Method of performing lower layer triggered mobility in wireless network

Abstract

The present disclosure relates to a 5G or 6G communication system for supporting a higher data transmission rate. Embodiments herein disclose a method for performing LTM. The method comprises: receiving, in an RRC message, an LTM configuration indicating whether the UE needs to perform one of RLC reconstruction and PDCP recovery during LTM to a candidate cell; receiving one of a DL MAC CE or a DL L1 message for triggering the LTM; performing a MAC operation including one of a complete MAC reset and a partial MAC reset; transmitting at least one uplink RRC message, the at least one uplink RRC message being transmitted within a specified time interval before the DL MAC CE or the DL L1 message is received; and performing at least one of RLC reconstruction and PDCP restoration based on the received indication.

Description

Technical Field

[0001] The embodiments disclosed herein relate to a wireless communication network (or wireless network), and more particularly to methods, user equipment (UE), and network entities for managing mobility (e.g., lower layer triggered mobility (LTM), etc.) in a wireless communication network. Background Art

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

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

[0004] Currently, in view of the services to be supported by 5G mobile communication technology, discussions on the improvement and performance enhancement of the initial 5G mobile communication technology are underway, and physical layer standardization of various technologies already exists, such as V2X (vehicle-to-everything) for assisting the driving determination of autonomous vehicles based on information about the position and status of the vehicle sent by the vehicle and enhancing user convenience, NR-U (new radio unlicensed) for system operation aiming to comply with various regulatory requirements in the unlicensed frequency band, NR UE power saving, non-terrestrial network (NTN) as UE-satellite direct communication for providing coverage in areas where communication with the terrestrial network is unavailable, and positioning.

[0005] In addition, in terms of the air interface architecture / protocol, standardization of various technologies such as the Industrial Internet of Things (IIoT) for supporting new services through interoperability and integration with other industries, Integrated Access and Backhaul (IAB) for providing nodes for network service area expansion by supporting wireless backhaul links and access links in an integrated manner, mobility enhancements including conditional handover and Dual Active Protocol Stack (DAPS) handover, and two-step random access for simplifying the random access process (2-step RACH in NR) has been underway. Standardization of various technologies has also been underway in terms of system architecture / services: 5G baseline architectures that combine Network Function Virtualization (NFV) and Software Defined Network (SDN) technologies (e.g., service-based architecture or service-based interface), and Mobile Edge Computing (MEC) for receiving services based on UE location.

[0006] With the commercialization of 5G mobile communication systems, the exponentially growing connected devices will be connected to the communication network, and thus enhanced functions and performance of 5G mobile communication systems and integrated operation of connected devices are expected to be necessary. For this purpose, new research related to the following technologies has been planned: Extended Reality (XR) for effectively supporting Augmented Reality (AR), Virtual Reality (VR), Mixed Reality (MR), etc., 5G performance improvement and complexity reduction by leveraging Artificial Intelligence (AI) and Machine Learning (ML), AI service support, metaverse service support, and drone communication.

[0007] In addition, such development of 5G mobile communication systems will serve as a basis not only for developing new waveforms for providing coverage in the terahertz band for 6G mobile communication technologies, multi-antenna transmission technologies such as Full-Dimension MIMO (FD-MIMO), array antennas, and massive antennas, metasurface-based lenses and antennas for improving the coverage of terahertz band signals, high-dimensional spatial multiplexing technologies using Orbital Angular Momentum (OAM), and Reconfigurable Intelligent Surfaces (RIS), but also for developing full-duplex technologies for improving the frequency efficiency of 6G mobile communication technologies and enhancing the system network, AI-based communication technologies for achieving system optimization by leveraging satellites and AI (Artificial Intelligence) from the design stage and internalizing end-to-end AI support functions, and next-generation distributed computing technologies for achieving service complexity levels beyond the limitations of UE operation capabilities by leveraging ultra-high-performance communication and computing resources. Summary of the Invention

[0008] Technical Problem

[0009] In a wireless technology such as the Fifth Generation New Radio (5G NR), a device (e.g., a smartphone, etc.) can move between different cells. Mobility is performed in the Radio Resource Control Idle (RRC_IDLE) mode using a process called cell reselection. Until NR R17, mobility was performed in the RRC_CONNECTED mode using a process called handover. Network-controlled mobility applies to UEs in RRC_CONNECTED. In NR, network-controlled mobility requires explicit Radio Resource Control (RRC) signaling triggered by the gNB. Handover in NR typically includes three steps, such as a handover preparation step, a handover execution step, and a handover completion step. The gNB can configure the UE to report measurements, and based on the reported measurements or based on its understanding of the network topology, the gNB can send an RRC reconfiguration message to hand over the UE from the source cell to another cell (hereinafter referred to as the target cell). The UE accesses the target cell and sends an RRC reconfiguration complete message.

[0010] In another solution introduced in 3GPP NR Release 16, the gNB can configure the UE with execution conditions for triggering a handover. Once the execution conditions are met, the UE can move to the target cell and send an RRC reconfiguration complete message.

[0011] In all these methods, the UE performs a handover by sending a layer 3 (RRC) message, which results in significant signaling overhead and latency issues. 3GPP specifications such as TS38.300, TS38.331, TS 38.321 are also considered relevant background.

[0012] 3GPP Release 18 is considering using lower layer (e.g., L1 / L2 layer) triggered mobility (also known as LTM) to address this issue. According to 3GPP, the goal of LTM is to achieve serving cell change via L1 / L2 signaling to reduce latency, overhead, and interruption time. The network (e.g., gNB, etc.) can configure multiple candidate cells for the UE to allow for quick application of the configuration to the candidate cells. The network can further send Media Access Control Control Element (MAC CE) or L1 signaling to dynamically hand over the UE from the source cell to one of the configured candidate cells. In addition, LTM can be triggered based on L1 measurements rather than L3 measurements. Therefore, LTM is lower layer measurement and / or lower layer triggered mobility (i.e., handover).

[0013] 3GPP provides for performing LTM without resetting the lower layers (such as MAC) to avoid data loss and reduce the additional latency for data recovery whenever possible. The gNB can configure LTM candidate cells for a candidate target cell via an RRCReconfiguration message, or configure LTM candidate cells for each candidate target cell via a CellGroupConfig. The gNB can further release or modify the candidate configuration.

[0014] It is desirable to address the above disadvantages or other deficiencies, or at least provide a useful alternative.

[0015] The main objective of the embodiments herein is to disclose a method for configuring a user equipment (UE) for LTM in a wireless network (such as a 5G network, etc.).

[0016] Another objective of the embodiments herein is to configure LTM candidate cells.

[0017] Another objective of the embodiments herein is to release LTM candidate cells.

[0018] Another objective of the embodiments herein is to configure an LTM reference configuration.

[0019] Another objective of the embodiments herein is to configure LTM measurements.

[0020] Another objective of the embodiments herein is to complete LTM via an RRC reconfiguration message.

[0021] Another objective of the embodiments herein is to configure L3 measurement configuration and radio bearer configuration during LTM.

[0022] Another objective of the embodiments herein is to configure a timer for LTM failure handling and one or more operations for handling LTM failure.

[0023] Another objective of the embodiments herein is to handle LTM and RRC reconstruction / recovery.

[0024] Another objective of the embodiments herein is to store the LTM configuration after a subsequent LTM.

[0025] Another objective of the embodiments herein is to handle L2 reset during cell handover.

[0026] Another objective of the embodiments herein is to perform LTM in NR, where the UE performs a subsequent LTM when the cell handover between L1 / L2 mobility candidates is completed, without an intermediate RRC reconfiguration.

[0027] Another object of embodiments of this document is to perform LTM in NR, where the UE is instructed on how to perform layer 2 resets during LTM (e.g., MAC reset / RLC recovery / packet data convergence protocol (PDCP) re - establishment / service data adaptation protocol (SDAP) reset).

[0028] Another object of embodiments of this document is to perform LTM in NR, where the UE performs cancellation of MAC procedures and MAC counter reset during LTM.

[0029] Another object of embodiments of this document is to handle the transmission of UE Assistance Information (UAI), MBS Interest Indication, and Sidelink UE Information NR during LTM.

[0030] Solution to the problem

[0031] Accordingly, embodiments of this document provide a method for performing LTM in a wireless network. The method includes: receiving, by the UE, in an RRC message, an LTM configuration indicating whether the UE needs to perform one of radio link control (RLC) re - establishment and packet data convergence protocol (PDCP) recovery during LTM to a candidate cell. In addition, the method includes: receiving, by the UE, a downlink (DL) MAC CE or DL L1 message for triggering LTM. In addition, the method includes: performing, by the UE, a media access control (MAC) operation including one of a full MAC reset or a partial MAC reset. In addition, the method includes: sending, by the UE, at least one uplink RRC message, where the at least one uplink RRC message is sent within a specified time interval before receiving the DL MAC CE or DL L1 message. In addition, the method includes: performing, by the UE, at least one of RLC re - establishment or PDCP recovery based on the received indication. In addition, the method includes: re - transmitting, by the UE, the uplink RRC message.

[0032] Accordingly, embodiments herein provide a method for performing LTM in a wireless network. The method includes: receiving, by a UE, a trigger for LTM from a network entity. Additionally, the method includes: performing, by the UE, at least one operation based on the trigger, where the at least one operation includes one of the following: a UL MAC procedure, resetting all counters of beam failure indication, listen-before-talk during LTM, and canceling a procedure for a BSR for triggering XR. The at least one UL MAC procedure includes one of the following: a triggered scheduling request procedure, a triggered buffer status report procedure, a triggered power headroom report procedure, a triggered consistent listen-before-talk (LBT) failure, a triggered beam failure recovery (BFR), a triggered sidelink buffer status report procedure, a triggered pre-emption buffer status report procedure, a triggered timing advance report procedure, a triggered recommended bitrate query procedure, a triggered configured uplink grant confirmation, a triggered configured sidelink grant confirmation, a triggered desired guard symbol query, a triggered positioning measurement gap activation request procedure, a triggered positioning measurement gap deactivation request procedure, and a triggered small data transfer (SDT) procedure.

[0033] Accordingly, embodiments herein provide a method for performing LTM in a wireless network. The method includes: generating, by a network entity, an LTM configuration. Additionally, the method includes: indicating, by the network entity, one of the following: whether the UE needs to perform RLC re-establishment and PDCP recovery during LTM to a candidate cell, and whether the UE needs to trigger RLC re-establishment during the execution of LTM based on a flag indication. Additionally, the method includes: triggering LTM based on the flag indication.

[0034] Accordingly, embodiments herein provide a UE including an LTM controller coupled to a processor and a memory. The LTM controller is configured to receive, in an RRC message, an LTM configuration indicating whether the UE needs to perform one of RLC re-establishment and PDCP recovery during LTM to a candidate cell. Additionally, the LTM controller is configured to receive a DL MAC CE or a DL L1 message for triggering LTM. Additionally, the LTM controller is configured to perform a MAC operation including one of a full MAC reset and a partial MAC reset. Additionally, the LTM controller is configured to send at least one uplink RRC message, where the at least one uplink RRC message is sent within a specified time interval before receiving the DL MAC CE or the DL L1 message. Additionally, the LTM controller is configured to perform RLC re-establishment or PDCP recovery based on the received indication. Additionally, the LTM controller is configured to retransmit the uplink RRC message.

[0035] Accordingly, embodiments herein provide a UE including an LTM controller coupled to a processor and a memory. The LTM controller is configured to receive a trigger for LTM from a network entity. Further, the LTM controller is configured to perform at least one operation. The at least one operation includes one of the following: a UL MAC procedure, reset all counters of beam failure indication, or listen-before-talk (LBT) during LTM, and cancel the procedure for triggering a BSR for extended reality (XR). The at least one UL MAC procedure includes one of the following: a triggered scheduling request procedure, a triggered buffer status report procedure, a triggered power headroom report procedure, a triggered consistent LBT, a triggered BFR, a triggered sidelink buffer status report procedure, a triggered pre-emption buffer status report procedure, a triggered timing advance report procedure, a triggered recommended bitrate query procedure, a triggered configured uplink grant confirmation, a triggered configured sidelink grant confirmation, a triggered desired guard symbol query, a triggered positioning measurement gap activation request procedure, a triggered positioning measurement gap deactivation request procedure, and a triggered SDT procedure.

[0036] Accordingly, embodiments herein provide a network entity including an LTM controller coupled to a processor and a memory. The LTM controller is configured to generate an LTM configuration from a network entity in a wireless network. Further, the LTM controller is configured to indicate one of the following: whether the UE needs to perform RLC re-establishment and PDCP recovery during LTM to a candidate cell, and whether the UE needs to trigger RLC re-establishment during the execution of LTM based on a flag indication. Further, the LTM controller is configured to trigger LTM based on the flag indication.

[0037] Accordingly, embodiments herein provide a method for performing LTM in a wireless network. The method includes: a network entity sending an RRCReconfiguration message including a list of LTM candidate configurations to be added or modified, a list of LTM candidate configurations to be released, a measurement configuration for LTM, and reference configuration information. Further, the method includes: a network entity receiving layer 1 measurements based on the RRCReconfiguration message. Further, the method includes: a network entity sending a MAC CE to hand over the UE from a source cell to a candidate cell after receiving the layer 1 measurements.

[0038] Accordingly, embodiments herein provide a method for performing LTM in a wireless network. The method includes: receiving, by a UE, an RRCReconfiguration message from a network entity, the RRCReconfiguration message including a list of LTM candidate configurations to be added or modified, a list of LTM candidate configurations to be released, a measurement configuration for LTM, and reference configuration information. Additionally, the method includes: receiving, by the UE, a MAC CE from the network entity to switch the UE from a source cell to a candidate cell based on the RRCReconfiguration message.

[0039] Accordingly, embodiments herein provide a method for performing LTM in a wireless network. The method includes: configuring, by the UE, a flag indicating whether the UE is to perform LTM to complete LTM or the UE is to send an RRC reestablishment (RRCRestablishment) in case of failure. Additionally, the method includes: configuring, by the UE, a first timer for performing access on a first target candidate cell. Additionally, the method includes: determining, by the UE, that the first timer has expired when attempting to access the first target candidate cell to complete LTM. Additionally, the method includes: detecting, by the UE, based on the determination that an RLF has occurred in the UE. Additionally, the method includes: attempting, by the UE, to select a suitable cell within the duration of a second timer and selecting a cell within the second timer value when determining that the selected cell is a second target candidate cell. Additionally, the method includes: performing, by the UE, one of the following based on the flag: initiating an RRC reestablishment procedure to access the second target candidate cell and indicating in the RRCRestablishment message that LTM has failed, and completing LTM by sending an RRC reconfiguration complete (RRCReconfigurationComplete).

[0040] Accordingly, embodiments herein provide a method for performing LTM in a wireless network. The method includes: performing, by the UE, cell selection while a timer is running. Additionally, the method includes: removing, by the UE, the configuration for LTM, where the configuration includes candidate cell configurations or measurement configurations for LTM during an RRC reestablishment procedure.

[0041] Accordingly, embodiments herein provide a method for performing LTM in a wireless network. The method includes: performing, by the UE, one of the following: receiving an RRC release message and transitioning to RRC_IDLE, or receiving an RRC release with a suspended configuration and transitioning to RRC_INACTIVE, or initiating an RRCReestablishment and completing cell selection while a timer T311 is running. Additionally, the method includes: releasing, by the UE, the configuration for LTM when receiving one of an RRC release and an RRC release with a suspended configuration, or when initiating an RRCReestablishment or performing cell selection while the timer T311 is running.

[0042] Accordingly, embodiments of the present disclosure provide a network entity including an LTM controller coupled to a processor and a memory. The LTM controller is configured to send an RRCReconfiguration message including a list of LTM candidate configurations to be added or modified, a list of LTM candidate configurations to be released, a measurement configuration for LTM, and reference configuration information. In addition, the LTM controller is configured to receive layer 1 measurements based on the RRCReconfiguration message. In addition, the LTM controller is configured to send a MAC CE to switch the UE from a source cell to a candidate cell after receiving the layer 1 measurements.

[0043] Accordingly, embodiments of the present disclosure provide a UE including an LTM controller coupled to a processor and a memory. The LTM controller is configured to receive from a network entity an RRCReconfiguration message including a list of LTM candidate configurations to be added or modified, a list of LTM candidate configurations to be released, a measurement configuration for LTM, and reference configuration information. In addition, the LTM controller is configured to receive from the network entity a MAC CE to switch the UE from a source cell to a candidate cell based on the RRCReconfiguration message.

[0044] Accordingly, embodiments of the present disclosure provide a UE including an LTM controller coupled to a processor and a memory. The LTM controller is configured to configure a flag indicating whether the UE is to perform LTM to complete LTM or the UE is to send an RRCReestablishment in case of failure. In addition, the LTM controller is configured to configure a first timer for performing access on a first target candidate cell. In addition, the LTM controller is configured to determine that the first timer has expired when attempting to access the first target candidate cell to complete LTM. In addition, the LTM controller is configured to detect, based on the determination, that a radio link failure (RLF) has occurred in the UE. In addition, the LTM controller is configured to have the UE attempt to select a suitable cell within the duration of a second timer and select a cell within the second timer value when determining that the selected cell is a second target candidate cell. In an embodiment, the LTM controller is configured to initiate an RRC reestablishment procedure to access the second target candidate cell based on the flag and indicate in the RRCRestablishment message that LTM has failed. In another embodiment, the LTM controller is configured to complete LTM by sending an RRCReconfigurationComplete based on the flag.

[0045] Accordingly, embodiments herein provide a UE including an LTM controller coupled to a processor and a memory. The LTM controller is configured to perform cell selection while a timer is running during an RRC reestablishment procedure. Further, the LTM controller is configured to remove the configuration for LTM, where the configuration includes a candidate cell configuration or a measurement configuration for LTM during the RRC reestablishment procedure.

[0046] Accordingly, embodiments herein provide a UE including an LTM controller coupled to a processor and a memory. The LTM controller is configured to perform one of the following: receive an RRC release message and transition to RRC_IDLE, or receive an RRC release with a suspension configuration and transition to RRC_INACTIVE, or initiate RRC Reestablishment and complete cell selection while a timer T311 is running. Further, the LTM controller is configured to release the configuration for LTM when receiving one of an RRC release and an RRC release with a suspension configuration, or when initiating RRC Reestablishment or performing cell selection while the timer T311 is running.

[0047] Embodiments of these and other aspects will be better appreciated and understood when considered in conjunction with the following description and the accompanying drawings. However, it should be understood that the following description, while indicating at least one embodiment and numerous specific details, is provided for purposes of illustration only and is not limiting. Various changes and modifications may be made within the scope of the embodiments herein without departing from the spirit of the embodiments herein, and the embodiments herein include all such modifications.

[0048] Before proceeding with the following detailed description, it may be beneficial to set forth definitions of certain words and phrases used throughout this patent document: The terms “include” and “comprise,” and derivatives thereof, mean inclusion without limitation; the term “or” is inclusive and means and / or; the phrases “associated with” and “associated therewith,” and derivatives thereof, may mean to include, be included within, interconnect with, contain, be contained within, connect to or with, couple to or with, be communicable with, cooperate with, interleave, juxtapose, be proximate to, be bound to or with, have, or have properties of, etc.; and the term “controller” means any device, system, or part thereof that controls at least one operation, such a device may be implemented in hardware, firmware, software, or some combination of at least two thereof. It should be noted that the functions associated with any particular controller may be centralized or distributed, whether local or remote.

[0049] In addition, the various functions described below can be implemented or supported by one or more computer programs, each of which is formed of computer-readable program code and embodied in a computer-readable medium. The terms "application" and "program" refer to one or more computer programs, software components, instruction sets, procedures, functions, objects, classes, instances, related data, or portions thereof suitable for implementation in appropriate computer-readable program code. The phrase "computer-readable program code" includes any type of computer code (including source code, object code, and executable code). The phrase "computer-readable medium" includes any type of medium that can be accessed by a computer, such as read-only memory (ROM), random access memory (RAM), hard disk drive, compact disc (CD), digital video disc (DVD), or any other type of memory. A "non-transitory" computer-readable medium does not include wired, wireless, optical, or other communication links that transmit transitory electrical or other signals. Non-transitory computer-readable media include media in which data can be permanently stored and media in which data can be stored and later overwritten, such as rewritable compact discs or erasable storage devices.

[0050] Certain words and phrases are defined in this patent document. One of ordinary skill in the art should understand that, in many if not most instances, such definitions apply to the prior as well as future use of such defined words and phrases.

[0051] Advantageous Effects of the Invention

[0052] Provided are a method and apparatus for efficiently performing measurements based on LTM configuration in a wireless communication system. Description of the Drawings

[0053] Embodiments disclosed herein are illustrated in the drawings, and like reference numerals throughout the drawings indicate corresponding parts in each of the drawings. The embodiments herein will be better understood from the following description with reference to the drawings, in which:

[0054] Figure 1 A timing diagram showing an LTM configuration and a completion process according to an embodiment disclosed herein;

[0055] Figure 2 A timing diagram showing a process for handling LTM failure according to an embodiment disclosed herein;

[0056] Figure 3 A timing diagram showing a process for handling LTM configuration during RRC reconstruction according to an embodiment disclosed herein;

[0057] Figure 4 A timing diagram showing a process for handling LTM configuration during suspension and resume according to an embodiment disclosed herein;

[0058] Figure 5 shows a timing diagram showing the overall LTM process according to an embodiment disclosed herein;

[0059] Figure 6 shows various hardware components of a UE according to an embodiment disclosed herein;

[0060] Figure 7 shows various hardware components of a network entity (e.g., eNB, gNB, etc.) according to an embodiment disclosed herein;

[0061] Figure 8 shows a flowchart of a method for a UE to perform LTM in a wireless network when performing RLC re - establishment and PDCP recovery based on an indication;

[0062] Figure 9 shows another flowchart of a method for a UE to perform LTM in a wireless network according to an embodiment disclosed herein;

[0063] Figure 10 shows another flowchart of a method for a UE to perform LTM in a wireless network based on an RRCReconfiguration message according to an embodiment disclosed herein;

[0064] Figure 11 shows another flowchart of a method for a UE to perform LTM in a wireless network based on a flag according to an embodiment disclosed herein;

[0065] Figure 12 shows another flowchart of a method for a UE to perform LTM in a wireless network when performing cell selection and a timer is running according to an embodiment disclosed herein;

[0066] Figure 13 shows another flowchart of a method for a UE to perform LTM in a wireless network according to an embodiment disclosed herein;

[0067] Figure 14 shows a flowchart of a method for a network entity to perform LTM in a wireless network based on an LTM configuration according to an embodiment disclosed herein; and

[0068] Figure 15 shows a flowchart of a method for a network entity to perform LTM in a wireless network based on an RRCReconfiguration message according to an embodiment disclosed herein. Detailed Description

[0069] discussed below Figures 1 to 15The various embodiments for describing the principles of the present disclosure in this patent document are illustrative only and should not be construed in any way as limiting the scope of the present disclosure. Those skilled in the art will understand that the principles of the present disclosure can be implemented in any suitably arranged system or device.

[0070] Referring to the non - restrictive embodiments shown in the accompanying drawings and described in detail below, the embodiments herein and their various features and advantageous details are more fully explained. Descriptions of well - known components and processing techniques are omitted so as not to unnecessarily obscure the embodiments herein. The examples used herein are only intended to facilitate an understanding of the manner in which the embodiments herein can be practiced and further enable those skilled in the art to practice the embodiments herein. Therefore, the examples should not be construed as limiting the scope of the embodiments herein.

[0071] For the purpose of interpreting this specification, the definitions (as defined herein) will apply, and where appropriate, terms used in the singular will also include the plural and vice versa. It should be understood that the terms used herein are for the purpose of describing particular embodiments only and are not restrictive. Unless otherwise stated, the terms "comprising", "having" and "including" should be construed as open - ended terms.

[0072] The words / phrases "exemplary", "example", "illustrative", "in an instance", "etc.", "and the like", "for example", "i.e." are used herein only to mean "serving as an example, instance or illustration". Any embodiment or implementation of the subject matter described using the words / phrases "exemplary", "example", "illustrative", "in an instance", "etc.", "and the like", "for example", "i.e." is not necessarily to be construed as being preferred or advantageous over other embodiments.

[0073] The embodiments herein can be described and illustrated in terms of blocks that perform one or more of the described functions. These blocks, which may be referred to herein as managers, units, modules, hardware components, etc., are physically implemented by analog and / or digital circuits such as logic gates, integrated circuits, microprocessors, microcontrollers, memory circuits, passive electronic components, active electronic components, optical components, hard - wired circuits, etc., and may optionally be driven by firmware. The circuits can be implemented, for example, in one or more semiconductor chips or on a substrate support such as a printed circuit board. The circuits constituting the blocks can be implemented by dedicated hardware, or by a processor (e.g., one or more programmed microprocessors and associated circuits), or by a combination of dedicated hardware for performing some functions of the blocks and a processor for performing other functions of the blocks. Without departing from the scope of the present disclosure, each block of an embodiment can be physically divided into two or more interacting and discrete blocks. Similarly, without departing from the scope of the present disclosure, the blocks of an embodiment can be physically combined into more complex blocks.

[0074] It should be noted that the elements in the drawings are shown for the purpose of this description and for ease of understanding, and may not necessarily be drawn to scale. For example, the flowcharts / timelines show the methods in terms of the steps required to understand aspects of the embodiments disclosed herein. Further, in terms of the construction of the device, one or more components of the device may have been represented in the drawings by conventional symbols, and the drawings may show only those specific details relevant to understanding the embodiments so as not to obscure the drawings with details that are obvious to those of ordinary skill in the art who benefit from the description herein. Further, in terms of the system, one or more components / modules of the system may have been represented in the drawings by conventional symbols, and the drawings may show only those specific details relevant to understanding the embodiments so as not to obscure the drawings with details that are obvious to those of ordinary skill in the art who benefit from the description herein.

[0075] The drawings are used to help understand various technical features easily, and it should be understood that the embodiments presented herein are not limited by the drawings. Therefore, the present disclosure should be construed as extending to any modifications, equivalents, and alternatives other than those specifically set forth in the drawings and the corresponding description. The use of words such as first, second, third, etc. to describe components / elements / steps is for the purpose of this description and should not be construed as sequential ordering / placing / occurring unless otherwise specified.

[0076] Embodiments herein implement a method for performing LTM in a wireless network. The method includes a network entity sending an RRCReconfiguration message that includes a list of LTM candidate configurations to be added or modified, a list of LTM candidate configurations to be released, a measurement configuration for LTM, and reference configuration information. Further, the method includes a network entity receiving layer 1 measurements based on the RRCReconfiguration message. Further, the method includes a network entity sending a MAC CE to handover the UE from a source cell to a candidate cell upon receiving the layer 1 measurements.

[0077] The provided method can be used to avoid data loss and reduce the latency of data recovery in a wireless network.

[0078] Now referring to the drawings, and more specifically to Figures 1 to 15 , in which like reference numerals consistently represent corresponding features in all the drawings, shows at least one embodiment.

[0079] Figure 1A timing diagram showing the LTM configuration and completion process in a wireless network (300) according to an embodiment disclosed herein is presented. The wireless network (300) can be, for example but not limited to, a 5G network, a sixth-generation (6G) network, an Open Radio Access Network (ORAN), etc. The source gNB provides an RRCReconfiguration message or a candidate cell Cellgroupconfig message for LTM for each candidate cell. Embodiments herein refer to the candidate cell RRC reconfiguration as candLTM-Reconfiguation and the candidate cell Cellgroupconfig as candLTM-CellGroup.

[0080] An example signaling for providing candidate cell reconfiguration is shown in Table 1 below.

[0081] [Table 1]

[0082]

[0083]

[0084] In an embodiment, a candidate cell can be reconfigured using candLTM-CellGroupConfig. The reconfiguration process is given in Table 2 below.

[0085] [Table 2]

[0086]

[0087]

[0088] In an embodiment, the gNB instructs the UE (200) to release the candidate LTM configuration, and the UE (200) releases the candidate LTM configuration accordingly. The UE (200) can be, for example but not limited to, a laptop, a smartphone, a desktop computer, a notebook, a device-to-device (D2D) device, a vehicle-to-everything (V2X) device, a foldable phone, a smart TV, a tablet, an immersive device, and an Internet of Things (IoT) device. The gNB sends a candLTM-CellGroupConfigToRemoveList (a list containing candLTM-CellGroupConfigId) or a candLTM-ReconfigToRemoveList (a list containing candLTM-ReconfigId), and the UE (200) removes all candidate LTM configurations identified by any candLTM-CellGroupConfigId in the candLTM-CellGroupConfigToRemoveList or by any candLTM-ReconfigId in the candLTM-ReconfigToRemoveList.

[0089] In an embodiment, the gNB can indicate whether the candidate LTM-CellGroupConfig or CandLTM-Reconfiguation is a full configuration or a delta configuration. If it is a delta configuration, the gNB indicates a cellgroupconfig or an RRC reconfiguration (e.g., candLTM-ReconfigId or candLTM-CellGroupConfigId) that can be used as a reference configuration (refConfigId). If the CandLTM-Reconfiguation is a full configuration, the configuration includes all configurations required by the UE (200) at the time of configuration. The UE (200) can directly apply the full configuration. If the CandLTM-Reconfiguation is a delta LTM configuration, the delta LTM configuration can only contain a part of the configurations required by the UE (200), and the UE (200) combines the delta LTM configuration and the reference configuration to generate a full configuration that can be applied.

[0090] If the gNB indicates the use of delta configuration and does not provide candLTM-ReconfigId or candLTM-CellGroupConfigId, the UE (200) uses the current source cell configuration as the reference configuration. In an embodiment, the gNB may explicitly indicate to the UE (200) in an RRC message to use the source cell configuration as the reference for the delta configuration.

[0091] In an alternative embodiment, the gNB may also provide an OCTETSTRING containing an RRC reconfiguration or cellgroupconfig, which may be used as the reference configuration instead of using refConfigId as the reference configuration.

[0092] In an example, the gNB may configure the UE (200) with a CandLTM-Reconfiguation including candLTM-RRCReconfig, where candLTM-ReconfigId is 1, 2, and 3. The gNB also indicates that the reference configuration (referenceConfiguration) to be used for ltmconfig 2 is 1 (i.e., refConfigId = 1). The gNB provides the reference RRC configuration or cellgroupconfiguration as the delta configuration with reference to 1.

[0093] The gNB may also provide the L1 measurement configuration LTMMeasConfig to the UE (200) in an RRC reconfiguration message to perform L1 measurements for LTM. LTMMeasConfig may be a CSI-RS measurement configuration.

[0094] For the configuration of contention-free RACH (CFRA) and RACH-free handover: When configuring the candidate cell configuration for LTM for the UE (200) in an RRC message such as an RRC reconfiguration, the gNB includes contention-free RACH (CFRA) resources for one or more of the candidate cells in the Cellgroupconfig IE. The gNB may also include resources (grant / resource blocks) for sending UL messages (e.g., UL MAC CE or L1 messages) in an RRC message such as an RRC reconfiguration for completing a handover without RACH (i.e., for performing a RACH-free handover). As described above, candLTM-Reconfiguation or candLTM-CellGroupConfig may include CFRA configuration and resources for handover completion.

[0095] In an embodiment, the gNB includes only one of the contention-free RACH resources or resources for completing a handover without RACH in the RRC configuration for the candidate cell (i.e., in candLTM-Reconfiguation or candLTM-CellGroupConfig).

[0096] In an embodiment, the UE (200) may receive, in an uplink media access control control element (UL MAC CE), resources for transmitting a UL message for completing a handover without RACH (i.e., for RACH-free handover). If the UE (200) receives both CFRA resources and UL resources for LTM (including the case where the UE (200) receives CFRA resources via an RRC message and receives resources for RACH-free handover via a UL MAC CE or an RRC message), the UE (200) uses the UL resources received for RACH-free handover to perform handover completion. If the UL message for handover completion cannot be successfully transmitted via RACH-free handover, the UE (200) may perform CFRA using the configured resources in candLTM-Reconfiguation or candLTM-CellGroupConfig or via contention-based RACH. When the UL message for handover completion cannot be successfully transmitted using MAC or L1 signaling, if the UE (200) is allowed to perform RACH, the gNB may provide a flag to the UE (200).

[0097] LTM Completion: In an embodiment, once the handover has been successfully completed (e.g., via a completion flag), the gNB indicates to the UE (200) whether to send an RRC message (e.g., NR RRC reconfiguration complete) or an L1 / L2 message (e.g., UL MAC CE). If the network indicates to the UE (200) to send a UL MAC CE, the handover procedure may be successfully completed once the UE (200) responds to the L1 / L2 trigger with a UL MAC CE (such as a C-RNTI MAC CE). If the network configures the UE (200) to send an RRC message to indicate handover completion, the UE (200) sends an RRC reconfiguration complete message.

[0098] Handling of Layer 3 Configuration during LTM: In an embodiment, the UE (200) may receive from the gNB a configuration message for adding or deleting or modifying radio bearers (data radio bearers or signaling radio bearers or MBS bearers, etc.) when performing L1 / L2 mobility. The UE (200) may delete / modify radio bearers during the execution of L1 / L2 mobility. The gNB may also add / delete / modify radio bearers from the gNB side. The UE (200) receives the configuration for adding or deleting or modifying radio bearers in the RRC message that configures or modifies the L1 / L2 mobility configuration.

[0099] In an embodiment, the UE (200) may receive from the gNB a configuration for adding / deleting / modifying measurement configuration (including but not limited to measurement object configuration, reporting configuration, measurement identifier configuration, measurement gap configuration, etc.) when performing L1 / L2 mobility. The UE (200) adds or deletes or modifies the measurement configuration during the execution of L1 / L2 mobility. The gNB may also add / delete / modify the measurement configuration from the gNB side. The UE (200) receives this configuration in the RRC message that configures or modifies the L1 / L2 mobility configuration.

[0100] In an embodiment, the UE (200) may receive from the gNB a configuration for adding / deleting / modifying application layer measurement configuration (e.g., as in appLayerMeasConfig-r17) or any other RRC reconfiguration IE when performing L1 / L2 mobility. The UE (200) adds / deletes / modifies the application layer measurement configuration during L3 mobility and performs the actions defined for the IE during the execution of L1 / L2 mobility. The gNB may also add / delete / modify the application layer measurement configuration when performing L1 / L2 mobility from the gNB side, or perform the actions of other RRC reconfiguration IEs. The UE (200) receives this configuration in the RRC message that configures or modifies the L1 / L2 mobility configuration.

[0101] L3 Configuration during LTM: In an embodiment, when configuring the UE (200) for LTM, the gNB excludes the configuration for adding / deleting / modifying measurement configuration (including but not limited to measurement object configuration, reporting configuration, measurement identifier configuration, measurement gap configuration, etc.) in the L3 message (e.g., RRC reconfiguration) that has been sent to configure the UE (200) for LTM.

[0102] In an embodiment, when configuring the UE (200) for LTM, the gNB excludes the configuration for adding / deleting / modifying radio bearer configuration (data radio bearers or signaling radio bearers or MBS bearers, etc.) in the L3 message transmission (e.g., RRC reconfiguration) to configure the UE (200) for LTM.

[0103] In an embodiment, when configuring the UE (200) for LTM, the gNB excludes the configuration for adding / removing / modifying the application layer measurement configuration (e.g., as in appLayerMeasConfig-r17) in the L3 message transmission (e.g., RRC reconfiguration) to configure the UE (200) for LTM.

[0104] As Figure 1 shown, in step 1, the RRC layer (102) of the gNB sends an RRC reconfiguration including candLTM-RRCReconfig or candLTMCellGroupConfig, LTMMeasurementConfig, completionFlag, CFRA / RACHless config, L3 configuration, etc. to the RRC layer of the UE (200). In step 2, the RRC of the UE (200) sends the RRC reconfiguration completion to the RRC layer (102) of the gNB. In step 3, the L1 / L2 of the UE (200) performs LTM (L1) measurement. In step 4, the L1 / L2 of the UE (200) sends the L1 measurement to the L1 / L2 (106) of the source gNB. In step 5, the L1 / L2 (106) of the source gNB triggers LTM by sending a UL MAC CE to the L1 / L2 of the UE (200). In step 6, the L1 / L2 of the UE (200) applies the received L3 configuration (if any). In an embodiment, in step 7, the L1 / L2 of the UE (200) sends the MAC CE (C-RNTI MAC CE) indicating HO completion using CFRA / CBRA / RACHless according to the configuration to the L1 / L2 (104) of the target gNB. In another embodiment, in step 8, the RRC of the UE (200) sends the RRC reconfiguration completion to the RRC layer (102) of the gNB.

[0105] Figure 2A timing diagram showing a process for handling LTM failures according to an embodiment disclosed herein is shown. In an embodiment, the UE (200) may be configured with a timer for performing access on a target candidate cell, and when the timer (e.g., Timer-LTM) expires, when attempting to access the target candidate cell to complete LTM, the UE (200) considers that a radio link failure has occurred in the UE (200). The UE (200) may attempt to select a new cell within the duration of a specific timer (e.g., Timer-CellselectionAfterLTM), and if a new cell is selected within the specified timer value, the UE RRC may initiate an RRC reconstruction process. In an alternative embodiment, the UE (200) may send a UL MAC CE or a UL L1 message to indicate that LTM has failed after selecting a new cell.

[0106] In an embodiment, the timer TimerLTM is the same timer for handover (i.e., the T304 timer in Technical Specification (TS) 38.331 V17.2.0). In an embodiment, Timer-CellselectionAfterLTM is the same timer T311 in TS38.331 V17.2.0. In an embodiment, TimerLTM is included in the LTM configuration of the candidate cell, i.e., in one of CandLTM-ToAddMod, candLTM-CellGroupConfig, or candLTM-RRCReconfig. In an embodiment, TimerLTM is included in the RRC reconfiguration of the source cell (such as RRCReconfiguration-v18xx-Ies in the previous embodiment). In an embodiment, Timer-CellselectionAfterLTM is included in the LTM configuration of the candidate cell, i.e., in one of CandLTM-ToAddMod, candLTM-CellGroupConfig, or candLTM-RRCReconfig. In an embodiment, Timer-CellselectionAfterLTM is included in the RRC reconfiguration of the source cell (such as RRCreconfiguration-v18xx-Ies in the previous embodiment).

[0107] In an embodiment, when the timer Timer-LTM expires, the UE (200) sends a UL MAC CE to the source gNB to indicate that LTM has failed. The UE (200) returns to the source cell based on the configuration from the network to send the UL MAC CE.

[0108] In an embodiment, when the timer Timer-LTM expires, the UE (200) performs cell selection within the duration of a specific timer (e.g., Timer-CellselectionAfterLTM). If the UE (200) selects a cell that is configured as a candidate cell for LTM, the UE (200) completes the LTM by sending an L1 / L2 / L3 message for handover completion. In an embodiment, the gNB configures the UE (200) with a flag indicating whether the UE (200) can perform LTM to complete handover or whether the UE (200) can send an L1 / L2 message or an L3 (RRC re-establishment) message that can also indicate that the LTM has failed.

[0109] As Figure 2 shown, in step 1, the RRC layer (102) of the gNB sends an RRC reconfiguration including candidate LTM configuration, TimerLTM, Timer-CellselectionAfterLTM, methods for handling failures, etc. to the RRC layer of the UE (200). In step 2, the RRC of the UE (200) sends the RRC reconfiguration complete to the RRC layer (102) of the gNB. In step 3, the L1 / L2 of the UE (200) performs LTM (L1) measurements. In step 4, the L1 / L2 of the UE (200) sends the L1 measurements to the L1 / L2 (106) of the source gNB. In step 5, the L1 / L2 (106) of the source gNB triggers the LTM by sending a UL MAC CE to the L1 / L2 of the UE (200). In step 6, the L1 / L2 of the UE (200) fails to complete the LTM within TimerLTM. In step 7, the UE (200) performs cell selection during TimerCellselectionAfterLTM. In an embodiment, in step 8, the RRC of the UE (200) sends an RRC re-establishment to the gNB-RRC (102). In another embodiment, in step 9, the UE (100) completes the LTM by sending an RRCReconfigurationComplete to the source L1 / L2 (106).

[0110] Figure 3 A timing diagram showing a process for handling LTM configuration during RRC re-establishment according to an embodiment disclosed herein is shown. In an embodiment, during the RRC re-establishment process, the UE (200) removes any measurement configuration for LTM. In an embodiment, the removal can be performed after cell selection while the timer T311 is running.

[0111] In an embodiment, the UE (200) removes all configurations for LTM (configured via candLTM-Reconfiguation or candLTM-CellGroupConfig) during the RRC reestablishment process, including all candidate cell configurations. The RRC reestablishment process includes various steps detailed in Section 5.3.7 of 3GPP TS 38.331. It can be performed when T311 is running. Alternatively, it can be performed after cell selection upon detection of a radio link failure (RLF) or upon receipt of an RRC reestablishment message.

[0112] In an embodiment, the UE (200) removes any incremental configuration shared for LTM for any candidate cell during the RRC reestablishment process. In an embodiment, the UE (200) removes the incremental configuration after cell selection when T311 is running, or alternatively, it can be performed after cell selection upon detection of an RLF or upon receipt of an RRC reestablishment.

[0113] If the configuration for LTM is a conditional configuration, the gNB may instruct the UE (200) to attempt to reconfigure LTM based on the condition after cell selection when the T311 timer is running.

[0114] During the reestablishment process (as in Section 5.3.7 of TS 38.331), if the UE (200) selects a cell where candLTM-RRCReconfig or candLTM-CellGroupConfig is available, the UE (200) may send an LTM completion message (L3 message or L1 / L2 message) instead of an RRC reestablishment to the cell. The UE (200) may decide whether to send an LTM completion message or an RRC reestablishment based on a flag received from the network (gNB).

[0115] In an embodiment, during the RRC reestablishment process (as in TS 38.331), the UE (200) stores candidate LTM configurations (e.g., candLTM-RRCReconfig or candLTM-CellGroupConfig). The UE (200) may store the configuration based on a flag (e.g., storeCandidateLTM) received from a network entity (100). Additionally, once the RRC reestablishment is successful, the UE (200) may restore the candidate LTM configuration. In an embodiment, the UE (200) decides whether to restore or release the candidate LTM configuration based on a flag (e.g., restoreCandidateLTM).

[0116] As Figure 3As shown, in step 1, the RRC layer (102) of the gNB sends an RRC reconfiguration including candLTM-RRCReconfig or candLTM-CellGroupConfig, LTMMeasurementConfig, etc. to the RRC layer of the UE (200). In step 2, the RRC of the UE (200) sends an RRC reconfiguration complete to the RRC layer (102) of the gNB. In step 3, the L1 / L2 of the UE (200) determines a radio link failure. In step 4, the L1 / L2 of the UE (200) performs cell selection while T311 is running. In step 5, the L1 / L2 of the UE (200) releases the LTM configuration, LTM measurement configuration, reference configuration, and all other configurations related to LTM. In step 6, the RRC of the UE (200) sends an RRC reestablishment to the gNB-RRC (102).

[0117] Figure 4 A timing diagram showing a process of handling LTM configuration during suspension and resume according to an embodiment disclosed herein is shown. In the embodiment, upon receiving an RRC release (such as an NR RRCRelease message) or an RRC release with a suspension configuration, the UE (200) releases any configuration (configured via candLTM-Reconfiguation or candLTM-CellGroupConfig) for LTM. In the embodiment, the UE (200) stores the configuration during an RRC release with a suspension configuration and further releases the configuration for LTM during an RRC resume process. The RRC resume process includes various steps detailed in 3GPP TS 38.331.

[0118] As Figure 4 As shown, in step 1, the RRC layer (102) of the gNB sends an RRC reconfiguration including candLTM-RRCReconfig or candLTM-CellGroupConfig, LTMMeasurementConfig, etc. to the RRC layer of the UE (200). In step 2, the RRC of the UE (200) sends an RRC reconfiguration complete to the RRC layer (102) of the gNB. In step 3, the RRC layer (102) of the gNB RRC sends an RRC release with a suspension configuration (suspendConfig) to the RRC layer of the UE (200). In step 4, the L1 / L2 of the UE (200) releases the LTM configuration, LTM measurement configuration, reference configuration, and all other configurations related to LTM.

[0119] Figure 5 A timing diagram showing an overall LTM process according to an embodiment disclosed herein is shown. As Figure 5As shown, in step 1, the RRC layer (102) of the gNB sends an RRC reconfiguration including candLTM-RRCReconfig or candLTM-CellGroupConfig, storeLTMConfig / candidateLTMStoreList / candidateLTMStoreMapList, and lowerLayerOpsGroup to the RRC layer of the UE (200). In step 2, the RRC of the UE (200) sends an RRC reconfiguration complete to the RRC layer (102) of the gNB. In step 3, the L1 / L2 of the UE (200) performs LTM (L1) measurements. In step 4, the L1 / L2 of the UE (200) sends the L1 measurements to the L1 / L2 (106) of the source gNB. In step 5, the L1 / L2 (106) of the source gNB sends a trigger LTM message to the L1 / L2 of the UE (200).

[0120] In step 6, the L1 / L2 of the UE (200) performs MAC operations for LTM, etc. In addition, the L1 / L2 of the UE (200) cancels applicable MAC procedures and resets applicable counters. In addition, the L1 / L2 of the UE (200) performs MAC / RLC reset / PDCP recovery based on the configuration. In an embodiment, in step 7, the L1 / L2 of the UE (200) sends an RRCReconfigurationComplete to the target gNB L2 / L2 104. In an embodiment, in step 8, the RRC of the UE (200) sends an RRC reconstruction to the gNB-RRC (102). In step 9, the L1 / L2 of the UE (200) stores candidates based on the configuration.

[0121] Storing LTM configuration: In an embodiment, for each candidate cell in LTM, the UE (200) receives from the gNB a configuration indicating whether other candidate cell configurations can be maintained for subsequent mobility. In an embodiment, this can be a flag indicating to maintain all candidate cells (e.g., storeLTMconfig, etc.). In another embodiment, this can be a list of candidate cells whose configurations can be maintained (e.g., a list of cell identifiers or indices of candidate cells, candidateLTMStoreList, etc.). The storeLTMconfig or candidateLTMStoreList can be provided by the gNB to the UE (200) in an RRC reconfiguration message.

[0122] In an embodiment, this information can be provided by the source cell in an RRC reconfiguration message. An example structure is shown in Table 3 below.

[0123] [Table 3]

[0124]

[0125] In an embodiment, the gNB is the source cell and provides a flag storeLTMconfig for each candidate cell. If the UE (200) has received the storeLTMconfig of the source cell or a candidate cell, the UE (200) stores the LTM configurations of all candidate cells. An example structure is shown in Table 4 below.

[0126] [Table 4]

[0127]

[0128] In an embodiment, the gNB is the source cell and provides a candidateLTMStoreList for each candidate cell. If the UE (200) has received the candidateLTMStoreList of a candidate cell, when the stored candidate cell has become the source cell, the UE (200) stores the LTM configurations of all candidate cells in the candidateLTMStoreList. In other words, during the LTM to the candidate cell, the UE (200) stores all candidate cells in the candidateLTMStoreList.

[0129] An example structure is shown in Table 5 below.

[0130] [Table 5]

[0131]

[0132] In an embodiment, the source cell provides a mapping other than candLTM-ToAddMod. The gNB provides a list of candidate cells (candX) and a list of mappings of the indices (candidateLTMStoreList) or cell IDs of the candidate cells whose configurations can be stored for each candX. Once the UE (200) moves to a cell in candX due to LTM, the UE (200) stores the LTM configurations of all cells in the candidateLTMStoreList (if available) (or updates the storage), as shown in Table 6.

[0133] [Table 6]

[0134]

[0135]

[0136] When the candidate identified by sourceCellId becomes the source cell, the UE (200) stores all the candidate LTM configurations in the candidateLTMStoreList, if available.

[0137] If sourcecellId does not exist in the CandidateLTMStoreMAP, or if the mapped candidateLTMStoreList does not exist in the candidateLTMStoreMAP, the UE (200) may not store any candidate LTM configurations when the candidate identified by sourceCellId becomes the source cell.

[0138] Handling of lower layer reset: In an embodiment, the gNB includes in the cellgroupconfig IE within the RRC message for the candidate cell configured for L1 / L2 mobility whether the UE (200) needs to perform a MAC reset during LTM to the candidate cell. The gNB may indicate to the UE (200) to perform a partial reset through an IE within the cellgroupconfig IE within the RRC message for the candidate cell configured for L1 / L2 mobility (e.g., within candLTM-RRCReconfig or candLTM-CellGroupConfig).

[0139] In an embodiment, the gNB indicates in the DL MAC CE or DL L1 message used to trigger LTM whether the UE (200) needs to perform a MAC reset during LTM to the candidate cell. In an embodiment, if the gNB has indicated whether the UE (200) needs to perform a MAC reset in the MAC CE or DL L1 message as described above and also in the RRC message, the UE (200) follows the indication in the MAC CE or DL L1 message and ignores the indication from the RRC message.

[0140] In an embodiment, the gNB includes a flag to indicate whether the UE (200) needs to trigger RLC re-establishment during the execution of LTM. In an embodiment, this information is included within the RRC message for the candidate cell configured for L1L2 mobility. In an embodiment, the gNB includes this flag for each RLC bearer configured for the candidate cell.

[0141] In an embodiment, the gNB indicates in a DL MAC CE or a DL L1 message for triggering LTM whether the UE (200) needs to perform RLC re - establishment during LTM to a candidate cell. In an embodiment, if the gNB has indicated in the MAC CE or DL L1 message as described above and also in the RRC message whether the UE (200) needs to perform RLC re - establishment, the UE (200) follows the indication in the MAC CE or DL L1 message and ignores the indication from the RRC message. If the gNB has indicated in the DL MAC CE or DL L1 message that the UE (200) needs to perform RLC re - establishment, the UE (200) performs RLC re - establishment for all RLC bearers during LTM.

[0142] In an embodiment, the gNB includes a flag to indicate whether the UE (200) needs to perform PDCP recovery / SDAP reset during the execution of LTM. In an embodiment, this information is included in the RRC message for configuring the candidate cell for LTM. In an embodiment, the gNB includes this flag for each radio bearer configured for the candidate cell. In an embodiment, separate flags can be used for PDCP recovery and SDAP reset.

[0143] In an embodiment, the gNB indicates in a DL MAC CE or a DL L1 message for triggering LTM whether the UE (200) needs to perform PDCP recovery / SDAP reset during LTM to a candidate cell. In an embodiment, if the gNB has indicated in the MAC CE or DL L1 message as described above and also in the RRC message whether the UE (200) needs to perform PDCP recovery / SDAP reset, the UE (200) follows the indication in the MAC CE or DL L1 message and ignores the indication from the RRC message. If the gNB has indicated in the DL MAC CE or DL L1 message that the UE (200) needs to perform PDCP recovery / SDAP reset, the UE (200) performs PDCP recovery / SDAP reset for all radio bearers during LTM.

[0144] In an embodiment, for each candidate cell, the gNB can provide a mapping of other candidate cells (such as cell id or index, etc.) that indicates whether the UE (200) needs to perform at least one of MAC reset, RLC re - establishment, and PDCP recovery / SDAP reset.

[0145] In an embodiment, for each candidate cell, the gNB may provide a list of candidate cells (such as cell IDs or indices), which indicates that if the UE (200) moves within these cells, at least one of performing MAC reset, RLC re - establishment, and PDCP recovery is excluded. If the UE (200) moves from any cell in the list to a cell outside the list, the UE (200) performs at least one of MAC reset, RLC re - establishment, PDCP recovery, and SDAP reset. If the UE (200) moves from a cell outside the list to any of these cells, the UE (200) performs at least one of MAC reset, RLC re - establishment, PDCP recovery, and SDAP reset.

[0146] [Table 7]

[0147]

[0148]

[0149] In an embodiment, a single flag in the MAC CE or L1 indication (DCI) is used to indicate and can be used to perform MAC reset, RLC re - establishment, PDCP recovery, or SDAP reset.

[0150] MAC cancellation and counter reset during cell handover in LTM: During LTM, the UE (200) cancels one or more of the following UL MAC procedures, such as the triggered scheduling request procedure, the triggered buffer status report procedure, the triggered power headroom report procedure, the triggered consistent LBT, the triggered BFR, the triggered sidelink buffer status report procedure, the triggered pre - emptive buffer status report procedure, the triggered timing advance report procedure, the triggered recommended bitrate query procedure, the triggered configured uplink grant confirmation, the triggered configured sidelink grant confirmation, the triggered desired guard symbol query, the triggered positioning measurement gap activation / de - activation request procedure, and the triggered SDT procedure. In an embodiment, this may be performed during the completion of LTM. In an embodiment, this may be performed after receiving the DL LTM trigger for cell handover.

[0151] In an embodiment, the UE (200) resets all counters of beam failure indication (BFI_COUNTER) or all counters of listen - before - talk (LBT_COUNTER) during LTM. In an embodiment, this may be performed during the completion of LTM. In an embodiment, this may be performed after receiving the DL LTM trigger for cell handover.

[0152] In an embodiment, the UE (200) performs the above cancellation and counter reset only when the MAC is reset during a cell handover during LTM. In an embodiment, when the MAC is not reset or not fully reset, or the MAC is partially reset during a cell handover during LTM, the UE (200) performs the above cancellation and counter reset.

[0153] In an embodiment, if the UE (200) initiates the transmission of a UE Assistance Information (UAI) message for a corresponding cell group (MCG / SCG) during a fixed time period (e.g., the last 1 second) before receiving the LTM trigger, the UE (200) retransmits the UE Assistance Information after LTM completion. The UAI can be sent by the UE (200) to provide assistance information to the network, e.g., for power saving or multi-SIM operation or to avoid in-device interference. In an embodiment, the UE (200) retransmits the UAI only when the UE (200) is still configured to provide relevant UE assistance information for the corresponding cell group.

[0154] In an embodiment, if SIB12 is provided by the target PCell, and the UE (200) initiates the transmission of a Sidelink UE Information NR message indicating a change in relevant NR sidelink communication / discovery-related parameters (i.e., a change in sl-RxInterestedFreqList or sl-TxResourceReqList) in the target PCell during a fixed time period (e.g., the last 1 second) before the LTM trigger, the UE (200) initiates the transmission of the Sidelink UE Information NR message after LTM completion. The Sidelink UE Information NR can be used by the UE (200) to provide information about the frequencies of interest, sidelink transmission resources, etc. to the network.

[0155] In an embodiment, if the UE (200) initiates the transmission of an MBS Interest Indication message during the last 1 second before the LTM trigger, the UE (200) initiates the transmission of the MBS Interest Indication message after LTM completion, e.g., in accordance with clause 5.9.4 of TS 38.331. The MBS Interest Indication message is used to provide information about MBS interest, such as the frequencies of interest.

[0156] In an embodiment, the retransmission of UAI / SidelinkUEInformationNR / MBSInterestIndication is performed only when the UE (200) performs RACH during the execution of LTM on the target cell after the completion of LTM.

[0157] In an embodiment, the UE (200) cancels the procedure for triggering the BSR for XR (using a new BSR table).

[0158] The following gives an example specification update according to TS 38.321. When receiving a trigger for LTM (DL MAC CE or L1 message for triggering LTM), the UE (200) performs the following operations:

[0159] 1> Cancel the triggered scheduling request procedure (if any);

[0160] 1> Cancel the triggered buffer status report procedure (if any);

[0161] 1> Cancel the triggered power headroom report procedure (if any);

[0162] 1> Cancel the triggered consistent LBT failure (if any);

[0163] 1> Cancel the triggered BFR (if any);

[0164] 1> Cancel the triggered sidelink buffer status report procedure (if any);

[0165] 1> Cancel the triggered pre-emption buffer status report procedure (if any);

[0166] 1> Cancel the triggered timing advance report procedure (if any);

[0167] 1> Cancel the triggered recommended bitrate query procedure (if any);

[0168] 1> Cancel the triggered configured uplink grant confirmation (if any);

[0169] 1> Cancel the triggered configured sidelink grant confirmation (if any);

[0170] 1> Cancel the triggered desired guard symbol query (if any);

[0171] 1> Cancel the triggered positioning measurement gap activation / deactivation request procedure (if any);

[0172] 1> Cancel the triggered SDT procedure (if any);

[0173] 2> Reset all BFI_COUNTERs; and

[0174] 1> Reset all LBT_COUNTERs.

[0175] Figure 6 FIG. shows various hardware components of a UE (200) according to an embodiment disclosed herein. In an embodiment, the UE (200) includes a processor (210), a communicator (220), a memory (230), and an LTM controller (240). The processor (210) is coupled to the communicator (220), the memory (230), and the LTM controller (240).

[0176] In an embodiment, the LTM controller (240) receives in an RRC message an LTM configuration indicating whether the UE (200) needs to perform one of RLC re - establishment and PDCP recovery during LTM to a candidate cell. In addition, the LTM controller (240) receives a DL MAC CE or a DL L1 message for triggering LTM. In addition, the LTM controller (240) performs MAC operations including full MAC reset and partial MAC reset. In an example, the MAC operation may be, for example but not limited to, cancellation of a UL MAC procedure. The UL MAC procedure includes cancellation of a triggered scheduling request procedure, a triggered buffer status report procedure, a triggered power headroom report procedure, a triggered consistent LBT failure, a triggered BFR, a triggered sidelink buffer status report procedure, a triggered pre - emptive buffer status report procedure, a triggered timing advance report procedure, a triggered recommended bitrate query procedure, a triggered configured uplink grant confirmation, a triggered configured sidelink grant confirmation, a triggered desired protection symbol query, a triggered positioning measurement gap activation request procedure, a triggered positioning measurement gap de - activation request procedure, a triggered small SDT procedure, and reset of all counters for beam failure indication or consistent listen - before - talk failure. In addition, the LTM controller (240) sends (re - transmits) an uplink RRC message, where the uplink RRC message is sent (re - transmitted) within a specified time interval before receiving the DL MAC CE or the DL L1 message. The RRC message sent by the UE (200) is one of UAI, SidelinkUEInformationNR, and MBSInterestIndication. The UAI is re - transmitted by the UE (200) when it is determined that the UE (200) is still configured to provide relevant UE assistance information for the corresponding cell group after LTM completion. In an example, the specified time interval is one second. Based on the received indication, the LTM controller (240) performs one of RLC re - establishment and PDCP recovery.

[0177] In another embodiment, the LTM controller (240) receives a trigger for LTM from the network entity (100). Based on the trigger, the LTM controller (240) performs one or more operations. The one or more operations include UL MAC procedures, resetting all counters of the beam failure indication, listen-before-talk during LTM, and canceling the procedure for triggering the BSR for XR.

[0178] In another embodiment, the LTM controller (240) receives an RRCReconfiguration message from the network entity (100) including a list of LTM candidate configurations to be added or modified, a list of LTM candidate configurations to be released, a measurement configuration for LTM, and reference configuration information. Based on the RRCReconfiguration message, the LTM controller (240) receives a MAC CE from the network entity (100) to switch the UE (200) from the source cell to a candidate cell. In an embodiment, the LTM controller (240) receives a candidateLTM configuration to release the candidateLTM configuration. In an embodiment, the LTM controller (240) receives a candLTM-CellGroupConfigToRemoveList from the network entity (100) including a list of candLTM-CellGroupConfigId to remove all candidateLTM configurations identified by the candLTM-CellGroupConfigId in the candLTM-CellGroupConfigToRemoveList. In an embodiment, the LTM controller (240) receives a candLTM-ReconfigToRemoveList from the network entity (100) including a list of candLTM-ReconfigId to remove all candidateLTM configurations identified by the candLTM-ReconfigId in the candLTM-ReconfigToRemoveList. In another embodiment, the LTM controller (240) receives an L1 measurement configuration for performing L1 measurements for LTM from the network entity (100) in the RRC reconfiguration message. In another embodiment, the LTM controller (240) receives an RRC message indicating to send an RRCReconfigurationComplete upon completion of LTM. In another embodiment, when the UE (200) sends an RRC reconfiguration complete message to the network entity (100), the LTM controller (240) configures the UE (200) to send an RRC message to indicate the completion of the handover.

[0179] In another embodiment, the LTM controller (240) configures a flag indicating whether the UE (200) is performing LTM to complete LTM or the UE is sending RRC Reestablishment during a failure. Further, the LTM controller (240) configures a first timer for performing access on a first target candidate cell. Further, the LTM controller (240) determines the expiration of the first timer when attempting to access the first target candidate cell to complete LTM. The first timer is included in the candidate cell LTM configuration, where the candidate cell LTM configuration includes candLTM-RRCReconfig. Based on this determination, the LTM controller (240) detects that RLF has occurred in the UE (200). Further, the LTM controller (240) attempts to select a suitable cell within the duration of a second timer and selects a cell within the second timer value when determining that the selected cell is a second target candidate cell. Based on the flag, the LTM controller (240) initiates an RRC reestablishment procedure to access the second target candidate cell and indicates in the RRC Reestablishment message that LTM has failed. In another embodiment, based on the flag, the LTM controller (240) completes LTM by sending an L3 message for completing handover.

[0180] In another embodiment, the LTM controller (240) performs cell selection while a timer is running during the RRC reestablishment procedure. Further, the LTM controller (240) removes the configuration for LTM. The configuration includes the candidate cell configuration or the measurement configuration for LTM during the RRC reestablishment procedure. In an embodiment, the LTM controller (240) determines that the UE (200) selects a cell where candLTM-RRCReconfig is available during the reestablishment procedure. Further, the LTM controller (240) sends an LTM completion message to the cell. In another embodiment, the LTM controller (240) makes a determination when sending the LTM completion message or RRC reestablishment based on a flag received from the network entity (100).

[0181] In another embodiment, the LTM controller (240) performs one of receiving an RRC release message and transitioning to RRC_IDLE, or receiving an RRC release with a suspension configuration and transitioning to RRC_INACTIVE, or initiating RRC Reestablishment and completing cell selection while the timer T311 is running. Further, the LTM controller (240) releases the configuration for LTM when receiving one of an RRC release and an RRC release with a suspension configuration, or when initiating RRC establishment or performing cell selection while the timer T311 is running. The configuration is configured via candLTM-Reconfiguation.

[0182] The LTM controller (240) is implemented by analog and / or digital circuitry such as logic gates, integrated circuits, microprocessors, microcontrollers, memory circuits, passive electronic components, active electronic components, optical components, hardwired circuitry, etc., and can optionally be driven by firmware.

[0183] The processor (210) may include one or more processors. The one or more processors may be general-purpose processors such as a central processing unit (CPU), an application processor (AP), etc., a graphics processing unit only such as a graphics processing unit (GPU), a vision processing unit (VPU), and / or an AI-specialized processor such as a neural processing unit (NPU). The processor (210) may include multiple cores and be configured to execute instructions stored in the memory (230).

[0184] In addition, the processor (210) is configured to execute instructions stored in the memory (230) and perform various processes. The communicator (220) is configured for internal communication between internal hardware components and communication with external devices via one or more networks. The memory (230) also stores instructions to be executed by the processor (210). The memory (230) may include non-volatile storage elements. Examples of such non-volatile storage elements may include a magnetic hard disk, an optical disk, a floppy disk, a flash memory, or in the form of an electrically programmable read-only memory (EPROM) or an electrically erasable programmable (EEPROM) memory. Further, in some examples, the memory (230) may be considered a non-transitory storage medium. The term "non-transitory" may indicate that the storage medium is not embodied in a carrier wave or a propagated signal. However, the term "non-transitory" should not be construed to mean that the memory (230) is non-removable. In certain examples, the non-transitory storage medium may store data that can change over time (e.g., in a random access memory (RAM) or a cache memory).

[0185] Although Figure 6 various hardware components of the UE (200) are shown, it should be understood that other embodiments are not limited thereto. In other embodiments, the UE (200) may include fewer or more components. Further, the labeling or naming of the components is for illustrative purposes only and does not limit the scope of the present disclosure. One or more components may be combined together to perform the same or substantially similar functions in the UE (200).

[0186] Figure 7Shows various hardware components of a network entity (100) according to an embodiment disclosed herein. The network entity (100) can be, for example but not limited to, a gNB, an eNB, a New Radio (NR) transceiver, etc. In an embodiment, the network entity (100) includes a processor (110), a communicator (120), a memory (130), and an LTM controller (140). The processor (110) is coupled to the communicator (120), the memory (130), and the LTM controller (140).

[0187] In an embodiment, the LTM controller (140) generates an LTM configuration. Further, the LTM controller (140) indicates one of the following: whether the UE (200) needs to perform RLC re - establishment and PDCP recovery during LTM to a candidate cell, and whether the UE (200) needs to trigger RLC re - establishment during the execution of LTM based on a flag indication. Based on the flag indication, the LTM controller (140) triggers LTM.

[0188] In another embodiment, the LTM controller (140) sends an RRC re - configuration message including a list of LTM candidate configurations to be added or modified, a list of LTM candidate configurations to be released, a measurement configuration for LTM, and reference configuration information. Based on the RRC re - configuration message, the LTM controller (140) receives layer 1 measurements. In an embodiment, the LTM candidate configuration to be added or modified included in the RRC re - configuration message sent by the network entity (100) includes at least one of the following: an identifier and an OCTET STRING containing the RRC re - configuration message, where the UE (200) adds a candidate cell. In an embodiment, the LTM candidate configuration to be released included in the RRC re - configuration message includes an identifier corresponding to the identifier included in the list of LTM candidate configurations, where the UE (200) releases the LTM candidate configuration identified by the identifier. The reference configuration information is an OCTET STRING containing the RRC re - configuration message. Upon receiving the layer 1 measurements, the LTM controller (140) sends a MAC CE to handover the UE (200) from the source cell to the candidate cell.

[0189] In an embodiment, the LTM candidate configuration includes one of the following: a configuration for modifying a radio bearer when performing one of L1 mobility and L2 mobility from the network entity (100), and a measurement configuration of the UE (200) for modifying a measurement configuration when performing L1 / L2 mobility from the network entity (100).

[0190] The LTM controller (140) is implemented by analog and / or digital circuits such as logic gates, integrated circuits, microprocessors, microcontrollers, memory circuits, passive electronic components, active electronic components, optical components, hardwired circuits, etc., and may optionally be driven by firmware.

[0191] The processor (110) may include one or more processors. The one or more processors may be general-purpose processors such as a central processing unit (CPU), an application processor (AP), etc., a graphics processing unit only such as a graphics processing unit (GPU), a vision processing unit (VPU), and / or an AI-specific processor such as a neural processing unit (NPU). The processor (140) may include multiple cores and be configured to execute instructions stored in the memory (130).

[0192] In addition, the processor (110) is configured to execute instructions stored in the memory (130) and perform various processes. The communicator (120) is configured for internal communication between internal hardware components and communication with external devices via one or more networks. The memory (130) also stores instructions to be executed by the processor (110). The memory (130) may include non-volatile storage elements. Examples of such non-volatile storage elements may include a magnetic hard disk, an optical disk, a floppy disk, a flash memory, or in the form of an electrically programmable memory (EPROM) or an electrically erasable programmable (EEPROM) memory. Further, in some examples, the memory (130) may be considered a non-transitory storage medium. The term "non-transitory" may indicate that the storage medium is not embodied in a carrier wave or a propagated signal. However, the term "non-transitory" should not be construed to mean that the memory (130) is immovable. In certain examples, the non-transitory storage medium may store data that can change over time (e.g., in random access memory (RAM) or a cache memory).

[0193] Although Figure 7 various hardware components of the network entity (100) are shown, it should be understood that other embodiments are not limited thereto. In other embodiments, the network entity (100) may include fewer or more components. Further, the labeling or naming of the components is for illustrative purposes only and does not limit the scope of the present disclosure. One or more components may be combined together to perform the same or substantially similar functions in the network entity (100).

[0194] Figure 8 A flowchart (800) is shown, which shows a method for a UE in a wireless network (300) to perform LTM when performing RLC re-establishment and PDCP recovery based on an indication. Operations (802 - 810) are processed by the LTM controller (240).

[0195] At step 802, the method includes receiving in an RRC message an LTM configuration indicating whether the UE (200) needs to perform one of RLC re - establishment and PDCP recovery during LTM to a candidate cell. At step 804, the method includes receiving one of a DL MAC CE or a DL L1 message for triggering LTM. At step 806, the method includes performing a MAC operation including one of a full MAC reset and a partial MAC reset. At step 808, the method includes sending at least one uplink RRC message. The at least one uplink RRC message is sent within a specified time interval before receiving the DL MAC CE or the DL L1 message. At step 810, the method includes performing at least one of RLC re - establishment and PDCP recovery based on the received indication. At step 812, the method includes re - transmitting the uplink RRC message.

[0196] Figure 9 Another flowchart (900) of a method for a UE to perform LTM in a wireless network (300) according to an embodiment disclosed herein is shown. Operations (step 902 and step 904) are handled by an LTM controller (240). At step 902, the method includes receiving a trigger for LTM from a network entity (100). At step 904, the method includes performing operations based on the trigger, where the operations include at least one of the following: a UL MAC procedure, resetting all counters of beam failure indication, listen - before - talk during LTM, and canceling a procedure for a BSR for triggering XR.

[0197] Figure 10 Another flowchart (1000) of a method for a UE implemented by a UE (200) to perform LTM in a wireless network (300) based on an RRCReconfiguration message according to an embodiment disclosed herein is shown. Operations (1002 - 1004) are handled by an LTM controller (240).

[0198] At step 1002, the method includes receiving from a network entity (100) an RRCReconfiguration message including a list of LTM candidate configurations to be added or modified, a list of LTM candidate configurations to be released, a measurement configuration for LTM, and reference configuration information. At step 1004, the method includes receiving a MAC CE from the network entity (100) to switch the UE (200) from a source cell to a candidate cell based on the RRCReconfiguration message.

[0199] Figure 11Another flowchart (1100) is shown of a method for a UE to perform LTM in a wireless network (300) based on a flag, according to an embodiment disclosed herein. Operations (1102 - 1114) are handled by an LTM controller (240).

[0200] In step 1102, the method includes configuring a flag indicating whether the UE (200) is performing LTM to complete LTM or the UE is sending RRC Reestablishment during a failure. In step 1104, the method includes configuring a first timer for performing access on a first target candidate cell. In step 1106, the method includes determining that the first timer has expired when attempting to access the first target candidate cell to complete LTM. In step 1108, the method includes detecting, based on the determination, that an RLF has occurred in the UE (200). In step 1110, the method includes attempting to select a suitable cell within the duration of a second timer, and selecting a cell within the second timer value, and determining that the suitable cell is a second target candidate cell. In step 1112, the method includes initiating an RRC reestablishment procedure to access the second target candidate cell and indicating in the RRC Reestablishment message, based on the flag, that LTM has failed. In step 1114, the method includes completing LTM by sending an RRC Reconfiguration Complete based on the flag.

[0201] Figure 12 Another flowchart (1200) is shown of a method for a UE to perform LTM in a wireless network (300) when performing cell selection and a timer is running, according to an embodiment disclosed herein. Operations (step 1202 and step 1204) are handled by an LTM controller (240). In step 1202, the method includes performing cell selection while a timer is running during an RRC reestablishment procedure. In step 1204, the method includes removing the configuration for LTM. The configuration includes candidate cell configuration or measurement configuration for LTM during the RRC reestablishment procedure.

[0202] Figure 13Another flowchart (1300) shows a method for a UE to perform LTM in a wireless network (300) according to an embodiment disclosed herein. Operations (steps 1302 and 1304) are processed by an LTM controller (240). In step 1302, the method includes performing one of the following: receiving an RRC release message and transitioning to RRC_IDLE, or receiving an RRC release with a suspension configuration and transitioning to RRC_INACTIVE, or initiating RRCReestablishment and completing cell selection while timer T311 is running. In step 1304, the method includes releasing the configuration for LTM when one of an RRC release and an RRC release with a suspension configuration is received, or when initiating RRC establishment or performing cell selection while timer T311 is running.

[0203] Figure 14 A flowchart (1400) shows a method for a network entity (100) to perform LTM in a wireless network (300) based on an LTM configuration according to an embodiment disclosed herein. Operations (1402 - 1406) are processed by an LTM controller (140).

[0204] In step 1402, the method includes generating an LTM configuration. In step 1404, the method includes indicating one of the following: whether the UE (200) needs to perform RLC re - establishment and PDCP recovery during LTM to a candidate cell, and whether the UE (200) needs to trigger RLC re - establishment during the execution of LTM based on a flag indication. In step 1406, the method includes triggering LTM based on a flag indication.

[0205] Figure 15 A flowchart (1500) shows a method for a network entity (100) to perform LTM in a wireless network (300) based on an RRCReconfiguration message according to an embodiment disclosed herein. Operations (1502 - 1506) are processed by an LTM controller (140).

[0206] In step 1502, the method includes sending an RRCReconfiguration message including a list of LTM candidate configurations to be added or modified, a list of LTM candidate configurations to be released, a measurement configuration for LTM, and reference configuration information. In step 1504, the method includes receiving layer 1 measurements based on the RRCReconfiguration message. In step 1506, the method includes sending a MAC CE to switch the UE (200) from the source cell to a candidate cell when the layer 1 measurements are received.

[0207] The provided method can be used in a wireless network to avoid data loss and reduce the latency of data recovery.

[0208] The various actions, behaviors, blocks, steps, etc. in the flowchart (800 - 1500) can be performed in the presented order, in a different order, or simultaneously. Additionally, in some embodiments, some of the actions, behaviors, blocks, steps, etc. can be omitted, added, modified, or skipped without departing from the scope of the present disclosure.

[0209] The embodiments disclosed herein can be implemented by at least one software program that runs on at least one hardware device and performs network management functions to control elements. The elements can be at least one of a hardware device or a combination of a hardware device and software modules.

[0210] The foregoing description of specific embodiments will so fully disclose the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and / or adapt such specific embodiments for various applications without departing from the general concept, and, therefore, such adaptations and modifications should and are intended to be understood as within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Thus, although the embodiments herein have been described in terms of at least one embodiment, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein.

[0211] Although the present disclosure has been described with various embodiments, various changes and modifications can be suggested to those skilled in the art. The present disclosure is intended to cover these changes and modifications that fall within the scope of the appended claims.

Claims

1. A method performed by a terminal, the method comprises: receiving a control message for a mobility LTM configuration triggered by a lower layer, the control message including at least one of first information for at least one LTM candidate cell or second information for a reference configuration; identifying at least one of the first information or the second information based on the control message; and performing a measurement operation of LTM based on at least one of the first information or the second information.

2. The method according to claim 1, wherein, the control message for the LTM configuration further includes third information for the measurement configuration of LTM, and wherein the measurement operation of LTM is performed on at least one resource based on the third information.

3. The method according to claim 1, further comprises: identifying the at least one LTM candidate cell for release in the case where the control message for the LTM configuration further includes fourth information for releasing at least one LTM candidate cell; and performing an operation of releasing the at least one LTM candidate cell.

4. The method according to claim 1, further comprises: receiving fifth information indicating that the terminal sends a radio resource control RRC reconfiguration complete message when the handover is completed; identifying that the handover is successfully completed; and sending an RRC reconfiguration complete message based on the completion of the handover, wherein the control message for the LTM configuration further includes configuration information for at least one radio bearer, and wherein the first information for the at least one candidate cell further includes at least one identifier of the at least one candidate cell.

5. A method performed by a base station, the method comprises: generating a control message for a mobility LTM configuration triggered by a lower layer, the control message including at least one of first information for at least one LTM candidate cell or second information for a reference configuration; and sending the control message for the LTM configuration to a terminal, wherein the measurement operation of LTM is performed based on at least one of the first information or the second information.

6. The method according to claim 5, wherein, the control message for the LTM configuration further includes third information for the measurement configuration of LTM, and wherein the measurement operation of LTM is performed on at least one resource based on the third information.

7. The method according to claim 5, further comprises: sending fifth information to the terminal indicating that the terminal sends a radio resource control RRC reconfiguration complete message when the handover is completed; and receiving an RRC reconfiguration complete message based on the completion of the handover from the terminal according to the fifth information, wherein, in the case where the control message for the LTM configuration further includes fourth information for releasing at least one LTM candidate cell, identifying the at least one LTM candidate cell for release, and the at least one LTM candidate cell is released, wherein the control message for the LTM configuration further includes configuration information for at least one radio bearer, and wherein the first information for the at least one candidate cell further includes at least one identifier of the at least one candidate cell.

8. A terminal, comprising: a transceiver; and at least one processor operatively coupled to the transceiver, the at least one processor being configured to: receive, via the transceiver, a control message for a mobility LTM configuration triggered by a lower layer, the control message including at least one of first information for at least one LTM candidate cell or second information for a reference configuration, identify at least one of the first information or the second information based on the control message, and perform a measurement operation of LTM based on at least one of the first information or the second information.

9. The terminal according to claim 8, wherein, the control message for the LTM configuration further includes third information for the measurement configuration of LTM, and wherein the measurement operation of LTM is performed on at least one resource based on the third information.

10. The terminal according to claim 8, wherein, the at least one processor is further configured to: identify the at least one LTM candidate cell for release in a case where the control message for the LTM configuration further includes fourth information for releasing at least one LTM candidate cell, and perform an operation of releasing the at least one LTM candidate cell.

11. The terminal according to claim 8, wherein, the at least one processor is further configured to: receive, via the transceiver, fifth information indicating that the terminal sends a radio resource control (RRC) reconfiguration complete message when a handover is completed, identify that the handover is successfully completed, and send an RRC reconfiguration complete message via the transceiver based on the completion of the handover, wherein the control message for the LTM configuration further includes configuration information for at least one radio bearer, and wherein the first information for at least one candidate cell further includes at least one identifier of the at least one candidate cell.

12. A base station, comprising: a transceiver; and at least one processor operatively coupled to the transceiver, the at least one processor being configured to: generate a control message for a mobility LTM configuration triggered by a lower layer, the control message including at least one of first information for at least one LTM candidate cell or second information for a reference configuration, and send the control message for the LTM configuration to a terminal via the transceiver, wherein the measurement operation of LTM is performed based on at least one of the first information or the second information.

13. The base station according to claim 12, wherein, the control message for the LTM configuration further includes third information for the measurement configuration of LTM, and wherein the measurement operation of LTM is performed on at least one resource based on the third information.

14. The base station according to claim 12, wherein, in a case where the control message for the LTM configuration further includes fourth information for releasing at least one LTM candidate cell, identify the at least one LTM candidate cell for release, and the at least one LTM candidate cell is released.

15. The base station according to claim 12, wherein, the at least one processor is further configured to: Sending, via a transceiver, fifth information instructing a terminal to send a radio resource control (RRC) reconfiguration complete message when the handover is completed, and Receiving, via the transceiver, an RRC reconfiguration complete message based on the completion of the handover from the terminal according to the fifth information, wherein the control message for LTM configuration further includes configuration information for at least one radio bearer, and wherein the first information for at least one candidate cell further includes at least one identifier of the at least one candidate cell.

Images