Method and apparatus for managing mobility of a user equipment in communication network system

Abstract

The disclosure relates to a 5G or 6G communication system for supporting a higher data transmission rate. The present invention relates to a method and system for managing the mobility of UE (101) in the communication network. Further, the method includes receiving, by the UE (101), a configuration from a network node apparatus (106). The configuration includes a lower-layer triggered mobility (LTM) candidate cell configuration. Further, the method includes detecting, by the UE (101) a condition for logging at least one of radio link failure report (RLF) or successful handover report (SHR). Further, the method may include logging, by the UE, Layer 1 (L1) synchronization signal block (SSB) measurements of the LTM candidate cells, wherein the LTM candidate cells are configured for reporting L1 measurements for the LTM in at least one of a radio link failure (RLF) report and a successful handover report (SHR).

Description

METHOD AND APPARATUS FOR MANAGING MOBILITY OF A USER EQUIPMENT IN COMMUNICATION NETWORK SYSTEM

[0001] The present invention relates to a wireless communication system, and more specifically, it relates to the management of mobility for a User Equipment (UE) within a communication network system.

[0002] 5G mobile communication technologies define broad frequency bands such that high transmission rates and new services are possible, and can be implemented not only in "Sub 6GHz" bands such as 3.5GHz, but also in "Above 6GHz" bands referred to as mmWave including 28GHz and 39GHz. In addition, it has been considered to implement 6G mobile communication technologies (referred to as Beyond 5G systems) in terahertz bands (for example, 95GHz to 3THz bands) in order to accomplish transmission rates fifty times faster than 5G mobile communication technologies and ultra-low latencies one-tenth of 5G mobile communication technologies.

[0003] At the beginning of the development of 5G mobile communication technologies, in order to support services and to satisfy performance requirements in connection with enhanced Mobile BroadBand (eMBB), Ultra Reliable Low Latency Communications (URLLC), and massive Machine-Type Communications (mMTC), there has been ongoing standardization regarding beamforming and massive MIMO for mitigating radio-wave path loss and increasing radio-wave transmission distances in mmWave, supporting numerologies (for example, operating multiple subcarrier spacings) for efficiently utilizing mmWave resources and dynamic operation of slot formats, initial access technologies for supporting multi-beam transmission and broadbands, definition and operation of BWP (BandWidth Part), new channel coding methods such as a LDPC (Low Density Parity Check) code for large amount of data transmission and a polar code for highly reliable transmission of control information, L2 pre-processing, and network slicing for providing a dedicated network specialized to a specific service.

[0004] Currently, there are ongoing discussions regarding improvement and performance enhancement of initial 5G mobile communication technologies in view of services to be supported by 5G mobile communication technologies, and there has been physical layer standardization regarding technologies such as V2X (Vehicle-to-everything) for aiding driving determination by autonomous vehicles based on information regarding positions and states of vehicles transmitted by the vehicles and for enhancing user convenience, NR-U (New Radio Unlicensed) aimed at system operations conforming to various regulation-related requirements in unlicensed bands, NR UE Power Saving, Non-Terrestrial Network (NTN) which is UE-satellite direct communication for providing coverage in an area in which communication with terrestrial networks is unavailable, and positioning.

[0005] Moreover, there has been ongoing standardization in air interface architecture / protocol regarding technologies such as Industrial Internet of Things (IIoT) for supporting new services through interworking and convergence with other industries, IAB (Integrated Access and Backhaul) for providing a node for network service area expansion by supporting a wireless backhaul link and an access link in an integrated manner, mobility enhancement including conditional handover and DAPS (Dual Active Protocol Stack) handover, and two-step random access for simplifying random access procedures (2-step RACH for NR). There also has been ongoing standardization in system architecture / service regarding a 5G baseline architecture (for example, service based architecture or service based interface) for combining Network Functions Virtualization (NFV) and Software-Defined Networking (SDN) technologies, and Mobile Edge Computing (MEC) for receiving services based on UE positions.

[0006] As 5G mobile communication systems are commercialized, connected devices that have been exponentially increasing will be connected to communication networks, and it is accordingly expected that enhanced functions and performances of 5G mobile communication systems and integrated operations of connected devices will be necessary. To this end, new research is scheduled in connection with eXtended Reality (XR) for efficiently supporting AR (Augmented Reality), VR (Virtual Reality), MR (Mixed Reality) and the like, 5G performance improvement and complexity reduction by utilizing Artificial Intelligence (AI) and Machine Learning (ML), AI service support, metaverse service support, and drone communication.

[0007] Furthermore, such development of 5G mobile communication systems will serve as a basis for developing not only new waveforms for providing coverage in terahertz bands of 6G mobile communication technologies, multi-antenna transmission technologies such as Full Dimensional MIMO (FD-MIMO), array antennas and large-scale antennas, metamaterial-based lenses and antennas for improving coverage of terahertz band signals, high-dimensional space multiplexing technology using OAM (Orbital Angular Momentum), and RIS (Reconfigurable Intelligent Surface), but also full-duplex technology for increasing frequency efficiency of 6G mobile communication technologies and improving system networks, AI-based communication technology for implementing system optimization by utilizing satellites and AI (Artificial Intelligence) from the design stage and internalizing end-to-end AI support functions, and next-generation distributed computing technology for implementing services at levels of complexity exceeding the limit of UE operation capability by utilizing ultra-high-performance communication and computing resources.

[0008] Embodiments of the present disclosure is to provide an apparatus and method for effectively providing a service in a wireless communication system.

[0009] In an embodiment, a method performed by a user equipment (UE) in a wireless communication system is provided. The method includes: receiving layer 1 / layer 2 triggered mobility (LTM) configuration information; identifying that a radio link failure (RLF) occurs or that a successful handover occurs; in case that the UE supports an RLF report for an LTM or a successful handover report for the LTM, setting a neighbor cell measurement field to include layer 1 (L1) measurement results for a master cell group (MCG) LTM candidate cells based on the LTM configuration information; and transmitting a report message including the neighbor cell measurement field.

[0010] In an embodiment, a user equipment (UE) in a wireless communication system is provided. The UE includes at least one transceiver; at least one processor communicatively coupled to the at least one transceiver; and at least one memory, communicatively coupled to the at least one processor, storing instructions executable by the at least one processor individually or in any combination to cause the UE to receive layer 1 / layer 2 triggered mobility (LTM) configuration information, identify that a radio link failure (RLF) occurs or that a successful handover occurs, in case that the UE supports an RLF report for an LTM or a successful handover report for the LTM, set a neighbor cell measurement field to include layer 1 (L1) measurement results for a master cell group (MCG) LTM candidate cells based on the LTM configuration information, and transmit a report message including the neighbor cell measurement field.

[0011] In an aspect, the objectives are achieved by providing a method for managing the mobility of UE in the communication network system. Further, the method includes receiving, by the UE, a configuration from a network node apparatus, wherein the configuration includes a lower-layer triggered mobility (LTM) candidate cell configuration. Further, the method includes detecting, by the UE a condition for logging at least one of radio link failure report (RLF) or successful handover report (SHR). Further, the method includes logging, by the UE, Layer 1 (L1) synchronization signal block (SSB) measurements of the LTM candidate cells, wherein the LTM candidate cells are configured for reporting L1 measurements for the LTM in at least one of a radio link failure (RLF) report and a Successful handover report (SHR).

[0012] In another aspect, the objectives are achieved by providing a method for managing the mobility of the UE in the communication network system. Further, the method includes configuring, by a network node apparatus, the UE with a LTM configuration that includes a channel state information (CSI) report configuration for LTM. Further, the method includes receiving, by the network node apparatus from the UE, L1 SSB measurement results for one or more LTM candidate cells in at least one of RLF report and SHR. The L1 SSB measurement results are received based on the UE being configured with the LTM CSI report configuration. Further, the method includes processing, by a network node apparatus, the received L1 SSB measurement results to support at least one of radio link failure optimization or handover failure optimization associated with at least one of LTM cell switch and L3 handover.

[0013] In yet another aspect, the objectives are achieved by providing the UE for managing mobility in the communication network system. Further, the UE includes a memory, a processor, and an LTM measurement log controller. Further, the LTM measurement log controller is coupled to the memory and the processor. The LTM measurement log controller receives a configuration from a network node apparatus. The configuration includes the LTM candidate cell configuration. The LTM measurement log controller detects a condition for logging at least one of RLF or SHR. Further, the LTM measurement log controller logs L1 synchronization signal block (SSB) measurements of the LTM candidate cells, wherein the LTM candidate cells are configured for reporting L1 measurements for the LTM in at least one of the RLF report and a Successful handover report (SHR).

[0014] In yet another aspect, the objectives are achieved by a network node apparatus for managing the mobility of the UE in the communication network system. Further, the network node apparatus includes a memory, a processor, and an LTM measurement log controller. Further, the LTM measurement log controller is coupled to the memory and the processor. The LTM measurement log controller configures the UE with the LTM configuration that includes the CSI report configuration for LTM. Further, the LTM measurement log controller receives L1 synchronization signal block (SSB) measurement results for one or more LTM candidate cells in at least one of a radio link failure (RLF) report and a successful handover report (SHR). The L1 SSB measurement results are received based on the UE being configured with the LTM CSI report configuration. Further, the LTM measurement log controller processes the received L1 SSB measurement results to support at least one of radio link failure optimization or handover failure optimization associated with at least one of LTM cell switch and L3 handover.

[0015] These and other aspects of the embodiments herein will be better appreciated and understood when considered in conjunction with the following description and the accompanying drawings. Itshouldbe understood, however, that the following descriptions, while indicating preferred embodiments and numerous specific details thereof, are given by way of illustration and not of limitation. Many changes and modifications may be made within the scope of the embodiments herein, and the embodiments herein include all such modifications.

[0016] The principal object of the invention herein is to manage the mobility of the UE in a communication network system.

[0017] Yet another object of the invention is to enable logging of Layer 1 (L1) synchronization signal block (SSB) measurements of LTM candidate cells in the UE (101) and reporting the logged L1 measurement results in at least one of the RLF report and the Successful Handover Report (SHR) upon a reporting occasion.

[0018] Yet another object of the invention is to handle T304 timer expiry associated with conditional LTM (CLTM) by reverting back to the UE configuration used in a source PCell except for the Packet Data Convergence Protocol (PDCP) state variables for signaling radio bearers (SRBs) associated with a master cell group (MCG).

[0019] Yet another object of the invention is to enable the network node apparatus to configure LTM candidate cells with ltm-Config, receive L1 SSB measurement results from the UE in RLF reports and SHR, and process the received L1 SSB measurement results to support radio link failure optimization and handover failure optimization associated with LTM cell switch and L3 handover.

[0020] These and other features, aspects, and advantages of the presentinventionare illustrated in the accompanying drawings, throughout which like reference letters indicate corresponding parts in the various figures. The embodiments herein will be better understood from the following description with reference to the drawings, in which:

[0021] FIG 1A is a block diagram that illustrates the UE for managing mobility in a communication network system according to embodiments as disclosed herein.

[0022] FIG 1B is a block diagram that illustrates the network node apparatus for managing the mobility of UE in the communication network system according to an embodiment as disclosed herein.

[0023] FIG 2A is a flowchart that illustrates a method for managing the mobility of UE in the communication network system according to an embodiment as disclosed herein.

[0024] FIG 2B is a flowchart that illustrates a method for managing the mobility of the UE in the communication network system by network node apparatus according to an embodiment as disclosed herein.

[0025] FIG 3 is a flowchart that illustrates a scenario of handling the conditional LTM failure according to an embodiment as disclosed herein.

[0026] FIG 4 is a flowchart that illustrates another scenario for handling the conditional LTM failure according to an embodiment disclosed herein.

[0027] FIG 5 is a flowchart that illustrates reporting L1 measurements in an RLF report according to embodiments as disclosed herein.

[0028] FIG 6 is a flowchart that illustrates reporting L1 measurements in Successful Handover Reports (SHR) according to embodiments as disclosed herein.

[0029] The embodiments herein and the various features and advantageous details thereof are explained more fully with reference to the non-limiting embodiments that are illustrated in the accompanying drawings and detailed in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. Also, the various embodiments described herein are not necessarily mutually exclusive, as an embodiment can be combined with one or more an embodiments to form new embodiments. The term "or" as used herein, refers to a non-exclusiveor, unless otherwise indicated. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein can be practiced and to further enable those skilled in the art to practice the embodiments herein. Accordingly, the examples are not be construed as limiting the scope of the embodiments herein.

[0030] As is traditional in the field, embodiments are described and illustrated in terms of blocks that carry out a described function or functions.　These blocks, which referred to herein as managers, units, modules, hardware components or the like, 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, hardwired circuits and the like, and optionally be driven by firmware and software. The circuits, for example, be embodied in one or more semiconductor chips, or on substrate supports such as printed circuit boards and the like.　The circuits constituting a block be implemented by dedicated hardware, or by a processor (e.g., one or more programmed microprocessors and associated circuitry), or by a combination of dedicated hardware to perform some functions of the block and a processor to perform other functions of the block. Each block of the embodiments be physically separated into two or more interacting and discrete blocks without departing from the scope of the proposed method.　Likewise, the blocks of the embodiments be physically combined into more complex blocks without departing from the scope of the proposed method.

[0031] The accompanying drawings facilitate understanding of various technical features. The embodiments are not limited by these drawings and extend to any alterations, equivalents, and substitutes. Terms like first, second, etc., are used for distinction and do not limit the elements.

[0032] Modern wireless communication systems, including Fifth Generation New Radio (5G NR) systems, are used to support User Equipment (UE) mobility across multiple cells within a communication network. This capability is essential for maintaining continuity of service as a UE moves geographically. Mobility management in 5G NR systems is generally performed through cell reselection procedures when the UE operates in a Radio Resource Control Idle (RRC_IDLE) mode and through handover procedures when the UE operates in a Radio Resource Control Connected (RRC_CONNECTED) mode.

[0033] In the RRC_CONNECTED mode, mobility management is network-controlled and is performed through explicit Radio Resource Control (RRC) signaling initiated by a network node such as next-generation NodeB (gNB). A typical handover procedure in NR includes handover preparation, handover execution, and handover completion. During these stages, the gNB may configure the UE to perform and report radio measurements. Based on the reported measurements or network topology information available at the gNB, an RRC Reconfiguration message is transmitted to initiate handover of the UE from a source cell to a target cell. The UE then accesses the target cell and transmits an RRC Reconfiguration Complete message.

[0034] An alternative mobility mechanism introduced in 3GPP NR Release 16 allows the gNB to configure the UE with execution conditions for triggering a handover. In this scenario, the UE autonomously performs the handover to the target cell upon satisfaction of the configured execution conditions and subsequently transmits the RRC Reconfiguration Complete message. However, such mobility mechanisms continue to rely on Layer 3 signaling involving RRC message exchanges, which may result in increased signaling overhead and latency. Furthermore, during handover execution, the UE may be required to apply a full configuration in accordance with section 5.3.5.11 of 3GPP TS 38.331, thereby increasing signaling complexity.

[0035] In dual connectivity scenarios, the UE may perform a Primary Secondary Cell Group Change (PSCellChange) or a Conditional PSCellChange, which may be configured by a Master Node (MN) or a Secondary Node (SN). In this context, PSCellChange and Conditional PSCellChange are categorized as Layer 3 mobility procedures similar to handover and Conditional Handover (CHO). PSCellChange and Conditional PSCellChange correspond to Secondary Cell Group (SCG) Layer 3 mobility, while handover and CHO correspond to Master Cell Group (MCG) Layer 3 mobility.

[0036] Another mobility mechanism supported in NR includes Conditional Handover with candidate Secondary Cell Groups (SCG(s)), which includes a Primary Cell (PCell) change with PSCell addition or change, executed by the UE when execution conditions associated with both a candidate PCell and an associated candidate PSCell are satisfied. Upon reception of a Conditional Handover configuration with candidate SCG(s), the UE evaluates the execution conditions simultaneously and terminates such evaluation once a PCell change or a PSCell change is triggered.

[0037] Despite the above-described mobility mechanisms, several technical challenges remain unresolved. These challenges include handling UE configuration when a Lower Layer Triggered Mobility (LTM) cell switch failure occurs due to expiry of timer T304, reporting radio measurements in Radio Link Failure (RLF) reports or in Successful Handover Reports (SHR) during radio link failure or handover failure events, and reporting radio measurements in RLF reports or SHR when the UE is configured for Conditional Handover with candidate SCG(s).

[0038] Thus, it is desired to address the above-mentioned disadvantages, issues, or other shortcomings, or at least provide a useful alternative.

[0039] In wireless communication technologies such as 5G NR, user devices are capable of moving across multiple cells within a communication network. Mobility is performed through a cell reselection procedure when the UE operates in the RRC_IDLE mode. Until NR Release 17, mobility in the RRC_CONNECTED mode is performed through a handover procedure. Network-controlled mobility applies to UEs operating in the RRC_CONNECTED mode and requires explicit RRC signaling initiated by a next-gNB.

[0040] Typically, handover in NR comprises three stages: handover preparation, handover execution, and handover completion. The gNB may configure the UE to perform and report radio measurements. Based on the reported measurements or network topology information available at the gNB, an RRC Reconfiguration message is transmitted to initiate handover of the UE from a source cell to a target cell. Subsequently, the UE accesses the target cell and transmits an RRC Reconfiguration Complete message.

[0041] An alternative mobility mechanism introduced in 3GPP NR Release 16 enables the gNB to configure the UE with execution conditions for triggering a handover. Upon satisfaction of the execution conditions, the UE autonomously moves to the target cell and transmits the RRC Reconfiguration Complete message. In all such mobility mechanisms, the UE performs handover through Layer 3 RRC signaling, which results in increased signaling overhead and latency.

[0042] During handover, the UE may be configured to apply a full configuration as part of a Layer 3 handover. When so configured, the UE applies the full configuration in accordance with section 5.3.5.11 of 3GPP Technical Specification TS 38.331. Handover and Conditional Handover (CHO) may be categorized as Layer 3 mobility procedures.

[0043] In dual connectivity scenarios, the UE may perform a Primary Secondary Cell Change (PSCellChange) or a Conditional PSCellChange, which may be configured by either the MN or the SN. In the context of dual connectivity, PSCellChange and Conditional PSCellChange are also categorized as Layer 3 mobility procedures. Specifically, handover, Conditional Handover, PSCellChange, and Conditional PSCellChange correspond to Layer 3 mobility. Further, PSCellChange and Conditional PSCellChange may be referred to as the SCG Layer 3 mobility, while handover and Conditional Handover may be referred to as MCG Layer 3 mobility.

[0044] Another mobility mechanism supported in the NR may include CHO with candidate SCG(s). The CHO with candidate SCG(s) is defined as the PCell change with addition or change of the PSCell, which is executed by the UE when the execution conditions for both the candidate PCell and the associated candidate PSCell are satisfied. Upon reception of the CHO with candidate SCG(s) configuration, the UE initiates simultaneous evaluation of the execution conditions for the candidate PCell(s) and the candidate PSCell(s). The evaluation of the execution conditions is terminated once the PCell change or the PSCell change is triggered. The UE refrains from executing the CHO with candidate SCG(s) until the execution conditions for both the candidate PCell and the associated candidate PSCell are fulfilled.

[0045] In the NR, the UE is configured for the CHO with candidate PSCells when the UE is provided with configuration parameters, including the condExecutionCond and the condExecutionCondPSCell.

[0046] For the CHO with candidate SCG(s), the UE may be configured with two triggering events for the CHO and two triggering events for the associated candidate SCG(s). Further, multiple candidate PSCells may be configured as being associated with the same candidate PCell in [Table 1].

[0047] CondReconfigToAddMod-r16 ::= SEQUENCE {condReconfigId-r16 CondReconfigId-r16,condExecutionCond-r16 SEQUENCE (SIZE (1..2)) OF MeasId OPTIONAL, -- Need McondRRCReconfig-r16 OCTET STRING (CONTAINING RRCReconfiguration) OPTIONAL, -- Cond condReconfigAdd...,[[condExecutionCondSCG-r17 OCTET STRING (CONTAINING CondReconfigExecCondSCG-r17) OPTIONAL -- Need M]],[[condExecutionCondPSCell-r18 SEQUENCE (SIZE (1..2)) OF MeasId OPTIONAL, -- Cond condReconfigCHO-WithSCGsubsequentCondReconfig-r18 SubsequentCondReconfig-r18 OPTIONAL, -- Need MsecurityCellSetId-r18 SecurityCellSetId-r18 OPTIONAL, -- Need Mscpac-ConfigComplete-r18 ENUMERATED {true} OPTIONAL -- Cond CPAC]]}

[0048] The execution condition required to trigger a conditional reconfiguration for CHO CPA intra-SN CPC without MN involvement, MN-initiated inter-SN CPC, MN-initiated subsequent CPAC, or SN-initiated intra-SN subsequent CPAC without MN involvement may be referred to as Further condExecutionCond. When two triggering events (Meas Ids) are configured for a candidate cell, the network ensures that both triggering events refer to the same measObject. The network configures at most one of condEventD1, condEventD2, or condEventT1 for the same candidate cell. For CPA, MN-initiated inter-SN CPC and MN-initiated subsequent CPAC, the network indicates only Meas Id(s) associated with condEventA4. For intra-SN CPC and SN-initiated intra-SN subsequent CPAC without MN involvement, the network indicates only Meas Id(s) associated with condEventA3 or condEventA5.

[0049] Further condExecutionCondPSCell may refer to the execution condition required to be satisfied for the associated PSCell to trigger execution of a conditional reconfiguration for the CHO with candidate SCG(s). The Meas Ids refer to the measConfig associated with the MCG. When two triggering events (Meas Ids) are configured for a candidate cell, the network ensures that both triggering events refer to the same measObject. The network indicates only Meas Id(s) associated with condEventA4.

[0050] A candidate PSCell may be associated with multiple candidate PCells. For the purposes of the present invention, version v18.50 of 3GPP specifications, including TS 38.300, TS 38.331, and TS 38.321, are considered relevant background.

[0051] The 3GPP Release 18 addresses latency and interruption issues associated with mobility procedures through lower-layer (L1 / L2) triggered mobility (LTM). According to 3GPP, an objective of LTM is to enable a serving cell change through L1 and L2 signaling to reduce latency overhead and interruption time. The network, such as the gNB, may configure the UE with multiple candidate cells to enable rapid application of configurations corresponding to the candidate cells. The network may transmit MAC CE signaling or L1 signaling to dynamically switch the UE from a source cell to one of the configured candidate cells. LTM may additionally be triggered based on L1 measurements or L3 measurements.

[0052] The 3GPP proposes performing LTM without resetting lower layers, including MAC, to avoid data loss and reduce additional delay associated with data recovery where possible. The gNB may provide an LTMCandidateConfiguration that configures LTM candidate cells through a single RRCReconfiguration message for a candidate target cell or through one CellGroupConfig for each candidate target cell or through any similar RRC structure or IE containing corresponding fields. For example, a new IE LTM-CandidateConfig may be defined as an Abstract Syntax Notation One (ASN1) sequence including CellGroupConfig and one or more additional information elements in the RRCReconfiguration. The gNB (gNB used in this invention can be any Radio Access Network node or network node or base station- for e.g. 6G base station) may further release or modify the candidate configurations. The UE may store the LTM configuration associated with one or more other candidate cells even after moving to a candidate cell through the LTM.

[0053] The LTM process is guarded by a timer referred to as an LTM cell switch timer. When the UE is unable to successfully complete the LTM within a duration defined by the LTM cell switch timer, the LTM is considered to have failed. In NR, the LTM cell switch timer corresponds to T304, which is also used for mobility procedures, including L3 handover, SCG addition, PSCell change, and conditional mobility. Behavior of the UE with respect to the start, stop, and expiry of the T304 timer is specified in TS 38.331.

[0054] The gNB may provide the LTMCandidateConfiguration that configures the LTM candidate cells through one RRCReconfiguration message for a candidate target cell or through one CellGroupConfig for each candidate target cell. Alternatively, the LTMCandidateConfiguration may be provided through any similar RRC structure or Information Element (IE) containing corresponding fields. For example, a new IE LTM-CandidateConfig may be defined as an ASN1 sequence including CellGroupConfig and one or more relevant information elements within the RRCReconfiguration. The gNB may further release or modify the candidate configurations.

[0055] The UE may store the LTM configuration associated with one or more other candidate cells even after moving to a candidate cell through the LTM. The gNB may provide the UE with configurations for performing LTM measurements for different candidate frequencies and candidate cells, as well as configurations for reporting based on the performed LTM measurements.

[0056] The gNB provides a reference configuration, an L1 measurement configuration, and a candidate cell configuration for the LTM. While 3GPP Release 18 supports the LTM within the same gNB central unit (CU), 3GPP Release 19 plans to introduce inter-CU LTM. For an SN LTM, both intra-SN LTM and inter-SN LTM may be configured simultaneously. For an inter-CU SCG LTM configuration, the SN generates an SCG part configuration, and the MN includes the SCG part configuration in an MN RRC configuration message. For the inter-CU SCG LTM, the LTM cell switch command MAC CE is transmitted by the source SN. Upon execution of the inter-SN SCG LTM, the UE transmits an MN RRCReconfigurationComplete message to the MN, the MN RRCReconfigurationComplete message including an SN RRCReconfigurationComplete message.

[0057] L3 measurements are typically generated from beam level L1 measurements by applying filtering using quanity configuration, measurement object configuration, reporting configuration etc.

[0058] Network implementation avoids simultaneous execution of both an MCG LTM and an SCG LTM. In Release 19, an inter-CU MCG LTM with an intra-SN PSCell change is supported. With respect to dual connectivity, the following scenarios may coexist: an inter-MN LTM and an intra-SN LTM, and an inter-SN LTM and an intra-MN LTM.

[0059] For the UE operating in dual connectivity, both the MN and the SN may provide the LTM configuration, including the LTM candidate cells and an LTM reference configuration. The MN and the SN may further provide the LTM measurement configurations to the UE. The SN transmits an inter-node RRC message CG-Config to the MN to inform the MN of the configurations used by the SN and to request configuration information that the SN is permitted to use. The MN transmits an inter-node RRC message CG-ConfigInfo to the SN to inform the SN of the configurations that the SN is allowed to use, as well as additional information.

[0060] L3 measurements are generated using L1 measurements and may be reported using measurement reports. Base station such as gNB may decide to trigger LTM based on the L3 measurements also.

[0061] The 3GPP Release 19 supports conditional LTM. The UE may be provided with one or more conditions based on L3 measurements or L1 measurements, and upon satisfaction of the one or more conditions, the UE executes an LTM cell switch.

[0062] In the prior art, the following structure in [Table 2] is used for defining the conditional LTM.

[0063] -- ASN1START-- TAG-LTM-CANDIDATE-STARTLTM-Candidate-r18 ::= SEQUENCE {ltm-CandidateId-r18 LTM-CandidateId-r18,ltm-CandidatePCI-r18 PhysCellId OPTIONAL, -- Need Mltm-SSB-Config-r18 LTM-SSB-Config-r18 OPTIONAL, -- Need Mltm-CandidateConfig-r18 OCTET STRING (CONTAINING RRCReconfiguration) OPTIONAL, -- Need Mltm-ConfigComplete-r18 ENUMERATED {true} OPTIONAL, -- Need Rltm-EarlyUL-SyncConfig-r18 OCTET STRING (CONTAINING EarlyUL-SyncConfig-r18) OPTIONAL, -- Need Rltm-EarlyUL-SyncConfigSUL-r18 OCTET STRING (CONTAINING EarlyUL-SyncConfig-r18) OPTIONAL, -- Need Rltm-TCI-Info-r18 LTM-TCI-Info-r18 OPTIONAL, -- Need Mltm-NoResetID-r18 INTEGER (1..maxNrofLTM-Configs-plus1-r18) OPTIONAL, -- Need Mltm-UE-MeasuredTA-ID-r18 INTEGER (1..maxNrofLTM-Configs-plus1-r18) OPTIONAL, -- Need M...,[[ltm-NoSecurityChangeID-r19 INTEGER (1..maxNrofLTM-Configs-plus1-r18) OPTIONAL, -- Need Mcltm-ExecutionConditions-r19 SetupRelease {CLTM-ExecutionConditions-r19} OPTIONAL -- Need M]]}LTM-SSB-Config-r18 ::= SEQUENCE {ssb-Frequency-r18 ARFCN-ValueNR,subcarrierSpacing-r18 SubcarrierSpacing,ssb-Periodicity-r18 ENUMERATED {ms5, ms10, ms20, ms40, ms80, ms160, spare2, spare1} OPTIONAL, -- Need Rssb-PositionsInBurst-r18 CHOICE {shortBitmap BIT STRING (SIZE (4)),mediumBitmap BIT STRING (SIZE (8)),longBitmap BIT STRING (SIZE (64))} OPTIONAL, -- Need Rss-PBCH-BlockPower-r18 INTEGER (-60..50) OPTIONAL, -- Need R...}CLTM-ExecutionConditions-r19 ::= SEQUENCE (SIZE (1..maxNrofLTM-Configs-r18)) OF ExecutionConditions-r19ExecutionConditions-r19 ::= SEQUENCE {ltm-CandidateId-r19 LTM-CandidateId-r18,executionCondition-r19 CHOICE {l1-Conditions-r19 LTM-CSI-ReportConfigId-r18,l3-Conditions-r19 SEQUENCE (SIZE (1..2)) OF MeasId} OPTIONAL, -- Need R...}ratherLTM-Candidatefield descriptionsltm-CandidateConfigThis field includes an RRCReconfiguration message used to configure an LTM candidate configuration.ltm-CandidatePCIThis field identifies the PCI of the SpCell of the LTM candidate configuration contained inltm-CandidateConfig.ltm-EarlyUL-SyncConfig, ltm-EarlyUL-SyncConfigSULA configuration used to perform the early UL synchronization procedure over an UL or SUL carrier.ltm-NoResetIDIf the network configures this field for one LTM candidate configuration, the network configures also for all LTM candidate configurations withinltm-CandidateToAddModListinLTM-Configand ensures that the UE has stored a value forltm-ServingCellNoResetIDwithinVarLTM-ServingCellNoResetID.ltm-NoSeurityChangeIDIf the network configures this field for one LTM candidate configuration, the network configures also for all LTM candidate configurations withinltm-CandidateToAddModListinLTM-Configand ensures that the UE has stored a value forltm-ServingCellNoSecurityChangeIDwithinVarLTM-ServingCellNoSecurityChangeID.ltm-UE-MeasuredTA-IDIf the network configures this field for one LTM candidate configuration, the network configures also for all LTM candidate configurations withinltm-CandidateToAddModListinLTM-Configand ensures that the UE has stored a value forltm-ServingCellUE-MeasuredTA-IDwithinVarLTM-ServingCellUE-MeasuredTA-ID. This field is absent iftag2is present for this LTM candidate configuration.

[0064] Further, the LTM-Config may be the IE used to provide the LTM configuration in [Table 3].

[0065] LTM-Config information element-- ASN1START-- TAG-LTM-CONFIG-STARTLTM-Config-r18 ::= SEQUENCE {ltm-ReferenceConfiguration-r18 SetupRelease {ReferenceConfiguration-r18} OPTIONAL, -- Need Mltm-CandidateToReleaseList-r18 SEQUENCE (SIZE (1..maxNrofLTM-Configs-r18)) OF LTM-CandidateId-r18 OPTIONAL, -- Need Nltm-CandidateToAddModList-r18 SEQUENCE (SIZE (1..maxNrofLTM-Configs-r18)) OF LTM-Candidate-r18 OPTIONAL, -- Need Nltm-ServingCellNoResetID-r18 INTEGER (1..maxNrofLTM-Configs-plus1-r18) OPTIONAL, -- Need Nltm-CSI-ResourceConfigToAddModList-r18 SEQUENCE (SIZE (1..maxNrofLTM-CSI-ResourceConfigurations-r18)) OF LTM-CSI-ResourceConfig-r18OPTIONAL, -- Need Nltm-CSI-ResourceConfigToReleaseList-r18 SEQUENCE (SIZE (1..maxNrofLTM-CSI-ResourceConfigurations-r18)) OF LTM-CSI-ResourceConfigId-r18OPTIONAL, -- Need NattemptLTM-Switch-r18 ENUMERATED {true} OPTIONAL, -- Cond LTM-MCGltm-ServingCellUE-MeasuredTA-ID-r18 INTEGER (1..maxNrofLTM-Configs-plus1-r18) OPTIONAL, -- Need N...,[[ltm-ServingCellNoSecurityChangeID-r19 INTEGER (1..maxNrofLTM-Configs-plus1-r18) OPTIONAL, -- Need Nltm-SK-Counters-r19 SetupRelease {SK-CounterList-r19} OPTIONAL, -- Need Mcltm-ServingCellExecutionConditions-r19 SetupRelease {CLTM-ExecutionConditions-r19} OPTIONAL -- Need M]]}SK-CounterList-r19 ::= SEQUENCE {sk-CounterList-r19 SEQUENCE (SIZE (1..maxSK-Counter-r18)) OF SK-Counter}LTM-ConfigSCG-r19 ::= SEQUENCE {ltm-ConfigurationSCG-r19 OCTET STRING (CONTAINING LTM-Config-r18) OPTIONAL, -- Need R}-- TAG-LTM-CONFIG-STOP-- ASN1STOPnonCriticalExtension SEQUENCE {} OPTIONAL}CG-ConfigInfo-v19xy-IEs ::= SEQUENCE {ltm-ReferenceConfiguration-r19 ReferenceConfiguration-r18 OPTIONAL,nonCriticalExtension SEQUENCE {} OPTIONAL}

[0066] The 3GPP specifications, including TS 38.300, TS 38.331, and TS 38321 version 18.5.0, are considered relevant background. In an embodiment, self-optimization in the NR may include the 5G NR radio access network. The 5G NR radio access network, also referred to as an NG-RAN, includes a plurality of NR base stations known as gNBs. These gNBs may be interconnected with one another through an Xn interface and may further be connected to one or more core network entities, including an Access and Mobility Management Function (AMF) and a User Plane Function (UPF). Each gNB may be logically divided into a centralized unit (CU) and a distributed unit (DU). The CU supports higher-layer protocol functions, including Service Data Adaptation Protocol (SDAP), Packet Data Convergence Protocol (PDCP), and RRC, while the DU supports lower-layer protocol functions, including RLC, MAC, and a physical layer. Each gNB may support multiple cells, with the multiple cells serving a plurality of UEs.

[0067] A large number of algorithms and configuration parameters are utilized in the NG-RAN. Identification of optimal radio parameters is complex, and network operators have conventionally relied on manual techniques, such as drive tests, to determine the optimal parameters. Such manual parameter tuning is resource-intensive and depends on multiple factors, including, for example, the number of users, the number of neighboring cells, the maximum throughput in a cell, and the average throughput in the cell. When a neighboring gNB (In this invention gNB also means any node with a similar functionality, such as a 6G radio access network node, 6G base station) is installed or a new service is introduced, many of the manual tuning operations are repeated. To address these issues, the 3GPP introduced Self-Organizing Network (SON) techniques in wireless technologies, including NR. The SON was first introduced in 3GPP Release 9 for LTE. The SON solutions are generally classified into self-configuration, self-optimization, and self-healing. A SON architecture may be implemented as a centralized solution, a distributed solution, or a hybrid solution. Mobility Robustness Optimization is the SON technique used to optimize parameters associated with mobility.

[0068] According to the 3GPP specifications, such as TS 38.300 V17.3.0, Mobility Robustness Optimization (MRO) is used to detect and enable the correction of several problems, including connection failure caused by intra-system or inter-system mobility, an inter-system unnecessary handover such as a premature inter-system handover from the NR to an Evolved Universal Terrestrial Radio Access Network (E-UTRAN) in the absence of a radio link failure, and inter-system handover ping-pong. The MRO provides means to distinguish the problems described above from NR coverage-related problems and other problems not related to mobility.

[0069] In an embodiment, a Radio Link Failure Reporting may be an RLF procedure. The RLF procedure is provided to allow a UE to regain the radio link in the event of a failure. Upon triggering the RLF procedure, the UE performs RRC re-establishment, where the UE performs cell selection to identify a suitable cell, the same cell being a possible outcome, and establishes a connection with the identified cell. A handover failure causes the UE to declare the RLF and is treated as a radio link failure in certain cases, with handover failures included in the RLF report. When the RLF is associated with the SCG, the UE may include information for the SON and MDT in a SCGFailureInformation element.

[0070] In an embodiment, a Successful Handover Report (SHR) provides the network with information regarding a successful handover. The SHR may provide the network with potential insights even when a handover is completed successfully, as a successful handover does not necessarily indicate that the procedure was entirely problem-free, for example, when the handover requires an extended duration to complete. Another type of successful report is a Successful PSCell Change or Addition report, also referred to as an SPR. The SPR contains similar information to the SHR and is generated when the UE performs a successful addition of an SCG or a change of the PSCell of the SCG.

[0071] The 3GPP TS 38.331 version 18.30 is also considered relevant background. The present invention addresses several issues related to mobility. A first issue concerns how the UE may handle its configuration during a Long-Term Mobility (LTM) cell switch failure caused by T304 expiry. A second issue concerns how the UE may report measurements in an RLF report or an SHR during a radio link failure or a handover failure. A third issue concerns the manner in which the UE may report measurements in the RLF report or the SHR when configured for the CHO with candidate SCGs.

[0072] FIG. 1A is a block diagram illustrating a user equipment (UE) configured to manage mobility in a wireless communication network, according to embodiments disclosed herein.

[0073] Examples of the UE (101) include, but are not limited to, consumer electronic devices (such as mobile phones and smartphones), tablets, wearable devices, computing devices (such as laptops, notebooks, desktops, workstations, etc.), Internet-of-Things (IoT) devices, automotive systems (such as connected cars, autonomous vehicles, and Vehicle-to-Everything (V2X) communication devices), enterprise devices (such as robotics), specialized equipment (such as medical devices and public safety devices), and media devices (such as gaming consoles and streaming devices).

[0074] Examples of the wireless communication network include, but are not limited to, cellular networks (such as 2G, 3G, 4G, 5G, Beyond 5G (B5G) / 6G, or other advanced cellular networks), local area networks (LANs) (such as Wi-Fi and Li-Fi), personal area networks (PANs) (such as Bluetooth, Zigbee, and Z-Wave), wide area networks (WANs) (such as satellite communication networks, Long Range Wide Area Networks, Narrowband IoT, and other low-bandwidth communication networks for IoT), metropolitan area networks (MANs), machine-to-machine (M2M) networks, ad hoc networks, and mesh networks.

[0075] The UE (101) includes a processor (102), an input / output (I / O) interface (103), a memory (104), and a Lower Layer Triggered Mobility (LTM) measurement log controller (105). The processor (102) is communicatively coupled to the memory (104), the I / O interface (103), and the LTM measurement log controller (105). The processor (102) is configured to execute instructions stored in the memory (104) and to perform one or more operations described herein. The processor (102) may include one or more processors, and may be implemented as a general-purpose processor (e.g., a central processing unit (CPU) or application processor (AP)), a graphics processing unit (GPU), a vision processing unit (VPU), and / or an artificial intelligence (AI) processor such as a neural processing unit (NPU).

[0076] The memory (104) includes storage locations addressable by the processor (102). The memory (104) may include volatile memory and / or non-volatile memory, and may include one or more computer-readable storage media. Examples of non-volatile storage elements include magnetic hard disks, optical disks, flash memory, and electrically programmable memories (EPROM) or electrically erasable and programmable memories (EEPROM). The memory (104) stores configuration information and parameters associated with Long-Term Mobility (LTM) operations for the UE (101). For example, the memory (104) may store: ltm-Config for configuring LTM candidate cells for a master cell group (MCG); LTM candidate cell configurations including synchronization signal block (SSB) configurations (LTM-SSB-Config-r18); LTM-CSI-ReportConfig for reporting Layer 1 (L1) measurements; LTM-CSI-ResourceConfig for channel measurement associated with each reporting setting of ltm-CSI-ReportConfig; radio link failure (RLF) report data structures; Successful handover report (SHR) data structures; logged L1 SSB measurements including SS / PBCH block-based L1-RSRP measurement results; measResultL1-NeighCells for RLF reports; neighCellsMeasL1ListNR for the Successful Handover Reports (SHR); packet data convergence protocol (PDCP) state variables for signaling radio bearers (SRBs) associated with the MCG; T304 timer configuration for cell-level transition measurements (CLTM); attemptLTM-Switch configuration; source primary cell (PCell) configuration parameters; and UE configuration data for mobility management.

[0077] The I / O interface (103) is configured to transmit and receive information between the UE (101) and one or more external or peripheral devices. The peripheral devices may include input / output devices associated with the UE (101).

[0078] The LTM measurement log controller (105) is coupled to the memory (104) and the processor (102). In an embodiment, the LTM measurement log controller (105) is implemented as an integrated circuit within the UE (101) and is configured to manage LTM measurement logging and reporting data for mobility management. In an embodiment, the LTM measurement log controller (105) includes a multi-core architecture in which different cores are configured to perform respective tasks, such as: logging L1 SSB measurements (e.g., SSB-RSRP) for LTM candidate cells configured using LTM-SSB-Config-r18; detecting RLF and / or SHR conditions; generating RLF reports and SHR that include L1 measurement results (e.g., SS / PBCH block-based L1-RSRP measurement quantities) on reporting occasions; managing measResultL1-NeighCells for RLF reports and neighCellsMeasL1ListNR for SHR; handling expiry of the T304 timer for CLTM; and, upon T304 expiry, reverting to the source PCell configuration while maintaining PDCP state variables for SRBs associated with the MCG, as applicable. In an embodiment, the LTM measurement log controller (105) includes analog and digital components to improve measurement logging timing, measurement accuracy, and reporting precision for the LTM mechanism. For example, the analog components may include a clock and timing reference circuit, and the digital components may include a microcontroller unit (MCU) and / or a digital signal processor (DSP) configured to manage L1 SSB measurement logging, process LTM-CSI-ReportConfig parameters, generate RLF and SHR reports including L1 measurement results, and manage configuration reversion based on PDCP re-establishment status during LTM cell switch failures.

[0079] Further, the LTM measurement log controller (105) logs the L1 SSB measurements of LTM candidate cells. These measurements include signal strength and quality metrics such as the Reference Signal Received Power (RSRP) and Signal-to-Interference-plus-Noise Ratio (SINR). Further, the LTM candidate cells are configured for reporting L1 measurements for the LTM in at least one of a radio link failure (RLF) report and the Successful handover report (SHR). The configuration parameters for these reports are defined in the network's measurement configuration settings, which specify the measurement intervals and thresholds. Further, the LTM measurement log controller (105) detects at least one of the RLF report or the Successful Handover Report (SHR) and includes in at least one of the RLF report and the SHR L1 measurement results based on the logged L1 SSB measurements for at least one of the configured LTM candidate cells upon a reporting occasion for at least one of the RLF report or the SHR. The controller ensures that the measurements are accurately time-stamped and correlated with the specific events that triggered the reports. The LTM measurement log controller (105) determines whether a T304 timer associated with CLTM in the UE (101) is expired and reverts back to the UE (101) configuration used in the source PCell upon expiration of the T304 timer associated with the CLTM except for the PDCP state variables for SRBs associated with the MCG. This reversion process includes restoring the radio resource control (RRC) parameters and re-establishing the connection with the source PCell.

[0080] In an embodiment, the logged L1 SSB measurements include the L1 SSB-RSRP measurement results. These results are critical for assessing the signal quality and making handover decisions. Further, the LTM measurement log controller (105) logs the L1 SSB measurements for LTM candidate cells configured with an SSB configuration within the LTM candidate cell configuration. This configuration includes parameters such as the SSB periodicity, beamforming settings, and measurement gaps. Further, the LTM measurement log controller (105) logs the L1 measurements for LTM in the RLF report for candidates configured with LTM-SSB-Config-r18 in NR. This ensures compatibility with the latest 5G NR standards and enhances the reliability of the measurements. Further, the LTM measurement log controller (105) logged L1 measurement results comprise SS / PBCH block-based L1-RSRP measurement quantities. These quantities are derived from the synchronization signal and physical broadcast channel blocks, providing a comprehensive view of the cell's signal environment. Further, the LTM measurement log controller (105) avoids logging L1 measurements when an LTM cell switch is based on L3 measurements. This selective logging helps in reducing unnecessary data collection and processing overhead.

[0081] Further, the LTM measurement log controller (105) is configured for reporting L1 measurements for LTM through CSI reports, and each Reporting Setting ltm-CSI-ReportConfig is associated with an LTM-CSI-ResourceConfig for channel measurement. These configurations define the resources and parameters for channel state information (CSI) reporting, ensuring that the measurements are aligned with the network's requirements. Further, the LTM measurement log controller (105) includes L1 measurement results in at least one of the RLF report and the SHR that are measurement results at the time of failure of LTM cell switch or L3 handover or radio link failure and are allowed to be different from any value previously reported in CSI reports. This flexibility ensures that the most recent and relevant measurements are reported, even if they differ from earlier reports. Further, the LTM measurement log controller (105) includes the L1 measurement results in the RLF report for a candidate cell configured for reporting L1 measurements for LTM even if the L1 measurement results for that candidate cell are not reported in CSI reports for LTM, including a case where the L1 measurement results are not reported because the network did not request them. This ensures that all relevant measurements are captured and reported, regardless of the network's immediate reporting requirements.

[0082] Further, the LTM measurement log controller (105), when the UE (101) supports RLF-Report for MCG LTM cell switch, includes the L1 measurement results in the RLF report for each neighbor MCG LTM candidate cell if SS / PBCH block-based L1-RSRP measurement results performed based on LTM-CSI-ReportConfig are available, setting measResultL1-NeighCells to include all the available SS / PBCH block-based L1-RSRP measurement results. This comprehensive reporting ensures that the network has a complete view of the signal environment for all neighboring cells. Further, the LTM measurement log controller (105), when the UE (101) supports a successful handover report for MCG LTM cell switch and the UE (101) was configured with ltm-Config including LTM-CSI-ReportConfig associated with the MCG when connected to the source PCell, includes the L1 measurement results in the SHR for each neighbor MCG LTM candidate cell if SS / PBCH block-based L1-RSRP measurement results are available, setting neighCellsMeasL1ListNR to include all the available SS / PBCH block-based L1-RSRP measurement results of the best measured cells other than the source PCell or target PCell. This ensures that the handover decision is based on the most accurate and up-to-date measurements.

[0083] Further, the LTM measurement log controller (105) logs and reports the L1 measurements in the SHR when the UE (101) is configured specifically for reporting L1 measurements for LTM through CSI reports. This configuration ensures that the measurements are collected and reported in a standardized manner, facilitating network optimization. Further, the LTM measurement log controller (105) includes the L1 measurement results in the SHR for a candidate cell when mobility that triggered the SHR is an L3 handover and not LTM cell switch as long as the UE (101) is configured for reporting L1 measurements for LTM for that candidate cell. This ensures that the measurements are relevant to the specific mobility event that triggered the report. Further, the LTM measurement log controller (105), when attemptLTM-Switch is configured and the T304 of the MCG expiry is caused by an LTM cell switch execution triggered by an indication from lower layers or upon fulfillment of at least one of CLTM evaluation conditions and LTM cell switch execution conditions, performs said reverting back to the UE (101) configuration used in the source PCell except for the PDCP state variables for SRB(s) associated with the MCG. This ensures that the UE (101) can quickly revert to a stable configuration, minimizing disruption to the user experience.

[0084] FIG. 1B is a block diagram illustrating a network node apparatus (106) configured to manage mobility of a UE (101) in a communication network, according to embodiments disclosed herein.

[0085] The network node apparatus (106) includes hardware and / or software components that facilitate communication between the UE and the network infrastructure. Examples of the network node apparatus (106) include, but are not limited to, radio access network (RAN) nodes such as base stations (e.g., macro cells, small cells, pico cells, femtocells), antenna and RF units (e.g., MIMO and beamforming units), and network-side mobility control entities. In an embodiment, the network node apparatus (106) further includes and / or is coupled to core network equipment (e.g., MMEs, S-GWs, P-GWs in 4G; AMFs, UPFs in 5G), edge computing nodes (e.g., MEC servers), transport / backhaul equipment (e.g., fiber links, microwave relays, Ethernet switches), network management systems and operation support systems (NMS / OSS), and security elements (e.g., firewalls, IDS, AAA servers). In 5G architectures, the network node apparatus (106) may include or be implemented as a centralized unit (CU), distributed unit (DU), and / or a radio unit (RU), and may support network slicing and virtualization technologies such as NFV and SDN.

[0086] The network node apparatus (106) includes a processor (107), an input / output (I / O) interface (108), a memory (109), and an LTM measurement log controller (110). The processor (107) is communicatively coupled to the memory (109), the I / O interface (108), and the LTM measurement log controller (110). The processor (107) is configured to execute instructions stored in the memory (109) and to perform operations described herein. The processor (107) may include one or more processors and may be implemented as a general-purpose processor (e.g., CPU or AP), a GPU, a VPU, and / or an AI processor such as an NPU.

[0087] The memory (109) includes storage locations addressable by the processor (107). The memory (109) may include volatile and / or non-volatile memory and may include one or more computer-readable storage media. Examples of non-volatile storage elements include magnetic hard disks, optical disks, flash memory, and electrically programmable memories (EPROM) or electrically erasable and programmable memories (EEPROM). The memory (109) stores configuration information and parameters associated with Long-Term Mobility (LTM) operations and mobility management for the UE (101). For example, the memory (109) may store: ltm-Config for configuring LTM candidate cells for a master cell group (MCG) and for configuring the UE (101) to report Layer 1 (L1) measurements for LTM in at least one of a radio link failure (RLF) report or a Successful handover report (SHR); synchronization signal block (SSB) configuration information for at least one LTM candidate cell within the LTM candidate cell configuration, including LTM-SSB-Config-r18; LTM-CSI-ReportConfig in which each reporting setting ltm-CSI-ReportConfig is associated with an LTM-CSI-ResourceConfig for channel measurement; received RLF reports including measResultL1-NeighCells; received SHR including neighCellsMeasL1ListNR; L1 SSB measurement results for configured LTM candidate cells; attemptLTM-Switch configuration; mobility execution timer configuration including T304 for cell-level transition measurements (CLTM); and mobility parameters for radio link failure optimization and / or handover failure optimization associated with at least one of LTM cell switch or Layer 3 (L3) handover.

[0088] The I / O interface (108) is configured to transmit and receive information between the network node apparatus (106) and one or more external devices, peripheral devices, and / or other network entities. The I / O interface (108) may include one or more wired and / or wireless interfaces for communicating with the UE (101), other RAN nodes, and / or core network nodes.

[0089] The LTM measurement log controller (110) is a dedicated hardware controller implemented as an integrated circuit within the network node apparatus (106). In an embodiment, the LTM measurement log controller (110) is implemented as an ASIC or FPGA block integrated with the network node modem / baseband and / or RAN processing circuitry. The LTM measurement log controller (110) is electrically coupled to the processor (107) and the memory (109) via one or more on-chip buses and / or a memory-mapped register interface, and is configured to perform time-critical LTM configuration provisioning, report reception handling, and report processing functions with deterministic latency.

[0090] In an embodiment, based on the processed L1 SSB measurement results and indicated failure conditions, the LTM measurement log controller (110) is configured to support radio link failure optimization and / or handover failure optimization associated with at least one of an LTM cell switch or an L3 handover. For example, the LTM measurement log controller (110) may adjust one or more mobility parameters and / or provide updated configuration outputs depending on whether a received report indicates a failure associated with LTM cell switch execution.

[0091] In an embodiment, the LTM measurement log controller (110) includes a combination of analog and digital circuits to improve timing determinism and processing accuracy of LTM report reception and handling. For example, analog components may include a clock and timing reference circuit, and digital components may include hardware state machines, dedicated parsing logic, and optionally an embedded microcontroller unit (MCU) and / or a digital signal processor (DSP) for configurable control, while the report reception, extraction, buffering, and timer supervision functions remain implemented in dedicated hardware circuits as described above.

[0092]

[0093]

[0094] Further, the LTM measurement log controller (110) provides to the UE (101) ltm-Config that configures LTM candidate cells for an MCG and configures the UE (101) for reporting L1 measurements for LTM in at least one of an RLF report and the Successful handover report (SHR). Additionally, the LTM measurement log controller (110) receives the measurements related to LTM from the UE to perform optimisations. Further, the LTM measurement log controller (110) receives at least one of the RLF report or the SHR including L1 SSB measurement results for at least one of the configured LTM candidate cells. These reports contain detailed signal strength and quality metrics, such as Reference Signal Received Power (RSRP) and / or Signal-to-Interference-plus-Noise Ratio (SINR), which are critical for evaluating the performance of the LTM towards candidate cells. Further, the LTM measurement log controller (110) processes the received L1 SSB measurement results to support at least one of radio link failure optimization or handover failure optimization associated with at least one of LTM cell switch and L3 handover. This processing includes analyzing the measurement data to identify patterns or anomalies that could indicate potential issues, and adjusting network parameters to mitigate these issues.

[0095] Further, the LTM measurement log controller (110) configures within the LTM candidate cell configuration an SSB configuration for at least one LTM candidate cell through the ltm-Config. This configuration includes specifying the SSB periodicity, beam parameters, and frequency to perform LTM. The SSB configuration is tailored to the specific characteristics of each LTM candidate cell, taking into account factors such as cell size, user density, and interference levels.

[0096] Further, the LTM measurement log controller (110) SSB configuration comprises LTM-SSB-Config-r18 in NR or equivalent structure in other radio access technologies. This configuration version includes advanced features such as enhanced beam management, improved synchronization signal design, and support for higher frequency bands. Further, the SSB configuration in the LTM measurement log controller (110) includes LTM-SSB-Config-r18. This ensures that the UE (101) can effectively decode the SSB signals and perform accurate measurements, even in challenging radio environments. The LTM-SSB-Config-r18 also supports advanced MIMO techniques, enabling higher data rates and better spectral efficiency.

[0097] Further, the ltm-Config in the LTM measurement log controller (110) includes LTM-CSI-ReportConfig and each Reporting Setting ltm-CSI-ReportConfig is associated with a LTM-CSI-ResourceConfig for channel measurement. The LTM-CSI-ReportConfig specifies the reporting criteria, such as periodicity and triggering conditions, for Channel State Information (CSI) reports. Each LTM-CSI-ResourceConfig defines the resources, such as frequency and time slots, allocated for CSI measurements. This configuration ensures that the UE (101) can provide accurate and timely CSI reports, which are essential for the mobility. The LTM measurement log controller (110) uses these reports to make informed decisions about triggering of mobility from source cell to one or more candidate cells.

[0098] Further, the L1 SSB measurement results are obtained by the LTM measurement log controller (110) from at least one of measResultL1-NeighCells included in the RLF report and neighCellsMeasL1ListNR included in the SHR. These measurement results provide detailed information about the signal quality and interference levels of neighboring cells, which is crucial for making handover decisions or LTM decisions. Further, attempt LTM-Switch and a mobility execution timer T304 for CLTM are configured by the LTM measurement log controller (110). The mobility execution timer T304 ensures that the handover process is completed within a specified time frame, reducing the risk of call drops and service interruptions. The LTM measurement log controller (110) dynamically adjusts mobility parameters, such as handover thresholds and hysteresis values, to optimize the handover process based on real-time network conditions and user mobility patterns.

[0099] Receiving L1 measurements only when the LTM related CSI reporting is configured (i.e when L1 measurements are used for LTM) reduces the measurement reporting load at the UE (101) and reduces the measurements transmitted over the air interface, and reduces the processing overhead at the network.. The LTM CSI reports are utilized even when the L1 measurement reports are transmitted in MAC signalling.

[0100] FIG 2A is a flowchart that illustrates for a method for managing mobility of UE (101) in a communication network system according to an embodiment as disclosed herein. At step 201, the method includes receiving by the UE (101) the configuration from the network node apparatus (106). The configuration includes the LTM) candidate cell configuration. At steps 202, the method includes detecting by the UE (101) the condition for logging at least one of RLF or SHR. At steps 203, the method includes logging, by the UE (101), L1 SSB measurements of the LTM candidate cells. The LTM candidate cells are configured for reporting L1 measurements for the LTM in at least one of the RLF report the SHR.

[0101] Further, the method includes performing by the UE (101) at least one of detecting at least one of the RLF report or the SHR and including in at least one of the RLF report and the SHR, L1 measurement results based on the logged L1 SSB measurements for at least one of the configured LTM candidate cells upon a reporting occasion for at least one of the RLF report or the SHR. Further, the method includes determining whether the T304 timer associated with CLTM in the UE (101) is expired and reverting back to the UE (101) configuration used in a source PCell upon expiration of the T304 timer associated with the CLTM except for the PDCP state variables for SRBs associated with an MCG. The UE (101) continuously monitors the T304 timer, which governs the duration for which the UE (101) should attempt to switch to a new cell before reverting to the original configuration. This ensures that the UE (101) may recover from the LTM cell switch failure using LTM configuration, by applying a LTM candidate configuration in relation to the source cell's configuration.

[0102] FIG 2B is a flowchart that illustrates for method for managing mobility of the UE (101) in the communication network system by network node apparatus (106) according to an embodiment as disclosed herein.

[0103] At step 204, the method includes configuring the UE (101) with the LTM configuration by the network node apparatus (101). The LTM configuration further includes the CSI report configuration for LTM.

[0104] At step 205, the method includes receiving, by the network node apparatus (106) from the UE (101), L1 SSB measurement results for one or more LTM candidate cells in at least one of the RLF report and the SHR. The L1 SSB measurement results are received based on the UE being configured with the LTM CSI report configuration.

[0105] At step 206, the method includes processing, by the network node apparatus (106), the received L1 SSB measurement results to support at least one of radio link failure optimization or handover failure optimization associated with at least one of LTM cell switch and L3 handover.

[0106] In an embodiment, the method includes providing by the network node apparatus (106) to the UE (101) ltm-Config that configures LTM candidate cells for an MCG. Further, the method configures the UE (101) for reporting L1 measurements for LTM in at least one of the RLF report and the SHR. The network node apparatus (106) sends configuration parameters to the UE (101), which include specific identifiers and measurement thresholds for the LTM candidate cells. This configuration enables the UE (101) to accurately report its measurements, facilitating mobility management. Further, the method includes receiving by the network node apparatus (106) from the UE (101) at least one of the RLF report or the SHR including L1 SSB measurement results for at least one of the configured LTM candidate cells. The RLF report is received after the UE (101) faced a failure and SHR is received after UE faces a near failure.The network node apparatus (106) processes these reports to evaluate the performance and reliability of the candidate cells. In addition, the method includes processing by the network node apparatus (106) the received L1 SSB measurement results to support at least one of radio link failure optimization or handover failure optimization associated with at least one of LTM cell switch and L3 handover. Further, the optimizations may be performed for too late handover failure, too early handover failure, or handover failure to wrong cell. The network node apparatus (106) employs advanced algorithms to analyze the measurement results, identifying patterns and potential issues that could lead to radio link failures or handover failures. This proactive approach helps in maintaining seamless connectivity and improving the overall user experience.

[0107] FIG 3 is a flow chart that illustrates a scenario of handling the conditional LTM failure according to an embodiment as disclosed herein.

[0108] At step 301, the UE (101) performs LTM cell switch execution triggered by fulfillment of LTM cell switch execution conditions for the MCG.

[0109] At step 302, the T304 timer of the MCG expires during or after the LTM cell switch execution, indicating that the mobility procedure has not been completed within the allocated time.

[0110] At step 303, the UE (101) reverts back to the UE (101) configuration used in the source PCell except for the PDCP state variables for SRB(s) associated to the MCG. In an embodiment, if the LTM cell switch timer T304 in NR expires and the LTM cell switch execution for which the timer expiry is triggered by a CLTM execution, the UE (101) reverts to the UE (101) configuration used in the source PCell except for the PDCP state variables for SRB(s) associated with the MCG. This ensures that the UE (101) can quickly return to a stable configuration if the cell switch is unsuccessful, maintaining continuity in communication and reducing the impact of any failures.

[0111] In an embodiment, according to section 5.3.5.8.3 of TS 38.331, upon T304 expiry (Reconfiguration with Sync Failure) or T420 expiry (Path Switch Failure), the UE (101) shall perform in [Table 4].

[0112] 1> if T304 of the MCG expires; or1> if T420 expires; or,1> if the target L2 U2N Relay UE (i.e., the UE indicated bytargetRelayUE-Identityin the receivedRRCReconfigurationmessage containingreconfigurationWithSyncindicating path switch as specified in 5.3.5.5.2) changes its serving PCell before path switch:2> release dedicated preambles provided inrach-ConfigDedicatedif configured;2> release dedicated msgA PUSCH resources provided inrach-ConfigDedicatedif configured;2> if any DAPS bearer is configured, and radio link failure is not detected in the source Pcell, according to clause 5.3.10.3:2> else:3> ifattemptLTM-Switchis configured and the T304 of the MCG expiry is caused by an LTM cell switch execution triggered by an indication from lower layers or upon fulfilment of CLTM evaluation conditions as described in 5.3.5.18.6:4> revert back to the UE configuration used in the source Pcell except for the PDCP state variables for SRB(s) associated to the MCG;

[0113] Further continuing the PDCP state variables after the failure allows the UE (101) to continue with the PDCP state variables for important SRB(s) if the UE (101) may recover the radio connection and helps to reduce the latency.

[0114] In an embodiment, if the LTM cell switch timer (T304 in NR) expires and the LTM cell switch execution for which the timer expiry is triggered by the CLTM execution based on L3 measurements and the UE (101) is configured for LTM-based recovery, the UE (101) reverts back to the UE (101) configuration used in the source Pcell except for the PDCP state variables for SRB(s) associated with the MCG.

[0115] In an embodiment, as per 5.3.5.8.3 T304 expiry (Reconfiguration with sync Failure) or T420 expiry (Path switch failure), the UE (101) shall perform in [Table 5].

[0116] 1> if T304 of the MCG expires; or1> if T420 expires; or,1> if the target L2 U2N Relay UE (i.e., the UE indicated bytargetRelayUE-Identityin the receivedRRCReconfigurationmessage containingreconfigurationWithSyncindicating path switch as specified in 5.3.5.5.2) changes its serving PCell before path switch:2> release dedicated preambles provided inrach-ConfigDedicatedif configured;2> release dedicated msgA PUSCH resources provided inrach-ConfigDedicatedif configured;2> if any DAPS bearer is configured, and radio link failure is not detected in the source Pcell, according to clause 5.3.10.3:2> else:3> ifattemptLTM-Switchis configured and the T304 of the MCG expiry is caused by an LTM cell switch execution triggered by an indication from lower layers or upon fulfilment of CLTM evaluation conditions based on L3 measurements as described in 5.3.5.18.6:4> revert back to the UE configuration used in the source Pcell except for the PDCP state variables for SRB(s) associated to the MCG.

[0117] Further continuing the PDCP state variables after the failure allows the UE (101) to continue with the PDCP state variables for important SRB(s) if the UE (101) can recover the radio connection and helps to reduce the latency.

[0118] FIG 4 is a flow chart that illustrates another scenario for handling the conditional LTM failure according to an embodiment disclosed herein.

[0119] At step 401, conditional LTM execution or the execution of the LTM cell switch is triggered by lower layers for the MCG.

[0120] At step 402, the T304 expiry occurs.

[0121] At step 403, a determination is made whether the PDCP entities of the SRB(s) were re-established during the LTM cell switch execution that failed due to T304 expiry.

[0122] At step 404, if the PDCP entities are re-established, the UE (101) reverts to the UE (101) configuration used in the source PCell.

[0123] At step 405, if the PDCP entities are not re-established, the UE (101) reverts to the UE (101) configuration used in the source PCell except for the PDCP state variables for the SRB(s) associated with the MCG.

[0124] In an embodiment, if the LTM cell switch timer, the T304 in NR, expires and the LTM cell switch execution for which the timer expiry is triggered by an indication from lower layers or by the CLTM execution based on L3 measurements and the UE (101) is configured for LTM-based recovery and the security configuration has not changed between the source and the target cells for the failed LTM cell switch, the UE (101) reverts to the UE (101) configuration used in the source PCell except for the PDCP state variables for the SRB(s) associated with the MCG. If the LTM cell switch timer T304 in NR expires and the LTM cell switch execution for which the timer expiry is triggered by an indication from lower layers or by a CLTM execution based on L3 measurements and the UE (101) is configured for LTM-based recovery and the security configuration has changed between the source and the target cells for the failed LTM cell switch, the UE (101) reverts to the UE (101) configuration used in the source PCell including the PDCP state variables for the SRB(s) associated with the MCG.

[0125] Further, if the LTM cell switch timer, the T304 in the NR, expires and the LTM cell switch execution for which the timer expiry is triggered by an indication from lower layers or by the CLTM execution based on the L3 measurements and the source and target cells are in two different CUs for an inter-gNB LTM cell switch, the UE (101) reverts to the UE (101) configuration used in the source PCell including the PDCP state variables for the SRB(s) associated with the MCG. For a failed LTM cell switch execution due to the LTM cell switch timer T304 in NR, if a field ltm-NoSecurityChangeID is configured for the LTM-Candidate IE and the UE (101) does not have any value stored for ltm-ServingCellNoSecurityChangeID within VarLTM-ServingCellNoSecurityChangeID or if the value of ltm-NoSecurityChangeID contained within the LTM-Candidate IE in ltm-Config or ltm-ConfigNRDC as indicated by lower layers or upon fulfillment of the CLTM evaluation condition based on L3 measurements is not equal to the value of ltm-ServingCellNoSecurityChangeID within VarLTM-ServingCellNoSecurityChangeID, the UE (101) reverts to the UE (101) configuration used in the source PCell including the PDCP state variables for the SRB(s) associated with the MCG.

[0126] In an embodiment, if the LTM cell switch timer, the T304 in the NR, expires and the LTM cell switch execution for which the timer expiry is triggered by an indication from lower layers or by fulfillment of the CLTM evaluation condition based on L3 measurements and the UE (101) is used for LTM-based recovery and the PDCP entity of the SRB(s) or the PDCP entity of the DRB(s) was not re-established during the LTM cell switch, the UE (101) reverts to the UE (101) configuration used in the source PCell except for the PDCP state variables for the SRB(s) associated with the MCG. If the LTM cell switch timer, the T304 in the NR, expires and the LTM cell switch execution for which the timer expiry is triggered by an indication from lower layers or by fulfillment of the CLTM evaluation condition based on L3 measurements and the UE (101) is for LTM-based recovery and the security configuration has changed between the source and the target cells for the LTM cell switch, the UE (101) reverts to the UE (101) configuration used in the source PCell including the PDCP state variables for the SRB(s) associated with the MCG.

[0127] Further, the UE (101) may be configured for LTM-based recovery if a flag allowing the UE (101) to attempt applying an RRC Reconfiguration corresponding to the LTM candidate such as attemptLTM-Switch is configured in NR. If the CLTM evaluation condition is based on L1 measurements, the lower layers indicate the condition to the RRC.

[0128] In an embodiment, as per 5.3.5.8.3 T304 expiry (Reconfiguration with sync Failure) or T420 expiry (Path switch failure). The UE (101) shall perform in [Table 6].

[0129] 1> if T304 of the MCG expires; or1> if T420 expires; or,1> if the target L2 U2N Relay UE (i.e., the UE indicated by targetRelayUE-Identity in the received RRCReconfiguration message containing reconfigurationWithSync indicating path switch as specified in 5.3.5.5.2) changes its serving PCell before path switch:2> release dedicated preambles provided in rach-ConfigDedicated if configured;2> release dedicated msgA PUSCH resources provided in rach-ConfigDedicated if configured;2> if any DAPS bearer is configured, and radio link failure is not detected in the source Pcell, according to clause 5.3.10.3:2> else:3> if attemptLTM-Switch is configured and the T304 of the MCG expiry is caused by an LTM cell switch execution triggered by an indication from lower layers or upon fulfilment of CLTM evaluation conditions based on L3 measurements and the PDCP entities of the SRB(s) are not re-established during the LTM cell switch execution as described in 5.3.5.18.6:4> revert back to the UE configuration used in the source Pcell except for the PDCP state variables for SRB(s) associated to the MCG.

[0130] In an embodiment for CHO with candidate SCG(s), the UE (101) sets the measurement results for the last serving PSCell measResultLastServPSCell by including the cell-level RSRP, RSRQ, and available SINR. When the RLF report is logged due to a handover failure that includes the PSCell change and when the RRCReconfiguration for the PCell handover also changes the PSCell and the handover has failed, the UE (101) logs measResultLastServPSCell by including the cell-level RSRP, RSRQ, and available SINR of the source PSCell. When the RLF report is logged due to a handover failure that includes a PSCell addition and when the RRCReconfiguration for the PCell handover also adds the PSCell and the handover has failed, the UE (101) logs measResultLastServPSCell by including the cell-level RSRP, RSRQ, and available SINR of the target PSCell. In the case of a radio link failure when a PSCell is configured or in a handover failure without a PSCell change, the UE (101) logs measResultLastServPSCell based on the available SSB and CSI-RS measurements collected up to the moment the UE (101) detected the failure.

[0131] In an embodiment, the UE (101) determines whether it supports an RLF report for CHO with candidate SCG(s). In an embodiment, the UE (101) may further inform the network of this capability through an RRC message such as a UE (101) CapabilityInformation message. In an embodiment, the UE (101) may determine or determine and report whether it supports SON / MDT optimizations for CHO with candidate SCG(s). The UE (101) supporting SON / MDT optimization for CHO with candidate SCG(s) supports the RLF report for CHO with candidate SCG(s).

[0132] In an embodiment, the UE (101) supporting the RLF report for the CHO with candidate SCG(s) logs and reports neighbor cell measurements measResultNeighCells excluding measurements of one or more of the source PCell in the case of a handover failure, the PCell in the case of a radio link failure, candidate PCells, and candidate PSCells configured as candidates for CHO with candidate SCG(s) (for example, configured with condExecutionCond and condExecutionCondPSCell in NR), and the source PSCell in the case of a PSCell change or the PSCell in the case that the PSCell is configured and no PSCell change occurs. The measurements may be SSB-based measurements or CSI-RS-based measurements.

[0133] Further, the measurements of one or more of the PCell, the source PCell, candidate PCells, and candidate PSCells configured as candidates for CHO with candidate SCG(s) (for example, configured with condExecutionCond and condExecutionCondPSCell in NR), and the source PSCell in the case of a PSCell change or the PSCell in the case that the PSCell is configured and no PSCell change occurs may be reported separately by the UE (101). The network receiving the separate measurements may further perform separate optimizations for the UE (101).

[0134] In an embodiment, the RLF report content determination, (section 5.3.10.5 of TS 38.331) is performed by the UE (101). The UE (101) shall determine the content in a VarRLF-Report as follows in [Table 7].

[0135] 1> for each of the configuredmeasObjectNRin which measurements are available:2> if the SS / PBCH block-based measurement quantities are available:3>If the UE supports RLF report for CHO with candidate SCG(s) and the UE (101) is configured withcondExecutionCondandcondExecutionCondPScell,4> set themeasResultListNRinmeasResultNeighCellsto include all the available measurement quantities of the best measured cells, other than the source PCell (in case HO failure) or PCell (in case RLF), and other than the source PSCell (in case of PSCell change) or PSCell (in case of no PSCell change), candidate PCells, and candidate PSCells which were configured withcondExecutionCondandcondExecutionCondPScell,ordered such that the cell with highest SS / PBCH block RSRP is listed first if SS / PBCH block RSRP measurement results are available, otherwise the cell with highest SS / PBCH block RSRQ is listed first if SS / PBCH block RSRQ measurement results are available, otherwise the cell with highest SS / PBCH block SINR is listed first, based on the available SS / PBCH block based measurements collected up to the moment the UE detected failure;5> for each neighbour cell included, include the optional fields that are available;4> else5> set themeasResultListNRinmeasResultNeighCellsto include all the available measurement quantities of the best measured cells, other than the source PCell (in case HO failure) or PCell (in case RLF), ordered such that the cell with highest SS / PBCH block RSRP is listed first if SS / PBCH block RSRP measurement results are available, otherwise the cell with highest SS / PBCH block RSRQ is listed first if SS / PBCH block RSRQ measurement results are available, otherwise the cell with highest SS / PBCH block SINR is listed first, based on the available SS / PBCH block based measurements collected up to the moment the UE detected failure;2> if the CSI-RS based measurement quantities are available:3>If the UE supports RLF report for CHO with candidate SCG(s) and the UE is configured withcondExecutionCondandcondExecutionCondPScell,4> set themeasResultListNRinmeasResultNeighCellsto include all the available measurement quantities of the best measured cells, other than the source PCell (in case HO failure) or PCell (in case RLF), and other than the source PSCell (in case of PSCell change failure) or PSCell (in case of no PSCell change), candidate PCells, and candidate PSCells which were configured withcondExecutionCondandcondExecutionCondPScell, ordered such that the cell with highest CSI-RS RSRP is listed first if CSI-RS RSRP measurement results are available, otherwise the cell with highest CSI-RS RSRQ is listed first if CSI-RS RSRQ measurement results are available, otherwise the cell with highest CSI-RS SINR is listed first, based on the available CSI-RS based measurements collected up to the moment the UE detected radio link failure;4> for each neighbour cell included, include the optional fields that are available;3> else4> set themeasResultListNRinmeasResultNeighCellsto include all the available measurement quantities of the best measured cells, other than the source PCell (in case HO failure) or PCell (in case RLF), ordered such that the cell with highest CSI-RS RSRP is listed first if CSI-RS RSRP measurement results are available, otherwise the cell with highest CSI-RS RSRQ is listed first if CSI-RS RSRQ measurement results are available, otherwise the cell with highest CSI-RS SINR is listed first, based on the available CSI-RS based measurements collected up to the moment the UE detected radio link failure;5> for each neighbour cell included, include the optional fields that are available;1> if the UE supports RLF-Report for LTM, for each neighbour MCG LTM candidate cell with the LTM-CandidateConfig contains ltm-SSB-Config :2> if SS / PBCH block-based L1-RSRP measurement quantities are available:3> set themeasResultL1NeighCellsto include all the available SS / PBCH block-based L1-RSRP measurement results of the best measured cells, other than the source PCell (in case HO failure) or PCell (in case RLF), ordered such that the cell with highest SS / PBCH block-based L1-RSRP (of all SS / PBCH block-based L1-RSRP measurement results for the cell) is listed first;

[0136] In an embodiment, the UE (101) supporting the SHR for the CHO with candidate SCG(s) logs and reports neighbor cell measurements, such as in measResultNeighCells in the NR, excluding measurements of one or more of the source PCell or the target PCell, candidate PCells, and candidate PSCells configured as candidates for CHO with candidate cells, for example, configured with condExecutionCond and condExecutionCondPSCell in the NR, and the source PSCell in the case of the PSCell change or the PSCell in the case that the PSCell is configured and no PSCell change occurs.

[0137] Further, the measurements of one or more of the source PCell, the target PCell, the source PSCell, the target PSCell, candidate PCells, and candidate PSCells configured as candidates for CHO with candidate cells, for example, configured with condExecutionCond and condExecutionCondPSCell in the NR, and the source PSCell in the case of the PSCell change or the PSCell in the case that a PSCell is configured and no PSCell change occurs, may be reported separately by the UE (101). The network receiving the separate measurements may further perform separate optimizations for the UE (101).

[0138] In an embodiment, according to TS 38.331, section 5.7.10.6, which relates to actions for successful handover report determination, the UE (101) shall determine the report content for the PCell in [Table 8].

[0139] <checks for SHR trigger>2> store the successful handover information inVarSuccessHO-Reportand determine the content inVarSuccessHO-Reportas follows:3> clear the information included inVarSuccessHO-Report, if any;3> if the UE is not in SNPN access mode, set theplmn-IdentityListto include the list of EPLMNs stored by the UE (i.e., includes the RPLMN);3> else if the UE is in SNPN access mode, set thesnpn-IdentityListto include the list of equivalent SNPNs stored by the UE (i.e., including the registered SNPN identity), if available;3> if the procedure is triggered due to successful completion of reconfiguration with sync, for each of themeasObjectNR, configured by the source PCell, in which the lastRRCReconfigurationmessage includingreconfigurationWithSyncwas applied; or:3> if the procedure is triggered due to successful completion of Mobility from NR to E-UTRA, for each of themeasObjectNR, configured by the source PCell, in which the lastMobilityFromNRCommandconcerning an inter-RAT handover from NR to E-UTRA was applied:4> if measurements are available for themeasObjectNR:5> if the SS / PBCH block-based measurement quantities are available:6>If the UE supports SHR for CHO with candidate SCG(s) and the UE is configured withcondExecutionCondandcondExecutionCondPScell,7> set themeasResultListNRinmeasResultNeighCellsto include all the available measurement quantities of the best measured cells, other than the source PCell or target PCell and other than the source PSCell or target PSCell and candidate PSCells, ordered such that the cell with highest SS / PBCH block RSRP is listed first if SS / PBCH block RSRP measurement results are available, otherwise the cell with highest SS / PBCH block RSRQ is listed first if SS / PBCH block RSRQ measurement results are available, otherwise the cell with highest SS / PBCH block SINR is listed first, based on the available SS / PBCH block based measurements collected up to the moment the UE sends theRRCReconfigurationCompletemessage if the procedure is triggered due to successful completion of reconfiguration with sync, or up to the moment the UE sends the EUTRARRCConnectionReconfigurationCompletemessage if the procedure is triggered due to successful completion of Mobility from NR to E-UTRA;7> for each neighbour cell included, include the optional fields that are available;Else>7> set themeasResultListNRinmeasResultNeighCellsto include all the available measurement quantities of the best measured cells, other than the source PCell or target PCell, ordered such that the cell with highest SS / PBCH block RSRP is listed first if SS / PBCH block RSRP measurement results are available, otherwise the cell with highest SS / PBCH block RSRQ is listed first if SS / PBCH block RSRQ measurement results are available, otherwise the cell with highest SS / PBCH block SINR is listed first, based on the available SS / PBCH block based measurements collected up to the moment the UE sends theRRCReconfigurationCompletemessage if the procedure is triggered due to successful completion of reconfiguration with sync, or up to the moment the UE sends the EUTRARRCConnectionReconfigurationCompletemessage if the procedure is triggered due to successful completion of Mobility from NR to E-UTRA;7> for each neighbour cell included, include the optional fields that are available;NOTE 1: For the neighbouring cells set included inmeasResultListNRinmeasResultNeighCellsordered based on the SS / PBCH block measurement quantities, the UE includes also the CSI-RS based measurement quantities, if available.5> if the CSI-RS measurement quantities are available:6>If the UE supports SHR for CHO with candidate SCG(s) and the UE is configured withcondExecutionCondandcondExecutionCondPScell,7> set themeasResultListNRinmeasResultNeighCellsto include all the available measurement quantities of the best measured cells, other than the source PCell and target PCell and other than the source PSCell or target PSCell and candidate PSCells, ordered such that the cell with highest CSI-RS RSRP is listed first if CSI-RS RSRP measurement results are available, otherwise the cell with highest CSI-RS RSRQ is listed first if CSI-RS RSRQ measurement results are available, otherwise the cell with highest CSI-RS SINR is listed first, based on the available CSI-RS based measurements collected up to the moment the UE sends theRRCReconfigurationCompletemessage if the procedure is triggered due to successful completion of reconfiguration with sync, or up to the moment the UE sends the EUTRARRCConnectionReconfigurationCompletemessage if the procedure is triggered due to successful completion of Mobility from NR to E-UTRA;6>else:7> set themeasResultListNRinmeasResultNeighCellsto include all the available measurement quantities of the best measured cells, other than the source PCell and target PCell, ordered such that the cell with highest CSI-RS RSRP is listed first if CSI-RS RSRP measurement results are available, otherwise the cell with highest CSI-RS RSRQ is listed first if CSI-RS RSRQ measurement results are available, otherwise the cell with highest CSI-RS SINR is listed first, based on the available CSI-RS based measurements collected up to the moment the UE sends theRRCReconfigurationCompletemessage if the procedure is triggered due to successful completion of reconfiguration with sync, or up to the moment the UE sends the EUTRARRCConnectionReconfigurationCompletemessage if the procedure is triggered due to successful completion of Mobility from NR to E-UTRA;3> if the UE supports successful handover report for LTM and the procedure is triggered due to successful completion of reconfiguration with sync concerning an LTM cell switch:4> for each neighbour MCG LTM candidate cell contained in the current UE configuration with the LTM-CandidateConfig contains ltm-SSB-Config :5> if SS / PBCH block-based L1-RSRP measurement quantities are available:6> set theneighCellsMeasL1ListNRto include all the available SS / PBCH block-based L1-RSRP measurement results of the best measured cells, other than the source PCell or target PCell, ordered such that the cell with highest SS / PBCH block-based L1-RSRP (of all SS / PBCH block-based L1-RSRP measurement results for the cell) is listed first, based on the available SS / PBCH block-based L1-RSRP measurements collected up to the moment the UE sends theRRCReconfigurationCompletemessage;

[0140] FIG. 5 is a flow chart that illustrates reporting L1 measurements in the RLF report according to embodiments as disclosed herein. At step 501, the UE (101) is configured with MCG LTM candidate configuration. At step 502, radio link failure or handover failure or LTM cell switch failure occurs. At step 503, the UE (101) logs and reports the L1 measurements comprising Synchronization Signal Block Reference Signal Received Power (SSB RSRP) in the RLF report for the LTM candidates that are configured with the SSB configuration within the LTM candidate cell configuration.

[0141] In an embodiment, the UE (101) logs and reports the L1 SSB-RSRP for the MCG LTM candidate cells configured with an SSB configuration within the LTM candidate cell configuration in the RLF report. An embodiment includes logging NR L1 measurements such as SSB RSRP for the LTM candidates configured with LTM-SSB-Config-r18 in the RLF report. An embodiment includes logging NR L1 measurements such as SSB RSRP for the LTM candidates for which the LTM-CSI-ResourceConfig indicates that the candidates are to be measured. If the UE (101) is not configured to report L1 measurements such as SSB RSRP in the CSI reports for an LTM candidate, for example when the LTM cell switch for the candidate is to be triggered using L3 measurements, the UE (101) does not log the L1 SSB RSRP for that LTM candidate in the RLF report.

[0142] In an embodiment, if the UE (101) is configured for a candidate to report L1 measurements for LTM through CSI reports (such as LTM-CSI-ReportConfig in NR) , the UE (101) logs and reports the L1 measurements in the RLF report. The logged and reported measurement results correspond to the values at the time of failure of the LTM cell switch, the L3 handover, or a radio link failure and may differ from any values previously reported in the CSI reports. Even if the L1 measurement results are not reported in the CSI reports for the LTM for a candidate configured to report such measurements, for example due to the network not requesting them, the UE (101) may include the L1 measurements in the RLF report

[0143] In other words, during logging, the UE (101) may determine whether the UE is configured to report L1 measurements for LTM based on an LTM-CSI-ReportConfig or a corresponding configuration structure.

[0144] Further, the UE (101) supporting the RLF report for LTM logs and reports the L1 SSB-RSRP for the MCG LTM candidate cells configured with the SSB configuration within the LTM candidate cell configuration in the RLF report. Typically SSB configuration may be included when the LTM-CSI-ReportConfig is configured and the UE (101) is configured to report SSB measurements.. In the NR, the L1 measurements for LTM are logged in the RLF report for candidates configured with LTM-SSB-Config-r18. The UE (101) avoids logging L1 measurements if the LTM cell switch is based on L3 measurements. This approach enables the network to optimize radio link failures or handover failures by processing L1 measurements for cells targeted for LTM based on L1 measurements rather than L3 measurements even if L1 measurements are also available.

[0145] FIG. 6 is a flow chart that illustrates reporting L1 measurements in SHR according to embodiments as disclosed herein. At step 601, the UE (101) is configured with MCG LTM candidate configuration. At step 602, near failure occurs (SHR conditions satisfied). At step 603, the UE (101) logs and reports the L1 measurements (SSB RSRP) in SHR for the LTM candidates which are configured with SSB configuration within the LTM candidate cell configuration.

[0146] In an embodiment, the UE (101) that supports the SHR for the LTM logs and reports the L1 measurements such as SSB RSRP for the MCG LTM candidate cells configured with an SSB configuration within the LTM candidate cell configuration in the SHR. In NR, the L1 measurements such as SSB RSRP are logged and reported in the SHR for the MCG LTM candidates configured with LTM-SSB-Config-r18. If the UE (101) is specifically configured to report L1 measurements for LTM through CSI reports, it logs and reports the L1 measurements in the SHR. The logged and reported measurement results correspond to the values at the time of successful completion of the LTM cell switch and may differ from any values previously reported in CSI reports. Even if the L1 measurement results are not reported in the CSI reports for LTM for an LTM candidate cell, for example, due to the network not requesting them, the UE (101) may include the L1 measurements in the SHR. The measurements are further reported for a candidate cell if the mobility that triggered the SHR corresponds to an L3 handover and not the LTM cell switch, provided that the UE (101) is configured to report L1 measurements for LTM for that candidate. This enables the network to optimize near failures for mobility by processing L1 measurements for cells targeted for LTM based on the L1 measurements rather than L3 measurements even if the L1 measurements are also available.

[0147] In an embodiment, the UE (101) logs NR L1 measurements such as SSB RSRP for LTM candidates for which the LTM-CSI-ResourceConfig indicates measurement of those candidates. According to 3gpp specifications, when the LTM-CSI-ResourceConfig indicates measurement of those candidates, LTM-CSI-ReportConfig also is provided. If the UE (101) is not configured to report L1 measurements such as SSB RSRP in the CSI reports for an LTM candidate, for example, when the LTM cell switch for the candidate is triggered using L3 measurements, the L1 SSB RSRP is not logged for that LTM candidate in the SHR.

[0148] Embodiments relating to the logging of L1 measurements in the RLF report are also applicable for SCG RLF, for example, in SCGFailureInformation. The UE (101) reports L1 measurements for SCG LTM candidate cells configured with the SSB configuration within the LTM candidate cell configuration. Similarly, embodiments relating to the logging of the L1 measurements in the SHR are also applicable for reporting near failure of the SCG, for example, in an SPR (Successful PSCell Change or Addition Information Report).

[0149] Further, the UE (101) may perform L1 measurements for certain LTM candidate cells based on the configuration for reporting L3 measurements and derive L3 measurements by applying a filter to the L1 measurements while avoiding logging and reporting this information in the RLF report or the SHR.

[0150] In an embodiment, the method enables the UE (101) to selectively log L1 SSB-RSRP measurements only for LTM candidate cells configured with SSB configuration (LTM-SSB-Config-r18) and avoid logging L1 measurements when LTM cell switch is based on L3 measurements, thereby reducing unnecessary measurement logging overhead and focusing on relevant L1-based LTM candidates for radio link failure and handover optimization.

[0151] In an embodiment, the method allows the network node apparatus (106) to obtain comprehensive L1 measurement results from measResultL1-NeighCells in RLF reports and neighCellsMeasL1ListNR in SHR, including measurement results at the time of failure that can be different from previously reported CSI values, enabling accurate analysis of LTM cell switch failures and L3 handover failures for the SON optimization of the LTM operations.

[0152] In an embodiment, the method provides intelligent PDCP state variable handling during T304 expiry for conditional LTM (CLTM) by selectively reverting back to source PCell configuration except for the PDCP state variables for SRBs associated with the MCG when attemptLTM-Switch is configured and T304 expiry is caused by LTM cell switch execution, thereby ensuring continuity of signaling radio bearer operations and preventing unnecessary PDCP re-establishment overhead during the CLTM recovery procedures for the UE (101).

[0153] In an embodiment, the method includes L1 measurement results in RLF reports and SHR for candidate cells configured for reporting L1 measurements for LTM even when the L1 measurement results are not reported in CSI reports, including cases where the network node apparatus (106) may not request them, and also reports measurements for candidate cells when the mobility that triggered SHR is the L3 handover and not LTM cell switch, thereby providing complete measurement information for mobility failure analysis regardless of prior CSI reporting status or mobility trigger type, which is essential for comprehensive SON optimization.

[0154] The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and / or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modificationsshouldand are intended to be comprehended 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. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the scope of the embodiments as described herein.

Claims

1.A method performed by a user equipment (UE) in a wireless communication system, the method comprising:receiving layer 1 / layer 2 triggered mobility (LTM) configuration information;identifying that a radio link failure (RLF) occurs or that a successful handover occurs;in case that the UE supports an RLF report for an LTM or a successful handover report for the LTM, setting a neighbor cell measurement field to include layer 1 (L1) measurement results for a master cell group (MCG) LTM candidate cells based on the LTM configuration information; andtransmitting a report message including the neighbor cell measurement field.2.The method of claim 1,wherein the L1 measurement results are ordered such that a cell with a highest L1 measurement result is listed first.3.The method of claim 1, wherein the setting of the neighbor cell measurement field comprises:in case that the UE supports the successful handover report, setting the neighbor cell measurement field to include the L1 measurement results for the MCG LTM candidate cells other than a source primary cell (PCell) or a target PCell.4.The method of claim 1, wherein the setting of the neighbor cell measurement field comprises:in case that the UE supports the successful handover report, setting the neighbor cell measurement field to include the L1 measurement results collected up to a moment at which the UE sends a radio resource control (RRC) reconfiguration complete message.5.The method of claim 1,wherein the L1 measurement results are L1 synchronization signal and physical broadcast channel (SS / PBCH) block (SSB) reference signal received powers (RSRPs).6.The method of claim 1,wherein the report message is one of the RLF report or the successful handover report.7.The method of claim 6,wherein in case that the report message is the RLF report, the L1 measurement results are obtained in the MCG LTM candidate cells upon detecting the RLF.8.The method of claim 6,wherein the report message is the successful handover report, the L1 measurement results are obtained in the MCG LTM candidate cells when the successful handover is executed.9.A user equipment (UE) in a wireless communication system, the UE comprising:at least one transceiver;at least one processor communicatively coupled to the at least one transceiver; andat least one memory, communicatively coupled to the at least one processor, storing instructions executable by the at least one processor individually or in any combination to cause the UE to:receive layer 1 / layer 2 triggered mobility (LTM) configuration information,identify that a radio link failure (RLF) occurs or that a successful handover occurs,in case that the UE supports an RLF report for an LTM or a successful handover report for the LTM, set a neighbor cell measurement field to include layer 1 (L1) measurement results for a master cell group (MCG) LTM candidate cells based on the LTM configuration information, andtransmit a report message including the neighbor cell measurement field.10.The UE of claim 9,wherein the L1 measurement results are ordered such that a cell with a highest L1 measurement result is listed first.11.The UE of claim 9, wherein the instructions executable by the at least one processor individually or in any combination further cause the UE to:in case that the UE supports the successful handover report, setting the neighbor cell measurement field to include the L1 measurement results for the MCG LTM candidate cells other than a source primary cell (PCell) or a target PCell.12.The UE of claim 9, wherein the instructions executable by the at least one processor individually or in any combination further cause the UE to:in case that the UE supports the successful handover report, setting the neighbor cell measurement field to include the L1 measurement results collected up to a moment at which the UE sends a radio resource control (RRC) reconfiguration complete message.13.The UE of claim 9,wherein the L1 measurement results are L1 synchronization signal and physical broadcast channel (SS / PBCH) block (SSB) reference signal received powers (RSRPs).14.The UE of claim 9,wherein the report message is one of the RLF report or the successful handover report.15.The UE of claim 14,wherein in case that the report message is the RLF report, the L1 measurement results are obtained in the MCG LTM candidate cells upon detecting the RLF, andwherein the report message is the successful handover report, the L1 measurement results are obtained in the MCG LTM candidate cells when the successful handover is executed.

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