Method for conditional switching

Abstract

The present disclosure describes a method for non-terrestrial network (NTN) conditional handover and RACH-free handover, the method comprising the steps of performing UE mobility prediction and grouping UEs, thereby making a determination of different suitable CHO configurations and / or a sequence of a plurality of CHO candidates, thereby pre-allocating UL grants; qoS requirements and mobility characteristics of the UE are considered.

Description

TECHNICAL FIELD

[0001] The Third Generation Partnership Project (3GPP) is a standards organization that develops protocols for mobile telephony and is known for developing and maintaining standards including the second generation (2G), third generation (3G), fourth generation (4G), Long Term Evolution (LTE), and fifth generation (5G) standards.

[0002] 5G networks have been designed as a service-based architecture (SBA), or in other words, a system architecture in which system functionality is implemented by a set of network functions providing services to other authorized network functions to access their services. A 5G network can include a plurality of base stations (e.g., next generation NodeB (gNB), etc.) that serve a plurality of cells within a particular area.

[0003] As a user equipment (UE) moves through a particular area, a cell change (referred to as a handover in connected mode) occurs to maintain connectivity between the UE and a serving radio access network (RAN). In addition, a cell transmits and receives data via a plurality of beams. The handover procedure can be triggered due to UE rotation or due to the presence of an obstacle (e.g., a wall, etc.) between the UE and a base station.

[0004] Conditional handover (CHO) allows a source cell to prepare a plurality of target cells for a UE for a future handover procedure. The preparation for CHO occurs between the source cell and the UE when radio conditions are good, at which time a handover is not yet needed to maintain communication. The UE determines that a CHO is necessary based on detecting a configured condition. Upon detecting a condition that necessitates a CHO, the UE performs the prepared CHO to one of the target cells. Since the preparation occurs during good radio conditions, it is more likely that the CHO will occur; whereas, during poor radio conditions, a handover between cells is triggered. BACKGROUND

[0005] NTN-TN (non-terrestrial network to terrestrial network) and NTN-NTN (non-terrestrial network to non-terrestrial network) measurements / mobility and service continuity enhancements are specified. For NTN-NTN mobility, cell reselection enhancements for earth-moving cells are specified, with timing-based and location-based cell reselection for quasi-earth-fixed cells in Rel-17 being considered as a starting point. NTN-NTN handover enhancements for RRC CONNECTED UEs in quasi-earth-fixed cells and earth-moving cells are specified to reduce signaling overhead. Cell reselection enhancements for RRC IDLE / INACTIVE UEs are to be defined to reduce UE power consumption, with NTN-TN mobility being prioritized.

[0006] At least for pre-allocated grants, to confirm RACH-less handover (HO) completion, the multiplexing LTE approach is known, i.e., using UE Contention Resolution Identity MAC CE, but the UE ignores the content of this field. If any other mechanism is needed for dynamic grants, further study (FFS) is considered. Considering supporting RACH-less handover combined with time-based CHO for NTN, the validity of pre-allocated grants and potential waste of reserved resources will be considered; when / how to provide dynamic grants in PDCCH.

[0007] However, in NTN RACH-less handover, the NW indicates the NTA in the target cell to the source cell The same , or the NTA is explicitly provided by the NW to be 0 RACH-less handover will be limited to NTN with the same orbit and speed. In NTN RACH-less handover, synchronization between source and target cells is not an issue. After RACH-less handover completion, the pre-allocated UL grant is released. The LTE approach to confirm handover completion is reused for both pre-allocated and dynamic grants. Further study on any enhancement for confirmation of RACH-less handover completion, e.g., the NW does not send the UE Contention Resolution Identity MAC CE, but sends PDCCH / PDSCH addressed to C-RNTI. Remove “Further study how to perform RACH-less UL synchronization to NTN target cell (FFS how to perform RACH-less UL synchronization to NTN target cell)”, UL synchronization handling in the target cell is the same for RACH-based and RACH-less handover, except for the way to acquire the NTA, further study on specification impact, if any.

[0008] At least the scenario of intra-satellite handover within the same gNB is feasible, and the scenarios of intra-satellite handover between gNBs, inter-satellite handover within the same gNB, and inter-satellite handover between gNBs can also be feasible, as long as the UE uplink transmission is kept synchronized by applying the correct timing advance (TA) pre-compensation in the target cell. Based on the above responses, there are some approaches to support RACH-less handover in NTN.

[0009] US 2021282061 A1 describes wireless communication methods, systems, and apparatuses for managing conditional handover (CHO) configuration. A source base station can configure a user equipment (UE) with one or more CHO configurations for a plurality of target base stations. The CHO configurations can provide one or more associated conditions for each target base station that can trigger the UE to initiate a handover to a particular target base station or deconfigure the CHO configuration, such as based on a measurement threshold of one or more target base station measurements, one or more source base station measurements, or a combination thereof. The CHO configurations can also include failure handling information to initiate one or more subsequent handovers in response to a failure of an initial handover attempt.

[0010] US 2022030483 A1 discloses a user equipment (UE) that can determine to perform a conditional handover procedure to transition from a source cell to a target cell of a plurality of candidate target cells. The UE can transmit, to the source cell, a conditional handover execution message to indicate the conditional handover procedure to transition from the source cell to the target cell based at least in part on determining to perform the conditional handover procedure. The UE can communicate with the target cell to transition to the target cell based at least in part on determining to perform the conditional handover procedure. Numerous other aspects are provided.

[0011] US 2022240138 A1 relates to a pre-5th-Generation (5G) or 5G communication system that is provided to support a higher data rate beyond 4th-Generation (4G) communication system such as Long Term Evolution (LTE). According to an embodiment, a method performed by a user equipment (UE) in a wireless communication system, the method comprising: receiving, from a base station, a radio resource control (RRC) reconfiguration message including conditional configuration information, wherein the conditional configuration information includes: identification information of a candidate cell; and configuration of the candidate cell; and performing one or more operations for conditional handover based on the RRC reconfiguration message.

[0012] US 2022167220 A1 discloses a handover configuration method, comprising: receiving target handover configuration information and handover configuration validity information, the handover configuration validity information comprising validity area information and / or validity timer information, the validity area information being used to indicate a validity area of at least part of the target handover configuration information, and the validity timer information being used to indicate a validity period of at least part of the target handover configuration information; in a case where a current cell of a terminal device is located in the validity area, in a case where a current time is within the validity period, or in a case where the current cell of the terminal device is located in the validity area and the current time is within the validity period, maintaining at least part of the target handover configuration information valid.

[0013] US 2022361055 A1 describes a method comprising: checking whether an indication indicates that a target cell is configured to store a first configuration and a second configuration for a terminal simultaneously, wherein the first configuration is based on a first conditional handover request and the second configuration dataset is based on a second conditional handover request; monitoring whether a source cell intends to perform a radio reconfiguration to the terminal after the source cell configures the first conditional handover for the terminal; cancelling the first conditional handover if the source cell intends to perform the radio reconfiguration and the indication does not indicate simultaneous storing; guiding the source cell to request the second conditional handover from the target cell if the source cell intends to perform the radio reconfiguration and the indication indicates simultaneous storing.

[0014] US 2022264397 A1 describes a method by a wireless device, the method comprising receiving an indication from a network node, the indication identifying at least a first configuration identifier for modification. The first configuration identifier is associated with a conditional reconfiguration. Based on the indication, the wireless device replaces at least a portion of the conditional reconfiguration. The wireless device determines that the first configuration identifier is associated with at least a first triggering condition for performing a conditional handover and stops monitoring for the first triggering condition.

[0015] US 2022078684 A1 describes a user equipment that supports conditional handover to one or more cells of a cellular network. The user equipment is configured to receive configuration data from the cellular network. The configuration data indicates conditions for a plurality of target cells of the cellular network that trigger a conditional handover to any of the target cells. The user equipment is further configured to check the conditions against an appliance and, in case of compliance, trigger the conditional handover.

[0016] US 2020154326 A1 describes a wireless transmit / receive unit (WTRU) that can receive a conditional reconfiguration message from a serving cell based on a measurement report, the conditional reconfiguration message including a triggering condition and configuration information to switch to a target cell based on the triggering condition. The conditional reconfiguration message can be stored, and the WTRU monitors the serving cell and the target cell for the triggering quantity to determine whether the triggering condition is met. When the triggering condition is met within a validity period, the WTRU then applies the received configuration information and initiates the handover to the target cell.

[0017] US 2021051537 A1 discloses apparatuses and methods provided for handover robustness. A UE receives a conditional handover (CHO) command from a source gNB, the command containing a set of candidate cells with corresponding triggering conditions; detects a handover condition of a target gNB belonging to the set of candidate cells; and performs a handover procedure towards the target gNB. In one embodiment, the conditional handover command is further configured with a validity timer that controls the validity of the handover conditions of the set of candidate cells. The validity timer is started upon receiving the conditional handover command, and is stopped upon detecting at least one event including that the handover conditions are satisfied and a normal handover command is received; the conditional handover command is set as invalid upon expiration of the validity timer.

[0018] US 2021360495 A1 is a disclosure relating to techniques for performing conditional handover and cell reselection along a known path. A cellular base station can select a set of conditional handovers for a wireless device. The set of conditional handovers can include information for a plurality of conditional handovers. The wireless device can receive the set of conditional handovers. The wireless device can perform a conditional handover to at least a first cell indicated in the set of conditional handovers based at least in part on the set of conditional handovers.

[0019] US 2022377633 A1 describes a user equipment that receives a plurality of conditional reconfigurations associated with respective conditions. The user equipment is to perform a conditional configuration upon satisfaction of the associated condition. The user equipment is thus to perform one of the plurality of conditional configurations upon satisfaction of the associated condition. The user equipment is to send an indication to a target radio network node, the indication indicating which of the plurality of conditional reconfigurations the user equipment performed.

[0020] US 2022338076 A1 provides a handover method and device. The handover method includes: a terminal device sending path information for determining a first cell to a network device; and the terminal device receiving conditional handover (CHO) configuration information corresponding to the first cell and sent by the network device, and determining a target cell based on the CHO configuration information corresponding to the first cell. According to the technical solutions provided in the present application, when the terminal device performs cell handover, the handover success rate can be improved.

[0021] US 2016345222 A1 describes a handover procedure in which a user equipment (UE) is preconfigured by a network node of a source cell with one or more target cells and associated conditions to be satisfied for the UE to autonomously decide when to perform handover. The UE can be preconfigured while in good radio conditions, connected to the source cell, and thus the UE does not face the risk of falling out of coverage of the source cell before handover to the target cell.

[0022] US 2019387440 A1 provides methods, systems, and storage media for exiting conditional handover and estimating user equipment mobility state. Other embodiments can be described and / or claimed.

[0023] US 2021051534 A1 discloses techniques for performing successive conditional handovers. A cellular base station can provide a wireless device with conditional handover information for multiple conditional handovers. The conditional handover information can include information for performing a conditional handover from a cell provided by the cellular base station to at least one cell, and information for performing a conditional handover from one or more of those cells to at least one cell. The wireless device can use the conditional handover information to perform multiple successive conditional handovers.

[0024] US 2022408323 A1 describes a wireless terminal comprising receiver circuitry and processor circuitry. The receiver circuitry is configured to receive a message. The message comprises one or more conditional handover configurations; at least one indication; and at least one trigger condition; each of the one or more conditional handover configurations comprises at least one identification of a candidate target cell, the at least one indication indicates whether the message is provided as a full configuration. The processor circuitry is configured to: store the one or more conditional handover configurations and the at least one indication; perform a handover to a target cell; and upon or after performing the handover, determine a validity of the one or more conditional handover configurations based on the indication.

[0025] 3GPP Rel. 17 indicates cell type / frequency / priority, cell reference location, distance threshold, time stamp / validity. In addition, autonomous estimation of serving time by the UE is well known. In addition, providing conditional handover configuration to the network is well described.

[0026] NTN to earth moving cells are at very high speed (i.e. UE mobility is negligible). One satellite can operate multiple cells / beams. Depending on the NTN constellation and beam coverage area, a large number of UEs will repeatedly perform conditional handover and / or RACH-less handover, which will result in repeated high network signaling load and overhead and service continuity challenges. SUMMARY

[0027] The problem to be solved is that the UE releases the CHO configuration after a successful CHO. Therefore, the new source gNB needs to provide the full CHO configuration every time. As a result, the signaling overhead of the new source gNB will be unnecessarily increased.

[0028] The solution to the problem described is that the UE keeps the CHO configuration after performing CHO. If the source gNB determines the same CHO candidate, it will not send the CHO configuration. If the source gNB determines that the CHO candidate has changed, the source gNB will provide an updated CHO configuration.

[0029] The proposed idea is related to wireless communication of mobile devices in communication, especially for conditional handover, configuration and mobility prediction.

[0030] It is beneficial that UE mobility prediction will help to enhance CHO configuration and ultimately improve service continuity. More efficient network signaling and overall less handover messages.

[0031] The proposed problem is solved by a method for conditional handover in a wireless communication system, the method comprising the steps of performing UE mobility prediction and grouping of UEs, whereby determination of different suitable CHO configurations and / or sequences of multiple CHO candidates is made, thereby pre-allocating UL grants; considering QoS requirements and mobility characteristics of the UEs.

[0032] The proposed problem is also solved by a method for conditional handover in a wireless communication system, the method comprising the steps of a user equipment (UE) keeping the conditional handover (CHO) configuration after performing conditional handover (CHO), and if the source gNB determines the same CHO candidate, the source gNB does not send a conditional handover (CHO) configuration; and for determining conditional handover (CHO) candidates, the gNB performs UE mobility prediction based on UE measurement reports or configures the UE to provide mobility assistance information, whereby if the source gNB determines that the conditional handover (CHO) candidate has changed, the source gNB provides an updated CHO configuration.

[0033] In some embodiments of the method according to the first aspect, the method is characterized in that the uplink (UL) grants are pre-allocated in a cyclic and / or semi-persistent manner.

[0034] In some embodiments of the method according to the first aspect, the method is characterized in that the gNB will use CHO configuration IDs to prepare / reserve multiple CHO candidate target cells, each CHO configuration ID representing a set / sequence of N neighboring CHO candidate cells, which are known to each gNB neighbor and enable more efficient signaling between gNBs.

[0035] In some embodiments of the method according to the first aspect, the method is characterized in that the gNB will prepare / reserve multiple CHO candidate target cells using CHO configuration IDs, each CHO configuration ID representing a set / sequence of N neighboring CHO candidate cells, which are known to each gNB neighbor and enable more efficient signaling between gNBs. The CHO configuration IDs are combined with UE mobility information for potentially updating the UE-specific CHO configuration and requesting / releasing handover / authorized resources from potential target cells.

[0036] In some embodiments of the method according to the first aspect, the method is characterized in that the CHO configuration IDs are combined with UE mobility information for updating the user equipment (UE)-specific conditional handover (CHO) configuration and requesting and / or releasing updated handover and / or authorized resources from potential target cells.

[0037] In some embodiments of the method according to the first aspect, the method is characterized in that the wireless communication system is a non-terrestrial network (NTN).

[0038] According to a second aspect, the disclosure relates to a device for non-terrestrial network (NTN) conditional handover and RACH-less handover, the device comprising a wireless transceiver, a processor coupled with a memory having stored therein computer program instructions configured to implement the steps of any one of the embodiments according to the first aspect.

[0039] According to a third aspect, the disclosure relates to a user equipment (UE) comprising the device of any one of the embodiments according to the first aspect, whereby the UE keeps the CHO configuration after performing CHO and communicates a UE measurement report and determines and reports UE mobility information, whereby this determines the measurement report.

[0040] According to a fourth aspect, the disclosure relates to a base station gNB configured as a source gNB, comprising the device according to the second aspect, whereby the source gNB does not send a CHO configuration if it determines the same CHO candidates, and in order to determine the CHO candidates, the gNB can either perform a UE mobility prediction based on a UE measurement report, or configure the UE to provide mobility assistance information, and if the source gNB determines that the CHO candidates have changed, the source gNB will provide an updated CHO configuration.

[0041] According to a fifth aspect, this disclosure relates to a wireless communication system in which a gNB, a first target gNB, other target gNBs, and a source gNB according to a fourth aspect include a processor coupled to a memory storing computer program instructions configured to implement the steps according to a first aspect, wherein the user equipment (UE) according to a third aspect includes a processor coupled to a memory storing computer program instructions configured to implement the steps according to a first aspect, and the wireless communication system is a non-terrestrial network (NTN).

[0042] This disclosure also describes a method for conditional handover and RACH-free handover in non-terrestrial networks (NTN), the method comprising the steps of: performing UE mobility prediction and grouping UEs, thereby determining a sequence of different suitable CHO configurations and / or multiple CHO candidates, thereby pre-allocating UL authorization; taking into account the UE's QoS requirements and mobility characteristics. Attached Figure Description

[0043] Figure 1 The timing advance from gNB to UE is shown, which allows the UE to adjust its uplink transmission.

[0044] Figure 2 This demonstrates timing advance and frequency pre-compensation;

[0045] Figure 3 This shows NTN cell broadcast (SIB19);

[0046] Figure 4 The conditional switching (CHO) is shown;

[0047] Figure 5 This illustrates a scenario involving random access / handover for a very large number of UEs;

[0048] Figure 6 This illustrates a conditional handover with handover cancellation signaling.

[0049] Figure 7 A scenario with an NTN satellite is shown;

[0050] Figure 8a / Figure 8b This illustrates a ground-to-ground mobile cell scenario indicating a distance threshold;

[0051] Figure 9a / Figure 9b This illustrates a ground-based mobile cell scenario with CHO candidates;

[0052] Figure 10 The CHO configuration is shown;

[0053] Figure 11 Conditional handover and RACH-less handover in RRC CONNECTED mode is shown;

[0054] Figure 12 Conditional handover and RACH-less handover in admission control for first target gNB RRC CONNECTED mode is shown;

[0055] Figure 13 Conditional handover and RACH-less handover in case of UE evaluating CHO condition is shown;

[0056] Figure 14 Flow diagram on UE side is shown;

[0057] Figure 15 Flow diagram on gNH side is shown;

[0058] Figure 16 Embodiments with value range and cell ID indication are shown. DETAILED DESCRIPTION

[0059] The detailed description set forth below, in connection with the appended drawings, is intended as a description of various configurations and is not intended to represent the only configurations in which the concepts described herein can be practiced. The detailed description includes specific details for the purpose of providing a thorough understanding of the various concepts. However, it will be apparent to those skilled in the art that these concepts can be practiced without these specific details. In particular, although terminology from 3GPP 5G NR can be used in this disclosure to exemplify the embodiments herein, this should not be seen as limiting the scope of the invention.

[0060] Some embodiments of the embodiments envisioned herein will now be described more fully with reference to the accompanying drawings. Other embodiments, however, are contained within the scope of the subject disclosed herein, the disclosed subject matter should not be construed as limited to the embodiments set forth herein; rather, they are provided by way of example to convey the scope of the subject to those skilled in the art.

[0061] In general, all terms used herein are to be interpreted according to their ordinary meaning in the technical field of the disclosure, unless a different meaning is clearly given and / or is implied from the context in which it is used. All references to a / an / the item, apparatus, component, means, step, etc. are to be interpreted openly as referring to at least one instance of whatever is being referred to unless otherwise indicated. The steps of any methods disclosed herein do not have to be performed in the exact order disclosed, unless a step is explicitly described as following or preceding another step and / or where it is implicit that a step follows or precedes another step. Any feature of any of the embodiments disclosed herein can be applied to any other embodiment, wherever convenient and appropriate. Similarly, any advantage of any of the embodiments can apply to any other embodiments, and vice versa. Other objectives, features and advantages of the enclosed embodiments will be apparent from the following description.

[0062] In some embodiments, the more general term network node can be used and it can correspond to any type of radio network node or any network node that communicates with a UE (directly or via another node) and / or another network node. Examples of network nodes are NodeB, MeNB, ENB, network nodes belonging to a MCG or SCG, base station (BS), multi-standard radio (MSR) radio node such as MSR BS, eNodeB, gNodeB, network controller, radio network controller (RNC), base station controller (BSC), relay, donor node controlling relay, base transceiver station (BTS), access point (AP), transmission points, transmission nodes, RRU, RRH, nodes in distributed antenna system (DAS), core network node (e.g., mobile switching center (MSC), mobility management entity (MME), etc.), operation and maintenance (O&M), operation support system (OSS), self-optimizing network (SON), positioning node (e.g., evolved serving mobile location center (E-SMLC)), minimization of drive testing (MDT), test equipment (physical node or software), etc.

[0063] In some embodiments, the non-limiting terms user equipment (UE) or wireless device can be used and they can refer to any type of wireless device communicating with a network node and / or another UE in a cellular or mobile communication system. Examples of UEs are target device, device to device (D2D) UE, machine type UE or UE capable of machine to machine (M2M) communication, PDA, PAD, Tablet, mobile terminal, smart phone, laptop embedded equipped (LEE), laptop mounted equipment (LME), USB dongle, UE category Ml, UE category M2, ProSe UE, V2V UE, V2X UE, etc.

[0064] Additionally, terms such as base station / gNodeB and UE should be considered non-limiting and do not imply certain hierarchical relationship between the two; in general, “gNodeB” can be considered as device 1 and “UE” can be considered as device 2, and these two devices communicate with each other over some radio channel. Additionally, in the following, a transmitter or receiver can be a gNodeB (gNB) or a UE.

[0065] As will be appreciated by one skilled in the art, aspects of the embodiments can be embodied as a system, device, method or program product. Accordingly, embodiments can take the form of an entirely hardware embodiment, an entirely software embodiment (including firmware, resident software, micro-code, etc.) or an embodiment combining software and hardware aspects that can all generally be referred to herein as a “circuit,” “module” or “system.” Furthermore, embodiments can take the form of program product embodied in one or more computer readable storage media having computer readable program code embodied thereon.

[0066] For example, disclosed embodiments can be implemented in hardware circuitry including custom very-large-scale integration (“VLSI”) circuitry or gate arrays, off-the-shelf semiconductors such as logic chips, transistors, or other discrete components. Disclosed embodiments can also be implemented in programmable hardware devices such as field programmable gate arrays, programmable array logic, programmable logic devices, or the like. As another example, disclosed embodiments can include one or more physical or logical blocks of executable code, which may, for example, be organized as an object, procedure, or function.

[0067] Furthermore, embodiments can take the form of a program product embodied in one or more computer readable storage media having computer readable program code embodied thereon. The storage media can be tangible, non-transitory, and / or non-transmission. The storage media can not encompass signals. In a certain embodiment, the storage media only employs program code to access code.

[0068] Any combination of one or more computer readable medium can be utilized. The computer readable medium can be a computer readable storage medium. The computer readable storage medium can be a storage device storing the code. The storage device can be, for example, but not limited to, an electronic, magnetic, optical, electromagnetic, infrared, holographic, micromechanical, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing.

[0069] More specific examples (a non-exhaustive list) of the storage device would include the following: an electrical connection having one or more wires, a portable computer diskette, a hard disk, a random access memory ("RAM"), a read-only memory ("ROM"), an erasable programmable read-only memory ("EPROM" or Flash memory), a portable compact disc read-only memory ("CD-ROM"), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing. In the context of this document, a computer readable storage medium can be any tangible medium that can contain, or store a program for use by or in connection with an instruction execution system, apparatus, or device.

[0070] Code for carrying out operations for embodiments can be any number of lines and can be written in any combination of one or more programming languages including an object- oriented programming language such as Python, Ruby, Java, Smalltalk, C++, or the like, and conventional procedural programming languages, such as the "C" programming language, or the like, and / or machine languages such as assembly languages. The code can execute entirely on the user's computer, partly on the user's computer, as a stand-alone software package, partly on the user's computer and partly on a remote computer or entirely on the remote computer or server. In the latter scenario, the remote computer can be connected to the user's computer through any type of network, including a local area network ("LAN"), wireless LAN ("WLAN"), or a wide area network ("WAN"), or the connection can be made to an external computer (for example, through the Internet using an Internet Service Provider ("ISP")). In some embodiments, electronic circuitry including, for example, a

[0071] Furthermore, the described features, structures, or characteristics of the embodiments can be combined in any suitable manner. In the following description, numerous specific details are provided, such as examples of programming, software modules, user selections, network transactions, database queries, database structures, hardware modules, hardware circuits, hardware chips, etc., to provide a thorough understanding of the embodiments. One skilled in the relevant art will recognize, however, that the embodiments can be practiced without one or more of the specific details, or with other methods, components, materials, and so forth. In other instances, well-known structures, materials, or operations are not shown or described in detail in order to avoid obscuring aspects of the embodiments. Reference throughout this specification to “an embodiment,” “embodiments,” or similar language means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, appearances of the phrases “in one embodiment,” “in an embodiment,” and similar language throughout this specification may, but do not necessarily, all refer to the same embodiment, but mean “one or more but not all embodiments.” Unless otherwise noted, the terms “including,” “comprising,” “having,” and variations thereof in the specification are meant to encompass the item listed and variations thereof as possible insubstantial equivalents of the item listed. Unless otherwise noted, enumerated lists of items do not imply any or all items are mutually exclusive. Unless otherwise noted, the terms “a,” “an,” and “the” refer to “one or more.”

[0072] The code can also be stored in a storage device that can direct a computer, other programmable data processing apparatus, or other devices to function in a particular manner, such that the instructions stored in the storage device produce an article of manufacture including instructions which implement the function / act specified in the flowchart and / or block diagram.

[0073] The code can also be stored in a storage device that can direct a computer, other programmable data processing apparatus, or other devices to function in a particular manner, such that the instructions stored in the storage device produce an article of manufacture including instructions which implement the function / act specified in the flowchart and / or block diagram.

[0074] The code can also be loaded onto a computer, other programmable data processing apparatus, or other devices to cause a series of operational steps to be performed on the computer, other programmable apparatus or other devices to produce a computer implemented process such that the code which execute on the computer or other programmable apparatus provide processes for implementing the functions / acts specified in the flowchart and / or block diagram.

[0075] The flow diagrams and / or block diagrams in the drawings are examples of architectures, functionality, and operations for possible implementations of devices, systems, methods and program products according to various embodiments. In this regard, each block in the flow diagrams and / or block diagrams can represent a module, segment, or portion of code, which comprises one or more executable instructions for implementing the specified logical functions.

[0076] It should also be noted that in some alternative implementations, the functions indicated within the blocks can occur in an order other than that depicted in the figures. For example, two blocks shown in succession can in fact be executed substantially concurrently, or the blocks can sometimes be executed in the reverse order, depending upon the functionality involved. Other steps and methods can be conceived that are equivalent in function, logic, or effect to those illustrated, with the scope of the present disclosure intended to include such equivalent steps and methods.

[0077] Although various arrow types and line types can be employed in the flow diagrams and / or block diagrams, these are merely meant as an example, and are not intended to limit the scope of embodiments. Indeed, some arrows or other connectors can be used to indicate certain directions in the context of example embodiments, such as the order of steps in a method implemented. However, these arrows do not imply a requirement for serial, or sequential execution, unless explicitly stated or otherwise readily apparent to one of ordinary skill in the art. In some instances, parallel execution can be more efficient, with various steps, or functions, being executed concurrently. Still further, the various steps, or functions, can be rearranged, combined, separated, and / or omitted, depending on the functionality involved.

[0078] The description of elements in each figure can refer to elements in other figures. Like numbers refer to like elements in all figures, including alternative embodiments of like elements.

[0079] The detailed description set forth below, in connection with the appended drawings and embodiments described hereinafter, is intended as a description of various configurations and is not intended to represent the only configurations in which the concepts described herein can be practiced. The detailed description includes specific details for the purpose of providing a thorough understanding of various concepts. However, it will be apparent to those skilled in the art that these concepts can be practiced without these specific details. While terminology from 3GPP 5G NR can be used in the present disclosure to exemplify embodiments herein, this should not be seen as limiting the scope of the invention.

[0080] The present disclosure relates to a wireless communication system, which can be a 5G NR wireless communication system, for example. More specifically, it denotes a RAN of a wireless communication system for exchanging data with UEs via radio signals. For example, the RAN can transmit data to a UE (downlink, DL), e.g., data received from a core network (CN). The RAN can also receive data from a UE (uplink, UL), which can be forwarded to the CN.

[0081] In the illustrated example, the RAN includes one base station, BS. Of course, the RAN can include more than one BS to increase the coverage of the wireless communication system. Each of these BSs can be referred to as an NB, an eNodeB (or eNB), a gNodeB (or gNB in the case of a 5G NR wireless communication system), an access point, etc., depending on the wireless communication standard that is implemented.

[0082] The UE is located in the coverage of the BS. The coverage of the BS corresponds to an area, for example, in which the UE can decode a PDCCH transmitted by the BS.

[0083] Examples of a wireless device suitable for implementing any of the methods performed at the UE discussed in this disclosure correspond to devices that provide wireless connectivity with a RAN of a wireless communication system and that can be used to exchange data with said RAN. Such a wireless device can be comprised in a UE. The UE can be, for example, a cellular phone, a wireless modem, a wireless communication device, a handheld device, a laptop computer, etc. The UE can also be an Internet of Things (IoT) device, such as a wireless camera, a smart sensor, a smart meter, smart glasses, a vehicle (manned or unmanned), a global positioning system device, etc., or any other device that can run an application that requires exchanging data with a remote recipient via a wireless device.

[0084] The wireless device comprises one or more processors and one or more memories. The one or more processors can comprise, for example, a Central Processing Unit (CPU), a Digital Signal Processor (DSP), a Field-Programmable Gate Array (FPGA), an Application-Specific Integrated Circuit (ASIC), etc. The one or more memories can comprise any type of computer-readable volatile and non-volatile memory (magnetic hard disk, solid state disk, optical disk, electronic memory, etc.). The one or more memories can store a computer program product in the form of a set of program code instructions to be executed by the one or more processors to implement all or part of the steps of the method for exchanging data performed at the UE side according to any of the embodiments disclosed herein.

[0085] The wireless device can also comprise a main radio, MR, unit. The MR unit corresponds to the main wireless communication unit of the wireless device for exchanging data with the BSs of the RAN using radio signals. The MR unit can implement one or more wireless communication protocols and can be, for example, a 3G, 4G, 5G, NR, WiFi, WiMax, etc., transceiver, etc. In a preferred embodiment, the MR unit corresponds to a 5G NR wireless communication unit.

[0086] Each gNB can be configured as a source gNB, a gNB, a first target gNB, other target gNBs.

[0087] Figure 1Timing advance from gNB to UE is shown that enables the UE to adjust its uplink transmission; the timing advance is a special command (notification) from gNB to UE that enables the UE to adjust its uplink transmission as shown here: this UL adjustment applies to PUSCH, PUCCH and SRS. For NTN, the long propagation delay requires timing relationship adaptation and UE pre-compensation - e.g. GEO round trip delay is x100s ms, while LEO round trip delay is x10s ms.

[0088] To accommodate the propagation delay in NTN, several timing relationships are enhanced by a common timing advance (Common TA) and two scheduling offsets K_offset and k_mac

[0089] - Common TA is a configured offset that corresponds to the RTT (Round Trip Time) between a reference point (RP) and the NTN payload.

[0090] - K_offset is a configured scheduling offset that needs to be greater than or equal to the sum of the service link RTT and the common TA.

[0091] - k_mac is a configured offset that needs to be greater than or equal to the RTT between the RP and the gNB.

[0092] DL and UL are frame aligned with an offset at the uplink time synchronization reference point (RP) by N TA,offset given in section 4.3 of TS 38.211. The offset k_mac is used for the delay of the application of downlink configuration indicated by MAC CE command on PDSCH (see TS 38.213) and the estimation of the UE-gNB RTT (see TS 38.321). The network can provide this offset when the downlink and uplink frame timing are not aligned at the gNB. k_mac is also used in the random access procedure to determine the starting time of the RAR window / MsgB window after Msg1 / MsgA transmission, which is disclosed in TS 38.213. N TA : reception of random access response or absolute timing advance command (MAC CE)

[0093] Figure 2Timing advance and frequency pre-compensation are illustrated. For the serving cell, the network broadcasts valid ephemeris information and common TA parameters. The UE shall have valid GNSS position as well as ephemeris and common TA before connecting to the NTN cell. To achieve synchronization, the UE shall calculate the RTT between the UE and the RP based on the GNSS position, ephemeris and common TA parameters before and during the connection to the NTN cell (see section 4.2 in TS 38.213

[38] ) and autonomously pre-compensate T TA As Figure 16 .14.2.1-1 is illustrated (see section 4.3 in TS 38.211). In connected mode, the UE shall be able to continuously update the timing advance and frequency pre-compensation. The UE can be configured to report the timing advance during the random access procedure or in connected mode. Event triggered reporting of timing advance is supported in connected mode.

[0094] Figure 3 It is illustrated that the NTN cell broadcasts (SIB19).

[0095] ntn-Config-r17 means validity period and epoch of ephemeris data, common TA parameters, k_offset, UL synchronization information,

[0096] referenceLocation-r17 means the reference location of the serving cell, e.g. for initiating measurements in IDLE / INACTIVE mode,

[0097] distanceThresh-r17 means the distance from the reference location of the serving cell

[0098] t-Service-r17 indicates time information about when the cell provided via NTN quasi-geostationary system will stop serving the area of its current coverage,

[0099] ntn-NeighCellConfigList-r17 is the list of NTN neighboring cells including its ntn-Config, carrier frequency and PhysCellId. This set includes all elements of ntn-NeighCellConfigList and all elements of ntn-NeighCellConfigListExt. If an entry in ntn-NeighCellConfigListExt lacks ntn-Config, the ntn-Config provided in the entry at the same position in ntn-NeighCellConfigList applies. If the cell beam is directed towards the ground, the cell reference location coincides with the sub-satellite point.

[0100] Figure 4 Conditional handover (CHO) is shown. Conditional handover (CHO) is defined as a handover performed by a UE when one or more handover execution conditions are met. The UE starts evaluating the execution conditions upon receiving the CHO configuration and stops evaluating the execution conditions once the handover is performed. Up to 8 CHO candidate cells can be configured, which is indicated by the CHO circle in Figure 4

[0101] Figure 5 Scenarios for random access / handover for very large number of UEs are shown; considering the large cell size for non-terrestrial networks, many devices can be served within a single cell. Depending on the constellation assumptions (e.g., propagation delay and satellite speed) and UE density, there can be a very large number of UEs potentially requiring to perform handover at a given time, resulting in potentially huge signaling overhead and service continuity challenges. The peak load during the RA procedure is alleviated by the RACH-less handover, and further enhanced by combining with conditional handover, at the cost of increased signaling load during the handover preparation phase.

[0102]

[0103] By dispersing the handover command signaling and handover execution occasions for UEs, the handover signaling concentration can be simply alleviated. The network can provide the configuration of the target cell in advance through CHO configuration. In addition, time-based CHO can be utilized to trigger CHO at the expected time. For example, the network configures various entering conditions for the time-based conditional event (i.e., CondEvent T1) among UEs. In addition, for each UE, the network also configures the RRM-based conditional event to be satisfied only under the configured entering conditions of CondEvent T1, such as CondEvent A4. By combining the two conditions, the UE automatically performs CHO at the configured occasion, thus achieving distributed handover execution among UEs. Therefore, the CHO-based pre-configuration can reduce the number of handover signaling by skipping the trigger indication, and due to the distributed handover execution, it relieves the RACH congestion.

[0104] During conditional handover, the ephemeris data of the satellite serving the candidate target cell, and the associated common TA parameters and Kmac are part of the essential configuration needed by the UE to initiate random access to the NTN candidate target cell. These are often included in the handover command (RRCReconfiguration). However, the CHO configuration can be stored in the UE for a non-negligible time before CHO execution, while the validity time of ephemeris data and common TA parameters can expire.

[0105] ​Multiple sets of ephemeris and common TA parameters can be transmitted in the CHO configuration message (RRCReconfiguratio), each set with its own epoch (time gradually moves towards the future) and validity time.

[0106] Figure 6 Conditional handover with handover cancellation signaling is shown. Conditional handover (CHO) is defined as the handover performed by the UE when one or more handover execution conditions are met. The UE starts evaluating the execution conditions upon receiving the CHO configuration and stops evaluating the execution conditions once the handover is performed.

[0107] Up to 8 CHO candidate cells can be configured.

[0108] 0 / 1. Same as steps 0, 1

[0109] 2. The source gNB decides to use CHO.

[0110] 3. The source gNB requests CHO for one or more candidate cells belonging to one or more candidate gNBs. A CHO request message is sent for each candidate cell.

[0111] 4. Same as step 4 in Figure 9.2.3.2.1-1 of section 9.2.3.2.1.

[0112] 5. The candidate gNB sends a CHO response (Handover Request Acknowledge (HOREQUEST ACKNOWLEDGE)) to the source gNB including the configuration of the CHO candidate cell. A CHO response message is sent for each candidate cell.

[0113] 6. The source gNB sends an RRCReconfiguration message to the UE containing the configuration of the CHO candidate cell and the CHO execution conditions.

[0114] 7. The UE sends an RRCReconfigurationComplete message to the source gNB.

[0115] 7a If early data forwarding is applied, the source gNB sends an EARLY STATUS TRANSFER message.

[0116] 8. The UE remains connected with the source gNB after receiving the CHO configuration and starts evaluating the CHO execution conditions for the candidate cells. If at least one CHO candidate cell fulfils the corresponding CHO execution condition, the UE detaches from the source gNB, applies the stored corresponding configuration to the selected candidate cell, synchronizes to the candidate cell and completes the RRC handover procedure by sending an RRCReconfigurationComplete message to the target gNB. The UE releases the stored CHO configuration after the RRC handover procedure is successfully completed.

[0117] 8a / b The target gNB sends a Handover Success message to the source gNB to inform that the UE has successfully accessed the target cell. In response, the source gNB sends a SN STATUS TRANSFER message following the principles described in step 7 of the intra-AMF / UPF handover in section 9.2.3.2.1.

[0118] 8c. The source gNB sends a Handover Cancel message to the other signaling connections or other candidate target gNBs (if any) to cancel the CHO for the UE.

[0119] Figure 7 A scenario of NTN with satellites having PCIs 1 to 14 is shown.

[0120] The source gNB sends a Handover Cancel message to the other signaling connections or other candidate target gNBs (if any) to cancel the CHO for the UE. Therefore, all resource reservations will be cancelled but the UE will arrive at the other configured target cell after the first CHO. One solution is defined by the 1st option: when configuring the UL grant, the target cell (during admission control) assigns a timer, which starts when the UE receives the RRCReconfiguration message (6.) or sends the Handover Complete (7.), which stops when the UE uses the UL grant. If the timer expires, the UE will release the UL grant.

[0121] Another option is to do it after the CHO procedure, which is defined by a further variation: if congestion is determined in any target cell, the target cell will indicate to the source cell to release the configured UL grant resources (update the CHO configuration) -> any validity timer related to the grant will be overwritten and stopped. The source cell provides the indication in different ways: RRC, MAC CE, PDCCH.

[0122] The benefit is that the target cell does not reserve the grant resources indefinitely but flexibly revokes the assigned grant.

[0123] The fact that the satellite motion is deterministic and repetitive is exploited.

[0124] The network or the UE performs UE mobility prediction:

[0125] The network performs UE mobility prediction based on consecutive UE measurement reports (e.g. RSRP values of serving cell and neighbor cells).

[0126] The UE determines and reports the distance to the serving cell reference point (SIB19) and the angle with respect to the reference vector and its own mobility vector (UE mobility information).

[0127] The network groups UEs and determines different suitable CHO configurations (set / sequence of CHO candidates; catalog (almanac) of predefined CHO configuration IDs, where each ID represents a sequence of suitable location-specific CHO candidates), e.g. depending on NTN almanac, UE measurements and / or UE mobility information.

[0128] The UE discards a CHO candidate cell only if the measurement is not available for the last N times or a new / updated CHO configuration is provided.

[0129] The source gNB sends a HANDOVER CANCEL message to other signaling connections or other candidate target gNBs (if any) to cancel the CHO for the UE, i.e. release pre-allocated resources, which will not become target gNBs based on CHO configuration ID and UE mobility prediction.

[0130] The network determines and pre-allocates UL grants using the UE’s QoS requirements and mobility characteristics, e.g. in a cyclic manner / semi-persistent manner.

[0131] If the network predicts a significant increase in cell load, the target cell will instruct the source cell to release the configured UL grant resources (update CHO configuration) and thus override / stop any running validity timer related to the grant.

[0132] If the network predicts a significant increase in cell load, the network can configure additional randomization in the CHO trigger timer of the corresponding candidate cell (e.g. based on the UE’s QoS requirements and mobility characteristics), which is signaled via delta configuration.

[0133] Figure 8a / Figure 8b An earth-moving cell scenario indicating a distance threshold is shown. The UE determines and reports the distance to a reference point and the angle with respect to a reference vector (predefined, e.g. latitude direction) and its own mobility vector -> enables UE mobility prediction CHO candidate sequence: {Cell#1, Cell#2, Cell#3}.

[0134] Figure 9 illustrates the scenario of moving cell towards earth with CHO candidates, where Figure 9a In Figure 8, cell #4 is shown to have a CHO candidate sequence: {cell #1, cell #2, cell #4} and Figure 9b In Figure 9, beam / SSB specific grants are shown.

[0135] Figure 10 CHO configuration is shown.

[0136] The network is aware of NTN constellation characteristics, where cell neighborhood relations are predefined and deterministic. Therefore, an ephemeris table of possible CHO configurations based on cell neighborhood relations and possible UE movement directions can be created. The gNB will use the CHO configuration ID to prepare / reserve multiple CHO candidate target cells. Each CHO configuration ID represents a set / sequence of N neighboring CHO candidate cells, which are known to each gNB neighbor and enable more efficient signaling between gNBs. The CHO configuration ID is combined with UE mobility information to potentially update the UE-specific CHO configuration and request / release handover / grant resources from potential target cells. A UE with high mobility can receive several CHO configurations with different CHO IDs. For example: 1st ring has 6 neighbors, 2nd ring has 12 neighbors -> ephemeris table of 6*12 possible configurations for configuring 2 successive CHO.

[0137] Figure 11 Conditional handover and RACH-less handover in RRC connected mode are shown; UE and serving gNB are in RRC CONNECTED state. The UE uses SIB19 to determine its mobility vector with respect to NTN movement. The UE sends a measurement report (UE mobility vector) to the serving gNB. Using QoS requirements, UE mobility, and additional meta-information available, the serving gNB groups the UEs and determines a suitable set / sequence of CHO target candidates (using ephemeris data). The serving gNB defines the CHO decision. The serving gNB sends a handover request (including QoS, mobility information, CHO ID) to the first target gNB and sends a handover request (including QoS, mobility information, CHO ID) to other target gNBs.

[0138] Figure 12Conditional handover and RACH-less handover in admission control with first target gNB with admission control is shown. Both first target gNB and other target gNB have admission control. First target gNB sends handover request acknowledgement to serving gNB, which includes pre-allocated UL grant + validity timer, NTA + validity timer, and cell load status. Other target gNB sends handover request acknowledgement to serving gNB, which includes pre-allocated UL grant + validity timer, NTA + validity timer, cell load status. Serving gNB determines CHO configuration, including set of CHO cell / beam candidates, UL grant + validity, NTA + validity, additional back-off. Serving gNB sends RRCReconfiguration (CHO configuration) to UE. UE sends RRCReconfigurationComplete back to serving gNB.

[0139] Figure 13 Conditional handover and RACH-less handover in case UE evaluates CHO condition is shown; UE evaluates CHO condition, detach from old cell, synchronize with new cell and sends RRCReconfigurationComplete (including CHO ID) to first target gNB. Before UE sends RRCReconfigurationComplete (including CHO ID) to first target gNB, serving gNB sends early status transfer to other target gNB. First target gNB uses CHO ID and future UE mobility information to update CHO (delta) configuration and sends handover success (including CHO ID) to serving gNB. Serving gNB sends status transfer to first target gNB. Serving gNB determines (using CHO ID) which handovers / resource reservations to cancel. Serving gNB sends handover cancellation (unfeasible target gNB) to other target gNB.

[0140] Figure 14 Flowchart on UE side is shown; UE receives SIB19 from serving cell, determines and reports UE mobility information (measurement report), receives CHO (delta) configuration, evaluates CHO condition, meets CHO condition? If these conditions are met, then perform CHO and report used CHO ID and terminate flow. If these conditions are not met, then evaluate CHO condition.

[0141] Figure 15A flowchart on the gNB side is shown; gNB configures measurement reporting (including UE mobility information), receives UE measurement reporting (including UE mobility information), uses UE QoS requirements and / or UE mobility information to group UEs, uses NTN ephemeris data (of neighboring NTN cells / nodes) and beam characteristics to determine a set / sequence of CHO candidate cells / beams, requests handover and UL grant allocation from identified neighboring NTN cells / nodes, receives handover confirmation (including UL grant + validity time, NTA + validity time and load status) from neighboring NTN cells / nodes, creates and sends (incremental) CHO configuration (including CHO candidates, NTA + validity time, UL grant + validity time and additional back-off timer (determined based on neighboring cell load)), receives CHO completion message (including CHO ID), determines which handovers / resource reservations to cancel, and the flow ends.

[0142] Figure 16 An embodiment is shown with indicated value ranges and cell IDs. For NTN cells, handovers are expected to occur frequently and repeatedly. A large number of UEs trying to perform CHO can cause severe congestion in the target cell. The serving gNB contacts potential CHO target cell candidates to request / reserve handover and grant resources. Based on predefined load thresholds, the target cell can request to introduce an additional back-off timer to delay CHO execution or provide a mapping to select a CHO target cell. The mapping is pre-determined by the network / target cell.

[0143] In Figure 16 this case is announced by cell #7:

[0144]

[0145] The proposed idea is related to wireless communication of mobile devices or IoT devices communicating via NTN. UE mobility prediction will help to enhance CHO configuration and eventually improve service continuity. Reducing network signaling: in the best case, only one complete CHO configuration (including a sequence of N suitable candidate cells) is provided, in the future, only incremental configuration updates will be provided after N CHO. If the CHO configuration is based on a catalog of predefined CHO configuration IDs (similar to ephemeris tables for satellite ephemeris data), signaling of the CHO configuration ID is already sufficient. Considering UE’s requirements at pre-allocation of UL grants will improve QoS (e.g., minimize handover interruption time).

[0146] Introducing additional randomization in CHO triggering can help to mitigate network congestion.

[0147] UE mobility prediction will help to enhance CHO configuration and eventually improve service continuity. Less network signaling is achieved. In the best case, only one complete CHO configuration (including the sequence of N suitable candidate cells) is provided, in the future, after N CHO, only incremental configuration update will be provided. If the UE does not delete but keeps the CHO configuration after a successful CHO implementation, further signaling can be saved.

[0148] Abbreviations:

[0149]

[0150]

Claims

1. A method for conditional handover in a wireless communication system, the method comprising the steps of: • performing UE mobility prediction and grouping of UEs, whereby a determination of different suitable CHO configurations and / or sequences of multiple CHO candidates is made, whereby UL grants are pre-allocated, • taking into account QoS requirements and mobility characteristics of the UEs.

2. The method according to claim 1, the method comprising the steps of: • a user equipment (UE) keeping the CHO configuration after performing conditional handover (CHO) and the source gNB not sending a conditional handover (CHO) configuration if the source gNB determines the same CHO candidates, • for determining conditional handover (CHO) candidates, the gNB either performs UE mobility prediction based on UE measurement reports or configures the UE to provide mobility assistance information, whereby the source gNB provides an updated CHO configuration if the source gNB determines that the conditional handover (CHO) candidates have changed.

3. The method according to any of the preceding claims, wherein uplink (UL) grants are pre-allocated in a cyclic manner and / or in a semi-persistent manner.

4. The method according to any of the preceding claims, wherein the gNB will prepare / reserve multiple CHO candidate target cells using CHO configuration IDs, each CHO configuration ID representing a set / sequence of N neighboring CHO candidate cells, which are known to each gNB neighbor and enable more efficient signaling between gNBs.

5. The method according to any of the preceding claims, wherein the CHO configuration IDs are used in combination with UE mobility information for updating user equipment (UE) specific conditional handover (CHO) configuration and requesting and / or releasing updated handover and / or grant resources from potential target cells.

6. The method according to any of the preceding claims, wherein the wireless communication system is a non-terrestrial network (NTN).

7. An apparatus for non-terrestrial network (NTN) conditional handover and RACH-less handover, the apparatus comprising a wireless transceiver, a processor coupled with a memory having computer program instructions stored therein, the instructions configured to implement the steps as claimed in claims 1 to 5.

8. A user equipment (UE), the user equipment comprising the apparatus according to claim 6, whereby the UE keeps the CHO configuration after performing CHO and communicates UE measurement reports and determines and reports UE mobility information, whereby this determines the measurement reports.

9. A base station gNB configured as a source gNB, the base station gNB comprising the apparatus according to claim 6, whereby the source gNB does not send a CHO configuration if the source gNB determines the same CHO candidates and, for determining CHO candidates, the gNB is capable of either performing UE mobility prediction based on UE measurement reports or configuring the UE to provide mobility assistance information and the source gNB will provide an updated CHO configuration if the source gNB determines that the CHO candidates have changed.

10. A wireless communication system wherein the gNB, the first target gNB, the other target gNB, the source gNB of claim 7 comprise a processor coupled with a memory having computer program instructions stored therein configured to implement the steps of claims 1 to 5: wherein the user equipment (UE) of claim 7 comprises a processor coupled with a memory having computer program instructions stored therein configured to implement the steps of claims 1 to 5 and the wireless communication system is a non-terrestrial network (NTN).

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