information) of one or more second cells (such as one or more neighboring cells), wherein the second cell is a non-terrestrial network (NTN) cell.

[0181] In the first step 1001, in response to the expiration of a first timer (such as T317) indicating that the validity of the previously acquired first cell information has expired, a second timer (such as T318 or a newly defined timer) is started.

[0182] In the second step 1002, the UE attempts to acquire the first cell information and the second cell information during the second timer period.

[0183] In the third step 1003, if the first cell information is not successfully acquired when the second timer expires, a Radio Link Failure (RLF) procedure is executed, regardless of whether the second cell information is successfully acquired. Alternatively, in the third step 1003, if the first cell information has been successfully acquired when the second timer expires, the RLF procedure is not executed.

[0184] In some examples, one or more conditions / criteria can be applied to determine whether to stop the second timer. For example: optionally, the second timer is not stopped in step 1002b when the first cell information is successfully acquired; and / or optionally, the second timer is stopped in step 1002c when both the first cell information and the second cell information are successfully acquired.

[0185] In some examples, it is determined whether the UE has the capability to acquire the second cell information. In this case, in the above second step 1002, if it is determined that the UE has the capability to acquire the second cell information, then the UE attempts to acquire the second cell information. If it is determined that the UE does not have the capability to acquire the second cell information, then instead of the above step 1002c, the second timer is stopped when the first cell information is successfully acquired.

[0186] Various normative examples will now be described.

[0187] Example

[0188] Example 1

[0189] In this example, the T318 timer is not stopped when SIB31 has been acquired, and no radio link failure is triggered if SIB31 has been acquired.

[0190] ------------------ Example based on 3GPP TS 36.331 V17.4.0 ------------------

[0191] 5.3.18 T317 expiry

[0192] The UE shall: 1> if in RRC_CONNECTED: 2> notify lower layers that UL synchronisation is lost; 2> start timer T318; 2> acquire SystemInformationBlockType31 (SIB1 in NB-IoT SystemInformationBlockType31-NB ); 2> if the UE has the capability to perform NTN neighbouring cell measurements using assistance information: 3> acquire SystemInformationBlockTypeXX (SIB2 in NB-IoT SystemInformationBlockTypeXX-NB ); 2> if the UE has the capability to perform NTN neighbouring cell measurements using assistance information: 3> upon successfully acquiring SystemInformationBlockType31 (SIB3 in NB-IoT SystemInformationBlockType31-NB ): 4> Notify the lower layer when UL synchronization has been restored.

[0193] 3> Once successfully obtained SystemInformationBlockType31 (in NB-IoT) SystemInformationBlockType31-NB )and SystemInformationBlockTypeXX (in NB-IoT) SystemInformationBlockTypeXX-NB ): 4> Stop timer T318; 2> Otherwise (for other UEs): 3> Once successfully obtained SystemInformationBlockType31 (in NB-IoT) SystemInformationBlockType31-NB ): 4> Stop timer T318; 4> Notify the lower layer when UL synchronization has been restored.

[0194] Note 1: SystemInformationBlockType31 (in NB-IoT) SystemInformationBlockType31-NB It can be broadcast on a narrowband or a different NB-IoT carrier than the frequency band configured for the UE.

[0195] Note 2: The exact time of UL synchronization recovery (when obtained) SystemInformationBlockType31 or in NB-IoT SystemInformationBlockType31-NB (The rest) is determined by the UE implementation, and can be derived from... epochTime The indicated subframe begins, and optionally, it can be started by... epochTime It begins before the indicated subframe.

[0196] ------------------ Example based on 3GPP TS 36.331 V17.4.0------------------

[0197] ------------------ Example based on 3GPP TS 36.331 V17.4.0------------------

[0198] 5.3.11.3 Wireless Link Failure Detection

[0199] UE should: 1> In the case of any DAPS bearer configured, only the target PCell is considered in the following operations; 1> When T310 expires; or 1> When T312 expires; or 1> When T318 expires and SystemInformationBlockType31 (-NB) is not obtained; or 1> when a random access problem indication from MCG MAC is received while none of the timers T300, T301, T304 and T311 is running; or 1> when a indication from MCG RLC is received, where the MCG RLC allows transmission on the PCell and indicates that the maximum number of retransmission has been reached for an SRB or DRB: 2> consider detecting a radio link failure, i.e. RLF, for the MCG; 2> discard any segments of the received segmented RRC message; 2> store the following radio link failure information into VarRLF-Report by setting the fields as follows: VarRLF-Report for NB-IoT VarRLF-Report-NB 3> clear any information (if any) contained in ; VarRLF-Report 3> set VarRLF-Report-NB to contain the EPLMN list stored by the UE (i.e. containing the RPLMN); 3> set plmn-IdentityList to contain the EPLMN list stored by the UE (i.e. containing the RPLMN); 3> set measResultLastServCell to contain the RSRP and RSRQ (if available) of the PCell; 3> set measResultNeighCells to contain the best cell measured excluding the PCell, ordered from best to worst measured quality, based on the measurements collected until the moment the radio link failure was detected, and set its fields as follows; 4> if the UE is configured to perform measurements on one or more EUTRA frequency bands, include measResultListEUTRA ; 4> if the UE is configured to perform measurement reporting on one or more adjacent UTRA frequency bands, include measResultListUTRA ; 4> if the UE is configured to perform measurement reporting on one or more adjacent GERAN frequency bands, include measResultListGERAN ; 4> if the UE is configured to perform measurement reporting on one or more adjacent CDMA2000 frequency bands, include measResultsCDMA2000 ; 4> if the UE is configured to perform measurement reporting on one or more adjacent NR frequency bands not related to NR sidelink communication, include measResultListNR ; 4> for each adjacent cell included, include the available optional fields; NOTE 1: The measurement quantities are filtered by the L3 filter configured in the mobility measurement configuration. The measurements are time domain measurement resource limited based, if configured. The cells in the exclusion list do not need to be reported.

[0200] 3> If available, set logMeasResultListWLAN to contain the WLAN measurement results, ordered in decreasing order of the RSSI of the WLAN APs, except for NB-IoT; 3> If available, set logMeasResultListBT to contain the Bluetooth measurement results, ordered in decreasing order of the RSSI of the Bluetooth beacons, except for NB-IoT; 3> If detailed location information is available, set the contents of locationInfo as follows: 4> Include locationCoordinates ; 4> Include horizontalVelocity , if available; 3> Set ailedPCellId to the global cell identity, if available, or, except for NB-IoT, to the physical cell identity and carrier frequency of the PCell where the radio link failure was detected; 3> Set tac-FailedPCell to the tracking area code of the PCell where the radio link failure was detected, if available, except for NB-IoT; 3> If a mobilityControlInfo RRCConnectionReconfiguration message containing was received before the connection failure: mobilityControlInfo 4> If the last RRCConnectionReconfiguration message containing concerned an intra-E-UTRA handover: previousPCellId 5> Include mobilityControlInfo and set it to the global cell identity of the PCell where the last RRCConnectionReconfiguration message containing was received; timeConnFailure 5> Set mobilityControlInfo to the elapsed time since the reception of the last RRCConnectionReconfiguration message containing ; mobilityControlInfo 4> If the last RRCConnectionReconfiguration message containing concerned a handover from UTRA to E-UTRA and if the UE supports radio link failure reporting for MRO for different RATs: previousUTRA-CellId 5> Include mobilityControlInfo and set it to the global cell identity of the PCell where the last RRCConnectionReconfiguration ​the physical cell identity, carrier frequency and global cell identity of the UTRA cell the message was received in, if available; 5> set timeConnFailure the elapsed time to the time elapsed since the reception of the last message containing mobilityControlInfo ; RRCConnectionReconfiguration ; 4> if the last message containing mobilityControlInfo was related to handover from NR to E-UTRA and the UE supports radio link failure reporting for different RAT MRO NR: RCConnectionReconfiguration 5> include and set it to the global cell identity of the PCell the UE was in at the time of reception of the last message containing previousNR-PCellId embedded in the NR RRC message MobilityFromNRCommand as specified in TS 38.331

[82] clause 5.4.3.3; mobilityControlInfo ; RRCConnectionReconfiguration 5> set to the time elapsed since the reception of the last message containing timeConnFailure embedded in the NR RRC message MobilityFromNRCommand as specified in TS 38.331

[82] clause 5.4.3.3. mobilityControlInfo ; RRCConnectionReconfiguration

[0201] 3> if the UE supports QCI1 indication in radio link failure reporting, except for NB-IoT, and there is a DRB with QCI 1: 4> include drb-EstablishedWithQCI-1 ; 3> set connectionFailureType to rlf ; 3> set c-RNTI to the C-RNTI used in the PCell; 3> set rlf-Cause to the trigger for which the radio link failure was detected; 2> if the UE is configured with (NG)EN-DC; and 2> if T316 is configured; and 2> if SCG transmission is not suspended; and 2> if SCG is not deactivated; and 2> if no NR PSCell change or NR PSCell addition is ongoing (i.e. T304 for NR PSCell as specified in TS 38.331

[82] clause 5.3.5.5.2 is not running in (NG)EN-DC): ​3> start the MCG failure information procedure as specified in 5.6.26 to report MCG radio link failure; 2> else: 3> if AS security is not activated: 4> if the UE is an NB-IoT UE: 5> if the UE is connected to EPC and the UE supports RRC connection re-establishment for control plane IoT EPS optimisation; or 5> if the UE is connected to 5GC, the UE supports RRC connection re-establishment for control plane IoT 5GS optimisation and the UE is configured with a reduced 5G-S-TMSI: 6> start the RRC connection re-establishment procedure as specified in 5.3.7; 5> else: 6> perform the actions upon leaving RRC_CONNECTED as specified in 5.3.12 with release cause "RRC connection failure"; 4> else: 5> perform the actions upon leaving RRC_CONNECTED as specified in 5.3.12 with release cause "other"; 3> else: 4> start the connection re-establishment procedure as specified in 5.3.7; ------------------ Example based on 3GPP TS 36.331 V17.4.0 ------------------

[0202] Example 2

[0203] In this example, a new timer is started after T318 stops.

[0204] ------------------ Example based on 3GPP TS 36.331 V17.4.0 ------------------

[0205] 5.3.18 T317 expiry

[0206] The UE shall: 1> if in RRC_CONNECTED: 2> notify lower layers of uplink synchronisation loss; 2> start timer T318; 2> acquire SystemInformationBlockType31 (NB-IoT SystemInformationBlockType31-NB ) as specified in 5.2.2; 2> upon successful acquisition of SystemInformationBlockType31(NB-IoT in SystemInformationBlockType31-NB ) is acquired: 3> stop timer T318; 3> inform lower layers when UL synchronization has been restored.

[0207] 3> for UEs with NTN adjacent cell measurement capability: 4> start timer T319; 4> acquire SystemInformationBlockTypeXX (NB-IoT in SystemInformationBlockTypeXX-NB ) as specified in 5.2.2; 4> upon successful acquisition of SystemInformationBlockTypeXX (NB-IoT in SystemInformationBlockTypeXX-NB ): 4> stop timer T319.

[0208] NOTE 1: SystemInformationBlockType31 (NB-IoT in SystemInformationBlockType31-NB ) can be broadcast on a different narrowband or different NB-IoT carrier than the frequency band configured for the UE.

[0209] NOTE 2: The exact time (after acquiring SystemInformationBlockType31 or SystemInformationBlockType31-NB in NB-IoT) when UL synchronization is restored is implementation dependent and can start at the subframe indicated by epochTime or before the subframe indicated by epochTime .

[0210] ------------------ Example based on 3GPP TS 36.331 V17.4.0 ------------------

[0211] Example 3

[0212] This example includes adding the RLF cause due to T318 expiry and failure to acquire SIB31 or new SIB.

[0213] ------------------ Example based on 3GPP TS 36.331 V17.4.0 ------------------

[0214] UEInformationResponse message

[0215] ------------------ Example based on 3GPP TS 36.331 V17.4.0 ------------------

[0216] Example 4

[0217] ------------------ Example based on 3GPP TS 36.331 V17.4.0 ------------------

[0218] 5.3.18 T317 expiry

[0219] The UE shall: 1> if in RRC_CONNECTED: 2> inform lower layers that UL synchronisation is lost; 2> for a UE with NTN neighbour cell measurement capability: 3> start timer T319; 3> acquire SystemInformationBlockType31 (SB-TC-RNTI in NB-IoT) SystemInformationBlockType31-NB and SystemInformationBlockTypeXX (SB-TC-RNTI in NB-IoT) SystemInformationBlockTypeXX-NB as specified in 5.2.2; 3> upon successful acquisition of SystemInformationBlockType31 (SB-TC-RNTI in NB-IoT) SystemInformationBlockType31-NB : 4> inform lower layers when UL synchronisation has been restored.

[0220] 3> upon successful acquisition of SystemInformationBlockType31 (SB-TC-RNTI in NB-IoT) SystemInformationBlockType31-NB and SystemInformationBlockTypeXX (SB-TC-RNTI in NB-IoT) SystemInformationBlockTypeXX-NB : 4> stop timer T319; 2> else: 3> start timer T318; 3> acquire SystemInformationBlockType31 (SB-TC-RNTI in NB-IoT) SystemInformationBlockType31-NB as specified in 5.2.2; 3> upon successful acquisition of SystemInformationBlockType31 (SB-TC-RNTI in NB-IoT) SystemInformationBlockType31-NB : 4> stop timer T318; 4> inform lower layers when UL synchronisation has been restored.

[0221] NOTE 1: SystemInformationBlockType31 (SB-TC-RNTI in NB-IoT) SystemInformationBlockType31-NBIt can be broadcast on a narrowband or a different NB-IoT carrier than the frequency band configured for the UE.

[0222] Note 2: The exact time of UL synchronization recovery (when obtained) SystemInformationBlockType31 or in NB-IoT SystemInformationBlockType31-NB (The rest) is determined by the UE implementation, and can be derived from... epochTime The indicated subframe begins, or can be started by... epochTime Before the indicated subframe.

[0223] ------------------ Example based on 3GPP TS 36.331 V17.4.0 -------------------

[0224] ------------------ Example based on 3GPP TS 36.331 V17.4.0------------------

[0225] 7.3 Timer

[0226] 7.3.1 Timer (providing information)

[0227] ------------------ Example based on 3GPP TS 36.331 V17.4.0------------------

[0228] Figure 11 This is a block diagram of an exemplary network entity that can be used in the examples of this disclosure. For example, Figures 1 to 10 The UE and / or gNB in ​​the example may include Figure 11 The network entity. Those skilled in the art will understand that the network entity may be implemented as a network unit on dedicated hardware, a software instance running on dedicated hardware, and / or a virtualization function instantiated on a suitable platform (such as cloud computing infrastructure).

[0229] Entity 1100 includes a processor (or controller) 1101, a transmitter 1103, and a receiver 1105. Receiver 1105 is configured to receive one or more messages from one or more other network entities (e.g., as described above). Transmitter 1103 is configured to send one or more messages to one or more other network entities (e.g., as described above). Processor 1101 is configured to perform one or more operations (e.g., operations as described above).

[0230] Figure 12 A block diagram illustrating a terminal (or user equipment (UE)) according to an embodiment of the present disclosure. Figure 12 Corresponding to Figure 1Example of a UE.

[0231] like Figure 12 As shown, the UE according to the embodiment may include a transceiver 1210, a memory 1220, and a processor 1230. The transceiver 1210, memory 1220, and processor 1230 of the UE can operate according to the communication method of the UE described above. However, the components of the UE are not limited thereto. For example, the UE may include more or fewer components than described above. Furthermore, the processor 1230, transceiver 1210, and memory 1220 may be implemented as a single chip. And, the processor 1230 may include at least one processor.

[0232] Transceiver 1210, collectively referred to as a UE receiver and UE transmitter, is capable of transmitting / receiving signals to or from a base station or network entity. The signals transmitted to or received from the base station or network entity may contain control information and data. Transceiver 1210 may include an RF transmitter for up-converting and amplifying the transmitted signals, and an RF receiver for low-noise amplification and down-converting the received signals. However, this is merely an example of transceiver 1210, and the components of transceiver 1210 are not limited to RF transmitters and RF receivers.

[0233] In addition, transceiver 1210 can receive signals and output them to processor 1230 via a wireless channel, and can also transmit signals output from processor 1230 via a wireless channel.

[0234] The memory 1220 can store programs and data required for the operation of the UE. In addition, the memory 1220 can store control information or data contained in signals acquired by the UE. The memory 1220 can be a storage medium such as read-only memory (ROM), random access memory (RAM), hard disk, CD-ROM, and DVD, or a combination of storage media.

[0235] The processor 1230 can control a series of processes to make the UE operate in the manner described above. For example, the transceiver 1210 can receive data signals containing control signals transmitted by a base station or network entity, and the processor 1230 can determine the result of receiving the control signals and data signals transmitted by the base station or network entity.

[0236] Figure 13 A block diagram of a base station according to an embodiment of the present disclosure is shown. Figure 13 Corresponding to Figure 1 An example of a RAN node.

[0237] like Figure 13As illustrated, the base station according to the embodiment can include a transceiver 1310, a memory 1320, and a processor 1330. The transceiver 1310, the memory 1320, and the processor 1330 of the base station can operate according to the above-described communication method of the base station. However, components of the base station are not limited thereto. For example, the base station can include more or less components than described above. Furthermore, the processor 1330, the transceiver 1310, and the memory 1320 can be implemented as a single chip. Also, the processor 1330 can include at least one processor.

[0238] The transceiver 1310 collectively refers to the base station receiver and the base station transmitter, and can transmit / receive a signal to / from a terminal or a network entity. The signal transmitted to or received from the terminal or the network entity can include control information and data. The transceiver 1310 can include an RF transmitter for up-converting and amplifying a transmission signal, and an RF receiver for low-noise amplifying and down-converting a received signal. However, this is merely an example of the transceiver 1310, and components of the transceiver 1310 are not limited to the RF transmitter and the RF receiver.

[0239] Furthermore, the transceiver 1310 can receive a signal through a wireless channel and output to the processor 1330, and transmit a signal output from the processor 1330 through a wireless channel.

[0240] The memory 1320 can store programs and data required for the operation of the base station. Furthermore, the memory 1320 can store control information or data included in a signal acquired by the base station. The memory 1320 can be a storage medium such as a Read Only Memory (ROM), a Random Access Memory (RAM), a hard disk, a CD-ROM, and a DVD, or a combination of storage media.

[0241] The processor 1330 can control a series of processes so that the base station operates in the above-described manner. For example, the transceiver 1310 can receive a data signal including a control signal transmitted by a terminal, and the processor 1330 can determine a result of receiving the control signal and the data signal transmitted by the terminal.

[0242] Figure 14 A block diagram of a network entity according to an embodiment of the disclosure is illustrated. Figure 14 A core network entity corresponding to Figure 1 is illustrated.

[0243] As Figure 14As illustrated, the network entity according to an embodiment can include a transceiver 1410, a memory 1420, and a processor 1430. The transceiver 1410, the memory 1420, and the processor 1430 of the network entity can operate according to the communication method of the network entity described above. However, the components of the network entity are not limited thereto. For example, the network entity can include more or less components than described above. Also, the processor 1430, the transceiver 1410, and the memory 1420 can be implemented as a single chip. Also, the processor 1430 can include at least one processor.

[0244] The transceiver 1410 collectively refers to a network entity receiver and a network entity transmitter, and can transmit / receive a signal to / from a terminal or another network entity. The signal transmitted to or received from the terminal or another network entity can include control information and data. The transceiver 1410 can include an RF transmitter for up-converting and amplifying a transmission signal, and an RF receiver for low-noise amplifying and down-converting a received signal. However, this is merely an example of the transceiver 1410, and the components of the transceiver 1410 are not limited to the RF transmitter and the RF receiver.

[0245] Also, the transceiver 1410 can receive a signal through a wireless channel and output to the processor 1430, and transmit a signal output from the processor 1430 through a wireless channel.

[0246] The memory 1420 can store programs and data required for the network entity to operate. Also, the memory 1420 can store control information or data included in a signal acquired by the network entity. The memory 1420 can be a storage medium such as a Read Only Memory (ROM), a Random Access Memory (RAM), a hard disk, a CD-ROM, and a DVD, or a combination of storage media.

[0247] The processor 1430 can control a series of processes so that the network entity operates in the manner described above. For example, the transceiver 1410 can receive a data signal including a control signal transmitted by a terminal, and the processor 1430 can determine a result of receiving the control signal and the data signal transmitted by the terminal.

[0248] The techniques described herein can be implemented by any suitably configured apparatus and / or system. Such apparatus and / or system can be configured to perform a method according to any aspect, embodiment, example, or claim disclosed herein. Such apparatus can include one or more elements, such as one or more of a receiver, a transmitter, a transceiver, a processor, a controller, a module, a unit, etc., each configured to perform one or more corresponding process, operation, and / or method step to implement the techniques described herein. For example, the operations / functions of X can be performed by a module configured to perform X (or X module). The one or more elements can be implemented as hardware, software, or any combination of hardware and software.

[0249] It will be appreciated that examples of the disclosure can be implemented as hardware, software or any combination of hardware and software. Any such software can be stored in the form of volatile or non-volatile storage such as a storage device (e.g. a ROM, whether erasable or non-erasable) or memory device (e.g. a RAM, memory chip, device or integrated circuit) or in the form of optically or magnetically readable medium (e.g. a CD, DVD, magnetic disk or tape etc) or in the form of carrier waves burried in modulated data signals.

[0250] It will be appreciated that storage devices and storage media are embodiments of machine-readable storage that are suitable for storing a program or programs comprising instructions that, when executed, implement certain examples of the present disclosure. Accordingly, certain examples provide a program comprising code for implementing a method, apparatus, or system according to any of the examples, embodiments, aspects and / or claims disclosed herein, and / or a machine-readable storage storing such a program. Further, such programs can be electronically transmitted as data signals over any suitable medium, e.g. wired or wireless connection bearing communications signals.

[0251] While the application has been illustrated and described in connection with certain examples, it will be understood by those skilled in the art that various changes in form and detail can be made therein without departing from the scope of the application as defined by the appended claims.

Claims

1. A method performed by a user equipment (UE) in a wireless communication system, the method comprising: identifying expiration of a second timer; based on the expiration of the second timer, informing a lower layer of loss of uplink synchronization and starting a first timer; receiving, from a base station (BS), a first system information block (SIB) associated with satellite information for a non-terrestrial network (NTN) cell; identifying that a second SIB associated with satellite information for a neighboring cell has been received from the BS; and stopping the first timer in case the second SIB is received. 2.The method of claim 1, in case the first SIB and the second SIB are received during the first timer is running, the first timer is stopped. wherein 3.The method of claim 1, in case the first timer expires and the first SIB is not received, a radio link failure (RLF) is detected. wherein, 4.The method of claim 1, the second SIB is configured with a validity duration. wherein 5.A method performed by a base station (BS) in a wireless communication system, the method comprising: transmitting, to a user equipment (UE), a first system information block (SIB) associated with satellite information for a non-terrestrial network (NTN) cell; transmitting, to the UE, a second SIB associated with satellite information for a neighboring cell; wherein a first timer associated with the first SIB and the second SIB is started based on expiration of a second timer. 6.The method of claim 5, in case the first SIB and the second SIB are received during the first timer is running, the first timer is stopped. wherein 7.The method of claim 5, the second SIB is configured with a validity duration. wherein 8.A user equipment (UE) in a wireless communication system, the UE comprising: a transceiver, and a controller coupled with the transceiver and configured to: identify expiration of a second timer; based on the expiration of the second timer, inform a lower layer of loss of uplink synchronization and start a first timer; receive, from a base station (BS), a first system information block (SIB) associated with satellite information for a non-terrestrial network (NTN) cell; identify that a second SIB associated with satellite information for a neighboring cell has been received from the BS; and stop the first timer in case the second SIB is received. 9.The UE of claim 8, in case the first SIB and the second SIB are received during the first timer is running, the first timer is stopped. wherein, 10.The UE of claim 8, in case the first timer expires and the first SIB is not received, a radio link failure (RLF) is detected. wherein 11.The UE of claim 9, the second SIB is configured with a validity duration. wherein 12.A base station (BS) in a wireless communication system, the BS comprising: a transceiver, and a controller coupled with the transceiver and configured to: transmit, to a user equipment (UE), a first system information block (SIB) associated with satellite information for a non-terrestrial network (NTN) cell; ​ transmitting, to the UE, a second SIB associated with satellite information for a neighbor cell, wherein a first timer associated with the first SIB and the second SIB is initiated based on expiration of a second timer.

13. The BS of claim 12, wherein wherein the first timer is stopped in a case that the first SIB and the second SIB are received during the first timer is running.

14. The BS of claim 12, wherein wherein the second SIB is configured with a validity duration.

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